LED Dominos Using a 555 Timer - The Learning Circuit

In the last lesson, we learned what happens inside a 555 timer to make it work. In today’s episode, Karen uses 555 timers to make LED “dominos”. Each unit has an LED connected to the output of a 555 timer and an LDR attached to the trigger. When the LDR senses light, the 555 is triggered turning the light on for a brief period of time. When multiple units are placed in a row, each one triggers the next. The duration that each light is on is determined by an “RC circuit” made of a resistor and capacitor. Changing their values can change the duration that the light is on : bit.ly/2rTbKMg
The idea for this project came from a video made by Randy Elwin back in 2011. Karen uses his idea to make a similar device to show off using a 555 timer in a monostable circuit. (Learn more about monostable circuits in the NEXT lesson about 555 timers.) Shining a light on the LDR triggers Pin 2 and the 555 is “set” on. The RC circuit connected to pins 6 & 7 eventually cause the voltage at Pin 6 to go High enough to reset the 555, turning the LED off.
Video Link: • Le Dominoux
Engage with the element14 presents team on the element14 Community - suggest builds, find project files and behind the scenes video: bit.ly/2MFMG0v
Visit the element14 Community for more great activities and free hardware:
Tech spotlights: bit.ly/2KLz0TS
Roadtest and Reviews: bit.ly/2KH4fj3
Project14: bit.ly/2wPnajx

[@element14presents]

Karen changed her design to run off a 9V battery, but that isn’t the only change. Look closely at both the original and then Karen’s schematic designs. Since the original design used a 3V battery, how does the difference in design change the behavior of the circuit? Post your hypothesis in the comments below!

[@arcadesunday4592]

More power substantially changes all of the circuit's variables?

[@toomanyhobbies8119]

Thanks Karen your projects make learning electronics interesting.

[@reasonablebeing5392]

Great project! Would like to see them in a circle so they would continuously chase each other's tail.

[@RandyElwin]

Nice educational video! Amazing how 50-year old electronics tech is still useful today.

[@chriso5355]

Very cool, I like the way you explain everything clearly and slowly and how it all works when put together, thank you 👍... Thanks Karen you make learning and sharping our skills😂 fun 👍❤️

[@arcadesunday4592]

That is so cool. You have a lot of Ben's influence! Great video!

[@onebeartoe]

Pretty cool, Karen!

[@artursmihelsons415]

Great learning circuit and cool idea! :) Basically, bare bones and nothing to program.. A little bit nostalgic.. i think, kids gonna love it..

[@MrCardeso]

Thanks, Karen!

[@sevensolutions77]

Nice project idea 😁👍

[@Electronzap]

That's a fun circuit!

[@1adamtroye]

you make a fantastic introduction for begginers i mean beg - ginners because that is what we are, Asking for Help to get started . i think as a level -58 all is i wanted to do shine an LED on something, but then it (bitMe) so in 4 months (some people learn easy i dont takes abit to sink in) LOL , i still no sweet f a, compered to what i want to know

[@HazeAnderson]

Great video! I will have to watch this one a few times. :)

[@Electronzap]

I was wondering where you wandered off to! :)~

[@adrianoscarlarrauri705]

Excellent !!!!

[@babasaly1]

Can you build the dominos units without the 555 ? only with resistors, capacitors, and transistors?

[@vyorkin]

Awesome video, thanks! 3:07 I believe R3 should be just 200 Ohm, not 220 kOhm (I understand that this is just a typo)

[@Cooee28]

Is the animation at 2:22 wrong? She's talking about pulling the trigger low and the overall 555 output going high, but I think the animator has mistakenly shown !Q going high instead. The animation isn't showing the inverter that should follow !Q and invert the high !Q into a low 555 output. (This is my first time learning about 555's. I might be misunderstanding something)

[@user-tc7zl9jb8w]

Can I Used push bottom switch in place of Flashlamp you that used?

[@agwe9378]

She's a good teacher. She's the first female teacher that ever made me understand something

[@ritaisabel8665]

Good

[@msmukta1544]

Wow

[@claytonbenignus4688]

Show us how to use the LM386 and the CD4060.

[@HazeAnderson]

they have data sheets you know xD

[@claytonbenignus4688]

@@HazeAnderson I am not far enough alont to know how to read those yet. Perhaps that would also make a good video.

[@HazeAnderson]

@@claytonbenignus4688 oh data sheets are incredibly difficult to translate into what you need to know ... but they often come with example circuits and that can bootstrap you into success.

[@freeelectronics7635]

You are apply 10k in #THE ... Soo how it will be High stage...????

[@americanrebel413]

2nd!

[@s.snagartechnical351]

Super is

[@PeterPerhac]

pro tip: to avoid breathing in dangerous solder and burning flux fumes, smoke a cigarette, so the nasties have to pass through a filter. 😀

[@ylh7877]

Gloves 🧤 please when soldering

[@naits7]

Why?

[@arcadesunday4592]

@@naits7 yea, why?

[@nixiefanaccount]

never had gloves while soldering. they get in the way, its really impractical

[@kjamison5951]

I work in the manufacturing industry - no one wears gloves when soldering, even when we have to use leaded solder...

[@HazeAnderson]

Just wash your hands!