My Circuit

Small cooling fans are used in some equipment for cooling semiconductor devices. The circuit given here is of a simple automatic speed controller for a 12V, 0.6W (or 1.2W) cooling fan that increases the fan’s speed when temperature rises, and vice versa. Circuit and working Fig. 1 shows circuit diagram of the speed controller for a small cooling fan. Resistor R1 limits the initial current for the motor and lowers the speed of rotation, if needed. The temperature control is done with one or more NTC (negative temperature coefficient) thermistors connected in series with the electrical motor. The number of thermistors depends on their power dissipation. Usually you cannot find low-cost NTCs with enough power dissipation. Therefore four of them in parallel are used here. This way power dissipation and self-heating of the NTCs are reduced. It is better to use NTCs with tolerance of ±2%. The NTCLE100E3 are available with nominal values of 3.3-ohm to 470-kilo-ohm and have maximum power dissi...

Amplifier circuit is very suitable to be used or applied in a narrow space such as in cars and so forth. Voltage amplifier is needed starting from 9 Volts to 17 Volts maximum. This amplifier circuit uses IC MPC575C, andsimilarities NEC575 . Power output is relatively very small, only 2 Watts. Schematics Amplifier MPC575C

Many electronic projects require the use of a small audio amplifier. Be it a radio transceiver, a digital voice recorder, or an intercom, they all call for an audio amp that is small, cheap, and has enough power to provide adequate loudness to fill a room, without pretending to serve a disco! About one Watt RMS seems to be a convenient size, and this is also about the highest power that a simple amplifier fed from 12V can put into an 8 Ohm speaker. A very low saturation amplifier may go as high up as 2 Watt, but any higher power requires the use of a higher voltage power supply, lower speaker impedance, a bridge circuit, or a combination of those. During my many years building electronic things I have needed small audio amps many times, and have pretty much standardized on a few IC solutions, first and and foremost the LM386, which is small, cheap, and very easy to use. But it does not produce high quality audio... For many applications, the advantages weigh more than the distortion an...

DESCRIPTION Contains information about building a small radio transmitter, which has a PCB 1.75" x 2.5" (45mm x 68 mm) and has a range of about 30 yards or so. The documentation with the circuit says the freq range is 100-108 MHz, but I have found it to be more like 85-100 MHz. The circuit is (of course) only mono, and accepts an audio input from either a microphone or other source. The input impedance is 1Mohm. The input sensitivity is 5mV and the max input signal is 10mV. The transmitted signal can be picked up on a FM radio. The circuit can be used for short-range transmission, eg. for wireless microphones. The actual circuit comes from a 'Kit', available from Veleman electronics (USA distributor is Tapto Corp., PO Box 1339, CLAREMONT NH-03743-US. UK distributor is High-Q Electronics, 382 Edgware Road, London, W2 1EB). The kit number is K1771. It is a very good transmitter. I bought the kit, and made the circuit, which worked very well. I wanted two transmitters, ...