Navigation Light Alarm Panel

[Silvertip]

Re: Navigation Light Alarm Panel

Learn more about what? LEDs, or ??.

As for discussing or debating, I suppose one could say I'm doing neither but rather I'm lecturing. This thread has had some suggestions that electrically won't work yet there seems to be reluctance that ohms law doesn't apply here. In situations like this I tend to prove the concept with a practical example. I'm merely proving that you cannot add a resistive element to any circuit without affecting its characteristics (in this case light brilliance). After I took the pictures of the series and solo bulb, I dug out a 12 volt relay and inserted the coil in series with the lamp because someone had suggest that as a solution. As expected, the bulb would not even light because the resistance of the relay coil was much higher than the bulb. Just trying to clarify some misconceptions here.

Electronic theory is not learned over night. Most technical colleges have a two year "electronic technology course" that results in an Associate Degree. Or you can knock yourself out with a four year EE program at any College or University.

As a brain teaser -- How would YOU test a handful of fuses given to you by your boss for evaluation?

 

[fish_on_the_deck]

Re: Navigation Light Alarm Panel

why would you need to add the resistor to the led if you were putting it in series with a filament bulb? (im not trying to start a pissing contest here just love learning new stuff and its been a while since my electrical class back in school)

You wouldnt, unless you need to reduce the current in that circuit further (in this case you would just buy a LED that can handle the current that the light pulls).

LEDs do have about a 0.7V voltage drop across them (depending on type), but do not have any resistance to speak of. You add the resistor in series with an LED only when it would otherwise be a short to ground and would produce currents only limited by the source (again... no internal resistance in an LED).

LEDs are just diodes that omit light when current flows through them... wikipedia a diode... its a check valve for electricity. It does not reduce curent flow as wiring a light bulb in series does... as silvertip's example shows.

yes, two incandecent bulbs of the same wattage in series will reduce light intensity by about half.

I agree that the LED in series is an easy and simple way to accomplish the indicator light. the buzzer alarm is a little more complicated, as the relay coil would likely reduce bulb intensity. I'm thinking a high input impedance Op-Amp design could be used.

Also the photocell idea is interesting... but since that is a resistive change, I would suggest looking into using a wheatstone bridge to forward bias a diode to input an op-amp maybe...

It is an interesting question...

 

[fish_on_the_deck]

Re: Navigation Light Alarm Panel

As a brain teaser -- How would YOU test a handful of fuses given to you by your boss for evaluation?

I would look at them and see it the filament was blown... haha

ok, that would only work on the clear ones... seriously though I would switch my multimeter to continuity and listen for the beep.

oh wait... was this a serious question?

 

[sasto]

Re: Navigation Light Alarm Panel

I would look at them and see it the filament was blown... haha

ok, that would only work on the clear ones... seriously though I would switch my multimeter to continuity and listen for the beep.

oh wait... was this a serious question?

Thanks for the answer....Mr Fish.

 

[Silvertip]

Re: Navigation Light Alarm Panel

It is a serious question! Here is how a EE handled that situation. He blew all the fuses, walked into his boss, dropped them on his desk and said "yup -- they are all good". Now then -- 1) they are no longer good since they were all blown. 2) There was no documentation done as to what current level they opened at. For all he knew a 10 amp fuse blew at 9 amps or 12 amps which may be outside the parameter for whatever project this fuse would have to protect. 3) What should have happened is that a circuit be designed to "ease" the current gradually up to the rated value of the fuse. A threshold (above and below the fuse value) should have been established and each fuse tested to see if it blew before its rated value or after it. The data then plotted/charted so the batch could be determined as acceptable or not.

By the way, I did insert a 12 volt relay in series with the bulb, and as expected, the lamp would not light. Again, as for an LED in series with a bulb, this results in a reverse alarm. One wants an indicator to light or an alarm to sound when the failure occurs, not the reverse. People will not likely notice an LED is NOT lit than one that is.

 

[fish_on_the_deck]

Re: Navigation Light Alarm Panel

What should have happened is that a circuit be designed to "ease" the current gradually up to the rated value of the fuse.

oh... thought you meant how to tell if they had been blown or not... haha... no wonder the question seemed a little simple.

yup... circuit could be as simple as a high current potentiometer to adjust current and an ammeter to measure it. Or just a variable / current limiting power supply... depending on the rating of the fuse if you had a large enough power supply.

for an interesting study try also holding at various current levels for a timed duration. Thermal breakers also will trip after sitting an a lower voltage for a set amount of time... not sure if fuses would do the same... would be interesting to see though.

true about the LED not being a real indicator... of course thats the same for the fiber optics.

 

[Silvertip]

Re: Navigation Light Alarm Panel

One last thing on LEDs and I've devoted enough time to this issue. LEDs are current driven, not voltage driven. That said, voltage still plays a role in LED circuit design since a small change in voltage can make a big change in current. Since a vehicle or boat electrical system can run as high as 14 volts (or higher in an unregulated system such as an older outboard) this is a definite consideration. Current limits for LEDs are quite low. In the NAV light example, the LED would definitely need a current limiting resistor. In this case it would need to be around 80 ohms and because of the current, it would need to be in the 1 - 2 watt range. I already ran a test using a relay coil with something over 100 ohms of resistance in series with the bulb and the bulb didn't light. With 80 ohms in that circuit one could expect nothing more than a glimmer of light. Use any of the LED design calculators to figure out resistor values. Here is just one.

Done - outa here.