[TriEmbed] Giving this Surface Mount Thing a Try - Transistor Help Needed

Fri Mar 21 20:19:31 CDT 2014

How big is your code?  If it is 8K or larger, you will have to go through
the pain of reducing it.  If it is much larger, you may not ever succeed.

If you decide to try the Tiny, I can help with examples of using pin change
interrupt.

---> Paul

From: Charles McClelland [mailto:chip at mcclellands.org] 
Sent: Friday, March 21, 2014 5:41 PM
To: The MacDougals
Cc: Glen Smith; TriEmbed Discussion
Subject: Re: [TriEmbed] Giving this Surface Mount Thing a Try - Transistor
Help Needed

Paul, 

I was planning on using the ATMEGA328 as that is what is on the Arduino Pro
Mini board.  Now that you mention it, I guess I could use the ATTiny84.  I
did try to use the pin change interrupt on the ATTiny84 but was not able to
get it to awake form sleep except with a LOW signal.  I wonder if that may
be a limitation of the Sleep library I am using.  

Back to the chip choice.  Please let me know if I am missing anything on
this list of pros and cons:

ATTiny84

            - Pros: Cost, size, number of external components required

            - Cons: This board uses both SPI and I2C so would need to learn
how to "bit bang"

            - Don't know - power / battery life?

ATMEGA328

            - Pros: More pins for inputs and indicators (thinking about
adding some more controls)

            - Cons: Cost, size, needs an external crystal

The easy choice would be to stay with the ATMEGA328 as I have the sketch
working and have developed and field tested the design over the past 6
months.  But, am I missing something that could sway me toward the Tiny?

Thanks,

Chip

On Mar 21, 2014, at 4:42 PM, The MacDougals <paulmacd at acm.org> wrote:

Since you are collapsing all of the breakout boards, what are your plans for
the processor?

As I recall, the reason for having to invert the signal was due to a
limitation on the external

interrupt pin of the processor.  Newer Atmel chips have pin change
interrupts on all pins

and can handle either edge.  So, if you go with an ATTiny 84 or similar, you
don't need the transistor.

---> Paul

From: TriEmbed [mailto:triembed-bounces at triembed.org] On Behalf Of Charles
McClelland
Sent: Friday, March 21, 2014 3:47 PM
To: Glen Smith
Cc: TriEmbed Discussion
Subject: Re: [TriEmbed] Giving this Surface Mount Thing a Try - Transistor
Help Needed

Glen, 

I am using EAGLE - it allows you to set the names so I guess I have to take
responsibility  - Resister Base (RB)  - I am learning so if there is a
better naming convention I should be using, I would be open to it.

Thanks,

Chip

On Mar 21, 2014, at 1:29 PM, Glen Smith < <mailto:mrglenasmith at gmail.com>
mrglenasmith at gmail.com> wrote:

Charles,

As Bill said, there are single gate IC's to do what you want, a quick glance
indicates the cheapest (in one'sie two'sie quantities) is $0.33. But there
are 2222 transistors available in SOT-23 packages: Jameco has them here: 

<http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?l
angId=-1&storeId=10001&catalogId=10001&freeText=2222%20sot-23&search_type=ja
mecoall>
http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?la
ngId=-1&storeId=10001&catalogId=10001&freeText=2222%20sot-23&search_type=jam
ecoall 
qty 10 available at $0.09 each. Or, to keep the comparison, DigiKey has them
here: 

<http://www.digikey.com/product-search/en?pv7=2&FV=142c0042&k=MMBT2222A&mnon
ly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25>
http://www.digikey.com/product-search/en?pv7=2&FV=142c0042&k=MMBT2222A&mnonl
y=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 
(for one'sie two'sie quantities) at $0.18 each.

It has been far too long since I did transistor circuit design to tell you
whether what you have will do the inversion you want, but you can hook it up
on a breadboard with your discrete's and see how it works.

Since I'm sending this note anyway, is there a reason why you chose RA, RB
RC designations? It took me a few minutes looking at your circuit to figure
out that it was a designator rather than a ResistorCapacitor (RC) network.
Maybe it is just what I'm used to working with. Which layout tool are you
using? KiCAD or Eagle? If one of them forces me to use RA, RB, RC - I think
I will use the other.

Glen

On Fri, Mar 21, 2014 at 12:46 PM, Bill Farrow <
<mailto:bill at arrowsreach.com> bill at arrowsreach.com> wrote:

Charles,

There are single logic gate ICs in surface mount which should do what you
want. Here's my quick digikey search.

<http://www.digikey.com/product-search/en?pv247=24&pv64=1&pv667=1&pv69=3&FV=
fff40027%2Cfff8019d&k=single+gate&mnonly=0&newproducts=0&ColumnSort=0&page=1
&quantity=0&ptm=0&fid=0&pageSize=25>
http://www.digikey.com/product-search/en?pv247=24&pv64=1&pv667=1&pv69=3&FV=f
ff40027%2Cfff8019d&k=single+gate&mnonly=0&newproducts=0&ColumnSort=0&page=1&
quantity=0&ptm=0&fid=0&pageSize=25

Bill

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