I'm using incandescent mini Christmas bulbs in my project. In testing I found the bulbs do not blow until the voltage is around 7 or 8 volts. Lights are connected to my Arduino with a MOSFET. All of the V+ in and GND are bussed together or are in parallel with the power supply.
Every once in a while one or two of the bulbs will blow. Might be workig fine an hour or so and then one blub is dead.
If I replace the blub everything is fine, and another blub blows.
Now when I look closely at the blub I can see a black ring inside the glass of the blub. I'm thinking this is indicating the light blew becase of a voltage spike? (Not sure.)
Am I correct in my assumption the blubs are blowing by a voltage spike? The arduino is powered separtly/USB to comptuer. The incandescent blubs are the only thing powered by the wall wart.
I'm thinking this is a voltage spike which is just happens to occur when the light is on. What' the best way to project this from occuring? A zener diode? Something like a 1N5919BG? And do I need a resistor?
Or would a better approach be to use a 9v or 12 v power supply with a 12 to 5 volt regulator.
I am hoping to power the Arduino with the same wall wart that's powering the incandesent blubs. Wall wart is from a Netgear router. Rated at 5v/2.5a Measured voltage is 5.5.