As you can see bellow I have designed a "somewhat" simple latching relay game buzzer.

For some reason I have just finished building it and it will not work, as it sits, there are no LED's even though I have them in the diagram they're actually globes. The speaker is just a buzzer.

A few things I have tested:

  • All globes work
  • All buzzers work
  • All relays work switch and latch
  • My 6V battery is charged and running
  • All momentary switches work

When I press the button it does nothing, and when I hold the button it does nothing.

Somewhat Simple latching relay game buzzer.

  • \$\begingroup\$ Why are two of the switches on the bottom unterminated? What is the make and model number of the relays? What is the mAH capacity of the battery? \$\endgroup\$ – tcrosley May 22 '14 at 16:57
  • \$\begingroup\$ The switches should be terminated, my bad sorry, the relays can be seen here: jaycar.com.au/productView.asp?ID=SY4060 and the battery is 12Ah. \$\endgroup\$ – user3118152 May 23 '14 at 2:36

Your schematic has several issues, but I think the main problem is that you have put some of the relay coils in series, and 3V is probably not enough to activate them. Your best bet would be to add some diodes so that you can activate the relays in parallel.


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ For a two-person circuit, it should be possible to use two relays; the NC contact of each should allow the other player's button to turn on that player's relay. The reset button should turn off both relays. I'm not sure if the design as shown would be reliable since RLY1 might kill power to the buttons before the relays have latched thoroughly. \$\endgroup\$ – supercat May 22 '14 at 20:10
  • \$\begingroup\$ @supercat: Yeah, it isn't a great design to start with, but I'm hoping that the fact that RLY1 is driven through a diode will slow it down a little bit and alleviate the race condition. \$\endgroup\$ – Dave Tweed May 22 '14 at 20:21
  • \$\begingroup\$ With your schematic how do we stop the other players from being able to press after one person already has? Is that what the diode's are for? so the relay is not activated via another relay? \$\endgroup\$ – user3118152 May 22 '14 at 23:39
  • \$\begingroup\$ It's the same as in your original diagram: The master relay cuts the power to all of the Player buttons as soon as any one of them is activated. \$\endgroup\$ – Dave Tweed May 23 '14 at 0:14

Try throwing some 10k resistors (or whatever value will still let enough current through to switch the relays) between ground and the grounded terminals of the relays to limit current. Your battery can only provide so much current, and maybe it's enough to switch a single relay, but not more than one.

  • \$\begingroup\$ This is a really poor answer. Your contention is that the battery has too much internal resistance, so your solution is to add more resistance? Can you explain how that works? \$\endgroup\$ – Dave Tweed May 22 '14 at 20:07
  • \$\begingroup\$ No, my thinking was that most or all of the current provided by the battery was flowing to ground in the first relay after the switch was pressed and preventing any of the other relays from turning on. The suggestion to add more resistance was to limit current. \$\endgroup\$ – aloishis89 May 23 '14 at 13:43
  • \$\begingroup\$ If I'm understanding correctly the resistors should go between the "off" coil and the ground to help force the current through to the other coils? \$\endgroup\$ – user3118152 May 23 '14 at 13:59

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