Moxa Technologies TCC-80I Ext. Power Supply, Serial RS-232 Port Power, Port Power Dissipation

Installation

Serial (RS-232) Port Power

The RS-232 port of the TCC-80I is designed with a female DB9 socket to connect directly to the host PC, with power drawn from the TxD, RTS, and DTR lines. Although the TCC-80I is able to obtain enough power from the combination of the three data/handshake lines, regardless of whether the signal is high or low, it is highly recommended to activate the “ON” signal for either the RTS or DTR lines. For those applications that do not use the handshake lines, a DC jack is provided for connecting a 5 to 12 VDC power supply via a USB power cord or external power adaptor.

TXD
RTS	RS-422/485
DTR	Devices
Serial Power Source/Data
±5 to ±12 VDC Signal

Port Power Dissipation

When installing an RS-232 port-powered TCC-80I converter, pay attention to the power consumption, RS-232 cable length, power provided by the serial port, and the RS-422 /485 transmission distance. In general, the TCC-80I itself gets 70 mW from the power source; a standard COM port on a host PC can provide 70 to 90 mW of power if the TxD, RTS, and DTR lines are connected. Moreover, the RS-232 cable length should be shorter than 15 m (@ 9600 bps) to ensure that less power is lost from the host/device to the TCC-80I. The rest of the supplied power is used for transmitting the RS-422/485 signal.

.Serial Port Power Compatibility

Serial ports use a diversity of interface chips, but the power provided by the different ports is not always the same. In fact, some of the ports do not provide enough power to activate the TCC-80I. The on-board COM1 and COM2 ports seldom have problems. The table shows the add-on cards and the serial-to-Ethernet device servers that have been tested as a good power source to drive the TCC-80I when their RTS/DTR is connected and in the “ON” state.

Multiport Serial Boards	Serial Device Servers
MOXA Smartio	MOXA NPort
CP-118U	5110/5210 V2.1
CP-168U V2	5410 V2.2
CP-104U V2	5610 V3.0 (or later)
CP-102U
MOXA Smartio	MOXA USB
CP-118EL Series	NPort U1110
CP-168EL Series
CP-104EL Series
	MOXA USB to Serial
	UPort 1410/1610

LED Port Power Indicator

The best way to ensure that the attached serial port provides enough electricity to the TCC-80I is to check the power indicator LED on the front panel. To do this, connect the TCC-80I to the target RS-232 port, and then turn the SW4 switch to the right to Test mode. If the LED lights up, the TCC-80I is receiving enough power. If the LED does NOT light up, you will need to attach the external power cord to the TCC-80I.

Note: Be sure to turn the SW4 switch back to Std. mode (the default) when you finish testing. When in Test mode, the TCC-80I WILL NOT transmit data.

Std. Test

Mode Mode

SW4

Optional External Power

Termination is a critical requirement for port-power devices such as the TCC-80I. In most circumstances, termination resistors are used when the RS-422/485 cable length is longer than 100 m. Regardless of how much the data signal dissipates, the termination resistors absorb more than 75 mW of power from the power source when the TCC-80I is unable to use the limited serial power. In other words, if long distance RS-422/485 transmission or termination is required, then an external USB power cord or DC power supply should be used.

Data

TXD

	RS-422/485
	Devices
USB Port Power Cord
Data
TXD	Long Range/
RTS
	Terminated
DTR	RS-422/485
	Connection

5 to 12 VDC Ext. Power Adaptor

By testing the TCC-80I at different baudrates and transmission distances, we have determined the maximum transmission distances that can be achieved when using serial port power. The test results are shown in the following table.

Port Powered Transmission Distance

Baudrate	RS-422/485	Embedded	Ext. Power
(bps)	Transmit	Terminator	Required
	Distance (m)
9600	1200	(ON) 120Ω	NO
19200	1200	(ON) 120Ω	NO
38400	600	(ON) 120Ω	NO
57600	300	(ON) 120Ω	NO
115200	150	(ON) 120Ω	NO

Switch and Jumper Settings

To change the operation mode, check the DIP Switch settings on the back panel.

			ON
		1		2	3
DIP Switch Settings
RS-422	SW1				SW2	SW3
	OFF				OFF	OFF
RS-422 with	SW1				SW2	SW3
Terminator	OFF				OFF	ON
4-wire RS-485	SW1				SW2	SW3
	ON				OFF	OFF
4-wire RS-485 with	SW1				SW2	SW3
Terminator	ON				OFF	ON
2-wire RS-485	SW1				SW2	SW3
	ON				ON	OFF
2-wire RS-485 with	SW1				SW2	SW3
Terminator	ON				ON	ON

DIP Switches SW1 and SW2 are used to select the operation modes (RS-422, 4W RS-485, or 2W RS-485). Termination is controlled by DIP Switch SW3.

Ext. Power Supply

The TCC-80I is designed to be connected to a standard 5 to 12 VDC power adapter if additional external power is required.

Transio TCC-80I User’s Manual Transio TCC-80I User’s Manual