# How to make a row of LED Lights light up individually?

Discussion in 'General Electronics Chat' started by peterk, Apr 5, 2009.

1. ### peterk Thread Starter New Member

Apr 5, 2009
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Hi everyone,

I haven't done electronics for probably nearly 30yrs! So you must forgive my ignorance. And that was quite basic. I would like to make a circuit board with about 8 LEDs in it. It must be powered by AA batteries (if possible!). When I press a tiny button, the first LED with light, then the next LED in the series will light and so on until it gets to the last LED. Every time I press the button the same process happens untill all the LEDs are lit. One final button push of the button and the LEDs go out. Could someone please let me know how I could build this? I would really appreciate this. Thanks Pete.

Mar 26, 2009
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3. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
How complicated do you want to get? This sounds like a job for a simple serial shift register, which can use either JK or Type D flip flops (which usually come 2 per package). There are probably chips that will do it directly too.

CMOS will work fine from 3V, and Red LEDs can be powered with it too, so I don't see a major issue there.

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A little thought later it occurs to me a 4017 will do it. Have you read my article?

Check out the "Making Patterns" chapter, it pertains.

Last edited: Apr 6, 2009
4. ### thatoneguy AAC Fanatic!

Feb 19, 2009
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718
Search for "Knight Rider" or "Nite Rider", it is essentially the sequence you are looking for, but manually clocked with a button rather than an oscillator, and in only one direction.

There are a few ways of doing it, depending on your preferences for circuits.

5. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Actually, if I read his post correctly he wants a bargraph, but it is unclear.

To PeterK, do you want one LED at a time, or a string? Either way the pattern generator will go it, though if you want a string I see some problems (been drawing the schematic).

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Anyhow, here is a schematic for a bargraph style, it uses a 9V battery because it solves a lot of gain problems with the transistors.

• ###### Light Chaser 04.GIF
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Last edited: Apr 6, 2009
6. ### thatoneguy AAC Fanatic!

Feb 19, 2009
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718
Re-reading it, I understand the "until all LEDs are lit", so apparently he's looking for a "Thermometer" output.

A 74xx193 shift register could do this with fewer components, giving 8 LEDs that light sequentially, until all are lit, then blank and repeat.

Tie A & B inputs high, put an LED w/resistor on each of Q0-Q7 outputs

A pushbutton switch on an RC circuit for debounce feeds CP (Clock)

Link $\overline{Q7 \cdot Q0} \rightarrow \overline{MR}$ This could be done with discrete components or NAND IC.

Each clock would load/advance a 1 in the serial in/parallel out shift register, when MSB+1 is reached, the device resets to all blank.

7. ### Bernard AAC Fanatic!

Aug 7, 2008
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Might like to read post by Oxbo Rene LED sequencing problem, Projects.
I like the 8 bit SR ,serial in ,parallel out [ 74C164 ]. Will sink 1.75 mA @ 5V so would use a driver for LED's [ ULN 2004AN, 7 darlington transistors in package ]. 8 would be nice if someone knows of one. The 51Ω is based on 2.5V LED may need adjustment.

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8. ### Mike2545 Active Member

Mar 26, 2009
116
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I already suggested that in the first responce