Hello

I'm new to this forum and have been doing some reading but I still need some help.

I have a male AC plug on my power panel. Currently, the AC plug only powers my PSU. But I would also like to connect a Apple USB charging block to it. I want to solder wire from the prongs on the usb block to the tabs on the back of the AC plug. Is this possible? I'm concerned about the possiblility of a backfeed. I know how to solve this on DC power...but I am not sure with AC power.

I have attached some pictures ect. Please share your expertise.

Thanks in advance,
Matt


This is what I want to do.

here are pictures of the build to give your guys a reference.
http://www.rctech.net/forum/radio-electronics/808132-power-supply-pit-box-build-thread.html

 

So the binding posts deliver 120V AC direct from the mains? That's mildly dangerous. (Sorry, I didn't read everything you linked.)

But anyway, why not take the female end off an extension cord and connect it to the binding posts? This would allow you to avoid altering your USB adapter.

If the binding posts are 12v DC from the PSU, you need a different USB adapter.

 

thanks for the quick reply

the binding posts deliver 12v @ 57A

the power supply is 120v @ 10.1A input...and 12V @ 57A output.

i don't want to connect the USB block to the binding posts. i want to connect the USB block to the back of the AC male. where the paint lines go.

i could get a 12v to USB adapter and use that. i don't want to do that because i don't want to have to turn on the PSU just to charge my phone with the usb port. i'd like to connect to USB port to the back of the male AC plug. i'm just concerned with connecting the PSU (input) and the USB block (input) to the same terminals (back of the male AC plug on the power panel). i'm not too familiar with AC and i am concerned with the possibility of back feeding or some other problem.


i know i could use a diode for a 12v system...but AC has me baffled lol

 

No, don't do that. If you attempt to solder wires to the USB charger module, you may kill it. Those terminals were designed to plug into a 120v outlet or extension cord.

I see you've removed the face from the USB adapter. That unit was not designed to be opened by the end user. Since you have violated the integrity of the enclosure, it is no longer safe to use. Throw it away; do not use it - you may expose yourself to line voltage if you do.

Your easiest solution would be to get an extension cord of suitable length rated for at least 15A that has two or more female outlets at the end where you wish to use the USB charger, plug your PSU cord into one outlet and your USB charger into the other. This way, when the cheap USB charger module fails, you simply unplug it, throw it away, and plug in a new one. They don't last very long.

Binding posts aren't usually rated to carry anywhere near 57A current, nor are standard banana plug jumpers - more like 10A is the safe working limit. Be aware that if you attempt to draw more current than that, you may have excessive heating.

 

This is a common and very frustrating problem when building electrical projects.

Don't worry about "back feeding" just connect it to the AC mains- the big problem is HOW to accomplish this without making an ugly, dangerous mess out of it.

1) you can solder some wire direct to the male plug pins of the USB charger (file the plating off first) then cover it with heat shrink tube and gobs of silicone. Now you can connect the wires to your mains... (yes you could kill it, just don't heat it up too much and it will work fine)

2) Cut off an extension cord and use the female socket to plug the USB charger in, solder the free end of the cord to the mains terminals.
This approach is "cleaner" but gets bulky, you still need to hold it all down mechanically so it cannot jiggle loose.

 

I was debating on just cutting the male end off a power strip and soldering it to the backside of the male AC plug on my power panel. Then Plugging the PSU into the power strip. But either way...I still need to get a usb port on my power panel. It would be easy to use a 12v-to-usb but I dont want to use the 12v out of the psu to power my usb port. I want the usb port to be live when I plug in the box to the AC

 

I'm just trying to figure out the best, most reliable, and safest way to add an AC-powered usb port to my power panel.

But I don't want the usb port to be powered by the 12v output of the psu though. As I dont want the psu to be on all the time

If I have to...I will power the usb port with my psu with something like the picture below. But that is a last resort.

I appreciate your guys help. I'm ok with DC power...but AC is a whole new monster lol

12-to-dual usb

 

Binding posts aren't usually rated to carry anywhere near 57A current, nor are standard banana plug jumpers - more like 10A is the safe working limit. Be aware that if you attempt to draw more current than that, you may have excessive heating.

You're right. These binding posts are rated for 20A and I have some that are rated for 60A on order. I use bullet connnectors instead of Banana jacks. I've never been a fan of banana jacks as they have a very small amount of contact surface compared to bullet connectors.

P.S. I cannot believe how many responses I've received so quickly. Out of all the forums I've been a member to over the years, you guys are by far the fastest responders ever! Thanks guys.

 

A really safe way would be a DIN rail outlet such as these: 651-5600461from www.mouser.com, but you would need the TS32 DIN rail too.

There are cheaper versions.

What I was looking for was a NEMA 5-15p flanged outlet. I think Hubble makes them that you could mount on the rear using two threaded standoff's and then wire to the back.

Something like this http://www.alliedelec.com/search/productdetail.aspx?SKU=70116156 using a threaded standoff if your in the US. You may have to go outside of the electronic hardware to get the length you need. Hopefully everything else will match up.

 

I was debating on just cutting the male end off a power strip and soldering it to the backside of the male AC plug on my power panel. Then Plugging the PSU into the power strip.

By "it" I think you meant the female end (the end away from the wall) ? If so, this is an OK solution to get a few extra AC ports up close to your box. Just pay attention to strain relief and make sure there is no mechanical threat to your cord.

But if you meant "it" is the male plug, don't do it. You may remember it's hot but other people and pets won't know.

 

I don't think you understand what I'm saying. I'm not sure how one would cut off the female end of power strip

 

I don't think you understand what I'm saying. I'm not sure how one would cut off the female end of power strip

One cut will "cut off" both ends! Your wording was ambiguous as to which end you would then be soldering to your box. To paraphrase Bill Clinton, it depends what the definition of "it" is.

 

I re-read my post. I apologize if it came across rude... that wad not my intent.

Lol. Good point. I'm not always the best at describing with words. I like picture books haha. To clarify, I would mount the power strip section in my toolbox and solder the end of the wire to my ac plug on my power panel.

Since it sounds like most of you guys have come to a similar conclusion. Don't do what I wanted to do in the first post.

With the power panel I have setup... what would be the best way to mount a USB port on my power panel and power it via the AC recepticle on the power panel?

 

Do you guys know if I will need to be concerned with backfeeding or anything else by soldering two items to the same ac recepticle? Like in this picture. Im not going to use this usb block per your guys recommendations. But I was still thinking of power something else with that ac recepticle.

 

Woha?

I was under the impression that a power cord went into the side with the binding posts and plugged into the wall?

Am I correct?

This http://www.newark.com/qualtek-electronics/710w-00-01/connector-power-entry-female-15a/dp/17B6886 is an AC receptacle of that universal style.

You can buy cords with that have a male and female end of that style. You can also buy cord that fit into the socket you have that "lock in place".

The cheap way to attach the USB PS, is to purchase a cord end. In the end, you might find a surge protected outlet strip to be in your best interest.

A standoff can be found here: www.mouser.com; search for 761-2263-832-SS as an example, I didn't check suitability. But, if you took the outket that I referenced earlier and mounted it on a standoff (check screw sizes) and then placed it on the back of your panel where you can put two through hole screws, you will have a nice strain relieved outlet. I'd put big piece of heat shrink around the side and use Locktite 222 on the front screws.

Long standoffs with small screws may be hard to come by. It looks like my source of them dried up. I had a source for square cross-sectioned ones. The longest "standoff" I made was like 19" long, but I had access to a lathe at the time.

 

yes you are correct. on the front of the power panel, a power cord plugs into the AC receptacle and then plugs into the wall.

 

Do you guys know if I will need to be concerned with backfeeding or anything else by soldering two items to the same ac recepticle? Like in this picture. Im not going to use this usb block per your guys recommendations. But I was still thinking of power something else with that ac recepticle.


No, problem.

Parallel ac. connections are the norm.

That's how home receptacles are wired.

 

on the backside of the of the power panel (pictured below), i want to solder leads on the back of the ac receptacle to power a usb port that i can mount to the backside of my power panel.

 

I embarrassed to admit, but I do the same thing in industrial control panels when I need a small inexpensive power supply.

Such as an LCD backlight.

 

Do you guys know if I will need to be concerned with backfeeding or anything else by soldering two items to the same ac recepticle? Like in this picture. Im not going to use this usb block per your guys recommendations. But I was still thinking of power something else with that ac recepticle.


No, problem.

Parallel ac. connections are the norm.

That's how home receptacles are wired.

so i could solder more than one device to the back of the ac receptacle and not have to worry about backfeeding or anything? thats good news.