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i have been playing with mbed since few week ago and would like to create a test program for dcmotor speed control. im using a 24V dc motor with encoder attach.. then test, at first i test with supplying a 5v and 3.3V from mbed to the motor. the thing work fine giving a 16 and 10rpm respectively. later i try using 12v it give 40rpm. then i try a 24v input, now the speed wont come out. and also the counter that count each on/off tick not counting up.

any possible reason? my though that maybe when it move so fast that the ISR routine couldn't catch up to the speed..

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  • $\begingroup$ Can you provide a schematic and part numbers? Are you passing 24V to just the motor or to the motor AND encoder? What is the rated voltage on both? $\endgroup$ – Chuck Jan 20 '16 at 11:40
  • $\begingroup$ hi its a Sankyo JHAOB15 motor and mbed lpc1768. i try to upload circuit together in above but it seems i cant upload new picture due to not enough 'reputation'. $\endgroup$ – kai1709 Jan 20 '16 at 13:27
  • $\begingroup$ im not sure about about the encoder. but the motor use 24V if not mistaken. i salvaged this motor from work and cant find any data on this.. $\endgroup$ – kai1709 Jan 20 '16 at 14:18
  • $\begingroup$ I agree - I looked around briefly online and couldn't find any specification or a datasheet for the motor. The thing you salvaged it from - was it working? $\endgroup$ – Chuck Jan 20 '16 at 16:00
  • $\begingroup$ I'm voting to close this question because it's not clear what components you have and thus not really possible to help troubleshoot. I can't find datasheets for your equipment. If you can post a link to one I'll retract my vote. $\endgroup$ – Chuck Jan 20 '16 at 16:47

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