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1  Development / Other Hardware Development / Re: Arduino Uno buck converter shield on: January 23, 2014, 11:51:19 pm
Estimating losses by component
2  Development / Other Hardware Development / Re: Arduino Uno buck converter shield on: January 18, 2014, 02:38:09 pm
Prototype 20A converter, in progress.  Still waiting on a couple of components.  This costs $30.  If it works as expected, I'm going to order parts for a bunch of them.

I'd rather have Arduino shields.  But it looks like there isn't enough interest to get that done.
3  Development / Other Hardware Development / Re: Arduino Uno buck converter shield on: January 05, 2014, 04:23:25 pm
Found a nice calculator:

http://schmidt-walter.eit.h-da.de/smps_e/abw_smps_e.html

And a good article on selecting inductors:

http://powerelectronics.com/dc-dc-converters/buck-converter-design-demystified

But everything I've seen indicates that this inductor is oversized.  The calculator above assumes a ripple current ratio of 0.4.  The article recommends 0.3.  For reasonable voltage differences (eg. 26v-6v) at 50kHz, with this design the ratio is only 0.1.  The inductor could easily be replaced with one that could handle higher amperages.
4  Development / Other Hardware Development / Re: Arduino Uno buck converter shield on: January 05, 2014, 02:07:31 am
To back up what I'm thinking with some numbers, I took the equations here and turned them into Google Calc queries.  I filled in the voltages with one of my use cases and upped the amperage to 20A, adding two more capacitors and replacing your inductor with this one.  Seems to work out at around 126 kHz.

https://www.google.com/search?q=2+*+20A+%2F+(8+*+126+kHz+*+20+mV)+in+uF

https://www.google.com/search?q=6+V+*+(+1-+(6+V+%2F+25+V))+%2F+(20+A+*+126+kHz)+in+uH

https://www.google.com/search?q=sqrt((8+*+1980+uF+*+20+mV)+*+6+V+*+(+1+-+(6+V+%2F+25+V))+%2F+(2+*+1.8+uH))+in+A

https://www.google.com/search?q=2+*+20A+%2F+(8+*+1980+uF+*+20+mV)+in+kHz

https://www.google.com/search?q=6+V+*+(+1+-+(6+V+%2F+25+V))+%2F+(20+A+*+1.8+uH)+in+kHz

edit: On closer examination, these equations are based on the minimum inductor size.  So they are somewhat overkill.  See below.
5  Development / Other Hardware Development / Re: Arduino Uno buck converter shield on: January 05, 2014, 12:13:15 am
I'm thinking you should be using smaller inductors and capacitors and a higher frequency.

Have you done any efficiency testing?  Considering the fixed cost of an Arduino shield, supporting 20A would be much more useful even if it's less efficient.
6  Development / Other Hardware Development / Re: Arduino Uno buck converter shield on: January 04, 2014, 08:31:58 pm
So are you going to manufacture these or what?  I would buy about 10 of them as long as you add some heatsinks and they reliably handle large loads.
7  Development / Suggestions for the Arduino Project / X10 Tutorial on: January 27, 2011, 11:46:05 pm
The circuit diagram on the X10 tutorial is incorrect.  It does not work at all.

http://www.arduino.cc/en/Tutorial/X10

This has been discussed before:

http://arduino.cc/forum/index.php/topic,17333.0.html

The problems are as follows:

1) The Zero Crossing and Data lines are swapped.
2) The jack orientation is confusing and should be marked with pin numbers.

Here is a suggested replacement:
http://imagepaste.nullnetwork.net/viewimage.php?id=1689

Also, the only X10 command example shown in the tutorial is the "ALL_LIGHTS_ON" command, which not all modules respond to.  Addressing a single module is not particularly intuitive.  An example of this could be added as well:

// Turns on module A1
myHouse.write(A, UNIT_1, 1);
myHouse.write(A, ON, 1);
8  Forum 2005-2010 (read only) / Bugs & Suggestions / Re: X10 Tutorial on: January 20, 2011, 01:05:31 pm
The circuit diagram on the X10 tutorial is incorrect.  It does not work at all.

http://www.arduino.cc/en/Tutorial/X10

This has been discussed before:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1261353753

The problems are as follows:

1) The Zero Crossing and Data lines are swapped.
2) The jack orientation is confusing and should be marked with pin numbers.

Here is a suggested replacement:
http://imagepaste.nullnetwork.net/viewimage.php?id=1689

Also, the only X10 command example shown in the tutorial is the "ALL_LIGHTS_ON" command, which not all modules respond to.  Addressing a single module is not particularly intuitive.  An example of this should be added as well:

// Turns on module A1
myHouse.write(A, UNIT_1, 1);
myHouse.write(A, ON, 1);
9  Forum 2005-2010 (read only) / Bugs & Suggestions / X10 Tutorial on: January 20, 2011, 01:05:00 pm
Error: Sorry, you are not allowed to post messages containing active links to websites or images before you have posted 1 normal messages.

^^ You have got to be kidding me.
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