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Momentary lockout Solenoid

Discussion in 'Homework Help' started by syntax_x, May 21, 2013.

  1. alec_t

    alec_t Well-Known Member Most Helpful Member

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    That's correct for D4, but why is the GND terminal of the 555 connected to +5V? I don't see how your trig arrangement can give you the lockout you asked for when you are effectively disconnecting the 555 supply (except when the trigger is held down)? The 555 and R4 don't seem to be doing anything useful in the above circuit; the relay is simply energised as soon as the trigger is pressed.
     
  2. syntax_x

    syntax_x Member

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    The GND terminal is connected to a +5v feed because it is the trigger lead from the guns pcb.

    When you pull the trigger, that lead is grounded and the screen registers a shot.

    Ive hijacked this ground to power the circuit so upon every trigger press the 555 is grounded and functions as a one shot 0.05 second pulse.
     
  3. syntax_x

    syntax_x Member

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    deleted
     
    Last edited: Jun 10, 2013
  4. dave

    Dave New Member

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  5. syntax_x

    syntax_x Member

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    Last edited: Jun 10, 2013
  6. syntax_x

    syntax_x Member

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    Ive been playing around with the driver for a few days now, this is where im at.

    Ive built the rapid fire 555, but i feel it has input lag..
    [​IMG]
    http://www.eugene.kizza42.com/555/rapid%20fire%20driver.asc

    As for the original driver, ive taken the Nmosfet out of the loop and tried having trig running straight to + OR ground but it didnt work for me and i cant figure out why,
    i thought 555's in momentary mode only really need 1 cap and 1 resistor (besides the cap on cv) like the following
    [​IMG]
    [​IMG]
    http://www.eugene.kizza42.com/555/Not%20Working.asc


    So ive had to do this for now to get it running again, Ive also noticed that when i have the 100r resistor in place it dims the LED on the relay to the point you can barely see it.
    [​IMG]
    http://www.eugene.kizza42.com/555/Current%20working%20solenoid%20driver.asc

    Im a little lost....
     
  7. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Your 'not working' circuit fails because, assuming 5V is a constant supply, the 'trig' input of the 555 is not taken low initially to start the pulse. R1C1 remedy that in the 'working' circuit, but their values were originally selected to prevent rapid retriggering. If, now, you want a rapid fire system then C1 can be reduced to, say, 47n.
    The resistor (100R) in series with the relay coil is unnecessary if the relay is a 5V coil type, unless the coil draws more than the 200mA for which the 555 output pin is rated. What is the coil resistance/current rating?
    Rather than grab the 5V from the gun trigger (presumably via some unknown resistor) it might be better to use a 5V voltage regulator powered from the 24V rail.
     
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  8. JoeJester

    JoeJester Active Member

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    Somethings to consider ... it looks like the pistol is a replica of the M1911 45 cal. There have been people who had a rate of fire of 550 rounds per minute or 0.109 seconds per round. One hand holding the weapon and the other working the trigger.

    If that is what your pistol replicates, I would build the circuit to allow that rate of fire. Of course, the person would be moving their trigger finger as fast as possible. Also you might consider the number of rounds in the clip and delay firing the time it would take to change the clip which is about one second according to the videos on youtube.

    Of course, if it's not the M1911, I would consider those the number of rounds, the rate of fire, and the delay for clip changes for whatever the weapon that pistol emulates.
     
    Last edited: Jun 10, 2013
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  9. syntax_x

    syntax_x Member

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    Thats some top info Joe! You know your guns :)

    I worked out the per round time by figuring out how long it takes to activate the solenoid (.04 seconds) rounded it up to .05 seconds and doubled it to allow for the solenoid to return to its original position.
    This allows for 600 rounds per minute.

    Now my brother practices button presses per second, i know it sounds strange but check this out.
    [​IMG]


    Well if hes doing normal button presses he can get around 130 per ten seconds, if hes using his fingernail and making his wrist "vibrate"
    he can achieve 170 presses per 10 seconds.
    Thats 1020 presses per minute!

    But id rather keep the rapid fire down to 500 hits per minute to allow for proper function of the recoil.


    Alec-t , the relay is rated at 20mA
    http://pdf1.alldatasheet.com/datasheet-pdf/view/194494/HONGFA/HFS40.html

    If i drop down to say a 47nf cap id have to use a 2.2m resistor to get the 50ms up down im looking for, is this advisable? will there be any significant change in input if a change the cap?

    I figured using the same caps as in the original driver was a good idea as the timings were pretty much the same just ones momentary and the other is astable.

    When using the nMOSFET do you think that maybe it isolates the input/output a little better?
    As the nMOSFET grounds the relay to activate it while without the nMOSFET i have to feed 5v into the relay run it and its always grounded.
     
  10. syntax_x

    syntax_x Member

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    As far as connecting the driver to a separate 5v feed, i have 2 power supplies, ones a 24v 6 amp dc, and the other has -5v, +5v and 12v.

    I was thinking of connecting the grounds of the two supplies and using the 5v feed and just the Nmosfet
     
  11. alec_t

    alec_t Well-Known Member Most Helpful Member

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    The NMOSFET would be preferable to the relay for a rapid-fire system IMO.
    You could re-run a sim with those figures in mind to see what the preferred cap value should be.
     
  12. syntax_x

    syntax_x Member

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    I did and it gave me the same caps, with a 250k pot its as fast and slow as I need.
     
  13. JoeJester

    JoeJester Active Member

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    Now if you used a 1uF capacitor and a 100 k fixed resistor, you would have .11 seconds That is 10 mS slower than your calculation in the quote of doubling the 50 mS solenoid time. That is also only 1 mS slower than the 550 rounds per minute calculation.

    You need to limit the number of rounds to include a reload. Most 9mm have 15 round clips
     
  14. syntax_x

    syntax_x Member

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    The one man army, Richard Miller, only has a six shot pistol and infinite ammo, plus reloads with his foot =]
    - Time Crisis...

    [​IMG]

    Having the pot there allows me to be silly or realistic with the fire rate.
     
    Last edited: Jun 12, 2013
  15. JoeJester

    JoeJester Active Member

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    Yes it does. It all depends on what you want to do.

    You can simulate reality and those "hot shots" racking up outrageous scores will have to refrain from "spray and pray" to making each shot count.

    Gun control isn't about spraying and praying. It's about putting the round where you want it to go.
     

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