Welcome
This project is about ‘DIY Motion Detect Automatic Light’ (two types) made using 555 Timer IC and IR pair (IR led as transmitter and Photodiode as receiver).
You might see or know other DIY where microprocessor is used, but why waste the good equipment when we can make it using a simple components. Right?
So, first let’s talk a bit about the 555 timer before our main project.
Here is the pinout of the 555 timer IC.
555 timer IC is one the most common and simple timer IC which needs only a few external component. It is mainly used in three ways, namely
1. Bi-stable multivibrator
2. Mono-stable multivibrator
3. A-stable multivibrator.
For our project we will be using 555 timer as Bi-stable and Mono-stable multivibrator. So, let’s begin with Mono-stable multivibrator.
Here is the circuit diagram for the mono-stable multivibrator.
As the name indicates, the circuit has one stable state i.e. OFF state and unstable state i.e ON state. To change the state from stable to unstable state a negative pulse must be applied to pin 2, which can be achieve by pressing the switch, keeping the voltage at pin2 below 2/3 of the supply voltage.
So, by pressing the switch the IC changes its state to ON. During that, the capacitor will charge through the resistor R. When the capacitor charge up to 2/3 of supply voltage, the IC will reset thus, being unstable and will return to it off state.
Using that, here is the circuit diagram of our project Mode 1.
The Switch is replace with transistor Q2, transistor Q3 and Relay will drive the AC supply with the IC and IR led, Photodiode and transistor Q1 are used as sensor circuit. For circuit working principle, I recommended watching the video @ https://youtu.be/t6RM3dDZ6Dg
With that being said, let’s move on to project Mode 2.
In Mode 2 the 555 timer is used as Bistable Multivibrator, which has two stable states i.e. ON and OFF. Here is the circuit diagram for Bistable Multivibrator.
The state of the bistable can be change by pressing the switch, which will toggle the state from ON to OFF or OFF to ON every time we press the switch.
Here is the circuit diagram for Mode 2 whose working principle is similar to Mode 1 except for the 555 timer IC.
Now, let’s gather the required component and solder it to perf board according to circuit given above.
See the video for the test result.
The circuit works well except the range for detection is a bit short since, we used IR pair. The maximum distance I can get is 20 cm. This might be a problem in some applications. However, it can be solved simply by using a PIR sensor instead of IR pair. Here is the circuit I design using a PIR sensor.
Thanks for your time. Hope you have a great time.