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This simple circuit can be used to program the PIC16F84 and similar "flash memory" type parts. It uses a cheap 555 timer IC to generate the programming voltage from a +5V rail, allowing the circuit to be powered from a computer’s USB port. The 555 timer (IC1) is configured as a free-running oscillator, with a frequency of about 6.5kHz. The output of the timer drives four 100nF capacitors and 1N4148 diodes wir-ed in a Cockroft-Walton voltage multiplier configuration. USB-Powered PIC Programmer Circuit diagram: USB-Powered PIC Programmer Circuit Diagram The output of the multiplier is switched through to the MCLR/Vpp pin of the PIC during programming via a 4N28 optocoupler. Diodes ZD1 and D5 between the MCLR/Vpp pin and ground clamp the output of the multiplier to about 13.6V, ensuring that the maximum input voltage (Vihh) of the PIC is not exceeded. A 100kΩ resistor pulls the pin down to a valid logic low level (Vil) when the optocoupler is not conducting. The circuit is compa...

Modern PCs rarely have a serial or parallel  port any more, to the great regret of any-one who experiments with microcontrollers every now and then. In the old days  it was very simple to use the parallel port  of a standard PC and program just about  any type of AVR microcontroller with it.  When you want to do that now, you’re first  obliged to buy a programmer that communicates with the PC via USB, which immediately raises the threshold of getting started  with these microcontrollers. The circuit presented here offers a solution to this. Simple USB AVR-ISP Compatible Programmer Circuit Diagram : As you can see from the schematic, this is  a very simple circuit, built around a cheap,  standard AVR microcontroller plus a handful of passive components. You may have  already observed that this microcontroller does not have a USB interface and the  circuit does not use a USB to serial converter either. The strength of this circuit is  found in the firmware. The USB interface  has bee...

Most of the time, in a cartoon or in a movie, whenever the character experiences an “Eureka!” moment, a light bulb would just appear on the head. Well, just in case your boss thinks that you are the dimmest bulb in the office, prove him or her wrong by picking up the £10.99 Bright Idea USB Lightbulb.     Yes sir, I think you do know just which direction I am heading with this – it is the perfect desk accessory which lets the world around you know just how many brilliant thoughts you would have come up with throughout the eight hours at the desk! Located right at the end of a sturdy and flexible arm, lies the Bright Idea USB Lightbulb which happens to be a fuss-free lamp, sans switches, where it will also not come with a lampshade nor any legs. No sir, it is up to that creative mind of yours to concentrate and deliberate over grand ideas. ou will find it emit a soft and soothing blue light as long as it remains plugged into any USB port, where it will shine some reassuring illu...

Power Stacker is a portable, modular, USB rechargeable lithium-ion battery pack. Stack them together for power hungry projects or separate them for smaller projects with this modular system. The Gerber, BOM, and .STL files are available below. Power Stacker does what other USB rechargeable batteries have failed to do, and that’s the ability to combine together for increased battery capacity or separate in to many small batteries for smaller projects. You can literally use the same Power Stacker batteries for many years across many applications! [ ]

This design is inspired by the Minty Boost but it fixes some of the issues that I had with it. The Minty Boost is limited to 600mA due to the LT1302 chip. The Super Boost uses the LM2700 which can push up to 3.6A. This will enable i-devices to draw up to there maximum of 1A which will enable a faster recharge. [ ]

This is a 5V to 12V DC-DC step-up (boost) converter circuitry that is especially ideal for the USB powered applications. First of all a USB port has two current supply modes. Before detecting the connected device, it supplies maximum 100mA to the load. After recognizing the device, it increases the output current up to 500mA. In this circuit, controller (LT1618) also provides two input current modes. 100mA and 500mA input modes can be selected by the user. Output currents are limited due to the increased potential difference at the output. When the demand of the load increases, output voltage will start to decrease. For example, if the circuit operates in the 100 mA input mode, when the load is 35 mA, the output voltage will be kept at 12V. But if the load increases to 50 mA,output voltage will reduce to 8V to maintain the constant 100 mA input current.

In this article I will discuss my own experiences about designing a USB sound card, which is the USBDAC. DAC is an acronym for Digital-to-Analog Converter because in a sound card, digital data representing the sound is converted into analog voltage that moves the speaker cone. My device is loosely based on the PCM2706 reference design. I will not go through the tecnical details but instead concentrate on my own experiences in the design of the device. This is to keep people not familiar with electronics, as well as newcomers to electronics design, interested. You will see that one working product is the result of many failed prototypes. [ ]

This circuit has been developed to add a USB charging port to a bicycle for charging a mobile phone. The input supply for the circuit is produced by a dynamo (6V, 3W dynamo) in the bicycle. The circuit uses few components, which help in keeping the size, weight and cost of the unit down. Circuit and working The circuit is based on LM2596-5.0 (IC1). Its configuration, with minor changes, generally reflects the recommendations included in Texas Instruments’ datasheet of LM2596-5.0. The IC provides all active functions for a step-down (buck) switching regulator, capable of driving a 3A load with excellent line and load regulation. The output of the regulator is 5V. It operates at a switching frequency of 150kHz, thus allowing smaller-sized filter components than what would be needed with traditional lower-frequency switching regulators. Fig. 1 shows the circuit diagram of the bicycle USB charger. Fig. 1: Circuit diagram of the bicycle USB charger    The alternating voltage genera...

Description  This simple device allows two computers to share a single USB printer or some other USB device, such as an external flash drive, memory card reader or scanner. A rotary switch selects the PC that you wish to use with the USB device, while two LEDs indicate the selected PC. The most common way to share a USB printer between two PCs is to use one machine as a print server. However, that’s not always convenient because it means that the server PC must always be on if you want to print something.  Real Circuit Image That can be a real nuisance if you just want to quickly fire up the other machine and print something out. It also means that the two PCs must be networked together, either via a hub/router or directly via an ethernet crossover cable. Another way is to use a dedicated USB print server. However, as before, this must be connected to an ethernet network, along with the PCs. Such devices also need their own power supply, generally cost well over $100 and are o...

When turning a computer on and off, various peripherals (such as printers, screen, scanner, etc.) often have to be turned on and off as well. By using the 5-V supply voltage from the USB interface on the PC, all these peripherals can easily be switched on and off at the same time as the PC. This principle can also be used with other appliances that have a USB interface (such as modern TVs and radios). USB Standby Killer Circuit Diagram : This so-called ‘USB-standby-killer’ can be realised with just 5 components. The USB output voltage provides for the activation of the triac-opto driver (MOC3043) which has zero-crossing detection. This, in turn, drives the TRIAC, type BT126. The circuit shown is used by the author for switching loads with a total power of about 150 W and is protected with a 1-A fuse. The circuit can easily handle much larger loads however. In that case and/or when using a very inductive load a so-called snub-ber network is required across the triac. The value of ...

Power shortage problems arise when too many USB devices connected to PC are working simultaneously. All USB devices, such as scanners, modems, thermal printers, mice, USB hubs, external storage devices and other digital devices obtain their power from PC. Since a PC can only supply limited power to USB devices, external power may have to be added to keep all these power hungry devices happy. This circuit is designed to add more power to a USB cable line. A sealed 12-V 750 mA unregulated wall cube is cheap and safe. To convert 12 V to 5 V, two types of regulators, switching and linear are available with their own advantages and drawbacks. The switching regulator is more suitable to this circuit because of high efficiency and compactness and now most digital circuits are immune to voltage ripple developed during switching.   Circuit diagram : USB Power Booster Circuit Diagram   The simple switcher type LM2575-5 is chosen to provide a stable 5V output voltage. This switcher is so s...

USB connector there are only 2 kinds, namely the connector type A and type B connector, as shown below. Type A connector used to connect the USB cable into the USB terminal on the back of the computer the last few years of production. Type B connector used to connect the USB cable into the USB terminal on the equipment, for a simple USB devices, such as mouse, usually do not use the connector B, to save cost in the cable directly connected to the inside of the mouse. Specified in the standard reference pesyaratan very strict to USB cable, not just the cable can be used, all the more for USB full-speed transfer of data to 1.2 Mega bps. So that the USB cable always sold as a ready-made, one end attached to the connector type A and the other end attached to the connector type B, no one sells it off the USB connector. On the computer, usually there are two terminals for connector type A, so it can easily be paired with 2 pieces of USB devices. Manufacturing company that makes the ...

PUB! is a Programmable USB Button on which you can program a sequence of keystrokes. When you press the button those keystrokes are “replayed” over a USB connection. The button (which is really a rotary encoder with a built-in push button switch) is programmed using an innovative and slightly quirky interface that does not require any custom software to be installed on your computer. All you need is a text editor like Notepad (for Windows) or gedit (for Linux). [ ]

Does this sound familiar: you buy a small piece of equipment, such as a programming & debugging interface for a microcontroller, and you have to use a clunky AC wall adapter to supply it with power? It’s even worse when you’re travelling and there’s no mains socket anywhere in sight. Of course, you can use the USB bus directly as a power source if the supply voltage is 5 V. If you need a higher voltage, you can use the USB converter described here. This small switch-mode step-up converter can generate an output voltage of up to 15 V with a maximum output current of 150 mA. The LM3578 is a general-purpose switchmode voltage converter. Figure 1 shows its internal block diagram. Here we use it as a step-up converter. The circuit diagram in Figure 2 shows the necessary components. Voltage conversion is achieved by switching on the internal transistor until it is switched off by the comparator or the current-limiting circuit. The collector current flows through coil L1, which stores en...

Here's a simple VHF FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio. The circuit use no coils that have to be wound. This FM transmitter can be used to listen to your own music throughout your home. When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player. To keep the circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606 [1]. This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency. The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency. USB FM transmitter schematics It is poss...