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121  Using Arduino / General Electronics / Re: 5 Ohm NTC to Arduino ADC? on: January 08, 2013, 04:31:31 pm
Your question was "What bias resistor should I use?" 

Put together a spreadsheet like mine and play around with the bias resistor value until you have a resolution you are happy with.

In terms of connecting it to the Arduino that is easy.

5V---------bias Resistor--Thermistor----------Ground
                                   |
                                   |
                                   |
                          Arduino ADC PIN
122  Using Arduino / General Electronics / Re: 5 Ohm NTC to Arduino ADC? on: January 08, 2013, 03:09:53 pm
I remember when I was working through a problem like this a while back, I set up a spreadsheet like the one that is attached and then played around with the resistor values until I got the resolution that I was happy with.  Maybe this will give you some ideas on how to set the problem up in a spreadsheet for yourself.
123  Using Arduino / General Electronics / Re: 5 Ohm NTC to Arduino ADC? on: January 08, 2013, 11:03:59 am
Where do you see on the datasheet the beta value of 3150.....or did you get that through your own empirical measurements?
124  Using Arduino / General Electronics / Re: 5 Ohm NTC to Arduino ADC? on: January 08, 2013, 10:32:53 am
Can you link to a datasheet for the particular thermistor?
125  Using Arduino / Project Guidance / Re: Moisture Sensitive Devices - How am I going to take these out for a trial fit? on: January 07, 2013, 09:40:46 pm
Hmmmm......can I do that in a regular oven that I cook in?

As long as the "regular oven" can reasonably accurately control the temperature.  Or, this is an opportunity to invest in a good kitchen thermometer.


Really?  Hey I may go ahead and open them up then.
126  Using Arduino / Project Guidance / Re: Moisture Sensitive Devices - How am I going to take these out for a trial fit? on: January 07, 2013, 09:33:50 pm
Hmmmm......can I do that in a regular oven that I cook in?  Probably not.....I may just have to risk it and place my order for the boards without test fitting them first.
127  Using Arduino / Project Guidance / Moisture Sensitive Devices - How am I going to take these out for a trial fit? on: January 07, 2013, 08:08:23 pm
I got my order from Mouser today for my most recent project and many of the devices came in these pouches:


IMAG0831 by jg1996business, on Flickr

This was my first project where I made the land pattern for most of the parts in Eagle myself.  I would like to test fit the parts on a printout of my board before I get the actual boards made but how can I do that if it says to use them within 168 hours of opening the bag?  It will take 3-4 weeks to get my boards made from iteadstudio.  Has anyone else run into this problem?
128  Using Arduino / General Electronics / Re: What is "ground shift problems"? on: January 07, 2013, 06:57:46 pm
Awesome!  Thanks again everyone!
129  Using Arduino / General Electronics / Re: What is "ground shift problems"? on: January 07, 2013, 06:52:48 pm
Thanks for all of the great replies everyone and I think I understand now.  So I mostly want to avoid a situation where the GND and PGND are sharing a single trace before they reach a ground plane?
130  Using Arduino / General Electronics / What is "ground shift problems"? on: January 07, 2013, 04:40:11 pm
On page 13 of the attached link, under the heading "Synchronous Operation", paragraph two is the sentence "Both grounds must be connected on the PCB at only one point, ideally close to the GND pin."  What does this mean in terms of board layout?  On page 17 is a picture of a recommended board layout which appears to show both GND and PGND connected to the same ground pad that the part's exposed thermal pad is soldered too.  What am I supposed to be avoiding here in terms of PCB layout?

http://www.ti.com/lit/ds/symlink/tps61201.pdf
131  Using Arduino / General Electronics / Re: Understanding a land pattern on: January 06, 2013, 06:20:41 pm
Thanks everyone!  Sometimes I get my perspectives mixed up smiley-confuse
132  Using Arduino / General Electronics / Re: Understanding a land pattern on: January 06, 2013, 12:02:52 pm
At the Top of Page 4 a label  titled "Pin Assignments"...
Quote
DSC and DRC PACKAGE
(TOP VIEW)
and the pins numbered from the left side down in a CCW directiion.

Bob

Ah......that makes sense.  Thanks!
133  Using Arduino / General Electronics / Understanding a land pattern on: January 06, 2013, 09:45:45 am
I am thinking of using the TPS61201 to supply 3.3V to my arduino project and it comes in a SON-10 package.  I am having trouble understanding the land pattern and the pad numbering on the last few pages of this data sheet:

http://www.ti.com/lit/ds/slvs577c/slvs577c.pdf

When I am looking at the page titled "Thermal Pad Mechanical Data" it shows the pin numbering as well as a pin 1 indicator on the thermal pad.  I just can't tell how I am supposed to be looking at it.  Is the drawing from the vantage point of a part that has the pads down on the board and I am looking at it from above, through the part to the pads....or am I looking at it as if the part is flipped upside down on its back and I am looking at the pads from the bottom?  It will make a difference as to how I number the pads in my land pattern.  If it is from the top looking down through the part then pad 1 on my board will either be in the top right or bottom left and if I am looking at it as if it is flipped upside down on its back then pad 1 on my board will either be bottom left or top right.
134  Using Arduino / General Electronics / Re: PCB Routing Tips? on: December 29, 2012, 05:10:16 pm
What would we consider to be non-trivial current as it relates to a .008 wide trace?  You can assume I am using the standard board associated with this service:

http://imall.iteadstudio.com/open-pcb/pcb-prototyping/im120418001.html
135  Using Arduino / General Electronics / Re: PCB Routing Tips? on: December 29, 2012, 02:00:42 pm
At the top of the IC on the left side there's some really fine lines that look like nets that didn't get routed.  It's a good start though!

Ya there is a couple that didn't get routed that I will have to do by hand.  I'm just wondering if the liberal use of vias to make things happen is a bad sign regarding my component placement.
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