AI Society 5 – Hardware Redux

Since beginning this project I have been trying to learn as much about electronics as possible, with this increase in knowledge I have come to realise a few things about the hardware choices I made in post 2 of this series.

All the power! Maybe?

The power solution seemed to good to be true, three 9800mAh batteries helping the ESP32 to last almost half a month? Outstanding! Except it isn’t. It appears to be a common scam, the manufacturers or even the resellers label the batteries with some lovely big numbers that just aren’t possible currently, with current battery chemistry the highest capacity you can get from 18650 batteries is 3300mAh. Looking back on it, it should have been obvious considering the size of the batteries compared to the size of phones and the difference in those capacities. Oh well, you live and learn, at least they didn’t cost much. You might be curious as to how much capacity they do actually have. Here is a video by GreatScott! that gives a great breakdown and demonstration. Having used these batteries in a few different things I would hazard a guess that mine most likely have less capacity than his.

What is the solution? I could buy legitimate batteries, which at most go to roughly 3300mAh, but I am planning to use mains or USB power for now. Yes that’s correct, I’m dropping solar power too. For now anyway. I want to keep the form factor of the nodes small, the panel I would need to provide sufficient power would take up too much space.

Finally, two critical components that I failed to realise I needed at the time, a balance charger and an SD card module for data storage. The balance charger is a little circuit that makes sure the cells (in this case each 18650 battery would be a cell), are balanced in terms of voltage. This is the one I bought to use for other projects.

Hardware Redux

Lets have a look at the original “shopping list” I put together. I’ve put a strike through the unnecessary components and added non essential ones with “(Optional)”.

So you don’t have to go back and look, the previous totals were £13.07 and £15.42, the separation of price was due to the price difference in solar panel size.

I could use three 3000mAh batteries to power some of the nodes, but it may well be cheaper and a better use of time to buy a prebuilt USB battery pack. Using three legitimate batteries would give me roughly 9000mAh, with an average draw of 75mA that would allow the node to run for roughly 120 hours, about a week. Not at all terrible and definitely something I may look at implementing in the future.

I am slightly weary of the AC to DC converter, the combination of fairly high voltage and cheap Chinese components does not instill large amounts of faith in the quality of safety of its implementation. However, I will be testing the converter before implementing it into the circuit.The idea behind its use is not so I can simply plug a node into the wall, but rather to allow me to “hide” the node inside of wall powered devices, such as a lamp or kettle.

There we have it, the new hardware list. I am certain going forward I will need to revise this again but for the prototype nodes this should be fine.