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Topic: Relays: splitting voltage from a power supply (Read 1 time) previous topic - next topic

Applmike

Hey all.

So, I'm designing a reef tank light controller using an Uno and a Relay Shield.

The goal is to create a dawn-dusk light cycle. The lights are LEDs, and they have a PWM controller that powers the LEDS, but needs a 0-10VDC input voltage to control the dimming level (this I would provide through programming the Arduino). I also have a set of 2 "moonlight" LEDs (total 4V required), which don't have a controller, and just need on/off control. There are also 12V fans that I need to have on when the main LEDs are running. Obviously the Arduino can't supply all that power, so I bought a Relay Shield that has 4 relays that can handle up to 30VDC each.

I already have 10V and 12V wall-warts for the existing setup (10V to provide dimmer voltage and 12V for the fans), but what I REALLY would like to do is craft a circuit which would use just one power supply that I could split the output voltage to provide the correct power to both the loads.

Does anyone have a good reference design on how to go about doing that?

Thanks.
#mike

CrossRoads

You can't 'split' a power supply voltage. You can have several circuits running in parallel from the same voltage supply.
You can have the 12V supply go to a DC/DC converter and create a 10V supply that way.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

dhenry

Quote
Does anyone have a good reference design on how to go about doing that?


Your controller likely works at 12v - it is odd to have something running off 10v. I would put a resistor (1k or even less if the controller consumes a lot of power) on the controller's rail to the 12v and see what happens.

Or you can read its datasheet / manual to be more definitive.

Applmike

Thanks.

I'm after doing exactly what computer power supplies do when I say 'split', if that makes it any clearer. You can get multiple voltages (I think those PS supply 5v and 12v?)
#mike

CrossRoads

Computer power supplies have multiple regulators, one for each desired voltage.
So you have 12V, and you need 10V and 5V, then you need a 10V and 5V regulator.
DC/DC switching regulators offer the most efficiency.
Example:
http://www.pololu.com/catalog/product/2104
How much current do you need at the various voltages?
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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