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Hello, sorry hoping I could get some help with this question. Im not sure what the convention is and cant seem to find anything online for question 4ai) and ii)

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Is it heat management? Eddy currents? How can internal resistance be reduced, especially for high output devices?

I apologize if this is the wrong sub and for the ignorance in this field.

Problem: my daughter’s car mirror light has a battery attached to it. We don’t want it to have a battery. It’s powered by usb in the car. I want the mirror to shut off when the car shuts off. I disconnected the battery from the board. Is that dangerous to leave open? What should I do if so?

So I’m taking an introductory circuits and a question asked me to draw a circuit where there is a voltage source, two resistors that carry the same current and one resistor that has a different current.

So I drew the voltage source connected to two series resistors where obviously the same current, then I made an open circuit which leads to back to the negative terminal of the voltage source. And then another parallel branch that has the third resistor.

Now technically I fulfilled my role, the third resistor will have zero current because of the open circuit and thus have a different current than the other two. Would this work or is it a cheesy method? The question just specified they had to be “different”. I easily see now the right way to do it

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Hey everyone,

I’m working on a project where I need to run a 5.5kW system designed for 60Hz on a 50Hz, 420-450V three-phase supply. The system requires both a frequency conversion (from 50Hz to 60Hz) and a voltage step-down to 380V +- 10%.

I’ve come across devices like the GoHz 10kVA frequency converter, which has both the frequency conversion and built-in step-down transformer capabilities, but I’m looking for something similar that might be more affordable or easier to source.

Does anyone have recommendations for reliable and cost-effective devices that can handle this? Or maybe other solutions?

Thanks in advance for your help!

Hey there! So I’ve recently gotten more into electrical engineering and tinkering, and i’m trying to get my mp3 player (on the left) to work with a removed vape Li-ion battery instead of the factory (dead) battery. However, when I tried, the wire I used burned through my electrical tape, and I tried a second time with better wire and it made the battery heat up a lot. What’s wrong here? I definitely have the + and - on the right pins, and they’re both 3.7v.

Product is a (United States) portable light source that mounts to a loupe/magnification glasses. The device no longer charges/holds a charge, hence seeking to replace the Li-Ion battery.

It's a few years old, and the company that manufacturers has EOL the item and no longer supports/stocks replacement parts. The battery is manufactured by another (United States) company, and upon contact advised they are an OEM/ODM and does not distribute nor sell direct to consumer.

Hence, it appears my options are limited. The main specs as printed on the battery that was removed are as follows:

7.4VDC 17.76WH.

Google searching yielded something kind of close...

7.4VDC 3000mAh for $25.99

7.4VDC 2600mAh for $29.99

offered by the same company on Amazon in two different sizes and the form factors are within my needs as well. Not that it matters, but mostly all of these types will be made in China.

So, they're both "pretty close" to the 2.4A capability I need, so any reason not to just go with the cheaper 3A version? Shouldn't really make any difference right? I don't have the schematic nor did I do any testing, but I imagine the wall outlet charger will have appropriate line regulation and possibly current as well, but certainly expect the charging circuit within the unit itself would manage proper charging currents and limit at 7.2V. Right? Please confirm. Last thing I want is a safety hazard and/or any weird issues.

Thanks.

Hello folks, i'm looking for suggestions...

I'd like to make a system that allows to wirelessly control/trigger lights around the apartment.

With lights i actually mean all those small, low power lights that are normally there to make ambience, like shelves backlights or those kind of led candles, or anything that normally would run out of a battery.

I was thinking that it would be nice to maybe attach a small lowpower wireless module that can give the signal to power on/off these lights. They don't cost much so i could easily buy more in case of need.

Have you ever done anything similar? I thought about wireless modules, maybe lora or mqtt that don't suck too much current, and then i can send over signals via nodered on a pi or maybe even the phone.

Suggestions of any type?

Bests

Hey y’all. Hope you’re having a good day. Attached to this will be a picture of a circuit. I’m using Node Voltage to solve and due to the nodes not being labeled, I decided to label them on my own. What I’m having trouble doing is solving for I3 for the super node. I have my super node equation but I can’t solve for I3, does anyone have any suggestions?

I was thinking about putting the node in the top right corner of the circuit, but then I can’t include the super node, but I would help me to solve for I3.

Good day! I am currently about to have my undergrad thesis, and I am looking to see if I can use harmonic filters on capacitor banks to reduce the harmonic load done on the banks. But before I go on with it, I would like to know if this is a study feasible for an undergrad student? If so, would it cost me a lot of money? I don't intend to do anything big, so long as I can prove that a harmonic filter helps with a capacitor bank, that would be good enough. I was told that my country does not use filters for the capacitor banks, hence why I did decided on this thesis topic. My counry uses 460/220v and 60hz, if that is any help.

I am also open to any suggestions for a thesis title, something with programming or maybe something needing to be improved upon would be fine too. So long as it answers a research gap, it'd be fantastic Thank you very much and sorry for your troubles!

As the title question suggests, I am wondering if a smartphone’s transceiver could be modified in terms of signal feed and timing to operate as an FMCW radar. I understand the regulatory aspects of the frequency bands, but from a technical point of view, is such a thing possible? Of course, it would likely involve firmware reprogramming, which might be restricted by the manufacturer. I would appreciate your input on this curiosity. :)

I am creating essentially a battery bank with an 18650. I plan on using an STM32L01 with some TI BQ products.

I want to use the analog channels on the uC to measure the various voltages on the board, including up to 24v on the input, up to 12v on the output, and the 18650 voltage.

I will obviously need to use a voltage divider to measure this voltage. However, this device will potentially go a long time between charges (maybe a year), so I want to minimize the leakage current through the voltage divider, but I will of course need enough current to get an accurate reading.

How much current do I need to get a good measurement (and really, what spec should I be looking at in the datasheet to determine this)? I know I can put a small (100nf) cap between the AIN pin and ground to help. I know I can size the voltage divider to be super resistant but then I would get bad analog readings.

I have also seen in the RPI2040 hardware design that I could also put a transistor on the voltage divider to turn on/off the divider circuit, but I don't really know how that would affect the voltage reading and how to size a transistor for that

More info: I won't be measuring voltages while the device is asleep. The microcontroller will probably be running at around 1.8V or something below the minimum 18650 voltage so I can just use an LDO to power the uC. I will be reading voltages at 10-100 Hz

Any advice helps! Thanks!

Is there a 6-20R with gfci protection?

Wondering what is being done on the countries with a line to ground voltage higher than 125V (like 127V) for the receptacles that needs gfci protection. I know that there is gfci breakers rated for 240V but is that the only way to provide protection or is there a 6-20R gfci rated receptacles.

So my company decided to let go a majority of the Technical Experts which included me this week. What is left a smattering of Junior engineers and middle management. In the waning weeks of my firing, there definitely was the hint in the air of moving away from creating IP and maintaining tacit company knowledge to a culture of using off the shelf technology and the heavy utilization of FAEs.

I mean it was understandable, from a ledger pov, that our positions were eliminated as we got paid twice to three times as much as a junior engineer new hire. Nevertheless, this was a very humbling experience for an old guard like myself. I wonder if this is the new face of engineering business moving forward.

Most interested in the cables going to the oven power supply

help, I need an electronic wiring diagram for the oven electronic circuit Amica EHCX 933 013 S. 

I have a christmas draw(?) for gifts. I'll gift someone from my class something that reminds of me to them. I think something about my major would be good. I'm in preparatory class so something easy(and cheap) to make will be better. What cool DIY projects I can make and gift to my friends?

I have this question in a EEE past paper and I can not find a definitive answer online or in notes which don’t contradict themselves. Any help would be appreciated.

Q. Assuming the CT is operated within the linear part of its magnetising characteristic (e.g. non-saturated), how will the increase of burden impedance impact the secondary current output from the CT (i.e. increase, decrease or no major impact)?

this equation for current division is wrong

inductor current should be replaced by \"capacitor voltage\". this mistake is probably because in earlier additions they started with RL circuits, then went to RC. So now that they made RC circuits first, they forgot to change this.

this is just kind of funny

the cover looks ehh

There were many other mistakes in it, errors in solutions for example. I'm just confused as to why a book in it's 9th edition would still have these glaring errors and problems.

I'm working on procurement strategy for our electronic BOMs at a smallish OEM, and whether I'm looking at Arrow, DigiKey, Mouser, etc, I can often get pretty varying leadtimes on the same part. Does anyone have some perspective on which distributor is the most reliable for that?

Also, I used to work at a firm with a SiliconExpert subscription which was super useful for working out lifecycle statuses. That sort of subscription isn't in budget at the new place for now. Anyone have advice on another one-stop shop site I can get component lifecycle updates? Ideally with the feature of uploading a spreadsheet listing all the parts, instead of looking them up one-by-one?

Thanks in advance.

I’m currently in community college planning to transfer for electrical engineering because I enjoy math and am interested in electricity and electronics. I am curious though what your jobs and career fields look like?

What if I have to make a jk flipflop using a d flip flop and some combinational circuit components? What techniques/strategies can I employ for similar questions?

Hi, I am designing an LQR controller for a fifth order synchronous generator model. The states consist of the electromechanical states : delta, omega and the exciter states: Efd, Vr, Rf. Theoretically, omega and Efd should evolve in different time scales for an impulse change in the mechanical torque input of the synchronous generator. However I only observe this time-scale separation for very low values of the AVR gain Ka. Does anyone know why this is happening?

I am designing the wiring layout and harness design for a simulated aircraft. There are 28VDC, 5VDC, 120VAC 400Hz and 5VAC 400Hz signals. The lights were all ran off of 5VDC, but there has been some desire to switch some of these sources to 5VAC. I originally was designing the power bussing to have isolated DC and AC supplies, that is, the AC neutral and DC Ground would be isolated from each other. Quite a bit of work would have to be done to realize this and another engineer posed the question what would happen if the AC neutrals touched the DC grounds. I originally thought this would be potentially destructive for the components hooked up, but I'm now second guessing. After some consideration, I now think this is an okay thing to do. At worst there may be some noise coupled on the DC Ground bars.

Is there any concern for this? Can an AC neutral be connected to other AC neutrals and DC grounds at the same time?