I'm working with some RGB LED strips. These are regular non integrated IC strips so the entire strip changes color instead of each individual led. Now I've done some calculations:
*EDIT. As pointed out by a used below, this was the wrong math, the final Current value ended up being 3 times as high, I'm not gonna correct the initial post here, but I've commented the correction after.
I have 14 strips, each one contains 120 rgb leds. According to Adafruit, a single diode in these leds requires 20mA of current to run at full brightness continuously. There are times when I need ALL the leds to display the while color so that means all three diodes (R, G and B) would consume a total of 60mA... I've got 120 of them per strip so that's 7200mA and I've got 14 strips so that's 100,800mA or 100.8 Amps of current. O_O. Oh well, if that's what it takes, then that's what it takes. The problem is that, there's a pretty good chance that I will have to tipple the amount of LEDs too to get the desired visual effect. One LED strip is long but it's too thin so I'll have to add two more for each "column". So if I have 14 columps (which right now is 14 strips) that means that It will be running 42 strips at once. And yep, there will be times when I'll need all of those LEDs to be white so that's 302400mA or 302,4 Amps of current.
Something tells me I would be better off making my own transformer and diode bridge with an appropriate capacitor set up to make a power supply that satisfies these stats.
Now where is this going to be used? This is an LED wall which will be used for backgrounds visuals at BAR and Club music performances so I assume these venues would be outfitted with the appropriate circuitry to handle this sort of a current draw. I'd have to ask beforehand. But considering that I'd be performing on stages that drive PA systems, lights and amplifiers on a regular basis, as well as refrigirators, ovens, stoves, air conditioners and so on, you'd think they should be able to handle this sort of thing.
Anyways. I'm looking for resources where I can find out how to build your own Transformer (picking an appropriate core, picking the wiring gauge and calculate the winding) As well finding out the values for the Diode Bridge and Caps for getting my 12v
12volt RGB LED strips have three LEDs in series, so 20mA per colour for three LEDs.
Three LEDs, all white, could consume 12volt/60mA.
Leo..
Oh, actually, you're right.
Each segment of 3 LEDs draws approximately 20 milliAmperes from a 12V supply, per string of LEDs. So for each segment, there is a maximum 20mA draw from the red LEDs, 20mA draw from the green and 20mA from the blue. If you have the LED strip on full white (all LEDs lit) that would be 60mA per segment.
So that's not 60mA per each led, it's 60mA per each set of 3 rgb leds running all 3 of it's diodes per led at full brightness, which makes sense since it runs off 12v. Ok so that means it's 120 leds per strip divided by 3 which lets me know how many 3-sets there are so that's 40 sets, 60mA each running at full white brightness so = 2400mA per strip.
Alright so that's already better. 14 strips is 33,600 mA. and if I were to go from 1 strip per column to 3 strips per column then it's 100,800mA or 100,8 Amps of current for the entire thing.
Ok, that's sounds more like it. Now about making the power supply. Any reliable resources that people usually link to when it comes to learning how to build your own power supply? Even from Chinese vendors, a 100a 12v power supply is going for about 110 bucks with about 80 shipping which means that the Canadian Border is going to sodomize me for another $70 for international goods and import charges. So Screw that. I'd rather buy a thick gauge wire, some caps and diodes (which, if bought individually, don't even have taxes applied to them) would cost less and may even be used on more than one.
But the appropriate hefty transformer is going to cost $100 and the required caps are also going to be expensive. Although I dont think the LEDs need lots of caps like an audio amp will.
What is the duty cycle? Can you use a car battery and a 10A charger to keep it topped up?
I hate to break it to you but there is no way you can build a 12 vdc 100 plus amp linear supply for anything even close to the cost of a switcher, it cannot be done unless you have a surplus transformer, diodes and caps. Further, you haven't even considered regulation. How close do you think you can get with off-the-shelf transformer voltages? News flash, you can't, it needs to be custom if you're looking to do an unregulated supply.
The bottom line is the difference required in raw materials, copper, iron and capacitance and it is is quite significant when you're dealing with 60hz (linear) verses 50khz or more (switcher).
BTW, don't count on Chinese switchers to delivery their "rated" output current, most don't. This is one of those things that if you try to go cheap, you'll probably end up paying twice. Once for for what you thought would work, a second time for what you really needed.
MorganS:
What is the duty cycle? Can you use a car battery and a 10A charger to keep it topped up?
Noy sure about the duty cycle. Also I don't think that a car battery will supply enough current to keep an anywhere between 70A to 100A of constant current for 30 min to an hour long show. And if I have to keep it topped up via a wall plug then isn't the battery redundant?
Google:
An average car battery has a capacity of around 48 amp hours which means that, fully charged, it delivers 1 amp for 48 hours, 2 amps for 24 hours, 8 amps for 6 hours and so on.
so that's almost 50 amps for for 1 hour, which is close but a power adapter for 50 amps is about 45 bucks on Ali or Ebay. Soooo it is pretty redundant. And it's not that there isn't an accessible wall plug on site, these are bars and clubs that are outfitted with a stage and AC wiring outfitted to drive Almplifies, Cabinets, PA system and lights at once.
And yeah, I'd assume that a transformer of that size would be pretty pricey in of itself which is why I'm looking at just buying a core and winding one myself.
Now let's say I can segmend the power supplies. Instead of one 100A+ power supply I can divide the lights into equal halves and power them from 2 separate 50A supplies. Or even divide it into quarters and use 4x 25A (or 30A to leave some overhead) power supplies. The total cost would still be about the same (1x 30A 12v power supply goes for $28.65 CAD sooo that's pretty much $120 for 4 of those... )
Not in parallel.
If you segment the strips conveniently, and ensure the grounds are tied together, you can drive each 'string' of LEDs with a smaller power supply - e.g. 5 or 10A for the appropriate number of LEDs n each segment.
This will also simplify your cabling requirements - using a much smaller gauge of wire, and even if you did manage to push 12V@30A in one end of the string - the power buss would burn out about half way along the chain, as the tracks and interconnects are probably only good for 10A at the very maximum. (12 x 30 = 360Watts = heat)
But you don't have the entire thing on maximum-brightness-white for the entire hour do you? That's why I asked about the duty cycle. If it's on 75% brightness but flashing half the time off and half on and then it only gets to 100% for a minute at the big finale, then you only need 37A of continuous charging capability. The car battery can supply surges of hundreds of amps for several minutes when required.
Or think about it another way: the 50Ah battery will be flat after 1 hour but at the same time you add the 50A charger for 1 hour. This gives you 100A for 1 hour. $45 plus a battery sounds cheap to me.
I suggest you use 24V led strips, which will need up to 60mA per 6 LEDs. Then the maximum current will be 16.8A which is much more manageable. You can buy a 24V 450W PSU off the shelf.
Alright, took me a while to get back home to respond. So here we go.
MorganS:
But you don't have the entire thing on maximum-brightness-white for the entire hour do you? That's why I asked about the duty cycle. If it's on 75% brightness but flashing half the time off and half on and then it only gets to 100% for a minute at the big finale, then you only need 37A of continuous charging capability. The car battery can supply surges of hundreds of amps for several minutes when required.
Or think about it another way: the 50Ah battery will be flat after 1 hour but at the same time you add the 50A charger for 1 hour. This gives you 100A for 1 hour. $45 plus a battery sounds cheap to me.
Definitely not at full brightness all the time. The LED strips color and value are synced to the music. It doesn't follow a pattern though. Each track has it's own orchestrated lighting show controlled my the music software. I'd probably need to have appropriate overhead though, don't I? I'll actually be dividing the LED wall into 4x sections and running them off their own 30A power supplies. This way I just need 3x more 30A power supplies.
dc42:
I suggest you use 24V led strips, which will need up to 60mA per 6 LEDs. Then the maximum current will be 16.8A which is much more manageable. You can buy a 24V 450W PSU off the shelf.
Never seen those whenever I googled for led strips. Will look into that. Are they any brighter than the 12v ones?
Southpark:
I'm thinking.....will the mains board allow for 100 amp? Maybe the bar and club switch board will allow it.
Most certainly not if I run them at full white at all times. I'm sure it can handle occasional peaks or short bursts of white.
