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Powering the ActivityBoard with an external 5v supply — Parallax Forums

Powering the ActivityBoard with an external 5v supply

David BetzDavid Betz Posts: 14,511
in Propeller 1
What's the best way of powering an ActivityBoard with an external 5v supply? Should I just cut a USB cable and wire it to my supply or is there another more elegant way to supply the ActivityBoard with 5v?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2016-10-21 17:47
    Any regulated 5V supply with a USB cable or connector will work, such as a cell-phone charger.

    This actually took me by surprise when I tried it, since I thought it would be necessary to reprogram the FTDI chip to keep the #PWREN pin low. But apparently this is not necessary. 'Not sure why not ...

    -Phil
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    Two options I use...

    1) https://www.parallax.com/product/750-00009
    2) https://www.parallax.com/product/28986
  • David BetzDavid Betz Posts: 14,511
    Chris Savage wrote: »
    Two options I use...

    1) https://www.parallax.com/product/750-00009
    2) https://www.parallax.com/product/28986
    Thanks but I sort of have to use a 5V supply not something bigger. My project has a 15V rechargeable battery and a 15V->5V converter that drives a strip of RGB LEDs. I want to power the ActivityBoard from the same 5V supply. Unfortunately, 15V is too much for the barrel jack on the ActivityBoard, right?
  • kwinnkwinn Posts: 8,697
    David Betz wrote: »
    Chris Savage wrote: »
    Two options I use...

    1) https://www.parallax.com/product/750-00009
    2) https://www.parallax.com/product/28986
    Thanks but I sort of have to use a 5V supply not something bigger. My project has a 15V rechargeable battery and a 15V->5V converter that drives a strip of RGB LEDs. I want to power the ActivityBoard from the same 5V supply. Unfortunately, 15V is too much for the barrel jack on the ActivityBoard, right?

    It's not the jack, it's the linear regulator. It has to dissipate a lot of power when the input voltage is that high. Essentially it would be a 10V difference times whatever the current draw of the circuitry is.
  • David BetzDavid Betz Posts: 14,511
    kwinn wrote: »
    David Betz wrote: »
    Chris Savage wrote: »
    Two options I use...

    1) https://www.parallax.com/product/750-00009
    2) https://www.parallax.com/product/28986
    Thanks but I sort of have to use a 5V supply not something bigger. My project has a 15V rechargeable battery and a 15V->5V converter that drives a strip of RGB LEDs. I want to power the ActivityBoard from the same 5V supply. Unfortunately, 15V is too much for the barrel jack on the ActivityBoard, right?

    It's not the jack, it's the linear regulator. It has to dissipate a lot of power when the input voltage is that high. Essentially it would be a 10V difference times whatever the current draw of the circuitry is.
    Yes, I understand that it isn't the jack itself. I just mean that I can't supply 15V to that jack and expect the ActivityBoard to work reliably.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    If you already have a 5V supply that you want to use, yes, just cut up a USB cable and use it to power the ActivityBoard. Just be careful to use the right wires from the cable!

    -Phil
  • David BetzDavid Betz Posts: 14,511
    Phil Pilgrim (PhiPi) wrote: »
    If you already have a 5V supply that you want to use, yes, just cut up a USB cable and use it to power the ActivityBoard. Just be careful to use the right wires from the cable!

    -Phil
    I was a bit worried about that. If I cut the USB cable, how likely is it that there is a red and a black wire inside to make it obvious which is plus and which is minus?

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    Leave some wire hanging from the USB-A connector when you cut it. Then you can measure voltages with it plugged in to see where the 5V supply wires are. Use a cell-phone charger to do this, not a computer or USB hub.

    -Phil
  • David BetzDavid Betz Posts: 14,511
    Apparently, I can supply 5V at one of the connectors next to the breadboard as long as I'm careful not to have something plugged into the USB port at the same time. Sounds a bit risky though.
  • RS_JimRS_Jim Posts: 1,753
    David,
    Any USB cord that I have cut into has had the + on red and- on black. I think it is a standard for USB.
    Jim
  • David BetzDavid Betz Posts: 14,511
    RS_Jim wrote: »
    David,
    Any USB cord that I have cut into has had the + on red and- on black. I think it is a standard for USB.
    Jim
    Good to know. Thanks for confirming. I ended up powering the ActivityBoard through the 5V header near the breadboard and that seems to work.

  • MikeDYurMikeDYur Posts: 2,176
    David Betz wrote: »
    RS_Jim wrote: »
    David,
    Any USB cord that I have cut into has had the + on red and- on black. I think it is a standard for USB.
    Jim
    Good to know. Thanks for confirming. I ended up powering the ActivityBoard through the 5V header near the breadboard and that seems to work.


    Here's a stupid little thing I made up for breadboard work, solid wires with the stranded soldered to them.
    20161022_132707.jpg
    1280 x 720 - 381K
  • David BetzDavid Betz Posts: 14,511
    MikeDYur wrote: »
    David Betz wrote: »
    RS_Jim wrote: »
    David,
    Any USB cord that I have cut into has had the + on red and- on black. I think it is a standard for USB.
    Jim
    Good to know. Thanks for confirming. I ended up powering the ActivityBoard through the 5V header near the breadboard and that seems to work.


    Here's a stupid little thing I made up for breadboard work, solid wires with the stranded soldered to them.
    That certainly looks like it would be easier to plug into a breadboard than the stranded ends.

  • MikeDYurMikeDYur Posts: 2,176
    David Betz wrote: »
    That certainly looks like it would be easier to plug into a breadboard than the stranded ends.


    It really neaded the small diameter color coaded heat shrink so the wires don't frey.
  • kwinnkwinn Posts: 8,697
    MikeDYur wrote: »
    David Betz wrote: »
    RS_Jim wrote: »
    David,
    Any USB cord that I have cut into has had the + on red and- on black. I think it is a standard for USB.
    Jim
    Good to know. Thanks for confirming. I ended up powering the ActivityBoard through the 5V header near the breadboard and that seems to work.


    Here's a stupid little thing I made up for breadboard work, solid wires with the stranded soldered to them.

    Here's what comes in handy for this kind of thing.
  • Peter JakackiPeter Jakacki Posts: 10,193
    Isn't it easier to leave the cable as is and just make up an inline plug? You know, get a full sized socket perhaps, connect your leads to that and the PCB so that any USB cable can be plugged in.

    Since all my boards include at least one extra pin on the prop-plug compatible programming header it is simply a matter of plugging my version of a prop-plug in to power the board and anything that requires more power than that is usually running off a higher voltage anyway but at least the logic is powered.
  • AribaAriba Posts: 2,682
    15 V on the Jack should not be a problem.
    The Activityboard (WX) has a Switching regulator with up to 26V input voltage for the 5V supply generation.
    Switching regulators don't transform the overvoltage into heat.

    It may even work with the 5V connected to the Jack.

    Andy
  • kwinnkwinn Posts: 8,697
    Ariba wrote: »
    15 V on the Jack should not be a problem.
    The Activityboard (WX) has a Switching regulator with up to 26V input voltage for the 5V supply generation.
    Switching regulators don't transform the overvoltage into heat.

    It may even work with the 5V connected to the Jack.

    Andy

    Good point. I was looking at the schematic of the older version #32910 which uses a linear regulator. The latest WX version #32912 uses a switching regulator which should be fine with the 15V input.
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