What is it?

This is a small module for efficiently driving and controlling solenoids at DC voltages. Requires ~12v (depends on your chosen solenoid, but should work from 6v to 24v).

Surface mount components ready soldered. Includes (unsoldered) JST-PH 2.00mm connectors and short leads. If you want to crimp your own leads I can reccommend the Iwiss SN-2549 crimp tool available from Amazon for a lot less than the offical crimp tool, or you can solder whatever leads you want directly to the PCB.

Operation

With 6-24v supplied to the board (J1) and a solenoid connected (J2), pull the enable pin low (J1 Pin1) to activate the solenoid (tested with a 5v and 3.3v logic level). The chip then supplies the maximum current as set by R1 for a duration (the 'keep time' set by C1) before settling back to the hold current (set by the chip. Not adjustable) all at the PWM frequency (~20kHz) set by R2.

By measurement current was about <200mA while in peak and <50mA in hold.

Note: The maximum activation frequency I've been able to get with this board is about 10Hz (on and off 10 times per second).

All boards tested with 12v solenoid. The values chosen for C1 (1uF), R1 (0R) & R2 (0R) are defaults and set the chip to its maximum frequency and hold and peak current. That works with the MCSMO0630s12std solenoid available from CPC (also tested with a micro solenoid)but if you can solder 0805 then you can change them to better suit other solenoids if required/necessary. Note: You may get better performance or efficency tuning the driver to suit your particular solenoids characteristics.

Note: According to the data sheet the chip can run from 6v to 27v, but as the electrolytic cap is 25v I'd suggest not trying this above 24v. I've also not had much luck driving the small low cost solenoids that you find on ebay & amazon as they require more current than this chip can supply so I'd suggest a solenoid of 30 - 60 ohms.

See the DRV120 datasheet for more detail.

Why did I make it?

I made this for use with drawing machines as 9G Servos can wear out surprisingly quickly when doing lots of fast pen up/down movements. I figured a solenoid would be a better option but driving solenoids isn't as straight forward as you'd think and I wanted something that would be more or less a drop in replacement for the servo.