EelLog: I heartz you.

So, it's valentines day, and my sweetheart wants us to make gifts for each other. This reminded me of something my dad made years ago:

I still don't understand how he made this. Most LEDs have a forward voltage of about 1.7V... Ok, an LED is not just a fancy light bulb, LED stands for Light Emitting Diode. A diode is one of the basic electronics components. It acts as kind of a switch, if the voltage is below a certain point, the current will not flow (switch off), once a voltage has been hit current flows (switch on) in the case of an LED, light is also produced. The other neat trick that an LED has, is that this is not symmetric, the reverse voltage is much higher than the forward voltage so it can be used to say, no Mr. Electron, you can't go that way, only this way.
But, anyway, as I was saying, I don't understand what my dad did here, cuz as I was saying, most LED's have a forward voltage of 1.7V, and he has 8 LEDs connected to a 9V battery: 9V/8LEDs = 1.125 V/LED. Did he have a source of 1V LEDs?

It is a cool idea and the most common LEDs are Green and Red (was not until the 90s that blue came down below 10$ each (and yellow does not count, it's ugly)), and I figured, hey Green goes with an X-Mass tree, so red would be great for a Valentines heart.

The first step is to "draw" a heart:

Then I printed it out on a piece of paper so that it would be about 2.5 inches (that is 6.35 cm for my civilized readers) square(ish). Next I hand drew 10 points where LEDs will go. I made this intentionally not quite match up. Our brains like to fill in the spaces and 10 points does not quite a heart make, so I am counting on the brain to fill in the the holes on each side by knowing were the points are on the other side.:

10? Uncle Eel you said 8 was too many but now you got 10?
Well, I am actually making two parallel circuits here each with 9V/5LEDs = 1.8V/LED Just over the forward voltage. This will last until the battery is down to 8.5 volts, which for a "9V" is pretty durned dead.

The circuit:

Uncle Eel, you had better stick to mechanical engineering, that is not a circuit, that is a circle!

True, but lets put some more detail into it:

Now we can see that the LEDs are in opposing directions on each side of the heart. So the electrons can only travel one way for one side, and the other way for the other side, making each side of the heart its own circuit that is only a part of the whole (I actually did not intend for that bit of symbolism, I just wanted more than 5 lights, I do so like it when the universe is poetic).

So, the design is done, lets go out to the shop and start building.
The first thing to do is pick out my LEDs. In looking over my collection I had 2 to pick from that were red and I had more than 10 of.
I bread borded 5 of each to see what they looked like:

The smaller ones are brighter, but you can't see in the photo, they are not that consistant. Also, the softer light of the bigger ones is kinda nice, so lets use those.

To get it all straight we are going to make a jig. So, we glue the template to a pice of scrap wood. And drill out the locations of the LEDs:

dig my new drill press!

Then we put the LEDs in place, and start soldering and clipping... err clip first, then solder. Note the direction and remember that the LEDs on the left are to be installed backwards from the ones on the right.