The pin is recessed and about 1mm in diameter - which seems impossibly small for 6.67A.
Because it doesn’t carry 6.67A. What you have there is a laptop power supply, probably an HP or Dell one. The current is carried on the inner and outer sleeve of the barrel. The centre pin only carries communication signals.
But you are correct - there does seem to be a recessed metal inner sleeve. I had looked for one, but couldn’t see one - tried again after your post (with a brighter light!)
I still need a chassis mount socket for it, though…
There is a 12v car lead - which makes me wonder if that centre pin is actually used at all…
I guess you could check if it’s a physical fit for an HP (or Dell or Samsung) one and then go to ebay or aliexpress and buy a corresponding “laptop charger socket”. Though they’re all board mount. I don’t know if any panel mount ones even exist.
Thanks for the suggestion - I think that there are inline adapters to a different plug, but finding a different coaxial plug that will handle that current could prove challenging.
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?
Ideally the logo should be something simple, because it gets displayed in many different places and usually pretty small. ~500x500px should be enough, and the main content should be inside a circle, because the corners are often not displayed.
A more detailed artwork is better for the bigger banner. Most communities seem to use something around 2000x1000px or so.
I would try and find a pinout for the specific battery. The connections will include V+ and V- and then some others like batt temp, and some other diagnostics stuff. I'm not intimately familiar with newer phone batteries, you may or may not be able to get the battery to charge if you dont have the right circuitry
Not entirely sure, but maybe these help you somehow:
The relay has a coil which requires 0.35W. The chip seems to have a maximum output current of 35mA.
The ‚switch on current‘ of an inductive load is usually 3 to 5 times higher than the ‚hold‘ current.
The valve may not have a free-wheeling-diode. This could create an issue by creating strange voltage spikes on all your supply voltages (connected by GND).
Yeah, decoupling cap here might as well just help OP fry the chip more effectively by ensuring it can sink all that current.
Solution here is probably a transistor/MOSFET that the chip turns on, which in turn turns on the relay. Relay coils are inductors, so that probably also needs a diode to protect the transistor from inrush current and also the kickback when it turns off: inductors resist changes, so it’ll try to keep sinking the current and result in temporary spike of very high voltage: spinningnumbers.org/a/inductor-kickback.html
There is a couple of things I would suggest looking into. First just make sure the LED strip still works, then try a adding a current limiting resistor to the strip, even if it already has one it could help. A unity gain buffer could help as well. I also noticed that there is no active regulator on it, and all the work is put on a zener so I would also say either jank in an active regulator or even easier, supply it with a regulated rail
I wouldn’t use the PAM2804. The datasheet recommends a PWM frequency of 500 Hz, and if you look at the “PWM Dimming: ILED vs. Duty Cycle” chart on page 5 you can see why - at 1 kHz there is already a significant reduction in the average LED current. The enable response just isn’t fast enough to modulate at 38 kHz - by the time you want to turn it off, it will barely be on.
This isn’t quite enough for your 38 kHz either, but it’s closer (and waaaay more complicated): MAX16834. The datasheet says it can do up to 20 kHz, but at a glance I did not see a particular spec that seems to actually limit that.
Here’s an article about fast switching LEDs. All the linked products unfortunately have supply voltage ratings above yours, so they won’t work. But it discusses the concept of shunt dimming, where you’d end up simply bypassing the current around the LED rather than actually turning off the current regulator. Inefficient, yes.
Hey, thanks for your comment. I’ll look into the MAX16834 as soon as I have time tomorrow. Also, how would I be able to use a constant current driver with shunt dimming? How would I go about calculating the time a constant current source takes to recover from a short?
How would I go about calculating the time a constant current source takes to recover from a short?
To the extent possible, I’d look for graphs of “load regulation” in the datasheet, which graphically depict the regulator’s response to a load change. But that seems like maybe an uncommon thing for LED drivers (neither of the two parts we’ve been discussing have those in their datasheets).
Alternatively, if the regulator lists its control bandwidth in the datasheet, you could use the old rule of thumb to relate that to the rise time. For instance, if you’re modulating at 38 kHz, and you want to be sure your rise time is less than 10% of a period, you’d want it to be less than 1/380,000 = 2.6 microseconds. From the article, you’d want a control bandwidth of no less than 0.35/2.6 microseconds = 133 kHz. (or you could just say you want a bandwidth at least 3.5x your carrier frequency).
Using that metric, the MAX16834 is more than capable - yet despite that, the datasheet suggests (not a hard spec) that PWM dimming is functional only up to 20 kHz. I don’t know how to explain that discrepancy. This is where I’d buy an eval kit and try it out to see what I’m missing.
I would just use a MOSFET and resistor to drive the LED if you are only using it in short bursts.
If you want to drive the MOSFET directly from the microcontroller pin, it will need a series resistor to limit the current since the gate has quite a bit of capacitance. If your microcontroller pins can handle 15-20mA, it will be able to switch an AO3400A fast enough without needing a gate driver.
Hey, thanks for your comment. I looked at using a resistor in series with the LED, but if my calculations were correct I could only power the LED less than 3W and 2W would be wasted.
Since the remote control signals are short and low duty cycle, you could use a capacitor to provide the peak current for the LED without going over the maximum current of the power supply.
Brilliant! Thanks you so much for taking the time and effort to help me with this - and for mentioning “CONNECTORBOOK.COM” so I can add that as a useful reference. Not a chassis mount but that always was a mission impossible to find, I suspect.
If it’s a high-current, high-frequency, or low-noise circuit then maybe the inductance or resistance of those traces would matter, but they’re very short so probably not.
If you’re mass-producing it, then sometimes the reflow or wave solder process works better if the traces leave the pads in particular ways. You’d talk to your manufacturer about this.
If this is a hobby project, you’re overthinking it; arrange them in a way that pleases you!
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