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Isolation switch


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Fish_in_a_Barrel



Joined: 30 Sep 2006
Posts: 673
Location: Perth, Western Australia


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Isolation switch

Does an SSR/car relay triggered by a small external switch meet the "battery isolator" rule?
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Post Mon Nov 05, 2007 8:28 pm 
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Spockie-Tech
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Joined: 31 May 2004
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Location: Melbourne, Australia


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I have not heard anyone ask that before, but my first thought is No.

SSR's are some form of silicon switches. One of the common failure modes for Fets is shorted (Fuses into a conductive blob inside), which means no reliable way of disabling power to the robot in the event of SSR failure.

If you can demonstrate the ability to remove a battery power lead from the robot in under 60 seconds as a "backup" disconnect method in the event of SSR failure, then it would be ok.
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Post Mon Nov 05, 2007 9:30 pm 
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Fish_in_a_Barrel



Joined: 30 Sep 2006
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I thought as much, just wondering. I guess the same would be true for a regular relay, in the case that a large current is drawn it would weld itself together.
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Post Mon Nov 05, 2007 10:17 pm 
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Spockie-Tech
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A regular relay does have a form of mechanical disconnect where the contacts are physically moved apart (by spring pressure), unlike a SSR

but I still wouldnt reccomend it as a safety shutdown system since I have seen many of them weld closed.

Is there some reason you want to use a relay or SSR instead of a mechanical switch or disconnectable lead ?
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Post Tue Nov 06, 2007 9:27 am 
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Fish_in_a_Barrel



Joined: 30 Sep 2006
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Location: Perth, Western Australia


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No special reason, just the usual that my robot is low on space, and I'm low on cash.

Looks like now is the best time to impost a whyachi switch anyway, since the exchange rate is good.
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Post Tue Nov 06, 2007 9:52 am 
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Spockie-Tech
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Hella 75amp switches from the local auto parts place are usually enough for most featherweights, or just use a 2 pin block connector that you can get to and unplug in under 60 seconds if cash is low. Smile

If you use the hella switch, it might be a good idea to remove the big chrome knob to prevent accidental inertia/shock switch off's
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Post Tue Nov 06, 2007 11:51 am 
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Rotwang
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Joined: 15 Jun 2004
Posts: 1586
Location: Vic


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http://robotcombat.com/marketplace_switches.html Actually it’s packaged by Narva as sold from bursons repco etc. Super cheat even sell them. Smile


http://www.narva.com.au/Switches_1.html


60018
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Post Tue Nov 06, 2007 12:24 pm 
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Fish_in_a_Barrel



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yeh, I have one of those sitting right in front of me. It just doesn't work in my design.
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Post Tue Nov 06, 2007 12:36 pm 
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Rotwang
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Joined: 15 Jun 2004
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Now if you built from the inside out instead of the outside in you wouldn’t have these problems. Smile
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Post Tue Nov 06, 2007 12:58 pm 
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Valen
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Joined: 07 Jul 2004
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Location: Sydney


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there is always a "bolt switch"
get some micro switches, then use a bolt that slides past them to activate the switch.
Use the normally closed contacts to power the bot. slide the bolt in to "safe" it. extra points for using the same bolt to safe the wep.
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Post Tue Nov 06, 2007 3:44 pm 
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dyrodium
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Joined: 24 Aug 2004
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Location: Sydney


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Very Happy I used that method for roadkill, along with the time where I was using a mono audio jack. Smile It works fine.
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Post Tue Nov 06, 2007 6:48 pm 
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