Hello,
I am redesigning a vending machine control system and am working on the motor control. The machine uses those augers/spirals to bring the product forward. My issue is with controlling an exact rotation for each motor. The motor is a 24VDC motor attached to a gearbox whose output shaft is D shaped around the outside. A SPDT snap action switch rides on the D shaft. The NO and NC outputs of the switch are connected to each other and those and the COM appear to be in series with the motor. There is also a diode and resistor present inside the gearbox but it is difficult to tell what they do. The diode appears to be reverse polarity protection and not reverse parallel with the motor. Removing the switch from the gearbox I was able to determine the switch spends about 1.3ms in a break before make state during the transition on both edges of the "D".
When applying 24V to the motor it continuously turns releasing and repressing the switch each rotation with no noticeable effect.
I have never used a SCR before so that it why I'm asking here. RadioShack doesn't sell any and I don't want to order just one to try it out.
What I would like to know is if a small SCR would be a good way to control these motors on the low side? I could hold the gate high long enough to get past the second transition of the switch then release it and the motor would stop when it finishes its rotation and reaches the first switch transition again. (This is when the switch transitions into the extended position when reaching the flat part of the "D".) The motors draw about 120mA so most SCRs I saw on mouser seemed plenty capable.
Thanks for your understanding and help. I don't want to order a dozen SCRs and find I had the concept wrong.
-GTech
I am redesigning a vending machine control system and am working on the motor control. The machine uses those augers/spirals to bring the product forward. My issue is with controlling an exact rotation for each motor. The motor is a 24VDC motor attached to a gearbox whose output shaft is D shaped around the outside. A SPDT snap action switch rides on the D shaft. The NO and NC outputs of the switch are connected to each other and those and the COM appear to be in series with the motor. There is also a diode and resistor present inside the gearbox but it is difficult to tell what they do. The diode appears to be reverse polarity protection and not reverse parallel with the motor. Removing the switch from the gearbox I was able to determine the switch spends about 1.3ms in a break before make state during the transition on both edges of the "D".
When applying 24V to the motor it continuously turns releasing and repressing the switch each rotation with no noticeable effect.
I have never used a SCR before so that it why I'm asking here. RadioShack doesn't sell any and I don't want to order just one to try it out.
What I would like to know is if a small SCR would be a good way to control these motors on the low side? I could hold the gate high long enough to get past the second transition of the switch then release it and the motor would stop when it finishes its rotation and reaches the first switch transition again. (This is when the switch transitions into the extended position when reaching the flat part of the "D".) The motors draw about 120mA so most SCRs I saw on mouser seemed plenty capable.
Thanks for your understanding and help. I don't want to order a dozen SCRs and find I had the concept wrong.
-GTech