Pages: [1]   Go Down
Author Topic: Arduino project "control board"... any thoughts?  (Read 487 times)
0 Members and 1 Guest are viewing this topic.
Johannesburg. UTC+2
Offline Offline
Faraday Member
**
Karma: 105
Posts: 4653
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Edit: changed the title from "Robot arm..." to "Arduino project..." since that might limit thinking. Yes that's what we'll use it for, but its purpose is much wider in general.

Morning all,

My daughter and I are keen to build the uFactory robot arm   which uses 3x standard servos and 1x micro.
    
She's just starting final year at high school and will almost certainly be following an engineering degree course after that: mech, elec, mechatronics, details tbd. I'm thinking that a decent robot arm will stand her in good stead for a few years. With a decent mechanical arm, it's realatively easy to change end-effectors, and of course the real thing is to be able to change the code at will, as of course one can do in an Arduino or similar.

So my thinking is to build a decent, long-lasting but well thought out control panel for this thing, so that it's easy to get at the wiring for sensors, motors, effectors and the like. Here's my current thinking and I'd really appreciate any thoughts. Early days yet, so no idea is too outlandish....

Arduino....
  • Well I have a Uno, thinking to use that and leave space for a Mega- pins, memory...
  • Or go for a Mega upfront?
  • Or something else?
  • Shields?... not anticipating anything, servos from digital pins. But make it accessible, maybe Ethernet for browser control

 Power is paramount. I'm thinking the following mains-based supplies
  • 6VDC at say 5A for the servos
  • 7-9VDC for Arduino barrel
  • 5VDC for miscellaneous sensors and I guess this could come off the Arduino. Maybe even go for a big 5VDC supply and run servos off there too, since most are rated 4.8 to 6

Arduino pin accessibility is important, since this is a test-bed and re-configuration will be needed. So:
  • Dedicate 4 digital pins to servo control, out to pins that fit those sockets on the end of servo wires
  • Dedicate 4 analog pins to 2x 2-axis joysticks, brought out to similar socket thingy
  • Dedicate 2 digital pins to joystick buttons, to sockets along with analog
  • Bring all other Arduino I/O to screw terminals
  • Bring out 2x grounds to terminals or a bus or something. I've read here that signal and power grounds ought to be kept separate

Switches, lights........
  • 2x 2 axis joysticks with 1x button each, maybe mount these on a pendant kind of thing like a game controller
  • A bunch of switches, momentary push, toggle, whatever. One side grounded, other side with fly-lead to go wherever.
  • Banks of LEDs, resistor built in for 5V, cathode grounded and anode fly-lead

Prototyping area
  • A normal solderless breadboard with power

Enclosure
  • All neatly built into a decent box, perhaps a sloping top thing
  • Mains leads safely out through grommets
  • PC fan built in maybe to force some air

EDIT... added LCD?
  • Add a 16x2 for general use? What's the best, connector wise?- I2C?
  • Or go for a GLCD or TFT?

EDIT... added Keypad
  • Might come in handy....

So guys and gals I'm open to ideas. If anyone has built such a thing I'm keen to hear.

Have a good one....
« Last Edit: January 07, 2014, 03:58:39 am by JimboZA » Logged

The Elders of the Internet know who I am
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

Queens, New York
Online Online
Faraday Member
**
Karma: 106
Posts: 3758
"Of all the things I've ever lost, I miss my mind the most" -Ozzy Osbourne
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I would personally go with the Due, it's faster and like the Mega, it has a lot of pins.  Another good reason is of course multiple serial ports, so you don't need to use software serial and risk any of your libraries using a timer that is already being used for the servos.

Interfaces:
It really depends on what you/she plans on doing with it. You could get a TFT with a touch screen to make it look high tech, or use say an android table or IPad via wifi or bluetooth. This would also double as a keypad and other various buttons, if needed. I would include the bluetooth anyways just so you can debug without needing to be connected to a computer.

Power:
There are some really good power units that are also quite compact and provide a good range of voltages. My friend had one, I'll see if I can get the name if it. If anything, you can make your own with a 12V power pack and use regulators to get the required voltages. This is not exactly what he had, but it is very similar 12 volt power supply

Accessibility:
You may want to make a breakout board, one with various connectors like Dupont pins (male and female) and some screw sockets.
« Last Edit: January 07, 2014, 02:45:14 am by HazardsMind » Logged

Created Libraries:
TFT_Extension, OneWireKeypad, SerialServo, (UPD)WiiClassicController, VWID

Johannesburg. UTC+2
Offline Offline
Faraday Member
**
Karma: 105
Posts: 4653
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I'll see if I can get the name if it

Thanks.... you do mean different voltages at the same time?

Quote
I would personally go with the Due

Due's 3V3 system seems an inherent drawback to me, but that might be ignorance. Certainly means one has to be very careful!

For example, what voltage does a servo expect on the signal line? I always just assumed 5V since the servo power is ~5V. Can a 3V3 signal control a servo?
Logged

The Elders of the Internet know who I am
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

Queens, New York
Online Online
Faraday Member
**
Karma: 106
Posts: 3758
"Of all the things I've ever lost, I miss my mind the most" -Ozzy Osbourne
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

His power supply put out 6, 9 and 12 volts at the same time, but it was an old unit and right now I'm having a difficult time finding it.

If you think the Dues 3v3 system will give you problems then your probably better off with a regular Mega Rev3, just to be safe. No point in spending money, only to find out it doesn't work.

This here is the closest I could find to his power supply. LINK
« Last Edit: January 07, 2014, 03:13:58 am by HazardsMind » Logged

Created Libraries:
TFT_Extension, OneWireKeypad, SerialServo, (UPD)WiiClassicController, VWID

Johannesburg. UTC+2
Offline Offline
Faraday Member
**
Karma: 105
Posts: 4653
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

What I think I'll do, is allow space for a Mega, and wire loads of terminals of one form or other, to accommodate the Mega, yet just use our Uno for now.

Quote
I would include the bluetooth anyways

That makes sense, long term. What's the generally accepted way to implement BT?
Logged

The Elders of the Internet know who I am
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

Queens, New York
Online Online
Faraday Member
**
Karma: 106
Posts: 3758
"Of all the things I've ever lost, I miss my mind the most" -Ozzy Osbourne
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You can implement the BT module any way you need to. But you also need to think about what you will be using to talk to the BT module, whether it's a computer or mobile device. You can come up with a bunch of commands to look for, or simply relay values.

Keep in mind iPhones and iPad are very picky when it comes to bluetooth modules, so not many of the cheaper modules work.
Logged

Created Libraries:
TFT_Extension, OneWireKeypad, SerialServo, (UPD)WiiClassicController, VWID

Johannesburg. UTC+2
Offline Offline
Faraday Member
**
Karma: 105
Posts: 4653
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I might be missing it, but I don't see physical dimensions in the specs here. Mega is same width as Uno I guess, for shields, but about twice as long? Anyone got actual dimensions for space budget?
Logged

The Elders of the Internet know who I am
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

Global Moderator
Dallas
Online Online
Shannon Member
*****
Karma: 209
Posts: 13016
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
7-9VDC for Arduino barrel
5VDC for miscellaneous sensors and I guess this could come off the Arduino.

Why?  Just get one really good 5V power supply for the Arduino and sensors.  Don't bother using the barrel connector.

Or, use a powered USB hub.  The hub can be the power supply when working stand-alone and the connection to the computer when developing.

Quote
Maybe even go for a big 5VDC supply and run servos off there too, since most are rated 4.8 to 6

Motors are electrically noisy beasts.  Even tiny ones.  Use a separate power supply.
Logged

Offline Offline
Edison Member
*
Karma: 30
Posts: 1021
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I am a big fan a terminal strips.   bring all sensor wires into the panel and land them on rows of screw terminals.
then, bring the wires from those to the board.

one benefit is that all your exterior wiring is neat and, if next year someone comes out with an Arudino tre, or you want to change the micro to some specific one the professor requires, it will be easier.
Logged

Pages: [1]   Go Up
Jump to: