Another Treadmill Motor Question

You are write it is a K. O. Lee, it was a cutter grinder to start with that i turned in to a surface grinder. I does't grind perfect but good enough for what i need. I scraped the ways and turcited the table, small mag, and it is a grinder.
 
I have a K.O.Lee "Knockout" too. Mine is on its original steel cabinet. Mostly I use it it grind end mills and resharpen the ends of punch and die sets. Nice little outfit,though I wish I had a larger surface grinder.
 
Depending on the treadmill the MCxx controllers may not have actual PWM control built in, It is quite often on the control panel board. I suspect that this is done by many manufactures to limt the repair options to Factory parts. Pulse Width Modulation control is mandatory if you are going to get smooth full or near full torque output from the motors. Many times this is not obvious as the PWM power supply is on the Power supply board and there is no obvious connections on the MCxx board itself. Just installing a 5K to 50K pot only gives you speed control because you are limitimg voltage and not suppling full current except at full RPM. In many cases I have seen this can only be determined with a scope and or the schematic.
Hope I am not restating the issue. I have used many of the MCxx boards from many treadmills and I am in the the process of making a PWM signal generator to use on a small drill press. The circuit is simple to build from 2 LM555's or a single LM556. You can find the circuits on Homemade Circuits. Just Google PWM circuit schematics.
 
dpstanfill said:
Depending on the treadmill the MCxx controllers may not have actual PWM control built in, It is quite often on the control panel board. I suspect that this is done by many manufactures to limt the repair options to Factory parts.
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No, they just do it to save money. The microprocessor that they use to handle the display has enough excess capacity to handle the motor control functions. There would be no point it trying to force people to use factory parts because no significant number of these machines are ever repaired. We get them.
 
one I picked up recently had a MC2100 controller which doesn't have PWM control onboard, but the MC40 and MC65 do as far as I can tell. At least, they come with a pot which is used to control motor speed however that is done.
 
You probably have a point there. I know I have gotten quite a few of them. I do know that part of the pulse controller circuit on the MC45 is on the power supply board and it gets its pulse from the control panel because I have one on my bench that i am building a PWM generator circuit for as we speak:congratulate:.
 
I've crossed my wires - turns out that none of the MC boards that I can find have PWM, they're all SCR or have a PWM signal generated off board. Not entirely clear as to the plus and minuses of either as I don't understand them well enough!
 
dpstanfill said:
You probably have a point there. I know I have gotten quite a few of them. I do know that part of the pulse controller circuit on the MC45 is on the power supply board and it gets its pulse from the control panel because I have one on my bench that i am building a PWM generator circuit for as we speak:congratulate:.
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If I had one of those I'd just drive it with an atmega68 and implement the closed-loop control in software.
mattthemuppet said:
I've crossed my wires - turns out that none of the MC boards that I can find have PWM, they're all SCR or have a PWM signal generated off board. Not entirely clear as to the plus and minuses of either as I don't understand them well enough!
Click to expand...
SCR controllers are PWM. They operate at 120Hz (twice line frequency) and modulate the pulse width by delaying the triggering of the SCRs. They work fine. In theory they introduce 120Hz vibration but you'll never detect it. They've been supplanted by high-frequency MOSFET PWM controllers due to cost and efficiency. As I mentioned above you can implement the closed-loop control in a microcontroller such as an atmega68 (Note that the inputs are not usually isolated, though. Depending on the design they could be connected to one side of the line or to the output of a line-connected full-wave bridge. This also goes for most MOSFET PWM designs). It's likely (though not certain) that the motor has an AC tachometer generator, typically 16 pole. It's easy to turn this into pulses for input to a micro. If not some sort of encoder is easily added.
 
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