HELP!?!? Adjustable PWM circut/ switchable to full

Need help building a PWM circut with an adjustable (wile in breadboard stage, and will be changed to a permanent duty cycle once i find a happy dimness) duty cycle. It also needs to be able to be switched to a 100% duty cycle. This will be used in the tail light of a motorcycle, volts range from 12.5-14.4 and needs to supply about 1/2 to 2/3 of an amp. i was thinking of a 555 circut, but am lost.

Why does the tail light need to dimmed, usually the wattage of the bulb is what is required by law to produce a legible plate at the required distance???

This will work. Change the output BD140 for something like IRF540 MOSFET and you can remove the arrangement around pin 4 for your application, just tie it to +V. **broken link removed**

use lm 3524 .short both the o/p of ic by varying control vtg u can obtain 0to 100% duty cycle control

what is tail light\