Controlling a Solenoid

Lynxmotion
1

There are a few threads about this, but I need some help still.

I have an ATMega128 and I need to control various solenoids. I haven’t received the solenoids yet, so I don’t know exactly how many amps they draw. It should be safe to assume less than 10 amps each.

I know I can use a relay or transistor circuit. I’m not sure which one would be best. I want to keep the component list small since I need to control multiple solenoids. I also want to make sure I don’t have any feedback that blows the microcontroller.

Which one should I go with?

Thanks a lot.

2

Are you going to control AC or DC. If you are controlling AC you can often use a solid state relay and drive it directly with the microcontroller. Check to see how much current it draws. You could also use a small DIP relay, some come with a suppressing diode inside, you need to know for sure though, otherwise add one externally. The DIP relays will control an amp usually and are pretty fast. Of course a transistor and diode to protect the circuit always works.

3

I found a DIP relay I think will work (handles 10 amps). I can’t tell if it has a suppressing diode inside, but I could easily add one on the outside.

jameco.com/webapp/wcs/stores … Id=664309&

For the same price, I found an h-bridge chip that I think will work.

search.digikey.com/scripts/DkSea … 4424CPA-ND

Can you use h-bridge chips to control solenoids? I like the h-bridge a little better because it is a lot smaller. It can handle 3 amps. I’m still not sure how many amps the solenoids draw because I haven’t received them yet. But I’m unsure whether it would work for the solenoids at all.

Thanks.

4

I got the solenoid info. They will draw around .5 to .8 amps. So I think I can use the SN754410 motor controller. I’ve just never tried controlling a solenoid like that.

It seems like it will work, but can anyone confirm?

Thanks.

5

You can use an H bridge but it isn’t necessary. Just use a transistor and a shunting diode. Here is a link to a great write up on controlling a solenoid:

kronosrobotics.com/Anotes/Relays.pdf

I have actually used DIP relays that are the size of a 14 pin IC and can be driven by a microcontroller. Some even have diodes built in, I think Kronos Robotics sells ones with diodes. They only control about 1 amp though so wouldn’t work unless you controlled the relays you just bought with those little DIP relays. I’m pretty sure the relay you found does not have a diode.