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From: "Reala" <->
Subject: Re: IR detection problem
Date: Mon, 9 Dec 2002 11:54:54 +0800
Organization: IMS Netvigator
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
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?
"Ken Taylor" wrote in message
> "Reala" <-> wrote in message news:email@example.com...
> > 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.
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