High all, I'm back! I was searching again for information on an application I have for the MC-60. I want to build a CNC Router/engraver, using a Chinese 400w spindle. The spindle runs at 3000RPM at 12vdc, and 12000RPM at 48vdc. It is a brushed PM Motor. I wish to limit the MC-60 to 48v out, thus the spindle RPM at 12k. Can I just add a fixed resistance to the speed pot to accomplish this? I have 2 other MC-60's in service running a tabletop mill and a sand muller, but they both are using the treadmill motors that came with them. Thanks for any help you can offer.

 

Do you have a link to the spindle?
Sounds heck of a high rpm if a DC PM motor.
Max.

 

http://www.ebay.com/itm/HXKJ-GS52-4...563229&hash=item4ae6b2ff5d:g:ZlkAAOSwBt5ZG7Gy

 

You could experiment with a fixed resistor, the motor will 'see' ~90vdc peak, but it most likely the insulation will stand that, just with the limited rpm, the mean current will produce 12krpm max. offload.
Edit: Should read ~90vdc not 190v.
Max.

 

You could experiment with a fixed resistor, the motor will 'see' ~90vdc peak, but it most likely the insulation will stand that, just with the limited rpm, the mean current will produce 12krpm max. offload.
Edit: Should read ~90vdc not 190v.
Max.

Hi There, The Icon MC60 controller is an SCR fired controller, very dirty power to motors, and requires a large inductor in series with the drive motors of any size. Your motor is small in comparison, so the inductor would be more for filtering than current support. I would have chosen another controller simply due to the aweful output SCR and Triac fired controllers can impart onto the motor power rails.
If you would like to reduce the output to ~48v, would you not need to "control" the PWM input at the 3 fast-on tab connections that usually take an isolated PWM signal from the interface board to run that control board. Setting up a pot across these tabs will also operate the controller, but be super careful, as those "Tabs" reside on a Hot-Grounded control circuit, meaning chances for problems, shocks exist while adjusting the pots or contacting the leads. A series resistor to limit speeds would still require a stable drive waveform(averaged DC Level) to even consider values. We also cannot connect a cobbled PWM speed signal to that MC60 without isolating things with an opto, as the interface board does.
Good Luck!

 

Hi,
I'm new to the forum. The schematic posted here (Rollins original 2009), along with some discussions in this and related topics, werevery helpful in my efforts to "reverse engineer" and repair my controller. I believe the description I've attached will answer some of the questions that have been raised.
MPW

 

I believe the description I've attached will answer some of the questions that have been raised.
MPW

Nice work!
Is that a re-reverse engineered schematic by you or taken off of one of the others?
Max..

 

Incidentally lifting R19 removes the function of requiring that the pot be returned to zero at power up.
When used in non-T.M. applications, removal of flywheel recommended.
Max.

 

Nice work!
Is that a re-reverse engineered schematic by you or taken off of one of the others?
Max..

Thanks. I drew it from scratch, in Eagle, following Mr. Rollins' arrangement, which seemed sensible, but repositioning some components for my aesthetics.
Yes, I recognize there are a lot of ways to modify the circuit behavior to fit other applications, but chose to stick with describing it to the best of my ability and leave changes to others.
MPW

 

I had started to reverse engineer it and came across quite a few errors in some of the previous reverse-engineered version.
(didn't get around to completing it!)
Max.

 

Hi, I'm new to the forum, wished I'd found it earlier. Chay, Max and Mpweir (and others) have done a very nice job helping others understand the MC-60 (and some circuits in general). Thank you for that. I have an MC-60 (rev H) I intend to use on a bandsaw and would like to disable the soft-start feature. I keep seeing a reference to lifting R19, but don't really understand how that would disable the feature. It seems you would need to keep Q7 from turning on and I don't see how lifting R19 would do that. Seems like lifting R27 on the base of Q7 would be the thing to do. Any help would be appreciated.

 

I believe RebelJD has the right idea. The phrase "soft start" means to me bringing the speed up slowly, which I think is strictly a result of C4 and the associated resistances which provide current to it. I consider U2A a "power up interlock" which prevents the motor running until the speed control has been returned to zero. It's not a bad idea to leave it functional, but I would lift R27 to disable the interlock. Speed changes will still be slow. Removing C104 or disconnecting one of its leads should allow quick response to the speed control and, incidentally, upon powering up. As I understand the circuit, lifting R19 would eliminate the "anticipatory" function of U1C, probably leaving the controller much less responsive to motor load. I encourage RebelJD to singly make these changes and report the results!

 

Also it is unwise to defeat the soft start if retaining the flywheel, otherwise it works fine in most applications without it.
Max.

 

Also it is unwise to defeat the soft start if retaining the flywheel, otherwise it works fine in most applications without it.
Max.

Mike and Max,
Thanks for your responses. I should have said I want to disable "Safe Start", not "Soft Start". In this particular application I would prefer not to return the speed reference pot to zero each time I start the machine. More of a nuisance than anything. Soft Start, or what I'd call controlled accel/decel is a nice feature that keeps from shocking the mechanical apparatus, and I would not disable that. I'm using an industrial Permanent Magnet DC Motor. Its a 102 volt motor rated 3/4HP at 2500 RPM. Just to test things out I did hook up the controller today and it works just fine, including the safe start feature I did not put an inductor in the armature circuit since I don't have one at this time. (Guess I need to go find an old treadmill on craigslist to steal parts from). The motor is physically larger than a typical treadmill motor and the bandsaw does provide some load even without cutting material. I'll do a comparison once I get an inductor in the circuit. The motor did run close to rated speed with the speed reference pot turned all the way up. The accel and decel were very appropriate for a bandsaw.

I'll try lifting R27 in an attempt to disable the safe start and post my results.

Jim

 

The series choke provides a few function, makes it slightly quieter at low RPM, smooths out the 'rough' DC to the motor and provides a bit of an impedance cushion to the motor.
Max.

 

The series choke provides a few function, makes it slightly quieter at low RPM, smooths out the 'rough' DC to the motor and provides a bit of an impedance cushion to the motor.
Max.

Ok here is an update. I lifted R27 and it successfully disabled the "Safe Start" feature. (remember this in an MC-60 Rev H). So the motor will now run at whatever setting the speed pot is at when power is applied. As has been pointed out several times, this is not something you want to do for use in a treadmill. But for many other applications such as machine tools, it may be desired. I also borrowed an inductor from my working treadmill (don't tell my wife) and as Max pointed out the motor does seems to run smoother at lower RPM's. Since my intent is to run at slower speeds to cut metal on my band saw I'll definitely be installing an inductor. I did not see a need to test things with R19 removed.

Thanks for all your help.

Jim

 

Thanks for the clear followup - nice to have theory confirmed!

 

Ok here is an update. I lifted R27 and it successfully disabled the "Safe Start" feature. (remember this in an MC-60 Rev H). So the motor will now run at whatever setting the speed pot is at when power is applied. As has been pointed out several times, this is not something you want to do for use in a treadmill. But for many other applications such as machine tools, it may be desired. I also borrowed an inductor from my working treadmill (don't tell my wife) and as Max pointed out the motor does seems to run smoother at lower RPM's. Since my intent is to run at slower speeds to cut metal on my band saw I'll definitely be installing an inductor. I did not see a need to test things with R19 removed.

Thanks for all your help.

Jim

So you confused me. Is it R27 or R19 to eliminate the Safe Start feature ?

 

I don't have the MC60 now but it was the resistor next to the pot slider terminal.
Just checked my notes, mine was R17, I believe 5.6k.
Max.

 

On the MC-60 I'm using, which is a revH, R27 was lifted to disable the safe start. So you'll need to look at the schematic for what ever version you are using to determine which resistor to lift.

In the way of an update I have finished the modifications to my bandsaw and could not be happier. Using a DC motor to slow the blade in order to cut metal works very well because you have lots of torque (armature current) available. There is very little or no speed reduction even when making heavy cuts likely due to the voltage regulation in the MC-60.

Jim