Is the operating time of a DPDT relay enough to power off a radio?

Discussion in 'General Electronics Chat' started by Justin Rouleau, Jan 10, 2018.

  1. Justin Rouleau

    Thread Starter New Member

    Jan 10, 2018
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    Some background: I have a camper van with a 320 AH battery bank and I want to add a switch and relay so I can power the stereo with those batteries when the vehicle is not running... I'm planning to use a DPDT relay so that I can switch both the 12V constant and the 12V ACC inputs to the radio. During normal (switch-off) operation, the radio will use the factory radio 12V constant and 12V ACC. During switch-on operation, both of the 12V inputs will be from the battery bank.

    The DPDT relay I'm using has a stated operating time and release time of 25ms max.

    So my question is, will this 25ms period is long enough to cause the radio to turn off / restart? And if so, will it be long enough to cause the radio to lose memory of presets, etc.?

    I have most of this wired up and ready but I'm still waiting on the wire harness from Amazon so I haven't been able to test yet.

    Thanks for your help!

    Radio: Pioneer AVIC-8200NEX
    Relay: Omron LY2-12VDC
     
    Last edited: Jan 10, 2018
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    The memory is wired to the Constant 12V wire, the amplifier is on the Auxiliary or Accessories, i would leave the memory wire permanently on the car battery and switch the Aux wire,

    you can use two Diodes instead.
     
  3. Justin Rouleau

    Thread Starter New Member

    Jan 10, 2018
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    Based on the wire gauge of the ACC wire, I'm fairly certain that is only used to tell the radio to turn on and very little current is drawn through that wire. If that's the case, then the 12V constant is the source for the amplifier, display, etc. and will need to feed off of my battery bank when the vehicle is not running to avoid draining the battery.

    I thought of using diodes, but I would expect power to be drawn from both sources depending on their state of charge which isn't ideal.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    The 12V constant input should take very little current.
    You should be able to leave it connected to the vehicle battery without it significantly draining the battery.
     
  5. Reloadron

    Distinguished Member

    Jan 15, 2015
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    Per other suggestions leave the 12 Volt constant just as it is. Switch the remaining 12 volt power. As to any hold up time during the switching process I would think about a large capacitor at the radio input. along the lines of a super capacitor. This also assumes the "radio" is not using a huge power amp drawing high current.

    Ron
     
  6. Justin Rouleau

    Thread Starter New Member

    Jan 10, 2018
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    Not sure why everyone thinks the 12V constant is just for memory... Short of taking apart the radio, I'm almost positive the 12V constant is the primary power source.

    Here's why:
    1) The 12V constant wire is approximately a 16 gauge wire while the 12V ACC is more like an 18 or 20 gauge wire.
    2) The pins where the connector plugs into the radio for the 12V constant and the ground are physically larger than all of the other pins including the 12V ACC.

    Both of these make it very clear to me that more power is drawn through the 12V constant than the 12V ACC.
     
  7. Justin Rouleau

    Thread Starter New Member

    Jan 10, 2018
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    I do think that a capacitor could be the solution though (assuming there's a problem).

    We'll see what happens when I finally get the rest of the wiring from Amazon and can actually test this.
     
  8. Reloadron

    Distinguished Member

    Jan 15, 2015
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    That's what I would do. I can't speak for all radios. My wife and I have GMC trucks and the always on is only memory and the smaller gauge wire. I have to agree, just try a few options and see what it does. I don't see where it will hurt anything. Then if switching time is an issue a capacitor is something to think about as a possible option.

    Ron
     
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  9. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    According to the manual, the Yellow wire is permanent 12V low current, the Red with fuse is ignition..


    https://www.manualslib.com/products/Pioneer-Avic-8200nex-4044226.html
     
  10. Justin Rouleau

    Thread Starter New Member

    Jan 10, 2018
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    I am aware that the yellow wire is 12V constant and the red wire is 12V ignition / ACC.

    Where are you seeing that the yellow is "low current" though?

    The yellow wire is the one that is ~16 gauge and has a larger pin vs the red that is ~18-20 gauge.
     
  11. Justin Rouleau

    Thread Starter New Member

    Jan 10, 2018
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    I got this all wired up last night and there is zero noticeable power loss when switching between power sources.
     
  12. joewales44

    Member

    Oct 8, 2017
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    i had a radio like that in a boat.
    it pulled current to store settings and would drain the battery in about 2 weeks or less.
    i never checked current draw but that was too much for me.
    i installed a battery switch to save the battery.
     
  13. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    That would suck, the AAA tow trucks don't float very well.
     
  14. Lyonspride

    Member

    Jan 6, 2014
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    Curious as to how your operating this relay............ I'm trying to do something where I use a relay to power a device ONLY when the vehicle ignition is off, but I don't have access to a feed from the ignition switch and i'm instead designing a low power circuit that senses when the battery voltage is over 13v (ie being charged by the alternator).
     
    Last edited: Jan 12, 2018
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