Pseudo Random Timer

Discussion in 'The Projects Forum' started by HubertH, Jul 25, 2013.

  1. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    Hi,
    I've been looking online and I've been searching this forum but I can't seem to find what I'm looking for.

    I'm a sports shooter in the Netherlands. We shoot competitions every once in awhile. One of the competitions is some sort of duel.

    What I'm looking for is this. Two red lights are burning. At the push of a button, within let's say 4 to 8 seconds the red lights go off and two green light come on. Two 'cowboys' or 'cowgirls' shoot at their target (a balloon). The first balloon to pop will turn on a light and shuts of the possibility of turning on the light of the second target.
    I think I have the second part under control with the use of PhotoElectric beams and some relays but I'm looking for the timer circuit and a connection to the PhotoElectric Beams.
    Any kind of help is greatly appreciated.

    I found a circuit on this forum from march 2009 but I don't know if I can use it?

    Thanks,

    Hubert
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Looks like that should work for your purposes. Do you have questions about how it operates?
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Looks ok, led connected to 555-2 should go to pin 3 and not Q1 base, but otherwise should give random times,what is the relay doing?
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A recent post for a bow & arrow pop-up target, OP dthx, used almost the same thing & can be slightly modified for your needs. It's still on breadboard.
     
  5. Bernard

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    This was origional from OP, MLD, for pellet gun pop-up target. U1, free running 10 kHx osc.; U2 random resistor selector for U3, one-shot; U4 controls on time for air valve.
     
  6. Bernard

    AAC Fanatic!

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    Here is verry rough outline:
    At power-up, all 555's except U2 are reset thru one OR input, U2 is set at power-up turning on Red light.
    Start SW is pressed, U1-3 goes hi, for a random time. Trailing edge of pulse triggers U3 & U4, turning on both Greens.
    A shot is fired breaking baloon #1 and IR beam is broken generating a + pulse triggering U5; #1 Blue comes on, U4 is forced into Reset as is #2 Blue. #2 shot has no effect. Power off--On resets all for next round.
    Need more inf. on lights & available power.
    U's are 555's or 556's, OR's & Inverters are 4000 seried IC's.
     
    Last edited: Jul 26, 2013
  7. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    Hi Crutschow,

    Thanks for your quick response.

    I think it operates as follows: at the activation of the circuit, with the switch in the top left corner, the timer starts. After a 'random' time the relay in the bottom right corner is activated. The push-button connected to 555-2 is used to reset the timer.
    What I can't figure out (and can't find in the thread the circuit originally was posted in) is, is what the minimum and maximum delay is.
    Is this delay determined by changing the values of the capacitors?
     
  8. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    Hi Dodgydave,

    Thanks for your quick reply.

    Like I said to crutschow, I don't know what the minimum and maximum values are. Are they seconds or is it minutes? If the led connected to 555-2 should go directly to pin 3 and not to Q1 base, where does Q1 base go then?
    I think the relay is activated after the random time timer.
     
  9. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    Hi Bernard,

    Thanks for your elaborate reply.
    I will have to study your drawing for a bit before I can comment on, or ask questions about it.
    I'm not an expert in electronics. I know most of the parts and what they do and I can build a circuit (have done in the past) but that's about it.
    What I can tell you so far is that I will have to build this entire thing from scratch so lights and power could be anything from a LED to a 230v lightbulb and from a double A battery to 230V AC.
     
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Maybe with some nunbers it will be easier to understand: 556's can replace 2 555's. For testing a resistor & LED can be connected to 555's with > on pin's 3. 12 V chosen for convenient driving of relays or LEDs.
    minimum random time is set with R 12 & max with R 3.
    U9-3 cap, C3, may need to be increased if power is slow to come up & also may pass logic level trash to U9, so may need to add a .1μF across R 14. Look it over & ask questions. I'm out of time for now.
     
  11. Bernard

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    I modified U6 slightly & grounded all unused pin 6's on 555's. U9-2, reset driver marked X goes to all 5 inputs marked with an X. U5-8 & U8-8 are returned to + 12V.
    Added a time chart to help understand ckt.
    Did you want both of the GREEN lights to go out when a BLUE comes on? As it is, first hit GREEN stays on with a BLUE ,other GREEN goes off & BLUE stays off.
     
    Last edited: Jul 30, 2013
  12. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    Allright Bernard, I think I understood most of your drawing. First I turned your drawing into a 'scheme', that clarified a lot . If you have time, could you look it over for me and see if I didn't miss anything.

    I have a few questions.

    1- Not all the pins of the 555's are connected, pin 5 (control voltage). Don't they have to be connected?

    2- On U9, where does the arrow on pin 2 go to?

    3- What are the X, Y and Z (when I think about it I think that Y and Z are the signals coming from the photoelectric beams once one of the balloons is shot)

    I think these are the questions so far.

    Thanks again
     
  13. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Welcome back, 'thought we had lost you.
    C6 is missing & should go to +12 V, inking failed.; C5 is missing; R15 is missing; Ground U5-6, U4=6, & U8-6.
    #1, pin 5 can float or tie to gnd thru .01
    #2, X missing on U9-2, covered in post # 11. Tie all X's together.
    #3, Y & Z are inputs from baloon burst ckt.
    Do not forget LED I limiting Rs, put Reds in series.
    Re do U6 & U9, really messed up.
     
    HubertH likes this.
  14. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    I've been really busy last week, but I'll have more time this weekend and next week.
    I see what happened, I drew my circuit from version #3. I completely missed the 2nd page with threads. Your last comments make more sense now.
    Let met put version #4, together with your last comments in my circuit first. If I still have any questions I'll get back to you later this weekend.

    To answer your question from post #11:

    No, the way you set it up with the first hit GREEN to stay on when the BLUE comes on is perfectly alright

    Thanks!
     
  15. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    Hi Bernard,

    I've built the circuit on a breadboard. The first time nothing happened so I thought I must have made a mistake building it. Took it apart and rebuilt it.
    This time, when turning on power, all LED's immediatly come on and stay on. I'll check my wiring again, guess I made another mistake or two...
    I'll keep you informed.
     
  16. Bernard

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    Aug 7, 2008
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    I wonder what crow tastes like because I'm going to be eating a lot of it. The OR gates should be AND gates operating as neg OR, so functionally I showed them as OR, then forgot what I was dooing & picked a 4071 instead of 4081. Add two more mistakes, U17-6 should go to U12-10, & U14-2 to U13-12. Will re-draw this afternoon & re examine.
     
  17. Bernard

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    Aug 7, 2008
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    This may work a little better; chalk it up to another senior- senior moment. Added R18 & 19 for testing without baloon break ckt. The AND's, 4081, are really neg. OR's so that with normal operation both inputs are high, output high, 555's ready. At turn power on, the X output momentarily goes lo, AND output goes lo,. making sure that all 555's are reset. When either Blue 555 is triggered by a hi on U10 or 11. one of the outputs is inverted, putting a lo on opposite Green & Blue, inhibiting them from responding to a second late hit. Added LED's for testing.
    For testing on breadboard, I would hook up each of the three sections separatly & test before combining them. U6 is the simplest. Might add a 1k & red LED from + supply & U9-2, to monitor neg pulse, X, at turn on . Might increase C5 to 1 μF if red flash is weak.
    U 1,2 & 3 are almost independent excepy for powerup reset, so connect the X. Can add a LED to U3-3 to monitor delay. Select R3 for the longest desired delay & R12 for shortest. One meg & 10 μF gives almost 10 sec. For overall shorter times, reduce C2.
    Pinout is the same for 4071 & 4081. If 4081 not available, use NAND & last inverter, U18 to re invert output. Pinout prob. different.
     
  18. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    I took your changes and put them in the circuit that I drew. I changed one thing though. You connected c6 to +12v and ground, I put it back on the connection between u2-13/u3-3 and ground. I let a simulation programm run it and it seems to work in that simulation. I'll put all the components on the breadboard tonight.
    I'll let you know what happens.

    THANK YOU.
     
  19. Bernard

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    Aug 7, 2008
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    C6 is a power supply glitch filter, & belongs +12 V & gnd. 2 missing pin #s, U10 out is p 4, U8 reset is pin 4. I BBd the new section & U6, LEDs all red. All worked as desired. Did you have a 4081?
     
  20. HubertH

    Thread Starter New Member

    Jul 25, 2013
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    I've found the 4081 yes. Going to put it all on the breadboard now.
    Yesterday I tried to rearrange the wires from the old setup. That was not a good idea! I'm starting from scratch now.
     
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