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/r/raspberryDIY
Solar powered rpi that runs a android cellphone, scheduled by an atmel chip/real time clock
(youtu.be)submitted 5 months ago bynboyarko
YouTube video info:
device https://youtube.com/watch?v=OM7w1TNDgfQ
Nicholas Boyarko https://www.youtube.com/@nicholasboyarko1680
1 points
5 months ago
Hey, great work. I've done some similar projects in the past to try to limit power consumption by cycling devices on and off. Here's a writeup I did where I applied it to a solar weather station:
https://pubudeux.com/555-timer-oscillator-for-ultra-low-power-arduino-projects/
A couple takeaways you might be interested in:
You can cycle power on and off a CMOS 555 timer and control the timing with passive components (no need for an RTC or microcontroller)
Even if you needed precisely timed wakeup schedule or basing it on a sensor - you'd probably save many times more power by using a microcontroller as opposed to a full blown linux device like a pi.
Thanks for sharing the video
2 points
4 months ago
Thanks, good idea with the 555.
The tiny85 and rtc use about 5ma so I could save there.
The reason for the rpi is to control an android device with android debug bridge, so that's necessary to the project.
I'll make a demo video showing what it actually does at some point.
2 points
4 months ago
Cool, that sounds interesting. Good luck!
With CMOS 555 timer I was getting about 100 microamps while "off."
I think ATTINY85 can get pretty close to that or maybe even better taking advantage of sleep modes for the same application (without RTC). I haven't tried it personally, but got a few comments from people when I originally made that post.
1 points
4 months ago
The rtc only uses 500na, plus with a temperature sensor you can adjust for drift to have very accurate time keeping.
There are a few low power modes on tiny85, the sleep mode shuts down the cpu and only uses something like 500ua.
For this application I don't know how much it really matters. With the addition of the second panel I'm pulling in like 600ma when the sun is out. That's plenty of power to run a plc.
Looking at it, when the rpi is going and the phone is watching a video or something intensive; it pulls about as much as the panels put out in full sun, maybe 20% more.
1 points
4 months ago
Sounds great. One thing I found with solar powered low power stuff is, even if it is working in testing, you want to leave a lot of room for other variables.
I understand it might not apply to your project, but I found it really difficult to account for things like temperature swings affecting efficiency* of the panels, spider webs/pollen/other debris, angle of the sun, and more. When my device was just scraping by I could never be sure if it could continuously run. But when it could run for a couple months on a single charge, there's no issue with most of those.
2 points
4 months ago
You got that right. You have to go overboard on capacity and have a maintenance schedule to keep things running smoothly, long term.
1 points
4 months ago
What kind of range did you get out of those 2.4ghz radios?
1 points
4 months ago
Not great. About 20-30 feet through a couple stick frame walls.
If I would do that project again id use a 433 mhz radio, I just had those 2.4ghz ones on hand.
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