Do these potentiometer numbers mean anything to anyone?

DPittman

DPittman

Ultra Member
Premium Member
VicHobbyGuy said:
I liked that large treadle when I had a Brother industrial machine. Does yours have a knee presser foot lift lever as well?
That Vevor drop-in repleacement would be looking better and better to me! :)
You could probably sell the treadmill motor setup and the old AC clutch motor to recoup some of the cost. But what's the fun in that? :)
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Yes my machine does have the knee operated foot lift (as well as the standard lever on the machine).
The machine did not have the original clutch drive motor setup when I got it but rather someone had replaced the motor but there was still a clutch driven pulley system but it was incomplete and very poor speed control. As you mentioned these machines were designed for a factory setting where there were skilled workers and productivity was important.

My sewing machine is a model 96k40 made in 1936. Simple really, but man alive was it ever well built! Super heavy cast iron frame. It still runs just as smooth as can be.

What the heck I going to do with a sewing machine? I'm not sure yet, I just could not pass the opportunity to tinker and maybe make something better.
 
DPittman

DPittman

Ultra Member
Premium Member
Susquatch said:
A courser pot will not change the voltage ratios. 25% will still be 25, 50 will still be 50, 75 will still be 75.

However, you can get logarithmic pots that will do what you think you want. Good luck finding the right one..... I don't recommend that approach. It sounds simple in your thinking of how the pot works but your thinking is wrong. Knock that whole idea out of your head and embrace the replacement controllers that others have suggested.

Alternatively, you could consider a trick that auto engineers have used for a hundred years. To give the impression of more engine response and power, we bias the throttle linkage so that less movement of the foot pedal gives more movement of the throttle itself at the beginning of its travel and less at the end. It's all in the linkage ratios and angles.
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The YouTube gods were smiling on me tonight! I found this video that explains alot of what my suspicions were but I'm not yet sure how I will implement the solution if need be

 
V

VicHobbyGuy

Ultra Member
It's also possible to change the resistance characteristics of a pot - the 'taper' and also the max resistance - by using a fixed resistor (which costs a few cents) in parallel with 2 of the pot terminals. This can be handy when you don't have the right pot value in your junk collection. Playing with an online calculator for resistors in parallel can be an amusing way to spend a bit of time. Or use a spreadsheet to do the calculations and graph the results.
 
jcdammeyer

jcdammeyer

John
Premium Member
None of that will change the physics of the motor and the SCR style controller. The motor will still have to be started at say 1000 RPM and then the pedal backed off to 200 RPM. Or whatever the speeds are.
 
V

VicHobbyGuy

Ultra Member
jcdammeyer said:
None of that will change the physics of the motor and the SCR style controller. The motor will still have to be started at say 1000 RPM and then the pedal backed off to 200 RPM. Or whatever the speeds are.
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It just ain't so...here's the SCR motor controller +bridge rectifier controlling the DC motor on my 7x14 Microlux lathe:
 
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V

VicHobbyGuy

Ultra Member
jcdammeyer said:
You're lucky. My motor and SCR controller doesn't behave the way yours does.
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Maybe you are buying too-good quality.. :)
Here's mine:
https://www.aliexpress.com/item/1005002074105818.html?
I used the same type of controller on my drill press with the treadmill motor, but on that one I used a pot which started the spindle at about 100RPM when it was full CCW. That's about the slowest speed that's useful from that treadmill motor. Those controllers are cheap and pretty rugged in my limited experience....if you ignore the power ratings and buy one of the bigger ones. One look at the heatsink and I know that my controller isn't really good to 10kW, despite the ad copy. :)
 
jcdammeyer

jcdammeyer

John
Premium Member
It's also possible that controller isn't an SCR even though they say that in the heading. Lower down they do say: "Using a new type of bidirectional high-power thyristor". A thyristor is still an SCR but bi-directional means it's a TRIAC. Do you put a bridge rectifier in front of it?
 
jcdammeyer

jcdammeyer

John
Premium Member
Now that makes a lot more sense. They are using a TRIAC and it's a simple light dimmer; so to speak. With the bridge rectifier the behaviour of the motor will be quite different from the SCR based controllers.
 
T

Tecnico

(Dave)
This seems like a good thread to tack this question onto since it's about driving treadmill DC motors......

I've browsed through some of the videos of Dazecars (Ref: post 45) and seen a comment he made about requiring a DC choke before the motor to limit the arcing seen at the brushes. He claims the motor won't last long without the choke.

Dazecars video, see 12:00 minutes.

Any thoughts from those in the know about this claim?

D :cool:

P.S. Scooped a working TM last evening on curbside giveaway week. :) I don't yet know if I can graft a PWM driver to the power board so I'm looking at my options.
 
whydontu

whydontu

I Tried, It Broke
Premium Member
Tecnico said:
This seems like a good thread to tack this question onto since it's about driving treadmill DC motors......

I've browsed through some of the videos of Dazecars (Ref: post 45) and seen a comment he made about requiring a DC choke before the motor to limit the arcing seen at the brushes. He claims the motor won't last long without the choke.

Dazecars video, see 12:00 minutes.

Any thoughts from those in the know about this claim?

D :cool:

P.S. Scooped a working TM last evening on curbside giveaway week. :) I don't yet know if I can graft a PWM driver to the power board so I'm looking at my options.
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My testing with a TM motor and controller is it needs the choke. There is likely one in the TM. Looks like a transformer but only has two leads.

There are just a few common TM motor control boards. What’s the part number on yours?
 
T

Tecnico

(Dave)
whydontu said:
My testing with a TM motor and controller is it needs the choke. There is likely one in the TM. Looks like a transformer but only has two leads.

There are just a few common TM motor control boards. What’s the part number on yours?
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None of the 3 treadmills I have, have chokes. It's my understanding that they were found with older SCR type drives. What makes you say they need a choke?

WRT boards, I have 3, one simple and only needing a pot added, it came with a slider pot, it's not an MC-60 though. The other 2 have digital control from the console. The latest is branded Horizon (China) and is P/N MLH0910PD but it also has MC1310AA01741 on it. That doesn't match up with any of the classic "MC" drives (MC-60 etc) Daze says are "common".

The third is labelled 0304-JI31, DCMD75 and the make is Bremshey, a European make. It does have pins marked S-up and S-down which may indicate speed control. Unfortunately that machine shows a system error and won't run so it's unlikely there's anything to gain by pursuing that angle. I've identified the PWM chip and I suspect it could be bypassed with a stand alone driver module with a nice LCD display which can be had from AliEx for about $7 delivered.

Before anyone gets the wrong impression I'm not skilled in electronic design/troubleshooting so I'm looking for low hanging fruit on getting these motors running. I'm looking to re-power my drill press and a project 42 power hacksaw at some point.

D :cool:
 
whydontu

whydontu

I Tried, It Broke
Premium Member
My TM setup uses an MC60 controller. Without the choke, scope on the motor leads showed a lot of ringing, and there is audible hiss/crackle from the motor brushes. Adding the choke drastically reduced the ringing and noise. I haven’t tried the same testing with a MOSFET controller.
 
T

Tecnico

(Dave)
OK, I'll put that on the list to look at, I'll get to drag out the 'scope and dust it off. :)

I've seen capacitors used to quiet power supplies (including the TM one I have beside me) but is this SRR case different where it's being pulsed?

D :cool:
 
whydontu

whydontu

I Tried, It Broke
Premium Member
Two different ways to get similar results. My understanding is materials science has evolved to develop higher capacitance values in smaller physical mass, while inductors are strictly bound by the physics of copper wire and ferrous cores. Problem is that to get into large inductance values, you need lots of turns, and at 20A current the wire needs to be pretty large gauge. An equivalent capacitor will be much smaller and cheaper, so DC supplies use capacitors. Old-school tube power supplies often used inductive filters since they ran at high voltage but low current, where inductors have an advantage over capacitors.
 
T

Tecnico

(Dave)
A capacitor or two does look like a more easily attainable solution and not especially expensive. The board sitting beside me has two 1000uf @ 200V & 85C on the output and I see similar listed at less than $10.00 each at Digikey. That's much easier than scrounging for something or cobbling up something from a transformer as Dazecars suggests.

Just looking at the board beside me I think the caps are downstream of the rectifier bridge but I think the switching device (driven by the PWM) is downstream of the caps so it may be cleaning up the power supply to the switching device but not the output of the switching section. This brings me back to wondering if capacitors at the output would be applicable. Your thoughts?

Thanks.

D :cool:
 
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