A project and a request for help - Page 1
Forum section: electronics / projects

author: msknight
author_rank: Regular Contributor
timestamp: January 16, 2025, 07:28:56 pm
content: Hi All, I'm working on a project and I'm at the last stage.The premise was simple. I put the washing out and then I come indoors and get engrossed in something. It starts raining and I don't know about it.I'm using Home Assistant and I bought a zigbee one hung low rain detector. The detector itself works well and I've got all the automations for Home Assistant to scream at me over the speakers, to get the washing in pronto... but the solar panel isn't worth crap and the rain detector has a distance that's not worth talking about.I converted the innards to an ESP32 board, shoehorned it in the original case with a charger and better battery (I don't have a 3d printer so I have to make do) and tuned the heck out of it for deep sleep ... but the remaining part is finding a solar panel that will give it enough strength on our grey British days to give it enough charge to last the next day. Easy enough in summer, but winter is going to be a challenge.Here is the project so far, with all the twists and turns -https://msknight.com/technilife/?p=2985The one remaining problem is sourcing a solar panel for outdoors with enough power to do the job. The ones I've bought so far, even on the now-disreputable site called Amazon... are coming in with one hung low crappy figures. After this evenings testing of a so-called 10w panel to find it's only 3w, I've wasted so much time and money on this rubbish, that I'm asking here... I need to source a panel which will generate 5v to feed the charger, at enough wattage to charge it on a grey day, which is ready to be mounted outdoors (I can't make cases) and preferably ready to be screwed to a fence at a 45 degree angle.Grateful for advice please.EDIT - The figures are in the project notes, but I thought I'd better summarise the figures here. The project is using a 1,000mAh battery to power an ESP32 C3 Zero. It can keep the power running for 40 hours. I need a solar panel to power a LiIon charger enough to charge that battery at least 50-60% on a grey winters day. - The actual run time will be longer than this because timers and automations will put the C3 into deep sleep for at least 12 hours in any 24.

author: DaJMasta
author_rank: Super Contributor
timestamp: January 16, 2025, 08:32:54 pm
content: It may be just that you need to dramatically oversize your solar panel because output drops so significantly in direct sun. It's also important to keep any portion of the panel from being shadowed, since even a small shadow will negatively effect the performance of the whole cell. Could also be related to temperature effects on your battery (less effective capacity when cold, harder to charge when cold.)Have you measured the current draw of your circuit? It could be that there are hardware (regulator, operating frequency, indicators, etc.) or software optimizations (less frequent communication, utilizing sleep states even in daytime operation) that could save some power draw and get your margins healthier even on overcast days.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 16, 2025, 08:42:11 pm
content: One approach would be to sample every few minutes, say anything between 1 and 5 minutes, and transmit only if raining. That will cut battery use dramatically. It will only need to transmit once in most cases.Another approach is a sound detector or rain detector in the house (attic) and plug it into a wall socket.

author: msknight
author_rank: Regular Contributor
timestamp: January 16, 2025, 08:45:01 pm
content: The current draw of the circuit during operation is lower than my USB ammeter can measure. 10mA thereabouts, occasional spike a little longer than this during transmission. I've got no way to measure it when it's in deep sleep... or correction ... I've got the tools, but no knowledge on how to use them.When it's running, it reads the rain sensor every 15 seconds and returns a value to HA every 2 minutes. If it notices a sudden spike from the rain sensor, then it doesn't wait and transmits immediately.The program is set to take its time from Home Assistant and it will go to deep sleep at 5pm and wake at 8am. It also presents a button to HA, where an automation says, "If there isn't any washing out by 1pm, then put it into deep sleep" ... so on days when there is no washing out, it is active for 5 hours, and on days where there is washing out, it's running for 9 hours... other than that... it's in deep sleep.