Pestvic Posted November 2, 2011 Report Share Posted November 2, 2011 Hey guys after searching for hours on this site I didnt find anything..... Anyway I had a simple question Can you run any LED's off the power of the input? Like say I want a LED to come on when you plug in the guitar. A Very small LED would be all I need. I just need a small Red LED to shine and show off the control cavity through this clear cover Thanks a ton guys! Im off to search google. Ill post here if I find anything so others can learn too. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted November 2, 2011 Report Share Posted November 2, 2011 Easy. Stereo jack, use the ring and sleeve as a bridge for the negative rail so mono jacks short them out. Look at how EMG circuits are wired. Quote Link to comment Share on other sites More sharing options...
Pestvic Posted November 3, 2011 Author Report Share Posted November 3, 2011 (edited) awesome would I need a separate battery source? Or is there some LEDs that run of that little bit of power? oh and I'm going to look for a wiring diagram on google or something. If you can draw one up really fast and make the process of searching faster I would really appreciate it Edited November 3, 2011 by Pestvic Quote Link to comment Share on other sites More sharing options...
Prostheta Posted November 3, 2011 Report Share Posted November 3, 2011 (edited) The tip of the TRS socket is marked "+" as that is the hot connection of the signal. Not the battery! Edited November 3, 2011 by Prostheta Quote Link to comment Share on other sites More sharing options...
Tim37 Posted November 3, 2011 Report Share Posted November 3, 2011 are you wanting to run a led off the pickup? if so its not gonna happen pickup just dont generate enough power. Quote Link to comment Share on other sites More sharing options...
Pestvic Posted November 3, 2011 Author Report Share Posted November 3, 2011 are you wanting to run a led off the pickup? if so its not gonna happen pickup just dont generate enough power. So I sill Still need a small battery source? I thought so... damn. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted November 3, 2011 Report Share Posted November 3, 2011 (edited) An LED doesn't conduct until the voltage difference across it exceeds the forward voltage (check the spec sheets). A typical guitar pickup is both too weak in terms of current "supply" and voltage (which is not constant anyway....read the differences between AC and DC) so even if it did manage to cause the LED to illuminate, the additional load on the coils would make the guitar sound like a bag of spanners. Kind of like trying to tow an anvil using a bicycle. Bikes aren't very good at it, and even if you did get it moving using that bike it would no longer be a very useful bike. Edited November 3, 2011 by Prostheta 1 Quote Link to comment Share on other sites More sharing options...
Dave_B Posted November 3, 2011 Report Share Posted November 3, 2011 (edited) ...even if you did get it moving using that bike it would no longer be a very useful bike. Prostheta, I tried to "Vote Up" your post but I wasn't allowed. <pros: I'll see what the member limit is. Can't access that function myself however. Sorry.> Edited November 3, 2011 by Prostheta Quote Link to comment Share on other sites More sharing options...
Pestvic Posted November 3, 2011 Author Report Share Posted November 3, 2011 for sure haha great analogy Ill throw in a AAA battery or something haha Quote Link to comment Share on other sites More sharing options...
Prostheta Posted November 3, 2011 Report Share Posted November 3, 2011 (edited) You'll need a better supply than a measly 1.5v as most LEDs have forward voltages in the range 2.0-2.5v or even higher for blue and white. At least two batteries, ie. a 3v supply. R = V/R V = Vcc-Fv R = (Vcc-Fv)/I R = (3.0-2.0)/2 = 0.5 (500R) At 2mA (low current LED) you'll need a 500R resistor if the forward voltage of the LED is 2.0v A reasonable quality AAA is rated about 1000mAh so in series you're looking at 500hrs, or at least on paper you are. Once the batteries start fading you'll experience voltage sag and those 500 will start looking more like 250. For example if the battery voltage drops to 1.4v per cell you'll see... (2.8-2.0)/0.5 = 1.6mA ...through the LED which will of course reduce the brightness. At 1.35v you're looking at 1.4mA The LED forward voltage is a significant proportion of your supply voltage which exacerbates the affects of sag. A 9v battery (actually constructed of 6x AAAAs) is a far more sensible proposition despite their lower mAh rating of about 550mAh. R = V/R V = Vcc-Fv R = (Vcc-Fv)/I R = (9.0-2.0)/2 = 3.5k On paper this translates through to about 157hrs however a 4.7k resistor would run the LED at a conservative 1.5mA for 366hrs. The sag will still exist however it will not be so pronounced. But what would I know. Go do some digging around on Google for LED resistor calculators and figure out how some basic circuits work. This isn't difficult stuff at all. Musicians are supposed to be able to count to twelve, so wiring up an LED for calculated values shouldn't faze you. Page two gives you the same information as I on how to wire a stereo jack to switch a supply on/off: http://www.emgpickups.com/content/wiringdiagrams/PowerTips_Tricks_0230-0190C.pdf Edited November 3, 2011 by Prostheta Quote Link to comment Share on other sites More sharing options...
ansil Posted December 4, 2011 Report Share Posted December 4, 2011 why not use a single aa and a dc step converter. also they do make small 1mm leds with a threshold closer to a diode but trying to find one readily available would be harder than just putting a battery in there http://www.muzique.com/news/not-a-joule-thief/ Quote Link to comment Share on other sites More sharing options...
irky Posted December 4, 2011 Report Share Posted December 4, 2011 (edited) An LED doesn't conduct until the voltage difference across it exceeds the forward voltage (check the spec sheets). That's not strictly true.....for example a typical 3mm blue led has a typical 'forward voltage' of between 3.2V & 3.4V....but it still lights up even if you apply as little as 2.9V-3.0V across it (depending on the specific LED) ...albeit way less bright, but by virtue of the fact it's lit means it's conducting! Here's the 1st datasheet I found typing 3mm blue led into goolge... http://www.farnell.com/datasheets/67038.pdf They're quoting a forward voltage of 3.8V, but if you check their graph it conducts from about 3.2V upwards. Edited December 4, 2011 by irky Quote Link to comment Share on other sites More sharing options...
Prostheta Posted December 4, 2011 Report Share Posted December 4, 2011 This is all still very irrelevant. What you're proposing is akin to attaching jump leads to a microphone expecting the signal to turn over an engine, whilst still having juice left over to produce a reasonably good audio signal. It's not going to happen no matter how much you look at data sheets, rub magic lamps or sacrifice lambs to consult the oracles. Quote Link to comment Share on other sites More sharing options...
irky Posted December 4, 2011 Report Share Posted December 4, 2011 (edited) This is all still very irrelevant On the contrary, if someone says something erroneous ...then the associated correction is *very* relevant. BTW I've absolutely no idea what you're going on about ....my response was not in response to the OP's request, but instead your mistake saying the LED doesn't conduct until the forward voltage is breached, here you go... "An LED doesn't conduct until the voltage difference across it exceeds the forward voltage" (check the spec sheets). ... yes a spec sheet is essential for establishing the actual parameters are, but clearly you didn't follow your own advice! Now what was all that about jump leads and microphones? (that could be quite useful for singers late for a winter gig due to a flat car battery - they'd have to sing loudly though, LOL). Edited December 4, 2011 by irky Quote Link to comment Share on other sites More sharing options...
Prostheta Posted December 4, 2011 Report Share Posted December 4, 2011 Relax guy. Whether an LED will conduct slightly or not when pushed by a pickup isn't really useful. It will hardly flicker, never mind illuminate an entire cavity. This is what the OP queried. Yes, I know they can be soft in that forward biasing region and make great devices in clipping circuits same as Germanium diodes. The fact of the matter is, they need a supplementary power source as a pickup just doesn't cut the mustard. For the purposes of simplicity, the specified forward voltage is enough to illustrate that an LED will not work satisfactorily in the proposed manner. I like analogy. It serves well when people don't have the time or inclination to sit down and learn esoteric arts or one-time dips into fields outside of their specific disciplines. Quote Link to comment Share on other sites More sharing options...
Pestvic Posted June 15, 2012 Author Report Share Posted June 15, 2012 wow i should of check back on this a while ago. Thanks for the info prostheta. Ill get this thing wired up Thanks everyone for the input. Quote Link to comment Share on other sites More sharing options...
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