Delay switch to close

Discussion in 'The Projects Forum' started by marinewonder, Aug 14, 2009.

  1. marinewonder

    Thread Starter New Member

    Aug 14, 2009
    1
    0
    Hello,


    I have a typical normally open switch on a device (my on-off switch) that I want to add delay when it closes and turns on the device.

    I want to have some adjustable control on that delay (1 to 5min), by some easily adjustable method like a mini POT.

    One concern is, everything will run off of the same 5v battery source. So I want to minimize the battery drain by the delay circuit as much as possible.

    I want to device to stay on after the delay, until the battery runs out.

    I want to use low-power components, and the circuit should be small, like a 555 with a few R's and C's.

    I am just not sure if the 555 is the way to go.

    I need to read up more on the 555, but with most everyone talking about triggered outputs, thats not really what I need.

    Thanks,

    -Marine
     
  2. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    IF you need a delayed power on, 555 can do. Go for the monostable mode. lots of ckts online. Also make sure you keep Pin 2 grounded.

    What is your load from the switch?? If it consumes more than 200mA, you will need relays and that consumes some power.
     
  3. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Have you considered expanding your horizons by using a PICAXE Microcontroller? It will provide you with the absolute minimum component count and they're cheap!
     
  4. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Do you really suggest a person to use a microcontroller with programming for a simple delay switch?
     
  5. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    By Golly I am! The PICAXE 08M is a 8 pin DIP that costs less than $4.00. Besides that fact, I've been Spicing a 555 circuit (just for laughs) so I could check the component count and complexity. So far.. No contest!
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Don't forget to include the cost of the programmer and the software in your cost comparison model.

    hgmjr
     
  7. RFactor

    Active Member

    May 1, 2009
    33
    3
    The software is free and the cable will cost about $1.50 if you make it up yourself but if you are only going to make one project with the PICAXE, you don't really need a "programming cable". The cable and software are reuseable for future projects.
     
  8. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Over the years most of us end up with a collection of extra cables that can be used. The early PICAXE was interfaced with a standard DB9 to DB9 but they changed it to the female DB9 to 1/8" stereo plug/connector arrangement to lower cost. ;)

    The Picaxe 08M can do anything a 555 will with less than 1/10th of the components. They ROCK and the programming editor is sweet! You don't even have to have the chip to test your code because the editor can simulate nearly everything. One single chip can replace oscillators, flip-flops, latches, ADCs and much much more. :cool:
     
    Last edited: Aug 16, 2009
  9. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    But for a simple delay its quicker in time and money to set a single resistor and capacitor and you are on. uC's are great but for such a simple application, to go for programming and flashing, wouldn't the 555 be easier?
     
  10. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    These schemes should satisfy either persuasion. The RC of the 555 circuit needs to be changed to the TS's liking. I didn't feel like waiting 5 min while spicing it. I still like my Picaxe.:D
     
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