What type of circuit is this? The teacher says it's voltage divider bias circuit, but I don't think so
u/Elegant_Hunt_4329 — 3 days ago
r/electronic_circuits
Can I use a 5pin relay like this or need a diode?
I’m looking at using a 5 pin relay two switch signals between 2 different relays and go into one input. Would I need a diode to make this work or could I wire it as shown?
u/DIYiphone — 3 days ago
RC controller won't work
So guys, I've bought RC "Drift" car from Temu, and RC controller seems to not work, no matter what batteries as long as they are 1.5v I put in, It won't turn on.
I have opened the controller and I saw some wire that seems to just be left there, not connected to other side, straight cut and left behind, is this normal or not, and if not, where should I connect it to?
Thankss :)
u/vnemus34es — 5 days ago
How to connect these male header pins?
Hello all, I’m on my soldering phase to create this homeThing DAP. But before I start soldering the headers onto my display and encoder PCB, I want to make sure I choose the correct headers (right angle or normal).
I’m not sure the general method to connect these male pins together. I have a feeling female-to-female jumper wires aren’t available in super short lengths to fit in a build like this.
Are there any other options? I’ve heard about a perfboard, I’m not sure if it’ll be a better idea. If so, maybe I’d have to use normal straight male headers instead of right angle ones?
u/BeginningRelative100 — 6 days ago
Turing jitter into true random numbers
I discovered that adding a single 1N4004 diode to a Schmitt trigger RC oscillator increases edge jitter by 15x, turning a simple 4-component circuit into a cryptographic-quality hardware RNG for microcontrollers.
I've done (What I think is) a pretty comprehensive write up of the project here:
https://siliconjunction.top/2025/12/04/practical-hardware-entropy-for-arduino-projects/
u/elpechos — 14 days ago
Breakout Board with non soldered headers
I recently got a breadboard and I want to prototype my parts. However, it seems using headers on the breadboard isn't very useful because the PCB placed on top of the headers (headers are placed on the breadboard) are not really secure. It's like the PCBs have to be tilted at an angle to get the most amount of contact with the header pins.
I'm using the correct pitch and width headers.
TLDR:
Do I really have to solder headers onto my PCBs so I can place the PCB+header on breadboard effectively?
Because if I don't do so, just placing the PCB onto the headers, the connection isn't very secure/reliable. Unless there's some fix? I want to continue using the breadboard.
u/BeginningRelative100 — 11 days ago
Circuit help needed for power input and output
I think that I am running into an engineering issue and I am a little bit flummoxed… (yes, flummoxed). Attached is a PDF of my circuit. Call this a board review.
Very simply put, the circuit supports a fan management system. There are two sensors that monitor temperature and humidity in two separate spaces. When there is a great enough difference between the two spaces, the fans are turned on using the relays and then run until the environments are equalized.
I have gotten a fab and assembled board that in the surface, appears and ohms out. Ground is ground where it should be and not where it should not be. The 3 voltage nets ohm out as well. The 12V net attaches where it should, 5v attaches where it should, 3.3v goes to the 3.3V input for the ESP32. However, being able to trace these nets does not guarantee anything but that, nets seem ok.
To test the board, I have hooked the board to a power supply to control the source voltage input. I have the power supply set for 12v @ .5A. When the power is applied to the board, the +12V from the power supply goes to about +6V and there is not any voltage that would seem correct. 5V is low at the output of the LM7805 and no 3.3V on the output of the LM317.
Visual inspection does not uncover any manufacturing errors. The LM7805 does get rather warm telling me that there is power loss. However, it is not too hot to touch and I do know that the LM7805 runs hot.
I am asking the community to take a look. I do not claim to be any kind of an electronics expert but I have played on on TV earlier in my career. Please provide any feedback you believe will help.
Link to schematic - https://replay.dropbox.com/share/XUMjAc4p0c51ki9P
u/ishron — 2 days ago
My first ever soldiered circuit
it used is to control 5 motors from a raspberry pi as well as sense a voltage drop across the resistor for current sensing and motor stall detection using an arduino nano as an ADC. It will be used to actuate fingers in a prosthetic hand for a uni project!
u/Z3temis — 15 days ago
How is the schottky diode connecting the two power sources here?
I'm new to electronics and I was watching video about practical uses of diodes
essentially the guy in the video said that when the external power supply (the 12v on the left) is working, then the diode is "off". But if the external power supply stops supplying voltage, the battery (on the bottom) start to supply voltage, keeping whatever your circuit is running.
My question:
what does the diode actually do here? shouldnt the battery keep supplying voltage even when the external power source is on? From what I can see, the diode is just blocking the external power supply from getting to the battery.
Here's the video I was watching with a timestamp:
https://www.youtube.com/watch?v=yPwYNUDkkZs&t=373s
u/Top_Coast2132 — 13 days ago
Light sensor on light fixture PCB
One of the Philips lights in my house has both a light sensor and a motion sensor.
However, the light sensor only triggers when it’s really dark. So I’d like to cover it up so that it thinks it’s always dark, and only the motion sensor is active.
Can anyone tell me which component is the light sensor?
u/zipzopzep — 18 days ago
220v switch with led
Hi all, I randomly got this switch from a guy and now that I'm building a new printer I decided to use this switch. It seems to have two separated circuits? Bc it says 220v on one side and on the other 12v maybe for the led. Now the question is how do I wire it to a psu? I found schematics online but they are all related to circuits including a battery, while I have Live, Neutral and ground.
u/Opening_Quality_6661 — 17 days ago
My latest in breaker popping fire causing tech (it also amplifies audio kinda)
u/antthatisverycool — 16 days ago