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Forum Index : Electronics : Treadmill motor controllers
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hiya I'm building a new band saw for the workshop. I would like to use the band saw on both timber and metal, so need to run the saw at high speed and low speed. Initially I had planned to use a nice old 1/2hp induction motor, with the usual fan belt type of drive to the bottom wheel. But I do have a couple of DC treadmill motors, in the range of 1hp to 3hp. So, having never used a treadmill motor before, I'm not sure on the best approach to drive it. I do have a motor controller for one of the motors, but it needs a PMW input to run and its old, the circuit board shows signs of corrosion. I've seen Youtube videos where a standard $20 triac AC controller ( like for varying the speed of a universal motor ) is combined with a bridge rectifier to control the speed of a DC treadmill motor. I wonder how well this works, its certainly cheaper than a "proper" DC motor controller for that sort of voltage. Has anyone played around with this sort of thing? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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renewableMark Guru  Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
I run a dc pump with something similar to this What Amps/volts would you need? Cheers Caveman Mark Off grid eastern Melb |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Glenn, I built my own bandsaw more than 20 years ago and its still running fine. Its using just an old 1/2Hp washing machine motor (2 speed) and I also fitted a 2 speed pulley reduction. At the slowest speed that thing will cut 12mm steel plate. Variable speed might be fine but not really necessary, as is a high power motor. If you are interested, I can take a few pics of the dusty monster. Mine is a 3 wheeler, that gives me a much bigger throat (I can cut 600x300mm foam for example)plus a 3m+ long blade which runs a lot cooler with metal. The wheels are home made too - of hard wood! One of the most useful things I ever built for my workshop. Klaus |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Treadmill motor sounds pretty cool. Any idea of their speed range (m/s) & what diameter rollers they use? Also, what sort of band speeds to the saws generally run at? Only know saw chain gets up around 18-20m/s. (Lol, and I've heard Salesmen quote 120km/h...). |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I'll post the DC motor figures tomorrow Phil. A controller for the DC motors would need to run off the 240vac mains, and output 50 to 250 volts at a wild guess Mark. I did have to replace a SCR in the motor controller for my little lathe a couple of months ago, and I thought the circuit was clever. It use 2 diodes and 2 SCR's wired as a bridge rectifier. Control was smooth and linear. I guess PWM would be the best option thought for a DC motor. Tinker I'll take some photos of mine over the next week as I build it. It uses 2 14 inch wheels made from 24mm MDF on a steel frame. I do have a small Ryobi band saw, very handy, but it keeps breaking blades due to the small wheels. I'm building this think based on what I could find in my junk pile. The 1/2hp motor is a nice looking 1950's Ozy made unit, will post a picture. I pulled it apart a few weeks ago, replaced a few wires, oiled it up and painted, looks the job. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Hi Gizmo, Many years ago when I was setting my workshop off the grid I was using a 15Kva Onan gas fired genset and running 3 phase motors. I was lucky enough to secure some VFD's and worked with a guru who could program these to get the best performance out of them. The first project was my Bridgeport mill where I fitted a new 2hp 3 phase motor wired in delta and programmed the vfd with the parameters to get the most out of the 2hp. Set the VFD to 100Hz so I could get double the speed and with a 3 wire control system, a 5K pot gives the speed control then one toggle switch is forward/reverse. Another toggle switch is ramp/coast so the spindle can stop straight away or just coast to a stop. Next was my old 4' flat bed lathe again with a 2hp 3 phase motor and 3 wire setup. Now when machining if one starts to get chatter changing the Hz soon overcomes the problem making machining that much more easier. My German toolroom lathe was already fitted with a 3/4 HP 3 phase motor so a smaller vfd was used. When machining under 1/2" the extra speed from the 100Hz available gets the speed needed for those fine accurate cuts needed. I scored a VFD from a scrap yard and fitted that to a 3 phase blower fan I got from the flour mill so now I can go from from a gentle breeze to a gale force wind in a 4" extendable tube perfect for a oil burner. I do have 1/2hp VFD and a 1/2hp 2 pole 3 phase motor to use on my surface grinder project and a spare 3hp VFD to use for other work around the shop. VFD's aren't cheap to buy new but they can found at scrapyards cheaply and 3 phase motors can be found for peanuts. I run everything of that 3Kw sinewave inverter I bought in '05 and now if I need even more grunt I can use my 16hp Listeroid Diesel with the 5Kw genhead. Regards Bryan |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I did look at VFD's. Bit more than my budget, but I would like to play around with one one day. This is the old induction motor.  It's a Crompton Pankinson, Australia made ( back when we made stuff ), 1/2hp 1435rpm motor. This is probably the easiest, most reliable and better looking option for the band saw. I have 3 DC motors. A 180v 1.25hp 4000rpm, a 130v 2.5hp 6700rpm, and a 220v 3hp 3400rpm. I found this circuit, looks similar to the circuit used to control my lathe DC motor.  Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
It would be possible to build a variable speed inverter just using the Ozinverter and making use of the variable frequency capability of the EG8010 chip. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Gizmo Check if that motor has a centrifugal start switch or is it capacitor start? Had one of those motors on the cement mixer and the centrifugal start switch failed at times and would stall the generator, could be a pain. Cheers Aaron Cheers Aaron Off The Grid |
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