whatever you end up with, i would use an iso automotive relay as the final link
they are rugged, cheap and widely available and you can get them with a socket and pigtail.
being double pole single throw, one n/c and one n/o
allows the relay to do double duty as well.
you can use a common npn transistor to control the iso relay, some of which can handle 60 plus amps, common ones are 30amps dc
some even come with clamping diodes built in, but generally you can provide your own for less money than having them built in and saves issues later down the road should you or someone put in a standard iso relay without the clamping diode.
also being made for automotive use, they tolerate high underhood temps, humidity, vibration, shocks and other abusive stuff that common electronic's don't fair so well dealing with.
cars/trucks use them to control just about everything imaginable, so they are likely the most manufactured relay on the planet in shear numbers.
at sub 2 bucks a piece for 30amp rated units (relay only, socket/pigtail extra)
their my interface of choice as a final control handle using microcontrollers.
here they are on ebay, with socket/harness for 2 bucks each!
http://cgi.ebay.com/ebaymotors/10-PACK-12V-12-Volt-30-40A-Automotive-Relay-Socket_W0QQcmdZViewItemQQ
_trkparmsZ72Q3a1205Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a1Q7c293Q3a1Q7c294Q3a50QQ_trksid
Zp3286Q2ec0Q2em14QQhashZitem2ea2c04233QQitemZ200299004467QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccesso
ries
bob g
