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#11
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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 |
#12
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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
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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 |
#14
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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 |
#15
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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 |
#16
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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 |
#17
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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. |
#18
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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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