New Probes Design

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OLD 2006/7 probe specifications: (Elsaify)

• Probe Sensors measure [Pressure, temperature, 3D tilt + polar coordinate N/S (magnetic detector), resistance, strain, Humidity (water detector), light detector, battery voltage]

• Probes wake up from sleep mode for few times per day according to remotely reprogrammable schedule (for example 6, 12, 24, 48 times per day ) to record sensor data and store it in the probe memory

• Each probe should be able to store at least 5000 reading of sensors data (about 2 years when recording 6 times a day)

• Low power, probe battery life time at least 5 years theoretically

• The probe sensor data are sent to the base station daily

• Ability to remotely change the probe firmware

• Wireless ad-hoc networking for hopping the data between probes to the base station

• Retrieve all recorded data and network communication from lost probes when they join the network again even after very long time and also the ability to add more probes later to the system

• smaller in size than last version

• RF communication between probes and to the base station has a larger range, using 174MHz with more radio power than the previous version, (uses Gang's home made tuned antenna) 173MHz radio unit

Probe sensors resolution and ranges: (Elsaify)

Temperature: resolution: 0.03 C º, ranges: -40 to +150 Cº 14bit

Pressure: resolution: 0.5 psi, range 0 – 100 psi 8bit

Strain: resolution: range 0 – 1023 10 bit

Resistance: resolution: resolution 30K, range 30K – 30M 10 bit

Heading: resolution 1º, range 0 – 360 9 bit

Pitch: resolution 1º, range -90 to +90 8 bit

Roll: resolution 1º, range -90 to +90 8 bit

Light reflection: range 0 – 1023 10 bit

Humidity: resolution 1%, range 1 – 100 % 7 bit

Battery: resolution 50 mV 10 bit

+ 2 bits Flags

12 byte data + date 2 bytes + time 2 bytes = 16 byte per reading

New probe parts list: (Elsaify)

Microcontroller :Microchip PIC18LF8722

Crystal :10.0MHz

RTC : DS3231SN , (available 30) (15 available)

Transceivers modules support 173-174 MHz: Radiometrix TX1H (BiM1-173.250-10), 173.250MHz, 100mw, (got 30)

Serial RS232: MAX3319E

RS232 Serial Hub:MAX205E ,MAX235


Temperature: ADT7301ARMZ

3D tilt/ Polar coordinate N: 3-Axis Compass Sensor Set Honeywell HMC1055

Humidity: sensirion SHT75

Pressure: Honeywell 24PCGFM6G 250 psig

Water resistance: own made bridge to measure from 30K to 30M ohms

Strain: (stress) (aluminum), 120Ω, 2.1 gauge factor

Light detector: TSL251R, Photodiode IPL 10020 BW

White Light LED for reflectance measurements (Rapid 55-1542 NSPW510BS) 30mA (100 pulse) 3.6V (4 max) Use 330 Ohm for 6mA pulse of > 20ms

Amplifiers and buffers and transistors:




Power supply IC: MAX1672EEE

Power control ICs:



Batteries: three SL-360/P, AXIAL Battery , from SONNENSCHEIN, AA, , 3.6V, ,2.3Ah

Diodes: MBRS130LT3 Schottky

Leds (for debugging, and turned off before deploying): 6 LEDs: Vbat in, VCC Power, TX, RX, Sensor Power, BiM1 power


Tantalum: 0.1Ω ESR, for power supply Ceramic: tolerance 5-10%, temp -55 to 85, 30ppm

Resistors: tolerance 0.1%, temp coeff

Coils/ Inductors: 10 uH for MAX1672.


Radiometrix BiM1 potting The test results are disappointing. The potting epoxy degrades the performance of the the RF module. Almost 80-90% of the RF power was lost. The potting of antenna has much worse result.- GZ

Light Test with Ice and Till It depends on the relative positions of the LED and the photo receiver. When the LED is very close to the medium surface (ice or till), normally the voltage read from the photo receiver is 140mV higher in the ice than in the till. -GZ

White LED was better than green. Swapped to that now. Short on time with high current probably needed.