adc with 0 to +24 v input range and 8 bit resolution

Discussion in 'The Projects Forum' started by Nishu Sachdeva, Mar 10, 2011.

1. Nishu Sachdeva Thread Starter New Member

Mar 2, 2011
2
0
hey guys,
i want to monitor 24v power supply through microcontroller.i m stuck while deciding the adc to use,as i want to use a 8 bit resolution adc with my microcontroller because of the limited number of ports.is there any adc with 8 bitresolution and 0 to +24v input range?how to find an adc with these specs,i have googled a lot bt cudnt find ne

2. beenthere Retired Moderator

Apr 20, 2004
15,815
282
You can always use a resistive divider to lower the voltage into the range acceptable to the A to D. you can use a buffer amp to prevent loading the divider voltage.

8 bits and 24 volts gives a resolution of just under 100 mv. Are you tracking the 24 volts, or monitoring its presence?

3. Nishu Sachdeva Thread Starter New Member

Mar 2, 2011
2
0
i have to track 24 volts but i dont understand how i would b able to track 24 v using voltage divider?moreover i have to monitor 8 more parameters such as current from ac mains,voltage of ac mains(after coming from ac to dc converter)..etc along with 24 volts dc,and then i would give it to a analog mux and then to adc or may use an adc with inbuilt mux.i think using voltage divider for each f dem would make my circuit very bulky?

4. beenthere Retired Moderator

Apr 20, 2004
15,815
282
Voltage dividers are very simple means of lowering a voltage into a range that can be measured, and still stay completely proportional to the original source. Another means is to use a trim pot and set the wiper at the correct output.

Your 8 bit converter can handle at least 5 volts. Setting the divider output at about 4.5 volts will let you track over- as well as undervoltage. Using high value resistors and an op amp buffer improves the performance. Here is a link to a calculator - http://www.raltron.com/cust/tools/voltage_divider.asp

As I indicated, 8 bits does not give much resolution. What kind of accuracy do you require?

As to AC line and AC current, you will need to use transformers to isolate your circuit. Yes, this will be a bulky package.