i have an odd project and need some advice on how to tackle this problem.
this is for a welding device, a inverter type TIG machine. mine is a tad older and does not have a pulsing feature. but given the controls built-in i can make a controller interface that can give me pulsing capability.
the foot pedal controller is a switch with a 3-wire pot. the pot is 10k-2watt with center wipe. i dont know how these 3 wires terminate in the welding machine, but i do know how the pot works in the pedal.
the switch is a on/off switch. when you press foot pedal the switch closes and the unit starts at lowest current setting, the wiper on pot is on one side of the pot, and when pedal is fully depressed the wiper is on other side of pot.
to make my pulsing work i need a way to flip the wiper from one side to the other using PWM. this wont work using physical pot, etc, so whats the best way?
example, pot connections A-B-C where B is wiper. in lowest pedal setting A-B is zero ohms and B-C is 10k ohms. at full pedal A-B is 10k ohms and B-C is zero ohms, thus a flip of the wiper from one side to the other.
currently, the unknowns are current vector and voltages seen on the pot.
for PWM i am figuring it will be adjustable 1-5Hz and 10-90% duty cycle
i would like to use dial pots for the PWM control for fast adjustments as needed. no display needed, etc. for flipping the wiper i would like it to be 100% non-mechanical.
I was thinking maybe two small solid state relays with one side of switched side tied to one side of other relay (the wiper), and then a 10k tied between the other ends of relay, then flip on/off the relays (one on while other off, then flip it to move the wiper)...?
any suggestions?
the attached pic is for example only, I would need to choose the right ssr, etc.
I can flip the opto's with 555, but 555 is not easy to make pwm the way I want it...... but if you have a good schematic to share using 555 I would use it as I have plenty of 555's on hand.
noticed I placed the 100ohm resistors in there to protect the A-C leads from connecting together if both opto's went on at same time. the 100's only affect min(start) and max(pulse) current by just a smidge..... but still 10k between A-C, etc.
this is for a welding device, a inverter type TIG machine. mine is a tad older and does not have a pulsing feature. but given the controls built-in i can make a controller interface that can give me pulsing capability.
the foot pedal controller is a switch with a 3-wire pot. the pot is 10k-2watt with center wipe. i dont know how these 3 wires terminate in the welding machine, but i do know how the pot works in the pedal.
the switch is a on/off switch. when you press foot pedal the switch closes and the unit starts at lowest current setting, the wiper on pot is on one side of the pot, and when pedal is fully depressed the wiper is on other side of pot.
to make my pulsing work i need a way to flip the wiper from one side to the other using PWM. this wont work using physical pot, etc, so whats the best way?
example, pot connections A-B-C where B is wiper. in lowest pedal setting A-B is zero ohms and B-C is 10k ohms. at full pedal A-B is 10k ohms and B-C is zero ohms, thus a flip of the wiper from one side to the other.
currently, the unknowns are current vector and voltages seen on the pot.
for PWM i am figuring it will be adjustable 1-5Hz and 10-90% duty cycle
i would like to use dial pots for the PWM control for fast adjustments as needed. no display needed, etc. for flipping the wiper i would like it to be 100% non-mechanical.
I was thinking maybe two small solid state relays with one side of switched side tied to one side of other relay (the wiper), and then a 10k tied between the other ends of relay, then flip on/off the relays (one on while other off, then flip it to move the wiper)...?
any suggestions?
the attached pic is for example only, I would need to choose the right ssr, etc.
I can flip the opto's with 555, but 555 is not easy to make pwm the way I want it...... but if you have a good schematic to share using 555 I would use it as I have plenty of 555's on hand.
noticed I placed the 100ohm resistors in there to protect the A-C leads from connecting together if both opto's went on at same time. the 100's only affect min(start) and max(pulse) current by just a smidge..... but still 10k between A-C, etc.
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