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Trying to figure out which relay I need for a project I'm working on. The source is a 12V battery, and I'm looking to turn on a 12v solenoid using a relay. I want the control voltage on the rely to be 5V, so I need a 5v relay capable of switching 12V. Found this relay but I'm not sure if I'm looking at it right. Would this relay be capable of doing what I want?

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  • \$\begingroup\$ We don't know how much current your load needs, nor what your available drive current is. \$\endgroup\$ – Ignacio Vazquez-Abrams Apr 15 '15 at 20:14
  • \$\begingroup\$ I guess you are locally generating 5V for the relay? \$\endgroup\$ – Andy aka Apr 15 '15 at 21:13
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In the comments, efox29 found a datasheet for this relay which will help in my answer. (Thanks!)


There are two parts of a relay to look at:


Coil

Your control voltage needs to match the coil voltage. They're both 5 V here. Good.

Your control output needs to supply enough current to make the coil work. The datasheet says that this relay takes 71.4 mA of coil current. That's quite a bit, and it's definitely more than an Arduino can source. I don't know what you're planning here - you should look at driving the coil with some sort of transistor driver.


Load

The relay needs to be able to withstand the load voltage when it's off. Here, the contacts are rated to 30 VDC, and the highest voltage in your system is 12 V. Good.

The relay needs to be able to pass all of the current into your load. The link says 10 A. You didn't say anything, so I can't confirm this. If your solenoid's required current is less than 10 A, this is fine.

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    \$\begingroup\$ found datasheet here - ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf coil current is 70-90mA. Arduino wont be suitable to drive it directly. Switching transistor needed. \$\endgroup\$ – efox29 Apr 15 '15 at 20:24
  • \$\begingroup\$ @Gregd'Eon just trying to water my garden .. have a little solar panel on the shed with 12V battery here is the soleniod dx.com/p/… does not list the amperage but I would assume its small ... I probably should fuse it somewhere in the mix \$\endgroup\$ – user379468 Apr 15 '15 at 21:06
  • \$\begingroup\$ The amperage will not depend on your battery's limit - if you want the solenoid to work, it demands a certain amount of current. That amount is the number you need to check. \$\endgroup\$ – Greg d'Eon Apr 15 '15 at 21:12

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