3 ms·

In an EV charger, it's more likely to be a contactor, which is similar to a relay but can better deal with high amounts of current. (Technology Connections has

In an EV charger, it's more likely to be a contactor, which is similar to a relay but can better deal with high amounts of current. (Technology Connections has a video on the differences https://youtu.be/VsNHrAzx5_w https://youtu.be/VsNHrAzx5_w) If you want more household relays to notice, it's common to find them in digital thermostats for central HVAC control signaling. I've also found them inside of ovens, and cars also have lots of them for things like the starter and headlights (although maybe not the latter in newer cars.)

dekhn 3y ago
I hadn't heard of contactor but that looks like it's just a subtype of relay? And I notice that it says contactors are used where relays start to top out, around 15A. Which is interesting because the max current I can configure my RAV4 Prime to is ... 14A. Either way I'm not opening up the little portable box that makes this noise. It's clear there's something physical clacking in there, not solid state.
- HeyLaughingBoy 3y ago
  Yes, the big deal with contactors is that they're designed to switch high-current inductive loads. Smaller relays may have problems with the arcing caused by a load like a motor welding the contacts together. So, they have bigger contacts to handle the current and strong springs and a powerful solenoid to open/close the contacts quickly and extinguish an arc before it has time to melt anything. The noise you're hearing is from the contacts opening and closing.
throttlebody 3y ago
Relays and contractors are the same. It's a coil physically movin some contacts together to allow current to flow. I got no idea why, where or how the naming came about or who decides. But i guess its the same as creeks and rivers, when does a creek become a river
- userbinator 3y ago
  The term contactor came from industrial machinery, while relay came from telecoms.
- SAI_Peregrinus 3y ago
  I'd say they're physically different, but logically the same. They're both a coil that moves some contacts to make or break a current path, but a contactor has physical differences which allow it to break much higher current. Contactors have features to ensure the arc resulting from breaking the connection can be extinguished, relays just assume no significant arc will form in the first place. It's like the difference between a pickup truck with a ball hitch & a class 8 semi-truck with a fifth wheel coupling for a 53' trailer. Both are just vehicles that tow a trailer, but the physical details of how they do that are different in important ways.
matheusmoreira 3y ago
> digital thermostats for central HVAC control signaling Now I'll never be able to unhear it either!

dekhn 3y ago

I hadn't heard of contactor but that looks like it's just a subtype of relay? And I notice that it says contactors are used where relays start to top out, around 15A. Which is interesting because the max current I can configure my RAV4 Prime to is ... 14A. Either way I'm not opening up the little portable box that makes this noise. It's clear there's something physical clacking in there, not solid state.

HeyLaughingBoy 3y ago
Yes, the big deal with contactors is that they're designed to switch high-current inductive loads. Smaller relays may have problems with the arcing caused by a load like a motor welding the contacts together. So, they have bigger contacts to handle the current and strong springs and a powerful solenoid to open/close the contacts quickly and extinguish an arc before it has time to melt anything. The noise you're hearing is from the contacts opening and closing.

throttlebody 3y ago

Relays and contractors are the same. It's a coil physically movin some contacts together to allow current to flow. I got no idea why, where or how the naming came about or who decides. But i guess its the same as creeks and rivers, when does a creek become a river

userbinator 3y ago
The term contactor came from industrial machinery, while relay came from telecoms.
SAI_Peregrinus 3y ago
I'd say they're physically different, but logically the same. They're both a coil that moves some contacts to make or break a current path, but a contactor has physical differences which allow it to break much higher current. Contactors have features to ensure the arc resulting from breaking the connection can be extinguished, relays just assume no significant arc will form in the first place. It's like the difference between a pickup truck with a ball hitch & a class 8 semi-truck with a fifth wheel coupling for a 53' trailer. Both are just vehicles that tow a trailer, but the physical details of how they do that are different in important ways.

matheusmoreira 3y ago

> digital thermostats for central HVAC control signaling Now I'll never be able to unhear it either!