So I have left the SDA, SCL and ground leads connected to the i2c port, and ran the Vcc through the regulator to a digital pin. Well the picture below says it all...

Hurray. I had a feeling 3.3v might not be enough which was why I quiried it with Jeremie. Anyway, happy days it's working now. One little thing though which is something Rich mentioned earlier. While testing this on K-9, his ping sensor servo is making a low level buzzing noise. It's not twitching, but sounds like it wants to. Other servos seem ok but they are well covered so it's difficult to hear anything, where as the ping servo is the only one that's exposed.

Why is that do you think?

I mentioned before that I had servo twitching when running in serial mode, hence the change to I2C. That was on a V3 board and I've no idea of the cause or the solution since I2C was better all round.

When I was using it in Melvin the neck servos would go rather mad almost causing damage. Again, I don't know the cause, if it's been solved or if the V4 would even suffer with this issue.

But on I2C the issue was not present at all.

Ok, thanks anyway Rich. Here's a little demo of what I was talking about. Nothing major but I would like to eliminate it if it were possible. I wonder if the guys at EZ HQ might know the cause?

Does it still do that if you move the servo to a new position and back to default? Has it only started since sending commands to an LCD?

When I had a similar issue it was on serial only and would only twitch when new commands were sent via sendserial. I don't believe the serial commands were the issue nor the sendserial control since nobody else has mentioned anything similar and the sabertooth uses serial.

Yeah I still does it after changing the servos position, and it's only started doing this sinse the LCD has been hooked up.

Sorry @Steve when I mentioned you could run the LCD at 3.3V I meant the first LCD you were trying, I had no idea about the second LCD you had.

In terms of the servo jitter, this is usually due to fluctuations in power. The LCD may be causing some voltage ripple on the power line. To remedy this you can try adding a large electrolytic capactitor (maybe in the 220-2200uF range) between VCC and GND on the LCD.

That sounds right, my Devantech LCD was browning out my EZ-B V3 (well when combined with the 2 neck servos). Tony advised adding a reservoir cap to solve it (I moved everything but the LCD to external power which solved it or hid the problem).

Since the Devantech LCD needs +5V it may pay to grab a 5v regulator and hook it direct to the battery, this may bypass the problem (it may not since it's still drawing from the battery but I know you don't like to solder - side note: I haven't forgotten your TIP circuit I just haven't got around to finding it yet).

@Jeremie.

No problem buddy. Probably a bit of a mix up my end too. Anyway all sorted now (pretty much). Thanks for the info about the jitter advice too.

@Rich.

I'll give running it straight off the battery a try tomorrow and let you know if it makes any difference. I'm not adverse to a bit of soldering, but your right, it's not one of my favourite activities. No problem on the TIP circuit dude. No rush.