stizzswizz
New Member
Hello,
I have been working on a this circuit for a while now and I am having some issues with timing.
Basically I have to make a circuit to trigger a secondary circuit that ignites a plasma. This is for a PECVD system where I work (semicondutor research center). The system sends out 2 signals that I need to use. One is a 15VDC signal telling me that the system wants the plasma turned on. The second signal is a 0-15VDC RF Power setpoint signal, (0V is 0W and 15V is 300W) I only want my circuit to output 15VDC when the 'plasma on' signal is 15V and the power setpoint is below ~3.0V (~10W). I have built a couple circuits that used opamps, setup as voltage comparators and with bench testing they worked great! However, when installed in the PECVD system, it worked good only when the power setpoint was below 10W. When the power setpoint was say...20W the circuit would output 15V for a fraction of a second. That fraction of a second triggered the ignitor when I didnt want to use it. The problem here is the plasma on signal goes high at like a 1/4 of a second (probably faster) faster than when the power setpoint is reached. I would like to isolate both signals as best as I can (via opto-couplers), and provide around a 300mW output to the secondary circuit.
I have currently been trying to use 555 timers to create a single pulse from the plasma on signal, take that pulse and delay it about 1/2 a second. The problem with the 555 that I have is that the plasma on signal is longer then the pulse so it keeps triggering. I have searched online and read alot in my text books on how to make a single shot circuit and it seems like it might work if I can make it auto-reset after a short period of time (1 sec?). I havent been able to find much info on auto-resetting though.
I would like to make the circuit digital if it can be done simply... I also have thought about using a PIC, but I am only familiar with Parallax stamps and the propeller. Plus, I think what I need is alot more simpler then I'm making it.
Late tonight I will try and upload some circuits I have made so you can see what I'm talking about.
Thanks,
Steve
I have been working on a this circuit for a while now and I am having some issues with timing.
Basically I have to make a circuit to trigger a secondary circuit that ignites a plasma. This is for a PECVD system where I work (semicondutor research center). The system sends out 2 signals that I need to use. One is a 15VDC signal telling me that the system wants the plasma turned on. The second signal is a 0-15VDC RF Power setpoint signal, (0V is 0W and 15V is 300W) I only want my circuit to output 15VDC when the 'plasma on' signal is 15V and the power setpoint is below ~3.0V (~10W). I have built a couple circuits that used opamps, setup as voltage comparators and with bench testing they worked great! However, when installed in the PECVD system, it worked good only when the power setpoint was below 10W. When the power setpoint was say...20W the circuit would output 15V for a fraction of a second. That fraction of a second triggered the ignitor when I didnt want to use it. The problem here is the plasma on signal goes high at like a 1/4 of a second (probably faster) faster than when the power setpoint is reached. I would like to isolate both signals as best as I can (via opto-couplers), and provide around a 300mW output to the secondary circuit.
I have currently been trying to use 555 timers to create a single pulse from the plasma on signal, take that pulse and delay it about 1/2 a second. The problem with the 555 that I have is that the plasma on signal is longer then the pulse so it keeps triggering. I have searched online and read alot in my text books on how to make a single shot circuit and it seems like it might work if I can make it auto-reset after a short period of time (1 sec?). I havent been able to find much info on auto-resetting though.
I would like to make the circuit digital if it can be done simply... I also have thought about using a PIC, but I am only familiar with Parallax stamps and the propeller. Plus, I think what I need is alot more simpler then I'm making it.
Late tonight I will try and upload some circuits I have made so you can see what I'm talking about.
Thanks,
Steve
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