texts:
I'm trying to design a motion sensor alarm. If there is movement in my house, the motion sensor will send out a signal which will be connected to an alarm that will make a loud noise. I'm currently trying to pick the right motion sensor(ZRE200GE) and I found this https://http://www.zilog.com/docs/PS0336.pdf.
The output signal is described as Measurement Amp.: Non-inverted type, gain 72.5 dB at 1 Hz, 0.4 to 2.7 Hz／-3 dB
I'm really not familiar with DB stuff. But a google search showed me that 72.5db is equivalent to 4216.96 Voltage ratio which is something I'm very skeptical about (Too high of a gain). Is this conversion correct? Here is the recommended circuit from the sensor datasheet:

Here's what I have so far. My gain is 2 which should give an output voltage of 10V if I power the sensor by 5V, and my cutoff frequency is 1Hz. Here V1 is the sensor that outputs 5V like a sensor. Is there any fault in my design?

Note: This design is based on the assumption that when there is movement, the sensor turns on the FET which will connect the Drain and Source, hence opamp would also get 5V(roughly, of course, ignoring voltage drop across FET).
Digikey Link


texts: Calculate R+ RC to stretch pulse from hall effect output

texts:
I have a Optek OH090U hall-effect.

I am trying to stretch a pulsed output by adding an RC circuit. Basically I want the output to be on (low) as long as there is a pulsing of the magnetic field and high when not pulsing. The present value for my pull up resistor is 960 ohms (24V/25mA = 960). Which provides the wave shown. My magnetic pulse a 70/30 duty cycle at 10Hz (65ms high, 35ms low). The output is normally high. With no magnetic field (stopped), the output transistor is OFF = +24V (pulled up by pull up resistor). Specs on downstream device's input: Input voltage 4.25-26.4 V Input resistance 5.4 kΩ

I would like to add a parallel RC in series with the pull up as follows:

Question: How to calculate R2 & C2 to stretch the 65ms pulse?
Thanks in advance!


texts: Would a parallel EEPROM ever output a value that it does not contain?

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I understand that when the address input to a parallel EEPROM changes from A to B, the output may show results that aren't the contents of either A or B, for a few nanoseconds.

Are these spurious outputs constrained to be values stored somewhere in the EEPROM?

Would an unprogrammed EEPROM (all 0xFFs) ever output non-FF values when the address changes?

(I expect the specs say that any value could be output, but I'm interested in what happens with current implementation technology.)

I'm asking because I have two EEPROM bits which will cause a bus conflict if they are ever both 0.  There will be no value stored at any address in the eeprom which has both bits as 0.


texts: Is this SSR a good choice for switching 16V AC/~8mA with an Arduino?

texts:
I'm quite new to actual physical "engineering" and I am just getting started.
My current project is to build a light switch, which triggers my room light via wifi.
I have two cables in my wall (like this) which - when connected - trigger a relais in my flats fuse box which switches the light. The two wires run on ~16V, and when connected have a short spike of current of about 4-8mA. This spike lasts for about a second and drops to 0 afterwards.
So my plan is to use this SSR with an ESP-01 3.3V (which has a maximum current of 12mA per pin, so that should be enough), wire up the two cables and the esp-01 with the SSR and let the ssr switch the light.
So a few questions:

Is there something obvious I missed? I'm still a beginner and trying to make sense of all these information, so there might be something I missed.

If I read the datasheet right, I need 10mA@6V to trigger the SSR, is that right? How can I map this to 3.3V? And what does RL under conditions @ minimum trigger conditions mean? Is this a resistance I put before the Pin?

Concerning the Pin-layout of the module: I guess the pins 1,3 & 4 are the ground pins for my ESP-01, a load on pin 2 triggers the optocoppler. I'm not quite sure about the pins on the AC side. What are the Pins T1, T2 and Gate for?
Thanks in advance for your help!


texts: I want to characterize the frequency inaccuracy of several silicon oscillators over temperature to see which one will work best in my end application.  If I populate the oscillator on a bare-board and solder a coaxial pig-tail to the trace/GND will that suffice?  Since the oscillator is designed to drive a high-impedance IC clock input, will it be able to drive the low (50Ω) impedance of the spectrum analyzer?  Do I need to add some special matching, DC-block, or bypass network?  I'd like to introduce the least amount of extra components possible as I'll have to take them into account in my measurements as well.


texts: Arc voltage on the relay's contacts when load is off

texts:
The contacts of the relay (not the coil of the relay) are connected in series with water boiler (2kW) and AC power socket (220V, 50Hz). Suddenly, relay stops its operation due to the electric arc which continuously appeared at commutation of high power electrical device.

The question is following. What is approximate voltage (EMF), which appears on the commutation contacts of the relay?

Additionally, the datasheet for the relay may be found here.

P.S. My colleague tells me that wire has no inductance, but I am not agree. The wire is of 5m length, so the approximate inductance is equal to L=8444nH, then U=L*dI/dt. dI and dt are unknown and I cannot even imagine approximate values.

P.S. If someone took the measurement for such kind of situation using oscilloscope, please share your results!


texts: Recommendation for RF simulation software that can do animations of wave motion through the model

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I am trying to get an intuitive visual spacial understanding of the behaviour of RF electromagnetism though different shapes and materials.
Being able to visualise the wave motion is really helpful. I learnt a lot form this simple 2D wave tank applet It is possible use it to get an understanding of various antenna types.
I would now like to learn about how microwave frequencies propagate through microstrip, distributed element filters and patch antennas. Is there software that can animate wave motion though these kind of models? My boss has Ansys which can probably do this, but it seems like the set up time using Ansys for a simple model is long and complicated. Perhaps there is something in between the complexity of the wave tank applet and Ansys that will do what I want.


texts: Can an Induction motor be called a BLDC motor if operated from a DC supply?

texts:
A BLDC motor is a Permanent Magnet Synchronous Motor which is powered by a DC supply via an inverter stage. Since the motor is externally commutated by the inverter and the supply is DC, it is called "brushless DC".

If the same scheme is applied to an Induction Motor, i.e An induction motor powered by a DC source via an inverter stage, will it be called a BLDC motor?

If yes, then why do BLDC like computer cooling fans and bicycle hub motors use Permanent Magnet Synchronous Motors instead of Induction? Permanent magnets are expensive and degrade over time. Wouldn't Induction motor be more economical in the case?


texts: General question about memory addresses with underscore

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total noob here.

Upgraded to a pi 4 recently, checking the BCM2711 ARM Peripherals manual I noticed the memory addresses have an underscore, for example, the physical main address is: 0x4_7C00_0000 to 0x4_7FFF_FFF. When programing for c / asm,  is it safe to use these as "0x47C000000" or do you have to use "0x4_7C00_0000"?

Thanks for your time.


texts: Guard Band Reduction in 5G compared to 4G

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Why is there less guard band required for 5G as compared to 4G .For 4G guard band are defined to be 10% of bandwidth on each side while guard band for 5G are defined in 3GPP 38.101-2. For ex If we take 15 KHz SCS and 10 MHz bandwidth guard band for 4G would be \$10MHz*0.1*2 = 2MHz\$ while for 5G it would be \$312.5kHz*2=0.625MHz\$ which is a drastic improvement.
(i) Why was 10% of bandwidth was chosen as guard band for 4G?
(ii)How has it been reduced in 5G?


texts: Why is the Triode operating region of a MOSFET named such?

texts: If triodes were used for amplifiers, why is the triode region generally used for digital and the saturation region generally used for analog? Am I missing a fundamental understanding of the MOSFET's characteristics?


texts: What is sample rate of DSO and what if we have a DSO with low value for sample rate?

texts: I bought a USB DSO and its sample rate is only 48MS/Sec. I never had any problems measuring normal signals from a function generator and other circuits. I have seen many DSOs with high sample rate upto 1GS/Sec. What makes those different from mine and can anyone describe when my scope will get stuck due to low sample rate?


texts:
The circuit I'm designing uses external capacitor to measure its ESR. I use MSP430 as a controller, capacitance of the external capacitor can vary between 100n and 10uF. The problem is I should somehow detect the moment when someone installs the external capacitor, so the MSP would turn off the sleep mode and start measuring.
It came to my mind that I can use a comparator for that. For ex, to power the external capacitor with DC (from DAC) and to detect voltage raise, but isn't the rise too small to detect? I got 500uV while modelling.
I heard there are some special connectors that are able to detect installation and switch the internal relay, but i wasn't able to find ones.


texts:
Im trying to build an electric wheelchair with mecanum wheels, and as you might know, each of its 4 wheels has to be independently powered for the chair to have holonomic motion.

With my desired speed to be around (brisk) walking speed only, say 1.15 m/s, and my mecanum wheels sized with a 4-inch radius, I know that I'm going to need a very low RPM (by my computations, ~110 rpm).

However, my computed power draw per wheel is around 300W, which is way large, that Im not sure if Im on the right track? My load capacity is somewhere around 136 kg, btw.

This brings me to my question: are my torque/rpm/power calculations correct?? (code-blocking it up for clarity)

per wheel:
r = wheel radius = 4 inches = 0.1016 m
circumference = 2pi(r) = 0.638 m
v = (max) running velocity = 1.25m/s
rpm = v(60/circumference) = 117.48 rpm

the chair:
u = coefficient of friction = ~0.7
N = normal force = mg
m = total mass (136 kg)
g = 9.81 m/(s^2)
vi = 0 (rest)
t = time to accelerate, say 2 s
a = acceleration = (v-vi)/t = 1.25/2 = 0.625 m/(s^2)

Finally:
Ftotal = uN + ma = m*(uN+a)
Fwheel = Ftotal/4 = 255. 248 N
Twheel = (Fwheel)(r) = 25.93 Nm

Pwheel = (Twheel)(rpm)(2pi/60) = 319 W

Is the power really supposed to be this large and my RPM that low?? Have I missed something?

Help/corrections would be very much appreciated!!


texts: Driving high voltage to ultrasonic transducer with Arduino

texts:
I'm trying to drive an ultrasonic transducer with an Arduino. I have the arduino putting 40kHz  out of pin 10 and I would like to step that up from a 5V square wave to 100Vp-p or anything near there. I have one of these 1:10 tunable transformers using this schematic:

It produces this type of signal (note, the probe is set to 10x):

I'm hoping to get something a bit more clean and consistent. Also, the availability of the above mentioned transformer is questionable. Because I'm using fully enclosed ultrasonic transducer, it's important that I give it this much driving voltage to get a nice response but I feel that if the signal was cleaner I wouldn't have to drive it so high.

I'm thinking a transformer is the best approach (I don't know this for certain though) but finding another suitable transformer seems to be next to impossible.

Does anyone have any suggestions on how to step up a 40kHz signal or even a better transformer to use?


texts:
I want to use a small 8 bit microcontroller which has only a single CAN rx/tx, i.e. Atmel 32c1, but in my application I need to be able to send and receive requests from two CAN buses.

I have read the datasheet for a particular transceiver, AMIS−42700 (http://www.onsemi.com/pub/Collateral/AMIS-42700-D.PDF), but I don't understand whether this physically joins the two buses or allows a microcontroller to receive and send on the two buses, like a mux.

I absolutely don't want the two buses joined for any other devices.

Is this possible by either using a transceiver or multiplexer? I feel the ideal solution would look something like a device which intelligently joins the two buses coming into the microcontroller and has a (perhaps gpio driven) mux on TX which I can change between writing messages to the two different buses to select a bus for writing.


texts: How does low voltage burn out induction motor

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I know that low voltage damages AC induction motors and usually under voltage protection relays are used to trip the motor in such conditions. But the theory behind that is confusing to me. After searching on the internet I found the below answer (still not clear enough for me.)

P=VI, motors are manufactured to deliver the power P. Since V reduces, to keep P constant, the current gets increased and damages the motor.

If this statement is correct supplying low voltage to a bulb should result in lighting it more brighter.

In a motor, the magnetic flux is the component which creates the rotational force, and magnetic flux depends on the amount of current flowing in the wire (not the voltage.) So my fact is if a high current flows through the stator coils is should create the required magnetic field and motor should work.

I know that I'm understanding something wrong here. Please, I hope an electrical engineer or some expert can help me understand the theory behind it.


texts:
The bleeper(buzzer) I am using is rated for 12 volts DC. It is a piezo electric bleeper and the frequency is created by an internal oscillator.

I am not aware with the functioning of peizo electric bleepers due to which I am not sure whether my estimate of 600 ohm minimum impedance is correct. My multimeter is not able to measure the resistance of this bleeper.

My question is, to calculate the impedance of this device, would it be safe to say that these type of devices consume at max 20mA? This would make the resistance a minimum of 600 ohms.

Have you come across small(around 1.5cm dia) bleeper that use more mA than this?
Do most of them consume less mA than this?

If it is any help, I attached this bleeper to a 220uF capacitor charged at 15V and the sound lasted for about 3 seconds.


texts: Current limiting rectifier with capacitive reactance (isolated)

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[UPDATE] I have answered my own question with links to experimental data and theory.  Please expand on that answer if you can for the reference of future readers. Thanks for replies so far and ongoing.[/UPDATE]
I have been trying to build a current limiting rectifier on the secondary of a SMPS.
I am building this to be used with any SMPS it is a general purpose concept rather than for the specific use case I am building it for which happens to be a constant current laser driver.
There are many simple driver circuits out there, but they all waste power with a current limiting resistor or with a current sense resistor.  The load resistance gets below 1 ohm in my application.
In a simple AC circuit with just a resistive load, you can use capacitive reactance to limit current with very low power loss.
I have been trying to combine this concept with a bridge rectifier to limit the current reaching the diodes to limit the current to the load.  This is where the simulation breaks down.
In the screenshot below I have three circuits simulated in LTSpice to demonstrate these ideas.
The first shows the basic example of just a load resistor with current limited by the reactance of the capacitor.  I can change the resistance as much as I want below the reactance of the capacitor and the current in the resistor is limited by the capacitor - this is what I want.  Of course, a larger resistor would dominate the limiting of current. 12A is my desired peak current as shown.
The second shows the rectifier circuit I will build, which is pretty normal and is there for reference.  There is no effective current limiting and the trace shows a peak around 140A.
The third shows my attempt to merge the above two circuits, to limit the current supplied to the diodes to thus limit the current supplied to the load.  But the simulation breaks down and tends to a zero current flow.
I have tried tuning the capacitor value.
I have been scratching my head over WHY it breaks down for days.
Thinking about the half cycles and polarity and current pathways etc.
In practical tests I mis-soldered and made a voltage doubler just trying things out.  I'm sure there is some theory I am missing.  I tried the above with a centre tapped transformer with the same outcomes.
The reason I am doing this is to save power and reduce cooling needs.  What actually goes on to tend the current flow to zero and how can I make this circuit work please?
As a secondary set of ideas: I have looked into LM317 and other designs.  I even thought about using comparators but the current sense resistor needs to be in series with the load which wastes power and limits current by itself with sub-ohm laser load.  I can't find any designs with a current sense resistor in parallel with the load that can have a high 100 ohms to limit power use (compensated for by the gain of an op amp for comparator use.)
Theory would be helpful because I wonder why there seems to be no low wastage method to do this that doesn't need a lot of components such as current transformers.
The voltage sources in the image are all the same 15V AC at 132kHz and represent the secondary coil of a SMPS transformer.


texts:
I have this simple circuit with a diode (with voltage drop \$V_d\$) and resistor in parallel, and another resistor in series with them both. The circuit can be seen in the diagram below.

simulate this circuit – Schematic created using CircuitLab

What is the voltage, \$V_o\$, across \$R_2\$? I think that when \$V_i<V_d\$, the diode does not conduct, so the circuit behaves live a potential divider, with \$V_o=V_i\frac{R_2}{R_1+R_2}\$. Otherwise, the diode behaves like a short circuit, so \$V_o=V_i-V_d\$. If this is true, the signal would look quite strange. That's what confuses me.


texts: Transfer function of complicated circuit

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If we have a circuit like this:

How can we make a good algebraic expression of the transfer function?
I tried to go step by step with circuit analysis and then write expressions for each part of the circuit by itself but then I get an extremely long and complicated algebraic expression that is impossible to work with.

How can we get an expression that is written in the standardized form? Like this:

Where
 \$H(s)=\frac{v_L}{v_i}\$

\$s = j \omega \$

\$n_1, ... ,n_m\$ are zeros and

\$p_1, ... ,p_n\$ are poles.


texts: MOSfet thermal design: die-to-package always DRAIN?

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All the MOSfet chips seem to have substrate = DRAIN, which means that the heat-dissipation path goes that way. It is assumed that the package DRAIN pin would conduct away most heat from the package to ambient.
Data sheets seem never to confirm this assumption:

Large power packages make thermal design obvious: one-of-three leads (DRAIN) is a large metal pad, meant to conduct heat. But small packages like SOT-23, TO-92 etc. have similar-size leads.
On these small non-obvious packages, is it safe to assume that DRAIN pin will always get most heated, when considering thermal design?


texts:
Let's assume I have ADC data come into my KC705 board, there Are a bit-clock and several data channels, I trying to use ISERDES to deserialize the serial data coming to my FPGA from one of the ADC channels.
I take the data from channel A and Bit Clk from the ADC, and connect it to selectIO interface I created, it doesn't really matter what I did there I just trying to test this out, so I getting in the output 6bits of data and clk divided from bit clock.
From my understanding, its should be a data and clock I can use in my design for my needs, so the first step I tried as is to connect it directly to ILA and there was a place error.
ok so I read here in the forum that using FIFO for cross clock domain, using the read clock as an internal clock from ClkWiz may solve the problem, but it didn't, with the FIFO together there is still the same place problem.
my schematics of the design:

the error:
[Place 30-126] Unroutable Placement! A BUFIO can only drive loads in the same IO bank. The following BUFIO clock loads are placed too far from the BUFIO to be routable.
adc_deserializer_inst/da0_deser_inst/inst/bufio_inst (BUFIO.O) is locked to BUFIO_X0Y22
adc_deserializer_inst/da0_deser_inst/inst/pins[0].iserdese2_master (ISERDESE2.CLK) is locked to ILOGIC_X0Y208

The above error could possibly be related to other connected instances. Following is a list of
all the related clock rules and their respective instances.

Clock Rule: rule_iotile_bufr
Status: PASS
Rule Description: An IO driving a BUFR must both be placed in the same clock region
adc_deserializer_inst/da0_deser_inst/inst/ibufds_clk_inst (IBUFDS.O) is locked to IOB_X0Y276
adc_deserializer_inst/da0_deser_inst/inst/clkout_buf_inst (BUFR.I) cannot be placed

Clock Rule: rule_bufh_bufr_ramb
Status: PASS
Rule Description: Reginal buffers in the same clock region must drive a total number of brams less
than the capacity of the region
adc_deserializer_inst/da0_deser_inst/inst/clkout_buf_inst (BUFR.O) cannot be placed

Clock Rule: rule_bufr_IoClkLds
Status: PASS
Rule Description: A BUFR driving any number of IOBs must be placed within the same clock region
adc_deserializer_inst/da0_deser_inst/inst/clkout_buf_inst (BUFR.O) cannot be placed
and adc_deserializer_inst/da0_deser_inst/inst/pins[0].iserdese2_master (ISERDESE2.CLKDIV) is locked to ILOGIC_X0Y208

I aware that going into the selectIO interface and changing the BUFR to BUFG or some combination of BUFMR with BUFR can solve this problem, but assume I don't want to touch anything inside the selectIO and just debug what going out from it somehow, is it possible? I doing the FIFO clock domain crossing wrong?
any help is appreciated, thanks!


texts: What kind of motor is this 14-lead beast?

texts:
I found a motor with a weared-out label (it is completely unreadable). No distingushable marks are found there, so I decided to measure it and to deduce what is could do for me.

The motor isn't large, has a length of roughly 4 cm (without shaft) and the diameter is also 4 cm. The shaft diameter is 2 mm. The motor is undismountable, so I prefer not to disassemble it. There is small hole which is closed with a rubber spile (could be seed on some photos).

Photos could be seen here: https://cloud.mail.ru/public/KMfC/qPB4TjRrC

The motor has 14 leads, which looked totally same. I labeled leads to distingush them and measured ohmic resistance between each pair of leads. In each measure the "+" of my multimeter (red lead) was connected to the motor lead specified in coloumn head, and the "-" (black lead) was connected to other lead which number is in the row head. The measured resistance is on the cross of that row and coloumn.

Motor shouldn't display any nonlinearity, so the measurement matrix has to be symmetric, but I made and kept all measurements, in "both directions". I.e. there are resistance value "from lead 5 to lead 1" and "from lead 1 to lead 5" which supposed to be same and the difference, if it is there, shows a measurement inaccuracy.

All valus in tables are in Ohms.

I discovered four lead groups. First two groups don't generate voltage when I rotate the shaft with my fingers, nor change resistance.

Group 1: leads 1, 5, 10, 13

        01      05      10      13
01      x       08.2    09.0    11.5
05      08.3    x       08.7    12.2
10      08.2    08.9    x       12.2
13      08.3    09.0            x

Group 2: leads 2, 7, 11

        02      07      11
02      x       12.0    09.4
07      11.5    x       09.3
11      09.6    10.0    x

There is 252 kOhm crosstalk between groups 1 and 2.

Other groups generate voltage when I rotate the shaft. Looks like this is Faraday effect:

Group 3: leads 3, 4, 6, 14

        03      04      06      14
03      x       40.0    23.9    41.9
04      40.0    x       23.5    41.6
06      23.9    23.5    x       25.3
14      40.1    39.7    23.7    x

Group 4: leads 8, 9, 12

        08      09      12
08      x       22.4 g  23.4 g
09      23.7 g  x       23.3 g
12      23.8 g  22.5 g  x

It looks like group 3 is windings connected in a star topology with lead 6 is the center of the star, while group 4 is a triangle.

What this motor is for, what are first two groups are for, why each group is different?


texts: What does "Piggy" mean in this Schematic?

texts:
What does the word "Piggy" mean in this schematic diagram?
I found some sections of a schematic where a part is denoted as "Piggy".
What does it mean?


texts:
I started an applied electronics course at my university and my teacher assigned us this assignment after a lecture on how to check the compatibility of two or more gates:

Output electrical parameters: $$ V_{OL}=0.37V \space V_{OH}=3.76V \space I_{OL}=24mA \space I_{OH}=-24mA $$
Input el. par.: $$ V_{IL}=0.9V \space V_{IH}=3.15V \space I_{IL}=-1 \mu A \space I_{IH}=1 \mu A $$
The output drives:

4 inputs
a resistance of 1kOhm connected to Vdd = 5V

I have to check the digital compatibility, she suggested to compare the voltages  and calculate and verify the currents.

I did the comparison of the voltages, I checked that Voh>Vih and Vol

My problem was on the currents. I split the problem in the two cases: H output voltage, L output voltage.
I am not sure on how to use the '4 inputs' and the 'resistance connected to Vdd' information


texts:
I am trying to fix an old three-phase drill.

The motor has 3 wires coming out of it, which connect to the three phases.

Connecting it to the power does nothing, and so I tested it with a multimeter, and saw that two of the wires coming from the motor are shorted together, but not with a good connection (~25ohm).

I am not educated on electricity beyond your common layman knowledge, and definitely not on why three phases are needed or how they are used (or indeed, what this term even means, beside the obvious 3 wires)

Therefore, my assumption at first was that this short is a fault somewhere inside the motor.

Then upon reconsidering, I realized that if the three phases are completely separate, and there is no 0/ground going to the motor, then how can the circuit be closed?

Is this short indeed a fault? how is there a closed circuit when the only lines going into the motor are power lines?

Thanks :)

/Edit

Given the useful answers and comments, I can only assume something inside the motor is bad.
This is because 1) Nothing at all happened when it was connected to electricity, not even anything bad. 2) The multimeter shows there is only a physical connection between one of the three pairs.
I will hopefully be able to test this further and supply photos tomorrow.
Thanks!

/After further testing

It seems I was misled, and the three phase socket in the wall didn't even have any power running to it. Whoops!

With actual power feeding into the motor, it sort-of tries to spin, with A LOT of resistance, and eventually after a few seconds manages to spin very slow. It gets very hot.

Because there is only a physical connection between one of the three pairs, I am guessing this means that only one of the phases actually does any work.

I'll try perhaps to fully open it, although I don't believe I have quite the right tools for the job.

Thank you a lot for the answers and explanations, at least I have some basic information about this subject that I knew completely nothing about two days ago :)

/Conclusion

The motor was sent to be fixed, and indeed the windings got ruined and had to be remade.

A big thank you to you all on educating me :)


texts:
I'm trying to get the small signal model for this circuit:

This is my attempt
I'm not sure where W1 should go. Should it be shorting out RD? Also R2 = RD on this circuit diagram


texts: Voltage across charging capacitor drops after some time

texts:
I have an RC circuit where I measure the voltage across the capacitor over time with a voltmeter. For the supply voltage I am using a 5V phone charger.

I know what is supposed to happen, the voltage on the capacitor is going to increase rapidly in the beginning and will slow down as it charges until it reaches the supply voltage.

What I am measuring however is very different. The first couple of seconds the voltage increases, like it should, until 3.9V and then starts to drop while the capacitor is still supposed to be charging.

I'm very curious as to how this can be explained.

Edit:

The capacitor's value is 150uF, the resistor is 20kOhm, the supply voltage is 5.22V measured with the voltmeter.


texts: Rating of diodes for relay coil spike suppression

texts:
How do I go about dimensioning a diode to suppress turn off spikes on a relay coil and what considerations are there apart from coil current.

I have a 12v 100amp power relay that I wish to use a diode across the coil of to minimise interference from inductive spikes fom the coil when the relay is turned off.

I do not yet know the coil current rating due to supplier intransigence, but a generic answer will assist me in using the correct diode in due course.


texts: Understanding the operation of a grounded gate P-channel MOSFET in a iPhone 6 charger

texts:
In the circuit below Q1701 is part of a charging circuit in an iPhone 6.

Since there are no datasheets available for the main components in the circuit I've been trying to figure out the operation.

With a charger disconnected:

S = 0V
G = 0V
D = 0V

Charger connected:

S = 5V
G = 4.29V
D = 5V

So this is where it leaves me confused, if a P-channel MOSFET turns on when it sees 0V at the gate (which I thought was the reason R1710 has it connected to ground) how is it turning on with 4.29V at the gate?


texts: Driving an audio speaker design questions

texts:
I have been dealing with some project in which I have some requirements to accomplish. For now, I am dealing with the first part and a quick story is,

I have to generate a sine wave at a certain frequency and then convert that signal into sound via using an 8 ohm speaker.
At least 1 W of power on the speaker.
Adjustable amplitude of the sine wave input of the speaker.

So what did I do:

I am using a wien-bridge oscillator circuit which looks like this to obtain the sinusoidal waveform. And what I get is a nice 16 Vpp (I assume 2 Vpp loss can be considered as normal) sinusoidal-ish waveform while no load is connected to the output of the opAmp. However, when the switch is being closed, i.e 8 ohm load(my speaker in this case) is connected to the opAmp's output, then the voltage on the speaker dramatically drops to 0(nearly 0) volts.

Now, If I did not do the math wrong, I need at least 4 Vpp on the speaker to reach required power rating. After all these, my need reduces to being able to have an adjustable 8 Vpp to 4 Vpp load voltage.

So, how should I proceed? I have thought of using a voltge divider network at the output with a potentiometer and a fixed resistor to tune the output voltage but I don't know that works, or if that can work then how should I arrange the values of the resistor and potentiometer so that I can safely drive an 8 ohm speaker.

p.s: Using job-specific IC's which will bypass design steps and give directly the desired outcomes are not allowed.

Allowed components:

Mosfets,
Bjts,
Capacitors,
Resistors,
Potentiometers,
DC batteries,
opAmps,
8 ohms speaker,
Switch, button,
Wire(needed to write after some brutal comments..)


texts:
I want to install MCCB for 750Vdc supply in traction application (Light Rail Transit). After finding some 750Vdc MCCBs, I looked for 1000Vdc MCCBs. All the 1000Vdc MCCBs are intended for photovoltaic application. PV MCCB standard is UL 489B whereas the usual MCCB standard is UL 489.

Why is MCCB 1000Vdc for PV?
What is the difference between UL489 and UL489B?
Is it okay to use the 1000Vdc PV MCCB for my 750Vdc traction application?


texts: I2C Bus getting Locked UP on Single Master - Single Slave System

texts:
I was trying to develop a I2C driver function for reading data from a proximity sensor(Cypress CY8CMBR3102) and initially the function worked very well and successfully. But while continuously reading data from the device, the slave is holding the SDA line low and the bus arbitration flag is set in the MCU(NXP MKE04Z64). This is blocking all further communication.

I tried the following fix in my code but it didn't work out.

Every time I want to read from the device, I keep the I2C pins as
GPIOs and check the level in the data bus.
The I2C module will be enabled only if the data bus is in high state.
If the Bus is held low, the SCL pin is clocked as a GPIO untill SDA
is released by the slave.

When I tested the above fix in the device, the code is stuck in the loop where I clock the SCL pin until SDA turns high again. Which means clocking SCL is not helping in releasing the bus from the slave.

However if I unplug the slave or do a power reset, the bus is released since the slave is being reset.

I'm still unable to find the cause of this issue. I monitored the lines using a DSO and didn't find any significant noise in the lines.

1. What could be the possible reason for this bus lock-up?

2. How to detect and recover once the bus is locked up?

The details of our setup are as follows:

-> Single Master - Single Slave

-> Master - NXP MKE04Z64 Arm Cortex M0+

-> Slave - Cypress CY8CMBR3102 Capsense Proximity Controller

-> 400KHz I2C clock

-> MCU pins are open-drain with 4.7K external pull-ups.

-> Master and Slave are in separate boards interconnected with a 6cm long wire.


texts: Can you pass resistance through analog mux?

texts:
I have a digital potentiometer that I want to calibrate by sending in my commands and then measuring what the actual resistance is. However, the resistance from the digital pot is (obviously) connected to other bits of the circuit and I'd need to isolate it to get an accurate measurement.

My question is, if I use this analog mux or something similar, can I feed my "resistance" through it ?

I do believe that the analog mux is really just a "switch" and there isn't anything fancy about them and that this would work but I'd like to make sure before I go ahead any further with it.

I appreciate your time and look forward to your opinions.

Thanks!


texts: Picking source resistance for impedance matching

texts:
I am trying to drive a piezoelectric transducer with maximum power transfer possible with minimum possible noise. In order to do that I am trying to implement LC matching circuit such as circuit described in below picture.

Websites that calculates L and C values for me ask for source and load impedance. Load impedance is fixed by the characteristics of piezoelectric transducer. However, I have the liberty of choosing the value of source impedance as it is from a gate driver with output impedance smaller than 10 Ohms. I can add just a series resistor to create my source impedance.

My question is that, is there any guidelines for choosing the value of source resistance?
I noticed that as I make it smaller and smaller, the power transfer at resonant frequency increases along with Q value.


texts: Measuring back EMF induced current with multimeter

texts:
I have built a solenoid with copper.
It is 19 cm long, it has 64 turns and the radius is 1.5 cm.
To trigger back EMF, I use a permanent magnet that has the same surface as the cross sectional area of the solenoid.
I put the magnet on one end of the solenoid and then rapidly pull it away.
The voltmeter shows indeed 1.2 mV. This value is pretty the same each time I driftly pull the magnet. Now when I do the same experiment but by using an ammmeter in series, I see 0.12 mA.
What I can't explain is this:
Given that the multimeter shows a total resistance of 0.1 ohms for the solenoid, I am expecting the ampmeter to show 12 mA instead of 0.12 mA. I checked the meter ranges and accuracy many times but can't figure it out. My hypothesis is that the 12 mA is the maximum current. But the ampmeter is measuring the current before it reaches the max value. Does that make sense? Given that I have no battery in my circuit?


texts:
I have following block diagram,

I am having trouble constructing structure function marks for this block diagram.
What concerns me is that OR state from State 5 to State 2 and State 6. I thought this can be written as

P(1) AND P(5) OR (P(2) AND P(6)) AND P(3) AND P(4)

but I can't evaluate it, I get lost from here... I thought first to solve in
brackets ie P(2) AND P(6) - > P(2)P(6)
But what concerns me now, is what should I first evaluate, OR statement or go as a flow goes?


texts: Creating a 5x5 keypad without using micro-controllers

texts:
This is my first question ever on stackexchange, so if i am unable to provide enough information or if i do anything wrong, please let me know.

I want to create a 5x5 keypad using 25 simple buttons, i could connect each column to a decoder output and record the decoder input to get the column number and connect the rows to a multiplexer to get the column number ( i think i understand this part), but i want to convert the row and column number to a 5 bit number (0-24), to represent the pressed button. Basically i want to apply this formula using discrete logic: [(5*row)+column)]. For Example coordinate (0,0) will be 0 and coordinate (3,4) will be 19. Also assume that only one button is pressed at a time.

Designing such a circuit through kmapping requires alot of hardware (ICs), is there a way to implement this using less hardware (ICs)?

This is part of a project, only micro-controllers are not allowed, any other TTL  hardware can be used.


texts: If a device is rated at 12 V/80 mA what does that mean as far as the length of time that it will draw 80 mA?

texts:
I have an electromagnetic device designed to hold a fire door open until either the circuit is cut or the building's electrical supply goes out. At which point the door is released and will close.

It is rated as 12 V/80 mA. What does that mean in terms of the length of time that the device will draw the 80 mA?

Should I read such a rating as 12 V/80 mAh or 12 V/.0080 h?

I'm doing some rough calculations as to how long a given battery combination would keep this device energized.


texts: Naively mixing two (or perhaps more) audio signals

texts:
this is my first question and I am very much a beginner in electronics so I apologize if this is a too stupid question.

I have Atari punk console and another small homemade audiomaking circuit. These two have mono audio signals as outputs and I would like to combine these as one in the simplest possible way. I know next to nothing about audio processing but I believe that the strength of the two signals is roughly the same.

What would a neat solution be? It would be really nice if I could extend the solution later on to more than just two signals but thats not really important.

Any hints, references, guides, links or ideas would be highly appreciated.


texts:
I'm an electronics hobbyist who's learning from wiring stuff together and searching the internet if something doesn't work. Hence my electronics knowledge is very patchy.
I recently found out that mains voltage cables (in my case 230 VAC) should not be run parallel to data cables, because that could cause interference and voltage spikes in the data signals caused by induction.
I'm working on a project right now, where I made exactly that mistake - lucky me that I didn't power it on with the data cables connected to the Raspberry Pi yet.
So now to my questions:

How far do I need to place the power cables away from the data cables?
Two power supply PCBs are rather close to the data cables as well (ca. 8 cm & 2 cm).
Could those become a problem?
Is it possible to damage the Raspberry Pi because of voltage spikes from the data cables caused by mains cables running parallel to them?
The mains cables are very close to the metal chassis (which is grounded). Could voltage spikes be introduced to the chassis and travel to the data lines even though the mains cables have been moved? (Forgive me if that's a dumb question.)
A cable powering two 75 W light bulbs runs over the data lines. Could that be a problem?


texts: Correct Phase (Bode) plot of transfer function

texts:
I've written the following question here:

  I've learned some basic rules to draw Bode plots and when it comes to Phase plot, some of them are:

  a single zero located in the left half of s-plane has a contribution of 0 degrees near origin and +90 degrees on high frequencies;
  a single pole located in the left half of s-plane has a contribution of 0 degrees near origin and -90 degrees on high frequencies;
  a single zero located in the right half of s-plane has a contribution of +180 degrees near origin and +90 degrees on high frequencies;
  a single pole located in the right half of s-plane has a contribution of -180 degrees near origin and -90 degrees on high frequencies;

  Note that if you do the math to find the phase by the transfer function, you may find that would be more intuitive to think:

  a single zero located in the right half of s-plane has a contribution of 0 degrees near origin and -90 degrees on high frequencies;
  a single pole located in the right half of s-plane has a contribution of 0 degrees near origin and +90 degrees on high frequencies;

  In the first set of rules, all poles would end up in -90 degrees for high frequencies and all zeroes would end up with +90 degrees for high frequencies while with the second way of thinking, all of them would start from zero.

  It may also makes sense to think that these last two rules are just a matter of adding +180 or -180 degrees in the cases above which may not change the results since the phase comes from the tangent function which allows us to do that (since \$tg(10^o)=tg(190^o)\$).

  However, making the second way, a zero in the right half of s-plane would have the same phase plot of a pole in the left halft of the s-plane.

  So, after all, is there a correct and unique rule?

And in a few seconds I deleted it because I came to this conclusion:

\$H(jw)\$ is represented by a complex number which has a magnitude and phase. And even though \$tg(\phi)=tg(\phi + 180^o)\$, rotating this complex number by \$180^o\$ would give me a different complex number.

However, when we have to calculate what is the magnitude and phase of this complex number \$Z\$, we have:

$$Z=a+jb , \space\space j^2=-1$$
$$|H(jw)|=|Z|=\sqrt{a^2+b^2}$$
$$arg(H(jw))=arg(Z)=\frac{b}{a}$$

So, if I rotate \$Z\$ +180 degrees, then:

$$Z=-a-jb$$
$$arg(Z)=\frac{-b}{-a}=\frac{b}{a}$$

So, again the same problem. Even though we can have two different complex numbers, Bode plot might have more than one result if we follow these mathematical procedures. How to distinguish between both?


texts: Reconize JK Flip-Flop operating edge: rising or falling?

texts:
This is a JK Flip-Flop image.

Using this image is there a way to know if the output changes on raising or falling clock? In other words, is input data
transferred to the outputs on the HIGH-to-LOW clock transitions or on the LOW-to-HIGH transition?


texts: I am simulating a difference amplifier circuit using LT1215 Opamp. I'm using LT1215 since I need supply voltage around 3V. The input voltage for both the terminals of the opamp is 200 μV   and 100 μV. The output should have been around 100 μV but I'm getting output 6.24 mV to 6.2mV. The  closed loop gain of the opamp is 1.


texts: How to calculate the total signal strength and phase shift of multiple signals in a reciever

texts:
I have a simulation to make where I have an array of transmitters that transmit the same signal. At a random point, which I have to consider as a receiver I have to measure the phase shift of the signals and also measure the total signal strength. The requirement is that the transmitter emit the same signal but with different phase offsets.

As far I understood because the transmitters are separated apart, the received signal is already is offset by some phase because they travel distances. Is my assumption right?
I know the formula to find the phase offset given the distance travelled of two signals - how do I calculate it for multiple signals? Or am I understanding the question wrong?
How do I calculate the total signal strength for all signals combined? I know for one signal, assuming a free space, line of sight connection I can use friis equation. But how do I use it for multiple signals?

Any help is very much appreciated. I am Software Engineer who have recently taken up Wireless communications course, and I'm not sure if I understand the motivation and meaning behind the simulation right. Thanks!


texts:
I am currently designing a circuit that includes a nichrome coil used as a heating element. The wall adapter is 25V 5A DC, which leads to different buck converters that takes it down to the appropriate voltages. The Buck converter that leads to the coil is set to have an output of 15A. The Flow to each component including the heating coil is controlled by a number of MOSFETS.

I have noticed that upon testing the heating coil (in testing I have separated the component being tested from the others so in this situation the power goes straight from adapter to buck to coil to MOSFET then back to buck), the MOSFET (which is rated at 30A and 60V) is overheating and melting. I have tried using heat sinks, splitting up the current between multiple MOSFETS, and added PWM to allow the MOSFETS time to cool down, but I can only make the PWM rest periods so long before I can no longer achieve the desired heat. Still with all of this, the MOSFETS heat up and begin smouldering.

Because of the amount of MOSFETS I've ruined and amount of dangerous fumes I've inhaled, I feel it is time to turn to the experts for insight.

My assumption is the circuit is in essence a short circuit, although I would have assumed the coil would have supplied ample impedance.

Does the fact that the buck converter is lowering the voltage mean that excess amperes are being drawn?

On a side but still related note, if the circuit is in essence acting like a short and drawing uncontrolled current, will this risk damaging the adapter?


texts:
Following this link, I made 0.1 inch footprint library in KiCAD. Also made the schematic symbol.

I need 2x14 pin 0.1 inch header. So after making the footprint, I see below error in the pcbnew after reading the netlist

  Module [U17]: Pad [~] not found

  .......

  Module [U16]: Pad [~] not found

It is complaining about 26 pins (not about the total 28 pins in those 2 headers). So it is recognizing only one pin per header (U16, 17 two different headers).

I think my schematic symbol that I made doesn't match with the footprint through hole circular pad. Attached images. Please suggest.


texts:
I want to implement an SDI-12 interface and I found this schematic online. The author says that the buffer translates the 3.3V voltage from the microcontroller to 5V for the SDI-12 line.
However, the buffer is SN74LCV1G240 which has the high-level input voltage (Vih) of 0.7 x Vcc, which is 3.5V at Vcc = 5V.
So it seems that it will not work as the author says. Am I right or am I missing something here?


texts:
I am having the following problems understanding the above circuit:

-I understand the part where the opto-coupler activates transistor T3 acting as a relay driver. I also understand that this would activate relay RL1. But how does relay RL(a) get activated to N/O? In fact, how do any of the relays marked RL(alphabet) get activated?

-When the relay is in the N/C position, how does power from the 12V SMF battery get to the output?

-The NAND gate N1 has both inputs at the same value. When the ac mains is working, wouldn't the NAND give 0 as output where as it should actually be giving 1?

Note: This circuit can be found at http://bestengineeringprojects.com/electronics-projects/advance-mini-ups/ along with an explanation. I can not make sense of the explainaion, hence this post.

Thanks


texts: Circuit diagrams for LED Chaser Christmas Lights

texts:
I'm looking for circuit diagramS for ~50 LED strip with lights running* repeatedly from the bottom to the top of the Christmas tree. I found simple solutions with only 13-15 LEDs, but this is, obviously, not enough for a big Christmas tree.

The circuit must be DC driven.

Thanks.

*By "running lights" I mean this: https://www.youtube.com/watch?v=9CCWvKmVIug


texts: Why can't mesh analysis be used for non-planar circuits?

texts: My book simply states this without any kind of explanation.


texts: Potentiometer with SPST Switch Wiring With Bypass

texts:
I'm stumped on wiring a 10K Ohm audio control potentiometer with spst switch into a LM386 amplifier circuit.

The pot I'm using is very similar to the one in this link:

https://www.radioshack.com/products/10k-ohm-audio-control-potentiometer-with-spst-switch

The LM386 amplifier circuit I'm using is the one in this link:

http://www.circuitbasics.com/build-a-great-sounding-audio-amplifier-with-bass-boost-from-the-lm386/

What I'm doing with this circuit is using it as a simple overdrive pedal for my guitar.  Eventually, I'm going to wire this circuit directly into the guitar's pickup wiring.

My circuit works great and I was able to use the above potentiometer as a volume knob with great success.

The only problem now is the pot's switch must be turned on in order for signal from my guitar to go to the amp.  When I turn the pot switch to off, the signal cuts off completely.

What I'd like to do is wire the circuit so when I turn the pot switch to OFF, the signal from my guitar gets routed directly to the amp.  When I turn the pot switch to ON, the signal from my guitar gets routed through the LM386 circuit.

Is this possible?

I know I could do this with a push/pull type of pot but I like the feel of the rotary switch pot.  Plus, I already have a few of them lying around.

Thanks for reading.


texts: USB cable for power delivery max voltage

texts:
I have a USB cable with the following markings on it

AWM 80°C 30V VW-1 28AWGX1P 24AWGX2C

Inside the cable there are 4 wires. I would like to use the VCC and GND wire as power lines, (not using the USB connectors, and was wondering what the max voltage / current would be for those wires.

Do these markings mean that up to 30V can be applied to the VCC (red wire) and GND (green wire) inside this cable ? And is there any indication on the amount of current that can pass through such a wire ? (The application will consume around 50mA, with perhaps some very small peaks upwards to 200mA).


texts: How do I operate SPI flash with FatFs in small RAM conditions?

texts:
I want to use SPI flash to store some log files. And I anticipate I can read those files with various devices, so FatFs is my choice.

Now the problem is, my microcontroller only have 16 KBytes of RAM. As most of them are occupied by the application, I can give FatFs at most only 1 KBytes.

SPI flashes usually have a very large erase unit (e.g W25Q64 is 4 Kbytes size). That's the minimum size that FatFs can operate on the SPI flash.

So how do I solve this problem? Or are there other flashes that can be erased in a smaller unit?


texts: How to tell if a solar regulator is MPPT or PWM

texts:
I have a solar cell charging a 12v battery via a maplin TPS 1230 solar charge regulator. By using some basic instrumentation and some simple maths (i.e. measuring the current and voltage on the input & output and multiplying to produce a figure for power) I determined that I wasn't getting as much power out of the system as I thought I should.

Having read-up on the subject, I believe this might be due to the solar charger being a PWM type - not very efficient. I've just ordered what claims to be a MPPT solar charge regulator (much more efficient). listing here

After placing the order I did a little more reading (yes, I know, I got this the wrong way round!) and discovered that apparently many cheap MPPT charge regulators from china aren't really MPPT after all - just PWM chargers with a different label.

When my order arrives, is there any way of telling if it really is MPPT or not?


texts: In an amplifier, does the gain knob boost or attenuate the input signal?

texts:
I'm thinking specifically about guitar amplifiers, but I'm guessing this applies to all audio amplifiers.
I understand the practical function of a gain knob, but what's not clear to me is whether the gain knob is simply a potentiometer that attenuates the incoming signal, meaning if the gain knob is all the way up, it's simply letting the signal through unaffected, or if the gain knob controls some sort of boost circuit that actively increases the input signal strength before sending it to the preamp.
Or does the knob somehow directly affect the operation of the preamp making it provide more amplification or something like that?


texts: Ways to determine polarity (dc) without a meter

texts:
I came across this question about how to figure out the polarity of a cell phone charger without a meter. This made me think of what methods you could use to figure out the polarity other than using a meter or any device that is better than a meter; and I thought it would be an interesting question for my first question here.

My answer was that you could use a LED or a diode to figure it out. Or you could use salt water, as long as the voltage is high enough (over 2 volts, I think,) you could place both leads into heavily salted water and the negative lead will produces more bubbles and corrode faster.

Another ideas I thought of would be to use a linear regulator and see if you destroy it (testing if you destroyed it would require a meter or at least a circuit where it was working originally.)

What other ideas/options can you think of? Like electromagnetic methods or even blowing up capacitors...

Edit

As @Juancho pointed out, when I said without a meter I meant without a multimeter (or a more advanced device.)

Edit 2

Since this is basically a thought experiment, feel free to make the voltage and current whatever you want, but try to point out the range if it matters. For example @DeanB's neon answer required ~70 volts.

There are some great answers so far, thanks everyone! I'm sure there must be more basic chemistry options, unfortunately I never took chemistry in school.

Edit 3

Building a meter is also a valid answer. In fact there really isn't a wrong answer, other then saying, "use a multimeter."

This is becoming quite cool, some very interesting and unique answers! Thanks everyone!

Another Answer

I found this elsewhere and thought it was interesting, however @Juancho already posted a similar answer.

  How MacGuyver might find out:

  Materials

  some insulated wire
  a compass
  a suitable resistor
  a stick of chewing gum
  a pencil

  Steps

  Wrap the wire around the pencil 20-30 times. Looking at it from the
  eraser end, the wire should be going around counterclockwise.
  connect wire #1 of your adapter to the clockwisemost end of the
  coil (still looking from the eraser end). In series, connect the
  resistor to the other end of the coil. Connect the other end of the
  resistor to adapter DC wire #2.
  chew gum (save the wrapper in case you need to defuse a bomb later
  in the afternoon)
  plug in the adapter
  hold the compass near the eraser end of the pencil 6) if the
  compass points toward the eraser end, #1 is the negative wire. If it
  points away, #1 is the positive wire.


texts: Measure Power Supply Noise Rejection at MHz and GHz

texts:
I'm trying to characterize the performance of a power supply module, one of the criteria being power supply noise rejection, in particular at different frequencies.

For testing 10Hz to 100kHz, I was planning on using a power opamp to inject a function generator onto the input power supply (12V, <2.5A). The bandwidth of the opamp stops you injecting frequencies any faster.

However, the power board is being used to power an ASIC which operates in the GHz range, and is sensitive to noise 1GHz to 40GHz. Realistically, I think most significant sources of noise and going to be 5GHz and below (Wifi, GSM/LTE-4G etc), so 5-10GHz test and measure is a reasonable target. The entire system will be running in a lab environment, which is supposed to be no mobile phones/wifi etc, but its rarely enforced and it's unlikely our customers will enforce it either.

The power supply board is a fairly typical cascade of LDOs hanging off switching regs, and we've never had issues with it, so I am not anticipating any problems with it. However, it has never been fully benchmarked before.

Can anybody think of a way to inject sine waves at high frequency onto a 12V, power supply? I have access to function generators, oscilloscopes and spectrum analyzers at 20/40GHz.

Perhaps some kind RF amplifier with a bias set to 12V?


texts:
How to prototype analog audio processing?

Should I merely trial with analog electronics or should I simulate the circuits in software first?

Particularly, I'm interested in discovering new forms of processing. Fine tuned designs over existing designs. I have ideas regarding "what I want to hear", but how should I attempt reaching it?


texts: asychronous finite state machine , minimization and encode states

texts:
Hey.
I have Moore type asychronous fsm. I need to minize it, then encode states and get excitation functions for JK flip flops and output.

I have problem with encoding. As far as I know anti race coding says that only one bit can change. Two bits can't change simultaneously. I minimized it to 4 states and i can't encode states because each state has transitions that need change of two bits.

Here's what ive done

Thanks for answering!!


texts: Amplifier for pulsed Radar motion sensor

texts:
I have a radar motion sensor, IPM-170.

The output of the sensor is as follows:
The AC motion signal is -+300uv and there is a DC bias around 150mv.

I am applying the following circuit so I can run my sensor in the pulse mode.

When T2 goes to the saturation, the IF signal (DC bias + AC motion signal) goes to the amplifier.
However, that high value of DC bias (150mv) enters my amplifier as a step input (a lot of frequencies) so it passes the DC blocking capacitor and it takes a long time to decay throughout the output of the two stages op-amps. Also, my AC signal would not be, of course, recognized during my limited ON period of the transistor.

How can I completely block that DC bias signal from the sensor?


texts:
I have a small touchscreen hooked up to a Raspberry Pi, powered by (and getting ethernet connectivity from) a 802.11af splitter.  Everything basically works.

Sometimes when I first walk up to the (capacitive) touchscreen, it behaves oddly - phantom touches, a bit of a 'static-y' feel as my finger gets close to the screen, etc.  It usually goes way if I touch the screen (even the edge) and leave my finger there for a few seconds.  I'm wondering if it could be caused by a grounding issue.

Should I be connecting the ground on my Pi to the in-wall conduit in addition to the ground wire coming from the POE splitter?  Or would that just cause more problems?


texts: How does temperature compensation work for strain gauge in wheatstone bridge

texts:
Wheatstone bridge is used for temperature compensation for strain gauges

If 2 strain gauges are connected like this figure. Due to temperature variation; the resistance Rg will change in the same way.

Lets say; the bridge is balanced at start.
R1/R2 = (RG+DeltaR)/(RG-DeltaR)

If strain gauge resistance increases due to temperature:
R1/R2 = (RG+DeltaR+RT)/(RG-DeltaR+RT)

How does this compensation work?

(RG+DeltaR+RT)/(RG-DeltaR+RT) is not the same as (RG+DeltaR)/(RG-DeltaR)

So gets the bridge unbalanced???


texts: Best practice when choosing a trim pot value

texts:
I have a basic comparator circuit I'm working on designing. I want one of the reference voltages to be tunable, so using a trim pot. My Vcc is 12V, so assuming a 1/4 watt pot, 1k seems like the lowest I should go. (12 * 12 / 1000 = 0.144 watts dissipated) I chose 10k for now, but I don't know why I chose that value. It's a common value, and seems fine.

What is the best practice when choosing a value like this and why? Lowest possible value for lowest noise? Something else?


texts: Step-down voltage directly or in intermediate steps?

texts:
Couldn't make up my mind :P

Characteristics:

12V-80V Vin (DC)

3.3V system

In general terms (considering architecture and design) is it better to do directly 3.3V from Vin or is it better to do some intermediate step in between before having 3.3V for IC-s (say 12V and then 3.3V OR 5V and then 3.3V)?

I have an option to get all my components to run on 3.3V. I have one cheap 5V tranceiver (3.3V IO compatible btw), but I find it pointless to have a 5V rail JUST because of it, when everything else is 3.3V. I can find the tranceiver in 3.3V as well.

But also I find buck converting 60Vin-max to 3.3V kind of a big step (low duty cycles, bigger components...) But having intermediate step without using it seems also a waste (extra components).


texts: Plannar Inductor Unacounted Parasitic Capacitance

texts:
I'm trying to determine the source of approximately 300pf worth of parasitic capacitance in a planar coil project I'm working on. I'm trying to find out how my numerical predictions line up with the manufactured design. I've done an array of different sizes and, I see a shift in resonate frequency that corresponds to ~300pf across all of them
The example below has the following parameters
Layers: 2
Trace Width: 0.205mm
Trace Spacing: 0.152mm
Number of Turns: 10
Inner Diameter: 5.08mm
Outer Diameter: 12.548mm
Board Thickness:  1.13mm
Self Inductance: 0.994uH
Total Inductance: 2.99uH
Parallel C: 1nF
Predicted Resonate Frequency (w/1nF C): 2.899MHz
Measured Resonate Frequency: 2.534MHz
I'm fairly confident in the predicted numbers as they match what the TI Coil Designer outputs If its to be trusted. Its the measured resonant frequency that's got me. I measured the frequency with a Rigol DS1054 in two ways

Apply a sine-wave swept across multiple frequencies and measured the input and output voltage.
Apply a 1Khz square wave and measure the output oscillations

I can account for 13pF from the scope input and 13pF from the probe input. Additionally, from paper I can approximate the capacitance between the two layers as the two plates of a donut-shaped capacitor, but at best, that only accounts for an additional ~13pF, for a total of 39pF.
There's no metal under the surface that would affect it, there is no ground place to couple to. I'm missing something, but I can't think of what it is.

simulate this circuit – Schematic created using CircuitLab


texts:
I have created two projects, one with a Tiny RTC and another one with the BM180 sensor to read barometric pressure and temperature.  Now I want to combine both.

I'm trying to connect both - the BM180 sensor and a TinyRTC clock module via. the I2C pins to my Arduino Uno (r3) and because I'm just a beginner I have some problems.

The BM180 works with 3.3V, but the TinyRTC is on 5V.  Can I just connect all the SDA together and all the SCL together?


texts: Switching between power sources using a P-mosfet. Problem with LDO

texts:
I'm trying to design a circuit to switch power supply from USB +5V to battery when the USB is disconnected.
This circuit will power a WeMos D1 mini board, which needs a 3.3V input voltage, so the USB 5V voltage is converted to 3.3V through a LDO regulator, while battery voltage is already 3.3V.

I'm trying to select the power source through a FDN340P p-mosfet, like in the diagram below, but it doesn't work because when USB is disconnected, and the battery power is applied to Vcc, it goes backwards into the voltage regulator and Vin rises to 3V, switching off the p-mosfet.

I've tried also putting a 1N4004 diode between Vin and the mosfet gate, but voltage doesn't drop across the diode (probably because current is too low?).

How can I keep the mosfet switched on when USB is disconnected?


texts: FT232R eeprom problem .. how to make PC recognize it

texts:
it's my first time to use FT232R ..
when i connected it to the USB for the first time .. my Windows recognized it well, and its drivers were successfully installed ..
and even after programming it once or twice more .. it was O.K.

i tried to program it another time .. but after this time it was unfortunately unrecognized .. and the windows keeps seeing it as "unknown device" :(

i tried some possible solutions .. as if i programmed something wrongly .. like connecting an external crystal, and resoldering wires to go to self-powered configuration ..
but it was useless ......
i hope somebody help me .. i think i need to recover its original eeprom .. but it's not recognized, so the programmer can't reprogram it

sorry for explaining too much


texts:
Using a STM32F407 if I generate a 200 Hz signal it looks like this:

If I want a higher frequency, for instance 10 kHz I get this:

I am using a PicoScope 2205A, resolution 8 bits at 200Ms/s, bandwith 25MHz.
Does anyone know what is happening ?
P.S I configured the pin as very high speed in the OSPEED register.


texts: Can I leave it unconnected pins in the level shifter?

texts:
My concern is that pins are connected between DB25 and TXS0108E, but are not connected between TXS0108E and the Header 5x2. There is only the tracks between TXS0108 and the Header 5x2, but there is no connection, the pins were not all soldered.

I can not guarantee that the respective pins connected to DB25 will not be energized, eventualy they can be. So, my doubt is, is there a problem if some pins connected in the DB25 does not have their respective pins connected to Header 5x2 ? This way they will be floating in on side and not in the other of the TXS0108.

Below is the circuit to illustrate.


texts: How does a DC clamp meter measure current?

texts: I understand that for AC clamp meters, a changing magnetic field induces a voltage/current in a wire loop and therefore it is possible to measure AC currents by induction. But how does a DC clamp meter work? In essence a DC current means a static magnetic field, and by Faraday's Law, no voltage/current is induced.


texts:
I have a question about pulse transformer ,regarding to isolation, EMI reduction and heating.

My PCB has 6 layers (4 signal and 2 power planes) and I am using pulse   transformer to isolate and convert 3.3 from/to 5V. Maximal output current is 200mA.
Switching frequency for this transformer is 600kHz.
Is it better to use ceramic or tantalum or electrolytic capacitor at output?

I am wondering, should I keep area below transformer without copper ( all layers and planes) or should I place GND or isolated GND polygons, maybe on top layer?

My first thought was to remove copper on every layer and plane, below, but then make some fills (outward) around isolated GND pin and connect it with couple of vias to internal plane.

For capacitors I placed ceramic at input because of lower ESR and tantalum at output because better voltage stability.

What are your suggestions?


texts:
I'm trying to implement a synchronous up-down counter in verilog with the following rules:

Counter only changes on rising edge of clock
When reset=1, count goes to 00, normal operation when reset=0
counting is enabled when en=1 and disabled when en=0 counts up when dir=0 counts down when dir=1
counting does NOT wrap. When counting down, does NOT go from 00 to 11 (i.e. stays at 00). When counting up, does NOT go from 11 to 00 (i.e. stays at 11)

So far my code is:

module counter
(
    input               clock,
    input               reset,
    input               en,
    input               dir,
    output reg [1:0]    count
);

  always @ (posedge clock) begin
    if (reset==1'b1 || en==1'b0) begin
      count=2'b0;
    end

    else if(en==1 && dir==0) begin //up count when dir=0
      count <= count+1;
    end

    else begin //down count when dir=1
      count <=count-1;
    end

  end

endmodule

This does everything except for the counting wraps. How would I make it not wrap?

Testbench below(comments say what the code should be doing)

`timescale 1 ns / 1 ns    // Time for each step, time precision
`define CLOCK_PERIOD        10

module main;
    reg         clock;      // Free running clock
    reg         reset;      // Input - reset
    reg         en;         // Input - enable counting
    reg         dir;        // Input - direction (0=up)
    wire [1:0]  count;      // Output - Counter output

    // Instantiate module
    counter    u1( clock, reset, en, dir, count );

    initial                 // Done once at start up
    begin
        $display( "Up/Down Counter (no wrap)" );
        $dumpfile( "dump.vcd" );
        $dumpvars;

        // Set initial values for inputs, asset reset
        clock = 0;
        reset = 1;
        en = 0;
        dir = 0;

        // Turn off reset after one clock
        #(`CLOCK_PERIOD * 1)
        reset = 0;

        // Wait for a while to make sure it does not count
        #(`CLOCK_PERIOD * 2)

        // Assert enable, should count up to 3 and stop
        en = 1;
        #(`CLOCK_PERIOD * 5)

        // Make sure does not count if we now deassert enable
        en = 0;
        #(`CLOCK_PERIOD * 2)

        // Set dir=1 but en=0, so should not change
        dir = 1;
        #(`CLOCK_PERIOD * 2)

        // Now enable, should count down and stop at 0
        en = 1;

        // Count back down, check if reset is ignored if not asserted
        // at a clock edge
        dir=1;
        #7
        reset = 1;
        #6
        reset = 0;

        #(`CLOCK_PERIOD * 5)
        reset = 0;

        // Leave time to stabilize
        #(`CLOCK_PERIOD * 4)
        $finish;
   end


texts: How do modern electric blankets implement thermal sensing/feedback?

texts:
I'm looking to build my own 12VDC controller for a low voltage electric blanket (specifically, this blanket http://www.amazon.com/gp/product/B0041RQXKE ). An obvious implementation with a microcontroller as a duty cycle timer, relay, and DC-DC converter would be easy enough, but surely the real controllers for these blankets do something more complicated with temperature sensing. How does that work, so I can emulate it?

I know old electric blankets would use a bimetallic strip along the heating current path to adjust duty cycle as a function of ambient temperature. Do modern blankets still just use ambient temperature or do they get temperature feedback from the blanket?

I realize that native 12V electric blankets exist, although I wasn't able to find one that was the full length of a bed or with a full featured controller. I'm also aware that I could use a small inverter to convert to AC then let the blanket's original controller convert back to DC, but I'm not willing to deal with the fan noise or efficiency losses.


texts: Problem with a circuit to measure of displacement

texts:
I designed and built a circuit to measure displacement.
I made a coil and connected a wein oscillator to the coil, which changes the voltage at both ends of the coil by moving an iron rod inside it, then by ideal rectifier, the voltage of the coil turned to DC voltage.
unfortunately, now the output of the circuit changes about 1% when the rod not changing and the rise of temperature can change the output about 4-5% for the rod to remain fixed.
Can you please help me to improve my circuit against the variation of the output? or if you know a better circuit, please suggest it.
Thanks and Beest Regards,


texts: Removing the smallest supply decoupling capacitors in multilayer boards

texts:
Hello  I want to make PCB for ADF5901 24GHz power amplifier, it says use 3 capacitor for each supply pin, 10pF, 1nF and 100nF. we have about 6 supply pin.
Can we remove 10pf bypass from all pins, If using 4 layer board with 2 parallel power plane?
How we can become sure that this is correct decision?
Answer that I've found from guys advise and answer, the engineers world is EV-boards and manufacturers recommendation, specially if you have no test equipment and time.


texts: Does a potentiometer need a resistor in series between power and ground?

texts: I have a potentiometer I use with a circuit to get data readings. This circuit is connected to an arduino mega 2560. I was wondering if I need a resistor in series with the potentiometer? Attached are two picture of what I mean, sorry if the circuits are a bit rough first time I have used an online schematic maker. I would also like to add that the potentiometer values are likely wrong, it was a generic one a friend gave me. All I know is that it goes from 5 ohm to 10k ohm.


texts:
I'm trying to replace a broken potentiometer on a Native Instruments Traktor Kontrol S2.
My guess is that it is from the Alps RK11K series.
From what I can see:
Part number: 103B 305C - I haven't been able to line this up exactly with any part but I think the "103B" represents 1B taper and the total resistance (I tested the resistance with a multi-meter).
Total Resistance: 10kΩ
Length of the shaft: 14-15mm (from the top of the bushing)
Pinout: 4 pins
Link to RK11K datasheet (pdf): https://tech.alpsalpine.com/prod/e/pdf/potentiometer/rotarypotentiometers/rk11k11/rk11k11.pdf
I've contact Alps but haven't got a response, any help on not only identifying the part but understanding any steps I could take to do it myself would be greatly appreciated.


texts: Current sensing for backup battery circuit with LiPo charger

texts:
I'm trying to design a circuit that provides backup LiPo battery power to a +5v rail. The rail is sometimes powered by an external USB supply and sometimes not - I want my circuit to act as a power sink when the USB supply is present and act as a source when it is not. The main difficulty is that the USB supply and the load are joined together in an external system and cannot be separated - the only interface I have to this system is the +5v rail at point A in the schematic below:

This is the best solution, I can think of, but it is incomplete. My main questions are,

Will the small resistance in series with the boost converter effectively prevent the battery discharging when Vusb is present?
How can I obtain the active-low enable input (EN) for the battery charger, that is high when the boost converter is providing current and low otherwise?
Can anyone suggest a better solution that charges/discharges a LiPo according to whether another power source is present or not, where the USB source and load are hardwired together and cannot be separated?


texts: Passive Peak Detection for microvolt input

texts: Hello I am trying to find a peak detection circuit that is as passive as possible (ideally no battery needed) that takes an input signal of around 700 microvolts pk-pk.  All of the passive peak detector circuits that I have found use diodes making it impossible for me to use them with how small my input signals amplitude is.  Are there any other options that work for envelope detection of very small signals without having to use a diode or amplifier?  Any references on where I could start would be appreciated as I am having trouble with where I could begin.


texts: The overall voltage gain in the circuit is not matching my simulation result. What am I doing wrong?

texts: The overall voltage gain in the circuit is not matching my simulation result, but all other calculations of the circuit is almost the same. What am I doing wrong?


texts: How to increase the power output of a shunt regulator?

texts:
Based on an answerable but closed question:

If a given shunt regulator does not provide enough power at the desired voltage, how can the output power available be increased?

This relates to the shunt element and series input resistor, but how?


texts:
I have the following circuit (source: EDN):

I understand the basic working principle of the circuit and it works fine when it is powered from a 1.5V source.
But when I power the circuit from a 9V source, by default it get's turned on instead of turning on only when the S1 switch is pushed.

So my question is:

what causes the circuit to get turned on by default, when the 9V is applied to it? Is it the leakage current of the transistors? Or is it something else?

I noticed that this behavior occurs only if C1 is discharged when the 9V is applied.


texts: Regulating battery overvoltage to an IC pin

texts:
I am trying to find the best approach for ensuring a stable voltage on a specific pin of my gate driver IC chip during any potential battery overvoltage. I am currently using the Allegro A4960 for sensorless BLDC motor control, and am trying to crank the voltage up to 48 volts; however, the max rating for the Vbb pin is 50V while the Vbrg pin is 55V. After speaking to some of the engineers at Allegro, they mentioned that it is fine if the two voltages of Vbb and Vbrg are not the same so if I am not exceeding it for Vbrg then I should be fine to lower the voltage on Vbb. The Vbb current while operating is in the low mA range (approx 15-25mA).

My question is whether or not a simple zener and resistor network would be suitable for this sort of application. If so, where would the ideal location be to decouple any high frequency noise as the Vin of this network is part of a shared power plane with the inverter for the motor. More specifically, I must decouple as close to the chip as possible, should this be done before the zener and resistor network, within it, or both?

Thanks in advance, any assistance is deeply appreciated!


texts: BGA seems to be somewhat of a showstopper for the diy community, especially with the newer more powerful parts being almost exclusively bga.  I know it can be done with the skillet/toaster oven method, but it seems like there is no way of inspecting for defects without an x-ray machine except   for maybe this method using toothbrush bristles.  So is reflowing using these methods relatively high yielding or is this just not worth doing at home?


texts: Coil winding sense in dual voltage power supply

texts:
Hello is the sense of the B winding in the transformer (same as A or opposite than A) can have any effect on the powered circuit?

Maybe due to the fact that the AC ripple of the negative rail  is out in phase with the ripple in the positive rail and then worse?


texts: How to make a HDMI signal be identified as HDMI instead of DVI?

texts:
I am experimenting with the HDMI port of an ULX3S FPGA board. I have been able to properly generate DVI signals with a resolution of 800x600 and framerate of 60 Hz. I am now trying generate actual HDMI signals (instead of DVI). I order to do so, I have modified the design to include the extra signalization required by HDMI. Before each row of pixel data, I am including the 8-pixel video preamble (as described in the HDMI 1.4b standard, section 5.2.1.1) and the 2-pixel video guard (as described in section 5.2.2).
The screen, instead of identifying the signal as HDMI, it still identifies it as DVI, with a resolution of 802x600, and shows a 2-pixel magenta column at the left of the image, so it seems that it is treating the 2-pixel guard as pixel data.
According to annex C.3,

An HDMI Sink, upon power-up, reset or detection of a new source device, shall assume that the source device is limited to the above behavior. Upon the detection of an indication that the source is HDMI-capable, the HDMI Sink shall follow all of the HDMI Sink-related requirements specified in this document.

I am not sure what a "an indication that the source is HDMI-capable" is. Is the inclusion of the video preamble and guards enough or is there anything else needed to have the sink identify the signal as HDMI instead of DVI?


texts: Why does this power opamp have MOSFETs at the output stage

texts:
I saw a post a few days ago.

Power Dissipation of Op-Amp
where I was actually curious about the circuit where they use BJTs all over the circuit but use 2 MOSFETS for the output stage.(also why are  they using JFETs?)

In most designs that I have seen online, only BJTs are used.

Is there any advantage of using MOSFETs instead of BJTs for the output?

Are MOSFETs not less linear than BJTs?
If so what is their advantage?

It would be great if someone can shed some light on it.


texts:
I am using the Explorer 16 Board for building a Accel connected by I2C .
Currently I have only the I2C part done and I am trying to tap scl1 & sda1 using oscilloscope. The accel has to connected yet to the the MCU!

But on oscilloscope I dont see any signals on both SCl1,SDA1, any help ? here is the code :

UINT config1 = 0,i=0;
UINT config2 = 0;

/* Turn off I2C modules */
CloseI2C1();    //Disbale I2C1 mdolue if enabled previously

ConfigIntI2C1(MI2C_INT_OFF);  //Disable I2C interrupt

config1 = (I2C_ON  | I2C_7BIT_ADD );
config2 = 157;
OpenI2C3(config1,config2);   //configure I2C1

IdleI2C1();
StartI2C1();
while(I2C1CONbits.SEN );  //Wait till Start sequence is completed
MI2C1_Clear_Intr_Status_Bit;


texts: How to solder wires onto pins of an RFID chip?

texts:
I want to integrate a sensor with NXP's NHS3152 (datasheet). To do this I have to solder the wires onto the pins of the RFID chip.
What tools should I buy to do this?
What is a good reference to learn how to do it?


texts: The influence of a potentiometer on photo-diode bias

texts:
I have a sensor which I have connected to an Arduino via SerialPort to get data readings.

There is a "screw potentiometer" (It's a screw that changes resistance which affects the output voltage).

If I decrease the resistance, my AnalogOutput of my Arduino gives me greater voltage units when my sensor is not exposed to what it is supposed to sense.
However, the maximum value is the same as before.

Have I decreased my sensitivity or increased it?

I have definitely narrowed my range of output values.

Here is a link to the sensor DataSheet


texts: Is the SPI Interface just a protocol or actual hardware?

texts:
I want to use the SPI interface between a PIC and an ENC28J60. However, there are no pins on the PIC called MISO or MOSI that I can use for SPI.

So is SPI just a protocol, which I can use with any PIC pin (by just using any I/O pin, for example, in the same way to communicate with a DH22 sensor), or is SPI hardware (like UART)?


texts:
I'm designing an MCU based acoustic guitar tuner. I've broken the frequency spectrum from note C2 (65.41 Hz) to note C5 (523.25 Hz) into many sub-bands to give the user an accurate depiction of what note they're plucking. The note letter, number, and an indication of whether they're slightly sharp, slightly flat, or well-tuned will appear on an LCD.

The problem is that I can't see a way to avoid a massive if-else chain to determine in which band the input frequency lies. I've got 66 cases of 'else if ()', and this seems very slow/inefficient/silly to me. I need to figure of what note they've played and get it out to the LCD before the next pulse comes in. At highest frequency, this gives me a little less than 2 ms. Just clocking out 32 bits serially to the LCD driver takes up a decent amount of those 2 ms, so I need to figure out in which band the frequency lies fairly quickly. Can I do anything to improve the software and avoid a ridiculous amount of if-else-statements?

Edit for more information:

I'm programming in C on an AVR ATmega. To associate a frequency with a note, I'm using the formula: frequency = 440 * 2^(x / 12), where x is the number of half-steps away from A4 (440 Hz). An input is well-tuned if it is within +/- 0.25 half-steps from its centre-frequency. It is considered flat if it is less than 0.25 half-steps from centre but greater than 1 half-step from centre (where the half-steps are negative with respect to centre). It is sharp if it is more than 0.25 half-steps from centre but less than 1 half-step from centre (where the half-steps are positive with respect to centre).

For example:

G2 flat = [92.5 Hz, 96.6 Hz]

G2 good = [96.6 Hz, 99.4 Hz]

G2 sharp = [99.4 Hz, 103.8 Hz]

Where G2 centre frequency is 98 Hz.


texts: hijack project microtransformer doesn't work well

texts:
I am working on a project that need to get energy harvest from smartphone headset jack.I find hijack project has a solution.the energy harvest circuit of it is below:

it use coilcraft transformer LPR6235PMR. datesheet is below:

http://www.coilcraft.com/pdfs/lpr6235.pdf

I built a circuit exactly the same and use my phone to generate an sine signal with 22khz.It turned out works fine partly.It indeed convert AC to DC.But power efficiency is only 10% probably.I find out the main problem is the transformer:If input frequency of sine signal is 580khz. everything is fine. But if frequency is 22khz as hijack's suggestion.the voltage draw about 80% percent at L1 part then increase 20 times. So turns ratio is only 1:4.

at first, I wonder whether or not LPR6235 can be as step up converter of smartphone audio output. Then I find lumu use this transformer.(LPR6235LMR turns ratio 1:10 almost the same)

someone also had  used it and worked fine.
http://www.avrfreaks.net/forum/harvesting-power-headphone-output

("My coil samples arrived from CoilCraft, part number LPR6235-253PMLB(20:1).
Feeding the primary with with one channel of 20KHz sine(highest frequency my iPod Sig. Gen. app will do) at max amplitude results in a no-load secondary of 13.6V p-p. This drops to around 10.5V with a 2k2 load resistor.
I reckon that, since I'm going to need one schottky anyway with a FET bridge, I might as well use a conventional bridge, since:
a) That will only introduce another approx. 0.5V drop.
b) I only need 3 to 3.5V anyway.
I will try paralleling up the L and R channels to see what effect that has.
John")

so I guess it should work. But I can't find what the problem is.why my transformer exactly the same one doesn't has 1:20 turns ratio.

SOS!!!!!


texts: Internal and external channels of ADC in a microcontroller

texts:
I am trying to select a microcontroller for my project. I need four ADC channels to sense various voltages and currents. In the datasheets of μC devices, internal ADC channels and external ADC channels are mentioned.

Can someone explain what is the meaning of this and also what is the difference between internal and external ADC channels.

for example:

MSP430 has 8 external and 2 internal channels.
STM8S105 writes 8 internal channels.


texts: Are there types of passive RFID tag which can connect to control logic?

texts:
its been a few years since i've done any electronics but have been asked to research the viability of an idea and have gotten stuck...

We want to transmit a timing signal from RFID readers which will be picked up by tags and used to control a simple switching of an led. The led will be on a powered circuit, and will fade over a few seconds, but essentially will be turned on when the reader emits the pulse.

I suppose this could be done with a standard RF circuit, but on some of the readers the communication will have to be 2-way (recognising a tag is within range and acting accordingly)

The reading/writing of data to the tags is not necessary at all.

Is it possible to use an RFID tag which can be used as a switch for the LED control circuit?

Would there be a better tech to use for this?

Thanks
Sean


texts: What are the tradeoffs when building a modular battery pack

texts:
I want to build a 120 v / 128 Ah battery for an EV conversion project (small car with short range). I plan to base this on 18650 size lithium-ion batteries (recovered from old laptop battery packs).

To enable distributing the batteries around the car, I would like to do this with a number of modules wired together.

My first idea was to have 34 modules (34 x 3.6 = 122.4 v) of 64 cells (assuming ~2Ah capacity, so 128 / 2 = 64) wired in series.

I could also do this differently with fewer modules of higher voltage.

What are the considerations here and what are the benefits/drawbacks of choosing modules of different voltage/capacity? If the modules are spread around the vehicle, would my initial idea of 34 modules in 64p configuration lead to more resistive losses?


texts: Communication between two arduino using digital pins

texts:
I want to virtually simulate a flow sensor with a second Arduino that is getting controls from a PC through Serial COM port.
The flow sensor is a hall effect sensor so it either transmits LOW or HIGH level.

Is it safe to directly connect a digital output pin from #1 Arduino to digital input pin in #2 Arduino? Should a resistor or a diode put between the two pins?


texts: How does 3 phase AC generate more voltage than single phase? Aren't the wires connected in parallel?

texts: If you connect two voltage inputs in series it results in a higher voltage, if you connect them in parallel it creates a higher capacity / max current, but voltage is unaffected. If you use 3 plugs, one to each phase of the AC line as shown below, why does this generate higher voltage rather than just higher current? I don't quite understand. Also what I don't get is how they can power something if the sum of the 3 phases is 0 volts (which is the reason that 3 phase is used).


texts: Unstable 11-13.8 volts to 12v regulator. DC-DC buck or Zener diode, how to do it better?

texts:
I have 12v power source Mean well PSC-60A with UPS function and acid buttery.
In datasheet says, that output can be regulated from 12-15V - but it's not true, because tested results for output was:

from 11v(when not connected to 220v and buttery discharged)
to 13.8v(when connected to 220v and battery charged)
impossible to regulate output to 12v on charging(min about 13v)
regulating output voltage affects to battery charging voltage (

How to get a output with voltage of not more than <=12 volts (+/- 0.5V) with max 2A load on peak (avg load 500-800mA) from this 11-13.8v source ?

Output should be less or equal to 12v.

Which option is better, how right:

use DC-DC buck converter, like  D-SUN MP1584 ?
or simple shunt regulator with zener like 1SMB5927BT3G  ?

Help me please with this.

Part of used scheme


texts: STM32CubeIDE / Keil IDE = Is code portable for STM32 Discovery board?

texts:
Somebody gave me an STM32F429I-DISC1 board to build a simple data logger.  I (blindly) went to the STM website and grabbed the STM32CubeIDE and ran the demo...board works fine.  Now I'm trying to get started on the project itself.

I see many examples of projects with the Keil IDE.  Can I just grab the source code from these examples and import it into STM32CubeIDE?  I assume I'll need to reconfigure (?) the I/O pins and hardware references, but will it generally work?


texts: Is there a current DAC which has 0 current (< 1 nA) for an input code of 0? I am driving an LED, so would it make sense to use bipolar supply rails (where a negative output would reverse bias the LED and give 0 current)? For my project the current error must be less than 1 uA and the FSR need only be greater than 200 uA. My current design uses an 8750 from ti, which has too high of offset current (0.01% of FSR = 2 uA).


texts:
I am using a capacitor which is rated for 630V DC. I want to know the AC voltage rating for this capacitor.
This is the capacitor.
This is its datasheet.


texts: Strength of a pulsed electromagnetic field

texts:
Forgive me if my question sounds a bit naive:

I have built a coil (no solid core) out of an insulated copper wire, and I calculated that it has 8 ohms of resistance. I tried it and it gave me the result I expected. I am using a professional (meaning - it can stand a lot of abuse) audio amplifier as a source of (pulsed) power. The amplifier automatically adjusts to different resistance - from 2 to 8 ohms. Currently it is running at 8 ohms.
Now, if I built another coil using exact same specs, EXCEPT 50% shorter wire, the coil would end up having 4 ohms of resistance right? That would further mean that it should give me a more powerful magnetic field I hope.
If I then connected this new coil to my audio amplifier, the amp would adjust itself to the new resistance, and hopefully would be able to deliver more power. This amp is rated at around 800w in bridged mode, at 8 ohms and much more (1200 W I think) at 4 ohms.

Am I right to believe that lower resistance coil will give me a stronger magnetic field all other things being equal?

Any input is appreciated!


texts:
I have an updatable project with stm32f407. Code produced by cubeMx. Updater code check new update from internet and if is avaliable write main program on 0x08020000(sector 5) and this updater code  on 0x08000000(sector 0 and sector 2 size is less than 32kb)

I am writing a code(will be like main project on sector 5) can update the updater code on sector 0

My problem is when I erase sector 0 AC6 give an error for address wrapping and  STM32 stop working. I think is because of sector 0 has a special situation. there is no problem with erase other sectors. Is there a anyway to erase sector0 with a embedded program? The problem begin after delete 1 sector. I dont know what to do. (sorry for my bad English)

                              for(data_sayac=0;data_sayac<=filelength/2;data_sayac+=2)
                              {
                                 // UPDATEDATA_ADDRESS defined 0x08040000 (sector 6 where my new updater data copied from internet)
                                 // UPDATEDATA_ADDRESS2 defined 0x08000000 (sector 0 where my new updater program copied from sector 6)
                                  Data1=Flash_oku_halfword(UPDATEDATA_ADDRESS+data_sayac);
                                  if(Flash_oku_halfword(UPDATEDATA_ADDRESS2+data_sayac)!=0xFFFF)  // if sector is not empty erase first
                                  {
                                     HAL_FLASH_Unlock();
                                     Get_Sector= FLASH_If_GetSectorNumber(UPDATEDATA_ADDRESS2+data_sayac);  // get sector number by address
                                     FLASH_Erase_Sector(Get_Sector,VOLTAGE_RANGE_3);            //erase sector
                                  }
                                  Flash_yaz_halfword(UPDATEDATA_ADDRESS2+data_sayac,Data1);  // write halfword

                              }


texts:
I have a 12 volt Ni Cad Screwdriver battery (to be exact, it is a Black & Decker Firestorm)  I would like to find the amp-hours of the battery. The battery doesn't say anything on it (except that it is 12 volts), and I couldn't find any info online. I have no amp meter for testing amps drawn/time, but I tested a 12 volt 21/5 watt bulb and it lasted around 45 minutes. I did the division of (21/5)/12 and got .35 amp hours if it lasted an hour, but it was only 45 minutes and that would be less than .3 amp hours. I don't think this is true. So am I doing anything wrong and if so, what should I fix, and how can I find the amp hours?

edit:  The model number of the pack is ps160 12v type 3 power pack

edit 2: I just figured out that the 21/5 means there is 2 filaments and doesn't mean "21 divided by 2" so I probably used the 21 watt because I used the brighter one.


texts:
I am working on a project that will digitize an audio signal from a standard RCA jack and transmit that signal using Bluetooth to a receiver and then convert it back to an analog signal which I will output to a speaker.

I know that I will need 2 microcontrollers that will handle Bluetooth as a receiver and transmitter. However, I'm not sure about what microcontroller will let me do this.

Would an Arduino BT (transmitter) allow me to send an audio signal wireless via Bluetooth to another Arduino BT that acts as a receiver? I'm not quite sure about the sampling rate or transfer bit rate that allows me to do this.


texts: What is the effect of multiple Register file ports of a CPU?

texts:
Register file ports are a means to get data in and out of registers in a CPU. The concept of having multiple ports is not too clear to me.

QUESTION

Assuming you have 2 read ports, does it mean different stages of a CPU pipeline can simultaneously read from the register file (same / different registers)?


texts: SIM900 Circuit Design. Where to connect PWRKEY of SIM900.?

texts:
I am designing a circuit for SIM900 with a MCU. I have never designed the circuit for SIM900 so thought of posting question so that someone can review it.
As per the datasheet, SIM900 works on power between 3.2v-4.8v. For this I have used LM317 with 150 & 370 resistors. So it will give output voltage of 4.33v. Below is the schematic for it:

VBAT is the output voltage of 4.33v.

Now in SIM900 I have connected TX RX pin to the MCU and have made connection for status and netlight, SIM Card connector. I have connected VBAT and GND. But I am confused with PWRKEY connections. Below is the schematic :

I don't have an idea about PWRKEY. I have a GSM Module and they are using a switch button for it which when pressed connect it to ground. But I do not want this. Is there any alternative for this. Also please review my circuit. Thanks.!


texts: What should i be concerned about when powering a 10A load from 120VAC

texts: I have something that needs to be powered 25 feet away from the wall(120V). The load requires 10A of current. I'm worried that line inductance would deform my input voltage and lead to a non ideal power factor. Are my concerns justified? Do i need to add a PF correction circuit near the input?


texts:
I am a beginner at electronics.

I don't have many tools and stuff, so I am forced to solder by hand.

I don't have a pcb to solder on, so I usually just solder the wires together, but it's really difficult without a holder.

Is there an easier way to do this? If not, is there a substitute for a wire holder?

Any help would be appreciated.


texts: 1.8v GPIO controlling 5v 10mA solid state relay

texts:
I have a Crouzet 84 134 900 solid state relay that I need to control with a 1,8V GPIO output from a Gumstix Overo Summit expansion board. I've tried the circuit drawn up for me in this answer, however my voltages are different and I don't know how to change it to make it work in my current situation.

I tried to modify the values using this "transistor calculator", and it said I needed a 100 ohm resistor instead of the 160 ohm. But when coupled to the relay, switching the GPIO output made no difference, the relay always got 5V and enough current to be on.

The GPIO output gives me 1.8V and 0.1mA. I have a power supply of 5v 2A available. The solid state relay requires 3-32V and 10mA. I have a few 2N4401 and 2N2222 available. Can I  do this with the components I have, or is it a too great amplification for the transistors or something?