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Deltang Tx2 Transmitter Module

Tx2 Connections
Tx2 pin labels

Tx2 is a radio module used to make a 7 channel proportional 2.4GHz DSM2 transmitter. It is compatible with DSM2 and all Deltang receivers. The range is suitable for indoors and small outdoor sites - 60m range is achievable outdoors.

Tx2 is a reprogrammed receiver with only 8 inputs so may be a bit quirky for some features! It is very much a DIY project which requires soldering external resistors, potentiometers, switches, battery and LED. It is intended to make a simple transmitter, eg: by connecting pots or converting an old IR or 27MHz handset.

Tx2 can control up to 7 proportional or switched channels. It has special options for trains to control speed, direction, inertia and lights.

Radio Range (top)

Tx2 uses a CYRF6936 RF chip. In an early datasheet the manufacturer claimed 'typical observed range' as being 15m in a Home context, 20m in an Office and 30m Outdoors. The manufacturer has removed this information from current datasheets. People sometimes get more than this range with Tx2 but range cannot be guaranteed.

Tx2 Aerial Orientation

Range is maximised when the Tx aerial is 'side on' to the model. It is weakest when the tip is pointed at the model. Range is also maximised when the signal is not obstructed. Water (including human body parts), metals, batteries and carbon fibre are examples of things that block signals.

The tip of the aerial must not make electrical contact with anything else (eg: switches, other wires).

Tx2 has an on-board 3.1v voltage regulator. Provided the voltage is over 3.2v, battery voltage is not normally important. However, flat batteries usually cause problems even when their voltage is over 3.2v.


Profiles (top)

Seven profiles are available to suit different needs. Unless specifically requested, Tx2 is supplied set to Profile 1.



Control Pin
PROFILE 1
Trains
(Tx22/Tx24)

PROFILE 2
Conventional
(5ch)
PROFILE 3
Trains
(Tx23)
PROFILE 4
Conventional
(7ch)
PROFILE 5
Trains
(Tx20)

PROFILE 6
Trains
(Tx21)

PROFILE 7
Simple 7ch
(Tx27)

Pin1 Ch1 + Ch6 analogue Ch1 + Ch6 analogue Ch1 analogue Ch1 analogue Ch1 + Ch6 analogue Ch1 + Ch6 analogue Ch1 analogue
Pin2 Ch2 analogue Ch2 analogue Ch2 analogue Ch2 analogue Ch2 digital (mid/low) Ch2 digital (mid/low) Ch2 analogue
Pin3 Ch3 analogue Ch3 analogue Ch3 analogue Ch3 analogue Ch3 analogue Ch3 analogue Ch3 analogue
Pin4 Ch4 digital (mid/low) Ch4 analogue Inertia analogue Ch4 analogue Ch4 digital (mid/low) Ch4 digital (mid/low) Ch4 analogue
Pin5 Ch5 digital (high/low) + BIND Ch5 digital (high/low) + BIND Ch5 analogue + BIND Ch5 analogue + BIND/REVERSE Ch5 digital (high/low) + BIND Ch5 digital (high/low) + BIND Ch5 analogue + BIND
Pin6 Inertia
(or Ch4/5 analogue)
REVERSE Ch6 analogue Ch6 analogue - Inertia
(or Ch4/5 analogue)
Ch6 analogue
Pin7 Ch7 analogue TRIM Ch7 analogue Ch7 analogue + TRIM Ch7 analogue Ch7 analogue Ch7 analogue
LED on PCB LED1 output LED1 output LED1 output LED1 output LED1 output LED1 output LED1 output
Pin8 LED2 output + PROFILE LED2 output + PROFILE LED2 output + PROFILE LED2 output + PROFILE LED2 output + PROFILE LED2 output + PROFILE LED2 output + PROFILE

To change the profile:

  1. connect pin 8 to 3.1V, with nothing else connected to pin 8 (needle nose tweezers are good for making the connection)
  2. apply power to Tx2
  3. the LED will show a flash pattern corresponding to the configured profile number - e.g. 5-pause-repeat for profile 5
  4. the pattern will repeat once and then advance to the next; after 7 flashes, the pattern will return to 1
  5. when the flash pattern is showing the required profile number, remove the connection between pin 8 and 3.1V
  6. when the LED has stopped showing the flash pattern, remove power from Tx2
    • the LED will either light solid or flicker if the selected profile has an inertia channel
  7. repeat steps 1, 2 and 3 then remove power to verify that the correct profile has been stored

See Profile Details for information on how to use each of the profiles.


Analogue Inputs (top)

Pins 1-7 are used as inputs to control Channels 1-7 or other functions. Analogue inputs are 'fully adjustable' (proportional) and can have up to 1024 positions. This is achieved by adjusting the voltage applied to the Pin with a pot or switch with resistors

Channel positions will be random if analogue pins are left 'floating' (unconnected). Profiles with Inertia must have a pot connected to that input (or be grounded) to avoid random behaviour on Ch1 (Throttle). It is also common for floating inputs to 'follow' another channel (instead of being random).

Reference Voltage

Tx2 Voltage Reference

To give predictable results, the voltage applied to an analogue input needs to be proportional to a 'reference voltage' which is known to give full scale measurements. Tx2 is powered through an on-board 3.1v voltage regulator. This is too high to use directly as the reference voltage. However, it is easy to create a 50% voltage with 2 equal resistors. So this principle is used to create a 1.55v reference (3.1 / 2 = 1.55v).

Analogue inputs therefore normally need to have components to adjust voltage between 0 and 1.55v (eg: with a 10k pot), and another resistor of equal value (eg: 10k) to halve the 3.1v Vref. Pots and resistors can be any equal value between 4k7 and 100k but 10k for both is a common choice (10k = 10 000 ohms).

Analogue Input Range - Throws

Tx2 uses 10bit resolution, this means that channels have 1024 positions.

  • 150% throws: 0-1.55v = 0-1023 = 0.9-2.1ms servo pulse.
  • 100% throws: 0-1.55v = 171-852 = 1.1-1.9ms servo pulse.

Digital Inputs (top)

Some inputs are classed as 'digital' which means the Pin can only have two states, High or Low. The state will be High when the Pin is over 2.1v (eg: 3.1v). The state will be Low when the Pin is below 0.8v (eg: 0v). When nothing is connected to digital inputs, internal resistors pull them up to 3.1v (High).

When a Digital Pin is High it makes the channel go either to a 'high' channel position (eg: 2.1ms) or a 'middle' position (eg: 1.5ms). When a Digital Pin is Low it makes the channel go to its 'low' position (eg: 0.9ms) in all profiles.


Train Features (top)

Motor Channel

The motor channel (1) controls speed; it will normally be connected to potentiometer with centre detentent, unless the receiver is configured for full-range throttle and separate direction channel.

Direction Channel

The Direction channel (3) will only have any effect with receivers or ESCs that require a second channel to set the Fwd/Rev direction. On Deltang transmitters (Tx20, Tx22, etc. the Direction switch is often used for directional lights.

Lighting Control

The Direction channel can be used to switch up to 4 lights on and off with Deltang receivers. The transmitter Bind button can also be used to switch up to 2 lights on and off.

Loco Selection

Deltang land receivers have a 'Selecta' feature which allows locos to be brought in and out of service without touching them. Tx22 has a 12-way switch to allow up to 12 locos to be active at the same time and control switched between them.


Switches (top)

The Deltang land-based receivers have a feature called Selecta which requires a multi-position switch. The wiring diagrams and resistor values in the tables below describe how to set Tx2 up for these. The default throws are 150% but use the values for 100% when that option is enabled. Any analogue channel can be used except those intended for motor control in trains (these are affected by the Inertia feature). The Selecta switch never connects the Tx2 input to 0v or 1.55v. So inputs can also be used for things like Binding which connect the input to 0v to be effective.


Trim Pot (top)

A separate potentiometer can be placed in parallel with a joystick pot to create a more easily adjustable 'mechanical' trim for each channel. Two examples are shown in the image link below.


Profile Details (top)

The remainder of this document provides detail information for each of the selectable Tx2 profiles. Profile 1 is the default, see the

Profile 1 (top)

Profile 1 is intended for trains and used in Tx22 and Tx24.

Control PinFunction
Pin1Ch1 + Ch6 analogue (Motor)Pin1 is expected to control motor speed using Channel 1 or Channel 6. Changes are smoothed by the Inertia feature.
Pin2Ch2 analoguePin2 is used to control the Selecta feature in Tx22 using Channel 2. Alternatively, Ch2 is a spare channel for any purpose.
Pin3Ch3 analogue (Direction)Pin3 is expected to control 'motor direction' using Channel 3 on receivers/ESCs that use a separate Direction channel. Alternatively, Ch3 is a spare channel which is often used for lights with Tx22.
Pin4Ch4 digital (mid/low)Pin4 is digital and has an internal pullup and is used to control Channel 4. It is at its mid position when high (button released) or low position (button pressed).
Pin5BIND + Ch5 digitalPin5 is digital and has an internal pullup. It requires a pushbutton switch or bind plug to pull down to 0v. The Transmitter will enter Bind mode if the Bind button is being pressed when Tx2 is switched on. The Bind button can be used to toggle Ch5 in normal use for lights, servo etc. It is also used to calibrate Ch1, Ch2 and Ch7 (see below).
Pin6 Inertia, Ch4 or Ch5 (analogue)By default, Pin6 controls Inertia. It modifies the Ch1 position and is not used for Ch6. Pin6 must be grounded or have a pot installed to avoid random Ch1 behaviour. The Inertia pot can be used to control Inertia, Ch4 or Ch5. The operator change change this at any time (see below).
Pin7Ch7 analoguePin7 is analogue and requires a pot or switch with resistors to control its value.
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits

Calibration

Tx22 has a Throttle pot that has a 'click' at the center position. When Throttle is used 'center off' it needs to be calibrated so that it centers accurately to make the 'click' match the 'off' position in the receiver. Tx22 uses Ch2 for a 12-way Selecta switch. Pin7 can also have a 12-way switch. These three channels can be calibrated so they generate the same values on all units. Calibration is done using the Bind button while Tx22 is on. Calibration has to be started within 1 minute of switching the transmitter on. Calibration normally only needs to be done once.

  1. Center the Motor pot.
  2. On Tx22 put the 12-way Selecta switch in the 6 o'clock position (assuming 1 o'clock is fully CCW).
  3. Do the same for Pin7 if it has a 12-way switch.
  4. Switch the Tx on. Within 60s, press and hold the Bind button.
  5. After ~20s the Led will go out for 2s and come on for 3s. Release in this time to only calibrate Ch1.
  6. After ~25s the Led will go out for 2s and come on for 3s. Release in this time to only calibrate Ch1+2.
  7. After ~30s the led will go off and stay off until you release the Bind button. This calibrates Ch1+2+7.

INERTIA or CH4/CH5 choice

The Pin6 pot can be used to control Inertia or Ch4 or Ch5. Only one function can be active at any time. Each time the procedure is followed the function will toggle between [Inertia] and [Ch4 or Ch5].

The Bind button is used as follows:

  • If the Bind button is being pressed when the Tx is switched on, the Tx will enter Bind mode.
  • If the Bind button is pressed for less than 20s at any time, it will normally control Ch5 (see notes below).
  • If the Bind button is pressed for 20s or more within the first 60s of switching the Tx on, it will perform calibration.
  • If the Bind button is pressed for 20s or more after the first 60s of switching the Tx on, it will toggle what the Inertia pot is used for.

To toggle what the Inertia pot is used for:

  1. Switch the Tx on and wait more than 60s.
  2. Press and hold the Bind button.
  3. After ~20s the Led will go out for 2s and then come on for 3s. Release in this time to select Ch4.
  4. After ~25s the Led will go off and stay off until you release the Bind button. This selects Ch5.
  5. Repeat steps 1 to 3 to select Inertia control.

Notes:

  • If the Inertia pot is being used for Inertia, the Bind button controls Ch5 when pressed for less than 20s.
  • If the Inertia pot is being used for Ch5, the Bind button has no effect on Ch5 but is still used for Binding and toggling what the Inertia pot is used for.
  • If the Inertia pot is being used for Ch4, Pin4 has no effect on Ch4. The Bind button controls Ch5 when pressed for less than 20s.

Profile 2 (top)

Profile 2 is a simple 5 channel transmitter.

Control PinFunction
Pin1Ch1 analoguePins 1-4 are analogue and require pots to control their values.
Pin2Ch2 analogue
Pin3Ch3 analogue
Pin4Ch4 analogue
Pin5BIND + Ch5 digitalPin5 is digital and has an internal pullup. It requires a pushbutton switch or bind plug to pull down to 0v (=active). It controls BIND on startup and Ch5 in normal use. Ch5 can only be at one extreme (position 0) or the other (position 1023). Ch5 cannot be reversed or trimmed.
Pin6REVERSEPin6 is digital and has an internal pullup. It requires a pushbutton switch or bind plug to pull down to 0v (=active). It controls channel REVERSE.
Pin7TRIM
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits


Profile 3 (top)

Profile 3 is intended for trains (Tx23).

Note:

  • If you don't need to control 3 trains, you can use spare inputs to control other things.
  • The TRIM feature will normally only be used if the motor control knob needs 'centering' more accurately.
  • The PROFILE change switch will not normally be needed.
  • There is no channel REVERSE feature.

Control PinFunction
Pin1Ch1 analogueMotor 1
Pin2Ch2 analogueMotor 2
Pin3Ch3 analogueDirection 1
Pin4Inertia analoguePin4 controls Inertia, it modifies the Ch1, 2 and 6 positions and is not used for Ch4. If Intertia is not required, Pin4 must be grounded.
Pin5Ch5 analogue + BINDDirection 2
Pin5 requires two switches:
  1. A toggle switch selects Direction2 using Channel 5 (between 0.13v and 1.42v).
  2. A pushbutton (or 'Bind' plug) pulls Pin5 down to 0v to set BIND.
The Transmitter will enter Bind mode if the Bind button is being pressed when Tx2 is switched on.
Pin6Ch6 analogueMotor 3
Pin7Ch7 analogueDirection 3
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits

Tx23 v204 and higher

Calibration

Tx23 has pots that have a 'click' at the center position. When Throttle is used 'center off' each pot needs to center accurately so that the 'click' on the Tx matches the 'off' position in the receiver. Calibration is done using the Bind button while Tx23 is on. Calibration can only be done within 60s of switching Tx2 on.

  1. Center the three Motor pots.
  2. Press and hold the Bind button for ~20s until the led goes off. Ch1, Ch2 and Ch6 should now be calibrated.
  3. Release the Bind button.

Profile 4 (top)

Profile 4 is a 7 channel transmitter.

Control PinFunction
Pin1Ch1 analoguePins 1-4 and 6 are analogue and require pots to control their values.
Pin2Ch2 analogue
Pin3Ch3 analogue
Pin4Ch4 analogue
Pin5Ch5 analogue + BIND/REVERSEPin5 requires a pot and pushbutton for BIND/REVERSE:
  1. The pot controls channel 5.
  2. The pushbutton pulls Pin5 down to 0v to set BIND on startup and REVERSE in normal use.
Pin6Ch6 analogue
Pin7Ch7 analogue + TRIMPin7 requires a pot and pushbutton if trim is required:
  1. The pot controls channel 7.
  2. One pushbutton pulls Pin7 down to 0v to set TRIM.
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits


Profile 5 (top)

Profile 5 is intended for trains (Tx20).

Control PinFunction
Pin1Ch1 + Ch6 analogueControls motor speed using Channel 1 or Channel 6.
Pin2Ch2 digital (mid/low)Has an internal pullup and is used to control Channel 2. It is at its mid position when high (button released) or low position (button pressed).
Pin3Ch3 analogue (Direction)Controls 'motor direction' using Channel 3 on receivers/ESCs that use a separate Direction channel. Alternatively, Ch3 is a spare channel which is often used for lights with Tx21/Tx22.
Pin4Ch4 digital (mid/low)Has an internal pullup and is used to control Channel 4. It is at its mid position when high (button released) or low position (button pressed).
Pin5Ch5 digital (high/low) + BindHas an internal pullup. It requires a pushbutton switch or bind plug to pull down to 0v. The Transmitter will enter Bind mode if the Bind button is being pressed when Tx2 is switched on. The Bind button can be used to toggle Ch5 in normal use for lights, servo etc. It is also used to calibrate Ch1 (see below).
Pin6-not used
Pin7Ch7 analogueRequires a pot or switch with resistors to control the channel value.
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits

Calibration

Tx20 has a pot that has a 'click' at the center position. When Throttle is used 'center off' it needs to center accurately so that the 'click' on the Tx matches the 'off' position in the receiver. Calibration is done using the Bind button while Tx20 is on. Calibration can only be done within 60s of switching Tx2 on.

  1. Center the Motor pot.
  2. Press and hold the Bind button for ~20s until the led goes off. Ch1 should now be calibrated.
  3. Release the Bind button.

Profile 6 (top)

Profile 6 is intended for Tx21 (trains).

Control PinFunction
Pin1Ch1 + Ch6 analogue (Motor)Controls motor speed using Channel 1 or Channel 6.
Pin2Ch2 digital (mid/low)Has an internal pullup and is used to control Channel 2. It is at its mid position when high (button released) or low position (button pressed). Pin2 is not used on Tx21 and can be left unconnected.
Pin3Ch3 analogue (Direction)Controls 'motor direction' using Channel 3 on receivers/ESCs that use a separate Direction channel. Alternatively, Ch3 is a spare channel which is often used for lights with Tx21/Tx22. Pin3 is pulled high or low with a 2-position switch on Tx21.
Pin4Ch4 digital (mid/low)Has an internal pullup and is used to control Channel 4. It is at its mid position when high (button released) or low position (button pressed). Pin4 is not used on Tx21 and can be left unconnected.
Pin5Ch5 digital (high/low) + BindHas an internal pullup. It requires a pushbutton switch or bind plug to pull down to 0v. The Transmitter will enter Bind mode if the Bind button is being pressed when Tx2 is switched on. The Bind button can be used to toggle Ch5 in normal use for lights, servo etc. It is also used to calibrate Ch1 (see below).
Pin6Inertia, Ch4 or Ch5 (analogue)Controls Inertia. It modifies the Ch1 position and is not used for Ch6. Pin6 must be grounded or have a pot installed to avoid random Ch1 behaviour. The Inertia pot can be used to control Inertia, Ch4 or Ch5. The operator change change this at any time (see below).
Pin7Ch7 analogueRequires a pot or switch with resistors to control the channel value.
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits

Calibration

Tx21 has a Throttle pot that has a 'click' at the center position. When Throttle is used 'center off' it needs to be calibrated so that it centers accurately to make the 'click' match the 'off' position in the receiver. Pin7 can have a 12-way switch. These two channels can be calibrated so they generate the same values on all units. Calibration is done using the Bind button while Tx21 is on. Calibration has to be started within 1 minute of switching the transmitter on. Calibration normally only needs to be done once.

  1. Center the Motor pot.
  2. If Pin7 has a 12-way switch, put it in the 6 o'clock position (assuming 1 o'clock is fully CCW).
  3. Switch the Tx on. Within 60s, press and hold the Bind button.
  4. After ~20s the Led will go out for 2s and come on for 3s. Release in this time to only calibrate Ch1.
  5. After ~25s the led will go off and stay off until you release the Bind button. This calibrates Ch1+7.

INERTIA or CH4/CH5 choice

The Pin6 pot can be used to control Inertia or Ch4 or Ch5. Only one function can be active at any time. Each time the procedure is followed the function will toggle between [Inertia] and [Ch4 or Ch5].

The Bind button is used as follows:

  • If the Bind button is being pressed when the Tx is switched on, the Tx will enter Bind mode.
  • If the Bind button is pressed for less than 20s at any time, it will normally control Ch5 (see notes below).
  • If the Bind button is pressed for 20s or more within the first 60s of switching the Tx on, it will perform calibration.
  • If the Bind button is pressed for 20s or more after the first 60s of switching the Tx on, it will toggle what the Inertia pot is used for.

To toggle what the Inertia pot is used for:

  1. Switch the Tx on and wait more than 60s.
  2. Press and hold the Bind button.
  3. After ~20s the Led will go out for 2s and then come on for 3s. Release in this time to select Ch4.
  4. After ~25s the Led will go off and stay off until you release the Bind button. This selects Ch5.
  5. Repeat steps 1 to 3 to select Inertia control.

Notes:

  • If the Inertia pot is being used for Inertia, the Bind button controls Ch5 when pressed for less than 20s.
  • If the Inertia pot is being used for Ch5, the Bind button has no effect on Ch5 but is still used for Binding and toggling what the Inertia pot is used for.
  • If the Inertia pot is being used for Ch4, Pin4 has no effect on Ch4. The Bind button controls Ch5 when pressed for less than 20s.

Profile 7 (top)

Profile 7 is used in Tx27 (model railway layouts).

Control PinFunction
Pin1Ch1 analoguePins 1-4 and 6-7 require pots or switches to control their values.
Pin2Ch2 analogue
Pin3Ch3 analogue
Pin4Ch4 analogue
Pin5Ch5 analogue + BINDRequires a pot/switch+resistors and pushbutton for BIND:
  1. The pot or switch controls channel 5.
  2. The pushbutton pulls Pin5 down to 0v to set BIND on startup.
Pin6Ch6 analogue
Pin7Ch7 analogue
LED on PCBLED1 output
Pin8LED2 output + PROFILE

Example Circuits


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