Word came down from on high, that I wasn’t to use 60/40 for teaching anymore. Usually went through about 1kg annually, and I had just stocked up. I think I had just gotten 8kg, or something like that, because of the bulk rebate, about a year before. And what was I to do? We weren’t allowed to have the solder on premises anymore.
So anyway, 60/40 for 1.0 and 0.7mm and some sn/pb/ag for 0.25mm. And no, I don’t have ventilation for my workspace, but I do have enough solder to last a couple of lifetimes.
What do you actually need? 1 microsecond with “decent bit” is not exactly a lot of information. An oscilloscope would fit that perfectly. How do they not work how you want them to? Who told you that you need something else?
Don’t charge LFP to 4.2 volt! The crude “check voltage and if below 3.6 V keep charging” is okay too as long as the maximum current is within battery spec. But measure while charging, don’t turn that off to measure the open circuit voltage.
An international parts order is too complex for such a small thing. I’m not in the USA or China. So no TP5000 for me, got to work with what I have.
I agree, no charging at 4.2 volts. The current charger I built seems to work well enough. I ran some tests and it charges within spec. The reason I turn off the charger to measure cell voltage is because otherwise I’ll mainly be measuring SMPS noise.
Anyway it beats the charger available in the local market, which is clearly unsafe, no matter how much they assure me that it’s ‘totally OK’.
Yes, in the sense that I’d expect it to use less power than in incandescent when lit and no more than a few watts when “off,” but I figure any kind of LED I could put in it and any sort of controller short of shoving in a full-blown Raspberry Pi 5 would be able to manage that.
Replacing the linear elements with switchers means more noise in the power lines. How much more, and whether it’s noticeable or tolerable will be down to you.
The linear regulators are still there. It’s the rectifier that gets replaced. I guess the main difference in the power side is the high frequency noise of the switching PSUs vs the low frequency ripple of the rectifier, I’m not 100% sure if 7x12s are immune to them at least at audio frequencies.
It’s great to see you exploring different platforms for your electronics inquiries! Regarding your setup with the variable boost converter, 18650 batteries, and the 12V LED strip, your analysis is on the right track.
The boost converter indeed stabilizes the output at 12V irrespective of the input voltage. In your scenarios, both setups - series and parallel configurations of the 18650 batteries - should effectively power the LEDs at 12V through the boost converter.
Your assumption about the parallel circuit draining faster than the series circuit due to the boost converter’s behavior is accurate. Since the parallel circuit offers half the voltage but doubles the current capacity, it will indeed discharge quicker compared to the series circuit.
Concerning the choice between parallel and series setups, there are trade-offs. The series circuit might experience fewer losses through the boost circuit due to its higher efficiency with higher input voltages, potentially reducing heating issues. However, as you mentioned, charging cells in series isn’t feasible with your TP4056 board, limiting your option to the parallel configuration.
Given your charging constraints, sticking to the parallel configuration seems more practical for recharging purposes. While it may drain faster, using the parallel setup is compatible with your charging board and allows for easier recharging.
I noticed your edit about the TP4056 board being compatible only with parallel charging, which aligns with your previous discovery. It’s a crucial factor to consider in maintaining the functionality and longevity of your battery setup.
If you want more insights on the efficiency differences or additional alternatives for charging in series, I have an informative post on converter types that delves into various setups and charging considerations, which might offer further clarification for your project.
Feel free to explore and let me know if there’s anything specific you’d like to dive deeper into!
If that’s not sensitive enough, another option is using a piezo element coupled to the case to detect vibration, with an op-amp or hex inverter to buffer + trigger the 555. However if you couple it too closely with e.g. the floor or furniture it will pick up nearby footsteps or cars. Might be good depending on the situation.
Are we talking a handheld flashlight? Or is it something a bit more hefty?
Reason I’m asking is the bearings in the fan and motors. A handheld flashlight is going to take a beating, and the bearings can easily be knocked out of alignment.
Replying to myself for informational reason. Modifying voltage was more or less successful. Both optocouplers transmit a reference voltage, so both need to be adjusted simultaneously.
This can be done by changing the value of R19, a 23.2k smd resistor close to the output terminals.
I’ve attached a 10k pot with a 10k and 6.8k resistor in series and successfully modified the voltage down to 22.5.
The power supply itself is a piece of crap though. It claims to handle 400W but anything over 150W causes the short circuit protection to activate, never mind overheating at 150W very quickly.
Are you able to measure the input current during a weld?
I suspect you might not have enough copper in the secondary. Fully insulated wires take up a lot of space; there’s a reason magnet wire is commonly used. Several parallel turns of e.g. 6mm^2 magnet wire would be preferable.
Your SSR generally should be in the phase, not the neutral.
I went down this road just as you. I found out that most MOTs are rather weak for 18650 nickel strips.
You need a transformer rated around 1500 watts. Most are 700-900 watts. I ended up wiring 2 transformers in parallel. Also, make sure to remove the transformer’s shunts. They are a form of current limiting and will impact your amps at the end.
Finally, make sure to carefully regulate your pressure with the copper tips. High pressure does indeed equal a weaker weld.
AC in general is also not the best for very short pulses of welds. I have found that 40-60ms work best for 0.2 with around 1000amps. Anything less didn’t weld tbh and the MOT couldn’t pull amps fast enough. I tried all sorts of windings and cable thicknesses. I finally chose 6AWG and I’m happy enough with 2 transformers.
Yeah don’t worry about it. Running a fan at a lower voltage than it’s meant for will result in slower fan speeds and a longer lifetime. Compared to the wattage an actual laptop will draw this is absolutely nothing. I power my soldering iron with an old laptop charger without issues.
Those plugs are generally used in 12V systems but they can handle higher voltages too. It’s the current you need to be mindful of for the most part, they can overheat if you try to power a space heater or something from that but a few fans won’t cause any issues.
Those adapters should definitely be fine for 24 V. Running the fans off 19 V will probably work, but they will run at slightly slower RPM (probably not a big problem for a filter).
Acording to the datasheet the TDA7294 uses -Vs and +Vs in the block diagram so i would assume it is intended to be used with DC power. If the module is specced for use with AC as well as DC, then this just means what you already suspected: it has an integrated bridge rectifier and most likely some sort of low pass for the rectified power (read: a bunch of big capacitors).
You could just go with a big transformer core that powers them all at the same time; many commercial amps do that and it works fine in general, provided you have enough margin for power spikes and the modules will not influence each other when connected in parallel to power.
In my opinion using separate transformers would be paranoid but it would work of course.
Edit: dont forget that this thing will produce heat. If you really go with an 800W transformer then you have to be able to cool about 400W in the worst case (going by the data sheet power dissipation of the chip and assumed transformer + rectifier efficiency of 90%).
which current and voltage do the LED strips need (5V, 2A would be something you could support with USB 2).
what output does the charger provide as a maximum? Is it enough to power both strips (5V and two times the A).
If these match it should work. Another topic could be the cable itself. Theoretically it could start to burn, if you try to channel to much current through it, but with simple USB I doubt it. If it is getting hot after some time, scrap your setup. This would be a fire hazard.
Fire hazard? Not really. The charger will not provide more than 5 V, 3.1 A or whatever its rating is. Even if the strip fails short circuit (unlikely, most LEDs blow open and there is at least a resistor in series anyway), nothing will receive more than 15 W of power. A 1m cable can safely dissipate that.
Worst case scenario, an LED fails short and its series resistor will receive over 6x its intended power (with 5 V across it instead of 2 V, and its current will increase correspondingly). It is soldered on power-dissipating flexible PCB and will probably not blow open. It will get the area somewhat hot and potentially melt the plastic in the back of the monitor while the rest of the strip keeps glowing but more dimly. Hard to tell if it could get over flammable temperatures with moderate heatsinking and only a few watts of power.
To keep safe, I would deliberately add resistance before the LED strip, using something like a 1Ω 5W resistor (or a shitty long cable). That way, the voltage drops significantly in case of a short. Also, the LEDs will run at lower-than-intended current, which prolongs their life and decreases risk of failure.
Edit: Some microwaves have a 0.8Ω 25W resistor as part of inrush, at least in 230V regions. Feel free to use that, it will happily handle a semi-short circuit. Or you know, an automotive fuse.
The safest option is replacing the whole setup with an LED strip that has no resistors (bare LEDs) and a constant current driver.
The LED strips use SMD 3528 LEDs which need 5V and the wattage is listed at 11.52W/min. The amperage isn’t listed but for those LEDs, I’m seeing 5Ah online. The charger provides 40W
You’re confused. W/m means watts per meter, and the “5Ah” is probably actually 5 A, or the current you can push through the strip (limiting the length to below 2 m).
Watts in a resistive example like yours is Volts x Amps. I would have been able to much better answer this question a year ago so forgive me if I’m misremembering the specs but I’ll answer since nobody else has. Two things that suggest to me this might be a bad idea:
Charger is 40W, that’s probably usb PD (I don’t know anything about QC so maybe I’m wrong). PD supplies more than 15W (5V x 3A) by stepping up the voltage, not the amperage. While stepping up either would likely be bad or very bad for some part of your circuit, don’t worry about that though; without the powered device telling it to, PD won’t activate. It should max out at 15W… I think. It depends on the resistance on the CC lines and using a splitter could screw up the resistance that tells the power supply which USB version to support so it can go up to 3A (15W). Sorry, it’s been a while since I’ve worked with USB power. 2 strips of 11W will need more power than that. Basically my concern is you won’t get adequate power out of the charger for one reason or another.
Where are you getting the 11.52W/min number? Watts don’t have a time unit and that much precision sketches me out. Almost as if someone who isn’t adequately educated measured the power straight off a multimeter once and just wrote that on a product page. Is the LED strip from a reputable manufacturer?
He meant watts per meter, not minute – the strips can be cut and rejoined. As for the 5 Ah, no clue.
The circumference of a monitor is more than 1 m, so a charger of 3 A at least will be necessary for each. This is why I prefer higher-voltage strips where less current is required and higher resistance is tolerable. Anyway, the power is quite high and this could cause overheating problems.
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