Wireless EQDirect - a Bluetooth connection to your Synta mount

2007 was the year that I bought my first dual-axis mount: an Orion Sirius EQ-G. This mount is virtually identical to the Skywatcher HEQ5 with the recent motorization. Apart from it being an affordable mount with decent performance, it also features lots of interest from enthusiast amateur astronomers, either eager to enhance the mount's performance (see the EQ6 Yahoo! Group), or even to give it advanced computerized control for free (see the EQMOD Yahoo! Group).

All facts mentioned above have influenced my final decision to get the non GoTo "SynTrek" variant of the Orion Sirius EQ-G (the GoTo version of the handcontroller is "SynScan"). Nine months later I decided to acquire an EQDIR module from Shoestring Astronomy, along with the EQCBL-01 mating cable. I then installed the free planetarium software Cartes du Ciel, the free and standardized ASCOM Platform (free, Windows platform), and the latest EQMOD ASCOM drivers allowed me to control my mount from my laptop. I was impressed by the relative ease with which all was installed and how the hardware and software collaborated without major issues.

The only real problem I witnessed was a mere usability issue: since I observe mainly on a small balcony or on a remote location, the cable connecting the mount to the PC was often in the way. For a permanent setup this most likely is not a problem, but in my case I was thinking in terms of «this can be done in a more user friendly way». Hence I decided to look at wireless solutions to replace the RS232 serial link with the mount.

One source of inspiration was Astromist, a fantastic astronomy planner and planetarium tool for Windows Mobile. On the Astromist Yahoo! Group I read several stories about a serial to Bluetooth module from AirCable, and started my search in Europe for such modules. Unfortunately these modules are quite expensive; it was a challenge to find one for less than €100. Eventually I found one candidate in the LM058 (which appears to be a rebranded product from Rayson).

Oh great! I can now eliminate the wireline connection between the EQDIR module and my laptop whith this Bluetooth unit. Yes, that's right... however these RS232 to Bluetooth modules still require power for their operation. Guess what: you can power them either via a dedicated (wired) wall wart or via a small USB cable. Aargh!

Next challenge was to provide the required power without adding an extra wire to the RS232 to Bluetooth module. There are 2 alternatives: either via battery power or by powering Pin 9 of the Sub-D connector. The former is not practical, so I decided to evaluate the latter. One option is to open the EQDIR module and solder a wire connection between the 5VDC output from the 78L05 low dropout voltage regulator on the tiny EQDIR PCB and pin 9 of the RS232 part. This will definitely work, but I decided to learn how to make a printed circuit board in this project. That was quite fun!

I will spare you the details of my endeavor (see the thread Orion Sirius EQ-G (Skywatcher HEQ5) made wireless on Cloudy Nights) but thanks to the help of a fellow ATMer I learned to use EAGLE Light to design printed circuit boards, and in addition I experimented with the toner transfer method as a cheap (but labor intensive) means of generating an etching mask.

Schematics of the circuit

Electric scheme of the wireless EQDirect interface

As you can see I have foreseen a DIP switch to be able to toggle the 5VDC power supply to pin 9 of the RS232 interface. Capacitors C1 to C4 can be electrolytic capacitors, but C6 and C7 need to be low ESR capacitors (e.g. Tantalum capacitors). C5 can be ceramic.

Overview of the printed circuit board

Overview of the printed circuit board

Etching mask, silk screening and drilling template. Note that the silk screening has not been not mirrored in this PDF!

Finished circuit

Finished circuit (opened) Wireless EQDirect and Shoestring Astronomy's EQDIR, side by side

Bill of materials

Components for an Orion Sirius EQ-G or Skywatcher HEQ5 mount (with a “RJ45” connector):

  • 1x single sided printed circuit board plate, minimum 78mm x 60mm
  • 1x MAX232 chip (RS232/TTL conversion) (1.80€)
  • 1x DIL16 IC socket (for the MAX232 chip) - optional (0.35€)
  • 1x Modular Jack (Ethernet), PCB mount, 90° (2€)
  • 1x Sub-D 9-pin male connector, PCB mount, 90° (1€)
  • 1x 7805 voltage regulator (provides 5VDC to the MAX232 and to pin 9 on the Sub-D connector) (0.50€)
  • 1x 1 channel DIP switch (allows switching on/off the 5VDC power supply to pin 9) (0.60€)
  • 4x electrolytic capacitor 10µF (16VDC) for the MAX232 (1€)
  • 2x Tantalum low ESR capacitor 1µF (35VDC) for decoupling the 7805 regulator (0.50€)
  • 1x ceramic (multilayer) capacitor 100nF for decoupling the power on the MAX232 (0.20€)
  • 1x short (50cm or less) Ethernet patch cable (1.50€)

Depending on the hobbyist's needs the following components can differ:

  • 1x TEKO TK560B project box (€17.50)
  • 1x LM058 RS232/Bluetooth module (about €75)

Total cost of my solution (excluding etching, tinning and soldering): about 100€.

Cristian's picture

Question LM058

Dear Oliver

I am writing to enquire about if you can help me with a LM058 setup problem, I send data from a PIC to LM058 (slave) and this one send to another LM058(master). The master send the data to another PIC that display them in a LCD. I test the tx (PIC-Slave -- Master-Hyperterminal) and the RX (Hyperterminal-cable-PIC) and work very well, but when I use the LM058 the RX don't work. I don't know if I have conect CTS with RTS for the comunication.


Thanks for your help

Cristian Gonzalez


Olivier Biot's picture

Configuring the LM058 module might help there

Hi Cristian, So far I never used 2 LM058 modules in a master/slave combination. According to the documentation the LM058 module defaults to the following settings:
  • Bits per second: 19200 bps (baud rate)
  • Data bit: 8
  • Parity: None
  • Stop bit: 1
  • Flow control: H/W
First of all, make sure to check these values with your design (including the PIC software; don't forget to check the clock speed of the PIC) and also by using the relevant AT commands for the LM058. I suggest to check the master/slave configuration of both modules (AT R?), then disable flow control (AT C0) and try again.
edinburgh accommodation's picture

Thnaks for your overview

I hope this does not turn out to be an example of where someone invests mega bucks in research, design, and development, and takes great care in giving to the market the best they can buy for their money, while trying to at the same time profitably recoup the costs of honestly bringing the product to the market, only to wind up having someone else come along who effectively copies it, does not have to recoup years of research and development, manufactures it in a land where patents are effectively meaningless, makes a slightly inferior product overall, and yet walks away with the bulk of the business.

kumar's picture


 hi everyone....I am using a controller setup.In which the controller alarm if there is any fault.In that can i take the alarm through bluetooth or wi-fi ?How much space it needs?....thanks 

OrionM42's picture

BluEQ Bluetooth Interface

I have a product called the BluEQ Bluetooth Interface. It was for sale on ebay and I have read about it on Cloudy Nights. This device is awesome because it requires no external power source and completely does away with the hand controller. This can potentially save a lot of money for someone ready to purchase an Atlas or Synta EQ6 model mount. All goto and extensive alignment and sync functionality can be had using ASCOM and EQMOD software.

Olivier Biot's picture

I don't know this product but it likely implements the same idea

Most likely the unit you refer to implements the same basic idea. It would have surprised me if nobody else came up with the same idea ;-) It is important to understand that this unit only provides a means to communicate from a serial port to a recent Synta (Skywatcher or Orion) mount, but that you still require a computer to translate Go-To commands into Synta commands (basically a train of commands to tell the mount which motor to move at which speed for how many steps). In practice any computer that supports the EQMOD ASCOM driver will do.The drawback of this approach is that you will need to haul a computer whenever you want to observe with Go-To. The SynScan Go-To hand controller provides you autonomy without the need of carrying a PC, laptop or netbook to your observing spot. In addition the SynScan controller provides an interface which allows many other systems to interact with the mount, e.g. Astromist, a very handy astronomy environment written by Cyrille Thieullet and available on a host of Palm and PocketPC devices.
Olivier Biot's picture

May be simplified

It appears the LM058 unit I used in Mark I of the Wireless EQDirect already features a MAX232 chip for converting the TTL signals into RS232 signals. This is intuitively obvious, since most components talk with TTL levels.
This means that in principle you could simplify the setup by only providing the 5VDC voltage regulator in the circuit for powering Pin 9 of the Sub-D RS232 connector. In other terms, connect pins 11 and 14 of the MAX232 chip, as well as pins 12 and 13. Or, stated more simply: connect pins 5 and 6 of the mount's RJ connector directly to pins 2 and 3 of the Sub-D RS232 connector.
The bill of materials then reduces to: 

  • 1x Modular Jack (Ethernet)
  • 1x Sub-D 9-pin male connector
  • 1x 7805 voltage regulator
  • 2x Tantalum low ESR capacitor 1µF (rated at 35VDC)
  • 1x short (50cm or less) Ethernet patch cable
patrick's picture

I have 2 questions

I have two questions.
1/ Is the 12V supplied by the RJ45 plug ?
2/ Would it be possible to substitute a wifi/RS232 addaptator instead of a bluetooth one ?
Thanks for the answer.

Patrick Dutoit

Olivier Biot's picture

Re: I have 2 questions

Hi Patrick,
The mount indeed provides 12VDC through 2 pin pairs (probably to allow for more current. This can be seen on the circuit schematics above: pins 1 and 4 are the common ground and pins 7 & 8 are at 12VDC.
I never played with RS232/WiFi modules so I can't help you there. Probably it should work as well, as long as the wireless link is "invisible" to your computer and the serial link appears as a (virtual) COM port.
Hope this helps,

Erdan's picture

This is the success story of

This is the success story of many of them who have tried stuff on their own for their own development. Indeed even I was amazed at the relative ease with which all was installed and how the unique hardware and software collaborated without major issues.

Max's picture


Hi at all
I have realized 2 times this circuit but it doesn't work. I don't know where 's the problem. I have rechecked many times all 2 circuit board and connection. Power from mount it's ok. The only doubt it's for max232c because i cannot find max232a and for the capacitor on the voltage regulator. ( not tantalium but electrolytic.) My notebook it's connected via usb to serial converter Any suggest for? Tnx and sorry for my english.
Bye  from Italy!

Max's picture


Hi at all
I have realized 2 times this circuit but it doesn't work. I don't know where 's the problem. I have rechecked many times all 2 circuit board and connection. Power from mount it's ok. The only doubt it's for max232c because i cannot find max232a and for the capacitor on the voltage regulator. ( not tantalium but electrolytic.) My notebook it's connected via usb to serial converter Any suggest for? Tnx and sorry for my english.
Bye  from Italy!

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