I frequently have a need for a variable supply when testing homebrew circuits, and the triple power supply is just what I need on the bench. With an amp out at 13.5 V, it will easily handle that QRP full-gallon. It even has 6 and 12 V AC available, for those rare filament-power circuits.
Posted on Saturday, August 22, 2009 • Category: Power Supplies
As is commonly the case, this supply was born of necessity. There is absolutely nothing special about the circuit, except that as shown, it is quite capable of up to 20 Amps intermittently or 10A continuous. Simply use a bigger transformer, bridge rectifier and more capacitors and output transistors
to get more current. The basic circuit should be good for up to 100A or so, using a 5A TO3 regulator IC, but it can obviously be increased further (if you really do need a 500A supply!).
Posted on Saturday, August 22, 2009 • Category: Test and Measurement
This new 50MHz Frequency Meter is autoranging and displays the frequency in either Hz, kHz or MHz. This makes the unit easy to read, as it automatically selects the correct range for any frequency between 0.1Hz and 50MHz and inserts the decimal point in the correct place for each reading.
The design is easy to build too, since it uses a programmed PIC microcontroller to do all the clever stuff. Apart from that, there's an LCD readout, a couple of low-cost ICs, two transistors, a 3-terminal regulator and a few sundry bits and pieces to complete the design.
Note that although we have specified this Frequency Meter at 50MHz maximum, most units will be capable of measuring frequencies somewhat higher than this. In fact, our proto-type meter was capable of making frequency measurements to above 64MHz.
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