Driving a DC motor /w 16f84a

[CluckShot]

here are a few tricks you may wish to try.
(1) MOSFETS love to be in parallel. This allows you to get the heat down a lot.
(2) Overdriving the control a bit on MOSFETS (50% or less) is generally safe and causes really fast response. Read the specs on you MOSFETS yours may be able to do this.
(3) Just for fun on the DC segment rather than killing the current entirely while running leave a modest few milliamperes hanging in the main drive coil at all times you are running the motor. It will drag the coil slightly but may affect current demand in the circuit a lot. This might well be worth the effort. This is a trick to prevent the collapse of the magnetic field in the coil of the DC motor. If it requires a voltage reversal, time this reversal when you are already into the next drive position some.

[Josuetas]

I didn´t read much of it, but you could do so many things!!.

First of all i would recommend a PWM always for this DC motors, they are really Current eaters, if the 16f84 don´t has it (it doesn´t) you can provide something with a simple timer, and a word counter. increase the counter on each interrupt an play with its value to decide if the pin goes HIGH or LOW. I really recommend to meet at last the 16f628 you get so many more stuff that you will never go back to 16f84, you´ll get for example a great PWM in one sentence.

I have in my hands the irf530 right now, it should make the work; I don´t have the greatest memory but i do remember that this Motor is an inductor and it will help you to use a diode (1n4004 or a Switcher if using PWM) to reduce peak currents on the level change from ON to OFF, you might have used this diode on relays for the same purpose.

If you can´t use different batteries for the motor and control (if you can then use an optocoupler) then be sure to add some capacitors to the uC Vcc-Vdd as close as possible (this is a classic one).

Don´t know if you are also using a Vreg if you are he is the one shutting down after heating.

Working with small batteries and getting power out of them is a real challenge, if you can go for a better source (you can usually do this for college asignments)

[fazan83]

I didn´t read much of it, but you could do so many things!!.

First of all i would recommend a PWM always for this DC motors, they are really Current eaters, if the 16f84 don´t has it (it doesn´t) you can provide something with a simple timer, and a word counter. increase the counter on each interrupt an play with its value to decide if the pin goes HIGH or LOW. I really recommend to meet at last the 16f628 you get so many more stuff that you will never go back to 16f84, you´ll get for example a great PWM in one sentence.

I have in my hands the irf530 right now, it should make the work; I don´t have the greatest memory but i do remember that this Motor is an inductor and it will help you to use a diode (1n4004 or a Switcher if using PWM) to reduce peak currents on the level change from ON to OFF, you might have used this diode on relays for the same purpose.

If you can´t use different batteries for the motor and control (if you can then use an optocoupler) then be sure to add some capacitors to the uC Vcc-Vdd as close as possible (this is a classic one).

Don´t know if you are also using a Vreg if you are he is the one shutting down after heating.

Working with small batteries and getting power out of them is a real challenge, if you can go for a better source (you can usually do this for college asignments)

I don't understand by what you guys mean PIC16F84a doesn't have PWM.
We can use the pulseout command right?

PULSOUT Pin,Period

I have create a robot using the DC servo motor using PIC16F84a and the Motor speed (modified DC motor) and position can be controlled using the PWM command.

To control DC Motor speed and to safe the power consumption we also can use the PWM method. But for DC motor we cannot easily control the angle of the rotation as the DC servo motor.

[ra68gi]

I don't understand by what you guys mean PIC16F84a doesn't have PWM.
We can use the pulseout command right?

PULSOUT Pin,Period

By PWM they mean hardware PWM module see data sheet of 16f8xx.
pic basic pro has got a command to use this its..
HPWM Channel, dutycycle, frequency.

PIC 16F84 does not have this hardware module so you can't use this command. But you do have a software pwm command..
PWM pin, duty, cycle. but the disadvantage is...
The PIC has to keep churning out pulses all the time not able to do other important things like adc measurement or rpm measurement etc which will be the feedback to control your motor. The second thing is the software pwm is only for a limited no of cycle & to keep it ON you need to give it or invoke the command again after the cycle is over.

Pulseout command is commonly used as clock or some cases in hobby projects to control servo motors. but in all these cases the micro is made to spend all its time only to generate pulse. Log on to rentron.com & you will find some nice examples to use pwm to fire IR leds.

Regards
Raghunathan.