rickwookie
Posts: 23
Joined: Sat Mar 03, 2012 11:09 am

New PoE Hat

Tue Mar 20, 2018 1:28 pm

Looking here: http://cpc.farnell.com/raspberry-pi/rpi ... dp/SC14884
it seems the new PoE Hat is going to be about £15. Well, yes that's a big improvement over the 3rd party PoE Hat solution available until now, which cost as much as the Pi itself, but it's still half the price of the Pi!

It seems then that this sort of thing is still the most cost effective way of powering the Pi, for those with PoE switches already in place:
https://www.ebay.co.uk/itm/263214610190 - and yes they are 802.3af compatible (not just passive PoE) although they're only rated at 2.4 A, but then the official new PoE Hat is similarly rated at 2.5 A, so I suspect that's a non-issue.
Also, in fairness this particular device is only 100baseTX, so you'd lose some of those nice gains on the 3B+, but I have seen similarly priced ones that do 1000baseTX, it's just that I've had no need for them ('til now ;) ). e.g. https://www.ebay.co.uk/itm/112531452045 available for under £7 from the same seller, in quantity.

This seems a little sad, because obviously a Hat is a neater solution, and I wonder what's on the official new Poe Hat that pushes the price up to £15? The fan? Do we need a fan? Could there not be a fan-less version for a lower price? Certainly, what's on this hat that means it has to be priced at about 3 times that of the official mains adaptor/wall-wart to microUSB 5 V PSU?

Anyway, I guess it's stick with the ropey old Chinese external loop-through solution until they come up with a 3rd party PoE Hat that makes use of the four new Ethernet jack break-out pins. :(

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23709
Joined: Sat Jul 30, 2011 7:41 pm

Re: New PoE Hat

Tue Mar 20, 2018 1:43 pm

Decent profit margin, so we can employ the staff to build more and better product, and send more profit on to the Foundation for educational purposes? Proper certification for FCC and CE compliance, ROHS, quality design?

Or you can buy from China.

(Note, the final pricing for the PoE HAT has not yet been finalised)
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
"My grief counseller just died, luckily, he was so good, I didn't care."

achrn
Posts: 374
Joined: Wed Feb 13, 2013 1:22 pm

Re: New PoE Hat

Tue Mar 20, 2018 2:48 pm

rickwookie wrote:
Tue Mar 20, 2018 1:28 pm
It seems then that this sort of thing is still the most cost effective way of powering the Pi, for those with PoE switches already in place:
https://www.ebay.co.uk/itm/263214610190 - and yes they are 802.3af compatible (not just passive PoE) although they're only rated at 2.4 A, but then the official new PoE Hat is similarly rated at 2.5 A, so I suspect that's a non-issue.
Have you actually tried pulling 2.4A from one? Did it work?

I have tried an identical-looking identical-spec ebay one, and it wasn't capable of booting a pi with external USB HDD attached, while a TP-Link splitter that's supposedly only 2A does the job no problem (with exactly the same 48V injector over exactly the same length of cable).

£15 for one that actually meets its specs is preferable to £5 but doesn't get halfway there, in my opinion.

rickwookie
Posts: 23
Joined: Sat Mar 03, 2012 11:09 am

Re: New PoE Hat

Wed Mar 21, 2018 9:08 pm

jamesh wrote:
Tue Mar 20, 2018 1:43 pm
Decent profit margin, so we can employ the staff to build more and better product, and send more profit on to the Foundation for educational purposes? Proper certification for FCC and CE compliance, ROHS, quality design?

Or you can buy from China.

(Note, the final pricing for the PoE HAT has not yet been finalised)
I think that was an unnecessarily curt response to a reasonable question. It would be irresponsible for the foundation to design, manufacture and then sell products at a loss. (Is that why the Pi Zero is always sold on a one per customer basis?).

I feel my comparison to the official Raspberry Pi mains adaptor pricing is a fair one. which presumably also has "proper certification for FCC and CE compliance, ROHS, quality design". Are they really that much cheaper to build and distribute than the new PoE Hat?

It seems from your response that a decision has been made to price it with "decent profit margin" that goes further than justifying the product in itself, but is inflated to subsidise your mainline products. This is a perfectly valid stance, after all these are all amazing prices:
Pi Zero £3.82
Pi Zero W £7.63
Pi Zero WH £10.68
Pi 3B+ £26.67

But since the price for the official PSU:
Official Raspberry Pi PSU £5.83
Allow me my disappointment at seeing:
RPI3-MODBP-POE £14.79

As for "(Note, the final pricing for the PoE HAT has not yet been finalised)"... ...perhaps someone at the foundation should let CPC know, since they're already taking orders for it.

rickwookie
Posts: 23
Joined: Sat Mar 03, 2012 11:09 am

Re: New PoE Hat

Wed Mar 21, 2018 9:18 pm

achrn wrote:
Tue Mar 20, 2018 2:48 pm
rickwookie wrote:
Tue Mar 20, 2018 1:28 pm
It seems then that this sort of thing is still the most cost effective way of powering the Pi, for those with PoE switches already in place:
https://www.ebay.co.uk/itm/263214610190 - and yes they are 802.3af compatible (not just passive PoE) although they're only rated at 2.4 A, but then the official new PoE Hat is similarly rated at 2.5 A, so I suspect that's a non-issue.
Have you actually tried pulling 2.4A from one? Did it work?

I have tried an identical-looking identical-spec ebay one, and it wasn't capable of booting a pi with external USB HDD attached, while a TP-Link splitter that's supposedly only 2A does the job no problem (with exactly the same 48V injector over exactly the same length of cable).

£15 for one that actually meets its specs is preferable to £5 but doesn't get halfway there, in my opinion.
I snapped up a few of the TP-Link units when Maplin had them on special offer for £9.99 all in. Thing is though, they where still a clunky solution, since they have a barrel type power connector, so it required iirc one USB A to barrel lead and then a female USB A socket to microUSB (OTG type) I think to finally get the power into my Pi. Hence my looking for the neater solution, which also turned out to by way cheaper. Similar in cost to the mains PSU in fact.

As for the power draw issue, I've not done any measurments, but I'd say you're pushing your luck trying to power an externall HDD even with the official PSU aren't you? I've only ever tried a PoE solution to power a Pi on its own.

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23709
Joined: Sat Jul 30, 2011 7:41 pm

Re: New PoE Hat

Wed Mar 21, 2018 9:33 pm

rickwookie wrote:
Wed Mar 21, 2018 9:08 pm
jamesh wrote:
Tue Mar 20, 2018 1:43 pm
Decent profit margin, so we can employ the staff to build more and better product, and send more profit on to the Foundation for educational purposes? Proper certification for FCC and CE compliance, ROHS, quality design?

Or you can buy from China.

(Note, the final pricing for the PoE HAT has not yet been finalised)
I think that was an unnecessarily curt response to a reasonable question. It would be irresponsible for the foundation to design, manufacture and then sell products at a loss. (Is that why the Pi Zero is always sold on a one per customer basis?).

I feel my comparison to the official Raspberry Pi mains adaptor pricing is a fair one. which presumably also has "proper certification for FCC and CE compliance, ROHS, quality design". Are they really that much cheaper to build and distribute than the new PoE Hat?

It seems from your response that a decision has been made to price it with "decent profit margin" that goes further than justifying the product in itself, but is inflated to subsidise your mainline products. This is a perfectly valid stance, after all these are all amazing prices:
Pi Zero £3.82
Pi Zero W £7.63
Pi Zero WH £10.68
Pi 3B+ £26.67

But since the price for the official PSU:
Official Raspberry Pi PSU £5.83
Allow me my disappointment at seeing:
RPI3-MODBP-POE £14.79

As for "(Note, the final pricing for the PoE HAT has not yet been finalised)"... ...perhaps someone at the foundation should let CPC know, since they're already taking orders for it.
Surprised CPC are selling them, since I am not even sure we have started making them yet. When I spoke to the guy who sets prices less than a week ago, he said the final pricing had not been decided.

As for profit margin, it will be appropriate. It won't be 'inflated'. We aim to target pricing so it is sensible. After all, there is no point in pricing something so high people won't buy it, or too low that it's not cost effective to sell. The Zero is an exception to that second one, but you can only buy one at the educational discount price so it's not quite the same. I cannot comment on the power supply BOM vs PoE BOM, but worth noting that the supply is sold in very large numbers, the PoE HAT will not get near those levels, so profit margins need to be higher to compensate for lower sales.

It always comes down to the customer. If they don't like the price, they don't buy it! Always a line to tread.

Of course, once the badly designed/manufactured PoE adapter bought from China for £6 catches fire (I believe someone reported this happening only the other day), that £14.79, or whatever it turns out to be, doesn't sound too bad.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
"My grief counseller just died, luckily, he was so good, I didn't care."

timrowledge
Posts: 1284
Joined: Mon Oct 29, 2012 8:12 pm
Location: Vancouver Island
Contact: Website

Re: New PoE Hat

Wed Mar 21, 2018 9:56 pm

If the Pi were $1 would you expect any accessory to be cheaper than that? If the Pi were priced in the realms of dev-boards in days gone by (like $100 or more, sometimes much more) would you be pleased with a PoE hat for $30?
Making Smalltalk on ARM since 1986; making your Scratch better since 2012

rickwookie
Posts: 23
Joined: Sat Mar 03, 2012 11:09 am

Re: New PoE Hat

Wed Mar 21, 2018 10:35 pm

jamesh wrote:
Wed Mar 21, 2018 9:33 pm
As for profit margin, it will be appropriate. It won't be 'inflated'. We aim to target pricing so it is sensible. After all, there is no point in pricing something so high people won't buy it, or too low that it's not cost effective to sell. The Zero is an exception to that second one, but you can only buy one at the educational discount price so it's not quite the same. I cannot comment on the power supply BOM vs PoE BOM, but worth noting that the supply is sold in very large numbers, the PoE HAT will not get near those levels, so profit margins need to be higher to compensate for lower sales.

It always comes down to the customer. If they don't like the price, they don't buy it! Always a line to tread.
Thank you for taking the time to respond to my query, I do appreciate it.

It's definately a case of the price needing to be right. I never even considered for one moment, for example, to buy that other 3rd party PoE Hat thingy that's around for £30.
jamesh wrote:
Wed Mar 21, 2018 9:33 pm
once the badly designed/manufactured PoE adapter bought from China for £6 catches fire
yeah that's possibly a little unfair and in danger of drifting into the Apple mantra of "buy our hugely overpriced lightning cables or all your children will die horribly when their iDevices explode in their face" FUD. I'm sure there are good and bad examples of the low-cost in-line PoE extractors out there! Aren't the RPi PSUs made in China anyway?

What I would say is that of all my years experience now in installing electronic equipment, and having to return to fix it if/when it fails, the low cost mains adapter is the culprit in the vast majority of cases. I hate to think how many otherwise perfectly functioning electronic devices people must have binned over the years simply due to needing a new PSU! Trouble is, there's not really a supply of slightly higher cost, but much more robust plug-top type PSUs out there, so it's always a case of go with the manufacturer approved one, and expect to have to return with 18 months when if fails again.

What's the point of me sharing this anecdote? Well, so far I've yet to have any failure of a device due to loss of PoE power! Now, I know the numbers out there are smaller, but there's still a lot of devices out there I've installed that are PoE (IP security cameras, touchscreen control interfaces, RF remote control receivers, WiFi access points, etc.). You could argue that, for example, if you had 24 PoE powered devices hanging off one PoE switch say, and the switch dies, you loose all 24 devices (tbh if it were a standard switch and they just lost their data connection, they may well be useless anyway, depending on the devices), but IME it never happens. On the other hand, without PoE, you end up with 24 separate little aforementioned crappy wall-wart PSUs (or something similar) and the chances of any one of them failing in a relatively short time is very high. For me that means a costly site-visit to replace a PSU, then again a few weeks later when another one dies, and so on.

I think by now you probably understand that I'm quite a fan of PoE powering things, and while it may seem like a niche option and the foundation may not sell many PoE Hats, if you price it right (hint < £10 including vat), you might be surprised at just how popular they become.

rickwookie
Posts: 23
Joined: Sat Mar 03, 2012 11:09 am

Re: New PoE Hat

Wed Mar 21, 2018 10:52 pm

timrowledge wrote:
Wed Mar 21, 2018 9:56 pm
If the Pi were $1 would you expect any accessory to be cheaper than that? If the Pi were priced in the realms of dev-boards in days gone by (like $100 or more, sometimes much more) would you be pleased with a PoE hat for $30?
I'm not quite sure I understand what point you're trying to make. Jamesh has already pretty much indicated that the Pi Zero is the only non-profit making device they sell. If the Pi were $100, they wouldn't have sold the however many million units they have.

The price of any accessory I would expect to be related to its cost to produce, not a factor of how cheap or not the device it attaches to is. This is why I was specifically comparing the PoE Hat to an alternative accessory for powering the Pi, namely the official PSU, and questioning it's price based on what appears externally to be a very simple accessory. I have no idea what any of the components on the PoE Hat are or cost individually, so I thought I'd ask, giving the example that I did of a very cheap accessory which I would assume would have to contain similar components.

BTW, the fact that you can buy something like The Raspberry Pi Camera v2 for only £20 amazes me (it's an 8 MegaPixel
camera!), let alone the amazing low price of the RPi 3B+ itself!!!

fruitoftheloom
Posts: 20769
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: New PoE Hat

Thu Mar 22, 2018 6:22 am

rickwookie wrote:
Wed Mar 21, 2018 10:52 pm
timrowledge wrote:
Wed Mar 21, 2018 9:56 pm
If the Pi were $1 would you expect any accessory to be cheaper than that? If the Pi were priced in the realms of dev-boards in days gone by (like $100 or more, sometimes much more) would you be pleased with a PoE hat for $30?
I'm not quite sure I understand what point you're trying to make. Jamesh has already pretty much indicated that the Pi Zero is the only non-profit making device they sell. If the Pi were $100, they wouldn't have sold the however many million units they have.

The price of any accessory I would expect to be related to its cost to produce, not a factor of how cheap or not the device it attaches to is. This is why I was specifically comparing the PoE Hat to an alternative accessory for powering the Pi, namely the official PSU, and questioning it's price based on what appears externally to be a very simple accessory. I have no idea what any of the components on the PoE Hat are or cost individually, so I thought I'd ask, giving the example that I did of a very cheap accessory which I would assume would have to contain similar components.

BTW, the fact that you can buy something like The Raspberry Pi Camera v2 for only £20 amazes me (it's an 8 MegaPixel
camera!), let alone the amazing low price of the RPi 3B+ itself!!!

The TP Link Kit is about the cheapest one can get from an established Brand, the downside is it is 5V 2A.

So likely cost with cables would be around £25.00 inc. Taxes & P&P

viewtopic.php?f=46&t=154158#p1008863

If the Official PoE Hat is around £20.00 Inc Taxes & P&P and can give a steady 5V 2.5A would consider that value for money.

Yes it may seem overpriced but at least it is well tested, conforms to safety standards and as a bonus puts a few pennies in the RPF to enable it to meet its charitable goals.
Retired disgracefully.....

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23709
Joined: Sat Jul 30, 2011 7:41 pm

Re: New PoE Hat

Thu Mar 22, 2018 9:45 am

rickwookie wrote:
Wed Mar 21, 2018 10:52 pm
timrowledge wrote:
Wed Mar 21, 2018 9:56 pm
If the Pi were $1 would you expect any accessory to be cheaper than that? If the Pi were priced in the realms of dev-boards in days gone by (like $100 or more, sometimes much more) would you be pleased with a PoE hat for $30?
The price of any accessory I would expect to be related to its cost to produce, not a factor of how cheap or not the device it attaches to is. This is why I was specifically comparing the PoE Hat to an alternative accessory for powering the Pi, namely the official PSU, and questioning it's price based on what appears externally to be a very simple accessory. I have no idea what any of the components on the PoE Hat are or cost individually, so I thought I'd ask, giving the example that I did of a very cheap accessory which I would assume would have to contain similar components.
I think this is where you expectation doesn't match what most companies do. Cost of accessories can often be completely unrelated to their actual cost to manufacture. You can see it in any number of industries.

There's an anecdote about the snow undercarriage/skids used on the Hercules aircraft. Cost to build is a few 10's of thousand dollars. Cost to buy is multi millions of dollars. Development cost is a part, but also, there are so few orders for them, that the individual cost is massively inflated. Of course, being a captive market helps.

Being more specific about the PoE HAT compared with the power supply. For the PS, AFAIK, we didn't design it, we specified it, and it's is made for us by a PS company. For the PoE we have had to design it ourselves, test it, get it compliance tested and rated, sort out a manufacturing line then manufacture it etc. So there is a whole lot more to its development that the PS. And since the sales figures are bound to be lower than the PS, there are less economies of scale.

Lots of things to consider that might not at first be obvious.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
"My grief counseller just died, luckily, he was so good, I didn't care."

mfa298
Posts: 1387
Joined: Tue Apr 22, 2014 11:18 am

Re: New PoE Hat

Thu Mar 22, 2018 12:06 pm

rickwookie wrote:
Tue Mar 20, 2018 1:28 pm
It seems then that this sort of thing is still the most cost effective way of powering the Pi, for those with PoE switches already in place:
https://www.ebay.co.uk/itm/263214610190 - and yes they are 802.3af compatible (not just passive PoE) although they're only rated at 2.4 A, but then the official new PoE Hat is similarly rated at 2.5 A, so I suspect that's a non-issue.
I've got one of them (or something very similar) powering a Pi3 which seems to work. Trying another one on the 3B+ I've just got it doesn't bring the link up (I'd used the same one to power a Pi1 a while ago so it should be working). My suspicion is that as the RJ45 plug only has two pairs wired the 3B+ isn't bringing up the link (based on very limited testing). I need to test with an SD card/other devices to see what works and doesn't work.
rickwookie wrote:
Tue Mar 20, 2018 1:28 pm
Also, in fairness this particular device is only 100baseTX, so you'd lose some of those nice gains on the 3B+, but I have seen similarly priced ones that do 1000baseTX, it's just that I've had no need for them ('til now ;) ). e.g. https://www.ebay.co.uk/itm/112531452045 available for under £7 from the same seller, in quantity.
I wonder if that really is a Gigabit version. The pictures seem to suggest there's still only two pairs connected inside the RJ45 plug, but then the images are about as likely to be correct as the description. At that price though I think I'll wait for the PoE hat, it may well arrive as quickly and is designed for the purpose.

mfa298
Posts: 1387
Joined: Tue Apr 22, 2014 11:18 am

Re: New PoE Hat

Thu Mar 22, 2018 1:11 pm

mfa298 wrote:
Thu Mar 22, 2018 12:06 pm
I've got one of them (or something very similar) powering a Pi3 which seems to work. Trying another one on the 3B+ I've just got it doesn't bring the link up (I'd used the same one to power a Pi1 a while ago so it should be working). My suspicion is that as the RJ45 plug only has two pairs wired the 3B+ isn't bringing up the link (based on very limited testing). I need to test with an SD card/other devices to see what works and doesn't work.
So with some testing it seems the issue is with a 2 pair cable plugged into a gigabit switch (not that surprising really). I expect the 3B+ is trying to negotiate gigabit speeds with the switch and then failing as two pairs are missing. Tested against two managed switches (Netgear and Extreme Networks).

Fixing the interface speed on the switch to 100MB will work but could lead to other issues (the Pi end also needs to be fixed to the same settings).

I suspect the same issue might hit those trying to use the cheapy passive cables as well to supply power down the unsued pairs (well unused for Fast Ethernet). Although I do wonder how a dumb gigabit switch will handle the scenario of only two connected pairs, will it struggle to bring the link up or will it drop back to some form of 100MB ethernet (possibly with autoneg off so potentially leading to other issues)

rotwang
Posts: 243
Joined: Sat Dec 07, 2013 1:12 pm

Re: New PoE Hat

Thu Mar 22, 2018 1:19 pm

Nobody ever needed glasses for defective hindsight, but here goes --
In some future incarnation (maybe pi4) would you consider using an 8-pin header for the PoE board, assigned as :-
4 pins -- centre taps of magjack coils
2 pins -- +5v and Gnd to pi
2 pins -- SDA and SCL for eeprom and fan control
with corresponding 8-pin on Pi.

That way the 40-pin header is completely untouched and free to have a HAT fitted, since I can see more uses for a processor with a HAT on the end of a PoE cable than not.

Just a thought, feel free to ignore or whatevere,
Roger

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23709
Joined: Sat Jul 30, 2011 7:41 pm

Re: New PoE Hat

Thu Mar 22, 2018 2:42 pm

rotwang wrote:
Thu Mar 22, 2018 1:19 pm
Nobody ever needed glasses for defective hindsight, but here goes --
In some future incarnation (maybe pi4) would you consider using an 8-pin header for the PoE board, assigned as :-
4 pins -- centre taps of magjack coils
2 pins -- +5v and Gnd to pi
2 pins -- SDA and SCL for eeprom and fan control
with corresponding 8-pin on Pi.

That way the 40-pin header is completely untouched and free to have a HAT fitted, since I can see more uses for a processor with a HAT on the end of a PoE cable than not.

Just a thought, feel free to ignore or whatevere,
Roger
I'll pass the thought on to the design dudes.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
"My grief counseller just died, luckily, he was so good, I didn't care."

epoch1970
Posts: 3712
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: New PoE Hat

Thu Mar 22, 2018 4:57 pm

I was curious about the price, I expected it to cost about as much as the Pi.
I've just spotted it at ~16€ ex-VAT from RS... I guess you're planning to sell much more units than I thought :)
Well done!
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

hippy
Posts: 5973
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: New PoE Hat

Thu Mar 22, 2018 5:24 pm

rotwang wrote:
Thu Mar 22, 2018 1:19 pm
Nobody ever needed glasses for defective hindsight, but here goes ...

That way the 40-pin header is completely untouched and free to have a HAT fitted
The challenge with that proposal is where to connect the PoE I2C ID EEPROM to. If it connects to ID_SC and ID_SD and is at the usual HAT ID EEPROM address it still precludes the use of a HAT on the GPIO. We also don't know how the fan is controlled.

Not saying it can't be done and is worth considering for a future Pi version.

Pithagoros
Posts: 580
Joined: Wed Nov 12, 2014 8:16 pm

Re: New PoE Hat

Thu Mar 22, 2018 5:38 pm

I don't think that comparing the cost of the PoE hat to the cost of the official PSU is a valid one.

If you don't have a PSU already then PSU is essential to getting the Pi working and the purpose of the Pi is to get it into more hands. PoE will never have that position, it's a different target buyer, the owner of a PoE switch,

achrn
Posts: 374
Joined: Wed Feb 13, 2013 1:22 pm

Re: New PoE Hat

Thu Mar 22, 2018 5:58 pm

rickwookie wrote:
Wed Mar 21, 2018 9:18 pm
achrn wrote:
Tue Mar 20, 2018 2:48 pm
rickwookie wrote:
Tue Mar 20, 2018 1:28 pm
It seems then that this sort of thing is still the most cost effective way of powering the Pi, for those with PoE switches already in place:
https://www.ebay.co.uk/itm/263214610190 - and yes they are 802.3af compatible (not just passive PoE) although they're only rated at 2.4 A, but then the official new PoE Hat is similarly rated at 2.5 A, so I suspect that's a non-issue.
Have you actually tried pulling 2.4A from one? Did it work?

I have tried an identical-looking identical-spec ebay one, and it wasn't capable of booting a pi with external USB HDD attached, while a TP-Link splitter that's supposedly only 2A does the job no problem (with exactly the same 48V injector over exactly the same length of cable).

£15 for one that actually meets its specs is preferable to £5 but doesn't get halfway there, in my opinion.
As for the power draw issue, I've not done any measurments, but I'd say you're pushing your luck trying to power an externall HDD even with the official PSU aren't you? I've only ever tried a PoE solution to power a Pi on its own.
It's completely irrelevant whether it's 'pushing my luck'. The TP-Link one works fine, 100% reliably. The cheap-from-ebay one that is advocated as a good solution, and tabled as a demonstration that the guessed PoE hat price is unreasonable, doesn't work.

I'd rather pay £15 or £20 for something that does work than £5 or £6 for something that doesn't. Pointing out that you can buy a cheaper one (that doesn't actually work) is not a useful contribution, in my opinion, and does not demonstrate anything about the price point being speculated over.

rickwookie
Posts: 23
Joined: Sat Mar 03, 2012 11:09 am

Re: New PoE Hat

Fri Mar 23, 2018 8:00 pm

achrn wrote:
Thu Mar 22, 2018 5:58 pm
It's completely irrelevant whether it's 'pushing my luck'. The TP-Link one works fine, 100% reliably. The cheap-from-ebay one that is advocated as a good solution, and tabled as a demonstration that the guessed PoE hat price is unreasonable, doesn't work.

I'd rather pay £15 or £20 for something that does work than £5 or £6 for something that doesn't. Pointing out that you can buy a cheaper one (that doesn't actually work) is not a useful contribution, in my opinion, and does not demonstrate anything about the price point being speculated over.
Ok, translate "pushing your luck" to exceeding the manufacturers specified maximum current rating. If you're not pulling more than 2 A powering the Pi AND an external USB HDD (which would surprise me), then you'd have every reason to expect the TP-Link unit it to work. If you're pulling more though, only expect it to work "100% reliably" until if fails! :P

The fact that the cheaper one "that doesn't actually work" is not useful... ...well how many did you try? It's not unreasonable to assume that you got unlucky with a duff one, and it would take a significant effort (and expense) to come to any conclusion regarding their failure rate. On the other hand, I could send you an whole box of 5 V 2.5 A PSUs that also "don't work", incidentally many of them made by the same manufacture that I believe makes the official Pi unit. ;-)

I'm not even the only person on this thread, let alone the only person in the world that has had success with the cheapo units.

My issue with the TP-Link tbh is mainly, as I think I've mentioned already, is the clunkyness off the chain of cabling that's needed. The item that I linked to, which you appear to have written off based on I'm not sure how many failures, is neater, but ultimately the Hat's definitely the way to go! :D (with the caveat that it appears to not allow further Hats to be added? This could be a deal breaker for a lot of use cases obviously).

mfa298
Posts: 1387
Joined: Tue Apr 22, 2014 11:18 am

Re: New PoE Hat

Fri Mar 23, 2018 8:53 pm

rickwookie wrote:
Fri Mar 23, 2018 8:00 pm
achrn wrote:
Thu Mar 22, 2018 5:58 pm
It's completely irrelevant whether it's 'pushing my luck'. The TP-Link one works fine, 100% reliably. The cheap-from-ebay one that is advocated as a good solution, and tabled as a demonstration that the guessed PoE hat price is unreasonable, doesn't work.
...
The fact that the cheaper one "that doesn't actually work" is not useful... ...well how many did you try? It's not unreasonable to assume that you got unlucky with a duff one, and it would take a significant effort (and expense) to come to any conclusion regarding their failure rate. On the other hand, I could send you an whole box of 5 V 2.5 A PSUs that also "don't work", incidentally many of them made by the same manufacture that I believe makes the official Pi unit. ;-)
He maybe talking about my tests yesterday where I proved that the PoE splitters like https://www.ebay.co.uk/itm/263214610190 will have issues on the Pi3B+. This is due to them only connecting two pairs inside the RJ45 plug meaning the attempts to negotiate a gigabit connection fail due to an air gap. In that case it's effectively a design fault and/or misuse of a product rather than anything else (I could get the same issue using a 2 pair cat5e cable).

You can make those PoE splitters work by forcing the speed to 100Mbit in some way. This could be a FastEthernet switch in the middle or fixing the Pi and Network port to 100/Full (but note you normally have to do that on both ends otherwise you'll get errors that aren't necessarily obvious). In my case I've found I can set the switch to limit that port to 100MBit and still do auto negotiation (co port 13 auto on speed 100, but that's only useful if you have the same type of PoE switch as me)

As for the Gigabit version of the same thing you linked to, maybe that will work (and the images are wrong - as they seem to only show 2 pairs), or they have the same issue (meaning the description is wrong), I'm not sure I want to waste that money to find out. Maybe the TP-Link is better and connects all pairs, or maybe it also has the same issue (maybe someone would like to open one up and see what's connected) - again I think I'll wait for the PoE hat as that will end up being a similar cost and is going to work (and may be available in the same time as a slow boat from China).

achrn
Posts: 374
Joined: Wed Feb 13, 2013 1:22 pm

Re: New PoE Hat

Sat Mar 24, 2018 11:14 am

rickwookie wrote:
Fri Mar 23, 2018 8:00 pm
achrn wrote:
Thu Mar 22, 2018 5:58 pm
It's completely irrelevant whether it's 'pushing my luck'. The TP-Link one works fine, 100% reliably. The cheap-from-ebay one that is advocated as a good solution, and tabled as a demonstration that the guessed PoE hat price is unreasonable, doesn't work.

I'd rather pay £15 or £20 for something that does work than £5 or £6 for something that doesn't. Pointing out that you can buy a cheaper one (that doesn't actually work) is not a useful contribution, in my opinion, and does not demonstrate anything about the price point being speculated over.
Ok, translate "pushing your luck" to exceeding the manufacturers specified maximum current rating. If you're not pulling more than 2 A powering the Pi AND an external USB HDD (which would surprise me), then you'd have every reason to expect the TP-Link unit it to work. If you're pulling more though, only expect it to work "100% reliably" until if fails! :P
With a meter set to detect peaks of width 5mS or more (which is the fastest my multimeter runs) the peak while booting is 1.27A, typical while not doing much is around 0.6A to 0.7A range, and working the disk (a recursive ls, for example) peaks at 1.19A. The shutdown process peaks at 1.23A. So no, I'm not exceeding the manufacturers rating, and no the ebay one wasn't capable of reaching its rating.

[As an aside, turning speed down a notch on my meter, which gives me a 20/s sample rate, but the minimum detected width of a spike is not documented, and the smoothing is not documented, peak during boot is 1.016A, and the recursive ls peaks at 0.952A, in each case this being peak from half a dozen runs.]

As previously noted, the cheap-from-ebay unit that can supposedly deliver 2.4A can't boot the Pi - it starts booting, then (presumably when the disk starts to spin up) fails and chunters. This is a B+v1.0 (rev code 0010) and a WD Elements 2GB USB disk. It's nothing to do with the 3B+.
rickwookie wrote:
Fri Mar 23, 2018 8:00 pm
I'm not even the only person on this thread, let alone the only person in the world that has had success with the cheapo units.
For completely unspecified values of 'success'. You maintain it's 802.3af compliant, apparently endorse the specification that it can supply 2.4A, but get strangely coy about what current you've actually drawn from it. Meanwhile criticising the PoE hat pricing (though there's been no official announcement of what the pricing is, I think), and tabling the cheapo chinese one apparently to demonstrate that the official hat should be cheaper.

I think that demonstrating that you can find a cheaper unit is irrelevant if you don't know or can't trust the specification of the cheaper one - it's really cheap to write '2.4A' on something, but that doesn't actually make it deliver 2.4A. However, I do trust that the official hat deliver its rating, and that to my mind makes it better value at £15 than an ebay-special at £6 that can't sustain 1.3A for even a few milliseconds.

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23709
Joined: Sat Jul 30, 2011 7:41 pm

Re: New PoE Hat

Sat Mar 24, 2018 11:44 am

As I implied above, if people are happy using a cheaper device, then they are happy using a cheaper device. I'm not going to stop them!

But as I said above, who knows how good the design is, who knows whether it adheres to the relevant standards, who knows if it is safe?

What we do know is the the profits from all Foundation products go towards developing new products, and keep the Foundation supplied with money to keep the charity going.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
"My grief counseller just died, luckily, he was so good, I didn't care."

Paul Hutch
Posts: 390
Joined: Fri Aug 25, 2017 2:58 pm
Location: Blackstone River Valley, MA, USA
Contact: Website

Re: New PoE Hat

Sat Mar 24, 2018 4:31 pm

mfa298 wrote:
Fri Mar 23, 2018 8:53 pm
Maybe the TP-Link is better and connects all pairs, or maybe it also has the same issue (maybe someone would like to open one up and see what's connected) - again I think I'll wait for the PoE hat as that will end up being a similar cost and is going to work (and may be available in the same time as a slow boat from China).
My experience is that TP-Link is 100% honest with their specs and will take back the item and refund your purchase if they made a mistake in the specs. So I would not hesitate to try out the TP-Link TL-POE10R adapter and return it if it doesn't work for Gigabit Ethernet as they claim. (I'm not doing it since I don't have a POE capable switch or injector yet)
https://www.tp-link.com/us/products/det ... OE10R.html

fruitoftheloom
Posts: 20769
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: New PoE Hat

Sat Mar 24, 2018 5:18 pm

Paul Hutch wrote:
Sat Mar 24, 2018 4:31 pm
mfa298 wrote:
Fri Mar 23, 2018 8:53 pm
Maybe the TP-Link is better and connects all pairs, or maybe it also has the same issue (maybe someone would like to open one up and see what's connected) - again I think I'll wait for the PoE hat as that will end up being a similar cost and is going to work (and may be available in the same time as a slow boat from China).
My experience is that TP-Link is 100% honest with their specs and will take back the item and refund your purchase if they made a mistake in the specs. So I would not hesitate to try out the TP-Link TL-POE10R adapter and return it if it doesn't work for Gigabit Ethernet as they claim. (I'm not doing it since I don't have a POE capable switch or injector yet)
https://www.tp-link.com/us/products/det ... OE10R.html

The specifications state 5V 2A :!:
Retired disgracefully.....

Return to “General discussion”