MTK 446 electronic timer: connections

MTK 446 model 2002

• Servo connectors: two sets of pins are stacked on top of each other on the lower right corner of the main circuit board. The lower connector is servo 1 and the upper connector, which has insulating plastic tubes fitted, is servo 2. The pin nearest the programming jack is pin 1 in the following table. It is wired as shown using a three pin unpolarised servo connector:
  
  

  Pin	Use	Wire colour
  1	Signal	White
  2	+ve supply	Red
  3	Ground	Black

  
  
• Tow hook: this connector is a flat, four pin unpolarised socket on a flying lead. All wires linking this socket to the timer are white apart from the Ground connection (pin 2), which is black. Pins are used as shown:
  
  

  Pin	Use	Switch closed (ON)
  1	Hook position switch	hook forward
  2	Ground connection	-
  3	Latch position sensor	latch closed
  4	OLA sensor (inertia hook only)	hook extended

  
  
• Battery connection: a standard Futaba red battery connector. The timer has the male side attached to it. This has two pins inside a polarised plastic shroud. It is not shown in this picture.
  
  
• Programming connector: the 3.5 mm stereo jack socket below the beeper. These together form the black block to the right of the main circuit board.
  
  
• Programming jumper: this is not connected during normal use. A special jumper, with its pins joined by a 1K ohm resistor, is inserted when the timer firmware is being upgraded.

MTK 446 model 2004

The serial number (e-block number) of these timers is written on the side of the white plastic mounting block.

• Servo connectors: two sets of pins are stacked on top of each other on the lower right corner of the main circuit board. The lower connector is servo 1 and the upper connector is servo 2. The pin nearest the programming jack is pin 1 in the following table. It is wired as shown using a three pin unpolarised servo connector:
  
  

  Pin	Use	Wire colour
  1	Signal	White
  2	+ve supply	Red
  3	Ground	Black

  
  
• Tow hook: this connector is a flat, four pin unpolarised socket on a four-way ribbon cable is used. The Forward connection (pin 1) has differently coloured heat-shrink insulation to the other pins. Pins are used as shown:
  
  

  Pin	Use	Switch closed (ON)
  1	Hook position switch	hook forward
  2	Ground connection	-
  3	Latch position sensor	latch closed
  4	OLA sensor (inertia hook only)	hook extended

  
  
• Battery connection: a standard Futaba red battery connector. The timer has the male side attached to it. This has two pins inside a polarised plastic shroud.
  
  
• Programming connector: the 3.5 mm stereo jack socket below the white mounting block.
  
  
• Programming jumper: this is not connected during normal use. A special jumper, with its pins joined by a 1K ohm resistor, is inserted when the timer firmware is being upgraded.

Tow hook and servo connections

Here the timer is removed from the model but still connected to tow hook and servo. The battery is not connected.

• Servo 1: the connector is plugged onto the set of pins nearest the board's surface with the black wire nearest the edge of the circuit board.
• Tow hook: the isolated white wire between timer and hook connector, at the bottom of the connector in this picture, connects to the 'hook forward' switch.

Connecting to a Palm PDA

The MTK timer can only be connected to a Palm PDA by connecting the cable supplied with the timer to the HotSync cable supplied with the Palm device. The MTK cable is terminated by the 3.5mm stereo jack that plugs into the timer at one end and a male D-9 connector, installed in a grey plastic hood, at the other. The plastic hood is sealed and contains circuitry powered from the D-9 connector that converts signals to RS-232 levels and handles hardware flow control via the Data Set Ready, Request To Send and Clear To Send signals. The Hotsync cable doesn't contain any active circuitry, but its pin-outs show that it is a cross-over, or "null-modem", cable.

Connecting to a Casio PDA

To be written

Connecting to a PC

The timer must be connected to a PC to upgrade its firmware. The firmware loader is configured to use COM2, so this serial port must be available on the PC being used for the upgrade: many laptops only have one serial port and so are unsuitable for this task. The connection to the timer is made using the standard programming cable supplied with the timer. However, both this cable and the PC's COM2 port have male D-9 connectors, so an additional adapter cable is needed between the timer's cable and the PC.

The adapter cable has two D-9 female connectors with all pins connected straight through, i.e. pin 1 to pin 1 etc. MTK can supply the adapter cable if one cannot be found locally. An alternative would be to use a female-to-female D-9 gender changer.