Hello, this is my first arduino uno project. I have a small 4W neon lamp powered by 12V 500mA power supply. I need to change the brightness of the lamp and occasionally switch it off and back on. I want to create a simulation of power outage or glitches in the light.
The lamp's power is connected to a circuit board with red and black cable. The board connects to both sides of the neon lamp with two cables.
Help out please :o
12V (twelve volt) Neon? ? ?
Real neon lights require high voltage (kilo-volts) so if you had a neon sign there would be a transformer to step-up the power line voltage.
You can try a [u]MOSFET driver circuit[/u] and it will probably work but we don't know anything about your lamp so you'll just have to try it.
DVDdoug:
Real neon lights require high voltage (kilo-volts) so if you had a neon sign there would be a transformer to step-up the power line voltage.
Really???? So the neon in my 240V iron has a HV transformer attached?
Neon signs might due to their size but not a small neon bulb. Some can be activated by as little as 50V.
It's a really small lamp: 3.5 – 4 W.
It does look like the 12 volt power supply drives some sort of voltage multiplier circuit. Can you show a picture of the underside of that printed circuit board and also the 'neon' lamp.
How, incidentally, do you know the power rating (3.5 - 4 W) of the lamp ?
It's listed on the product page as Energy consumption: 3.5 - 4 W.
This is the lamp > https://www.amazon.de/Butlers-Leuchte-Flamingo-leuchtende-Deko-Lampe/dp/B01DTNOU5K
Pink flamingo 
Not much to see on the back of the circuit board...
I wasn't expecting that: https://www.amazon.de/Butlers-Leuchte-Flamingo-leuchtende-Deko-Lampe/dp/B01DTNOU5K
But, yes, that is a neon lamp. You may be able to control the brightness with some sort of pulse width modulation, say controlling the base of that transistor D882. However, it is not completely clear to me what that circuit is doing. . It may be partly self oscillating. The transformer appears to have 5 taps. The diode/capacitor pairs are probably a voltage doubler. With a neon, reducing the voltage is not a satisfactory way of dimming it because, at a certain point, it fails to strike.
6v6gt:
With a neon, reducing the voltage is not a satisfactory way of dimming it because, at a certain point, it fails to strike.
This might be perfect for me in creating the glitch effect, I'm trying to achieve. I don't need smooth control and reliable transitions between states. The more random and unstable it appears the better!
Looking again, it appears to be some sort of flyback circuit. That transistor marked D882 could be a 2SD882. The diodes appear to be on the primary side of the transformer and are not, contrary to what I previously said, part of a voltage doubler.
The transistor has on it something like a logo – encircled letters WXDH (the w is very tiny, smaller than the other letters, so not sure of it completely). Then standalone letters 637x and D882. Nothing comes in google for this combination, so not sure if it is any help.
Ah, I found this spec sheet > http://wxdh.cc/Upload/产品参数/三极管/2SD882-10352872825.pdf
You are right @6v6gt, it is a 2SD882 by the manufacturer WXDH
Also found this 470uf 25V electrolytic capacitor, which is also on the board
I discovered this tutorial, which uses a transformer to have a neon lamp pulse, blink, etc. The issue is that my lamp doesn't have this extra power and ground cables coming from the transformer, which i can connect to the arduino.
Or is it possible to connect the red and black cable of the lamp to the arduino and then to the lamp's circuit board?
What do you guys think?
So I connected the arduino to the power cables of the lamp, on the green side of the board (to the part of the cables protruding on the side opposite of the transistors). The black cable connected to the ground of the arduino and the red one to 11. I then ran the led-pulse.js from the above mentioned tutorial. The brightness of the lamp did go down and it was flickering for a moment.
Unfortunately the arduino now stopped responding. Green and yellow light are on and it is discovered and recognised as connected in the IDE app, but if I try to upload something I receive an error: avrdude: stk500_recv(): programmer is not responding
Guys please help out at my first steps with the arduino 
I haven't looked at the circuit but it is never a good idea to connect anything with high voltages to a micro without some sort of protection like an opto isolator or relay. I think you may have fried the board. Try disconnecting everything, power cycle the Arduino and try again.
You got caught badly there. The author of that "instructable" describes herself as an artist.
Anyway, in principle and has already been pointed out, connecting 12volts to an arduino pin is a bad idea, if that is indeed what you did.
It is possible that the 12 volts has simply cleared the original configuration of the Arduino (fuses). You could try burning a boot loader onto it, but this process requires another Arduino.
If you want to switch the power to that circuit board from an Arduino, you should use a P channel mosfet and an opto coupler (with appropriate resistors - a pullup for the mosfet and a current limiting resistor for the opto coupler led ).
Ok first things first. My girlfriend has a photon, would it possible to burn the bootloader on the uno with it?
You could try to load the ArduinoISP on to the photon (STM32 - which I don't know anything about). It won't work if the sketch addresses (ATmega328p) registers directly, but if it compiles, it should function.
