Reddit:Electronics

As one of like 3 people who absolutely loves cat whiskers when I stumbled upon a paper from the 1920s known as “the Crystodyne principle” I got real excited, then I realized I don’t own zincite and ya I know the paper itself says you can use galena and fools gold but I’ve over used fools gold and if I’m gonna buy galena why not spend that money on zincite, but then I had a genius idea “what if I made the crystal!” So then I got to work (spent like 5minutes finding out how zincite forms) and discovered it’s just the mineral equivalent to zinc oxide so I heat treated some zinc WITH A MASK NO ONE WANTS ZINC PLATED LUNGS, and to my surprise it worked 2nd try. The hardest part had to be actually making the circuit because “the Crystodyne principle” doesn’t tell you how to make an amplifier only that you can so like any responsible science fella I just started shoving crap together based on half complete knowledge till it worked and then when I got it to work I needed to figure out how to A. Remove unnecessary components B. Increase volume C. Decrease static. And this is the circuit I came up with. To test it I put the earpiece in my ear under a pair of headphones and tapped the mic against an auto transformer. I also managed to use it to amplify an electric kazoo.

Je travail sur un projet d'arrosage de plante autonome souhaite moi bonne chance 😂😉

All thanks to one single person who believed in me & pushed me to do it!

Yesterday I started up an old Soviet gas discharge rectifier ВГ-176.

Fixed a couple of old broken carriage clock recently with some STM32s, e-displays & some bling.

Setup:
* Microcontroller - NUCLEO_L432KC
* Display - Waveshare 2.9" & 3.7" E-Paper Displays
* Sensor - DHT Temperature & Humidity Sensor with 100k pull-up resistor between the 3.3V rail and the DATA/OUT line.
* Power - Voltage Regulator HT7333 and Micro USB 18650 Lithium Battery Charger Module
* Bling - Some pencil art with gold surround, gold run on transfers & corner protector gold filigree

How it works:

1. The teacher first scans their fingerprint to unlock the system.

2. Students then scan their fingerprints.

3. The system identifies the student using the fingerprint sensor.

4. It records the student's attendance along with the exact date and time from the RTC module.

5. The student's name and attendance status are displayed on the LCD.

6. An SMS is automatically sent to the parent informing them that the student attended the lecture

7. Attendance data is also sent to another number in a form hat can be stored digitally.

Last year I built this , then i visited tech feast with this, people there showing AI language translators, automated water filling and packaging machines, computer vision systems, custom PCBs, and projects that looked like actual products.

Meanwhile, my project was basically a small box with a fingerprint sensor and LCD

Now I'm motivated to build something much bigger this year, but no good idea is coming in mind

Can anyone share there project they might have built in there college times

Im so happy that it even works! Took me about an hour.

200 kva fireworks 😅

Hi all, not sure if this post fits, but I really wanted to share my first real project.

For my 3rd Year in Electronic Engineering at the University of Pretoria we were tasked with building a line following robot from scratch. For this assignment we worked in a group of 2 people.

The exact task was: Build a line following robot using the PIC18f45k22 as your uC. Program it fully in PIC-assembler. Build all relevant sensors (Touch and Colour) from scratch. Design your own PCB. The robot (MARV) needs to be able to detect any of the 4 (Green, Red, Blue, Black) colours and follow them.

This large task was broken into smaller sub-practicals that had to be completed throughout the semester (While doing other subjects).

I'll break down the project into these smaller components to explain what I did a bit better, this is also where I add that English is not my first language so please excuse that.

Practical 1: Colour sensing.

For the first practical we had to design a colour sensor from scratch. We ended up going with a reversed biased Photo-diode (SFH-213) over a resistor into a standard non-inverting negative feedback amplifier using a MCP6001 as our op-amp. We designed a 3d printed housing to hold 5 of these in a row. Then we used a RGB-LED that illuminates the surface of which the colour is being measured. The PIC controlled the LED's by strobing the colours while taking measurements of the sensor with the ADC. The colours were shined one after another and different values were taken to determine what colour is what while moving the sensor over a calibration strip. There is a lot more that was done but this is a good enough summary.

Practical 2: Motor control, navigation and integration.

For this practical the sensors had to be integrated with a line following algorithm as well as motor control. After a calibration sequence the PIC would wait for you to select a colour which it should follow, after this it sits in a waiting state until the basic capacitive touch sensor is pressed, where-after it starts moving by sending PWM signals to a motor controller based on the L298M. This stage also had us designing a PCB for the first time, figuring out how linear voltage regulators, decoupling capacitors and many more things worked. This stage is the lunch box on wheels, this is also where our robot got her name, Jessica. Once again this is just a quick summary.

Practical 3: UART, I2C and polish for raceday!

For this practical an EEPROM (24LC16B) had to be communicated with over I2C to store calibration data. A serial to UART chip (MCP2221A) needed to be utilised to talk to the PIC over USB. This is the stage where Jessica gained her sleek 3d printed chassis and her PCB arrived.

I've glossed over all the technical things of the code to try and keep this short-ish.

This is also where the coolest part of the project happens. Race-day, All other groups compete in a head to head race, where the fastest robot wins big prizes for there teams. This evens is sponsored by big companies such as RS, Wurth, Hensold and many more.

In race day my team finished 2nd, and we won a cash prize, unfortunately not the grand prize of a 3d printer with other goodies, but at the end of the day I'm still chuffed with the result.

Feel free to ask any questions, I wanted to add more but this is just a reddit post after all. If someone wants a more in-depth look at our code just let me know and I'll share a github link. If your interested in seeing the race in action also let me know and I'll link the live stream of the race.

4 months ago I shared the progress of our Open Access Health Tracker from V1 to V2. Today I wanted to share the progress from V2 to V3 on a schematic level. And it's massive.

3x3cm PCB, 3 meters of traces and maxing the capabilities of JLCPCB. Plus an additional 2-3 PCBs for sensors not shown. Next up SLP instead of PCB.

I'm designing a fully-automatic turntable from scratch called the Statimatic STM-01, using:

- A Teensy 4.1

- Stepper for tonearm elevation

- Stepper for tonearm azimuth movement

- Stepper for azimuth clutch

- Demultiplexer, to split elevation/azimuth stepper signal

- Multiplexer, to handle input buttons (like "play" or "pause")

- Shift register, to handle output LED statuses

The "turntable" part isn't finished yet (nor is the automatic movement), so I'm just using an AR-XA as the turntable for now.

I like records, and I like making stuff, so I decided I wanted to make a turntable. I know it isn't practical, but hey, I'm having fun with it! Please excuse the absolute mess that is the wiring.

It is open source, though I'm not sure if GitHub links count as self promotion, so I'll play it safe and leave that out.

[group 4b][variant 4b] 0x0_ = MISC Opcode Name Description

0x00	NOP	No operation
0x01	HLT	Halt CPU execution
0x02	INT	Trigger software interrupt
0x03	CLC	Clear carry flag
0x04	SEC	Set carry flag
0x05	CLI	Clear interrupt enable flag (disable interrupts)
0x06	STI	Set interrupt enable flag (enable interrupts)

0x1_ = MOV Opcode Operands Description

0x10	reg, reg	Copy value from register to register
0x11	reg, [mem]	Load value from memory address into register
0x12	[mem], reg	Store register value to memory address
0x13	reg, #imm	Load immediate value into register
0x14	[mem], [mem]	Copy value from memory address to memory address
0x15	[mem], #imm	Store immediate value to memory address
0x16	reg, [reg]	Load value from address held in register (pointer read)
0x17	[reg], reg	Store register value to address held in register (pointer write)

0x2_ = ALU Opcode Name Description

0x20	ADD	Add register to accumulator
0x21	ADC	Add register to accumulator with carry
0x22	SUB	Subtract register from accumulator
0x23	SBB	Subtract register from accumulator with borrow
0x24	AND	Bitwise AND with accumulator
0x25	OR	Bitwise OR with accumulator
0x26	XOR	Bitwise XOR with accumulator
0x27	NOT	Bitwise NOT of accumulator
0x28	CMP	Compare (subtract without storing result, sets flags only)
0x29	INC	Increment register by 1
0x2A	DEC	Decrement register by 1
0x2B	SHL	Shift left, MSB goes to carry, LSB set to 0
0x2C	SHR	Shift right, LSB goes to carry, MSB set to 0
0x2D	ROL	Rotate left through carry, MSB goes to carry, carry goes to LSB
0x2E	ROR	Rotate right through carry, LSB goes to carry, carry goes to MSB

0x3_ = JUMP Opcode Name Description

0x30	JMP	Unconditional jump to address
0x31	JZ	Jump if zero flag set
0x32	JNZ	Jump if zero flag clear
0x33	JC	Jump if carry flag set
0x34	JNC	Jump if carry flag clear
0x35	JS	Jump if sign flag set (result negative)
0x36	JO	Jump if overflow flag set

0x4_ = STACK/CALL Opcode Name Description

0x40	PUSH	Push register onto stack, decrement SP
0x41	POP	Pop value from stack into register, increment SP
0x42	CALL	Push PC onto stack, jump to address
0x43	RET	Pop PC from stack, return to caller
0x44	IRET	Pop PC and flags from stack, return from interrupt handler

Github repo with all docs and files: https://github.com/mrFavoslav/8bit-cpu-MESAx8
The 8-bit ALU might not work perfectly at the moment. I recently moved some parts of the design around, so there's a good chance a few wires got messed up or misaligned in the process. Any feedback or bug catching is highly appreciated!

I'll be posting my progress here and on https://www.favoslav.cz/blog/

Finally! I made a perfect pcb on a CNC with a UV mask 🔋. I really love how the copper looks under the mask.

This is a portable lab device help to do experiment like diodes bjt amplifier gain and act as a function generator

On the bottom left it is shown next to its accompanying vacuum tube power supply, not a single semiconductor used in the whole setup. Wiring is horrible, and its performance reflects that. But at least it looks nice. Uses a 2" diameter 902 CRT, and is based mostly on a 1945 RCA schematic for this tube.

The CRT only runs at <600V (schematic specifies 577V, mine only runs on ~400V), which is remarkably low for a CRT but it definitely still hurts. Uses two 6SJ7 pentodes for vertical and horizontal amplification with a Type 884 thyratron for sawtooth generation. Has x-y mode and internal/line/external sync. Rectification is done with a Type 80 for B+ and a 6AU4 for the negative CRT supply (grounded anode).

The tube could maybe use some magnetic shielding and I am trying to figure that out, but for now I just keep the power supply away from it to eliminate the interference. Whole thing uses a little over 60W when running and is fused accordingly.

This is by far my highest-effort electronics project ever, and I am very glad to be done with it! I started this project over a year ago before, I got my real oscilloscope. Whadaya think?