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Old 04-12-2010, 18:53   #16
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Hi daddle!

I'm too busy (getting ready to go sailing for a few weeks) to agree or disagree with you, but what if the load is insignificant compared to the battery capacity? Or, as is much of the time, the batteries are being charged, either by wind/solar, or the engine? Are you giving me food for thought, or are you saying that it is useless to have separate CB panels for the electrically "noisy" and "quiet" components?
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Old 04-12-2010, 19:18   #17
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Ahhh....you make the question complex enough that it becomes an engineering project.

I'd say follow all the general rules. Good batteries. Marine quality devices. Short wires properly sized. Properly installed marine terminals. Run the positive wires next to the negative wires.

Having separate panels for sensitive devices and disruptive devices is a good idea if needed. It's inconvenient to have the SSB reset the instruments, certainly.
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Old 05-12-2010, 06:41   #18
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If you have good low resistance paths from the breakers to the battery then it doesn't matter that inductive and resistance loads are " mixed". It all one one common ground and feed anyway. It's " good practice" to separate them and run seperate grounds back through their own panels to the batteries. Good practice is often specified to make up for lack of understanding of basic electricity amongst installers. It's always amusing to see arguments over " good practice" and first principles .

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Old 05-12-2010, 13:24   #19
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Escape-
Last time I did this I tried to keep "used together" stuff next to each other. i.e., nav lights all together. Instruments and radio (which is by itself) together, since they normally all go "on" as soon as we come aboard. And since that's usually #1, they can go to the top, or corner, followed by other groups that are "firstest". Cabin lights all together. Macerator breaker <G> anyplace obscure but close to the pressure water pump and other "plumbing". And since the bilge pump gets a prominent "find it in the dark" corner location, the other "water stuff" probably will be next to it.

Ask yourself also, if I have to stay on the helm and send some newbie below in the dark to turn things on, can I just say "Turn on the top right..." or do I have to tell him to get a flashlight and start hunting?

Eventually a pattern forms and you'll find one "best" way to group things. Including a couple of empty/spare slots, one hopes.

I also added in an aluminum panel box, about the size of a sardine tin, with spike protection and a warning buzzer on the "instrument" breaker. Just a couple (redundancy) of spike protection devices, a fuse and a piezo buzzer, so that if there's a serious power spike the devices should clamp it right at the panel. And if the devices blow, or there's high voltage on the output, the piezo buzzer should go off. Apparently voltage spikes are one of, if not the #1, cause of mysterious electronics deaths. 15V protective devices are cheap, usually under a buck apiece, from electronics houses.
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Old 05-12-2010, 14:09   #20
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Shipshape,

With regards to separating the noisy buss from the quiet buss, you have a point if you go through the combiner switch for everything, but must you? If you were to take the quiet buss directly off of the house bank you would get the desired effect most of the time. Think of the house bank as a big bucket full of water with two hoses coming out of it. In your case you run a single hose from the bucket to the switch then a y to both busses. When you turn off a motor on the noisy buss the flow shuts off suddenly and you get a pressure pulse through the entire system, just like the water hammer effect in plumbing when flow is cut off suddenly. If you have two separate hoses coming from the bucket when you shut off the motor you still get the pressure pulse, but it travels back through the bucket which absorbs almost all of the force and almost no pressure is transferred to the second hose.

While water and plumbing isnít perfectly analogous to electricity, sometimes itís close enough illustrate a point without getting into the physics of back EMF, collapsing magnetic fields, etc, since most people have experienced the effects of water hammer at least once.

Since the banks ate technically still on the same circuit, if you need to combine the banks youíll still get power everywhere you need it. The limiting factor is that if you are measuring amps coming off of your bank through that circuit you would be missing the amps going to the quiet buss.
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Old 05-12-2010, 18:04   #21
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Im just about to actually install the new panels. Have a 1/0 feed for the panels from a main positive bus at the battery switches along with a 1/0 ground back to the main ground bus that feeds the dual shunt for metering. Pretty sure I have the panel layout figured but am interested in the idea of voltage protection for my instrument circuits. What sort of devices was hellosailor referring to that would provide surge protection on a 12 volt circuit? Im pretty much a raymarine whore at this point so everything is on seatalk with one run of 8 guage postive and negative going to the autopilot for power, all the other instruments get thier power via sea talk cables.
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Old 05-12-2010, 18:05   #22
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Hellosailor , what devices did you use transzorbs , mov's etc usually the problem with these is currently ability . The biggest problem on any 12v network with big loads is " load dumping " such transients are several 100 milliseconds long and can easily overwhelm surge suppressors .

Don't quite get the piezo buzzer , how is it wired in ?

Dave
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Old 05-12-2010, 18:25   #23
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TVS - Thyristors | Newark.com

Thyristors, zorbs, even zener diodes set up as a crowbar across the power line and a ground. With a fast-blow (i.e. "instrument") fuse in one leg, so if it takes a surge and conducts, it will look like a crowbar short and the fuse will blow if the surge has significant power or duration. Cutting off instrument power completely, but blocking a surge.

If I could recall how I got the piezo wired in...<G>...I think in-line with the protection devices, so that if the "crowbar" conducts the piezo has to sound, at least until the fuse blows.

Not perfect--but an attempt at protection. I used multiple devices (i.e. zener + zorb in parallel) to try compensating for the fact that one might be slow while the other might be easy to burn out, or prone to burn out over time.

Since the protection is only installed after the breaker, on the instrument-online power line, the worst "dumping" they would see is from the instruments themselves, and those are fairly small sources. In theory the battery swamps out the heavy dumps. Maybe this is real protection, maybe its worthless, but for under $20 including the breadboard and box (the most expensive part of course!) I felt it was worth a shot.

I'm told that most manufacturers won't include spike protection in their devices simply because if they do, if will eventually fail, and then the customers complain about why it failed or why it wore out. If the whole thing just blows out--they can blame your electrical system and sell you a new one. Much easier, who can argue?
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Old 06-12-2010, 09:36   #24
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Okay I see the link but tell me what exactly am I doing here? Leaving the breaker for my instruments is an 8 guage positive lead to the Autopilot. All the instruments get their power via SeaTalk cables.
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Old 06-12-2010, 14:41   #25
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Typically you would supply power to something (such as the autopilot) and then the Seatalk buss can distribute the power to the other instruments, OR they may have separate power leads. If yours are all being fed by the buss, then you would install the spike protection somewhere convenient in between the instrument breaker and the autopilot. In theory, at the base of the autopilot to give it the best protection against anything the wires picked up. In practice, probably just as effective if installed at the breaker panel where it was "more power stuff" all in one place.

The 8g wire is sized to prevent voltage drop to the loads. Rash guess...maybe all your instruments, including the autopilot, and their lights, draw...5A? 10A? more if there's a radar in there?

You want to connect the surge protection devices with one end on the positive line, the other end immediately to ground. Preferably the same ground line that runs to the autopilot and Seatalk bus. So if there's a point where both lines run out of the breaker area and come together to go aft--that's a good point for the surge protector.

If you're viewing this in a fixed width font it won't look like dogs'dinner:

Breaker+[=]+++++++++++++++++++Autopilot & Seatalk
Panel 0 |
0 |
Ground-----------------------------------------Autopilot & Seatalk


Where you see the 0 and | characters? That's how you hook up the spike protection, from the + to - wires, right across them. The [=] is intended to show the fast blow fuse location, after the breaker, in the instrument power line, but before any spike protection.

The fast blow fuse should be sized for just what your instruments need--including the autopilot under full load, radar under full power, whatever the equipment needs. It is not there to protect the wire, the breaker is doing that, so don't be surprised if you've got maybe a 15A breaker and a 5A fuse, that's OK in this case, each is there for a different reason. If one of the spike devices conducts, and it is a fast surge/spike, the fuse will ignore it. If it is a larger or longer surge/spike, the fuse blows. The lower the rating on the fuse, the faster it blows. (Which is also why it needs to be a fast-blow instrument type fuse, not the more common and forgiving slow-blow fuse.)

Since fast-blow fuses aren't always easy to find, also buy a small box of spares. Another buck or three, label and keep someplace where they won't get lost.<G>


Device specifics:

If you hook up a diode "this way" it conducts. if you reverse the polarity it doesn't. With a zener diode, it doesn't conduct at all until the voltage is reached, i.e. with a 15V zener diode it doesn't conduct until it sees 15V, then it acts as a short circuit. You can find web articles about how the diodes are marked and which way to connect them, I'd suggest that since they are cheap, you buy a couple of spares because it is not unusual to smoke one the first time around.<G>

Other devices don't care about polarity, you need to check the specs on each type.

I know the guys at DigiKey are great at tech support, Newark probably also is, either should be able to tell you what components they have in stock that will do the right job inexpensively. Or point you to some manufacturer data sheets that have clear diagrams and explanations. If you can wire up a cabin light and switch, this is just one step more.<G>

These days...who knows, maybe some car stereo places are selling spike protectors for car stereos, it's the same "twelve" volts. Your target is probably going to be 15 volts, since a "12" volt system is really 14.4 at full alternator voltage, and NEVER exceeds 14.4 unless there's a problem. This would also protect your instruments in the event of a regulator failure putting 17V into the system. Or, if you accidentally powered up the instruments while doing a 15V+ equalizing charge on the batteries.
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Old 06-12-2010, 14:54   #26
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Okay I think I get it. I like the idea of the zener diode better I think than the fuse. You are right in that my instruments are all fed power via sea talk. Power from the dist panel goes to the autopilot then sea talk cables do the rest. My autopilot is hydraulic and offshore in a seaway it can take 10-15amps and the run round trip might be 40' hence the 8 guage wire. But the other instruments are pretty miniscule power draw, radar on its own circuit. Its not so much the amperage Im concerned with. Its the voltage. So yes protecting from a 15 volt or higher spike is what Im after. Zener diode then huh?
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Old 06-12-2010, 15:14   #27
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Using a crowbar to protect from spikes is like using a wrecking ball to swat flies. It'll work, but it's a bit hard on the walls. The Ziener once triggered causes the SCR (Thyristor) to conduct until the fuse blows then you have no power on your instrument buss until you replace the fuse. Since you'll get a spike above 15V almost every time you get some back emf on a 12v line you'll trigger the crowbar. You'll need a boat load of fuses. The transorbs will help a lot, but they wear outas they get a little bit damaged everytime they absorb a spike. Unfortunately they don't show any outward signs that they need replaced. Another method of absorbing voltage spikes is using a large capacitor connected between power and ground. This will act a lot like the battery as far as spike absorbsion is concerned. The problem is that it will hold a charge once power is removed if it is not discharged and unlike a battery it has little internal resistance and can dump all of it's energy in microseconds. It can give one quite a jolt even at relatively low voltages.
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Old 06-12-2010, 16:08   #28
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"The Ziener once triggered causes the SCR (Thyristor) to conduct until"
Except, the Zener is not being used to make anything conduct, it is just being used by itself as a crowbar. And crowbar protection is considered standard and adequate for many simple needs.
From personal experience, the fuse does not and will not blow from ordinary spikes in the millisecond range. Even fast-blow fuses are not that fast.
Yes, capacitors can absorb spikes but apparerntly, some get past them. Caps are not protection enough, and they won't protect against things like "oops, that's equalizing voltage" whereas a crowbar will reliably protect the instruments from a regulator failure.
Zener diodes are old school (compared to transzorbs or other devices that are faster and slightly more expensive) but they are the standard component for that purpose. Caps are used more for filtering, not purposed for spike and overvolt protection. And remember, every excess volt you shove into a capacitor--is gonna come back out the other end. That's still not protection.
If you use the zener in this mode without adding a fast-blow fuse, remember that the zener now becomes the "smallest wire" in the circuit when it is conducting. It is possible for the zener to fail, either literally blowing apart (hooray!) or shorting out, in which case there's a fire risk if that main breaker doesn't blow. I wouldn't consider the fuse optional. If you are afraid to put it as shown, then stick it right on the base of the zener, so at least if the zener shorts out, the fuse blows and ends the short.

Sparky says: Fuses good, fire bad.
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Old 06-12-2010, 21:20   #29
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Regular lights are pretty much immune to the effects but these spikes are death to LEDs and LEDs are expensive. When you see complaints about LEDs not lasting it's probably spikes or corrosion
Any good LEDs light fittings should come with some form of voltage regulation and surge minimization also I would not fiddle with a Seatalk bus unless Raymarine recommend it. Their system comes adequately protected. Zener and fuse? Once the fuse is gone so is the protection. Zener and resistor work adequately and so are freewheeling diodes. Beware of these new multistep chargers which float at 16.7V.
Hello Hellosailor sounds like you are able to source zener these days.

Quote:
Originally Posted by chala View Post
The battery monitor is protected against voltage spikes by a 10-ohm resistor and a 16V zener diode
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Old 07-12-2010, 10:39   #30
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Sounds like a lot of soldering and sourcing of small components from am electronics store. Is there not soemthing I can buy off the shelf that can be easily wired in where the positive wire leaves the distribution panel?
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