texts:
I would like to create a dummy load for this so-called "Deacy Amp":

This is a low power germanium transistor / transformer driven push-pull amplifier for driving a small 4 ohm or 3.2 ohm speaker. After playing around with this circuit for a day it seems it is sensitive to the load. So my question is, what is the best way to load this amp in a way that will yield a complex frequency response. Ideally I would like to see a lot of middle frequency with notches and dips and peaks and so on.

I don't care if the load makes a little noise so enclosing a small 4 ohm speaker in a sound-resistant box is fine.

Another idea, that may be wildly misguided, is to take two 8 ohm speakers wired in parallel and mount them face-to-face possibly right against each other. How would this affect the frequency response of the amp's output? Would it increase the load or cancel it or magnify the complexity or have no effect or what? What if I used two slightly different speakers?

UPDATE 1:

Another idea is to use these "tactile transducers" which are effectively voice coils without the cones:

tactile transducers

I could attach these to plates of different sizes and weights sandwiched together with foam spacers to dampen the sound. The impedance of each plate would increase at it's resonant frequency and allow me to create a wide variety of frequency responses.


texts: Input / output voltage standards for modular analogue synthesizer

texts:
I'm investigating building a modular analogue synthesizer, and learning electronics along the way.

I want to get a firm understanding of the supply voltage, inputs and outputs specification that is generally adopted, between each of the modules.

For example I'm aware a 15V power supply seems common; and 1V/Octave for the VCO. Is this correct? Is a +15v, -15v supply used? Also what is the output spec for the audio VCO?

Could anyone recommend further reading for these generally specifications and ratings?

I'm very new to this, and I'm starting with looking into the fundemental principles of a VCO, but want to build my experiments with the common specifications in mind - to drive to a useful goal. I don't want to just build a project thats out there, but learn the principles, design and build - I might not end up with the most stable modules.

No doubt pioneers such as Moog set initial standards, but keen to learn what the standard electrical spec for analogue synthesizers are, and how these expand out into the music studio.

Hope someone can help further.

Thanks in advance,
Alex


texts:
In our current design we are using a 3.5 mm headset jack with a normally open switch. The jack is waterproof, now in the scenario when the jack is filled with water, assuming salty water the switch will close (contact established by water). In that case, we will need to detect it as fault and not enable the headset left and right output.

How do I detect that kind of scenario?


texts: What is the difference between an emulator and a debugger?

texts:
In my experience I've used (to some degree) both emulators and debuggers. I've used them both for loading binaries (containing production code) into flash memory. I've also used them while developing programs in C and C++. On one hand you have your expensive $10,000 emulator (like the Lauterbach) or you have your humble Atmel JTAG ICE3 debugger (roughly $90). In my limited experience in roles involving embedded systems, I guess I've never really gotten down to the nitty gritty where I've needed to notice the difference.

One of my co-workers thinks that an emulator would allow you to directly connect to a processor and control it via JTAG. So I guess they are saying that you'd also be able to see dissassembly and be "attached" while stepping through the running embedded software. Is this true? If that's true then it is the only difference I could see. What are some other difference between the two?


texts: Power a laptop LED backlight with NiMH batteries

texts:
I'm powering a laptop LED backlight with an external 24,8V power supply, because I have problems with the internal WLED driver. The display used to work at 27V, but with the 24,8V of the power supply it's just fine.
Now, I want to use three 8,4V NiMH batteries connected in series to power the LED's while working without a plug. With fresh charged batteries, I get around 30V. Will it damaged the LED circuit? I know that the voltage will drop quicky, but I would like to use the batteries as soon as I remove them from the charger. If that's dangerous, can someone suggest an circuit to achieve a constante 27V with the three 8,4V batteries?

Thanks, best regards.


texts: Figuring out mininum/maximum clock frequency [VHDL]

texts:
I made my first design in VHDL with arctgs and sums and now I'm trying to synthesize it into an FPGA.

However, before that I need to understand more about:

How to discover how many clock cycles my design takes?
How can I discover the maximum (is there a minimum also?) frequency that my design accepts?

Can someone give me some guidelines please?


texts: Single Button Power Switch and Mode Selector

texts:
I am currently creating an embedded project and would like to know what you all think is the best way to proceed.

My setup at its most basic is an ATMEGA328P, a simple momentary pushbutton, a 2500mAh 18650, and an 11 LED ring run by a WS2812.

I am using the FastLED library for running the WS2812. I can only have one button that will be tasked with both power and mode functions (cycle through 10 stored presets). Think long press is power on/off and short press is next mode.
Would it be appropriate to place the ATMEGA328 in SLEEP_MODE_PWR_DOWN, turn off BOD and the ADC, and just let it sleep waiting for the interrupt from the button? If it's drawing on the order of 150nA (which I've seen in my research) I think this would be a very acceptable way to proceed. I would just use a P channel MOSFET triggered by the ATMEGA328 to supply power to the WS2812 driven LED ring.

Is there another and or better way to do this? Is it a bad design principle to not have a way to cut power to the processor in the event something goes wrong? (The battery will be internal and not removable).

Thanks!


texts: Lithium Ion Battery Charge & Discharge via Shared Input & Output Lead

texts:
I'm seeking to rebuild a few ancient NiCad & NiMh batteries for some vintage laptops I'm fond of, and in the process would like to convert them to Li-Ion. I'll be placing the lithium cells behind off the shelf BMS boards and the original output voltages from the packs are suitable to multiples of 3.7vdc:

13.2v (full charge) for one, so using 6x 18650s at 3S
7.2 (full charge) for the other, and planning to use 8x 14500s at 2S

Where I'm running into trouble though is charging. To charge the lithium cells safely and completely, I'm planning to use small Li-Ion/LiPo charge boards with built-in voltage boost (i.e., to get from the wall wart's 7.5v to 8.4v) and protection circuitry. I don't want to modify the laptops themselves or their chargers, and want all the Li-Ion conversion gear to exist inside the new battery packs. That presents a challenge because the laptops charge and discharge from the same 2 conductors.
I'll need a circuit to steer current through the charger or bypass it depending on whether the laptop is running on AC (charging) or battery (discharging). Every charging circuit I've researched features a separate input / source vs. output / load. I drew up the below circuit using P-channel FETs in 3rd quadrant operation, but immediately realized the BMS is feeding into the charger.
Best I've been able to come up with is is placing a current-sensing IC (e.g., LT1494) at the positive input/output and using its output to trigger the gates of two FETs, one enhancement and one depletion. I.e., if current is flowing into the battery, the charger's FET is turned on and the BMS' FET is turned off, and visa versa.
Seems like there must be a better way?


texts: SOT-23 Component Identification with label EJVK2

texts:
Trying to debug a broken circuit board and the component circled in red seems to be key to understanding the behavior. I've scoured the internet as best I could, but cannot find any reference to anything even starting with EJ
I searched:
https://www.sphere.bc.ca/download/smd-codebook.pdf
https://www.digikey.jp/en/pdf/m/micro-commercial-co/mcc-smd-marking-codes
https://alltransistors.com/smd-search.php?search=EJV
Any tips for where to look next?


texts:
Are there any values of \$\alpha\$ for which it is possible to find a state-feedback gain for the system by bringing all closed-loop poles to zero? If your answer is affirmative, find a feedback gain yielding the desired closed-loop poles. If you believe there are no such values of α, explain why. Are there values of α for which a state-feedback stabilizing controller can be found?

$$
x(k+1) =\begin{pmatrix}0&1&1\\0&\alpha&0\\1&2&2\end{pmatrix}x(k) + \begin{pmatrix}0\\0\\1\end{pmatrix}u(k)
$$

$$
y(k) = \begin{pmatrix} 0 & 0 & 1 \end{pmatrix} x(k)
$$

From the first part of the question, it is clear that the question wants to know if it possible to design a deadbeat controller, and if I calculate the controllability matrix of A I get

$$
\begin{pmatrix}0&1&2\\0&0&0\\1&2&5\end{pmatrix}
$$

Is this enough to prove that there is no deadbeat controller? If I try and find the feedback vector K = \$\begin{pmatrix} 2 & X & 3\end{pmatrix}\$, were X is a value that can't be extracted from solving the characteristic equation of (A - BK). Is this further proof of there being no $\alpha$ to enable deadbeat control?

In the second part they are looking for a stabilizing controller (i.e. one that places all closed-loop poles in the open unit circle). How would I find this? I'm not sure what the question wants because from my understanding I thought the feedback vector was the one that stabilized the system. Any help appreciated.

Note: Exam revision, Not a homework question.


texts: Help me find the best PCB design and why that is the one?

texts:
From the worst to the best design due to impedance parameters that affect the signal i would do it as a) > b) > d) and c) because c) is the one with the lowest lenth and lowest curves, am I right?

EDIT: I know that all the designs could work but I want to know which one is the best one and the reason for that.


texts: Determining the duration that a battery can power a device

texts:
I am a little confused on how to determine the duration that a battery can power a device if you know the load's current requirements and the Amp-Hr rating of the battery...

Also, how do you determine the current you can draw from a battery if you know the time that a device needs to operate and the Amp-Hr rating of the battery?

Thanks


texts: Find higher voltage among several voltages without MCU or ADC

texts:
I have 13 sensors with voltage outputs, each sensor can provide a voltage up to 3.3 volt, so I have 13 voltage lines. My goal is to somehow sort these voltages without using any MCU or ADC chip for minimizing price and space. Besides I do not need the exact value of each line. I am wondering is there any analog circuit for doing that for me?

I've just googled something like multiple analog voltage comparator, but no result found.
In a nutshell I want to find which line has higher voltage with minimum space and price and circuitry. If no analog solution found, best option is a MCU with 13 INDEPENDENT ADC channels and very low conversion time. I want to compare these lines just in a moment (e.g. 100 us) so time consuming ADC conversions in the MCUs may affect the result.


texts: How to calculate the value of a current sense resistor for use with an ADC?

texts:
My goal is to measure the output current of a 4-output voltage regulator (LTM4644) whose maximum current per output is 4A. I use the LTC2975 Power System Manager.

The datasheet of this component provides the following information about the built-in ADC:

I therefore assumed that I have to use the ADC's full-scale voltage to calculate the value of the current sense resistor:

Rsns = 170mV / 4A = 42.5mOhms

Then I found the DC2428A circuit diagram published by Linear Technology and whose application is similar to mine. The circuit diagram makes mention of a 10mOhms sense resistor, which implies:

Vin_adc = 0.01 * 4 = 40mV.

Why did LT engineers choose this specific sense resistor's value? Does it means that the measure will be less precise with a 10mOhms sense resistor than a 40mOhms one?

I have a very little understanding of note 4 and I suppose that's why I don't know why calculations are not based on the full-scale voltage value...

Thank you in advance for your help!


texts: Understanding the difference between CAN IDs and PIDS on OBD-II

texts:
I am trying to understand the CAN protocol for reading the diagnostic information from a car. For example, I know that on the car I am working on uses CAN identifier 0x7E0 as a query and 0x7E8 is the response sent back.

I am using a Vector GL1000 logger, and I am writing the code for this. The GL1000 uses a C-like language, and for me to retrieve information it uses the following format:

VAR Variable1 = CAN1 DATA (can-id) [bitA bitB]

And for example if I wanted to retrieve the engine coolant temperature, the PID is: 05.
I understand my variable will look like so:

VAR Variable1 = CAN1 Data 0x7E0 (or is it 0x7E8?) [ bitA bitB]

I am stuck, because I don't know if I should use the query or the response CAN ID, and I don't know what bitA & bitB should be if I want to retrieve the engine coolant temperature.

I know this is far fetched, but Vectors IT cannot help me. Is there a way I can clarify such a far fetched question?


texts: Switching HV DC relay on crashes microcontroller

texts:
So I´ve designed a PCB for a Pre-/Discharge Circuit for a 400V DC system which is controlled by a STM32 microcontroller.
When powered the program waits for 1s and then starts by switching the (precharge) relay on the PCB and one of the accumulator insulation relays (AIR) to allow current to flow thru a 1k resistor into the capacitors of the system.
After a calculated time the second AIR closes and completes a circuit without the resistor.

When testing the circuit with no connected load everything works just fine but with the accumulator on one side and the load on the other the microcontroller apparently gets stuck in some kind of loop of switching the first relay, then resetting and the relay gets released, and so on.

Below is the basic schematic of how the power supply is handled and the circuit used to switch all relays.

How can I stop the relays from chattering? What is causing this in my circuit?

Layout:


texts:
I Have spent hours trying to figure out how to complete the maximum safe working voltage and cannot match the answer below.

I can find the total capacitance by using the series capacitor formula.

Thats easy .
I also know the total current must be found using the formula I = V/Xc. Xc being reactance
My attempt to find the total safe working voltage:
As they all have the same current going through them the current stays the safe therefore. I = Va/Xca    = Vb/Xcb     = Vc/Xcc
**I have researched forums after forums and this is as far as I can get.
Please dont report me as this is as far as I can go and I have tried my best. I feel like I deserve the derivation now.
Cheers.
**


texts: understanding transmission line signal integrity through simulations

texts:
I need to simulate how signals are reflected based on the source, load and line impedances and how the signal integrity is effected by the spacing between different traces on a board, traces on the same level as well as different layers, traces of single ended and differential nature.

I want to see how the signal waveform is effect by the factors mentioned above through simulations.

Which software can be used to do this? I am sure that all PCB designers have to do this all the time. I want to do this as an exercise to understand this phenomenon and have a better understanding of it.


texts: Help me understand triac maximum current and when to use a heatsink

texts:
Datasheets list , under Absolute Maximum Ratings
RMS on-state current = 16 A, for example.

1)How do I know if this is free air maximum current or properly heatsinked?

2)How can two triacs in identical packages have different maximum current?

3)If the answer to 1 is "with heatsink", how do I determine the maximum free-air current?


texts: I want to show that full wave rectification equation is correct by Proteus

texts: I want to verify the full wave rectification equation using Proteus, but I get wrong voltage values. Please if any body knows how to do it, tell me.


texts: Very low frequency compact 555 timer circuit

texts:
I am not an electronics engineer. Just working on a project (hobby) that requires me to build a circuit. I just want a timer that turns on an LED after 1 hour. A button will be used to reset the timer which will again turn on the LED in an hour.

I have already made a circuit using a 555 timer IC. For few seconds(19s) of switching, the circuit works fine. I have used this online calculator with C = 0.1mF, R1 = 10kOhm and R2 = 270kOhm. For 3600s, I would either need C=20mF or a very high resistance and equivalent capacitor.

I have been looking online for components but couldn't find any ceramic capacitor of this value. Electrolytic cap are too big in size and I need my circuit to be really small (circle of dia 3cm). I am stuck as there are too many questions now and I dont have the expertise to answer them and can't find much info online

Should I go for a large capacitor or a large resistance? Or is there another way altogether?
I cam across SMD components that seem to be very small in size. But their voltage rating is like 30V. Will this work with a 5V supply?
Is there any other way to achieve this, keeping the circuit as small as possible.

Thanks


texts: Resources to understand robot locomotion and Gait functions

texts:
Recently I have been watching Robert Full's talks on TED. He has some obscenely interesting works on robot locomotion. This has intrigued my curiosity and I have been trying to understand his works. I have tried to read many papers on these type of works but I have been unable to understand as I don't have the basics of these things.

Can anyone please direct me to a resource (ebooks, websites, video/audio lectures, forums etc.) where I can understand the basics of Robot Locomotion and gait functions?


texts: Microphone preamplifier doesn't give expected gain

texts:
I was designing a microphone pre-amplifier circuit for Wireless Noise Monitoring application.
I used an electret microphone AOM-5244L-R-53724 (datasheet: http://www.puiaudio.com/pdf/AOM-5244L-R.pdf)and an amplifier  connected to a 9V power supply.
The multisim simulation of the circuit with a function generator gives the expected gain of around 7.8. But the same circuit in the breadboard with the microphone gives the gain of only around 5.
Please let me know what improvements are needed in the circuit to get the expected gain of 7.8?

Output from the oscilloscope:


texts: Voltage spikes on output of zero crossing triac optocoupler

texts:
I have one connection of the output of the coupler connected to the gate of a triac. The other connection is to one side of the triac. This side of the triac is also connected to a 77 ohm load. At the other end of the load is the L side of a 240vac power supply.

The other side of the triac is connected to the neutral line. Thus when opto turned on the neutral is connected to the load. No problems with the 77 ohm resistive load.

I also then connected the L and N to a 240vac electric motor. This blew up the optocoupler. This was obviously a voltage spike from the motor.

I can put the motor on a separate lead which solves the problem. However if I use the same lead as the 77 ohm resistive load can anyone suggest a protection for the optocoupler? The motor needs to be on at the same time as the 77 ohm load is activated.


texts: JBC soldering iron cartridge thermocouple type

texts:
I have recently bought a T245-B soldering iron handle and a C245064 cartridge. These are both made by JBC. I have tried to find the thermocouple type online but have had a range of answers from type k to j and n. I know for a fact that the voltage drop is proportional to a type k up until 100C.

Does anyone definitely know which type of thermocouple is used in their cartridges?


texts: 555N vs. 555P? One works, the other does not!

texts:
I've implemented a water level indicator using a 555 timer. It works fine when I use 555N, but the output is always high when I replace it with 555P. I don't understand.

I have tried four 555Ps to rule out the possibility of a faulty IC, but it still doesn't work. Meanwhile 555N works (I've checked with two ICs).

I googled it and found that there is virtually no difference between them. So, why is this happening?

Link to falstad circuit

Circuit diagram:

This 555N works:

This 555P doesn't work:


texts: Microcontroller with two USB interfaces and high speed (480Mbps)

texts:
Possible Duplicate:
  USB host to host connector with PIC18F2550

I'm working on my final year project and designing a host-to-host (PC-to-PC) USB connector with a microcontroller in between. Is there any microcontroller that can operate at high speed (480Mbps) and also have two USB interfaces? If there is non, what other technologies or functionality are practical to designing such a connector.


texts: Voltage dip at source side during heavy loads due to Internal Resistance

texts:
In any application, during initial start-up/load step, there is an high current requirement. Due to this high current requirement, there is a dip in that connected voltage rail.

I researched on why there is a dip in the voltage rail during start-up/load step condition. Upon researching, I found that the voltage dip is caused due to the internal resistance of the voltage source. During high currents, some voltage is dropped across the internal resistance of the voltage source and the remaining voltage is only is available at the voltage source terminals.

But the internal resistance of the voltage source is very minimal,right? If it is so minimal, then why do we have a voltage dip that is observable at the load side?


texts:
I found this 1W guitar amp design on the Internet:

http://www.diale.org/punch.html

And I am trying to build it on the protoboard. I could not find the IC TDA7052, instead I've got the a TDA7052B. According to the datasheet, the difference is that it has one extra pin for volume control (pin 4), which I connected to an 1M potentiometer, like this (and I am hoping that wire below is ground):

I am using a 12V DC input.

Now, I can't see the difference of what I have built and the schematics, but clearly there is something wrong. The speaker output on open circuit is about 12V when volume potentiometer is at maximum, with no input. First that I believe that the mean DC voltage should be around 0, otherwise it will have a constant current drain. Second that, according to my calculations, to have a 1W power output at the 8 Ohm speaker, the peak tension must be at most 4 / sqrt(2) = 2.83 V. At the measured 12V, the power would be much greater. Indeed, if I turn it on, the IC will quickly get too hot. If place 270 Ohm resistance between the speaker outputs, it will get too hot, instead.

Here it is:

For someone with more experience in analog electronics, it should be obvious what is wrong. Can you please help me?


texts: How to show opamp noise contribution in LTspice .noise calculation

texts:
When doing system noise calculations using LTspice using the .noise instruction, I can plot the total output noise and I can plot all the individual noise contributions to output noise from all components that contain some resistance (resistors, caps, inductors, voltage sources, even transistors) by clicking on them. But this selection method does not work for opamps.
How can I plot the noise contribution of individual opamps ?


texts:
Can anyone explain to me why there are 2 maximum voltages/amperage for both AC and DC like  below ?

10A 250VAC   10A 125VAC

10A 30VDC    10A 28VDC

I was thinking that the one on the left is for normally open and the one on the right for normally closed ?


texts: Logic analyzer: multiple circuits, one ground

texts:
I will receive soon my first logic analyzer but I'm wondering something:

There's only one ground on the analyzer. What if I want to measure at the same time two circuits with two separate power supplies? Can I just use one ground? Should I bridge the two grounds together? (Should be possible as it's the same voltage and I think the sum of current of the two circuits is lower than the maximum current on the ground of both individually.)


texts: Considerations for connecting 5 pin wire cables and interfaces to USB?

texts:
I found a module breakout board that has a generic looking 5 pin USB internal motherboard looking plug. The module comes with a 5 pin connector which is in the second picture below.

My ultimate goal is to connect to my computer's usb port. Is there an easy way to solder on a usb? I am confused as the interface looks NOTHING like a usb port. Can someone give me some advice on how to connect this? thanks!


texts: Increased current draw in data transmission circuit

texts:
Ok so here's my question. I'm fairly new to electronics research, my background is chemical engineering, but I'm attempting to improve my understanding of basic circuits and data transmission for my work. For this issue; I have a problem, and a solution, and I'm trying to work backwards to figure out why that solution solves that problem.

What I'm working with is a device that's transmitting data. DC voltage is supplied to a device, the device then attenuates the DC voltage to create a modulated current  which is sent back to a computer and interpreted as a digital information signal. An issue was occurring where a new version of these devices would not transmit any data all. The way it was explained to me was that the new versions were not drawing as much current as anticipated so the modulated current being sent back was not high enough to be interpreted as a logical 1, so the computer was essentially receiving all 0's.

I don't have specifics about the circuitry of the end device, nor any diagrams or anything like that, but I have the solution. To solve this problem one standard ~10,000 ohm resistor was installed, that's it. Again I don't know exactly where or how. I want to know how this could work.

My only theory that makes sense to me is that this resistor must have been installed in parallel to the circuit, reducing overall resistance and allowing enough current to flow that the computer could distinguish the incoming modulated current between logical 1's and 0's. Does this sound on track at all?? I'm sorry if this was confusing, but it's a bit of a puzzle and I'm very curious to see if my theory is correct and to learn a bit more about electronics. Thank you. Ask questions if you have any.


texts: Ham Transceiver to computer Interface design question

texts: I am building a Ham transceiver to computer interface, which has the RS232 port controlling the PTT on the radio. The circuit currently calls out for a 1.2K resistor in series with the RTS line and the 4N25 optocoupler's input. If I use a 4N35 optocoupler, which has higher minimum CTR and lower Vce(sat) test conditions, what sort of change should I make to the resistor's value?


texts: Minimum resistance for a home circuit to not have short circuit

texts: Say the circuit breaks at 10A, and we got 220V like in Europe. If I stick a wire directly from one hole in the outlet to the other, there will be a short circuit. But what is the "treshold resistance" for not having a short circuit? It seems that R = V/I = 22 Ohms would be minimum resistance to not break the circuit. So if this thinking is correct, any appliance should have at the very least 22 Ohms resistance? And finally do some small appliances put in extra resistors just to not cause a short circuit?


texts: Are there logic analyzers for large signals (5+ volts)?

texts:
I've used logic analyzers for <5V signals but I'm curious if there are analyzers for larger voltages.

Since logic analyzers don't display analog levels, could you use a logic analyzer to check for digital changes that occur at 12V?


texts: How to determine if a voltage is regulated and rectified using AN8008 multimeter?

texts:
Sorry, but this is probably a stupid question.
I have a motorbike and I need to find a wire that provides a fully regulated and rectified DC voltage. Especially at idle, a load like an LED light will flicker when it's not attached to a regulated and rectified wire. The main headlight receives an unregulated voltage on my bike.
I have the AN8008 multimeter:
https://www.amazon.com/ANENG-AN8008-Multimeter-Resistance-Capacitance/dp/B076GZK62B
I want to use it to test various devices in the front of the bike to see if any of the wires are providing a regulated and rectified voltage, but I don't know which mode I should use. The frequency varies tremendously with engine RPM, and when I test the voltage it reads ~12V, but that doesn't tell me if the frequency is staying steady or not.


texts: Operation explanation of a low-swing differential receiver (amplifier)

texts:
The following figure shows an example of a low-swing differential receiver given in Hall's Advanced Signal Integrity for High Speed Digital Designs

However, I cannot figure out how this circuit works as a differential amplifier. Could anyone help me explain the function of this circuit?
Thanks.


texts: STM32 NUCLEO-F302R8 UART : RX pin does not trigger RX callback

texts:
I'm using an STM32 NUCLEO-F302R8 and wish to communicate with it using any UART instance (1,2,3) through its RX/TX pins.
So far, I've managed to read from the TX pin but never managed to send messages to it via an RX pin. It simply does not react to any signal I put on any RX pin.
Any idea what I could try to make any UART RX pin work from somebody who went through a similar experience ?
All comunications done through USB work and the TX pins output correctly-encoded data (confirmed using a USB-UART conversion cable)
I've used several setups, but the most viable one is with another NUCLEO :
PC --(USB TX)-> STM32(1st) --(UART TX)-> STM32(2nd) --(USB TX)-> PC

I've tried:

using USART1, USART2, USART3
all combinations of solder bridges configurations : SB13 & SB14 on/off, SB62 & SB63 on/off
3 different NUCLEO boards to rule out hardware fault
baudrates 115200 and 9600
using the USB-UART cable directly on the NUCLEO's RX pin (it's a 3.3V level)
using the CN3 RX/TX pins

Here are the relevant initialization functions.
Any idea or question is welcome.
Additional notes :

The project is configured through CubeMX
It uses DMA and ADC.

    /* USART2 init function */
    static void MX_USART2_UART_Init(void)
    {

      huart2.Instance = USART2;
      huart2.Init.BaudRate = 9600;
      huart2.Init.WordLength = UART_WORDLENGTH_8B;
      huart2.Init.StopBits = UART_STOPBITS_1;
      huart2.Init.Parity = UART_PARITY_NONE;
      huart2.Init.Mode = UART_MODE_TX_RX;
      huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
      huart2.Init.OverSampling = UART_OVERSAMPLING_16;
      huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
      huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
      if (HAL_UART_Init(&huart2) != HAL_OK)
      {
        _Error_Handler(__FILE__, __LINE__);
      }

    }

    /* USART3 init function */
    static void MX_USART3_UART_Init(void)
    {

      huart3.Instance = USART3;
      huart3.Init.BaudRate = 115200;
      huart3.Init.WordLength = UART_WORDLENGTH_8B;
      huart3.Init.StopBits = UART_STOPBITS_1;
      huart3.Init.Parity = UART_PARITY_NONE;
      huart3.Init.Mode = UART_MODE_TX_RX;
      huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
      huart3.Init.OverSampling = UART_OVERSAMPLING_16;
      huart3.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
      huart3.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
      if (HAL_UART_Init(&huart3) != HAL_OK)
      {
        _Error_Handler(__FILE__, __LINE__);
      }

    }

    /**
      * Enable DMA controller clock
      */
    static void MX_DMA_Init(void)
    {
      /* DMA controller clock enable */
      __HAL_RCC_DMA1_CLK_ENABLE();

      /* DMA interrupt init */
      /* DMA1_Channel3_IRQn interrupt configuration */
      HAL_NVIC_SetPriority(DMA1_Channel3_IRQn, 0, 0);
      HAL_NVIC_EnableIRQ(DMA1_Channel3_IRQn);
      /* DMA1_Channel5_IRQn interrupt configuration */
      HAL_NVIC_SetPriority(DMA1_Channel5_IRQn, 0, 0);
      HAL_NVIC_EnableIRQ(DMA1_Channel5_IRQn);
      /* DMA1_Channel6_IRQn interrupt configuration */
      HAL_NVIC_SetPriority(DMA1_Channel6_IRQn, 0, 0);
      HAL_NVIC_EnableIRQ(DMA1_Channel6_IRQn);

    }

    /** Pinout Configuration
    */
    static void MX_GPIO_Init(void)
    {

      /* GPIO Ports Clock Enable */
      __HAL_RCC_GPIOC_CLK_ENABLE();
      __HAL_RCC_GPIOA_CLK_ENABLE();
      __HAL_RCC_GPIOB_CLK_ENABLE();

    }


texts: Why does "flashing" prevent ghosting on E-Ink displays?

texts:
Anybody who owns an E-Ink device (like a Kindle) will be familiar with the phenomenon of "flashing" -- basically, when turning a page, the device will first flip all of the pixels to black, then draw a "negative" of the page, and then invert the whole thing.

The Wikipedia page for "Electronic Paper" gives a brief description of the problem, and attributes it to the need to prevent the "ghosting" of the previous image onto the new one. This is corroborated by my own evidence: if I use the KDK to write an application that doesn't flash the screen, the ghosting is evident.

My question is, why does ghosting happen, and why does flashing prevent it? I have a rough understanding of how E-Ink works (thanks to the aforementioned Wiki article), but nothing there explains to me why ghosting occurs, or why reversing the charge a few times alleviates the problem.


texts: Can acrylic latex spray paint be used as a DIY solder mask?

texts:
I have recently begun etching my own circuit boards for miscellaneous Arduino projects and I need to apply a solder mask so that my copper traces don't oxidize.

I bought this acrylic latex spray paint for a different project, but I am wondering if it could be used as a solder mask.

My thought is that I would solder my components on first and then spray the board.  Possibly, I would just cover any sensitive components with a small piece of masking tape first, but largely I wouldn't even think this would be necessary(?).

Any thoughts or reasons why this would mean certain doom for the board or, more importantly, why this may be unsafe or a fire hazard?


texts: Units, ten and hundred in a 7-segment display (LOGISIM)

texts:
I need to know how to represent in units, ten and hundred on a 7 segment display in logisim.
I need to do a college job that is necessary to convert 8 bits from binary to BCD, from this a carry lookahead adder and after the sum separate the result in unit, ten and hundred, in case of overflow, an '' E '' message appears on the display, I would like to know how to make the separation to put in unit, ten and hundred!


texts: Best approach for building multiple rail isolated dc-dc converter - Multiple isolated DC from single DC source

texts:
I would like to obtain or build a converter that takes DC in, and has multiple (i.e. 6 or 8) isolated outputs. Step up or step down is not important, but might be useful, however is less important than figuring out the overall way of achieving this.

I can design to accommodate with respect to the DC input voltage.
Output I require 6 or 8 isolated 5-25V (ideally around 7V) outputs. Each output needs a capability for 15W.

My initial thought is some kind of TL494 circuit as an inverter and a transformer / inductor with several separate windings.

Has anyone got any ideas, or even schematics, of how I might (cheaply) achieve multiple isolated outputs from a single DC source?

Each of the isolated outputs are intended to drive a buck converter based CC / CV circuit. I understand this is a complicated way of going about things but it is part of a wider idea that I want to test.

I have scoured the internet and its not clear how one might easily achieve this.

Thank you in advance.


texts: Using GPIO to control multiple leds via transistors

texts:
I'm trying to control 16 LEDS with the GPIO ports of a Raspberry Pi using transistors. All 16 can potentially be illuminated together. I'm trying to figure out if I can use approach B to save PCB space by merging the resistors, or if I must go with A (or they're both wrong?):

Version A:                                                                       Version B:

If B is possible, does it affect how I calculate the value for R7 (all LEDs being identical)?

Right now I'm using LEDs that peak at 20mA (a bit too bright actually) with 3.3V forward voltage. But I can switch those out for different ratings if necessary.


texts: XBee (S2) Voltage Divider to Read Input 12v Alarm Output Pins

texts:
I have an XBee Series 2 and I was trying to detect an input from a signal which was 12v, so I used a voltage divider with R1=220k and R2=24k, I checked the output voltage with multipmeter and it was 1.2v, which is what XBee S2 input pin is meant to get, however the XBee was not able to detect that input, could you please tell me why was it? could it be because the output current (Io) from the voltage divider was so low that it couldn't detect it? if so what register values should I use.

Also my second question is what if I want to power XBee from the output of that voltage divider, what register values should I used if I am to power it from the same voltage divider?

Basically I want to use XBee (S2) to get power from a Texecom Premier 24 alarm system, and also want it to read the status of the output pins (digi output) and send signals to a remote server wirelessly, but since XBee data input pins cannot read 12v signal which is why I had to use a voltage divider but still it was not been able to detect the signal, which is why I'm thinking may be the register values I used were not the correct ones for this setup.

I'll really appreciate if someone could help me with this, as I seem to be getting no where on my own because of having very limited knowledge of electronics

Thanks


texts: Atmel Studio Does not fire accurate timer interrupt

texts:
i have atxmega256A3u with external 16Mhz crystal, i set the system clock to use that oscillator source as

uint8_t n,s;
    OSC.XOSCCTRL = OSC_FRQRANGE_12TO16_gc        /* 12 - 16 MHz */
    | 0 << OSC_X32KLPM_bp         /* 32.768 kHz XTAL OSC Low-power Mode: disabled */
    | 0 << OSC_XOSCPWR_bp         /* Crystal Oscillator Drive: disabled */
    | OSC_XOSCSEL_XTAL_16KCLK_gc; /* 0.4-16 MHz XTAL - 16K CLK */
    OSC.CTRL|=OSC_XOSCEN_bm;

    n=(CLK.PSCTRL & (~(CLK_PSADIV_gm | CLK_PSBCDIV1_bm | CLK_PSBCDIV0_bm))) |
    CLK_PSADIV_1_gc | CLK_PSBCDIV_1_1_gc;
    CCP=CCP_IOREG_gc;
    CLK.PSCTRL=n;
    // Wait for the Oscillators to be stable
    while (!(OSC.STATUS & OSC_XOSCRDY_bm));
    n=(CLK.CTRL & (~CLK_SCLKSEL_gm)) | CLK_SCLKSEL_XOSC_gc;
    CCP=CCP_IOREG_gc;
    CLK.CTRL=n;
    OSC.CTRL&= ~(OSC_RC2MEN_bm | OSC_RC32MEN_bm | OSC_RC32KEN_bm | OSC_PLLEN_bm);
    PORTCFG.CLKEVOUT=(PORTCFG.CLKEVOUT & (~PORTCFG_CLKOUT_gm)) | PORTCFG_CLKOUT_OFF_gc;
    SREG=s;

and i am trying to generate timer0 interrupt every 500ms as

uint8_t s;
    s = SREG;
    cli();
    Timer_0_Disable(&TCC0);
    //TCC0.CTRLA=(TCC0.CTRLA & (~TC0_CLKSEL_gm)) | TC_CLKSEL_DIV1_gc;
    TCC0.CTRLA=(TCC0.CTRLA & (~TC0_CLKSEL_gm)) | TC_CLKSEL_DIV256_gc;

    //TCC0.CTRLA = TC_CLKSEL_DIV1_gc;
    TCC0.CTRLB=(0<<TC0_CCDEN_bp) | (0<<TC0_CCCEN_bp) | (0<<TC0_CCBEN_bp) | (0<<TC0_CCAEN_bp) | TC_WGMODE_NORMAL_gc;

    TCF0.CTRLD=TC_EVACT_OFF_gc | TC_EVSEL_OFF_gc;
    TCC0.CTRLE=TC_BYTEM_NORMAL_gc;
    TCC0.INTCTRLA=TC_ERRINTLVL_OFF_gc | TC_OVFINTLVL_LO_gc;

    TCC0.INTCTRLB = TC_CCDINTLVL_OFF_gc | TC_CCCINTLVL_OFF_gc | TC_CCBINTLVL_OFF_gc | TC_CCAINTLVL_OFF_gc;
    HIRESF.CTRLA &= ~HIRES_HREN0_bm;
    // Clear the interrupt flags
    TCC0.INTFLAGS=TCF0.INTFLAGS;
    // Set Counter register
    TCC0.CNT=0x0000;
    // Set Period register
    TCC0.PER=0x7A11;//500 ms
    // Set channel A Compare/Capture register
    TCC0.CCA=0x0000;
    // Set channel B Compare/Capture register
    TCC0.CCB=0x0000;
    // Set channel C Compare/Capture register
    TCC0.CCC=0x0000;
    // Set channel D Compare/Capture register
    TCC0.CCD=0x0000;

    SREG=s;

this code is work fine using codevisionAVR but in atmel studio7 the timer take more than 500ms to generate the interrupt
have any suggestion please!


texts: Is it okay if I make the same PCB trace twice?

texts: I'm new to PCB Design and use EasyEDA. I'm currently designing a PCB with around 50 connections, I did 48 of them myself and ran the AutoRouter for the other two. But the AutoRouter has made the other 48 traces again as well (on top of the existing traces). Is this okay? Or do I have to manually remove all duplicate traces?


texts: Why are they called schematic "capture" programs?

texts: What are you capturing the schematic from?  Makes me think of a butterfly net or something.


texts: Is B pin of BJT always in the middle of three pins of the plastic and metal casing kind of BJT, or only in either one, or it's not?


texts: Why Characteristic Impedance must be 50 ohms?

texts:
Where does this number come from?

For single ended it must be 50 ohm and for differential pairs 100 ohm. Why?

For PCB with controlled-impedance these are that common numbers. Outside of the PCB you can find others numbers for characteristic impedance. But what is the reason of use these numbers for the PCB tracks?


texts: How to polarize a signal before sending it to the antennae

texts:
I am an electronics noob and searched around the FAQ and this question seems askable. My questions are:

How can I create polarized signals and are there any parts I need to be aware of to easily do so? (not receive and filter out polarized signals but send them)
Do I need a different oscillator for each type of polarized signal I want to send out?


texts:
Hi im a newbie when it comes to electronics, I want to design a robot similar to this:

http://www.me.berkeley.edu/ME102B/Past_Proj/f09/1%20BearClaw%20Tennis%20Ball%20Collector/design.php

The thing is, the link doesn't specify what power supply was used. The above robot uses two of this DC motor:

https://www.pololu.com/product/1103

If i am not mistaken, this motor operates at 12V and 5A.
So 2 motors will require 10A at 12V?
So to operate for one hour would I need at least a 12v 10Ah battery?

If this question deserves to be closed please allow it to be answered first.

+++++++++++++++++++++++++ EDIT ++++++++++++++++++++++++++++++==

i have to power and Aruidno UNO R3 board as well, will powering it directly with a 12V 5Ah SLA battery work?

+++++++++++++++++++++++++ EDIT ++++++++++++++++++++++++++++++==

i have just discovered that the Bear Claw robot (linked to above) uses only 6 AA batteries (from the looks of it in the Media section of the site). How can that be sufficient to run two of those motors in the link above? Doesn't high torque mean higher current requirements and so a NiMH battery's capacity won't be enough?


texts: How to get A, B and C values for this thermistor?

texts: I wonder if it's possible to extract A, B and C values for TTF-103 thermistor from datasheet. Those values needed to calculate resistance using Steinhart–Hart equation.


texts:
This is a related question to How to fix this in an enclosure without glueing.

However, for a protoboard/PCB, how could I attach it to the enclosure? The bottom of the enclosure has holes for attaching, but it doesn't have screw thread. How should these holes be used and how can I attach a PCB?

Glueing is not what I want, in case I want to add/change components on the protoboard later.


texts:
I am trying to understand how does the Triac gate current sinking work. Please consider the following circuit example:

source: http://www.electronics-tutorials.ws/power/solid-state-relay.html

the question is about resistor R2. The author states:

  Consider that the output triac of the opto-isolator has switched ON at
  the peak value (90o) of the 120VRMS AC supply voltage. This peak
  voltage has a value of: 120 x 1.414 = 170Vpk. If the opto-triacs
  maximum current (ITSM) is 1 ampere peak, then the minimum value of
  series resistance require is 170/1 = 170Ω’s, or 180Ω’s to the nearest
  preferred value. This value of 180Ω’s will protect the opto-coupler
  output triac, as well as the gate of the BTA06-600B triac on a 120VAC
  supply.

  If the triac of the opto-isolator switches ON at the zero crossover
  value (0o) of the 120VRMS AC supply voltage, then the minimum voltage
  required to supply the required 50mA gate drive current forcing the
  switching triac into conduction will be: 180Ω x 50mA = 9.0 volts. Then
  the triac fires into conduction when the sinusoidal Gate-to-MT1
  voltage is greater than 9 volts.

As I understand this, if the MOC3020 is turned on when the AC is at at least 9V, the triac will be turned ON and 0.5W will dissipate on R2. But what happens If I leave the MOC3020 ON? The voltage will arise to 120 V and the current will reach 1A on the triacs gate driver. Does this circuit assume that MOC3020 will be turned off as soon as as possible after the firing pulse and will be never turned on later than when the sin voltage reaches 9 V? Or does the current on gate driver diminish as soon as the triac start conducting?
I would appreciate an explanation.


texts: Turning the output of an opamp into a square wave

texts:
I have a 5Mhz signal which is being amplified by an OPA847 opamp.

In good conditions I get a voltage swing of ~120mV output from the opamp, in bad conditions I get a slightly noisy ~80mV p-p.  I am hoping for the final circuit to be single supply, the current test setup uses -5v/+5v.

The scope trace below is from good conditions, modulation can be seen in two places where the phase inverts:

My question is quite simple: what is the best way to turn this signal into a square wave for processing by digital logic?

I have considered standard digital logic gates but I don't believe the swing is large enough.  I have also considered a comparator with the input signal (biased at Vcc/2) compared to a fixed Vcc/2.  I assume this would need some hysteresis but am still not sure if it's the most practical solution.


texts: I have seen this rechargeable battery back up circuit on web.The resistor is used to limit the current.The diode in series is mainly to prevent the back feeding the power supply during battery operating mode.But I am not sure what is the application of another diode which is in parallel to the resistor.What would be the impact if we I remove the diode.


texts: Why are some mounting holes connected to ground?

texts:
Why are plated mounting holes connected to ground ?

I read that if you are connecting your board to chassis ground, then it should be connected at only one point and connecting say 4 mounting holes to ground and then screwing them into the chassis seems to not be desired.  Why ?

If you have 3 PCBs that fit into one large enclosure, what is the proper way to mount them ? Plated vs unplated ? Grounded ? Star configuration to chassis ?


texts: Choosing Components for a Discrete Delta-Sigma ADC

texts:
I'm going to be designing a discrete delta-sigma ADC to be built on a PCB. I think I understand the basic concept, but I will need to order components fairly soon. Here's my problem: while I have learned about op-amp/comparator parameters, I don't know which parameters I should prioritize when choosing parts for my application.

The design I'm considering will look something like this:

Since the op-amp is configured as an integrator, input offset voltage/current could be a major problem.

I'm currently considering using a TL07x-series op-amp.
Would the DC offsets of this device be problematic?

When choosing comparators, should I be more concerned about propagation delay, hysteresis, or input offsets? I am currently considering the LM393, KA319, and the LM311.
What other considerations should I take into account? Are my concerns even warranted, considering that my goal is not a high-performance device?

Notes:

I will be manually soldering the PCB, meaning that I would prefer DIP packages, though I can work with SOIC.
My goal is to get a working design, it does not need to have high accuracy.
The device does not need to operate at high frequencies, though something that can work at (44.1ksps or higher) would be nice.

Summary: I am wondering if the input offsets introduced by both the op-amp and the comparator at the input stage will cause the integrator to drift significantly, or if the capacitor will be charged/discharged quickly enough for errors introduced from DC offsets to be negligible.


texts:
I would like to have some advice on the power amplifier in the diagram below before building it. Will be used as guitar amplifier.

The current rises significantly with as input frequency rises. I do not understant why totally.

I also do not understand how the quiescent current for Q5 should be chosed.

Thank you,
Have a nice day,


texts: I am prototyping (point to point wiring only) a digital circuit with multiple shift register IC's to be clocked simultaneously at 500Khz. The distance between the clock source and the IC clock pins is going to be about 5 inches max. How should I lay this out to make sure it works?


texts: TP4056 or LM2596 which is better for solar mobile phone charger?

texts:
I am new to electronics, so please bear with nonsense questions, if any.

I want to make a Solar Mobile phone charger. I found various ways in internet to do that. I am confused between using TP4056 module and LM2596 module.

I have two solar panels - a 6V 100mA panel and a 9V 200mA panel

I have to make a 5V 1A DC output to charge my mobile phone through USB.

Allow me to describe the advantages (what I understand) of using either module.

TP4056 - This module is basically used to charge Li-ion batteries with 3.7V DC. But it has also a 5V DC output tertminal. From the datasheet of  TP4056, I found that typical input supply current is 150 microA. But the output of my solar panels are much larger.

LM2596 - This is a switching mode regulator. It efficiency is higher. I can set the output voltage to 5V (from a wide range of 4-40V) DC by adjusting a screw. Here is the datasheet of LM2596.

Now, I want to know the following things.

Which solar panel should I use?
Which module is better to make the charger - TP4056 or LM2596?

Thanks in advance.


texts: How can I generate a frequency of 5 GHZ with a crystal


texts: Run a simple AC motor with batteries using a wall charger for double and triple A batteries as the inverter

texts:
I'm trying to put an electric motor on my bike going from gas to electric and was wondering if somehow I could use a normal battery charger that charges my triple and double AAA batteries as an inverter.

Can I flip the capacitors or do some kind of change to the battery charger to make a 120V 60Hz AC motor run on batteries?

Here are some pics showing what I mean:


texts: Logism: Rising-Edge J-K flip-flop outputs 0 when J = 1 and K = 0

texts:
According to the truth table of the J-K flip-flop:

When J = 1, K = 0, and CLK (Clock Signal) = 1, Q = 1.
FYI, the flip-flop is a Rising-Edge flip-flop. Below are the timing diagrams which show the values of J_input, K_input, OfficialClock, and Give_Merchandise as a function of time. When J = 1, K = 0, and CLK (Clock Signal) = 1, my flip-flop outputs 0 in Column 8 of the below timing diagram (which is obviously contradictory to the truth table).
J_input:          0 0 0 0 0 0 0 0 0 0 1 1 0
K_input:          1 1 1 1 1 1 1 1 1 1 0 0 1
OfficialClock:    1 0 1 0 1 0 1 0 1 0 1 0 1
Give_Merchandise: 1 1 0 0 0 0 0 0 0 0 0 0 1


texts: RF amplifier, why don't two cascaded amplifiers work?

texts:
I am currently working on an amplifier circuit for an 8MHz signal (around -40dbm.)
The amplifier is based on an IC chip (LM7171 bin).
The problem is, the amplifier works perfectly individually (correctly gives +20dB gain,) but when we cascade two of them together, it only amplifes +6dB in total.
It is supposed to give +40dB gain. It is probably not a problem of op-amp saturation.
Below is how we cascade our circuit.  (VCC=15V, Vee=-15V)

The datasheet is here.
Decoupling capacitor is also connected between the source.

update:
For decoupling, I use 4 capacitors for each amplifier (Vcc=15V, Vee=-15V.)

Both op-amp work well individually (without connecting them together.)
When I meassured the midpoint between two op-amps, it gives +20dB gain. This circuit is on a breadboard.

Update2:
(Please note that this is not the circuit I have now, this is what I had before. Notice that in the picture, the two op-amps are not connected together. I can't take a photo of the current circuit because I don't have them with me. But the only change I make is simply connect them together and change the Rg value a little bit).


texts: Can we declare Schmitt triggers to have memory? Can we call their output levels states?

texts:
Are Schmitt triggers able to be declared as having memory? Can we call their output
levels states?


texts: Detecting transient voltages in a wall wart

texts:
Background

I have now three smartphones (SGS3 [neo], max 77686 or so) lying around, all more or less dead due to a broken voltage regulator. Since I am not a fan of coincidences, I suspect a broken wall wart somewhere around in my apartment, but I not only  have too many to just throw them all away, I also currently don't have a scope to measure things.

Required Idea

Since I am suspecting transient too-high voltages that destroyed the S3s regulator, I want to build a simple circuit that can detect those. For normal DC (or rather low frequency AC) I can come up with some ideas (monoflop, comparators, zener etc.) that can be the base of a circuit, but I have no idea about how fast the transient can be.

Since those are all smpss, I think their working frequency is at most 200kHz so the voltages to detect should probably be in that timing area. I don't have much experience in what circuits would be a good idea to detect the voltages that I am searching for fast enough.

So what would be a good design idea for a circuit that detects, lets say anything above 5.5V that lasts at least 5µs (or if you have experiences with mentioned voltage regulators smaller times when they are likely to damage the regulator circuit)? Although it is sylvester soon and everyone appreciates some blowing up tantalum capacitors due to overvoltage, I would prefer something reusable with not too much components, that is also nothing that requires a microcontroller or similar.


texts: LiPo charger MCP73831 does not light an LED with it's STAT pin when done charging

texts:
I'm trying to charge a LiPo with MCP73831 with 2 LEDs for status. I have an amber LED D1 which is on when VUSB is getting power from the USB connector, which means that it's charging. And a green LED D2 that should also light up when the battery is fully charged.

I'm having no luck getting the green LED D2 to light up when the charge is complete. I can see that the USB draw drops to near zero, and after being plugged into USB power for hours, the green LED will never light up. It's clearly done charging and the battery output voltage measures 4.2V, which is expected for a fully charged single cell LiPo battery.

Interestingly, when I poked around with the multimeter I got the green LED to illuminate. When I measured the voltage between GND and VBAT the green LED turned on while the probes were in contact with the circuit. When I removed the multimeter probes, the green LED immediately turned off.

So two questions:

Why doesn't the STAT pin output HIGH when charging is complete as the datasheet claims it should? (which should light the green LED D2)
Why does measuring the voltage between GND and VBAT cause the STAT pin to output HIGH?
Does the multimeter measuring between GND and VBAT effectively place a high Ohm resistor between the two? And if so, would that fix this? Why?

Links to relevant things:

MCP78381 Datasheet
These are the specific ICs.
These are the batteries
Full circuit and PCB here


texts: Watt/Amp Hour, Watt/Amp Minute Confusion

texts:
I am somehow very confused about amp/watt hour and minutes. I am trying to size a battery to see how much load I can get away with before it hits the 50% discharge zone.

I plan on connecting a modified sine wave inverter (3.6W idle), microcontroller (14W max) that will be attached to the inverter, an actuator (motor1), and rotisserie motor (motor2).

My problem is that motor1 has an inrush current of 4.6A and the motor2 has one of 10A. Talking to the makers of both, it appears these happen almost instantaneously for about 0.2 sec at worst case when they both start and stop due to inertia.

Otherwise motor1 draws 3.2A and motor2 draws 5.5A (both run 12V). For both motors they will only be on when they need to be turned and they will only be in motion for at most 2 min at each time.

This is a school experiment so I'll estimate I would run each motor 30 times in a day during the same time the controller and inverter are on. How would I go about calculating how much load I would consuming?


texts: If I understood the correct sign convention it's as shown in the below sketch


texts: I'm looking for a three-state inverting octal buffer for a replacement part for an old microprocessor lab. The package should be DIP. Ucc should be on pin 20. Chip select should be at pins 1 and 19 and active on low, so that the buffer is in high impedance state unless both enables are low. The input/output ports should be next to each other with even pins as input and odd as output. What this would be in practice is a 74540 IC with the described pin configuration or a 74366 with 20 pins. Help would be appreciated.


texts:
I'm building a machine that uses a single stepper motor connected to a gearbox. I'm running it at full steps and I seem to only be able to reach 1000 steps per second with a 200 step/rev motor. Much higher and it stalls and makes a lot of bad noise. I really would like to be going at least 2000 steps.

Here's some specifics on the hardware:

Machine originally used 3700 rpm, 12vdc 0.144hp motor.
Stepper is 1200 oz-in wired bipolar parallel: http://www.automationtechnologiesinc.com/products-page/stepper-motors/nema-34-high-torque-stepper-motor-1200-oz-in-half-inc-single-shaft-with-flat
Geckodrive G201x set at 6 amp.
600w 12v voltage booster. Tried setting output to 36v, 60v, and 80v but same results.
Controlled by Arduino Uno clone

The original machine used a pulley between the motor and gearbox. Because I don't want slippage, I've switched to a gear and chain setup, but I think the gear ratio is reasonably similar. I had hoped that this stepper was powerful enough to replace the original DC motor, but it doesn't seem to be able to run quite as fast. Did I pick the wrong stepper?

On a related note, is there any way to do a comparison between a stepper and a regular old DC motor? Or is that comparing apples to oranges?


texts:
I have a question regarding the SS411 sensor.
I have this sensor mounted on a BLDC motor. The magnets (neodymium) are placed with 0.02 mm precision. When spinning at a constant RPM, the sensor output square wave has the low pulse longer than high pulse. At any RPM, it is up to 10 % longer for the low pulse but is not constant - it varies randomly.
I even made a test setup with 4 magnets to see if the low pulse length variation is related to magnets but it is not, the low pulse still varies ramdomly.
The pull-up resistor is 1K5 and the supply is 5 V.
Do you have any opinions why this could happen? I'm familiar with BJT storage time that affects the turn-off time - could that by the case? (the sensor has a BJT open collector inside, according to the datasheet).
Thank you.


texts: How do I monitor voltage on a circuit even when switched off?

texts:
Here's the situation: I have a baby. Soon, I'll have two. So I don't really like spending half an hour trying to get him to sleep and then somebody rings the doorbell, waking him up.

I've already installed a switch on the doorbell circuit which disables it. I'd still like to know if somebody is trying to ring it though. For simplicity sake, lets say it's a simple light bulb that I'm always looking at, so it doesn't need to stay on. (Just a momentary flash will do).

The diagram on the right is the simple doorbell circuit. On the left, I have my indicator circuit with the 12v relay I assume I'm going to be needing. I believe the relay coil needs to go in parallel with my switch, but I'm not sure if this will work. Do I need a resister between the two?

What am I missing to complete this solution?

****EDIT:** Maybe I did myself a disservice by oversimplifying. The indicator isn't a lamp, it's actually my alarm panel which can monitor for either an open or closed circuit (but not a good idea to put the actual bell on that same circuit). This will allow me to be notified of a doorbell signal by email/text message, or whatever method I choose, even if I'm away from home.

Additionally, I have a dog that barks regardless of whether the doorbell is disabled or not. This is probably outside the scope of the question, however.


texts: Are unearthed metal cases actually unsafe?

texts:
Take a look at this picture:

It shows that if there is a fault with a device, current will flow from Live to Earth, hence you don't feel an electric shock.

However, I don't completely understand how much of a safety increase earthing a home appliance causes. From what I've read, "Earth" is a long metal rod driven quite deep into the soil to get a good connection. Most houses are concrete or wood.

From what I understand, if I touch a faulty appliance which doesn't have an Earth connection, the expected path of current is from Live -> through my body -> through a layer of wood or concrete -> into the soil. Surely if you need a long metal rod into the soil to get a good connection, the foundation of wood in your house cannot provide a current path.

I don't deny there is some added protection (perhaps if I decided to touch a faulty appliance while inside a bath, or outside on wet soil), but is not having an earth connection really unsafe?


texts:
Inspired by this blog post, I decided to put together a simple ring oscillator that transitions through 3 different LEDs. My schematic is almost identical the one in the blog post except that I used 2N2222 NPN transistors instead of MOSFETs. However, the LEDs are not oscillating. All three slowly light up and then stay on. What am I doing wrong?

My schematic:

Picture:


texts: How to detect charger connected to cut off battery and use externall power

texts:
I'm working on project which is supposed to be user friendly. It will usually run on battery and highest expected current draw is around 6A, but usually around 2A. I will probably use Li-On battery, perhaps 2 in series with equalizing and charging protection module.

I want to connect it via USB to PC for data transfer AND charging, or just power bank, or adapter only for charging.

As I am more programmer, than electrical engineer so I'm unable solve this problem. I need some sort of "power switch" which would be able to detect power from USB to charge battery and cut off battery output not to feed power back to USB and charger.

I thought about connecting the LED strip directly to discharge port - that would eliminate one branch of this problem. But there still remains the problem of switching Arduino power from battery to USB.

I found Adafruit charger which seems to solve this problem, however its rated only up to 1A.
So I need that, but for up to 6A.

When searching around the internet I came across MOSFET in P channel configuration. If I understand them well they should basicaly "switch off" when they get voltage on Gate.

If this is a good way to think could you please help me how should I connect it all up?

If it's not the right way please point me in better direction.


texts: how switch mode regs work - am I correct

texts: Hi I just watched a video tutorial explaining how switch mode regulators work. I want to confirm I've understood correctly. The inductor used in a switch mode power supply is there to provide power to the load when the internal pass transistor is switched off right? Am struggling to find the exact inductor used for the minty boast usb charger, it wouldn't matter if I was to use one with a higher inductance right?  It uses 10uH inductor btw


texts: How it is determined whether an equal sign can be used within the boundaries?

texts:
Why equal signs weren't used for limits(r < a, a < r < b, r > b instead of r <= a, a <= r <= b, r >= b)?
Two concentric spherical surfaces of radius a and b = 2a are in vacuum and
they are evenly charged with charge quantities Qa = Q and Qb = 2Q. The reference point of zero potential is at infinity.
Gauss's law was used to determine field in each area
Electric field:

(r < a)
E = 0
(a < r < b)
E = Q / 4πε0 * r * r
(r > b)
E = 3Q / 4πε0 * r * r

Potential:

(r > b)
Ф = 3Q / 4πε0r
(a < r < b)
Ф = Q * (a / r + 1) / 4πε0a
(r < a)
Ф = Q / 2πε0a

Another example:
The conducting sphere of radius a = 10 cm is surrounded by a concentric layer of dielectric of relative dielectric constant εr = 2 of radius b = 20 cm and is in the air. The sphere is loaded with charge Q = 10 nC
Electric field:

(r < a)
E = 0
(a <= r < b)
E = Q / 4πε0εr * r * r
(r > b)
E = Q / 4πε0 * r * r

Potential:

(r <= a)
Ф = (Q * ((b - a) / εr * a + 1))) / 4πε0b
(a <= r <= b)
Ф = (Q * ((b - r) / εr * r + 1))) / 4πε0b
(r >= b)
Ф = Q / 4πε0r

Third example:
The conductive sphere of radius a, loaded with the amount of electricity Q, is located inside a concentric metal spherical shell of radius b and thickness
c - b. The system is in a vacuum.
Electric field

(r < a) E = 0
(a <= r <= b) E = Q / 4πε0 * r * r
(b < r < c) E = 0
(r >= c) E = Q / 4πε0 * r * r

Potential:

(r >= c) Ф = Q / 4πε0r
(a <= r <= c) Ф = (Q * ((b - a) / rb + 1 / c)) / 4πε0r


texts: How to protect OpAmp output from short circuit to +Vcc?

texts:
I am using an OpAmp to amplify an input signal that ranges from 0-3.3V to a 0-5V range. The output must only be greater than 0 if the input signal is as well.

If I understand it correctly, if +Vcc were shorted to the output, the output would be constantly at 5V. Is there a way to protect against this error case?

I have tried to come up with something or find an existing solution, but I'm rather new at electronics and maybe I'm missing the right terminology.

EDIT: I changed the schematic according to Huisman's comment.
The possible reason for a short between +Vcc and the output could be that something(a loose wire, metal shavings, etc.) physically connects the two OpAmp legs, that there is a break between the tracks on the pcb, or anything else, really. For safety considerations I'm supposed to assume a short occurs, no matter how it actually happens.

simulate this circuit – Schematic created using CircuitLab


texts: Electromechanical or Solid State Relay Low Duty Cycle 1/2 HP Motor

texts:
i'm hoping someone can help me decide the best relay (in my scenario) for controlling a 1/2hp inductive load from 110-120v motor. I've spent numerous days researching this and hoping someone with more experience could help me clarify a few things, as i'm still new to this and trying to learn as much as I can.

Relay will be controlled by some type of microcontroller, probably an ESP32 or maybe even a Pi (not sure yet), but would be 3.3v or 5v GPIO to control the relay.

Application:

110-120v 1/2 HP electric motor --- 7.2a at full load
Runtime anywhere from 30-60 seconds, twice a day (up to 10 times a day, with ~30 second runtime)
Installation will be inside sealed IP65 enclosure with DIN rail
Microcontroller or Pi Zero W (undecided as of now) will be mounted on DIN rail

Possible Solutions

SPST/SPDT Electromechanical Relay (SPST more than likely)
40a Solid State Relay (i've found clips for DIN rail mounting for these)
Din Rail SPST Relay - TBD

Questions/Concerns

SPST Electromechanical Relay Lifespan - One concern of mine is the lifespan of an electromechanical relay, given the fact that my setup could essentially have up to 10 on/off cycles per day --- what kind of lifespan could I expect for an electromechanical relay in my type of setup with an inductive load from a motor?
Inductive Load on Electromechanical Relay - One other concern I have is that the relay would be driving an inductive load from the motor ... do anybody have any experience, warnings, suggestions, or thoughts on this?
Solid State Relay Heat - My concern regarding the solid state relay is the heat generated from it, as I have seen a lot of them that require a heatsink ... my question is, with my load only being a max of 7.2a and runtimes being very low (30-90 seconds max), is this something I would need to be concerned with? I ordered both relays to test with, and some temp strips to get max temp it gets to, but wondering if anybody has any insight or history regarding this?
Price Points - The electromechanical relays tend to all be cheaper in price, but in my project is it worth the ~$5-10 savings as in regards to having an SSR which would have a longer lifespan than the EMR? If my prototype turns out to work well, I may eventually want to turn this into a commercial product, so price at that time would be a concern, but I also want to consider quality/lifespan of product based on having a lot of cycles on the relay.
DIN Rail Mountable SPST Electromechanical Relays - As my project will be inside an enclosure with DIN rail, my first thought was to look at buying an SPST EM relay, but my concern with that is regarding the protection of the GPIO from the MC ... does anybody have experience using any of these, or what I should look to make sure is included in the relay to protect the MC (like snubber circuit)? I'm not sure if there's a specific term used for DIN rail relays that specifies it has some type of snubber circuit integrated in it.

I'm tending to lean towards going with the solid state relay as an easier implementation method, with a longer lifespan, and not having to deal with building a snubber circuit for MC protection (unless I can find a DIN rail SPST with it built in), or have enough time & money to build out a PCB to handle this.

Hoping that someone with a little more experience in this than I have could provide any feedback based on past experiences or knowledge. Thanks ahead of time for your help, and for taking the time to read this


texts: Minimum input voltage for this Transistor circuit

texts:
I have a circuit below, which I am using in a Coil Gun to amplify a pulse which is generated when a projectile passes close to a coil. I was able to get it to work, however I had the question of what is the maximum voltage that I can pass as an input to this circuit(at the microphone pin)?

My guess is that it would be just maximum ratings of the transistor from the datasheet, but is there anything else that might effect that value?


texts: How can I verify the max power theorem in a buffer opamp?

texts:
I was thinking since the buffer makes the output follow the input the power should be the same in a buffer opamp circuit and a resistive load.
There is the next circuit (the expected power was .5W, and besides the wattmeter is bad connected, I dont know why us 250uW)

then with the opamp

I was expecting the opamp does not draw energy (ideally) and then the same power should be the same in either circuits, so why isnt the same power output?


texts: Timestep error for Logistic Map in LTSPICE

texts:
I am building a logistic map circuit in LTSPICE. So far, I've prepared this:

The factor of 25 after the second AD633 is for increasing the scope of the parameter values. However, this circuit always gives me timestep error. I have tried changing the solver to alternate, changing Gmin values, etc. I checked every part of the circuit individually and they seem to work well.

I checked the voltage values just after the second sample and hold. They are going in Megavolts. I am guessing the sample and hold isn't properly configured or isn't working as it should, leading to non-convergence.

Netlist:

R1 N010 N009 1k
V1 N009 0 10
R2 N001 N003 1k
R3 N002 N001 1k
V3 P001 0 12
V4 0 P002 12
R4 N010 0 1k
XU1 N010 N001 P001 P002 N002 TL071
XU2 N002 0 N003 0 P003 0 N005 P004 AD633
V2 P004 0 15
V5 0 P003 15
XU3 N005 N008 P005 P006 N007 TL071
R5 N008 0 1k
R6 N007 N008 3k
V7 0 P006 15
V8 P005 0 15
XU4 N004 0 N007 0 P007 0 N006 P008 AD633
V9 P008 0 15
V10 0 P007 15
V6 N004 0 8
A1 N006 0 N011 0 0 0 N013 0 SAMPLEHOLD
V11 N011 0 PULSE(0 1 0 1u 1u 0.5 1)
A2 N013 0 N012 0 0 0 N003 0 SAMPLEHOLD
V12 N012 0 PULSE(1 0 0 1u 1u 0.5 1)
.tran 10
.lib ..\sym\EXTRA\AudioOpamp\TI\TL071.301
.lib AD633.SUB
.backanno
.end

Any help with this is appreciated. Thank You!

Edit: I tried using AD633 with high frequency (100Hz) sine wave, and it gave me timestep error. I think that's what's causing problems. It worked well only at a frequency of 0.01Hz. What's the get around to this? Is the AD633 faulty?


texts:
Would it be reasonable to implement a soft ON/OFF button like this?

My design requirements in short:

Enable the system power from a single-cell LiPo battery immediately after the ON/OFF button has been pressed.
The system power is controlled via an active-high enable pin of a switch mode DC/DC converter, and not switched directly.
The system should keep powered on, also during possible microcontroller (MCU) resets.
Subsequent button pushes should have no effect on the running device.
Button events should be readable by the MCU.
The MCU can actively turn off the system, after pressing the power button down for X seconds.
Low power usage, and ideally almost no power usage in OFF state.
No specialized ICs (and ideally no discrete MOSFETs, preferably a solution that only uses simple digital logics).

My old attempt looked like that:

To my surprise it works pretty well, but I had two problems with it:

The system turns itself off when the MCU soft-resets itself, i.e. when it loads a new program to RAM from an SD card (SYS_POWER GPIO was reset).
It is common to keep the ON/OFF button pressed for a while until the device shuts down, but that isn't possible with this diode based "OR gate". The button must be released for the shutdown to happen...

I'm currently trying to find a simpler solution, and sketched up the idea above in Logisim. The key is to use a storage element like a flip-flop.

(One problem I see with that solution is that the flip-flop would need to be powered by the battery directly. - (The flip-flop could possibly replaced by a S-R latch, but invalid states could occur... Or the OR gate could be replaced with three diodes, one additional input connecting the power button directly to the system power enable pin. Then the flip-flop would need to react to the falling edge, and be powered on after system power comes up. But that seems dangerous and overly complicated...))

By the way, I'm currently trying to learn more about electronics and I'm no expert at all. - This is a hobby-level microcontroller project, designed in KiCAD.


texts: How to read the device ID of a dataflash memory

texts:
I am trying to read the device ID of a serial flash memory by using the SPI connections on an mbed. In the datasheet for the serial flash memory W25Q80 there is this figure.

The following is the code I'm using to try to read the device ID.

#include "mbed.h"

SPI spi(p5, p6, p7); // mosi, miso, sclk
DigitalOut cs(p8);

Serial pc(p9, p10); // tx, rx

int main() {
    // Setup the spi for 8 bit data, high steady state clock,
    // second edge capture, with a 1MHz clock rate
    spi.format(8,0);
    spi.frequency(1000000);

    // Select the device by seting chip select low
    cs = 0;

    wait(1.0);

    pc.printf("response from sending 90h: %d\r\n", spi.write(0x90));
    pc.printf("response from sending 00h: %d\r\n", spi.write(0x00));
    pc.printf("response from sending 00h: %d\r\n", spi.write(0x00));

    cs = 1;
}

All I read are 0s. Sometimes it reads 128 or 255. That's wrong, right?


texts:
I am new to designing something to be powered by USB. Ideally It can either be plugged in to an adapter to a UK wall plug, or a powered USB port on another device. I have the circuit design in place using Kicad but I've never powered a device using USB.

Is is simply just connecting V+ to the bits that need power, ground to the bits that need ground and a 1uF capacitor connector between the two (if so which way should they be connected)? Or is this wildly wrong?
I don't need any data transfer to D+ and D- have been left open. Do these need to be connected to ground with pull down resistors or something?
Id like to get this right so I can do it when designing other products.

Im powering an attiny and some 5mm LEDs


texts:
Diode problem

Used 1N4148 in combination with 100 microfarad cap, circuit gave output 14.5V and 45uA on 200 Ohms load.

But, when I use 1N4007 or FR207, they do not work, nothing on multimeter.

Can anybody explain it? Why diodes do not work?
Please, feel free to clarify details of my question.

P.S impedance matching network is not included yet

Transmitter is a horn antenna (approximately 20 dBi), receiver is a half-wave dipole antenna approximately 2 dBi, radiated power  (800 watts from microwave oven at 2.45 GHz), distance between reciever and transmitter is 1 meter


texts: What is causing this weird decaying waveform on one of my MCU pins?

texts:
See image. Camera shot of my oscilloscope.

I'm having this weird problem with my project. I'm using a dsPIC33FJ128GP802 DSC/MCU. In this application, I'm sync-separating a CVBS signal using a LM1881 and feeding it into the MCU (channel 1.) The MCU is set up to interrupt on pin change. This part works correctly, and it drives an on screen display which I have written perfectly.

But, the weird part is that on each interrupt I'm briefly pulsing the pin RB12 to debug something. This is causing the weird decaying waveform on channel 4!! I'm expecting only a brief pulse, but it takes almost 64 microseconds (the line time) to decay to zero, almost like there is a very large capacitor on the pin (but there isn't.) Also, you can see the same effect on the falling edge, as the interrupt also triggers on that. What could be causing this? It has me completely lost!

I am using this code in my ISR:

TRISBbits.TRISB12 = 0;
asm("nop");
PORTBbits.RB12 = 1;
asm("nop");
TRISBbits.TRISB12 = 1;
asm("nop");

The nops are to ensure read-modify-write problems don't occur, but it happens with or without those nops.


texts: Why only odd harmonics after signal is amplified? *Plots inside*

texts:
Why do I get only odd harmonics appearing? This not only happens at saturation of the transfer curve, but also in the linear portion of the curve.

I make an input signal and the power of this will saturate the amplifier.

So the details of the amplifier is that I have a a transfer curve for power in and power out. I also have a transfer curve for power in and phase deviation. Then I make a phasor that amplifies each point on the signal to do AM and PM of the amplifier.

This is basically how I do it

My input signal, x(t), is the sum of two sine waves

For each point on the transfer curve above I apply Amplitude and Phase modulation by using this array

modulating_phasor[] = (power_out / power_in) * exp(i*phase_deviation)

Then I look at my input signal and lookup where its value matches the input power of the transfer curve and use that location in the modulating_phasor array

output_signal[] = x(t) * modulating_phasor[location]

This makes the output signal complex array so I take the absolute value and for parts that should be negative, I multiply that location on by -1 by finding the correct location on input signal.

Now this is my output and no matter what my input level on my signal is, I always get odd harmonics!


texts: Calculate base resistor of PNP transistor in switching circuit with variable resistance

texts:
I would like to read analog input on my Raspberry Pi using various resistive sensors I represent in the schematic below as potentiometers (R5 ad R7). I need to be able to switch the circuits on and off (high-side) through GPIO pins. I am new to electronic schematics and figuring out how to build circuits on my own so I have a few amateur questions concerning the base resistors (R1 and R3) and the circuit in general.

Raspberry Pi specific information:
The wiper pins on the potentiometers go to a MCP3008 ADC as the Raspberry Pi does not have analog input pins. I am using a linear voltage regulator to provide 3.3V to avoid using the 3.3V rail which, I have read, can only provide 50mA. The ADC will also be powered by the 3.3V coming from the regulator.

General information:
I have been following a few tutorials which calculate the base resistors of the two PNP transistors (R1 and R3).

A Raspberry Pi specific video states that the base resistor must be calculated using the β value of the resistor and the current of the circuit after the collector (R2+R5 and R6+R7). This would put the base resistor past 3M Ω assuming a β value of 75 and a current (Ic) of 0.06mA. Not that I have experience to judge, but this seems awfully high.

The tutorial on Sparkfun seems to contradict this and states that "1mA to 10mA will usually be enough" in terms of base current. If I use a 1K Ω resistor as the base, I will get 3.3mA to the base of the transistors.

The vast majority of Arduino tutorials, although they use NPN transistors, seem to have less than a 10K Ω resistor on the base of their transistors reguardless of what they are switching.

Questions:
The obvious question here is which calculation is correct? How would I find the amount of current needed to saturate the 2N3906 transistor by its datasheet? I'm not sure which number I'm looking for as I'm not used to reading datasheets or why each value is negative (I assume it's because the transistor is PNP although that doesn't answer my question).

Bonus: Will the circuit behave correctly if the potentiometers (R5 and R7) are replaced by a photoresistor that runs straight to the ADC? Does it matter that the digital pins are from the Raspberry Pi powered and the VCC in this circuit are powered from a different source although the voltage is the same(ish) and they share a ground?

Thanks.

simulate this circuit – Schematic created using CircuitLab


texts: Transistor as a switch in active or saturation region?

texts:
I am working on a circuit in which a load (a DC motor at 6V and 1A max current) needs to switch on or off. The controlling voltage (voltage at base) will be 0 to 3.3V.

I am planning to use 2N4401 transistor. My question is I can use my transistor in active or saturation region when turned on. I can select the resistor values accordingly. However, I am not sure when one mode is preferred over other and why.

Does operating in active region will cause my transistor to overheat as Vce will be equal to excessive voltage left in the collector circuit.
For example, if Ib = 1mA, Current Gain of transistor (Beta) = 100, Vcc = 10V, my load resistance = 10 ohms. Then, a current 0.1 A will flow in collector circuit and my load will have 1 V drop. Then, the excess voltage of about 9 V will be across Vce? Is this a problem for active region?. What if a connect a resistance of 50 ohm in series with my load in collector circuit? The resistance of 50 ohm will still keep the transistor in active region but it will reduce the Vce to 4V.

What if I have a load and I want to push only a specific current and design my circuit to operate in active region when turned on and Vce will be calculated to be low so that power dissipation will be quite less.


texts: How to easily calculate transfer function of an LC filter

texts:
Consider a simple LC network:

simulate this circuit – Schematic created using CircuitLab

Is there an easy way to compute its transfer function in the Laplace domain? I would consider as "transfer function" the ratio \$ H(s) = V_{out} (s) / V_{in} (s) \$.

I am looking for a hint to proceed (consider the branches? The voltages? The currents? KVL only or KCL only?) and I'm not asking others to do my homework.


texts: Review and question about AD9838 circuit

texts:
I have tried to come up with a schematic of using AD9838. I used the eval. board schematic and modified it to my needs. The eval. board schematic can be found on page 9 here:

AD9838 eval. board schematic

And my versions looks like this:

I have some concrete questions:

The capacitor marked with red is not recommended in the data sheet and I don't know if it has any big effect except noise reduction. Should I keep it or not?
The capacitor marked with green, I can not mentioned in the data sheet and I want to know what it does and if I have to include it.
The two capacitors marked with blue is also not mentioned and I wonder how they effect the signal.
The capacitors marked with yellow I assume are the bypass/decoupling caps?
This circuit can be used with a 16 MHz crystal oscillator. I only have the HC-49 crystal and the recommended one is a Epson SMD with 3 ports. Can I connect the HC-49 directly to the MCLK pin or do I need to add additional components (resistor, capacitors?). This should be in the area marked pink. What do you recommend?
Any other corrections/improvements are appreciated!

Here is the data sheet of the AD9838


texts:
I am using an uni polar BLDC motor. For speed control I am using PI closed loop.

During acceleration I am able to get speed as expected. Once I am crossing set point, I need to slowdown motor. If I am removing PWM (0% duty cycle) or applying less PWM as calculated by PI loop, speed is decreasing as if natural run down.

How I can bring speed down to get similar acceleration and deceleration slope.

Please help to understand what scheme usually adapted to decelerate in BLDC motor.

Update:
My BLDC motor configuration is diagrammatically shown below.


texts: I am creating a small car which can change its direction upon collision with a wall or an obstacle. For example, if the car is going north, upon collision it will start going south. I have no idea how to detect the collision.


texts: Can we observe addresses, data and other signals on the microcomputer buses by an oscilloscope, a LED or even an ordinary DC voltmeter?

texts:
Microcomputers are dynamic devices that are synchronized by a clock oscillator. So the signals (E, R/W, CS, A15-A0, D7-D0...) appear on their buses only for parts of a microsecond and, as the buses are common for all the microcomputer system, they are constantly changing...

The question is, "What should we do to stop all these signals so that to observe them by ordinary means?"

I must admit that this is more a tricky puzzle than an ordinary question because I and my students already have found an answer in the laboratory of microcomputer devices:)


texts: Managing CRT dangers for student hobbyists

texts:
What are the main dangers of breaking down or tinkering with CRTs? From my electrical engineering background, I understand that typical CRT designs include very high capacitance that can be dangerous even when the device is unplugged. I also know that there are additional risks simply from working with a very large vacuum tube.

A friend was concerned that a young student might be getting in over her head by attempting a breakdown of electronics with a CRT, so he asked me about the risks, but I don’t have enough expertise in this particular area. Just how dangerous is that kind of project? Are there precautions you can take to mitigate the risks, that would be simple and safe enough for a child or teenager? Is this a project for experts only?


texts:
I have some devices which have purple LED's in them.  I need to make another one, but don't know anything else about the LED to buy more.

How can I determine the forward voltage and maximum current in order to get similar LEDs?


texts: Do NPN and PNP phototransistor switch complementarily?

texts:
I am trying to understand whether there is a difference in the switching characteristics of NPN and PNP phototransistors.

My understanding is:
NPN: current flows when light is incident, no current without light

PNP Option 1: current flows when light is incident, no current flows without light

PNP Option 2: current flown when NO light is incident, no current flows with light

Is option 1 or option 2 correct?

Many thanks.


texts: Master-slave JK flip flop (74HC73) doesn't toggle

texts:
I'm designing a traffic light using two BCD counters and a JK flip flop. The simulation works perfectly on Proteus, but not in hardware (PCB).
The traffic light is required to count from 40 to 0 in some color, and from 20 to 0 in the other color, and repeats again and again.
Here is my simulation:

What happens in hardware is, sometimes the JK flip flop doesn't toggle when the counter resets.
In simulation, when both counters reach zero, the TCD will become zero. Hence, the JK flip flop will receive a falling edge and toggles, and also the counters will reset to either 20 or 40 depending on the flip flop state.
I'm not sure what makes this doesn't work well on hardware. I verified that my connections matches what in simulation. I suspect there is some timing issue that Proteus doesn't consider.


texts:
I am trying to build a circuit from a schematic where capacitance units are not defined.  The diagram shows a non-polar capacitor with 0.01, and another with 0.001. What should I assume for units? uF pF nF F or something else? If I have to guess I will guess uF, since most of my capacitors are labeled in uF.  I feel like this is a really dumb question, sorry about that.  I did try to find an answer on my own, though.

The diagram is the following:


texts: Negative Voltage Shift from Blocking Cap for Amplifier

texts:
Recently I have been working with the Analog Devices AD797 op-amp in LTspice, and have been getting poor performance from the amplifier when using a low-amplitude signal. This is my circuit in LTspice:

The voltage source I am using is a sine wave at 40KHz with amplitude of .125 V, parallel capacitance of 3.4nF and series resistance of 4KΩ. I am trying to mimic the hydrophone that this circuit will eventually be an amplifier for, so these numbers aren't random. Also, I have set the gain of the amplifier so high because this circuit will eventually need to amplify voltages much lower than .125 V. I believe my problem is with the blocking capacitor / highpass filter I use on the output of the voltage source. Vin is consistently lower than the amplitude of the voltage source and V2 looks identical to Vin, except it has been shifted negatively by a few millivolts. The following screenshots are what I see in LTspice when simulating the circuit.

The second image include the output of the amplifier, which reflects this negative shift of the input signal. I am a relative beginner, and my understanding of reactive circuits is shaky. Any help with eliminating / minimizing this negative shift between Vin and V2 would be much appreciated. Thanks

Here is a link to the AD797 datasheet. http://www.analog.com/media/en/technical-documentation/data-sheets/AD797.pdf


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I have a DC/DC converter outputting 5.18 VDC @ 25% load (1 Ohm resistor). If I measure the voltage at the green nodes it fails out of tolerance, if I measure the voltage at the red nodes (before the line resistance) it passes tolerance. (See Figure 1)

The tolerance is 5.18 VDC +/- 0.155 VDC.

There is a line resistance of 0.1 to 0.5 ohms on each output, the wiring is pretty long in this case. I understand there is a voltage drop proportional to current flowing, at this case there is about 1.75 A flowing at 25% load.

1.75A * 0.5 Ohms = 0.875 VDC Voltage drop for each output wire. I get why that is failing.

However when I am measuring the voltage output at the red nodes, it is in tolerance, but the same line resistance 0.875 VDC voltage drops are still connected to the load resistor because the current is still flowing through them to get to the load (in parallel with the DMM). So why does this pass? Wouldn't the line resistance add to the load resistance in either case?


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Ok this is probably a basic question, but I understand how SR latches work except one thing.

In the R input and S input you can make them 0 or 1.....but what about the input lines next to them (That rely on the output of the R or gate or S or gate)......what do those "Start" out as.

I assume it's Zero.....but with the very first clock signal (To R or S)....it hasn't gotten the output line from the other OR gate yet...so how can it get a first output.

Like lets pretend the first clock signal is R=1 and S=0 ....what about the R or gates input line next to it (that relies on the S OR gates output).....how can it get this on the first "input" signal. It confuses me?

Do we just assume it's zero or what?

edit: Since the question is confusing, the Input line RIGHT below the R (They both go into the top OR gate, im talking about the one right below it). Since it is dependent on the S output....if it's the first "Clock" signal...what would it be set to? Zero? Since obviously it has to wait for the output of S before it can actually be set to anything...but initially what is it considered.


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I made a scheme of 16-bit decoder in ISIS by AND's, XOR's etc. and now I want to use this scheme to make my own device. The block with ports. How to do this? I found videos, where people make block and its ports, but I have never seen how to use my own scheme to make my own device.

I've made this in ISIS:

It's working. And I need to take this circuit:

And make a simple block of it. Something like this:

Something, that I can save to library and use it later.


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texts:
I am trying to recover some videos on a Video8 tape and was wondering how in general how analog video was written to tapes. I've been researching the NTSC specification and it seems like there are these vertical and horizontal sync signals. I am wondering if these signals are written to the Video8 tapes during record, or if only video frame data is recorded and the sync data generated upon playback by the playback device?

A little bit of old school electronics, but it would be helpful if any of you more experienced folks have any idea.


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texts: I'm modifying my DC train system to control the trains from a small chip onboard (arduino or spark core) and I want the trains to be able to know where they are and the controller to know where they are too. There are multiples way to do track detection (a train is on the tracks) but that doesn't tell me what train. I ordered some basic rfid ics to test but I'm bot sure that will work at speed and they are pricey. I thought about maybe using IR but worried that reflections will throw me off. I'd like to have id 12 or so id points around the track so I know what train is where at all times. Any thoughts on how to do this?


texts: Is there a "Design Patterns" for synthesizable RTL?

texts:
For software, the book Design Patterns is a set of patterns for doing common things in software and it gives software practitioners common terminology to describe some of the components they need to create.

Does such a book or resource exist for synthesizable RTL or RTL in general?  Things like common pitfalls, design trade-offs, deadlock considerations, and interface design.