Hello friends!! Welcome to TechStudyCell. In this video, we will mainly talk about the
combination of a series-parallel circuit of multiple LEDs. and accordingly, we will calculate
the resistance value and measure the voltage and current reading in the multimeter. In my previous video, I have already talked
about the basics of the series-parallel LED circuit, you can find the link in the description. This video will be really helpful if you want
to make LED lights in your home. If you did not yet SUBSCRIBE our channel,
please do SUBSCRIBE and press the bell icon to get notifications for the upcoming videos. So let get started. In this example, we have connected 16 LEDs
in a series-parallel combination. There are total 8 parallel
strings 1, 2, 3, 4, 5, 6, 7, 8, so, total 8 parallel strings. and each parallel string contains 2 LEDs in series. As the forward voltage of each LED is 3 volt,
so the voltage drop across the string is 3+3 = 6 volt. And as there are total 8 strings and each
string getting 0.02 Amp current, so to measure the total current in the circuit, we have
to multiply 0.02 with 8, as there are 8 strings.
So the current in the circuit will be 0.16
Amp. So 0.16 Amp current will flow through this
resistor. And each string will get 0.02 Amp. Now we will measure the voltage drop across
the resistance. As the voltage drop across the string is 6volt
and the input voltage is 12volt, so we can easily get the voltage drop across the resistor,
which is (12 – 6) =6 volt. Now, we know the current through the resistor,
which is 0.16Amp, and the voltage drop across the resistor which is 6 volt. Now, we can easily calculate the resistance
value for this circuit, first, we have to get the voltage drop. As the voltage drop across the LED is 6 volt
and the input voltage is 12volt. SO this is the voltage drop across the resistor.
And the current through the resistor will
be 0.16 Amp. And if we calculate the value we will get
37.5-ohm. So here we have to use a 37.5-ohm resistor
for this circuit. Now we will calculate the wattage value of
the resistor, for that, we already know, the the voltage drop across the resistor which is 6 volt. and we have to multiply voltage drop with the current through the resistor, which
is 0.16Amp. And if we multiply these two values we will
get 0.96watt. So for this circuit, the wattage value of
the resistor should be greater than 0.96 watts. So we have to use a 1-watt resistor. we can not use 0.5 watts or 0.25 watts. And as you can see, I have made this circuit
on the breadboard. Here you will find 8 parallel strings, 1,
2, 3, 4, 5, 6, 7, 8. And each string contains 2 LEDs in series.
And this is the GND terminal. And this is the +ve terminal. You can see, I have used 2 resistors in series
10-ohm and 27-ohm in series to get total of 37-ohm. Now we will connect the supply to the circuit
and observe the reading in the multimeter. Here you can see, I have connected this multimeter
to measure the current through the circuit, and I will use this clamp meter to measure
the voltage across the resistor and the LEDs. Let me turn on the supply. In the reading, you can see, it is showing
the Ampere reading which is 0.143. which is very close to 0.16 Ampere. Now we will measure the voltage across the
supply. It should be close to 12 volt. You will see the reading in the clamp meter
and it showing 11.6 volt, which is the input voltage of the circuit. Now we will measure the voltage drop across
the resistor. Here I have used 2 resistors, 10-ohm, 27 ohms,
to get total 37-ohm. So let me show you the voltage reading across
the resistor, which should be close to 6 volts. In the clamp meter, you can see the voltage
reading is 5.4volt, which is very close to 6 volt.
Now, we will measure the voltage across each
LED string. Let me show you, each case we will get the
result 6 volt. I am measuring the voltage across each LED
string, and you can see it showing 6 volt. You can see the reading in the clamp meter. The voltage drop across each string is 6 volt. Now again the reading is very close to our
calculated value.
I want to add a point that for this circuit
we have calculated the wattage value of the resistor should be 1-watt minimum. But I have used 0.25-watt resistors, as I
don't have any 1-watt 37-ohm resistor. So if I touch this resistor, it is getting
very hot, So I can not use this circuit for a long time, as I have used very low wattage
resistors. So while designing any circuit, you should
always take care of the wattage rating of the resistor. In this case, I should use 1-watt resistor. I hope after watching this video, you can
easily design any LED circuit, and calculate the resistance value. You can also check my other video regarding
the forward voltage and current of the LEDs. If you find this video helpful, please hit
the like button, and share it with your friends.
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