op amp Signal conditioning--help

[nimeshasilva]

Hi all..

I'm doing a project, which I think I'll need some help from you guys.
I have a light sensor (TSL251R) and its output voltage is 3.3V max. I need to fix the sensor bit far from the control board (about 5m) so that I think I need some sort of analog signal conditioning to interface it to an ADC in my PIC16F887 and measure the light level.

So I hope to do it like this.the sensor board should supply with 12V (to compensate the voltage drop through the long cable, Hope to use a screen, twisted cable for the purpose to reduce the noise) and put a 78L05 and supply the sensor with 5V. And then, the sensor output voltage (0-3.3V max) should amplify to 12V and transmit back to the control board (in other words, 0-3.3V should convert to 0-12V full range). in the control board, the incoming signal (0-12V) should attenuate to the safer level (0-5V) in order to measure in the ADC.

Can anybody suggest me a better circuit to do this???? I'm a noob on the op amps and hope you'll help me.

Thank you

 

[crutschow]

The op amp requirements are determined by the required circuit frequency response and gain, which you have not stated.

 

[godfreyl]

The shielded cable is a good idea. Other than that, I think you're being overly cautious.

The sensor only draws 1 to 2 mA of current, so the voltage drop with 5m of cable will be completely negligible. I would power it with 5V from the microprocessor board, and just add a decoupling cap close to the sensor. You also lose very little accuracy if you connect the sensor output directly to the ADC input. IMHO, it doesn't need to be amplified.

 

[nimeshasilva]

The shielded cable is a good idea. Other than that, I think you're being overly cautious.

The sensor only draws 1 to 2 mA of current, so the voltage drop with 5m of cable will be completely negligible. I would power it with 5V from the microprocessor board, and just add a decoupling cap close to the sensor. You also lose very little accuracy if you connect the sensor output directly to the ADC input. IMHO, it doesn't need to be amplified.

Thanx for the reply..

But this is not a hobby project. This project is going to be implemented in highly noisy environment, which several large AC motors and other noisy equipment are running. So, because of the low voltage of the sensor output, if any noise is coupled, and reading is go wrong, I'm finished...