replace potmeter on motorctrl with digital potmeter to use arduino to controll

Other Hardware General Electronics
1

Hi!

I bought a few of these to control some fans and I would like to do it with my arduino. At the time i did not know it was a 500k ohm potmeter on those speed ctrl and thought i could replace it with a mcp4131 or similare, but i can only find 10k and 100k of these, and as a complete novice i'm now stuck...

Just to explain my idea:
I have to control the air temperature in my server room, for this i have 2 fans(220v ~200w), one in and one out, this should be ctrl by one arduino with an DHT22 and two speed ctrl.

Additionally i have a third fan in the middle of the room to get some of that heat up into the house in the winter time, i also want to ctrl this fan so it keeps the right temperature and don't cook us alive in the living room.. For this ctrl i'm thinking one arduino and two DHT22(living room+basement), +speed ctrl ofc, if the temp in the basement is too low, it stops the fan so we don't freeze upstairs, and if the room temperature in the livingroom is too high or too low ctrl the fan by those values.

As said, i'm a novice and do this most for fun, i can ctrl them manually, but automation would be the key to (the wives) happiness.. :grin:

Any thoughts and or ideas? Thanks for taking the time to help me :slight_smile:

2

JensO:
automation would be the key to (the wives) happiness..

Not necessarily, if it's visible. :slight_smile:

3

Just for the record... we do not collectively call them "potmeter". We say Pot or Potentiometer.

4

What is the voltage across your potentiometer, excluding the wiper (center pin). Digital potentiometers normally only work up to 5V.

5

nor do they handle much current. more external hardware required.

6

Hi,
The device you have chosen is a VERY CHEAP and VERY DANGEROUS device to replace its pot and connect to anything.
The pot will be at 220Vac so connecting a digital pot is not possible the way you want to do it.

1001×1001 83.8 KB

Remember ALL of this device is at mains potential.

Also a lot of fans do not like electronic speed controls like this.

Tom... :o

7

I thought ac voltage wasn’t controllable by pots and you mush use a variable frequency drive?

I have never controlled an ac motor with a pot only dc.

8

JayMan:
I thought ac voltage wasn’t controllable by pots and you mush use a variable frequency drive?

I have never controlled an ac motor with a pot only dc.

google; AC motor scr triac
Tom... :slight_smile:

9

Thanks for all the feedback, guess it wont be as easy as i thought.. guess a servo and a 3d print is next. :slight_smile:

10

  1. The AC fans are likely synchronous or induction motors so can't be speed controlled by a triac circuit.
    Consult the datasheet for the fans concerned...

  2. That circuit is high voltage, so cannot possibly use a digipot on it, the voltages across the pot will be in
    the 100's of volts range. Its also floating on top of live mains voltage so needs full galvanic isolation anyway.

  3. You can control temperature by turning the fans on and off on a timescale of minutes, use PID and very
    low frequency PWM. This is commonly done for heating controllers, and this problem is similar except
    you are switching on the cooling. Suitable SSRs or relays with snubber circuits could be used (ac fans are
    inductive enough to require good snubbing).