RGB UV IR test bench: controller and power sizing

A university test bench often starts with three fixtures: an RGB bar, an ultraviolet bar and an infrared bar. The purchasing list looks simple until independent colour selection, brightness control and camera timing enter the design. This procedure turns that list into an electrical plan. It separates the decisions that follow from circuit arithmetic from the details that must come from the selected light's documentation.

1. Record the electrical interface before choosing a controller

Create one worksheet row for each independently driven LED circuit. Record its rated voltage or regulated current, maximum continuous load, connector, polarity and permitted operating mode. Keep a series-wide connector table separate from a model-specific wiring diagram. A familiar plug designation alone does not describe the complete RGB harness.

Distinguish three common arrangements. A constant-voltage light accepts its specified DC voltage through internal current-limiting circuitry. A constant-current light needs a driver that regulates LED current within its compliance-voltage range. A light with integrated electronics may accept DC power plus separate trigger or communication inputs. Applying the same supply to all three arrangements is not a valid shortcut.

Start with continuous illumination at the documented rating. Select light controllers after the load worksheet is complete. Use strobe overdrive only when both the light and controller specify compatible peak current, pulse width and duty-cycle limits.

2. Count circuits rather than housings

For an RGB fixture with separate colour inputs, assign channels as follows:

A six-channel controller is a useful starting architecture for this arrangement. It is not proof that a particular controller supports a particular RGB light. Check whether the light has separate two-wire leads, a shared common conductor, or an internal addressable driver. The controller must match that arrangement as well as the load ratings.

Two complete sets require ten outputs if every colour and fixture must remain independent. Connecting two lights to one output makes them a group, and is appropriate only when the drive design permits parallel loads and the combined demand fits that output. Never connect controller outputs together to obtain extra current.

3. Size both the outputs and the supply

Check the per-channel limit first, then the controller's shared total limit. Six outputs rated at a certain current each do not imply that all six can deliver that current simultaneously.

Consider an illustrative bench whose documented continuous loads are 12 W red, 10 W green, 10 W blue, 18 W UV and 16 W IR. These are example design inputs, not specifications for a catalog kit. Suppose all five circuits are confirmed 24 V constant-voltage loads and controller overhead is 4 W.

The LED load is 66 W. Including the controller gives 70 W, or approximately 2.92 A at 24 V. Allowing 25 percent engineering headroom gives 87.5 W, approximately 3.65 A. A 24 V, 100 W supply can therefore be considered if its derating curve still allows at least 87.5 W at the installed temperature and input voltage.

The largest channel draws 18 / 24 = 0.75 A. With the same design allowance, select an output supporting at least 0.94 A continuously. Also verify the controller supports the full 66 W LED load. For a converting driver, account for conversion losses in the supply calculation instead of treating output watts as input watts.

Review power supplies for input voltage, enclosure, protective earth, ventilation and output terminals. A controller with an AC input and internal supply may eliminate the separate DC supply entirely. Do not purchase both until the power diagram identifies where each belongs.

4. Specify the complete cable set

A stated lead length describes the light's cable; it does not establish that a controller, extension, mating connector or mains cord is included. List each connection separately: mains to supply, supply to controller, controller to each colour circuit, and camera or computer to controller.

For every connection, record the two mating connector types, cable length, conductor rating and pin-to-pin map. Draw the viewing direction beside each connector. Pin positions viewed from the cable side can appear reversed relative to the mating face. Select connection cables from that map, and identify any custom breakout harness explicitly.

Keep the DC runs short enough to limit voltage drop. For example, a 0.8 A load through a complete outgoing-and-return conductor resistance of 0.5 ohm loses 0.4 V. Measure voltage at the light while operating; a correct reading at the supply terminals can hide loss in the cable and contacts.

5. Commission colour selection before adding PWM

1. With power removed, verify polarity and connector orientation against the exact unit drawing.
2. Start the approved circuit with current limiting and a low brightness setting.
3. Enable one channel at a time and record the observed colour, current and camera response.
4. Test the permitted combinations and the total supply load before saving the operating settings.

Red alone, green alone and blue alone provide separate wavelength conditions. Simultaneous RGB can appear white after balancing the three intensities. Equal command values do not guarantee neutral white because LED efficiency, spectra and camera response differ. RGB mixing also does not add a dedicated white LED channel.

Use fixed exposure and gain when comparing samples. The existing multi-wavelength sequencing guide explains how separate colour exposures can improve contrast. Keep the object stationary while collecting a sequence unless motion is explicitly compensated.

For custom PWM, obtain the permitted switching topology and frequency range before designing the circuit. A useful timing check is that 1 kHz PWM has a 1 ms period: a 100 microsecond exposure spans only one tenth of that period and may see very different illumination between frames. Prefer continuous light for initial measurements; use documented hardware triggering or verified PWM timing when shorter exposures require it.

6. Freeze a purchasing list that can be wired as delivered

The final list should identify the lights, channel assignments, controller, any external supply, every cable or adapter, mounting hardware and the camera-control interface. Mark optional diffusion and polarizing accessories separately from standard contents. Specify whether the system must support all lights simultaneously or only a documented sequence.

For UV and IR tests, include suitable shielding and the laboratory's optical-safety review; visible brightness is not a measure of exposure. Verify camera sensitivity and filters at the intended wavelength. UV fluorescence imaging measures emitted light from the sample, while reflected-UV imaging needs an optical path that passes the excitation wavelength. Confirm which experiment is intended before selecting the camera filter.

Finish with a wiring diagram and a measured acceptance record. Successful commissioning means each requested lighting state produces a repeatable image, the electrical limits remain satisfied, and the bill of materials includes every connection needed to reproduce that result.