LED Sequencer 110416

Discussion in 'The Projects Forum' started by allenpitts, Apr 16, 2011.

  1. allenpitts

    Thread Starter Active Member

    Feb 26, 2011
    Good afternoon all about,

    Built an led chaser kit from Rainbow called CL-2
    that uses four of the outputs from a Johnson 4017 decade counter driven by a 555 timer to make a four led chaser of forty-eight LEDs It lights the first, the fifth, the ninth... then the second, sixth, tenth etc to create a marquee effect. Looks pretty cool.
    Got to thinking about a an LED sequencer kit from Chaney built a while back.
    Because it uses all ten outputs, could use this as the heart of a system
    that lights LEDS 1, 11, 21, 31... then 2, 12, 22, 32... then 3, 13, 23, 33.. and there by have a chaser much larger than the Rainbow 48.
    I have been experimenting with this system and have developed several questions. (Is it ok to ask more than one quesion in a post?)
    1. Where is the upper limit? I think it is limited by the amperes running through the system. Using a nine volt battery I connected twelve LEDs
    to one of the 4017 ouputs and the LEDs got a little dimmer but were still bright enough to create the effect. But if 12 LEDs could be connected to each of the 4017 outputs then a chase with 120 LEDs could be achieved. Can the the total number be calculated?
    2. My research online seems to indicate that there are a number of variables: voltage drop, milliamps flow, and the color of the LED.
    When I connected the thirteenth red LED to the single out put of the 4017 I had to use a different bag of LEDs. It didn't work. Checked the LED with a simple resitor circuit and it was OK but it didn't work in the chaser circuit. Also tried a green LED with same negative result. Is there a wide variance in the deisgn specs of LEDs? How can one tell or test the specs from one red LED to another?
    3. Hoping to increase the brightness of the LEDs I substituted a 12 volt wall wart for the none volt battery. (This ac adapter says that it is 12 volt on the device but when I hooked it up to a a digital multimeter and the adapter tested at outputs 17 volts.) When I did that the circuit began to act wierd so I went back to 9 volts. But then the circuit quit working altogether. Troubleshooting indicated that the 555 timer had been fried. I thought that the 555s would take 15 volts and that an extra two would'nt hurt it but evidence seems to contradict. Can I get any increased LED brightness with increased power supply?


    Allen in Dallas
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Yes u can ask any no. of questions.

    LED's have different voltage drops and wide range of power ratings.
    The voltage drop and forward current is not the same for all the colors. In fact these things changes when color changes.

    The reason you fried ur timer is that the wall wart was not regulated and the light load voltage was too much for the timer.

    You better find a suitable PSU if you want to meddle with that much LED's.

    The upper limit is always ur total Load Power, which can be quite easily calculated.
    LED's brightness varies with voltage but increasing the voltage is a bad Idea. To Vary the brightness you should vary the current. There is always a resistor which is used to fix the current flowing via a resistor thus adjusts the brightness.

    It is a good idea to produce ur working schematic. So we can suggest ways to improve it or change it to ur needs.
    Last edited: Apr 16, 2011
  3. Wendy


    Mar 24, 2008
    All you need to do is increase the current on an LED, but don't exceed the LEDs rated maximum. In other words, drop the resistance.

    This is not rocket science. Chapter one of my article basically explains LEDs. To do research hint that you are over thinking this. I've helped several other people with sequencer projects, they can be different from each other and still not be that deep.

    LEDs, 555s, Flashers, and Light Chasers

    It covers LED basics, many different pattern makers and light chasers, and how to drive them reliably.

    So, keeping it simple, what are you wanting to do?
  4. allenpitts

    Thread Starter Active Member

    Feb 26, 2011
    Good afternoon R!f@@ and Bill Marsden,

    Will do research draw schematic and repost.
    Go easy on me. I am a computer programmer not an electronics
    engineer so I will do my best.
    What is a PSU (TLA? [three letter acronym])
    Allen in Dallas
  5. Wendy


    Mar 24, 2008
    Power Supply Unit. Usually (but not always) refers to a computer power supply. Tanner's and BG Micro usually have really good deals, and both can be walk in for you if you want.