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### Topic: 12v > 5v linear scaled voltage divider (Read 1 time)previous topic - next topic

#### Suaveman

##### Nov 26, 2012, 05:53 am
I want to use a rf pwm dimmer that only works at 12v (~8-13v range when measured using a dc voltmeter), as an analog input to an arduino. This will be used to dim several buckpucks attached to digital outputs. I understand some kind of voltage division is necessary.

Its for a backup led light system, and the dimmer will be powered by a stable 12v dc, provided by a sepic converter (since the sla will kick out anywhere from 11-14v). Now, keeping this as simple as possible, can i just use a pot on the output of the dimmer to bring the output down to 5v, while keeping a linear 0-5v range to use as an input to the arduino?

Well, i just tested this with a 1k ohm pot, and it seems to work fantastically. I adjusted it to kick out 0-5v on the pot center pin to the 0-5 ref, ground and positive are attached to the 12v out on my rf dimmer, and the ground for the pot is wired to led - on the buckpuck. All i need to do is wire the pot output to the arduino input, and i can use that to scale the pwm output on the digital arduino outputs. Pretty simple  .

One question though, for the 0-5v ref out, coming from the pot center pin to the arduino analog in, do i need to ground the pot ground to the arduino instead of led - on the buckpuck, or both? What pin if so?

Thanks

#### robtillaart

#1
##### Nov 26, 2012, 09:31 pm
I would recommend a voltage divider that splits in [1:2]

GND -----[10K] ------(Arduino)-------[20K] ----- 12V+-2 DImmer.

If the dimmer fluctuates to 15 VOlt the arduino wil get 5 Volt, at 12 Volt the Arduino will get 4 Volt which still has 800 analog steps

30K at max 15Volt ==> max 0.5mA
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

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