Telegraph Key Switch

A Telegraph Key is used for sending Morse code, and it's sometimes called a Morse Key. This isn’t exactly a Telegraph Key but the design is similar enough that we’re going to call it that.

We were inspired to build our version after seeing the one that Martine Segers built.

We’re going to use a few specific LEGO parts, but we’ll also highlight some alternate parts you can use.

Besides the normal bricks and baseplate we’re using the following parts:

2 x LEGO Beam 11 (32525 / 64290)

2 x LEGO Brick 1 x 2 with Axle Hole ('X' Opening) (32064)

1 x LEGO Tile 2 x 4 (87079)

1 x LEGO Axle 6 (3706)

1 x Rubber Band

If you don’t have any 1 x 2 bricks with axle holes you can instead use two LEGO Brick 1 x 2 with Hole (3700).

You’ll also need some bushings to hold the axle in place. You can use the LEGO Half Bushing (32123 / 42136) or LEGO Technic Bush 1/2 with Teeth Type 1 (4265) or LEGO Technic Bush 1/2 with Teeth Type 2 (4265).

We'll start by creating the lever.

Place the axle through the two beams at the center with the two 1 x 2 bricks with axle holes on either side.

Add two 2 x 4 bricks to a baseplate. (If using a small baseplate make note of the position so you can fit the whole mechanism.)

Add two 2 x 2 bricks centered on top of the 2 x 4 bricks.

This will serve as the support platform for the lever mechanism we've already assembled.

Add a 2 x 4 brick to the baseplate.

And then add a 2 x 4 flat tile on top of it.

Check the positioning by placing the lever mechanism on the support bricks.

The beams should touch the center of the flat tile.

Add two 1 x 2 bricks beneath the opposite end of the lever.

Check that the beams of the lever touch down on top of the Stopper Bricks.

We're going to temporarily remove the lever mechanism and the Stopper Bricks we added in the previous step.

We'll add them back after we add the rubber band.

Next we'll use our Rubber Band and a 2 x 2 brick to create our spring mechanism.

Place the rubber band under the brick and then stick the brick down to the baseplate.

Add the lever mechanism back in place.

Wrap the Rubber Band around the beams so they get pulled down towards the brick.

Add the Stopper Bricks back into place and test the lever movement.

With the full assembly complete you should be able to test the action of the lever.

Do you get a good satisfying "click!" when pressed down? Does the lever spring back into place when released?

If it's all good then we're ready to add conductivity to our switch.

Grab that roll of 1/4" Maker Tape!

Remove the Contact Brick (the one with the flat tile) and add Maker Tape to it.

Add a few pieces across the top as shown.

Layering a few pieces right in the center will help the lever make better contact when pressed down.

Add a strip of Maker Tape down the center of the beams so it holds them together.

Leave enough at the end so it can wrap underneath at least 1.5 centimeters.

Reminder: If you cut a piece that is too short you can just add another piece and layer it on top. Maker Tape is conductive on the top and the bottom!

Add two more strips of Maker Tape, again leaving enough at the end to wrap around to the bottom of the beams.

With the Maker Tape applied you can put the Contact Brick back in place.

Our switch is almost ready to use! We just need to add the electrical connections so we can use it in a circuit.

We'll build a simple circuit with a Battery and an LED for our switch to control.

We've got just enough room on our small baseplate to fit a Crazy Circuits Battery Holder and LED.

Run a piece of 1/8" Maker Tape from the Contact Brick of the switch to the Negative side of the Battery Holder.

Add a piece of Maker Tape between the Positive side of the Battery Holder and the Positive side of the LED.

Make sure your parts are aligned properly! The white rings around the holes on the Crazy Circuits parts indicate Negative (or Ground).

In Step 18 we added Maker Tape that connected to the Contact Brick, so now we need to add Maker Tape that will connect to the lever side of the switch.

Maker Tape is flexible (a great quality) so we'll use a strip that runs from the Maker Tape on the top of the lever beams down to the baseplate.

Make sure there's some slack so the lever can still move freely.

If you have issues with the middle of the Maker Tape sticking to anything you can always use a piece with most of the backing still in place.

The final connection! We just need to add some 1/8" Maker Tape to connect the Negative side of the LED to the 1/4" Maker Tape we added in the previous step.

With our circuit complete, it's ready for testing!

Press that lever down! Did the LED light up? If not, recheck the previous steps to make sure you didn't miss anything.

Make sure you're using a fresh battery as well!

We connected our Telegraph Switch to our Bit Board and programmed the micro:bit to make beeps... Yes, it's Morse Code!

What else could you use this lever switch for? Perhaps a piano with multiple keys/switches/notes?

Make something awesome with your switch!