Identifying the motor type in a microscope stage - Page 1
Forum section: electronics / projects

author: amaschas
author_rank: Regular Contributor
timestamp: September 13, 2024, 04:12:38 am
content: In the continuing saga of my attempts to get and old 2-axis microscope stage working, I've run into a bit of a roadblock in identifying the type of motor that drives the two axes. I initially assumed it was a 2-phase stepper motor, but I've found some information that indicates it might be a servo motor instead. The motor in question looks like this:I has 4 leads, a red/black pair and a blue/white pair. The blue/white pair is marked +/-, and the red/white pair is unmarked. There's also a symbol on the top that you can sort of see here:There's also an encoder mounted on the end that has 4 blue leads:I've found similar motors being sold:https://www.capitolareatechnology.com/escap-23hd-motor-11-216e-204-1-leica-pn-302-050087-003.htmlhttps://myvisionsurplus.com/products/escap-motor-gear-23hd11-216e-204-5And this post which describes it as a servo with an attached encoder, but the motor in this post has 6 pins total, whereas mine has 8 if you include the encoder:https://rogerparks.com/instructional/escap-16-gear-motor-encoderIn the documentation for the controller for this type of microscope stage, however, the pinout for the motor inputs would seem to indicate that it's a stepper, as the motor pins for the axes are documented in this format on page 7 of the linked PDF:Motor 1, Phase 1 +Motor 1, Phase 1 -Motor 1, Phase 2 +Motor 1, Phase 2 -https://www.marzhauser.com/fileadmin/Dateien/Downloadbereich/Steuerungen/TANGO/Treiber_Firmware_und_Dokumentation/TANGO_Desktop_E/TANGO_Desktop_Operating_Manual_EN_130409.pdfAny help in identifying what kind of motor this is would be appreciated!

author: H.O
author_rank: Frequent Contributor
timestamp: September 13, 2024, 04:47:31 am
content: Definitely looks like a PMDC servo motor.Tachometer on the back (blue wires), motor armature (red wires) and with the encoder mounted on the output shaft.The ESCAP16 gearmotor with encoder you link to lacks the tachometer, hence 2 wire less.

author: Benta
author_rank: Super Contributor
timestamp: September 13, 2024, 11:39:46 am
content: Stepper.The first sentence in your documentation reads:"The controller TANGO Desktop, hereafter named "controller", is a device for driving 2/4 phase stepper motors."The motor is only the top small cylinder, the large cylinder is the gearbox/reduction.

author: amaschas
author_rank: Regular Contributor
timestamp: September 13, 2024, 04:27:47 pm
content: Quote from: H.O on September 13, 2024, 04:47:31 amI was also under the impression that I should be able to drive the motor from the red/black pair, though the blue/white pair is marked with +/-. Is there a good way of determining which is which without potentially damaging the motor?Quote from: Benta on September 13, 2024, 11:39:46 amIs there a way of definitively testing whether its a stepper rather than a motor/tachometer pair?

author: amaschas
author_rank: Regular Contributor
timestamp: September 13, 2024, 07:53:52 pm
content: Some additional info, the resistance for the red/black wiring pair is ~10Ω which seems high for a motor winding. The blue/white pair is 164Ω however, which makes me think the red/black pair is the motor.

author: H.O
author_rank: Frequent Contributor
timestamp: September 13, 2024, 08:40:32 pm
content: Yes. The larger "body" of the assembly will be the motor so motor on the red wires, tacho on the blue wires.If it was a stepper the resistance across the two pairs would/should be equal.10Ω isn't really that high for a small motor of the type we're talking about. If you look at, for example, theMaxon RE16 seriesits resistance ranges from 0.4Ω to >300Ω depending on which voltage it's designed for. Had it been a motor for a RC car then 10Ω would be high.You're overthinking this. Use a lab power supply with current limit set to <1A and apply a couple of volts across the red wires.

author: moffy
author_rank: Super Contributor
timestamp: September 14, 2024, 12:10:40 am
content: If the Tango drive is what is used to drive the motor then it is definitely a stepper motor as Benta suggested quoting the manual, maybe a defective stepper but definitely a stepper.

author: ajb
author_rank: Super Contributor
timestamp: September 14, 2024, 08:09:05 pm
content: It would be really weird to have the leads come out of opposite ends like that if they're all for coils within the motor. Just based on the physical arrangement it looks a lot more like a DC motor + encoder/tach than a stepper as H.O. said in the first reply.Quote from: Benta on September 13, 2024, 11:39:46 amThat'd be an ENORMOUS gearbox for that size of motor, especially considering the linear stage is presumably driven by a fine pitch lead screw!I found the attached datasheet for a motor with a similar part number, 23DT12, on RS's website (couldn't find the actual product), which also looks to be about the right size and shape, and is clearly a brushed DC motor. Note the diagram on the bottom left of the page, which clearly shows the motor in the middle with what is clearly a tach/encoder on one end and a gearbox on the other, just like we see in the OP's photos.It's possible that the 23HD11 is a stepper in the same body, but Portescap, as they're now called I guess, doesn't list any stepper or BLDC motors with a 23mm body diameter as far as I can see. Neither part number shows up on their website, so my guess is that they're older series, or possibly special order, but most likely the same basic motor.Quote from: moffy on September 14, 2024, 12:10:40 amAssuming that's the right version of the manual that goes with this particular stage -- it's entirely possible that at some point they switched between stepper and DC servo arrangements, or that this is a different variation. We also know from OP'sother threadthat this is for a Leica-branded stage, so short of more documentation, there's really no guarantee that's the right controller for what the OP has anyway.

author: amaschas
author_rank: Regular Contributor
timestamp: September 17, 2024, 07:16:56 pm
content: OK, managed to assemble a working cable and test the motor, and it is in fact a DC motor with an encoder and tachometer. My only remaining point of confusion is that the encoder has 4 wires instead of the expected 3, but I'm going to poke around with my scope and see if I can get pulses out of it.

author: H.O
author_rank: Frequent Contributor
timestamp: September 17, 2024, 08:06:25 pm
content: 3 wires? This isn't like a mechanical front panel type encoder. It's an optical encoder, it needs a power supply (5V usually) and outputs A/B quadrature signals, usually TTL leverl but can also be open collector type. Many encoder has differential outputs but with only 4 wires that's not the case.