Need help from you EE guys to figure this out

Discussion in 'Electrical & Radio' started by jadfer, Mar 5, 2017.

  1. jadfer

    jadfer Well-Known Member

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    I made a button conversion 'drop in' kit a while back while I was going to school on electronics. Time has passed and I no longer remember why I did what I did on the board. For a Spektrum radio I can just duplicate the board and all will be well but as I am working on one for an HK radio.. things have become complicated.

    The problem is that in the past I have followed the schematic that we probably have all followed: vg600-schematic-delta.jpg

    Which, correct me if I am wrong, shows the two firing buttons in series. When wiring the buttons directly, with wires literally soldered to the switches themselves, this is very easy to follow. In my case I am using pre-wired and terminated buttons with 2 pin plugs so as a visual learner it makes it much harder for me to figure out.. however I did in the past.

    IMAG0304.jpg

    IMAG0305.jpg

    The Spektrum's use 6 wires for the channel so you get the standard 3 wires per pot. I have no idea what each color does other than by looking at the diagram above, yellow and white must be the signal wires. I have no idea how I figured that out at this point as I don't have access to my pictures from the Spektrum installation.

    I now want to alter the HK which has only 4 wires, which means a shared power wires and 2 signal wires.

    IMG_2996.JPG

    IMG_2993.JPG

    So.... the questions:

    1. Spektrum - How do I determine what is the function of each wire?
    2. If you look closely at the board I made for the Spektrum it seems I put them switches in parallel (or did I?) as the supposed 'red' wires are jumped together. According to the button drawing I should have connected the side of the button designated as 'black' to the 'red' of the next button. Instead I connected the 'red' together and have no idea why.. much less why it still works.
    3. I am unable to figure out the HK buttons because I can't figure out why my Spektrum board works when the schematic says otherwise.
    4. How do I determine red/black/signal on the HK? I did a continuity test and it seems the outside wires which are black and yellow are shared on both pots but .. which is 'red' and which is 'black'? Does it matter?

    Any help from those in the 'know' would be greatly appreciated.

    Thanks

    Johnny
     
  2. Kevin P.

    Kevin P. Well-Known Member

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    My guess, others probably know more
    1) Like you said, you have 2 sets of 3 wires. One set is Black/White/Red, the other set is Green/Yellow/Orange. White and yellow are the signal wires, which are the 'green' and 'yellow' wires in your diagram.
    2) Not sure/I recommend going with the diagram
    3) Go with diagram
    4) I don't think which is red and which black matters, since the circuit is symmetric the only difference will be which 'side' of the channel the button actuates (which can be switched by reversing the channel). You'll have to split the black and yellow to send it to both sets of switches, then use blue as one signal wire, and purple as the other signal wire
     
  3. Kevin P.

    Kevin P. Well-Known Member

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    Here is mine, used 2.2 kOhm resistors across each switch, signal wire goes to both switches like the diagram. I try to practice the KISS principle whenever possible
    pushbutton conversion 023.jpg
     
  4. jadfer

    jadfer Well-Known Member

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    Thanks, that is the typical button layout in a radio I have used in the past. With the board I wanted to have something I could do in advance and drop in to a radio in a few minutes. It works fine.. I just don't remember why I did what I did or WHY it works.. given that it seems to vary from the provided schematic.

    I addition.. I didn't want to cut any wires which would allow me to return this to its original condition... both for resale and for warranty reasons.
     
  5. jadfer

    jadfer Well-Known Member

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    I tried a 2.2k and a 1.1k with the Hobby King radio and when using a button the servo swings to the end but does not return or it starts to return very very slowly. What would that be a symptom of? 2.2k too much? 1.1k too much?
     
  6. SteveT44

    SteveT44 Well-Known Member

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    Maybe the HK radio has 10K pots?
     
  7. jadfer

    jadfer Well-Known Member

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    Thanks Steve!!!

    Although the value was not the issue it got me thinking and after checking the board I found two jumpers that were missing. I added them just now and EUREKA!! A working drop in board for the HK. The biggest issue was that I bought the sockets and pig-tails for the plugs on ebay (which took a while to identify and more than 1 try) and it turned out to be a smaller pitch than my standard perf board. I tried several ways to make one but lacked the right guage wire to do so. I came across the answer by mistake after looking at the pigtail plugged into the socket.. and the 4 pins exposed... I just plugged those straight into the connector on the radio and it worked. I will secure it with some method but it goes on pretty tight.

    Here is a link to the socket and pig tail if you want to make your own or make it easier.. no cut wires...
    JST X ZH connector sets

    I will post pictures of the finished product later.
     
  8. jadfer

    jadfer Well-Known Member

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    Here is a pic of the finished product. I used 3.8K and 2.2K across the switches, I like the throw of the 3.8K better .... making the lexan cover and mounting buttons tomorrow. IMG_4133.JPG

    I would say this completes the project... a drop-in push button mod for the HK Radio .. no cut wires.. and I can return it to factory condition.
     
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