Joggler Side USB Port Current Source Capacity

cbredfred · Post by **cbredfred** » Sun Mar 18, 2012 7:04 pm

There has been some speculation, in various threads on this forum, that the Joggler is incapable of supplying much current to device that are connected to it.
If you have a read of the USB specifications it states that a "Unit Load" is 100mA and that a USB 2 port should be able to supply 5 unit loads which equals 500mA.
Have a read of Wikipedia's "Power" section of the following USB article:

http://en.wikipedia.org/wiki/Universal_Serial_Bus

Here is a photo of my Samsung Galaxy S charging off the Jogglers USB port.

: Steady Current drawn by an intelligent device

As you can see it is pulling 480mA.

Here is another photo of my meter showing a MAX reading of 840mA, which is the current required to overcome the inertia of the disk and get it spinning.
This current draw is very short, but the Joggler copes.

From what I can see the Joggler can deliver all the current that it is specified to.

WARNING: Tangent follows!!!

In this second photo it is easier to see the USB break out cable that I made in order to better figure out USB problems.
All I have done is split a cable and provide test points and a jumper for each of the 4 wires.
When I want to measure the current I remove the jumper in the red wire and connect my meter across the test points for that wire.
The Galaxy S follows the rules and doesn't pull more than 500mA because the data leads aren't shorted. If the Settings/About Phone/Status screen was showing on the Galaxy, you'd see under "Battery Status" that it would say "Charging(USB)". If you connect it to a charger that has the data leads of it's USB port shorted, you'd see the Galaxy draw 590mA and the "Battery Status" would say "Charging(AC)".
Of course it gets way more complicated if we start chucking Apple devices into the mix.
An iPhone Charger(5w) can provide 1A of current to the phone. How does an iPhone know that it's connected to an iPhone charger and not some more feeble device?
Instead of shorting the data leads together, the charger puts 2.6v on pin 2 and 2v on pin 3 (pins 2 & 3 are the data leads), and so the iPhone knows it can pull up to an Amp without biting the hand that feeds it!

If you connect an iPad up to that same iPhone Charger it also will pull an Amp, however, if you connect it to an iPad Charger(10w) it will see that it has 2v on pin 2 and 2.6v on pin 3 and so it can take the gloves off and pulls 2 Amps!!!

Post by **roobarb!** » Mon Mar 19, 2012 12:19 am

cbredfred wrote:From what I can see the Joggler can deliver all the current that it is specified to.

Good work - that myth about USB power and the Joggler has been around for far too long. Hopefully now it can finally be put to rest! Joggler Mythbusting!

Mevi · Post by **Mevi** » Mon Mar 19, 2012 4:56 pm

I charge both my iDevices with the iPad charger. Nice and quick!

Great work, cbredfred

Juggler · Post by **Juggler** » Thu Mar 22, 2012 2:42 pm

There must be some upper limit of the current that the Joggler can supply, as when I put a Samsung 2.5" hard drive in a USB enclosure directly into an OpenPeak joggler, the drive won't spin up. The enclosure has a power supply plug, so I plugged this into a 400mA 5V Huawei mobile phone charger and the drive did spin up when the Joggler was switched on and provided some additional current. The XUbuntu I had on the hard drive then booted.

In doing this, some nasty looking stuff happened, which I will write about, but it does put me off using any device that allows current to flow back into the Joggler's USB port.

A cheapish powered hub I have appears to power the devices plugged into the hub, but does not allow current from the power supply to flow back into the host, the hub is connected to. I don't know if I can use this to get a Windows to boot, but will be having a go soonish.

Actually I cringed a bit when I first read this thread as I have damaged two USB sockets, one on a desktop and another on a laptop, by charging an Ericsson T29 (yes, it was a few years a go !), which was on what appeared to be a straight through cable. This was after numerous charges and over several months. The phones port is not USB, it was just wired up to the +5V and ground on a USB plug, and I think the phone would take as much current as it could get or needed. It also powered a few LEDs on the desktop when the desktop was switched off and the phone was still plugged in - i.e. current was flowing the other way and the phone was powering parts of the desktop !

So my experience would be that yes you can draw more than the 500mA, but if you do so for extended periods and over some time, it may be that something goes in your Joggler and it will no longer provide +5V on the side USB plug.

cbredfred · Post by **cbredfred** » Thu Mar 22, 2012 3:14 pm

By showing the photo of a HDD pulling 840mA from a Jogglers side USB port I wasn't advocating that as something one should do daily, I was just trying to emphasize the fact that the Joggler can provide the fully specified 5 unit loads of the USB 2 specification. The HDD being used for those tests uses about 250mA once it's up and running and I normally run it from a powered Belkin USB hub with a Y-Cable as seen in the photo in the VOIP thread.
I'm still in the tinker phase with Windows on the Joggler and so haven't gotten my head around leaving HDD's permanently spinning in a production environment let alone how I would power them in a neat and tidy fashion from a Joggler and it's power supply (might make a Y-Cable that would have a female for the Jogglers PSU and then males for the Joggler and a powered hub).

My Belkin USB Hub must have a blocking diode in it so that it doesn't feed the USB host. However, the cheapo silver USB hub that you can see in the photo with the Galaxy S charging from it, causes some horrific sound effects from the Jogglers speakers if it is being powered from an external PSU and the Jogglers PSU is disconnected!!!

cbredfred · Post by **cbredfred** » Thu Mar 22, 2012 3:31 pm

As for your experience with charging your Ericsson phone, devices are supposed to negotiate with the USB host regarding how much current they can draw before they draw it.
I think that the USB spec never dreamed that it would become the de facto standard for charging gadgets of all kinds.
Just because some enterprising soul whips up a cable to connect your newly acquired shinny piece of kit to a USB socket, doesn't mean that your USB socket is going to thank you for violating it's specification in such an ungentlemanly fashion.

Who knew that all these wonderful chips actually run on smoke, and that when you let the smoke out...they stop working!?!?

gegs · Post by **gegs** » Thu Mar 22, 2012 3:59 pm

cbredfred wrote:By showing the photo of a HDD pulling 840mA from a Jogglers side USB port I wasn't advocating that as something one should do daily...

Now you tell us...

cbredfred · Post by **cbredfred** » Thu Mar 22, 2012 4:24 pm

Post by **hawsey** » Thu Mar 22, 2012 11:43 pm

So funny lol

Juggler · Post by **Juggler** » Fri Mar 23, 2012 9:59 pm

cbredfred I think you've done some great work here and are doing stuff in other areas that I'm really interested in too. I just wanted to give some of my past experience of my most "ungentlemanly violations of the USB port" and what happened. I am not that familiar with the USB specification, but I have seen somewhere that if a device does draw too much current then the port should cut off providing power, till say a system reboot, or something along those lines. I've never seen that happen, though.

The device I used for "violations" just took what current it could get as it was wired directly to the +5V and ground on the USB port. All the USB port knew was that current was being drawn. It was about 10 years ago, when not that many phones had USB on them. I guess it could be like some of the USB toys/novelties, which just take power from the port.

I agree with you if the device is a proper USB device then it should be OK with the Joggler. What is good, is that we are sharing our experience of using various devices on the Joggler's USB port. So if there are some "dangerous" consequences, it would be shared. I was using a non-usb device and paid for the abuse by getting 2 USB ports which would not provide power, permanently. They still worked, but I had to use a powered device with them.

I did a few searches on this and there is a USB working group on charging/powering devices through USB, so I guess they may behind some of the charging info you posted above. I'm starting to wonder now if I can use all my old 64MB USB thumb drives with phone chargers to make cheap, warm glow night lights !

On smoke in the machines... I once saw a chip pop; a little halo of smoke came out, leaving a small "divot" in the centre of the chip's package. It was quite a surreal experience !

Post by **pete** » Mon Mar 26, 2012 8:59 pm

cbredfred; great stuff you posted.

I can verify that the Joggler will shut off if you short out the USB port from some playing around I was doing where as I plugged the external USB port upsidedown such that the metal shielding was shorting out all four USB leads. I did not break the Joggler as it came back to life on its next boot.

Post by **hawsey** » Sun Jun 22, 2014 9:40 pm

So I am posting in the right thread now I hope .

So from the above if I say plug in a tablet and a phone in to the side port of a joggler running say PNP III each device will ony draw so much current I.e shared so it would just take longer to charge is that right ?
Thanks

cbredfred · Post by **cbredfred** » Mon Jun 23, 2014 8:04 pm

I feel the need for a disclaimer coming on!

If you let the smoke out of your Joggler it's on your on head.

Unless you have built some kind of a "Y" cable that will let you plug 2 USB devices in to one port, then you are going to be using a hub of some sort, either powered or not.
If it is a powered (has its own power supply) USB hub then your devices will be negotiating with it for how much current they are allowed to draw and not the joggler.
If its an unpowered USB hub then I'm not sure what will happen. There are lots of cheap hubs out there and I have no idea if any of them play by the rules laid out in the USB standards as far as negotiating current draw.

Most tablets come with a 2 amp (2000mA) charger, most phones with a 1 amp (1000mA) charger. Let's assume that they don't instantly blow the beans out of your Joggler when first connected...You are now charging devices that normally require 3000mA (2000+1000) to achieve decent charging times with 500mA (Jogglers USB 2 specified port) of current so it will take 6 times longer to charge your kit than on their own (supplied) chargers.
My first generation iPad would indicate that it is not charging when connected to a hosted (able to transfer data and not just for charging) USB port even though it really is. Not sure what your Nook will indicate.

If you want to see some of what is going on with USB charging, then the following inline meter is a good place to start:
http://www.amazon.co.uk/PortaPow-Monito ... B00DF2485S

It won't show you what voltages are on the Data leads (see first post in this thread).

If you decide to buy a multi-port USB charger then this one seems to work well:
http://www.amazon.co.uk/Family-Sized-De ... B00GYNW1TA

It has SOOOO much smoke crammed into it that it can charge FOUR tablets (assuming 10w 2A per) at the same time!
It also negotiates with each device connected to it as to how much current it is allowed to draw.
This means that it changes the voltage on the data leads until the device understands that it can draw the maximum that it needs to charge quickly.
Some multi-port USB chargers have the ports labeled "Apple", "Samsung", "Universal" and will only charge at full speed if you get plugged in to the correct port.
The one I linked to has 5 ports and all ports should work for all devices (Apple, Samsung etc).

The bottom line with USB charging...Just like Forest Gump's mother used to say "Life is like a box of chocolates, you never know what you're gonna get!"

Post by **hawsey** » Mon Jun 23, 2014 8:29 pm

Ha ha Forest Gump you are right , thanks for all the info

That charger looks a real beastie ...
It seemed to charge the nook pretty well , I think I will just use one charge device per joggler tho , will be safest .

Alas as far as smoking Jogglers are concerned you are too late my friend , I accidentally plugged in a laptop charger in my work van in to the Joggler and a small bang and a bit of smoke was the end of that one

The worrying thing is I quite liked the smell of the smoke it gave off !!

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