Input protection with diode packs

Other Hardware Sensors
1

I'm making a datalogger which will connect to various sensors in a motor vehicle, including things like the ignition drive pulse.

I understand that vehicles are notoriously prone to inducing voltage spikes in their wiring, and of course the ignition drive pulse is notoriously spiky anyway, exceeding 350V.

My instinct it to protect all the digital and analogue inputs with a series resistor - maybe 10k, or more? - to limit any destructive currents, and then to have a pair of Schottky diodes on the input to limit the pin voltage to no more than 0.2V beyond the 0V and 5V rails. I've shown what I mean in the attached diagram. I should add that this arrangement appears to work perfectly.

The thing is, having two diodes for each input takes up quite a lot of circuit board space. As this must surely be a common requirement, are diode packs available for such an application? I had in mind something that looked like an IC, with Vcc and GND pins, a row of inputs and a row of outputs. This would be much neater than rows of diodes.

However, I can't find anything like that at any of my usual suppliers. Is there such a thing? Or am I going about this the wrong way? All thoughts, advice, reactions and mocking laughter welcome! :slight_smile:

Input.PNG
Input.PNG718×452 5.67 KB

2

The ATmega chip has clamping diodes inside. Your diodes will be parallel to that, making one of them useless. The ATmega pin can have 1mA pushed into the pin, that means with a very high resistor, the diodes are not needed (as long as the current is below 1mA).
For good protection, a voltage divider should be used (two resistors), then your two diodes, then 1k resistor to Arduino pin. The total impedance at the Arduino pin should be below 10k for maximum accuracy.
I use 1N4148 diodes, they are fast and don't leak like Schottky diodes.

3

Google search reveals a lot of "diode arrays", but it's hard to obtain circuit diagrams from the sellers.

SN74S1053 looks like what you want.