Introduction to the Light Sensor¶
We use a phototransistor as our light sensor - a phototransistor is a device that converts light particles (photons) to electrical current and amplifies it. We use this sensor to simply detect the presence of light. Overview below.
How it works¶
The sensor has a translucent lens on the top to let in as much light as possible. When light particles (photons) hit the base area under the lens, light energy generates electrical current and then this generated current is amplified with a transistor or a set of transistors on the collector part.
The sensor is located on the same side of the PCB board as the button in the SimplePack (so the front) and in the SimpleIndustry, it's on the right side when you have the device on it's back in front of you with the rounded top further away from you than the flat bottom.
The sensor is sensitive enough to notice changes in light intensity even when light shines on the other side of the device, but if you have a use case where the device is in a fixed position, it's always better if the device faces the light source.
Things the light sensor can measure and report¶
The light sensor in our device cannot tell you precise lumens - although the sensor is perfectly capable of this in lab conditions. However, the device is sealed in its IP 68 compliant case and the intensity of light that reaches the sensor can vary because of several factors (e.g. artificial light vs natural light) and so the device can be used to determine binary presence of light (on/off). This is done with a light threshold & hysteresis.
Common use cases¶
- Monitoring the usage of lights in corporate offices
- Very simple monitoring of manholes
- Making sure packages are not opened while they are being delivered
- Monitoring facility open hours
- Finding where energy costs could be cut
- And more...