A few people have asked me about my modified Meade controller as seen in my photographs here...

My post about my power supplies for the controller and camera.

So I thought I would post some info here to help those thinking of doing the same.
ONLY try this if you are used to doing electronics and using a soldering iron etc. Be careful !

I did not like the idea of using clamps to hold down the buttons on the controller as it seemed a bit unreliable and slow to manipulate also its yet another thing to remember to carry around with you.
So I decided that it would be good to use some toggle switches instead. As space is limited in the Meade controller case I thought I would attach a small ABS box to the controller and wire the switches through to the controller via a small hole.

As you can see in my photographs I have used two M3 bolts with Nylocks on to attach it to the controller case.

The Meade controller case came apart by simply running a flat blade screwdriver around the side of it, slowly easing it apart bit by bit. I then removed the ribbon cable to the display (very careful with this).
Then it simply popped out of the front of the case to reveal the the top side of the PCB.

Once I had opened it up fully I used a DVM to track down how the 4 push buttons were wired so I could decide how to wire my toggle switches to them. As you can see in my 3rd image, all 4 buttons have a common connection so I only need to connect to one of these points and use this as my common connection on all 4 of my toggle switches. (Thats the GREEN wire you can see in the 2nd image). This common connection from the switch pads on the PCB go to the left side of R17.

I then traced each of the four connections to more suitable soldering points on the PCB, I did not want to solder directly to the switch pad areas as I thought it would be good to be able to still use the buttons as normal.
I traced all 4 connections to four surface mount resistors that were in a row as seen in my 3rd drawing.
Now I knew which points I needed to wire to I soldered 5 wires from each of the resisitors and passed the wires through the small hole into the side box and soldered them as seen in the 2nd photo.

The toggle switches I have used here are low power SPST toggle switches but you can use SPDT, DPST or DPDT ones as we only need to be able to make a conection in one position.

IF YOU are going to wire yours like this then I would suggest you also use a DVM set to "continuity beeper" mode.
Simply put one DVM probe on the switch pad of the PCB and see if it goes to where I have shown it on my layout diagram.
PCB manufactures change the layout with each issue of board so you really need to confirm yourself rather than just wiring it the same as me.


Here is a photograph of my modified controller with toggle switches. To use it just set all 4 switches UP before you power up the unit. Setup your shot then then set one or two (i.e. right/UP) to the down position and away it goes.





Here is a photograph from the rear with the back cover of the box removed showing the wiring to the switches.




Here is my wiring diagram of which points on the 494 controller to solder onto. It represents the PCB as seen from the top (where the buttons press onto)...


My drawing is not really a detailed diagram as it was just for me to see where I needed to solder to but hopefully you get the idea. I think that when I first tried it UP was actually down so I had to swap those two wires with each other.
You will have to look for the row of resisitors as I have shown it, once you have located them use the DVM to confirm the wiring is as per my unit.

UPDATE : ** See my photograph version in a later post where I have marked up the connection points.


Hopefully this will help.
Any questions please feel free to ask away.
Andy

That's quite rad! Nice work.

Hmm, makes me wonder if I could do something similar with buttons, like those ones that you push and they stay in, and you push them again and they pop back out. They could be positioned in a mount directly over the existing buttons on the controller.

Very cool - great way to hack an existing device, thanks for posting this =)

!c

You could replace the existing buttons with ON / center OFF / MOMENTARY switches, but would probably have to build out the front panel to allow for the extra depth.

Here is a marked up photo of the points on the 494 PCB that you need to solder to. (I have used the photo provided by Thomas).
I have marked up the ends of the resistors with an X and its function.
You need to solder a wire for each of these four controls plus one for the common.

Route all 5 wires out of the way of anything and out of the case.

Click the image to enlarge it so you can see the connections to the resisitors.
Any more questions let us know.
Andy

Yes you could use swtiches like that such as...
Latching press on/press off push switch.

The reason for using toggle switches was so it was very obvious if they are activated. But if you really want to use push switches then you could use illuminating ones so its obvious if its pressed. Such as these...
Latching press on/press off push switch with illumination.