Electronic gear shifting

Discussion in 'The Projects Forum' started by solomondg1, Oct 7, 2009.

  1. solomondg1

    Thread Starter New Member

    Oct 7, 2009
    For my SAE formula car at school I want to make drive by wire paddle shifting. The 1st step is I need something to physicly shift the sequencial gear box. I was looking at linear actuators but they are expensive. I dont need as much percision and control as a servo but if its cheap I will consider it. Im looking for something that can apply a decent amount of force(like 10 pounds max) in a linear direction. This needs to run on a 12v and I will control it with either a PIC controller or logic gates. Also If possible I would like something (or a ciruit) that can detect the reistance of the shifter. If it encounters a certain amount of resistance I want it to stop.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
  3. solomondg1

    Thread Starter New Member

    Oct 7, 2009
    Interesting idea(preselected gearbox) but I have found a different solution. In this solution there is a electric motor with a 4 lobe cam on it that hits a lever. The way it works is when the driver presses the shifter it goes to a PIC controller which tells the motor to start spinning. The motor's cam pushes up or down on a lever that up shifts or down shifts. At a certain point the cam loses contact with the lever which drops back to the center position. A fraction of a turn later one of the lobes of the cam trigger a switch which is connected to the PIC and when that signal is recieved the PIC stops the motor's rotation.
    This is a good design but I dont want to use a PIC controller but rather logic gates in its place. Sorry I cannot post a picture of the design because its under copyright. Here is my rendering:
    The cam is on the left, the shifter is on the right, the switch(closed in picture) is on the bottom left of the cam.
    Move the lever up, it shifts up, down, it shift down.
    I have thought of many ways ot do this, from using 555 timers to using flip-flops but I cant figure it out.
    Here is what needs to happen
    There is a switch on it that is normally closed lets call it B
    When the motor starts spinning switch B opens
    When the motor spins through 1 shift(1/4 revolution) the cam pushes on the B switch again.
    What needs to happen is the following:
    Driver presses and releases paddle shifter(a switch, lets name it A) which starts rotating the motor
    As soon as rotation starts, switch B is open.
    When the motor spins to a certain point switch B is pushed, which should stop the motor.
    Simple but there are a couple of exceptions
    If switch A is held closed instead of being released, nothing should change and the motor should still rotate and stop when B is closed again.
    If switch A is pressed several times before B has time to open and close again, that input should be disregarded.
    These exceptions are safety precautions so if the driver holds the trigger to long it wont switch more then 1 gear and if the driver presses the trigger several times during a shift, it wont affect anything.
    Last edited: Oct 7, 2009