One of the main elements of automation in street lighting, along with timers and motion sensors, is a photo relay or twilight relay. The purpose of this device is to automatically connect the payload when it gets dark, without human intervention. This device has also gained immense popularity due to its low cost, affordability and ease of connection. In this article, we will analyze in detail the principle of operation of the twilight switch and the nuances of its connection, and also tell you how to make a photo relay with your own hands. It will not take much time and effort, but it will be pleasant for you to use a self-assembled device.
Content:
- Relay design
- Assembly instructions
Relay design
The main element of the relay is a photosensor; circuits can use photoresistors, diodes, transistors, photovoltaic cells. When the illumination on the photocell changes, its properties change accordingly, such as resistance, states of the P-N transition in diodes and transistors, as well as voltage on contacts photosensitive element. Further, the signal is amplified and the switching of the power element that switches the load occurs. Relays or triacs are used as output control elements.
Almost all purchased items are assembled according to a similar principle and have two entrances and two exits. The input is supplied with a mains voltage of 220 Volts, which, depending on the set parameters, also appears at the output. Sometimes the photo relay has only 3 wires. Then zero is common, a phase is supplied to one wire, and with the required illumination it is connected to the remaining wire.
At connecting the photo relay it is necessary to read the instructions, pay special attention to the maximum power of the connected load, the type of lighting lamps (incandescent, gas-discharge, LED bulbs). It is important to know that lighting relays with a thyristor output will not be able to work with energy-saving lamps, as well as with some types dimmers due to design features. This nuance must be taken into account so as not to damage the equipment.
Let's look at a few diagrams for self-assembly of a twilight switch at home. For example, let's look at how to make a triac night light with a photocell.
Assembly instructions
This is the most elementary photo relay circuit of several parts: a Quadrac Q60 triac, a reference resistor R1, and a photo of an FSK element:
In the absence of light, the triac key opens completely and the lamp in the night light shines at full incandescence. With an increase in the illumination in the room, the voltage on the control contact is shifted and the brightness of the lamp changes, up to the complete attenuation of the light bulb.
Note that the circuit contains lethal voltages. It is necessary to connect and test it with special care. And the finished device must be in a dielectric case.
The following diagram with relay output:
Transistor VT1 amplifies the signal from the voltage divider, which consists of a photoresistor PR1 and a resistor R1. VT2 controls the electromagnetic relay K1, which can have both normally open and normally closed contacts, depending on the purpose. The VD1 diode shunts voltage pulses during coil disconnection, protecting the transistors from failure due to reverse voltage surges. After examining this circuit, you can find that its part (highlighted in red) in functionality is close to ready-made assemblies of the relay module for arduino.
Having slightly altered the circuit and supplemented it with one transistor and a solar photocell from an old calculator, a prototype of a twilight switch was assembled - a homemade photo relay on a transistor. When the solar cell PR1 is illuminated, the transistor VT1 opens and sends a signal to the output relay module, which switches its contacts, controlling the payload.
If you still have questions, then watch the video, which also tells in detail how to make a photo relay with your own hands:
Here, in fact, is all the information about assembling a photo relay with your own hands. We hope the provided diagrams and video tutorials helped you make a twilight switch from improvised means!
You probably don't know:
- How to make a motion sensor
- Connection diagram of a spotlight with a photo relay
- How to assemble a time relay with your own hands