Connect with us

Need a simple circuit to reset a device very X minutes

Discussion in 'General Electronics Discussion' started by supak111, Mar 16, 2017.

  1. supak111

    supak111 ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★

    323
    4
    Apr 29, 2012
    Hey guys looking for a simplest circuit to just power cycle a 12v device OFF and back ON even say 5 minutes. Is there any simple off the shelf module that can do this? or perhaps a simple circuit that can?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    8,994
    1,785
    Nov 17, 2011
  3. supak111

    supak111 ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★

    323
    4
    Apr 29, 2012
    Thanks Harald. I was hopping for something super cheap and simple as I might try selling this gadget once finished.

    Digital timer is too expensive, it would add too much cost unfortunately
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    8,994
    1,785
    Nov 17, 2011
    What's your cost limit?
     
  5. SalRu

    SalRu

    12
    0
    Mar 16, 2017
    Hello,

    I am not sure this solution can be suitable for you..

    But what about using a monostable with NE555 and a transistor to drive the output?


    Hope to be helpful!
     
  6. supak111

    supak111 ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★

    323
    4
    Apr 29, 2012
    At most few dollars and hopefully it isn't big like the timer. Btw this is only restarting a tiny bluetooth module which doesn't drew much current at all.
     
  7. SalRu

    SalRu

    12
    0
    Mar 16, 2017
    If the blt module has a reset pin the 555 should be the best option!

    Anyway you can try to supply the module through the 555 monostable and see what happens:)
     
  8. Bluejets

    Bluejets

    3,288
    651
    Oct 5, 2014
    If this needs to operate on a continuous basis, ie off, on, off, on etc then the op will need to look at astable configuration.
     
  9. supak111

    supak111 ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★

    323
    4
    Apr 29, 2012
    Yea I was thinking about using the 555. I think I just figured something out even simple and cheap. There are these $1 555 delay timer modules with a relay on them. I have a few at the house.

    What if I connect it like this picture. The timer would count off say 5 minutes, it would activate the relay and because of that it would cut power to itself and restart the 5 minute countdown again...

    [​IMG]
     
  10. Bluejets

    Bluejets

    3,288
    651
    Oct 5, 2014
    If a few milliseconds off is enough, sure.
     
  11. AnalogKid

    AnalogKid

    2,261
    636
    Jun 10, 2015
    Not nearly enough. The timer changes state when the timing capacitor is charged up (to 1/3 Vcc). If you then remove power to the timer, the 555 cannot discharge the cap.

    There are adjustable and programmable cycle timers on ebay that will do what you want, but 1 second out of 300 is a very high duty cycle. This is one of the reasons I don't like the 555 for multi-minute periods, but it can be done. A modified version of the standard 555 astable can be tweaked to a 300:1 duty cycle, but the timing cap will be huge and the long period will vary with room temperature.

    Another way uses the CD4060 to make one pulse every 256 counts. A 5 minute cycle would produce a 1.2 second pulse.

    ak
     
    Last edited: Mar 17, 2017
  12. supak111

    supak111 ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★

    323
    4
    Apr 29, 2012
    Yup just tested this and it wont work. OFF state is too short like you guys mentioned so when the module comes back ON it only holds ON for about 10 seconds instead of 300 probably because the cap is still full.
     
  13. AnalogKid

    AnalogKid

    2,261
    636
    Jun 10, 2015
    What to you want the output of the timer circuit to do:
    1. Toggle a reset pin on the bluetooth device.
    2. Open the 5 V or 3.3 V supply to the device.
    2. Open the GND to the device.
    4. Other.

    ak
     
  14. supak111

    supak111 ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★

    323
    4
    Apr 29, 2012
    Device is a BT module with a relay on it (proximity-switch), its not just a simple little BT module. I want to keep the BT in discovery mode and that only happens first 5 mins I believe. Just cutting power to the whole device puts it back to discovery which is my goal.

    BT module on it is a rda5851s I believe. If I could just reset the BT module that would be great but I cant seem to figure out what pin the reset is nor would it even reset it back into discovery mode if I did find the reset pin.

    Ill take some pics of the whole device with the rda 5851s on it soon.

    For now what about this:

    [​IMG]
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,152
    2,671
    Jan 21, 2010
    Simplest (for a certain definition of simple) would be a 6 pin microcontroller. It may be able to power the Bluetooth device from is output pin. If not, add a MOSFET and a resistor.
     
  16. Bluejets

    Bluejets

    3,288
    651
    Oct 5, 2014
    So like AK says, what do you want the circuit to do?
    If continuously cycle on and off you could use the 555 in astable mode.
    Set your on off to whatever via rc arrangement on 555 terminals 6,7 and 2.
    Forget your wiring arrangement that cuts power to the timer, leave it powered and run your bt from the relay only.
    No??
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-