Wireless Focuser Switch Box.
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Like a lot of SCT owners I have a refractor piggy-backed on top of it. This scope does duty as a guide
scope as well as a wide field imager. In order to use the scope remotely I needed a way to remotely 
focus it.  So I purchased a 2nd Meade 1209 focuser from Astro Mart. The Meade Micro-Focuser is an
inexpensive alterative to the other focusers available and works well with FocusMax or @Focus 
from within CCDSoft. The problem was the Paramount ME like most other mounts only has one focuser 
port. I needed a way to control both focusers remotely. The solution was a Reynolds Electronics wireless 
RX-5 receiver interface board and a RWS-434 demodulator. This is the same receiver and demodulator I 
used to control the shutters on my dome. The reason I went with a wireless interface is it didnít require 
any external cables be attached to the mount  That means there are no cables connected between the RA 
and DEC axisí of the mount to get snagged during operations. Also as mentioned above I already had the
transmitter setup and operational for the shutter control system, and I had two spare demod boards. I 
did have to change the address of switchbox receiver so the transmitter could talk to it without interfering 
with the shutter control system. When I finally got to the point of doing the assembly I found I didn't 
have a spare project box laying around so I used an old plastic diskette case, which worked out very well.
 
  Focuser #1 plugs into the jack on the right, Focuser #2 is next to it on the left. The jack on the far 
lower left is the power plug. The switch box will accept a DC voltage in a range from 7.5 to 24 volts. But 
there is no benefit to providing more than 12 volts DC as the excess voltage is just dissipated as heat. 
The plugs used are standard 1/8" stereo headphone plugs. I purchased them from Radio Shack (part 
#274-246). The plug also came from Radio Shack in a pack of 2 (part # 274-284). The whole assembly
weights about 3 or 4oz. 


The focuser is control by the modified shutter control GUI (seen above) that I wrote in Visual Basic. 
Now I have the ability to manually select which focuser I want to control. I also wrote 2 separate non-
interactive programs. They are named "Focuser1.exe" and "Focuser2.exe".  Either program can be 
executed as a stand alone program or called from within a script for automated focuser selection.  They 
are also defined as a button on the script bar within CCDSoft, which allows one click focuser selection.




The above image shows the wiring diagram for the switchbox. The switchbox is configured so the relays 
onboard are in the latching mode. Looking at the top left of the drawing above you will see the plug that 
comes from the switch box. This plug connects to the focuser plug on the mount where the original single
1209 plug was connected.  

Directly down from the plug, the focuser jacks are shown. This is where the two Meade 1209 
Micro-Focusers plug into.  I have Focuser#1 currently connected to the piggy-backed Stellarvue 102A, and 
#2 is connected to the 10Ē SCT.  

 The Yellow wire only ties the base of the jacks and plugs together and isn’t connect to the switchbox.  The
Black wire is for the tip of the plug and the Red is for the middle section.  The switchbox is controlled by
sending ASCII commands to the transmitter.  For example if a bit pattern of “0000” is sent to the transmitter
the relays on the controller will be set to their normal state. (0 = OFF, 1= ON). This will select Focuser #1 as it i
s connected to the side of the relays that default to the Normally Closed (NC) position. 

Focuser #2 is not selected because it is connected to the Normally Open (NO) side of the relays. The opposite is true
when a bit pattern of 1001 is sent. This sets the top set of relays (ones with the Red wires connected),  and the
bottom set of relays (Black wires) to the Normally Closed configuration.


The relays are defined as D0, D1, D2 and D3. The “D0” is the relay with the red wires attached and is represented
by the “1” on the right side of the bit pattern “1001”. The two zeros in the middle are the two 5 volt digital relays
(“D1” & “D2”) that aren’t currently being used.  These are the only 2 relay that produce voltage. The other two relays
just close contacts. (I am thinking using  the “D1” & “D2” relays to power an illuminated reticule). The 5 volt power
for those relays can be turned on by sending a bit pattern of “0110” “D3” is the relay at the bottom (Black wires).

Any bit pattern can be selected to energize whatever
combination of relays the user desires.

To send the “1001” bit pattern to the switchbox  the command chr$(9) is sent from the Visual Basic program since
“9” is the decimal equivalent of the binary “1001”. The command string also contains the address of the receiver
so the transmitter knows which receiver should execute the command from the control program. In  addition the
string is prefixed by a receiver sync byte (170), so the complete command string assuming the a receiver address of
"1" would look like this: 
                                        For I = 1 To 4 ' Loop 4 times
                                             MSComm1.Output = Chr$(170) & Chr$(1) & Chr$(9)
                                             Pause 250 ' Pause 250mS
                                        Next I

Just like the shutter control system, each command for the switch box is sent 4 times to ensure the command reaches
the receiver. This is done since the communication between the transmitter and receiver is only one way, there is no
acknowledgement that the command was actually received. This means there is no retransmission should something
interfere with the signal.  More info about assembling, programming and commanding the transmitter can be found
here.
 

 The image on the left shows the switch box mounted to the side of the Versa-Plate. The switchbox is light
enough it can be held in place with double sided tape. The system was tested in all positions to verify the 
box would clear the base of the mount; and that the signal quality was reliable even when the receiver's 
antenna was placed at a 90 degree angle to the transmitter, or the scope was positioned between the 
transmitter and receiver. The image on the right shows the switch box opened. Using the diskette box as a 
case allows easy access to the electronics for future connections, receiver address changes or troubleshooting. 
The two spare 5 volt digital outputs can be seen in the center. 
Future enhancement to the will include a jack to plug in an external control pad for manual focusing while at
the scope. The addition of the LazyFocus has allowed the focusers to be control locally via buttons.  It also
solved a problem with the Meade 1209 micro-focuser not being ASCOM compatible.  I "Y" cble will be 
installed in the future that will allow the Paramount to also control the focusers.
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