On Fri, Jan 10, 2025 at 01:37 PM, Dan Kahn wrote:
Sabre diagram
Did you leave out a series resistor for the LED?
While you can power a LED from a button lithium cell because of the high internal resistance will limit the current, 3 or 4 NiCads will dump a lot of current, I've spot welded with 4 D cell NiCad, N cells would provide a lot less current but still enough to put a LED at serious risk of "burning" out.
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I fought NiCad's every working day from October 29, 1979 until May 23, 2003, lost more battles then I won.
Our Sony electronic TV field gear used 12V NiCads with ~"C" cells. Sony electronics had a hard, absolute lower voltage cut out of 12V. Not 11.8 but 12. Perfect for creating memory.
I used a Rat Shack PC DVM, spare PC, printer port to drive a relay with a resistor to draw 2A, the PC would record the number of minutes a battery would stay above 12V. This allowed me to weed out failing cells.
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While Sony's batteries were obscenely expensive, that cost was less then a busted video production.
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I have serious doubts, as in "there is no way on earth to make that circuit work, if will fry the NiCads and there is no easy fix."
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Perhaps you could use PIC or PICaxe to monitor the NiCad voltage and charge when needed.
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On a personal note, I was very active in the 1980s, early 1990s, with SkyWarm, a system that used amateur radio as tornado spotters. My wife and I used iCom IC-2AT that came with NiCad battery packs. They had active charge control that sort of almost worked....but we switched to alkalines because NiCads were not worth the hassle.
Intersil (or some company) made a smart IC designed to charge NiCads. A friend swore by it and had great success. I was too busy with work and home life to etch a board and play with the IC. Sadly my friend passed in August and I'm not sure of the manufacturer.?
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There are opamp based smart NiCad chargers but, even with surface mount parts, I doubt you could squeeze it in the original case.
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A stun gun is nice, a can of bear spray will stop a raging bull. Personal experience. Dropped the sucker to jis knees and I skedaddled over the fence.
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If your stun gun uses NiCad, how old is it?
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It might be time to upgrade to a system with NiMH or Lithium-ion batteries.
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A friend of my wife has a stun gun with a damn bright LED with a "dazzle" function.
Press the flashlight button 2 (or 3) times really fast and the LED flashes in a "random" pattern that will disorient you if it used in the dark.
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BTW, I have a no name "made in West Germany" personal alarm that uses 6 AA cells, and has a battery powered siren. I found this pretty small metal box about the size about the size of a paperback with a pin, I pulled the pin and the resulting sound was so loud I couldn't think. No one in the thrift store could.
I managed to push the pin back in and the shop owner begged me to take it away.
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I worked at a facility that frowned on firearms (as in we'll fire you on the spot). We backed up to an economically distressed area, I had to work really late several nights, I wore ear plugs on the way to my car, one night I was confronted by a group of yutes and pulled the pin.?
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To quote a song from my childhood....
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Yeah, they ran through the briers and they ran through the brambles
And they ran through the bushes where a rabbit couldn't go?
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A NIST reference calibrated sound meter says the unit produces 130dB.
You might consider an audible deterrent.....
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