simple 1 minute delayed push button

Discussion in 'Homework Help' started by ajzero, Nov 7, 2015.

  1. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    Hi all,

    I have a toy with sound effect, when I push a button on it, it plays a sound.

    I want to turn this toy into a 1 minute timer, so that when i push the button on it, it will play a sound after 1 minute.

    I tried to find a control circuit for this, but all I can find is timer circuit that stays ON for 1 minute.
    Please help!! Thank you!!
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    So why not use the timer that stays on for 1 minute to provide a one minute delay before activating the circuit that plays the sound?
     
  3. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    I tried this with a 2 stage time delay circuit using two 555 timers, and it's working exactly what I wanted. However, I dont like the fact that the circuit is always drawing power from the toy. I would appreciate if someone could suggest a more power efficient and simpler circuit using as few components as possible. thanks!
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    You might use a very low power MCU. Perhaps one of the 8-pin PICs or similar would suffice.
     
  5. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    Thanks for the reply. Im relatively new to circuitry, can you recommend 1 or 2 of these "8-pin low-power PICs", or similar models for me to research on? thanks
     
  6. crutschow

    Expert

    Mar 14, 2008
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    You might use the CMOS versions of the 555 (such as the LMC555).
    They draw much less power.

    A very simple circuit is just to use an RC delay into the gate of an N-MOSFET.
    You may have to tweak the resistor value to get the desired delay but it takes essentially no added power after it's activated.

    What is the battery voltage of the toy?
     
  7. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    The toy uses three 1.5V cell batteries. I built this 2 stage time delay circuit with two 555 on the toy, and the batteries are dead after 2 days...
    [​IMG]

    @crutschow Can an RC delay into the gate of an N-MOSFET do exactly this? Can you please provide me a sample of such circuit?
    Also, with such a circuit, how long would three 1.5V cell batteries last, if the toy's speaker is activated 5-6 times a day, 5 days a week? Thanks a lot for your help!
     
    Last edited: Nov 13, 2015
  8. crutschow

    Expert

    Mar 14, 2008
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    After a little further though I realized that my simple N-MOSFET idea won't work from a momentary button push.

    What type of 1.5V cells, AA, AAA, ...?

    I think using CMOS 555's may be the easiest modification to lower the battery current.
    Each CMOS 555 draws only about 100μA nominal so the toy should run well over 6 months with AA alkaline batteries.

    For even lower currents here is a modification to a standard 555 that reduces the standby current to essentially zero.
    It requires the addition of a CD4050 buffer IC to switch the power to the 555 as shown below:

    555 Low Pwr One-Shot.PNG
     
    Last edited: Nov 14, 2015
  9. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    the batteries are L1154F button cell batteries (very tiny).

    looks like my best option is to hunt down some CMOS555. since LM555CN is the only 555 timers my local electronic store has. I'll also try to switch out the button cell batteries with 3 alkaline AA batteries.

    I'm currently using two 100uF capacitors in the two stage timer circuit. do I need to use the smallest possible capacitors to reduce power consumption too?
     
  10. crutschow

    Expert

    Mar 14, 2008
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    The capacitor size has a negligible effect on the total power consumption which is mainly determined by the quiescent current drawn by the 555.

    Also after some further thought I realized that the circuit I posted would not work with two 555s.
    Edit:
    I modified the circuit by adding diodes to OR the inputs to the CD4050 buffers for proper operation as shown below.
    The six buffer gates in the package are paralleled to increase the output drive capability of the output.

    555 Low Pwr One-Shot.PNG
     
    Last edited: Nov 15, 2015
    ajzero likes this.
  11. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    Thanks a lot!
     
  12. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    Hello, it's me again...

    I finally got my hands on some low power timers (TS555CN).
    However, after I swapped out the LM555CN timers, the circuit doesn't work anymore o_O
    Here is the circuit and its values. Would really appreciate it if anyone can give me some pointers. Thanks!
     
  13. crutschow

    Expert

    Mar 14, 2008
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    Connect Reset pin 4 to V+ on both timers.
    CMOS circuits do not like any inputs to be left open since they can float to an undefined state.
    You may be able to get by with not tying the Reset input to V+ on the bipolar 555 but not for the CMOS 555.
    (In general it's not good practice to let unused inputs open on any circuits.)
     
  14. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    Thanks for the quick reply crustchow! I connected both timers' pin 4 to V+, but it still didnt work. The final output is always high.
    I tested both CMOS 555s on a breadboard, they both work fine with a delayed ON circuit, so I don't think they're defective. Is there anything else that I can try...?
     
  15. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    I don't see anything that says what happens after the 1 minute delay - enable the player continuously, make a start pulse, etc. Here is a 1-minute delay circuit. One minute after power on or a button push, Q14 goes high and stays high. Push to restart.

    ak
    MinuteDelay-1-c.gif
     
  16. crutschow

    Expert

    Mar 14, 2008
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    Double check all the wiring with an ohmmeter.
     
  17. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Here is an updated version with the inhibit changed for lower power operation. Current through external components after the timer has halted itself is less than 3.5 uA.

    ak
    MinuteDelay-1-c.gif
     
  18. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    You want to delay the sound for about 1 minute after pressing the button, correct?

    Tell us about the current switch you depress to get the toy to work? Can you draw that schematic?
     
  19. ajzero

    Thread Starter New Member

    Nov 7, 2015
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    This is the updated circuit, (I use the 100K resistor and LED to test the circuit in place of the speaker circuit).
    This works perfectly fine with the normal 555s, but with the CMOS 555s, the LED is always on when the power is connected. My guess is that there's a problem with the transistor portion? but I am not sure...
    Screenshot at Dec 10 23-04-01.png
     
  20. Picbuster

    Member

    Dec 2, 2013
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    What you want is:
    poweron button sound 1 minute
    auto power off.
    This is simple think first..... use a P mosfet at the input.
    button pulls gate low powering the system. ( trigger to replace with a cap.)
    make sure that gate circuit is low for one minute.
    After one minute the gate goes up an power is disconnected.

    an other enhancement replce xtor with fet no collector current leak while off.
    ( depending on xtor type)
     
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