Hello everyone,
I've searched the archives for an answer for this, and although I didn't find any, I did see a lot of interesting future projects
I have a Bench top Mill. It's small, but I can use it to mill out printed circuit boards, metal parts for RC models, and plastics.My problem is with plastics. At full speed the plastic melts and gums up my tool. At slower speeds the motor stalls and the tool breaks.
I have a Ubuntu program that controls the mill, EMC2. I put an encoder on the motor to help control the speed, but the speed really fluctuates. I put an oscilloscope to watch the control pulses. They were definitely trying to do something. Then I put the scope on the voltage to the motor. I was surprised at what I saw. It's a DC motor, but it's powered through a bridge rectifier and controlled by a triac. Since the computer program can't reference the zero crossing, well, that's the problem I believe.
What I want to do is replace the bridge and triac with a DC power supply and use a IGBT to control the motor. I ordered the parts and wired it together. Just a bridge and capacitor, I shouldn't need anything more elaborate should I? I've got a little more ripple then I expected, but more capacitance should take care of that.
My question/problem has to do with the transistor. It's not turning on. I have a opto-coupler with the collector tied high, and the emitter bringing up a voltage divider tied to the base of the IGBT. The data sheet says it needs 20 volts (emitter to base) to conduct. Do I need a current limiting resistor in the base? I just don't have any experience working with them.
Thanks and my best regards
I've searched the archives for an answer for this, and although I didn't find any, I did see a lot of interesting future projects
I have a Bench top Mill. It's small, but I can use it to mill out printed circuit boards, metal parts for RC models, and plastics.My problem is with plastics. At full speed the plastic melts and gums up my tool. At slower speeds the motor stalls and the tool breaks.
I have a Ubuntu program that controls the mill, EMC2. I put an encoder on the motor to help control the speed, but the speed really fluctuates. I put an oscilloscope to watch the control pulses. They were definitely trying to do something. Then I put the scope on the voltage to the motor. I was surprised at what I saw. It's a DC motor, but it's powered through a bridge rectifier and controlled by a triac. Since the computer program can't reference the zero crossing, well, that's the problem I believe.
What I want to do is replace the bridge and triac with a DC power supply and use a IGBT to control the motor. I ordered the parts and wired it together. Just a bridge and capacitor, I shouldn't need anything more elaborate should I? I've got a little more ripple then I expected, but more capacitance should take care of that.
My question/problem has to do with the transistor. It's not turning on. I have a opto-coupler with the collector tied high, and the emitter bringing up a voltage divider tied to the base of the IGBT. The data sheet says it needs 20 volts (emitter to base) to conduct. Do I need a current limiting resistor in the base? I just don't have any experience working with them.
Thanks and my best regards