[TriEmbed] TriEmbed Digest, Vol 7, Issue 16
Charles McClelland
chip at mcclellands.org
Sun Dec 15 22:27:03 CST 2013
Pete,
I think that your idea of a “start to finish” process for making a printed circuit board would be fantastic. My hope is to be ready to start that process in the coming month or two. I hope that in addition to making the circuit smaller and more reliable, i can take out some of the high costs of these “breakout” boards I have been buying from Sparkfun.
For all,
I have taken the advice of the group to heart and moved my trail traffic counter from a Piezo electric sensor to an accelerometer - v4.
Here are some lessons learned in this process and a couple areas where I am very open to suggestions:
- Accelerometers are very cool. I have created sketches to characterize the orientation of my board and I have a number of ideas for other uses - thank you all for the suggestion.
- The inexpensive accelerometers like the MMA7361 suggested in a previous post are all analog. I got it working but saw a few disadvantages primarily that the accelerometer and Arduino need to be close to one another and it tied up three analog lines which needed to be read and summed to create a “trigger” for a knock.
- The accelerometers which have I2C communications are more expensive but they added the interrupt functions I was looking for. I went with the MMA8452 which was the lowest priced but also had a “tap” sensor
- I could not find an inexpensive i2C real time clock which could work on 3.3V. So, I am stuck with the expensive DS3234 on the SPI bus with the SD Card. Any suggestions here? A 3.3V 1307 perhaps?
- Getting sleep to work is still an issue, turns out the at the Arduino will only come out of sleep when the interrupt goes LOW and the accelerometer’s interrupt goes to HIGH when it is triggered. Ugh.
- Unless I want to put an inverter chip on the board, I may be stuck here. Idle mode allows for more options (RISING and HIGH) to trigger the interrupt but it does not save much power and is very flakey on the Pro Mini.
- My next “to do” is to enable batch writes to the SD Card reader and see if I can put the card reader and clock to sleep between events to save power since my Arduino has insomnia
Thanks again for all your help. I was able to finish my v3 board and send off to a friend in Connecticut for field testing so I am making progress.
Chip
On Dec 15, 2013, at 1:00 PM, triembed-request at triembed.org wrote:
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> Today's Topics:
>
> 1. interesting electronics info sources (Pete Soper)
> 2. Short presentation idea for next month, reminder about
> TriEmbed @ Splatspace & call for volunteers (Pete Soper)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 15 Dec 2013 08:57:04 -0500
> From: Pete Soper <pete at soper.us>
> To: triembed at triembed.org
> Subject: [TriEmbed] interesting electronics info sources
> Message-ID: <52ADB530.9000509 at soper.us>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Here's the blog site of the Australian engineer David L. Jones:
>
> http://www.eevblog.com/
>
> Dave is the animated half of a regular podcast called "The Amp Hour" here:
>
> http://www.theamphour.com/
>
> -Pete
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sun, 15 Dec 2013 12:38:35 -0500
> From: Pete Soper <pete at soper.us>
> To: triembed at triembed.org
> Subject: [TriEmbed] Short presentation idea for next month, reminder
> about TriEmbed @ Splatspace & call for volunteers
> Message-ID: <52ADE91B.7010600 at soper.us>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> I just noticed the Sparkfun Eagle file for a size 0805 capacitor defines
> a very much smaller pair of pads than the corresponding file in the
> Adafruit Eagle library. Of all the areas where I would have expected
> everybody's spec to be the same, this would be on the short list. It's
> one more thing that is driving me to the conclusion that making/using my
> own component library isn't just about making up for components that
> have no CAD files. (And another realization close on the heels of this
> one: if I end up having to do custom device description files anyway,
> what is the real advantage of the "relatively vast" set of Eagle files
> out there vs the corresponding ones for KiCad? I think the only
> remaining reason to use Eagle for full custom designs is that there
> never seems to be time to stop and learn KiCad.)
>
> A few nights ago I did an initial, trivial first test of my new reflow
> oven. It worked perfectly, although there was a minor temperature
> excursion during the cool down part of the cycle. As soon as I can
> remember where I put the bag of itsy bitsy FETs I'll try out the oven
> with some Adafruit bare breakout boards that look like this:
> https://www.adafruit.com/products/1230
>
> It wouldn't be within the rules for the TriEmbed meeting room to
> actually run the oven next month ("second Monday" the 13th, meeting room
> TBD), but if folks are interested I could do a quick 20 minute "start to
> finish" tutorial about designing a simple board, getting the PCB made,
> soldering it, etc with, say, 10 minutes for Q&A. Maybe I'll have the
> software for the very powerful Adafruit USB microscope figured out by
> then so it doesn't create weird color distortions. But the distortion
> can be kind of cool. Here's a shot from the recent TriLUG Holiday Demo
> party: http://bitser.net/images/FXOS8700CQ-on-paste-stencil.jpg
>
> If anybody else has an idea for a short presentation please "speak up."
> I say "short" because we seem to be doing well with a format allowing
> plenty of time for folks to network and see and talk about the gizmos
> and gadgets brought to the meeting, current problems, etc. This would
> seem to work very well as a complement to TAR (Triangle Amateur
> Robotics) meetings @ NCSU on 1st Mondays. I think if we get
> announcements and short presentations out done by 8pm at the latest
> we'll preserve this format for TriEmbed meetings.
>
> Don't forget there is a TriEmbed meeting at Splatspace in Durham
> starting at 2pm on Saturday the 21st. Scott Hall is back in mostly
> sunny North Carolina but has a conflict and can't preside over this
> meeting this month but will presumably resume his duties in January. My
> bias for this month's meeting will be the hands-on activities that we
> could do at meetings at TechShop but cannot do at the NCSU meetings,
> namely soldering, drilling holes, the occasional accidental loss of
> magic smoke, etc. If you'd like to join in this fun or just want to
> watch or get help or get in out of the cold, please consider attending.
> Details are on the web page athttp://triembed.org <http://triembed.org>,
> but there are Meetup pages for this meeting and another meeting that
> will overlap this meeting and that might be of interest:
>
> TriEmbed Meeting @ Splatspace December 21st, 2pm
> <http://www.meetup.com/splatspace/events/dhqlpgyrqbcc/?gj=ro2_e&a=ro2_gnl&rv=ro2_e&_af_eid=dhqlpgyrqbcc&_af=event>
>
> DigiFab Meeting @ Splatspace December 21st, 1pm
> <http://www.meetup.com/splatspace/events/154053902/?gj=ro2_e&a=ro2_gnl&rv=ro2_e&_af_eid=154053902&_af=event>
>
> NCSU students and faculty staff: Charlie West did a great job of being
> the official NCSU rep at past TriEmbed meetings, but he needs a break.
> We need one or more students and/or faculty or staff members who can
> simply agree ahead of time to be the official rep(s) for a given meeting
> to satisfy the meeting agreement with the university. There doesn't need
> to be anything specific involved with this beyond attendance of the
> meeting, although helping with pre-meeting communication within the
> university would be very welcome. If you can help with this just drop a
> line to mailto:coordinators at triembed.org and include your name and
> (emergency) phone number and the meeting(s) you can commit to attending.
> There's zero harm in having multiple reps and we can hopefully arrange
> something like signup genius for subsequent meetings. Charlie, Paul
> MacDougal and I thank you in advance for helping with this!
>
> -Pete
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