Does this sound right? - NEMA question
 

On Apr 10, 6:10 pm, "Roger Long" wrote:
Goofball_star_dot_etal wrote:

it is odd. Is your radio model here?
http://www.standardhorizon.com/?cmd=...s&DivisionID=3

Yes, it's this one:

http://www.standardhorizon.com/downl...323&FileCatID=...

I left the manual on the boat because I didn't start wondering until the
drive home.

Looking at the PDF version (thanks for the link), I see that the radio calls
both wires "NMEA IN", one is + and the other - so connecting to ground makes
sense. But, why wouldn't they just do that inside the radio and have you
just connect one wire?


Noise rejection. A balanced, or bifilar connection, is immune to
external signal interference, same like for low impedance microphone
lines. The (-) connection is not a ground.

Terry K

Does this sound right? - NEMA question
 

"Roger Long" wrote in
:

Thanks Larry, you are a treasure.

(c; Aw, P'shaw....Twern't nuthin' (blush)

I think I have it straight now although I had to look carefully at the
timing of your posts since the second appeared higher in the list.

No network here. My set up is about one baby step past a pencil and a
parallel rule. The handheld GPS is wired directly to the fuse for
the depth sounder and knotlog. The GPS "Data Out" line goes directly
to the radio "Data +". The radio "Data -" goes to the ground block on
the same screw that GPS power - connects to. The radio is on a
separate fuse.

That'll work.

It sounds like I can expect to hear the GPS talking to the radio in
the background. Would it be a good idea to put a switch in the data
line near the radio so I can silence it in conditions where I am
having trouble hearing or understanding or just don't like the noise?
I would probably leave it off most of the time as I'm only wiring this
up for the cool factor and so I will have my position handy if I ever
need to call for help and don't want to have bring the GPS in from the
steering station.

No, it's not that easy. The unbalanced, unshielded NMEA serial lines
RADIATE RF noise, but mostly not high enough to bother the VHF, which is
FM and fairly immune, anyways. These unbalanced NMEA lines eat the HF.
Our Icom M802/AT-130 and insulated backstay get eaten alive. If you're
going to talk on HF, we just shut off the ELECTRONICS MASTER SWITCH and
do without until we're done using the HF, even receiving a WEFAX. The
emergency VHF (Icom M59) and Icom M802 HF are on separate circuits so we
can do this, safely, and still monitor Ch 16 at sea. Shielding it is
damned near impossible because the instruments, themselves, in their
unshielded plastic cases radiate some of it...(sigh) You won't see it on
your VHF. Running it continuously is important for safety. If the radio
has a constant stream of GPS data, and shows the lat/long properly, a
Channel 70 emergency call is simply pressing the emergency button for 5
seconds. You won't have time to fool around hooking the GPS up while the
hull is flooding or in horrendous seas. Run it all the time.


The radio data lines go to a two screw terminal block. When I
purchase a back up GPS, I will probably dedicate that one to talking
to the radio so I still have position data available if the one in the
cockpit mount goes overboard.

Any old GPS will feed the radio. Hell, I bought a Garmin GPSMAP 185 for
$12 at a thrift shop and found the improved, new GPS antenna online for
$38 to fit it. They're really cheap and first class GPS receivers
because Garmin refuses to support the proprietary chart plugs that feed
them any more, trying to dump the next generation of profit margins on
us. My Garmin looks brand new because it was always stored under its
custom face cover...which I also got in the $12 package...(c;

BTW I have a ferrite core on the GPS lead. When I install the
autopilot, I'm going to avoid tying the power supply to in in the same
convienient cable run as the GPS and lead it separately with its own
ferrite core.

All for naught. You'll never be able to stop the NMEA from radiating.
Don't waste your time on cores and tin foil.


Another question that just popped into my mind:

When flying, we were religious about making sure that all power to the
radios and instruments was turned off before starting or stopping the
engine. I use my two battery bank as a single battery (for reasons
discussed at length a couple years ago). Am I at risk of frying or
shortening the life of my simple electronic items? I've gotten away
with it for two years as have apparently many other people. Saiing
involves frequent engine starts and shut downs while navigation is in
progress so a voltage suppressor in the power supply to the
instruments would be a better solution than an avionics master switch
such as I had on the aircraft.

Here's where Lionheart shines. When I took over her electronics suite,
electrical power came from whatever was closest to whatever box needed
power. How awful. My captain is a little forgetful, so I installed a
completely separate 12VDC bus for all the equipment, except the Icom M59
emergency VHF and Icom M802 for the reason of the noise, above.

This separate power bus has a fuseblock at the helm for the helm
instrumentation, one at the nav station for the nav station radios and
instruments, one in my side of the V-berth for my computer and one in the
captain's playroom (aft cabin with sheepskins..(c;) for his computer.
The bus is rated for 50A and is so fused next to the Main Electronics
Contactor behind the helm (which in the Amel is the overhead cupboard
over the galley sink by the boat's main breaker panel.) This contactor,
a continuous-duty, 150A power contactor from NAPA Auto Parts, pulls 1/4A
to run its main coil all the while the boat electronics is on. The
contactor coil runs through a nice brass marine push-pull off-on switch
to the house power bus, where the contactor also gets its main DC power
to run everything. A BRIGHT red power panel light is right next to the
push-pull switch, and makes a really nice night light for the main cabin
without ruining your night vision at sea. His Immenseness goes right by
this light on his way to the yacht club up the hatch, so instantly
notices he has left the whole electronics load running by mistake and can
push the button in to shut it all down, throughout the boat, ONE
TOUCH!...(c; We like our simplistic ideas on Lionheart.

As the electronics bus gets it power off the monstrous two-bank 660AH
main house batteries DIRECTLY and CANNOT be hooked to a A-B-Both-OFF
switch in the OFF position, it is impossible to connect it to an unloaded
alternator, putting 20somthing VDC to the expensive electronics...unless
some complete idiot has pulled the monsters out of the bilge....??
Starting the engine/alternators (it has 2) has no effect on voltage until
the charging current racing at 120A into the house beasts causes them to
rise towards being charged.

If you have the electronics hooked to the starting battery, YES DO NOT
OPERATE ANY ELECTRONICS WITH THE STARTER! Awful transient voltage spikes
are caused by inductive kick in the starter....

Larry
----
A skilled marine electronic technician/instrument metrologist available
for service to exotic shipwrecks like Titanic....(c;

Does this sound right? - NEMA question
 

"Larry" wrote in message
...
"Roger Long" wrote in
:
[.. major snippage..]

BTW I have a ferrite core on the GPS lead. When I install the
autopilot, I'm going to avoid tying the power supply to in in the same
convienient cable run as the GPS and lead it separately with its own
ferrite core.

All for naught. You'll never be able to stop the NMEA from radiating.
Don't waste your time on cores and tin foil.

The cores *might* help. They will knock the high-frequency edges off the
NMEA signals, and will even turn some of the signal/ground common-mode
signal into a balanced signal by acting as a balun (balanced to unbalanced
transformer). The cores will only do this for the high-frequency
components, but that's where the radio interference comes from. Even if the
box radiates, choking off the connecting wires with the ferrites will reduce
the signal that gets into your antenna.

I'm not guaranteeing that this will help enough to make a big difference,
but it might be enough to be useful. If they will fit, try running the
wires through the ferrites a couple of times (through the hole, around the
outside, and back through the hole in the same direction). This will
significantly improve the ferrite's effect on HF signals. Put on two or
three ferrites. It all adds up, until it doesn't.

I've found that it is much easier to clean up this type of interference by
using ferrites than by trying to shield small devices. For a critical
application, a combination of shielding, bypassing (with capacitors), and
external ferrite chokes may be required, but for the typical boat situation,
you can get 80% of the way there by just using the ferrites. I used to do
this for a living, bringing computer and telecom products into compliance
with FCC and international radio interference regulations.

But, as Larry points out, sometimes there just isn't a reasonable fix.
Shutting stuff down will definitely do the trick in that case.

-Paul

Does this sound right? - NEMA question
 

"Larry"

If you have the electronics hooked to the starting battery, YES DO NOT
OPERATE ANY ELECTRONICS WITH THE STARTER! Awful transient voltage spikes
are caused by inductive kick in the starter....

Well, there is the first good reason I've heard for a separate starting
battery on my boat although I've always agreed that all powerboats and
larger sailboats should be set up that way.

Although my total electronics package is only about $1500, I'd still like to
protect it, primarily so I don't fimd myself without something up in the
wilds of Canada.

Options:

1) Remember to always run down the companionway and flip the instrument
switch I start or stop the engine. Not good in heavy traffic areas or to
goose the boat out of a potential jam in tight spots and fluky winds.
Anything requiring memory at my age is always suspect:)

2) A waterproof Instrument Master Switch next to the starter button. Easy
to implement, visual reminder. Only drawback would be waiting for GPS to
find birds again after starting or stopping engine unless I remember to
press any key to keep it going on batteries.

3) A NC relay wired into the starter circuit that disconnects the
instruments when the starter button is pushed. When the button is released
however, isn't there a chance that the magnetic fields could still be
collapsing through the starter coils after the relay releases? I was taught
on aircraft that shutdowns are more of a hazard than starts. Same GPS
restart issue as above.

4) One of my scientist girlfriends back in Woods Hole a few decades ago was
always fiddling with something called a voltage clamp while studying squid
nerves. Isn't there something that could be inserted in the feed to the
instruments that would restrict voltage spikes? There isn't on aircraft
but, if you ever want to hoot and hollar, get a tour behind the panel of a
GA aircraft. Not much progress since the Wright brothers there. Parts are
incredibly expensive because the FAA requires them to be replaced with
factory original or equal and Radio Shack doesn't sell stuff that cheap and
crude.

5) Install an aircraft size (for my little engine) starting battery totally
separate except for a VSR or battery combiner to charge the house bank after
the starting battery is brought back up. Since these mostly seem to connect
the batteries when the engine is running, it seems like start/stop
transients could still find their way through. Space is a big issue with
this option on my boat as is getting into the engine room to install and
properly anchor another battery box.

I'd really like to go with 3) or 4) if you think they would work and could
point me in the right direction.

BTW I spent most of yesterday morning gonig up and down the ladder on the
boat, walking around the boatyard, and squirming in and out of the engine
room being filmed for the Titanic show. The producer thought the short "who
is this masked naval architect?" clip should show me working on my boat.
The editor may ditch it later but there's a good chance you will see my boat
and engine room on the next Titanic show. It's currently scheduled for July
first but may be moved up. You'll see why option 5 doesn't appeal.

--
Roger Long

Does this sound right? - NEMA question
 

On Thu, 12 Apr 2007 05:34:42 -0400, "Roger Long"
wrote:

Isn't there something that could be inserted in the feed to the
instruments that would restrict voltage spikes?

Yes, it's called a zener diode and they come in different voltage
ratings.

http://en.wikipedia.org/wiki/Transie...pression_diode

http://www.electronics-manufacturers...rotectors.html

Does this sound right? - NEMA question
 

On Thu, 12 Apr 2007 14:22:04 GMT, Charlie Morgan
wrote:

You may have trouble finding a zener diode rated at enough amps,
though.

In actual practice the zener diode is usually wired in series with a
resistor sized to limit amps at a safe level. Transient spikes
contain very little actual power in electrical terms, only high
voltage which zener diodes shunt to ground.

That said, I've been operating boats with sophisticated electronic
systems for many years, have never taken precautions when starting the
engine(s), and have never experienced any transient related failures.

Does this sound right? - NEMA question
 

"Charlie Morgan" wrote in message
...
On Thu, 12 Apr 2007 09:59:39 -0400, Wayne.B
wrote:

On Thu, 12 Apr 2007 05:34:42 -0400, "Roger Long"
wrote:

Isn't there something that could be inserted in the feed to the
instruments that would restrict voltage spikes?

Yes, it's called a zener diode and they come in different voltage
ratings.


You may have trouble finding a zener diode rated at enough amps,
though. You might do better by wiring in an LM7812 voltage regulator
at each instrument you want to protect. They are rated at 1 amp output
if you mount them on a heat sink.

The 7812 will lose a significant amount of voltage across it. The 7812
drops about 2V if I recall correctly, so if your battery is putting out
12.5V, for example, the regulator output will only be around 10.5V. If the
battery is above 14V, the output would be held at 12V (the drop may only be
1.5V, but the principle is the same).

There are other regulators with much lower dropout voltages, but you will
still lose something, which will cause your electronics to flake out sooner
as the battery discharges.

There are high-power clamping devices called MOVs (Metal Oxide Varistors)
and SADs (Silicon Avalanche Diodes), that could be used, but the problem
with any clamp (Zener, MOV, SAD) is that the current levels you get in a
starter-motor inductive kick will be quite high, so you need to introduce
some series impedance -- a large choke, for example. This will limit the
current the clamp has to handle. It gets complicated pretty quickly, if you
are going for bulletproof. MOVs also have pretty gradual clmaping
thresholds, so they probably will only be good for clamping 18V+ levels
anyway. SADs have tighter specs, but the other problems remain.

I recommend a separate battery for the electronics, if you can figure out
how to charge it. Better still is having a house battery and a starting
battery.

-Paul

Does this sound right? - NEMA question
 

"Roger Long" wrote in
:

3) A NC relay wired into the starter circuit that disconnects the
instruments when the starter button is pushed. When the button is
released however, isn't there a chance that the magnetic fields could
still be collapsing through the starter coils after the relay
releases? I was taught on aircraft that shutdowns are more of a hazard
than starts. Same GPS restart issue as above.


Relays aren't that fast. That would work fine. You could also INCREASE
the dropout time of the relay with a big electrolytic capacitor across the
relay coil that would hold it closed until the capacitor discharged through
it....just a few hundred milliseconds would be necessary....

Of course, with the momentary shutdown, you'd have to reboot all the stuff
because it all uses electronic power switching, not an on-off mechanical
switch...which takes some time.

Larry
--
We'll watch for your boat....(c;

Does this sound right? - NEMA question
 

Paul wrote:

You may have trouble finding a zener diode rated at enough amps,

For just a depth sounder, knotmeter, portable GPS, and radio is that likely
to be a problem?

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.

I'll confess though, I'm trying to figure out how to work a starting battery
into the engine room. It would have to be aircraft or motorcycle size but
that should get my little diesel going. People have started them with a
handful of flashlight batteries taped together.

--
Roger Long

Does this sound right? - NEMA question
 

Wayne.B wrote:


That said, I've been operating boats with sophisticated electronic systems
for many years, have never taken precautions when starting the
engine(s), and have never experienced any transient related failures.

When you think of all the single battery small motor boats out there, many
of which have a far more extensive set of electronics than my boat, it does
seem like this could be one of those "always wear clean underwear" kind of
things. OTOH my understanding is that it is not so much a matter of things
blowing out or dying when you start the engine as it is of their life being
shortened as the transients eat away at the connections inside the IC chips.
If something dies this way, you might never know that it could have had a
few more years if protected.

I remember now that I often found the GPS off or looking for birds again
after starting the engine when coming into the harbor. I was always too
busy at the time with getting sails in and such to think about it. Now, I
wonder. The depthsounder and knotlog seemed unphased.

--
Roger Long