[TriEmbed] Trail Traffic Counter Update and Lessons Learned

Charles McClelland chip at mcclellands.org
Tue Nov 26 15:48:56 CST 2013


Bill, 

Wow, I did not know that there were such low-cost options for the accelerometer.  I need to take a look at that.  

I have field tested this counter a few times now and I believe the most flexible packaging is to put the board in a water proof box that can be buried and the sensor at the end of a 6’ wire so the sensor could be put into the tread way or attached to the underside of a board, log or bridge.  I have already lost one sensor to the process of attaching / detaching the sensor to an object in the tread way and that was motivating me to make the sensor cheap and easily replaceable.

I am not sure I made the right choice in moving from the DS1307 which was certainly easier to work with.  I switched for two reasons - 1) all the micro SD options I saw were SPI so, I had to dedicate four wires to that already.  2) For some reason, the I2C leads (A4 and A5) are not on the periphery of the Pro Mini board and are not convenient to connect.   Thinking ahead, the DS3234 also seemed to be easier to move to a PCB as it does not require any external components other than a battery.  That said, I will take another look.

Thanks for your thoughts

Chip


On Nov 26, 2013, at 4:02 PM, Bill Farrow <bill at arrowsreach.com> wrote:

> Hi Chip,
> I was suggesting the use of an accelerometer at the last meeting. Some
> of these devices have are programmable to wake up the microcontroller
> when there is a knock/tap. I was thinking that the entire board,
> including the accelerometer, could be built into a strip of wood or
> plastic that the riders would go over.
> 
> The MMA7361 accelerometer dev board is available on ebay for under $3.
> For production, these SMD chips are around $1 each.
> 
> Why did you switch from the DS1307 RTC ? Was it just to consolidate
> buses ? I would reconsider this if I were you.
> 
> Bill




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