Showing posts with label indicator. Show all posts
Showing posts with label indicator. Show all posts
Wednesday, December 18, 2013
12V Lead Acid Battery Charger with Indicator
Some of you might wonder why a charger is needed at all, to charge a 12 Volt battery from a 12 Volt source! Well, firstly the "12 Volt" source will typically vary anywhere from 11 Volt to 15 Volt, and then a battery needs a controlled charge current and voltage, which cannot result from connecting it directly to a voltage source. The charger described here is intended for charging small 12 Volt lead acid batteries, such as the gelled or AGM batteries of capacities between about 2 and 10 Ah, using a cars electrical system as power source, regardless of whether the car engine is running or not.
I built this charger many years ago, I think I was still in school back then. On request of a reader of my web site, Im publishing it now, despite being a rather crude circuit. It works, it is uncritical to build, and uses only easy-to-find parts, so it has something in its favor. The downside is mainly the low efficiency: This charger wastes about as much power as it puts into the battery. The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors connected as emitter followers, which in turn drive the voltage doubler proper.
The doubler has power resistors built in, which limit the charging current. The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit. The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so dont leave this charger permanently connected to a battery.
If you would like to do just that, then add a second diode in series with D3! There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA. There is an auxiliary output, that provides about 20V at no load (depending on input voltage), and comes down as the load increases. I included this for charging 12V, 4Ah NiCd packs, which require just a limited current but not a limited voltage for charging.
Note that if the charge output is short-circuited, the over-current protection of U2 will kick in, but the current is still high enough to damage the diodes, if it lasts. So, dont short the output! If instead you short the auxiliary output, the fuse should blow. I built this charger into a little homemade aluminum sheet enclosure, using dead-bug construction style. Not very tidy, but it works. Note the long leads on the power resistors. They are necessary, because with shorter leads the resistors will unsolder themselves, as they get pretty hot! The transistors and the regulator IC are bolted to the case, which serves as heat sink. The transistors dont heat up very much, but the IC does.
Readmore...
I built this charger many years ago, I think I was still in school back then. On request of a reader of my web site, Im publishing it now, despite being a rather crude circuit. It works, it is uncritical to build, and uses only easy-to-find parts, so it has something in its favor. The downside is mainly the low efficiency: This charger wastes about as much power as it puts into the battery. The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors connected as emitter followers, which in turn drive the voltage doubler proper.
The doubler has power resistors built in, which limit the charging current. The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit. The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so dont leave this charger permanently connected to a battery.
If you would like to do just that, then add a second diode in series with D3! There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA. There is an auxiliary output, that provides about 20V at no load (depending on input voltage), and comes down as the load increases. I included this for charging 12V, 4Ah NiCd packs, which require just a limited current but not a limited voltage for charging.
Note that if the charge output is short-circuited, the over-current protection of U2 will kick in, but the current is still high enough to damage the diodes, if it lasts. So, dont short the output! If instead you short the auxiliary output, the fuse should blow. I built this charger into a little homemade aluminum sheet enclosure, using dead-bug construction style. Not very tidy, but it works. Note the long leads on the power resistors. They are necessary, because with shorter leads the resistors will unsolder themselves, as they get pretty hot! The transistors and the regulator IC are bolted to the case, which serves as heat sink. The transistors dont heat up very much, but the IC does.
Source: Homo Ludens
Wednesday, September 25, 2013
Low Cost Battery Condition Indicator
This design combines power-on and low-battery indication, can operate with any battery voltage up to 15V, has very low current drain (2mA or less) and costs less than $3.50 with new parts. When the battery voltage is above a predetermined minimum, power on is indicated by what appears to be a steadily lit LED. In fact, the LED is being pulsed by a free-running relaxation oscillator formed by IC1c, one gate of a 4093 CMOS quad Schmitt NAND. The frequency of this oscillator should be at least 50Hz, so that it appears to be continuously on while at the same time drawing far less average current than a steadily lit LED.
The series resistor for the LED needs to be selected for each battery voltage, to limit the current to a safe vale or you could use a fixed resistor and a series trimpot for flexibility. Low battery voltage is indicated by the LED pulsing at around 1Hz. The battery voltage is monitored by transistor Q1 and trimpot VR1. Once the voltage at its base falls below 0.6V, Q1 turns off and Q2 turns on to enable the 2-gate oscillator formed by IC1a and IC1b, which runs at 1Hz. The pulses from this oscillator are inverted by IC1d to gate the LED oscillator on and off. Calibration can be done with a variable bench power supply set to the lowest battery voltage you will accept. Power up the circuit and adjust VR1 until the LED pulses once per second.
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The series resistor for the LED needs to be selected for each battery voltage, to limit the current to a safe vale or you could use a fixed resistor and a series trimpot for flexibility. Low battery voltage is indicated by the LED pulsing at around 1Hz. The battery voltage is monitored by transistor Q1 and trimpot VR1. Once the voltage at its base falls below 0.6V, Q1 turns off and Q2 turns on to enable the 2-gate oscillator formed by IC1a and IC1b, which runs at 1Hz. The pulses from this oscillator are inverted by IC1d to gate the LED oscillator on and off. Calibration can be done with a variable bench power supply set to the lowest battery voltage you will accept. Power up the circuit and adjust VR1 until the LED pulses once per second.
Tuesday, September 3, 2013
Off Hook Telephone Line Indicator
The circuit is designed to connect in parallel with the telephone line, to monitor and detect if any telephone in the same line is busy, with the indication of the LED and which is self-powered so that it does not provide any load on a telephone line.
Light Emitting Diode (LED) – a semiconductor diode that is commonly a source of light when electric current pass through it Metal Oxide Semiconductor Field Effect Transistor (MOSFET) – a device utilized for switching and amplification of signals BS108 – a 250 mA and 200 Volts small signal MOSFET designed for high voltage, high speed switching applications such as relay drivers, CMOS logic, line drivers, TTL or microprocessor to high voltage interface and high voltage display drivers Diode Bridge – also known as bridge rectifier which has four diodes arranged in a bridge configuration where the output voltage has the same polarity with either polarity of the input voltage 1N4007 – a general purpose plastic rectifier with reverse voltage from 50 Volts to 1000 Volts and forward current of 1.0 Ampere
When none of the telephone lines is in use or on-hook, the voltage across the line is around 48V. In this state, the gate of transistor Q2 is shorted to its source during the conduction of Q1. This causes the LED to be disabled while Q2 is turned OFF. When one telephone extension along the telephone line changes to off-hook or in use condition, a voltage drop from 5V to 15V is detected. This will in turn cause Q1 to turn OFF because of the very low voltage across the gate of Q1 which is equal to 6% of the line voltage. Transistor Q2 then will be biased at around half of the line voltage.
Off-Hook Telephone Line Indicator Circuit Diagram
The sudden line drop of voltage triggers Q2 to light up the LED that will give a sign that the line is in use. Using the same line, the circuit is unseen with other telephone devices. A current-limiting resistor is used to maintain the low current of LED1 while the local telephone line parameters dictate the variation of other component’s values. The power of the circuit is provided by the telephone line. Other voltage protection may be used with some reliable design in addition to the current-limiting resistor. This is important to avoid any grounding effects from conducting surfaces within the circuit.
To ensure that transistor Q1 is fully biased while the line is free or not in use where LED1 is OFF, a 500K ohm MOSFET trimmer is used for the desired adjustment. A MOSFET is a three-terminal semiconductor component with a conducting channel in its output and a built-in capacitor at its input. To increase the values of any of the two resistors connected to the gate of Q2, a 200V MOSFET can be used in the place of Q2 if BS108 is not available. However, plain transistors like the bipolar junction can be used but with lower values to allow greater currents to pass through the line that is not in use. The bridge rectifier comprising of four 1N4007 diodes are performing the conversion of AC input into DC output.
MOSFET can function in two ways. The first is known as depletion mode wherein the channel shows its maximum conductance in the absence of a voltage on the gate. The second way that the MOSFET can function is known as enhancement mode wherein the device is not conducting even in the absence of a voltage on the gate because no channel is produced. A channel is being created with the application of a voltage to the gate. To generate better conductivity, greater voltage to the gate is required.
MOSFET drivers are applied in electronic motor control for different types of motors. Also, they are specifically used with long duty cycles, high operating frequency above 200 KHZ, lower output power, and wide load variations. The largest application of MOSFETs are the switched mode power supplies and in battery charging applications. In transducer drivers for high power devices such as light bulbs and motors, large current output with a small input is provided by MOSFETs. Since they are more non-linear than BJTs while producing less distortion, they can be utilized with Hi-Fi amplifiers. In constructing integrated circuits, MOSFETs are very useful since they can be made very compact. Although MOSFETs can get damaged by static electricity at higher voltages, they still provide several advantages as compared to other transistors which include faster switching time than BJT, lower losses than BJT, very small switching current, and least effects of temperature.
This telephone line indicator does not only tell when a telephone line is in use if a plurality of telephones are all setup to the same telephone line, but also prevents interruptions during personal calls. Additionally, it can also help to prevent costly and unwanted disruption of modem calls and fax, it alerts a person when a call is done and the phone is free to use, and the LED light indicates the line is in use.
To avoid any injury, it is a prerequisite to take extra precautionary measures when connecting any circuit to the telephone lines, which can produce life-threatening voltages during normal operation. During a lightning storm, it is better to keep distance from telephone lines.. Legal aspects are imposed in different countries for connecting things to telephone lines. The circuit should be better built with a plug-in cord for easy removal in case of fault occurrences. Otherwise, it would be best to consult a licensed telephone operator.
Light Emitting Diode (LED) – a semiconductor diode that is commonly a source of light when electric current pass through it Metal Oxide Semiconductor Field Effect Transistor (MOSFET) – a device utilized for switching and amplification of signals BS108 – a 250 mA and 200 Volts small signal MOSFET designed for high voltage, high speed switching applications such as relay drivers, CMOS logic, line drivers, TTL or microprocessor to high voltage interface and high voltage display drivers Diode Bridge – also known as bridge rectifier which has four diodes arranged in a bridge configuration where the output voltage has the same polarity with either polarity of the input voltage 1N4007 – a general purpose plastic rectifier with reverse voltage from 50 Volts to 1000 Volts and forward current of 1.0 Ampere
When none of the telephone lines is in use or on-hook, the voltage across the line is around 48V. In this state, the gate of transistor Q2 is shorted to its source during the conduction of Q1. This causes the LED to be disabled while Q2 is turned OFF. When one telephone extension along the telephone line changes to off-hook or in use condition, a voltage drop from 5V to 15V is detected. This will in turn cause Q1 to turn OFF because of the very low voltage across the gate of Q1 which is equal to 6% of the line voltage. Transistor Q2 then will be biased at around half of the line voltage.
Off-Hook Telephone Line Indicator Circuit Diagram
The sudden line drop of voltage triggers Q2 to light up the LED that will give a sign that the line is in use. Using the same line, the circuit is unseen with other telephone devices. A current-limiting resistor is used to maintain the low current of LED1 while the local telephone line parameters dictate the variation of other component’s values. The power of the circuit is provided by the telephone line. Other voltage protection may be used with some reliable design in addition to the current-limiting resistor. This is important to avoid any grounding effects from conducting surfaces within the circuit.
To ensure that transistor Q1 is fully biased while the line is free or not in use where LED1 is OFF, a 500K ohm MOSFET trimmer is used for the desired adjustment. A MOSFET is a three-terminal semiconductor component with a conducting channel in its output and a built-in capacitor at its input. To increase the values of any of the two resistors connected to the gate of Q2, a 200V MOSFET can be used in the place of Q2 if BS108 is not available. However, plain transistors like the bipolar junction can be used but with lower values to allow greater currents to pass through the line that is not in use. The bridge rectifier comprising of four 1N4007 diodes are performing the conversion of AC input into DC output.
MOSFET can function in two ways. The first is known as depletion mode wherein the channel shows its maximum conductance in the absence of a voltage on the gate. The second way that the MOSFET can function is known as enhancement mode wherein the device is not conducting even in the absence of a voltage on the gate because no channel is produced. A channel is being created with the application of a voltage to the gate. To generate better conductivity, greater voltage to the gate is required.
MOSFET drivers are applied in electronic motor control for different types of motors. Also, they are specifically used with long duty cycles, high operating frequency above 200 KHZ, lower output power, and wide load variations. The largest application of MOSFETs are the switched mode power supplies and in battery charging applications. In transducer drivers for high power devices such as light bulbs and motors, large current output with a small input is provided by MOSFETs. Since they are more non-linear than BJTs while producing less distortion, they can be utilized with Hi-Fi amplifiers. In constructing integrated circuits, MOSFETs are very useful since they can be made very compact. Although MOSFETs can get damaged by static electricity at higher voltages, they still provide several advantages as compared to other transistors which include faster switching time than BJT, lower losses than BJT, very small switching current, and least effects of temperature.
This telephone line indicator does not only tell when a telephone line is in use if a plurality of telephones are all setup to the same telephone line, but also prevents interruptions during personal calls. Additionally, it can also help to prevent costly and unwanted disruption of modem calls and fax, it alerts a person when a call is done and the phone is free to use, and the LED light indicates the line is in use.
To avoid any injury, it is a prerequisite to take extra precautionary measures when connecting any circuit to the telephone lines, which can produce life-threatening voltages during normal operation. During a lightning storm, it is better to keep distance from telephone lines.. Legal aspects are imposed in different countries for connecting things to telephone lines. The circuit should be better built with a plug-in cord for easy removal in case of fault occurrences. Otherwise, it would be best to consult a licensed telephone operator.
Monday, September 2, 2013
Battery Voltage Indicator Using SN16889
This battery voltage indicator electronic project is designed using linear voltage indicator SN16889 (manufactured by Texas Instruments) or MC16889 (manufactured by Motorola). The circuit below allows lighting, depending on input voltage of one or more LEDs. Maximum voltage at which all LEDs light is adjusted using potentiometer P1 to 15 volts. D7 can be red LED indicates a battery voltage too high. D6 LED green indicates a correct value and the battery voltage LEDs D5, D4 and D3 yellow indicates a battery voltage too low.
Battery Voltage Indicator Circuit Diagram
Battery Voltage Indicator Circuit Diagram
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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