Power consumption and LED spacing

A project log for Board for modular LED wearables

Board design which makes it easy to attach LED light strips (APA102). No soldering is required by the maker who is using this board

Sander van de BorSander van de Bor 01/20/2019 at 21:410 Comments

The new LED strip works great with the board. The pin-out is the same, and at a first glance the entire strip looks the same, but there are some differences:

The top show the new strip, and when you look closely, you will notice the smaller chip. These are SK9822 chips instead of APA102. Not an issue and the actual LED on the board is SK9822 already. The strips are thinner and more flexible, 0.34MM vs 0.46 of the APA102 strip. The FPC connector is recommending strips around 0.3MM, so the new strip should work better. Unfortunately I have been using the 0.46mm and this might have damaged the connector and these new strips are loose in the connector, but could be held with some super glue if needed.

I tested the entire strips by connecting a 8A power supply to the end of the strip, and turned all the LED's to full brightness, white color:

You will notice that the inside of the strips is white (where the power source is located) but appears more red toward the end. My power source is not sufficient enough and since the RED led has the lowest voltage forwarding, it is the only LED turning on.

An LED usually requires about 20mA to be as bright as possible without causing any damage. Since the strip above is 5 meters long, with 60 RGB LED's per meter, it requires 5 meter X 60 RGB leds X 3 leds per RGB X 20mA = 18000mA, or 18A. I need a larger power supply.

In this project we are only using small sections of the strip, but keeping an eye to the power consumption is still very important. We want the wearable to last as long as possible. This can accomplished as follows:

  1. Use less LED's:
    Above you can see how two different strips blend the colors through the Nu-Foam used in the wearable. The upper shows 60 LED's per meter while the bottom show 30 LED's per meter. You can see some dark spots between the 30 LED's per meter strip, so I usually stay with the 60 LED's per meter. But you can see above that you don't have to put the LED's close to the end of the wearable, the colors distribute pretty for through the Nu-Foam.
  2. Use patterns where not all LED's light up at the same time:
  3. Change the brightness. There is usually not a big difference between 50% and 100% of the brightness, and sometimes it appears better to the eye.

The largest battery I use in most of my projects is 1200mAh. It is recommended to charge and discharge the battery at a rate of 2 times the capacity, so at a maximum rate of 600mAh. Most of my wearables last up to 4 hours before a recharge is required.