230V DC (sorry, not AC) motor speed control - looking for simple circuit - Page 1
Forum section: electronics / general

author: Yellofriend
author_rank: Regular Contributor
timestamp: July 19, 2019, 04:01:26 am
content: I am looking for a simple circuit for to speed control a 230V AC motor.Motor power is about 10WI saw those really cheap 2000W controller on Aliexpress etc. for a few $, but question is if they can handle very low loads?What controls the speed anyway? Frequency or voltage? Currently there are 2 switch positions, full power to the rectifier, then to the motor, and half power with one extra diode inbetween.Anybody has any information, or a useful link?

author: Brumby
author_rank: Unknown
timestamp: July 19, 2019, 04:37:06 am
content: There are a number of different types of AC motor.If you want relevant suggestions, then I would suggest providing some specific details - such as the normal usage of such a motor as well as specifications, if available, and include photos of the motor and any information plates or stickers. (Please make sure photos are clear and appropriately sized.)

author: soldar
author_rank: Super Contributor
timestamp: July 19, 2019, 09:45:30 am
content: Motor power is about 10W. There is a good chance it is a shaded pole motor in which case voltage controls speed.Quote from: Yellofriend on July 19, 2019, 04:01:26 amThat makes no sense to me.Better give us more info on the motor.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 19, 2019, 02:25:17 pm
content: Quote from: Yellofriend on July 19, 2019, 04:01:26 amThat would be a universal motor (a small one at that) and as such, a triac motor controller will work nicely.

author: Benta
author_rank: Super Contributor
timestamp: July 19, 2019, 04:41:16 pm
content: At 10 W it's not a universal type. All odds are that it's shaded pole..

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 19, 2019, 05:31:05 pm
content: The series diode for half power won't work if it's shaded pole. Perhaps the "diode" is actually a diac and triac in one case specifically designed for reducing AC power? (I have never heard of one of those with just 2 leads, but it's possible.)A quick test to see if it's a universal motor is to connect a DC bench supply to it and turn the voltage up to 30V or so. If it turns (slowly), it's a universal motor.

author: Yellofriend
author_rank: Regular Contributor
timestamp: July 21, 2019, 06:56:58 am
content: Quote from: soldar on July 19, 2019, 09:45:30 amYeah, something didn't really add up. Probably a brain blockage.... I adjusted the clarity slider now ;-)The motor is a type 5512 DC 230V motor, something like that:http://www.dsdmotor.com/ProductShow.asp?ID=224(mine is a sort of no name motor though)So the AC 230V comes in,Higoes to the rectifier, then to the motor,Lowdoes the same via one diode before the rectifier to take one wave half off.I tried a dimmer, does not work. Today tried my adjustable transformer, very little effect.

author: soldar
author_rank: Super Contributor
timestamp: July 21, 2019, 07:20:26 am
content: Quote from: Yellofriend on July 21, 2019, 06:56:58 amThat makes no sense to me. Can you post a schematic?Quote from: Yellofriend on July 21, 2019, 06:56:58 amIn the title you say it is an AC motor. Now you say it is DC. You need to make up your mind and be sure. Just because it looks like something from the outside does not mean it is the same thing.Quote from: Yellofriend on July 21, 2019, 06:56:58 amWhat kind of dimmer? Triac? PWM?Quote from: Yellofriend on July 21, 2019, 06:56:58 amUnder what conditions? Under load? What voltage? What speed? How are you measuring?This is confusing. Can you post a photo of the motor and a schematic of what you are doing?

author: Yellofriend
author_rank: Regular Contributor
timestamp: July 21, 2019, 08:54:31 am
content: I did a quick drawing with the Digikey online tool. That's about how it looks.

author: soldar
author_rank: Super Contributor
timestamp: July 21, 2019, 12:19:29 pm
content: That schematic looks good.My guess is that voltage will control power/speed. If you connect the thing at full power (not through the diode) and use lower AC voltage or a triac power control (NOT PWM!) it should work.

author: Yellofriend
author_rank: Regular Contributor
timestamp: July 23, 2019, 01:50:57 am
content: Quote from: soldar on July 21, 2019, 12:19:29 pmI will try a triac/diac control like this one:From this linkI have some old HT32 (diac) and Q4015LT (and Q2015L5) around and see how that works out.(the old parts are from the drawing below, I may even have a complete module of that around)

author: SteveyG
author_rank: Unknown
timestamp: July 23, 2019, 06:52:46 am
content: Quote from: soldar on July 21, 2019, 12:19:29 pmJust note many TRIAC dimmers have a minimum load - 10W may not be enough for it to work properly.

author: Yellofriend
author_rank: Regular Contributor
timestamp: July 23, 2019, 02:24:50 pm
content: Quote from: SteveyG on July 23, 2019, 06:52:46 amSeems not to work with that Q4015L5 (70mA ), no difference between the three switch positions. Can I change a R to get a higher current? Or some sort of different triac? (I have the same module as a 110VAC version with a Q2015L5, I give that a try tmr.)

author: soldar
author_rank: Super Contributor
timestamp: July 23, 2019, 02:35:57 pm
content: Triac control dimmers can have problems with very small loads and also with reactive loads. My suggestion would be to put the motor in parallel with a light bulb . That solves both problems at once and you can see if the control is working by the brightness of the lamp.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 23, 2019, 03:01:30 pm
content: Quote from: Yellofriend on July 21, 2019, 06:56:58 amIf your motor is similar to the one posted in the link, it is a permanent magnet, DC brushed motor.The best way to control it, is with a full wave SCR control. There are many examples in General Electric's "SCR Manual Including Triacs and Other Thyristors".I have a copy at home, right now I am at work, let me find a suitable circuit and will scan it.

author: Dr. Photon
author_rank: Contributor
timestamp: July 23, 2019, 08:06:41 pm
content: Another option would be to rectify the incoming AC into DC, and then use a MOSFET (and a catch diode on the motor) to control the motor via PWM. Many of the small tabletop mills and lathes from china use DC brush motors controlled this way (some use PWM MOSFETs, some phase angle controlled triac).