Master blown fuse indicator

Discussion in 'The Projects Forum' started by planenuts, Nov 28, 2009.

  1. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    This thread answers part of a question.
    I have several remote fuse indicators ala Marsden. I want to have a master indicator for them. Plan is to pick up all LED circuits to the right of the resistor and run to a master blinking LED. The master needs to be testable and resettable with a single momentary switch. Can anyone point me to the field of study to accomplish this?

    Thanks,
    John
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Welcome to AAC, John

    When you hijack a thread - http://forum.allaboutcircuits.com/showthread.php?t=17050 -, it it hard to know who is being answered. So now you have your own.

    The field of study is Electronics. One way to do what you want is to place the individual indicator LED's where one light sensor can see them, and use it to blink the master failure indicator.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    Short of putting a relay (or some other switching element) in series with the fuse I don't think there is much of anything you can do. It would make a dandy master cutoff though.
     
  4. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    Beenthere,

    It seems as if I committed a faux pas by titling my post "new wrinkle". By "hijacking" do you mean taking the thread on a tangent? That I should have just started a new thread?

    Re your suggestion of an opto-electric sensor, is there some relatively simple way to sense the LED current to signal a transistor to turn on the the master?

    Bill,
    I don't want to introduce an additional point of failure by putting a relay in the fuse circuit, but what about using the 20ma current of the LED to trigger a relay/transistor with it's own circuit for the master? Seems like the Master LED is now blinking. How can I "reset" it to non-blinking, ready to blink upon the next blown fuse?
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    It is always simplest to have one set of questions and answers in a thread. You question changes the topic away from an indicator to a new circuit.. Answers may be hard to sort out without a new thread.

    As in many things electronic, there is more than one way to do it. Any intact fuse will have a very small voltage drop across it, whereas a blown fuse will have the full line potential/source voltage across it.

    Some details might be nice at this point. How many fused circuits, what sort and magnitude of voltage in each, that sort of thing. Getting to a reset before the circuit is realized is very theoretical.
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    You could put an opto-isolator in series with each of your individual indicators, then use the output of the opto-isolators, connected in parallel, to trigger the Master Indicator.
     
  7. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    Beenthere,
    I've got 6 circuits all at 12vdc. 5 of them draw about 3-5a and one could draw up to 10 but sees 5 most of the time.

    Bill, thanks for the opto-isolator idea. I don't know what those are but I'll find out and come back.

    John
     
  8. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    http://forum.allaboutcircuits.com/showpost.php?p=106414&postcount=8

    If you mean this indicator, yes. Just put the optocouplers' LEDs in series with the resistors and LEDs, and parallel all their output transistors with their emitters to ground and the open-collecter(s) to what ever you want.

    Ken

    Sorry Bill, I missed your post.

    Then realized I already had a schematic drawn up for an AC version, so dropped some components for a DC one. It can be expanded to cover as many fuses as you need.

    Added groungd to relay circuit
     
    Last edited: Nov 29, 2009
  9. Wendy

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    Mar 24, 2008
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    Weren't my idea, I think someone else posted it. When I'm doing line voltage I use a neon and resistor in the same concept. I wonder if it would trigger an opto sensor?
     
  10. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    OK Ken, I'm sort of with you. I basically understand what an opto isolator is now. I found this on Mouser:
    http://www.nteinc.com/specs/3000to3099/pdf/nte3042.pdf

    I see most of the terminology of the O-I is accounted for in your post but not sure of
    "and parallel all their output transistors with their emitters to ground and the open-collecter(s) to what ever you want."

    I'm taking your post to mean the cathode of my LED indicator goes to the anode of the O-I and the O-I cathode to ground. The O-I emitter pin goes to ground as well and I connect my blinking LED cathode to the collector pin of the O-I. Yes?
     
  11. KMoffett

    AAC Fanatic!

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    Back up two posts. I added in a schematic.

    Ken
     
  12. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    Ken,
    Thanks for that but what is Q1 2n3906?
     
  13. KMoffett

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    Dec 19, 2007
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    It's a transistor used to drive the relay. The optocouplers don't have enough drive capability for a relay. If you only wanted an LED indication for the master, replace R2 with an LED (anode to +12V) and eliminate Q1, D2, and the relay.

    Ken
     
  14. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    Great! That's exactly what I want. Thank you.
    At the risk of overstaying my welcome..., once the master LED is blinking and I have acknowledged it, I want to shut it off until the next fuse blows which should turn it back on. How is this accomplished?
     
  15. BillB3857

    Senior Member

    Feb 28, 2009
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    Easiest way would be to put in a DIP switch in series with each of the collectors. Normal operation, all switches closed. Blow a fuse, see the indicator, acknowledge by opening the proper section of the DIP switch. After fuse replacement, return all DIP switch sections to closed position.
     
  16. KMoffett

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    Dec 19, 2007
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    First, for the LED to blink, you have to buy a blinking LED. ;)

    Another circuit. The inputs to the optocouplers (not shown) are the same as in my previous schematic. When a fuse blows it turns on the individual LED D1 and triggers the SCR that turns on the Master LED D. Pushing SW1 shorts out the SCR and turns off the master LED when the button is released. But the individual fuse LED remains on as long as its fuse is out. Another fuse blown will cause the same process. The buzzer or Sonalert can be placed across the master resistor/LED if an audible indication is also desired. Again, this is expandable to any number of fuses.

    With this circuit, the LED at each fuse would not be necessary, only the resistor and optocoupler.

    I will have to say that I have not tried this with optocouplers, only alarm switches. But I think that if the output transistors are in saturation it should work as well.

    Ken
     
    Last edited: Nov 29, 2009
  17. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    Bill and Ken,

    Hey, I must be getting educated because I knew I had to use a blinking LED:D

    It probably would have been helpful to know the application for this. I'm wiring up an instrument/avionics panel for a plane I built. See attachment(this is one's not mine, but is the same model and with very similar markings and state of completion)The airplane is all electric meaning it doesn't use magnetos or mechanical FI/carburetor. All my engine essentials (electronic fuel injection, pumps, and ignition) run off of two battery busses on the firewall. So my fuses for these items are not visible in flight, hence the desire of blown fuse indicators on a cockpit fuse panel and a master flashing LED right in front of the pilot.

    So while Bill's solution follows the KISS principle, Ken's is more in the line of what I had in mind where one button handles all the fuses and lends itself to a tidier installation.

    One additional feature that I would like is a test for the blinking LED using the same SW1 button. I can see how to do it with another (ON) switch, but would like the cleaner option of combining reset with test. And then I'll leave you guys alone;)

    Thanks again,
    John
     
  18. KMoffett

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    Consider it done...well it was already there. If you push SW1 any time, the master LED come on and stay on as long as SW1 is held down. :)

    I'm surprised these are fuses rather than panel breakers.

    Ken
     
  19. planenuts

    Thread Starter New Member

    Nov 28, 2009
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    RE LED test circuit: Wonderful!

    Breakers are the industry norm. But amongst amateur builders about 1/2 use fuses. We subscribe to the idea, put forth by the amateur builders' popular electrical guru Bob Nuckolls (Aerolectric Connection http://www.aeroelectric.com/ ) that there should be no single electrical event that demands my attention in order to complete my flight. If a fuse blows, it's for a reason, and I have a redundant system so there's no need to divert my attention from flying the airplane. Fuses are also gobs cheaper and more versatile as you've demonstrated. I've got about 25 circuits so at $30-40 / breaker, it adds up fast.

    Thank you again for all your help,
    John
     
  20. KMoffett

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    OK, a caveat. This circuit has not been tested in a high electrical noise, vehicular environment. SCRs can be triggered on by noise spikes in an electrical system. I don't see this happening if all the fuses are intact. But if a fuse were blown and the master indicator reset, it might be possible for electrical noise to re-trigger the master. This would require another reset, without an indication of a new problem. This is just conjecture on my part as I have not built the system with the optocouplers or tried ones I have built on a noisy power system. I know this last sounds a lot on the legal disclaimer side, but you will have to verify for yourself that it will work, as I have no way of testing it.

    I was a low time pilot, and understand the risks and rewards of flying. Thought for a long time about building, but don't fly now, so it feels good to help.

    Ken

    PS, I like Aeroelectric's Warranty Disclaimer. ;)
     
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