Switch-mode driven 1.5V bulb, Portable unit – 3V battery supply This device was designed on request; to control the light intensity of four filament lamps (i.e. a ring illuminator) powered by two AA or AAA batteries, for close-up pictures with a digital camera. Obviously it can be used in other ways, at anyone’s will.IC1 generates [...]
0-30 VDC STABILIZED POWER SUPPLY Schematic This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few milliamperes (2 mA) to the maximum output of three amperes [...]
A photo of the Revision-A preamp is shown below. You’ll see that there are two dual opamps, but the schematic only shows one. This is the main part of the Rev-A update – the output section now has gain (which is easily selected), and a better buffered low output impedance. The remainder of the circuit [...]
The circuit of AM transmitter is designed to transmit (amplitude modulated) DSB (double side band) signals. A modulated AM signal consists of a carrier and two symetrically spaced side bands. The two side bands have the same amplitude and carry the same information. In fact, the carrier itself coveys or carries no information. In a [...]
Micro Power AM Broadcast Transmitter In this circuit, a 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configuration. The oscillator frequency can be either fixed by a crystal or made adjustable (VFO) with a capacitor/resistor combination. A 100pF capacitor is [...]
The power amp board has remained unchanged since it was first published in 2002. It certainly isn’t broken, so there’s no reason to fix it. The photo below shows a fully assembled board (available as shown as M27). Using TIP35/36C transistors, the output stage is deliberately massive overkill. This ensures reliability under the most arduous [...]
dual regulator power supply circuit Voltage Regulators low power consumption IC 78W series used in our instrumentation is now so cheap they are an economical alternative to simple regulators NPN-stabilizers. In addition, they offer the benefits of better regulation, current limiting / short circuit protection to 1000 mA shunt and heat down if the electricity [...]
