Flashing LEDs in series: SOLVED

It's my first post here , so I hope I'm asking my question at the right place. I'm doing a project for my son. It's a flying eagle logo, and he wants me to install approximately 150 chaser white leds in series.I'm using 5mm white leds, and I was wondering if I could make them flash with a 555 timer and some 4017 ics, or if there would be a better and easier way to make it work.He doesn't want me to use led strips. I tried it on a breadboard with 1 555 and 1 4017 ic and 10 leds and it's working great. I really hope someone could give me some ideas.I'm a beginner, so that's why I don't know all the ways to do a project like that. Thank you in advance. PS: If needed I can provide a pic. of the flying eagle logo.

by moe24
October 13, 2018

1 Answer

Answer by mikerogerswsm

10 leds in series is about 20V plus some for the current limiting resistor. If you want 150 leds the best way to do it is in 15 groups of 10. Then your voltage will still be 20V and the current will be 15 x 20mA = 300mA. You will need to buffer your 4017 output with a beefy power stage.

ACCEPTED +2 votes
by mikerogerswsm
October 13, 2018

Thank you very much for your response. The only thing I don't quite understand, is the part where you say "buffer your 4017 output with a beefy power stage.". My english is not too good, so I don't clearly understand all the english terms people are using. I'm really sorry about that.

by moe24
October 14, 2018

You have enough volts but you need more current capability. An emitter follower using a power transistor should do it.

by mikerogerswsm
October 14, 2018

Thank you,now I understand. Would a 2N3904 NPN be suitable for that?

by moe2024
October 14, 2018

Not really, it is only rated at 200mA continuous. Try 2N2219 or 2N2222.

by mikerogerswsm
October 14, 2018

Thank you very much for your help. It's really appreciated.

by moe24
October 14, 2018

Another method would be to have no electronics but to have one flashing led in each chain, then the chains would flash independently, so overall there would be a sparkle rather than all-on/all-off.


by mikerogerswsm
October 14, 2018

So, I wouldn't need any 4017 ic and 555 timer ? I would just need 1 flashing led on each row of regular leds ? Is that what you're saying ?

by moe24
October 15, 2018


by mikerogerswsm
October 15, 2018

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