All posts in the 'DIY projects' Category
You can build this FM receiver with just one MPF102 FET Transistor and a few of electronic components.This radio is sensitive enough to tune 20 stations across the FM band, some with volume high enough to drive a small PM speaker. The ability to tune 88.9 MHz and 89.1 MHz is testimony of its selectivity. The signal-to noise ratio rivals that of the better walkman type radios.In this exciting project, not only will you have a very unique one transistor FM receiver, but also be in-store for making home-made air-core coils. And even more than that, when you finish ‘your’ project, your journey has just started. With your now-working FM receiver, you can start experimenting with many wonderful things. [more]
This article shows you how to to build your own a simple ECG device & heart monitoring system. The signal from the body is being amplified, filtered to remove the noise, sampled by an Analog to Digital converter and then sent to your computer through RS232.This project use the famous instrumentation amplifiers device from Analog Devices(AD620).[more]
This is 75 Meter QRP SSB Transceiver.The transceiver switches the 4-element 1500 ohm xtal BPF ends between the inputs and outputs of the two SA602s to reverse the signal flow for R/T operation. Since no IF amplifier is used in the design, 20 dB of additional receiver gain is produced by the 2N2222 receiver RF amplifier, while automatic gain control (AGC) is produced by the peak DC swing of the LM386 output passed through a rectifier and filtered by a capacitor and fed to the gate of a BS170 enhancement mode FET acting as a variable resistor across the input of the LM386.[more]
This rain detector will give you a heads-up the instant it starts to rain, hopefully giving you time to close windows and bring in possessions. The battery-powered circuit draws virtually no current when the sensor is dry and the current consumption is low when the buzzer is activated so a couple of AA cells will last a long time. Alternately, a molded power supply with a simple voltage regulator to drop the voltage to 3 volts could be used. The circuit is basically a handy flasher circuit that operates well on only 3 volts using ordinary silicon transistors. When the circuit is triggered, the buzzer is pulsed about once per second.[more]
In this flashlight, each LED/resistor combination consumes 4.5volts at 30mA or about 135mWatts. The ballast resistor alone consumes 1.1volts at 30mA or about 33mWatts. Therefore, 25% of the power being drained from the batteries is lost in the resistor of each LED chain.[more]
