texts: STM32 SWO & OpenOCD with Variable SysClock

texts:
I have been using SWO with STM32 chips for debugging for a number of years.  I have managed to side-step this issue until now.  I would like to be able to use SWO for debugging while varying the SysClock frequency.

This is an issue because OpenOCD requires that I specify the SysClock when setting up SWO:

tpiu config internal swv uart off 48000000

This works fine at a fixed HCLK frequency of 48MHz.  But as soon as I change HCLK, either up or down, the data coming from the port is garbled.

In hardware, I am taking SWO straight from the CPU into an ST/Link SWD interface.  The documentation for openocd does not mention how to deal with a varying HCLK (or, if it does, I have not found it).  I have found hints online that using Manchester encoding might work.

I have tried using both UART and Manchester modes.  Both work at fixed frequencies and neither appear to work when changing the clock speed.

Is it possible to configure openocd for SWO with a varying HCLK?  If so, how does one do it?


texts: Why are the resistors in an AM modulator necessary?

texts:
In preparation for the amateur radio exam, I have been following the preparation course material by DJ4UF. In the section about modulation it presents this diagram of a simplified AM modulator.

The low frequency signal (NF) and the high frequency carrier wave (HF) are added, the diode cuts off one half-wave and the resonant circuit "recreates" the previously cut off half-wave. The result is a amplitude-modulated signal. So far so good.

What is the purpose of the 47k resistors? The explanatory text mentions that they are necessary to "add the currents in the diode". What would change if we remove them and just directly connect them to the diode?


texts: Why would touching a rubber insulated spark plug wire causes current to go through your finger?

texts:
I'm trying to understand the physics. The spark plug has a gap of 0.9mm.
Why would the current go through the insulation resistance, the finger resistance and the air gap between the finger and the engine ground instead of traveling a much less resistance through the 0.9mm gap?


texts: How can an LED series continue to work after an LED goes bad?

texts:
Just what the title says.
An LED series should probably go dead after an LED goes OC. There are strings out there in the market where the series continues to function even though one, or more LED dies.

I'm guessing the series is not a real series but something more complex... How would I achieve something like this? I'm guessing perhaps the series provides multiple paths somehow..


texts: Difference between MISO/MOSI and TxD/ RxD

texts:
What is the difference between USART and SPI ?  There are [TXD/RXD] for USART and [MISO/MOSI/SCK/SS] for SPI.
I know that SPI is a synchronous protocol but USART is hardware. But, what's difference between Synchronous part of USART and the hardware ?


texts: Circuit analysis of op amp non-inverting integrator

texts:
I've been trying to figure this out for a while to no avail. Could someone help me out?

So far I've tried computing KCL around a couple of different nodes but wasn't able to get a model describing the entire circuit. I also tried working backwards from the given equation but wasn't able to get anything out of it.


texts: What are (if there are any) the major applications/implications of relativistic electrodynamics in engineering?

texts:
I was wondering about the relativistic and covariant formulation of classical E&M and Maxwell's Equations. Does they have any major implication in engineering (not exclusively talking about electrical eng, but i think it might be the majorly affected)?

I've once heard that relativistic electrodynamics plays a role in artificial neural networks, but i couldn't find any related bibliography.
So, to sum up

What are the major applications of relativistic electrodynamics to engineering?


texts: Remove electrolytic capacitors for a class-D amplifier

texts:
I'm referring to this schematic TPA3251 Evaluation Module, pg. 18

Question:

Our current board design has an SMPS (flyback, 36V, ripple 50mV) & amplifier (TPA3251) in the same PCB (4 layer.) Due to space limitations and cost issues I'm thinking of removing some of the components to save the space and cost.

Is it possible to remove electrolytic capacitors C31 and C46 (2200uF) for the PVDD line at the amplifier side?

Currently, our SMPS already has 3 output capacitors at the output (1200uF, 50V.) Is there any impact?


texts:
I have a simple circuit with a 7447 chip driving a 7-segment LED.  The 7447 input pins A=1, B=2, C=4, D=8 apparently float high as logic 1.  Using momentary pushbutton switches, I short various combinations of the pins to ground, and I get the expected digit on the display-- e.g. connecting D to ground shows the digit 7, connecting B and C to ground shows 9, etc.

Now I'm trying to change the circuit so the pushbuttons bring the input pins high instead of low, so I tried putting 10k pull-down resistors on the inputs.  However, if I short any of the inputs to ground via 10K resistors, nothing happens-- I no longer get any digits displayed.

So I'm wondering 1) why don't the pull-down resistors work, and 2) what's the simplest way to reverse the operation of the pushbuttons.  I'd prefer not to have to deal with things like inverting buffers or changing the mechanics of the pushbuttons, making them normally closed instead of open, etc.

TIA

Carsten


texts: 4-20mA with 12V sensors using ADS1115 ADCs

texts:
I am currently designing a 4-20mA current loop with external sensors which work at 12V DC. I saw a differential application on the datasheet of the ADS1115 ADC, but the simple shunt resistor I believe would be OK in my situation.  I would like your opinion on the GND side of the shunt resistors, is a 100 ohm (R25) resistor enough?

On a MAX31865ATP there is an analog ground for the analog part of the schematic.

Should I also isolate my 4-20mA or doesn't it matter, because I only need to measure the current passing through the known shunt resistors?

**keep in mind that (R21 to R24) are the same part

Also, is my assumption of the 10 ohm shunt good, providing that the ADC reads from -0.3V to 0.3V? Or should I put a bigger resistor and extend to the input limits of my ADC?


texts:
I'm using MP2359 for converting 12V from 20V.

Datasheet: http://www.monolithicpower.com/desktopmodules/documentmanage/api/document/getdocument?id=269

I'm using the recommended sch and layout designs (SCH on the first page).

My resistors are 2K and 24K to have 12V, and I use the recommended Wurth inductance just for being sure about everything. My Schottky is SS24, which is basically the same as the recommended one (it's not available in my place).

Now P#4 (Enable) is connected to P#5 (In) thorugh a 100K resistor to enable immediately as there is voltage on the input side, and I have a tact switch also on P#4 which connects it to GND when I press it. (Reset button)

Currently there is no load on the output, just a 22uF capacitor. (will drive relays later)

If I turn on the input power, it creates 12V nice and smoothly.

However, if I press the reset button, and release, the chip dies, and shorts P#5 and P#6 (input and output), resulting high voltage on the output.

I'd love to hear something useful of the root cause of this. Burnt 6 pieces just today while trying to analyse what is happening.

What I have tried?

I was constantly monitoring the output at the capacitor.
If I turn down the input, after a few seconds voltage collapse to 0.
Turning it back again output goes up to 12V.
Repeated this a few times (but always waited for the 0 voltage after turning off) -> always succeeded.
Then push the reset button (Enable pull down to GND), wait for 0V @output.
Upon releasing the reset button, output goes above 12V until it reach the input voltage.

EDIT

DC5V has a load of a microcontroller. DC12V has currently no load on it (it is connected to a SI2307 P-MOSFET's source)

After pressing the TACT, MP2359 on the left dies, but MP2359 on the right doesn't.


texts: How is electron concentration maintained to hole concentration in intrinsic semiconductor?

texts:
I know about E-H pair generation because of which in an intrinsic semiconductor the numbers of free electrons=number of holes. In terms of Fermi level, fermi level shifts when the temperature is varied and the product of the density of states and fermi function becomes asymmetrical. How it is then that electron conc. remains equal to hole concentration ?

With temperature Ef changes . Depending on the effective masses, Ef shifts either towards CB or VB. How is concentration still maintained from these equations in the picture?


texts:
I drew a simple design with few capacitors just to learn how component links work in altium desginer. (Image 2, pic a)

I checked manualy one by one all capacitors and I saw that UIDs are matched with pcb document. (Image 1, pic a)
In Project -> component links -> Perform Update, a message popup "component links are up to date" appeared.

I tried to change the designators of my schematic between two components. (Image 2 pic b)
After I executed the changes on pcb document I checked again their UIDs manually. I saw again that the UIDs are still matched correctly. (Image 1 pic b)

However, when I hit again, Project -> Component Links... -> Perform Update, a message inform me that "Component links modified in... 2 Links modified"
Which are those two links and how were they modified? The UIDs seemed to be matched even before I perform update.

Can someone explain that to me?


texts: How does this fire alarm system transmit data on two-wire?

texts:
In the fire detection industry, analogue addressable systems use control panels and detectors (and devices such as interfaces) which communicate with each other by means of a protocol.

What protocol is this?

Can anyone help me find information about it?


texts: Why does my LED strip list maximum power as 45W while the LEDs added makes 37.5W?

texts:
My 5-meter LED strip with 30 WS2812B per meter lists "Maximum power: 45W". However, if I calculate it I get:

WS2812B max current draw * voltage * number of LEDs
= 50 mA * 5 V * 150
= 37.5 W

Is the rest of the power due to voltage drop along the wires? Do regulations require a margin of error? Is there any other effect that I'm not taking into account?


texts:
First time-poster. Grateful for the site.  I'm trying to reverse engineer the intermediate circuitry of a 1960s vintage marine tachometer made by a now defunct firm called Airguide. Airguide referred to the black box as a "transmitter."

The circuit works. I jimmied together a pulse generator and the tach responds.  I'm hoping to figure out what the guts are so I can make a reproduction for other tachs that lack a "transmitter."

There are a couple of real stumpers because they're unlabelled, hidden, or just plain mysterious. And the components are caked with conformal coating that's like concrete. Can't test individual elements.

Hidden between the Erofol II and what I assume is a capacitor (the cylindrical one) is a component I don't recognize.  It's shaped like a resistor, is painted green with a black stripe near the lead.  There's a label which includes "8.0" and what could be the bottom half of a "K."

There are also two components that resemble overhead walkways with what appears to be exposed wiring. Each has a lead coming off between the two ends. The signal going to both the plus and minus sides of tach. Both are connected either directly or indirectly to the plus and minus sends to the tach.

I'm not capable of drawing a full schematic, but I've tried to trace the circuitry in case the pics are not enough information.

I realize that with 6 mystery components and no testing ability it may be impossible to define what's going on in this gizmo, but any thoughts would be appreciated.

3/2 20:16 CST

Einar, sorry to take so long to respond.  I've been trying to figure out voltage/rpm.  The numbers look odd to me.

I used a PWM generator (12 V, 50 percent duty cycle) connected to the meter through the circuit.  I measured voltage at several steps.  No nice round numbers. Results are in this chart:

Here's a picture of the setup:

I will review your latest and try to make some educated guesses.

First is N. Inconsistent. Rises with RPMs.  X-axis should be the Hz of each sample.  Couldn't get Excel to display them. Same as in above chart:  95, 100, 190, 312, 380, 455.

Should we continue via email?  I'm at billcatlin@comcast.net if that seems like a good idea.  The site is warning me to that I'm making extended comments, but I don't have standing to switch to chat.  Thanks again!

3/3/20 16:44 CST  Next try

I'm still very fuzzy on the difference between Q and Coulombs per second and amps, but an old HeathKit multimeter my father-in-law gave me measures DC amperage.

Hz     μA
455   107
380    92
312    76
190    47
100    26
95     24.5

Here's a pic of the ol' gal in action:


texts:
I need to introduce a delay to the output of an astable, it needs to be in the order of 10 micro seconds.

I have read that optical cable is good for delays, which makes sense for small delays, but I have no access to optical cable for the project I am working on. The ideal solution would be some components / IC's. I am working with a square wave, so the signal can be assumed to be digital


texts: How to drive a signal between two ICs on two different boards and power domains

texts:
I have two ICs, one on board A and one on Board B. Each of the ICs are powered by 5V on their respective boards that are generated by 12V that each board gets.

The concern is that each of the boards has its own separate 12V to 5V regulator.

How do I make sure the high levels are correct when IC on board A drives a signal to IC on board B?


texts: Connection for 11,12 and 14 in the relay based water pump setup

texts:
I have a question regarding a relay based water pump setup which is triggered by a float sensor in the water tank.
As you can see in the figure,
I have two relays which are single phase AC.
Both relays are RM22LG11MR Schneider.
Data sheet are hereSchneider electric
Numbers 11, 12, 14, A1 and A2 are based on European EN50005 relay terminology as indicated here.
Though there is not much info
The actual setup is like this that as soon as water level in the water tank (not shown in the figure) falls down, the float sensor activates relay 1 via the "Min" connection. Note that relay 1 is in "Fill" mode
The "12" pin from Relay 1 charges the relay 2. But Relay 2 only activates the waterpump when the water level in the pump is above E2.
The connection 14 of Relay 2 is directly connected to the power cable of the waterpump.
Later if the water in the pump falls below E1, the pump stops pumping water in the tank.
As relays are AC, A1 and A2 can be swapped, and hence A1 is connected to main power supply.
But i am not sure what is the difference between 11, 12 and 14 in this case, and if the connections in the figure fit the purpose.
Any help would be appreciated. Thanks


texts: How to prioritize a current path in a circuit

texts:
Here's my problem:

I have a power supply rated at 5V, 2.1A

I need this to feed two devices, both running at 5V

Device one is a single-board computer that can consume anything between 0.5A and 1.5A depending on what it's doing.
Device two is a battery charger, which is happy to take anything it can get up to (and quite possibly beyond) 2A, and equally happy to take no power at all.

I need a way to feed device one with as much current as it is demanding right now, and give whatever is left to device two.  In order to stay within the PSU limits, I'm going to be limiting the input current to 2A.  I'm a beginner, and from my limited understanding (so please correct me if I'm wrong) the chances are that device one could end up current-starved otherwise.

I'm not happy with simply making two fixed current-limited paths (1.5A to A, 0.5A to B) - I really do want any excess current delivered to device B, if there is any available for it.

The only thing I can think of is to dynamically monitor the amount of current currently going to devices A and B, and to throttle down device B by opening and closing current-limited gates with transistors (or using a variable current-limiting circuit controlled by a digital pot) with a microcontroller until the sum of the two is less than (2A minus a safety buffer), along with some caps in there to keep things running during switching.  However, that sounds a bit complex for something that I have a gut feeling ought to be much simpler, and possibly involves using some kind of specialized IC that I don't know the name of in order to search for it.

This is a problem I feel I'm going to run into with other things as well - not just charging a battery, so I'd like to know if there's any way (simpler than the complex microcontroller solution I imagined earlier) to manage the current distribution in a circuit when the supply doesn't meet the demand - some way to simply say "current goes here first, and what is left over goes there"


texts: Why are these readings violating ohm's law? (Are they?)

texts:
I'm brushing up on my high school electronics knowledge and I decided to experiment with a small acquarium pump I had lying around. I took some measurements with a multimeter and the results confuse me to no end. The readings don't appear to correspond with Ohm's law, the current draw appears to differ, etc, and now I'm stumped.

I have this small pump hooked up to two AA batteries. According to the (sparse) data sheet, it's rated for 3V and draws a current of "< 460mA". Using the multimeter to read the battery voltage (with nothing connected) I got 3.18V, which makes sense because they were fresh AA batteries. I then decided to connect the pump and read the voltage on the two connectors on the pump. This read 2.9V, which was surprising to me because apparently 0.28V had disappeared. The wires from the battery to the pump are both only a couple of centimeters long, so this seems like a lot of voltage to lose on such short wires. I then inserted the multimeter in the circuit and measured 0.19A. Finally, I measured the pump's resistance, which was 3.5 Ohms.

Now, according to Ohm's law, U = I * R, so 0.19A * 3.5 Ohm = 0.665V. A far cry from 3.18V or even the 2.9V I measured on the pump. How is this possible?

Trying something else, I hooked up the pump to a 5V molex connector from an old PC's power supply. Measuring voltage on the molex connector, I get 5.04V. Measuring on the pump's connectors, I get 4.92V. Inserting the multimeter in the circuit, I suddenly read 0.28A. So apparently, the pump suddenly draws 200mA more than it did before, which seems weird: isn't a component supposed to just draw the current it requires? Throwing these numbers in Ohm's law gets me 4.92 / 0.28 = 17.575. Also not the 3.5 Ohms I measured.

Finally, I decided to add some resistors to drop the 5V from the molex down to roughly 3V. I added a couple of 1 Ohm resistors in series which resulted in a measured resistance of 4.3 Ohms. Now, if I insert the multimeter into the circuit I get 0.24A, yet again a different current. Measuring voltage across the resistors I get 0.98V, and measuring across the pump I get 3.93V. 0.24A * 4.3 Ohms = 1.032V, which isn't the 0.98V I measured.

I'm apparently missing something fundamental about circuits or Ohm's law, but I can't figure it out. I considered the fact that the pump's resistance changes when it is connected, but then it still doesn't make sense that the values I measured on the resistors don't follow Ohm's law either. What am I missing?


texts:
I know that some multimeters measure capacitance by applying a constant current in a time Delta t, measuring the voltage difference before and after the current was applied, and solving

I = C * (Delta V) / (Delta t)

How do they measure an inductance?


texts: USB power noise insulation (SDR-related)

texts:
I am working on a small board which would allow to connect RTL2832 SDR dongle & HF converter to a PC while using power from battery & separate linear regulators.

The idea is to eliminate noise from USB power supply. I wanted to connect data pins of USB connections for PC & RTL2832, and have 1 Megaohm resistor between ground pins, so that ground of the HF part is floating, but somewhere close to PC's ground.

The problem is that inside RTL2832 dongle there in an 1.5KOhm pull-up resistor from it's local 3.3V source to D+ pin (to indicate device speed), and this ruins the whole idea of detaching grounds. This also seems to kill the idea of having an inductor between grounds of PC & HF parts, so that they are insulated for high frequencies (as current through pull-up resistor is different depending on bit being transmitted).

What are the common solutions for this problem, and how can I insulate as much as possible PC & RTL2832+HF converter parts to minimize power & ground noise?


texts: Why is the red diode in my RGB led burning out?

texts:
I have been working on a simple circuit that uses a 10mm RGB led. I have had the same problem again with the red diode dying out after maybe a day. This time I thought I fixed it, but I guess I'm wrong. I have a 330 ohm resistor connected to it, which based on ohms law and the data sheet should be enough, but it just seems to stop working when I turned it on. What might be the problem of this.

Information on the circuit:
It's basically a simple thermometer that gives you a idea what the tempature is based off of the color of the RGBled. It uses a attiny85 to control everything and a LM 35 tempature sensor
9 volts is the input to a LM7805 regulator which then feeds to the chip. Then from the outputs of the chip a 330 ohm resistors is connected from the chip to all the anodes.

The data sheet of the LED:
http://cdn.sparkfun.com/datasheets/Components/General/YSL-R1047CR4G3BW-F8.pdf


texts: Why does this circuit require such an high resistance?

texts: So I'm new to this and this may be a dumb question, but why is there such high resistance in this circuit when the current/voltage of it isn't that high? A 1M Ohm resistor to the collector seems like too much.


texts:
I am new to SE and this seemed like the best place to ask my question, I apologize if is not.

I am pursuing a MS in Electrical Engineering with a focus in embedded systems/architecture.  I want to pursue a career in firmware and embedded systems development.

I can take two more courses from the computer science department and I would greatly appreciate advice from anybody with experience in this field on which 2 of the following 4 courses would be most beneficial for a career in embedded systems.

Intro to Compilers:
Techniques for translating modern programming languages to intermediate forms or machine-executable instructions/their organization into compiler. Lexical analysis, syntax analysis, semantic analysis, data flow analysis, code generation. Compiler project for prototypical language.
Operating Systems (graduate level, I already took the undergrad):
Conceptual foundation of operating system designs and implementations. Relationships between operating system structures and machine architectures. UNIX implementation mechanisms as examples.
Computer Networks:
Concepts, principles, protocols, and applications of computer networks. Layered network architectures, data link protocols, local area networks, network layer/routing protocols, transport, congestion/flow control, emerging high-speed networks, network programming interfaces, networked applications. Case studies using Ethernet, Token Ring, FDDI, TCP/IP, ATM, Email, HTTP, and WWW.
Wireless and Sensor Networks:
Enabling technologies, including hardware, embedded operating systems, programming environment, communication, networking, and middleware services. Hands-on experience in programming tiny communication devices


texts: CMOS Circuit, Finding Output Switching Frequency

texts:
I'm tasked to analyze the power usage of a CMOS circuit, but I cannot figure out the output switching frequency.

Every 10ns, the circuit is stimulated with input vectors

1110, 1111, 1101, 1111, 1100, Repeat

and the output of the circuit is driven by the expression ABCD.

Since CMOS circuits only draw significant power when switching, I need to find the output frequency, but I'm confused on how to do this.

The output of the circuit is

0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0 ...

It switches for the first 4 inputs but on the fifth, going back to the first one, it doesn't switch.

So every 50ns, it switches every 10ns for the first 40ns and then doesn't switch for the last.

I don't think I can just say the period is 10ns since it doesn't switch on the last input, so how can I find the frequency?


texts:
I measured the turn-on and turn-off behavior of an LM741 and found a weird phenomenon I cannot explain myself.
I built an inverting amplifier with an amplification of 10.

Why is there such a weird kink just before the output crosses 0V?

(CH2: output; CH1: input)

(CH2: output; CH1: input)


texts: Calculate balance between signal and noise to allow 32 kbit/s transfer

texts:
I have to calculate proper balance/ratio between signal and noise ( S/N ) in decibels ( dB ), to be able to transfer data over the channel at 32 kbit/s. Channels bandwidth is 100 kHz.

I was given no formula or additional explanation to have as a start off, the textbook we are using is horrible and I can't reach my professor for explanation. I have to prepare for a exam so thanks for any help in advance.

Add:
I did however pick up a formula used to solve a similar problem where the signal/noise ratio has been provided in dB and the formula goes: \$ W \cdot log_2 \bigg ( 1 + \frac{S}{N} \bigg) \$ This problem stated that the channel allows bandwidth between 400Hz and 3600Hz so \$ W = 3600 - 400 = 3200 Hz\$

But I have no clue how to proceed from here.


texts: Using a Ebike controller for a hobby BLDC

texts: I am looking for a BLDC controller around 750W-1000W. I have yet to build the motor itself but am thinking it will fall within the operating range of 48-60v @ 10-15amps. When I look online I notice their are a lot of fairly cheap controllers for E-bikes. Can I just pick one of these up and use one of these with a SMPS? Furthermore - do these e-bike controllers only operate at specific voltages/amps? Or will they work within a range inside of whats advertised (generally speaking)?


texts: Start and Close Depending to Engine Status

texts:
I have an interesting question, which I really don't know how to do it or it is even possible.

Problem:
I want to start a computational unit (ex: raspberry pi) when the engine starts. If the engine goes down, it should close itself but a soft close from the software.

Need: I should detect the status of the engine.

Constraints: I can not attach anything to the engine or ignition key circuit. I only have the power line from the battery. The power line does not close even if the engine is not working.

Question: Can I detect the status of the engine from the power line? How?

Thanks.


texts: Need to Identify unknown components D53, CT7 and 22X

texts: Please help me to find unknown components


texts: Are KiCad's horizontal 2.54" pin header and 90 degree pin headers equivalent?

texts:
I was experimenting with PCB layout in KiCad and noticed that the Connector_PinHeader_2.54mm > PinHeader_1x06_P2.54mm_Horizontal footprint and a physical 90 degree pin header I have do not seem to match, as seen in this photograph:

The physical pin header in my possession appears to be designed to have the plastic spacer in contact with the PCB, with the other half of the pins used for contact with the female connector.
On the other hand, KiCad's footprint resembles more an upright header laying down on the PCB with a bend to go through the pad further down than most upright headers' pins extend.
I was unable to find anything which resembled the KiCad component through any of the component suppliers I typically use.  Is it a real thing, and does it have a name?  If not, does KiCad have an equivalent to the real component?


texts: What is this fluctuation I get when I use the DC electronic load?

texts:
I have a buck converter. I am loading the buck converter using an electronic load - EA-EL 9200-18T
When I load 100mA at the output of the buck converter, I get this waveform:

To try to find out what the fluctuation is, I changed output current scope channel to AC coupling mode and got this:

The frequency of the output current fluctuation happens to be around 120kHz. Where does this 120kHz come from, and how can I eliminate it?
Even with the DC electronic load turned OFF, and all the input voltages turned OFF, but (the equipment is connected), I get this 120kHz:

I also see a low frequency riding on top of the signal :

However, If I use a rheostat as the DC load for the buck converter, I am not getting any fluctuations as shown below:

Can someone tell me from where the 120kHz is coming from and how to eliminate it?
In some cases, I get 50Hz fluctuation riding on the signals. I suppose that is because of the electricity (AC frequency of 50Hz - which powers the oscilloscope and other electronic equipment's in the test bench) coming from the power outlets which couple to the oscilloscope probes via air. Am I correct?


texts: Altium Designer - Cannot change Designator rotation

texts:
In the PCB editor, I want to set a designator rotation to 45 degrees. However when I try and set its rotation to 45 degrees, it automatically resets it to 0 degrees.

I found that I can still change the rotation by 90 degree increments. I also have other designators that are at a 45 degree rotation. I suddenly cannot change the designator rotation, except in 90 degree increments.


texts: Identifying open switches in a serial circuit

texts:
I have an equipment that includes a circuit made of a bunch of NO switches arranged in serial. This circuit includes a LED that turns on when all the switches are closed. When one or more switches are open I need to identify which ones are open. The following image depicts the existing circuit:

simulate this circuit – Schematic created using CircuitLab

My first approach was to put resistors in parallel with each one of the switches and measure the voltage with an ADC input. This kinda works but I feel it will not be very reliable so I'm looking for a different way to do it.

Can anyone suggest a better way?


texts: Adapating a single cell Li-ion battery voltage to 3.3V low power application

texts:
I'm planning to use a single cell Li-ion battery to power up a custom made circuit.
I'm planning on using a ESP-12E module board as the application will need to connect every once in a while to internet to gather data, acquire sensor data, before displaying them on an e-paper screen, and then fall in a deep-sleep for a given time.

So globally the application tends to be low-powered, with currents ranging from approximately 50µA to 500mA.

Knowing this, the problem is that I'm not sure how to design the power supply.
I first planned to use a LDO regulator, but my protection chip allows voltages down to 2.5V. So I was planning to allow the circuit to function with voltages down to 3V.

I looked toward Buck-Boost converters, and the LTC3440 chip seemed to fit my needs. However, the datasheet doesn't mention how it would behave in low load current situation (<1mA).

Consequently, my question is:

Should I review my application voltage range higher, meaning that it should consider voltages ranging from something like 3.5V to 4V+, or is the LTC3440 Buck-Boost converter would do a great job whatsoever and allow the application to work between 3V to 4V+ power?


texts: I'm comparing a couple of GNSS front-end modules. Is a lower In-band IIP3 point better or worse than a higher one?

texts:
I would typically compare the small signal gain and noise figure first. One of the FEMs requires an external matching component but other that they are very similar in terms of cost and foot-print size.

I reviewed this website tutorial on the differences between -1dB compression and 3rd order points but still not sure how the point (-9dBm or -7.3dBm) will ultimately affect the performance or linearity of the amplifier.

[


texts: Triac Operation: Gate connects to A1 not working?

texts:
I have tested the above circuits and found that I can switch on the triac with the circuit at the top, but not with the bottom circuit.

In my understanding, the Triac can be triggered on no matter the gate is positive or negative, the main difference is I may need a larger gate trigger current (Ig). I have lowered the gate resistor value but still cannot switch on the Triac, why?

Note: I know it is not related to the optocoupler, because when I am testing it, I even shorted pin 4 and pin 6 of the optocoupler and it still does not work


texts: What is the purpose of this plastic strip of tape on some circuit boards?

texts:
I was cleaning an old mechanical keyboard from ~2013 the other day and noticed this strip of thick plastic tape covering a circuit on the smaller PCB that the power connector is wired into.  I have noticed this on other electronics before but I haven't been able to find a clear answer on why it's there and what it actually does.
Furthermore, is it important?  Can it be replaced?  The underside of the tape that isn't touching anything gathers dust and debris and can't be cleaned off very easily due to it being adhesive and everything.
Here is a poorly focused pic:

If it is important, is there a proper way to clean it or replace it?  If it isn't clear, I am not very familiar with PCBs or their functionality on a detailed level.


texts: Formatting DDS Sine Wave output to unsigned decimal

texts:
Currently, I am working with the DDS core on Vivado, using Verilog, to generate a sign wave using a phase width of 7 and output width of 12. I understand that DDS formats the output in 2's complement / signed decimal. However, I am required to output only unsigned decimal through a DAC module.

The current unsigned decimal sine wave looks like this:

Desired output (currently in signed decimal):

What is the best way for me to offset the 2s complement output data to be just positive values from 0 to AMPLITUDE?


texts: I am simulating a speaker system with tweeter, woofer, and midrange speakers. I know my values for the components are all correct, but the output plot is a little off. The passbands should be a little below 0dB, but are at -20dB. The phase angle plots are correct though. Below is a screenshot of my circuit and the graph. Please help as to why this isn't working.


texts:
I want to use a raspberry pi or arduino to create linear motion, back and fourth, my current goal is to make the pushing part for a baby rocker, but also a swing-rocker as a next project
I have looked at linear actuators, but they seem slow and very loud. Ideally I want something like this
https://www.youtube.com/watch?v=qfmFS7nY2hU, but there is very little information on these and Im suspecting they are out of my price range anyway
The closest hobbyish Ive found is this https://www.youtube.com/watch?v=wHdFdw1hLzE or similar, but Id prefer a real product
Iv run out of things to google at "Magnetic Linear Motor", can anyone help me find a product that works with RPi or Arduino or at least a push forward,towards a quiet Linear motion with variable speed


texts: Current source with such low noise even possible?

texts:
I am thinking about how or if it is even possible to build a particularly low-noise voltage-controlled DC current source. I need currents of up to 1.7 A (DC) while keeping its output noise below 1.7 nA/sqrt(Hz) (roughly for a frequency of 10 Hz). At least, this value is slightly higher than the shot-noise limit of sqrt(2 q 1.7 A) = 0.74 nA/sqrt(Hz). However, do you think that such a value can be achieved in practice?

Many thanks for your comments!


texts: Emitter follower for parallel LED switch

texts:
I’m trying to confirm that the solution posted in https://electronics.stackexchange.com/a/60868 will work for my application.

I have four yellow LEDs with a 2v drop (yellow) and 30mA max current I’d like to control via a single low current MCU GPIO pin with 3.3v logic.  I’d like to pull from the unregulated power supply fed from USB or 3xAAA batteries in series (~4.5v).

If VIN measures 4.5-5v, with the base either 0v or 3.3v, emitter at 2.6v, I’m getting ~24 ohms needed to limit the LEDs to  25mA each (100mA total).  This is assuming 700mv BE drop.

Does this work with saturation and everything that entails this configuration?  I’m still very new to this, but I’m trying to setup the transistor as a current amplifier so that the GPIO pin stays well below 12mA and the fluctuating unregulated VIN can be used to feed to current for the LED load.

Thank you!


texts: Why does changing an 'add' to a logical or devour 7 CPLD macrocells?

texts:
I have a design that's synthesizing to about 50 macrocells.

I have this section of code:

module levers2(
     input [2:0] LL,
     input [2:0] RL,
    output reg [10:0] DIVISOR,
    output reg FAULT
    );

reg [10:0] grid[0:63];
wire [5:0] tmp = (LL<<3)+RL;
(snip)

tmp is for all intents, an address line.  I have two 3-bit input lines and I'm combining them to make a 6-bit address line.  So I shift LL by three bits and add RL.  When I synthesize, I get a 47 macrocell result.

However, if I change the operator to a logical or:

wire [5:0] tmp = (LL<<3) | RL;

The design synthesizes to 54 macrocells.  That's 7 macrocells lost for what?!

I would think a bitwise or would be efficient and easy, much easier than an add which has the extra baggage of the carry.

Can anyone shed some light on what's going on?

EDIT ---

I determined it was using more macrocells by using ISE's reporting mechanism.
I also tried a few different things (but not the concatenation operator mentioned below) and everything added 7 macrocells except for the 'add'.  I was happy that the behavior was consistent.

As a side note, I added a single 3-input OR to my top-level schematic and fed it three signals (fault outputs) from different modules.  This added 9 macrocells.  You can bet I found a new way when I saw that, heh.


texts: Replay Philips Livingcolors remote signal

texts:
I have a Phillips Living Colors Lamp, which comes with a remote control. I'd like to be able to capture/replay the signal of the remote control so I can control the lamp with a microcontroller (Arduino).

I have no idea which kind of signal the remote uses (infrared/bluetooth/...). Does anyone know how I can find out which signal the remote uses and how I can capture and replay the signal cost efficiently?

I already managed to capture & replay a TV remote IR signal with an Arduino using this tutorial.


texts: Designing a transformer with low usage time but high power output for small interval of time

texts:
I want to design a transformer ideally for arc welding purposes. The thing is that I want it to be designed in a way that the windings allo overloading of the transformer itself.

For example I had a transformer from old radio, the area of core of the transformer was no more than that of a normal 100 watt transformer but when I shorted the secondary leads of transformer at around 40 volts the calculated power output was 650 watts! The varnish inside the transformer started boiling after a minute or so. But I used that transformer for two years, at least at 200 watt (not full time).

Now the thing is that this property of being able to be overloaded is related with number of turns per volt of the transformer. To be more specific, in normal transformers we divide 7.5 by core area in inches to get number of turns per volt. I know that to make "overloadable" transformer we have to do with this number (7.5) but I want to know figures to be in safe range without tripping my breaker at no load or frying the transformer before I even put any load on it since these transformers have high no load current, and have a working transformer at the end.

Thanks for reading my question.


texts:
simulate this circuit – Schematic created using CircuitLab

Hi,

I have a low battery detection circuit here. When the voltage of the battery goes below 10.5, I have an LED flashing (Uses the NPN transistor and the I/O "1"). This part of the circuit works great. But I also have a shutoff circuit in place where if the voltage of the battery continues to fall and reaches a 2nd threshold, the relay that has BATT and BOUT included in it opens. My first prototype worked well but I was using a relay with a coil voltage rating of 5V (The voltage of CPNP could be as high as 11 V when the battery is at good health). That relay was getting hot.

So I replace that relay with one that is rated up to 12V. But now the system isn't quite working the way it should. If the voltage of BATT is good, the relay turns on like it should, but it will not turn off at the threshold I have set. I noticed when the threshold is met, the collector (CPNP) voltage drops, but still above on 1 or 2 volts which is still enough to keep the relay on. I have added a flydiode to the relay coil as well as placed a 47k ohm resistor on the emitter and base of my PNP resistor but I still get the same result.

Should have I Used a FET instead for this? Is it possible before I place the flyback and the 47 kohm resistor, that I damaged the transistor? I notice when I have OUTPUT 2 set to be low  (LM358 <1 volt), there is a still a significant voltage on the PNP side of that 4.7 kohm resistor (between 0.6 to 0.7 away less then emitter). So I think the main goal is to fix the issue with CPNP voltage, how can I make that get closer to zero?


texts:
I wish to power my Raspberry Pi 4 from a 12V DC battery and to do that I purchased these two products:

Pololu 5V, 9A Step-Down Voltage Regulator D24V90F5
USB 2.0 Type-C Connector Breakout Board

I tested the regulator and it works beautifully – by powering the Pi via its GPIO power rail pins 4 and 6 – it sustained a ~2.4A load with no problems at 4.98-4.99V.

For the life of me I don't understand what I'm doing wrong on the USB Type-C cable part, I get ~4.8V and dropping hard when increasing load when I try to attach the USB connector.
Steps taken so far:

removed the 5.11kΩ pull-down resistors on CC
attached a 10kΩ pull-up on each of the two CC ports (supposedly advertising a 3A capable source if I read the USB Spec correctly).
shorted D- and D+ together

I tested the USB Type C cable with an AC adapter and a native DC 5V powerbank so that's not the culprit.

Do I really need a Power Delivery controller or am I missing something?

PS: this is the consumer's (Raspberry Pi's schematic), it seems to correctly be wired as a sink with 5.11kΩ pull-down:

PPS: soldering job between regulator and usb-c breakout


texts: Ripple on input of Buffer, Non-Inverting

texts:
I am using M74VHC1GT125DT1G a non inverting Buffer IC. See attached image .
I have capture input and output waveform,problem is even when my input is constant high the output is switching.

MODEM TS is:- UART TX line of ARM 9 Processor

I doubt on ripple on input line. But when i checked datasheet is has below parameter. It looks line it can tolerate ripple.
Any suggestion.


texts:
I have built a circuit according to Dimming 230V AC with Arduino, with two output channels. The basic principle is:

An ATtiny does zero detection via an optocoupler; when AC crosses 0 V, it triggers an interrupt.
After a certain delay (e.g. pi/2), the ATtiny fires the TRIAC for phase cutting.

The Triac is a BT136-600E with an IRMS = 4 A and Ipeak = 25 A.

We have connected four (not seven, as originally written) 35 W halogen lamps to each output. This is about 500 mA when they are all on.

When testing it with one lamp, the circuit worked as desired. With all 4 lamps, one Triac simply broke apart. Why/how can this happen?

Measurements

The measurements below are always with a single 28 W halogen bulb.

After the comments, I have built a new board with a BTA316-600D which stands 16 A rms. It is now attached to an Aavid 5297 heatsink which can dissipate 14 W of heat at ambient temperature of 45 °C, which is the maximum power dissipation of the BTA316 at 12 A.

The halogen lamps have a cold filament resistance of 136 Ω (measured with the Ohm meter), which would result in 1.7 A (rms) flowing through the filament of each lamp while it is cold, as opposed to 120 mA when it is hot.

To measure how much current is really flowing and when, I started with a 0.5 Ω 3 W shunt in series to the halogen lamp. The current flowing through the halogen lamp would then be calculated by the voltage drop across the shunt resistor.

Trying to measure the voltage drop with a Picoscope failed because, as I then learned, the ground reference of the scope probe is connected to the case ground and thus also to the USB wire ground and my Laptop ground and finally the power plug ground, which triggered the RCD fast enough to prevent additional harm.

The next attempt was to use one probe on each side of the resitor, this time with a Rigol DS1054Z which can measure 230 V AC. However, the measurements turned out to be too imprecise and too low-res to measure mV differences at the 230 V range. The delay of the voltage difference is a bit odd too.

I had the opportunity to get some measurements with a current clamp (yellow) and a differencial probe (green) connected to a Keysight 4000 X. Here, the measurements while the dimmer was active were as expected. The current stayed below 1 A while ramping up. However, when just turning on AC power (with a power cable with built-in switch, as used for turning lamps on and off), we measured peaks up to 10 A during < 200 ns.

While this gives some insight into what is happening, it does not answer the question for me. The current flowing through the Triac while ramping up is relatively low. The peak when turning on AC is weird (why does it occur?), but very short as well.

This is the schema:

Pictures

A close-up of the triac, the two parts bent apart for better visibility.


texts: Which color should be soldered to which connector for an earphone jack

texts:
I have an earphone plug having four colored wires (gold, red, green, blue) and a jack with four connectors:

I need to know which colour should be soldered to which connector.


texts:
I have 2 MCUs and I want to connect them together over I2C bus. MCU1 will be Master while MCU2 will be Slave. Only these 2 MCUs are on the bus. This configuration is fixed and I cannot change it.

There are 2 scenarios. In first scenario only MCU1 and MCU2 are on the bus. While in a second scenario there are some additional I2C devices also connected on this shared bus.

My main purpose to connect them as above is to send data from MCU2 (Slave) to MCU1 (Master).

So far what i understand about I2C is that it is a command-response protocol. The master gives command to slaves, and then the slaves respond to this command and send their data to the master. The slaves cannot send their data on their own without receiving the command first.

If the master wants to receive 32 bytes of data from the slave then what command will it send to the slave and then how will the slave assert that it has received the valid command for data send? I think this is called 'block-mode' data transfer.

My slave address is fixed as 0x08.


texts: Inside a multiplexer, can it work if i use a Pmos instaed of Nmos to reduce number of inverter?

texts:
To works well, inside a multiplexer we need the input signals inverted, but can we use a pmos instaed of a nmos with a inverted signal to delete the inverter?
Is there any thouble? PSpice give me some problem.

For example i try on PSPice a multiplexer 2 -> 1


texts: Help me set constant current to 1.5mA output and LED to 20mA

texts:
I don't understand enough to accomplish this, constant current output to 1.5mA LED current to 20mA its simply been too long since I learned these things. Im only modifying an existing (likely popular) circuit.

Greatly Appreciated.


texts: Threshold voltage of a pseudo nmos inverter

texts:
How can I find the Vm of a pseudo nmos inverter? Since I dont know the Vds of neither of my transistors I cant determine in which region they are.

The circuit and some parameters are in that link. Wn = 9u is missing there tho.

EDIT1:

LTSpice Netlist

M1 N002 N003 0 0 T15DN l=0.6u w=9u
M2 N001 0 N002 N001 T15DP l=0.6u w=3u
V1 N001 0 5V
V2 N003 0 5V
.model NMOS NMOS
.model PMOS PMOS
.lib C:\PROGRA~2\LTC\LTSPIC~1\lib\cmp\standard.mos
.include T15D_models.txt
.dc V2 5 0 0.1
.backanno
.end

T15D_models.txt

.MODEL T15DN NMOS LEVEL=3 PHI=0.7 TOX=9.5E-09 XJ=0.2U TPG=1
+ VTO=0.7 DELTA=8.8E-01 LD=5E-08 KP=1.56E-04
+ UO=420 THETA=2.3E-01 RSH=2.0E+00 GAMMA=0.62
+ NSUB=1.40E+17 NFS=7.20E+11 VMAX=1.8E+05 ETA=2.125E-02
+ KAPPA=1E-01 CGDO=3.0E-10 CGSO=3.0E-10
+ CGBO=4.5E-10 CJ=5.50E-04 MJ=0.6 CJSW=3E-10
+ MJSW=0.35 PB=1.1
.MODEL T15DP PMOS LEVEL=3 PHI=0.7 TOX=9.5E-09 XJ=0.2U TPG=-1
+ VTO=-0.95 DELTA=2.5E-01 LD=7E-08 KP=4.8E-05
+ UO=130 THETA=2.0E-01 RSH=2.5E+00 GAMMA=0.52
+ NSUB=1.0E+17 NFS=6.50E+11 VMAX=3.0E+05 ETA=2.5E-02
+ KAPPA=8.0E+00 CGDO=3.5E-10 CGSO=3.5E-10
+ CGBO=4.5E-10 CJ=9.50E-04 MJ=0.5 CJSW=2E-10
+ MJSW=0.25 PB=1


texts: Same circuit for Multiple Asynchronous PRESETs / CLEARs

texts: I'm using a dual JK flip flop (IC 74109) in my circuit. I want to keep one of the two flip flops cleared initially, and want to preset the other.So, I intend to use the asynchronous preset and clear pins along with standard resistor-capacitor circuit to achieve this. My question is, can I use only A SINGLE R-C circuit to initially trigger BOTH the asynchronous inputs? I know I can ideally, but are there any practical issues?


texts: Why can't the HC-SR04 sensor detect objects that are very close to it?

texts:
I am following this worksheet and I am struggling to understand the following piece of code:
# Stop when the Echo pin is no longer high - the end time
        while GPIO.input(pinEcho) == 1:
            StopTime = time.time()
            # If the sensor is too close to an object, the Pi cannot
            # see the echo quickly enough, so we have to detect that
            # problem and say what has happened.
            if StopTime - StartTime >= 0.04:
                print("Hold on there!  You're too close for me to see.")
                StopTime = StartTime
                break

I have implemented the worksheet's instructions and the code and when the sensor is very close to the object, I see the ...You're too close... message on the console. However, the condition StopTime - StartTime >= 0.04 and the associated statement ...You're too close.... make no sense to me.
If StopTime - StartTime is greater than a specific value, does it not mean it is taking longer than we want for the pulse to reach the Echo pin? Does that not in turn mean that the object is too far (rather than too close) for the sensor to detect it?
As far as I know, the echo pin is initially zero. When it gets the return pulse, the echo pin changes from 0 to 1. We record this instant as the start time. We then wait for the echo pin to change back to 0 from 1. This instant is recorded as the end time. This StopTime - StartTime check is happening while the echo pin is 1 and we are waiting for this pin to become 0. So if the echo pin is 1, the echo pin has already sensed the return pulse, hasn't it?


texts: Strange LED behavior: Why is there a voltage over the LED with only one wire connected to it?

texts:
I am encountering a strange problem when I measure the voltage across an LED. Please see below picture:

As you can see, I only connected 1 wire ("-") of adapter and used a multimeter to measure the voltage drop across the LED and I found there is ~-2V on the LED! There is no loop in this circuit, so it should have no volts drop across the LED. I have used other multimeters, but I still measure that negative voltage so it's not a multimeter problem.

I'm really sure it's an LED problem, but I have never seen this behavior before. I'm also not familiar with the manufacturing of LEDs, so I don't know what's happening on this LED.

This LED correctly lights with a forward voltage and does not light with reverse voltage. However, the important issue is when I use this LED as a test fixture, it causes the reference voltage (GND) to shift so the output voltage is different.

My question is: Have you seen this behavior on an LED? What is the possible problem on this simple LED?


texts:
I have a simple program basically increment the counter every time I get an interrupt. The code is something like this:

void ISR(void)
{
  static int counter=0;
  counter++;
  GPIO_SET(PIN1); // set the gpio pin
  DELAY(10); // some short delay so that we can see it in scope nicely
  GPIO_RESET(PIN1);//reset the pin
  clearFlag();

}

The event (actually it is a timer) that triggers this ISR also triggers some other stuff (DMA, basically every 8 event I should get a DMA interrupt, this is by design of the code)

In the DMA ISR code, I have another GPIO pin set/reset. Now:

When I look at the events (timer output on a pin and DMA toggle), on the scope I see 8 events correspond to each DMA cycle. So far so good.
When I look at the PIN1 at the scope, I only see 6 events two of them are lost and this is very consistent, always the same 2.

I don't have anything that takes very long time in the ISR and I am puzzled by the fact that  ISR routine is not get called every time I get the event.

I am hoping this is a set up issue on my side, any ideas where to look. This is something so basic that it should just work. This is a new processor from ST, therefore there is a chance that it is a bug but I am kind of refusing to believe something this basic is not working.

The part is new STM32F2.. Compiler is Crossworks.. No optimizations, debug code.. run off the mill settings, nothing fancy.

I am really looking for a pointer to where to look.. Not hoping you guys would debug for me.. What would cause this? Under different circumstances I would assume timing of the ISR is the issue but I disable the ISR code with #if 0 to avoid these timing issues.. So, it is not timing.. What else it could be?


texts: How do you choose the exact width for PMOS/NMOS in your design?

texts:
I'm designing the following function:
$$F = ((A'+B) \times (A+B'))'$$
This is the schematic:

Now I know that in general PMOS width has to be 2-3 times that of NMOS width. But how do you decide exactly what width in the first place? I know there are considerations to keep in mind such as the area, rise and fall times, current etc.

Do we simply pick a value for NMOS and make PMOS 2-3+ times of that then play around with it to optimize the performance as required? If its more complicated than that, then what parameters do I need to know in order to calculate the width?


texts:
I recently came across this intriguing instrument from the 1970s(?):

It's a "Universal Bridge" made by Wayne Kerr.

It's not a type of device I've come across before and I'm curious what these are (were?) used for.


texts: How to transform field strength as a function of frequency

texts:
According to the EN 55022:2006 standard max electric field strength should be:

40 dBμV/m for 30–230 MHz
47 dBμV/m for 230–1000 MHz

I am a little bit confused, I don't know how to calculate the field strength for this frequency range as a function of the frequency. I can't measure it, I just want a theoretical estimation.

The basic field strength formula is:

$$ E  = \frac{\sqrt{30*P}}{r}    (V/m)$$

or

$$E  = \log_{10}\bigg(\frac{\sqrt{30*P}}{ r}*10^6\bigg)*20  \frac{dBμV}{m}$$

So we have the field strength as a function of the distance measured (in M) and the power of the antenna (in W).

But how can we transform this formula to include the frequency. I believe the unit is dBμV/(m · MHz) , but I don't know the formula. Please help.


texts: Steps for troubleshooting Ethernet Cable

texts:
A 100 ft ethernet cable (terminated with RJ45) tests:

The first four cycles should light up green (the first is dark).   Is there a good procedure to systematic narrow down location of the misconnected RJ45 connector or a break in the line?
Any lessons learned are appreciated.  Thank you.
UPDATE:
I found Ethernet breakout boards in a project box.  Maybe a 9V can be connected?  Perhaps the odd terminals can be tied to the + side of a 9V battery and the even terminals connected to the negative terminal?


texts:
I'm trying out making PCBs for the first and I'm using the UV photo resist method. It seems to me I have the exposure and developing working very well but I'm having some issues with etching. I'm using standard ferric chloride for now.

Here is my developed board, it was exposed for 2 minutes (Ignore the spelling mistake!)

Then this is the result of the board that was taken out as soon as the last bit of copper was etched away.

So as you can see traces on the right have dissapeared and others have thinned a lot compared to the width of the tracks after developing.

I've been doing the etching outside in a little plastic container and takes around 8 minutes. I have not heated the etchant.

Does anyone have any thoughts on what is going wrong?

Thanks


texts: Node analysis: estimating variable current branches

texts:
Is there a way to get the number of potential currents that could be in a circuit? (Note: in the following circuits ignore the Resistor value, I've just added a resistor with the default schematic value, but pretend that each resistor might have a different value).

For example, in the following circuit, there would be one:

In this circuit there would be two (ignoring R1=R2):

And in this circuit there would be 7:

My initial thought was the formula would be:

+1 current for each connection from the Voltage source
(+) number of outgoing connections for each connection point where it has either >1 incoming connections or >1 outgoing connections (ignore ground). Another way to put it is degree at the node > 3

Is that correct, or is there a better/simpler way to find the number of potential current sources?


texts: Update very old, very low voltage (10V) Nutone doorbell system to new 16V chime

texts:
I have a Ring video doorbell that is connected and functioning to the old doorbell wires, which I measured at 16V.
I also have a old Nutone Scoville 10 V, 5 VA transformer tucked in a very hard to reach space in a stairwell (see picture). This transformer creates a very annoying buzz constantly, and I'd like to pull it. I believe that it is somehow stepping down the voltage to 5 V to work with the doorbell chime.
However, I was unable to get a suitable reading on the chime. When at rest, it measures 0.20 V and then drops to about 1 mV when the doorbell is rung.
My theory is that I could simply buy a new 16V doorbell, throw away this transformer and connect the two red wires in the picture to each other. Since the Ring is at 16 V, that tells me there is another transformer hidden under the floor that I don't hear and can't see.

But I'm not sure exactly how these old transformers worked and can't find any instructions online. Thank you for your help.


texts: Digital voltage stabilizer relay diagram

texts:
I am using this voltage stabilizer relay diagram below, which provides a 16 step-up level. I need to edit it, so that I can made it to work as step-down in case of high voltages such as 245 and above. I need to make at least two step-down steps from the 16 steps. So in total, I should have 14 step-up and 2 step-down steps. What should I do to make this happen, based on the diagram?

(Original Google Drive image link)


texts: Finding the worst case and best case 4-bit Ripple Carry Adder

texts:
"The below diagram represents the 4-bit ripple-carry adder. In this adder, four full adders are connected in cascade. C0 is the carry input bit and it is zero always. When this input carry ‘C0’ is applied to the two input sequences A1 A2 A3 A4 and B1 B2 B3 B4 then output represented with S1 S2 S3 S4 and output carry C4."

How can we know that the worst case gate delay from A1 B1 C0 is 8 and the bast case gate delay is 2 in a 4-bit Ripple Carry adder?

PS: i just found this image and some text online.


texts:
I am trying to use an LPC11C24 microcontroller to send digital values to a DAC8718 to convert to an analog voltage value. I am attempting to communicate via SPI and I am using mbed.h with the SPI.h capability to send an arbitrary stream of bits to the DAC. However I am not seeing any output on the DAC output. I am communicating via a PCAN-USB dongle. Here is my code:

#include "mbed.h"

CAN can(NC, NC);
DigitalOut chipsel(P2_0);

int main() {
  // Init CAN
  can.frequency(125000);
  // Main loop
  SPI device(P2_3, P2_2, P2_1);
  device.frequency(1000000);
  device.format(16,2); // 16 bits
  chipsel = 0;
  chipsel = 1;
  float response;

  while(1) {
    response = device.write(0xFFFF);
  }
}

What am I doing wrong and what should I do to record output on the DAC?


texts: WiFi module says "mini PCI-e format" with "USB host interface" - what does this mean?

texts:
The specifications of a WiFi module meant for embedded projects, says --

mini PCIe format
Host interface supports USB.2.0
Works with any board with mini PCIe.

Not sure about the interplay of mini PCIe and USB here. Are those 2 options / alternatives for each other ?


texts: Can I break batteries by putting them in the wrong way?

texts:
If I put in batteries the wrong way (+ and - sides reversed), is there a risk that I will break them? Or the device? Or start a fire?

In particular, I am talking about rechargeable Ni-MH eneloops and cheap electronic toys for kids, and most of the time not all of the batteries are put in the wrong way, just some of them are reversed (which is probably even worse, right).


texts: Power supply unit with two negative and positive outputs

texts:
So I am trying to add a power supply unit, which takes one input and supposed to provide one output:

IN: 85-265V AC

OUT:12V DC; 25A (max output power 300W)

However, when I look at it, it clearly has two negative and positive output terminals. I am not sure why is that and what I supposed to do with the second positive & negative output terminals, maybe someone could explain me?

The photo: the manual says +V  +V  -V  -V  stand for 2 positive and negative output terminals, L & N for live and neutral input terminals:

You can find the manual here

Thank you!


texts: Can I replace an 8Ohm 1W speaker with a 8Ohn 0.5W speaker?

texts:
I don't know power is handled through speakers. Can I replace this 1W speaker with a 0.5W speaker in a computer?

From what I understand, it's the load which determines how much power something will draw. So does that mean that this speaker will only draw 0.5W or is the speaker receiving 1W, possibly damaging the poor little thing?

Here is a photo of the two speakers. 1W on the left, 0.5W on the right.


texts: Why is the secondary winding of a current transformer shorted?

texts:
I understand that the secondary circuit in a current transformer cannot be left open, as it will result in a very potential difference being induced in the core of the transformer and permanently damage it.
However, I'm having trouble understanding why the secondary winding is always shorted. Shouldn't it actually have a high resistance, since the voltage is high and current through it is low? Or is there perhaps a definition of 'shorted' which refers to something other than a low resistance path?


texts: How is "Gerber" pronounced? By "gerber" I am referring to the type/class of files generated for PCB manufacturing. I could imagine the first "g" being pronounced with a "g" as in "girl", or a "j" as in "jerk".


texts:
I am trying to control an OSRAM XENARC 66140 35W HID (High-intensity discharge) Lamp with a circuit which contains Texas Instruments UCC2305. I have obtained 4 original lamps from OSRAM and tried on my controller circuit, 3 of 4 are worked correctly and gave light, however one lamp did not emit any light.

Then I have checked this not working lamp with a test setup implemented for 66140 and it worked. So the lamp is not actually damaged.

I have considered that there are little differences that can not be easily observed between working and not working lamps and my controller circuit is not be able to tolerate this differences. I can not say that the electronic design of my circuit is totally wrong because 3 of 4 66140 lamps are working troubleless. But I did not understand why one of that lamp's behavior -which I tried and saw on test setup and working.

If you share your comments it may be solve my problem.


texts: What is the meaning of the "lasso loop" on circuit diagram?

texts:
I've never seen this "loop" structure in a circuit diagram before.

Pin 6 has a line that loops around the lines from pins 5 and 9.
Pin 7 has a line that loops around all other lines, except the ?resistor? between pins 1 and 6.

  NOTE: This pinout diagram is for the db9 connector on a Nellcor Pulse Oximeter


texts: How to limit negative voltage on uC input pin

texts:
I'm trying to design a pulse induction metal detector to increase my EE skills a little bit.

I started to sketch out the transmitting stage, which is just a MOSFET that switches current through a search coil and limits the back-emf for further processing.

What I want to achieve is to pull a pin on my microcontroller high (+5V) when the transmit pulse starts and pull it back to low (GND) when the back-emf sets in i.e the voltage goes negative on test point 2 (TP2).

The microcontroller pin is therefore connected to test point 3 (TP3) and the problem I have is that the transistor is still open (?) and the voltage drops to -12V, which kills the input pin on the microcontroller.

So my question is how could I improve the design to only have +5V or GND on the microcontrollers input pin? I've already tried to place a diode after the emitter but this still leaves a negative voltage of about -0.7V ...

Thanks for any advice!

PS: The TVS diode clamps the voltage to +/- 12V

RESPONSE TO ANSWER


texts: Can this circuit drive directly a led ( or even supply a BJT )

texts:
I've this PIR board:
https://www.mpja.com/download/31227sc.pdf
the chip output has already a 1KOhm resistor in series, so, since the one voltage of the chip is 3.3 V I guess I could connect directly to a led without having to add another resistance. Is this true? I just want to use that layout for testing, then the signal would go to a micro controller I/O. Just for the sake of completeness, since there is the 1K resistor on the out, I should drive even a saturating BJT directly, without adding any other resistor, isn't?

Did try, it works, but barely visible so added the BJT without any addtional resistor on the basis.


texts: Why is my Sample and Hold circuit not working

texts: I have two of these circuits on a board which are both behaving identically. ie. neither is holding a sampled voltage but rather just passing the input directly to the output (indicated as with the input switch closed).With the switch open and no charge on the cap I would expect to see ~-8V at the Anode of D2 in order for the FET to be completely off but it sits at 0V....is this right? The Voltages indicated are with the input switch open.  The circuit is copied from an original schematic. Please help me get this working. Thanks:)


texts:
An electromagnet is lifting/pulling large pieces of iron, from a distance $r$.
Is there an induced EMF in the coils of the electromagnet due to the change in flux?

Another configuration would be the piece of iron is rotating around the electromagnet is there still EMF induced?

I'm confused because if a ferromagnet is introduced to a magnetic field, there is  a change if flux, however, is the magnetic field produced by the ferromagnet = to the external magnetic field?
Also are there large voltages induced?


texts: What power motor should be used to power a Segway-like device

texts:
I am planning on building a personal transportation device which will either be a skateboard with a motor etc or a Segway-like device.

I will have two wheels and must be capable of getting me to move from still-position to at least 20-30 km/h for fun/fast transportation.

The device will be controlled by an Arduino (for some other cool features)

My problem is selecting an electronic motor. Where should I look? What type of motor?
It must probably be a DC motor, but what should I be looking for?

Voltage
Wattage
Amperage
Size

Maybe also what type of battery & speedcontroller should be used with it? It needs to be able to go at least 20 min on a cycle - hope it won't become too expensive.

Thanks

Take note: This is just a fun project so I have a very small budget


texts: SPI and pullups. Is it ever used in open collector configuration

texts:
Is SPI ever wired as open collector in devices calling for the use of pullup resistors? Everything seems to point to it usually being totem pole but I wonder if there are exceptions.

The only pullup really required seems to be on the chip select, but sometimes a pullup on MISO seems to be used also for reliability/robustness reasons.

Can someone describe minimal pullup/pulldown requirements for SPI buses, and answer if totem pole configuration is the standardized driving method for SPI?


texts:
I was wondering if it's necessary to add a 1KOhm resistor on a digital input that listens to HIGH signals (3.3V) or I can just feed the 3.3V to it without any protection.
I'm making a circuit to enable an IC that listens to HIGH(1) and LOW(0) signals so I added an SPDT slide switch that selects between 3.3V and GND. The question is if a series 1K resistor on either 3.3V or GND lines is necessary.
The schematic:

EDIT: New Circuit


texts:
I'm trying to design a low power PIR motion sensor, but there seems to be a dearth of information about it. I know how the pyroelectric sensor works, and I know what the waveform looks like, but how do I make a small, low power circuit that can actually detect that? The ideal thing would be to use an existing chip, but it seems like there are so few of those, none of which are really readily available.

I've found a few circuit diagrams:

but as you can see, they vary massively in complexity. Ideally I want the simplest, lowest power, smallest one possible, but I'm lost on where to draw the line. The BISS0001 manages to do it at like 50uA, which I feel like I could not get close to.


texts: Optimal duty cycle in Forward converter?

texts:
So as far as I understand the Forward topology:
The duty cycle set by the controller in CCM mode is constant assuming constant input voltage and constant output voltage. The duty cycle is independent on load, right? (Of course in DCM it is load dependent, but now continue with CCM)

So if I know the nominal input and ouput voltages and the transformers primary to secondary turns ratio, I can calculate the duty cycle it will operate with ( \$d=\frac{Vout}{Vin*n} \$, approximately of course, for being more precise I can calculate with the diode forward drop + other losses). Now the freely chosen parameter of these is the turns ratio, so by choosing its value, I can set the duty cycle of the operation.

The question is, what duty cycle should i go for? What are the main factors that I should take into account when choosing the duty cycle?
The topology I'm planning to design is with reset winding. Is it better to use most of the available time for reset? (I mean minimazing t_off-t_reset, limiting it only to safety margin to get proper reset)


texts: Sizing a diode for a desired current and switching capabilities

texts:
I was planning to use the following circuit with a 1N4148 diode for a PWM between 0.5kHz upto 30kHz:

In another forum someone mentioned 1N4148 is too small and it needs to be replaced with a bigger one, but fast with 1A DC rated which would be more than enough.

But in simulation very small current passes through diode:

And this is the MOSFET power plot:

What would be the reason to go for a bigger one?

I'm hesitating between a 1N4933 and a 1N4001-T.
Both has 1A "Maximum average forward rectified current".

1N4001-T is called Switching Diode, 1N4933 is called Fast Switching Plastic Rectifier.

Are they both fast enough for this circuit where PWM can be up to 30kHz?
I don't know how can I approach this issue of choosing the right diode here.


texts: How secure are station clocks (using DCF77)?

texts:
In the Netherlands, we have clocks at train stations like on the one on the image below.

In order to get the time as precise as possible, the clocks read the time from the DCF77 signal. (As far as I know, for the sake of this question, let's say it is the case.) DCF77 is a longwave time signal from Germany used in mainland Europe.

My question is, how secure are these clocks?

What would happen if I would broadcast a completely other time on the same wavelength near such a clock? Would the time change?

Disclaimer: I'm absolutely not planning on doing this. (Otherwise, I would have found out myself.) I'm just curious about how secure these clocks are.


texts: What's up with TI TIVA's SPI controller?

texts:
UPDATE: The issue with debugging someone else's code is you just have to assume everything is being coded correctly. I just checked datasheet and there was this BSY (bus busy) flag bit in status register. I just made it so that it waits for BSY bit to get reset and now the ~CS behaves properly. Sorry.
Working on TIVA-C 123GH6PM. Sending data over SPI lines does not produce the desired result. I am sending 3 bytes of data in one ~CS cycle and using the Freescale frame format. The ~CS line goes high before sending the last byte.

If I send 2 bytes of data, the same thing occurs - the last ~CS goes high before I have the 8 clock cycles.
The only workaround I found was adding some delay before pulling ~CS high or sending another byte of data which of course doesn't get sent.
This is my write subroutine :
void SPI_write(uint8_t data)
{
    *(__IO uint8_t *)&SSI2->DR = (uint8_t)data;
    while((SSI2->SR & (1<<0))==0);
}

I tried type casting as you see above as I have worked on STM32 before and that has data packing, and typecasting there pulls ~CS properly, just as a last ditch effort.
Why does the ~CS line behave so strange? Is there a proper solution to solve this?
PS: I have selected the data size to be 8 bits just in case that comes out as a suspicion. If the full code is needed, I shall update the post with it,, just let me know


texts:
For a project I need a zero crossing wave like this

Its generated by an inductive coil of a distributor of a car engine where that signal triggers a CDI (capacity discharge ignition) when it falls from positive to under -0.3v.
My target is to reproduce or at least mime such a zero crossing wave with a PWM wave using an Arduino Nano in a car environment.
In the circuit below I tried this by using a 2N3904 NPN transistor where the -5 volt are provided by an ICL 7660.

But with this circuit it results only in a +1v/-1v PWM (screenshot below) and not in a +5v/-5v PWM … actually a +2.5v/-2.5v PWM would be sufficient.

My question is: how can that circuit above be optimized to get at least a zero crossing +2.5/-2.5v PWM.
Thanks a lot in advance and sorry for the first complicated question attempt.


texts: General Engineering - Organizing Information, Ideas, Projects, Reference Material, Physical Parts etc

texts:
As you work on project and learn new things there is information and things learned that you want to refer to in the future.  The commonly used things are not a problem, when used enough you usually remember.  But there ends up being thousands of pieces of app notes/ personal notes / how-to's etc that are occasionally useful.

Then there is all the locations, where the project source code repository is, the library files for 3D / Schematic / PCB and all the other assets.

Then there is all the tools such as compilers, IDE's and the required versions of each that were used to create the project files.

Then there is all of the To-do's, project tasks, stuff that needs to get ordered, stuff that maybe could be ordered for experimentation/research in the future.

Then there are all the books that should be read at some point in time.

Once you end up with enough of these "things" to track you can end up spending most of your time just curating the collection of these things, if you want to attempt to keep things organized.

Is there any ideas from anyone as to how you manage the overwhelming amount of information, projects, ideas and things and the relationships between them all?  I hate having to re-learn stuff if it is not documented enough but I also hate searching for things I stored previously if it is not organized well enough.


texts: High current melting a spanner - what's happening?

texts:
Just a couple of guys doing fun things with a DIY low voltage very high current transformer. One of the things is putting a spanner on a brick and touching the two ends with an extremely thick copper cable carrying several thousand amps.

The spanner then becomes red hot and melts. And here we come to the question:

Why does the spanner turn red hot at the ends first and then later towards the center? I would have thought uniform current would have heated it evenly


texts: We tested AC-DC converter(AC to 15V, 2A). problem is when i ON/OFF a FAN, which is connected on AC line, voltage spikes appears on DC output of 15V. (2V pk to pk). If i am measuring with tip and barrel method of oscilloscope, spikes may come down upto 0.5V pk-pk. How can i reduce this below 50mV pk-pk? and what is the reason for this?


texts:
Given the below pictured 1S parallel battery configuration that draws 20 amps (for example), with the pictured connections, what would the approximate current flow among the various spots along the bus-lattice be (not 'how many amps does each cell provide')?
Could the current distribution be further diluted by adding additional diagonal bars between cells?
I realize that if/when this parallel group gets put in series with other groups, the series connections will all carry the full 20A, but I'm specifically curious about intra-parallel current flow.


texts: Design a digital controller for minimize the settling time

texts:
I have a system of digital control with unitary feedback, with the following transfer function:

$$G(z)=2\frac{(z-0.5)(z-2)}{(z+0.2)(z+1.5)}$$

I need to use a digital controller:

$$C(z)=K\frac{z-\beta}{z-\alpha}$$

And the purpose is minimize the settling time as much as possible and calculate the settling time for this new situation.

I design the root locus for \$G(z)\$:

Poles: \$z=-1.5\$; \$z=-0.2\$

Zeros: \$z=0.5\$; \$z=2\$

Break points:

\$z=-0.615\$; \$z=0.948\$

What are the values for \$\alpha\$ and \$\beta\$ for the controller and what is the value for the new settling time?


texts: Could sliding down a slide damage my camera?

texts:
Specifically one of those plastic spiral slides - I was at the playground with my children yesterday and when we went down the slide there was enough static generated to stick our hair on end. Of course my son has more hair than I do by now...

Anyway, there was a drastic increase in charge - such that I could feel the buildup as we got closer to the ground. And when we grounded it felt like a jolt from my feet to my hair. I'm not super intimate with electricity, but from what I know that seems like it was a lot.

I had my cell phone in my pocket, and was wearing my DSLR around my neck, but both devices seemed to be un-damaged by the voltage - I'm guessing it just didn't pass through them.

Is there a circumstance where the static could damage these electronics, based on how I was holding them or something? Or are they designed well enough that they would withstand this staticy sort of shenanigans?


texts: How does electromagnetism factor into inductively coupled RFID systems

texts:
LF and HF RFID systems use inductive coupling to supply the tag with power.

UHF RFID systems use antennas to send electromagnetic waves, the power supplied to the tag comes from the transmitted power of the tx antenna.

As far as I understood, there are no electromagnetic waves used in LF and HF RFID systems, is that correct? In certain literature they are grouped together as an explanation for the skin effect was given as

"An electromagnetic wave impinging on a conductive object penetrates to an extend known as the skin-depth.... It is apparent that at 125 kHz, water and water-containing materials have essentially no effect on RFID Operation"

But 125 kHz is in the LF category so it uses inductive coupling instead of electromagnetic waves.


texts:
I have 4 12v batteries, and 2 mppt charge controllers. I want to run the batteries in a series to get 48v. The two charge controllers are 12/24v output. Is it possible to charge 2 batteries with each controller while they are still in the series?
I could buy a single charge control that will do 48v but i already have these two on hand.


texts: How does the Colpitts oscillator provide positive feedback?

texts:
This is a Colpitts oscillator in a common-emitter configuration:

For oscillation to occur, there must be a positive feedback. But I'm confused how can this oscillator provide a 360° degree turn for the input signal.
At time t=0, DC current passes through RF choke and goes to C1 branch and L-C2 branch which both goes straight to ground. I added the polarity for C1, C2, and L above. From what I can see, the polarity for C2 forward biases more the base-emitter diode thus the collector current sinks and collector voltage decreases. This seems to contradict the preceded polarity (which is positive). With this, I think voltage will not build-up and oscillate.
What am I missing?


texts: When is it relevant to consider a trace as a RF transmission line

texts:
I'm building a simple Greinacher based RF Power meter for the PMR band i.e 446MHz.
I intend it to work as a confirmation device and not something really acurate.
The circuit is quite simple:

The led is for visual control if the system works well.
I have obtained the Following routing (without the LED):

From left to right: I have the input SMA, with a transmission line adapted to 50Ohms.
Which goes into the C1 capacitor, then in the diodes, and then in the C3 capacitor.
Is it relevant to consider the trace between C1 and D1 and between D1 and C3 as transmission lines?
They are short L < 4mm, for a wavelength of around 70cm.
For the moment I have used the embedded calculator in kicad to find the dimensions of the transmission line used :


texts:
I'm connecting a Digi XBee radio to a Kinetis microcontroller and would like to know how to control reset. The XBee datasheet describes the reset pin 5 as both input and open drain output:

Additionally, the Kinetis GPIO port controller can configure pins as either push/pull or open-drain output:

I think that to reset the radio, I need to do the following:

Not configure the pin direction (input/output) at boot, effectively leaving it floating.
To start reset, configure the pin as output and enable open drain.
Wait for at least 200ns.
Reconfigure the pin as input.
Wait for the radio to drive the pin low.

Is that right, or should I drive the pin low at step 2 instead of enabling open drain? Also, is my reasoning correct that the radio will eventually drive the pin low, so I should reconfigure the pin as input and poll until that happens?
I just want to clarify this as I've wasted a lot of time on similar issues before.


texts: How to power a 24V 2.5A DC motor with a switching power supply?

texts:
I need to power a windshield wiper motor at 24V. Switching mode power supply shuts off.
The motor, rated 50 W, runs at 12V (50 RPM) or 24V (110 RPM).  It's exactly the same one this guy has in this youtube video.

PROBLEM
I have a a 24V 5A switching power supply that works fine with a 24V incandescent lamp. But if I connect the motor, it spins for less than a second and the power supply shuts off (the onboard LED turns off.) I'm pretty sure the inrush current skyrockets briefly and causes the shutdown.
QUESTION
Is it possible to power the motor using my current PS?
What do I need exactly?
I don't need variable speed control or anything fancy or expensive.


texts: Why aren't non-isolated DC-DC converters made for high wattage applications?

texts:
I am new to electronics. I am presently studying DC to DC converters.

One thing I noticed is that most of the people are using isolated stepdown converters like half bridge, full bridge, or resonant LLC converters for conversion such as 400VDC in and 28VDC out at 1kW. But there are no non-isolated converters like buck converters.

I am just curious to know why this is so?
I am trying to build one AC to DC converter at 1KW, where my boost PFC gives 400VDC output.

I think 7% duty cycle is normal to drive given with the technology we developed (as D = 28/400 => D = 0.07), still i am unable to find any manufacturer who makes such PMIC with that small duty cycle at high power such as 1KW.


texts: Does anyone know of a chip which can extract the colour burst from a PAL or NTSC video signal? Then, I would need to start an oscillator of the right frequency (4.43361875 MHz for PAL, and 3.579545 MHz for NTSC) and keep it oscillating once this frequency is established. If the signal is PAL, I would also need to phase shift this oscillator on every other line. Ideally, I would use just one crystal for both but I don't think the two frequencies could be derived from one crystal. It is required that the module support both PAL and NTSC; I'd like to avoid producing two types for different systems. In other words, I need some way to synchronise to a colour burst. I'm sure such devices must exist; most broadcast PAL/NTSC TVs would use one, but I'm having no luck.


texts: When does the reset on a 74HC164 Shift Register occur?

texts:
I don't have a 74HC164 on hand to try and I'm not 100% sure from reading the datasheet.

If for example I've got a bunch of LEDs lit up from the outputs of the 164 and I pull the reset pin LOW will

A) all the outputs be immediately set to LOW as soon as I pull the reset pin low

or

B) all the outputs will keep their current state until the next clock pulse when all the outputs will be pulled low.

I'm waiting on some of these to arrive in the mail to experiment with but would love to be able to get my schematics in order while I wait. Thank you!


texts: Device that transmits signal to computer

texts:
How would I be able to send a notification or email/msg of some sort to my computer after an event has taken place from elsewhere. To be more specific, when a tripwire is tripped, (LDR/Laser beam) how would i be able to send a signal to my computer over wifi that it has been tripped?
Sorry if my question doesn't really make sense, I'm very new to electronics.


texts: unknown circuit symbol rectangle with arrow

texts:
I've never seen this symbol before but my wiring diagram is full of it. I also have searched for lists of symbols but it isn't among them. Does anybody know what is is? It is from my wiring diagram of a Yamaha RS 125.
https://pasteboard.co/HX0dVKZ.jpg
(the image was to large so i uploaded it to pasteboard so it wouldn't get compressed)

But this is the symbol in question.


texts: I am trying to convert my 9.6V NiCad drill to run off a 12V Li-on battery. When I connect the Li-On directly, the motor only just slightly spins and stops. The only way I can get it to work is using a Step-down Buck Converter. Initially I thought it needs 9.6V to start working, but nope works fine at 12.3V too, just not when connected directly to the battery. What am I missing? How do I get it working connected directly to the battery? Does the DC motor need a starting capacitor?


texts: Is it really problem if 0,3 voltage more than required applied in digital multimeter?

texts: Does it negatively affect if more 0,3v voltage than Power Supply (PS) required by general digital multimeter (DMM) supplied ?. I have a DMM with PS requirement of 2 x 1.5v AA battery and in hand is 2 x 1.65v battery. Can I just safely apply the 3.3 v into the 3v PS requirement of DMM which would be 10% extra power than should be ?


texts: is it a bad idea to use voltages higher then 12v for electrolysis based hydrogen extraction?

texts:
I am currently using twelve volts from my power supply, it works fine but I do have the ability to put more then that, up to 2kv, I am using salt water - I know, this produces chlorine gas, I have that sorted.

If I was to, stupidly, put 240V or more either AC or DC, would it be advised to use a less conductive electrolyte? I am aware that this method requires a lot of power.


texts: Creating a power supply for a small machine

texts:
I bought a small automatic pipetting machine, but the machine does not have a way to regulate how much liquid is emitted. I would like to modify the power supply that I bought with the machine to be a timed power source that could be adjusted between several time settings until an optimal time is found for my pipetting purposes. The device that has this feature pre-built in cost ten times the version that I bought. The power supply needs to be 12V DC 1A, but otherwise, I do not know how to construct the timing part. I'm thinking a 555 chip, but I really do not know.

Specific question: How do I create a power supply that supplies 12V DC 1A for a varying amount of time on a breadboard?


texts: Unused Op-Amp in Photodetector setup, but only occasionally

texts:
I am designing a modular system that will take 9 or 16 photodiode inputs, depending on its setup, and put them through an op amp. The diodes and the op amps are on different PCBs, connected by pin headers and sockets.

The schematic looks like this:

However, some of the time some diodes will not be present (i.e. D1 will be missing), because on the modular diode board there may be only 9 diodes (if configured that way). The remainder of the components will still exist, as they are all on the same PCB.

The datasheet says to do this with the unused op amps:

I can see no way to make either of these circuits by only modifying the schematic at the point where D1 is inserted, because the design of the PCB means all the + inputs are always tied to ground.

I effectively have one place to make changes, so the question is what to do with the - input. Leave it floating, connect it to a voltage divider, connect it to ground or supply via a resistor (or no resistor). I realise the situation is not ideal. Any suggestions?


texts: Can a normal USB C panel mount socket be used to receive USB PD?

texts: I'm building a lamp that has (up to) three wall-mounted units connected to a central control box. Each one gets three low-voltage control signal wires and 12V 3A DC power. I'm figuring that a USB PD cable is going to be best for this, just for convenience, but I'm having trouble finding USB PD panel-mount jacks.


texts: Layout suggestion for transimpedance amplifier guard

texts:
I want to know what is best way to layout a transimpedance amplifier circuit like below. We have amultiplexer that picks the gain resistor  and a feedback capacitor. (I am  not worried about VGND position and also resistor values just for demonstrations.) I know you have to keep the feedback resistor and capacitor close to opamp but in this case I can not.

simulate this circuit – Schematic created using CircuitLab

Should anything change in the layout below? Should I connect the feedback resistors in one side or both sides? (Yellow line, loop to reduce trace length.)

Also if you have suggestion on layout or circuit to reduce noise effect since the sensor produced very little current (10nA-100uA.)

I want to know should I cover sensor+ trace  surrounding with via to GND or VGND (I think it should be GND) and where should I put the guard?


texts: How can I use "favorite via" during routing with Altium?

texts:
I've set up a few via favorites within Altium, butI can't seem to figure out how to cycle through the various presets.

How can I cycle through favorite via presets during routing ?


texts: Changing the standard "message" on PIC24F shown on Android

texts:
I am working on an android accessory development.
Currently whenever I plugin my Android device to the PIC24F (which I had programmed in the PIC24F) but I haven't installed in the Android phone

It display:
"Accessory Development Starter Kit (PIC24F) for Android(tm)

No installation applications work with this USB accessory. Learn more about this accessory at the microchip"

I tried using MPLAB to read/access and find the sentence but there isn't any result.

How can I modify the sentence?

The software I am using:

MPLAB IDE Version 8.73 MPLAB C Compiler for PIC24 and dsPIC v3.30

The device/tools I am using:

DM240415 - PIC24F Accessory Development Starter Kit for Android


texts: Feeding an antenna with a YIG oscillator

texts:
Assume I have a YIG tuned oscillator (2-10GHZ), output power 10-20mW, and an ultra wideband antenna corresponding to this range.
Is there a problem with feeding the antenna directly with the oscillator (using coax + balun if necessary), or is a "in-between" buffer needed ?


texts: How many hairy crazy ants does it take to short out an electrical system?

texts:
I read an interesting article about an invasive ant species the other day and was amazed by the following paragraph:

  The ants can bite, but the biggest danger is that they're attracted to circuit boxes. The reason isn't known, but their sheer numbers can create an ant bridge between connections, shorting out entire electrical systems.

The journalist that wrote that probably doesn't know any more about electrical engineering than I do, so I thought I'd ask some of you guys... If this is good reporting, how does this happen?

Related questions:

How many ants do you think it would take to create a bridge between connections?
What would you do to protect your equipment from these ants?
Any theory into why they are so attracted to circuit boxes?
Or is this just bad reporting?


texts: Why not SRAM for FPGA in image processing?

texts:
I'm beginning with VHDL coding and I've done some basic image processing on my development board.

I've noticed that most FPGA development boards often use DRAM (SDRAM, DDRAM) as RAM.
For example, I'm using a FPGA dev board from TERASIC and it uses DRAM.
Although DRAM memory seems to be cheaper that SRAM (Static RAM), from my point of view it is not optimized for image processing, let me explain:
DRAM data is accessed by block, SRAM data can be accessed (addressed) byte by byte (or word by word, or 36 bit at a time, whatever). This feature is more matched to image processing, for example, a simple mean filter where a pixel is the mean of its neighbour, say

Pix(x,y) = (Pix(x-1,y-1) + Pix(x,y-1) + Pix(x+1,y-1) + Pix(x-1,y) + Pix(x,y)
           + Pix(x+1,y) + Pix(x-1,y+1) + Pix(x,y+1) + Pix(x+1,y+1))/9

is difficult to do with DRAM, you need to have an internal buffer of at least two lines to memorize lines y-1 and y (doing the processing on the y+1 line). Also it seems to take a huge amount of time to Quartus to do this simple processing (I'm using 2ports FIFO).

If the board had used SRAM like IS61LPS25632A from ISSI for example, the processing would be straightforward since the address of a pixel can be for example

ByteAdress <= x + (LINEWIDTH*y);

From a hardware point of view, with 9 read/write memory clock cycles the process is done for one pix and with some tricks in parallel processing this can be improved I suppose.
Then, is my understanding true? If not, where is the mistake?

EDIT:

Using internal FPGA RAM is not an option for me since there is not enough memory inside the FPGA device I use (Cyclone III) and I don't know if paying for a more expensive development kit just to have some more RAM inside FPGA is judicious.

My question is more related to code efficiency. Say for example that one has 8MB of SRAM. From my point of view, the code produced with this kind of RAM will be more efficient (speed and buffering) in the case of 2D processing (like image processing) because true random access is well suited for accessing data with (big) offset between then, like on this statement:

ByteAdress <= x + (LINEWIDTH*y);

Reorganising information is time consuming. I use a camera that outputs data pixels sequentially, line by line. I can only store these data on two port FIFO RAM component built with DRAM. I can't do even a simple transposition before storing the data with this. Surprisingly I didn't find any code on the web that deals with this 2D problem.


texts: 3.3V Oscillator AC couple to 1.5 Vp-p input

texts:
I'm using MICRF220 (origin from MICREL, now Microchip, Sadly, I can't find a suitable place to ask my question. It seems Microchip has not a suitable forum for this chip yet!!!) It can receive external reference input. But it only give specification for AC couple.

May I use DC coupling?
If using AC coupling, I only have OSC with 3.3V output. So, I have two choice, one is a resistor divider followed by a coupling capacitor. Another is simply a series resistor followed by a coupling capacitor. Which is better?
Any better replacement for this chip?


texts: I am a new bee to PCB designing. While reading articles I have found people talking about "covering even number of layers with blind via". I have talked to a local PCB manufacturer and they said the same thing and they said they can't do via like 1-2 and 2-3, but they can do 1-3 and 4-6 (Assuming 6 layers board). For it seems that if I connect an internal plane to an external layer (Say 1-2), then I can't connect the internal plane (2) to any other layer. Is it the case? I am really confused with this. Can someone explain in detail with possibly a picture?


texts: Which zener diode types are proper for clamping the swithcing input signals

texts:
My question is about determining the type of zener diode for the secenarios where the zener is used to clamp a switching pulse input. For clarity I draw the below example circuit section:

Regarding the above circuit, the zener is used in the circuit to clamp Vin to Vout. So the zener must clamp and must be able to work properly for a switching input.

Now if Vin was an almost constant voltage I would use a zener diode under the category of "voltage regulator".

Here is an example of zener type options from a provider:

But in my case the incoming voltage Vin to be clamped will not be constant; it will be for example a pulse train i.e. ON OFF voltages with max frequency of 1kHz.

If the voltages to be clamped is such kind I described, what type off zener diode should be used in a design? And what parameters should be checked in datasheet if the diode can work properly under a desired switching frequency?