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ANY IDEA ABOUT SIMPLE DAC

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Fragrance

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pic16f876 max518

HI ALL FRIENDS

I want to build a simple dac based on opamp vari the out put 0 to 5v
when input pulses vari any help full idea will be appreciated
 

Vonn

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try to see these pdfs

w*w.eeng.may.ie/~rlawlor/Courses/GE210/Lecture_Notes/ Lct_21_Digital_to_Analog_Conversion.pdf

w*w.technology.ewu.edu/Tech408/Chapters/Chapter13.pdf

w*w.phys.cmu.edu/physics_33228/labs/lab8.pdf

Regards,
 

Tornado

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Hi Fragrance, are using a PIC on this? Is pulse changing in frequency
or pulse width? Please explain more, attach some waveform.

Tornado
 

Fragrance

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Tornado said:
Hi Fragrance, are using a PIC on this? Is pulse changing in frequency
or pulse width? Please explain more, attach some waveform.

Tornado
hi firend

i am using pic and pluse is pluse width type
 

Aoxomox

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Hi Fragrance, simple way is to LP filter your PWM singal in order to obtain an analog signal. The corner frequency of this LP filter should be at half (or less) of your PWM base freqency.
The analog resolution is approximately equivalent to your pulse width resolution.

the coding of your desired analog value into a pwm timer value will take some time or memory.

This DAC works if you don't need high performance and/or high speed.

could you tell us about your application???


aOxOmOx
 

Tornado

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Hi Fragrance here I have a Proteus design with hex file
for you to test, if you need my assembly code PM me.
I worked on PIC16F876. But easily can be changed to
other PIC types.
Also if you need faster response read the text in the
schematic.

Regards
Tornado
 

C-Man

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If you use 16F628 you can use the PWM output to generate your reference voltage (use a RC lowpass filter) and connect this generated voltage to one of the built in comperators and use the other comperator input for the signal you want to measure.

You could also use a R/2R resistor network on some free pins to generate a voltage with the resolution you need (might need an opamp as a buffer for the output signal).

If your application is not time critical you can generate a sawtooth voltage and measure your analogue value with it, other wise you could start with VCC/2 and if your voltage is lower continue with VCC/2 - VCC/4 (otherwise VCC/2 + VCC/4) until you find your voltage.

Should in theory be possible in 8 steps :)

best regards
 

svicent

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Another idea is to use MAX517, MAX518 or MAX519
2-Wire, Serial, 8-Bit DACs with Rail-to-Rail Outputs. The MAX517/MAX518 are available in space-saving 8-pin DIP and SO packages.
 

jochez

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Use a R2R net and a OP amp. It's not the best, but it works.
 

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