Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

DIY simple band-pass filter

This filter was designed to filter the 1kHz frequency of the telemetric signal from environmental noise. The filter itself is straightforwardly built with acceptable electronic parts worldwide. This filter can be used in any circuit because of its simplicity. The circuit contains a minimal amount of parts, including one general-purpose NPN transistor with coefficient 50…70 and more. Such filter blocks may be connected in series directly one to another(second IN first OUT). This way, filter gain may increase up to 1,2…2.

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DIY USB to RS232 adapter

Sometimes you need to connect some device to a COM port, but the computer doesn’t have one, especially a laptop. There are two ways – go and buy a USB to COM adapter or build one. So if you decided to build a USB to COM(RS232) adapter, there is one solution. This adapter is straightforward to build as there is a single-chip USB to UART bridge (CP2102). This chip from Silicon Labs supports USB2.0 full speed. Internal Resistors are required for the USB interface, integrated clock, internal 1024 -byte EEPROM for Vendor ID, Product ID serial number, power descriptor, and other information. SP2102 USART part support almost all standard features of RS232 communication including handshaking, Databits (5, 6, 7 and 8); 1 or 2 stop bits; odd, even, mark, space, and no parities; baud rate from 300bps to 1Mbits.

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Controlling graphical 128×64 LCD based on KS0108

HQM1286404 is a pretty old graphical LCD module, but it is still popular. KS0108 driver controls this LCD. LCD backlight color is yellow-green. I think this is an excellent choice for many projects where graphical information is needed for several reasons – you can find libraries around the internet to start working in just a few minutes. Several tools can also be used to generate character arrays and graphics. The hardest thing for me was to find the correct wiring as the datasheet I have was for the next PCB revision (HQM1286405) as mine are HQM1286404, so don’t be mistaken as I did. Here is the correct pin-out of LCD:

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Very simple IR detector that controls relay

The circuit of this Infrared(IR) detector circuit is a simple light relay which triggers when infrared light is applied to phototransistor Q1. This device can be used in control systems. When infrared light is OFF, Q1 transistor and relay K1 are normally closed.   When IR diode is transmitting IR light phototransistor Q1 opens and thus relay K1 triggers because current starts flowing through Q2 transistor. Construction can easily be modified when circuit output is connected to microcontroller or other device. Sensitivity so the distance can be controlled by changing IR diode D1, using more sensitive phototransistor Q1 and adjusting R2 resistor. Original source: https://cxem.net  

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Protect you car from rusting using cathode protection

Car owners know, that small scratch may cause a rusting which will expand even under painted areas. Fighting rusting is a pretty hard task. There are lots of methods that car keepers are using to prevent from rusting. Many are using anti-rust coating, but it has shortcomings – success depends on how good it has been done. The rusted area needs to be cleaned with care and sometimes requires to disassemble some pieces of a car. Such an operation requires a decent amount of time and constant control. Besides, the car is always in a stressed environment: cold, salt, water, vibrations, stones, and other harsh conditions. There is still a chance of damaging surface coating. For constant prevention from further rusting, there is an electronic device used which requires only one installation. Cathode rusting protection isn’t a new thing. It has been used for protecting various objects on top and underground. Ships are actively using cathode protection, which is aggressive in salty waters. The idea is to use a special protector who melts in salty water instead of the protected metal. Water piping companies who use metal pipes first of all paints pipes with protection coating then wrap them in…

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DIY 4x22W car audio amplifier based on TDA7384

I decided to make a pretty simple but powerful enough audio amplifier. For this, I’ve chosen quad-bridge car audio amplifier IC – TDA7384, which has four input and four output channels with a power capability of 4x35W. If connected to a car battery where the operating voltage is about 13.2V, then each channel can give 22W what is more than enough for me. This amplifier I probably will use to test audio processor TDA7313, which is still in the development phase. I didn’t find much information about this chip on the internet, so I decided to build it and try it independently.

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Alternatives of MAX232 in low budget projects

Sometimes when you work on low-budget projects or don’t want to go shopping for max232 or similar IC, you can save your time and money by using other TTL to RS232 converter. We usually used to use a MAX232 chip like this: Max232 IC is a specialized circuit that makes standard voltages as required by RS232 standards. This IC provides the best noise rejection and very reliable against discharges and short circuits. If your project is more advanced and has to reliable you must use specialized RS232 to TTL converter IC’s. As I said Specialized is more expensive than other solutions.

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Connect Nokia 3310 LCD to LPT port

I found this circuit really simple and interesting. It is effortless to drive Nokia 3310 graphical LCD using a simple LPT cable and some PC software. First of all, connect graphical LCD to LPT port according to the following circuit: The graphical display needs about 3.3V of supply voltage, while LPT gives about 4.5 -5V. This is why diodes are used to reduce voltage by the formula:

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Simplest dor-bell based on AVR microcontroller

This circuit is so simple, and generated sound may look ugly, but on the other hand, this is a good starting point for newbies with AVR projects. This circuit is made of one IC AT90S2313 (may be substituted by Attiny2313). The circuit is low power and reliable as it consists of very few parts (if SMD chip used, then it can be placed inside a postcard): A microcontroller can be powered by using from 2.7 to 6 V power supply. If the AT90S2313 microcontroller is used, then you need to connect a crystal resonator. If ATtiny2313 is used, you can use an internal RC clock source and reduce the number of parts needed. Transistors can be any general-purpose transistors. If the sounder requires less than 20mA of current, you may connect it directly to the port pin. After reset, the circuit starts the program and plays a melody one time. After that, it goes to power-down mode. Crystal frequencies may be chosen from 32768 to 10MHz. Firmware is written for 10MHz. If you use a different clock source, then reduce SoundTab coefficients in the source code and rebuild it. Download Source code

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