Help with DC adapter

[jj5]

Hi there. I needed a 19.5V DC adapter so I purchased one of these: 19.5V 2.31A AC Adapter Charger for HP Split 13 X2;HP Stream 11 13 14 Series;Pavilion x360 x2 11 11t 13 15;Elitebook Folio 1040 G1;P/N 721092-001 PA-1450-56HA Power Cord.

The adapter arrived today and looks like this:



The problem was that when it arrived it had the wrong sort of adapter, like this:



So I decided to attach my own adapter, like this:



But when I cut the adapter off and stripped the wire I found three wires, not two as I was expecting:



I plugged in the adapter and used my multimeter to measure voltage across the wires, but I couldn't get any reading. Not sure where the problem might be. Figured I should ask because I don't want to short anything out doing experiments on wires I don't understand...

So my questions are: which two wires should I expect to be able to attach to my new adapter? Do I need to short any of these wires to enable power through the device? Why are there three wires?

[gnuarm]

These days most laptops have a comms signal for the computer and the power supply to exchange information.  The power brick tells the laptop it's max power or something equivalent and the laptop decides if it is going to charge from it.  That's the third wire.

Until the laptop tells the power brick to turn on, you will get no power from the brick. 

You bought the wrong type of power supply. 

I can't see from your photos what is going on with the pins.  Normally the connectors on these bricks will have an outer barrel, an inner barrel and a pin in the center.  Does the connector you cut off have the center barrel and pin? 

[jj5]

I used my continuity tester to check the wiring of the three wires to the original adapter which I cut off. The outside was to black, the inside of the barrel to red, and the pin to white, as far as I could tell (it was hard to be sure my multimeter probes were properly positioned). Is there anything I can do to get a useful voltage out of this thing? I already cut the adapter off so I think a return is out of the question!

[gnuarm]

I used my continuity tester to check the wiring of the three wires to the original adapter which I cut off. The outside was to black, the inside of the barrel to red, and the pin to white, as far as I could tell (it was hard to be sure my multimeter probes were properly positioned). Is there anything I can do to get a useful voltage out of this thing? I already cut the adapter off so I think a return is out of the question!

Just tell them that was how you received it and sound angry that they are ripping you off!  lol

You would need to figure out the protocol of the interface and build something that will do the same thing.  My guess is the power brick has something in it like a one-wire device with its data.  That would require some sort of very simple MCU in your adapter to talk to the brick.  It would have to run off the power on the white wire, since there is none on the red wire. 

I assume you realize you will need a small perf board to solder the wires to, etc. 

[jj5]

Thanks Rick! I would really love to figure out how to reverse engineer this thing, just for the sake of the exercise. I can put the three wires into a breadboard for experimenting. How do I go about figuring out the protocol? Should I use my scope to see what happens between the white and black wires when I power-on? Can you help me figure out the protocol? If you can instruct me I will do what you say!

[jj5]

I've got this thing wired up, what's the first step?

[gnuarm]

Thanks Rick! I would really love to figure out how to reverse engineer this thing, just for the sake of the exercise. I can put the three wires into a breadboard for experimenting. How do I go about figuring out the protocol? Should I use my scope to see what happens between the white and black wires when I power-on? Can you help me figure out the protocol? If you can instruct me I will do what you say!

The easy way is to look it up on the Internet.  Use one of the laptop names and look for a power supply protocol. 

Otherwise, you need to know the timing details which would be hard to figure out by exploration.  When you plug in the power brick, what voltages do you get on the red and white wire assuming black is ground?

[jj5]

When I plug the power in the red black pair jumps briefly to 12V but then settles into open circuit. The white black pair goes to 15.44V.

[jj5]

Hey Rick, I made a quick video to show you what happens when I measure voltages on the wires: https://youtu.be/ApvlTKbqNNc.

[gnuarm]

When I plug the power in the red black pair jumps briefly to 12V but then settles into open circuit. The white black pair goes to 15.44V.

I don't know what you mean by "open" circuit.  The voltage is zero on the red line, then goes up to 9.3, then  1_.__  I think the meter is overvoltage on the red wire.  I'm guessing your meter is 3.5 digits, so that setting probably maxes out at 19.99V and you are seeing a bit more than that.  Try changing the range to 200V max.

[MrAl]

Hi there. I needed a 19.5V DC adapter so I purchased one of these: 19.5V 2.31A AC Adapter Charger for HP Split 13 X2;HP Stream 11 13 14 Series;Pavilion x360 x2 11 11t 13 15;Elitebook Folio 1040 G1;P/N 721092-001 PA-1450-56HA Power Cord.

The adapter arrived today and looks like this:



The problem was that when it arrived it had the wrong sort of adapter, like this:



So I decided to attach my own adapter, like this:



But when I cut the adapter off and stripped the wire I found three wires, not two as I was expecting:



I plugged in the adapter and used my multimeter to measure voltage across the wires, but I couldn't get any reading. Not sure where the problem might be. Figured I should ask because I don't want to short anything out doing experiments on wires I don't understand...

So my questions are: which two wires should I expect to be able to attach to my new adapter? Do I need to short any of these wires to enable power through the device? Why are there three wires?

Hi,

Some of these just use a resistor or thermistor or just a switch so the battery can tell the wall wart to shut off if something is wrong.  Unfortunately, it would vary by manufacturer as to what method they use so you'd have to find out from them or find it on the web. If you could get a working genuine wall wart you could test it but that could be very difficult and if you get it wrong, it could turn dangerous as these types of battery packs are nothing to play around with.  Better to get a working wall wart by far even with the extra cost.  A fire could cost you a lot more.

[jj5]

Oh, yes, you're right! It's delivering slightly more than 20V so I needed to go to the next level. Seems to me like there's 20V across the red black pair. Not sure why I couldn't read that before. Maybe I can just hook this up and it will work. I will try that again...

[MrAl]

Oh, yes, you're right! It's delivering slightly more than 20V so I needed to go to the next level. Seems to me like there's 20V across the red black pair. Not sure why I couldn't read that before. Maybe I can just hook this up and it will work. I will try that again...

Just be careful the wrong protocol could make charging dangerous.
Why didn't you just buy the right adapter.

[jj5]

I don't know what you mean by "open" circuit.

I'm a novice and I misunderstood. The multimeter goes to "1" when it's overloaded. I thought that it went to "1" when it was "open circuit", that is, zero volts. But of course that's not how it works. At least I'm learning...

[gnuarm]

I don't know what you mean by "open" circuit.

I'm a novice and I misunderstood. The multimeter goes to "1" when it's overloaded. I thought that it went to "1" when it was "open circuit", that is, zero volts. But of course that's not how it works. At least I'm learning...

So, what is the voltage?  Is it about 20V?  Does it remain at 20V?  That would be odd, but it might only let you draw a low current before shutting down, or the comms sets a higher current.

[jj5]

I'm a novice and I misunderstood. The multimeter goes to "1" when it's overloaded. I thought that it went to "1" when it was "open circuit", that is, zero volts.

The reason I made this mistake is that when the multimeter is in resistance mode it shows "1" when there's an open circuit (i.e. no load). So just the confusion of a novice getting used to using his equipment.

[gnuarm]

I'm a novice and I misunderstood. The multimeter goes to "1" when it's overloaded. I thought that it went to "1" when it was "open circuit", that is, zero volts.

The reason I made this mistake is that when the multimeter is in resistance mode it shows "1" when there's an open circuit (i.e. no load). So just the confusion of a novice getting used to using his equipment.

So, what is the voltage?

[jj5]

So, what is the voltage?  Is it about 20V?  Does it remain at 20V?

Yes, it's about 20V. I put a load across it using a 1M potentiometer and it delivered voltage for a while but I burnt out the pot (magic smoke!) when I decreased the resistance too much.

[gnuarm]

So, what is the voltage?  Is it about 20V?  Does it remain at 20V?

Yes, it's about 20V. I put a load across it using a 1M potentiometer and it delivered voltage for a while but I burnt out the pot (magic smoke!) when I decreased the resistance too much.

Ok, are you good to go?

[jj5]

Ok, are you good to go?

Not sure yet. I will hook this thing up to a better load for testing but won't be able to get that done today. I will let you know how I go tomorrow! Thanks for your help!

[ozcar]

What do you intend to power with this adaptor?

[jj5]

What do you intend to power with this adaptor?

I want to use it to power a RIDEN RD6006 power supply.

[MrAl]

What do you intend to power with this adaptor?

I want to use it to power a RIDEN RD6006 power supply.

Hi,

Oh, that's a very different application.  It should work one way or another as long as you don't exceed the max input voltage.

The problem with wall warts to charge Li-ion batteries (a lot of laptops) is that those batteries are dangerous if not charged exactly right so better to have the right wall wart to begin with.
Li-ion batteries can catch fire or worse explode and burn out like a blow torch for several minutes if not charged right, and charging is the most dangerous time.  There are lots of videos of this on the web that illustrate what can happen.

Power supply regulators generally do not complain about the input supply except for certain types like for example some Li-ion charger controllers which require a 5v only input.

[gnuarm]

What do you intend to power with this adaptor?

I want to use it to power a RIDEN RD6006 power supply.

Why don't you just buy a power supply that works from the mains power, instead of needing yet another supply to power the other supply???

[ledtester]

What do you intend to power with this adaptor?

I want to use it to power a RIDEN RD6006 power supply.

Why don't you just buy a power supply that works from the mains power, instead of needing yet another supply to power the other supply???

The RD6006 is a buck converter that has a configurable CC mode which is what I bet the OP is relying on to charge the li-ion batteries. Another forum member has developed an alternative firmware which improves the UI and adds more features. More info is available at:

https://www.eevblog.com/forum/testgear/ruideng-riden-rd6006-dc-power-supply/msg4971583/#msg4971583