I am having trouble comming up with an adjustable timer circuit that will osc at 15Khz. Well the biggest problem is the math for the RC. 50% duty cycle. It has been years that I have messed with these 555's and can't remember the math.
I will try to discribe what I already have:
Pin 1 - Gnd
Pin 2 - 6
Pin 4 & 8 to plus voltage = VCC?
a 2.2K from Pin 7 to Pin 6
Pin 3 to a 22 ohm resistor with a 10K pull down resistor to ground driving the gate of a IRF740 MOSFET. Source to ground, Drain to an automotive 12V ignition coil.
Now from the adjustable power supply, (26VAC output, 110VAC input hooked to a fan speed control so to vary the trans output voltage). There is a full wave bridge and cap (220uF 50V) on the output of trans. 2 - 2K 1/2Watt resistors (1K) on the plus side to my 555. Now to vary the frequency a bit.
If I hook up a 2K pot from vcc to pin 7 what will I need for R Total?
There is also a 10uF cap on pin 5. There may be other parts of this circuit I don't need, so I guess what I am trying to do is vary the high voltage from the ignition coil from 6KV to say 10KV at 12Khz to 15Khz.
The circuit I have varies the output of a flyback transformer. I just need to make it work on an ignition coil.
I will stay tuned tomorrow for more info if needed.
Thanks.
I will try to discribe what I already have:
Pin 1 - Gnd
Pin 2 - 6
Pin 4 & 8 to plus voltage = VCC?
a 2.2K from Pin 7 to Pin 6
Pin 3 to a 22 ohm resistor with a 10K pull down resistor to ground driving the gate of a IRF740 MOSFET. Source to ground, Drain to an automotive 12V ignition coil.
Now from the adjustable power supply, (26VAC output, 110VAC input hooked to a fan speed control so to vary the trans output voltage). There is a full wave bridge and cap (220uF 50V) on the output of trans. 2 - 2K 1/2Watt resistors (1K) on the plus side to my 555. Now to vary the frequency a bit.
If I hook up a 2K pot from vcc to pin 7 what will I need for R Total?
There is also a 10uF cap on pin 5. There may be other parts of this circuit I don't need, so I guess what I am trying to do is vary the high voltage from the ignition coil from 6KV to say 10KV at 12Khz to 15Khz.
The circuit I have varies the output of a flyback transformer. I just need to make it work on an ignition coil.
I will stay tuned tomorrow for more info if needed.
Thanks.