How best to create a low power usage solar powered micro transceiver unit - Page 1
Forum section: electronics / general

author: philbx1
author_rank: Regular Contributor
timestamp: June 03, 2011, 10:09:30 am
content: Hi all.First off, just thinking aloud here.Just some thoughts on how I'd implement a low power consumption (and low cost)remote solar powered station with a long-range 433Mhz transceiver.There may be many ways to do this, and I thought it might be fun to get some ideas from you all.OK, first we have some 'standard' components, and some unknown options.The MCU (client) will need to send back a 'heartbeat' signal via wireless every 5 minutes.If the remote station is in 'operational' mode it will need to send back info every 1 minute to the 'host'.The remote unit may be switched back to 'heartbeat' mode by the controlling (host) station at any time.1. To keep things simple, the MCU will be an Arduino board. There are other boards out there which may be better at power consumption, but for now we'll settle on a 'standard' - I don't use Arduino's BTW,but do know people who use these (at a higher - maybe not so much smarter level)...2. Scrap the onboard regulator circuit as it uses too much power (even in sleep mode).2b. Create a low power (LDO) regulator circuit for the Arduino board at 5vDC.2c. Use an existing power management IC (more info to be obtained on this yet).3. The solar panel will need a charge controller for a battery. Let's say a 12v 10w panel or now,and a 12v 12aH SLA battery.4. If the solar panel can't sufficiently charge the battery (ie. drops below 11 volts), then the unit needs to shut down completely via a latching relay (maybe a blinking LED to indicate though).5. The MCU goes into sleep mode for maybe 10 seconds, then checks status.Now, we have possibly 2 relays (or FETs) used in this.6a. Relay #1 controls the power to the whole unit. This would probably be a latching type relay so that once power is removed from the circuit only manual recharging and user intervention would be involved.6b. Relay (or FET) #2 powers the transceiver only when required.So, most of my ideas involve power management.Only one question I can think of initially..Is there a 'monolithic' chip which would handle MOST of this, or is it better to DIY?Any other ideas are much appreciated, and as I mentioned, this is just me thinking aloud..

author: Trigger
author_rank: Regular Contributor
timestamp: June 03, 2011, 12:09:52 pm
content: Quote from: hissyfet on June 03, 2011, 10:09:30 amWhat type of data are you trying to send back?If you have an Uno then the chip is an Atmel Mega328P which is picopower capable. You can use a high efficiency buck regulator to cut down on power usage and if you take advantage of the picopower capabilities you can cut down power usage quite a bit as well.You can put some supercaps on the board and shut off the regulator when power starts getting low. If you sleep it aggressively some decent caps will power the MCU for quite a while. When the caps drop below the brownout threshold then the signal shutting off the regulator is gone and the caps are recharged. You can shut the regulator back off when the caps hit their target voltage.A video demonstrating cutting power usage with picopower