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  1. M

    measure a voltage across of a dc motor

    hello,i am trying to measure a square wave(pwm) with amplitude 3V, so when i try to measure it with a multimeter across my motor,should i watch the next: Vmultimeter=3*sqrt(duty cyle) is it correct? because sometimes i am watching more than 3V on my multimeter across the motor about 3.7V but i...
  2. M

    pwm to control a dc motor

    if suply voltage is 5V and my duty cycle is 60%,the average voltage across my motor is 5*0.6=3V(max allowed) so if i have the duty cyle 60% as i said ,why i can´t give a supply voltage higher than 3.5V,i want until 5V, my motor won´t read more than 3V with supply=5 because my duty cycle is 60%
  3. M

    pwm to control a dc motor

    http://imageshack.us/photo/my-images/705/sinttulo2mn.jpg/ i tried this circuit but with a transistor BD135 not a 2n2222A and when i tried to supply the 555 with more than 3.5V,the motor consumes more than its maximum current allowed 0.3A why is this happenin ?because my duty cycle is 60%(to get...
  4. M

    pwm to control a dc motor

    dc range i don´t know if it takes the average or rms,which is the different? the formula V=Vpeak*sqrt(duty) is with rms or average? and i tried with a transistor BD135 but when the supply voltage for the circuit is higher than 3.5V the motor consumes its maximum current o.3V,why?
  5. M

    pwm to control a dc motor

    the motor must be which i said you, i am gonna change the transistor to a BD135,which can have 1.5A at its colector should it works? and one question more: when i check the voltages with my multimeter,i see the effective voltage ? so to calculate the peak voltage the equation is ...
  6. M

    pwm to control a dc motor

    MY MOTOR no load has 0.3A and max efficient has1.05A motor works between 1.5V and 3V max in the datasheet of transistor 2n2222A: 0.8A max colector ,but we never have this value because we don´t have load(no gearbox) on the motor,so the max current will be 0.3A,YES?so it won´t be a problem...
  7. M

    pwm to control a dc motor

    and one question more when the transistor is on cut-off which voltage is watching the motor,7V ? because the voltage maxium for my motor is 3V. or it won´t affect because the motor doesn´t recieve energy?
  8. M

    pwm to control a dc motor

    i tried it too, with that current but the same problem and when i try to see if the transistor is on saturation with the oscilloscope i see the next signal: http://imageshack.us/photo/my-images/821/imageniqb.jpg/
  9. M

    pwm to control a dc motor

    hello,i am trying to control a dc motor (1.5-3) with a transistor 2n2222a, at the 555output i have (supply voltage-1)=7-1=6V and the circuit is attached my transistor has gain=40 and the maximum load of y motor will be 0.3A,so i need at my base a current at least I=0.3/40=7.5mA to get...
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