Interface/Protect Microcontroller for Automotive Use...

[adamey]

I want to use a micro (PICAXE) in an automotive environment. My main concern is interfacing inputs (which can vary from 10-15V and may contain transients much higher - up to 50-60V).

I thought of using a resistor divider with a zener. Does this sound OK, or will the 50-60v transients be too much? BTW, not all inputs would have such large transients (only the inductive loads), so if it's too expensive then I could use different protection for different inputs.

 

[nsaspook]

I want to use a micro (PICAXE) in an automotive environment. My main concern is interfacing inputs (which can vary from 10-15V and may contain transients much higher - up to 50-60V).

I thought of using a resistor divider with a zener. Does this sound OK, or will the 50-60v transients be too much? BTW, not all inputs would have such large transients (only the inductive loads), so if it's too expensive then I could use different protection for different inputs.

Use opto-isolators on the inputs/outputs. Vishay / Small Signal & Opto Products (SSP) - ILQ2 - Optocouplers / Optoisolators - Optoelectronics & Lighting - Allied Electronics

 

[Diver300]

Zeners with a series resistor are very robust, if you can use a large enough resistor. If you are just trying to sense voltage, then the resistor can be large. The resistor and zener will heat up during a transient, but for <1 second duration transients, that isn't a problem.

 

[adamey]

^ The transiets are very short from collapsing coils. Usually less than 1ms. It is for detecting on/off voltages of various circuits and swithces. So I guess zeners it si