texts: Oscilloscope waveform shows overlapping levels, second harmonic?

texts:
What could be causing this 40 GHz signal to look like two overlapping waveforms on a 63 Ghz real time oscilloscope? On the scope I see the signal out of a 40 GHz signal generator outputting a CW sine wave as:

It looks like it overlaps, and then on the color grade persistance when I try to take a histogram for jitter I see the two peaks in the histogram. When I just take a single shot I see:

It looks like it actually is wiggling with 4 different hi and low voltages.  When turned down to 35 GHz, it doesn't show the behavior:

I just want to sanity check that this isn't due to a scope setting, the sampling is at 160Gsps [Edit: I previously incorrectly said 80 Gsps] and I varied the memory depth from Kbps to Mbps.  Does it look like it is some second harmonic causing this?  Is it more likely due to the signal generator (a VNA outputting CW) itself, or bad connectors in the cabling giving bad VSWR?

Thanks for tips and hints!


texts: What does division order mean in Rayleigh Fading?

texts:
So I'm just beginning to understand how Rayleigh Fading works and I'm trying to model some different modulation schemes with Rayleigh fading channels. I'm doing this on MATLAB where one of the necessary parameters is something called division order but this isn't really explained on the MATLAB documentation.

Having a little look around I saw it being mentioned that division order is degrees of freedom but then, on Wikipedia, it says that the Rayleigh Distribution is pretty much the chi distribution with two degrees of freedom. Can division order be degrees of freedom? If so, what does this actually mean in the context of Rayleigh Fading?


texts: Trying to get the most out of 48V 500mA switch

texts:
I am sorry, I don't have a lot of experience with electricity, but I'm going to give this a shot. What I'd like to do is utilize a switch, that is part of a large device. When the device turns on, the switch is bridged. I'd like the switch to power a light, as the device turns on. However the switch is limited to 48V 500mA, and I can't change it because it is within the components of the machine.

After looking on the forum I found that 48V 500mA is equivalent to 12V 2A, but I also read it wouldn't be smart to have higher or lower volts running through the switch than it is rated for.

I have uploaded a picture above with a way I thought to create the circuit.

120V 20A comes out of the wall to a 48V 500mA power adaptor. The power would then be consistent with the switch and a simple circuit could be made. I couldn't find a 48V 500mA adaptor online so I was wondering about having a higher voltage run through the light, then through a resistor (to lower it for the switch rating), into the switch, and back to the adaptor.

Does anyone know of a 48V 500mA power adapter out there I could buy? Would the circuit work this way, or would I need a resistor, then an amplifier on the other side of the switch?


texts: Why are some electronics seemingly unbreakable (phones) and others very fragile?

texts:
Specifically I am wondering about the mechanical strength of the surface mount connections in consumer electronics. Are some tougher than others?

I've had a few experiences where an electronic device (single board computer, intel camera, intel edison), has fallen once from a small height and as a result has become completely useless - doesn't turn on isn't recognized by computer etc.

On the other hand I have dropped my iPhone multiple times, and know lots people who have practically dropped their phones off of buildings, but apart from a shattered screen the phone almost always retains its functionality.

So why is this the case? Do phone companies expect consumers will drop their phones and make them tougher. If so why aren't all devices (cameras,SBC's,etc) made to this standard of toughness?


texts: Noise reduction strategies in electrophysiology

texts:
When recording electrical signals from cells (in a dish or inside a living human or animal body), one major problem is to increase the signal to noise ratio.
These signals are usually in the 10uV to 100mV range and are generated by very low power sources that can yield currents in the order of nanoAmps.
Often signals of interest fall within 1Hz-10KHz range (most often 10Hz-10KHz).
To make the matters worse usually there are lots of noise generating tools that are necessary to be around (in the clinic these are other monitoring, diagnostic and therapeutic devices in the lab these are other monitoring, scientific devices).
To reduce the impact of noise and increase the signal to noise ratio, there are a few generally applied rules like:

If possible use a current amplifier (often called head-stage), an amplifier with very high input impedance and rather low voltage amplification or even no voltage amplification. very near to the signal source (body).
To connect the source (recording electrodes) to the first stage amplifier (head-stage) use wires that don't have shields (to avoid capacitative distortions of the signal).
Avoid ground loops
When possible use differential amplifiers (to cancel the induction noise from the electromagnetic sources around).
Always use Faraday cages and grounded shields (usually Aluminium foils) to cover the signal source and anything connected to it (body, equipment ...).
You can't do this without proper filters (usually a 10KHz high cut and a low cut that depending on the signal may be anywhere from 1Hz to 300Hz )
If you can't get ride of the mains noise (50Hz or 60Hz in different countries) and only if your signal covers that range you can use active filters like Humbug http://www.autom8.com/hum_bug.html

My question is: Are there any other suggestions that I missed? Is any of these suggestions flowed or wrong?
Usually people in this fields (like me) do not have formal education in electrical engineering  and sometimes there are myths passing from a teacher to student generation after generation without proper evidence. This is an attempt to correct this.
EDIT:

if possible use batteries or very well regulated power supplies in all your devices, including any pumps, microdrives, monitoring devices, even you can put filters on the mains of your computers (although this usually is not a serious issue).


texts: Reliable sensing method for device inside a parcel to detect when/if the parcel is opened?

texts:
I'm wracking my brain for reliable ways for an electronic device to detect when/if the parcel it is sealed inside is opened.

The device will be sealed inside the package and activated via Bluetooth by the sender and then queried again by the receiver to confirm there was no tampering before taking delivery.

At this stage the enclosing parcel could be a box, envelope, or wrapping paper - the only restriction that it completely encloses the contents along with the sensor and possibly packaging material - but that may include further restrictions if I can't come up with an infallible detection method.

My first thought was a simple ambient light sensor - but the tamperer would just need to open the package in a darkroom.
Another thought is to actively pulse an illumination source and then average the amount reflected back from the inside of volume from multiple directions (to account for the device shifting inside the package).

Any strategies come to mind? I'm hoping this may already be a solved problem somewhere.


texts:
The Problem
I’m having ESD issues.  Specifically, my device is failing when 4KV is repeated discharge on the aluminum enclosure of my device. I have already made improvements to harden my design, but I want to look for other areas that might be causing me troubles.
One possible issue is that my power board might be acting as an antenna, transferring EMF to the power management IC. Completely redesigning my device so that everything is on the same board would be the best solution, but for a multitude of reasons, I need to stick with current design described below.
Does the way I bring in my external power look like trouble?  If so, is there anything I can do to mitigate the problems? Thank-you in advance for any help you can provide.
The Device
My device is a portable USB device that can be powered over USB but also via a 9V DC connection.  The device consists of two boards inside an aluminum enclosure.  As this is a portable USB device, there is no earth ground.
The main board (4 layer) has all the digital and analog circuitry for my design.  The top board (2 layer) supports the 9V DC connector and a LDO to bring the voltage down to 5V before going into the main board.  The reason I’m using the power board at all is due to a lack of space on the main board and the need to be able to properly cool the LDO, which needs to be able to supply up to 500ma of power.
I’m including pics of the boards, showing how they are connected, as well as schematics for the power board and the power section of the main board.


texts: Why Protons travel through the membrance but electrons travel through the wire?

texts: In the case of having two electrodes (anode and cathode). I will always hear that positive ions will jump from one electrode to the other causing the electricity to flow the wire. How come only protons only jump between electrodes and electrons too. Is there a layer that only allows protons to travel? and are there different types of those layers?


texts:
It is sometimes useful to think of bandwidth in terms of how long it takes to transmit each bit of data.

Say we have a series of bits 100101101 to transmit and they are represented as +5V(1) 0V(0).

What is the transmission of each single bit in terms of electrons flowing in the cable ?
What does +5V mean for electrons that represent the bits ? (faster electrons or longer duration of flow of electrons)

Do we wait for a bit to reach the other side before sending the next ?


texts: JFET Voltage-Divider Bias calculation question

texts:
For the circuit above how is this formula for I(D) derived, a V(D) of 7v was given in the question?

i know that IS=ID how come RD is being used in the foRmula  and not RS?


texts:
I know that kind of things could be done by thyratrons, but wikipedia says that they are being phased out by semiconductor devices.

Could anyone suggest which kind of devices can switch on that fast and pass that much current?
I've checked thyristors - and all I can get seems to be 1us switch-on time...

I don't need to have 1000A for more than 0.1-1 \$\mu\$S, so I have reasonable thermal budget.

That's for not-so-simple TEA laser.


texts:
I've tried to make a shift register by myself. The syntax is correct but i'm not sure if this could a good design... i commented the statements that concern me...

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

    entity ShiftRegister is
    generic(n : natural := 8);
    port(x : in std_logic_vector(n - 1 downto 0);
         clk : in std_logic;
     shift : in std_logic;
     w : in std_logic;
         y : out std_logic_vector(n - 1 downto 0));
end entity ShiftRegister;

architecture arch of ShiftRegister is
    signal y_int : std_logic_vector(n - 1 downto 0);
begin
    process(clk)
    begin
    if rising_edge(clk) then
        if w = '1' then
            y_int <= x;
        elsif shift = '1' then
            y_int(n - 2 downto 0) <= y_int(n - 1 downto 1);
            y_int(n - 1) <= '0';
        end if;
    end if;
    y <= y_int;
    end process;
end architecture arch;


texts: Digital Compass and Magnetic Declination Angle

texts:
I have a digital compass of HMC5883L and I want to measure orientation with it. The doubt that arise is about the magnetic declination angle. From the definition of declination angle, it is the the offset angle of Magnetic North from True North.

Therefore if I happened to be on a location which the declination angle is equal to zero. That means the angle that I measured with the compass should be an angle with relative to True North?
If the declination angle is positive, I should subtract the measured angle with the declination angle?

I tried to find use the digital compass to control the direction of a drone. I plan to control the direction with bearing calculation of two coordinates and use the digital compass to control the drone orientation. But I could not obtain a reliable result

Is it because the magnetic field line at my location appeared to be horizontal and instead of vertical? I remembered that my bearing calculation was made with a normal Cartesian XY axis.

FYI: I happen to be on the Borneo Island, the place marked with a blue cross on the map.


texts: Using Lego Mindstorms Inventions motors with arduino

texts:
The specific kit I am talking about is this one
http://www.oreillynet.com/pub/a/network/2000/01/31/mindstorms/

How can I integrate these motors with an arduino.


texts: is there a standard name for surface-mounted 0.1" pitch DIP packages?

texts:
I've seen several boards that have ICs that look very similar to standard through-hole DIP packages (in particular, the packages have pins on 0.1" pitch), but the boards do not have any holes for the pins of those ICs.

Surface-mount components with 0.05" pitch are called "SOIC".
What is the standard name (or a popular name) for these components with 0.1" pitch that are intended to be surface-mounted?
(E.g., components such as the
Fairchild DF04S,
Shindengen S1ZB60-7072,
CEL PS2501AL-1-F3-A,
Toshiba TLP172G,
etc.)
I expected the datasheets for these components to mention some standard name -- like datasheets for other components mention standard packages such as "TO-92", "DPAK", "TQFP", etc. -- but I don't see one.

Is there a standard name (or a popular name analogous to "dead-bug construction") for the process of attaching standard through-hole DIP components to a board without holes?
(The process involves folding their leads one way or the other, gull-wing or J-lead).


texts: converting lots (100+) of analogue audio sources to RTP/UDP/'IP packets'?

texts:
I was 50/50 posting this here or another board.. hopefully it's in context and maybe I can get some help!

Basically I have a scenario where I'll have just over 100 analogue audio sources (50 in and 50 out) from 50 devices. I'll need to differentiate between the sources at a server to process each device individually. This is a communications thing, and has nothing to do with music.

Now.. I could invest in a huge mixer that converts from analogue to digital (ADC). But we're getting into big figures!

I've got a VoIP background, and know that the bandwidth on an ethernet port is certainly capable of accepting way more than 100 ports of audio.

So my question is.. Is there a small module I can purchase that will take an analogue signal and convert it to UDP and some sort of codec, and forward it on as network packets?

Is there anything you can suggest reading that may help?


texts: Can I wire a USB Type B connector to a Micro-B connector?

texts:
I'm looking into wiring a Raspberry Pi Zero (USB Micro-B) to my 3D printer (USB Type B). I can easily do this using some adaptors (Micro-B → Type A → Type B), but I would prefer to just connect them directly with a footprint as small as possible.

Looking into this I found these tables at Wikipedia: Host and device interface receptacles, USB - Wikipedia which seems to illustrate that such connections are not possible (or maybe just that they're not standard).

Would a directly wired connection between the Type B connector and the Micro B connector work?


texts:
Above is represents an isolation amplifier: http://www.prelectronics.com/pdf/2284-2358-US.pdf

The input comes from a DAQ and output will go to a motor. An isolation amplifier is used as in my illustration.

But when I check GND_input and GND_output with continuity test, they are connected. Arent they supposed to be disconnected electrically?


texts: Joining ground between ESP32 and LED Strip from single power supply

texts:
I'm driving an APA102 LED strip from an ESP32. Both are powered from a single 12V power supply that is brought down to 5V using a high-current (10A) buck converter.

This works fine when I join the grounds of the ESP32 and APA102, and I get massive signal degradation without the joined (flickering lights etc.).

I know this is common practice when using multiple power sources (and I'm happy to keep the joined ground), but I didn't think it would be needed when both the ESP32 and LED strips are powered from the same power supply.

Why is the joined ground required in this configuration? Also, am I putting my ESP32 at any risk in this configuration?

It may be relevant that I'm powering the ESP32 dev board via its micro USB port using a custom USB cable that connects to the buck converter's outputs.


texts: uC controlled MOSFET based LED Dimmer stops responding

texts:
I've designed and implemented LED Dimmer driven by PWM from Adruino Pro Micro (CLONE) with software based on MySensors library.

See the schematic attached below.

The idea is really simple:

uC is separated from MOSFETs with popular octocouplers (LTV 847 in this case),
Arudino Pro Micro is power supplied from PC via USB cable,
Arduino Pro Micro is communicating with PC with serial line and simple
protocol (MySensors),
MOSFET is driven by PWM from Arduino Micro (as mentioned, uC is separated from MOSFETs with octocouplers),
There is on board thermometer to verify if temp is not getting too high,
There are 4 chanells where I am able to attach 12V LED stripes to control and dim.

Generally I am - or was - satisfied with how it worked, as all worked well (all integrated and managed by domoticz).

Yesterday I tried to change dim level of one of the strips and there was no response. I tried to turn on other stripes and there was no response either. When I was sending commands (on, off, change dim level) I noticed that they were received by Arduino (I observed onboard LED blinking when I was sending commands), however MOSFETS didn't respond at all (no chanage in dim level of LED that was ON and no response from LED strips that I tried to turn on).

This happened after few weeks (I guess 1 month...) of using the dimmer, dimmer started working properly after turning it off and on (unplugging power supply).
I noticed that temperature of the environment where dimmer was placed was around 33degree celsius (it remaind more less same for the mentioned period).

What is the matter? Is it something with the circuit? If so, what shall I change in it to avoid situation as explained? Is there anything I could add here to make the description more clear?


texts: Is MOSFET gate threshold voltage a limit or minimal "Full-on" switching voltage?

texts:
I've been shopping for some mosfet transistors, for a starter kit, and noticed listings that state a mosfet is suitable for 5v logic, but the data sheets says Gate Threshold is 1-2v.
4v gated mosfets, which are closer to 5v, by the same seller are not advertised as suitable.

I understand that applying Vgs voltage to the gate will switch the mosfet on, but how does it interact with different voltages?

So for example if a mosfet had Vgs range of 2-3 and I applied voltage ranges of 0-1,2-3,3-7 to it I assume it would go something like this (correct me if I'm wrong):

0-1v - off
2-3v - on with proportional conductivity (with 3v having maximum).
3-7v - heat/burn?


texts: Prevent design to power up when updating firmware in flash memory

texts:
I have an FPGA based design using the MachXO2 by Lattice. I wanted a quick, easy and clean way to perform firmware updates, which are frequent, so I decided to use an external flash memory (AT25SF041 by Adesto) to store the bitstream and set the FPGA to configure itself using Master SPI Mode. The memory is used to supply the bitstream only, it's not used again after boot.

In order to perform a firmware update, the user has to:

Remove power from the device
Attach a provided cable in the corresponding socket
Update firmware using a dedicated application
Remove the cable and power the device

The socket essentially contains the SPI and power pins of the Flash Memory while the cable is a USB to SPI. The block diagram is depicted below:

As you may notice, when the cable is connected is going to fire up the entire device which is what I am trying to avoid. After consideration, I decided to use a diode between the Flash power pin and the main power supply, as depicted below:

According to the AT25SF041 datasheet, p.33, the Active Current when performing a reading operation below 20 MHz (FPGA uses 2.08 MHz) is typically around 3 mA. In the same page is mentioned that the IC will operate fine with a supply voltage between 2.5V - 3.6V.

A diode has a typical voltage drop of 0.7V, which results in a supply of 2.7V. Additionally, considering that the active current is so low, the drop will probably be a little bit reduced. Also by choosing a diode of a generally lower voltage drop things will be even better.

Based on the above, I did assemble a prototype employing a diode, and everything worked fine. I used two different diodes to verify that it works, a 1N4001 and a PH4148, and it worked with both of them. (Of course I will use a more appropriate diode in the final design)

My questions

1) Is this a sane solution? Although it works fine, I am still a little bit worried it may causing or might cause a problem which I am not aware.

2) The FPGA requires 2 pull-up resistors in order for Master SPI mode to operate. They are not required using the cable, but they are getting power. Is it a problem if a pull-up resistor is powered although it is not needed? I think not but I would like some verification on that. The cable I am using now, if it matters, is C232HM by FTDI, which utilizes a FT232H IC of the same company.

Any suggestions and alternatives are welcome. Thanks in advance!


texts: Why the capacitive divider in this output stage?

texts:
I have this output driving stage, reverse engineered from a generic Chinese mist generator:

The goal is to drive the piezo transducer with a given frequency (more or less 1.7MHz or 2.4MHz depending on the transducer) to put it in resonance. It will then do its work and turn water in vapor (more or less, details are not important).
In my understanding it works in this way: from the left come the gate drive wave (at 1.7MHz or whatever, square wave), the MOSFET will charge the coil like a storage choke in a flyback converter and on gate release the inductor will dump the stored energy on the load, down right.
The upper right components are a standard RCD snubber to keep the coil in reset and quench transients, the two resistors are current shunts to help finding resonance (the frequency varies slightly with load and environment).
The 'load' is the thing which baffles me: the transducer in resonance is equivalent to about 1.7nF (body parasitic) in parallel with a couple of ohm (the 'transducing' resistance). Why the two capacitors? Couldn't they simply dump the power right on the transducer or is that some kind of impedance matching network?
At first it could seem that the 22n is here to resonate and cancel with the storage choke (unknown inductance, for now) but in a pulse transfer situation like this what is the 'source impedance' of the discharging choke?
EDIT: in theory, at least when doing power conversion, the storage inductor is modeled as a current source with the ESR in series, however a) current sources have the internal impedance in parallel and b) does matching work with current sources too?
As for the 220p I think it could be a protection to avoid overstressing in case the transducer gets accidentally detached or maybe some help in shaping the pulse (to let pass thru all the higher harmonics in the square wave).


texts: Is there a way I can connect 1 or 2 batteries to a CPU Fan that I dissasembled to check what voltage it is so I can use it at the highest speed?


texts: AD8556 instrumentation amplifier not working!

texts:
I was wondering if someone would be willing to draw a complete schematic to help me get a AD8556 working.

I currently have it set up like this:

But the output just sticks at 1.58V. Bias current?


texts: Driving a RGB Led strip with a RGBW controller

texts:
I have a RGB LED strip (Common +) that I want to drive using a controller that expects the strip to also have a W (White) channel.

So what I am basicly looking for: As soon as the controllers W output is HIGH I want all three R, G and B inputs on the strip to be driven HIGH.

How would I realize this? I could insert diode's between the RGB lines and connect the W output of the controller to all three strip inputs, but then I would have a voltage loss.


texts: NOT gate with an NPN (2N3904) transistor not working?

texts:
I have the book Getting Started In Electronics, by Forrest M. Mims III, and it has an RTL NOT gate schematic that looks pretty much the same as this:

(source: electronics-tutorials.ws)
About a month or two ago, I was starting to get into RTL logic (had already done logic in video games like Portal 2 (2-bit adder I built using laser logic) and Minecraft (lots of little redstone things, some 8-bit like an 8-bit ALU)). Anyways, a while back ago, with RTL I got a NOT gate working, and even an AND gate using 3 not gates and some sort of OR gate (can't remember how I built any of them). Recently I peered into my book, built the gate, then connected my battery pack that I got from RadioShack (two AAs, 3 volts total in the pack) aaand...nothing. The red LED did not light up, even if I switched on the input.
Yes, the batteries are working and contain plenty of charge, as I changed them and then connected a plain LED and a resistor to test them and the LED lit up as expected.
The resistors I used were 10k ohm, and the transistor an NPN 2N3904. Can someone direct me maybe what I did wrong (maybe a clear picture or video of this on a breadboard)? I am highly confused.
EDIT: I figured it out! Don't really know what I was doing wrong at first (probably grounded something wrong) but it is working now.


texts: How to know how much current is generated?

texts:
My input voltage is 4.5V. Based on this datasheet here, where do I reference in the datasheet to obtain the respective desired output current?

Some background info:

This is the schematic diagram of the entire circuit of my project.

The 4.5V goes to Pin 1 of the Battery Charge Controller. I need to know how much current comes out of Pin 5.

Thank you!


texts:
I dissasembled multiple RFID devices to study their design. The following reader attracted my attention:

This is a four layer PCB, the anntenna seems to be 4-turn symetric and is layed out on the two internal layers of the PCB. You can see the cross-overs right next to the print "REV:B...".

The thick solid plane on top (which is also on bottom) is NOT the antenna, it is connected to ground, and has has small vias on the edges of the plane.

The reader antenna and parametrics of this reader are very similar to another one, but the reading distance with this reader is much better than with others, yet having the same NFC chip from NXP

What I really wonder is the fact that there is a solid copper ground plane over the antenna. Usually RFID design guides recommend to not route any signals or ground near antennas and keep antennas away from large copper surfaces or metal plates. It is very interesting, that this cheap generic reader from China, is way better than genuine other readers with the same size.

The following questions are unclear to me:

Why is this ground plane on the sntenna?
2.) Does the plane influence the reading distance (positively,) and if yes, why?
In which case would such a design would be needed?


texts: Using internal pulldown to pull esp8266 logic pin low

texts:
I'm trying to design a linear actuator with limit switches that both deactivate the motor drive and also signal my micro-controller that the switch is active. I plan on using a DRV8871 motor controller with an esp8266 MCU and SPDT limit switches. My plan is to connect the pwm output to NC, the DRV8871 to COM and the limit active input pin to NO. The DRV8871 states that there is an internal 100k pulldown on the inputs, so if I use something like a 10M pull up on the limit active pin this should successfully pull the pin low to signal the limit is active (as well as disconnecting the pwm output from the DRV input). What are some potential issues I may run into with design / would it work at all?

simulate this circuit – Schematic created using CircuitLab

notes / secondary questions:

This entire setup is duplicated for each drive direction so reversing the motor away from the limit switch is not an issue.
I'm trying to convince the guy I'm prototyping for that the design is decent enough to buy the components and try it out (which is why I haven't just tried it myself yet)
would it perhaps be better to instead (or additionally) use a lower value external pull down on the DRV module so that I don't need such a high value pull up?


texts: Can I use an Arduino board as a USB encoder?

texts: Just what the title states; given an analog signal, would an Arduino board be able to both digitize, and encode the signal in a USB frame?


texts:
I'm facing a weird behavior on SOME boards based upon CC3220SF.
Scenario

I have 20 units of my custom PCB, designed following the Design Reference Guidelines from Texas Instruments and - like they suggest - "copying" the layout from the demo board
most of them work fine, and they have passed the CE tests

The issue
Some of them, instead, wakes up periodically from the hibernation state claiming a GPIO interrupt the reset cause.
This should not happen because I disabled any wakeup policy for GPIO:
const PowerCC32XX_ConfigV1 PowerCC32XX_config = {
    .policyInitFxn = &PowerCC32XX_initPolicy,
    .policyFxn = &PowerCC32XX_sleepPolicy,
    .enterLPDSHookFxn = NULL,
    .resumeLPDSHookFxn = NULL,
    .enablePolicy = false,
    .enableGPIOWakeupLPDS = false,
    .enableGPIOWakeupShutdown = false,
    .enableNetworkWakeupLPDS = false,
    .wakeupGPIOSourceLPDS = PRCM_LPDS_GPIO13,
    .wakeupGPIOTypeLPDS = PRCM_LPDS_RISE_EDGE,
    .wakeupGPIOFxnLPDS = NULL,
    .wakeupGPIOFxnLPDSArg = 0,
    .wakeupGPIOSourceShutdown = 0,
    .wakeupGPIOTypeShutdown = PRCM_HIB_RISE_EDGE,
    .ramRetentionMaskLPDS = PRCM_SRAM_COL_1 | PRCM_SRAM_COL_2 | PRCM_SRAM_COL_3 | PRCM_SRAM_COL_4,
    .keepDebugActiveDuringLPDS = true,
    .ioRetentionShutdown = PRCM_IO_RET_GRP_1,
    .pinParkDefs = parkInfo,
    .numPins = sizeof(parkInfo) / sizeof(PowerCC32XX_ParkInfo)
};

I call Power_shutdown(0, 300000); but when MCU wakes up I find:
PRCMSysResetCauseGet() == PRCM_HIB_EXIT
PRCMHibernateWakeupCauseGet() == PRCM_HIB_WAKEUP_CAUSE_GPIO.

Test I've made
As said this not happen to all boards. So, at first, I was looking for something hardware. I set up a test firmware:
void ApplicationTask(void)
{
    InitSimplelink(ROLE_STA);
    ledOn(); // turn on a LED so I can easily see when the MCU is active

    for (;;)
    {
        Platform_Sleep(5000);
        powerShutdown(300000);
    }
}

The "reference" board (one that works fine) exhibits the expected behavior: the LED turns on for 5 s, then the MCU hibernates for 300 s (I also changed this time - no matter).
One of the DUT board wakes up every 2 seconds, while another every 20 seconds at room temperature. Changing the temperature the interval changes a lot: at about 40 °C the interval is shorter, about 4 s. At about 10 °C is about 39 s.
I wasn't able to reproduce the issue on the "working" boards - even changing the temperature.
Furthermore, I tried to read the Slow Clock Counter (the clock that runs even in hibernation state) and it seems consistent with the real time - i.e. it doesn't change (a lot?) with temperature.
Question
The question is quite straightforward: what do you recommend in such a situation to deeply understand what's happening?
UPDATE
Using a very thin nozzle to my hot-air gun, I was able to heat each IC on my board. No effect at all until I went to the MCU itself: just after applying warm air to it the interval dropped instantly from 22 s to 1 s.
Schematic


texts: How to measure multiple objects' weights with load cells and Raspberry Pi 4?

texts:
I am working on a class project that involves a raspberry pi and strain gauge load cells. .

The goal is to measure the weight of two or more objects using a set of two load cells (In the picture it uses 4, but for this case, I think two can do the job). As we may know, a load cell needs a hx711 in order to change analog into digital. This picture is using a combinator in order to group the signals of the load cells into one output that goes to the hx711.
My problem is that I am not sure how to track two or more different objects' weight only using one hx711. Would this be entirely possible, or I must use a combinator and a hx711 per two load cells? If so, is there another alternative to using the hx711?

Thank you very much for your time and help.

Resources:

https://www.sparkfun.com/products/13878
https://learn.sparkfun.com/tutorials/getting-started-with-load-cells/all


texts: MOSFET for directly switching 24 Volt loads - any reason not to use the IRL8743PBF?

texts:
I am searching for the best solution for using a Raspberry Pi 3 to control a 24 Volt load at modest amperage.

It seems like the best choice is the IRL8743PBF because it can be switched to fully-conductive by a 3.3 Volt logic signal and can handle at least an amp of current flow without a heat sink.  Plus it can plug into a breadboard.

Specifications Datasheet (PDF)

I've found that it can be purchased in 5-packs via the slow boat for $2.55 with free shipping HERE.

Question:  Is there any reason not to use this one?


texts: I want to do some expermenting with BT positioning in the NRF device. Will a QORVO QPC7512 50 Ohm switch work with two antennas feeding an nRF52811? Last time I checked Nordic no have reference design for low end product.


texts: Joining a raspberry Pi to an external hard disk cage power supply

texts:
I have an external SATA hard drive enclosure that has its own power input. I would like to be able to run a Raspberry Pi from the same power input.

The enclosure takes a 12VDC input (currently I'm using a 1.5A power supply but I'm sure I have a 2A one lying around somewhere) and converts it to a SATA power input for the drive. The hard drive says it wants 0.65A from the 5V on the SATA power, and the RPi draws 1A from its 5V input at most. The intended setup is for a small NAS so the Pi will be using its ethernet port on the usb hub chip but no peripherals after the original setup (which can be done when powered normally).

So, is it possible/sensible to split the 5V cable on the SATA power and hook it up to a µUSB to power the Pi, bearing in mind the variable power consumption of the drive and Pi?
If not, why?


texts: Wire the green ac earth wire in wooden chassis?

texts:
My own power supply is just about finished. Since i live in Europe the voltage here is 230v, from that it goes into my step down transformer that steps down the voltage to around 20 V AC and then into the power supply, etc.

If I check in a normal PC switching power supply the AC ground/earth is connected to the chassis of the power supply. Since i have a wooden chassis for my power supply how do i connect the earth wire to be "safe"? I understand all the risks of working with AC voltages and i try to be as careful as I can. Can I just put some "metal piece" inside of my wooden chassi and connect earth to that?

And just to clarify the AC wire I have contains of 3 wires, One live wire, one ground wire. and one green earth wire. Looks like this:

I have the exact same colors of my wires as the pic.

Pictures of the transformer I'm using:


texts:
To "somewhat" quote Rick Hartley, "the energy isn't in the traces & planes but in between", I'm now wondering, when I use the following stackup:

Sig
GND
PWR
Sig

You would have energy between layer 4 and 2 in case of a 'HIGH' signal on layer 4 right? So that means the distance between current and return current become larger than needed. Isn't it better then to use the following stackup:

Sig/PWR
GND
GND
Sig/PWR

Asking this because I see a lot of PCB's being designed in the first stackup topology.
In addition i have another question. Somebody told me I could also make a mix in layer 3 of GND and PWR. I wonder, is this a good idea, to mix different potentials on one plane? why or why not?
If you were to use this method of mixing GND and PWR in layer 3, how would you do this? adding only PWR polygons under IC's, or definately not?


texts: How does a circuit regulate current in response to a lower voltage?

texts:
Brief background, I studied physics in college and am learning EE on-the-job through Art of Electronics and this wonderful website.

So this is a follow up to a previous question I submitted here yesterday. I was trying to see what could have gone wrong when I wired a bunch of devices in parallel and then ran them under-voltage. In the comments, I was informed that I should pay attention to P = IV in that the devices I'm using will try to maintain a fixed power rather than respond according to V = IZ.

I'm not entirely clear on this so I was hoping someone could enlighten me as to what kind of circuit could be drawing more current in response to less voltage. I always understood current and voltage to be proportional on a fundamental level, regardless of the load, since the voltage is the energy source. But, if we take the fluid flow analogy, perhaps there's some sort of "thinning of pipes" when a lower voltage is applied.

How does a circuit pull more current when it doesn't get the voltage it wants with respect to a constant minimum power?

What kind of circuit keeps a constant power?


texts:
I would like to make an ultrasonic sensor. For reciever part I have found this scheme: (source: www.kerrywong.com/2011/01/22/a-sensitive-diy-ultrasonic-range-sensor/)

Instead of LPC662 I would use LM358 dual amp. What values should I use for resistors and capacitors? Could I use 3.3V for Vcc (I am using ESP8266, which runs on 3.3V). There is no application example for serial use of the LM385 in datasheet.

EDIT:

What about transmitter? Is this scheme ok? Would it work on 3.3V?


texts:
I'm designing a keypad in VHDL and for protection purposes I disable pressing a second or more keys while one key is being pressed. Example while I'm pressing "7" a press of "2","3","5","4","1","0" etc. will be ignored and no tone will be heard. Each valid key press generates a tone. My keypad is consisting of 3 columns and 4 rows, 12 keys. I have 3 states in my FSM and I scan each column for a valid key press(states: scan_column1, scan_column2, scan_column3). I switch from state to state under the condition when no key is pressed. This way if I am scanning column3, all key presses in column2 and column1 are ignored and unseen. Now I have a final problem lets say I'm pressing "7" , tone of 7 is heard, I'm still holding my finger on "7" and then I press "3", 3 is of course ignored, but I'm still holding "3" and then I release "7", then 3 becomes a valid press and tone of "3" is heard. But 3 is not a new pressed key, it was being pressed while 7 was pressed, so I want to avoid tone generation in this case. Any suggestions? Because this is an ongoing project I can't upload my code :(

More details about my keypad


texts: Improving PCB layout for regulator circuit

texts:
I've made a layout around an Allegro A4490 triple buck regulator, with four optimization goals:

minimize loop area/change in area when switching
keep the ground attachment of the input and output capacitors and the flyback diode together
avoid cutouts in the ground plane, and at least keep deviations for return currents short
prefer vias in slow signals with small current (i.e. the "enable" and "power on reset" traces)

I have two fixed voltages, and one that can be adjusted using a potentiometer; in addition the outputs can be switched individually, or a jumper can be used to keep them on, and an active-low reset signal is generated when the supply is outside the target range.

As a result, I now have a layout where a trace runs through the middle of a 0603 capacitor, which limits the trace width to 0,3mm:

Do I want to change the layout so I can have wider traces, or is that irrelevant anyway because of the pad size?
Is there a downside to running that trace below the capacitor?
The datasheet allows up to 2A on the output side, however I'd presume I need to account for more on the LXn traces (i.e. the FET output). How much more?

Last, if there is a glaring error in the design that immediately jumps at you, I'd like to know.


texts: Disassembly of a soldering station - dangers?

texts: I recently came into possession of an old soldering station. It doesn't work very well - the tip doesn't get hot enough to melt solder, so it'ls pretty useless. I've opened it up to strip it for parts. It contains very few - a nice illuminated switch I can make use of, a large transformer and a 470nF 250V poly capacitor. Is it safe to just go ahead and desolder these parts?


texts: Name of an enclosure in the shape of a DIP

texts:
Years ago, in a junk bin far away, I saw a device which was a small plastic box with protruding pins in the form of a 14-pin DIP — so that you could solder jumpers or small axial components to the inside end of the pins, close it up, and have a module of your own design that could be plugged into a DIP socket.

What would these be (or have been) called?

I have a use for one, if I can find it. (Of course, I could abuse a DIP socket by soldering or just pushing individual leads into it, but in my experience, sockets have shorter (or thicker) leads and a shape not best suited for plugging into a socket, and it would be an open frame rather than enclosed. If that's my only option, I'll take it, but I'd like to evaluate the alternative I once saw.)


texts:
Today I opened an old adapter to salvage the transformer and found this component which I also desoldered.
What is this component and what is it used for?

It seems to have a resistance of 10 Ohms as shown and it's labeled as R1, but the joule is confusing me, so I don't think it's a regular resistor. I haven't been able to find anything online.


texts: how does single supply op-amp work while its non-inverting input is connected to ground?

texts:
In HCNR200 Datasheet, the page 11, figure 13-A, there is a sample that confused me.
In this sample, the Vin is applied to the inverting input and if the electric current passes through PD1, PD1 voltage goes to zero and finally when PD1 voltage reached to zero, the voltage on inverting input is around zero, but a bit more than non-inverting input voltage.
So, how does op-amp output go to higher than zero and adjust the current of LED?
And for right side op-amp, how does op-amp output go to more than zero while its non-inverting input is connected to ground and inverting input is going to higher than it?

*Op-Amps are powered by a single supply.


texts: How do I read analog devices that produce relatively high voltage?

texts:
I found a sensor recently that emits ±90V (AC) on stimulus.  How would I go about reading this from an arduino?

Update

I didn't think there were so many options.  :)  The kind of thing I'm looking at is a piezo vibration sensor.

The current is small, but 90V sounds like a lot (and I'm kind of new to electronics, so I don't really understand what high voltage/low current means in terms of damaging stuff).

If it were just 90V DC then I'd get the voltage divider idea, but reversing polarity sounds like it could be a bad thing.  Perhaps voltage divider + a diode or two (or a rectifier) would work?


texts:
I am looking for an AGC (Automatic Gain Control) which outputs not only the normal output but also another output which tells you what gain it is using.
I need this for an automatic voltage meter I am building; it doesn't have to be an AGC just some kind of device which changes its output voltage if the input voltage is out of the scale I am measuring, but tells me the gain so I can know the input voltage. I was thinking maybe comparators that if I pass a certain voltage it changes a voltage divider.


texts: why use sum of product and not product of sum in programmable logic array and programmable array logic

texts: I am confused why only SOP(sum of product) are used in PLA and PAL and not POS(product of sum)


texts:
Here I have two options but both are giving me a problem.
op_1) make my own C function  to read count which is similar to Arduino shiftIn() function but I don't know how to do it ...
Actully Arduino have ready made library for HX711 24bit ADC and into that library I get following function which return me adc_count
long read(void)
{
    // wait for the chip to become ready
    while (!is_ready())
        {
        // Will do nothing on Arduino but prevent resets of ESP8266 (Watchdog Issue)
        yield();
    }

    unsigned long value = 0;
    uint8_t data[3] = { 0 };
    uint8_t filler = 0x00;

    // pulse the clock pin 24 times to read the data
    data[2] = shiftIn(DOUT, PD_SCK, MSBFIRST);
    data[1] = shiftIn(DOUT, PD_SCK, MSBFIRST);
    data[0] = shiftIn(DOUT, PD_SCK, MSBFIRST);

    // set the channel and the gain factor for the next reading using the clock pin
    for (unsigned int i = 0; i < GAIN; i++)
    {
        digitalWrite(PD_SCK, HIGH);
        digitalWrite(PD_SCK, LOW);
    }

    // Replicate the most significant bit to pad out a 32-bit signed integer
    if (data[2] & 0x80)
    {
        filler = 0xFF;
    } else
    {
        filler = 0x00;
    }

    // Construct a 32-bit signed integer
    value = ( static_cast<unsigned long>(filler) << 24
            | static_cast<unsigned long>(data[2]) << 16
            | static_cast<unsigned long>(data[1]) << 8
            | static_cast<unsigned long>(data[0]) );

    return static_cast<long>(value);
}

Here in this function they have used the shiftIn() function.
How to implement this using C language ?
op_2) I have written my own read() function which return ADC count but I get garbage value ....
unsigned long read(void)
{
    unsigned long count,dout;
    uint8_t i;
    count = 0;
    dout = 0;

    if(isready() == 1)
    {
        GPIO_ResetBits(GPIOC,PD_SCK);
    }
    else
    {
        for(i=0;i<24;i++)
        {
            GPIO_SetBits(GPIOC,PD_SCK);
            delay(1);
            GPIO_ResetBits(GPIOC,PD_SCK);
            dout = GPIO_ReadInputDataBit(GPIOC,DOUT);
            count = (count | dout) << 1;
      delay(1);
        }
   }
    GPIO_SetBits(GPIOC,PD_SCK);
    GPIO_ResetBits(GPIOC,PD_SCK);
    count = count >> 1;
    return count;
}


texts: Driving 12 Seven Segment Displays from an Arduino

texts:
I will be using the 14 input/output Arduino. My goal is to create a plane radio console for use with a flight simulator. I am very competent at writing code, but have little knowledge of electrical engineering. There are 3 readouts on the panel I am making, which will display the different frequencies. I need to be able to directly control each 7 segment display of the 12 total digits needed.

Which shift registers would I need in order to properly wire this? I want to use as little of the pins on Arduino as possible as i need to also wire up 3 rotary encoders and two On/Off switches.

Is this possible? If so, which Shift Registers do I need, and what Make/Model?


texts: Can 16A relay be used instead of 8A relay?

texts:
I have a relay with 12V and 8A, it was not working properly. I want to change it with 12V 16A relay is that possible? Because I am thinking amper is the power of relay. If a relay can open 16A circut with 12V, It can easly open the 8A. Am I right?
This is relays Finder is broken,

Omron which is I want to use


texts:
Basically I want to measure high side current through a 1 Ohm shunt with this configuration:

The circuit works perfectly in a simulation. However on a bench it doesn't produce any meaningful output. The only voltage that I see on the output is a constant 700 mV. When I put a load on a circuit and draw more than 1 amp the only thing that changes is that a small ripple adds on top of the 700 mV offset. When I check the voltage drop on the resistor with a voltmeter it is the expected 1 volt or so.

When I place the 1.2 Volt battery instead of the resistor at the inputs, the output is almost exactly the voltage applied, so the circuit works fine in that case.

I thought that maybe I am trying to operate the opamp too close to the rails so I tried to use voltage dividers as so:

Still the output was the same 700mV.

I can't understand why does the circuit measure the battery voltage and can't do so with the resistor voltage drop.

I'd switch to the low-side measurement however I already have the power PCB printed with the shunt on it so I am still trying to make it work, and also want to understand why this circuit doesn't work.

Edit:
Here is the opamp output vs load current graph, where the load is changed from 2 amps to 0 amps.

Edit N2:

I made changes according to some of the suggestions and now the circuit works relatively well. First of all I increased the loop's impedance by increasing the resistor values. Next I biased the opamp to 1.5 volts. I also fiddled with power supply itself to reduce noise. The circuit looks like this:

Thanks to everyone now it at least doesn't spew out random nonsense and increases voltage with applied load. I haven't checked for linearity yet but it's a start.


texts:
We are currently designing a large PCB where multiple engineers are contributing to the
schematic layouts in Altium Designer 13. We decided to use a hierarchical layout for our design so that each engineer works independently on their sub-system to be integrated in a top sheet at a later stage.

In order to keep things neat we tend to use a lot of harnesses in our schematics. This has been causing some problems when running ERC checks on the schematic. In general we tend to pass a harness to a lower sheet through a sheet entry, extract the contents of the harness (using another harness creator), and connect the extracted elements to their respective locations using net-names. The problem is that this tend to cause multiple names to be assigned to the elements of the harness. For example, if a harness called H has elements A and B we tend to connect the net name A and B to the elements when we extract or create the harness. Altium however names the elements H.A and H.B when using a harness with these elements. This causes an error (or warning) for multiple net names if that option is selected in the ERC. Is there an easy way around this behaviour or should we be drawing our schematics in a different manner?

We do not want to disable the multiple net names warning/error as this has previously helped us to find a few bugs. Also I know we can extract the elements by explicitly using the H.A and H.B syntax in the sheets but it is usually quite helpful to visually see on the sheet what all the elements of a harness are.

What I would like to see is that there is an option so that the multiple net name checker
takes H.A and A as being equivalent for net name purposes. Currently we have to step through all the warnings and explicitly assign an ERC ignore cross for each net that causes this behavior.


texts:
I want to implement a s-curve trajectory generator for a motor controller, but I'm struggling with how it should behave to be useful. There are different papers out there with the implementation for s-curve generation, but none seems to take the time to the destination as input.

How I imagine a trajectory generator:

Input: Pos_Dst, T_to_Dst, Pos_is, Vel_is, Acc_is, Vel_max, Acc_max,
Jerk_max
Output: Pos_ref

T_to_Dst (Time to destination) seems not to be taken into account in real generators, why? Is it hard to run it online? I think this might be really useful, since it uses the boundary conditions on Vel, Acc and Jerk only if necessary.


texts: Turn off PNP BJT with high impedance output

texts: I am making PCB where I need to turn off PNP BJT with my MCU. But my MCU is only 3.3V and it can't reach emitter voltage. So, it is good practice to turn it off by setting output pin to high impedance or should I waste my precious space on PCB for another NPN to drive PNP?


texts: SEN0192 Microwave Doppler sensor sensitivity

texts:
I've integrated this doppler microwave detector to a raspberry pi 3 b+ and have been bench testing it -- and it works fine waving my hand in front of it.

I've now moved it to the area where it needs to be detecting and it doesn't seem to work through the window! It's a double pane window, and I'm standing in front of it moving. My foot is moving inches from the window and the detector leaning against the window. The sensitivity is set all the way up to just below where it triggers constantly with no motion nearby.

I don't understand --- my understanding is this sensor should work through walls and glass.

Or maybe not?

  Even using the lower frequency 10 GHz spectrum means that 5G coverage would only exist inside of untreated glass windows, but likely nowhere else inside of a building.

What the heck is untreated glass?

Is it possible I have a defective unit? (Purchased locally through Jameco.)

...just to make sure also I have the orientation right -- the most sensitive side is NOT the side with the metal box, but the opposite side. Which orientation also has the widest spread? The card positioned in portrait or landscape?

Is the power output just not strong enough for my needs?  Is there a better solution/product?

Specifications:

Working Voltage: 5V + 0.25V
Working Current (CW): 60mA max., 37mA
typical
Interface: Gravity 3-Pin interface（Digital）
Size:
48.5x63mm
Emission parameters:

Detection Distance: 2-16M continuously adjustable
Emission Frequency: 10.525 GHz
Precision
Frequency Setting: 3MHz
Output Power (minimum): 13dBm EIRP
Harmonic Emission: < -10dBm
Average Current (5%DC): 2mA typ.
Pulse Width (Min.): 5uSec
Load Cycle (Min.): 1%

Reception
Parameters:

Sensitivity:(10dB S/N ratio)
3Hz to 80Hz Bandwidth: 86dBm
3Hz to 80Hz Bandwidth Clutter: 10uV
Antenna Gain: 8dBi
Vertical 3dB Beam Width: 36 degrees
Level 3dB Beam Width: 72
degrees

Edit:  Ah, this is possibly based on the HB100, which has more detailed specs.


texts: Can you cross Live and Neutral traces on opposite sides of a PCB?

texts:
Can 230V live and neutral traces be crossed over if they are on the top and bottom side of a PCB?
I know there are requirements for creepage and clearance; if that requirement is less than the thickness of the PCB, is it ok and safe? Do the requirements apply through the PCB laminate?


texts: setting up LDO with variable output current (+diagram)

texts:
After reading on regulators, and asking few questions here and there, I think I should change my circuit to the following scheme :

These images are from datasheet of the LDO regulators (both MIC29302A).

Questions :
Does the first curve mean that the output voltage will change with changes in output current?
(since the required current will be anything from zero to ~920mA as the LEDs will be turned on/off).
if so, Should I adjust the first regulated voltage (marked in red in diagram) to 5.8v or what?
Basically I want constant voltage for the LEDs (the voltage marked in blue in diagram).
and need to adjust all other parameters (other regulator voltages?) for this purpose.


texts: What is the name of this small connector?

texts: I need an extension cable for the Raspberry Pi camera sensor (the PCB is too big.)


texts: Parallel transmision lines reflection at the source

texts:
Question:

There's a 9 V battery with output resistance of 50 Ω, at time t = 0 it is connected to two lossless transmission lines connected in parallel: LTx1 and LTx2.
Both lines are identical, with characteristic impedance of 50 Ω, except for the load connected at the end of each one: an open circuit in LTx1 and a short circuit in LTx2.
The time it takes a wave to travel from end to end of either line is T, find the voltage distribution of both lines at time T = 5T/2.

Here's my solution so far:

At time t = 0 the source sees two 50 Ω impedances in parallel, so the initial wave that propagates through both lines is 9 * (25/75) = 3 V.
At time t = T in Ltx1 the 3 V arrives at the load and 3 V are reflected back, meanwhile in LTx2 -3 V are reflected back.
At time t = 2T, there should be 6 V everywhere in LTx1 and 0 V in LTx2, the +3 V wave and -3 V wave arrive at the same time to the joint where both lines and the source meet.
I've no idea how to handle the reflections at this joint.


texts: Tips for wire-to-pad and wire-to-wire soldering?

texts:
After a simple flashy-LED kit's worth of practice, through-hole soldering is fairly straightforward. What I'm still having trouble with is wire-to-pad and wire-to-wire soldering.

The first problem is keeing stuff still. Blu-tac helps but gets melty, and I've never used a "third hand" that was worth a damn. Is it worth paying more for a better one? Any other tips?

My particular application is soldering 0.1" SIL sockets to flat flex cable (me again!). Would solder paste and the heat gun attachment on my butane iron work well?


texts: Ceramic Capacitor whistle in DC-DC Converter

texts:
I have designed a 24V Input, 5V and 30W output DC-DC converter (TPS40170) which is working fine under normal conditions.  This was approved with an evalboard.

But my load is being switched with a frequency between 100Hz-17kHz - I can hear an audible sound.

I first thought:

I have to change the capacitor package. I moved from 0805 to 1210 footprint. But this does not solve my problem.
I even increased the value of capacitor from 4x22µF (0805) to 3x47µF (1210). This did not solve the problem
Using the evalbord and making the same test, I am also getting the same sound.

I am now thinking to increase the frequency to more than 20kHz which on test is working, but my µC on the SPI-Bus will not handle this case.

What can I do to solve this problem  withhout changing my µC and also increase the frequency (more than 7kHz which is the maximum.)


texts:
Traditionally ring mains for lighting have been (relatively) low current AC mains typically at 110/230VAC.

It makes sense these days to replace that with lower power, lower voltage wiring to more diectly drive LED lights (and wallwarts repolacements?).

The question being, what is the optimimum voltage? I assumed previously that 12VDC would be best but I am seeing lighting products and dev kits running from 48VDV (not to mention 24VDC).

Obviously, double the voltage, halve the current. But at some voltage point various regulations kick in (depending on jurisdiction).

Righ now, in my house, the ring mains is fused at 5A per floor. At 12VDC that would be a 60W limit for LED lighting. Just about enough for me, but 24DVC would provide 120W which is more than enough.

Are there any standards in place for this kind of repurposing of existing wiring?

Ultimately, I am looking to run almost everything from solar/battery


texts:
I’m looking at a  TAP controller for the implementation of JTAG, but I’m not sure what which part of the diagram the top left circuit is refeering to.
Are the boundary scan cells just D-flip flops?


texts: How to calculate resistor values for a VGA DAC

texts:
I have an FPGA and want it to drive a VGA monitor. I want more than 3 bits of color so I need a DAC of some sort. So I want to make a resistor dac.
My plan is to have 3 bits per subcolor. So total of 9 bits per pixel. I know VGA monitors have an impedance of 75 ohm that I need to take into account, and I know they need 0 for black, and 0.7v for white.(per subpixel)

Problem is I don't know how to continue with this info, I believe I need to use algebra for this, but I'm still learning that and therefore have some issues calculating the correct resistor values.

So first I think I need to figure out what resistor value I need to get 0.7 v taking into account the 75 ohm to ground. Which wounds like a resistor divider to me, if I'm correct, when I use 3.3v as input, I'd need a 280 ohm resistor to approximately get 0.7v.(I used the formula on the wikipedia page for resistor dividers)
But I don't know how to continue from here.
How do I know what 3 resistor values I need that would give me the correct voltages?(Also, bit 2 needs to give more voltage than bit 0)

Can anyone help me with that? And also explain what you are doing to get me the values so I can learn it too?

In case I do need to use algebra, I only know the basics like solving 3x+3=2x+7 so a little help there would be appreciated.

Thanks!


texts: How to prevent battery drain when loaded?

texts:
I have a circuit consisting of 4 relays and 3 dc motors, with 4 diodes, resistors, and leds connected within. I have two 6 volts battery from the UPS. I need to obtain a negative voltage so I do workarounds with the two 6 volts battery so that the terminals are +6, GND, and -6 volts.

The problem is, the battery gets drained (or the voltage supply decreases to 2 volts) when the circuit is fully constructed. Proper output cannot be obtained. (By the way, each component of the circuit perfectly works well)

I am planning to have a separate voltage supply or battery for the relays and the dc motors. I wonder if this is the right thing to do.

What can you suggest?


texts:
I am working on a project that requires me to design a controller knowing the following specifications:
"The controller performance must be consistent under varying conditions. The rotor must respond rapidly as it moves in small steps of unity. For each step, the controller must get the rotor position to within 2% of its final value in less than 1s and must eventually reach unity. During your research, you found out that packaging would get damaged if the base position exceeds 6% of the final value with this quick response. In addition, if the operator enters a unity sloped linearly increasing input then the output must eventually track the input and be at most 0.1 degrees away."
From the previous paragraph I can deduce that:
damping ratio = 0.667
natural frequency = 5.996 rad/s
damped natural frequency = 4.47 rad/s
damping ratio x natural frequency = 4 rad/s
I tried two types of solutions for this problem: the PID controller and the Lead-Lag Compensator and I'm stuck at both and don't know how to continue.
For the PID controller:
I tried the following code on MATLAB which gives me all the specifications required for a unit step input (settling time under 1 sec, maximum overshoot doesn't exceed 6%, and reaches unity at steady state.) However, I cannot only follow this since I still have to show mathematical calculations that would lead me to the results I got on MATLAB. (Also, I still haven't used the fact that it is 0.1 degrees away at ramp input, I have no idea where to use this.)

num = [1 1]
den = [1 10 9 19]
Gp = tf(num,den)
H = [1]
s = tf('s')
CL = feedback(Gp,H)
step(CL)
hold on
%%
Kp = 600
Ki = 1
Kd = 50 %killing the overshoot
Gc = pid(Kp,Ki,Kd)
CL_control = feedback(Gc*Gp, H)
step(CL_control)
grid on

How can I mathematically design a PID controller from what I got on MATLAB?
For the Lead-Lag compensator: I tried different ways to design this compensator mainly from the book Katsuhiko Ogata-Modern Control Engineering (5th Edition) -Prentice Hall (2009) and other methods I have found on the internet. But it seems that every time I come up with the result, the root locus of the new system doesn't go through my new desired points ( s = -4 + 4.47j ) and I'm having problems in getting the static velocity error constant Kv.
The new root locus is NOT going through my desired points, I want to know why and how can I fix it.
Further info:
We're dealing with a unity feedback loop.
The following is the transfer function of the plant:
\$\ \frac{s + 1}{s^3 + 10s^2 + 9s + 19}\$


texts: What is the best method for reverse voltage protection of a microcontroller

texts:
When connecting a USB to TTL cable to flash a microcontroller (ESP32), I want to provide reverse voltage protection because connecting the pins in the wrong direction is easy to do and will destroy the processor.

The USB to TTL cable outputs 3.3V and the ESP32 needs at least 3V to function, so the voltage drops needs to be very small. The ESP32 also requires up to 500mA of current.

I am not sure if using a diode or using a MOSFET is the best method of protection for this low voltage application.


texts: Magnetic core memory construction, and proper cores to use

texts:
I'm looking to experiment with magnetic core memory. I want to make a small magnetic memory module for use with a micro controller.

There is a post on stack exchange itself that gave lots of relevant info, but most of it seemed to be using old stock of magnetic cores built for the task of magnetic core memory.

Most of the old stock for the magnetic cores seems to be quite expensive, I'm just looking to experiment with a small quantity. (I don't need, say, a container of 45,000 cores) Is there any such ferrite ring manufactured right now that would be suited for this?

I was looking at these cores on Digikey, would they be appropriate for the task?


texts: Digital pot (MCP41100) as LED strip dimmer

texts:
I want to be able to dim a led strip with a MCP41100 but I have no idea how to connect the digipot to the led strip...

It is connected to an ESP8266. I will have to figure out how to address the digipot from the ESP8266.

Here is the datasheet


texts: Which motor is suitable for a sun tracker one axis?

texts: Which motor is suitable for a sun tracker one axis and two axes and one of the specifications of this motor has high torque?


texts: Desoldering mosfets on a heatsink at once

texts:
I'm trying to desolder 4 IGBTs and a diode all connected to a heat sink but it's not going well , I tried adding solder to help melt the old one but it didn't work well, I'm using a 100 watt soldering iron and the pump. How should I do this task?

Top and side view


texts:
Can anyone check my timing diagram for me? I have my exam tomorrow and just want to make sure I am understanding these correctly:

Any feedback is appreciated.
Thanks in advance


texts: Power OFF then ON an ESP8266 when GPIO0 go low (aka reset ESP without nRST pin)

texts:
I need to flash some ESP8266 based devices that does not have the nRST pin accessible, but only:
VCC, GND, RX, TX, GPIO0
As programming board I'm using an old NodeMCU board that has this auto-programming circuit:

Due to the nRST pin is not accessible, by now before start programming I perform these steps:

disconnect VCC
bridge-connect GPIO0 to GND
reconnect VCC
programm
disconnect VCC
remove GPIO0-GND jumper
reconnect VCC
normal running

This is a very time consuming task, how can I make a simple circuit to do this?
Do a NPN transistor acting like switch on VCC and driven by nRST do the trick?


texts: How to decrease distortion/noise of LM386 amplifier at max gain and volume?

texts:
From my previous question, I've made LM386 amplifier and it works better than LM1458 amplifier. I've added gain and bass boost in my LM386 amplifier.

How to decrease distortion/noise of LM386 amplifier which occurs at max gain and volume?
Is using pin7 which is the bypass can fix the problem?
Is there other way to improve my amplifier or do i lack something which can improve my amplifier?

additional questions:

Since i have Bass boost, how to add treble control?
How long can LM386 last(hours) when playing music using regulated power supply(9v)?
What will be the effect of using 6 ohms speaker instead of 8 ohms speaker?

Edit:

fixed postion of C6 and R4

Schematic diagram updated: (sorry for the mistake I've done, updated again.)

after changing the position of R4 and C6, I've noticed the increase in volume. But when i changed the connection of C4 from pin4 to output(pin5) bass boost doesn't work anymore and when i put the bass boost to minimum the sound turns off also even the volume is maxed, that's why i connected C4 to the pin4. Is there a way to fix it or should i still connect c4 and pin4?

simulate this circuit – Schematic created using CircuitLab

Thanks for all the comments and suggestions, and it was successful,


texts: Directionality and gain: yagi versus parabolic antenna

texts:
I have a very remote cabin at 1000m (3000f), where I have close to no phone reception, so lately I have been trying to research as much as I can fathom of radio basics, but still without being able to conclude on anything with regards to what kind of antenna design is the optimal for my usecase and why it would be the right.

I was thinking of buying a parabolic antenna, directed at the closest tower down in a valley some 5km away, after reading up on various types. As repeaters are illegal to use (unless you are a phone company) in Norway, I was planning on just connecting (via RG58+SMA) the roof top antenna to a whip in the main room of my cabin. Hopefully that would enable us to make calls inside at this remote location.

  Greater directionality can be obtained using beam-forming techniques
  such as a parabolic reflector or a horn. Since high directivity in an
  antenna depends on it being large compared to the wavelength, narrow
  beams of this type are more easily achieved at UHF and microwave
  frequencies.

As GSM (900 MHz) is in the UHF range, a 60cm x 90cm parabolic antenna with a gain of 16 dBi seemed like a great fit.

But then I found a Yagi-antenna with a gain of 28 dBi(!), and I was a bit dumbstruck. The way I understood the thing with gain was that it was closely related to directionality: more omnidirectional would mean less gain and vice versa.

If a parabolic design had greater directionality, how could a smaller (in surface) Yagi still have a higher gain?

Obviously, I am not a professional after using a few hours reading up on quads, dipoles and whip-designs on Wikipedia, but I would like to understand how the things I buy work on rough level, so hoping you'll cut me some slack :-)


texts: Got a 12v 30a PSU but minimum output is 21v

texts:
Some months ago I got one of those cheap switch PSU from Aliexpress. Now I started to work with it and befor plugging in to my electronic device (which requires 12v) i noticed i could not get lower than 21v (glad i checked).

I though, ok, i got a wrong labelled unit, but after opening it I saw a big label on a (coil? internal transformer?) with a 12V 30A text.

This opens two possibilities:

The labeling is still wrong and this is the culprit.
Something else is failing.

I saw some big caps and took pictures, perhaps some engineer or hobbyist will be able to tell me if those caps would work on this unit (to rule out mis-labeling) and if the unit is consistent with a 12v one, perhaps someone can help me out in what to look/measure?

Thanks!


texts: Simulate physical FM Transmitter circuit on Matlab Simulink

texts:
I am new to matlab. I was working on a simple modulator that I have to simulate. I've faced a problem with connecting the output frequency from the resonance circuit to the scope, A red dotted line appears. After further googling and searching in mathworks, I've found a converter to connect them.

Now my problem is in the input signal. I am applying a signal generator to the input which is the join that collects a capacitor and resistor to the transistor base, the below images shows the whole circuit :

Now I found this converting tool :
https://www.mathworks.com/help/physmod/simscape/ref/simulinkpsconverter.html

But it still cannot be connected to the joint that I want. check this:

Anyone can suggest what's wrong with this type of connections and how to fix this? Noting that I am using matlab 2018.


texts: BJT Common Collector not swinging "negative"

texts:
I have an R2R DAC generating a 0-3.3V sine wave. This sine wave is fed into a non inverting op amp with a gain of 2. Then I'm trying to drive a 0.5W 50ohm speaker with a common collector amplifier. The common collector is connected to the output of the op amp via a capacitor. Vcc is 9V.

What is causing the signal to not go "negative"?

Green is the base of the NPN. Blue is at the junction of the emitter and R3. Red is at the junction of R4 and C2.


texts: What is the device used to diagnose bad eletronic hardware?

texts: I'm quite new to electronics repair and was wondering what is the device that is used to diagnose electronic hardware such as chips and power voltages. I'm not talking about a multi meter, but the ones that look like a big box with the wavey lines on the screen. Someone told me they use that to measure power current in eletronics to see if they are bad or not.


texts: Is there any reason some pins don't not work as GPIO on ATmega?

texts:
I got an ATmega8515 and this simple code inside main():

void main(void) {
    DDRD = 0xFF;
    PORTD = 0xFF;

    while(1){}
}

I expect to see all the pins high, but PD5-PD7 are still in hi-Z state. No alternative function is configured - these are the first lines of the function! Any ideas please? Is it a compiler bug?

Have tried this on two MCUs bought from different suppliers, not likely for both to be defective.

P.S. I use cross-avr-gcc 5.4.0-1.14 under openSUSE 42.3

P.P.S. Once in awhile I faced something similar, playing with optimization (-O) flags helped. Does not do now.


texts: Use GPIO pin of PIC on a general way and also with a led

texts: What should be the best way to connect a led on GPIO pin to work as an indicator but also as GPIO for use in other things. Should I connect it in a serial way? but I think Ill have a voltage divider, or in parallel way?


texts:
Not sure if this is the correct place to ask such a question, but here goes.

Ok so I mess around with an old 80's drum machine a lot.
It's based around an old 8031 Processor Program code is stored on a 27c256 eprom and sound data is stored on 2 x 27c040 mask roms.

The 27c256 in this machine holds the OS and also the data table containing the names of the various drum sounds and the start addresses for each sample. and in this chip there is data either side of the table.
I already make customised eproms for the machine, but I am limited to only 'replacing' the data in this table, which confines the machine to 47 different sounds.

I had an idea, and want to put it out to the heads to see if I'm talking rubbish or not..

The existing OS has quite a lot of space left at the end of the file (FF) Is it at all possible to hack the firmware so that at the point where it would read the table, insert the instruction to JUMP to another part of the firmware and read in a table that is larger in length with more samples etc. (lets say 100 sounds instead of 47 or something) and then at the end of this, JUMP back to where the end of the old table resides in code.

In essence I'm talking about bypassing a part of the code and replacing it with a larger piece. I know that of course I cant just make whats already there bigger as it would move the rest of the code, which as I understand would break then.

I'm currently replacing the data in the table by just patching the bytes that are already there.

Perhaps I'm talking jibberish, perhaps I'm not.

thanks
Brad


texts: What is the minimum voltage for general loads and peltier units

texts:
I am confused with "power ratings" on devices and electrical components.

First, what is the power rating on a home appliance or a electrical component saying when it is 12V? Is it saying "we would prefer a 12V power source"? OR "we need at least a 12V power source?" or "we can't take more than 12V power source"? Or does the answer depend on the device/component? (ie some are minimum, some are recommended, some are required)
Home appliance says it is 12V. But we plug it into a wall power point which is 230V power source (in New Zealand). How are these two compatible?


texts: How to reset ATmega328P fuses using Arduino Pro Mini and USBasp programmer?

texts:
I think I bricked two ATmega328Ps when I was trying to burn new bootloaders using Arduino Pro Mini, the USBasp programmer and the Extreme Burner AVR software. I had two ATMega328p with bad booloaders and I intended burn the correct bootloader to the chips.

First I connected the USBasp programmer to my Arduino Pro Mini equipped with an ATmega328P. I verified that communication was good as I could read and write to EEPROM. All was excellent.

I was using the following fuses:

LOW Fuse Byte=0x62
High Fuse Byte=0xD9
Extended=0xFF
Lock = 0xFF
Calibration = 0xFFFF FF8A

Then the following happened:

I killed the 1st chip when I only pressed button ERASE CHIP on the programmer.
I killed the 2nd chip when I wrote the following fuses to it:

LOW Fuse Byte=0xFF
High Fuse Byte=0xDA
Extended=0xFD
Lock Fuse = 0xCF

In both cases I had the following error message:

Cannot Communication with chip
Power On failed

avrdude output similar messages:

RC=-1. No answer...
(avrdude -c usbasp -p m328p -U lfuse:w:0x62:m -U hfuse:w:0xd9:m -U efuse:w:0xff:m )

How can I solve this problem?

How can I reset all the fuses to factory default to make the chips respond again?


texts: Could I connect USB wires to this mysterious device?

texts:
In a treasure box, as I call the boxes full of old computer electrical parts, I have found a device marked HannStar MV-4 94v-0 0611 E89382. I'm intentionally linking you to google search so that you can see that it finds nothing at the moment.

The MAC address has been censored.

I can see promising USB pins on the PCB. This made me think the device can work via USB. However the number of colored wires exceeds that of USB - it was originally connected to mainboard of laptop.

The device has MAC XXXXXXXXXXXX on the other side. I believe it's a Bluetooth or Wi-Fi transmitter - that would be very useful for Raspberry Pi.

I have tried to contact HannStarr but their website really sucks and their contact form does not work beyond capability of Firebug (which I usually use to repair broken pages). This was my message meant to them (in case you can send it):

  Hello, I have somehow salvaged a nice piece of hardware made by Your
  company.

  It might be a little old, but I'm very interested in using it (as an
  engineer).

  Can I please ask you for any technical documentation you are allowed
  to share about it? It's marked HannStar MV-4 94v-0 0611 E89382. Here
  is an image of it: http://i.stack.imgur.com/xvhOr.jpg.

  I will be very grateful,
  ****** ***** - *******@*****.**

  PS: Making <input> field 300px high doesn't allow for multiple lines of text. Tell this your webmaster. He should, instead, use <textarea>


texts: Why is Vbe a constant 0.7 for a transistor in the active region?

texts:
I'm going to take an example of a simple common emitter amplifier. Forget about biasing and things for now, but focus on the crux of this circuit. As how I understand it, a voltage between the base node and the emitter node is varied which is ultimately amplified by the transistor, causing an inverted (amplified version) of the original signal to appear at the collector node.

Right now, I'm working through a book; Sedra/Smith, Microelectronics.

Throughout the chapter I'm working through, it says that in the active region, Vbe is assumed to be 0.7V. This just does not make sense to me, how can Vbe stay constant when that itself is the input variable for an amplifier stage? This might have started to make sense to me if I was looking at at a CE stage with an emitter resistor (emitter degeneration), where the remaining voltage could be dropped across the resistor. But this is not the case, so enlighten me!

simulate this circuit – Schematic created using CircuitLab


texts:
I'm facing a weird problem.
I have written an UART and a FSM. This design just print some text on the screen automatically, just after loading the bitstream.
The problem is: when I load the bitstream, the text is printed withour error, but when I press the reset button to get that text printed again, what I see (in most of the cases) are strange and illegible characters.

Do you know what could be the problem?

Link to my current design: https://github.com/salcanmor/SRAM-tester-for-Cmod-A7-35T


texts: Using a Zener to protect devices from solar overvoltage

texts:
I am making some pretty crude devices that are directly powered from solar panels. The instability is not an issue, but I want to avoid over-voltage.

I am using two 100W panels in series and want to make sure on a very (very!!) sunny day it does not exceed 30V.

If I use a 30V Zener diode alone would that be OK? Looking at the power curve am I right to assume there will be no power if a Zener shorts it? Does the panel try to fix the current so the voltage drops?

This is opposite to a constant voltage supply that would make it blow up? Or have I missed the point?


texts: Is my DC-motor strong enough to move this amount of weight?

texts:
I’m thinking about building a robot just with some old parts I have.
The main thing is the motors. I have 2 DC Motors
Specs below. (It’s a MFA975D Series with gear ratio 49:1)
Operation range(Voltage): 12V
No load - Speed 147RPM
Nm = 1,8
The tracks of the robot will be caterpillar from old tires, driven by chains onto a gear.
My robot might gonna weight approx  40kg
How do i calculate of the motors are strong enough and what speed would I be travelling in? Only horizontal no degrees inclined.
EDIT
Thanks for helping me with my issues guy, i appreciate it a lot! The 2 motors have to run in a controlled loop. So when I want to go forward both motors go forward, and same as backwards. When I wanna turn, the motors gonna work in opposite direction of each other.
The things I want to know is , could it be possible to even use that motor standard, or should it need to be gear lower, for more torque? And how I’m calculating the speed of a my machine with this motor, my weight, the friction (Rubber vs Asphalt).


texts: Back-to-Back N-MOSFET inrush current limiting

texts:
I try to develop an application where I need to switch 55V at 20A in both directions using MOSFETs.
Because of the high current, I decided to use N-MOSFETs (because they are available with lower rdson) back to back and using a photvoltaic MOSFET driver to switch the gates.
My problem now is that the load I try to switch has a lot of capacitance (about 20 mF) which kills my MOSFETs every time because of the high power dissipation during the switching transition.
I already tried to to use an RC Lowpass to drive the gates more slowly through the threshold but the power dissipation is still too high, peaking at 200W (see simulation)

Is there any way I can limit the inrush current using this back to back topology?


texts:
So I have a Bosch L5077 180A 12v deep cycle sealed Pb battery for my solar setup. I bought it recently (2 weeks ago) but since the weather was rainy the last 2 weeks and the solar panels didn't produce any significant power, I keep charging it on-grid with a 10A 3-stage smart charger.

Assuming that this battery can hold a capacity of 180AH which is around 2kWh of energy, the battery is almost fully drained (11.3v) before even consuming 1kWh or so.

So, in 6 hours of usage which usually reaches the threshold in which the inverter shuts down, I'm using a 43'' 50w LEDTV, one 32'' 35w LEDTV, a laptop charging (60w/hour) and few home led lights opening now and then.

With a quick calculation we have :

43'' LEDTV 50w x 6 hours = 300W

32'' LEDTV 35w x 6 hours = 210W

Laptop charger 60w x 6 hours = 360W

Inverter 1500W consumption, let's say 30w x 6 hours = 180W

And the lights which shouldn't be more than 100watts total in those 6 hours as I don't use much the lights.

The result is 1050w of energy consumed and the battery is fully drained.

Where did the rest of 85 amps went to ?
The charger is always charging fully the battery, when the battery is fresh charged it will show a value of 13.6V in PWM charger, while 2 hours later it will show between 13.4-13.5V so I guess the battery can't be damaged so soon.

Any ideas ?


texts: High Speed Input Protection (High Impedance, 12 V Tolerant, ESD-Safe)

texts:
I am struggling with an input protection design for my FX2LP logic analyzer (3.3 V microcontroller with 5 V tolerant pins).

I wanted to achieve the following constraints for the 8 input pins of the logic analyzer:

high impedance (> 50k)
high speed (16 MHz, 62.5 ns signal period)
12 V tolerant (continuous)
threshold voltage of 2 V (already matches the FX2LP specification)
ESD protected (2k V)
3.3V or 5V supply

So far I have been looking at the following ideas:

Buffer IC
ESD Protection Diode + Zener Diode (for continous 12v over-voltage protection)
Using an TVS Diode array for continuous over-voltage and ESD protection

1) Buffer IC

The CD4050BPW fulfills all input voltage requirements, but seems too slow (propagation delay of 70 ns and rise time of 80 ns with 5 V input)
It was suggested here 2.

2) ESD Protection Diode + Zener Diode (for continous 12v over-voltage protection)

A regular zener diode however seems to cause too much capacitive load, reducing the maximum signal frequency 3.

3) Using an TVS Diode array for continuous over-voltage and ESD protection

I was looking into the SLVU2.8-4, and starting a simulation in spice based on the data mentioned here 4.
By doing so I realized: The high impedance (added via a resistor before the TVS) causes a low input current which results in slower diode charge times.

To give a better picture, here is a screenshot of the simulation run with 3 different resistors (500, 5k and 50k):

Good signal quality seemed only possible with the lowest resistor (500 Ohm)
The SLVU2.8-4 already has a "extremely low" Junction Capacitance of 5 pF.
So realizing a high impedance, ESD-protected and continuous 12 V tolerant input with just a TVS Diode array seems difficult to me.
(Of course, it could also be that my results are wrong?).

I am still quite new to electrical engineering and I might be taking a completely wrong approach.
So if you have some ideas how to achieve this (maybe Digital Isolator ICs or a faster buffer IC?), I would be very grateful to hear about it!

Thanks a lot!


texts:
I'm in the pencil-and-paper stage of building a radio receiver that has the following characteristics:

AM shortwave/HF
three fixed frequencies - 3.33, 7.85 and 14.67 MHz
single upper sideband with full carrier
BFSK modulation, varying between 2025 and 2225 Hz at 300 baud
The bands are allocated between 170 and 700kHz of BW, which I think includes guard band

Keeping the focus of this question narrow, to only the frontend - between the antenna and the preselectors -

If feasible, it would be nice to receive all three channels at once, though I understand that that would increase cost and complexity, and the bands might interfere with each other on the board. Failing that, it would be nice to have digital switching between the above frequencies, or mechanical if that's not at all possible.

If I have an antenna tuning varicap, perhaps I could have fixed capacitors across the first and second antenna selection circuits so that it's possible for all three stations to be tuned at the same time.

If I were to build simultaneous receive sections after one wideband antenna, each with their own preselector, what would a power splitter circuit look like? How would this affect impedance matching?


texts: Convert digitalWrite() in Arduino into STM32

texts:
I am trying to translate my arduino code into stm32 code for my own learning.
I was trying to convert the following code into stm32 code
      digitalWrite(main2, HIGH);
      delay(main_delay);
      digitalWrite(main1, LOW);

by using the following but it wasnt working. It would be really appreciated if you guys can help me out.
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_Delay(1000);
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;


texts: Does the order of components going to ground count?

texts:
Building a PCB, following the schematic there would be a specific order of the components going ground, but if I decide to let the signal go to ground in another point as shown in the schematic, would it affect the signal?

in the picture:

If I take R3 and plug it to ground after R21 instead of after R2, it still goes to ground, but the order is different.

Does it affect the signal? Does the output signal change?


texts: AL1676-30A LED Driver output current rating

texts:
I was asking about the Al1676-30A LED Driver produced by Diodes Incorporated.
(Product Overview)

The specified LED Driver is listed in Mouser Electronics website to provide 3 A of current to the connected load, however, when I was reading the datasheet of this product I have found in the recommended applications that the recommended maximum output current is only <=300 ma. So what is the difference between the recommended application value and the value specified in the product description. (Datasheet)


texts: Can someone justify shifting current sources iam not able to understand how it is done


texts:
I'm designing an 8-bit computer, trying to stick with low-cost components available in 1984+/-3. Following a previous question, I've completed the 6845-based hardware, except that I have no clue how to generate the RGB video signal.

I looked at the schematics of many computers of the era, especially the Amstrad CPC and the BBC Micro, but found that everything was done in an opaque ULA, with no details about operation.

I have the hsync and vsync from the 6845, and my design is now able to produce synchronously for each pixel a N-bits value for each R-G-B component, either in parallel or serialized via shift registers. What then?

I suppose I should feed the values to some DAC able to convert those to analogic signal, but I saw nothing of the kind on the schematics. It looks like they are feeding video ram values, character rom and color latches into the ULA and then, presto, direct to the video connector!

Do those ULA include DAC too, or is the video output standard digital after all, or (most probably) am I missing something?


texts: A question on the meaning and model of microphone impedance

texts:
I’m a little perplexed by the circuit model and meaning of a high or low impedance microphone. Here is an example where someone at this page is trying to investigate the effects of low or high mic impedance:

But my question is more primitive and fundamental here. The dynamic microphone is made of moving coil and the electret mic is made of capacitor. But Rm above is modeled as the output resistance of the mic.

My questions are:

1) What is Rm in real? Is it the DC resistance?? Or is it the inductive reactance of the coil or the capacitive reactance of the capacitor at particular frequency? If so isn't it wrong to model it as a pure resistor(Rm) in the circuit analysis? Is there better way to model the microphone impedance as a source and Thevenin equivalent?

2) When we say high impedance or low impedance microphone do we mean the output impedance hence Rm in the above diagram?

Edit:


texts: What is the ideal resistance for a 2N3904 base resistor value when using RTL logic?

texts:
I have a ton of 2N3904 transistors and would like to use them for my RTL logic project.  Based on what I could figure out on the web, and the parts I had, I've gotten logic gates to work quite well with the following values:

simulate this circuit – Schematic created using CircuitLab
Although this works fine, I'm a bit concerned about what I've read on the data sheet for the 2N3904.  It states that the Base-Emitter Saturation Voltage has the following specs:
Ic = 10mA
Ib = 1.0mA
Ic = 50mA
Ib = 5.0mA
I'm having a hard time understanding what that means exactly.  If you calculate the current for the base input with Ohm's Law, we get I = 5 / 10000 = 0.0005.  Am I correct that this is 5mA?  I replaced R2 with a 5K resistor and it switched the same, which would be 0.001 or 10mA.
Like I said, it is working at the moment.  I just want to make sure that I purchase the right resistors for the job.  I know that the goal is for the transistor to be fully saturated, however I don't know if this is how that is done or not.
Thanks,


texts: identification SMD 3 Pin 3x1.5mm code 4B C39 for stereo camera

texts:
I am trying to build stereo camera using android or iphones. The pcb is from a wired selfie stick and works well. By using 2 pcb's with one push button, simultaneous photos can be taken. I have looked at the SMD code book and think the device is a sot23 BC8598 but frankly not sure.pcb is 1 button and 1 smd.
The pcb is attached to the phone with a 4 pole 3.5mm audio jack, it emulates the volume control of an earphone with mic.
If someone could point me to an explanation as to why this works and all the resisters I have used haven't I would be grateful.
Yours hopefully
Steve


texts:
I am looking into Power Line communication (PLC) as a means for smart metering. It looks totally possible to send the data from the meter to the source of the power supply or the transformer.

Most of the smart meters use Wifi. Are there any technical/practical challenges to implement a PLC based smart metering network? Thanks.


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I have a 74HC595 shift register that I shift bits into from an 5v Arduino. The pins on the shift register is connected to the base of 2N3904 BJT's through a 4.7kOhm resistor. I have noticed that if I include the base resistor, my current to the base is 12.8uA and if I don't the base current is 13.1uA.

Since the figures are so small, do I even need a base resistor?

I should mention that I am trying to build a circuit for one of those fancy LED cubes. On the schematics are shown 2 diodes, but that will be expanded to 8 LEDs for each shift register.

simulate this circuit – Schematic created using CircuitLab


texts: PCB design for outdoor use without coating

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I am making a PCB for a home project: a small weather station that I will place outdoors to collect data. There is now a question of environmental resistance.

I can mill out the PCB for free on a relatively old machine. This means that I will not get any protection against the elements out of the box.

My question then is: how quickly will the PCB degrade when left outdoors (in a housing) with only tin covering the copper and are there any relatively cheap methods of protecting the PCB against the elements?


texts: LTspice gain enhancement sallen and key highpass simulation

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I have been trying to simulated a filter and amplification circuit. In one of the stages I am using a LP Sallen and Key circuit and another I am using a HP Sallen and Key circuit. I can successfully get the shape of the filter in LTspice AC analysis with 307kHz being my center frequency, but when I add gain enhancement the shape completely goes away. The first image is my calculations for my component values. The first image below is my LP filter circuit and the resulting AC analysis. The second image is my circuit when I add gain enhancement and the resulting AC analysis that exits. My calculations are at the bottom.

I am hoping to get the same or similiar shape to the filter without the gain enhancement, but would just like a higher gain. Looking at the datasheet of the LT6233 the gain bandwidth is 320MHz. Does anybody know what I might be doing wrong?

simulate this circuit – Schematic created using CircuitLab

With Q=1.5, ωo=307000*2π and H=20 we can find the component values for each:

C3=(2*Q/ωo)*((H-1)/H)=1.477*10-6
C2=1/(2*Q* ωo)=1.728(10-7)
C4=2*Q/ ωo=1.555(10-7)
R3=R4=1     R1=R3*H/(H-1)=1.0526        R2=R3H=20

Then, normalizing each component to C4=1nF, we get:
C4n=C4*(1nF)/C4=1nF          C2n=1.111(10-10)≈0.1nF          C3n=9.5nF≈0.01µF
R3n=R4n=R3*C4/(1nF)=1555Ω≈1.6kΩ     R1=1637Ω≈1.6kΩ      R2=31.1kΩ≈30kΩ

I am not 100% confident in the source I got these notes from and after simulations I found that I needed to cut out C3


texts: What "bus turnaround" delay should my PSRAM have?

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I have a PSRAM driven by an STM32. One of the timing options for the STM32 is the bus turnaround FSMC_BusTurnAroundDuration. The ARM reference manual (see page 1250) says:

  These bits are written by software to insert the bus turnaround delay
  after a read access only  from multiplexed NOR Flash memory to avoid
  bus contention if the controller needs to drive  addresses on the
  databus for the next side-by-side transaction.

Now my PSRAM is not NOR Flash and does not multiplex the data and address lines, so I assumed that FSMC_BusTurnAroundDuration is a "don't care" in my case. However, when I set

FSMC_BusTurnAroundDuration = 0;

then the ARM crashes. Any value between 1 and 15 doesn't crash the ARM.

Why is the bus turn around duration relevant for my PSRAM?


texts: External power supply necessary to run two stepper motors from a RPi?

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I am following this tutorial for a CNC laser engraver. I have two stepper motors from some old DVD drives and two L9110S H-bridges to control them.

I am now working on putting it all together and ran into some confusion when setting up the power supply for which I cannot find much information on within the guide. Could I connect the 5V at pin 2 of the RPi to both the H-Bridges to run the stepper motors or will I need to look at an external power supply for this? If external, what could I use? I have seen examples of 4 AA batteries in series, will this do the job?


texts: OmniVision CMOS sensor package name for camera modules?

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I seen few camera modules by OV, that come on a flex cable like the one below (OV2640)

How does this package called? I see on the OV website COB, CSP, uCSP,CLGA, but I suspect they're without the enclosed lens and cable. Does OV makes those, or some third party buys the sensor and mounts the lens/cable?