Hello everybody
I'm using the DAC of arduino DUE to have a variable voltage to be converted into 0-20 mA .. (using the ad694)
but it accepts the input voltage 0-2.5 V .. Arduino DUE dac has 0.55V - 2,75V range ..
is possible to adjust the tension ?
how do I fix ?
sorry for my English
Don't output the maximum value.
Hi, I just asked a similar question about voltage to current conversion with the DAC here: 4-20mA output from Arduino Due DAC - Project Guidance - Arduino Forum
Might be helpful.
The problem si the minim value! 0,55 V
Hi, looking at http://www.analog.com/media/en/technical-documentation/data-sheets/AD694.pdf
Another problem you might have is that it looks like it takes either 0-2 or 0-10 V, not 0-2.5V. But again, as James said, simply do not output the maximum value from the Due. As far as the minimum value goes, it looks like you can adjust the input buffer (look at pins 15 & 16, there is an ADJ and Voffset). Maybe someone more knowledgeable can explain further, but I think that's what you are looking for.
If you need a current output, you're pretty much going to need an external op-amp to do voltage-to-current conversion. That same op-amp can compensate for the goofy offset and range of the Due DAC, as well as scaling the output to give the range you want. You won't get a passive circuit to give you what you need.
Regards,
Ray L.
dimare_gabriele:
The problem si the minim value! 0,55 V
I did not notice before. My Due does the same.
You would probably need to build a buffer (maybe using an op-amp) to offset the signal back to 0V.
thatcadguy:
Hi, looking at http://www.analog.com/media/en/technical-documentation/data-sheets/AD694.pdfAnother problem you might have is that it looks like it takes either 0-2 or 0-10 V, not 0-2.5V. But again, as James said, simply do not output the maximum value from the Due. As far as the minimum value goes, it looks like you can adjust the input buffer (look at pins 15 & 16, there is an ADJ and Voffset). Maybe someone more knowledgeable can explain further, but I think that's what you are looking for.
On datasheet is written that for output 0-20mA need a input range of 0-2.5V .. or not?
( page 5 of the datasheet , table top right )
RayLivingston:
If you need a current output, you're pretty much going to need an external op-amp to do voltage-to-current conversion. That same op-amp can compensate for the goofy offset and range of the Due DAC, as well as scaling the output to give the range you want. You won't get a passive circuit to give you what you need.Regards,
Ray L.
Could you show the circuit to be realized ?
Thanks !
dimare, check out that other topic I linked to, Wawa actually found a great solution -- Analog Devices has several chips that have an SPI interface and 0-20mA out so that you don't have to worry about voltages from the DAC. I am going to use an AD5420 myself.
hello everyone ... after doing tests with the integrated ad694 , with poor results .. ( inprecisioni ) .. I found out that I can use as a 0-5V or 0-10V range also ... any of you know a Dashboard with i2c that communicates with arduino and output dAC converts 0-10v?
Don't bother with the internal DAC on the Due, its very poor.
I have completely solved this problem using a simple operational amplifier. Look at my site: http://ardupiclab.blogspot.it/ for the scheme and explanations.