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Thread: Using a relay to auto-power on HDD and power inverter

  1. #11
    What can I say? I like serial. Curiosity's Avatar
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    OK, here's a quickie. This will control power to the inverter 3 with options. Switch to right - only with key on, switch middle stays off and switch left always on.

    To use just an on/off toggle as in the original, connect it to the right 2 wires only.
    Attached Images Attached Images  

  2. #12
    Constant Bitrate Startingline13's Avatar
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    Wow, that basically cleared everything up for me and made it 100x easier.

    My only question is the blue 86: what's that?

  3. #13
    Raw Wave
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    Ha ha! The blue is the "centre pole" - the one that gets flipped from battery to ignition (and through off if it's a 3-position).

    So hence the blue connects the ACC/IGN or Batt+ +12V to the relay's actuation coil (86) whose other side is grounded (85). (Hence when 12V across 86 & 85, the coil energises and "pulls in" the relay contacts - ie, connects 30 to 87 - hence powering the inverter (and any other 12V thing you want powered - a 30A relay should handle at least a 300W load - ie 300W inverter.

    Alas I dislike those "wiring diagrams" - I prefer the "circuit diagram". But that's because I have no problem translating the circuit into real connections - and I prefer to see the circuit's operation.
    But both have their uses. It's just that nerds don't need the wiring stuff - except when not nerdy enough, or too tired, or checking why the circuit fails or smokes!

    I might eat my nerds and post an equivalent circuit later.... Then the operation should be fairly obvious....

    EDIT#1 - for Curi below - yep, ain't it a ship! I hate passing ships in the night.
    About time I beat you at something though!

  4. #14
    What can I say? I like serial. Curiosity's Avatar
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    You don't have to use blue. I'm just using different colors for fun. 85 and 86 are connected to a coil. When electicity flows through, it creates a magnetic field and closes the contacts on 30 to 87. So one side of the coil is grounded, and the other side is connected to a switch, then to power (or ACC in this case). Think if the blue and green as connected when the switch is on.

    Edit: Ah, beat me to it!

  5. #15
    What can I say? I like serial. Curiosity's Avatar
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    I think the simple diagrams are much easier for the non-electronics guys. Schematics might make it harder for them to visualize it as in what wire goes to what. Keep It Simple.

  6. #16
    Raw Wave
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    POST EDIT: Ha - Lucky I checked before posting, otherwise I might have got the ships.
    You are absolutely correct Curiosity.
    Hence why in these forums post physical or wiring diagrams - it shows HOW to connect & wire.
    But I tend to be more conceptual and get across ideas or explain the "real workings". And hence I provide general circuits or schematics. (Besides, I usually do NOT have the detail nor experience of the others.)
    My last line in this replay vents that frustration....
    It's sometimes the difference between showing and teaching.
    (And again, sorry for my poor & big pics below...)
    /end POST EDIT


    Rather then append to my last post (since I post-edited in a comment...), here are a couple of figs.

    Sorry about the size etc, but the first shows the circuit of Curi's quickie above.
    With the exception of the battery, the RED rectangle contains Curi's quickie "circuit".
    I added the Ignition Switch & Battery to enable images rather than text to "label" each connection or wire.
    I also added fuses as an indication of where they may exist, else as prompt that the should exist - but usually my drawings have a note that fuses etc are NOT shown - it gets too cluttered, and fusing as "always assumed" anyhow....LOL!

    And instead of showing the ground "wire" (aka negative, zero-Volt or 0V, or Batt- etc), I have used a typical earth or ground or chassis symbol - just assume those strange lined triangles are all connected together. That saves drawing one electrical connection (and it's related clutter) but often reflects reality - we ground to the chassis or body etc.
    (Actually I ave used the "earth" symbol. There are other but similar ones for chassis or 0V etc. But if drawn differently on the same circuit, they probably mean different "grounds" - eg for digital systems there is usually a "power ground" and a "signal ground".)

    Likewise a +12V or +V or Vs could be used for the battery or IGN +12V supply, but I have drawn the +12V connection.

    And speaking of clutter, normally text is not used - the symbols or image should convey all functionality.
    But appropriate text is occasionally needed - like "12V" for the battery, or that it's an Ignition Switch etc.
    But things like relay terminal numbering is usually omitted because that can be determined from other sources. (We may use other relays that do not use that DIN numbering convention.)
    But there is nothing to prevent redundant or extra information - it depends on the target audience.

    Is that "clearer" that Curi's quickie drawing so show how it works? Not that it shows what it looks like in reality, and below is NOT a good drawing.... (I'm even poor at quickies!)




    And since I took the above drawing from the drawing below - and since below is relevant to a a charge controlled "latching" relay which must be manually turned off (handy for PCs!) as I mentioned earlier - I've included it below.
    It should be self explanatory except that I now see I omitted the word "But.." in one (parenthesised) comment.
    I even used a "picture" of the diodes instead of their circuit representation - it's obviously a "circuit" diagram I made for some car forum...
    A lot more I can say, but it's too much already...




    PS - "Physical" representative drawings where it is easy to understand the functionality? I wish.....

  7. #17
    Constant Bitrate 4ofakind's Avatar
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    Ok dumb question alert!!!

    Do relays provide instant or timed connections? What would I need to add to this diagram to delay the connection between my ignition and an opus psu say 30 secs? Is it even necessary? I plan to install a pc in an old truck with a carb, may require a couple cranks before starting. I don't want to harm the psu.

    Thanks,
    Mal

  8. #18
    Raw Wave
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    Relays are instant, though delayed versions exist.

    You can delay turn-on etc with an RC delay (Resistor-Capacitor) as shown f.ex at the12volt.com in their Relay section, but I wouldn't use that if you are referring to my diagram above if it is triggered by the alternator charge-lamp circuit.
    Although alternator-regulators can power a few or several 2W-3W bulbs, they may not like surging into a discharged capacitor.
    You instead need a buffered circuit - eg, an RC delay the controls a transistor or FET that turns on the relay. (This is often preferred anyhow so that smaller capacitors and lower power resistors are used, or so other timer or logic circuitry can do the control.)

  9. #19
    Constant Bitrate Startingline13's Avatar
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    Sorry guys, I've had a busy couple of weeks and finally have a chance today to put this thing in.

    So:

    From the relay:

    Black wire gets grounded
    Red wire gets connected directly to the switch on the inverter
    Yellow wire goes ACC/IGN
    White goes to 12+

    Is that correct so far?

  10. #20
    What can I say? I like serial. Curiosity's Avatar
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    I smell smoke. Can't find white or yellow in this thread, so probably not.

    If you look at my drawing up there, red is the power to the inverter, not the switch. If you want to go the switch route, there are 2 connections on the switch to make contact. So 2 wires would go there.

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