^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 -~----------~----~----~----~------~----~------~--~---
