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I'm trying to wire up the SRD-05VDC-SL-C mechanical relay to a Particle Photon and/or Arduino (not the version that is on a breadboard), and am a bit confused by the datasheet.

I device I am switching on/off is 12 VDC, and I understand NO vs NC..but am not so clear on Coil 1 vs Coil 2.

What I have so far: enter image description here

Basically I've hard-wired a 12 VDC source into Coil 1, while Coil 2 is being driven by a DO on the microcontroller through a transistor to bump up the current to the needed 70+ mA. Is that correct? What is common for..?

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  • \$\begingroup\$ The SRD-05VDC relay is inteded to be operated from 5 Volts. For 12 volts, you need an SRD-12VDC. \$\endgroup\$ – Peter Bennett Jun 29 '16 at 15:50
  • \$\begingroup\$ Yup. Wired the wrong VCC source..should be corrected below. Thanks! \$\endgroup\$ – David Hagan Jun 29 '16 at 18:03
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Coil 1 and Coil 2 are simply the two terminals of the relay coil.

Common is the moving contact of the relay. When the relay coil is not powered, the common contact is connected to the NC (normally closed) relay contact. When power is applied to the relay coil, Common is connected to the NO (normally open) contact of the relay.

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  • \$\begingroup\$ Okay. So Common should be the 12VDC source then? And then one side of the coil should be the DO line (through a transistor), and the other is...? \$\endgroup\$ – David Hagan Jun 29 '16 at 10:50
  • \$\begingroup\$ NC, COM, and NO are the relay contacts, and should be connected as required to control whatever you wish to control with the relay. \$\endgroup\$ – Peter Bennett Jun 29 '16 at 15:52
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So I've modified it to this, which I think may work?enter image description here

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  • \$\begingroup\$ Note that convention in schematics is to have the positive supply at the top and the negative supply (or ground) at the bottom. \$\endgroup\$ – Ignacio Vazquez-Abrams Jun 29 '16 at 12:37

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