View Full Version : problems when driving 3 steppermotors

04-15-2005, 06:04 PM
Hai everyone,
i am into a project of vending machine using printer carriage motor(unipolar) each working at 12V and 3 to 5 ohms at each coil. i use a pic16f877 with usb based ICD and driving the steppers using Tip122 darlington drivers(not in saturation mode i.e 10K base resistor) from 8255PPI driving one coil at a time. I use 5A 9V ac transformer with a 10A bridge box type with no bulk capacitor for motors but 7805 reg with 1000uF and 100uF for IC's getting from same supply. when driving individual motors every thing works fine, but when i try to work out even 2 motors the motor strucks and doesnot rotate properly. when in debug mode when i step by step executescommands, it executes in random order and then it hangs. my friend suggest me to include a bulk capacitor for motor or else it may be due to noise and emf when 2 motors work at same time affecting the micro power lines over the limit. can any one advice me how to solve this problem........ if any one came across this kind of problem if bulk capacitor is req can any one suggest me value?.

04-16-2005, 01:17 PM
5A transformer probably is not enough to run the two or more motors at a time, check the potential with two motor loads ....