texts: Understanding the Practical Application of a Simple Antenna made from Coax

texts:
I am here today to gain a deeper understanding of the fundamentals of using antennas in RC applications. I am trying to understand what exactly is going on with a particular 2.4GHz receiver a picture of which is attached.

It's somewhat difficult to see, but these are 2 small coax wires soldered to the board with the center conductors soldered to pads separate from the shielding (obviously) which I assume is just grounded. So I have 2 questions:

Would these 2 wires be 2 separate antennas or 2 halves of a single dipole?
In what way does the shielding effect the antenna? Specifically, if you were to cut the wire down (significantly changing the overall length of wire) but strip away shielding such that the exposed length of center conductor is unchanged, how would this effect the performance of the antenna?


texts: How can I calculate the maximum output power?

texts:
I need some advice to my summer project, I would like to get max 150mA from 220V. After some research I build up the following circuit:

In the A and B point I would like to connect a bulb and control the power on the light this is why I'm using the X2 TRIAC. In the C-D point I would like to connect a Li-Ion battery charger(MCP73871-Microchip), because I also need a battery to provide the necessary power when the X2 is off. To regulate the voltage I also would like to connect a buck regulator(MCP1603) on the output of the MCP73871 to have a constant voltage. After this I will connect a microcontroller to control the power on the bulb. The control circuit need max 40mA of current(microcontroller+buck regulator+charger+sensors).

My question are:

Am I in a good way?
Is this concept good, where can I improve this circuit/idea and how?
How can I calculate the maximum and minimum current in the C line?
If I would have a 200mAh battery than a 100mA charging current would be sufficient? What is the minimum charging current for 100mA


texts: What happens on the STM32 when two pins are configured to have the same alternate function?

texts: Reading through the STM32F051 manual, it looks like it's possible to configure the same alternate function on two pins; for example, you could have multiple USART1_TX pins at the same time. Or for example the more problematic case of two USART_RX pins. The manual is silent on this case. Is this legal/safe? Is this useful?


texts: Benefits of using an External A/D converter with ATmega128

texts:
I am new to electronics and working on my first project.  Can someone explain why you would use an external A/D converter instead of the on board one?

According to Mplabs the ATmega128 has a  8-channel 10-bit A/D converter? is it just less accurate?


texts:
I have a digital down counter which is supposed to count from 9 to 0 and then it goes back to 9 (bottom) but it only goes back from 9 to 8 and then back to 9 and I don't understand how it works.
Note that before I made that circuit I had connected the inputs of the gates to Qbar without a NOT gate of each JK  flip flop but it counted until 1 so it didn't make the job it had to make.

What am I missing?


texts:
For our senior project we are making an electronic door lock controlled by a raspberry pi. We created a proposal which was approved for all the specs for creating the device which we have to abide by. In our proposal we specified that we would use a DC Motor for a broad range of options.

We found that a solenoid was a great way to accomplish our project. However when we asked for approval our advisors repsonse was:

  Not sure how a solenoid is a DC motor.  Please explain.

So I looked up the definition of an electric motor which is:

  An electric motor is an electric machine that converts electrical
  energy into mechanical energy

Which I think fully describes a solenoid because a solenoid works by using current through the coil (electric energy) which creates a maganetic field which creates linear motion (mechanical enegry) to move the metal post.

Would you agree or disagree with this assessment?


texts: Is this a limit switch design? What switches needed for this project?

texts:
I wish comments on how to best achieve a design involving two limit switches on a DC motor, but which does not reverse the motor.

I've researched this design already on this forum; here's my work, I could not find an answer hence this post.

Circuit for a DC motor with 2 microswitches reversing direction

(and several related posts)

My design does not involve reversing a motor.

Operation of device:  a programmable timer controls an AC power supply, AC2.  A seperate AC source, AC1, powers a heat lamp controlled by a AC Thermostat.  AC2, via a transformer, powers a DC motor.  The DC motor has a shaft that always rotates clockwise, and an “arm” that contracts two “limit switches” (SIC: not sure if that’s the right term!) such that: (1) when Limit Switch 1 touches (brushes past) the DC motor Arm at point “A”, the power to the DC motor is cut (but the heat lamp continues to operate on its own circuit).  Then, after a certain time, the DC motor is activated (powered on), by the programmable timer (or is there a better way?), and the DC motor shaft continues to rotate until the Arm touches Limit Switch 2, whereupon the power to the DC motor is cut for a certain predetermined time, and the process repeats. How to build this, using off-the-shelf components?


texts: conventions in signals naming in datasheets

texts: What does it mean when the datasheets lists the signals between parentheses as shown in the figure below?


texts:
I have a circuit like this:

I am using a LT1719 for the Schmitt trigger. The Schmitt input signal is intended to be a 6 kHz waveform of 0.6 V pk-pk amplitude.
When I test the Schmitt with an individual signal using a function generator, it is working like this: enter image description here.
It means that the Schmitt working individually. However, when I connect the passive LPF output to the Schmitt trigger, there is no Schmitt output even though the LPF output is has a DC value of almost 0.7 Volt. (While is was totally zero crossing before connecting to Schmitt).

I have checked using a buffer between LPF and Schmitt to reduce the loading effect but there was no output again.
Can you please help me. Thanks.


texts: problems with Lattice Reveal Analyzer - JTAG chain with multiple devices on the chain

texts:
I have a board with JTAG chain with 2 devices - (1) TI MCU (2) Lattice MachXO2, in the chain.
To be able to program the FPGA, I'm using this configuration in Lattice Diamond:

and as can be seen the programmer successfully program my FPGA device:

so next step I want to use Revela Analyzer for my FPGA design,
So I created a really simple Reveal project that running on a clock coming from an external oscillator and check really simple logic inside the FPGA.
The next step is to configure my Analyzer:

Because I'm using multiple devices in JTAG Chain, I added the XCF file which the Programmer created as the GUI requested.
In the last step when I trying to run some waveforms, I get this error:

Any idea or lead to why I getting this error?
anyone worked with multiple devices on JTAG chain and had a hard time debugging the FPGA device and can tell me how he encounters some of his problems?
any additional information will be given if someone asks for it.
Thanks!!


texts: Low Budget Environmental Chamber - Product Testing

texts:
We have a product in which we are experiencing failures due to rain water (presumably) penetrating the case and dripping onto the circuit board. I believe we have the source of the leak identified and fixed, however, I'd like to perform some thorough testing. I'd like to simulate a few different situations...

High ambient temperature (~120 F). The other extreme would be nice but I can't imagine an economical means to generate low temperatures.
I'd like to cycle between wet/dry such that it experiences a deluge and then a drying cycle. I want to see if the gaskets sealing the enclosure are affected by cycling.
I'd like to create a humid environment as well.

At the moment I envision a simple 4'w x 8'l x 8'h enclosure with a basin of water. A pump would circulate water from the basin up to the top of the enclosure where it would feed through a PVC pipe with aerators/sprinklers pointed directly at the devices under test. Just above that (so as not to get wet) a few 200W infrared heat lamps would be directed at the devices as well. The whole enclosure would be sealed with a 30mil poly.

My budget is roughly $400. Any suggestions or thoughts on how to get the most bang for my buck?


texts: Problem driving 4 PhotoMos relays with Rasberry Pi and FET

texts:
I am using 4 PhotoMos relays to switch some signal lines and have ended up the board below to switch a bank of four relays (the datasheet for these is attached at the end).

The relays are powered via the 5v line and switched on via a GPIO pin attached to a transistor. I am using a Pi v3 and the standard power supply rated (5v, 2.5a) This setup seems to work in some instances and not others, specifically it reliably switches on 3 out the 4 relays (but not consistently the same 3). I have doubled checked the board for shorts or misconfiguration but all seems in order.

I am relatively inexperienced and heading out of my depth and would be grateful if someone could review the board and recommend whether it is good, bad or ugly and whether there is any modifications I need to make for reliable operation.


texts: Interface method to measure loss tangent of a leaky capacitor

texts: I have a sensor which functions essentially as a leaky capacitor. The resistance between electrodes with a dielectric in between is the measured parameter. The capacitive reactance is large, on the order of 10e3 to 10e6 ohms, however the resistive component is small, on the order of 100 micro ohms. I want to measure the loss tangent of the capacitor. To do this I’m going for a Schering bridge, then an amplifier circuit. Is this the best way to go about this problem? The bridge values have to be very precise to balance it, is there a method that doesn’t require such precision? Cheers


texts: Calculate capacitance i.a. via reactive power

texts:
The ampermeter of the following circuit shows 10A (AC) and the voltmeter 220V (AC).

Furthermore its known that:

$$ cos\varphi=\frac{2}{3} \\ f=50Hz $$

I calculated the following:
$$
P=UIcos\varphi =1466.67W \\
Q=UIsin\varphi = UIsin(arccos(\frac{2}{3}))=1639.78var \\
R=\frac{P}{I^2}=14.67\Omega
$$

Now I also want to know the capacitance C. I found the solution to be:
$$
C=\frac{I^2}{2\pi fQ}=\frac{I}{2\pi fUsin\varphi}=94,1\mu F
$$
But I do not really understand the formula. Can someone explain me how it is derived?


texts: Why do layout footprints for Crystals often define via keepouts?

texts:
For example, one of the EagleCAD standard footprints for an HC-49U package through-hole crystal (mounted horizontally, so that length of the "can" lies against the PCB) looks like this:

The green "shaded" area is the vRestrict area, which restricts the placement of vias in the designated area for design-rule checking (DRC). Why is this an important consideration? A follow-on question that is begging to be asked in follow up, is why not also a bRestrict and tRestrict to prevent any copper (e.g. a ground plane or a signal), and is that something I should do anyway?


texts: How do I see the resonance of a high-impedance coil with a VNA?

texts:
When it comes to measurements with VNA, my experience tells me that whenever there is a "dip" in the S11 parameter, your takeaway should be that there is a resonance there (this is how the bandpass of a filter or an antenna is most commonly calculated).
However, for circuits with very high Z, basically everything is reflected, so you cannot really use S11 to measure them. In fact different sources in literature indicate the "series/transmission" as the correct setup to measure a high-impedance DUTs, whose Z is then calculated through S21.
How can I identify the resonances in this case? In the following example I measured a big coil and saw both how its S-Parameters as well as the impedance calculated from them looks like. I do not believe there is a resonance by marker 1, but I might be wrong.


texts:
Just an art project with a D.C. Motor running at 5 volts. I'm interested in the aesthetics of the switch and am looking for something vintage in look. Question: what types of switches can I get away with/search for? Will most anything that completes a circuit between two wires suffice?

Thanks in advance.


texts: PCB/SoC component licensing restrictions

texts:
Let's say I plan on building a consumer electronic system (some electronic product). This system would have a PCB and a plethora of various components: LEDs, transistors, resistors, light sensors, microphones, a power supply, etc. I would obtain these from a distributor or perhaps even directly from a manufacturer.

In addition to purchasing them from a supplier, do I also owe royalties or other licensing-based fees for each of these components? What criteria/factors drive this answer?


texts: Current and power analysis for DC Buck Converter simulation using PSpice

texts:
I have a simulation circuit in PSpice that I got from digikey for my part I ordered. I simulated and found my configuration outputs the correct voltage but I need to do further analysis on the current and power.

In the physical design I don't have the load resistor R3 or the current pulse source. I understand the voltage pulse / current pulse source being used in the transient analysis but I'm not sure if the current pulse affects my ability to read the current output.
(Also the output does achieve 3.3V I just grabbed an earlier point before it was complete.)


texts:
We are using RTL8152B ethernet to USB PHY for one of our projects, After debugging the board I found the IC to be abnormally warm even when there is no network traffic. I probed using the Multimeter and found that pin 12 which is connected to decaps 41 and 42(in the schematic) showed 0.5V but should have reported 1.05V voltage according to the datasheet, to rule out cap failure I removed it and checked the resistance and it was showing 39ohms which wasn't the case in other boards. I did some digging and found out some useful links which I have included in this post.
After reading those sites I thought maybe because of the wrong schematic the IC has failed but I'm not certain. I want to know whether I have connected the center tap and diff pairs properly i.e. pulling those lines to 3.3V. page 17 of the guideline doc says that PHY side CT pins are connected to cap and 0 ohm which is DNP but in my schematic, it's pulled to 3.3V. Please do note that we have a POE block too, I have a crude understanding that CT pins are used for power delivery. But the board with the issues doesn't have POE block populated. On another Chinese forum, someone mentioned that removing the pull-up on the CT line reduced current consumption. I want to know whether the schematic is wrong and is the PHY current mode line driver or voltage mode and what's the role of the ct pin in driving the signals.
If someone could shed some light on this issue I would be grateful.
Thanks in advance
Layou guideline
Chinese blog

Datasheet of PHY
RJ45 magnetics


texts:
I want to connect a BJT as a zener diode, that is operating in the avalanche mode when the Base and Emitter is reverse biased. My question is if the data sheet states the forward current for Base and Emitter, is this current still relevant in reverse bias mode, or is it less for some reason?

Cheers

Kv


texts: BJT power dissipation - Which value to use? (Ta vs Tc)

texts:
I'm using a TIP120 (Darlington pair BJT) brought to saturation for a project of mine. I have \$V_{CE(sat)}=1V\$, \$I_C=2A\$, \$V_{BE}=2.5V\$ and \$I_B=0.005\$A, which give me a total power dissipation of:

\$P_D=V_{CE(sat)}*I_C+V_{BE}*I_B \approx 2W\$

When I look up the component datasheet to check the absolute maximum ratings, there are two values given for power dissipation: one at 65W (@ \$T_C=25°C\$) and one at 2W (@ \$T_A=25°C\$), as seen on the image below:

So my question is: what is the difference between the two values? What is the difference between \$T_A\$ and \$T_C\$?

Sorry if this is a common question, I've searched everywhere to try and answer that question, but search engines are not very helpful when I want to know the purpose of parameters found in electronic datasheets (if there exists a glossary for the most common parameters found in datasheets somewhere, and someone has a link, I'd be very happy to use it!).

I suspect that I should use the first value for some reason, but given that my calculated \$P_D\$ value is pratically the same as the second one, I don't want to take any chance and destroy my future setup, making all that magic smoke escape...

Thanks!


texts:
I am unable to run ltspice simulation. I have tried changing the solver to alternate, adjusting Gmin and Trtol, Changing integration method. Always get the same error.

Error message: Analysis: time step too small; initial timepoint: trouble with schmitt-instance a:u1:4


texts: Measuring Frequency Synthesizer specifications

texts:
I need to measure all the electrical specifications of the Frequency Synthesizer KSN-2346A+ from Mini Circuits that appears in this datasheet: https://www.minicircuits.com/pdfs/KSN-2346A+.pdf

but the problem is that there's no information about how can I start. For example, in that datasheet an Evaluation Board (TB-567+) is mentioned, but I don't know if I have to use it or not, or why would prefer using it or not. And there's no Application Note or nothing. The evaluation board "datasheet" is just the circuit that it uses, but nothing is specified.

So I would like to know where can I get more information, or if any of you used this circuit or measured something similar or anything. I'm reading about others Frequency Synthesizer but I need to measure the specific characteristics of this one.

This is what I understand from the TB-567+ datasheet:

in CON4 I have to put a signal generator with an output impedance of 50 ohms and a frequency of 15 MHz.
in CON2 I have to put a DC signal of 10V

So,

what do I have to connect in CON1?
I suppose that CON5 can be measured with a Spectrum Analyzer. Is that OK? Or is there any other instrument that is better?
what do I have to connect in CON3?

Thanks


texts: Are the DRC errors in eagle software really important?

texts:
I am new to eagle Software and designing few development boards. When I finish my design and check for DRC Errors, I get lot of Dimension and overlap Errors. Components like spark fun SMD Crystal has many Dimension Errors and I am not getting rid of them.

I have also checked the DRC Errors in eagle examples like MSP430F5529 launchpad. The layout has got DRC Errors by default.

My doubt is whether I should take these Errors seriously or should I just give the generated gerber files to the fabrication!

I have attached the Screen shot showing DRC Errors to Crystal I was talking about.

Another Picture showing width error which I am not able to understand

This is a Picture representing small gnd to gnd Routing. Even this is showing a width error. Am I Routing wrong between different components?


texts: How effective is using a LQFP type breakout board to test microprocessors?

texts: There are many LQFP breakout boards available on the market today. An example can be found here. I was curious as to their effectiveness in prototyping microcontrollers. I'm speaking of building circuits that will allow for basic programming of the chip, and nothing more. My main concern is that higher frequency clock signals may become distorted if ran through a breadboard. Thank you in advance!


texts: What's the differences between a Resolver and a Synchro?

texts:
I understand a Resolver is a kind of Synchro, and a Synchro has 3 windings, 120 degrees phased from each other, while a Resolver has only 2, 90 degrees phased.

Both of them are used in agle measurement of a shaft, but it's not clear to me when to use one or the other and what are the benefits of each of them and disadvantages?

I can find lots of information about Resolvers and Synchros but I couldn't find any relating the two of them. A good example for resolvers applications and operation can be find here

As you can see in the documentations, Synchros can be used to track motion between two safts using jut 2 synchros...so if they are so "cool" why do people bother to use resolvers? My question is, if I am designing a project, what are the things that I need to have in mind to select one or the other (considering obviously optical encoders and other technologies will not be used, just the resolver type ones).


texts: How to use MOSFETS for single-button on-switch and input signal to microcontroller

texts:
I'm trying to create a single button circuit for the purpose of both powering on a microcontroller (probably an arduino) and then allowing the microcrontroller to control its own power (power itself off) and accept further presses of the same button as input ( functionally like the power button on a smartphone: Hold it down when the phone's powered off and it starts. Push it again when the phone's operating and it will bring up your power menu ).

From research it seems MOSFETs might be the way to go, and from reading I've planned a circuit. I have no experience with MOSFETs though (my first batch are on order now), and am not aware of the potential pitfalls. Attached an example circuit regarding which I have a couple of questions.

The intention is: when the button (a momentary switch ) closes the circuit initially, current is allowed to pass through M3 ( P-Channel MOSFET with no voltage at the gate ) through M1 ( N-Channel MOSFET with voltage currently applied to the gate ) and through to VIn. In the MicroControllers setup routine, it asserts D1 high, applying voltage to the gates of both M3 and M2, closing M3 and the startup circuit, and opening M2 which is now the persistent power circuit. The micro-controller can then choose to shutdown by asserting D1 low, which will shut off M2 and cut off the power.

Now the circuit is open and the power is on, the switch can be used as an input to D2.

1) Obviously... should this circuit work in theory?

2) Do I need to protect the MOSFETs against initial power burst with capacitors to ground or equivalent?

3) Is controlling M3 and M2 with the same voltage that they are allowing to pass like trying to pull yourself up with your own shoelaces? Should I buffer the supply in some way?

4) The example circuit at  wikipedia  shows a resistor connecting the gate to GND. Is this necessary? Should current be allowed to flow past the gate leg of a MOSFET?

5) Is introducing an input voltage to a digital input of a microcontroller before it has programmed its inputs and outputs safe? (Connection to D2 on power up).

---------- Edit 1 ----------

The duplicate question does provide an alternative (and it would seem quite robust circuit ) that achieves what Ive laid out above ( I hadn't found that answer in searching... Sorry ) My aims though with this question are:

1) To establish if this, or a corrected version, is a feasible circuit without the extra step of the regulator. Most arduinos and equivalents already have one on board, without the enable pin.

2) To understand a little more about MOSFETs.

From answers and comments below @Dave Tweed and @Joe Hass, is the the Threshold Voltage subtracted from the voltage across source and Drain then? Ie. If I supply 10V and the nMOSFET has a a threshold of 5V I can expect 5V at drain going to Vin? (And this doesn't happen in reverse with pMOSFETs?)

@Jon Watt thanks for the example. That answers most of what I'm looking to do, minus the digital input signal. A question though that may seem obvious, is R2 essentially a pull down resistor to keep the gate low when no input is applied from CTL?

Ideally this would be a standalone modular power circuit which you could put on a board and interface with any particular uC setup, with just Vin, Gnd, Vout, Shutdown and Input pins. Whether Shutdown and input are high or low logic doesn't really matter.

Also, in case the detail helps, for my particular application at the moment, I'm looking to have absolute power shut off, as this is for devices that should retain their charge over a long time and will only be sporadically used (once a day). So no sleep mode draining even minimal resources.

If I can understand the threshold problem, and nobody thinks this is beyond possibility, I'll have another go at drafting some potential circuits.


texts:
On a serial data link characters are transmitted data rate of 9600 baud. if characters are 8 bits and there is one start bit and one stop bit per character, then what is the number of characters transmitted per second.

Can someone explain to me how to get the answer.The given question is a multiple choice question (MCQ), so a short answer would work.Thanks in advance


texts: How does this carry look ahead block work?

texts:
This is a carry look ahead adder :

This adder is known to calculate one or more carry bits before the sum. From the figure we see that carry look ahead block calculates the carry C1,C2,C3,C4 . But i don't understand how does it do that ?  How does this block calculate the carry before the sum ?


texts: Adjustable linear led driver? Linear, not PWM

texts:
I'm working on a product that requires an led to output currents varrying from 0mA to 350mA and as many possible levels in between (~1000 would be sufficient I suppose). I CANT output a PWM signal to the led because that would defeat the purpose of my product (This is important).

Does anyone know an integrated circuit that allows this level of current control? Otherwise does anyone have an idea of how I could build a circuit to do this? I have thought about Voltage Controlled Current Sources built with op amps, but I have no experience with these or know of any specific circuits.

It also must be able to run off of batteries.

The LED is going to be moving at an extremely fast rate through the air and has to maintain a solid beam of light rather than a blink. thats why i can't use PWM.


texts:
For example, say that a system requires an input voltage of 5V, however, you only have a source that can provide 1V. The use of a voltage amplifier is obviously the solution to the problem. However, since closed loop systems with negative feedback are ideal for stability etc. and hence are used instead of open loop configurations (except for oscillators), but doesn't a close loop change the dynamics of the entire system? Because the new gain is given as:

So obviously the gain in closed loop is less than the open loop (as expected), but now the device that requires a 5V input cannot run as the output voltage is considerably less (beta is 0.5). I have made a MicroCap-12 simulation to convey what I am trying to ask:

So my question is, how to make thse configurations equivalent such that the closed loop outputs a voltage of 5V? Is it just adding another amplifier to amplify the voltage 1.43V to get to 5V? If so then what is the point of making it closed loop (other than stability)?
Thanks.


texts: Counting trigger events with oscilloscope

texts:
I need to count the trigger events number (how many times synchronization took place). The trigger mode is Normal on negative slope of one of channels (1-st).

Oscilloscope is Lecroy dda-120:

So it is a pretty old one. However - pretty powerful with a lot of math functionality. But I was not able to find anything to count the events (I've just found how to skip needed events number).

Any help would be appreciate: link to a full datasheet (I don't have one and didn't find any on the web), any information which would help to find needed setting, may be any collateral way...


texts: 12V LED strips in series with a 24V power supply?

texts:
I am purchasing 50x - 1Meter / 12V / 72 LED /Rigid SMD 5730 strips directly from china.  I don't know the LED manufacturer, nor the resistor being used.  (yes, this is a gamble)

The strip is one that could be cut at every 3rd led.  So, it seems that every 3 LEDs is wired in series, and there are 24 groups of 3 wired in parallel.

Each strip is specked out at 12V/18W.  I would like to take 2 strips, and wire them in series with a 24V 18W power supply.

(By series, I do not mean chaining them in parallel and calling it series like the billion articles polluting my google searches)

My question is, can I wire two 12V strips in series using a 24V power supply?  It seems like I can, but am worried I am overlooking something that I don't even know to ask, or I do not have enough information without the LED spec sheet.

Thanks!


texts: I have a little drone project that use among others thing two camera,these two camera use a battery Olympus LI-100B (Li-ion battery 3.6V 1350mAh ). On the drone the source of power will be a 3s 5200 mAh 11.4 V, i also will have a voltage converter to 5V, So should i just step down from the 5v to 3.6 and power the camera with it or there more in the story ?


texts: Long enumeration in VHDL to recognize a state machine

texts:
In order that Quartus II recognizes a state machine in a case / when statement the case must be applied on an enumerated type.
In my code I am using a case on integer number going from 0 to 230. And there are a lot of ranges like "when 34 to 50 =>" for instance.
What is the best and shortest way to enumerate in this case based on an integer? In order to let quartus recognize the state machine which helps me to analyse my implementation.


texts:
My knowledge is very basic. For this question I consider n-channel enhancement mode MOSFET.

I see some MOSFETs have 3 terminals, while others have 4 terminals. This forth terminal is the base terminal, and I think it makes sense to me. If the gate terminal is at a higher potential than the base terminal, the channel will form near the gate terminal.

However, the three terminal ones need the gate to be at a higher potential than the source to form the channel, and that confuses me a bit. What if the potential difference between the p-type body and the gate terminal is just high enough to form a channel on its own? Why would I need a potential difference between the gate and the source then?


texts: Triggering a relay for a set period of time when voltage drops below a certain voltage

texts:
So I need a circuit, that will trigger a relay for approx. 10 seconds when the supply voltage of the device drops below 12.5 volts.

Can anyone help me out?  And also what might I need to change int he circuit to select different trigger voltages?  for example if I wanted 11.5V trigger instead of 12.5V.  Thanks


texts: Does the pin order matter for an EPS12V 8-pin +12V connector?

texts: I am sleeving my PSU and somehow managed to get the pin order of the EPS12V 8-pin +12V connector mixed up. I know which sides the 12V and grounds belong on the connector, but am trying to figure out if the actual order of each color wire matters. From what I've gathered there is both 12V1 and 12V2 rails present, so I'm not sure if they can be interchanged with other 12V pins. Likewise, does order of black ground wires matter?


texts:
I am trying to make a timer for myself. I select how long the timer runs for via a switch. The timer should begin counting down via a tilt sensor (or just a momentary button/switch to start) and count down until time expires. When time is up, an LED lights up for 5 seconds or until the start signal is triggered again. When the timer is not active, I would like the circuit to be completely interrupted so as to not drain the battery. I would like the whole thing to be run on a coin battery. I was thinking a small relay to interrupt the battery, but I'm not sure how to make that work at all.
I am new to designing circuits and need help speccing out the components. I am leaning toward using a microcontroller to run the logic on. Is the PIC10F200 a good choice for this? Are there other MC's I should look at instead? I suppose that I could design this with a 555 or similar chip but I think the flexibility of a MC would be nice if I don't want to change the circuit to make changes. Plus it needs to consume very little power to prevent eating up the battery.
Again, the requirements are:

coin battery operated (CR2032)
Tilt switch triggers the timer
Timer length is 60 seconds to 20 minutes, selectable via switch.
LED lights up when timer is done

Any thoughts?


texts: Darlington transistor heats up : regulating transformer output

texts:
I am in great need of a 12v DC transformer. So I built one using some components I have lying around: the case of the transformer I have says 220 to 12V (which I don't trust because the voltage on the first smoothing cap is ~27V with no load/small load. The real DC voltage should have been 12/1.4 = 8.5).

simulate this circuit – Schematic created using CircuitLab

I am still testing this circuit and it almost works.

Boths caps used are 1000uF
R1 is actually a cap but I set it at 2k (max is 5k). This just sets the current on the diodes as the transistors uses very little of the current.
The transformer regulator is made with 18 diodes in series which drop ~12V. I don't have a Zener.
U1 is a 5v regulator MC78M05BDTR. It can take up to 500mA which is enough for the attiny85 and the two 7 segments displays (they are not always on) Datasheet
BD679 is a component I had at hand. Datasheet. Ic(max) = 4A (way more than what the circuit draws). Ib(max)=100mA
My digispark circuit is blinking at around 2Hz two 7 segment display.
As measured between Vout of the transformer regulator and U1, it draws :

157mA(max) at 9.6V(when displays are on).  16V on C1
20mA(min) at 10.6V(when displays are off). 24.7V on C1
Thus the maximum power is around 1.5W(max) and 200mW(min). The collector current is ~ the emitter one so I used that value when I calculated the transistor's power.

Tests with different loads:

1K load:      10.81V  9.13mA   26V on C1
100ohm load   10.16V  101.4mA  19.26V on C1
In these cases it works perfectly and it doesn't heat up.

The problem is that after approximately 20 seconds the regulator transistor BD679 starts to heat up and....cool down...and heat up...  Weird enough without the output filtering capacitor C2 it takes longer to heat up. The problem seems to be connected to the frequency at which I power the displays.

But I still can't figure it out: why does it heat up? Is it because of wrong wiring(and then I should fix it) or just because too much power is drawn from it (in this case it's normal to heat up).


texts:
I am confused about the concept of using a pin offset in bit banding. EG, given that PORTA has a base address of 0x40004000 and the 5th bit has an offset of 0x0080, the address of the pin should be 0x40004080
and I use this address to read/write to this bit.
My questions are :
1 - Is this address in the 1 MB bit band region or it's in the alias ?
2 - How can the sum of two different bins offsets + the base port address allows us to write to the two pins simultaneously? is it some sort of a mask ?
sorry if my questions are not clear, I am really confused.


texts: Designing a Morse code transmit/receive shoe

texts:
Thank you for considering my general question, which I assure you is serious!

I want to build -- or have built -- a magnificent shoe that can convert taps (front of the shoe) into Morse code and transmits it (two taps of the heel) to a remote computer to then run a "define: " query in Google. Then, upon automatically receiving the definition translated back into Morse code, receive the code transmitted from the computer to a small vibrating unit inside the shoe, which will play out the definition in a series of Morse code vibrations. The one tap of the heel will be for 'spaces'.

What do you think? Is this achievable if I consult with a physical electrical engineer and a shoe-maker?

(the purpose is for a magic trick that I am working on)


texts: I  am working on a PCB design layout, 3 PCB traces, 350kHz pulse signals (logic 3.3V and 0V) are to send via PCB traces. are there any design rules for this type of signaling through PCB traces?


texts: Frequency and phase response of various filters

texts:
I have been set the task, by my Computing teacher, to write a program to simulate a variety of fixed electronic filters (the circuits are fixed.) The goal is to plot amplitude and phase against frequency.

The problem is, a lot of the math involves complex numbers. For example simulating even a simple RC filter requires an understanding of complex impedance - something I don't understand (yet - still in college electronics education.)

Are there any "simple" formulas which can compute the response of a filter accurately?

Is there a good web resource for how to understand this?

A list of formulas for frequency vs phase and amplitude?

Ideally, I could extend it to all types RC as well as LC filters and other types like Butterworth, but that might get really complicated.


texts:
I saw a circuit that power series a RC parallel circuit, please refer its circuit picture as in the below.

My questions is, 1). Is it a filter? 2). What is its purpose? 3). What is its theory?

Kind regard, Zu Wang.

simulate this circuit – Schematic created using CircuitLab


texts: Eagle libraries for Automotive Header connectors

texts:
I am working on a diagnostic tool for automotive application that will be able to check wire integrity and offer a very quick way for technicians to know if there are any physical wiring faults while beginning an electrical diagnostic.

The connectors I will be interfacing with are fairly complex (never less than 100 pins) and are sold in bulk, however I have had zero luck finding any Eagle libraries for any of them, despite combing through Google, Eagle dev, and calls to TE, AMP, and a bunch of vendors. All of the connectors whose Eagle files I need even have the same "node", Automotive Headers. Anybody have tips for where I could look for these pretty niche, but still high volume connectors?


texts: Why is only the fundamental frequency component said to give useful power?

texts:
In most books it's said that the harmonic content in an AC line does not transfer power (just the fundamental frequency does), but no explanation. It seems intuitive, but why is that true?

Edit:
In the context of electrical power, so I'm imagining a distorted current waveform and a sine wave voltage.


texts:
1) As written in the task the L and H should be greater than 20h and impedance should be 50 ohms. Please help to adjust these parameters so that after changing the L and H I still get 50 ohms.

2) In the codes, in the last, I am not able to understand the Tolerance testing Part.

Codes:

%Clearing variables in memory and Matlab command screen
close all;
clear all;
clc;

%Problem data
L = 10;
H = 4.5;
h = 0.5;
w = 0.6;
epsilon_0 = 8.854*10^-12;
epsilon_r = 3.05*epsilon_0;

%Dimensions of the simulation grid in x (xdim) and y (ydim) directions
xdim=50;
ydim=50;
dx = L/xdim;
dy = H/ydim;
N_strip1x = floor((L-h)/2/dx); % number of node along x axis of the left strip
N_strip2x = floor(N_strip1x + h/dx); % number of node along x axis of the left strip
N_strip1y = floor((H-w)/2/dy);
N_strip2y = floor(N_strip1y + w/dy);
r = cos(pi/(xdim/L))+cos(pi/(H/ydim));
alpha = 1;
%Initializing initial Potential matrix & boundary conditions for V_init
V=zeros(xdim,ydim);
V(N_strip1x,N_strip1y:N_strip2y) = 1;
V(N_strip2x,N_strip1y:N_strip2y) = 1;

%Initializing maximum number of iterations
max_iterations = 500;
Z0 = zeros(1,max_iterations);
figure,
for i = 1:max_iterations
    clc
    display(['iteration n° ',num2str(i),'/',num2str(max_iterations)])
    V_old = V;
    for x = 2:xdim-1
        for y = 2:ydim-1
            % evaluate on the same line of the strips
             if x == N_strip1x && y > N_strip2y && y  N_strip2y && y  N_strip1x
                V(x,y)=epsilon_r*V_old(x,y)+alpha*(((epsilon_r*V_old(x-1,y)+epsilon_r*V_old(x+1,y)+epsilon_r*V_old(x,y-1)+epsilon_r*V_old(x,y+1))/4)-epsilon_r*V_old(x,y));
                V(x,y) = (1/epsilon_r) * V(x,y);
            end
            %evaluate outside the strips
            if x > N_strip2x || x  N_strip2y && y  N_strip2y && y  N_strip1x
                    V(x,y)=epsilon_r*V_old(x,y)+omega(o)*(((epsilon_r*V_old(x-1,y)+epsilon_r*V_old(x+1,y)+epsilon_r*V_old(x,y-1)+epsilon_r*V_old(x,y+1))/4)-epsilon_r*V_old(x,y));
                    V(x,y) = (1/epsilon_r) * V(x,y);
                end
                %evaluate outside the strips
                if x > N_strip2x || x  0
            break
        end
    end
    n_iterations(1,o) = i;
end
figure,
plot(omega,n_iterations);
xlim([0.9 1.02]);
xlabel('Omega')
ylabel('Number of iteration')
title('Plot of number of iteration versus omega')


texts: Time of charge of capacitor of complex circuit

texts:
I'm a newbie in this area and was reading about the time it takes to a capacitor to get charged known as τ = RC.

The question is, how do you calculate such time when a circuit is formed by more elements? Say I have a voltage attached to R1 which is attached to another R2 in parallel with a capacitor. What would the value of R be in this case?


texts: Misunderstanding of output impedance and linearity

texts:
When I read about Thevenin equivalent, it is mentioned it only applies to "linear circuits".

But I also see in texts and tutorials showing how to measure the output impedance of an actual device which is complex such as a power supply or a transducer. They measure the output impedance and equate the device to a single power/signal source with a single output resistance/impedance.

But these devices are composed of non-linear circuits. And the whole idea of Thevenin applies to linear circuits.

How come we can employ Thevenin in these devices conceptually? Is a power supply or a transducer a linear circuit?


texts: What temperature should I expect by lighting 3W-LEDs?

texts:
I have a PCB with 10 LEDs (reference : SPHWH2L3D30ED4TPK3) which will each dissipate 3 W (forward voltage of 3 V and 1 A passing through). The PCB is a circle with a diameter of 20 cm and LEDs are evenly distributed.

I need to know, when all LEDs are on, what the temperature of my PCB will be. But how can I approximate it ?

The datasheet of the LEDs is here : http://www.to-nichi.co.jp/pdf/led/LH351B.pdf

The only thing that they mention is the junction to solder thermal resistance, which is max. 6 °C/W. Normally the formula is : T_J = P*R + T_A. But I do not have the junction to ambiant resistance...

If you have any advice it would help. :) Thanks


texts:
How can Gilbert Cell circuit provide linear gain variation even though ID-gm relationship is nonlinear?
As I undertstand it, the vcontrol (the voltage at the gate of M5 and M6) changes the biasing current of M5 and M6.
This current are then copied by the current mirrors to M1-M4.
The ID of M1-M4 define their gm which defines the gain.
But we know that ID-gm relationship is nonlinear and ID M1-M4 change pretty wide.
Still I got not exactly but quite linear gain vs vcontrol.
Appreciate any hints or if you could point me to the right direction.
The x axis of the plot below is the differential control voltage that is used to vary the gain.


texts: Non-Inverting Op-Amp noise on the output when touched

texts:
I am using a non-inverting op-amp circuit (shown below) to linearize the output of multiple analogue force sensors. This is the circuit recommended by the manufacturer in their electrical integration document.The circuit is working and I am able Toggle between sensors by driving GPIO low for active sensors and high impedance for disabled sensors. However I have observed a larger amount of noise and oscillation in the output of the opamp when I apply force to the sensor with my bare hands. This noise is almost negligible when I apply force to the sensor whist covering the sensor with an insulative material.

I have found by increasing the capacitance of C1 to from 47pF to 1uF I have been able to eliminate the noise and oscillation. (Why is this?) however this is at the cost of having to increase the time between sensor readings to the point where it is not feasible for my application. The reason I must wait between sensor readings is the large capacitor will hold the voltage of the previous sensor for some time when I toggle between sensors.I have the following questions:

What is the likey cause of the noise/oscillation (image show below)
How can I eliminate this noise?
What is the purpose of C1 and why does increasing C1 remove the noise/oscillation.


texts:
I'm not an electrical engineer, I'm not even close to knowledgeable in electronics. But could someone explain to me how the switch on this actually provides power to the motor above?

I don't see anything that connects the ends of the battery to the actual wires that connect up to the motor. What am I missing?


texts: I want to simulate VDD rise. For example I want to raise 1.2V VDD to 4-5 Volts for tens of microseconds and lower back to 1.2V. Suppose I have a high rise and fall time pulse generator (200-500 picoseconds). My concern is that some digital ICs (like CPUs) have some capacitors on them to filter supply parasitics and serve as charge reservoir. Do these capacitors hinder the high rise and fall time of the signal generator because of their time constants? Can I still get a fast changing VDD in spite of the capacitors? Thank you.


texts: Obtaining Poles and Zeros from frequency response

texts: What is the process of obtaining the poles and zeros from frequency response plot or data. Any reference or Matlab code will be great help


texts:
For the following AB power amplifier VBB/2 is large enough such that both Qn and Qp are on for no input signal Vi, if output voltage is large and positive, it may be assumed that most $$i_{L} \approx i_{N}$$

What justifies this assumption?


texts: Bit error rate calculation for LIN protocol

texts:
I am having this microcontroller - S32K142 64 Pin 5V Core voltage
Microcontroller Reference Manual
I am using an 8MHz external clock.
I want to calculate the Bit error rate of my LIN Communication.
My LIN Communication Baud rate is 19.2kbps.
My questions :

Can I use the LPUART Module in the Mirocontroller for the LIN Communication?

How to find the Bit error rate for the LIN Protocol communication for my baud rate of 19.2kbps and external clock of 8MHz.

I found this below from the reference manual. But not sure, how to calculate the Bit error rate from this.

How to calculate the SBR Register value, OSR and the LPUART ASYNCH Module clock?

Please help


texts: Cutoff frequency of stacked low pass RC filters

texts:
How can I determine the cutoff frequency of a filter between V1 and the output marked with the red arrow?
All resistors and capacitors have the same value.
In the picture is a stack of battery cells (V1, V2, V3) that is connected to balancing circuit on the right.
What confuses me is how to treat R2 since it is "shared" with V2 cell.


texts: Full steps of coding and uploading source code to a micrcontroller,Bootstrap, bootloader,startup code

texts:
Correct me if I'm wrong.
I'm studying embedded systems, and I learned to develop a simple blinking LED project in C:

Writing source code.
Pre-processing source code.
Customizing and converting source code from c into assembly.
Compiling assembly code into object code.
Using linker script and including startup code crt0.o for linking and creating executable image.
Running controller.
Waiting for oscillator to be stable,power supply being stable too.
reset code starts at reset vector.
hardware initializing code starts.
startup code starts.
entry point of code "main".
main end executing.

I want to know what is the job of startup code after ending main. I read there is a job for it after application being terminated.

Secondly I'm confused between bootloader and bootstrap.

at last I believe there is a code embedded by manufacturer that is responsible for uploading my image file into my controller. what is it exactly?
most of readings refer to bootloader, others tell bootloader is not essential.


texts: MPU6050 showing inconsistent angle values

texts:
I'm using this Arduino code to calibrate and read from an MPU6050 accel/gyro sensor from an Arduino Mega.

The calibration and reading of values seemed to go well. However, I'm seeing some inconsistent values reported from the gyroscope. When my apparatus is placed flat, it correctly read a pitch of 0 degrees. When I tilt it forward by 90 degrees, it reads a fairly accurate -89.6 degrees. However, when I tilt it backward at -90 degrees...it reads -26 degrees.

Why is this? Could this be caused by mis-calibration, interference, or is it possible my MPU6050 is damaged or defective?

The default orientation of the board is with it flat, so the z-axis points "up". However, I've mounted the sensor with the y-axis pointing "up" and the z-axis points forward/backward. Would this effect calibration? Other than having to remap, my axis when reading data (which I'm doing), I haven't read any warnings about needing to explicitly enter this re-orientation into the MPU6050 code.


texts:
This question got me to wondering if there is a maximum theoretical voltage.  It seems to me there's a limit to how much positive or negative charge you could have--say, a container full of electrons and a container full of protons.

Edit, since it seems I'm not being understood:  Voltage is caused by a difference in potential between two points.  It seems to me that this potential is inherently limited by the fact that it requires particles to carry it.  I am NOT talking about a failure due to arcing.


texts: Why isn't my the LTspice cutoff frequency for my multiple feedback low pass filter not matching?

texts: I am designing a 6th order multiple feedback lowpass filter with cutoff frequency at 1000 Hz. I wrote a matlab script that calculated the capacitor and restore values. I combined all transfer functions together and got a bode plot with exactly 1000 Hz for my cutoff frequency, 6th order rolloff. FYI the gain K = 1. I even checked it with an online Butterworth multiple feedback lowpass calculator and got the exact same values. Now, when I build the schematic in LTSpice, the cutoff frequency is skewered and I cannot figure out why. Either it is something about multiple feedback topology is the issue, or I am missing something in LTspice. Any solutions or explanations to why LTspice is not giving me the correct bode response? Down below is my MATLAB plot, the online filter calculator, and my LTspice schematic and bode plot.


texts: What level of a square wave signal should be safe for TV receivers?

texts:
I am experimenting a bit with TDR (time domain reflectometry) and for it I am generating a square wave with up to 10kHz and a rise time of about 1-2ns.

Now I would like to put that thing to use and see if I can figure out more about some cable tv cables in a house where there seems to be signal reflection issues.

Unfortunately I can not disconnect all the TVs that are connected, so while my measurements may disturb reception, they may not be so high as to damage the TV set (or any other receiving device, or amplifiers).

While I can find lots of anecdotal descriptions that suggest the limit to be anywhere between 100mVpp and 1Vpp when I look at some professional TDR test equipment, their test signal level is specified to be 6V. However their signal is specified as a "half sine pulse" and not a square wave, and I have no idea if the higher frequency content of my square wave at such high levels will be any more harmful, considering the device is most likely coupled via a small capacitance to the tv cable.

So what is a likely safe level for such a square wave, and why is that so (e.g. because regulations require it, all industry amplifiers accept at least xVpp etc.) ?


texts:
I would like to design a comparator circuit with hysteresis, which will provide a PWM signal in the output as shown in figure 2. The first input of the comparator circuit will be a sinusoidal signal as shown below in figure 1 and the other input of the comparator fed by a triangular waveform. Is there any circuit which is suitable for this comparator circuit and for this purpose?

The power supply voltage is VDD=1.2V.

Which should be the DC level and the amplitude of the triangular waveform to achieve this purpose?

figure 1

figure 2


texts: Solar cell understanding of current vs applied voltage

texts:
I've been reading about the theory of solar cells, and doing some circuit simulations using the idealized model of solar cells. But I still feel like I have some problems understanding how the solar cell behaves and would like to check some things.

My understanding is that the current source in the solar cell model produces a variable current that depends primarily on irradiance, ranging from zero amps to the short-circuit current. Depending on the voltage applied to the solar cell, a portion of this current will flow back uselessly through the diode while the rest will flow out of the solar cell into the load. The voltage at which maximum power is extracted from the solar cell is the maximum power point.
So then my question is, if I have a battery, with a proper undervoltage/overvoltage circuit, and I connect it directly to a solar panel (ignoring any blocking diode for now), then the voltage across the battery will dictate the voltage across the solar panel, and some current will flow from the solar cell to the battery as long as the battery voltage is below the panel's VOC. The amount of current flowing in the battery will be given by the solar panel's I-V curve at any given battery voltage.
If I select the solar panel such that its maximum power point is achieved at a voltage near the nominal battery voltage, then the battery will extract reasonable power (near the maximum power point) from the panel, without needing an MPPT controller.
As I understand it the main downside of this approach is that the VOC will drop at low irradiances, moving the panel's maximum power point, such that the battery may charge inefficiently (or not at all if VOC falls too much) in low lighting conditions. The VOC also depends on the cell temperature.
And what an MPPT controller does is to apply a specific voltage across the solar panel to reach the maximum power point, by presenting a varying load to the panel, and then regulates that voltage to whatever voltage the battery needs, so that the solar panel can work efficiently across more lighting conditions and more diverse battery chemistries.
Is my understanding correct?


texts:
I trying to create a circuit with only one 555 to send HIGH on output(3) for very short time, like 200ms, then set LOW for something like 20~30 seconds.

Then I'm just need turn on circuit, then:
a) fast HIGH (~200ms)
b) long LOW (~20-30s)

I already able to make a "default" 555 circuit with stable HIGH/LOW in same timing (1000ms/1000ms), but I'm getting trouble to make this with different HIGH and LOW timmings.

Thanks.


texts: N-Mosfet switch circuit strange behavior laboratory power supply

texts:
I'm dealing with an N-Mosfet switch circuit to control, through PWM, the temperature of a heater resistor. The mosfet is a IRFS7430-7PPBF.
The load is driven at 12V and has a power rating of 80W.
Since I want to drive the load resistor with pure unfiltered PWM, I chose a mosfet with a very low RDSon and I didn't care much about the PWM signal carrier frequency. I'm driving the gate with 5V logic signal and I can provide current in excess of 20 mA. I tried to set different values of PWM frequency to drive the gate of the mosfet. At frequencies in range of several tens of thousands of herts (62.5 KHz) the mosfet gets very hot already at 70% duty cycle (3-4 A). Gradually decreasing frequency helps the mosfet to run very cool until no temperature difference can be felt at around 200 Hz. I explain this because of the switching losses in the mosfet which are very high due to a high internal capacitance.
However the mosfet is getting far hotter than I initially calculated. Why is this happening? Is it normal?
I'm fine running the mosfet at very low frequencies since I want also to be low in EMI emissions. The strange thing that I noticed is that the benchtop laboratory power supply which I am using to power the circuit starts behaving in a very strange way at low PWM frequencies. Even if I am far beyond the power and current limits of the power supply, it starts continuously changing the displayed value of voltage and current, as it couldn't hold those values. Then the C.C. and C.V. (current control and voltage control) lamps start blinking. These behaviour does not happen at high PWM frequencies. I tried to investigate whether a filter capacitor across the power terminals would help but it does not seem to produce any effect. I'm afraid that the circuit is producing some dangerous disturbances back to the power supply. How could I solve this?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm back working on my friend's 807 tube transmitter. I've had some previous posts on this and I'd like to thank all the people who responded for your help!

I bought an oscilloscope and a dummy load and almost instantly figured out the power problem. It's the 807 screen grids. With the current schematic, the 807 screen grids run at about 100v. Power output calculated across the dummy load is 4 watts RMS. If I increase the screen grid voltage to 250v, the output jumps to more than 10 watts RMS. The tube manual for dual 807s, class A, calls for 600v plates (which I have) and 300v screens.

Here's the problem: When I increase the screen grid voltage on the 807s, the modulation disappears. In the diagram, you'll notice the switch that controls the 807 screen grid voltage, also controls the EL84 audio amplifier plate voltage. What is the correlation here? What can I do to fix it? Do I need more peak to peak voltage on my input? I'm currently using an old cell phone with a tone generator for testing. Input voltage to the jack and 12AX7 is about 1.5 Epp.

Any help would be appreciated! Schematic is below. Thanks!


texts:
For some reason I have many bits with value 1, even if they are supposed to be turned off.
I tried to debug it with some LEDs and Keil uVision debugger. uC is STM32F103 The situation is:
I have 2 pins configured as output and 1 as input.

GPIOA->CRL = 0x00000228;

When I try to read IDR register(that contains input values, accessed with GPIOA->IDR) I expect to get something like 0x00000001 or all zeros if input is low. But for some reason I get 0x0000BF01, which means I have this stuff on input - 1011111100000001, which is obviously I don't have since I don't even use these pins.

What I tried:
From datasheet I found that reset state for pins is 4=0100. So I tried

GPIOA->CRL = 0x44444228;

This gave me values on IDR 0x0000BFF8, still werid.
Then I tried to also manually reset CRH register

GPIOA->CRH = 0x44444444;

This also didn't change anything.

Sometimes it outputs 0x0000B000... I don't know, maybe its a little random(noise pickup?).

What can be the problem? Do I assign something in a wrong way?

Basically this is all my code in the main, in the while I just access GPIO->IDR:

RCC->APB2ENR|=RCC_APB2ENR_IOPAEN; // Enable IOPA
GPIOA->CRL = 0x44444228;
GPIOA->CRH = 0x44444444;

And yes, I know that I can use std_periph library, my question is to learn why things happen that way, not to find workaround.

SOLUTION
Text below is valid for stm32f103, not sure about other stm32s.
It turned out that pins 12,13,14,15 on port A are for JTAG and CAN signals stuff, so they are "reserved" and not usable, unless you remap JTAG to somewhere else. Basically just don't use pin 12 to 15 on port A, you can ignore it by masking needed register or in case you want to read specific bits std_peripgh gpio library has GPIO_ReadInputDataBit(GPIOx, uint16_t GPIO_Pin) function, where you can also OR the pin numbers together.
The way I figured it out is that it was always same bits, I just erased the whole chip with STM32 ST-LINK Utility and checked if these bits are high again - and indeed they were high.
ALSO! Pins 3 and 4 on port B are also reserved for SWO and NJTRST and are also go high on freshly erased chip, so I suppose it is better NOT to use PB3 and PB4.


texts: How to combine 2 Solar panels for double A

texts:
Sorry I'm still a rooky in electronics so forgive me if I make obvious mistakes.

I have 2 small solar panels. 5v 160mAh. The 5v is alright for my project and I thought I could double the current by combining them. I read on the internet that I should connect them in parallel but I dont get the desired result.

All measurements are made under a lamp so not ideal conditions, I know. The Voltage stays the same at around 4.74V. But the current stays at around 0.06mA. Thats exactly what 1 Solar panel achieves. Not the expected 0.12mA.


texts: How to listen to radio communications from a transmitter?

texts:
I have two devices communicating at a frequency which I don't know. I want to listen to that communication so that I can replicate one of the devices and fool the other. Basically I want to reverse engineer the protocol.

So I would first need to detect the frequency, then I would need to translate the communication signals into some sort of (binary?) code so that I could start on reverse engineering the transmitted packets.

How should I go? What hardware do I need?


texts: Wireless DC motor controller circuit protection

texts:
I'm using an off-the-shelf 2 channel wireless relay/switch to control a 12 V DC motor. The motor is attached to a wheel which can be manually turned and generate back EMF.  How should I place diodes between the motor and the controller to prevent damage to the controller circuit?

My question was badly thought out ... the circuit looks like this:

When neither relay is activated, the motor is shorted.  If the motor is turned by hand, I assume it will damage it.   How can I prevent this?


texts: How precise are fluorescent lamps when mass produced? Is their emitted spectrum really identical or is it possible to detect a difference between two random lamps using appropriate filters with photo-diodes to calculate the amplitude of each spectrum peak and have some kind of Id for each lamp?


texts: How does to reverse items in an array type

texts:
I have a function that works with string passed to it. The string should be defined as "a to b" rather than "a downto b". I have the following questions:

How to find out if the string passed is defined in ascending or descending order?
Why do strings not have index 0? The minimum index is 1.
I have string p is 1 to 10, while string q is 10 downto 1, assigning one to the other generates error:

Fatal: (vsim-3607) Slice range direction (downto) does not match slice prefix direction (to).

Why?
How do I assign p to q or q to p in this case?


texts: How to obtain the dwarf2 file with STM32Cube IDE

texts:
I'm trying to simulate a project for an STM32F103C6 in proteus ISIS but for debug purposes labcenter's people says that I need the .elf file and the dwarf2 file (both of them in the same folder), then I' found that GCC generates the dwarf 2 file with the option -gdwarf-2 what I've put in Project Properties -> Build steps and in the pre-build command I've wrote the command -gdwarf-2, it didn't worked so I've changed the command to the post-build commands in the same tab. I've also noted that in Tool Settings are several options for what I think is to choose the type of dwarf file that is going to be made during compilation but the only options are none, minimal (-g1), default (g) and maximum (-g3).
After I did this the output of the compilations shows the following message:
20:27:10 **** Incremental Build of configuration Debug for project Cubex ****
make -j4 all
gdwarf-2
make (e=3): El sistema no puede encontrar la ruta especificada.
make[1]: [makefile:81: pre-build] Error 3 (ignored)
arm-none-eabi-size  Cubex.elf
text      data    bss     dec     hex   filename
16752      20     1796   18568    4888  Cubex.elf
Finished building: default.size.stdout
20:27:28 Build Finished. 0 errors, 0 warnings. (took 17s.509ms)

What I suppose means that it couldn't make the dwarf2 file due the message "El sistema no puede encontrar la ruta especificada" (The system can not find the specified path). The .hex file from STM32Cube IDE is working well in Proteus but I want to see the source code for debugging
Can anyone help me and explain how to obtain the needed files. Just before somone suggest me to do that I can tell that I've asked in ST community and I didn't have an answer yet.
Thanks in advance for the help.


texts: Large-Signal Analysis of Diode-Connected MOSFET

texts:
I know that diode connected devices act as resistors in small-signal domain.
However, two diode connected devices can also be used to divide a large signal DC voltage based on the square-law equation. I understand that and I was just doing some analysis to see what the exact Vin-Vout relation is but I’ve gotten a bit lost:

Any ideas on how to proceed. I was hoping to get some nice relationship based on the ratios of the two FET sizes.


texts: CPU cache write policy - evict already dirty? + storage of memory address

texts:
I'm reading about cache in wiki https://en.m.wikipedia.org/wiki/CPU_cache and the following phrase seems not clear.

  Also, a write to a main memory location that is not yet mapped in a write-back cache may evict an already dirty location, thereby freeing that cache space for the new memory location.

There could be writes from 1) peripherals and 2) CPU cache.  For 1) I do not see meaning in the phrase at all.  For 2) I understand computer need to write from cache to new location which was not in cache. Then that location becomes mapped to that cache line.  Again I do not see any evictions.

Do I miss Something?

Added: found other part I could not understand and could not find good place via Web search where it is explained in a clear way (tags + index,  how and where memory location is stored).  Please point to good detailed article.


texts: What is the loop logic of I2C driver in EFR32LG14

texts:
I am not sure regarding the logic of I2C API of efr32fg14 in the code bellow.In the main part in the end as shown in the API manual bellow,we use I2C transferinit, then we have some loop then indicated that measurement is still in progress and thats it.
The question is why my data is in i2c_rxBuffer?
Why its not in result variable ?
Basicly in C we transfer data from right to left. so we tranfer data from i2c_rxBuffer to the left side,why its the other way around?
Another thing is the logic behind the  result == i2cTransferInProgress loop.if i understand it correcly they say  if tranfer is still in progress then do something.Ok the tranfer ended where is the recieved data?
Thanks.
There are three important elements.
1)I2C_TransferSeq_TypeDef i2cTransfer;
2)I2C_TransferReturn_TypeDef result;
3)i2c_rxBuffer
https://siliconlabs.github.io/Gecko_SDK_Doc/efr32mg1/html/group__I2C.html

#include "stddef.h"

#include "em_system.h"

#include "em_device.h"

#include "em_chip.h"

#include "em_cmu.h"

#include "em_emu.h"

#include "em_gpio.h"

#include "i2cspm.h"

#include "si7013.h"

#include "sl_sleeptimer.h"

#include "graphics.h"

#include "em_adc.h"

#include "bspconfig.h"

uint8_t com1[1] = {0xE3};

uint8_t i2c_rxBuffer[3];

int main(void)

{

I2C_TransferSeq_TypeDef i2cTransfer;

I2C_TransferReturn_TypeDef result;

I2CSPM_Init_TypeDef i2cInit = I2CSPM_INIT_DEFAULT;

/* Chip errata */

CHIP_Init();

// Enabling clock to the I2C, GPIO, LE

CMU_ClockEnable(cmuClock_I2C0, true);

CMU_ClockEnable(cmuClock_GPIO, true);

CMU_ClockEnable(cmuClock_HFLE, true);

// Starting LFXO and waiting until it is stable

CMU_OscillatorEnable(cmuOsc_LFXO, true, true);

I2CSPM_Init(&i2cInit);

// In order to enable the I2C0_SCL function in PC10 you need to use ROUTE 14

// In order to enable the I2C0_SDA function in PC11 you need to use ROUTE 16

//Also note that there's a GPIO pin PD15 that need to be set to high in order to route the signals to the sensor,

// Using PC10 (SCL) and PC11 (SDA)

  GPIO_PinModeSet(gpioPortC, 10, gpioModeWiredAndPullUp, 1);

  GPIO_PinModeSet(gpioPortC, 11, gpioModeWiredAndPullUp, 1);

// GPIO_PinModeSet(gpioPortC, 10, gpioModeWiredAnd, 1);

//  GPIO_PinModeSet(gpioPortC, 11, gpioModeWiredAnd, 1);

  //Si7021 switch on

  GPIO_PinModeSet(gpioPortD, 15, gpioModePushPull, 1);

  // Enable pins at location 15 as specified in datasheet

  I2C0->ROUTEPEN = I2C_ROUTEPEN_SDAPEN | I2C_ROUTEPEN_SCLPEN;

  I2C0->ROUTELOC0 = (I2C0->ROUTELOC0 & (~_I2C_ROUTELOC0_SDALOC_MASK)) | I2C_ROUTELOC0_SDALOC_LOC16;

  I2C0->ROUTELOC0 = (I2C0->ROUTELOC0 & (~_I2C_ROUTELOC0_SCLLOC_MASK)) | I2C_ROUTELOC0_SCLLOC_LOC14;

  i2cTransfer.flags=I2C_FLAG_WRITE_READ;

  i2cTransfer.addr=0x80;//address with write

  i2cTransfer.buf[0].data=&com1[0];  // Measure Temperature, Hold Master Mode

  i2cTransfer.buf[0].len=1;    //1 byte E3 measure temp command

  i2cTransfer.buf[1].data=i2c_rxBuffer;

  i2cTransfer.buf[1].len=3;    //LS MS checksum

while(1)

{

  result=I2C_TransferInit(I2C0,&i2cTransfer);

  // Sending data

   while (result == i2cTransferInProgress)

   {

    result = I2C_Transfer(I2C0);

   }

}

}


texts: Bad Practice - Charging Lithium Batteries while powering circuit?

texts:
I'm using a 2s BMC to charge a 2s2p lithium battery pack (7.4v, ~6Ah).  The output of the charging circuit is the same as the input - they're not separate.  As a result, when I want to charge the batteries, I just hook up 8.5v to the +P and -P terminals and let the BMC do its thing.

Is this bad practice?  Is there any potential damage to the batteries if I am charging them AND the power from the charger is powering the circuit (the circuit normally powered by the batteries) at the same time?

I don't believe so off-hand, but I've heard that too much ripple on the voltage supply for the BMC can cause issues where it has a hard time detecting the charge status of the Li-Ions.

Thanks!


texts:
I'm drawing a board with an MCU (running at 32 MHz), some serials and an analog video section (mux and amplifiers).
I kept the video section physically separated from the digital one: i.e. it's placed on the right part of the board, while all digital signals run on the left. There are no digital tracks that cross analog ones.

I tried to keep video signals perpendicular to each other and, where not possible, to place among them a ground pouring to minimize cross-talk.

I'm afraid about power supply noise.
The source is a DC-DC converter, placed on the left-most side of the board.
From there, I routed two big traces (100 mil), one to supply the logic section and another to supply the analog one.

I think in this way the digital noise is minimized. The ground plane is the same, but between the digital and analog area is connected just in one point.

In which way I could further clean and filter the power supply trace near the analog side? By-pass capacitors along the track are enough or you would recommend some LC filter? The expected maximum current is about 300 mA @ 5V.


texts: How to condition supply voltage for project

texts:
I am working on a circuit that is powered by a regulated 5V external power supply.

However, since I will be directly powering a Micro-Controller from this 5v supply, I was wondering how I should 'condition' the voltage from the power supply.

In other words, what circuitry do I need to implement between the 5V output of my power supply and the 5V VCC line of my Micro-Controller?

Obviously I can't pass the 5v from the power supply through a 5v regulator, so I was wondering if there is any other simple alternative to ensure the voltage from the 5v PSU remains at a constant 5V.


texts:
One of the projects I am working on requires a number of photo-interrupters to be used.

I was wondering if someone could explain how to use them correctly? I was thinking something like this:

simulate this circuit – Schematic created using CircuitLab

The problem, is I don't know how to pick a photo-interrupter and transistor for this to work.

Edit:

I just realized that I probably didn't give enough information. Please see the amended schematic:

simulate this circuit

Edit:
I just thought of a better phrasing of my question.
What should I look for in the specs that tells me what the values for these:

simulate this circuit

Edit:

So, would this next schematic work?

Or even something like this one if I got the correct current?

Edit:
I believe I found the photo-interrupter I will use, but I am not sure if the above circuit can power it.
(Each of the current limiters 'CVCCs' are adjustable

IR Diode Forward Current    50mA
IR Diode Reverse Voltage    5V
Transistor Collector Current    20mA
Photo Transistor Collector-emitter Voltage  30V
Photo Transistor Emitter-collector Voltage  5V

What I get from that is:

The LED needs 50mA

The phototransistor needs 20mA

and I have no idea about the voltage, as I can't make sense of what they said.

Any help unraveling this puzzle appreciated.

Edit:

As I said, I think my problem is that I don't know what voltage these are running at. I got two values for the voltage of the photo-interrupter, and I don't know which one to use.

Photo Transistor Collector-emitter Voltage  30V

Photo Transistor Emitter-collector Voltage  5V

I have no idea what Collector-emitter voltage is.


texts:
I am trying to debounce a button.
Here is my result so far after placing a 1uF ceramic capacitor in parallel with the button:

This should work as an input to my Arduino 5V since it has High: U >= Vht = 3.0 V and Low: U <= Vlt = 1.5 V.
I guess this means my Arduino has a Schmitt trigger on its input pins?
I want to send my trigger signal to another digital input (a framegrabber that starts recording images on rising edge and stops on falling edge) and I do not know if it has a Schmitt trigger on its input.
I am therefore looking for a Schmitt trigger IC that can clean up and make my signal TTL 5V digital.
Could you recommend such an IC that is DIP (not surface mounted) and can be bought in small quantities?
I think I understand how I could debounce using the Arduino by measuring time from rising edge and making sure that a falling edge is not delivered too soon after that.
However I would prefer to do this in hardware for the learning experience.
Unless that is software debouncing is somehow better than hardware debouncing.


texts:
Here is the document that I am reading :
https://www.emcfastpass.com/wp-content/uploads/2017/04/an15.pdf

And here is the assertion :

I understand that a current flowing through a trace which encircles a large physical area can radiate magnetic field. As the current varies in function of the time, the magnetic flux will also vary. So according to the Faraday's law, a voltage varying according to the magnetic flux will be induced accros the traces which see the fluctuating magnectic flux. I understand that it will produce common mode noise as there will be loop antenna between the line/neutral and the ground but why it will not produce differential mode noise as there will be a loop between the line and the neutral ? I read that the loop length have to be equal to the wavelength to have a perfect reception/transmission. So @ 1 MHz, it means a loop length of 300 meters ? So the difference is probably because the ground-line/neutral loop are larger than the neutral-line loop ? Isn't it ?

Thank you very much :D Have a nice day !


texts: Control flow rate of a solenoid valve using PWM

texts:
I'm hoping to control the flow of chemical by shutting a solenoid valve periodically over short intervals, similar to this video: https://youtu.be/O49mqn33vBI?t=6
Does anyone know if conventional solenoids can be controlled by PWM to produce, say, 500 cycles per minute? Is banging a 'conventional' solenoid that rapidly a good idea usually? By conventional solenoids, I mean those found in coffee machines and others commonly available:

If not, how are PWM solenoids constructed differently?
Any thought appreciated.


texts:
I have made the below circuit:

simulate this circuit – Schematic created using CircuitLab

I made the Arduino output turn on for 1 second, and off for 1 second(repeating square wave). I hear a faint clicking noise but suspect that full switch contact isn't being made as when I connect an LED to the NC pin of the relay, it is always on. And in the NO pin it is always off(this is why it seems to suggest that switch movement isn't being made fully). The relay I am using is the Aromat DS2YE-S-DC5V. It is the one with 8 pins in total.(Yes, the schematic is simplified for the relay, but the question is about if the coil is fully energizing). Is there something wrong with my circuit which is preventing the switch to move to the other contact completely? If you need any more info please ask.


texts: Determining an equation for the current after the switches close

texts:
I know that the solution of of the form i(t) = A*sin(wt + phi), I am really confused where to start in finding A, w and phi however. Here is the circuit in question:

The switches close at time t=0


texts: Arduino nano + microSD module + ethernet module does not assign IP address

texts:
I would like to create a small web server to enable or disable devices via ethernet connection, except that the network module and the SD reader did not seem to work if connected simultaneously.
That is, if I remove the SD reader the Ethernet module starts to work perfectly.

Below I leave the current version of code used for the tests:

#include <SPI.h>
#include <Ethernet.h>
//#include <SD.h>
#include "SdFat.h"

SdFat SD;

#define SS_ETH 10
#define CS_microSD 9

byte mac[] = {
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
};

IPAddress ip(192, 168, 1, 177);

EthernetServer server(80);

void setup() {
  Serial.begin(9600);

  pinMode(SS_ETH, OUTPUT);
  digitalWrite(SS_ETH, HIGH);

  Serial.println("Initializing SD card...");

  if (!SD.begin(CS_microSD)) {
    Serial.println("initialization failed!");
  } else {
    Serial.println("initialization done.");
  }

  // start the server
  server.begin();
  Serial.print("server is at ");
  Serial.println(Ethernet.localIP());
}

void loop() {
  // LOOP
}

output produced by the program via serial:

Initializing SD card...
initialization done.
server is at 255.255.255.255

If instead I remove the microSD from the reader and restart the circuit I get:

Initializing SD card...
initialization done.
server is at 0.0.0.0

Hardware:

Arduino Nano
W5100 ethernet module ( https://www.ebay.it/itm/SHIELD-MINI-W5100-modulo-ETHERNET-per-ARDUINO-ART-CV05/262454631406?hash=item3d1b83dbee:g:ltYAAOSwHsRYE0KC )
microSD reader ( https://www.ebay.it/itm/Lettore-micro-SD-card-reader-writer-pic-arduino-raspberry-shield-ART-CL06/261625448910?hash=item3cea1789ce:g:tF0AAOSwAYtWOclu )

Wiring diagram

pin 9 -> CS microSD
pin 10 -> SS Ethernet
pin 11 -> MOSI
pin 12 -> MISO
pin 13 -> SCK

simulate this circuit – Schematic created using CircuitLab

Update 1:
Thanks to the suggestions of @Juraj I tried to disconnect the MISO pin of the SD reader and the IP assignment was successful.
Furthermore the SD.h library has been replaced with SdFat.h ..

The card reader has an LVC125A level converter as shown in this image: https://e-radionica.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/d/s/dsc_1819.jpg

Also here is the LVC125A level converter datasheet: https://www.alldatasheet.com/datasheet-pdf/pdf/171748/TI/LVC125A.html

UPDATE 2: a hardware modification to the reader is required to solve the problem since the MISO pin remains permanently enabled.
https://forum.arduino.cc/index.php?topic=360718.msg2942160#msg2942160


texts: Methods for electronic flatulence detection

texts:
I would like to build a electronic flatulence (fart) detector. I was thinking of methane because detectors are readily available, but I read http://en.wikipedia.org/wiki/Flatulence and it says:

  However, not all humans produce flatus that contains methane. For example, in one study of the feces of nine adults, only five of the samples contained archaea capable of producing methane.

Oxygen, nitrogen, carbon dioxide are listed but I think they would be too common in normal air. That seems to leave:

Hydrogen
Hydrogen sulfide
Methyl mercaptan
Dimethyl sulfide
Dimethyl trisulfide

Does anyone know if practical sensors are available that detect those gases or have other ideas? I think somewhere around the $20 or less mark would be good, so I wasn't really seeking a full professional solution like gas chromatography that may normally be used.

The application is for under office type chairs, so maybe heat detection could be used although I'm not sure it would be posible to tell the difference between the desired event and someone just sitting down on a cold chair, although maybe a pressure sensor could be used along with some filtering to not trigger until the temperature had stabilized a bit.


texts: Identify this automotive flat-pinned connector

texts:
This connector is from the wiper controller on an old Jeep Cherokee.  (The relay seems to have destroyed the board.)  Most of each blade is housed in plastic and the tips plug into matching female pins.  Each pin seems to be individually soldered onto the PCB.

In the housing, they look like this.

Here's what the females look like.

What is this type of pin/connector called?  I would like to buy replacements.


texts: UART not fast enough for debug purpose, what alternatives exist?

texts:
This problem is related with debugging an FPGA design implemented in Intel/Altera FPGA.

A custom debug mechanism has been introduced into the design. This new part of the design writes into a FIFO when certain events occur during design operation. The data exchanged and the events that caused this exchange are stored in this FIFO. The FIFO is then read by a Nios II. After some basic processing (check what is contained in the data), the Nios prints out a trace to a JTAG UART. This trace describes what events are occuring as the design operates and the value of the data moving from one part of the design to another. A Nios terminal runs on the computer to print the messages on the screen.

Using signal tap, system console or any other method is not possible as the events in the system and the data moving from one place to another must be presented in a human readable form over several seconds of design operation.

Now here is the problem. It seems that the calls to printf are too slow. The FIFO soon overflows and when this happens, information about many events that occured does not get written into the FIFO. The data rate into the FIFO cannot be predicted as it is not filled at a constant rate. Increasing the FIFO depth or increasing the depth of the buffer in the JTAG UART is not sufficient. Using alt_printf or some other form of optimization also does not fix the problem.

Since printf with JTAG UART is too slow, what alternatives exist? Since this is not a development board but a custom PCB, I do not have many pins available to use for debug purpose. There are many possibilities of course.

EDIT:

The trace looks like this:

START
MSG 0 DL
  MSG 0 UL
  DATA1 3200 DATA2 350
MSG 1 DL
  DATA1 500
  NO REPLY
MODE2
MSG 0 DL
  MSG 3 UL
  DATA1 400 DATA2 100
MSG 10 DL
  DATA 0x100
  NO REPLY
MODE1
...

Please note that the above is a very oversimplified view but you get the idea.


texts:
I have a dead battery from my Tivoli Pal radio that I wish to replace. It is a NiMH 7.2V 1400mAh like this one (the mAh being the only difference I guess).

Would it be safe to take the connector off the battery pack with four two of these in serial connection? Would that give me the same end result?


texts: Aren't actuators mechanical devices, and so aren't they part of the mechanical system?

texts:
I am currently studying Mechatronics: Electronic Control Systems in Mechanical and Electrical Engineering, seventh edition, by William Bolton. Chapter 1 Introducing Mechatronics has the following figure:

I am a bit confused about this. Aren't actuators mechanical devices, and so aren't they part of the mechanical system, rather than separate from it? Or am I misunderstanding what qualifies as a "mechanical device"?
I would greatly appreciate it if people would please take the time to clarify this.


texts: Purpose of solid plane on flex in wireless earbuds

texts:
I'm looking at a teardown of Sennheiser Momentum wireless earbuds. It is a rigid-flex design that folds into the casing:
￼

My question is about the flex that sticks out to the right in the picture above. Here is another picture with the part I’m wondering about circled in red:
￼

When folded into the casing it would end up facing out toward the plastic.

The Earin M-2 wireless earbuds also have something similar:
￼

What is it and what does it do?


texts: Ethernet Link is going down while applying EFT pulses on Power Port

texts:
We have conducted our system for EFT test as per IEC-61000-4-4. We have applied EFT on the AC side of the AC-DC power supply. We are using the power supply HWS50A-12/A from TDK-Lambda. As per the manufacturer claim, the power supply has the protection against EFT and it is compliant. Also, we have given protection circuits on our board on DC power entry. While applying the pulses on the AC side, we are noticing that the ethernet link is going down and it automatically comes up. I have connected the Ethernet cable from my board to a laptop and it was continuously pinging. While applying pulses the link is going down and that time only it will come back and it will continue the ping test automatically. Can any help me to solve this issue?
I have attached the  and the i.
Best Regards,
Shafeeq


texts: What should I do with the unused diode in the SOT-323-3 (SC-70-3) package?

texts:
I'm planning to use one of this diode in my circuit. But the package contains two of them. I chose it mainly because of its 3ns reverse recovery time. How do I use them in my circuit?

I have three options in my mind if you won't suggest a forth one.

Use one, leave the other open.
Connect them parallel.
Use one, connect the unused device pin to a rail with a very large resistor.

How do I get the best switching characteristics?


texts:
I am given this circuit

The voltage at each inverting ends should be 0, since the non-inverting ends are grounded.  However, given that VIN is positive, there's a current flowing between each of the non-inverting ends (through the capacitor and resistor: hence to me it's equivalent to saying that the voltage through a series capacitor-resistor circuit is 0 even though there's current through both components).  How can this be the case?


texts: Instrumentation amplifier with capacitor in the feedback network of the first stage

texts: Instrumentation amplifier with capacitor in the feedback of the first stage. Is this a second order filter or should be analyzed as just first order filter parallel coupled at Rg. Av = 1+2Zf/zg  z2= Rf//C1 Z1 = Rg. Anybody have any idea how to analyze such a circuit?


texts: Christmas lights - how many strands can I connect?

texts:
I am putting lights around my house this season, and am finding myself concerned about safety and what the company who makes the bulbs says is safe.  I think they are being way over-cautious, because they say we can only connect two strands.  But I'm reading different things on the web, and I'm not sure which is correct.

I want to connect six strands of incandescant C9 bulbs, which have 25 bulbs each (150 bulbs total).  I've carefully read all the safety instructions, but the only recommendation for how many strands to connect is on the box itself, and it says only two.  This is very inconvenient because there will be three extension cords going across our yard and walkway.

I found this equation via Google:
Number of total bulbs = Volts from your outlet X amps on your circuit X 80%/Wattage from a single lamp

So for a 120V  outlet, and a 15A circuit, and each bulb having 7W, we should be ok with 205 bulbs.

And so, is it ok to connect all six of these strands, with the above equation in mind?  Is the company that makes the lights just being super-cautious so that they don't get sued?  What would be the major concern (blowing a fuse, or something else)?

And to clarify previous questions, my lights would in this case be connected in series (if it were possible to safely do so). Each strand is wired in series.


texts: General queries about polygon pour - PCB Design

texts:
I finally decided to build my very own battery operated GPS device. So I started designing the PCB and i am having hard time understanding certain things.
Here are the details of the board

2-Layer board.

Contains GPS receiver and Bluetooth 4.1

Battery Management unit ( with charging current of 2A )

A Buck-Boost Converter  ( 1.6Mhz, ILmax= 1.2A)

Controller with 32Mhz Crystal
How do I decide if I need a Polygon pour? Should the poly always be ground? How does poly affect the performance of the GPS or BLE?

Thanks


texts: Laser Diodes to work it in high temperature

texts:
The power of laser diodes, made of GaAs, is limited by its power loss and the maximum operating temperature. Theoretically, the semiconductor material itself can be operated up to an intrinsic temperature of 650°C. Practically the operating temperature is limited at 250°C, because the electrical contacts, made by soldering with a high lead solder (300°C melting temperature).
the question is how can make or let this component to work with high temperature is that by electrical contacts in attaches in a circuit?
That's which allow an application with a maximum of operating temperature and of course i have to consider to and ensure the thermal expansion and the mechanical stability.


texts: Running a low voltage stepper motor with a A4988 and 5V power suply

texts:
I got this little car I built using two of these motors and A4988 drivers.

It was running with a 12V power supply, but I'm trying to get it on a battery and running for about 8 hours. thought I could use one of those phone power banks that give 5V,
but I tried using a 5V power supply and it doesn't seem to work.

Thought maybe 5V is not enough for the driver, but they say here that it should do:
Can I drive a low voltage stepper motor with an A4988 driver?

Any idea what the problem could be? (I'm also open for other solutions)

By the way, don't know if it matters but the power also goes to the Arduino controlling the thing.


texts: Power a 12V Solenoid and a RPi Zero with the Same Wall Socket

texts:
I'm building this circuit using an RPi Zero and this 12V solenoid.

I would like to be able to power the RPi and the solenoid from the same wall socket using a single power supply. For example, I've been using a 5V 2.5A switching power supply to power the RPi, but am open to other options.

How would I go about doing this? I'm open to using a rechargable battery pack to power the solenoid if it can be recharged via the power supply or RPi. Size is a consideration - smaller components are better. Any input is welcome!


texts: Are there any ways to improve this ISR - STM32F401RE?

texts:
I am currently coding a flight controller from scratch and am currently working on the module to decode the incoming PPM signal. Keeping in mind that this is an ISR, I've limited its functionality only to read the channel values from my receiver. It is working totally okay, but I wanted some feedback and improvements on the same (if possible). The ISR is as follows:

    void measureChannel(){
   int elapsedTime = t.read_us();
          //if any pulse shorter than 1000us, discard as garbage
   if(elapsedTime < 900){
        t.reset();
        return;
    }

  else{
        //if start/stop sequence, then set currentChannel = 1 and begin to read
        if(elapsedTime > 2100) {
                currentChannel = 1;
                t.reset();
                return;
            }
        //read channel value
        else if(elapsedTime >= 1000 && elapsedTime <= 2000){
                if(currentChannel == 1){
                        channelVal[0] = elapsedTime;
                        currentChannel = 2;
                        t.reset();
                        return;
                    }

                else if(currentChannel == 2){
                        channelVal[1] = elapsedTime;
                        currentChannel = 3;
                        t.reset();
                        return;
                    }

                else if(currentChannel == 3){
                        channelVal[2] = elapsedTime;
                        currentChannel = 4;
                        t.reset();
                        return;
                    }

                else if(currentChannel == 4){
                        channelVal[3] = elapsedTime;
                        currentChannel = 5;
                        t.reset();
                        return;
                    }

                else if(currentChannel == 5){
                        channelVal[4] = elapsedTime;
                        currentChannel = 6;
                        t.reset();
                        return;
                    }

                else if(currentChannel == 6){
                        channelVal[5] = elapsedTime;
                        currentChannel = 0;
                        t.reset();
                        return;
                    }
            }
      }
}

The relevant global variables and various instances are initialised as follows:

    Timer t;
    InterruptIn ppmPin(PB_5);
    uint16_t channelVal[6];
    uint8_t currentChannel = 1;


texts:
Regarding the following potentiometer with switch can someone please tell me what is the difference between it's switch rating power and maximum operation voltage?

It's a bit too complicated for me to be honest. Can't get my head around that.

The potentiometer is supposed to be used as volume control and in addition as a power switch for my amp running with 16v. Would this one suit my needs?
http://www.alpha-product.net/Img/R1231GS.pdf

Thank you


texts: How to controll windowed watchdog (WWDG) with dynamically scaling CPU frequencies?

texts: I have a project using ARM Cortex M4 with scaling CPU frequencies dependent on the workload. I would like to use the WWDG because it allows a lot more options like interrupt on watchdog. Question is: is there any standard workaround for variable time length CPU tick?


texts:
Am wondering if there are any risks involved in putting two (5V) car cigarette lighter adapters in parallel. They will be part of a setup replacing the car stereo, so will be connected to the "ignition" wire, not the cigarette lighter.

The two adapters I have are very different in appearence, and one of them is rated 1.5A, the other one unknown. I need something like 2.5-3A.

I assume both of them contain surge protection, which is one reason for using them.

Any reason for not two in parallel?

Clarification: parallel as in output sides connected.


texts: Implications of having duplicate case statement in verilog/system verilog design module

texts:
Are there any implications if you have a design module as shown  below where you have a duplicate case statement (duplicate case  2'b01 :)? As far as I known the execution is via precedence, so the second duplicate statement doesn't get executed. In terms of fabrication and any other reasons why this may not be ideal or it doesn't matter.
module jk_ff (input j, input k, input clk, output logic q);
 always @(posedge clk)
 case ({j,k})
 2'b10 : q <= 1;
 2'b11 : q <= ~q;
 2'b01 : q <= 0;
 2'b01 : q <= ~q;
 default : q <= q;
 endcase
 endmodule


texts: Determining the number of lighting fixtures

texts: This may be more of a common sense question but I would like to expand my horizons on the subject. My research tells me that lumens = surface area x foot-candles. So if I am lighting up a 50' x 50' room to achieve 40 foot candles, I need to install a 100K lumen fixture, or 10 10K lumen fixtures. But the equation doesn't take into account the height at which the fixtures are installed and how far they need to be positioned from each other. Also, the equation only applies to ideal conditions, say an empty room. But in an industrial environment where you have machines and equipment in the way, the equation will yield an estimate that is lower than what's actually required to achieve the desired ft-candles. I know this is not rocket science, but I would like to hear how others have tackled this. Thank you for your time.


texts: Time average for two caches , cpu and ram

texts:
I have a CPU, with two caches, L1 and L2, with access time T1 and T2 respectively.
and The time to access RAM is Tm.
The hit ratio for L1 is a, and the hit ratio for L2 is b.

Is the mathematical type of time average this or not?:

Taverage = aT1 + (1-a)T2 + (1-a-b)Tm

(T1 , T2  << Tm)


texts:
This is my first post here, so please give me feedback on how I can improve in the future.
Background
I am trying to reverse engineer a Becker Grand Prix Stereo Radio with an external amplifier.
On the back of the Radio, there is a 7-pin DIN connected with some pins jumped using a factory plug. Pin 4 is connected to pin 5, and pin 1 is connected to pin 3. Basically the plug is jumping these pins so that the output is connected to the amplifier.
The diagram is supposed to for wiring an aux jack to the radio.
Pinout in English

Radio Out Right Channel
Car chassis ground
Amplifier input Right channel
Radio Out Left Channel
Amplifier input Left Channel
Audio Ground
On/Off Switch.

.
Question
What I'm trying to understand is the purpose of the 4.7k Ohm resistors on diagram 1?
Are these used to reduce the current of the aux (line) signal?
Some diagrams have it, others omit it.
Please let me know if I need to clarify.
Thank you very much.


texts: Changing the frequency of a flashing LED

texts:
I have the following circuit, and I am required to explain how changing various components will affect the LED flashes. I understand that if the capacitor or resistors are changed it will make the LED flash faster or slower, however I'm unsure as to exactly why or if a relationship exists between these factors.

If the capacitance is increased, it takes longer for the capacitor to charge and discharge --> longer time between the LED being on and off?

Will the change of resistors affect the LED a lot? If so, which one will have the greatest effect?

Does changing the voltage of the power source affect anything?


texts: Will a monitor work if I make a VGA cable with common return and ground?

texts:
This has been bugging me for a while but will a monitor unit work if I make common ground for returns for RGB and the ground?

A bit scared to test it on my monitor.


texts: Weird behavior of 'soundcard' oscilloscope

texts:
This is what I did

I expected a nice square wave on my soundcard oscilloscope software but I'm getting this

What is happening ?