Film & Photography Lighting
How to Connect Hybrid CCT Tunable LED Products
In recent years, white LED products with "tunable" or "CCT adjustable" features have grown in popularity. Particularly in applications such as film and cinema lighting, the ability to adjust, on the fly, the color temperature to match the color balance of ambient or external lighting conditions is an invaluable feature.
Unfortunately, with added flexibility comes added complexity when it comes to controls. In this article, we will go over two options for controlling LED products such as our own FilmGrade WHITE HYBRID Flex Strip and LED Flex Panel.
Anatomy of a Hybrid LED Product
The operating principle of a hybrid LED product is actually quite straightforward. Typically, it involves two types of LEDs (i.e. tungsten and daylight) that are placed on two separate circuits. By adjusting the relative brightness between the two LED colors, the color temperatures blend together, creating a color temperature that lies somewhere between.
The mechanism behind hybrid white color mixing is similar to a traditional shower faucet that has a "hot" and "cold" - by adjusting the relative amounts of each, you can dial in your desired color temperature.
Therefore, it is important to understand that the fundamental mechanism behind adjusting the color temperature is based upon dimming and adjusting the brightness of each white color circuit.
A typical hybrid white LED product will include three input wires. Below is an example of the FilmGrade WHITE HYBRID Flex Strip :
- Black wire: 24V Input (Positive)
- White wire: Daylight ground (Negative)
- Yellow wire: Tungsten ground (Negative)
The black wire acts as a "common positive" terminal. What this means is that both the daylight white and tungsten white circuits share this electrical connection.
As an initial test, if you connect a power supply with 24V+ to the black wire, and 24V- to only the white wire, you will see just the daylight white LEDs illuminate. If you then connect 24V- to only the yellow wire, you will see just the tungsten white LEDs illuminate. If you connect both the white and yellow wires to the 24V- wire, you will then see both colors illuminate simultaneously.
This isn't very interesting or useful, of course, since it only provides for 3 different fixed color modes. To achieve a fully controllable system, we now need to introduce a controller.
Method 1: Use a Dedicated DMX or RF/WiFi Controller
The first method involves use of a controller designed specifically to adjust two or more LED output channels. For example, our own DMX decoder allows for DMX control of up to 5 different channels. This will require a DMX controls system, which is commonly used in theatrical and studio applications. For the average user, DMX is most likely overkill, and the details of which would be beyond the scope of this article.
For a basic residential or household application, a color tunable LED controller can be purchased quite inexpensively. They will typically be controlled via an RF remote, or WiFi or Bluetooth app via smartphone.
Unfortunately, most of these products will introduce flicker and would not be safe for use in film & photo applications.
Method 2: Flicker Free Manual Dimmer Solution
NOTE (Feb 1, 2021): We are currently investigating some dimming performance issues observed with this setup. We recommend using alternative setups until this issue has been further investigated and resolved.
A relatively inexpensive and reliable way to achieve flicker-free color tuning and dimming would be to utilize our FilmGrade Flicker-Free LED Dimmer.
The dimmer features a simple manual turn-dial and is designed to adjust the brightness of single color LED strips. But, as we discussed above, a hybrid white LED strip product is, essentially, two LED circuits in one.
Below are the connection diagrams that would allow one to use 2x manual dimmers to control the relative amounts of tungsten and daylight output.
For this to work, the two dimmers must be connected to the same power supply. The reason is that if the two dimmers pull power from two different power supplies, their voltage levels may not match, causing performance issues.
1x PN 3092 (24V power supply)
3x PN 7094 (Female DC jack adapter)
2x PN 7093 (Male DC Pigtails)
2x PN 3081 (Flicker Free LED Dimmer)
1x PN 3002.HY (Hybrid LED Strip)
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