texts:
Our client uses some third party software and devices for their internal work. They print 600 pages per shift and now they wanted to eliminate paper usage without changing their existing systems.
There are LaserJet printers that are connected with desktop PCs and thermal printers that are connected with some small handheld devices which read data from third party cloud server.

Wanted Solution:
I was wondering if we cloud make some kind of programmed wifi enabled USB device (lets say ESP8266) that acts like a printer for PCs and handheld devices. When this device is connected it should be detected as printer and what it does is simply accepts prints and send it to our cloud server.
I know how to deal with all the cloud communications. What I just wanted to know is how to make my device detected as printer and access the file? Do I need to burn some kind of printer drivers in it or what.

Desktop OS: Windows 7
Handheld Device OS: Linux
Printers: HP LaserJet
Thermal Printer: Black Copper
Printer Ports: USB A

EDIT
I know that there are various apps for print to pdf but we cannot use them because we dont have rights to directly copy files from these systems. External storage is disabled and we cannot even copy files and send over internet from this restricted pc. So we have only option to read that is coming to printers.
This is something similar that I want: USB Printer Emulator
https://www.pclviewer.com/resources/capture/identity.html


texts:
I am building a solar MPPT tracker. First of all: what I understood from MPPT is that MPPT units transfer the maximum power available from a solar panel at that time to the load. This can be done by changing the duty cycle of the boost converter. My questions are, assuming my load is constant:

By changing the duty cycle what is happening (please explain from basics)
I heard that MPPT is effective only if the output load is variable - is that true?
How is the duty cycle changed? (please explain the algorithm)
What is the 'partial shading condition' and how is MPPT implemented in this effectively?


texts: Does stage Sy of instruction have to wait till all earlier instructions has executed their corresponding stage

texts:
I am trying to understand execution of instruction in RISC pipeline.
Can stage Sy of instruction I2 execute before stage Sy of I1? That is, in below example, will it be allowed to run I2's ID in C3 as ID stage is free in C3, or it has to wait till I1's ID is executed, that is, it can execute only in C5?

I assuming multiple stage buffers which allsows I2's IF occur in C2 even when I1 is stalled in C2.
Column Cx stands for clock cycle x.
Row Ix stands for instruction x.
IF is instruction fetch stage.
ID is instruction decode stage.
EX is execute stage.
Dashes in cell indicated stalls. This may be because I1's ID stage depends on some input from earlier instruction (not shown in table.)


texts: Misconceptions about layout of DC to DC step-down converters

texts:
I have noticed, in my opinion, some misconceptions in the layout of the majority of DC to DC step-down converters.

I've seen in many PCBs that the trace that goes to the input of the converter (point A) and the trace that goes from the output to the power inductor (point B) are usually too thick. In my opinion it doesn't have to be thicker or same thick as the trace of the output of the power inductor (point C - LC circuit).

The voltage at point A and point B in respect to ground are (usually) the same, so the current is much lower than the output at the trace C.

So, why do many engineers use thicker trace for those nets? Am I missing something?

Moreover, in many PCBs especially high density boards the power components may be seperated in both sides which I think they should be on the same side. And the input loop should share the same ground path with the output loop. Is that correct?


texts: Quick question about the L200 circuit limit

texts:
I need some help on how to calculate the output current.. Datasheet:

http://www.zen22142.zen.co.uk/Circuits/Power/l200.pdf

I want to use the (Figure 2. Programmable Current Regulator.) But i don't understand the Io = v5 - 2/R

Is 5 - 2 = PIN 5 minus PIN 2 or something else? Could anyone give me an example? Thank you!


texts:
In the 802.11 MAC, there are several parameters such as the RTS/CTS threshold, Binary Backoff timers and NAV (Network Allocation Vector) timers to name a few.

Is it possible to obtain information about these parameters in real time at the application layer? In other words, let's say that there's a computer that is receiving data via a Wifi chipset. Is it possible for an application running on the computer to access information about the NAV timer (for example) in real time, and then make decisions accordingly? Or is it that such decisions can only be made at the MAC layer?


texts: Can i use welding cable as primary coil for Tesla coil?

texts:
I am trying to make DRSSTC (see NOTE1) and struggle to find copper tube for my Tesla coil, so I'm looking for other stuff that I can use for the primary coil. Now I think, can I use welding cable like Lincoln Moswell welding cable 35mm as the primary coil?
I want to use this cable because its easy to set and avaible on local store near my house.

NOTE1: DRSSTC means double resonant solid state Tesla coil. Here's one example: https://www.loneoceans.com/labs/drsstc2/


texts: AC circuit with unusually placed transformer

texts:
Here's the circuit:

simulate this circuit – Schematic created using CircuitLab

$$I=2.25,0° mA$$
What's the $$n=N1/N2$$ of the transformer so that on R3 most power is dissipated. Power? U1?

What I don't know is what to do with the transformer. When it's in parallel I know. I just need help with that, else I think I would manage.


texts: Trying to solve a circuit containing 2 current sources and 1 voltage source and resistors: what am I doing wrong?

texts:
Here is the schematic and the values given. This is for a Coursera test on Linear Circuits I am taking and where I am stuck :-(

Doing KCL and KVLs I get this:

$$
\frac{V_a-V_b}{R_1}=I_1+i_B\\
i_A+I_B=I_2\\
-I_2+\frac{V_a-V_b}{R_1}+\frac{V_b}{R_3}+\frac{V_1-V_b}{R_2}=0\\
-V_1+(i_B+i_C)*R_2+(i_D+i_C)*R_3=0\\
\frac{V_b}{R_3}=i_D+i_C\\
\frac{V_1-V_b}{R_2}=i_B+i_C
$$
and with iD=I1
$$
V_a-V_B-i_a*R_1=R_1*I_1\\
i_a+I_B=I_2\\
V_A*\frac{1}{R_1}+V_B*(\frac{-1}{R_1}+\frac{1}{R_3}-\frac{1}{R_2})=I_2-\frac{V_1}{R_2}\\
R_2*i_B+i_C*(R_2+R_3)=V_1-I_1*R_3\\
V_B-R_3*i_C=R_3*I_1
$$

This gives this matrix A*X=B with this solution in Matlab

I1=10*1e-3; I2=30*1e-3; V1=10; R1=800; R2=100; R3=300; R4=1000;

A=[1 -1 -R1 0 0; 0 0 1 1 0; 1/R1 (-1/R1+1/R3-1/R2) 0 0 0; ...
    0 0 0 R2 (R2+R3);  0 1 0 0 -R3]
B=[R1*I1; I2; I2-V1/R2; V1-R1*I1; R3*I1]

X=linsolve(A,B)
X=inv(A)*B

with

X =

 -103.5000  Va
   -7.5000  Vb
   -0.1300  iA
    0.1600  iB
   -0.0350  iC

Which unfortunately is wrong :-(

Where is my mistake? What am I doing wrong?

This seems such an easy circuit...

Thanks.


texts: How to calculate power draw per rail, to see if Power Supply can handle the load?

texts:
I am purchasing this power supply for a computer I am putting together.

http://www.mini-itx.com/store/information/picoPSU-160-XT.pdf

and while in discussion with a rep, they spoke about not overloading any rail, as I could damage the power supply;  However it does mention

  Overload protection
  Over load protection will be effected when either of the loads (+5V & +3.3V)
  exceeds > 150% Max Load.

but not the 12V rail....

it gives a chart with max current with the voltage which I understand Power = Current * Voltage, but how do I calculate how much each component uses, especially if it uses more than one "rail."  i.e., a Molex uses a 5.5v and a 12v pin, so how would I know how much the 5.5v rail is using, and how much the 12v rail is using?

There is only one 3.3v, one 5v, and one 12v rail, correct?

Here is a breakdown of my components and their estimated power consumption.

  Component Estimated Wattage

  Intel Core i5-2400 3.1GHz Quad-Core Processor 11W - 95W

  Noctua NH-L9i 57.5 CFM CPU Cooler 5W - 10W

  Asus P8H61-I R2.0 Mini ITX LGA1155 Motherboard    7W - 30W

  G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory   9W - 9W

  Samsung 850 EVO-Series 250GB 2.5" Solid State Drive   2W - 10W

  Noctua NF-A4x10 4.8 CFM 40mm Fan  1W - 5W

  Noctua NF-A4x10 4.8 CFM 40mm Fan  1W - 5W

  Noctua NF-A4x10 4.8 CFM 40mm Fan  1W - 5W

  Total:    37W - 169W

NOTE:  This build is not meant for heavy tasks, no gaming, no editing, but maybe light programming, so I HIGHLY doubt I would overload anything, but I 100% want to make sure.

Any advice on how to calculate my usage, tips to set me in the right direction, or even just a plain answer would be appreciated.

Thank you for your time.


texts: What is pros&cons of using a unipolar stepper as bipolar?

texts:
I know that it is possible to drive a unipolar stepper motor as if it is bipolar. Clearly, for example, we can ignore center tap wires of a 6-wire unipolar stepper and drive it using a bipolar stepper driver through A+,A- and B+,B- wires.

In such a case, do we loose or gain something, in terms of, let say, step angle, torque, speed, necessary current, etc?

Thanks


texts:
I designed a Half-Bridge power supply using Gate Driver Transformers to drive my two MOSFETs. It's working great, I winded the two transformers around very small toroids with some turns, I didn't calculated anything, they just worked!

Now, I'm trying to understand how to select a proper gate driver transformer. My switching frequency is 100kHz so I'm aiming for a rising/falling times of about 300-400ns or even lower. I went to DigiKey and found this 1:1 ratio transformer. It claims a primary inductance of 10mH.

On this page I found this picture:

According to this my inductance should be between 0.5 and 2mH so 10mH is too much. I tried to do some calculations using di = v dt / L. I'm powering my driver transformer using a 6A peak MOSFET driver (MCP1407) with a 12V output, at 100kHz and with 50% duty cycle:

di = 12V * (5*10^-6 / 10*10^-3) = 6mA!!!

Only 6mA? I'm pretty sure I'm really missing something big, this drivers have high peak currents to rapidly charge/discharge the gate capacitance of the MOSFET.

So my questions are:

Isn't 10mH a really big inductance for a fast transition?
According to the picture, the inductance for 100kHz should be between 500uH and 2mH, why can't it be lower (or higher)?
How do you exactly select a gate driver transformer and how can you calculate how fast the current/voltage will rise on the MOSFET's gate to ensure proper rise/fall times?


texts: Interfacing ultrasound receivers and emitters with a microprocessor

texts:
I have bought ultrasonic receivers and emitters to play with (see datasheet here). I also have an STM32 processor devkit with DAC and ADC pins readily available.

How should I connect the ultrasonic equipment to the STM32? Do I need interfacing resistors/capacitors for best results or protection? Are there ressources online explaining interfacing considerations?


texts:
I have this a MegaMo SY3056 BLDC Spec.PDF

And beside the cables that are connected to the ESC i have thses encoder cables:

How can i read this encoder? and what values do i get?

Can i know the absolut position of the motor ?


texts: Using L293 H-Bridge to drive DC motor with PWM

texts:
I want to drive an DC motor with ability both to change direction, and torque. Obvious solution: PWM + H-Bridge. I've been planning to use a PSoC4 for controller, and L293DNE for the H-bridge, which seems like a pretty standard choice. I've been pondering choosing some circuit to drive power supply with PWM, but reading the L293DNE datasheet, I saw it has  'Enable' pins - 1,2EN, 3,4EN.

Can I just drive the EN pin with PWM signal to achieve variable torque/speed, or will that cause problems, e.g. faster overheating or something like that? Are there other caveats I should consider (e.g. 'fast motor stop' instead of just 'power disconnected' resulting in some weird dutycycle:torque curve?) Should I add some more circuitry besides what's pictured if I drive 'EN' with PWM?


texts: how can I current-limit a Raspberry Pi 2 USB host port so phones/tables do not try to charge

texts:
Although my use case is specific to Raspberry Pi, I think the question is a general USB Host port question.

When a phone/tablet (especially iphone and ipad) is connected to a Raspberry Pi 2, if its battery getting low, it will successfully charge from the RPi2 USB port.

The problem is, even with a 2A power supply to the RPi2, when a larger phone or tablet is charging that can wreak havoc on other USB devices or the RPi2 itself. (I discovered this by having an application start crashing but only when the RPi2 was connected to an iPhone 6S plus with a battery at 50% or less.)

I know some hubs, such as bus-powered hubs, somehow inform a connected phone "don't even try to charge yourself", so I assume there is a way to have a Raspberry Pi's USB ports do the same, eg, inform connected devices that the maximum current available is 100ma.

How can a RPi2 (or its USB port) be modified so it informs attached USB devices not to try charging from the port.

Note: I do need an active data connection, I just need to prevent the attached phone or tablet to not draw too much current for the RPi2 to handle.


texts:
Planning to build a 72V 18650 battery pack with used laptop batteries. I have a few questions to what happens when you have different batteries.

What happens to batteries in parallel with different voltages? Say, five batteries are rated at 4V and one is rated at 3V. What will be the overall voltage of the group?
What happens if batteries are in parallel with different capacities? Say, five batteries have 4000 mAh and one has 3000 mAh?
What happens to batteries in series with different capacities? If one group has 10 Ah and one has 20?

Overall, if I have batteries with different internal resistances, capacities and voltages, which are the most important? Should I group based on internal resistance, capacity or votltage?

EDIT:

OP here 2 years later haha. I ended up making this battery. I got a bunch of used laptop batteries for free and connected the ones with similar capacities, voltages and resistances into a large 48 V pack. It worked perfectly for 1.5 years and then it failed (didn't catch fire). Overall a risky but fun project!


texts: Energy consumption when cell phone charger connected to socket but not to phone

texts: When my cell phone is charged fully, it says 'Please remove charger from wall socket to save energy'. How am I wasting energy if the charger is connected to the socket but the phone is not connected? I thought you only consume energy when you connect the phone.


texts: Voltage divider to measure Van De Graaff generator

texts:
Imagine one wanted to measure the discharge from a Van De Graaff generator using an oscilloscope. The voltages are way beyond what a typical scope and probes can handle. I was thinking about how a voltage divider could be used to make this possible, but I am aware that the overall resistance of the voltage divider circuit would slow down the discharge from the Van De Graaf (since it's effectively a capacitor discharging).

What would be an effective way to measure the discharge from something like this?

PS: I am aware that you can calculate it, as you know the capacitance of the metal dome from its radius, but I'm curious how this is measured.


texts: Cutoff frequency of transfer function at -6 dB

texts:
I'm trying to design a second order low-pass filter using the following transfer function:

\$\ H(s)=\frac{f_c^2}{s^2 + 2 f_c s +f_c^2} \$

with cutoff frequency fc = 3400 Hz

Whenever I plot this, the cutoff frequency is at -6 dB instead of -3 dB. I'm not really sure what I'm doing wrong. Here's my Matlab code:

fc = 3400;

s = 1i*logspace(0,6,1000);

H_d = fc^2 ./ (s.^2 + 2*fc*s + fc^2);

semilogx(abs(s), 20 * log10(abs(H_d)))


texts:
Microchip PIC16F15323 topic
I have source code that compiles fine under Microchip's mpasmx
Somewhere in there I may have a bug as unlikely as that may seem.
I would like to debug my code.
I have MPLAB IDE and also MPLAB X IDE
MPLAB IDE doesn't let me say it is the P16F15323
MPLAB X IDE demands that I set the compiler before it will let me make a project but it doesn't have any place to do that.
Is there some way to tell one of these to stop its silly nonsense and work?
Is there an alternative that is simple to use?


texts: With a SMPS charging a capacitor bank. What is the power rating of the SMPS?

texts:
I'm working on a project to build a 24VDC to 250VDC switch mode power supply for the purpose of charging a capacitor bank. The capacitor bank will be rated at 250V and 180mF. So, the prime power source is a 24V battery and we need to bump up the voltage to 250V to charge the capacitor bank. The capacitor bank will initially have 0V. I'm trying to narrow down which SMPS topology I should use since they have different applications in terms of power output.

The capacitor bank needs to be fully charged in 1 minute. I calculated the resistance value (67 ohms) for the RC time constant. This would mean that the current draw from the capacitor bank would be 3.73A at time = 0. So, the instantaneous power at that time would be 250V * 3.73A = 933W. Is this the value I should use to decide which SMPS topology to use?

But as the capacitor bank is charging, the current draw from it decreases exponentially which would change the power output of the power supply. So in this case, would the average power output be the number I should use?

Thanks in advance for any help!


texts: How to show a long sentence on character LCD by using bascom?

texts: I want to show a long message that going to differ every time and it's 3 lines or less. This message comes from Sim900. I cant show the whole sentence on my 4x20 lcd. how can I print it in several lines?


texts: How to use a logic level shifter for 1602 LCD

texts:
please bear with me as I am very new to electronics. I am trying to connect a NodeMCU dev kit (ESP8266) with a 1602LCD. I am using an i2c converter to interface with the LCD. The LCD requires 5V. I think the nodemcu dev kit (esp8266), uses 3.3v for it's digital outputs but it does have a VIN on the module so it regulates that 5V to 3.3v internally. I bought a logic level converter because I read that I would need one.

The LCD however works fine without the logic level converter so I am confused. Does this mean it is safe to use it as is? I googled on how to connect a bi-directional logic level converter but I am confused about the power connections.

This is how my circuit looks right now:

How should I connect the bi-directional logic level converter (if needed) ?

Also, Would it be possible to add three 5mm leds to this circuit with the power source I am using? I am not sure which resistors to use because I just want to use the LEDs as power indicators and it doesnt have to be bright.

Any help would be greatly appreciated.


texts: I need for a project an IC which should generate a digital signal with a length given by an I2C-signal, i.e. if I send the IC "50" (or something similar with the same meaning), I want to get 50 "on-off-sequences" with a given speed (via I2C, too) with a high level of 5 V. I was thinking of an counter controlled via I2C. Is there something suitable for me? Or should I approach my problem in a different way?


texts:
There is a scenario: There is a certain box which emits acoustic signals at 30kHz and you are trying to detect these signals using some sort of detector.

I was wondering, would it be more efficient to make a band pass filter for this or some sort of high pass filter to recognise the existence of these signals?

In regards to a high pass filter, this is easily done for example you can use a second order high pass filter since it attenuates more sharply than first order e.g:

This could be used to find values we need.

The magnitude response could look something like:

However, how exactly would you be able to make a band pass filter which incorporates both a high pass and low pass element such that only a certain range of frequencies could be used?

Many thanks for any help.


texts: How to check if specific peripheral interrupt is enabled in NVIC?

texts:
I'm using an STM32F4 Discovery board with ST's standard peripheral library (SPL). I have a situation with a circular buffer: timer interrupt is polling buttons and filling a circular buffer every millisecond if a button is pressed, with an index of that button. The main loop then takes it out of the circular buffer and executes the appropriate command. Both of these actions require multiple steps (checking and changing indices to circular buffer, ...).

When this is happening in the main loop, the timer interrupt has to be disabled for that short while (so that the indices don't get messed up), but I don't want to disable all interrupts just for that. Also, it is preferable for an interrupt to still be serviced if it happened while it was disabled.

I tried to do this by disabling the timer interrupt for that specific timer (TIM6 in my case) in the NVIC (but left it enabled on the timer itself). But then I found out that there is no way for me to check if interrupts were disabled in the first place - before disabling them (I can't enable interrupts again if they weren't enabled before, as it can mess things up).

So my questions are:

How do I check if a specific peripheral interrupt is enabled in the NVIC? (There are only EnableIRQ and DisableIRQ functions.)

I tried checking value at

NVIC->ICER[((uint32_t)(IRQn) >> 5)];

and

NVIC->ISER[(uint32_t)((int32_t)IRQn) >> 5];

but they come out 0 even if the interrupt is enabled.
Will the interrupt still be served (if it occurred when it was disabled on NVIC side only) when enabled again?


texts: Single resistor powering multiple LEDs in parallel where current through resistor is lower than max allowed current for an  individual LED

texts:
While writing an answer about using multiple diodes connected to a single resistor, I stumbled upon a case about which I haven't read a lot: What happens when we set the resistor so that it sets the current to be within safe levels for a single diode and then connect several diodes in parallel to it?

The LEDs themselves should be safe from overload, becasue the current is limited. I expect that in the LED case, the distribution of current among them will not be equal since those with lower initial forward voltage will get more current and will be brighter. After a while the forward voltages will match and the current distribution will stay uneven.

Is there anything else that will happen? I've read the answers in this question and some of them mention oscillations, but don't elaborate on the topic.


texts: On Freescale iMX31, how can I translate SDRAM address to CPU address?

texts:
[This is a re-post of https://stackoverflow.com/q/5346225/69172]

I'm new to iMX31 and embedded systems, please help me to understand the translation from SDRAM address to ARM CPU address, especially in "special" command modes of the SDRAM controller.

Here is the SDRAM initialization code I have problem with:

    ldr r0, ESDCTL_BASE_W
    mov r2, #SDRAM_BASE_ADDR /* 0x80000000 */

    ldr r1, =0x92100000 /* Precharge */
    str r1, [r0]
    ldr r1, =0x0
    ldr r12, =0x80000F00
    str r1, [r12]

    ldr r1, =0xA2100000 /* Auto-refresh */
    str r1, [r0]
    ldr r1, =0x0
    str r1, [r2]

    ldr r1, SDRAM_0xB2100000 /* Load Mode Register */
    str r1, [r0]
    ldr r1, =0x0
    strb r1, [r2, #0x33]

    ldr r1, =0xFF
    ldr r12, =0x81000000

The RAM I have is Micron LPDDR MT46H64M32LF, and this code follows the initialization procedure nicely, but in PRECHARGE step, where is the address 0x80000F00 coming from?

From iMX31 reference manual I learned that during the PRECHARGE step, I need to set SDRAM pin A10 to HIGH which will therefore result a PRECHARGE ALL. Here is the text on PRECHARGE from RM:

  ...While in this mode, an access (either read or write) to the SDRAM/LPDDR address space will generate a precharge command cycle. SDRAM/LPDDR address bit A10 determines whether a single bank, or all banks, are precharged by the command. Accessing an address with the SDRAM/LPDDR address A10 low will precharge only the bank selected by the bank addresses, as illustrated in Figure 19-75. Conversely, accesses with A10 high will precharge all banks regardless of the bank address, ...Note that A10 is the SDRAM pin, not the A10 bit ARM address bus. Translation of the SDRAM A10 to the corresponding ARM address is dependent on the memory configuration.

And here is another text on multiplexed address bus during “special” mode:

  During “special” mode, for example, precharge mode (SMODE=1) or load mode registers (SMODE=3) there is no address shifting, means that CPU address A0 is mapped on MA0 at all memory width. For example, in order to drive MA10 bit (for the precharge all command) the CPU A10 bit should be set (for both 16 or 32 bit external devices). The same logic is valid for the load mode register command, as can be seen on the initialization routine example on Section 19.5.4.1, “SDRAM Initialization.”

According to the text above and assuming A0 is the first bit of 0x80000000, setting A10 to 1 should give address 0x80000400, not the 0x80000F00 in the code. Why???

The code snippet I showed here is supposed to work with DDR. For SDRAM, it actually uses 0x80000400 in PRECHARGE.

Is there anything related to the characteristics of DDR? And how can I get the proper translation between SDRAM pins and ARM CPU address?


texts: Based on the included pictures, what kind of connector is this? Each pin is about 1.18mm in width and there's about a 3.96mm pin-to-pin width

texts:
I thought this might be a JST-VH connector based on dimensions, but it doesn't seem to look like one. I didn't have much luck with google images, so I thought to ask here. Thank you!

Also, This connector is from a power supply.


texts: How sharp will be a pulse sharpened with microwave transistors in a schmidt trigger configuration?

texts:
My hope is to make a 7-10V pulse generator, with pulse width in between the 100ps - 1ns.
I think simply to use microwave transistors 2SC3356 in a Schmidt trigger configuration to sharpen a pulse of 200ns rise time (say).
For me, this seems more conventional, simple and cheap than using e.g. SRD diode techniques.
Unfortunately, I'm insufficiently skilled to understand from the datasheet of the transistor above how fast can I hope the rise time of the pulse be.
Any insight ?


texts: Using an unconnected audio splitter degrades audio signal quality?

texts:
Consider that you have one of the following:

These are used to connect 2 male audio connectors into only one female connection.

Since I can't find, for now, where I have the audio cable extension, I've decided to connect 2 cables in the female connections, but leave the male connection disconnected.

Will this setup degrade the sound signal quality?


texts: Might I be better off using a TIP122 Darlington than a FQP30N06L MOSFET?

texts:
This is a followup to:

Simple ESD protection for MOSFETS

I built the circuit described in the above post using FQP30N06L MOSFETs and after several hours of testing two of the MOSFETS died at nearly the same time. I am not certain why. The big worry is that when they failed, they became dead shorts which, if I hadn't gotten to the kill switch in time would have damaged the solenoids.

Anyway, I am considering going to TIP122s because they have a similar pinout (BCE vs GDS); replacing the 100ohm gate resistor with a 330ohm base resistor; and dropping the TVS diode.

The main reason I'm considering making these changes is familiarity and robustness. I've never seen a Darlington fail without an obvious cause (mostly accidental over-current), and I don't have much experience with power MOSFETs.

Are there any big disadvantages that I might not be considering? And is it reasonable to suggest that Darlingtons are more robust, or at least more forgiving?

@Andy The TVS diode that I used is the P6KE6.8CA-E3/54


texts:
I am studying full-wave rectifier now.

here is the circuit that I made and then I connected oscilloscope between K and L.

As I've learned from the classroom, this circuit has to make full-rectified signal

However, when I measured the voltage between point K and L, I got this result.

I've tried to think what is the problem here, but I can't figure it out.
Is it kind of related to floating ground?

I really don't know what's the problem here.

Can you help me please?

thanks ahead.
and sorry if I sound like rude...I am studying English as well...


texts:
My question is very simple i think, but i would be really gratefull if anyone can help me with this.
When i want to write in the fpga memory using the classic following line code:
             type RAM_ARRAY is array (0 to 127 ) of std_logic_vector (7 downto 0);

Does that code, creates a new memory using the fpga resources or it writes directly in the fpga built in memory?
And if the answer is the first one, how can i write directly in the built in memory of the fpga so that way i dont use more resources.
Im using as reference this code:
https://www.edaplayground.com/x/3Zs
This is my code:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

entity RAM_SP is
generic(
        constant memory_depth : integer := 256; -- numero de palabras de la memoria
        constant memory_lenght : integer := 8   -- numero de bits por palabra
     );

Port (
     data_in : in std_logic_vector(memory_lenght - 1 downto 0); -- datos de entrada
     address : in std_logic_vector(memory_lenght - 1 downto 0); -- direccion de memoria
     W_R : in std_logic;  --Escribe con '0' y Lee con '1'
     data_out : out std_logic_vector(memory_lenght - 1 downto 0)-- datos de salida
    );
end RAM_SP;

architecture Behavioral of RAM_SP is
type mem is array (memory_depth - 1 downto 0) of std_logic_vector(7 downto 0); --Una memoria de 256 palabras de 8 bits
signal memory : mem; --Asocio la memoria creada a la señal/palabra/constante memory
signal addr : integer range 0 to memory_depth - 1; --Creo una señal que puede tomar valores enteros de 0 a 255
begin

process(address, data_in, W_R)
begin
    addr <= conv_integer(address);
    if(W_R = '0')then
        memory(addr)<=data_in;
    elsif(W_R = '1')then
        data_out<=memory(addr);
    else
        data_out<="ZZZZZZZZ";
    end if;
end process;
end Behavioral;


texts: What are some common applications of the MOV? (Metal Oxide Varistor)

texts:
The owner of a broken washing machine recently asked me to examine a damaged circuit board he had found inside. Using the schematic I was able to determine that the charred area formerly contained a device labeled MOV. I found several of these devices on the board and now gather they were Metal Oxide Varistors, which can be used for over voltage protection.

Considering this board appeared to be a low power supply of some sort (transformer, rectifier, transistor etc.) and also contained a blown 0.5A fuse, what was the most likely function of the blown MOV?

In general, what are MOVs used for in PCB designs? Real world circuit examples would be great.


texts:
I would like to ask a few questions that are probably not difficult for engineers to figure out. Personally, I am not an engineer but want to learn about radars. I am having trouble understanding the equation in a book by Merrill Skolnik. The text says the attenuation factor is \$e^{-2\alpha R_{max}}\$

Based on the pictures and what you know:

Is it saying in the text that \$-2\alpha R\$ is equal to \$-4.34\alpha R\$  or am I misunderstanding?
Is the e in the equation the number that is about 2.718?
How can Rmax be both left and right of the = sign? Am I supposed to calculate Rmax and then redo the equation with the attenuation factor?

I would really appreciate some assistance on this.


texts: Change taps on primary or secondary side of transformer?

texts:
I have a 5500/380V Dyn11 transformer, with possible tap settings of 0.95, 0.975, 1.00, 1.025 and 1.05 on both primary and secondary side.

Due to high loading, I want to change the tap settings to either 0.975/1.00, or 1.00/1.025. However, I'm not sure on what side of the transformer I should change the setting.

My intuition tells me that it makes more sense to select the primary side, but I'm not certain.

One reason for changing the setting on the primary side is: The current is much higher on the secondary side, thus increasing the number of windings there will cause higher losses.
Another one: More windings might lead to saturation (I would however think that the transformer was designed so that this won't be a problem).

Does the transformer type play a role? Does it matter if the transformer is Dy, Yd, Dd, Yy etc? How will it affect the impedance?

Will there be any side-effects of selecting one or the other? Are there any reasons for choosing to change the settings on the secondary side?

Thanks!


texts: How to decrease the motor Speed without losing the maximum Torque

texts:
I am using MDS40A motor driver(http://www.cytron.com.my/viewProduct.php?pcode=MDS40A&name=SmartDrive40) to drive a power window motor (12V, brushed motor) similar to the one at (http://www.cytron.com.my/viewProduct.php?pcode=MO-PW-R&name=Power%20Window%20Motor%20%28Wira%29%20-%20Right). I am using PWM generated by Arduino to control the speed of the motor. As I use lower value of PWM to get slower speed (the current gets reduced as well), the torque of the motor is drastically reduced. I am using Arduino Uno.

What I have understood is that with PWM, the voltage and current are not affected by the duty cycle. Torque depends on available current, while RPM depends on available current or amount of time it is ON. When the motor is ON, it resists load (accelerates) and when it's OFF it does not resist load (gets slowed by load/decelerates), hence RPM can be controlled by amount of time motor is ON, while torque stays at max due to max current at ON period.

I want to decrease the motor speed without losing the maximum torque. Can anyone help me on this? Can it be done with code?


texts:
I want to calculate the LM339 comparator power efficiency, so I thought the best way is to calculate the output RMS power and the Power dissipation and the quiescent(DC) power then will get the input power.
then Eff=Po/Pin
but I have a problem in calculating the DC power?
I'm i doing it right? and how to calculate the quiescent power for the comoparator as there is no Iq in datasheet?


texts: Which cache type is better for bus watching?

texts:
I am studying for an exam about memory (mostly cache) and I ran across a multiple-choice question from a few years back:

Which cache type is recommended for bus watching and is also used in multiprocessor systems?

 a. write-through cache
 b. write-back cache

I understand that bus watching means that each cache snoops the bus to see what requests are sent form other caches to the main memory, but I don't really understand which answer is correct.

First type (write-through) would just update everything to the memory every time something is updated and the latter would just keep data in cache to be faster and to me it seems that both could work.

Any help is appreciated.


texts: Reverse current in a wire (flip flop current directions)

texts:
I'm working with 0 to 5 volts. I was wondering if there was any way, preferably with transistors, less preferably with ICs, to "flip flop" the 5 voltage magnitude across a single wire. For example, current would first move from left to right, then 10ms later from right to left, then 10 ms later from left to right, etc.

I would prefer to keep the voltage at 5 volts in this case. I'm wondering if this would require me to add a negative supply (-5V min). If this is necessary, can you please explain how i would go about flipping the current in this later case?

I have two possible applications involving a grounded and ungrounded load of approximately 100 kOhm.


texts: Is it possible to find the voltage Vx using mesh analysis? if yes, how?

texts:
Good day! Is it possible to find the voltage Vx from this network using mesh analysis? any help is greatly appreciated! below is a picture of my work. thank you!

Data:

I1 = 5A
I2 = 3A
I3 = 1/3A


texts: Project circuit current consumption calculation

texts:
I'd like to calculate how much my project circuit is drawing for estimating the duration of my battery.
My circuit consists of a near-real time sensor which is measuring and sensing some data over WiFi.
My project is alternating 1 minute of deep sleep with 3 seconds of active time during working hours (~8 hours a day), and for the rest of the day could be deep sleeping, or just off.
Let's take the case where it is operating ~8h a day, then it is off:

1 minute deep sleep - current consumption: 1,18 mA
3 seconds active - current consumption: 55,0 mA
1100 mAh battery

So I've estimated the duration of my battery like this

passive consumption in 1h = (60 minutes / 1 minute) * ((1 minute*60 seconds)/3600 seconds) * 1,18 mA
active consumption in 1h = 60 * (3 seconds/3600 seconds) * 55,0 mA
battery duration (h) = 1100 mAh / (passive + active consumption)

Is my calculation right?

If I would also consider the case of a continuous operating case, so adding those 14h of pure deep sleep, how could I do that? Would I just need to add to the passive consumption already calculated the passive consumption in 14 hours?


texts:
On my board I have an LAN8720AI QFN24 package.  When I route it via FreeRouting I get this:

As you can see most pins are routed fine but some like pin 18 (RMII_TXD1) just goes straight up instead of right and up. As this is my first bigger design with a smaller microcontroller I was wondering if that is actually all right to do or if I should change that myself to make it look a bit better.


texts:
I am trying to find this exact cable - does anyone know what this is called?
1980's Roland TB 303 Bass Synthesizer.

These are jumpers between traces. I want to know where to get this cable and why it would be used all over the synthesizer. Is being wound like this more resistant to EM interference and prevents emitting EM ?


texts: Is a 1.8v supply too low for driving a long bus?

texts:
I'm designing a circuit comprised of two boards separated 23 inches away and connected through a ribbon cable which carries an I2C bus (400Khz) and various interrupt digital signals, plus VCC and GND.

Since it's a battery powered device I initially chose a supply of 1.8v (which is the minimum common voltage between the various ICs), but after reading some white papers I realised that such low supply could be way too prone to pick noise for such a long bus. A possible solution is to increase the supply to 2.5v or even 3v, but I would like to be sure since I would loose around a 25% of battery life.

So the question is, is a 1.8v supply too low considering the length of the bus? And if so, would 2.5v be enough?


texts:
I'd like to modify a color changing candle (example) circuit so it can be turned on without lighting the actual candle. It uses a photodiode and a optical fiber alongside the wick to cycle the RGB LEDs as long as it's burning.

I've found out I need to supply about 30 uA with a external power source (another 3V battery with a 100k resistor) to the PD leads to substitute its function in the circuit. Sourcing current from the two CR2032s to the PD doesn't work.

Is there any easier modification without the need of a external power source?


texts: STM32WB55 NUCLEO CONNECTION WITH SMATRPHONE USING BLE

texts:
I'm trying to find a solution for my project about connection between STM32WB55 NUCLEO and PHERIPHERAL DEVICE (SMARTPHONE) via BLE PROTOCOL. I can transmit more than one "enviromental sensor" per time but i can't see them on my smartphone. I used to modify feature mask bit according to table of BlueST protocol. If i need humidity and temperature i wrote 0x0C. Anyone have suggest to solve these issues? I'm in trouble and need help, thanks. More to add is (i solved or i thought  to have solved it) but i encountered an other problem, i haven't got real sensor so i smìimulate them using some variables and now i can see both updating but only one in the correct way. If someone can solve this issue i can attach my atollic project.
Thanks


texts: How can a ESP8266 GPIO pin voltage be higher than source voltage?

texts:
I have a project that uses an esp8266 12F module and have recently had 2 boards fail on the same pin. It is GPIO12 and is being used as an input with the internal pull-up enabled. The pin is connected to a float switch that can be in the on/off position for long periods. I noticed when trying to troubleshoot this issue and by testing other boards i have, that when the pins are set to pull-up enabled the voltage goes to a higher level than the supply voltage. The difference ranges from +.04V to 0.39V+!! Which is above the rated voltage for this mcu's pins.
This makes my brain hurt. I know you can boost voltage but generally this is done with a high frequency switch and analogue components. I wouldn't expect this effect to be accidentally replicated either.
My project does use interrupts on one of the other pull-up pins, if this somehow has some influence.
I have noticed this higher voltage on the other two pins I have running pull-ups as well. Any insight would be greatly appreciated!

Update from comments on a now-deleted answer:
The regulator I use is the AZ1117CD and is rated for a max of 18V input. Apologies for misleading [with the wrong part number AP1084D33L on the schematic]. I just used the footprint from a previous design and missed the name change on that. Although I agree that the inductive loads could have an issue I do have external protection on both of those loads and I don't think the blown pins could have been caused by this [...]. However, the increased voltage is noted on raw new esp8266 12F modules I have before connecting external components. I have just booted them up with a bench power supply (at 3.3V) loaded the same code that is running the project mentioned and measured the voltage on the 3 pins set to input with a pull-up namely Gpio12, 2 and 0. This is why I originally left off the schematic. As I am still baffled how a pin can have a higher voltage than the MCU input without any other voltage anywere near it.
Just as a side note the pins weirdly blow in a strong pull to 2,8V and are being read as LOW but this is outside the scope of the current question.


texts: Is PIC microcontroller PIC16C72 and PIC16F72 almost the same from a programmer's perspective?

texts: I just wrote a program to use in PIC16F72. I was trying to simulate it on Proteus and I found that Proteus doesn't have that microcontroller in its library. I read somewhere that PIC16F72 and PIC16C72 are almost the same. So does that mean I can write a program for C72 and use it on F72?


texts: Programming SAM uC family without ATmel Studio

texts:
I've designed a board that used a SAM uC (Cortex M0+). I don't want to use the ATmel Stduio, I want to learn how to use eclipse and arm-gcc and OpenOCD ( still can't understand, what this one is for ?). So  my question is it possible to do that and if yes, does anyone has hint how can I proceed ?

I've installed the 3 parts,and this is the farthest  I could get:


texts: can someone help with this question with capacitors

texts:
Please I need help solving this one, the book is Thomas Floyd 3rd edition Electric circuit fundamentals.
The final answer is supposed to be \$ \text{0.0052 } \mu F\$

The ac source frequency \$f=141471 \text{ Hz}\$, \$X_{C_2}= \text{562 }\Omega\$, and \$X_{C_{23}} = \text{321 }\Omega\$.

my steps are as follow :

i find frequency of the ac source from reactance 3 , then
i find Xc2 , after that i find current going through C2
i find equ capacitance of 2 and 3 and their equivalent reactance
then i find drop voltage on the equ reactance
find reactance of C1
then the calue of C1 capacitance


texts: How to get data sent to a LED strip each 400 ns?

texts:
I want to send data to a LED strip. This has to be done roughly every 400 (or 800 ns), depending on the data (a 0 or 1 to be sent).

unsigned long  counter  = 0;

I did a test with my STM32F103C8T6 with this code in the loop:

while (1)
{
    GPIOC->BSRR = GPIO_PIN_13; // Set GPIO
    counter++;
}

I ran in debug mode, to be able to check the counter value. After roughly 10 seconds, I suspended the program and checked the value for counter. It had value 27822623. This means that each counter takes about 10 / 27822623 = 3.5942E-07 seconds / counter increment, which is 359 ns/counter increment.

However, all I do here is setting the GPIO pin which is one offset pointer, an assignment and an increment. And this takes the 'gigantic' long time of 359 ns. In my real application I need to go to the next byte, check if it is a 0 or 1, depending on that to send the above command to set, or a reset command of the pin (which takes an additional bit shift). How can I perform this within (or actually appr. around 400 ns?)

The STM32 is set to 72 MHz (maximum speed).
I haven't any additional interrupt running.

How can I send data at 400 ns manually?

(I tried SPI: not reliable enough, sometimes clock pulses are skipped and resulting data). Interrupts via a timer will be even taking more time since it contains interrupt flow (via HAL).

Update

New application to test better:

unsigned long  counter  = 0;

In main:

while (1)
{
    GPIOC->BSRR = GPIO_PIN_13; // SET
counter++;

    if (counter == 10000000)
{
    HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_14);
    counter = 0;
    }
}

Update
Below the disassembled code (more than I thought):

152                 GPIOC->BSRR = GPIO_PIN_13; // SET
0800122e:   mov.w   r2, #8192       ; 0x2000
08001232:   ldr     r3, [pc, #36]   ; (0x8001258 <main+64>)
08001234:   str     r2, [r3, #16]
158               counter++;
08001236:   ldr     r2, [pc, #36]   ; (0x800125c <main+68>)
08001238:   ldr     r3, [r2, #0]
0800123a:   adds    r3, #1
0800123c:   str     r3, [r2, #0]
159               if (counter == 10000000)
0800123e:   ldr     r2, [pc, #32]   ; (0x8001260 <main+72>)
08001240:   cmp     r3, r2
08001242:   bne.n   0x800122e <main+22>
161                   HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_14);
08001244:   mov.w   r1, #16384      ; 0x4000
08001248:   ldr     r0, [pc, #12]   ; (0x8001258 <main+64>)
0800124a:   bl      0x80004e0 <HAL_GPIO_TogglePin>
162                   counter = 0;
0800124e:   movs    r2, #0
08001250:   ldr     r3, [pc, #8]    ; (0x800125c <main+68>)
08001252:   str     r2, [r3, #0]
08001254:   b.n     0x800122e <main+22>
08001256:   nop


texts: What exactly is a Flash emulator, and how does it work?

texts: I read about a flash emulator. Can someone tell me what exactly a flash emulator is, and explain how it works? Is it synonymous with an in-circuit emulator?


texts: Using 32 bit variable in microcontroller to find elapsed time

texts:
I am trying to establish a time line (updated by soft counter) which would never end within embedded system product lifetime. For this purpose I think of using a 32-bit variable i.e.
volatile uint32_t ulTimeline;
The timer interrupt is served every second where this ulTimeline is incremented by one. So the maximum time this variable can count up to is 2^32 seconds -----> 136.19 years
The getCurrentTime() simply returns the value of ulTimeline.
On this time line I am using referenceTime = getCurrentTime() and getTimeDifference(referenceTime) to find elapsed time.
I am looking for efficient approach to manage time, can someone point out side effect of this implementation?


texts:
I have an TM4C123GH6PM, I have also the board EK-TM4C123GXL with that MCU. I am new to microprocessors and still studying to learn. I have to implement a project with a Bluetooth module, which connects over UART to a host MCU. I want to know if I can use this MCU for the host.

The MCU will read an analog signal, and must sample continuously and periodically with a rate of at least 8000-10000 samples per second. In real time, this data will be forwarded directly to the UART and sent to the Bluetooth module. My questions are,

First of all, is this possible with this MCU?
Secondly, I know how to use UART and how to use ADC basically, but
how do I configure ADC to run periodically and continuously - if that
is not the default- ?
Thirdly, as I know, the UART operates with 10 bits when there is only
one stop bit and no parity bit, the remaining is 8 bits, how do I
workaround to get 12 bits of data per sample from ADC, other than
truncating?


texts: how to charge 2 Lithium ion 18650 batteries in Series and Parallel

texts:
i want to charge my 2 lithium ion batteries in series and parallel.
as per my knowledge
for single cell Capacity 3350mAh as per datasheet
charge voltage: 4.2 V DC
Charge current: 0.5C (1700mA)
cut-off current: 0.02C (68mA)
for 2 cell in parallel as per my understanding it will be acting as high capacity single cell of capacity 6700mAh and voltage 3.6 V DC
charge voltage: 4.2 V DC
Charge current: 0.5C (3400mA) as connecting in parallel will increase the capacity
cut-off current: 0.02C (136mA)
for 2 cell in Series as per my understanding it will be acting as high voltage single cell of capacity 3350mAh and voltage 7.2
charge voltage: 8.4 V DC
Charge current: 0.5C (1700mA) as connecting in parallel will increase the capacity
cut-off current: 0.02C (68mA)
individual cell voltage should be monitored for safety
please check this and guide me if i misunderstood this


texts: STM32 Interrupt Priority (preemption) Problems

texts:
I have another problem (High resolution system timer in STM32) which I have tracked down (mostly) to this issue, and have created a test case here for the simplest STM32 processor I could find (on the STM32VLDISCOVERY board).

The problem is that I cannot get a higher priority interrupt to interrupt a lower priority one.

In the example, LED1 is flashed slowly by the SysTick interrupt, LED2 is flashed by the main loop.

Expected outcome

When BTN1 is pressed, the EXTI0 interrupt is called, it flashes LED2 quickly until the higher priority SysTick interrupt is fired, and then it exits. LED1 keeps on flashing as before.

Actual outcome

When BTN1 is pressed, the EXTI0 interrupt is called, it flashes LED2 quickly. The higher priority SysTick interrupt is never fired, LED1 never flashes and the LED2 continues to blink quickly.

Any ideas? Is interrupt preemption something that has to be turned on somehow?

#include "stm32f10x.h"

typedef char bool;
volatile bool toggle;

void delay(void) {
    volatile int i = 100000;
    while (i-- > 0) {
    }
}
void delaySlow(void) {
    volatile int i = 1000000;
    while (i-- > 0) {
    }
}

// Toggle LED1 on SysTick
void SysTick_Handler(void) {
  if (toggle = !toggle)
    GPIO_SetBits(GPIOC, GPIO_Pin_8);
  else
    GPIO_ResetBits(GPIOC, GPIO_Pin_8);
}

// On EXTI IRQ, flash LED2 quickly, and wait for a SysTick
void EXTI0_IRQHandler(void) {
      bool lastToggle = toggle;
      GPIO_SetBits(GPIOC, GPIO_Pin_9);
      while (lastToggle==toggle) { // wait for systick
        // Flash LED2 quickly
        GPIO_SetBits(GPIOC, GPIO_Pin_9);
        delay();
        GPIO_ResetBits(GPIOC, GPIO_Pin_9);
        delay();
      }
      GPIO_ResetBits(GPIOC, GPIO_Pin_9);

      EXTI_ClearITPendingBit(EXTI_Line0);
}

int main(void){
  GPIO_InitTypeDef GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |
                         RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOD |
                         RCC_APB2Periph_GPIOE, ENABLE);
  // set preemption
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_4);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_All;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  GPIO_Init(GPIOB, &GPIO_InitStructure);
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  GPIO_Init(GPIOD, &GPIO_InitStructure);
  GPIO_Init(GPIOE, &GPIO_InitStructure);
  // button
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  // leds
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  // systick
  SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8);
  SysTick_Config(0xFFFFFF); // 24 bit
  NVIC_InitStructure.NVIC_IRQChannel = SysTick_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; // Highest priority
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
  // exti 0
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x0F; // Lowest priority
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x0F;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;
  NVIC_Init(&NVIC_InitStructure);
  GPIO_EXTILineConfig(GPIO_PortSourceGPIOA, GPIO_PinSource0);
  EXTI_InitTypeDef s;
  EXTI_StructInit(&s);
  s.EXTI_Line = EXTI_Line0;
  s.EXTI_Mode =  EXTI_Mode_Interrupt;
  s.EXTI_Trigger = EXTI_Trigger_Rising;
  s.EXTI_LineCmd = ENABLE;
  EXTI_Init(&s);

  while (1)
  {
    // Flash LED2 slowly
    GPIO_SetBits(GPIOC, GPIO_Pin_9);
    delaySlow();
    GPIO_ResetBits(GPIOC, GPIO_Pin_9);
    delaySlow();
  }
}


texts: Isolated power supply for a cascaded multilevel converter

texts: I would like to build a cascaded multilevel converter. Each module should be supplied by an isolated power supply around 100VDC. Using available bench power supplies is not practical, because they could not be cascaded to build more than 240VDC. In addition, since the switching frequency of modules is around 100kHz, an earth leakage due to high-frequency operation could happen causing a damaging on gate drivers of modules. Any solution?


texts:
I'd like to connect R-Pi serial to PC's RS232 port without IC (such MAX3232), using only diode (thus block negative voltage to 0V), voltage divider resistors, and common BJT.

For TXD (RX from R-Pi perspective):
Using my USB-to-RS232 adaptor, measured voltage level for logic high is 7.5V, 6.85V after 0.65V diode voltage drop, so I'll use 270:220 ohm resistor for 3.07V (for 10 mA current) - 3.36V (no current, no voltage drop) divided voltage. Current is limited to about 10 mA with 490 (270+220) ohm resistance.

For RXD (TX from R-Pi perspective):
Borrowing power from DTR line, switch it using BC557 PNP transistor (DTR to collector; emitter to RXD) with base connected to R-Pi's TX in series with 680K resistor (for limiting drawn current to 0.5 mA).

My question is: will this work? (I'm not sure whether impedance of the connected pins will affect this simple circuit). Thanks in advance for your response.


texts: Using higher capacity rechargeable batteries in device

texts: Is there anything inadvisable about replacing a device's original NiMH batteries with others of much higher capacity? (For example, a cordless phone comes with 500 mAh cells, and I'd like to exchange them with 1500 mAh cells.) I'm thinking that the charging algorithm may be designed specifically for lower capacities, and will never fully charge the higher capacity cells, so the whole exchange might be an exercise in futility (or might even degrade the cell).


texts: What voltage to charge a single NiCd cell?

texts:
Ok. I have researched and not found any results abt this question. What is the voltage range for charging a single NiCd cell?
I also have another question: what is the recommended constant current amount (C) for a series of 10 NiCd cells, and are there any other things to consider when charging that many batteries in series?


texts:
What is this camera component called?
I was recently taking apart my old laptop and found that the webcam module had this circular component that screws on and off. I saw that it contains the lenses, and behind it is the sensor. I attached a high quality photo I found online to show what I'm referring to.
I wanted to see if I could find more information about them online, but unfortunately couldn't find much at all. I can find data about the camera sensors (the square part below it), but not of the lens itself. I'm not looking for information for this exact model, just "generic" lenses.
Does anyone know what keywords to search to find information about these small "module" lenses? Or examples of manufacturers that produce these? I've been searching for the past day but am struggling, so any help is appreciated!


texts: STM32 "USB Device" vs. "USB OTG HS" - what is the difference?

texts:
I recently downloaded the stm32 app for MCU search and found out that for example STM32F429 has "NO" in "USB Device" peripheral, while it says "YES" in "USB OTG FS" and "USB OTG HS". Which is quite surprising since STM32F429 is fully functional as USB Device, i.e. it supports all the libraries and USB classes.
Some other MCUs have "USB Device" stated in it, eg. STM32L052

Then I tried to check CubeMX and found out that there is USB_Device peripheral in their search(and again STM32F429 does not include it, USB stuff is done through OTG).

It may be quite easy question since I suspect that USB Device simply means the one that does not support OTG, but I am not sure, usually MCUs use OTG anyway(and moreover there is only one library, so why state "NO" in USB peripheral). I couldn't find information about it in google or in CubeMX documentation.

I am not really concerned much about it since USB OTG HS seems to work OK with the library, but I'm wondering about terminology.

I understand that probably ST forum is a better place for this question, but many topics there are just don't get answered or answered after 2 years have past. :)

Thanks.


texts: Inductor selection for a switching regulator

texts:
This is somewhat related to this question, but hopefully a bit broader.

I'm selecting components to fill out an lm2734. This regulator will take a 9-12V (11.1V nominal) input down to 5v @ 1A max. They provide guidance for selection on page 12 of the datasheet, and using the formulae there, I arrive at an inductance value of 4.9uH.

My question: what do I want directionally here (size and cost notwithstanding, and assuming the output current and DCR are correct), an inductance value that's within some percentage of the one calculated above, or just a value that's higher? Should I just be using the largest inductor I can fit to minimize ripple current?

To recheck my work, I looked at the sample circuits they provide in the DS, and calculated the inductance for them to compare to the inductor value they recommend. They seem to be taking inductor values as much as 2x greater than the formula suggests (which may also mean that I'm just doing it wrong). E.g.

for a 12V in / 3.3V out @ 1A configuration, I get 4.3uH, and they recommend a 4.7uH inductor
however, for an 18V in / 1.5V out @ 1A configuration, I get 3.1uH, and they recommend a 6.8uH part.


texts: CMSIS vs HAL vs Standard Peripherals Library

texts:
So I'm switching from PICs to ARM and I bought an STM32F4 discovery board.
So far I understand that to program it you can either access all registers directly in memory (obvious way) and also there are 3 main libraries you can use to make your life easier.
Now my question is, which one of those 3 (CMSIS, HAL, Std Peripherals Lib) is the most LOW level one? ie. the one with the less overhead. My goal is to learn the controller's inner workings and not make my life easier (only a little), so I would like to know which of these is closer to the core without resorting to use assembly.


texts: Do signal input, signal output and dual supply ground reference connect together at some point?

texts:
I have a circuit on veroboard that contains dual supply opamps. I need to send input signal and measure output signal. The input port has a return path we usually call ground and so does the output port. The dual supply input to the circuit has positive supply port, negative supply port and ground terminal since some components in the opamp circuit are connected to be to ground. Note that the opamp circuit is sallen key filter implemented using LM324N.

Do I connect the input signal, output signal and dual supply ground together?

The dual supply is generated using dual bench supply. The middle positive and negative terminal pair from the two internal supplies is connected together to generate ground reference. Below is the picture. Can't upload schematic.

There seems to be a problem. The output is distorted. The first stage output is below in yellow.

What could cause such distortion in an opamp? The fourth opamp is floating and not used. This type of distortion appears on the input signal of the first stage only after power up and then seems to get worse as seen above.


texts: Increase voltage drop required to saturate PNP BJT to avoid noise

texts:
I have this circuit which must signal +3.3V or 0V depending on the switch status.
The the switch is about 20 meters away and is getting EMI from mains.

I realized that it only takes -0.7V of interference on Vb to make the transistor saturate causing a false switch pressing event on my ESP.

How can I increase this gap in say 2 or 3 volts so it becomes less sensitive to EMI?

I thought of series diodes on base like this (which is cheaper than shielding the cables) but is it correct?


texts: 79XX datasheets show differing capacitors on input and output. What is correct values and types to use?

texts:
I am making a power supply using a 7812 and 7912 regulator. It's 24 VAC in through diode bridge, resulting in about 18V positive and negative. I'm planning to use a 1000 uF capacitor on each side and then go into the voltage regulators.

The regulators I have are ON Semiconductor MC7812BTG and MC7912BTG. The datasheets for both of these regulators shows .33 uF on the input and .1 uF on the output. If I check other datasheets for LM7912, I see other values and specifically tantalum caps. They even recommend 10x the value if using electrolytic.

Can anyone tell me what is correct? Is there a difference between MC78XX / MC79XX and LM78XX / LM79XX (other than manufacturer)?

ON Semiconductor MC79XX

TI LM79XX


texts:
When I look at, let's say an iPad AC adapter, the input/output rating on the charger states:

Input: 100-240V 0.45A (AC)
Output: 5.1V 2.1A (DC)

I know that the input and output ratings are maximum. The AC voltage in my country is 230V. Through a simple calculation, I can deduce the following (correct me if I am wrong):

Input power: 103.5W
Output Power: 10.71W

Now, my question is this: what is the true power drawn from the wall socket? Is it 103.5W or 10.71W? If it is 103.5W, then I presume the iPad adapter is 10% efficient?


texts:
I have a a electromagnetic level switch with DPDT contacts. Its rating mentioned is 230Vac, 60VA, 1A. My concern is what will be the DC equivalent for this rating.
I have 24Vdc available from PLC and will current rating change or remain constant if the voltage varies.


texts: How can I electically isolate two sprinkler controllers 24VAC working on the same output (master valve)

texts:
I have an old 24 zone sprinkler controller and I'm trying to move 16 zones to a "smart" sprinkler controller. I have a master valve that has to be switched on to provide water downstream to the other zone valves 1-24. In this case the old controller and the new second controller will both have to be wired to turn on the same master valve and will share a common ground wire.
The manufacturer of the smart controller recommends to use a $45 "isolator" per controller to protect them. I was thinking I could use diodes for isolation. Any ideas? $90 for isolators is more than I payed for the controller, I'd rather put something together myself but not sure where to start.
I could put the master valve on a separate power source and use solid state relays to trigger the master valve. Is that even necessary?


texts:
Anyone familiar with relays mechanical or otherwise? I would like to be able to switch on/off up to 250W (120V) load using a microcontroller.

Will be used to control lighting to an aquarium.


texts:
I have a system with an RS-485 bus master and up to 12 slaves. The master and slaves are located in different assemblies and are connected with an RS-485 bus that is inside a cable harness. The cable harness also provides power and other comms. The RS-485 bus is twisted shielded pair with 24 gauge conductors. All connectors are -38999 with 20 gauge contacts. There is no guarantee all slaves will be connected to the bus so I cannot route the bus into a slave and back out to shorten stub length. Data rate will be greater than 1Mbps - goal is 10Mbps if bus architecture will support it.

Total bus length is estimated to be about 12 feet long. Each stub on the harness is estimated to be about 6 inches from the main part of the harness. Stub length inside the slave assembly is about 2 feet. Stubs on the main harness are separated by about 8 inches.

My question is what is the best practice for 'attaching' a stub to the bus. Should each stub be spliced into the main twisted shielded pair? Or should the main bus be crimped into a single pin at each stubs' terminating connector, i.e., pin acts as splice for main bus? Or, is there a better option such as the inline bus couplers found in MIL-STD-1553 buses?

Edit: The question is about whether splices or two wires in a single pin is a better method for tying into a bus or does it matter. It is understood shorter stub lengths are better and termination will only happen at the extreme ends of the bus (not on stubs).


texts: 20A current measurement with hall effect sensor

texts:
I am not aware of drawing more than 1A over PCB traces. We are planning to use ACS712 hall effect current sensor linked below:

https://www.amazon.in/KitsGuru-KG134-ACs712-Current-Arduino/dp/B00YY3UK6S

Can anyone help with the width and depth of the traces for such higher currents?

How far should I place other components including microcontroller?

Should I have heat sink or such arrangements?

Or should I solder copper wire with 5mm thickness to connectors and place sensor module above it?

Thanks in Advance


texts: Where can I find common circuitry implementations of different computer system components?

texts:
Mostly out of interest, I'm trying to understand common circuit-level implementations of computer components. I understand that implementations may differ widely, but I'd like to see examples. It would be great to see a lot of this stuff in one place, if such a website (or book) exists. Here's a list of the kind of components I'm trying to understand:

RAM
Flash memory
Data + Address buses
HDD's
NVRAM
ALUs
Any processors, relatively simplistic ICs
etc...

Here's a good example of the kind of thing I'm talking about:
http://www.righto.com/2014/10/how-z80s-registers-are-implemented-down.html

About 2/3's into the article, a circuit diagram is given that shows the register implementation.

It would be cool to see some of everything, to the point where one could have enough knowledge and resources to conceptually build (almost) an entire computer in their mind out of fundamental circuit components.

Does anyone know of such a resource?


texts:
I always assumed that the shape of the antennas was important; a vertical monopole for pitch and a horizontal loop for volume, thinking that this minimized their interference with each other.  But it seems they actually operate more in the range of 200-500 kHz.   At these frequencies a good antenna would be hundreds of meters long, and the use of different frequencies for each antenna is sufficient to prevent interference.

On the other hand, the Moog Etherwave schematic has a bunch of coils in series with the antennas, which could be electrical lengthening?

Most descriptions I've read explain that it's just the human's capacitance to ground that detunes the oscillators, so any shape of metal will do, since it's just acting as a capacitor plate.

This page describes something different, though, which I don't understand:

  Beyond 4 inches (10cm) RF heterodyne theremin pitch variations are caused from changes in the "radiation resistance". This is the total RF electro-magnetic power radiated from the pitch antenna divided by the square of the net current flowing into the pitch antenna. The pitch field is a dual electrical/magnetic equilibrium, not just a capacitive field as so commonly state.

Some more explanation here

Is this correct?  What's wrong with the capacitance explanation?

More:

http://www.thereminworld.com/silicon_chip_theremin_modifications.html

  Linearizing the pitch sensitivity - I found that the upper octave was much compressed and that the highest notes I wanted to play were so close to the antenna that accurate vibrato wasn't possible. A way to linearize the response is to put an inductor in series with the antenna.

http://www.dogstar.dantimax.dk/theremin/thersens.htm

  This effect is partially offset by the nature of the LC tuned circuit, the frequency of which depends on the inverse square-root of capacitance. This is the main reason, I believe, why oscillators based on a single pole (only one reactive component, i.e. capacitance) never took hold for theremin use. I, and probably many others, have experimented with RC oscillators in an effort to get rid of those pesky coils; even the ordinary NE555 timer can be used for this purpose. However, in such circuits the oscillating frequency is inversely proportional to capacitance, rather than square-root of capacitance, and the "square-law" effect is correspondingly a lot worse. Another way of looking at this is that sensitivity (dF/dC) of the RC circuits is proportional to 1/C2 instead of 1/C1.5 in the case of the LC circuit.


texts: Can someone please explain the necessity of impedance matching when designing an antenna?

texts:
I am making an antenna for my technical research.  I am a grade 12 STEM strand.  I don't have any background information regarding antennas. In  exploring through google I gradually learned the basics.
I am working with this title "TWO STEERABLE DISC YAGI-UDA ANTENNAS ATTACHED WITH A DIPLEXER." It is  for 4G and 3G mobile  network. Any tips?
I  don't want to fail but I find  it really  hard to find  all  the necessary information in designing an antenna.
I plan to  make  two disc antennas, one for specific frequency band for  3G and one for specific frequency band  for  4G and I will combine the two cables in a diplexer because diplexer  works if low  and high frequency is  connected and can coexist in one  port.


texts: Equivalent solution to soldering STM32F103C8T6 Board

texts:
There is this project I am doing and part of it I will be using a STM32F103C8T6 Board.
Unfortunately, I do not have a soldering kit as i for now I cannot solder the pins of the board.
Is there an equivalent solution to this? Like buying on online that is already soldered or is there anything else that I could buy and then it would not be necessary to solder the pins.
I would most probably order the stuff from amazon/ebay in Germany


texts: Creating -24V @ 750 mA from a Variable DC lab supply

texts: I need -24V and 750 mA to run a certain part. What would be the best way to do so given that I have a power supply that gives me 24-28 volts and 2A of current. I need to do so because I need to create the -24V with respect to the ground of my positive power supply for my application. I have looked at various DC DC converters but none of them can provide that high a current. Also haven't been able to find any other power supplies which would work. Thanks a lot for your help!


texts: Where can I source extra long headers from

texts:
I have recently purchased a sparkfun protoboard that I wish to stack above an ethernet shield. (I have 2 different ethernet shields, an Arduino one and a seeed studio enc28j60 shield.)

The problem I have is that if I use the supplied headers, or even the longer "Arduino Stackable header" then the magjack from the ethernet shield below contacts the protoboard. This happens before adding the components at the front of the board, I suspect that if I solder those in the header won't even make reliable contact.

So, I'd like to source some extra long headers, either male-male or male-female would be fine. I did notice that the Arduino ethernet shield has extra long headers - does anyone know where to source those or any other 1.5cm long headers from?

It would be awesome if the supplier had a reasonable shipping rate to Australia, but I'll take whatever I can get. :) I have searched farnell without luck so far, but the number of products is a bit bewildering so there is a chance I have overlooked the perfect header.


texts: Why are most BLDC motors designed to operate on low voltages?

texts:
The vast majority of brushless DC motors I encounter operate on low voltages such as 1.5V to 24V. Obviously, if the intended application is for runnning strictly on battery power, it makes sense. I do, however, occasionally see them in some modern household appliances and they use relatively complex power supplies to operate at the same low voltage range.

What is the reason for not designing them to operate at 90V to 220V range. Is the circuitry for commutating the motor at higher voltages more expensive or less efficient?


texts:
I've been given the following simple pnp transistor circuit where β=20 and Veb=0.7V and I'm trying to find the emitter current:

I have the solutions but they don't agree with my results.

My attempt:
$$V_{eb}=0.7=>V_e-V_b=0.7\\=>(10-10\times I_e)-I_b\times 1000=0.7\\=>9.3=10I_e+1000I_b\\=>9.3=10I_e+1000\frac{I_e}{β+1}\\I_e=0.161mA$$

The solution from the manual:
$$I_e=\frac{10V-0V}{10KΩ+\frac{1MΩ}{β+1}}=0.174mA$$

Why are the results different? And more importantly, how exactly did the second equation come up?What does it mean? Maybe an equivalent resistance was used there (maybe) but also, why is the voltage difference 10 in the numerator? A voltage difference of 10-(-10)=20V would perhaps make more sense, wouldn't it? Of course, I can't understand what the second equation represents so I can't make guesses.


texts: Are there still sensors for a pen-type barcode scanner?

texts:
In 1980 there was HEDS-1000. in 2005 - HOA6480. In 2006 - HEDS-1300. Those were precision sensors with resolution as low as 0.13 mm at 4 mm distance. Now they are all discontinued and I cannot find a replacement. The only somewhat similar devices are "focused" (AKA "arrowhead") reflective sensors from TT electronics (like OPB702, OPB703, OPB740, etc). But they do not even mention any resolution or feature size in their specs and do not list barcode reading as a supported application. There are also reflective line reader sensors, like OPB739RWZ, but they require mush shorter operating distance (up to 1 mm).
Am I missing something? How do people these days make small feature scanners when full image sensor is not warranted?
Are there still some classes of sensors that I missed?
(I already have PWM to drive LED, Op-Amp and ADC to read sensor, stepper to drag the target, all I need is a sensor).


texts: When is it appropriate to connect two steppers in series?

texts:
I'm considering building a machine that would have 4 axes, two of which would require two steppers each to allow for the desired mechanical layout. These pairs would have to run synchronously. That's six steppers in total. Given that the hardware I have at hand (a ramps 1.4 board) has only 5 A4988 drivers, I need to decide if I

connect two steppers in parallel to one driver
connect two steppers in series to one driver
should look for a board with 6 drivers, which would be considerably more expensive and less widely available.

Two steppers in parallel

The current is split between the two, and exactly how it is split depends on the individual characteristics of each stepper and its load. If one stepper fails, the other will continue to work. The driver's set current will now be supplied to just one stepper and possibly kill it.

Two steppers in series

Both steppers get the same current. The driver would have to supply at a higher voltage to do this, but that should be within bounds with a reasonably low current setting (for example with two 6V steppers and a 12V supply). If one fails open, the will be no current in the other steppers equivalent coil. Both steppers would appear fail in the same way (and stay in sync).

I guess that for this application it's more appropriate to connect the stepper pairs in series, but I might be wrong and there are surely more details to consider. I guess I mainly ask because I never connected two steppers to one driver, and doing so in series "just doesn't feel right". Please help me fill the gaps. The approach seems to be backed by this answer on 3d printing SE: https://3dprinting.stackexchange.com/a/6885/9559


texts: Help designing a circuit working with PWM and polarity swapping

texts:
Hi all I'm after some advise for a circuit I'm trying to design.
I have an existing circuit that drives two low power bulbs. This is my signal circuit and runs on 12v, has a switched negative and uses PWM to make the bulb fade in and out as it transitions between on and off.
I have two, much higher power bulbs, I would like to turn on when the lower power bulb is on. This second bulbs circuit has a switched live.
I figured I could use a relay to switch the polarity of my lower power signal circuit to drive the higher power bulbs on a higher power circuit. Problem is, due to the PWM, the relay flicks wildly on and off as the bulb fades in and out.
So I thought I could try and smooth out the PWM using some form a low pass filter. Whilst I haven't tested yet I would assume I would need a rather large capacitor as the relay coil would require quite a lot of power to keep it energized.
So my question, is there a better way to solve this problem? It would be even better if my higher power bulb could be faded in and out too but if it makes it simpler just having it turn on and off would be great.
Thanks for any advice anyone can offer. I'm a software engineer, not electrical so sadly this is like magic to me.
edit
Just to add a little more information
The existing circuit:

2x 5w 12v D.C. bulbs
constant live
PWM controlled transitions between states (on/off)
non PWM controlled when in the on state.
incandescent bulbs

Second circuit:

2x 21w 12v DC bulbs
switched live
incandescent bulbs

Desired outcome:
The first circuit to act as a signal for the second circuit, not to drive it directly. I think the extra bulbs would be too much load. The first circuit is switched ground, the second switched live so something would need to translate anyway. If the second circuit could inherit the PWM that would be great but if not thats fine.
What i tried:
Using a relay. It worked, the new bulbs were powered using the first circuit as a trigger. However due to the PWM the relay flicks on off very rapidly during the PWM phase.
I tried researching how to smooth the PWM signal and that's when i read about low pass filters. However i don't think that would be suitable to smooth out the relay trigger. So wondered if there was a better way to solve this problem.
Thanks again.


texts: Getting signal from high voltage side of PCB to low voltage side

texts:
simulate this circuit – Schematic created using CircuitLab

I am designing a PCB that has both a high voltage side and a low voltage side.
They are separated by roughly 8mm.
There are I/O lines on the high side that, most of the time, input a very low voltage/low current signal connected to an op amp and then to an ADC in an MCU.
These same input lines are also used to output a high voltage signal for a very brief period. Obviously the low voltage side has to be protected from these high voltage output.
Typically I would use a couple resistors and zener diodes, but in this case, I still need to get a signal across to the low voltage side.
How is this done?
In case you're wondering, this is for an AED with a novel delivery mechanism that I've tested.
Low voltage is the ECG sense while High Voltage is the shock.
The PCB is for a somewhat production prototype.
edit:  simplified schematic (ignore component names) and simplified PCB layout added


texts: Where are the depletion PMOS transistors?

texts:
In school, I was taught about PMOS and NMOS transistors, and about enhancement- and depletion-mode transistors. Here's the short version of what I understand:

Enhancement means that the channel is normally-closed. Depletion means the channel is normally-open.

NMOS means the channel is made of free electrons. PMOS means the channel is made of free holes.

Enhancement NMOS: positive gate voltage attracts electrons, opening the channel.
Enhancement PMOS: negative gate voltage attracts holes, opening the channel.
Depletion NMOS: negative gate voltage repels electrons, closing the channel.
Depletion PMOS: positive gate voltage repels holes, closing the channel.

It's been six years since I started doing design work for a living, and on at least one occasion I've wanted (or at least thought I wanted) a depletion PMOS transistor. It seemed like a good idea for a bootstrap circuit for a power supply, for example. Yet no such devices seem to exist.

Why are there no depletion PMOS transistors? Is my understanding of them flawed? Are they useless? Impossible to build? So expensive to build that a cheaper combination of other transistors is preferred? Or are they out there and I just don't know where to look?


texts: NodeMCU with JHD162A Lcd module display issue

texts:
I have uploaded a program to NodeMCU, to print "hello, world" on JHD162A 16x2 LCD module. But the text doesn't appear on the LCD display. Instead just black blocks appear on the first row on the LCD. I assume it's a hardware related issue since the software worked in simulation.

I powered the NodeMCU and the LCD using 5v DC from 7805 voltage regulator IC.
The 12v input to the IC is provided using a 230v AC  to 12v DC adapter with 2A max current out.

I have placed a 680 ohms resistor to the anode of the lcd back led, also a 1K resistor between the Vss and Vee of the lcd to set contrast. I am using D0, D1, D2, D3 pins of the nodemcu to the D7, D6, D5, D4 data pins of the lcd. The RW is connected to the gnd pin of nodemcu. The RS and E pins are connected to the D8 and D7 of nodemcu.

#include <LiquidCrystal.h>

const int RS= D8, EN = D7, d4 = D3, d5= D2, d6 = D1, d7 = D0;

LiquidCrystal lcd(RS, EN, d4, d5, d6, d7);

void setup()
{
lcd.begin(16, 2);
lcd.print("hello, world!");
}

 void loop()
{
lcd.setCursor(0, 1);
lcd.print(millis() / 1000);
}


texts: Why is the voltage drop across this transistor the full voltage of the battery?

texts:
I am currently learning about transistors from allaboutcircuits.com.

He presented the following schematic:

He claims that when the transistor is in its cutoff state, V.output will read the full voltage of the battery, which he stated earlier to be 15V. Why is this? Shouldn't the voltage reading be smaller than 15V since of the voltage needs to be dropped across the resistor at the top of the circuit? Is he neglecting the resistance of the resistor for teaching purposes, or am I missing something?


texts: Pros and Cons of 3 Different Transducers

texts:
What are the pros and cons of using these different transducers?

I can't find see what the difference would be between either of them? I mean, they are all used in converting energy right?

Linear variable differential transformer (LVDT)
Variable-area capacitive transducer
Variable-separation capacitive transducer

Thanks guys


texts: What are the differential voltage technology used for PCIe gen 4, gen 5 and gen 6?

texts:
I have been studying various IO standards used for various PCIe generations? I understand that PCIe Gen-3 uses LVDS, LVPECL and PCML.
I would like to learn what are the standards used for other generations.
Q1) From, TI application note, LVDS is limited unto 3.125 Gbps. So, what if the PCIe requirement is more than 3.125 Gbps?
Q2) How the maximum data-rate is determined?


texts:
i want to assign a black color to Ground Plane (GND 0), it's shape is polygon and it's color is gray like shown on below image, i have two questions:

is this a possible polygon shape to implement ?

i don't know if the other non GND tracks are too close to Ground Plane like i draw on below image, between this PCB circuit is for real implementation/assembly on a real presensitized board.

How do i change the color of the Gray Polygon Area of the Ground Plane, from Gray to black ?

i can only change the color of the tracks.

i followed this video: https://www.youtube.com/watch?v=nkzfqQw_wRg
and did the same for my Ground Plane.

on Display Menu -> Color/Visibility (Color Dialog Window), none of the active colors are Gray, they only black and white (like i want), but the Ground Plane is Gray, but i want this Ground Plane Area with a black color.

sorry my english is not good.


texts: Rotation span of SparkFun ROB-09065 servo

texts:
Does anybody know what the rotational span of the ROB-09065 servo from SparkFun?

And even better, is there a datasheet available anywhere?


texts: Is there a programmable variable resistor

texts:
I have a current signal that can vary in amplitude. I currently have a transresistance amplifier
which uses 330 Ohm resistors.
However the amplitude of this signal can vary and I would like to be able to
change the gain, when required from a micro controller.
Is there anything like an SPI part that alters resistance on command ?


texts:
I have 2 pins and primary function should be A/B RS485, but is possible that I also put RS232 (Rx/Tx) chip on same bus and then control which one I want to use from microcontroller.

I was thinking about MAX232 and MAX481 and enabling and disabling them trough power on/off controlled by microcontroller driving transistor.

Is there any single device that does this?


texts: How to use IO pins in PIC microcontroller as PWM?

texts:
I am trying to use a PIC18F4520 microcontroller to drive 8 servo motors. For this I need 8 PWM signals, but the PIC unit has only two built in PWM. So, I decided to use some normal I/O pins as PWM, and searched how to do that. I found some hardware based solution like using extra IC's or software based solution as using interrupt based PWM. But why can't I just use this code segment:

while(1)
{
PORTA.RA0=1;
delay_ms(10);
PORTA.RA0=0;
delay_ms(10);
}

The pin is high for 10ms and low for 10 ms.So the cycle period is 20ms. Shouldn't this create a 50Hz signal with 50% duty cycle? Or am I missing something?


texts: What purpose are the transistors serving in this CRT oscilloscope circuit?

texts: So this is part of a CRT oscilloscope diagram, and I don't understand the function of the transistors on the bottom right, Q18 and Q19. Their outputs (41 and 42, crossing through the dotted line) go directly to the horizontal deflection plates. Furthermore, this diagram says the base voltage is 1.2V, but all three points on each are measuring 20-30VDC for me. Keep in mind this scope is broken, something's wrong with the horizontal sweep circuit. I just need to understand the purpose of these transistors and what kind of voltage they're supposed to be carrying to even attempt to diagnose this thing. Thanks a heap in advance.


texts: Battery current measurement with shunt resistor

texts:
I want to use a shunt resistor to measure the current that flows from and in a battery. The current is set by power supply for charging(positive current) and by electronic load for discharging (negative current). I want to amplify the voltage drop over the shunt resistor with instrumental op amp that gives a gain equal to 50.4. The op amp that I'm using is AD620 with Rg resistor equal to 1k with tolerance 0.1%.
I want to send the output of op amp in ADC converter to acquire the measurement.
The problem is that the results aren't what I expected, shown in figure, and I don't understand which is the problem.
In figure there is a comparison with hall-effect sensor(black line), instead the red line is the current measured by shunt.

simulate this circuit – Schematic created using CircuitLab

The second figure shows results obtained connecting one of shunt terminal to ground


texts: What do the product and sum symbols mean in digital systems?

texts:
I have some questions in a professor's material and in that questions there are the mathematical symbols for product and sum receiving numbers as parameters as following:

∑(0,3,4,6) =∏(1,2,5,7).

The question ask me to prove that for circuit with three inputs

∑(0,3,4,6) =∏(1,2,5,7).

This is not clear to me.


texts: Why is the Voltage Gain 54 dB instead of 50 as stated in the problem?

texts:
Here I'm trying to find the overall voltage gain. I did everything correctly, except out of nowhere, the gain in dB was 54dB, not 50dB. I don't know why. Here's the solution:

And here's the figure (or problem statement)

Can someone explain why?


texts: How to work out the interface of an LCD?

texts: If I got an LCD, and I didn't know anything about it, and there were no markings on the pins, how would I go about interfacing with it?  For example, I got this small (around 2.5") colour display out of an old printer, I tried everything I could, looking up a datasheet, asking on forums, but I was unable to get it to work. What is a general process I could use? Is there like, a few common interfaces I could use?


texts:
Can I get a 150V DC output from the circuit below by using LM317HV-MIL?  As the voltage input I will be using a 160V unregulated input voltage from a rectifier.

If so, is there anything that I have to be careful such as power ratings, Vmax, Vce, etc. of the resistors, transistors, capacitors, etc.?

Here is the datasheet: http://www.ti.com/lit/ds/symlink/lm317hv-mil.pdf

Thanks for your help in advance.

EDIT1:

Datasheet says, " Since the regulator is floating and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, or in other words, do not short the output to ground."

What I did not get is if the input is 160V, I will need C1 have a voltage rating higher than 160V as well as C2 and C3. Is that right? Also, what should be the power ratings of the resistors R5 and R4. Could you help me to calculate the required power rating? For 150V, I calculate it as around 5W. What the R4?

EDIT2:

How about this?


texts: If a load is placed onto a DC motor, will the current increase?

texts: When a load, such as a weight on string, is placed into a motors axle, will this cause the current to increase?


texts: How does toggle action in a JK flip flop change to alternate states? When both inputs are 1 ,the output of nor gates is forced to 0,then how come they toggle ?


texts:
When measuring the AC voltage across a DC battery (CR2032), and I am getting 6v.
The DC voltage across it is 3.01 volts.
I also tested on a 9 volt battery; again the same thing. I am reading about 20 v AC and 10v DC.
I am using MASTECH MAS830L multi meter. I also used another multimeter, and I get the same result.

When I am putting the multimeter probes in the same polarity with the battery, I am getting the AC voltage, but none if I put the probes in reverse polarity.

Why is this happening?


texts:
I have a router with 2m wire, and it would be really useful to extending it a little. I was thinking about cut in somewhere and add 2 'nipple' (not sure if proper word) to connect them with new 3m wire. I checked current wire and there is some info:
2468 YIHUAXING 300V 1A 18AWG.
I have two questions:

Can I do that and will that be secure for device and people?
Since I cant buy this one, and dont see anything with 'AWG' in my local stores what should I care about? V and A I assume, anything more?


texts:
I am looking at prototyping a buck based MPPT solar cell system but am mainly confused by how the solar cell I-V characteristics are manipulated by the buck converter to give the optimum power to the load. I believe it is essentially an impedance matching but am struggling to see it mathematically.

Lets say I have a 12V nominal 130W solar cell, that at max power is rated @ 7A39 @  17V6 and I am trying to charge a 12V battery. Being a 12V battery it requires 13V2 to 14V4 to charge.

Now looking at the model below, the load could be modelled by a 12V voltage source, but how does one apply the standard buck converter ideal equations (ignoring losses as just trying to keep it simple).

Is there a mathematical equation/explanation of how the buck converter presents a 17V6 7A39 load, i.e. 2R38, to the solar cell, which is actually a 12V battery but requies 14V4?


texts:
I'm making this speaker where I have 2 12v batteries in series giving 24v an amp.
and a PSU giving 24v to the same amp.

I wanna make a circuit that switches off the batterie link between each other and the Amp when the PSU Is live.

so only the PSU is giving power to the Amp

:D


texts: Best humidity level for electronic shops?

texts:
What is the best humidity level for an electronic shop? On one end of the scale, you will have problems from corrosion due to high humidity and condensation, but at the other end there will be serious problems from ESD.

I've worked in shops at either extreme end of the scale, and would imagine the ideal level being around 50% relative humidity. Thoughts?


texts: How synchronous buck converters continue to operate in light load conditions

texts:
simulate this circuit – Schematic created using CircuitLab

For all intents and purposes lets assume this basic power stage of a synchronous buck design above. Let's also assume a steady state operating condition.

When in steady state, it can be shown that a portion of the inductor current in this particular circuit is negative. My question is - given this "light load" condition, and given an gate drive IC that does not account for any sort of pulse skipping, diode emulation etc, how can a constant current of ~33mA be delivered when the SW2 is "closed" and SW1 "open"?

My initial thoughts are that C1 is supplying the energy necessary to keep the load ~33mA. Given that

We can estimate the amount of total charge the capacitor has stored. But how long can that capacitor supply energy to the load "R1" before the switching cycle must restart? Isn't charge flowing from C1 to GND through SW2 as well?

I'm aware that there is ripple associated with these values - however in an attempt to simplify the matter i have left them out. I am just trying to better understand the load current given "light load" conditions above. Thanks for the help.


texts: Why does stator current increase with increasing load in a synchronous motor?

texts:
Isn't the current, coming from the 3-phase source of the stator, constant? We don't change the source, so how does the current change? Is a voltage induced because of the magnetic field of the rotor?

This leads me to another question which might help: Does the rotor's magnetic field of an induction motor affect the stator's current value?


texts: RC circuit with both DC and AC input voltages

texts:
In my circuit, V3 creates a DC signal at 2.5V. V2 creates a sine wave that 0.2V peak to peak centered at 0.1V.
I'm wondering why at Node 1, the voltage is a sine wave with 0.2V peak to peak that is centered at 2.5V? I understand that the C1 is supposed to remove the DC component of V2, but is there a way to reason through this using Kirchhoff's voltage law?


texts: What's the point of this thick trace in my PCB?

texts: I'm looking at a trace that goes from Pad 2 of a component to pin 22 of the QFN. What's the point of the thick trace at the beginning if it ends up being as small the pin where it is run?


texts: Why do my mosfets keep breaking/ dont work?

texts:
or the past few weeks I've been trying to control a 48-volt DC motor with 4 12-volt batteries, an Arduino, and a mosfet. Even though the datasheet says it can run up to 60 volts and 110 amps, as soon as I hooked up my mosfet it got really hot and stopped ignoring commands from my Arduino and ran continuously.

After this I tried removing one of the batteries but after it's been hooked up to a different mosfet it works for 15 seconds or so, then the mosfet stops working. I'm just lost at this point. If anyone could help me with why the mosfets keep breaking I would greatly appreciate it.

Here is a link to the data sheet of my mosfets, IRF3205.

http://www.irf.com/product-info/datasheets/data/irf3205.pdf

This is what my setup looks like.

Long story short my setup makes my mosfets super hot and makes them no longer functional and i would m
like to know why.


texts: How does the ELPF and XTAL inputs on the ADV7180 recommended circuit work?

texts:
I am looking at the recommended circuit for the ADV7180 by Analog Devices and trying to understand some of the reasoning behind the design choices. I realize some of these questions may be a lack of understanding of some fundamental concepts and would really appreciate if someone could explain them to me.

I know that the XTAL inputs are used for the 28.63636Mhz crystal but I don't understand how they came up with the circuit shown. What is the purpose of the additional resistors and the capacitors in this case?

For the ELPF input, from reading the datasheet all I could get was that it is the "External Loop Filter" pin and must be placed as close as possible to the IC. What is the purpose of this pin and again, how does the recommended design work?

The data sheet can be found here: http://www.analog.com/media/en/technical-documentation/data-sheets/ADV7180.pdf


texts: Why can a voltmeter still measure potential difference if it has a (theoretically) infinite resistance?

texts:
I am a physics teacher who did engineering and hated all things electrical! Hence when my students sometimes ask me how a voltmeter can measure the potential difference between two points if there is no current passing through the voltmeter. I can only assume that it is because having an infinite resistance is impossible, but I have never had the confidence to answer this without worrying about feeding them incorrect information.

My idea as it stands is that the resistance of a voltmeter is only theoretically infinite, in which case there will be a current flowing, however small, that can be used somehow by the voltmeter of a predetermined resistance to calculate the actual potential difference.

Can somebody explain whether I am along the right lines with this and help me explain this in definite terms or at least disabuse me of my assumptions and tell me the correct idea?