An Inexpensive APRS Weather Station

How To Build One

There are two kits you need to get for this weather station. The first is the outdoor sensor. It costs about $80 and can be bought online from the AAG. This kit provides the sensor unit (some assembly required) and an interface that allows you to hook it up to your PC. They are slighly misguided in thinking a PC is a good weather monitoring platform :-), but we can forgive them this error because they provide us with a nice sensor package. In addition to the wind/temperature unit, they also sell a rain guage, also supported by this project.

The second part you need is the display unit. The kit is available from TAPR ( If you are truely impatient or have lots of spare parts around, you can of course just build the station based on the schematic and instruction manuals below. Links for the datasheets on big stuff (like the micro and display) are available on the links page.

Schematic. (pdf)
This is the board schematic. This circuitry will support both a standard "build-and-go" weather station and can also be used as a general purpose 1-Wire development station too, all the necessary hardware for the P&E debug support is included.
Assembly manual (pdf).
This is the assembly document. It is written for the TAPR board, but if you are the type that likes to roll your own, this is still handy as not only a construction reference, but also as a checkout guide. This manual takes you from counting components up through a powered up board with a verified LCD and verified 1-Wire bus. This manual is intended to be useful during the construction phase, then pretty much useless unless you break something.

This is the manual that ships with the kit from TAPR.

Operations manual (pdf).
This manual takes over where the assembly manual leaves off. It starts with the sensor calibration process and shows you how to operate the unit including all the display features as well as interface features. Features are being continually added to this project, so this manual will be continuously updated. As you download new software, you may want to get the latest version of this manual to go along with it.

(New for releases 1.12.5 and greater)
In an effort to better support solar powered applications, release 1.12.5 and beyond support the ability to digitize the battery voltage for display and transmission as well as control a radio. Suggested circuits for these two OPTIONAL circuits are shown below. If you do not want to digitze your battery voltage and want a simple 00.0V on the display for battery voltage, ground port B bit 7 (J6 pin 1).
WARNING! Adding this circuit does interfere with the P&E toolsets ability to boot up correctly. If you do plan on needing to use that toolset, provide a way to be able to easily remove R10. The issue is that in order to boot up in the correct debug mode, Port C bit 0 must be high on the rising edge of reset. There is a 10K pullup resistor on the main board, but this circuit pulls down harder. This circuit does not interfere with the Mon08 downloader.

Item #Part Description Ref Des.Quan
1 Xtal Osc, 32.000MHz U1 1
2 Xtal Osc, 9.8302MHz U2 1
3 IC,Motorola MC68HC908GP32 U3 1
4 IC, Maxim MAX232CPE U4 1
5 IC, LM7805 linear regulatorU5 1
6 LCD, 2x20 with backlight DS1 1
7 LED, Red DS2 1
8 Ferrite, Bead L1-L7 7
9 Resistor, 2.2K R1 1
10 Resistor, 10K R2-R10 9
11 Resistor, 1.5K R11 1
12 Resistor, 470 R12 1
13 Potentiometer, 10K VR1 1
14 Cap, 10uF 16V Electrolytic C1,C2 2
15 Cap, 0.1uf 50V Ceramic C3-C7 5
16 Cap, 1uf 16V Electrolytic C8-C12 5
17 Diode, 1N5817 Schotky D1 1
18 Diode, 1N4148 D2,D3 2
19 Header, 3-terminal OJ1,OJ2 2
20 Switch, momentary, N.O. S1-S4 4
21 Switch, momentary, N.C. S5 1
22 Connector, barrel J1 1
23 Connector, RJ11 J2 1
23 Connector, DB9 female J3,J4 2
24 Connector, DB9 male J5 1
25 Header, 14-terminal J6 1
26 Heatsink, TO-220 U5 1
27 Case N/A 1
28 Wall-Wart (7V or more) N/A 1

This page was last updated March 26, 2006.