Gordon wrote:
matt_colie wrote:
Gordon wrote:
I have a SH 300i chartplotter with all the standard alarms, etc.
The audible alarm is the same beep as the keyboard input beeps so is
not loud. It is not adjustable and there is no remote alarm jacks.
So, with it mounted at the helm and you're at anchor and taking a nap
below, how do you hear the anchor drag alarm?

I thought of a baby monitor but most, if not all, require ac at the
xmitter which would be another pain.

So, any suggestions?

I'm trying to get a schematic for the alarm circuit from SH but I
doubt they will come through.
Gordon
Gordon,

If you search, you can find baby monitors that run on low voltage DC
from a wallwort and that could be replaced by a small regulator on the
ship's power. The receivers are usually battery powered.

I had the same complaint form an owner that could not hear the alarms
(I think it was a 180) while at the helm and under sail.

We could not get any service information or assistance from SH. I
could not isolate the key beeps from the alarms.

We were able to crack the box open and tap the board at the speaker -
it is a micro speaker that gets fed a square wave - so the signal was
about 1v at 300hz. That was enough to drive an switching circuit that
could fire a good old Sonalert. He can hear that.

Good Luck

Matt Colie

What does the switching circuit look like? And which Sonalert?
The 180 is the same machine as the 300 so this should work.
Thanks
Gordon
BTW, the SH tech is supposed to be snail mailing me a schematic.

It seems like you got a more cooperative tech than I found. - Good

The Sonalert was just a typical 3~24VDc that I had in my junk box.

I tapped the power off the main on the board, but I am brain fading on
the switching circuit was simple, but I think I had to do it backwards
from what I wanted. The driver appeared to be an open collector so the
signal pull down and not a zero to high. So it used a diode and an RC
to the base of a small signal PNP (again from the junk box) to create a
zero to high to drive the Sonalert.

With an actual schematic, you can probably do better, but this made a
happy owner and that is what I want.

Matt