Pinout for TMC2209 Stepper Driver (6121)?

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twrackers
 
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Pinout for TMC2209 Stepper Driver (6121)?

Post by twrackers »

I got my first two TMC2209 Stepper Driver boards (https://adafru.it/6121) today. I cannot find labels on the boards to identify the six screw terminal positions, and the page on Adafruit's site doesn't refer to a Learn page, a schematic, or a pinout diagram. Where do I get this information?

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by adafruit_support_bill »

The pin labels should be in the silkscreen next to the terminal strip.

https://learn.adafruit.com/adafruit-tmc ... rd/pinouts

Image

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Re: Pinout for TMC2209 Stepper Driver (6121)?

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You're right. Found them once I put my good eyeglasses on and dug up a small flashlight.

Oh... now there's a Learn section for the part. Published yesterday. 8-|

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by twrackers »

Followup questions re: TMC2209 stepper driver:

Detailed description for the TMC2209 states that it has
Potentiometer to set current limiting, up to 2A
The detailed of the NEMA-8 Mini Stepper Motor (https://www.adafruit.com/product/4411) states
3.9V rated voltage (you can drive it at a lower voltage, but the torque will drop) at 600mA max current
  • Would the potentiometer on the stepper driver probably be linear when adjusting the current limit from near zero to 2A, so that I can find where to set it for 600mA?
  • If I set the potentiometer properly, and am feeding 5V to the +/- screw terminals, will the current limit circuitry bring the voltage to the motor down to around the motor's 3.9V rated voltage?

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by adafruit_support_bill »

Would the potentiometer on the stepper driver probably be linear when adjusting the current limit from near zero to 2A, so that I can find where to set it for 600mA?
I would expect the pot to be linear, but I will double-check on that.
If I set the potentiometer properly, and am feeding 5V to the +/- screw terminals, will the current limit circuitry bring the voltage to the motor down to around the motor's 3.9V rated voltage?
The current rating is the important one. The 'rated voltage' for a stepper is just the maximum DC voltage that will keep within the rated current spec. But stepping is not DC and while stepping, the TMC2209 may apply voltages up to the supply voltage - but will monitor the current in real-time to keep it within the limit. See this guide for details:
https://learn.adafruit.com/all-about-st ... aw-1460534

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Re: Pinout for TMC2209 Stepper Driver (6121)?

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it is linear (all trimmer pots are)

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by twrackers »

it is linear (all trimmer pots are)
The trimmer pot, yes. The response of the 2209 chip, input voltage-to-current limit, is that?

So if I understand that guide correctly, the NEMA-8 stepper, rated for 3.9V DC, coupled with the TMC2209 set to 600mA, should work properly with a 5V DC motor supply, especially if left in the default StealthChop mode. Especially since the Shop page for the TMC2209 lists the NEMA-8 stepper as an option to be added to the shopping cart, I would hope someone at Adafruit has tested the two together.

I'll look at the driver chip's datasheet, if the trimmer creates a 0-1.25V level to adjust for 0-2A current limit, then I would guess if I can find that connection on the board, I should try to set that voltage to (0.6 / 2.0) * 1.25 or 375mV if it's a linear relationship. It would've been nice if that signal had a test point on the board. Might be easier to set the trimmer's position by measuring its resistances between its contacts while the board is powered down. I'm open to suggestions.

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Re: Pinout for TMC2209 Stepper Driver (6121)?

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The current rating is the important one. The 'rated voltage' for a stepper is just the maximum DC voltage that will keep within the rated current spec. But stepping is not DC and while stepping, the TMC2209 may apply voltages up to the supply voltage - but will monitor the current in real-time to keep it within the limit. See this guide for details:
Might be a good time to pull the o'scope out. :D

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by adafruit_support_bill »

The voltage change should be linear. But trim pots are tiny and hard to position precisely. For critical adjustment, you can measure the reference voltage on the wiper pin of the pot (the one on the top-center).

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by twrackers »

Ah, I think I understand now.

At its maximum, the NEMA-8 stepper can handle 600mA per coil, when being driven with 3.9VDC when the motor is stopped (no back EMF). Two coils in parallel, ~7 ohm each, that works out to about 5W power being dissipated to get maximum torque.

My application is to rotate a model railroad turntable (151mm diameter) slowly (~0.25 RPM), with pulley gears and a drive belt reducing the stepper's speed by 13.5:1, meaning the torque required from the stepper is reduced by the same ratio. So this stepper needs very little torque to move the mechanism, so 600mA is way more than necessary. Actually, it works out that the 200 step/rev stepper, being microstepped by 1/8 and geared down 13.5:1, works out to 21600 microsteps per rotation of the turntable.

The TMC2209 will apply as much voltage as it has available at the beginning of each microstep when the back EMF is at its max and therefore the instantaneous current is at its minimum, and cut off (I think) when the current increases to the preset limit. The resulting pulse just has to be long enough that there's enough energy (plus a bit) in each pulse to get the stepper to do each microstep under load.

As long as the driver is getting more than the motor's max of 3.9VDC (such as 5V) and the current setting on the driver is set to a fraction of 600mA, the stepper should move properly under load without dissipating nearly as much heat in the coils or the driver. Fortunately my digital multimeter came with a temperature probe so I can check this out.

So does this sound about right?

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by adafruit_support_bill »

Sounds like you've got the basic idea.
The TMC2209 will apply as much voltage as it has available at the beginning of each microstep when the back EMF is at its max and therefore the instantaneous current is at its minimum, and cut off (I think) when the current increases to the preset limit. The resulting pulse just has to be long enough that there's enough energy (plus a bit) in each pulse to get the stepper to do each microstep under load.
The driver does not cut the current completely when it reaches the limit. Instead, it starts to PWM the current so that the average current remains at or below the limit. The Trinamic drivers can fine-tune the PWM cycles to optimize torque and positional accuracy (spread-cycle) or efficiency and low-noise (stealth-chop).
https://www.analog.com/en/lp/001/secret ... ntrol.html
https://www.analog.com/en/resources/app ... n-015.html

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Re: Pinout for TMC2209 Stepper Driver (6121)?

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The driver does not cut the current completely when it reaches the limit. Instead, it starts to PWM the current so that the average current remains at or below the limit. The Trinamic drivers can fine-tune the PWM cycles to optimize torque and positional accuracy (spread-cycle) or efficiency and low-noise (stealth-chop).
Oooohh, even better. :D

(We need real emojis here. ;) )

Definitely sticking with stealth-chop, considering my application (model railroad setup on display at train shows), smooth (microstepping) and stealthy are primary goals. Those and being able to ramp speed up and down for a rotation operation (hence using STEP and DIR pins). With my gearing down, I think I've got positional accuracy covered.

May get one of those variable DC supplies for testing purposes too.

My example of what I'm going for (recorded in Oct 2017, Kinugawa-Onsen, Japan).
(Suggest opening in new window, and turning volume down a bit. Loud toots.)
https://www.youtube.com/watch?v=b_h3vgIZHSo

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Re: Pinout for TMC2209 Stepper Driver (6121)?

Post by adafruit_support_bill »

So you are modeling Japanese steam. N scale?

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Re: Pinout for TMC2209 Stepper Driver (6121)?

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Not just steam, but yes. Drives some of the club members here a tad crazy, but that's me. <grin> And yes, N scale, specifically modular T-TRAK. And the train show here in Richmond VA this weekend is another chance for me to do so.

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