• Electronics and Embedded Programming V3
    1,545 replies, posted
  • [QUOTE=Chryseus;36980791]Got most of it off *vomit* so it looks (and smells) a lot nicer, going to get some Brasso to polish it to a nice shine and finish it off with some wax.[/QUOTE] I don't know if putting wax on the components is a good idea, since these things tend to get warm on the inside... If my tube radio has been playing for a few hours, the whole chassis of the thing gets warm.
  • [QUOTE=masterburner;36986916]I don't know if putting wax on the components is a good idea, since these things tend to get warm on the inside... If my tube radio has been playing for a few hours, the whole chassis of the thing gets warm.[/QUOTE] I'll only be waxing the outside, it will be a thin coating so heat shoud not be a problem.
  • [QUOTE=masterburner;36946725]The easiest solution I think is to get a stereo potentiometer. That's basically 2 pots on the same shaft.[/QUOTE] Thanks.. great idea and it works wonderfully!
  • Grandparents gave me a nice old MAP sensor, hoping it still works. Not sure what I could use it on though. [IMG]http://i50.tinypic.com/10rsrd0.jpg[/IMG]
  • So enabling i2c drivers on the raspberry pi is a bit of a pain in the ass and requires recompiling the entire kernel. I'm currently still compiling, but I hope I can finally access the i2c (and spi) devices afterwards :)
  • [QUOTE=LoneWolf_Recon;36990356]I2C gives alot of people problems :( Or maybe thats just me[/QUOTE] It's because it's not compiled in the images provided on raspberrypi.org. Here's a pretty comprehensive guide on how to compile the newest kernel. Just note that you have to transfer the old config file, then run "make menuconfig" and enable the i2c and spi module. [url]http://elinux.org/RPi_Kernel_Compilation[/url]
  • [img]http://i.imgur.com/E99Jr.png[/img] Sorted out the rectifier, I think I'm going to just use a half-wave rectifier to save on parts and space, The transformer is only small so my usable maximum current is probably only in the 250mA region which does not really matter much I just want a decent dual rail supply which are pretty much required for experimenting with op-amps and many transistor circuits unless you want to screw around with single rail operation which is not always ideal. (Note: the negative rail in blue is offset from 0V on purpose for visual clarity)
  • So I ask dad to keep a lookout for something to knick at the electronic waste section of the recycling center as he's dumping some old TV's. Half an hour later he comes back with nothing less than a goddamn keithley instruments 155 microvolt meter. It goes from 1µV to 1kV and supposedly has better than 150nV resolution at 1% accuracy. Don't know about that though, it has a cal sticker dated 22/4 1970. Still all that seems wrong with it is that the batteries are dead, they're old style pp6 9 volt batteries, think I'll just replace it with modern 9 volts after I clean out this melted sticky 40 year old foam tape. Other than that, one of the mounts on the pcb has cracked and obviously I'll need to recalibrate it at some point.
  • Gotta love finding junk where you work. Working in the HVAC field has netted me an old Carrier 3-phase motor speed controller which had, among other things, 2 rather beefy 400uF 1000V capacitors. There's also a rather large ceramic mystery part which, considering it's bolted to the rather large heatsink, is likely the do-whatsit that delivers the final 3-phase output (anywhere from 40Hz to 240Hz if I recall). I was also able to nab an old water-cooled condenser coil from an old ice machine which, with a few alterations, should work nicely for another project I've been working on.
  • [QUOTE=Zero-Point;37012885]Gotta love finding junk where you work. Working in the HVAC field has netted me an old Carrier 3-phase motor speed controller which had, among other things, 2 rather beefy 400uF 1000V capacitors. There's also a rather large ceramic mystery part which, considering it's bolted to the rather large heatsink, is likely the do-whatsit that delivers the final 3-phase output (anywhere from 40Hz to 240Hz if I recall). I was also able to nab an old water-cooled condenser coil from an old ice machine which, with a few alterations, should work nicely for another project I've been working on.[/QUOTE] Pics of the condenser, please? I'm working on a similar project
  • [QUOTE=Zero-Point;37012885]Gotta love finding junk where you work. Working in the HVAC field has netted me an old Carrier 3-phase motor speed controller which had, among other things, 2 rather beefy 400uF 1000V capacitors. There's also a rather large ceramic mystery part which, considering it's bolted to the rather large heatsink, is likely the do-whatsit that delivers the final 3-phase output (anywhere from 40Hz to 240Hz if I recall). I was also able to nab an old water-cooled condenser coil from an old ice machine which, with a few alterations, should work nicely for another project I've been working on.[/QUOTE] [img]http://theelectrostore.com/shopsite_sc/store/html/media/transistors-igbts/skm145gal123d-semikron-igbt-skm-145-gal-123d-123-d-new.jpg[/img] IGBT perhaps?
  • Reading up on it, I bet that's what it is too. Has alot of pins in it though so I thnk it's safe to assume there's multiple devices in this one module. Methinks I could use it to make an inverter should I ever get that windmill off the ground. Score!
  • [QUOTE=DrLuke2;37016972]looks more like a normal BJT with some diodes in it[/QUOTE] [url]http://www.newrock.com.cn/PDF/IGBTMD/SEMIKRON/CHOPPER/SKM145GAR123D.pdf[/url] It's an IGBT module
  • [QUOTE=DrLuke2;37016972]looks more like a normal BJT with some diodes in it[/QUOTE] I searched for an IGBT image so guess what it is.
  • So I just fired up my keithley 155 using an ATX power supply to get +-12 volts. It originally runs off of four 9 volt batteries to get +-18 volts but I don't have any 9 volts at home right now so +-12 had to do for a test. As far as I can tell it works just fine, not horribly out of spec either though I was comparing it to the readout of a $10 multimeter and only measuring down to a few millivolts. The µvolts range was almost completely unuseable due to the switching noise from the atx psu but I just wanted to see it was working. Gonna order a 10 pack of 9 volts from dealextreme for $10 within the week probably and once they arrive I'll make a neat installation and then I'll take pictures and upload them here and probably on the eevblog forums.
  • You'll probably get more value if you invest the 10 dollars in better batteries at your local store (+ it won't take a year and a half to arrive)
  • [QUOTE=LoneWolf_Recon;37013792]Pics of the condenser, please? I'm working on a similar project[/QUOTE] For you to know if it's a similar project you'd have to know what I'm doing, which as far as I know, I've not mentioned it. :v: [img]http://img29.imageshack.us/img29/3508/20120731210637.jpg[/img]
  • [QUOTE=Zero-Point;37028134]For you to know if it's a similar project you'd have to know what I'm doing, which last I heard I've not mentioned it. :v: [img_thumb]http://img29.imageshack.us/img29/3508/20120731210637.jpg[/img_thumb][/QUOTE] Does it pertain to a cooling project/goal? (Thank you btw)
  • [QUOTE=LoneWolf_Recon;37028157]Does it pertain to a cooling project/goal? (Thank you btw)[/QUOTE] The plan is to use it as a heat exchanger for my mineral oil computer so I can refrigerate the oil, yes. Though looking at it now it might be too big to be used effectively as an evaporator. Might be able to get away with it by slowing the flow of oil through it so I don't get some insane super-heat numbers, but I dunno. I might be better off asking my old HVAC instructor if he has access to any old water fountains destined for the scrap yard, the heat exchangers in those might work better, but then again they might be too small, too. I'll see what Google can find out about this thing before I proceed any further, though. And yes, I do have a compressor/condenser coil already, gutted them out of a 5,000BTU/H window unit. It was a R-410A system, but the idea is to use R-134a instead, which the oil used is the same for both so there's no issue there, and a 410 compressor can certainly handle any pressures 134a could ever hope to exert under normal operating conditions. Yeah, yikes, this thing is designed to handle 1.66 tons of refrigeration. Starting to think it may not be suitable after all. I might still be able to get away with it, if I reduce airflow over the condenser I can effectively "trick" the thing into acting like a 1/2 ton system. But still, this is sad news as it means I've likely just salvaged a very bizarre-looking door-stop.
  • You'd have to keep that mineral oil pressurized pretty good, I can imagine it just collecting once its condensed in that unit. Agreed, you might want to start small.
  • [QUOTE=LoneWolf_Recon;37028806]You'd have to keep that mineral oil pressurized pretty good, I can imagine it just collecting once its condensed in that unit. Agreed, you might want to start small.[/QUOTE] The pump being used is a 320GPH fountain pump, but yeah, once it starts getting chilled it'll thicken up pretty good. It's veterinary-grade mineral oil, so no real specs on the pour-point and what-not. Some preliminary reading shows that, at least with air-based systems, a larger evap coil compared to condensing coil isn't a huge deal (except it causes humidity problems. This is me caring. :geno: ). Since it's mostly an experiment anyway and not likely to ass-fuck the compressor, I might just try it out anyway and hope for the best. I'm not planning on getting the oil to 0 degrees F anyway, mostly just aiming for a 40F ambient temp. Should keep everything cool while still maintaining the oil in a mostly liquid state so it can do its job. I mean hell, 5,000 BTU/H is kind of over-kill since the maximum power-draw on the system in question is less than 350W (1195.25 BTU/H roughly), but meh, the compressor was dirt-cheap. Can't beat a working compressor with condenser coil for $60. :v: Absolute worst-case scenario, I might just go redundant and make heat exchangers for both the GPU and CPU and use the mineral oil purely as insulation (though obviously it would get cooled too, and cool the other shit like MB/RAM).
  • Hopefully that mineral oil is at a low enough viscosity for the compressor. You have any ideas on how I could make a compact expansion valve? Just make a pinch point?
  • [QUOTE=LoneWolf_Recon;37029292]Hopefully that mineral oil is at a low enough viscosity for the compressor. You have any ideas on how I could make a compact expansion valve? Just make a pinch point?[/QUOTE] Coiled capillary tube or piston orifice would be your best bet. You can even wrap a good portion of the cap-tube around the suction line to increase super-heat (prevents liquid refrigerant from reaching the compressor, that would be bad) and increase sub-cooling. Simply pinching the tube *might* work, but it'd be an imprecise method at best. Danfoss has a program somewhere that allows you to compute the length and gauge of cap-tube you need for various things. And the mineral oil isn't going into the compressor at all, most HFC refrigerants don't play nice with mineral oil nor, in some cases, alkybenzene.
  • [QUOTE=chipset;37023046]So I just fired up my keithley 155 using an ATX power supply to get +-12 volts. It originally runs off of four 9 volt batteries to get +-18 volts but I don't have any 9 volts at home right now so +-12 had to do for a test. As far as I can tell it works just fine, not horribly out of spec either though I was comparing it to the readout of a $10 multimeter and only measuring down to a few millivolts. The µvolts range was almost completely unuseable due to the switching noise from the atx psu but I just wanted to see it was working. Gonna order a 10 pack of 9 volts from dealextreme for $10 within the week probably and once they arrive I'll make a neat installation and then I'll take pictures and upload them here and probably on the eevblog forums.[/QUOTE] You could always put +12V on the positive terminal and -5V on the negative terminal, giving you an effective 17V. Close enough, eh? :v:
  • [QUOTE=Zero-Point;37033442]You could always put +12V on the positive terminal and -5V on the negative terminal, giving you an effective 17V. Close enough, eh? :v:[/QUOTE] The keithley needs dual rail supply, one at +18 volts and one at -18 volts. It uses four 9 volt batteries to achieve this by connecting it like this: [img]https://dl.dropbox.com/u/59112523/9voltbatterydualsupply.png[/img] You can achieve this using any two isolated power supplies, the reason this thing uses batteries is because any other power supply would have been too noisy for the really low level measurements. I just used an atx power supply to see if it worked at all while I wait for the batteries. To do what you propose I would need two atx power supplies that I would have to mod to be mains earth isolated, and it would all be very unnecessary because I just wanted to see if it worked and +-12v did that just fine.
  • Very, very informative video on good electrician practices. I hope you'll learn new tricks from it. [media]http://www.youtube.com/watch?v=BCcD55jDsA0&feature=related[/media]
  • You know, for a country which hates gore in their video games, they sure know how to make their safety videos graphic as fuck. Edited: Finalizing the overlay for the programmer. Not sure what else to change. Any ideas? [IMG]http://i11.photobucket.com/albums/a166/ballsandy/100_3018.jpg[/IMG] I also need two new knobs. the ones I got are too big and interfere with the big EPROM TEXTOOL socket and leave no room to not what each position does.