Help to build an output 4-20mA signal

[johnnykay]

I am looking to create a light sensor and send the output as a 4-20mA signal to the PLC. I am unsure how to create a circuit in order to create the output signal. If anyone would be willing to help, it would be greatly appreciated!

 

[Vartile]

Have you looked up such chip manufacturer that is called Burr-Brown (now part of TI). They have 4..20mA chips both receivers (RCV420) and transmitters (XTR115, XTR116).

You might get better answers if you give the information what is now in your light sensor design.. Ie. which format is the output in (Hz, Ohm, Current, Voltage, PWM, etc.)

Sensor -> Amplifier -> Interface

One option is to use voltage output and convert the output to 20mA max output with some resistors and Ohms law. This would be the quick&dirty option.

 

[Mickey]

Why not just buy one.

http://skyeinstruments.info/index_htm_files/Light Sensors with 4-20mA amplifiers.pdf

 

[shooter]

i do a lot with these xtr circuits. especially Pt100 sensors
they are analog and with correct setup and calibration they are just fine.

 

[RDS]

We have one of these : http://plcsensors.com/pdf/301_CES_R.1_7-8-10.pdf
sensors to control the lighting in our warehouse. It's a place to start.

 

[Lancie1]

Why not just buy one.

Very interesting. The Skye Instrument company is right there in JohnnyKaye's UK, and they even have different Skye models for different wavelengths of light. What more could a guy want?