Lamp Cooling for Entertainment Lighting

One of our clients, a manufacturer of Entertainment Lighting needed a mechanism to shut down the power to the lamp in case the cooling fan failed. It was vitally important because the expensive lamp would experience catastrophic failure if adequate cooling wasn’t provided during its operation. Our client’s chief lighting designer contemplated using a mechanical air vane switch to test if there was air flowing to the lamp; however, because of the high voltages used in these lamps, there was a real possibility that a metal vane or switch would produce arcing; which would be as catastrophic as lamp failure.

To his delight, we were able to provide a safer, more reliable, and more cost-effective solution.

We offered them our 120mm axial cooling fan which had more airflow (160 CFM)  and less noise ( 50 dB(A)) than the existing fan. More importantly, it featured a third wire that was used to trigger a relay to shut down the power to the lamp if the fan’s rotor stopped moving. There was little chance of this built-in approach causing arcing and it required only one additional component, an inexpensive quarter watt resistor, to implement it.

Having solved their problem, the designer presented us with other issues needing solutions. He was upgrading one of their lights that used a Chip on Board (COB) LED. The previous model was able to use just a heat sink for cooling; however, the new model operated at a higher power level and became unacceptably hot after extended use. The obvious solution was to use a fan in conjunction with the heat sink to increase cooling. However, since the new COB produced significantly more heat the fan would need to provide a large amount of airflow, as much as 50 CFM to be effective and it had to be small enough to fit into a very tight space (approx. 70 x 70 x40mm). Since this light would be used in theatrical settings its noise level would also need to be less than 40 dB(A). Our client was not able to find a fan with those attributes. Luckily, we had a solution. We suggested that they use two of our 70x15mm fans in series. This configuration provided over 55 CFM of airflow and kept the fan’s noise level below 38 dB(A). Finally, they asked us for a way to control the fans speed based on the temperature of the COB. Normally this type of functionality would be implemented by the customer using a Pulse Width Modulation (PWM) controller and sensor; however, in this case, our client faced a looming deadline and did not have time to design and test a new circuit. We were able to help them by providing a version of our fan that had the sensor (thermistor) and circuitry built in.  With our help, they were able to meet their production schedule without compromising their design goals.