Hello,
here is my problem
i need to detect the speed of a DC motor.
so i should use an increment speed encoder.
for this I need a timer to count the pulses,and calculate the speed.
unfortunately,i'm out of timers in my application
is there an external circuit to add with the encoder so you i can get an analog speed value.???
or i don't have to use a timer in the first place ????
Help please

 

Is it one particular dc motor? If you able to choose a motor with a dedicated feedback signal, get one.

Otherwise, if you can't change the motor, what is the application for the motor? What will the analog signal you generate ultimately be used for?

 

...
is there an external circuit to add with the encoder so you i can get an analog speed value.???
...

Yes, there is.

 

here my project that i'm working with

http://forum.allaboutcircuits.com/showthread.php?t=30865

What will the analog signal you generate ultimately be used for?

so i can read it with my pic,rather than reading pulses directly.

#steveb
can you tell me more about this circuit,i guess its an external digital/analog converter!

 

Instead of the encoder you can use a small dc motor driven by the shaft of the main dc motor. It will act as a dc generator and its Vout will be directly proportional to the speed of the main motor. The dc out can be measured with one available ADC channel on your pic.

Alberto

Well ,i thought of this ,but its not practical,the dc generator need space,which i don't have...thanks

 

For DC motors,24V, 125 to 450W, try All Electronics. For an analog V speed signal: use reflective sensor with alternating white/black segments on disc or drum [shaft ], differentiate output to obtain uniform pulse, integrate with a current bleed, to give V porportionate to speed.

 

For DC motors,24V, 125 to 450W, try All Electronics. For an analog V speed signal: use reflective sensor with alternating white/black segments on disc or drum [shaft ], differentiate output to obtain uniform pulse, integrate with a current bleed, to give V porportionate to speed.

ok, i didn't really understand,but i'll try it.thanks

 

found a good motor with speed control,and it looks really interesting
http://www.allelectronics.com/make-a-store/item/DCM-346/PRECISION-GEAR-MOTOR-W/-SPEED-CONTROL/1.html
I'll try to find how this was made