Controlling 12V Solenoid using Piface

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.

what is SPICE ?

also I bought MOSFET Power Control Kit(https://www.sparkfun.com/products/10256) and successfully able to operate solenoid using piface digital output pin. but it is overheating now :-(

Spice is a "golden-oldie" electronic circuit simulator. I remember working with it in the 1980's. and even then it was an "old" program. Nowadays there are GUI frontends, but the calculations are still done mostly with the "old code".

Your mosfet is about 0.05 ohms. So at 1A (you look up and report back what your solenoid actually uses!  it uses even less, 0.45A) you would get a voltage drop of about 0.05V. This would, at 1A generate about 50mW of power. This is so very little that it is hard to measure. So if it is overheating, there is something wrong. Show us your circuit (draw a circuit diagram of how you WANTED to connect things. Then also show us a picture of your actual build!).

Now for solenoids, the problem is that the solenoid will generate a voltage spike when it is turned off. If you turn it off often, that can cause heating. The mosfet is specified to tolerate a bit of misuse (*) in this area, but it is possible that you are exceeding the "a bit" part.... :-)

Still, the freewheeling diode may be a good idea anyway: it can't hurt (if connected right side up).

(*) Many electronics engineers will say you HAVE to provide a freewheeling diode, but this mosfet is SPECIFIED to work without one, as long as certain requirements are met.

as internal resistance of your device is 27ohms it may not heat up mosfet... if mosfet heating up slowly then its fine put some heatsink..

as internal resistance of your device is 27ohms it may not heat up mosfet... if mosfet heating up slowly then its fine put some heatsink..

sorry for confusion, it is not mosfet heating up, it is a Solenoid which is overheating.

if your leaving the solenoid energized then it will be drawing 500mA at 12V meaning 6W of heat dissipation

if it is excessively hot then I would suspect it is not 12V 500mA or requiring a lower holding voltage as described above