e002022.pdf

AUDIO & HI-FI

infrared remote control

for Sony MZ-R30 MiniDisc Walkman

a useful add-on for a popular player

The MZ-R30 MD

recorder comes

with its own

cable-operated

remote control,

which is primar-

ily designed for

Walkman-ish operation. However, Brian

Houghton’s own application for recording

choral rehearsals needed to have a means of

controlling the stop/start function from a loca-

tion that made cable control impossible. Here’s

how Brian solved the problem — elegantly and

without breaking the bank.

Rather than starting straightaway with

the technical description of the project

it may be interesting to tell you some of

the design history.

I found the website “The Minidisk

Community Pages” on http://www.amu-

lation.com/minidisc very helpful with

information on how the Sony MZ-R30

remote functions are controlled by dif-

ferent resistance values across a pair of

wires.

Initially a 173-MHz licence-free

“HomeCall “type transmitter and a

suitable receiver was obtained, and the

receiver mounted in a control box with

some CMOS logic. This RF system

Design by Brian Houghton G4BCO

Elektor Electronics

2/2000

Figure 1. Modification to

the remote control cable

supplied with the Sony

MD MiniDisc walkman.

XLR Free

Socket (Rear)

works well up to 100ft, but is slow to

respond (5 seconds) and only allows

for the one function, in this case

“pause”. The details of this remote con-

trol can be found on :

http://www.amulation.com/minidisc/mzr30_

remote_radio/index.html.

Several emails from people regard-

ing that design, were received and one

in particular from someone who

wanted some help with a college pro-

ject to build a full function IR remote

control within a budget of £50. This

spurred the author to have a go.

Remote Pod connections:

1 wht Right Channel

4 1

2 yel Ctl Pin 4

3 gry Ctl Pin 2

4 red Left Channel

5 brn Common

3 2

Mini

Socket

XLR Free

Plug (Rear)

990075 - 11

this magazine.

Any button press

will place 0 volts on

the selected diode(s)

to pull down the data inputs of the

encoder IC1. Any data input going low

will ‘wake up’ the encoder chip, start

the 455 kHz oscillator and the encoded

data stream will be output from pin 17

(Dout) driving the two transistors and

subsequently the two infrared sender

diodes. A low value series resistor

(2.2

Figure 2. The remote pod

can still be used if you

give it a connector again.

function is shown in

tabular form in the

circuit diagram. Note

that pushbuttons S10

and S11 have to be pressed simultane-

ously to transmit a RECORD com-

mand. This is done to prevent inad-

vertent selection of the RECORD

mode.

D ESIGN

This design logically splits into two

parts:

➧

The hand held transmitter contain-

ing the function select push button

switches, encoder and infrared trans-

mitter.

R ECEIVER / DECODER

UNIT

The Sony MZ-R30 requires a number

of specific resistance values to recog-

nize certain functions selected via its

remote input socket: The resistance

values and associated functions are

shown in Table 1 . The code in the third

row is the decimal value of the 4-bit

data used by the IR encoder/decoders.

The use of type

4016 analogue

switches (IC3, IC5,

➧

The receiver/decoder containing the

infrared receiver, decoder and resis-

tance ladder selector analogue

switches.

) enables the IR diodes to be dri-

ven with high current pulses, although

the average current is only 10 mA per

transistor. The large electrolytic capaci-

tor C1 is essential to overcome the rel-

atively high internal resistance of the

two AA or AAA batteries.

The relation between pushbutton

number, transmitted

code and the associ-

ated MD recorder

Ω

The remote control connector on the

Sony MD Walkman is unique and

unfortunately is not obtainable as a

spare item, and since the whole remote

cable is £50 to purchase separately, it

was decided to perform minor surgery

on the existing cable.

Figure 3. Circuit diagram

of the hand held control.

R EMOTE CABLE

MODIFICATIONS

The remote control pod was opened

and the existing cable disconnected. A

mini XLR 5-way socket was fitted to

the free end of the old cable. This cable

is then suitable to connect the IR Con-

trol Unit to the Sony Walkman. The

modification is illustrated in Figure 1 .

A new cable was made up using 5

fairly thin wires, stripped from some

multicore cable, and a length of 3 mm

heatshrink sleeving, with a mini XLR 5

pin plug at one end and the old remote

control pod on the other. This enables

normal cable remote functions to be

made via this ‘adapter cable’. The con-

struction is illustrated in Figure 2 .

CODE FUNCTION

Bt1

"0"

"1"

"2"

"3"

"4"

"5"

"6"

"7"

"8"

"9"

Spare

Prev/Back

D2 6

D2 7

Next/FWD

D26, D27 = LD271

100µ

16V

100n

PAUSE

STOP

Volume –

Volume +

MARK (Rec)

MODE (Play)

RECORD

(in stop or pause)

10k

BC550

ADOUT

IC1

HT12A

D11

D13

D15

D17

D20

AD11

AD10

AD9

AD8

D12

D21

D24

OSC2

OSC1

10M

D14

D18

D22

D25

H AND HELD

TRANSMITTER

The circuit diagram of the hand held

control box is given in Figure 3 . The

key component is a Holtek HT12A

remote control encoder chip. The (con-

densed) datasheets of this interesting

and versatile chip appear elsewhere in

S11

D10

D16

D19

D23

"Shift"

S10

100p

455kHz

100p

"0"

"1"

"2"

"3"

"4"

"5"

"6"

"7"

"8"

"9"

D1 ... D25 = 1N4148

990075 - 13

Elektor Electronics

2/2000

IC3a

1N4001

LP2950CZ5.0

IC4

IC5d

D 3

2µ2

25V

4µ7

16V

IC3d

4k7

R18

R19

R20

BC547

100n

IC6c

JP2

R17

ADOUT

TEST

X/Y

IC6d

IC1

R16

JP2

HT12D

IC6b

IC2

IC5a

4028

R15

XLR-Socket

OSC2

OSC1

56k

IC3c

R14

R13

IC6a

R11

R12

JP1

10k

BC550

IC3, IC5, IC6 = 4016

SFH505A

SFH506

IC2

IC3

IC5

IC6

IS1U60

IC5b

IC5c

IC3b

100n

R21

R10

990075 - 14

Figure 4. Circuit dia-

gram of the remote con-

trol receiver/decoder.

Elektor Electronics

2/2000

IC6) in conjunction with a resistor net-

work (R7-R20) offers a simple and

cheap method of selecting the required

resistance value.

A Sharp IS1U60 IR receiver IC

detects the IR carrier and its output is

inverted by T1 and fed to the HT12D

decoder IC which latches the original

4 bits of data. This data is then pre-

sented to a BCD/Decimal decoder

(IC2, 4028) which selects one of nine

analogue

switches. These

in turn select the

appropriate point on a resistor ladder

to be used by the MZ-R30 for the

selected function. The condensed

datasheet of the HT12D IR decoder

Figure 5. PCB copper track layouts and component over-

lays. Cut the board to separate the transmitter (below)

and receiver (top) section.

COMPONENTS LIST

990075a

R12

R14

Receiver/decoder

(Board section 990075a)

R18

R19

R13

R10

R17

R16

R15

Resistors:

R1 = 56k Ω

R2,R3 = 10k Ω

R4,R20 = 4k Ω 7

R5,R6 = 2k Ω 2

R7 = 27 Ω

R8,R13,R15 = 1k Ω 5

R9,R10 = 1k Ω 3

R11 = 56

IC4

Ω

R12 = 1k Ω 8

R14 = 150 Ω

R16,R17 = 2k Ω

R18 = 100

IC1

JP1

Ω

R19 = 5k Ω 6

R21 = 680 Ω

P1 = 1k Ω preset H

Capacitors:

C1 = 2 µ F2 25V radial

C2 = 4 µ F7 16V radial

C3-C7 = 100nF

Semiconductors:

D1,D3 = low-current LED

D2 = 1N4001

T1,T2 = BC550

IC1 = HT12D (Holtek) (Maplin)

IC2 = 4028

IC3,IC5,IC6 = 4016

IC4 = LP2950-CZ5.0

Miscellaneous:

JP1 = SFH506-36

S11

Transmitter

(Board section 990075b)

Resistors:

R1,R2 = 10k Ω

R3,R4 = 2

Ω

IC1

D10

R5 = 10M Ω

D23

F 16V radial

C2,C3 = 100pF

C4 = 100nF

S10

Semiconductors:

D1-D25 = 1N4148

D26,D27 = LD271 or similar IR LED

T1,T2 = BC550

IC1 = HT12A (Holtek) (Maplin,

Farnell)

Miscellaneous:

S1-S11 = pushbutton, PCB mount,

Multimec or D6-R-RD

BT1 = 2 off AA or AAA penlight

battery

X1 = ceramic resonator, 455kHz

(e.g., SB455E) (Mainline, 0870 241

0810)

Elektor Electronics

2/2000

Capacitors:

C1 = 100

remote control input of the MD30-RZ

via a short cable.

The function of the test jumper, JP2,

is discussed further on.

The receiver/decoder may be pow-

ered by just about any wall adaptor

capable of supplying 8-12 V DC at

about 100 mA.

appears elsewhere in this issue.

A common analogue switch (IC3a)

controlled from the IR decoder (VT)

pin is used to gate the output, since the

4-bit data is latched by the decoder and

always selects the last switch that was

used. The minimum selectable resis-

tance (function “Preview/Back”) is

1000

in the circuit diagram. Alternatively,

you may want to use a mini XLR chas-

sis plug. The pinout is then as follows:

C ONSTRUCTION

The printed circuit board you will need

to build this project is shown in Fig-

ure 5 . The first thing to do is separate

the receiver and transmitter sections

with a jigsaw.

To keep cost as low as possible,

these are single-sided circuit boards.

They contain a few wire links which

should be fitted before anything else.

The PCBs are easily stuffed using

the parts list and the component over-

lay. Be sure to fit all polarized compo-

nents the right way around, that is,

diodes, LEDs, transistors, electrolytic

capacitors and ICs. Although they are

neither expensive nor hard to get

(Maplin), the HT12 ICs are best fitted

in IC sockets.

The transmitter board has a number

of diodes fitted at the solder side of the

board . The IR sender diodes may be

fitted with reflector caps to boost their

directivity.

The author fitted his version of the

handheld control in a type HH1 plain

box from Maplin. This had enough

space to incorporate a holder for two

alkaline rechargeable AAA cells.

Pin 1:

audio left

S ETTING UP

The only setting up required is to

adjust the 1 k

Pin 2:

pin 1 of IC3a

Pin 3:

preset P1

preset to compensate

for the resistance of the analogue

switches. This is done as follows:

Ω

Pin 4:

audio right

pre-

set potentiometer, P1, is used to add

approximately 700

Ω

and to achieve this, a 1k

Ω

Pin 5:

audio common

Ω

in series with the

Alternatives to the IS1U60 include the

Siemens SFH505A and SFH506. Their

pin functions being different from the

IS1U60, you have to pay attention to

the way they are connected to the

board.

The output of the remote control

receiver is wired to a suitable miniature

socket which is then connected to the

a) Install jumper JP2. This links R20,

the 4.7 k

total resistance of the two ana-

logue switches. A bright LED, D1, is

also switched on at the same time to

indicate correct operation.

The resistance value associated with

a control code appears across JP2, the

output of the circuit. A suggested con-

nection to a mini-DIN socket is shown

Ω

resistor from the com-

mon rail of the network, to 0 V.

b) Connect a DMM on a suitable resis-

tance range to be able to measure

7,050

Ω

, across the output pins 2

and 3 on the XLR connector.

c) Power up the receiver/decoder and

select code 4 “Stop” on the remote

hand held control.

d) Adjust preset P1 to give 7,050

Ω

the DVM.

e) Remove power, pull JP2 and dis-

connect the DVM.

f) Connect the receiver/decoder to the

MZ-R30 and test all functions.

Table 1. MiniDisc Walkman remote control codes

Function:

Resistance:

Code:

Preview/Back

1,000 Ω

Next/Forward

3,627 Ω

(990050-1)

Pause

5,156 Ω

Stop

7,050 Ω

Design editing:

L. Lemmens

Volume (–)

8,400 Ω

Article editing:

J. Buiting

Volume (+)

9,900 Ω

Mark

11,900

Ω

Mode

14,000 Ω

Record

19,500 Ω

Elektor Electronics

2/2000

300

Ω

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