GuppyHJD
Posts: 26
Joined: Sat Jan 20, 2018 3:37 am

Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 2:18 am

Hello,

I have been thinking about a project to monitor if the main power to a boat loses power. The boat has a 50a shore power cord - two phase 125v legs.
I have considered a split core power transformer. I have looked at connecting some data feed from the inverter.
I am thinking - what if I used a non-contact voltage detector type circuit.

Something like https://makezine.com/projects/non-conta ... -detector/

Instead of using a battery, I was thinking of using the 3.3v pin on the RPi and ground pin.
I am wondering if I should isolate the Rpi with an optocoupler or just a photo resister on the LED in the detector in the project above.

I am not interested in the voltage or current, just if it is ON / OFF. I will then have the RPi send an SMS text.

Suggestions?

pcmanbob
Posts: 10170
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 8:56 am

I very much doubt that circuit will work at 3.3v , you might get it to work at 5v,

then you could use an opto isolator in place of the LED to interface it to the pi gpio to monitor the input.
We want information… information… information........................no information no help
The use of crystal balls & mind reading are not supported

boyoh
Posts: 1529
Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 11:37 am

Might I suggest using a small mains relay connected to the mains power supply protected by a fuse

This will be on 24/7 . Then using a pair of normally closed contacts to switch the 3.3v to the Pi in/put.

When the power fails the relay will de-energize , the N / C contacts will make to switch the 3.3v to the Pi

Use a rechargeable battery on trickle charge to keep the Pi powered up


3.3v rail-----------------( N/C )---------------( 1k )--------------GPIO IN/PUT

The 1kr is for protection

Regards BoyOh
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

GuppyHJD
Posts: 26
Joined: Sat Jan 20, 2018 3:37 am

Re: Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 2:15 pm

BoyOh,
The mains are connected to two inverters so I do not have an outlet or circuit that is not always energized. I do not have a good place to put the relay. This has me looking at using a SCT013-000 but have not figured a circuit for that either. I am still learning electronics so am being careful with the mains and not wanting a fire.

boyoh
Posts: 1529
Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 6:52 pm

GuppyHJD wrote:
Mon Feb 24, 2020 2:15 pm
BoyOh,
The mains are connected to two inverters so I do not have an outlet or circuit that is not always energized. I do not have a good place to put the relay. This has me looking at using a SCT013-000 but have not figured a circuit for that either. I am still learning electronics so am being careful with the mains and not wanting a fire.
From BoyOh

You say the system is not always energized , how are you powering the Raspberry Pi ?, the Pi must be energized 24/7
If there is no current flowing the C/T can not produce a secondary voltage . If you use a voltage sensor this might mean
using a battery , using this method you could use a LDR to monitor voltage sensor indicator light .

Is there any Indicator light that is on when power is going to the Boat . If so you could use the LDR method

Advice Learn basic electronics before building complicated projects.

Regards BoyOh
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

hippy
Posts: 8566
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 7:07 pm

I would just use a relay powered by the incoming feed. When that fails the relay will switch a contact which connects a battery to a Pi, Arduino or other micro, which powers-up, sends its SMS message, shuts down or goes into low power mode.

KISS.

A slightly more complicated circuit involving relays or solid state switching can be used to give zero or near-zero power consumption except when sending the SMS.

GuppyHJD
Posts: 26
Joined: Sat Jan 20, 2018 3:37 am

Re: Non Contact Voltage Detector Mashup

Mon Feb 24, 2020 11:44 pm

OhBoy,
What I wrote is "The mains are connected to two inverters so I do not have an outlet or circuit that is not always energized" - The system is ALWAYS energized. Even when the mains are turned off, the batteries and inverters still provide 120v to the circuits. The RPI will be plugged into one of the normal 120v outlets.
Henry

JohnsUPS
Posts: 188
Joined: Fri Jul 06, 2018 2:13 am
Location: USA

Re: Non Contact Voltage Detector Mashup

Tue Feb 25, 2020 12:26 pm

All that you need is a current sensing switch - something like this:
https://www.nktechnologies.com/current- ... ng-switch/
or this:
https://www.veris.com/Category/Current- ... cTrip.aspx

These are basically current transformers with built in switches that turn on at various trip points. The ones that are self powered could be connected directly to a Pi (probably will need a pullup resistor also). Once the current is above a threshold (determined by the actual sensor you get) the switch inside of the unit closes.

The one sitting on my desk right now is a Veris Hawkeye 800, and it would be perfect for your application (although a bit pricey). Shop around, I'm sure you can find one that is cheaper.

GuppyHJD
Posts: 26
Joined: Sat Jan 20, 2018 3:37 am

Re: Non Contact Voltage Detector Mashup

Wed Feb 26, 2020 5:04 am

JohnUPS

Thank you. If I read the datasheet correctly the Vertis unit switch threshold is 15amp. I contacted both companies for a product that will trigger at 1amp.

JohnsUPS
Posts: 188
Joined: Fri Jul 06, 2018 2:13 am
Location: USA

Re: Non Contact Voltage Detector Mashup

Wed Feb 26, 2020 11:30 am

GuppyHJD wrote:
Wed Feb 26, 2020 5:04 am
JohnUPS

Thank you. If I read the datasheet correctly the Vertis unit switch threshold is 15amp. I contacted both companies for a product that will trigger at 1amp.
Guppy,
Not sure what model you were looking at......they have many to choose from with various features.

I actually tested the unit that I have, and the low switching threshold of the Hawkeye 800 is 0.25A, and will handle up to 200A. I believe it switched on when I tested it at about 200ma (0.02A), so it would probably be fully "on" at 250ma.

boyoh
Posts: 1529
Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: Non Contact Voltage Detector Mashup

Wed Feb 26, 2020 4:45 pm

Pick a problem that would effect the operation of your boat if it arose...Monitor this problem and to let you know if it arose

I would consider batterie low level as a problem , this could be monitored using a simple ZENER DIODE circuit

Use this to trigger the Raspberry Pi to send you a signal

When you are at sea off shore , how do you charge your batteries Sola Power / Wind Power / Deiseal Generator ?

Regards BoyOh.
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

GuppyHJD
Posts: 26
Joined: Sat Jan 20, 2018 3:37 am

Re: Non Contact Voltage Detector Mashup

Thu Feb 27, 2020 4:15 am

Boyoh,
Thank you.
Yes, Low Battery would be something I can monitor.
When not connected to shore power, the batteries are charged via engine alternators and/or generator.

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