K8055 - VM110 How To Control A Motor

Hi, this weekend i bought a K8055 USB kit to improve the control side of a small coil winding jig. I have a degree in software engineering so a board that enables me to use computer based logic to control electronics was perfect! I constructed the project without any problem. Once constructed i opened up the control application, ran the output test and marvelled at the flashing LED’s. I then tested the outputs with my multi-meter and got the expected results. It was at this point i thought all my problems had been solved… How wrong i was.

Moving on i connected up a small 5v motors to the PWM output and got nothing… so i connected it to the analogue output and again nothing, i tried my multi meter on the analogue output and got a variable voltage, so i thought the USB wasnt outputing enough power so i attached an external 5v supply as described in the manual, again nothing. So i tested the motor directly from the PSU and it ran a dream. So i started to wonder if the motor was to large… thinking such i connected up the smallest motor i have (a mobile phone vibrator) and again nothing.

So i searched on google to see if anyone else had a similar problem and found a reply on this forum which states that the 8055 will not control motors… i was agasht to say the least, the only reason for my buying of the kit was for the 2 PWM outputs which were to control the 2 small motors needed for my experiment. Once i was over the shock i began to look for an easy solution to this problem and found nothing that wasnt too expensive, in american or extremely complicated. I know my electronics knowlage is somewhat limited but i had hoped this board would allow me to increase my experience.

Can someone please tell me of a quick, easy and cheap solution to enable this board to control 2 motors?

Many thanks in advance

Tim

It seems that you may have to strengthen the output current capability of the card with external transistors.

At the analogue outputs there are 1k5 series resistors as short circuit protection for the operational amplifiers. This is why you can’t drive the DC motor directly from these outputs.
To these outputs you have to add external NPN transistors connected as emitter followers to drive the motors.

The PWM outputs should be capable to drive small DC motors without any modifications if the motor current is below 100mA.
The problem may be that your motor is drawing more than 100mA of current. You may check this by measuring the motor current when you drive it directly from the 5V supply.