DIY USB Cable for EQMOD
Do you want to control your EQ mount from your computer using EQMOD? That's where the EQ-DIR cable comes in! Need an EQ-DIR cable but can't wait for shipping? Or maybe there are no local dealers in your area? Here's how you can DIY a USB EQ-DIR Cable using parts from Amazon and lying around at home! More information can be found at EQMOD's page.
Note: This tutorial is for SkyWatcher/Orion mounts that are controlled through the RJ-45 Hand Controller jack. Compatible mounts include the HEQ5 PRO, AZEQ5, AZ-EQ6, EQ6-R, EQ6-R PRO (earlier versions without the built-in USB port), EQM-35 PRO, and Orion Sirius, and Orion Atlas mounts. Should work with ASIAIR as well!
Second note: no, a normal USB to RJ45 cable from Amazon will not work. No, a normal USB to RJ45 Serial cable will not work, either. The EQDirect cable uses its own pinout!
Materials List + Tools
For this build, you will need:
1 x FTDI TTL232R or Prolific PL2303 USB to Serial Breakout Cable (5V)
1 x Ethernet cable (CAT5, CAT5e, CAT6, etc.) with male RJ45 jack, OR
RJ45 female socket/keystone jack (optional)
Electrical tape and/or heat-shrink tubing
Multimeter (optional but recommended)
Soldering tools (optional but recommended)
Circuit Summary + Diagram
RJ45 PIN 4 → "GND"
RJ45 PIN 5 → "RXD"
RJ45 PIN 6 → "TXD"
Your cable will specify which wires correspond to which colours.
Typically, GND will be black.
On the PL2303, typically: RXD = GREEN, TXD = WHITE
On the TTL232, typically: RXD = YELLOW, TXD = ORANGE
Making an EQ-DIR cable is actually pretty simple. All you need to do is make sure your wires are connected to the right pins on your RJ45 jack. In a nutshell, we'll be following the diagrams above and simply matching wires together. Note: J0 represents an RJ45 Male jack — looking head-on directly at a male jack with the tab facing upward, pin 1 is the far left pin, and pin 8 is the far right pin.
There are several ways you can do this:
The simplest method — requires the least specialized equipment: Cut part of your ethernet cable to expose the individual wires inside (there should be eight of them). Use a multimeter to determine which of the little wires corresponds to which pin on the RJ45 jack. You can then strip the wires inside the ethernet cable, and strip the wires of the USB-Serial adapter, and then twist the bare wires together or solder together to form a connection. Remember to insulate each connection with heat-shrink tubing or electrical tape.
USB to RJ45 Female — if you want to use your hand controller's cable instead of an ethernet cable: Use an RJ45 female housing (these can be found at your local home improvement store). Use your multimeter to check that the pins listed on the housing correspond to the right pins. Then, cut off any header sockets (the black things in the image below) if you have any, and place the USB-Serial adapter's cables into the grooves for the right pins. Then, using a punch-down tool if necessary, secure the cables into place. Cover the housing with heat-shrink or electrical tape to protect the connections. This method is best for those who want to have flexibility in the length and serviceability of their EQMOD cable, as the ethernet cable can be switched out whenever — whether you want a different length, or whether part of the ethernet cable is broken.
Important: I highly recommend testing the cable with EQMOD to make sure it can detect your mount, before making anything permanent (i.e. before sealing off any connections or doing any soldering). If you are using the first method, twist the wires together and isolate them from each other, but do not solder before testing. If you are using the second method, you can use wires to make a temporary connection like the image shown below.
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!- WL
That's it for the electrical parts! Seal off your connections however you desire, and happy imaging!
A few more important notes:
For the HEQ-5, the COM port baud rate (bits per second) should be set to 9600.
For EQ6-R Pro, the COM port baud rate (bits per second) should be set to 115200.
Ensure that the correct COM port is selected in EQMOD.