need help!! on adc 0808 - Electronic Circuits Projects Diagrams Free

plotoyee · 26th February 2004, 06:37 AM

hai everybody....
im now using the adc0808 to convert the human voice into the digital form. but there is no output shown?? why??
where is the problem??
thanks for ur help

mozikluv · 26th February 2004, 06:40 AM

hi,

how about posting your circuit, we are all dreaming with what you did.

ops:

**Nigel Goodwin** · 26th February 2004, 06:43 PM

Quote:

Originally Posted by plotoyee

hai everybody....
im now using the adc0808 to convert the human voice into the digital form. but there is no output shown?? why??
where is the problem??
thanks for ur help

What's wrong with the 8 outputs at the bottom right?.

plotoyee · 26th February 2004, 07:11 PM

yea i can get the output from the adc. it give me all high although no input signal is given...

Roff · 26th February 2004, 09:43 PM

Quote:

Originally Posted by plotoyee

yea i can get the output from the adc. it give me all high although no input signal is given...

It sounds like you are assuming that leaving the input floating equates to zero volts in. It really equates to undefined volts in. To test for operation, connect the ends of a 10k potentiometer to Ref+ and Ref-, and connect the wiper on the pot to the input. Vary the pot setting and see that the output code does what you expect.

plotoyee · 29th February 2004, 10:39 AM

Quote:

Originally Posted by Ron H

Quote:

Originally Posted by plotoyee

yea i can get the output from the adc. it give me all high although no input signal is given...

It sounds like you are assuming that leaving the input floating equates to zero volts in. It really equates to undefined volts in. To test for operation, connect the ends of a 10k potentiometer to Ref+ and Ref-, and connect the wiper on the pot to the input. Vary the pot setting and see that the output code does what you expect.

actually i try to conver the sound input signal into digital
is it posible to do that way??
if not how should i conver the signal into digital form??

Roff · 29th February 2004, 03:46 PM

Quote:

Originally Posted by plotoyee

Quote:

Originally Posted by Ron H

Quote:

Originally Posted by plotoyee

yea i can get the output from the adc. it give me all high although no input signal is given...

It sounds like you are assuming that leaving the input floating equates to zero volts in. It really equates to undefined volts in. To test for operation, connect the ends of a 10k potentiometer to Ref+ and Ref-, and connect the wiper on the pot to the input. Vary the pot setting and see that the output code does what you expect.

actually i try to conver the sound input signal into digital
is it posible to do that way??
if not how should i conver the signal into digital form??

I was only trying to tell you how to test the converter, not how to use it. I haven't used the ADC0808, but it doesn't look very suitable for audio conversion unless you only want voice quality (low bandwidth). You need a sample and hold, you have to wait for it to settle before you can start the conversion, and the conversion time is 100usec (maybe half that if you run at the maximum clock rate). You would also need an anti-aliasing filter in front of the sample and hold. I think I would look for a faster A/D.

plotoyee · 29th February 2004, 04:55 PM

oic.
thanks.
im using that adc to convert human voice. so it is sutable to used this ADC.
what is sample and hold means. and how do i built it.

plotoyee · 29th February 2004, 04:59 PM

oic.
thanks.
im using that adc to convert human voice. so it is sutable to used this ADC.
what is sample and hold means. and how do i built it.

Roff · 29th February 2004, 09:40 PM

Surely you know how to use Google. Search for "sample and hold".
A sample and hold samples the audio (in this case) periodically, and holds that sampled value steady until a conversion can be completed. The A/D will give you erroneous results if the input voltage changes during a conversion cycle.

plotoyee · 1st March 2004, 06:25 AM

thanks
Ron H

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26th February 2004, 06:40 AM	(permalink)
mozikluv	adc 808 hi, how about posting your circuit, we are all dreaming with what you did. ops: __________________ \"NONE BUT THE BRAVE DESERVES THE FAIR\" ~Shakespeare~

26th February 2004, 07:11 PM	(permalink)
plotoyee	yea i can get the output from the adc. it give me all high although no input signal is given...

29th February 2004, 04:55 PM	(permalink)
plotoyee	oic. thanks. im using that adc to convert human voice. so it is sutable to used this ADC. what is sample and hold means. and how do i built it.

29th February 2004, 04:59 PM	(permalink)
plotoyee	oic. thanks. im using that adc to convert human voice. so it is sutable to used this ADC. what is sample and hold means. and how do i built it.

29th February 2004, 09:40 PM	(permalink)
Roff	Surely you know how to use Google. Search for "sample and hold". A sample and hold samples the audio (in this case) periodically, and holds that sampled value steady until a conversion can be completed. The A/D will give you erroneous results if the input voltage changes during a conversion cycle.