Hi,
I am working on a project involving a BD139 transistor heating up and a sensor measuring the temperature. I have to use a PIC18F452 to implement the control algorithm and the interface to a computer.
I built my circuit and i use a PWM port as an output to control the collector of the BD139. The sensor (an LM5DZ) is attached to the transistor with termal paste and it's output is read through the channel 1 A/D converter (PIN A2) on the PIC18. The control algorithm is a PID with antiwindup i wrote.
Now for some specs:
Supply voltage: 5VDC
A/D Converter: 10bit Sigma-Delta
PWM 20Mhz
My problem is that my measurements are really noisy as my 10bit A/D gives me a minimal resolution of 0.5°K with a max temp of 500°K witch is way too high for my requirements.
So i thought of using some kind of amplifyer to multiply the voltage from the sensor (10 mV/°K) by a factor 5, or 10 to achieve resolutions of 0.1 °K or 0.05°K.
My first idea was a Non-Inverting Op-Amp (with 2kOhm direct and 8kOhm feedback) cos it is simple to implement, but i know too little about electronics to figure out possible drawbacks.
How am i to highen the input voltage for the A/D Converter? Is a non inverting op amp Ok?
Thanks a lot
Bye
I am working on a project involving a BD139 transistor heating up and a sensor measuring the temperature. I have to use a PIC18F452 to implement the control algorithm and the interface to a computer.
I built my circuit and i use a PWM port as an output to control the collector of the BD139. The sensor (an LM5DZ) is attached to the transistor with termal paste and it's output is read through the channel 1 A/D converter (PIN A2) on the PIC18. The control algorithm is a PID with antiwindup i wrote.
Now for some specs:
Supply voltage: 5VDC
A/D Converter: 10bit Sigma-Delta
PWM 20Mhz
My problem is that my measurements are really noisy as my 10bit A/D gives me a minimal resolution of 0.5°K with a max temp of 500°K witch is way too high for my requirements.
So i thought of using some kind of amplifyer to multiply the voltage from the sensor (10 mV/°K) by a factor 5, or 10 to achieve resolutions of 0.1 °K or 0.05°K.
My first idea was a Non-Inverting Op-Amp (with 2kOhm direct and 8kOhm feedback) cos it is simple to implement, but i know too little about electronics to figure out possible drawbacks.
How am i to highen the input voltage for the A/D Converter? Is a non inverting op amp Ok?
Thanks a lot
Bye