PowerZ USB
WTF
as taken from the issue tracker ticket here
Vierlex and anlumo are researching the possibility to create a new addon for the Metalab in addition to the PowerZ: A four-port USB 2.0 version of it that is compatible with iPhone, iPad and all other devices that don't use the USB charging standard.
We looked into commercial solutions and were unable to find any that suits the needs of the Metalab. We would like to integrate the PowerZ USB with a new version of the regular PowerZ.
anlumo has decided that the best option for this is to not integrate an existing power strips like the original version of PowerZ, since this is a finicky solution that has to work around the size constraints of that specific product.
Additionally, anlumo obtained a few 5V/9A open frame power supplies for free from a very generous sponsor (who had them lying around and not needing them). These can be used for supplying power to 4 USB sockets, which should be enough for Metalab use.
One issue with the current PowerZ is that sometimes, people plug in their notebooks and begin to work, and after a while, they notice that no power is supplied. After a lengthly bug hunt, they discover that the PowerZ itself is not plugged in. This issue can be resolved by showing some kind of obvious power indicator on the power socket panel.
Additionally, power demand of the items plugged into the PowerZ has been a frequent question. This issue and the previous one can be solved together by adding an amperemeter display (which are available as a complete package, measurement and display). When the display is off, it is obvious that no power is available on the socket. Otherwise, it displays the current currently flowing.
The case can be constructed by using the in-house CNC. Material could be ABS, PET or Acrylic?
USB
The iPad needs a specific setup of resistors to accept a charger for 2A charging:
both need 49.9kΩ to GND and the following resistor to 5V:
BOM
These items have been ordered (ETA January 2014):
- Power Inlet Socket with Fuse
- Amperemeter AC 0-10A
- European Power Socket for Panel Mount
- Dual USB-A Female for Panel Mount
All of these items are panel mount compatible, and can be connected without any PCB.
Still to order:
- Resettable Fuses - PPTC PPTC 1812 6V 3.0A SMD
- 49.9kΩ
- 43kΩ
- 75kΩ
- PCB for USB
- Case?
Cables are available at Metalab.
Historical Text
The iPad is the most demanding device for this application, and needs 1.5A-2A to charge, which means 10A in total. Thus, I propose the following power supply:
It uses convection cooling (thus is silent), has <300mW no-load power consumption and has 80% efficiency. These properties were deemed very important and aren't available on cheaper parts (or PC power supplies).
The iPad needs a specific setup of resistors to accept a charger for 2A charging:
both need 49.9kΩ to GND and the following resistor to 5V:
I'm not sure whether we're really capable of soldering a lot of 2mm SMD resistors… That's up for discussion. UPDATE: Meta and wizard told me that we have access to a reflow oven, so SMD is the way to go!
Additionally, we would like to add self-resetting fuses to the ports to avoid burning them down (by drawing 11A from a single port). This would fit the bill: Bourns MF-MSMF125-2
It would be cheaper to make multiples of these at the same time.
materials & costs
- Fuses: €0.461 × 5
- 49.9kΩ: €0.046 × 10
- 43kΩ: €0.023 × 5
- 75kΩ: €0.118 × 5
- Board (Conrad price): €0.80
- USB socket: €0.98 × 5
- Power supply: €35.63
- Molex 6pin: €0.27
- Molex 3pin: €0.107
- ICE power socket w/ 10A fuse: €4.62
- Power cable: €5.10
- Cabling: ?
- Casing: ?
total costs, except for the ones marked with “?”: €54.90 + €10.98 VAT
Jour Fixe said it will finance 3 of these devices
