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AxGrap posted:Currently working on a minivan entertainment system via raspberry pi but it's not too interesting. May pop in for advice. NONSENSE. That'll be interesting.  There's an Arduino thread here that has some overlap with RPi stuff that might come in handy too.
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Jul 17, 2023 06:53
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Cory Parsnipson posted:NONSENSE. That'll be interesting. There's also a raspberry pi thread
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Jul 17, 2023 13:05
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AxGrap posted:Hey friends, I want to make myself known a little cause I'll be dropping in when I have the time. I love projects but have been sidelined by having kids and life in general so I'll be in here to ask for advice. Currently working on a minivan entertainment system via raspberry pi but it's not too interesting. May pop in for advice. Hi, I'm the weirdo serving up 24TB of files from a Raspberry Pi, you should definitely drop by the RPi thread.
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Jul 17, 2023 13:48
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minivans can be pretty entertaining
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Jul 17, 2023 16:50
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Splode posted:There's also a raspberry pi thread Wuuuut. Bookmarked. Thanks!
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Jul 17, 2023 17:09
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I keep hesitating to use my precious few RPi's for anything because they're so loving hard to get for not-scalper prices these days.
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Jul 17, 2023 17:17
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Cory Parsnipson posted:NONSENSE. That'll be interesting. What he said. If people will listen to me talk about radios that are decades old with tubes, they'll listen to your attempts at entertaining your rugrats.
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Jul 17, 2023 19:13
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Thanks all! Well I'm hooking into the aux for the rear entertainment center, and that's more or less working, there is some noise but I think that's the adapters fault. What I'm stumped on is trying to either save state and power down and up gracefully, or failing that, running it off a battery which gets charged when the car is running, and just leaving it on. It would be pretty frustrating for the kids if they lose all progress in a movie or game every time I stop driving. I've read there is a signal sent out via the 12v charger when it gets turned off but I'm pretty early into looking into it. The math on running the pi directly off the battery looks like it would last a week w/o driving but that's a gamble I don't think I should take.
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Jul 17, 2023 21:06
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AxGrap posted:Thanks all! Well I'm hooking into the aux for the rear entertainment center, and that's more or less working, there is some noise but I think that's the adapters fault. What I'm stumped on is trying to either save state and power down and up gracefully, or failing that, running it off a battery which gets charged when the car is running, and just leaving it on. I would look into putting a rechargeable battery in between your 12V source and the Pi, and then use one of the GPIO pins to initiate a poweroff on voltage loss. A typical cell phone battery should be able to keep the thing running for hours: plenty of time to shut down. The SD card on the Pi is super sensitive to power loss during write, though. Like, destroy-the-entire-filesystem sensitive. There's some nerd on the RPi thread who can explain more about this, but it might be worth considering using a read/only operating system like Alpine with something more robust mounted for read/write.
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Jul 17, 2023 21:27
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I managed to toast a Arduino Nano clone. Guess who's putting 24v, 19.5v, and 12v on all their barrel jacks now? Cheap lesson at least. Kinda crazy that these all use the same exact connector with no real standard to let you know without examing the brick itself.
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Jul 17, 2023 22:38
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AxGrap posted:It would be pretty frustrating for the kids if they lose all progress in a movie or game every time I stop driving. I've read there is a signal sent out via the 12v charger when it gets turned off but I'm pretty early into looking into it. Run it off the ignition with a relay. You're not the first person trying to run an accessory off their car's electric system. Automotive relays are really common, with all kinds of switching methods. The most common kind of automotive relays are single pole, but you can always run multiples in parallel. This thread helped me years ago to operate a pair of SPDT relays as a crossover switch. Also, they do make automotive capacitors that could probably save your Arduino as it shuts down after ignition is shut off. Is 1 whole farad enough? Car audio guys with all their amplifiers use them to keep the headlights from dimming. Seriously. Car wiring is its own thing that has been around for decades and putting computers in cars has been a thing since at least the turn of the millennium, before we had low power, single board solutions. Back when iPads were new, people were cramming them in their dashes... kid sinister fucked around with this message at 23:20 on Jul 17, 2023 |
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Jul 17, 2023 23:11
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kid sinister posted:Seriously. Car wiring is its own thing that has been around for decades and putting computers in cars has been a thing since at least the turn of the millennium, before we had low power, single board solutions. Back when iPads were new, people were cramming them in their dashes... When I was a kid, my dad bought a black and white Sears television that ran off 12VDC, added a 9V voltage regulator, and hooked the Atari 2600 to it, so we could play video games in the covered back of the pickup truck, on the bench seat with seatbelts he got at the junkyard and bolted in. My dad is cool.
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Jul 18, 2023 00:16
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Let the RPi power its own relay. Use diodes to OR the ignition and an RPi gpio + relay driver. When the ignition is turned off, the RPi stays on until it decides to turn off its gpio (i.e. under software control). I sort of expect such a circuit is already available from the RPi/car nerd community. Or you could adapt a turbo timer to do something similar.
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Jul 18, 2023 00:35
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Yeah I gotta ask around, but cursory googling didn't get me anywhere solid. I'm more of a puzzle pieces recipe kinda tinkerer, not super sure of myself making my own components etc. A lot of stuff to look into so far thanks all.
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Jul 18, 2023 00:39
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cruft posted:When I was a kid, my dad bought a black and white Sears television that ran off 12VDC, added a 9V voltage regulator, and hooked the Atari 2600 to it, so we could play video games in the covered back of the pickup truck, on the bench seat with seatbelts he got at the junkyard and bolted in. Your dad literally made Homer's car of the future, complete with separate seating for kids with video game to keep them quiet. 
kid sinister fucked around with this message at 00:59 on Jul 18, 2023 |
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Jul 18, 2023 00:51
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Straight Into the Trash  This board has 12 toggle switches, placed using a footprint I drew for another board. But the holes were a bit loose on that board, and the switches weren't held precisely in place. So I tightened up the tolerances, perhaps more than I should have. I might have gotten away with it too, if I hadn't also chosen to go with HASL instead of ENIG to save $15 and a day of manufacturing time. But the tolerances stack, and HASL is thick, and the toggle switches will not fit into the plated holes. FML. It's possible I could force them in with hot air, but I think I'll just order some new boards. It's 2-layer, so manufacturing time is quite fast. Also Sendcutsend just emailed me to say that some of my parts are not manufacturable as specified, and also they've already cut them.
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Jul 20, 2023 22:20
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Oof. Been there, it sucks. Can you nip off one side of the switch terminals with a side cutter? If nothing else just try to fit up all your other parts to make sure there aren't any other changes needed. KiCad can print board layouts at 1:1 scale, I usually do that now before sending out the design and place the parts just to make sure they look OK.
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Jul 20, 2023 23:04
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The factory already has the new gerbers. Gotta act fast because it's already 11 AM Friday in Shenzhen, and I want to make sure some engineering question doesn't stall it over the weekend. I also need to rev some of the sheet metal parts, but I don't want to commit those until I at least try out the rev 1 parts. This will add a week of schedule, but reduces the likelihood of needing a rev 3.
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Jul 21, 2023 04:16
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ryanrs posted:It's possible I could force them in with hot air, but I think I'll just order some new boards. It's 2-layer, so manufacturing time is quite fast. You couldn't salvage them with a hand drill bit?
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Jul 21, 2023 05:13
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Oval holes.
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Jul 21, 2023 05:40
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File
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Jul 21, 2023 05:47
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No I am not going to file 72 solder lugs. I am going to pay $70 and wait 6 days for a perfect pcb. It's ok to scrap hosed up pcbs. I've patched up many small mistakes, but this one was too much.
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Jul 21, 2023 05:53
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Fair
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Jul 21, 2023 06:01
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Using a regular labscope for car work? I've googled it and it seems no. Or use a differential probe. I mean I got my 40mhz hameg scope already, I wanted to look at the fuel injectors and perhaps what sort of pulses the ECU is putting out. But apparently since it's a ground referenced scope it could throw of all kinds of readings and even be potentially dangerous for the scope. Though the hameg should be rated for 400 volts and the injectors should not go that high I believe, and with a 10x probe to boot? Sounds safe though maybe I will get the wrong readings due to ground reference on what is a floating system? But you could get around that using a differential probe I understand, or putting your scope behind an isolation transformer (that has seemed a mite controversial in the past). The car I am working on was built 1989 so older than the scope. Differential probe purchasing time, or should I get a battery scope if I wanna mess around on cars?
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Jul 23, 2023 10:23
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The 'proper' way to do it would be with an isolated differential probe. I use these ones at work. They can take a 700V input, scale it down to 7V, and then pass that signal across an isolation amplifier to a BNC output so that your scope is never electrically connected to the input signal. Unfortunately they can be kind of expensive. I'm kind of surprised that the cost of the things hasn't dropped over the last few years since the core isolation function can be done with something like an AMC3336 (digital output) or ADuM3190 (analog output) for about $10 USD. I guess certifying a high voltage device and selling into a very niche market keeps the price up.
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Jul 23, 2023 12:09
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That is pretty crazy, 10x the cost of my scope.
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Jul 23, 2023 12:27
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If the car is already galvanically isolated, can't you just clip your ground lead wherever you want?
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Jul 23, 2023 18:10
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Micsig differential probes are like $180, I got one when I was building high voltage power supplies cuz I wanted to characterize the output noise without exploding my scope.
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Jul 23, 2023 19:14
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I bought a vintage isolation transformer off eBay for like, $80
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Jul 23, 2023 19:17
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Vintage, as in “doesn’t have a ground plug/pin” I hope? From what I understand isolation transformers do gently caress all nowadays unless you separate/ leave off the ground pins
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Jul 23, 2023 20:03
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Yes, but I don't really understand what you mean. Are you saying you can buy isolation transformers that are grounded together on the input and output? Why
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Jul 23, 2023 20:11
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I don't know much about cars. Is there any reason you couldn't intentionally earth ground the chassis and then use a non-differential scope probe appropriate for the voltages being measured?
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Jul 23, 2023 20:53
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Automotive power is typically pretty dirty with lots of inductive stuff dumping current. Having the "12v" line go up to 100v for 10-100ms isn't unusual
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Jul 23, 2023 22:20
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A cheaper option (and also something I've done) is to just get a 1:100 "high voltage" probe: https://www.amazon.com/Goupchn-Voltage-Oscilloscope-Probe-P4250/dp/B086V9B67C/ref=sr_1_2 It's like 20 bucks, but you have to trust that the only thing between the scope and the high voltage is a big resistor.
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Jul 23, 2023 22:37
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ryanrs posted:The factory already has the new gerbers. Gotta act fast because it's already 11 AM Friday in Shenzhen, and I want to make sure some engineering question doesn't stall it over the weekend. Boards are done. They shipped out from the factory 5:30 AM Monday morning, Shenzhen time (66 hours). I should have them by Wednesday. This is for a 2 layer, 2 oz copper, HASL board manufactured by PCBWAY with default speed (no expedite). I've been really pleased with pcbway's speed and quality.
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Jul 24, 2023 00:09
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Your single-ended 10x scope probe will have an input resistance of 10 megs. A few hundred volts into that is all of a few tens of microamps into whatever the scope uses for overvoltage protection circuitry. Check your manuals of course, but it's not going to be able to do much damage. To give you a point for comparison, the docs for the low-end Rigol say it can tolerate 300V RMS at the BNC, so 3kV at the probe tip if the probe can somehow handle that. I think that's fine just about anywhere in a car but a sparkplug wire.
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Jul 24, 2023 00:37
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run the scope from the cigarette lighter so you can debug on the go
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Jul 24, 2023 01:15
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Foxfire_ posted:Automotive power is typically pretty dirty with lots of inductive stuff dumping current. Having the "12v" line go up to 100v for 10-100ms isn't unusual What he said. Spikes as solenoids and motors activate/deactivate are the norm. Hell, car audio guys will install full farad capacitors on their amps to keep the headlights from dimming.
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Jul 24, 2023 01:46
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I spec all my automotive power supplies for +100V on the input. Low current devices get a MIC5283 120V linear regulator. If I need more current, then a switcher like the LT7101 105V step-down. These spikes are short-lived, so the linear regulator does not need to worry about peak power dissipation at 100V. If the fault is persistent, the regulator will go into thermal shutdown, which is fine. ...that said, I would plug my Tek scope's 10x probes straight to the injector coil and not think twice. High-impedance input protection ain't that hard, and I'd expect a scope manufacturer to get it right.
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Jul 24, 2023 02:23
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ante posted:Yes, but I don't really understand what you mean. Are you saying you can buy isolation transformers that are grounded together on the input and output? Why Yes that is what I’m saying… it’s pretty dumb imo https://youtu.be/XBsQ3sZ45Fk
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Jul 24, 2023 02:26
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