Hi, I wish to make a smart solenoid driver.
I was going to use some standard relays, but after some research I think the benefits of a smart driver are worth it, these being:
1) Less mechanical wear from ramping up and down the current (soft on/off).
2) Reduced power consumption (holding current only needs to be 1/10th of switching current), thus a much smaller power supply is required.
The solenoids draw 1.25A at 24V. Now I just need a method of allowing less current to flow to the solenoids. I have tried using a Power Darlington pair (MJ3000) in a TO-3 package mounted to a large heat sink. It got very hot and unstable.
I was thinking of a switch mode supply to drop the voltage, but then because I need to drive 12 solenoids, I am reluctant since then I would need 12 large capacitors and 12 large inductors (keeping component count down is critical!).
I found this beauty: VN380 (SMART SOLENOID DRIVER
SOLID STATE RELAY)
Basically it preforms all the smart functions described in 1 & 2 above. It seems like a rare item. So I am looking for an alternative common part (if it breaks down, I dont want people to battle to repair it).
Any idea of a general route to try, or a component that would make my life much easier. The best I can think of is passing a PWM micro controller output through a low pass filter (DTA conversion), then boost the signal through a voltage follower, and then onto the gate of a MOSFET which would drive a solenoid. I am not to sure about MOSFETS being half on. As far as I know they are more suited for ON/OFF applications.
Can you think of something better? I know you smart people can! Thanks for any advice.