Control AC compressor with MCU

Hello, have small project involving work with AC/Cooling stuff. I must be able to reduce speeds of compressor and measure temperature at different locations - all I have so far is simple cheap NTCs.
I am not sure how to control 120VAC with MCU - maybe output a synthetic sine wave and amplify it.
Wonder if anyone have done such project
:wink:

I think the term you are missing is VFD - but first what compressor? You need to provide details of the kit
you have before anyone can begin to help!

It is a 500W/120VAC 60Hz compressor for 5K BTU unit. VFD is nothing else but wave generator

If you want to buy a VFD, you use the search term "VFD" not "wave generator" though...

Anyway can you provide the needed details of the kit, for instance a photo of the motor nameplate? We
shouldn't just blindly assume its a single phase induction motor...

OK. I will figure out something. This is more like electronics level related to controlling ac voltage with dc.
MCU could serve as the pwm driver or switching subcircuit.

Hi,
Is this an educational project or a commercial project?

Can you please tell us your electronics, programming, Arduino, hardware experience?

Controlling AC motor speed is not easily done, is the motor 3phase or single phase.

There is nothing simple about a VSD.

Will the motor and compressor be suitable for variable speed and do you have a cooling fan for the motor when it is running at low speed.

Tom... :slight_smile:

Do you know if the refrigeration compressor will even work at a reduced speed?

Paul

Compressor will work with different speed and even with different frequency if it is low range.

I built very simple circuit but it kind of increases voltage for some reason from 110v to 900V (..?)
Just two hexfets no coil - I guess it is some kind of voltage multiplier because of mosfet charge

Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Is the motor single phase?

Can you please tell us your electronics, programming, Arduino, hardware experience?

Is this a school/college/university project?

Thanks.. Tom.. :slight_smile:

Right now I can't ) I'm improving current circuit - controlling gates requires higher vgs-th voltage

I built very simple circuit

That is an excellent way of destroying an expensive compressor -- you might even get an impressive explosion!

Do wear eye and face protection, in case molten metal is splattered about.

Deous:
Compressor will work with different speed and even with different frequency if it is low range.

Just remember the starting torque is the same, no matter what the running speed is.

Paul

Paul_KD7HB:
Just remember the starting torque is the same, no matter what the running speed is.

Paul

I tried to lower speed with variac - all was ok - no explosion or weird stuff - heard that compressors are controlled with variable speed to increase their lifespan and decrease power consumption in ac units

Deous:
Compressor will work with different speed and even with different frequency if it is low range.

I built very simple circuit but it kind of increases voltage for some reason from 110v to 900V (..?)
Just two hexfets no coil - I guess it is some kind of voltage multiplier because of mosfet charge

Deous:
Right now I can't ) I'm improving current circuit - controlling gates requires higher vgs-th voltage

From the first comment you seem to have no idea about your circuit.
But when we offer help, which needs essential information such as a schematic, you give us nothing but the fact you have another problem.
STOP!!!!
If you do not have a basic schematic drawn, even in pen/pencil and paper, then draw one.
As you have found you have very high DC voltages which are extremely dangerous.
Please answer all four questions in post #8 ! ! ! !
Tom.... :o :o :o