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12V Timer

Discussion in 'Electronics & Electrics' started by RP_Automotive, Nov 26, 2018.

  1. RP_Automotive

    RP_Automotive Member

    Joined:
    Apr 19, 2006
    Messages:
    199
    Hi all,

    I have a 12V device I'd like to test over a long period and run on a couple of programmed sample rates as below. I've found a few timers on ebay and the like that are close, but hoping to find something that can do everything.

    First 24hrs: Turn on and run constantly
    24hrs > 3 months: Turn on and run for ~5mins once every hour.
    3+ months: Turn on and run for 10mins once every 12hrs.

    The supply voltage is from a 10.8V Lithium battery pack. The device that will be connected can run on anywhere from 8 >20V but can have power draws of up to 5W, so the timer will need to be able to handle that.

    The device will also have to run without any intervention, so happy to pay a premium for good quality stuff.

    One left field requirement is that the PCB must be able to fit in a 1.25" I.D. Tube - Length has no restriction.

    If there is nothing off the shelf and someone here can build something, or recommend a place to build something, I'm happy to pay for it.
     
  2. Jazper

    Jazper Member

    Joined:
    Jul 28, 2001
    Messages:
    2,434
    Location:
    Melbourne Australia
    What device is it attached to/driving ?
    How long do you need the lithium pack to last, and what's the capacity?
    Will it be charged during the time or not?
    Did you want to log the results or have any sensors (eg battery power?)
    Did you need something else?

    PM me if you can't answer some of these questions publicly - happy to help

    This is pretty easy to build with Arduino. Could probably even do it with an ATTiny..

    Parts list:
    1x Arduino Nano (5v)
    1x H bridge -link is to my favourite one. Overkill, you could probably do this with a bistable relay but for size reasons and cost reasons this could work.
    1xRTC module (Don't technically need this, but you're better off with it than without it)
    1x CR2032 battery for the RTC
    1xBuck switching regulator (5v)
    1x prototyping board (cut to size you need)
    A few small capacitors
     
    Last edited: Nov 26, 2018
  3. OP
    OP
    RP_Automotive

    RP_Automotive Member

    Joined:
    Apr 19, 2006
    Messages:
    199
    Hi Jasper, answers below:

    What device is it attached to/driving? - A bunch of sensors and electronics, a CPU then processes the data and transmits data.
    How long do you need the lithium pack to last, and what's the capacity? We already have this covered - as long as the timer has low power draw, then we are fine. The Lithium packs are fairly beefy 112Ah @ 10.8V
    Will it be charged during the time or not? No
    Did you want to log the results or have any sensors (eg battery power?) Nope, all it needs to do is turn the device on at off at the programmed intervals.
    Did you need something else? Not at this stage, but it is apart of a wider project so there's plenty more opportunities if you're interested.
     
  4. Jazper

    Jazper Member

    Joined:
    Jul 28, 2001
    Messages:
    2,434
    Location:
    Melbourne Australia
    Pm'd for more info.
     

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