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#1 buckeyestargazer

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Posted 18 February 2020 - 10:34 PM

If an electrical connector says it is rated at 10A and also rated at 50v,does that mean at 12v the amperage can be higher?

I'm putting together a custom 4 outlet dew controller and each port will have a max current of 5A. So the power port needs to be able to handle 20A. I'm just not sure if the above power connector (10A 50v) will do the job.

#2 bdyer22

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Posted 18 February 2020 - 10:41 PM

Volts * Amps = Watts.  So 10A * 50V = 500W.

so if you convert to 12V then 500W/12V is approx 41Amps.  Just need to step down the power to 12V



#3 buckeyestargazer

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Posted 18 February 2020 - 10:48 PM

Volts * Amps = Watts. So 10A * 50V = 500W.

so if you convert to 12V then 500W/12V is approx 41Amps. Just need to step down the power to 12V


OK thanks. Next question, will 18awg wire handle this? It is rated for 16A but again that's at a higher voltage.

#4 dogbiscuit

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Posted 18 February 2020 - 10:48 PM

At 12V you are still limited to 10A


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#5 dogbiscuit

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Posted 18 February 2020 - 10:54 PM

OK thanks. Next question, will 18awg wire handle this? It is rated for 16A but again that's at a higher voltage.

The rating is what it is.

if it's rated at 16A, don't exceed 16A.  Voltage doesn't enter into it except for the insulation rating.

 

For the connector the rating is not stated in watts, but V and A.

The V rating and the A rating both apply.  Exceed neither.


Edited by dogbiscuit, 18 February 2020 - 10:59 PM.

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#6 bdyer22

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Posted 18 February 2020 - 10:57 PM

OK thanks. Next question, will 18awg wire handle this? It is rated for 16A but again that's at a higher voltage.

 

The wire should have a rating, follow that.  and you should have fuses for each of your connections to your max amperage of 5 amp.  Better to burn a fuse than you equipment.


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#7 buckeyestargazer

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Posted 18 February 2020 - 11:01 PM

Here's what I'm looking at.

https://www.amazon.c...ob_b_asin_title

#8 gr5org

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Posted 18 February 2020 - 11:30 PM

Do not multiply these 2 values to get watts.

 

If it's rated to 10 Amps that means putting more than that amount might get the wires too hot and you might start to melt things.

 

If it's rated to a certain voltage it means that if you go over that then the insulation might leak or allow sparks or some other problem with high voltage across the insulation.


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#9 TOMDEY

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Posted 18 February 2020 - 11:32 PM

YIKES! Good thing for you to ask. Ampacity is entirely voltage independent/invariant. Whether you are running at 1 volt or 50 volts, that connector can handle no more than 10A and no more than 50V. You cannot exceed either, safely. The wattage has nothing to do with it. BTW, the voltage spec is RMS if it is sinusoidal, fundamental-only AC, or regulated DC. Otherwise, must consider higher harmonic spikes.

 

PS: The reason that connectors and wires are rated for Ampacity is because they have internal impedance, which causes them to heat up, as a function of current, not voltage. The reason they also have a voltage rating, is because their insulation can withstand that, without arcing to short circuit. Either failure mode can/will cause a fire! Our DIY forum here is wonderful... but helpful suggestions are often not fully-vetted, lot of us just bloviating off the top of our heads. Often electrical, mechanical, chemical suggestions that are... risky. But, that's my world, too. I've made just about every mistake possible, and no doubt working on experiencing more!

 

And also prudent to keep substantial safety margin on all specs. We amateurs generally tend to underbuild and overstress our equipment, often to failure.   Tom


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#10 dogbiscuit

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Posted 18 February 2020 - 11:34 PM

Here's what I'm looking at.

https://www.amazon.c...ob_b_asin_title

Are you planning to use 4 of these as your outlets?  4 of these in parallel could feed 10 amps each

 

But if you plan a single connector to feed 4 downstream 5 amp outlets you will exceed the rating of this connector.

 

Think about how much heating power you really need for dew control.

I haven't made made a dew suppressor, so maybe I'm wrong about this but  5 amps @ 12 V is 60 watts X 4 outlets is 240 watts, enough to keep your coffee hot. No kidding. Seems like a lot of current at 12 V for dew control. 

I'd be very surprised if you would ever use more than 10 A for dew suppression. I think the 10 A connector would really work for you.

But maybe you have plenty of scopes.

 

I recommend you check with others who have made these dew suppression things how much power you actually need.  I think it would be just a few watts.



#11 don clement

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Posted 18 February 2020 - 11:42 PM

OK thanks. Next question, will 18awg wire handle this? It is rated for 16A but again that's at a higher voltage.

Also depends on the length of the wire.

 

Don



#12 buckeyestargazer

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Posted 18 February 2020 - 11:52 PM

The power port is to feed 4 outlets.  Each outlet has a 5A fuse.  

Regarding the power draw, the highest power draw of any dew strap I have seen is 52w or 4.1A at 12v.  I want to make sure that the whole controller can handle the full max current, which would be 16.4A.  In actual practice, most dew straps use far less current than that.  

 

So I guess I need to find a 5.5 2.1mm power connector that is rated for at least 18A. 



#13 Cfreerksen

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Posted 18 February 2020 - 11:57 PM

Just use powerpole. A very robust connector. Used by many.

 

https://powerwerx.co...34aAh5qEALw_wcB

 

Chris


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#14 buckeyestargazer

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Posted 19 February 2020 - 12:00 AM

Just use powerpole. A very robust connector. Used by many.

 

https://powerwerx.co...34aAh5qEALw_wcB

 

Chris

I thought about that and I might need to go that route.  I thought that a 5.5/2.1 barrel connector would be more universal.  



#15 jefffed

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Posted 19 February 2020 - 12:38 AM

Just to chime in, I would go with unwired connectors and solder my own wire onto them.  They are shown on the same amazon web page. The Chinese are infamous for over rating their products. Alternately there is a ton of Radio Control car battery connectors that would do the trick on ebay.



#16 marcosbaun

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Posted 19 February 2020 - 07:51 AM

YIKES! Good thing for you to ask. Ampacity is entirely voltage independent/invariant. Whether you are running at 1 volt or 50 volts, that connector can handle no more than 10A and no more than 50V. You cannot exceed either, safely. The wattage has nothing to do with it. BTW, the voltage spec is RMS if it is sinusoidal, fundamental-only AC, or regulated DC. Otherwise, must consider higher harmonic spikes.

 

PS: The reason that connectors and wires are rated for Ampacity is because they have internal impedance, which causes them to heat up, as a function of current, not voltage. The reason they also have a voltage rating, is because their insulation can withstand that, without arcing to short circuit. Either failure mode can/will cause a fire! Our DIY forum here is wonderful... but helpful suggestions are often not fully-vetted, lot of us just bloviating off the top of our heads. Often electrical, mechanical, chemical suggestions that are... risky. But, that's my world, too. I've made just about every mistake possible, and no doubt working on experiencing more!

 

And also prudent to keep substantial safety margin on all specs. We amateurs generally tend to underbuild and overstress our equipment, often to failure.   Tom

That's right. If the maximum specification is 10 amps, this limit should not be exceeded.



#17 kathyastro

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Posted 19 February 2020 - 08:57 AM

The wire should have a rating, follow that.  and you should have fuses for each of your connections to your max amperage of 5 amp.  Better to burn a fuse than you equipment.

The fuse is there to protect the wiring (and its surroundings) from fire, not to protect your equipment.  If the fuse blows, it is because the equipment has already failed and is toast - that's why it is drawing more current than it is supposed to.  You need to prevent the wiring (and the malfunctioning equipment) from overheating and starting a fire, and that, not protecting the equipment, is the job of the fuse.


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#18 buckeyestargazer

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Posted 19 February 2020 - 09:15 AM

Thanks all.  I got the answers I needed.



#19 dan_h

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Posted 19 February 2020 - 10:15 AM

 

So I guess I need to find a 5.5 2.1mm power connector that is rated for at least 18A. 

You won't find such a connector. It is physically too small to properly connect to the size of wire needed to carry that much current reliably. 

 

Even though a wire can carry its rated current without burning up, the wire resistance may be enough to cause significant voltage drop over any useful length.   For example, 50 meters of 18 gauge wire has 1 ohm resistance. This would have a voltage drop of 1 volt for every amp required.  At 5 amp load, 12 volts in is only 7 volts coming out.   Even a 10 meter length of 18 gauge wire looses 0.2 volts/amp or 1 volt at 5 amps and 3 volts at 15 amps.  Voltage drops in wiring can cause electrically noisy systems and cause strange equipment behavior and damage. 

 

So even though the contacts in the connector will carry the needed current, you can't connect large enough wire to carry that current any practical distance.  You are much better off to use a connector designed for power connections and able to mate with appropriate wire. 

 

dan


Edited by dan_h, 19 February 2020 - 10:18 AM.


#20 don clement

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Posted 19 February 2020 - 12:18 PM

What I did one time to carry more current in an available standard connector e.g. DD50 was to parallel many pins and wires.

 

Don



#21 Bob4BVM

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Posted 19 February 2020 - 02:52 PM

What I did one time to carry more current in an available standard connector e.g. DD50 was to parallel many pins and wires.

 

Don

You can take that path, but "path" is the key word if you do.

When paralleling wires & connectors to increase ampacity, each line has to be exactly equal in resistance (ohms) or the lines will NOT share  the load current equally !.  The current imbalance can be drastic with even a slight ohmic difference.  We are talking differences of milli-ohms.

 

That is why when paralleling high-current cables, the individual parallel wires are measured to exact equal lengths. The problem is bad enough that the NEC prohibits paralleling wires smaller than AWG 1/0 in power systems.

 

Adding a multi-pin connector to the mix adds another level of imbalance as the connection resistance must also be equal. Again, differences of milli-ohms will matter. Best to avoid the issue by using properly sized wire & connectors for the small DC currents we deal with here.

 

Look into the high-current stuff used by drone hobbyists, they deal in very high currents at low DC voltages, typically 20-100 amps at 8-12Vdc.

Below is a common connector rated at 60A. It has a slightly smaller twin good for 30A. Easy to find & very cheap.  Gold plated, handles large wires, and is polarized to prevent reverse-connection. The best hi-amp DC connector I have used.

 

CS

Bob

 

drone amass xt30 connector.png


Edited by Bob4BVM, 19 February 2020 - 02:57 PM.

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#22 bdyer22

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Posted 19 February 2020 - 11:09 PM

The fuse is there to protect the wiring (and its surroundings) from fire, not to protect your equipment.  If the fuse blows, it is because the equipment has already failed and is toast - that's why it is drawing more current than it is supposed to.  You need to prevent the wiring (and the malfunctioning equipment) from overheating and starting a fire, and that, not protecting the equipment, is the job of the fuse.

Yes, you make a good distinction about the role of the fuse.  I was thinking about the dew strap (in this case) being connected to the scope.



#23 don clement

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Posted 19 February 2020 - 11:18 PM

You can take that path, but "path" is the key word if you do.

 

That is why when paralleling high-current cables, the individual parallel wires are measured to exact equal lengths. The problem is bad enough that the NEC prohibits paralleling wires smaller than AWG 1/0 in power systems.

 

Adding a multi-pin connector to the mix adds another level of imbalance as the connection resistance must also be equal. Again, differences of milli-ohms will matter. 

 Guess I was lucky. I did take care to use exact length of  Teflon insulated silver plated copper wire that was carefully soldered to each pin. Also used way over kill on wire size/ number of parallel wires vs current used. I think I also used the largest gauge wire that would fit each pin. Thanks for the info and warning.

 

Don



#24 555aaa

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Posted 20 February 2020 - 03:33 PM

I wouldn't believe any electrical spec for any part on Amazon. I would believe the vendor data from Mouser, Newark, digi-key, etc who live and die by selling electrical and electronic parts.
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#25 mdavister

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Posted 12 March 2020 - 08:59 AM

I know alot has been answered already, but I'd also like to add that those DC barrel type connectors are typically rated for far less current. Some of the typical ones are 2.5 to 5 Amps max (depending on manufacturer). The ones the OP has chosen have multiple contacts around the circumference (which should help), but a similar part states a contact resistance of 30 mOhms. At 10 Amperes flowing, that's 3 Watts dissipation in the connector. It will get quite hot under these conditions. The other manufacturers that rate their connectors at lower current also specifiy a contact resistance of 30 mOhms, so I think that the 10 Ampere rating is very optimistic, and possibly a rating at which it _can_ do, but it can't for long. For steady state operation a more conservative rating would be better.

 

I would also highly agree with 555aaa about which data to trust. Amazon (at present) is flying a little loose with specs and ratings for components. Trusted distributors are the best to go by for "official" ratings.




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