Proposed Circuit For Treadmill PS and Speed Control ----> Need Help Refining Ckt.

Thread Starter

rmartini

Joined Dec 4, 2016
27
Proposed Circuit For Treadmill PS and Speed Control ----> Need Help Refining Ckt.

I would like to build a power supply and speed controller for a typical 0 to 130vdc treadmill motor.

I have found and complied the following schematics into the final circuit I would like to build.
Attached is a PDF file of this schematic

I am capable of designing, printing and etching my own PCB's.
My over-all knowledge in electrons is limited. I have a very good understanding on electronics.
I mainly build per-designed and proven circuits.
I understand all the components in my design and how they work.
What I am lacking is the skill to refine this design, add to, add enhancements , delete from, or substitute components. Would also be nice to know if I made any mistakes here in actual design and/or concept.

I would be very appreciative if someone could take a look at this schematic and comment on it.
This is basically three schematics complied into one. There is a simple and basic bridge rectifier, a simple 555 based PWN control, and a simple low voltage section. The low voltage section is actually copied from All About Circuits it is a schematic of a MC-60 treadmill controller prepared by Tom Rollins ("trolley1").

Again, please take a look and feel free to offer any suggestions.

Thanks

NOTE: I have revised the Schematic and it is to be found in a later thread.

15 Dec 2016
Latest schematic shown on post # 39
 

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MaxHeadRoom

Joined Jul 18, 2013
21,412
That is a typical 555, PWM, but what kind of Power tool? As if this is for a tool spindle you may be dissatisfied with the results.
Max.
 

Thread Starter

rmartini

Joined Dec 4, 2016
27
Max,

This would be used on a drill press or a small milling machine, replacing the standard AC motor.
As you may know, these motors are frequently re-purposed for those uses.

Not sure I understand what you mean by, "tool spindle"
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Thread Starter

rmartini

Joined Dec 4, 2016
27
Thanks for your reply. I do appreciate your input.
The basics of type of motor for use on certain type of machines is not what this thread was started for.

Regarding your comments in motor shaft. and pulleys. There are several options I've found. These motors all seem to have a 17mm shaft. Threaded on the end for a flywheel and serpentine type belt, which would not be used. 17mm pulleys can be found and there is also the possibility of using a bushing on the 17mm shaft and fitting that with a 3/4" pulley. And yes... I do understand the need to utilize different gear ratios via stepped pulleys as used on the machine with the original AC motor. Have not yet worked out gear ratios, that would come later. And no.. this would not be used to directly drive a cutting tool. As in... "tool spindlel".

I thought this forum and thread was to help on circuit design and not on the use of a particular motor for a particular end use.

I'm hoping to have someone address my questions as I asked in my original post.
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Alec_t

Joined Sep 17, 2013
11,641
What is the stall current of your motor? The IRFP250 is rated for 19A at Tc=100C, but may be unhappy with the start-up (stall) surge current.
 

Thread Starter

rmartini

Joined Dec 4, 2016
27
Robert,

I did thank you for your input and mentioned that I did appreciate your knowledge.
I think I understand your need to talk about the final use for a particular type of motor.
No doubt you have knowledge in that area. These motors are used successfully for my intended purposes. The problem is finding or building a controller that is better suited for the end use. The Treadmill controller is designed to be just that, a treadmill controller. I have looked for a prebuilt solution, Problem is if they can be found they are expensive.

I posted this thread to address my questions regarding my proposed circuit.
So far, I have not received any comments that address my original questions.
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AnalogKid

Joined Aug 1, 2013
8,590
The 555 block circuit shows the motor connected to the +12 V supply. Is this correct, or an error. Based on the rest of the schematic, shouldn't this motor be connected to the high voltage source?

The main circuit GND, to the right of the DC motor, is incorrect. This point should be connected to the MOSFET source, the bottom end of the bulk capacitors.

ak
 

Thread Starter

rmartini

Joined Dec 4, 2016
27
What is the stall current of your motor? The IRFP250 is rated for 19A at Tc=100C, but may be unhappy with the start-up (stall) surge current.
Thank You Alec,

Not sure of the stall current of the motor. Motor spesc are as shown from the label on the motor. The IRFP250 was the exact same MOSFET as used on the original treadmill controller. Could easily factor in a higher rated FET. It seems that the specs I read for the FET rated it at 200V 30 amps. Coud be wrong here. The bridge ckt and my diode across the motor are higher rated than that of the original ckt.

This motor for my use would be for a small bench top drill press. Used for drilling and light occasional milling operations. Starting under a heavy load would not be a normal situation. Stalling the motor with a heavy would
most likely not occur. Although, not entirely impossible..

Looking at my schematic. I'm not sure if the ground connection I have between R9 and D9. Is that correct?
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Thread Starter

rmartini

Joined Dec 4, 2016
27
The 555 block circuit shows the motor connected to the +12 V supply. Is this correct, or an error. Based on the rest of the schematic, shouldn't this motor be connected to the high voltage source?

The main circuit GND, to the right of the DC motor, is incorrect. This point should be connected to the MOSFET source, the bottom end of the bulk capacitors.

ak
I should have omitted the motor and mosfet connections in that inset showing the PWM circuit. The output from the 555 would be connected to the FET as shown on the main schematic.

So if I understand you correctly.... the ground I show to the right of the motor should actually be placed between the filter caps and the source of the FET.

I also question my placement in the low voltage ckt where I have a ground connection between the R9 and D9.

If my understandings are correct let me know and I will revise and repost my schematic.

Thanks very much.
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MaxHeadRoom

Joined Jul 18, 2013
21,412
Max,

This would be used on a drill press or a small milling machine, replacing the standard AC motor.
As you may know, these motors are frequently re-purposed for those uses.

Not sure I understand what you mean by, "tool spindle"
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If for a drill press the DC T.M. motors work fine.
And yes the original circuit will work, but you do not have the refinements that the T.M. or KB type controllers have in the way of current limit, acceleration control etc.
For many decades, DC motors operated fine as tool spindle motors, they were replaced due to the cost of maintaining, brushes etc.
Max.
 

Thread Starter

rmartini

Joined Dec 4, 2016
27
If for a drill press the DC T.M. motors work fine.
And yes the original circuit will work, but you do not have the refinements that the T.M. or KB type controllers have in the way of current limit, acceleration control etc.
For many decades, DC motors operated fine as tool spindle motors, they were replaced due to the cost of maintaining, brushes etc.
Max.
Max.

Thanks once again. The reasoning for my design is to end up with a very simple and basic controller.
I mentioned previously that the original TM controllers have many features not necessarily need or wanted in my proposed application.

If you feel that I might need to incorporate certain "refinements", then please let me know, That is exactly my intent of starting this thread.
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Thread Starter

rmartini

Joined Dec 4, 2016
27
Up-Dated & Corrected Schematic Posted

Because of the comments made by AnalogKid I have revised my Schematic and it is posted here.

NOTE: The Schematic has been further revised. See Post #27
 

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Thread Starter

rmartini

Joined Dec 4, 2016
27
Max, You wrote:
"Never quite seen that configuration of the Mosfet in series with the bridge before?"

Well MAX not sure what you mean here. That part of my circuit was cut and pasted from another schematic. Not saying that was correct.
Actually, it mirrors the same way the MC-70 controller is designed. That is why I incorporated that into my design.

If it is in error then that is what I am wanting to know here.
What would you suggest?
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MaxHeadRoom

Joined Jul 18, 2013
21,412
The diagram I posted is the customary way, it shows a 6v supply but the same configuration as the one I tend to use, with the Mosfet between the motor and -ve common.
The same as the circuit you have in the inset in post #1.
I see you have revised it, The way you had It will not work, do you have the schematic for the MC-70?
Max.
 
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Thread Starter

rmartini

Joined Dec 4, 2016
27
Ok Max,

So you think so far my revisions are correct?

No I do not have the schematic for the MC-70. I have the PS. Which was not working when I got it.
I managed to get the high and low voltage sections working again but was not able to repair the logic section.
To many SMD IC's which I suspect are a problem. I can run the motor with the MC-70 by manually controlling the FET. I posted to another thread here regarding a separate DC motor PWM pre-built control. I have not tried that approach yet because I am waiting on replacement MOSFET's. I blew the one I had on the MC-70.

If I had the actual Schematic for the MC-70 I would have posted it here.

Regarding the MC-70.... I don't think I have ever seen anyone wire-up and use one of those controls as they do with the MC-60's Since the MC-70 is one step below a MC-2100 perhaps it is closer to the later design. I think that there might be more logic passing between the MC-70 and the main board from the control panel. The LWH lines between the two boards are the only route for any logic between the two boards. In other words I'm not certain if my MC-70 worked as it should I would be able to control the motor speed by connecting a pot to the LWH connector.
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AnalogKid

Joined Aug 1, 2013
8,590
D3 and D4 are directly in parallel with the top half of the bridge and serve no function. Delete them.
Connect the left side of R9 to the big + sign.
Delete D9. Connect R9 directly to D10. Delete that GND connection.
Add a 470 uF 25 V cap in parallel with C2. This filters the rectified AC.
Calculate the peak current through zener D10 and compare that to the data sheet.
Calculate the power dissipation in R9. Use a resistor with at least twice that power rating.

AND - this thread violates the terms of service for this site.

ak
 

Thread Starter

rmartini

Joined Dec 4, 2016
27
D3 and D4 are directly in parallel with the top half of the bridge and serve no function. Delete them.
Connect the left side of R9 to the big + sign.
Delete D9. Connect R9 directly to D10. Delete that GND connection.
Add a 470 uF 25 V cap in parallel with C2. This filters the rectified AC.
Calculate the peak current through zener D10 and compare that to the data sheet.
Calculate the power dissipation in R9. Use a resistor with at least twice that power rating.

AND - this thread violates the terms of service for this site.

ak
Again thanks AnalogKid.

I will look at the changes you suggest although I do think I have a question or two for you before I repost the up-dated schematic. Not clear on exactly what you are suggesting I change on a couple of connection points. I'll get back to you tomorrow after I have a chance to take a serious look and trying to fully understand your changes.

Please explain what you mean about how, "this thread violates the terms of service for this site."
 
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