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  1. #11
    I have one of those relay boards (or at least one that looks remarkably like it) - I drive it directly with the 5V out from a CNCUSB Mk2/9 board digital output - no issues.

    I'd measure the DC resistance of your relay coil...I'd wager you can probably short out that output 100 Ohm resistor (which should then see sufficient current to energize the relay) ...else play on the safe side & put something like a 10 ohm resistor across it (i.e. in parallel with it)
    Last edited by HankMcSpank; 11-08-2015 at 09:03 PM.

  2. #12
    You may have a faulty board. Try hooking it up to a 5v power supply and see if you get a relay operating with 5v from the same supply. Some boards I have switch the relay on with 0v and off with 5v. Also check the jumpers.
    Last edited by cropwell; 11-08-2015 at 10:19 PM.

  3. #13
    Actually ignore my last post...if your relay board is the same as mine, from recollection the 5V from your driving IO pin, doesn't energize the relay directly, but does so via a tranny/fet. Are you supplying the relay board with a separate 5V supply?
    Last edited by HankMcSpank; 11-08-2015 at 10:32 PM.

  4. #14
    Quote Originally Posted by HankMcSpank View Post
    Actually ignore my last post...if your relay board is the same as mine, from recollection the 5V from your driving IO pin, doesn't energize the relay directly, but does so via a tranny/fet. Are you supplying the relay board with a separate 5V supply?
    BOB is supplied with 24v, relay board with 5v. I use different supplies for galvanic isolation of BOB, sensors,etc.
    project 1 , 2, Dust Shoe ...

  5. #15
    Quote Originally Posted by Boyan Silyavski View Post
    BOB is supplied with 24v, relay board with 5v. I use different supplies for galvanic isolation of BOB, sensors,etc.
    Boyan Can you show just how you are connecting the relay to the board you might have to connect the -ve grounds to each other.
    ..Clive
    The more you know, The better you know, How little you know

  6. #16
    Quote Originally Posted by Clive S View Post
    Boyan Can you show just how you are connecting the relay to the board you might have to connect the -ve grounds to each other.
    He will definitely need to connect the two boards PSU 0V rails together, else all he'll have is two independent supplies with their respective 0Vs floating wrt one another. As mentioned in my last post, my relay board uses a FET/tranny on the input ...the switching/control voltage does not drive the relay coil direct. Therefore if your board is like mine, the notion that the "Pokeys57CNC does not output enough current on output 5v pins to switch a external relay" a misnomer (the input impedance of the relay board will likely be extremely high so will sink very little current at all)
    Last edited by HankMcSpank; 15-08-2015 at 02:57 PM.

  7. #17
    Guys, so i have BOB powered by separate 24VDC PSU and relay board powered by 5VDC PSU. Both grounds are connected/the earth, the body.

    So you say now i need to connect the together the 2 - /minus / pins of both the PSUs?

    Makes sense though i have never done that before on other boards and they worked
    project 1 , 2, Dust Shoe ...

  8. #18
    Without a diagram of your particular situation, all we have to go on is this....

    Quote Originally Posted by Boyan Silyavski View Post
    Hi, how do i deal when a board / Pokeys57CNC does not output enough current on output 5v pins to switch a external relay / 8 channel relay board 5vdc /??
    If you get a multi-meter & see what the resistance is between the Pokeys57CNC 0V rail & the relay board's 0V rail ....if it's high resistance , then there's no common path (& therefore this is why your relay's aren't switching).... you will need to link the 0Vs on both boards together. Voltage is always 'with reference to another point' ...i.e. the 5V on your Pokeys57CNC is in reference to the Pokeys57CNC 0V, the 5V on your relay board is in reference to your relay board's 0V...the only way you can make the 5V on your Pokeys57CNC mean anything to your relay board is to commonize the 0V rails on both boards....join them together.
    Last edited by HankMcSpank; 17-08-2015 at 11:44 AM.

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