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Simple DC motor driving with one transistor and PIC

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BlackOps

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dc motor diode transistor simple

Hello!

i've found one DC motor at home.

i was testing it with battery, and it seems to work from 3v voltage, and it also worked on 6v...i suppose its range is up to 9 or 12 maybe. and when i changed polarity of battery its rotation direction also changed.
first question right now: how can i find out its main characteristics without any datasheet, just by measurement?

now i am going to control its work using PIC16F917. for now, its the first test, so i am not going to control direction or speed. i want to make it rotate every 5 second for 5 seconds.

so the first thing i am going to do is to write program in ASM, which turns HIGH one of the PIC pins for 5 second, and does it every 5 seconds. this is not problem.

next is:

1. choose between HIGH SIDE DRIVE and LOW SIDE DRIVE (no need for H bridge drive, cuz i am not going to control its direction), which one should i choose?

2.what must be the values for all the parts? which parts to buy? R1,R2, transistor, Diode D1?
i also saw on the H bridge drive schematic that there is inverter right before transistor, and i also saw it on some LOW side drive circuits...but on this circuit i dont see this inverter....so it is not needed? (this schematic is also from microchip)
if it is needed in which part i can have it, which part to buy?

3. what must be the Vcc value? the same 5v which comes to microcontroller? or i can apply more voltage to Vcc?

4. the ground of the drive circuit and the ground of the microcontroller is same?

5. i wont corrupt my PIC? :)
 

Roma_te

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affect diode dc motor

About your schematic. I did not understand why you put GND to anode of D1? It will short your transistor and your control impulses does not will hawe effect.

>2.what must be the values for all the parts? which parts to buy? R1,R2, transistor, Diode D1?
Transistor should provide maximal current more than current of your motor, and its shut-off voltage should be more than logic one of your microcontroller.
Diode D1 protects transistor of overloading after switching off of transistor its parameters does not influence on poerating mode and requirements to this diode are not high, so any diode you have you can put there.

>i also saw on the H bridge drive schematic that there is inverter right before transistor, and i also saw it on some LOW side drive circuits...but on this circuit i dont see this inverter....so it is not needed?
In this schematic you will switch on motor by logic 1 of controller and switch off by login 0. If you will put inverter it will be opposite.

>3. what must be the Vcc value? the same 5v which comes to microcontroller? or i can apply more voltage to Vcc?
You can use different voltages.

>4. the ground of the drive circuit and the ground of the microcontroller is same?
Grounds of this drive circuit and microcontroller should be the same. In opposit case this circuit will not work
 

BlackOps

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motor transistor pic

Roma_te said:
I did not understand why you put GND to anode of D1? It will short your transistor and your control impulses does not will hawe effect.
well i took the schematic from one of the Microchip notes, but what about the resistors?
 

Kurenai_ryu

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simple dc motor control schematic

an microchip appnote??? a H-bridge has 4 transistors and 4 diodes but for a single transistor the diode should be at the load (the motor) maybe use an ULN2003 or just check it's internal circuit...
 

Roma_te

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simple dc motor controller

...but what about the resistors?
Resistors depends of shut-off voltage of your transistor. In the most cases it is possible to find recomended cirquits for selected transistor and put the same resistors.
 

    BlackOps

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jhbbunch

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dc motor driving transistor

The resistor to ground is just to make sure no charge can build up at the MFet gate. It will bleed it to ground. Fets are very static sensitive devices. A 100K should be fine. A 100K for the series resistor should also be fine. Don't forget, the MFet gate has an essentially infinite input impedance. And get rid of that ground from the diode. A mfet grounded at the source and drain is not going to work.
 

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