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Asked — Edited

Fuse Question

(appoligies if this is a dupicate post)

I am trying to build a robot (full sized K-9) and am contemplating putting in a fuse.

I'm using a lead 12v battery, which has connections to a sabertooth 2x12, ez b board, servos, 2 motors (says 14 amps at max load), a car antenna, LEDs, sparkfun mp3 trigger, speaker, multiplexer (to switch from RC to EZ b), and digital picture frame. Wiring will generally be 16 gauge. Connectors are powerpole. I may add a power distribution board.

I realize this is a hard question to answer since I don't have the entire circutry built yet, but can someone give me a ballpark answer with regards to what strenght fuse to get? I found a good article from the Society of Robotics website, but it's getting a little over my head.

thanks in advance,


Thanks. I acutally had ordered a fuse holder that would go directly off the battery at the moment. What rating / strength of fuse(s) would be appropriate (especially for the EZ B and motors, which are the biggest expenses in this build).

Here's what I do;
As DJ said put in a few circuits. I like to put larger items like large motors and sensitive things like the EZ-B on their own circuit. I also group smaller stuff together. However the more things on a circuit, the harder it is to trouble shoot if the fuse blows.

Which brings us to the fuse; Once you know what your going to put on a circuit you need to measure the amps it pulls under full load. You'll need to get a Multi Volt tester that is able to measure amps also. Then learn how to use it. It's as simple as learning the settings on the tester for what you will use it for and the levels of current you need to test. For example when testing amperage you place the two leads in the circuit (just like the wire running from connection to connection) and turn on the device to as full of a load as you can. Watch the amp meter and it will read the amperage level. Put in a fuse just a little higher then the reading. Example: meter reads 1.7 amps, use a 2 amp fuse. I always use a Slow Blow type fuse because without getting too deep here it will take more stress or surge before it blows. It's a little more forgiving.

As far as EZ-B goes I learned that the more you have it do the bigger fuse it needed. I started running with a 2 amp slow blow just fine. When I started running an H-Bridge the fuse blew. That's good. I just stepped up the fuse size a smidgen. Again, this is where your Amp Meter will come in handy.

Hope this helps,
Dave Schulpius
Thanks DJ and Dave it certainly helps me:)
Thanks, guys!
Excellent information here.

Glad to help. Odd though that this only showed up yesterday. I sent this post 4 weeks ago! "Such strange goings on" (quote from Young Frankenstein).