Towards re-illuminating my kitchen workspace…
Currently there are still CF tubes mounted below the cupboards in my kitchen. The switches are beginning to fail one by one. No replacements to be found anywhere. No offense intended, but they’re of an ultra-cheap Chinese kind (even with fake CE signs). The problem is that the housing is way too small to fit any kind of switch that can be considered as “safe” for 220V. I’m planning to replace these with 12V LED modules. This is an idea on how to drive them with an ATtiny2313 + MBI5168 constant current driver (quite cheap).
To compensate for the internal voltage drop in the driver and give it some leeway to regulate, at least 13.5V are required for this LED module. The maximum permanent permissible current is 240mA and it takes about 12.6V to make that happen, but this is going to change if it warms up or cools down. I think I’ll get a 15V switching power supply, quite similar to laptop power supplies. The cheapest powerful one I could find costs about 20€ and can supply 3.8A at 15V and even supports more than one output voltage. A much smaller 15V 1A one can be had for about 22€. The small one would be good enough for 4 of these LED boards.
Now all I need to do is find a good looking and proper means of mounting these modules + a small board with the microcontroller and driver chip. I’d prefer some sort of aluminium rail that gives it a professional look and feel. And I need to design the driver board of course ;-)
At a supply voltage of 15V, the power lost in the driver chip is quite low. I couldn’t feel any significant temperature rise above ambient. Good. The LED boards got hand-warm, so they’d benefit from using aluminium rails for mounting the hole works.
The code can be found here.
And this is what the waveforms driving the driver chip look like. Top trace: data line, bottom trace: clock line. The latch is not shown, as this old scope only has 2 channels.