Measuring ripple voltage

Measuring ripple voltage

This webpage describes a highly efficient LED dimmer, or a dimmable LED flashlight, or a switching current source, or whatever you want to call it. Cheap, single-IC, uses commonly available parts, easy measuring ripple voltage build. Oh, and if you don’t know how to calculate R, this project is not for you. And of course the reference voltage generation, which is a story of its own.

Here is the complete circuit diagram. EDIT the original Xfig file with Xfig, also on Windows. 2, so if you publish anything based on these files, you must also publish your own source files. Two common criteria are price and availability, so I won’t repeat these everywhere.

I usually try to steer clear of SMD devices for projects like these. Again we’ll study the circuit from left to right. Repeat note: datasheets are listed below. 273-102, which is 100µH and thus useless.

The alternative of course is to only buy the ferrite core, and wind the coil yourself. 273-104 which is reported to need approx. Variable inductor, as found in FM radios. Okay, it has a ferrite core, but only a very small coil. Probably 50µH since two in series gives 100µH behaviour. As with Conrad, only available in some countries. Velleman 1000L3 choke, also iron-powder core but you have to look very carefully to see that.

Already useful, but three in series works much better. Also 1mH, but now a small-signal type. 100Ω resistance of the very thin wire. Quite useful if you have nothing else, but inefficient due to the resistance. Labeled “104” on the top, meaning the same as standard color code. Useless even with all windings in series.