Heavy duty 12V regulators for automotive power?

I'm building a large Arduino controlled LED setup powered off deep cycle batteries attached to a vehicle. The Arduino's will regulate themselves, but I need something to power all the LEDs (a combination of RGB strip and some high-current LEDs). Its my assumption that its not safe to power these straight from the ~14.5V output, I'd love to hear that I'm wrong. Assuming I'm not, does anyone have a recommendation for how to regulate this down to 12V? Either a product that can handle the entire load (probably ~50-60A) or individual ~10A regulators?

I think you'd be okay as long as the Arduino itself is not sinking current thru the LEDs. Use one the cigarette lighter USB power sources for 5V. Use discrete transistors, part like TPIC6x595, etc. that are good for 50V sources. Connect all the grounds together.

There's all kinds of them available. http://www.amazon.com/b?ie=UTF8&node=10981751

Yeah, I have a number of 5V regulators to drive the Arduino and some other 5V devices, I just wasn't sure what to do about the 12V components. I'll take a look at the TPIC6x595's, my current prototype is using TIP120's for the 12V LED strips (though I have ordered some mosfet for a similar purpose at someone else's recommendation).

TPIC6B595 use MOSFETs to sink current. They work great for driving LED strips.

Cool, conveniently TI has free samples for those so I'll try some out.

random_vamp: Its my assumption that its not safe to power these straight from the ~14.5V output, I'd love to hear that I'm wrong.

I've hooked it up directly to 14.5 (float charge)

the rope strings (5050 RGB) do get quite warm, and with the surface mounted resistors they use could be a little higher .... but they did work for the few minutes i had them connected with ill effects , I use a cheap ($3 from ebay) 12vdc 1amp power supply (240ac) perfectly day in day out....

Something as simple as 2 diodes in series with the 14.5v supply should bring it down to a safe enough current for you to have no issues with those strings of LED's...

Ok, after further investigation I think I really do need a heavy-duty 12V regulator for this project. While the voltage may be 14.5V when the alternator is running, its 12.5V when the batteries are the only power source, so I can’t just use diodes or heavy duty resistors to reduce the voltage. So I either need a bunch of individual regulators that are beefier than the L7812CV’s I have (they’d need to drive a max of 6A if one of these RGB LED strips was at its max), or preferably one (or a couple) of massive regulators to provide power to the whole system.

I’m sure the latter must be out there, I just don’t know what product to look for.

(And to catch up on the above, I have P16NF06’s replacing the TIP120’s and they appear to work fine with much less heat than the TIP120’s. I haven’t tried the shift-register based MOSFETs yet, but I suspect at this point in the project I’d rather just go with what I know works)

http://www.fairchildsemi.com/ds/LM/LM7805.pdf -- page 24, Figure 14 shows how to implement a transistor to increase current output.

Also, the dropout voltage of a LM78XX is typical 2V. That means your input voltage must be (regulated voltage + 2V) greater than 14V to regulate to 12V.

Not all LEDs are created equally. Have you checked the specs for these "12Volt leds"? The specs may tell you the maximum voltage. If they were designed for use in vehicles, then I would expect them to be ok.

Chagrin: http://www.fairchildsemi.com/ds/LM/LM7805.pdf -- page 24, Figure 14 shows how to implement a transistor to increase current output.

Ok, thats useful to know.

Also, the dropout voltage of a LM78XX is typical 2V. That means your input voltage must be (regulated voltage + 2V) greater than 14V to regulate to 12V.

Yeah, using the LM7812 direct from the deep cycle batteries was resulting in 11.7V. I realized I actually have another option here that may be better, if I can figure out how to make the charging work. This setup actually has 2 12V deep cycle batteries, so I could in theory use them in series to generate 24V and use some of these regulators:

http://www.amazon.com/Converter-Regulator-Voltage-Reducer-Step/dp/B00AO0PCMW

However I'm not sure I could charge that directly off the alternator.

so I could in theory use them in series to generate 24V and use some of these regulators

I would suggest against increasing voltage to 24V, to end up back at 12 volts.

I would suspect that the leds are sorta forgiving. Check their specs, but I would suspect they should work between 10 volts, and 15 volts (just guessing).

jackwp: Not all LEDs are created equally. Have you checked the specs for these "12Volt leds"? The specs may tell you the maximum voltage. If they were designed for use in vehicles, then I would expect them to be ok.

The primary LEDs are these strips:

http://www.amazon.com/gp/product/B0085IXEYS/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1

So the standard 5050 based RGB strips. There was above mention of them generating a decent bit of heat when run off 14.5V.

(Unfortunately I don't have a 14.5V power supply and I can't just run my car all night in my shop to see what happens)

Ok, if you don't want to run the leds at 14.5, worried about the heat, just use a/some 12 volt regulators. If the engine is not running and the battery gets below 14 volts, your leds will still work. Have you tried your leds, at less than 12 volts? How low will it go?

jackwp: Ok, if you don't want to run the leds at 14.5, worried about the heat, just use a/some 12 volt regulators. If the engine is not running and the battery gets below 14 volts, your leds will still work. Have you tried your leds, at less than 12 volts? How low will it go?

As I mentioned above, I tried using a 7812 regulator, however those are rated for much less than the ~6A max of a 5m length of the RGB strips (which are common positive, so I can't power each color channel separately). My 1ft test strip did fine with the 11.5V the regulator was producing off the battery.

but I need something to power all the LEDs (a combination of RGB strip and some high-current LEDs).

So what do the data sheets say about these LEDs?

random_vamp: I'm building a large Arduino controlled LED setup powered off deep cycle batteries attached to a vehicle. The Arduino's will regulate themselves, but I need something to power all the LEDs (a combination of RGB strip and some high-current LEDs). Its my assumption that its not safe to power these straight from the ~14.5V output, I'd love to hear that I'm wrong. Assuming I'm not, does anyone have a recommendation for how to regulate this down to 12V? Either a product that can handle the entire load (probably ~50-60A) or individual ~10A regulators?

I am running a couple of these LED 5050 (not RGB just white) 1 metres strings in my car without any regulation and have been doing so for about 12 months now - i notices that the first set of 3 LEDS has failed - somewhere around the middle of the strip.

At the price for these - i would not complain - just hook them straight to the car power and throw them away every couple of years and start again

Craig

50-60amps of LEDs is a lot of LEDs. That being said....using logic level MOSFETs to drive the LEDs/strings, constantly measure the 12-14.7volts and then use PWM to control the duty cycle of the LEDs. At 12v run at 100% duty cycle. At 14.7....14.7/12=.81, so drive the LED's at a max of 81% duty cycle. It's the average power of the LEDs that kills them (assuming the switching frequency isn't to low). It's like passing your hand through a flame. If you do it quickly enough, it won't burn you. Too slowly and well..... Regular MOSFETS need 8volts or more to guarantee full on. Logic level MOSFETs guarantee full on with a logic level of 3-5v. Also note that the pins of the arduino can not switch a MOSFET full on and full off quickly because the gates require a large charge current to switch them on. There are MOSFET drivers that can provide the 1-2amp instantaneous charge current. Adds some complexity, but now you can switch high currents at high frequencies(100khz). If you don't turn on and off quickly, the MOSFETS will heat up more than you want. I've switched 10amps at 500Hz using the digital output pin driving a MOSFET. In a nut shell: Measure battery voltage, use that to control the max duty cycle, use a PWM freq. of about 500Hz, and drive the MOSFET gate through a resistor to limit the gate current.

“12-volt” LED strips run just fine on the 14,4V maximum voltage in a car. There is absolutely no reason to try to invent the wheel again, regulating the voltage down a volt or two.

A linear regulator won’t work anyway, you’d be looking at a DC/DC converter for that kind of job.

Hundreds of people are using 12V LED-strips on cars, trucks and boats with no problems what so ever.

50-60 Amps (720 Watts) BTW ? Are you covering the entire car in LED’s ?

// Per.

One easy/cheap way to keep the voltage down a bit is to connect 3 or 4 high power diodes in series. If you put a switch in paralles to these 4 diodes, you can flip it on when the engine is not running, to get the 12 volts again. I am assuming your batteries are being charged by the engines alternator right?