Showing posts with label for. Show all posts
Showing posts with label for. Show all posts
Thursday, December 26, 2013
Reanimating Probe for AVR μC
AVR device not responding, When this discouraging message appears while you’re programming your Atmel microcontroller, that’s where the problems really begin! The problem is of ten due to incorrect programming of the fuse bits. This is where the unblocking probe comes into play.
Once the whole thing is powered up, all you have to is use one hand to apply the tip of the probe to the microcontroller’s XTAL1 input and then use your other hand to go ahead and program it with your favourite sof t ware. And there, your microcontroller is saved! The electronics are as simple as can be, the aim being to design something cheap and easy to reproduce. It consists of an oscillator generating a rectangular wave at around 500 kHz, built using a 74HC04. This circuit will also work with a 74HC14, but depending on the make of IC, the frequency of around 500 kHz may vary by around ±50 kHz. This doesn’t affect the operation of the probe.
Reanimating Probe for AVR μC Circuit diagram :
The unblocking board is connected using a ribbon cable, terminated with two female HE10/10 connectors. The pinout of the HE10/10 connector is the same as used in the majority of circuits, but of course it can be adapted for an HE10/06 connector.
The first connector is connected to the board to be unblocked, which allows powering of the electronics. The second connector is connected to the ISP programmer (STK200 compatible). The contact at the crystal is made using a needle, to ensure contact even through a board that has been varnished. There’s no need to unsolder the crystal for this operation.
The PCB design in Eagle format is available from : www.elektor.com
Author : P. Rondane - Copyright : elektor
Source :http://www.ecircuitslab.com/2012/08/reanimating-probe-for-avr-c.html
Tuesday, December 24, 2013
Universal Tester for 3 pin Devices
Most 3-terminal active components can be tested statically using just an ohmmeter. But when you have a lot of these devices to test, the procedure soon becomes boring. That’s where the idea came from to combine fast, easy testing for these types of device into a single instrument.
The unit described here enables you to test NPN and PNP bipolar transistors, N-or Pchannel FETs or MOSFETs, UJTs, triacs, and thyristors. Regardless of the type of device, the tests are non-destructive. Universal connectors allow testing of all package types, including SMDs (up to a point). The unit lets you change from one type of device to another in a trice. It avoids using a multi-pole switch, as they’re too expensive and hard to find.
Here’s how to build a versatile instrument at a ridiculously low cost. IC1 is a 4066 quad CMOS switch which will let us switch between bipolar transistors and FETs. LEDs D1–D4 tell us about the condition of the test device, when we press the ‘Test’ button. The 4066 can only handle a few milliamps, not enough for the other component types to be tested, hence the reason for using relay RE1. This 12 V relay offers two NO contacts. The first applies power to the UJT test circuit, the second applies it to the triac and thyristor test circuit.
Extensive testing has shown that the best way to test UJT transistors is to do so dynamically, with the help of a relaxation oscillator. Net-work R11/C1 sets the oscillator frequency to around 2 Hz. On pin B1 of the UJT we find a nice sawtooth, which is not of much interest to us here. However, pin B2 gives good but very short pulses. IC2, wired as a monostable, lengthens these pulses so they can be clearly seen via LED D5.
The relay’s second pole is going to drive the thyristor’ sortriac’s trigger pin. The value of R18 is a good compromise with respect to the varying trigger currents for this type of device. Resistor R17 is important, as the hold-ing current must be high enough for a triac; 250 mA is a good compromise. LED D6 tells you if the device is in good condition or not; but watch out, the test result must be con-firmed by briefly cutting the power in order to reset the triac.
On the web page for this article [1] you’ll find the author’s CAD files (PCB layout and front panel) along with some photos of his project. On the prototype, the LEDs and the ‘Test’ button were wired onto the copper side of the PCB. The six female connectors for the devices being tested were salvaged, but there are lots of models available on the market (the pitch is standard). The test cable crocodile clips must be as small as possible for testing SMD devices.
Source : http://www.ecircuitslab.com/2012/05/universal-tester-for-3-pin-devices.html
Tuesday, October 8, 2013
SOFT START MECHANISM FOR L200 VOLTAGE REGULATOR ELECTRONIC DIAGRAM
SOFT START MECHANISM FOR L200 VOLTAGE REGULATOR ELECTRONIC DIAGRAM
Ic (constant current) is charge capacitor C, where Ic = Vsc/R.
The output reaches its nominal value after the time ton. Vo-Vsc=(Ic.ton)/C.
ton=C.[(Vo-0.45)/0.45].R = CVoR/0.45.
Vo follows the voltage in pin 2 at less than 0.45 volt. It is because voltage of more than 0.45 V can’t be produced between pin 2 and pin 5.
Friday, September 27, 2013
Switch Timer Circuit For Bathroom Light
This 9-minute timer switch can be used to control the light in a toilet or bathroom. The timer is started by pushing S1 and stopped by pushing S1 again. If you forget to turn it off, the controlled light will go off after nine minutes. If you need the light on continuously non-stop, you need to press S1 (turn on) and then S2 (cancellation of timer) within 9 minutes and in this case the light will be on until you switch it off with S1.
Circuit diagram:
IC1 is a is 4013 dual flip-flop. Flip flop IC1a is toggled on and off by switch S1 and it controls the relay which is switched by FET Q2. IC1a controls IC1b which is connected as an RS flipflop to enable or disable IC2, a 4060 oscillator/divider. This has its timing interval set by the components at its pins 9, 10 & 11. The relay should have 250VAC mains-rated contacts and these are connected in parallel with an existing wall switch.
Author: Rasim Kucalovic - Copyright: Silicon Chip Electronics
Sunday, September 1, 2013
Alarm Indicator for High Temperature Reading
The circuit has been designed to provide an alarm with the use of a buzzer when sensing high temperature by using a thermistor.
These bipolar transistors form a Darlington pair to produce a very high current gain that is much higher then each transistor taken separately. This is made possible when the current amplified by the first transistor is further amplified by the second transistor. The overall gain is equal to the two individual gains multiplied together.A Darlington pair is designed in such a way that the collectors of both transistors are attached together and the emitter of the first transistor is directly coupled to the base of the second or output transistor. The base current of the output transistor is equal to the emitter current of the input transistor. When several transistors are used, it can form a cascade connection and the total current amplification factor will be very high since it is a product of current amplification factor of respective transistors.
Alarm Indicator for High Temperature Reading Schematic
When the Darlington pair conducts in this circuit, it causes the relay K1 to close thereby triggering the buzzer to produce sound due to the increase in temperature that is more than the predetermined value. The location of the thermistor should be far enough from other components of the circuit to prevent inhibiting their temperature. The circuit is powered by a 9 V battery for ease of transportation but a dedicated power supply can be provided is the circuit would be in a permanent location. A load, like a lamp or a LED, can also be connected to the contacts of the relay to produce a light indication or notification of the occurrence of excess temperature. Since the circuit is well insulated, the thermistor, connected to the circuit with a plated cable, can be submerged to water to cool down or reset the sensitivity and will not cause any short circuit. Doing this will regulate the trimmer.
This circuit can be designed not only by setting a detection of high temperature but can also be modified to be set on detection of low temperature in some industries. It can be used for refrigeration, walk-in freezer, or walk-in cooler systems and other environments that are sensitive in temperature. Some circuits incorporating high temperature alarm modules are being used in motor vehicles to detect the occupancy wherein the temperature element senses a highly dangerous temperature in the passenger compartment of a motor vehicle and energizes the occupancy sensor to determine the presence or absence of an occupant. In the absence of the occupant, the sensor de-energizes after a period of time while an audible alarm is triggered to create attention to the motor vehicle in the presence of an occupant. This type of alarm can be reset with the use of a key.
Having a temperature alarm can provide benefits like protecting valuable equipment due to high temperature, low temperature, or sometimes high humidity. Other high temperature program can be used to protect against air conditioning failure or against the heating system to turn off. On the contrary, low temperature program can be used against heating system failure by aiding to prevent frozen pipes. The alarm can also reduce downtime by receiving a telephone call and being notified of a possible power loss or failure before the damage occurs in an equipment.
The Darlington pair used in the circuit can also be used as an important component in a switching device while high power Darlington transistors can be used in emergency power supply and in control circuits for AC and DC motor control. These applications make the Darlington suitable for switching large currents in high power circuits.
- Thermistor – one type of resistor used as temperature-sensing element which demonstrates a large change in resistance proportional to a small change in temperature because of the composition of its semiconductor material.
- BC550 – an NPN general purpose transistor with low current and low voltage used for low noise stages in audio frequency equipment.
These bipolar transistors form a Darlington pair to produce a very high current gain that is much higher then each transistor taken separately. This is made possible when the current amplified by the first transistor is further amplified by the second transistor. The overall gain is equal to the two individual gains multiplied together.A Darlington pair is designed in such a way that the collectors of both transistors are attached together and the emitter of the first transistor is directly coupled to the base of the second or output transistor. The base current of the output transistor is equal to the emitter current of the input transistor. When several transistors are used, it can form a cascade connection and the total current amplification factor will be very high since it is a product of current amplification factor of respective transistors.
Alarm Indicator for High Temperature Reading Schematic
When the Darlington pair conducts in this circuit, it causes the relay K1 to close thereby triggering the buzzer to produce sound due to the increase in temperature that is more than the predetermined value. The location of the thermistor should be far enough from other components of the circuit to prevent inhibiting their temperature. The circuit is powered by a 9 V battery for ease of transportation but a dedicated power supply can be provided is the circuit would be in a permanent location. A load, like a lamp or a LED, can also be connected to the contacts of the relay to produce a light indication or notification of the occurrence of excess temperature. Since the circuit is well insulated, the thermistor, connected to the circuit with a plated cable, can be submerged to water to cool down or reset the sensitivity and will not cause any short circuit. Doing this will regulate the trimmer.
This circuit can be designed not only by setting a detection of high temperature but can also be modified to be set on detection of low temperature in some industries. It can be used for refrigeration, walk-in freezer, or walk-in cooler systems and other environments that are sensitive in temperature. Some circuits incorporating high temperature alarm modules are being used in motor vehicles to detect the occupancy wherein the temperature element senses a highly dangerous temperature in the passenger compartment of a motor vehicle and energizes the occupancy sensor to determine the presence or absence of an occupant. In the absence of the occupant, the sensor de-energizes after a period of time while an audible alarm is triggered to create attention to the motor vehicle in the presence of an occupant. This type of alarm can be reset with the use of a key.
Having a temperature alarm can provide benefits like protecting valuable equipment due to high temperature, low temperature, or sometimes high humidity. Other high temperature program can be used to protect against air conditioning failure or against the heating system to turn off. On the contrary, low temperature program can be used against heating system failure by aiding to prevent frozen pipes. The alarm can also reduce downtime by receiving a telephone call and being notified of a possible power loss or failure before the damage occurs in an equipment.
The Darlington pair used in the circuit can also be used as an important component in a switching device while high power Darlington transistors can be used in emergency power supply and in control circuits for AC and DC motor control. These applications make the Darlington suitable for switching large currents in high power circuits.
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