im just making a one off project for my own car, would i get many problems if i just used caps by the regulator and zener to try and stop spikes goin into the opamp. what sort of problems would i end up with.

This is just the first part, once i get the circuit worked out iv got to try and make the code for the pic work to, im never gona finish this project.

 

Probably none, try it and see.

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well i think the best thing for me to do is setup a test board with an opamp and no filters and then add zeners, caps etc and scope it as im doing it so i can see what effects they have on the circuit.

the only thing i really need to no is how do i work out what resistors in my attenuator to use so i dont effect the sensor signal, shorly if i have low value resistors its gona effect the sensor so what is the been way to work out what could been effected.

many thanks for all the help you have given me, bit of a big project to start on but you have given me alot to research and i will be going through your tutorials to get a better understanding as well.

 

Experimentation is the best way to learn.

After you've burnt out a few bits and bobs and run out of money you tend to learn a lot faster, read a lot more and get things right more often lmao.

 

how the hell do i no if what i am connecting to the signal is not gona effect the signal.

 

when you desided to make your high resistance voltage divider, how did you no what resistor to use, i guess i could select loads of different resistors to do a 1/10 divide but how did you no they would not effect the signal.

do you think people are getting bord of me yet.

 

If you've got a sensor which is 4000 ohms at its maximum resistance and 12 ohms at its minimum resistance then a divider of 1k+2k would load this up with 3000 ohms which obviously isn't very good.

You just need to work out the max/min resistances of the sensors to work out how much your potential divider will alter the values of them.

 

You don't until you try but the higher the input resistance the less chance you have of affecting the signal. The only issues are how high you can go before the opamp starts behaving strangely or you start picking up stray noise on your signal cables.

Around 1 meg ohm input resistance is a fairly safe value for car sensors and a decent opamp.

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Probably

 

cheers, im gona have a play around with dispalying battery voltage and then move on to a simple coolant temp sensor and just play around with different resistor values to see how they effect the sensor signal.

thanks for all the help so far, i been i will need alot more yet.

 

Look at optoisolaters too