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How many digits? You could also just use a shift register for the decimals of each digit.
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Dec 4, 2019 17:38
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Cojawfee posted:How many digits? You could also just use a shift register for the decimals of each digit. Like 8, and yeah I was just throwing that idea around too. Shift registers designed to drive LED's are reasonably cheap, and I think I have enough board space to throw one up for each digit...
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Dec 4, 2019 19:42
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I managed to brick a security camera DVR trying to update it's firmware last week. A replacement is on the way. I opened it up and there's a JTAG port on the board. How hard would it be to get firmware off a good one and manually reflash the bricked one? The header marked JTAG is 1x6 while the one next to it marked TTL DEBUG is 2x5.
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Dec 5, 2019 18:33
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kid sinister posted:I managed to brick a security camera DVR trying to update it's firmware last week. A replacement is on the way. I opened it up and there's a JTAG port on the board. How hard would it be to get firmware off a good one and manually reflash the bricked one? You'd need to figure out what kind of chip it is and if it's got its lock fuse bits set first, then maybe.
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Dec 5, 2019 18:47
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Most micros these days have protections in place to prevent ROM dumping... fuses as mentioned, but also some encrypt the image, and still others may implement various forms of authentication to check that only a signed or valid ROM has been loaded, and won't boot otherwise. Any manufacturer worth their salt is going to enable the protections these days.
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Dec 5, 2019 19:00
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If you already have JTAG hardware, you could see what comes up when you scan the JTAG bus. I agree it is likely the chip is locked, but you never know.
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Dec 5, 2019 19:19
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Any manufacturer worth their salt also won't have a product that can be bricked by a bad update. Give it a shot - Maybe the JTAGulator would be useful. It's mind blowing how many companies still don't protect their poo poo
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Dec 5, 2019 19:22
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My Rhythmic Crotch posted:Most micros these days have protections in place to prevent ROM dumping... fuses as mentioned, but also some encrypt the image, and still others may implement various forms of authentication to check that only a signed or valid ROM has been loaded, and won't boot otherwise. Any manufacturer worth their salt is going to enable the protections these days. Define "these days". This DVR is 15+ years old. It still uses IDE hard drives.
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Dec 5, 2019 23:10
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If it's that old, go for it. Hell google for it and maybe you can find the ROM dump already out there.
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Dec 6, 2019 16:30
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Nevermind this.
Unperson_47 fucked around with this message at 23:54 on Dec 7, 2019 |
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Dec 7, 2019 23:27
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Welp, I can't find my JTAG adapter, so the point is moot anyway. Grrrr.
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Dec 8, 2019 00:36
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I have a LED array (amber-orange, flickers to simulate fire) that I have set up in a handheld lantern for a night parade once a year where everyone's carrying lanterns, very atmospheric. Because candles are boring. But the 12V power source it came with - 8 AA batteries - is bulkier and heavier than I like and I don't really need that much up-time because it's 45 minutes at the most. I'd like to switch it out for, say, a rechargeable 9-volt battery or two, tucked away in the top part of the lantern, and I suspect I need a step-up voltage regulator like this one: https://smile.amazon.com/Pololu-Step-Up-Voltage-Regulator-U3V12F12/dp/B016VGT6Q0 but I have no idea how to wire it up. Does anyone know of any place that has instructions or a video for something like this? Thanks.
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Dec 11, 2019 02:41
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9-volt batteries have an extremely small capacity and if you boost them it'll be even less. Like literally a tenth of a single AA. If 8xAA is giving you 45 minutes, the boosted rechargeable 9v will be like 5 minutes or less. The best power-to-weight ratio is going to be from an RC lithium-polymer cell like this: https://www.amazon.com/OVONIC-2200mAh-Battery-Evader-Airplane/dp/B07CVCKHQ8/ Each of those has about the same energy capacity as your 8xAA unit but is about half the size and a third of the weight. The voltage is close enough that it should be a direct swap -- just cut the wires to the AA pack and solder on an appropriate connector. You will need a special balancing charger; there are fancy models that can do any number of batteries of different chemistries for about 50 bucks, but if you're only going to charge these specific packs, this 12-dollar one will do https://www.amazon.com/Blomiky-Charger-11-1V-Balance-Battery/dp/B072K5LHGM/ e: oh, I misread, you don't need it to last as long as the AA pack. Look for a 3S lipo pack of whatever capacity you think is appropriate -- 2000mAh will last as long as the AAs, 1000mAh about half as long, etc.
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Dec 11, 2019 02:55
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Strings of LEDs are often unsophisticated. Have you tried just touching a 9v battery to it?
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Dec 11, 2019 02:56
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Sagebrush posted:9-volt batteries have an extremely small capacity and if you boost them it'll be even less. Like literally a tenth of a single AA. If 8xAA is giving you 45 minutes, the boosted rechargeable 9v will be like 5 minutes or less. It's supposed to last ~12 hours on the 8 AAs, so I'd be fine with less than an hour. I haven't tested that though. ante posted:Strings of LEDs are often unsophisticated. Have you tried just touching a 9v battery to it? It's this thing, actually. And I'm still in the theoretical stages of further futzing with this thing, to the point where I don't actually have any 9v batteries in the house. I don't use them for anything else. I should probably try that, but I'd also want to test the actual time it can go before I commit - I didn't realize the capacity was that small.
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Dec 11, 2019 03:30
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If an alkaline AA has about 3000 mah, and that thing normally lasts 12 hours, then that's about 250 mA per hour. You could stick four CR2032 coin cell batteries together to get 12 volts and it should last about an hour. I don't know if that's how longevity of batteries, works, I'm not a battery guy. But you could just stick four coin cells together and see how long it lasts with that. Get two of these guys, put them in series and you have 12 volts. Cojawfee fucked around with this message at 06:04 on Dec 11, 2019 |
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Dec 11, 2019 06:00
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Cojawfee posted:If an alkaline AA has about 3000 mah, and that thing normally lasts 12 hours, then that's about 250 mA per hour. You could stick four CR2032 coin cell batteries together to get 12 volts and it should last about an hour. I don't know if that's how longevity of batteries, works, I'm not a battery guy. But you could just stick four coin cells together and see how long it lasts with that. Oh hey, there's an idea. Thanks!
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Dec 11, 2019 07:01
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Hold up, coin cells can't put out very much current at all. Test it before you buy too much stuff.
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Dec 11, 2019 08:43
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Lemniscate Blue posted:It's this thing, actually. Cojawfee posted:If an alkaline AA has about 3000 mah, and that thing normally lasts 12 hours, then that's about 250 mA per hour. You could stick four CR2032 coin cell batteries together to get 12 volts and it should last about an hour. I don't know if that's how longevity of batteries, works, I'm not a battery guy. But you could just stick four coin cells together and see how long it lasts with that. evil_bunnY fucked around with this message at 12:56 on Dec 11, 2019 |
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Dec 11, 2019 12:47
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I have a bunch of 2S 3500mah packs I made for Fatshark goggles. They have the right connector for that as far as I can tell, are sightly larger than a 9V, and will last about 12 hours. They weigh 100 grams or so. Send a PM if you want...
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Dec 11, 2019 15:23
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evil_bunnY posted:That literally says 5V-24V on the input side so use a 4-bank AA holder and get on with your day, no need to modify anything else. Holy crap, I hadn't even noticed that. insta posted:I have a bunch of 2S 3500mah packs I made for Fatshark goggles. They have the right connector for that as far as I can tell, are sightly larger than a 9V, and will last about 12 hours. They weigh 100 grams or so. Send a PM if you want... PMed, thanks.
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Dec 11, 2019 23:49
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insta posted:I have a bunch of 2S 3500mah packs I made for Fatshark goggles. They have the right connector for that as far as I can tell, are sightly larger than a 9V, and will last about 12 hours. They weigh 100 grams or so. Send a PM if you want...
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Dec 12, 2019 00:17
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They're also explicitly designed for low-drain applications like laptop batteries, so really they're perfect for this. They didn't take off for Fatshark packs because I suck at marketing them and it wasn't really worth it.
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Dec 12, 2019 03:33
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Well I apparently haven't fixed whatever issue was causing my thing to lock up, but I have managed to make the lockup actually trigger the WDT reset thanks to the flag suggestions from this thread. I know that because the thing has a beeper on it that is currently just used to signal when it's done starting up, and it restarted and beeped at me at like 3 AM last night and I had to get up and investigate what the suspicious beep was 
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Dec 13, 2019 16:16
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I'm going to add Bluetooth to an 80 year old radio and I'm thinking of the best way to power it. It's an AM radio, so no switch mode power supplies. I can get 6.3V AC off the heater lines for the tubes, but that's not DC. I could use a Bluetooth receiver board like this one. It appears to have a voltage regulator on its input. Would I just need a rectifier and a smoothing cap?
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Dec 14, 2019 03:08
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kid sinister posted:I'm going to add Bluetooth to an 80 year old radio and I'm thinking of the best way to power it. It's an AM radio, so no switch mode power supplies. I can get 6.3V AC off the heater lines for the tubes, but that's not DC. I could use a Bluetooth receiver board like this one. It appears to have a voltage regulator on its input. Would I just need a rectifier and a smoothing cap? 6.3VAC rectifies to 5.6VDC. This is the perfect spot for a linear regulator. Full-wave rectifier + smoothing cap (3000uF for 100mA draw) -> this thing's LDO linear regulator = win.
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Dec 14, 2019 05:18
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Thanks! Now there's the issue that this radio doesn't have an input. I'd have to convert stereo to mono as well. I guess I'd put left and right RCAs on it to make the input more useful, do the mono conversion inside, then plug that Bluetooth board in with a stereo Y cable. I suppose I could repurpose that police band switch that's obsolete now to switch it to Bluetooth...
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Dec 14, 2019 18:03
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love spending like 12 hours chasing some elusive + unpredictable sensor signal bug in a project before thinking “you ruled out some trifling grounding horseshit hours ago, right? ....right??”
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Dec 14, 2019 20:55
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^^^^^^ that's slightly more fun than searching a half hour for a tool that was in front of you the whole time. Do there exist little brackets or panels to side mount a single switch or do I have to make my own? I basically need to mount a SPDT switch to the side of a wood cabinet to poke out the open back to switch between the radio and bluetooth for that project I mentioned above. Are there premade switch accessories for this? I'm lazy and don't want to drill a hole in a tiny piece of metal to mount a subminiature switch. I wish this came with an SPDT. The styling is even retro: https://www.amazon.com/dp/B002ZIYDOE/ref=cm_sw_em_r_mt_dp_U_utz9DbBP5HYXB kid sinister fucked around with this message at 03:05 on Dec 15, 2019 |
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Dec 15, 2019 03:02
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You might be able to change out the switch in the middle. Looks like the outer ring unscrews, there should be at least a few that fit the cutout. If you don't want to pay industrial prices*, you are probably expected to drill a hole in something. *allen bradley or siemens or someone like that will gladly sell you a $100 box with a $50 switch in it. At least it will be a nice box and switch. taqueso fucked around with this message at 03:20 on Dec 15, 2019 |
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Dec 15, 2019 03:16
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Well I found one.... .STL file. drat I wish I had a 3D printer. This is like the perfect job for one. If anyone is interested, I did find a couple products out there in the automotive world for this. The problem is that they were all for bigger 1/2" round holes for toggles or even larger rectangular holes for rockers. I didn't find many for mounting single switches though. They were usually for mounting multiples. I've got an L bar of aluminum in the basement that will work. Time for a drill and Dremel! kid sinister fucked around with this message at 18:06 on Dec 15, 2019 |
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Dec 15, 2019 17:56
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babyeatingpsychopath posted:6.3VAC rectifies to 5.6VDC. This is the perfect spot for a linear regulator. Full-wave rectifier + smoothing cap (3000uF for 100mA draw) -> this thing's LDO linear regulator = win. I misspoke earlier. I forgot these were 7xx tubes. They take ~7 volts. I double checked and the heater lines put out 7.2 VAC. Does that change things? Speaking of rectifiers, I already burnt out mine. It was a DF005. It's making funny waves on the oscilloscope now on its input and output. All I had wired up was 7.2VAC -> DF005 -> 3300uF 10V cap, no load. The voltage on the cap probably should've been higher I admit. Will these things burn up if you don't attach any load? All I had attached was my oscilloscope and DMM to the output. I still can't figure out how to properly size a rectifier by the way. If anyone could help me with that, you'll be my new best friend.
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Dec 15, 2019 22:40
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kid sinister posted:I misspoke earlier. I forgot these were 7xx tubes. They take ~7 volts. I double checked and the heater lines put out 7.2 VAC. Does that change things? 7VAC is still fine for the LDO. Rectifiers generally have a maximum voltage rating (which shouldn't be a limiting factor for you, as it'll be much much higher than your operating voltage for pretty much all bridge rectifiers) and a current rating (this will be the main one you care about). It'll also have a forward voltage drop which you'll need if you want to calculate how much power is going in to your linear regulator, but not critical. The current will be the main one. Check that your expected load is and make sure you give yourself a bit of headroom. As for how your rectifier blew up, no idea, that's very mysterious. They're usually very tough. They're not the kind of part that dies without a mark like a MOSFET, they tend to be visibly burnt.
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Dec 15, 2019 23:29
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Splode posted:The current will be the main one. Check that your expected load is and make sure you give yourself a bit of headroom. The board I'll be powering can also be powered via micro USB and that maxes out at 500mA. I may be powering a pre amp too to feed thw Bluetooth board with this same powers supply I'm cobbling together. It's the same deal: micro USB with optional screw down power terminals. Even if they're maxed out, that's only 1A total. I got no idea what's going on with this old stuff. I swear I got a gremlin at my work bench. Stuff there just doesn't want to behave when I attach test gear. A couple months back, I was fixing an old tube oscilloscope. The line was blurry and crooked in the middle, so I hooked up my new Rigol scope to it (thanks again everyone here for the recommendation, I love it). As soon as I touched my probe to the horizontal tube input, the line on screen instantly snapped into shape. So I disconnected the probe at the scope and the line behaved! I ended up having to add a shunt capacitor to the pin I touched to fake the probe being attached all the time. I love juryrigs.
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Dec 16, 2019 17:23
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I figured out what caused my rectifier to burn up. Apparently if I place one scope probe on the heater lines feeding the rectifier and a second scope probe on the DC output lines of the rectifier, it would fry the rectifier. I must have united both sides of the rectifier through the oscilloscope's shared probe grounds. Does anybody know which pin is the negative on a puck-style rectifier? Only the + pin is marked. Part # W01M.
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Dec 16, 2019 22:37
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kid sinister posted:I figured out what caused my rectifier to burn up. Apparently if I place one scope probe on the heater lines feeding the rectifier and a second scope probe on the DC output lines of the rectifier, it would fry the rectifier. I must have united both sides of the rectifier through the oscilloscope's shared probe grounds. It's usually the opposite one. Doing an image search of that part number shows one that's marked: 
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Dec 16, 2019 23:01
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Mine only had the maker's mark, part # and a plus sign. Dang. They're across from each other. Well doesn't that just make a single sided board inconvenient to organize? I got it hooked up now. Can someone explain how a bridge rectifier with no smoothing cap is making a sine wave at a voltage higher than its rating? All 3 W01Ms I bought do this.
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Dec 16, 2019 23:24
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kid sinister posted:I got it hooked up now. Can someone explain how a bridge rectifier with no smoothing cap is making a sine wave at a voltage higher than its rating? All 3 W01Ms I bought do this. Also, is your device powered from the wall and are your probe grounds bonded to equipment ground in your scope?
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Dec 16, 2019 23:52
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Probe ground is connected to rectifier -. Yes, this radio is powered from the wall, but it has a transformer inside so it's isolated. Yes, my scope's probe grounds are tied to the plug ground.
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Dec 17, 2019 00:18
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Are you sure there isn't some center tap that isn't also tied to a common equipment ground?
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Dec 17, 2019 01:32
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