Why did you make these?
I made similar menorahs last year to give away to friends as gifts. Many people suggest I try to sell them, so here we are.
Where can I buy one of these?
How are the two menorahs different?
The only real differences are shape and size. The Model II is somewhat larger, and the Model I is more compact -- great for those unfortunate Hanukkah business trips.
Can I adjust the brightness?
Not without major menorah surgery. The brightness was set as a compromise between battery life and visibility. I think it looks fine in a partially darkened room. If you really want a brighter menorah, the LEDs can go much brighter, but each of the very small 220 Ω resistors leading to the LEDs need to be replaced with a lower value. It would certainly be a great way to practice your desoldering/soldering skills. You could go down to about 80 Ω, I'd say.
These are printed circuit boards. Are they safe to handle?
Yes. The hanukiah operates at safe voltage. The boards and most components on them are lead free. The only exception is that I used a small amount of leaded solder to attach the terminals battery box. That said, if there are littles ones around who are apt to put this in their mouth, this is not the menorah for you.
How do I clean this menorah?
You can wipe it down with a damp cloth. If it gets very dirty, you can first remove the batteries and wash it with 90%+ isopropyl (rubbing) alcohol.
Is the menorah open source?
No. I made the schematic public on this page, but I'll keep my rights to the PCB artwork. I'm also keeping the code running on the microctontroller to myself. I didn't lock the chips, so I guess people can steal the binary, but I won't be providing the source code. However, I have provided an example of a simpler but functional sketch as a starting point if people want to hack their menorahs.
How does it work?
It's very simple. There are three chips on these boards, plus 18 light-emitting diodes, or LEDs -- two for each "candle", and a handful of other components to tie it all together. One of the chips is a Atmel microcontroller (ATTINY84), which runs a small program to read the buttons and implement various effects. Most of the LEDs are driven by two shift registers (74HC595) , one on the left and another on the right. The microcontroller can shift in bits to each of these registers to indicate which lights it wants on. It can do this many times per second to create various effects. The shamash LEDs are driven directly by the microcontroller's output pins.
What is the "secret message" mode?
When I designed this, I knew I had put in a microcontroller that more than capable enough to flicker some LEDs for Hanukkah, so I wondered, what else could I do with this thing? I was looking for something a bit more difficult. I remembered a toy from my youth, a "wand" that you could wave and show a secret message that could only be seen if you moved the wand. It relied on "persistence of vision" to form an image in your eye. I decided to mimic that in the menorah.
When you press the "night" button in "secret message" mode, the menorah lights LEDs in a pattern that -- if the menorah is moving -- will form letters and words. Because the menorah has no way to sense if it is moving and how fast, it flashes the LEDs at a pre-set rate, which means that it doesn't work quite as well as the old 1980's toy, but it can still be read if you try enough times.
Can the menorah be customized? Can I get it in a different color?
Funny you should ask. Yes, this is possible, but only if you order a largeish batch. Contact me to learn more.:firstname.lastname@example.org.