The hand controller for the ZWO Electronic Automatic Focuser (EAF) is an expensive piece of plastic, at a whopping $39.90 USD at the time of writing!
Here's how you can make your own for $15 or less! This build has been tested on the 5V EAF.

For this build, you will need:

– 1 x 4-pole (3 bands) 3.5mm male audio jack (<$10, OR free if you have an extra headphone jack lying around!)
– 1 x 4.7k Ω resistor ($1 for a multi-pack at a local electronic components store)
– 2 x push buttons — 2 pin, normally-open, momentary ($1 each at a local electronic components store)
– 1 x 2-way (3-pin) sliding switch (1$ at a local electronic components store)
– Some copper wire
– Soldering tools
– Multimeter (optional but recommended)
– Prototyping PCB (optional) ($2 at a local electronic components store) OR small wooden/plastic board (optional)
– Hot glue gun + hot glue sticks (optional)
– Hot glue gun + hot glue sticks (optional)
– Plastic or wooden enclosure (optional)

Shorting the Sheath (S) of the audio plug to R1 or R2 will result in movement of the EAF, whereas the resistance between Sheath (S) and Tip (T) determine speed:

SHEATH → R1 = "DOWN"
SHEATH → R2 = "UP"​

SHEATH → 0.0 Ω → TIP = FAST
SHEATH → 4.7k Ω → TIP = SLOW

The circuit for this hand controller is fairly simple. First, prepare your four-pole audio jack. If your jack has two ends (whether one male or one female or two male), cut off one end and expose the four individual wires inside. Make sure that the end that's still attached to the cable is male. Use a multimeter to identify which of the four lines corresponds to which pole on the male jack (or read the data sheet!). In order of furthest to closest to the plastic housing, the poles will be referred to in this guide as TIP, R1, R2, and SHEATH.​

It is recommended to connect components by soldering them together. If you would like to use a prototyping PCB, you can solder components to the board, and then connect them together by soldering wire connections between components. If you are using a plastic or wooden backboard, you can use hot glue to secure soldered components to your backing board.​

Connect a length of wire to the line corresponding to the SHEATH. This will serve as your common ground. This means that power passing through every component will pass through this wire.​

Branch out three lines from the common ground and connect them to one pin on each of the buttons, as well as the middle pin of the two-way switch.​

For one button, use wire to connect the other pin to the line corresponding to R1, and for the other button, connect the other pin to the line corresponding to R2.​

Use wire to connect one of the two outer pins of the two-way switch directly to the line corresponding with the TIP. Connect the other pin to one end of the 4.7k resistor, then use wire to connect the other end of the resistor to the line corresponding with the TIP.​

Congratulations! You have completed the hand controller circuit! If you would like, you can create a housing for your hand controller to make it more durable, or use hot glue to seal off the wires to protect the circuit from the elements.

Thanks for reading this tutorial, and clear skies to everyone! If you have any comments or questions please don't hesitate to let me know! I've attached below some pictures of mine, that I made out of materials I got at my local electronic components store.​​- WL