This fun MakerShed item will switch 120vac at 15 amps, on as little as 3
volts signal:

http://www.makershed.com/PowerSwitch_Tail_II_p/mkps01.htm

I don't know much about iOS development, but if you have access to the
docking port, 3 volts should be easy to muster.

Also, mumble mumble Arduino mumble mumble?

On Tue, Nov 20, 2012 at 10:58 AM, Chris Fitzpatrick
<[log in to unmask]>wrote:

> Wow. Thanks Thomas. That helps a lot.
>
> Looking over this, I started wondering if it might be possible to actually
> trigger the relay using voltage from tablet's audio jack. I've seen people
> do this with cell phones and camera flash triggers, although I doubt I can
> get 5V DC out of the audio jack without amplifying it...or I find a relay
> that can go off 600mV or whatever I can get from the jack.  I'm probably
> stuck using an iPad, since my wife has one i can use to build the prototype
> and iOS has a pretty good barcode reader library.
>
> b,chris.
>
>
> On Mon, Nov 19, 2012 at 4:38 PM, Thomas Bennett <[log in to unmask]
> >wrote:
>
> > On our 3M self checkout, the desensitizer is activated when the barcode
> is
> > read (by a laser scanner) if I remember correctly, the patron is already
> > logged in to the system.  You might be able to get something from an
> > electronics store to first, replace the manual switch with and electronic
> > switch that operates on 5 volts(I think it is 5 on USB), then some how
> have
> > this connected maybe with a usb hub that the scanner is on.  There may be
> > other
> >
> >
> >
> > From reef central forum:
> > The voltage supplied by a usb host or powered hub is between 4.75 and
> > 5.25VDC. USB 2.0 specifies 5VDC @ 500ma max.
> > The relay you would need would be a 5VDC relay, with the contacts rated
> > for 110 -125VAC. These are available, however the load rating is often
> low
> > ~1 amp or less. (not all inclusive)
> > Small 1A SPDT Relay, 5v, OMRON
> > http://www.allspectrum.com/store/small-1a-spdt-relay-5v-omron-p-512.html
> >
> > Also from reef central:
> >
> > I have all the parts to build a USB AC power center, but haven't gotten
> > around to trying it.
> > The problem here is that a USB port is a serial port.
> > While you MIGHT be able to get away with just wiring up one USB serial
> > line to a relay and forcing that pin high, you can only do one device.
> > My design uses the DALLAS 1-wire switches and a USB adapter.
> > You can string together hundreds of these devices onto just TWO wires and
> > drive and query all of them using a Linux file system called OWFS ( One
> > wire file system ).
> > All of the devices on the interface show up in the linux filesystem as
> > files.
> > To read the status, you just read the file, to change the device status (
> > closed or open ) you just write to the file.
> >
> > Honestly the simplest way to experiment with this stuff is to use a
> > computer parallel port.
> > You have a LOT more pins and they can be set via peeks/poke from the OS.
> >
> > Another option is a USB to parallel port converter or a USB relay board.
> > http://www.virtualvillage.com/usb-po...stamp-bs2.html
> >
> > Also check these guys out:
> > http://bb-elec.com/welcome.asp
> >
> >
> > Hope this helps,
> >
> > Thomas
> >
> > ====================================================
> > Support Request                http://portal.support.appstate.edu
> > ====================================================
> > Thomas McMillan Grant Bennett           Appalachian State University
> > Operations & Systems Analyst            P O Box 32026
> > University Library                                Boone, North Carolina
> > 28608
> > (828) 262 6587
> > Library Systems
> > http://www.library.appstate.edu
> > ====================================================
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> >
> > On Nov 19, 2012, at 4:09 AM, Chris Fitzpatrick wrote:
> >
> > > Hi,
> > >
> > > I'm working on designs to build a self-checkout kiosk for our Koha
> > system.
> > > Seems pretty straight-forward except the book desensitizer part.  All
> the
> > > desensitizers I've every used only had an on/off switch.
> > > Has anyone ever seen or used a desensitizer that can
> > > be programautomagically triggered?
> > >
> > > Hoping to use an iPad or Nexus, so something that's not windows only
> > would
> > > be ideal, but looking for anything right now...
> > >
> > > thanks for any pointers/suggestions....
> > >
> > > b,chris.
> >
>