Menorah with LED "candles" that are lit using a shamash (helper candle)

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Menorah555 is an LED menorah (also known as a hanukkiah) that uses flickering LEDs to simulate the candles. The shamash (helper candle) is removed and used to "light" the other candles.

I had made another LED menorah years ago, driven by a microcontroller, but it is lost somewhere in our house. I'm not sure where it went. I'm sure it will be found some time, but as of 2021, it's still missing, probably in some interdimensional portal. So, I decided to make another LED menorah. Although it would be much easier to use a microcontroller again and it would be more flexible, this circuit is instead designed around multiple 555 timers, because. . .ummm. . .Ok, I have no good reason other than, "I wanted to!" So there! Don't judge me.
Files are under version control at Video is at

The Menorah555 assembly consists of three main parts: the printed circuit board assembly (PCBA), the LED flame diffusers, and the bent acrylic base. Details (excruciating) on each of those follow.


The Menorah555's schematic and PCB were designed in KiCad 5.1.12. There are only a few different parts to the schematic since much of it is repeated for the eight non-shamash candles.

The main parts of the schematic include the shamash, current limiter, candles, and power-on reset.


The shamash candle, like all the other candles, is designed with an LED that looks like a standard T-1 3/4 LED with a 5-mm diameter, but it actually has a chip inside that applies PWM to the LED in a way that simulates a flickering candle. Using this type of LED eliminates the need to use a separate microcontroller to create that effect. A 330-ohm resistor is put in series with the LED to limit the current and set the brightness.

Since the shamash is removed and used to "light" the other candles, it needs a power source to keep it lit during that time, maybe 30 seconds. That role is filled by a 0.5-F supercapacitor. That is 0.5 farads, not microfarads, so it holds a LOT of charge. In fact, this holds way more than necessary, but I wanted a capacitor that would lay flat to give the suggestion of a cylindrical candle shape. This supercap charges in a couple of seconds, but actually keeps the LED lit for 10 minutes before it gets noticeably dim and is still very dimly lit at 20 minutes, so you can really take your time lighting the other candles!

A common barrel-style power connector was used so that the shamash PCBA can be unplugged from the mainboard and used to light the other candles.

Current Limiter

The menorah has a micro-USB connector so that it can be powered with a USB charger or battery pack. These power supplies are designed to supply at least 500mA, although they may supply more. However, the inrush current on the 0.5F supercap may be much more than that and it could send the power supply into an over-current condition. Since this is undesirable, a current limiter circuit was added to prevent this.

This current limiter is not very precise, but there is no need for great precision because we don't need an exact current, as long as it's less than 500mA.

The current limit is set by the value of the current-sense resistor, R28, which is 1.33 ohms. When power is first turned on, the base of transistor Q10 is biased by R29, which turns on Q10 and allows a larger current to flow through Q10 from collector to emitter. The current flows through the current-sense resistor to the shamash supercap, which begins charging.

When the supercap first begins charging, it is essentially a dead short, except for its equivalent series resistance. If the current through the 1.33-ohm resistor R28 reaches ~450 mA or more, the voltage drop across R28 is above 0.6 V. When combined with the ~0.6 V voltage drop across the Q10 base-emitter junction, this means that the total voltage drop is more than 0.12 V and is enough to turn on the two diodes in D10. When D10 starts conducting, it reduces the current going into the base of Q10, which reduces the current going into the collector. Thus, the current ends up getting regulated so that i = V/r = 0.6V/1.33Ω = 450mA, give or take a bit. This will vary due to temperature variations and tolerances, but that’s close enough.

The current through a capacitor follows the equation i=C dV/dt, so when the capacitor is charged with a constant current, dV/dt = i/C = 450mA/0.5F = 0.9V/s. Thus it only takes a couple of seconds before the supercap is charged enough to turn on the LED.


The candle circuit (duplicated eight times) has more parts than it needed because I started to add another feature, but I needed to place an order for PCBs if I wanted them to arrive before Hanukkah was over. Thus, when it came to a choice of minimizing the BOM or maximizing the features, or having the...

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Schematic for rev A

Adobe Portable Document Format - 207.93 kB - 12/23/2021 at 04:22


  • Video on YouTube

    Glenn.Kubota (gee.k)12/20/2021 at 15:47 0 comments

    I made a YouTube video showing the menorah and only used open-source tools to create it, just as I only used open-source tools to design the menorah hardware. Since this was my first time trying to edit a video for YouTube, it may have taken me as long as it took to design the menorah :)

  • Just a bad solder joint

    Glenn.Kubota (gee.k)12/18/2021 at 04:08 0 comments

    Easy enough. There was just a bad solder joint on the LED current-limiting resistor. Was it my fault or can I blame it on gremlins?

  • And...the shamash LED has stopped working

    Glenn.Kubota (gee.k)12/17/2021 at 23:17 0 comments

    Ok, Hanukkah is over, but I wanted to take photos for this page. Debug time! What is it? Assembly error? Design error? Sabotage? Who knows?

  • First build

    Glenn.Kubota (gee.k)12/05/2021 at 23:56 0 comments

    The first build (rev A) is working just in time for the end of Hanukkah. The LEDs light when the shamash magnet is brought near the reed switches. I reworked it a bit to add one diode because the 0.5F supercap keeps the shamash lit for more than 20 minutes when power is turned off. The diode drains the charge quickly when the power switch is turned off, but allows the shamash LED to stay on for a long time when it is pulled out to light the other LED candles.

View all 4 project logs

  • 1
    Assemble PCBs

    Solder the components to the PCB. The parts can all be soldered by hand, except for the USB connector, which must be reflowed with an oven, hot air, or hot plate. Sorry about that! Note that the barrel power jack should not be soldered flush to the board, but should be offset so that the shamash PCB will align with the main PCB.

  • 2
    3D Print the LED Diffusers

    The LED diffusers can be FDM printed with no support. They can be pushed down onto the LEDs without any adhesive, although you can certainly use some if you really want to be sure they don't fall off.

  • 3
    Cut the Acrylic Base

    If you have a laser cutter, use that to cut the acrylic to the correct shape. If you don't have access to a laser cutter, you can cut it with a bandsaw or jigsaw and then sand and polish the edges. Don't drill the holes yet, unless you are really confident in your acrylic-bending skills.

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