The standard countryside yokel reply when asked for directions applies, " Arrh, If you need to get to there, I wouldn't be starting from here".
For battery powered LED lighting - you shouldn't be using 12v LED strips. You should be using bare LEDs and a constant current supply. Converting cell voltage to 12v, only to use (probably) resistors to limit LED current isn't the way to go.
You will lose far more, efficiency wise, starting from there, than you are worrying about losing in the series or parallel considerations.
But then, you'd design the required power source and then the charger associated with it - not start with a charger, which then constrains your battery pack topology.
For this application you should be using a bench power supply with current limiting, not a "serial bulb" (I assume you mean a fuse, which is designed to break at a low current, however these are most typically rated for several amps, not typically in the mA range). You can set the voltage and a current limit. If the current goes beyond the limit, then the power supply will drop the voltage to keep the current below the limit or latch off. You can get a fairly cheap one for about $50-60 off of eBay, which won't be the best but is sufficient for hobby use
Hey, thanks for your reply. By serial bulb I mean a incandescent lamp in series with the circuit. I was looking for a cheap and diy option, but I'll take a look on a bench power supply. I still need to get me a decent one anyways.
Ah. It's not going to be possible to size it because the bulb is then acting as a resistor essentially. Unless you know what the equivalent resistance of the circuit you're testing is, and it draws a fixed current, you aren't going to be able to cap the current; Adding a resistor (or bulb) is just going to drop the input voltage and you will probably end up having other issues
It has the high current because it's cold, it only needs a short time to heat up and light up and the majority of circuits can handle very short overcurrent really well because the connections need to heat up before they break. Using a lightbulb for current limiting works pretty well.
The Internet corollary to Murphy's Law: If you post something, it's public forever unless you need it later, then it'll have link-rotted. Anything you want to delete will be archived, anything you want to save will be deleted.
My Electromagnetics is a bit rusty, apply a healthy measure of skepticism:
I’d say the two fuses are there to protect the transformer itself.
In the example you use, the upstream of the transformer would be protected by the 280V fuses but the transformer itself will have to suffer the overcurrent, and could be damaged by it. If the transformer is dipped in cooling oil, the overcurrent could even lead to an explosion.
As for the TUV inspection, the two fuses would be desirable for any TUV cert, and they would be required if there is any chance of explosion.
Definitely no chance of an explosion here. I’m not sure what the transformer is rated at off the top of my head but it is fused at 3A on the low voltage side and 2A on the high voltage side and I know it is rated for well over that. It’s a pretty beefy (5-10lb air cooled) transformer for the all of 0.5-1A it actually typically supplies on this machine.
I am actually leaning towards TUV being the explanation though because your comment just reminded me that we actually got dinged by them before on a different piece of equipment because we didn’t have fuses on the DC side of a DC power supply despite the AC side having a fairly restrictive fuse directly upstream of that power supply which should have prevented any catostrophic failure on its own. I’m willing to bet the rules are the same for transformers.
Honestly… I kinda think three microcontrollers is way overcomplicating things preemptively. I would try just a single MCU first, and see if the response time is adequate. If there’s any sort of noticeable input lag or delay, then try the multiple MCU route.
Unfortunately, the best method by far for identifying bad components is “have a spare you can try instead” or “take suspect parts and swap them into a known-good system.”
I.E. test your parts.
Memory and hard drive tests are the first thing you should run, for almost any problem, just because they’re so low-effort. Swap them into a separate system to test, if possible, and definitely make sure you’re running tests from a USB stick or CD-ROM, to help eliminate as many variables as you can.
PSU is a good bet after those, for intermittent problems, since the ENTIRE rest of the computer relies on it, and unreliable power can cause really weird and unpredictable failures. But there really isn’t much you can do to TEST a PSU without buying an electronic load tester that’s gonna cost you more than a new PSU itself. If you don’t have anyone to borrow from, a spare PSU is really a solid investment.
On the topic of lithium polymer charging, it has this to say:
Charge and discharge characteristics of Li-polymer are identical to other Li-ion systems and do not require a dedicated charger. Safety issues are also similar in that protection circuits are needed. Gas buildup during charge can cause some prismatic and pouch cells to swell, and equipment manufacturers must make allowances for expansion. Li-polymer in a foil package may be less durable than Li-ion in the cylindrical package.
However this is not a lithium polymer battery, and as it’s a 32700, it is not a prismatic or pouch cell either. It is a lithium iron phosphate (LiFePO4) cylindrical battery in metal housing. Battery University does have them listed in their table of chemistries (in case you’re curious), but they don’t seem to have much detailed information. Enough to build a charger though :)
Anyway, thanks for your reference in any case! I’m not responding to criticize you, only to improve the utility of this conversation in case someone else finds it on search :)
The flash chip is a common 16 MiB SPI NOR flash. An easy way to read or write it would be to use flashrom on a single board computer like a Raspberry Pi.
Unfortunately, that router is not supported by OpenWrt or DD-WRT, so you probably won’t be able to do much with it.
It’s probably not a good idea for actual use, but if you’d like to experiment: looks like the 3-pin devices U4 and U5 on the upper right provide feedback through the optocouplers next to the class Y cap north of the transformer. I bet those are LM431 voltage references (or similar). The passives around them provide filtering, but two of the resistors should form a resistor divider for the Ref pin (lower right pin if the single pin is on top). That divider sets the voltage.
Thanks. I ordered the 24V model in hopes of adjusting it down to 22V. I will use that to keep a 7s Li-Ion battery at a minimum charge level whereas a solar panel array may increase that voltage higher. It looks like the 24V model’s capacitors need to be changed as well since they can’t handle the Li-Ion batterys’ max charge voltage.
Don’t think I can solder on plastic, plus it would create new thickness and I don’t think that would help some sandwiched membranes, but I’m going for double sided copper tape, that should help I hope.
Theres plenty of smaller, lower volume silicon fabs doing larger scale work, like Cmos 1micron and some doing sub micron down to what was cutting edge ~15 years ago.
Honetly kinda crazy that only one manufacturer can do the current modern stuff, but barely anything other than high end CPU need to be that small.
Perhaps slightly adjust your logic a little and see what it does.
Read from the sensors first, then enable and connect to wifi, send the data, then disconnect. That would reduce the maximum power draw as only one function is active at once.
Small edit: I have a MagTag ESP32 board with circuitpython that can’t read onewire devices while the wifi is active. Whether that’s because of supply instabilities when wifi is transmitting, or interrupt conflicts, or just plain poor programming in the onewire drivers or the wifi drivers, I don’t know. But reading the devices first and then connecting to wifi and sending the data afterwards works.
Hmm I’m not sure of the pin drive currents on the Pico, but can you power the sensors off a pin? At least then you can programmatically power cycle them if you need to.
The Pico also has a watchdog, you could set it up to give it a reboot if things don’t respond in time. It doesn’t solve the issues of course but at least it gets it back to a workable state. And if the watchdog fails, or it works but there’s still no USB serial, then that would point towards power instabilities or somesuch.
can you power the sensors off a pin? At least then you can programmatically power cycle them if you need to.
Not really, at least I wouldn’t really know how. The sensor needs +3V, GND and two data pins, and the pico only has one 3V out, that seems to connect directly to the voltage regulator. I guess, I could try to use a GPIO pin as a switchable 3V out, but that seems rather hacky.
The Pico also has a watchdog, you could set it up to give it a reboot if things don’t respond in time. It doesn’t solve the issues of course but at least it gets it back to a workable state
Unfortunately, a simple machine.reset() seems not to be enough. I didn’t use “real” watchdogs, but what a Java dev knows: try/catch. I wrapped the entire loop in a try/except block and simply call machine.reset() if something goes wrong. That does work sometimes, but not always. Of course the possibilities are a) some exception isn’t getting caught b) there is some electronic issue, maybe the SPI interface to the DHT is “stuck” or not properly reset. I can resolve the problems by completely disconnecting the device for a while from power.
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