Video Amplifiers for the Mirror Screw
The light sources for mirror screws based on my work, consist of a dozen or more of high brightness LEDs, in colors or white, typically connected in parallel or series-parallel. Shown here are two amplifiers, capable of handling the full range of video frequencies for as many as 40 LEDs in various series/parallel hook-ups. The upper circuit is one developed by Peter Smith of Scotland, member of the NBTVA and has been well proven by the successful use by of many of the members in the NBTVA. In its original form, the circuit could also separate sync pulses from the video signals. In my method of operation however, sync is not required, so those associated components have been removed. Club members are able to purchase printed circuit boards for Peter Smith's amplifier at very low cost.
The amplifier in the lower portion of this schematic is one I developed that uses an operational amplifier capable of providing up to 3 amperes output along with a wide frequency range. I have actually used this amplifier successfully more than a dozen times and for as many as 36 LEDs. Both of these amplifiers require a 12 to 18 volt positive DC power supply. A single supply works on Peter Smith's circuit, whereas my amplifer requires a second negative 5 volt supply. The power supply that I use produces positve 15 volts at a relatively high current of .3 amperes peak. It also provides a negative 5 volts at .1 amperes. (PY)