I've built a chain drive with a 24V DC motor salvaged from a mobility scooter to raise and lower my milling machine head. Specs on the motor are unavailable, but I'm guessing 1/2 HP based on the horsepower resistor on the speed controller PCB.

This is not for CNC (never!) and I planned to power the motor with a re-purposed Meanwell SP-500-24 power supply...500 watt / 20A

I'm not an electronics guy...more of a Rube Goldberg, actually...so I'm soliciting advice on what I need to do to make sure the motor will start under load (the weight of the milling head) and not burn up the supply or anything else.

Also have a question about using a diode on the power feed. Since the motor will be reversed using a DPDT relay, I'm not sure if a diode is necessary and if so, where to install it.

Thanks for any help you all feel like offering.

 

I never use a SMPS for motor control, if I can help it, the simple power transformer and large bridge rectifier would be better IMO.
Do you intend any RPM control? If so what is the controller type?
The diode is used across the coil and reverse biased, diode striped end to +ve.
Max.

 

I was planning on using the PWM controller that was used with the motor in the scooter, however I do not necessarily need variable speed once I determine the speed the motor should run with 3:1 ratio sprockets and the built-in reduction of the lead screw and manual crank gearing.

Using a transformer and rectifier would be great (and preferred), but the size of the transformer required might be an issue. However, being rather limited in my understanding of sizing transformers, my guess is that it would require 2300VA. One that size is A: more expensive than a factory lift kit for the mill head, and B: not something I have in my basement inventory.

Then again, I'm not sure if my calculation of the VA rating is correct.

Thanks!

 

For what its worth, here's what I was planning on using:

Motor: CTM #PV2R040R

CONTROLLER: IPC AUTOMATION #910-3522-008

AC/DC SUPPLY: MEANWELL SP-500-24

 

You might get away with it with that controller as you have a certain amount of control and current limit.
Although a bit late for you, the popular way is to use an ex treadmill motor and controller, these run direct from the AC supply so no separate power supply or transformer needed.
Max.

 

I have a few 90v treadmill motors and controllers, but the treadmill motors are rather large, physically. Since the 24v motor I have is pretty compact, and I don't need the torque or speed of the 90V motors, I went with the 24v.

I'll give it a try, and use some 15A DC breakers I have to protect everything. I'll measure the current as I go.

Thanks

 

Success. I just connected the motor to the power supply with spring loaded DPDT switch and it works like a champ. No speed control. Motor only pulls @ 3 amps under full load, which surprises me.

I may need to slow it down a little, and put couple limit switches on the mill column, but I can do that easy enough with stuff I have laying around.

Thanks for your help.

 

Motor only pulls @ 3 amps under full load, which surprises me.

Probably due to the gearing involved, gearing down to slow speed also has the added advantage of increasing torque and dropping load on the motor.

 

Probably due to the gearing involved, gearing down to slow speed also has the added advantage of increasing torque and dropping load on the motor.

Yes indeed.

Now that I know it works, I'll be swapping out the chain and sprockets with a 5M timing belt and pulleys...where I'll calculate the ratio needed to get the speed right...and not worry with a speed controller at all.

 

Yes indeed.

Now that I know it works, I'll be swapping out the chain and sprockets with a 5M timing belt and pulleys...where I'll calculate the ratio needed to get the speed right...and not worry with a speed controller at all.

@Imbecile
You can place a diode/rectifier across the 24V power supply output, but not across the motor as you will be reversing polarity/direction. A better approach if you wish to minimize arcing at your switch would be to use an appropriately sized bipolar TVS (transient voltage suppressor) device across the motor terminals.