Here is an app note from NXP on capacitor bypassing.
Bypass capacitors are applied between the power supply pins VCC and GND of integrated circuits. They reduce both the power supply noise and the effect of spikes on the supply line. They also provide instantaneous current demands of the integrated circuit as it switches. This application note describes the different properties of bypass capacitors and provides a guide to their use.
Properties and application of bypass capacitors - [Link]
The basis for this tube preamplifier started out as a post in the Super simple single stage tube preamp thread on the website Forum. One of the members (see Mark’s 4S Universal Valve Preamps) had suggested building a Super Simple Single Stage Preamp (“4S” Preamp for short) and there was much discussion concerning various tubes, gain, noise, etc. and several designs were presented using various dual triode tubes. Then the proverbial gauntlet was thrown down with the phrase “switch from 12AU7 to 12AX7″. My answer was to design a universal line stage preamplifier that would work well with an entire range of tubes. Thus was the 4S Universal tube preamplifier born.
4S Universal Preamplifier for 12A*7 Tubes - [Link]
Make your own computer speaker system. This simple and inexpensive project will let you set up a small audio amplifier circuit and let more sound out your computer.
A simple audio amplifier circuit based on the LA4440 IC. This circuit will take your computer’s headphone level output and amplify it to drive a pair of external speakers. If you are listening to music or movies on laptops and computers, this is a useful little project for you. Laptop speakers are never loud enough to give satisfying listening. They give users the ability to hear something, but for anything like music or movie soundtracks they are very poor performers. The output from a laptops built in speakers is just too low, and this circuit addresses that low power with some additional amplification.
This circuit uses an LA4440 and some supporting components to give you much more power, while retaining a small package that you can use. The LA4440 is a dual channel audio power amplifier, with low distortion, and a good frequency range. Using 2 channels, the LA4440 will output 6 watts per channel, that can drive much larger speakers than a laptop can hold. When you set up a small enclosure(s), a 12V power supply, and an audio jack connection to the laptop you’ll have a nice enhancement to your laptop audio enjoyment.
Laptop Audio Amplifier - [Link]
Do you need high-quality measuring equipment? Now it´s the right time to profit from a 20-30% discount.
At an occasion of 65-years anniversary of company Fluke, we bring you a special offer of measuring devices sets.
Visual IR thermometer Fluke VT02 + Digital multimeter Fluke 175
Fluke VT02 – revolutionary combination of a thermometer with a visual display (picture in a visible spectrum blended with an infrared one), -10…+250°C, pyroelectric matrix technology, storage to a uSD card
Fluke 175: True RMS, basic accuracy 0.15%, CATIV 600V
Price 695Eur (common price is 894 Eur)/without VAT
Digital multimeter Fluke 115 + contactless voltage tester Fluke LVD2 + Fluke C90 pouche
Fluke 115: True RMS, AC/ DC current, CATIII 600V
Fluke LVD2: 2 sensitivity levels (already from approx 12.7cm) , 90-600VAC, integrated LED torch, CATIV 600V
Price 189 Eur (common price is 257 Eur)/ without VAT
Digital multimeter Fluke175 + voltage tester Fluke T110 VDE
Fluke 175: True RMS, basic accuracy 0.15%, CATIV 600V,
Fluke T110: voltage and continuity tester AC/DC 12-690V, LED indicator with 12LED, vibration (tactile) indicator, phase rotation, 30mA test (RCD/FI), IP64, built-in LED torch, CAT IV 600V
Price 199 Eur (common price is 268 Eur)/ without VAT
DMM Fluke 179 + clamp adapter for AC current measurement Fluke i400
CATIV 600V, True RMS, basic accuracy 0.09%, measurement of current up to 400A/ AC via a clamp adapter.
Price 299 Eur (common price is 399 Eur)/ without VAT
All 3 multimeters (115, 175 and 179) have these features: automatic/ manual range selection, dangerous voltage indicator, analogue bargraph with a great refresh frequency of up to 32/40x/sec, Capacity up to 10000 uF, AC/DC current 10A (20A/30 sec), max. count up to 6000. Mutual comparison will provide you the following document and in this demo you can try some functions of the 17x series.
Top quality Fluke measuring devices for great prices - [Link]
12V Lead acid battery low voltage indicator, to monitor battery condition during long term storage.
This is a simple circuit that will indicate a low voltage on a 12V lead acid battery. Many that have golf carts, small EV’s, RV’s, or solar power banks for homes have a number of 12V lead acid batteries to maintain and this circuit will help protect your investment while not using these batteries. When stored, batteries will self discharge, and if left for too long, will self-discharge to a damaging level. This circuit will light an LED when the battery voltage decreases to 11.6V. When the LED turns on, charge the battery to prevent the battery from dying on the shelf.
Only a few parts are needed in the small but useful circuit. The BC557 PNP transistor controls the lighting of the LED. The BC557 transistors base is biased by the 10V zener diode. As long as the battery voltage stays above 11.6V, the zener keeps the base of the BC557 transistor high. When the battery becomes discharged, the zener stops conducting and the base bias goes low, and BC557 begins conducting, and the LED alerts you to the low battery voltage. You can use a variable resistor to fine tune the low voltage indication, and/or use a set resistor when you have a good value figured out.
Battery Self Discharge Indicator – [Link]
fowkc published his latest project the mains frequency display:
I wanted to make a display that could show the mains frequency to 3 decimal places. I’d be using the same seven-segment display modules that I used in my UNIX clock, so all I had to do was design the part that would work out the frequency.
Mains frequency display - [Link]
Dave celebrates the classic 555 timer IC by building the Evil Mad Scientist “three fives” discrete timer kit. Some scope measurements and an explanation of the internal 555 timer circuitry follow.
EEVblog #555 – 555 Timer Kit - [Link]
Zak Kemble writes:
While working on an update for my CPU Usage LEDs project, I thought why not just make it into a universal RGB LED controller? The CPU Usage LEDs controller took a value between 0 and 255, worked out what colour it should be and then fade to that colour. This was very limiting; changing what colours it used and how it fades required a firmware update. With this universal RGB LED controller the host software does all the work and the controller is simply told what brightness the red, green and blue LEDs should be. To make it as easy as possible to interface with the controller I created a library which deals with all the LibUSB stuff.
AVR USB RGB LED controller - [Link]
STMicroelectronics have announced the LSM6DB0, the latest addition to its iNEMO family.
It packs a 3-axis accelerometer, 3-axis gyro and low energy ARM-based Cortex processor in a tiny 3 x 3 mm package.
This chip is designed to interface with baseband chipsets that don’t have a sensor co-processor. Additional external sensors can also be hooked up via its I2C interface, allowing the on-board processor to take care of all sensor-related functions to help minimize application latency at a system level. The device is fully compatible with all of the latest mobile operating systems including Android Kit-Kat 4.4. The sensor’s performance is the result of true 6-axis sensing, where both the 3-axis accelerometer and 3-axis gyroscope are manufactured on the same chip. They operate synchronously at the same output data rate,combinig correlated, true six-degree-of-freedom motion and not just separate acceleration and angular-rate inputs. [via]
A 6-axis Inertial Motion Sensing Device - [Link]
Lightning detector that flashes when lightning strikes nearby.
This circuit picks up and amplifies signals in the 300 kHz range, where lightning makes a lot of noise that can be picked up with a radio. The antenna and receiver are tuned to 300 kHz, with the receiver’s output connected to an amplifier that drives the lamp flashing circuit, alerting you to lightning in the area.
Use the potentiometer to reduce the sensitivity to noise and still be able to detect lightning strikes. In addition to lightning, this circuit will also respond to noise from motors inside appliances like refrigerators, washers, and air-conditioners. Another easy way to affect the sensitivity is to take off the antenna, or lengthen it depending on the conditions. To get some confirmation while tuning the detector, you can tune an AM radio to the bottom the of the dial as well.
You can use this circuit to track weather, and be prepared for it. The circuit is small enough and can be placed in a project box or waterproof container to use, on a boat for instance. The lamp can be replaced or even used alongside a buzzer in this circuit to give an audible alert as well, so that constant monitoring of the circuit is not necessary.
Simple Lightning Detector - [Link]