TEMPERATURE SENSORS

DESCRIPTION

The temperature sensors use RF 433MHz transmission, up to 6 can be installed.
The temperatures measured with a DS1721 from Maxim (DALLAS Semi Conductor) are in the range -55°C to +125°C.
The power is done with 2 batteries 1V2 which can be charge through a connector without need of open the box.
The voltage of the batteries is also transmitted to the server, this allows to send an alert in case of low voltage.
The measurement interval is about 7 minutes 40 seconds to 8 minutes (spaced 4s by sensor),
The duration fof the transmission is about 800ms with 156ms at 18mA and 646ms at 43mA, the consumption in idle is 27uA.
This results is (18mA*156ms/3600s = 0.8uA/h + 43mA*644ms/3600s= 7.7uAh) * 7 times by hour + 27uA/h idle = 86.5uA/h.
With 800mAH batteries : (800/0.0865)/24h/365j = 1 year without charging.

Below the bloc diagram, note that the boost 5Vto 12V is there to used the full power of the RF transmitter.

SCHEMATIC

Download here the schematic in PDF format

BILL OF MATERIAL

The bill of material below shows only the components to be placed.

Top side Ref Description Manufacturer / reference U12 IC PIC12F675 SO8 Microchip U13 IC DS1721 SO8 Maxim (DALLAS Semi Conductor) U11 IC MAX1724 SO8 Maxim U7 IC MP3902 SO8 MPS D1,D3 Diode 30V 200mA BAT54T1G SOD123 ON SEMICONDUCTOR L4 inductor 10uH 300mA min 1812 all brand L3 inductor 22uH 600mA min 1812 all brand Q1,Q2 transistor PNP 100mA SOT23 like BC856, BC807 .. all brand Q3 transistor NPN 100mA SOT23 like BC846 all brand C22 Capacitor 10uF 10V X5R 0603 all brand R29,R33,R34,R35,R37 Resistor 220KR 5% 0603 all brand R30 Resistor 10KR 5% 0603 all brand RF MODULE RF Module 433MHz TX433N TX433N by Velleman or other

bottom side Ref Description Manufacturer / reference C23 Capacitor 4.7uF 16V X5R 0603 all brand C28,C26,C29 capacitor 10uF 6V3 or 10V X5R 0603 all brand C24 capacitor 100pF 0603 all brand C25,C27 capacitor 100nF 0603 all brand R26 resistor 510K 1% 0603 all brand R27 resistor 59K 1% 0603 all brand R28 resistor 26.1K 1% 0603 all brand R31,32 resistor 220K 5% 0603 all brand R36 resistor 10K 1% 0603 all brand

PCB

- The board which has 21x28mm dimensions is a part of the PCB F00105 with 100x100mm dimensions.

- So, you need to cut it to get the PCB of the sensor board.

Download the manufacturer files here

ASSEMBLY

Below the assembly, The PCB has components on both sides.

Note that two PCB sensor are include on the PCB F00105, this is the reason why

two assembly are shown.

Assembly :

Picture top view :

Picture bottom view :

Download the top and bottom views here in PDF format     

BOARD PROGRAMMING

The sensor's programming can be done with a Pickit 2 :

STEP 1 : connect the board to the Pickit 2 :

STEP 2 : Launch the software Pickit 2, be sure OSCAL is well recognized

STEP 3 : Program

Below, the zip file containing the binary files (HEX) to flash.

Binary files     

They are named Thermometer_#0_ID0x00.HEX to Thermometer_#5_ID0xA0.HEX, #0 correspond to sensor 1 and #5 to sensor 6.

After programming, you must put a jumper like below, this reduces the consumption in idle from 150uA to 27uA.

KIND OF SENSORS

Three kind of enclosure are possible :

Internal use with external antenna

Internal use with internal antenna

External use with solar cell

MOUNTING AND CABLING SENSOR WITH INTERNAL ANTENNA

Cabling

Inside view

MOUNTING AND CABLING SENSOR WITH EXTERNAL ANTENNA

Cabling

indide view

;MOUNTING AND CABLING EXTERNAL USE SENSOR

Cabling

Inside view

SOFTWARE

Data's transmission is done by radio, by default the sensor is in idle with low consumption (27uA),
It wakes up every 7 minutes 40 seconds to 8 minutes (spaced by 4s by sensor to avoid transmission overlap).
It measures the batteries voltage (duration 32us)
Initialize the temperature IC an read it (duration 156ms)
Then transmit the datas (duration 644ms)
The Radio transmission protocol is propriatary and defined as it :

Below the zip files with the sources to be compile under MPLAB 8.92 or later.

Sources files     

Copyright François Callanquin, December 2014

Contact : fcallbox@free.fr