I want to connect five OV2640 cameras via FPC to an ESP32 on a custom PCB. Is this generally possible and does the ESP32 have enough power for this or do I need an ESP32 for each camera? The frames per second are not so important as the cameras will be used as QR code scanners. Which components allow to run so many cameras with...
I suppose you could use a bus or something to cycle through the cameras one at a time?
Why not use a lower-resolution I2C camera module? I2C allows multiple devices to be connected to the same I2C port, as long as they have different addresses. You can also use one with lower resolution for QR I suspect.
An alternate method would be to buy QR-code recognition modules, with some form of serial output. Then connect all of those to the ESP32, if you can do 5 software serial ports. More expensive this way though.
I'm in the habit of being consistently unsatisfied with my own work. Even by achieving my initial goals, I learn new ways it could have been better, and it instantly becomes mediocre in my eyes.
I think this is a good habit of mine, but it requires that I attempt to accomplish meaningful work constantly. It doesn't matter too much to me exactly what I make, as long as it's something (sometimes it's code, but sometimes it's a nightmare of brass and iron and science).
Coding is not the only thing software needs. It needs bug reports, documentation, graphical designers, funding, how-to videos, and so on. There are many problems to solve and many ways to contribute, requiring a diverse set of skills!
There's a neat math proof that proves you can code if you can follow a flowchart. However, if you don't like coding, it's unlikely to be of particular interest and perhaps those other methods of contribution would bear more fruit!
Creating new content to share on Lemmy is another way to help it grow! Tell us worthy tales, share your best thoughts!
Utopia? Flying jetson cars? Mole people living underground? Everything’s on fire and humanity ends? I’m just curious about anyone’s thoughts in general 😀
Hello, I recently bought a USB A to C cable and it is pretty weird. It is a USB A to USB C cable, seemingly USB 2.0 but the A connector has 5 pins, the 4 pins of USB 2 and what looks like pin 7 of USB 3.0 so in the middle of the back row, the other pins of USB 3.0 are not there and the plasting moulding only allows for that one...
In my experience, if they don't include the conductor in the connector, there will generally not be a wire for it in the cable. So replacing the USB-C connector is probably not going to add any functionality.
I have a stack of USB-A to USB mini/micro cables that are a bit like this. Two conductors, only do charging. So if I replace the connector, there's no wire to connect the D+ / D- lines to. It's quite possible the manufacturer of your cable had some similar or otherwise reduced feature set in mind, and wanted to save 5 cents of copper.
I also have some cursed cables that have normal ports, but only two wires inside the cable (power/ground), or are otherwise out-of-spec in ways that make the data lines mostly fail. These have wasted quite a bit of my time over the years.
Hello, we are making a thesis where we use MOSFETs as an alternative radiation detector. So to explain it, it works when the mosfet is irradiated with an external radiation source; its voltage threshold increases, which will be used to determine the radiation dose. I'm currently asking for help on how we measure the voltage...
Hey I messaged them a bit, this is an undergraduate project with no budget (so a MOSFET tester is out of budget). I also suggested a sort of sweep method using an MCU and some op-amp glue, but I don't think they have sufficient background to get this kind of thing working yet (in fact I barely do, so probably it won't 'just work' with whatever I came up with off the top of my head).
What I was thinking is perhaps they can set Vds and Vgs to fixed values such that a particular MOSFET conducts a fixed current, e.g. 100mA, somewhere near-ish the start of the linear region. Then record the Vgs required to achieve this current for each of a set of MOSFETs, say a few dozen (because of part variation).
Then after exposing them to varying amounts of radiation (a few for each exposure level), put them back in the same test conditions and measure how the output current has changed, what Vgs will restore the same current, draw some graphs, discuss the advantages and disadvantages relative to the Vth method with regards to radiation dosimetry, conclude, and call it a day.
Think it would work? No need for an MCU or signals processing this way, so the science can get done with the tools they have.
Also I never had free access to strong radiations sources in undergrad, so am a little jealous. I barely got to use tritium, and that sparingly.
I’ll go first You can do it alone but you’ll run into problems. Others that have been through it have solved those problems. Ask around if you recognize a problem and you’ll most likely receive the best solution
I'm taking apart a broken tape recorder produced in the 70s (a Tesla B57, made in Czechoslovakia), to harvest some parts (inductors, switches, ...) and maybe reuse the case for some project....
Mostly I just work in a well ventilated area. Oh and for sure disconnect power before desoldering anything.
Other than that, I avoid taking apart microwaves (beryllium, high voltage), anything with a CRT (imploding glass, high voltage), and high voltage transformers (transformer oil, high voltage). Also any medical equipment (chemical hazard, radiation hazards, biohazard, high voltage, imploding glass). Oh and no unexploded munitions for reasons that should be obvious (people still salvage these in my country and it sometimes doesn't end well).
I find a hot air rework station+tweezers a much faster way to salvage than jamming a hot iron into boards. Also lets you salvage SMT components, which are most of the better parts these days. For 1970s stuff, it's mostly through-hole, I'd test the parts before trying to reuse them. Capacitors especially. Got to love those big transistors from our side of the Iron Curtain though.
Grind it into dust, add sand, pour molten non-recyclable plastic into it (e.g. recyclable plastic with too many impurities). Market it as a weighted ballast material e.g. for the base of IKEA lamps.
I’ve been looking for a simple low-voltage cutoff circuit for a 12v SLA battery, but many of the ones I find have reviews saying that the protection circuit itself drains the battery slowly as well. Is this just inherent in the design, where it has to draw a little to measure the voltage, or are there low-voltage cutoffs that...
No, it's not possible to do it without current draw. You can do it with really, really low current draw though.
Ignoring MOSFET stages for the moment, I could design a system that could do this, with a power consumption of under 0.1 uA when in the low-voltage cutoff state.
I'd use a TPL5110 and an Attiny10 to do that.
Alternatively, if ~50 uA is OK (it really should be), then I'd just use the Attiny10 on watchdog timer, and save the cost of the TPL5110.
If I absolutely did not want to use the SLA to power that system (as an academic exercise), I'd use a separate CR2032 coin cell. That ought to last 3-5 years. Or if there's ambient light, a calculator solar cell and a supercapacitor would make it self-powered. I could design a system that could last overnight on just a few hours of ambient light during the day. Modern microcontrollers are a marvel!
The amount of power drawn by a reasonably designed system should be many orders of magnitude less than the self-discharge of the battery. So not worth worrying about unless it's very poorly designed for some reason.
Hi, I found an old cellphone battery (from a Pixel3A phone) and I’d like to reuse it for my robotics experiments. (link to images: imgur.com/a/Oj09tai)...
Well, for #2, there are excellent modules based on the TP4056 that cost 1$. They charge lithium-ion batteries only. So check the label (yes, I know it clearly says Li-ion but don't trust strangers on the internet for safety facing stuff...), if it says Li-ion, then these are great.
For #1, probably one of those fat traces in the flexible cable is BAT+ and the other is BAT-. I would look for a way to safely remove the plastic coating in such a way that I can't accidentally short circuit it. For example, exposing the copper for BAT+ on one side, and BAT- on the other.
I tried with cooked bone, that tends to be what I have more of lying around :D
I don't recall the voltage I tried, but it was probably something in the range of 5-9v. I didn't try with a very thin slice, it was a few mm thick. Probably a thinner slice is the thing to try. That's a bit hard with bird bones (hollow), so maybe I'll have to cook something else. I don't have a microtome, so I'll have to cut some thin slices by trial and error.
I would hazard a bet that orientation matters. The studies that measured bone piezoelectricity seemed to suggest some orientations made more sense than others, but I don't recall what exactly. In any case, they had... very different applications in mind.
However there's a weird little caveat -- some papers attribute the piezoelectric effect to organic collagen fibers. Others attribute it to the inorganic component (apatite). In the end this paper seemed to have a reasonable measurement process so I've just ignored the exact cause of the piezoelectricity for the moment. From their tests, orientation of the bone is highly important.
They use an applied voltage of 100V then amplify (100db). I'm reasonably competent working with moderate voltages, but would prefer to try something under 30v as a matter of convenience (e.g. what I can reach with a DC-DC boost converter).
Normally though, I just hook up a crystal oscillator to a hex inverter @5V or to an MCU with some caps. I'm not entirely sure how I'd build an equivalent circuit at 30V! Doing unnatural things with crystal oscillators hasn't really come up much in my studies or career.
So I wanted to design a children's toy, where the electronics could last 100 years (ignoring mechanical abuse). I figured some people here might be interested....
What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it)....
I suspect the reason it's not working, is something I don't currently have the tools to measure.
With an OK reflected light microscope I could work out whether there's a glass or clear epoxy coating on the silicon. With an alpha spectroscope, I could characterize the source better. Tools are cheap in Asia, but the space to put them costs a fortune...
So I'm going to shelve this for now and maybe try to build a BJT amplifier for a PIN photodiode detector. I've etched some boards. Fingers crossed.
the smart thing of course would be to buy a scintillator crystal, but I hate the inelegance of it. It shouldn't be necessary.
I've gotten a similar circuit to work. Good shielding on the preamp was indeed key.
That was like 12 years ago though. Back then I used a battery. I probably know enough to get it working with a switched power supply now, which would be way more convenient.
The PIN diodes aren't cheap though! Also some are export controlled. Not the one from that project though. I have a few around that I'll use if I can't get this to work.
The BJT method is attractive due to really low cost. I never managed to get it working though. There are enough independent reports of the method working online that I think it's possible, but the documentation hasn't been sufficient to easily replicate it.
It might be something boring like some manufacturers put a clear coating (e.g. glass) on the internals of a type of transistor, and others don't.
Wow, OK. It failed pretty hard. Fail on the light test, and failed to switch with the base saturated. Also measures a resistance close to zero between all pins.
I'm actually quite surprised! The potting compound 'surgery' went very smoothly, like peeling off a sticker. Well, these things happen when abusing semiconductors I guess. I've got spares, so no big deal. If it fails again, I'll go find an alternative BJT that does not have potting compound.
Maybe -- easy to check, at least. I'll just shine a light on it :)
The coating came off pretty easily though. The bonding wires pass visual and mechanical inspection, and do not short on the case or other parts of the transistor.
No bicycles/skates? Fine. (i.imgur.com)
ESP32 with multiple cameras
I want to connect five OV2640 cameras via FPC to an ESP32 on a custom PCB. Is this generally possible and does the ESP32 have enough power for this or do I need an ESP32 for each camera? The frames per second are not so important as the cameras will be used as QR code scanners. Which components allow to run so many cameras with...
What software do you use for PCB design?
I’m interested in learning how to make a proper PCB rather than perf board with wires all over the place.
Not Electronics related: Banner and logo of this community?
Is there a reason why the banner and logo of this community are just the reddit logo?...
Does anyone else feel extremely annoyed when things are even slightly imperfect?
Specifically about technology, like are bugs on your device's OS, a program, app or game having issues, or a website/platform....
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What do you feel like life will be like on earth in 100 years?
Utopia? Flying jetson cars? Mole people living underground? Everything’s on fire and humanity ends? I’m just curious about anyone’s thoughts in general 😀
Weird cable with USB A connector with 5 pins
Hello, I recently bought a USB A to C cable and it is pretty weird. It is a USB A to USB C cable, seemingly USB 2.0 but the A connector has 5 pins, the 4 pins of USB 2 and what looks like pin 7 of USB 3.0 so in the middle of the back row, the other pins of USB 3.0 are not there and the plasting moulding only allows for that one...
MOSFET as Radiation Detector
Hello, we are making a thesis where we use MOSFETs as an alternative radiation detector. So to explain it, it works when the mosfet is irradiated with an external radiation source; its voltage threshold increases, which will be used to determine the radiation dose. I'm currently asking for help on how we measure the voltage...
What piece of wisdom about life are you able to provide others?
I’ll go first You can do it alone but you’ll run into problems. Others that have been through it have solved those problems. Ask around if you recognize a problem and you’ll most likely receive the best solution
Safety tips when disassembling old electronics?
I'm taking apart a broken tape recorder produced in the 70s (a Tesla B57, made in Czechoslovakia), to harvest some parts (inductors, switches, ...) and maybe reuse the case for some project....
Can anyone here recommend a good, simple 12v low-voltage cutoff?
I’ve been looking for a simple low-voltage cutoff circuit for a 12v SLA battery, but many of the ones I find have reviews saying that the protection circuit itself drains the battery slowly as well. Is this just inherent in the design, where it has to draw a little to measure the voltage, or are there low-voltage cutoffs that...
Reuse cellphone battery for robotics
Hi, I found an old cellphone battery (from a Pixel3A phone) and I’d like to reuse it for my robotics experiments. (link to images: imgur.com/a/Oj09tai)...
Since bone is piezoelectric, can I make a working oscillator from it?
I've wondered this occasionally over the years, but never got it working....
A nightlight with orientation control
So I wanted to design a children's toy, where the electronics could last 100 years (ignoring mechanical abuse). I figured some people here might be interested....
Transistor particle detector not functioning as expected (voltage.vn)
What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it)....