Post code.

.... and pic 

Moral of the story: hook things up exactly as the recipe says, before you change things for local requirements.

Wait.... disregard that comment... the instructions tell you to power the servo from the Arduino's 5V pin....don't do that...

Hi gang....

I went to get a DS1307 RTC and the required 32.768kHz 12.5pF crystal.

They didn't have a 1307, so I took a 1302 instead.... I know the interfacing is different and have found a library for it.

BUT.... only when I got home did I realise that the 1302 requires a 32.768kHz crystal of 6pF, but I had purchased one of 12.5pF.

Is that likely to be a problem? (Confession: I don't even know what it means for a crystal to have a capacitance, although I do know what a capacitor is...   )

TIA,

Jim

You should check the voltage at the shield output.

Check the datasheet for the L298 chip: it loses a minimum of 1.8V, rising to a loss of 3.2V at 1A and 4.9V at 2A. Your 7.4V battery will therefore at best be giving 5.6 which would be ok for the 6V motor I guess BUT it depends what the no load current of the motors are.

If you have an ammeter, hook the motor to the battery and measure the no load current... double that for two motors, and if you're up in the vicinity of 1 amp you may well be shy of voltage at the motors. (Edit... or check the motor datasheet) (More edit... and of course the voltage loss will increase when the motor is under load and requires more current.)

Sounds like a power issue.
Do you use the 5V pin of the Arduino to power the servos ?
The 5V pin can not supply enough current, not even for one servo.
You need a seperate power supply of 4.8 to 6V for the servos.

OP already said this....

Also the servos are powered separately. (not via arduino board.)

About half-way down this page you can see how to switch a load with a digital pin and an NPN:

Load is "above" the NPN, between V+ and collector
Arduino digital i/o pin is to base, thru a resistor
Emitter is to ground.

Just remember though that the internal resistor is a pull-up, while your original post spoke of pull-down, so the high / low logic is reversed when you go the internal route.

Always take the wires from two opposite corners then it doesn't matter how much rotation is on the switch it is still the correct two wires.

Good thinking, Batman

Classic case for using Serial to debug, with an "I'm here" print from inside an if, and a "valX=...." at any time you would expect a variable to change.

That code looks ok to me- I don't see anything obviously wrong.

So two suggestions:

Enable Serial and add some serial.print lines so you can (for example) see the changes in val2 so you can see it's doing anything
Swop the wiring for the pots so you can see if they both actually work, ditto for the servos.

The pins on those 4-pin buttons confuse the carp out of me- could never remember which pins were always joined, and which are switched.

Anyone using them may find the attached pic helpful......

discover why using pin 4 to control a servo will get you into trouble.

And why is that? Just in case I missed that memo, I tried it and it works fine...

--->rather from its own supply with the ground from the servo linked to the Arduino ground.
This is why I hesitated to connect servo to other supply. I read your line in a book but don't quite understand it.
I have attached my board, could you please check my comment in there is correct way of connecting the breadboard for servo power? Many thanks in advance.

I connect this servo to arduino board's 5v slot, do you mean that slot does not have enough power to run this servo? If so, why does it just turn randomly (back and forth)?

Ok, so it seems you have connected the servo to the Arduino for power.... all sorts of weird behaviour seems to happen when that's how servos are hooked up. And of course it may damage the Arduino...

Have a look at the pic I've attached... note that the Arduino is powered in whatever way suits you, the servo has its own power, and the servo ground is connected to the Arduino ground. Yellow to Arduino i/o pin, of course.

But I don't think that's the OP's problem: sounds to me like it's running amok (ok, he says moving in a pattern), not just finding its centre.

Re my comment on setting the servo pin as output: would that have any effect?

You don't need this line:

Code:

pinMode(LEFTFRONTSERVOPIN, OUTPUT);     //sets the left servo signal pin to output 

.... but I have no idea if it being there will make the servo do what you describe.

How is it powered?- always better not to have it powered from the Arduino; rather from its own supply with the ground from the servo linked to the Arduino ground.