5v USB hub - UK Vintage Radio Repair and Restoration Discussion Forum

Oldcodger · 23rd Oct 2015, 9:38 pm

Not sure which section to ask for help on this in .
Components & circuits?
Computing ?
Or here ?
Mods, please move as needed, and you have my sympathies as needing the wisdom of Solomon.(Grovel /grovel)
possibly me being cheapskate, but in true tradition of VRR, why chuck something that has not failed .
The original PSU was rated as 5vDC @600mA ,something that seems a bit low on current to me, as the hub is marked as 5v DC 2A.
The external 5v supply to my four port USB hub die on me. But like most blokes on here ,I've got a saved supply ( sad isn't it that we are hoarders by nature), and I've found a 10v DC 1.2A , and from various projects ( yet to complete) a supply of LM7805 2A ,with plenty of 10&100nF caps .
Alternate idea would be to use an unused 5v supply on PC ,but I'm not happy about this idea.
So apart from standard LM7805circuit with .1uF in and out, I'd welcome any other suggestions for possibly other problems ( something like a 1-10 uF output smoother and a ripple rejection inductor- got an old PC mother board filled with ferrites ).

cmjones01 · 23rd Oct 2015, 9:44 pm

Your standard 7805 circuit will work fine. There should be no need for extra capacitors or inductors: USB hubs typically have decoupling capacitors at the sockets anyway, and USB devices normally have their own internal decoupling.

Just make sure that your regulator circuit is well-constructed: if something shorts your 10V supply to the 5V output, the damage to your USB devices could be expensive!

Chris

paulsherwin · 23rd Oct 2015, 9:55 pm

If you have a look inside the hub, you may find that the supply goes straight into a 7805 anyway, so there may be no need for external regulation.

Hubs don't need a lot of power in themselves. In fact they will usually work using the USB 5V supply from the host device. However, they will need their own supply if you want to hang lots of power hungry USB powered devices from them, such as hard drives or scanners.

MrElectronicman · 23rd Oct 2015, 11:55 pm

I have been looking for a 5V DC power supply for my Raspberry pi's, and I found a PSU that came out of an old printer which can produce 30V DC at 1 Amp.

Using an LM2575 switching regulator to provide 5 Volts I can get 3 Amps out of it, in fact I have used 2 LM2575's to provide almost 5 amps which is more than enough for my purposes.

Oldcodger · 24th Oct 2015, 12:29 am

Quote:

Originally Posted by paulsherwin

If you have a look inside the hub, you may find that the supply goes straight into a 7805 anyway, so there may be no need for external regulation.

Hubs don't need a lot of power in themselves. In fact they will usually work using the USB 5V supply from the host device. However, they will need their own supply if you want to hang lots of power hungry USB powered devices from them, such as hard drives or scanners.

I don't really want to get into the HUB,depending on the labels, my hub needs a 5v supply at 2A . So, it wants 5v , so I'll give it what it wants, and not expect it to regulate over that. on my PC ,I've got 4 ports,mouse/keyboard /printer scanner(with own power supply) ,and additional 4 port hub,which will have a power hungry USB powered scanner on it .(Just in case scanner is too greedy, the hub and PSU are sacrificial elements). one home brew PSU and a cheapo hub is better/cheaper than a new MOBO. IMHO.

Oldcodger · 24th Oct 2015, 12:33 am

Quote:

Originally Posted by cmjones01

Your standard 7805 circuit will work fine. There should be no need for extra capacitors or inductors: USB hubs typically have decoupling capacitors at the sockets anyway, and USB devices normally have their own internal decoupling.

Just make sure that your regulator circuit is well-constructed: if something shorts your 10V supply to the 5V output, the damage to your USB devices could be expensive!

Thanks, Chris- I follow the belt braces and bit of string construction policy .I've already had a nasty experience of a hub taking out one device .

jjl · 24th Oct 2015, 12:44 am

Downstream ports on self powered USB 2.0 hubs must each be able to supply 5V at 500mA to be compliant with the standards. Hence the 5V, 2A rating for a 4 port hub.
A 7805 based supply will not comply for a 4 port hub.
All of the USB hubs I've encountered draw power either from the upstream host (PC) port or an external 5V supply. They contain neither linear nor switch mode regulators.
You need a 5V external supply that can provide at least 2.1A to allow for 4 ports and the hub's logic supply.

John

AC/HL · 24th Oct 2015, 11:49 am

I have a couple of external HD cases connected via USB. The connecting cables each have
two USB connectors at the PC end, to enable higher currents to be drawn.

KeithsTV · 24th Oct 2015, 12:21 pm

Although the USB 2.0 (and the USB 1.1) spec says each port must be able to supply 500mA, in practice a port can usually supply much more. The 5V supply is usually fed from the PC 5V supply via a power controller IC which switches the supply and monitors the current. If it detects an overload it will switch off the output which will not return until the overload is removed. The current limit in these ICs can vary between 700mA and 1.3A. Many of the USB powered hard drives rely on this to cope with the spin up current of the drive which is usually several time the running current.

The later USB 3 spec has upped the current from a USB port to 900mA to cope with these USB powered drives. USB 3 ports can be easily identified as they have a blue insert rather than a white one. They are compatible with USB 2 and USB 1 devices.

I believe there is also a USB specification for ports that support charging devices such as phones and Ipads. These I believe can supply up to 2A.

Keith

Ed_Dinning · 24th Oct 2015, 4:25 pm

Hi, if you are using a 78 series reg and there is significant capacitance on the output, it is advisable to connect a diode backwards across the reg (cathode to input). This allows the output caps to discharge , but not through the regulator, destroying it.

Ed

G6Tanuki · 24th Oct 2015, 4:41 pm

Quote:

Originally Posted by KeithsTV

I believe there is also a USB specification for ports that support charging devices such as phones and Ipads. These I believe can supply up to 2A.

This is generally a "power-only" USB though - as implemented for chargers and the horrible "dual 13A and two USB charger outlet" wall-socket replacements.

An attached device should be able to divine - by sensing the resistance between different conductors - whether it's connected to a proper bidirectional-digital-and-power USB outlet or a power-only one, and tailor its current demands accordingly.

Oldcodger · 24th Oct 2015, 4:54 pm

Thanks to jjl & Keith ,I now have an idea why the original psu failed. It was an on line purchase and I had no idea of the current needed for USB,and thought it was quite low. Closer look at the old PSU shows in very tiny lettering the power output as 5v at 600mA. I seem to remember problems after I brought the old USB scanner back into service,after I found W7 drivers.
AC/HL -I had thought of similar with PC, as I only use 2 out of the 4 HDD supplies(12v+5v) ,but no idea if this might cause a conflict on data/power within the PC .
JJL- that's given me the idea of using only two of the four ports with a 2A 7805 and a 9v 2A PSU as a temporary measure( that would take the Keybd and mouse off the system and free up enough ports ) . Would that provide sufficient power to comply /
I've found that my MB has capacity for another six ports ,but these need to be connected via headers.

arjoll · 25th Oct 2015, 11:50 am

Quote:

Originally Posted by KeithsTV

I believe there is also a USB specification for ports that support charging devices such as phones and Ipads. These I believe can supply up to 2A.

Quote:

Originally Posted by G6Tanuki

This is generally a "power-only" USB though - as implemented for chargers and the horrible "dual 13A and two USB charger outlet" wall-socket replacements.

There are power-and-charging USB ports that can supply higher current and support data transfer - HP business laptops used to have at least one, although I haven't seen them for a few generations now.

Oldcodger · 26th Oct 2015, 12:34 am

Out of curiosity ,today I tried using the 4 port hub as a connect through, with my mouse. Two ports powered the Mouse, but no comms to PC , the other two ports failed to power the mouse. So sadly I suspect that HUB is FUBAR, and any investigations are worthless,with using a two port PSU and a 2A regulator However, the question of whether an unused HDD 5v supply could be utilised remains open .Anyone with knowledge on the use of a 5v RAIL on an used HDD supply rail might look at this and offer an answer.
Gladly- son has come up with answer- an old surplus to requirements 4 port belkin hub, with a 2.1( or more) A supply.

23rd Oct 2015, 9:38 pm	#1
Oldcodger Nonode Join Date: Oct 2014 Location: West Midlands, UK. Posts: 2,181	5v USB hub Not sure which section to ask for help on this in . Components & circuits? Computing ? Or here ? Mods, please move as needed, and you have my sympathies as needing the wisdom of Solomon.(Grovel /grovel) possibly me being cheapskate, but in true tradition of VRR, why chuck something that has not failed . The original PSU was rated as 5vDC @600mA ,something that seems a bit low on current to me, as the hub is marked as 5v DC 2A. The external 5v supply to my four port USB hub die on me. But like most blokes on here ,I've got a saved supply ( sad isn't it that we are hoarders by nature), and I've found a 10v DC 1.2A , and from various projects ( yet to complete) a supply of LM7805 2A ,with plenty of 10&100nF caps . Alternate idea would be to use an unused 5v supply on PC ,but I'm not happy about this idea. So apart from standard LM7805circuit with .1uF in and out, I'd welcome any other suggestions for possibly other problems ( something like a 1-10 uF output smoother and a ripple rejection inductor- got an old PC mother board filled with ferrites ).

23rd Oct 2015, 9:44 pm	#2
cmjones01 Nonode Join Date: Oct 2008 Location: Warsaw, Poland and Cambridge, UK Posts: 2,677	Re: 5v usb hub Your standard 7805 circuit will work fine. There should be no need for extra capacitors or inductors: USB hubs typically have decoupling capacitors at the sockets anyway, and USB devices normally have their own internal decoupling. Just make sure that your regulator circuit is well-constructed: if something shorts your 10V supply to the 5V output, the damage to your USB devices could be expensive! Chris __________________ What's going on in the workshop? http://martin-jones.com/

23rd Oct 2015, 9:55 pm	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: 5v usb hub If you have a look inside the hub, you may find that the supply goes straight into a 7805 anyway, so there may be no need for external regulation. Hubs don't need a lot of power in themselves. In fact they will usually work using the USB 5V supply from the host device. However, they will need their own supply if you want to hang lots of power hungry USB powered devices from them, such as hard drives or scanners.

23rd Oct 2015, 11:55 pm	#4
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Re: 5v usb hub I have been looking for a 5V DC power supply for my Raspberry pi's, and I found a PSU that came out of an old printer which can produce 30V DC at 1 Amp. Using an LM2575 switching regulator to provide 5 Volts I can get 3 Amps out of it, in fact I have used 2 LM2575's to provide almost 5 amps which is more than enough for my purposes. __________________ David

24th Oct 2015, 12:44 am	#7
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: 5v USB hub Downstream ports on self powered USB 2.0 hubs must each be able to supply 5V at 500mA to be compliant with the standards. Hence the 5V, 2A rating for a 4 port hub. A 7805 based supply will not comply for a 4 port hub. All of the USB hubs I've encountered draw power either from the upstream host (PC) port or an external 5V supply. They contain neither linear nor switch mode regulators. You need a 5V external supply that can provide at least 2.1A to allow for 4 ports and the hub's logic supply. John

24th Oct 2015, 11:49 am	#8
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: 5v USB hub I have a couple of external HD cases connected via USB. The connecting cables each have two USB connectors at the PC end, to enable higher currents to be drawn.

24th Oct 2015, 12:21 pm	#9
KeithsTV Nonode Join Date: Aug 2007 Location: South Bradford, West Yorkshire, UK. Posts: 2,573	Re: 5v USB hub Although the USB 2.0 (and the USB 1.1) spec says each port must be able to supply 500mA, in practice a port can usually supply much more. The 5V supply is usually fed from the PC 5V supply via a power controller IC which switches the supply and monitors the current. If it detects an overload it will switch off the output which will not return until the overload is removed. The current limit in these ICs can vary between 700mA and 1.3A. Many of the USB powered hard drives rely on this to cope with the spin up current of the drive which is usually several time the running current. The later USB 3 spec has upped the current from a USB port to 900mA to cope with these USB powered drives. USB 3 ports can be easily identified as they have a blue insert rather than a white one. They are compatible with USB 2 and USB 1 devices. I believe there is also a USB specification for ports that support charging devices such as phones and Ipads. These I believe can supply up to 2A. Keith

24th Oct 2015, 4:25 pm	#10
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: 5v USB hub Hi, if you are using a 78 series reg and there is significant capacitance on the output, it is advisable to connect a diode backwards across the reg (cathode to input). This allows the output caps to discharge , but not through the regulator, destroying it. Ed

24th Oct 2015, 4:54 pm	#12
Oldcodger Nonode Join Date: Oct 2014 Location: West Midlands, UK. Posts: 2,181	Re: 5v USB hub Thanks to jjl & Keith ,I now have an idea why the original psu failed. It was an on line purchase and I had no idea of the current needed for USB,and thought it was quite low. Closer look at the old PSU shows in very tiny lettering the power output as 5v at 600mA. I seem to remember problems after I brought the old USB scanner back into service,after I found W7 drivers. AC/HL -I had thought of similar with PC, as I only use 2 out of the 4 HDD supplies(12v+5v) ,but no idea if this might cause a conflict on data/power within the PC . JJL- that's given me the idea of using only two of the four ports with a 2A 7805 and a 9v 2A PSU as a temporary measure( that would take the Keybd and mouse off the system and free up enough ports ) . Would that provide sufficient power to comply / I've found that my MB has capacity for another six ports ,but these need to be connected via headers.

26th Oct 2015, 12:34 am	#14
Oldcodger Nonode Join Date: Oct 2014 Location: West Midlands, UK. Posts: 2,181	Re: 5v USB hub Out of curiosity ,today I tried using the 4 port hub as a connect through, with my mouse. Two ports powered the Mouse, but no comms to PC , the other two ports failed to power the mouse. So sadly I suspect that HUB is FUBAR, and any investigations are worthless,with using a two port PSU and a 2A regulator However, the question of whether an unused HDD 5v supply could be utilised remains open .Anyone with knowledge on the use of a 5v RAIL on an used HDD supply rail might look at this and offer an answer. Gladly- son has come up with answer- an old surplus to requirements 4 port belkin hub, with a 2.1( or more) A supply.