Though a Christian by personal faith in Jesus Christ, I am not big on Christmas decorations except for the traditional Christmas tree. However, this 555 flasher project is an exception. This is a take-off on the previous Firefly Lights Circuit posting. I had a strip of four tiny PCB’s remaining, so I built them up before separating them — and never did separate after observing operation. The result is nothing short of amazing. Instead of boring repetitive (predictable) flashing, they are in no way synchronous. This makes for a captivating watch — something like watching a fire… Hang this on your Christmas tree as an ornament.
Does not do justice — really much better to the eye…
555 Christmas lights Photo
Bill of materials
Use copy and paste function to fully populate the miniboard.
This is different than the standard 555 oscillator circuit in that the LED is placed in the capacitor reset line (pin 7). By doing so, overall current is reduced and the high peak LED current does not flow out of the battery. Since the forward drop of the LED can interfere with the reset threshold voltage when the battery voltage is low, the capacitor charge source is via pin 3, the output. In this way, while the capacitor is rapidly resetting via pin 7, it is also being slowly discharged via pin 3 that follows pin 7. That way if the capacitor voltage has a difficult time discharging to the reset voltage (3V or lower), it has a little help via the charge source.
Otherwise operation is unaffected.
Total current drain is in the order of 500uA. A 9V battery can power this for months. 12V is brighter but less convenient because small 12V batteries are uncommon. Each section can stand alone and has an individual reverse polarity diode. You may think that this diode may be eliminated, but destruction is instant if the battery is accidentally connected reverse.
This can be assembled either in a strip of (4) or (6) flashers — all (6) sections are bussed together. Three expresspcb.com miniboards yield a total of 18 (4) position, or 12 (6) position flashers. My prototype has (4) different LED colors, but the BOM lists (6) LED colors. Perhaps you can locate other colors you like better. I actually purchased my LEDs on eBay—they have some good deals. C1 is 10uF for bright LEDs such as White, Blue and Green—to help equalize brightness for dimmer LEDs, I simply piggybacked (2) 10uF capacitors to get 20uF.
You may be able to see this on the photo.
Great group project
As a group project, students can learn how to identify, handle and solder small SMD devices, and test. The smallest device is the common 0805 size and even I (at my age) can handle this stuff. Smaller sizes such as 0603 or 0402 is “electronic dust” in my opinion and do not lend itself to hand assembly. The finished piece is an interesting curio that will not get discarded. Purchasing all components for a group gets the volume up and price is significantly reduced.
Check LED polarity with DVM on Vf function before soldering to PCB…
Artwork needs checked
The updated artwork is not yet proven — proceed at your own risk…
For the future
555 Four LED low drain Battery Monitor
For unto you is born this day in the city of David a Saviour, which is Christ the Lord. And this shall be a sign unto you; Ye shall find the babe wrapped in swaddling clothes, lying in a manger. And suddenly there was with the angel a multitude of the heavenly host praising God, and saying, Glory to God in the highest, and on earth peace, good will toward men. Luke 2.11-14 (KJV)
Free King James Version (English) download — I like the Quickverse Program — powerful search engine…