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Solar SOX This is a pretty basic LPS driver I’ve had for years. Originally designed for running a 26w SOX direct from 12V DC as would be found in a solar PV installation off-grid. On a test, over a year or so, I felt the lamp didn’t last as long as I would have expected, so the ballast may under run the lamp slightly. The design includes a circuit protection fuse and a couple of diodes in reverse bias to prevent damage from wrong polarity connections. Oddly there are 3x 100R resistors in series for each of the transformer T1 feedback coils. I have simplified these to 300R in the diagram. It may have been there was a 24V version using the same p.c.b. layout. Keywords: Gear

Solar SOX

This is a pretty basic LPS driver I’ve had for years. Originally designed for running a 26w SOX direct from 12V DC as would be found in a solar PV installation off-grid. On a test, over a year or so, I felt the lamp didn’t last as long as I would have expected, so the ballast may under run the lamp slightly.
The design includes a circuit protection fuse and a couple of diodes in reverse bias to prevent damage from wrong polarity connections. Oddly there are 3x 100R resistors in series for each of the transformer T1 feedback coils. I have simplified these to 300R in the diagram. It may have been there was a 24V version using the same p.c.b. layout.
_IMG0192.JPG _IMG0193.JPG SOX12v.jpg 2020-06-28_Venture_HIT250W21HOR21DU214_5K.jpg _IMG0194.JPG
Lamp/Fixture Information
Manufacturer:Solatek
Model Reference:ST116 SOX inverter
File information
Filename:SOX12v.jpg
Album name:Tuopeek / Gear
Keywords:Gear
Filesize:539 KiB
Date added:03 Jul 2026
Dimensions:1966 x 2500 pixels
Displayed:75 times
DateTime Original:2026:07:03 10:31:13
Exposure Time:1/250 sec
FNumber:f/5.6
File Source:Digital Still Camera
Flash:No Flash
Focal length:55 mm
ISO:450
Model:NIKON D3400
Software:Adobe Photoshop Elements 2.0
White Balance:0
URL:https://trad-lighting.net/gallery/displayimage.php?pid=1369
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Comment 1 to 3 of 3
Page: 1

Max   [Fri 03 Jul 2026 at 15:33]
Those three resistors in series may be there so as to meet a minimum power dissipation that cannot be met with a single 1/4W resistor. At what frequency does this circuit operate?
Tuopeek   [Fri 03 Jul 2026 at 21:59]
The frequency measures at 30kHz with a close to triangular waveform. Hadn't thought of sharing the load in series arrangement but could be.
Max   [Sun 05 Jul 2026 at 15:37]
30 kHz is not unusual for such circuit, but a triangular waveform is not optimal for SOX lamps. Not sure if that's the cause of the reduced lamp life though.

Comment 1 to 3 of 3
Page: 1