The inverters in a CMOS CD4069 can be used for both analog as well as digital applications. This Design Idea illustrates this by using all six inverters in a 4069 package to make a closed loop, duty-cycle-based capacitance meter with a full scale deflection below one picofarad. Click here for more info
The popular 555 timer can be used as a PWM/Class-D amplifier for musical instruments or other applications. It can use a wide supply range of 4.5-16V and produce 200mA of drive. The audio is fed to the 555’s CV (control-voltage) pin.
This Design Idea presents two simple, cheap drivers for headphones and audio lines. The drivers were designed for electric guitars and violins, but have many more applications. For such simple applications, noise and THD are not a primary concern and they were not measured. Click here for more info.
Piezo pickups are definitely useful, but they have one really serious problem: Impedance matching. Having an impedance mismatch is like having your car in the wrong gear, and piezos really need to see a very high input impedance to sound good. Click here for more info.
This is the circuit of the tester, and it is not intended as any kind of real 4-20mA interface. However, it can be used to test receiver units and their associated analogue to digital converters, software, etc. That is exactly what it was designed for, and it works very well indeed.
Although piezoelectric elements have been used for shock and vibration detection for some time, this circuit provides a low-cost alternative for solid-state general-purpose impact sensing. The circuit uses a standard piezoelectric device (PZT) to detect a mechanical shock or vibration in its vicinity Click here for more info
Measure capacitors from 1pF to 10uF in 6 ranges, use your multimeter as a display
This digital thermometer circuit diagram uses a common 1N4148 diode as the temperature sensor. The temperature coefficient of the diode, -2 mV / 0C is exploited for this application to create an accurate electronic thermometer.
To display the measured temperature, a digital multimeter is used and so we can measure temperature values from -9.990C up to +99.90C.
Calibration of the digital thermometer
To set the minimum level (00C), place the diode in a glass of water filled with crushed ice (check the temperature first with a normal thermometer) wait until the thermometer shows zero degrees centigrade. Set P1 so that the digital voltmeter will display 000 when the diode senses zero degree centigade.
To set the maximum level (1000C), place the diode sensor into a boiling water and adjust P2 so that the digital meter exactly displays 99.9.
This is a simple LM358 microphone preamplifier schematic diagram. The pre-amp circuit is very easy to build and.. it's a low cost project... The variable resistor R5 is to adjust the LM358 op-amp gain. The LM358 has dual op-amp circuit modules, you may use a single LM358 to build two channels mic preamplifier.
R1, R3, R4 = 10K R2 = 1K R5 = 100K-1M Potentiometer
C1 = 0.1uF C2 = 4.7uF/16V IC1 = LM358 dual op-amp single Mic = Electret Microphone
The weak electric organ discharges (EODs) of gymnotiform knife fishes can be readily amplified with a wideband amplifier
connected to submerged electrodes. The output from such an amplifier can then be monitored with audio speakers or digitized
for subsequent analysis. Commercially available devices are expensive and usually require mains electrical power. Here we
provide design notes and instructions for the construction and calibration of a cheap, portable, battery-powered, AC-coupled
Build this hydrophone and start listening to mammal and other biosounds. See also Pizeo preamplifier circuit on this page
This circuit detects metal and magnets. When a magnet or metal is brought close to the 10mH choke, the output frequency changes.
The sweep generator is an indispensable piece of measuring equipment for testing the frequency response of AF amplifiers, filters, and loudspeaker systems. At the heart of this design is the wellknown Type XR2206 function generator chip from EXAR. Click here for more info
This simple high impedance amplifier is suited to boost the output signal of a piezo-disk making it to a microphone, geophone, hydrophone or use it as accelerometer sensor. Click here for more info
Build your own WiFi 2.4GHz antenna? Why not? It is one of the fun parts in playing with WiFi technology.
It is advisable to install the regulator near the battery, it is necessary that there are minimal drop in tension on the cable between the regulator and the battery, so that it can correctly measure the battery voltage and act accordingly.