texts: Differential high voltage measurement using a transformer

texts:
I have questions about the limitations of using a mains-rated power transformer (e.g. a small 6VAC 1VA PCB mount transformer) as a cheap differential probe, so that waveforms can be safely observed on an oscilloscope.

My questions refer to this schematic, which is not intended as a real circuit but to allow me to refer to the various elements:

simulate this circuit – Schematic created using CircuitLab

Vin1 and Vin2 are any two points in a mains-powered circuit across which the differential measurement is desired. R1 represents a standard scope input impedance.  For now let's ignore R2, C2, C1, R4, and R5.

My understanding is that with an ideal transformer, this is a safe way to accurately display a typical mains voltage waveform.  However, a real transformer will have some common mode leakage represented here by C1. This should mean that the transformer's "CMRR" (as it were) deteriorates as higher and higher frequency content appears across it.

My main question is: will this common mode issue present a danger to an oscilloscope when probing a circuit like a phase angle controller with fast edges? Will the high voltage, high frequency content be capactively coupled straight across the transformer, resulting in a short via the shell of the scope's BNC connector?
If this coupling could be a problem, would the addition of a simple filter like R2 C2 suffice to solve it, assuming that the user did not mind the loss in measurement bandwidth?
Are resistors like R4 and R5 a sufficient way to minimize loading on the circuit being measured?


texts:
I have been developing a software for scalar control of three phase induction motor with squirrel cage rotor. This control method is based on voltage-frequency characteristics of the motor. The used motor nameplate contains 400V, 50 Hz and the stator is in wye connection. Based on these values I expect that the slope of the voltage-frequency characteristics will be \$K_1 = \frac{(\sqrt(2)*400)}{(\sqrt(3)*50)} = 6.5\,V/Hz \$. The problem is that I would like to rotate the motor at 60 Hz. Based on the above given voltage-frequency characteristics the operating point would be in the field weakening region. I had an idea that I can prevent the field weakening of the motor by changing the slope of the voltage-frequency characteristics \$K_2 = \frac{(\sqrt(2)*400)}{\sqrt(3)*60)} = 5.4\,V/Hz \$ i.e. the nominal stator volatge would
be achieved at 60 Hz and not at 50 Hz (please see the attached graph).

Is it possible or is this idea wrong? (I see that below the 60 Hz the magnetic flux of the motor will be lower than the nominal value. But the motor starts with no load and the load torque is applied as soon as the motor achieve the no load speed.) Thanks for any ideas.


texts: What happens to voltage source if I take out both volt and current with separate circuit using diodes and then combine both separate circuits?

texts:
I have 3.8V and 1.2Ah battery. I will use a step up circuit that gives 5v and 200mA output using 2v in (from my battery). Then I will use blocking diode to take voltage only(5v) and I don't need current from this circuit. Again I will also use a step down circuit that gives 1v and 2A output using 3.5v in (from my battery). Then I will use another blocking diode to take current(2A) only and I don't need voltage from this circuit.

So can I get 5v and 2A output in this way from a 3.8V and 1.2Ah battery? And now what will happen with my battery?

I need to understand that if I can get more power out of the circuit than comes out of the batteries. To extrapolate what I want to do, imagine I want to power my house  with 240V @ 100A (24KW). I want it with a 1V @ 100A (0.1KW) power source combined  with a 240V @ 1A (0.24KW) power source.

If to power my house with 1v@100A(taking the current only from here using blocking  diode) and with 240v@1A(taking the voltage only from here using another blocking  diode) and combine both of this to get 240@100A.

Is it possible? Well if it is  possible I will again feed back the 5v and 2A output to battery to recharge it. So  before being the battery empty(if) I will be recharging it again by the estimated  output from the combined circuits.

Will the battery really be empty after producing  separately stepped volt and current or can I get volt(5v) and current(2A) greater  than my battery (3.8V,1.2Ah) in this way?

Does my thinking have a hope? My step up and step down circuits are as following as example:

http://www.alibaba.com/product-detail/DC-DC-2-0-5-v_1547670640.html?spm=a2700.7724838.102.7.vDaE3Z

http://www.amazon.com/DROK-Converter-4-5-24V-Rrgulator-Constant/dp/B00C4792T2/ref=sr_1_16?ie=UTF8&qid=1436885493&sr=8-16&keywords=current+regulator


texts: Fake TL072/TL074 IC's - how does the economics of it work?

texts:
I've reached the conclusion that all my TL072's and TL074's bought via AliExpress from China are fakes. Both SMD and THT versions. Most likely they are LM324 or similar. The particular problem I've had is the slew rate being waaay off specification, something like 30 times slower than specified which is easily seen in my VCO as the output square wave starts to slew into triangles at around 4 kHz.

I've heard of counterfeits and blacktopping, but this seems like something else. I'm so surprised that there is any money to make out of this. I mean, I pay very little money (€7 for 100 TL074CDR for instance). This for a perfectly looking cut strips of 100 of a reel:

There can't really be blacktopping and re-packaging going on for that kind of money, can there? Can the source factory itself be faking the labels?

Any insight on this? I've tried to google counterfeits and how to spot them, but it seems most sources are old and covers blacktopping and the like. This really can't be it. Factory rejects wouldn't be like this where everyone of them has a way-out-of specification slew rate, would it?


texts: Activate CE pin of a LDO voltage regulator with a momentary switch

texts:
The situation is as follows:
I have a 3.3V regulator that I would like to turn on and off by a momentary switch connected to its "CE" pin.
This regulator has an input from a 3.7V battery and an output to a microcontroller (3.3V).
My question is, what is the simplest possible circuit that can be used so that pressing the switch once will turn the regulator off and then on again?
I cannot use software with the microcontroller as my intention is to turn the system off completely and I would not be able to turn it back on.


texts: Can aluminum solder paste be used in electronic circuits?

texts: Is a paste like Solder-It Aluminum Solder Paste ALP-21 suited for electronics? Are there going to be any issues with the solder under constant current due to chemicals in the paste or something like that?


texts: What are those "cheap" parts kits made of

texts:
I hope this will not be categorized as buying related question because my question is not really on should I buy this or this.

I usually find some parts kits, usually resistor/capacitors/trimpots, like 100 caps for 2€/3$. I've already try one pack of these from Kemo, the values in the pack are totally random but I got some good surprises too (like a bunch of 10K 1% resistors and 550ohm 2% resistors). For the moment I just use them when prototyping the project.

My question is do you know how they can be so "attractive" from a pricing point of view ?  I have my little idea, but not sure. I think it's most of them "old parts" or unselled stock from closed companies. (due to the "look" and some have a bit of corrosion). I ask because I've also thinked at a moment about harvested parts from broken electronics as some "feels" like harvested parts.

Do you have any ideas about these cheapos parts ? Is it a dangerous choice ?


texts:
It looks like every chip manufacturer has their own CAN bus TVS product nowadays, e.g. ON Semi NUP2105, Semtech 2492SQ, Bourns T24CAN, Nex PESD2CAN and many others.

What is common for all of them is surprisingly high stand-off and breakdown voltages, typically around 24 and 30V. These seem to be inline with ISO 11898 max bus voltage specification for 24V systems. Way too much for 12V systems.

Furthermore, most transceivers are designed to work of 5V supply and 3.3V devices becoming more common. There is no way these drivers can put up more than 5V on the line, and even if we add generous common mode tolerance it still be nowhere close to TVS specs.

While doing my research I've stumbled upon this interesting board from TI, demonstrating various ESD protection circuits. All of them use SM712 diodes, designed for RS-485. They have much lower and asymmetrical breakdown specs -7..12V, which seems to be ideally suited for CAN.

So, my question would be this: why manufacturers keep churning those high-voltage devices and why devices like SM712 are nowhere to be seen except on those obscure TI boards?


texts:
So I have made a low pass filter and plotted the transfer function of it. However, I know I need to also use another opamp to correct the phase shifting/ gain. What design should be best to add on to the output so that it doesn't invert or change the transfer function, just shift it vertically? I have tried inverting and non inverting but both flip by graph. Help please?!?

EDIT: This is what I tried, but it didn't just simply shift the graph (phase shift) but flipped it.

EDIT 2: Yes! I used the non-inverting op amp and it worked! I just accidentally had Vin/Vout instead of Vout/Vin.


texts: It isn't like lightning strikes the wires. And surely the whole apparatus is designed to be water-proof. So what is it that causes power outages during thunderstorms?


texts: Electronic aspects of iPhone 3.5mm audio output

texts:
I am working for a while now on a small project of building an external mic for the iPhone to be hooked in parallel to headphones (via the 3.5 mm jack). Basically, I want to replace the iPhone's original headset microphone with another microphone, but still use the headphones to listen.

Below is an image of the prototype structure (based on 2 existing products, but it is actually not working; probably due to impedance issue):

Some clarifications on the image:

item #5 - split point between microphone jack and headphones jack.
item #4 - iPhone plug 3.5 mm
item #3 - a microphone which for now is NOT working since the iPhone
seems NOT to identify it (probably impedance issues - it's impedance
about is about 650 Ohm)
item #2 - simple headphones jack (any headphones with 3.5 mm plug can
hook there)
item #1 - microphone jack hooked to the external microphone I have
for now.

I would like to focus my question on the electrical aspects of my project for now. Known data I gathered so far (please feel free to correct any mistake you identify):

iPhone supply's 1.5 V on the TRRS 3.5 mm jack.
the TRRS plug of iPhone is built of from 4 pins: Left/Right/Ground/Mic

Questions:

What's the power consumption per EACH part of the iPhone headset?
Each part means that there are 2 components - headphones &
microphone and I need the separated power consumption (especially
the microphone!)
What's the current the iPhone drive on the headset microphone and what's the current driven on the headphones?
Read some other answers on the impedance topic, that the iPhone identifies external microphone (on the headset for example) only if the impedance is ±1650 Ohm, but than, I read another answer which claims the required impedance is ±5000 Ohm. Any ideas what is correct?
Should I plan that the microphone impedance (includes the wire) to be 1650 Ohm (or 5000 Ohm based on the answer I will get for question #3) OR the whole prototype (microphone + wires + regular headphones I will hook to 3.5 mm connector) should be together the 1650 Ohm / 5000 Ohm?
Is this correct to say that the 1.5 V supplied by the iPhone 3.5 mm audio output, means that the right/left/mic pins are positive contacts with 1.5 V vs. the ground pin (means that we have 3 parallel circuits sourced by one 1.5 V power source).


texts: difference between magnetic rotary encoder and mechanical rotary encoders

texts:
As i found so far there are two types of incremental encoders for rotational position/speed calculation/detection application.

1)magnetic incremental encoder ICs eg:- SSI, SPI or I2C interface , 8bit to 16bit resolution up to 30000rpm, also these are programmable.

2)Absolute or incremental encoder mechanical type eg:- 10000rpm 2500ppr

which type is better ? in terms of performance, reliable, life time, error % at higher rpm (higher frequencies)?

I am going to use encoder to measure speed and crank angular position of an engine at 10000rpm using FPGA


texts: Adjusting the voltage for a small speaker

texts:
I have a 4Ω 3W speaker and I plan to use it with MAX98357A amplifier. I need to make sure the speaker receives optimal voltage. When I test the voltage output from the amp playing nothing, I get 2.5V. I assume this is how zero level looks like, and when sound starts playing, it would oscillate between 0 and 5 volts. I don't have oscilloscope to confirm this, though.

From the P=V²/R I can calculate the voltage: V=sqrt(P*R)=3.46 volts. I am not sure whether that is safe with my amp that gives 2.5V at rest. I am looking for advice whether I should adjust the voltage coming from the amp.


texts:
Let me create a scenario to better illustrate the problem
I have 1500 pens that I want to individually actuate upwards with 3 different distances, ex: 10mm/15mm/20mm
I thought I could use a solenoid to do this, but I'm not sure if this is the best option and how accurate the solenoid will be, another point is that speed is very important to me, that's why I'm initially not considering servos for example.
Thanks for the help!


texts: Interfacing tri-state logic across 3v3/5v. Do buffers mirror all three logic states?

texts:
(This is just learning/hobby stuff...)

I have a 5v (tri-state TTL, ZX Spectrum) bus and I want to interface some non-5v tolerant 3v3 chips to it.

I think I need buffers or transceivers for the level conversion.  (Is a buffer just a latching transceiver?)

Will a buffer or transceiver send all three logic states (high, low and tristate/high-Z) across the level change?

Could anyone recommend suitable ICs, either 8 or 16 bits wide, in DIP or DIY-solderable surface mount packages?


texts:
I have this MOSFET Driver IC Datasheet.
This is in follow up to this question.
I want to validate the block by testing.
My block specifications -
Input Gate Voltage -5V
Drain to Source voltage Range : 9V to 16V
Maximum Drain Current - 7.5A.
Can someone tell me what are the important tests that I need to perform to validate this IC function entirely. What are the major points where I need to check in this IC (like basic things like Rds drop between drain and source which the MOSFET is ON, propagation delay between the input enable and the output). Like there, can someone help me with the list of tests?


texts: What does the Arduino ethernet shield connect to?

texts: I am thinking about buying an Aurdino ethernet shield, but I am not sure what it connects to. On the back of my iMac there is a blue plug which goes into the computer, which I think is the ethernet plug. Would I just plug that into the ethernet shield?


texts: What are the tolerances for the maximum current a battery can supply?

texts:
After a lot of research and experimentation I have come to learn that the sentence "This is a 1.5V, 2800mAh battery" is entirely a lie.

(i.e., the potential difference between the terminals of a battery changes over time and the shape of the graph is dependent on battery chemistry, ambient temperature and current draw, as is the useful energy capacity. Finally, many things which are colloquially called "batteries" are actually cells, and this is important as it has a bearing on both of the above.)

What I want to know is, if I have a 12V battery of lithium cells whose spec sheet says it will deliver 9A and I attempt to draw 9.5A from it, am I heading for a quick trip to the burns unit? What about NiMH or other chemistries?

How much headroom ought I leave and what are the factors (temperature, "C" rating, duty cycle, anything else) I need to consider?


texts: Can NiMH batteries charge at cold temperatures?

texts:
While I am aware of the risk associated with charging Li-ion below 0 °C and that
 the charge acceptance for a NiMH battery decreases with rising temperature,
I am finding conflicting information when it comes to charging NiMH batteries below 0 °C.

Battery University
in Table 1 claims that 0°C to 45°C is the charging temp range.

Energizer in Figure 13 claims that the battery will charge at -10°C

Is it possible to charge any NiMH battery below freezing? Is it dependent on the actual battery itself? If it is not able to be charged, why not?

Thanks,

SNM


texts: DC-DC converter, 12V to 400V? Is this possible?

texts:
To be able to charge a high voltage battery (~400V) from solar panels I need a dc-dc converter that can boost up the voltage from the low voltage system (~12V) to the higher voltage.
The power needed is about 400W, or 1A at the output.

I have read that it is not practical to boost more that a factor of 6, and this is a factor of about 30-35.

Would two boost (step-up) converters connected is series work or is there a better solution?


texts: What is the controlled variable in this particular case?

texts:
I have a question, maybe you can help me because I am not sure of the correct definition.
As an example I have a plant with a measured output y in a closed loop system. But as the feedback variable I use y' = y + 100 to substract this from the setpoint.
Does the calculation of y' belong to the plant and is y' the controlled variable then?
Or is y the actual controlled variable and how is y' then called?
Thank you in advance for your help!


texts: Can someone help me explain I2S timings when it comes to master and multiple slaves

texts:
I am just getting stuck as to what's happening.
Below explains the functionality of each of the hardware and how they interact with each other to give you a better idea of the situation.
HARDWARE USED:

Audio Codec: PMOD:I2S2
STM32H753ZI: MCU
ESP32: MCU

NOTES:
ESP32 (Master)

Uses I2S to send stereo audio samples to the STM32 (slave)
It samples stereo audio at 48kHz

STM32 (Slave)

Receives and sends stereo audio samples from the ESP32 (Master) and to the DAC (Slave)
It doe DSP on the stereo audio samples

PMODI2S2: DAC (Slave)

Receives and sends stereo audio samples from the STM32 (Slave) and to speakers

This is using no DSP (Unity IIR Filter)

DIAGRAM:

THE PROBLEM:
In the code of the ESP32 the I2S timing are as follow
 i2s_config_t i2s_config = {

    .mode = I2S_MODE_MASTER | I2S_MODE_TX,
    .sample_rate = 48000,
    .bits_per_sample = 24,
    .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,                           //2-channels
    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
    .dma_buf_count = 6,
    .dma_buf_len = 60,
    .intr_alloc_flags = 0,
    .use_apll = true,                                        //Default interrupt priority
    .tx_desc_auto_clear = true                                              //Auto clear tx descriptor on underflow
};

So this essentially tells me the ESP32 is going to create a:
$$ SCLK = 2channel * 32bit * 48kHz = 3MHz$$
$$ MCLK = 256 * 48kHz = 12.28MHz$$
                                                    or

$$ MCLK = 384 * 48kHz = 18.4MHz$$
$$ LRCLK = 48kHz$$
that's fine, understood I2S standard, now in my STM32 code ill setup the I2S to match the timings of the ESP32 as such:
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_WSINV_I2S;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_DATALEN_24BIT;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_FIXCH;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_CKPOL_FALL_RISE;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_I2SSTD_I2STAND;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_CHNEL_32BIT_WIDE;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_I2SCFG_SLAVE_FULLDUPLEX;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_I2SMOD_I2S_PCM_MODE;
                       SPI3 -> I2SCFGR |= SPI_I2SCFGR_DATFMT_LAlign;

This matches up with the ESP32 timings, so everything should work. as Datalength = 24bit channel length = 32bit and the rest of the I2S standard, MSB first, left align, etc
The DAC says in the datasheet it can autodetect timings listed here.

Perfect, the DAC can support 256x and 384x ratios at 48kHz and a bit timing up to 24 bit on the SCLK.
HOWEVER, when I run the code and test, the audio sounds its skipping and audio sounds faster (Its high pitched and sounds fast forwarded like mickie mouse haha).
WHAT I FOUND OUT:
If I change the bits in the ESP32 to 16 bits, it works no problem, sounds good. I further tinkered with it and found out it doesn't matter what data length nor channel you have it at on the STM32 if the ESP32 bit is set at 16, it sounds normal with data length of 16/24/32 and a channel length = 16/32
Why's that? This is ruining my understanding, I thought the bits determine the SCLK frequency, so how does it make sense if I change my ESP32 bit to 16 to get a SCLK = 1.5MHz and in the STM32 I can have a SCLK of = 3MHz and still works?
I know the STM32 is a slave which is kinda confusing and doesnt generate these signals then whats the point of configuration the data length and channel length at all then?
UPDATE 1:
When putting back my DSP filters I noticed that changing it to 16/24 data length now causes massive static like sound, and the only thing that fixed it was putting it to 32 data length


texts: Cheap, compact 3.7VDC -> 400kVDC (continuous) converters

texts:
I recently bought some inexpensive and compact (about the size of a 18560 battery) 3.7VDC -> 400kVDC converters. I can confirm they work, and based on the breakdown voltage of air, estimate the output voltage to be in the region of 400kV. Output is continuous and not pulsed.

In principle I guess it would probably be built around the following stages:

 DC to AC inverter
 Step up AC with a number of transformers in series
 Rectify AC to DC

Unfortunately the circuit is all epoxied up so I can not learn how they did it. My questions are as follows:

 Do you think the steps I mentioned above are correct?
 Did they use a cascade of transformers for voltage multiplication because of the continuous output?
 I would be grateful for even a rough pseudo circuit schematic to help me understand what is going on.


texts: Steering wheel with optical or multiturn

texts: i have a logitech formula force feedback wheel , and i'd like to change the rotation of wheel from 180 to 900. I know that i have to change the pot, but i don't know what type of pot i should use. I've been thinking in using an optical one, but i don't have any ideea how to do it. I could also use a multi turn one but i know these things aren't so strong.If someone can explain how and what should i use step by step i'll be thankfull. And sorry for my english ;)


texts: Help with figuring out the particular requirements of this circuit

texts:
Sorry for if i say anything incorrect

I am trying to create a circuit  that can control a BLDC. motor  ...quite simple and easy but i want the source of power to be switchable/interchangeable  ...orignally  from a battery then when a switch is pressed for the power to come from a  super capacitor  bank ...the capacitor bank will of course also be recharged by  another method

my issus comes as i am unsure about the correct requirements , specifies and how many super capacitors should be in parallel  and series in order to give the same output as the battery as i do not want the ESC to cut out...


texts: How to measure gasoline:oil ratio for 2-stroke motor?

texts:
For some reason I am obsessed with instrumenting my small fishing boat.  I'd like to have a continuous measurement of the gasoline:oil ratio in both my main (70HP) motor and kicker (7.5HP); I have a tank for each, so a display for each.

I will be using an Arduino of some sort.  I'm not looking for the wiring or code, but what kind of sensor to use.  I'm assuming there is some sort of sensor that will give me a resistance or voltage or ?? change that's proportional to the gasoline:oil ratio (50:1 to 100:1 is typical).

Google turns up bazillions of air/gasoline sensors, but I doubt they'd work.

If nothing exists, I'll start experimenting.  But it's gasoline, so any pointers to existing work would be appreciated.


texts: Are the capacitors highlighted really needed for proper operation of the circuit?

texts: When I refer to TI's reference design for the charging chip I do not see those capacitors. Upon researching I found out that they are smoothing capacitors. Why are they used here and are they really necessary for the circuit to work and what would be the consequences if I remove them ?


texts: Understanding of two stage DC coupled complementary amplifier

texts:
I am struggling with an complementary amplifier and unable to compute the value and equations. My target is to identify the working of the circuit, its total gain and equations. After studying many circuits I learned that:
Gain of 1st stage A1 = 4700 / 200
Gain of 2nd stgge A2 = 1600 / 200  (I dont know if this is correct)
total gain A = A1 * A2  (I dont know if this is correct)

Q point for active region for 1st tage is
Icq1 = (V1 / (R6 + R1)) / 2

Q point for active region for 2st tage is
Icq2 = (V2 / (R2 + R3)) / 2  (I dont know if this is correct)

V6 = V4 + 0.7

I0 = I6 + I4

I6 = Icq1

I4 = Ib1 + Ie2 => Ib1 + Icq2

Ic1 = B * Ib1  With this equation I can calculate the required Ib for beta and Ic1 = Icq1

This is how far I go but I still don't know how this works.
I want equations for the total gain and for the resister value selection because this is reference circuit and I don't have actual transistor Q7 and Q8 with reference beta values.
Now if I use any other good transistor then the beta will change so we need to calculate new resister values to set the circuit in active region and total gain of > 32 dB. Also the bandwidth is > 3 Mhz. Input type is video signal.


texts: Minimum number of transistors to implement cmos logic of this function

texts:
I have designed the following circuit to implement cmos logic of :

\$out=\overline{(a+b).\overline{c}+e.(\overline{f}+\overline{g})}\$

I’m looking for optimal circuit with minumum number of transistors, is there any better implementation?


texts: How to solve electric shock issues in this system?

texts:
When I measure the potential difference between for example a 12V DC output device's one output terminal such as a power supply's or a transducer's and the "earth ground", I see 50Hz voltage signal with around 160V amplitude in oscilloscope. Its not always 160V sometimes less depending on the transducer and the output.

An example with a 12V DC power supply:

I turn on the power supply.

I measure the voltage between its plus and ground terminals and it is 12V as expected. So far so good.

But if I measure the voltage between any one of the terminals of this power supply and the "earth ground" of a power outlet, the voltmeter shows like 99V rms.

This was peculiar so I wanted to see the signal on a scope.

Here is the oscilloscope output when the probe's tip is connected to one of the terminals of the power supply:

An example with a scope.

I experience the similar phenomenon with a turned off oscilloscope.

The scope is turned off in this example. When I plug the scope's power cord to mains outlet with a 2-prong AC power cord and measure the potential difference between the scope's GND and the "earth ground" of the outlet I measure like 48V rms voltage.

But if plug the scope's power cord to mains outlet with a 3-prong AC power cord and measure the potential difference between the scope's GND and the "earth ground" of the outlet this time I measure zero volt.

Floating outputs?

Am I experiencing floating outputs in both cases?

In power supply case I can see that the floating terminals with respect to the earth ground can be the reason, But I don't get why there is a potential difference such as 48V between a turned of scope's GND( whe the scope uses a cord without an earth pin) ant the "earth ground" of the outlet.

Question

In the below system we are getting electric-shocks at the output of amplifiers or end of BNC cables:

I named the points to make the question clearer.

A1, A2, A3, A4 are amplifiers for some transducers(model 101 in this case). PSU is a power supply which provides DC power to the amplifiers. PSU is connected to the mains outlet via a 3-prong power cable where L is line, N is neutral and E is earth ground as shown in the illustration.

"dc" are the plus terminals and "gdc" are the ground terminals of the power supply which powers the amplifiers.

Output of the amplifiers are sent to a DAQ system via BNC cables. "out" are the inner/signal carrying wire of the BNCs, and the "gb" ground/shield of the BNCs.

DAQ system has analog inputs and they are single ended and all the grounds are connected to the earth as shown in the illustration.

In this system when the PSU is on, and when none of the the BNCs are connected to the DAQ inputs we get electrocuted. I measure sometimes like a 60V rms AC voltage between one terminal of the BNCs and the "earth ground". But when connecting any of the BNC to the DAQ system this floating voltage disappears.

1-) Is this voltage occurring because of the floating power supply PSU? Is this voltage dangerous?

2-) How can I solve this issue? Should I connect the "gdc" to the earth or "gb" to the earth?

3-) DAQ side is single ended and grounded all the way to the earth through PC's motherboard. If I make non-floating outputs by wiring PSU DC GND to earth would that create ground loop issue this time?


texts:
I'm currently working on a UV-C germicide lamp, and among the things I have to do, is to drive four 83V OSRAM 21283 G55T8/OF 55W G13 T8 Tubes. Here's a link to the tube, and the datasheet.

My question is, how to power each of these lights? Being that they are rated 83V as opposed to 110V or anything closer to that. Also, I'm assuming they work with AC (and I hope this isn't a stupid observation), but there's no clear indication of that. Is this correct?

I don't have much experience in terms of installing lights, but being that this qualifies as fluorescent I know at the very least it could use a ballast.

I'd like to be pointed out what has to be between the 110V AC source and each of the tubes. And I'd also like to know: Is a direct connection between the base and the source (through the driver, of course) out of the question?


texts: 12V variable-speed fan as a function of temperature using 555 timer

texts:
I would like to turn the car fan into a variable-speed fan using a the analog temperature sensor of the car, and a 555 timer.

While temperature decreases, resistance (of the sensor) increases. Can I use this information in a ratio R1/R2 (below) to change the pulse width of the 555 timer, and by that changing the speed of the fan? Can this be done?

R1: the resistance of the sensor
R2: determined resistance


texts:
Basically, what I'm trying to do is a circuit that maintains the output ON for about 10min after a switch has turned OFF.

In another words, a rising edge of the input will raise the output immediately, but a falling edge will take 10min to drop the output OFF.

This diagram will explain better:

A switch will be connected to the input, and a relay to the output.

I thought this would be a piece of cake, but it's giving me quite a headache.

Initially I tried using a falling edge detector to trigger a 555 ci in monostate mode, but no matter what configuration i use I keep getting a pulse form output, which is not what I need.

I also tried a bunch of flip-flop and 555 combinations that I've stumbled to, but none of them worked.

I'm completely open to different approaches on this, and don't need to use the 555 ci. There is only two requeriments that I would like to meet:

1) Preferably powered by a 12v source.
2) It must be controled by a ON/OFF switch.

Any guideline would the much appreciated.


texts: Which wireless module should I use for 40Kbps communication with low-power consuming?

texts:
I'm now making battery-powered wireless high-refresh-rate AHRS module and it needs continuous wireless communication around 40Kbps(160bit * 250packets/s) with iPhone.

What I found were Wifi-direct, Bluetooth EDR and Bluetooth LE.
I thought Bluetooth LE would be best because it contains 'low energy' in its name and it's newer than EDR, and so on.

However, what I found some figures below while googling.

link

I think the image above means that BLE communication cannot achieve over 200 packets/s, especially on iPhone.

link

And also, BLE consumes more energy compare to Bluetooth BR/EDR at 40Kbps according to the plot above.

Are those both information correct? If then, should I give up to use BLE and find other choices like old-friendly Bluetooth EDR?


texts: BJT voltage divider biasing and thevenin equivalent

texts: I am studying BJTs and I came across this configuration. My book applies Thévenin equivalent to the base and I do not understand how it does that, it does not make sense as there is base current to take into consideration. I kind of know about Thévenin equivalent circuits but I do not really understand how it works when I think of solving the same circuit by normal means(node analysis, KVL etc) I just cannot. Can you explain what is going on like I am an idiot?


texts: Is over-voltaging a DC fan, and then reducing speed with PWM a bad idea?

texts:
I have an 18V system and I need to run some fans off of the 18V rail.  I've been using 24V fans with PWM control and they work fine (although are slower than their fully rated 24V speed).  Now we can't seem to get enough 24V fans to build the next batch (even without PWM, they are out of stock everywhere).  Would running a 12V fan on my 18V and never going above 66% PWM work?  Or will this fry the 12V fan instantly?  Or will it work for a while but with reduced fan life?  Short of finding more 24V fans or the world inventing 18V fans, what's the best way here?
I don't have 12V available on the system, nor do I have enough room to add a DCDC that is large enough to handle the current for all of the fans.
A loosely related SE post


texts: Why is the chassis used as ground in automotive electrical circuits

texts:
Automotive electronics generally use the metal chassis as the negative ground connector for the DC circuits. Obviously this saves something on wiring. Is there an electrical reason for this approach?

(I am not asking why negative instead of positive, but why metal frame instead of wire.)


texts:
I know voltage is electrical potential difference between two points. So, I think must be calculated:

Voltage = Electrical Potential at A - Electrical Potential at B

Can someone explain where does the ohms law relation: V = IR comes from in this?
Is it possible to calculate voltage with electrical potentials given?


texts: timestep too small error with non-linear capacitor - how to handle possible discontinuous points

texts:
I am using LT spice to simulate a thermal problem involving a phase-change material (a paraffin).
[
with the paraffin modeled as a non-linear capacitor and resistor (the capacitor represents the heat capacity, the resistor the thermal conductivity:

Note: the thermal resistance is simulated as a voltage-controlled current source because a normal resistor can't handle if() statements in its value, even in parameters.
For thermal simulations, the voltages in the circuit equate to temperatures in Kelvin and current equates to heat-flow. (See, for instance, Learn LTSpice: A Tutorial
The non-linear capacitor has the equation
Q = {PCM_mass_g} * if(
    V(Heat_In) <= ({Tm} - ({epsilon}/2)),
    (x*{Cps}),
    if(
        V(Heat_In)>=({Tm}+({epsilon}/2)
      ),
      ({Cps}*{Tm}+{Hfus}*{Cpl}*(x-{Tm})),
      (
        ({C3}*((x-{deltaTc})**3)) + ({C2}*((x-{deltaTc})**2)) +({C1}*(x-{deltaTc}))+{C0}
      )
    )
)

epsilon is a small band around the melting point. Below temperature = (Tmelting - epsilon/2) the thermal capacity has the value for a solid; above (Tmelting + epsilon/2) it has another value for the liquid form, and within the epsilon band it is a complex polynomial that describes the heat of fusion for the material.
The equation should be reasonably continuous, at least it is in the spreadsheet:

But whenever the simulation voltage V(a) hits (Tmelting-epsilon/2) LTSpice throws a "timestep too small" error.
I will be most grateful for any suggestions as to how to get around this!


texts: How to keep a relay closed until electricity is given again

texts:
I send current through relay to turn on relay. I want to keep relay turned on even after i stop current flow. Then again when i send current the relay should close.

If i send current through relay, the bulb should light. Then i stop current through relay and the buld should stay light. Then after some time when i send current through the relay again, then the buld must be turned off. Any ideas?


texts: Transient voltage of an inductor in an RL circuit

texts: In the circuit of the above problem, at time t = 0-, the inductor can be modeled as a short circuit as the circuit is at steady state. The 20 ohm resistor can be ignored since all current flows through the short circuit. I think this means that the voltage through the inductor at t = 0- is 0 V, since it is part of the ground node. It seems that at t = 0+ the inductor voltage should also be 0 V, as the source voltage is 0 V, but this is not correct. At time t, the correct value of inductor voltage for t ≥ 0 is -8e^(-8t) u(t) V, where u(t) is the Heaviside function. From this expression, the inductor voltage t = 0- is 0 V, while at t = 0+ it is -8 V. How can these values of inductor voltage be interpreted?


texts: How to choose connecting wires and switches for a motor-battery set

texts:
For a project I'm using 4 12V, 35AH lead acid batteries in series which powers a 400W, 48V bldc motor. The maximum current the motor would draw from the battery set is 12A.

How should I choose the type and rating of wires that connects the 4 batteries in series?

How should I choose the type and rating of wires that connect the battery to the motor unit?( I haven't arrived at the length of these wires yet)

I also have to provide a kill switch for the circuit. How do I choose that?

This is how the motor control unit is :


texts: How are the bitflip and row hammering effects taken care of by micro controllers in critical systems?

texts:
Bitflips/random hardware faults and row hammering are some  of the things which could damage the memory. Do the current breed of latest microcontrollers, used in embedded systems, have any mechanism to detect these?
I’m not aware of how this is handled and can anyone provide some insights on this?


texts: Choosing a RF Detector Circuit for my Sweep Generator

texts:
My newly acquired sweep generator (wobbulator) doesn't have an inbuilt RF detector circuit unlike some others (some Wavetek models).  So, I decided to build one.  I was quite surprised at how many variations of this relatively simple circuit are out there and now I'm not quite sure which one I should build.

The basic types break down into a) those that block DC and those that don't and b) those that filter/smooth and those that don't.  Here are some examples:

The circuit above with slight variations is often suggested for my use-case.  It seems to rely on the input impedance of the oscilloscope (in my case) which is typically 1MOhm, with the resistor in the diagram chosen to provide an RMS output. Am I right in thinking that this version will only rectify, but not smooth the RF signal?

Here are variants of the one above, but with smoothing (the 2nd one is w2aew's rf probe circuit):

There are also the non-DC blocking types that are used in AM detector circuits, but I think I can ignore those ones.

So, my questions are: has anyone built anything like this for their sweep generator and which circuit did you use?

Why wouldn't I want to include the 2nd capacitor to filter the rectified RF (the sweep range is from about 100 kHz to 120 MHz)? (I'm thinking the second types have a much lower input impedance).

EDIT:

I realize some out there will have no clue of what I'm talking about.  So, here's a great youtube video that explains everything: https://www.youtube.com/watch?v=szC2RJRmlgI


texts: Replacing Electrical System with a Gain?

texts:
I have a system containing both a mechanical and an electrical part, as shown in the block diagram below. I am interested in simplifying this block diagram by eliminating the electrical part and replacing with a suitable gain block.

The electrical system can be described by \$V = iR + Li + αẏ\$, where \$α\$ is the relationship between the magnetic field induced voltage and the velocity.

Gain \$i\$  =  \$1/L\$
Gain \$j\$ = \$R \$
Gain \$c\$ = \$α\$ (not part of the electrical system)

I am aware of the dominant pole approximation, where poles closer to the origin will dominate the response. I plotted the poles of my whole system below and it can be seen that one of the poles can be eliminated.

This shows that the system can be reduced to a 4th order system (from a 5th order). I have performed all calculations to get the required fourth order transfer function, by eliminating the left most pole.

Since the integrator of the electrical system is linked with the derivative, this must be eliminated.

Question:

I am interested in simplifying the block diagram and not just the transfer function. What calculations must be performed to replace the whole electrical system with a gain block?

I found that simply replacing the whole electrical system with a gain of 1, retains the same exact response, but this was not done from first principles or via calculations. How can one explain the removal of the electrical system blocks with a gain intuitively?

I am looking for a general approach of how to simply block diagrams by replacing electrical constants with a gain block. Any help would be appreciated.


texts: What specifications matter when comparing TVS ICs?

texts:
I have been wanting to update a design I have to include a USB to UART Bridge and while looking at the datasheet for the CP2102N saw what is in the image below.  I have never worked with a TVS before so I am not entirely familiar with their specifications.

When the datasheet says to use "SP0503BAHT or equivalent USB ESD protection diodes (Recommended)" what exactly determines a TVS is 'equivalent' or 'better'?

While searching around I came across this post which has the TI TPD4S012 listed as a suitable USB TVS.  I'm not looking for someone to verify that the TPD4S012 is a suitable replacement for the SP0503BAHT, rather, the understanding of what to consider when choosing.


texts:
Ok This might sound dumb but I am trying to get an equation for the radiation intensity of a pyramidal horn antenna in spherical coordinates. I got a whole bunch of books and they all have the same equation:
$$
\mathbf{E}_\theta = \frac{j\, e^{-j k r}\, E_0\, A\, B\, (1 + \cos(\theta))\, \sin(\phi) ...}{8\, \lambda\, r}
$$
$$
\mathbf{E}_\phi = \frac{j e^{-j k r} E_0\, A\, B\, (1 + \cos(\theta)) \cos(\phi) ...}{8\, \lambda\, r}
$$

Ive got like 4 different text books about the subject and the all of them have those exact same equations. But not a single one says what \$r\$ is anywhere. Anybody know what this is?

Sorry to ask but I've been searching for hours. Can't find a single source that explicitly says what \$r\$ is.


texts: How does not using common-mode feedback drive my outputs to the rails?

texts:
Consider the following circuit in Fig 9.31 (a)

Now, essentially, summarising the block of text, it seems that due to some mismatch between PMOS and NMOS devices or fluctuations in bias voltages, the current that Iss/2 pulls may not equal what the PMOS current sources and thus this leads to the voltage at X or Y increasing or decreasing until those currents match.

So problem solved right? Here come's my question, why do people and books say that without common-mode feedback, my output will get driven to the Vcc or GND rail if the currents matched? Won't the scenario I just explained happen and our MOSFETs may go into linear region but why would the outputs go to the rails? I don't see where that is coming from. I can understand if there's a huge mismatch that would happen but some mismatch, the voltage should just go up or down at the output, it shouldn't reach the rails.


texts:
In ISE, it is possible to select various "Startup Options" for the generate FPGA image by right-clicking "Generate Programming File", selecting "Process Properties", and then clicking "Startup Options". The listed startup options are:

StartUpClk
DonePipe
DONE_cycle
GTS_cycle
GWE_cycle
DriveDone

This document gives explanations for StartUpClk, DonePipe and DriveDone. What exactly is the DONE_cycle startup option? (And while we're at it, what are GTS_cycle and GWE_cycle?)


texts: 8-bit BINARY for (3) 7-segment display using Shift and Add-3 Method

texts:
We have been told by our professor to create an 8-bit Adder-Subtractor and will display an output in decimal instead of just using LED's in Multisim. We know that in order to do this, we need to actually use (3) 7-segment display in order to have an output of 255 which is the equivalent of 11111111.
Unfortunately, based on some examples found on the internet, most of the available IC's that can be used in order to convert 8-bit into BCD is unavailable in the library of Multisim. So, we come up with a solution to create a custom IC that follows the truth table for Shift and Add-3 algorithm.
Moving on, this is the truth table we've used to recreate an IC for "Add-3"

This is the circuit inside of the IC that we have created in Logisim.
In order to have an output in (3) 7-segment display, we've found a video in youtube that says the easiest way to implement the convertion of binary to decimal is to use the Shift and Add-3 approach.

Of course, we have followed what was shown in his circuit diagram.

And we come up with this circuit that we've made using Logisim (for simulation/testing). However, there are some error that we have encountered during runtime and we're having a difficulty finding it in the circuit. Here are some example.

As you can see here, the leftmost bit which is the 128 has been set to "HIGH" but the output is displaying an incorrect value of 15_. The display should be 128 in decimal as well.

Obviously, the 3rd bit has been set to "HIGH" and the output should be 32

And here it should be 16.
Can anyone help?
Reference:
https://www.youtube.com/watch?v=sdH2lKiuCjg


texts: Standard doping concentrations for Si and GaAs Solar Cell (as well as other standard values)

texts:
I am doing a MATLAB project where I need to plot the current of a Silicon and GaAs Solar Cell under Air Mass 0 and Air Mass 1 conditions. I have used solar irradiance data to calculate their photocurrent density (\$I_L/A\$) and am now attempting to plot their I-V curves using these two formulas:

and

I currently have \$I_L/A\$. But I need to find standard values for A, \$N_c\$, \$N_v\$, \$N_c\$, \$N_d\$, \$D_n\$, \$D_p\$, \$\tau_n\$, and \$\tau_p\$ for GaAs and Si photodiodes.

I have Googled for such specs and it seems no one has a simple example of standard values for these photodiodes so I am wondering if someone here could give me some standard values or refer me to a website that has them.


texts: What kind of connection to use between two circuit boards that move with respect to each other?

texts:
I need to connect two circuit boards - one with a microcontroller, power circuitry, display, etc to another with several sensors on. The connection will require somewhere between 4-10 lines - 5V power, ground, I2C data and clock, possibly plus some interrupts. The circuit boards will be mounted at right angles with respect to each other.

The crucial problem is that the board with the sensors on will need to move constantly with respect to the board with the microcontroller on. The degree of movement will be small - only a few centimetres, and it will be mainly in one axis (perpendicular to the sensor board, parallel to the microcontroller board). The movement will be irregular in nature - the movement will respond to the sensor input. The movement will be driven by a powerful servo, so the speed and acceleration of the movement may be quite jerky / fast.

So what kind of connection can I use between the boards that will be reliable for this kind of movement? I've seen various kinds of flat flex connection used in consumer products. Is that kind of connection reliable over years of many millions of movements every day? What kind of connection would be used in more reliable applications like automotive or aerospace?


texts:
Here is a table which shows the différence between GaN and SiC:

I have no knowledge about physics of components. I have just some bases. In the above table I do not see real difference between SiC and GaN. Nevertheless, it is said that GaN is better than SiC in power electronic field. If it is the case, based on this table, why the properties of the GaN are better than the SiC in the field of power electronics/SMPS?


texts: In Razavi's Design of Analog CMOS Integrated Circuits, how does he manipulate equation 8.5 into 8.6 below?


texts: Electrodes and number of pins in vacuum tubes

texts:
I am confused regarding the terminology 'diodes', 'triodes' etc and the number of pins in these elements. If a diode has a cathode, an anode, and a supplementary anode (the control grid or plate) and each electrode are assigned to a pin in order to receive or give electricity, shouldn't the diode being a triode really, since it must have three pins?

If the current enters from the cathode and exists from both anodes, I'd say this element should have three pins. Why is that it is called a 'diode' instead? -- unless one counts only the number of anodes, that is...

Thank you


texts: What's the right way to read ID and CFI info from flash memory chips?

texts:
Our product has flash memory chip, but we have used more than one variant. The first is a SST/Microchip one and the second is a Spansion/Cypress.

To determine which type is mounted, I read the flash ID and the CFI info from the chip. But this is not working stable.

Read ID:
  write 0x0AAA, 0xAA
  write 0x0554, 0x55
  write 0x0AAA, 0x90

Enter CFI:
  write 0x00AA, 0x98

Before reading the ID, I send a reset (write 0x0AAA, 0xF0 ).

Now the first problem is: for the Cypress chips, I need to send a reset before the 'Enter CFI', otherwise the 'Enter CFI' will fail. But for the SST it's the other way around.

And second problem is that even the 'read ID' will sometimes fail for the Cypress chips.

How can i create a generic and stable solution for this?


texts:
I have a two LVDS Ports (A & B) coming from deserializers connected to a 10.25" TFT display.

lvdsaclkp, lvdsaclkn, lvdsa[0:3]p/n
lvdsbclkp, lvdsbclkn, lvdsb[0:3]p/n

VESA:

JEITA:

What is the difference between these two formats? I understand that the bit pattern in each pixel data is different but each pixel data bunch (odd/even) has 28 bits (7 x 4 = 28). Should it not be a multiple of 8?

How to calculate the data rate in this scenario?

LVDS clock frequency = 45.25MHz


texts: How can I convert an audio PDM bitstream into analog form?

texts:
I have collected PDM bitstreams from MEMS microphones and I'm looking to convert them into analogue form. Does anyone know some practical implementation details on how to do this (beyond a quote from Wikipedia that states this only requires a low pass filter)?
Edit: copied from the comments below
I have some sample PDM bitstreams stored in Excel and I'm looking to convert to amplitude in Matlab.
The row just has an numerical sequence identifier (0, 1, 2, 3, 4, 5, 6 etc...) and then a 0 or 1 for the L and R. For the low pass filtering, how do I pick the design criteria (like the different frequencies)?
The sampling frequency is 4MHz, the max frequency of the sound that can be picked up is 50kHz (mics are being used in an ultrasonic application), PDM bitstreams was captured using digital inputs on a Picoscope oscilloscope. PDM data was not filtered, the raw PDM data from the mics was captured.
Edit: Raw FFT of PDM data:


texts: why my active piezo buzzer doesn't give any signal as an input?

texts:
I wanted to use my active buzzer as a vibration sensor like the knock lock project of the arduino starters and problem is I can't get any output out of it
I expected that that it is because the oscillator associated with the piezo element in the active buzzers but I couldn't figure out why and I couldn't find any topics talking about this issue either so if any one could explain why it's not giving any output on vibrating and a solution around this problem ( if any ) would be appreciated.
Link of the Datasheet:
https://components101.com/sites/default/files/component_datasheet/Buzzer%20Datasheet.pdf


texts: The Relationship of Power and Heat to Length of a Folded Resistor

texts:
This question is a follow-up to a previous question of mine (The Relationship of Power and Heat to Length of a Resistor).

We make heaters in our lab. They are 1.5 inches long and are made using 0.005-inch-diameter (36 AWG) nichrome wire that is folded back-and-forth onto itself five times so that if you were to look at a cross-sectional area of the heater, you would see six wires.

We want to start making some heaters that are twice as long (3 inches) but still have the same heat output per cross-sectional area of heater. In other words, we want to keep the power of these heaters constant for a given point along the heater; since the heaters are twice as long, they should put out a total of twice the heat, but at a given point along the heater, they will be outputting the same heat. The heat output per cross-sectional area of heater should be the same for both heaters.

We currently use a 12-volt battery to power the 1.5-inch heaters (they are in parallel). The resistance of these 1.5-inch heaters is about 23 ohms, and thus the current through each one is about 0.52 amps. These heaters are powered for 3 seconds every 15 minutes so that they provide heat pulses for our sensors.

If I make the 3-inch heaters the same way (i.e., if I fold the same exact nichrome wire 5 times so that a cross section of the heater has 6 wires, but, for these 3-inch heaters, each fold is twice as long), I believe I would have to double the voltage to get the same heat output per cross-sectional area of heater because of the reasons mentioned in my previous post (The Relationship of Power and Heat to Length of a Resistor). The fact that the nichrome wire is folded is throwing me off, though - am I correct in my thinking, or is there something else I'm missing? If I'm missing something, what am I missing, and what is the reasoning behind it? Thank you!


texts: Quality parameters to include in contract with hardware supplier

texts:
my company (not related to electronics at all) is now getting a simple control board for a product designed by a third party. The very same third party will also be in charge of building such control boards, realistically for the lifetime of the product.

Last time such an arrangement was made no quality specifications (MTBF, DOA, maximum acceptable number of returns from clients, ecc ecc) were made and it turned out a mess. Low quality design, 1% DOA and 8% failure rate within first year. Still, since no "quality agreement" was signed beforehand we were unable to get compensated or to obtain the design and get it reviewed/built somewhere else.

What clauses and what defectivity threshold should I include in the contract?


texts: Sound sensor not working when connected to DC motor

texts:
I made a small circuit to control a DC motor with a sound sensor, using an ATtiny 85 and an L293D.

It worked on breadboard, but now that I have a prototype PCB it ceases to work. Whenever I connect the DC motor, my sound sensor reacts as if it was detecting sound non-stop. As soon as there is contact, the sound-sensor LED lights up.

I am not sure where to start. I added 10nF capacitors to the ATtiny and sound sensor, a 10uf Electrolytic and a 100nF to the motor to the battery to reduce electrical noise. I am not sure where to start to debug this.


texts: How to make SMT32 chip programmable while it stuck in Standby mode?

texts:
From my mislead I put HAL_PWR_EnterSTANDBYMode() in the code whithout any wakeup behaviour, which made my chip unable to debug via SWD interface. So I can not either erase, upload new code or do anything with this chip.
I have an Aliexpress ST-Link V2 dongle for programing and debug. I connected the terget to the dongle with the following wires:

3,3V
GND
SWDIO
SWCLK
NRST

I hoped that NRST will hold the target from running my broken code, but it is still not programmable and debuggable (I turned Reset behaviour setting to "Connect under reset").
The second thing I tried is to connect BOOT0 pin to VCC while power up. The problem is that my chip is STM32G030F which has BOOT0 and SWCLK on the same pin (PA14). So I tried to power up while PA14 (BOOT0) was connected to VCC and then - I disconnected PA14 from VCC and connected PA14 (SWCLK) to USB dongle. Same thing: no effect.
What else can I do to wake up my chip from standby mode?


texts: What causes long-term RTD reading drifts?

texts:
I am working with a controller that was designed to read multiple types of inputs including 3 wire RTD signals.

In some cases, we have observed the controller suddenly spike up +15 degrees and sustain that temperature reading for a long period of time; that is, until someone touches the plastic connector plugs inside the controller.

This is the first time I've heard of a long-term error like this, and touching non-conductive plastic connectors doesn't seem like it would effect the RTD circuit.

This only happens at certain locations, so we don't believe it's 100% a circuit design issue, but moreso a noise / wiring issue.

We had many of the original design's input circuitry have our sensor processor IC lose its programming and cease to function. This was due to suspected noise from high-voltage / high-frequency equipment (compressor fans / motors) ran near the controller. We improved the input protection by adding protection diodes and additional ground connections. We also changed the input voltage reference to 4.75 V from 15V, and removed the ferrite from the input reference and removed ferrite from the paths to the signal gnd. The signal ground is a floating ground layer of copper in the controller not connected to the incoming AC Earth connection.

The controller is powered with 120/24 VAC, and has a switching transformer that provides a 4.75 V DC power line to the analog input card for the RTDs. The output of the RTD IC is 4.096V.

The biggest mystery is that the temperature swings out, then never corrects itself. We have many explanations as to why the temperature would swing, but the IC we use has automatic calibration and our firmware should have a filter that compensates for any noise. However, the unit will show a temperature 15-20 degrees high, and won't correct itself until somebody touches their finger to the plastic connector plugs.

Any ideas without diving too much into the circuitry?


texts: I've heard about acid traps and that they are something from the days of yore. But what are they and how are they created?


texts:
I have not understood what the AC load line for a BJT is and while drawing the AC load line for a BJT, the collector emitter voltage VCE and the collector current IC  are related as,
IC = -VCE / (RC // RL)
Where RC is collector resistance and RL is the load resistance.
So, according to this equation, the load line should pass through origin but that does not happen. Why doesn’t it happen?
Thank you.


texts: Connecting 2 identical led RGBW controllers with 12V led strips same length into a 24V Power supply

texts:
Ok, some bad decisions took place and now i am stuck with no money and:

24V 8.33A  power supply with 2 channels.
Magic Home 5V-12V-24V RGBW wifi Controller 192W max (got them from here)
15m of 12V 5050 RGBW Led strips with 5.76W/m. (got them from here)

And now i have to make them my main living room lighting (total space of 5m x 6m ).
I was thinking about connecting the 2 controllers in parallel to each other having exactly the same length of leds attacked to each of them, and controlling them with google home thus, making them open only at the same time, creating a "voltage divider".
Like this:

simulate this circuit – Schematic created using CircuitLab
My question now is:

Is this safe?

Is this the best solution considering i cant afford a big 12V supply?


texts: Data Sheet Inconsistencies with TI LM2672N

texts:
I'm a novice with Electrical Engineering, and am having a difficult time coping with inconsistencies in a particular data sheet.
Texas Instruments LM2672N-5.0 Data Sheet
Like many data sheets, TI provides example circuits for using their chip. However, unlike other data sheets I've seen (so far), it's riddled with inconsistencies, such as capacitor sizes, placement, etc:

Even within the same diagram, there are inconsistencies:

How should one interpret these diagrams and recommended component values?


texts:
I downloaded PSpice 9.1 Student Edition from Electronics Lab (basically the first google result for "PSpice Student Edition"). I am trying to follow some basic circuit tutorials and I get the point where I am trying to add the part "VDC" to add a basic voltage supply....and it's not in my parts list!

I went to the "Add Library..." and added every library that was available, but still no luck.

What gives? How can I include a basic DC voltage source in my circuit?


texts:
I am putting a bank of 5 LED toggles on my boat.  I don't want to have 5 more terminal ends connected to my battery post.  Not sure how I should proceed on this.
Run all 5 wires back and then into one terminal end?
Run one wire up from the battery and then split it?
Thinking of putting in inline fuses on these toggles as well. Doubt that I will need them and they will just control lights and maybe a small pump.  Would it matter if I put the fuse before or after the toggle?
Thank you.


texts: Help with understanding op amp circuit using diodes at the output

texts:
I'm trying to understand this circuit and having trouble figuring out how the diodes will affect it:

I'm trying analyze this and understand how \$V_{\text{out}+}\$ and \$V_{\text{out}-}\$ will be affected by different values of \$V_i\$ but I am unsure. I believe \$V_{\text{out}+}\$ will see a higher voltage with lower \$V_i\$ values and once \$V_{\text{out}+}\$ is past 0.6V the current will go through both of the diodes and \$V_{\text{out}-}\$ will begin to see an increase. I'm unsure of what to think about the op amp in the center though.


texts: My Geiger counter exploded and I don't know why

texts:
For some background, for the past few months I have been trying to collect all the elements on the periodic table. I bought a Geiger counter for the more radioactive elements (specifically the GQ GMC-600 Plus if that helps.)
Anyway, I have been using it for about 3 months and its been awesome, right up until about 20 minutes ago.
I was extracting some Americium from a smoke detector and placing it on the sensor to test how radioactive it was.
I've extracted Americium before, and I did nothing different from what I have done in the past without incident.
Huge bang, ears ringing, drop everything on the ground and run.
That's how loud it was. I thought I accidentally made a nuclear bomb or something (monkey brain turn on when loud noise. Logically I know that 90 microcuries of Americium is not going to "go nuclear" as they say.)
It was only on the sensor for about 5 seconds, and the last reading I saw was it getting to about 700 microsieverts/second. Again, I have done this in the past several times with another equivalent sample of Americium with no negative consequences.
Yeah, so now the Geiger counter is fritzed up. Can't turn on or off well, sticks to one screen and detects nothing. I have no idea what is wrong with it.
It could have been the capacitor blowing up, it could've been the Geiger-Muller tube itself, but I really don't know what I'm looking for. I'm not really an electronics guy, and my heart is still racing. also its 2AM and I need sleep
I have not been able to find a similar story. I just want to know what the heck happened, or even where to start looking.
Edit: After Further Investigation, it was absolutely the Geiger Muller Tube that blew up.
I still have questions.


texts: AVR Serial communication using DB9 Connector

texts:
I was using a PL2303 chip before to perform serial communication with an atmega128. It recently started getting hot and was not being detected by the computer anymore. These chips are not readily available so I was wondering if I can purchase a usb to serial cable and somehow use that to do serial communication. I spotted a serial to usb cable that even uses the PL2303 converted.

Any help is appreciated.


texts:
Hi I'm using the MM5451 led driver chip to source current for my led matrix. Am told that the chip has open drain outputs. To source current from the chip do I just connect the anode of my led to the output then connect the cathode to my circuit gnd? Also am unsure how it limits the current going to each led? The datasheet says 40ma is the absolute max for each output.

http://www.micrel.com/_PDF/mm5450.pdf


texts: Capacitive Coupling Between Adjacent Conductors

texts:
I have been unable to find a definitive answer to my questions after some extensive browsing online.
My question involves the coupling between two adjacent conductors (wires, PCB traces, etc) due to the electric field between the two.
Now, from some basic tests on an oscilloscope and function generator I can clearly see that an AC waveform radiated from one antenna wire is picked up an appears as noise on the adjacent wire. The noise level is such that the amplitude increases in proportion to the proximity to the antenna.

It was my understanding that this coupling would occur also with DC current as the "antenna" wire would emit a static electric field which would produce a "static equilibrium" in the receiver wire (with an albeit small current).

I guess the my fundamental question concerns why time varying E field couples voltage in nearby conductors by a static field does not.
Am I right in my assumption that the charges within the receiver conductors will redistribute (similar to the Skin Effect) in that charges will orient themselves to oppose the incoming field in a static E field?
Apologies for the simplistic nature of this question, however many online resources only provide an analogous explanation to that of capacitors.

If someone could provide a better physical explanation in regards to the results I am experiencing, it would be much appreciated.


texts:
I've two short questions regarding circuits with a transistors or diodes:

1) The following circuit with two diodes: Does it produce an electrical short for B=1 (5V) and for B=0 there is V[out]=1? Is this correct?

2) Does the following transistor circuit represent a logical NOR (all resistors are equal)?

Thanks in advance!


texts: My multimeter is rated for 600V but I need to measure a 10kV AC source. I was thinking of building a voltage divider but I wouldn't know how many resistors it would take to safely measure this high of voltage.


texts: Is this pulse transformer in saturation?

texts:
I have the following schematic:

RB3 is connected to PIC microcontroller digital output.
I am wondering is it possible to know from the output voltage waveform is this pulse transformer in saturation.

2V/div - 500us/div

Blue signal is from the PIC and the purple one is output from one of the pulse transformer's secondary windings.
On the first image, the PIC's signal is 50us wide. On the second image, PIC's signal is 500us wide and it can be seen that the pulse transformer stopped responding to the voltage on primary coil.

Are these images enough to say that this pulse transformer is in saturation?
Unfortunately I don't have any datasheet for transformer, it's very old and manufactured by VAC.


texts:
I have designed a small MCU circuit which is to be supplied by a 3.3V DC supply.

Since this is a small subcircuit which will be mounted upon other PCB's, I need to consider ESD (at least on the power supply).

The circuit input power pin is connected to a PI filter, two capacitors and a ferrit bead, mainly to suppress noise, but will this be sufficient to protect against ESD?

I have been looking at different TVS diodes and application notes, but they all seem not to mention power lines, is this because the capacitance on power net is normally enough to shunt any ESD?


texts: What is the ALS and BLS pin for on the ISL83204A full-bridge driver chip?

texts:
The datasheet for the ISL83204A full-bridge driver chip documents "low sense" pins that connect to the source of the bottom N-channel MOSFETs. As those are typically connected to ground, what is the function of these pins?

The data sheet does not mention these pins, except briefly as follows:
Absolute max: +/- 2V compared to GND.
Normal operation: +/- 1V compared to GND.

There's a diagram that shows "optional" resistors below the ALS and BLS pins, which look like current sense resistors, but there's no mention of whether this chip has current sense, over-current shut-off, or anything like that.


texts: What would "push to open" mean in the context of this switch?

texts:
I'm not an electrician, but I have a basic understanding of circuits

I had bought a switch that was labeled NC, and when it was unpressed, the light connected to the switch turned on

When it was pressed, it turned off the light

I'm looking at this product right now
https://edwards-signals.com/index.cfm?pid=69&level=48

and it says "push to open" and "push to close"

does "push to open" mean the same as NC?

Logically it seems to make sense that way, but the different terminology is tripping me up, and I just wanted to confirm before making a large purchase


texts: MOSFET voltage beyond Vgs(th), but lower than Vgs max absolute rating

texts:
I am a little confused about the Vgs(th) for example if I use a value a little greater than the specification about the Vgs(th) not the max rating

for example I am using a P-Channel MOSFET if I apply 3.3V on the gate it will open the circuit? or does nothing because it value is greater than the VGS(th) -0.45 to -1.5

what is the difference between SQJ411EP  and this SUB75P03-07 talking in Vgs(th) in case I want to use them as switch

My specs are:

Vcc 5V

Vgs 3.7v

I am driving a 4A load

Thanks


texts: All opamps have off set voltage at the output. Does this mean that it is never ok to cascade op amp stages?

texts:
In several places I have seen that sallen key low filter stages are cascaded together to create multiple order filters. Each opamp connects to the next via resistors. This means that DC voltage is simply passed to the next stage. Shouldn't this be impossible since op amps have offset voltage and this will lead to errors in subsequent stages?

Putting in a capacitor does not seem reasonable since for a low pass filter.


texts:
I am new to signal analysis and I need to remove noise from an accelerometer recording. 2 accelerometers are mounted a machine and recorded vibrations at 500 Hz. The aim is use vibrations to differentiate working situations, we expect increased vibrations on certain situations.

The figure below shows recording for one channel.

Machine started to work at 250 s and stopped at around 3100 s, the recordings before and after shows noise from other sources. These noise sources are also exists during the machine's working time. Figure below shows  fft for noise and signal+noise.

What I need to do is remove the noise from recordings. What kind of filter should I use?


texts: What effect does the drain resistance have on the output voltage of the logic gate?

texts: The logic gate is meant to be a NOR gate, but how does changing the value of \$R_{D}\$ affect the output voltage? Doesn't increasing the value of RD always make Vout lower because of voltage division. The only  exception I can think of is if both MOSFET are in cutoff and there is no current. I would appreciate it if someone could verify the relationship.


texts:
I'm designing a Zilog Z80A-based computer for fun and profit, limiting myself with what components were available around year 1984+/-3, and trying to get the lowest possible cost that could be achieved at this time.

For the arbitration of video RAM access, I plan either to add some wait state to the CPU (same as was done on the Amstrad CPC) or make a bus request when the beam is in the visible part of a scan line (I will use a Motorola 6845). But I'm not happy with either solution, and would prefer to keep most of the RAM for the applications.

My question is: can I put the VRAM completely outside the Z80 address space and access it with I/O (with a port to set the foreground/background pair and the cursor position registers, the latter position increasing automatically with each character sent on the output port)? Can it be done with what gate arrays were available at the time? I want to avoid using a dedicated video chip like the MOS VIC-II.

For the non-adressable RAM (>64K), I'd also like to access it with I/O port, with one port selecting the address, and another to read or write, the address register increasing with each IN or OUT.

Same question: can it be done without using a dedicated controler or MMU?


texts:
I have built the circuit in the diagram below with a couple of minor changes. I desire 3 DC outputs - +12, -12, and +5 volts. So, the changes I made is to use an MC7812BTG for the +12 and an MC7912BTG for the -12. Then I simply added an LM7805CT after the 7812 to get my +5. I made 2 heatsinks from a couple of L brackets I had laying around. I also added LEDs to the 3 "rails" so that I could verify they are operating. Everything else is the same as the diagram.

This is for a very small modular synthesizer case. I tested the power supply with no load and it checked out fine. Then I installed 4 modules with approximately 350 mA draw on +12 and 100 mA on -12. The +5 volt rail was not used at all. I powered the case on and it all worked as expected for about 35 or 40 minutes. Then the modules glitched and the audio "froze". These are digital modules. Anyway, turning the power switch off and back on restored the function of the synth, but just a couple minutes later it glitched again. That's when I realized how hot the case was underneath where the voltage regulators are at.

My main questions are:

Am I pushing the regulators too hard by supplying 25 volts and dropping it to 12? Should I consider a 24V transformer?
What would a "proper" heat sink consist of for these regulators? Is my "L" bracket piece of metal (3/4" wide, 1/8" thick, and 4" long, bent to L shape at center) just not enough of a heatsink?
If the 7812 is overheating, what is occurring to make the modules "glitch"? (overvoltage, undervoltage, etc.)?

Thanks in advance for any advice, comments, or stern reprimands.


texts: Maximum error expected as a percentage of full scale

texts:
I was given an exponential transfer function and told to approximate it as a straight line connecting the end-points and find maximum error expected as a percentage of full scale.

Finding the approximation was easy enough.  Now I have no idea what maximum error expected as a percentage of full scale means.  I found one equation that I think might work:

$$e = \frac{\Delta t}{t_{max} - t_{min}} $$

But I don't know what \$\Delta t\$ is or how to find it.


texts:
I have built numerous 555 circuits over the years. I recently had to built a Monostable 555 cct. as per this site :  http://www.allaboutcircuits.com/vol_6/chpt_8/4.html

The cct. is used in a motor vehicle. When the remote control is pushed to open the doors, it sends positive 12V to this Monostable cct. to initiate it and a 3 Amp Power Transistor pulses the siren momentarily to indicatse "unlocking" by audible means.

The issue I have is that Rt and Ct used to time the output pulse is not short enough. I replaced these components to the smallest values I could get, but the output is still "too long". Teh siren makes a "chooow" sound instead of "chow". Sounmds too unprofessional or after-market.

Any ideas to get a short pulse (nearly a few micro seconds) out of this old 555 cct. ?


texts: Is there such thing as a Bipolar Wall-wart?

texts:
Looking for a UL approved device that gives +9V and -9V from the 120VAC wall.
I need the +/-9V to power a circuit and I don't want to make an extra PCB.
My alternative is to have two 9V wall warts but who wants to plug things in twice? What happens when the end user loses one of the chargers?
EDIT: where can I buy one? I need to pull at least 2A from either side


texts: Eagle configure autorouter to solder components (except vias) only on bottom layer of double sided PCB

texts:
In double sided PCBs it is difficult to solder through hole components like IC bases, headers, etc. in the top layer. Normally the Eagle autorouter places the solder pads on both sides. That is, in a through-hole IC base some pins should be soldered in the bottom layer and some in the top layer. But I need routes in the top layer and vias.

Is there a way in the Eagle autorouter to tell it to avoid soldering in top layer? Please see the "Design requirements for hobby boards" and "Turned-pin IC sockets" sections of Joe's Hobby Electronics: Making double-sided PCBs for more information about the problem.


texts: What's an idiomatic way to detect posedges inside a FSM in Verilog?

texts:
I'm getting started with Verilog, using FSM patterns. I'm finding that something I keep needing to do is to wait in a particular state until I see a leading edge of a  (much slower) signal.

What I always end up doing is something like this:

module (... syncsignal input ...)
reg oldsyncsignal;

case (state)
  STATE_WAIT:
  begin
    if (syncsignal && !oldsyncsignal)
    begin
      state <= STATE_CONTINUE;
    end
    oldsyncsignal <= syncsignal;
  end
end

I'm becoming less and less convinced this is a good idea, partly due to various edge cases (what happens if syncsignal goes high when I'm not in STATE_WAIT?), and partly because I haven't seen anything like it in other code I've seen.

This must be a requirement which comes up a lot. What's the standard way to do this?

I'm using the Warp dialect of Verilog for the Cypress PSoC devices.


texts:
I need to detect small high and low peaks in the battery voltage while in use. The goal is to help estimating the end of the battery charge by its change in impedance, since my circuit uses the battery in predictable cycles of high/low consumption. It's a long term li-ion battery charge (weeks usage) so other methods are unavailable or very very expensive.

So, my idea is to use a variation of the sample & hold peak detector circuit but my reset would use a FET to short the hold capacitor to vbat instead of discharging the capacitor to ground. That would help reducing battery consumption at sample resets since the capacitor only needs a small voltage jump to reset. The largest good capacitor I could find at a reasonable price is 4.7µF.

I will be taking measurements every ten seconds, so my sample and hold circuit must be very low leakage (<3mV/10s would be ideal). The thing is, if I use a MOSFET to reset the capacitor, I'm affraid its body diode's leakage could be of concern, slowly discharging the capacitor in the "sample" phase, thus altering the measurement. Unfortunately, none of the MOSFET datasheets I've read characterize the body diode's leakage, much less over the temperature range (I need 50~60°C).

So, what kind of FET is there that I could drive with 3.3V logic have no body diode, or has a documented reverse leakage below 1µA@60°C when in off state (any direction). Vbat would be in the 5~9V range.


texts: What is the best way to power a 90v DC motor?

texts: I have a 90v 22amp electric motor, I want to use it to make an electric scooter, what is the best solution for a power supply. I've looked at using an inverter, but I then get insufficient amperage. I would like the battery to be as small as possible, but this is rather difficult because of the high power needs of the motor. Any ideas or suggestions would be much appreciated.


texts: How to make a SPDT switch without a switch itself

texts:
So I would like a SPDT switch to use on my PCB, but I encounter two problems.

I need to be able to run 30A DC through the switch.
I do not want to take alot of space, (i found 15A switch, but using two takes WAYYY too much space)

Something I considered is using a  dip switch to control a power MOSFET for over 30A, however I realize that is only SPST not SPDT. Does anyone have suggestions?
This is a circuit on a Printed circuit board. My goal is to be able to Run 30 Amps from the board, through to either a current sensor or a relay (in series with the current sensor). Prety much I always want the circuit to be current sensed, however I don't want the circuit to always pass by the relay. I want to manually control if the current passes through the relay or directly to the current sensor.
Incase of confusion - I do not want to know how to control a relay. I want advice on building a circuit that switches between two different outputs, with one solo input (the 30A trace)


texts: how to control brushless dc servo motor?

texts:
I have one of this motor and would like to make a controller for it ( just a speed controller with regulator that change speed from zero to maximum. ). I know micro controller and embedded system, but have no idea about power electronics part.

The technical literature does not say much about it. any help regarding how to run it will be good.

I have model no: QB01700 A00. ( 24 Volt , Peak Current 36 A )


texts: Running a "cheap" DC motor in low stable RPM?

texts:
There is a cheap brushed DC motor type that is often used in toys:

Usually these are 3.3V with a no-load RPM over 10k. The advantage is that are very cheap. Under $1 at 1pcs. I am wondering if using any kind of "smart" control scheme it would be possible to control them so they'll spin at 10 RPM or less. Large torque not required.


texts: Eagle: Circular area under component colliding with traces

texts:
I am creating a PCB layout in Eagle and I noticed that when I add in the ground plane, there are two unfilled circular areas under the usb mini type B socket.  Does that area need to be empty?

I have some traces going under the USB socket, is it okay if I leave them there?


texts: 8086 µProcessor | Proteus Simulation | 7 Segment & Stepper Motor

texts: I am trying to silmulate the 7segment& stepper motor with 8086mp using proteus.Program compled succesfully but when iam running it schematic capture iam getting an error called  program load address is beyond the internal memory range which i couldn't understood.Kindly waiting for a quick answer.


texts: Best Hardware for Accurate Point Tracking System

texts:
Here is what I am trying to accomplish:

In the middle of a room, I have a mechanism with a laser diode mounted on it that can be moved in all axis by a motorized pan/tilt head type device. This mechanism is to stay fixed in the middle of the room at all times.

Now say that I have a phone for example. I want to be able to walk around the entire room all whilst having the laser pointer constantly following and aiming at the phone with as much accuracy as possible.

Which hardware, if any, should I use in this circumstance to help accomplish this? I can mount anything needed on both the tracking device (laser) and device being tracked (phone).

This is my first time working on a tracking system of any type. I have attempted a fair amount of research on the topic, but I am still left in a haze. Mostly everything I find has to deal with a camera tracking/following a point, but I would like to avoid this method if possible.

If more info is needed, let me know.


texts:
Consider the following

The voltage Vin is on the top plates of all capacitors. The top half capacitors are charged to a voltage of Vin-Vref and the bottom half capacitors are charged to a voltage of Vin.

Next, we switch the circuit to the following:

The 2C capacitor on the top-half side now has GND on it's bottom plate and Vin has been removed from the common node.

The question is "What is the voltage on node Vdac?" now

My answer:
After switching the circuit to the second state, the top plate of the 2C capacitor on top side now must go to Vin-Vref so as to maintain the same charge on it. If this capacitor top plate has Vin-Vref on it and all the other capacitors still have Vin on their top plates, then charge redistribution must occur.

My confusion is regarding the ratio of the charge redistribution. I'm trying to draw the capacitive divider but I'm having trouble now:


texts: Radically different behavior between ceramic and electrolytic capacitors in electret microphone circuit

texts:
I've been trying to set up a microphone circuit for use in an AVR, essentially just to detect levels of noise. I observed some strange behavior in the amplified circuit I set up, so i elected to strip the circuit down to its base functional unit to see if I could figure out what the problem was. Schematic follows.

simulate this circuit – Schematic created using CircuitLab

The resources that I've used to build this circuit all seem to indicate that the type of cap used doesn't matter, so I opted for the higher-capacitance electrolytic. This did not behave as expected.

The following is a waveform captured from the circuit using an electrolytic cap.

Now, the ceramic cap:

To be clear, these waveforms are captured while the room is quiet. blowing into the microphone produces a response.

The ceramic capacitors I have do not dampen the 60Hz noise to my liking, and it seems silly to wire a bunch of them in parallel when I have a few much larger electrolytic caps.

I've tried a few different sizes of electrolytic caps, with the same result.

I've tried reversing the polarity, with the same result.

Why am I seeing this discrepancy? How can I remedy the situation?

Additionally and secondarily, is there an established best practice for using a microphone with AVR?

EDIT turns out i'm seeing this effect because my cheap chinese power supply has a poor rectifier :^)


texts: I'm having issue getting thick tin-lead 63/37 solder on Alloy 42 lead frame

texts:
I'm using Kester 2235 flux and using robotic solder dip so heights are static.
I'm measuring thicknesses using x-ray fluorescence, they keep coming up very low.
Should I be using an initial scavenge pot?

What temperatures work best for getting greater solder thickness?

I've tried turning my preheater temperatures down, my solder temperatures tried between (230 - 250°C).
I've tried turning my immersion time in the solder down to 1 second.
The part has four sides, so it is turned and dipped, and then turned until each side has been dipped.

I'm fluxing -> preheating -> dipping.

What are methods I can use to increase solder thickness?


texts: I have sketched my integrated circuit for an RFID tag. How do I make it to a real physical product?

texts: I'm in a situation where I want to create a real prototype of an RFID tag. I have sketched all the IC in a paper. I got a problem, I want to build this to a real size RFID tag and we want to create the IC ourself if it is possible. I know a little about the process of creating a real physical product. So could someone experienced in this field help me with the next steps for creating a real physical product. What kind of equipments is needed for creating an IC?


texts: Designing a PCB with multiple supply voltages

texts: I'm in a process of designing a 2 layer PCB for my device. The device is a master control board, and there will be 10 daughter boards. Various peripherals and things will be connected there: I need 3V3 for all my STM32 micros, 12V for the MOSFET drivers, 5V for the relays, and also there will be another voltage from a programmable bench PSU. All of these voltages will have common grounds, except for the 5V for the relays, which are optocoupled. What is the best strategy when routing my PCB? Should I just place a big ground plane on the bottom and connect everything? Or perhaps a star topology?


texts:
I've got a 12V power adaptor (3.8A). And it got two fuses in it (T3.15AL250V, 3AL250V, one of which (3.15A) has blown, along with mosfet, current sense resistor, 450V cap, and IC. I replaced all failed parts, except the fuse (soldered jumper, since I don't have 3.15A fuse for now).

What is the point of two fuses in series? I've never seen anything like this before.


texts: How do I calculate current usage from two sets of 5050 LED lights of varying lengths?

texts:
I have a 10 metre set of 12VDC "5050" LED lights (RGB). The manufacturer/distributor (from eBay) quote these LEDs as being 10.8W per metre (108 W for 10 metres). But they also quote (on their eBay advert) 1.2A for 5 metres (2.4A for 10 metres).

I currently have a 6A power supply driving these lights without any problems.

I'm confused because I thought Power = Current x Voltage - so the current should be 9A (not 2.4A?).

I'm guessing that the LEDs draw a lot less than advertised anyway as I have them on 'fade effect' so they just fade between solid colours (i.e. at most two of the RGB LEDs on at one time).

I want to connect another 5 metre set of lights to my installation. I've read that, due to current consumption, it's best to connect these in parallel.

However, I'm not sure how to calculate the power/current consumption in order to work out whether I will need to upgrade my PSU?

Also, I'm worried that due to the different resistances of the two strips (one 5 mtrs and one 10 mtrs), one will be significantly brighter than the other or it will cause other problems?

Could you shed any light :) on this please?


texts: If multiple SPI slaves exist with different SPI modes, is it sufficient to have separate CS lines for each?

texts:
SPI allows multiple slaves to be connected together in two ways. One is Multiple-Slave-Select Configuration and the other is Daisy-Chain Configuration. Since the different slaves may be entirely different devices, I think that Daisy-Chain Configuration is not usually possible.

Is it always possible to use a Multiple-Slave-Select Configuration when we wish to connect multiple masters to a single master SPI? Uptill now I have come across scenario where the logic levels (atleast output) of a slave may not be compatible or a slave may not have tristated output when CS is not asserted (which I find strange). Are there any other problems too?


texts: Conventional current in a power amplifier?

texts:
I recently learned that electricity doesn't actually flow from + to - but the other way around..

So my question would be: if I was using a 2 channel power amp and connected a speaker to it with the positive wire on the left channel (+) and the negative on the right channel (-) would I get the output of the left channel or the right channel?

I thought the (-) terminal on an amp was just to take the signal and ground it.


texts: How does a capacitor affect the flow of the current?

texts:
I understand that the capacitor is like a secondary DC source when it's almost fully charged. What I don't understand is the way it behaves in a circuit.

It discharges itself when it's full or when it is the only DC source in a closed circuit?

Consider this slow-speed oscillation example:-

The Programmable Unijunction Transistor (PUT) and the capacitor are connected in parallel, thereby the voltage is the same for both of them. But I don't see why the PUT depends on the capacitor. Even if the capacitor acquired the entire current till it gets full, wouldn't the electrons go from the DC to the PUT directly?


texts: LM317 TO-220 heat sinking: Junction to case or junction to pad?

texts:
I have some LM317 ICs (TO-220) that I'm using on a power supply. I'm trying to figure out the heat sink values necessary to keep the IC under safe operation.

All of my requirements are with 700 mA current, however Vi-Vo varies. For an example, the maximum Vi-Vo I have is 12 V. So the power dissipated is 8.4 W.

So I got the following thermal resistance values from the data sheet:

  Junction to ambient: 19 ℃\W
  Junction to case: 17 ℃\W
  Junction to pad: 3 ℃\W

I'm using a thermal tape to fasten it to a heatsink. I can do the calculations myself, but my problem is that I'm confused if I should consider the junction to case or junction to pad thermal resistance value? The junction to case resistance seems too high. If I use that for heatsinking calculations, I find that no heatsink can save me from overheating it. But junction to pad gives me hope.

Which one of the following is correct?

Junction temperature = Ambient temperature + Pd * (Junction to case + thermal interface material + heatsink thermal resistance)
Junction temperature = Ambient temperature + Pd * (Junction to pad + thermal interface material + heatsink thermal resistance)**

I'd like to avoid swithcing regulators as much as possible, I already have these ICs and switching regulators will add unwanted complexity here.


texts:
I encounter problems with my UART receiver module. It is supposed to work at 9600 bauds without parity bit and only one stop bit.

The problem is that my UART misses some characters (or to indicate that it received some characters) in a non-deterministic way.

My two main but unsucessful ideas about this problem were

1) a problem with the reception with the clock at 9600Hz, it is maybe not accurate enough or I don't have any error margin. I tried oversampling but it did not solve the problem.

2) A problem with the acknowledge coming from the outside (CPU). I use a little trick with a DFF to let the CPU acknowledge correctly his reading while having a much higher clock that the receiver (50MHz vs 9600Hz).

I am perfectly sure that my clock is at 9600Hz (I am able to receive correctly a lot of characters).

Here is the small code of the receiver I use.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity UART_Receive is
    port(
        clk_9600Hz   : in std_logic;
        reset_n      : in  std_logic;
        ackNewData   : in  std_logic;
        ready        : out std_logic;
        dataToRead   : out std_logic_vector(7 downto 0);
        Rx           : in  std_logic
    );
end entity UART_Receive;

architecture RTL of UART_Receive is
    signal counter     : unsigned(3 downto 0);
    signal buffer_read : std_logic_vector(7 downto 0);
    signal lastData    : std_logic_vector(7 downto 0);
    signal newDataReady: std_logic;
begin
    dataToRead <= lastData;

    process(ackNewData, newDataReady)
    begin
        if(ackNewData = '1') then
            ready <= '0';
        elsif(rising_edge(newDataReady)) then
            ready <= '1';
        end if;
    end process;

    process(clk_9600Hz, reset_n) is
    begin
        if reset_n = '0' then
            lastData    <= (others => '0');
            counter     <= (others => '0');
            buffer_read <= (others => '0');

        elsif rising_edge(clk_9600Hz) then
            if counter = 0 and Rx = '0' then
                counter <= counter + 1;
            elsif counter = 9 then
                counter  <= (others => '0');
                lastData <= buffer_read;
                newDataReady <= '1';
            elsif counter /= 0 then
                buffer_read <= Rx & buffer_read(7 downto 1);
                counter     <= counter + 1;
            end if;

        end if;
    end process reg_slow_process;

end architecture RTL


texts: 7.2VDC and 6VDC power supply from 12V transformer

texts:
I have a Arduino MEGA2560 clone, 5pcs of standard size servo motor (model MG996R) and 2 pcs of micro sized servo motors (model 9G), which I have to supply with DC power. And because the micro Servo 9G can use only 6V and the Arduino and standard Servos can use 7.2V, I'm quite confused about power supply of the whole board.

Here's the table of operating voltages:

Arduino mega2560 (recommended): 7-12VDC

Arduino mega2560 (limited): 6-20VDC

Servo MG996R: 4.8-7.2VDC (current at 6V: 0.5-0.9mA, stall: 2.5A)

Micro Servo 9G: 4.8-6VDC (current at 6V: 0.25A, stall: 0.96A)

I already have 4 new toroid transformers, which I attempt to use in this project, but still don't know what schematic should I use. I have:

2pcs primary: 230V secondary: 12V [S=30VA]

and

2pcs primary: 230V secondary: 11.8V [S=50VA]

The whole thing got stuck for me, because I don't know what schematic should I use to transform 12VAC or 11.8VAC to 7.2VDC AND is there a possibility to make from 1 toroid transformer 7.2V and 6V? If so, what schematic would be proper for this?

And in case if anything helps, I do have exact this DC-DC modul, which I can use at this project.

Would be really gratefull to whoever would help.


texts: How to get 6V DC motor running using PWM through STM board

texts:
First image is edit of image 2.
Use this circuit to build unidirectional motor control using PWM.

Ignore 3v pin, MOSFET can be any mosfet having small threshold gate-source voltage eg, 30N06, Fairchild TO52-AA.
These MOSFETS are very small, it will be not easy to connect it to bread board. Everything after the first image are questions.

simulate this circuit – Schematic created using CircuitLab

I have taken help from previous posts to redraw the circuit, but the 6v motor is not driving at all.
However, instead of connecting PD12 pin, if I connect 5v pin from STM board , motor rotates good without PWM.
MOSFET Gate is connected to PWM signal, Drain is connected to motor and Source to Ground.
Frequency used in STM board for the pin is 10kHZ.

Details of mosfet used is here.

Also, there is an onboard LED connected to pd12 pin in stm32f407 board, it blinks as written in the code, this shows that PWM signal is working fine.

What changes should be done so that motor can be controlled unidirectionally using only the software code written for board? what is wrong here.
Is the signal of 10-20mA from microcontroller not enough for MOSFET to amplify it?

Confused.