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  1. #1
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    home switch on stb4100

    i am trying to figure out how to wire up a limit/homing switches to my break out board (stb4100) the one i have has one connection for all homing and one connection for limits my question is does anyone have a pic of how to hook this up i have a induction proximity switch npn type with a power supply of 24 volts dc.

  2. #2
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    Re: home switch on stb4100

    I found this diagram online
    Attachment 426874

    the solution to your question depends on details like the part number of your proximity switch

    the LJ12A3-4-Z-BX proximity switches for example have a 10K pull up resistor built in
    that can cause problems when the switch is powered by a 24V supply and you are connecting it to a 5V logic circuit

    you may be able to parallel several proximity switches and
    connect the the black out wire to the stb4100 input and blue switch negative to the stb4100 input commom

    going by a photo of the stb4100 I have made a guess of the possible inputs and
    would add the diode shown on my diagram to stop the
    stb4100 input from going over +5V if you are using a proximity switch with a built in pull up resistor

    Click image for larger version. 

Name:	stb4100  connection to proximity switch.jpg 
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ID:	426876


    if you measure the open circuit voltage between the -V terminal used as the switch common and an input

    and the input opto-isolator input is powered by a 5V supply you should see 4 to 5V across the terminals and you should find 5V at the vias
    (plated through holes ) in this photo taken from the manual

    Attachment 426878

    if its +24V at the vias the resistors limiting the LED current will be about 1500 to 2200 ohms

    john

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    Re: home switch on stb4100

    i am using urbest 8mm detecting distance sensor inductive proximity switch npn no dc 6-36v i am using a power supply of 24v dc i tested out tonight put the resistor on the hot lead (brown) to the input lead (black) the resistance was 22k ohms and it fried it up then i tried to hook up the resistor inline with the input lead (black) to the break out board side it dropped the voltage down only 1.3 volts my question is can i just use a 3 or 4 ohm resistor inline to get volt drop to 5v or will that not be sufficient and would eventually burn up also? will a diode stop this from happening . i also see the opto-isolator you included would that be enough to send a 5 volt signal without having to hook the resistors and diodes? i guess that takes place of soldering all the separate components into one board correct>

  4. #4
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    Re: home switch on stb4100

    I need more details of the proximity sensor than "urbest " and can't see how you burnt a 22k resistor with a 24V DC supply

    (current with resistor connected to 24V = 24/22000 = 0.00109 A
    power dissipated 0.00109 x 24 = 0.026W )

    can you measure the open circuit voltage between a stb4100 input terminal and the switch common V-

    Attachment 426898


    assuming your NPN proximity sensor uses the same wire colour coding as a LJ12A3_4_Z_BX

    can you measure the voltage between the black output wire and blue negative supply when the brown supply wire is connected to +24V

    whats the voltage when your proximity switch is on and when its off ?

    LJ12A3_4_Z_BX internal circuit
    Attachment 426900

    John

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    Re: home switch on stb4100

    the power supply is 24v but the readable output is 22.3v it was a 22ku ohm resistor but i neglected to have a diode between the brown 24v to the black input lead the measured reading at the time before it burnt up was 21.6 v without being flagged it dropped down to .620v when flagged, i ordered last night the opto-isolator 24v to 5v will hook up the black lead to high side of isolator after going thur it will deliver 5v to input side that should do it? i see your schematic and see the diodes before the 10k ohm resistor to black wire and the the 2ohm resistor to input side of breakout board the opto-isolator looks like the diagram you have posted with the resists and diodes, with the same placements of both resistor and diodes only $7.00 per board figure i only need two input one for limits and one for homing. so hopefully this should remedy this issue

  6. #6
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    Re: home switch on stb4100

    Attached Thumbnails Attached Thumbnails opto isolator.jpg  

  7. #7
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    Re: home switch on stb4100

    I am not convinced the 22K resistor is the correct value - 22000 ohms ( red red orange gold ? )

    what colours are the coloured bands around the resistor ?



    Did you measure the open circuit voltage between a stb4100 input terminal and the switch common V- ?

    if so what voltage did you measure ? (see first diagran in post 4 )


    with the proximity switch only connected to the 24V DC supply

    if your switch has an open collector output like this
    Attachment 426920

    the output should be 0V when its on and when its off

    the only time you should see the output at +24V is when a pullup resistor is connected between the output and the positive supply

    either like the 10K resistor inside the LJ12A3-4-Z-BX as shown in post 4

    or when you have an external pull up resistor

    thats why I need to know the part number to find the proximity switch data sheet


    knowing what the open circuit voltage between a stb4100 input terminal and the switch common V- is

    will determine how you can connect the proximity switch to the stb4100

    if the open circuit stb4100 voltage is +5V and the proximity switch output switches between 0V and +24V

    you can not connect the proximity switch output directly to the stb4100 input without further investigation !!!!



    you can only connect the proximity switch output directly to the stb4100 if

    1) the open circuit stb4100 voltage is +5V and the proximity switch output both on and off is 0V
    or
    2) the open circuit stb4100 voltage is 24V and the proximity switch output switches between 0V and +24V


    John

    PS
    just read post 6

    once I have the answers I will have a closer look at which version of the opto isolator board you need

  8. #8
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    Re: home switch on stb4100

    the part number is LJ18A3-8-Z/BX

  9. #9
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    Re: home switch on stb4100

    also the resistor colors were brown three black lines and then a brown line

  10. #10
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    Re: home switch on stb4100

    so the proximity switch is a LJ18A3-8-Z/BX and has an internal 10K pull up resistor

    the brown three black lines and then a brown lines decodes as 100 ohm 1%

    when connected across the +24V supply and the proximity switch output

    when the switch is on the current through the resistor will be

    24/100 = 0.24A

    power dissipated = 0.24 x 24 = 5.76 W !

    so any 1/2 or 1 W resistor will burn

    you do not need to add any pull up resistor


    the last piece of the puzzle

    what's the open circuit voltage between a stb4100 input terminal and the switch common V-

    Click image for larger version. 

Name:	open circuit  switch input voltage.jpg 
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ID:	426990

    John
    Attached Thumbnails Attached Thumbnails open circuit  switch input voltage.jpg  

  11. #11
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    Re: home switch on stb4100

    While waiting for the voltage measurement between the stb4100 input terminal and the switch common V-
    and if possible the current when an input is connected to the V- via your multi meter set to the 200 mA range

    I have been looking at the resistor values found on a 24V to 5V opto-isolator board

    and been speculating on the values to expect on a 24V to 24V board
    as I have not found one up to now

    Click image for larger version. 

Name:	24v to 5v opto isolator and predicted 24V to 24V board.jpg 
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Size:	72.6 KB 
ID:	427026

    John
    Attached Thumbnails Attached Thumbnails 24v to 5v opto isolator and predicted 24V to 24V board.jpg   24v to 5v opto isolator and predicted 24V to 24V board.jpg   24v to 5v opto isolator and predicted 24V to 24V board.jpg  

  12. #12
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    Re: home switch on stb4100

    sorry john i was measuring the input and the brown leads off the proximity sensor wasn't getting what you wanted, the voltage off the breakout board from the neg lead on the board and input pin on board is 20.6 now does mean it can handle the 22 volt current or do i still need a resistor to lower voltage?
    i thank you for your patience and understanding you obviously gathered i know little to nothing about electronics

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