Sensor to detect current flow for Neon Sign

Other Hardware Device Hacking
1

Hi, I have an Arduino project where I need to detect that voltage is flowing to a Neon sign by attaching a sensor to the voltage wire - this is traditional Neon, so 2000+ volts. I only need to read that voltage flow is ON or OFF (no levels). Is this something that a Hall sensor can read, or are there other suggestions?

Phil

2

It is extremely dangerous to connect anything to a 2000V power supply, other than the neon sign.

I would detect whether the neon sign is emitting light, using a light dependent resistor, photodiode, etc.

3

I suspect you are wanting to measure the AC voltage, which does not "flow". Just put an insulated wire from the Arduino A/D pin close to the neon sign wire lead. You will quickly get your signal.

4

Voltage doesn't flow, current flows. Hall effect sensors pick up the magnetic field associated with flowing current, but the current flowing into a neon sign is tiny and I doubt very much that a hall effect sensor would notice it.

A very well insulated wire, by which I mean rated for at least 10kV, close to the supply wire will probably pick up enough signal, but I suggest a 10M Ohm resistor in series.

I warn you that neon light transformers produce lethal voltages and it concerns me that you are using them while the questions you ask indicate that you don't know the basics of electricity, and are therefore putting yourself at serious risk. Please find someone local who understands the risks and how to mitigate them to help you.

5

Thanks for reply, and apologies for my braindead description in the question - yes, it's the current the flows, and in this case is extremely small - but the voltage is high to excite the neon gas. I would never mess around with the voltage directly, and what I got from these answers is that a small wire close to the supply, may pick up enough signal (maybe with 10 Ohm in series).

I have tried the optical method as well, and that's still on the table, just wanted to see if there was another way,

Thanks all.

6

I was going to suggest using an electric fence tester and sensing the light from that, but @jremington's suggestion simplifies that by one step :slight_smile:

7

Not 10 Ohms!
10M Ohms.

8

Based on previous responses:

  1. I will not mess in any way with the high voltage neon power supply lines - I understand the risks and will keep away.

  2. I am also investigating the optical detection method and have both CDS photo resisters and photo transistors. Room is tight on the sign, and placement may be an issue, but I'm looking into it.

  3. Latency maybe an issue so I want to look at multiple options.

  4. I only need to detect if current is flowing, not make any measurement.

In regards to the project, I have the actual sign in hands now, and the neon power supplies are very close to the tubes to light - Hongea Neon Power Supply, Input 100-250 ac 5-25w, Output 3kv at 30m.

Any further suggestions on whether to use a Hall effect sensor on the input side, or try the "insulated wire" on the output side. I have time to make experiments.

Thanks.

9

Would you accomplish the same thing by sensing the input to the power supply? That's easier to accomplish with an AC current sensor.