Fantastic Atom Expander

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Here is the schematic, PC board pattern, and parts placement for a "Fantastic Atom Expander". This circuit produces an "exploding atom" effect using 98 LEDs.


This is the schematic of the Fantastic Atom Expander

PC Board Layout

This is the printed circuit layout for the Fantastic Atom Expander

Parts Placement

This is the parts placement for the Fantastic Atom Expander


Total Qty.
C110.1uf Mylar Capacitor0.1uF Ceramic Disc Capacitor
IC114017 IC
IC21555 Timer IC
L1-L9898Jumbo LED (any colour but blue)
Q1-Q552N3904 NPN Transistor
R114.7k Resistor
R21680k Resistor
R3-R74470 Ohm Resistor
MISC1PC Board, 9V Battery Snap, IC Sockets


  1. The LEDs can be any colour but blue. For a very interesting effect, make one ring red, the next one green, the next one orange, then yellow, etc.
  2. The transistors can be most any inexpensive NPN transistor (2N2222, PN2222A, Etc.).
  3. For a very interesting (and expensive!) effect, replace the 2N3904's with 2N3055 power transistors on heatsinks and use 12 V 500ma incandescent bulbs instead of LEDs.

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Fantastic Atom Expander
Thursday, January 29, 2015 11:49:45 PM
This schematic is wrong, first they are connecting the pins 1-7 and other pins, they are already connected inside the 4017B chip, most retarded thing in the schematic, then transistors are flipped in the wrong direction, Most stupid thing ever "" PIN 13,15 are going to the ground but they are also resetting the chip "" WTF is that if you look in the 4017B datasheet you can see the gates and all the connections there ( functions of all the pins ).

(Editor's notes: 1 and 7 (etc.) are not connected internally. They are connected in the schematic to reduce the number of outputs while still providing a smooth count. The transistors are not backwards. Pin 13, etc. are tied to ground to prevent them from floating.)

Fantastic Atom Expander
Sunday, February 10, 2013 6:18:05 AM
Verry lousy schematic do it right or do nothing att all!!!!!!
Fantastic Atom Expander
Sunday, May 27, 2012 5:41:48 AM
verry rare .bad drauwing circuit and layout not logic
Fantastic Atom Expander
Sunday, August 02, 2009 5:20:54 PM
J means Jumper
Fantastic Atom Expander
Thursday, April 16, 2009 10:34:22 AM
What yhe J letter means? It appears like J1, J2, J3, J4, J5 and J6! Thanks!
Joćo Silva Brito
Fantastic Atom Expander
Thursday, April 16, 2009 9:59:32 AM
It's just me or its missing from the parts placement de led place or number 85. From my count is 97 leds not 98!?!? Please advise!
Joćo Silva Brito
Fantastic Atom Expander
Thursday, April 16, 2009 7:02:54 AM
Hello! Could you please send me or improve the showned Schematic because i can't see all the numbers in the ICs. It's really important! Thank's!
Fantastic Atom Expander
Friday, January 23, 2009 10:38:13 AM
Is it a one-shot deal, or does it provide a continuous series of expanding light effect ? Thanks
Fantastic Atom Expander
Tuesday, October 14, 2008 12:41:35 AM
circuit diagram is not clear
Fantastic Atom Expander
Wednesday, April 23, 2008 12:59:36 AM
I built my atom expander following the design on this page. But it didn't work at first because the capacitor was to small. Eventully after trying many capacitors a 220pf(0.22uf) worked and gave me a working project. So i don't know what happend, everything else is right it was just the capacitor. oh well, anybody building the project, if it doesn't work and the ic's are working make the capacitor a bit bigger like a 220pf.
Fantastic Atom Expander
Saturday, March 15, 2008 8:27:24 PM
This circuit works very well! I bought a couple of these in kit form from a couple of years back. I substituted ultra-bright LEDs for the "100 for a buck" red ones that came with the kit. Red on the outer ring, then amber, green, blue, pink (yes PINK), and then an 8mm white in the center. Changed resistor values where needed and it works just great. I've run it from various voltage sources anywhere from 6V to 12V with no problems. The transistors get a little warm but the duty cycle is low enough that it is not an issue.
Fantastic Atom Expander
Thursday, March 13, 2008 2:17:00 PM
## ali ##This circuit will never WORK! because u need to use 8 diode on out pins the output is triggering a transistor which will amplify the signal to usable levels without the draw on the output Pins.
Fantastic Atom Expander
Thursday, December 27, 2007 8:59:46 AM
You cannot combine colors on the same circuit; LED's are not lamps. They are non-linear devices. Reds want to drop about 1.8 volts, yellow about 2 volts, green 2.1 (new technology green ~3.5), and blue ~3.5 volts. You can usually get by parallelling the same color on one circuit, but they won't all be the same brightness (and one might burn out). Parallelling for example a red and a green, the red gets all the current (because of its lower voltage drop). Being non-linear, the best circuit is a series resistor for each LED --- the LED will set its own voltage. Calculate the series resistor by taking the supply voltage, subtract the LED voltage, and divide the result by the current (.010 amps for most LED's). If you use only one resistor per color, then multiply the current (.010 amps) by the number of LED's (24 for the outter ring). Example: Blue LED R = (Vs - Vled) / I led R = (9 - 3.5) / (.01)(24) R = 5.5/.24 R = 23 ohms Be sure the resistor can handle the power: P = (I**2)(R) P = (.0576)(23) P = 1.3 watts I suggest a chip resistor for EACH Light Emitting Diode. LES's will be safer, resistors cooler, and the world geopolitically safer (maybe not the last one)...

(Editor's notes: Just a note that the version I made with a rainbow of different LEDs has been working fine for over 10 years.)

Fantastic Atom Expander
Wednesday, November 28, 2007 8:20:05 PM
.can i lessen the no. of led's use?and what would be the adjustments in using only half of 98leds.
Fantastic Atom Expander
Tuesday, October 23, 2007 5:21:46 AM
looks like a really fun project. it there anyway i can build to use blue leds? any info would be very helpful. thank you
Fantastic Atom Expander
Saturday, September 29, 2007 6:10:40 AM
i just want to know will this thing work or not

(Editor's notes: Yes.)

Fantastic Atom Expander
Wednesday, August 15, 2007 9:55:15 AM
This circuit "OR-ties" the outputs of the 4017 counter, which is not the best methodology. The circuit should be modified to include OR gates (either sections of type 4071 ICs or discrete diode-resistor gates). Otherwise, the 4017 will be stressed and may burn out. Also, many types of 555 timer ICs, when used as a clock, may cause unreliable counting in the 4017. Use a clock comprised of one section of a 40106, along with a resistor and capacitor, instead.
Fantastic Atom Expander
Sunday, August 12, 2007 3:01:35 PM
It*s verry OK !
Fantastic Atom Expander
Thursday, August 09, 2007 6:08:09 PM
the layout for the ic is too small..i suggest using a matrix board..
Fantastic Atom Expander
Thursday, August 02, 2007 9:36:41 AM
do you have a running circiutt on this project
Corey Duma
Fantastic Atom Expander
Friday, July 06, 2007 8:46:47 PM
I find the pcb to be terribly confusing. the only thing that i like about it is that it is to scale. I wound up using MSpaint to remove the lower half.
Fantastic Atom Expander
Monday, May 28, 2007 12:47:45 PM
This circuit will never WORK! because u need to use 8 diode on out pins

(Editor's notes: It works great.)

Fantastic Atom Expandertt
Monday, May 07, 2007 10:48:56 AM
The numbers are not clear,
Fantastic Atom Expander
Sunday, April 15, 2007 1:07:11 PM
read the parts list, ul find the ic number...
Fantastic Atom Expander
Friday, March 30, 2007 8:00:01 AM
????? whats with the numbers on the IC's
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