Wireless sensor network with IEEE 802.15.4™ 2.4 GHz RF Transceiver MRF24J40
Wireless sensor networks are a relatively new brand of the wireless applications, are used for environmental monitoring, military applications, security devices and more. Here we will try to build a complete wireless sensor network using Microchip devices you can order free, like PIC microcontrollers and the transceiver MRF24J40.
Technical data:
PIC18F4320 Datasheet
MRF24J40 Datasheet
Application Note AP965
Microchip Stack for the ZigBee™ Protocol
If you are an Eagle user, you can find here the layout of a 2-sides pcb and the MRF24J40 footprints for the QFN package:
Download MRF24J40 footprints for Eagle
Download MRF24J40 PCB for Eagle
Download Eagle from Cadsoft.de
In this study we look at the MRF24J40 datasheet to make a PCB antenna for our circuit; but certain quotes doesn't appear in the documentation. Here we try to provide these quotes, after some simulations with the tool used by Microchip's designers: the Ansoft HFSS simulator version 10.
This is the picture from the MRF24J40 datasheet. All dimensions are in milimeters. Note that some values doesn't appear, for search them we will test some dimensions with the HFSS simulator.
The copper layer on a PCB is thin, about 35micron. This is the thickness of the PCB antenna.
Now we can build the complete pcb in two layers to make the transceiver working!
Download the EAGLE library with the PCB antenna for 2.4GHz
Download the complete PCB
Bill of materials (copy of MRF24j40 datasheet):
Quantity |
Component Name |
Reference Description |
Value |
Description |
Vendor |
Vendor # |
Cost |
1 |
CAP3528 |
C1 |
2.2 μF_Tant |
Capacitor TANT, 2.2 μF, 25V, 10%, SMD |
Kemet |
T491B225K025AT |
x10=4.5€ @ rswww.com |
4 |
CAP0402 |
C23, C37, C38, C43 |
0.5 pF |
CAP, Ceramic, 0.5 pF, 50V, NP0, 0402 |
Yageo America |
0402CG508C9B200 |
|
2 |
CAP0402 |
C21, C54 |
20 pF |
CAP, Ceramic, 20 pF, 50V, 5%, C0G, 0402 |
Murata Electronics |
GRM1555C1H200JZ01D |
|
4 |
CAP0402 |
C19, C44, C55, C58 |
27 pF |
CAP, Ceramic, 27 pF, 50V, 0402, SMD |
Panasonic - ECG |
ECJ-0EC1H270J |
|
1 |
CAP0402 |
C40 |
47 pF |
CAP, Ceramic, 47 pF, 50V, C0G, 5%, 0402 |
TDK Corporation |
C1005C0G1H470J |
|
2 |
CAP0402 |
C52, C63 |
10 nF |
CAP, Ceramic, 10000 pF, 16V, X7R, 0402 |
Kemet |
C0402C103K4RACTU |
|
2 |
CAP0402 |
C39, C45 |
100 nF |
C0402C104K8PACTU |
Kemet |
C0402C104K8PACTU |
|
1 |
CAP0402 |
C48 |
180 pF |
CAP, Ceramic, 180 pF, 50V, C0G, 5%, 0402 |
TDK Corporation |
C1005C0G1H181J |
|
1 |
CAP0603 |
C53 |
2.2 μF |
CAP, Ceramic, 2.2 μF, 10V, Y5V, 0603 |
Taiyo Yuden |
LMK107F225ZA-T |
x10=7.30€ |
1 |
CRYSTAL_ABM8 |
Y3 |
20 MHz |
Crystal, 20.000 MHz, 18 pF, FUND, SMD |
Abracon Corporation |
ABM8-20.000MHZ-B2-T |
x25=25€ |
1 |
MRF24J40_QLP40 |
U1 |
|
MRF24J40, Single Chip Transceiver |
Microchip |
MRF24J40-I/ML |
|
1 |
IND0402 |
L1 |
4.7 nH |
Inductor Multilayer, 4.7 nH, 0402 |
TDK Corporation |
MLK1005S4N7S |
x10=5€ rswww.com |
1 |
IND0402 |
L3 |
5.6 nH |
Inductor Multilayer, 5.6 nH, 0402 |
TDK Corporation |
MLK1005S5N6D |
x10=5€ rswww.com |
2 |
IND0402 |
L4, L5 |
10 nH |
Inductor Multilayer, 10 nH, 0402 |
TDK Corporation |
MLK1005S10NJ |
x10=5€ rswww.com |
2 |
RES0402 |
R20, R22 |
0Ω |
RES, 0Ω, 1/16W, 5%, 0402, SMD |
Panasonic - ECG |
ERJ-2GE0R00X |
|
1 |
RES0402 |
R19 |
10K |
RES, 10 kΩ, 1/16W, 5%, 0402, SMD |
Yageo America |
RC0402JR-0710KL |
|
1 |
HDR6X2 |
J2 |
|
.100" Socket/Terminal |
Samtec |
LST-106-07-F-D |
|
Informations above are for users that will build the chip radio board. For this project, however, we decided to buy some boards from Microchip website. These boards are named PICDEM Z Daughter Card. Click here to go to Microchip Direct .
Here there's a description of the PICDEM Z Daughter Card connector; we will use that for our applications.
 |
|
The first node implementation is for using the PICDEM Z with a PIC16LF876A. IMPORTANT: YOU MUST CHOOSE THE "LF" PIC, THAT ALLOW A POWER SUPPLY FROM 2.0V TO 5.5V. The classic PIC16F876A allow power supply only from 4.0 to 5.5V, too high for this application. In fact, the PICDEM Z Daughter Card requires 3.3V.
This is the node schematic:
Download the node eagle project.
This is a photo of the "sender" node built with a lm317 regulator to make the 3.3v power supply.
Programs for this circuit (three versions, one sender and two receivers). A system with tho nodes programmed in this way not works well yet; if you are any suggestions to make it works please email us!! -> engineering@netsons.org
Program1.zip
Program2.zip
Program3.zip
Power management
For allowing the power giving from a couple of AA batteries (supply 3.2V with fresh alkaline batteries, but this value can raise down to 2.4V with old batteries or rechargeable ones.) we need a simple DC-DC boost converter, to furnish always the 3.3V supply.
The circuit chosen is the MAX858 from MAXIM, that allow from 0.8 to 5V input voltages, and provides a selectable output of 3.3V or 5V. The only components required are a 47uH inductor and some capacitors. The schematic with this voltage regulator is not yet completed.
Last revision: March 22, 2008
