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I am attempting to wire this relay http://www.canakit.com/4-port-usb-relay-controller.html to this lock http://www.southco.com/en-us/em-05. I have done some work with Arduinos before, but I am not an electrical engineer, therefore I am having trouble figuring out how to wire these 2 together in order to get the relay to power (and open) the lock. Any help would be appreciated!

The relay channels each have NC, COM, and NO. The lock has GRD, POW, SIG, COM, and NO.

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  • \$\begingroup\$ Do you have a power supply available? If so, what voltage/current rating? \$\endgroup\$ – John Honniball Nov 21 '14 at 15:13
  • \$\begingroup\$ I do, it's DC 9V. \$\endgroup\$ – martin122089 Nov 21 '14 at 15:16
  • \$\begingroup\$ 100mA. Forgot that in my last comment :) \$\endgroup\$ – martin122089 Nov 21 '14 at 15:26
  • \$\begingroup\$ But the lock module has a "typical operating current" of as much as 600mA (at 12V; it accepts as low as 8V). Surely you won't be able to use a 9V, 100mA PSU? \$\endgroup\$ – John Honniball Nov 21 '14 at 16:00
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    \$\begingroup\$ I also have a PSU that outputs DC 12V, 2A. \$\endgroup\$ – martin122089 Nov 21 '14 at 16:19
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Connect the lock's brown Ground to the power supply negative terminal, and the red Power lead to the power supply positive. Also connect a relay "COM' terminal to the power supply positive. Connect the relay "NO" terminal to the lock's orange control wire.

The lock's microswitch terminals could be used to provide an indication that the lock has actually operated.

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  • \$\begingroup\$ Thanks so much, your wiring scheme was correct. Regarding the second part of your answer about the microswitch terminals, could you elaborate on that please? How would I use the microswitch to determine if the lock has actually operated? \$\endgroup\$ – martin122089 Dec 2 '14 at 14:50
  • \$\begingroup\$ As I read the datasheet, the microswitch will be closed when the latch is fully retracted (door is unlocked). You could use this switch closure to light a light to indicate the door is unlocked, or to provide an input to a microcontroller to confirm operation of the lock. \$\endgroup\$ – Peter Bennett Dec 2 '14 at 17:39
  • \$\begingroup\$ I want to use this microswitch in tandem with a Raspberry Pi in order to lock and unlock the lock (which is already working) and also to tell if the lock bolt is retracted or not. So would I be attaching the COM of the microswitch to the COM on the relay and the NO to one of the GPIO pins on the Raspberry Pi? \$\endgroup\$ – martin122089 Dec 2 '14 at 21:14
  • \$\begingroup\$ You would connect the microswitch to the Pi GPIO just as you would connect any other switch or pushbutton. \$\endgroup\$ – Peter Bennett Dec 2 '14 at 21:52
  • \$\begingroup\$ Alright, I will give that a try. Thanks for all your help! \$\endgroup\$ – martin122089 Dec 2 '14 at 22:14
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You'll need to start by connecting up the power supply. Wire the negative terminal to the negative side of the lock. Then connect the positive side of the lock to the N.O. terminal of the relay. Finally, connect the positive side of the power supply to the Common terminal of the relay. You've actually got four relays there; pick one and ignore the rest.

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    \$\begingroup\$ The lock apparently includes a microcontroller, so it needs power full-time, and is controlled by the Control input on pin 3 \$\endgroup\$ – Peter Bennett Nov 21 '14 at 19:06
  • \$\begingroup\$ @PeterBennett in that case, my answer is wrong. Please disregard it. \$\endgroup\$ – John Honniball Nov 22 '14 at 0:22

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