Sunday, October 25, 2015

Using output pads on Deltang receivers

Introduction

This article assumes you have a basic knowledge of installing Deltang equipment for controlling the motor of a battery loco, and have reached the stage where you'd like to make use of some of the output pads to operate lights or other accessories such as triggering the whistle on a soundcard. If you are unfamiliar with Deltang radio control equipment, then you might find Getting started with Deltang r/c in the garden useful.

To keep things simple, I will focus on the Rx60/Rx61 and Rx65 receivers as these are the ones I have used most extensively - but the general principles shown here apply to the majority of the other Deltang receivers on offer. Hopefully, once you have grasped the basics, you will be able to use the information on the Deltang website to explore other options.

This article is organised into the following sections
  • Soldering to the pads. How to solder to the pads without frying your receiver
    • Choosing a soldering iron
    • Tinning
    • Soldering
  • Which pad? Which pads do what on the receivers.
    • Using pads for lighting
      • Directional lighting
      • Using Pads A and B on an Rx65b for directional lighting
      • Interior lighting
    • Using pads to trigger effects on soundcards 
      • A cheap Greetings Card module
      • MyLocoSound
      • DigiSounds (MTroniks / Peter Spoerer)
      • Technobots programmable 
    • Using pads as inputs 
  • Conclusion

Soldering to the pads

Probably the most daunting aspect of using the pads, is having the confidence to actually bring a soldering iron close to the tiny circuit boards to fix wires on to the output pads - particularly on the Rx60 receiver. The Rx65 is only marginally more expensive than the Rx60 and so, if you have the space to fit it, you might find using an Rx65 the better option if your are not too confident. The Rx65 has larger pads which are slightly further apart, and so makes soldering a bit easier.
Deltang Rx60
Deltang Rx65
If you are already familiar with soldering techniques you can skip the next section, but I am assuming there are some who might find a beginners' approach helpful

Soldering iron

First, and most important of all, is to buy a soldering iron with a very fine bit. I use an Antex XS iron which has interchangeable bits (Maplin product code FR12N). I use the finest 0.5mm No. 55 bit (Maplin product code N85DS).

Tinning

Something I have learned from experience is the importance of having a well-tinned bit. The secret to tinning successfully seems to be to apply the solder to the bit while it is heating-up - before it reaches its full operating temperature.

Similarly, the wire and the pad need to be tinned before they are joined. I use multi-core solder, apply the well-tinned bit to the wire or the pad and almost immediately touch the interface between the bit and the piece with the solder. Once the solder has flowed, the bit is removed. Here you can see an Rx65 receiver with the supply and motor pads tinned (on the left hand side), Pads 2 and 3 (bottom right), pad C (upper left hand side), pad 5 (Upper right) and one of the negative supply pads (Upper left) tinned and ready to receive leads.

If you have bought a receiver shrouded in heatshrink sleeving, you will need to cut the sleeve to give access to the pads which need to be soldered. Make sure you know which pad(s) you will be using, so that you only remove the sleeving from the section(s) of the board required. (see Which pad? below)

Soldering to the pad

Provided the pad and the wire have been properly tinned with solder, soldering the wire to the pad is relatively easy and straightforward. The tinned end of the wire is held against the pad, the tip of the soldering iron is tinned with a small blob of melted solder and then touched against the wire and pad. The blob of solder on the iron helps the heat to flow quickly to the joint and so the iron needs only to be held against the joint for a second, thus reducing the risk of cooking the chips on the board.

Which pad?

Deltang receivers are supplied with their pads ready-programmed for a range of functions which might be needed by modellers. However, the function of each pad can be reprogrammed to tailor the receiver to the specific needs of the user (see How to re-program Deltang receivers).

To work out the function of each pad for a recently purchased receiver, you need to access the information provided on the Deltang website. For example, the information on the pads given for the Rx60 is:


1. DEFAULT SETUP
Item

Setting Details
P1 Front Light Auto action, LED2 enabled

P2 Rear Light

Auto action

P3 On/Off Direction switch (Ch3)
On when channel is Low, Momentary action
P4 On/Off Direction switch (Ch3)
On when channel is High, Momentary action
P5 On/Off Bind button (Ch5)
Start off, toggle when channel is Low, Latching action

So, what does this all mean? I've decided the best way to explain the outputs is to give some examples.

Using pads 1 and 2 for directional lighting on the Rx60/61 and Rx65b

Pad 1 (P1) and Pad 2 (P2) are set-up to automatically provide power for direction lighting (provided they are only powering LEDs). P1 will power a front light when the loco moves forward and P2 will power a rear light when the loco moves in reverse.

I used the P1 and the P2 outputs on my IP Engineering Lollypop railcar (see How I constructed an IP Engineering Lollypop railcar).

I could have kept things simple and had white LEDs in the lamps facing forwards and a red LED in the rear lamp, and wired-up both white LEDs to P1 and the red LED to P2, like this:

Bear in mind that, regardless of the input voltage (in this case 3.6v from three NiMh batteries), the output from the Deltang receiver is 3.3v. This voltage is what is used to calculate the values of the resistors which must be used in series with the LEDs to limit the current (usually to around 20mA). There is a useful calculator for determining the value of the resistors here - http://led.linear1.org/1led.wiz - but in general, I find 100 ohm resistors are fine for connecting to LEDs powered from Deltang pads.

For this little railcar, I actually used bi-colour LEDs so that the leading lights showed white and the trailing lights showed red whichever direction the railcar was travelling. The circuit for this set-up was (with the addition of 100 ohm resistors in the negative leads to each LED):


Using Pads A and B on the Rx65b for direction lighting
A slightly different approach needs to be adopted when using pads A and B on the Rx65b. As with Pads 1 and 2 on the Rx60 and the Rx65b, these pads provide automatic direction lighting but whereas pads 1 and 2 provide 3.5v outputs and so can be wired as shown with the Rx60 examples, Pads A and B provide 0v outputs when triggered. This means that when using pad A or B, an LED has to be connected the other way round - the cathode on the LED (ie the shorter leg) is connected to the pad and the anode (ie the longer leg) is connected through a resistor to the positive battery lead. The value for the resistor will therefore be determined by the supply voltage from the battery.

If you are uncertain about the parameters for your LED you can assume that:
  • the forward voltage or voltage drop across a red, yellow or green LED is generally 2v
  • for white or blue the forward voltage is generally 3v. 
  • while some white LEDs can operate safely with higher currents, you can assume that most LEDs operate satisfactorily at 20mA or 10mA. Bright white LEDs, for example, will give a relatively high level of light at 10mA or 5mA. Decreasing the current used for lighting will, of course, increase what's available for driving the motor.

My two larger diesel locos both have LED powered front lights which are connected to Pad A. Originally, I used Pad 1 for the front lighting and so used a 100 ohm resistor.

Lately, I have taken to using Pad A and, because I am now connecting the LED to my 12v supply, I use a 470 ohm resistor:

Note: For the purposes of the calculation, I assumed my supply was 12.5v (three li-ion batteries freshly charged can reach this voltage) and I knew the forward voltage of my LED was 3.3v. I went for 20mA as, although my white LED could take up to 30mA, I prefer to include a safety margin.

So why bother to use Pad A rather than Pad 1? Quite simply, Pad A provides an additional feature which is quite useful. The output from the pad mirrors the state of the LED on the receiver. As my receivers are hidden away inside the bodies of the locos, I can't see when the receiver is searching for the transmitter and when it has located it. If ever I want to re-bound the receiver to another transmitter, I can watch the front light until it starts flashing rapidly to show the rx is in bind mode. Once the rx has located the transmitter, the front LED headlight goes into its normal directional lighting mode. This LED2 feature wasn't available on the Rx60s when I bought them, though I see it is now provided by default.

Using pads for interior lighting

On the Rx60, Pads 3 and 4 and on the Rx65b pads 6 and 7 respond to the direction switch on a Deltang transmitter (Channel 3). So, on the Rx60 Pad 3 comes on when the switch is flicked one way and Pad 4 when the switch is flicked the other way (usually Pad 3 for down and Pad 4 for up - but you may need to experiment to check this). I used Pad 3 of the Rx61 in my railbus to operate the interior lighting ......

........ (as well as Pads 1 and 2 to power the headlamps in each direction). (see How I constructed a pair of Ford type railmotors)

 Originally, I had four LEDs in each carriage for the interior lighting and so needed to use a transistor switch in the circuit to avoid overloading the receiver (see How I made a simple transistor switch). However,  four LEDs looked far too bright for 1930s interior lighting and so I reduced the number to two per carriage. This meant I could also do away with the transistor switch

I also used just one 100 ohm resistor for the two LEDs connected in parallel (assuming 3.3v supply, 2v forward voltage, 7mA current (because I wanted them to be dim)). However, connecting LEDs in parallel with one resistor is generally frowned upon as it assumes the LEDs in the circuit have exactly the same electrical characteristics - if not, one LED could become overloaded. However, as I had sourced the warm white LEDs at the same time from the same supplier and I was not running them at full power, I felt it would be OK. This online resource calculates the required values for resistors in parallel circuits - http://ledcalc.com/#calc

Using pads for triggering sounds

So far, I have had experience of four different types of soundcard (MyLocoSound, MTroniks/Peter Spoerer DigiSounds diesel soundcard, the Technobots programmable soundcard and a cheap sound module from a greetings card), but they all follow a similar approach. The cards all needed at least one input from the receiver to, for example, trigger the horn or whistle. In all cases, these triggers required a 0v input - in other words, they needed the input lead to be connected to the negative terminal of the supply battery to trigger the sound.

A Greetings Card sound module
The simplest system was using the module from a 'musical' greetings card. This was bought online from China for the princely sum of £1.29 (including postage).

After recording the sound of a horn (using the microphone and record button provided), the mike, record button, LED and batteries were removed and the board wired into the same battery supply as that used by the Deltang Rx65b receiver (a single 3.7v li-ion battery). The 'play' button was removed and the lead (not the one leading to the negative supply on the board) was soldered to output pad C on the Rx65b. Pad C is triggered by the bind button on any of the Deltang transmitters (Channel 5). As Pad C provides a 0v output when triggered, this was ideal for sounding the horn.

You'll see (or rather hear) from the video that I have also used another greetings card module to provide an engine sound. This is not triggered by the receiver (though it could easily be using another pad, but it would need to be re-programmed or inverted (see below) to provide a 0v output). I retained the 'play' button for triggering the engine-sound board (see How I modified a cheap greetings card module into a soundcard).


MyLocoSound soundcards
Four of my locos are presently equipped with MyLocoSound cards. Two have the older original type of card which uses small preset potentiometers to adjust the card's settings, such as volume, whistle tone and chuff rate. The other two are equipped with the more recent Universal card, which is adjusted by using a TV style remote control. The Universal card also has several more effects which can be controlled by the user, such as guard's whistle, safety valve and brake pump.

As indicated above, with a Deltang Rx65, it is very easy to trigger the whistle or horn (or any other effect) on a MyLocoSound card. To trigger an effect on the MyLocoSound card the relevant input needs to be connected to 0v or the negative terminal of the power supply. Pad C on the Rx65 gives an output of 0v when it receives a low signal on Channel 5 from the transmitter (see table below from the Deltang website)
mSettingDetails
Purpose:Rx65-22Train with Tx22 transmitter
Red wire positive (+)
Black wire negative (-)
Battery3-18v
Observe polarities
H1 outputMotor
Ch1
Integrated forward/reverse ESC for brushed motors
Center off
F1 output 'A'
(P13)
Front Light
H1 (auto)
0v when on, disconnected when off; LED2 enabled
F2 output 'B'
(P14)
Rear Light
H1 (auto)
0v when on, disconnected when off
F3 output 'C'
(P15)
On/Off
Ch5
Start disconnected, 0v (on) when channel is Low
Momentary action
P1Front LightAuto action, 3.5v when on, 0v off
P2Rear LightAuto action, 3.5v when on, 0v off
P3On/OffCh2, Idle high, 0v when channel is Low, Momentary action
P4On/OffCh4, Idle high, 0v when channel is Low, Momentary action
P5On/OffCh5, Start high, toggle when channel is Low, Latching action
P6On/OffCh3, Idle low, 3.5v when channel is Low, Momentary action
P7On/OffCh3, Idle low, 3.5v when channel is High, Momentary action
P8ServoCh1, Standard servo
P9ServoCh2, Standard servo
P10ServoCh3, Standard servo
P11ServoCh4, Standard servo
P12ServoCh5, Standard servo

On Deltang transmitters, pressing the bind button does just this and so, if Pad C is connected to the whistle input on the card, the whistle or horn will sound when the bind button is pressed. To protect the receiver from excess current passing from the soundcard (which operates at 5v) it is advisable to put a 1k resistor in the connection from the pad to the trigger terminal on the soundcard.

As indicated above, the MyLocoSound Universal soundcard has several other effects and so, if the trigger terminals for these effects could be connected to 0v through the receiver, then they could all be triggered by the transmitter. At the time of writing, Pad C, Pad 3 (Channel 2) and Pad 4 (Channel 4), are the only ones on the Rx65 as bought which provide 0v in response to signals from the transmitter. This is OK if you are using an aero transmitter or a Deltang Tx20, as these can send signals on Channels 2 and 4. However, if you are using a Tx22, the only other channel which can be triggered is through the direction switch (Channel 3). Pads 6 and 7 respond to this channel but they provide 3.5v outputs rather than the 0v required by soundcards. One solution is to reprogram the pads to give 0v (see How to reprogram Deltang receivers) but another approach is to use a simple bit of electronic wizardry to change a 3.5v output into a 0v output.

Adding a transistor inverter circuit instead of reprogramming


Recently, I decided to use an Rx65b to trigger the five sound effects on the most recent MyLocoSound Universal Steam Soundcard. As I was using a Deltang Tx20 transmitter, I could use the buttons on the transmitter to energise channels 2, 4 and 5 which would send 0v from pads 3, 4 and C on the Rx65b to the soundcard but I couldn't use the direction switch (Ch3) unless I reprogrammed pads 6 and 7 to give 0v. Realising that many garden railway modellers would be daunted by the prospect of reprogramming, I  decided to explore another option; adding a small transistor circuit to the pads to invert their outputs from 3.5v to 0v (see How I triggered MyLocoSound effects with a Deltang Rx65b). 

With the addition of two transistors and four resistors (a total outlay of around £1.00), and a tiny bit of soldering, I now have a fully functioning remotely operated soundcard - literally with all bells and whistles!

The DigiSounds small / narrow gauge diesel soundcard
This soundcard sounds impressive, as it uses genuine digitised diesel sounds. In addition to the horn, the card includes start-up and engine-off sound effects. As with the MyLocoSound card, these effects are triggered by connection of the relevant inputs to 0v. I installed a DigiSounds card in my IP Engineering Jessie.

Triggering the horn was straightforward, I simply connected the input on the card to Pad C (or Pad 5) on the Rx65b. To trigger the engine start-up, I decided to reprogram pad 3 to respond to the direction switch on any of the Deltang transmitters (Channel 3) - see How I installed a Deltang Rx65 in my IP Engineering Jessie loco. Pad 1 was used for the direction lighting to power the front headlight (pad 2 is shown connected in the photo as I originally wired the loco in reverse).

Eventually I rewired her to make use of Pad A for the headlight

Here she is in action after the installation


The Technobots / Alan Bond programmable soundcard

I came across this soundcard recently as I wanted a different sort of sound for my other diesel (a scratchbuilt Fowler-inspired loco) rather than using another DigiSounds card.

 The Technobots card generates the sounds electronically, rather than having digitised sounds. While some realism is lost, what is gained is programmability. There are ten different 'voices' provided on the card and each of these can be tailored to meet the specific needs of the user.

Initially, it appeared that this soundcard would be incompatible with the Deltang system as it is designed to fit between the receiver and the ESC, an option which is not normally available with Deltang receivers. However, undeterred, I explored different ways of enabling the card to be synched and triggered by my Deltang transmitters. Ultimately, I decided to use an Rx65b to control the motor on the loco and an Rx102 to communicate with the soundcard. The trigger for the horn was taken from pin 5 on the Rx102, through a 1k resistor to the Aux input on the card (the white wire in the photo below).

For more information on this project see How I integrated a Technobots soundcard with Deltang receivers. As you will see from the article, there was more than one way driving the sound effects, I opted for the approach which best suited my needs.

Using pads as inputs

In addition to driving devices, the pads on Deltang receivers can be used to input information to the card. The Rx65b includes built-in features which enable the motor to be controlled automatically. These features include - station stop mode (the loco slows to a stop at a station, waits, then continues on its way), buffer stop mode (the loco reaches the end of a siding, slows to a halt and does nothing until the operator moves the speed knob), and auto-shuttle mode (the loco reaches the end of the track, slows to a stop, waits and then moves off in the opposite direction). The length of time it takes to slow down and the length of waiting-time can be programmed by the user (see How to program Deltang receivers).

To enable the loco to know when it is required to stop, one of the pads needs to be connected to a reed switch (a switch which is activated when it comes close to a magnet). The other side of the reed switch is connected to 0v, so that when the loco passes over the magnet, the pad is triggered by being grounded to 0v (in the same way as the effects on the soundcards above are triggered).

So far, one of my locos has been programmed to operate in auto-shuttle mode on the 32mm gauge mine feeder line on my railway (see How I programmed a Deltang Rx65b to operate in shuttle mode).

I am planning to program another two of my locos to operate in station-stop mode, so that on balmy summer evenings, I can relax in a deck-chair with a cool drink while a couple of trains happily chug around my railway stopping at stations without my intervention.

Conclusion

In my opinion, the great virtue of the Deltang radio control system is its versatility - not to mention the diminutive size of the equipment, the quality of its design, its cost-effectiveness and the range of features it provides. In this article, I have touched upon some of the things which can be done with Deltang receivers. Pads can be used to operate a range of devices, such as driving a servo for remote uncoupling or playing a preset sequence of LEDs in an array.

In addition to using Deltang receivers within locos, I have also used them to remotely control points on my railway (see How I operate my points by remote control). With a little bit of imagination and ingenuity, they could equally be used to control virtually any lineside gadget or accessory.

I hope this little introduction has been helpful and that it provides you with sufficient confidence to have a go yourself.

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