Ongoing test with an HID uplighter

This picture shows the business end of the HID uplighter I designed and built for my study room at home. This luminaire originally contains three high-pressure discharge lamps: a Philips CDM-tm 20W/830 (not shown here), an Osram HQI-TS Excellence 150W/D (center), and a 100 W UHP burner mounted in a quartz jacket (right). Such combination enables the production of white light over a wide color temperature range, made possible by their independent control. The HQI-TS and the UHP are driven with dimmable ballasts, which enables even more flexibility. The UHP burner emits UV-A and -B radiation which, combined with the other lamps, enables the production of artificial daylight, which is useful to compensate for the many dark and rainy days that we have here in the Netherlands.

I am now testing a modified configurations because I found that the produced light lacks some "solar" quality. More specifically, the spectrum lacks in orange and red. To remedy this problem, I first tested the addition of a 50 W SDW-TG white sodium lamp to the system. While this approach worked well, I could not integrate the lamp in the already crowded luminaire. The next best thing is the Philips CDM-TC Warm, which was designed precisely as an energy-efficient alternative to the SDW. While the compact metal halide lamp can be integrated in the system, its wattage (70 W) is just too great for the intended application and Philips never made a 35 W variant of it. I eventually found a solution while experimenting with the thermal balance of HID lamps. I found that by adding an insulating sleeve around the lamp and a side aluminum mirror so as to return some radiant energy back to the burner it is possible to run the lamp satisfactorily on a CDM 35W ballast. The lamp assembly can be seen during operation on the left side of the Osram HQI-TS. So far I have been using this configuration since April this year, and I am really happy with the result. The next step will be the full integration of the modified CDM-TC Warm 70W and its 35 W ballast to the system.