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Ed
 
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Default GPS Anchor Drag Alarm Ideas?

I have one with an external connection. I hard wired a large piezo
buzzer (Low power draw LOUD alarm-radio shack) it works great... if you
find the right GPS here are a couple hints....
-Put a switch inline with it... When mine goes off I get up but by the
time I get up to the bridge, I have woken the whole crew....A timer
switch is better because it resets itself.... otherwise put it somewhere
you won't forget to turn it on at night...
-make sure you use it during the daytime to get an idea of the
sensitivity needed... Mine was waking me up all the time in the begining
until I figured out how to use it with changing tides etc. 2 anchors
(Main and a kedge against the shore) work best for my vessel
-My next project is to add a motion detector to the cockpit area to
alert me to anyone boarding, exiting (Afraid of newbies falling over) or
trying to steal my dingy.




Len Krauss wrote:

My GPS (with an anchor drag alarm feature) is not located in sleeping berth.
Even even if it were, its alarm is barely audible, and certainly not
adequate to arouse a person from a sound sleep (unless the GPS were strapped
to one's ear.). Additionally, a GPS antenna wire would need to be run to the
berth -- not a big problem, but what's the point if one can't hear the alarm
anyway.

Perhaps there's some kind low-power amplifier that could be placed next to
the GPS, or possibly a transmitter with remote alarm receiver. But it might
need to be tunable, so just any kind of noise doesn't set it off.

I was hoping that there might be a defined NMEA sentence output by the GPS
when an anchor drag condition is sensed, but none exits from what I've been
told. If there were, it might be possible to detect it in order to trigger a
loud alarm of some type.

Would welcome any and all suggestions for off-the-shelf or custom anchor
drag alarm systems.

Thanks,
Len


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Default GPS Anchor Drag Alarm Ideas?

On Sun, 11 Jan 2004 14:17:44 -0500, Ed wrote:

I have one with an external connection. I hard wired a large piezo
buzzer (Low power draw LOUD alarm-radio shack) it works great... if you
find the right GPS here are a couple hints....

Here's an idea....requires no power, always on the job, depending on the type, and good company...
The old-fashion MK 1 DOG
Norm


-My next project is to add a motion detector to the cockpit area to
alert me to anyone boarding, exiting (Afraid of newbies falling over) or
trying to steal my dingy.




Len Krauss wrote:

snip
  #13   Report Post  
 
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Default GPS Anchor Drag Alarm Ideas?

On Sun, 11 Jan 2004 13:55:44 -0500, "Len Krauss" wrote:

Hi Steve,
Thanks for that alram-out power limit tip and the excellent schematic!
Len


As usual, there's always a ton of ways to do any task.

The schmatic refered to above specifies a relay with as low as 120 Ohms coil resistance. At 12
Volts, this equates to 100 mills, meaning some heat will be generated, however small, inside the
GPS. I admit the alarm wouldn't be on very long in most cases, unless no one was aboard.

If it were me, I'd buffer the GPS output with the trusty 2N2222 to drive the relay. The advantage
is that it'd be trivial to incorporate a "alarm off" switch... and a sesitivity contol, just in case
the GPS output was analog (transistor, which I'd find hard to believe), and didn't have well-defined
logic levels.
Norm
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Meindert Sprang
 
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Default GPS Anchor Drag Alarm Ideas?

wrote in message
...
On Sun, 11 Jan 2004 13:55:44 -0500, "Len Krauss"

wrote:

Hi Steve,
Thanks for that alram-out power limit tip and the excellent schematic!
Len


As usual, there's always a ton of ways to do any task.

The schmatic refered to above specifies a relay with as low as 120 Ohms

coil resistance. At 12
Volts, this equates to 100 mills, meaning some heat will be generated,

however small, inside the
GPS. I admit the alarm wouldn't be on very long in most cases, unless no

one was aboard.

If it were me, I'd buffer the GPS output with the trusty 2N2222 to drive

the relay. The advantage
is that it'd be trivial to incorporate a "alarm off" switch... and a

sesitivity contol, just in case
the GPS output was analog (transistor, which I'd find hard to believe),

and didn't have well-defined
logic levels.


The fact that the output switches to ground and can take 100mA max, tells
me, as an electronics designer, that the output IS a switching transistor.
No analog values, just a hard switch to ground, with a maximum so called
saturation voltage of about 0.1V. This means that at 100mA the heat
dissipation inside the GPS is a whopping 10 milliwatt. No need to add an
extra transistor.

Futher, it says that the maximum current is 100mA and therefore the relay
coil may not be less that 120Ohms. There's nothing wrong in using a relay
with a coil of 500 or even 1000 Ohms, to reduce power and 'heat' any
further.

Meindert


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Default GPS Anchor Drag Alarm Ideas?

On Sun, 11 Jan 2004 23:54:29 +0100, "Meindert Sprang" wrote:

wrote in message
.. .
On Sun, 11 Jan 2004 13:55:44 -0500, "Len Krauss"

wrote:

Hi Steve,
Thanks for that alram-out power limit tip and the excellent schematic!
Len


As usual, there's always a ton of ways to do any task.

The schmatic refered to above specifies a relay with as low as 120 Ohms

coil resistance. At 12
Volts, this equates to 100 mills, meaning some heat will be generated,

however small, inside the
GPS. I admit the alarm wouldn't be on very long in most cases, unless no

one was aboard.

If it were me, I'd buffer the GPS output with the trusty 2N2222 to drive

the relay. The advantage
is that it'd be trivial to incorporate a "alarm off" switch... and a

sesitivity contol, just in case
the GPS output was analog (transistor, which I'd find hard to believe),

and didn't have well-defined
logic levels.


The fact that the output switches to ground and can take 100mA max, tells
me, as an electronics designer, that the output IS a switching transistor.
No analog values, just a hard switch to ground, with a maximum so called
saturation voltage of about 0.1V. This means that at 100mA the heat
dissipation inside the GPS is a whopping 10 milliwatt. No need to add an
extra transistor.

Futher, it says that the maximum current is 100mA and therefore the relay
coil may not be less that 120Ohms. There's nothing wrong in using a relay
with a coil of 500 or even 1000 Ohms, to reduce power and 'heat' any
further.

Meindert


I agree with your points. I guess it's up to the alarm device builder to choose
the method.
But, also as an electronic designer, I generally don't like to approach max values.
I use a conservative 25% of ratings as a design goal, based on reliability charts.

Moot point, but don't most silicon transistors have a Vsat of about .2 Volts?
I wouldn't be surprised if the device in question was actually a FET.
Norm


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Meindert Sprang
 
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Default GPS Anchor Drag Alarm Ideas?

wrote in message
...
On Sun, 11 Jan 2004 23:54:29 +0100, "Meindert Sprang"

wrote:
I agree with your points. I guess it's up to the alarm device builder to

choose
the method.
But, also as an electronic designer, I generally don't like to approach

max values.
I use a conservative 25% of ratings as a design goal, based on reliability

charts.

Don't you think the device builder took the same precaution and used some
transistor or fet capable of 0.5 ot even 1 A?

Moot point, but don't most silicon transistors have a Vsat of about .2

Volts?
I wouldn't be surprised if the device in question was actually a FET.
Norm


Quite possible.

Meindert


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Len Krauss
 
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Default GPS Anchor Drag Alarm Ideas?

Ric,

That sounds like it could work with my handheld GPS, with it and the GPS
powered by boat's battery. Of course my GPS 48 has no alarm-out connection.
But, I wonder how hard it would be to open the GPS case and find the
internal audible alarm device contacts and give it a try. If successful, I
could install some sort of permanent connector thru the case. Whadda
think??? Ric or anyone, please provide any tips, do's/don'ts.

I'd plan to use a three-wire alarm, where very low current (5ma) operates
the trigger and the alarm itself is powered by boat's battery.

Your 420's a really fancy machine and I couldn't agree more about it being
dumb not to have an external alarm connect on it. All the internal alarms
are useless as far as I can tell. (Perhaps that's because there are no tides
and few currents and winds affecting anchored boats in Kansas, or maybe
people don't sleep on boats there.)

Thanks,
Len


--
You don't mention what kind of GPS you have - but are you sure there is no
means to connect an external alarm? My GPS (a Raymarine 420) had a totally
useless "alarm" that wouldn't wake a sleeping mouse, so I pulled it to

bits
and connected an external alarm. I subsequently discovered that Raymarine
will actually do this as a free after market mod, realising that it was a
bit dumb to ever build something with an inaudible alarm.




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Ric
 
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Default GPS Anchor Drag Alarm Ideas?


"Len Krauss" wrote in message
...
Ric,

That sounds like it could work with my handheld GPS, with it and the GPS
powered by boat's battery. Of course my GPS 48 has no alarm-out

connection.
But, I wonder how hard it would be to open the GPS case and find the
internal audible alarm device contacts and give it a try.



That's what I did. I just found the feeble little buzzer, soldered some
leads to it, fed it to a MOSFET gate, then used the battery to power a
siren.


Thanks,
Len


--
You don't mention what kind of GPS you have - but are you sure there is

no
means to connect an external alarm? My GPS (a Raymarine 420) had a

totally
useless "alarm" that wouldn't wake a sleeping mouse, so I pulled it to

bits
and connected an external alarm. I subsequently discovered that

Raymarine
will actually do this as a free after market mod, realising that it was

a
bit dumb to ever build something with an inaudible alarm.





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