Hi. I've a bit of electronics experience, just enough to get me in trouble.
I'm planning a long-game type prank on one of my friends. Next year, when we're both at Le Mans 24h I'm going to fit some kit to his race car that plays a 5-second (inoffensive) MP3 every time his brake lights go out. I need to get him back after last year. I've already got and sourced a pair of particularly loud passive 8ohm PA horns, a small automotive audio amplifier that will run the horns, a wiring "take off" loom to gain my switched 12v/earth (and cause strictly no damage to the car - that's not the aim here) and a programmable greetings-card sound module (under it's own battery power) that plays when the contact switch is closed. I have the entire thing running perfectly on a bench in isolation.
I however need help figuring out the electronics to trigger the module as the line voltage in the brake lights drops to zero (not as it goes high - I'd easily be able to do that with just a standard relay). I can easily interrupt the bullet connector to the central high level brake light without damage but have no idea what goes between. Google seems to suggests a 555 but I'm unsure?
Any help REALLY appreciated.
I'm planning a long-game type prank on one of my friends. Next year, when we're both at Le Mans 24h I'm going to fit some kit to his race car that plays a 5-second (inoffensive) MP3 every time his brake lights go out. I need to get him back after last year. I've already got and sourced a pair of particularly loud passive 8ohm PA horns, a small automotive audio amplifier that will run the horns, a wiring "take off" loom to gain my switched 12v/earth (and cause strictly no damage to the car - that's not the aim here) and a programmable greetings-card sound module (under it's own battery power) that plays when the contact switch is closed. I have the entire thing running perfectly on a bench in isolation.
I however need help figuring out the electronics to trigger the module as the line voltage in the brake lights drops to zero (not as it goes high - I'd easily be able to do that with just a standard relay). I can easily interrupt the bullet connector to the central high level brake light without damage but have no idea what goes between. Google seems to suggests a 555 but I'm unsure?
Any help REALLY appreciated.