[Tech1] Technology is not so mysterious after all

[Bernard Newnham]

My "Technology is not so mysterious after all"  project this year has 
been the continuing story of "How to weigh a beehive using modern 
technology".

My neighbour David likes to weigh his beehives regularly, and then not 
bore us at all (at all!) with lots of graphs.  He uses a spring balance 
and some kind of tilting routine.  He has a physics PhD, so I asked why 
he didn't do it in some electronic fashion. This has taken me on a trip 
into modern electronics, a whole new world. There are few individual 
components, and they aren't familiar. How about an HT7333-A TO92 250mA 
LDO? (ebay £3.99 for ten). They are to keep your 3.3v at 3.3v, I learned 
along the way.

First - how do you weigh things?  You need load cells, and an 
amplifier.  The cells have a bendy piece of metal attached to a 
resistor. Bend them and the resistance changes, the amplifier amplifies 
the tiny result.  £6.88 the set on ebay.

Initially I connected  the amplifier to a Raspberry Pi, because I had 
one.  Result - I could see changes. But a Raspberry Pi isn't suited to 
being under a beehive down the garden, so I moved to an Arduino Nano. 
I'd used them before on another project (£3.70 on ebay).  It worked a 
treat, I even connected up a tiny OLED display to show the results (ebay 
£3.80)  .  A friend has a 00 gauge railway, so I made the OLED/Nano 
sequence train times as they do on stations because it's the ideal size. 
I was rejected for being in the wrong time period. I did learn about I2C 
though, useful later.

Of course, this thing has to sit under a beehive down the garden, so 
there are actually a number of disparate problems still to solve. First 
the load cells needed to be mounted so they could freely bend.  Chris 
Woolf and his 3D printer kindly solved this bit with some purpose 
designed plastic mounts.  Then the completed cells need a frame, two 
identical frames in fact, locked together with the cells between them. A 
company called Metals4U sold me 8x1m lengths of rectangular steel tubing 
- the most expensive single part at around £25. Strange that very 
complex electronics is so much cheaper than basic metal.

I have a mig welder that I've used very rarely. The good thing about 
welding is that you can be really rubbish at doing it and still manage 
to glue things together.  I made one error that I had to angle grind 
apart, but when I had redone it and ground down the weld, it's almost 
invisible. Result - two beehive size frames with cross bars for mounting 
electronics boxes.

So waterproof NoMoreNails  and a few cable ties, and the unit is 
together - but two more big hurdles to jump.   I can't run a cable from 
down the garden, so not only do I have to find a source of power, but a 
way of sending the info. I had to move on from the Arduino to an ESP8266 
NodeMcu . No, I hadn't heard of it either, but it's a microcontroller 
with wifi. You program it with the Arduino IDE system. On the kitchen 
table I set it all up, and after a few days and some cursing it connects 
to my wifi and sends readings to tech-ops.co.uk where it's processed 
with a touch of PHP onto a web page.  The test page is 
http://www.tech-ops.co.uk/hives/result3.php which is ongoing.

And now it needs powering. Solar is the obvious thing, so I bought solar 
panels - £11.99 on ebay. And a controller and a LiPo battery, plus boxes 
and battery holder. Plastic boxes are more expensive than complex 
electronics, too. The controller was a bit obscure. Based on a MCP73871 
chip (me neither), the module came without instructions, nor are there 
any online, just descriptions of what it could do if only you knew how. 
I hunted, but gave in and just connected the various wires in the 
labelled places.  When the sun shines there are lights that flash . What 
they actually mean I don't know, but the battery charges and the 
weighing machine weighs.

So, the other week, it was basically ready to be tested outside. Then I 
got a bit ambitious. For £2.09 you can buy a tiny BMP280 module that 
transmits temperature and pressure. I connected one up, and the ESP8266 
NodeMcu overheated and died. I think it was maybe coincidence, but I've 
bought two replacements just in case (ebay £9.48).

Tomorrow, solder sucking with help from Pauline to remove the broken 
part, then a refit, and the project continues. I need to complete it 
whilst the hive is small and the bees are inside. So a cold day in 
January to fit the thing, and then we shall see.

And all because this time last year i said to David "Why can't you do 
that electronically?"

B
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://tech-ops.co.uk/pipermail/tech1_tech-ops.co.uk/attachments/20201230/976a901e/attachment.html>