Power tools such as Metal cutting mills and lathes, Drill presses, bandsaws, sanders and more may require .5HP to 2HP motors with the ability to fine tune the speed while maintaining torque.
Coincidentally most Treadmills use a 80-260 VDC motor with a suitable HP rating and a PWM motor speed controller to allow the user to change the belt speed and keep a good constant speed and torque while running on it.
There are Commercial DC Motor/PWM controllers available or you can build the PWM circuit from scratch and buy all the components seperately but you will spend a lot of time and money either way. All the parts you need are on the treadmill.
Tear your own apart or get one on Ebay.
(shameless self-promotion below)
Motor/controller combos on Ebay
Safety and Disclaimers- You should have some knowledge of electricity and the dangers of household current and know your abilities/inabilities. Serious injury may occur to you or others from use/misuse of these motor set-up. If you are in doubt DO NOT ATTEMPT. IT CAN KILL YOU. Any Crazy Ideas found here REQUIRE your testing. Your appliction and use of any ideas here are all on you and you agree I cannot be held liable. You equipment should have On/Off safety switches, Fuse protection, ground wires on your machine as required and your power source should have ground fault interupters, circuit breakers,properly grounded sockets and cords and always unplug equipment before tinkering and any other safety practise I am forgetting to mention.
Step 1: Motor Vid
Testing the motor/controller
Step 2: The PWM Circuit Board
For a complicated description of a treadmill PWM (Pulse-Width-Modulation) controller you can visit
You can visit wikipedia for a better definition of PWM.
But basically (as best I can understand) it's an efficient speed controlling circuit that pulses the Voltage and the width of the signal to the motor off and on thousands of times per second. This transfers more power to the load and wastes less power to heat than a resistive type speed controller.
PWM style controller Trim Pots- located near one of the edges of the board.Each Set for specific motor
MIN (Minimum speed-Touch if you dare) adjusting MIN Trimpot may affect MAX, may be necessary to adjust both until desired levels are achieved
MAX (Maximum speed-Touch if you dare) Note that MAX adjustment may affect MIN
IR COMP (Inrush compensation-Don't touch)Improves load regulation by providing minimal speed fluctuation due to changing loads. If the load presented to the motor does not vary substantially,the IR adjustment set at a minimum level. Excessive IR comp will cause control to become
unstable causing motor cogging.
CL (Current Limiting-Don't touch)The CL Trimpot sets the current which limits the maximum current to the motor. Also limits the AC line inrush current to a safe level during startup.
ACCEL (Acceleration Time Period, 0-full speed in seconds)I've never seen one on a treadmill circuit card, only on commercial PWM DC motor controllers. There must be something on the treadmill board that sets the time value..resistor perhaps?
Step 3: The Speed Pot
PWM circuits uses a Pot (Potentiometer)to adjust the speed from 0 RPM to Max RPM . The Potentiometer can be of the rotary type or linear sliding type. The potentiometer is usually rated 5 or 10K Ohms. Typically 0 Ohms is no movement and 10K Ohms is full speed (unless you have your Pot High and Low wires swapped...then it's visa versa). Keep in mind the motor may not even begin moving till 2 or 3 K Ohms (actual value varies) and you can't really start the pot at 2 or 3K Ohm position either because the treadmill motor controller requires 0 Ohms on start-up (Kind of annoying).
The Pot talks to the circuit board through 3 terminals usually marked High,Wiper and Low (or H,W,L).
Some controllers use a digital console to change the motor speed. You dont want to scroll through programmable selections, excercise routines and heart beat monitors just to change the motor speed on your lathe.
Solution: Throw it away and replace it with an appropriate Pot(usually 5 or 10K Ohm Pot). The digital console interfaces the PWM Circuit board the same way that The speed Pot does. through those 3 terminals (on some marked G O H or L W H and colored black, white and red or S1,S2,S3, colored Blue, Grey, Orange.
You should also use a switch for ON and OFF. The Pot is for speed control once the machine is running.
Step 4: Types of Treadmill Motors
I have seen 3 types of motors.
DC Permanent Magnet with PWM controller (Great for torque at all speeds).2 wires to the motor (Usually).
DC motor with Armature-voltage DC Motor Control. (Great for torque at all speeds).4 wires to the motor. 2 run to the shunt-field current , 2 run to the armature. Vary the voltage applied to the armature, vary the speed. Not all 4 wire motors are Armature Voltage controlled. Some have 2 wires that are part of a thermal protective circuit. The ones I have seen are usually both blue.
AC motors. (Probably not any better than the AC motor your'e thinking of replacing).Motors are running at a constant. Incorporates a special sliding pulley.Changing the belt speed is done manually-controlled with a cable that changes the size of the pulley's diameter. Larger motor pulley diameter faster belt speed, smaller pulley slower belt speed (I think).
The DC motors vary in size but most are Permanent Magnet,have brushes, a flywheel,and have either tapped holes or a bracket or flange welded to the case for mouting. They typically can range from 80-120VDC but as high as 260VDC. The HP's 1/2 to 3.5HP (treadmill duty rating), Upper end RPM 2500-6000, 5-20 Amps.
The Max RPM isn't as critical when you can adjust to any RPM within the range and keep a near constant torque.
You can reverse the direction on the DC motors by reversing the polarity. Simply swap the 2 motor wires (usually Black & White or Black & Red)at the terminals on the PWM circuit card. Remember if you reverse the direction of the motor you can't use the flywheel as it is. Because of left hand threads it could come off. Drill tap and set-screw the flywheel to the shaft
Step 5: Drive Pulleys and Belts
Most treadmill motor flywheels serve also as the pulley. They fit a fancy flat belt with 5-10 "v" grooves. The driven pulley that mates with this belt originally drove the large roller that the treadmill belt rode on. Reusing the plastic roller pulley is near impossible. Very few motors actually come with the common Automotive 4L style belt pulley. Solution: Remove flywheel and replace with normal V-belt pulley. *If the flywheel you take off had fins for cooling the motor, replace it with either a blade mounted to the shaft or an externally powered fan*
Taking the flywheel off can be a pain. The flywheel are left-hand 4m thread and can really be cinched down or corroded onto the shaft. Chuck the flywheel end in a vise and turn the shaft on the opposing end Clock-wise and the flywheel may come off.
Some Motors don't have 2 shafts. The shaft on the brush side is usually hidden under the bearing housing. For the stubborn or single shaft motors I use a hacksaw and run the motor on low speed and use it like a metal lathe and saw the pulley through once or twice. It always comes off easily when you turn the nut into 3 thinner nuts rather than one wide nut. Just make sure you don't cut into the motor shaft. Eyeball it close and then test it by turning it with a pair of vise grips until you are through the threaded portion.
Or.... If you don't mind the flywheel...
You can use the motor(at a very low speed) as a metal lathe and carve a suitable groove to fit the belt of your choice. It can be a bit tricky (dangerous) as your cutting tool is not fixed. ** USE eye protection, gloves, faceshield etc.**
A rat tail file will work for a round belt or a small bastard file can carve a v shaped groove for the common automotive style belt.
Remember again- If you reverse the direction of the motor you can't use the flywheel as it is. Because of left hand threads it could come off. Drill tap and set-screw it.
Step 6: More Idiosyncrasies
There are some small but solveable problems using these set-ups. I think a lot of these issues could be fixed with trim pot settings but the exact amount of adjustment and the values for each vary too much, are vague and unpublished or unknown to the average person. If you come up with better solutions PLEASE let me know so I can update them.
problem 1) Treadmill motors have a 3-4 pound fywheel. Engineers calculate the energy stored by spinning this heavy flywheel to obtain Horsepower ratings referred to as "Treadmill Duty Horsepower". Any quick changes in speed aren't noticed because of the kinetic energy still stored in the flywheel. Sometimes you can hear the motor totally turn off till the flywheel spools down and balances the motors RPM with the respective setting on the rheostat. If the load is restored or the speed setting raised above the motor's present speed, the motor turns right back on. Solution: remove the flywheel. Some of that kinetic energy will be stored in the piece of equipment you are powering but if not then some horsepower could be lost.
problem 2) When starting up a treadmill you wouldn't want it to start up at full speed while you are on it. If the rheostat is not set to the lower end of the resistance value the circuit will not start. Now you have the Motor/controller combo on your drill press or mill and it won't start because the rheostat is not set in the start position.
Solution: Turn the rheostat to the start position before turning on.
Step 7: My Treadmill Powered Tools
This is my Drill press converted to a mill. I got it at the junkyard for $10. It had a bad AC motor. The Crossfeed table is from Enco and the new motor is off of a treadmill also from the junkyard. The motor and belts drive it just like the original motor did. It drills and mills fine. The treadmill motor mount was identical to the original AC motor mount. I experimented with the original 2 belts but quickly got rid of the extra belt and step pulley and went with one belt. There was no need for moving belts up and down the step pulley anymore. The motor keeps good torque at all speeds.
[http://www.faireandfoundry.com//robs%20hobbies/treadmill_tools.html My Treadmill powered Mill/Drill]
(Future pics of Sewing machine mod will be here)
The machine is the 1940 style heavy duty leather machine and had its own 4 ft bench and a 50 LB friction clutch motor hooked up to a treadle. The machine and bench just would not fit in my garage. am fitting it with one of these set-ups and have tested it enough to know it will work. The foot control is off of a newer sewing machine that used an AC motor speed control circuit also utilizing a Pot. I tore out the rest of the circuit and replaced the Pot with the 10K Ohm Pot my treadmill motor speed control needed. Now I can operate the sewing machine in my living room like a normal portable machine. It has as much torque as the original clutch motor and will sew right up your arm.
Step 8: Motor Mount Styles
This is 4 of the styles I have found. All pictured are DC motors. All except the last one are the permanent magnet type. The lower left motor image has a mount almost identical to the mounts on the AC motors found on drillpresses and such.
Step 9: Foot Speed Control
This is a sewing machine foot control that I modified to run a motor set-up I plan on powering an old industrial sewing machine with. The circuit inside was originally for controlling an AC motor so it is only good for mounting your potentiometer. Remove all the circuitry of the original controller (i.e. resistors, pot SCR's and such)and mount your speed Pot. It takes some adjustment of the placement but it can be done. I can now control the treadmill motor with my foot from a few RPM to full 4000 RPM.
Step 10: Schematics/Pics
This is some Schematics and Pics I have collected. Most Treadmills have one taped to the plastic belly panel. If you have a schematic you would like to contribute email me. The PDF's download very slow but the detail is worth the wait so be patient. Just right click it and open in another window and check out the rest of the instructable while it downloads.
Step 11: Reader Submitted Contraptions
Ball Pitching Machinehttp://www.youtube.com/watch?v=oEUYII-SYGg
Participated in the
Burning Questions: Round 5