Newbie need help with LED semiconductor strobe circuit

Thread Starter


Joined Feb 3, 2010
Hi everybody. I'm pretty new at electronics. I am an apprentice electrician so I understand most of whats been said here.

I have been doing research on a strobe circuit that could flash one group of leds 3 or 4 times then flash a second group the same amount of time. I have attempted to use the 555 timer with a 4017 decade counter. It will work, but I found this other circuit that does the same thing but without the chips.

I have been trying to re-produce this circuit but can't seem to do it. I think it has a semiconductor installed. I have attached some pictures of the circuit I'm trying to re produce. On the back side of the circuit board there was a black epoxy blob that I removed to figure out whats happening.

Inside the blob there is a tiny square something that does conduct but can't get an ohm reading through it.

It seems to be a really simple circuit except for the black blob part. Any ideas?
Lights flash simultaneously or Lights flash one after the other

I put the circuit operating on youtube:

This circuit uses:
(2) S8550 transistors,
100uF cap,
(2) diodes,
I think one zener diode,
electrolytic cap it say 104 on it,
(2) 1.6k resistors connected to transistors,
560 ohm res. located next to cap,
and a 5.6k resistor next to the 2 diodes.


Last edited:


Joined Jul 17, 2007
Yeah, prying the epoxy blob off wasn't a great idea.

If you want to get away from using multiple ICs for such projects, you should have a look at microcontrollers aka uC's, MCU's. The learning curve can be steep in the beginning, but once you "get the hang of it", you can do a heck of a lot with a very low component count.

Thread Starter


Joined Feb 3, 2010
Yeah it was an ic, fortunatly I have others. I am gonna reseach micro controllers a bit and see what I can make of it. Other wise I'll stick with the 555 timer and 4017 decade counter

Thread Starter


Joined Feb 3, 2010
Basic pattern, but using multiple Led's (4 red 2 white 2 blue) and a 9v battery.

Red leds to flash 4 times: R1 R2 flash the same time then R3 R4
Blue to flash 4 times: B1 then B2
White to flash once: W1 then W2 wig wag style headlights

That's why I think I should go with a 555 and a 4017.

I would like to use a pic chip but I know nothing about programming right now, and because I'm in school doing my elec. apprenticeship I'm bogged down with studying and homework and don't think I can fit anything else in brain right now.
Maybe after school I'll research into programming.