Re: DIY digital compass: electronics experts needed!
 

Seems quite reasonable. Take a look at the RN-41 BT module, it has a built in antenna and is cheaper at digikey. I haven't looked at the datasheet but they claim a 30mA power draw when transmitting, which is less than you have estimated: http://www.rovingnetworks.com/rn-41.php

While it may be slightly easier to prototype with complete modules like arduino you will have to start again when you move to your final design. If you use one of the common, low end microcontrollers from Microchip (PIC) or Atmel (AVR) you should find very cheap programmers and free development tools exist along with loads of example code for i2c and serial comms. HTH

Re: DIY digital compass: electronics experts needed!
 

I think meant to put down the rn-21 actually because physical integration looked easier. It still needs an external antenna according to the DS. I think I pulled 100mA off the datasheet somewhere but maybe it was the wrong one, thanks for pointing that out.


The arduino has the same chip I picked out, the ATmega328. In fact given it's creative commons, starting with an arduino schematic and adding bluetooth / magnetometer to it may be the best solution.

The one thing which is different from board to proto is the bluetooth module, and I am unsure that is a big deal. In fact I think for prototyping it may be better to use what was used with the n900 push http://blogs.nokia.com/pushn900/wp-c..._guidev1.0.pdf

It is going to be in the sheet but not in the prototyping total.

I am going to update the original sheet. I would have used a smaller battery but there is nothing on sparkfun between 100mAh and 1100mAh right now.

Re: DIY digital compass: electronics experts needed!
 

So, do you think we could get money from Nokia to build what they should have put in in the first place? :P

Of course push n900 is for flashy, not for "I want to get navigation directions when I'm walking and have to stop at a crosswalk" which I see as being the first basic app.

Re: DIY digital compass: electronics experts needed!
 

Well, if that's the main goal....I think I just solved your problem!

Behold the latest in high-tech navigation gadgetry:

http://www.dealextreme.com/details.dx/sku.8388

(since satire doesn't come across in writing...please note this is intended to be VERY tongue-in-cheek)

Re: DIY digital compass: electronics experts needed!
 

I know someone who lost several job interviews before he got a GPS due to showing up hours later, and still needs a GPS for routes he has used dozens of times ... a standalone compass would not help him much. :)

Re: DIY digital compass: electronics experts needed!
 

Feel free to take this as a joke-post too, but...

With an old-fashioned compass, I guess one could build a contraption that would hold the compass in front of one of the cameras and use image recognition to get the bearing...

Re: DIY digital compass: electronics experts needed!
 

Well, I wasn't suggesting that the compass would replace the GPS..rather the bolt-on electronic compass that is being proposed in this thread ;)

Re: DIY digital compass: electronics experts needed!
 

I think it would take him at least 30 seconds to reorient himself every time he stopped. :)

Of course this might be a more interesting way of using the compass:

http://www.exothermia.net/monkeys_an...aptic-compass/

Image processing an analog compass would work if the compass is at a known orientation, but would be a hassle to use.

Re: DIY digital compass: electronics experts needed!
 

Well, lucky for your friend the N900 is also a phone so he can call a taxi rather than getting lost :p

Re: DIY digital compass: electronics experts needed!
 

The other thing being, now I can just listen to the robot voice tell me where to go on the headphones and not have to pull out the n900 at all :)