From: "Reala" <->
Subject: Re: I/O logic problem
Date: Fri, 6 Dec 2002 17:09:50 +0800
Organization: IMS Netvigator
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Thank you for your reply.
The system is run at 5V.
Would you to draw a simple circuit diagram for me, because i am weak in
my email: firstname.lastname@example.org
Moreover, my mcu have 4bit resolution A/D converter. Can I use this to solve
"Paul Burke" wrote in message
> Reala wrote:
> > According to my knowlegde, normally, we input 4V or above for 5V system,
> > is High. 0.5V or below, it is Low.
> For HCT high is 2.0V or above, low is 0.8V or below.
> > I use a MCU, according to the datasheet, Input High is 0.8VDD minimum,
> > Low is 0.2VDD maximum.
> What voltage is this thing running on? Whatever you use, theses are the
> signal levels you need to work with.
> I use a IR sensor series with a resister. When IR
> > applied on the sensor,
> > current flow through the sensor and resister. So, by detecting the
> > drop at the resister, we can detected IR.
> > VDD-----R----------IR detector----GND
> > ^
> > Vg
> > However, my problem is that: IR source which I want to detect is too
> > compared working environment. IR in the working enviroment cause the IR
> > decter "semi-on", so, the voltage Vg is about 4V (off my IR source).
> > When i turn on my IR source, it is 3.5V.
> You need an amplifier circuit to remove the background IR. This is
> usually done by a low- pass filtered version of the signal to the non-
> inverting input, and the unfiltered signal to the inverting input. You
> only see rapid changes at the output. Use a Schmitt buffer to interface
> this to your MCU.
> Paul Burke