Choosing Capacitor Value for ws2812b LED Strip

Other Hardware LEDs and Multiplexing
1

Hello,

Some places recommend using 450uf 25V while others 1000uf 35V.

Can someone explain in short what is the factors taking into account when choosing the capacitor value?

My Setup

  1. Power Supply 5V 6A -> LED STRIP 144 LEDS Max amp draw around 4A - 5A

OR

  1. LIPO Battery 12V -> Step down converter 12 - 5V -> LED STRIP 144 LEDS
  • In this case should it matter that the first power source is 12V ?
    where should I install the CAP?

Thanks

How control an Arduino Nano and power a 24 LED ring over the same USB connector?
2

Either cap will be ok but 1000uF probably be better. A larger value cap will be better at smoothing out sudden changes in demand for current from leds. It should be placed across the 5V & 0V wires close to the strip. The voltage of the cap is not relevant, as long as it exceeds 5V, so a 16V cap would also be ok. For the same uF value, caps with lower voltage rating will be physically smaller.

You will probably not be able to find a 450uF cap, 470uF is more usual.

3

PaulRB:
Either cap will be ok but 1000uF probably be better. It should be placed across the 5V & 0V wires close to the strip. The voltage of the cap is not relevant, as long as it exceeds 5V, so a 16V cap would also be ok. For the same uF value, caps with lower voltage rating will be physically smaller.

Thanks so the Volt value is just a limit number where too much will harm the capacitor, I got that part thanks.

I still don't understand the uF value - I get it means the number of Farads per volt or something but does it correlate to the amp draw?

Why should I choose 470 or 1000?

Thanks again

4

The capacity is not Farads per volt, it is just Farads. It is a measure of the electrical charge in Coulmbs that the cap can hold for each volt across it. So a 1000uF cap will hold 5000uC of charge when connected to a 5V supply.

If there is a sudden increase in the current demand from the leds, the cap can satisfy that more quickly, being closer to the strip than the power supply. Without it, sudden changes in current demand would put stresses and strains on the whole circuit, such as sudden voltage drops, which would reduce the life of all components involved. A lower value cap will provide less protection from this than a higher value. But don't go crazy. A very high value cap will be much more bulky and expensive but not increase the protection significantly more.

5

PaulRB:
The capacity is not Farads per volt, it is just Farads. It is a measure of the electrical charge in Coulmbs that the cap can hold for each volt across it. So a 1000uF cap will hold 5000uC of charge when connected to a 5V supply.

If there is a sudden increase in the current demand from the leds, the cap can satisfy that more quickly, being closer to the strip than the power supply. Without it, sudden changes in current demand would put stresses and strains on the whole circuit, such as sudden voltage drops, which would reduce the life of all components involved. A lower value cap will provide less protection from this than a higher value. But don't go crazy. A very high value cap will be much more bulky and expensive but not increase the protection significantly more.

Ohh ok very interesting, I ordered 1000uF and 16V value Capacitor, I feel like 25V or 35V is an overkill.

I have another question regarding long LED strips.
I read that after 10meters there is a reduction in voltage so it's recommended to add another power suplly.

Is it possible to Power the next LED strips with a new power suplly and only connect the GND to the GND of the end of the first LED Strip ? while VCC & GND to the next LED strip and the Signal also obviously.
Or I need to buy a special amplifier

6

You can use multiple power supplies or a single supply with more current. Use good quality thick wires for the power and feed power in at multiple points or at both ends of the strip. With multiple supplies, connect the grounds but keep the +V isolated from each other, getting different sections of strip. Either way, connect a large cap for each section of strip as close to the strip as you conveniently can.

1 Like
7

PaulRB:
You can use multiple power supplies or a single supply with more current. Use good quality thick wires for the power and feed power in at multiple points or at both ends of the strip. With multiple supplies, connect the grounds but keep the +V isolated from each other, getting different sections of strip. Either way, connect a large cap for each section of strip as close to the strip as you conveniently can.

Thanks it was very helpful :slight_smile: I'll do that !