Robots have always amazed human eyes. Robot can be a defined as an intelligent mechanical system capable of performing tasks on its own. There is no question about the form of robot. It’s all up to you, who build it. Here we talk about a ‘proof-of-concept’ on making robots. It may look a bit crappy with no sensors or digital electronics involved but will definitely give a base on the working of a robot and hands-on feel about everything. This solar powered robot is actually a BEAM (Biology, Electronics, Aesthetics and Mechanical) robot with a Miller solar engine and a single motor. On the long run, you will be able to add more motors, sensors and whatever that makes your robot more humanly. This is a simple project for electronics enthusiast and as the robot starts rolling it will surely to delight your heart.
What is a BEAM robot?
This is a simple project for hobbyist. Actually this solar powered robot is a BEAM robot. Without the use of a microcontroller or processors, we can easily design a beam robot. Instead of processors or controllers, beam robot uses active & passive components .i.e. discrete components and sensors for its working. So the design of the BEAM robot is simple and is less sensitive to damage and also it is more tolerant to different types of environment. Using this BEAM robotics we can easily develop a simple and efficient robot. In this simple project section, we describes about the design of a BEAM robot using solar power.
The Beam solar powered robot circuit consists of a few components, mainly a solar cell, motor, capacitor, transistor, diode, resistor and a 1381 voltage detector. It is basically a simple circuit, used to collect the solar power generated by a solar cell and this power is stored in a capacitor as its charging power. Then the power is discharged from the capacitor and this discharged energy controls or drives the motor connected to the circuit. This repeated process will move the Beam solar powered robot in a cyclic fashion.
Working Principle of Beam solar powered robot:
Our Beam solar powered robot is based on the principles of Miller solar engine (Miller engine). In this circuit, we use a 1381 IC, which is a voltage detector IC. The 1381 IC is commonly used to reset the CPU and Micros, when the power supply voltage drops off. Similarly, in this circuit, 1381 detects and provides a switching, when the input voltage crosses the upper and lower threshold voltage limits
In the Beam solar powered robot, we are using two solar panels of 3V 25mA.Which is connected in parallel mode, so we can get 3V, 50mA power supply from this panels. The solar power generated by this solar panel, charges the capacitor C2. The capacitor stores this power and the voltage across the capacitor (C2) rises with the time. When this voltage across the capacitor (C2) reaches the trip point (trigger point) of the 1381’s, the IC will turn on and the corresponding voltage is applied to the base of the transistor Q1.When the voltage from the 1381 reaches the cut in voltage of the transistor, the transistor gets turned on and provides a current to the motor and the motor starts running according to the voltage from the transistor. The motor will run until the discharge voltage of the capacitor will reach a value (i.e., trip point minus 0.3V) of 1381. Then the 1381’s voltage is not sufficient to turn on the transistor, ultimately the transistor goes in to the quiescent state. And the solar panel resumes charging the capacitor. And then the cycle repeats as above. And as a result, the Beam solar powered robot starts dancing or moving according to the intensity of light variations, that falls on the solar panels.
There are many varieties of 1381 parts available. You can choose appropriate 1381 part, that will provide the required voltage for triggering the motor and also suit with the ratings of the solar panel and other components in the circuit. Also the performance of this circuit can be adjusted by choosing proper values for the capacitor C1 and resistor R1.
A signal diode is used in our circuit. But in actual working model, we can discard this diode. The function of this diode is to prevent the battery discharge through the solar panels. But in this Beam solar powered robot, we are not using a battery. But the design of our Beam solar powered robot is based on the principles of Miller solar engine, so it is desirable to show a diode in the circuit diagram. So, we can use any signal diode and the specifications of the diode are not as much important.
- Solar Panel: 3V 25mA (2 No:s)
- Resistor, R1: 100Ω
- Capacitor, C1: 0.22 µf
- Capacitor, C2: 3300 µf
- Signal Diode D (Optional)
- Motor, M: 2V(Small one, like motor inside a cd Walkman or player)
- 1381 IC : 1 No. (CMOS voltage controlled trigger, Get one which should matches the voltage across the 2V motor
- Transistor, Q: 2N3904