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12V PWM Motor/Light Controller - The diagrams are for 12V
operation only and there are high side (common ground) and low side (common
+12V) versions. The low side version of the circuit uses an N Channel FET,
the high side version of the circuit uses a P Channel FET. N Channel devices
tend to handle more current than P Channel devices, they are also less
expensive. The high side version of the circuit is useful when one side of
the load has to be grounded....[G. Forrest Cook]
27 MHz FM Receiver - The FMR-201 is a crystal controlled single
channel receiver, comprising of receiving, decoding and open collector
output sections….(circuit added 08/07/06)
27 MHz Receiver - This is a simple RF receiver mainly for low-distance
digital radio receiver application. The analog output of this circuit should be
connected to a schmitt-trigger signal conditioning circuit with a proper value
capacitor (from collector of T3). L1 for 27Mhz is about 10 turns, 6 mm diameter coil
body. …....
27MHz/ 49 MHz Walkie Talkie - Lots of people are requesting walkie-talkie
and RF remote control schematics, so here is some. Building these circuits needs
special equipment and expertise in RF circuits. If you are going to experiment with
these circuits, please....[Peter Jakab, Electrical Engineer, Engineer of Informatics]
4 MHz Amplitude Modulated RF Source - A while back I needed an amplitude
modulated signal source at 4 MHz. This circuit was literally thrown together
with parts laying on the bench. I built it dead bug style on a piece of copper clad
board. It should work with little or no modification, other thano get it to oscillate,
and at higher frequencies, you might have to reduce the capacitor values a little.
Just be....(schematic / circuit added 6/07)
4-Transistor Transmitter (Paul C. Sherby) - This circuit provides an FM
modulated signal with an output power of around 500mW. The input microphone
pre-amp is built around a couple of 2N3904 transistors (Q1/Q2), and audio gain is
limited by the 5k preset trim potentiometer. The oscillator is a Colpitts stage,
frequency of oscillation governed by the tank circuit made from two 5pF ceramic
capacitors and the L2 inductor....[Tony van Roon's circuit]
60 Hz modulator records process variables - 02/16/98 EDN-Design Ideas....The
circuit in Figure 1 allows you to record process variables (4 to 20 mA,0 to 10V dc]on
a three-phase power monitor designed to record only ac waveforms. Many of se recorders
have a seventh channel, normally used for recording neutral current, which you can use
as a process-variable input. The circuit operates....[Design Idea by Warren Jochem,
Research Triangle Institute, Research Triangle Park, NC]
