Voltage reversing driver

Hi all

Im working on a project using a central locking solenoid/linear actuator (not 100% sure which) and need to be able to reverse the voltage going to it very quickly.

The project involves forcing a leaver open (when an input is given) and holding it there, allowing contents to feed into a container (timed at ~ 1/10 second), before closing the lever again (un-timed but needs to be as fast as posable). It does not need to hold the leaver closed and must power off when the cycle is compleate.

So, Triggered >> Leaver open >> Hold open for 1/10 sec >> leaver close >> power off, wait for re-trigger.

The leaver is free moving and not spring loaded, the power source at current is an 11.1v 2200mAh battery ratted at 20C. The input will be a push to make micro switch.
I need the Circuit to be as small as posable because space in the housing is limited.
Cant be made with Micro controlers/PIC's as i have no way of programming them!

The design i went with 1st:

(Not yet built or tested)
The input triggers a 555 set up for 'one shot' monostable with a logic 1 out put held high for 1/10 sec. I estimated the time taken to fully open the lever under load as being about 1/20 second (its only moving about 2cm, but to be safe i'm going to call it 1/10 sec). This out put will be connected a DPST replay to drive the 'open' action of the ever.

The second part will be a delayed 555 time going high 1/5 second AFTER the trigger input and staying high for 1/10. (this gives the circuit time to fully open, the feed action to complete before closing). the out put is then connected to a second DPST replay to drive reverse voltage to close the leaver before powering off totally until re triggered.

Problem i can for-see
I doubt the 555 timer can handle the amount of current my battery is going to kick out, is there a way of limitating this easily or is it worth running via a separate power supply (IE 9V battery).

Is there a way of wiring fets to give the same effect as a DPST relay as this will save space.

Secondly can you suggest any other circuit that will do this better than my amateurish design .

Thanks in advance for your time, Bigfish312

The

fet bridge circuit... you are using 8 AA NiMHs and are worried about space? how much current do you need for the solenoid? relays can be very slow... and the solenoid response time will be determined by the coil inductance and you need clamping across it...

actually they make relays smaller than you can hotwire electronics for that... like this one: Digi-Key - PB1112-ND (Manufacturer - D3202) at 7x15x11mm

its not 8x nimh's its a compact three cell lipo, but it it one reason space is limited (its taking up most of it)

bigfish312 said:

its not 8x nimh's its a compact three cell lipo, but it it one reason space is limited (its taking up most of it)

Click to expand...

ok was just going by the voltage... that relay is most likely smaller than you could hack together as a circuit... you did not say how much current you actually need not how many actuations you expect out of the battery.

no idea what the cycles per charge will be as there is no info on the accuator i'm using (got it from a scrap car we had) tho i do suspect it may be drawing more than 2A, i haven't got a multi meter here but will check when i get a chance too use one. the battery can kick out 40+A so twas why i was thinking of a power Mosfet.

bigfish312 said:

no idea what the cycles per charge will be as there is no info on the accuator i'm using (got it from a scrap car we had) tho i do suspect it may be drawing more than 2A, i haven't got a multi meter here but will check when i get a chance too use one. the battery can kick out 40+A so twas why i was thinking of a power Mosfet.

Click to expand...

put a lab supply on it and turn up the voltage till it trips and see what the current is at ( in a lab supply there is a voltage adjust and a current meter on the supply )

the current at 12 volts is what your transistor needs to hand but the current plus 10 or 20% is all you need to operate it.

i suspect it is more like 0.5A

Dan