Re: Chartplotter alarm

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

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