up down led sequencer

Posted on Feb 7, 2014

I have a 10 light LED bargraph, I want to make the LED`s light one after the other until all the LED`s are lit, and then have the circuit cycle back down until all the LED`s are off again. A simpler (analog) way is a LM3914 - Dot/Bar Display Driver operating in the bar mode. If you put a triangular ramp voltage at the input, the LEDs will light up

up down led sequencer
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in sequence, and then go out in sequence. I`ll have to order some cd4011`s tomorrow. I only have a few cd4013`s in my parts bin. I`ll look at the data sheets and see if I can improvise. Thanks for the schematic Collin55. I built a circuit using a LM3914. The only problem I ran into was using a 555 as a triangle wave generator. The top and bottom LED`s would stay lit for a disproportionate time, and it was hard to adjust the span and time constant. If I turned one pot it would affect the range on the other. That`s why I tried building the circuit using the 4017. I wanted to make something that would use a pulse instead of depending on a changing voltage. I was hoping to make the flow seem more constant. I`ll also look into the function generator chips Crutschow, might be a good alternative to a 555, especially since I`m trying to run it at a very low frequency. Boncuk, 5 LED`s would be fine. I`ve been searching high and low for a circuit I could use to do this, but all I could find was a Knight Rider circuit. Do you have a schematic One digital approach would be to use a bidirectional shift register such as the 4-bit CD40194. You can connect as many in series as you need. You would connect the LEDs to the shift-register parallel outputs (through drivers). Then you connect the "shift right" direction to logic high ("1"). This will sequentially illuminate each LED on each clock pulse. When you get to the last LED you reverse...

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