Photograph via snooOG

This subreddit is dedicated to both amateur and professional engineers that want to build cool stuff at home, challenge themselves to learn new technologies, learn from each others' designs, and showcase their side projects.

This subreddit is dedicated to both amateur and professional engineers that want to build cool stuff at home, challenge themselves to learn new technologies, learn from each others' designs, and showcase their side projects.

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2

Fixing flex cable

I'm planning to fix this flex cable for a camera as a pratice project, should i solder the wires to the inside of the bend or outside.

1 Comment
2025/01/04
06:55 UTC

2

Trying to identify Q108 (glued to heatsink) in plasse seventy power amp . Unlabeled in schematic and gives no Key

Any advice would help thanks

0 Comments
2025/01/04
05:39 UTC

1

Led matrix dead?

I just recently received this led matrix from ali and I'm only able to get half of the matrix to power up and the other half has random pixels that are always on when powered. Is this a bad matrix or lack of power? Currently being powered via a 5v 2a brick with a stripped USB cable. This is being used for a esp32 matrix panel using WLED with config set to 256 pixels.

https://preview.redd.it/v370f6lqowae1.jpg?width=3072&format=pjpg&auto=webp&s=5347fd916bdf0c9780ac5654b9f042077949953f

3 Comments
2025/01/04
04:38 UTC

1

DIY Bluetooth speaker re-wiring help

Hello Everyone, I’m working on a Frankenstein speaker systems and I wanted to consolidate the three power cables into one. There are three components.

  • The sub, which came from an audio speaker set, with a built in amp. It uses a standard plug. - The car amp, which uses 12v.
  • the Bluetooth adapter, uses 5v.

I’m an amateur when it comes to this. What do I need to re-wire everything so that I can just plug in the standard plug. I appreciate any advice or tips. Thank you.

11 Comments
2025/01/04
00:18 UTC

1

Need some help figuring out how to power a different laptop monitor on an old laptop

TL;DR: I'm trying to figure out if I can get a better resolution out of my laptop. Surprisingly, there's a significant difference on the pin-out for this laptop, and what I had presumed would be a simple hardware swap is proving to be much more complicated. From what I can tell, there's no internal hardware differences between the 1080P laptop and the QHD laptop (same video card, same battery, same power supply, etc..) but there is a significant difference on the motherboard's pin-out.

Hey all! I have a Razer Blade from 2016 that I just bought used on Ebay and am in the process of getting it fixed up to be my daily laptop. I am not unused to laptop repairs, and bought a laptop with some issues. Primarily, the track pad was reported to not be working, the battery was dead, the keyboard wasn't functioning properly, and the wireless card stopped functioning.

I managed to fix all of this stuff by moving the motherboard to a new chassis (keyboard and trackpad issues solved), replaced the battery, and replaced the wireless card. It's all good! But there was something I had noticed: the laptop in 2016 was sold in two varieties: one with a 1080p monitor, and one with a QHD 3200x1800 monitor with a touchscreen. I saw that I could get a used functioning monitor on Ebay for $50, and figured I'd see if it's a direct fit.

It turns out it is a direct fit, and I can even get video output from it! The only issue: there's a different pin-out for monitor power from the motherboard to the monitor. I figured there'd be a bunch of unused pins because of the touchscreen component, but I didn't account for the fact that the motherboard itself would have a different pin-out. So when I plugged the monitor in and booted the machine, the backlight wouldn't come on. I could see video output, but only by shining a light directly at the screen, which is not really useful.

At first, I figured that these monitors probably had the same voltage requirements since it's effectively the same chassis with a different monitor, but after finding the specs, I am not so sure, and this is where I need some help.

The video output functions properly, and is properly detected by my computer, and I can tell because I was able to see video output when shining a light at it. It even properly detected the resolution. I just need to figure out how to power the backlight, and therein lies the issue.

At first, I had presumed that I just needed to simply solder a jumper between the positive and neutral to match up with the red and black wires on the monitor's power cable, but taking a look at the specs, the backlight for the current display shows input voltage as a max of 21.0V, and a max of 312mA. Further, there appears to be a LED driver integrated. Whereas the QHD panel shows no WLED driver, 22.4±1.6V and a max of 20.8mA.

I am confused because power consumption for these seems relatively the same (3.8W on 1080p vs 3.55W on QHD), and I am thinking this discrepancy is a data entry issue, but I am concerned about the voltage difference.

My question: does this seem like a simple process of simply providing power to the correct pins, or does it seem that there's going to be significant differences?

Here's some photos of the power connectors:

Original power connector (red arrow indicated keyed connection)

QHD power connector (top)

QHD power connector (bottom)

So there's 8 pins used on the 1080P connector, and 18 used on the QHD connector. Again, not sure how many of these are used for powering the backlight, and how many are used for the touch screen, but I don't care about the touch screen. I just want to power the backlight, and have no idea what the other connections would be for.

Any suggestions, please feel free. I was thinking about buying a bench power supply to get this sorted out, but realized that I might be missing something, and could potentially ruin the perfectly good laptop. I definitely don't want to disassemble the monitor to get further into this, because that would require surgery and I'll probably end up breaking the glass.

For the record, the features between these monitors are as follows:

  • LP140WF3-SPD1 - 1920x1080, 720p camera, stereo microphone
  • LQ140Z1JW01 - 3200x1800, 720p camera, stereo microphone, touchscreen

I'm not certain as to how many of these wires are used for data transmission, but I am assuming that most are not, and I do not care if the camera or microphone do not function.

Edit: for all those people looking to try this out with a 14" 2016 Razer Blade, model RZ09-01953E72 . This is for posterity/google.

Thanks!

3 Comments
2025/01/03
23:55 UTC

1

Electric motor troubleshoot

TLDR; 1-phase 230V 2.2 kW motor trips breaker. Deformed cooling fan and uneven resistance when turning by hand. Lost cause or salvageble?

I recently bought a table saw that wasn’t running. Owner said it had justed stopped and now it tripped the breaker when he tried to start it.

I’ve disassembled the saw and removed the motor. The cooling fan was deformed (looks like it’s from high temp) and rubbing on the motor housing.

I’ve measured resistance across all three terminals (1 and 2 are connected to the starter capacitor) with 10, 8 and 2 ohms across pairs 1-2, 1-3 ans 2-3 respectively.

When I turn the motor by hand (after removing the fan) it feels heavier to turn for roughly a quarter of the rotation.

Is it worth it to try and save the motor (a new original is ~300 € and a generic around 150)? If so, what should I do next?

2 Comments
2025/01/03
21:58 UTC

2

Old Michigan State Police RV-26 Police Globe - replacement bulb issue.

Hello!

Someone gave me an item from their retired collection to repair. It’s an old Michigan State Police Bulb Topper - you know, the red globe!

I cleaned it up and tested it out. I’m getting 12V as I should. I connected an LED strip to confirm that the bulb connections were working. They were. It was spinning and lighting up.

The replacement bulbs arrived that they purchased for me. Model 35PAR36SP5 from Bulb America. These are 35W/12V bulbs.

Something is off, though, when I connect one bulb and apply power, the bulb is really dim. Using my bench power supply, it’s wanting 12V at 4A.

If I connect the second bulb, the unit won’t lull more than 4A, and everything stops spinning and the bulbs are extremely dim.

If I increase voltage to 18V, they start to get brighter, but I know that’s not how they are designed.

Is this the totally wrong bulb or something?

I’m perplexed.

Thanks!!

3 Comments
2025/01/03
21:51 UTC

3

Best IOT Cloud and device communication protocol ??

I am building a smart hub like google nest hub, amazon echo etc with raspberry pi cm4 or cm5 that works over the cloud instead on directly connecting to smartphone for example if the hub have 5 or 6 devices connected like lights, fans, doors etc I want to these devices to be controlled over internet anywhere in the world so the hub will be connected to my own backend cloud service and when I want to control it I will communicate via my backend and hub if I want to turn on a light I will go to my mobile app and through rest api from mobile app I will send the commands to my backend and my backend will send the command to hub

This needs to be scaled for example my backend should be able handle millions of hubs and each hubs with their connected devices

So no one will be able control others hub or anything like

What is the best protocol for this considering the scalability and security

My Finding are

Mqtt: they are easy to setup, low power, and many good things but each hub needs its own topics and each topic should be encrypted in a way that no one can publish to any other topics

Websocket: best for security and handling connections but might be hard to maintain if connection losses occurs or socket breaks

Is there anything better or if not mqtt or websocket?

4 Comments
2025/01/03
21:09 UTC

2

Replacing Real Time Clock Battery (SUPER BEGINNER)

Hi all,

I recently purchased an IQue player (Chinese N64) as its something I wanted to experience as I am learning chinese and thought it'd be awesome to play animal crossing in Chinese. After purchasing, it came to my attention that the real time clock's internal battery is now dead. The board uses an ST M41T0 serial real-time clock. I am determined to make this work, and want to do the battery replacement myself. This would be my first time doing this, and I have 0 idea what type of battery to buy to do the replacement. I do understand the basics of soldering, but am unsure what type of battery I need.

Thank you for any advice.

4 Comments
2025/01/03
19:28 UTC

14

Hey, any tips for getting rid of/stopping these forsaken solder bulbs from forming on the other end of perfboards while connecting pads with solder? Already ruined a circuit for me and don't wanna mess up anyother. Anything at all is much appreciated, thank you!

43 Comments
2025/01/03
19:04 UTC

4

CD4511 fidget project

I got inspired by a video on the CD4511 ic to make a fun little toy to play with. The chip converts the 4-bit binary state of the 4 switches into a digital number on the 7 segment. The microcontroller shows the binary number on a 4-digit display above the switches. Here's a link to the project on EasyEDA.

https://preview.redd.it/vhopkarthtae1.jpg?width=1000&format=pjpg&auto=webp&s=e0c904d68daadb893ed7d3e62d8f3781317719d1

0 Comments
2025/01/03
17:53 UTC

2

I need to trigger some audio files from push button

Hi folks - Im looking to find some kit that can allow me to press a couple of buttons to trigger some sound samples, MP3 / Wav. Im ok with audio so I can source the sounds and get them onto an SD card so I was thinking of the Sparkfun Lilypad Mp3, with a PSU and a speaker but them I reas a couple of reviews saying it was problematic.

Im guessing one of you good people can suggest a solution ?

5 Comments
2025/01/03
17:00 UTC

3

Hii, why won’t my relay close?

I have a 120V 10Amp relay (standard arduino one) hooked up to a 12 volt battery and a dc motor. The battery is connected through an 8 amp fuse meaning it shouldn’t be able to draw more than the 10 amp rating of the relay. And all the pins of my raspberry pi pico w work individually. The relay switches when there isn’t power applied through it, but when I connect the battery and motor, it stops switching off. It turns on and then stays. I thought it might be an overamp issue and noticed it worked when I hooked it through a thinner gauge wire, so I ordered a 6ohm 50watt resistor to try and cut the power down just a little. It’s a very interesting issue, as it shouldn’t be able to draw more than 10 amps? So I don’t know why the relay wouldn’t close? I dunno, but I am gonna try the resistor see if that fixes it but if anyone has any other ideas do tell!

11 Comments
2025/01/03
16:15 UTC

3

How should I make the christmas lights light up without the controller.

So I have this christmas lights, and I ran over the controller with a lawn mower.

I want to light up the LED's without the controller. How should I wire it, and with what voltage?

https://preview.redd.it/t7fv8djqxsae1.jpg?width=5120&format=pjpg&auto=webp&s=8e709aa87169101945c7d15f335647e260930d4f

This is the same controller controller

This is what I have

0 Comments
2025/01/03
16:02 UTC

0

How do I power this?

I am new to electronics - building smart validation and need to control humidity by adding a couple of waterproof fans. The ones that I just ordered are 12v and have the 2pin connector which I am not exactly sure how to power.

I am looking to get both fans (ideally) to be connected to the same power source (which I will connect to a smart plug) but I am not able to find something like ‘dual 2 pin to 12v USB. Only 3-4pin connectors or 5v plugs.

I got the female 2 pin to usb from the mini drone I bought years ago, but it’s 5v, the fans are 12.

I am using breadboard that is powered by 12v, I thought it could strip the 2 pin connector and add it there, but this means that when I need to turn off the lights the fans will go out as well, which is not ideal.

13 Comments
2025/01/03
14:36 UTC

5

Is there some varnish to protect PCBs?

Hello I hope this is a right enough subreddit. I'm making a earring with a small PCB, I wanted to know if I can use some sort of varnish or similar liquid/substance to soak it into, in order to make it shiny and at the same time protect it. I saw this one for clay (https://www.amazon.com/Water-Based-Gloss-Varnish-Transparent/dp/B0053DXGRI/) and I was wondering if it could be ok.

Thank you in advance!

14 Comments
2025/01/03
14:24 UTC

7

New resistor on TP4056 doesn't show same resistance value?

Hi everyone! I'm trying to use the TP4056 to charge some 10440 li-ion batteries. I wanted to lower the output current from 1A to about 250mA, so I picked up some 4.7k ohm resistors to swap the R3 resistor with.

I use through hole resistors hoping that it would be easier but I'm having a hard time soldering them onto the R3 pads reliably. You can see one of the R3 pad is ripped off. Seems like the USB C tp4056 have smaller resistors than the micro USB ones.

I found another solutions where the resistor is soldered directly on the prog and temp pins. There is video on YouTube where he solder it on the R3 and GND pin near the USB.

I figure perhaps I can solder the resistor directly on the Prog pin and GND as shown in the image to make it easier for myself but when I measure the resistance value is showing 3.2k ohm instead of 4.7k ohm?

Any idea what could have caused this? I desolder the resistor and measure it to made sure it's 4.7k ohm. I've made sure the new resistor isn't touching the R3 pads as well.

Is it necessary that I solder the resistor on prog and temp pin directly? Thanks in advance!

5 Comments
2025/01/03
11:22 UTC

0

Nitecore i4 repair

1 Comment
2025/01/03
10:18 UTC

35

Does this look right ? (first circuit)

28 Comments
2025/01/03
09:38 UTC

2

How to affix/orient this switch

https://imgur.com/a/aI0WjBY

I need to attach this switch to a panel and have a couple of questions about the specifics.
There are two washers - one with a little tag that sticks up. I understand they both go behind the panel, but, do I turn the washer with the tag around so it sits flush against the back of the panel? Also, which way round does the switch go? Is the side you see in the picture up? I hope that makes sense and apologies for my incredible lack of knowledge.

5 Comments
2025/01/03
08:24 UTC

0

Just bought new speakers but don’t know how to wire

13 Comments
2025/01/03
06:05 UTC

3

Looking for good Flux

I've been looking up different types of Flux, for PCB repairing and I've landed on 8342 from MG Chemicals.

It comes with 2 different applications, Jar or Syringe

How long does a Syringe last, I've heard its the more efficient option but its more expensive whilst having a good 1/5 of the product.

2 Comments
2025/01/03
04:01 UTC

2

Automotive blade fuse to protect AC-> DC transformer?

Edit: [SOLVED] I’m working on a small system and want some extra protection. I have a single point of AC mains that is run through a IEEE 3 prong removable style power cord module that has a switch with a built-in 15A cylinder style replaceable fuse. From that point, the AC is branched out to 3 separate brick transformers for 24, 12, and 5vDC. I realize that a fuse behind a fuse isn’t an optimal situation, but along with some other positives I can think of, it will be useful to have a service disconnect for the individual voltages given that none of the transformers have a physical O/1 switch. As long as they are sized appropriately (and yes I mean amperage rating by sized), would it be acceptable to use blade fuses?

7 Comments
2025/01/03
03:47 UTC

1

Is there a way to make a switch for a 30 pin LVDS (2 input -> 1 output)

I have a device that I would like to convert the LVDS output to HDMI. I have tried one of these adapters, but I have had no success. I am wondering if the mainboard is hardcoded or has a handshake of sorts for the display EDID.

I have been able to connect the original display to an HDMI -> LVDS adapter (https://www.amazon.com/dp/B09F5T5LJC?ref=ppx\_yo2ov\_dt\_b\_fed\_asin\_title)

That adapter works great.

What I am trying to accomplish is using the original mainboard (this is on an infinity gametable 32") and having that going to a LVDS -> HDMI. Then putting that HDMI to the KVM. However the first link in this post is suppose to convert the LDVS 30-pin to a HDMI. But in this case I get no output. So my next thing to try it maybe having a hard switch or something like that to just change the LVDS. (it would be 100% okay if I have to turn the power off. I dont think the monitor would be happy with a hot-switch)

Unless there is a way to get the EDID from the monitor (since the 2nd link allows me to use the screen as a normal monitor) and flash that or emulate that on the LVDS -> HDMI adapter.

the end goal is to be able to switch from and hdmi input or the original mainboard.

Any help would be much appreciated!

https://preview.redd.it/ml1e2p7d5pae1.jpg?width=1600&format=pjpg&auto=webp&s=6525d0b5a28385be97d5e84bff44b68adb82a2ae

1 Comment
2025/01/03
03:16 UTC

4

Moisture sensor pcb question

The sensor is just a tinned PCB but I was thinking maybe it would last longer if I put a layer of solder on them or if that would mess with their ability to make measurements?

7 Comments
2025/01/03
02:40 UTC

0

Looking to build my own Android tv from alibaba or scrap parts..

Based on my research so far, I'll be working with the LED panel, Android TV PCB board, power supply, and LEDs for the backlight.

Has anyone attempted something similar before? I'm looking for advice on which PCB to buy from Alibaba and any general recommendations you might have.

Thanks in advance!

4 Comments
2025/01/03
01:35 UTC

15

Anyone know what this part is called?

My friend bought an old fan and when trying to fix it this came across, if he connects the motor direct to the wall it works but at full speed, he says that that thing with the wires that looks like a fusible needs to be replaced, but we were unable to find out what is that part called. Any help would be appreciated, we think that if that part is replaced the fan should work fine

16 Comments
2025/01/02
23:49 UTC

2

Need help combining mono audio cables(gnd,sound) into a stereo line (gnd, L, R) without shorting Right and Left

Hi i started a little DIY project of adding a female aux jack to my Walker Razor Quad BT headsets
but i have run in to a small predicament

i have suscefuly added the port and wired it directly into the left speaker but since my audio in line is mono
im having trouble figuring out how to connect it to the right speaker

as far as i can tell shorting connecting both the L and R speaker to my mono output will cause the speakers to short which means i no longer have Stereo on them?

my first thought was using a diode to ensure the mono out put leads to both speakers without the current flowing back from R to L or L to R but im having trouble finding a diode that works with such low voltage (0.7V - 2V)

is there a suitable diode or another way?
bonus question:
is there a way to pervent the Mono current to flow into the controller?

https://preview.redd.it/fklp31vhjnae1.png?width=566&format=png&auto=webp&s=5a24ec8afddefe48b0827c8cc220def941c158a1

20 Comments
2025/01/02
21:54 UTC

2

TTP223 module LED is always on

I have this Touch module, I have wired a 3v battery pack to the VCC and GND it seems to work, when I touch the module the Rea LED indicator turns on and when I let to turns off, now when I connect a LED to it the LED constantly stays on, and when I touch the module it turns the LED off, I want it the other way round I want the TOUCH to turn the LED on, I've tried everything, any help would be appreciated! P.S I'm sorry I'm very new to this

0 Comments
2025/01/02
20:48 UTC

3

Anyone know this 2 pin connector?

Found a Fluke 77IV that’s just missing the 9V connector

https://imgur.com/a/Jv6BptT

3 Comments
2025/01/02
19:45 UTC

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