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View Full Version : How does this work?


thestug
2011.10.23, 09:59 PM
http://www.youtube.com/watch?v=Ro4afPIGg5I

How does the exhaust backfire work only when they release the throttle instead of when they are on the throttle? Could someone explain how to build this?

I-Lap
2011.10.23, 10:38 PM
The LEDs only conduct in one direction.
It won't conduct and light up when the polarity is "forward", but it will when reverse is applied. When the throttle is released, the board must apply a little reverse for braking, so they light up.

All they have there is a resistor and LED in series with the motor.

The one in the video used a 220 ohm resistor inline with the led. The longer lead of the led would go on the motor +.

You can find all that stuff locally at Radio Shack.

.

thestug
2011.10.23, 11:02 PM
The LEDs only conduct in one direction.
It won't conduct and light up when the polarity is "forward", but it will when reverse is applied. When the throttle is released, the board must apply a little reverse for braking, so they light up.

All they have there is a resistor and LED in series with the motor.

The one in the video used a 220 ohm resistor inline with the led. The longer lead of the led would go on the motor +.

You can find all that stuff locally at Radio Shack.

.

Would the value of the resistor change for different motors? I didn't know LEDs conducted in only one direction. Is there a way to get lights to come on bright when I brake , but always stay on a lower brightness when not braking?

I-Lap
2011.10.26, 10:22 AM
The resistor would depend on the battery voltage. You could tweak it up or down a bit to get weaker/brighter flashes.

For the solid light portion, the easiest way would be a second LED/resistor wired to battery power put behind the backfire LED. It would shine through it, especially with clear LEDs.

wildthing
2011.10.27, 06:04 AM
There are also some auto-blinking LEDs...that would blink randomly when there is power from the throttle

benmlee
2011.11.04, 07:30 PM
FWIW, Those lights are not suppose to simulate back fire. Is for turbo engine where they inject some fuel during exhaust stroke while the throttle is closed. The fuel burns in the exhaust and keep the turbo spinning for instant boost when driver gets back on gas. That is why you see fire coming out of exhaust. Of course for racing only. Totally not smog legal.