From: Gary Tait
Subject: Re: IR detection problem
X-Newsreader: Forte Free Agent 1.92/32.572
Date: Mon, 09 Dec 2002 11:41:43 -0500
NNTP-Posting-Date: Mon, 09 Dec 2002 11:42:43 EST
Organization: WorldCom Canada Ltd. News Reader Service
On Mon, 9 Dec 2002 11:54:54 +0800, "Reala" <-> wrote:
>Thank you for your help.
>I do not have experience in doing "modulation".
>Would you mind to tell me more about how to implement this in MCU?
>Do you mind that I turn on and off my IR source at 40kHz?
>And receive a 40khz signal?
>but my IR source is so weak and the background IR is varied...Do I need to
>handle this issue?
Depending on your coding ability, a 40Khzsignal is rather easy to code
(or use a compiler with a library to create fixe frequency waveforms)
The signal is easy to receive, by using an IR receiver module form a
TV or VCR.
>"Ken Taylor" wrote in message
>> "Reala" <-> wrote in message news:firstname.lastname@example.org...
>> > Hi,
>> > I am development a device to detect "IR".
>> > The function is simple: my IR source applied when push the ON button.
>> > my IR source detect my IR source and
>> turn ON the indicator LED.
>> > However, the problem is that: my IR source is weak compared with
>> > background IR. It is ~0.2uA current go through my sensor
>> > and resistor if my source applied. However, the background source
>> > provides ~1.5uA current.
>> > I can increase the value of resistor,
>> voltage drop/change by my
>> > IR source increase. V=0.2uA X
>> However, as the background IR is varied,
>> > so, the Voltage drop by background IR also chagning. Increase R is
>> > not a good solution. Unfortunately, It is difficult to increase
>> > my IR source. I use MCU to develop this device. It have a
>> > 4-bit ADC. the resolution of each step is 0.125V.
>> > Any idea to detected my IR source without malfunction by background IR?
>> > Thank a lot.
>> > Reala
>> Modulate your source, say with 40kHz, and detect the modulated signal
>> than a 'carrier wave'. Gives better protection against sun-strike.