regarding PmodAD2 converter

[freeman988]

Hello  , i want to purchase PmodAD2 from digilent (link below) , to convert 3 analog voltage inputs rated at 50v (inputs for the spartan 3e board)

 

i wonder if will i need to get a voltage module adapter or sensor to reduce the 50 volts to suitable voltage that can be converted by the PmodAD2. If so, what component do you recommend me to buy.

 

Thank you

 

With best Regards   

 

PmodAD2 link:

http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,401,933&Prod=PMOD-AD2

 

Spartan 3E board link:

http://www.digilentinc.com/Products/Detail.cfm?NavTop=2&NavSub=451&Prod=NEXYS2&CFID=7596564&CFTOKEN=fa03a7672cc367fb-F841DD50-5056-0201-029071F4B91BCA6E

[hamster]

Depending on how robust you want it to be, a simple two resistor voltage divider will work quite well - for example a 15k and 1k in series will bring 0V - 50V the voltage down to 0V - 3.125V.

 

However... bad things would happen if this is built on a breadboard and the 1K was to accidentally fall out (or otherwise fail), as it would then put the full voltage into your PMOD. It might be wise to put a diode in there acting as a clamp, to ensure that the ADC inputs never get greater than about 3.7V.  This is the closest thing I could find in Google - you  would connect the ADC at the location pointed to by the "0-3.7V" label,

 

Ignore the R values shown - R1 should be 15K and R2 should be the 1K. 

 

 

Anyhow, it will work perfectly well without the diodes, it is just that the fault scenarios are pretty nasty/expensive!

[Alex]

Hi, just give my two cents. I guess you may need to buy regulator or some sort of transistor to bring down the analog signal to 3.3V. Perhaps, other community members can tell you how to do that.