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8 channel voltmeter (help)

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arash_micro

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Hi.
I was make 8 channel voltmeter (0-5) with diffrent inputs.It works good in proteuse but in real when i

connect a voltage to channel 0, it's affect will change the other channels voltage.How can i solve this?
Thanks.
 

IanP

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Couldn't read your attachment ..
Anyhow, try this: connect 100kΩ (or more) pull-down resistor between each input and 0V (GND) ..
It is possible that through internal capacitancies one input charges the other inputs ..
Regards,
IanP
 

arash_micro

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I allready use 10k pulldown res but no change was apear.and another problem is that chanel 1-7 was not work good .when i connect them to 5v it shows 4.357
 

dunn

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arash_micro said:
Hi.
I was make 8 channel voltmeter (0-5) with diffrent inputs.It works good in proteuse but in real when i

connect a voltage to channel 0, it's affect will change the other channels voltage.How can i solve this?
Thanks.
In proteuse (I guess) you have infinate input resistance.

In the real world you do not have infinate input resistance.

Try using opamps (voltage follower configuration) to input the voltages.
 

arash_micro

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The big problem is that channel 0 works good but other channel not.
 

wizpic

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What are you using to display your readings on
Is it a GLCD

If so i can give you some code to play with

wizpic
 

arash_micro

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no i'm using 4*20 lcd for showing 8ch (realtime) and i use ht-picc.
 

wizpic

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arash_micro

if you have got real life circuit up and runnimng try this file i have set it up the same as your drawing the only thing i'm not sure of is all you transistor and buttons are ment to do

wizpic
 

garg29

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Use opamps, maybe like OP07. with Gain=1.(ie add a buffer stage) before u feed your signals to adc.

Regards,
Garg
 

wizpic

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arash_micro

have you tried my code yet ?
does it work differntly to yours ?

some feed back would be nice

wizpic
 

arash_micro

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no it was just hex and i culdent understand what was that.
 

wizpic

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arash_micro
the hex file you can copy it into the proteus folder and select and sim it or burn the hex file into the pic your using and run it in real time (in your circuit) just like yoou would of had to you hex file you would of created

let me knwo if you need any more help


wizpic
 

wizpic

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If you can try it and lets us know how you get on wuth it.I'm just Curious to see if it has cured your problem. because normally if it works in proteus it work the same in real life. Now i have tested that on my development board and it works ok to me. see you need to eliminate your software or hardware as i said if it work in proteus then it should work the same real time very rare that i find you get different results

wizpic
 

ragabs

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please can u send ur circuit drawing as an image
i think it will be easy to help u if i can see ur HW, anyway ur problem will be
--crosstalk between chanels
--the input reistance of each channel
--ground loops

if u send ur circuit i can send u modifications to try it
 

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