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*LM35 Temperature Sensor | *LM35 Temperature Sensor | ||
*555 Timer astable oscillator | *555 Timer astable oscillator | ||
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*charge pump | *charge pump | ||
*diode for forward drop bias voltage | *diode for forward drop bias voltage | ||
*diode logical or | *diode logical or | ||
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*RC timer | *RC timer | ||
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*diode rounding circuit | *diode rounding circuit | ||
*row and collumn connection | *row and collumn connection | ||
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*transformer | *transformer | ||
*voltage multiplier and voltage doubler | *voltage multiplier and voltage doubler | ||
+ | *integrator | ||
+ | *diode full wave bridge | ||
+ | *H Bridge | ||
+ | |||
+ | An H bridge is an electronic circuit that causes current to flow in one direction or the other ( from a singel ended power supply ). Often used for motor control [[motor driver]]. | ||
+ | It is an electronic double pole double throw switch. | ||
+ | [http://code.rancidbacon.com/ElectronicsElectronics] See Section on ''H-Bridge'' | ||
+ | *Simple Oscillator circuits | ||
+ | *Current mirrors | ||
+ | *RF Mixers | ||
+ | *Tranistor Current Mirror | ||
*[[Colpitts Oscillator]] | *[[Colpitts Oscillator]] | ||
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See the sections on: Op amp Non Inverting Amplifier, Op amp Unity Gain Buffer .... | See the sections on: Op amp Non Inverting Amplifier, Op amp Unity Gain Buffer .... | ||
− | + | [http://www.amplifiersite.com/ AmplifierSite.com] | |
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== Current Sense Resistor ( Shunt Resistance ) == | == Current Sense Resistor ( Shunt Resistance ) == | ||
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Discussion: | Discussion: | ||
− | I you have a lot of components that use the same voltage put them in parallel. This is how most lights in a house are wired. Each individual light can be turned on and off without changing the current or voltage in the other lights. With a bit of math you can show that the two resistors act like one resistor of value R = | + | I you have a lot of components that use the same voltage put them in parallel. This is how most lights in a house are wired. Each individual light can be turned on and off without changing the current or voltage in the other lights. With a bit of math you can show that the two resistors act like one resistor of value R = R1 + R2 /( R1 * R2 ). When you need a resistor of a different value than you have you can sometimes “make it up” using a parallel connection of resistors you do have. Two identical resistors in parallel are equivalent to one of half the resistance. A parallel circuit can have more than 2 resistors, there can be 3, 4, ... You can find out more about parallel circuits in the references. This circuit should be contrasted with the Series Circuit. Parallel circuits can also be used with other components, the equations vary, for capicators the capacitances add in a parallel circuit. |
More information: | More information: | ||
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Use this circuit when you want to convert AC to DC at significant current in order to provide DC power to another circuit component, it can be also used as a very low precision "precision rectifier". Basically similar circuits are sometimes used as demodulators for AM signals. | Use this circuit when you want to convert AC to DC at significant current in order to provide DC power to another circuit component, it can be also used as a very low precision "precision rectifier". Basically similar circuits are sometimes used as demodulators for AM signals. | ||
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+ | Circuit: | ||
+ | [[Image:pds.png | Pull Down and Switch ]] | ||
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+ | Where | ||
+ | *R_PULLDOWN resistor which normally keeps the output low ( ground ). | ||
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Discussion: | Discussion: | ||
There are many variations of this circuit, sometimes in combination with center tapped transformers, sometimes with multiple diodes ( as in bridge circuits ). | There are many variations of this circuit, sometimes in combination with center tapped transformers, sometimes with multiple diodes ( as in bridge circuits ). | ||
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+ | Links: | ||
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+ | * [] | ||
<!---------------------------------------------------------------------> | <!---------------------------------------------------------------------> | ||
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this is a stubb, almost no useful content | this is a stubb, almost no useful content | ||
− | Use this circuit when you want to know the | + | Use this circuit when you want to know the peake voltage of an AC of time varying DC voltage. It typically differes from a power rectifier in that the circuit needs |
its own source of power, it does not pass thru the power of the input voltage, it also differes in that the typical voltage drop of the power diode ( in the range of .5 to 2 volts ) is largely eliminated. This is a signal processing circuit. | its own source of power, it does not pass thru the power of the input voltage, it also differes in that the typical voltage drop of the power diode ( in the range of .5 to 2 volts ) is largely eliminated. This is a signal processing circuit. | ||
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+ | Circuit: | ||
+ | [[Image:pds.png | Pull Down and Switch ]] | ||
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+ | Where | ||
+ | *R_PULLDOWN resistor which normally keeps the output low ( ground ). | ||
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Discussion: | Discussion: | ||
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Links: | Links: | ||
− | * [ | + | * [] |
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− | + | <!---------------------------------------------------------------------> | |
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This high side switch usually requires the base voltage of Q to be VPLUS_VDD plus the turn-on voltage of the transistor to turn all the way on. Another approach to the high side switch that requires a lower turn-on voltage is to use a PNP transistor as the switch. The base of the PNP is pulled up to VPLUS_VDD and connected to the collector of a small signal NPN transistor, Q2. Q2's emitter is connected to ground and its base is connected to the input signal through a current limiting resistor -- now the problem is that a high voltage is required to turn the switch off. | This high side switch usually requires the base voltage of Q to be VPLUS_VDD plus the turn-on voltage of the transistor to turn all the way on. Another approach to the high side switch that requires a lower turn-on voltage is to use a PNP transistor as the switch. The base of the PNP is pulled up to VPLUS_VDD and connected to the collector of a small signal NPN transistor, Q2. Q2's emitter is connected to ground and its base is connected to the input signal through a current limiting resistor -- now the problem is that a high voltage is required to turn the switch off. | ||
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== Transistor Emitter Follower == | == Transistor Emitter Follower == | ||
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*R_LOAD represents the resistance of the load | *R_LOAD represents the resistance of the load | ||
*Q is a npn bipolar transistor | *Q is a npn bipolar transistor | ||
− | *VPLUS_VDD is the power supply for the | + | *VPLUS_VDD is the power supply for the LED |
The current to drive the circuit is approximately the current to drive the load divided by the beta of the transistor. Use a Darlington connected transistor for a very high beta. | The current to drive the circuit is approximately the current to drive the load divided by the beta of the transistor. Use a Darlington connected transistor for a very high beta. | ||
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*[http://en.wikipedia.org/wiki/Common_collector Common collector From Wikipedia, the free encyclopedia] | *[http://en.wikipedia.org/wiki/Common_collector Common collector From Wikipedia, the free encyclopedia] | ||
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== Transistor -- Push Pull Circuit == | == Transistor -- Push Pull Circuit == | ||
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*[http://chungyan5.no-ip.org/vc/trunk/AltiumDesigner6ProjectFiles.zip?root=7segment_LEDs&view=log AltiumDesigner6ProjectFiles] | *[http://chungyan5.no-ip.org/vc/trunk/AltiumDesigner6ProjectFiles.zip?root=7segment_LEDs&view=log AltiumDesigner6ProjectFiles] | ||
*[http://www.dnatechindia.com/index.php/Tutorials/8051-Tutorial/7-Seg-Interfacing.html Interfacing Seven Segment to Microcontroller] | *[http://www.dnatechindia.com/index.php/Tutorials/8051-Tutorial/7-Seg-Interfacing.html Interfacing Seven Segment to Microcontroller] | ||
− | + | == Schmitt Trigger == | |
+ | Use this circuit when you want to sense if an input is either high or low. The circuit elmininate inputs that are "in between" and stops small noise signals from causing the input to rapildy oscillating from high to low. | ||
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+ | Circuit: | ||
+ | [[Image:opamp_st.png | Schmitt Trigger ]] | ||
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+ | Where | ||
+ | *RIN input resistor -- when this inputs more current than the positive feedback resistor the output switches to the voltage at the input, else it stays at the output voltage it has already reached. Typically lower in value than RFB. | ||
+ | *RFB positive feedback resistor the output voltage is feed back to the input and keeps the output at its current voltage. | ||
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+ | Discussion: | ||
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+ | The circuit is used to switch between two states even in the presence of noise. This is an somewhat unusual op amp circuit as it uses positive not negative feedback. See the references for a better explanation and variations on the circuit. | ||
+ | Schmidt Triggers are also available as integrated circuits which require no external components. | ||
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+ | More Information: | ||
+ | *[[OpAmp Links]] | ||
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== Oscillators == | == Oscillators == | ||
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Used to generate a voltage that depends upon light level. With the LDR on the "high side" the voltage will go up when the amount of light goes up. | Used to generate a voltage that depends upon light level. With the LDR on the "high side" the voltage will go up when the amount of light goes up. | ||
− | You need to use a resistor in series with the light dependent resistor, this combination lets a variable current flow through the circuit. The voltage across the resistor will vary with the light brightness ( so will the voltage across the LDR, the two will total | + | You need to use a resistor in series with the light dependent resistor, this combination lets a variable current flow through the circuit. The voltage across the resistor will vary with the light brightness ( so will the voltage across the LDR, the two will total to input voltage. ) What size resistor should you use? A ruel of thumb: Put the LDR in medium brightness and mesure its resistance with a ohm meter. Use that value resistor then in medium light you will get 1/2 the input voltage at the output. |
Circuit: | Circuit: | ||
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*[http://itp.nyu.edu/physcomp/sensors/Schematics/WheatstoneBridge Wheatstone Bridge] | *[http://itp.nyu.edu/physcomp/sensors/Schematics/WheatstoneBridge Wheatstone Bridge] | ||
*[http://physics.kenyon.edu/EarlyApparatus/Electrical_Measurements/Capacitance_Bridge/Capacitance_Bridge.html Capacitance Bridge] This one is an antique. | *[http://physics.kenyon.edu/EarlyApparatus/Electrical_Measurements/Capacitance_Bridge/Capacitance_Bridge.html Capacitance Bridge] This one is an antique. | ||
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== Further Reading == | == Further Reading == |