random ADC0808 output values.

[romel emperado]

guys I followed the project poster in this forum about interfacing adc + 8051 but i got unexpected result

here’s the link :  http://www.engineersgarage.com/microcontroller/8051projects/interface-ADC0808-using-clock-AT89C51-circuit

 

 

my vref is 5v ..

 

i know that the adc output is in the range of 0 – 255 in binary..

 

when i input

1v  the output of ADC is 51 (correct output)

2v  the output of ADC is 102 (correct output)

3v  the output of ADC is 153 (correct output)

 

but when i input 4v it will go back to 51 which is for 2v..

 

that is my problem… what should be the problem in this case?

[dagakshay]

please try that thing again what you saying realy unexpected one……

try to increase it first till full extent and decrease it to the lower extent and check the increasing and decreasing o/p of ADC…. check you connections once again…let me know the results

[romel emperado]

it okay if i full adjust the POT to maximum at it reads 5v and if zero the POT it read zero

the only problem is when i input between 4v to 5v the output value of ADC is in random.

 

I simulated that project in proteus and I found that error and I was thinking that problem is only in proteus but after I connected it in real hardware I got the same error.

 

 

 

[dagakshay]

can you send me your project and proteys files

[romel emperado]

hi  dagakshay,

 

this is the file that you are asking to me..

 

inside the rar file the whole project file is inlcuded and the proteus file..

 

I cleaned that codes for you..

 

http://ifile.it/02qaef9

[Ahmed]

Hi There

I have the same problem whene i put 8-chanal the chanal read random value????

But i found same project in the net with DC motor but give me the real result but don’t know how!!!????

i but my program in the net simulation (meains DC motot microcontroller) and give my exact resalt…..

 

this is the 2 proteus simulation MAIN(my simulation) & NET simulatin

 

REAPLY US if any one knows the problem…..

 

 

http://www.4shared.com/file/385dUqBd/ADC_Help.html

[romel emperado]

hi ahmad.

 

i will check that…

[romel emperado]

i already check your example codes…

 

 

same here.. i notice that if the input value of ADC in each channel is less that 4v the value is correct and then if more between 4v and 5v the value is in random…

 

i want someone who could explain that to us why is the weird thing happening when we use ADC0808..

 

weeks later i made a project using adc0804 but it is working fine but when i use adc0808 im stuck because of that random values..

 

i tried many example code from defferent forums but all the results are the same.. always random values..

[Ahmed]

Hi Romel

my friend after trying to solve the problem I asked my self what happend if i repeat the ADC0808 connection with the microcontrollor???

so i do it and don’t know how the procedure going well and give me exact result….

 

 

check this out and give me the report

 

http://www.4shared.com/file/uN0OPEdI/My_Design.html

 

GREADS to all

[romel emperado]

test

[romel emperado]

i dont know what happen to this forum i cannot post or edit my post..

 

 

yeah! you got it correct right now!. i will check your prevoius post and check what’s going on maybe it will solve my problem too..

[romel emperado]

hi ahmad.

 

I know now what’s your problem with your previous design.. your input voltage is in random that’s why your voltage reading also is in random… lol hehe check it

[romel emperado]

guys i post consecutively because I cannot edit my post here i dont know what happening to this forum..

 

 

 

 

hi ahmad,

 

what version of protues you are using?

[Ahmed]

Hi Romel.

I thing my previuse design the Vref was not correct but i remomber i check it with DC voltmetor it gives me 5 V and the IN0 determined the voltage correct but the oather going wrong, some times the software pass in errer however i repeat the design in case….

 

my fraiend i use Proteuse version 7.6 SP0 Pro with crack on win 7…

if you need me to upload it just tell me & i will this to y

 

Good Luck

 

Ahmed

[romel emperado]

yeah.. pls upload 

 

how did you run the proteus in win7? some of my friends tell me that its not running on win7..

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