need help.. frequency to voltage converter using PIC - Page 2 - Electronic Circuits Projects Diagrams Free

natasya · 6th October 2009, 01:18 AM

thanks mr rb..

but i dont understand..
can u explain how it function...
thanks again...

be80be · 6th October 2009, 02:19 AM

It works like this It don't work. All he posted was how to get 1 volt by pulsing RB0 at 1000hz
You still need to cheak for 100 hz 200 hz and so on.

Which means you have a little more then this

Code:

btfsc PORTA.0 ; first wait for input to be low
 goto $-1

 btfss PORTA.0 ; now wait for input to go high
 goto $-1

this will not tell you if it was 10 100 or 1000hz all it will do is give you 1 volt on RB0 if RA0 is high

Mr RB · 6th October 2009, 02:33 AM

Have a think again.

The system I posted makes exactly one output pulse for every input pulse. Zero error and infinite resolution.

The 200uS output pulse is always the same period, again zero error.

It will make 0.1v for 100Hz, 0.3v for 300Hz, 1v for 1000Hz etc just as the OP asked.

be80be · 6th October 2009, 02:44 AM

RB what you posted just scales PORTA,0 by 10 and outputs on PORTB,0
PORTA,0 = 100hz then PORTB,0 scales to 1000hz the code you posted will do that.

natasya · 6th October 2009, 07:56 AM

thanks all...
i think i has understand it..
can you give the value for R&C and how to calculate the delay and output voltage..
for example, the PWM amplitude is 10 volts.
high delay is 99uS and low delay is 1us will give approximately 10 volt.
if high is 90 and low is 10, how to calculate the voltage output??

is it i was understood??

birdman0_o · 6th October 2009, 08:22 PM

The output of the PIC cannot be more than 5V. The mark/space time ratio will determine the voltage after the filter (percent of 5V).

natasya · 7th October 2009, 01:14 AM

that mean if high is 10uS and low is 100uS the output voltage is 10/100 x 5v = o.5 v ???

Vizier87 · 8th October 2009, 03:45 PM

Quote:

Originally Posted by be80be

He can I was just letting use what he had

I thought 'he' was a girl. Natasya?

natasya · 18th October 2009, 08:21 AM

anybody can explain more??

natasya · 26th October 2009, 04:24 AM

hye all..
i has try to change pwm to dc voltage..but failed in simulation..how to use low pass filter to convert pwm to dc voltage??

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6th October 2009, 01:18 AM	#16
natasya	thanks mr rb.. but i dont understand.. can u explain how it function... thanks again...

6th October 2009, 02:19 AM	#17
be80be	It works like this It don't work. All he posted was how to get 1 volt by pulsing RB0 at 1000hz You still need to cheak for 100 hz 200 hz and so on. Which means you have a little more then this Code: btfsc PORTA.0 ; first wait for input to be low goto $-1 btfss PORTA.0 ; now wait for input to go high goto $-1 this will not tell you if it was 10 100 or 1000hz all it will do is give you 1 volt on RB0 if RA0 is high __________________ Burt http://mybe80be.com http://stores.shop.ebay.com/mybe80be__W0QQ_armrsZ1

6th October 2009, 02:33 AM	#18
Mr RB	Have a think again. The system I posted makes exactly one output pulse for every input pulse. Zero error and infinite resolution. The 200uS output pulse is always the same period, again zero error. It will make 0.1v for 100Hz, 0.3v for 300Hz, 1v for 1000Hz etc just as the OP asked.

6th October 2009, 02:44 AM	#19
be80be	RB what you posted just scales PORTA,0 by 10 and outputs on PORTB,0 PORTA,0 = 100hz then PORTB,0 scales to 1000hz the code you posted will do that. __________________ Burt http://mybe80be.com http://stores.shop.ebay.com/mybe80be__W0QQ_armrsZ1 Last edited by be80be; 6th October 2009 at 03:43 AM.

6th October 2009, 07:56 AM	#20
natasya	thanks all... i think i has understand it.. can you give the value for R&C and how to calculate the delay and output voltage.. for example, the PWM amplitude is 10 volts. high delay is 99uS and low delay is 1us will give approximately 10 volt. if high is 90 and low is 10, how to calculate the voltage output?? is it i was understood??

6th October 2009, 08:22 PM	#21
birdman0_o	The output of the PIC cannot be more than 5V. The mark/space time ratio will determine the voltage after the filter (percent of 5V). __________________ Mike My website: www.ElectroBird.net

7th October 2009, 01:14 AM	#22
natasya	that mean if high is 10uS and low is 100uS the output voltage is 10/100 x 5v = o.5 v ???

18th October 2009, 08:21 AM	#24
natasya	anybody can explain more?? Last edited by natasya; 18th October 2009 at 08:31 AM.

26th October 2009, 04:24 AM	#25
natasya	hye all.. i has try to change pwm to dc voltage..but failed in simulation..how to use low pass filter to convert pwm to dc voltage??