Garmin 128 Anchor Alarm

[HinewaisMan]

Have an old Garmin 128 which came with the boat on board, all wired up and working fine as a backup GPS.

Since it’s a far lower power drawer than our main Raymarine kit, we tend to also use it as our anchor alarm – again it works fine.

The only downside is that the “beep” is not too loud and I’ve always been a tad concerned that we might not hear it in the stern cabin.

So went to wire it into our main alarm system this weekend.

It should have been a simple job – connecting the ground side of the alarm to Pin 7 – but when I tested the circuit first with the multimeter, I found a constant low voltage (<1V) – and in connecting the alarm in, got a constant low sound – even when the anchor alarm is not activated.

The manual is no help and I don’t want to open the unit up since I believe it’s moisture sealed.

Anyone got any ideas? If not, well, we’ll just leave things as they are.

Ta

P

 

[GrahamM376]

Our Garmin 152 anchor alarm was also useless so I used the external alarm wire to activate a latching relay with 90db sounder. Continues sounding until I press the cancel button on the relay circuit.

 

[NickRobinson]

Hi-

I have had a look at my (paper) manual for my 128.

The wiring diag shows a relay across the pin 7 yellow and the pin 1 red.

Nick
(who wants to send routes to the 128 from the Laptop and then to the NASA repeater)

 

[macd]

The manual is no help

That's odd: my manual tells you exactly how to do it.

To connect an external alarm, connect the ground side of the alarm device to the YELLOW harness lead (100mA DC load max.)


Yellow is Pin7, as you say.
The pos side of the alarm connects to Pin1 (Red).

Works a treat.

I suspect your problem may have been trying to connect to a speaker too big for the unit to drive.

 

[prv]

You've connected the -ve side of the alarm to the GPS; where is the +ve side coming from? You mention an alarm "system", which makes me wonder if it's coming from some other circuit whose voltage is not quite at the same level as the one the GPS is on.

Presumably, in the un-alarmed state the GPS holds its alarm pin at the same level as its incoming supply. So a sounder fed from the same supply will see no potential difference between the two sides and will not sound. But if you're feeding the sounder from a circuit whose "+12v" is a volt higher than the GPS circuit's "+12v" then you have a P.D. and a current will flow.

Pete

 

[HinewaisMan]

That's odd: my manual tells you exactly how to do it.

To connect an external alarm, connect the ground side of the alarm device to the YELLOW harness lead (100mA DC load max.)


Yellow is Pin7, as you say.
The pos side of the alarm connects to Pin1 (Red).

Works a treat.

I suspect your problem may have been trying to connect to a speaker too big for the unit to drive.

OK, badly put in my first post - there's no troubleshooting bit in the manual that's any help.

I wired it up as per the diagram - and the alarm's a baby piezo buzzer with a max current draw of 8mA.

What's odd is that there seems to be a constant tiny current flowing all the time - and nothing happens when the alarm goes off - just the same tiny flow.

Was wondering as much as anything if there was some setting I'd missed?