Deltec Cozmo Bedienungsanleitung PDF herunterladen (Seite 128)

Technical Information

116

Safety features and fault detection

Hardware safety features

Key hardware safety features include a watchdog timer

circuit, motor driver and motor watchdog circuits, and a

voltage detector circuit. Each safety circuit performs a

unique function to ensure the overall safety of the

pump.

Watchdog timer circuit

The microprocessor must send an appropriate signal to

the watchdog circuit at least once per minute. If the

microprocessor does not send this signal, the circuit

initiates a “time out” and shuts down the pump control-

ler.

Watchdog timer circuitry is provided to monitor the

status of the microprocessor, disable the motor, and

cause the pump to beep if the microprocessor malfunc-

tions. The microprocessor must “strobe” the watchdog

circuit at least once per minute in order to prevent the

watchdog from performing it’s reset function. The

microprocessor tests the watchdog circuit on every

power up.

By setting a flag in the memory and not strobing the

watchdog, the microprocessor can force a watchdog

time out. After being reset, the microprocessor checks

the status flag to see if this was a time out test. If it was,

the microprocessor continues it’s normal power up

routine. If the reset occurred when the microprocessor

was not expecting it, the microprocessor “traps” the

event, an alarm is given (either beep or vibrate), and an

error message appears in the display.

Motor drive/motor watchdog circuit

Motor drive circuitry is composed of a series of FET

transistors, passive components, two voltage compara-

tors and the second microprocessor. The second micro-

processor times how long the motor runs each time it is

turned on. If the motor runs for longer than the primary

microprocessor specifies, the circuit times out and

disables the motor. A unique feature of this circuit is

that control lines to and from the microprocessor circuit

allow the microprocessor to perform the complete

functional test of the motor drive circuit without run-

ning the motor. The microprocessor performs this test

every several minutes to assure its continued functional-

ity. An input from the watchdog circuit prevents motor

operation if the watchdog timer expires. The software

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