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Time to solder. Can anyone help a beginner?

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  • Time to solder. Can anyone help a beginner?

    Ok, I have a 5.6" mobile authority lcd in my dash. The thing is that I took it out of its casing and made a custom mount for it behind the dash. Unfortunately, I still need access to the contrast/color/power buttons so here's my problem. I'd like to wire momentary buttons to the controller board and then mount the buttons elsewhere. I'm not quite sure how to do this though. I can splice wires which is how I've always done my electrical work but i don't know how to do it with this. Here's how it looks.

    There's a small controller board with the 5 buttons (power, contrast +, contrast -, color +, color -). At the bottom of the controller board is 7 wires (1 red, 6 white) that goes to the lcd.
    It looks like this:

    Each button has 4 contact points (square buttons, one contact point in each corner) on the controller board. I have momentary buttosn from radio shack with two contact points each. How do i do this? Should I solder? Is there any way to tap into those wires instead? I have no idea what to do.

    Thanks for any help.

  • #2
    You could probably tap into the wires pretty easily. Do you have access to a digital camera? It'd be easiest if we could see the actual circuit diagram.


    • #3
      My guess is that 6 of the wires go directly to the buttons, one to each, and the 7th wire (red one???) is the common, which runs to the other end of each of the buttons.

      I doubt there are 4 different contacts per button -- they're probably all tied together so if you hit the button at an angle it will still send a signal. The RadioShack switches you mentioned should work fine.

      ...but this is all guesswork until we can see a picture (front & back) of the controller board.

      If you have a DMM with continuity (beeps when the probes touch each other), you can play around with the LCD off and see what button connects which two wires together. I'm sure you will find that it is setup with 1 common and 6 different signal leads.
      Jason Johnson
      Yorba Linda, California

      MPC Phase IV - *** PENDING ***


      • #4
        That was my first guess too, but there's only 5 buttons . The buttons with 4 contaces are tactile switches, that are small, flat, grey, and have a tiny black button, right?

        We really need to see the circuit.


        • #5
          Well the wire thing didn't really make sense to me because theres 7 wires and 5 buttons. I will post pics tommorow though so thanks for the quick replies!



          • #6
            The power button might not share the same ground as the other buttons. That's why there would be an extra wire. Check it out.


            • #7
              I forgot to mention that there is a small led in the power button. I'm sure that takes up a wire as well (the red one??). I'm going to go take pics now and put them up shortly.

              thanks for the help so far.


              • #8
                I appologize for the lack of quality in the pics... they were taken quickly. =( Hope they help though.

                Here is a shot of the top of the controller board.

                you can see the 4 grey buttons and the power button the left with the red led inside.

                here is a shot of the underside of the board

                here is a shot of the wires. There are 6 white wires and 1 red.

                and here is a shot of the buttons i plan on using.

                hope this can help someone explain to me what i need to do. thanks a million!


                • #9
                  Uh, it would help if you could focus the camera
                  Techonlogy on Wheels


                  • #10
                    I know, i took them quickly before work. I'll be able to take better/clearer pics when i get home tonight.



                    • #11
                      Looks real simple. Those are simply tactile SPST momentary switches on the PC board.

                      You can leave them there, and solder a length of wire to both sides of the switch contact...if you had a VOM you could figure out which solder points are the switch contacts and which ones are just for mounting.

                      Use some stranded wire, 24 gauge would do it, your pushbuttons will work fine also.

                      Having the wire soldered directly on top will be weak structurally so tape it down good to keep it from pulling off.

                      current projects


                      • #12
                        So basically, i solder one end of the switch contact i bought to one end of the controller board and the other end of the switch to the other contact point for the button on the controller board??


                        • #13
                          my advice would be to solder 7 equal legnths of wire onto the pcb(Printed circuit board) in the right locations (If this is not possible, then splice the wires), then run the wires to your desired destination. Once you have the 7 wires there, you can map out the buttons back on the pcb, and find out which wires each switch connects to. Once that is done, solder the new switches to the appropriate new legnths of wire.

                          About the 4 contacts on each switch, it's just 2 sets of each contact. You will notice that only 2 of the 4 contacts are actually connected to anything.

                          [This message has been edited by annoyingrob (edited 02-24-2001).]


                          • #14
                            oh,and by the way, the red wire will almost CERTAINLY be the common (The one they are all connected to).


                            • #15
                              Do i need to connect anything to the red wire then?

                              also, if i splice the wires, what do i connect them to? the buttons i purchased have to contacts. one goes to the wire, what about the other contact... ground?

                              Thanks for the help!