Inside an Automotive Gauge Stepper
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- Опубліковано 12 вер 2017
- Taking apart a stepper motor that is used to move your speedometer or other gauges in your GM, Chrysler, etc vehicles. This one is from a Chevy truck but its used in many brands. Pretty basic, not an amazing video but I hope its mildly entertaining.
Very interesting video. Thanks for posting. I'm about to change the motors in my trailblazer and already have them on order from amazon. I'd like to add some details. The round magnet on the rotor shaft is very much like a bar magnet mounted on a shaft with the poles 180 degrees apart. Because the bottom stator pole is larger than the two upper ones, the magnet will always come to rest with one or the other pole aligned with the large bottom stator pole. If you could energize only the large bottom stator pole so it repels the rotor pole near it, the rotor would turn but whether it turns clockwise or counterclockwise would be unpredictable. So for clockwise rotation the left hand coil must be energized to repel the bottom of the stator as mentioned above while the upper left stator pole will repel the opposite, upper pole of the rotor magnet, forcing it to a predictable 180 degree clockwise rotation. Pulsing the left coil again but with opposite polarity would result in an additional 180 degree step of rotation. The same sequence would be used for pulsing the right hand coil for counterclockwise rotation. Energizing either coil will always result in energizing the lower stator pole but only the upper stator pole necessary to get the correct direction of rotation is energized strongly enough to set the rotor in motion. If two subsequent pulses of the same polarity were erroneously applied to the same coil, the rotor would not move when pulsed the second time. Therefore for multiple steps in the same direction, the same coil must be pulsed with alternating polarity.
No doubt cleaning the gears and shafts will help, but I think the problem with bad steppers of this type is with the way the magnetic cores inside the coils after a period of time, may not be held in close magnetic contact with the stator pole pieces. With the two halves of the plastic housing being held together with clips around the edge, the flat steel spring around the needle shaft will gradually cause the plastic halves to bow outward, thus allowing the coil cores to become loose and create poor magnetic connections. A repair may consist of a tiny droplet of "Krazy-Glue" or similar adhesive on the joints between the coil cores and the stator cores to help insure a reliable magnetic contact. This type of glue results in the thinnest possible gap. This may be a better repair than simply cleaning although cleaning should be done as well. Don't worry about the layer of glue between the metal parts acting as an electrical insulator. Only magnetic flux flows here and the larger the gap the weaker the flux. The magnetic flux will have a complete magnetic circuit from either coil core, through the bottom pole piece, then through the air gap into the rotor magnet, through the air gap from the rotor to the upper pole piece and finally back to the coil's core.
Another great video, very informative, have a cluster to repair in a few days, thanks for posting this!
Thanks so much! My only goal with this channel is to share whatever knowledge I can with others who want to learn. I really appreciate the comment and the subscription!
Thank you for taking the time to explain this. It is very usefull information
You're very welcome!
The small black gear the tiny one with 5 or 6 teeth is the one that fails the plastic axle shaft brakes.
Thank you for showing the inside. Someday I might modify one for co-axial instrument, by replacing one shaft with a hollow shaft.
Absolutely. I'd be interested in seeing that. After replacing so many of these for people, its nice to learn more about the hows and whys.
You may be interested in using gears from a quartz clock movement for such an instrument. Unfortunately the motor in a quartz clock is unidirectional and contains only a single coil but otherwise operates identically to one of these steppers. I think the biggest issue would be you're stuck with 12:1 or 60:1 reduction ratios.
You can buy dual shaft versions. They look like two of these stacked on top of each other.
From the looks of it, changing the pins to come out the front would be as easy as making new holes and flipping the coils. Is that the case?
Don’t even need to make holes as they are already there (at least on my X27.589 model they are). I just ordered some X27 steppers not fully researching and got the 589 version instead of the 168 version. Took one apart and found the parts are totally modular and flipping the coils let you put the pins on the back through the already available arms. I think I’m going to mod this one further and remove the stop peg and make it fully 360 degree. I bought a bunch to allow for testing, modding etc.
You know that noise at 6:18 is the gear teeth stripping, right?
Hey you have the exact same Fluke meter I do......
The air core stepper motors are really hard to find. Can these be interchanged? These are really cheap right now on places like Amazon and FleaBay
No. Air core gauges (which are not stepper motors) use an entirely different method to drive them, called sine-cosine. The needle is tied directly to the shaft, and moves in 1:1 ratio with it.
These are more like a 3 phase stepper with two windings. The tiny core turns many times, stepped down by that huge gear so the needle moves a fraction of a degree for each complete cycle.
Is there a certain way of putting the needles back? I took mine off and now they don't work
I just push them back on. I line them up with the far left line on the gauges when I do.
6:17, "It doesn't feel good though". Ya, that's because you are stripping gears like a brute. The ratio is very high and you would have to be a lot more careful turning the shaft to get that little rotor to turn.
I'm aware of over torqueing a gear set.. That's not what I was referring to in my statement. Rather I was referring to the feel of the rotation. I know how the gears work, just not why these motors fail, as this was a dead motor, which is why I took it apart for the video.
@@FixitFrank ah sorry to sound insulting. :) I have seen stepper motors like this before, but I never heard of them being used as a gauge. My first Google search returned your video which I watched with glee... until you twisted those gears, haha. After watching your video, I looked online and see a bag of these motors sells for $20! I have always wanted analog meters to come back and maybe these are a way. The facts they are used as analog gauges in a vehicle is hilarious, and cool. I didn't see anything in the motor for rotating to a zero position, so maybe the electronics just rotates the gauge needle into a stop?
Did you take this motor out of a vehicle?
Yes, this is actually from an old GM Guage cluster. I think it was a suburban or a chevy 1500. The symptoms we're either the guages sticking when the ECU shut down or they don't respond properly when operating. The sin/cosin signals were checked in the vehicle so the guage motors were the culprit. I've rebuilt dozens of guage clusters for folks and figured there wasn't much on UA-cam showing the insides. So I took the used motor and went at it. I kind of figured it was obvious that it was a used broken motor. Hence the teardown. It's a common failure in a lot of vehicles.
They seem to use the sin/cosin driver to zero them. Some are purpose made for the thing they indicate too. I can't use a gas guage for an rpm etc. That applies more to the older aircore type it seems. I don't know a ton about the motors themselves which is partly why I posted the videos. I'm hoping someone knows what wears out in them (aside from me torquing on it) while in the guage cluster. I guess it's just wear and tear on the bearing surfaces but if it's magnetism failing or some other cause, maybe it can be avoided or the motors can be repaired instead of replaced.
@@FixitFrank I have used thousands of stepper motors and never has a motor failed from magnetic problems. They either fail for mechanical reasons or from overheating (where the coils begin to short because the laquer on the wires melts or burns. Judging by the appearance of the plastic housing and lack of bearings on the little tiny rotor, I'm guessing the place where the rotor contacts the housing has worn enough for the rotor to jam on the gears somehow. You would probably need a microscope to inspect the holes and compare them with a new one. If the motor is $2 then probably it is not worth investigating. Maybe some dry lube on those rotor holes might take up the additional tenths of wear.
I've seen coils damaged on over stressed NEMA motors before(really just motors in general) but yeah I don't see that here. I suspect you are right about the wear on the bearing surfaces and the lack of cost effectiveness in repairing them. I was hoping to see if there is way to prevent it but most likely they are designed for a price point and the usual adage of 'you get what you pay for' applies here. If I am paying $26 on prime for 6 motors, a soldering iron and some solder and a desoldering pump, the soldering gear and shipping are the majority of the cost. I bet those motors are around $2 or less a piece retail...
Unrelated, I am really impressed with that Delta printer you made... I have an old Kossel Delta that needs some life breathed back into it. That smoothie edge firmware looks like its way better than the old Kossel firmware.
@FixitFrank &All There's another video on YT that says the magnetic (5-6 tooth) commutator gets bent; straighten it out and the stepper should work again.
Next time I get one, I will try that. I wonder why they bend?
They are plastic, they break
Do you have a video similar to this one with the other stepper motor?
Do you mean the air core motor type? I do not a the moment but you make a good suggestion. I will make one shortly.
FixitFrank yes that one.
& awesome i hope to see it soon.
I need to remove the resistor from my old air core stepper motor (without breaking it) & then transfer it to the new stepper motor. Supposedly these resistors arent made anymore.
I should have it posted in the next 2 days. Thanks!
@@JoseHernandez-ez6sd Are you sure you meant "resistor"?
Are there any replacement stepper motors for a 2007 Suzuki Grand Vitara???
It sure looks like these are the same. I'd still recommend pulling out at least one old one and google that number to be sure.
FixitFrank
the number is very different, its: M200890664051553. I’ve tried that number everywhere and can’t find it.
@@dinotapia1 If it looks the same, you could give it a shot. Just buy them from a place you can return them too if they dont work.
The „other“ motors you showed are called „air core“.
I knew they use a sine/cosine configuration but did not know the name. Thank you!
Correct, two voltage values following a sine/cosine is needed to drive these. In terms of smoothness, the air core drives would be the nicest. Unfortunately the are not common anymore and hard to find.