Hi
I am proposing to use the attached circuit in a car project. The input will switch with a high side from the car battery and the outputs will switch high side using P channel mosfets.
My question is really what is the best way to power the Arduino whilst keeping it protected?
Power must come the car and not a separate power supply.
The input must be switched by 12v fed from the car battery and the outputs must be switch on the high side hence the P channel mosfet.
The diagram shows just one input switch but this will be replicated so there are 6 inputs in total and the same for the outputs. I will use some of the analog pins as digital.
Is the regulator shown in the picture okay for this? I have used this in lots of projects but this will be my first project that involves drawing power from the car battery the sole source of power.
I do realise that all the grounds will be joined together and that the power for the Arduino will flow through the regulator. Is there a better way of doing this please to protect the arduino?
My concern is that I have to use high side switching mosfets and have heard that the arduino can be damaged if output voltage is allowed to feed back to it. Unfortunately relays are not an option as some of the loads require faster repeated switching on and off than a relay can provide.
I would welcome any comments or suggestion and your help is very much appreciated.
Chazza
Looks like that should work. However, the automotive electrical environment is extremely harsh, and you need protection from transients that may reach several hundred volts, and possibly also from polarity reversal.
Use your favorite search engine to look up "automotive electrical transient protection".
Thank you. I plan to add diodes to power inputs/outputs to prevent the polarity reversal. On the spikes do you think adding zener diodes will be sufficient?
I will read up on your suggestions
Regads
Chazza
What's appropriate kind of depends on a cost-benefit analysis. If it's the computer running safety-critical systems like engine, steering, or brakes, yeah you need to put all the protections possible onto that. A hobby project doing non-critical jank? Not nearly as important, and you can rebuild it if it does somehow get fried.
I have some super-secret protection circuits that I designed after watching a seminar and spending some time with data sheets.
Don't try to guess - lots of people want to be an inventor and so come up with the Zener solution because it's "their" solution. But it isn't the best.
