I'm looking for a few suggestions for a circuit to control a hydraulic machine (automatic wood splitter) I'm working on. As the mechanics off the machine are nearly complete, I'm needing to start thinking about the electrical controls for it. I've worked on and designed circuits in the past, but am looking for someone to check my ideas, and I'm open to any possible suggestions.
The machine consists off 2 double acting rams, with each direction controlled by solenoid valves (ie 4 solenoid valves). Basically, one ram moves, activates it's limit switch, then the next one in the sequence moves, and so on.....
My initial toughts are to use a PIC (already have programmer + a couple
16f84s kicking around), but the problems are with the interfacing and power supply.
The power supply will be from a 12v lead acid battery (will vary from 11V upto 16V depending on charge off battery, and if it's being charged while the machine is in use).
To power the hydraulic solenoids, I was planning on using relays with 12V coils, which will be switched via transistors driven by the PIC. The relays will have diodes placed across the coil, to eliminate voltage spikes when released.
My main concern lies with the limit switches. Do I use them to directly pull the voltage off the PIC pins used for input, high or low? Or would it be better to use some form off optoisolator to isolate them from the pic?
thanks for any help moray