LED flashing unit. - how do I make one?

[1CheeseLouise]

Here's my story: I bought a license plate frame for my motorcycle. It has 4 banks of LED lights. I want to wire it to my brake lights. That's the easy part. But, I want them to flash. Can I get them to flash in sequence? at 12v, it takes 0.1 to 0.2 amps to get full intensity. What parts do I need and a schematic drawing? Please help! My life depends on this! People want to drive into the back of me (they've done it before) Please don't refer my paranoia to the 'Psychiatric Forums'. I just want to be so annoying to the driver behind me that he doesn't forget I'm there and run into me like the last momzer did! I'm always finding myself behind annoying cars and their drivers. I think it's my turn.
Oh yeah. flashing maybe 1/4 to 1/2 second, random ok.
And my familiarity with electronics assembly? Well I last did this in 1990!

 

[Jiggy-Ninja]

You should probably make sure it's legal first. There might be laws against mounting anything around a license plate that could obscure it or make it harder to read.

 

[mdjensen22]

In a lot of states, flashing red or blue lights is a no-no (always flashing).
Flashing lights associated with your brake lights is generally legal/accepted though.

You can do this a few ways...one of the cheapest/easiest will be with a flasher relay.
They are bimetallic strips that heat when current passes through them and open as a result. When they cool down, they close and allow current to pass again (then repeat).
The flash rate is controlled by the amount of current that passes through the relay. For LED loads, an extra load resistor is usually added to maintain a normal flash rate.

 

[Bassalisk]

If its legal, you will need transistors, few capacitors, and resistors.

Simplest you can go(as far as I know) is 2 transistors, 1 pnp, 1 npn, resistor and a capacitor.

http://www.josepino.com/light/transistor_led_flasher

One more thing you want to know, is that with capacitor you are controlling the rate of flashing. So bigger capacitor, you will get fewer flashes than the small ones. (time needed to discharge small capacitor is shorter, than the bigger one)

You go a bit far, and build astable multivibrator.

http://www.reprise.com/host/circuits/transistor_flasher.asp