Recent Questions - Electrical Engineering Stack Exchange most recent 30 from electronics.stackexchange.com 2022-05-29T04:47:19Z https://electronics.stackexchange.com/feeds https://creativecommons.org/licenses/by-sa/4.0/rdf https://electronics.stackexchange.com/q/621492 0 What is the maximum voltage that can be used on a modified RG6 Coax Cable to turn its insulator into an Electret? Jeff Owens https://electronics.stackexchange.com/users/314469 2022-05-29T04:19:38Z 2022-05-29T04:19:38Z <p>The idea is to make an electret, using coax cable. This has been done before, but not through the following method.</p> <p>The material for would be based using an RG6 Coax Cable:</p> <p>Center core - copper</p> <p>Dielectric insulator - Teflon, PTFE</p> <p>Metallic shield - copper</p> <p>Plastic Jacket - removed depending on its melting point</p> <p>Method:</p> <p>The Plastic Jacket is removed.</p> <p>The cable is trimmed so the center core’s copper wire protrudes past the insulator’s ends. So, looking at the cable, the center wire sticks out both sides. These two ends are then connected to each other, making the positive electrode.</p> <p>[Please note, as a conductor, the center core’s copper wire can take 3 amps. It has now been repurposed from conductor to an electrode.]</p> <p>The metallic shield does not protrude the dielectric. It stops where the teflon stops. The metallic shield makes the negative electrode.</p> <p>[The metallic shield has now been repurposed as an electrode.]</p> <p>The cable is heated to the dielectric’s melting point (phase shift). The melting point is 327 degrees Celsius</p> <p>Charge is run to the modified central wire, now the positive electrode.</p> <p><strong>What is the maximum voltage that can be used?</strong></p> <p><strong>What type of instruments could be used to achieve this?</strong></p> <p>Result (desired):</p> <p><strong>This method should produce an electret that’s charge formation is directed from its dielectric center to its dielectric periphery.</strong></p> <p>Note:</p> <p>The original method used 30 kV. The charge was run from cable’s end to end, as a conductor, not between two electrodes, as a capacitor. Its dielectric was polyethylene, melting point 105 degrees Celsius. It was heated to a temperature to approach that.</p> <p>If needed - PTFE (dielectric constant 2.1 MHz, Volume resistivity &gt;10^18 ohm x cm, Surface Resistivity</p> <blockquote> <p>10^18 ohm/sq)</p> </blockquote> <p>Thank you :)</p> https://electronics.stackexchange.com/q/621491 0 Difference between voltage measuring from induction motor junction box and VFD output terminal user11004178 https://electronics.stackexchange.com/users/307108 2022-05-29T04:14:37Z 2022-05-29T04:14:37Z <p>I want to measure stator voltage of VFD fed induction motor. It's common to measure from juction box, which should be the exact stator voltage of induction motor, but I wonder if it's possible to measure the voltage from VFD output terminal. What's the difference between the voltage from VFD output terminal and from motor junction box? Is the motor junction box voltage merely a filtered version of VFD terminal voltage?</p> https://electronics.stackexchange.com/q/621487 0 BTA16 for 1hp motor kdm6389 https://electronics.stackexchange.com/users/159628 2022-05-29T03:28:28Z 2022-05-29T03:28:28Z <p>I have following component:</p> <ol> <li>ESP8266</li> <li>BTA16</li> <li>MOC3021</li> <li>Compressor-Motor {Rated :(Single Phase, 220V, 1hp=0.75kW, 1450rpm) (with 2 big capacitor 20uF, 50uF of 400V)}</li> </ol> <p>I don't know equivalent, L or C or R of Motor.</p> <p>I want to ask</p> <ol> <li>can BTA can handle motor-load?</li> <li>(since it is rated for 16A, and 120A for 20ms). Do I need snubber RC, but I don't know how to calculate RC if so(I am from CS/IT, zero knowledge of EEE) power-loss due to snubber?</li> <li>is there any circuit diagram to refer for switching such high load. All I get is diming controlling speed, I want just on/off. (no-fast-switching t&gt;10s)</li> </ol> <p><img src="https://i.stack.imgur.com/ZSIuS.png" alt="schematic" /></p> <p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fZSIuS.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p> https://electronics.stackexchange.com/q/621482 0 Will reversing the polarity of a K thermocouple damage it? Feynman137 https://electronics.stackexchange.com/users/276815 2022-05-29T02:31:01Z 2022-05-29T03:25:30Z <p>I have a K thermocouple connected to a <a href="https://www.mouser.com/ProductDetail/Maxim-Integrated/MAX31855KASA%2BT?qs=ffX8NcjNb2TujkrPyW1z%252Bg%3D%3D" rel="nofollow noreferrer">MAX31855KASA+T</a> IC supplied by 3.3V. I mistakenly reversed the polarity and was taking reading from it for about 1hr. I am noticing the instrument is now somewhat inaccurate. Freezing water was registering 10F and boiling water about 180F. Did the polarity reversal damage the instrument? I have replaced the IC but am still noticing the inaccuracy.. Isn't this just measuring the dV across two dissimilar metals, I imagine this would be pretty robust.</p> https://electronics.stackexchange.com/q/621480 0 Which matrix index should be used when Y (admittance) is shown to compose a circuit segment mapped to an ABCD matrix? Y21? Other? KJ7LNW https://electronics.stackexchange.com/users/256265 2022-05-29T01:25:11Z 2022-05-29T01:25:11Z <p>I would like to cascade a serial capacitor with a shunt inductor to form an L-match network by multipling two ABCD parameters and convert the result to S-parameters that represent the composite network. As a starting point, the capacitor's S-parameters were converted to an ABCD matrix using transforms <a href="https://www.researchgate.net/publication/3118645" rel="nofollow noreferrer">from here</a>. Now I need to create an ABCD matrix for the shunt inductor.</p> <p>To avoid <a href="https://xyproblem.info/" rel="nofollow noreferrer">the X/Y problem</a>, ultimately this is my question, but please also address the questions at the bottom to help my understanding of the situation: <strong>How do you transform an ABCD matrix to form a shunt so I can multiply it (chain) with another ABCD matrix?</strong> (related questions below)</p> <p>Here is what I've discovered so far:</p> <p><a href="https://youtu.be/rfbvmGwN_8o" rel="nofollow noreferrer">This video</a> shows how to create an ABCD matrix for various circuit segments. For my purpose, this frame shows the ABCD matrix for the shunt component (the inductor, in my case):</p> <p><a href="https://i.stack.imgur.com/yg4u2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yg4u2.png" alt="Serial and shunt ABCD matrix parameters" /></a></p> <p><strong>Questions:</strong></p> <ul> <li><p>Given a two-port Y-parameter matrix representing the inductor, which Y matrix index would I use for the &quot;C&quot; value of the ABCD matrix pictured above?</p> <ul> <li><p>Intuition says to use <span class="math-container">\$C=Y_{21}\$</span>, but I think that means the remaining indexes (11, 12, 22) are lost information so, for example, the <span class="math-container">\$Y_{11}\$</span> input admittance behavior would not present in the composite circuit after the two ABCD matrixes that represent the serial capacitor and shunt inductor are multiplied. Is this a a correct interpretation?</p> </li> <li><p>If so, Is there a more accurate way to transform the 2-port 2x2 Y matrix into a shunt ABCD matrix where no information is lost?</p> </li> </ul> </li> </ul> https://electronics.stackexchange.com/q/621478 -1 2 input voltage detector ba lao https://electronics.stackexchange.com/users/314455 2022-05-29T01:13:40Z 2022-05-29T01:13:40Z <p>I am going to build a &quot;2 input voltage detector&quot;.</p> <p>If the 2 input voltage crosses or reaching the same value, the output toggles (from 0V to 1V or 1V to 0V).</p> <p>by the way these 2 inputs require very large impedance to the detector because these input nodes are sometimes temporarily floating, supporting by capacitor.</p> <p>How to build this circuit?</p> https://electronics.stackexchange.com/q/621477 0 How do the 5 elementary two-port networks map to unbalanced networks with a common ground? KJ7LNW https://electronics.stackexchange.com/users/256265 2022-05-29T00:28:10Z 2022-05-29T00:41:36Z <h3>Background (questions below)</h3> <p>I've been trying to understand how to use S/Y/Z/A-parameter matrixes to create circuits mathematically with 2-port components in series, parallel, and ground-shunt. For example, each elementary twoport element below might be an inductor or capacitor.</p> <p><a href="http://qucs.sourceforge.net/tech/node98.html#SECTION001613000000000000000" rel="nofollow noreferrer">This page</a> gives a good explanation of the of the possible elementary two-port combinations and the math to combine them:</p> <p><a href="https://i.stack.imgur.com/3rBpP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3rBpP.png" alt="Two-port transformations of elementary twoport networks" /></a></p> <ol> <li>parallel-parallel: Y-parameters: <span class="math-container">\$Y = Y_{1} + Y_{2}\$</span></li> <li>cascaded twoports: A-parameters: <span class="math-container">\$A = A_{1}\cdot A_{2}\$</span></li> <li>series-series: Z-parameters: <span class="math-container">\$Z = Z_{1} + Z_{2}\$</span></li> <li>series-parallel: H-parameters: <span class="math-container">\$H = H_{1} + H_{2}\$</span></li> <li>parallel-series: G-parameters: <span class="math-container">\$G = G_{1} + G_{2}\$</span></li> </ol> <h3>Commentary</h3> <p>Converting the balanced-2-port networks (1) &quot;parallel-parallel&quot; and (2) &quot;cascaded twoports&quot; to an unbalanced-2-port network with a common ground seems trivial, just ground a port on each side and you have it (right?).</p> <p>But what about #3-#5? I've tried re-arranging them on paper to see what they might mean in an unbalanced common-ground sense but I've not made any meaningful progress.</p> <h3>Questions:</h3> <ul> <li>Can circuits #3-#5 be mapped to an unbalanced network with common ground? <ul> <li>If so, what would they look like when drawn as a schematic?</li> </ul> </li> </ul> https://electronics.stackexchange.com/q/621476 0 HC05 Bluetooth Module with Pi Pico Not Discoverable Rafael Zasas https://electronics.stackexchange.com/users/314465 2022-05-29T00:04:53Z 2022-05-29T00:04:53Z <p>I have a HC05 Bluetooth module wired up to my Pi Pico with the following code.</p> <pre class="lang-c prettyprint-override"><code>//Example script of USB serial #include &quot;pico/stdlib.h&quot; #include &lt;stdio.h&gt; #include &quot;hardware/uart.h&quot; int main() { const uint LED_PIN = PICO_DEFAULT_LED_PIN; gpio_init(LED_PIN); gpio_set_dir(LED_PIN, GPIO_OUT); // Initialise UART 0 uart_init(uart0, 9600); // Set the GPIO pin mux to the UART - 0 is TX, 1 is RX gpio_set_function(0, GPIO_FUNC_UART); gpio_set_function(1, GPIO_FUNC_UART); while (true) { gpio_put(LED_PIN, 1); sleep_ms(250); gpio_put(LED_PIN, 0); sleep_ms(250); uart_puts(uart0, &quot;Hello world!\n\r&quot;); sleep_ms(1000); } } </code></pre> <p>The bluetooth module is blinking rapidly but I cant see it when searching for devices on my android phone or laptop.</p> <p>Is there some configuration steps I am missing?</p> <p>Am I able to set master/slave/Automatic modes with the PICO or do I need an Arduino?</p> https://electronics.stackexchange.com/q/621474 2 Does this AC to DC + breadboard setup have the ability to kill/severely hurt me? DonutGaz https://electronics.stackexchange.com/users/274262 2022-05-28T23:39:23Z 2022-05-29T02:21:17Z <p>I'm currently building a PC peripheral that uses an AC to DC converter to power a set of DC fans. I'm not a trained EE or electrician, so I want to make sure I'm not putting myself a risk with this setup.</p> <p>Essentially, I have the AC to DC converter pictured below with a screw terminal block on the DC end plugged into my breadboard power rails:</p> <p><a href="https://i.stack.imgur.com/DLgZS.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DLgZS.jpg" alt="AC to DC converter" /></a><br /> <a href="https://i.stack.imgur.com/r3tEq.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/r3tEq.jpg" alt="My precarious-looking DC screw terminal block" /></a></p> <p>Assuming I'm using a standard 120V US outlet, am I putting myself at serious risk? I know it doesn't take much current to kill someone, so I get really concerned with this exposed wiring when I see this can output 3A at 12V.</p> https://electronics.stackexchange.com/q/621473 0 Stm32CubeIDE ADC interrupt code generation Ike https://electronics.stackexchange.com/users/314466 2022-05-28T23:35:40Z 2022-05-28T23:35:40Z <p>I configured the ADC interrupt and its priority in the Stm32CubeIDE configuration pannel but the autogenerated code does not mention them at all, other than others configuration e.g. HAL_NVIC_SetPriority(EXTI4_15_IRQn, 1, 0); HAL_NVIC_EnableIRQ(EXTI4_15_IRQn); Do we need to declare them for complementing ? /Are they done somewhere else implicitly ?</p> <p>In another project, I configured the DMA to store ADC values with DMA interrupts, I found that we can use HAL_ADC_ConvCpltCallback without enabling the ADC interrupt. Someone could explain it?</p> <p>Thanks</p> https://electronics.stackexchange.com/q/621471 0 What does \$\beta\$ represent with respect to the length of a transmission line? KJ7LNW https://electronics.stackexchange.com/users/256265 2022-05-28T23:18:39Z 2022-05-29T00:12:35Z <p>The picture below shows the ABCD parameters for a transmission line of length <span class="math-container">\$l\$</span> from <a href="https://youtu.be/rfbvmGwN_8o" rel="nofollow noreferrer">this video</a>.</p> <p><strong>Question: What does <span class="math-container">\$\beta\$</span> represent?</strong></p> <p><a href="https://i.stack.imgur.com/CMY2A.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CMY2A.png" alt="ABCD Parameters of a transmission line" /></a></p> https://electronics.stackexchange.com/q/621469 0 Can I use a connector at a higher amp if its lower voltage? user2508385 https://electronics.stackexchange.com/users/76751 2022-05-28T22:57:14Z 2022-05-28T23:16:27Z <p>I'm making a PCB board where I'd like a barrel connector rated for 10 amps. I have been using part this part which is rated for 10 amps at 50V.</p> <p><a href="https://www.digikey.com/en/products/detail/globtek-inc/JACK-C-PC-10A-RA-R/8597889?s=N4IgTCBcDaIFIEEDCBpAtEtAFTBGADAmgEoIAUxAlCALoC%2BQA" rel="nofollow noreferrer">https://www.digikey.com/en/products/detail/globtek-inc/JACK-C-PC-10A-RA-R/8597889?s=N4IgTCBcDaIFIEEDCBpAtEtAFTBGADAmgEoIAUxAlCALoC%2BQA</a></p> <p>My PCB board however only runs at 5V. Can I safely use a barrel connector that's rated for, 6 amps rated for 48V, but at 5V and 10 amps? Or are parts rated for 6amps at any voltage?</p> <p>I'd like to get my cost down and switching to a cheap plastic unshielded barrel connector saves me $2.75 per board.</p> <p><a href="https://www.digikey.com/en/products/detail/tensility-international-corp/54-00129/9685438" rel="nofollow noreferrer">https://www.digikey.com/en/products/detail/tensility-international-corp/54-00129/9685438</a></p> https://electronics.stackexchange.com/q/621465 0 Software disable brownout detection (BOD) on ATmega328p maxschlepzig https://electronics.stackexchange.com/users/56807 2022-05-28T21:58:48Z 2022-05-28T22:40:27Z <p>I'm trying to disable the brownout detection (BOD) of a ATmega328p at runtime, before putting it into power-down sleep like this:</p> <pre><code> set_sleep_mode(SLEEP_MODE_PWR_DOWN); cli(); // disable interrupts sleep_enable(); sleep_bod_disable(); sei(); // enable interrupts sleep_cpu(); // ...zZz...zZz...zZz... sleep_disable(); </code></pre> <p>But this doesn't work. That means I measure no difference in power consumption during power-down sleep: 17 µA before and after (MCU runs at 3.3V)</p> <p>For comparison, disabling BOD via the efuse (i.e. I set it to 0xff with avrdude) does work as expected, i.e. after that the power-consumption drops to 0.13 µA during power-down sleep. (which pretty much matches what is specified in the datasheet)</p> <p>Is there some pitfall I'm missing here? Is the above power-down/BOD sequence sub-optimal?</p> https://electronics.stackexchange.com/q/621455 0 Diode-connected BJT vs base-emitter BJT diode vs diode ONLYA https://electronics.stackexchange.com/users/251585 2022-05-28T20:35:03Z 2022-05-28T23:09:47Z <p>I was having a look at the circuit design of Keithley 236 SMU. You can find this part of the circuit in the Keithley 236 Service Manual.</p> <p><a href="https://i.stack.imgur.com/LThGm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LThGm.png" alt="Circuit Diagram" /></a></p> <p>Q47 is a BJT. Only the base and emitter are connected, which means it is used as a diode.</p> <p>I also made a simulation to compare these three variations, which seems not a lot of difference. (Pink is voltage, blue is current) <a href="https://i.stack.imgur.com/xthAr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xthAr.png" alt="Simulation" /></a></p> <p>My questions are:</p> <ul> <li>Is it better to use diode-connected BJT to enhance its flowing current without affecting too much the forward voltage in this circuit?</li> <li>Are there any particular reasons against using a normal diode or a diode-connected BJT in the original design?</li> <li>What are the differences among those three kinds of diodes (i.e. diode-connected BJT vs base-emitter BJT diode vs diode)? (I know there is an answer about diode-connected BJT and diode <a href="https://electronics.stackexchange.com/a/497546/251585">here</a>.)</li> <li>In this design, all these three &quot;diodes&quot; are used. How could I determine which one to use in the design?</li> </ul> <p>My initial guess is the cost and part availability but I would like to know if there is any design consideration about this.</p> <h2>Edit - This is where diode-connected BJTs are used in this design.</h2> <p><a href="https://i.stack.imgur.com/4dGDa.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4dGDa.png" alt="additional schematic" /></a></p> https://electronics.stackexchange.com/q/621450 4 Slew rate of two stage OTA sumita sahu https://electronics.stackexchange.com/users/200117 2022-05-28T19:55:08Z 2022-05-29T03:37:20Z <p>I have learnt two stage opamp designing from books and yourtube videos, but have always failed to understand slew rate formula which is I5/Cc(I5 is bias current of M5 and Cc is compensation capacitor). Always thought that slew rate should depend on load capacitor and not compensation capacitor. After thinking a lot I finally simulated by giving opposite phase square wave to input and looked at all current values. It looks like the load capacitor is getting charged by second stage PMOS and discharged by second stage NMOS. It seems like the contribution of current from first stage is very small. If this is true shouldn't the slew rate be a function of current of second stage transistors and load capacitor?</p> <p>I have attached one image for your reference, the up arrow means voltage is going from zero to vcc and the down arrow means voltage is going vcc to zero. <a href="https://i.stack.imgur.com/GXZGv.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/GXZGv.jpg" alt="Slew rate of OTA" /></a></p> https://electronics.stackexchange.com/q/621447 0 An analog voltage level keeper ba lao https://electronics.stackexchange.com/users/314455 2022-05-28T19:37:37Z 2022-05-29T03:54:45Z <p>How do I build an analog voltage keeper?</p> <p>The reason is that I have an electrical node and the fact is that its voltage drops over time.</p> <p>I can simply increase the capacitance value. It works, but for my circuit design this is not allowed as I have a certain timing constraint.</p> <p><a href="https://i.stack.imgur.com/4FeSB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4FeSB.png" alt="enter image description here" /></a></p> <p><a href="https://i.stack.imgur.com/5TTjd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5TTjd.png" alt="enter image description here" /></a></p> https://electronics.stackexchange.com/q/621370 1 Reading ADC value on a button press Noman https://electronics.stackexchange.com/users/262268 2022-05-28T06:15:48Z 2022-05-29T04:46:10Z <p>I have a keypad matrix that outputs the voltage level based on the button pressed. Normally, it outputs a maximum voltage (3.3V) and at the press of the button, it outputs the corresponding voltage level based on the voltage dividers (from 0 - 3.3V.)</p> <p>What I want to do is instead of constantly reading the ADC to determine which button was pressed, I want an interrupt to be generated when the button is pressed and then start the ADC conversion so I only have to enable the ADC when a button was pressed. Currently, I have ADC in continuous mode, an interrupt is generated when ADC conversion gets completed and I have an if statement to check that if the value is not 3.3V, then I process the data for the button press. This, I believe, is not an efficient way of doing this. The keypad schematics are added below.</p> <p><a href="https://i.stack.imgur.com/Ggewf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ggewf.png" alt="Keypad" /></a></p> https://electronics.stackexchange.com/q/621350 1 Nichrome strip and resistor Fouad II https://electronics.stackexchange.com/users/314337 2022-05-27T23:23:14Z 2022-05-29T01:11:51Z <p>I'm trying to build a heater connected to 220 VAC, 50 Hz using a nichrome strip (2.3 Ω/m) and I'm going to use 1 meter or less (60 to 70 cm).</p> <p>I know that this setup won't work at all with 220 VAC so my question is: can I add a resistor in series to reach the desired wattage which is 750 W to 1 kW? If yes, what is the resistor value? And are there any other solutions?</p> <p>P.S. I also have nichrome wire with 1.75 Ω/m.</p> https://electronics.stackexchange.com/q/621325 1 Howland current source for negative currents Nick https://electronics.stackexchange.com/users/210097 2022-05-27T19:23:14Z 2022-05-28T22:44:25Z <p>I am currently in the process of utilizing the design of Howland in order to derive a source that is able to provide an <span class="math-container">\$I_{out}\$</span> between <span class="math-container">\$0A\$</span> and <span class="math-container">\$30A\$</span> at the output load <span class="math-container">\$R_L\$</span>. <a href="https://i.stack.imgur.com/KG5uD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KG5uD.png" alt="enter image description here" /></a></p> <p>As you can see from the figure, the op-amp is configured similar to a differential amplifier. The output current can be calculated using the equation <span class="math-container">\$I_{out} = \frac{k \cdot V_{IN}}{R_s}\$</span> whereby <span class="math-container">\$k\$</span> is given as <span class="math-container">\$k = \frac{R_2}{R_1}\$</span>. The output of the op-amp drives the N-MOSFET and by varying the input voltage <span class="math-container">\$V_{IN}\$</span> at the non-inverting input, the desired amplitude of the current can be set. The voltage <span class="math-container">\$V_{IN}\$</span> comes from a DAC.</p> <p>I am able to achieve the desired currents however I am now asking myself if it is possible to use this kind of circuit in order to achieve currents in the interval between <span class="math-container">\$0A\$</span> and <span class="math-container">\$-30A\$</span>. I am not sure if this is simply a task of using a P-MOSFET and connecting it's drain with ground and applying a negative voltage of <span class="math-container">\$-18V\$</span> at the load. I tried simulating this kind of situation however I was not able to achieve the desired result. Any help on this matter would be appreciated.</p> <p><strong>EDIT:</strong> I came up with a possible circuit for my problem: <a href="https://i.stack.imgur.com/22vo6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/22vo6.png" alt="enter image description here" /></a> I am now using a P-MOSFET where the drain is connected to the negative supply rail which I increased for now to <span class="math-container">\$-50V\$</span>. The same also applies to the positive supply rail. Additionally, I also changed the op-amp used to drive the MOSFET and removed the op-amp in the positive feedback path.</p> <p><a href="https://i.stack.imgur.com/2f84A.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2f84A.png" alt="enter image description here" /></a> As you can see from the DC-sweep, I am now able to control the current through the load by applying a voltage between <span class="math-container">\$0V\$</span> and <span class="math-container">\$-3.3V\$</span>. The formula for the output current still applies, however now the sign is inverted. As I intend to control the output current with a DAC, I would have to use an inverting amplifier in order to convert the voltage of the DAC to a negative one. As suggested by Jens, I included a Zener-Diode between the gate and the source. Are there any additional improvements for this circuit possible?</p> https://electronics.stackexchange.com/q/621274 -2 Setting up equations for current, voltage and power analysis of linear electrical net Rafsan https://electronics.stackexchange.com/users/314371 2022-05-27T12:35:50Z 2022-05-29T03:12:21Z <p>The directions of currents are throwing me off a bit.</p> <p>I think I should use mesh analysis here, but I'm not sure about the exact equation. For example, in the topmost mesh, should I write -120v + 20i1 = 0? I can share the equivalent resistance if needed.</p> <p><a href="https://i.stack.imgur.com/4Hkc0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4Hkc0.png" alt="enter image description here" /></a></p> https://electronics.stackexchange.com/q/621094 -1 The purpose of capacitors in a ZCD circuit of dimmer V.Ajall https://electronics.stackexchange.com/users/182611 2022-05-26T08:00:28Z 2022-05-29T01:20:32Z <p>I was searching the net looking for some high-voltage zero-cross detection circuit for a dimmer. Then I found this circuit on the net:</p> <p><a href="https://i.stack.imgur.com/HUPOL.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HUPOL.jpg" alt="enter image description here" /></a></p> <p>But on the first try after zero seconds, one of the 0.1 μF capacitors exploded. The capacitor was of the polyester type.</p> <p>My first question is: why are the 0.1 μF capacitors needed, and second: if they are really needed, what sort of capacitor is suitable for this circuit? Should the preceding resistors be changed to 100 kΩ? The H11aa1's datasheet states that the diodes' forward current is 0.01 A.</p> https://electronics.stackexchange.com/q/572171 0 Is it normal to have 0 volts between the AC inputs of diode bridge rectifier? miracle genuis https://electronics.stackexchange.com/users/288574 2021-06-21T12:47:40Z 2022-05-29T01:04:25Z <p>I have some basic knowledge about electronics. I am trying to repair an ATX 250W power supply.</p> <p>In the picture below, I measured 0V with my DMM between points C and D (AC inputs of diode bridge rectifier.) I was expecting 220V AC.</p> <p>Measuring with the DMM set to &quot;diode,&quot; the bridge rectifier entries give me this:</p> <ul> <li>FC = 0.5</li> <li>FD = 0.5</li> <li>EC = 0.5</li> <li>ED = 0.5</li> </ul> <p>These measurements lead me believe that the bridge is OK. Why is there then 0V between the AC inputs?</p> <p>Measuring the capacitors with DMM set to &quot;capacitor&quot; gives me the right values (off by about 5% or so.)</p> <p>When measuring the capacitors with the DMM set to resistance 200M, I get 1. I was expecting the value to rise as they charge but since they are 2.2nF (orange) and 4.7nF (yellow), I suppose they may be charging fast.</p> <p>The voltage between points A and B is 220V AC (Since A and C are the same point, is this mean C and D are shorted ).</p> <p>Does anyone have an idea what could be wrong these observations?</p> <p>The image below shows the wiring of the components in the power supply.</p> <p><a href="https://i.stack.imgur.com/oeoch.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oeoch.jpg" alt="enter image description here" /></a></p> <p>the back of the board <a href="https://i.stack.imgur.com/Vq7Qi.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Vq7Qi.jpg" alt="enter image description here" /></a></p> https://electronics.stackexchange.com/q/509892 0 Condenser microphone + LM386 + Arduino treb https://electronics.stackexchange.com/users/257389 2020-07-11T14:37:31Z 2022-05-29T02:39:55Z <p>I found this simple circuit and I set it up with BCM-9767P, LM386N and tried to write out the values I get. The problem is that the values seem to be constant and don't change with the environment sound level. I think I followed everything on the circuit, even changed the microphone resistor according to its database.</p> <p>How can I make it work?</p> <p><a href="https://i.stack.imgur.com/QDkFt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QDkFt.png" alt="wiring diagram" /></a></p> <p><a href="https://i.stack.imgur.com/U6jGx.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/U6jGx.jpg" alt="photo of breadboard circuit" /></a></p> https://electronics.stackexchange.com/q/478435 0 sinusoidal bldc LUT synchronization Bud https://electronics.stackexchange.com/users/177666 2020-01-29T08:09:06Z 2022-05-29T04:09:35Z <p>i trying to control 3 phase BLDC motor. I already done 6 step commutation which works fine. Now i going for sinusoidal control. Have studied more about sinusoidal control in bldc and got some idea.</p> <ul> <li>I created sin LUT table for 360 degree using = 127.5 + 127.5(sin x ) 0 &lt; x &lt; 6.28 radians</li> <li>My table size 2^8=256 </li> <li>table {127,.....255......127......0......127}</li> <li>By using the table i get good sin wave and i also generated 3 sin wave which are phase shifted 120 degree each other</li> </ul> <p><a href="https://i.stack.imgur.com/eQxRB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eQxRB.png" alt="enter image description here"></a> <a href="https://i.stack.imgur.com/Sv4pw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Sv4pw.png" alt="enter image description here"></a></p> <ul> <li>But i am struggling how to interface this sin LUT with hall sensor angles. I knew that by using PLL logic we can achieve.</li> </ul> <p>Some one clear explain me about hall sensor synchronization with sin LUT. Hope that will help me. </p> <p><strong>Edited</strong></p> <p><a href="https://i.stack.imgur.com/Qq6e2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Qq6e2.png" alt="enter image description here"></a> In the above image, yellow= input pwm to fet &amp; green = phaseA to gnd </p> <p>The Output wave look ok but motor consumes more than 10amp at 15hz speed. Any guess why its like that. I am confused,.</p> https://electronics.stackexchange.com/q/477616 1 Substitution + Superposition with RLC circuits Bemipefe https://electronics.stackexchange.com/users/174938 2020-01-23T20:42:36Z 2022-05-29T03:03:25Z <p>Consider the following circuit:</p> <p><img src="https://i.stack.imgur.com/3zNB0.png" alt="schematic"></p> <p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2f3zNB0.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p> <p><span class="math-container">\$E\$</span> is a constant voltage source. The switch is closed at time <span class="math-container">\$t = 0\$</span>. The request is to calculate the generic equation for <span class="math-container">\$i_L(t)\$</span>.</p> <p>Using the PSC convention i get the following Kirchhoff equations:</p> <p>1) <span class="math-container">\$L{ {d i_L} \over {dt}} -v_c = 0\$</span> (KVL)</p> <p>2) <span class="math-container">\$v_c -E -i_R R= 0\$</span> (KVL)</p> <p>3) <span class="math-container">\$-i_R -i_C -i_L = 0\$</span> (KCL) </p> <p>After few substitutions and algebraic manipulations I get the differential equation which describe the circuit: </p> <p><span class="math-container">\$-{d^2i_L \over dt^2} -{1 \over CR}{di_L \over dt}-{1 \over CL}i_L = -{E \over CLR}\$</span></p> <p>(Replace <span class="math-container">\$i_C\$</span> with the capacitor law on the <strong>3</strong>. Replace <span class="math-container">\$i_R\$</span> form the <strong>2</strong> in the <strong>3</strong> then replace <span class="math-container">\$v_c\$</span> from the <strong>1</strong> in the <strong>3</strong>.)</p> <p>The answer is correct but I want to find the same equation using a different method. By assuming the state variable as known I can replace <span class="math-container">\$L\$</span> with a current source and <span class="math-container">\$C\$</span> with a voltage source (I just applied the <strong>Substitution theorem</strong>). Then using the <strong>Superposition theorem</strong> I obtain these three circuits:</p> <p><img src="https://i.stack.imgur.com/MB3zW.png" alt="schematic"></p> <p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fMB3zW.png">simulate this circuit</a></sup></p> <p>The current directions are the same of the original circuit. I get these two equations:</p> <p><span class="math-container">\$v_L = 0 + v_C + 0\$</span></p> <p><span class="math-container">\$i_C = -i_L - {v_C \over R} -{E \over R}\$</span></p> <p>After replacing <span class="math-container">\$v_L\$</span> and <span class="math-container">\$i_C\$</span>:</p> <p><span class="math-container">\$-L{di_L \over dt} = 0 + v_C + 0\$</span></p> <p><span class="math-container">\$-C{dv_C \over dt} = -i_L - {v_C \over R} -{E \over R}\$</span></p> <p>However by replacing <span class="math-container">\$v_C\$</span> in the second equation with <span class="math-container">\$-L{di_L \over dt}\\$</span> I can't get the same equation obtained with the Kirchhoff laws. Not only the signs are different but also the coefficients of each term are different.</p> <p>What am I missing ? Can this method applied for every AC circuit ?</p> https://electronics.stackexchange.com/q/427362 0 Some questions about a servo motor driver input ratings cm64 https://electronics.stackexchange.com/users/184379 2019-03-15T11:17:55Z 2022-05-28T23:04:15Z <p>A <a href="http://www.ni.com/pdf/manuals/AKD_Install.pdf" rel="nofollow noreferrer">servomotor drive</a> input can be supplied either 3-phase or single phase. The photo of the driver nameplate is shown as follows:</p> <p><a href="https://i.stack.imgur.com/7Dx9r.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7Dx9r.jpg" alt="enter image description here"></a></p> <p>Does that mean in full/nominal load if this drive is supplied single-phase, it will draw 9.9 Ampere rms current through line? This makes sense to me because I=P/V so I = 2.38KVA/240 is around 9.9A. I might have ignored power factor(?)</p> <p>But FL current is written as 9.9/4.6 A. Does that mean in case of three-phase power input the total current drawn will be 4.6 A. How can we calculate 4.6 Ampere from 2.38KVA? </p> <p>motor nameplate:</p> <p><a href="https://i.stack.imgur.com/WvvAh.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WvvAh.jpg" alt="enter image description here"></a></p> https://electronics.stackexchange.com/q/422426 0 Can I simply add a 240V Neutral to SONOFF TH10 when replacing wall thermostat John https://electronics.stackexchange.com/users/212905 2019-02-15T08:31:02Z 2022-05-29T02:00:45Z <p>So, I have purchased a SONOFF TH10 wanting to use it to replace my wall mounted thermostat.</p> <p>The thermostat has 2 connections: Always-Live and Switched-Live (which is activated of course by the position of the temperature dial in relation to the room temperature). This then returns to the central heating control.</p> <p>The SONOFF however, has a Live-in, a Switched Live-out, Earth and and also needs a Neutral mains connection (I assume for its own internal power.) It also has a temperature sensor input.</p> <p>So, in order for me to use the SONOFF to replace my wall thermostat, I need to run the following connections: </p> <ul> <li>Neutral cable from mains supply to the SONOFF</li> <li>Earth cable from mains supply to the SONOFF</li> <li>Thermostat Always-Live -> SONOFF Live-in</li> <li>Thermostat Switched-Live -> SONOFF Switched Live-out</li> </ul> <p>In principle, is this the correct way to wire it, folks...?</p> <p>I am happy with mains cabling, and I fully understand the dangers of 240V mains wiring, but I have also learned it is never a bad idea to seek confirmation from others.</p> <p>Many thanks.</p> https://electronics.stackexchange.com/q/415225 1 how to avoid brownout caused by a multimeter on esp32 Alok Y https://electronics.stackexchange.com/users/208809 2019-01-04T16:21:30Z 2022-05-28T22:38:35Z <p>I am using the VOLTCRAFT VC130 multimeter for measurement of current through my esp32. The microcontroller runs perfectly with two 1.5V batteries(~3V as read by multimeter in voltage mode). But when I put the multimeter in current mode between power supply(batteries) and esp32 in series for the monitoring the current. The brownout detector triggers. The brownout voltage level is 2.43 V +/- 0.05 for the esp32.</p> https://electronics.stackexchange.com/q/399282 13 What is this weird EMV pin on my credit card? Ian Carroll https://electronics.stackexchange.com/users/200227 2018-10-04T02:35:25Z 2022-05-29T00:07:43Z <p>I recently got a Venmo card, which is my first card with contactless support. I was looking at the EMV pins and noticed a very weird design. In the middle of the ground pin, there is this long, thin pin extending into it that I've never seen before.</p> <p>It has ~5 MΩ between it and the ground, so it doesn't seem like just an aesthetic feature. What does it do (and why isn't it on most cards)?</p> <p><img src="https://i.stack.imgur.com/qzx07.jpg" alt="Venmo card" /></p> https://electronics.stackexchange.com/q/197826 2 Overheating heating element Espen Moen https://electronics.stackexchange.com/users/90310 2015-10-29T08:29:55Z 2022-05-29T03:38:18Z <p>I'm making a system that is going to heat water in a 25 liter tank to a given temperature and keep the water on this temperature with a precision of +/-0.5 °C. As I have done some research I have decided to control the heating element with a zero crossing solid state relay and control this relay with an Ardunio. The heating element is 230VAC, 3kW.</p> <p>My question is, for how long can I run constant current through the heating element without overheating it? I mean, if I turn the hot plate on my stove on max, will it run constant current through the element or will this still be pulses and how to determine the pulse width and time between these pulses?</p>