anyone here a licensed electrician or electrical engineer?

Discussion in 'Tele Home Depot' started by Newbcaster, Sep 27, 2020.

  1. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert
    So, I actuallly dont think I have enough information about these LED's but perhaps one of the above who actually knows about 921 replacement bulbs(car, truck rv interior LED's and backup lights)



    https://www.amazon.com/gp/product/B0761TSXF4/?tag=tdpri-20

    I need 11 of these wired in parallel. A resistor has to be placed between each one on the positive leg(anode)

    the negative gets wired to a fret and also to the bridge. When one depresses the string, bulb lights up.

    I suspect I don't know 3 things

    1) the value of a resistor necessary to do the job

    2) power supply. what kind how much, how big,

    3) how much current is this


    Actually this part does scare me quite a bit. I dont want to electrocute myself.

    I know voltage is DC 12v
    I know Watts is 3 watts

    Ohm's says Amps should be .4 BUT, elsewhere in the customer reviews a guy says its 1.3ADC because he has specific product knowledge the seller doesnt list.

    I contacted the seller, crickets. yes I can return it but I'd like to use these if I could.

    Anyone have any ideas? I suspect im sorta on the right track. Its always better to ask though.
     
  2. Digital Larry

    Digital Larry Friend of Leo's Gold Supporter

    Posts:
    2,309
    Joined:
    May 30, 2017
    Location:
    Silicon Valley, CA
    #1 I would not get these things, they are assemblies of chip LEDs. Just get some chip LEDs to begin with.

    https://www.mouser.com/datasheet/2/445/150080RV54050-1838969.pdf

    #2 The LEDs above draw 20 to 40 mA apiece at about 2.4 volts. Since they will go on and off individually, you need a power supply capable of supplying 40 mA * 11 at 2.4 volts at the very least. It is good design practice to put series resistance into this type of circuit, which reaches sort of a balance without blowing up the LED.

    40 mA * 11 = 440 mA.

    Now I don't know whether it's possible that they could all go on at the same time, but let's assume that's possible and you don't want to blow anything up. So get a 5 volt supply capable of 1 amp output.

    #3 to get 20 mA you would take 5.0 volts, subtract the 2.4 forward voltage of the LED. You now have 2.6 volts. Divide that by 20 mA, same as multiplying by 50. 50 * 2.6 = 130 ohms. Standard value of 120 ohms would give you a little more current, but still within 40 mA.

    You will not come anywhere close to electrocuting yourself with this.

    Sorry, I will now add guidance if you really want to use these big things. I guess they are going to be mounted on the face of the guitar, or somewhere else?

    These are designed to run off 12 volts. 3 watts at 12 volts means 250 mA. So you will need a 12 volt power supply capable of supplying 250 mA * 11, or 2.75 amps. In general one doubles power ratings, so make that 5 amps minimum. It's a little short of doubling.

    You won't electrocute yourself with this, but if you manage to short 12 volts at 5 amps directly to ground I'll wager you'll get some sparks.

    Finally, P = IV. Power = current * voltage.
    3W = I * 12.
    I = 3/12 = 1/4 amp each (250 mA)

    These are designed for automotive applications and AFAIK take 12 volts directly. If there is some regulation on there it's part of the module.
     
    Last edited: Sep 27, 2020
    pixeljammer and Newbcaster like this.
  3. dogmeat

    dogmeat Tele-Afflicted

    Age:
    69
    Posts:
    1,862
    Joined:
    Oct 12, 2017
    Location:
    Alaska
    there are direct replacement LEDs for the 921. I believe what you posted is plug & play, no other action required. if you are making your own, a standard LED wants about 800 to 1k ohms on each LED to limit current at 12vdc. I have used 680s too

    how are you using them
     
    Newbcaster likes this.
  4. Switchy

    Switchy Tele-Afflicted

    Age:
    50
    Posts:
    1,273
    Joined:
    Nov 15, 2019
    Location:
    Arizona
    I don't know what's going on here, but those LEDs are cool, and I could have fun with some of those.
     
    Newbcaster likes this.
  5. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert

    I am wiring 11 of these in parallel under a fretboard. need to know resistor value.
     
  6. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert

    I will definitely look at mouser. dunno why i didnt think of them b4. Still. If i could uses the ones i purchased, how would you go about doing it? Thanks for replying. i appreciate this.
     
  7. TeleTucson

    TeleTucson Tele-Afflicted

    Posts:
    1,725
    Joined:
    Aug 6, 2016
    Location:
    Tucson, AZ

    This sounds really sketchy. You're really trying to connect a wire to each fret on your guitar???? I can already see the mess of wire on the neck. What, solder them? I can smell your neck burning. When you depress a string, you get two frets - you'll need to devise circuitry to combine the current through the two current paths corresponding to each fret pair with each pair needing to go to different LEDs even though each pair shares a fret with it's neighboring pair.

    It sounds like you want a different display outcome from each fretted note. Why not just get a polychromatic tuner and find a way to display it as you'd like? I still have the free android one from Pitchlab that cost *nothing* and even has different colors for each note, and no messy wires.
     
    Deeve and Newbcaster like this.
  8. Digital Larry

    Digital Larry Friend of Leo's Gold Supporter

    Posts:
    2,309
    Joined:
    May 30, 2017
    Location:
    Silicon Valley, CA
    Second half of my post talks about using the actual module. I don't know how you are going to get 11 of those under your fretboard though... they look like they're an inch in diameter.
     
    Newbcaster likes this.
  9. Informal

    Informal Tele-Afflicted

    Posts:
    1,082
    Joined:
    Jan 16, 2013
    Location:
    SoCal

    This is the correct answer.

    Just because the bulb# lines up, The odds of cheap led's working correctly... in a somewhat modern vehicle, are slim.


    I bought a handful for various positions in a 2015 Ram truck.... None of them worked without throwing an error code, until I dropped enough $$ to a company who understood what the CBUS was willing to settle for.
     
  10. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert
    It's an 8 string with a humongous neck. The nut is 2.25 inches :)
     
  11. 24 track

    24 track Doctor of Teleocity Silver Supporter

    Posts:
    16,220
    Joined:
    Nov 6, 2014
    Location:
    kamloops bc
    buy the units and bread board your setup experimenting with different value resisters to see what works ,I did a usb powered unit at 5 volts ,(I wired 15 bright white LEDs and when I was looking for the right resistor I ended up using a 1 ohm resister and it worked fine , one unit i resister ), then hook up all 11 and use different value across the last one to see what works . you may only need one limiting resister for the whole array or you may need individual resisters for each panel of leds .

    I usually use a 98 ohm , or 470 ohm limiting resister for a single bright LED depending on a 5 volt or 12 volt supply, so what you need to determine is what will work for a single array of the leds you need then as they will be switched between bridge and the fret , what resistence if any is caused by that circuit then calculate the value of resister needed for each led array.
     
    Last edited: Sep 28, 2020
    Newbcaster likes this.
  12. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert
    So do you think I need a resistor between these and if so, what is the value?

    Sorry if I'm being stupid. Better to be stupid now though.

    I do have a breadboard. Was thinking about one of those portable battery phone chargers to put on the strap if this works.

    Guys if this works, it will be a miracle. Outside of finance and literature I'm not the brightest tool in the shed.
     
  13. Digital Larry

    Digital Larry Friend of Leo's Gold Supporter

    Posts:
    2,309
    Joined:
    May 30, 2017
    Location:
    Silicon Valley, CA
    As I have never used the module in question, I'm just going to say that what I told you is based on my understanding of electronics theory and yes I do have a degree in EE and worked as a designer for 15 years. I'm assuming you hook these directly to 12 volts like you would any automotive bulb. Someone brought up "CBUS" a few posts back, though, and I have no idea what that is.
     
    Newbcaster likes this.
  14. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert

    Oh I'm not questioning you at all. Infintely better at this than I am.

    But do I need a resistor between each of the 11 and what value?
     
  15. ghostchord

    ghostchord Tele-Meister

    Age:
    52
    Posts:
    123
    Joined:
    Aug 5, 2020
    Location:
    Vancouver, BC, Canada
    As the above poster says this module you linked to takes 12V. The power is voltage times current so solving for 3W we get 250mA. Ohm's law is V=I*R which is something else, you've calculated the resistance.

    You should not wire these in series. You should wire them in parallel. No resistors, just make sure you have a 12V supply. 11*0.25 = 2.75 so you're gonna need at least 2.75Amps.

    I'm not an EE but I play one on TV (or listened in my physics class, or something like that).

    (i.e. your power supply to light all of those simultaneously would be 12V 2.75A ... since power supplies often specify ... power... you could just say you need a 12V 11*3 = 33W power supply... That's like a laptop class power supply, lots of options there...)
     
    Last edited: Sep 28, 2020
    Newbcaster and Digital Larry like this.
  16. ghostchord

    ghostchord Tele-Meister

    Age:
    52
    Posts:
    123
    Joined:
    Aug 5, 2020
    Location:
    Vancouver, BC, Canada
    I'll also concur with the other guys that you probably don't want this automotive module thingy. Unless you want to light up your entire house with the guitar... Or something. The module is big and it probably gives a lot of light. There are a lot of other options here. Individual LEDs or smaller modules. Maybe if you can tell us more about the application we can give you specific advice...
     
    Newbcaster likes this.
  17. Dan_Pomykalski

    Dan_Pomykalski Tele-Meister

    Age:
    30
    Posts:
    298
    Joined:
    May 16, 2019
    Location:
    Madison, WI
    I began reading this but realized about halfway through I wasn’t retaining any of the information...

    OP, this guy seems to know what he’s talking about...

    Also, as far as the resistor value, I believe you can go down to 240 ohms. The higher you go, the dimmer they’ll be.

    I also agree the voltage needed to power LEDs isn’t going to be lethal.
     
    Newbcaster likes this.
  18. Dan_Pomykalski

    Dan_Pomykalski Tele-Meister

    Age:
    30
    Posts:
    298
    Joined:
    May 16, 2019
    Location:
    Madison, WI
    If getting this phrase wrong wasn’t intentional, I question the “literature” part.
     
    Newbcaster likes this.
  19. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert
    Oh well its wonderboy. I have a thread for a guitar I've long wanted to finish. I wrote a kind of BBC- style "Connections" piece and started a thread.

    Needless to say it didn't generate as much interest as I had hoped.

    Basically its an 8 string guitar with 24 gold jescar semi stainless frets, super jumbo, and the body and neck are ratio scaled up in size so that it looks dimensionally correct.

    The fret markers are large rainbow colored numbers in clear epoxy.

    I want as much light coming out of those numbers as can be had.

    It will be scalloped. I'm embedding the leds in the wood of the neck, not the fretboard.

    Since there's no radius to the fretboard you won't see it.

    This is an off the rails super shredder. 20200921_112332.jpg 20200921_112332.jpg
     
    Captain Nutslot likes this.
  20. Newbcaster

    Newbcaster Tele-Holic

    Age:
    46
    Posts:
    681
    Joined:
    May 10, 2015
    Location:
    Gilbert
    Did you say that to Shatner when he boldly went and split the infinitive?

    I break rules. Its what I do. Who comes to a place where they build telecasters and talks about an 8 string super shredder?

    This guy!!

    In all seriousness though I'm soooo grateful to tdpri and the people in this forum. Ive completed exactly zero guitars in all the years I've been here, but reading everyone's success and failures have helped me immensely. And the advice, like on this thread is top notch.

    I will soon finish this though. Soon.
     
    Blue Bill likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.