With the price of high quality ruggedised mini video cameras and transmitting equipment falling rapidly, many people are now attaching FPV (first person view) cameras to their radio controlled planes, helicopters, and cars with very impressive results.

One common problem though is interference. When radio transmitting equipment is powered by the same power source as motors, servos etc, interference (noise) can add lines and other unwanted effects to the transmitted images.

The camera and transmitter need a very stable fixed voltage – e.g. 12.0 Volts – as anything else will damage the sensitive electronics. Therefore a voltage regulator is required. For their high efficiency and small dimensions a switching type regulator would appear to be the obvious choice, but this type of regulator generates yet more interference. Therefore a lower efficiency linear regulator must be used.

In the second half of this excellent article The Tricopter V2.6HV David Windestål from Sweden explains in detail how he built a very stable interference suppressing linear regulator around the LM2940 low dropout voltage regulator.

This is almost identical to our standard REUK 12V regulator but the components L1 (1mH coil) and C1 (low equivalent series resistance ESR also known as low impedance 22uF capacitor) have been added working together to make an LC filter (Wikipedia: electronic filter) to strip out any noise from the ESC (electronic speed controller) and everything else connected to the same battery pack.

With a 16.8V LiPo battery pack fitted in his DIY tricopter and a transmitter drawing 300mA, the regulator only has to get rid of 1.5W of heat, so only a small heatsink was required resulting in the finished regulator ended up small and light which transmits video which is “crystal clear [without] a hint of interference”.