Ahh, so simple, but so elegant. That should work rather well. The other option is to just use a couple of transistors and capacitors, but I don't know how well you could control the on time for. I would make one right now, but my electronics time right now is being taken up by making a synthesiser.
-Gregory On Sat, Aug 22, 2009 at 11:33 AM, Modena <[email protected]> wrote: > > 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 > > > --~--~---------~--~----~------------~-------~--~----~ You are currently subscribed to the "R/C Tank Combat" group. To post a message, send email to [email protected] To unsubscribe, send email to [email protected] Visit the group at http://groups.google.com/group/rctankcombat -~----------~----~----~----~------~----~------~--~---
