GrowFlux Blog

RJ style connectors for dimming grow lights

Posted by Eric Eisele on


Many legacy HPS lights, older LED grow lights, and even some of the latest non-waterproof LED lights from top brands use Registered Jack (RJ) style connectors for 0-10V dimming signaling. These connectors are convenient because RJ style splitters and cables are widely available and economical, however these connectors are not waterproof and may not offer the best reliability in a commercial setting.

There is no official industry standard around the use of these connectors or the specific connector to be used, and there is little information around compatibility across the various brands that use this style connector. This article breaks down all of your RJ connector questions. 


1. What is the difference between RJ11, RJ12, RJ14, etc? 

There are many different types of RJ style connectors. We'll focus only on the ones commonly used for dimming grow lights. Mechanically, all of these connectors can inter-mate, even though some have a different number of contacts and positions.

We have tested dozens of grow lights (LED, HPS, and CMH) over the last decade and haven't encountered one that needs all six wires. As a result, we have designed the RJ Adapter to mate to any grow light using one of the below RJ style connectors. 

RJ Type Number of wires Number of positions
RJ9 4 wires 4 positions
RJ11 4 wires 6 positions
RJ12 6 wires 6 positions
RJ14 4 wires 6 positions


2. Which brands use RJ11, RJ12, or RJ14 connectors? 

HPS lights that use RJ style connectors include Hydrofarm, Phantom, Dimlux, Luxx, Iluminar, and Gavita. In some cases, lights have been updated to remove the RJ connector and replace them with a sealed connector. Visually check your light for the connector type as the product documentation for many legacy lights is hard to obtain. 

LED lighting brands that have used RJ style connectors at some point include Horticulture Lighting Group, Luxx, Mammoth Lighting, Spider Farmer, and Upowertek. 


3. Which pins are used for dimming? 

The pinout for a typical RJ9, RJ11, RJ12, or RJ14 connector is shown below along with the pin assignments. Note that there are two pins for dim+ and dim- respectively. We recommend always wiring all four positions, this way if only two positions are connected inside your light, you will still have a dimming connection. 

RJ9 RJ11 RJ12 RJ14 dimming connector for grow light (GrowFlux)


3. How to daisy chain a dimming signal to multiple lights

We recommend using GrowFlux's daisy chain cables from our Universal Dimmer product family - this way most of your wiring will be waterproof, your installation will be future proof when you eventually upgrade your lights, and you will benefit from more robust cabling which uses UV resistant, UL rated 22AWG cables for runs up to 200 feet. 

Alternatively, RJ style splitters and RJ cables can be used to daisy chain the signal to multiple lights (not available from GrowFlux). Keep in mind that some lights have an 'in' and 'out' RJ style connector, so you may not need to use splitters.

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Dim-to-off on horticultural lights

Posted by Eric Eisele on


LED grow lights most often utilize a 0-10V analog wiring interface to receive dimming signals from lighting controls. These dimming interfaces are built into the LED driver (pictured below) and connect to a lighting control system, which then sets a control voltage on the 0-10V dimming line; the driver in turn senses this voltage and sets the LED driver output appropriately in response. Modern high power LED drivers used in the horticultural lighting industry utilize an additional feature - dim-to-off to shut the power supply down and turn the LEDs off entirely. 

An Inventronics LED power supply

How does dim-to-off work?

Dim-to-off is not an industry wide feature, and therefore it is often implemented differently across power supply manufacturers. For most manufacturers, the power supply is designed to shut the output down when the 0-10V control voltage is set to 0.5V or less; for some manufacturers, this lower limit is 1V. The diagram below shows the dimming response curve for an Inventronics driver, which is commonly used in horticulture:

Inventronics 0-10V dimming curve

How dim-to-off saves capital costs

Conventional lighting without dim-to-off requires that growers and integrators to eliminate mains AC controls that disconnect lights from AC power to turn lights off. This is most often done with contactor panels in large commercial grow facilities (pictured below). Smaller grow facilities may use plug in timers or relay boxes designed to turn off grow lights. For larger facilities, contactor panels for horticultural lighting may reach hundreds of thousands of dollars and can add months of engineering and installation to a project timeline. 

Contactor panels in a commercial greenhouse



Some 0-10V dimmable lights don't dim-to-off

While dim-to-off is a relatively new feature, only being built to most high power LED drivers in the last several years, 0-10v lighting controls are not new. 0-10V controls have been in use for decades in the general lighting industry, and have most often been used in conjunction with light switches or switched AC circuits to turn lights off. Most conventional 0-10V lighting products from the general illumination industry and 0-10V lighting controllers do not support dim-to-off, so it is important to verify that your lights and controllers support dim-to-off before making a purchasing decision. All GrowFlux lighting control products support dim-to-off. 

Some lights that are marketed with 1-10V control, which most often means that the lights do not dim-to-off. However, just because a light indicates support for 0-10V dimming, this does not necessarily mean that the light supports dim-to-off. The lighting manufacturer must explicitly state that the lights support dim-to-off. 


Most grow light controllers can't reliably dim-to-off

Since there is no unifying industry standard around 0-10V control, controls providers and lighting manufacturers have not managed to make the process of pairing up lights and controls easy. Most often, growers have trouble with dim-to-off once 10 or more lights are added to a single wired 0-10v dimming interface, resulting in unpredictable behavior. 


GrowFlux's Universal Dimmer features enhanced support for dim-to-off lights

GrowFlux's Universal Dimmer is designed to support the widest range of horticultural lighting manufacturers, and includes control circuitry and software that intelligently manages the 0-10V interface, ensuring that your lights always turn off when directed. The Universal Dimmer can reliably dim-to-off up to 50 lights on a single 0-10V interface. 

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