Hi
Thank you for your replies. I will try and elaborate and answer your questions the best I can as I am a beginner at this stuff.
The project goes like this. When a travelling irrigator gets to the end of the paddock a micro switch is activated turning on power to the project. A solinoid is to be activated to open a valve to operate a small sprinkler from the time it hits the end of the paddock until a preset time. I had thought the switch would act directly transister pair base to start this one.
A timmer (LS7212 seems to work well on bread board with the exception of a short pulse on power up which I have not figure out how to deal with) will count down a set number of minutes (say 15) and then activate another solinoid that will operate a valve that fills a hydrailic piston closing the large main water feed to the machine. The timer will set its output port high when the delay period is complete. Again I thought this would act on a pair of transistors to activate the capacitor circuit.
The circuit is 12v and the latching solinoids are designed for 9-12v operatation as appose to mains supplied systems that use 24VAC for the solinoids.
When the capacitor is discharged and the switch is shut feeding 12 volts into it passes a pulse through to the solinoid and it latches. My understanding is that no more current is required other than this initial pulse and charging of the capacitor. When the SPDT switch is moved to the other position the capacitor discharges and creates a pulse in the other polarity to the initial pulse and this resets the solinoid.
I could use a SPDT relay but was trying to get away from the large holding current for this, but I suspect I may have to revisit it.
In terms of base resistor, I have tried all sorts, but with no luck, The last attemps was about 500R. I was just feeding 12v or G into the bases of the pair of Transistors by moving a wire around on the breadboard for now.
Since posting the original port I went out and got a couple of mosfets. 1 P-Channel and 1 N Channel. I managed to get the circuit to work with the exception of not being able to common the gate lines to operate of one input signal. I have from each gate a 1M resistor to high for the P-CHannel and low for the N-Channel and 10R in series to the gate. It was at least passing enough current quickly enough to generate a pulse that would operate the solinoid. I am guess when operating them on the same control line (again just moving a wire from G to 12V to trigger) that they are both on at one stage and dampen the pulse to prevent it operating. The capacitor does charge upto 9.5 volts (battery 12.2) but only discharges down to 3.0 volts when the drain mosfet is activated. Not sure if this matters or not.
Anyway, I am not sure if that is any clearer,
Regards Blair