Last Updated: 4/1/01



WM-918/WX200 Schematics


About these schematics

These schematics were drawn from an Oregon Scientific WM918 weather station purchased Oct 1999 (USA version). Older or newer units may differ.

Useful and verified user modifications have been included.

The LCD display is not included in these drawings. Also some circuits terminating in the micro-controller IC have a question mark indicating the exact pin number could not be determined because of the epoxy package.

All components are labeled as they appear on the silk screen. Since the rear board lacks pin numbers for the ribbon cables the pins are labeled left to right. Layout shows this arrangement.

Component values or part numbers were read directly from the device or from the Radio Shack listing.


Values were omitted when they could not be confirmed.

Corrections and additions are welcome. Send to Subject: WM918.

The original Circad format files are available from the above email address. They range in size from 10Kb to 85Kb except the drawings with inserted images, they are 1.1Mb each.

All the drawings were originally created in size A landscape (11" x 8.5") except Layout which is size A portrait and MPU which is size B (17" x 11").

These schematics were created using CIRCAD'98, a demo program from

The files are in GIF image format.

File Name File Size Description Sheet # Size
WM918_Interconnect.gif 89K Interconnect board and sensor cables 1 A
WM918_Layout.gif 32K Main unit major component diagram 2 A portrait
WM918_Rear_Board.gif 48K Rear board including interconnect cable 3 A
WM918_Main_A.gif 39K Main board regulators and RS232 circuits 4 A
WM918_Main_B.gif 45K Wind, pressure and rain sensors 5 A
WM918_TH_Sensor.gif 88K Thermo-hydro sensor unit 6 A
WM918_MPU.gif 77K MPU, MCU and misc. main board items. 7 B
aboutschematics.rtf 5K About these schematics -- --


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