Y Min Input Not Working

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  • January 6, 2018 at 1:34 pm #10734
    CBeamUser
    Member

    I just finished installing NC limit and homing switches to my machine. I have them all wired and all of them work except the y min input. I fairly postie the problem is on the board because I swapped the wiring of my Y Max switch with my Y Min switch and the Y min switch and wiring all worked properly. However the input for the Y min seems to not to work. McGarth suggested I posted about my problem here to see if you could offer me any help. He also suggested that I check the continuity between the screw head of the Ymin connector and the bottom of the PCB with an ohmmeter, which I did and I got a reading of 3 ohms. I then check the continuity of the bottom of the board all the way to the switch and there was continuity their also. Any other suggestions for what might be up?

    January 6, 2018 at 5:54 pm #10735
    cmcgrath5035
    Moderator

    Me again
    Here is a copy of the schematic page for a tinygV8h, the most recent
    https://github.com/synthetos/TinyG/blob/master/hardware/v8schematics/v8h/tinyGv8h%20-%20schematic%20page1.pdf
    As you can see, All Max/Min ports are pulled high (3.3v) by a 2.7k resistor and bypassed to ground by .22uF. This provides some degree of noise conditioning for the lead.
    I’ll assume you have a VOM or DVM. with tinyG energized (does not have to be moving), probe the Ymin lead at tinyG while you operate, then release the limit switch, monitoring the voltage. It should toggle between 3.3v and ground.

    From your original message, I am assuming that you ran a test sending Y from some position toward 0 and axis hit the limit switch but kept driving the motor.

    So now, with tinyG energised but the motors relaxed (by default, this is two seconds after a reset), manually move your Y toward 0 and observe the voltage at Ymin. Is the gantry movement mechanically triggering the switch, causing Ymin to go from ground to 3.3V(on voltmeter)

    It may be helpful if you post your parameter settings for a look.
    Run $$, copy the results to a cloud drive file and post URL for us to look.

    • This reply was modified 6 years, 10 months ago by cmcgrath5035.
    January 6, 2018 at 8:38 pm #10737
    CBeamUser
    Member

    With tinyG energized (does not have to be moving), probe the Ymin lead at tinyG while you operate, then release the limit switch, monitoring the voltage. It should toggle between 3.3v and ground.

    I performed this and when the switch wasn’t tripped the VOM read .03 volts. When the I tripped the switch the VOM read .11 volts. I checked all my other switches to see how they would react and I would read around .03 volts before they got tripped and when they were tripped they would read 3.1 volts.

    So now, with tinyG energised but the motors relaxed (by default, this is two seconds after a reset), manually move your Y toward 0 and observe the voltage at Ymin. Is the gantry movement mechanically triggering the switch, causing Ymin to go from ground to 3.3V(on voltmeter)

    I performed this also and just as before the Y Min lead would read .03 volts before tripped and just .11 volts when it was tripped.

    Here are the parameters I have on the Tiny G.
    Tiny G Settings

    January 6, 2018 at 9:43 pm #10738
    cmcgrath5035
    Moderator

    In your parameters,
    [ysn] y switch min 0 [0=off,1=homing,2=limit,3=limit+homing]

    Is this perhaps because you were experimenting withsettings?
    Appears your parameter set says home to Ymax – ?

    But those settings would not affect your Ymin = .11 V open circuit (switch open).
    There is something shorting the pin to ground, almost as ‘short’ as a closed switch.
    Solder blob, leaky/defective 0.22ufCap, other board defect could be responsible.
    As a final test, remove the wire from the Ymin terminal, Still read about 0.11V on the terminal screw. If so, something defective on board.
    Contact Synthetos again, “Ymin terminal shorted to ground” on new tinyG, add a link to this thread

    January 7, 2018 at 12:42 am #10741
    Zootalaws
    Member

    Just as an FYI:

    I have installed my TinyG onto the back of my gantry and fitted my limit switches to the gantry and the X-axis itself, triggered by screws protruding into the path of the gantry on X and Y axes, rather than running them all the way around the machine. Initially I used a long USB cable, but now have a wireless solution using John Lauer’s fine Serial Port JSON Server a spare Raspberry PI 2 and Chilipeppr:

    http://chilipeppr.com/tinyg

    http://chilipeppr.com/tinyg#com-chilipeppr-widget-serialport-download

    This cuts down on the length of wire needed to half the width of your gantry – 750mm/2 in my case.

    I didn’t bother with shielded cable, I just braided AWG18 hookup wire to reduce the chance of EMF interference. Ask your daughters how to braid 🙂

    John’s Chilipeppr solution isn’t perfect for third-world internet connections, but you don’t have to use it – just the SPJS component.

    You can use the Universal GCODE Sender, for example:

    • This reply was modified 6 years, 10 months ago by Zootalaws.
    January 7, 2018 at 9:06 am #10748
    cmcgrath5035
    Moderator

    I check the continuity between the screw head of the Ymin connector and the bottom of the PCB with an ohmmeter, which I did and I got a reading of 3 ohms. I then check the continuity of the bottom of the board all the way to the switch and there was continuity their also.

    When you ran this test, was the wire lead connected to the terminal?
    You might want to recheck if not.

    When using small gauge stranded hookup wire, frequently one of the super fine wire strands misses the terminal and can get grounded to nearby ground on the PWB

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