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the nicker
Jan 12, 2005
oh

Factory Factory posted:

Power and signal are entirely separate and there's no problem getting your +5V and +12V and +3.3V from entirely different sources, as long as you make sure nothing's cross-wired and about to release magic blue smoke. The only potential issue is if you're using a single-wire signal that relies on ground, but that's simple, because you can bridge the ground no problem between 5V and 12V. In fact, shared ground is probably the better idea.

Cool, so I can just straight up bridge them? I don't need any sort of protective circuitry? I think my signal does rely on ground, I'm using this circuit below (except with the pi instead of a U421). Will I need a different resistor since I'd be working with 12v?

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Factory Factory
Mar 19, 2010

I can do sex. It's just alien sex.


I don't think so, but my knowledge here is kinda derivative. Shared ground is extremely common in multi-rail PSU design and tends to alleviate a number of issues when working with multiple voltages. If you know that your two power sources will have wildly different ground states, then bridging might indeed cause problems, but that shouldn't be the case - for low voltages and currents like these, "near zero" will be pretty darn well near zero.

Might be best to head to the electronics thread in CC -> DIY to ask.

Fly
Nov 3, 2002

moral compass

ante posted:

Yeah, but as mentioned, he just needs a photo interrupter switch. Like this:



If he takes apart a printer to get the rollers/motor assembly to feed the user money, he'll also find a whole shitton of those switches.
It could be cheaper to get an old opto-mechanical computer mouse (the kind that use a ball), and use the photo-diode and ir-diode pair from one axis, but then you have to mount them on a circuit board yourself. It is cheaper though. In fact, I used a a pair from a mouse to replace a pair in my laser printer that I accidentally burnt out by connecting the diode to the fan power. :-o

Paul MaudDib
May 2, 2006


Is there any way to reduce the CPU usage (not just changing nice level) of applications like SABNZBD+ and Samba Server without adversely affecting security (the usage presumably being a result of SSL)? Either of those applications is pretty much capable of maxing the CPU all on their own during a full-speed transfer. Also, Headphones has continuous high CPU utilization, on the order of 50%, regardless of whether I'm using it or not. Anything I can do to cut those down?

Paul MaudDib fucked around with this message at May 15, 2013 around 01:22

Billa
Jul 12, 2005

What do we do with a drunken whaler...
What do we do with a drunken whaler...
Early in the morning...


I'm really sorry for asking this but I don't really want to read 38 pages to find the answer to this question (and again I'm sorry as it has probably been asked a lot of times) but...

Could you please tell me good links for projects and stuff? I got the other day a Rpi and I'd like to start doing things with it and learn.

HATE TROLL TIM
Dec 14, 2006

Kickstarter Hate Criminal


Billa posted:

I'm really sorry for asking this but I don't really want to read 38 pages to find the answer to this question (and again I'm sorry as it has probably been asked a lot of times) but...

Could you please tell me good links for projects and stuff? I got the other day a Rpi and I'd like to start doing things with it and learn.

W..what are you looking for exactly? I mean, that's a pretty generic request...

Billa
Jul 12, 2005

What do we do with a drunken whaler...
What do we do with a drunken whaler...
Early in the morning...


HATE TROLL TIM posted:

W..what are you looking for exactly? I mean, that's a pretty generic request...

That's more than enough, thanks man.

MohawkSatan
Dec 20, 2008


Does anyone know if it would be possible to hook 10 RPis together to create the world's smallest, goofiest, weakest supercomputer?

Skarsnik
Oct 21, 2008

I...AM...RUUUDE!


Yes

http://www.southampton.ac.uk/mediac...rcomputer.shtml

Mugaaz
Mar 1, 2008


Used one of these babies as a CA and RADIUS server for wireless EAP-TLS authentication. Had to teach myself Linux since I barely used it before. It was actually pretty painful to be honest, had trouble finding good documentation, and everything I found was incomplete or contained errors. Had a lot of problems where I'd get errors that in no way guided me to what the problem was. However, I struggled through it and it all worked out. I plan on using these more in the future, saved tons of money compared to any of the alternatives.

MohawkSatan
Dec 20, 2008



Excellent.

Paul MaudDib
May 2, 2006



quote:

The whole system cost under £2,500 (excluding switches) and has a total of 64 processors and 1Tb of memory (16Gb SD cards for each Raspberry Pi).

Yes, flash memory is totally the same thing as SDRAM

HATE TROLL TIM
Dec 14, 2006

Kickstarter Hate Criminal


Paul MaudDib posted:

Yes, flash memory is totally the same thing as SDRAM

...

It never says that? Storage is colloquially called memory sometimes, you know? They are memory cards, after all.

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DEAD MAN'S SHOE
Nov 23, 2003

We will become evil and the stars will come alive

As its a supercomputer the flash memory may well be used as swap memory!

I've never tried a swap that large, and the latency may be massive but given the guy made a cluster out of R-PI he's probably daft enough to try that too.

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