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From: "Bob Nelson"
Subject: Re: IR repeater using Sharp GP1U59
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Fri, 18 Oct 2002 01:31:10 GMT
NNTP-Posting-Date: Thu, 17 Oct 2002 21:31:10 EDT
Organization: Cox Communications
I've tried the circuit shown on the third link and did have success
generating a signal with the sharp module but the modules I have are part of
a pre-made IR detector device that I can't seem figure out. The circuit is
I'd hate to tear into all these devices and wire just the module. It's a
pretty simple circuit but I'm a total beginner and can't figure what the
bylogic at lycos dot com
"Lizard Blizzard" wrote in message
> Bob the Builder wrote:
> > "Bob Nelson" wrote in message
> >>I recently aquired a few of these IR detection devices and I was
> >>if anyone had any experience with these or could help with a design to
> >>repeat the ir signal. I'm a total novice with circuit design but can
> >>a schematic. I'd like multiple inputs repeating the signal to multiple
> >>Here's the device:
> >>Here's the inside:
> >>email: bylogic at lycos dot com
> > I've used the Sharp IR detector / decoders before. The units contain a
> > photodiode, amplifier, limiter, bandpass filter, demodulator,
> > integrator, comparator, and an open collector output transistor. The
> > device receives an on-off modulated IR signal (typically 40kHz) and
> > outputs a signal representing the On and OFF periods. For the ON
> > period, the output is LOW, for the OFF period, the output is weakly
> > pulled up to the supply voltage (about 100K Ohms). In order to repeat
> > the IR signal as demodulated by this device, it is necessary to
> > re-modulate it at the desired frequency. The accuracy and stability
> > requirements of the system define the type of oscillator needed. The
> > simplest method is to use a CMOS 555 timer IC connected as an astable
> > mulivibrator (oscillator) tuned to the desired frequency (typically
> > 40kHz). Modulation is accomplished by using the output of the Sharp
> > device to drive a logic level P-channel MOSFET (gate) connected to +5V
> > (source), and the anode of an IR LED (drain). The cathode of the IR
> > LED is connected to one end of a current limiting resistor (47 Ohms or
> > so). The other end of the resistor is connected to a logic level
> > N-Channel MOSFET (drain). The source is connected to ground (+5V
> > return). The gate is connected to Pin 7 of the CMOS 555 timer IC and
> > to one end of a pullup resistor (4.7k). The other end of the resistor
> > is connected to +5V. Pins 4 and 8 of the 555 are connected to +5V, pin
> > 1 is ground. Pin 3 is connected to a resistor (17.86k Ohm, use 5k Ohm
> > trimmer in series with 15k Ohm) whose other end is connected to pins 2
> > and 6 as well as a capacitor (0.001uF). The other end of the capacitor
> > is connected to ground. Pin 5 has no connection. This configuration
> > gives 50% duty cycle at a frequency determined by; f=1/(1.4*R*C).
> > In this way, the IR LED will be turned on by the N-CH MOSFET at a
> > frequency controlled by the 555, but only when the P-CH MOSFET is
> > turned on by the output of the Sharp device being low (IR signal
> > signal present).
> > A similar oscillator circuit is shown in:
> > http://www.robotroom.com/Infrared555.html
> > If higher accuracy and stability is required, a crystal controlled
> > oscillator/ divider could be used. A 74HC4060 is a possibility.
> Or better yet, forget about all this foolishness of demod and modulation
> and just use a simple amplifier, like the following.
> This is the circuit that you want to build. It has to be tuned, and if
> you have two different appliances on differente freqs, then it won't
> work with both appliances. That sucks.
> > Bob
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