# Designing circuit from scratch

Inspired by chotu bot model.
So started to explore circuit designing.
@Ashish_Pardeshi sir suggested to start with basic design of circuit for glowing small led light and also to find value of each component with drawing circuit on paper.

After finding value I started to make and collect things which I required to make circuit.
So, today I purchased the following things to start

9V battery - 30₹
Resistance - 2₹
LED - 2₹
Battery cap - 5₹

So, their are two methods 2 find resistance value ohm’s law and krichoff law.
Let’s discuss this to improve basic foundation related to circuit.
@Farhan @ravi312 @jtd @G_N @ARYAN32

4 Likes

How to use kvl law to balance the resistance

The forward voltage drop of the LED is (assume) 2 V.
Any voltage source you use to light it up will have to be at least 2 V or more. Nothing will happen if your source is, for example, 1 V. Also, ALL voltage sources have some amount of internal impedance, so ideally, you need something a little bit more than 2 V to light up a 2 V LED.

With that, the voltage that needs to be “dropped” by the “current limiting resistor” needs to be

(Voltage of Source)-(FWD Voltage drop of LED)/Current.

So, at 9 V supply, and 2V drop across LED with 20 mA current flow, you get
=(9-2)*1000/20
=7000/20
= 350 ohms

3 Likes

Ohhh…
Ok I will use coin cell then adjust,
Ok thanks @Anool

Means I use extra 9v
To light up led
And it is difused

You mean the LED fused?