LED regulator needs for art car?

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playastewart
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LED regulator needs for art car?

Post by playastewart » Thu Aug 07, 2014 2:21 pm

Does anyone know if I need a fuse or regulator for this set up on my art car? Motorcycle battery to 5 LED strips (see diagram)

I tested a few LED's here and there and some of them burned out from too much juice via just testing the strips with clips to a 6v lantern battery. Would suck to have an epic fail out there for lack of a simple part. I can't seem to find any real info from ye ol google. Thanks!

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keves
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Re: LED regulator needs for art car?

Post by keves » Thu Aug 07, 2014 2:27 pm

Are your strips 5V?
Assuming they are 5V and battery is 12V, you definitely want a regulator.
A very simple solution that worked well for us is using a UBEC such as this - http://www.hobbyking.com/hobbyking/stor ... 3A_5v.html or http://www.hobbyking.com/hobbyking/stor ... ipoly.html (but generally any one that outputs 5V and can handle 12V in would work).

Cheap, relatively reliable (but they do die/arrive dead so get spares) and easy to replace if the need arises...

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Captain Goddammit
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Re: LED regulator needs for art car?

Post by Captain Goddammit » Thu Aug 07, 2014 4:57 pm

Yep, that's the golden question: what voltage LEDs have you got?
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playastewart
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Re: LED regulator needs for art car?

Post by playastewart » Fri Aug 08, 2014 1:04 pm

Oh thanks all! Here is the info:

12V DC 3528 SMD LED strip
Length:16.4 ft./5 Meter 300 LED lights per reel.
Total LED's about 1000 (some of them I cut down or didnt need full reels in each piece of my art car, such as the skull)
Power consumption - Only 4.8W/m
LIfe: 50,000 hours

These are running back into a terminal box and attached to this battery:
12v 18AH Motorcycle Battery (http://www.amazon.com/51913-R1100RS-R11 ... le+Battery)

Thanks for the replies, I'll look into how voltage regulators work.

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BBadger
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Re: LED regulator needs for art car?

Post by BBadger » Fri Aug 08, 2014 2:01 pm

Your LED strips will usually have a resistor per-LED; they will regulate the current themselves if you provide their required voltage. Cheap strips will use a single resistor for current regulation, and as LEDs burn out, more current goes into neighboring LEDs potentially causing a chain reaction of failures. So make sure you have decent LED strips that regulate on a per-LED basis.

There is also a lot of current going through those strips. The on/off switch you use should have back-EMF protection (i.e. a reverse-polarity diode). Most relays will have this built in, and your power supply may also provide this protection. A fuse could be helpful too, but it'd be more to protect the battery than the strips in case something shorts. You should spec it for total current going into the strips, though I'm not sure what the margins on the current should be.
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Re: LED regulator needs for art car?

Post by Captain Goddammit » Fri Aug 08, 2014 2:06 pm

I'm not understanding why a 6-volt battery fried any of your 12-volt LEDs, unless they are wired such that they needed to remain at full length and cutting them down decreased their voltage requirement (and tolerance).
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Re: LED regulator needs for art car?

Post by playastewart » Sun Aug 10, 2014 3:19 pm

Cool thanks! I ordered a regulator and hope to have an update here tues or wed with pics.

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Re: LED regulator needs for art car?

Post by BBadger » Sun Aug 10, 2014 5:05 pm

The only reason those strips should get fried is either with static discharge, too much overall voltage, or they're super cheap types that only have a single regulating resistor, not resistors for each LED.

Some regulators aren't really "regulators" either. They'll have huge spikes in voltage and may be way out of spec. So make sure you get something decent and try to measure the voltage too.
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Re: LED regulator needs for art car?

Post by playastewart » Sun Aug 10, 2014 6:45 pm

So what brand of LED strips do you recommend? I've just been getting them if amazon. Like the egoal $13.00 strips.

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Re: LED regulator needs for art car?

Post by BBadger » Sun Aug 10, 2014 8:10 pm

I'm not sure without inspecting them directly. Often the strips are okay, mostly because they're designed to be cut and they're manufactured in bulk.

It's often the ones that are "strings" rather than strips that are crappy. They use the same kind of design that Christmas lights use, and like Christmas lights, when one bulb goes out, the others suffer. The better Christmas lights cause half the strand to go out so that you can replace the dead bulb. The cheaper ones will just keep on chugging along, allowing the current that should be going through the now-dead bulb/LED to now go through the others. This causes the other lights to be overpowered, which shortens their lives further, causing more failures and exacerbating the situation. Usually after one light will go out, the remainder will soon go as a result.

For your strips: buy a cheap multimeter and use the volt-meter to make sure that the power coming out is about 12V. Those LED strips don't need exactly 12V, but they won't like having too much voltage. 12.7 V is probably fine.

If you put in a switch, and you probably will, don't connect it between the voltage regulators and your LED strips. Put the switch between the battery input of the voltage regulators. The voltage regulators help protect the LEDs from the input, and also switching can create a giant "spike" of current and voltage that can kill more delicate electronics (like your strips). Plus, then you won't be powering your voltage regulators even while in the "off" state.

Check the switch rating and make sure that its DC-current rating is above the current needed for your strips. Do note that if you're converting between different voltages, the current must compensate. For example, if you're converting from 6V to 12V, the needed current at the input is double what is needed at the output because it has to make up twice as much voltage. In fact, it will use even more current because the conversion efficiency is not perfect. Many regulators will report 90% efficiency under ideal conditions, but to be safe, use something like 70-80% as an efficiency rating.

Your switches will have an AC/DC current rating at a specified voltage. They're not the same, even if the AC voltage is much higher. If only one current rating is provided, make sure it is sufficient for your project and that the specified DC voltage rating is above the voltage it will be switching.

For example, if you buy 15 meters of these LED strips they are rated at 1.2A of current per meter at 12V; the current that will pass through your switch will be 15 * 1.2A = 18A. This is at 12V. If you're powering these from a 6V power supply, you'll need twice that amount of current -- 36A -- to compensate. Factor in only 80% efficiency and you have 45A of current. If you have multiple runs, you could put a lower-rated switch for each run so you don't need a single 45A switch.

In your case, you're using a 12V power supply and don't need to convert voltages or switch as much current; your strips also don't use quite as much current (0.4A/m). Still, at 5 x 5 meters, you're still looking at 10A of current to switch; make sure you get an adequate switch. Also make sure to SEAL your switch up so that dust doesn't get inside it. The dust can corrode the contacts, increasing resistance, and possibly causing them to overheat. I would buy some extras and bring a soldering iron along just in case. Get some heat-shrink tubing too, to cover up things. Using large gauge wire, like speaker wire, will also reduce resistance and be far less prone to breakage. Make sure to use strain-relief measures to protect against mechanical or vibrational damage. Putting your wires into aluminum conduit on your car will work wonders for protecting the wiring from damage due to vibrations, people, the elements, bumps, etc.

That 10A is also going to deplete your motorcycle battery pretty quickly. You'll get about an hour of runtime before you should recharge. Have you considered buying a 12V 110AH lead-acid battery at Costco or Walmart?

If you're using a 12V battery, you probably don't need the voltage regulators. However, it would still be good to protect your strips from the current spike.

To help protect your LED strips, you can put capacitors at their inputs to smooth out the voltage spike. Select some electrolytic capacitors with high uF ratings and a voltage rating above your required voltage (in this case, 12V). Capacitors like these will work and they're not very expensive. Electrolytic capacitors have a strip on the side of them with pill shaped "minus" symbols that points to the lead that should be connected to ground.

Solder up one of these in parallel with each of your strips. In other words, the negative lead of the capacitor attaches to the ground connection of your strip, and the positive lead connects to the +12V connect leading to your strip:

Code: Select all

                    +------------
                    |
+12V ===o===========o 12V
        |           |
    16V | +         |
    ---------       |
    capacitor       | LED strip
    ---------       |
 1000uF | -         |
        |           |
GND ====o===========o GND   
                    |
                    +------------
Try to keep them as close as possible to the strip. Before you solder the capacitors to your strip, be sure to short the leads of the capacitor (touch them together) to discharge any accumulated charge.
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playastewart
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Re: LED regulator needs for art car?

Post by playastewart » Thu Aug 14, 2014 6:38 pm

So here's the update.

I wired up the voltage regulator and it didn't work. I then decided just to test to see if I can power from the battery to voltage regular to a test bulb - that worked. But when hooking it up to my LED's, nada.

So ... I just wired it all straight to the 12v (along with a 12v rated switch) and walla...Here's what she looks like. Even if it only lasts an hour, which is probably about my max of sobriety time anyway - then it's back to camp for beer ;-)

Thanks for the info, that's a lot to digest, I've never even heard about capacitors. So much learn, but it's fun.

Image

Image

and the regulator that did not work

Image

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BBadger
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Re: LED regulator needs for art car?

Post by BBadger » Thu Aug 14, 2014 6:56 pm

Wait, so you were hooking the 12V-output regulator to a 12V input? Yeah, that won't work. Depending on the regulator's design (boost or buck), the voltage needs to be higher or lower than the output. Boost means the input voltage is lower than the output voltage. Buck means the input is higher than the output voltage. It's convenient if you're running 5V strips on a 12V source. For a 12V battery to 12V strips, direct off the battery should be fine.

One last thing, you might consider buying a PWM dimmer. Those LED strips are plenty bright at lower output levels and you can save some battery life by reducing the brightness to an appropriate amount.

Anyway, it looks good!
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