DC wire gauge question

[mjs483]

I'm following the instructions on this thread for my stirplate build. One of the things needed is a small amount of scrap wire to connect the power switch to the potentiometer. My question is, what types and gauges of wire are suitable for this?

I know I can probably just cut some extra wire off of my pc fan and not worry about it, but I might as well learn a thing or two through this project . I have some stranded 14 gauge copper wire from a home improvement project, but something tells me that is not the wire I want. What are the dangers of using the wrong gauge wire in 9v-12v dc power projects?

 

[lschiavo]

The wire needs to be sized for current regardless of ac or dc. You can always oversize wire. It is only undersized wire that will be dangerous (too much current=heat).

 

[mjs483]

Ah ok. Well then I suppose the stranded 14 gauge I have will work.

 

[DevilsCreekBrewing]

14ga is serious overkill.

What is the amperage of the transformer you are using?

 

[lincoln]

for small project i mostly use 22 awg, which is good for 7 amps, next size i keep is 18 awg fo stuff from 7 to 15 amps (for projects only not house wiring)

link

 

[mjs483]

Ok, yeah it looks like the DC transformer I'm using has 22 awg according to the markings on the wire. It had a pretty long cord so I cut off some extra to use as my scrap wire.

A couple of other things... I noticed that my transformer's output is 9V, 500mA and my PC fan is DC 12V, 0.2A (200mA). Am I going to burn out the fan with this transformer? Seems over 2 times the amps is a little much.

Also, my transformer does not have a black and red wire just two black ones, but one of the black ones has white/gray dashed line painted on it. Any idea which is the ground? I suppose a quick round of trial and error should solve that one though...

 

[lincoln]

well some basic electricity, think of water in a pipe. voltage is the pressure the water is under and the current is the volume, or how much is flowing. your transformer can supply up to half an amp and the fan required .2 amps. now the fan takes more pressure to run at full speed, 12v while the transformer only puts our 9v. for a stir plate i don't think it matters that much since you will not be running the fan at full blast.

I am assuming that the transformer is a plug in type (id wall wort) i can never remember which is witch polarity. easiest is to just strip and twist the wires form the fan to the ps and see if it spins the right way, if it runs in reverse swap them.

 

[BrewBeemer]

I am assuming that the transformer is a plug in type (id wall wort) i can never remember which is witch polarity. easiest is to just strip and twist the wires form the fan to the ps and see if it spins the right way, if it runs in reverse swap them.

Many muffin fans will only run with the correct polarity connected to them and will not run at all with reversed polarity. It will act as if no power at all was connected if reversed. This besides the internal thermal overload protection taking app 10 seconds to cool down and close the circuit again.
The real pigs but have more torque for example are 120mm muffins like NMB or Minebea Co Ltd that are 12 VDC and draw 0.72 amps. Higher current plus more torque even at reduced stir bar speeds.

 

[Espi]

well some basic electricity, think of water in a pipe. voltage is the pressure the water is under and the current is the volume, or how much is flowing.

IMO the best way to explain it and use it quite often at my job..

 

[lschiavo]

Ok, yeah it looks like the DC transformer I'm using has 22 awg according to the markings on the wire. It had a pretty long cord so I cut off some extra to use as my scrap wire.

A couple of other things... I noticed that my transformer's output is 9V, 500mA and my PC fan is DC 12V, 0.2A (200mA). Am I going to burn out the fan with this transformer? Seems over 2 times the amps is a little much.

Also, my transformer does not have a black and red wire just two black ones, but one of the black ones has white/gray dashed line painted on it. Any idea which is the ground? I suppose a quick round of trial and error should solve that one though...

The transformer rating is the maximum load it will supply safely. It should be sized equal to or larger than the load. The transformer does not push current the load pulls it.

I used 14 guage for my stirplate (had it laying around) as long as it is rated for the current and fits on the terminals it will work fine.

 

[BrewBeemer]

Ok, yeah it looks like the DC transformer I'm using has 22 awg according to the markings on the wire. It had a pretty long cord so I cut off some extra to use as my scrap wire.

A couple of other things... I noticed that my transformer's output is 9V, 500mA and my PC fan is DC 12V, 0.2A (200mA). Am I going to burn out the fan with this transformer? Seems over 2 times the amps is a little much?

You can have a 500 amp 12 VDC power supply feed that 200mA fan without a worry just have the 22 gauge wire fused for protection. This would not be practical for the application by size and cost but just as safe as your 500mA wallwart. The larger 1,000mA or 1,500mA wallwarts are my favorites allowing me to run other items off it as well to handle the inrush current of a motor or fan starting.

 

[mjs483]

Nice analogy with the water and pipe. Thanks for all the replies too, that really sheds some light on this stuff. Can't wait to get this thing running this weekend