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*LM35 Temperature Sensor | *LM35 Temperature Sensor | ||
*555 Timer astable oscillator | *555 Timer astable oscillator | ||
− | * | + | *diode for forward drop bias voltage |
− | * | + | *row and collumn connection |
*charge pump | *charge pump | ||
− | * | + | *transformer |
+ | *voltage multiplier | ||
*diode logical or | *diode logical or | ||
+ | *RC timer | ||
+ | *diode full wave bridge | ||
*H Bridge | *H Bridge | ||
− | An H bridge is an electronic circuit that causes current to flow in one direction or the other ( from a | + | 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. | It is an electronic double pole double throw switch. | ||
− | + | [http://code.rancidbacon.com/ElectronicsElectronics] See Section on ''H-Bridge'' | |
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− | + | *Simple Oscillator circuits | |
− | * | + | *Current mirrors |
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*RF Mixers | *RF Mixers | ||
− | * | + | *Tranistor Current Mirror |
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*[[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 ) == | ||
− | A current Sense Resistor is a low value of resistor that is placed in | + | A current Sense Resistor is a low value of resistor that is placed in parallel with some other circuit. We can then measure the voltage across the resistor to compute the current. If the resistor has a low value compared to other components we can ignore the effect on the circuit. We use the word shunt when the voltage is measured by a device that has a fairly low resistance itself. We then have to do a more careful calculation of how the current is shared by the two devices. |
Circuit: | Circuit: | ||
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Where | Where | ||
*R shunt resistor used to sense the current ( and divert it from the meter ). Usually much less in value than the internal resistance of the meter. | *R shunt resistor used to sense the current ( and divert it from the meter ). Usually much less in value than the internal resistance of the meter. | ||
− | *METER meter or other device used to measure the voltage across the shunt | + | *METER meter or other device used to measure the voltage across the shunt reistor. Often the resistance of the meter is ignored ( if high ). |
*BATTERY a battery or other voltage source. | *BATTERY a battery or other voltage source. | ||
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Discussion: | Discussion: | ||
− | In the old days a sensitive meter, say 50 mv full scale, would be used with a set of shunt, some looking like metal bars, to measure a wide range of currents, up to and exceeding 50 amps | + | In the old days a sensitive meter, say 50 mv full scale, would be used with a set of shunt, some looking like metal bars, to measure a wide range of currents, up to and exceeding 50 amps. |
+ | There are many inaccuracies in this entry. A current sense resistor must go in series in order to carry the same current as the load. Putting the resistor in series guarantees that it will carry the same current as the load because of Kirchoff Current Law (KCL). The current in the current sense resistor can then be determined from the voltage across it by Ohm's Law, and this will be the same as the current in the load. The technique described in this entry would only work if the the impedance of the network which the sense resistor was connected across was precisely known. However if the impedance of the network is known, there is no need for a current sense resistor as Ohms Law could give the current directly. Finally, the schematic omits a load and the symbol for the battery is upside down (assuming the author intended ground to be the lowest node on the schematic and voltages to be positive). -LPM | ||
− | + | More information: | |
#[http://www.scienceshareware.com/bg-current-monitoring.htm Scienceshareware.com's How A Precision Resistor Is Used to Measure / Calculate Current and Power in an Electrical Circuit.] | #[http://www.scienceshareware.com/bg-current-monitoring.htm Scienceshareware.com's How A Precision Resistor Is Used to Measure / Calculate Current and Power in an Electrical Circuit.] | ||
#[http://www.maxim-ic.com/appnotes.cfm/appnote_number/746/ High-Side Current-Sense Measurement: Circuits and Principles] | #[http://www.maxim-ic.com/appnotes.cfm/appnote_number/746/ High-Side Current-Sense Measurement: Circuits and Principles] | ||
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Discussion: | Discussion: | ||
− | The idea here is that R2 is a current sense | + | The idea here is that R2 is a current sense reistor. When the sense voltage across R2 reaches about .7 ( for silicon transistors ) Q2 begins to conduct and diverts the base drive from Q1 cutting its output current. So the max. current from the circuit is reached when I*R2 = .7. This circuit can be used to protect amplifiers ( including push pull amps. ), power supplies and other circuits; or it can be used as a constant current circuit. It is not a precision circuit, but it is cheap, simple, and effective circuit. |
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#[http://freecircuitdiagram.com/2008/08/27/variable-adjustable-current-limiter-circuit/ Variable (Adjustable) Current Limiter Circuit ] This is a bit more complicated version using a transistor to drive a darlington transistor, with the limit being adjustable. | #[http://freecircuitdiagram.com/2008/08/27/variable-adjustable-current-limiter-circuit/ Variable (Adjustable) Current Limiter Circuit ] This is a bit more complicated version using a transistor to drive a darlington transistor, with the limit being adjustable. | ||
#[http://forum.allaboutcircuits.com/showthread.php?t=32709 Current Source for Resistance Measurement] | #[http://forum.allaboutcircuits.com/showthread.php?t=32709 Current Source for Resistance Measurement] | ||
− | #[http://powerampdesign.net | + | #[http://docs.google.com/gview?a=v&q=cache%3Axoux8Ax7B_UJ%3Awww.powerampdesign.net%2Fimages%2FAN-12_The_Problem_with_Current_Limit.pdf+amplifier+current+limit&hl=en&gl=us&pli=1 The Problem with Current Limit] Discusses this circuit as applied to a power amplifier. |
#[http://www.instructables.com/id/Constant-current-LED-Tester/ Constant current LED-Tester] Simple application of the circuit as an LED tester. | #[http://www.instructables.com/id/Constant-current-LED-Tester/ Constant current LED-Tester] Simple application of the circuit as an LED tester. | ||
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The amount of ripple in a simple circuit like this can be determined from the supply frequency voltage, output current, and the capacitance. The amount of time without any input voltage is 1/2f. Given an output current I, the charge transferred is is I/2f. The voltage sag is then just the charge divided by the capacitance, or I/2fC. An inductor added to this circuit will compensate for voltage sag by inducing a voltage if the current starts to drop. | The amount of ripple in a simple circuit like this can be determined from the supply frequency voltage, output current, and the capacitance. The amount of time without any input voltage is 1/2f. Given an output current I, the charge transferred is is I/2f. The voltage sag is then just the charge divided by the capacitance, or I/2fC. An inductor added to this circuit will compensate for voltage sag by inducing a voltage if the current starts to drop. | ||
− | + | More Information: | |
<!---------------------------------------------------------------------> | <!---------------------------------------------------------------------> | ||
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== Light Emitting Diode ( with current limiting resistor ) == | == Light Emitting Diode ( with current limiting resistor ) == | ||
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*[http://www.evilmadscientist.com/article.php/throw Some thoughts on throwies] interesting notes on the resistor normally used with an LED. | *[http://www.evilmadscientist.com/article.php/throw Some thoughts on throwies] interesting notes on the resistor normally used with an LED. | ||
− | == Op | + | == Op amp Non Inverting Amplifier == |
Use this circuit where the signal you have is not as large as you want, or cannot provide enough current. It is called non inverting because a positive input produces a positive output ( An inverting amplifier produces a negative output when given a positive input ). | Use this circuit where the signal you have is not as large as you want, or cannot provide enough current. It is called non inverting because a positive input produces a positive output ( An inverting amplifier produces a negative output when given a positive input ). | ||
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More Information: | More Information: | ||
*[[OpAmp Links]] | *[[OpAmp Links]] | ||
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<!---------------------------------------------------------------------> | <!---------------------------------------------------------------------> | ||
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Discussion: | Discussion: | ||
The values of RIN and RFB are not very critical and are normally 0 ohms, just a straight connection. The op amp here is a quad or 4 op amp part, we are using just one section of it. Power needs to be supplied to pin 8 and 4 in the usual way for op amps. | The values of RIN and RFB are not very critical and are normally 0 ohms, just a straight connection. The op amp here is a quad or 4 op amp part, we are using just one section of it. Power needs to be supplied to pin 8 and 4 in the usual way for op amps. | ||
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More information: | More information: | ||
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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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* [http://roguescience.org/wordpress/?page_id=11 Roguescience Arduino Tutorials 4.2 Pull-up/down resistors, debouncing] | * [http://roguescience.org/wordpress/?page_id=11 Roguescience Arduino Tutorials 4.2 Pull-up/down resistors, debouncing] | ||
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Discussion: | Discussion: | ||
− | The circuit above is very basic. Practical circuits normally include filter capacitors on both the input and the output. Most regulators protect against both over temperature and over current. Regulators come in various voltages both positive and negative. They also vary in maximum current output. There are also adjustable regulators, ways of using regular regulators as adjustable ones, and ways of boosting the current output. The spec sheets often describe how to do these things. Voltage regulators “use up” a couple of volts of the input voltage, low drop out regulators have use less, cost more. It is a good idea to check the specification for any regulator you are going to use. The LM78xx ( positive ) and LM79xx ( negative ) are quite common | + | The circuit above is very basic. Practical circuits normally include filter capacitors on both the input and the output. Most regulators protect against both over temperature and over current. Regulators come in various voltages both positive and negative. They also vary in maximum current output. There are also adjustable regulators, ways of using regular regulators as adjustable ones, and ways of boosting the current output. The spec sheets often describe how to do these things. Voltage regulators “use up” a couple of volts of the input voltage, low drop out regulators have use less, cost more. It is a good idea to check the specification for any regulator you are going to use. The LM78xx ( positive ) and LM79xx ( negative ) are quite common. |
More information: | More information: | ||
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*[http://en.wikipedia.org/wiki/7805 7805 From Wikipedia, the free encyclopedia] | *[http://en.wikipedia.org/wiki/7805 7805 From Wikipedia, the free encyclopedia] | ||
*[http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html Simple 5V power supply for digital circuits] | *[http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html Simple 5V power supply for digital circuits] | ||
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== Transistor Low Side Switch == | == Transistor Low Side Switch == | ||
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An example calculation would be nice, and will appear later. | An example calculation would be nice, and will appear later. | ||
− | This circuit is sometimes called "grounded-emitter configuration". | + | This circuit is sometimes called "grounded-emitter configuration". |
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More Information: | More Information: | ||
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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 == | ||
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shows a "simple" noninverting gain circuit, | shows a "simple" noninverting gain circuit, | ||
and explains what all the "extra" parts do. | and explains what all the "extra" parts do. | ||
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[[Category:Components]][[Category:Schematics]] | [[Category:Components]][[Category:Schematics]] |