FollowupID: 686534 Submitted:
Wednesday, May 12, 2010 at 17:29
Dumb question? No such thing. Only answers and people (ie - not J&V!!).
To expand on the above...
Just a teeny weeny little bit...
Pins are fine - more below.....
For the record.... ideally an extension cable with taps/junctions etc.
Noting that all suggestions below are for this low voltage 12V DC example only - not AC systems etc.... (Yes John!)
And the next two text blocks can be skipped of you think pinning or wire-wrapping is achievable.
Where fuses are user replaceable, it can be "tapped into" with a thin wire etc - usually that's in the +ve supply (and -ve/gnd/earth is the metal chassis) - BUT that can be awkward, and if you do NOT know the internal connections, how do you know any drop is not caused by internal switches etc. Though fuses are usually the first electrical item - even before power switches.
Then there is the flying lead method - pins, nails and jumper-leads with alligator clips etc.
The main hazard
is accidental shorting of the +12V & ground, but an upstream fuse should blow if the jumper lead doesn't melt & flame first (if the short is downstream of the jumpers - ie, at the fridge).
is underrated jumpers that can get hot (and flame & melt insulation etc), but the ~5 Amps involved should be ok.
BTW - the voltage test is done at the end of the cable - not at the fridge: You are not interested in the voltage drop from the jumpers (unless it is so bad that the fridge does not operate).
Then the wire-wrap method: With THIN wires, wrap their conductors around the load's connector pins (since all loads should have male connections).
Insulated wires may not be necessary if there is no chance of shorting to chassis or each other.
They need to be thin enough to enable the power socket (lead) to be inserted properly.
Then, lastly, there is someone's brilliant suggestion of inserting pins....
This should not be done on voltages higher than (say) 50V.
This is probably the most common method used by the experienced that do not have a proper junction/splitter, and by clever else stupid DIYers.
If it is obvious which part of the cable is +ve and -ve it should be fine.
You then stick a pin through each insulation to hit the conductor (or pass through).
But do NOT pass a pin through one conductor into the other - that's a short circuit. Even though that should blow the upstream fuse, there is the ongoing problem of the insulation hole between the conductors, and possible contamination....
But other insulation holes can be plugged etc (silastic maybe?).
NEVER do this for domestic mains and other hazardous voltage appliances!
Above are the 5 common methods - the first is "approved"; the others may not be. And those others have their hazards.
BUT, the load/fridge itself should NOT be damaged by those hazards.
IE - the hazards
involve shorting BEFORE the load. This is normally ok - you may blow the crap out of the battery or upstream distribution (fuses, cabling), but the load should be fine. Exceptions may include loads with large capacitors (ie, audio systems), and where repeated shorting occurs (ever heard "maybe a short blew your light bulbs"? - how does a short blow light bulbs? - except through repeated shorts or intermittent bad contacts that cause excessive thermal cycling etc... LOL (excluding inductance)).
Hence ensure a reasonable sized fuse - say 5 or 10 Amps - enough to handle the fridge and any inrush current.
If a short does occur, there can be sparks, flying plasma & noxious fumes. Wear safety glasses. Consider a suitable fire extinguisher. Update your insurances or Ambulance Subscription. And Will.
And be aware that voltage measurements do not involve large currents - a hair strand of copper will do.
A typical powered DMM measuring 12V takes well under 1uA (one-millionth of an Amp).
Hence pins and tap-wires can be as thin as anything. If they break, you will measure zero or random voltages.
Being thin means a small current to blow the short. Hence skin and carpet burns won't be as bad. (Do not do this near unlit gas-venting stoves, near petrol-station vent ducts, in wheat silos etc.)
Too much ramble? You confessed to being and avid DIYer, so I gave you the lot FYI. (Good - there are like-minded people on this site! At least DIY minded - but maybe far more concise & verbally gifted!)
Assume the standard no-care and no-responsibility riot act (even if it means nothing LOL!).
Unless you are plagued by heaps of disasters, try it.
Next step - WHERE are the voltage drops - grounds? +12V? Protection (fuses/breakers etc)?