Sunday, August 18, 2013

Arduino Trivia Buzzer System Update

So a quick update on my Arduino Trivia Buzzer System.  Last time, I gave you a basic schematic for the handheld buzzers.  Since then, I've completed 8 more handheld buzzers that are ready to be painted.

I needed a break from the handheld buzzers, so I thought I'd work on the control box.  One of the issues I'm having is that I don't really have the space/tools available to make the finished, shoe-box sized control box in my apartment.  Unless I can con my brother into making one for me, I'll have to find the room sooner or later, but in the meantime, I wanted to get some other work done for it.

The handheld buzzers connect to the control box via a phone cable, and the keystone jack must then connect to the Arduino as well as to an indicator LED on the control box.  To avoid trying to push too much current out of each digital pin, all LEDs are turned on by instead having the digital pins connected to a transistor, which then connects the LEDs and resistors to a 5V source.  This is wired as such:

A simple enough circuit.  The "handheld buzzer" portion is completely held within the handle of the buzzer, so that wire just needs to be connected to the transistor via the keystone jack.  However, I still need TWENTY-FOUR of these!  Since I don't have the control box itself built, I wanted to be able to easily connect the wires to this transistor setup once I have it ready with the keystone jacks, LEDs, and Arduino installed.  I did NOT want to have to solder these connections when everything's done, which would also make servicing/replacing the transistors a nightmare.  So I bought a project board from Thai Shine along with some female headers.  Unfortunately, the largest board they sell is about 3" x 5", but as you can see, I had enough room (barely).  I'd have loved to make it easier to follow what's what (which would have been easier to solder with more space!), but the board was just too small for that:

Each row doesn't look exactly the same because I kept changing my mind how I wanted to connect them to the female headers.  The middle row was the easiest since I was able to use the long wires of the resistors to connect everything instead of having to make jumpers (as in the bottom row).  The other two rows were completed before I realized how much easier it would be to do it this way.  Figures.

My soldering skills leave much to be desired, but I tested each transistor setup and they work just fine.  This will be nice because I'll just need to connect everything with a male header when I have the physical box ready.  There are 3 connections for each transistor (digital out, control box LED, handheld buzzer LED), and a single connection for the 5V source.  So that's still 73 wires I have to connect, but at least I don't have to solder them.

At this point, I'm somewhat at a standstill until I get the physical control box built.  I have the week off, so I might just bite the bullet and go to Home Depot and have them cut some pine down to make a box roughly the size of a shoebox (see below for awful sketch of control box).

4 wallplates with 6 jacks each, for 24 handheld buzzers.  Single jack on side for the host's reset switch.  Red 5mm LEDs on top of the control box are there to show when someone has buzzed in, as well as to show the reset animation when the host has reset the system.  The LEDs light up at the same time as the ones on the handheld buzzers (they're wired in parallel), so you can see who's buzzed in both on the control box and on the contestant's handheld buzzer.

I know some people have asked for schematics of everything, and I'll put those up as I'm able to (I need to actually build/wire this stuff first).  I plan on putting together a really long howto for this when I'm done so I can post it on here for people to use as they please.  But my priority is to actually finish the damned thing and have it working before I try to tell people how to build their own.

I'll update as I'm able to.  I start my first real medicine rotation a week from tomorrow, so I really need to get as much done this week as possible.

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