Turtle Sense/Phase Two

Phase two is starting up.

People

• User:Dave -- Electrical engineering
• User:Sam -- Project manager / Software
• User:Tom -- Engineering support
• User:Eric -- Fundraising / Community liaison
• User:Chuck -- Documentation/fundraising
• VOLUNTEER NEEDED -- Web Design and data display

Overview

The plan for Phase Two is to create about 30 boards for installation in the Outer Banks of North Carolina during the Spring and Summer of 2013. The design is based around creating a sandwich of off the shelf boards (one for low power computing and the other for telemetry). Both of these boards will be plugged into headers on a custom mother board we will design. Every thing on the mother board will have through-hole components to make the board as easy as possible to assemble. The idea is to have a set of instructions on this web-site which will allow anyone who can do basic soldering to order the parts (from the manufacturers) and quickly assemble a board, install it on a nest (with approval of the appropriate agencies) to communicate with a website we will construct to monitor and collect the data from the nests.

Engineering

Components

Turtle egg sensor

This would be unchanged from the phase one design that uses plastic ping-pong balls (not good ping-pong balls, but cheap plastic knock offs) and a temperature/motion sensor pre-installed on a small circuit board (Qty 1 Price=$14.95). Assembly involves cutting a small slot in a ball, putting in some silicone caulk, inserting a sensor board attached to a cable into the caulk, and then filling the rest of the ball with caulk. A ball cut in half covers the slot and makes a thorough seal with the silicone.

Mother board

The mother board will be custom made and have two rows of headers for attaching a pre-fabricated processing board based on the TI MSP430 CPU and another two rows of headers for prefabricated telemetry boards. Each of these boards already have their own power regulators built in, but there needs to be an additional power regulator for the telemetry board on the mother board to regulate battery power down to the voltage required by the telemetry board. The regulator, headers, and other components on the mother board will all be through hole components that can be easily soldered to the mother board making it easy to assemble for anyone with basic electronic soldering experience (think hacker space events and high schoolers). The mother board will be approximately 2.5 inches by 1.9 inches. We can purchase 3 boards for $51 plus shipping. We might be able to cut each board in half (full size is 2.5 inches by 3.8 inches). This can be done with a hack saw. For larger production runs, we can get the boards pre-cut to the optimum dimensions and the price would be a little less per unit (about $7 each for a run of 30). Other components on the board should total under $15. Total cost per board $20 to $25 each.

Processing board

We've found a pre-assembled processing board made by Oilmex Ltd, that is based on the the ultra-low-power MSP430FR5739 processor by Texas Instruments. The MSP430-HFR5739 board has all the essential components needed. There is a header on the board for easy programming, and a connector which we can use for plugging in the cable to the turtle egg sensor. The MSP430FR5739 CPU has 16K Bytes program FRAM, 1024 Bytes SRAM, 10-bit A/D converter, 16-channel comparator with voltage reference generation and hysteresis capabilities which we can use for monitoring the battery voltage, three enhanced serial channels (capable of I2C, SPI, or UART protocols), hardware multiplier, real-time clock, five 16-bit timers, and more. The board also has power supply filtering capacitor and a 3.3V voltage regulator. There are two rows of headers for each pin of the microprocessor which we will use to plug this board into the mother board. The dimension of the board is 2.15" × 1.10". The boards cost only $19.53 qty 1 and are available from microcontrollershop.com.

Telemetry board

We plan on using plug in Terminus boards made by Janus. The Janus GSM865CF v1.1 GSM/GPRS Modem with GPS works with AT&T and T-mobile. For Verizon we can use the CDMA864CF v3.0. The boards are interchangeable and will plug into our motherboard. The cost is roughly $140 qty 1 and are from the manufacturer, Janus.

Other components

The only other components necessary are the cable and connector for the turtle egg sensor (a couple of bucks at most), an antenna for the telemetry board (GSM and GPS), which costs about $20 (perhaps more if reception is a problem). The units should operate for roughly 4 months running on 4 or 8 low self-discharge NiMH Batteries. The batteries and holder (TBD) which should cost less than $25. Also, anyone creating these devices will need the hardware necessary for programming the microprocessor (more about this later).

The cost of the total project should be around $200 to $250 per unit after start up expenses, and not counting telephony charges.