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ignition/accessory distribution


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jnz01 
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Location: Wisconsin, United States
Posted: January 13, 2010 at 12:14 PM / IP Logged  
I have multiple gauges, lights, and switches that all need power from a 12v accessory. What would be my best way of connecting these items. Can I run a relay off the ignition harness to a distribution block where I can plug items in as I need. How would I go about wiring this, would I need separate distribution blocks one for constant, ground and switched or can I supply a large power source to the relay and pull power from there.
tommy... 
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Posted: January 13, 2010 at 7:42 PM / IP Logged  
You're going to be hooking/unhooking these...? Do you want them to act as an ignition or accessory circuit...? Do you have any idea how much current you will be pulling with the lights...etc...? There is alot of connectors...On my board i use these terminals...similar to a terminal cup on a sub box...I have them wired to 12v and ground...(the ones you push down to insert wire)......Mostly for checking radio's...bench-testing stuff...All low current...! Wire size, and fusing would be next to consider...? Hence the current question...
M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!
oldspark 
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Posted: January 13, 2010 at 8:12 PM / IP Logged  
I agree. What from what?
The things you describe are usually powered directly from the vehicle's wiring or existing circuits - they are usually not high power devices (assuming lights are indicators/bulbs as opposed to driving lights etc).
Some gauges etc may need to be on when cranking (ie, IGN circuit)or off when cranking (ie, ACC circuit).
jnz01 
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Joined: December 31, 2009
Location: Wisconsin, United States
Posted: January 14, 2010 at 2:39 PM / IP Logged  
I do not know how much amps these items will draw, I've tried to do a quick search, but came up with nothing. What I am wondering is if I can attach a distribution block of a relay coming from the ignition so I don't have to have so many wires coming from the single ignition wire. This will be permanent, and how many items can I put on a single relay output, and what gauge should the power input be? I have 5 2" aftermarket gauges, two small 9" led lights, and 6 single led bulbs. Also for power and ground for each item how does everyone get power to each item, run separate power wires?
oldspark 
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Posted: January 14, 2010 at 10:21 PM / IP Logged  
I doubt you are looking at more than an Amp or 2.
The LEDs only require a thin wire (ie - a mere 50mA rating should suffice, so 0.5A or 1A wire is overkill but fine.
Unless others object or see an issue....:
Just wire it to the existing meter circuit.
If that circuit blows a fuse, then run the new stuff via a relay energised by the meter circuit. The relay could get power from the battery via a 5A or 19A fuse etc.
(If you have existing electronic instruments or sensitive stuff, a (reverse-biased) quenching diode across the relay solenoid (85, 86) is recommended.)
howie ll 
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Posted: January 22, 2010 at 12:27 PM / IP Logged  
I have a 4mm cable (= 8 gauge?) directly from the battery with a 60amp maxi at the battery end. This powers 2 relays, one ign, one acc, then distributed to an added fuse box with Lucar (faston) receptacles.
oldspark 
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Posted: January 22, 2010 at 7:48 PM / IP Logged  
I tend top do similar, though lately I have been using circuit breakers rather than fuses for the main/battery end (with smaller fuses or breakers at the equipment end).
This arose mainly from a fridge circuit (via a relay from the battery relay to fridge whilst the vehicle is charging) that blew the main fuse (it wasn't yet alarmed).
But since the I have tended to use circuit breakers for things like headlights/lights (d'oh!) and "main power feeds" to smaller circuits (eg, battery to audio & accessories via dedicated cable/bus as above).
tommy... 
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Posted: February 04, 2010 at 2:18 PM / IP Logged  

oldspark wrote:
I tend top do similar, though lately I have been using circuit breakers rather than fuses for the main/battery end (with smaller fuses or breakers at the equipment end).
This arose mainly from a fridge circuit (via a relay from the battery relay to fridge whilst the vehicle is charging) that blew the main fuse (it wasn't yet alarmed).
But since the I have tended to use circuit breakers for things like headlights/lights (d'oh!) and "main power feeds" to smaller circuits (eg, battery to audio & accessories via dedicated cable/bus as above).

I've always heard the opposite... especially for electronic components...Here is one's reasoning...

Reliability:
In my opinion and from my experience, circuit breakers are less reliable than fuses (especially when the breaker is mounted in the harsh environment under the hood). Quality fuses like ANL and Maxi fuses have a solid element (no solder connections) and will almost never have an intermittent or poor electrical connection. A circuit breaker will eventually have higher contact resistance than when it was new. This is especially true if the breaker has been tripped (by overcurrent) more than a few times. If you're going to compete and can't take a chance of having a problem like a bad connection in the power line, you should use a good quality fuse. Now I know that people have had fuses blow in competition but it was because the fuse was not properly rated, not because the fuse was defective.
M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!
oldspark 
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Location: Australia
Posted: February 04, 2010 at 5:25 PM / IP Logged  
I agree! And thanks for highlighting it. (Very few electronic appliances use breakers, and those that do usually have downstream internal fuses to protect the circuitry.)
I should have emphasised the fridge & headlights application, and as a "master" fuse - ie, wiring protection.
IE - non electronic loads, or where an automated re-try is desirable (as opposed to once blown, dark forever or off wine and melted chocolates), or when not for individual load protection.
And I was focused on gauges (usually not fully electronic) and Howie's 60A maxi fuse (ie, distribution protection, not load protection).
Though I should point out that some breakers are far superior to fuses - they can be far quicker, more sensitive, and have programmed response.
Fuses are a thermal response that adds resistance to a circuit (and as current increases).
Not so for all breaker types. But most auto etc breakers are thermals too.
As to contact resistance etc - without exercise it's similar to an unremoved fuse.
With exercise, they remain clean like "whetted" car points (eg - RCBs or "safety switches" (sic) require/suggest regular testing).
With excessive overcurrent tripping, contact deterioration should not occur, but that can be a quality issue, else refer to specs.
For competitions - use a fuse if you are allowed to change it, else use a new breaker. Otherwise, as in racing, use a breaker.
And when fault finding, use a breaker if it's cheaper or less hassle than fuses.
jnz01 
Member - Posts: 7
Member spacespace
Joined: December 31, 2009
Location: Wisconsin, United States
Posted: May 07, 2010 at 1:05 PM / IP Logged  
If I were to run a separate accessory circuit for these items what gauge wire would you recommend.
I have 5 2" aftermarket gauges
Led underglow
two 9" led bars
and I plan to add more in the future it just seems everything wants switched power and rather than running everything to one wire I like the idea of a relay triggered from the accessory wire in the ignition. What gauge wire should I run for the constant 12v, trigger, ground, and wire to the distribution block. Also what gauge wire from the distribution block to the accessories.
Thanks a lot for the help.
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