I have a new question relating to my halloween staff. I have recently seen references to using a capacitor, I think on the power wires, to somehow protect the LEDs. Does my staff need this? I have 300 WS2812Bs powered at 3.7 volts by 5 18650 batteries. If I do need a capacitor, where does it go, and what value would I need? I should mention that I do have a resistor in series with the data line, to protect the first pixel, but I think the capacitor issue is something different. Thanks!
The capacitor is used to help smooth things out if the power draw to the LEDs changes abruptly, for example when the display quickly goes from bright to dark to bright.
You’ll want to use a 1000uF capacitor with a voltage rating of 16V (or higher is fine too). It goes between the positive and negative wires feeding the LEDs. Observe the capacitor’s polarity when writing it up.
Awesome, thanks Marc!
If you power your staff with Lithium batteries please make sure you have a undervoltage protection. Below 3.6V those batteries discharge dramatically.
The real problem is that if you get below 2.5V the cells get irreversibly damaged. Then they can lay in your house even for a week or so and suddenly burst into flames.
Use a under-voltage detector to switch everything, also your µC, off.
@Juergen_Bruegl That’s a good point I hadn’t considered. The nanos and smaller strip of leds inside the skull are powered by the USB charge board from the power bank, which I’m guessing would provide that kind of protection, but the main LED strip on the staff is connected directly to the batteries, through a switch. I think I will add a relay that is powered by the power bank, to break the connection between the batteries and LEDs when the charge panel is off.
@Karl_Tinsley there are power banks that do other don’t have a undervoltage protection circuit. Here is something nice and simple https://www.adafruit.com/product/3428
If you connect it to the right Mosfet you can save the head aches with relays. (see here in section 5: https://github.com/GyroGearloose/FASTLED-using-a-push-button-to-switch-entire-installations-ON-and-Off/wiki)