I have a “wall wart” power supply that plugs in to a 120volt outlet. The kind of supply one uses for chargers and small devices. The power supply got wet and is no longer producing power. The output is 12V and 1.6Aamps. I have spare power supplies that are rated for 12V and 1Amp, and 12V and 2.5Amp.
Will either of those work? The device being powered is a charging stand for a phone. Would the lower amperage supply simply mean a longer recharge time? Would the charging stand draw only the current it needs and allow me to use the higher current supply?
Thanks
The 12v/2.5 amp will be fine. The amp rating is the maximum it can provide and the device will only take what it needs. So, it’s ok for the power supply to have a higher amp rating, but there can be problems if it has a lower rating (and the device tries to draw more than it’s rated for, which isn’t always the case).
And the volts match, so that’s not an issue. However, unlike amps where the device takes the amount of amps it needs, the power supply only offers one option for volts. In this case, 12 of them. Plug it in and there’s 12v ready to go. If your device is only rated for 5v, you might let the smoke out.
As for if the smaller one would work and just charge slower, I think so, but it probably depends entirely on how both devices are designed. It might charge slower, it might blow a fuse inside the power supply.
If the failed power supply was 12 V and could produce up to 1.6 A, then the 12 V power supply than can produce up to 2.5 A should work fine.
One caveat, though: if the failed supply produced a regulated 12 V, then any any replacement supply should also produce a regulated 12 V; do not use a 12 V unregulated power supply.
I’ve used power supplies on laptops that could not produce the amperage listed. They do indeed work, taking longer to charge. Generally though, a power supply that produces less current than required will have smoke come out the back.
Thanks all. Using the supply with the greater than required current rating is what I figured would work.
Check your polarity!
Look at it like this. Your microwave might be rated at 4 amps, but you plug it into a 15 amp outlet with no problem. But if you plug it into a 240v outlet, you will have a problem.
That’s a good idea and the label of the old and new power supply likely have a small diagram, but it’s really rare to see standard power supplies that aren’t negative on the ring and positive on the tip.
^ A quick check of my Blood Pressure machine confirms that and there’s even a little diagram on the unit itself (smart). However, the white noise machine in the kitchen does NOT have a diagram on the unit (un-smart) although the wall wart does and it’s +tip/- ring. Now if you’d like to examine my Big Old Box of Ancient Power Adaptors, God knows what all you’ll find. If any of youse guys need some kind of off-the-wall wart, I’ve probably got it; just ask, please take one. Or ALL of 'em. I just can’t toss them out! Why doesn’t Mr. Maudlin DO something before it’s too late? Oh, God!
I mean, FWIW, if I need to power some random thing, especially if it’s something potentially sensitive or something I made, I’ll check the polarity (with a multimeter if there’s no diagram).
ISTM, a lot of devices these days have some protection against incorrect polarity. I feel like I’ve seen ones that will just not work if the polarity is backwards (a simple diode should take care of that, right) and some that route anything positive to one side, regardless of which side it came in on. But that’s just little things I’ve picked up on from watching BigClive and ElectroBoom.
I’ve gotten better at throwing out old transformers. While I still have plenty that plug into god knows what, I’ve at least started throwing out the unknown ones that appear to be 20+ years old and seem to weigh about a pound. It’s an arbitrary reason to decide if I keep it or toss it, but it helps. Now I might have 5 or 10 that belong to an unknown device instead of 20 or 30.
Plus, I picked up a cheap bench power supply. So at least for playing around, I have pretty much whatever voltage or amperage I want without having to rely on old transformers.
That’s why I keep coming here – picking up tips; I’ll check them out, thanks.
What’s the best disposal method for transformers, et al? Hate to landfill them; I’d just give them to someone if I knew who, if anyone, might want them.
In that case, it’s “BigCliveDotCom” and ElectroBOOM, both on youtube. For the most part, BigClive takes [electronic] stuff apart or ‘take it to bits’, as he says. ElectroBoom generally builds things. They’ll both explain what’s going on and make diagrams, but ElectroBoom does it more like a college teacher.
Also, the shocks ElectroBoom gets, while often pre-planned, aren’t fake or CGI, he’s getting shocked, he just has a high tolerance for it. But still, that Jacob’s Ladder falling on him, I cringed as soon as I saw it leaning.
Much obliged, Joey_P.
Interestingly, all guitar effect pedals require the power supply center to be negative and the outer ring to be positive.
Radio Shack stores were great when you needed something like an AC adapter; they had ones that could be set to various voltages and amps, and came with various tips to fit.
And, those tips could be put on either way so you could reverse the polarity. In fact, buying one of these at Radio Shack is where I learned about that little polarity diagram.
This took a bit more searching than I thought it would, but it was basically just like this.
I wonder if there’s a reason for that or if that’s ‘just how it is’. In fact, when I went looking for that link, the transformers that were ‘reverse polarity’ (outside positive/inside negative) were listed as being for guitar pedals. Likely just to get people looking for power adapters that use ‘guitar pedal’ in their search terms. But still, learn something new everyday.
How wasteful is it to put a diode bridge on the input, so the polarity of the charger does not matter?
Okay, here’s how ignorant I am: is it possible it has something to do with electric guitarists grabbing a “hot” (electrically) mic while touching their guitar cable?
I don’t think so.
I’m not sure why guitar effect pedals are different. I recall reading somewhere that it made it easier to disconnect an internal battery when the adapter plug was inserted into the mating receptacle on the pedal.
^ Yes, I’ll buy that! Good show.
Here’s what I could find. I kinda understand, but a schematic would make more sense. From here.
Most electronic devices and their power supplies have center-positive polarity, so why do pedals have center-negative polarity? Because many pedals work with either a battery or a power supply; and, to preserve the life of the battery, it is disconnected from the circuit when either (1) a power plug is inserted or (2) the input plug is removed. This is accomplished by connecting the battery’s negative terminal to the input jack’s ring contact and the battery’s positive terminal to the sleeve shunt on the power jack. When the input plug is inserted, it completes the circuit for the negative battery terminal. When a power plug is inserted, it breaks the circuit to the positive terminal of the battery. Power jacks do not have a shunt for the center (pin) contact, so a center-positive power supply would not work in this type of circuit.
So I’m guessing it’s because they started out with batteries only and needed, or rather wanted, a way to have them automatically disconnect the battery when the cord is pulled out. That part makes sense. Then they added on a way to also make the battery stop powering the pedal when a power supply was plugged in, but because of the first part, it required the ring to be positive, for, reasons. And now that’s just how it is.
There’s probably some ways to move back to center positive, but at this point I don’t think it really matters.