The following is a light range response test of an ALS-PT204-6C/L177 Ambient Light Sensor made by Everlight. DigiKey part number: 1080-1019-ND
The test indicates that the usable range of the sensor is approximately 3 F Stops giving a useable output range of 0.7 to 4.25 volts.
The ALS-PT204-6C/L177 Ambient Light Sensor was used in the SMA23 - A New DCC & DC Car & Loco Detector - Differential Absolute Position Detector (DAPD) circuit found at the Model Railroad Hobbyist magazine's web site.
The following are self-compensating photodetector circuits. The values of the resistors in series with the light sensors may need to be determined by testing the circuit after installation.
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
01 February, 2017