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PersonFromPorlock posted:I have a small collection of old TVs and most have no input besides over-the-air VHF. I have an old Ramsey TVC6 kit (three, actually) that's swamped out by WiFi when the transmission antenna is more than a couple feet from the receiving antenna. I don't have an answer for you but one of the suggested uses of that thing is "Hidden camera fun" and wow
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# ? Feb 11, 2021 01:39 |
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# ? May 28, 2024 06:03 |
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Yeah, there's no hidden camera here. It will be playing BluRay collections of old TV shows. It advertises a 300 foot range but I struggle to get more than one foot from it. In the other thread, someone suggested wrapping it in foil and grounding the foil. I'll try that, but meanwhile, what else can I do? PersonFromPorlock fucked around with this message at 01:52 on Feb 11, 2021 |
# ? Feb 11, 2021 01:45 |
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Also where did you hear the "replace R12 with a wire link" thing? Because going by that schematic R12 is between the antenna and ground (I think it's helping with impedance matching), so connecting a wire link in its place will just short out your antenna. e: Actually it's possible R12 is connected to some trace on the other side of the board I can't see, that drawing has the top and bottom layers merged so I can't actually tell what it's connected to. e2: I found this weirdly lovely picture of the actual schematic and R12 is indeed between the antenna and ground: Shame Boy fucked around with this message at 01:59 on Feb 11, 2021 |
# ? Feb 11, 2021 01:52 |
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Also, are you sure that it’s your WiFi swamping the TV broadcast signal? I’m not an RF wizard but the North America VHF TV frequencies (60MHz for channel 3 I think) are nowhere near 2.4GHz or 5GHz that’s used for WiFi. 2.4GHz is like the 40th harmonic of 60MHz. Have you turned off your WiFi to see if that’s the problem? e yeah my gut feeling is that your WiFi would have to be broadcasting at “cook a whole hog” levels of power to disrupt that far away in the spectrum, and 2.4GHz WiFi rules are pretty strict about out of band interference at least in the spectrum neighborhood. I used to have to wrangle the WiFi FCC and European tests for the hardware team I worked with and they were a pain about unintentional radiation outside the immediate channel. csammis fucked around with this message at 02:16 on Feb 11, 2021 |
# ? Feb 11, 2021 02:10 |
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csammis posted:Also, are you sure that it’s your WiFi swamping the TV broadcast signal? I’m not an RF wizard but the North America VHF TV frequencies (60MHz for channel 3 I think) are nowhere near 2.4GHz or 5GHz that’s used for WiFi. 2.4GHz is like the 40th harmonic of 60MHz. Have you turned off your WiFi to see if that’s the problem? Yeah I was thinking that too, I bet it's more likely to be the switch mode power supplies that are in literally everything today either interfering with the VHF signal directly or getting picked up in the transmitter and amplified along with the video. Definitely try the shielding with foil thing.
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# ? Feb 11, 2021 02:14 |
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Reposting my idea hereForseti posted:But anyway, I don't doubt the WiFi is affecting you I just think it's affecting the transmitter rather than the TVs. The TV antenna is unlikely to have a good response at 2.4GHz, the whole point of the antenna and tuner is to selectively pick out a narrowish band of frequencies. The antenna and tuner should be greatly reducing (attenuating is the fancy official word) the signal for all other parts of the spectrum than the part you care about, which is the channel you have selected.
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# ? Feb 11, 2021 02:15 |
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Removing r12 was just something I was told, on Instructables I think. The reason I think it's the WiFi is the picture gets better the further from it I get and is swamped-out entirely within a few feet.
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# ? Feb 11, 2021 02:39 |
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building a computer but I let someone borrow my ESD bracelet. never fear just copper tape doubled back on itself with a grounded wire lead wrapped around the midsection, and with a crude hook/loop clasp made from some scrap wire in my brass bin. screwed with the hook geometry to fine-tune the fit and keep it snug and in contact with my skin. looks like rear end but not bad for a 5-minute cobbled-together replacement
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# ? Feb 11, 2021 02:54 |
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A simple way to narrow down what part if any of the WiFi is at fault: * Put the broadcaster in an area you know to be bad * Unplug your WiFi router and see whether the TV improves * If it does, plug the router back in and log into its management interface and disable the 2.4GHz channels and see whether it’s still okay But in any case Forseti and Shame Boy are probably right, you should shield the TV transmitter internals as best you can.
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# ? Feb 11, 2021 04:37 |
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Ambrose Burnside posted:just copper tape doubled back on itself with a grounded wire lead wrapped around the midsection, and with a crude hook/loop clasp made from some scrap wire in my brass bin. screwed with the hook geometry to fine-tune the fit and keep it snug and in contact with my skin. looks like rear end but not bad for a 5-minute cobbled-together replacement haha, nice. Do you have to be very delicate with it?
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# ? Feb 11, 2021 04:42 |
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Copper tape is really sturdy. The solder point to the wire looks like the most delicate part, but if it breaks, he can just wrap the wire around before soldering it next time
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# ? Feb 11, 2021 04:45 |
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PersonFromPorlock posted:Removing r12 was just something I was told, on Instructables I think. The reason I think it's the WiFi is the picture gets better the further from it I get and is swamped-out entirely within a few feet. Maybe they meant remove it and leave it open instead of shorting it to ground? I'd believe that could help with the built-in antenna since I doubt it has a 75ohm characteristic impedance. What are you powering this thing with? Does it work better with a 12V battery installed very close to the board instead? I'm wondering if your wi-fi interference is at least partially conducted EMI through your supply.
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# ? Feb 11, 2021 05:09 |
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Ambrose Burnside posted:building a computer but I let someone borrow my ESD bracelet. never fear That's not actually how a (correct) ESD wriststrap is wired. There should be a ~1Mohm resistor between the part connected to you and ground. It provides a path for charge to drain, but makes there not be a low-impedance path through you if you touch something live. Fine for touching computer parts while its off though.
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# ? Feb 11, 2021 05:54 |
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Foxfire_ posted:That's not actually how a (correct) ESD wriststrap is wired. There should be a ~1Mohm resistor between the part connected to you and ground. It provides a path for charge to drain, but makes there not be a low-impedance path through you if you touch something live. Fine for touching computer parts while its off though. I learned a thing just now, ty. Also unpowered computer parts seem to be pretty esd hard as I think you’re alluding to. I’ve assembled a few dozen systems over time and some in really bad esd conditions (dry room on carpet with socks on) and never gotten an issue. LTT and electroboom have a fun video where they discharge esd from a gun to pins on some memory through themselves to try to kill it. https://youtu.be/4SjOv_szzVM Now I know enough to touch a grounded chassis at least.
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# ? Feb 11, 2021 06:01 |
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Modern electronics are pretty robust. Older CMOS was quite vulnerable, which is why you'll see greybeards scandalised by people not bothering with wrist straps. However, I've got a design currently that I've never had a problem with in the two years I've been throwing around bare PCBs, but my coworker (who wears a lot of fleeces) has fried literally six of them. One particular IC is the culprit, every time. We're designing it out of the next revision.
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# ? Feb 11, 2021 06:10 |
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Actually, while we're talking about this circuit can I point out how weird it is they used a 7808 with two diodes to get 9V and not just... a 7809? Is there a reason for that or did they just buy a million 7808's by mistake and had nothing to do with them?
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# ? Feb 11, 2021 06:22 |
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PeesonFromPorlock, Speaking of power supplies, if it turns out you really just need more power, you can try overvolting the thing. The easiest way to do that is to connect the negative side of your supply to ground and the positive side of it to JMP1, with the switch off. Maybe 9.5 or 10V to start out. I didn't compute what voltage the smoke starts at or anything so turn up the supply slowly and make sure nothing gets warm. It's probably good for at least an extra volt. If you find a voltage you like you can replace D2 or D3 with a few diodes in series to get the +9V rail to there, about 0.5V per extra diode. E: Shame Boy posted:Actually, while we're talking about this circuit can I point out how weird it is they used a 7808 with two diodes to get 9V and not just... a 7809? Is there a reason for that or did they just buy a million 7808's by mistake and had nothing to do with them? It's also possible they wanted to have options for supply voltage. Chose the regulator with the minimum voltage they might want and slapped some combo of diodes and jumpers on the board to configure it. 3 supply voltage options with 1 board version. Can even swap the regulator to get anywhere from 5V to 13V in steps of 0.5V-1V. Stack Machine fucked around with this message at 07:25 on Feb 11, 2021 |
# ? Feb 11, 2021 06:37 |
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Stack Machine posted:What are you powering this thing with? Does it work better with a 12V battery installed very close to the board instead? I'm wondering if your wi-fi interference is at least partially conducted EMI through your supply.
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# ? Feb 11, 2021 07:33 |
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PersonFromPorlock posted:The great big transformer that came with it. I don't know why it has to be so large, but it is. Probably because the thing is horribly sensitive to environmental and power supply noise and a switch-mode would kill it. I agree with foil shielding as the first step.
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# ? Feb 11, 2021 14:30 |
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It doesn't really affect the recommendation, but I should pedantically correct myself and say that limiting the frequencies to just the ones you're interested isn't the WHOLE point of the antenna+tuner (pretty true of the tuner though I think). The antenna is the electrical analog of the horn on a gramophone or trumpet; it helps the RF signal transition from the copper wire medium to air more efficiently (and the other way around on the receiver). They can also be directional to send more of your signal power in the direction you want it, but your application is probably not very directional.
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# ? Feb 11, 2021 15:17 |
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Foxfire_ posted:That's not actually how a (correct) ESD wriststrap is wired. There should be a ~1Mohm resistor between the part connected to you and ground. It provides a path for charge to drain, but makes there not be a low-impedance path through you if you touch something live. Fine for touching computer parts while its off though. whoops, good catch, thanks in other news, here's the first of two planned 1ohm/5w ballast resistors for my 3d printer resin vat heater, think it came out ok (please do not scrutinize the solder joins they're not my finest work) i used half-round copper jeweller's wire as both electrical buses and thermal bridges, the idea was for the round part of the wire to contact the ceramic resistor casings and for the flat side to act as a nice big pad against the tank side. the resistors don't actually contact the buses well so the thermal aspect probably won't work well, but they're sitting on a thermal pad so it shouldn't matter. if i stick with these long-term I think i'll pot them in metal-filled epoxy with the bus wire flats exposed on the bottom for the best thermal performance Ambrose Burnside fucked around with this message at 18:31 on Feb 11, 2021 |
# ? Feb 11, 2021 18:29 |
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Ambrose Burnside posted:whoops, good catch, thanks Not sure if metal-filled epoxy would short it out or not, I've never actually used it, but might wanna test first to be sure. Also you probably know this but you can get specific thermally conductive / electrically insulating epoxy, I use it to glue small heatsinks to things sometimes.
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# ? Feb 11, 2021 18:31 |
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Shame Boy posted:Not sure if metal-filled epoxy would short it out or not, I've never actually used it, but might wanna test first to be sure. Also you probably know this but you can get specific thermally conductive / electrically insulating epoxy, I use it to glue small heatsinks to things sometimes. jbweld steel-filled is specifically advertised as electrically-insulating and is the only product they recommend for electrical potting so I'm comfortable giving it a shot, a single $8 syringe should barely suffice for two units. and yeah, ideally i'd use the proper MG chemical potting compound but at $40 a pot it's a pretty penny for questionable gain, i suspect i'll shelf this entire mk1 apparatus once my silicone heating belt shows up Ambrose Burnside fucked around with this message at 18:37 on Feb 11, 2021 |
# ? Feb 11, 2021 18:35 |
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Can confirm, have tested JB Weld and it is not conductive. Dunno how thermally conductive it is, though. Smooth-On and some other companies make thermally conductive silicones that I've been meaning to play with. Could be fun to pot some of my projects so like, the entire thing is one solid heatsink.
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# ? Feb 11, 2021 18:49 |
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Reading an LCD datasheet and noticed an excellent feature: Wow! e: At least it's got specifications for "folling time" This thing is from Sharp, I didn't expect it to be this bad Shame Boy fucked around with this message at 19:06 on Feb 11, 2021 |
# ? Feb 11, 2021 19:03 |
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Ambrose Burnside posted:whoops, good catch, thanks Thinking back on the things you've posted, you really have the most appropriate avatar in this thread. Everything you make looks like it should be a museum exhibit of electronics from the 1800s. I don't mean this in a bad way.
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# ? Feb 11, 2021 19:13 |
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Cojawfee posted:Thinking back on the things you've posted, you really have the most appropriate avatar in this thread. Everything you make looks like it should be a museum exhibit of electronics from the 1800s. I don't mean this in a bad way. weird things happen when unreconstructed blacksmiths apply their skills to industrial-age enterprises
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# ? Feb 11, 2021 20:51 |
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Hey, thread. I've got a really weird motor thing and I'm not quite sure what its deal is. I got a few of these from a factory surplus shop a few years ago, and immediately chalked them up to "DC brushed motor with a wheel", but now that I finally get one out for a project, its actually weirder. Two capacitor-like things are soldered to the power wires. One is from motor + and - (decoupling, sure, no problem), but one of them is in series with the ground wire by means of the motor chassis (what??). I thought maybe it was some kind of AC motor, except the other end of the original wires go to C battery terminals, and also the wires and motor are tiny. When I power it with 5~12VDC, it's super fast for a bit, then slows way down, as if a capacitor in series was charging up and choking off current (which matches my expectation). Before I tear it apart, it must have been wired this way for a reason, right? Anyone have any thoughts? The decoupler is labeled 104K, the series one has a bunch of tiny writing I can't make out easily from this angle. EDIT: if anyone cares, the project is this trillion-to-one gearbox I'm building as an art project. Stabby McDamage fucked around with this message at 02:04 on Feb 12, 2021 |
# ? Feb 12, 2021 01:57 |
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Stabby McDamage posted:Hey, thread. I've got a really weird motor thing and I'm not quite sure what its deal is. I got a few of these from a factory surplus shop a few years ago, and immediately chalked them up to "DC brushed motor with a wheel", but now that I finally get one out for a project, its actually weirder. Two capacitor-like things are soldered to the power wires. One is from motor + and - (decoupling, sure, no problem), but one of them is in series with the ground wire by means of the motor chassis (what??). This looks more like salvage than surplus. Blobs of hot melt and capacitors with long uninsulated leads dangling in midair looks like something someone else cobbled together in the lab, which could also explain the strange schematic. Not conclusive, so feel free to get more opinions, but that's my instinct. KnifeWrench fucked around with this message at 02:12 on Feb 12, 2021 |
# ? Feb 12, 2021 02:07 |
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They actually came in sealed bags, like a component from some kit you might build. The motors are mounted to foam wheels with various mounting ears, so I was thinking some automation rollers or something. They're ungeared direct drive, so not likely for a car/robot. If nobody has any ideas why this is actually cool/good in a day or so, I'll tear em up and do em normal. It may be an incorrectly done version of this.
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# ? Feb 12, 2021 02:15 |
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I think that capacitor-looking thing in series with ground might be a polyfuse/resettable fuse. They trip from self-heating at a rated current then they reset after they cool down. They don't last that many cycles but they survive more tripping cycles without requiring replacement than an ordinary fuse!
Stack Machine fucked around with this message at 02:29 on Feb 12, 2021 |
# ? Feb 12, 2021 02:26 |
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It can't be a DC motor with that circuit diagram. There is no DC path to ground
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# ? Feb 12, 2021 03:06 |
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Yeah, that series thing is for sure a PTC
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# ? Feb 12, 2021 03:27 |
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Stabby McDamage posted:EDIT: if anyone cares, the project is this trillion-to-one gearbox I'm building as an art project. Oh, going by the picture I figured you were building this thing: https://www.youtube.com/watch?v=72C_4L8Vu2o
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# ? Feb 12, 2021 03:36 |
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ante posted:Yeah, that series thing is for sure a PTC That makes a lot more sense. Now I gotta figure out why it slowed down. Maybe I overvolted it? Oh well, now I have stuff to go on. Thanks! Shame Boy posted:Oh, going by the picture I figured you were building this thing: It has that effect, just over the course of between 5 minutes to 10000 years, depending on where in the gears you put the thing. It's designed so that continuous input rotation at like 300 rpm for a century yields about a degree turn on the output. I'm going to redesign the faux marble plate on the output side to have a "gear" as part of its geometry that physically can't spin, and yet you'll never get to see it break in your lifetime.
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# ? Feb 12, 2021 04:48 |
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Inspired by Arthur Ganson? I’ve been meaning to build something like that for a while too. Yours looks pretty nice!
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# ? Feb 12, 2021 04:54 |
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Pretty cool, similar idea to this thing that LOOK MUM NO COMPUTER just built https://www.youtube.com/watch?v=xu9Wid465o8
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# ? Feb 12, 2021 05:01 |
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Forseti posted:Pretty cool, similar idea to this thing that LOOK MUM NO COMPUTER just built Jesus christ I had to route and solder like 20 individual LED display digits for a project once and that was torture, I can't imagine building that thing
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# ? Feb 12, 2021 05:09 |
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Yup, now that I know what to search for, I confirmed it's a PTC. Set for 750 mA, which I must have tripped when I pushed voltage to 5V -- mechanism appears designed for 3V. Thanks again!
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# ? Feb 12, 2021 05:30 |
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Stabby McDamage posted:That makes a lot more sense. Now I gotta figure out why it slowed down. Maybe I overvolted it? Oh well, now I have stuff to go on. Thanks! PTC gets hot, its resistance goes up, voltage drop across it goes up, voltage motor sees goes down. Stabby McDamage posted:It has that effect, just over the course of between 5 minutes to 10000 years, depending on where in the gears you put the thing. It's designed so that continuous input rotation at like 300 rpm for a century yields about a degree turn on the output. I'm going to redesign the faux marble plate on the output side to have a "gear" as part of its geometry that physically can't spin, and yet you'll never get to see it break in your lifetime. I understand it's not the point, but whenever I see things like this I always think "that turns until it takes up enough slop in the gears, then just stops because there's not enough torque to turn that many gears" Foxfire_ fucked around with this message at 05:44 on Feb 12, 2021 |
# ? Feb 12, 2021 05:41 |