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31  Forum 2005-2010 (read only) / Troubleshooting / Re: 5v Wall Wart to Arduino's Vcc and Gnd on: June 16, 2008, 01:31:05 pm
Oops, I meant the Vin pin (there's no Vcc on my Diecimila). But it sounds like it will get internally regulated on the Arduino board anyway. Thanks!

Will there be any issue with powering the Arduino from 5 volts? The specs call for a 6+ volt supply...
32  Forum 2005-2010 (read only) / Troubleshooting / 5v Wall Wart to Arduino's Vcc and Gnd on: June 16, 2008, 12:41:49 pm
Do I need a 5v regulator in between the wall wart and the Arduino's Vcc and Gnd? Thanks!
33  Forum 2005-2010 (read only) / Interfacing / Read battery level on: January 04, 2008, 03:31:16 pm
Does anyone know how to make Arduino aware of its battery level? For example, before the Arduino dies completely, I'd like to have it blink a LED to alert the user that the battery is dangerously low on charge. Maybe by somehow regulating the voltage and passing it to an analog input? Thanks for any help.
34  Forum 2005-2010 (read only) / Interfacing / Re: RGB LEDs and color balance? on: January 07, 2008, 04:25:43 pm
I haven't tried getting a better white, and I don't think I will, but my approach would be to start with all three at 255, then subtract a little as needed to make it look better. For example, if values of 255-255-255 are "too red," I might try 240-255-255.
35  Forum 2005-2010 (read only) / Interfacing / Re: RGB LEDs and color balance? on: January 07, 2008, 03:24:30 pm
I have the Sparkfun triple-LEDs, and I've been playing around with them for a while (messing with Arduino and pwm and stuff). Overall, I'm quite happy with them.

I've made no attempt at perfecting their white-balance, but they definitely don't output a perfect white when all on. On the other hand, any two on produces great cyan, magenta, and yellow. Yellow is not quite as good as the cyan and magenta, but still fine IMHO. Red, green, or blue by itself is perfectly color-accurate, of course.

When viewed from the side, the LED's color is good, but when the LED is pointed at the wall or something, you can distinctly see three circles of red, blue, and green (I think that's the actual order).

If I have time, I'll try different values to subtract from each color to see if I can get a better white.
36  Forum 2005-2010 (read only) / Interfacing / Re: XBee Pro and Arduino on: January 07, 2008, 03:48:30 pm
AFAIK, you can just swap an XBee for an XBee Pro, because they're pin-compatible. But don't take my word for it!

If you're willing to do some soldering, I found a supplier for an XBee Shield Kit without the XBee. At $12, it's *much* cheaper than buying the preassembled shield + XBee from SparkFun or something. You can find it here: http://www.nkcelectronics.com/freeduino-arduino-xbee-shield-kit.html

If you're set on going Pro, you might want to wait until MaxStream releases a Series 2 version of the XBee Pro, which will include a new chipset with true mesh networking capabilities and a very similar command set (I think). Here's the MaxStream website: http://www.maxstream.net/

Are you going to use an XBee with your computer, too? You might be interested in this: http://tinyurl.com/2uo3fp

Hope that helps!  smiley
37  Forum 2005-2010 (read only) / Interfacing / Re: Help with battery monitor circuit on: January 08, 2008, 08:30:09 pm
Thank you all for your advice!  :smiley

One last thing-- some of these examples measure voltage, and some measure current. Which would be more important in regards to battery life and warning of power starvation, for lack of a better term?
38  Forum 2005-2010 (read only) / Interfacing / Re: Help with battery monitor circuit on: January 07, 2008, 11:13:01 pm
Thanks for the reply!

I *did* get the datasheet for the 8211, but I'm still having trouble understanding it. There are multiple examples, and all the circuit design terms confuse me   smiley-sad

I also found some Maxim "fuel gauge" battery monitors, which give estimated remaining charge in % and mAh. They looked perfect for what I want, but they're only available in surface-mount packages, not DIPs like the MAX8211.

The voltage divider and analog-in approach seems more desirable, because it's an analog reading, not just a 1 or 0. I would probably have the Arduino-powered device send it's battery voltage via serial to a computer, which would log the voltages until the thing dies (one-time calibration). Then, that value would help the Arduino know when it is going to run out of power.

kg4wsv, does that sound good? I'll look into the voltage-divider thing. Thanks!
39  Forum 2005-2010 (read only) / Interfacing / Re: Help with battery monitor circuit on: January 07, 2008, 09:47:12 pm
That's great and all, but I need to know things like manufacturers or part numbers!

Does anyone know how to design circuits for the MAX8211?
40  Forum 2005-2010 (read only) / Interfacing / Re: Help with battery monitor circuit on: January 07, 2008, 04:52:37 pm
What do you mean? Is an analog analyzer a part/circuit or something that would allow me to read the voltage from an analog input?
41  Forum 2005-2010 (read only) / Interfacing / Help with battery monitor circuit on: January 07, 2008, 03:40:20 pm
Hi,

First off, I just want to let you know that I'm no electronics engineer, and that's why I'm posting this. Here's what I want do do:

I would like to be able to monitor the voltage of a battery pack connected to my Arduino Diecimila when it's not powered via USB. That way, it could alert me or go to sleep or something when it is about to run out of juice.

After searching around, I've found two possible options:

The former, with a couple lines of Arduino code, would give me a percentage of battery remaining (I think) (example: "Warning: battery is at 25% of 9V").

The latter, with the correct circuit, could be read with a digital input (high for low battery, low for battery ok). The problem is, I don't know how to design a correct circuit for it.

Any help would be greatly appreciated. Which approach would be better, and how would I go about implementing it in hardware? Thanks in advance!
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