There are simple testers like this. It’s rather overpriced for what it is, but it would be trivial to make one yourself. That will only do a continuity check though. If you want to know what the current or speed ratings are, you will need to read the chip in the cable.
Just based on my experience and knowledge of these batteries, which is not that much really, don’t take any of this as gospel.
Constant voltage current-limited power supply is probably the easiest way to charge it, a regulator + current limited supply like you mention would be one way of achieving that, will waste a lot of the power and charging speed will be limited by how much heat the regulator is able to dump (which for a typical TO-220 regulator without heatsink is like a watt or two? So you’d have a max charge current of like 0.5-1.0 amp)
Your current approach probably also works just fine, but i’m not sure how good it is for the batteries in the long run
You can find charger for sale online though, at least modules that you can solder up to a battery holder or whatever, i would go for one of those if you plan to use these batteries for a longer period of time
I’d order online if there was a LiFePO4 charger on the market. However, in my country I’ve been unable to find one, and importing (excise & duties, paperwork) is more work than building it myself. I’ll also likely need a design that I can cheaply include on custom PCBs for manufacture (not for sale to end-users, but for internal use by maintenance technicians).
I gave it a test on a cell today and it seems to charge fine and at a reasonable rate – but in a sudden flash of brilliance, I forgot to physically connect the ADC pin to the battery, so it couldn’t shut off. Well, that’s what testing is for I guess.
Anyway after fixing this, it looks like I can call this a win and move on. If it undergoes destructive optimization, I’ll report back here with a warning to others.
There are really charging curves that should be followed to avoid damaging the cells.
You want to charge up to a certain voltage at a current (related to the battery capacity I believe) and when the cutoff voltage is hit, you switch to constant voltage (the max voltage of the cell) and then slowly drop the amperage as the battery is topped off.
I’m not sure about your cells, but some LiFe are 95-98% full at 3.45-3.5 volts, but the problem is that the voltage curve is really flat from 40-50% charged up to 95%. So you need really accurate measurement if you want to charge to 95%. The last 3-5% is when the battery ramps up to 3.65v and really is the riskiest part of the charge. It’s also the highest wear part of the battery use, if you can avoid charging it all the way up to that your cells will last much longer.
My normal lithium battery charger automatically slows its charging speed as battery voltage nears its capacity. I could set it at 1000mah and it will step down to less than 1/10 of that before charging is complete.
It’s just that it’s really tricky to charge the final bit because the middle 80% is such a flat voltage curve. They have a 1000x life when they’re taken care of.
It’s tricky to stop at the right point, because lithium iron only have a very small voltage increase between like 40% and 90% and they ramp up to full voltage right near the limit of their capacity.
What you are talking about is nothing special at all and not following a charging curve. The curve automatically looks the way it does when charging CCCV. Constant Current -> Constant Voltage.
The Original Saleae logic analyzer (or one of its clones -> search for “Compatible Saleae”) or a LA104 (maybe with custom firmware) or maybe a DSlogic pro or ChronoVu. You can also browse the HackADay Archive to find an analyzer that suits your needs (e.g. build your own, or based on a pico). It all depends on the resolution/speed you need and usecase.
USB isolator, $10 saleae clone and sigrok/pulseview setup is very simple and cheap (except for the isolator).
These LEDs are not shift registers. In fact, if you look closely, there’s no input and output pin, only one data line. That’s because each LED in this strand is pre-addressed from 0 to 100. Whenever it receives the NeoPixel data, it picks out the n’th color data (matching to its pre-address) and displays that. You cannot change the pre-address, its fixed permanently - or at least, we have no idea how to re-address it.
Yes, I read that bit. I’m trying to find out more.
They are obviously made in bulk, somewhere in china, since they are quite common, and cheap. Unfortunately, I’ve only found them in pre-built products, and none actually identify the chip model.
They obviously can be programmed (at least once) since you can buy arrays of at least 400. There is no way a factory is making 400 different chips, given the end price.
If your coil was oscillating, then perhaps an iron core moving through it would cause perturbations which are detectable. But that would require extra logic to compare the expected oscillation frequency with what the coil is actually oscillating at.
Since you say that tilt switches are not an option – for reasons I’m not entirely sure I understand – another option is to have a linear Hall effect sensor mounted nearby a small magnet. If the magnet moves relative to the sensor, then that is a change which can be acted upon. A linear sensor makes it possible to use a trim pot to tune the sensitivity.
i failed to mention the most important aspect of the project: (near) zero power consumption when idle.
it is a vacuum (that kinda looks like r2d2) that i want to play some r2d2 noises when used.
it is hauled around on a construction site on the scaffolding and wont be in an upright position while idle or in usage, so tilt switches didnt make sense to me.
i plan to run it from a coincell or maybe 2 aa, but it should only draw power when the sensor is triggered so the power should last years if i understood the 555 timer correctly. that means accelerometers and linear hall effect sensors are out too due to microcontrollers and thus power draw.
somebody else mentioned vibration sensors (SW-18010) that look promising.
Soooo turns out mouser had a classical unit conversion error so they wrote 28 times as much airflow than there actually is in the fan specs so im not going to use fans in my flashlight as 2 watts of cooling matters so little that if i just use convection it would cool more.
These seem good and mouser has ip58 ones which are perfect for me. Maybe ill use two of them for example. But im ordering a few because if they dont work im gonna abandon the fan idea. Still cool fans. As for heatsinks the whole flashlight is one. Its a really high power, small flashlight(hotrod). It uses two 14500 lithium cells(basically aa size) to power a boost converter with more than 70 watts. Even tho the boost converter is really efficient the leds produce so much heat that the light overheats in seconds. So thats why i want to test if fans help.
Yeah but its still months from completion. I want to machine it from aluminium but im explorimg all possibilites before i start ordering parts/writing software. When i learn to use github im gonna upload all the files with a permissive license because i want to contribute to the flashlight community.
In seconds? Wow. I think you’re right, you might need more than a small fan!
It might be worth exploring heat pipes or peltier effect coolers. The latter makes the problem worse (they are inefficient and generate a lot of heat) but your LED can be locally cooler if you can e.g. move all that extra heat into a big heatsink (also condensation can be problematic).
One cheap source of heat pipes for testing could be old graphics cards – they often outperform simple copper heat sinks. Use thermal epoxy to stick your LED to it and see if the performance is acceptable. On the exotic end of things, you could also water/oil cool it, or (carefully) make your own thermal grease from industrial diamond powder for a small boost in thermal conductivity.
Also even at 95% efficiency, it sounds like your boost converter has some heat to dump too!
Yeah the problem is the light makes so much heat(the boost as well) that i cant dump it into the air with high enough efficiency. The bodys going to be aluminium and the pcb copper.
Hm, that reminds me! If you’re designing your own PCB, some manufacturers will make the PCB out of aluminum for you instead of FR4. This is commonly used for high-intensity LED lights to help keep them cool.
Here’s some random info about them so you can see what I mean:
I was already planning to use a copper core pcb. This is pretty common among insanely powerfull lights. The flashlight community has some great examples. But most of these lights use resistor based voltage regulators which waste a lot of energy in the form of heat so im trying to improve on the traditional design.
I figured you already had some type of adapter already. Either the one you linked, or the DC connection from the printer. If that’s the case, then it’s ridiculously easy to do a DC to DC adapter. If you do not have a DC supply and just need a 24v power supply, splurge on something like this.
Honestly you’d probably be fine with your original idea. But, that means you can’t charge your laptop while printing and, the 24v power supply I linked to is cheaper than your original idea.
Disclaimer: not at all an expert on this, this is just my thoughts based on what i’ve heard, please correct me if i’m wrong
Normal power supplies are CV, so you don’t have to worry too much about that, CC supplies are a bit more niche
If you want to be able to run the amps at full power, you’ll have to add up all their rated powers and find a psu that is rated for that, it could also be wise to go with one slightly larger as well, as power supplies tend to get a bit noisy when they’re close to the limit (the voltage they give out gets noisy that is) which reduces the audio quality
what are the input for the amps? You say they have built in rectifiers and everything? Can they be aupplied by mains directly? What is the max input voltage?
Do you have a multimeter? Or other way of gauging the resistance of the new traces?
I don’t know the specific product you’ve used, and my experience with conductive paints and glues is almost nonexistent. But what I remember is that it was neither useful as a glue or a conductor. So I suspect that the resistance of the trace is too great to be used for traces going into the 100s of mm.
If my suspicion is correct, then maybe you can fix it by using the paint to attach something with little resistance in parallel to the paint traces. Maybe stripping a multicore wire and using a single strand of copper, lay it down on the trace and paint over it? Or cutting the traces out of tinfoil and gluing them down to the existing traces with some of the paint?
I don’t have any improvements to offer but I want to mention that I saw a crazy video that used a circuit breaker as a spot welding device. The concept is pretty much right and it is as cheap as it can gets, but it is electroboom kind of crazy and the guy even hurt himself on camera while using it.
He burnt himself off a 12v battery. Increase the voltage by the amount you want to live dangerously at the benefit of getting better weld. It also suggests using two MCBs in series in case one of them does not trip for any reason.
I would make sure the solder connection between wire and resistor is very solid, and then encase the stuff in heat shrink tubing with glue in it. (Adhesive Lined Heat Shrink Tubing)
Are the changes in pitch alone, or does the amplitude change as well?
What happens if you set the frequency to something extremely low? I know that 50Hz is unusable, it will flicker, but does something still hum at 50Hz? What about if you increase the frequency in steps until you approach 200Hz?
Your multimeter couldn’t measure anything when you went to 25kHz? That may be an issue of the microcontroller not supplying enough current to charge the gate capacitance on the mosfet in time, or not drain it fast enough to turn it off. If you disconnect the esp from the rest of the circuit, can you measure something then?
If yes, then you’ll want to use a push pull pair for driving the mosfet. Or get a mosfet driver, but a bc547/bc549 pair and a bit of passives will be fine, available in through hole, and considerably cheaper.
If no, then either the esp can’t go that fast in this implementation (was it a software PWM?) or your multimeter doesn’t work in that range.
Interesting suggestions, I would not have tried such low frequencies except based on your suggestion and it turns out that going very low, below 1000Hz and even down to 100Hz causes the power supply whine to almost entirely go away. I also have a 470uF capacitor in between the power rails now too.
This range is a usable - there is no visible flickering even at very low duty cycles.
From what I understand in the reference guides the LEDC library attaches directly to the 80mhz or 40mhz esp32 hardware clock for PWM. Intuitively I’d have guessed that higher frequency would always mean less discernable audible feedback, but seems not in this case.
This range is a usable - there is no visible flickering even at very low duty cycles.
Before deciding on the frequency, and then mounting the strip in a position where the LEDs are directly observable, you should try moving the LEDs fast relative to your eyes. Eg. take the end of the strip and wave it from side to side. You may notice flicker at frequencies below 200Hz.
Ok, good thinking. I settled on 1000Hz and also made it something in remotely reconfigure should the need arise. That combined with the other suggestions, and getting a better power supply has made the system whisper quiet now.
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