I’m powering Fez cobra with usb from my laptop using a display. Display is running with no problem despite usb is not from power source. What is the voltage powered by usb laptop? And is this okay?
It could work but you will probably run into problems sooner or later. You need a powered hub or power back as the display needs a good power source.
But there is no chance of overheating the regulators due to over voltage? Or doing permanent damage to board or display? The problems I might see in the future that you are refering to could be mediated by buying usb power source?
No you will not damage the board if you use USB. If the power is not enough ten the board will not work but it will not cause any damage.
I’ve found that this works just fine to power an EMX and Cobra:
http://www.maplin.co.uk/single-usb-power-supply-227636
Question:
What is the upper limit on the FEZ cobra 5V in/out pin?
I have a regulated wall wart that varies from 5.1V (no load), to 5.05V (slight load) and 5.0V (heavy load). I also have similar behavior with the 5V rail on my converted ATX power supply. I would like to be able to use both of those power sources when I develop on my Cobra.
I would think that the components on the FEZ Cobra would not have any problems until upwards of 5.2V but I cannot seem to find a datasheet that would confirm my suspicions. I wanted to check it with the experts here to see what they think. Would a no load input voltage of 5.1V cause any problems for the parts on the Cobra? (I am scared to hook up those supplies for now.)
Thanks guys,
Matt
You should be okay
Hey guys I’m looking into building a prototype using the FEZ Cobra and looking into power options. I’ll be running the Cobra with a 4.3" touchscreen off a LiPo battery. I’ve found several good 5V step-ups but nothing for 6V.
Can you recommend something or will I be able to get away with powering the system off 5V? (I do plan on allowing use of USB/Ethernet).
Use 5V and tap right on the 5V pin on Cobra. Take a look at LT1308B, specifically at its step-up/step-down configuration.
Thanks Gus!
I’ll be ordering parts this week and we should see one heck on a nicely modded Cobra in a week or two. Portable game playing Cobra with MP3 decoder, thumbstick, 6 buttons & 4.3" LCD. 8)
Why not use USB joystick?
Portability; I don’t want the user to have to carry anything around with them to be able to play games or whatever else they want to do. I’m picking up some ShapeLock too for the prototype’s enclosure. In then end we should end up with something looking a bit like a PSP…only cooler because it’s FEZ!
There are some really small USB pads that you can mount inside your enclosure. Or even take the USB pad apart and only use its inner ciruit. Only because USB is easier to handle in code and uses less processing power than decoding signals in software.
I was planning on using interrupt ports…would USB actually be faster? If so I’ll definitely look into it. Also want to make sure to keep the costs down for the users too. That’s why I’m looking at modding out a Cobra. Might be cheaper to add on a little extra to the existing board the custom build one.
At the moment it looks like even at full retail prices I could supply mods to users at sub $100
I added replaced the LM1117 with a TO-220 package and heat-sink(used one thrown away during a board repair). Ran both 9vdc and 12vdc with no problems. If you can’t(or don’t want too) solder then there is this company called www.coolinnovations.com that builds heat sinks that will work for this application. They are a pain to mount in this area and can only dissipate about 7 degrees Celsius so I chose not to use them but they are a viable option for up to 9vdc @ <750ma.
Can one connect a 6V source as well as host USB?
USB host doesn’t take power in so I am not sure what you mean.
I suggest you study the schematics
I must have had the term mixed up. If I am connected to the development host (eg debugging mini usb cable), can I also have 6v power hooked up?
Yes, no problem to have external power connected to your board and also the board connected to your PC by USB cable at the same time.
Hey I’m building a prototype using the FEZ Cobra for my thesis. I’ll be using the TFT display, can I use this regulator - LM2670-5V - as my Power Source? I’m scared I might destroy the unit. I already have one. But I want to make sure I can use the regulator first.
Thanks 