# crazy idea or ?? led dominos

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#### MrDEB

##### Well-Known Member
been hooked on playing Mexican train and the dots from across the table are sometimes hard to read so I had an "off the wall" idea of dominoes with colored leds.
using small #13 batteries or perhaps bigger since the #13 are only 1.4 volts
have the battery slide within a cylinder encased in the dominion so it turns on the leds when face up.
one issue is color variety since train is played using double 12 dominions.
mulling ideas around.

#### dr pepper

##### Well-Known Member
Interesting you'd need a load of batteries to make it work though.
How about inductively coupling the 'noes to each other and powering the led's from one source, you'd need to regulate brightness across them all.

#### k7elp60

##### Active Member
been hooked on playing Mexican train and the dots from across the table are sometimes hard to read so I had an "off the wall" idea of dominoes with colored leds.
using small #13 batteries or perhaps bigger since the #13 are only 1.4 volts
have the battery slide within a cylinder encased in the dominion so it turns on the leds when face up.
one issue is color variety since train is played using double 12 dominions.
mulling ideas around.
If you would like, I can show you how to connect LED's in parallel and use a 3 volt lithium battery run them all. I have made a number of badges the size of business cards and about 1/2" thick that use that principal. The individual symbols would be about the size of domino in mexican train.

#### JonSea

##### Well-Known Member
The idea falls apart pretty quickly when you consider the capacity of batteries that size and the number of LEDs you'd need to light up each dot (assuming individual LEDs for each dot).

Mexican Train is played with dominos having up to 12 (16?) dots on each end - a maximum of 24 (32?) per domino. The dots are also colored: black, red, green, yellow, blue and pink. Since you can't get black LEDs, you might replace those with white LEDs. The white, blue and pink LEDs will have a high forward voltage, probably even greater than a 3 volt lithium cell can provide.

Ignoring the voltage issue for a moment, a #13 hearing aid battery is designed to power a 1500 ohm load - less than 1mA. Not much chance of powering 32 LEDs with any brightness for any length of time. A better option might be a 3-volt 2016 or 2032 lithium cell. These can provide 15mA for short periods of time. And you'll probably need 2 per domino to get enough voltage to operate the white, blue and pink LEDs. Looks like you can get 2032 cells for about a buck a piece...x 91 dominos x 2 = \$.

Something a little more practical to use material like Rowmark ColorCast Acrylic. This material is clear on the top with a thin laser-engravable color layer on the bottom. In this article, I show how the material can be laser-engraved to let an LED shine through the desired areas. Engrave the dot patterns for each domino, and put a single LED behind each end to illuminate the dots. You'd still need a butt-ton of batteries but at least they'd last longer...and all the dominos would have about the same battery life since each battery is powering just 2 LEDs.

#### k7elp60

##### Active Member
Well part of the circuit could be with LED's. I have been using a CR2032 lithium coin cell, .650 dia and.125 thick. I have blue and white LED's that are both very bright on 1 ma each. The forward voltage of the blue is 2.5v and the white is 2.5v. The attached photo is of a badge I made for haloween about 10 years ago. The LED's are blinked on/off about every second. I generally wear the badge for about 4 hours at a time. I don't remember when I last changed the battery. The letter B has two strings of 5 red in parallel, and the O's have 4 in parallel. I build a constant current source and measure the Vf of the LED's and match them and the connect them in parallel.

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