Found this in a box of circuits-all related to Arduino, but haven't a clue about this one-about 8 X 5 cm. Any suggestions?

 

You need to take note of all the IC devices and probably it will shed some light.
Or do some searching on Ebay for the same picture!
Maybe a SCR/Triac/PWM controller etc.

 

You need to take note of all the IC devices and probably it will shed some light.
Or do some searching on Ebay for the same picture!
Maybe a SCR/Triac/PWM controller etc.

Sure does look like a PWM motor controller.

 

Looks like an AC to DC power supply board.
Edit: or a motor controller as said above.

 

Gbj2510 is a 700v Vr(rms), 25A If(avg) bridge rectifier.

The 3 connectors are labelled M+ M- Load, + - PWM and, hard to read, I think DC... AC ...0

My guess is there's a few big MOSFETs under the PCB.

My guess is a DC brushed motor controller maybe for 110v motor?

 

Looks like an AC to DC power supply board.
Edit: or a motor controller as said above.

It seems to have a PWM input and a "load" marked "M" plus two terminals which I surmise are power input.

 

You can see at least one or maybe two large device on the heatsink under the PCB.
The No's on the IC's should add some definite clues, there appears to be one 4 pin opto-isolator.

 

Thanks everyone. I'm even less than a novice at electronics, so I appreciate the help. The clue was "PWM motor control". Using that, I located an image at purelogic.ru. It is indeed a pwm control, often used with Mach3. Even found a diagram, although all in Russian. Thanks again.