# LED Strip setup on stairs. Unsure which power supply will work for 1200 LEDs

EDIT: Added a solution that may work. Please see the bottom for update.

As you can see in the photo, (sorry for the bad schematic, I am new to this) I want to have sufficient power to all the LEDs but am not sure how strong a power supply I will need for this to work without burning the LEDs. I see I'll need 5v since everything is powered by 5v, but I'm not sure how to calculate the amperage.

This is going to be used on each stair for a total of about 18 steps. Each LED strip will be about 1m long with 1ft of wire connecting each strip. At the bottom step, I will be using about 2.5m of wire to reach the power source (the plug in the wall). Would any gauge wire be fine for this?

If anyone sees any flaws with my design, I would appreciate any help as I am new to this and am trying to set this up for my mother who seems very excited for it. I don't want to mess it up and cost her a lot of money. FYI i didn't include the negative side to not confuse people with my poorly drawn schematic, but it would follow the same path as positive, only backwards.

Parts from Amazon.ca

ESP8266 Wifi Controller Could only post 2 links: amazon.ca/gp/product/B01F5ALLFM/ref=ox_sc_act_title_1?smid=AZP2XD12VOJLM&psc=1

PIR Motion Sensors Could only post 2 links: amazon.ca/gp/product/B019SX6ZR6/ref=ox_sc_act_title_6?smid=A3BYPBV6CTUPBO&psc=1

So i have now found what might work but still want to make sure with everyone here that it is a good option as i know there are multiple ways of doing this now. I found this in an adafruit tutorial.

I would use a 5V 80A power supply with 3 power outs. As i am new i would appreciate any suggestions on which fuse and which bus bars to get. (Tried researching but i cant find one that looks like the schematic). I live in Canada by the way in case you send links to local shops.

I would use busbar 1 for PIR sensor 1(bottom of the stairs), Busbar 2 for ESP8266, and Busbar 3 for PIR sensor 2(top of the stairs)

• Have you tried (no. of LEDs * 0.3) / 5 + a bit more? – Paul Uszak Aug 24 '17 at 20:24
• that ESP8266 is about 4x too expensive. use 18 or 16 awg for the main connectors. – dandavis Aug 24 '17 at 21:26
• Interesting. I've also set up LED strips on the stairways and plan to set them up to cover new 5000 sq ft of aluminum/steel decking I'm building, next summer. I also have created motion detection using a combination of sensor systems (ultrasonic, PIR, and radar and using a Kalman filter for data fusion) for a kitchen situation to force the stove to go inactive if anyone leaves the room for longer than a set time (safety regarding developmentally disabled daughter.) +1 for the question. – jonk Aug 24 '17 at 21:30
• Is there a reason why you want an addressable RGB strip? If this is just for lighting, you can get the much cheaper white strips. – jonk Aug 24 '17 at 21:33
• Well my mother is a "bling" type person who wants cool effects etc. So i plan to add cool lighting effects using the ESP8266. Programming is more my forte so i shouldnt have trouble figuring that out but i am really stumped trying to figure out all the electrical work. I was thinking to run the power up the left side of the stairs and have the LED strips just branch off at every step all connected to the main line. Not sure if this changes the amount of power needed as in my head it would seem like i can get away with less power. – Shane Aug 25 '17 at 1:20

WS2812B LEDs are a lot of fun, and fairly easy to handle. That said,

Would any gauge wire be fine for this?

NO!!!

You need a wire large enough to carry the current without too much voltage drop. All wires have some resistance, which means the voltage drops over the length of the wire. According to Ohm's law, the more current flowing through, the bigger the voltage drop.

The WS2812B module contains 3 LEDs(Red, Green, Blue) with each color drawing up to 16mA according to this post https://www.disk91.com/2014/technology/hardware/ws2812b-leds-current-consumption/comment-page-1/

assuming you have 60 LEDs/m, 18 strips of 1m, that give you 60*18*3*16 = 51,840mA or about 52A max, which is no joke. This is if you turn all the LEDs to white at full brightness.

Your description is not very explicit on this point, but if you try to daisy chain all the strips, it is not going to work. Only the data wire needs to go from the output of strip N to the input of strip N+1. Power needs a more direct path.

simulate this circuit – Schematic created using CircuitLab

If you try to build that power path with a single set of wires, you will need 2*(2.5+17*0.3)=15.2m of wire carrying that big current. Of course this is an overestimate, since strip 1 will reduce the current in the wire by about 3A at 2.5m, strip 2 by another 3A at 2.8m, ... and so on. Weather you want to do the actual math or not, that means thick wire. My recommendation would be no more than 1V drop over the entire length (in theory the modules work down to less than 4V) or about 60mV/m. at 60A this means 0.001 Ohm/m or AWG 5 !!! It is gigantic. Less conservative estimates might give you up to AWG 8 ...

An other strategy can be to have one set of wire connecting each strip directly to the power supply. This will be a cable management nightmare, but allows you to use smaller wires. 3A, 15m, 1V => 0.02 Ohm/m => AWG 18 to 21 (same computation as above)

simulate this circuit

Of course, you can also have a hybrid approach, with one wire power a few led strips instead of a single one. By now I hope you get how to compute things. You could also have multiple power supplies (one at the top of the stairs, one at the bottom) reducing the length of the wire. You could increase the voltage in your supply wire and have a localized step-down transformer for each strip. Or a bunch of strips.

Possibilities are endless, but always remember Ohm's law!

• I would recommend a distributed approach. You could run 3 strips from a 10A power supply. So run mains voltage up the stairs and every 3 strips put a 10A 5V power supply. This keeps your currents and cable losses to a manageable level. You still need reasonably thick cable but normal household power cabling should do fine. Old PC power supplies are bulky and noisy but are often a good source of cheap high current 5V or 12V power. – Andrew Aug 25 '17 at 9:40

When you see in the other answers that you are likely to draw 50 - 70 A plus, your takeaway should be that your trying to do it the wrong way in using a single monolithic 5 V power supply.

The WS2812B strip you are buying is about 18 W/m (with 60 devices) this represents about 3.6 A per meter strip (one step).
Your 18 steps therefore need about 65 A in total @ 5 V and a total power requirement of about 324 W.

My suggestion would be to utilize a small DC-DC Buck convertor (24 - 5 V) for the LED strip on each step. This reduces the current requirement for the long cable runs.
You can readily buy a 24 V to 5 V @ 5A convertor for about $2. Use this as a search term on Ebay, "5x DC-DC Step Down Buck Converter Power Supply Module 24/12/9V to 5V 5A 25W". Your mains powered 24 V DC supply now only needs to deliver 13.5 A, and becomes another readily available Ebay item to feed the DC-DC convertors. Look at this for reference. There is a huge number of 24 V 15 - 30 A power supplies available at a range of prices. If you run separate wires from the mains power supply to each group of six DC-DC convertors (<5 A), then you could use simple figure-8 cable or even garden light cable to distribute the power. I'd strongly suggest you put in line fuses in each of these wire pairs (one 5 A fuse for each wire pair should be effective). If you found it more cost effective you could even use 3 separate 24 V 5 A power supplies, with each one feeding 6 steps DC-DC convertors. Note: you would of course still have to run your digital signal wire through each of the LED strings ...though I'd suggest even here that you use more ports on your MCU and run 3 groups of digital signal wires to each of the suggested group of 6 steps. You can use a cable guide to show the currents for each cable. You can get medium current flat cable (either festoon cable or speaker flat cable) that will serve for 24 V distribution. For example, this speaker cable would work well for 24 V. • Thank you for this information. The only thing i'm thinking is that this may become messy/hard to hide if i have a buck converter on every step as the lip of each step is not that wide. Also, do you mean to put in line fuses between the buck converter and the LED strip? This would also add to the "bulk" on each step. I do see that this would solve my power supply issue though. Is there another way this can be done without having a buck converter and fuse on EVERY step. Maybe every 6 steps? – Shane Aug 25 '17 at 15:32 • Put fuses between the +24 V DC and each group of DC-DC convertors. If you try to distribute 5 V DC from a central location then the high currents mean that you will need very large cable sizes, 10AWG or larger. Distribution at 24 V gets you down to 22 AWG cable. – Jack Creasey Aug 25 '17 at 17:23 I won't rephrase the others' excellent answers, you said it all, except..... This LED outputs 12-16 lumen at full power, which equates to about 50 lumen/W which is realistic. Now you have about 1000 LEDs, so at full power you will have 16000 lumen. This is ENORMOUS. Considering the surface area of one step is about 1m x 20cm, or 0.2 sq.m, and if all the light from one 60 LED strip lights up that step, you got 960lm over 0.2 m2, or 4800 lux. Some recommended illuminances: • Office work 500 lux • Fine mechanical works ie watchmaking 2000 lux • Microsurgery 5000 lux So your problem is that you got about 10x more LEDs than you need. Solving this also solves your power problem. • good point. I did not consider that issue. My WS2812 strips don't look that bright, but maybe I just got swindled, or maybe I have never concentrated that many in in such a small area. Can be re-purposed as a burglar repellent system, can't wait to see it featured in the next Home Alone movie :) – MAB Aug 28 '17 at 21:26 • LOL, I wonder what the effect would be on zombies. I suggest building a mock model and setting all LEDs to 100%, see how bright it is. If you already bought the strips, there's nothing wrong in using them at low powers. – peufeu Aug 28 '17 at 22:37 60 milliamps per rgb led for full brightness all on white. 0.06 * 1200 = 72 Amps. 72 Amps * 5v = 360 Watts of power at just 5V. That's a non trivial amount of power. And that does not take into account power loss or the power supply ideal load of 85%. Minimum let's say 450W 5V supply. As to wire gauge, the smaller the wire the higher the resistance. The larger the load the higher the voltage drop across that resistance and heat issues. I suggest nothing smaller than a 20 AWG wire pair per led strip. • I really appreciate you taking your time to help. Those power supplies are quite expensive at around$100. Would it be a viable option to power the LED strips with multiple smaller power supplies? Maybe 3 every 6th step (i have 18 stairs). Would this ensure that the led's are the same brightness throughout, or would it also be gauranteed to have the same brtightness throughout with the first option using just 1 power supply? – Shane Aug 24 '17 at 21:58
• With multiple supplies and with 1 supply, the issue is properly wiring the led strips so that the high resistance of thr flexible printed circuit they are do not cause a problem. You can use multiple supplies. Their output grounds would have to be connected but not their 5V wires. Data would still connect through. I'll add a picture for this, but its been answered multiple times. – Passerby Aug 24 '17 at 23:02