I got the parts to populate my battery powered Carambola carrier last week, and today I finally powered it up.

The board (made by seeedstudio's fusion PCB service) just contains two buck regulators, to provide 3.3V and 5V from a 2S LiFe battery, and a header with the same pinout as the standard Carambola carrier board's 0.1 inch header.

I've only populated the 3.3V supply so far.

The Carambola is drawing about 140mA at the battery.

Here are a couple of photographs: https://picasaweb.google.com/1105008541 ... /Carambola

The layout and schematic are here: https://www.dropbox.com/home/Public/Carambola%20Carrier

Thank you to the person who posted the Carambola Eagle footprint.

Tom

Dropbox said:
The Folder "/Public/Carambola Carrier" does not exist.

At that much current draw the Carambola won't last long with that battery. I'm assuming you're going to use that for some kind of RC model or Robot.
In order to save a little power I'd suggest you deactivate the unused Ethernet ports (there's a thread on how to do that).
I've gotten about 1 1/2 hours from my 1100mAh LiPo that way.

Here's a working link: https://www.dropbox.com/sh/8ulx6tmhki3n ... %20Carrier (I think)

Thanks for the tip NaYthan -- yes, I'm going to use it for an RC ship, so I definitely won't need ethernet.

Oh, a ship, that's a new one. I hope you'll add lots of functionality to make it worth using a Carambola (well, actually the Carambola is so cheap that I'm considering using it in every project that can benefit from some kind of wireless interface, but having it inside an RC model promotes an extraordinary feature list).
I wish it was more battery friendly though.
Keep us posted on your M.S. Carambola

Isn't the Carambola a fairly small part of the current draw of a vehicle? I'm expecting the electric motors on my ship to draw something like 700mA, so 140mA for the Carambola isn't too bad. Luckily with ships of a reasonable size weight becomes a non-issue, so I'll have at least 4AH.

My next step is to get i2c going to some AVR IO processors for servo control (steering and ESCs).

Features I'd like to add include:

- Webcam
- Compass and autopilot (just keeping the set heading, not actual position and navigation)
- Telemetry (motor current, battery voltage)
- Lighting and smoke generator control

on later warship models I also want to coordinate turret movements realistically.

Well, assuming your motors run constantly and you use the 1100 mAh battery:

Carambola + Motors together use 840mA, leading to a maximum runtime of 78 minutes.
Motors without Carambola use 700mA, leading to a maximum runtime of 94 minutes.

If you can reduce the current draw of the Carambola to 100mA the combined current draw would be 800mA, leading to a maximum runtime of 82 minutes.
4 minutes of extra runtime for 40mA current saving is not a bad deal, so while the current draw of the Carambola seems fairly small compared to the motors it can still have a significant impact on the runtime (not that 78 minutes wouldn't still be enough for a single charge).

If weight is not an issue you should get at least the >5000 mAh LiPo's from HobbyKing or eBay (they're fairly cheap there). With one 5200mAh battery I can drive my Tank for well above 2 hours (with each of the two motors drawing about 2A plus the rest of the electronics, of course not run continously, but in a normal use case).

But my concern about the Carambolas current draw for battery powered applications wasn't RC related (although right now that's my main application for these boards). Imagine you wanted to create a mobile device (like a PDA, mobile Hot Spot or whatever), then the lack of any power scaling on the Carambola will unfortunately suck dry any reasonable battery in just a couple of hours


EDIT:
I've had great success in attaching a Propeller based microcontroller system to the second serial port of the Carambola. It's 3.3V already, so no level shifting required. Through it my Carambola based tank drone has access to motor control (two motors), servo control (as many as there are free pins on the Propeller), GPS, dual Compass, current monitoring and voltage monitoring (for each Cell individually). The Carambola itself delivers the video feed.

The great thing about the Propeller is that there's a community behind it. Granted, not as big as for the AVR, but very helpful. Also with the Propeller Object Exchange you can download Code that implements most drivers you'll need. You'd only need to code the data processing logic and not have to care much about the low level communication protocols involved (great way to quickly build a new prototype).

What about underclocking the CPU? For your application, you probably don't need 320Mhz. Has anyone tried to underclock the carambola?