CV DMX Decoder Technology

How constant voltage DMX decoders turn a DMX512 signal and a DC supply into PWM dimming for LED strip, from 1 to 40 channels.

LT-820-5A, D5A, LT-912-OLED and BC640 DIN rail constant voltage DMX decoders

Overview

What are CV DMX decoders?

A constant voltage DMX decoder is the link between a DMX512 control system and 12V or 24V LED strip. It takes power from a separate DC supply and the DMX signal from the master, and dims each output channel to the level the master sends.

Our range runs from single-channel decoders for one run of strip to 40-channel DIN rail units for large installations, at 3A to 12A per channel. Most support RDM for remote addressing, and many have an OLED display, selectable dimming curves and 16-bit resolution for smooth low-level dimming.

DMX512 in, constant voltage PWM out
1 to 40 channels, 3A to 12A per channel
5–24V, 12–24V or 12–48V DC input
Address set on the display, by DIP switch or by RDM
Dimming, CCT, RGB, RGBW and RGB+CCT control

CV decoders at a glance

Input signal: DMX512, RDM
Output: Constant voltage PWM
Channels: 1 to 40
Current: 3A to 12A per channel
Supply: 5 to 48VDC
Dimming: 0–100%
DMX ports: XLR, RJ45, terminal
Mounting: Surface or DIN rail

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The technology

How a CV DMX decoder works

The decoder reads the DMX512 line and picks out the channels starting at its DMX address. Each DMX value from 0 to 255 sets the brightness of one output.

Each output is a MOSFET switch on the negative side of the strip. It switches the DC supply on and off thousands of times a second, and the share of time it is on, the PWM duty cycle, sets the brightness while the voltage stays constant.

The DMX signal also passes through the decoder to the next one on the line. Many decoders boost the signal as it passes, and the last one on the line takes a 120Ω terminator.

Simplified illustration: the decoder reads four DMX channels from address 001 and dims the strip's red, green, blue and white with PWM from the DC supply.

Channels

Matching channels to the LED strip

Each colour of each zone needs its own DMX channel and decoder output.

Strip type	DMX channels per zone	Zones per universe	Example decoder
Single colour	1	512	LT-811-12A, 1 × 12A
Tunable white	2	256	D4H in CT mode
RGB	3	170	D4A / D4B, 3 × 8A
RGBW	4	128	LT-820-5A, 4 × 5A
RGB+CCT	5	102	D5A / D5B or LT-905, 5 × 5A

Multi-channel decoders such as the LT-932-OLED split their outputs into several zones, each with its own addresses.

Our range

CV DMX decoders compared

Ratings from each decoder's datasheet.

Decoder	Channels × current	Input	Set-up and DMX ports
LT-811-12A	1 × 12A, plus 0-10V out	12–24VDC	OLED, RDM, 16-bit
LT-820-5A	4 × 5A or 3 × 6A	5–24VDC	OLED, RDM, 16-bit
D4A / D4B	4 × 6A or 3 × 8A	12–48VDC	Display, RDM, terminal (A) or RJ45 (B)
D5A / D5B	5 × 5A, 4 × 6A or 3 × 8A	12–48VDC	Display, RDM, terminal (A) or RJ45 (B)
LT-D4L	4 × 6A or 3 × 8A	5–24VDC	DIP switches, RDM, XLR-3, RJ45, terminal
D4H	4 × 4A or 3 × 5A	5–24VDC	DIN rail, display, RDM
LT-905	5 × 5A	12–24VDC	RDM, XLR-3, RJ45
LT-912-OLED	12 × 4A	12–24VDC	OLED, RDM, XLR-5, RJ45, terminal
LT-916-OLED	16 × 3A	12–24VDC	OLED, RDM, XLR-5, RJ45, terminal
LT-924-OLED	24 × 3A	12–24VDC	OLED, RDM, XLR-3, XLR-5, RJ45, terminal
LT-932-OLED	32 × 3A	12–24VDC	OLED, RDM, XLR-3, XLR-5, RJ45, terminal
BC640-DIN-DMX-40	40 × 3A	12–24VDC	DIN rail, RJ45, terminal

Output power is the supply voltage times the total current: for example, the LT-932-OLED gives up to 2304W at 24V.

Benefits

Advantages of CV DMX decoders

Why a separate decoder and power supply suits DMX LED strip projects.

High channel counts

Up to 40 outputs in one unit for large multi-zone schemes.

Choose the supply

Use any suitable 12V, 24V or 48V DC supply, sized for the load.

Smooth dimming

16-bit resolution and selectable curves for flicker-free low levels.

RDM

Find decoders and change their addresses from the RDM master.

Easy set-up

Set the address and mode on the OLED or digital display.

Protected outputs

Short circuit, over-current and over-heat protection on most models.

Selection & set-up

Choosing and setting up a CV DMX decoder

Count the channels: 1 to 5 per zone, depending on the strip type.
Check the current: keep each channel's strip current within the decoder's rating, and the total within its maximum.
Match the voltage: the decoder's input range must cover the strip and power supply voltage.
Size the supply: allow the full strip load plus around 20% headroom.
Set the address: enter the start address on the display, DIP switches or from an RDM master.
Wire the line: daisy-chain the DMX to each decoder and terminate the last one with 120Ω.

Related technology and products

Complete the system with a master and power supplies:

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Max. channels

12A

Max. per channel

16-bit

Dimming resolution

48V

Max. DC input

Where CV DMX decoders are used

Wherever LED strip is controlled from a DMX system.

Architectural

Facade, cove and outline lighting in many zones.

Hospitality

Bar back, ceiling and feature strip lighting.

Entertainment

Stage, club and venue lighting from a DMX console.

Retail

Shelf, window and display strip lighting.

Exhibitions

Stand and showroom effects programmed per event.

Control panels

DIN rail decoders in central lighting control cabinets.

FAQ

CV DMX decoder questions

A constant voltage DMX decoder sits between a DC power supply and the LED strip. It reads the DMX512 signal from the master controller and switches the supply to each output channel with PWM, so each colour or zone of strip is dimmed to the level the master sends.

A DMX decoder has no power supply inside. It needs a separate 12V or 24V DC supply and only does the dimming. A DMX LED driver combines the mains power supply and the DMX dimming in one unit. Decoders suit high channel counts and existing DC supplies, while drivers save space and wiring.

Count one channel for each colour of each zone: 1 for single colour, 2 for tunable white, 3 for RGB, 4 for RGBW and 5 for RGB+CCT. Then check the strip current on each channel is within the decoder rating, from 3A to 12A per channel in our range, and that the total does not exceed the decoder's maximum.

RDM, Remote Device Management, adds two-way communication to the DMX line. With an RDM master, you can find each decoder, read its settings and change its DMX address without going to the decoder itself. Most of our CV decoders support DMX512 and RDM.

Most of our decoders have an OLED or digital display with buttons, where you enter the start address from 001 to 512. The LT-D4L and LT-830-8A use DIP switches, where the address is the sum of the switches turned on. RDM decoders can also be addressed from an RDM master.

CV DMX Decoder Technology