Schematic & Wiring Diagram

This FanTemperature Controller circuit design technique to adopt a more ancient as its objective is to vary the fan speed in relation to temperature with a fraction of counting and avoid using special-purpose integrated circuits, often difficult to obtain.

R3-R1-R4 and P1 are connected as a Wheatstone bridge in which R3-R4 generates a fixed two-thirds of the supply of "reference" voltage, P1-R1 generates a temperature-sensitive "variable" power and Q1 is used as a balanced bridge detector.

P1 is adjusted so that the "reference" stress "variable" is equal to a temperature just below the critical value necessary, and under the base of Q1 and the condition of the issuer are located in the same tensions and Q1 cut. When the temperature rises above this R1 "balance" the value of P1-R1 voltage falls below the "reference" value, so that Q1 is polarized, pulse charging C1.

This is because the circuit is supplied by a 100 Hz half-wave voltage from the mains supply by means of the D3-D6 diode bridge without filter capacitors and fixed to 18V by Zener diode D1 and R9. Therefore the supply of 18 volt DC circuit is not true, but it has a trapezoidal shape instead. C1 provides a variable lag phase pulse train related to temperature and synchronized with the mains "zero voltage" point of each half cycle, resulting in minimal change RFI SCR. Q2 and Q3 form a firing device, which generates a short pulse suitable for driving the SCR.

This FM wireless microphone is easy to build and has a useful range of transmission (over 300 meters outdoors). Despite its small number of components and an operating voltage of 3V to easily penetrate over three floors of an apartment building. You can tune anywhere on the FM band (87-108MHz) and its transmissions can be picked up at any point of view of the FM receiver.

The coil (L1) should be approximately 3 mm in diameter, 5 turns 0.61 mm copper wire. You can vary the Tx frequency by simply adjusting the distance between the coils. The antenna should be a half wavelength or quarter-time (100 MHz, 150 cm or 75 cm).

Parts list:

• T1,T2,T3: 2N2222 transistor
• R1: 10k 5%
• R2: 33k lin.
• R3: 12k 5%
• R4: 5.6k 5%
• R5: 2.2k 5%
• R6,R8: 47k 5%
• R7: 470 ohms 5%
• R9: 180 ohms 5%
• C1,C2: 47nF
• C3: 1nF
• C4: 33pF
• C5: 5.6pF
• C6: 8.2pF
• C7: 10nf
• L1: 3mm in diameter with 5 turns 0.61 mm copper wire
• K1: SPDT toggle switch
• Other parts: 2 AA battery holder, Electret microphone, antenna wire

Here is a 7 segment counter circuit based on IC 74LS90 TTL.This can be used in conjunction with several circuits where a counter to show the progress adds a little more attractive. This circuit accepts any TTL compatible logic signal, and can be extended easily.

This a stereo tone control circuit built using LM1036 IC. This control circuit bass / treble tone level, volume and balance between the right channel and left channel (Input 1 and 2). You can use this circuit for stereo applications such as car radio, television and audio systems, MP3 player, DVD player, ipod and more. An additional control input allows loudness compensation to be made simply. The circuit must be working with a supply voltage of 9V to 15V DC.

Each tone response is defined by a single capacitor chosen to give the desired characteristic. By changing the values ​​of capacitors connected to the tone control unit, you can control bass and treble levels. pin 3 and pin 18 of IC are for acute and pin 6 to pin 15 for bass.