Hi ,
I was testing my motors and drivers , and I made the circuit but nothing happened . So I took the A4988 out of the breadboard and placed another one , it was working . After testing a bit , only 1 driver out of 3 works . The one that was OK and worked when I tested doesn't work .
Is that a software problem or hardware ?
(I have read similar posts they weren't the same)
(After a while the a4988 is a little bit warmer than room temperature but not hot . maybe 2 % warmer than room temperature , but not working at all)
and here's my schematic and code :
//simple A4988 connection
//jumper reset and sleep together
//connect VDD to Arduino 3.3v or 5v
//connect GND to Arduino GND (GND near VDD)
//connect 1A and 1B to stepper coil 1
//connect 2A and 2B to stepper coil 2
//connect VMOT to power source (9v battery + term)
//connect GRD to power source (9v battery - term)
int stp = 13; //connect pin 13 to step
int dir = 12; // connect pin 12 to dir
int a = 0; // gen counter
void setup()
{
pinMode(stp, OUTPUT);
pinMode(dir, OUTPUT);
}
void loop()
{
if (a < 200) //sweep 200 step in dir 1
{
a++;
digitalWrite(stp, HIGH);
delay(10);
digitalWrite(stp, LOW);
delay(10);
}
else
{
digitalWrite(dir, HIGH);
a++;
digitalWrite(stp, HIGH);
delay(10);
digitalWrite(stp, LOW);
delay(10);
if (a>400) //sweep 200 in dir 2
{
a = 0;
digitalWrite(dir, LOW);
}
}
}
Hi
my 'schematic' is the commented parts on the code , no actual schematic I just found this sample code here and used it .
I'm using a (regulated) power supply set to 9v ( 0.5 A ) and I guess that's more than enough for a stepper with 100+ ohms of resistance .
The code makes one counter-clockwise revolution followed by a clockwise .
If the drivers are actually damaged it may be due to a loose connection between the driver and the motor. Breaking that connection (or allowing it to break) while the system is powered is very bad for the driver.
I can't imagine any software problem that could damage the driver if it is properly connected.
A pencil drawing of the connections is much more reliable than a text description. It is very easy to misunderstand a description. Just post a photo of the pencil drawing. There is a good connection diagram on Pololu's A4988 webpage. By the way it is also good to have a pencil drawing of the ACTUAL connections in case they differ from the INTENDED connections.
I also tried using them with your code and the connections here , on the polulu website but it doesn't work .
I guess it's the loose connections (I guess these boards are REALLY fragile if a motor getting disconnected destroys them)
I also remember taking the motor away unaware of this fact .
but is there any tests to make sure the board is destroyed before I buy another one ? (like , testing the coil outputs to see if there is any electricity there ?)
I think if you wire the A4988 correctly and the motor does not move with simple code you can be fairly sure it is damaged.
I don't think the problem is so much that the boards are fragile as that there is a lot of uncontrolled energy released when the connection to the motor coil is broken so you get a very high voltage spike.
Motive power involves field energy. When the current gets turned off, the field collapses and usually there's at least a diode in the motor driver shunting it off. But that's when the circuit is together, otherwise where does it go?
For small motors, a ULN2803 can be used as a driver. It has protection built-in. It might or not need a heatsink, each channel is 500 mA up to 50V max (200 mA 12V easy) and IIRC (anyone?) you use 4 to 6 channels to run a stepper.
The ULN2803 has 7 channels, there's an 8 channel ULN28XX that costs a lot more.
Perhaps FETs would be better, then you'd have to wire protection circuitry as well.
I might be getting lazy, I ordered 4050's for voltage leveling. They're protected too.
I just found this sample code