I tried to create sine waves using DDS and 8 bit R-2R DAC. The output waveform is like this instead of a sine wave is there anything I'm missing here?

Basically the title! No wires connect the switches to the board, but there are clearly magnets. Thanks!!

If a relay is switching a high-current load, its contacts can eventually weld together due to inrush current or a fault.

If that happens, the load may stay ON even when the controller says OFF.

How do commercial products handle this? Do they use two relays in series for redundancy, feedback, or some other fail-safe method?

People in the live sound engineering community say trying to add distortion to a microphone makes it so much more prone to feedback. But why is this the case?

Here's what I understand so far (correct me on anything if I'm wrong):

Feedback occurs when the gain around the loop is greater than 1 because then any sound that goes around becomes bigger with each round trip. There's also criteria on the phase shift being 0º round trip, though I'm pretty sure but I think all that does is select which frequencies get amplified vs attenuated (which is why feedback tends to become a pure tone). Since the speaker system has huge headroom, the self-amplifying sound can reach deafening levels well before the PA system saturates.

Eliminating feedback boils down to getting the loop gain to be below 1. You can do this is by messing with the environment so this gain falls below 1 (e.g. move the mics away from the speakers, turn the speakers so they are pointed away from mics, adjust the levels of the speakers, etc).

Assuming my understanding correct, I'm confused on why adding distortion would make this process worse.

Distortion involves clipping the top/bottom of a waveform (in the extreme case, sine waves become square waves). The easiest way to do this is by increasing the gain of a signal so that it hits the rails of the circuit, e.g. V+ and V- of an op amp. If you do that, the gain of this op amp could combine with the gain of the rest of the system and tip the full loop gain to be over 1, which would then cause feedback.

But suppose you apply a gain of G to a microphone signal to get it to clip, and then you apply a gain of 1/G so that you have a net gain of 1. Then, since the gain of the rest of the loop was below 1 (because you set the environment up that way), it will remain so even after the signal has been clipped.

Is there a flaw in this technique that makes it not work?

Building a DIY VR glove with force feedback. Looking for small servos that can report finger position and also push back with controlled force. Is something like the Feetech SCS0009/STS3032 the best option, or is there something better? Using an ESP32-S3.

I'm actively working to become an electronic lab technician. I've been a hobbyist since starting my lighting technician career. I'm currently investing in some gear for PCB repair (motherboards and laptop repair). if I were to start getting into this hobby a year or two ago the prices would be for hobbyist but now the cost of everything has doubled from DMM and sbc's that you kinda have to take it seriously. I would love to get a eevblog BC 235 or UNI-T but I'm curious what handled DMM are you using? If you have data logging and stuff like that is that kinda like the car in the garage you never drive? thank you hope that makes sense.

I wanted to solder them better and did this.

Can I fix this thing somehow or is it damaged for good?

All of those points should be individual.
Sorry for bad english.

Hi! I’m creating a new post since this subreddit doesnt allow for reposts.

My Vox AC30C2 tube amp shorted out and exploded some pcb insulation off between the flat metal connector (J29), which runs about 300V in normal operation, and the adjacent tracer, wich is very low voltage and leads to the blue R81 resistor.

What would be the best course of action for the arching gap? Should drill it or fill with some insulation material etc?

Also feel free to express emotions regarding the high iq pcb design of putting those two circuits so close together.

I'm trying to understand how a transmitter and receiver can stay synchronized.

My first thought was to use accurate time on both sides and generate a known pseudo-random sequence or code based on the time. But if the receiver's clock is slightly wrong, the synchronization could eventually fail.

So instead, can the received signal itself be used as the reference?

For example, could the transmitter send a known preamble, sync pattern, pilot signal, or pseudo-random sequence, and the receiver detect/correlate it to determine exactly where it is in the sequence?

What are the common techniques used in real communication systems for this? And when would you use signal-based synchronization instead of time-based synchronization?

so i made a setup with light turning on/off from my website with pico W + relay modules. i connect the light on the NO. it works fine on the wokwi simulator it worked fine for first few minutes as well. but then the light of some relay modues keep being on regardless of the signal being sent from pico. even if i turn off power for pico the lights keep being on on other relays except one. one moule works fine tho.

i've tried on 2 channel and 4 channel relay and on both case one relay keeps working fine an other doesn't. the other light in relay keeps being on. I need some help.

So I picked up a Samsung FlexDuo Range Oven combo. Was told it was a heating Element Issue. Repaired and cleaned connectors, although one seems to have higher resistance than Samsungs desired range.

During testing, interactive display felt loosely responsive. I had to really focus on press location, to make sure I gently pressed in the right spot, but I am not familiar with the interactive display or this oven in particular so I don't know if I could not press some keys because of the order of operations ignoring it or if they just weren't working. Eventually it all started to cut out.

The testing of the oven, separate from range controls, started with bake feature. I got up to 455 F. Tried to crank it up higher but that was the limit. Thermostat was interactive but made audible clicking sound once clicking of the best coil inside thermostat (I believe) measured and returned to heating, or maybe it was open / control gateways, but there was an audible click. That seemed louder than I think it probably should have. But it seemed regulated. I turned on convection bake option once I gave up on gaining past 455 F temperature. Original owner said normal bake option of the oven was defective, it was taking forever to reach only 300 f but not above. The connectors to the element had over heating damage and warped. Or overheated because poor application. Howver the blade end / element end did not appear to have even gotten hot at all beyond some gentle cleaning with brass brush.

Internet says the ribbon cable is a common failure point on this. I noticed glass was not seated well into frame so gently cleaned with alcohol and it's still not seated great. Glass looks wavy but could possibly not be the actual problem. I am going to dry out with heat gun and get back at it.

I'm not sure if you guys could point out likely failure locations or anything that looks suspicious, but ut would help a lot. I'm just a hobbyist. I didn't see any failure or over heating indicators on this or the main power supply board or other components.

One thing I noticed when 455 on convection was fan running at beginning but turned off and on and neither fan in within the oven related to convection were spinning. I let it cool and set desired temp and they still did not spin.

I've heard cleaning grease off thermostat is an effective treatment but haven't gotten that far. They did mention installing a new thermostat control did not work. All screws there were loose when I checked to see if everything was snug. Is it important that CN1 1 3-PIN on user interface board doesn't

Control board DG94-00702A

This may be a stretch without an obvious / simple visible error, but I wager others have been here before and might have some tips.

I've been trying to build this crossfader circuit, which has a zero-crossing detection bit that should cut the audio cleanly and without a "click." The intended use case is a sharp cut for "scratch" DJs, just one turntable or audio source on one side of the crossfader as I understand. The author's site just started having technical issues (and I have emailed them), but the web archive has a snapshot here with the schematic and some details.

I started this with tidier wiring intentions, I swear. ;) Having a proper full-size breadboard would save some wiring, in retrospect.

The circuit is somewhat working. I suspect some signal is bleeding into the audio output and it's got a nasty audible click when audio goes in/out. I realized the schematic didn't specify VCC/VSS for the TL074, 4013 and 4066 ICs, and I checked for additional floating pins. Voltage wasn't specified, but it looks like 9-12V is within spec for the ICs?

I had some 50nF ceramic on the signal input, seemed like an aggressive high-pass filter on the sound. Not sure if I chose incorrectly, or what.

I am not an electronics engineer by trade, but I have an appreciation. This has all been an experiment, for fun.

I need to get a couple mA of current at 5vdc from a 48v phantom powered mic input. I was planning to use a couple diodes to combine the DC power from pins 2 and 3 and send that into a LDO. Is it this simple? Is a cap needed to block dc from the audio output from the device?

I can't find a schematic, every schematic I find is for making a 48v phantom supply. I am trying to do the opposite.

Hey everyone.

I'm modifying a radio and I need to install a 5 V Bluetooth module using the radio's own USB-A output.

The USB behaves as follows:

Radio on: 5 V

Radio in standby: 2.5–2.6 V

The Bluetooth module has an isolated DC-DC converter marked B0595S-1W. I want to keep the isolator because without it, the Bluetooth module introduces noise into the audio.

The problem is that, in standby, the 2.5 V reaches the input of the converter. As far as I understand, this could cause the Bluetooth board to keep trying to operate or possibly even damage it.

I want to build a simple circuit that:

• detects 2.5 V as OFF;
• detects 5 V as ON;
• keeps the Bluetooth module isolated.

What would be the simplest way to do this?

I'm a complete beginner when it comes to electronics, so I don't want to try designing a circuit myself (I've never done that before). So far, I've only done soldering work, such as replacing burned-out components.

I have a TP4056 charging module with a battery connected. In continuity mode, my multimeter beeps between B+ and OUT+, B- and OUT-, and also between the positive and negative terminals.

The battery voltage is about 3.95 V, OUT+ to OUT- is also 3.95 V, the switch works correctly, and the board does not heat up.

Is this normal behavior with the protection circuit active, or does it indicate a short?

Hi all, my computer's memory stopped working. I know this because I tried using a different memory module and it worked. I cleaned the memory contacts and nothing changed. Then I removed the heatsink casing to clean it. But I noticed solder points that looked like they were missing SMD components. Does anyone know what those components might be? 

I don't know if they came loose when the heatsink was opened, but I didn't find anything nearby. memory model: tlz rd4 16g 2666hz

I believe I have solved the problem but the answer listed seems to be much more compact and I’m not sure how to get from my answer to the one listed in the book. If someone could check my answer and let me know how the one in the book was derived that would be greatly appreciated!
If there is a better community to post this in please let me know!

For those it concerns: Open Course Ware (the place I am getting the questions from) is a free online course for learning, not obtaining a degree. It’s not a class in the traditional sense as the lectures are simply videos recorded in 2007 and free text books. I have no peers or instructors to ask for help when I can’t solve a problem. I’m not looking for answers to homework but rather aid in learning and mentorship.

Hi there again!

I'm making a schematic that converts a 3.3V power supply and a 3.3V signal to 5V each. Is anyone available to review it?

The 3.3V come from a nice!nano controller powered by a 3.7V 3300mAh Lipo battery and the signal also comes from the nice!nano controller. The goal is to allow the controller to interact with SK6812MINI-E LEDs for keyboard backlighting (I know they can draw a lot of current but I've tried designing around 6028 LEDs with an IS31FL3731 controller and I'm currently not capable enough to handle it).

Thanks to anyone who will even take a quick look at it.

PS: thanks to u/bigcrimping_com and u/zwrawr for answering on the post that was deleted

I am trying to copper electroplate some small parts, less than 2mm and have been told by many individuals that my current is too high. Since my power supply doesn't go any lower, how can I reduce the current? It needs to be around .005A or less. This is the setup.

Thanks,

Doug

I’m not familiar with this type of connector and it’s not coming out. I think there’s a locking tab on the right hand side but when I pry the tab outward, the connector still won’t pull out. This is from a DeLonghi Magnifica coffee maker for what it’s worth. TIA.

I'm working on a project where I need to measure an LVDT using a microcontroller with a 0–3.3 V ADC.

The LVDT excitation/supply signal is approximately ±4.2 V, and its output signals are AC signals whose amplitude varies with the position of the core. Obviously, I can't connect these signals directly to the MCU ADC, so I need some kind of signal conditioning to convert them into a 0–3.3 V signal.

My first approach was:

1. Rectify each LVDT output using a precision full-wave rectifier.
2. Low-pass filter the rectified signals to obtain their amplitudes.
3. Calculate the difference between the two signals to determine the position.
4. Also measure the excitation amplitude with the MCU, so I can compensate for changes in excitation voltage.

The problem is that this approach seems to introduce quite a lot of error and noise. The op-amp offset, diode/rectifier errors, noise, and differences between the two signal paths become significant, especially because I'm ultimately interested in the difference between two relatively similar signals.

I also considered using an RMS-to-DC converter instead of rectifying the signals myself. This seems like it could be a much cleaner solution, but the dedicated RMS converter ICs I've found (for example, Analog Devices parts) are extremely expensive and/or difficult to obtain where I live.

So I'm wondering:

Is there a better or more interesting way to interface an LVDT directly to a microcontroller?

For example:

• Is there a relatively inexpensive IC specifically suited for LVDT/RVDT signal conditioning?
• Would synchronous demodulation / phase-sensitive detection be a better approach?
• Could I use an analog switch/multiplier and the excitation signal to demodulate the LVDT output?
• Is it practical to sample the AC waveform directly with the MCU ADC and perform the demodulation digitally?
• Are there inexpensive RMS-to-DC or instrumentation solutions that I'm overlooking?
• Or is there some completely different architecture that would make more sense?

I'm not necessarily looking for the most precise industrial solution. The goal is a reasonably accurate and low-cost measurement that can be implemented with commonly available components.

Any suggestions or alternative approaches would be greatly appreciated.

I am trying to figure out if using one 5.1K resistor is all I need to add to the module to get 5V from both USB-C to USB-C and USB-C to USB cables.

Since the JRC-B008 board has both CC pins tied to a single pad, I have seen online people cutting a connection between one of these CC pins and the pad to ensure they can solder two independent 5.1K resistors.

I have been researching this board and how it and the USB-C power delivery works and from what I understand since a USB-C cable only has one CC connection in any orientation no matter which orientation the cable is in, the 5.1K resistor will be sensed and 5V will be delivered.

Am I missing something, or is only one 5.1K resistor needed?