Unfortunately I having problem with a new A4990 board. I’ve wired it up to an Arduino Mega for testing,
without any PWM, only constant logic states applied to it, just to check the rot. directions of the motor, but the motor wont move at all. The INH pin is pulled up to 5V,
the motor driving voltage is 12V (I = 120 mA). The EF1-EF2 pins iare stay LOW all the time, independently from the logic input states, (even when the motors are detached) I’ve already tried all combinations from the truth table. I’ve three of these modules and non of them work so far, so maybe I’m the one who doing something wrong. Thanks for your help in advance guys!
Do you have a datasheet or any specifications for the motor and power supply you are using? Can you post pictures that show all of your connections including any soldered connections you made?
Thanks for your response, I using a Chieftec 750W (CFT-750-14CS) PSU, the motor is an RK-3700cc-14230 12V DC brushed motor, which was work fine with other boards like the L9110 dual H-bridge module. Here are the pictures about the setup:
Thanks for posting those pictures. It is possible that motor is trying to draw too much current though the driver which is tripping the overcurrent protection on it. If you add pull-up resistors to the EF1 and EF2 pins, you can check for an overcurrent fault condition, described in Table 3 of the A4990 datasheet. You might also try to disconnect the motor and then power the system to see if you have a voltage between pins OUT1 and OUT2.
Thanks for the suggestion, you were right, an overcurrent condition occurred when the motor starts. When I’ve limited the current with 10R resistor, it works fine. However it is a bit strange how the IC acts in some situations:
the motor winding has a 10.5R resistance and I’ve added an extra 4.7R in series so the max current in that case was 0.8A (measured as well) and the current limiting suddenly switched on with 20kHz and 93% duty cycle, out of phase, and the motor stopped rotating. However it works fine with 10R series resistor,so thanks again for your help!
