Motor driver not working, digital HIGH only 0.5 V

I'm trying to get these motor drivers (chipset: L6203: datasheet) and motors (MAXON m97336 A 2) to work, without luck yet:

I attached motor and 24V/GND to one side, and GND, IN1, IN2, EN, SE to Arduino GND and 4 Digital Pins. When the digital pins are connected to IN1, IN2, EN and SE, and I tell them to be "HIGH", I can measure only 0.5V on them with a voltmeter. When disconnecting them with the motor driver and measuring, I get the wanted 5V. Why do they have 0.5V when connected?

It appears that your device is overloading the arduino outputs. I take it the SE connection is the "sense" input to the L6203. If so then why do you have it connected to an arduino pin (input or output ? you don't say which). It surely should be getting some form of current feedback signal from the motor driver.

What make of module is containing the L6203, do you have a circuit diagram of it and how you have connected it to the arduino.


Thanks for the reply jackrae.
Problem is that I dont know how these drivers work, and I dont have any diagram. They appear to be self-made...
I tried also without connecting SE, just IN1, IN2, EN, put them to digital Outputs and set them to HIGH to see what happens, but nothing happend.

You have an idea what signals to feed to the driver from arduino or if there is a library that would do the right thing?

I see this is your second post on the subject.

Without a circuit of what's in the green box you really are shooting in the dark

Suggestion :-

Disconnect motors, disconnect all arduino side connections, connect supply and grnd to green box, couple green box ground to arduino grnd. Now set one arduino output high. Connect In1 to this pin, does it go low. Record results. Repeat tests for In2, En and Se in turn using the same arduino pin.

What are the values of the resistors within the box connected to In1 and In2. If you have a test meter what is the resistance from both sides of these resistors to the grnd terminal.

Would it be possible for you to get a high resolution photograph of the circuit board foil side and the same of the component side. If so, also advise what each resistor value is. With this information it MIGHT be possible to create a circuit diagram.


Finally I had some time to work on this. I made a circuit diagram with everything I could see inside:

Couldnt measure these "Pearl Resistors?" with the multimeter, they are described with "BYV27/100". The resistors are painted in red, the devices that are red on the board are blue in my diagram (sorry for the confusion actually).
The resistances from IN1 and IN2 to ground are both 4.7k.
There was just one character I couldnt recognize which is a "?" in my diagram.

Does this motor driver diagram look familiar to anybody?

I will also connect the HIGH arduino pin to all inputs and report the results here, maybe tomorrow.

Those "pearl resistors" are diodes:


I will also connect the HIGH arduino pin to all inputs and report the results here, maybe tomorrow.

What you should do is this:

  1. Draw a proper schematic of the circuit based on your trace diagram, known parts (driver IC, resistors, and diodes), and "unknown" parts (the red devices on the PCB - though I suspect they may be capacitors).

  2. Find out what goes where -exactly-, and how that circuit compares to any reference design on your datasheet (I haven't looked at it).

  3. Hook up the driver to a motor and power source (for the motor/circuit).

  4. Then hook up a "dummy" 5V logic supply (four 1.2 volt nicad AA batteries would be OK - you could probably even get away with 3 1.5 volt AA alkaline batteries), and test the circuit that way.

Take the Arduino out of the loop, and probe with your schematic in front of you (after reviewing it and attempting to understand it, if you can). If you can get things to work without using the Arduino, then you'll either discover what you are doing wrong (maybe you have things connected wrong or such?), or maybe it -is- drawing too much current. To find out, put your multimeter in series with the dummy logic source, set it to measure current (around 1A), and probe again to see what current it is pulling; if its over about 25 mA, then it is too much for the Arduino (you'll need to use a transistor or something to increase the current availability).

Thank you all for the replys, this brought me a lot further!

With an external 4.5V power source: GND to GND, +4.5V to EN and IN1: the motor finally turns in one side, with +4.5V to EN and IN2, it turns the other side around. The current-meter displays alternating 0.00 A and 0.01 A, so it should really be around 10 mA per arduino pin? The website says: "DC Current per I/O Pin: 40 mA" so this shouldnt be a problem..?

I also tried with a 12V 1A power source for the Arduino, with USB disconnected. Still the same result, digital high pin goes low (0.3V) as soon as I connect them to EN or IN pins...
When measuring current through these high pins, it displays 0.00 A. So it is no short circuit?
I will try this with another Arduino board if I can find one somewhere soon... Any further help is surely appreciated too!

And as the motor now turns with the external power source, I dont think its necessary to draw another schema of the circuit? It already took 2 hours to draw this one :slight_smile: