Deltec Cozmo Bedienungsanleitung PDF herunterladen (Seite 255)

249

Technical Information

Safety features and fault

detection

Hardware safety features

Key hardware safety features include a watchdog

timer circuit, motor driver and motor watchdog cir-

cuits, and a voltage detector circuit. Each safety cir-

cuit performs a unique function to ensure the overall

safety of the pump.

Watchdog timer circuit

e microprocessor must send an appropriate signal

to the watchdog circuit at least once per minute. If

the microprocessor does not send this signal, the cir-

cuit initiates a “time out” and shuts down the pump

controller.

Watchdog timer circuitry is provided to monitor

the status of the microprocessor, disable the motor,

and cause the pump to beep if the microprocessor

malfunctions. e microprocessor must “strobe” the

watchdog circuit at least once per minute in order to

prevent the watchdog from performing its reset func-

tion. e microprocessor tests the watchdog circuit

on every power up.

By setting a ag in the memory and not strobing the

watchdog, the microprocessor can force a watch-

dog time out. Aer being reset, the microprocessor

checks the status ag to see if this was a time out test.

If it was, the microprocessor continues its normal

power up routine. If the reset occurred when the mi-

croprocessor was not expecting it, the microproces-

sor “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 com-

parators and the second microprocessor. e second

microprocessor times how long the motor runs each

time it is turned on. If the motor runs for longer than

the primary microprocessor species, 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 running the motor. e micro-

processor performs this test every several minutes

to assure its continued functionality. An input from

the watchdog circuit prevents motor operation if the

watchdog timer expires. e soware veries this

function during the watchdog test described above.

Voltage detector circuit

Low voltage detection is performed by part of the

watchdog circuit and by the microprocessor via

soware. 3 low voltage levels are detected. e rst 2

levels are detected by soware and the 3rd by hard-

ware. e 1st level to be reached is the Low Battery

Warning threshold, which occurs when the battery

voltage decays to a point where less than 10% operat-

ing time is available. An Analog to Digital Converter

(ADC) built into the microprocessor allows the

microprocessor, via soware, to monitor the battery

voltage. At the Low Battery Warning threshold, the

microprocessor enables an alarm (either beep or vi-

brate) and displays the low battery alert in the display.

When the battery voltage drops to a point where it

is too low to guarantee proper motor operation, the

microprocessor via soware stops delivery, generates

an alarm (either beep or vibrate), and a depleted bat-

tery alarm message appears in the display. When the

battery voltage drops to a value where operation of

the microprocessor cannot be guaranteed, a hardware

reset circuit is triggered which places the micropro-

cessor in reset. is prevents ambiguous micropro-

cessor operation as the battery voltage continues to

decay. e hardware reset continues until the battery

is completely depleted or it is removed. Once the

pump controller goes into low battery shutdown, only

replacing the depleted battery with a new battery will

clear the condition.

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