usb FireWire and self supplied MBs

Design Concepts
1

hi all

i ve always supplied my MBs with the usb hub, of course with the limitation of not having a lcd and with power problem from time to time.

I also added lately a GP IR sensors to my modified MB64e (see my posts in this topic http://www.midibox.org/forum/index.php?topic=5270.0) but i get a lot of jittering also due to the unstable power supply (usb)

I also happily switched to a powerbook g4 OSX ppc, as you might know apple always supported the FireWire protocol/connection.

Usb is dominating the market so i can easily get a cheap (and very small) MIDI/usb interface and mount it on my box and have a single cable to connect to the computer and supplying the box.

Now it is impossible to find such a small and cheap usb/FireWire interface but FireWire has 6 Watts of power, that at 5 volts makes 1,2 Ampers , right? i am not an electronic geek but that has to be right, please confirm if you can.

usb has only 0,5 ampers not even the half of it.

Here we go now: why no to use a cable with two plugs: a usb and a firewire: the usb will connect to the usb/MIDI interface transmitting and receiving MIDI and powering ONLY the usb/MIDI interface while i will use ONLY the power pins from the FireWire plug to feed the box, lcd, GP sensors and whatever can be supplied with 1,2 Ampers.

In my powerbook usb hub and FireWire are so close to each other and i almost don t use the Firewire.

Of course this is only of any interest for those who want a self supplied MB with straight connection to computer and you will have to carry a special cable for the box.

Let me know what you think

simone

2

directly from Apple s web site:

Power

Input voltage range: 8 to 33 V

Input power range: approximately 1 W

Output voltage range: approximately 18 V to 24 V

Output power range: up to approximately 15 W

mmmm sounds different from what i ve fund out before.. does anybody know the right specification? thanks

simone

3

Hi,

mmmm sounds different from what i ve fund out before.. does anybody know the right specification? thanks

The specs. directly from the IEEE1394a (Firewire 400, Apple):

8 to 33 VDC, 1,5 A, max. 48 W

Thats the theory.

But be warned. As you already recognized from the apple web site: Not all Hosts are providing the power mentioned in the specification.

I would not recomment to take any power directly from the Bus. Some thoughts on that:

  • As IEEE1394 Harddisks become popular many Users reportet defect mainboards. Today almost every external Firewire HDD has is own power supply …

  • If you you have any short in your box you surely will destroy your mainboard. Fuses are mostly not fast enough for this issue.

but i get a lot of jittering also due to the unstable power supply (usb)

This noise you also get from the firewire Port because of the switching power supply.

Just give your box a solid nice wallwart and you won’t have to think about all those bad issues … :wink:

greets

Doc

4

hi thanks doc

you don t really know how stubborn i am :wink:

so what i guess is that firewire offers a “variable” voltage output and that the output can be regulated (“asked”) by the slave device?

i don t think there will be any problem with the mainboard, i ve already shortcircuited the usb and my powerbook just get stuck and gives me a screen with the following instruction: press the power buttons for a few seconds …  :slight_smile:

anyway if anybody has some more infos about firewire and how to use the power coming from it .. here is your thread …

thanks

simone

5

Sorry cimo,

… it’s just me again.

Here are the wikipedia items of  Firewire with a lot of useful links and information:

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

hope this helps.

greets

Doc

6

.. be sorry for my laptop !!  :cry:

  thanks, i am browsing all those links around but i can t really find out anything about how to regulate the voltage coming from a FireWire port, i guess it s autoregulated but i can t figure out if it s hardware regulated (is it possible?) or by the driver ..

.. i am interested on this because i plan to build a “selfsufficient” little portable music installation: in the beginning i am going to use a car battery but i plan to buy solar panels when i will have some spare money or fund the project somehow… i plan to supply the laptop and then get all the necessary power from the laptop down to all the controllers, i really like the “plug n play” style..

.. if you have some info about that FireWire stuff .. i ll be here around

simone

7

sounds like a good idea but why power it all from your laptop

i built my traktor controller to be powerd from car batteries etc so it can be powerd from solar power

8

yes i understand that but that would be a perfect solution both for car battery and normal house use.If i could do it (getting more power form the firewire) i d switch immediately to MBlc and add a couple of lcd

simone