Ignition Coil Voltage Spike Resets Arduino Through Relay

Hi all,

First of all, keep in mind that I am not an Electrical Engineer or have any formation in electrical components, as so, something I may say wrong, please correct me.

I recently have made a working bench project. One of its purposes is to have an emergency shutdown system that is extended to software I am using to control it.

My issue is that I am controlling for the first time a combustion engine ignition coil with that same safe condition switch. To be safe, the engine "mass"/GND is connected to the ignition coil in normal position. This means that the circuit is normally closed and the engine can't start. So, in order to start up the engine the order from the software must be given to the arduino so the respective relay may change state and open the engine ignition coil system. This way, is the only way I could assure a global shut down, case the a system failure.

My problem is when I do actually put it to practice! All relays are function, both all at the same time, individual changed, etc.. But once I am prepared to start up the engine, at the first spark the arduĂ­no resets! At least all the relays turn to first state condition when boot up first time! I say this because usually my insurance that the arduino have reseted is the background LCD off and on. I do not have actually access to the arduino with the panel display I have. As so I only meant to disassemble if the problem is from arduino assemble. As I mentioned it is a working project.

For consideration I am using a Ywrobot 4 relay board:

It is connected to the arduino only! I have read that it should be wired to an external supply! As it require to adapt the panel already build up I am trying to manage other solution, though it will be something I will do try this week. I am supposing that the relays are isolated from their terminals from what I know, and the problem is not of a somehow inductive voltage/current is passing through the relays to the arduino circuit.

The current from the power supply is enough to boot up 5 more circuits like this, so I am not considering that is a voltage drop issue. In this case could this be solved adding a capacitor to the Vin on the arduino?

In case the problem may be from the engine ignition coil amount of voltage what could be the solution?

Thank you all!

Please supply a drawing of the coil connections and how you are controlling it.