LED grow lights are becoming the centre of attention to overcome the seasonal changes and fulfil the increasing food, indoor gardening or medicine demand since grow lights allow you to cultivate a wide range of plants during any time of the year and any climate in the world.
Unlike any other LED lights for the human beings, LED grow lights’ density is always much higher thus there are more lights connected to a single dimmer while there are many type of dimmers in the market so here in this article, we will discuss about using 0-10v dimmers and how many fixtures we can put on a 0-10v dimmer.
What is dimming, and how does it work?
Before moving towards our main topic, let us look at the few basic terms and concepts that we are going to use.
Dimming, as the word shows the meaning itself, it means reducing the light output of a lamp or light fixture in order to get a suitable environment. It is usually measured in lumens (lm). Dimming the lights also saves energy a lot and reduces the operation temperature thus increases the life time and reliability of the light fixtures.
In this article, we will focus on 0-10v dimming. It is one of the earliest and simplest electronic light control protocol from fluorescent era. The control signal is DC voltage that varies between zero to ten volts.
Why are LED lights employed for growing plants?
Light plays a preeminent role in plant growth, but the natural light source is insufficient for plant growth during some seasons and in some regions of the world. This is why additional light sources are used to overcome these problems.
In the past, high-pressure sodium lamps and metal halide lamps were used, but these lamps generate high radiant heat, which is not very energy efficient. LEDs are a very sustainable and energy-efficient greenhouse lighting source. Here are some of the reasons why LEDs are used in plant growth.
- Less energy consumption. (Up to 70%)
- Simple electronic dimming function.
- Reduction of heat stress on plants.
- Long life time and low maintenance cost.
- Control over the spectral composition of red, blue, green, and far-red wavelengths.
How does 0-10V dimming work with Grow Lights?
0-10V is a low voltage dimming system defined by IEC-60929 Annex E.
The drivers are usually connected to 0-10V dimmer by a dimming cable which has two wires (dim+ and dim-). When these two wires are open or dimming voltage is higher than certain level like 9V or 10V, the light output will be at 100% level. And the light output goes down linearly or logarithmically with dimmer output voltage to minimum level until less than 1V. For a driver with dim to off function, when the dimmer output is less than certain level i.e. 0.5V, or wires are shorted together, the dimming driver will set the light level at the minimum or 0.
How many fixtures can you put on a 0-10V dimmer control?
Before answering this particular question, let us look at some of the basic terminologies considered in determining the number of fixtures. There are two types of 0-10v dimmers.
● Passive Current Sinking Dimmer:
These dimmers can only sink current because they are passive devices composed by transistors, diodes, resistors and zener. Those dimmers are low cost and utilized in simple residential and commercial systems.
It is quite easy to find 0-10V dimmers in the market and the major players are Lutron, Leviton, and Wallstopper in US and Philips, Osram and Honeywell in Europe.
● Active Dimmer:
In more complex control systems, active dimmers or controllers are often utilized to realize different light environments or light purposes. There are wired control systems using protocols like PLC, RS485, DALI and DMX etc. and wireless systems using bluetooth, Zigbee, LoRa, NBIOT and WiFi etc.. The dimmer transfers those protocols to 0-10V dimming signal thus common LED drivers can be controlled.
● Number of Fixtures per 0-10v dimmer:
The number of fixtures or blasts that can be connected to a dimmer mainly depends on how much current that dimmer can sink or source and how much current the driver source or sink.
For active dimmers, the data below typically shows the sink and source current capability from the datasheet, the max sourcing current is 100mA, and max sinking current is the same.
Then we have to check the current needed to control a single driver, and the figure below typically shows the current a driver needs. According to IEC 60929 standard, a blast should source the current, and it also specifies a maximum blast source current of 2 mA and a minimum of 10 µA. Not all drivers or blasts follow this standard. However, it can be used to determine the approximate information drivers or blasts which are being in use.Most of the driver dimming interface is current sourcing so only the sourcing current data is provided.
If we know the sourcing capabilities of a blast or driver, it is very easy to determine the number of blasts that a single control circuit can control. The value can be found by taking the sinking ability of control and dividing it by the source current of each blast of the driver.
For example, we know that the sink current of the dimmer is 100mA (100,000 µA ), and the sourcing current of the LED driver is 450 µA, then the max. allowable quantity should be 100,000 µA /450 µA =222pcs.
Other than sink /source capabilities, the following factors will help you determine the number of lights on per 0-10v dimmer.
- Always see the dimmer manufacturer specifications.
- Every dimmer is different. So, their specified current output will determine the number of fixtures that can be controlled.
- The length of the wire and the splices (joints) will also affect this value. The too long dimming cable or too many joints can have voltage drop so as to lead to inaccuracy.
- The uA sink/ source on the driver 0-10 V circuit.
If the capabilities of control and specifications of the blasts are known, then the maximum number of blasts on a circuit can be determined.
What is a dim to off feature, and why is it important?
This excellent control mechanism eliminates the need for a relay bank on a circuit to avoid inrush current problems. These problems are caused due to repeated turning on and off a large number of LED drivers simultaneously.
uPowerTek’s IP67 0-10V dimmable LED driver can dim to off at 0.5V and dim on at 0.7V. It means that setting the dimming control voltage to something below 0.5V will shut off the output of an LED. The supply will remain power but in a shallow power sleep state until the voltage is again brought up at 0.7V. These drivers are compatible with most of the controllers and drivers.
Make a larger 0-10V dimmable grow light system with single controller
Using single controller to control more than 50 lights or even more can be a challenging job for two reasons:
- Controller current sinking capability
- Dimming voltage drop with long dimming cable
- Noise and interference among large number of drivers by the dimming cable
So to overcome this issue and save cost for controllers, installation and maintenance, uPowerTek provide the active daisy chain function for the light designers.
For smaller system to further eliminate the main controllers, uPowerTek driver provides the master mode to operate as the controller. By tuning the output of the master driver, all the other drivers connected to the master driver change the output simultaneously with the master driver.
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Q：What happens if too many fixtures are used on a single dimmer?
LED drivers with dimming capabilities have some specifications related to source current from their dimming circuit.
If you add too many fixtures, the amount of current running in the circuit will exceed the value that the dimmer is capable of sinking. It will cause the driver unable to be dimmed to desired level.
Q：Are LED grow lights different from regular LED lights?
Standard LED lights only provide illumination but LED grow lights are for vegetation and flowering. For this reason, LED grow lights have a more special spectrum of red, green, and blue for better photosynthesis. And the installation density or a system power density is much higher than conventional LED lights.
Q：Will a driver be damaged if the dimming control voltage is above 11VDC?
Usually, there is a design margin of LED driver dimming circuit. Take uPowerTek LED driver, for example, the max. allowed voltage listed in the datasheet is 20Vdc. It will break at around 50Vdc input. Please note that this is only applied on uPowerTek LED drivers, different brand LED drivers have different designs.
LED grow lights offer energy saving, low heat, and spectrum optimization to be compatible with plant growth. With all the information provided in this article, we can have an idea of “how many fixtures or grown lights you should attach to a 0-10V dimmer?” so as to make a better choice regarding their number and usage.