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Very simple IR detector that controls relay

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

Quality music sound in the car

Most of the driver’s car is more than a vehicle. Sometimes people spend hours in the car every day and listens to the news radio broadcast and listens to music. Having good quality music sound in the car requires more than good speakers and power amps, but some smart solutions are also needed to make it sound better. There are plenty of publications on how to DIY a good car sound system at home in the current time. Even the best power amplifier does not guarantee that car music will sound like Hi-Fi class. The main problem is the hard installation of the audio-system inside the vehicle. In many cases, speakers are installed where ever they fit in the car. But there is also no clear answer where it is the best place to install speakers and how. The most common mistake is to place powerful high-quality speakers in the rear shelf while the speaker’s front position is installed or not at all. Such an audio system installation gives a feeling like he is sitting back to the scene.

How PCB files are transfered to circuit boards

When you are done with a clean period of task – designing, drawing a circuit, and tracing a PCB, you need to transfer a design to a real board. Here starts what I call a messy part of the design. When designing at home, there are several options – to use prototyping boards or make PCB by yourself. You have to transfer the PCB image to a board with a copper layer in the second option. There are several methods of doing this: direct transfer with glossy paper where the image is printed with a laser printer or more advanced ultraviolet exposure. This way, the PCB image is printed on paper or film directly from the program window without keeping in mind PCB file formats. A different situation is when fabricating professional PCB’s. Each company that fabricates PCB boards always announce what type of file formats they support. So if you are going to order a PCB, better check with them to save your time. The most common and standard format is the so-called Gerber file format. Almost all layout tools can produce Gerber files. If you want to preview your generated Gerber files, there is a nice free Gerber…

PCB routing considerations

One of the hardest tasks when fabricating PCBs is a Printed Circuit Board(PCB) routing. There are no unified rules on how properly board should be routed, and it would be impossible to write them as the situation on each board is different. One of the general rules is that the shortest routes are the best because longer routes tend to generate more noises or pick them up from different sources. Every conducting material acts as an antenna, no exception with PCB routes. No secret that each route acts as a small transmitting and receiving antenna. So one thing is to keep in mind when routing PCB is to route short as possible. Another concerning area is a cross-talk or cross-coupling between routes. This effect appears when two traces run along with each other, and energy from one trace route couples to another. This effect is obvious in high frequency digital and analog circuits. This effect can make the device dis-functional because only of the cross-coupling effect. These defects are hard to determine as the electrical circuit board is correct. If this effect is noticed â€“ the only solution is to cut traces off and run separate wires instead. It is…

Microcontroller Simulators and emulators

Sometimes you haven’t the ability to flash a microcontroller to test program functionality in the development phase. For this, there may be many reasons, like you don’t have a prototype ready or you need to test parts of code, and so on. For this, there are software simulators used that simulates microcontroller work without microcontroller itself. Simulators usually don’t have a connection to the real-world all operations are simulated in software. A microcontroller simulator is a program model that imitates its work. Modern simulators now simulate arithmetic operations and I/O operations and even peripherals like timers, ADC, USART, I2C, and so on. In many cases, it is possible to prepare the whole project using the simulator and then burn compiled code to a real microcontroller. Simulators usually allow: debugging at source code level; follow operation time in slow motion but with real-world values; connect stimulus signals like they are real-world signals. The simulator can be expressed as several blocks interconnected with each other:

Protect you car from rusting using cathode protection

Car owners know that small scratches may cause 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 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 disassembling some pieces of a car. Such an operation requires a decent amount of time and constant control. 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.

How does tri-state buffers work

Those who work with microcontrollers probably know about data buses. Only one device(memory, peripherals) connected to the bus can work at one moment. Only one unit can directly connect to the bus beside the CPU, which usually is a host. So decoding circuit determines the desired unit and connects it to the bus. Other devices are effectively disconnected so that they wouldn’t have any effect on bus operations. Tri-state buffers carry them out. Tristate buffers allow isolating circuits from the data bus. This means that circuit is switched to a high impedance state. Usually, we know dual state circuits with two logical levels, “0” and “1”. But there is also widely used tristate logic, where it can switch I/O to a high impedance state. Tristate logic can simply be made by two transistors: Using such a circuit we can have the following output results according to input variations: Q1 Q2 Output OFF OFF High Impedance OFF ON 0V ON OFF +5V Simply speaking when the output pin is in a high impedance state it is physically disconnected from the circuit.

Using Gray code for rotary encoders

Gray code is well known and widely used in angular movement systems where angular positions have to be known. Gray code encoder can be constructed pretty easily by masked wheel where tracks are read with photocells. Did you look at the picture and thought for yourself that gray code is the same binary code. Well, no… the main problem with binary systems was using binary code in tracks; there are many positions where several tracks change state simultaneously. This may result in an error. Actually, in gray code, only one track can change at the same time during rotation. So then, if an error occurs, the resulting error will be only one bit. Gray code is easy to convert to binary this task can be done by any microcontroller using a lookup table:

Nonlinearity and span of transducers

When the developer selects a transducer for their projects, they have to look through various parameters and then select the part that best fits the design needs. This time let’s look at some transducer characteristics that can be found in specifications. Transducer Range First of all, let’s clear out what is a range of a transducer. The range is understood as maximum and minimum input and output signal. For instance, we can take a simple thermal sensor which input range can be from -50 to 120ºC and output range of 0 to 5V. The range can be understood as measured signal range and working environment parameters like working temperature range, power supply voltage range, etc. Full-scale deflection – Span Span is the maximum variation in the input or output. Span can variate due to an error that is mostly linear and can be adjusted. Span error is measured in percents, which shows how much the output value is different from the correct value. Another linear error close to span error is zero offset. This error occurs because of calibration errors or other changes like aging or environmental conditions change. Zero offset error is a constant overall range. It can be…

X-10 interface for home automation projects

Simply speaking X10 protocol allows transmitting data over power lines. X10 uses a PLC(Power Line Carrier) technology. How does this work? The specification says that each time a 60Hz AC signal crosses the zero line,, a 120kHz burst is is transmitted with a duration of 1ms. One crossing burst forms one information bit. Simply speaking if we needs to form â€œ1â€ you need to burst at the first crossing but not at second and for â€œ0â€ is reversed pattern – you need to burst at the second cross but none on first.