TinyFPGA

Posted under DIY, Educational, Technology on January 24th, 2021 by

Back to FPGAs after a long time. Time to refresh the basics with this TinyFPGA board. Trying to get the toolchain up and running today. Maybe a small project soon. 😀

It’s an open source project with a Lattice FPGA iCE40LP8K-CM81 with 7,680 four-input look-up tables and 41 I/O pins. Has 8Mbit SPI Flash. Should be exciting to get started on this with an entirely open source toolchain.
Back when I was an undergraduate, all we had were expensive Xilinx boards and toolchains with no tutorials/guides anywhere. Had to reach out to Xilinx reps via phone to get some help to get it working(and beyond a point you needed to pay them). Oh, how this FPGA segment has exploded in the last few years. Has anyone played with these? Any small user project suggestions are welcome.

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Capacitive Dropper

Posted under Back to Basics, Educational, Teardown, Technology on December 27th, 2020 by

Probably one of the most common and cheap power supply circuits used to power low current applications directly from AC. You would have used these for sure at your homes in LED night lamps, fan regulators(Maybe a future post when I get time) or any of the cheap gadgets that plugin directly to your mains AC supply. The elegant part of the circuit is that it removes the need for a bulky transformer and can be built with very few components.

LED Bulb Teardown
LED Bulb Teardown
Circuit Schematic
LED Schematic with a capacitive dropper

The pictures are of LED night lamp which plugs into mains directly. It consists of a higher wattage in-rush current limiting resistor(R1, during turn ON of the device, so as to not let a large current through initially), and a capacitor(C1) in series with the mains(Instead of another resistor). The capacitor is designed to give impedance without losing power as heat at 50Hz. The resistor (R2) is a large wattage resistor which acts as a bleeder resistance to discharge the capacitor when the device is OFF(To avoid shocks if you touch it). The overall circuit has a poor Power factor but has low active power consumption. This is basically all because of the capacitive dropper circuit section.

The rest of the circuit is a four-diode bridge rectifier to convert to DC, and an electrolytic capacitor(C2) to smooth the DC at the output. This is really not needed if you really wanted to skimp on parts. LEDs will work fine on AC(you may see flickering though sometimes).

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