Simple Speed and Direction control, using HobbyKing components

 

Simple speed and direction control, using HobbyKing components

Thanks to Greg from Sandstone and Termite Railway for these instructions

Required:

• 1 x HK-T4A-M1 Hobby King 2.4Ghz 4Ch Tx & Rx (Mode 1) (Tx and Rx must the same version!)

• 1 x TGY-20A Turnigy 20A BRUSHED ESC (electronic speed control)
  1 x Turnigy TG9e or TG9 micro servo

• 8 X AA batteries for the transmitter, (LSD from Hobbyking)
  1 x DPDT switch (for direction control)

• 1 x piece of styrene or brass about 30x30mm.
  Batteries for the loco.

Transmitter (Tx)
The Tx is a 4 channel unit, but use 2channels initially.

It has 2 joysticks, each of which can move up/down and left/right.

This is a 'mode 1' Tx which just means the right hand up/down stick does NOT spring return to centre as the other 3 movements do.  See "Mode 3 Transmitter" for a conversion that adds an extra loco.

It's used for the loco speed control (throttle).

It also has 4 'fine adjustment knobs - set them to centre position and leave them!

Across the bottom, there are 4 'servo direction' switches with REV and NOR positions.

Set the THR to REV and the others to NOR. (For an unknown reason the throttle to be set to REV, for it to work!)

4 channels are labelled:

• RUD = channel 4 = left stick, left/right movement.

• THR = channel 3 = right stick up/down movement.

• ELE = channel 2 = left stick, up/down movement.

• AIL = channel 1= right stick, left/right movement.

Used AIL = channel 1 = right stick, left/right movement for forward/reverse. (In reality any of the 3 except the throttle (THR) can be used.

 

Receiver (Rx)

 

 

  The motor speed controller (ESC=Electronic Speed Control)

This is rated at 20 amps, according to the data sheet, the speed controller can have a max input of 10, AA cells, (approx 13V max) this limits your loco to that many.

Note; it has a 5V output (Battery Eliminator Circuit or BEC) to power the Rx.

This is fed back along the 3-core cable, so no extra power wiring is needed; there is no need to plug anything into the BAT socket on the Rx.

As the stick is pushed up, more volts are fed to the motor.
It comes with an instruction sheet, so read it!

It has 2 small plugs at the motor end to select if you are using LiPo or NiMH batteries, or whether you want a brake applied to the motor when the throttle is set to zero (Do NOT Engage Brake for this application).

Binding

 which is just telling the receiver which transmitter it should listen to.

Each Tx is manufactured with a different code or channel, there are 4.2 billion different codes so the chances of there being 2 transmitters with the same code in the same place are pretty small.

Binding just programs the Rx to know its transmitter’s code 

To BIND the transmitter to the receiver follow this step by step procedure  

NOTE;You only have to do this once!

• Plug your ESC into servo channel 3 of the Rx. The black or brown wire (0V) goes to the right   and the red to the left; this provide the 5V supply to the Rx.  See picture above for pinouts

• Put the binding plug into the BAT socket of Rx. (this is just a wire that joins 0V to the sig wire in the BAT terminal.)

• Apply battery to the ESC. You should see a red LED blinking on the side of the Rx.
  Now hold down the Bind-Range-Test Button on the Tx , and turn the Transmitter on.

• After about 3 to 10 seconds the Rx LED will stop blinking and go steady.

• Remove the binding plug and that’s it.

NOTE: That was the only time you will ever turn the RX on before the TX.
In normal operation  always turn the TX on first, followed the R.

Direction

Direction control

 This is the servo with some of the typical attachments that fit on the white splined shaft.

The shaft rotates 45 degrees one way with the stick up (or right) and 45 degrees the other way when you push the stick left.  It then returns to its central position when you release the stick.
 

It is used to operate a Double Pole Double Throw Switch for motor direction change.

 

 

Superglue the switch to the servo as shown so the centre of the Switch is in line with the servo shaft. A rubber band has been used for the picture to show positioning.

 

Make a 'plate' to attach too the servo arm (The one circled in red above) to knock the switch over when the servo operates.

It's roughly the shape shown in red (don't forget the bit hidden under the arm, and is about 40x20mm. It has to be a wide at the switch arm as the length of the arm travel from one position to the other.

Attach it to the servo arm by just twisting a couple of bits of wire, shown orange.
 

 

Solder wires to the switch terminals, using the configuration shown in the picture, on the underside of the switch. This is how the motor voltage is reversed.
 

Plug the servo lead into the Rx channel 1 (right stick, left/right) and operate the switch. Adjust the arm position and file a bit of the cam till it works.