texts: INA219 current sensor not working properly with DC motor

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I use INA219 module to read DC motor current for control propose.
I connect INA219 in series with motor as shown in schematic.

simulate this circuit – Schematic created using CircuitLab
The control signal is 31.25kHz PWM.
when motor turn CW (A = 0,B = 1) it work normally but in reverse (A = 1, B = 0)
the current reading look very spiky and INA219 not respoding after I stop motor shaft by hand.
After some investigation. I found negative voltage on osciloscope.
Setup  A = 1, B = 0 probe on pin A reference to Gnd.

Then zoom into falling edge.

My assumption is the negative voltage that below maximum rating of INA219 did something cause its to reset.
My questions are

What happen here why negative voltage is too high?
How to solve this problem?
(Optional) Any tips to measure DC Motor current?.

Additional Data
This is my setup.


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I'm building a project with multiple RS-485 senders ("masters") and one receiver:

simulate this circuit – Schematic created using CircuitLab

I'm using one MAX485 as receiver connected to a Serial>USB adapter and all the other ones are "masters" sending data from sensors.

If I'm losing some data when multiples masters are sending data at the same time that's not a problem (I'm doing some collision detection with a checksum), but I have some questions:

Is there any risk of damaging chips, if one is sending a high bit (0V because it's UART) when others are staying high (idle or low bit)?
Do I need to turn off the DE pin of my MAX485 chips when I'm not sending data, to let other masters talk?
If yes, even if I have an Arduino next to each MAX485, it's not this one that is sending data (TX on the schematic, it's a serial sensor) and so I don't know when it's going to "talk", should I follow the SAE J1708 wiring? Are the capacitors and the resistors necessary for a short network?

Any other advice?


texts: Phototriac for low voltage AC motor control without external triac

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I have a circuit that does not work as expected. It uses a MOC3023 phototriac to directly control a 12V AC pump.
Since the motor is very low power I assumed I wouldn't need an external triac. This may very well be my mistake, but I still want to use the situation to learn from my mistakes and directly understand the problem.
I have an AC LED module (with rectification) that I use to test. It can be controlled using my circuitry without problem. When I connect the pump instead though, once the phototriac is triggered it latches and won't turn off again.
I then replaced the MOC3023 with a MOC3043, wich is the same plus zero crossing detection, since I thought the inductive load may cause some issues there. With absolutely no luck, the result is the same.
My two questions are is the external triac absolutely mandatory and if so, why?
The second one is why does the phototriac latch up when a inductive load is present?


texts: Thermoplastic-based touch panels: why not?

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(I'm new to EE.SE, so I don't know if this is on-topic here. Please forgive me.)

From what I understand, capacitive touch technology relies on coating one side of a resistive material with a conductor; this conductor is usually indium tin oxide, and the resistive material is almost always glass or some substance based on glass.

Why can't the resistive material be replaced with a thermoplastic, such as PMMA/acrylic or polycarbonate? Surely, that would make the panel quite a bit stronger than the glass-based panels that are used. Edit: This is definitely possible.

If this is possible, why don't any manufacturers produce plastic-based projected capacitive touch panels? (Or is there one that does, and I just haven't come across it?)


texts: PI controlled linear voltage regulator with overcurrent protection

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I designed a simple linear voltage regulator for high voltage application around 500V which is controlled by a PI controller.

Schematic 1 shows the raw design using a bipolar transistor to control the mosfet. The PI controller is build using operational amplifiers and works well. The feedback is a simple voltage divider because the output is around 400V.

How would you guys implement a current limitation? My first idea was a simple comparator which adds a maximum value to the feedback deviation input of the PI controller but I'm not sure about the stability in this nonlinear case.


texts: Easiest way to connect two pins when an output is off?

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I'm planning to build a switch that turns off the power supply to my Raspberry Pi when an integrated circuit (ATtiny 85) output pin is low. The power supply (Adafruit PowerBoost 1000C) goes off when the EN pin is connected directly to the ground. I've been trying to use an NPN transistor inverter circuit to do this, but I haven't had much luck. I can use the transistor (without inverter) to turn the power off when its base goes high (connecting the EN to collector and ground to emitter), and I can use the transistor inverter to turn on/off an LED when base goes low/high, but the inverter circuit actually turns power on when base is low, power off with base high (like the transistor circuit WITHOUT an inverter). It may be that there's an internal pull-up resistor in the PowerBoost that's somehow interfering.

I'd like to be able to connect the ground to EN when my IC output is low so I can save batteries and put the ATtiny in sleep mode. The Pi will be off far more than it will be on.

How can I get this to work? I tried a PNP transistor but seemed to have the same problem. I'd prefer not to use a relay because I don't have a low enough voltage one. I've got lots of semiconductors, though.


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I don't know what's wrong... I have an ATTiny13 which gives a dummy impulse turning a fan on and off every 2 seconds; so the plan.

I attach two power sources (for dummy purpose) before and after the optocoupler (5V on the top right; and DV on the center bottom). In the experiment both have 5V but it has to be tested like this.

When I put an LED behind the opto instead of the fan, it shines bright and nice. When I replace it with the fan - you see it trying to move but without enough power so he just move 1mm until the power goes off again.

I just circled the optocoupler part.

It would be very nice if someone has a clue why there is such a voltage drop through the optocoupler.

EDIT: After the answers below I came up with this working solutions (it seems so).


texts: Why there is no resistor in an AM Detector?

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Consider the simple AM detector below:

Inductor L1 and capacitor C1 builds the "tank circuit", which purpose is to filter all frequencies, except the selecteded one. However, I'm having trouble to fully understand this circuit.

In my understanding, the circuit above would not work, because the antenna is shorted with the diode D1. The diode is receiving the same voltage as the antenna, so the tank circuit is, theoretically, not interfering in the output.

If I was trying to build a tank circuit to select a specific frequency, I would do something like this:

simulate this circuit – Schematic created using CircuitLab

With this configuration, the resistor acts like a "voltage divider", and the frequency plot would be similiar to this:

(To select frequencies near 600kHz)

Of course, if I try to simulate the same circuit, but without the resitor, Vout becomes the same as Vin, since there would be a short between them. But this is exactly the case in the AM detector! How it works, then?

Any help is appreciated,
Thanks!

Obs.: The AM detector I showed is used in almost every AM received schematic I found.


texts: How many bytes can be sent in a single i2c message?

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I've been working with i2c lately between a beaglebone and an Atmel 328P where the Atmel controls a number of devices under the direction of the beaglebone.  In order to accomplish what I've done so far I have been using the Adafruit_I2C library for Python.

From what I understand about i2c (I have read numerous articles about the protocol) all the comms that happen between the start and stop conditions (not counting the control bits) is simply a 7 bit address and a number of 8 bit bytes for the payload. Nowhere have I ever seen anything about how long this payload can be. That is what I am specifically after.

Now in using the Adafruit library it makes a number of assumptions. Specifically, all of its functions are modelled around reading or writing values (usually 8 or 16 bits) into or out of registers (on the addressed chip). They also have a writeList() function, which presumably they intended to write to a number of consecutive registers.

Their writeList() function though can only handle a maximum of 32 bytes of data. I am wondering: is this a real limitation of i2c or is it an arbitrary limit set in their library?


texts:
I'm planning to switch between two power sources DC and USB with an Arduino like below diagram.

What I'm going to do is cut off the DC V+ wire when I insert the USB jack to the Arduino for uploading the code and then returning to the DC power again when I remove the USB from the board.

Is there any problem with my diagram below?

By the way, the Arduino should be always powered.


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I want to model a single one master and two I2C Slaves on a bus. I want to determine how long I can make the I2C Trace to the last/second slave.

How to model the length of the I2C Bus in LTSpice? Should I be using a transmission line model?


texts:
First of all, sorry for trivial question. While googling came across the current circuit, but I'm puzzled how to connect this circuits:

There is 4.5V out put where to connect this, and the whole circuit as well?
Is K2 is the output of the circuit?

P.S.
Could you please mark, where am I suppose to connect?


texts: What is the smallest metal object you can ground yourself with?

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Say I am installing a new CPU in my desktop motherboard and I am interested in grounding myself (by touch or one of those nifty bracelets) to avoid damaging my components.

What is the nature of grounding? Does grounding effectiveness correlated to the size of an object, the conductance of the object, its connection to the soil-earth, a combination of these or other factors?

I'd imagine touching a matchbox car with plastic wheels has a different effect than shaking hands with a life-sized gold statue of Michale Faraday, half embedded in the earth and contacting bedrock.


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I want to generate 1-150Hz+ three phase AC. Output voltage at maximum frequency would be around 240VAC and current around 40A. I have a few 60Hz three phase induction motors, drive shaft coupler, and a 480VAC feed three phase VFD. Yes I can build an excitation supply if needed.

What type of generator would I need to get the above output? What should I know about overspeed and induction motors?

EDIT1 additional information:

simulate this circuit – Schematic created using CircuitLab

I am expecting a three phase sinusoidal waveform out of the generator to the DUT. About the generator type, can I get an induction motor to make the 40A I need? Do I need a synchronous generator, nonsynchronous generator, AC generator, ect?


texts: Microelectronic Circuits SEDRA/SMITH Multisim

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I'm reading Microelectronic Circuits written by Sedra and Smith. There is plenty of examples and problems to solve which include using Multisim and PSpice. However I'm using the newest software (version 13.0) and unfotunately files on CD from textbook were created in older version (probably 10.0). Is there any possibility to run these examples?

Anybody read this text book and run all examples? Why PSpice problem sets were created to different exercises comparing to Multisim files?

Regards


texts:
I'm a beginner. I was going through the Nand flash memory layout. It is given that, page layout can be,

Data area & Spare area alternatively.
Data area in the beginning & spare area at the end.

I'd like to know why the latter is preferred in most cases. Because, I referred DM37x, OMAP 35x and many others, which follow the second layout. Thanks in advance.

Please direct me if I'm in the wrong part of Stack Exchange.


texts: Why can current phones act as Wi-Fi routers, but not as mobile broadband (3G, 4G etc.) routers?

texts:
Many of today's smartphones enable users to share their own internet connection with others via Wi-Fi through tethering.

However, from what I understand, current Wi-Fi has much shorter range and needs a lot more power than mobile broadband, such as 3G or 4G (or whatever tech the phone uses for internet in the first place).

What are the obstacles for using mobiles as effective mobile broadband routers?


texts: My strands of LED Christmas lights are not polarized, and I don't understand how that works

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I have several long strings of LED Christmas lights. Each bulb socket is obviously polarized, with one contact being much lower than the other and the LED bulbs only fit in one way. But the plug at the end of the strand is not polarized, I can plug it in to the outlet in either orientation.
I can't figure out how this works, it seems to me that they should only work in one orientation. The lights are cheap and there is no obvious additional electronics in them.
One thing I noticed is that, if I pull a bulb, all of the bulbs in the string of lights and any attached strings of lights go out, not just the ones behind that bulb. I don't know if that has anything to do with it.


texts:
I have a power LED that requires 600mA at around 25 Volts. Since there are mainly 24 Volts and 36 Volts power supplies available on the market for a reasonable price, I needed to choose a 36 Volts model, because otherwise (at 24 Volts) the LED would be undervolted and probably draw a lot less than the nominal 600 mA. So this decision is already made and not part of the question.

But now for the constant current control: I found two models of constant current DC-DC converters, one rated for up to 36 Volts input, and the other for up to 56 Volts (for those interested, they are the Meanwell LDD-600L and LDD-600H, but that doesn't matter for the question).

I wonder if it is safe to choose the 36V input model and drive it with my 36V power supply, or if I should rather choose the 56V model.

In other words, can I generally assume that the manufacturer has already included a safety margin into the 36V input voltage rating, so that it can operate at this voltage for an indefinite amount of time. Or would prolonged operation so close to the upper boundary of the spec result in severely reduced life span?

At least as far as I can see, the datasheets seem to give no indication about that.

By the way: buying an already current limited power supply is not an option because I would need three of them (it is actually an RGB LED) because of cost and because I want PWM control.


texts:
i tried a little cct for charging mobile battery.....it consist of four 3.7V Li ion batteries,Voltage is controlled by 7805 regulator.....i got 4.91V at charging pin after diode ........mobile charging indicator blinks but battery doesn't got charged i.e  if battery is at 56% it remains there after an hour......

Practically i am learner in this field.......after troubleshooting i concluded that current isn't enough for charging.........

i found this forum quiet helpful for newbies and electronics hobbyists....

Help will be highly appreciated...........


texts: Electrical frequency of motor with different stator and rotor poles

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I know the formula to find electrical frequency when we have RPM and rotor poles of a synchronous machines which is f=RPM/60*pole pairs.
I think the assumption here is that the number of rotor poles equals to number of stator poles.
I want to understand what happens if the rotor poles numbers are different than stator pole numbers.

Does the above equation hold?
What other changes occur in motor operation and why would anyone have both pole numbers different?


texts:
This is a question from this application note:
http://www.atmel.com/images/doc8003.pdf

In section 3.2 on noise it says that adding some amount noise into the signal helps in increasing the resolution of the oversampling converter. It says if LSB toggles due to noise and we are averaging 4 of the samples then the quantization step is halved. I do not understand how is the quantization step becomes half. Could anyone explain this?


texts: Difference between 1206, 0805 and 0603 SMD resistor

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What is the difference between a 1206, 0805 and a 0603 SMD resistor, as far I know they all have a resistance of 10.7K?

I going to need one for my little 5v DC buck converter.


texts: I have worked many years with AVRs and know that its ADC has an internal capacitor that if charged well can measure AC voltages (applying an AC voltage gives a number). But what I don't know is that if this is just a feature made by intrinsic nature of them or they are designed to do that. In other words, how reliable this measurement is as a RMS measurement and if this is applicable, should I cut the input signal to remove the negative part of it (for example by a diode) or the pure peak-peak voltage is applicable?


texts: Power Dissipation in Subtractor Op-amp Circuit

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How much power can be assumed to be dissipated through the resistors of an op-amp configured as a subtractor like the one below?

Theoretically, a very very small current should pass, but I don't know what the minimum power dissipation I should choose for a real circuit for, say, R3 and R4 being 22 kΩ and R1 and R2 being 20 kΩ.


texts: Easy way to probe signals on a multi-conductor cable?

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I have a device that I need to reverse-engineer. This device has a large multi-conductor cable -- over 20 wires that are jacketed into two circular bundles. I'll need to look at all these signals with an oscilloscope.  (Note that I have no need to disconnect and reconnect individual wires, I just need to look at those signals.)

I know of a couple of not-so-easy ways to do this. I could strip off a bit of insulation on all 20 wires (and hope I don't short those bare parts together when I'm shuffling the wires around). Or I could completely sever the cable, get some perf-board, and assemble a short perf-board intersection that takes all 20 wires, puts a jumper in series, and then resumes the cable run.

Is there any easier way to do this? Are there any off-the-shelf items out there to make it easier to probe a whole bunch of wires without issues? Or is there any easier way to do this by hand...?


texts: Mitigating Transitory Effects on Current Shunts

texts:
I have an application where a Current shunt is used to measure system current by a battery management IC.

The value of this shunt determines which value of current is considered by the IC as a short circuit current, I'm using a 0R010 shunt, and the IC considers a short circuit when it sees 100mV across it, therefore, my short circuit current is set to 10A.
However, I have a motor in my system, and it generates a peak current of over 25 amps.
The IC tolerates short circuits for no longer than 50mS, but my peaks last around 70mS. Is there a way for me to add some circuitry in Parallel with the shunt so my peaks are "transparent" to the IC?
I'm thinking perhaps a snubber or something like that, but I've never had to snub a shunt before (if that's even possible).

I know that I could just decrease the value of the shunt, but I really don't want to do that, since detecting shorts above 10A in regime is quite necessary to my application.

I also thought about adding more bulk capacitance downstream this shunt, but that also increases turn-on currents a lot (more capacitors to charge) and my board space is quite limited.


texts: When measuring a resistor with a multimeter does polarity matter?

texts:
When measuring the resistance of a resistor using a multimeter does it matter if I turned the resistor around and have the probes at opposite leads?

Should I get the same results?


texts: Using MOSFET to control heating element using PWM and calculations

texts:
I am panning to build a soldering station and would like get myself clear about driving MOSFET to control heating element using microcontroller.

Microcontroller will be ATmega328p (Arduino Pro Mini) and MOSFET planning to use is IRLZ44N. Heating element rated 50W at 24V .

I am planning to use PWM frequncy around 30 kHz. Is there anything bad with this frequencey particulary for this application?

As per MOSFET datasheet.

\$t_{d(on)} = 11 ns\$
\$t_r = 84 ns\$
\$t_{d(off)} = 26 ns\$
\$t_f = 15 ns\$.

If I want to limit total ON and OFF time within 1% of a PWM cycle. Then least PWM cycle druration I can have will be (\$t_{d(on)} + t_r + t_{d(off)} + t_f) \times 100 = 13600 ns\$. So I can use PWM frequencey upto 73529 Hz (73 kHz) without problem. Could you please confirm my calculations are correct?

Is it necessary to have MOSFET driver circuit instead of driving MOSFET directly with MCU output pin for this application?

My calculation tells I can directly drive MOSFET with MCU output pin. As per the datasheet \$Q_g = 48 nC\$. With PWM frequencey 30 kHz, maximum current required to charge/discharge MOSFET gate will be:

\$48 \times 10^{-9} / (1 / 30000) = 0.00144 A = 1.44 mA\$.

(Update: My above calculation is incorrect as per @Unimportant's comment below. Without resister it would take \$48/95 = 505 mA\$ to charge the gate, which is undesirable for ATmega328p IO pin. So, there should be a resister or gate driver)

So, current will be well within the allowed limit (40 mA) and I think MOSFET can be directly driven by IO pin in my application. Could you please confirm my finding?

Thanks in advance.


texts:
We are working on a blood glucose meter that will measure BG readings through radio waves with a frequency between 60-70 GHz.
That range is necessary to allow penetration through the tissue and we think that it can do a really good estimation with an accuracy comparable with invasive methods.

The main problem is that we don't have a clue about how economically feasible is to buy transmitter and receiver that work in such high frequency or how difficult would be to (find someone to) build them.

Has anyone had experience in working to/building these circuits?
How difficult would be to build an RF TX/RX that works in EHF?


texts: Role of Electrolytic Capacitors and whether they can be replaced by Film capacitors in battery operated power converters

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In battery operated power converters such as motor controller ( half bridge or full bridge ) bulk capacitance is placed across Vdd and Gnd . I thought this was unnecessary since the input is DC and batteries can be considered as "big capacitors" . But after reading i found some of the reasons are :

a. Provide energy in case of high current draw at start , and absorb energy at stop (generated by inductive load).

b. Reduce Ripple current which causes overheat and over voltage .

Is there any more reasons ? which is more important ripple current specification or capacitance ?

For example :
Assume there is a system that uses 1500uF capacitors with 3.3 A ripple current ,17mohm impedance at 100khz .
The same company provides 560uF Capacitor with 2.18A ripple current 20mohm impedance at 100khz.

if two of 560uF are paralleled we will get roughly 1100uF with 4A ripple current  , is this better or worse than a single 1500uF in the case of a motor controller ??
if Ripple current is more important than capacitance then what about using Film (Polypropylene) capacitors since they have very tempting characteristics. But they will have much lower capacitance about 15uF but current rating of 10A or more ?


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Short Version:  Does "30mA exclusive of load" mean the minimum draw while idling, or avg. draw?

Long Version:  While designing a circuit to interface with a radar sensor similar to this, I've noticed that the current draw listed specifies "30mA, exclusive of load.  At first I would imagine that by this they would mean that the device itself draws 30mA without anything attached to it drawing power, but there isn't any way or need to attach accessories etc. to this device.

Would 30mA be the minimum power draw, average power draw, or what?


texts:
I have a 48 V 65 W power supply plugged into my Kill A Watt meter.

I'm not so sure it is as efficient as the label suggests.

These are the calculations I have made:

$$S = V \cdot I$$ in  VA the apparent power.
$$232.6~V \cdot  0.25~A = 58.15~ VA$$

$$pf = P/S ~ [W]/[VA]$$

so,

$$P = V\cdot I\cdot pf ~[W]$$

$$27.4~W/58.15~VA = 0.41~ [pf]$$

Does this sound like the efficiency of a power supply marked VI?

Whilst I realise pf is not efficiency, my understanding is that to be more efficient the pf has to be high (close to 1) and this looks like I have less than half?

I have seen that efficiency, of a  class VI power supply, should be a minimum efficiency of 86 % and this doesn't look like its near this?

Am I wrong?


texts: Implementing a delay is easy but I wonder is it possible to advance a signal? if so then is the circuit more complex than delay? I was just doing a DSP problem of plotting signal x(-n+k) and there are two ways we can do so by folding and delaying or by advancing and folding. I thought may be delay is better way cause it probably would be easier when it goes in terms of implement circuit. I have no idea if that logic makes sense or not?


texts: How can I design my PCB in a way I can debug the Atmel microcontroller on board?

texts: We are designing a board around Atmel SAM4E microcontroller, and use Atmel-ICE for debugging/programming. To save space, we would like to avoid including the whole ICE connector. Which are the minimum set of required pins so that I can still program and debug over SWD?


texts: LTSpice common emitter amplifier distortion

texts:
I have a (hopefully not too trivial) question regarding this simple LTSpice-circuit.

I would expect the output to be (ideally) a sine wave, but when probing Vout
what I get is this:

Now what I do not understand is why the output is not symmetric about 0V.
I'd like to know what exactly is causing this and how it can be prevented. I'm still new to circuit design so I'd be great if someone could help me out here.


texts: Defining wire jumper inside IC in software

texts:
Since I'm using Eagle to try to form a single-sided PCB and the autorouter completed my circuit by 99% (2 airwires to go), I thought of constructing my circuit so that I insert a flat jumper wire underneath the IC so that its nicely hidden.

Currently I'm using inductors as wires but the appearance looks like they will take up too much space in the IC. Same goes with resistors and capacitors.

What can I do to successfully add wires directly under the IC and still satisfy the ERC? Is there a specific library that allows this?


texts: Is it possible to drive TTL inputs from 3.3v microcontroller

texts: I need a quick heads up on a problem I am trying to solve at work. I'm trying to connect to a parallel data port on an interface module we use to access smart cards. The port has an 8bit input and an 8 bit output with associated strobe/ready pins. I have a microcontroller board with an ARM cortex (mbed.org) which would be perfect to interface to these ports to my PC for test purposes. The ARM board has loads of i/o but its a 3.3v part. I have used it with your typical 2 line LCD display (5v part) with no problem (I know the ARM i/o is 5v tolerant) and I can control the LCD no problem. What I'm wondering is, is it ok to assume that I can drive any 5v TTL level input from a 3.3v output pin ? I'm happy that I can read the 5v ttl levels as I said the ARM Cortex chip's documentation says it 5v tolerent. The connection will be very short (<10cm).


texts: Buck converter MOS Drive resulting in overheat

texts:
With the schematics below, which is a low side driven DC/DC buck converter similar to this post:

The LINE voltage is about 300 VDC and controls a 24V halogen lamp connected to J1. C2, C3 are rated 450 V.

It's for a special lab application system, so no worries about voltages and isolation.

The mosfet is driven with IRS44273 at 15 V and about 20 kHz and the MOSFET STD13NM60N which is rated 600 V and 11 A.

I've checked the mosfet safe operating area and I'm well within its range.

However, the MOSFET exploded about 2-3 seconds after switching on the circuit and seems to have had an arc around the switching node and adjacent ground and traces. Not sure which fault was first.

With a line voltage of 30 V the system works fine but the mos heats quite a bit.

With a scope I probed the gate of the MOSFET and the edges are sharp so it seems the driver works as expected.

My thermal design is not optimal, but I don't think that would make a big difference over a few seconds.

Is there something I'm missing in this design? I suspect high transients happening in the switching node causing an arc on the PCB. I have a clearance of 1.1 mm under soldermask which should be plenty enough at this voltage.

EDIT:

PCB layout (I need to add better thermal, I will redo the layout as well):

EDIT:

Here is TI buck converter calculation sheet if it can be useful for anyone.


texts: Flyback diode placement for solenoid valve simulation circuit

texts:
I am working on a project where I want to fake the presence of a solenoid valve in a control unit on a car so that the control unit does not give an error message.
The output of the control unit is a 12V PWM signal with about 2 kHz.
I measured the solenoid valve with an LCR meter and found a resistance of 5 ohms and an inductance of 10 mH.
I now want to simulate this solenoid valve with a simple coil. Since there are no coils with the exact inductance and DC resistance, I will use a 10 mH coil with 0.5 ohm resistance and a 4.5 ohm resistor in series.
Since I don't have any information on the ECU circuitry, I'm assuming I need a flyback diode for my inductor. Now I am not quite sure where to place it. Parallel to the coil with 0.5 ohm or parallel to the series connection of coil and resistor with 5 ohm?
The aim is that the control unit does not notice that the solenoid valve has been replaced by my coil.
I would be grateful if someone could give me an answer and a short explanation. The control unit costs 2,000€ from the manufacturer... I would be happy if it didn't go up in smoke as soon as I switched it on.


texts: ESP8266 "rom" boot code is overwritten when upgrade firmware?

texts:
You can flash the firmware using ESPTOOL with a command like

./esptool.py write_flash 0x00000 my_app.elf-0x00000.bin 0x40000 my_app.elf-0x40000.bin

this will overwrite the SPI FLASH chip with a new contents. But if you overwrite 0x0 region is the bootloader that allows flash the chip through UART lost? or is it a real rom mask code?


texts:
I have a 24V sensor that outputs high when it detects something. I want it to output LOW when it detects something so the lamp (24V 18mA) stays off.

My solution for this problem was using a not port with transistor and resistors.

Any help that requires less hardware?


texts: Total DC resistance of thin-film resistor with truncated contact pads

texts: I would like to calculate the DC resistance across a rectangular patch of resistive material with contact pads that are less than the resistor width.  The resistive material is a thin film with a sheet resistivity given in ohms per square (S).  If the contact pads were the same width as the resistor width the total DC resistance (R) would simply be the number of squares in the sheet multiplied by the sheet resistivity, ie. if P=W then R=S*(W/L).  However, the fringing currents would seem to create a more complex situation.


texts: Why peltier elements have smaller heatsink on cold side?

texts:
I have seen in nearly all configurations that Peltier elements are mounted with huge heat sinks on hot side as compared to tiny ones on small side.

Is this just a way of explaining the need of heat sink on hot side? Or are there any real benefits of smaller heat sink on cold side? Would an element work better(produce lower temperature on cold side) with equally sized heat sinks?


texts: What is the voltage across the circuit shown

texts:
This is the basic simple question. When I connect this circuit there is voltage seen in VM2.
According to me, no current flows through R5, therefore there should be no voltage across the resistor, and resistor should act as open. Therefore VM2 should be zero.

Can anyone help me why it is like this?

Well I appreciate your answers. If I use simple resistor divider with the diode whose forward voltage drop is 0.6V, I am reading voltage in voltmeter as 3.88V. Is this because of any other phenomenon, can somebody please explain.

It should have read 2.5V.


texts:
I want to build starter and simple auto self-watering system.
I need the pump to take the water from a bucket, which means I need to check the water level on it and alert if too low.

I want to do it as simple as I can. Do you think something like this will work? YouTube Example

In the video you can see the following diagram:

While the water will be on the 2 cables end.

I will implement it on Attiny85.

Thanks to @ignacio-vazquez-abrams I found this product:
.
I will try it out.

Thanks!


texts:
Let's say an induction motor speed is 1150 RPM and no load condition is 1185 RPM.
How do we find the regulation speed? What does regulation speed mean in relation to an induction motor?


texts: I’m looking to purchase a refrigerator for my van.  I plan to have an inverter installed and a battery bank.  AC refrigerators are much cheaper than DC so I prefer to go that route if possible.  The AC refrigerator has a power drawl of roughly 300KWA per year while the DC refrigerator drawls roughly 48W.  The battery bank I’m planning is 200A at 12V and the inverter is 3000VA.  Can you tell me if I can get away with the AC refrigerator and how much, if any loss I’ll be dealing with?


texts: Pull-up resistor - why input pin is pulled to ground when the switch is closed?

texts:
Let's say 1 is an input pin.

So when the switch is "OFF" (open circuit), the output is almost equal to Vcc since there's no current. 1 is pulled to Vcc.

When the switch is "ON" (closed circuit), 1 is pulled to the ground and there's a current between Vcc and the ground. But why 1 is not pulled to Vcc when the circuit is closed? Assuming Vcc is 5V, how much voltage goes to 1 when the circuit is closed?

If 1 is pulled to ground when the circuit is closed, does it mean that the ground has higher voltage than Vcc in this case?

UPDATE:

All answers are appreciated and all of them helped. Thanks a lot for the effort.


texts: What is this "drive circuit" for CCD sensor referenced to?

texts:
I had a look at the TCD1304DG CCD sensor which I consider using in a project. The datasheet is pretty lucid, but I couldn't figure out what the following diagram is supposed to say:

Is this just a common way of illustrating an analog signal?


texts: Simple electrical circuit calculation problem

texts:
I stumbled upon a problem I cannot seem to find the answer for this circuit:

I don't know how the proper term in English is on this, but on the picture the "drsnik" means a "slider", you know the one that splits the resistor basically in two smaller resistors. In this picture the "slider" is on exactly 50%, so it splits the resistors in half.

This is what I had been given: U = 30 V, R = 49 Ω. I need to figure out what the voltmeter would display. All of the resistors are equal and 1,2,3,4,5 represent potentials.


texts: Help with understanding op amp terminal voltages

texts:
I've got a circuit that I am simulating to help understand how a latch-up prevention circuit that is being used in a design works. The circuit:

My question: As i increase the DC voltage V3 at the -ve terminal the voltage at the +ve terminal also increases without any feedback loop. Could someone please explain this? Eg. V3 at 4V increases the +ve voltage to 3.29V:

And V3 at 5.75V increases the -ve voltage to 5.03V and causes Vout to flip from -4V to +4V (as desired. Vout is connected to the gate of a FET that pulls V3 to ground). The difference between the voltages is always approximately 0.8V:

Calculating the voltage at the -ve terminal it should always be 4.7k/1M+4.7k *-5V = -23.4mV but this only seems to be true when V3 is close to zero.

Part of the original circuit:


texts: Designing State Diagram for a 2 input sequence detector

texts:
For a lab exercise I have to design a 2-input sequence and Im struggling with the state diagram, as It has 2 inputs, i've designed it with one input before. the sequence to be detected is 1032 which can be written as:

  \$ A_{0} \text{ |  0 0 1 1} \$
  \$ A_{1} \text{ |  1 0 1 0} \$

So how should I go about designing this state diagram?


texts:
I need constant current 100mA source (120 channels of them) with as much low output tolerances  as possible (so I don't want to use for example LM317 +resistors).

I found Supertex CL7 chip (+- 5%)

But there is problem, because I need to circuit my load one one side to GND. Here in this Chip load is between Vdd and Vout. Do you think I can circuit my load between Vout and GND?

Do you maybe have any other solution?


texts: Will a 0402 0.01 µF ceramic capacitor next to a 0402 0.1 µF ceramic capacitor have any power decoupling benefits?

texts:
I always understood that the point of using smaller capacitors in parallel was to provide low impedance at higher frequencies than the bigger capacitors, because the higher capacitance capacitors 'usually' had larger packages, so the parasitic inductance negated their capacitance from a certain frequency and up.

However, if both caps have the same packaging (0402 in this case), is there any benefit at all?


texts: Current sense amplifier for high voltage (100-150V) low current (20 mA) application

texts:
I have an application where I need to measure the current on a relatively high voltage rail. The problem is that the current on the rail is quite low, only about 20 mA.

Because of the high voltage, high side sensing isn't an option. Has anybody got any experience with low side current sensing in high voltage, low current applications? Which current sense amp would you suggest/how would one go about this?

Thanks,

Peter


texts: Which power supply choose for lineal actuators?

texts:
I have two actuators each of them with the following characteristics:  16 inch, 12v, load 750 N, travel speed 10mm / s, duty cycle 25%

BUT Current Draw is not specified, and I have no access to the datasheet.

I think in some scenarios:

-> let's say each actuator is of 2.5 Amps then I need a power supply of 5A Amperes.

-> let's say each actuator is of 4 Amps then I need a power supply of 8A

-> let's say each actuator if 6.5A Then I need a power supply of 13A

The thing is I dont know the Max Current Draw of each actuator, then my doubt is:

What happens if the current of my power supply is too much bigger than the current I need for the lineal actuators. Let's say the lineal actuators need for both 5A and my power supply is of 10 A.
What happens if the current of my power supply is too much lower than the current I need for the lineal actuators. Let's say the lineal actuators need for both 13A and my power supply is of 10 A.

Then I don't know what happens in that scenarios, and also in muy situation Which power supply would be the more convenient to buy?

Thanks in Advance.

Best Regards


texts:
I have just taken this trace of my Loadwave form for  PWM controlled halogen dimmer.

I was wondering if anyone could identify the cause of the transients below or above zero volts for each polarity.
That is, why does the waveform seem to dip below zero (or above) when switching.

This was taken with my USB oscilloscope and the PWM frequency is 31.25kHz

The circuit composed of two mosfets who PWM the power to a halogen bulb from a toroidal transformer.

The leads to the bulb are quite long.

Any indication as to what is causing this would be of great help!


texts: Measuring the frequency of a 120v variable frequency drive with arduino/pic

texts:
Riffing off of this post-- Reading the frequency of an AC signal using an arduino

I'd like to use an arduino (not committed to a model, and would also like to have the ability to consider PIC/rasberry pi/Rabbit in the future) to measure the frequency of a 120v variable frequency drive in the realm of 30Hz-80Hz of an analog signal. My AC supply 9-12V is powered the VFD to bring the voltage down followed by a bridge rectifier and a regulator to power the arduino and also perform the measurement.

I'm confused about prepping the signal. This is two fold. The variable frequency drive uses PWM and a 16k switching frequency. Can I assume that some of the 16K PWM noise will be lopped off by the transformer or do I need to make some kind of filter so that I'm not getting "false positives"?
What kind of input(s) do i feed the signal into for the counting/measuring? Analog, Counter? Please explain the considerations and why.
Can I use a voltage divider followed by a rectifier to lower the lower the voltage and send it to an analog input and just count the rising edge?
Since I have control over the amplitude and is there any reason for op-amps? When I've seen this in similar examples most of them assume a much smaller amplitude. If the amplitude is within operating range of the input is there any reason that you can't go directly to an analog input?
Do i care that arduino can't measure negative voltages? Unclear if this means it cannot register a - waveform or if I need to make sure a negative voltage doesn't pass through to one of the pins.
Do I need to implement a form of hysteresis or is this unnecessary?


texts: Are PV panels convenient without incentives?

texts:
I finally finished a project in which I designed a 55 kW of PV system for a 50 kW load and I finally calculate costs and revenues over 20 years. I found that with a 25% of incentives for the cost of inverter and PV panels, I have a negative NPV (net present value, is the sum of the net cash flows over some years actualized, in my case over 20 years) of -75k€ more or less while without the PV plant the NPV is -52k€ more or less. I tried to increase the incentives up to 75% and at this point, the NPV is almost the same in the case of the PV plant and not. So if incentives increase from now on, after 20 years we will have a positive profit.
I have 2 questions, especially for those that have a bit of experience in this field:

Do these results sound reasonable for you?
If yes, from an ECONOMICAL point of view ONLY, why one person should buy solar panels without incentives? I live in Italy and here the incentives are 110% but ONLY on PV plant with a size that is less than 10 or 20 kW (I don't remember exactly the size) and with a lot of other constraints.
Yes PV panels have a great positive impact on the environment, but nobody will buy solar panels without 100% at least of incentives.


texts: Short and open circuit in radio frequency

texts:
I have been recently reading a bit on RF design, in particular stub matching.

However one point that I failed to grasp is how open and short circuits at high frequencies work. In particular why does the below stub not produce a short circuit:

What is the physics behind this that allows this circuit to function?

Another related question is, "creating an RF short circuit that is DC-open" which mentions a RF short can be created with a quarter wavelength open-stub. I understand that with a open-stub of appropriate length a RF short circuit can be produced. However the question is:

Does this RF short circuit have the same meaning as our normal short-ciruit i.e. very high current flowing?
What is the physics or reasoning that I can produce a short circuit with a DC-open?


texts:
Can we find the value of \$i'\$ in this circuit, considering \$I\$ and \$R\$ are known?

Using Kirchhoff’s Current Law we have that \$I = i + i'\$.

If the dependent source voltage was \$ki \;, \; k \neq R \$ then from Kirchhoff’s Voltage Law we would have
\$(k-R)i=0\$, and since \$ k \neq R \$ we have that \$i=0\$, so \$i'=I\$.

What happens when \$ k=R \$, as in the picture above? Kirchhoff's laws are theoretically satisfied for every value of \$i\$. Should we assume that \$i\$ is zero again? Or better, does \$i'\$ and by extension \$i\$ have a fixed value?

Thank you in advance


texts: Why voltage is the same after placing a resistor?

texts:
simulate this circuit – Schematic created using CircuitLab

Hi.
I'm testing a very simple circuit with a multimeter.
In Ohm's Law, a resistor should affect the voltage, but in my circuit it doesn't happen.

I'm using a Raspberry and on PIN 1 I have 3.3v at 0.076A.
What I've did is very simple, I've connected a Resistor to my Raspberry voltage source, and I've connected the other side of the resistor to the multimeter and the multimeter to Raspberry GND pin.

By measuring the voltage I've obtained same result as circuit without resistor (3.3v) and by measuring the current I've obtained 0.026A.

Why?


texts:
I want to create a 0.8V reference derived from 5V using voltage divider and buffered using OPAmp.

This is my schematic

I will be using this voltage reference for signals upto 10 Mhz (in peak detectors).

Do I need to worry about the Unity Gain bandwidth of Op AMP used as buffer?

Thanks,


texts:
I am trying to run a counter on Digilent Atlys Spartan 6 xc6slx45 development kit, which changes counts on clock edge.
I am new user to Verilog, so I don't know how to give clock to my program from Xilinx board.

Thanks!


texts:
I am new to this site and a little desperate too as I am no electrician. I purchased some led lamps (3w, 12V) to replace a series of G4 20w lamps I run in my household. Since the wiring is in the wall I would like to leave current configuration and just replace the current power supply and the current lamps to LEDs.

My problem is that I am uncertain of the power supply required to run 5 led lamps as shown in the diagram below. This is how currently everything is wired and I think lamps are in parallel?. Sorry but as stated earlier I am no expert! Can anyone help me?

Thanks and regards,

Xmuni


texts:
We are looking for a solution to use a 3 phase network to supply a 1 phase load.

We are aware of the LeBlanc, Scott-T and Open-Delta arrangements. However they don't meet our requirements as the link below explains.

http://carroll-meynell.com/technical-3phase

We are also aware that 12 leg 3 phase alternators can be reconfigured to 1 phase and ask why can't a similar concept be used in a transformer?

Basically we are looking for a transformer configuration (with no electronics) which will present a single phase load as balanced on a 3 phase network. The transformer may not be optimal in terms of efficiency or may need to be oversized.


texts: batteries connection series-parallel vs parallel-series

texts:
In searching combining batteries connections I have found two different ways:

a) connect batteries first in series and then each in parallel

b) connect batteries first in parallel and then in series

Is there any difference regarding end voltage/capacity ? If not, what's preferable ?

Thank you in advance.


texts: What is the purpose of the optocoupler in this circuit to drive the mosfet/relay?

texts:
I'm currently trying to understand a circuit for an ESP8266 relay board. As you can see in the schematics below, an optocoupler is used to drive the relay mosfet. I do not understand, why they are using an optocoupler for the control signal.

As far as I know an optocoupler is used to galvanically isolate two circuits from each other, to make absolutely sure, that no voltage spikes, EM-noise, ... will be induced into the microcontroller.

But in that case it doesn't make sense, because the relay is using one common GND and 3.3V Vcc, so why isolating the control signal?

Do I miss something, why the optocoupler is still a good idea?

Thank you very much!


texts: What do I need to know about leakage current?

texts: I recently suggested a plan of removing one end of a resistor from a breadboard to remove it from the circuit in order to measure its resistance, but my mentor suggested that this won't work for high precision measurements (0.025% error) because of leakage current entering the DMM. I haven't heard of leakage current before. What do I need to know, and how might leakage current affect my designs?


texts: Two electrolytic filtering capacitors near or far away from each other?

texts:
I have a PCB where I placed a 100uF capacitor near the power supply connector, for power filtering. This capacitor is too big so in my next design I want to use two 22uF capacitors.
My question is: should I place them near each other and near the power connector, or place one of them near the power connector and the other one on the oposite side of the PCB, for uniform voltage stabilization?
The PBC is 80mm x 50mm and the power supply connector is near the 50mm left edge.
EDIT: this circuit is a 24V to 3.3V signal converter only using resistors and transistors, no uControllers or ICs. The signals are square waves with max 50Hz.


texts: Stereo heaphone doesn't work properly when the balance is centered

texts:
I have an old headphone (Philips SHP1900) and it used to work fine, until the day which I accidentally stepped on it... Since then, when I listen to music, the instruments sound really loud and the voice sounds like it's far away.

First I thought that the problem was at the jack plug, but I replaced it and the problem persisted. Then, after a while, I figured this out: if the balance is in the middle the sound is wrong. When I set the balance all the way to the right, I get the right channel sound from both speakers; the same happens if I set it to the left (left channel on both speakers).

Well, I checked the whole cable, bending it to see if the sound gets back to normal if i bend it but found nothing. Next step then was to check the wiring inside the cups.

All the articles I read said that the if the left and the right wires are touching then all you're gonna get is mono. So imagine my surprise when I opened the left cup and founded that the green (left) and the red (right) wires are soldered together in the same spot...

I don't know what could be causing this odd behavior, or if the fact that the two wires are together could be the reason (I doubt it because they came like this and it used to work...).

Does anyone know I can fix this?

Any help is appreciated!


texts: why does the milling machine require FR4 material

texts: At a hackspace I frequently attend, there is a milling machine called the Roland Modela MDX-20 Desktop Miller. We use this milling machine to make pcbs however the technician there stresses we must use FR4 material on the miller why? What so special about FR4?


texts: When a microcontroller is in debug mode, does it freeze the entire MCU?

texts: I have a PSoC with debugging functionality ( I am sure other MCUs have similar functionality) which allows you to place the system in debug mode and you are then able to step through program execution, view register values, etc.. When in this configuration does the entire system halt and wait for you to "step through" the code? or are there more processes running in the background?


texts: Can an USART peripheral works (in Synchronous mode) with only TX, RX and Clock lines. And without the other left handshake signals (CTS, RTS, DTR, DCD)?


texts: Current and voltage complex diagram for a transformer

texts:
I was wondering how would a complex diagram for current and voltage look both for an ideal transformer and for a fully coupled lossless transformer. The diagram for a coil looks like this:

The ideal transformer looks like this and the current and voltage are:

The fully coupled lossless transformer:

So all and all I'm looking for two diagrams, one for the ideal and one for the fully coupled lossless transformer that contain both currents and both voltages on it. I think that the diagram for ideal transformer is supposed to look like this, but I'm not sure:


texts: Chip overheats insantly, could it be a result of having burned it while soldering?

texts:
I am trying to use this IMU from sparkfun, but when I connected it to a power source it got extremely hot (I noticed it because of the smell, I'm pretty sure it's fried), and I'm trying to troubleshoot why this happened. I've checked that the circuit is wired correctly (I only wired the Vcc, ground and three other pins), so I think i might have broken it while soldering. At first I tried to solder the pins with a soldering iron that was not appropriate for electronics work (too hot and had the tip very oxidized) and let it make contact with the joints for quite a long time, so I think might have burned it then. My question is, would this behavior be explained by that? I don't want to buy another chip before first being sure of what happened to this one.

Here's what the breakout board with a header soldered to it looks like (I wired the VDD pin to the 3.3V pin in an arduino 101, the GND pin to the arduino ground pin, the SCL and SDA pins to the arduino's I2C pins, and the INT pin to the arduino's 12 pin):


texts: Measuring light levels with a photodiode and an ADC

texts:
I'm trying to use a photodiode to measure light levels via an ADC on an ATMega168.  I've got the microcontroller code working properly (measuring values on a pin and reporting it as an led brightness) but I'm having trouble getting the photodiode to report a voltage dependent on light levels.

I see that I could accomplish this with an op amp (here) but I'd like to be able to do this without an op amp if possible.  I have a 5 volt source and I'd like to make the photodiode spit out values between 0 and 5 volts.  Is there a crafty circuit I could use for this purpose that doesn't require an amplifier? I'm asking this question because I'd like to know how to use a photodiode for this purpose (I don't want to use an LDR). Thanks!

edit

Oh yeah, here is the datasheet for the photodiode I am using.


texts: Increasing voltage from a neon sign transformer

texts: I am buying a neon sign transformer that is current limiting and iron core for my CO2 laser. I don't know the exact voltage i need but it should be around 15,000 +-1000 volts. Can i "easily" add 1000 volts to it by maybe sending it to a warping of copper coils. I don't want to buy this and then be stuck with a expensive transformer that is to low of voltage.


texts:
I'm using the MMA8453Q for motion detection. The accelerometer is mounted such a way that when it is stationary, X & Y axes are at 0g & Z-axis is at 1g.

My usecase is:
A tilt across any axes beyond 45 degree should generate an interrupt.

I have enabled motion detection with threshold 0.707g. For X & Y axes the motion detection works properly & interrupts when tilted beyond 45 degree. But, for Z-axis, even while it is untouched it interrupts as by default it reads 1g.

Is it possible for me to correct this 1g and make it zero-g offset?

The description for the OFF_Z (User offset correction registers) mentions the following:

  The 2’s complement 8-bit value would result in an offset compensation
  range ±256 mg

And, when I referred the application note AN4069, for calibration, they subtract from 0g,0g & 1g for X, Y & Z axes respectively. This makes me feel suspicious whether I could achieve a tilt detection across Z-axis.

Kindly suggest me how I could achieve my usecase.


texts:
I have this IC - Advance regulating PWM

I would like to understand how does the timing resistor and capacitor section works. Sorry for the beginner question but I am unable to understand this section.

The resistor in the RC circuit, will determine the rate of capacitor charging and discharging and that too when R and C are connected in series.

But in this IC, it is given as The timing capacitor provides the ramp signal. How does the charging and discharging of the capacitor take place? I dont see the timing resistor part involved in doing this. Can someone please explain clearly.

Thanks


texts: What's the minimum equipment rating required to perform testing in production environment?

texts:
I would like to purchase a Power supply to test my unit in production environment. The power supply is expected to support a production yield of 1 Million units per year. As per one of the test requirements, I am required to supply/output 100 Amps of current for 5 seconds at 2Volts DC. One of the DC supply I am looking at could supply 110A at 10V. I want to know if it's a good idea to buy this power supply since it rated for only 10% above the maximum UUT required current.
Could someone name a Standard (any free resources if available on the internet) that would contain such guidelines?
Thank you.


texts:
I was creating schematic from  a pcb but could not understand what the component in the image is for.

The name written on the component is L386. At first i thought that it is a voltage regulator like 1117 but when i checked it the left pin and the middle pin are shorted with resistor placed above it. Then i checked , maybe it was lm317 in sot223 package but such high value of resistor is present so it was ruled out. The resistor that is present on the other side and is of 640K


texts: Why is 370HR used for controlled impedance rather than FR4?

texts: I tried to put together a quote for a 4-layer PCB with controlled impedance (Displayport, so 100ohm differential +/- 10%). I used the online quote tool on Advanced Circuits (4pcb.com). The quote couldn't be generated automatically, and when I called they said is because I had checked the "controlled impedance" box but I still had "FR-4" (default) as the dielectric. They said the quote can only be generated if I select 370HR as the dielectric or some other specific one (I think the other was 185HR). Why is that the case? What is special about these "HR" dielectrics that make them better suited for controlled impedance?


texts:
At a test, I was given the following circuit and i was told that it will oscillate and it was required to mention the condition and frequency of oscillation :

I tried thinking in many ways but i always conclude that it won't oscillate !

so I tried simulating it using Cadence OrCad using different combinations of R and C values, but the circuit didn't oscillate.

Could you please help me ?


texts: Oscilloscope probe changes the frequency of the signal

texts:
I have a microcontroller that outputs a 50% duty cycle PWM signal at 500kHz. That is then connected to the gate of a MOSFET. Now, I want to measure the PWM signal at the gate of the MOSFET. If I connect the probe, to measure it, I measure 15Hz and the signal is no longer a square, but a "sawtooth like". If I don't connect the probe, the MOSFET is switching at 500kHz.

I have a SIGLENT SDS1102DL oscilloscope, its channels are rated 1MOhm and 16pF. Is this the reason the frequency decreases?

How can I overcome this problem?


texts:
I have a few questions about what this code does and how it works:
x <= '{default:'1} ;

What is the purpose of the "default" keyword ?
What is the purpose of the inner single quote apostrophe before the 1 in this case ?
What is the purpose of the inner single quote apostrophe before the { in this case ?


texts: If I have three button cells in series, and one of them dies, will the whole circuit still function at a lower voltage or will it stop flowing?

texts:
If I wire three button cell batteries in series, their voltages should be summed. Now, if a battery dies, let's say BAT3 for the sake of example, will the circuit operate at 6V or will it stop working? I would assume, due to the way series circuits are defined. that it would stop functioning, but then I realize that a battery is conductive, making me think that current would still flow, just at a lower voltage.

Which scenario would happen? I've provided a simple circuit diagram below.

simulate this circuit – Schematic created using CircuitLab


texts: I am building a small cigar box speaker with an lm386 and think it would be cool to have a working analog VU meter on the front. There are obviously a lot of cheap ones from China which I would be interested in for this project. My question is can this even be done? Most of them say 3 to 10 watts on the lowest side. Are there any analog options for something as low as 1 watt?


texts: I recently took apart 2 DVD readers? Might have been burners too, but my question is why can't I see the lasers? I tried using both 2 and 4 AA batteries hooked up according to this diagram http://d13z1xw8270sfc.cloudfront.net/origin/58770/diode_wiring_diagram.jpg . I can feel the diode heating up after about 5 seconds, but I can't see the actual laser. Thanks for the help.


texts: Where should an ISR be declared in a library?

texts:
Suppose I have a library consisting of TWI.h and TWI.c which contains an ISR defined according to AVR-GCC syntax. For example:

ISR(TWI_vect)
{
   switch(TWCR)
   {
       ...
   }
}

Should the ISR code go into TWI.h or TWI.c? Or should I put the full ISR in TWI.c and put some sort of ISR "prototype" in TWI.h?


texts: Why HAL_I2C_Master_Transmit always returns HAL_BUSY?

texts:
I'm trying to use I2C between an STM32F103C8T6 development board and an Arduino Uno.

However, I always get a HAL_BUSY error when I call HAL_I2C_Master_Transmit in the code below.

(I used 10K pullup resistors at SCL and SDA) on the STM32 side and a logic level converter between STM32 and Arduino.

How can I send messages from the STM32 to the Arduino?

int main(void)
{
  ...
  MX_I2C1_Init();

  char buffer[16];
  strcpy((char*) buffer,  (const char*) "Test 1");

  while (1)
  {
      HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_14);
      HAL_Delay(1000);

      if (HAL_I2C_Master_Transmit(&hi2c1, 8, (uint8_t *) buffer,  7, 1000) != HAL_OK)
      {
          HAL_Delay(1000);
      }

Settings (all default):

  hi2c1.Instance = I2C1;
  hi2c1.Init.ClockSpeed = 100000;
  hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;


texts:
A 5V LED should run for a predefined time period once a button is pressed. The LED should be illuminated for the same duration as the button is pressed, but only once the button is released  and illumination should last at least 5 seconds. The time deviation should not be more than 2 seconds. Since the controller needs to be positioned on the backside of a wood panel, only limited physical space is available (the smaller the better). A 5V power source is provided for. The project is part of an art project that is to be displayed on a music festival in the summer of 2020. At least 200 of these panels+controllers are needed, so cost should be reduced to a minimum.

Previously (prototype), an Arduino Nano was used. Now, cost and size need to be reduced further. What would be the minimal components required to complete this task?


texts:
I have The following circuit network (link to multisim) and i am asked to find the transfer function, the max and min value, the cutoff frequency, angle and the type of the filter.

[the actual problem][2]][2]

I have done the calculations and found that the circuit is a low pass filter, and its cutoff frequency is  26842 Hz which is awfully high and therefore i am very worried that i have gotten something wrong. I also found that when w=0 the value for the transfer function = 0.6803 and when w approaches infinity the value for the transfer function =0 and hence i concluded that it was a low pass filter. here is my calculate for the transfer function:

$$H_w=\frac{1}{(((R1+R3)*(j*w*C))+(((R3*R1)/(R2))*(j*w*C))+(R1/R2)+1)}$$

here is how it looks after i plug in the values for the resistors:
$$H_w= \frac{1}{(1.47 + j*w*0.000054562299999999998836925505310975)}$$

j represents the imaginary number. Basically you can see that if w=0 i get 1/1.47= 0.6803

Anyone can varify this is correct for me? and if so any chance that that "anyone" knows how verify that with multisim as i cant read the graph it produce. Please help.

[2]: https://i.stack.imgur.com/kcbNM.png


texts: DC/DC converter solar without current variation?

texts:
I have built a solar charger by using a linear voltage regulator (LM7805) that outputs 5V from a solar panel which can deliver a maximum of 18V. It works fine, but the current is very low and there is a lot of heat coming out from the voltage regulator.

I read here and there that a better option for this would be to use a DC/DC converter (or buck converter) which, according to Wikipedia is a device that rises up the current while dropping the voltage.

Now, it would be great to have a constant 5V output like I do now, but I'm afraid that the oscillation in the current is not so good for charging a phone, but I base this on pure intuition, therefore I would like to hear an opinion on this.

Will a buck converter have a large current interval as the sun goes behind the clouds?
Can this interval be regulated?
Is it harmful to have a large interval of current for charging a phone?
What type of buck converter should one look at if one plans to buy a bigger solar panel in the future?


texts: How do metal cases work with connectors & isolation?

texts:
I have troubles understanding how do metal cases behave in some cases.

Case 1:
I made passive attenuation box for amplifier(basically L-pad resistor), simple configuration:
Amplifier => attenuation box => speaker
It has 1/4 jack sockets on input and output like this one

And pot resistor with metal on it's case

Everything works fine, but as soon as I touch case or any metal part of pot with my hand it starts screaming from a speaker high-pitch sound. Why does it do that? Other commercial equipment uses the same jacks with metal cases and it has no problems with touching the case. And I can't ground it obviously because it is passive and input is floating from transformer.

Case 2:
On other powered devices without ground connection(example - guitar FX pedals) you also have metal case with metal jacks and it doesn't have any problems with touching either metal case or pots.

In both of these cases I don't see what's the trick here, at first I though I wire something in a wrong way, but there is no way to wire socket in such a way so that sleeve would not touch case - since the outer plane of socket touches case, obviously sleeve of connector will touch it no matter how you wire stuff internally.

So basically the questions are - how to properly wire metal parts that touch the case in order to make case out of the circuit.
I really tried to google that by myself, but it seems that most of people have no troubles at all with it, maybe I miss very basic thing.

Thank you for reading such a long question.


texts:
I am confused by the datasheet of the AFG3021C: https://www.tek.com/link-click-count?nid=75006&url=https%3A//download.tek.com/datasheet/AFG3000C-Arbitrary-Function-Generator-Datasheet-75W282817.pdf

I am interested in the THD of a generated sine wave, but the data sheet specifies THD as less then 0.2% and harmonic distortion as <-40 dBc, which just doesn't add up to me.

What is the difference between harmonic distortion and THD? What I am interested in is the RMS of the harmonics divided by the RMS of the fundamental.


texts:
I want to use an inverting amplifier to linearly shift and convert a signal with voltage range -10...+10V into 0 ... 3.3V for an ADC of a microcontroller. I wanted to use the circuit presented in this post.

Instead of the 40 Hz source I would input the -10...+10V supply and instead of -15V I want to use a -12V supply.

1.) Which supply voltage range should the OpAmp have? I mean the output should only be in the range of 0 ... 3.3V, my resistor feedback network will take care of that. Or does it have to cover the sum of the two input voltage maximum and minimum (i.e. -22V and 2V)?

2.) Are there any constraints regarding the DC-bias supply (-12V)? Must it have a low output impedance (< 1 Ohm)? Does it matter whether I would use a Linear Voltage Regulator or a Voltage Reference (as long as the rated current of the device is not exceeded)?

3.) General question: Can I use an OpAmp that is specified for a supply range of +-5V...+-15V (i.e. dual supply) also as single supply? For example V_supply_- = 0V and V_supply_+ = 5V

Best regards and thanks in advance!


texts: Isn't it possible today to make a down-transformer without coils, without the idea of induction? After all, the AC reaches every voltage in-between, so all we have to do is keep cutting the power flow and only letting current pass when the wave is at the desired voltage. Of course, this will be a series of pulses but it can be smoothed out with capacitors.


texts: Robustness of voltage grid system or railway grid

texts: Can somebody explain to me how robust the high voltage grid systems and railway grid systems are against shorting? For example, if a thinner bare wire or cable falls on two wires of the HV cable, will it cause the grid to trip or get damaged? Or if the two HV wires of the grid carrying two different phases somehow come in contact with each other momentarily, will the grid get damaged?


texts: SPI/I2C chip, CS# pin pullip for I2C operations

texts:
I have a question regarding all sensors offering to work in either SPI or I2C mode.

I am having some issues working with a MPU9250, but think it is a general question:
When working in I2C, the MPU SD0 pin must be connected to ground or VCC for adress selection, and the SPI CS# pin must be connected to VCC throught a pull-up resistor.

Does anyone have knowledge about this communication mode selection, in particular: is the resistor on the CS# line mandatory for the chip to communicate throught I2C

Thanks In advance


texts: Arduino compatible H bridge behaving unexpectedly

texts:
I have built an h bridge in a circuit simulator for controlling my brushed DC motor such that it can work with 5v supply from Arduino Uno here is its link to play around with the circuit Circuit Simulation link

Now to start the motor I need to first turn on S5, S1 and S2 and then turn off S2 and S1 really fast (to not damage Arduino) , when I turn off S2 THEN S1 (and keep S5 on) current starts to flow through load (cool ,nothing unexpected happening) but if I first turn off S1 THEN S2 (and keep S5 on) current starts to flow through ALL transistors (try doing it in simulation), why is that happening ,why while turning off S1 and S2 sequence matters
Second Problem
When I decrease the load to 10 ohms current starts to flow through all transistors why is that happening and can I fix it


texts: How to dynamically adjust a timer with STM32

texts:
I've got this timer (TIM4) that's in PWM mode.  I'm outputting one PWM channel and i want to wait a bit, and then grab the latest ADC samples from a DMA conversion.

TIM4 -> ARR is 4096
TIM4 -> CCR1 is dynamic, but it starts around 200

I want to start at the rising edge of the TIM4 pulse, wait half the of the Pulses on-time, and then grab the latest and greatest DMA samples...Here's a snippet of what I've got going on:

Where things seems to come unglued is the line:  TIM5->ARR = TIM4->CCR1/2;.
What is strange, is that if I put a constant in there, like TIM5->ARR = 20;, it works fine...It doesn't fire in the middle of the on-pulse of TIM4, but it does fire at the 20/FCLK you would expect.

I read DM00236305.pdf, but I couldn't make sense of what they were talking about with Shadow registers, which is what I think my problem is.  I also tried to follow what was said here, but that was also rather vauge, and I wasn't sure if it applied, since he was talking about output compares rather than auto-reload registers.

How do I adjust TIM5->ARR to track to one-half of what is in TIM4->CCR1?

void TIM5_IRQHandler(void)
{
  /* USER CODE BEGIN TIM5_IRQn 0 */

    HAL_GPIO_WritePin(GPIOA, TX_Pin, SET);
    HAL_TIM_Base_Stop(&htim5);
    while(!(DMA2->LISR & DMA_LISR_TCIF0));
    motorDummy_FOC.curr_a_sense = ADCValue[0];
    motorDummy_FOC.curr_b_sense = ADCValue[1];
    update_PWM(&motorDummy_FOC);
    HAL_GPIO_WritePin(GPIOA, TX_Pin, RESET);
}
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim){
  if (htim == &htim4){
    HAL_GPIO_WritePin(GPIOA, RX_Pin, SET);
    GPIOC->ODR = 0b0000000000000110;
    //TIM4->CR1 &= ~(1<<0);
    MX_TIM5_Init();
    TIM5->ARR = (TIM4->CCR1/2);
    HAL_TIM_Base_Start_IT(&htim5);
    HAL_TIM_Base_Start(&htim5);
  }

}
void HAL_TIM_PWM_PulseFinishedCallback(TIM_HandleTypeDef *htim){

  if (htim == &htim4){
    GPIOC->ODR = 0b0000000000000100;
    HAL_GPIO_WritePin(GPIOA, RX_Pin, RESET);

  }
}

void update_PWM(motorFOC *c){
  if(c->curr_b_sense < c->curr_b_commanded)
  {c->i_feedback++;}
  else if(c->curr_b_sense > c->curr_b_commanded)
  {c->i_feedback--;}
  TIM4->CCR1 = c->i_feedback;
}


texts:
I'm trying to make a buck converter which produces an output voltage of 3.3V with a load of around 1 amps when the input is around 220v AC.
This basically means converting from 311v DC to 3.3v DC.
I'm basing my circuit on

What I wanted to ask, is such a circuit feasible? Practically not theoretically. It seems quite simple.
I calculated the inductance at around 26uH, and capacitance to be a minimum of around 50uf, However I'm using 100uF on both the input and output capacitors..
I have a duty cycle of around 1% since the output voltage is tiny in comparison to the input.


texts:
I am confused in definitions of VOH and VOL in VTC of inverters. My textbook says this graph:

but shouldnt the y value corresponding to VIL be VOH and y value corresponding to VIH be VOL OR Is VOH and VOL the largest and smallest voltage in the system respectively?
I also saw this photo in my reference book which I think is correct:

But in my textbook they have written the whole book based on what I told earlier, for example when they are discussing resistive load inverter like

they drawed its VTC like this:

the textbook is kang and leblebici and refrence book is weste and harris.
So which definition is correct?? Because when I do analysis of circuits VOH coresponding to VIL will be different from VOH = maximum voltage in system and thus my Noise margin definitions might go wrong.


texts: Want to replace push-button with IR receiver

texts:
In the diagram below I want to replace that push-button switch Sw1 with IR receiver, I tried a lot with different combination with IR receiver and tried with transistor but I failed, so, please how can I achieve that.

thanks for advice.


texts: Capacitive load - Matching Right Crystal and Caps for oscillator circuit - DS1302 RTC - cut and trim

texts:
CL = (C1 * C2) / (C1 + C2) + Cstray

I have a 12.5pf crystal. DS1302 is happy with 6pf.
what is trim capacitors to make him happy using 12.5pf?

12.5-6=6.5pf

(6.5*6.5) / (6.5+6.5) + cstray= 3.25pf + cstray

(13*13) / (13+13) + cstray= 6.5 pf + cstray

so assume cstray is 0, I need 2x 13pf capacitors?

I kinda answered my question, but that is only my guess. My main question will be: what exactly is the Capacitive load? Seems to me that the crystal itself has a Capacitive load (12.5pf in my case); the DS1032 chip has a Capacitive load (6pf), the 2 trimming capacitors obviously have a Capacitive load and last but not least, the PCB board has a Capacitive load (typical 1-5pf?).

The DS1302 also has 2 internal caps: CL CL. if DS1302 is only happy with 6pf load crystal, is that mean that the values for these 2 caps are 6pf and Cstray being 3pf?

CL = (C1 * C2) / (C1 + C2) + Cstray
6pf= (36)/(12) + 3


texts: VHS(C) tape speed issues - how does the speed change for different modes?

texts:
I have a VHS-C camcorder that has a lot of trouble keeping constant speed for the main tape motor (even with the battery fully charged). Most of the time it's way too fast (similar to fast forwarding), but at the beginning of the tape it's often too slow (I'm guessing the new-ish tape is too heavy for the 1993 thing? Though it's the standard 30min one). It works correctly once in a blue moon. It doesn't seem like it's an LP/SP issue, considering it sometimes works and, most importantly, it looks way too fast even for SP (also, it's sped up even during recording). I opened half of the camcorder to see if there are any obvious mechanical issues to no luck.
So here comes the question: how is the speed for play/fast forwarding regulated? Are there different pins/voltages for the motor itself, or does this weird rubbery roller press and slow down the tape? Or should there be gears with different diameter that the mechanism switches between, to get the appropriate reel speed? I'll probably risk opening the whole thing up to try and fix it, but at least I'd like to know what to look for. Last time I opened up a VCR was around 2004 :(
EDIT: it's probably not a tracking issue either as it's supposed to adjust the tape of the head and not the reels (correct me if I'm wrong). I tried cleaning everything


texts:
Considering the following scenario:

A designer wants to connect 3 devices on a PCIe x4 finger edge connector, commonly found on mother boards.
All 3 devices will be populated on the same PCIe card.
One device has 1 port of 2 lanes i.e (1 x2 PCIe port)
Remaining two devices have 1 port of 1 lane (1 x1 PCIe port) each.

Scheme 1:

Scheme 2:

I've seen scheme 1 in the datasheets of some PCIe switches.
I want to know if a PCIe switch is really required in this case.

What if we omit the switch and just split the PCIe lanes as in scheme 2?

Will it be a legit PCIe network?

If yes then how will bus numbers be assigned?

Kindly ask if there is a need for clarification.

Edit 1:

Quote from PCI_Express_Base_Specification_Revision_3.0 :

  The ability to split a Port into two or more Links is optional.
  An example of this behavior would be a x16 Port that may be able to configure two x8
  Links, four x4 Links, or 16 x1 Links.

More Information can be found under heading 4.2.4.10.1. Required and Optional Port Behavior


texts: Is it possible to use J1939 and CANOpen on the same bus?

texts:
Please correct me if i'm wrong. The way I understand it, J1939 is based on CAN2.0b and uses 29 bit identifiers. CANOpen is based on CAN2.0a and uses 11 bit identifiers.

If for example, you have a controller that is communicating with various sensors using J1939 but you'd like to add another module on the bus using CANOpen, would they compatible?


texts:
I read in documentation of AT89C51RC2, that I can make one of 5 ports to generate PWM signal if I set properly some registers. Some things I don't understand. I don't know what PCA counter is and how it behaves. There is what I came up with according to documentation.

CEX0 equ P1.3
CCAPM0 equ 0DAh
CCAP0L equ 0EAh
CCAP0H equ 0FAh
CL equ 0E9h
CCON equ 0D8h

DSEG at 30h

CSEG

    ORG 0000h
    AJMP START

START:
    MOV CCAPM0,#10000010B
    MOV CCAP0H,#0FFh
    MOV CCAP0L,#0FFh
    ORL CCON,#01000000B

MAIN:

    MOV R6,#0FFh
    DJNZ R6,$

    MOV A,01000000B
    XRL A,CCON
    JNZ null

 LJMP MAIN

 null:
    MOV CL,#0
    MOV CCON,#01000000B
    LJMP MAIN

END

I don't know which direction the CPA counter counts, whether it is needed to reset it, I don't know If I forgot to set some registers. This code doesn't work. Looks like the counter doesn't even count.

Any suggestions?


texts: Max baudrate of FT2232H in synchronous FIFO mode

texts:
In datasheet at FT2232H chip:

  The FT2232H has the following advanced functions:

  ...
  Single channel synchronous FIFO mode for transfers upto 40 Mbytes/Sec.
  ...

I configure device with the recommended settings, according to FTDI application note AN_130 and other.

When in the program I call FT_SetBaudRate() function, maximum value of baud rate is 8_000_000, which provides the max speed 8 Mbytes/sec (parallel interface). Attempts to set the upper baud rate are throw error FT_INVALID_BAUD_RATE.

So, how can be reached the maximum promised speed?


texts: State-Space Model of a Buck-Converter in DCM

texts:
I have a problem getting the State-Space Representation of an Buck-Converter in DCM.

There are 2-Switch Cycles between one Period.

If the Switch is closed the Circuit looks like:

after applying KVL you get for the State-Variables:

\begin{align}
 \dfrac{\mathrm di_L}{\mathrm dt} = \dfrac{1}{L}\cdot(U_{in}-u_C)\\
\dfrac{\mathrm du_C}{\mathrm dt} = \dfrac{1}{C}\cdot(i_{L}-i_{R}).
\end{align}

The same Procedure can be done when the switch is open:

so the State-variables are:

\begin{align}
 \dfrac{\mathrm di_L}{\mathrm dt} = -\dfrac{u_C}{L}\\
 \dfrac{\mathrm du_C}{\mathrm dt} = \dfrac{1}{C}\cdot(i_{L}-i_{R}).
\end{align}

so there is a Procedure in extracting the State-variables.

I would like to know how to get:
\begin{align}
\dfrac{di_L}{dt}= ...\\
\dfrac{du_C}{dt}= ...
\end{align}
when the Buck-Converter is working in DCM.

edit:  In https://core.ac.uk/download/pdf/53187372.pdf at (page 20-21) the author is trying to describe how he get to his solution, but i cant understand this way (or the way he describes it)


texts: How do I make this bidirectional switch work with inductive and capacitive loads?

texts:
I designed the bidirectional switch seen below. But right after, I realized that it would only work with resistive loads. However I want this to be a general purpose product, which will also control capacitive and inductive loads (e.g.; an electric motor).

What kind of changes should I make on it?

Typical application:


texts: Provide full specifications of the given IC?

texts:
I have searched a lot in the internet about this IC, but I didn't get any answers. The markings are:

9903AJ
DM74LS94N


texts: Does heatsink transfer plate thickness matter?

texts:
I'm designing a water block for a liquid cooling system.  It will be acrylic on 5 sides and copper on the side that attaches to a CPU heatsink/fan.  What I'm stumped on is the thickness of the copper side of the block.

A thicker sheet of copper can hold more total heat energy, but once the system reaches equilibrium that heat still needs to go somewhere, so I'm limited by the thermal interface between the water and copper, and then the copper and heatsink.  So my gut instinct is that thickness doesn't matter.  However, I often see cooling blocks advertised online as having extremely thick copper transfer plates, making me wonder if this is actually an important spec.

I understand that if my water block is larger than the contact area of the heatsink a thicker plate will help transfer more heat to the heatsink, but in this case assume that the water block, transfer plate, and heatsink interface are all the same size.

Does transfer plate thickness really matter when sandwiched between coolant and heatsink?


texts: How is mobile communication(between pilot and ATC ) made possible from airplanes?

texts: I have heard that communication using mobile phones begins to degrade when used on a vehicle moving at speeds above 200 km/hr due to doppler effect as described here (p-22). How is this limitation overcome in airplanes. What is the specific technology used to overcome this limitation.


texts: How to turn on a device with only 1 wire between itself and switch?

texts:
TL;DR
I want to send a signal between 2 isolated DC-powered circuits using only single wire connecting them. If possible, I'd like to avoid wireless solutions.
Details
I have a broken doorbell installation which I'm trying to fix. Doorbell itself operates on rather low voltage (around 6V). This is a weird custom installation, which most likely doesn't work, because something happened years ago to the initial power supply. I wasn't able to trace the cables to any useful culprit.
What I was able to deduce so far:

There's a switch outside the apartment with 2 dead cables coming from inside of the wall,
There's a doorbell inside the apartment with different 2 cables coming from inside the wall,
I know for sure that 1 cable is going through the wall directly to the doorbell.

In the simplest form, the circuit must have looked in the past somewhat like that:

simulate this circuit – Schematic created using CircuitLab
What I want to do is to make 2 separate circuits with 2 separate power sources. First one for the swtich outside the apartment and the second one for the bell inside the apartment. I want the first circuit to notify the second circuit that someone pressed the button via 1 existing cable. I guess it is possible, but I'm not sure what components do I need to use to make it work.
At first I thought about 2 microcontrollers (even something arduino–like like DigiSpark USB). The first microcontroller would send a HIGH signal through that 1 wire to the second microcontroller  — then the second one would turn on a doorbell.
Then, I though that maybe I can use less dark magic and make use of basic components like... transistors?
In the end I want to have something like the following:

simulate this circuit
What magical components can I use in a place of Magic 1 and Magic 2?
PS. Yes, I marked a doorbell as an LED.


texts: I want to buy this current sensor from eBay. I couldn't find how it works, but I presume it works like the other ones through induction. On many sites it says it has a maximum current of 5 amps, but I'm wondering what would happen if a higher current would be used? Specifically I'd like to sense something up top 15 amps.


texts: Upgrade BLDC motor controller (ESC) to higher wattage (replace mosfets/shunt)

texts:
I was wondering if I could upgrade my current bldc motor controller (three phase motor)(*) to a higher wattage/output power by doing the following modifications:

Replace mosfets with higher power rates ones (higher amps, lower Rds(on), equal or higher voltage rating )
replace shunt with much thicker one (and recalibrate)
Improve cooling of mosfets (bigger heatsink, perhaps some activate cooling with eg a fan)
use thicker wires/leads on the pcb to account for the higher amperage

Would these mods enable me to increase the power output of the controller by for example 3 times (if I choose mosfets that can handle the required amount of amps/ can handle the voltage and potential voltage spikes(Note: I will keep the battery voltage the exact same as before the mod, I am currently using 84volt (20s)))?

Would I need to make any other mods in order for this to work (other than the ones I've mentioned above in the list? For example would there be other components I would need to replace because the original components will likely not be able to handle the increased amps?

Would there theoretically be a limit to how much I can increase the power output using these modifications (for example would it be doable to increase the power output 10 fold if I choose the right components? I know this won't be very practical since I'll need much more cooling and much thicker wires but it's more of a theoretical question) and what would be the issue causing this limit ? (ignoring possible issues like not being able to fit enough mosfets in the controller, the controller becoming too heavy etc.)

*info about the controller/setup:
It's a 72v-84v 1000-1200w (three phase) BLDC motor controller (rotor position determined using 3 hall sensors). The motor is an outrunner with permanent magnets in the rotor. Currently has a shunt mod increasing the power to perhaps 1400watt. The battery is 10p20s.

If anything is unclear/incomplete about my explanation please let me know and I'll try to clarify.

Thank you very much!


texts: Mechanical vibrations picked by an audio amplifier (Strange microphone efect when there is no microphone)

texts:
I opened today my Philips audio system (30W woofer + 20w satellites) because it has a lot of noise.
There is something weird with that amplifier: when I knock into the circuit board with my finger nail I hear in the sub-woofer a noise EXACTLY as when you knock with your finger into a microphone. To make it clear, doesn't sound as a component not being well soldered (one that randomly connects/disconnects when you touch it). The noise is very smooth and "high fidelity" (if i can call it like that) exactly as a microphone (connected directly on the mainboard).

I spoke into the circuit board (yes laugh if you want) but it won't pick my voice. However, the slightest touch of the circuit board will reproduce the sound into the woofer. So, it works only for very low frequencies.

I can upload a video (with audio track) if necessary.

I know that loose coils of inductors can create this effect but there is no single coil on that circuit board. What can create this effect?

Update:

It is not on the input. I shorcuted the input of the amplifier and knocked into the circuit board. The sound is still there. But the sound is soooo smooth, I cannot believe it could be a loose component.


texts: Determining closed loop stability by nyquist criterion

texts:
G(s)H(s)=2.2/s(s+1)(s^2+2s+2)

how to determine the closed loop stability using the nyquist criterion and how should I start implementing on matlab


texts: non-inverting current sense op amp output unstable during the measurement

texts:
I would like some advice on how to solve the following problem. The following circuit is motor driver with current sense circuit. The circuit run motor at cca 30mV when is not under load, but when the load is applied to motor, measuring voltage rise up to 500mV, hold It for 2 second and shut down driver. When I want to measure voltage between "unstable point" and gnd there is a big problem with stability. When i measure voltage with FLUKE 179 multimeter and original test probes I get cca 500 mV under load which is good.
If I add an extra crocodile wire (10-20cm) to test probes there is cca +- 100mV difference in measurement. Only if I add 1M Ohm resistor between "unstable point" and crocodile wire and 1M Ohm resistor between gnd and second test probe, I can add an extra crocodile wire after resistors and the measurement is right (+- few mV difference).
If I add cca 20cm extra crocodile wire on "unstable point", then add 1M Ohm resistor between crocodile wire and test probe, there is again +- 50-100 mV difference in measurement (even if there is a 1M Ohm resistor connected after 20cm crocodile wire). If I add 1M ohm resistor only on "unstable point" and not to gnd probe, there is also cca 50mV difference. Also I notice that if I touch "unstable point" with my hand, voltage on that point collapses so I suspect that the noninverting op amp circuit is unstable or the voltage range of measuring (30mV - 500mV) is to low to handle external disturbances. It's funny that crocodile wire without any load connected between multimeter probes and "unstable point" effect on measurement.


texts:
I have a family friend which likes to sleep with a direct connection to earth. This question is purely to do with safety, nothing to do with what you or I or anyone for that matter believes about this practice, just purely about safety.

My initial thoughts were that it is completely safe to plug in to the earth socket of the mains, my initial thoughts were that if any appliance in the house did fail, the electricity would take the path of least resistance into the earth and not into some poor person wearing an earthing bracelet, otherwise aren’t all properly earthed metal devices potentially dangerous?

So I read in a few places that this isn’t necessarily safe, so I was thinking perhaps to put a microamp fuse in series with the bracelets cable.
Would this break the circuit in the unfortunate event of a failed device or lightning strike? What would the appropriate current be?

ESD bracelets use a 1M ohm resistor, but for ‘medical earthing’ It doesn’t allow the excess voltage to leave (after measuring it with voltmeter).


texts: I need  a symmetrical power supply for some op Amp applications. I did a research about symmetrical power supplies. And I've found that circuit on this site. It seems very easy but I try it on simulation software and it works. I was wondering that do you guys think it is suitable for basic op amp applications?


texts:
I tried to evaluate the frequency of the following oscillator:

The loop gain \$\beta(j\omega)A(j\omega)\$ is:

To find frequency I must impose the condition:

$$\angle \beta(j\omega_0)A(j\omega_0)=0$$

but I don't know if the term \$1-(RC\omega_0)^2\$ is positive or negative. The angle is different in the two cases.

Thank you for your help.


texts:
This is the most interesting thing I have seen! I have built a DDS that sends data (D0-D7) to a DAC (ADV2175). The design worked fine and I just have a low frequency alias noise (a question here). This noise was present on all my ground planes (This is in prototyping stage and that's not unexpected from the test PCB).

I started tracing the noise path by disconnecting wires to see when the noise is gone. Surprisingly even after disconnecting all VCC and GND connections (+ all VREF and logics gone to 0 or 1) the noise was present yet. The more unexpected behavior is when the DAC is just connected to DATA port+ CLK pin (all coming from the source FPGA, NO VCC or GND), it continues working and a sine wave is produced (but with the same noise)!!!

First I thought it may receive its VCC/GND form the logic 1/0 fed into it but if it was correct, it should not have produce 0x00 and 0xFF levels, but it makes those levels correctly (I changed 0xFF data stage to another level and a notch appeared on top of the waves. this shows it can build oxFF correctly).

This is a big challenge for my PCB design, as if this device really takes its GND from the data port, instead of the dedicated pins, I will have a hard time for designing a reliable ground plane for it (the return voltage should go back to a logic noisy environment and analog-digital ground plane isolation may be impossible).

Can anyone explain what is happening there?


texts:
I recently purchased a Amcrest ProHD IP2M-841W 1080P camera where the initial configuration is done over some kind of audio signal, a companion app for mobile phones which, at the end of the configuration phase plays a masked "sonar ping"ish sound, barely audible were some kind of clicks and whistles which reminded me of 90s-era dial-up internet.

I've heard this technology is sometimes used in TV ads and similar, paired with malware in phones to track people's viewing habits but I'd never imagined it useful for programming hardware settings into a difficult-to-access device.

I tried researching programming using audio signals, serial and SPI modulators/demodulators and turned up nearly nothing, anything mentioning ultrasound yielded results about ultrasonic depth sensors and CV topics.

What is this technique of programming using audio(& visual?) signals called, and does it require (or benefit from) special hardware, is it reliable, etc?

It seems ideal for first-time configuration of embedded systems, or diagnostics.


texts: Add a passive hardware token using a 3.5mm jack

texts:
I have a box that I made for my niece, which allows her to exchange voice messages with me. It is powered by a Raspberry Pi and features two buttons, a LED, a microphone and a speaker.

Now, for Christmas I want my niece to be able to exchange these voice messages with various friends (4, 8 or 16) and relatives by plugging in a hardware token to the device, featuring a picture of that person.

I am now looking for the most simple way to add this functionality.

Preferably using a 3.5mm jack socket because they are readily available from used devices / headphones
Preferable a passive device (Capacitors + Resistors)
Preferably by attaching it directly to the Raspberry Pi
Preferably without using a AD-converter, since the Raspberry Pi does not have this built-in.
Easy to use by a 3-year-old

So using a 3.5 mm plug with 3 pins I could add attach power to one pin and either connect or disconnect the other two from that pin, which would leave me with two bits, resulting in 4 people (in addition to me as the default, if the socket provides a switch when a plug is inserted).

If I had an analog-digital converter I could add a voltage-divider to the three pins and use the voltage as an indicator. However, the Raspberry Pi does not have that built-in so I am looking for a smart way to achieve this using one of the GPIO pins.


texts: What are the properties of an N-bit microcontroller?

texts:
I've heard of 8 bit microcontrollers and 16-bit microcontrollers.  I've even heard about 7 bit microcontrollers and 1 bit microcontrollers.

What are the general attributes of these groups?  How do I choose which type to use for a project?


texts: What electrode material can I use for electrical discharge machining?

texts: Can I use an electrode made of melted soldering wire in electrical discharge machining (EDM) instead of copper or graphite? I think it is very easy for me to make electrode by using melted soldering wire by casting. Will it work on  EDM?


texts:
Im using a DS1233A IC with a battery (Li-Ion 4V) powered PIC18F26J50. The battery powers a LM1117 3.3V regulator. The problem i have is when lights go out for long period of times, the battery discharges under the threshold voltage (2.88V).

When the power comes back, it starts loading the battery, but the charging is so slow, that when the voltage is nearing the 2.88V, the reset pin on the IC goes berserk, turning on - off dozens if not hundreds of times until it stabilizes, but every time this happens, the PIC just tilts, and the only way for it to start working is manually reseting it by pulling the battery out and reinserting it, wich is the very issue i want to avoid because its a device located in remote areas and too hard to just go and reset it manually.

Tried the internal brownout reset on the PIC before using the external IC, but it didn't work, i guess because of the same reason the IC doesnt work, and its the extremely slow voltage rise of the battery, wich turns the PIC into a brick.

Is there a solution to a problem like this using what i have?

Thanks for any help!


texts: I'm kinda new to designing. I have a task at hand which I hope a kind soul is willing to guide me to right direction. I need to design a 2 output flyback converter. First Output would be (12V x 5A = 60 watts). 2nd Output would be (8V x 5A = 40 watts). Vin would be 230V AC, 50Hz. I have sourced through the web but there isnt much help in designing for beginners. Such as how do I calculate Cin, the Snubber, Cout and stuffs like that. I was planning to use the UC3844 as my Controller IC but the datasheet was too complex and only convered based on UC2845. Was planning to add a control feedback circuit from the output to the PWM IC. Thanks in advance.