RELAY8 8-Channel Relay Driver Shield

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charlest
Posts: 73
Joined: Sat Jul 27, 2013 6:08 pm

RELAY8 8-Channel Relay Driver Shield

Post by charlest » Thu Sep 12, 2013 10:20 pm

Hi, I was wondering whether your "RELAY8 8-Channel Relay Driver Shield" would be able to control a work light set such as Arlec 1000W Halogen Worklight With Tripod?

http://www.bunnings.com.au/arlec-1000w- ... d_p7070522

cef
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Freetronics Staff
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Re: RELAY8 8-Channel Relay Driver Shield

Post by cef » Fri Sep 13, 2013 5:50 am

First off, each light on that tripod draws 500W, so you would need a relay that will handle around 2.5A at 250V on the switching side to switch each individual light on/off. If you're controlling both at once, that would need to be 5A switch at once.

BTW: I've suggested 2.5A to allow for the fact that some AC supplies vary by a large margin, particularly old wiring (tends to be <240V) and outback locations (eg: Some parts of WA are known to hit ~260V regularly), so I'm deliberately leaving a reasonable margin for error.

If you can find a relay that draws less than 110mA to energise the coil (which must match the voltage you use to power the shield), and can handle the AC switching requirement, then yes, it should work.

That said, I'd suggest you look at SSR's (Solid State Relays). These are designed for driving large voltages at fairly decent currents. You can happily drive these off the RELAY8.

You can pick up SSR's for $5-10 each off eBay or other places. eg: http://www.ebay.com.au/itm/SSR-25-DA-So ... 0776557335

SSR's can generate a bit of heat when switching large loads, so you should consider making sure that the "metal base" is adequately cooled (eg: attached to a larger piece of metal to act as a heatsink). While it should not be live when connected to AC, it should probably be considered as such, and not connected to a grounded metal case.

NOTE: The above link on eBay was simply one that I found. I'm not specifically suggesting it's any better/cheaper than any other specific product. This should also not be considered as a specific recommendation for that product. If you have no electrical wiring knowledge (or even if you do) please consult an qualified electrician for specific wiring details and/or to perform the wiring and/or sign off on the work before connection to mains.

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