Matt circuit

Since one of the servers owned by the author would not start up by itself after a power failure this little circuit was designed to perform that task.  The older PC that concerned did have a standby state, but no matching BIOS set-ting that allows it to start up unattended. Although a +5 V standby supply voltage is available, you always have to push a but-ton for a short time to start the computer up again. Modern PCs often do have the option in the BIOS which makes an automatic start after a power outage possible. After building in the accompanying circuit, the PC starts after about a second. Incidentally, the push-button still functions as before.   The circuit is built around two golden oldies: a NE555 as single-shot pulse generator and a TL7705 reset generator. The reset generator will generate a pulse of about 1 second after the supply voltage appears. The RC circuit between the TL7705 and the NE555 provides a small trigger pulse during the falling edge of the 1 second p...

Tiny white LEDs are capable of delivering ample white light without the fragility problems and costs associated with fluorescent backlights. They do pose a problem however in that their forward voltage can be as high as 4 V, precluding them being from powered directly from a single Li-Ion cell. Applications requiring more white LEDs or higher efficiency can use an LT1615 boost converter to drive a series connected array of LEDs. The high efficiency circuit (about 80%) shown here can provide a constant-current drive for up to eight LEDs. Driving eight white LEDs in series requires at least 29 V at the output and this is possible thanks to the internal 36-V, 350-mA switch in the LT1615. The constant-current design of the circuit guarantees a steady current through all LEDs, regardless of the forward voltage differences between them. Although this circuit was designed to operate from a single Li-Ion battery (2.5V to 4.5V), the LT1615 is also capable of operating from inputs as low as 1 V w...

Setting up an electric guitar is not rocket science, but it is something that a lot of guitarists shy away from. True, if you do this wrong, you can make your guitar play badly, but if you learn to do it right, you could save yourself a lot of cash. I should probably preface this by saying that today we are only going to do a basic setup. This is enough most of the time, but occasionally more is required, such as filing the nut, or doing some fretwork. If you want to set up a tremolo too, go to this post first: Setting Up or Adjusting a Stratocaster Tremolo Also, if you're setting up a Les-Paul-style guitar, you might prefer to have a look at this blog post: http://diystrat.blogspot.com/2012/09/how-to-set-up-gibson-les-paul-style.html So what does a basic setup involve? Let me break it down for you, as follows: 1. Checking and adjusting neck bow (how straight the neck is) 2. Checking and adjusting saddle height 3. Checking and adjusting the intonation (how far back or forward the s...

The circuit described here is a step-up converter to drive 20 LEDs, designed to be used as a home-made ceiling night light for a child’s bedroom. This kind of night light generally consists of a chain of Christmas tree lights with 20 bulbs each consuming 1 W, for a total power of 20 W. Here, in the interests of saving power and extending operating life, we update the idea with this simple circuit using LEDs.  Power can be obtained from an unregulated 12 V mains adaptor, as long as it can deliver at least about 330 mA.  The circuit uses a low-cost current-mode controller type UCC3800N, reconfigured into voltage mode to create a step-up converter with simple compensation. By changing the external components the circuit can easily be modified for other applications. To use a current-mode controller as a voltage-mode controller it is necessary to couple a sawtooth ramp (rising from 0 V to 0.9 V) to the CS (current sense) pin, since this pin is also an input to the internal PWM com...

Tiny white LEDs are capable of delivering ample white light without the fragility problems and costs associated with fluorescent backlights. They do pose a problem however in that their forward voltage can be as high as 4 V, precluding them being from powered directly from a single Li-Ion cell. Applications requiring more white LEDs or higher efficiency can use an LT1615 boost converter to drive a series connected array of LEDs. The high efficiency circuit (about 80%) shown here can provide a constant-current drive for up to eight LEDs. Driving eight white LEDs in series requires at least 29 V at the output and this is possible thanks to the internal 36-V, 350-mA switch in the LT1615. The constant-current design of the circuit guarantees a steady current through all LEDs, regardless of the forward voltage differences between them. Although this circuit was designed to operate from a single Li-Ion battery (2.5V to 4.5V), the LT1615 is also capable of operating from inputs as low as 1 V w...

Every year I notice that I have little issue waking up at 7am during summer months, yet waking up at 8am during winter is always unpleasant. Some quick research led me to find that the body is gradually woken up by light, which is why products such as the Phillips Wake-Up Light exist. However, with a starting price of £60 for the (very) basic version, I’ve opted to make my own smartphone-connected, automated wake up light instead. [ ]

This is a simple 120 V : 24 V , center - tapped ( CT ) control transformer and four additional components can do the operation. This circuit outputs a clean about 120 volt - 200 volt at 60 Hz and can supply up to 20 Watt . The circuit is self starting and free running. See this simple inverter circuit below : Transistor Q1 and Q2 use 2N5877 or similarity .If Q1 is faster and higher gain than Q2 , it will turn on first when aplly the input power and will hold Q2. Load current and the transformer magnetizing current the flows in the upper half of primary coil, and auto transformer supplies the base drive (two transistor) unti the transformer saturates.The transformator can use the 3A CT transformer an use the secondary coil for input and primary coil use to output, And input use the 12 volt secondary coil. Use 12 battery to power input , such as 12 V accu. You can use the circuit at the time of death PLN electricity , using 12 volt battery or accu , you can turn n a fluorescent...

The latch-up alarm described here is based on single IC NE555, configured as an astable multivibrator. The timing components are selected such that the oscillation frequency of the multivibrator lies within the audio range. Instead of a flip-flop stage, an opto-coupler (MCT2E) is used for latching of the alarm.  Under normal condition, pin 4 of IC1 is pulled to ground via resistor R2, and its output at pin 3 is held  ‘low’. Circuit Diagram: When switch S1 is pressed momentarily, transistor T1 conducts to bring reset pin 4 of 555 to logic  ‘high’. As a result, IC1 is activated and the alarm starts to sound. Simultaneously, the LED inside opto-coupler glows and the phototransistor conducts. As a result, trigger transistor T1 gets base bias via phototransistor and resistor R6. The alarm sounds continuously until reset switch S2 is pressed. When switch S2 is pressed, transistor T1 is switched  ‘off’ to bring pin 4 of IC1 to logic ‘low’ and the alarm is disabled.  So...

It is impossible to imagine present day society without any batteries. Count the number of gadgets in your house that are powered from batteries, you will be stunned by the number of batteries you will find. The majority of these devices use penlight batteries and if you’re a little environmentally conscious you will be using rechargeable batteries. A few years ago these batteries were invariably NiCd types. However, these batteries suffer from a relatively high rate of self-discharge and from the so-called memory-effect. It is now more common to use NiMH batteries. The advantage is that these batteries do not suffer from the memory-effect and generally also have a much higher capacity, so that they last longer before they have to be recharged again. From the above you can conclude that every household these days needs, or could use, a battery charger. A good charger needs to keep an eye on several things to ensure that the batteries are charged properly. For one, the charger has...