Astable 555 timer – 8-bit computer clock – part 1


Our computer’s clock is built using several 555 timers. The first is configured as an astable oscillator. See for more.

Part 2:
Part 3:
Part 4:

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You can get all the components used in this video from any online electronic components distributor for a few dollars.

Complete parts list (everything in this video):
1x 555 timer IC
1x 1MΩ potentiometer
2x 1kΩ resistors
1x 100kΩ resistor
1x 330Ω resistor
1x 2µF capacitor
1x 0.1µF capacitor
1x 0.01µF capacitor
1x LED
Solderless breadboard
22 gauge wire
USB charger and cable or some other 5v power source

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  1. Jr. Jackrabbit says

    Was watching the Hello World from scratch video. Everything was going fine until he pulled out the clock module and then I suddenly felt way out of my depth lol. So I've come here to figure out what this is all about.

  2. Sean Nolan says

    To get a square wave, make the two resistors the same and put a diode around the lower resistor

  3. Jorge Rangel says

    This is valuable content

  4. Pranav Kumar says

    i have a problem, when using the formula and i want the time high=time low i get Resisor(a)=0 ohms. I am not able to understand what i did wrong.

  5. Shunya says

    16:32, i think that 10 32 is breadth and height respectively of capacitor in mm

  6. Luigi Trabacchin says

    i have a silly question … if every chip need a capacitor, or at least is suggested… why they don't make it built in ? there is no closer than built in … is space the problem ?

  7. Timothy Carpenter says

    The 555 is simple – but the thing I hate about the 555 is the drift that makes precision and high speed clocking difficult or impossible.

  8. abbasi qaisar says

    sir need your whatsup number iam from pakistan

  9. Jim Knight says

    When you say impedance are you sure you don’t mean inductance?.

  10. Jim Knight says

    I’ve been involved in electronics for 43 years and have never seen such a tutorial so clearly explain the function of a 555 timer, you are an excellent teacher and I wish you had been a lecturer at college when I was there.

  11. abbasi qaisar says

    sir where from you i want study from you iam from pakistan

  12. Electronics Craft says

    Why Ben eater never reply to coments

  13. Erkan Bas says

    Turkish subtitles please

  14. FatiTank Drawings says

    All redstoners liked that

  15. ludwig josh says


  16. Monko Games says

    Weird, so my capacitor was hooked up backwards. Haha, i put my white strip facing the same way as yours but I guess the strip is the negative end. The light was just solid.

  17. 8000ice says


  18. Viktor Szépe says

    @eaterbc Could you add a playlist called "Primer to binary logic" start from the basics and going up to more complex components?

  19. e-vboy says

    I liked this design so much I got it down to three chips and designed a PCB:

  20. Jeff Stone says

    What I'd like to know is what those sounds that aren't in any language sound like

  21. Rabiraj U says

    Hey brother, try to connect with a power bank. Because i have checked even its mentioned dc output from chargers..they will produce little ac on it.

  22. Francisco Lopez says

    How did you go about choosing what resistors and what cap value to use? I get the 220 ohm for the LED but idk why you chose such high resistors for pins 6 and 7!Love your videos man!

  23. Arvind Sami says

    I've begun working in circuits. One thing I've never quite got the hang of (and apologies for it), is the flow of energy? Is the earth a source or sink. It seems like resistors are put before earth, so I would assume that's where energy is being pulled from?

  24. GPWT says

    Wow microshem

  25. Punit Daga says

    As a computer engineering student, this is Gold. Thank you. I was always curious about how the 555 works and now I've got it.

  26. NULL says

    You got raided by LTT

  27. Gayatri Savarkar says

    How do i get a square wave generator at home without an ic? Ive got some resistors, some capacitors and a dc supply and not much basically, and i need to test a clock triggered circuit. Theres no way of getting a 555 amid lockdown. Is there a way to get a clock with all ive got?Great video, and that simplified diagram of 555 is actually a part of our syllabus at +2 or 12th class level for the electronics course, i always messed the two comparators but after this video i probably wont!

  28. andymouse123 says

    The best available

  29. Bruno Stroobandt says

    Very good explanation. : I made an extension for that. To light up 2 LED's with 1 output. (1 LED simultaneously.) You can use this for example with a model railway as a flipping traffic light. YouTube :

  30. Kirill Azarov says

    We have this, and some people will still prefer to watch the news.It's a crazy world we live in.

  31. David Crafts says

    The problem with the 1uF that measured 2uF is an old problem with aluminum electrolytic capacitors.
    The (capacitance * rated voltage) or 'CV' of electrolytic capacitors tend to roughly match their volume. Thus, a 5uf/10V cap will be about the same volume as a 1uF/50V cap. If the rated voltage (50V) is much higher than the applied voltage (5V), the capacitor will increase the measured capacitance or 'form up' in an effort to make 'CV' come out right. In the case of caps on a power supply, all we care about is the minimum capacitance. If they 'form up' a little, it's not a problem. If the actual value is important, such as a timing capacitor, aluminum electrolytic capacitors are a very poor choice. Ceramic or film are much better.

  32. theShagg50 says

    His videos are very underrated

  33. Rami Ghazzawi says

    Those are reject capacitors.. similar to cheap cereal brands.. they were defective at ratings.. so sold cheaper

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