210 SERIES SIGNAL MONITOR
OPERATIONS MANUAL
Eberle Design Inc. Page 10
6.6 24VDC LOGIC INPUTS
The Cabinet 24VDC input, CU Watchdog input, and External/Manual Reset inputs are processed by a
PIC16F687 microprocessor U41. Opto-couplers U28, U31, U36, and U38 provide electrical isolation
between Logic Ground and Neutral.
6.7 DISPLAY
The front panel LED display is multiplexed by the row driver U3 and the column driver U1. The scan
rate is approximately 60 Hz. Display data is shifted into U3 while individual columns are selected by U1
using the SPI interface.
6.8 PROGRAM CARD AND SWITCH INPUTS
The program card and configuration switch inputs are scanned through a diode matrix using row drivers
U32 and U33. Column drivers U34 and U35 select the column to be read. These devices transfer data
to the main MPU through the SPI interface.
6.9 RMS-ENGINE
The RMS-Engine is a Microchip PIC18F24K22 (U37) single-chip high performance RISC
microcomputer executing proprietary firmware that calculates true RMS voltages for each input
channel. The resulting data is transferred to the main MPU via the SPI interface. The analog to digital
converter (U39) provides the voltage measurement data for the RMS-Engine approximately every 6
microseconds. Analog multiplexers (74HC4051N) select the appropriate channel for sampling. Op amp
circuits U40 provide a buffer circuit.
6.10 POWER SUPPLY
The switching power supply is based on a MIC38C43 (U20) fixed frequency current-mode PWM
controller. The AC Line is full wave rectified and charges capacitor C78 to approximately 170 Vdc. The
PWM controller switches current from C78 through the transformer T1 using transistor Q4 at
approximately 200 KHz. The transformer couples this energy to the secondaries and provides the
following output voltages: VDD=+5 Vdc, VCC=+8 Vdc, VGG=-8 Vdc, VEE=-5 Vdc, VCCL=+16 Vdc,
and VDDS=+5 Vdc. Opto-coupler U26 provides feedback to the controller for regulation.
To Next Page
Loading...
Need help?
General