http://img30.imageshack.us/img30/322/imagevz.png
Why is the led off if i use a resistor?
If i remove the resistor the led is on?

How can i use voltage source in proteus?
It may be 5V or 10V.

Thank you.

 

Hello,

There must be a voltage source at the input of the regulator.
This must be at least 2 Volts higher than the output voltage.

Greetings,
Bertus

 

What is the input voltage to your 7805 voltage regulator?


You need to have a voltage source connected to the input of the regulator.

Your resistor is very large ... at 20 mA, it would drop 30 volts. Your LED is probably 1.5 Vf @ 20 mA. With a 5 volt supply, you would need a much smaller resistor.

 

What is the input voltage to your 7805 voltage regulator?


You need to have a voltage source connected to the input of the regulator.

Your resistor is very large ... at 20 mA, it would drop 30 volts. Your LED is probably 1.5 Vf @ 20 mA. With a 5 volt supply, you would need a much smaller resistor.

Hello,
How did you calculate 30 volts?(V=IR)

 

Your resistor value is too big.

 

Ohm's law. E = IR , so .02(amps) X 1500(ohms) = 30(volts).

 

Your LED is probably 1.5 Vf @ 20 mA. With a 5 volt supply,

How can i know this(about a led)?
What's 1.5vf?

 

Leds are pretty standard. It's easy to google up drops for different colors of diodes. Vf means the forward voltage drop which is the voltage measured accross it when it is forward biased (LED is actually a diode). . 1.5Vf means that when conducting 1.5 Volts are dropped accross it.

 

Ohm's law. E = IR , so .02(amps) X 1500(ohms) = 30(volts).

But it was only 1K resistor.
1k=1000(ohms) is it correct?

 

sensor. You want 20mA trough your led correct ?

The led will drop 1.5V. If you have a 5V supply it means you want the resistor to drop 3.5V accross it.

Calculating (5V-1.5V) / 0.02A we get 175 ohms.

So the resistor needs to be 175 ohms for this setup to work. With a 1k resistor the diode is deprived of current

 

Your diagram showed a 1k5 .... that's 1.5k or 1500

 

Your diagram showed a 1k5 .... that's 1.5k or 1500

Thank you for your information.
I did not know that 1k5 means 1.5K(kiloohms).

 

sensor. You want 20mA trough your led correct ?

The led will drop 1.5V. If you have a 5V supply it means you want the resistor to drop 3.5V accross it.

Calculating (5V-1.5V) / 0.02A we get 175 ohms.

So the resistor needs to be 175 ohms for this setup to work. With a 1k resistor the diode is deprived of current

http://img35.imageshack.us/i/35855855.png/
You are right.
But i can't find any resistor less than 1k in proteus/ISIS 7 pro.
I got 0R1.
What does it mean by 0R1?

NB:This time the led is on.

 

Hello,

A resistor od 0R1 is a resistor of 0.1 Ohms.
Can't you edit the properties of the resistors?
I do not use the simulator but some have the option of a rightclick on the resistor,
so a popup box shows up to edit the value.

Here is a list of standard resistor values:
http://www.educypedia.be/electronics/resistancevalues.htm

These values can be muliplied by 0.01, 0.1, 1, 10, 100, 1K, 10K, 100K, 1M.

More information on component coding can be found in the links of this page:
http://www.educypedia.be/electronics/datacomponent.htm

Greetings,
Bertus

 

Thank you.

 

Have you read this?

LEDs, 555s, Flashers, and Light Chasers

The section on LEDs covers it pretty well.