TheEquineFencer
New Member
I'm really new at working with elecronics so please bear with me. This is my first project and I need some help. I've built an O2 monitor that I want to drive a set of solenoids,(injectors) from it. I want to use individual TIP42 transistors for the switching. I have the thing working now driving one injector but want to drive a total of 8 from the same source. I'm using a 4N25Optoisolator driven from the LED on the monitor to turn on/off the TIP42. How do you parallel the 8 TIP42 Transistors so they will all work? Do they need some sort of isolation? At the present time I have the Terminal #5 on the 4N25 from the Voltage source,12VDC, also on the TIP42 Emiiter, going into the 4n25, coming out Terminal #4 going to the base of the TIP42, ahead of the resistor, to switch it off when the 4N25 is turned on from the O2 monitor. I have a 1663 Ohm resistor from the Base on the TIP42 to ground. The injector is connected to the Collector and to ground. Basicily I have the load on all the time and the Opto cuts it off by making the base more (+) than (-). Thanks, Floyd.