# Need help designing 3-20 led chasers (sequential lights)

#### Modelbldr

Apr 20, 2022
10
Looks suitable. The overflow (pin 11) from the top 4017 routes the clock from the 555 to the lower 4017 once the top 10 LEDs have been lit. Then back to the upper 4017 once 2nd set of LEDs has been lit.
Thanks.

#### Modelbldr

Apr 20, 2022
10
I'm attempting to simplify this to one battery and set of ICs. I have added two circuits of LEDs on pinouts 4 and 7, and 10 and 1. Will this work? I need three circuits of 20 LED chasers.

#### Attachments

• LED chaser circuit diagram 4 28 22 0021024_1.jpg
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#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,804
This circuit has a few flaws and will not work.
1. 2 V are not enough to power the circuit. 5 V is a minimum.
2. Pin 15 (reset) of IC3 is unconnected (floating). This means IC3 may randomly reset, thus interrupting the flow of the LED sequence.
3. This is not three circuits of 20 LEDs but one circuit of 60 LEDs. The LEDs will light up in the sequence of LED banks on these pins of IC3: 3 2 4 7 10 1
4. Once the last LED has been turned on and off again, there will be a long pause while IC3 counts through pins 5, 8, 9 11.
Look up the circuit in post #9. There you see pin 15 (reset) of IC3 connected to the first unused counter output (pin 7). In your circuit the connection would have to be from 5 to 15. This will remedy issues #2 and #4 of the above list.
You still need to supply a higher operating voltage.

Issue #3 is completely unresolved. What is the effect you want to achieve?
• Have 3 LED chasers run completely snychronous - use e.g 9 V supply voltage and instead of a single LED use 3 LEDs. Then group the LEDs such that from each series connection one LED belongs to one group. This will give you three groups of simultaneously blinking LEDs.
• Have 3 LED chasers run in sequence, one after the other - your design can be used with the above mentioned modifications.
• Have 3 LED chasers run completely asynchronous - build three of the 20 LED chasers from post #9.

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