Oyster conversion – #2 – 24W

Conversion of oyster luminaire to LED discussed a first conversion effort. This article describes a conversion of a oyster that used a T8 32W flourescent tube.

First step was to strip the magnetic ballast, power factor correction capacitor (if fitted), clips for the tube, labels that are misleading, and to check / provide the needed protective earth connection.

The LED plate used is that reviewed at LED plate analysis – 24W round plate with driver but with a new driver that delivers 260mA (though rated at 300mA).

Above is the 24W LED plate. The plate has 48 0.5W 5730 LEDs in a 24×2 configuration. If we allow that the 24W rating is total input power, driver loss is typically around 2W so the LEDs themselves will draw 22W. We expect that the voltage at 22W will be around 80-85V, and will require ~275mA current. The original LED driver supplied (180mA) is not capable of that current and was discarded. A nominally 300mA LED driver was procured for about $10 for five, and they fall short, delivering 260mA but that is good enough for this implementation. Continue reading Oyster conversion – #2 – 24W

LED plate analysis – 24W round plate with driver

This article reviews a 24W LED plate and driver commonly sold on eBay and Aliexpress for around $12.

Above is the 24W LED plate from the sellers pics. The plate has 48 0.5W 5730 LEDs in a 24×2 configuration. If we allow that the 24W rating is total input power, driver loss is typically around 2W so the LEDs themselves will draw 22W. We expect that the voltage at 22W will be around 80-85V, and will require ~275mA current. It is shown here with a 220mA LED driver or 80% of what is required for 22W. Continue reading LED plate analysis – 24W round plate with driver

(How) does this balun work? (Tonna / F9FT balun for Yagis)

This article proposes an explanation of how the balun used on some Tonna Yagis works.

It appears Tonna no longer manufactures these antennas, I do not know if this design is novel. I do not recall seeing them used by other manufacturers, they may be protected by patent.

Above is a pic of the balun structure on a 2m antenna.

Above, the manual shows that the black sleeve on the balun sleeve would be slid up over the coax connector, making a neat finish. There are slightly different versions for 70cm antennas. Continue reading (How) does this balun work? (Tonna / F9FT balun for Yagis)