Small DC motor won't start - Page 1
Forum section: electronics / projects

author: gaminn
author_rank: Frequent Contributor
timestamp: November 01, 2023, 11:54:49 am
content: My cheap Chinese motor is sometimes not able to start. There is short circuit current into motor, but first I have to move manually its shaft and then it starts rotating.The motor is 6V DC, its commutator has 3 lamellas, stall current is approx 1A. Dimension 25 mm diameter, 50 mm length. It is like motor previously stopped in a position where it can't recover and start again. Mechanically, the motor is not stuck.Any idea why this happens and if it is possible to somehow avoid this situation? Yes, I know, buy better motor...

author: Gyro
author_rank: Super Contributor
timestamp: November 01, 2023, 01:10:05 pm
content: If it's a 3 pole motor then I suppose it might just be possible that the brushes are so misaligned that they get bridged by a single commutator segment. I think your final conclusion is probably the right one - unless you want to open it up and start bending with the brush springs.

author: CaptDon
author_rank: Super Contributor
timestamp: November 01, 2023, 01:37:52 pm
content: China should ship their products directly to the U.S.A. landfills and incinerators and avoid flustering the middle man A.K.A. 'Consumer' or 'Customer'. They probably ran a couple thousand for a company with a Q.A. / Q.C. acceptance program and the 'duds' were sold on the Chinesium Garbage Market often called Ebay and such. You could buy another chinesium motor hoping it is better than the one you got. As the other poster stated, it either has a shorted winding or a bridged commutator section. Hook it directly to a car battery, it'll either go or blow, either will be fun to watch.

author: gaminn
author_rank: Frequent Contributor
timestamp: November 01, 2023, 02:05:56 pm
content: So from electrical point of view, is there any other situation where the motor can be stuck other than both brushes shortcircuited via single commutator lamella?We already contacted Maxon and they will offer some motor based on our needs, but of course, there is a huge price difference 10 USD vs almost 200 USD. Do you know any other reputable manufaturer, maybe based in China/Taiwan?

author: gaminn
author_rank: Frequent Contributor
timestamp: November 01, 2023, 02:08:00 pm
content: We purchase the motor from company called TT motor. To be honest, the motors don't look that bad and we have only like 3 % defect rate, which is probably good for toys...

author: tridac
author_rank: Regular Contributor
timestamp: November 01, 2023, 02:10:01 pm
content: Yet more cheap chinesium, by the look of it. To start, 3 segments on the commutator is not nearly enough to guarantee starting. Cheap, cost engineered design right down to the floor. Would expect to see 6 or more on a motor of that size. I would just bin it a find a better quality, if a bit more expensive motor...

author: Benta
author_rank: Super Contributor
timestamp: November 01, 2023, 05:01:40 pm
content: Johnson Electric made good motors for industry and automotive, but that was back in the Hong Kong days.Now that Hong Kong is China, I don't know how the quality is.Worth a try.https://www.johnsonelectric.com/en

author: MarkR42
author_rank: Regular Contributor
timestamp: November 15, 2023, 09:49:07 am
content: Those motors are not very high quality but very cheap. I have had them fail but never had one which won't run when new.If your yield is so low it's a problem, consider changing supplier.

author: CaptDon
author_rank: Super Contributor
timestamp: November 16, 2023, 03:16:29 pm
content: I wonder if Mabuchi still exists as a motor manufacturer? Bob Carver used them in the series of amplifiers I specialize in repairing. I think they are a 5 segment commutator. I can usually restore them to good health by cleaning the crud from between the commutator segments and using GM Dextron A.T.F. as a bronze bushing lubricant. Recently due to O.E.M. motors being hard to find I have been installing brushless 12vdc fans with good quality bearings (a.k.a. expensive).