I am having real issues driving these things. I breadboarded an A4988 and it seemed to work fine, so I made a PCB.
Now I just cannot get this thing running.
It does spin, but a 1 legged ant in a coma has more torque. They appear to be 160 step.
I believe issue lies in that the A4988 actually needs 8v on the motor supply side to work correctly.
It does run through the A4988 at 5v, but it clearly isn't right.
Just wondering if i throw 8v through the A4988 and see what happens. I do have spares.
At the end of the day, these steppers are supposed to drive camera lens.... no way that could happen (I don't think). Nothing I have seen shows me they have anywhere near enough torque to drive any kind of gear arrangement.
I am driving them with this base code (other libraries I have tried throw up the same results)
#define stepper1 8
int stepperSPEED = 1000;
byte stepdelay = 50;
int movesteps = 160;
void setup() {
Serial.begin(9600);
pinMode(stepper1, OUTPUT);
Serial.println("Online");
}
void loop() {
Serial.println("Testing stepper 1");
for (int i = 0; i < movesteps; i++) { // steps in a rotation
digitalWrite(stepper1, HIGH); // sets the pin on
delayMicroseconds(stepdelay); // pauses for ## microseconds
digitalWrite(stepper1, LOW); // sets the pin off
delayMicroseconds(stepdelay); // pauses for ## microseconds
delayMicroseconds(stepperSPEED); // stepper speed
}
}
You may be able to use the A4988, but motor supply voltage must be over 8V. The A4988 is a current regulating driver, the voltage is not so relevant so long as the coil current limit is set correctly. How to set current limit.
No Breadboarded it again and same result.... not sure what has occurred there.
I can run the little stepper at 8v, but boy does it get hot. That's no good. I know steppers get hot, but this melted the plastic gear I had on the shaft for rotation indication after 60 seconds.
Very annoying, as the stepper mechanism I made is lovely... just can't drive it!
Could try a DRV8834, but is that likely to be any different....
I was going to grab a couple of DRV8834's.... but very annoyingly they are not the same footprint as a A4899 (even though it says it's a direct replacement).
You must set the coil current limit properly to use 8V. Did you set the coil current limit? Set the current limit (follow the instructions in my previous post) at the lowest possible and work your way up.
Then you didn't adjust the current correctly. As already stated the A4988 is a current controlling driver. It is mandatory to set the current correctly. If this is done, the voltage at Vmot doesn't really matter concerning the temperature of the motor.
But maybe the current cannot be set as low as the motor needs. Then you need another driver.
I thought you started with the current pot at zero (fully anti-clockwise). Usually, the stepper doesn't even move.
Turn it clockwise until the stepper starts.
This one starts right off the bat. Not much torque to it, but it starts. It also cooks as well at fully anti-clockwise.
Turning it VERY slightly up to get better torque (as in 5 degrees) melted the gear
The linked motors have 19 Ohms, which is high enough impedance that you don't really need a current limiting driver. A brushed DC motor driver like this one will work with 3V for the motor power.
To be specific, you could easily make a controller using those. You'll still need a driver.
I think the basic problem you have is that you seem to not be able to use a >8V power supply, is that correct? You could probably run your steppers from a ULN2803 driver if they are unipolar-compatible steppers (I think they are. didn't check) and sequence the steps from the Tiny85. But at lower voltages, you may not get the torque you need since that driver is old and has a high saturation voltage of about 1.3V so if you have to drive it with 5V, your motor will only see 3.7V.
It's up to you to decide if that's enough torque. But yeah, it's fairly trivial to drive a stepper. You don't even need the library; it's literally like 5 lines of code.
[edit]
After typing all that, I looked at your link and no, the 2803 can't drive those. They are 4-wire motors so they need a bipolar driver. So now we're back to seeing if the 4988 problem is solvable
