EEVblog #555 - 555 Timer Kit

555 timer is used in capstone motor speed control in Revox B77 reel to reel tape recorder

Ok, I'm curious. What can you do with those cut-off pin tails? This isn't the first time I've heard someone say to keep them.

Can a 555 timer be made using a
2 comparator ic741
1 flipflop ic
Npn pnp bjt
Output driver circuit ?
Could it work as a 555?

These are still around, along with the LM741 kit they make (~$40 each kit). Very cool and I just ordered a set to build and play with. They will make great (functional) desk displays!

One suggestion I have for them... I wish they permitted you to mount and provide connections in one corner/edge of each kit the actual IC chips, so you can not only compare their real size, but allow you to connect them for use like the full size does.

lol at electrons will fall out :D

666 timer from hell

learning how to build

Got mine today :) looking forward to building it.

edit: the 'legs' are now aluminium instead of plastic

I learned early on to read the directions for kits I was building, even simple ones with the silk-screen labeling everything, because there are almost ALWAYS some components where the silk-screen is shown or labeled backwards from the reality of some components included in the kit, and they added the correction info to the kit instructions.

nice work station.......

"3 5's" ..??? iv never heard it called that here in the U.S.

I hate PCB's with opaque soldermask. They make traces difficult to follow.

Your soldering doesn't seem good with double layer PCB, may be your skilled speed not matched with used soldering iron wattage vs heat sinking PCB. the best way that I felt with manual soldering to complete certain set of components earlier and go for the 3prong component later.

AWESOME!!!!! Thank you so much for sharing your knowledge!!!!

Dave, thank you for making this video. I realize this is from years back, however, I just bought this kit (Jan 2021) and was a little hesitant about putting it together for whatever reason. After watching your excellent video I actually feel confident that I can do the job following your guidance, and be aware of the mistakes too, which also are good tools to be aware of. Thanks for the tutorial and no it wasn't boring for me to watch and I learned quite a bit about several things along the way.

Never pull resistors from paper tape, as it does leave adhesive goo on the wire leads... Simply use your side cutters and cut the wires at the paper tape. The leads are plenty enough long to leave a few mm in the paper tape.

I was taught that you put the iron onto the joint, then you place the solder between the iron and the component and pad and use the solder to immediately form a solder bridge so everything heats up to temperature quickly.

This was great man! I know you don't think it was very exciting, but I'd watch this kind of stuff all day! Thank you so much! By the way, I'm loving my new EEVblog Bryan DMM!!

Oh, im also a Fan of the 555 and i have soldered the same great Board from the Evil Mad Scientist is nice and hang above my Workbench i give some Boards of these to Childrens to have a nice Solder Projekt

FUN Fact: Hartley Oscillator (Pacemaker) was made by mistake by putting in wrong transistor

I wonder if this circuit has the same 55.5kHz modulated with 55.5Hz 🤔😉
L.E. Nice videos! Keep them coming!

I have bought the 555 board from eveil mad scientist and i wonder if i replace all the components with 1% tolerance resistors and better transistors will that make a significant difference in the performance.???

@EEVblog You worried far too much if I didn't want to watch your video I wouldn't have. We can always fast forward anyway!
Going to try to make a comparator from transistors so this video was just what I needed.

Can you not just add a valve to stop all the electrons falling out?

A complete slab of Blu Tac works just fine to hold them all in place for soldering. And it is reusable time and time again.

I wouldn't be watching your stuff but for Arduino which got me into it all.

This reminds me of the visible V8 engine model kits .I hope Americans get really annoyed hearing the correct pronunciation of the word "Solder " . Not Sodder , say it properly bastards. Lol ,Cheers

uncle mad max. it can be good when we use +30v 10 output transistors. to drive big igbts and mosfets by making bootstrap drive

When I saw the resistor values I wanted there to be three 5k resistors instead of using 4.7k..

잘보고 갑니다.

Great chip and excellent kit. I actually sat through it all without FF! Was wondering for about 4-5 minutes how long it would take you to notice the missing resistor soldering.

One of the resistors is upside down.

Hallo there. Might I ask you whether you could make a video regarding Monostable multivibrator with two BJT's? Personally, I cannot handle the capacitor's discharge. That window of moment does not quite make sense. To make it more specific:

1) Before we apply the pulse (in other words, at the stable state), the left pin of the capacitor is @ Vcc volts and as for the right pin, I cannot clarify whether it is @ V_B2 = 0.7 Volts or @ Vcc, and this is because the right pin of the capacitor contacts directly V_B2 and also Vcc through a resistor (let us name it R1). As we all know, the higher voltage rules, so among 0.7volts and Vcc, I think that the right pin of the capacitor is (also) @ Vcc volts and not @ 0.7volts.
2) Now we apply trigger pulse (which has to have a minimum voltage value, I think Ib = Vcc/Rc1/beta or something, please, correct me):
i) Q1 -> SAT => Vc1 -> 0volts
ii) capacitor starts to discharge from the left pin and soon the left plate of the capacitor goes @ 0volts.
iii) from now on, I get somewhat confused. Sites say that capacitor now holds a reversed (negative) charge @ -0.7 volts and thus V_B2 = -0.7volts (?????) that drive Q2 -> OFF. But, as I already mentioned, how is that possible in a moment that B2 is still connected to Vcc via R1? (R1 is the left resistor and is between Vcc and the right pin of the capacitor. Sites call it R2 usually, but I named it R1 so that to divide components into area 1 and 2 (left and right area)). I drew a circuit which unfortunately I cannot upload here, but I will try to describe it. We have a Vin. We connect its positive pole to both of the pins of a capacitor but in the one cable we interfere Rc1 and to the other we interfere R1> Rc1. I also tried a rendering where I grounded Rc1 (GND = negative pole of Vin). In LTSpice, nothing magic happens, it just shows that soon the voltage across the capacitor 's pins are ΔV = Vcc - Vcc = 0.
Other blogs say their own story, for instance, when capacitor is empty, is starts to charge via this path: Vcc->R1->capacitor->Vc1->Ve1=GND. Is this a truth or is this their own scenario?


Would it be as hard as that to make an explanatory video? A slow-motion cartoon video would be really helpful. Thank you and excuse me for interruption!

Looking to get one of these to mount on my wall. Cheaper and cooler than a painting. Would love to see you do the 741 kit as well.

I came for the kit but stayed for the Ausi accent .

Usually the E and C are reversed....

Heeeey where's the two diodes.....? I want my two diodes, too! LMFAO 😁😊😊

That is definitely smaller than what I thought it would be as well, and yeah I laughed when you said the board manufacturer putting their stuff on their pissed you off because while I agree completely! LOL this was really great video, I used to 555 all the time it's an awesome yep, I learned from Forrest Mims on I first started playing with them via the old Mini notebooks he made --- I actually JUST remembered the first thing I used it for when I learned about it -- a DC to AC inverter to drive my telescope that blew up, so designed and built a new one from scratch while using a center-tapped transformer, etc. Power transistors, etc. So a 12 volt DC to 120 volt AC, variable frequency (run it from your car when out in BFE, etc. 😊😊

35 bucks?! really? you get that pcb printed for 7 bucks delivered from china, and of course that's for one off things. if you order 1000 of those you pay postage only once. resistors are 1 buck in 1000 quantities. transistors just slightly more and the terminals can't be that much more either. 10 bucks would be a maximum to price this for. this is educational only.

7 years late, but the one thing I don't like about this kit is the black solder mask. It's the kind of thing you add to a product when you DON'T want people to be able to easily see how your circuit works... which kind of defeats the purpose of this kit.