Philips M1353A Baby Accessories User Manual


 
Recorder Interface Board (M1353-66510)
Chapter 6 Theory of Operation 59
Recorder Interface Board (M1353-66510)
The Recorder Board provides the interfaces to the recorder and the display. The recorder
interface consists of:
The parallel/serial converter for the thermal array data.
A heating timer to control the heating pulse for the thermal array. The voltage from a
thermistor on the thermal array is A/D converted and the CPU programs the heating
timer with a value which compensates the ambient temperature.
The recorder sensing hardware consists of a reflective light sensor that detects the black
marks on the paper and paper out. A battery supervisor circuitry checks for valid
battery voltages, and this is read by the CPU Board. The display interface uses the
same parallel/serial converter as the recorder. The board also contains test hardware
which is not shown in the diagram.
+24V is blocked by capacitor and supplied to the thermal printhead.
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