are you building 10 tanks Chris? :-)
On Aug 22, 9:13 am, "Chris. b" <[email protected]> wrote:
> ^great news! if you ever get this circuit into production I'll take
> 10! I would love a .5 second "open time" (valve that is) and a 5-10
> second load time for semi acurate reload times
>
> Chris. b
>
> On Aug 21, 10:08 pm, Modena <[email protected]> wrote:
>
>
>
> > I have progress!
>
> > Catching up on 30+ years of electronics evolution, I discovered that
> > the 555 timer chip can be wired in monostable mode, also called "one-
> > shot" mode. In this mode it can be activated by a momentary
> > pushbutton, upon which it activates an output pin, said pin stays high
> > for a time period derived by changing values of two components, a
> > capacitor (C) and a resistor (R), at expiration of time the pin goes
> > low again.
>
> > The timing delay is calculated with T(secs) = 1.1 x R x C
>
> > where R is resistor in ohms and C is capacitor in farads. Apparently
> > the 555 can reliably goes as low as 10 milliseconds for this timing
> > cycle, and as high as many many hours, and wiring multiple circuits of
> > this type in series can give you days and days, not that I need this,
> > but I thought it was cool anyway.
>
> > therefore a 22uf cap and a 10k resistor will give 1.1 x 10000 x
> > 0.000022 = 220 milliseconds
>
> > I have built such a circuit on a breadboard and am happy to say it
> > works.
>
> > I used a 22uf cap and a potentiometer resistor adjustable from 0 - 10k
> > ohms. I connected the output of the 555 to a 12v LED, and can see the
> > difference in length of flash when adjusting the pot, yay! This gives
> > me 0 - 220 (approx) milliseconds of adjustable "on" time. This
> > adjustability is critical with a homemade canon as different valves
> > are going to vary on air flow, and I don't have a marker-engineering
> > R&D department :)
>
> > When you push the button, the output goes high and the timing cycle
> > starts, milliseconds later (depending on where the pot is set) the led
> > switches off (output goes low again). It matters not if you release
> > the button before the end of the timing cycle or if you hold the
> > button in, it is a one-shot circuit, to "fire" again you must release
> > the button and then press it again.
>
> > To accomplish the second part of my requirement (delay to allow
> > reload) another similar circuit can easily be connected in series.
>
> > The one-shot circuit diagram is all over the net, but I used the below
> > one as a reference as it seemed to have more protection built in than
> > other examples I looked at:
>
> >http://www.circuitdb.com/circuits/id/107
> > (tis the one on the right, and I have my 10K pot in place of the 47K
> > resistor shown in the diagram)
>
> > here is a pic of the buggery box, not pretty even for a prototype but
> > it works like a champ :)
>
> >http://www.holnet.net/images/tank/20090821/555%20one%20shot%20timer%2...
>
> > runs of 12vdc
>
> > In practice the output pin will switch a small solid state relay,
> > which will switch the air valve.
>
> > Canon firing-range data will determine if I guessed the right values
> > for my resistor and capacitor, but being adjustable up to 0.22 seconds
> > I think it will be ok and if not it can be easily changed.
>
> > Ben
> > Electronic-Battlefield Warfare Regiment - Southern Tankers
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