# All Questions

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26 views

### DIY USB Power Hub

I'm looking to see if assembling my own USB hub is an option. I need to charge 20 devices via Micro USB at once. Data transfer is not needed. Is anything stopping me from getting a 5V 20A power ...
20 views

### Increase emf received from a coil without changing flux source

I have a situation where I'm trying to increase the amount of power received by a coil. To my understanding, I can increase the emf (voltage) by doing one of 4 things: Increase the number of coils (\\$...
27 views

### Dual supply source, how to do the switching?

I'm designing a circuit that I'd like to normally power from a 12-36VDC source, but want to have the option of also powering it via the USB connection during configuration. I've chosen the LMR16030 ...
21 views

### Requirements for PCIe Bifurcation on SBC

I'm looking for clarification on what actually needs to happen in order for a device to support PCIe bifurcation. Some forums say it's motherboard dependent, making me think it's not tied to the ...
37 views

### How to power up a project with 3 devices, between 0 and 12 volts

I'm working on a project which involves a DC heating element, a computer fan and an Arduino/ESP8266. I'd like to use one power supply for those devices..... The requirements: The heater needs a ...
78 views

### How to increase pcb trace width after fabrication

I am new to pcb design and my first designed pcb is burning, I have checked some traces and I found this: C18 capacitance is 0.1uF and 100V rated. The problem is that slim trace width is only 0.2mm....
20 views

### Working of INA826 instrumentation amplifier for Pt100 RTD

The schematic below contains an INA826 used to amplify the resistance of the Pt100 RTD across J1. Gain is set to 10 through the 5.49K ohm resistor. Is this ciruit amplifying only the voltage across ...
42 views

### Replacing TO-220 MOSFET with SMD DPAK

This MOSFET IRFBG30 is being used in an old design. It even has a little heat sink attached. The FET is used as a current limiter. During normal operation, a current about 13 mA passes through it. ...
42 views

Please bear with me as I'm not too experienced with this. I'm attempting to use an ADC to get readings from a photodiode. From what I understand, I should likely use an op-amp as the range of the ...
12 views

### 12 V PWM fan and Wemos D1 Mini - ground loop?

Newbie here. I'm trying to power a 12 V 4-wire fan and a Wemos D1 Mini from the same power source. The aim is to use a Dallas DS18B20 temp sensor and increase/decrease the fan speed as per the temp ...
29 views

### STM32 SDIO FATFS

I'm using SDIO (1-bit mode) with an STM32F429 Discovery board to read from and write to an SD card. The code below works, I've seen that it does, the problem is it seems to randomly choose when to ...
66 views

### Why this H-bridge with only N-channel FETs didn't work?

Based on this answer here in StackExchange and the Motorola article it cites, I've designed a dual h-bridge motor driver with push-pull transistors to switch the FETs faster, layed out a PCB in KiCad ...
72 views

### Why doesn’t voltage drop to 0 when a capacitor becomes fully charged?

This is my understanding so far of what capacitors are and how they work, if it helps to answer my question at a level I can understand: A capacitor is composed of two equally sized conductive plates ...
11 views

### Connecting Grid Tie Inverter to Solar charge controller

I've got simple solar panel - PWM charge controller with 10A max load output - 12V battery setup. I've ordered MPTT 600WATT grid tie inverter. My question is - if I connect higher load than 10A to ...
59 views

### What is this connector symbol?

I'm working on a PCB design homework in PADS and I've come across a symbol that I have never seen (circled in red below). It is of a filled in rectangle with a triangle below it. I'm thinking it ...
47 views

### How to convert 0-3 V (PWM range) to 0-24 V (device voltage requirement)

I have an Arduino with some PWM pins, output range is 0 to about 3 V and I need 0 to 24 V range. I need to active a solenoid.... A Hydraulic Proportional Solenoid A 12v and 5v source is also ...
39 views

### Possible water damage to keyboard pcb [on hold]

Can’t find an appropriate answer so far. Spilled water on kb last week. Unplugged and dried. Kb was fine for 2 days, then all the far left buttons stopped working as well as the number pad 7. Tried ...
22 views

### Find electron-hole recombination rate?

In an n-type semiconductor, the thermal equilibrium electron concentration (n0=1015/cm3) and the intrinsic carrier concentration (ni=1010/cm3). The mean life time of minority carriers is 1us. The ...
14 views

### Custom lamp project for a non-engineer - Help needed [migrated]

I'm trying to build custom 3 bulb lamp. About me: Biochemistry major so very far from electrical but I've built RC plane models before so I know soldering and stuff. Nothing really about electrical ...
90 views

### What modulation is this?

I'm currently learning about signal modulation and fail to figure out the modulation of this signal - maybe someone can help me with it? The software is GNURadio and the device capturing the signal ...
50 views

### Reflect IR beam off reflector instead of emitting straight to TSOP receiver

I have a working set-up to detect beam breaks using an IR LED, modulated at 36kHz, and a TSOP receiver connected to a comparator. It outputs the count via Arduino. The range is about the width of a ...
44 views

### Timer Protection Circuit

I need to create a circuit that sends out a signal only if the input it on for longer than a specified time. Lets say 20 seconds for this example. So if the input to the circuit was pulled high for 10 ...
30 views

### What does it imply when substrate terminal of Nmosfet is short-circuited with the source terminal? [on hold]

What does it imply when substrate terminal of N-MOSFET is short-circuited with the source terminal?
35 views

### Making a frequency measurement meter with LCD display

I am currently making a frequency meter using PIC 18F4550 micro controller. Here is my code written in Mikroc pro for PIC: ...
26 views

### Shaded pole speed control with PWM

I have a fan with a shaded pole motor and I installed this PWM for speed control. At the moment everything is working well, speed adjustment is sensitive and the fan is barely moving at about the 60% ...
27 views

### Activating a relay when certain voltage received (Water injection system)

I decided to build a simple water/methanol injection system for my car and now I'm thinking about a simple way to activate the water pump only from certain boost level. For the boost reading I'm ...
30 views

### Where can I get TSMC technology files for NMOS and PMOS?

I need to simulate circuits based on PMOS and NMOS. Is there any online resource from where I can get the TSMC technology files?
63 views

### Is it possible to confine radio frequency signal?

I would like to build a confined enclosure(like a 50cm cube box) to limit and perform RFID scanning only within the box, not interfered by the RFID tags laying outside the box. My intention is to be ...
42 views

Most commercial headphones are advertised to have sensitivity greater than 90 dB/mW. But to my understanding, even with 100% efficiency that's not possible (if we use 10 log (I/I0) where I = 1 mW, we ...
35 views

### Voh value not provided

I have this EEPROM IC where I want to check the logic level compatibility with another IC. But here Voh value is not given. I have observed this in my other IC also. Why is the Voh value not provided?...
51 views

### How could I power a 775 motor with batteries? [on hold]

I am using a 775 motor to drive a system of pulleys with some load. This is the motor that I bought: https://www.ebay.co.uk/itm/775-DC12V-4500RPM-Motor-D-Style-Axle-Mini-Generator-DIY-High-Torque-...
98 views

### Question about differential signals as input of an operational amplifier

I'm studying the circuits which are used to implement operational amplifiers. For example, I've studied the two stages amplifier (in which the first stage is a differential amplifier with differential ...
51 views

### FreeRTOS crashing when adding new queues

I am new to FreeRTOS At the beginning I created 3 queues and everything worked fine. Until I needed a new 4th and 5th queue. When ever I initialize the queues with ...
46 views

### Power supply amp converter [on hold]

I wish to provide power to 40 x TP4056 LiIon single cell charger modules. These modules require 5V input - all inputs will be connected in parallel to a 5V 40A supply. Each of these modules is ...
63 views

### What are the covers behind the terminals for in lead-acid batteries?

Some lead-acid batteries have two extra covers behind the terminals (See the images below). I understand that the 6 holes in the row in front of the terminals are used to water the cells. But what is ...
51 views

### Poles and Zeros of a Transfer Function

I am trying to understand the physical meaning of poles and zeros of a transfer function. Can someone help me how to understand the Figure 2b in the link below? What does the height of the cone ...
28 views

### AC resistance of LVAC transmission line

I'm currently working on a project to determine the transmission losses in an LVAC line, as part of an off-grid distributed generation system. The manufacturer of the cable has given me a DC ...
503 views

### Pass USB 3.0 connection through D-SUB connector

I need to pass a USB cable through a vacuum chamber wall, for which we have only D-SUB passthrough flanges available. So I cut a USB cable in half and soldered a D-SUB connector to each half. For USB ...
41 views

### I2C setting MCU as both slave and master at the same time

Hello everyone I'm working on a new project with the TI MSP432P401R microcontroller. I want to have 2 separate I2C buses. I2C bus 1 will set the MCU as the master, whereas the DAC and the pressure ...
26 views

### Motor controller oscilations with flyback diodes

Have some motor controller oscillations with flyback diodes when they were added to the build. They emerge with higher rates of signal amount making by controller. So there is a need to reduce the ...
20 views

### Repair Sound Device Mix Pre 6 battery sled [on hold]

I am using a audio recording device SOUNDEVICES Mix Pre 6 with several powering options. One of them is a battery sled, the MX L Mount for the famous SONY FP970 battery. The adapter can hold 2 and ...
210 views

### ADC Calibration - Vdd calculation

In documents and lots of online sources there is a formula as follows, $$Vdd = 3.3V * \frac{VREFINT_{CAL}}{VREFINT_{DATA}}$$ But I cannot get why CAL value is in the numerator and RAW data is in ...
65 views

### Limited Gain Op-Amp transfer function

At the nodes (R1 and R2) and (R4 and Ro) I applied Thevenin Equivalent. and the circuit reduces to this: Now my problem is: I am somehow unable to find the Vout/Vin out of these Thevenin Equivalent ...
821 views

### Strange LED behavior

I am encountering a strange problem when I measure the voltage across an LED. Please see below picture: As you can see, I only connected 1 wire ("-") of adapter and used a multimeter to measure the ...
46 views

### Hard fault on only one of two identical STM32F405 boards

So I've made two prototypes of a new custom board with a STM32F405RG microcontroller at heart and while one of them works totally fine, after a few seconds or more I'm getting a hard fault on the ...
43 views

### Multiple Power Supplies Powering Long LED Strip - Proper Way to Ground

Please refer to the above diagram. The 2 power supplies are each placed in the opposite end of the led strip. I will be connecting the signal ground and the power ground just before it connects to ...
37 views

### Single phase appliance on 3-phase circuit

Is it possible to have a single phase socket on a 3-phase circuit? It is a 3-phase radial circuit on a 16 A breaker. The last 3-phase socket on the circuit basically wants converting into a single ...
52 views

### Max startup current for Vacuum cleaner motor

We used the vacuum cleaner motor 2200W 220v in one dental device (vacuum former) as you can see here: So now one of our custumers said when they used this device the power cable is warmed and when ...