Why not just connect all the resistors together with one straight trace, and put on trace between that and the cap. They’ll save copper and make the board cheaper.
I know of no PCB fab house that prices production on how much copper is etched out of the foil (even though they recycle the dissolved copper afterwards). On the contrary, i usually got the advice of leaving as much copper on the board as I could, as it makes their life easier (and balancing becomes very easy).
Would they really? I made only one PCB so far, but there your price was independent of design. I also don’t think they save a significant amount of copper either way. Would they notice at all? When you etch away the copper from your PCB you would need to measure how much copper your etchant took in and I would imagine that’s not worth the effort. Feel free to correct me if I’m wrong though.
Seems your linked website as a very believable conclusion attached to it. I have a similar issue where the relay module would behave erratically. In my case it was when the relay module/595 chips received power before the Arduino was fully powered up. It’s unlikely that a load affects your relay module as they should never be connected to the main circuit.
I guess something like a pulldown resistor on the SER, CLK and RCLK pins would solve the issue since that would kill any noise. The noise is probably the kind of voltage that BARELY registers as HIGH but highly random.
That or making the relay module only turn on after the microcontroller has finished starting up using a mosfet or something.
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’m puzzled - you describe wanting to add a headphone jack (eg an output jack socket into which headphones can be plugged) - yet you seem to actually want a socket that provides auxiliary input.
However, if you are indeed trying to add external input and are disconnecting the inputs to an amplifier - you might want to tie those disconnected inputs to ground.
My bad - yes I mean an AUX input I thought I would’ve needed to ground the unused lines (not sure if I should connect to ground directly or with a resistor) - you think that could be the cause of the whine? The whine comes from the front speakers too. And I really can’t understand how and why I can still get some signal from the stereo…
It’s usually a good idea to look at what’s normally connected, when breaking a circuit, and replicate that. Which I seem to remember is a 10k resistor with a parallel capacitor (being too lazy to go back and look again). You could try the same combination, in place of the added input cable, on the lines that you plan to use and see if it whines. If not, add the cable(s) and try again. That may stop it happening on all channels.
There are two muting methods - open circuit the input (via a switch or a gate) - in which case there will probably still be some signal transfer through capacitive coupling - especially if the amp side of the open circuit is high gain. Or short the signal path to ground - and that short will have some impedance and thus the signal is only attenuated and not removed all together.
Turning the amp gain to far higher than it ever would be in practice is hardly a fair test. There aren’t many amps that will be noise free under those conditions - and, in this case, there will be a signal to amplify, albeit highly attenuated.
It’s good to be cautious - cascade failure can be waiting to bite. Never direct connect unless unavoidable - add a series capacitor, if you can. Yes, not usually a good idea to provide a dc path unless essential and, even then, current limit it if possible.
It’s usually a good idea to look at what’s normally connected, when breaking a circuit, and replicate that. Which I seem to remember is a 10k resistor with a parallel capacitor (being too lazy to go back and look again).
There’s a resistor, then parallel capacitor and resistor to ground, and finally a capacitor to the amp. I could try replicating the parallel pair if that could help
add a series capacitor, if you can.
Would that be a polarised capacitor for protection? And on both the original and my added lines?
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.
the first thing i'd do is connect the GND from your arduino and from your power supply. At the moment there does not seem to be a common ground or it is off picture.
The circuit works when there is a common ground (makes sense ofc but originally I thought they had to be separate), I didn’t want to put 5V and 12V on the same rail of the breadboard. Now what I find strange is that even without the 5V input voltage, I still get 10V at the output of the Op-amp which is very confusing.
You want hysteresis and an energy gap - which means putting energy into the system. You could use a latching relay to minimise insertion loss, however the loss in a conducting MOSFET can be pretty minimal.
SLAs self-discharge, of course.
If the load versus time is predictable, you could use a latching relay and delay voltage checking until the time window for potential cut-off. Or make it entirely period based and not test at all.
It may be that you never need to sense voltage, if your time period between recharging is small enough.
Many operate on that basis - the time interval between recharging may be out of their control (in our case, once, we only had mains electricity between 2am and 4 am each day…) and they provide themselves with enough battery capacity to last that time interval, with a reserve. So no low voltage cut off necessary. So no testing necessary.
If I was to guess I’d say the purpose is to establish familiarity… assuming this community migrated during the great reddit migration… also i think it looks cool so…
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.
That doesn’t actually mean it’s OK, there are cases where transistors and other descrete components are “semi-burnt” (tests check out, yet it doesn’t work or doesn’t work as it should). The ”not so reliable" test would be to use a multimeter and see the voltage drop between B-E and B-C. The definitive test would be to make an actual amplifier circut, use the transistor in it and see if it works and if it distorts the sound (there are also cases where the PN substrates are somewhat depleted or damaged, either through use or a manufacturing error, so it works, but distorts the signal).
Do the light test, see if that passes, then do the multimeter test, see if that passes as well. If they both check out, 99% chance the transistor is OK. That 1% can be eliminated with the test circuit amp test.
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.
Hm… don’t know why that happens, never made a particle detector, but I have modded TO-3 cased transistors to be photodectors, they usually worked great.
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.
Even on the equipment where you do get a graph of efficiency vs load, the line usually only starts at 10% load - that’s where your 70% efficiency figure is for.
As noted, at 0% load efficiency is by definition 0%.
In addition to the voltages being different between real-RS232 and "TTL"-serial, they're also swapped. On a DB9 you probably have something approximating RS232, where mark=-9V and space=+9V, but the debug header is likely mark=+3V and space=0V. So even if your inputs can handle a wide voltage range, the sense is inverted, which is why you'll get garble.
(For example, when the line is idle it's at the 'mark' voltage and the receiver knows a character is incoming when it transitions to 'space' for one period (the start-bit). If mark and space are swapped, the receiver will see 'space' most of the time and only detect a character starting when there are some 'mark' bits in the middle of a transmitted character. It'll never actually synchronize correctly with the transmitter.)
You can figure out what you've got with a multimeter and checking what the voltage is on the TX pin when it's idle.
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