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Date: 18 April 2018. Making a Plug-In AC Voltage Meter.


A couple years ago I bought an AC powered nightlight. I plugged it into an outlet in my galley. Eventually I broke the plastic part that lit up. The LED was blue and still functioned. I thought the base section might be of use someday so I tucked it into a junk drawer. Then it came to me: I could make my own plug-in AC meter from the broken nightlight and an AC meter I had on hand. Here's how I did it.

Eons ago I ran across some cheap AC meters on eBay. Here's one I bought for a couple bucks:

I had originally planned to cut a hole in my cabinet and permanently mount the meter.

One thing I find comforting is being able to easily check voltage. For my DC system, I have a multitude of meters scattered about Seaweed. I wanted to permanently mount a few AC meters too. I had envisioned looking up from my dinette and confirming the power supply was stable.

This is another of those Good Ideas acquired and not installed. That is a BIG PROBLEM for me: getting items and then not utilizing them immediately. The money is spent so of late I have been attempting to use up the goods I have already. So far, well, I'm not doing spectacularly at that. Yet.

As for the meters, better sense came to me before I cut a hole in my cabinet front. I am the worst at cutting a straight line in anything. I can draw one but when a power tool is in my hand suddenly things go wonky. It is not pretty.

So the thought was to buy a plug and wire the meter into the plug. That way I could simply plug in the meter and have my voltage displayed. The demise of my nightlight gave me the opportunity to test my theory.

Everything works in Theory. Sometimes I wish
I'd been smart enough to name my boat Theory!

First I dismantled the nightlight. This is what I found:

The AC meter is below the nightlight in this photograph.

The inside of the nightlight is rather straight forward.


Photos repeated for comparison

As you can see in these pictures, the prongs are directly behind those two larger bumps. That is where the power comes into the nightlight. I knew that one side would be positive and the other ground.

I attempted to solder the connections on the meter to the greenboard at those two large bumps.


I would love to be able to say that I knew which was which. I did not. I was careful to do all testing AFTER I had completely closed the unit. AC is not for the faint of heart. People die from stupidity and carelessness.

Be safe! A ten dollar solution is available.

Affiliate link

Eversame AC Voltage Meter



My attempts at soldering were pathetic. Nothing worked. The wires were not sticking. I had to rethink the problem and figure out a way to attach the meter wires to the plug.

I dismantled the nightlight further. This is what I ended up doing:

Note the RED DOT of polish on the plug. That's the positive side.

For this meter/illustration the BLUE ARROW points to positive and the GREEN ARROW points to  ground.

My soldering skills are apparently nonexistent at this time. Instead I stripped the meter wires back about one inch. Then I twisted the wires. Next the wires were wrapped through and around the holes at the base of each prong. (See BLUE and GREEN arrows above.) Two dots of liquid electric tape secured the wires.


Side Note: If you do not yet have liquid electrical tape in your arsenal, at some point you might want to pick up a container. It is handy to have though I don't know that this is essential gear.


On the right I've linked you to the red version of Gardner Bender Liquid Electric Tape.

The reason I have chosen this specific brand is because of the container! Most of them are in tin cans. The cans rust so removing the lid becomes problematic. This lid will rust too, however it will not stick to the plastic container quite so firmly.

These products do dry out once opened.

Affiliate link

Gardner Bender Liquid Electric Tape 4oz Red

Note to Self: Next time I open the can, coat the threads of the lid with Vaseline.


So after I had secured the meter wires to the nightlight plug I put it all back together. It worked!



Now that I've shown you how to make this on your own for just a few bucks, let me tell you what I'd suggest if you can afford to do so: Buy one. Seriously, already put together, no problems and probably works a-okay.

Here is an affiliate link for one under $10

Eversame AC Voltage Meter



Mine works fine. It was made from parts already paid for and aboard Seaweed. For me, this is Good Enough.

Side Note regarding the red dot shown on my electric outlet: That denotes the wider prong of the plug. It lets me know which way to plug the AC cord in, even when my glasses are off.

To you and yours, use what you have and make do or do without. But in this case I would seriously suggest you spend the ten bucks and buy a Eversame AC Voltage Meter. You will not be sorry.

Happy cruising.

Do you have a real plug-in AC meter?
And, if you go to marinas regularly, do you check dock power before plugging in your boat?

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2018, 2023

Categories: Gear, In the Bilges, Recommendations,

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