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Zener – one diode for many uses

Zener diodes are specially designed diodes (heavily doped) that have low reverse voltage breakdown. Due to this characteristic, Zener diodes are connected backward to regular operation. If Zener is forward biased, it acts as an ordinary diode with a forward voltage drop at 0.6V. Zener diode backward voltage breakdowns may range from 2.4V up to 100V. Honestly speaking, if you need like 1.2V, then probably you need to connect two forward-biased diodes in series for 0.6V+0.6V = 1.2V drop.

Rethinking AVR DDS3 signal generator project

These things happen all the time. When you start a new project but from the beginning start feeling that it’s not what you wanted. Usually, they end up collecting dust. I think there is nothing shameful because it is better to fail than do nothing. There are thousands of examples where people start new projects with enthusiasm, but they never reach the daylight. But without those efforts, we wouldn’t see other great projects and products. Not all of them are made from the first try. It’s been over a year since the announcement of the AVR DDS3 signal generator. As you have noticed, there is no progress so far on it. And I am going to give up on it for a couple of reasons. From the beginning, I didn’t feel comfortable with it.

Understanding 1-wire interface

1-wire devices are commonly used in many applications. You probably are familiar with the famous DS18B20 digital temperature sensor in the TO92 package. They can be powered and interfaced using the same single data line plus the ground return, of course. 1-wire originally was designed by Dallas Semiconductors Corp., which is also a major provider of 1-wire devices like temperature sensors, timers, real-time clocks, memory, and the well-known iButton. 1-wire interface is a bidirectional, half-duplex slow serial communication standard. It doesn’t use any clock signal. When talking of speed, the standard data rate is 15.4kbps. But there is possible to overdrive 1-wire communication to up to 125kbps.

Thermoelectric effect and modules

Thermoelectric devices are seen very often in various appliances: small refrigerators, semiconductor chip coolers, medical chillers. The thermoelectric effect works in both directions – it can generate temperature difference when current flows, or it can induce current when the temperature difference is applied. About thermoelectric effect It is known for more than 100 years. Several scientists discovered this effect in one or another way. Probably you’ve heard the Peltier effect. Jean Charles Athanase Peltier discovered that if you apply an electrical current to two materials’ junction, it gets cold or hot (depending on current direction).

Did I just increase DS1022CD bandwidth four times?

Probably you are already familiar with the famous DS1052E hack where guys were able to double and even triple bandwidth. It happens that on my table is DS1022CD scope with 25MHz analog bandwidth. And this hack doesn’t apply to my model. We all know that the same series Rigol oscilloscope models tend to have identical hardware, whether 25MHz, 50MHz or 100MHz analog bandwidth. Of course, the sampling rate (400MHz) stays the same. So it all lies in the software. I felt that someone would figure out how to do this with this pretty old oscilloscope. And here it is – a hackaday pointed to a piece of great news – a simple way of changing the model from DS1022CD to DS1102CD, which converts analog bandwidth from 25MHz to 100MHz. This is quite a step without spending a penny. Andreas Schuler (aka Krater) shared a simple method of doing this without using any serial interfaces and firmware updates. By following his step by step guide, you can do this as follows:

Diodes – how to choose one

Diodes are semiconductor devices commonly used for many purposes. In general, you can imagine a diode to be a valve that passes current in one direction and stops it from flowing back. The first thing that comes to mind – this might be a good choice for reverse voltage protection. In reality, things are a bit different. First of all, diodes aren’t perfect devices. They have a so-called forward voltage drop, which is about 0.7V for standard diodes. If inserted diode into the power supply, say 5V, the after protection you will get 4.3V where part of voltage is lost in the diode. If you want to go this way, choose the Schottky diode instead, which has a smaller forward voltage drop. A forward voltage drop occurs when the diode is forward biased what means current flow from anode to the cathode.

Testing LCD keypad Shield for Arduino

Recently I’ve got an Arduino LCD keypad shield. I haven’t decided yet where it will be used. But why not plug it into an Arduino board and see it working. The shield was initially introduced by DFRobot, who has some cool open-source stuff, including robotics-related. This LCD keypad shield is a cheap and convenient solution for adding 2×16 LCD and five push buttons (+1 reset) to Arduino design. LCD here is interfaced using 4-bit mode and occupies 4 (D4), 5 (D5), 6(D6), 7(D7), 8(RS), 9(E), and ten digital pins. Pin 10 is used to control the LCD backlight through the transistor key. All five buttons are connected to a single Analog pin 0 using a resistor-based voltage divider. This lets us keep other pins for general use. The shield is designed to work with 5V based boards.

Thoughts on interfacing piezo vibration sensor

piezo vibration sensor test with oscilloscope

Some time ago, I purchased a MiniSense 100 Vibration sensor. I probably had some project in mind, but it happened that it dived into drawer among other “to do” things. I thought it’s time to try a few things with it. Piezo sensor MiniSense 100 is very sensitive with a pretty good frequency response and is linear (±1%). As you can see, high sensitivity is achieved with a 0.3-gram inertial mass at the end of the film. As there is a hole in the mass, you probably can screw in an additional mass and increase sensitivity even further. Probably there is no need to explain where such a sensor would be helpful. These could be vibration/ motion sensors, impact sensors, and other areas where motion and acceleration are involved. Usually, sensitivity is 1V/g. Where g is standard gravity or standard acceleration due to free fall and is equal to 9.80665m/s2. As a mechanical device, it also has a resonant frequency of 75Hz. At this point, sensitivity reaches 5V/g.

Simple dummy load for basic testing

I bet you face many problems in the design process where you need to test the power supply or LED by providing/drawing constant current regardless of voltage change. Such a device is called a dummy load. You can find lots of DIY dummy load projects, and we won’t be talking about commercial ones right now. Nick found out that most DIY dummy loads tend to be complicated or unavailable. So without struggling, he decided to start his own simple and reliable load. He wanted it to be simple, self-powered, and indestructible. Indestructible means that it won’t burn in a voltage range up to 30V. With BTS141 FET this became possible as it has built-in over-current and over-voltage protection built-in. Controlling is done with a simple potentiometer attached to operational amplifier positive input. Negative input is connected to the current sense resistor. The project is OSHW which can be found on Github as re:load. [source]

Understanding and interfacing LDR – light dependent resistors

LDR (Light Dependent Resistor) is a simple, cheap electronic device. This is a resistor in which resistance varies depending on light intensity. You’ve probably seen typical LDR in some projects where light intensity must be considered. They can activate light switches and alarms, adjust display brightness, and more. Light-dependent resistors can be of different types. They vary in light-sensitive material used. Visible spectrum LDR is made using Cadmium Sulphide (CdS) or Cadmium Selenide (CdSe). This material is sensitive to the wavelength range from 400 – 850nm. For the near-infrared spectrum (1μm – 3μm), there are PbS or PbSe materials used. For the deeper infrared range (3μm – 1000μm), there are InSb and InAs.