Showing posts with label time. Show all posts
Showing posts with label time. Show all posts
Wednesday, September 10, 2014
Diode recovery time
Understanding the parameters of "diode recovery time" .For prospective technicians are still learning and inexperienced, they generally recognize only two kinds of parameters of a diode, namely:
A similar experience we had some twenty years ago when a new SMPS first introduced on the television. When there is a diode voltage B + is broken. And then we replace the diode from the outside (our point of diode being sold in stores, rather than the official service) diode turns hot and soon broken. We think that the replacement diode voltage or current is less bulky. Then after replacement with a larger, but the result remains the same damage. Finally we order the diode with the same part number, and when the part arrived and was installed wrong results immediately.
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- The maximum working voltage (bias voltage when he gets back - or when not deliver - or when "off")
- The maximum operating current (when he gets a forward bias voltage of - or as leads - or when "on")
| Fast Recovery diodes |
Then why the diode is purchased in the market is hot and faulty? Actually there are many other parameters that have a diode. One more thing to be understood by a technician is called a "diode recovery time".
Common diode rectifier is used for the power supply circuits of 50Hz, when he gets forward biased diode voltage will deliver ("on"). Then, if the bias voltage is turned upside down then the diode does not turn into leads ("off"). If the diode is then mounted on a high-frequency ac voltage. So when given the diode forward bias voltage will deliver ("on") as usual. But when the bias voltage is turned upside down, apparently indirect diode can turn into "off" quickly.
There is a delay of a minute to "off" so that when the bias voltage is turned "off" there is still a bit of reverse leakage current. If the frequency of the ac leakage current was further compounded the greater the return. Reverse leakage current is what causes the diode to be hot.
Diode recovery time is a parameter of a diode which shows the "time" needed for the change of position "on" to "off" position. The smaller the value the better the recovery time is used at high frequencies.
Based on the parameters of the diode recovery time, then this type of diode is classified into:
- Diode general, for the rectifier AC voltage
- Fast Recovery Diode, used in the circuit and the flyback SMPS with a frequency of approximately 35 Khz
- Super Fast recovery diode, used in SMPS circuits with a frequency of about 70 to 80 Khz.
- Tips to find the diode equation.
- If we can not get the diode with the same part number, then we will usually replace it with another part number. We will replace the diode with the diode used in the same location. For example, diode B +-A model of the television is broken, then we will replace the B + diode that is used by television B or C.
Saturday, August 9, 2014
Real Time Clock Using the PIC16CXXX
A very simple real time clock electronic project can be designed using the PIC16CXXX microcontroller family , designed by Microchip Technology . This real time clock electronic project uses the Timer1 module, from a mid-range PIC16CXXX microcontroller, to control a low-power real-time clock. Timer1 was chosen because it has its own crystal which allows the module to operate during sleep.
Upon power-up, the device is initialized with the display starting at 12:00 PM, and Timer1 is configured to generate an interrupt (every second). The Timer1 overflow interrupt wakes the device from sleep. This causes the time registers (HRS, MIN, SECS) to be updated. If the SECS register contains an even value (SECS<0> = 0), the colon (":") is not displayed. This gives a visual indication for each second. Then the device returns to sleep.
Real Time Clock Circuit Diagram
Upon power-up, the device is initialized with the display starting at 12:00 PM, and Timer1 is configured to generate an interrupt (every second). The Timer1 overflow interrupt wakes the device from sleep. This causes the time registers (HRS, MIN, SECS) to be updated. If the SECS register contains an even value (SECS<0> = 0), the colon (":") is not displayed. This gives a visual indication for each second. Then the device returns to sleep.
Real Time Clock Circuit Diagram
For setting the clock are used three keys : SELECT_UNITS Key (S1) selects which units are to be modified (hours, minutes, off), the INC Key (S2) increments the selected units and CLR_MIN Key (S3) clears the minutes and seconds (useful for exactly setting the time ) .
This simplify design use a standard Hitachi LCD display module and some other electronic parts .
The RA2:RA0 pins are the control signals to the LCD display, RB3:RB0 acts as a 4-bit data bus, and RB7:RB5 are the input switches. The OSC1 pin is connected to an RC network, which generates an approximate 4 MHz device frequency. Because Timer1 operates asynchronously to the device, the devices oscillator can be configured for RC mode.
Timer1’s crystal is connected to the T1OSI and T1OSO pins. A good choice for a crystal is a 32.786 kHz (watch) crystal.
This electronic project and source code was designed by Mark Palmer Microchip Technology Inc.
Download Source code
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