Propeller Proto Board - Can it be powered via USB?

OakGraphics

Hello Gang,
This might seem like a silly question, but I was wondering if the Propeller Proto Board with the prop-clip installed, would be able to get the power from the USB-port of the prop-plug.·· I see VSS on the prop-plug, and I assume I could get GND from the USB shield.· But is the Prop-plug giving or taking VSS?· (i.e. it is sourcing or needing VSS?)
Or would that be a bad idea?
Otherwise I will just get a wall-wart, as I know the USB would only give me like 100ma 5VDC most-likely.·
·

Bean

I don't know if it will work for you, but my Prop Dongle is powered by USB. You don't need a prop-plug or anything else either. Just plug it into a USB port and program it.

http://www.hittconsulting.com/products/propdongle/

Bean

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.iElectronicDesigns.com

·

Phil Pilgrim (PhiPi)

Vss is ground. The positive supply is called "Vdd". The 3.3V supply derived from the FT232R's internal regulator would not be able to source enough current to handle the Proto board. Although the 5 volts available directly from the USB port could be regulated down to 3.3V with an external regulator, there's more to it than just tapping this voltage. I suggest you look at the FT232R datasheet and app notes for the requirements.

Short answer: No.

-Phil

OakGraphics

Okay - thought so. I will be looking for a Wall-Wart for the prop Proto board now. (have the proto board)
Thanks,

Joerg

I am powering my development system (UMDL) directly from USB. The 3.3V are regulated via a LM1117T-ADJ (so other voltages can be easily realized). See the attached schematics. This way i do not need any power source but my PC connecting the dongle on one port and the hardware on an other port. This is the simplest way to have maximum comfort.

Saluti Joerg

Paul_H

I guess I'm doing it an easy way... I wired a the 5v leads on a usb cable to a dc connector plug for power.

My proto boardworks great, and nominally powers a gps and servo module too.

Paul

Phil Pilgrim (PhiPi)

The reason I said "no" is because the USB specs define how much power can be drawn before the device is enumerated by the PC and how the load, subsequent to that, must be brought on line via a "soft start" circuit. That said, it's obvious from the success of those who don't take these measures that most PC's USB ports are pretty forgiving about the loads that are drawn and when. At the very least, however, Bean's inclusion of a PTC polyfuse in the +5V line should be taken as an indication that some measures are necessary to protect your PC from shorts and other overloads.

-Phil

Bean

Phil is right. I damaged one of the USB ports on my new computer because I had a short. Now the port no longer works (no power).

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.iElectronicDesigns.com

·

deSilva

Phil Pilgrim (PhiPi) said...
Bean's inclusion of a PTC polyfuse in the +5V line should be taken as an indication that some measures are necessary to protect your PC from shorts and other overloads.

These are well shown in Joerg's diagram above.

I use the "alternative" plug from 4D for some time now, where USB 5V is (unprotected!) available at its fifth pin. This worked fine so far.. Note that both sides of the 4D-plug differ (GND/RESET switched!) This has confused me for some time...

Joerg

It seems to be a certain request for powering the propeller hardware via USB, so i have completed my recently uploaded schematics.
The layout (USB-R1) can be used as a power source for devices requiring less than 3.5V at 400mA max.
I have added an optional 28 pin DIL socket for the use with experimental boards. For easier soldering there is a top layer,
but the layout works also as a single layer PCB.


Saluti Joerg

Mike Green

As Bean discovered, there are specifications for the power available from a USB port. Read the USB spec and follow it if you don't want to damage your computer (particularly laptops). There are limits on the current that can be drawn before the USB bus is initialized and limits on how much can be drawn by an 'ordinary' device and by a 'high-power' device. The FTDI chips follow this spec.

Paul Baker

When we test products which have a USB connection, we always make the connection through a powered hub, that way if something catastrophic happens you only need to replace the hub.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Joerg

In theory the USB port should be able to deliver 100mA at the plugin time and up to 500mA max. But since this is pure theory i am puting the 400mA polyfuse in my designs. More information can be found at http://www.usb.org.

For a more save operation the following article from Elektor may be helpful:

www.elektor.de/jahrgang/2006/juli/usb-sicherung.64233.lynkx (in German)
or
www.elektor.com/magazines/2006/july/usb-fuse.58056.lynkx (the English version)

this is an electronic USB fuse. the article is also available in French and Netherlands.

If somebody needs a voltage above 5V, then the following design can be used:

www.elektor.de/jahrgang/2007/juli-august/usb-wandler.196790.lynkx (the original text in German)
or
www.elektor.com/magazines/2007/july-august/usb-converter.197508.lynkx (the English version)

a more detailed document can be found on my homepage
www.systech-gmbh.ch -> electronics -> USB-Wandler1

I hope this may helpful

Joerg

PS: it was the article for USB-Wandler1 which has introduced the Propeller chip to me. (ELEKTOR has sent me a protoboard!)