Core Electronics Forum

Replace Mini Stepper/Gear Motor

Hi Support

I’m looking for a replacement miniature stepper or gear motor for an educational toy called “Night’n Day Solar Time Rotating Globe”.

Unfortunately the manufacturer can’t offer any help at all because this product has been discontinued and that was it!!!

Also unfortunately the current stepper motor doesn’t have any important details on it such as the voltage/gear ratio or RPM etc.

It only has what looks like an in house part number " 6SH24-305 150722S6 " or it could be “6SM24-305 150722S6”.

The dimensions are"
D = 24mm
H = 18mm
Shaft or Spindle Height = 10mm
Distance between centre of mounting screws=31mm
It has 5 wires attached.
The end of the wires are attached to male plastic part width=10mm fitting into female part w=12mm

Other important information:

The circuit plates has a 5V printed next to the male plastic box where the stepper motor plugs in.

I found a stepper motor (SKU: SS108990003)
on your website which looks very similar in size and appearance to my one but unfortunately it only has 4 wires attached.
Would you have a similar size motor with 5 wires?

I hope I have given sufficient details and information.

I have attached images for your reference

Looking forward to hearing from you.

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The 5 wire is unipolar and 4 wire is bipolar. I think a 5 wire unit can be used as a 4 wire but I don’t think there is any way of using a 4 wire as a 5 wire.
It looks like this would have to run at a precise speed to rotate the globe 1 revolution in exactly 24hrs. I think more information would be required before a suitable replacement selected.
Tried Google on those numbers, no hits so you are probably correct in assuming this is an in house part number.
Cheers Bob
PS. Looks like there are a lot of gears in the bottom (looking at the pic) so if you work out the gear ratio you should be able to come up with the required RPM which would be a bit of a start.
Need to count a lot of teeth though.
Are you sure the motor is dead. I think these things are pretty robust. You might start with a continuity check on each winding. There are 2 centre tapped windings, the centre taps joined to give the 5th (common) wire. A continuity check from the common to each of the other wires should be the same resistance. Any departure from this (like open circuit) would indicate a potential problem. Looking at the board pic I think a pretty fair guess would be the centre wire to be the common.
Cheers again Bob

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Hi Peter,

What an interesting project, it reminds me of the story of the Antikythera mechanism, but in reverse. It’s a pretty amazing thing to read about, just linked its wiki below incase anyone is curious :grinning_face_with_smiling_eyes:

As for working out the appropriate voltage and ratio for your part, you should be able to grab a multimeter and check the voltage across the pins (although I would expect just 5VDC which was labeled on the board). Personally, rather than trying to mod a stepper to try and achieve the same functionality as the original, I’d say it would be much easier for you to simply replace the board entirely, use your own stepper motor which is approximately the same, and control it with a microcontroller such as an Arduino or one of the ESP32 boards and an appropriate driver. That way as Bob said, you can also set your own speed so that it keeps time accurately like the model used to and possibly even add the functionality of skipping between different points in time to see what the orientation looked like.

I’ve attached a link to some parts that you should be able to use with a tutorial on how to use stepper motors in order to throw this together. You may need to experiment a little to get it tuned in, but that’s all part of the fun! Please let us know if you have any other questions.

or you can use this hat rather than the driver if you want to use it for other projects that need more motors:

All the best with your project Peter!

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Hi Bryce

Thanks very much for your very informative and encouraging feedback.

I’ve just finished reading more about the amazing Antikythera mechanism which has given me more encouragement and reasons to try and get Planetary Globe working again (hopefully if possible)!!!

I would love to undertake your excellent suggestion and detailed instructions on replacing the entire circuit and working mechanisms but unfortunately this is way beyond my knowledge and expertise in electronics…even basic 101 junior beginners class!!!

At this stage the best I can do is start counting the number of “shark teeth” on the 12 or 13 cogs
(as Bob suggested) and hopefully this will be helpful and enough information to find a suitable replacement stepper.

Replacing the motor is probably the limit of my electronics skills that I have to hopefully get it working again.

Thanks again Bryce

3 Likes

Hi Bob and Liam

Thank you both today for your comprehensive feedback and analysis and help you are providing.

I did try the motor again and it just made a humming noise without turning at all.

I presume the circuit is still working because there is a small lamp switch attached to the circuit and the lamp works when I plug the power on.

I have now counted the number of teeth on all of the cogs (and yes, I’m still sane!!!)

There are 12 cogs in total.

Cog 1 = which attaches to stepper has 16 teeth and 18mm diam from teeth ends.

Cog 2 = which is the first cog the stepper turns has 65 teeth on the outer and 32 teeth around the inner hole. It is 67mm diam from teeth ends.

Cogs 3 to 12 have 96 teeth on the outer and 32 teeth on the inner. They are all 98 mm diam from teeth ends.

I also measured the gap between the steel pins in the male plastic casing on the circuit and the distance is 2mm between all of the 5 pins.

Hope this information is helpful and useful.

And I also like to add that your team has been so supportive and patient in the time you have given so far.

It certainly is much much more than what the manufacturers offered to help.

Thanks again

Peter

3 Likes

Hi Peter
Where was the motor when this test carried out, back in situ (in the globe) or “free standing” out on the bench.
Have you measured the resistance of the windings. Between the “common” (5th wire) and the other 4 wires. They should be pretty much all the same. This will go a long way towards deciding if the stepper is actually faulty or not. You could spend many days searching for a replacement for a perfectly good stepper with no end result.
Cheers Bob

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Thanks for your reply Bob.

I tested the motor whilst in the globe and outside free-standing on the bench and there was no movement at all, just the humming noise.

I tried turning the black cog attached on the spindle using my fingers whilst the power was on and the cog turned step by step anticlockwise but it stopped turning when I took my fingers off the cog.

I even removed the cog from the spindle to test if the spindle on the motor would turn by itself and it didn’t, just making humming noise.

As for your other suggestion, unfortunately as I’m not tech savvy and don’t have enough electronics experience, I don’t really know how to carry out the resistance wire tests and I don’t own any testing equipment either or know how to use them.

As you know unfortunately there isn’t enough information on the motor to find the exact replacement and the instruction booklet that came with it doesn’t have any info either.

If it’s any benefit I can try to take the motor apart and count the number of cogs in there etc and maybe that will gives us some clues to find a suitable replacement?

Let me know if it’s worthwhile doing that?

Thanks

Pete

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On that, here are some very handy links and videos that’ll help out:

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Peter.
Not having any multimeter or anything to take measurements or the knowledge to use them makes things pretty difficult.
The fact the stepper does turn with a bit of help may indicate the stepper itself could be OK.
It may be that the voltage to drive it has died somewhat or the full voltage is not getting to where it is supposed to be for some reason. Could be as simple as a dry solder joint or poor connection somewhere, my guess would be the “common” (5th wire) circuit as this probably be the main voltage supply for the stepper.
I don’t think there is any advantage in dismantling the unit at this stage. The idea of counting gear teeth to establish the ratio between stepper gear and globe and thus RPM required is OK if you were going to start again with Arduino or something else. To replace this stepper you need to know how many steps per revolution and whether or not the unit uses micro stepping etc. As you can see calculating the RPM at the stepper output is only part of the story.
Do you have any mates who dabble in this sort of thing. You really need to firstly establish the common wire. Then find someone with a 5 wire stepper drive laying around who can check it. The driver may be 6 wire to accommodate separate centre taps, just connect the commons together.

I notice on the pics the track going to pin 2 on the connector has a couple of test points marked VCC. This may be the common. Finding this common is not too difficult but pretty hard to explain in print but is something you or a friend need to do. There are some checks that can be done but a 5V power supply capably of a couple of amps or maybe more would be needed. but first the availability of the required power to drive the stepper needs to be established.

I would advise against rushing out to try and buy a stepper at this stage as it could finish up just being an unusual paper weight.

It sounds like you need some face to face help as without even a basic multimeter and some idea of its uses this could be pretty difficult to resolve remotely. Perhaps someone else with a bit more experience with steppers may be of assistance. I like to learn something new every day too.

There is one golden rule that has been working for many years. When you have a problem the first checks should be the power supply(s).

Sorry for the bit of delay but I had almost finished this yesterday evening when we lost power until about midnight.
Cheers Bob

4 Likes

Thanks very much Bob for your thorough reply on your weekend time, and for the rest of the team for your patience and support with an amateur like me. Very much appreciated.

Unfortunately I don’t have any friends that dabble in the electronics field but I’m determined to try and give it a go myself before I give up and use the whole globe as a paper weight or a door stopper!!:rofl:

I’ve decided to purchase a good multimeter this weekend and look at the tutorial videos you sent to carry out the tests you recommended.

But firstly I just want to clarify a few things.

  1. You have so far mentioned “Continuity” test and “Resistance” test…do they mean the same thing or are they separate tests?

  2. I’m a bit confused.
    Is the “common wire” and the “5th wire” the same thing?
    In your opinion, which wire “colour” is the Common wire? You mentioned the 2nd pin and VCC on the circuit board. Am I safe to presume that “orange” is the common wire as a starting point? The Orange wire is no.2 on the circuit board and it is the middle wire on the motor.

Also I have done a research google on the globe online and unfortunately it doesn’t have any details on the motor which is a bummer!!!
It just mentions what you brought up in your first reply that the motor has to do 1 revolution in exactly 24 hours!!!

I’m attaching a few more clearer images for your reference.

Thanks very much


2 Likes

Hi Peter
Firstly it is the globe that has to do 1 rev per 24hrs. The motor on the other end of all those gears has to run at a speed which will achieve this.
Good on you for having a go. Get a multimeter, read all you can about it and try to get a handle on what it does and what it is used for. Really have a play. But read up first. This would be a case where “when in doubt read the book” does not apply. Read first.

To answer your questions:

  1. In essence yes. “Continuity” is confirming you have a circuit or connection. It may not matter what the actual “resistance” is. When you want or need to know what the “resistance” is the meter will tell you. Expressed in ohms or Ω. Please read up on this term and get a feel for what it means.
  2. Yes, they are both the same, sorry for the confusion. For the sake of clarity assume the stepper has 2 coils. Each one has a tap or connection at the centre. These centre connections are joined and taken to the outside world as a 5th wire or “common”. This then connects to stepper power supply or ground depending on the drive configuration. The “ends” of each coil are then switched in sequence to rotate the motor 1 “step” at a time. The direction controlled by the switching sequence.

Now you have your multimeter, have done some research and reading on basics, Volts - Amps - resistance (ohms or Ω) and are reasoably familiar and confident with your meter.

Now to check your motor windings. Each half coil will have resistance. Call this XΩ for now. It is reasonable to assume that the full coil will be 2XΩ and both coils will be the same. We will start assuming the orange wire to be common. It doesn’t really matter. Now with your multimeter set to read ohms or Ω connect one lead to the orange wire. Connect the other lead to the remaining 4 wires in turn and note (write down) the resistance reading for each. If our guess at common is correct you will read XΩ to each of the other wires. If we are wrong you should read 2XΩ to 3 of them and XΩ to the 4th. This wire will then be the common. Repeat the measurements using this wire as common and measure to the other 4. All should read XΩ.
As a further check measure between any 2 of the remaining 4 wires and you should read 2XΩ. disregarding the common measure between each wire to every other wire of the 4 and you should read 2XΩ.

If all this works out OK it would be reasonable to assume the stepper is probably OK and the problem lies elsewhere. It would still be good to connect that stepper to a driver to confirm it is OK. I don’t know how this can be achieved easily.

You may even get to explore some other uses for your multimeter. I have a feeling that may be the case.
Cheers Bob

3 Likes

Thanks for your encouraging reply Bob.

I wish I would have purchased the multimetet a few days ago and did the readings as you suggested.

Here are the readings in ohms approx.
I presume that for 5 wires there can only be 10 results?

I did all of the readings twice.

O+R = 77.3
O+Y = 0.0
O+BR= 78.4
O+BL= 77.8
R+Y = 0.0
R+BR= 154.4
R+BL= 156.6
BR+BL=154.4
BR+Y = 0.0
Y+BL = 0.0

Can I safely assume that the yellow wire is the problem since all the yellow combinations are reading zero?

I tested the connection of the yellow wire to the motor and the connection is ok, just like the other wires. It’s not loose or appears to be broken from the outside.

Are there any more tests that I can do?

Can we salvage this motor?

Cheers, Peter

2 Likes

Good deduction Peter.
It would appear that the orange wire is the common. If it were not there would have only been 1 reading of 78Ω.
It also appears there is something wrong with the yellow connection. What I don’t understand is how it reads a short circuit to everything (0.0Ω). If that were the case everything would read 0.0Ω.
If it were open circuit I could understand these figures.
I wonder if you are interpreting the readings correctly. Do you mean 0.0Ω ie; a short circuit, or 0.0 no connection.
You could do one more thing for us. Tell us EXACTLY what the meter reads with the 2 leads joined together and EXACTLY what it reads when apart ie; not touching anything.Thanks.
Cheers Bob

4 Likes

Apologies for the confusion on my part Bob.

What I meant to say that there was no reading on the machine at all.

I just thought that I’d let you know that it was a zero reading🤷‍♂️

Images attached

By the way, I have already purchased one of your stepper motors SKU: ADA58

I should be receiving it one day next week.

2 Likes

That explains it. That means infinity or open circuit. To be accurate it means a resistance beyond the meter range. I don’t know what that is for that meter.
Well that means we have an open circuit coil which is on the yellow wire. probably not very easily repairable if at all. See what happens with the one you get. The wire colours will probably be different. I had a bit of a browse and there does not seem to be any standard or reasoning behind various colour schemes.
You will at least be able to identify the common using the method above.
Cheers Bob

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Hi Peter.
Not one of MY stepper motors.
Apart from purchasing a few bits I have no commercial affiliation with CoreElectronics at all.
Participating in this forum keeps the old grey matter active and can be interesting, that’s all.
Cheers Bob

5 Likes

Hi Bob and Team

I’ve received the motor from Core ADA858.

I’ve taken the readings and assumed that Red is the common. And I think the readings confirm that it is…Am I correct?

I’ve noticed that the ohms readings on the old motor are approx 3.5 times larger than the new motor… will this be a problem?

Also the female pin on the new motor doesn’t fit the male casing on the circuit board.

The measurements are:

Circuit board casing is 12mm w, from plastic edges. Dis from centre of 1st pin to 5th pin is 8mm. The female plastic on wire tips (yellow)on current motor is 11mm w.

New motor. Width of plastic on wire is 13mm.

Not sure what to do now???

I’ve attached the images.

Thanks Pete




Uploading: 20210201_113139.jpg…

Hi Peter
Congratulations, you have just successfully carried out your first exercise with your new multimeter.
I would have thought you would have been supplied with a wiring colour scheme with the new motor. Very slack if it wasn’t provided.
Googled that part number, lots of info.
You are right, Red is common. Orange is coil 1, Pink coil 2, these are 1st pair. Yellow is coil 3, Blue is coil 4, these are 2nd pair.

Yes the resistance reading could make a huge difference. It basically means the new motor could require 3.5 times the current than the old one. The driver circuitry may not have enough “grunt” to drive it.

Connector: There are several different pin pitches with this type of plastic connectors.
You will have to measure accurately.
One is 2mm which you have previously measured on your existing connector. I am assuming this was an accurate measurement.
One other is 2.54mm which it seems you may have on your new motor.
It is possible the actual pins are the same. You are the only one who can verify this.
The pins (female in fact) are removable. Through the hole in the side you should see a tiny spring clip which pops out when the pin is inserted and prevents it from coming out.Using a very small screw driver press this clip in and withdraw it by gently pulling on the wire while holding the clip in. Not too hard with practise but at first you may find it awkward.
If they are the same you should be able to fit the new pins into the old connector.

Identifying coils in old motor. This is the next problem and short of dismantling the old motor i don’t have a solution. They are effectively connected together because the centre taps are connected. You at least need to identify the pairs of coils. Only one actually as the 2nd pair will be the other 2 wires.

As long as the common is correctly identified I think there is a logical way of doing this and getting the new motor connections correct.

CAN SOMEONE MORE CONVERSANT THAN ME WITH STEPPERS HELP OUT HERE PLEASE.

Peter be aware that because of the lower resistance the original driver may not have the capability to drive this motor properly. The other problem of course is the shaft RPM has to be the same as the original. This is a direct relationship between the gear box ratio and the number of steps per revolution. as long as it all finishes up the same all good.
Cheers Bob

Useful link:28BYJ-48 Stepper Motor Pinout Wiring, Specifications, Uses Guide & Datasheet

3 Likes

Thanks for your very comprehensive reply as usual. I had to put my thinking cap to really decipher your reply and follow your instructions and reply to your questions correctly.

Unfortunately I don’t have a proper measuring instrument but I tried to get as accurate as possible with my trusty ruler.

  1. The new motor didn’t come with any explanations on the colour coding.

  2. Yes I did try and be as accurate as possible on my measurements.

  3. I have now removed all of the pins and the new pins are slightly larger. I tried to fit new pins in the old Yellow casing but they are slightly larger and would not go in easily, so I haven’t tried to force them in.

  4. As far as identifying the wires on the old motor, can I safely assume that positioning in order of the wires (from left to right)leading from from the old motor to the female yellow casing when it is connected to the circuit board should be the same order when I attach the wires from the new motor.

If this assumption is correct then without having to guess which 2 pairs go together then the I would put the new wires in this order from (left to right)…Pink,Yellow,Orange,Red,Blue

  1. Would you like me to try and gently squeeze the new pins in the old casing by slightly closing the tips using a pair of pliers to see if they fit?

  2. If we are able to successfully fit the new motor in the old casing and attach it, will there be any damage to the circuit board because of the large difference in resistance?

  3. Are we able to find a new 5 wired motor that would match the same ohm readings based on all of the information available to us now?

I have attached more images for reference.

I have used the common wires in both motors to compare in the images.
(Orange and Red)

Thanks very much, Pete









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Hi Peter.
Will try to answer in order

  1. That is a bad omission. I would be inclined to complain although I found the colour code on the web without much trouble.

  2. Always good to be accurate. I find digital callipers invaluable for this type of thing. there is not much difference between 2mm and 2.54mm but it soon adds up.

  3. If the pins are different they won’t fit so don’t try and force them. How are your soldering skills. Without trying to get new pins and crimping them on joining the wires is another option. Cut the old wires about 50mm from the pin and do the same for the new ones then put the new connector aside. Solder the old pins with the 50mm wire onto the new wires. Put some heat shrink tubing on the wires before joining then slip this over the solder joint for insulation. Shrink down with hot air.

  4. As long as the common (Red in this case) goes to pin 2 it is anybody’s guess where the others go. I think one of 3 things will happen. It will rotate ok, it will jiggle back and forward or it will go in reverse. I am not really sure.I think there is a logical way to sort this out involving swapping connections. I have seen this described somewhere but I will need some time to find out where.
    In my last reply I asked for some help regarding this. May have to see if any is forthcoming.

  5. Definitely NOT.

  6. Very likely. I personally would not fit this motor without further investigation. Your basic power supply that drives the whole thing may not be capable. I don’t think the original manufacturers would leave that much head room.

  7. Would be the safest way to go. You would still be taking a chance on the steps per revolution and the gear ratio providing the correct end result but without info on the original motor I don’t see any other way out.

If you are feeling adventurous you may have a very close look at the original motor. Inspect the connector pins and the crimps. It is not unknown for the crimps to be on the plastic instead of the wire which could work for a time then fail. Push the female pin onto the connector and make sure contact is good. give the wire a bit of a pull to make sure no breaks up under the plastic. You can’t do any more damage so VERY CAREFULLY dismantle the unit to inspect internal joints. Soldered joints are the most likely points to get hidden breaks under insulation due to solder “wicking”.
Watch the gears don’t go everywhere if you have to remove the gear box cover.
You just may get lucky and find something repairable.

Finding a replacement?? Element 14 may have enough filters to narrow the search a bit. You (and I) will have to have a look. At least we know the winding resistance that may be a start.

Cheers Bob

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