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Problem with the output of DAC0808

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andihong

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the DAC0808 circuit need a 8bit digital input connector to works ? right ?

but without digital input, my circuit already have a voltage between 2-4V, then i tried to connect the 8bit digital input connector, it's still the same.


can you give me a solution for this ?


thank you.
 

milan.rajik

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Zip and post your circuit in image format or Proteus format.
 

Vbase

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If you can't show us your circuit then at least tell us about your conclusions.
 

andihong

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here my circuit, same as DAC0808 datasheet..

DAC.PNG
 

hobbyckts

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Are you feeding anything at the input side?
 

andihong

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Are you feeding anything at the input side?

8 bit digital input ?
there is no change even if i give digital input, still 2-4V.. it's just around that voltase..

is there any way to check every components ?
 

Vbase

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Is the LF351 connected to supply of +/-15V ?
If the positive supply is +5V instead of 15V you get the output that you have.
 

andihong

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Is the LF351 connected to supply of +/-15V ?
If the positive supply is +5V instead of 15V you get the output that you have.

i give 3 Voltage input there,
1. 12V
2. -15V , using IC 7915
3. 5V..

but the output Voltage is 2-4V..
 

hobbyckts

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what is the operating voltage of your opamp which you have used in your circuit. That could be the only reason that you are not getting correct voltage levels
 

paulfjujo

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i give 3 Voltage input there,
1. 12V
2. -15V , using IC 7915
3. 5V..
but the output Voltage is 2-4V..

Where are your checkpoints voltage ?
add them on the schematic ...

"diviser pour mieux regner !"

1) test first without the buffer AOP ..
see schematic test of datasheet ..only one resistor on output of the DAC
don't forget that A1 is MSB bit !
test output with all inputs of DAC grounded .. to get 0V as output
after use only A1 (MSB bit) conneted to +5V (logical level 1) ..
you must get 5V if our Vref is 10V (half range output)

2)... after see the problem with AOP..
 

andihong

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what is the operating voltage of your opamp which you have used in your circuit. That could be the only reason that you are not getting correct voltage levels

Where are your checkpoints voltage ?
add them on the schematic ...

"diviser pour mieux regner !"

1) test first without the buffer AOP ..
see schematic test of datasheet ..only one resistor on output of the DAC
don't forget that A1 is MSB bit !
test output with all inputs of DAC grounded .. to get 0V as output
after use only A1 (MSB bit) conneted to +5V (logical level 1) ..
you must get 5V if our Vref is 10V (half range output)

2)... after see the problem with AOP..



-------------------------------------------------

is there any problem with the circuit from the photo in post #4, the circuit i get from the DAC0808 datasheet.
i am using 5000k ohm resistor, is that the right one ? there are 2 resistor using 5000k ohm.

maybe i should just using 5k ohm ?
 

andihong

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Where are your checkpoints voltage ?
add them on the schematic ...

"diviser pour mieux regner !"

1) test first without the buffer AOP ..
see schematic test of datasheet ..only one resistor on output of the DAC
don't forget that A1 is MSB bit !
test output with all inputs of DAC grounded .. to get 0V as output
after use only A1 (MSB bit) conneted to +5V (logical level 1) ..
you must get 5V if our Vref is 10V (half range output)

2)... after see the problem with AOP..

now i solved the problem about voltage, but now the new problem.

there are LSB and MSB from 8bit connector on DAC, i connect that to arduino using pinMode, its still 0V. there are no changes after all..

when connected, i try to test the voltage of LSB dan MSB on DAC, and the voltage is below 1V even if i give input 5V from pinMode..

is there any way to check the IC ?
 

paulfjujo

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Code:
5000k ohm resistor ?
there is a point after 5 value => 5 K ohms !
maybe the additional 000 is to tell accuracy needed here . because 5K is not a standard value.
4,7K, 5,6K
except when uing accurate resistor at 1% or 0,1% of accuracy.
To check , you can use 4,7K + 330 ohms
 

andihong

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Code:
5000k ohm resistor ?
there is a point after 5 value => 5 K ohms !
maybe the additional 000 is to tell accuracy needed here . because 5K is not a standard value.
4,7K, 5,6K
except when uing accurate resistor at 1% or 0,1% of accuracy.
To check , you can use 4,7K + 330 ohms

yes, that resistor make me confuse, i already change it to 5k6 ohm. and the problem of output voltage is solved. now about how the DAC works, it not even work when i give 8bit input to DAC..


any solution ?
 

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