ANTENNA MODELS

ANTENNA MODELS BRANDON HOUSE TROON AYRSHIRE KA10 6HX SCOTLAND

Frequently Asked Questions and Answers

Loco conversion

  • What do I need to start?
  • Do I need a separate transmitter for each locomotive?
  • How much does it cost to convert each locomotive?
  • Can any locomotive be converted?
  • Can the equipment be fitted in a separate vehicle?
  • Batteries

  • What is the difference between a battery and a cell?
  • What not to do with NiCad batteries?
  • How to I test the health of a NiCad cell?
  • How do NiCad (Nickel Cadmium) and Nickel Hydride batteries compare?
  • What is the memory effort?

  • Loco Conversion

    What do I need to start?

    A speed controller, transmitter, receiver, charger, charging socket, on/off switch and batteries for the locomotive and for the transmitter. If you are picking up power from the track you don't need locomotive batteries, but you will need a rectifier/smoother.

    Do I need a separate transmitter for each locomotive?

    No, but it is useful. You can use one transmitter and switch between locomotives by changing the crystal. However, since the transmitter/receiver/crystal package is relatively cheap, buying the receiver and crystal separately only saves about £7. Having a separate transmitter for each locomotive means that locomotives can be operated at the same time and allows a transmitter to be associated with a locomotive so that the holder of that transmitter is always the driver of that locomotive.

    How much does it cost to convert each locomotive?

    This depends on the batteries used, but about £100.

    Can any locomotive be converted?

    It hasn't been done in Z gauge yet, but apart from that, pretty well any locomotive can be converted, although very small locomotives are more difficult. The smallest locomotive known to be converted is a Lima Class 08 shunter, but for such a small locomotive, a new motor and chassis was essential. In O gauge, anything can be converted, but very small locomotives may require quite extensive rebuilding, so coupling a van holding the radio gear can make life easier.

    Can the equipment be fitted in a separate vehicle?

    Yes, the radio control gear can also be fitted in a separate vehicle. This allows the same equipment to be used with several models, although it does mean that the locomotive is no longer a self-contained entity. For very small models, such as some pre-grouping tank locomotives, the extra space afforded by coupling another vehicle is very helpful. There is a sort of a prototype precident in the Class 03 diesel locomotive which were often coupled to another wagon to ensure that they would trigger tracks circuits reliably.

    The radio control van is fitted in the same way as the locomotive would normally be, complete with a speed controller, batteries, receiver, and charging socket, but instead of connecting the wires to the motor, they are fitted to a socket on one end of the vehicle. The locomotive has a plug for connection to this socket and which is then connected to the motor. It is important that the plug be on the on the locomotive and the socket n the van, because the socket will be powered from the batteries, and in a plug were used at this end it may short out.

    This method can also be used to convert a 2 rail locomotive to radio control operation. A switch can be fitted to the model to take the motor power either from the track pickup or from the plug which would be connected to the radio controlled van. It is most important that a double pole change over switch be used so that the motor is completely isolated from the track. This avoids interference being picked up from the track, and also avoids the danger of the radio controlled van powering the track, and any other locomotives which might be sitting on it.


    Batteries

    What is the difference between a battery and a cell?

    A battery is a collection of cells, where a cell is an individual chemical energy producing device. However, an individual packaged cell is colloquially known as a battery.

    What not to do with NiCad batteries?

    NiCad batteries are fairly indestructible, but they will be irreparable damaged by reverse charging (i.e. being connected to the supply the wrong way round). Therefore, be very careful when wiring up because one mistake will loose you the set of batteries.

    Reverse charging can happen in another way. If you allow the batteries to completely discharge and then continue to draw current from them, not all the batteries will go flat at exactly the same time. The batteries with some charge left in them will then start to charge the completely flat batteries, resulting in reverse charging. When the model stops due to low power in the batteries, the batteries are not completely flat, but will continue to discharge if you leave the model switched on. As a result, if the model stops due to the battery discharging, switch it off to avoid and change of damaging the batteries. Also, avoid leaving the model switched on for extended periods (overnight, for example), in case the same thing happens.

    Reverse charging can be avoided by connecting a diode in parallel with the battery anode connected to the diode cathode and vice versa. Any reverse charge will therefore be diverted through the diode and so not damage the battery. For most models, however, this precaution is not necessary.

    Circuit to prevent reverse charging

    How to I test the health of a NiCad cell?

    The voltage across a NiCad cell should normally be about 1.5 volts with no load connected, falling to about 1.2 volts whenever a load is connected, or lower if the battery is discharged. The no load voltage of about 1.5 volts is constant for a healthy cell even if discharged, although you may only see that with a digital multimeter, as a cheap analogue meter may draw enough of a load from the battery when measuring its voltage to show a lower voltage.

    A faulty cell is likely to show a voltage of about 0.7 volts.

    How do NiCad (Nickel Cadmium) and Nickel Hydride batteries compare?

    Nickel Hydride batteries have a higher energy density than Nickel Cadmium batteries, so batteries are smaller for a given capacity. This is useful if you have a small model which it is difficult to fit the required number of batteries in to. They also do not contain cadmium, and do not therefore require special disposal.

    What is the memory effort?

    The memory effect is where if a battery is repeatedly used in the same way, it looses the ability to be used in any other way. For example, if a battery is repeatedly fully charged and then only discharged down to 50% capacity, and then recharged, it will then only be capable of holding half its charge, even though it is fully charged. For this reason, occasionally fully discharging batteries is useful. However, the memory effect only occurs where the use is very repetitive, as it would be in a video camera, for example. In model railway applications, the load on the batteries is very variable, so the memory effect is unlikely. Also, the batteries sold by Antenna Models are manufactured in such a way as to minimise the memory effect.

    ANTENNA MODELS

    Antenna Models Brandon House Bentinck Drive Troon Ayrshire KA10 6HX Scotland +44 (0)1292 310 903

    j.m.irvine@ieee.org