3.8PLATEN POSITION DETECTOR

The printer has a built-in platen position detector for detecting whether the platen unit is opened or closed. This detector is a mechanical switch which is designed to be in a CLOSED state when the platen unit is closed and to be in an OPENED state when it is opened.

The combination of the platen position detector with the paper detector in Chapter 3.7 will make it possible to detect the position of the platen.

The external circuit should be designed so that it detects output from the platen position detector in order to detect the platen OPENED state, or, so that it detect output from the paper detector in Chapter 3.7, so as not to activate the thermal head in the absence of paper. Otherwise, the thermal head may be damaged or the life of the head may be shortened significantly. Activate the thermal head when the platen unit is CLOSED by detecting the output from the platen position detection, and in the paper presence state by detecting the output from the paper detector.

3.8.1General Specifications

Maximum rating:

7 V DC, 1 mA

Contact resistance:

70 mΩ maximum

3.8.2Sample External Circuit

Vdd (5 V)

R=10 kΩ

LTP F Series

To CPU Port

HS

C=0.1 ∝F

GND

Mechanical switch

GND

∗The mechanical switch is opened when the lever is in an OPENED state.

Figure 3-16 Sample External Circuit of the Platen Position Detector

Note that there is a time lag between the time when the thermal head stays in a completely upwards or downwards position and when the lever position detector starts to operate.

Always use the capacitor shown in Figure 3-16to prevent the switch from malfunctioning due to chattering.

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