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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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| # ? May 13, 2013 16:20 |
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| # ? May 23, 2013 00:05 |
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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.
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| # ? May 13, 2013 16:41 |
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ante posted:Yeah, but as mentioned, he just needs a photo interrupter switch. Like this:
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| # ? May 14, 2013 02:29 |
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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 |
| # ? May 15, 2013 00:06 |
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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.
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| # ? May 16, 2013 20:25 |
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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... W..what are you looking for exactly? I mean, that's a pretty generic request...
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| # ? May 16, 2013 21:31 |
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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.
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| # ? May 17, 2013 07:40 |
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Does anyone know if it would be possible to hook 10 RPis together to create the world's smallest, goofiest, weakest supercomputer?
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| # ? May 18, 2013 06:30 |
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Yes http://www.southampton.ac.uk/mediac...rcomputer.shtml
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| # ? May 18, 2013 06:53 |
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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.
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| # ? May 18, 2013 07:33 |
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Excellent.
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| # ? May 18, 2013 13:58 |
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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 
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| # ? May 18, 2013 15:42 |
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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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| # ? May 18, 2013 20:52 |
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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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| # ? May 18, 2013 21:06 |
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DEAD MAN'S SHOE posted:As its a supercomputer the flash memory may well be used as swap memory! I'm considering building one a) just for the hell of it, b) because it's cool, and c) you can get a decent computer with a bunch of pis and a little work relatively cheap.
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| # ? May 18, 2013 22:14 |
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MohawkSatan posted:I'm considering building one a) just for the hell of it, b) because it's cool, and c) you can get a decent computer with a bunch of pis and a little work relatively cheap. What do you mean by "decent" here? They say it cost "under £2,500 (excluding switches)." That's a significant amount of money for a not-particularly-powerful computer. If you wanted to learn about writing highly parallel software, MPI, and other supercomputing, it might not be a bad way to play around with concepts. If you're trying to actually crunch data, though, there are much smarter ways to spend the same money.
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| # ? May 19, 2013 02:22 |
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I mean decent enough to run a few older games like Jagged Alliance 2, a controller for a small robotics project of mine, and of course, it;d be a great way to lean about parallel computing and supercomputers. I've got the 20mm ammo can for an old autocannon I'm slowly turning into my Pi case, and it's still got a ton of room, enough so that I could probably fit another 7 RPis in without too much effort. So far it's a Pi, 1tb hard drive, flexible keyboard, small speakers, a small fan, and space for a 15inch flatscreen HDMI monitor in the lid. So hey, if I can get 8 pis in there, that'd be pretty great. There's still plenty of space in it, and there'll be even more if I get a more modern 1tb drive or find a solid state drive that'll work.
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| # ? May 19, 2013 05:17 |
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MohawkSatan posted:I mean decent enough to run a few older games like Jagged Alliance 2, a controller for a small robotics project of mine, and of course, it;d be a great way to lean about parallel computing and supercomputers. I've got the 20mm ammo can for an old autocannon I'm slowly turning into my Pi case, and it's still got a ton of room, enough so that I could probably fit another 7 RPis in without too much effort. So far it's a Pi, 1tb hard drive, flexible keyboard, small speakers, a small fan, and space for a 15inch flatscreen HDMI monitor in the lid. So hey, if I can get 8 pis in there, that'd be pretty great. There's still plenty of space in it, and there'll be even more if I get a more modern 1tb drive or find a solid state drive that'll work. With all that room I'd consider filling the bottom with 2000mAh 18650 Li-Ion batteries. If you can fit 20 of them in there, that's 40Ah worth of power; that would comfortably run 8 RPi's for 10 hours. A portable supercomputer would be awesome!
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| # ? May 19, 2013 06:39 |
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I'm pretty dumb when it comes to DIY computer stuff, but my friend set me up with retropie and I have felt like a 10 year old on Christmas for 3 days straight. It's so cool having a tiny little reto console hooked up to my TV. I really wish the thing had an on/off switch though.
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| # ? May 19, 2013 06:43 |
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HATE TROLL TIM posted:With all that room I'd consider filling the bottom with 2000mAh 18650 Li-Ion batteries. If you can fit 20 of them in there, that's 40Ah worth of power; that would comfortably run 8 RPi's for 10 hours. A portable supercomputer would be awesome! I was in fact thinking of that. I've got a bit of space under where the speakers will be going, so it might work. In the meantime though, it's powerbar all the way.
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| # ? May 19, 2013 08:09 |
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MohawkSatan posted:I was in fact thinking of that. I've got a bit of space under where the speakers will be going, so it might work. In the meantime though, it's powerbar all the way. You might also want to look into headway cells: http://www.manzanitamicro.com/produ..._id=29&vmcchk=1 Big cells, but lots of capacity. I use them in my e-bike and they work great.
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| # ? May 19, 2013 16:59 |
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I am having a problems saving while using Retropie. My save games are wiped 75% of the time when I turn it back on. The best advice I can find is that you need to properly shut it down after using it, but it also seems to crash after any extended use. Any advice would be appreciated.
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| # ? May 21, 2013 06:05 |
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I've been trying to set Retropie up myself but haven't quite finished - I remember something about savegames from the documentation I'm following. Here, I found it: On first boot, EmulationStation is going to have you run through the button configuration for navigating the menu in EmulationStation (Please take note: Configuring EmulationStation controls will not configure your controls for the emulator. We will get to that later) Use left and right on your keyboard to select an emulator, then up and down to select a ROM, and then press enter to run it. Default controls use the A,S,Z,X keys for the button pad, Enter and Shift for start and select, and arrow keys for D-pad. Esc will exit the game, and F4 will exit the EmulationStation frontend and bring you back to terminal. Take note that pressing Esc from the game will dump the save data to the Pi keeping your save games. However the only time it does save your game to the memory is when you press Esc – not when you press save in the game. If the system is powered off before Esc is pressed, your save file will not be written to memory.
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| # ? May 21, 2013 14:04 |
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| # ? May 23, 2013 00:05 |
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Yeah, I saw that too. So the reason it's not saving must be related to the crashes. 70% of the time that I use it for more than an hour or 2, trying to exit back to emulation station just brings me to a black screen with a white dot in the middle. I don't know if that problem is specific to me though because I can't find anyone else on Google having the same problem. As it stands, it's not even worth trying to play a game that uses save states.
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| # ? May 21, 2013 18:22 |
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