Technical Aid to the Disabled

Project 98-11245

REV D 3-Nov-1998

Addition of radio remote control to a toy train for a child with cerebal palsy.

(Click on images for higher resolution view)

Transmitter

This is an Oatley Electronics TX2 with the pushbuttons and 12V battery clip removed. A new PCB is fitted which includes a 12V low current regulator and pin headers for the control switches, indicator LED, and power socket.

The design was modified to transmit continuously and to invert the logic sense of the pushbuttons. The completed PCB was then mounted in a small plastic box, with the following external attachments;

an indicator LED that shows transmitter active,
a 2.5mm standard DC supply socket,
two 3.5mm sockets for the pushbuttons.

A data sheet (Page 1, Page 2) for the encoder and decoder chips was faxed from Kitsrus of Hong Kong.

Receiver

This is Oatley Electronic's 318MHz receiver module from their two channel UHF remote control kit, mounted at right angles to a board containing the remote control decoder chip (A5885M, left) and a PIC 12C509 microcontroller (left of centre).

The microcontroller detects the button presses and drives a logic level power MOSFET 2SK2175 (right of centre), which drives the locomotive motor. A 5V regulator (bottom right) provides regulated logic power.

The black area to the right is for power switch clearance.

See also the circuit schematic and the code (final burn to 12c509).

Power

The locomotive tender has a battery compartment for six C size batteries, to which is attached an inline fuse (2A), a power switch, and a pin header socket.

Assembly

The receiver board sits vertically within the rear of the tender, with the indicator LEDs facing upwards. Room is provided on the PCB to allow clearance of the power switch mounted on the side wall.

A pin header socket is attached to the cable to the locomotive, and uses the two outer pins leaving the centre pins free.

Unfortunately, the power socket is not keyed, increasing the risk of reverse polarity connection and subsequent failure.

External Controls

The indicator LEDs are visible through the original switch mounting hole. The LED closest to the power switch is a CPU heartbeat indicator. The other LED lights when the transmitter is active.

Locomotive Interconnect

The cable from the tender to the locomotive required re-sheathing with heat shrink tubing. The plug is marked to indicate the direction it should face when inserted in the locomotive tail.

Final View

That guy must have a sore back by now.

Parts List

How much did it all cost?

Technical Aid to the Disabled Project 98-11245 Revision AX1 12th October 1998 Transmitter Supplier Part Description Cost Qty Price Jaycar MP-3002 12V DC 150mA Plugpack 12.95 1.00 12.95 Jaycar PP-0512 2.5mm ID 5.5mm OD DC Plug 1.30 1.00 1.30 Jaycar WH-5543 Heatshrink 1.95 0.16 0.31 Jaycar PP-0524 2.5mm DC Bulkhead Socket 2.25 1.00 2.25 Jaycar PS-0123 3.5mm Bulkhead Socket 1.60 2.00 3.20 Stock N/A Plastic Box 4.00 1.00 4.00 Stock N/A Veroboard 45mm x 35mm 2.00 1.00 2.00 Stock N/A Wire 0.50 1.00 0.50 Jaycar HM-3211 Pin Header 0.05 8.00 0.40 Jaycar HM-3218 Pin Header Socket, 4 pin 0.65 1.00 0.65 Jaycar HM-3217 Pin Header Socket, 2 pin 0.50 2.00 1.00 Jaycar ZR-1004 1N4004 1A 400V Diode 0.08 1.00 0.08 Jaycar RE-6130 100uF Electrolytic 0.35 1.00 0.35 Jaycar RZ-6648 10uF Tantalum Capacitor 1.00 1.00 1.00 Jaycar RC-5348 0.01uF Ceramic Capacitor 0.30 1.00 0.30 Jaycar ZV-1542 78L12 Voltage Regulator 1.20 1.00 1.20 Jaycar RR-0596 10k 0.25W Resistor 0.40 2.00 0.80 Oatley TX2 Keychain Transmitter 15.00 1.00 15.00 Transmitter Total 47.29 Receiver Supplier Part Description Cost Qty Price Jaycar WH-5543 Heatshrink 1.95 0.16 0.31 Stock N/A Push on, Push off switch 1.00 1.00 1.00 Jaycar SZ-2015 Inline Fuse Holder 1.10 1.00 1.10 Jaycar SF-2194 2A 3AG Fuse 0.25 1.00 0.25 Jaycar HM-3218 Pin Header Socket, 4 pin 0.65 2.00 1.30 Stock N/A Veroboard 35mm x 85mm 3.00 1.00 3.00 Stock N/A Wire 0.50 1.00 0.50 Jaycar RE-6130 100uF Electrolytic 0.35 1.00 0.35 Jaycar RZ-6648 10uF Tantalum Capacitor 1.00 1.00 1.00 Jaycar RC-5348 0.01uF Ceramic Capacitor 0.30 1.00 0.30 MicroZed IC 7805 7805 Voltage Regulator 0.45 1.00 0.45 MicroZed IC 12C509-4 PIC12C509/04/P 8 pin RISC CPU 3.00 1.00 3.00 Jaycar RR-0572 1k 0.25W Resistor 0.40 2.00 0.80 Jaycar ZD-1692 3mm Red LED 0.13 2.00 0.26 Oatley 2SK2175 2SK2175 TO-220 Logic MOSFET 2.60 1.00 2.60 Jaycar HM-3211 Pin Header 0.05 8.00 0.40 Oatley 318MHz UHF Rx Module 16.00 1.00 16.00 Oatley A5885M Decoder Chip 2.00 1.00 2.00 Jaycar RR-0620 100k 0.25W Resistor 0.40 1.00 0.40 Coles Alkaline C Cells 2.23 6.00 13.37 Receiver Total 48.39 Project Total 95.68

20-Oct-1998