Robs' New Panel

Normally I advise people to wait until the weather warms to build panels.  I was unfortunate enough to be forced into putting Robs' panel together early.  The amorphic panel that I was using to keep his battery topped off over the winter failed to do its job at all.  $100 POS. Fortunately, I had an experimental panel fail, and I was able to recycle its cells for this one.  How's that for thinking ahead.  If I didn't have them already strung together I probably wouldn't have been able to put this together.  It's just too cold to do any serious work with the cells, the temperature difference would have led to some serious breakage.

Anyway, Rob has power now, I don't know yet if his battery is damaged.  I'm in the process of getting some meters in so I can see what's going on, and I still need to get his motors going again.  I'm tired of kicking him around the garden.

New Project - My Plant Sitter

Actually, it's an old project that has been in the works for the last several months.  I call them my plant sitters.  I've always had plants around, but I have also always had problems keeping them watered.  Not just doing the watering, but getting other people to help with the chore has been a nightmare. Nobody can decide what "dry" is.  Some people will water on a schedule, others will water when it's convenient.  My problem is remembering to do it at all.  So a long time ago I decided these plant sitters were a must. You can buy something like this, but they cost $15-$30 and they only monitor the moisture.  Mine can do more.  Even though what you see is a moisture monitor, I actually built and programmed them to be able to water the plant via a pump or electric valve.  When the plant needs water the led and pump come on.  They go off again when the soil is wet.

In this iteration I just mounted everything on the battery case.  I had originally intended to hang the whole mess off the side of the pot.  That would have worked, but I was worried about the chip getting wet.  This version also just has steel pins for the moisture probe.  They will need replaced eventually.  So far though, it's working just fine. I want to add gold plated pins and a strobing led or make this one blink, maybe in the next version.  I soldered everything to a socket and hot glued it all to the battery case.  I programmed an AtTiny85 chip and armed my project.  Then I decided to just stick everything in a jam jar.  That way everything will stay dry and it looks nice too.  It's not a done project, but it is moving past the first prototype stage.  I just have to add the parts to make it do what I want.  I suppose actually, there will be some tweaking to do, but not too much.  Now I just need to go replicate this a few dozen times.

Update: Bevy Bot - a Partial Success?

Well, here we are again and this time I have a partial success - and pictures.

Let's start off with some pics from the rebuild.  Some of you may have never seen a peltier device so here's a picture.  I circled it in pink for you.  It's actually a device that's about 1.5"x1.5" that has 127 couples of dissimilar materials (bismuth and something else).  What those materials are, changes how well the device works.  The cheap versions that you find on the auction sites really are cheap, not just in a financial sense.  In my picture here, you see a commercial grade unit.  It's so much better than the others that I burned up.


Anyway, I installed in a 6 gallon cooler.  It's a misconception that you want to put the "bigger" heatsink outside.  Or is it?  Which would you say is bigger?  The one on the inside is spread out more, but the one that I put on the outside is more dense.  It has more actual aluminum.  So it's not actually bigger in size, but it is bigger in volume.




In the end though, they still weren't enough to get things cold.  So I made them better.  In this iteration I added some copper pipes to the heatsinks and am pumping water through them.  The inside isn't finished yet (none of it is actually "finished").  I'm still waiting on my new pumps, which should be here next week.  I had a pump inside, but it died.

Without the pipes I had fans on the heatsinks, and that didn't work very well at all.  I couldn't cool the hot side enough to do any good.  Now at 1 amp, cooling starts.  This photo was taken at 2.2 amps.  That's ice covering the fins.  They are reading at around 20 degrees Fahrenheit.  I think I could get them colder.  Is that cold enough to cool my bevies?  I'm not sure.  I was able to get water down to 46 degrees Fahrenheit, in an hour, before the pump died, so I think so.  With the fan on I have only been able to get water down to about 50 degrees, it keeps the unit from freezing over, but that's about it.
 

So now what?  I'm still waiting on parts, but I still need to work on distributing the cold on the inside, and then I can start perfecting it.  Because, this whole contraption is going to be a robot, I don't have to worry about carrying this thing around.  That's good, because as it sits right now, it weighs about 100 pounds, bevies included.