A Novice Project: Could Use Some Help Identifying Best Parts

[system]

I am working on my first “major” project, a coin-op automata.

I realize it’s most likely overkill, but what I decided to do in deference to my novice status was to break down each major function of the device into its own “section.” That way, I only have to work out how to wire up and program each section to do its thing. I also figure this means that one section doesn’t interfere with the others (if the lights don’t come on, the motors and sensors will still do their thing). I figured I'd treat the whole thing like a bunch of smaller modular parts fitted into the whole.

Then all the sections will be slaved to a “master” controller board. Basically the master will tell each board when it should do its thing, that board will run its little program, and all the master board then does is display on a 4-digit LCD the number of times it’s run this cycle (thought it might be a good idea to have a basic count of how many times the automata runs, especially so I can learn how many runs the machine goes through before I have to start worrying about swapping out the batteries/power supplies).

What I want to determine would be the best components recommended for each section’s tasks.

Here is the basic breakdown of what the automata is expected to do:

1. Coin slot detector triggers when nickel dropped in slot.
2. 2 Stepper motors swing open front panels to reveal automata interior.
3. Hidden RGB LED strip lights up, music box music begins to play, 3 DC Motors spin various parts of the automata of the interior around.
4. Music reaches end. All motors stop.
5. A card dispenser spits out a single card.
   6.The system waits until the PIR sensor detects movement (the viewer picks up and takes the card).
6. The lights dim to black as the stepper motors close the front panels.
7. Master board registers the new cycle and adds it to the counter displayed amount.
   END

The only additional things I want to try and make possible is that I want a wifi shield hooked to the master board so that, with an Arduino app on my iphone, I can send a simple command to run the cycle without needing a coin dropped to start it (could be fun to occasionally secretly hit the button to make the device seem to spontaneously “start itself”). Also, the goal is to make this thing relatively portable (can be set atop a table or podium) and not have a visible means of power supply (i.e. an AC wall wart), so all of these would have to be powered by their own individual arrays of battery setups (I also figured if each section only has to worry about powering its own components, this should be doable even though the back section will of course have a mass of variously-labeled batteries that feed to their respective sections).

I’ve included a very simplified diagram (again, forgive the novice lack of technical precision). On the diagram I’ve mapped out all the different sections and a note about what component I was thinking would best serve.

I already know this will be a real Frankenstein with all the separate sections and their respective wiring and power.

But anyone who cares to take a look and has any suggestions, I would appreciate it. I already have been learning thanks to hunting around the forum and Google about shift registers, which might improve the payload the average section can handle more than I'd originally thought in this first sketch. So this sketch will obviously be getting updated as I learn more about what components are best designed with a given use in mind.

Thanks again for any input.

[jbarchuk]

No, it's not mostly overkill, it's 90% overkill. Modular is cool because when two pieces doesn't work you disconnect them and find out why they work independently but not together. That modularity works for both mechanical and logical systems But you don't have any 'interconnected' items - it's all linear.

I don't think you realise how spectacularly -annoying- simply -maintaining- the levels of 'disconnectedness' you have designed will become. 4 Arduinos require 4 totally different sketches. Each sketch will require more volume of code just to talk to the master Arduino than is consumed by the individual item it's controlling.

You're also up to 5 motor shields. DC control is about the simplest control, and the most vastly produced addon so there are tons of options.

At ebay look up 8 channel relay board. But that's only for unidrectional board, and no speed control.

If you need speed control you need a FET board.

If you need to reverse a motor you need an H-bridge board, which generally includes speed control.

The RGB LEDs are a very common separate board also.

Yes, the wifi and MP3 are shields.

We're up to SEVEN SHIELDS. Now think about disconnecting the 4th shield from the stack, unplugging the top 3, pulling off the 4th, plugging the top 3 back on, doing whatever, and reversing the process to restack them. Sometimes modular isn't convenient, to the point of extremely annoying.

It won't work 'stock' anyway because there are a limited number of address pins to the motor shields. You'll need to bend wires out and flywire them down to other address pins. Now you can't even 'simply' unplug a shield from the stack without also unplugging/replugging the flywires. (There may be incompatibility between the couple of required shields anyway. Not likely, but don't -deliberately-make things any more complicated than is unavoidably necessary.)

This whole stacked thing also DRASTICALLY multiplies the power consumption!!! It'll need enough batteries that are half of the box's weight!

I -was- gonna say yes you can add a switch panel that powers each of these separate boards to make you feel better about everything I talked you out of, but it's unnecessary and you will never use them. Again, there is no mechanical interconnectedness. To disable an item you do that in software. But again this system is so 'linearly-simple' that there won't -be- much debugging. Start with the first required items - display and 'on' switch. Then work on further mechanical items one at a time. Along the way, you won't be doing any disconnecting/disabling of any of the previous items, and by the time you get to the last item it's finished.

All of the above can be controlled by a Mega. (Possibly an Uno but I haven't counted up the IO pins.)

Modular is good. But that doesn't mean writing the letters m o d u l a r on separate pieces of paper, because it makes it much more difficult to read. I understand you want to break the project into different sections, and you -did- that part right, but you have gone as far as printing the letters on separate pieces of paper, and mailing them to 7 different states. Gotta reign it in or it'll become extremely unwieldly.

[system]

Thank you. With that input I can start to re-tool the plan to allow for much more compact interworking of the relevant parts. I'll look at a Mega and see about updating the notes accordingly.