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I am currently working on an LED powered flood light that can be controlled via an arduino. The problem I am facing is selecting the proper relay. I'm a programmer by profession and dabble in electronics as a hobby, so there's always the chance that I am overlooking something obvious, which might be the case here.

What I have is an led driver (110-220AC - 288v, 900mA DC). I figure there are two ways I can go about controlling this circuit with an arduino. I can either place a relay between the LED bank and the DC 288v side, or I can place a relay before the driver/powersupply and switch AC. However every time I find a relay I believe will work, one of the specs is off. Either it won't have a high enough current rating, or the max voltage will be too low. The closest one I have found is this guy here and I have a feeling I'm way off. It's only rated at 500mA which won't work as I'll be pushing 900mA, but another thing that caught my eye is that it says "maximum switched power: 10W". The circuit this relay would be responsible or controlling would be upwards of 200 - 230 watts, so I'm guessing this is a deal breaker as well?

What type of relay does one use to control a high wattage circuit with a low voltage micro-controller (in this case an arduino)?

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    \$\begingroup\$ Switch the AC live side. I'm surprised you're having trouble as this seems to be a common arduino use case: rapidonline.com/… \$\endgroup\$ – pjc50 Sep 21 '16 at 13:33
  • \$\begingroup\$ I guess the LED driver you have doesn't happen to have an on/off logic-level (or similar) control input, but maybe you could find one that does. \$\endgroup\$ – Andrew Morton Mar 29 '17 at 18:33
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Switching can be done on high or low side, AC or DC. Safety in the off state is a consideration and if isolated or not.

Low side DC switching makes it easy to perform with optoisolation and a very low swing between open circuit voltage and ground. Opto MOSFETS exist or one can use Optotransistors and MOSFET if soldering or wiring in sockets is feasible for you. Relays with high voltage >=400V start with 24V For safety you should consider a relaiable switch that will not turn on from a power line transient contact arc when being serviced. but more info is needed for me choose what is best, since the "best" criteria is not given and ther are no datasheets on anything nor installation environment.

Relays perform worse on power supplies due to the inrush current of the storage caps unless it has soft start. Zero crossing photo triac switches exist but are typically more expensive due to packaging.

I would say a DPDT relay on both DC outputs +/- is safe , effective but may cause issues with the supply without any specs.

Any scenario can have problem when the power supply is an unknown.

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It depends how often you want to switch on and off your circuit. Mostly mechanical switches are recommended for this applications such as this and this. If you think mechanical relays are not good enough, you may should think about TRIAC. I haven't work with triac myself.

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You can use photo triac coupler MOC3022 family and TRIAC BTA316 family. With this solution you can drive up to 16A with the input of 10mA.

http://2.bp.blogspot.com/_UHfDXCEzDKI/TO8pyxnPkgI/AAAAAAAAALw/Wfu7PLXDkI4/s1600/Untitled.png

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It will be easier to switch the AC side as the zero-crossings provide an opportunity for the switch (whether a relay or a semiconductor) to turn off without dissipating a large amount of instantaneous power.

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Look up a Crydom CX380D5. I suspect you may be able to drive it with a 5V output from the Arduino and it should handle the load. It would switch the input to your supply.

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