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How to read a saw curve signal, with an analog input

From a couple of Sony plasma screens, that I have had my hand on, I got these "SONY 1-680-078-11".

I thourght they where temperature sensors, since they where placed spread around on the inside, like to measure diffenrent parts of the system.

I have figured out how to hook them up to some power and I get this saw curved signal, that I can alter by applying heat to the transistor.

This is how it looks in my oscilloscope.

DS203 screen shot

When applying heat or cold to the transistor, the whole curve moves and the interval on each teeth stays the same.

Any good ideers on how to read this with an analog input?

I would like not to have to sample the whole curve and take the higest value. Since that would cost alot of CPU time.


This is a test for Birdmun, with a 1uF capasitor.

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What are you going to use this in and how are you going to apply it?  Sorry I didn't ask right away-sometimes I get so impressed with the fact that I know a little bit about something this cool that I forget why I started learning it.

Since it is a heat sensor as I was hoping for. My plan is to make some small devices, to put around my house. They should then report back to my server and store the values in a database. That way I will be able to adjust my room temperature right in all the rooms. I will also be able to see how my furnace is performing and distibuting the heat.

I tried the 220uF and a 10K resistor and the wave action has smoothed out. Thanks Oddbot.

I turns out that these small boards are based on the LM35DZ heat sensor. I might try to detach one and build another circuit which makes more sense reading.

The fun of trying never stops. :)

A simple RC filter will help average this out. Try using a 10K resistor from the sensor output to the analog input and a 220uF capacitor from the analog input to ground. If there is still too much ripple then increase the value of the capacitor.


If you attach it directly to an ADC channel and read the values over a time interval (.1-.5 seconds) in a serial window ( debug on Picax) you should get some Idea of whether it's possible. If that doesn't work you may need a specialized translation circuit or a voltage divider (meaning what's varying is resistance, not voltage) or you may even try putting it on a digital channel. You may also be guessing what the function of these is incorrectly-any transistorized circuit will show sensitivity to heat.