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“Simple” volt/amp question

Discussion in 'Power Electronics' started by exaccord, Apr 5, 2019.

  1. exaccord

    exaccord

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    Apr 5, 2019
    I bought a doorbell camera. The doorbell camera requires hard wired 8V-24V - 600mA input. I don’t have a hard wired doorbell, only a wireless one.

    I know that I can buy a transformer to reduce voltage from 120 to 12ish volts. Most of those transformers give a lot more than .6A.

    My questions is, what would be the easiest/safest way to accomplish this task? I don’t want to run a bunch of wires around the house.
     
    Last edited: Apr 5, 2019
  2. exaccord

    exaccord

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    Apr 5, 2019
    Forgot to mention, I would rather not have to replace a 9 volt battery all the time.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The camera data states that the camera requires 12 V and draws up to 600 mA.
    The amperage on any power supply is what the power suply is able to deliver as max. current. This value needs to match or be greater than the value stated on the camera label (compare this to your mains outlet which is capable of powering a small 5 W LED lamp as well as a 2000 W heater).

    A transformer alone will not suffice as it will output AC. You need a DC power supply. An inexpensive 12 V / 1 A wall wart will be perfect for this application.

    If you don't want to run the camera on batteries you'll have to accept a few wires for the camera. At least power supply, possibly video (unless the camera transmits vidoe over the air).
     
  4. exaccord

    exaccord

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    Apr 5, 2019
    Sorry, I should’ve been more clear. It is a Simplisafe doorbell camera, and it’s designed to run off of the normal doorbell voltage that houses usually have. My doorbell wires are non existent. As I understand it, the doorbell power is AC, typically (8-24V)

    I know a diode takes AC and “converts” it to DC, is there an easy way to reverse that?
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    9,370
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    Nov 17, 2011
    In that case it should run off a standard transformer.

    There are ways but not that easy. Does that mean you have a DC supply available? In that case the camera may run off a DC supply as well, depending on the design of the internal power supply. Today commonly switch mode power supplies are used which work on rectified AC, That kind of power supply has good chances to work off a DC supply as well.

    A standard 9 V block battery has a typical capacity of around 500 mAh. Your camera will drain this kind of battery in less than 1 hour. At 600 mA (although that is the max. current, average is usually les) no battery will last very long. Even a bulky 45 Ah car battery would last around 73 hours (3 days) only. A mains powered supply is imho the only meaningful option.
     
  6. exaccord

    exaccord

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    Apr 5, 2019
  7. BobK

    BobK

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    Jan 5, 2010
    Be very careful. If it is like other doorbell cams, you cannot simply connect the power supply to it. This is because the standard wiring in the house has the doorbell short two wires which lead through the doorbell chime. If you simply install a power supply, pushing the button, you will short the supply to the doorbell. The instructions should recommend a series power resistor needed if you hook it up without a traditional solenoid type of chime.

    Bob
     
  8. exaccord

    exaccord

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    Apr 5, 2019
    I couldn't find any recommendations from them for my setup, I even called twice.

    Correct me if Im wrong, but if I took the neutral on the power supply leads, and grounded that, and hooked up the hot in line with the doorbell camera, would that work?
     
  9. Bluejets

    Bluejets

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    Oct 5, 2014
    If you are referring to the ac plug pack secondary you mentioned above, then no.

    FYI "hot" and "neutral" are terms used for mains wiring, not low voltage.
     
  10. exaccord

    exaccord

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    Apr 5, 2019
    So what is my solution for this? Someone much smarter than me in this department has to know a fairly easy way.
     
  11. hevans1944

    hevans1944 Hop - AC8NS

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    Probably not. Where are you getting "the hot" lead from? If this comes from a low-voltage AC transformer, the "usual" procedure when connecting a doorbell (or chime) is to wire the power supply "hot" and "common" to the doorbell through a normally-open push-button switch. Pressing the switch completes the circuit from the power supply to the doorbell. The wireless Simplisafe video doorbell is wired in parallel with, or it replaces, the door-mounted switch. The power it receives is through the doorbell, and this will be be low enough to not activate the existing doorbell until someone by-passes (shorts out) the Simplisafe by momentarily pressing either the existing doorbell button or the button on the Simplisafe. The Simplisafe should recognize this behavior and create video for wireless streaming via a local area wi-fi network to your cell phone, unless the retard ringing the doorbell holds it depressed. If you don't already have a doorbell connected to a doorbell transformer, you will need to provide a transformer and insert a resistor in series with one of the two output leads to simulate a doorbell and limit current to the Simplisafe wireless video doorbell.

    It could be that Simplisafe has anticipated all this and now includes current-limiting that would allow their device to be connected directly to a low-voltage transformer output. Please let us know how all this had worked out for you.
     
  12. Bluejets

    Bluejets

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    Oct 5, 2014
    When one needs circuits, one has to run cabling, simple.

    When trying to explain the intended setup it always helps to provide some wiring arrangement drawing, no matter how basic.
    Block diagrams help also.
     
    davenn and hevans1944 like this.
  13. exaccord

    exaccord

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    Apr 5, 2019
    Any idea what type and size resistor I would likely need, given this transformer, and knowing I need 8-24V 600mA

    https://www.amazon.com/Reliapro-ADU...ywords=12v+ac&qid=1554469131&s=gateway&sr=8-9

    I realize I sound a little ignorant, it’s because I am. I have a little experience in the world of electronics. As in 2 classes in high school. (Well the same class twice because I enjoyed it so much.) so any help is appreciated.
     
  14. BobK

    BobK

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    The simplisafe instructions seem to ignore the problem, yet there are complaints on forums about it not working without a traditional doorbell installed. I have the SkyBell, here is what they say:

    If would do just that.

    Indeed, we had an electronic bell and it did not work with it (I installed without reading the instructions, as usual :eek:)
    Solved the problem by installing an old style doorbell, which the lovely wife Morticia prefers anyway.

    Bob
     
  15. exaccord

    exaccord

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    Apr 5, 2019
    Glad someone else doesn't read instructions...

    It sounds like I could buy the aforementioned power supply and apply a 10ohm/10w resistor on the hot wire and hook up both wires to the doorbell cam. I understand that they are different products and require different voltages/wattages/etc. but that should be a good place to start?

    OR - I could install an old school doorbell. This sounds like a lot of work, but maybe simpler. Do you have a good tutorial you could point me to?
     
  16. Ylli

    Ylli

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    Jun 19, 2018
    Do you want the doorbell camera to be your actual doorbell, or is the wireless unit going to remain as the active doorbell?
     
  17. hevans1944

    hevans1944 Hop - AC8NS

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    Any way you go, you will have to install a pair of insulated, small-gauge, "doorbell wires" between your Simplisafe device and an external, low-voltage transformer. Wherever the transformer is installed, you need to also install a current-limiting resistor OR a traditional electro-mechanical doorbell or buzzer, as suggested by @BobK. Try ten ohms, ten watts, for starters for the resistor, OR install a cheap doorbell or buzzer from a big-box home improvement store.
     
  18. exaccord

    exaccord

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    Apr 5, 2019
    I assume the better way to do it is to have one doorbell that works both devices. Sounds like I’m running wires... thanks for all of the help, I’m sure someone else in the world will find this helpful as well.
     
  19. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    If I understand the Simplisafe design philosophy, they just want to make it "easy" to install a video-equipped "doorbell" using existing doorbell wiring to obtain power for the video. Good luck with that. Should work if you know what you are doing...
     
  20. BobK

    BobK

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    Jan 5, 2010
    Both Ring and SkyBell also work that way. The Difference is they warn you about it in the intructions and give you alternatives.

    Bob
     
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