Expansion Io Board

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Expansion I/O I/F Circuit Usage

These instructions are valid for the TEC 372, 472, 572, 672, 872.

Expansion I/O graphic

S1 = Switch

V1 = Signal Voltage in Volts = not to exceed 24 volts

R1 = Load Resistor in Ohms

I = Current in Amps

In order to trigger the printer, the expected input across pin 15 to pins 1-5 is 1.6 Volts at 10 Milliamps. This gives us an effective resistance of 160 Ohms for the purposes of our calculations. Remember to calculate the power dissipation of the resistor.

I must never be greater than 15 Milliamps

Important calculations:

R1 = (V1/I) - 160

Power dissipation = R1*I^2

Example:

R1 = unknown

V1 = 24 Volts

I = .01 Amps

R1 = (24/.01) - 160

R1 = 2400 – 160 = 2240 Ohms or a 2.2 K Ohm resistor

Power dissipation = R1*I^2

Power dissipation = 2240*.01^2

Power dissipation = .224 Watts

So you would require a .5 watt resistor to leave a margin of safety.