Assembly Instructions
| Model Railway DCC Turntable Accessory Decoder for Arduino Nano – Kit |
| DCCSC1.A4988.Kit.Nano |
Package Contents
In your package you should find the following…
1 x PCB ( DCC Stepper Control Interface for Aruidno Nano)
1 x Pack 1 – DCC Interface
1 x 6n137 8 pin chip ( black or white in colour )
1 x 8 pin DIN socket
1 x Diode ( orange in colour )
1 x 1k Resistor
2 x 10k Resistor
2 x 10 pin female header
2 x 5 pin female header
1 x 2 pin screw terminal
1 x 3 pin screw terminal
1 x Pack 2 – Power Supply
1 x 7805 Voltage regulator ( Heat sink not provided but must be used )
1 x 100uf 50v Cap
1 x 47uf 50v Cap
1 x 1uf 50v Cap
1 x 2 pin screw terminal
1 x Pack 3 – A4988
1 x A4988 Control daughter board
2 x 8 pin female header
2 x 5 pin male header
2 x 2 pin screw terminal
Assembly.
The assembly is split in to 3 parts – [Pack 1 – DCC Interface], [Pack 2 – Power Supply], and [Pack 3 – A4988].
Take time to make yourself familiar with the parts and where they should go.
Pack 1 – DCC Interface
Taking the parts from Pack 1 – assemble the DCC Interface by soldering the parts to the PCB as follows
| Step | Action |
| 1 | Solder the 8 pin DIN socket to the PCB |
| 2 | Solder the two 10k resistors to R1 and R2, following the PCB image as an orientation guide ( horizontal ) |
| 3 | Solder the Diode to the PCB, making sure the BLACK ring is at the top. This is important. |
| 4 | Solder the single 1k resistor to R3, following the PCB image as an orientation guide ( vertical ) |
| 5 | Solder 1 of the 10 pin and 5 pin female headers to the top row of the Arduino Nano (v3) holes. |
| 6 | Solder the other 10 pin and 5 pin female headers to the bottom row of the Arduino Nano (v3) holes. |
| 7 | Solder the 3 pin screw terminal so that the wire input holes are facing outwards ( I/O GND and PWR ) |
| 8 | Solder the 2 pin screw terminal so that the wire input holes are facing outwards ( DCC ) |
| 9 | Push the 6n137 chip in to the 8 pin DIN holder, pin 1 top left corner ( signified by a dot on the chip ). You may need to align the pins in order to make it fit. |
This completes the first part and should look like this – notice the diode has its BLACK STRIP at the top.
Part 2 – Power Supply.
The power supply circuit is designed to take power from a 12 – 16v DC supply and convert it to 5v for the logic circuit.
| Step | Action |
| 1 | Solder the 2 pin screw terminal so that the wire input holes are facing outwards ( downwards ) ( – + ) |
| 2 | Solder the 100uF 50v Cap in position above the 2 pin screw terminal soldered in step 1. The negative terminal of the cap is on the left. |
| 3 | Solder the 47uF 50v Cap in the position to the right of the A4988, and above the 7805. The negative terminal of the cap is on the top. |
| 4 | Solder the 7805 voltage regulator so the top pin is the voltage in, the middle is GND and the bottom pin is the voltage out ( 5v ). This will usually mean the heat sink is on the right facing the edge of the board. Fit a heat sink to make sure there is adequate heat dissipation. |
| 5 | Solder the 1uF 50v Cap below the 7805. The negative terminal of the cap is on the bottom. |
This completes the second part and should look like this – notice the cap orientations, and which way the 7805 is facing.
Pack 3 – A4988
The last pack is the A4988 daughter board and the connections for the stepper motor.
| Step | Action |
| 1 | Solder one 2 pin screw terminal on the left so that the wire input holes are facing outwards ( downwards ) ( 1B 1A ) |
| 2 | Solder one 2 pin screw terminal on the right so that the wire input holes are facing outwards ( downwards ) ( 2A 2B ) |
| 3 | Solder 1 of the 8 pin female headers to the top row of the A4988 holes. |
| 4 | Solder the other 8 pin female headers to the bottom row of A4988 holes. |
| 5* | Solder the 2 – 5 pin male headers above the A4988 holes |
This completes the second part and the whole board should look like this ( with out the heat sink fitted to the 7805 ) – I have plugged an Arduino Nano in already..
A4988 Information.
The A4988 is a stepper motor controller by Pololu. You can find a wealth of information on their website https://www.pololu.com/product/1182 including how to connect a stepper motor.
*WARNING*
Never connect or disconnect a stepper motor while the A4988 is powered – damage can be caused to the A4988. ALWAYS DISCONNECT POWER from the A4988 ( remove the power source ) when connecting or disconnecting the stepper motor.
Here is a pin out of the A4988
Here are the connections from the A4988 to the Arduino.
| A4988 Pin | Arduino Pin | Purpose |
| STEP | D4 | Control the step of the stepper motor |
| DIR | D5 | Control the direction of the stepper motor |
| ENABLE | D6 | Enable the Stepper Motor |
| VDD | +5v | Logic Power supply |
| GND | GND | Ground |
The last column of pins above the A4988 are designed to allow the user to set the five different microstep resolutions (down to 1/16-step).
The top row of the 5×2 pin headers are connected to +5v. the bottom row are connected to the A4988 pins ( Sleep, Reset, MS1, MS2, MS3 and Enable ). With no jumpers connected, MS1, MS2 and MS3 are in the LOW position ( in relation to the above table ). To set a MicroStepping to high, use a jumper to connect the A4988 pin to +5v – hence making it HIGH.
E.g. for Eighth Step – place a jumper on MS1 and 5v , and MS2 and 5v. For Full steps, place no jumpers.
Important : Make sure there is a jumper between the SLEEP and RESET pins.
This completes the assemble of the kit. I hope you had fun building it.
Please fully read the Pololu product web page, and the FAQ here… https://www.pololu.com/product/1182/faqs