Power Supply

Power supply is also one of the very important factor which should be considered while building a Robot. Generally for any project or any Robotics competition, only 12/24 Volts AC or DC are allowed. And most of the robotics parts like motors, microcontrollers, IC’s, LED’s, sensors etc uses only DC voltages of 12 V and 5 V. So for our study we concise our self to 12 V and 5 V DC voltages and learn that how can we provide our bots these voltages.

In case of providing power supply, we have generally two options.
1. Using an Adapter to convert AC mains to required DC, or
2. We can use a Battery of required voltage and ampere.

While choosing any one of them we must have to take care of two things; one is its rated voltage i.e. the output voltage of the battery or adapter, and the other thing is its rated current i.e. the maximum current that could be drawn from it.
Mostly we forget to consider the second term while choosing a power supply for our bots and in result of which we have a Robot which doesn’t able to run at its full efficiency and speed. Less current means less power and less power means less torque, and if we does not supply a proper power to our bot then our bot can’t able to perform properly.

In case of Adapter, the maximum current and output voltage are mentioned at the back of the box. But in case its not mentioned there then we could easily determine it by using a voltmeter and an ammeter. To measure voltage just take two terminals of the voltmeter and touch them at the positive and negative points of the output of adapter after switching it on, this reading maybe positive or negative but don’t worry just see the magnitude(value) which is the output voltage of the Adapter. Now to measure max current we have to follow the same procedure, but we should take care that the rating of ammeter must be higher than the output current, which can either be guessed or asked by someone. But if you can’t able to determine then I prefer you to take ammeter of rating higher than 20 Amp.

Now, in case of battery you can check the output voltage as similar as for adapter, but don’t ever try to check its current by previous method, BATTERIES SHOULD NOT BE SHORT CIRCUITED. So how to check its current??? Well no need to check the current output of the battery because the battery mostly provides a high current if its not exceptionally small and try to discharge them as fast as possible, and the highest discharging rate is always written on the battery. But if you are using small batteries with low current and voltage rating, then you can increase both by connecting several batteries in series or parallel or in both arrangements at the same instant.
To increase voltage, connect the batteries in series. The resultant voltage is the sum of the voltage outputs of all the cells combined.
To increase current, connect the batteries in parallel. The resultant current is the sum of the current capacities of all the cells combined.

Why two different voltages? The answer for this question is, most of the DC motors require a 12 Volts input to run properly but almost all the electronic components like IC’s, Microcontrollers etc require a small voltage of 5 V. So for designing an Autonomous bot we need both the voltages. But in case if you can’t able to get the two different power supply and only have 5 V, then we can use a toy motor instead of a 12V DC motor because a toy motor just require 5V to operate.

Now, for different voltages on the same bot with only one power supply, we can either use a potential divider or a zener diode or a voltage regulator IC.(?) Don’t worry if you don’t know about these components, in next few lesson we’ll discuss it all.