1. Member Since
    Jun 2017
    Jun 29, 2017, 3:45 AM - 9v led power question #1

    I am building a wiring kit for the polar lights 1/350 refit . I know there are some absolutely awesome lighting kits available but my wallet groans and so does my wife when I price them . Since I'm fairly handy with wiring I'm building my own.
    My question is will what I'm building work with a 9v power wall supply. Here's what I'm building. I have a 9v wall supply, from there it goes into a terminal block and splits into 8 circuits with switches, I have designated them as warp lighting, impulse lighting, interior lighting, flood and docking ports lighting, strobes, navigation, thrusters and shuttle bay landing lights.
    the strobes circuit, navigation lights , and shuttle landing lights are controlled by simple 555 boards im making. the warp and impulse circuits will be changed by just turning one off and the other one on.
    There are a total of 92 leds in the kit. 74 of them have a forward voltage range of 3 to 3.4 volts and a current of 200ma, and have resistors of 330 ohm, 1/4 watt. The other 18 have a forward voltage of 1.9 to 2.1 with a current of 200ma, and have resistors of 390 ohms , 1/2 watt. The largest circuit, the interior, has 28 leds and may get split into two to lighten the load . The remaining circuits are between 5 and 10 leds each. I think I should be ok with 9v but I just wanted a second opinion so I don't turn it on and it goes streaking across the room on 🔥 like the enterprise in the third movie
  2. RPF Premium Member Antsnest's Avatar
    Member Since
    May 2015
    Jun 29, 2017, 6:54 AM - Re: 9v led power question #2

    It's not the voltage, but the current capacity of your adapter you need to consider.

    Firstly the LEDs will be rated for 20ma, not 200mA, but the resistor values you mention sound right so that's probably just a typo. So 92 LEDs at 20mA each is a total current draw of 1.84A. If your adapter can supply that, you'll be ok.
  3. Gone but not forgotten.
    Member Since
    Dec 2007
    Danville KY
    Jun 29, 2017, 7:04 AM - Re: 9v led power question #3

    This is why I prefer to run models off power supplies instead of batteries, no need to worry about run times with large circuits.
  4. Member Since
    Jun 2017
    Jun 29, 2017, 11:52 AM - Re: 9v led power question #4

    Yep that's a typo! They are only 20ma. That's what happens when I type before coffee. The adapter is 9v 2amp 15watt. Should be fine if not adjustments can be made.
  5. Member Since
    Dec 2011
    Jun 29, 2017, 12:20 PM - Re: 9v led power question #5

    One thing folks may want consider lies in how/where the models will be displayed.

    We go to several contests regularly each year (Wonderfest, Eaglequest, somtimes IPMS etc). Not all contests have electric avail and some want to charge upwards of $200 a week for an electric outlet $200 is not a typo :-)

    My son designs his circuits for 12v. The "standardization" on 12v came about early on, as some of the contests we go to are a week long (IPMS) and we don't necessarily stick around town the entire time (we sightsee while in that part of the country) and can't be there to change the batteries. 12V came about since its easy to power not only LEDs but stepper motors and arduinos off of 12v. The first year or two he used regular D cells. But later we standardized on 14ah gel cel batteries. Invested in three of those and a very good charger that can bring the batteries back from a below 3v level, and are able to charge the batteries overnight. His latest model has 3 (maybe 4?) arduinos controlling lighting. About 30-40 LEDs, 4 12v stepper motors + an arduino and the associated motor controllers piggybacked on board. Obviously in this model the steppers are the main consumer.

    When we're at home, he uses 12v wall warts while building and testing his designs.

    On the flip side, a few years back, my youngest built a Romulan BOP with fiber optic lighting and had I think 6/8? LEDs. That was powered off 12V setup of AAs and ran all week at IPMS without a battery change. He later did a portal gun and that had about 20? LEDs and a dedicated circuit designed to control the lighting (no room for arduino inside). That was powered off of 12V setup of AAs as well, the batteries had to be changed once during the week. Both of those models are setup to have a 12v wall wart plugged into to them when at home or at electricity friendly setup sites.

    The other nice thing about using a standard V for all of your matter if you ultimately choose 6, 9, 12. You learn what your LEDs like for resistors and the resulting light levels. When I buy LEDs I buy them in bulk and try to repeat from same suppliers/mfg. Makes it easier going forward with other models (eg reduce the time to figure out) and developing their associated lighting design. For my oldest who still builds; between friends, university and work, anything we can do to maximize his time on "creation" of models rather than reinventing the wheel figuring out lighting basics, is a good thing.

    Click image for larger version. 

Name:	IMG_0308.JPG 
Views:	40 
Size:	2.07 MB 
ID:	739804
  6. RPF Premium Member
    Member Since
    Sep 2016
    Jun 29, 2017, 12:50 PM - Re: 9v led power question #6

    If battery life is a concern, you could invest in low current LEDs. 2mA and even 1mA LEDs are out there now. Surprisingly hard to find though.
  7. Member Since
    Nov 2016
    Jun 29, 2017, 4:56 PM - Re: 9v led power question #7

    I just soldered together two sets of string LEDs we had on the deck railings, probably over 100 total. They were hooked up to solar rechargeable packs that gave up the ghost. I put them on small bench power supply and it took 2.6 v to get them to glow, 3 volts for full brightness. I put in a 75 ohm resistor and a Tamiya plug and will use 1800mAh 7.2v NiCads I had leftover from RC tanks. I bet they'll co a loooooooooong time on a single charge.

    You can easily get everything you need to run off a 9 volt battery (or less) and it you think ahead, incorporate a terminal so you can use either a battery or a wall unit, in case you do bring it to a show.

    Arduino would do everything you ask (and then some) and they run on 7-12 volts input, 5 v out. I'm not suggesting you use Arduino (Although they are incredibly cheap, most likely less than the cost of individual parts), just pointing out that LEDs use a very little current when arranged properly.
  8. star-art's Avatar
    Member Since
    Jan 2002
    Cascade Mountains USA
    Jul 4, 2017, 3:43 PM - Re: 9v led power question #8

    Good points about the batteries. But, I started out using 12V in a filming model I built and discovered it created a problem I wasn't expecting. Running individual LEDs that need only about 3 volts each, your inline resistors must dissipate a lot of power. Since resistors are best kept close to the LEDs they protect, it means the circuit boards with the resistors are often inside the model. When you have lots of individual LEDs to light, this can cause a tremendous heat buildup. Letting the resistors get hot is not a good idea.

    I find that a 5V source is best for individual white LEDs. You can chain two white LEDs in series and run them nicely on 9V. If you chain three white LEDs in series you can run them safely on 12V. This minimizes wasted power dissipation and also the buildup of unwanted and possibly unexpected heat inside the model from the resistors.

    For most LED strip lighting, 9V is really the minimum needed. They also run just fine on 12V, but make sure it's a well regulated supply. Even a slight over-voltage can cause LED strip to draw much more current than you might expect, potentially overloading your circuit. With that in mind, ALWAYS measure the exact current draw of your circuit to verify it is within specs.

    I would NOT run a 1.8 A circuit through an adapter rated at 2A. That is too close to the limit to be safe. My general rule for "de-rating" circuit elements is to double everything. So, if I knew my circuit will draw nearly 2 Amps, I would use an adapter rated to handle at least 4 Amps.
  9. star-art's Avatar
    Member Since
    Jan 2002
    Cascade Mountains USA
    Jul 4, 2017, 6:01 PM - Re: 9v led power question #9

    PS I wrote an article on lighting a spaceship model built for filming. Even though the magazine has gone out of business, I was able to preserve a copy of the article and I've posted it here:

    You don't need to be a member of Facebook to see the article. It is available to everyone.
  10. Member Since
    Jun 2017
    Jul 16, 2017, 11:07 PM - Re: 9v led power question #10

    First I want to thank everyone for helping me out and giving me advice. I settled on 9v 2a adapter and that will get wired into a 8 circuit fuse block. There will be a 9v battery connector on each of the eight circuits to switch to battery power for shows. The only thing I'm still working out right now is the fuse size for the circuits I was thinking a 3 amp because 2a would blow as soon as it was plugged in

Similar Threads

  1. Replies: 4
    Last Post: Nov 16, 2014, 11:55 PM
  2. LED / power supply question
    sycor, Replica Props
    Replies: 2
    Last Post: Oct 11, 2012, 5:35 PM
  3. Need some LED/power help
    jedibugs, Replica Props
    Replies: 13
    Last Post: Jul 11, 2012, 5:50 PM
  4. Replies: 44
    Last Post: Jun 19, 2009, 2:39 PM