Solar cell power for small transmitter - battery/cells required? - Page 1
Forum section: electronics / projects

author: niko20
author_rank: Newbie
timestamp: June 02, 2019, 03:04:13 pm
content: Hi all,I built a small Part 15 Am transmitter which reaches about @100ft around my house, which I then loaded up an arduino with a MP3 DFPlayer chip and an sdcard full of Art Bell's greatest shows. I figured I would let Art live on AM around my property "forever" by transmitting his content.The circuit is powered currently with a 12 volt AA battery container (8 AA batteries). I'd like to add solar power to keep it working "indefinitely" but I don't know if I understand everything fully in order to use solar.I found quite a few 12 volt solar cells on Amazon that should provide plenty enough power. I measured current draw and my device draws around 15ma for the transmitter and I am guessing maybe another 10ma max for the MP3 player chip, so total just above a 1/4 watt. Thinking even a 1/2 watt panel would be plenty strong IMO. BUT that depends on any battery/charging situation.I know Solar cells can vary voltage sometimes up to 20 volts or so during the day - my RF circuit isn't really going to be affected much by that, and the arduino can handle up to 20 or so volts, and the MP3 player (DFPlayer) is running off of the 3.3V pin off the arduino (nano). I could throw a 12V reg in there to be safe i guess though.The thing I'm unsure of is, I probably still need a set of batteries in there to keep it running at night and also just to "smooth out" the solar cell voltage I'm assuming. However, if I did put batteries in there still, I'm assuming they have to be rechargeables of some type? Would the solar cell just recharge them on its own or do I have to somehow build a "charge regulator" circuit?It sounds like the idea of adding a solar cell may be quite a bit more complex than I thought. What if I used one of those 5watt solar "cell phone" charger panels such as from Harbor Freight?I searched a bit but didn't find anything yet where a solar cell has a regulator built in.Would something simple like hooking the solar panel to a 13.3 regulation (LM317T or something) then directly to the battery, then having the batteries also in parallel to the circuit, work well enough? Kind of wired up how a car alternator is wired? (Battery directly hooked to circuit, solar cell hooked to + and - on battery through a 13.3v regulation so it's high enough voltage to charge when the suns out). Would the solar cell then be able to charge the batteries? What type of batteries should i use in the battery pack?

author: soldar
author_rank: Super Contributor
timestamp: June 02, 2019, 04:09:38 pm
content: So the circuit woks at 12 V but how much current?If you want it to work when there is no sun shining you will need batteries, obviously.

author: mark03
author_rank: Frequent Contributor
timestamp: June 02, 2019, 04:16:08 pm
content: Why solar? Shouldn't this be using some sort of free zero-point energy? Tech that the government is trying to suppress?

author: soldar
author_rank: Super Contributor
timestamp: June 02, 2019, 04:20:47 pm
content: If it is in or near the house the simplest and cheapest way is to use a mains adapter.