http://ghonis2.ho8.com/rebelmod450d16c.html

The pictures on that page are impressive - I hope you achieve something similar!

Q: why do you want to cool the camera so much ? special effects? sensitivity? ...

Sometimes when you are doing long exposures (really long) you get extra sensor noise from the heat that is generated from the process of capturing the image. Astrophotographers come across this problem quite a lot I believe, so maybe geoland is doing something similar.

Good job with the board in the photo, it looks really slick.

If I understand you correctly, perhaps it would be worth quickly knocking together an FTDI breakout board of your own, and adding the appropriate holes to connect the chip to the emasculated USB cable.

It shouldn't be too hard to solder that chip with a bit of solder paste and an iron and you solve the problem of having to somehow thread a connector or having to solder the wires to the small connector pads - much more mechanically reliable.

What's the USB used for - just for programming or for control etc?

To the original poster - http://jmsarduino.blogspot.com/2009/05/click-for-press-and-hold-for-b.html

To get a rough idea of current usage you could hook up a multimeter in ammeter mode.

I like the option to choose between 3v3 and 5v, but I would be worried about accidentally changing the switch to the wrong setting and breaking something. Any chance of a jumper? Or a few holes to put pins for jumpers?

From the looks of the schematicon the SparkFun site you should use the two TX lines for the level conversion, and ignore the RX lines. Connect the 3v3 to the LV side, and the 5v to the HV side.

If this doesn't work, then there's something else wrong with the setup or the code.

We’ve made some minor additions to the Arduino connectors to make them more flexible.

Does that mean they've fixed the pin spacing?

Always connect the grounds together, otherwise nothing will work properly.

To use this method, connect two appropriate MOSFETs (maybe a 2N7000?) in-line with the SDA and SCL lines, with their gate pins tied to 3v3. The source side should be towards the high voltage, the drain side to the 'high' 5v voltage.

As for using both 5v and 3v3 from the Arduino at the same time, yes you can, not a problem. A large breadboard which has the split power rails might be useful for this to help separate.

If you want to stick with the logic level converter, what's the part number?

Edit: If anyone can't be bothered to download the PDF, here is the circuit diagram. There is a textual description in the PDF which might be useful.

Check page 43 of this PDF (i2c spec).

Does that help with the problem?

Link courtesy of this page.

I was under the impression that i2c didn't require a voltage level converter as it is the pull-ups that provide the high voltage, and the SDA/SCL pins only connect the line to ground when required. Just use the 3v3 supply for the pull-ups, which I think are included on the board?

Could you not just use the 555 timer in the standard astable configuration?

Then just link up the LEDs so they light alternately as in the attachment, presuming that is what you are after.

Would it not make more sense to simply install a mobile-device-friendly theme as an option for users to choose?

Doesn't require any special software.

It might be that the leads on the part are too fine a pitch for the PCB fab service you have selected, and there might be issues when making the boards.

Eagle should have one. Look in the Atmel library for the Mega8 part.