Site Alert ©

 

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Warren Brown VK3BYD

March 2006

 

Introduction

Description:

Site Alert is a device that connects to the serial port of a UI-DIGI[A] APRS[B] Digipeater. It is used to provide local site information from a remote Digipeater site via APRS Telemetry data.

The data is transmitted every 30 minutes and includes the average of four supply voltage readings, current in building temperature, number of PTT’s and the current mode of the Site Alert. The Parameter, Unit and Equation messages are sent three times a day.  (Further information on APRS Telemetry can be found in  reference 1.)

 

Should the average voltage fall below a pre-programmed value Site Alert will turn off the Low Battery output until the average voltage reaches the upper pre-programmed value. This output can be used to control an external relay to remove power from the TNC and Radio. The battery alarm or the external alarm inputs will cause an APRS Item and an APRS Message to be transmitted. Further information on external alarm inputs can be found in the Installation Instructions.

Site Alert uses an Atmel AT90S2313 micro-controller, ADC0831 Analog to Digital converter, Dallas Semiconductor’s DS1820 Temperature sensor and DS1307 Real Time Clock.

Updates:

Software version ’F’ (Sept 2005) has the following changes:

1)          Message numbering has been added to all messages from Site Alert

2)          Slight format change to message text.

3)          Removal of Max / Min transmissions

4)          Added Time Zone Character

 

Software version ’C’ (Oct 2004) has the following changes:

1)       Equations are now only sent three times a day

2)       It no longer checks for negative temperatures (If –ve they will be rounded to Zero).

3)      The ‘mycall’ command has been changed to allow for sending messages through an APRS email sever. This change requires more careful entering of the ‘mycall’ data.

4)       The Low Battery Alarm is only transmitted ~four times then Site Alert will “turn off” the Low Battery Opto.

5)       A message (only) will be sent when the voltage becomes high enough for Site Alert to “turn on” the Low Battery Opto.

6)       Alarm input 1 has a lockout period of 9 minutes. That is once an alarm has been received on Input 1 no further alarms on that input will be recognized until after 9 minutes has passed.

 

Limitations:

1. Voltage readings will only be accurate for voltages above 8.1 Volts and below 19.9 Volts.

2. SiteAlert Local Commands must be correctly formatted, there is NO checking for the validity of the entries.

3. Site Alert will only do one thing at a time which may make it appear to not respond to commands from the serial port. I would recommend following the instructions in “Settings” “First Time” when inputting commands.

4. This limitation may also delay the initial send of an alarm message. However, this limitation will not cause a significant problem during normal day-to-day running.

Disclaimer:

Do Not use this device for any application where human life is at risk or property damage may occur.

The developer takes no responsibility holy or implied for the use or performance of this product And offers no warranty of any type on this product.

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Block Diagram:

 

 

 

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Operation:

Local Commands:

When entering commands attention must be paid to the correct format and length, as there is NO checking for valid data. All settings are non-volatile.The serial port is set for 9600 Baud 8N1. Site Alert does not output Line Feeds with its Carriage Returns, so you may want to set your terminal program to add Line Feeds to incoming lines.

The Run / Command switch must be in “Command” to enter commands. 

Command	Description	Example	Max number of Characters	Initial Value
?	Serial port test, response’s with all settings.	?	n/a	n/a
In(1/2)	Text for item name for each of the alarms	I1Door.	6	INPUT(1/2)
A	Latitude	A3800.00S	8	3800.00S
O	Longitude	O14450.00E	9	14450.00E
C	Suffix of site call sign used in item name	Cxyz	3	RGR
S	Full site callsign for “formatting” msg’s	SVK3RGR-1	9	VK3RGR-1
M	My call sign for message direction & free text	MVK9XYZ	See below	See below
V	Switch off/on voltage  lllhhh*   (VLVH)	V120130	6	115130
T	Setting of time hhmm	T0230	4	n/a
Z	Setting of Time Zone Character	Zz	1	z

* lll - is the low voltage threshold or VL

* hhh - is the high voltage threshold or VH

Time (T):

Sets the time in the internal clock.

This will impact on when the daily max/min transmissions will occur (these are preset to be sent at 09:00 Site Alert clock time).

Zone (Z):

Sets the Character added straight after the time as transmitted in Alarm Messages.

Some suggested values are, E-east, C- central, Z-utc, L-local, etc.

Latitude & Longitude (A/O):

These values set the location of the “item” which appears for alarms. It is recommended that they should be close to the actual location of the device.

The formats for longitude and latitude are dddmm.nn<EW/NS>. “ddd” is three digits for degrees. “mm” is two digits for minutes. “nn” is two digits for decimal minutes. For longitude it is either “E” for East or “W” for West and for latitude it is either “N” for North or “S” for South.

Switch Off/On Voltage (V):

These set the voltage at which the Site Alert will disable and re-enable the PTT of the Digi (versions B and b) or turn off and on the Low Battery Opto (versions b and above) . It is entered without decimal points with the disable value first eg. ‘118138’

Input’n’ & Call Suffix ( In/C):

These are used to produce the name of the Item eg. ‘I1AC-OFF’ and ‘CRGR’ becomes when sent as an alarm from input 1 ‘AC-OFFRGR’

MyCallsign (M):

This is the callsign to which the alarm message will be sent and includes optional text to be inserted before the actual Alarm message. This feature allows for adding an e-mail address before alarm message.

For example “EMAIL    :user@isp.com.au” the text MUST BE entered with the correct number of spaces to pad the callsign out to the required nine characters (see Reference 1:). If an e-mail address is not required a space should be added after the ‘:’ eg “VK3BYD   : “

Maximum number of characters for MyCallsign is 47 characters, which includes all spaces.

SiteCallsign (S):

This is the callsign to which the Telemetry “formatting" messages will be sent to. It MUST equal digi’s callsign including SSID.

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Remote Commands:

Turning the “Connect Led” in the UI-Digi ON will prevent Site Alert from turning off the Low Battery Opto should the battery voltage fall below the “VL” value. If the TNC’s Connect Led is turn on once the battery has fallen below the “VL” value but before the three alarm messages have been sent then Site Alert will not turn off the Relay Output once it has sent the third Low Battery message. This allows the Site owner to prevent Site Alert from automatically turning off the radio should it be required, eg during an emergency.

 

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Messages, Items & Beacons:

 

Telemetry Beacon	T#141,061,132,073,009,032,00000000,SA3VE8!
Sent every 30-Min.	^ Status Indicator (see note 1)
	^ Site Alert Version
	^ digital data (not used)
	^ Site Alert’s Hours & Minutes
	^ Traffic counter (PTT’s)
	^ Site Voltage (*10) i.e. = 13.2 Volts
	^Site temp in deg C (*2)
	^ Sequence number
Item	)LOWBATRGR!3800.00S414450.00En SiteAlert
Sent at time of alarm and at every 30 Min beacon until alarm is cleared. Or four times for low battery alarms
	^ Longitude
	^ Alarm number (see note 2)
	^ Latitude
	^ Alarm Name (see note3)
Message	:VK3BYD   :  LOWBAT RGR 4 08:00z SiteAlert
Sent at time of alarm and at every 30 Min beacon until alarm is cleared. Or four times for low battery alarms
	^ Time Zone character
	^ Time of msg
	^ Alarm number (see note 2)
	^ Site Name
	^ Alarm Name (see note3)
	^ Callsign Message is destine for
Message	:EMAIL    :user@isp.com.au LOWBAT RGR 4 08:00z SiteAlert
Sent at time of alarm and at every 30 Min beacon until alarm is cleared. Or four times for low battery alarms
	^ Time Zone character
	^ Time of msg
	^ Alarm number (see note 2)
	^ Site Name
	^ Alarm Name (see note3)
	^ Callsign Message is destine for
Message	:EMAIL    :user@isp.com.au OK RGR 0 09:00z SiteAlert
Sent when low battery alarm is cleared. And there are NO other active alarms.
	^ Time Zone character
	^ Time of msg
	^ Alarm number ( see note 2)
	^ Site Name
	^ Alarm Name (see note3)
	^ Callsign Message is destine for
Equations	:VK3RGR-1 :EQNS.0,0.5,0,0,0.1,0
Sent Daily at about 0030, 0900 & 1630 Hrs (Site Alert time)
Parameter	:VK3RGR-1 :PARM.Temp,Battery,TX
Sent Daily at about 0030, 0900 & 1630 Hrs (Site Alert time)
Units	:VK3RGR-1 :UNIT.Deg.C,Volts,PTT's
Sent Daily at about 0030, 0900 & 1630 Hrs (Site Alert time)
Status Beacon	>SiteAlert VK3BYD
Sent Daily at about 0900Hrs (Site Alert time)

 

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Notes:

1) Status Indicator:

The status indicator appears at the end of the version number in the Telemetry beacon.

‘Blank’ = normal operation, ‘!’ = Low Battery alarm is active, ‘*’ the TNC’s Connect LED is on

 

2) Alarm Number:

The table below can be used to calculate the alarm number.

3) Alarm Name:

The alarm name will always be the highest priority alarm.

4) Low Battery Cut-Out Delay:

When the voltage falls below ‘VL’ SiteAert waits for approx 2hrs after before turning off the Low Battery output (cut-out) to allow for 3 to 4 alarm messages to be sent. Therefore it is recommended to set ‘VL’ slightly higher than usual to compensate for the additional 2 hours of operation.

 

Once power is restored and the upper voltage limit ‘VH’ has been reached it may take up to an hour (normally 1/2hr) for the Low Battery output (cut-out) to switch on. This is to protect against intermittent power restores. Once power is enabled an OK Message is sent. (SA takes the average of 4 voltage readings over ½ an hour starting at 00 or 30 past the hour SA time, to determine the final values of ‘VL’ & ‘VH’.)

 

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UIDigi Settings:

In the Digi, the ‘AUX’ input settings must be programmed. The recommend values are:

 

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Circuit Diagram:

The circuit diagram for Site Alert version 3F can be downloaded here.

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Installation:

First Time:

Clock:

The internal clock will need to be initialized the first time Site Alert is powered up. This is done by fitting link “SET CLK” before power is applied and not removing it until the first telemetry beacon has been sent. Once set it will keep time whilst power is connected to Site Alert and / or while the Real Time Clock back-up battery is fitted.

Settings:

Site Alert will need to clear its buffer of all messages before any commands can be sent. For initial setup I would recommend connecting Site Alert to you PC’s serial port in command mode.Fit the “SET CLK” link, apply power and then wait. The first Telemetry beacon will be sent after approximately 7 minutes, then remove the “SET CLK” link and adjust any settings that require changing.

General:

 

Connect LED:

The TNC’s Connect led is available on its RS232 port and is automatically connected through to the Site Alert.

Traffic Counter:

Site Alert will transmit the number of local transmissions made by the UIDigi between the 30-Min beacons. See also comments in Limitations.

PTT Output:

If power is removed form Site Alert and the TNC is connected to the radio via Site Alert, the radio’s PTT may be activated. This of course is only a problem whist people are working at the site as Site Alert is normally connected to the site’s battery supply.

Alarm Inputs:

The alarm inputs are Opto Isolated, the “source” voltage is supplied internally from the Site Alerts 12-volt supply, so the inputs only need to be “pulled” to ground.

Maximum current available from the Alarm Inputs to ground equals (“supply”-0.6V) / 1K Ohm. Typically 12mA.

Power Supply:

To insure Site Alert can accurately report the battery voltage it should be connected directly to the Site’s battery, or if the battery is a long way from the equipment it should be connected at or before the first point at which the other equipment connects to the battery.

Low Battery Output:

This is an Open Collector output; the transistor is normally on when Site Alert does not have a Low Battery Alarm. Changing of links on the solder side of the PCB can reverse this. The BD139 transistor is rated for 1 A.

 

( In version C the Opto Output is rated at 150 mA. The output is normal active i.e. will sink current whist the voltage supplied to Site Alert does not meet the alarm conditions.)

 

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Sample Data and Pictures

 

View pictures of the Site Alert 3 proto-type.

 

View telemetry and messages sent frome Site Alert.

 

See data collected from some of the Site Alert’s in service in the VK3 APRS network.

 

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Appendices:

Further Information:

At the time of writing there are Programmed Micro’s and PCB’s available.

Anybody who is interested in this project can contact me on e-mail at “vk3byd ‘at’ wia.org.au” .

 

References: