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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 > > ==================================================== > > > > Confidentiality Notice: > > This communication constitutes an electronic communication within the > > meaning of the Electronic Communications Privacy Act, 18 U.S.C. Section > > 2510, and its disclosure is strictly limited to the recipient intended by > > the sender of this message. If you are not the intended recipient, any > > disclosure, copying, distribution or use of any of the information > > contained in or attached to this transmission is STRICTLY PROHIBITED. > > Please contact this office immediately by return e-mail or at > > 828-262-6587, and destroy the original transmission and its > > attachment(s), if any, if you are not the intended recipient. > > > > 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. > > >