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General suggestions or questions about the SparkFun Electronics website
By EmbeddedMan
#46686
Some EasyDriver users have experienced trouble getting them running smoothly, or running at all. I wanted to summarize in one post all of the good ideas I've heard (and seen) to troubleshoot ED problems. If you're having trouble, check each of these things out and you may save yourself quite a bit of trouble.

1) The ED requires at least 7V at the motor power input. And this power needs to be clean and have enough current. The maximum that the ED can draw is about 1.5A, so make sure your power supply can handle it. I normally use the 12V lines from old computer power supplies and it has never let me down.

2) The 'smoothness' of your steps will be dependent upon several factors. The setting of the current limit pot on the ED is the most important one. For each motor and power supply voltage, you will want to adjust the pot for the 'smoothest' operation. Note that this does not always mean 'maximum current'.

3) Does your ED seem to step differently as you touch the current adjust pot with your finger? If so, the pot is probably set in the 'open' position (between 5V and 1V of output to the REF pin - pin1 of the driver - where the REF pin is floating) and so your finger is adding noise and screwing things up. Turn the pot about 1/4 turn clockwise and try stepping again - now your finger shouldn't affect things.

4) The maximum step rate you can get the ED to do depends a lot on the motor and the power supply, but about 1 to 2 KHz is all I can get out of many of my motors. Raising the power supply voltage (all the way to 30V if you want) will help this out a lot, but remember to re-adjust your current sense pot if you do change your motor input voltage.

5) Using large stepper motors may prove a disappointing experience. With really large motors, the ED doesn't have enough oomph to do the microstepping right, and you will be disappointed with the resulting torque. NEMA-17 sized motors are just about perfect for the ED.

---- Adjusting the current sense pot ----

How do you adjust the current sense pot? Here's one way I've done it and it really works well.

A) Solder on a wire to pin 1 of the driver chip (the pin closest to the current adjust pot) or put your volt meter there. Turn power to the ED on (with the motor connected) and turn the pot clockwise until you see where it goes from about 5V, down to zero or .1V, and then jumps up to 1V or so. That point where it jumps to 1V is where the ED will deliver the minimum current to the coils (about 150mA/phase). If you then continue clockwise to 5V, that's where it will deliver maximum current (about 750mA/phase). So set the pot to 1V.

B) Now hold the direction pin either high or low, and pulse the step pin once every 20ms. It will take about 30s to deliver 1600 steps at this rate, which for a 400 step/rev motor is 1 rev.

C) As the stepping is happening, very, very slowly turn the current adjust pot clockwise. Feel the motor shaft with your hand. Notice what happens to the stepping - different things will happen with different motors. Some motors will start out real smooth and even at 1V, and then hit a point somewhere around 2.5V where the stepping becomes real rough. Some will start rough and then get smooth. Just experiment, feeling, listening, and slowly adjusting the pot.

D) As a reference point, with the stepper motor that SparkFun sells, 1.5V is about the perfect setting (I've found). Very nice smooth steps, and considerable torque.

Please post any more ideas for troubleshooting/testing EasyDriver boards here if you think of them.

Thanks!

*Brian
By pa.ul
#46715
today i tested ramping with ED (minebea nema-17)

ramping up to 40 microseconds:
i start with 400 microseconds delay and decrease -2 each step until 40 microseconds delay

ramping down from 40:
same but reverse increase +2 each step

result is smooth start and stop while running at max speed in between

ED is connected to an iduino

paul
By EmbeddedMan
#46727
pa.ul,

That is a very nice top speed. One thing to note is that top speed is very dependent upon load - just letting my motors spin, I can get them up to much higher speeds then when they are actually mounted to my CNC mill. Torque in a stepper motor is proportional to speed.

*Brian
By pa.ul
#46816
Brian,

today I was more than pleased, when I connected the stepper to a 1:250 gearbox.

no need to change delays or ramping
and really strong torque on the output-side of the gearbox

backlash is very small and so it is no prob for the apllication

nice evening
paul
By SamStaubin
#68197
Hi... Easy Driver 3 works fine but without torque !

It's 12 volts step motor with 3.6 degree per step. I tried 4 other step motor... same probleme. I tried to change currrent potentiometer....

No torque mean, I can stop de rotation with two finger.. it's normal ?

I made my own PCB with A3968...same probleme. ? so whats wrong !!!??
By EmbeddedMan
#68210
Sam,

I'm not sure what's going on there. I can tell you from experience that at low speeds, I can NOT stop the shaft of my stepper motors with my fingers when they're being driven at 24V with my EDs.

One thing to think about is the resistance of the stepper motor coils.

At 12V, your motor needs to have coils with resistances of less than about 16 ohms or the chopper circuit won't operate.

Also, if you sent a 100Hz step rate into the ED, and very slowly adjust the pot on the ED, can you feel or hear any difference as you rotate the pot around?

*Brian
By SamStaubin
#68215
Thx EmbeddedMan

The motor I use have 70 ohms per coile.. is it too much !? What you mean by ?"the chopper circuit won't operate."

Also, if you sent a 100Hz step rate into the ED, and very slowly adjust the pot on the ED, can you feel or hear any difference as you rotate the pot around? I made the test..I hear little difference but not torque won't change..

Other question for you.. I tested 5 volts step motor with ED.. I pull out de regulator and put wire between pin 1 and 8... voltage in, voltage out. The probleme still the same.. with 18,5 ohms step motor.. It's less than big one... normaly it supposed work. Did you make so test with this set up ?

From datasheet...A3967
Load Supply Voltage Range Operating 4.75 – 30 V

Thanks a lot!
By EmbeddedMan
#68270
Sam,

70 ohms is OK, it just means that the chopper circuit will never 'engage' and you won't ever get any microsteps. Even if the driver had zero resistance, at 12V, the maximum current that could go through the coil of your motor would be 171mA. (V = IR) I think the lowest that you can set the current adjustment pot would be about 150mA, so you could probably just barely get some small microstep action going at the lowest setting. That's why you don't hear much (if any) change as you rotate the pot - with that high of a resistance, the chopper driver circuit never trips and generates microsteps because there isn't enough current flowing through the coil due to its resistance. (The motors I use on my Fireball CNC mill are 4.4 ohms across each coil.) I've never tried motors with as much resistance as you have, but they still should work, just at reduced torque. (As I believe torque is proportional to current in general.)

So maybe everything is working properly, it's just a lack of current that is causing your low torque.

I'm very surprised that the 5V (18 ohm) motor doesn't give way more torque. The ED should have no problem delivering almost the full 700mA into that motor.

What is the current rating of your 12V power supply? Is it well regulated?

*Brian
By SamStaubin
#68507
Thanks for the explanation.

I tried three différent power supply.. max 1.5 amp.
By macegr
#68508
SamStaubin wrote:Other question for you.. I tested 5 volts step motor with ED.. I pull out de regulator and put wire between pin 1 and 8... voltage in, voltage out. The probleme still the same.. with 18,5 ohms step motor.. It's less than big one... normaly it supposed work. Did you make so test with this set up ?
I think you still WAAAAY don't understand. Did you actually pull out the voltage regulator and run a wire from pin 1 to pin 8? Does this mean you were attempting to power the 5V stepper motor from a 5V power supply? Put the regulator back in, attach the 5V motor, and use the 12V supply. With chopper drive circuits, you are supposed to put as high a voltage into the motor as possible, and then the driver will regulate the current to the desired level. This will overcome the motor winding inductance and deliver much more power at higher speeds. I regularly run 3.1V motors on 24 and 30 volt supplies (not with the easydriver, but a similar chip).
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