MAKE YOUR OWN SLOT MACHINE
COIN
MECHANISMS
CONTROL SOUND/ VIDEO AND COMPUTERS
Control circuits
The momentary electrical contact from the coin
mechanism needs a circuit to get the machine working.
I started off using simple
relay circuits but now use small industrial computers called PLCs.
Here are the
various options:
|
Timers A simple coin operated machine could have a timer triggered by the coin mechanism. All electronics catalogues have delay timers, and some types have a ‘one shot’ option, which enables them to be triggered by a pulse. (in this case , the pulse from the coin falling through the coin mechanism). Timers cost £20-30, from any electronics catalogue
|
 |
|
 |
 |
Holding relays A simple relay latching or holding circuit can also be useful. In the basic circuit (left) switching A on momentarily will energise the relay, which will then stay energised until switch B is broken. In the circuit below (which I used on my early machines), switch B is a cam switch on the output shaft of the geared motor. The momentary coin switch A will cause the motor to rotate one complete revolution and then stop. |
|
|
|
Cam Sequencers The geared motor rotates the cams
slowly. Each cam has a microswitch pressing against it. Using one of the
cam switches as B with the circuit to the right, this will rotate
one revolution every time a coin is inserted. As each cam can be
individually adjusted, lots
of different elements can be made to switch on and off during the’cycle’.
RS components sell a cam sequencer for about £50. |
 |
|
|
 |
Intelligent Relays These are probably the simplest form of digital electronic control. Kits including software and connecting cable to a PC cost about £150. Its not difficult to get a basic program running (you drag and drop elements like timers and logic gates into a block diagram on the screen). I've used them for simple machines like postcard dispensers, though I wouldn’t recommend them for anything elaborate, because following the logic becomes difficult and editing is less easy than the initial programming. Click here for a beginners guide I wrote when teaching a friend
|
|
|
|
Programmable Logic Controllers These are my favourite controllers. I use the
Mitsibushi FXS1 series, about £300 for 14 outputs, or £180 for 6 outputs.
The advantages are that sensors and switches go in one side and relay
contacts come out the other – there’s no soldering and everything is
very robust and protected against voltage spikes etc. The stepladder
programming language is very versatile, and quick once you’ve got used
to it. The drawback is that it does take time to get the hang of the
programming – you definitely need the full printed manual to get far.
I’ve been using them for 15 years so I can’t now remember how I
learnt. If anyone has an recommendations of books or other training
material, please write and I’ll add it to this section. |
 |
|
|
PIC chips
These are complete microprocessors on a chip, and cost as little as £1. Using them needs a bit more knowledge of electronics than cam timers, but they are now taught in schools. I’ve done a few simple projects with Picaxe ( programmed in basic) and Arduino (programmed in C++).
Picaxe is the simplest and most commonly used system in schools. They even now sell a flowchart program that makes them almost like programming lego mindstorms. In the UK Rapidelectronics sell a good selection of Picaxe stuff, but if you can afford £40, you can buy a board complete with a chunk of prototyping breadboard which makes a beginner's prototyping of outputs much easier. The microcontroller chips themselves can only handle tiny currents, so to make motors and lights etc work, you need extra components - but all the details are easily accessible online.
I love Arduino, its story is so romantic. A group of Italian engineers, laid off after Olivetti went bust, used to meet in a bar called the Arduino. They decided the world needed an open source microcontroller and its been a huge success. I find C++ less intuitive than basic, with lots of conventions I don't understand. However, its more versatile - it will easily spit out serial data which I find very useful for controlling cheap MP3 players and LCD displays. But the best thing is that because Arduino is open source, there's a huge fan base and lots of forums. So the code for almost anything you could want to do is posted online (see arduino/playground) and that if you get stuck you can post a question in one of their forums. My most recent question was answered within two minutes! I went to a beginners weekend workshop in london (run by tinker.it) and it was brilliant. I didn't understand everything at the time, but it gave me the confidence to start trying things for myself.
