Universal Standalone Watchdog Timer
Internal PC OEM version
3201 Highgate Lane
St. Charles, MO
Trademark and Copyright Information
UWDT is a Trademark of Industrologic, Inc. 2007
This document is Copyright (c) 2007 by Industrologic, Inc.
All rights reserved.
No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or scanning, for any purpose other than the personal use by the purchaser of this product. Industrologic, Inc. reserves the right to revise this document at any time without obligation to notify any person of such revision. Industrologic, Inc. assumes no responsibility for any errors that may appear in this document.
Whereas effort has been made to make the information in this document as useful and accurate as possible, Industrologic, Inc. assumes no responsibility for the application, usefulness, or completeness, of the information contained herein. Under no circumstance will Industrologic, Inc. be responsible or liable for any damages or losses including indirect or consequential damages or losses arising from either the use of any information contained within this manual or the use of any products or services referenced within this manual.
Industrologic, Inc. reserves the right to change any product's features, specifications, documentation, warranties, fee schedules, and conditions at any time and without notice.
Industrologic products are provided as printed circuit board level assemblies. Some Industrologic products may include mechanical packaging assessories which are provide for the purchaser's convenience, and are not intended to be final assembly enclosures.
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Industrologic's obligation under this Warranty is limited to replacement with a new or repaired unit to the original purchaser. The unit must be returned, and replacements obtained from Industrologic, Inc. or the Distributor or OEM from whom it was purchased.
This warranty will not apply if, in the judgment of Industrologic, Inc., damage or failure of the product has resulted from accident, alteration, misuse, abuse, connection to or operation with incompatible signals or power sources, or improper installation.
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condition, for a full refund of the purchase price only, to the original
purchaser, within 30 days of purchase.
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Warranty or repair units must be returned with postage and insurance paid by purchaser. Industrologic, Inc. is not responsible for damages or loss during shipment.
Universal Standalone Watchdog Timer
Internal PC OEM version
The Industrologic UWDTPC is a standalone watchdog timer circuit that can be
triggered with a wide variety of digital output signals or LED drive circuits
from a microcontroller or single board computer, or with RS-232 serial data
from any communication protocol.
It can be used to increase the reliability of nearly any microcontroller board,
single board computer, or personal computer system by monitoring a signal,
and activating the reset circuit if the signal is no longer present.
The UWDTPC has been designed to allow easy installation inside typical computer
enclosures containing motherboards and power supplies, including personal
computers and Mini ITX systems.
Summary of Features
- Based on discrete logic and relay drive circuitry
- Powered by 5 volts from common PC disk drive/floppy disk drive connector
- 2 pin .1 inch header for triggering with digital input (or hard disk activity LED) signal
- 2 pin .1 inch header for reset relay signal
- 10 pin header matching PC serial port connection for triggering with RS-232 data
- Normally open isolated relay contacts for reset function
- LED indicators for trigger and relay activation
.062" FR-4 glass epoxy printed circuit board, 2.75 inches by 2.25 inches
P.C. Board assembly has holes available for mounting to enclosure or #6 standoffs.
Power supply requirements-
Power supply voltage: 4.8 to 5.2 volts DC regulated (from disk drive power supply connector)
Power supply current: Less than 1 ma with relay and LED's not activated
Relay current: approximately 60 ma
LED current: approximately 15 ma
Temperature: 0-50 degrees Celsius (32-122 Fahrenheit)
Humidity: 30 to 80 percent, non-condensing
RS-232 trigger signal-
Transmit signal from PC connected through diode and 10K series resistor
Circuit can be triggered by baud rates up to 19200
Digital trigger input-
Optoisolator input, LED voltage drop of 1.2 volts
Minimum current required: 2 mA
Both positive and negative connections isolated from ground to allow current source or sink
Current limiting series resistor to allowing direct connection to LED circuit or switched voltage
Maximum voltage: 30 volts, AC or DC
Maximum current: 1 amp
Manufacturer's type: Omron G5V-1-DC5 series or equivalent
The standard optoisolator current limiting series resistor is 220 ohms,
which allows the UWDTPC to be triggered by both LED circuits and digital
outputs. OEM customers many specify other resistor values.
The standard UWDTPC trigger timing is set to approximately 5 1/2 minutes,
and the relay on time is approximately 1 second, both with a tolerance
of +/- 20%. OEM customers may specify other timing ranges.
Monitoring RS-232 Signals
The UWDT can monitor an RS-232 transmit signal from a serial port.
The RS-232 trigger signal is connected to pin 3 of a 10 pin (5 pin
by 2 row) .1 inch header matching common PC serial port interface
cables. The pinout of this connector allows a flat ribbon cable
with female header connectors to be connected from a PC serial
port header to the UWDTPC. Ground is available on pin 5 of the
header connector, so if a simpler two wire connection is desired,
a 2 pin female header connector can be used at pins 3 and 5.
Monitoring Digital Signals
The UWDTPC can monitor a digital output signal or a signal used to
drive an LED, such as a PC hard disk drive "activity" LED. The
digital trigger signal is available on a 2 pin .1 inch header with
both the positive and negative connections isolated from ground,
which allows either an active high or active low signal to be used
as a trigger.
If the trigger signal is a hard disk activity LED, the connections
normally made to the LED can be connected directly to the HDLED
header, observing the polarity (plus and minus connections).
For a microcontroller or single board computer with a 5 volt power
supply, a digital output can be used to trigger the UWDTPC in either
of the two following ways. The output must be capable of sourcing
or sinking 17mA if the standard 220 ohm resistor is installed. 1.
If the trigger signal is an active low digital output, it should
be connected to the HDLED minus and +5 volts connected to HDLED
plus. 2. If the trigger signal is an active high digital output,
it should be connected to the HDLED minus and +5 volts connected
to HDLED plus.
Watchdog Timer Operation
When power is applied to the UWDTPC it begins in an inactive state.
Both LED's and the relay will be off. When ready to begin using
the circuit, the device being monitored should begin sending
trigger signals, either by sending RS-232 data or by producing
pulses to the digital trigger input.
The green LED (L1) will them come on, indicating that the watchdog
timer is receiving trigger signals and is "armed". From that point
on, one of the trigger signals must continue to occur or the
circuit will time out and the relay will activate momentarily.
The green LED will go off when all trigger signals stop and the
red LED (L2) will come on when the relay is activated.
end of manual