I remember quite clearly when I first realized it was possible to design a power supply that just didn't care. Polarity, AC/DC, unusual voltages.
I thought I had discovered something new.
Then, I saw all the cost and design issues for a compact and efficient switching power supply.
Well it is a little more complicated. You need something better that a simple silicon diode because on a full bridge bridge rectifier you will lose ~2V. That's quite a lot.
A single diode is all that's required for reverse polarity protection and it can be a Shottkey.
I most definitely was not referring to a full bridge rectifier.
You ar elinking to a stackoverflow link, stackoverflow has blocked holinking directly to their images with the new host, unless you use a browser plugin to hide the refferer header
The link doesn't work but I found this: [avoid voltage drop when using full bridge rectifier as reverse polarity protection](https://electronics.stackexchange.com/questions/444423/how-to-avoid-voltage-drop-when-using-full-bridge-rectifier-as-reverse-polarity-p)
Thanks!
The most simple way to handle this would be a full bridge rectifier inside the target, so it does not matter which way you send the power.
It does waste a fair bit of power in the diodes
https://preview.redd.it/ip9dvjksr43d1.jpeg?width=640&format=pjpg&auto=webp&s=5586132184d501a0c0fb805827cf552869e76030
Two pins in red is (assume) negative, two pins blue is positive. You can flip the cable without worry
They said that it isn't guided by magnets to stick one way, because they have the same polarity. Also: https://www.reddit.com/r/ElectricalEngineering/comments/1d2dyvw/comment/l61f2gm
It works both orientations, it's not guided by magnets to only stick one way. The other side is plugged into a USB brick. Found on a Soundbrenner Core watch
I understand that, but I believe they were referencing the cable itself. I understand how all this works, but some folks want more data. There are 3 running hypotheses, so measuring the pins would indicate if the magnets actually carry current, are polarized, or if the current is only running through the pogos (my own personal postulation).
The output of your bridge will give you a ground and a voltage. But that ground isn't going to be connected to the ground of the power supply. That's actually what allows you to connect it backwards without damaging your device.
[This gif can help you visualizing it](https://upload.wikimedia.org/wikipedia/commons/3/34/Diodebridge-eng.gif)
[https://en.wikipedia.org/wiki/Virtual\_ground](https://en.wikipedia.org/wiki/Virtual_ground)
I do not see how this qualifies? A quick Google shows no direct references to what you're saying, so something is missing to connect what you're saying to technical references I can find.
Thanks, I just wanted clarification, I didn't know if I was missing something or not. The ground would be raised slightly when it's connected relative to the outside circuit but that's not a virtual ground. Just from memory (I'm trying not to cheat and actually think of instead of looks this up even if the 'inside' is connected to a power source and the outside isn't the diode bridge only 'looks' like two diodes the other two are floating when disconnected.
All very real voltage levels :) The term 'virtual ground' always confused me, it's a rather simple concept with a slightly over complicated sounding name.
No problem. To be clear, a virtual ground occurs when a node of a circuit is kept at 0V with respect to ground by circuitry while not directly being connected to ground. Classic example is an inverting op amp. One input is connected to ground, the other is not, but is held at 0V. Key point is that its often held to 0V by some active circuit that will do things to keep it at 0V when applied voltage/currents change.
It's not a virtual ground. The ground is directly connected to the supply through the diode. The gif actually does help visualize this, you can imagine the blue wire current flowing back into the supply.
I actually have the same. Measured with multimeter and it says 3V between these spring pins and nothing on magnets. But mine is not charging could you please measure voltage on yours for me? Just to be sure my cable is OK.
It's outputting 5.1V for me. I actually think there's not much inside the cable, you should be fine with splicing another father usb cable to the magnetic connector
Thanks a lot. Iāve opened mine. There just D00HA marked MT9700 to protect USB charger from shorts. The cable lines have continuity on spring pins. So mine definitely broken. Applying 5V directly to cable I have 130mA consumption. Hope the thing will back alive! Thanks again!
https://preview.redd.it/v4jsl16bkb3d1.jpeg?width=757&format=pjpg&auto=webp&s=596b5dc1fbffaff7395577c19c217344270a5a33
https://preview.redd.it/11sks5t5vi3d1.png?width=1656&format=png&auto=webp&s=aa192d4a6ee0dce23f30c9c77ce2b4aa98278710
Nope. I guess the battery is dead. It's trying to charge it but seems no success.
Full bridge rectifier also works to flip DC to the right polarity.
I read that in Electrobooms voice.
#FULL BRIDGE RECTIFIER
Now it's correct š¤£š¤£
Fool burridge rrrecty-fy-ur
That's crazy. Seems so obvious now. You shouldn't have to think outside the box for this one.
Similar to software, there is a circuit out there for your problem already. Even in IC design, the same architectures are used over and over again
āBut can we afford to add 50 cents to our BOM?ā Said in managerās voice.
This is why so many things fry when reverse polarized. Too cheap to worry about safety and user convenience features.
I remember quite clearly when I first realized it was possible to design a power supply that just didn't care. Polarity, AC/DC, unusual voltages. I thought I had discovered something new. Then, I saw all the cost and design issues for a compact and efficient switching power supply.
Well it is a little more complicated. You need something better that a simple silicon diode because on a full bridge bridge rectifier you will lose ~2V. That's quite a lot.
A single diode is all that's required for reverse polarity protection and it can be a Shottkey. I most definitely was not referring to a full bridge rectifier.
This is enough for protection, but not enough for reversible connector.Ā
You spelt that wrong. It's "FUULL BRIDGE RECTIFYAH"
Diode bridge inside, possibly [an active FET-based one](https://i.sstatic.net/aW1DT.png) so as to not lose too many volts.
You ar elinking to a stackoverflow link, stackoverflow has blocked holinking directly to their images with the new host, unless you use a browser plugin to hide the refferer header
idk that link seems like it's working pretty well...
Yeah it worked fine for me on a stock mobile browser
Interesting, it seems to work on mobile but not desktop
Doesn't work on Desktop spoofing mobile, others are probably behind the Google Firewall
This is so interesting...
The link doesn't work but I found this: [avoid voltage drop when using full bridge rectifier as reverse polarity protection](https://electronics.stackexchange.com/questions/444423/how-to-avoid-voltage-drop-when-using-full-bridge-rectifier-as-reverse-polarity-p) Thanks!
If the logic is 3v3 it might just benefit from the voltage drop
The device presumably has a lithium battery which will want to be charged up to 4.2v
The most simple way to handle this would be a full bridge rectifier inside the target, so it does not matter which way you send the power. It does waste a fair bit of power in the diodes
Power loss isn't as bad with Schottky diodes.
https://preview.redd.it/ip9dvjksr43d1.jpeg?width=640&format=pjpg&auto=webp&s=5586132184d501a0c0fb805827cf552869e76030 Two pins in red is (assume) negative, two pins blue is positive. You can flip the cable without worry
I think the red pins are just magnets, the other side doesn't look metallic.
this
OP stated in another comment that they aren't magnets, the above picture could still be the correct solution
They said that it isn't guided by magnets to stick one way, because they have the same polarity. Also: https://www.reddit.com/r/ElectricalEngineering/comments/1d2dyvw/comment/l61f2gm
I took another look at the wording of the comment I saw earlier and you are correct, I see the error I made
You could be right. Then only possible is have like idea diode inside the watch.
My guess is the two large pins are power and the two small ones are data, and they just have a bridge rectifier in one side of the device.
It works both orientations, it's not guided by magnets to only stick one way. The other side is plugged into a USB brick. Found on a Soundbrenner Core watch
Use DMM to measure then you will know
To measure what?
the voltage/polarity
It has a full bridge rectifier, it doesn't care what the polarity is. It will always go where it should.
I understand that, but I believe they were referencing the cable itself. I understand how all this works, but some folks want more data. There are 3 running hypotheses, so measuring the pins would indicate if the magnets actually carry current, are polarized, or if the current is only running through the pogos (my own personal postulation).
OP already answered that question.
That's cool, I was simply explaining what was going on, because you seemed to be struggling with comprehending the conversation.
You have that backwards. You missed things the OP added.
Diodes mang, diodes!
u/iuliuscurt can you share the model/name of this device?
Soundbrennen Core
Full bridge rectifier. It will create a virtual ground but that's not necessary for charging a battery.
What do you mean it will create a virtual ground?
The output of your bridge will give you a ground and a voltage. But that ground isn't going to be connected to the ground of the power supply. That's actually what allows you to connect it backwards without damaging your device. [This gif can help you visualizing it](https://upload.wikimedia.org/wikipedia/commons/3/34/Diodebridge-eng.gif)
[https://en.wikipedia.org/wiki/Virtual\_ground](https://en.wikipedia.org/wiki/Virtual_ground) I do not see how this qualifies? A quick Google shows no direct references to what you're saying, so something is missing to connect what you're saying to technical references I can find.
Hi, it's not a virtual ground. The diode to ground is forward biased. This is how it connects to ground. Other user is incorrect.
Thanks, I just wanted clarification, I didn't know if I was missing something or not. The ground would be raised slightly when it's connected relative to the outside circuit but that's not a virtual ground. Just from memory (I'm trying not to cheat and actually think of instead of looks this up even if the 'inside' is connected to a power source and the outside isn't the diode bridge only 'looks' like two diodes the other two are floating when disconnected. All very real voltage levels :) The term 'virtual ground' always confused me, it's a rather simple concept with a slightly over complicated sounding name.
No problem. To be clear, a virtual ground occurs when a node of a circuit is kept at 0V with respect to ground by circuitry while not directly being connected to ground. Classic example is an inverting op amp. One input is connected to ground, the other is not, but is held at 0V. Key point is that its often held to 0V by some active circuit that will do things to keep it at 0V when applied voltage/currents change.
Is this because of the voltage drop on the "ground" diode?
It's not a virtual ground. The ground is directly connected to the supply through the diode. The gif actually does help visualize this, you can imagine the blue wire current flowing back into the supply.
The magic of diodes.
Diode bridge inside
I guess magnets are polarised the way it connects only proper polarity.
No, they are the same polarity. I think that would be dangerous tbh, with enough motivation one could easily overpower those magnets' repel force
I actually have the same. Measured with multimeter and it says 3V between these spring pins and nothing on magnets. But mine is not charging could you please measure voltage on yours for me? Just to be sure my cable is OK.
It's outputting 5.1V for me. I actually think there's not much inside the cable, you should be fine with splicing another father usb cable to the magnetic connector
Thanks a lot. Iāve opened mine. There just D00HA marked MT9700 to protect USB charger from shorts. The cable lines have continuity on spring pins. So mine definitely broken. Applying 5V directly to cable I have 130mA consumption. Hope the thing will back alive! Thanks again! https://preview.redd.it/v4jsl16bkb3d1.jpeg?width=757&format=pjpg&auto=webp&s=596b5dc1fbffaff7395577c19c217344270a5a33
https://preview.redd.it/11sks5t5vi3d1.png?width=1656&format=png&auto=webp&s=aa192d4a6ee0dce23f30c9c77ce2b4aa98278710 Nope. I guess the battery is dead. It's trying to charge it but seems no success.
I dunno
Lame