How the SOLAR POWER TOWER works . . .
`
`ISSN 1030-2662
`
`07
`
`SILICON
`CHIP JULY 2002
`
`$6 INC GST
`60*
`NZ$ 507
`siliconchip.com.au
`PROJECTS TO BUILD -SERVICING -COMPUTER S - VINTAGE RADIO - AUTO ELECTRONICS
`
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`9
`
`771030 266001
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`
`CODE-HOPPINGCODE-HOPPING
`
`4 CHANNEL4 CHANNEL
`
`UHF REMOTEUHF REMOTE
`
`
`UNIQUEUNIQUE
`
`HAM BANDHAM BAND
`
`RECEIVERRECEIVER
`
`
`PhonePhone
`
`HeadsetHeadset
`
`AdaptorAdaptor
`
`July 2002
`
` 1
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
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`
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`Apple EX1026 Page 1
`
`

`

`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
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`
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`Apple EX1026 Page 2
`
`

`

`Contents
`Contents
`
`Vol.15, No.7; July 2002
`
`FEATURES
`FEATURES
` 7 Victoria’s Solar Power Tower: A World First?
`It’s 1000 metres tall, sits on top of a massive greenhouse and will generate
`200MW of electricity. And it could be built in Victoria – by Sammy Isreb
`30 Applications For Fuel Cells
`Third article in our series looks at the advantages and applications of fuel
`cells – by Gerry Nolan
`65 Review: Tektronix TDS 2022 Colour Oscilloscope
`It boasts a colour LCD screen, measures to 200MHz is very easy to drive.
`And it’s all packed into a remarkably compact case – by Leo Simpson
`
`PROJECTS TO BUILD
`PROJECTS TO BUILD
`10 Telephone Headset Adaptor
`Keep your hands free with this simple low-cost project. It can be used with
`any phone that uses RJ11 modular plugs and sockets – by John Clarke
`18 A Rolling Code 4-Channel UHF Remote Control
`It has a long range, its rolling code is virtually unbreakable, it uses a keyring
`transmitter and it’s ideal for use with garage door controllers – by Ross Tester
`56 Remote Volume Control For The Ultra-LD Amplifier
`Revised preamp board lets you add our Remote Volume Control unit to the
`Ultra-LD Stereo Amplifier – by John Clarke & Greg Swain
`70 Direct Conversion Receiver For Radio Amateurs; Pt.1
`It covers from 7-7.3MHz, can tune both Morse and SSB signals and reads
`out the tuned frequency in Morse code! – by Leon Williams
`
`COMPUTERS
`COMPUTERS
`68 Creating Your Own Rules For Tiny Personal Firewall
`Tiny Personal Firewall lets you create your own tightly-defined packet filtering
`rules. Here’s how to go about it – by Greg Swain
`
`SPECIAL COLUMNS
`SPECIAL COLUMNS
`40 Serviceman’s Log
`If it look’s easy, it probably isn’t – by the TV Serviceman
`80 Vintage Radio
`The Airzone 500 series receivers – by Rodney Champness
`
`DEPARTMENTS
`DEPARTMENTS
` 2 Publisher’s Letter
` 4 Mailbag
`25 Subscriptions Form
`36 Circuit Notebook
`53 Product Showcase
`
`55 Silicon Chip Weblink
`86 Ask Silicon Chip
`89 Notes & Errata
`94 Market Centre
`96 Advertising Index
`
`www.siliconchip.com.au
`
`Victoria’s Proposed 200MW
`Solar Power Tower – Page 7.
`
`Rolling Code 4-Channel UHF
`Remote Control – Page 18.
`
`Revised Preamp With Remote
`Volume Control For The Ultra-LD
`Stereo Amplifier – Page 56.
`
`Direct Conversion Receiver For
`Radio Amateurs – Page 62.
`
`July 2002
`
` 1
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
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`Apple EX1026 Page 3
`
`

`

`PUBLISHER’S LETTER
`
`Is our electricity
`too cheap for solar
`to succeed?
`Our feature article on solar power in the March
`2002 issue certainly stirred up a lot of interest.
`We are still getting letters on the subject. Some
`people have strongly disagreed with the article
`while others have generally agreed while taking
`issue with our stance on the Greenhouse effect.
`Funnily enough, quite a few people cannot
`appreciate or totally discount the concept of “pay-
`back period” for a substan tial investment in solar
`panels. They equate it with any other household
`purchase. We don’t go along with this at all since, apart from a general warm
`fuzzy feeling about “doing the right thing by the environment”, solar panels
`don’t actually increase your comfort level in everyday living and they certainly
`don’t have a big payback, no matter how you do the sums.
`Since we are of this opinion, people then automatically assume that not
`only are we against the concept of installing solar cells but we are such
`“red-necks” that we don’t care about the environment. Nothing could be
`further from the truth. I have written many editorials about energy wastage
`over the years and I still think that we as a nation are very wasteful in our
`use of energy and raw materials.
`The real problem concerning solar cells is that in general, our electricity
`prices are too cheap, and this applies particu larly to domestic off-peak
`hot-water rates. It is this cheapness of electricity which results in such long
`payback periods for solar cell installations in metropolitan areas.
`There is another way of looking at the relative cost of our electricity. Just
`compare your quarterly bills for electricity and telephone, including your
`mobile. When you get right down to it, no-one would argue that telephones
`are more important to everyday comfort and welfare than electricity. Just
`think of winter heating, electric blankets, hot showers in the mornings,
`ease of cooking, refrigeration and all those other benefits which come as a
`result of having a reliable electricity supply and which we take for granted.
`Yet I’ll wager that virtually everyone who reads this editorial pays far
`more for their telephone services than they do for electricity. Consider
`also the enormous investment and in frastructure we have in producing
`electricity, compared with that for telephones. Looked at in this way,
`surely electricity is relatively very cheap while phones and mobiles are
`far too expen sive.
`Until solar panels become a lot cheaper or electricity rates go up quite a
`lot, solar panels will not be a practical investment for more homes in met-
`ropolitan areas of Australia.
`
`Leo Simpson
`
`www.siliconchip.com.au
`
`Publisher & Editor-in-Chief
`Leo Simpson, B.Bus., FAICD
`
`Production Manager
`Greg Swain, B.Sc.(Hons.)
`
`Technical Staff
`John Clarke, B.E.(Elec.)
`Peter Smith
`Ross Tester
`Jim Rowe, B.A., B.Sc, VK2ZLO
`Rick Walters
`
`Reader Services
`Ann Jenkinson
`
`Advertising Enquiries
`Leo Simpson
`Phone (02) 9979 5644
`Fax (02) 9979 6503
`
`Regular Contributors
`Brendan Akhurst
`Rodney Champness, VK3UG
`Julian Edgar, Dip.T.(Sec.), B.Ed
`Mike Sheriff, B.Sc, VK2YFK
`Philip Watson, MIREE, VK2ZPW
`Bob Young
`
`SILICON CHIP is published 12 times
`a year by Silicon Chip Publications
`Pty Ltd. ACN 003 205 490. ABN 49
`003 205 490 All material copyright
`©. No part of this publication may
`be reproduced without the written
`consent of the publisher.
`
`Printing: Hannanprint, Noble Park,
`Victoria.
`Distribution: Network Distribution
`Company.
`Subscription rates: $69.50 per
`year in Australia. For overseas
`rates, see the subscription page in
`this issue.
`Editorial & advertising offices:
`Unit 8, 101 Darley St, Mona Vale,
`NSW 2103. Postal address: PO Box
`139, Collaroy Beach, NSW 2097.
`Phone (02) 9979 5644.
`Fax (02) 9979 6503.
`E-mail: silchip@siliconchip.com.au
`
`ISSN 1030-2662
`
`* Recommended and maximum price only.
`
`2
`
` Silicon Chip
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
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`
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`Apple EX1026 Page 4
`
`

`

`The nearest thing you can get to “unbreakable” . . .
`
`A Rolling Code
`4-channel UHF
`Remote Control
`
`This is one very clever remote control. With rolling code, it’s
`close-to-impossible to electronically “crack”. With four channels, all
`either latching or momentary operation, it’s extremely versatile. With
`a sensitive prebuilt receiver, it’s long range. With up-to-16 keyring-size
`transmitters, it’s go-anywhere. And the kit even includes the keyring!
`
`By Ross Tester
`
`Whether you want to
`Whether you want to
`control a garage door
`control a garage door
`or gate, a car and/or
`or gate, a car and/or
`home alarm, or perhaps
`home alarm, or perhaps
`remotely turn lights or
`remotely turn lights or
`anything else on or off,
`anything else on or off,
`this high-security sys-
`this high-security sys-
`tem is just what you’re
`tem is just what you’re
`looking for!
`looking for!
`Inset top right are the
`Inset top right are the
`pre-built, aligned and
`pre-built, aligned and
`tested receiver (top) and
`tested receiver (top) and
`transmitter (bottom)
`transmitter (bottom)
`modules, shown here
`modules, shown here
`same-size.
`same-size.
`
`18
`
` Silicon Chip
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
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`
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`
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`Apple EX1026 Page 5
`
`

`

`We’ve presented a number of
`
`remote (radio) control dev-
`ices in the past. None has
`been more secure than this one. To
`guess the code combination, you’re
`going to need something like 23 billion
`years. But don’t bother: the next time
`it’s used, the code will have changed
`anyway.
`That’s the advantage of a rolling
`code (or “code hopping”) system. We
`explain what this means, and does,
`later in this article.
`Suffice to say at this stage that it
`makes one v-e-r-y secure system. For
`all intents and purposes, it is impos-
`sible to electronically “crack”. Go on,
`give it a go – we’ll see you in a few
`million years or so!
`The transmitter
`It’s probably not necessary to say it
`but there are two parts to this project,
`a transmitter and a receiver.
`First of all, there is the tiny
`4-channel “key-ring”
`transmitter which,
`fortunat-ely, comes
`99% pre-assembled.
`We say fortunate-
`ly because it’s just
`about all SMD (sur-
`face mount devices)
`which, while not
`impossible for the
`hobbyist to work
`with, requires some
`rather special han-
`dling. You are
`spared that!
`All you have to
`do with the trans-
`mitter PC board is
`solder on the two
`battery connec-
`tors and place it
`in the case (with
`battery).
`The battery contacts are slightly
`different: the one with a spring is for
`the negative battery connection – it
`goes on the righthand side of the PC
`board with the only straight side of
`the PC board at the bottom.
`You may find, as we did, that some
`of the holes for the battery connectors
`are filled with solder. This is easily
`melted during installation.
`Once this is done, it’s just a matter
`of assembling the board in its keyring
`case. Incidentally, the keyring case
`and battery are all supplied in the kit.
`The transmitter itself is in the li-
`
`SPECIFICATIONS
` UHF (433MHz) licence-free (LIPD band) operation
` Long range – prototype tested to 100m+
` Pre-built and aligned transmitter & receiver modules
` Rolling-code (“code hopping”) operation (7.3 x 1019 codes)
` Receiver “learns” transmitter coding
` Receiver can handle up to 16 remotes
` Transmitter can handle any number of receivers
` 4 channels available, each either momentary (push on, release
`off) or latching (push on, push off) via jumpers
` Code acknowledge LED and channel status LEDs
` Each channel relay contacts rated at 28VDC/12A (single pole,
`changeover)
` 12V DC operation (6mA quiescent; 150mA all relays actuated)
`
`cence-free 433MHz LIPD band (it’s
`actually on 433.9MHz). As with most
`devices of this type these days, it is
`based on a SAW resonator (that stands
`for surface acoustic wave, so now
`you know!). This keeps the circuit
`very simple but enables excellent
`performance.
`Without wanting to get into the nit-
`ty-gritty of SAW resonator operation,
`in essence it controls the RF side of
`things while a dedicated chip controls
`the complex digital coding.
`The receiver (which we’ll get to
`shortly) can handle up to 16 transmit-
`ters so if you have a really big family or
`maybe have a secure company carpark
`you want to give a certain number of
`people access to, you can do so simply
`by purchasing more transmitters.
`The transmitter has four push-
`but-tons, one for each of the four
`channels.
`Of course you don’t have to use all
`four channels – just one will control
`
`most garage door openers, for example
`– but it’s nice to know there are four
`channels available.
`And before we move off the trans-
`mitter, up to three channels can be
`pressed simultaneously and the re-
`ceiver will react to all three (it won’t
`handle four at once, though).
`Finally, as well as multiple trans-
`mitters, you can use more than one
`receiver if you wish.
`Each receiver “learns” its trans-mit-
`ter(s) so you can have a multiple
`system controlling, for example, the
`garage door, the car doors, the car
`
`alarm, the home security system – in
`fact, anything your little heart desires.
`The receiver/decoder
`Now we move on to the heart of the
`system, at least the bits you have to
`put together to make it work.
`In fact, there are two parts to the
`receiver as well. There is a 433MHz
`receiver module which comes assem-
`bled, aligned and ready to go. This
`solders into an appropriate set of holes
`on the main PC board once you’ve
`finished assembling that board.
`The main PC board contains the
`electronics which process the output
`from the receiver.
`The receiver checks the incoming
`code and if valid, sends a signal to one
`of four outputs depending on which
`button was pressed on the transmitter).
`From here, depending on how the
`four jumpers are set on the board, the
`signal goes either direct to an NPN
`transistor relay driver (for momentary
`operation – the relay is energised
`while the button
`remains pressed)
`or to a D-type flip-
`flop and then to
`the transistor relay
`driver (for alternate
`operation – press
`once and the relay
`latches, press again
`and the relay re-
`leases).
`T h e f l i p f l o p s
`change state (toggle)
`each time a postive
`going pulse appears
`at the clock input.
`This is achieved by
`the connection from
`the Q-bar output to
`the D input via an RC
`network.
`The circuit has a
`power-up reset. When
`power is first applied, the Q outputs
`of the flipflops are reset low by the
`0.1µF capacitor and 1MΩ resistor on
`the reset (S) inputs.
`Reset is caused by sending the reset
`inputs of all flipflops high. Once the
`capacitor is charged, the voltage at the
`reset inputs of the flipflops falls to vir-
`tually zero, allowing normal operation
`It is perfectly acceptable to have a
`mixture of momentary and latched
`modes amongst the four channels. It’s
`up to you.
`But if you only require momentary
`
`July 2002
`
` 19
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
`Downloaded by Virginia Brown (#56424)
`
`IPR2022-00602
`Apple EX1026 Page 6
`
`

`

`Q1
`C8050
`
`Q2
`C8050
`
`K
`
`A
`
`C
`
`E
`
`K
`
`A
`
`C
`
`E
`
`K
`
`A
`
`C
`
`+12V
`
`RELAY1
`
`+12V
`
`RELAY2
`
`NC
`COM
`NO
`
`NC
`COM
`NO
`
`+12V
`
`RELAY3
`
`NC
`COM
`NO
`
`10M
`
`+5V
`
`0.1 Fm
`
`2.2k
`
`LED1
`
`l
`
`D1
`
`4.7k
`
`B
`
`LED2
`
`l
`
`D2
`
`2.2k
`
`4.7k
`
`B
`
`LED3
`
`l
`
`D3
`
`2.2k
`
`J1
`
`1 2
`
`Q Q
`
`6
`
`S
`
`D
`
`IC1a
`CLK
`
`R
`
`4
`
`10M
`
`13
`
`J2
`
`12
`
`Q Q
`
`8
`
`S
`
`D
`
`IC1b
`CLK
`
`R
`
`10
`
`10M
`
`6
`
`S
`
`D
`
`J3
`
`5 3
`
`9 6
`
`0.1 Fm
`
`0.1 Fm
`
`IC1 PIN14,
`IC2 PIN14
`
`10
`
`9 8 6
`
`3
`
`433MHz
`RECEIVER
`MODULE
`
`IC1, IC2: 4013
`D1-D4: 1N4004
`
`ANTENNA
`
`11
`
`170mm
`
`TEST
`POINT
`
`4.7k
`
`B
`
`LED4
`
`l
`
`D4
`
`2.2k
`
`4.7k
`
`B
`
`Q3
`C8050
`
`Q4
`C8050
`
`E
`
`K
`
`A
`
`C
`
`E
`
`+12V
`
`RELAY4
`
`NC
`COM
`NO
`
`J4
`
`1 2
`
`Q Q
`
`IC2a
`CLK
`
`R
`
`4
`
`10M
`
`13
`
`12
`
`Q Q
`
`8
`
`S
`
`D
`
`IC2b
`CLK
`
`R
`
`10
`
`5 3
`
`9 6
`
`0.1 Fm
`
`0.1 Fm
`
`74
`
`PB1
`
`LEARN
`
`12
`
`5
`
`1k
`
`A
`
`K
`
`l
`
`LED5
`
`LEDS
`
`K A
`
`1M
`
`7805
`
`Q1-Q4
`C8050
`
`IN
`
`OUT
`
`GND
`
`C
`
`EB
`
`D1-4
`
`A
`
`K
`
`+12V
`
`REG1 7805
`IN OUT
`
`COM
`
`0.1 Fm
`
`100 Fm
`
`+12V
`
`GND
`
`100 Fm
`
`0.1 Fm
`
`+5V
`
`IC1 PIN7,
`IC2 PIN7
`
`2002SCÓ
`
`4-CHANNEL UHF "ROLLING CODE" REMOTE CONTROL RECEIVER
`
`Fig.1: the circuit of the “control” section of the receiver unit. We haven’t attempted to show the 433MHz receiver itself, nor
`the transmitter, as these are both pre-assembled modules, saving you a lot of difficult work!
`
`action (for example, as needed by some
`door openers/closers) the flip-flops,
`along with their associated RC network
`components and the four header pin
`jumper sets, could be left out of cir-
`cuit. (You’d then need four links on
`the PC board to directly connect the
`receiver outputs to their respective
`transistors.)
`Along with spike suppression di-
`odes across each relay coil, part of
`
`each relay driver circuit also includes
`an acknowledge LED to give a visible
`output of what’s happening.
`There is also a “valid signal ac-
`knowledge” LED attached to the
`433MHz module, which lights when
`valid code is being received.
`Each of the four identical relays has
`contacts rated at 28VDC & 12A, so can
`be used to control significant loads.
`The wide track widths on the PC board
`
`also allow high currents.
`The relay contacts could, of course,
`also be used to switch higher-rated
`relays or you could replace the ac-
`knowledge LED with an opto-coupler.
`The relays themselves are single
`pole but have normally open (NO) and
`normally closed (NC) contacts. These
`states refer to the unenergised state of
`the relay (ie, the NC contacts go open
`when power is applied to the relay coil
`
`20
`
` Silicon Chip
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
`Downloaded by Virginia Brown (#56424)
`
`IPR2022-00602
`Apple EX1026 Page 7
`
`

`

`ASSEMBLING THE
`REMOTE CONTROL:
`The photo above shows seven of the
`eight parts you should find when you
`take the bits out for the remote control
`(the battery is missing!).
`Above centre shows the two battery
`connectors soldered in place on the top
`of the PC board, above right shows the
`same thing from the other side. Don’t
`mix up the connector with spring and
`the connector without.
`Finally, the photo at right shows the
`PC board in place, with battery, in
`one half of the keyring case. The blue
`pushbuttons are all on one plate – they
`fit in as shown but can easily fall out.
`As you push the two halves of the case
`together, make sure the pushbutton
`plate stays in place. The keyring itself
`also fits into the notch in the case as
`you push the two halves together.
`
`and vice-versa).
`The only other components on the
`board are a simple 5V regulated sup-
`ply, consisting of a 7805 3-terminal
`regulator and a couple of capacitors.
`This supply powers the 433MHz
`module and the 4013 flipflops. The
`relay coils are powered direct from
`the 12V supply.
`Construction
`Start by soldering in the two bat-
`tery terminals to the transmitter PC
`board, in the positions shown in the
`photographs.
`Place the completed board in
`the keyring case, making sure the
`push-buttons stay in position.
`Push the two halves together with
`the battery in place (and the right
`way around – see pictures), with the
`keyring clip sandwiched between the
`two halves.
`One screw holds the two halves of
`the transmitter case together.
`Press each of the four buttons and
`
`ensure that the LED lights each time.
`If it does, you can be reasonably sure
`that the transmitter is working prop-
`erly. Put it to one side while we move
`on to the receiver.
`Receiver board
`As usual, check the receiver PC
`board for any defects before assembly.
`Then solder in the resistors, capaci-
`tors, diodes, IC sockets (if used) and
`the four header pin sets (which select
`momentary or latching function).
`If you use IC sockets, make sure they
`go in the right way around – the notch
`is closest to the edge of the PC board.
`The “learn” pushbutton switch sol-
`ders in place between the IC sockets.
`These have two pairs of pins which
`are not identically spaced – the switch
`should be an easy fit in the PC board
`if you get it the right way around. If in
`doubt, check the “closed” state with
`your multimeter.
`Now solder in the semiconductors
`– the regulator, diodes, transistors and
`
`the LEDs as shown on the component
`overlay. Watch the LED and transistor
`polarities – each is opposite to its
`neighbour!
`The last things to be soldered in
`place before the 433MHz receiver
`module are the four relays and the six
`output terminal blocks. The relays will
`only go in one way but the terminal
`blocks could be mounted back-to-
`front, making it almost impossible
`to get wires into them! (The “open”
`side of the terminals go towards the
`edge of the board, in case you were
`wondering!)
`At this point, check your assembly
`for any solder bridges, dry joints or
`missed joints.
`You might also now solder in the
`three wires – two connect 12V power
`while the third is the antenna. Make
`the power leads the necessary length
`to reach your supply.
`When the antenna wire is soldered
`in, measure exactly 170mm from the
`PC board and cut the wire to this
`
`July 2002
`
` 21
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
`Downloaded by Virginia Brown (#56424)
`
`IPR2022-00602
`Apple EX1026 Page 8
`
`

`

`Learning and testing
`Looking at the board with the
`outputs/relays on the left side, move
`all header pins to the right side
`(latching).
`Apply power and you should see
`absolutely nothing happen. So far,
`so good.
`Now press the “learn” button once,
`then within 15 seconds press button
`one on the keyring transmitter for a
`second or so. Button one is the one all
`by itself on one side of the transmitter.
`The receiver then learns the encr-
`yp-tion from the keyring transmitter
`– and remembers it.
`Now all four buttons on your trans-
`mitter should alternately close and
`open the appropriate relay and light/
`switch off its associated LED.
`Change the four jumpers over to
`
`NC
`
`COM
`
`NO
`
`NC
`
`COM
`
`NO
`
`NC
`
`COM
`
`NO
`
`NC
`
`COM
`
`NO
`
`RELAY1
`
`RELAY2
`
`RELAY3
`
`RELAY4
`
`GND
`
`+12V
`
`D1
`
`LED1
`
`2.2k
`
`4.7k
`
`Q1
`0.1Fm
`
`LED2
`
`2.2k
`
`D2
`
`D3
`
`2.2k
`
`LED3
`
`C8050
`
`LED4
`
`2.2k
`
`D4
`
`4.7k
`
`Q3
`
`0.1Fm
`
`Q4
`0.1Fm
`
`4.7k
`
`REG1 7805
`REG1 7805
`
`+
`
`0.1 Fm
`100 Fm
`L M
`J1
`10M
`
`0.1 Fm
`
`IC1 4013
`
`C8050
`
`Q2
`0.1Fm
`
`4.7k
`
`PB1
`LEARN
`
`1
`
`L M
`
`0.1Fm
`
`10M
`J2
`
`LED5
`
`100 Fm
`+
`
`VALID
`DATA
`
`GND
`
`DOUT
`
`+5V
`
`TP
`
`VT
`
`D0
`
`LA
`
`D1
`
`NC
`
`D2
`
`D3
`
`1k
`
`TP
`
`433MHz RECEIVER MODULE
`
`1
`
`ANT
`
`GND
`
`ANT
`
`L M
`
`J3
`10M
`
`IC2 4013
`
`10M
`J4
`
`TX1
`
`L M
`1M
`
`length. This makes it resonant at
`433MHz.
`You should not have any bare
`wire(s) emerging from the end of the
`antenna – this could short onto some-
`thing nasty and do you/it/something
`else some damage! If necessary, wrap
`a little insulation tape around the end
`of the antenna wire – just in case!
`Plug the two ICs into their sock-
`ets, again watching the polarity. The
`notches should line up with the notch-
`es in the sockets (assuming you got the
`sockets right!)
`OK, we’re almost there. Place the
`receiver module in its appropriate
`holes along the edge of the PC board.
`It will only go one way (incidentally,
`take care not to move the coil or touch
`the trimmer capacitor).
`Solder each of the module pins into
`position (there are 13 of them – don’t
`forget the two by themselves) and your
`receiver is finished.
`Power supply
`The receiver unit is designed for
`12V battery operation and power re-
`quirements are pretty modest. At rest,
`(ie, no relays operating), it draws only
`6mA and even with all relays actuated,
`the current is just a smidgeon under
`150mA.
`Therefore, most alarm-type bat-
`teries (eg, SLAs) will be more than
`adequate.
`We had it operating for a couple of
`weeks on a 7Ah 12V gell cell, period-
`ically pressing the remote control just
`for the hell of it, without recharging
`the battery. In fact, at the end of this
`
`22
`
` Silicon Chip
`
`Fig.2 (above): the
`component over-
`lay of the receiver
`module with the
`full-size photo-
`graph at right. Just
`to confuse you,
`we’ve shown the
`board turned 180°
`compared to the
`diagram above!
`
`time the battery voltage changed only
`a few tens of millivolts – probably not
`much more than you would expect
`during shelf life.
`Therefore, just about any 12V bat-
`tery would be acceptable, even a cou-
`ple of 6V lantern batteries in series or
`even 10 C or D-size Nicads.
`Of course, you could also use just
`about any garden-variety 12V or 13.8V
`DC (nominal) plug-pack supply.
`The relays won’t worry about a
`few extra volts and the circuit has
`the on-board 5V regulator to ensure
`the electronics get the right voltage.
`Any DC plugpack over about 200mA
`capacity should be fine.
`
`the opposite way and all four buttons
`should now pull in a relay and light a
`LED while ever they are pressed – and
`release it/dim it when let go.
`And that’s just about it. Now all you
`have to do is select the jumpers the
`way you want them and connect the
`external devices you wish to control.
`Note that each relay has a normally
`open and normally closed connection
`as well as common, so you have a lot
`of flexibility at your disposal.
`Want even more security?
`We mentioned before the one major
`drawback with any remotely con-
`trolled security application, whether
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
`Downloaded by Virginia Brown (#56424)
`
`IPR2022-00602
`Apple EX1026 Page 9
`
`

`

`What is “Code Hopping” or “Rolling Code”
`
`These two names usually refer to the same thing – in a nutshell,
`a security system for a security system.
`It’s a way of preventing unauthorised access to a digital code
`which might be transmitted via a short-range radio link to do
`something: open a garage door, lock or unlock a car and perhaps
`turn its own security system on and off – and much more.
`But before we look at these terms, though, let’s go back in time
`to the days before code hopping and rolling code.
`Short-range radio-operated control devices have been around
`for a couple of decades or so (at least, in any volume). The earliest
`ones that I remember simply used a burst of RF, at a particular
`frequency, with an appropriate receiver.
`It’s not hard to see the shortcomings of such devices. Simply
`sweeping the likely band(s) with an RF generator attached to an
`antenna would more often than not achieve the desired result
`(desired for the intruder, that is).
`It didn’t take long for crooks to latch on to this one (do you like
`that metaphor?). So manufacturers decided to make it a bit harder
`for them by modulating the RF at a frequency (or indeed multiple
`frequencies in some cases) “known” to the receiver.
`Some used the standard DTMF tones generated by phone
`keypads because they were very cheap and made in the millions.
`“Oh, gee,” said the crooks. Now we’ll have to use an RF oscillator
`with a modulator. Or maybe even a DTMF keypad!”
`Duh! (Still, it probably seemed like a good idea at the time. . .)
`Ever one step ahead, the manufacturers went with this (then)
`new-fangled digital stuff and made each transmitter send a
`particular code which was matched to the receiver. This was
`usually done by way of DIP switches in both transmitter and
`receiver.
`With eight DIP switches (probably the most common because
`8-way DIP switches were common!), you would have 28 or 256
`codes available. So you and your next-door neighbour could have
`the same type of garage door opener on the same frequency and
`the odds would be pretty good that their door would stay down
`when you pressed your button.
`The problem with this, though, is that the transmitter spurted
`out exactly the same code every time (unless, of course, both sets
`of dip switches were changed). Enter the crooks again.
`With a suitable receiver, called a “code grabber”, if they got
`within a few tens of metres of you they could scan for the RF signal
`and record your code without you knowing anything about it (for
`example, as you left your car in a carpark and pressed the button
`on your remote to lock the doors and turn on the alarm).
`Once you’d gone, they simply “played it back” using the same
`code grabber. Presto, one missing car. Or one house burgled, etc etc.
`Even without a code grabber, a smart intruder with the right
`equipment using digital techniques and trying eight combinations
`per second, could crack the code in no more than 32 seconds – and
`probably much quicker.
`It’s hard to believe the gall of some organisations openly flogging
`such devices, euphemistically disguising them (justifying them?)
`with names such as vehicle lockout recovery systems or disabled
`vehicle recovery systems. Then again, lock picks are sold for
`professional locksmiths, aren’t they?
`Now we move on a little. Microchip, the same people who brought
`you those ubiquitous PICs, invented a system called KeeLoq – better
`known to you and me as a rolling code.
`
`What this does is simply present a different code every time the
`transmitter button is pressed. Of course, that’s the easy part. The
`really clever part is that the receiver “learns” the algorithm which
`controls the code so it knows what code to expect. Once learnt,
`the receiver is effectively “locked” to that transmitter.
`Actually, it’s even cleverer than that, because the transmitted
`code is, for all intents and purposes, random (as far as any external
`device is concerned). But the receiver can still work out what the
`code is going to be in advance. If it gets the right code, it actuates.
`If not – you’re out in the cold, baby!
`The chances of the same code being transmitted twice in a
`person’s lifetime is possible – but remote (at four transmissions
`per day, every day, it’s reckoned to be about 44 years!)
`Heart of this system is a Microchip proprietary IC, the HC301. It
`combines a 32-bit hopping code generated by a nonlinear encryp-
`tion algorithm with a 28-bit serial number and six information bits
`to create a 66-bit code word. The code word length eliminates the
`threat of code scanning and the code-hopping mechanism makes
`each transmission unique, rendering code capture and resend
`techniques useless.
`Even if it didn’t code-hop, 66 bits allows 7.3 x 1019 combinations,
`which according to Microchip would only take 230,000,000,000
`years to scan!
`The chip itself is also protected against intrusion. Several impor-
`tant data are stored in an EEPROM array which is not accessible
`via any external connection. These include the crypt key, a unique
`and secret 64-bit number used to encrypt and decrypt data, the
`serial number and the configuration data.
`The EEPROM data is programmable but read-protected. It can be
`verified only after an automatic erase and programming operation,
`protecting against attempts to gain access to keys or to manipulate
`synchronisation values.
`If the code is changed every time a button is pressed on the
`transmitter, what happens if, say a child starts playing with the
`remote control and continually presses buttons away from the
`receiver? OK, here’s where it gets really clever (and you thought
`it was clever enough already, didn’t you?).
`If the button is pressed say 10 times while out of range of the
`receiver, no problem. But if it is pressed more than 16 times, syn-
`chronisation between the two is lost. However, it only takes two
`presses of a button in range to restore sync. No, we don’t know
`how either. That’s Microchip’s secret!
`And speaking of button presses, there are a couple of other
`clever things they’ve done. At most, a complete code will take
`100ms to send (it could be as low as 25ms). But if you manage
`to hit the button and release it before 100ms (difficult, but pos-
`sible), it will keep sending that complete code. If you hold down
`the button, it will keep sending that same code. And if you press
`another button while the first is held down, it will abort the first
`and send the second.
`As you can see, KeeLoq is a very robust system. Sure, it’s not
`absolutely foolproof – nothing is (eg, there’s not much protection
`if they simply steal your transmitter!). But for most users, it gives
`almost total peace-of-mind. That’s why the system has been adopt-
`ed by so many vehicle entry/exit and alarm system manufacturers,
`access controllers and so on.
`And that’s the system that’s used in the remote control unit
`presented here.
`
`July 2002
`
` 23
`
`www.siliconchip.com.au
`
`Copyright © 2021 SILICON CHIP Publications.
`Copyright © 2021 SILICON CHIP Publications.
`
`Downloaded by Virginia Brown (#56424)
`Downloaded by Virginia Brown (#56424)
`
`IPR2022-00602
`Apple EX1026 Page 10
`
`

`

`that be for a car, a building or anything
`else: what happens if someone pinches
`your remote control?
`It is possible to protect yourself
`against the casual button pusher on
`a stolen control – at least to some
`degree.
`Having four channels at your dis-
`posal, in this remote control system,
`gives you the possibility of increasing
`security rather si