XBEE Based Wireless I/F Device Onboard Configurable to Analog Temp Probe Or RS232 Electronic Scale

XBEE Based Wireless I/F Device Onboard Configurable to Analog Temp Probe Or RS232 Electronic Scale

Closed - This job posting has been filled and work has been completed.

Job Description

The design is for a XBEE based wireless I/F device which can be configured to convert an analog signal from the temp probe reference device or convert an RS232 digital signal from an electronic scale reference device; power supplied by on card 9V battery. Details on the two reference input devices are given below. Following that;
- Components
- Functions
- System block diagram
- Success criteria
- Deliverables
Wireless Temperature Probe 0 - 100 Deg Celsius
Based on Type J Thermocouple Digital Thermometer Sensor Probe 4" Temperature Controller http://www.ebay.com/itm/Type-J-Thermocouple-Digital-Thermometer-Sensor-Probe-4-Temperature-Controller-/111045750856?pt=LH_DefaultDomain_0&hash=item19dad7b048
The following is a description of the Thermometer Sensor Probe;
Thermocouples work on the principle, that when connected to two different metals across a span with a temperature difference, an electronic circuit is generated. The voltage of the generated circuit changes with variations in temperature in predictable ways. Common thermocouples weld together nickel and chromium (called Type K), copper and constantan (Type T) or iron and constantan (Type J) and place the weld at the very tip of the thermometer probe.
Wireless Scale
Based on http://www.alibaba.com/product-gs/1064450301/Digital_scale_computer_interface.html
Food Scale (or similar and integrated to communications board via scales built in RS232C I/F)
Power Supply: AC or rechargeable battery, Battery 4V/4AH
Rated Load: 3kg~30kg
Accuracy: 1g~10g
Capacity: 3kg,6kg,15kg,30kg
Function: Over-load protection
Pan size: 210*288mm
Based on the following components;
Xbee transceiver Digikey part 602-1275-ND
MAX232 RS-232 <>TTL converter
Other ancillary components as necessary
Functions:
- Weigh scale:
o Transmit weight on receipt of request weight message
- Temperature Probe:
o Transmit temperature on receipt of request temperature message
- General:
o Powered by onboard 9V battery
o 2 sided circuit board
o Follow std design principles i.e. add bypass capacitors to ref signal, analog input, and power connections

System Block Diagram
+-----------+ +-----------+
|Onboard 9V + | |
|Power Supply |Scale |
| | | |
+-----+-----+ +-----+-----+
| |
| |
| |
+-----v-----+ +-----------+ +-----v-----+
| | | | | |
|XBEE Mmodule<-----+Max232 +<----+RS232 Interface
| | | | | |
+-----------+ +-----------+ +-----------+
^
|
|
+-----+-----+
| |
|Temp Probe |
| |
+-----------+
Success criteria:
- Schematics and board layout in Eagle or Vutrax circuit cad
- XBEE transceiver programmable with interface board https://www.sparkfun.com/products/8687
- Onboard configurable between weight, temp sensing, or both functions (jumpers, switches, etc.)
- 2” x 3” double sided circuit board
Deliverables
- Schematics and board layout in Eagle or Vutrax circuit cad

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