Many audio mixer circuits have been published here. But I think, this one is the
simplest of them. This very simple audio mixer circuit uses only one transistor. The
base emitter junction of the transistor is biased by the diodes D1 and D2.The signals to
be mixed are directly coupled to the base of Q1.Each input lines are current limited by
using a 33K resistor. With the used component values the collector current is around 1mA.
Notes.
The circuit can be assembled on a Vero board.
The circuit can be powered from 15V DC.
Gain of the individual channels can be adjusted by adding a 10K POT in series to the lines.
Read more: http://www.circuitstoday.com/single-transistor-audio-mixer#ixzz1PMB3sU8r
24v Flasher circuit
The circuit shown here works from 24V DC and can flash two 24V bulbs alternatively. The circuit is nothing but an astable multivibrator operating at 1Hz and 50% duty cycle. The
lamp to be flashed is connected in place of the collector resistor (Rc) of a typical
design. 2N3055 transistors which are well known for their ruggedness are used here. They
can handle collector currents up to 10A. So a wide range of lamps (in terms of wattage)
can be connected to this circuit. Circuit Diagram. Notes. Assemble the circuit on a good
quality PCB. Use 24V DC for powering this circuit. Lamp L1 and L2 can be 24V/25W type.
It is advised to fit the transistors with heat sinks. Flashing rate can be modified by
adjusting the values of R1, R2, C1 and C2.
Read more: http://www.circuitstoday.com/category/lighting-circuits#ixzz1PMCTWF1Z
