vtl1180ny

I'm also trying to figure out what he's getting at... The PS is grounded, the ground runs to the case... The box on top with the binding posts is 12v and doesn't need to be grounded.... I ran the switch into the neutral wire, it's a 110v switch, the power LED runs off the 12v side and I have a fuse on the 12v side...

dpaton

Neil-
You really need to chill out dude.

If you'd bothered to read the rest of the thread, you'd have noticed that I've already gone over grounding, several times.
I've also gone over which prong goes into which part of the outlet. I explained the difference between hot and neutral, the color code, and the basic safety requirements for these supplies.

And I did it all without coming off as a holier-than-thou jackass, which you seem to have failed at.

Most of the supplies the guys are using are anything but POSs. They're the same supplies that are OEM'd to hundreds of companies every day and function without fault in products for years. Internally, they're no different than the supplies from Novak and others. All that's required is a careful observation of the directions and a reasonable amount of common sense.

As far as them being a fire hazard, they're no worse than the hot lightbulbs people have for lighting their pit space or the nitro fuel that the gas guys use all the time. Racers are pretty good about not causing things to burn.

We're all nice polite people here at RCTech. Why don't you try it out.

vtl1180ny-
Always switch the hot side of the circuit. Neutral is usually pretty close to 0V. Hot is always 120 or more. Keep them volts in check...switch the hot lead.

-dave

kickind

Wow, dpaton you sure have a lot of patience. Thanks for throughly explaining a very tricky situation, several times.

If I follow this correctly, this power supply will work for plugging my charger into it. I have a Digital Intellipeak, and the power supply on it is the worst part. It overheats and then I have to wait for it to cool off to finish charging. This other supply would take its place and allow me to charge more efficiently, right?

Thanks for the help. I have always wondered what use the power supplies would have.

David

dpaton

I do what I can.

It looks like it. Plug the chargers DC input into the power supply and flip the whole mess on. Justmake sure to follow all of the relevant directions, here, on your supply, and for your charger.

Well, if you get the really big ones like I have (15lbs, 75A), they do double duty as welders (if you make a mistake) cooling fans (if they're lightly loaded) and door stops (when I'm not at the track).

-dave

kickind

Speaking of cooling fans, I have several leftover computer fans that I know I can hookup to cool batts and such. How could I do that to work off this power supply?

disaster999

iTrader: (1)

make sure that the fans are 12VDC!! then just hook up the red to positive, black to negative, and leave the yellow wire if your fans have any!

kickind

Okay thanks, just wanted to make sure that I wasn't going to feed to much power to the fan.

disaster999

iTrader: (1)

theres nothing to worry about..the fan is only gonna take what it needs...the supply isnt force feeding the fan!

Geek

Does anyone have any leads on a power supply with more amps (20 or 30) that is in a similar "project form" resulting in a great price?

Also - what does the average computer fan (3") draw in amperage?

tia gents.

Edward.

dpaton

The average computer fan pulls between 0.02 and 0.1A. Nothing to worry about.

As far as sources, google will tell you all kinds of things if you search for 'surplus switching power supplies' and a few variants. I've had good luck in the past with MPJA.com.

-dave

Geek

What is the difference between a linear power supply and a switching power supply?

dpaton

I'm going to assume a very basic knowledge of electronics here. If you lack that, there are some very nice introduction books at your local library that will get you started.

Everbody have their thinking caps on? Good..

A linear power supply works using a big transformer and series pass regulation. From the wall plug, 120VAC goes into one side of a hunk of iron and copper, and ~11VAC is spit out the other side. That 11VAC hits a block of 4 diodes called a full wave bridge rectifier, that changes the signal from normal looking ac to full wave DC. The full wave DC hits a bank of capacitors which takes care of most of the ripple and makes it look like relatively stable 15VDC (full wave DC is ~1.414x the AC value, minus a little for loss in the diodes). The amount of ripple is dependent on both the current required of the supply and the type, size and number of capacitors used for filtering. Now we have an unregulated linear power supply, the same kind you'll find in a lot of audio amplifiers. The output of the supply will vary with the wall voltage, and still has a little bit of ripple to it. If that's alright, we're done, but for the sake of this example, we want a regulated 13.8V out. So....
That 15V then hits a linear regulator, either a single chip type or one made of discrete transistors, and anything that's above the 13.8V output voltage gets turned into heat. It's not particularly efficient, but results in a whole lot of very clean power (Further discussion of regulator topoligies is left as an exercise to the reader).
Large regulated linear supplies generate heat, weigh a ton, and are expensive, because big transformers and big capacitors (required for 60Hz) cost a lot of money.

A switching power supply also has a transformer and capacitors, but they're much smaller, because before the transformer is a piece of circuitry that turns 120VAC at 60Hz into 120VAC at a much higher frequency, usually several hundred kHz. That high frequency AC then feeds into a very small transformer (because transformer and capacitor physical size is partially determined by the frequency they're used at) stepping the voltage down to a managable 11VAC +/- a little. That very high frequency AC hits some capacitors which turn it into ~14VDC with some very high frequency ripple (cap's don't ever filter out everything). Next the voltage hits an inductor, which is basically a big coil of wire, and that helps filter out some of the high freq. hash too. Finally there are some little caps, and another little inductor. At this point there is usually a connection back to the oscillator at the very beginning (called a feedback loop), so that it can adjust it's output to maintain a perfectly regulated output, kind of like a speed control works to vary the voltage to a motor, but over a much smaller range. Switching power supplies are lighter and cheaper for large supplies becuase they use smaller "expensive" components (transformers, caps) and more efficient, because the regulation scheme they use doesn't discard extra voltage as heat, it tweaks the circuit so it goes away.

-dave

Geek

Thanks for the input... makes sense.

In RC is there any advantage to using a linear? For example would a dyno be better served having a more consistant power source? Or would it have an impact on a GFX charger?

dpaton

Modern switchers and regulated linears give the same kind of nice, clean, steady DC output. The only difference is when you have a very dynamic load at the edge of the supplys current rating (ie, a subwoofer amp at full voume). As long as the current rating of the supply is sufficient, there's no reason at all to not use a switcher for RC gear. Your chargers and dynos won't know the difference.

Would you rather choose a 14A switchmode supply that's 10x4x2", weighing 1.5lbs, or a 14A linear, at 10x10x10" and 15 pounds? I know which one I'd take to the track...

-dave

AE Racer

Can someone give me a link to a cord with ring terminals on home depot's or lowes's website? I went to lowes and they said they only had 220v cords with ring terminals. Dpaton, did you have to put the ring terminals on the cord yourself? Did you have to solder them on?

Thanks