EDI 242L Manual de instrucciones - Página 6

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The Model 242L/244L operating voltage is generated by a high efficiency isolated switching

power supply. The resulting bias voltage supplied to the Input circuits is electrically isolated

from both 24VDC Logic Ground and AC Line Neutral. The VDD supply for the microcontroller

and display elements results from a post regulated 5 Vdc.

1.5.2 INPUT CIRCUIT

Resistors R21, R7, R8, R25, and R19 (R22, R9, R3, R26, and R20) provide the input bias

and voltage scaling circuit. The resulting voltage at U20.3 (U20.4) is then processed by the

microcontroller U20. Gas tube CR2 (CR3) and diode CR 14 (CR16) provides input electrical

transient protection.

1.5.3 MCU CIRCUIT

The microcontroller U20 processes the input voltages to perform the voltage threshold and

pulse width filtering functions. All signal processing is performed in the digital domain and

controlled by firmware embedded in the microcontroller. This unit does not rely on analog

delay, pulse, or comparator circuits for processing the input signals.

1.5.4 OUTPUT CIRCUIT

The output driver Q7 (Q8) is isolated from both the AC Mains and the internal GND reference

of the Model 242L by opto-couplers U8 (U9). CR9 (CR6) provides electrical transient

protection for the output driver Q7 (Q8).

1.5.5 DISPLAY AND SWITCH CIRCUIT

The LED indicator DS1 (DS3) for the channel output is driven directly from the microcontroller

U20. The input TEST switch SW1 (SW3) can be used to force the input state to the active

status.

1.5.6 POWER SUPPLY CIRCUIT

The main power supply is a fully isolated switching design. The cabinet 24VDC input voltage

is used to drive switching controller U18. The transformer T1 is used by controller U18 to

generate the isolated and regulated 19 VDC input bias voltage VCC that drives the input

circuits. The opto-coupler U21 and reference U25 provide the closed loop feedback to the

power supply controller U18 for regulation.

A second regulator U26 generates the 5.0 Vdc internal supply voltage VDD used by the

processor circuit from the 19 VDC bias. Inductor L2, C29, C31, and C24 filter the regulator

U26 output to provide clean VDD to the processor.

1.6 MAINTENANCE

The Model 242L/244L requires no adjustments or preventive maintenance.

1.6.1 TROUBLE ANALYSIS

The following list should be used to trouble-shoot the Model 242L/244L installation. If the

Model 242L/244L unit itself is suspect, see Section 1.6.2 for a complete internal testing

sequence.

Neither channel responds to DC inputs

Power supply fault

The Model 242L/244L requires a nominal 24 Vdc input voltage. The unit will

operate at voltages as low as 10.8 Vdc, however, an input voltage below this may

result in the unit entering a reset state. In this case, the unit will appear to be non-

functional.

Channel does not detect all inputs

Eberle Design Inc.

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