1. Monolithic ICs: A monolithic circuit is built into a single stone or single-crystal, i.e. in monolithic ICs, all circuit components are integrated on a single layer.
2. Hybrid or multichip ICs: As the name implies, the circuit is fabricated by interconnecting several individual chips. Hybrid ICs are widely used for high-power audio-amplifier applications from 5W to more than 50W.
   

   But this in not the only basis for classification of ICs, for reference ICs can also be classified based the arrangement of pins :

1. Single-in-line package:

   A single row of pins protruding from the bottom of the body of the IC, numbering is done by holding the IC upwards and reading from left to right.
   

2. Dual-in-line package:

   Two rows of pins protruding from the bottom of the IC’s body. Their numbering is done just like we saw earlier, it starts anticlockwise from notch. There is an exclusive space in the breadboard for DIL Packaging:
   
   

3. Quad-flat package

   (mounted on the surface): The pins splay on from all four directions. QFP ICs might have anywhere from eight pins per side (32 total) to upwards of seventy (300+ total). How is their naming done? They do have a notch too, and thus, we pick the first pin and move anticlockwise.
   
   

4. Ball Grid-array package:

   (e.g microprocessors)
   
   

So how do we use these ICs? We mount them to our circuit boards. Do you know how these are mounted? IC’s are mounted mainly using two techniques:

1. Through Hole Mounting:

   There are holes in the boards, and in these holes, the pins of ICs are stuck in, and then soldered on the other side. Through hole mounting is more robust and is used in military equipment.
   

2. Surface Mounting:

   They are a bit difficult to mount, as they have to be soldered “on” the surface, and thus require some equipment.
   

   Above IC’s are permanently mounted, they can’t be replaced easily. What if we need different ICs

   These ICs can either be permanently mounted, or can be mounted on a stand, and can be easily replaced.

Based on whether they are programmable or non-programmable:

1. A programmable logic device (PLD)

   is an electronic component used to buildreconfigurable digital circuits. These PLDs have undefined functions at the time of manufacture. Before the PLD can be used in a circuit, it must be programmed (reconfigured) by using a specialized program.

2. Non-Programmable Logic Devices:

   The operation of these ICs cannot be configured by a program. The internal circuit design or “wiring” consists of logic gates and has a fixed function.

Naming and numbering of an IC:

Before jumping further, you should know a bit ofIC Logic Families. A logic family refers to digital integrated circuit devices which are constructed with a combination ofelectronic gates. A family has its own power supply voltage and distinct logic levels.

All IC chips have a two-part serial number. The first part of the serial number delineates the information of the manufacturer. The second part of the serial number indicates the technical specifications.

Many IC manufacturers produce identical chips with the same technical specifications. In the case of the serial number “MC74HC00", the “MC” field indicates the manufacturer Motorola and the “74HC00” field indicates that the chip is a Quad 2-input NAND gate IC.

Another naming convention for the 7400 Series ICs:

SN - Manufacturer (Texas Electronics)

74 Series - Shows the series the corresponding temperature range belongs to.

HCT - The sub-family

04 - Shows the device type.

But it should be noted that there is no global naming standard for naming ICs. The part or manufacturer details are provided so that they can be used for reference purposes. Not to mention, you can always google a series number to find its datasheet.

Common ICs used in Robotics

Now that we know how fabulous ICs are, let’s dive into their usage in robotics.

Motor Driver ICs

The microcontroller used in our robots can't control the motors directly because most of the microcontrollers operate on low voltages and require small amounts of current to operate while the motors require relatively higher voltages and current. Thus, the current cannot be supplied to the motors from the microcontroller. This is the primary need for motor driver IC. Motor drivers act as an interface between the motors and the Microcontroller.

There are different types of motor driver modules used:

L293D Motor Driver:

L293D is a typical Motor driver or Motor Driver IC which allows DC motors to drive in either direction. L293D is a 16-pin IC that can control a set of two DC motors simultaneously. The direction can be controlled too. It means that you can control two DC motors with a single L293D IC!

L293D IC Pinout Diagram

The L293D motor driver IC actually has two power input pins ‘ Vcc1’ and ‘Vcc2’.

Vcc1 is used for driving the internal logic circuitry of the motor driver IC, which should be 5V.

( It must not be greater than 5 V )

From Vcc2 pin theH-Bridgegets its power for driving the motors which can be 4.5V to 36V (for L293D IC). And they both sink to a common ground named GND.

Output Terminals:

The L293D motor driver’s output channels for the motor A and B are brought out to pins OUTPUT1, OUTPUT2 and OUTPUT3, OUTPUT4 respectively.

You can connect two DC motors having voltages between 4.5 to 36V to these terminals. It can supply a maximum current of 1.2A.

Direction Control Pins:

Using the direction control pins, we can control whether the motor spins forward or backward. These pins actually control the switches of the H-Bridge circuit inside L293D IC. It contains two H-bridge circuits controlling direction of one motor each.

How does the H-bridge control the direction of the motor? Try to recall. You already know this answer from the concepts shared in previous blogs

If you can recall, Kudos! If not, refer tothislink.

The spinning direction of a motor can be controlled by applying either a logic HIGH(5 Volts relative to ground) or logic LOW(Ground) to input pins.

The IC has two direction control pins for each channel. The INPUT1, INPUT2 pins control the spinning direction of the motor A while INPUT3, INPUT4 control motor B.

Speed Control Pins:

ENABLE 1, 2 and ENABLE 3, 4 are used to turn ON, OFF and control speed of motor A and motor B respectively.

The ENABLE 1, 2 pin controls the H-bridge of left side (one with INPUT1 and INPUT2 pins). When ENABLE 1,2 pin is high i.e it has 5V supply then Ieft side input and output pins are enabled and H-bridge is turned ON. When ENABLE 1,2 is low then H-bridge is turned off, making motors stop in all conditions. However, when PWM power supply is provided to these pins we can actually control the speed of motors. We can also control speed by giving pwm power supply to INPUT pins. We will study about PWM (Pulse Width Modulation) in detail in further blogs.

L298N Motor driver module

L298N Motor Driver Module contains a 78M05 5V Regulator along with the L298 IC. It works the same as L293D but is more powerful. It can take power supply upto 46 volts. It can supply a maximum current of 2A.

Op-amp:

An Op-Amp, short for an Operational Amplifier, is the workhorse for all analog electronics. It’s a type of an amplifier, and an amplifier is defined as a circuit that produces output signal greater than its input signal. Generally, the ratio of value of output signal and input signal is called gain. More precisely it is the ratio of the output signal amplitude to the input signal amplitude, and is given the symbol "A".

Internally, it has a complex circuit (a bunch of resistors, some capacitors, etc), but for now, let’s just concentrate on its properties.

Like other amplifiers, it also has some “gain”. That means if we put an X signal here, then I will get a signal AX, where, A is the gain factor.

(input) x --> [A] --> Ax (output)

The gain A is generally high, i.e, in the range of 105to 106.

The op-amp is represented by the symbol shown here.

The two input pins, V+ and V-, are called non-inverting and inverting pins respectively. And Vs+ and Vs- are supply pins.

Now the output voltage, Vout is proportional to the voltage between the two input pins, i.e,

V0 = A * ( V+ - V-- )

Vout or V0 can go both positive or negative w.r.t. the ground.

So this output is proportional to the difference of input voltages. The results are plotted on the graph given left. Notice the graph after Vsat? This Vsat ,the saturation voltage, is less than the highest possible gain voltage of an op-amp and is the maximum possible voltage, reason being, the gain voltage is very high and it is impractical for op-amp to produce such voltage. Thus the limit is capped to the supply voltage and Vout = Vsat.

The slope in this graph is the gain A.

Coming back to the question of the meaning of inverting and non-inverting voltages, let’s take a look at the equations given above the diagram.

As the Vin varies, let’s say V+ increases, the difference Vin also increases, thus increasing the gain.

↑ Vin =↑ V+ - V-

As the V- increases, the difference Vin decreases, thereby decreasing the overall gain.

↓ Vin = V+ - V- ↑

Thus, V- is inversely proportional to the overall gain. Therefore it is called an inverting voltage. On the other hand, on increasing the V+, the gain also increases. Hence, it is called the non-inverting voltage. If this explanation is bit clumsy for you, look it another way,

Let’s set the V- voltage to ground (zero) and then calculate the Vout using the same equation,

Vout = A*(V1) . Here the voltage Vout is directly proportional to the Voltage V1. Hence the voltage V1 is called the non-inverting voltage.

For the V- , the equation for Vout would be:

Vout = A*(0-V2)

Vout = -A*(V2)

The Vin and V- are in opposite phase, i.e, if V- increases, the Vout decreases. Hence it is called the inverting phase.

Now beware, when schematics of the op-amp are drawn on paper, the plus and minus could be reversed, and accordingly, you have to make sure you are proceeding with the correct signs!

Op-amp as a comparator:

So what do you understand by comparator? A tool to compare things, right? Here we compare two voltages. The next question that will pop-up in your mind is HOW? Well, when you have learned how an op-amp works as an amplifier then the answer to this question is not so difficult.

Let’s assume we have two voltages V1 and V2 to compare. Let’s give V1 as input to V+ and V2 as input to V--. There are two types of comparators, depending on the reference point we choose to compare i.e. whether we take V1 as a reference and compare V2 with respect to it or vice-versa.

To understand better have a lookhere.

555 Timer IC

It is used in a variety of one-shot or delay timers, pulse generation, LED and lamp flashers, alarms and tone generation, logic clocks, frequency division, power supplies, and converters, etc, in fact, any circuit that requires some form of time control as the list is endless. The internal block diagram and working of 555 Timer IC are given below.

As you might have learned through your secondary school, these three resistors are used to create reference voltages, creating 1/3 Vcc and 2/3 Vcc of supply voltage Vcc.

Next-up is a comparator, it is used to “compare voltage”, for example, for its two input terminals, inverting and non-inverting, if the input voltage is higher for the positive terminal, the comparator will output 1, otherwise, it will output 0. The first comparator negative input terminal is connected to the 2/3 reference voltage at the voltage divider and the external “control” pin, while the positive input terminal to the external “Threshold” pin.

On the other hand, the second comparator negative input terminal is connected to the “Trigger” pin, while the positive input terminal to the 1/3 reference voltage at the voltage divider.

So using the three pins, Trigger, Threshold, and Control, we can control the output of the two comparators which are then fed to the R and S inputs of the flip-flop. The flip flop can also be reset anytime using the reset pin, additionally resetting the whole 555 Timer IC.

The Q-bar output of the flip-flip goes to the output stage or the output drivers which can either source or sink a current of 200mA to the load. The output of the flip-flip is also connected to a transistor that connects the “Discharge” pin to the ground.

There are primarily three modes of operations named Astable, Monostable, and Bistable. Each mode represents a different type of circuit that has a particular output. Learn more about ithere.

Voltage Regulator

For a start, different electronics require different voltages. A microcontroller may require 5V, your motors perhaps 12V.

Consider the case of Li-Po Batteries, the nominal rated voltage is 3.7V/cell, but they are never at a constant voltage. The image shows how a typical battery voltage changes over time.

See the drained battery zone, what if the sensor you are using is sensitive to 5V and then the battery drops!! Thus we need a Voltage Regulator to rectify this issue.

While using some electronic components, we might need to increase or decrease the voltage to fulfil our purpose. As the name suggests, the Voltage Regulator also adjusts the incoming voltage to the desired and acceptable limits.

There are two types of VRs: linear and switching.

Linear Regulators :

It works by automatically adjusting the resistance via a feedback loop(“Feedback” is the process by which a fraction of the output signal, either a voltage or a current, is used as an input, in this circuit,negative feedbackis used) , accounting for changes in both output current and input, all while keeping the output voltage constant.

The 78xx series voltage regulators are the most popular linear voltage regulators which produce positive fixed DC voltages. For negative voltages we have 79xx series. “xx” corresponds to a two-digit number and represents the amount (magnitude) of voltage that voltage regulator IC produces.

Eg: LM7805 produces +5V and LM7812 produces +12V.

All other IC’s of this series have similar structure.

Four 7800 series linear voltage regulators, each with a different voltage output: 5V, 9V, 12V, 15V

78xx series ICs have built-in protection against a circuit drawing too much power. They have protection against overheating and short-circuits, making them quite robust in most applications.

Switching Regulators:

These regulators such as buck (step-down), Boost (step-up), and buck-boost (step-up/step-down), require a few more components as well as increased complexity of how various components will affect the output. Switching regulators are far more efficient in terms of power conversion where efficiency plays a big role, but linear regulators work very well as voltage regulators in low-voltage applications.

Microprocessor and MCU

We’ve been this far but we still don’t know how a robot makes decisions and processes data? Logic Gate ICs? But didn’t they make an ambiguous, huge, and complex circuit even just to do simple operations like additions? There are devices available that process data. Take your phone, for example, it can do a lot of operations rather than simple addition in such a small size. What gave this device such powerful abilities. They are *drumroll*

Microprocessors and Microcontrollers

Microprocessors and microcontrollers process information according to the instructions given with the input and generate an output.

This is how a microprocessor and a microcontroller look like: