# Questions tagged [circuits]

Use for questions primarily about circuit design, components, testing or other practical applications.

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### What does a Sad Face on a circuit board mean?

I have a Fisher and Paykel Washing Machine (model number WL80T65C, well past warranty) which got rained on (a lot) and one of the capacitors blew up. I've done an amateur replacement of the capacitor ...
132 views

### Help with closed loop heat controller (for a non engineer)

I am interested in setting up a controller which can modulate the output of 2 hotpads based on input from an infrared thermometer. The hotpads have their own dials, but I am considering controlling ...
442 views

### I want to understand this pneumatic circuit

I have trouble understanding the following pneumatic circuit diagram: I am new to reading circuit diagrams and i am unfamiliar with some of the symbols. I would appreciate if somebody could explain ...
82 views

### How do I calculate voltage at an LED in parallel?

I have this circuit: If D2 was a resistance, I could just combine it with R2 to get some composite resistance that I could put in series with R1. That way, I could calculate the resistance of the ...
152 views

I am having trouble finding a 3.4 µH through hole inductor that is in stock right now. I was wondering if I can just place 2 inductors that add up to 3.4 µH in series to solve this problem. I am not ...
161 views

### Simultaneously charging and transmitting data to an android phone using usb

Dear engineers, I have to make an engineering project which is a portable solar phone charger. One thing I need to do in it is to somehow charge the phone (android) from the battery (which is charged ...
2k views

### How do you find “this” Vx in the given circuit?

So I was told that $V_x$ is equal to 10V. I tried reasoning out why $V_x$ was 10V and this is what I got: -You can treat the Vx as an open circuit which means current does not flow through the ...
38 views

### What's the most practical way to measure angular velocity for small rotations?

I'm looking to measure the angular velocity of an arm as it moves. It seems to be a difficult thing to research, since the term 'angular velocity/frequency' is usually reserved for other areas of ...
273 views

### What does this Logic Circuit do?

So I have to analyze this circuit, with inputs C0, A0, B0, A1, B1, A2 and B2, and outputs S0, S1, S2 and C3. It's been suggested I don't use a truth table to figure it out. I need to find out what the ...
2k views

### SolidWorks circuit simulation?

I use Labcenter Proteus Circuit simulation - you create circuit design, then apply current and see simulation in action - for example leds are blinking, or motor is rotating. If there is ...
306 views

### Thevenin equivalent impedance in laplace domain

I can't understand why $Z_{th}$ doesn't include $3\ \Omega$ resistance.
75 views

### Replacement components?

I'm building a tracker for a high altitude balloon but some of the components are out of stock and may not be in before our launch date. I'm good with an iron but have limited engineering knowledge. ...
679 views

### Unknown circuit component with glass encapsulated contacts

This is an unsoldered circuit component that had two metal pieces that weren't making contact inside a thin glass tube. What is this? I haven't seen anything like it before.
48 views

### Units for plasma etching of circuits: A (with degree symbol)/min

Background: I'm a statistician working with a design of experiments example regarding plasma etching of circuits, and unfortunately, the author does not define what is meant by the units used for the ...
1k views

### What is the purpose of the capacitors on LDO Regulator Circuit?

What is the purpose and benefit of the two capacitors on both the input and output pins of a LDO Regulator?
240 views

### Designing a Voltage Divider [closed]

I am struggling to solve this problem and my available time conflicts with my professors available time. Could any of you offer me some help, perhaps describe the method I would use to solve such a ...
124 views

### Looking for a device that breaks the circuit if the voltage gets too low

I'm looking for a device that breaks a circuit once the voltage of my battery gets too low. This to protect the battery. Example: I have a 12V battery, once it reaches ~11V the huge voltage drop ...
220 views

### How can I calculate overcurrent from over voltage for the AP9101C IC

I designed a battery charging, protection, and boost circuit for a project I am working on. However, I made a complete noob mistake and forgot to find the overcurrent value for the battery protection ...
21 views

### Transferring the project from “Altium Design” to “SolidWorks” while maintaining silk-screen printing, sizes and everything else

I want to transfer the PCB project to solidwork from altium design, I read forums on how to do it better, and so: Save to STEP. The option is good and working, but I did not like the option, since ...
25 views

### Electrical component most likely to fail in window AC unit after power surge?

I have a window AC unit, 115 VAC, 10 amps. Power went out earlier in the week due to the big storm on the east coast and once it came back on every LED on the control panel was lit (not typical) and ...
107 views

### Can I connect a power supply main (SPH) and inverter main (SPH) with common neutral to a TP MCB?

I have limited knowledge of MCBs and just doing research to secure my kitchen. I want to connect my power supply main and inverter main with common neutral to a TP MCB. This MCB will be placed in the ...
47 views

### Comparisons of multiplier circuits

Could someone please explain some of the advantages/disadvantages of the wallace multiplier circuit vs a shifting and adding multiplier circuit vs an shift register multiplying circuit? We went over ...
88 views

### How can I get final value of $V_{out}$ at $t=∞$ in RC circuit?

I can obtain the transfer function in this RC circuit. $$\frac{V_{out}}{V_{in}} = \frac{1}{(RCs+1)}$$ When $V_{in}$ is set to $10V$, how can I get final value of $V_{out}$ at $t=∞$? I tried to use ...
37 views

### Switching a Circuit on-and-off In-step with the Rotation of a Drive-shaft (Mechanically)

I'm working on a project. The Salient part here is a drive-shaft connected to a bearing, onto which a simple circuit is mounted. I want to switch the circuit on every $π$ and off for the other $π$ of ...
25 views

### How do they get more signals simultaneously inside a node of a neural network? [closed]

Why the circuit does not freeze/lock when the signals SUM ? But the electrical signals are SUM together in what sense? This question is about neural network circuits because I don't understand what ...
45 views

### Circuit to provide position control for double action hydraulic actuator

I was wondering how to construct a hydraulic circuit to control a hydraulic double acting piston/actuator enabling the electronic control of the piston extension. I have found the following pneumatic ...
46 views

### Is it possible to build a DIY RLC circuit for a classroom demonstration?

I was describing the mathematics of RLC circuits to my students, and was wondering if it's possible to build an actual RLC circuit with coils of wire and an inductor and a variable capacitor. The ...
262 views

### I am trying to create an op amp based negative voltage regulator

I am trying to find simulate an op amp based linear regulator negative voltage regulator circuit. I have done the circuit for positive voltages, but does not know how to do it for negative voltage. ...
57 views

### My output is much lower than I expect it to be for my transistor-zener diode voltage regulator

I have created this simulation ( see below) of a transistor and zener diode voltage regulator. The output is supposed to be a steady 5 V. But it is like the top bit s cut, to an approx 4.4 V value, ...
107 views

### Adding an R2R Digital to analog converter inline with TRS connector

I am trying to create a simple R2R DAC, maybe 8-16 bits. I want to be able to that type of DAC inline to a headphone line. Since the an 8 bit R2R DAC will need 8 pins, how exactly do I wire up a TRS ...
238 views

### Ideal op amp circuit with variable voltage gain, how do I calculate the current?

I am currently calculating various quantities for the circuit shown below. However, I am stuck on how to calculate the current (Ix) and the input resistance (0 output current). The circuit is an ideal ...
299 views

### How the electronic circuit control laser diode? [closed]

I find this scheme here 1 - is data stream come from computer. This 'data' is an electric signal moudulated by the n°2 2 - this is the electronic circuit inside printer that a) activates the corona ...
2k views

### No Voltage appearing on Pspice

I am trying to compelte this question, however when i run the simulation there is no voltage atall on the output votlage, and cahnging the capacitor value as requested in the question does not chane ...
39 views

### Overcurrent protection, limit for nominal current or stall?

Background: I'm currently working on a robotics design that will drill through soil. I have selected a 48V motor who's nominal current is 3.17A and has a stall current of 42A. I will be driving the ...
18 views

### Thermal Capacitance - Convention for Modeling of Electrical Equivalent

As an EE, I am very comfortable with the mapping of thermal quantities to their electrical equivalents. However, understanding how thermal capacitances should be connected is driving me crazy. this ...
71 views

### BJT Output Characteristics Question

Ok, so I am pretty confused at the moment with a question that I have been given to work out by my lecturer and was wondering if I could get some guidance with it. I will attach images of the question ...
18 views

### Calculating the water pressure knowing the circuit that tracks it

I'm not very good at physics, but I've got a problem that I really need to solve. On the second picture you can see a pipe with flowing water. The point of this mechanism is to lit a LED whenever the ...
110 views

### Designing a loaded voltage divider?

I was wondering how to design this circuit in depth, since I have no idea what to do.
67 views

### How to choose type of output from a water level switch?

I need to buy a level switch for a quench tower water drainage system. I intend to use its output directly to open a solenoid valve to drain the tank when the switch detects water and close it ...
39 views

### How to prototype this circuit using an Arduino and breadboard?

I'm trying to build this circuit for a force transducer such that the data is logged by an Arduino Uno. I have the op-amp recommended in the schematic, but I haven't been able to get stable readings ...
71 views

### Mosfet switching circuit

I am trying to make a MOSFET switching circuit where its gate input is 12V clock pulse. Now when I put the load between (Vdd) and (Drain), there is no drop voltage VDS, but when the gate input falls ...
214 views

### Calculating gain of an overall system. Analogue electronics

Our professor has given us a review for a upcoming exam. But he has never done anything like this question and it has stumped a quite few of us. We are hoping someone can walk us through this so we ...
682 views

### Multi Ratio Current Transformers

I encountered a problem in measuring electrical energy using a multi ratio current transformer (CT). The catalogue of CTs is unavailable. I have little information about the type of CT I am using. I ...
134 views

### What are the various lumped element dynamic system models called?

What are the various lumped element dynamic system models called? By lumped element dynamic system models, I mean the various nodal models comprised of things that look like capacitors, inductors, ...
72 views

### Help with reading resistor color codes

I'm having a difficult time identifying a resistor's value as I can't find the golden / silver tolerance line. The problem is that I can't see a silver or gold line here! They're both brown on both ...
312 views

### Is battery-charge-stop-at-XX-percent circuitry not cheap? [closed]

I'm curious why IBM/Lenovo ThinkPad line is basically the only manufacturer/brand of mobility devices that includes circuitry and software that allows one to vastly prolong battery life of laptops ...
135 views

### Simulation of RC circuit using Proteus

I am learning how to use Proteus and I have come across the charging and discharging of a capacitor problem. My main problem is on how to use the graph feature of Proteus to simulate how the voltage ...
55 views

### Circuit analysis, voltage in and voltage out

I want to solve $V_o$ in terms of $V_i$ from the following circuit. $R_1=95.7 \Omega, R_2=9.1 k\Omega, R_3=1.0 M\Omega$ So the solution is form $V_o=kV_i$ and I want the factor k. I know that:...