Controlling 12V Solenoid using Piface

You will need a switching amp capable of handling an inductive load.  I am off to my office, I will dig some drawings out of my compy there and post them in a couple of hours.  If you are in a hurry, I have posted them previously, maybe you can find the drawings by searching this site using my name, dunno.

assuming your using the PI Face Digital, you can use the relays to drive the solenoid and you should have no problems

it will need a separate 12V 500mA supply though, preferably 1A

look out for Dons circuit later too to help clarify how to connect things up

Also, can you characterize your on time and duty-cycle expectations?  Solenoids that are on for a long time can be energized at one power level and held at a lesser one to minimize dissipation.  Can you also tell us the type of power source/system you intend to deploy?

The final DOF is hard clamp or soft clamp.  The hard clamp is cheap and effective.  The only downside for some mechanical situations is that it (the solenoid) lets go precipitantly when it is de-energized.  A soft clamp would be more elaborate and compute intensive to design, but would yield a smoother response in this phase of operation.

I cant find drawing on this site using your name, can you please post it again, thanks

I am trying to emulate touch screen tapping, so it will be frequent forward and backward motion. I am having 12V DC power adaptor as my power source 

This one is a little big for the situation, you only need about half an ampere, but it is illustrative, I'll keep digging.  All the stuff at the bottom is integrated into a three-terminal package.  It is an NPN Darlington pair:

This site isn't taking JPEG images right now, it seems.

Hello D_Hersey,

I do apologize for the inconvenience we are working on the image issue and hope to have it resolved as quickly as possible.

Thank you,

Jamie

NVM, still can't dl images.

I would use a TLP351 logic optocoupler for my first stage.  Output is CMOS push-pull totem pole.  This is how I would get from logic voltage to solenoid voltage.

I would follow with a complementary-symmetry bipolar stage.  NPN pull up, PNP pull down, bases bussed and connected to the output of the optocoupler.  Emmiters bussed and connected to the load, far side of load to (solenoid)V-.  Collectors go to respective sides of the solenoid supply.  NPN energizes coil, PNP catches spikes.

I would simulate the stuffing out of this using SPICE before I attempted to assemble this, for you have little reason to trust me, or authority (not that I represent authority) generally.  Try and measure the inductance of your coil so you can input it to SPICE.

Use Qs rated for at least a coupla amperes, we like to employ design-margin, esp. in one-offs.

Image is still not up :-(