Ramsey Electronics rrw1b User Manual

Ramsey Electronics Model No. RRW1B

Have you ever been frustrated with the range of your remote
controls? Tired of having to bounce your IR remote off of
ceilings and walls? Do you want to run your system from
another room or floor? Here is the answer to your prayers!
Extend the range of your remote controls through walls, around
corners, and even from outdoors!

• The separate IR Receiver module (RRW1A) with sensitive element

can receive your remote control’s signal up to 36 feet away before
re-broadcasting it wirelessly!

• The receiver (RRW1B) reconstitutes the radio signal using a PIC

micro-controller to restore noisy or weak signals and then re­broadcasts the IR remote’s signal to your components via a wired
high-efficiency IR LED.

• Extend the range of your remote control to greater than 100 feet

wirelessly beyond the receive range of the IR sensor. Greater than
300 feet with a directional antenna pair (available separately).

• Works with almost any remote control (38 kHz carrier), does not

need to be programmed.

• Operate from 8V to 16V AC or DC. Use our AC125 wall adapters

for long operation.

• LED indicator lets you know when you are receiving an IR signal

or not.

RAMSEY TRANSMITTER KITS

• FM100B Professional FM Stereo Transmitter

• FM25B Synthesized Stereo FM Transmitter

• MR6 Model Rocket Tracking Transmitter

• TV6 Television Transmitter

RAMSEY RECEIVER KITS

• FR1 FM Broadcast Receiver

• AR1 Aircraft Band Receiver

• SR2 Shortwave Receiver

• SC1 Shortwave Converter

RAMSEY HOBBY KITS

• SG7 Personal Speed Radar

• SS70A Speech Scrambler

• BS1 “Bullshooter” Digital Voice Storage Unit

• AVS10 Automatic Sequential Video Switcher

• WCT20 Cable Wizard Cable Tracer

• LABC1 Lead Acid Battery Charger

• IG7 Ion Generator

• CT255 Compu Temp Digital Binary Thermometer

• LC1 Inductance-Capacitance Meter

RAMSEY AMATEUR RADIO KITS

• DDF1 Doppler Direction Finder

• HR Series HF All Mode Receivers

• QRP Series HF CW Transmitters

• CW7 CW Keyer

• CPO3 Code Practice Oscillator

• QRP Power Amplifiers

RAMSEY MINI-KITS
Many other kits are available for hobby, school, Scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.

RRW1B1 KIT INSTRUCTION MANUAL

Ramsey Electronics publication No. MRRW1B Rev 1.1

First printing: January 2002 MRW

COPYRIGHT 2002 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York

14564. All rights reserved. No portion of this publication may be copied or duplicated without the
written permission of Ramsey Electronics, Inc. Printed in the United States of America.

RRW1B • 2

Ramsey Publication No. MRRW1B

Price $5.00

KIT ASSEMBLY

AND INSTRUCTION MANUAL FOR

RRW1B WIRELESS REMOTE

REPEATER KIT (Receiver)

TABLE OF CONTENTS

Introduction ............................................4

Circuit Theory ........................................5

Learn As You Build ...............................7

Parts List ...............................................9

Assembly ............................................. 10

Testing .................................................14

Using the RRW1 Pair ..........................15

Schematic ............................................16

Parts Layout ........................................17

Troubleshooting ..................................18

Warranty .............................................. 19

RRW1B • 3

RRW1B INTRODUCTION

Welcome to the RRW1B kit (and if you don’t have the time, the wired and
tested version). Let’s take a moment to help you understand the basic workings
of IR remote controls and how the RRW1 pair works. This will better help you
understand what you are about to build. As simple as it may look, the RRW1
system is one of the best remote repeaters money can buy thanks to some
specialized technology we have added to restore normally unusable signals.
We will get more into that in the circuit description section.

The RRW1A and RRW1B system is used to extend the normal range of your
IR remote controls. The RRW1A receives the signal from your IR remote
control, converts it to an RF signal and then transmits it over the air. The
RRW1B receiver then receives the RF signal, reconstitutes it, and then sends it
to an IR LED to control your components.

Many stereo component manufacturers skimp on the IR receiver sections of
their equipment so the range of the remote is very poor. Have you ever thrown
your remote at the power switch because the darn thing wouldn't work from
across the room?!. This system helps to surmount that very problem. Another
common use is control your unsightly stereo components that are hidden within
a cabinet while you’re entertaining. The system allows your remote to control
these items while they are tucked away inside of a cabinet (or even locked
away for security reasons) with only the RRW1A exposed so it can relay the
information!

To use my house as an example, the stereo components are positioned
behind the couch and it is very cumbersome to have to reach way up with the
remote and beam it backwards in order to control them. Half the time it doesn’t
work even work for me because the batteries keep popping out of the remote (I
lost the remote’s back plate a long time ago in one of the many apartments I’ve
rented in the past, but that’s another story)! I don’t want to have to re-arrange
the room (that is the Wife won’t let me!) just so the remote will work better.
Instead I use the RRW1A in front of the couch someplace and have it relay the
signal back to the RRW1B to control the equipment for me.

To increase the effectiveness of this kit, we take advantage of a high­sensitivity IR receiver element which claims on its specification sheet to work
up to 11 meters (about 36 feet) away from the remote control (that’s about 10.9
meters further than my VCR remote works!). Now I can truly atrophy on the
couch when my favorite program comes on and feel the pounds start packing
on! “Hey… another bag of chips when you get a chance Honey!!”

RRW1B • 4

RRW1 PAIR THEORY OF OPERATION

The RRW1A (transmitter board) may look quite simple but there is actually
quite a lot being done inside each one of the parts. Many individual compo­nents are packed inside of the IR receiver part (U2) itself; so many in fact that
if it was built up with discrete components, it would never fit in this little kit
case. Inside of the part there is an IR detector diode, amplifier, AGC circuit,
bandpass filter, a peak-hold circuit, an integrator, comparators, and an output
amplifier. Heck, the part is a kit in itself! Just be glad it’s all in one nice module
and ready to go.

IR remote controls send out their data on a 38 kHz carrier much like the way
your FM radio does. By modulating the carrier signal with the data you want to
send, it is possible to increase the range of the transmission and decrease in­terference from other IR sources like ambient light (the sun pumps out lots of
IR!!!). The modulation style used with remotes is called OOK (on off keying).
In a nut shell, OOK modulation means the IR LED is switched on and off at a
rate of 38 kHz in order to send the needed data. The digital data being sent
(ones and zeros) is composed of a certain duration pulse for a one and a dif­ferent duration pulse for a zero. There are pauses with no carrier in-between
each one and zero data bit being sent for easy determination of the bit
boundaries. A common format for this type of data transmission is called
60/30 PWM. While this may sound complex, it really is not. Let’s take a closer
look.

PWM stands for Pulse-Width-

0

Modulation, meaning we
change the on-time of the LED
within a certain amount of time.
If we send data at a rate of 1

1

bit per second (bps), each bit
would take up a second of
sending time. To represent a 1,
the LED may be switched on

0Sec 1Sec

IR Remote
Output

0Sec 1Sec

IR Detector
Output

and off at 38 kHz for 60% of
the one second time frame (0.60 sec.) of it. For a 0, the LED will be switched
on and off at 38 kHz for 30% of the time (0.30 sec.) of the entire second.

RRW1B • 5

0

1

When the IR detector on the RRW1A (transmitter board) “sees” a 38 kHz IR
signal, the output of the detector goes low (it is inverted). When there is no 38
kHz signal present the output idles high. On the output of the IR detector you
won’t see the 38 kHz, just the data that the 38 kHz represents from your IR
remote control. This data from the IR detector is then used to switch on and
off a 433.42 MHz oscillator. Instead of switching an LED on and off at 38 kHz,
we are now switching an electrical field on and off at a rate of 433.42 MHz.
This acts as our new carrier frequency for the wireless part of the kit.

The oscillator section is a Colpitts style oscillator formed by Q2, C7, C8, R6,
and X1. The oscillator is turned on and off by Q3 through resistor R4 in accor­dance with the received IR data. When a data pulse is detected by U1, its out­put goes low pulling the base of Q3 low to turn it off. When Q3 turns off, the
collector (R3, R4, and Q3 junction) is pulled high so the needed bias voltage is
applied to R4 causing Q2 to turned on and begin oscillating with the surround­ing parts. Turning Q2 on and off performs the on-off data keying (OOK modu­lation) that we require to re-broadcast the IR signal.

The RRW1B (receiver board) has a specialized receiver chip which is also
set at 433.42 MHz. The receiver detects whether or not a 433.42 MHz field is
being broadcast and only sets its data output high if a signal is present. The
RRW1B will replicate the transmitted data by turning its data out pin on and off
at the received data rate. To re-send this data, we have to modulate a 38 kHz
carrier again in accordance with the data the IR detector puts out. By using a
micro-controller the data output from the IR detector can be sampled and a
Pulse Width Modulated (PWM) signal at 38 kHz can be generated in accor­dance with the detected data.

By using this method with a micro-controller, we can add some intelligence
to the regenerated signal as well. The sample IR remotes we have looked at
send their data at a rate of around 2400 bits per second. This means that our
minimum pulse length for a zero should be 1/2400 x 0.30 seconds long (125
uS). Consider this example, let’s say that the signal from the IR remote is
weak and it fades out due to interference from some other IR source before
the data pulse is finished (i.e. 80 uS instead of 125 uS). The micro-controller
will continue to send the 38 kHz until 125 uS is up, not allowing the re­transmitted signal to drop out the way the original source did. This error cor­rection feature can be disabled in case you have a strange remote that is not
compatible (to this point we have yet to run across one that doesn’t work). Re­move the jumper from J21 to disable this feature and have U21 blindly re­create the data it sees.

Once the micro-controller on the receiver board has re-generated the 38 kHz
carrier (modulated by the data), its output is buffered by a transistor stage that
drives the high power IR LED used to control your equipment.

Wow! There’s a lot going on here!

RRW1B • 6