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BattleMaster posted:It's not that I want to add a layer but that I want to justify not having a ground layer in the first place just because with my current plan I can have all but one signal be on one layer only. But if it ends up being necessary to have a ground layer and two signal layers I will design it that way. If this is for a hobby circuit, just solder a wire, or even better a ribbon over a trace to create an air bridge crossover. That's the old school, and admittedly not very scalable way of dealing with complexity in wiring.
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Jan 19, 2017 04:48
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silence_kit posted:If this is for a hobby circuit, just solder a wire, or even better a ribbon over a trace to create an air bridge crossover. That's the old school, and admittedly not very scalable way of dealing with complexity in wiring. It's for something scientific but the person who did the work I'm improving got good results with something much worse. Even then I think that sort of solution is a little jankier than I want to go with. I'm probably going to end up going with a ground plane and keeping all the sensitive stuff on one side and the non-sensitive stuff like power and those logic signals on the other though. BattleMaster fucked around with this message at 05:18 on Jan 19, 2017 |
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Jan 19, 2017 05:06
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It's not totally a wacky idea--it is actually used in some commercial products. If it is just for some circuit that will sit around in a lab, I still say that it isn't a horrible option. If you are skilled with solder assembly and use a ribbon, it actually can be a pretty high performance option, like even suitable for GHz frequencies.
silence_kit fucked around with this message at 05:25 on Jan 19, 2017 |
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Jan 19, 2017 05:10
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Just for the sake of not being all mysterious for no reason I may as well talk about what I'm doing. I'm building an experiment for measuring alpha particle stopping power using a gas electron multiplier detector with a 2D arrangement of 16 plates. The previous version of the experiment looks like this:  The big board with the big resistors on it is the GEM stack, the green board is the preamp, and the other small board with the DIP-8s on it is an array of 10 solid-state relays for switching which collector plate is hooked up to the preamp. The chamber it's in is vacuum-tight and gets evacuated of air and filled with low-pressure P-10 gas (10% methane, 90% argon) and the alpha particle source is positioned so that the particles pass through the sensitive volume of the GEM as soon as they leave the collimator. The charge pulses that reach a given collector plate are proportional to how much energy the particle lost as it travelled through the section of the detector above that plate. The preamp creates pulses with heights proportial to this collected charge and the pulses are shaped with a shaping amplifier and then counted with a multichannel analyzer. Alpha particles lose different amounts of energy at different points along their path so by selecting the different plates you should get peaks at different places in the spectrum. And if you have a way to calibrate the detector (which I need to come up with) you can read the energy directly from the MCA's spectrum. I want to get all of the electronics and the 16 collector plates onto a single 3 inch by 5 inch board. 3x3 inches is taken up by the GEM stack and and 3x2 inches is left for the electronics and high-voltage resistor divider. I increased the collector plates to 16 for better spacial resolution and am using a higher-quality 16:1 mux which should have much better characteristics than a huge array of those cheapo generic SSRs. Even my worst ideas I've posted already should be better than what we already have, but I may as well do things the best way possible the first time around. BattleMaster fucked around with this message at 05:32 on Jan 19, 2017 |
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Jan 19, 2017 05:18
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I want to make an electric burner that can go inside a super-insulated box, and I want to keep it as simple as possible. These are electric burners: https://www.google.com/search?q=electric+burner&source=lnms&tbm=isch I want to basically put a heating element like those into a fireproof, insulated box, and have a knob that controls temperature, and not risk any wires/components melting themselves at ~500 Fahrenheit max. What would be the best way to do that? a) Is there a circuit I can have outside the box that can figure out exactly how hot the heating element is by measuring it's resistance, and cycle it on/off to modulate the box temp? b) are there bi-metal switches (i.e. like you'd find in a fridge) that I can put inside the box to adjust the cutoff temp beforehand?
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Jan 19, 2017 07:37
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BattleMaster posted:Just for the sake of not being all mysterious for no reason I may as well talk about what I'm doing. I'm building an experiment for measuring alpha particle stopping power using a gas electron multiplier detector with a 2D arrangement of 16 plates. Okay but what is the aluminum foil doing, I assume it's the most important component
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Jan 19, 2017 07:50
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ate all the Oreos posted:Okay but what is the aluminum foil doing, I assume it's the most important component I think it was supposed to be shielding for the wires connecting between the SSRs and the huge bank of toggle switches. When I got my hands on it it had been replaced with some flexible metal tubing.
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Jan 19, 2017 08:21
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Foil is the most important part of any experiment in which it is present. Don’t mess with a grad student’s foil.
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Jan 19, 2017 08:22
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if you really needed a low-noise jumper, you could maybe use a length of shielded wire, or maybe coax?
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Jan 19, 2017 08:47
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Zero VGS posted:I want to make an electric burner This screams "not a hobby project" at full volume. That said: quote:a) Is there a circuit I can have outside the box that can figure out exactly how hot the heating element is by measuring it's resistance, and cycle it on/off to modulate the box temp? a) measuring temperature is pretty straightforward with a properly selected thermistor and a lookup table. I've only ever done this with a microcontroller, which would also be handy for experimenting with your control algorithm. I'm sure there's a pure analog way to do it, but I don't know how painstaking the calibration would be, or how reliable. I'm guessing there are several good reasons that electric burners are usually rheostats instead of thermostats. b) Possibly, but I doubt they're common at the temperature range you're talking about. I would also caution against the general idea of putting any but the bare minimum electronics in a cavity that reaches burner temperature. 500 degrees is serious business, and you'll need heavy duty industrial stuff to be near it, not to mention the stresses from thermal cycling. Which brings me back to my first point. See if you can't do what you want with a relay controlling A/C power upstream of a commercial burner. Put all your custom electronics (except the sensor, of course) in a separate box and keep it as far away from the heat as is practical.
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Jan 19, 2017 14:54
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Super long-shot here. I have a USB battery bank I like (Limefuel Rugged), but it's dead. I disassembled it last night, and suspect the SUN4007 charge controller, based on it getting extremely hot when I try to charge it (no cells or any load connected). Anyway, the SUN4007 seems to be unavailable now. Anybody know of a similar SOP8 charge controller I could substitute? Or a good place to ask about this?
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Jan 19, 2017 16:26
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Zero VGS posted:I want to make an electric burner that can go inside a super-insulated box, and I want to keep it as simple as possible. Go buy a used electric oven on Craigslist. That way when something catches on fire it's not entirely your fault.
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Jan 19, 2017 19:19
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KnifeWrench posted:This screams "not a hobby project" at full volume. That said: It's rheostats are very cheap, have basically nothing to go wrong, and fail safely when they do fail. But really, there's almost no advantage to a temp controlled burner in common cooking scenarios. (Other than baking, but ovens are already temp controlled.) For boiling it's always 100c no matter how hard the boil is, and if it's too fast or too slow it won't affect it over the short term and over the long term the cook corrects it. Frying is more short term dependant on heat throughput, but the cook should be right there to prevent burning, and a temp controlled burner couldn't do anything to prevent burning (or fire) anyway. Less common techniques might benefit from it, but sous vide needs to know the temp of the food itself, not the burner. Candy making might be helped? Poaching too, but I'd think you'd have similar issues of burner vs liquid as sous vide.
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Jan 19, 2017 22:16
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Zero VGS posted:I want to make an electric burner that can go inside a super-insulated box, and I want to keep it as simple as possible. Look on eBay/Amazon for a PID controller + K type thermocouple + relay combo, should be roughly $15-$30 bucks. Attach the thermocouple as close as you can to whatever it is you actually want to measure (there will be a huge temperature gradient between the heating element itself and what it is actually heating). The controller will pulse the element to maintain the temperature setpoint, usually within a couple degrees. If you want a knob instead of buttons, you can do something similar with an arduino and a MAX31855K to interface it with a thermocouple, but it's much more work than something off the shelf.
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Jan 19, 2017 22:51
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I've got an squealing PSU which I'd prefer not to chuck and isn't easy to get inside. I presume it's an inductor which is vibrating at a resonant frequency which depends on the current, hence higher loads making it noisy? Is there anything I can put on the output to help reduce squeal - like more inductors or caps, or do I need to get inside and swap out components?
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Jan 19, 2017 23:17
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Good chance it's a fan, too
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Jan 20, 2017 02:44
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Platystemon posted:Foil is the most important part of any experiment in which it is present. I literally pulled foil out of the trash while angrily staring at someone during grad school because the stuff they'd thrown away casually had been treated with a heat-resistant matte black paint so that it would absorb stray light from an optical system. It later ended up being wrapped around a camera system as part of a makeshift video pupilometer. For anyone who doesn't keep foil around their electronics workspace, it's handy for keeping stray bits of molten solder off of work surfaces, keeping hot-plates clean during reflow, catching SMT components being flicked off of irons during de-soldering, and a myriad of other uses separate from its shielding abilities. Also, ZeroVGS, I'm curious what you're building.
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Jan 20, 2017 05:04
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Aurium posted:But really, there's almost no advantage to a temp controlled burner in common cooking scenarios. (Other than baking, but ovens are already temp controlled.) For boiling it's always 100c no matter how hard the boil is, and if it's too fast or too slow it won't affect it over the short term and over the long term the cook corrects it. Frying is more short term dependant on heat throughput, but the cook should be right there to prevent burning, and a temp controlled burner couldn't do anything to prevent burning (or fire) anyway. If I'm going to get into it, I currently have six 2'x2' vacuum insulated panels (it's like a ceiling tile, wrapped in heat-sealed aluminum and the air vacuumed out), arranged as a box and held together with food-grade 500f silicone caulking, with a steel box as a stonger shell over all that. I'd be sneaking the thermocouple in through a joint and caulking that in place. So, this is an 2'x2'x2' box that insulates like a thermos bottle, and steam can escape through the lid if there's any pressure. I want the temperature control so that I can keep stews at a simmer (or baking stuff, anything I put in the box), while using just the right amount of wattage to do it and no more. This is going to be an RV battery-based oven/stove that is super energy efficient. rawrr posted:Look on eBay/Amazon for a PID controller + K type thermocouple + relay combo, should be roughly $15-$30 bucks. Attach the thermocouple as close as you can to whatever it is you actually want to measure (there will be a huge temperature gradient between the heating element itself and what it is actually heating). The controller will pulse the element to maintain the temperature setpoint, usually within a couple degrees. Thanks, I'm looking at this one since it works with 24v DC which is the battery I'd be using: https://smile.amazon.com/Inkbird-Digital-Temperature-Controller-ITC-100VL-24/dp/B00AE25716/ The one thing that is a bit confusing, is says the relay is 3-32vdc input, but the other side is 24-380 AC. Isn't the relay just making a connection on that side, when the 3-23vdc control dictates? Why does it have to be AC? If I wanted to have 24vdc to control the PID and also send something like 24vdc 300w from the battery to a heating element when the thermocouple says the temp is below the setpoint, is this the best way to go?
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Jan 20, 2017 05:23
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Zero VGS posted:The one thing that is a bit confusing, is says the relay is 3-32vdc input, but the other side is 24-380 AC. Isn't the relay just making a connection on that side, when the 3-23vdc control dictates? Why does it have to be AC? It might not have to be, but from my limited personal experience I can tell you that Inkbird products don't have the greatest documentation, so it's a crap-shoot. This might be helpful: http://electronics.stackexchange.com/questions/13429/can-i-use-a-solid-state-relay-to-control-a-dc-current It sounds like a nifty project. If you're looking for something low-draw (which would be preferable for battery longevity) you might be able to get away with something far less powerful than an actual burner given your insulation. If you don't mind long bake times, a modest halogen bulb might be an easy heat source.
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Jan 20, 2017 06:20
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Jamsta posted:I've got an squealing PSU which I'd prefer not to chuck and isn't easy to get inside. Does it make a characteristic 60Hz or 120Hz hum? If you're not sure there are phone apps that can do an FFT of the mic audio to tell you. Assuming it is 60Hz related noise I've had issues like that in the past where some transformer or inductor winding has popped free of whatever was holding it in place and is vibrating due to Lorentz forces. The way I tracked that one down was to take the cover off and use a fiberglass rod to probe around on the part in question (transformer in my case) until I found the loose winding that would stop squealing when pushed by the rod. The winding had been shellacked in place but had broken free. I painted that area with epoxy and after it cured the squeal went away.
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Jan 20, 2017 06:24
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Zero VGS posted:If I'm going to get into it, I currently have six 2'x2' vacuum insulated panels (it's like a ceiling tile, wrapped in heat-sealed aluminum and the air vacuumed out), arranged as a box and held together with food-grade 500f silicone caulking, with a steel box as a stonger shell over all that. I'd be sneaking the thermocouple in through a joint and caulking that in place. At first I wondered why you'd quote me instead of some of the other people who actually gave advice as to how to actually do it. Then I got to the end and you were talking about cooking with it. I had no idea my attempt at background info as to why rheostats would be common was actually relevant to the problem at hand. But since it is, like others said, you'd be best off measuring what you're heating, not the burner itself, or it'll take much longer to get up to temperature, as heat flow between things is proportional to difference between the hot and cold areas. The total power used shouldn't be very different, but it could easily be the difference between minutes and hours to heat up. That said, I don't think I'd just stick an industrial thermocouple right in my soup. poeticoddity gave you a link to why most SSRs can only switch AC, even regular relays can have wildly different ratings for DC and AC. At arc extinguishing eating the contacts can be a a major problem. When the contacts open up an arc forms, but with AC the voltage drops to 0 twice every cycle, and carrier ions stop being generated. If these carrier ions dissipate or are removed or neutralized the arc won't reform. With DC the arc is continuously going, and these ions are continuously being generated, and it becomes much harder to neutralize or remove them. http://electronics.stackexchange.com/questions/22194/relay-power-ratings-ac-vs-dc http://www.studyelectrical.com/2014/05/principles-and-methods-of-arc.html
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Jan 20, 2017 07:07
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Zero VGS posted:The one thing that is a bit confusing, is says the relay is 3-32vdc input, but the other side is 24-380 AC. Isn't the relay just making a connection on that side, when the 3-23vdc control dictates? Why does it have to be AC? Electromechanical or not, switches will have a higher AC voltage rating than their DC voltage rating. http://electronics.stackexchange.com/questions/156901/switch-current-rating-ac-vs-dc Don't assume, especially if your relay circuitry isn't designed by you and is purpose-built with a specific use case in mind.
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Jan 20, 2017 07:26
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Aurium posted:That said, I don't think I'd just stick an industrial thermocouple right in my soup. Why not? That's what a Thermapen is.  In all seriousness, Thermoworks sells a range of K and T probes for oven, grill, smoker, and submersed use alongside their industrial probes. http://www.thermoworks.com/Handheld-Probes/Probes?show=48
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Jan 20, 2017 07:37
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I see, so the relay is actually timing itself to disengage it's contactors or whatever, when the AC voltage is 0, so it doesn't damage itself. I think I found what I would want: https://www.ringhotwater.com.au/universal-oven-thermostat-16-amp-240-volts-50-320-c-220mm.html That's an oven thermostat with capillary probe. So I could just stick the probe in so it makes good contact with the cooking pot or whatever. That particular model says it is rated at 240VAC 16amp, so I should either stick to AC or ask the manufacturer if it can support a heavily de-rated DC scenario?
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Jan 20, 2017 07:49
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Zero VGS posted:I see, so the relay is actually timing itself to disengage it's contactors or whatever, when the AC voltage is 0, so it doesn't damage itself. There's also safety concerns with relays, since breaking a DC arc is much harder than breaking an AC arc since there's no zero crossings. This probably isn't an issue with what you're trying to do but good to keep in mind if you ever do any higher voltage DC stuff.
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Jan 20, 2017 08:22
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ante posted:Good chance it's a fan, too Sorry, forgot to say it's a sealed laptop-style AC/DC PSU with no fans. PDP-1 posted:Does it make a characteristic 60Hz or 120Hz hum? If you're not sure there are phone apps that can do an FFT of the mic audio to tell you. It changes frequency depending on the current. Low currents no noise, higher load/current it gets higher frequency. Way higher than 60hz, probably in the khz range. Guessing either way I can suppress it externally, and it's an open-up job? Dang! Cheers
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Jan 20, 2017 13:18
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Zero VGS posted:If I'm going to get into it, I currently have six 2'x2' vacuum insulated panels (it's like a ceiling tile, wrapped in heat-sealed aluminum and the air vacuumed out), arranged as a box and held together with food-grade 500f silicone caulking, with a steel box as a stonger shell over all that. I'd be sneaking the thermocouple in through a joint and caulking that in place. If you're still considering this option (A PID controller should offer better temp stability and accuracy), you can simply buy a DC-DC relay/SSR (which should also be readily available on Amazon) instead of using the DC-AC one. On the off chance that you aren't already aware, if you're using a 24v source, don't expect to be able to use it effectively with the electric burners you've linked that are rated for 110v; a 110V 300W element will only output like 14W on 24V. rawrr fucked around with this message at 13:56 on Jan 20, 2017 |
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Jan 20, 2017 13:51
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MisterOblivious posted:Why not? That's what a Thermapen is. Thermapens own and you can get calibrated probes too!
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Jan 20, 2017 14:37
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I've got an old Amiga expansion board that doesn't work right. It's got 3 PLCC chips that I want to re-seat because my PLCC extractor tool just bent and scratched the chip's case trying to pop them out. I presume they're stuck due to oxidation, which could be why the board doesn't work. How can I get them out?
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Jan 22, 2017 18:34
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Luigi Thirty posted:I've got an old Amiga expansion board that doesn't work right. It's got 3 PLCC chips that I want to re-seat because my PLCC extractor tool just bent and scratched the chip's case trying to pop them out. I presume they're stuck due to oxidation, which could be why the board doesn't work. How can I get them out? It's probably more that some (all?) PLCCs can be really hard to hold on to with the puller. And it gets worse as you scrape up the bottom of the chip making attempts. Plus some brands/sizes of PLCC sockets are super tight. Especially if they haven't been used much. Concentrate on sideways pressure and getting the feet to 'grab' the chip before you pull up. You can lever the chip with a screwdriver to get some room for the puller to get purchase and I've had success doing that, but it is easy to crack the corner of the socket so I wouldn't actually recommend it. We see a fair amount of socketed PLCCs in some old boards we work on, and replace our pullers occasionally as they wear out. You might be able to file the feet a bit to get some purchase, but I've never tried since the pullers are $4 or something. e: This is the style of extractor/puller I mean:  taqueso fucked around with this message at 21:20 on Jan 22, 2017 |
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Jan 22, 2017 21:16
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I did end up getting them out but no dice on the board working  Oh well.
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Jan 22, 2017 22:11
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Autodesk have released their updated version of Eagle after buying out CadSoft , and basically if you haven't switched to KiCad yet, now is a good time. Always on subscription only pricing is the main thing people are upset about, the standard licence is limited to 2 layers (it was 4), and routable area for the free version has been halved. Chalupa Joe fucked around with this message at 19:23 on Jan 23, 2017 |
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Jan 23, 2017 07:30
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Chalupa Joe posted:Autodesk have released their updated version of Eagle after buying out CadSoft , and basically if you haven't switched to KiCad yet, now is a good time. Why? (Even) worse interface, too much pressure on paid services, stability issues, or what?
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Jan 23, 2017 19:16
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Star War Sex Parrot posted:Playing around with an X-band (~10GHz) VCO+PLL: 
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Jan 23, 2017 20:29
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Chalupa Joe posted:Autodesk have released their updated version of Eagle after buying out CadSoft , and basically if you haven't switched to KiCad yet, now is a good time.
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Jan 23, 2017 23:02
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Solidworks has a free education version I believe, as does Inventor I think? Solidworks is also very available depending on your stance on  which is preferable to murder.The inbuilt solidworks tutorials are good enough to get you to a competent level too, so all you need is a copy.
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Jan 23, 2017 23:32
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I honestly thought that Autodesk would get it right and go with something akin to the Fusion360 model, which offers a very powerful, ungimped hobbyist license and implement some integration features between Eagle and Fusion360. That way they can have a pretty comprehensive toolchain that includes pcb schematic/layout and 3D CAD and CAM.
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Jan 23, 2017 23:50
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They might still do that, but as a new product. Eagle360 or something. Fusion and inventor have been pretty successful, I bet the solidworks devs are making GBS threads themselves. I had a quick look at fusion the other day and it looks like I wouldn't have to relearn much if I swapped over. I wouldn't really miss SolidWorkaround either. It would be really nice to have a more integrated approach to importing from altium. Solidworks does an awful job and makes a huge mess
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Jan 23, 2017 23:57
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The new Eagle pricing model is pretty crazy bad for hobbyists - Want more than 2 signal layers? Gotta shell out mad cash, forever Pimping Circuitmaker again. It's great, free, and has no restrictions that affect usability. coyo7e posted:I've been taking AutoCAD this semester as a basis for learning to use CAD software however, the machines in the school lab have SolidWorks, and frankly I'd kill to get a copy of it (and a machine capable of running it). Dude, use Fusion360. I use SW professionally, and Fusion360 at home, they're drat near identical. Feels more like different versions of a product than something from an entirely different company.
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Jan 24, 2017 01:28
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Wow, really? I'm really new to all this digital drafting and design software so I'm not sure which features and stuff are in different solutions. I saw someone demonstrating how you can design a valve in solidworks and then virtually manipulate it to "physically observe" whether or not it had enough tolerance to not knock against itself as it moves and I just went  And I have been using Circuitmaker a bit, it's pretty slick but now that I'm in class I have to spend most of my time drafting (2D  - but most of my classmates can barely hold a mouse so welp) floor plans and calculating fluid dynamics and thermal exchange than electronics, so I'm trying to capitalize as best I can on gleaning all I can from all the software tools I come across.  edit: is there a CAD or similar thread, somewhere? I'd love to bookmark one if there is. coyo7e fucked around with this message at 03:57 on Jan 24, 2017 |
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Jan 24, 2017 02:59
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