# Need advice on simple game circuit

• posted

I'm currently designing an electronic circuit that will be used in an exhibit display. As I am not an Electrical Engineer (my major is Aerospace Engineering) I'm not too fluent with this stuff. First let me explain the circuit generally, and then I will get to my question.

The exhibit is for an open house for my school's College of Engineering. It will be a trivia-based game that simulates NASA's mission control and emphasizes the teamwork between the astronauts and controllers on the ground. The game works like this: players work in teams of two, one person as the mission controller and one as the astronaut. The mission controller reads a multiple-choice trivia question (choices a, b, and c) and they decide what the answer is. Each answer tells them which switch on the electronic board in front of them to flip. If they get it right, a light on their scoreboard lights up and they move on. If they get it wrong, the master alarm goes off and they have to reset it before moving on to the next question. If they get three master alarms before finishing all ten questions, they crash and lose. Otherwise the first team to complete all ten questions wins.

This is an extremely simple circuit with switch/lamp pairs in parallel. The whole thing will be running directly from the wall and powering christmas lights, cut off the string and soldered into the circuit, because I'm trying to make this as simple, inexpensive, and quick-and-dirty as possible. There will be two separate circuits, one for each team. The layout is something like this (the following is ASCII art and requires a monospaced font):

+--A/C Power--+ | | | +-FUSE----+ GND | +-----+-----+-----+ | | | | / / / / Power | A | B | C | switch O O O O | | | | +--+-----+-----+--+ +-+ | | | | Switchbox | GND | | +----+-+-+--------+ | | | +--O--+ | | +----------+ |score | +-+ | |board +---+ Master | | | Alarm | GND | | +----------+

In the above, lamps are designated with O.

The A/B/C switch/lamp pairs represent one question with three possible answers. There will be ten of those groups (so 30 switch/lamp pairs) in the full game, as well as 10 lamps on the scoreboard (each lit by a separate output from the switchbox). The switchbox simply lets me have several different sets of correct answers, and I have that all worked out with some 37-pin D-sub connectors-- each "scenario" will plug into the top of the unit like an old Atari cartridge and connect different answers (A/B/C) to the scoreboard if they're correct or the alarm if they're wrong. Let me know if you need clarification on that, or if you have a better idea, but I think I have that figured out.

Now that I've explained the circuit, here's my question:

I don't really know how I'm going to handle the master alarm. In an ideal situation, flipping the switch on the wrong answer triggers an alarm lamp and a buzzer. Then when a pushbutton is pressed, the lamp and buzzer turn off, and one lamp on the "strike board" is lit up, indicating how many wrong answers you have so far. Once all three lamps on the "strike board" are lit, the game is over. The player will also have to undo the answer switch s/he flipped, to flip the correct one.

I'm thinking I could probably do this as a separate circuit with a relay, but I would like to keep this running on the same power supply as the rest of the circuit (no transformers or batteries).

Any ideas? Anything at all would be helpful.

- AeroIllini

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• posted

This is an ideal application for a small micro PLC. You can easily program all of the necessary logic functions for the player switches and the alarm, and use the same selection connector idea or some switches feeding several inputs, to set up the correct answer. This is much easier than the relay logic you will require to accomplish everything with hard-wired logic. You would need to program the PLC, however. It is not difficult, but it takes some practice if you are new to it.

I would seriously consider running this as a low voltage system, rather than line voltage, for safety. If you use the PLC, you can run it on line voltage and use the auxiliary 24 VDC supply from it for the switches and lights.

Ben Miller

• posted

Thanks for your response.

I had considered using a programmable device, but since I am neither familiar with programming in assembly nor able to transfer my program to the device, I decided against it. My budget is very small, and I don't have free access to a device programmer.

Shortly after I posted I realized that it would be fairly trivial to add a

9V or 12V DC transformer to the mix. After all, Christmas lights are just light bulbs, and they should do fine on a diet of DC current.

Would it be possible to create the logic I need with diodes and/or capacitors? I really only need the Master Alarm sub-circuit to perform the following:

User flips a switch -> Buzzer sounds, "Strike 1" lamp lights. User presses Master Alarm button -> Buzzer is silenced, "Strike 1" stays lit. User flips the switch back to its original position. User flips the switch again -> Buzzer, "Strike 2" lamp. ("Strike 1" still lit.) User presses M.A. button -> Buzzer silenced, "Strike 1" and "Strike 2" stay lit. User flips the switch back to its original position. User flips the switch one more time -> Buzzer, "Strike 3". Game over. User presses Reset button.

The initial triggering switch needs to be the same in all three instances because any one of 20 or so switches in the full circuit could trigger the alarm.

- AeroIllini

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