how can i connect 1000 led in series with 3.6 forwrd volt. of 3.6v and 20mA

[rahol]

how can i connect 1000 led in series with forwrd volt. of 3.6v and 20mA

hello
i am making and led board that display fixed alphabet.
so my requirement is that each led must have a constant forward voltage drop of 3.6v and 20mA flowing through the led.. please help me out



thanx in advance

 

[jeffrey samuel]

Connect it to a suitable driver of about 3.6 kV this is not so pleasant

So kindly split the panel of LED into several sub divisions and they can be used to power the LED in a segment

Power rating for 100 LED will be 360 V and current of 2A so splitting the setup into divisions of 100 then it becomes more feasible

 

[chuckey]

In the UK any voltage above 70 DC or 50V AC is considered dangerous, so I would split the panels to have these sort of voltages on them. Do not earth any part of the circuit but put a earth leakage relay down to earth, so if you accidentally touch something at the 70V end of the chains the earth current will trip the main supply to off.
Frank

 

[jeffrey samuel]

Yeah the more you split the serial connection the more safer you are to use this setup

 

[rahol]

my input voltage to series connection of LED is 9V DC .. so my question is that can this series connection of 100 LED can glow with 3.6 constant forward voltage drop and 20mA ??
Is this input voltage is enough?

 

[chuckey]

With only 9V, you can only use 2 LEDs in series with a resistor in series with them. 2 LEDs will drop 2 X 3.6 V = 7.2V, so you have to drop 9 - 7.2 V across the resistor at a current of 20mA, so its value is 2.8/.02 = 140 ohms. So you will need 500 140 ohm resistors :-(
If you can use 12V then 3 LEDs per chain with a resistor, volt drop is 3 X 3.6 = 10.8, resistor = 1.2/.02 = 60 ohms. Only 333, 60 ohm resistors + a 420 ohms for the odd LED.

Frank

 

[jeffrey samuel]

That is not possible to drive 1000 LED we need 500 of such type of drivers to supply the whole set up of LEDs

 

[rahol]

so is there particular ic for drivers?? if there then please tell me??

 

[FoxyRick]

It's not a case of telling you a driver ic.

Think about your power requirements and do some simple arithmetic. Also, please tell us all the information to begin with; it saves us telling you things that turn out to be not relevant.

As has been pointed out to you, each LED it series needs 1x 3.6V. So two in series need 2x3.6V, three need 3x3.6V, etc. Clearly the most you can do with 9V is two LEDs in series. Chuckey kindly calculated the series resistor that you also need to control the current through the two LEDs.

So, keeping things simple, you need 500 lots of the above, all wired in parallel across your supply. Since each of the above draws 20mA (the LED's forward current), you will need to supply 500x20mA = 10A of current from your 9V supply. Can it provide that much current?

Using a higher supply voltage would be much better, as you should now be able to realise.

What exactly is the specification of your power supply, and can it be changed?

 

[jeffrey samuel]

I don't think you are understanding our point here

It is not feasible to drive the LEDs using a single driver of 9 V supply there are a lots of complexity in design there so revising of your design is what is adviseable

 

[rahol]

ok thank you chuckey sir.. i will make the connection for 12v input for 3 LED and make the connection in parallel with 3 LED in series.
thank you all.

 

[prashanttyagi85]

ya
if you are going to change your driver to 12v then if it is possible to convert it to 24v then you should go for it (in my opinion). it will reduce the losses for your convertor.
i also think that you should go for a perticular letter i.e. for a letter you have to make your series parallel connection for per letter and then make each letter in parallel combination.

 

[jeffrey samuel]

But this will also be useful for driving about 6 LED with a single driver and a lot of drivers are needed Better split the design into parallel combination of LED matrices to prevent this loss

 

[prashanttyagi85]

ok its better