Ramsey Electronics RRW1A User manual

RRW1A •1
Ramsey Electronics Model No. RRW1A
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!
•IR Receiver module with sensitive element can receive your
remote control’s signal up to 36 feet away before re-broadcasting
it wirelessly!
•The separate receiver (RRW1B) reconstitutes the radio signal
using a PIC micro-controller to restore noisy or weak signals and
then re-broadcasts 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.

RRW1A •2
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.
RRW1A1 KIT INSTRUCTION MANUAL
Ramsey Electronics publication No. MRRW1A 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.

RRW1A •3
RRW1A WIRELESS REMOTE
REPEATER KIT (Transmitter)
Ramsey Publication No. MRRW1A
Price $5.00
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 Diagram .........................17
Troubleshooting ..................................18
Warranty..............................................19
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone [phone]
Fax [phone]
www.ramseykits.com

RRW1A •4
RRW1A INTRODUCTION
Welcome to the RRW1A 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 high-
sensitivity 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!!”

RRW1A •5
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 compo-
nents 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 in-
terference 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 dif-
ferent 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-
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
bit per second (bps), each bit
would take up a second of
sending time. To represent a 1,
the LED may be switched on
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.
0
1
0Sec 1Sec
0
1
0Sec 1Sec
IR Remote
Output
IR Detector
Output

RRW1A •6
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 accor-
dance with the received IR data. When a data pulse is detected by U1, its out-
put 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 surround-
ing parts. Turning Q2 on and off performs the on-off data keying (OOK modu-
lation) 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 accor-
dance 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 re-
transmitted signal to drop out the way the original source did. This error cor-
rection 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). Re-
move the jumper from J21 to disable this feature and have U21 blindly re-
create 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!

RRW1A •7
RAMSEY “LEARN-AS-YOU-BUILD” ASSEMBLY STRATEGY
Be sure to read through all of the steps and check the boxes as you go to be
sure you didn't miss any important ones. Although you may be in a hurry to see
the end results, before you switch on the power be sure to check all wiring and
components (especially capacitors) for proper orientation. Also check the board
for any possible solder shorts and/or cold solder joints. All of these mistakes
could have detrimental effects on your kit - not to mention your ego!
Kit building tips:
Use a good soldering technique - let your soldering iron tip gently heat the
traces to which you are soldering, heating both wires and pads simultaneously.
Apply the solder on the iron and the pad when the pad is hot enough to melt the
solder. The finished joint should look like a drop of water on paper, somewhat
soaked in.
Mount all electrical parts on the top side of the provided circuit board.The top
side is silk screened with the part number reference designators for easy
positing of the components. When a part is installed, it should be placed flat to
the board with the leads slightly bent on the backside of the board to prevent it
from falling out before soldering in position (1). The part is then soldered
securely to the board (2-4) and the remaining lead length is then clipped off (5).
Notice how the solder joint looks on close up, clean and smooth with no holes
or sharp points (6).

RRW1A •8
This project will not work as well as you may wish if you just slap it together
without following good assembly techniques and all of the instructions. No
matter how clear we may think our manual is, if you have any questions give us
a call at the factory instead of jumping to conclusions. We will be happy to help
you with any problems may run into.
It is always good practice to mount the parts AS LOW AS POSSIBLE to the
board. A 1/4” lead length on a resistor not mounted close to the board can act
as an inductor or an antenna, causing all sorts of problems in your circuit. Be
aware though that there are stand up components in your circuit. They don’t
need to be squished to the board, but keep the portion of the resistor closest to
the board mounted right on the board.
For each part, our word "Install" always means these steps:
1. Pick the correct part value to start with.
2. Insert it into the correct PC board location, making sure the part is
mounted flush to the PC board unless otherwise noted.
3. Orient it correctly, follow the PC board drawing and the written directions
for all parts - especially when there's a right way and a wrong way to solder
it in. (Diode bands, electrolytic capacitor polarity, transistor shapes, dotted
or notched ends of IC's, and so forth.)
4. Solder all connections unless directed otherwise. Use enough heat and
solder flow for clean, shiny, completed connections.
Keeping this in mind, lets begin by sorting out our components and cross-
checking them against the parts list to make sure we have received everything.
NOTE TO NEWCOMERS: If you are a first time kit builder you may find this
manual easier to understand than you may have expected. Each part in the kit
is checked off as you go, while a detailed description of each part is given. If
you follow each step in the manual in order and practice good soldering / kit
building skills, the kit is next to fail-safe. If a problem does occur, the manual
will lead you through step by step in the troubleshooting guide until you find the
problem and are able to correct it.

RRW1A •9
PARTS SUPPLIED WITH YOUR RRW1A (TRANSMITTER) KIT
Capacitors
1 2.2 pF ceramic capacitor (marked 2.2) [C7]
1 8.2 pF ceramic capacitor (marked 8.2) [C8]
3 47 pF ceramic capacitors (marked 47) [C1,4,6]
1 0.001 uF ceramic capacitor (marked .001 or 102 or 1 nF) [C3]
1 0.01 uF ceramic capacitor (marked .01 or 103 or 10 nF) [C2]
1 0.1 uF ceramic capacitors (marked .1 or 104 or 100 nF) [C5]
1 10 uF electrolytic capacitors [C9]
1 1000 uF electrolytic capacitor [C10]
Resistors
1 220 ohm resistor (red-red-brown) [R7]
1 270 ohm resistor (red-violet-brown) [R6]
1 470 ohm resistor (yellow-violet-brown) [R1]
1 2.2K ohm resistor (red-red-red) [R2]
2 4.7K ohm resistors (yellow-violet-red) [R3,8]
1 10K ohm resistor (brown-black-orange) [R5]
1 22K ohm resistor (red-red-orange) [R4]
Semiconductors
1 IR Sensor Module [U1]
1 1N4000 series rectifier diode (black with white band) [D2]
-Note that 1N4000-1N4007 diodes may used.
2 2N3904 NPN transistors (marked 2N3904) [Q3,4]
2 2SC2498 UHF NPN transistors (marked C2498 or C2570) [Q1,2]
1 78L05 5V voltage regulator (marked LM78L05ACZ ) [VR1]
1 Large Green LED [D1]
Miscellaneous Components
1 33 nH 4-turn coil [L1]
1 DPDT PC mount pushbutton switch [S1]
1 2.1 mm DC power jack [J1]
1 433.42 MHz saw resonator (TO-39 Metal 3-pin case) [X1]
1 6” piece of #20 buss wire

RRW1A •10
ASSEMBLY OF THE RRW1A
Assembly of the RRW1A is straight forward but it does require some time
and patience. To get our bearings, we will start by mounting the power jack
and move on from there. It serves as a good reference point for the other
parts.
1. Install J1, the 2.1 mm power jack. Be sure to get a solid connection to
all three pads as this will have to take some mechanical strain during
normal use. Use ample solder (without ‘globbing’ it on of course).
2. Install R6, the 270 ohm resistor (red-violet-brown).
3. Install C7, the 2.2 pF ceramic capacitor (marked 2.2). C7 acts as the
feedback path for our “Colpitts” style oscillator. This capacitor combined
with the next one (C8) and the saw resonator (X1) make this circuit
oscillate at the required frequency. Note that this is one of the rare
exceptions to installing at 90 degree angles. This part is actually installed
at a 45 degree angle to keep lead lengths as sort as possible. This goes
to show how important it is to keep your lead lengths short! Even a small
amount of trace can introduce inductance that may prevent our oscillator
from working properly.
4. Install C8, the 8.2 pF ceramic capacitor (marked 8.2).
5. Install C3, a 0.001 uF ceramic capacitor (marked .001 or 102 or 1 nF).
6. Install L1, a 33 nH 4-turn inductor. Be careful not to distort or crush this
when installing it.
7. Install Q1, one of the 2SC2498 transistors (marked C2498 or C2570).
Pay close attention to the Parts Layout Diagram and the silkscreen on the
circuit board for proper orientation (the flat side is a good indicator). Right
next to Q1 is Q2 (another 2SC2498 transistor) so make certain to use the
correct mounting holes.
8. Install Q2, another 2SC2498 transistor (marked C2498 or C2570).
Again note the orientation of the flat side before soldering.
Transistor Q2 provides the amplification needed to keep the 433.42 MHz
RF oscillator going. Q1 and its surrounding parts form a special buffer stage
which isolates the antenna from the oscillator. If it wasn’t for this buffer stage,
the oscillator could stop working whenever things like your fingers or a metal
object are nearby. This pair working together forms a very stable oscillator
which resists a lot of external changes to maintain performance!
9. Install X1, the saw resonator (TO-39 metal case). This is the
component that determines the operating frequency of the oscillator by
interacting with the feedback capacitors surrounding Q2. Note the
silkscreen on the circuit board for proper orientation.