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.
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.
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 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
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.
No, it's not possible to do it without current draw. You can do it with really, really low current draw though.
Ignoring MOSFET stages for the moment, I could design a system that could do this, with a power consumption of under 0.1 uA when in the low-voltage cutoff state.
I'd use a TPL5110 and an Attiny10 to do that.
Alternatively, if ~50 uA is OK (it really should be), then I'd just use the Attiny10 on watchdog timer, and save the cost of the TPL5110.
If I absolutely did not want to use the SLA to power that system (as an academic exercise), I'd use a separate CR2032 coin cell. That ought to last 3-5 years. Or if there's ambient light, a calculator solar cell and a supercapacitor would make it self-powered. I could design a system that could last overnight on just a few hours of ambient light during the day. Modern microcontrollers are a marvel!
The amount of power drawn by a reasonably designed system should be many orders of magnitude less than the self-discharge of the battery. So not worth worrying about unless it's very poorly designed for some reason.
I once got inspired by this: scoollab.web.cern.ch/diy-particle-detectorIt uses photodiodes instead of BJTs. Advantage is that you can get some which are easy to decap. I did not get it to work :/ but also did not spend so much time. I think what is really important is to properly shield the circuit from electromagnetic radiation, use a battery (low-noise) and also shield the detector from light.
I've gotten a similar circuit to work. Good shielding on the preamp was indeed key.
That was like 12 years ago though. Back then I used a battery. I probably know enough to get it working with a switched power supply now, which would be way more convenient.
The PIN diodes aren't cheap though! Also some are export controlled. Not the one from that project though. I have a few around that I'll use if I can't get this to work.
The BJT method is attractive due to really low cost. I never managed to get it working though. There are enough independent reports of the method working online that I think it's possible, but the documentation hasn't been sufficient to easily replicate it.
It might be something boring like some manufacturers put a clear coating (e.g. glass) on the internals of a type of transistor, and others don't.
The lamp intensity won’t vary in a shunt regulator because the current through the shunt resistor is constant. The current through the zener diode varies to split that current with the load. Otherwise, yes it will work, however you will have fewer choices of resistance and will not be able to make the regulator as efficient.
Any particular shunt resistor that you have in mind? You are correct that the lamp brightness would remain the same whilst in the regulated zone. I was more thinking of operation outside that region - eg in a short condition. Having a lamp as the series resistor would reduce the fault current compared to using a fixed resistor.
Not sure what you you mean by “fewer choices of resistance”. The lamp would be the series resistor - other than that, what resistor did you have in mind?
Standard resistors come in many standard values and many power grades, meaning you can pick a resistor that minimizes source current for your application. Incandescent bulbs come in different rated voltages and powers, but they are far from precise or standard.
Depending on the design, shunt regulators come with short protection for free without relying on a PTC fuse (incandescent bulb or otherwise). You’re absolutely correct that the positive tempco of a bulb will reduce short circuit current, but how by how much and whether it is worth it depends on the application and the properties of the bulb itself.
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