solar power supply + backup power - Electronic Circuits Projects Diagrams Free

mabauti · 13th February 2008, 08:54 PM

Yep, it's me again >_> , taking advantage of this great forum

Anyway...

I'm looking for a simple circuit about solar power supply with a backup power for nightly operation.

The circuit I have consumes 20mA @ 5V (it is a clock + thermometer )

Links and ideas are welcomed

**Krumlink** · 13th February 2008, 09:58 PM

The CLock/Thermometer looks really cool!

For a House supply oops (EDIT)
As for Solar power back up, I would get high wattage solar panels and charge up a battery bank (think car batteries) and run a 120VAC inverter on it. Not very descripitve, but should point you in the direct direction.

FOR YOUR CIRCUIT
Seeing that it only draws 20ma at 5V, lets make it safe that it could for what ever reason start to want 50ma. I would get a 6W solar panel (12V 500ma) and run that into a 5V regulator. That should work great, and for night time put a 9.6V battery or whatever voltage would suit it and attach that across the input voltage (12V solar panel) and ground it electrically to the solar panel. Make it a NiCd or NiMH. This is just a vague suggestion, I would wait for some of the other pros to state their opinion too.

Good Luck

Kryten · 14th February 2008, 06:26 PM

i would def go for batteries meant for use with solar panels, cos car batteries are ment to have large amount of power drawn from them and are not so good for long "light" discharge

Hero999 · 15th February 2008, 04:50 PM

Six NiMH cells powering a LM2936-5.0 will do.

You can eailly trickle charge the batteries at C/10 using a simple series resistor and schottky diode, to prevent them from discharging back into the solar cells.

mabauti · 16th February 2008, 08:15 PM

Any schematic 999? >_>

Hero999 · 16th February 2008, 10:17 PM

The circuit for the LM2936-5.0 can be found on the datasheet.

Here's a circuit for a simple battery backup.
http://www.electro-tech-online.com/a...ple-dc-ups.pdf
http://www.electro-tech-online.com/e...battery+backup

Replace the 1Ω resistor with a higher value that will trickle charge the NiMH cell at a safe current.

Replace Rl with the LM2936-5.0 circuit.

mabauti · 17th February 2008, 10:13 PM

Thank you for the info Hero999

Kryten · 26th February 2008, 04:53 PM

ooooppsss I guess i missed about the battery sizing all together

srmd · 19th March 2008, 11:21 AM

Thank you for the information

Super_voip · 21st March 2008, 05:22 PM

It looks like the LEDs consume most of the power. Is it feasible to turn them off, or reduce the power to them?

13th February 2008, 09:58 PM	#2 (permalink)
Krumlink Moderator Join Date: Aug 2007 Location: Michigan, USA Posts: 1,528	The CLock/Thermometer looks really cool! For a House supply oops (EDIT) As for Solar power back up, I would get high wattage solar panels and charge up a battery bank (think car batteries) and run a 120VAC inverter on it. Not very descripitve, but should point you in the direct direction. FOR YOUR CIRCUIT Seeing that it only draws 20ma at 5V, lets make it safe that it could for what ever reason start to want 50ma. I would get a 6W solar panel (12V 500ma) and run that into a 5V regulator. That should work great, and for night time put a 9.6V battery or whatever voltage would suit it and attach that across the input voltage (12V solar panel) and ground it electrically to the solar panel. Make it a NiCd or NiMH. This is just a vague suggestion, I would wait for some of the other pros to state their opinion too. Good Luck __________________ Visit my website! http://www.freewebs.com/electronic-hobbyist

14th February 2008, 06:26 PM	#3 (permalink)
Kryten Experienced Member Join Date: Oct 2007 Location: Stavern, Norway Posts: 162	i would def go for batteries meant for use with solar panels, cos car batteries are ment to have large amount of power drawn from them and are not so good for long "light" discharge __________________ Simplicity rules Good enought - its perfect My virtual city Are you a Chemist?

15th February 2008, 04:50 PM	#4 (permalink)
Hero999 Experienced Member Join Date: Apr 2006 Location: England Posts: 6,983	Six NiMH cells powering a LM2936-5.0 will do. You can eailly trickle charge the batteries at C/10 using a simple series resistor and schottky diode, to prevent them from discharging back into the solar cells. __________________ What's so bad about Microsoft? Get Opera it's simply a superb browser.

16th February 2008, 10:17 PM	#6 (permalink)
Hero999 Experienced Member Join Date: Apr 2006 Location: England Posts: 6,983	The circuit for the LM2936-5.0 can be found on the datasheet. Here's a circuit for a simple battery backup. http://www.electro-tech-online.com/a...ple-dc-ups.pdf http://www.electro-tech-online.com/e...battery+backup Replace the 1Ω resistor with a higher value that will trickle charge the NiMH cell at a safe current. Replace Rl with the LM2936-5.0 circuit. __________________ What's so bad about Microsoft? Get Opera it's simply a superb browser.

26th February 2008, 04:53 PM	#8 (permalink)
Kryten Experienced Member Join Date: Oct 2007 Location: Stavern, Norway Posts: 162	ooooppsss I guess i missed about the battery sizing all together __________________ Simplicity rules Good enought - its perfect My virtual city Are you a Chemist?

16th February 2008, 08:15 PM	#5 (permalink)
mabauti Experienced Member Join Date: Jun 2006 Posts: 80	Any schematic 999? >_>

17th February 2008, 10:13 PM	#7 (permalink)
mabauti Experienced Member Join Date: Jun 2006 Posts: 80	Thank you for the info Hero999

19th March 2008, 11:21 AM	#9 (permalink)
srmd New Member Join Date: Mar 2008 Posts: 4	Thank you for the information

21st March 2008, 05:22 PM	#10 (permalink)
Super_voip Experienced Member Join Date: Jul 2007 Location: Brisbane, Australia Posts: 300	It looks like the LEDs consume most of the power. Is it feasible to turn them off, or reduce the power to them?

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