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It would complicate construction a lot and not look as nice, but what about using off-the-shelf perf? Make edges out of flat metal, then throw a perf backer into the open hole in the middle.
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Jun 28, 2023 20:03
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Yes, I know that's a solution, I just can't bring myself to do it. Manually cutting and attaching perforated metal to a laser-cut part only makes sense if I value my time less than the laser robot's time. And the results will be uglier and technically worse (much less panel stiffness).
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Jun 28, 2023 20:14
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p.s. I am currently unemployed. The fact that my time is actually worth less than the laser robot's time makes me even less inclined to do it.
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Jun 28, 2023 20:24
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Make it out of fr4
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Jun 28, 2023 21:49
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Needs bends. But I think you are on the right track! I just re-priced a bunch of parts in galvanized steel and they are substantially cheaper than aluminum, maybe half. Downsides: a steel version will be heavier, not as shiny, and will need substantial redesign for the less stiff steel (since it's thinner material).
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Jun 28, 2023 22:00
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ryanrs posted:p.s. I am currently unemployed. The fact that my time is actually worth less than the laser robot's time makes me even less inclined to do it. I call shenanigans! By this logic, if you were earning $300k / year, you'd be more inclined to do the manual labor. But I think you'd be precisely as disinclined to do it!
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Jun 28, 2023 22:43
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but my budget for neat projects would be way higher
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Jun 28, 2023 23:06
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ryanrs posted:Straight up desolder STI3470 and throw it away. Replace it with some other 3.3V buck regulator. Solder wires to feed the right signals to the new regulator board. Well, the first thing I did was try the more advanced strategy: I desoldered the popped chip:  Then I replaced it with the chip off of the SparkFun thing you had me buy:  Then I powered it up and tested those pads at the top marked "3.3VD" and "GND" and I'm wondering why they're reading 19.5 volts... Ah yes, just because two voltage regulators have the same package and I got the orientation correct, it apparently doesn't mean they have the same pinout:   So like, should I put the SparkFun thing back together like I got it, and just solder the output wires to those aforementioned 3.3VD and GND pads on the PCB? Is that the "correct" way to get the juice to the display? Zero VGS fucked around with this message at 02:51 on Jun 30, 2023 |
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Jun 30, 2023 02:49
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Zero VGS posted:So like, should I put the SparkFun thing back together like I got it, and just solder the output wires to those aforementioned 3.3VD and GND pads on the PCB? Is that the "correct" way to get the juice to the display? OK I went and did that... worked like a charm. Now my whole 38-watt, 1000-nit display is powered by a single USB-C cable, with a 20v trigger for the backlight rail, and the SparkFun chip doing an additional buck down to 3.3v for the signalling rail. The panel and the eDP adapter are both running much cooler from the amps being lowered. Thanks for the pointers!
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Jun 30, 2023 05:14
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I don't think they meant take the chip off the sparkfun board and put it on your board, as that can lead to disastrous results as would have happened if you didn't check the voltage on the outputs. Different chips have different pinouts and have different capacitor and resistor requirements. So yeah, wire the output of the sparkfun board into the appropriate spots on your board. Though if you can wait, you can always just order a STI3470 from aliexpress (seems like that's the only place that has them) and make your board work correctly. That is, if it was just that chip that failed, and not something else on the board.
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Jun 30, 2023 05:50
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Yeah, you need to use the Sparkfun board, because all the little resistors and capacitors are specific to the exact IC. So run wires from the Sparkfun PCB to the 3.3V, GND, etc traces on your original pcb. You only need to desolder the STI3470 chip itself. The passives surrounding it can be left in place (they won't do anything with the chip gone). Glad it's up and running again!
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Jun 30, 2023 05:51
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I'm always impressed when modern electronics somehow gets fed 10 times the voltage it's designed to take like in this case or like when my dumb rear end connects poo poo wrong and yet is apparently just fine as long as you disconnect it quick enough
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Jun 30, 2023 14:06
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I hooked up the pic running the motor driver in my senior capstone project backwards several times and even released some smoke and it just kept on trucking.
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Jun 30, 2023 18:46
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Shame Boy posted:I'm always impressed when modern electronics somehow gets fed 10 times the voltage it's designed to take like in this case or like when my dumb rear end connects poo poo wrong and yet is apparently just fine as long as you disconnect it quick enough Both times, when I blew up the original 3.3v regulator, and when I wired in the new regulator with the wrong pinout so it gave 19.5v on the 3.3v rail, I had the display unplugged and was confirming with the multimeter first. Otherwise I'm sure I'm sure my bumbling would have cost me $200.
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Jun 30, 2023 19:58
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ryanrs posted:I just re-priced a bunch of parts in galvanized steel and they are substantially cheaper than aluminum, maybe half. Halogen load bank is back in business! This time in galvanized steel instead of aluminum.  All I had to do was lower my standards re. weight and appearance! 
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Jun 30, 2023 20:24
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Cojawfee posted:I hooked up the pic running the motor driver in my senior capstone project backwards several times and even released some smoke and it just kept on trucking. I once had a PIC successfully running my blink code for about ten seconds at 12v
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Jun 30, 2023 21:25
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ante posted:I once had a PIC successfully running my blink code for about ten seconds at 12v Yeah I had an ESP running for a solid minute perfectly fine at... way too high a voltage, and only figured it out when I grabbed it and it burned me immediately 
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Jun 30, 2023 22:09
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My dumb Ethernet stack weekly update: Filled-in blocks below are done or working-ish as of now, blocks with no background color are to-do. Last week I had just gotten the green hardware working to the point that the Rx chain would dump received data into a memory buffer. This week was mainly working on the grey boxes - the main Ethernet packet decoder, a packet buffer manager for holding incoming/outgoing packets until they can get processed, and the Address Resolution Protocol (ARP) block that converts between IP addresses and Ethernet MAC addresses. The packet buffer manager holds several linked lists of statically allocated buffer memory - one list of Rx packets coming in from the DMA, one list of Tx packets waiting to be sent out by the DMA, one list of packets that are fully received and waiting for the CPU to come process their info, and one list of free packets that everything else either pulls from or recycles old packets to. The linked list structure means the CPU only has to move around pointers to data during the ISRs, it never moves the actual data itself. The Ethernet protocol unit translates Tx/Rx packets between Internet Protocol and Ethernet formats with the help of the Address Resolution Protocol that maintains a mapping between known IP/Ethernet address pairs and establishes new mappings when a new IP address is seen.  Also, I don't think I showed this last time but here's a screenshot of the communication between the external PHY chip and the MAC hardware on the microcontroller. The top two lines are the clock and data for the MDIO interface that lets you read and write to registers on the PHY chip. In this case we're reading the general status register and the dashed vertical orange line on the right shows that the Status Summary bit is a 1 meaning everything is OK and PHY is working normally. The bottom two lines are the Rx dibits, they clock two bits in at a time at 50MHz to get the full 100Mbit/s data rate. 
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Jul 1, 2023 00:01
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you will need an ssl box for posting
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Jul 1, 2023 00:41
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ryanrs posted:you will need an ssl box for posting They won't be secure but I do plan on having simple sockets that plug into the UDP/TCP boxes. The sockets would have a port number, a pointer to a transmit function and another pointer for a receive callback. Like really that DHCP block should be connected on UDP port 68 for clients, 67 for servers. Then I could have another socket connected from TCP to an IRC server process and we could all post like it's 1983.
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Jul 1, 2023 01:52
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I'm working on modifying a thing (a light) that has a potentiometer that controls the power supply for dimming. The only marking I can see on the pot is "B104", is that all I need to pick out a matching part?
Bad Munki fucked around with this message at 05:44 on Jul 1, 2023 |
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Jul 1, 2023 05:30
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Looks like it is a 10k pot.
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Jul 1, 2023 05:38
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Okay, new Q: my understanding of the pinout on these is that pins 1 and 3 are on opposite ends of the full resistor, the film or whatever mechanism it is, and pin 2 sweeps along that resistive material. On the board I'm looking at replacing I have the DIM+ wire from the supply going to pin 2 and one of the other pins (not sure, either 1 or 3), and DIM- from the supply going to the other end pin (3 or 1, respectively.) What's that doing? I feel like it would want to be wired up to just 1 and 2 or 3 and 2? Like this is how it appears to be wired, courtesy Paint:  Can someone explain to me what's going on there? Seems simple I just haven't messed with pots really at all.
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Jul 1, 2023 05:44
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Doubt it matters, but some pots possess different linearity of their curves. Would only matter if you’re specifying a rotational angle to a resistance.
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Jul 1, 2023 05:45
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Bad Munki posted:Okay, new Q: my understanding of the pinout on these is that pins 1 and 3 are on opposite ends of the full resistor, the film or whatever mechanism it is, and pin 2 sweeps along that resistive material. On the board I'm looking at replacing I have the DIM+ wire from the supply going to pin 2 and one of the other pins (not sure, either 1 or 3), and DIM- from the supply going to the other end pin (3 or 1, respectively.) What's that doing? I feel like it would want to be wired up to just 1 and 2 or 3 and 2? Think of the pot as having “resistance per unit distance”, and the farther along the wiper is the more resistor it has to pass through, hence greater resistance. Like physically imagine a long resistor with a “bypass” wiper touching it. And I usually do wiper + one end, I don’t see why it wouldn’t work.
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Jul 1, 2023 05:46
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PRADA SLUT posted:Think of the pot as having “resistance per unit distance”, and the farther along the wiper is the more resistor it has to pass through, hence greater resistance. Like physically imagine a long resistor with a “bypass” wiper touching it. Right, that's how I understand it, but I was wondering why they'd have one and and the tap tied together like that. e:  There's nothing on those soldered terminals on the right, they just filled 'em for fun I guess. Bad Munki fucked around with this message at 05:52 on Jul 1, 2023 |
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Jul 1, 2023 05:49
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Bad Munki posted:Right, that's how I understand it, but I was wondering why they'd have one and and the tap tied together like that. It's not really doing anything. The current will go from Dim+ through the wiper and out to Dim-. The left side of the resistor and the wiper at the same potential, so nothing will happen between them. Maybe they just wanted to have every pin connected to something just in case.
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Jul 1, 2023 05:51
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Cojawfee posted:It's not really doing anything. The current will go from Dim+ through the wiper and out to Dim-. The left side of the resistor and the wiper at the same potential, so nothing will happen between them. Maybe they just wanted to have every pin connected to something just in case. Okay cool, thanks. I'll probably match their approach just for good measure, but wasn't sure if there was some real reason like it alters the curve or something. Actually applying my covid-addled brain, I just threw my meter on it and it looks like 0-100k linear, which matches my googling. Bad Munki fucked around with this message at 05:58 on Jul 1, 2023 |
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Jul 1, 2023 05:53
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Bad Munki posted:Right, that's how I understand it, but I was wondering why they'd have one and and the tap tied together like that. If the wiper fails, wiring it up like that ensures that the circuit is still completed, just locked at the highest resistance value. This may or may not matter for a given application but it can be a failsafe in some situations.
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Jul 1, 2023 06:06
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Makes sense! In this case, it’s for a grow light, and I think max resistance maps to max brightness, so having the light still able to be powered on in that state would be desirable.
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Jul 1, 2023 06:27
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Yeah the reason you wire it like that is because as the wiper moves it's... a physical object rubbing another physical object, so it can't really guarantee 100% constant continuity as its moving. By tying one end to the wiper like that you can ensure that it never goes fully open, there's always at least the entire resistor between the ends if nothing else. It's just good practice.
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Jul 1, 2023 06:40
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Shame Boy posted:Yeah the reason you wire it like that is because as the wiper moves it's... a physical object rubbing another physical object, so it can't really guarantee 100% constant continuity as its moving. By tying one end to the wiper like that you can ensure that it never goes fully open, there's always at least the entire resistor between the ends if nothing else. It's just good practice. I always wondered why this is done, thanks!
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Jul 1, 2023 07:09
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Bad Munki posted:Actually applying my covid-addled brain, I just threw my meter on it and it looks like 0-100k linear, which matches my googling. 104 = 10e4 = 100,000 ohms
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Jul 1, 2023 07:25
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Always hated that convention, I really feel 104 should be 10'000 Ω (1.0⨉10^4).
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Jul 1, 2023 07:52
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longview posted:Always hated that convention, I really feel 104 should be 10'000 Ω (1.0⨉10^4). What would 124 mean in your system?
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Jul 1, 2023 13:55
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BattleMaster posted:If the wiper fails, wiring it up like that ensures that the circuit is still completed, just locked at the highest resistance value. This may or may not matter for a given application but it can be a failsafe in some situations. In the center-tap configuration, wouldn’t it just fail open?
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Jul 1, 2023 17:27
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Lots of good info from this thread as always, glad I asked. So as part of this project, I’m refactoring the controls from these lights into a single unit. Individually, that little pot lives in a housing like this:  It’s 1mm steel, call it 70x40x40. Open on the bottom. I want to have all five of my pots in a single housing, and it’s all low voltage so I could pretty easily print up a housing and cut some steel sheet for the face to hold the actual bits, but I’m wondering if anyone knows of a source for something similar, but just, say, twice as wide? Just noodling over the idea of a ready-made solution I guess. I’m sure a market exists for blank enclosures like this where one would just need to drill it out for the controls.
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Jul 1, 2023 18:54
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DigiKey, Mouser, Newark, etc. all sell enclosures like that. This one from DigiKey looks like it could do the job if you mill out the bottom. You might have to remove those internal ribs too. Or just find another model, those vendors have literal thousands of boxes to choose from.
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Jul 1, 2023 19:07
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So I'm playing around with a couple raspberry pi pico W's, setting up wifi and MQTT clients and such. It's easy enough to have one push data and the other consume, and there's a few free online MQTT brokerage services, so that's all OK. But why does it seem hard to find a generic android app that lets me monitor a few feeds and graph them, maybe set an alarm to get a nice android notification, provide it's own feed value / control value back to the micros, etc... Am I missing something obvious? I don't want to write an entire android app to get notified if the temperature goes above 40C and turn a solenoid on and off manually. I see literally one app that looks like it does this sort of stuff. Rescue Toaster fucked around with this message at 19:14 on Jul 1, 2023 |
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Jul 1, 2023 19:08
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Is there a good source for magnetic pogo pin connectors? I've got a pair of headphones (Sennheiser hd560s) that I have loosely converted to Bluetooth with a VOCE BT LE audio adapter and it works great but I'd like to make the adapter easily removable for charging. There's plenty of USB magnetic adapters (which I know are a bit janky but it charges at like 150mA so it's probably fine). I can't find a 3.5mm magnetic adapter and am assuming I need to make my own.
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Jul 1, 2023 19:44
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