[Ronja] Testing switching time of an LED

[Bruce M Simpson]

Deepak Mishra wrote:
> 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 ??

Build the RONJA Audiofire module.

You still need to pass current across the PIN diode in order to have 
something to measure, other than resistance. You can connect the PIN 
diode to the 'scope directly if your probe is sensitive enough, I 
believe a standard X10 probe should be fine if your scope is calibrated 
correctly.

>
> 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 ?

Build the RONJA Hertz module.

cheers
BMS

>
> 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 
> <mailto: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
>     <mailto:xask.linus at gmail.com>>
>     To: "Twibright Ronja" <ronja at lists.pointless.net
>     <mailto: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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