ADC calculations in the voltmeter project - Electronic Circuits Projects Diagrams Free

sahu · 29th October 2009, 06:09 PM

i am working a voltmeter project.it is based on 16f676. but don't understand ADC calculations in the voltmeter project . i see also Electronic Circuits it is not working properly. and c lang. also

MikeMl · 30th October 2009, 12:01 AM

The A/D input to a Pic is usually ratiometric with respect to the Vdd pin, meaning if it is a 10 bit A/D, it will read out 1023 (2^10-1) when the analog input is the same as Vdd. That means you have to know what Vdd actually is; 5V is not good enough. You have to know if it is 4.87V or 5.04V.

Sceadwian · 30th October 2009, 12:11 AM

Does that particular pic not have an internal voltage reference? I'm used to AVR's which although they can use VCC as a voltage ref also generally have an internal bandgap voltage source of around 2.54 volts, so long as the VCC voltage is above the internal circuitry's threshold for regulation. (not sure what that is off the top of my head) the ADC results will be unaffected.

sahu · 30th October 2009, 05:02 PM

Quote:

Originally Posted by MikeMl

The A/D input to a Pic is usually ratiometric with respect to the Vdd pin, meaning if it is a 10 bit A/D, it will read out 1023 (2^10-1) when the analog input is the same as Vdd. That means you have to know what Vdd actually is; 5V is not good enough. You have to know if it is 4.87V or 5.04V.

dear sir
thank for replly, pl more exaplane and example....

MikeMl · 31st October 2009, 03:25 AM

They say it better than I can...

sahu · 31st October 2009, 04:12 PM

Quote:

Originally Posted by MikeMl

They say it better than I can...

thank you i read it. if any problem,then i contact you

Noggin · 1st November 2009, 12:23 AM

Don't contact him, ask for more help on the forum. If you PM him, then the other forum visitors don't benefit from your question and his response.

sahu · 1st November 2009, 02:15 PM

Quote:

Originally Posted by Noggin

Don't contact him, ask for more help on the forum. If you PM him, then the other forum visitors don't benefit from your question and his response.

[ask for more help on the forum.] it is my mean. not PM to him

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29th October 2009, 06:09 PM	#1
sahu	ADC calculations in the voltmeter project i am working a voltmeter project.it is based on 16f676. but don't understand ADC calculations in the voltmeter project . i see also Electronic Circuits it is not working properly. and c lang. also

30th October 2009, 12:01 AM	#2
MikeMl	The A/D input to a Pic is usually ratiometric with respect to the Vdd pin, meaning if it is a 10 bit A/D, it will read out 1023 (2^10-1) when the analog input is the same as Vdd. That means you have to know what Vdd actually is; 5V is not good enough. You have to know if it is 4.87V or 5.04V. __________________ Mike ML.

30th October 2009, 12:11 AM	#3
Sceadwian	Does that particular pic not have an internal voltage reference? I'm used to AVR's which although they can use VCC as a voltage ref also generally have an internal bandgap voltage source of around 2.54 volts, so long as the VCC voltage is above the internal circuitry's threshold for regulation. (not sure what that is off the top of my head) the ADC results will be unaffected. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

31st October 2009, 03:25 AM	#5
MikeMl	They say it better than I can... __________________ Mike ML.

1st November 2009, 12:23 AM	#7
Noggin	Don't contact him, ask for more help on the forum. If you PM him, then the other forum visitors don't benefit from your question and his response. __________________ A rectangular bear is just a polar bear after a coordinate transform. -- I dunno who. A recent study shows that research causes cancer in rats. -- I dunno who said that one either.