# volt sensor bord to 300v ac

Hallo

I would like to make a simple guide ring for a turbine, which turns on the relay when when a certain voltage is reached.

can I buy a simple printer that can measure up to 320V ac and convatere it to 0-5V?
a bit like B25 Voltage Sensor Board (but it can only take 25v)

MVH Bruno

How accurate do you need the reading? Does the trigger point need to be variable?

You could put the high voltage onto a transformer to bring the voltage down to a max of say 5vac, rectify then feed into voltage divider to limit the Arduino input voltage.

Weedpharma

where do I get a transformer that can scale 80 times down?

I should be able to turn on an output when the voltage reaches 400v

400volt AC is ~565volt peak, and ~1130volt peak/peak.
Leathal voltages. I hope you know what you're doing.

If you can't find a transformer for that voltage, use two transformers.
Two 230volt primary windings in series, and the secondary windings parallel.
Measure polarity before you do this.
Use two identical small mains transformers with a low secondary voltage, e.g. 4volt or 6.3volt.
Measuring peak/peak voltage with the A/D might be more accurate than rectifying.
Leo..

But how accurate?

This is required information.

The Arduino analogue can only read 0 to 1023. Even if you have accurate glitch free low voltage signal, you only get 2 analogue values per volt up to 400v.

What is the use of this sensor?

Weedpharma

HI,

You should be able to get a 415Vac to 24Vac transformer, rectify and filter the DC, then scale the low voltage output to 5V.

Can you tell us your electronics experience?

Tomâ€¦

I am a trained electrician. 4 years of training in Denmark. High voltage is not a problem.

I see two ways for solving your problem. Either you get a device that detects the specific voltage level (limit indicator) in the primary circuit, and transmit that signal through some isolation (opto coupler...) to the Arduino, or you use a transformer of sufficient maximum primary voltage, and add a limit indicator to its secondary winding.

A transformer doesn't require an additional auxiliary voltage to function, so that it's easy to install. I'm not familiar with limit indicators, perhaps there exist some which get their operating power from the monitored voltage. In either case the bottleneck is the high primary voltage, above usual mains voltage.