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Author Topic: Relays: splitting voltage from a power supply  (Read 982 times)
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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.
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#mike

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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.
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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.
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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.
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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?)
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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?
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Arduino for Teens available at Amazon.com.

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I'm after doing exactly what computer power supplies do when I say 'split', if that makes it any clearer.

In that case, use individual regulators whose input tied to the same power rail. That way, you get different output voltages (determined by the regulators used).

Computer psus work quite differently.
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