Does this sound right? - NEMA question
 

On Apr 12, 1:46 pm, "Roger Long" wrote:
Since I'm only concerned when the starter is engaged, how about wiring in a
bypass with a NC relay that opens whenever the engine key is turned on?
When the alternator is going, low voltage shouldn't be a problem and I would
then have no voltage drop when sailing and drawing on the batteries. Since
I have a diesel, the engine is stopped before I turn the key off.

If that starter motor created spikes so destructive as to overwhelm
protection already inside electronics, then a typical zener diode is
only a bucket trying to stop a flood. Why is maritime electronics
often more expensive? Properly designed electronics include circuits
that make a trivial 'starter motor' spike irrelevant. Low voltage
also is not destructive and is made irrelevant by those same circuits.

Meanwhile, a destructive transient is called load dump. So critical
as to be defined even by SAE J1455 and ISO 7637-1 standards. Also
easily created if special consideration is not made to battery
switchover circuits.

Load dump is defined by one manufacturer with peak voltages of 80 to
100 volts and duration of 300 to 400 milliseconds. ISO defines it as
a voltage spike of up to 270 volts.

Most 12 volt electronics designed to withstand load dump are rated
for at least 60 volts. Examples of why a power adaptor is not
purchased on price and why another poster has never seen such damage.
How many replies even knew that load dump (not a starter motor) is the
destructive transient. A problem so common and so well understood as
to even be defined with SAE and ISO standard numbers.

Meanwhile, designs to make load dump irrelevant also make lesser
'starter motor' spikes also irrelevant.

Does this sound right? - NEMA question
 

On Thu, 12 Apr 2007 14:08:42 -0400, "Roger Long"
wrote:

I remember now that I often found the GPS off or looking for birds again
after starting the engine when coming into the harbor.

That's because of momentary low voltage turning the unit off. It
happens on my boat all the time when I crank those big diesels.

Does this sound right? - NEMA question
 

On Apr 12, 5:24 pm, Charlie Morgan wrote:
Warning to all onlookers: w_tom is a well known usenet kook.

Charlie Morgan suggested using "an LM7812 voltage regulator at each
instrument you want to protect." when it is only rated for about 35
volts input. If Charlie was posting with technical knowledge, then he
knew the 78xx series has long been insufficient for mobile operation.
The OP has a choice. Either believe a poster who cites professional
standards and knows the 7812 as a defective solution. Or believe the
person who uses insults and personal attacks to prove superiority.

The 7812 recommendation is repeatedly bogus.
1) Its maximum input voltage is 35 volts.
2) It requires more than 14.5 volts input to maintain 12 volts
output.
3) Anything a 7812 might accomplish is already inside electronics.
4) Even National Semiconductor, that also manufacturers a 7812,
instead recommends other voltage regulators for mobile service. If
Charlie Morgan had basic technical knowledge, then he might have
recommended products from National's automotive line. He did not even
know basic electrical information.

Charlie Morgan again posts personal insults. His own post is in
error for above four reasons - and numerous others. Who is the kook?
One who recommended solutions, numbers, AND industry standards? Or
one who foolishly recommended the 7812 because he never read
manufacturer datasheets nor learned basic facts?

If Charlie Morgan had technical knowledge - and he clearly does not
- then he could have recommended this voltage regulator that actually
claims load dump protection, reverse voltage protection, and low
dropout voltage:
http://www.national.com/pf/LM/LM2931.html

But then Charlie did not even know what load dump is. All posts
from Charlie are suspect as technically naive - as demonstrated again
here.

Previously Charlie attacked another poster who only asked what DSL
filters do. Charlie. He asked whether it was a high pass or low pass
filter. Charlie replied, "yes" and proceeded to insult that poster.
His entire technical reply was to mock that poster. Nothing new in
Charlie's behavior here. His personal superiority means we can ignore
his 100% defective 7812 recommendation?

Charlie Morgan posts are not to be trusted. How does one know? He
does not even know the limits of a simple 7812 regulator. His entire
technical reply is justified by personal insults. I expect him to
continue with those insults. Charlie does not like it when we learn
how little he actually knows. He did not even know something so well
understood as load dump.

Does this sound right? - NEMA question
 

I contacted Garmin about this very issue. Here's what they told me, I
tried it and it works just fine.

The way to connect these units together is to join the brown (data
out)
from your 76 to the VHF NMEA in (+). The NMEA (-) wires need to be
tied
to the same ground as the 76 black wire. The NMEA out (+) will not be
used; neither will the data in on the 76. After you get the wiring
accomplished, you will also need to change a setting on the 76 so it
will communicate in the same language. To do this, press the menu
button twice to go to the main menu. From there select setup and then
tab over to interface. It should be set a Garmin, you'll want to
press
enter and then select the option NMEA. They should now be
communicating
freely.


Peter
a/v Now or Never!

On Apr 10, 1:16 pm, "Roger Long" wrote:
I hooked up the NEMA output from my Garmin GPSmap 76x to my Quest radio this
morning.

The radio has a NEMA in and NEMA out line and shows them connected to wires
of the same color for a GPS by the same company. A few pages later there is
a table for NEMA connetions to various brands of GPS.

Both fixed mount and portable Garmin's show the NEMA out line from the GPS
to be connected to the :Data In" in line on the radio. The radio "Data Out"
line is indicated as connecting to "Black - Neg Ground". I therefore put a
wire from the ground block where the black negative lead from the GPS power
cord attaches and ran it to the Quest radio "Data Out" lead. I'm sure this
is what it said to do but it seems odd.

I haven't turned anything on yet so, if anyone can confirm that I did it
right or head off melting something, I would appreciate it.

Please: only if you know. I hate those post responses that start out, "I
haven't got a clue but here is what I guess."

--
Roger Long