simple programmable relay question

Discussion in 'The Projects Forum' started by dmaxben, Oct 27, 2006.

  1. dmaxben

    Thread Starter Member

    Oct 27, 2006
    11
    0
    Hi everyone...been trying to figure this out how I would build this kind of circuit... its for a REALLY weird application so bare with me :)

    I have a chevy truck with an allison automatic transmission...It is completely electronically controlled with 5 PWM solenoids and 1 PWM/VBS solenoid so nothing has to "physically" move in the trans to shift between any gear.

    the shifter in the truck moves basically a simple selectable ground switch on the transmission that the trans computer interperates as driver shift signals

    theres 4 normally open switches, A, B, C, and O. When grounded in in certain orders/logic correspond to certain "gear requests" from the driver.

    For example, when the shifter is moved to "drive", it moves the positional switch which grounds A and P and leaves B and C open. Moving the shifter to "3rd gear" grounds out all 4 wires, etc....

    ok so now that ive bored you guys with that heres what I want to do.

    Instead of moving the shifter manually to "3" "2" or "1" (if I want to hold a gear and not have it shift automatically in "drive), I wanted to try to make some programmable IC that would control 4 SPST relays connected to each of the 4 signal wires. But the relays would be controlled in a specific order by two normally open momentary switches. So for example you press momentary switch #1, it will open relays 1 and 3, and close relays 2 and 4. Press momentary switch #1 again and it switches to the next sequence of opening relays 1 and 4 and closing 2 and 3. And on down thru 4 different combinations.

    Then you press momentary switch #2 at any time and it will reverse the sequence and go back one step.

    So basically press momentary switch #1 and it adjust the relays to make the transmission computer think I moved the shifter from "drive" down to "3", then press momentary switch #1 again and it changes the relays to a different combination to make the trans computer think I moved the shifer to "2" etc.. then at any time I can press momentary switch #2 and have it effectively go "up" one step in the sequence...

    The goal being to make some IC/relays that acts as a sort of "tip-tronic" circuit with "upshift" and "downshift" buttons. I looked around google for complex programmable relays with 4 relay outputs and 2 analog inputs, but im not sure if I need something that complex...:confused:

    Kinda wierd, but just something I wanted to mess around with cause no ones done it before :D

    thanks again for the help
    ben
     
  2. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    We really need to know the content of the "etc..." part, to do the logic for it.

    I don't think you need relays, 4 transistors should do (plus the logic or a microcontroller).

    What's the impedance of these inputs on the gear box ?
     
  3. dmaxben

    Thread Starter Member

    Oct 27, 2006
    11
    0
    logic is as follows:

    gear.......signal wire A........signal wire B....signal wire C.....signal wire P

    park..........OFF..................ON.....................ON...............OFF
    reverse.....OFF...................OFF....................ON...............ON
    neutral.....ON.....................OFF...................ON................OFF
    1............ON......................ON....................OFF..............OFF
    2...........OFF.....................ON....................OFF..............ON
    3...........OFF....................OFF...................OFF..............OFF
    drive......ON....................OFF....................OFF...............ON

    ON = open circuit
    OFF = grounded

    I dont think impedance is really an issue, the TCM (trans computer) just looks at whether the wires are grounded or not. The PNP switch (shifter position switch) is simply grounded to the chassis so specific impedance across the signal wire I wouldnt think would be that important. To test it I took the signal wires coming from teh TCM and grounded them manually (by hand) on the chassis and hte TCM responded perfectly.

    almost like some sort of "collapsing" relay or something would be needed? Give it momentary power and that triggers it and it "moves down one output", give it reverse polarity on the momentary switch and it moves up on latch. That would make it sequential and only require two momentary switches to move up or down. Then from those 4 outputs on that special relay, I could hook each of those outputs up to 4 relays with diodes, so at each output of the collapsing relay, it would trigger the other 4 relays in a specific order maybe??
     
  4. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    A PIC Microcontroller can drive some transistors which can then drive relays to do that or you could test and see just the transistor would work.

    http://www.voti.nl/swp/index_1.html

    If that's more than you care to do there are 'basic stamps' from Parallax
    http://www.parallax.com/

    It would be possible to set up a logic chain to do that as well but it's less flexible.
     
  5. dmaxben

    Thread Starter Member

    Oct 27, 2006
    11
    0
    I was also thinking about trying to run a "sequence relay"...because that would toggle "up or down" one step at a time in a fixed sequential order, all try that microcontroller link, thanks again for all the help

    Ben
     
  6. xushirui

    New Member

    Apr 7, 2009
    8
    0
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