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Reply to "PW Whistle Detection Circuit"

JTrains posted:

I’m looking to build a few whistling accessories in the Post War style that respond to the classic whistle activation DC offset.  In place of the usual whistle tender relay, I’d like to build a discrete circuit. 

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Well, before releasing Gerbers I think it prudent to define the goal.  As I understand the OP, the idea is to replace the obsolete and somewhat finicky Post War relay with a solid-state equivalent...just as the ERR Hobby Corner page describes.  So is that it?  Is the objective just to convert this to an OSH Park ready design to get the bare boards for $2 (free shipping)?

Or is it to identify exactly what these "whistling accessories" are and potentially integrate those circuits...or perhaps realize that the accessory is a DC device (like a 1.5V DC horn circuit) and use the DC detector to trigger a 50 cent power transistor/FET rather than a spendy SSR or bulky relay?

I found C and D size battery holders as illustrated earlier on eBay:

c and d battery holder converters

If one of the "whistling accessories" is indeed a 1.5V horn battery circuit, that might be a fun project.  I don't have such an accessory myself but I suppose there might be some benefit to cramming the DC offset detector and battery-replacement within the confines of a D holder(?).

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