Wiring question: Going from larger wire to smaller wire

[atlbraves49]

I could use some tips on the following setup..


Will have a larger wire (i think its 14 AWG) going into a metal box, but then inside the box i need to switch over to smaller wires (breadboard type) for the circuitry inside. Is that possible? And if so, how do i go about making that switch over.


Just a basic idea of what I am talking about.. the red wire is the larger wire, and the blue wire is what's connect to a breadboard inside the box

http://img3.imageshack.us/img3/737/wiringgr8.jpg

 

[OmCheeto]

I could use some tips on the following setup..


Will have a larger wire (i think its 14 AWG) going into a metal box, but then inside the box i need to switch over to smaller wires (breadboard type) for the circuitry inside. Is that possible? And if so, how do i go about making that switch over.


Just a basic idea of what I am talking about.. the red wire is the larger wire, and the blue wire is what's connect to a breadboard inside the box

Either solder the wires together or use a wire nut.

 

[gunslingor]

Or used a connector block of some sort. They have ones specifically for converting wiresizes. Search on Digikey.com.

 

[atlbraves49]

I guess another question is.. can breadboard type wires handle 25W? Id like to put my power mosfet and resistor on a breadboard and connect them that way.. i just want to make sure the wires can handle it too.

 

[berkeman]

I guess another question is.. can breadboard type wires handle 25W? Id like to put my power mosfet and resistor on a breadboard and connect them that way.. i just want to make sure the wires can handle it too.

If you mean the little white spring-contact 0.1" grid breadboards, no. They should have a spec for the max current per contact -- I'd guess it's around 100mA, but it could be less. The little white plugboards are for low-power digital and analog prototyping.

You will be needing heat sinks to the metal case for your power prototype, right? You can prototype low-power control circuitry on the breadboard, and using flying wires up to the power stuff mounted on heatsinks.

BTW, depending on your power device, its tab (or whatever) may not be ground. You may need a piece of mica between the power device and the heat sink -- check the specs of the device. And it helps to use heatsink grease -- gives a lower Theta J-A.

 

[atlbraves49]

im talking about something like this:
http://www.allelectronics.com/make-a-store/item/PB-400/SOLDERLESS-BREADBOARD-400-CONTACTS/-/1.html

was planning on inserting the power mosfet:
http://www.irf.com/product-info/datasheets/data/irf640npbf.pdf

in series with this resistor:
http://www.ohmite.com/catalog/pdf/tch.pdf

with typical breadboard wires

and both the power mosfet and resistor will be fitted with their own heatsinks
http://www.aavidthermalloy.com/cgi-bin/stdisp.pl?Pnum=6396bg
http://www.futureelectronics.com/en...-accessories/Pages/4002283-593002B03400G.aspx

 

[berkeman]

im talking about something like this:
http://www.allelectronics.com/make-a-store/item/PB-400/SOLDERLESS-BREADBOARD-400-CONTACTS/-/1.html

I don't see a contact rating, but I'd still guess about 100mA max. What currents are you wanting to run through the breadboard?

 

[berkeman]

Also, remember that 22AWG wire is only rated for 7A, so you need to think about what wire size you will need for the power wiring inside the box:

http://www.powerstream.com/Wire_Size.htm

 

[atlbraves49]

I don't see a contact rating, but I'd still guess about 100mA max. What currents are you wanting to run through the breadboard?

not sure exactly but probably
anywhere between 0.5A and maybe 5A?

if not a breadboard, what kind of board should i use to make these connections?

 

[berkeman]

not sure exactly but probably
anywhere between 0.5A and maybe 5A?

if not a breadboard, what kind of board should i use to make these connections?

The next step up from the white plugboards is to use 0.1" spaced prototype boards, which have a plated-though hole per pad on that spacing. They come in lots of different form factors and styles:

http://images.google.com/images?hl=en&q=prototype+board+plated&gbv=2

Even that is going to be problematic for 5A current levels. You can probably use the protoboard up to about 500mA to 1A, and then beyond that you will either need to just use soldered fly-wires, or make your own PC board with wide traces:

http://www.desmith.net/NMdS/Electronics/TraceWidth.html

 

[Proton Soup]

how many components you looking at here? if it's just a few, i wouldn't even bother with things like plated-through hole perfboard. just grab a piece of plain perfboard with no metal, just holes. cut to size and put on standoffs in the box. then just poke all your components through the holes and solder up appropriate size wires. easy-peasy. it won't be pretty, but it's hidden in the box.

 

[MATLABdude]

Since this thread is trending towards simpler and simpler...

Assuming you solder a few components together, and don't have any perfboard you can use hot glue to insulate and add extra robustness to your circuit. TIP: use a heat gun or a blow driver to reflow the glue and make it look less like you hot glued your circuitry together. Great for waterproofing / encapsulating small circuits.

Think of it as a poor man's potting compound / epoxy. I suppose you could use electrical tape, but I'm not so much a fan of that, since it tends to get pretty messy and falls apart depending on conditions and how much you paid for the roll. Hot glue also usually comes off pretty clean if you rub at it, and make a cut or few.

It could be worse. I remember reading about a pita breadboard a while ago, and an associate of mine used cardboard for a temporary job.