Relay for cbc/xbc?

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Hoop1101
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How would you safely connect a relay to a CBC or XBC to run a 1.5amp device? Specific relay and part numbers would be extra helpful!

baobrien
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for most low draw relays, you could probably just attach the coil in any orientation straight to the motor port. I haven't tried it, but I don't see why it wouldn't work. I don't think most small relays would draw more than the motors.

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KIPR Matthew
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*!* This will void your warranty *!*

The current h-bridges on the XBC and CBC use the TI sn754410ne h-bridge to drive the motors. As is these can handle up to 1A per motor port. The beauty of these is that you can use them in parallel (piggyback them) and get up to 2A per motor port! (see: http://forum.sparkfun.com/viewtopic.php?f=14&t=22462) If the device you want to drive is less than 2A, you can add the extra h-bridge and you will be good to go.

Just wire it into two of the motor pins. Just make sure the device you are powering is plugged in to the port in the correct direction and only drive the port one way (I suggest Forward for simplicity fd();).

If you really want to void your CBC warranty, there are two extra h-bridge sockets already on the board, so you just need to add two more chips (~$1 ea.)!

You can the h-bridge here: http://app.arrownac.com/aws/pg_webc/0,1086,,00.html?application=SEARCH&a...

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Jeremy Rand
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I don't know if this is useful for you, but if you have a Create available for your project, you could also use the LSD2 pins on the Create Cargo Bay Connector. The current limit is either 1.5A or 1.6A, depending on which documentation you believe. This may be easier to setup than what Matt said, and it won't void any warranties. (Not that I have any problem with voiding warranties!) Of course, this is useless if you're not using a Create.

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Hoop1101
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Thanks everyone! Great information. I hadn't thought about the cargo bay port either.

Jeremy Rand
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No problem. Let us know if you have any luck. :-)

-Jeremy Rand
Senior Programmer, Team SNARC (2012-2013), Norman Advanced (2010-2011), Norman HS (2008-2009), Norman North (2005-2007), Whittier MS (2003-2004)
2012-2013 VP of Tech, 2011 President, Botball YAC (2009-2013)
Mentor, Alcott and Whittier MS