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👉 Graphene is the thinnest compound known to man at one atom thick, the lightest material known, the strongest compound discovered, the best conductor of heat at room temperature and also the best conductor of electricity known.   👉 Other notable properties of graphene are its uniform absorption of light across the visible and near-infrared parts of the spectrum and its potential suitability for use in spin transport. 👉 Bearing this in mind, one might be surprised to know that carbon is the second most abundant mass within the human body and the fourth most abundant element in the universe (by mass), after hydrogen, helium and oxygen. 👉 This makes carbon the chemical basis for all known life on earth, making graphene potentially an eco-friendly, sustainable solution for an almost limitless number of applications. 👉 Since the discovery of graphene, applications within different scientific disciplines have exploded, with huge gains being made particularly in high-frequency electronics, bio, chemical and magnetic sensors, ultra-wide bandwidth photodetectors, and energy storage and generation.

Graphene - What Is It? 👉 Graphene is a single layer (monolayer) of carbon atoms, tightly bound in a hexagonal honeycomb lattice. 👉 It is an allotrope of carbon in the form of a plane of sp2-bonded atoms with a molecular bond length of 0.142 nanometres.  👉 Layers of graphene stacked on top of each other form graphite, with an interplanar spacing of 0.335 nanometres. 👉 The separate layers of graphene in graphite are held together by van der Waals forces, which can be overcome during exfoliation of graphene from graphite.

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Op-amp parameters 👉 Open-loop gain is the gain without positive or negative feedback. Ideally, the gain should be infinite, but typical real values range from about 20,000 to 200,000 ohms. 👉 Input impedance is the ratio of input voltage to input current. It is assumed to be infinite to prevent any current flowing from the source to amplifiers. 👉 The output impedance of the ideal operational amplifier is assumed to be zero. This impedance is in series with the load, thereby increasing the output available for the load. 👉 The bandwidth of an ideal operational amplifier is infinite and can amplify any frequency signal from DC to the highest AC frequencies. However, typical bandwidth is limited by the Gain-Bandwidth product. GB product is equal to the frequency where the amplifiers gain becomes unity. 👉 The ideal output of an amplifier is zero when the voltage difference between the inverting and the non-inverting inputs is zero. Real world amplifiers do exhibit a small output offset voltage.

10 Things You Can Do with Software-Defined Radio 1. Receive broadcast radio 2. Amateur radio 3. Radio astronomy 4. Track ships via AIS transmissions 5. Track aircraft via Mode S transmissions 6. Set up a DRM transmitter 7. Build a GSM network 8. Experiment with LTE 9. Learn how Global Navigation Satellite Systems work 10. Invent the wireless future!

Software-Defined Radio (SDR) 👉 Software-defined radio is a concept according to which RF communication is achieved by using software to perform signal-processing tasks that are typically performed by hardware.  👉 Software-defined radio (SDR) provides a reusable—and, to some extent, “future proof”—radio platform utilizing an RF to baseband transceiver and digital processor architecture. 👉 SDR can improve system performance, reduce system size, and minimize design risk and time to market by facilitating the use of available production-ready hardware and software reference radio designs. 👉 High end defense electronics, wired and wireless communications, and industrial and instrumentation applications have migrated to forms of SDR as their fundamental radio solution.

👉 One example of this — they stored the passcode to an electronic door lock on a patch of conductive cloth sewn to a shirt cuff and unlocked the door by waving the cuff before of an array of magnetometers. 👉 They used conventional sewing machines to embroider cloth with off-the-shelf conductive thread, whose magnetic poles start out in a random order. The researchers were able to physically align the poles in a positive or negative direction, which can correspond to the 1s and 0s in digital data, by rubbing a magnet against the fabric. 👉 The team was able to successfully interact with magnetized cloth with a smartphone it was in the user’s pocket.  👉 Further research is towards developing custom textiles that generate stronger magnetic fields and are capable of storing a higher density of information.

Data Storage and Interaction using Magnetized Fabric 👉 The UW computer researchers have created smart fabrics that may store information, from security codes to ID labels, while not having any installed hardware or sensors. 👉 The researchers at UW exploited previously unexplored magnetic properties of an off-the-shelf conductive thread. The information can be read using sensors in present smartphones, used to enable navigation. 👉 “This could be a fully electronic-free design, which implies you’ll iron the smart cloth or place it within the washer and drier.”  👉 “You can consider the material as a hard disk — you’re really doing this data storage on the clothes you are wearing.”

Unlock The Door To Future With Smart Fabric The introduction of conductive threads and wearable electronics together with the introduction of Lilypad Arduino microcontroller and Google’s Project Jacquard has revived the interest in the everyday article of clothing as a computing and interaction platform.

Let’s look at the last part of the schematic. 👉 A crystal oscillator is used to feed a 24MHz clock signal to the master clock input of the AD9833. 👉 FSYNC, SCLK, and SDATA are connected to the SPI bus of the microcontroller. 👉 Two decoupling capacitors are used near the VDD pin, one with a value of 0.1µF and another one with a value of 10µF. 👉 Another decoupling capacitor is needed for the 2.5V internal voltage regulator; this is near the pin CAP and has a value of 0.1µF. 👉 One more capacitor is needed between the COMP and VDD pins for decoupling the DAC bias voltage; it has a value of 10nF, as indicated by the datasheet.

AD9833 Board Let’s get to the main PCB.   👉 There is an ATMega328p-AU microcontroller, the same used on the Arduino Uno but in an SMD package. 👉 To program the MCU, a 6-pin connector called AVR-ISP is placed next to it. It has two pins for power (+5V and GND) and four other pins for communication: MISO, MOSI, CLK, and RESET. 👉 We will be using only one user input component, a rotary encoder with an integrated switch. This will be our control element to set the frequency, signal type, and other settings. The signals from the rotary encoder are routed to two interrupt pins on the microcontroller, PD2 and PD3 (D2 and D3 on the Uno), and the switch goes to an available pin that can act as an input;PD1 (D1 on the Uno).  👉 A plain green LED is hooked up to pin PD7 (D7 on the Uno), for debugging purposes or to display status. The display used is a simple LCD with an HD44780 controller, which has 16 lines and two columns and includes a backlight. 

Will see the main controller unit with little explanation tomorrow..

Power Supply section 👉 To smooth out the output, two large capacitors, each 1000µF rated at 35V has been used. 👉 In addition, to remove the ripple, two voltage regulators are used, the classic LM7812 and its sibling the LM7912, which is used for negative voltages. 

Hardware There are two main parts regarding the hardware aspect of this build: the power supply and the main PCB containing the function generator IC and the microcontroller.

The aim is to build a reliable function generator that can go up to 1MHz in frequency, up to 9V in amplitude, and that allows you to choose between sinusoidal, triangle, and clock (i.e., rectangular with 50% duty cycle) signals. 

👉 A DDS function generator is a digital arbitrary waveform generator, meaning it uses a digital-to-analog converter (DAC) to build a signal. 👉 It also has read only memory (ROM) where it stores amplitude values for specific waveforms at various time intervals based on a sampling frequency (Fs). 👉 Let's say we have a DDS signal generator with an 8-bit DAC and it outputs a sinusoidal signal at 100Hz with a sampling frequency of 800Hz. 👉 Because the Fs is eight times the frequency of the sine wave, an engineer or, more likely, a computer needs to extract from a real sine wave eight amplitude values from t = 0 to t = 2π. 👉 This amplitude interval is [0, 255] (1111 1111 in binary = 255), which corresponds to the interval [-1, 1] with a real sine wave. 👉 Below is a comparison between the real sine wave and the one outputted by our imaginary (and low-performance) DDS function generator.