Need Help!- Testing Motor

[mahkeymike]

Im new to CNCz, so I'll start off by saying hello everyone.
Now i'll explain my situation...

I bought a DC right angle gearmotor off ebay that i should recieve on monday.I have 7 days to return if its defective, but im tight on cash this month, and i have no way of testing it.I plan to buy a KB Electronic KBWS-15 speed controller as soon as i get my income tax refund, but thats a few weeks away.
Im looking to build something cheap to atleast test it to make sure it works, and also beable to adjust the speed.I know i wont get very accurate results with a simple cheap circuit, but im fine with that.
The problem im having is i found ways to build a simple cheap speed controller, but the information i found was pretty vague.
One way was to use a cheap router speed controller.And another was to use a Rotary fully variable 5A-120V AC fan speed controller with a Bridge rectifier, and a Capacitor to smooth the voltage.Problem with that idea is that it says to use a 25A/600V rectifier, which i can not find locally, and also did not specify what uF/Volt Capacitor to use.Here are the specs of the Motor:
Bodine 4535 42A5BEPM-5N
130VDC
1/4 HP
FF 1.0
RPM 250
1.8A
42 LB-in
10:1 Ratio
Duty CONT

Thats about all i know about the motor.I found a 15A router speed controller, and a Rotary fully variable 5A-120V AC fan speed controller, but the largest rectifiers i could find are as follows: 8A 600V half wave(KBU805) and Full wave 4A/400V, 6A/200V, and 25A/50V. Would it be possible to use multiple rectifiers in either series, or parallel to achieve 25A/600V? Or would any of those i mentioned be sufficient with the motor specs i listed?As far as the capacitor needed, i found some 680uF/200V caps i got out of an old power supply, but yet again im not sure if those are also sufficient.

Sorry for the long post, any help would be greatly appreciated.

Mike

[Al_The_Man]

What are you using it to control? As 250rpm is a bit limiting.
You could just use a bridge across the 120vac to test at near max speed.
You would not need the cap to test it.
You could use either the 4A/400v or 6A/600v and fuse it accordingly.
A Triac (AC) type controller would probably work into the bridge for some kind of control until you get the KB.
Al.

[mahkeymike]

Originally Posted by Al_The_Man What are you using it to control? As 250rpm is a bit limiting. You could just use a bridge across the 120vac to test at near max speed. You would not need the cap to test it. You could use either the 4A/400v or 6A/600v and fuse it accordingly. A Triac (AC) type controller would probably work into the bridge for some kind of control until you get the KB. Al.

Well the project im working on only calls for a motor to run between 100-200 rpm max with 30+ lb-in of torque.I believe im well within that range with this motor.My only real concern right now is that when it arrives tomorrow, i can test it "safely" before the 7 day return policy expires.Eventually i do want to get a more accurate speed controller like a KB, but it would be nice to beable to also test how the motor operates the mechanics (flywheel,drive arms,linear shaft..ect) at different rpms.Incase i need to make any adjustments before i get a KB speed controller.

I was just confused about the bridge rectifier because every place i found information on running a 130vdc motor from a 110-120vac source, says to use a 25A/600V bridge rectifier.I wasnt sure if that was a minimum requirement, or a "just to be safe" requirement.

But what do you mean by "fuse it accordingly"?Are you saying i should for example,put a inline 6A fuse between a 6A/200V rectifier and the motor?Or a fuse closer to the motors rated Amps?

Sorry to sound like such a newb, Im actually pretty good with electronics,i just never worked with any electronics needing more then 12vdc.

Its just scary knowing this much current can kill you, ya know?

[Al_The_Man]

If it is just to test the motor and you do not really require speed control, the bridge across the supply should work.
Often a larger capacity bridge is spec'd in just because the price difference across the range is very little, so it does not cost that much to build in overkill.
I noticed you show a KB PWM drive, I would think the SCR type may be cheaper for this application, it does not require a Bridge or power supply etc.
I suggested the fusing because if all you want to do is test the motor the fuse will blow before damage to the motor or bridge, in the case of anything being wrong in the motor.
Al.

[mahkeymike]

Originally Posted by Al_The_Man If it is just to test the motor and you do not really require speed control, the bridge across the supply should work. Often a larger capacity bridge is spec'd in just because the price difference across the range is very little, so it does not cost that much to build in overkill. I noticed you show a KB PWM drive, I would think the SCR type may be cheaper for this application, it does not require a Bridge or power supply etc. I suggested the fusing because if all you want to do is test the motor the fuse will blow before damage to the motor or bridge, in the case of anything being wrong in the motor. Al.

Yeah accurate speed control isnt crucial.But audiable noise will be.From all the research ive done, the KB speed controller i mentioned, claims to reduce audiable motor noise.Until i test the motor, i really wont know how loud it will be @ 200 rpm.If its acceptible with this cheap way of controlling the speed, i may not even bother getting a KB.Im just concerned about noise,and burning the motor out.

So what amp fuse do you suggest?

[Al_The_Man]

I have never really been bothered by the SCR switching noise, it is not that bad, especially on a motor your size.
It is more like a kind of purr, and not really anymore than an induction motor with a fan.
I use PWM BLDC servo motors and they have a habit of really whining especially at the lower rpm.
Go with a 5amp slo-blo fuse, tops.
Al.

[vger]

One quick low speed test could be done with 12V from your car battery.

Steve

[keebler303]

A car battery should work fine to see if it is functional. You could also just put one diode inline with the 120 AC and run it from that. It will not be terribly nice, but should get the motor running without hurting anything. That will give you half wave rectification and somewhere around 60 VDC applied.

Matt

[mahkeymike]

I drove 30 miles to get a 25A/600V full wave rectifier and 10uF 250V capacitor today...lol

Tommorow i'll solder everything together and post back the results.

Thanks for all the your input everyone.

[mahkeymike]

Well the motor works, and is pretty quiet even @ 130v , but if i adjust the knob on the fan speed control to below 90v it becomes really jumpy.I think my only option is to buy a speed controller.Kinda sucks because i really dont need accurate speed control, but if i want to go from say 100 rpm's to 150 rpm's to 200 rpm's, i want the transition to be smoother.