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I am using this supply to provide 12V to my system.

https://www.amazon.com/gp/product/B07D9FTC77

I have a DC-DC voltage adapter that converts the 12V down to 5V to power a Raspberry Pi Zero. (The 12V is needed to power something else in the system.)

When using the LED driver, the Raspberry Pi seems to work fine.

However, I am using a sensor with the Pi that does not work properly. If I switch to a regular 12V power supply (like a wall wart) everything works perfectly.

Is there something different or wrong with this LED driver? I get the same 5V reading no matter which supply I use.

If this is not the correct type of supply one should use for powering a Raspberry Pi, are there any affordable, waterproof supplies like this that are? Because every waterproof supply I can find seems to say it is for LED lights (though this one even says it is also for other things like computer equipment.)

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    \$\begingroup\$ Sorry, Kyle, but you've linked to an Amazon ad rather than a datasheet with proper technical specifications. There's a reason Amazon is cheap. Most of the sellers don't provide datasheets or technical support. Our policy is "No datasheet? No sale!". We're not their tech support department, I'm afraid. \$\endgroup\$ – Transistor Oct 27 at 22:55
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    \$\begingroup\$ How could you go wrong? ★THE DRIVER HAVE AMAZING WATERPROOF EFFECT ★THE MOST SAFETY OF THE DESIGN PHILOSOPHY : ★THE BEST OF AFTER SERVICE \$\endgroup\$ – John D Oct 27 at 23:49
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    \$\begingroup\$ @Transistor So if I find some power supplies with a datasheet, what should I look for in that datasheet to provide proper power to a raspberry pi? \$\endgroup\$ – Kyle Oct 28 at 0:12
  • \$\begingroup\$ Define the sensor measurements and fault. is there an EMI switching crosstalk issue? Try earth Gnd 0Vdc \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 28 at 0:31
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    \$\begingroup\$ What is the sensor? Often for analog sensors run off of cheap, noisy supplies a simple solution is to include a linear regulator to generate a more stable power line for the sensor. \$\endgroup\$ – user1850479 Oct 28 at 17:03
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It's likely a constant voltage supply, but it's probably cheap and badly filtered. Issues with sensors typically result from too much switching or ac noise. A multimeter won't see those fluctuations, you'd be able to see them with an oscilloscope. Adding bypass capacitors or even larger 1000uF capacitors to help filter the DC side of the line could help.

Alternatively, it could be that your load is too small for the supply to regulate properly. You normally want your load to be between 10 and 90 percent of the supply's rating. At 8.5 Amps, anything less than 850 mA may cause issues. The RPi brings down the 5V to 3.3V internally and could be filtering out any noise but your sensor may not.

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LEDs don't care about voltage noise and have a high tolerance for ripple voltage. So, when a constant voltage power supply is marketed as a "LED driver", and it's cheap and comes without a datasheet... you can very often expect low accuracy, high output ripple and a lot more noise than from an actual power supply.

Output capacitors and filters cost money, and money is expensive...

If it works with a wall wart and doesn't work with the LED driver, that's probably the issue. If the sensor is at the end of a long cable it could also be common mode noise from the badly filtered "power supply".

Anyway. Personally I avoid unbranded, unspecified products.

are there any affordable, waterproof supplies like this

That's a bit weird since the Raspi is not waterproof. So if you build a waterproof housing for the raspi, you might as well use a bigger waterproof box and put one of these inexpensive power supplies inside. If you want more watts there are other models. That's probably why you can't find a waterproof supply that isn't a LED driver -- there is no customer for a waterproof wall wart. Should it plug in a waterproof mains socket?...

If you really want a waterproof supply there are indeed plenty sold as LED drivers, but note this one has full specs about output voltage ripple, EMC compliance, etc. Plenty of other models, if you want Power Factor Correction, cables instead of wires, etc... Note waterproofing the connection to the wires is left as an exercise to the reader. And it's still a LED driver, so load regulation is worse than on a product marketed as "power supply".

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  • \$\begingroup\$ "money is expensive" You don't say... \$\endgroup\$ – Mast Oct 28 at 22:26
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Without an oscilloscope, you are going to struggle to find the root cause of this. The other answers are all good pointers to a solution, but in the end it is very hard to build electronics without suitable test equipment. Unfortunately 'scopes are not cheap (you'll want something with specs similar to an entry-level Rigol), but without being able to see what is going on everything you try will be a guess.

Switching components around until it works is a totally plausible way to solve this problem, but if your goal is to learn and explore then I'd try and get access to an oscilloscope.

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It seems like your power supply is not having good filtering capacity So as a solution you can use

schematic

Or else still you get some ripples I suggest you to use π (Pi) filter

schematic

simulate this circuit – Schematic created using CircuitLab

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LED driver supplies stabilized current.Voltage is for reference purpose only and can be carried.depends on load. Some of led supplies come withwarning not to turn on without load. You don't know what output voltage if the load less than 8.5 amps. 5v stabilizer could be damaged.

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    \$\begingroup\$ Hi, Without proper explanation, your statement: "LED driver supplies stabilized current" is false. Some LED drivers are constant current, yes, but constant voltage drivers also exist. For confirmation, here's a random LED supplier explaining the difference & here's a page of the constant voltage LED drivers from manufacturer Mean Well. If 1 fixed output voltage is shown, it's probably a constant voltage driver. \$\endgroup\$ – SamGibson Oct 28 at 17:32
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    \$\begingroup\$ The driver he links is a constant voltage, not constant current LED driver, so this is not his problem (although using a constant current driver might cause problems had he done that). \$\endgroup\$ – user1850479 Oct 28 at 21:34
  • \$\begingroup\$ Yes, you right. Constant voltage power supply can be used for some LED arrays which have resistors inside, !ike some led strings. so the problem could be the pulsation. \$\endgroup\$ – user263983 Oct 28 at 22:18

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