Radio Control - 75 MHz Receiver Super Socket

by Paul Norton

IMPORTANT UPDATE

The Super Socket in not needed and should NOT be used with the new 2.4 GHz Revolution Train Engineer receiver. The Revolution receiver does not suffer from the radio range problems that plagued the 75 MHz receiver, so the RFI chokes on the Super Socket are not necessary. Aristo-Craft sell a correct Plug and Play board with screw terminals for the installation of the Revolution receiver in non-Plug and Play locomotives.

Other than the RFI chokes, the differences between the Super Socket for the 75 MHz receiver and Aristo-Craft's, Revolution receiver adapter board or their Plug and Play board is the wiring for the lights and the fuses in the motor traces.

Pin 6 of the 75 MHz receiver provided positive power for the lights at a constant 20 volts, maximum 200 milliamps. This would be the blue wire on the 75 MHz receiver adapter board or screw terminal 6 on either end of the Super Socket.

If you hold either the Revolution receiver adapter or Plug and Play board up to the light you will see that the trace on the boards passes beside pin 6, but is not connected to it. On both boards the power for the lights is provided directly from either track power or battery power. Positive power for the lights would be the blue wire on the adapter board or the screw terminal labeled "HD COM" on the Plug and Play board. There are diodes in the traces of both boards to ensure that the power provided is always positive when the track power polarity changes or the battery pack is wired backwards.

If you wanted to use the Super Socket with a Revolution receiver with battery power, you could unsolder and push the pin holder for pin 6 out of the IC socket to isolate it. A jumper from the positive power input, either trace 1 or trace 12 depending on how the socket was wired and hooked up to the battery, to trace 6 would provide positive battery power for the lights. Be aware this is full battery power, not 20 volts like the 75 MHz receiver.

If you wanted to use the Super Socket with a Revolution receiver with track power, you could unsolder and push the pin holder for pin 6 out of the IC socket to isolate it. Jumpers with a diode in each, from both traces 1 and 12 to trace 6 are required. The diodes must be installed so only positive power is allowed to pass to trace 6 when track power polarity is changed. Again, this is full track power, not 20 volts like the 75 MHz receiver.

Both the Revolution receiver boards have fuses in the traces between the motors and receiver. I assume this is to protect the receiver from shorts when using track power.

If you are using battery power with the Super Socket, and the track power pick-ups have been removed or isolated, fuses in the motor leads should not be required. A fuse between the battery pack and receiver however, is always a good safety measure.

If you are using the Super Socket with track power, fuses in the motor leads would be a good idea. A fuse between the receiver and track power wires is also a good safety measure.

If you are going to use a Revolution receiver in place of a 75 MHz receiver, it might be easier and safer just to buy one of Aristo-Craft's, Plug and Play boards and replace the Super Socket with it. I used one to convert my USA Trains S-4 diesel switcher to on-board, radio control and battery power. I will use two more when converting my GP-9s.

Over the next half year, you will see the 75 MHz receiver information on our club web site change or disappear. The article on installing a 75 MHz receiver in a Bachmann Annie will probably remain, as there were no radio range problems with the receiver in the tender away from the motor. It can also be used in trailing power cars as long as they are not motorized.

Because of the range problems our club members encountered with the 75 MHz receiver in diesels, I removed the article about installing it in a Plug and Play FA-1. It was replaced with an article on installing the Revolution receiver in the FA-1 instead. There are absolutely no range problems with it, and it is loaded with other features such as momentum and soft reverse.

While there are still articles on our web site about installing the 75 MHz receiver in a non-Plug and Play FA-1 and RS-3 using a Super Socket, these will probably be replaced over the next year. Knowing the large scale market, I assume very few people would be willing or able to build a Super Socket. These articles will be replaced with articles using Aristo-Craft's, Plug and Play board and the Revolution receiver in non-Plug and Play locomotives.

SUPER SOCKET INTRODUCTION

This article details the assembly of a Super Socket for the installation of an Aristo-Craft 75 MHz receiver.

The socket is easy to assemble and there are many advantages to using it.

Once the socket is installed, wiring the battery, motor blocks, and lights is easy. Terminal blocks on each end of the board allow the wiring to be inserted and connected by turning down the screws. If the motors and lights are operating in opposite directions, undo four screws and change the motors wires over.

The large chokes on the board suppress radio noise generated by the motors and greatly improve radio range. Radio range problems have plagued the 75 MHz receiver, but with this board, capacitors across the motor terminals, and a telescoping antenna on the transmitter reliable and immediate radio response of 100 feet or more is possible.

Resistors mounted on the board allow the use of power efficient LED lighting. LEDs provide constant and directional headlights that cast a very prototypical, long, bright beam.

This socket and a lithium-ion battery pack can be used to convert most USA Trains and Aristo-Craft, 4-axle diesels to on-board, battery power and radio control. The socket can also be used for track power and radio control, by connecting the track power wires to the board instead of the battery pack wires.

ASSEMBLING THE SUPER SOCKET

The board is 12 rows (traces) down by 44 columns (holes) across. It is cut with a razor saw from a circuit board available from All Electronics under catalog # ECS-4.

Fasten the 12-pin, terminal blocks to the ends of the board with superglue (AC) as shown. The blocks should be flush with the ends of the board, and their pins in the columns 2 and 43. The openings for the wires should face out.

The terminal blocks are manufactured by Phoenix Contact and are available from DigiKey Canada, or Digikey.com under the manufacturer's part number 1725753.

Fasten with superglue, the front 24 pin IC socket and the rear 20 pin IC socket to the board as shown. Their pins are should be in columns 13, 16, 29 and 32. The pins of the 75 MHz receiver should line up with the outer row of each socket. These sockets are available from most electronic shops.

Insert the leads of the chokes in columns 6, 8, 37 and 39 of rows (traces) 3 and 10 of the board. The chokes are available from All Electronics under catalog # CR-224.

Flip the board over and solder the chokes, the IC sockets and terminal blocks to the board. A good soldering iron of at least 30 watts and thin solder wire will be required. The traces must be properly fluxed and heated, before the solder is added and allowed to flow. Trim the excess from the leads.

Flip the board back over. If LED lighting is being installed insert the leads of two resistors of the proper value in trace 6 on both sides of the front IC socket as shown. If light bulbs are being used, resistors may or may not be required depending on the voltage of the bulbs. Flip the board over and solder the resistors to the board. Trim the excess from the leads and keep it.

The Ngineering web site has a great tutorial on LED lighting circuits. It also has interactive calculators to determine the value of resistors required for a particular circuit. These are good links to read and add to your favorites.

In order for the chokes and resistors to function, their traces must be opened between the leads of each. Use a 1/8 drill bit in a pin vise to drill out the traces as shown.

Flip the board back over. Bend two, U shaped jumpers from the excess leads cut from the resistors. These are used to join the two traces on each edge of the board. These correspond to pins 1 and 2, and pins 11 and 12 of the receiver. Insert the jumpers in column 11 as shown.

Flip the board over and solder the jumpers to the board. Trim any excess lead material from the jumpers.

There is no need to insulate the pins of the rear IC socket holding the ten pins of the 75 MHz receiver. Aristo-Craft have confirmed George Schreyer's findings that the pins are there only to hold the rear of the receiver in place. They are isolated from each other and all traces on the receiver.

When finished, clean the board with flux remover or rubbing alcohol and allow it to dry.

Congratulations, you can now plug in your 75 MHz receiver, and fasten the required wiring to the terminal blocks.

POOR MAN'S SOCKET

Some people found the terminal blocks expensive to purchase. Locally they are about $7.50 each plus taxes at Reset Electronics. The Poor Man's Socket however, can be made without the convenience of the terminal blocks. The wiring for the receiver, motor(s) and light(s) can be soldered to the board instead.

NOISE SUPPRESSION FOR MOTORS

Please Note: Soldering 0.1 uf capacitors across the locomotive motor terminals is required in order to help suppress radio noise generated by the motors and achieve maximum radio range.

My Aristo-Craft, Plug and Play, FA-1 already had noise suppression components soldered across the motor terminals, but I found that the 0.1uf capacitor worked better.

If you are installing capacitors in the motor blocks of a USA Trains diesel, I suggest removing the brass rods and slip on connectors and replacing them with wires soldered directly to the motor terminals. Every mechanical connection has the capacity to radiate noise.

The capacitors are available from All Electronics under catalog # 104D50.

BLACK KAT ANTENNA

Have you tried a Black Kat antenna? I have used them in all my 75 MHz receiver installations. It may not provide any better range than the metre long wire antenna, but it's two inch length certainly makes it easier to install.

The Black Kat antenna is available from E Cubed R/C

Black Kat antennas and all the components required to build either a Super Socket or a Poor Man's Socket can be purchased by OVGRS members by contacting Paul Norton. See the Items For Sale Section for details