I have a project where I am incorporating a Peltier cooler (uses 4.5 amps at 12 v or 6.4 amps at 16.4 v) for use as a dehumidifier. I would like to be able to actively control the temp of the Peltier using PWM. I would like to keep the temp a few degrees below the dew point (if I run it at full power all the time it runs at -10 to -30 C and just makes ice).
Before actually installing this circuit into my setup I decided to test it using a 12v 4.5 Amp halogen lamp. For my test circuit I have exactly the setup shown on this website connected to digital pin 3 of an uno. http://bildr.org/blog/wp-content/uploads/2012/03/rfp30n06le-arduino-lightbulb.png
The first power supply I tried was a wall adapter type (12v 15 Amp). Instantly the adapter made a terrible buzzing noise and within a minute or two died. I purchased a larger computer power supply capable of putting out 35 Amps on the 12 v line. Although it doesn’t kill this power supply it still makes a horrible buzzing when the PWM is anything below 255 (loudest buzz near the 0 end). The light and Peltier work(ed) fine without the PWM on both power supplies.
What is going on? I assume feedback from the arduino circuit is messing with the switching regulators or other electronics in the power supply. How do I solve this problem? I have a few thoughts some seem impractical and some I just don’t know if they will work. - Battery tied to a recharging circuit - Battery supplies the power to the circuit (rather impractical) - Decoupling capacitors – I tried a couple arrangements using 100 uF and 220 uF liquid caps and it seemed to do nothing but I know almost nothing about the size, placement or type of cap I should use for this application - New power supply – maybe there is a type of plug in power supply that is not subject to this interference Thanks for any help you can give!!