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

Ease H-Bridge on MOSFET IRF7105 transistors

I think I don’t have to explain what is H-Bridge circuit. Well it is mainly used to drive DC motors that they could be run forward and backwards. Circuit often used in robotics. Usually there is a need to build small powerful and with good characteristics H-Bridge. One solution is to use IRF7105 p and n channel MOSFET pair coated in SO8 SMD case. As you can see MOSFET’s have a good characteristics for driving direct current like maximum current is 3.5A for N and 2.3A for P channel. Main thin here is a voltage drop on transistors which depends on Rds resistance. Controlling is very ease. You may use MCU or any manual switch to produce control levels on F1, F2, B1 and B2 wires: F1=0, F2=1, B1=0 and B2=1 – motor turns forward; F1=1, F2=0, B1=1 and B2=0 – motor turns backwards; F1=1, F2=0, B1=0 and B2=1 – motor stop. Source: www.ironfelix.ru

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Connect Nokia 3310 LCD to LPT port

I found this circuit really simple and interesting. It is really simple to drive Nokia 3310 graphical LCD by using simple LPT cable and some PC software. Firs of all connect graphical LCD to LPT port according to following circuit: 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 formula: 4.5V-0.7V-0.7V=3.1V. LCD pin numbering on Nokia 3310 LCD is as follows: Graphical display is controlled by PCD8544 controlled. Download Controller specifications here:PCD8544.pdf As you have noticed LPT port data pins are used for data transfer and powering of LCD: When hardware part is done it is time to draw some images on LCD. For this download control program (Pascal source is included in package too). Software is written to drive ports directly in DOS or win98 operating system. If you are using Win2000 or XP you might want to read: Program LPT and COM ports easily under windows NT-2000-XP. I have copied One of solutions here: Download PortTalk and unzip it in separate folder somewhere. Then copy allowio.exe directly to the directory where is you program which you want to run. Then create shortcut of…

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Simplest dor-bell based on AVR microcontroller

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

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How to measure wind direction

I found this wind direction measurement circuit simple and interesting. If you are doing some home automation project, this might be another sensor that can be included in you project. For Wind direction measurement you will need a circle from some material (you might even use CD disc.) Then stick an arrow on top. One end of arrow should have a fin. Other end of arrow sould have piece of magnet. Then put eight magnetic sensors around the circle in the magnets way. See drawing: I think working of this sensor is very obvious. Turning Arrow depending on wind direction turns ON magnetic switches. Circuit has 8 outputs corresponding to wind direction. These outputs can be connected to simple indication circuit, which can be in your room: Depending on switch turned on the led indicator shows where the wind blows. Of course this sensor can be easily adapted to any embedded system and display results on LCD or log changes in EEPROM memory for further analysis.

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I2C EPROM programmer

Sometimes you just need to program I2C EEPROM chips and don want to invest any bucks to it, then you should consider I2C EPROM programmer from https://www.lancos.com site originally designed by Claudio Lanconelli. This is very easy to build and use circuit but it supports 24C01, 24C02, 24C04, 24C08, 24C16 24C32, 24C64, 24C65, 24C128, 24C256, 24C512 I²C Bus EEPROM, auto detects 24XX EEPROM capacity For I2C EPROM programmer you need to download PonyProg programeer software from www.lancos.com .Choose “Easy I2CBus” from the Options – Setup menu and the parallel checkbox on WindowsNT/2000 you have to select “AVR ISP I/O”.

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