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14,608 questions with no upvoted or accepted answers
3k views

### DRC tool for Gerber files

Do you know any tools which perform design rule checking for Gerber files of PCB and are suitable for using in batch mode on a remote server? Something similar to what BatchPCB or FreeDFM uses (I ...
380 views

### Switch from JTAG to SWD with bitbang sequence on STM32F103VB

I am trying to switch from JTAG to SWD without any external devices. Why? Because I would like to use the SWO pin to send a stream of logging information to another device. To accomplish this ...
368 views

### Digital Signal Cables Penetrating a RF Shielded Room

Disclaimer: I'm not a trained electrical engineer...I'm a recent Computer Science grad with about ten years experience as a RF test tech. I don't know everything, and to me, experience reigns supreme ...
5k views

### STM32F407 + LAN8720A + lwIP + FreeRTOS = No received Ethernet frames

I'm trying to bring up a PCB that uses an STM32F407 and LAN8720A Ethernet PHY, and I can't seem to receive any Ethernet frames — even though I have no problem transmitting frames. Hardware setup I ...
181 views

### Which part of some LED TV screens acts as two gratings crossed at non-straight angle?

Some modern LED TVs display the following diffraction pattern (photos taken from this question): In my answer to another question about the origin of this pattern I explained that this should be due ...
107 views

### Black Pad. Will heat remove the gold from an ENIG finish?

I have a batch of new PCBs with ENIG (electroless nickel / immersion gold) surface finish. My assembly house has had two unsuccessful attempts at populating the boards. We're trying to troubleshoot ...
107 views

### “Temporary boost” supercap

I have a 12VDC load (up to 10A) that functions correctly down to 8VDC. Sometimes (frequency: many seconds max, many minutes typical) the power source has a very brief (few milliseconds) drop to 7V. ...
4k views

### Stability factors of a voltage divider bias circuit

I am trying to derive the stability factors of a voltage divider bias circuit. I could derive S,S', however, I'm facing some problem with the derivation of S''. Please help me in this regard. How to ...
60 views

### Calculate sheet resistance in finite element method

I have a simulation with several polygonial mesh cells (Voronoi-mesh) and their centers of gravity $P_i$, each with its own electrical potential. Every cell has the same height $h$ all over. How ...
117 views

### Voltage Controlled Current Source - help needed

I am designing a voltage controlled current generator for the currents in a range from 0 - 2.5mA. The load resistance is within the range of 0 - 5k Ohms. I decided to go with difference amplifier ...
257 views

### What antenna is this?

I just disassembled an external FM antenna designed for an old Asus laptop. I expected to find some circuitry and a monopole or some other simple antenna. However, what I found was the antenna shown ...
341 views

### Design of cavity filter

I try to design a Chebyshev bandpass filter for 6 GHz as a coaxial cavity filter. I know that the filter can be designed with the aid of the coupling coefficients between the resonators and the loaded ...
522 views

### LM386 guitar practice amp circuit not working, need help finding mistake

I'm very new to electronics and I built this guitar amp circuit on a breadboard: and it was working really nicely. Now I've decided to put the circuit on a universal PCB which I'll use in the actual ...