texts:
I have done the circuit in the picture :

from here

(modified  Question):

So two LEFT MOSFET (IRF9540 & IRF540) will be overcharged and so heating and  DC motor speed is constant and didn't change by difference pulses as ENABLE signal (PWM) from an IC555 (VBat = 12v) and (v-A or V_B=12v)
so what do you think?!

I simulated this circuit in Proteus (combined with an IC555 for PWM and you could see its image:

You could get Sim file in :

http://filepi.com/i/BNIZOTG

Simulation works, but the value of the RV1 potentiometers doesn't change during the simulation and the motor speed doesn't change by changing the potentiometer value during the simulation. I have this problem too in the real board when I am changing the ic555 potentiometer the motor speed doesn't change and it is only constant at some specific speed!!! (there is no PWM pulse!!!)

Maybe if I change its biasing part it will work.

And I have another question:
What would be happened if I will drive a MOSFET with nominal Vgs (like 10V) and how no load in its drain .is it overheating!?
I think its don't work correctly in biasing of IRF540 MOSFETs. So could you help me to make it correct?


texts: Filtering an ADC input with an RC low-pass filter

texts:
I use an instrumentation amplifier to amplify low voltage signals from a sensor.
The max. amplified output voltage is 3V. Im using this ADC: http://ww1.microchip.com/downloads/en/DeviceDoc/22088c.pdf.
It has 4 channels that are multiplexed. Every 5 seconds all 4 channels should be sampled with 18bit mode (3.75 SPS). The internal sampling capacitor of the ADC is 3.2pF. I have put a RC low-pass filter like you can see in the following schematic in front of every ADC input channel. I realized that there is a significant voltage drop accross the 100kOhm resistor expecially (about 60mV drop for a 1.5V amplifier output voltage).
Now my question is, why is that? What values from the datasheet of the amplifier do i need and how can i calculate what is happening here? Do I need to take the leakage current to compute an average current? As this is a delta sigma ADC, im not sure what frequency I need to take to make calculations. I hope you can point me into the right direction. I also want to use C2 as a resevoir for the sampling capacitor because im multiplexing between multiple channels and I do not want to offset the current measurement with some voltage of a previously sampled channel. Hints, specifications and formulas I need for this to calculate would really help a lot! Thank you very much.

simulate this circuit – Schematic created using CircuitLab


texts: Partial fraction decomposition of Laplace transform

texts:
I have a sinusoidal input beginning at time (t = 0).
\begin{equation}
x(t) = e^{j \omega_0 t} \cdot u(t).
\end{equation}
The Laplace transform of my input is:
\begin{equation}
X(s) = \dfrac{1}{s - j \omega_0}.
\end{equation}
The Laplace transform of my output is:
\begin{equation}
Y(s) = H(s) \cdot \dfrac{1}{s - j \omega_0}, where \ H(s) \ is \ assumed \ to \ be \ a \  rational \ transfer \ function
\end{equation}
The next bit I don't understand. I can apparently decompose the transform of the output as:
\begin{equation}
Y(s) = \dfrac{A_1}{s-p_1} + \dfrac{A_2}{s-p_2} + \cdots + \dfrac{A_N}{s-p_N} + H(j \omega_0) \dfrac{1}{s- j \omega_0}
\end{equation}
Why has the argument of H(s) changed such that the transform of the unit impulse response is now \$H(j \omega_0)\$? Why is \$H(j \omega_0)\$ assigned to the fraction with \$s- j \omega_0\$, shouldn't there it be an arbitrary constant for all the fractions?


texts: EEPROM and CONFIG macros on PIC with HI-TECH compiler

texts:
I have seen 2 lines of source code that I can't find documented anywhere. They are:

__CONFIG (0x03d4);
__EEPROM_DATA (0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);

I assume that __EEPROM_DATA() writes data to the eeprom at address 00-07 in the source code above is this correct?

As for the __CONFIG() I don't understand why its a hexadecimal, typically it uses macros from the header files so what does it mean?


texts: How interrupts handle does work on a physical layer

texts:
I want to understand how HW IRQ does work on a physical layer. I ask my question considering a specific example. As known after a packet coming to a network adapter a hardware interrupt is signalling. Wiki says that

  an interrupt is a signal to the processor emitted by hardware or
  software indicating an event that needs immediate attention.

I know that OS will be invoke a corresponding interrupt handler when the interrupt's type will be detected. But I don't understand how does CPU detect and distinguish incoming interrupts. Now I ask my questions:

First, why CPU does know that the interrupt is coming from network adapter, but not from other devices?

Second, Where does interrupt handlers registered in CPU? Is there exist a specific CPU's area which contains handler's addresses registered by OS?


texts:
I use an opamp driver to pump several amps through an LED. My circuit is below.

simulate this circuit – Schematic created using CircuitLab

When the input is low, I see a small leakage which I suspect is due to Offset Voltage of the opamp between the +/- terminals. 500uV is the Opamps' input offset voltage and the leakage current is 1mA.

I like to avoid this leakage but it is not easy to fix the offset voltage of the Opamp. How can I modify this circuit to avoid any leakage?

My input is a digital signal between 0 and 2.5V.


texts: I'm connecting a Raspberry Pi to an LED and this video tutorial says that I need 270 Ω resistors. I only have 100 Ω, 1 kΩ, and 10 kΩ resistors with me. Is it okay if I use the 1 kΩ resistor?


texts: Electric board clicks and the output VDC is higher than the input AC

texts:
I've been working on fixing my treadmill's electric board in the past 2 weeks, and I learned a lot about electronics through this process. But for sorry I can't get it working, yet. I'm providing here all my findings & steps and I'm looking forward for your assistance.

My treadmill showed me an Err2. I watched many videos and they all agreed on bad an IBGT (In some videos they changed the biggest capacitor (Cylinder shape) and some resistors). I checked my IGBT and it read (0L).

I replaced the faulty IGBT. I tested the new one using the diode mode. But unlike all the videos that says put the positive lead on the Collector (Center leg) and the negative lead on the Emitter to get a reading, in my case it gives 0L. But when I put the positive lead on the Emitter & the negative lead on the Collector, it gives a reading 0.391v. These tests were conducted when the electric board is disconnected from the treadmill cables.

After I replaced the IGBT, I connected the board again to treadmill & turned it on & pressed the start button. But it didn't start nor it showed Err2 (Conditionally, read below).

But there're a lot of observations

Notes

I have 247AC input
My motor works on 180 VDC, 16 Amp

1st try and findings

I powered up the treadmill
When I pushed the start button, I heard a click sound (I watched a video that explained it's because of faulty capacitors which causes the relay to make this clicks & the refrigerator not to start)
The motor didn't start and no errors was on the screen.
- If I power down the treadmill & start it in a few seconds later, it shows the Err2
If I power it down and wait for a few minutes before powering it up, step two takes place.

2nd try and findings

This try takes place if I wait a few minutes after the 1st try
I detached the motor from the board terminals
I connected my DMM to the DC terminals in the board
I powered up the treadmill, the reading took a minute to reach 126VDC (It goes fast at first, and slowly in the last few volts).
Once I pressed the start button, I heard a click sound in the board & DMM reading jumped instantly to 260VDC
I powered down the treadmill, and the reading gradually went down.

Capacitors

All chemical cylinder ones look good, no leaking nor bulging on the top. I didn't detach them for testing (Yet). I accidently touched the biggest capacitors (470 uF 450 WV) with the soldering iron at the top-edge, it removed about a mm of its outer isolation material.

Rectifier diodes

Their readings within the normal range of 0.3 : 0.7v using diode test mode.

Except 2 of them

The 1st rectifier readings are 0.190v on both sides when I connect (++ -- & +- -+) when connected to the board, and 0.420v (++ --) & 0L (+- -+) when detached from the board.

The 2nd rectifier (Which's directly on the path of the IGBT that I replaced), it read 0.540v when I connect (++ --) & 0.790v when I connect (+- -+) when its connected to the board, but when I detached it, it read 0.540v when connecting (++ --) & 0L on (+- -+).

GBJ bridge rectified

Tested it in diode mode and the readings are around 0.425v

So, where do I go from here?

Do I go detach resistors, capacitors & relay to test them?


texts: How can I make battery supply power when wall adapter supply is disconnected?

texts:
Hello, I have a question about battery charging and power supplying. I'll go with picture for better understanding

Starting from using 12V 1A wall adapter, Power will be supplied to My Raspberry PI through 5V rail. My plan is as follows :
1. Down convert 12V to 5V.
2. The converted voltage will be connected to both 5V rail and VIN for battery charger (LTC4067)
3. When wall adapter is connected, output of 12V to 5V regulator will supply power for RPI directly through 5V rail.
4. When wall adapter is disconnected, stored energy in 4.2 LI-PO battery will be supplied to RPI.

I know that recommended input voltage for RPI is 4.75~5.25 and expect that 4.2V LI-PO battery supplies  quite insufficient voltage.
My questions are here :
a. Is boosting output voltage of LTC4067 to 5V necessary?
b. If so, is it okay to just connect the boosted voltage to 5V rail?( in aspect of backward protection)

I'm really really unskilled novice and I don't know much about constructing circuit. I would be appreciated if you answer this question.


texts:
In this circuit

Why is there a resistor if the ground already is 0V?


texts: Louder Horn / Circuit / Different Speaker to be louder

texts:
The main goal is to make our current speaker louder. The second goal is to use a speaker with a smaller form factor than our current horn that is louder.

We are using a 24Vp-p DC circuit (push +12V / pull -12V off of a 12V source) that we are using PWM to send different frequencies to an 8 ohm Horn. According to the horn datasheet it is designed to use a 24Vp-p square wave. http://www.promover.com.tw/en/main_index.php?menu=product_inside_item&p_id=541

The signal looks like this.

If I put a 33uF capacitor in series with the horn then it looks like the image below. The image below shows a horn circuit signal with no capacitor and a horn circuit signal with a capacitor stacked on top of each other. The 33uF capacitor helps block the DC which I think is a good thing, but it is quieter and that is not what we are going for. According to this website http://education.lenardaudio.com/en/07_horns_2.html they recommend using a 47uF capacitor for 800 Hz to 8KHz Are there any cases where filtering the signal can make it louder? I am only familiar with filtering a signals that are outside of the bounds of a speaker frequency response. I do not know of any ways to change a circuit to make a horn louder.

Is there anything that I can do to make a single horn louder for this circuit?

We looked into an 8 ohm speaker as we are looking into a smaller profile http://www.visaton.com/en/industrie/breitband/fr10_8.html and it was not as loud as the horn even though it has a better frequency response and higher wattage ratings. However, while doing some research it appears that horns are very efficient at being loud, and speakers need to have a properly sized / ported cabinet in order to achieve maximum loudness.

According to the internet a 4 ohm speaker is not louder than an 8 ohm speaker due to the amplifier has trouble sourcing enough current for a 4 ohm speaker for the same loudness as an 8 ohm speaker. However, wouldn't a 4 ohm speaker be louder in my case assuming that the PCB and wires are capable of handling the extra current and my 12V rails stay at 12V?

The frequencies that we are interested in are 100 Hz to 2.5 KHz. Our horn is used for playing solid tones and different buzzer / car alarm sounds and audio clarity is not of too large of a concern as it will not be playing back music or voice audio.

So to summarize, my three questions are.

Is there anything I can do in my circuit in order to make the horn louder other than using a higher voltage which is not an option?
Is there a better type of horn or speaker that uses a thinner profile than our current horn, but is louder and has a better frequency response (100 to 2.5 kHz)?
Will going to a 4 ohm speaker be louder than an 8 ohm speaker in this case?


texts: When a coil is wrapped around a ring of non magnetic material, is the path length (l) the circumference or the diameter of the ring?

texts:
I'm doing some practice questions on magnetic fields:

  A coil of 300 turns is wound uniformly on a ring of non-magnetic material. The ring has a mean circumference of 40cm and a uniform cross-sectional area of 4cm^2. If the current in the coil is 5A, calculate (a) the magnetic field strength. (b) the flux density and (c) the total magnetic flux in the ring.

For (a) I have rearranged to get Magnetic field strength = (Number of coils * Current) / length.
In this instance is the length the mean circumference or the diameter of the ring?


texts: Fiber-coupled diode laser in an SMD package?

texts:
Does anyone manufacture a fiber-coupled diode laser in an SMD package?

Something like this, but smaller.


texts:
I'm trying to figure out how to connect a linear pushbutton sensor to a Microchip PIC.

The problem is: the sensor has an 5V output and only 3 pins (VDD, Sensor and GND). I need to power the sensor with a VDD different than the one my PIC is running on. But this means I should either connect the 5V ground to my 3V ground or do an analog reading without connecting the sensor's ground to the side of my microprocessor.

Is there any way to do this? I already have a PCB so besides the resistor divider to convert the 5V, I don't have any room for another component.

Note
The 5V and 3V power supplies have to be isolated from each other.

Edit
I have sacrificed the separate ground planes in order to connect the sensor. This works.


texts: Powering a radiator fan with 12V DC power supply

texts:
I want to run an old VW Fox's radiator fan on a 12V DC power supply.
I have managed to burn out two of the PSUs so far. They work for a while but after a while they start overheating and die.

I am now trying a car battery charger. Haven't had it on for longer than 10 minutes as I don't want this one to burn out too.

There are no indication of voltage, amps or anything on the fan itself so it might have more or less volts than needed.

Please tell me what am I doing wrong.


texts: Determining voltage requirement of unknown circuit board

texts:
I have a vintage, home-built metal detector from the 50's/60's with a simple circuit board.  It apparently had a home-built battery pack that plugged in but it is now missing (9-volt battery style terminals but spaced far apart).  There is one transformer labeled 6v6/5koms that drives the speaker.  No IC's, all simple components.

I imagine it's either 6v or 9v but I'm curious to know how to determine a best guess.

update:
The PP9 battery was what I needed based on the plug.  Thanks also for the suggestions on how to test it.  Much appreciated.


texts: Battery Charger Drawing Too Much Current

texts:
I am working on a project where I am switching between a solar panel and a 20 volt, 5 amp AC to DC wall adapter to charge a 12 volt lithium iron phosphate battery. I am using a Morningstar Duo solar charge controller to safely charge the battery. However, when I connect the wall adapter to the controller it draws up to 7 amps (when it is only rated 5 amps) and causes the supply's voltage to drop.

Now it appears that the PCB board on the battery is damaged.

Anyone have any insight on what might be causing the problem or how to safely limit the current being drawn.

Thanks a lot everyone who takes the time,

Matthew

Link to charge controller:

http://www.morningstarcorp.com/products/sunsaver-duo/


texts: Why is the output DC voltage of full wave rectifier not equal to the RMS of the original AC input?

texts:
https://www.electronics-tutorials.ws/accircuits/average-voltage.html

https://www.electronics-tutorials.ws/accircuits/rms-voltage.html

I understand that the RMS of an AC voltage is the magnitude of the equivalent DC voltage in terms of power produced,so I expected that when the AC voltage is rectified, the output DC voltage would be equal to the RMS of the original AC (assuming no other voltage drops for diodes.)

When used to compare the equivalent RMS voltage value of an alternating sinusoidal waveform that supplies the same electrical power to a given load as an equivalent DC circuit, the RMS value is called the “effective value” and is generally presented as: V eff or I eff.

In other words, the effective value is an equivalent DC value which tells you how many volts or amps of DC that a time-varying sinusoidal waveform is equal to in terms of its ability to produce the same power.

V DC = 0.9 * V RMS


texts:
I'm building a xenon flash unit with a power of 50Ws (300V 1000uF capacitor).

I need to trigger it from a microcontroller. For that I use a MOC3041 to opto isolate my µC from the HV circuit and command my thyristor (MCR12DG). This one trigger a HV coil to light up my xenon tube.

Here is the schematic :

The Igt of my MCR12DG is 8mA, so I set a resistance of 1.6K, VTrans is 14v.

Here is the spec of TCP3308 trigger coil:

It's the first time that I use an SCR, and may be something is missing ?

Is my SCR correctly chosen for my application ?

EDIT:

Here is a correction with a MOC3023 as suggested. The main term is now connected to the SCR in order to turn it off. A 2N3904 is used to trigger the led from the uC and a 500ohm resistor to limit the current through the MOC3023.

But now as I connected my main term to 200v.I use 2 resistor and a capacitor connected to the main term as recommended by the application note AN-3003 for inductive load.

Is this correct ?


texts:
Apologies if this isn't the right StackExchange site to go to, seemed like the best option.

I 3D printed a phone cradle for myself that was built for use with right-angle USB connectors. My phone has a USB-C port and the cradle does its job, but with a minor annoyance: I have to hold the cradle down in order to remove my phone from it because the USB-C plug clips into place (as it normally should!).

But for the cables I'm using for my cradle(s), I'd like to stop them from clipping on so I can just slide my phone out of the cradle without needing both hands to do so. Is this possible?

While writing this question, I did find this question and answer with a diagram that shows the retention springs, and while I appreciate knowing where they are now, I can't easily envision a way to restrain, break, or remove the springs to accomplish what I want to do.


texts: direct ac mains to MCU pin for zero crossing detection

texts: to detect Zero Crossing of ac mains, can i connect an EFM8 pin configured as input directly to 220V ac via a resistor?


texts: Help driving an old Vacuum Fluorescent Display

texts:
I recently salvaged a VFD from scrap, and am currently trying to get it to display light (not worrying about actual numbers/letters yet, just trying to get it to light up).

I've read up about these devices (Including this question) and as far as I understand it, the required conditions for operation are:

Sufficient current passing through the filament to induce thermionic emission
30-60V bias from filament to segment, segment positive
Zero bias from grid to anode (this part I'm unsure about)

The current setup:
A 9V battery powers a comparator-controlled boost converter circuit that charges a 150µF capacitor that acts as the HV power supply. The negative of the capacitor (call it ground for convenience) is connected to the filament, while the HV output (I've ramped up the voltage from 0 to around 70V) is connected to one of the segment terminals on the display. A 3V battery of two new AA cells (2.87V nominal) was connected across the cathode filament, to serve as the 'heater' supply.

I've read confusing information about the grid connections - some sources said to connect it to the HV supply, others said to bias it only slightly positive. I also tried leaving the grid unconnected. None of these configurations produced any light.

A picture is attached below of my (addmittedly rudimentary) circuit. (the 3V battery is not shown, but it was connected across the extreme left and right pins on the display)

The HV lead off the capacitor is the long yellow wire that travels over the ICs.

I'm fairly sure the vacuum is intact, since the getter spot is still black.

simulate this circuit – Schematic created using CircuitLab

I'm not sure how to proceed. I've checked the cathode with a DMM set to resistance, and it reads about 13 ohms, but I'm unsure about what the expected value would be.


texts: What is the meaning of output voltage and current?

texts:
I have a 5V power supply with DC output rating: 5V @ 1500mA. It could power my High Torque servo very well.

I, however, have a fairly used 9V Alkaline battery. I shorted this battery and I measured the current to be ~3 Amps using a multimeter.

Later on, I connected this battery to a 5V regulator to power my High Torque servo, and it doesn't seem to be drawing as much power as my 5V DC power supply.

My question is, what does 5V @ 1500mA mean exactly? Is 1500mA the maximum current it draws or the minimum? If it's the maximum then my 9V battery seems to produce more current than the power supply, but that's not the case.

And why are power supplies not equally as powerful even though the voltage measure maybe similar.

My guess is that it all boils down to less internal resistance produces more current, and my 5V DC power supply has less internal resistance.

Is the internal resistance of my 5V DC power supply then: 5V / 1.5 A ?

Or maybe this doesn't even have anything to do with internal resistance.


texts:
I am conducting research on wind turbines, specifically into how many hectares wind farms use.

I have come across the phase 'installed capacity'. If wind farms typically use up 10 hectares per megawatt of installed capacity does this mean a two megawatt turbine requires 20 hectares of land? Or does it mean the total power capacity of the windfarm?


texts:
EDIT:  Please read the whole post before automatically down voting. I KNOW the diagram is crap.  That is what I am asking about.  It isn't my diagram.

Original post:

I Web searched a bit and searched this site, but I didn't really see a good answer.

I thought line level voltage was insufficient to switch a transistor and I thought an audio signal coming out of an amp or preamp was a sine wave anyway.

I thought those things made the seemingly simple idea of driving LEDs to pulse with sound or music a little more difficult.  Microphone input -> preamp -> rectify it to make a nice fat on/off dc signal -> drive something.

But I see this:
leds respond to sound

with a circuit that looks like:

I see other circuits (one at Instructables I think) that essentially do the same thing- connect the line level voltage directly to some transistors.

My question: I haven't a clue what is going on here.  Why does this work- or does it really?  What is happening?  Is it that the "audio source" is really headphone/speaker level and not the line level it may be billed at and thus enough to saturate the transistor?  Does this look like a recipe for disaster?

EDIT:  Trying to focus things per Red Gritty Brick.  I know the diagram is crap.  How would you do it right?


texts: Simulation of inverting summing amplifier not working and finding it's parameters

texts:
I have a project to create circuit of inverting summing amplifier with 3 inputs and a simulation on it. I am using capture (OrCAD Pspice) and so far I got to the circuit you see below, at the end of this wall of text. The circuit is supposed to have the following parameters:

Av1 = 1
Av2 = 2
Av3 = 3
f max = 20kHz

And that's it. Since I do not have the value of any resistors I should use in my circuit I have picked a random number - in my case:

Rf = -6k Ohm
Ri1 = 6k Ohm
Ri2 = 3k Ohm
Ri3 = 2k Ohm

Please note that I am not even sure that Rf can have negative value, but if it doesn't I am not really sure how I can make the voltage gain positive as the equation is:

Av1 = -(Rf/Ri1)

The second problem is that I can not get the simulation to work. I am not sure which one should I use (probably the AC sweep?), but I have tried using Time Domain, DC Sweep, AC sweep, Bias points. Not even one of them worked. I tried changing the sources between AC and DC, but I keep getting flat only lines. The only thing that works in my simulation is that with increasing the voltage through resistors their current increases. I am pretty sure the simulation I get should look something like the one shown here - I tried to make my circuit diagram pretty much the same to the one in that post, but it still doesn't work.

Here is the diagram itself:


texts: Trying to understand a transistor data sheet

texts:
So I have been researching on how a bipolar NPN transistor work. Here are my understandings:

In order to turn on a transistor, you need to apply a voltage (from base to emitter) to overcome the depletion region, that voltage is usually 0.7Vdc
Once the transistor is "on", as the base current increases, the current flowing from the collector to emitter will also increase proportionally by a hfe constant

Armed with this knowledge, what I should expect to see in a data sheet should be the following:

The minimum current/voltage to turn the transistor on (voltage needed to overcome the barrier)
The maximum current allowed at the base to avoid damaging the transistor

How do I navigate the data sheet to obtain this data?
Finally, there is a DC current gain chart in the data sheet, here are my questions

Why they used the collector current instead of the base current? shouldn't this makes more sense to use the base current? because you would think "if I have x amount of current in the base, I will get x amount of current from collector to emitter?
What if your Vce is larger than 1.0Vdc? say 5Vdc? what would the gain be then?

Datasheet:
transistor
https://www.onsemi.com/pub/Collateral/2N3903-D.PDF
Relay
https://www.circuitbasics.com/wp-content/uploads/2015/11/SRD-05VDC-SL-C-Datasheet.pdf
Circuit I am trying to solve

Thank you
As you can see from the diagram, the relay will only turn on is if there is 5Vdc and 71.4mA across it. Knowing this fact, how do I determine the current I need at the to achieve this?


texts: Do I need a charge controller with BMS on 18650?

texts:
I have a 40W 22V solar panel, and 4S 18650 with a charge controller connected to them.
When I connect my panels directly to the BMS I get 2A and my voltage drops to 15~16 volts.
Question is, do I still need MPPT to send power to my BMS?
My whole grid is 16.8V and I have a buck converter before any appliance that must work. (Mostly LEDs, Peltiers, couple of Arduinos, modem, router, network switch, etc.)
Another thing is, I tried a buck converter. It lowered the open voltage to 16.8 and connected to BMS, I still get 2A and my panel voltage drops to 16V.
I want to design my own controller (with Arduino Mega, yes I need that many pins) to cut power from panels at night and some other things (data logging, cellphone monitoring, web panel monitoring, emergency charger, current monitoring, cell monitoring,  etc.)
I'd appreciate your advice.
P.S: My battery bank is made up (recently updated)  40P4S (160 batteries in total) and this 40W panel is just my first concept and I will upgrade once I have a foolproof system.)
P.S2: I thought about adding a light detector next to my panel and add a relay to cut power from panels (and yes I will use MOSFET, this is just a concept ) but I feel it's cheating, I prefer to rely on panel voltage.
Maybe I could put an ACS712 after my panel and monitor the current from there, once it hits 0.01A I could turn off the MOSFET and monitor the voltage from and once the voltage is more than 20V turn on the MOSFET?
I'm a programmer by day, electrician and IoT and green energy enthusiast by night.
I have an elliptical bicycle with dynamo charging those batteries and I workout with that.


texts:
I have 3 Atmel MCU based BLE scanners, each uses TI CC2540 based BLE module (PDF User Manual) chip to scan for the advertise packets (bluetooth Beacons) around.
There are approx.  10 Beacons at a time around the scanner sending advertisiment packets every 100ms. The scanner needs only Minor, Major and the txPower of the each beacon.

The scanner sends an "AT+DISI" (start Beacon discovery s. User Manual) command over serial interface to the BLE Module and waits for the data response.

Everything works fine, but the time, until all data completely arrives takes around 5 seconds.

Since I want to scan for the Beacons one or two times a second, I need to improve the scanning time.
Some possible options I thought about:

connect 5 BLE modules to the microcontroller using serial port expander, successively send scan command with 1s time offset and at the same time collect data recieved so data arrives every second.
Make use the 8051 MCU inside the CC2540, which may improve the speed, since no serial communication to external MCU is needed.
Develop custom BLE profile, which has less payload and Beacon / scanner firmware that sends / listens on the constant frequency.
Using another chip / technology

What is the best way to scan for a dozen of the BLE Beacons one-two times a second?

Related questions I read:

How to scan for all available beacons with BLE – similar scenario, except I have 10 beacons at a time and less than a second to scan.
BLE scan interval and window


texts: Need to maintain 5v to load during supply switch over

texts: I know what I want but not sure how to achieve it! I have car dash cam supplied by 5 volts. I've set up a 5volt power bank to run the dash cam when parked and wired up a relay operated by an Accessory circuit to switch from car battery power (via a 5v usb adapter) to power bank battery when the car is parked. Very rough circuit diagram below. Problem is that the fraction of a second it takes for the relay contacts to switch over causes the camera to switch off and back on, causing data loss and/or having to reformat the SD card. What I need is a 'simple' capacitor circuit to maintain the 5v on the camera for that split second! I'm no expert so would really appreciate some advice on what components to use, and suggested values.


texts: Question about 74LS164 8-bit serial in parallel out shift register

texts:
With the 74LS164 8 bit parallel out serial shift registers, I'm confused about a few things. In the datasheet (page3) on the logic diagram why do they suggest using an active low inverter before the active low pin on the clear line? Is this for some sort of buffer?

My second question is if this is a 8-bit register why on the clear-shift-clear timing diagram (page 2) do they have 11 clock pulses? Would we be limited to 8 clock pulses before the registers are full and 11 clock pulses result in potential loss of data?


texts: Transistor biasing, Large Resisor values

texts:
simulate this circuit – Schematic created using CircuitLab

In above circuit the base of Q1 acts as a level-shifter from 3V-50V at it's base to 2.8V. The base of Q1 is driven by PNP open-collector outputs thus R2 holds the Q1 in it's off-state when the input signal is not asserted. The output pull-up can be rather large (22k) since speed is not too important but power-consumption is.

This gives a collector current of:

$$ I_{C(min)} = \frac{2.8\mathrm{V}}{22\mathrm{k\Omega}} = 0.13\mathrm{mA} $$

This leads to a small required base current, even when underestimating the current gain and providing a 30% error budget:

$$
h_{FE(min)} = 100 \\
V_{BE(sat)} = 0.75\mathrm{V} \\
I_{B(min)} = 1.3 \frac{I_{C(min)}}{h_{FE(min)}} = 0.0017\mathrm{mA}
$$
As noted above the input voltage at the base relative to ground is in the range of \$V_{in(min)}=3\mathrm{V}\$ to \$V_{in(max)}=50.4\mathrm{V}\$ which imposes the following restrictions on \$R_B\$:

$$ R_{1(max)}   = \frac{V_{in(min)} - V_{BE(sat)}}{I_{B(min)}} = 1.3\mathrm{M\Omega} $$

According to those calculations \$R_1=1\mathrm{M\Omega}\$ and \$R_2=10\mathrm{M\Omega}\$ would be sufficient.

However, I wonder whether there are any drawbacks choosing resistors in the Mega-Ohm range for transistor biasing.


texts:
I am going to use the SM42HT47-1684A stepper motor, its datasheet is following:
http://p.globalsources.com/IMAGES/PDT/SPEC/001/K1052328001.pdf

In the datasheet the rated voltage of the motor is 2.8 V.

I found a drive chip, which can achieve the required resolution, it is the following:
http://www.st.com/web/en/resource/technical/document/datasheet/CD00255075.pdf

The minimum motor supply voltage in the drive chip is 8V. Does this mean, that the motor can't be directly driven from this chip?
I have chosen this chip, because I'm going to use microstepping with 1/32 or 1/64 resolution.
Is it recommended to look for an other drive with lower motor supply voltage?


texts: How do I supply 200-ish mA to servo connected with Adafruit's PCA9685?

texts:
For a project in school I have to build a robot playing a bass guitar.

To play the notes I planned to plug 16 servos to Adafruit's PCA9685 but it doesn't supply enough Amps to the servos. How can I power the servo motors externelly but still controll them via the PCA9685? I know that I don't have enough amps because the PCA9685 is able to controll much weaker servos, but these aren't powerful enough. Can anyone help?

I use the Raspberry Pi 3 model B+ to control everything and several BMS-410C as my servo motors.


texts: Electrode shape in a triggered spark gap?

texts:
I was reading about spark gaps which are triggered with a third electrode, and I think that the concept is pretty straightforward, but the resource described the usage of a third electrode which would be shaped like a ring or washer:

The article didn't really describe why the trigger electrode would be shaped like a disk instead of, say, a wire or some other pointed shape.  Is a ring shaped electrode a more useful shape for causing a discharge, or are trigger electrodes just generally made this way?


texts: With a transformer center tap, why are the two resulting circuits out of phase by 180*?

texts:
I'm trying to understand how the power in my home works, and the part I'm having trouble with specifically is why in the step-down service transformer, the resulting out-of-phase 120V "hot" lines are out of phase by exactly 180*.

I understand in a step-down transformer a center tap halfway in the middle would result in half the voltage because there are fewer coils, but why would each of these circuits be out of phase by 180*?

What about if there is more than one "center tap?" Perhaps 3 instead of one? Would the resulting circuits be out of phase by 90*?


texts:
I want to setting up a micro coreless motor (5*20 size) for quadcopter.

I use BD139 transistor, PWM from STM32 (31kHz PWM frequency) and 500mA li-polymer battery for this work, but the maximum speed of motor is not enough.

When I connect the battery to the motor directly, its speed is very good. However when I use the transistor with PWM, this speed reduces. I know that it is due to output resistance of the transistor.

What should I do to increase the maximum speed of the motor, when I use a transistor?

Do you know a better transistor or driver for this work?


texts: Circuit analysis using an op-amp (non-ideal integrator)

texts:
I've the following circuit:

simulate this circuit – Schematic created using CircuitLab

My question is, is my method right to find the output voltage in relation to the input voltage?

My Work: The circuit can be analyzed by applying Kirchhoff's current law at the node \$\text{V}_2\left(t\right)\$, keeping ideal op-amp behaviour in mind:

$$\text{I}_1\left(t\right)=\text{I}_3\left(t\right)+\text{I}_2\left(t\right)\tag1$$

In an ideal op-amp we know that \$\text{I}_3\left(t\right)=0\$. So we can write:

$$\text{I}_1\left(t\right)=0+\text{I}_2\left(t\right)=\text{I}_2\left(t\right)\tag2$$

For \$\text{I}_2\left(t\right)\$ I used Laplace transform:

$$\text{i}_2\left(\text{s}\right)=\frac{\left(\text{v}_2\left(\text{s}\right)-\text{v}_{\space\text{out}}\left(\text{s}\right)\right)\cdot\left(1+\text{R}_2\cdot\text{C}\cdot\text{s}\right)-\text{R}_2\cdot\text{C}\cdot\text{V}_\text{c}\left(0\right)}{\text{R}_2+\text{R}_3+\text{R}_2\cdot\text{R}_3\cdot\text{C}\cdot\text{s}}\tag3$$

And for \$\text{I}_1\left(t\right)\$ we can write (in the s-plane):

$$\text{i}_1\left(\text{s}\right)=\frac{\text{v}_\text{in}\left(\text{s}\right)-\text{v}_2\left(\text{s}\right)}{\text{R}_1}\tag4$$

We know that \$\text{I}_1\left(t\right)=\text{I}_2\left(t\right)\$ and \$\text{V}_2\left(t\right)=0\$, so we can write:

$$\frac{\text{v}_\text{in}\left(\text{s}\right)-0}{\text{R}_1}=\frac{\left(0-\text{v}_{\space\text{out}}\left(\text{s}\right)\right)\cdot\left(1+\text{R}_2\cdot\text{C}\cdot\text{s}\right)-\text{R}_2\cdot\text{C}\cdot\text{V}_\text{c}\left(0\right)}{\text{R}_2+\text{R}_3+\text{R}_2\cdot\text{R}_3\cdot\text{C}\cdot\text{s}}\tag5$$

Which simplifies to:

$$\frac{\text{v}_\text{in}\left(\text{s}\right)}{\text{R}_1}=\frac{\text{R}_2\cdot\text{C}\cdot\text{V}_\text{c}\left(0\right)-\text{v}_{\space\text{out}}\left(\text{s}\right)\cdot\left(1+\text{R}_2\cdot\text{C}\cdot\text{s}\right)}{\text{R}_2+\text{R}_3\cdot\left(1+\text{R}_2\cdot\text{C}\cdot\text{s}\right)}\tag6$$

And I know that \$\text{R}_3=\frac{1}{\frac{1}{\text{R}_1}+\frac{1}{\text{R}_2}}\$, so:

$$\frac{\text{v}_\text{in}\left(\text{s}\right)}{\text{R}_1}=\frac{\text{R}_2\cdot\text{C}\cdot\text{V}_\text{c}\left(0\right)-\text{v}_{\space\text{out}}\left(\text{s}\right)\cdot\left(1+\text{R}_2\cdot\text{C}\cdot\text{s}\right)}{\text{R}_2+\frac{1+\text{R}_2\cdot\text{C}\cdot\text{s}}{\frac{1}{\text{R}_1}+\frac{1}{\text{R}_2}}}\tag7$$

  Question: Am I right about my relation between the output and input voltage?


texts: Multi MOSFET IC for Controlling 12V LED strips with Arduino

texts:
I am planing to make an arduino shield for some Home Control jobs (e.g. switching 433MHz RC Sockets, measuring temperature, check if windows are closed and controlling RGB LED lights.)
My base unit is an Arduino Mega 2560 and actually I have made the circuit on a breadboard with 6x N-channel MOSFETs (type: BUZ 71A / STP16NF06), to control my 2 RGB led Strips on via the PWM ports of the Arduino).
The problem is, that they are too big in space for the shield i am designing, so I am looking for a IC, that combines at least 3x N-channel MOSFETS or any other way to save the space on my board.
additional information: I am Switching 12V LED strips (3m of them and some headroom would be nice) according to the datasheet the maximum usage of the strips will be ~3A per color/channel at a supply voltage of 12V


texts:
I recently ordered a LCD TFT 3.2 inch touch display from aliexpress:
ILI9341_3.2_TFT_LCD

I'm currently going through documentation for the chip (ILI9341_documentation) and I can't "connect" all the pins on the pcb of the display to the pins on the chip in documentation.

My plan is to use 16 bit parallel interface, but pins IM0, IM1, IM2, IM3 are not accesabe as it seems, so I am not sure if to use 8080 I or 8080 II for 16-bit protocol or if I can even use 16 bit parallel.

Q1: What protocol is to be used?

I understand that pins DB[15:0] are for the 16 bit parralel data, top 6 pins are SPI, BL is backlight, RST = reset, WR = WRX, RD = RDX, CS = CSX,

Q2: so is RS = D/CX?

Q3: What is SDCS?

Thank you for your help!


texts: I need to buy a 6-7m long SMA to rp-SMA cable to connect a Wifi radio unit (2.4 GHz and U.FL connector) and an external antenna (2.4 GHz and SMA connector). The longest ones on Farnell and Digikey are 300 mm long, but Google shows some suppliers. As I have never dealt with high speed cables and connectors, I would very appreciate if someone who knows these could advise me how I should select a cable that would cause less distortion on the signal: if I should pay attention to any parameter on the datasheet or should I avoid a cable that is made of a specific material, or what else?


texts: How do I add a tag like this in Multisim so it's very convenient to copy-paste it


texts: Current sensing in H bridge for Stall detection-Purpose of Diode

texts:
I have a circuit, which is powered from two 1.5 V AA battery. It has a MCU and PNP - NPN Hbridge for driving motor. The motor (RF-300CA-11400) datasheet is here in this [Link][1]. The Motor will be turned in one direction for around 2 seconds or stall happens, whichever is earlier. and will be turned in opposite direction for 1-2 seconds appropriately. No sudden (few ms) change in the direction of motor expected.

My objective is to detect whether the motor is running and to also stop the motor as soon as the motor stalls.
Stalling current is 170 mA.
Typical load current is 70 mA.
Battery voltage: 2.2 to 3 V.

The present circuit is as follows:

Question: For high side current sensing, even without diode, i would see a drop and recognize that as stall current or load current appropriately. What might be the value addition/intelligence of the diode which is in between the battery and the H bridge?

PS: I am not sure about diode part number and i am unable to share the design reference
Thank you for your time


texts: Does anyone recognize this debug connector?

texts:
I'm looking at a board with this debug interface and I would like to know what it is so I can consider it in future designs. The scale below is 1 mm gradient.

It looks like something off the shelf that I've seen before. There is also a Tag-Connect interface elsewhere on the device so I wouldn't be surprised if this too was COTS in some way.

Anyone recognize it?


texts: 10cm tube light source (see photo) - what is it?

texts:
I'm just trying to work out what this is:

Neither the tube nor the blue box has any markings whatsoever that I can see. The tube is about 10cm long and appears to be transparent plastic with white stripes on the outside and a long thickish white filament in the middle. The blue box has one 2-pin JST-PH connector on the side that goes to power (the red and black wires) and two 3-pin JST-PH connectors on the other side (just one is occupied with the connector for the light tube).
I'm guessing the blue box is an inverter and that the tube contains some kind of electroluminescent wire. The wire in the tube doesn't look at all blue but when it lights up the color is blue and quite bright. It can turn on and off quickly without any blinking, i.e. it's not a mini fluorescent tube.
I'm interested in replacing this part so any pointers as to what it is would be very welcome.

Answer
With the keywords cold cathode tube from @Justme, it proved simple to track down this item. I even found the identical design inverter (blue with the circular array of air holes). It appears to be a Logisys product. Their website seems to have been offline since 2017 but this item appears to be their 4" Cold Cathode Light Kit with Single Tube (with a blue tube, they also have various other colors). You can still find the details here on the Wayback Machine.


texts:
I am building a SMPS using the fairchild Semi FSGM300N Power switch. FSGM300N Datasheet
If that datasheet link is walking wounded try FSGM 300N datasheet

I used the design tools provided by fairchild semi to get the following diagram . But all parameters are given, except the value of the EMI filter Lin (red circle in the diagram).I will need to know how to calculate the value of Lin. Looking at the datasheet, the reference design uses 30mH. I do not know if that is a fixed value? This is my first SMPS design.

Any thoughts please?

Thanks y'll.


texts: Any side effects of Initialisation and de-initialisation of STM32F0 MCU I2C pin frequently?

texts:
I have one port on my MCU and want to re-define its functionality.
Is it possible that something wrong/strange happens if I do it in my main() function?
I regularly switch the funtion of the pin in millisec jobs (eg. between I2C and UART)

I appreciate your help :)


texts: Gain factor in real Resistance and Reactance (AD5933)

texts:
I'm trying to develop a system for bioimpedance measurement with the IC AD5933.

The AD5933 is a high precision impedance converter system that combines a frequency generator with a 12-bit, 1 MSPS, Analog-to-Digital converter. The frequency generator allows an external complex impedance to be excited with a known frequency. The signal in response from the impedance is sampled by the on -board ADC and a discrete Fourier transform (DFT) is done by  an on-board DSP engine.

The DFT algorithm returns both a real (R) and imaginary (I) data-word at each frequency point along the sweep. The impedance magnitude and phase are easily calculated using equations.

To convert this number into impedance, it must be multiplied by a scaling factor called the gain factor. The gain factor is calculated during the calibration of the system with a known impedance connected between the VOUT and VIN pins.

The measured impedance at the frequency point is given by:

My problem is that I need to use only the real (Resistance) and imaginary (Reactance) information, rather than the Impedance Magnitude.

Because the equations of body composition require, for example:

So, my question is:
How do I apply the gain factor only in real (Resistance) and imaginary (Reactance) values?

Tks!


texts: Whats is the relation between long MOSFET Turn-Off time and oscilloscope probe capacitance

texts:
I have a tri-state MOSFET array to control a 12V charliplexed led matrix. My question is that in the oscilloscope I see that the PMOS has an off curve that does not make sense to me, searching the forum I came to this answer, which states that the capacitance of the oscilloscope probes should be the cause. However, I do not understand how that happens and how can I do to verify if indeed the PMOS is shutting down as fast as I expect, I'm trying to avoid a shoot-through situation.
The MOSFET array is a DMC2400UV. The Turn-off Delay time is 13.74 ns and Turn-off Fall time is 10.54 ns.
Schematic of the MOSFETS array, the whole system is composed of 9 of these.

For the oscilloscope images: Yellow is OUT1, Blue is PMOS1 and Pink is a HIGH-Z port (might be Out3)
Effect at 1ms switching time

Effect at 20ms switching time


texts: Why is the input impedance of an emitter follower defined as \$\Delta V_{B}/\Delta I_{B}\$, as opposed to \$V_{B}/I_{B}\$?

texts:
In The Art of Electronics, chapter \$2\$:Transistors, page \$65\$, the author defined the input impedance \$r_{in}\$ of the emitter follower below

as \$r_{in}=\Delta V_{B}/\Delta I_{B}\$. Why did he use variations of \$V_{B}\$ and \$I_{B}\$?

I thought the input impedance was defined as the input voltage \$V_{in}\$over the input current \$I_{in}\$, what am I missing?


texts: What happens to mains voltage in the event of a short circuit

texts: I mean before it trips the circuit breaker.


texts: Designing an Electromagnet for a Digital Clock

texts:
I'm trying to design a digital clock that will use several electromagnets and iron filings to show the time.  Each digit should have 7 electromagnets that turned on and off to attract the metal shavings through white plexiglass (I'm also considering using immersion oil to make it easier for the filings to reform).  However, I'm stuck on how to design the electromagnet itself.  I initially started with a solenoid, however, I quickly learned that the shavings will mainly attract two ends, leaving the middle of the digit line with no definition.

I'm looking for advice on how this might be done.  Will wrapping the wire vertically instead of horizontally be a better choice?  Should I use a different shape altogether?

Thank you,


texts: Can someone identify this transistor and/or resistor component?

texts:
I stumbled upon a weird transistor or resistor component which I can't place. Here is a simplified version of the circuit:

I am pretty sure that the transistor on the bottom is an N-MOS transistor which pulls out low if in is high. The weird component at the top seems to serve as pull up resistor but looks more like a transistor than anything.

Can someone identify the component?

Note: I saw the component on a presentation slide which I don't have access to. I had recreated the circuit from my notes, and thus can't provide more information.


texts: I am creating a circuit that includes a 24vac sprinkler solenoid. I need it to be portable so I'm planning on using DC current rather than AC. What is the best way to do this? If I just use straight DC current, will this harm the solenoid?


texts: How do I treat a PMOS compared to an NMOS in small-signal analysis?

texts:
What exhaustive list can I use to determine the differences between NMOS and PMOS devices when doing small-signal analysis?

Equivalently, what are the fundamental differences between NMOS and PMOS devices, and how do related terms (i.e. treshold voltage, which is either positive in NMOS and negative in PMOS, or positive in both but with reversed polarity in PMOS, affecting many formulas) differ between them?


texts:
Just wondering if it is possible to detect the presence of an SD card when it is being used in SPI Mode?

It would appear that the card detect/data 3 pin (CD/DAT3) is used as a chip select (CS) pin when in SPI mode.

If this is true, then how does one detect the presence of an SD card being used in SPI mode?


texts: Bluetooth device identification & information during pairing

texts:
Let's say I'm creating a device that communicates with the computer using Bluetooth.
I'm at the point where pairing and exchanging data between the device and the computer works.

Is there anything in the BT specification that allows the BT device to "inform" the
computer where to get the drivers/software upon pairing?

Pair the device with the computer
Some information is passed to the computer (Windows for example)
The computer then informs the user where the required software can be downloaded


texts: Atmel UART - use interrupts or cyclic implementation?

texts:
I want to write a program that intercepts serial communication between two microprocessors. Therefore I chose the Atmega 162 featuring two UARTS. Now I want to decide if I write the code using interrupts (which makes things more compilacted)

or just in a cyclic way

read from UART
process data
write to UART

The packets are fixed size are 42 bytes on one line and 12 bytes on the other line. Between the single packets is a gap with ~1 ms.

The question: Do you agree to use the cyclic (fixed) way instead of interrupt driven way?

Theres no code up to now, but here you can find the project page


texts:
Refer the representational schematics for voltage sensing by ADC (SAR). I read somewhere to balance the P and N lines add R3 = R1||R2. How come R1 and R2 parallel combination could be considered as contributing error voltage at P so that N has to be R3=R1||R2. Could somebody shed some light as to how the actual current path is balanced?

simulate this circuit – Schematic created using CircuitLab


texts: Why does the impedance of a parallel RLC circuit approach infinity at resonance?

texts:
Pretty new to this stuff so apologies if I get some words wrong.
In the book I'm reading they described a parallel circuit with a resistor capacitor and an inductor powered by a current source. They say the capacitor has impedance \$\frac{1}{j\omega C}\$  and the inductor has impedance \$j\omega L\$ and the resistor has resistance \$R_{p}\$. The resonant frequency is when the magnitudes of the two impedances of the capacitor and the inductor are equal i.e. \$\omega_0^2 = \frac{1}{LC}\$. But when I use the parallel resistance formula I get the impedance of the circuit should be
$$\left(\frac{1}{R}_p + j\omega C + \frac{1}{j\omega L}\right)^{-1}$$
But  at resonant frequency where \$\omega C = \frac{1}{\omega L}\$ this comes out to \$R_{p}\$, not infinity. So I'm struggling to understand what they're trying to say here.
To clarify some things here's the page from the book I'm reading. (Electronics with Digital and Analog Integrated Circuits by Higgins)


texts: How does a CM choke reject common-mode noise while allowing the signal of interest?

texts:
As far as I know a CM choke is nothing but a transformer(?).

How does it block common-mode noise and pass the signal of interest? Should we think of it as an LR filter? And how to size it if we know the signal of interest? A pictorial explanation with a circuit diagram ect helps to understand.

Edit:

Below are two scenarios where an isolated(floating/battery powered) sensor S signal is measured by an ADC device and the system is single ended. The coaxial cable’s two wires somehow are victim of CM noise. As you see the CM noise is the spike superimposed on the half sine wave desired signal:

So in the first scenario(upper diagram) I can see how the CM blocks this spike now.
But in the bottom diagram there is an attempt to remove the same spike with a LPF where the LPF’s ground is the signal ground as usual. Will this attempt also remove the spike or not?


texts:
I am designing an Ethernet circuit ( my reference design is the Ethernet circuit in stm32f767 nucleo).
The  crystal drive level required by the Ethernet transceiver (LAN8742A/LAN8742Ai) is 300 uW.
LAN8742A DATASHEET
I will manufacture the board at JLCPCB. I didn't find 25.000MHz crystal with the required drive level in their SMT parts library.I found this one X1H025000FK1HA-X with 300 uW max level drive.
Crystal Datasheet
My question: Can I use it?


texts: The bitwise complement of a floating point number's binary representation

texts:
I wonder if the bitwise complement (NOT) of a floating point number's binary representation of a number is the same number but with a change in its sign?

Thank you to all possible references to articles or documentation.


texts:
I'm reading the book http://www.cs.indiana.edu/~geobrown/book.pdf and I have a question regarding the Exercise 3.1.2 on page 50.

It ask to set a watchpoint on i. I set a watchpoint but it never break the code. I tried breakpoint a function as the book said and it worked.

It is related to tool stlink?

thanks :)


texts: Attaching a heatsink to a DRV8825 stepper motor driver

texts:
I'm using the Pololu DRV8825 Stepper Motor Driver to control a NEMA 17 Steppermotor with an Arduino.  The stepper motor requires 1.7A current.  According to the driver specs on the Pololu website, if the current draw is higher than 1.5A per coil, I will need a heat sink.

The problem is that I'm not sure exactly where the heatsink should be mounted, or how to mount it.  Furthermore, the driver is very small and most heatsinks i've seen are larger than it.  Is there a specific type of heat sink that I should use for this device?  Where should it be mounted?  How should I mount it?

Front Side:

Back Side:


texts: IR receiver output pulsating instead of constant one('5V') or zero ('0V')

texts: I am trying to detect the size of different bottles on a conveyor belt and for that I thought of using IR transmitter and receiver but I am not getting desired output. I want the output of IR receiver to be constant '1' or '0' but instead I am getting a pulsating output. Since I am not good at designing electronics circuits, therefore, I downloaded a circuit from internet and implemented it. Now, please help me troubleshoot the problem in the following circuit:


texts: How do circuits calculate the remainder of an n-bit number when divided by another n-bit number?

texts:
I am looking for a way to calculate the remainder of an n-bit number when divided by another n-bit number.
For example, 1000 mod 0011 = 10.
How is this done on a computer?


texts: Help With Buffer Amplifier/Filter Type Circuit

texts:
I’m having trouble with a circuit I designed and I would be greatly appreciative if I can get some help here.

The circuit I designed is a buffer amplifier type design intended to take two channels of audio input from a passive monitor controller, sent to either the resistor circuit, or low pass filter (as seen in the schematic), and then to the second opamp (which has a trimpot to control DC offset for each channel), and then sent as an audio output at unity gain (or near unity gain). The circuit is powered with +/-15VDC, taking a 36 VDC power supply and sent through a virtual ground type divider and regulated with 7815 and 7915 voltage regulators (although I’ve tried disconnecting the power section and using a bench power supply setup to provide + and – voltages with the same problems).

I designed the circuit using the falstad applet and I’ll attach the text for the circuit so you can see for yourself how I imagined it would work, and I’m attaching images of my schematic, screenshots of my oscilloscope, and images of my soldered perfboard circuit.

When I try to input a 120Hz, +/- 2V sine wave with my function generator, all I get from the output is a mostly flat voltage. It wiggles and shows occasional noise and whatnot when I try tuning the trimpot, but what you see in my image is basically the gist of it. In addition, the opamps (OPA2604APs) get a little warm, which I don’t think is a huge problem, but the 7815 gets pretty hot.

https://imgur.com/a/Q97WvE3

Schematic:

Regulated Virtual Ground Circuit:

Top View:

Channel 1 and Channel 2, Buffer amplifier/filter:

One channel buffer/filter:

(The question editor is now telling me that I need more "reputation" to post more links. You can find all the images at the imgur URL that I posted at the end of my description.)

Falstad circuit simulation

The following are URLs for the relevant datasheets:

media.digikey.com/pdf/Data%20Sheets/Texas%20Instruments%20PDFs/OPA2604.pdf

hep.upenn.edu/SNO/daq/parts/lm7815.pdf

hep.upenn.edu/SNO/daq/parts/lm7915.pdf

vishay.com/docs/28193/mkt373.pdf

globalsources.com/gsol/I/Slide-switch/p/sm/1142899729.htm#1142899729


texts:
I've got these LED candles with a remote:

I've owned a few different models of LED candles in the past, and these ones are the best so far. They have a great-looking, strong light, and realistic flame movement. They come with a remote for turning them on and off.
The problem is... The remote is underpowered. I have four of these candles (the two that aren't in the picture are on a different shelf) and I often have to get out of my bed and get closer to each shelf when I press the buttons on the remote, otherwise the candles don't register them. Getting out of bed is one of my least favorite activities.
Is there some kind of hack for increasing the strength of the remote? If there was a product that I could attach to the end of the remote that took the signal and amplified it, I'd buy that. Or over-voltage the remote? Any other ideas?


texts:
I am looking to pass my 24-bit RGB color value through a DAC, but my resolution of the DAC is 12-bits.

Would I have to reduce the resolution of each channel to fit it on my 12-bit DAC?
Is there a way to still pass a high resolution 24-bit RGB value in multiple cycles (but it would be out of sync)?
Would getting a 24-bit DAC solve the issue?


texts: How To Check If An Oscilloscope Is DC Capable

texts:
I am busy working on some analogue synthesizers at the moment and just got the hang of OP-amp to some degree. I want to invest in a decent Oscilloscope something like 50Mhz-100Mhz.

So based on advice 50Mhz+ (Ray Wilson Make: Analogue Synthesizers), should be fine however apparently it needs to be DC capable. I was looking at a potentially buying a Hantek DSO5102P which appears to tick most of the boxes.

However I cant find anything saying it is DC capable. So I started viewing other scopes and found similar problems. They do not explicitly state they can handle DC which left me confused. How do I read a scopes specifications to ensure it is DC capable?


texts:
I'm planning to create a Control Box for my Home Solar System which will involve using a microcontroller (STM32F103C8T6) as my control system. This uC will handle my current sensing for power monitoring, data logging to an SD Card, Battery Bank capacity detector, and a lot more. I was planning to add a "poor man's UPS" by using a Supercapacitor to power the uC only and make sure that it shuts down everything safely before going to standby mode.

Based on the datasheet of the uC that will be used, its maximum current draw is 150 mA. I'll be assuming that this is at 3V3, which will equate to around 22 Ohms. Will this assumption be correct? Can I use this value to determine the Capacitor discharge rate?

I will be going for the worst case scenario and assume that the uC will draw 300 mA of current. That means that at 3V3, this will equate to 11 Ohms of load.

simulate this circuit – Schematic created using CircuitLab

Since supercapacitors usually are rated at 2V7, I have to put 2 in series to give me a maximum voltage of 5V4 with a total capacitance of 250 F. Using the capacitor discharge equation, this will give me around 176 seconds, which is more than enough to shut everything down and go to standby mode.

EDIT: I used the capacitor discharge equation to get this time value. The voltage drop that I allowed is from full charge which is 3.5 Volts up to 3.3 Volts.

Based on this link, during standby mode, the uC will only consume around 70uA of current, which means that the capacitors will keep my uC alive for around 8 days. Are my calculations correct? Or are there other things that I should be aware of?

EDIT: The 8 days that I was talking about was still from the same capacitor discharge equation. 691200 seconds is roughly 8 days. The 50k Ohms resistance is from R=V/I which is 3.5V/70uA=50k Ohms.


texts: Fixed Frequency Control of Multi-Resonant Converters

texts:
I am currently designing a SMPS based on the half-bridge LCC converter. Due to my application, it is desired to operate the converter at a fixed frequency. I also wish to optimize the passive components, which is not possible at variable frequency. Since I can't regulate through frequency modulation, here are some of my alternatives:

Use a pre-regulator. A buck or a boost converter before the LCC
converter can regulate the input voltage to the half bridge according
to Vout, hence achieving regulation. This is simple, but we need
extra active switches, inductors etc.
"Bang Bang" control - turning the switches ON or OFF depending on the
output voltage. Seems like a simple technique, but from what I
understand, it still modulates through frequency while keeping duty
cycle and phase constant.
Hybrid hysteretic control - With LLC converters, new IC's are
available that use the resonant capacitor current to modulate the
switches ON and OFF. Again, this uses frequency modulation to achieve
output voltage regulation. I like this method as it reduces the second order, non-linear system to one that is first order and easier to control as a result.

Are there any other ways that can be used to achieve hysteretic control while maintaining a fixed frequency? I have seen some research use a phase-locked loop to "lock" the hysteretic window to a fixed frequency deviation. Could this be added to standard HHC control IC's to manipulate the hysteretic window?


texts:
I'm reading an article about voltage smoothing and I intuitively understand why we need capacitors in output power supply circuit to provide stable voltage. But I can make out this

and

why does \$i_D\$ decreases from an value at \$\theta_1\$ to 0 at \$\theta_2=\pi/2\$? apparently there will be some different currents that pass through capacitor and resistor as long as the source is higher > 0.7V (diode voltage) allowing current pass the circuit .


texts: Op-amp differential amplifier circuit for inputs greater than positive rail

texts:
I'm trying to get the difference of two DC signals using an op-amp difference amplifier circuit. The gain will be 1. The difference will be around 1-5v. The inputs could be as high as 50v though.

Examples:

1. Vin+ = 50v, Vin- = 48v, Vout = 2v
2. Vin+ = 2v,  Vin- = 0v,  Vout = 2v

The problem is this would need the op-amp's inputs to be capable of going up to 25v. Is there a way round this? I have absolutely no idea how to solve this!

Edit: Using two potential dividers before the op-amp circuit that reduce the signals by 90%, followed by the difference amplifier with a gain of 10 would work but this would degrade the accuracy of the result by a factor of 10? Edit 2: And those dividers would have to be very stiff compared to those in the differential circuit

simulate this circuit – Schematic created using CircuitLab


texts:
I read somewhere that this can be used for the reverse polarity protection in the circuit. But I am quite confused with its operation. Can somebody help me with this.

simulate this circuit – Schematic created using CircuitLab


texts:
As I am a beginner at electrical engineering, I try to figure out the reccomended operation conditions for H-bridge SN754410 (http://www.ti.com/lit/ds/slrs007b/slrs007b.pdf).

I intend to supply with: VCC1: 5 V, VCC2: 9 V. The input signal, I see that has to be 2 - 5.5 V. What about current in case I have a 2 V input signal?


texts: How to emulate potentiometer to control electric vehicle?

texts:
I'm trying to control an electric vehicle, say scooter. Vehicle throttle meant to be controlled with potentiometer like on the picture. And it works just fine with 10K pot.

Now I want to control throttle electronically, thus I make some analog voltage with microcontroller and scale it appropriately to match HIREF - LOREF with op amp.

I check the THROTTLE voltage with oscilloscope and it is just fine, but motor controller doesn't seem to react. What can be the case? Isn't it voltage controlled? Can I emulate potentiometer with some circuit?


texts:
I built a VCA with a that2180 using a 470nF tantalum capacitor and a 20k resistor as audio input.

As source I feed an output coming from an Arduino with a opamp which creates a 0-3.2volt output sine. The sine looks fine on a scope. I want to remove the DC offset, so any VCO can be connected, not just my own.

I connect the output of the opamp at the arduino to the that2180 cap. The cap seems to distort the sine at the input. When I bypass the cap all is fine except for the offset, I'd like to remove the offset ofcourse.

On the leftside of the oscilloscope picture you see the result when the cap is added, on the right the input when the cap is not there, so straight at the output of the Arduino opamp. (the oscilloscope is connected at the input of the vca. On the rightside of the oscilloscope picture just before the 20k resistor without the cap (and showing the correct sine but 0-3v) and on the left with the cap given the funny sine (but without the DC component)

I've tried adding a 1k resistor to ground, but no joy.
I've tried using 4,7uF elco instead of tantalum, still no same quality sine.
I've simulated the sine source, opamp and tantalum cap in LTSpice, which look good there.
I've tested also with a proper signalgen, no issues.

What can I do to remove the dc offset and not lose the quality of the sine? Or rather why does my arduino opamp output give such a weird output when the cap is added?
Should I level shift at the arduino opamp (not having a negative powersupply at the board though)


texts:
I would like some help in choosing the right accelerometer for my application. I have been looking at a lot of accelerometers from various major manufacturers and have done some testing on one of the accelerometers to get the required result. Basically, I am looking for an accelerometer that would give me an accuracy of a maximum of about 0.5 degrees over the whole 360 degree cycle. The sensitivity of various accelerometers is usually given in 100's mV/g etc, but could anyone tell me as to how do I get the accuracy out of this? I have all the datasheets of the various accelerometers but I am unable to understand as to how do I relate the accuracy to the sensitivity or do I look for something else in the datasheet.

Main idea: Yeah, I need to use an accelerometer. Basically, I have rotation sensors to measure an angle via these accelerometers and have a system using four of these sensors together requiring an overall system accuracy of 1%. Taking that into account, I am looking for achieving an accuracy of 0.5 degrees on each sensor/accelerometer so that the overall accuracy remains below 1%.

The accelerometer that I have used earlier is: MMA8451Q and the accuracy that I got with it went up to about 2.5 degrees at 90 and 270 degree angles. It had a sensitivity of 4096 counts/g. Since this was not good enough, I have started looking at other options that would provide me with the required accuracy. Any suggestions?


texts: Logic gates with Mosfets and Transistors

texts:
Does anyone have a link for the list of all the configurations of BJT and MOSFET which create the logic gates?

Like for NAND gate below:


texts: I know a diode can short out and fail closed. Is it possible for a diode to fail in the open position, and what would cause this to happen?


texts: 90 degree phase shift in transistor network

texts:
I am analyzing an amplifier circuit that looks like the following:

The input signal is provided by the 60 Hz sine wave generator.

When I ran the transient analysis on the potential of the signal and the current through the two LEDs, I got the following (interesting) plot:

Wow! It appears that the current through the LEDs is -90 degrees out of phase with the input. However, I have learned that it is supposed to be 180 degrees out of phase, because the transistor has a negative gain with no phase shift. Why is this so? Am I neglecting some important detail?

Thanks for your help.


texts: Simulation of tuned circuit with initial inductor current gives flat zero

texts:
I'm playing with ngspice, and wondered if I could get a signal out of a simple RLC circuit using an inductor with initial current.  There are no power or current sources.  The results aren't what I expect, probably because I did something blatantly stupid and not seeing it.

My .cir file:

simple RLC with initial inductor current
C1  1 0   22uF
L1  1 0   6mH    IC=1A
R1  1 0   10kOhm
.end

Using the ngspice command line,

tran 100us 20ms
plot v(1)

But the plot is flat zero.     Why is that?

I expect the voltage at node 1 to increase from 0V at t=0, peak, and continue on as an exponentially decaying sine.  My tran timing may be whacky off, but I should see something, maybe just a linear initial rise, or a spike.


texts:
I am trying to understand the physical meaning of poles and zeros of a transfer function. Can someone help me how to understand the Figure 2b in the link below?

What does the height of the cone indicate? And what do the different color rings in the cone indicate?

The Link

TIA.


texts: Is there a common embedded console library

texts:
Does anyone know or of use a standard set of source files for a simple embedded console?

I've been doing embedded work for a few years now, and I have a set of console code files I have reused in several situations.  I've searched the web before for common console code, and I have not found a standard library.

I have tried using different RTOS solutions, and I have written my own console's that work A-OK. I'm just hoping to find a standard reference implementation to recommend to others, or to work on and with to improve quality and number of developers on a project.


texts: In this BJT circuit why can I apply a voltage divider in the resistors?

texts:
I presume that I can remove the capacitors since the circuit uses DC, but then I don't understand why I can apply a voltage divider in the 30K and 20K resistors since the base is connected between them.

My professor changes the circuit into this:


texts: Circuit biasing problem for differential pair circuitry

texts:
How to bias this differential circuit correctly ?

Additional Information:

Vdd = 3.3V and This differential circuit is connected in negative feedback manner to a CMOS inverter.

Note: this is not homework question. I am a self-learner and whatever useful replies I get will be used to debug https://github.com/promach/frequency_trap

Edit for clarification
It seems like I have a similar differential amplifier as in Figure 4.54(a) below:

Why does the first term of A1 ends up as Ad while the second term ends up as Acm ?

Is the following test circuit the right way to measure open-loop gain of my Gm2 circuit block ? note: now I have asymmetrical input rather than symmtrical differential pair


texts: Thevenizing a Circuit when current through load is a paramter

texts:
The question is to find the current i in the following circuit.

simulate this circuit – Schematic created using CircuitLab

My Attempt:

I considered \$10\:\Omega\$ resistor as the load.

Finding \$V_{th}\$:

I removed the \$10\:\Omega\$ resistor from the circuit. This makes \$i=0\$. So, the CCCS doesn't supply any current and hence I opened it. The final circuit looks like this:

simulate this circuit

I calculated \$V_{AB}\$ to be 270 V which would be my \$V_{th}\$.

Finding \$R_{th}\$:

I attached a 1 V Voltage source across AB. Next, I nullified all independent sources and removed the \$10\:\Omega\$ resistor from the circuit. Again, \$i=0\$ and I opened it like before. The circuit looks like this:

simulate this circuit

\$R_{th}=\dfrac{1}{i'}\$

\$i'=\dfrac{1}{60}\:A\$

\$\Longrightarrow\:R_{th}=60\:\Omega\$

From the Thevenin Equivalent Circuit, I got the current \$i\$ to be \$\dfrac{24}{7}\:A\$.

And I know this is wrong because I did the same problem using Superposition principle and got the right answer (\$i=1.8\:A\$).

Is there anything wrong with what I did?


texts: How to program/configure ADF5356 with out using the evaluation board?

texts:
I understand how to program ADF5356 on the evaluation board

http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/EVAL-ADF5356.html

Using

http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/sdp-s.html?doc=EV-ADF5356SD1Z-UG-1087.pdf

and the available software.

But how would I program the ADF5356 if I purchased it in this package:

https://www.xmicrowave.com/product/xm-a5y9-0409d/

Or if I just purchased the ADF5356 chip to use in another circuit.

I like the look of the xmicrowave products, does any here have some experience with them?


texts:
I need to make an 8 bit adder with 2 4-bit look ahead adders.I spent a lot of time reading about it and I think I get the gist of how it works, but I can't seem to get this. I spent a lot of time thinking about it and am stuck.

So from the picture, at the end of a 4 bit cla, a generate and propagate is sent out and I assume that I need to somehow connect it to the first C in the second cla(looks like c1 in the pic; basically, first C input). I don't know if that's correct and if it is, I don't know how I should do it. Am I supposed to use some sort of MUX gate? A diagram would really be appreciated.


texts: Resistors - metal film or carbon film and what values?

texts:
I am buying a bunch of resistors as a start to my electronics hobby. These are the values I have chosen:

100, 470, 1k, 4k7, 10k, 33k, 47k, 100k, 470k, 1M

Most of my projects will involve microcontrollers, such as the Arduino and other AVR ones. I have two questions which I would appreciate replies to.

Should I purchase carbon film or metal film resistors, and why? As I understand from my research, metal film tolerate heat better, and are more precise. Price is not something to consider too much as they are essentially the same. Carbon film resistors are $0.01/resistor, and metal film are $0.012/resistor.
Should I add or remove any resistor values from the aforementioned list based on my intended use for them?

Thanks.


texts: How can I setup a shared library between a bootloader and an application?

texts:
I am in the process of implementing over-the-air updates on a CC2652 microcontroller using the OpenThread stack. As far as I know a bootloader has to be able to operate independently from the application and be as small as possible. But for the bootloader to download the new firmware by itself it will have to implement the OpenThread stack which will add quite a lot to its size.

I was wondering if it is possible to share the OpenThread stack between the two. I have heard it is possible to place the functions of the library in a specific place in memory and to then share the address with the application but I don't know how to do this. How can I assign a specific region in memory to a library and how can I tell two separate applications, the bootloader and the real application, to use this region?


texts:
I would like to make a board which can be plugged directly into the USB port of a computer, instead of using a separate male "USB-A" connector. I have seen this system used for very small USB memory keys, such as this one. How would I lay out a PCB with such a "connector" built in?

I am using Eagle. Does anyone have a library for it? Can anyone suggest another way to do this?


texts: In power electronics supplies when  a common mode choke is used at the supply or before a converter (say a synchronous rectifier) , does it mean the choke is used to avoid common noise coming from the rectifier side to supply or is it implemented to control the common mode currents  or noise coming from the source or supply itself ?


texts: How to amplify the envelope of a signal at envelope demodulator?

texts:
I have a wave with ~ <10% modulation. Is there any way to amplify the envelope of a signal at the envelope demodulator end? You can barely make out the envelope in the image below but I think I need to amplify this otherwise the diode will be in an "off" position and it doesn't demodulate the signal.

This is the output of my envelope detector using the above waveform as the input

A schematic of my envelope detector can be found below


texts: Power management at thermal power station

texts:
I have weird question, but I hope somebody can give at least hint what should I read to understand the concept.

Imagine situation:
There is thermal power station and a city that takes power from it. As I understand power station works 24/7 and providing electricity. Now what would happen if all the houses will stop using any electricity? I mean every electric device in the city is turned off.

The questions are:
Will it affect station at all?
If it will affect what will go wrong and what is used in case of such situations?
How long will it take for something to burn out(maybe transformer, idk).

Note: complete city turn off is of course theoretical, but I suppose similar situation can happen if for example at night almost everyone is sleeping at city and load on power station gets smaller like ~40 times.


texts: Combinational logic delay is greater than clock period

texts:
Suppose you have a combinational circuit between two registers driven by a clock. What will
you do if the delay of the combinational circuit is greater than your clock signal? (You can’t
resize the combinational circuit transistors).

My answer to this is that we should introduce a buffer between the clock and the second flop such that:

  Tnet + Tc-to-q - Tskew <= Tclk

where Tnet=delay of the combinational circuit
      Tc-to-q= flip flop delay
      Tskew = difference in clock arrival timings at the two flops

Is there a better answer?
Thanks in advance.


texts: Building a T flip-flop with enable and reset using only a JK flip-flop that has no enable or reset, and use some necessary logic gates

texts: I am confused about whether if I should use don't cares to fill in the J and K on the state table, or just use keep and change. If I use don't cares I will not get any Q inputs (as seen on the K-maps), thus I am not sure if I can design the flip-flop correctly or not without the Q.


texts: DIY solar tracking system without any sensors

texts:
I'm building a tracking system for my university project. We will use two solar panels, one without tracking system and other one with tracking system and see the results if it's worth it or not.
But I got a idea, if I know right tracking system's goal is get many power as possible. So instead of using sensors to measure solar radiation density, can I use a voltmeter to measure solar panel's output and use the code of little bit try and error?
Like code change the angle little bit (every five minute) and if it has increased the output keep the change until the maximum ratio is achieved.
I know code will be almost impossible to write but I was always interested in machine learning systems and it seemed great way to start.
Solar panels are 50*40cm and output is 12-19 V 30-60 W (values not certain because we didn't decide panels yet).


texts:
In the above circuit, the D5 diode acts as a freewheel discharging the primary coil energy after generating the spark (is that correct thinking?)
What would be the function of the D3 diode? Would it help to recharge the capacitor with the remaining energy in the primary of the coil after the spark occurs?
I have already seen some circuits in which there is a diode only in one or the other D3 or D5 position, how can you improve the capacitor charging with the remaining energy of the coil?


texts: Through node analysis, how do i find the unknown?

texts:
I have this circuit
I have to find \$V_a\$ and \$V_b\$, when I tried to do so, using node analysis I had the Equation \$\frac{V_a}{6} + \frac{V_a-12}{3}+\frac{V_a-V_b}{5} - 6 - 2 = 0\$ and \$\frac{V_b}{22}+\frac{V_b-20}{4}+\frac{V_b-V_a}{5} +2-3=0\$. Solving it simultaneously, I got \$V_a = 23.29 \text{V}\$ and \$V_b=21.51 \text{V}\$. When I simulated it using Circuit simulator applet, the simulation says that \$V_a = 24.4 \text{V}\$ and \$V_b\$ is \$25.4 \text{V}\$. Can someone point out where did I go wrong? Thanks!


texts: exceeding an analog ammeter printed scale

texts:
I have a ~$10 DC ammeter I mail ordered however long ago, on the display is printed Dagatron 7203 and on the lower right side of display is an upside down U followed by an upside down T then 2.0

It is a ~2" square meter, with an analog display of 0 to 1 amp , with major markings every 0.2 amp with a minor marking of 0.01 amp.

I used this gauge playing around charging lead-acid 12v automotive batteries.  I now want to use it to measure parasitic drain on an installed car battery.

My question is: what happens if DC current draw exceeds the 1 amp marking of the ammeter?  I expect current to be well below 1 amp when I have this gauge connected, but in the event I open the car door and interior lights go on which is maybe around a 5 amp draw what would happen to the ammeter?  Will it survive undamaged if it sees current greater than 1 amp?  When exceeding the ammeter display how much over and for how long is reasonable to expect no damage?


texts: What is the value of the opposing voltage created by the inductor?

texts: Assume I've connected an inductor to a DC or AC source. The voltage across the inductor due to the source current would be L di/dt. But we know that the inductor induces/creates a voltage to oppose the source voltage. My question is, what is the value of this opposing voltage. Surely it can't be L di/dt because then the opposing voltage and source voltage would be equal thus making current to be zero, right?


texts: Differential to single-ended conversion - transformer or instrumentation amp?

texts:
I need to convert the output of differential output DAC to single ended. It's a 2 Vpp signal with a 1 V common-mode output. The output is 100 ohms. Should I use a transformer or a instrumentation amp. to do this conversion? The output could be up to 10 MHz (it's a communication signal) and the power is < -10 dBm.

Update 1 Since the signal is a RF communications signal, there is no DC component.

Update 2 Avoiding a +/- power supply would be nice, so in that case, a transformer would be better, correct?


texts:
I've been trying to get the Microchip RN4678 bluetooth module working so I can start having fun with it, but I'm having very very limited success. The problem is the fact that the datasheet states:

To enter Command mode, type $$$ into the terminal emulator. Once RN4678 enters
Command mode, it sends the string CMD via the UART to indicate the start of Command
mode session.

I'm doing exactly that, along with every variation and am getting no response. Here's my setup. First things first I've got it plugged into a breadboard like this:

I'm using a stock TTL programmer based around the FTDI232R, and it's all being controlled and monitored from the OSX program Serial. Here's the settings I'm using in serial.

Observations from my troubleshooting so far:

The chip itself is working fine. I can connect to it through the
mBIoT utility iPhone app, and it sends and transmits data from phone to computer and vice versa fine, so I know the module isn't dead.
The modules CTS pin doesn't get pulled low unless there is a paired connection. When my phone is connected I can pipe data through the RN4678 from computer to phone with hardware flow enabled just fine, but as soon as I disconnect my phone, I cannot talk to the module at all.
I've looked into the option of the modules "fast-mode" being activated by default, where the original "$$$" command doesn't work, and instead you have to pull a specific pin low. So I went around, and pulled each pin low individually and had no success.

Right now it just feels like theres a hidden pin in there that needs to be pulled in some sort of direction. I've had a good look at the Pictail Reference design for this module and I'm faily sure I haven't missed any pins.
If this is ringing any bells for anyone, or if you have any ideas I should try I'd really love your help. Here's the corresponding Datasheet and User Guide for this module.


texts: Is it possible to connect USB 3.1 Type C to ESP32?

texts:
So, I once looked at the pinouts of USB 3.1 Type C:
and I found out that there were RX and TX pins, but they had + and -. Is it possible to connect the serial pins to the ESP32,as there are two on my module and two on the USB type C:, how would I manage with a RX+/- and a TX+/-.  Are there any other pins that are supposed to be connected other than the serial pins, GND and VBUS to VIN?


texts:
I am designing a simple programmable LED screen system as an exercise, and I need a non-standard type of SRAM (16x5) so I am designing the memory circuits. I have looked everywhere (Digikey, TI, National Semiconductor, etc.) for a chip that is just a sense amplifier for SRAM and I haven't found anything. I called TI and they said they didn't make anything like that, but I may be able to use a comparator for that. My question is, is it possible to wire up, say, a LM339 as a sense amplifer? And if so, how?
Thanks


texts: 555 positive and negative edge detector?

texts:
Is there a circuit using the 555 (without additional logic gates) that creates a positive pulse when it detects a rising or falling edge?

The goal is to have a circuit that detects when a signal goes from
5v --> 0v & 0v --> 5v. When an edge accrues it outputs a (preferably) positive pulse.


texts: What type of level shifter will work in this circuit

texts:
This circuit will probably not work. If I understand it correctly, the high valued R2 resistor in this level shifter (Sparkfun BOB-12009) will prevent logic HIGH to show up on the input of the sensor block.
A non-inverting level-shifter is important, otherwise I can not use the built-in SPI of the Raspberry Pi.
My questions are:
1.) In the case I can not modify the Sensor Module in any way:
What type of level shifter will work correctly in such case? One built from discrete parts would be preferred. I could learn more from it and I could build it without buying new components.
2.) In the case I can freely change all resistor values in the circuit:
Will the following modification solve the problem?

R1: 10k,
R2: 2k,
R3: 5k,
R4: 10k


texts: Connect LED from audio output without it blinking?

texts:
I have a circuit in which I want a pre-built stereo amplifier kit (with + and - outputs for each speaker) to drive a speaker and an LED in parallel. The circuit works, however is there any way to stop the LED flashing with the audio output? In the circumstances the LED drive has to come from the amp, and therefore has to have an audio signal input. Will some kind of transistor do it? Any help is much appreciated.
EDIT: I want the LED to be constantly on, instead of flashing. Sorry for confusion.


texts: Why are lightbulbs considered resistive load?

texts:
A lightbulb (a plain old incandescent lamp) is typically brought up as an example of resistive load.

Yet the filament is actually made of several feet of very thin wire cleverly coiled to form a filament which is about one inch long. Clearly coiling the wire this way makes the filament more or less similar to an inductor. Yet lightbulbs are not considered inductive load.

Why are lightbulbs considered resistive load with a filament made of coiled wire?


texts:
I have a project where I'm looking to power a ESP32 module with 3.3 V and a logic level shifter with 5.1 V.
The project will be powered by between 5 and 24 V. So my plan is to have a buck converter that brings the voltage down to 3.3 V and powers the ESP32, the same 3.3 V will go to a boost converter to bring it back up to 5.1 V.
I've selected the MT1470 for the buck converter and the MT3608 for the boost converter.
I've got the following questions on my circuit:

Is it at all feasible?
I've added the Schottky(D3) diode to prevent voltage from going back from the inductor (L1), and I then that's going to the feedback resistor (R2) to make sure that the voltage drop from the diode is not affecting the ESP32 and the boost converter, is it unnecessary?
Do I need another diode after the R2?

Any other suggestions or comments are greatly appreciated


texts: Can a battery be damaged by charging it with wrong amperage PSU?

texts:
Can a battery (specifically a lithium-ion type that you would get in a small portable electronic device) be damaged by charging it with a 5V 1A PSU, where the manufacture specifies as 5V 2A PSU?

Similarly can a charging a device that requires as 5V 1A PSU with a 5V 2A PSU damage the battery?

If the battery was not damaged in either of the above examples, could other electronics in the device be?


texts: I want to build an FM transmitter. How does this circuit work?

texts: I have been tinkering with AM transmitters but now I would like to build and understand FM transmitter circuits. I came across this circuit in a electronics projects book but it does not explain at all how the circuit works. I would love if somebody could explain every part of the circuit.


texts: Current draw when using transformer without a core as an electromagnet

texts:
I'm making an electromagnet for a vibratory feeder and have run into something I don't understand. I'm using a transformer with the secondary and the bottom of the core removed as an electromagnet.

I roughly understand how reflected current in the secondary of a transformer acts on the primary to create load, and that the load is minimal without it.

But why when I remove the secondary and break the core 'loop' does the current suddenly skyrocket? It seems that the current draw is now near what it should be for DC current of the same voltage.


texts: Power Supply Rejection Ratio for Battery Powered Systems

texts:
Analog Devices just brought out several LDO regulators claiming double the power supply rejection ratio of competing devices, and targeting these devices at battery powered devices.

However, I thought that batteries were quite noiseless, as opposed to powering up  your device via a switchmode power supply where (i would have thought) a very good PSRR would be handy.

Why would PSRR be a crucial factor in battery powered systems?


texts: What is the principal of Inductive Conductivity sensor?

texts:
What is the principal of Inductive Conductivity sensor which uses two coupled coils to estimate conductivity?

Image Source

I understand that the eddy current losses changes with the conductivity, and eddy current loops may increase total mutual coupling, however, I am not very sure how conductivity is measured in these sensors. Is it by estimating the resistance of the loop, or just fitting the measured voltage to pre-calibrated data?

  For example, this paper says (Edit: Not the same as above - this uses two coupled coils)

  we can conclude that the emf2  is related with the medium through the variable /mu which is related with the amount of salts dissolved in the water.

(emf2 is induced voltage in secondary coil) however, to my understanding, permeability is independent of the conductivity, instead, imaginary part of the permittivity is determined by the conductivity


texts: Digital control CC/CV boost DCDC chip/module?

texts:
Are there any hobbyist-affordable non-isolated DCDC boost chips or modules which could be controlled digitally via microcontroller with internal digital CC/CV support? Surely, it is possible to use regular boost IC, stick there bunch of opamps, ADC, DACs... It's a mess and alot of work.

Maybe there are some DCDC modules with LCD displays (like these) which are easily hackable to get full digital control over them? Or I have to use regular boost modules and hack in digital potentiometer/manually sense current?

For this application I need to step up 48V to ~90V with 0-700mA (LED strip) current with 10 independent channels.

Update: ideally this is some sort of IC which I can operate like lab power supply: send via I2C commands like "V=37.32 I=0.371 ON" - and it works in CC/CV mode automatically like a lab power supply. But I2C controlled LED driver which can only do CC would work too, if I can set and sense current.


texts:
I am programming a Cortex M3 bare-metal to talk with SPI Flash. One of the configuration bits of an SPI control register is FRF (Frame format). It can either be set to SPI Motorola mode (0) or to SPI TI mode (1). (See the ARM reference manual page 695 here.)

The datasheet of the SPI Flash (available here) does not give indication regarding which mode I should use.

What are the two different modes, and which should I use for the specific Flash chip I am using?


texts: I am designing a very simple device, which absolutely needs to be inexpensive, total BOM cost < $1.00 including the MCU (at 10k+ units). This device would benefit from knowing its orientation, which could be binary - vertical / non-vertical. I do not need the granularity of an accelerometer just a reliable way to determine single axis position in a binary format. After a google search, I am still empty handed, I have only been able to find full blown accelerometers which start at around $0.40. I was hoping to get something fo $0.10 or less (at quantity). I would love to get some input on any options for this.


texts: Protect exposed metallic components from ESD

texts:
I suppose that a PCB covered into a plastic case it's protected from directly touching it and from possible ESD damage from direct contact. But there is some exposed PCB components like USB connector that can be accidentally touched and that are connected to board GND.

Board can be damaged by touching this components?

If the answer is affermative, how it's possible to avoid this. Avoid to connect this components metallic to GND or connect them trough a resistor?(like 1MOhm)


texts: Improve mosfet spice model for LT spice solver

texts:
I have a SI7460DP spice model that I would like to use in a DC DC buck\boost converter (LT8390). I'm using the standard LT spice file generated by LT powercad (boost converter going from 12 to 15V). Regardless, in a simulation as soon as I replace the mosfets with this one, the solver dies and refuses to simulate, I can leave it running overnight and I'm getting ps/s of simulation time (that means it would take 1e9 seconds to simulate 1 second of simulation, I dont' have that kind of time).

Even relaxing gmin abstol and cshunt in the simulation can't make up the difference for this model (which is poorly written).

The problem must be in the mosfet model, anybody have any idea why this model is crap and any way I can improve it?

At first glance the capacitance's are zero, that can't be a good thing as the mosfet would be switching instantaneously and confuse the solver. Most of vishays models are like this.

*Dec 10, 2012
*ECN S12-3004, Rev. C
*File Name: Si7460DP_PS.txt, Si7460DP_PS.lib
*This document is intended as a SPICE modeling guideline and does not
*constitute a commercial product datasheet. Designers should refer to the
*appropriate datasheet of the same number for guaranteed specification
*limits.
.SUBCKT Si7460DP 4 1 2
M1  3 1 2 2 NMOS W=5393522u L=0.25u
M2  2 1 2 4 PMOS W=5393522u L=0.40u
R1  4 3     RTEMP 3.3E-3
CGS 1 2     3000E-12
DBD 2 4     DBD
*******************************************************************
.MODEL  NMOS       NMOS ( LEVEL  = 3               TOX    = 7E-8
+ RS     = 4.5E-3         RD     = 0               NSUB   = 1.85E17
+ KP     = 1.29E-5        UO     = 650
+ VMAX   = 0              XJ     = 5E-7            KAPPA  = 1E-2
+ ETA    = 1E-4           TPG    = 1
+ IS     = 0              LD     = 0
+ CGSO   = 0              CGDO   = 0               CGBO   = 0
+ NFS    = 0.8E12         DELTA  = 0.1)
*******************************************************************
.MODEL  PMOS       PMOS ( LEVEL  = 3               TOX    = 7E-8
+NSUB    = 3E16           TPG    = -1)
*******************************************************************
.MODEL DBD D (CJO=1400E-12 VJ=0.38 M=0.36
+RS=0.1 FC=0.5 IS=1E-12 TT=5E-8 N=1 BV=60.2)
*******************************************************************
.MODEL RTEMP RES (TC1=9E-3 TC2=5.5E-6)
*******************************************************************
.ENDS

Source: https://www.vishay.com/docs/76626/si7460dp.zip