I have set up approx 11-12 meters of WS2815 strip lights connected to ESP32 controller. I did a lot of research before starting.
I have two questions:
Is there any way to tell if a logic level shifter is needed. I have 15ft + run of cable between the controller and first pixel, I would have assumed that because of this a logic level shifter would be required. However, without one, everything seems to work as intended. Is there a way that i can verify how much voltage the data line is receiving at the first pixel? I am not able to get a good reading from this as it seems to be a changing value in the mV scale. I have connected a higher quality shifter (74HCT125) - (the cheap ones from amazon were not working well) to bump the voltage on the data line from 3.3 back up to 5V. It seems to work but no different than without the shifter. Is it necessary? Is the only way to determine if its necessary is by observing the lights during effects and such and not by taking a measurement somewhere?
I am sensing 12V to the beginning and the end of my approx 11M lenght. To me, the colors all look pretty near perfect to the eye (compared to only powering from the beggining). However, near the middle of my run I am measuring 8.6V which is the lowest point. Ideally this would be as close to 12V as possible, however, if i am satisfied with the performance of the lights, is a 3rd power injection truly necessary? Other than optimal performance, if I leave it as is with 8.6V being the lowest voltage in the middle of the strips, is there any negative effect in terms of the lifespan of the LEDs? It would be really nice to not have to add an additional 30ft power injection run at the further point if I didnt really need too.
Unfortunately the need for a level shifter is more about timing and “digital waveform shape” than it is about a measured voltage. You’ll find out about needing one the more complex your data stream becomes. On the plus, if you’re happy with your current results you can live with it as is. Adding one later is usually not a huge deal.
If you’re seeing a drop to 8.6V, that’s a loss of 3.4V which is pretty significant. Try running your strip at 100% bright white and measure again, that will give you worse case stress on everything. One simple way of evening out the drop is to move your both your current injection points from the ends of the strip towards the middle. If you move the front end wire 1/4 towards the back and the back end 1/4 towards the front, you’ll distribute the worst case drop as evenly as possible across the whole strip.
That technique should be able to cut the drop to 1.7V, which should be more acceptable. If not, you’ll have to add more injection and/or move to bigger power wire.
Yes was always mesuring voltage at max brightness and color set to white to ensure true max load. Since my LED strip is in my gazebo, 10ft x 12 ft rectangle shape, it made sense to inject power at the closest corner to the controller going in both directions. The data line goes from one side all around to the end. Again, I dont see any significant visual change when injecting 12V in the middle, but this would bring me to almost 11V at all points on the strip, rather than 8.6V in the middle, which I agree, is not optimal at all. I will consider wiring the additional power run.
Since I have the shifter already I guess i will just wire it in. I was just hoping that I could take some sort of mrasurement somewhere to see if it is actually doing anything. Hard for me to know since there isnt a visible different when the lights are in operation.
If you’re not doing “complex” effects with your lighting and you get by without flicker initially, you may be okay without the shifter. Unfortunately there’s nothing to say things won’t change in the future and you may need one. Not the most reassuring statement (I know) but on the other hand, I have a number of larger strings I put up that don’t have and never had a shifter and work fine (but some have become problems…)
The voltage drop issues are further complicated by the fact that the entire string itself is a “wire of a certain size” with its own voltage drop. That’s why a 400A 12V supply placed right at the start of a strip will still see a major voltage drop after 500 LEDs even though the PS can supply more than the strip needs. The wire that interconnects each of those LEDs is too small to supply all of them at once. Each LED-LED connection has a very small drop that adds up over the whole strip.
My comment on moving the injection wires is intended to let you use your injection “power supplies” to drive fewer interconnected LEDs on each side of the injection point. That means the voltage drop of your injection wire becomes the significant drop not the sum of all the little drops of the interconnecting wires.