Resistor color code

A resistor is the most important electrical component in almost every electronic circuit, it can limit current to any load such as led, transistor, opamp, etc. We must read resistor color code if we want to know the resistive value, tolerance, temperature coefficient. Resistors have different color bands (3,4,5,6) the more color bands the more resistor's information.Now let's start with 3 bands resistor color code.

The above resistor has only 3 bands First digit, Second digit, and multiply. A 3 bands resistor color code has fixed +/-20% tolerance that means if color code value is 1,000 ohms the real life resistive value may be +/- 200 ohms. 
4 band resistor color code

A 4 bands resistor color code has tolerance value color strip, the resistor on an above picture has 5% tolerance. This type of resistor uses in a regular circuit such as television,radio,washing machine.

5 bands resistor color code

A 5 bands resistor color codes have third digit color bands.
1(first digit) 0(second dig…

DIY toggle touch sensitive switch

Hello everyone, today I'm going to show you how to make a touch sensitive switch, the switch makes you control light,motor just by touch the switch. The switch is very long life and safe to operate even your hand wet because you can put the touch sensor behind any plastic plate and make a touch sensitive light switch or you even can put the circuit in a lamp and make a touch lamp.

This circuit uses CD4013BE d flip-flop IC . When you touch the touch sensor( The red module on the above picture) The sensor send output high to CD4013BE pin3 and make CD4013BE pin 1 change state to on or off once.
However, CD4013BE output current not high enough for a relay to operate(yellow-black box on the above picture) so you need a PNP transistor(BD140) to amplify current for a relay.
You can remove R4 and LED if you don't need light indicator in your project.
This circuit uses 5 volts DC to operate so you need a transformer and it cause your overall circuit big but you can buy a tiny 220/110 v AC to 5 volts DC transformer to eliminate the problem, the transformer cost around 3$. I use a transformer because I want to make simple and safe circuit and the transformer life expect is 100,000 hours or 11 years!!!
Hi-Link 100 - 240 AC to 5 volts DC switching transformer.

Electronic components list:

IC1 CD4013BE
Transistor BD140 PNP type
5 volts relay
TTP223b touch sensor module
R1,R3,R4 = 2 Kilo-ohms
R2 value is 100 kilo-ohms
LED = warm white led but you can change it to another color as you wish

Circuit test video.

Enjoy hobby world!!!


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