I bought a sewing machine recently and it came with a very sensitive pedal. They sell this other pedal which makes it possible to sew very slowly. £60 felt like a ridiculous price for this piece of plastic, but I'm not an electrician (I know some basics). Can someone please help me understand what the difference here is? Is it possible that I could achieve the same result by a simple modification? All I can see is the VR2 resistor missing in the new one.

UPDATE:

TL;DR: The "OLD" pedal is the same board without the VR2 trimmer. Removing VR2 from the OLD pedal gives the same 0–460 kΩ range and the same slow-speed control as the NEW one. I'm returning the new one and keeping the modified old one.

Thanks everyone for the helpful comments. I didn't expect so many!

I did some testing, and here's what I found.

Resistance measurements (VR1 range)

First test: With VR2 set to its max, the old pedal was much easier to control and I could start slowly. The new pedal still felt a bit nicer, though. I put that down to the extra ~60 kΩ at the top end.

The mod: I cut VR2 off the old pedal and measured again. It now has exactly the same range as the new one (surprise, surprise). So VR2 really was the only difference between the two boards. And yes, on the NEW board they simply cut off VR2.

Result: I tested both pedals again and can't tell them apart. The modified old pedal gives me great control at very low speeds, while still being able to go full speed. I personally don't need the adjustability VR2 enabled at all.

Verdict: I'm returning the £60 pedal and keeping my modified old one.

To those who asked about the price of the old one - it came with my sewing machine (bought at Hobbycraft UK), but it's also being sold here for £47. To be fair, this shop offers you the NEW one as a free upgrade, but only when it's in stock. That's where I bought the NEW one from. Hobbycraft did not offer that upgrade, nor sells the new one.

What is the correct way to measure voltage of a sound signal on a speaker? And also what voltage range should the meter be in?

A friend of mine has an expensive sound system and one of the speakers doesn't work. I took my multitester over and tried to measure voltage on the one that does work, so I could see what the normal reading is, but it read 0 V. I expected it to change, but I expected to see at least some voltage on the meter, but it never did.

I put the common/black probe on the negative/ground terminal of the speaker, and the positive probe on the positive terminal. The speaker worked, but no voltage showed.

Thanks

This is from the service manual of a Pioneer SX-9000 receiver I'm working on. Have I just been working on this too long, or is there a legit mistake in the schematic? I feel like the C+ and C- labels are incorrect for the bottom going towards the push switch unit, but my overthinking is really thwarting me here.

Can anyone help me build this logic circuit in multisim? A logic circuit subtracts two signed four bit numbers A = A3A2A1A0 and B = B3B2B1B0 by calculating A-B. The circuit has two outputs (Y and Z) and operates as follows: a. If A = B, output Z = 0 otherwise it is one. b. If A < B, output Y = 0 c. If A > B output Y = 1. Using the 74LS83, design and implement the circuit in MultiSim. The 74LS83 is a 4- bit binary adder. I've done up to this far, but then I realised that there needs to be two outputs only.

My son's toy walkie-talkie set came with a faulty speaker. The first photo shows it in-place - it's marked 8 Ohm, 0.25 W, and I measured the diameter as 29 mm.

I bought a replacement from AliExpress here, matching the impedance, power rating and physical size - as shown in the second photo (sorry it's blurry). But when I connected it up, the sound output was *much* quieter than the original.

Have I just bought a poor-quality speaker? Should I try one from a more reputable source, such as this one from DigiKey? Or maybe step up to a 0.5W speaker? How else might I increase the volume to match the original? Thanks!

Iv just bought this solder radio kit and I can’t get any radio stations to come up if anyone could help please im new to electronics and would like some guidance thank you

It reads A810 and its like a SOT23-6 but some sites say it could be XC9208A103M but that component has SOT23-5.

This are the connections I could recreate.

Does anyone sell a non-conductive, esd-safe tool for flipping switches in small surface mount DIP switches? Something with a small hook and a poking point?

I’m using a screwdriver to flip switches on a powered, expensive device during testing procedures, and it makes me a little nervous that I might accidentally short something etc. (I’m using a wrist strap, esd jacket, and esd shoes already)

Not sure if this is the correct sub but I have this light that turns on with a button but shuts off after a few seconds. I would like to make it stay on until I disconnect it from power via usb or plug?

or is that the capacitance is much greater than the frequency at that point

So I am working with a board with this kind of heatsink on a chip but it was glued with a white epoxy glue which I have never used. Now the board is OK I need to get this glued again but I tried with UV resin and it just doesn't work.

I'm looking to have a hardware shutoff for a MIPI-CSI device. In this case it's a IMX415 camera module. If I just cut power to it, will these be any potential damage to the device, or should I look to have a full MIPI switch to also make sure the data lines are disconnected? By cutting power is there any potential to damage the device? Then re-enabling power should theoretically also power it back on? Any risk of the initialization going wrong?

Can anyone show me a recreation of this on a mini bread board and in Tinker-cad. Please I'm a design student I don't know what any of this means 😭

Pointing to things that would help me understand would also be appreciated

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Theres no marking next to this component. Unsure exactly what it is ? Any ideas ?

Cheers.

Kds9 2h1?

I’m guessing it’s a sensor of some sort but I have no clue and Google won’t tell me.

2 damaged pins where do we connect each pin?dose multimeter test work here?its for r2 side i think

So I've been using TVS diodes in all of my projects without really understanding how they protect the circuit, so I decided to do a few simulations

I got the ESD generator model from an article I simulated it and it worked correctly, but when I tried to apply the generator to a circuit I'm working on it didn't do anything?

What's the right way to do this? how do you guys simulate ESD events with accordance to IEC 61000-4-2??

ok so basically i have this membrane keyboard from razer (razer ornata v3 x) and i raged a little too hard and hit my desk using my keyboard. after that it stopped responding to my clicks but the rgb still works. i was wondering on how i can fix it and what is currently wrong with it? ill add a couple of pics i took

I’m not to good with how computers work so I took a computer/networking class and they let me take some stuff from broken computers (speakers, power supplies, batteries, that kinda stuff) and something that caught my eye is a lot of them had a BJT attached to the outside of the front of the grounded case and whenever I looked up why it was there all I got is what a transistor is.the transistor is a 2n3904, my theory is it’s like temperature regulation or some other version of using a component to do something it wasn’t made for.

Markings: B500K

Shaft: D type, 6mm dia, 11mm length. Push stroke 4mm, approximately 270 degree rotation

Bushing/mounting threads: 9.6mm diameter, 1mm pitch, length 10.5mm

Switch type: Push lock

I'm having no luck on mouser!

looks like a resistor but the band colours (silver, grey, brown, gold) dont really match up with how resistor band colours are supposed to be ordered im pretty sure. this is on an applevision 1710 crt and is on the deflector board. saw sparks fly out the bottom while it was on and found that this component was charred on the bottom. i also recapped this board recently, so that might be related. am i stupid and reading the colours wrong? please help!

I’m building a system using an ESP32, a relay module and a 5V solenoid.
The setup was previously working correctly, but now the solenoid doesn’t activate at all.
My setup:
ESP32 development board powered through USB.
Relay module with S (signal), V (power) and G (ground) connections.
5V solenoid connected through the relay.
Separate DC power supply for the solenoid.
Breadboard and jumper wires.
A web application built using Replit that sends activation commands to the ESP32.
The problem:
The solenoid doesn’t move.
The relay doesn’t make any clicking sound.
I’ve compared the wiring with photos of the previously working setup.
The wires appear to be connected securely.
I may have deleted the original Arduino source code, although I haven’t confirmed whether the firmware on the ESP32 was overwritten.
I haven’t measured the voltage or tested the relay independently yet.
What I need help with:
Can someone identify any obvious wiring mistakes from my photos?
I’m particularly interested in whether the relay is receiving power correctly, whether the ESP32 connections are correct, and what would cause the relay to stop clicking.
I’d appreciate specific troubleshooting steps to identify the actual fault rather than replacing components unnecessarily.
I’ve attached photos of the current wiring and the previously working setup.

I am working on an old animated Santa for a customer and I am stumped. I would really appreciate any input y'all might have on this....

Here is the schematic as well as I was able to reverse engineer it - www.RobotsAndComputers.com/temp/Santa.pdf

OK... when I got it, the battery pack as disconnected, the switches were wired wrong and the S8550 transistors were shorted, as well as one of the H8050's. I fixed all of that and it kinda sorta works. D1 checks ok, as do all of the resistors and capacitors. The IC (which is an encapsulated blob) SEEMS to be working right, but... .

The way this is supposed to work is that when you press the button SW2, the front of his coat will open (M2). When that reaches it's limit (either TP12 or TP13, not sure which right off hand), that motor stops and the platter inside spins (M1) while the lights flash (P1) and it plays Christmas music (Q8 and the speaker). When that times out (if SW1 is in DEMO) or you press SW2 again, the front of his coat should close (M2) and everything stops.

As I have it now, the platter spins, the lights flicker and the music plays. What DOESN'T work is M2 - the doors (the front of his coat).

Without the motors connected, the voltages between R1 and R6 seem to be alternating correctly. They also seem to be alternating correctly between R1 and Q3 as well as R6 and Q3.

If I am understanding this circuit correctly, the Truth Table is as follows:

P2 on / P3 off / P4 on = M2 fwd P2 off / P3 on / P4 on = M1 rev P2 on / P3 off / P4 off = M1 and M2 fwd P2 off / P3 on / P4 off = M1 and M2 rev

I'll admit that H-bridges are not my forte, especially when you go throwing the middle connection in, so I may be completely off about that.

When I connect the motors back up, though, so long as the limit switch (P3) says that the doors are open, M2 doesn't spin and M1 spins (and the lights and sound work). When you press SW2, everything just stops. M2 doesn't reverse.

If P3 is open on both sides, SOMETIMES M2 will spin continuously, ignoring the limit switches.

If I measure M1, ohmwise, I am getting about 11.5Ω across M1 and 6.4Ω across M2.

I am wondering if the mixmatched resistance has anything to do with my issue? If not, can you see anything that I have missed or need to check? I am at my wits end and this is REALLY making me look bad!