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I asked this question on the IoT Stack Exchange, but was directed here.

I am pretty new to electrical components, but I have been a software developer for years and want to get into hardware and use it as a hobby around my house.

I recently acquired some motion lights and I thought that I would add an esp8266 to it so that I would be notified when motion is detected (when the light goes on).

So, I took the light apart, soldered a line onto the neutral wire (white) and one on ground (negative line of LED in the circuit), and measured it's voltage, which is 10.5 V when the light is off and 8v when the light is on. I need 3.3 V to power the esp8266 so I put in the LD33V voltage regulator like I have used in previous projects to go from 5 V to 3.3 V to power an esp8266.

However, when I do it this time, I get 1.47 V coming out of the VOUT and not 3.3 V. I've tried multiple LD33V regulators, and other voltage regulator models, and everytime the voltage is lower than 3.3 V.

I'm not sure why that would come out lower than 3.3 V if the input is well over that. Why would the regulator take out more than it should? I've searched the internet and not found an answer, so I am hoping that someone can explain why this occurs and how I can remedy that.

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    \$\begingroup\$ What is the input voltage when the output is too low? I suspect the problem comes from the supply of the LD33V. \$\endgroup\$ – Edesign Jan 16 '17 at 8:41
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    \$\begingroup\$ Is in fact, the voltage you measured an AC voltage and not a DC voltage? \$\endgroup\$ – Andy aka Jan 16 '17 at 10:04
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    \$\begingroup\$ To have any chance of success, you need to supply the info (inc photos) requested in comments to your original question on the IOT Stack. They also raised very valid concerns due to your terminology, that you might be dealing with AC or even lethal mains voltages! With respect, you are trying to reverse-engineer something which you don't know, can't supply the schematic & which requires skills over and above an "electronics beginner". I suggest you would be more likely to succeed (and also safer) getting physical help e.g. from a "maker space" etc. \$\endgroup\$ – SamGibson Jan 16 '17 at 13:29
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    \$\begingroup\$ The fact that you're measuring any significant voltage between your neutral and ground wires indicates that you have a wiring issue in your house. Neutral is supposed to be grounded and shouldn't measure more than 1 or 2V away from ground and only when there's some heavy appliance drawing current on that circuit. Also, you shouldn't be playing with mains voltages - go buy a power supply. \$\endgroup\$ – brhans Jan 16 '17 at 13:32
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    \$\begingroup\$ Joel - The latest comment kindly given by @brhans exactly highlights one of the problems in your question: You used the word "ground" which might mean "mains ground". Personally I doubt you mean "mains ground", since you say the negative of the LED is connected to that point, so it is a normal path for current (which mains ground is not). However without a schematic diagram and photos, we are all left guessing and making different interpretations of what you mean - and when dealing with mains voltages, guesses could be lethal! Please reconsider this project, or at least, supply photos. \$\endgroup\$ – SamGibson Jan 16 '17 at 14:21
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It appears that your neutral and ground have an "offset" voltage of about 1.8V DC. So, when you measure the output of the regulator, you only see about 1.5V.

There is definitely a serious problem when neutral and ground are not at the same voltage level. It appears that your voltage converter is one of those cheap, non-isolated supplies and it is very dangerous to use in earth-grounded circuits. If you grab the lamp and your feet are wet, you could end up electrocuted!

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