My PWM brake light power

Hi..
i had this 12 inch led strip laying around so i decided to stick it at the back of my car and connect it with brake light wiring. So i did that and it was kind of boring to see turning on and off with the brake light. So i decide to PWM it. I simply used a uC and made a beautiful fading in and out(with 3 pattens since i had so much program memory left).

To keep things simple i connect the uC power and the switching transistor with the brake light + and -. Every time the brake paddle is pressed the uC boots and starts doing PWM and goes off when break is released. This on and off may happen 3 to 4 times per seconds depending on driving.

Will this turning on and off the uC kill it or reduce its life?

I don't believe the on/off cycles will have much affect on the uC life time.

However, in order to reduce the number of cycles, you could insert a reasonably large capacitor on the 5 Volt line in order to keep the uC powered between rapid brake presses. For example, you could provide sufficient capacitance to keep the uC operating for say 5 sec after the peddle is released.

The Brake + line could be connected to an input of the uC via a resistive divider so that the uC can be programmed to only drive the LEDs when the brake peddle is pressed.

ljcox said:

I don't believe the on/off cycles will have much affect on the uC life time.

However, in order to reduce the number of cycles, you could insert a reasonably large capacitor on the 5 Volt line in order to keep the uC powered between rapid brake presses. For example, you could provide sufficient capacitance to keep the uC operating for say 5 sec after the peddle is released.

The Brake + line could be connected to an input of the uC via a resistive divider so that the uC can be programmed to only drive the LEDs when the brake peddle is pressed.

Click to expand...

if the power cycle wont harm my uC i am happy. i thought about a big capacitor but then thought we dont press the break paddle so rapidly its not practical.

By "big capacitor" I had one of about 330 uF.

If you want to do this, I can calculate the actual value you need - if you tell me what current the uC draws when in Sleep.

[QUOTE="ljcox, post: 1204833, member: 11819"big capacitor" I had one of about 330 uF.

If you want to do this, I can calculate the actual value you need - if you tell me what current the uC draws when in Sleep.[/QUOTE]
Hi. Thanks. I decided not to connect a Cap. My concern was uC, I am happy with my work.

Thanks for helping me out.