Led diode blinking

Thread Starter

Ernesto3

Joined Jul 2, 2022
2
Hi, does anyone know what types and measures of components I need to bulid one diode flash circuit. I know that I need to connect led, transistor and resistors in series, and capacitor in parallel with them but I do not know what voltage I need and measures of components.
 

Alec_t

Joined Sep 17, 2013
13,229
Welcome to AAC!
If you Google "LED flasher schematic" you will find numerous circuits with component values marked on them, suitable for driving a typical low power LED (one with a maximum drive current of about 20mA). High power LEDs would require something a bit more specialised.
 

ThePanMan

Joined Mar 13, 2020
520
We need more information.
A WHOLE LOT of "More" information.

What kind of LED's?
What voltage do you WANT it to operate on?
What is your skill level with electronics?
What pattern do you want it to flash?
What rate of flash?
How many LED's?
What's their forward voltage(s)?
How much space do you have to work with?
How much money do you want to spend?
Do you have any idea on how to get started?

Help us help you.

Oh, and yes, welcome to AAC.
 

Thread Starter

Ernesto3

Joined Jul 2, 2022
2
A WHOLE LOT of "More" information.

What kind of LED's?
What voltage do you WANT it to operate on?
What is your skill level with electronics?
What pattern do you want it to flash?
What rate of flash?
How many LED's?
What's their forward voltage(s)?
How much space do you have to work with?
How much money do you want to spend?
Do you have any idea on how to get started?

Help us help you.

Oh, and yes, welcome to AAC.
Thank you,
I will use 12v LEDs
I want to use probably 9v or 12v
I started with electronics about 1 month ago
First I planned to start with one flashing diode than, more of them, and at the end to be able to create real transimiter and reciever for example for remote control car or something else.
 

Tonyr1084

Joined Sep 24, 2015
7,199
I will use 12v LEDs
A 12 volt led is likely a standard LED with a resistor built into its circuit. LED's aren't "Voltage" driven, they're "Current" driven. A typical 5mm LED has a forward voltage somewhere between 2 and 3.5 forward volts (Vf). If using such an LED on 12 volts you'd subtract the Vf from the supply voltage (12V). Then you'd calculate for the amount of current you want to run through your LED. 20mA is a common current for LED's.

The math:
(12V - Vf) ÷ 20mA = Ω
If the LED has a 2.5Vf then:
(12V - 2.5Vf) ÷ 20mA = 475Ω

You mentioned use of a 9V source:
(9V - 2.5Vf) ÷ 20mA = 325Ω

Notice in each case the different voltage source means a different resistor to create the necessary current for the LED. But 20mA can be too bright. If you wanted to use 5mA you substitute the numbers. For a 12V source you'd calculate a 1.9KΩ resistor. For a 9V source - a 1.3KΩ resistor. Since you're more likely to find a 2KΩ standard value resistor your current would be slightly less than 5mA (4.75mA) with a 12V source. Simply divide the voltage (V-Vf) by the resistance.
 

Sensacell

Joined Jun 19, 2012
3,098
The transistor is supposed to be backwards so that it has avalanche breakdown of the emitter-base (max allowed voltage is only 5V) then it and the large capacitor become an oscillator to blink the LED.

This is a great example that shows how being complexity-phobic gets you into trouble.
While this single transistor circuit can oscillate, it relies on poorly defined properties of the transistor and will work with some transistors and not with others of the same type. It's also very sensitive to the supply voltage, too low and it will not cause breakdown of the BE junction. Build a the standard two transistor multivibrator circuit, a few more parts, but almost guaranteed to work- with almost any transistor.
 

MrAl

Joined Jun 17, 2014
9,633
Hi,

Today most people today would use a 555 timer. Millions manufactured and sold. Simple applications.
To get more control use an Arduino.
 
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