Hi all, I'm looking for a circuit, either a kit, or built that will flash low wattage 12 volt lamps AT RANDOM. I need to flash about 25 bayonet bulbs, a bunch at a time but completely random. Like if I just used old style flashing bulbs with the bi-matalic strip inside. Also it would need the capability to change speed. Does anything like this exist without spending a lot of money??
The usual source of "random" signals is a pseudo-random binary sequency generator.
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The sequence of "0" and "1" states it produces isn't actually random, but a long enough shift register won't repeat itself for quite a while and is random enough for your kind of application,
Horowitz and Hill's "Mastering the Art of Electronics" has a useful section on the subject in chapter 9.32.
These days a professiona engineer would realise the shift register and the exclusive-OR gate in a programmable logic array or a single-chip microprocessor, but you can still buy cheap CMOS shift registers and OR-gates, and use the shift register's parallel outputs to drive the gates of 25 cheap N-channel MOSFET transistors to control your lamps.
A little off the beaten track, but it might work. (?)
Get a box and attach little strips of metal inside so that the edges line up close to each other. Each pair of strips will form one switch. The gap between the metal strips should be small, maybe 0.1 inches apart. Connect it all up.
Then fill the box with ball bearings and shake. Adjust amount and size of ball bearings until you get the effect you want.
MacGuyver up some way to shake the box and you're done!! :)
"John Fields" schreef in bericht news: snipped-for-privacy@4ax.com...
The 555 solution looks promessing. But you may need to take measures to prevent the individual circuits from "seeing" each other. I once experienced that similar circuits synchronized after some time. Never had the change to look after the cause but I guess they influenced each other via the power lines. For the same reason the gates-solution may not randomize.
Steve doesn't seem to want to simulate lamps with mechanical flashers
- he's merely asking for something similar.
This doesn't seem to cut into the sales of LED-based flashing lights
Sonce the 555 doesn't have a lot of common mode rejection, this is unlikely to be true. I suppose that anybody silly enough to propose wiring up 25 555-based drivers has to be silly enough to be unaware that buying twenty-five identical resistora and capacitors is likely to get you parts from the same manufacturing batch, which will be much closer in value that the specified tolerance, so there might not not be a lot of unit to unit variation between the array of 555-base flashers to prevent the switching spikes from one part from triggering all the other parts that are close to switching, and eventually forcing most of the flashers to cycle in concert.
The kind of elaboration that often goes wrong ...
You really do want Steve to do a lot more soldering that he has to, don't you.
Are there an endless supply of wet-back wiremen in Texas who will work for peanuts?
PLA's? uP's??? That's like using a cruise missile to kill a mouse. Google "relaxation oscillator". P.U.T.'s are still available from ON Semi (and maybe others) for about a dime ea. Freq can be varied by varying the charging resistor. Add an NPN to the output to drive the load.
5 or 6 parts per flasher output should about do it. Art
G > Interesting problem. G > Kudos to mpm (alias Rube Goldberg) for the ball bearing solution. =A0LOL
G > Don't they still make LED's with blinking circuit built in? G > Do those have good common node rejection? G > Do they end up synching up with each other?
JT > I think it's a given that, unless you have phenomenal VDD filtering, JT > relaxation oscillators tend to at least "semi-sync".
Would the blinker LED's at least make the amount of filtering required more readily attainable?
G > Could the LED's with blinking circuit inside be used G > to drive FET driver transisters?
Jim Thompson seems to forget that he can't read my posts, so he hasn't actually read what I posted on the 19th. It's not a fully worked out solution - I haven't specified a clock generator to clock the pseudo- random binary sequence generator, nor specified the the CMOS shift registers that you might use to build it or the "n" and "m" numbers for a particular pseudo-random binary sequence generator - but I could do it in a couple of minutes. It isn't exactly rocket science, even if John Fields finds it intimidating.
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