DC motor position control (not speed/direction) - Page 2 - Electronic Circuits Projects Diagrams Free

rngd · 21st December 2007, 10:42 AM

Quote:

Originally Posted by bryan1

Simply do some maths mate 56:1 worm drive gearbox, say 4:1 V-belt reduction drive to the pv frame. As you should know a DC motor's speed is controlled by voltage so depending on the condition required the voltage can be selected.
ie: 1. finding the right equal position for both led's to output the same voltage say 6-12 volts
2. Go to sunrise position at dusk pump 24 volts in for quicker travel.

By using an industrial wormdrive gearbox and further reduction with the V-belts will ensure enough rigidity to withstand huge gales.

Now for the led's do a simple test wire 2 led's up in parrallel with the output going to a gate on a fet which is connected to another led to show the circuit works. Now powerup a third led to shine directly into the 2 led array and watch the fet turn on. Simple isolated supply and a good test proving that led's DO output a voltage when exposed to light.

Hope that helps

cheers Bryan

Actually, I'm just building a very small tracker with a 5W panel, 12 V battery and a small DC motor, so I can't change up the voltage for quicker travel. Doesn't matter though, I'll just run it at the same speed. The motor will be <12V and running on low current.

Anyway, I just wanna get your confirmation and see whether I understand things correctly : Each time I send a pulse of current of a certain length from my PIC to my DC motor (which is connected to a gearbox), the motor will make my panel rotate, take for example, 5 degrees.
Increase in the gearbox ratio decreases the degrees of panel rotation (when the pulse length is kept constant).
Increase in the pulse length increases the degrees of rotation (when gear ratio is constant).
The amount of rotation (degrees) is calculated using the values of the gearbox ratio and also the pulse length. And when these values are set the panel will rotate the same amount each time a pulse is sent.

Is this correct ? Sorry to make something simple sound so complicated !

Thanks.

**Nigel Goodwin** · 21st December 2007, 10:56 AM

Quote:

Originally Posted by rngd

Anyway, I just wanna get your confirmation and see whether I understand things correctly : Each time I send a pulse of current of a certain length from my PIC to my DC motor (which is connected to a gearbox), the motor will make my panel rotate, take for example, 5 degrees.
Increase in the gearbox ratio decreases the degrees of panel rotation (when the pulse length is kept constant).
Increase in the pulse length increases the degrees of rotation (when gear ratio is constant).
The amount of rotation (degrees) is calculated using the values of the gearbox ratio and also the pulse length. And when these values are set the panel will rotate the same amount each time a pulse is sent.

Is this correct ? Sorry to make something simple sound so complicated !

Only very roughly correct, by using simple timed pulses the motor will move varying distances, depending up on load etc.

Like I suggested, a pair of light sensors (or four for two axis) would allow you to track the sun - it doesn't even need a processor, there have been many such circuits for doing this using just opamps as comparators.

rngd · 22nd December 2007, 08:15 AM

Quote:

Originally Posted by Nigel Goodwin

Only very roughly correct, by using simple timed pulses the motor will move varying distances, depending up on load etc.

Like I suggested, a pair of light sensors (or four for two axis) would allow you to track the sun - it doesn't even need a processor, there have been many such circuits for doing this using just opamps as comparators.

So I just let the motor run until equal light falls on the sensors, then open the limit switches to stop the motor.
OK, thanks.

**Nigel Goodwin** · 22nd December 2007, 02:34 PM

Quote:

Originally Posted by rngd

So I just let the motor run until equal light falls on the sensors, then open the limit switches to stop the motor.
OK, thanks.

No, the limit switches are only to stop the mechanism going further than it should, your control system shuts the power off during normal tracking.

rngd · 22nd December 2007, 04:05 PM

Quote:

Originally Posted by Nigel Goodwin

No, the limit switches are only to stop the mechanism going further than it should, your control system shuts the power off during normal tracking.

Oh, OK, for turning off the motor during normal tracking I just use transistors.

**Nigel Goodwin** · 22nd December 2007, 04:33 PM

Quote:

Originally Posted by rngd

Oh, OK, for turning off the motor during normal tracking I just use transistors.

Or relays?.

rngd · 23rd December 2007, 12:38 PM

Quote:

Originally Posted by Nigel Goodwin

Or relays?.

Oh yea, or relays too. They would probably be simpler to implement also I think.

civictypeR · 29th January 2008, 01:47 PM

now you want is to control speed what , why dont you use L293 chip . go google it up , it is cheap and used PWM to control it , but the chip has to fit your motor's current specification . There are 2 versions chip , one is for the higher current and another one is for the lower. Using L293B to control my motor which runs in high current . Direction I think if you need that feature then you need to send pulse so that it can move at a certain angle . but the angle will not be accurate unlike servo motor

hope this helps
pirate civictypeR

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29th January 2008, 01:47 PM	(permalink)
civictypeR	DC motor control now you want is to control speed what , why dont you use L293 chip . go google it up , it is cheap and used PWM to control it , but the chip has to fit your motor's current specification . There are 2 versions chip , one is for the higher current and another one is for the lower. Using L293B to control my motor which runs in high current . Direction I think if you need that feature then you need to send pulse so that it can move at a certain angle . but the angle will not be accurate unlike servo motor hope this helps pirate civictypeR