Hi all. I am back with a new post after an extremely refreshing trip and in this post I will be covering some very commonly used ICs and components in beginner and techfest level robotics. This is NOT an exhaustive list. It is just an indicative compilation. Also, along with the brief function and purpose of each IC, I have also provided the links to various datasheets. I hope you will benefit from this.
Common application: If you plan to use the AC power available through the commonly seen 3-point connections to power your robot/application, you will need a step-down transformer. These transformers are easily available at any electrical shop. After stepping down the 220 Volts to say, 25 Volts by using a suitable transformer, you need to rectify the AC voltage to get DC voltage. Diodes are used for this purpose. This schematic shows how it is done.
The question that immediately comes to mind is, why do I need a transformer? Why not directly use the diodes for rectification? The answer lies in the datasheet, which states that the peak reverse voltage across the diode should not exceed 100 Volts. Practically, it should not exceed 60-70 Volts. Now again you will ask, why not use a diode of a higher rating? Well, they are costly and bulky. So, peace out.
Voltage regulators - http://www.datasheetcatalog.org/datasheets/228/390068_DS.pdf
Common application: Suppose you have managed to somehow get a DC power source- either using the transformer-rectifier circuit or some other source- but you can’t use this source directly because your components requirements, what do you do? Use a voltage regulator. The 78XX series is the most popular series of voltage regulators. These are 3-pin ICs having Input, Common and Output pins. The standard values to which you can bring down the DC voltages is 5,6,8,9,10,12,15 and 24 Volts. The maximum input values for all but 24 Volts regulation is 35 Volts whereas for 24 Volts regulation the maximum input is 40 Volts. Practically, the values should not exceed 30 Volts. Also, note that to achieve regulation, the minimum input should be at least 2 Volts higher than the regulated value. Therefore, to achieve 5 Volts regulation using IC 7805, the input should be at least 7 Volts.
Common application: So you have a problem statement at hand that requires you to measure the temperature and make the robot act accordingly. Here is your solution: AD590 is a temperature transducer IC whose output is a current proportional to the temperature. The output relation is linear with a change of 1uA/K. This output is converted into a voltage by connecting a resistor in series and measuring the potential drop across the resistor. The typical range of input voltage is 5-25 Volts (Maximum: 30 Volts).
Common Application: Don’t have an AD590? Go for this IC then! LM 35 has a linear increase factor of 10 mV/deg C. What’s more? LM35 is cheaper than AD590. But for applications that involve sending temperature measurement data across longer distances, AD590 is better as in LM35, the circuit will suffer from potential drop across the connecting wires.
Common Application: Need to acquire a signal in which noise is the more dominant signal (body signals or voice recognition in a crowded surrounding, for instance)? AD620 is an instrumentation amplifier IC and is a very popular choice among robotics enthusiasts. Very high gain is possible without significant loss in linearity. Supply voltage range is 5 Volts to 18 Volts.
Accelerometer Analog O/P - http://www.sparkfun.com/datasheets/Components/ADXL330_0.pdf
Common application: Enjoy the tilt-based games in your smartphone? Awed by the sheer intelligence of a self balancing vehicle? Here lies the trick! Accelerometer ICs like ADXL330 measure the tilt of the IC in all three axes and provide an analog output proportional to the amount of tilt. Interfacing a sensor to a controller is a tough task and accelerometers are among the toughest to work with. But is sure is fun when you see your interface working successfully J
Accelerometer Digital O/P - http://www.freescale.com/files/sensors/doc/data_sheet/MMA7660FC.pdf
Common application: This is also an accelerometer IC that provides a digital output corresponding to the tilt. This digital IC is interfaced to the controller using I2C protocol (huh?). More on this later.
Common application: I have already discussed this motor driver IC in a previous post. Check it out.
Common application: Light dependent resistors are a very important class of photodetectors. The resistance of LDRs increases as the luminous intensity decreases and vice versa. One of the disadvantages associated with LDRs is the low speed of response called memory effect. But, a beginner should definitely take its interfacing up as a project.
Common application: LEDs have been used as indicators for a long time now and will be continued to do so for ages. Generally the potential drop across an LED is 1.7-1.8 Volts. The ideal connection involves a resistor in series with the LED so as to limit the current to a value around 10-15 mA. The maximum tolerable current is 30 mA but operation at this current for long reduces the life span of the LED. As we say, LED ‘phook jaayegi’. Going through the datasheet of an LED is suggested.
Common application: Making a line follower or a micromouse? Or working on a project that involves control based on digital input from various sensors? This is the IC to go for. LM324 has 4 comparators that can help you achieve discretization of your analog output. Or simply, switch between ON and OFF states based on value of input.
Common application: Yes, this is the universal IC. Yes, this IC needs no introduction. Yes, this IC can’t take less than 12 Volts bi-polar supply. Yes, the source and sinking current is restricted to a maximum of 40 mA. Its applications are unlimited. It can be used in designing controllers, filters, comparators etc.
Hope this will help you find your datasheets whenever you need one :)