Reddit:Electronics

Bought a 24GHz radar module to tinker with and, after a few tests and experiments, ended up designing this board to make further testing a bit easier with the eventual aim of designing my own radar system or close!

Has been a really enjoyable learning experience so far. Time to start writing some 1’s and 0’s now!

So this is my latest draft for a railsplitter with low noise that is ment to be an accessorie fir my 60V 5A power supply. You could add 1uF film+100nF ceramic between Q5 and Q6 Collectors, and 100pF on Q1 base to Q1 emitter for lower transients and risk for oscillation. If you parallel 2 tip35c + tip36c you could go around 8-10A unbalanced load with propper cooling. As long as the load is symmetrical then this circuit should be able to handle several amps (Atleast 10A). It might be hard to see but i added a 1000uF 80v electrolytic capacitor 1 uF film 100v and 100 nF ceramic 100V at the input for more stability. Can't say for sure that this works like it's intended as i haven't simulated or built it yet, I just now finnished the schematic, will post the results once i am finnished with it. If it works like intended then it could be a good way to be able to run amplifiers using single rail PSU. And the Voltage/Ampers is limited by what components you use. If you switch the small signal bjt's/drivers to over 100V+ and use mosfets as power stage you could theoretically drive ±50V and 50+ Amps.

A really good space for me and my projects.

Worth noticing is the home made ESD gun that can deliver 7-8kV discharge, and a really primitive compressed air tank made of an old fire extinguisher connected to a small airbrush compressor. Perfect since it's non oil tech. Use it mainly for my hot air soldering station. Below the blue compressor there is a homemade heat chamber for temperature tests. Really bad pic but it can be seen on the overview picture. Also my latest project that i'm working on, that i have named USBpwrMe connected to the bench power supply output. Enjoy :):)

Hello everyone! About 2 months ago on a whim I ordered 6x of these IV-11 VFD tubes from eBay, and decided I wanted to design and build my very own VFD tube clock! After getting good tips and feedback on reddit, prototyping everything on a breadboard, designing a custom PCB, and soldering it all together, here's the finished result! This is my first real personal project as a new EE major and I'm thrilled with how it turned out.

The clock runs on an Arduino Nano Every with 6x daisy-chained 74HC595 shift registers and UDN2981A high-voltage source drivers, one pair per tube. The anode and grid rails run at 25V from a boost converter, and the filament runs at 1.5V from a buck converter, all from a single 5V USB supply.

A full writeup covering design decisions, schematic, and PCB layout is on my GitHub Repo. Stars are appreciated! :)

Work in progress! I was inspired by numerous #Minecraft inspired IRL compass and the fact i could not buy it was the driving force to develop one.

The needle animation works fine; it is the first step in order to make the final product.

I built it from ground up (Custom LED matrix, 3d printed housing), if anyone needs more details on the hardware or anything related to the project feel free to comment and ask away.

P.S. It is still a prototype so it's a little a little janky and the custom PCB is held by some tape.

I designed DC spot welder controller up to 4kA+ which can be powered from high current source or extrenal 12VDC source. I want to setup it with 4s or 2p2s LEV40 pack.

If it passes the tests I will make it open-source.

Functions:

- Settable amount of energy into the weld in reasonable time with 50us control loop

- Autopulse with settable delay for example pulse will be send after 300ms after shorting electrodes

- Manual trigger (no delay)

- Measuring source voltage

- And maybe others

Made a simple online tool for minimizing Boolean logic: https://www.logic-solve.com/

Drop in a truth table or PLA and it gives you the optimized version along with Verilog/VHDL/C output and a K-map view. Runs locally in the browser for smaller designs.

Figured it might be useful for some of you working on digital stuff. Especially folks working with hardcore, transistor or relais computers. With this you can minify your designs.

For more detail: https://blog.mehmetasaf.me/bts7960/

The image quality isn't great, but considering I got them for free, it's not bad.

These are a couple of auxiliary sensor enclosures I made for my Farmbot. The first box is power distribution and housing for i/o of the RS485 7 in 1 soil sensor and an array of moisture sensors. All through USBC ports and RJ45. 24v for the 7 in 1, 5v for the extra USB power ports and the Max485. Not pictured is the max485 circuit and the associated wiring. Box two is a relay enclosure to control 120v pumps and lights.

All with custom faceplates to identify the ports so nobody mistakes the RS485 port for a standard USBC. Pretty simple stuff but it's still fun.

Built this last year based on Ben Eater’s 8-bit computer design using 74LS series ICs on breadboards.

Implemented core modules including registers, ALU, program counter, memory address register, and control logic. The LEDs are used to visualize bus states and output during execution.

Biggest challenges were signal stability and debugging wiring issues across multiple modules. Getting consistent clock behavior also took some iteration.

Overall, it was a great hands-on way to understand how a simple CPU operates at the hardware level.

I found a piece of a laptop with a fingerprint scanner from 2007 in a junk bin. Surprisingly, it works perfectly with Windows 11 and reads my fingerprint without any problems. It requires a 3.3-volt voltage regulator to power it. I 3D-printed the enclosure and came up with a pretty good device.

Thing of beauty! Wanted to clean it before testing it but its so pristine inside :O

If you saw my last post about accidentally frying my CH32V006 dev board into a working state, this is the next chapter of that mess.

Quick recap: I'm building a custom CH32V006 dev board for OpenServoCore, my project to turn cheap MG90S-class servos into smart actuators with a Dynamixel-style single-wire UART. After the 0.84V rail saga, I had a working board. Time to bring up the Rust bootloader (tinyboot) over UART.

Except UART didn't work.

Specifically, TX worked perfectly. I could blast "Hello world" out of the chip all day. But sending anything into the MCU? Total silence. The HAL driver is essentially the same as the V003, which works fine, so I was pretty sure this was hardware, not firmware.

I scoped the RX line while shoving a stream of 0x55 (UUUUUU…) into it from the host. Quick one-liner if you've never used it:

Alternating 1s and 0s, perfect for scoping.

What I expected: a clean 0V to 3.3V square wave. What I got: a 180 mV ripple sitting on top of 3.3V. Min 3.20, max 3.38. The line was being held high so hard that my USB UART adapter could only sag it by a couple hundred millivolts when it tried to send a zero. Touching RX directly to ground snapped it cleanly to 0V, so the wiring was fine. The driver just couldn't drag it all the way down.

Back to the schematic. The RX line passes through a 74LVC2G241 tri-state buffer that handles the half-duplex direction switching. TX_EN low = listen (DATA -> RX), TX_EN high = talk (TX -> DATA). I'd been picturing this buffer as a passive switch, like a piece of wire that conditionally connects two nets.

By now you electronics gods here probably already figured out what's the issue by now, but I didn't...

Anyways, when TX_EN is low, that buffer is actively driving RX with whatever it sees on DATA. And DATA sits at 3.3V via its own 10K pullup when the bus is idle. So the buffer was reading 3.3V on DATA and pushing 3.3V back out of its high-side MOSFET onto RX with ~24 mA of drive and very low R_DS(on). I was fighting a CMOS push-pull output stage with a USB UART chip. The buffer won. Always.

The firmware workaround is to assert TX_EN while reading. That disables the DATA -> RX path and lets RX fall back to its own pullup, which the host can actually drive. Confirmed it live by poking 3.3V onto the TX_EN pad and watching the ripple snap into a clean rail-to-rail square wave. It's such a satisfying flip on the scope.

The real takeaway, however, is thatTX_EN isn't really a transmit enable. From firmware's view it looks like one, but electrically it's a mux select that picks which buffer drives the bus. Calling it "transmit enable" is what put me in this mental hole in the first place.

For Rev B, the actual fix is a hardware jumper that lets RX bypass the buffer for plain UART mode. Why hardware and not just firmware? Because tools like wchisp use the UART to read/write the CH32's Option Bytes outside of any firmware I control. If my UART depends on my firmware to function, a fresh chip or a half-flashed bootloader can lock me out of recovery. Recovery-path peripherals shouldn't depend on firmware to work.

If you want a more details with scope photos, the schematic, a video of the workaround in action, here is the full writeup.

Teardown video does go over the related PCBs at the component level, with plenty of components being discussed and pointed at. Discussion of various board sections. Thought it might be of interest to some folks here.