calebzulawski
Posts: 46
Joined: Tue Jan 31, 2012 6:00 am

Various hardware questions: SDHC, Portable PSU, Wifi

Mon Jul 30, 2012 7:26 pm

To preface my questions with some context, I have a fairly simple robot using an Arduino as its main processor, but I've been looking for more processing power, hence using the Raspberry Pi (which Newark/element14 says has shipped!!)

SDHC
After looking over the forum I'm utterly confused which SD card to buy. Some people say class 4 is most stable, class 6 is faster but less stable, and class 10 cards wouldn't even boot. But now I've read that class 10 cards okay? I think I'm going to get either an 8 or 16 GB Transcend class 10 (they're very cheap here). What is the state of class 10 cards and the Raspberry Pi now? Are class 6 cards still considered better?

Portable PSU
Okay, this is something I'm totally unfamiliar with. I'm looking for something to power not only the RPi but a powered USB hub (for peripherals) for an extended period of time (a couple hours would be nice). I know there are portable USB supplies, but has anyone else used these to make a powered USB hub? If I buy a power supply with USB output, replace the power and ground leads in a (non-powered) USB hub with those from the PSU's output? (btw, I'm an EE student so I'm not afraid of soldering some wires, I'm just not sure what to do with USB). Does anyone have any suggestions for good PSUs or USB hub configurations?

Wifi
I suppose once I get a portable powered USB hub working, wifi is fairly straightforward as long as I use a compatible dongle (I've seen the list, things are looking pretty good for RPi and USB wifi). Does anyone have any suggestions of which dongle to use? Range isn't that important, I just want to be able to keep a connection with my router or PC through some walls at most 100 feet (30ish meters for those of you not in the US)

PaulCheffus
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Joined: Tue May 29, 2012 2:51 pm
Location: Lincolnshire UK

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Mon Jul 30, 2012 7:34 pm

calebzulawski wrote: SDHC
After looking over the forum I'm utterly confused which SD card to buy. Some people say class 4 is most stable, class 6 is faster but less stable, and class 10 cards wouldn't even boot. But now I've read that class 10 cards okay? I think I'm going to get either an 8 or 16 GB Transcend class 10 (they're very cheap here). What is the state of class 10 cards and the Raspberry Pi now? Are class 6 cards still considered better?

Wifi
I suppose once I get a portable powered USB hub working, wifi is fairly straightforward as long as I use a compatible dongle (I've seen the list, things are looking pretty good for RPi and USB wifi). Does anyone have any suggestions of which dongle to use? Range isn't that important, I just want to be able to keep a connection with my router or PC through some walls at most 100 feet (30ish meters for those of you not in the US)

Hi

SDHC
I have a Transcend 8gb class 10 card and it boots fine with the latest Raspbian image from 15/07

WiFi
I use an Edimax EW7811UM wifi dongle which appears to work for me though my router is almost next to the Pi.

Cheers

Paul
Procrastination - The Thief of Time.

calebzulawski
Posts: 46
Joined: Tue Jan 31, 2012 6:00 am

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Mon Jul 30, 2012 7:38 pm

Okay, thanks for confirming on the SD card. The direction some threads were going was really concerning me, but this makes things much easier. Also, I'll look into that wifi dongle.

cupcake
Posts: 59
Joined: Sat Jan 21, 2012 9:00 pm

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Tue Jul 31, 2012 4:14 pm

calebzulawski wrote:Portable PSU
Okay, this is something I'm totally unfamiliar with. I'm looking for something to power not only the RPi but a powered USB hub (for peripherals) for an extended period of time (a couple hours would be nice). I know there are portable USB supplies, but has anyone else used these to make a powered USB hub? If I buy a power supply with USB output, replace the power and ground leads in a (non-powered) USB hub with those from the PSU's output? (btw, I'm an EE student so I'm not afraid of soldering some wires, I'm just not sure what to do with USB). Does anyone have any suggestions for good PSUs or USB hub configurations?
This is something I'm also wondering about. I pretty much the same question in a different sub-forum here (link).

This must have been done by others before so I'm hoping there will be a straight-forward answer to it.

calebzulawski
Posts: 46
Joined: Tue Jan 31, 2012 6:00 am

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Tue Jul 31, 2012 4:18 pm

I've actually figured out how to do that, I'll whip up a schematic to show you, it's incredibly (but deceptively) simple. The bigger problem I'm having at the moment is providing 6V to the servos but 5V to the electronics, but that might be solved with a UBEC and 5V voltage regulator (I'm still waiting on some more informed opinions on that!)\

Ok let me make the schematic, I'll reply in a minute.

calebzulawski
Posts: 46
Joined: Tue Jan 31, 2012 6:00 am

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Tue Jul 31, 2012 5:01 pm

Here's the schematic, feel free to ask about anything if you're confused!
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cupcake
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Joined: Sat Jan 21, 2012 9:00 pm

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Tue Jul 31, 2012 7:43 pm

calebzulawski wrote:Here's the schematic, feel free to ask about anything if you're confused!
Thanks, looks understandable. You use a single power source to directly power both the RPi and the powered HUB over USB. You ensure to cut off the data cables of the power source's USB cable. You then connect RPi and HUB using only the data part of a USB cable (i.e. no power whatsoever in between them).

So what are you using as a power source to make this portable? A rechargeable 5V battery?

calebzulawski
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Joined: Tue Jan 31, 2012 6:00 am

Re: Various hardware questions: SDHC, Portable PSU, Wifi

Tue Jul 31, 2012 7:52 pm

I'm not really sure yet, but probably a 7.2ish volt li-po rechargeable battery pack with a 3A UBEC reducing it to 6V for the servos, and a 1.5A 5V 7805 voltage regulator supplying 5V to the electronics.

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mahjongg
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Re: Various hardware questions: SDHC, Portable PSU, Wifi

Tue Jul 31, 2012 7:59 pm

calebzulawski wrote: SDHC
After looking over the forum I'm utterly confused which SD card to buy. Some people say class 4 is most stable, class 6 is faster but less stable, and class 10 cards wouldn't even boot. But now I've read that class 10 cards okay? I think I'm going to get either an 8 or 16 GB Transcend class 10 (they're very cheap here). What is the state of class 10 cards and the Raspberry Pi now? Are class 6 cards still considered better?
Its not so strange that you are confused, as the situation concerning SD-cards is very much in flux, and some info is now outdated. So yes, the situation was that Class 10 cards wre a problem, until someone noticed that the GPIO's the interface used someone forgot to enable some pullup resistors, after that most class 10 cards started working! Obviously cards can still be problematic, especially as there are fake cards, that claim to be 2GB, but are actually 1GB. Hopefully the wiki should be fairly up to date, as it can constantly be updated, unlike other resources (no guarantee there though).
calebzulawski wrote: Portable PSU
Okay, this is something I'm totally unfamiliar with. I'm looking for something to power not only the RPi but a powered USB hub (for peripherals) for an extended period of time (a couple hours would be nice). I know there are portable USB supplies, but has anyone else used these to make a powered USB hub? If I buy a power supply with USB output, replace the power and ground leads in a (non-powered) USB hub with those from the PSU's output? (btw, I'm an EE student so I'm not afraid of soldering some wires, I'm just not sure what to do with USB). Does anyone have any suggestions for good PSUs or USB hub configurations?
Same situation as for the PI itself, if you want a portable system, you will need a portable power supply that provides exactly 5V at the required currents, many people use a 9V or 12V battery, and a cheap cigar plug USB output converter, as used to power USB devices such as iPods in a car.
calebzulawski wrote: Wifi
I suppose once I get a portable powered USB hub working, wifi is fairly straightforward as long as I use a compatible dongle (I've seen the list, things are looking pretty good for RPi and USB wifi). Does anyone have any suggestions of which dongle to use? Range isn't that important, I just want to be able to keep a connection with my router or PC through some walls at most 100 feet (30ish meters for those of you not in the US)
The most I can say is that most WiFi dongles won't work directly on the PI's USB ports, and require the power from a powered hub. For portable systems I would recommend a low power device, that is one based on a low power conscious chip set. But obviously one for which open source software exists, especially as the code needs to be compatible with the ARM6 architecture of the PI.

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