Reddit:Electronics

A antenna tuner circuit which incorporates the resistance of the panel meter light into the accuracy of the meter. One must wonder why they would do this. They no longer support this unit so the bulb is hard to find. It is an axial lead bulb much like a axial lead resistor. I could replace the bulb with a resistor that is the same ohms as the bulb, I suppose. No back lit meter then but at least the meter would work again. Dumb design.

i had one mechanical keyboard after getting bored i tried to reverse engineer it but i couldn't send any usb data or i could not see much on the terminal when i tried to see if it listens to the data and after opening i saw that it only takes +5v and gnd plus the processor something like BYK.. was a hard coded chip that doesnt listen notes i was newbie to hardware and really scared to try anything. so i gave up but seeing my brother have a kreo rgb keyboard it gave me some boost to open it up and i learned so much and burnt my hand while trying to solder.

heck i even burnt the solder iron's wire itself (sniff sniff whats that smell).

so the plane was that i would use a mcu as esp 32 or pico that listen to my command and can do anything that i want .

first month really ....

i bought a mulitmeter and did the traces of all the rows and col sicne there was no pcb and other design files there i didnt know how keyboard matrix works at all i went rhough whole thing.. after getting all the traces and nothing them i was really soul scattered by the fact how this whole thing worked but then i got to know this was a common thing everyone knew this.

after this i took pico as the main mcu why...

1. it was small
2. it has higher clock speed.
3. it was one sale since the esp was on boom and the price of pico was dropped
4. it has more computer power that i needed for Fourier transform for disco light that i wanted for the custom rgbs i would put there

quickly after that i ran into a problem of less gpio also

after that i took a longer time to solder since i was learning and it was very scarry to solder on the pcb but as i did i grew more confident .. after burning my finger prints.

i bought a io expander because of 6 rows and 17 cols it got burnt and again tried that was jittering the one signal was affecting other signal. so i gave up 3-4 cols and went for the gpio full on.

The RGBs... Hardest

the rgb i had to cut each rgb strip stick them all on each keys then use the single core wired without the cover and solder each joints aroung 300 small pieces of them total 600 joints appx and it was tough because heating one end would make other end heat up also.

but since i cascaded 100 of them the voltage kept decreasing and it was 0.5v at the end so i just provided supply from both of rows and it worked and there was no deeming and jitters.

thats it... if u want to know about the logic behind it then u can ask me i will add it most of things and testing and all the stuff is in the video

I had a lego pack sitting around that I has sorta messed up years ago for somthing, desided see if I could jam a 9v to 5v converter in it, to say the least I sorta went way smaller than I actually needed, in theory it can take 1.5 amps, I wont get even close to that using it, to help with the heat it has some copper sheet attached the sits against the AA to help spread heat from it, parts used are two 10UF caps, ceramic 0.47UF on 9v side and a ceramic 0.1UF on the 5v side, the souldering is a little rough, but this is the smallest thing Ive ever made by far, Im sure it would be better if I did it a few times.

TI sells a light-sensing IC (OPT3001). Since it needs to detect light, the package is clear. I think this is very cool. A couple pictures have a quarter for scale.

video

Really baffling decision, my last order from them was only a few months ago. Apparently Linux is no longer a "standard" operating system!

Have been using the SpaceMouse Enterprise for about 3 years, always think the surrounding buttons are among the worst, both the feel and layout are awful. Today the delete key stopped working, so I took it apart to repair, also as a good opportunity to see what's inside. I thought it would be some crappy key switches, to my surprise, it's membrane. It feels strange to see such a relatively expensive device using membrane keypads.

Small share: I'm building a connected mailbox (ESP32 + LoRa) that notifies me when the mail carrier passes by, and I wanted the transmitter unit (inside the mailbox, battery-powered) to draw as little current as possible. Instead of going with classic deep sleep, I went with a full hardware power cutoff using a MOSFET.

The circuit comes from Random Nerd Tutorials:
https://randomnerdtutorials.com/latching-power-switch-circuit-auto-power-off-circuit-esp32-esp8266-arduino/

The principle: a contact (a push button in their design, a reed switch on my mailbox flap in mine) briefly wakes the board through a P-channel MOSFET, then a GPIO takes over to keep the power on while the program runs, and cuts everything off itself once its job is done.

The only thing I added compared to the original schematic is a small capacitor, to avoid an unwanted power cut if the contact happens to open again just before the GPIO has had time to take over.

I read the different values on each tap in can capactor the get a single matching cap with equal or greater voltage and temp. Then set them as you see on a daughterboard, binding all grounds to a common ground post. Then run wiring to the appropiate terminal or junction of where that value capactor was in the circuit before. I find this way an efficient and orderly way to replace older multi-can capactors. The daughter board is attached to chassis by one or two small, "L" brackets.

From left to right:

Intel B8702A

Fujitsu MBM27C64

SGS M2716F1

Motorola MCM27A08

Mostek ET2716Q

Eurotechnique ET2716Q

SEEQ DQ27128

Intel QD2716

TI TMS2764

Testing a .001 uf 6000v door knob capactor for leackage, both passed at least up to the 600v this IT-28 Capactor tester can run. Not the 2000 to 3000 volts that are possible in a SB-220 but it should be close enough if the "eye" does not close at 600v they should be good.

The old paper wound caps were replaced with new metal electrolitic caps, and bleed resister array which bleeds voltage off caps when unit is turned off. New metering board on the front of the power pack to feed readout meters on front panel. Older chokes and caps were removed from botyom grid circuit and the grid was grounded to chasis for better stability. A soft-key was built and added to the amp key up circuit to ne compatable with modern radios. Old coax and wiring replaced to higher temp and voltage rated material.

Rf choke replacement

Dreading placing those SMDs… I need a PnP 😭