Circuits with PIC micro's & analog IC's



RF Spectrum Analyzer using DVB-T USB dongle RTL2832U-R820T-DVB-T-SDR-DAB-FM

Great instruments to measure signals in the VHF, UHF and up to the GHz range. 

Probably the cheapest RF spectrum analyzer on the market - and it works!

The wide band, RF spectrum analyzer spans a frequency range of about 24 MHz up to 1766 MHz, which makes it ideal for use in a broad array of RF-related applications:

- Make relative measurements on antenna to find directivity
- Compare the gain of one antenna to another
- Make relative measurements on transmitted power
- See what signals are in the air
- Listen to radio communication
- EMI testing
- Etc
All info you need regarding installation the software here, click on the "software": Software
Now you can also install on windows10!
Here you can download wide scan spectrum analyzer software click here
Version for analyzer with HF-input click here

If you like the software, please support us by clicking  on some of the links with advertisement
Like to buy a spectrum analyzer for less than 30$? Click here
Like the software? Donation is welcome see here below! What about 1$?

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Design transistor amplifiers

Design common C, E or B amplifier with this great program. Click here for more info 

LED Current Regulator circuit

This Design Idea circuit regulates the current through one or more LEDs, making it almost independent of supply voltage. Its main advantage is a very small dropout voltage, which can be less than 100mV. Click here for more info

RS485 Design rules

100 IC, 200 transitor  and 50 555 Timer Circuits

DS1820 Temperature sensor to USB connector

It is a little board with an Atmel AVR (ATtiny45/85) microcontroller that can be used to connect Dallas/Maxim 1wire temperature sensors like the DS18B20 to the USB port of a PC. Some linux software that allows reading the temperature data is included. The whole USB implementation is done in software, using the great AVR-USB library from Objective Development.
Click here for more info

Computer Sound Card Provides Simple Internet-Based Appliance Remote Control

Using a standard PC-sound card and straightforward circuit, you can implement low-cost on/off control of home appliances via the Internet. Click here for more info

Serial Port Temperature Sensors - Serial Hardware Interface using DS18S20

Simple interface to connect the DS18S20  temperature sensors via a PC's serial port, click here for more info

Precision synchronous detection amplifier facilitates low voltage measurements°

Simple Electronic Load Controller (ELC) Circuit for Hydro Power Systems

Simple DIY ECG + Pulse Oximeter using LM324

The goal of this project is to collect heartbeat information on a computer with minimal cost and minimal complexity.  I accomplished this with fewer than a dozen components (all of which can be purchased at RadioShack). It serves both as a light-based heartbeat monitor (similar to a pulse oximeter, though it’s not designed to quantitatively measure blood oxygen saturation), and an electrocardiogram (ECG) to visualize electrical activity generated by heart while it contracts. Click here for more info.

Split supply from single voltage

As shown, the “trick” is to employ a negative regulator (e.g., the venerable 7905/LM320) to produce the positive output rail, taken from the positive side of the power source. Click here for more info

Cheap RF modules made easy connect RF to USB

These cheap RF modules usually come in a pair, with one transmitter and one receiver. A pair can be bought on ebay for as cheap as $4, and even as cheap as $2 a pair if you buy 10 pairs.

Much of the information on the internet from people's projects is sketchy and not very comprehensive. I test these modules out, and show how to get good reliable serial comms direct from USART -> USART, and I also show how to greatly speed up the data rate and reliability by using an alternative bit encoding system.

Earthquake Detector

Earthquakes are exciting, but also mysterious. Living in such a seismically state or country, there are earthquakes all the time that most people don't even feel! Build this simple detector, click here for more info

Picofarad meter using one chip

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

555-based class-D headphone driver makes great practice amp

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.

Three chip ECG simulator

Two 555s and a quad NAND-gate IC can simulate an electrocardiograph signal and a -y-wave radioisotope signal for applications in nuclear medicine. Click here for more info.

Gamma Radiation Detector

Build this simple gamma radiation detector, click here for more info.

Simple ambient light photometer

Novel Q-meter

This instrument determines the Q (quality factor) of a resonant circuit, crystal, or resonator by measuring its series resistance at the resonance frequency. Click here for more info

Simple capacitance meter bins parts

This Design Idea describes a simple two-chip CMOS circuit that can sort capacitors into 20 bins over a wide range (100pF to 1μF), using 10 LEDs to display the value range. Click here for more info.

Piezo Buffer in a  Mint-box

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.

Tiny pH-meter

The repeatability is around 0.01 pH and the accuracy, while depending on how well you will calibrate it, is around 0.02 pH. Click here for more info.

An Easy to Build Shielded Magnetic Loop Probe

Light Pollution Meter

You installed the circuit in a small plastic box, and mounted banana plugs on the bottom of the box spaced so that they would plug directly into the DMM. This combines the controller with the DMM, so there is one less thing to hold. The red LED pilot lamp was mounted so that it provides illumination of the DMM readout.  Click here for more info.

Measuring RF with a Voltmeter

Simple diode detectors may be constructed to enable ordinary VOMs to measure RF
voltages ranging from a few hundred millivolts to the breakdown voltage of the
diodes. Click here for more info

Bird tracker

With an old computer and 30 dollars worth of off-the-shelf components, you can gear up with cutting edge avian monitoring technology and help save the birds.
Click here for more info.

An Equivalent Series Resistance Meter

The ESR of an electrolytic capacitor is normally just a small fraction of an Ohm for a high capacitance, low voltage capacitor (such as a 1000µF, 16V cap), and can be as high as two or three Ohm for a low capacitance, high voltage cap (1uF, 450V). Click here for more info

4 - 20 mA current loop tester using LM358

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.

Low Pass SubWoofer filter.

With the manufacture that to you we propose you can make a active filter in order to you lead a loudspeaker of very low frequencies. With this you will place one bigger speaker between the HIFI speakers of you. Click here for more info.

Simple function generator using XR2206

Function Generator is an essential laboratory equipment. The module described here is based on high quality XR2206 IC. 1Hz - 2MHz XR2206 Function Generator is capable of producing high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Coarse frequency adjustment is accomplished using 4-DIP switch for the following four frequency ranges; (1) 1Hz-100Hz, (2) 100Hz-20KHz, (3) 20KHz-1MHz, (4) 150KHz-2MHz. Frequency output can be fine tuned using P1 and P2 potentiometers. Click here for more info.

Low cost impact sensor

 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


2 Watt AB audio amplifier using BD139 and BD140

Adjustabel regulated powersupply with LM317 and LM337

 LM555 timer in 6 to 12V DC/DC converter

ECG simulator using 555 timer

 Learn about ECG and build a simple simulator with 555 timer. Click here for more info

Current loop 4-20mA tester

Simple picoampermeter circuit

One opamp and few resistors make this fine picoampmeter. Click here for more info


Add on Capacitance meter using 74C14 gates

Measure capacitors from 1pF to 10uF in 6 ranges, use your multimeter as a display 

 Click here for more info

Capacitance meter using two 555 timers

5 measuring ranges, 100pF to 10uF

Click here for more info



Simple FM transmitter using CD4049 inverters

Buid this simple circuit. Click here for more info

Burglar  alarm using 555 timer

 Sleep save, Click here for more info

Audio level meter VU-meter using LM3915

Simple one IC Vu-meter. Click here for more info

Measure conductivity in water with 555 timer circuit

Program for Basicstamp, Click here for more info

Ultrasonic distance meter with uP

Reduce relay current

Very simple way to reduce relay current, click here for more info

High Voltage Adjustable Power supply using LM317HV

Simple tracking transmitter

Diode thermometer using multimeter as 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.

Simple  DC Fan Controller

ECG simulator

Simple Lock-in amplifier

Phase-shift generation and monitoring by a simple circuit

Simple LM358 Mic Preamplifier

 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.

Parts List:
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 

preamplifier with volume and tone control using TL072

A portable bio-amplifier for electric fish research: design and construction

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
wideband bio-amplifier.

Click here for more info


Piezo Preamplifier

Phantom powered piezo preamplifier

Click here for more info

Build a Hydrophone

 Build this hydrophone and start listening to mammal and other biosounds. See also  Pizeo preamplifier circuit on this page

Click here for more info


A Guide to Constructing Hydrophones and Hydrophone Arrays for Monitoring
Marine Mammal Vocalizations

MARINE MAMMAL VOCALIZATIONS, Click here for more info

Make your own hydrophone

Build a cheap hydrophone from a common microphone, step by step guide.

And start listening to undewater sounds, from whales, doplhines and other biosounds

Click here for more info Publish

CMoy is a very simple portable headphone amplifier

Build this simple high quality headphone amplifier, it is a CLASSIC!  Click here for more info

CMoy headphone amplifier  for Altoids box

Learn how to build CMoy headphone amplifier and fit it into Altoids box.  Click here for more info

METAL DETECTOR Circuit using555

This circuit detects metal and  magnets. When a magnet or metal  is brought close to the 10mH choke, the output frequency changes.  

Pulse metal detector using many 555 timers!

A Homebrew antenna impedance bridge

Build this simple but good DIP-meter. Click here for more info

Design Small loop antenna in excel


Here is a simple to use calculator for small loop antennas.  aa5tb_loop_v1.22a.xls



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

1 Hz to 100 kHz Function generator using XR2206

Bass Fuzz box

Simple but effective bass fuzz circuit with one transitor.

 Click here for more info



Piezo-disk Preamplifier

 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

100W Power Amplifier using TDA7294

 Build this simple 100W amplifier.

 Click here for more info

 Buy TDA7294 cheap here

Homebrew Outdoor Antenna 2.4 GHz wifi

Build your own WiFi 2.4GHz antenna? Why not? It is one of the fun parts in playing with WiFi technology.

 Click here for more info


Simple solar cell regulator

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.

 Click here for more info