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| Micro Controllers Discuss all aspects of micro controllers - building them, coding them, etc. All controllers are welcome - PIC, BASIC, Z8 Encore!, etc. |
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1st October 2009, 10:37 AM
| #1 |
 need help.. frequency to voltage converter using PIC
my project is frequency to voltage converter using PIC. but i dont know suitable PIC for my project.. i am also dont know how to complete this project.. the project is to read input frequency and give the output in voltage.. for example like below.. input (hz) / output (v) 100 / 0.1 200 / 0.2 300 / 0.3 can i use 16f887a or 16f873?? i hope you all can help me.. thanks to all.. | |
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1st October 2009, 01:58 PM
| #2 |
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there a easy way to do this and it works with any pic you check for frequency say on porta,0 Then output a voltage on portb using it as voltage divider like in the pic | |
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1st October 2009, 02:05 PM
| #3 | |
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1st October 2009, 03:20 PM
| #4 |
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Nigel I'm not as smart as you I don't know whats it proper name but it works i used with the stamp. This gives greater details http://www.allaboutcircuits.com/vol_4/chpt_13/3.html | |
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1st October 2009, 03:42 PM
| #5 |
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Natasya, what is the output supposed to do? How are you going to read the output voltage? | |
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2nd October 2009, 02:36 AM
| #6 |
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There's an easier way to do it. Everytime an input pulse / edge is detected you just get the PIC to make a fixed-period output pulse. Then average the output pulses into an RC filter. So if you want 100Hz = 0.1v (ie 1000Hz = 1v) just generate a 1000Hz/5 output pulse. Or 200uS. The benefit of this is that you can use the very bottom end PICs for it, like 10F or 12C series. | |
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5th October 2009, 01:30 AM
| #7 |
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thanks all... actually i dont want use voltage divider... can i use the output in PWM and convert it to voltage??? MR RB, can yo explain in more detail what was you wrote here?? Thanks.. | |
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5th October 2009, 01:41 AM
| #8 | |
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And you have the idea you test for 100hz then send a higher 1000hz which would give you 1 volt peak put a 10uf cap on it and it will look like 1 volt Last edited by be80be; 5th October 2009 at 01:44 AM. | ||
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5th October 2009, 02:15 AM
| #9 |
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Bebe, do you have a schematic handy you could show the OP, what you said is a little confusing.
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5th October 2009, 02:38 AM
| #10 |
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Something like this would work your testing for 100hz if a 100 hz in you send back out a 1khz which with a filter capacitor looks like 1 volt If you want .1 volt send a 10khz out Last edited by be80be; 5th October 2009 at 02:39 AM. | |
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5th October 2009, 03:40 AM
| #11 |
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Why not use an LM2917 frequency-to-voltage converter? Is it strictly PIC-based?
__________________ -The kinda guy who would improvise so much that you'd say "Here's 50 bucks for your Gigantron" http://vortexelectricaz.blogspot.com | |
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5th October 2009, 03:44 AM
| #12 | |
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5th October 2009, 05:02 AM
| #13 | |
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The beenfits are that it is very simple, you onlt need a simple PIC (no ADC or DAC or timers needed) and it has infinite resolution, which is impossible to get with a R2R DAC or any 8bit DAC. | ||
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5th October 2009, 09:52 AM
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MR RB, has you done this project?? can u help me by sending the program and circuit... thanks... | |
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6th October 2009, 01:01 AM
| #15 |
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This is all the help you should need. The code goes something like this; Code: ; Super simple freq - voltage converter. RomanBlack Oct 2009 ; connect input to PIC pin RA0 ; connect output RC filter from PIC pin RB0 ; 200uS delay means 1000Hz input = 1v DC output start btfsc PORTA.0 ; first wait for input to be low goto $-1 btfss PORTA.0 ; now wait for input to go high goto $-1 bsf PORTB.0 ; set output high nop ; enough nop's here to make 200uS delay nop ; or use your own 200uS delay code nop ; (etc) bcf PORTB.0 ; set output low again goto start | |
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| Tags |
| converter, frequency, pic, voltage |
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