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6V Ultra-Bright LED Chaser


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For anyone who has the same problem that I discovered and fixed. I designed this project almost 10 years ago. This problem occurred on two projects that were 8 and 9.5 years old.
The first LED remained lit when it should be turned off and each blinked LED had a light trail behind it.

The cause was one LED leaks current when it has a reverse bias voltage. I didn't want to replace the leaking LED because the replacement LED will probably look different.

The output of the 74HC4017 driver IC goes high to turn on an LED when the transistor that drives the cathode low blinks it for a moment. Then during the pause in the chasing when all the LEDs should be turned off the transistor is turned off. During the pause the IC driver is reset which causes its first output to go high. The first LED should not light because the transistor driving its cathode low is turned off.
BUT all the other IC outputs are low during the pause then the leaking LED conducts which lights the first LED.
I fixed it by adding a 1.8k to 10k resistor parallel with the first LED and adding a 10k resistor from the collector of the transistor to the positive supply.

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