gordon861
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Why USB-C ?

Fri Mar 13, 2020 11:59 am

Sorry if the answer to this is to obvious but, why was the choice made to power the Pi4 via a USB-C connector?

I understand the logic of using the micro-USB on the earlier versions because there are so many power supplies out there that can do the job.  But USB-C power supplies that can provide enough power for the Pi4 are so thin on the ground that your choices are limited to ones dedicated to the job and regular USB charges that you plug your own lead into often top out at around 2.0-2.4 amps.  Also USB-C male-female extension cables are difficult to find and/or expensive, I assume because a USB-C cable must meet the USB-C specs.

So why not use a regular power connector like a 5.5 x 2.1mm DC power plug, as used in so many other places?

This would open up so many more options to power your system.  If you wanted a longer power lead, not a problem.  5 volt DC power supplies are very easy to source so you could use a larger one to power a cluster of Pi4 units.

Again sorry if there is an obvious fault in my thinking but I would love to know the answer..

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RaTTuS
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Re: Why USB-C ?

Fri Mar 13, 2020 12:01 pm

because usb-c is common and easy
So why not use a regular power connector like a 5.5 x 2.1mm DC power plug, as used in so many other places?
there are no standards - and will result in burnt out pi's
usb-c has standards
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dustnbone
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Re: Why USB-C ?

Fri Mar 13, 2020 12:05 pm

I can see the reasoning behind abandoning micro USB, it's a terribly fragile connector. It's ubiquity is really all it had going for it.

As far as using a barrel jack, problem I see with that is there's no standardization for voltage (or even polarity!) with that connector as there is with USB-C.

If it were a barrel jack I predict melted blown up Pis all over the place. Worst thing that is likely to happen from connecting a USB-C plug is a Pi that doesn't turn on.

Way better than blown up and melted.

gordon861
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Re: Why USB-C ?

Fri Mar 13, 2020 12:21 pm

I figured the non-standardised standard connector would probably be the problem. But considering the power draw for a Pi4 is so high you seem to be stuck with dedicated Pi4 power supplies to ensure you have the required power.

We now have a complicated 22/24 pin plug standard to deliver what could be achieved by a 2 core wire.

The barrel connection is probably not the answer but I don't think USB-C is either.

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rpdom
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Re: Why USB-C ?

Fri Mar 13, 2020 12:26 pm

gordon861 wrote:
Fri Mar 13, 2020 12:21 pm
I figured the non-standardised standard connector would probably be the problem. But considering the power draw for a Pi4 is so high you seem to be stuck with dedicated Pi4 power supplies to ensure you have the required power.

We now have a complicated 22/24 pin plug standard to deliver what could be achieved by a 2 core wire.

The barrel connection is probably not the answer but I don't think USB-C is either.
The USB-C does have USB2.0 data connections too.

Most decent USB-C power supplies should be good enough to power the PI 4B. especially now the PD resistors are fixed.

Maybe the Pi 5 will have full PD on it and accept higher voltages to generate the 5V required on board. (Just idle speculation, not a wish list. I guess that the Pi 5 spec is well developed already).
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andrum99
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Re: Why USB-C ?

Fri Mar 13, 2020 12:27 pm

gordon861 wrote:
Fri Mar 13, 2020 11:59 am
...
USB-C power supplies that can provide enough power for the Pi4 are so thin on the ground that your choices are limited to ones dedicated to the job and regular USB charges that you plug your own lead into often top out at around 2.0-2.4 amps.
...
Since the Raspberry Pi first launched in 2012 the advice has always been to use a good quality power supply that can supply a stable 5V up to and including the load which the particular model of Raspberry Pi you are using places on it. This advice has not changed. For several years now we have also had the option of purchasing an official Raspberry Pi power supply, which takes the guesswork out of this. The official PSU is avaiable at low cost for those people who do not already have a suitable power supply. Many phone chargers do in fact work, for example I have two phones which come with USB-C chargers and they both successfully power the Raspberry PI 4B 4GB models which I have.

It is not true to say that most USB-C chargers can only supply 2 to 2.4A - they tend to be rated higher than micro-B chargers since phones that have USB-C also have fast charge modes, and those fast charge modes need chargers capable of supplying larger currents.

Heater
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Re: Why USB-C ?

Fri Mar 13, 2020 12:27 pm

I love a good solid barrel jack connection as much as anyone. Except as already mentioned there is no standard and it is a world of chaos and pain.

I recently got hold of an Nvidia Jetson Nano and wanted to power it via it's barrel jack.

No probs I thought, I have a box full of wall warts and other power supplies with barrel connectors on their leads. I also have a ton of barrel adapters.

Well, guess what? They were all kind of different voltages. Their barrel connectors were all kind of different shapes and sizes. I could not find one that had the correct voltage and current rating and the correct size/shape connector on it. If I really wanted one I would have to buy it. In the end I cut a lead off one that had the right barrel plug, threw the wall wart away and hooked p the lead up to a 5v supply I had on the bench.

Conclusion: Using a barrel connector would be a really bad idea for the Raspberry Pi's target audience.
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fruitoftheloom
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Re: Why USB-C ?

Fri Mar 13, 2020 12:28 pm

gordon861 wrote:
Fri Mar 13, 2020 11:59 am
Sorry if the answer to this is to obvious but, why was the choice made to power the Pi4 via a USB-C connector?

I understand the logic of using the micro-USB on the earlier versions because there are so many power supplies out there that can do the job.  But USB-C power supplies that can provide enough power for the Pi4 are so thin on the ground that your choices are limited to ones dedicated to the job and regular USB charges that you plug your own lead into often top out at around 2.0-2.4 amps.  Also USB-C male-female extension cables are difficult to find and/or expensive, I assume because a USB-C cable must meet the USB-C specs.

So why not use a regular power connector like a 5.5 x 2.1mm DC power plug, as used in so many other places?

This would open up so many more options to power your system.  If you wanted a longer power lead, not a problem.  5 volt DC power supplies are very easy to source so you could use a larger one to power a cluster of Pi4 units.

Again sorry if there is an obvious fault in my thinking but I would love to know the answer..

It was explained in the Release Blog last June:

We’ve moved from USB micro-B to USB-C for our power connector. This supports an extra 500mA of current, ensuring we have a full 1.2A for downstream USB devices, even under heavy CPU load.

https://www.raspberrypi.org/blog/raspbe ... w-from-35/

The Official Power Supply is extremely good value for money:

https://www.raspberrypi.org/products/ty ... er-supply/
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rpdom
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Re: Why USB-C ?

Fri Mar 13, 2020 12:36 pm

Heater wrote:
Fri Mar 13, 2020 12:27 pm
I love a good solid barrel jack connection as much as anyone. Except as already mentioned there is no standard and it is a world of chaos and pain.

I recently got hold of an Nvidia Jetson Nano and wanted to power it via it's barrel jack.

No probs I thought, I have a box full of wall warts and other power supplies with barrel connectors on their leads. I also have a ton of barrel adapters.

Well, guess what? They were all kind of different voltages. Their barrel connectors were all kind of different shapes and sizes. I could not find one that had the correct voltage and current rating and the correct size/shape connector on it. If I really wanted one I would have to buy it. In the end I cut a lead off one that had the right barrel plug, threw the wall wart away and hooked p the lead up to a 5v supply I had on the bench.

Conclusion: Using a barrel connector would be a really bad idea for the Raspberry Pi's target audience.
The barrel jacks can be a world of hurt. Different sizes - external, internal and length. Different voltages and current limits. AC or DC. Polarity. Smoothed or unsmoothed. Regulated or unregulated. Hot or Cold (ok, maybe not that). Not to mention many weird custom versions such as multi pole, and I've seen ones that are a mutant version of Barrel, TRRRS and Phono/RCA in the same plug!
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jahboater
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Re: Why USB-C ?

Fri Mar 13, 2020 12:44 pm

Unless the PSU is sold with the Pi?

Then all the issues with unsuitable chargers, thin cables, voltage drops, etc would go away.

The price increase might not be acceptable, but then the 4GB Pi4 is selling like hot cakes.
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Heater
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Re: Why USB-C ?

Fri Mar 13, 2020 12:59 pm

Not acceptable to me. Many of my Pi have been installed using power supplies other than wall warts. I would not want to have to pay for a wall wart with every Pi only to throw it away.
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Technocolour
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Re: Why USB-C ?

Fri Mar 13, 2020 1:12 pm

Increased functionality. From the obvious (USB) to being able to power it through a laptop.

The world of barrel jacks is a big non standard jungle, people would blow up thier Pis unless you increased the cost of the power section of the pi, for just about no really good reason.

After the resistor fix, the original thought about being able to use a discarded USB PSU farting around the house is retained.

Garvan
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Re: Why USB-C ?

Fri Mar 13, 2020 2:58 pm

Clicking on this link and selecting the type I need tells me "there are no global supplies for this model".That said, I do have a working wart, official or otherwise, I don't really know.

What I want is more options in design. I am looking for a power supply where I can change the plug to what I need and add a switch to the power line so I can install it into the back of a TV cabinet where I have limited space.

gordon861
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Re: Why USB-C ?

Fri Mar 13, 2020 3:11 pm

Technocolour wrote:
Fri Mar 13, 2020 1:12 pm
The world of barrel jacks is a big non standard jungle, people would blow up thier Pis unless you increased the cost of the power section of the pi, for just about no really good reason.

After the resistor fix, the original thought about being able to use a discarded USB PSU farting around the house is retained.
The barrel jack was just an example of an option, considering most people need to use the Pi branded PSU anyways they could have used any type of connector, it only needs two wires.

The discarded second hand PSU might have made sense with micro-USB where every device came with a new charger but not so much with USB-C because there isn't so many old chargers knocking around that state that they can do the 3A supply.

Also, a Pi4 PSU with a longer lead would probably help.

pica200
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Re: Why USB-C ?

Fri Mar 13, 2020 3:14 pm

USB-C
  • is much more robust than microUSB
  • can handle more current
  • has standardized voltages
  • supports the old USB 2.0 interface of the SoC
On top of that everything is slowly switching to this new connector. microUSB will eventually disappear. Do you need any more reasons?

edit:
Most people just buy the official power supply, yes but that doesn't mean you should use propritary connectors. If you have a working, good power supply you can just reuse it.
Last edited by pica200 on Fri Mar 13, 2020 3:26 pm, edited 1 time in total.

ejolson
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Re: Why USB-C ?

Fri Mar 13, 2020 3:25 pm

From what I understand, the idea moving forward is for the industry to design a complicated, expensive, multipurpose and easily-broken plug that would never succeed in a free market and then pay officials to pass a law that makes it a required government standard used on all devices in order to optimise E-waste.

While I've broken numerous micro USB B connectors, mostly by stepping on them, and never an Apple lightning connector, I've also yet to break a single USB C plug. While this may be because I own only one such plug specially designed to work with the original Pi 4B, it seems to fit securely and it works just fine.

I don't think USB B will simply disappear, but rather all the devices and cables will be thrown into the tip instead, perhaps reappearing in 10 years as they are dug up to make way for a housing project.
Last edited by ejolson on Fri Mar 13, 2020 3:28 pm, edited 1 time in total.

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Re: Why USB-C ?

Fri Mar 13, 2020 3:27 pm

pica200 wrote:
Fri Mar 13, 2020 3:14 pm
USB-C
  • is much more robust than microUSB
  • can handle more current
  • has standardized voltages
  • supports the old USB 2.0 interface of the SoC
On top of that everything is slowly switching to this new connector. microUSB will eventually disappear. Do you need any more reasons?
Nope.
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Re: Why USB-C ?

Fri Mar 13, 2020 4:25 pm

gordon861 wrote:
Fri Mar 13, 2020 3:11 pm
Also, a Pi4 PSU with a longer lead would probably help.
Yet more pain. Longer lead means more voltage lost on the way, which means more "low voltage" problems for the Pi.
Similar reasons for avoiding switches on the DC power lead.
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DAI-X
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Re: Why USB-C ?

Sat Mar 14, 2020 10:45 am

If you really really really want to power your Pi using a barrel jack, wire one in to the +5v and GND on your GPIO. You will lose overvoltage protection though I think.

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davidcoton
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Re: Why USB-C ?

Sat Mar 14, 2020 10:53 am

DAI-X wrote:
Sat Mar 14, 2020 10:45 am
If you really really really want to power your Pi using a barrel jack, wire one in to the +5v and GND on your GPIO. You will lose overvoltage protection though I think.
The TVS diode remains in circuit, but there is no polyfuse on the Pi4B. So if you must (IMO, foolishly) use a barrel jack, you should wire an external polyfuse between the socket and the Pi. Then you will have some protection for when you plug in a PSU with the wrong voltage or polarity.
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DAI-X
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Re: Why USB-C ?

Sat Mar 14, 2020 11:07 am

The TVS diode remains in circuit, but there is no polyfuse on the Pi4B. So if you must (IMO, foolishly) use a barrel jack, you should wire an external polyfuse between the socket and the Pi. Then you will have some protection for when you plug in a PSU with the wrong voltage or polarity.
Ah, I suspected the 4B might be different (my 4B uses official supply). I'm still in the older Pi model mindset. I think I have only one Pi powered via GPIO.
When using a non-standard supply I tend to use buck converters with USB out so I still use the Pi USB supply.

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Re: Why USB-C ?

Sat Mar 14, 2020 1:05 pm

I've resorted to barrel jacks to power a couple of my Pi projects. It was convenient to mount a panel mount jack on a portable setup that was in a case. The power supply I use is a 5V 4A that comes with a nice beefy cable and a barrel connector. It looks like your typical laptop power supply. On the plus side its easy to plug in, there is no upside down. The down side is making sure thats the only power supply I ever plug into that Pi. I'm very careful that way so its not an issue for me.
My other setup is a breadboarding rig setup on an open beam frame. Pi 3B+ (soon to be a Pi 4b) 7inch touch screen analog audio amp, etc. Trying to power this setup with a 2.5A power supply is iffy at best. Especially if I have a couple of servo's or motors hooked up. So I went with the big brother of the supply above. 5V 10A with a barrel connector. I have poly fuses in place on this setup. There was no 3A USB C Pi power supply when I built it. Even that may not be enough for this setup.

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Re: Why USB-C ?

Sat Mar 14, 2020 1:43 pm

davidcoton wrote:
Fri Mar 13, 2020 4:25 pm
gordon861 wrote:
Fri Mar 13, 2020 3:11 pm
Also, a Pi4 PSU with a longer lead would probably help.
Yet more pain. Longer lead means more voltage lost on the way, which means more "low voltage" problems for the Pi.
Similar reasons for avoiding switches on the DC power lead.
That would all be compensated for in the design.
You would still have 5.1V 3A at the connector.

ejolson
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Re: Why USB-C ?

Sat Mar 14, 2020 2:43 pm

bensimmo wrote:
Sat Mar 14, 2020 1:43 pm
davidcoton wrote:
Fri Mar 13, 2020 4:25 pm
gordon861 wrote:
Fri Mar 13, 2020 3:11 pm
Also, a Pi4 PSU with a longer lead would probably help.
Yet more pain. Longer lead means more voltage lost on the way, which means more "low voltage" problems for the Pi.
Similar reasons for avoiding switches on the DC power lead.
That would all be compensated for in the design.
You would still have 5.1V 3A at the connector.
Compensated by using 12 gauge solid copper wire? Or 24V delivery with a DC to DC converter at the Pi end? What is wrong with using a power strip with a switch and a mains extension cord?

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bensimmo
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Re: Why USB-C ?

Sat Mar 14, 2020 2:55 pm

I have no idea, why one wouldn't use and extension lead before the PSU.

I'm just commenting that they would alter the voltage into the longer inline switched wire to compensate for the extra voltage drop. Maybe using a thicker gauge.so it would give 5.1V and a capability of delivering up to 3A at the usb-C end.

'they' being the manufacturers of the PSU.

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