Posted on Monday, May 2, 2011 • Category: Test and Measurement
As electrolytic capacitors age, their internal resistance, also known as "equivalent series resistance" (ESR), gradually increases. This can eventually lead to equipment failure. Using this design, you can measure the ESR of suspect capacitors as well as other small resistances. Basically, the circuit generates a low-voltage 100kHz test signal, which is applied to the capacitor via a pair of probes. An op amp then amplifies the voltage dropped across the capacitor’s series resistance and this can be displayed on a standard multimeter. In more detail, inverter IC1d is configured as a 200kHz oscillator.
Its output drives a 4027 J-K flipflop, which divides the oscillator signal in half to ensure an equal mark/space ratio. Two elements of a 4066 quad bilateral switch (IC3c & IC3d) are alternately switched on by the complementary outputs of the J-K flipflop. One switch input (pin 11) is connected to +5V, whereas the other (pin 8) is connected to -5V. The outputs (pins 9 & 10) of these two switches are connected together, with the result being a ±5V 100kHz square wave. Series resistance is included to current-limit the signal before it is applied to the capacitor under test via a pair of test probes. Diodes D1 and D2 limit the signal swing and protect the 4066 outputs in case the capacitor is charged.
Posted on Monday, May 2, 2011 • Category: Remote Control
This circuit consists of Transmitter and Receiver section. The circuit can be used to control home appliances within a range of 30 meters. In open area, you can expect a range of 100 meters. The circuit comprises HT12 Encoder and Decode IC's. HT12 Encoder is used in the transmitter (remote) circuit where as HT12E is used in receiver circuit. The Encode IC encodes the 4 bits of data and transmit it serially to to RF Transmitter module. These 433Mhz transmitter and receiver modules operate using ASK Modulation.
Posted on Sunday, May 1, 2011 • Category: Remote Control
This is another remote control for my RF light switch. Pretty much the same as before but on a smaller PCB. Also ended up putting it in an old Maxim sample box.
I found a couple of button nubs in my junk box so decided to go with those. Even so I had to raise the buttons with pieces of rubber. A piece of tape keeps the buttons from falling out when the box is opened and also adds some tolerance for misalignment.
Posted on Saturday, April 30, 2011 • Category: Remote Control
The function of the device is very simple. Any IR remote than can be programmed to use the Sony protocol will work. The module outputs the device code (TV/VCR/DVD/AUX) and the button pressed, so the device can be used on as many different projects as your remote has devices (usually four). The numeric keys output the number of the key (0 outputs a 0, etc.). The function keys all output unique numbers. Note that not all buttons are available depending on which device you have selected. The VCR setting seems to use most of the keys on the remote. Also note that the first key pressed after the device is powered up does not output what it should. All subsequent numbers are correct. Luckily, all of the numbers so generated make a number different than any of the key codes, so it doesn't cause any problem. This could even be used to let the device know if it has just been powered up or rebooted. I have no idea why it does this.
Posted on Friday, April 29, 2011 • Category: Headphone Amplifiers
Here is a simple 100W HI-FI MOSFET Amplifier.
The main feature of this amplifier is a simple design and assembly. Simplicity of the circuit by looking at the circuit you expect amplifier to be simple. It should be noted that many hi-end amplifiers have a very simple but good quality designs. General technological theory is due to fewer parts, fewer problems. Additionally power to supplement your system is quite effective. Power supply transformer is very important. 8 Ohm output for a 35 - 0 to 35 V and at least 3 amps per power amplifier is recommended that a transformer can be transferred. Naturally, the two substations will be required for stereo use.
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