ADT490Panel Theory

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System Power Supply Grounding

‣Circuit separates positive / negative from Ground

‣Ground fault - resistance to ground ≤ 10 kΩ‣System power supply

‣Line - black‣Neutral - white (return)‣Ground - green

‣Exterior components bonded to Ground

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Power Supply

‣ Output 27 to 30 Vdc

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Power Supply Fault Analysis

‣ Power on - how do we know?‣ Disconnect or breaker station - looking for?

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Power Supply Checklist

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Power Supply Checklist 2

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Battery Charger Concepts

‣ 2 x 12 V or 4 x 6 V batteries‣ To charge requires 27.4 to 28 V‣ must be recharged to 70% within 12 hours (ULC)‣ 5 to 35 mA - float Charge‣ Fast Charge - larger‣ Battery Condition Monitor‣ Ammeter in Series to check the Charge rate (A)‣ Can check power supply with DC & AC Voltage

Measurements

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Battery Charger Concepts

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Electrical Supervision

‣ small current though an EOL Resistor‣ no current though an EOL Capacitor‣ Power resistors

‣ approximately 200 Ω‣ 1 volt each‣ about 2 W

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Electrical Supervision

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Detection - Open Circuit

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EOL Resistor Function

‣ Limits current through wiring‣ Regulates the voltage in the circuit

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EOL Capacitor Function

‣ Siemens System 3 or MXL‣ EOL Capacitor‣ Blocks DC‣ Smooths ripple voltage

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Detection Circuit with EOL Capacitor

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EOL Capacitor Waveform

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EOL Capacitor Waveform

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Locating Faults

‣ Voltage on open EOL Capacitor circuit is 20.5V (System 3) & 21.5V (MXL)

‣ Voltage before the break‣ 0 V after the break

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EOL Relays

‣ Mostly used on security systems or‣ 4 wire devices

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EOL Relays

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Wiring Architectures

‣ Class B‣ Class A‣ Split Class B‣ Tee-Tapped

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Class B Wiring - Placement or Location Supervised (87%)

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Class A Wiring - Placement or Location Supervised (8%)

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Class A Wiring - Greater Reliability

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Class B Wiring with Tee-Taps

‣ Tap is unsupervised‣ Reason each device is checked for open - S537‣ Some vendor use twice EOL size for main run and

single tap

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Class B Wiring with Tee-Taps

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Addressable Loop - no EOL

‣ A fault cannot disable more than 1 Zone

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Signal Circuit Supervision

‣ Terminal may indicate polarity in alarm - not always‣ 24 VDC can be as low as a few volts‣ Shorts causes a circuit Trouble

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Signal Circuit Alarm Operation

‣ Device could be reverses - rings supervision not alarm‣ Don’t exceed 85% of Current - Why?

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Class A Signal Circuits

‣ Class A good for opens‣ Not good for shorts - Why?

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Speaker Circuits - Supervision

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Speaker Circuits - Alarm

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Speaker Circuits - Alarm

‣ 25 Vrms 20 and 40 mA for speaker + 5 mA for EOL‣ 70.7 Vrms 7.1 and 14.1 mA for speaker + 7.1 mA for

EOL (equivalent to 1/2 W Speaker)

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Split Speaker Circuits

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Split Speaker Circuits

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Telephone Circuits

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Improperly Connected Signals

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