Ignition Coil Driver

[maca_404]

Hi I am using this circuit as a driver for a ignition coil,

When the coil is arcing between the HV output and the negative post of the coil which is connected to the mosfet all is good. How ever if the HV is arcing directly to earth as in the diagram say for example a spark plug which is connected to the negative side of the supply it blows the 555 timer after two arcs.

It seems the design posted is flawed should there also be a 1n4005 diode on the negative supply to the 555 timer to protect it from the HV discharge ?

Thanks for any ones help.

 

[(*steve*)]

You may need to post that diagram again.

 

[maca_404]

Here is the direct link I don't know why the image did not show up, Thanks Again.

http://circuitzoo.com/wp-content/uploads/2010/09/CarIgnitionCoilDriverCircuitDiagram.jpg

 

[maca_404]

I have tried adding a diode on the negative side of the supply on the above diagram, but again the same I can let it arc between the car coil output and the diode connected to the drain of the mosfet and I have run it like this for an hour but as soon as I let it arc to the negative side of the supply as it would in a real life situation it blows the 555 timer. Any ideas about the only other thing I can think of is a 12v zener on the input ?