[Ronja] Testing switching time of an LED

[Arun Krishnan]

Hi Deepak,

I don't think a 555 can clock to the 10Mhz you'll need to test your LED
at. 

But I'm thinking you can measure the rise and fall time just by a single
pulse and a CRO that has enough resolution.

Regards,
Arun


----- Original message -----
From: "Deepak Mishra" <xask.linus at gmail.com>
To: "Twibright Ronja" <ronja at lists.pointless.net>
Date: Fri, 21 Mar 2008 20:00:19 +0530
Subject: Re: [Ronja] Testing switching time of an LED

Thanks ,
I had this basic idea in mind that I must apply a fast input square wave
signal to the led and check the output using a scope on the photo diode.

But the basic problem is I am such a new bie that I am not sure if i
should
connect
the photo diode directly to the oscilloscope and with resistor in series
or
what ??

And how do i generate a square wave signal of the desired frequency ?
I have heard of the 555 timer, do I have to use the breadboard ?

I good with software, but not so good at hard ware, I hope you get the
idea
?

Thanks anyway!
Cheers,
Deepak


On 21/03/2008, Arun Krishnan <arunk at speedpost.net> wrote:
>
> Hi Deepak,
>
> You'll need to hook up the LED to a simple square wave generator and use
> a fast photodiode connected to a CRO to measure how fast it is
> switching. There are other methods where you could program something
> like a microcontroller to measure it, but the easier way would be to use
> a CRO.
>
> Regards,
> Arun
>
>
>
> ----- Original message -----
> From: "Deepak Mishra" <xask.linus at gmail.com>
> To: "Twibright Ronja" <ronja at lists.pointless.net>
> Date: Fri, 21 Mar 2008 19:13:44 +0530
> Subject: [Ronja] Testing switching time of an LED
>
> Hi all !,
>
> As always, I am having trouble find the LED HPWT-xxxx-xxxx.
> So I am going to test some LED manufactured in my country (India) easily
> available at low costs.
>
> I mainly want to test the rise/fall time of the LED and its not in the
> datasheet.
>
> I am an electronics newbie, so could somebody point me to an electronic
> circuit and a way to measure
> the rise and fall times of the LED ?
>
> Cheers,
> Deepak
>
>
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