8/8/8 kits, USB and power supply

[Target]

Hi,

Two questions from a phidgets newbie:

1) I want to hookup three 8/8/8 kits to my PC (I need to process some 16+ analog inputs from my simulator). Can I use the USB HUB to connect the 3 boards to eachother, having only one USB cable to my PC, or do I need a PC with 3 USB ports?

2) I've read somewhere that I need a power supply when using more than one 8/8/8 kit. Is the power distributed from one "powered" 8/8/8 kit to the others via USB, or do I have to power them all separately?

Thanks in advance,

Target.

[alandyer]

While Matt is on vacation I will take stab at addressing your queries:

1) Phidgets does not have any special USB standard. Each card is a USB device.
Therefore, you can connect as many USB devices (cards) as a given hub supports.
I am using 7-port USB hubs on my sim with 7 cards plugged into each hub.
Have a look at Project Magenta's flight sim. They have nice video explaining
their wiring for a Boeing 737NG overhead panel.
I think they talk about USB hubs in video
http://www.projectmagenta.com/videomain.html

2) Each card that requires its own power, requires own power supply.
You don't want all that current routed through that expensive server :)

Regards,
Alan.

[Target]

Alan,

Thanks for your answers, but I have to admit that they're not completely clear to me... :o

- The 8/8/8 kits have a 2 port HUB. If I connect kit #1 to my PC, is it possible to hook up kit #2 and #3 to #1 via the HUB?
- About the power supplies: how do I know when a card needs its own power (for the moment I'm only interested in the analog inputs)

Cheers,
Target.

[alandyer]

I see what you want to do.
Daisy-chain those interface cards power lines.
Those cards do have DC out as well as DC in for power supply.
You do raise an interesting question:
How many of those power lines can one daisy chain?

We're going to have to defer to Matt on this one :)

[mauriceb]

Target,

I am pretty sure you will need 2X 6V power supplies. Basically, any of the Phidgets interfaces do not need a power supply unless they also feed another card.

So, in your case:

1st card: Power supply + 2 USB cables- One cable going to 2nd card and one going to PC

2nd card: Power supply + 2 USB cables - One cable going to 3rd card and one coming from 1st card

3rd card: No Power supply needed - One USB cable coming from the second card

You don't have to worry about overloading the USB output on the PC. If it is asked to supply more current that it can, it simply shuts off and you need to reset by cycling the power on & off. As far as the PC is concerned, it is only supplying one output and this should not overload the USB port.

An alternative is that you can use a powered USB Hub, connect all your cards to it and one connection to the PC. Would also work but more expensive & not really needed.

Maurice