Are you sure about those numbers ?
800mAh is 0.8 Ah, doesn't that mean a 2.5 Ah will last about 3 times longer ?

I know of steering engines that do exactly what you described.
They use a windshield wiper motor (at 24 volts) for electrical steering, which can be controlled by autopilots.
Be aware that when you do this, your steering wheel will be turning when the motor is controlling it, which is a real danger.
The system i know of, has some kind of clutch that connects either the wheel or the motor to the steering axle.
The motor or steering wheel aren't directly coupled with the rudder, but are controlling a hydraulic sytem but those are commercial vessels.

Thanks guys.
That adafruit solution is interesting, and not too expensive.
I asked because i was just wondering what drawbacks there could be by doing it that way.
And to save pins so you can use your Arduino also for inputs or other outputs.

The other boards that involve an extra controller are way too espensive.

The 2nd photo shows 8 components at the connector, which are probably resistors.
And each relay has a component, probably a transistor.

So yeah, you can measure the current drawn per input at that input to see if it's Arduino compatible, and the total current drawn by the board in case all relays are enabled.
Last one is probably somewhere close to 750 mA.

Today (well, yesterday actually)i received the 4 servos i ordered (no plans, just to play around).
Played a bit with the sweep sketch to test them.
While playing, i saw that the servos stop working whenever the signal wires is disconnected.
They do not return to center or end position, they just stop at the point the last instruction told them to go.
Reconnecting that wire just starts the servo to continue to the point the sketch is running at that moment.

So is it a good idea to switch servo's and command those with just a few lines and extend the total number of servo's this way ?
If not, why not ?
So power would stay connected, and only pin 9 (std pin in the sweep sketch) would be connected to a different servo, perhaps by using a 74hc595.

Still not 100% clear.
Are these 2 linear motors running separately or are they alwyas running at the same time, in opposite directions ?
If you don't need PWM to control the linear motors, you'll need 4 pins to control them in case they are to be controlled separate.
And 2 in case they need to be running in parallel (one to switch the direction and 1 to switch the power to the motors).
You can then switch by relay (all DPDT).
You need PWM to control the servos.
This PWM is a software hack in the library as far as i understand, but i'd guess you have plenty of pins to control your motors, and don't need a motorshield.

Het gaat nogal van de hak op de tak in deze thread.
Als jullie wat meer structuur aanbrengen, word het voor jullie zelf ook wat overzichtelijker.
Maak dus een stappenplan en houd je daar zoveel mogelijk aan.
Das de basis voor projecten (het maakt niet uit hoe groot of klein die zijn) en dit zouden jullie intussen moeten weten.

Nope not even that.
I didn't use my soldering iron, just used some stuff i have around here.
Have some 90 degrees male jumper headers and used that.
This way i could plug the cable directly to the Arduino board, and still use a jumper wire and the resistor to power the display
So the cable is still intact.

I'll have a look at using the ADXL345 as is with my UNO R3, thanks for the link.

Code:

void loop(){   
  if(Serial.available() )
  {
    processSyncMessage();
  }
  if(timeStatus() == timeNotSet)
    Serial.println("waiting for sync message");
  else     
      digitalClockDisplay();
  delay(1000);
}

Nothing happens on your display ?
Comment out the first line in that loop:

Code:

void loop(){   
/*  if(Serial.available() )
/  {
    processSyncMessage();
  }*/
  if(timeStatus() == timeNotSet)
    Serial.println("waiting for sync message");
  else     
      digitalClockDisplay();
  delay(1000);
}

You should see the "waiting for sync message" message on your screen.
What other hardware (Arduino) do you use ?

I have just extended the wire length to about 44 centimeter by using 2 male - male jumper wires and a female-female jumper wire.
Works just the same.
To confirm i changed the text a bit and this change was also OK.
Extending it this way to a total of over 1 meter resulted in display of garbled data.
So you don't need to use extremely short wires and can extend wires when needed.
But like always, don't use wires longer than they need to be.

I also have an I2C 1602 display.
I'll have a try at using these 2 together soon.
Can't try the ADXL345 yet, waiting for the ttl to 3 volt converter to arrive (has been on its way for 3 weeks now so hope to have it next week).

By the way: this display doesn't seem to answer to Nick Gammon's I2C scanner, the 1602 does.

Didn't you do that already ?
In your pic above it seems you removed the female plug and soldered pins to the original wires.
That's essentially the same as what i did, but my little attempt saved some time because i didn't have to solder.

I know about I2C addresses, but figured that a display is an output and connecting 2 outputs with the same address would result in displaying the same stuff twice.
There would be a problem when data is supposed to go 2 ways, like when using some sensor.
Does the display answer to the data from Arduino ?

By the way:
The ssd1306 datasheet mentions a way to select an other address.
I have no idea if this can be set different with this crius board.

Played around some more.
Just tried to connect both displays at the same time.
The first one is connected to pins A4 and A5 using those jumper pins.
The second one connected to the SDA and SCL pins next to the reset button, using 6 centimeter jumper wires.
Power supply of the second display connected via 100 Ohm to vcc pin of the ICSP connector (don't know if that is a good idea).
This results in damaged data on both displays, and removing display 1 still gets damaged data to display 2, so the wire length of 6 cm is already too much.
Wouldn't expect that, maybe splitting the I2C wires an other way will solve this.

So @desmondttm123: try wires as short as possible, like 0miker0 did.
And try the 100 Ohm resistor.

I guess this means this display can't be used together with other I2C devices.
That would be a shame, i was planning on using it to display ADXL345 results.

Heb je wel uitgezocht of digital2 wel vrij is en niet word gebruikt voor je motorshield ?
wanneer je schakelaar open is, trekt de weerstand digital2 naar 5 volt en wanneer de schakelaar gesloten is wint die schakelaar het van de weerstand en ligt digital2 aan GND.
Probeer eens wat er gebeurt als je de weerstand aan 1 zijde losneemt.
En waarom gebruik je niet de interne pullup ?
Spaart je een weerstand uit.
Kijk of digital2 wel vrij is om te gebruiken en niet al gebruikt word door je shield.
Word ie wel gebruikt, kies dan een andere wel vrije pin.
Als je dit niet weet, probeer dan een willekeurige andere pin totdat je hebt wat je wil, maar dan kun je wel ff bezig zijn.
Adafruit is een grote speler in de Arduino wereld.
Ik zou niet vreemd opkijken als ze een aantal motorshields hebben (zou me verbazen als dat niet zo is).
Daarom ga ik niet eens bij hen kijken of ik wat over die shield kan vinden voor je, tenzij je een verwijzing naar het betreffende product geeft.
Adafruit is ook goed genoeg wat betreft documentatie.
Dus gegevens over jouw shield (mogelijk zelfs schema's) kun je daar zonder twijfel terugvinden.

Got it !

It is an initialisation problem.
Searching the interrnet brought me to a page i visited already.
I tried everything on there except cutting and resoldering 1 pin of the flatcable to a RC network.
None of that worked, but this must have been a problem in the examples.
So i read all over there and found a tip which is very easy to try:
Add a 100 Ohm resistor between the power supply and the module.
The resistor and the capacitance of the leads on the board are assumed to make just enough delay for the driver to finish the reset.
So i tried again, and voila !

Both displays work correctly now.
Have a look at the photo.
Tip in case someone likes to make a photograph of his display: dim it a lot or else your camera has trouble focussing, set it to 20h or less (i used 08h).

I thought the envelope said worst class mail.