Reddit:Electronics

Tried to use it to light some LED’s though I think the circuit expects a battery voltage to use as feedback as it has very low output current otherwise. Short circuit current was 300mA

Current setup 😅

ESP32 + RFID + SDR + random modules

Not sure if this will fully work yet…

But it’s getting interesting 👀

Any ideas what I should add next?

There must be a T48 UV erasing addon with the EPROM blank check.

270-280nm 800mW diode.

I have been designing PCBs to carry a small microcontroller, an RS485 transceiver, an LED and the associated balance of plant required to make lights for my ROV. Space is at a premium, so track sizes are being chosen to minimise real estate used.

KiCad has a netclasses setup page that uses IPC 2221 requirements and PCBway capabilities. I have come up with a sensible set of pre-defined values

https://philipmcgaw.com/kicad-traces-net-classes/

It is 3-rd LCD panel in a month with the same issue, backlight stopped working, there was one resistor still measuring 270 Ohm so we know what it should be, all others are open circuit or in xx MOhm range. No signs of corrosion or overheating anywhere, just crappy components, never have seen this issue. It is planned obsolence or bad combination of materials in resistor. Share your experience with similar cases.

Its a jdm 030 usb charge board but which one of these is the fuse ( that i should replace ) after a short circuit. And is it worth replacing it ?

We used to have a wired door bell button as a garage door opener near the back door inside the house. The wiring got damaged in an area new wiring couldn’t be rerouted during renovation.

Came up with this solution - took a garage door opener apart - connected wires to a decora style momentary switch and soldered other end to the pads for the buttons on pcb.

Added a whip antenna to over come shielding of electrical box and drywall. To maintain the 9 inch whip antenna, drilled a small hole in electrical box and fed it into wall.

Works perfectly.

I used to use PCBWAY years back for a long time, doing over 100 high value jobs with them and they were good. I never had any real complaints. I moved over to JLCPCB due to the majorly lower cost a few years ago and to be honest I also couldn't complain with their service for a good amount of time.

I have been using them for prototyping for about 3 years with the occasional small batch run up to 200 pieces of fairly basic stuff like ESP32 etc. Recently I have started a small business that uses a reasonbly complex setup of USB at 5Gb/s and MIPI CSI at 2Gb/s with the corresponding high value parts of the image sensor and CYUSB CX3 transceiver. I have now made 4 batches.

Batch 1 of 5 pieces:
- Issues with the TMC2209, no communication and occasional explosions for no apparent reason. They would just lock up and sink full current through windings thus killing themselves.

Batch 2 of 5 pieces:
- No issues

Batch 3 of 25 pieces:
- The CYUSB chip would just NOT boot, it would sit in a reset state and nothing I could do would change that. Small changes had been applied to the PCBs over the batches but the schematic and layout remainded IDENTICAL for the CYUSB part of the design. This delayed by project by 3 months. Infineon were very helpful and spent a really good amount of time helping to debug the design comparing the new design from schematic to gerbers to xrays, they deemed the design was identical from their perspective and put it down to a PCB fabrication fault. This affected all 25 PCBs.

Batch 4 of 5 pieces:
- I decided to make another batch of boards while supplying my own CYUSB chips - they work no problem now.
- TMC2209 is blowing up again, replacing with parts from Digikey solve the problem 100%.
- I have an STM32 for house keeping on the board. Never touched this part of the design from the first batch, it now runs but I cannot maintain SWD debug without disconnect and now unable to program it via the bootloader...

Every time I order a batch I get a different outcome. No question JLCPCB uses fake parts intentionally or unintentionally. The outcome is the same. For me I'm going to be moving to a alternative Chinese supplier with free issued parts.

There's not a lot of love for the JT these days. Nevertheless they crossed my mind the other day and I couldn't help but put one together. I was as always amused by their ability to drive an led from incredibly low voltage. I had it down to 0.39V at one point.

The age old issues cropped up immediately when I wanted to make an led last on a button cell for a long time. They're great at pulling out some juice at low voltages, but not so good when the cell is brand new. Which is a shame. If one of these could take advantage of all the power in a button cell, they'd last much much longer obv.

There's all kinds of regulated varieties on the internet. Most of them rely on negative feedback at the cost of high base (or drive) current. In many cases, the amount of power being consumed by the base circuit was using more power than the led itself. This is primarily due to using a low value resistor into the base of a bjt. To regulate the power (often voltage), a second transistor diverts some of the current to ground. As power consumption grows, more base current is diverted until these balance out over the range of input voltages.

If the drive current and positive feedback could be controlled without wasting most of it, a ton of power could be saved. So I came up with this; a jfet between L2 and the base resistor. Instead of diverting current in the bias circuit to ground, it is directly regulated with a variable "resistance."

Of course to control the jfet would require a floating negative voltage that was proportional to the power being consumed by the boost circuit. So I added an additional winding, L3, to provide an isolated supply that would rise and fall with the rest of the joule thief. Then it was a simple matter of using a low power (low Vf diodes and small ceramic caps) rectifier with a pot to dial in the control voltage.

Jfets have an incredibly high impedance, and I used a 2 megaohm pot so the control circuit utilizes very little power.

Anyway I've been rambling. I thought the idea was neat and now I have a working version to see how long it lasts.

If anyone is interested, I can post a schematic. This is nothing special, but a fun detour from the actual projects I've been working on.

My spine hurts all over. 201 leds are smaller than a grain of salt! Even harder to solder on a home made pcb! Plus all the time troubleshooting broken tracks and drilling holes by hand. Those blobs kf solder you see are vias that link the rear and front copper tracks together. Did I mention my spine hurts?

“The use of WD-40 Specialist Contact Cleaner may result in damage to the laptop motherboard and is therefore not recommended for such applications.”

This i my workbench in the basement. Really happy with the layout and space. MIssing basically nothing more than a real heating system. At the moment working on a testjig for a pcb

This bench of mine has served me well for many projects including fixing a lot of things for family and friends. My current project is fixing that vacuum tube oscilloscope in the 5th picture. I’m also currently rearranging my drawer layout so things are still half labeled at the moment.

A rare kot of vintage military-grade circuit boards originating from Cold War-era radar infrastructure, consistent with systems such as PAVE PAWS. These boards represent a time when electronics were engineered for absolute reliability under mission-critical conditions. Each unit features meticulously arranged multi-channel circuitry, shielded modules, precision-tuned components, and electromechanical relays — all indicative of early high-performance signal processing design. The construction alone tells the story: hand-calibrated elements, gold-edge connectors, and robust analog architecture built to operate continuously in high-stakes environments. This is not consumer hardware. It is a preserved fragment of early warning defense technology — a physical artifact from an era defined by vigilance and engineering excellence. Ideal for: • Advanced collectors of military or Cold War technology • Display in studios, offices, or curated spaces • Engineers and historians of early electronic systems Condition: Untested. Original vintage condition with visible signs of age consistent with long-term storage. Available Serious only

Pictured is the offender, my custom 84V 480A brushed DC motor driver. While testing, I had to make some adjustments to the rev1 routing, since apparently I forgot to run DRC before sending it to the fab. Tried to change the logic power supply to the FET drivers from 12V to 5V, forgot to cut one trace, and ended up bridging 5V to 12V. I used a lead acid battery instead of a current limited power supply for testing, connected it to my laptop without a USB isolator, and... well, I no longer have a laptop.

I wonder how I'll explain to my professors why I won't be able to submit my paper draft that is due tonight.

About Chua's citcut:
https://www2.eecs.berkeley.edu/Pubs/TechRpts/2009/EECS-2009-20.pdf

My implementation:
CHUA custom PCB board (thank you, JLCPCB!), TL082 op amps
signal conditioner board (from +/-6V to 0 - 2V, from +/-1V to 0-2V)
X/Y simple scope - Teensy4.0+ ILI9341 SPI display.

Video: https://imgur.com/a/R0H5TSl

Just some quick soldering in my free time. Wanted to see if its possible to bodge a 50 Ohms dummy load. Its not perfect since it picks up a lot of noise without any EMF shield and the impedance is not exactly 50 Ohms with these resistors.

So the design is ready and working in LTSpice.

The red graph shows the voltage of the L3L4 transformer, that can be seen in the middle of the circuit. The voltage oscillates roughly between +10 and -10 kV.

The blue graph shows the voltage difference between the upper and lower CW circuits output.

Was tinkering this rainy weekend, initially just playing around with assessing noise performance of a couple of amps, which quickly reminded me about input offset at higher gain. Using a pack of 8x fresh AA cells for most of these measurements, in an inverting amp with gain of 101 (5% error possible). The low-voltage amps were tested with 3x fresh AA cells, just under 5V.

The homebrew op amp is made from non-sorted 2N3904/2N3906, circuit from Figure 2 of https://sound-au.com/project07.htm

The vintage part numbers were generally vintage mid-1970s to late-1980s. Only a single amplifier was measured in every case.

Nothing too rigorous but amusing to see how well they general conformed to datasheet typical. Pleasantly surprised how good the modern ST variant of the LM324A is. Just sharing in case anyone else finds it interesting.