turn on and off a led with resitance, capacitor and diod

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iurelectr

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Dear friends,

what is the relation between a resistance a capaitor and a diod in order to turn on and off a led?

imagine 5 V in the source

All the best,
iurelectr

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its hard to tell you.... so first put your circuit on the thread so that one could do try...
 
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If you are giving 5V , a 220 Ohm resistor in series is enough to take care of the current shoot up.

For normal LED's the current should be limited to 20mA.

Hope this help...
 
any body else who tell me circuit diagram of on/off switch by input 12 volt current.when will input current ON so switch will be ON but when input current will be OFF but out put current have ON.and second time when we will ON input current so output will OFF.
 
**broken link removed**

Here is a circuit... I think I will use this first approach and then try to add the led somewere...probably next to V0.
The idea is to have a value at wich the diod will discharge and make a led go on (so I can think about puting the led next to the diod...)

Thanks
 
you are unable to make proper link so follow these steps...

1. see this image and do as written there-


2.

and then close this window

3.

do this and post your attatchment
 
your link was from your hard drive so it was not possible to access image so follow as i have said in my above thread...
 
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If the LED is connected to VO and ground then it will blink one time and maybe will burn out when the battery is connected.
The LED needs a series current-limiting resistor and the capacitor needs a resistor to discharge it when the battery is disconnected.
The diode does nothing.
 
usage of capacitor...

Thanks.

I think that I have a problem when you say:
"the capacitor needs a resistor to discharge "

How do I make a capacitor charge and discharge simply with a resistor?
The objective is to make the led blink.

Regards
Have an excelente 2010
 

dear, capacitor always need a path to discharge. you use a resistor with this capacitor for its discharging.
 
If you want the LED to blink on and off over and over then you must drive it with an oscillator circuit.
 
Hi

Here is what is stated the simplest form of LED plasher using a CAP. and a resitor.The exapmple also uses two legs of a transistor.It also as the opp requests how and why this circuit enables an LED. to flash. Not tried it myself.

Simplest_LED_Flasher_Circuit
 
Now I saw the example with the transistor... it seams great! thank you very much!

But I have one question: where do you connect the base of the 2N2222?
 
Hi

Read through the website as the text explains how the circuit works.The base of the transistor as been cut off as it's not required!!

Also follow the links on the site as extra info is supplied.

Also

Quote from site-

"If the resistor that charges the capacitor is too low in value (or if the power supply voltage is too high), the current through the transistor will not become low enough for the transistor to turn off. If the resistor that charges the capacitor is too high in value (or the power supply voltage is too low), the capacitor will not be able to charge to a high enough voltage to enable the transistor to turn on. This is because the transistor draws as small amount of current before switching on."
 
error in circuit

Hi friends,
I have done the circuit with two transistors...but it doesn't work...
Why? I don't know help me please.

I'm using 12 Volts being the positive connected to the resisitor 330 ohm and the negative
to the capacitor (negative part) and to the negative of the led.

In fact, the led turns on but doesn't switch.

With the resistor of 330 ohm the circuit doesn't light on the led...just without that resistor...

Thanks.
Regards
Rui


 
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