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I wish I could find the link for the video I'm thinking of, it was the best. A wall of little parts drawers, with a robotic arm behind that could zip around and open/close drawers. Combined with a database tagging all the various parts, as well as voice control, you'd stand in front of it and say, "Capacitor" and all the capacitor drawers would light up. Then you'd say, "ceramic, 22 picofarad" and a bunch of drawers would go dark, leaving the relevant ones. And so you'd say "through hole" or something and get down to just one or two drawers, which you could then have it open automatically, you'd grab your parts, tell it how many you took, and walk away (if I recall, it closed the drawers when it decided nobody was standing there.) This was on a wall that was like 12x6? Probably had, what, a couple thousand drawers? My memory is a bit fuzzy. Anyhow, do that.
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Aug 7, 2013 01:59
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Bad Munki posted:I wish I could find the link for the video I'm thinking of, it was the best. A wall of little parts drawers, with a robotic arm behind that could zip around and open/close drawers. Combined with a database tagging all the various parts, as well as voice control, you'd stand in front of it and say, "Capacitor" and all the capacitor drawers would light up. Then you'd say, "ceramic, 22 picofarad" and a bunch of drawers would go dark, leaving the relevant ones. And so you'd say "through hole" or something and get down to just one or two drawers, which you could then have it open automatically, you'd grab your parts, tell it how many you took, and walk away (if I recall, it closed the drawers when it decided nobody was standing there.) This was on a wall that was like 12x6? Probably had, what, a couple thousand drawers? My memory is a bit fuzzy. https://www.youtube.com/watch?v=uIaPYj399VI Something more practicle for inventory managment: http://ecdb.net/about.php
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Aug 7, 2013 02:22
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Well it's a lot smaller than I remembered, but there's no reason you couldn't make it bigger!  Terminal Entropy posted:Something more practical  >
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Aug 7, 2013 02:32
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PDP-1 posted:Also - inventory management. Today we just try to remember what parts we noticed were running low whenever we put in an order for some project, and it can be hit-or-miss at times. I was thinking of hanging a couple of clipboards around where folks could write down stuff we are low/out of, and we'd scratch off items whenever we ordered replacements. Any other/better suggestions? If we get the Digikey order in by 5 it's here by 10:30AM the next day.
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Aug 7, 2013 06:23
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Bad Munki posted:I'm having a hard time finding consistent-seeming package names for crystals. https://www.sparkfun.com/products/539 If height is an issue, I'd recommend always checking the datasheet to see that particular item's height; those don't seem nearly as fixed. The SMD variants have the terminals bent, as you've noticed. There are a bunch of subsets of HC-49 but I think they're all fairly similar. When looking for SMD crystals, I pay attention to the case dimensions as I'm not sure if there are any specific footprints. For example: https://www.sparkfun.com/products/8581 I'm pretty sure any 5mmx3.2mm smd crystal would fit. Glancing at mouser, there are 2500 crystals with those dimensions and just glancing at the product pictures I suspect they (all the four terminal crystals, at least) will share a common footprint. Unfortunately, some frequencies aren't available in some packages so you'll end up with a small collection of footprints for each size you'd used lately. Crystals only have so many pins, so it makes sense to just call them whatever size they are and locate the pads on opposite corners.
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Aug 7, 2013 16:51
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Something that occurred to me the other day...could one use crystal oscillators as very high-Q passive filters? I'm sure it's been done, but I've never come across it myself.
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Aug 8, 2013 18:11
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Cyril Sneer posted:Something that occurred to me the other day...could one use crystal oscillators as very high-Q passive filters? I'm sure it's been done, but I've never come across it myself.
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Aug 8, 2013 18:17
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tonberrytoby posted:You mean the SAW( Surface acoustic wave) filters that are used as RF filters in your cellphone? You need pretty specialized technology to make those. Maybe. I gather these SAW filters are an example of such a usage? What is the complication in literally replacing an LC filter with a crystal? (To be clear I'm referring only to the crystal, and not an electronic oscillator that includes the crystal + other components)
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Aug 8, 2013 18:22
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Cyril Sneer posted:Maybe. I gather these SAW filters are an example of such a usage? More precisely if you just plop in a normal crystal you can theoretically use that thing as a bulk wave filter pretty easily. Though I don't know of any applications where that is done. But for higher order filter you can't couple multiple crystals because their coupling is too lossy. You also can't just attach a tuning screw. Therefor for practical filters you need to microstructurise your crystal very exactly and threedimensionaly, to realize a full higher order filter path on the single crystal. Making SAW filters is an as specialized process as growing semiconductors.
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Aug 8, 2013 18:34
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Cyril Sneer posted:Something that occurred to me the other day...could one use crystal oscillators as very high-Q passive filters? I'm sure it's been done, but I've never come across it myself. tonberrytoby posted:You mean the SAW( Surface acoustic wave) filters that are used as RF filters in your cellphone? You need pretty specialized technology to make those. Unless I'm mistaken, SAW filters are distinct from crystal filters. SAW filters rely on a transducer that converts a signal into a vibrating surface of a material, which travels across the face of that material, and then a second transducer + amplifier to pick up the vibration convert it back to a useable signal. Crystal filters use a crystal as a series element in a circuit, and rely on their resonance to create a band-pass filter. This is apparently useful for radio bullshit. SAW filters, on the other hand, rely on the more complex effects of the SAW in/on the material. I honestly have no idea what these are, but I'd assume it has a more complex frequency response than a crystal, and probably introduces a weird phase response too. Also something about the dispersion relation in the SAW filter...something. Honestly a physics degree only lets me bullshit so much. Hopefully someone has a better clarification.
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Aug 8, 2013 20:56
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Slanderer posted:Unless I'm mistaken, SAW filters are distinct from crystal filters. SAW filters rely on a transducer that converts a signal into a vibrating surface of a material, which travels across the face of that material, and then a second transducer + amplifier to pick up the vibration convert it back to a useable signal. Crystal filters are also the same, only they use slightly more boring crystal shapes. The used materials are pretty similar. And you use pretty much the same piezos to convert from electrical to acoustic signal. Only with simple quartz filters you can use the piezo directly as resonator without adding any extra stuff. vvv Interesting. I think theoretically you should get worse results than with only one quartz that way, because your coupled quartzes have an increased bandwidth. VictualSquid fucked around with this message at 22:02 on Aug 8, 2013 |
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Aug 8, 2013 21:39
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I used some standard crystals for filtering a square wave into a somewhat usable sine wave, it certainly worked better than any LC filter would. I just put them in series.
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Aug 8, 2013 21:41
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JawnV6 posted:If we get the Digikey order in by 5 it's here by 10:30AM the next day. Ditto, it's like magic! Amazes me every time. Best way to have inventory control is see through bins and/or a really proactive lab tech who manages that stuff. Something like a weekly/monthly checkup depending on how much parts you go through. Relying on the clipboard method will not work, trust me. My favourite person is someone who uses the last of something then puts the bin away. and puts the bin in the wrong spot to boot.
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Aug 9, 2013 02:22
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Same with Newark/Farnell. I don't know if it's just the contract they have with my university, but all my components are here on the first FedEx truck in the morning, if ordered by 5. It's super impressive 
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Aug 9, 2013 05:06
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Speaking of suppliers, are there any EUans in the thread? Any good international alternatives to TME? (Not that I've had any problems with TME.) EDIT: Actually there is one problem: the website and especially the product search seems really confused by all the languages they 'support'. 3D Megadoodoo fucked around with this message at 08:33 on Aug 9, 2013 |
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Aug 9, 2013 07:58
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Jerry Cotton posted:Speaking of suppliers, are there any EUans in the thread? Any good international alternatives to TME? (Not that I've had any problems with TME.)
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Aug 9, 2013 08:09
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tonberrytoby posted:We usually order our general stuff at RS ( not to be confused with R&S). Or sometimes at Farnell. I switched to RS when all the other vendors started to play 'who can charge the most outrageous shipping fees', but now that CPC have gone back to 'free shipping' (presumably because it cost them too much business to charge £16 shipping on a £5 order...) I'm less strict about where I order from.
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Aug 9, 2013 13:24
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RS mostly, Farnell if I have to. I'll also use Mouser but it has to be a larger order to get the free shipping. IMO RS are usually a little cheaper, they have a warehouse near me and they charge 4euro for courier delivery.
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Aug 9, 2013 16:05
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I'm hoping this is the best suited thread for this, as it's very much been a learning experience for me. This post may be a bit long and rambling, but there are some somewhat coherent questions at the end... The story so far is that I've got an Ecler Nuo 3.0 DJ mixer that has failed. Basically, I turned it off, then on again really quickly while fumbling with cables at the back, and the house circuit breaker tripped. The mixer has an internal fuse, which blew when the power tripped, I replaced the fuse and it blew/tripped the power again, so I figured that something was a bit more seriously wrong. The mixer has an internal power supply, that gives plus/minus 17 volts. I disconnected the power supply board and rigged up the kludgy circuit pictured below to verify that the fault was on the power supply board, and not in the audio circuitry (the PSU board is the smaller board on the metal plate with the big blue thing on it):  I used two 9v batteries for the -18V rail (actually closer to 17V, they were kinda old) and the bench supply for +17V, wiring the +terminal of the batteries into the ground of the bench supply. With this setup the mixer worked OK, if only for a few seconds at a time (I'm guessing the old 9V batteries weren't too happy providing the amount of current required). Anyway, this is a strong indication that the fault is with the power board; so I took the board out and had a look. The only obvious thing I could see wrong were these crispy looking resistors:  I do have a service manual for the power supply board, which is here: http://www.ecler.de/uploaded/downloads/50758644efac8.pdf This contains the sentence: "The current is sensed at the primary coil using three resistors shunted to Q102's source. A zener diode, D108, avoids these resistors from burning in case Q102 is shorted.". Sure enough, those three resistors are the crispy ones on the board! (Click here for annotated schematic). Edit: And also, R116 is fried too, this is the one that controls the gate of Q102, also pictured (bottom left, above the 1R0 resistor). Anyway, so I whipped those resistors off the board, tested them, and the magic smoke has indeed escaped; two of them don't conduct at all, one is registering around 200K Ohms when it should be 4.7 Ohms. This is where my lack of knowledge of AC/power supplies comes to bite me; I've got no experience of with these kind of circuits at all, let alone fault finding or safely testing them. My limited understanding of the circuit is: Optocoupler IC105 is looking at the output voltage via a potential divider; when it hits ~35V, it turns on, telling IC103 to send narrower pulses through the FET Q102, this is how the feedback/voltage regulation mechanism works. IC103 senses current on pin 5 when Q102 is conducting. When Q102 is conducting, there's a path to ground through the 3 dead resistors. The Zener D108 should limit the voltage on that pin to 4.7 volts. When Q102 is not conducting, the dead resistors should pull pin 5 to ground... Am I on the right track? For the more specific questions: 1. I intend to replace those resistors, but I'm curious as to why they blew in the first place (the service manual implies it's something to do with the current limiting). Is the Zener likely to have gone too, as that's the thing that was supposed to be protecting them? (I've no idea how robust these things are). 2. Why would these resistors no longer conducting cause fuses to blow, rather than the supply not working at all? (I'm having a hard time picturing how the various bits operate/interact). 3. Is there a recommended easy/safer way of testing the board once I've replaced the resistors? I'd rather avoid tripping the circuit breaker in my house if possible... I guess I need a power strip with a really sensitive integrated circuit breaker or something? 4. The service manual also suggests that it needs a minimum of 100mA load to start up, I'd rather not hook it into the mixer straight off in case bad things happen; any ideas for what I could use as a test load? Thanks in advance for any help/suggestions! Cunning Plan fucked around with this message at 20:22 on Aug 10, 2013 |
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Aug 10, 2013 19:42
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a) If you're not qualified as a service technician you shouldn't really be servicing switch mode power supplies since they normally have around 320+V DC in them when powered up. b) Seems like you've done a decent job fault finding so far, this is where application specific knowledge starts to come in The fault is definitely in the power supply (although a fault in the mixer could have caused a fault in the power supply). The resistors are burned so replace those, they're used to measure current due to the voltage drop across them when current flows. The zener diode is probably just there to clamp the voltage to prevent the controller IC blowing up. Do you know how to use a diode tester? If not look that up first, first check the rectifier diodes D101-D104, they're fairly likely to blow and will always cause the fuse to blow if they do fail. 1N4007 is a really common diode so if you need to order them get at least 20. Note that you can check those diodes in circuit, just connect the meter over each one and if it's short both ways then it's broken, if 0.6V one way and some other larger value/OL the other then it's fine. You need to check Q102 as that's another likely candidate for failing especially when those resistors burned up, the simplest check is to put the diode tester across the drain and source (check the datasheet for pinout), again if it's shorted both ways it's pretty much definitely broken. Also check gate-drain and gate-source, if either one reads 0V both ways it's broken and needs replacement. If it's broken you should check Q101 and D112 too, and possibly prepare for IC103 to be broken. If Q102 is fine then I wouldn't worry too much. The zener diode should be fine but it can be checked with the diode tester too. There's three more slightly burnt resistors on the board, I think they're R122-124, I'd check those too. R121+R130 and D109 are also components likely to fail. Is C105 (the big one probably) or any other electrolytic capacitors bulging? They need to be replaced if they are. My guess is something like this may have happened: Q102 fails to short, burns resistors, this kills the diode rectifiers which kills the fuse despite resistors going open circuit. Diodes D110 and D111 are also worth checking while you're in there. To safely work on the primary side of switch mode supplies that are powered up you need an isolation transformer, if you don't have one then don't touch the primary (mains) side of the transformer or any parts connected to it while it's live, also make sure the main filter cap is discharged before working by waiting a few minutes or connecting a resistor across it without touching the terminals with your fingers and letting it discharge. Resistors at about 200 ohms (or 5 1k resistor in parallel) between V+ and ground and V- and ground will provide a load sufficient to start the supply, but they will get fairly warm so don't use them for longer than you have to. Ps: get a few extra power resistors just in case you miss something the first time
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Aug 10, 2013 21:11
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Good tips longview, think you pretty much covered the common things that are probably broken (seriously I don't what it is with audio equipment and power supply death) with it. Also, we kicked off a new nerdy thing project log subforum, so if you want to post and log about your electronics project, they are more than welcome there as well.
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Aug 10, 2013 21:22
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Thanks for the great advice longview! In answer to your first point, I'm absolutely not a qualified service tech, but do have a healthy respect (or fear) of high voltages; I'll definitely be careful... I've got a bit of experience playing around with smaller scale stuff, this is my first foray into anything mains-connected. I've had a quick look at the rest of the resistors, they seem OK as far as I can tell with them being in circuit. I started checking the diodes with the multimeter diode test function, but I'm getting some weird readings on some of them (due to them being in circuit I think). I'll probably take them off the board tomorrow and do them in isolation. Sadly it looks like the FET (Q102) is broken, and as you suspected, shorted. I'll probably start stripping the board down and test each component individually; thankfully it looks like the parts on there aren't too pricey, so I think it's probably worth an order to Mouser rather than giving in and sending it off to a service center just yet...
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Aug 10, 2013 23:28
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Does anyone have experience opening up and modding a Nexus 7 or another tablet? I'm considering picking up an old N7 (edit: or a Sero 7) for cheap and sticking it into my car (NB MX-5 Miata). The thing is, I don't think there's going to be as much space around as in larger cars that I've seen the N7 installed, and the bezel will of course get in the way: So, 1. If taken apart, can the bezel be cut/ground off the short edges at least? Pictures of the replacement digitizer layer suggest that there's nothing there 2. The camera appears to be removable and not soldered on, would there be anything preventing me from extending it and using it as a dash or reverse camera? I'm going to pull out the existing head unit as soon as it's convenient to see what's going on back there, but if anyone's already done something like this, suggestions would be appreciated as that would the a first for me. And I'm talking about cutting up the tablet rather than the dash because it's actually cheaper to replace, should I gently caress something up 
mobby_6kl fucked around with this message at 14:57 on Aug 11, 2013 |
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Aug 11, 2013 14:38
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I've not torn one down myself, but just a heads up that you might run into issues if you wanted to extend the camera and use it as a reversing sensor; no idea what sort of interface it uses, but odds are it's not designed for long cabling runs like that!
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Aug 11, 2013 18:05
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Yeah I'm gonna bet the camera is soldered directly to a board using some soldering method that will not appreciate being disassembled.
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Aug 11, 2013 19:10
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It's not actually soldered on, though the connector looks like it could be challenging to extend: That's probably still a good point about the interface not being able to handle long distances. Just running it up to the dash would be nice too, but I guess I'll have to try it to find out. On the up side, after more research it appears that a rooted Nexus 7 can just connect to a regular webcam.
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Aug 11, 2013 19:43
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You may not even need to pull it apart depending on what's going on behind the dash, Mighty Car Mods did a similar thing with an iPad that they just taped into the back of the center console surround. https://www.youtube.com/watch?v=u-ALYArl5S4 You'd need to find some way to hide the bottom bezel but I assume you'll be covering the large hole in the dash anyway.
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Aug 12, 2013 09:15
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I am trying to find some cheap and small connectors to deliver 12V in and out of a box. However, I am failing. Perhaps I am not searching with the right keywords? My requirements are: 1) Waterproof-ish (no specific requirements, anything better than IP x0 is acceptable) 2) Small (20mm or less in all dimensions - I want to minimize the size of my box if possible) 3) Held by more than friction on the contacts (a tab, nut or whatever - it will be used in a moving system, so should not come apart easily) 4) For 2 wires, <5 A, 12 V Looking in farnell.com database, I only find super expensive things like http://uk.farnell.com/binder/09-0404-80-02/socket-sealed-panel-2way/dp/1122569 (I assume that price is per piece) or huge industrial plugs or basic frinction-held power plugs like you see on old phone chargers and whatnot. Is there some standard search term I might be missing here? Or are my requirements really so rare? Do you know some plug/socket to recommend me? EssOEss fucked around with this message at 16:17 on Aug 12, 2013 |
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Aug 12, 2013 16:15
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EssOEss posted:I am trying to find some cheap and small connectors to deliver 12V in and out of a box. However, I am failing. Perhaps I am not searching with the right keywords? Neutrik do some waterproof mini-XLR connectors & sockets, that should be suitable, and probably secure enough.
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Aug 12, 2013 16:26
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Looking through the Neutrik catalog is like magic, they'll take pretty much any connector and put a XLR-style housing/mounting solution around it.
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Aug 12, 2013 16:58
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EssOEss posted:I am trying to find some cheap and small connectors to deliver 12V in and out of a box. However, I am failing. Perhaps I am not searching with the right keywords? http://www.adafruit.com/products/743#Description
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Aug 12, 2013 17:02
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EssOEss posted:I am trying to find some cheap and small connectors to deliver 12V in and out of a box. However, I am failing. Perhaps I am not searching with the right keywords? Go poke around your local auto parts store. They have tons of waterproof connectors designed to carry 12v. EDIT: Something like this: http://www.ebay.com/itm/1X-wes-New-2-Pin-Waterproof-Electrical-Wire-Connector-Plug-Motorcycle-Car-Marine-/400466225453 n0tqu1tesane fucked around with this message at 02:43 on Aug 13, 2013 |
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Aug 13, 2013 02:30
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I have a problem that is a bit over my head and need some advice. At my work we have two receivers that lock up about once a week. Currently we are having the master control operators power cycle the devices by unplugging them. This isn't the best solution but it has been working for over a year now. But since the IRD's are located next to a couple of pieces of critical news equipment and the fact that sometimes I think my co-workers are idiots, I'd like to have a remote switch to cut power to the device. I'm thinking that a relay based solution would be the best way to go with the power wire connected to the NC side of the relay and having a remote switch toggle it open. I did some looking on the internet and there is a product that seems perfect, Powertail Switch II, but it is out of stock at most places for the next month or so. Other projects I saw used a pre-built board with a NPN transistor (https://www.sparkfun.com/tutorials/119) so that it can be used with a arduino-type device. Since I would rather just have a simple SPST toggle switch, this is overkill? Do I need to have all that extra stuff from the above link or could I just roll my own relay device with a suitable 110V 10A relay (the IRD is rated to draw 1.5 amps with an inline fuse blowing at 2 amps, 60 watts max draw)? So correct me if I'm wrong, but is this a good list of what I'll need: 110V 10 amp relay (http://www.mouser.com/ProductDetail/Omron-Industrial/MY2N-AC110-120S/?qs=sGAEpiMZZMtSzCF3XBhmW1LHcIr8U6Kt8DBx7gPjAjI%3d be ok?) appropriate relay socket sacrificial power cord SPST toggle switch power supply suitable to actuate the relay extra wiring suitable for the switch (is cat 5e good enough for the low voltage stuff or should I use plastic box to house everything in (outlet box or project box) Assuming I get this to work, would having it wired a different way make any difference? I'm thinking about doing the same for our news department to turn on and off the various TV's they have on set. We are using four of the belkin wireless surge protectors but I would like to have it wired up so that they can control it from their automation with something that is used to trigger GPI/GPO's.
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Aug 13, 2013 23:50
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That seems right to me. I bet you could also do a neat timed restart by adding some circuitry to power the relay with a capacitor connected to the line.
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Aug 14, 2013 00:25
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Perhaps you could save the extra power supply by using a relay with a 110 AC coil. Or use a 12/24V AC relay and use a transformer as a power supply (although this is simple in theory it might not save any money/space over a DC power supply). Are you sure you need all this and not just a light switch in a outlet box from home depot? Also, if I were doing this I'd probably be shopping McMaster. They'll have these basic control relays/switches etc and make searching for them much easier.
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Aug 14, 2013 01:19
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asdf32 posted:Perhaps you could save the extra power supply by using a relay with a 110 AC coil. Or use a 12/24V AC relay and use a transformer as a power supply (although this is simple in theory it might not save any money/space over a DC power supply). While a light switch in a box would be nice, I'd like to have the switch mounted about 20-25 feet from the device it will be controlling the power. I could run AC or romex under the floor (raised floor in our master control room), but I'm not sure that would be up to code or really all that friendly to the several dozen video/audio wires already present. Plus I'm trying to keep this simple on the off chance I leave this job, I'd rather not leave something for future engineers to be confused by. The only reason I'm looking through the mouser catalog is we have an account with them and I'd rather not fight with accounting about getting reimbursed.
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Aug 14, 2013 04:34
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diremonk posted:While a light switch in a box would be nice, I'd like to have the switch mounted about 20-25 feet from the device it will be controlling the power. I could run AC or romex under the floor (raised floor in our master control room), but I'm not sure that would be up to code or really all that friendly to the several dozen video/audio wires already present. FWIW, a light switch is a hell of a lot easier to reverse-engineer/figure out than some crazy relay arduino contraption. Not that I think you shouldn't do it. I'd be more than happy to lend my expertise to make your project as complicated as possible 
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Aug 14, 2013 06:07
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We used to have test systems hooked up to something like this. If you've got a computer nearby it would be pretty simple to set up a script to power cycle it once a day. Or set up VNC so you can do it from anywhere on the network.Delta-Wye posted:Not that I think you shouldn't do it.
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Aug 14, 2013 18:03
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Would it be possible to just repair the faulty equipment so you don't have to unplug it every week? Though my vote is still for over-engineering a massively complicated solution that nobody but you will understand. Job security!
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Aug 15, 2013 00:24
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diremonk posted:While a light switch in a box would be nice, I'd like to have the switch mounted about 20-25 feet from the device it will be controlling the power. I could run AC or romex under the floor (raised floor in our master control room), but I'm not sure that would be up to code or really all that friendly to the several dozen video/audio wires already present. One alternate version that could get you around having to deal with electrical code issues would be to run a 5V or 24V DC control line out to a SSR/relay near the unit you want to turn off. Most electrical codes don't worry about anything under 50V and the low current DC line wouldn't interfere with nearby analog signals.
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Aug 15, 2013 03:07
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