Close; as it turns out, it is a snubber resistor :)
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- 3 yr. ago
Thank you very much for your detailled answer, this resolves my question and I can sleep peacefully again :) The device is also fixed; as I wrote in response to BigDanishGuy, the problem was caused by a connected pressure switch. The circuit board seems to have no issue at all.
I solved it, thanks for your help :)
The relay winding is powered directly by the mains and current can only be interrupted by the main power switch and one of the two pressure switches. As there was electrolyte in the connecting gas line when I got the device, I'm suspecting the switch is damaged and doesn't have enough hysteresis anymore, causing the rapid switching.
- The heatsink is for a triac doing phase angle control. The second pressure switch is supposed to be set to a lower pressure and if it closes, it inhibits the phase angle control, stopping gas production. The problematic pressure switch seems to be just a redunandancy that removes power from the entire circuit using the relay.
- As I found out, "manually affecting the circuit driving the relay" is just operating the main power switch, and that works without any issues.
- There is no discrete transistor in the circuit :)
My solution was to move the set points of the two pressure switches further apart (there are screws on them for that), so the switch inhibiting the triac triggers first again.
Thanks for your tips :) I already finished drawing the schematic, this resistor was the last part I hadn't clearly identified. Now I just need to understand it :D
I don't know how serious your project is and how much reliability and predictability you need; but regarding
I would need a 2-300ohm resistor in series to protect the microcontroller
I will just say: I have yet to kill an AVR.
I haven't used any gate drivers yet, but I remember an introductory video about MOSFET control that helped me a lot, and at about 7:40 he shows his go-to setup.
And again, I don't know your requirements, but my default logic level MOSFET is the SI2302. It's available from a bunch of different manufacturers, has a threshold voltage less than 1V and can conduct several amps continuously.
I have no clue about wireless earbuds in particular, so I won't be of help with question 1.
But I could give you some general remote help. I don't know how successful that will be with probably limited tools and documention, but I'm willing to try :D
Is this a thing? Have you encountered resistors with 5 color bands without a multiplier?
With all other resistors on the board, my measurements match the color code. This one is the only exception.
I don't know what you mean with high value though, 151 is not really close to an open circuit :/
As stated I measured; the question is how and why the measurement is so far off from the encoded resistance, and why those values are so strange no matter how I read them.
Broken solder joints is a very good idea, thank you. I already found one earlier, but I haven't resoldered them all yet.
The relay is not performing as intended. The circuit board is controlling an electrolysis reactor which works fine until apparently the pressure switch decides the H2/O2 pressure is high enough and it tries to turn the reactor off. At that point the relay goes brrr, switching on and off very fast, producing a lot of sparks, and it stops when the fuse blows. Deactivating the pressure switch "fixes" the problem, but that is dangerous in itself.
Ask Electronics @discuss.tchncs.de Resistor Identification
The horizontal bar is commonly used to indicate ground, meaning the part of your circuit you define to be at 0V. So they are all connected, yes.
I've never seen a capacitor symbol with a dot until now. I only know them on transformer symbols where they are used to denote polarity.
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For a moment I was so confused as to why the European Space Agency is attacking Minecraft servers.
I can highly recommend surgical scalpels to work on PCBs. It also sounds like the shorting of the two pads only has to happen once to flash the firmware, so maybe you could use one of those cheap needle probes to temporarily get contact with the via under the ripped off pad.
They are only a solution if you use a gate voltage higher than 5V, in which case NPN would probably also work. Try to use maybe 6V or 7V to control the NPN base and see if that improves your situation. But as that voltage is impractical to get from the Arduino outputs, PNP/PMOS would be another solution.
Edit: If I understand your issue correctly, then your choice of transistor is not the problem. The problem is that you are forcing them to be less conductive than they could. If a p and an n doped region touch, they form a diode. In an NPN transistor, you therefore have a diode between base and emitter, which is also indicated by the arrow in the transistor symbol. A silicon diode drops around 0.7V, and because its steep I/V curve, that's more or less independent of the current passing through it. When you apply 5V to the base (ignoring the small drop over the base resistor), you're forcing the emitter to sit at around 4.3V. But that would not be possible if the transistor was fully conductive, because that then the emitter would be shorted to the collector sitting at 5V. The transistor has no choice but to increase its resistance between collector and emitter in such a way that it also drops 0.7V there, ultimately limiting current through your laser. The same would happen with a FET, just that the voltage drop between source and drain would be determined by its threshold voltage, not the 0.7V diode drop of the NPN.
The Arduino Nano uses 5V logic, so PNP/PMOS should work.
I don't know much about lasers. Also, I don't entirely understand your schematic. What is connected to J5 and J6?
That being said, my first thought is: Why you are using an NPN transistor for high-side switching? I would try switching it out for a PNP. If that still does not work, then a p-channel MOSFET. There are more than enough FETs btw that don't need any external driver for use with an Arduino, or even with 3.3V systems.
You make a copy of the code ("fork") for yourself, make edits, then request that your changes be accepted into the original project ("pull/merge request"). Someone from the project has to check the edits, make that decision and hit accept or decline.
I duckduckgoed "SOT23-6 boost converter" and found a picture of an IC with similar markings - I'm now pretty sure the component is an FP6291 switching regulator by Advanced Analog Electronics.
If you look on page 3 of the datasheet, the "AL" identifies the part, and the following numbers are the year of production and the wafer lot number, so they could really be anything. The pinout matches as well, given a few inaccuracies in your schematic, which I think I can confirm on the images. Thanks for the image of the PCB against the light, that was very helpful.
Pin 1 would be on the bottom right, connected to the inductor L1 to boost the voltage, with the other pins arranged counter-clockwise. Pin 2 should then be connected to your PCB ground; to confirm, you could use a multimeter in continuity mode to measure to the BAT- and 5- connections. The right side of R4 should also be connected to ground, and 24 kΩ would set the current limit of the IC to 2A (page 7). On pin three is one of the mistakes in your schematic as far as I can tell, I think that pin is really connected to the point between R6 and R5, for output voltage feedback. I also think R6 is meant to read "84D", which would be the resistor code for 732 kΩ with 1% tolerance. If you calculate the output voltage of the regulator with the 0.6V feedback voltage from the datasheet and 732k/100k resistors, it comes out to 4.99V, which would be compatible with the USB 5+/5- stuff. Connecting EN to VCC (pin 4 to 5) is also common to permanently enable an IC, but I think there's another error in your schematic: I'm pretty sure those two pins are directly connected to BAT+ instead of through C4, and that C4 instead connects from those two pins to ground to stabilize the input voltage.
Edit: Would you post of link to the product on AliExpress? I'm interested now :D
There's no way U1 is charging the battery. How would it? If the connection labeled USB is the power source, it's only connection to U1 is through a 100k resistor and a reverse biased diode. Also, charging AA batteries? Sure, you could plug in some NiMH cells, but then the device would need to have explicit instructions telling you that this is indeed a charger and to only ever insert rechargable AA battery cells.
If you desolder U1, you should drop about 0.5V of your battery voltage across D1 and maybe the remaining 2.5V will be enough for the other components to do something, but I doubt they will be very effective in whatever their purpose is.
Stargate @lemmy.world Fresh Import From Chulak
Thank you very much :) If you already were aware of the exception for resistors with gold/silver in the fourth band that MrOtingocni mentioned, where have you encountered that before?