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| Mystery motor - how to measure? |
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| loply:
Hi folks, I just picked this motor up at a boot sale, the seller reckons it's came from one of those kids motorised scooters, where apparently it was running off 12v DC. I want to use it on a project I've been working on to motorise the leadscrew on my lathe w/ a PWM controller. I had been thinking about this for a while but didn't have a chunky enough motor. I kinda thought a small one from China off eBay would do if it was geared down to 60rpm or so, but I'm concerned it will result in variable leadscrew speed if there's a lack of torque, so this big one is more reassuring! Excuse my complete ignorance but I'm not sure if voltage even matters? Are DC motors designed for a specific voltage or will it run fine on a range? Secondly, for measuring the current I was thinking about hooking it up to a big 12v motorbike battery that I have handy. I presume the battery will be able to supply whatever current the motor requires, and then I can measure the current it's drawing so I'll know what size power supply I need to buy? And lastly! Any suggestions about how I can find out the RPM? Is the only way with a tacho of some kind? Cheers, Rich |
| John Rudd:
--- Quote from: loply on September 11, 2011, 07:52:38 AM ---Hi folks, I just picked this motor up at a boot sale, the seller reckons it's came from one of those kids motorised scooters, where apparently it was running off 12v DC. Excuse my complete ignorance but I'm not sure if voltage even matters? Are DC motors designed for a specific voltage or will it run fine on a range? Secondly, for measuring the current I was thinking about hooking it up to a big 12v motorbike battery that I have handy. I presume the battery will be able to supply whatever current the motor requires, and then I can measure the current it's drawing so I'll know what size power supply I need to buy? And lastly! Any suggestions about how I can find out the RPM? Is the only way with a tacho of some kind? Cheers, Rich --- End quote --- I assume this is a permanent mag motor? The torque it develops is a function of voltage..What voltage range were you thinking of? The current the motor draws depends on the load you place on the motor. Shaft speed could be measured with a tacho.. |
| loply:
I guess it's a permanent mag motor, it has two wires and feels like any other DC motor I've dealt with when you twiddle the shaft :clap: I was thinking of running it on 12-18v depending on the current required. I have a few little 12v DC adapters lying around but mostly they only give out around 1-1.5a... I don't know if this is enough? If not then I was planning on buying a laptop power charger which can be had up to 4/5a but are usually 15v or 18v... I don't know if this voltage would be too high for the motor since it allegedly was ran at 12v in it's OEM life? |
| nearnexus:
Try running it off of a 12 volt car battery charger, if you have one that puts out about 5 amps or more. Depending on resistance, A higher voltage will probably create more heat. You can run some motors at a higher voltage - eg early 6 volt VW beetle starter motors can be run from 12 volt when people converted the system to the higher voltage. To measure the RPM you will need a laser or mechanical tachometer. |
| dickda1:
Laser tachometers are very cheap and easy to use. Hate to keep posting ebay stuff, but this is what it looks like: http://www.ebay.com/itm/New-Digital-Laser-Photo-Tachometer-Non-Contact-RPM-Tach-/130550327907?pt=LH_DefaultDomain_0&hash=item1e6567ea63#ht_1501wt_1002 -Dick |
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