Electronic Turn
Friday, 5 August 2016
Electronic Turn: Supervised Learning
Electronic Turn: Supervised Learning: Supervised learning is when when we have data in a paired form. To understand it lets consider an example. Suppose there is a chocolate...
Tuesday, 21 June 2016
Basics of IR
IR sensors are composed of an IR emitter and an IR receiver.
IR emitter is simply an IR LED (Light emitting diode) which emits infrared light when supplied with a voltage. You can check this in action using a camera phone and looking into the LED. You will see a purple colored light coming out of the LED.
IR LED is connected in forward biased as shown in the figure.
IR receivers are photo diodes, that is they show more diode characteristics when more light falls on them. And because of this property IR receivers are connected in reverse biased. How this is helpful ?
Well these sensors are used with microcontrollers and microcontrollers understands voltage levels.
The voltage developed across IR receiver will change if its resistance changes (use simple voltage division rule with the current limiting resistor).
Initially the IR receiver has some resistance when connected in reverse biased due to ambient light. However when IR rays from IR emitter fall on the receiver, the receiver will show more diode like characteristic, that is its resistance will increase (reverse biased ). So voltage developed across it increases. This voltage is detected by microcontroller. Now we can use this to implement certain logic in the code.
IR emitter is simply an IR LED (Light emitting diode) which emits infrared light when supplied with a voltage. You can check this in action using a camera phone and looking into the LED. You will see a purple colored light coming out of the LED.
IR LED is connected in forward biased as shown in the figure.
IR receivers are photo diodes, that is they show more diode characteristics when more light falls on them. And because of this property IR receivers are connected in reverse biased. How this is helpful ?
Well these sensors are used with microcontrollers and microcontrollers understands voltage levels.
The voltage developed across IR receiver will change if its resistance changes (use simple voltage division rule with the current limiting resistor).
Initially the IR receiver has some resistance when connected in reverse biased due to ambient light. However when IR rays from IR emitter fall on the receiver, the receiver will show more diode like characteristic, that is its resistance will increase (reverse biased ). So voltage developed across it increases. This voltage is detected by microcontroller. Now we can use this to implement certain logic in the code.
Friday, 20 November 2015
Resonance in electrical circuits : Deriving the frequency equation for series resonance
The current in a series RLC circuit varies with frequency as shown in the graph
Current is calculated as
At critical frequency current is
Combining these two we get
at resonance impedance of the circuit is simply R. Now writing Io =V/R and substituting value of Z
Cancelling V from both sides and taking reciprocal on both sides
To get rid of j (equivalent i of imaginary number), write the right hand side expression in terms of it's magnitude form
square on both sides
and simplify
Now square root both sides
Substitute in value for inductive and capacitive impedance in terms of omega,L,C
Further simplify
This is a quadratic equation in ω.
Because of +- sign there are two different
quadratic equations. So considering one at a time
Now calculating roots of the above quadratic equation
Now here there are two possible roots. Since frequency cannot be negative so
considering positive root.
lets call this ω1 (lower cut-off frequency)
Now considering the second quadratic
equation
calculating roots
Now just for observation if you factor out R/4L
form inside the squared root, we can see that the term is actually greater than R/2L term, so this term cannot be negative as will make our frequency negative which is fundamentally wrong.
So choosing the positive root
Lets call this ω2 (higher cut-off frequency)
We can write both the roots together as
Saturday, 24 October 2015
Flip-Flops (part 1)
Flip-Flops are basic storage electronic components and are made using gates. Gates are connected in certain configuration which make it capable of maintaining its state. This state then further plays a role in deciding the next output.
Consider a simple AND gate circuit:
If we set A=1, B=1, C=1 the output Y would equal 1. However the moment we change the inputs to A=0, B=0, C=0 the output Y changes to 0. Now this can be seen as the loss of the i bit information which was present in the circuit.
Now consider the following circuit
For this circuit if you set R=0 and S=1, Q' would be 0 (this is because for a NOR gate if at-least one input is 1 the output is 0). So we can be sure that output Q' is 0.
Now this Q' is fed to the above NOR gate and since R=0 the output Q is 1. You can verify this from below NOR table.
What if you set R=1 and S=0, well its quite intuitive (opposite of R=0 and S=1 condition), and this would set Q=1 and Q' = 0.
Note that Q and Q' are complementary, that is if Q=1 then Q' should be 0.
Consider a simple AND gate circuit:
Now consider the following circuit
For this circuit if you set R=0 and S=1, Q' would be 0 (this is because for a NOR gate if at-least one input is 1 the output is 0). So we can be sure that output Q' is 0.
Now this Q' is fed to the above NOR gate and since R=0 the output Q is 1. You can verify this from below NOR table.
NOR Truth Table |
Now here comes the interesting part, after setting, R=0 S=1, if you change inputs to S=0 and R=0, the value of Q and Q' does not change! This is because when R is set to 0, Q' which was already 0 (from previous output) and this would give Q =1. Similarly when S=0 and Q=1(from previous output) Q'=0.
Note that Q and Q' are complementary, that is if Q=1 then Q' should be 0.
In the same way you can verify for R=0 S=1 condition. You will find the outputs does not change when you change back to R=0 and S=0.
So we successfully stored our first bit of information in a circuit!
This circuit is called as latch or a Flip-Flop more precisely a SR Flip-Flop, which is one of the types of Flip-Flops.
The following SR-FF truth table summarise the result:
So we successfully stored our first bit of information in a circuit!
This circuit is called as latch or a Flip-Flop more precisely a SR Flip-Flop, which is one of the types of Flip-Flops.
The following SR-FF truth table summarise the result:
In the table Qn is the value of Q before applying the inputs. Since there is just two possible values Q could take 0 and 1, these combination have been added for every common pair of inputs (S R).
In fact when you power the circuit (by applying power to Vcc of the Flip Flops IC) the circuit would attain either a state with Q=0 (called as reset state) or Q=1 (called as set state). This happen because both the NOR gates have slightly different propagation delay time.
You must have noticed that when inputs S=1 R=1 the output is undetermined this is because when either of the inputs is 1 for a NOR gate it tries to output 1. In this case both Q and Q' would try to attain a 1 state which is not possible (try putting in values of S R and figure out).
So this is all about basics of Flip Flop. In my next post I will talk about a new FF called JK FF which does not get into any problem of undetermined condition.
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