light counter image

  Light Sensor Counter
      from KEUWLSOFT

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light sensor counter image

Light Sensor Counter

In this app, the light sensor in your device is continually monitored and when the detection level is crossed, the counter is increased by one.

Can be used to count each time a light source shines on the sensor. Or alternatively, shine a light on the sensor and count each time the light beam is broken.

• Illuminance values in lux (lumens per square meter) or foot-candles.

• Detect on rising or falling past the detection level.

• Reduce double counts with optional no-count wait after detection.

• Graph to show illuminance values.

• Counts indicated on graph and with optional 'click' sound.

Light sensors will vary in sampling speed, resolution and accuracy from one device to the next. For indication only.

User Guide

The light sensor returns illuminance values in lux, where 1 lux = 1 lumen per square meter. You can also select units of foot candles (lumens per square foot) in the settings. 1 foot-candle = 10.7639 lux.

The zero button resets the counter and clears the graph.

The pause button pauses measurement until it is pressed again.

Long tapping on the counter value allows its value to be copied to the clipboard.

Note that light sensors will vary in sampling speed, resolution and accuracy from one device to the next. Therefore this app is for indication only.

Count Detection

Level – To detect a count event, the measured illumincance must cross the count detection level given in this section and shown on the graph with an yellow line. Use the arrows to adjust the level or enter a value by tapping the edit button.

No re-count time – To avoid signals being detected to close together, a wait can be added so that another count will not be registered until after the wait period has passed.

Direction - Select whether to detect counts either when the signal rises from below to above the detection level, or falls from above to below the the detection level.

count detection settings
Count Detection Settings


The graph shows the light sensor readings versus time. It is auto scaling by default and scrolls once filled. If auto scale is turned off in the settings, then the scale can be manually set by panning or pinching on the graph. If the count detection level is within the auto scaled range, it is shown by an yellow line. When the signal crosses this line in the right direction, a count is registered and a red circle appears. A subsequent fainter line follows where another count event cannot be registered as determined by the detection settings. After which the trace returns to the original colour indicating that another count will be registered once the input level once again crosses the count detection level.

When auto scale is off, or the detection is paused, the graph can be manually scaled. A single touch allows the graph y axis scale to be moved up or down, or in the case of the x-axis, pan back to see more recent data. A double touch, i.e. pinching on the graph can change the scales of either axis. Since, the graph is small, using fingers on opposite hands can make this task much easier.

The graph y-scale can either be linear or logarithmic as selected in the settings.


Clicking the cogs button at the top left of the screen brings up a settings menu:

Illuminance Units – The illuminance can shown in either lux or foot candles.

Auto scale graph Y-Axis - The Y-Axis of the graph will be auto scaled when not paused. Otherwise panning or pinching on the graph can change the axis scales.

Logarithmic Y-Axis - The Y-Axis of the graph will be logarithmic if this option is checked. Otherwise the graph Y-Axis will be on a linear scale.

Stay awake – Check this option to stop the device from sleeping.

Sound On – Button presses and counts will make a click sound if this is enabled.

Beep when count detected – If both the sound and this option are on, then a 'click' sound will be played every time a new count is detected.

Vibrate On – Button presses and counts can cause the device to vibrate if this is enabled.

Vibrate when count detected – If both this and vibrate are on, then every time a count is registered the device will vibrate.

Measurement Speed – Three speed options for the update interval.

Reset to defaults – Resets all preferences back to their default values and zeros the counter.

Edit counter value – Use this if you need to adjust the counter value.

Edit detection values – You can also edit the detection values here, typing in the values rather than using the arrow buttons.