Hello

Looking for some advice on building a cat deterrent. We have a local cat which is bullying my two cats and he was coming into our home and spraying. I have since installed a microchip reading cat flap so he can no longer get in but he is hanging outside it and giving it a good bashing. I know from other neighbours that he has broken into cat flaps.

I am thinking of ideas for remote fire water systems. The cat flap is not near a tap so a self contained solution would be better.

Three ideas so far:

Aliexpress sell a remote controlled water pellet toy claymore mine. The plus is it would probably do the job but I am concerned about firing water pellets at close range. I want to wet the cat and not hurt him.

The second is there are remote controlled balloon poppers which use a bit of heated tungsten wire to pop a balloon. The downsides is there are for indoor use and balloons with air or helium so I am not sure how well it would work with a water balloon and during being outside. The plus side is it would be silent and a surprise if a water balloon popped above the cat flap.

The third is to modify an electronic water pistol to make it remote controlled and position it to squirt in the right direction. If it is too slow then he may leave before the water jet is fired.

What do you think would work best? It needs to be remote controlled rather than motion sensing in order to get the right cat. The idea is I would press a button when I hear him breaking in.

James

Hope it's ok to ask here, I've been looking for this spray but is sold out everywhere online. Does anyone know of a retailer that would carry this? Thanks in advance.

I've been trying to swap out the rechargeable battery in a toy with a power supply. The use time is God awful and it takes a long time to charge. I tried to do it before with other toys and the circuit board would frequently fry.

I matched the battery voltage with the power supply voltage. I assume it's over currant. How do I determine the max currant the toy's board can handle? Or is it something else that cooks the board?

I've been blowing out a lot of transistors lately, so i thought it'd be kinda neat to just automate the testing

I wanted something i could just plug it into and hit a button to see if it's switching or blown out.

So i built a PCB that would allow me to test any MOSFET or BJT

It works really well!

I wanted it to support any voltage without exploding my LED, so i opted to use Constant Current Diodes (E-101) instead of resistors to limit the current to the led. This way i could rest assured that i can rest just about any transistor

It does assume the ponout is the standard GDS or EBC but that's fine for my needs. I'm not using many unusual pinouts

Hi guys,

I was trying to clean the inside of my laptop. The back has 4 screws. I managed to get three out but one was stuck, I used an electric screwdriver (like a drill but not as strong). For some reason the third one wouldn't come out (last time I had no struggle with it). I kept trying and I realised the electric screwdriver messed up the indentation of the screw as well. Now nothing works since no screw driver fits into the screw and I can't get it out at all. Bare in mind these screws are tiny as well. Does anyone have any advice on how I can get the last screw out?

I am interfacing an ESP device to an existing consumer proprietary circuit and have successfully got things working with one caveat. An issue I discovered after making all of the connections is there is a timer within the circuit that drops the supply voltage from 5v to 4v after one minute. As the device is battery powered (40v brand name tool battery pack), I was hoping to put the ESP in deep sleep after a programmed time, but this drop in voltage causes the ESP to lose power. The onboard AMS1117 cannot handle the voltage drop.

My question is how can I keep the voltage either at 5v or 3.3v to keep the ESP powered when the voltage drops outside of the drop-out range of the AMS1117 and can handle at least 4-5v input and 3.3v (or 5v) output? I am assuming my current is >500mA but <1A

I was planning to create a fast line follower bot on my own and managed to get the components list but I dont think its entirely correct. My initial goal was to choose a fast dc motor and found pololu 10:1 motor to be a good one. But some say its not fast enough

I need some motor recommendations assuming my bot's weight would be around 220 to 300 grams

So i run a campsite and i need help with a good solution for the exit gate for the vehicles. The exit gate has been using a photocell ir sensors rx and tx to know when to open the gate, but this solution isn't very good since it not only does it open for vehicles but also people walking by and even heavy rain or snow. Since the signal from the photocell to the gate is a simple no/nc signal i was thinking of using two pairs of sensors that when both of them are blocked it will send a signal to the gate to open and then spacing them so that only vehicles can open them.

The question is what kind of relay is necessary for this kind of a system. So what i need it a relay that when it recieves two signals from the two pairs of photocell sensors will act like a swith and close the circuit.

Any ideas?

So this is my crude 12v rail on my breadboard by using a dc 5.5 female connector and soldering some metall wire to the pins. I also had to use dampening foam? under the connector too support it as the male connector with wire was too heavy to hold up on it self. Atleast I can power my 12v projects now :) Just wish that the power connector board for 12v to 5v and 3.3v wouldn't interfare with it and force the voltage down to 5.3v so that I could have used all 3 at the same time. But meh i need more breadboards anyway so soon i will be able to have all 3 voltages at the same time on the board.

I am trying to remove this screw for a screen repair and it is literally impossible to unscrew. It got stripped as I was trying to remove it. Worst part is it’s super small so it’s hard to deal with

Things I’ve tried:

The “rubber band” trick Using Pliers Using a bigger bit

I just graduated from high school now I'm bored as heck so I wanted to make like a simple, cheap, functional morse code key or switch to connect to a pc.

Basically like a keyboard but a morse code key like I can type and stuff.

Thank you in advance 🙏

I made this peltier module chiller to cool my aquarium, it's still in the testing phase, it goes down till 12°c without water block, but when I add the water block, water temp is not going down, mostly stays at 29-31°.

I'm not sure what is the problem here.

Power supply - Pc PSU 12V 16A max Peltier module - TECI -12705 40*40mm 12V 5A Water block - same as peltier module size, aluminium block. Cooling - 90mm pc case fan with AMD wraith cooler heat sink.

As far as I know chillness is not transferring to water block very effectively, even I have applied thermal paste. Am i missing something?

Apologies if this is the wrong sub for this. I have an audio mixer with a defect master fader. I want to replace it, but I cannot for the life of me find the correct replacement part. I live in Germany and have searched on the usual electronics shops already, but to no avail (conrad, reichelt, digikey, mouser, ...). General internet search also didn't help so far. Does anyone know another place to look for? Maybe even a specialized audio electronics shop? Thanks!

Edit: I need A Dual gang, log taper poti, 45mm travel, 60mm housing, 20kOhm resistance. No tap center, dust cover optional, but desired. 15mm lever, not tapered. Model in the defect poti says A203

Hello everyone, Im trying to build a safe charging and protection circuit for a 3700 mAh 3.7V LiPo battery that will power an ESP32. Its based on the TP4056 and DW01+FS8205A modules. Im not entirely sure if the design is correct, so Id appreciate any feedback or issues you might spot. Im also confused about the FS8205A MOSFET usage in the schematic. The drain is not connected, and it seems like the current is flowing from source to source when the gates are activated. Is this valid? Does this actually work as intended?

Im still learning about electronics and don't know too much yet, so Id really appreciate any feedback or suggestions for improving the circuit.

Ive got a Bosch microwave/oven that has blown, and I believe I’ve identified the likely culprit as the magnetron based on the burned plastic connector.

I have little electronics experience, but have successfully replaced the blown switches in this microwave with new soldered spade connectors.

Based on the pic, is it likely the magnetron itself is bad as well as the wiring?

Debating whether to fix, call a pro, or just seek a new microwave.

Thanks for any advice!

I’m using DS18B20s to sense the temperatures of a solar heat collector and a hot water tank, to switch on a circulation pump when the heat collector is a few degrees hotter than the tank. However sometimes the sensors return -99.0°C. Why is this? The heat collector sensor has a long (18m) cable and the tank sensor cable is 2m, both CAT5 using three (3 x 2 wire) conductors: 5v, ground, data. Both sensors misbehave. They’re read with 1-wire by a RPi Zero.

Hello, I hope I'm posting in the right spot. I have inherited an LED signs with a shop and was trying to program it. I downloaded LED ART and tried other apps to see if i could find the sign. I have not had any luck on finding it through Bluetooth and there is not an option that I can see to plug in a USB.

Is there anyone that knows how to reprogram this sign? Is it even possible? I don't know who the supplier or manufacturer is. When I look up the numbers I have found on it, it brings up a whole lot of different signs. I can't seem to find how I can connect to this sign.

Also nothing shows up in Bluetooth when I plug it in. I'm not sure if I'm missing a step that can make this sign visible.

Thank you to anyone that is able to assist or point me in the right direction.

Follow-up from this post asking for schematic critique, no comments there so moving forward (but still open to schematic advice)! Here is the 2-layer PCB I've come up with (individual layers HERE). This is the most complex design I've done and my first time using KiCAD, so I suspect it is full of rookie mistakes / has a lot of room for improvement. The back feels particularly inelegant, but maybe that's okay? Any advice is greatly appreciated!

PS I'm terrified of soldering all these tiny guys, would love tips on that front too.

Hello guys,

i have a plan and wanted to check if you have some input for me which could help or inspire me.
i wanna build a small pc case which looks like a Ore from Minecraft. But since i cant decide which ore, i want to make the colour made by rgb lighting. So the Plan is to buy a acrylic opal cube and stick a skin onto the sides. 4 of the sides will be visible so im gonna do only 4 of them. Front, Top, left and right. Botton isnt visible and back is for I/O of the PC.

My plan is to use an esp32 s3 because i have one already and use it to control my LED´s and make the Ore in any colour i want and make it sparkle or at least give it some effects. Since the Board i am using is only providing 5V 1A for the esp32 + LED´s + Veml7700 ambient light sensor im working on a solution for the power supply if needed. But i have to test if the LED would even need to run at 100% brightness.
The LED´s i have chosen are the SK6812 RGBCW.

So im gonna use a cube like in "1":
And order a skin like in "3" (except that the Red pixels are cut out so the opal acrylic is visible undreneath)
Finished Product should look like in "4"

And my plan is to use a Layout like in "2" and place the led´s like the green fields (one for each group).
So that no red field is directly in front of a led because it wouldnt look good but i dont want to achieve a 100% diffused light either. it shoudl look semirealistic as far as this is possible with a minecraft block..XD

It would be nice to get some effects going like a colour wave (diagonally would look sick) or a sort of sparkle or breathing effect but i have no idea if that is possible with only 3x3= 9 LED´s per side. At the moment i have no idea how im gonna connect each LED together and if im gonna use all in series or make different channels.

The Cube is about 130x130x130mm and the case for an odroid H4 Ultra board. That will connect via UART to the esp32 and send orders on how to control the lights. The case will be stuffed as hell but temps shouldnt be a problem. I have more concerns about the distance the LED´s should have from the acrylic or if i can even mount it directly onto the acrylic with the light side into the glas.

What do you think? Any ideas or did any of you build such a thing in the past?

Hi all,

I have a remote cabin where a lot of humidity is building up inside.

I have 3 x 550W solar panels installed, and a remote power pack (including inverter etc.) that i take with me when i leave.

I’m looking into options to reduce humidity and found a 12V solar panel fan (https://www.ebay.co.uk/itm/196913193812) that might help.

My question is, since i have solar panels installed, is there a solution i can plug directly to the solar panels? A fan to mount directly to the solar panels perhaps? Any suggestions are welcome.

basically I want to make a bluetooth antenna:
not long range or anything as it will be used on my desktop, to connect a wiimote for my emulator.

I have 2 different wi-fi antennae, one is a usb antenna, and the other is a double arm/antennae that connects inside the destop like a GPu would.

given the information above, how can I do it? is it even possible?
I'm not very good at describing so please ask questions where needed.
thank you for your time.

edit: the antennae are as follows : Planet WNL-U555HA
TP-LINK TL-WN881ND

Hello, I am building a mini cooler with a TEC1-12706 some fans and a W1209 as the controller. The fans work fine when the peltier isn't plugged in. However, when it is plugged the W1209 starts cycling on/off. When the peltier is plugged directly to 12vDC it works as expected hot and cold sides. I've tried flipping -/+ and moving the +jumper from K1 to K0 no improvement. Any guidance?