1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

accessory lighting question

Discussion in 'Automotive Electronics' started by GalloGiro, Jan 25, 2016.

  1. GalloGiro

    GalloGiro New Member

    Jan 25, 2016
    hi guys, my name is Ray. signed up on this forum to learn more about electronics and heard this was the best forum to be on. I have a question, hope you guys can give me some insight

    I currently finishing the restoration of my 1959 impala, it is a back to stock build but have my own personal touches and customization done to it. in the trunk I plan to do an infinity mirror using 12 volt bulbs I say about 50 in total mounted under the trunk lid and on the side panels inside the trunk (I do auto upholstery). incase you don't know what an infinity mirror is its a mirror base, then the bulbs along the edges and around anyting placed in the middle and topped by a one way mirror with the reflective side toward the base mirror. when the bulbs are turned on it gives the illusion of infinite depth.

    my question is, the lights I want to come on when the trunk is opened along with the trunk light, or activated by hidden switch. is it possible to have that many lights at once in a series or do I need some kind of capacitator or resistor? I know dash lights, parking lights and tail lights are all in a series but not sure if they are direct or have a resistor or capacitator. also I'm confused because I know you need one for L.E.D. bulbs if you wire in a series, it seemed too confusing so I thought bulbs would be easier. thanks in advance guys
  2. GalloGiro

    GalloGiro New Member

    Jan 25, 2016
    also if anyone would know how I could make them musical dancing lights or chasing lights that would be great. thanks guys
  3. JimB

    JimB Super Moderator Most Helpful Member

    Sep 11, 2004
    Peterhead, Scotland
    Welcome to ETO.

    First of all the word is capacitor not capacitator, and that is not what you need here for this application.

    If you are using LEDs, each LED must have a resistor in series with it.
    It is possible to connect several LEDs in series and use one resistor for the chain of LED.
    How many LEDs can be connected in series depends on the colour of the LED.

    It is also possible to buy LEDs with the correct resistor built in. These will be sold as 12 volt LEDs, or whatever voltage they have been configured for.

    Careful !
    Not sure exactly what you mean here.
    Do you mean the LED replacements for the old filament lamps? If so, yes the LEDs will be connected in series and there will be a resistor wired into the unit.
    Do you mean the light units on the car? In which case, no, they are connected in parallel.

    That is all for now, I have to run away as I have an appointment in 20mins or so.

  4. dave

    Dave New Member

    Jan 12, 1997

  5. shokjok

    shokjok Member

    May 14, 2008
    Alberta, Canada

    Your hidden switch idea could be a magnet in the deck lid mounted close to a reed switch inside the body. When the trunk is opened, the lights will dance.
    The circuit power must be switched. You don't want a parked and closed vehicle to have its battery drained by a pirate hot circuit like this one.
  6. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Oct 30, 2010
    JimB pretty much covered it.

    Standard LED's have a parameter called Vf that has a range. You can buy a bunch of LED's and select them by Vf. Don't worry, it's easy.

    The amount of LED's in series cannot exceed the sum of all of the Vf's. Whatever is left has to have a resistor. e.g. (4*2.1)=8.4. R= (12-8.4)/If.
    If is the operating current and is typically 10-20 mA. R<=8.4/20e-3 in the case above. Resistors have a power rating and you can use P>(20e-3)*(20e-3)*R
    Resistors only come in certain values and power ratings, e.g. 1/8, 1/4/, 1/2 and 1 W

    Colors complicate things, because each color has a different Vf. Sometimes you can buy LED's within a certain illumination range.

    So, with multiple colors, you can use a few LED's and a single resistor. If you string multiple colors together, they may not have the same brightness.
    One resistor per LED generally solves that problem.

    This datasheet http://users.ece.utexas.edu/~valvano/Datasheets/LEDorangeHLMP-D401.pdf shows how colors have been binned and the variations of Vf for different colors. There is also a viewing angle spec.

    Here's a blurb on how to read the datasheet: https://learn.adafruit.com/all-about-leds/the-led-datasheet

    12 V replacement LED's are typically made with a series/parallel arrangement of LED's.

    Its not that hard to understand,

    One simple way to do LED's is to wire every other one and alternate the power. it tends to make them look moving.

    A much harder way is a "color organ" where each audio frequency band is shown in colors and the intensity by the amount of energy in each band.

    A "pattern generator" is complex.

    "relays" can be used to use a lower current source to turn on a high current device. One typical application is the "horn relay". It uses a low current contact in the column and activates a higher current load.

    Your 1959 could have positive or negative ground, LED's don't like to be installed backwards. With more than 3 in series, they will likely survive a reverse application of 12 V. A LED/RESISTOR sin series will likely survive.
  7. Dr_Doggy

    Dr_Doggy Well-Known Member

    Aug 11, 2007
    Infinity mirrors are so cool! I have always wanted to put a propeller LED array in one:

    also similar:

    12v bulbs are in parallel to each other but series to trunk switch, resistors needed if any bulb is <12V you would need to wire each bulb separately and ensure that you dont overload fuse/wire current, plus control method required,
    leds are way better in this regard , they look better, less power and you can get i2c programmable ones , but then need microcontroller to run them, plus a way to upload/control your pattern (unless you want to reprogram every time) .... this could require programming knowledge if you do your own
    have seen factory controllers but dont know how good they fair, or what they can do specifically:

    something like this, careful though, im not sure if that one is i2c(leds controlled individually):

    stepping down to 5v is easy with a "buck converter" make sure it meets current demands of LEDS.
    lots of projects using the i2c out there if you google "rgb led strip i2c "

Share This Page