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Crowbar Circuit

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pmather

Joined: 17 Sep 2009
Posts: 33

Posted: Thu Nov 19, 2009 11:24 am Post subject: Crowbar Circuit

If anyone is interested I've posted a circuit and veroboard layout for a 

tested and working crowbar circuit based on the MC3423 chip on the blog for 

my Wittman Tailwind build. Total parts cost around $5.



http://tailwindbuild.blogspot.com/2009/11/15th-november-2009-overvoltage-crowbar.html



Click on the pics/diagrams to enlarge



The variable resistor allows the crowbar voltage to be set as required and 

compensates for differences in the internal reference voltage on the MC3423.



Best regards



Peter

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 20, 2009 5:25 am Post subject: Crowbar Circuit

At 12:35 PM 11/19/2009, you wrote:

 	  Quote: 	
		  



If anyone is interested I've posted a circuit and veroboard layout 

for a tested and working crowbar circuit based on the MC3423 chip on 

the blog for my Wittman Tailwind build. Total parts cost around $5.



http://tailwindbuild.blogspot.com/2009/11/15th-november-2009-overvoltage-crowbar.html



Click on the pics/diagrams to enlarge



The variable resistor allows the crowbar voltage to be set as 

required and compensates for differences in the internal reference 

voltage on the MC3423.


	


    Some thoughts based on lessons-learned:



    You need to select the trip time delay capacitor

    for something on the order of 50-100 milliseconds.

    Further, depending on how "twitchy" the SCR is,

    you may experience nuisance triggers of the SCR

    due to very low energy but fast rise-time

    noises on the bus. These are effectively dealt

    with by tying a 10 ohm resistor from SCR gate

    to ground (which may mean a commensurate increase

    in gate drive requirements from the MC3423).

        Bob . . .



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