You can use the information on this site COMPLETELY AT YOUR OWN RISK. The modification steps and other information on this site is provided to you "AS IS" and WITHOUT WARRANTY OF ANY KIND, express, statutory, implied or otherwise, including without limitation any warranty of merchantability or fitness for any particular or intended purpose. In no event the author will be liable for any direct, indirect, punitive, special, incidental or consequential damages or loss of any kind whether or not the author has been advised of the possibility of such loss.
Circuit modifications implemented on your setup could invalidate any warranty that you may have. Use this information at your own risk. The modifications involve direct access to the stepper motor controls of your mount. Any "mis-control" or "mis-command" / "invalid parameter" or "garbage" data sent to the mount could accidentally activate the stepper motors and allow it to rotate "freely" damaging any equipment connected to your mount. It is also possible that any garbage or invalid data sent to the mount could cause its firmware to generate mis-steps pulse sequences to the motors causing it to overheat. Make sure that you perform the modifications and testing while there is no physical "load" or dangling wires on your mount. Be sure to disconnect the power once this event happens or if you notice any unusual sound coming from the motor assembly.
Figure 1 shows a diagram that will allow you to directly connect your PC to the Mount's DB9 Handcontroller Port. The port contains both the 12V power lines and the two TTL level serial data lines. It allows the user to send the commands from the PC's serial port to the mount's handpaddle DB9 port. The circuit utilizes two major components; a RS232C-TTL converter (MAX232) chip and a 5 Volt voltage regulator (7805) that supplies power to the max232 chip. The 7805 source of power comes from pins 1 and 8 of the mount's DB9 connector. Extra care should be provided in avoiding these lines to be interchanged/shorted to the TTL level lines (pins 9 and 6). Pins 5 and 4 are ground pins.
Figure 1: Circuit Diagram for Direct PC access through the mount's DB9/RJ45 connector
An EQDIRECT-USB convertor consists of a combined USB serial port that provides TTL outputs. Such a device is avilable from FTDI called the TTL232R, and comes integrated into a USB cble and connector. Please be aware that FTDI produce a similar product, the TTL232R3V3, but due to lower signaling voltages this will not work (the mount expects to see a minimum 4V active high signal). A driver is installed on the PC and the TTL232R appears as a standard windows COM port. There is an additional advantage in that unlike many usb-serial devices the com port number of the FTDI device, once assigned, will not change when plugged into a different physical USB port.
A wireless EQDIRECT can be constructed using a Bluetooth Slave Transceiver unit. These unites can be found on Ebay, often shipping direct from China. Look for units that contain a reference to HC06 or HCO5 in their description/documentation, HCO6 boards can be either Master or Slaves - you need a Slave device. An example of what you are looking for is shown below.
The units themselves consist of a transceiver module attached to a base board (sometime refered to as a backplane). The transceiver modules themselves are 3.3V devices but the base boards add a little extra functionality such as a wider power supply range, status LED, in some cases I/O vlotage mapping to other levels such as 5V TTL or RS232, and a header connection. If you wish you can use a transceiver module by itself to make your EQDIRECT-BT but it is usually no chaepar than buying a combined transceiver/baseboard unit which is easier solder/connect due to its header. Be aware that the baseboards are also available without transceiver modules attached - so be careful when buying..
The simplest EQDIRECT to construct is one based on a "5V TTL signaling, 5V power" bluetooth unit as these can interface directly with the mounts communications lines. However, these devices tend to be more expensive and harder to find.
units are more common, some will allow a supply of to 6V but Tx/RX
signaling is still expected to be at 3.3V. The mount motor
controller should require a minimum "high" signal of 4V (min. active
high) on its
Rx data pin and so some extra circuitry is
required to interface the mount to this type of bluetooth unit.
This said the unit I tested (and shown above) works flawlessly without
needing these additions even though I can't explain why!
You will need a Bluetooth enabled PC or an external Bluetooth USB dongle. On initial bluetooth pairing you may be required to enter a pair code (default is usually "1234" unless your specific transceiver documentation specifies otherwise). If presented with a pair of virtual COM ports then use the one labled "Outgoing" as the EQDIRECT port.