# Can my relay handle his kind of abuse? or will it die?

#### A Homeschoolers Workbench

Joined Jul 26, 2016
142

#### AlbertHall

Joined Jun 4, 2014
11,100
No you can't do that.
One of these might do the job, though I'm not certain what minimum current it can be set to switch at.

#### A Homeschoolers Workbench

Joined Jul 26, 2016
142
No you can't do that.
One of these might do the job, though I'm not certain what minimum current it can be set to switch at.
Big surprise there "One of these" one of what
AIDayley

Joined Jul 18, 2013
22,640
If switching with an Arduino why not use a Triac, with zero cross switching opto to drive it?
Look up Fairchild app note AN-3006, or you could use an off the shelf SSR.
Max.

#### A Homeschoolers Workbench

Joined Jul 26, 2016
142
I know pretty much nothing about Triacs do you know of any good places to learn about them
AIDayley

Joined Jul 18, 2013
22,640
Here is the basic circuit, very simple using a MOC316x series opto (IC1).

The MOC3022 series are random trigger, you need zero crossing type, also that triac is a little light at 8amps.
AN-3006
Max.

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#### A Homeschoolers Workbench

Joined Jul 26, 2016
142
If I where to use that then I might as well use a arduino.
Thanks for the idea
AIDayley

#### crutschow

Joined Mar 14, 2008
26,732
If I where to use that then I might as well use a arduino.
I doubt that you can build an Arduino circuit to detect AC current cheaper than that ebay device.

Joined Jul 18, 2013
22,640
You can also pick up a ACS712 on a board for $1.60 off ebay. Max. Thread Starter #### A Homeschoolers Workbench Joined Jul 26, 2016 142 I doubt that you can build an Arduino circuit to detect AC current cheaper than that ebay device. You are incorrect in that assumption, I can get an arduino pro mini for 2$ but that Current Sensor Module is 12$, I think I am going to try to use a Triac, again does anyone have a good source on Triacs so I can learn about them. AIDayley Thread Starter #### A Homeschoolers Workbench Joined Jul 26, 2016 142 I had misunderstood your intention a little. You can also pick up a ACS712 on a board for$1.60 off ebay.
Max.
If I where to use one of them, is there a schematic which I could use?
Thanks
AIDayley
ps Thank you for putting time into this.

Joined Jul 18, 2013
22,640
The Allegro PDF on the chip has some applications, you should be able to integrate it with a MOC3162 as in the Fig 1 in the AN-3006 or in post#7.
Have you ever used Picmicro's?
Max.

#### A Homeschoolers Workbench

Joined Jul 26, 2016
142
No I have not

#### PlasmaT

Joined Feb 19, 2015
61
Use a resistor parallel to the relay coil. This will reduce current across the relay coil.
Based on the current the motor needs to operate, you may have to choose a resistor of low resistance.
for e.g. If the motor needs 15A, then consider a 0.4 Ohm resistor (a shunt resistor) to give about 5V for the relay to operate.

#### AlbertHall

Joined Jun 4, 2014
11,100
Use a resistor parallel to the relay coil. This will reduce current across the relay coil.
Based on the current the motor needs to operate, you may have to choose a resistor of low resistance.
for e.g. If the motor needs 15A, then consider a 0.4 Ohm resistor (a shunt resistor) to give about 5V for the relay to operate.
Then you will need a 5V AC relay.

#### PlasmaT

Joined Feb 19, 2015
61
Yes. But note that the resistor will have to have the required wattage and heat sinking is required. Well 90W
Or as AlbertHall has already suggested, use a current sensor and then drive the relay.
Alternatively use a hall effect sensor to detect the magnetic field around the 15A wire and then link it to the relay.