120V switching 12V relay?

[Peel]

Usually relays have a low amp line that switches a high amp device that has larger gauge wire. Or a low voltage line that switches a higher voltage circuit. Does there exist a relay that does the opposite? I want to have my 120V shore power switch a 12V line so that I can put a low voltage indicator LED on my switch panel without running 120V into that area of the boat. Searching my local boat supply store's website, Amazon, and general Googling doesn't seem to yield anything (maybe I'm just using the wrong search terms)

Or is there a better way to accomplish this without a relay? Again, I don't want to introduce 120V into the switch panel area that is currently exclusively 12V.

[Wotname]

There are plenty of AC relays. Provided the relay can be operated by 120VAC, the contacts can be used to switch a 12V LED assuming you have a 12V source near the relay location or are willing to run a 12V supply to that area.

[Peel]

Originally Posted by Wotname

There are plenty of AC relays. Provided the relay can be operated by 120VAC, the contacts can be used to switch a 12V LED assuming you have a 12V source near the relay location or are willing to run a 12V supply to that area.

So something like this (Amazon Link) that only mentions 120VAC would work?

[RaymondR]

Small transformer, diode, resister and a LED.

[smac999]

The coil will 120v on a 120v relay. . You can put whatever you want though the switch. The amp rating will vary with what you put through.

[Wotname]

With respect Peel, if you are having to ask this question, I'm not convinced you should be messing with the 120VAC.

[Lepke]

Look for relays with a 110v coil. One shown is as cheap as $2 on ebay. Some come with base, some sell base separately and some are all in one.

[Peel]

Originally Posted by Wotname

With respect Peel, if you are having to ask this question, I'm not convinced you should be messing with the 120VAC.

I’m actually quite familiar with 120VAC systems having rewired my home, and am also comfortable with 12VDC systems, but have never interfaced the two other than installing a battery charger and inverter.

[Lancerbye]

Any 120 volt relay will do the job . The coil only has to be rated for 120 volts. The contacts have to be rated for the current going through them. Look at electronic stores for supply. I shop online with Digi-key. Fast response

[stormalong]

Originally Posted by Peel

I’m actually quite familiar with 120VAC systems having rewired my home, and am also comfortable with 12VDC systems, but have never interfaced the two other than installing a battery charger and inverter.

Well apparently you do not understand the concept of a mechanical relay. The contact ratings are maximums, there are no minimums.

[dfelsent]

Originally Posted by stormalong

Well apparently you do not understand the concept of a mechanical relay. The contact ratings are maximums, there are no minimums.

There are minimum load currents specified for relays. This is because without an adequate load the contact materials used will slowly build up oxide layers until the contact resistance becomes quite high.
Relays designed for small signals typically use precious metals in the contacts instead of silver or silver alloys.

https://www.te.com/commerce/Document...=CS&DocLang=EN

In addition certain types of solid state relays require AC loads and a minimum load as well.

If it were me I’d use any old 120v mechanical coil relay and not worry much. It may fail some day but if it’s not a critical application that’s ok.
Use a sealed relay if you find one cheap to help avoid the oxidation on the contacts.

[Marc13]

To decouple the 120V and limit the current, you can put a 220 nF capacitor on each wire connected to the 120V in series with a high brightness LED. It takes capacitors sized for 250V and install them between the 120V and each wire connected to a terminal of the LED. The maximum current supplied to the LED will be approximately 5 mA. It will light up every second alternation but it will already be very bright if the diode is at high brightness (L-1154ZGW, L-1503CGDK or L-57SRSRD at Radio Spares). The two 220 nF capacitors in series are equivalent to a 24 Kohm resistor at 60 Hz.

[RigBig]

If I get what you're saying that you just want an indicator light to come on when your shore power is on then don't listen to any of the advice you've received so far. Just wire in a 120Vac indicator lamp.

[Cadence]

Originally Posted by Peel

Usually relays have a low amp line that switches a high amp device that has larger gauge wire. Or a low voltage line that switches a higher voltage circuit. Does there exist a relay that does the opposite? I want to have my 120V shore power switch a 12V line so that I can put a low voltage indicator LED on my switch panel without running 120V into that area of the boat. Searching my local boat supply store's website, Amazon, and general Googling doesn't seem to yield anything (maybe I'm just using the wrong search terms)

Or is there a better way to accomplish this without a relay? Again, I don't want to introduce 120V into the switch panel area that is currently exclusively 12V.

Sounds like you want a 110v coil and 12V contacts. They are readily available.
DC contacts are different than AC contacts so current rating is not the only thing, however I doubt you will find AC contacts in 12V. anyway.

[Marc13]

Yes, but he wants to limit the risk of wires with 120V on his 12V electrical panel. It is safer with the capacitors at the start of the wires of the LED.