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5V linear regulator with L4940V5

May 17, 2021 — BarryK

I built a little 5V linear regulator for a "5W" solar panel in 2016:

Fast forward to 2021, and I am building another, using a low-dropout linear regulator with higher current rating, 1.5A compared to 1.0A previously. This new regulator is the ST-Microelectronics L4940V5, that I posted about recently:

I used the same circuit as in 2016, with 0.47 microfarad and 22 microfarad capacitors on input and output.

This time though, I have placed the USB Type-A female socket inside the toothbrush-head holder, and twin wires coming out to directly solder onto the solar panel. This is to reduce weight.

I constructed it in the same manner as in 2016, just soldering wires together, no circuit-board, and construction was well underway when I realised that the USB socket is not sufficiently anchored.

Considerable force is required to insert and remove a USB male plug. I fixed it by firstly shaping a small piece of plastic that the USB socket can grip onto. This is to prevent the socket from being pulled out of the housing when the plug is extracted:


Another problem is that is is very fiddly soldering the wires directly together, without a circuit board substrate, particularly the pins of the USB socket.

The other thing I did to hold the USB socket in place, and also to anchor the twin flex, was to inject some potting adhesive into the bottom of the housing, after it was closed up. I used K-705, which is clear adhesive:


The clear one is quite runny, and stays runny for an hour or so after pouring. It doesn't skin quickly like silicone sealant that we buy in hardware stores. Has to be left overnight.

From the photo, it looks like the black and white ones are less runny. Interesting.

Anyway, next day it was ready for testing. It doesn't look pretty with the holes I burnt into it with a soldering iron, but it functions, and the USB socket stays in place:


Weight is 14g. It would probably have turned out lighter if I had used a piece of veroboard. Like this one from Altronics, could just cut a tiny piece off it:

...hmmm, will do it that way next time.

The test was conducted yesterday, and we are mid-winter here. Sky was cloudy, but was thinning out briefly, and I took readings as quickly as possible. The panel is the CLAITE "10W", and plugged into a small lithium battery bank, via a voltage & current monitor.

The sunlight kept changing, but averaging, managed to get a reasonable reading. Got a 0.2V drop, from input to output, 4.5V into the battery bank, at 0.5A.

What that means, is the regulator is dissipating 0.1W (watts) as heat. It feels slightly warm to the finger, after running for several minutes.

The power coming from the panel is 4.7V times 0.5A, which is 2.35W.

That means the regulator is running at a percentage loss of (0.1 / 2.35) * 100, which is 4.2%. That means the regulator is running at 95.8% efficiency, which rivals the switching regulators.

Another thing I mentioned in a previous post, if you are hiking and carrying this on your backpack, near your head, the linear regulator will not be radiating RF (Radio Frequency) waves into your head.  

Tags: light

TH1P tent design using SolveSpace

May 13, 2021 — BarryK

The first post about the new project, "TreeHugger 1P" tent, was about short carbon-fibre poles:

Now, I have used SolveSpace to create 2-dimensional and 3-dimensional views. I must preface this post by stating that this is very exploratory, and I do not know if this design will become an actual physical tent. I know nothing about tent design, and can barely use a sewing machine, so it will be "venturing into unexplored territory" if I do actually have a go at sewing it.

Here are the SolveSpace files. This is using SolveSpace version 3.0. Some OS distributions only package 2.x, and these files cannot be opened in 2.x. EasyOS 2.7.3 has 3.0. Here they are, gzipped. You will have to un-gzip them:



Another thing that I want to state up-front: if, in the unlikely event that someone sees something in this design that they think is patentable, I claim that every aspect of this design, and features of this design that I will reveal in later blog posts, is free, open-source, public-domain, no restrictions whatsoever in copying, modifying, or using.

I have made this statement because in some countries, the USA in particular, just about anything can be patented. The original concept of patents was to protect new inventions, however, that (in my opinion) got corrupted, and now even just the tiniest twist of an existing concept, the most trivial idea, can be patented. This is a massive money-earner for some companies, such as Microsoft. Anyway, onward ho...

Here is the first SolveSpace file, 2-d views:


And now I can reveal why I have named it "tree hugger". The head-end can be tied directly against a tree trunk, as the head-end has a vertical wall.

Yes, it could be away from a tree, with cord to tie the head-end to a branch, or it could sit on a trekking-pole or any other pole, with cord to a stake in the ground.

However, I love the idea of being tied right against a tree trunk. I have previously posted about how to sit comfortably inside a tent, with various ideas such as sitting cross-legged with bracing to hold the lumbar-region of the spine erect.
A tree trunk gives you an instant backrest! Inside the tent, lean back against the tree, maybe with something rolled-up to support the lumbar region, and hey, comfy!

I have posted previously about the difficulty I have with crawling in and out of a tent. One issue I have is a degenerated lower-back vertebrae. The TH1P design has side-entry that has step-in and step-out. You can see the label "flap", that is the outer fly. It can unhook from the corner stake and fold back over the ridge-line, exposing a zippered entry to the inner tent.

The angle of the zippered entry is such that you can just step-in and step-out.

In summary so far, the design has these great features:

  1. Spreader-bar at the top for head-space.
  2. Vertical wall at head-end to lean against a tree trunk.
  3. Fold-back fly and inner mesh zipper opening angled for step-in and step-out.

The other side of the fly can also unhook and fold back, if extra ventilation is required.

The 3-d view shows that there are two ridge-lines, and I have highlighted the surface formed by these in yellow:


However, to improve water runoff, I plan to join the two ridgelines into one, about halfway down. This is incredibly complicated to calculate, how to cut the fabric. This is where the "dressmaker's dummy" that I constructed should come in handy.

One thing that I am uncertain about is sag. The ridgelines will sag, no matter how tight the cords at each end are pulled. I don't know whether to try and compensate for this when cutting the cloth. Once again, erecting it on the dummy frame should be helpful.

The above 3-d drawing also shows one side of the inner mesh tent.

The length of the inner mesh tent in the above drawings is 180cm, which I intend to increase a little bit. I am 177cm, about 5 feet 10 inches, but I think a bit more length is needed. The foot-end of the sleeping bag will extend a bit beyond my body-length. Though, I do usually sleep on my side, slightly curled. I think will add another 5cm (2 inches).

There are some more details, that are not apparent from these simple drawings. These details are in my head, and will be explained later.   

Tags: light

Miniwell water filter kit

May 12, 2021 — BarryK

I am continuing to iterate through the gear that will go into the Daylight Lumbar Pack, aiming to reduce the total weight from 4.5kg to 3.5kg. Earlier this year, I reconsidered the base load, without shelter and sleeping gear:

The water filter kit had a Sawyer Mini, a flat bottle, tube and syringe. I reckoned that the syringe could be left home, so the weight was 82g:


There are two serious problems with that kit...

Firstly, I have discussed in previous blogs about the bottle wanting to stay flat and being a pain to fill from a pond surface.

I found a foldable TPU bottle that has a natural tendency to stay open, and can be filled from a pond surface in a few seconds. So I am now using this one instead of the Sawyer bottle, and it even weighs less -- I am using a lid from a soft drink bottle and total weight of bottle is now 21g. This is what I purchased, 500ml dark green (so as to distinguish from my clean-water TPU bottles, that are all light blue):

Secondly, The Sawyer Mini is very restricted in how it can be used, by not having threads on both ends. So, it has been retired, and I am now using a Miniwell filter:

This has a 28mm thread on both ends, opening up lots of extra possible configurations. You could, for example, squeeze directly from one TPU bottle into another. As the clean-water bottle can be rolled up and most air expelled, there is no problem with screwing it onto the outlet of the Miniwell filter and filling it with filtered water.

Here is a photo of my new kit:


For minimalist hiking, only the filter and bottle are required. Weights:

Miniwell filter
TPU bottle

The "dirty" water bottle also has another use, with the bidet. If you haven't been following my blog posts, here is one about a portable bidet:

However, those other parts in the above photo are very useful. One problem with filtering water is that it takes time. If you arrive at a campsite, or anywhere where there is a water supply, it could take some time to fill up the filtered-water bottles.

Of course, a way around that is to just put the "dirty" water into all the bottles, and always drink through the filter. But for now, I won't go that way.

What is really nice is to have a plastic bag filled with water and let gravity do the job of filtering. That way, you can be doing other things, setting up tent or whatever, while the filtering happens. Here is a photo showing those other parts in action:


...that little white thing is a hose clamp. Bottom-left, using a plastic single-use shopping bag, they weigh virtually nothing.

You see the guy drinking from it, but a rolled-up TPU bottle could be screwed-on and left to fill, while you are off doing other things.

Here are the weights:

Silicone tube
Hose clamp

The grand total then becomes 105g. I do not want to be going up in weight, though these extra items are very useful.

The silcone tube is very heavy. Measuring with my measuring tape, ID (inside diameter) is 5.5mm, and OD is 8.5mm. Quite thick walls. I could replace with thinner tube, and reckon knock the weight right down, to under 10g.

That clamp is not really needed, only have to crimp the tube to stop water flow, could do that with an elastic band. So could end up with a total weight around 84g, almost same as before. But much more versatile.

Note, that tube is required for gravity filtering, as there has to be a certain head of water to get enough pressure.

Oh, one more point about the Miniwell kit: a syringe is not required for back-flushing. Any old flexible plastic bottle with 28mm thread will do. Fill it with clean water, even tap water when you reach civilization, screw onto the filter outlet-end, and press very firmly. Another advantage with having threads both ends!

EDIT 2021-05-24:
I have purchased silicone tube with 5mm ID (inside diameter) and 6mm OD (outside diameter), so the wall thickness is only 0.5mm. Very thin, so kinks easily, but it works. Although only 5mm ID, it still fits onto the Miniwell filter and to the gravity-bag adapter. The silicone tube supplied with the Miniwell kit is 60.5cm long. I purchased 100cm of this thin tube, and will use the entire length for gravity-feed, as the more water-head the better.

The new tube, 1 metre, weighs just 13g. Bought from here:  

Tags: light

Poles for TreeHugger 1P tent

May 11, 2021 — BarryK

I have come up with a design for a tent, and tentatively given it the name "TreeHugger 1P". The "tree hugger" name will become apparent as the construction progresses. The "1P" means one person.

If you look back through my blog posts, under category "light", you will see some tents/tarps that I purchased that are held up by a pole. A single-pole tent may use either a trekking-pole or a carbon fibre pole -- I have a couple of the latter.

With a single pole holding it up, the inside walls and floor are going to be a triangle shape. At the top will be a ridge, and if you sit up inside the tent, the tent walls will be pressing both sides of your head.

My Six Moons carbon fibre pole is 117cm long, so if that is holding up the outer skin, the fly, of the tent, then the inner mesh tent will be lower. Not a good experience if you want to sit up.

Here is a photo of the inner mesh tent, single-pole design (not counting the short foot-pole), taken on a hike earlier this year:

img0 can see the very constricted head room! The experience is worse than might be determined from looking at the photo.

Blog post about that hike, February 2021, experimenting with my Daylight lumbar pack:

Tents that have two trekking poles have much more head room, for example the Dan Durston X-Mid, that I posted about recently:

My TreeHugger is planned to stay with the single-pole design, except I will design it to tie up to a branch rather than sit on a pole. Though, I will make it optional, the 117cm carbon-fibre pole or tie to a branch.

So, I am going to have that problem of very squashed head-room. To alleviate this, the tent is going to have a "spreader", a 25cm long carbon fibre pole, held horizontally just above the head. I purchased these poles, 24.8cm long, 6cm OD, 4cm ID glossy:

...however, looked online today, and that item is no longer sold. That is, I have them, purchased before they were withdrawn. If anyone wants to reproduce my tent design, there are other vendors, but they sell in 50cm lengths, for example:

I don't know what this stuff is like to cut, presume that a hacksaw would do it.

As the tent is going to be draped over the horizontal spreader-pole, I also purchased plastic end caps, to help protect from tearing the tent, 6mm black:

The weight of each 24.8cm pole is 5.5g, with the end caps, 6g. I plan to use two of these, one as a head-spreader, the other at the foot-end. At the foot-end, the pole will be vertical. Total weight added to tent: 12g. Having to count these grams very carefully, as one major goal is extreme light weight -- targeting putting this tent into my Mountainsmith Daylight lumbar pack. Photo with end caps attached:


And that is also why I wanted poles no longer than 25cm. The tent will roll up and fit into a stuff sack and lie flat inside the lumbar pack. same for any backpack, it will be short enough to lay horizontal.  

TreeHugger 1P, "th1p" for short, is a new project, and I plan to post as each step is completed. My sewing skills are minimal, but, we shall see. Also, having no prior tent-design experience, there is an element of uncertainty how the ideas in my head will turn out in the final product. How does that saying go? "...where angels fear to tread".

EDIT 2021-05-12:
I also purchased alternative end-caps. These are silicone, 5.7mm ID (inside diameter), black:

They are more substantial, likely to stand up better to usage. Photo, showing the other type alongside:


These silicone end caps are probably the better choice for the vertical foot pole. Hmmm, probably for both poles. 

EDIT 2021-05-18:
Found a vendor on Aliexpress that sells the carbon fibre tube in 25cm lengths:   

Tags: light

Glueing silnylon fabric versus sewing

May 08, 2021 — BarryK

I am planning to sew my own tent, and have purchased some very thin silnylon fabric for that purpose:

...yep, all the way from Slovenia, as couldn't source it in Australia. Remarkably, it only took a week, shipped by DHL.

This is 10D (denier) fabric, very thin, and coated both sides with silicone so also very slippery. Extremely difficult to sew, so when I watched this video on glueing silnylon, was most intrigued:

A snaphot from that video, showing trying to pull the glued pieces apart:


...he was unable to pull the two pieces apart.

In previous work with constructing solar water distillers, I determined that silicone sealant bonds very strongly to existing silicone sealant, so it looks promising bonding two silicone-coated fabrics together. This I had to try!

I also have a piece of ripstop nylon from Spotlight:

...doesn't say that it is coated with anything, so presume not.

The silicone adhesive that the author of that video used, is expensive, but in the comments there is another one mentioned, that is, a flowable silicone sealant, Permatex Windshield and Glass sealant 81730, which is available locally, from Repco. So bought a 42g tube of that.

Experimented with both fabrics, silnylon to silnylon, and silnylon to ripstop, left 24 hours, then did the pulling test. Here is a photo of the ripstop glued to the silnylon:


Yes, a very strong bond. HOWEVER, if I grab the two pieces separately, at the ends, then they can be very easily pulled apart.

What this means is that the strength is longitudinal only. Would "longitudinal" be the correct word? Anyway, if there is any weakness at the join, a tear can start and will rapidly spread.

I found that the ripstop teared off more easily.

I then repeated the experiment with Selleys acetic-cure 401 RTV silicone sealant, this stuff:

Did not thin it, just spread it fairly thinly, left for 24 hours.

Same thing, it tears apart quite easily. However, the silnylon to silnylon is a noticeably stronger bond (compared to the Permatex sealant), almost to the point where I might trust it to construct a tarp. But still, once a tear starts, the tent will fall apart in strong wind.

There is one area where I think glueing is a good idea, at tie-out reinforcements, as this guy does:

...the glueing could be done carefully so that there is no weak point where a tear could start.

So, conclusion is that I will still sew the tent, but consider glueing tie-outs.  

Tags: light

Test SLAR 5W 5V solar panel

May 07, 2021 — BarryK

Continuing the saga of testing these little photovoltaic solar panels, here is the previous test:

I came across one on Aliexpress that is sold with or without the USB 5V regulator, so I bought the one without:


It has a slightly thicker substrate than previous ones tested, so is more rigid. Weight is 90g. Brand name is "SLAR".

Today is Friday, May 7, 2021, and I setup the panel outside at 10.00am. Measured solar intensity at 810W/m2, ambient temperature 22 degC, blue sky, no clouds, slight breeze.

Got the measurements started at 10.15am, finished at 10.20am. Then again measured solar intensity, 820W/m2. The cell temperature, IR detector held about 50mm from surface, 46.5 degC.

Here is the plot:


The peak power point is about 4.8V @ 0.7A, which is 3.36W. Well well, this vendor is being honest, in contrast with other recent purchases. This is mid-morning on a winter day, sun low in the sky, so expect more power at midday, and in the summer.

That voltage-current curve has a very sharp knee, then rapid drop-off. This would indicate high quality cells.  

Tags: light

Bottle cap glued to portable bidet

April 29, 2021 — BarryK

I have posted about a "portable bidet" to use when hiking:


It works, however there was one incident. Too enthusiastically squeezing the bottle, the bidet popped off and fell into the toilet bowl.

Someone did ask on the Aussie hiking forum, why can't you buy these with screw-on threads?

Interesting question. I followed that one up, and purchased three different bidets that come with small squeeze bottles. These all have screw-on caps. They work OK, however for hiking I want the cap size to be "28mm diameter", for compatibility with Coca Cola and many other soft plastic bottles available in shops. Those three all had larger diameter caps.

So, solution is to glue a cap on, which I did today:


...problem solved!

That cap is from one of these "BONLOX" folding TPU bottles:


These have a 28mm screw thread, and it is pretty much the same thread as on a Coca Cola bottle, and the thread also screws OK onto the Sawyer Mini water filter.

There are a lot of these foldable TPU bottles for sale on eBay and Aliexpress, and if you are wanting to buy one, do not buy the "AONIJIE" brand -- these are 28mm but the thread is weird and the Sawyer Mini will not screw onto it. I also have another brand of water filter that will also not screw onto it.

I have tested "BONLOX" and "LIXADA" TPU folding bottles, their threads are OK.

Now for usage...

My new portable bidet can be screwed onto any (?) soft-drink bottle, including these TPU folding ones. However, I found that the 500ml TPU bottle is a bit too floppy. So have ordered the 250ml size, see if that feels better when held upside down in one hand.

Practically, a small plastic Coke bottle is good. With the TPU bottle, water starts coming out as soon as you upend the bottle -- which you could get used to I think.

These TPU bottles are great for hiking, as they are extremely light weight and fold up very small. That "BONLOX" 500ml only weighs 19g without the cap, and the cap is 13g.

So I could just use the 250ml TPU bottle for use with the bidet, sans cap. Hardly adds any weight to the backpack. Could put a Coke bottle cap on it, so as to keep the air out when rolled up -- those Coke caps weigh less than 1gm.

One technical detail: I used "plastic glue" from Bunnings. There are a couple of different brands. They are a super-glue with a separate primer stick. They will glue any types of plastic together. And being a super-glue, it grips immediately, so you have to get the position exactly right the first time -- as I found when tried to slide it slightly and it wouldn't -- but still turned out OK.

So it is looking like the hiking kit will have this new portable bidet, and probably the 250ml TPU bottle (sans cap).  

Tags: light

The best double-wall trekking pole tent

April 26, 2021 — BarryK

The title is really a question rather than a statement. for those who hike with trekking poles, this tent, two poles required, is looking like the best of the best:


It is the Durston X-Mid, in 1P and 2P versions. Dan Durstan is a young fellow, who reconsidered the design of trekking pole tents from first principles, and came up with this design.

I first got interested in it from this thread in one of the Australian hiking forums (and Dan has also posted to this thread):

I don't know where it is manufactured, I would guess China, from the fairly low price. Dan gets a new lot in, and they are all sold just about straight away.

What really intrigues me is, having put up many tents with a gazillion stakes and guy lines, the ease of erection of the X-Mid. See video:

It is a rectangle, only requires four stakes, then you insert the two poles. Layout of the 1P:


A lesson here, a clever young person can still come up with something new and innovative.

Negative points? Well, it does require a larger flat area than most other trekking pole tents. And I don't hike with trekking poles!   

Tags: light