Overview

When shipping temperature sensitive products, it may be necessary to monitor the temperature and time exposure to indicate product spoilage. Current devices range from limited mechanical devices to more expensive electrical ones.

Although relatively inexpensive, the mechanical devices rely on a fluid state change and are ruined once tripped. The electronic devices are more durable and accurate but are somewhat expensive.

This device can complete on price with the mechanical devices while delivering some of the features of the more expensive electrical ones.

Current Products

Complete Unit Exploded Back Exploded Front

Operation

This simple device has port that connects eZ430-F2013 Development Tool main board. This way it can be field programmable like the target board. The user can set a high and low temperature range and a time limit for each. While programming, a jumper allows the device to be powered by the eZ430-F2013 Development Tool or, if removed, powered by the on-board battery.

A miniature pushbutton switch resets the device. Upon reset, the device is in its initial state. Every 5 seconds, the Power LED flashes briefly.

Once per minute, it takes a reading from the TMP100 temperature sensor. All three LED’s flash briefly in sequence to indicate a read. If the temperature is above or below the set temperature range, it will count the minutes that the device stays out of range until a threshold time is exceeded or the temperature returns within the limits. If it returns within range, the counter is reset. If not, the High and/or Low LED indicator(s) will flash at the same rate as the Power LED indicating that the shipment may be in jeopardy. Once the device has been triggered, the reset switch will ready it for the next shipment.

A small enclosure was designed for this project. In order to do this, all parts were drawn in AutoCAD 3D. The enclosure’s bottom locks the PC board in place for easy assembly. Using a small screwdriver, the bottom can be removed for battery change or reprogramming.

The listing provides a C code sample using the I2C protocol with the TMP100. In addition, the sample includes use of dual timers to trigger the 5 and 60 second interrupts.

Note: Software from www.expresspcb.com was used for schematic and PC board design. Several prototype boards were produced for about $60.

Schematic

Bill of Materials

B1 3V Mouser 534-3002 & 658-CR2032
C1 100n Mouser 581-0603YC104JAZ2A
C2 1n Mouser 581-06031C102JAZ2A
D1 PWR-GREEN Mouser 604-AM23SGC-F
D2 LOW-YELLOW Mouser 604-AM23SYC-F
D3 HIGH-RED Mouser 604-AM23EC-F
J1 IO Mouser 575-501201
JP1 SHUNT Mouser 538-22-28-4360
R1 330 Mouser 71-CRCW0402-330-E3
R2 330 Mouser 71-CRCW0402-330-E3
R3 330 Mouser 71-CRCW0402-330-E3
R4 47K Mouser 71-CRCW0402-47K-E3
SW1 SWITCH Mouser 506-FSM2JSMA
U1 MSP430F2013 Mouser 595-MSP430F2013IPW
U2 TMP100 Mouser 595-TMP100NA/250
X1 33KHz Mouser 695-CM200S-327KF-U
Top Case ABS Plastic
Bottom Case ABS Plastic

Project Files

C Program Code & Source Material - Temperature Sensor

PC Board Component Layout

Front

Back

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