Relay's isolation

Hello, I have a questions about the usage of relays.

I bought an electromagnetic relay :
http://www.volumerate.com/product/diy-1-channel-5v-relay-with-lamp-382151?utm_source=vr&utm_medium=productbysearch&utm_campaign=search#specifications-detailinfo

And i have questions about how to use this thing.

  1. I connected it to a power socket ( using a plug, a lightbulb socket+lightbulb, and the relay itself ), and i wired the 2 wires to the NO and COM wire-socket ( is that a word ? ) There was a third socket, labeled NC but i didnt use it. The "small" problem was that i took the relay into my hand when i plugged the plug, and it tazed me super hard, like my whole arm shook... I suspect that it came from the solder on the bottom of the card... Can you confirm it ? Also, what precautions should i take while handling it ?

  2. How does it works ? Why is there 3 pins ( VCC, IN1, GND ) ?
    How do i plug it to controll it from the arduino ?

The "small" problem was that i took the relay into my hand when i plugged the plug, and it tazed me super hard, like my whole arm shook... I suspect that it came from the solder on the bottom of the card... Can you confirm it

I assume you had it plugged into the power line?

Also, what precautions should i take while handling it

Don't touch anything while it's plugged-in to dangerous voltages! :wink: And, mount it in come kind of enclosure so nobody else touches it either.

  1. How does it works ? Why is there 3 pins (VCC, IN1, GND ) ?

First, you don't just have a relay, you have a relay module, which is a PC board with a relay, a driver circuit, and a couple of LEDs. That's good, you usually need a driver circuit to drive a relay with the Arduino.

[u]Here[/u] is a schematic for a SPDT (single-pole, double-throw) relay without the driver.

There are 5 terminals. Two for the coil, and three contacts. Notice that there is no electrical connection between the coil and the contacts, so if you are switching AC power the AC power is totally isolated from your low-voltage circuitry.

"C" is common and it's connected to "NC" (normally closed contact) when the relay is not energized. When the relay is energized, "NO" (normally open) gets connected to common. NC and NO are never connected together.

How do i plug it to controll it from the arduino ?

Connect VCC to 5V and GND to ground. Connect IN1 to the Arduino output pin of your choice, and program that pin to control the relay.

Since you bought something from an unknown manufacture and a flakey supplier, you don't get a schematic or complete-detailed specs. :wink:

Thanks ! I'll try that tomorrow !
I assume a High position activate the electromagnet, while a Low position deactivate it ?

I assume a High position activate the electromagnet, while a Low position deactivate it ?

No, as stated in the product description, the relay is active low. This means the relay coil is energized and the C and NO terminals are closed (~zero ohms) when IN1 pin is a logic LOW.

There is also a link to a downloadable copy of the schematic, just be aware that the site is in Chinese. 继电器-Q1.pdf_免费高速下载|百度网盘-分享无限制

It might be in your best interest to experiment with dc powered items until you get a grasp on the electronics thing. Mains voltage can kill you if not handled properly (ie; don't handle it), and can also start fires.

I experimented, and it works ! But it's a bit weird, i had to connect the gnd AND in1 to the ground... Am i doing something terribly wrong ?

tinman13kup:
It might be in your best interest to experiment with dc powered items until you get a grasp on the electronics thing. Mains voltage can kill you if not handled properly (ie; don't handle it), and can also start fires.

Thanks you for the advice, i'm taking a lot of precaution since the incident !

Active low means that when the signal (IN1) is LOW (0V/GND) that the relay will connect the NO to the COM.

The Arduino's job is to pull that IN1 to GND as a means of control, your fiddling is just doing what you're probably trying to have an Arduino do.

But it's a bit weird,

No it is not. It is called sinking current and is the more normal way of turning things on with logic. It is only beginners who think that sourcing current is the "natural" way to do things.