Saturday, 16 December 2017

Perioperative Management of INR

Eventually one finds that some sort of small surgery is needed, for those of us on warfarin (perhaps after a large surgery such as a heart valve replacement) the management of INR around that is important. In my case a colonoscopy was required.



This post is about my experiences in the perioperative management of my INR around my colonoscopy and thus is here also as a guide for those who (like me) self manage.

Starting point

My Gastroenterologist requested my INR to be managed down to ≤ 1.5 pre the 'procedure', which formed the basis for this "experiment" in validating my INR management and the predictive usefulness of my simple data model for INR.

Warning

Don't fuck with this stuff if you don't have a clue. You may get hurt, and that hurt may be permanent. Instead get a clue and start by having a read my other posts on INR management (use the INR tag in the tag list) keeping records and being on top of your own health. Reach out to me for assistance if you wish (see later).

Summary position


  • With good data you can manage your INR down to a suitable level for a small procedure probably without need for heparin (but be prepared for needing it)
  • I have again verified my model in an actual experiment but with better data gathering than before
  • I was perhaps too conservative in my management strategy (but who knows)
  • the outcomes were all good
  • I took a Heparin shot in the middle of the 'recovery of INR' phase (for "just in case"), pehaps it was too conservative but what the hell ... 


Premise

I manage my own INR (as you'll find on this blog for instance here). In making this a bit more predictable (rather than just gut feel heuristic) I have developed a data model on how my INR behaves. Previous surgeries (some yars back now) have given me some data to work with, and years of managing myself has allowed me to collect and analyze response due to various "oops" events such as "I missed a dose".  This post is based on that and my reading and understanding of the literature. In particular the following article is a useful advice on exactly this topic:



found in full here. I urge you to read it.

From that article I found the following points of significance which guided my strategy:

Summary
The perioperative management of patients on long-term warfarin therapy poses particular problems. This situation is exacerbated by the absence of randomised trials. The strategy used is based on the assessment of each patient's thromboembolic and bleeding risks. These determine the need for withholding warfarin and switching to heparin. Most patients having minor procedures can continue to take warfarin, provided that they are closely monitored and local measures are used to ensure adequate haemostasis
My primary take outs are highlighted but as always, read the above carefully and see it in context.

Risks of temporarily withholding warfarin 
The risks are difficult to quantify due to the lack of randomised trials examining this issue. They vary according to the indication for the warfarin therapy.
The article goes on to iterate some major risk groups:



Which in my case is the simple fact that I have a modern bileaflet mechanical aortic valve ... which puts me in about the lowest risk category ... the same may be true for you too.

Next:

Do the benefits of anticoagulation outweigh the risks?
The approach to the management of anticoagulation in patients with prosthetic valves undergoing non-cardiac surgery remains controversial. The need for perioperative anticoagulation in patients with mechanical heart valves has been questioned in a recent review. The authors argue that for every 10 000 patients with mechanical heart valves who are given perioperative intravenous heparin, three thromboembolic events are prevented at the cost of 300 major postoperative bleeding episodes

Think about those numbers the prevention of three thrombo events vs 300 major bleeds.

Now as a background, one of my friends (about the same age as me, but not on warfarin) had a colonoscopy the week before me. He had a life threatening bleed (and was taken from his home by ambulance to a local hospital then transferred to a more major hospital when they couldn't stop the bleeding.

I have also had a friend die of a GI bleed ... Clotting has a major and important role in survival.

Lastly the literature is full of examples of people who have had low INR for extended periods that have come to no harm ...


Shit like this takes a long time to form, who knows how low for how long they were. So maybe we are just too conservative? Probably that's a good research question too.


So I took my management of this from that perspective; IE my risk of a clot (low) vs the (higher) potential for a bleed.

Management Strategy

I decided to monitor my INR daily and to cease warfarin a day earlier than my model predicted I would need to cease to achieve the target that the Gastroenterologist had given me. I wanted to do this because I wanted to make sure that bleeding wasn't a factor.

My process was this:

  • measure INR daily (in the AM, usually about 8am)
  • my usual dose time is 7pm
  • I charted INR and dose
  • the graph below has INR on the LHS Y axis and dose in mg on the right axis
  • the bars represent actual data and the lines part of my model
  • my colonoscopy was Wednesday

So, lets look at the data.


As it happens my model was quite close in predicting my INR reduction (not shown), which fell to below 1.5 by tuesday (as I had expected it would).

This meant that I went into my procedure with my INR of 1.2 (measured in the AM) for a 2pm procedure. Which is consistent with my goals of reduced bleeding complications.

I decided to not recommence warfarin on the evening of the procedure but wait for the next day. It is on this point I feel that the collected data shows that  I was a bit too conservative. I believe that I could have resumed warfarin that evening and the data shows this to be correct.

My INR continued to fall on Friday (down to 1.1) and so in prudence I went to my local hospital seeking a heparin shot. I (happily) met a very good young Doctor to whom presented my INR data in support of my request for the heparin shot. He reviewed my data and was quite supportive of my approach. You see, if you're organised and detail oriented you can get support from the medical community ... even if you fall outside the box.

The strategy I employed was (using my model) to get my warfarin levels back up to a level which would resume my anticoagulation as before the process began. I did so in a manner to avoid any over shoot "spikes" in INR (due to over dosing) while allowing the INR to climb in a manner which is reasonable. My model showed me that by day 5 I would be coming within "safe" territory, and by Saturday I would be within my desired theraputic range (2.0 ~ 3.0) .

The accuracy of the model after reaching INR 1.5 seems to be wanting. I believe this is because there are "lags in the system" which means that the INR response to the warfarin may be delayed. I normally factor in a 4 day rolling average to the model to predict the rise. As you can see it is close to that, but not perfect ... meaning there are some more research questions arising from this research.

Discussion

This process has enabled me to feel much more comfortable in managing my INR and has given me added validation that my (albeit simple) model of INR behaviour in my system works. Certainly there are parameters which need better tuning, but in terms of Pareto Principle we have 80% of the benefits here already.

Based on my model I feel that I could have reduced my window of withholding my warfarin by ceasing later and resuming later. This would have still had my INR at less than 1.5 for the procedure and raising to above 2 sooner. By ceasing as soon as I did it allowed my INR to drop further than needed and take longer to then recover the desired levels.

However is this result bad? No, I don't think so. For the need of coagulation in my GI tract is not known, meaning it may be that I benefited from the extra time to heal. So for the sake of a single heparin shot two days after my procedure (on Friday, restoring AC levels required and perhaps also washing out / allow the destruction of any early stage thrombosis) I was able to give good coagulation to the site of injury (some polyps were removed) and act in a prudent manner.

Lastly my model has given me something important; Quantative  INR recovery estimates. This is a good source of confidence. We rely on "knowing" the future to feel less anxious about things. Knowing nothing is what you do when you gamble, knowing something can take much of the anxiety out of things and helps plan.

Much of the operation of my model is not clarified here in this blog post. That is deliberate, for until I decide what to do with my intellectual property I'd like to keep the cards close to my chest.

I hope this has been of benefit to some of you.

If you are a valver, and want to work with me on your INR management please feel free to comment with your email address. Comments are moderated and I will not publish a comment with an email address.

I won't charge you anything for my assistance but I will require you work in a rigorous manner in collecting data, and taking your warfarin. I will also need a base data set of some months of weekly INR readings to build your data model from. Without all of that ... it just can't happen.

Last but not least:

Acknowledgements

I would like to take the opportunity to thank my Gastroenterologist for her great team and well executed event. Everyone was professional, caring and understanding. Asked good questions and gently demanded good answers. Everything went well from the admission through to the recovery.

Thanks Olga (you know who you are).

Also I would like to thank Michele for her kind donation of some XS strips which has saved me about $100 in this instance (cos INR tests aren't free) and will in all likelihood give me another 6 months of tests too. {HatTip}

Thanks Michele, much appreciated!


Tuesday, 12 December 2017

Chainsaws (for around the home)

as it happens I have the occasional use for a chainsaw. Back in 2010 my lovely wife wanted one for the cutting trees in the yard but wanted an electric one. I think she was pleased / surprised when I put up no resistance (indeed encouragment) for her to buy an electric one. It was $99 and has been a "bottler" as we say in Australia.

I was cutting up a tree that I had to fell in the back yard of my new place and while I used the petrol one (that's Gas for Americans who don't realise that Gas is not actually a gas, or benzine for my European readers) to fell the tree and cut off the major branches I soon had the desire to drag it all closer to the house and use the electric to chop it up (firewood and then take the scraps to the dump).


The little (Bunnings) Ozito is a champ. It starts when you pull the trigger, and the oil feed just simply works. Indeed it sliced through green tree log with almost exactly the same speed as the Petrol one (which actually has a new chain that was first used on this exact day) even though the chain on the Ozito has cut down a few trees.

This is the thickness of the trunk of the "Californian Pepper Tree" I cut down and then cut into chunks with the Ozito.


And this is the little Ozito cutting down a small palm in the back yard of where my wife and I used to live.



Now I appreciate quite a lot of King Wang followers sledge the electric chainsaws as being gutless or being tethered to an electrical outlet. Its obvious that the electric supply need is there, but let me have a go at answering about the gutless part of this.

The little Ozito has a 1800W motor and a 14" bar. Being electric it will probably always put out a consistent power (as long as you have consistent power). Now lets assume that the motor is something like 80% efficient, that would still give us about 1,440 Watts of power (or for the maths challenged 1.4kW).

This is a new Husqvarna petrol chainsaw which I believe is comparable to my electric in many ways:


First note the difference in price ... $99 for the Ozito and $649 for the Husqvarna ... sure you can get a Ryobi for less (my Ryobi is about $210 right now, but you can bet it won't last you as long as either the Husquvarna or the electric).

Then you'll observe that that Husquvarna rated output is 1.5Kw which is actually quite close to the power output of my electric. I'm willing to bet that the Ryobi is less (as they aren't even willing to publish that).

However the petrol chainsaws power output is likely to fall to lower with a few issues:
  • motor wear over time (as the rings wear)
  • quality of fuel (did you get the premix right?)
  • is the air filter blocking things?
  • did you use ethanol (polluted) fuels, what is the octane?
  • is the fuel filter blocked at all (does it choke or bog down)
While the electric will be about the same over its service life (and came with a spare set of carbon brushes when I bought it (I'm still on the first)).

I've had the little Ozito now for about 6 years. It stays in storage with no fuss. A quick pull down and clean prior to storage is ideal, but compared to the petrol all I have to do is clean the blade (not drain the fuel system). A lazy operator may just put it away, as the bar oil constantly supplied may be enough to protect the bar and chain during storage. I usually spray the chain all with a round of Lanox (or WD40 if you don't have Lanox) ... For occasional use its really hard to knock the electric.

Now one of the reasons my wife wanted an electric chainsaw was that she has been involved in forestry most of her life. She has a Masters Degree in Forestry and her father owns a wood cutting business. So she knew well that while out in the forest you may not have power, but around the home (or the business place) that electricity was far more reliable. She's struggled with starting petrol chainsaws before and knows that you tend to struggle during the starting, and stink of fuel oil after doing a job.

My petrol chainsaw is a Ryobi 42cc one (so similar in some ways to the Husquvarna above). It is a bit temperamental to start and if the fuel filter is blocked (from say, letting the fuel dry out in it while in storage) then all bets are off. If the carburetor is a bit blocked or the plug oiled up then it will be a bitch to start. You may need a can of this handy:



No such problems with the electric. Indeed the only thing negative to say about the electric chainsaw is the obvious thing - it needs electricity.

So if you're cutting down / sawing up stuff in the urban / suburban areas then I reckon that you'll be glad you bought an electric too.

Monday, 4 December 2017

Bitcoin ski jump

Back a while ago (2013) I wanted to put $1000 in to see where it went. But I was unable to actually buy any ..


Then there was the Mt Gox disaster ...

In February 2014, Mt. Gox suspended trading, closed its website and exchange service, and filed for bankruptcy protectionfrom creditors.[6][7] In April 2014, the company began liquidation proceedings.[8]
Mt. Gox announced that approximately 850,000 bitcoins belonging to customers and the company were missing and likely stolen, an amount valued at more than $450 million at the time

So I'd say that if I had been able to buy some, and hadn't had my coins stolen that looking at the latest bubble that I'd grab my cookies and profit take, to enjoy the ride down before the crash which I reckon is due ...


right about now. So lets see how wrong I am

Sunday, 26 November 2017

Camera Related Illness

In a previous post I'd identified a number of Camera  Related Illnesses.

Recent conversations have put me in the position to recognise another;

Gollum Syndrome:

This affliction causes a pathological fear that using the camera exactly as it was designed to be used will cause harm to the camera. In particular people freak out when they have to change lenses (when it is an interchangeable lens camera) or that mounting a lens for which the camera was designed (such as a 300mm lens) will cause the camera to spontaneously break.


TREATMENT: I believe this illness to be untreatable in the context of modern city living, perhaps being conscripted as an army photographer may assist.

DISCUSSION: this illness is exacerbated by (or perhaps dependent upon) being a sheltered city person without the faintest clue. Anyone who actually uses their cameras for nature photography (not visits to the Zoo) quickly discovers "shit happens" (like field changing a lens, or a mild sprinkle of rain) and the camera still works. If the photographer request trauma counselling :- slap them.


Sunday, 12 November 2017

semi abandoned cottage


I was out for a drive the other day (to see what I could see) and found the gorgeous cottage situated in about the most wonderful spot you could imagine. Great views and great location geographically speaking. Right on the edge of the plateau, so moist (unlike further west) and "very changable" atmospheric weather (ok, I mean it rains a lot)


I get the feeling it was built in stages as money arrived and needs expanded (a familiar story) and has some very interesting curved roofing over the veranda ...

From the back it was equally compelling ...


and you can see a hint of the weather I mentioned approaching. You can see (looking carefully if you load that picture up) that the back wall not only seemed to have been an internal wall at some stage, but shows sign of that same curved roof in the top of the wall over by the door.

Inside that window (in the old section) we see a little of the decay of semi-abandonment


... as it apparently still used by someone (I assume stockmen) occasionally.


Looking at the exposed tin roof, with plenty a gap, you can be sure it will be as cold as a "witches tit" in there and a place by the fire prized when the winter winds and drizzle are happening ...

Still, people were poorer then and life was tougher.

Time passes and things pass into history. Its sad to see things pass, but then that is the way of things. It is our privilege simply to witness them...

Thursday, 2 November 2017

I've warned you before...


Hey, you!



I've told you before, if I see you here again I'm going to give you a thrashing



Right!

Now to make it clear, I'm going to shit all over this motorbike so you know who's place this is...

Tuesday, 31 October 2017

Radio labelled

I took the first steps yesterday on the path to determine if I am as yet clear of my 2011 gifted surgical infection.

After two uncomfortable debridment surgeries in 2012 & 2013 and constantly being on oral antibiotics since 2012, we (my specialist and I) decided to begin investigating if there was any bacteria remaining. Our plan is to see if a PET scan shows any metabolic activity that isn't mine.

So I got shot up with radio-labelled glucose and jumped into this...



Naturally I was a bit radio active for a while...


Which was kinda cool.

Will report progress.

Thursday, 26 October 2017

a Quick trip to Mount Perry


a mate of mine was recently up (from here) at Mount Perry, and I thought: "what the hell" I'll go have a look.

I've never been there (although I've been all around it by about 100Km in any direction) and so I thought I'd share some of the experience.

So, after you turn off from the main road (A3) you eventually find yourself looking at dirt ...



with some creek crossings (which may be impassable when wet).

The township of Mt Perry is nestled in a tight valley:


This is from the Western side (looking East, in the late afternoon)

It turns out there is an interesting feature just near the town, a railway tunnel was dug when there as a brief mining boom. It was cut through a hill on the way to Gin Gin, but was never used as a railway. Instead now its a road.


So I took a trip out along there to see ...

There was some nice old country "Australiana" such as abandoned schools (with cows) ...


and some nice scenery.

Eventually I got to the tunnel (which you can drive through)


Here is a quick video of going into the tunnel mouth:

In the entrance there are swallows nesting ...


but further in (in about the middle) is a colony of bent wing bats.

Attempting to focus on this swirling mass of bats was essentially a fools errand, so I took one shot with a normal lens and hoped to freeze something with that.


Which I did ... you'll notice if you load this image some discreet red circles around bats in flight. This is from the middle right, and shows what I believe to be a pair of the "bent wing" bats and I believe too, a clutch of young huddled in the roof.



As mentioned, I recorded them with my audio recorder...so you can put on your headphones and enjoy the walk through the tunnel with me if you like:



I hope you enjoyed the small excursion.

Friday, 20 October 2017

The Cheapie controller is MPPT - not PWM

Well I've had a better chance to fiddle with this now, and I'm quite sure that this little UEIUA CPS-2420 controller is properly an MPPT controller (unlike the views of others)

So here is my evidence for that. PWM will essentially pull the panel voltage down to very close to the battery charging voltage. This is because it can't do voltage to voltage conversion. Given that people normally run a "nominal" 12V panel, which is often open circuit at 21V this is less of an issue than it may seem. Panels usually  have its maximum rated power at a voltage something like 17V ... in the case of my black 100W panel is actually 17.8V (... which is of course at the maximum obtained measuring at Standard Conditions , namely full sunlight but with a panel temperature of 25°C). So the drop from there to 13 or so optimal for charging isn't a significant loss. Such would be a case of a panel at more or less optimal voltage match for the purpose, and PWM just has to groom it a little.

But if you run panels in series not in parallel then things change and PWM is at a disadvantage.




So in the above experiment we see that with two panels in series we are clearly getting MPPT because:

  • circuit voltage of the two series panels was brought to 38.6V
  • the panel was delivering to the MPPT controller 1.5Amps
  • the battery was being held at a charge voltage of 13.5V
  • with an observable 3.56 Amps going into it
were this system a PWM system this would simply not happen.

So the youtube reviews you may watch on this controller make what I believe to be the error of solely determining the capacity of the controller based on a panel which is already closely matched to the usage (battery charging) and measure what it puts out into the battery.

I've already shown (in previous posts) that the system is capable of delivering a few extra amps to the load without taking all that power from the charging. In a previous experiment (with one panel) I was able to deliver 3.5Amps into my load (from the load port) while still pumping 0.56Amps into the battery (3.5 + 0.56 = 4Amps) yet it failed to deliver 4 amps to the battery when simply charging the battery. This leads me to see that it can (and does) produce more amps, but only if the entire system requires it (in its view).

Clearly this new test demonstrates that the controller is able to deliver the full panel capacity to the "system"(given as also observed the panel temperature pulling down its maximum power delivery capacity). 

This word SYSTEM is the critical point. The controller is intended to be a part of a system, not just a stand alone battery charger. As such if we take that viewpoint and explore its capacity as a system we can see that it is delivering the capacity of the panels into the system, and not just pumping it into the battery.

I went and did a second test (because the sun came out as I was writing this) and found the following:
  • two panels in series was loaded by the controller to produce 6.48 Amps @ 20 Volts input into THE SYSTEM.
  • the controller then poked 6 Amps into the battery @ 13.2 Volts (you need to recall that battery at rest unloaded is a different voltage to the battery under charge and the controller has NO WAY to know what the resting state of the battery is until perhaps night)
  • the controller still fed the load with 3.5 Amps @ 12.8 Volts
so if this was PWM we would still only get a maximum Amps of 5.5 (the short circuit amp rating and ignoring panel temperature) yet it was able to feed 6 + 3.5 = 9.5 Amps into the system

Considering that the combination of the two cells was in theory only able to deliver 11amps,  that this controller pulled 9.5Amps to feed to the other two demands on the system is pretty darn good.

Clearly MPPT, not PWM.

If your goal is to shove the most power from your panel into a battery (from which you draw load in parallel to charging) then (as observed) the CPS-2420 MPPT controller is perhaps not your best bet, especially if you have only one panel producing (an open circuit) voltage of around 20V.

For that role I've found the little T20 (which I bought earlier because it was cheap) to be at an advantage there as it puts out a few more amps into the battery (with nothing on its load) than the CPS-2420 does.

Its a nicer looking unit in some ways but perhaps more confusing because it has more options, allows you to configure more and the menu is not straight forward to navigate ... this is them side by side,


With two solar panels in series the T20 it was still only delivering the same amount of amps as with one panel (and pulling the whole rig down to the lowest common denominator voltage) which is what PWM does. Here it is on the two panels (which in series produce the same amps, but double the volts).



as you can see its not able to take advantage of the potential 40V available to it. Because its PWM.

So where does this leave us?


It means to me that the choice of which controller needs to be a decision based on "what are you goals".

In fact I still like this little white controller (even though it lied about being MPPT and is really PWM) because it provides some additional features which I find useful. I mainly use it with a small panel (10W) to keep the battery conditioned on my ride on lawn mower.
I like that I can set it up for myself:
  • battery max voltage (so it won't over charge and will cope with a variety of battery types)
  • battery min voltage (where it will kill the load were I running one, and should it go below a voltage value I set)
  • a display of the current battery voltage (so I don't need to pull out my multimeter to test it)
  • I can leave it alone and know its doing its sole job
Keeping my mower battery trickle topped up (in a good manner and voltage sensitive) is an ideal usage. The mower sits idle in winter and can result in dead battery (from self discharge and sulfation). This controller and a 10W panel prevents that.

Even if you wanted to a run a short term load off your battery then this little controller does well as long as you manage that load yourself.
If you have timed operations in mind then this little controller does that too ... if you want more amps out of it then you'll have to run your panels in parallel (to minimise the losses of voltage, while doubling your amps). Just make sure you've got your diodes set up right with that ...

As I've read elsewhere PWM isn't simply worse than MPPT, it provides things differently and at a lower cost (although at this price point that's moot).

As it happens these two controllers are amazingly low cost and both do things differently, so picking one will be determined by your needs, your setup and your system.

Following are some sections from pages on the web which I have found salient (and their URLs for reference):
From this link

The preceding discussion of PWM vs. MPPT may cause some to wonder why a PWM controller would ever be chosen in favor of an MPPT controller. There are indeed instances where a PWM controller can be a better choice than MPPT and there are factors which will reduce or negate the advantages the MPPT may provide. The most obvious consideration is cost. MPPT controllers tend to cost more than their PWM counterparts. When deciding on a controller, the extra cost of MPPT should be analyzed with respect to the following factors:
1. Low power (specifically low current) charging applications may have equal or better energy harvest with a PWM controller. PWM controllers will operate at a relatively constant harvesting efficiency regardless of the size of the system (all things being equal, efficiency will be the same whether using a 30W array or a 300W array). MPPT regulators commonly have noticeably reduced harvesting efficiencies (relative to their peak efficiency) when used in low power applications. Efficiency curves for MPPT controller are printed in their corresponding manuals and should be reviewed when making a regulator decision.
2. The greatest benefit of an MPPT regulator will be observed in colder climates (Vmp is higher). Conversely, in hotter climates Vmp is reduced. A decrease in Vmp will reduce MPPT harvest relative to PWM. Average ambient temperature at the installation site may be high enough to negate any charging advantages the MPPT has over the PWM. It would not be economical to use MPPT in such a situation. Average temperature at the site should be a factor considered when making a regulator choice.
3. Systems in which array power output is significantly larger than the power draw of the system loads would indicate that the batteries will spend most of their time at full or near full charge. Such a system may not benefit from the increased harvesting capability of an MPPT regulator. When the system batteries are full, excess solar energy goes unused. The harvesting advantage of MPPT may be unnecessary in this situation especially if autonomy is not a factor.

and this link suggests too:
The Solar input nominal voltage must match the battery bank nominal voltage if you’re going to use PWM
So if you do have a single "nominal 20V" panel (which probably puts out its max power point at 17, but amps at 14 will still be close to max), then you are matching the battery to the nominal voltage (especially when its a hot climate like Australia) and so you'll see less advantage to MPPT. Which I think is the other testers issue; I don't think he applied sufficient voltage advantage for MPPT to give its best run.

So know your needs and pick you animal :-)

Lastly

I like to do things in a scientific manner, if you have any issues with my conclusions then proper scientific method would suggest that you examine my methods and identify what I did wrong. Try and replicate the results if you can before just slamming me.

Thursday, 19 October 2017

territory intruder

I've had problems with Wrens being ... well bird brained about things before (here). But now that I'm living more or less in Wren Country its becoming more common.

Sitting at the table this afternoon I was conscious that the Wren "territory calling" sound was becoming a bit more acute ... so I looked out the window and sure enough, this Wren had found another rambunctious intruder ...


It alternatively attacked the other bird and sat calling for the rest of the tribe (Wrens are group birds with one dominant male) to assist with driving this intruder off ...


The regular "shopping bag over the mirror trick" seemed to work ... and I have enough bird guano on the bike to start a company selling it..

Friday, 13 October 2017

Cheapie MPPT Controller further discussed

well we had sunlight worthy of mention today, so I thought I'd extend the testing I did on my cheapie controller and give it a quick whirl with one of my 100 W panels.

Now first up lets say that the panel is specified as:

  • Max Power = 100W
  • Open Circuit V = 21.6
  • Short Circuit A = 5.97
  • and "Rated V" = 17.8 (projecting the MPP?)
  • and "Rated A" = 5.62
which is interesting as it implies (to my limited understanding of Solar Panel Specs) that the maximum power of 100W is at 17.8 @ 5.62 

So I thought I'd wire it up to my system in quick way with the following diagnostics:
  • Volt Meter (Fluke 11)
  • Ammeter (Lexa cheapie in Amps)
  • 150A Watt / Power Analyzer (ebay jobbie)

Knowing that some items can suck more peak power than my MPPT controller may be able to stand and deliver, I thought that I'd wire my load directly to my 120AH battery. So here is that.




and for those who can't quite follow the mumble, the summary position is that less amps were going into the battery than was being sucked out of it. In particular the charger was putting about 1.6A into the battery while the little fridge was sucking out 2.89 A ... a short fall of power.

I wondered why the controller was not putting enough into the batteries to balance the load.

So here are the few more measurements I mumbled about at the end...




So the summary position is that the contoller has no way of knowing what is being drawn from the battery (what load its under) and (I assume) it assumes no load. There are controllers which incorporate this sort of externality with a thing (commonly? occasionally??) called a shunt sensor. This doesn't have one.

So my findings are that with my single 100W panel will give through more power, but interestingly it seems that it (the controller) won't push in (to the battery) much more than 3Amps (not shown in the video, I turned off the fridge giving more available power).

Which could of course be because controller reckons that's as much power as the battery can handle. After all it has no way of knowing what the battery capacity is ... is it 50Ah, or is it 100Ah, or is it ...

None the less with a load (on the load so the controller knows about it) it does take more from the panel. My load (the small fridge) is about 3.5 amps meanwhile the battery is getting 0.57A (in this specific example), which steps up to over 2 amps if I disconnect the load . So,  3.5 + 0.57 = 4.07 amps

Does this mean that the controller isn't MPPT?  Where did that power go?

Well as I identified in my first post (with a small panel into a small battery):

The little embedded system did a great job of ramping up load and determining the system capacity autonomously and heuristically. Best indicator of its effectiveness was that it put 0.67Amps into my battery when the panel is rated (and I've measured it) to 0.55Amps at full short circuit load. This is about a 27% increase in power over PWM.

you only get that sort of step up in amps with Voltage to Voltage conversion ... or MPPT. I believe that the evidence supports that it is (indeed, I demonstrate that it is in subsequent posts (eg this one), some of my other readings made it unambiguously clear that it must be MPPT as not only was it putting more amps into the battery than the panel was producing it was keeping the pair of  panels at 38V ).

Also as I mention in the video the panel got to 69°C which means that we need to re-work the figures (because these things conform to known physics). This is coefficient is about 0.4 per degree variant from standard (of 25C) that the panel temp gets to. In my case its; about 44 degrees above 25 giving about 18% loss or in other words dropping my max A figure to about 4.15A ... or pretty close to what we got.

Where does this leave me?

Well it means that (depending on my fridge) I'm going to need more power input than I currently have or the system will basically just wear the battery down in the evenings which it won't be able to recover in the day time.

So, lets have a look next at what a second panel does for this ...

Wednesday, 4 October 2017

Cheapie MPPT controller (updated)

Well, normally I have the view that you get what you pay for. However often what things cost is a reflection of a complex mix of R&D costs, what the market will bear, profit motive ... A few other things.

Well China is now going very seriously into Solar Energy and it's not surprising that they are making efficient electronic devices to do small scale solar.

So with this in mind I bought a cheapie eBay controller and thought I'd see what it did.



This is it, and unlike ones I've seen reviewed on YouTube, this has two inductors.

It's the model CPS-2420 and it comes adorned with precious little documentation.

So, today I got it, and put it to the test. I attached it to a 12V flooded lead acid car battery and with a DMM (Digital Multi Meter) on it and found that it put my panel to about 17V and pushed 13V into my battery. Rough figures because it was constantly adapting output as the battery took charge and as the light conditions changed.

The little embedded system did a great job of ramping up load and determining the system capacity autonomously and heuristically. Best indicator of its effectiveness was that it put 0.67Amps into my battery when the panel is rated (and I've measured itto 0.55Amps at full short circuit load. This is about a 27% increase in power over PWM.

If you don't know the difference between PWM & MPPT then I suggest you do some reading, alternatively this YouTube link has a great and detailed overivew:


But in a nutshell its a way of getting the most power out of your solar photovoltaic panels and into your storage (battery).


This is the review of another similar model (the CPY version) by Adam Welch, but mine is the CPS version (and 20Amps) and as you can see looks a bit different to his.


So in some ways I prefer mine, and either way its Fukken Amazing for $30

UPDATE

I've  just done a quick test with two multimeters (one for amps, one for volts) and an inline wattage meter (that does both amps and volts) inline with another (bigger) panel...


So, on an overcast time I was getting

0.32Amps @ 12.98V into my battery while the panel was 0.41A 13.88V

now this doesn't take into account the losses in the two meters, which while small won't be nothing. I know for instance that my DMM showing Amps has an resistance (including leads) of about 0.5 Ohm which of course is significant.

Basically its not particularly efficient at very low light conditions.

Saturday, 30 September 2017

(DIY) coffee banger - updated

well, having moved house twice since 2012 when I wrote about my coffee banger last I felt the need for a new one in my new place. As per my last post (here) I still don't see the point in paying $30 for what is essentially a waste holder (holding it before it gets transferred to the bin).

So let me introduce my Mk2 coffee banger:


I was inspired by some connections of roof gutter drainage pipes that were for connecting and angling the pipes.

This is essentially two pieces of 90mm PVC-U, one a 22.5 elbow bend and the other a "cap".



Pressed onto the bottom, the cap makes a good removable base, which is handy because often after a few days the coffee in the bottom of the banger is a bit hard to clean out. This design just allows the bottom to come off with a twist (its a tight seal, nearly, but not watertight), yet the rim on the cap keeps the damp grounds from leaking out.

I used my dremel to cut some (rough) grooves to hold my traditional "stick" in place, with some assistance from a bit of hot melt glue which will no doubt come off easy as the stick (inevitably) needs replacement.


The bend makes an almost ideal angle for striking the banger stick with the coffee handle and the "rim" catches the splashes from small amounts of water left in the handle.

So, in summary, its:

  • durable
  • cheap (less than $5)
  • easy to make
  • easy to clean
win win!

Wednesday, 27 September 2017

Moons, Stars & wind mills

Nothing much to say, but I enjoyed being out taking this shot


Sunday, 17 September 2017

Snapseed and noise (but from where?)

The other evening I was out walking (to watch the ISS go over) and took this image with my Oppo F1 phone (it being the only camera I happened to have with me) while I was out. (Note, blogspot seems to be causing posterisation on the images I load with its recompression of gradients ... Uhgg)


I took it with the phone/cam set to RAW so that I'd be able to play with the image later (cos I already know how much better that can be). I put it into Snapseed (which has become my default phone image processing tool) and applied my basic preferred steps and was disappointed by then noise it had in the image. I wanted it for Facebook so knowing it was going to be scaled back anway (meaning noone would notice) I cropped it a bit and resized it down and loaded it up. So wonding if the processing of HDR Scape was introducing the noise I pulled this image out of the same DNG file and had a look around. Even at this scale the noise is clear..


so lets have a pixel peep ... (cos even scaled back it looks a bit 'rough')


quite noisy ... and applying a little HDR (I've found gentle HDRI to adjust the brightness and at a low filter level cleans up a lot of vignetting) to it only made this worse.


I tried a few tools to remove the noise and was resigned to it being "how it is" at an ISO over 1000 (1229 actually) in low light.

Then it occured to me "I wonder what DCRAW Mobile would render" as I know DCRAW has wavelets for noise control. So while I was unable to see any difference using those parameters, DCRAW did a significantly better job.


without seeming to make the image any softer really (no sharpening applied, but I think Snapseed always does a bit).

So while this makes me feel comfortable that I can push my phones limits that bit more, it also makes me wonder what Snapseed are doing. I suspect that they may be adding noise in their process because (to save space) they may work with lower bit depths. Its well known that adding noise can cover gradient posterisation caused by inadequate bit depth. If you are interested I suggest reading this article over at the University of Chicago (totally worth the read for the technically inclined). The author examines how you can keep apparent tonal range with reduced bit depth (faster to process) as long as you have enough noise to cover it up.

NB: from that page




Given how fast Snapseed processes my DNG files (compared to DCRAW) it makes me wonder if they are not doing something like that. I already know (from asking the developer) that once the conversion from DNG to a demosiaced image occurs they only work in 8 bit ... hmmm ... I for one would be very interested to know why there is so much more noise even without the HDRI filter.

So I have reached out to the developer of DCRAW Mobile to ask if the wavelets are actually doing anything and hopefully they'll comment back here. Perhaps even answer if the slowness of demosaic in DCRAW is exacerbated by lack of threading on phones.

Meanwhile, my final image is this one, which somehow I find not quite punch enough but anyway:



Friday, 15 September 2017

The Kicked Down Sand Castle Effect

Imagine you are a kid down at the beach building an elaborate sand castle. Your family gets there early in the day and in between swims you build this great structure.

You spend hours between swims and a bit of belly boarding adding to this castle.

Then someone (like your mean brother) comes along and kicks it over and you're in tears about it.

Depending when it happens in the day (say early) you may start again and build on that foundation and make a better castle. If it was nearly time to go home you may just give up and walk away, being mad at your brother all the way home (and perhaps for some time to come).

This is how I have come to currently understand my own grief at the loss of my wife.

The metaphor is not too far from the truth because we are all only here on this "beach" for an amount of time. We eventually "go home" and must leave behind all we have made here. Yet when we are building our sand castles we are not thinking of "when we leave" we are absorbed in the the thing we are making, in making it better, in making it "just right". Sometimes we've only seen the sand castles of others, and we shape our own on that. Other times we've also had a little experience in building them in previous summers when we were younger, so we can do a better job.

Although we know that we must eventually leave them, we may harbor the idea that it will be there again tomorrow (sometimes it is). When the time comes to pack up and go home many will plead for a little more time, no matter we always look back at what we made as we are leaving the beach. But if we have it leveled down before our eyes it somehow hurts more, because we are attached to it and because it seems so unfair.

Past the initial shock and spending time in reflection (not just being upset, although there is surely a time for doing only that)  I came to see that without Anita, all that I'd built was smashed and meaningless. I soon also saw that my time on the beach was drawing to a close and there seemed less point in trying to rebuild.

Unlike sand castles much of what we have in life is needed to live comfortably; the houses we live in, the furniture we use, the stuff we have. Much of it is needed to make our lives comfortable, easier and doing things more convenient.

I don't believe I have enough time to ever make a castle again but I'm trying now to make something. Its not easy and I'm always struck with "what's the fucking point" ... I regularly think "fuck, can I just go home early". Of course some do just that.

As I've reflected earlier this happened to me at an awkward time, too old to really ever be able to build a decent sand castle again, too young to just "go home early".

So now I've bought another house, in a different place. There is much that needs doing to it, but its actually livable right now. Its small enough that I don't need to attempt anything grand, but enough work to keep me "on task" for some years.



Many times I feel like its all too hard, and I wonder "what the fuck have I done". But having kicked the can down the road for some 5 years now, I have decided its time to try. Its a total break from where I've been and in some ways like nothing I've ever done before.

Lets see what I make of it.

Wednesday, 13 September 2017

Camping Cooking at Home

I haven't been camping for a while now (just day trips), mostly because of the unsettled life I currently lead (indeed I feel like I'm camping most of the time sometimes). So I thought I'd share some cooking ideas which I essentially adapted from what I make and eat when I go camping.

Camping cooking is (well for those who aren't packaged food types) identified by the following points:

  • easy to make and serve
  • easy to be carried (no need for refrigeration)
  • easy to clean up
  • good nutrition (energy which you need and vitamins too)
Oats features in my cooking a lot actually. Not "instant" oats, but just good stout rolled oats, which look like this in the pan:


For this recipe I basically use a non-stick frypan (to minimise my efforts needed in stirring). 
So one of my favorites: savoury oats


Ingredients: chopped leek, sliced salami, sesame oil, chilli flakes, oats, water.

Method: Fry the chilli and leek in the oil for a bit, toss in the salami. 
Mix a wet slurry of Oates and pour that in. 
Cover and reduce heat / flame to minimum. 5 minutes later whack on the plate, add a little Tabasco sauce if you like ...



For an extra dash of colour add a quick sprinkle of Paprika powder at the frying stage (helps release the aroma of the paprika)

Enjoy

Saturday, 2 September 2017

keeping away the "GrassHoppers"

In my family at least we have a tongue in cheek way to call Kangaroos "grass hoppers", not the least because they hop out of the grass at you.

So motorcycling around up here at the moment the use of a tool for that is intended to make encounters with the little furry lovelies less likely by making them aware of me sooner. They are little ultrasonic "whistles" and look like this.



A quick video



I'll let you know how it goes

Thursday, 31 August 2017

Flogging a Dead Phone (for pixels)

well my Oppo F1 is not exactly dead, but it is in the view that they are no longer sold new by Oppo (perhaps you can get one somewhere).

The reason for this post (which will be of little interest to even less people than usual) is to provide an answer to a question which was asked of me recently:

Which is better: DNG (*and then process the DNG, with say Snapseed) or the Ultra HD mode
So I set about to answer this question...

Firstly lets look at some images, the overview I took, which has plenty of "natural detail" and is at a distance where the blur caused by atmosphere isn't going to effect things (like a mountain range):



I took (essentially) 3 shots the Ultra HD, then a DNG (which then automatically takes a) JPG.

Basically the Ultra HD mode uses some upscaling and combines (as near as I understand it) a number of images and attempts to work out the sharpest portions of each image to:

  1. jam together the best bits to make an over all
  2. upscale it and save it to a JPG

Lets take a look

So lets dive into the pixel peeping now shall we? First lets look at a segment of the OOC (Out Of Camera) JPG and the Ultra HD at the same level of detail (which means that the UHD will be shown at 50% so they are effectively comparable.


To me there are no surprises ... the two images look close, with the usual "over sharpened look" to the OOC JPG. Nothing screams out at us however.

I've never understood the mental masturbation over MegaPixel Madness, and I'm willing to bet that 99% of the images from these phones will end up on Facebook or some other social media and therefore scaled down ... very very few will end up being printed taking advantage of the 4000 pixel width ... but most of the "selfieObsessed" users attracted to the King Wang name will not even understand any of the above anyway ...

The next step is to look at the UHD more closely and compare that to the OOC JPG. To make this easier I did a bicubic upscale in Photoshop of the JPG so we can see clearly:


This makes it pretty clear (to me at least) that the final written JPG just doesn't have the "right stuff" to make an upscale work ... meaning that this is a win to the UHD image. Probably because the image is upscaled prior to the mushy crummy JPG algorithm that Oppo uses is applied to the OOC JPG (meaning its likely it does it in an uncompressed image space, perhaps even RAW).

Ok, so now lets take the DNG (which I've already established to be heaps better than the OOC JPG in so many previous posts it does not bear repeating), Starting with the DNG (processed in Snapseed with not much more than a straight conversion, which is of course then saved as a JPG by Snapseed) and then upscaled in Photoshop to compare to the UHD at 100%



Which is very close, but to me actually gives better tonals in the ridge of the rear wheel arch (the rust and cracked paint more clearly defined). So even upscaled the DNG is competitive to the UHD

As well (as a side benefit) we have the opportunity to do more post processing (without getting posterisation of the sky)  from the DNG than we would from the UHD (because we're dealing with more bits at starter).

For the hell of it I thought I'd downscale the UHD to compare it at 100% with the Snapseed to see if there was something in that:



Which to my eye looks pretty good (although I prefer the colour balance of the DNG over the UHD).

So what's the point and what's the benefit to a photographer? Are there drawbacks?

Advantages , Similarities and Drawbacks

As it happens the DNG is about the same physical size as the UHD shot (even though its a JPG), but the nod goes to the DNG because its actually a little smaller (should you be pushed for space on your phone) at 25Mb vs 26Mb (for the UHD) : advantage DNG

A drawback of each is that you have to remember to engage that mode (either RAW or Ultra HD), however the UHD has the additional drawback that (because it takes multiple images) you have to hold the camera steady longer ... or get a crummy shot. advantage DNG

Because the UHD is a JPG, you can (assuming you want to) just get a big print made directly from it and know that (printing to 140cm monster prints) you'll get a much crisper print than from a regular OOC JPG and won't need to bother with processing software or mussing up your hair : advantage UHD

Myself I'll keep using DNG because I happen to be OK with the use of Snapseed (or other future advances in DNG processing), however I hope this has helped you to work out what you'd like to do and why.

:-)