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Stepper motor driver for telescope mount - Page 2 — Parallax Forums

Stepper motor driver for telescope mount

2

Comments

  • It is and it doe's.

  • evanhevanh Posts: 15,264
    edited 2023-09-14 00:57
  • bbrienbbrien Posts: 561
    edited 2023-09-16 23:08

    That's the one I am interested in at this time. inputs are 3.3v from a propeller1.

  • bbrienbbrien Posts: 561
    edited 2023-09-17 01:04

    I may be having a problem with the JK flipflop 4027,. I was testing the output of pins 1 and 2 and the voltage out on 1 is about 3.3V and the V.O. of pin2 is only about 1V I don't think this is normal and quits after about 40 seconds. see picture.

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  • jmgjmg Posts: 15,149
    edited 2023-09-17 04:00

    @bbrien said:
    I may be having a problem with the JK flipflop 4027,. I was testing the output of pins 1 and 2 and the voltage out on 1 is about 3.3V and the V.O. of pin2 is only about 1V I don't think this is normal and quits after about 40 seconds. see picture.

    Something is very wrong.
    Not only is 1v severely loaded, but pin 2 should always be opposite phase of pin 1.
    Check you have proper ground and power.

    That's the one I am interested in at this time. inputs are 3.3v from a propeller1.

    You will need some form of level shift, from the 3v3 logic, to the Vmotor powered CMOS logic. (6~9V ?)
    Maybe CD40109 or CD4504 etc

  • Christof Eb.Christof Eb. Posts: 1,116
    edited 2023-09-17 05:33

    @bbrien said:
    I may be having a problem with the JK flipflop 4027,. I was testing the output of pins 1 and 2 and the voltage out on 1 is about 3.3V and the V.O. of pin2 is only about 1V I don't think this is normal and quits after about 40 seconds. see picture.

    Hi,
    As said before. I am sure you can get a lot of èxcellent help here in this forum. But only if you share your complete setup and actual code! What is your supply voltage V.stepper (=8V?) and how do you do the level shift? Level shift means that the propeller outputs something like 2/3 of 3.3V for High and the step driver needs 2/3 of V.stepper for to recognise this as High.
    Also in the last photo the scope settings cannot be read!
    Christof

  • Are these similar to the TC4427 CMOS drivers because I already have them.

  • I discovered the set and resets were tied together but not to ground , that's fixed. Will retest tomorrow.

  • jmgjmg Posts: 15,149

    @bbrien said:
    Are these similar to the TC4427 CMOS drivers because I already have them.

    Yes, those TC4427 CMOS gate drivers are fine too.

  • bbrienbbrien Posts: 561
    edited 2023-09-17 20:14

    I have installed one of the TC4427 chips between the step line and the clock pins of the flipflops and tested the outputs of each flipflop and I get a 5v clock pulse on the output and a 5v high on the output prime pin, on the other flipflop the output prime pin stays low and the output pin goes high and pulses low but not at the same frequency,(half?). is this as it should be or not.?

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  • jmgjmg Posts: 15,149

    @bbrien said:

    I have installed one of the TC4427 chips between the step line and the clock pins of the flipflops and tested the outputs of each flipflop and I get a 5v clock pulse on the output and a 5v high on the output prime pin, on the other flipflop the output prime pin stays low and the output pin goes high and pulses low but not at the same frequency,(half?). is this as it should be or not.?

    It's not clear which pulses are where, but narrow pulses on the motor side are certainly incorrect.
    The dual FF form a ring counter that shifts right or left, based on DIRN, and should always divide by 4. The two FF's are identical, but just 90' out of phase.

    See waveforms here
    http://www.hteck.ca/electronics/stepper-motor-drv/sm-driver.html

  • Motor pulses come from the output pins of the flipflops. the first picture is from pins 1 and 2 , and second picture is from pins 14 and 15. also about the circuit in "hteck.ca" is the circuit board a production or a prototype.

  • jmgjmg Posts: 15,149

    @bbrien said:
    Motor pulses come from the output pins of the flipflops. the first picture is from pins 1 and 2 , and second picture is from pins 14 and 15. also about the circuit in "hteck.ca" is the circuit board a production or a prototype.

    Something is very wrong in your setup.
    Check your wiring and decoupling.
    The 4 FF outputs should all have the same clk/4 & 50% square waves.
    Only the phases should vary.

  • Made final corrections to the circuit including replacing the 4027 & 4030 chips I have a good traces at the gates but I had to turn off the H Bridges so I think the transistors are at fault also.

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    2560 x 1920 - 1M
  • jmgjmg Posts: 15,149
    edited 2023-09-19 21:21

    @bbrien said:
    Made final corrections to the circuit including replacing the 4027 & 4030 chips I have a good traces at the gates but I had to turn off the H Bridges so I think the transistors are at fault also.

    That is now 'as-expected' :)

    If things are being damaged, you may want to add more active clamping to the supplies. eg something like a 1W~5W zener 10~12V, across Vmotor, for a 9V system, low speed.
    10uF is modest decoupling, for motor drive, maybe 100uF to 470uF is better.
    With no clamping and small power caps, the motor flyback energy causes a higher dV on the supply. (0.5LI^2 = 0.5CV^2)

  • Most of the problems involved; wiring going to the wrong pins or forgetting to install a ground. The motor doesn't have much chance of rotating while there is no pulse going to the motor. Have 100uf at motor in to gnd. Please show where put Zener in circuit.

  • jmgjmg Posts: 15,149

    @bbrien said:
    Most of the problems involved; wiring going to the wrong pins or forgetting to install a ground. The motor doesn't have much chance of rotating while there is no pulse going to the motor. Have 100uf at motor in to gnd. Please show where put Zener in circuit.

    Good progress :)
    Straight across the 100uF should work fine.
    Zener needs to be higher than the operating voltage, and comfortably under the lowest ABS MAX rating, which will be 18~20V.
    You want minimal Zener current during normal operation, and decent clamping when needed.

  • On that Zener , should the cathode be on the negative?

  • jmgjmg Posts: 15,149

    @bbrien said:
    On that Zener , should the cathode be on the negative?

    Normally the stripe connects to +ve.
    It will be obvious if you connect it backwards, it will clamp the supply ! :)

  • bbrienbbrien Posts: 561
    edited 2023-10-09 23:06

    The circuit in post # 33, I am still trying to use but I am getting more and more confused. the stepper that I am using,#42PM 48L BZ, is behaving strangely in that 1 coil when used alone turns clockwise no matter which pair of wires is used and the other coil turns counterclockwise again no matter which pair of wires one connects( any pair from the dual H bridge.) What gives. Also what is causing the gate signal to phase 180 degrees instead of the 90 degrees seen in the "wave forms" as seen in earlier post.

  • jmgjmg Posts: 15,149
    edited 2023-10-10 01:06

    @bbrien said:
    The circuit in post # 33, I am still trying to use but I am getting more and more confused. the stepper that I am using,#42PM 48L BZ, is behaving strangely in that 1 coil when used alone turns clockwise no matter which pair of wires is used and the other coil turns counterclockwise again no matter which pair of wires one connects( any pair from the dual H bridge.) What gives. Also what is causing the gate signal to phase 180 degrees instead of the 90 degrees seen in the "wave forms" as seen in earlier post.

    The second image in post #45 is what you should have.
    Do you have a rotary encoder ? - you should be able to just buffer the encoder with your bridge fets, and have the stepper follow the encoder as a simple motor/bridge sanity check.

  • bbrienbbrien Posts: 561
    edited 2023-10-10 04:48

    No encoders in my system, probably a cheep stepper unit. The second image in #45 is at the gates with the power to the transistors disconnected.

  • jmgjmg Posts: 15,149

    @bbrien said:
    No encoders in my system, probably a cheep stepper unit. The second image in #45 is at the gates with the power to the transistors disconnected.

    I was meaning find a rotary encoder in the junk box, and connect it as a test.
    You can also make a rotary encoder with a rotary switch with 2 banks.
    Even 2 lever microswitches can be used to give a wrist-roll style test.

  • I'm a little bit lost, a rotary switch has 4 or more contacts and are in a circular pattern? also how would I connect this up. My "junk box" was moved to Thailand. Sorry, I not smart enough. What can you tell me about the circuit at the bottom of post #42.

  • jmgjmg Posts: 15,149

    @bbrien said:
    I'm a little bit lost, a rotary switch has 4 or more contacts and are in a circular pattern? also how would I connect this up. My "junk box" was moved to Thailand. Sorry, I not smart enough.

    Another option is to grab a mouse wheel encoder from an old mouse, or from aliexpress,
    And use that as a test method.

  • Christof Eb.Christof Eb. Posts: 1,116
    edited 2023-10-12 09:49

    There is no need for an encoder. Just mark the spindle with some color dot or stick some adhesive tape to the spindle and you can see how it moves.

    @bbrien , I have had a look at your posts. Since mid 2016 you are trying to let a step motor spin.
    I was wondering, how I could help you.

    I could offer to do a write up using a breadboard, P1 (I have some older module similar to the FLIP module), SPIN1, a Polulu A4988 driver module, a Polulu 1206A step motor, ( plus some parts like LEDs and a good power supply). It would be absolutely necessary for you to buy exactly the same step motor and driver module + breadboard, because you need a stable and reliable starting point. With those parts it would be possible to communicate much better. There are datasheets available for those, and we do know, that they work.

    Also communication would -frankly speaking- have to be very much more extensive and precise, because here for example we readers don't know enough about your real setup to help you efficiently. You would need to post photographs and much more text descriptions.

    Would you be willing to go this way?
    Christof

  • bbrienbbrien Posts: 561
    edited 2023-10-12 18:20

    Ok Christof, My stepper is A Model 42PM48L BZ. it came with a Orion Astro view but I think that It may be modified because when I connect the A coil to the A bridge it moves clockwise and if I reverse the leads it rotates clockwise and if I use the B coil and connect to the A bridge in the same manner it rotates counterclockwise even if you connect the leads backwards it still rotates ccw. The motor only has 4 wires in the plug which is a modular phone jack.

  • Christof Eb.Christof Eb. Posts: 1,116
    edited 2023-10-13 08:31

    Hi,
    I put that minitutorial together in that other thread. It is an offer. Do it with new and known parts. It works. After you have successfully repeated the experiment you can then switch over to this unknown and perhaps defective motor.
    Until the parts arrive you could measure resistance between all ! combinations of the leads and also to the motor housing -a matrix- and post them here.

    You have described some connections partly but we don't know nothing of the rest of the setup or if this is now working.

  • I have tested the leads and verified. The motor is connected from Mod. Jack on motor to Mod. Jack on enclosure which has the Prop.1 with supporting circuits and hand controller. The leads from Mod. Jack on enclosure are for A coil are red and black and leads from B coil are green and white. test between red and black show continuity and the same for green and white. No continuity between red and green or white and between black and green or white. Using circuit in post #33.

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