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6 Jun 2010

In this Instructable user comodore will show us how to make a simple fast blinking LED light that you can attach to your bike or any where you want. It blinks more than 3 times in a second.

How to make a fast blinking LED bike light - [Link]

2 Responses to “How to make a fast blinking LED bike light”

  1. Audioguru Says:

    As usual, this Instructable was made by the author who admits it is his first electronic project. His errors show that he knows nothing about electronics:
    1)The LEDs are in parallel instead of in series so most of the battery power is wasted and simply heats the battery.
    Also, LEDs are not matched so in parallel the one with the lowest voltage will use most of the current then it will burn out. Then the next one or all remaining LEDs will burn out.
    2) The LEDs do not have a current-limiting resistor.
    3) The battery does not have a supply bypass capacitor to keep the 555 oscillating as the internal resistance of the battery rises as it runs down.

    I wonder if the little 9V battery will last a few minutes before it is dead?

  2. Audioguru Says:

    I just read the entire project.
    The schematic that I saw first does not agree with the instructions because it is missing the current-limiting resistor.

    There actually is a 330 ohm current-limiting resistor feeding a total of only about 22mA or less to all the LEDs in parallel so they will be very dim and the 9V battery will last a long time.
    The battery will last much longer if the timing resistors for the 555 oscillator are calculated for a shorter duty-cycle and the LEDs will look the same brightness.

    The comments on the project are a joke because most are wrong.

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