texts: Replacing 6 series AA alkaline batteries with NiMH batteries – how do I compare possible arrangements to optimise usable capacity?

texts:
I want to replace a battery pack of 6 AA 1.5V alkaline batteries arranged in series, with rechargeable NiMH batteries in an old transistor megaphone in such a way as to optimise the capacity. The existing battery pack is a typical 2×3 arrangement and it is connected with a PP3/PP6 snap connector. I want to use rechargeable batteries to reduce electronic waste.

I'm aware that usable capacity is subject to the device's cut-off voltage, the discharge curve, and the efficiency of the batteries given the temperature and load characteristics. Given that this is an old device and probably not designed with a low cut-off having rechargeable 1.2V batteries in mind, I'm concerned that 6 cells isn't enough and want to include a 7th.

Although I'm aware that rated capacity is a generally misleading figure, I don't understand why my naïve calculations seem to be several times out from what I'd expect judging roughly by the mass/volume of the batteries. Are PP3s really that bad?

In the battery compartment there is space for 4 of the following 5 arrangements (see note 2 below) for which I'm demonstrating these naïve, seemingly false calculations. (In the case of arrangement #4, there is also space for a small adaptor I made using 3 snap connectors required to connect the batteries in parallel.) This is roughly related to how ‘big’ the batteries are and relates loosely to their volume, so these arrangements are likely to be applicable to other devices as well.

(#)  Arrangement                    Combined       Charge    Total energy
                                    rated voltage  capacity  capacity[1]
(1)  6 AA 1.5V alkaline in series   9V             2100mAh   15.12Wh = 54.432kJ
(2)  6 AA 1.2V NiMH in series       7.2V           2400mAh   17.28Wh = 62.208kJ
(3)  7 AAA 1.2V NiMH in series      8.4V           950mAh    7.98Wh = 28.728kJ
(4)  2 PP3 8.4V NiMH in parallel    8.4V           200mAh    3.36Wh = 12.096kJ
(5)  14 AAA 1.2V NiMH; 2 series[2]  8.4V           950mAh    15.96Wh = 57.456kJ

Note 1: The ‘Total energy capacity’ is a naïve estimation based on the charge capacity and 1.2V per cell mean voltage.
Note 2: 14 AAA batteries in a (1+√3)×5 arrangement (i.e. rows of 5, 4, 5) can occupy approximately the same cuboidal space as 2×3 AA batteries. I've included this for the general case; however, in this instance the battery compartment has rounded corners so the arrangement wouldn't quite fit.

That is not what I'd expect at all – not even close; PP3s look to be about 2 and a bit times the volume of a AA, so I'd expect the total energy capacity of arrangement #4 to be about 70% that of #2, but this rough estimation suggests 19%! I'm guessing that the rated charge capacity is rated in respect to a ‘typical’ load, so the efficiency of each rating is probably vastly different, and therefore can't be used to reliably determine the actual energy storage capacity which would be underestimated by a different amount in each case. In the case of arrangement #4, the combined internal resistance is halved (i.e. ‘internal conductance’ added), so it would be more efficient and would deliver more energy per battery given the same load, as compared to just a single PP3. In arrangements 1–3 the IRs are added. Arrangement #5 has half the combined IR as #3.

For what it's worth, the megaphone is a pulsing load rated 5W maximum power draw, and it's operated outdoors in the UK so the batteries probably generally operate with a temperature between 5°C and 25°C depending on the time of year. I'm trying to find datasheets for the NiMH batteries I use (Maplin L32BJ, L29BJ, and L31BJ for AA, AAA, and PP3 resp.) to actually see for myself the true data of what's going on with these figures, but I haven't yet obtained any. However, specifics aside, these figures seem to be so far out that a better general understanding of how to compare rechargeable replacements for battery packs of 6 AA alkaline batteries would be generally useful because I've seen such battery packs on other types of devices as well.


texts:
I'm trying  to control a WS2811 Led strip with an ESP32.
I'm using a logic level shifter to convert the 3.3V output of the ESP32 to 5V.
I bought this level shifter (txs0108e) https://fr.aliexpress.com/item/32404824354.html but I cannot manage to use it properly.

The leds are flickering and are not the good color.
What is strange is that if I touch all the pins of the level shifter with my fingers it works perfectly. It works also perfectly when I touch the "data input" line of the strip with one multimeter probe (if my explanation are not clear I can try to upload a video).

Here is the wiring diagram :

Do you see any problem with this wiring or without this level shifter for this application ?
Do you have any idea why it works only when I touch the level shifter whith my fingers ?

Thanks


texts: Is it worth using Fuzzy logic in stating SOC

texts:
I am using a PIC18F controller and it handles a Battery Management system with Adc inputs..So the handling is based up on the Adc of Battery voltage and Current.I trust fuzzy can be used to determine states between High and Low.In this case How much Battery charge available is the State..and based up on that it will respond to the loads.So If the SOC is high it will use maximum load and if less minimum load.

I'm tired of using many conditional statements in the code.:) . I  have had a theoretical class on fuzzy while in college and i understand that we can judge properly the conditions b/w Full SOC and Low Soc.

Is it i'm trying unnecessary things to give high load to the system or on the right track.I just need the s/m to judge intelligently.
I will appreciate your inputs.

Thank you


texts: ARM Cortex M Power Consumption -- Sleeping with Higher Clock Speeds vs. Lower Clock Speeds

texts:
I'm starting with Cortex M processors, but I have lots of experience with 8bit MCUs.

Say I have a buffer that needs to be updated every 5ms.  There is an interrupt that goes every 5ms and the buffer is updated and the required calculations execute.  The MCU goes back to sleep, until the next interrupt occurs.

At 500KHz on my 8051 MCU, this task takes 3ms.  At 32MHz on my 8051 MCU, this task takes (made up number) 0.2ms.

On the 8051, I found that it required less current to actually run the MCU at 500KHz and sleep for less time between the 5ms interrupt, versus running it at the fastest speed (32MHz) and sleeping longer.

On a PIC, it was the reverse results.  It was better to run the MCU fast, and sleep it quickly.  (PIC has some great AppNote on power saving, and they call out both approaches.)

For the Cortex M processors, is it more energy efficient to run the system quickly and sleep it quickly?  Or should you aim for the slowest clock speed?

I understand this calculation is kind of task dependent, obviously if you need a 48MHz interrupt (or whatever the MCU max clock speed is), this is a moot point.

But in general, what have you guys seen when power profiling your systems?

I'm sure the Cortex M uses less energy per MHz increases per the datasheet, but I'll be darned if my 8051 says the same thing but in reality doesn't work like that at all when I started mixing in the power saving modes.


texts: Why are voltage and current directly proportional?

texts:
So, I thought I had an understanding of Ohm's law, but after thinking deeply about it, the direct proportionality between voltage and current doesn't make a lot of intuitive sense to me.

So, when I first learned about circuits, voltage in a circuit was compared to the height of a waterfall. However, according to Ohm's law, given a constant resistance, increasing voltage should increase current. But with the waterfall analogy, it doesn't make sense that a higher height would make more water flow per second. Simply making the waterfall taller shouldn't make water fall from the top any faster than it would if it were shorter. Also, the greater height giving the water more time to accelerate to a faster final velocity also shouldn't make for more current, because wouldn't that mean the individual water droplets would get more and more spaced out as they fell, so the amount of water passing a point per second would stay the same since the higher velocity of the water droplets is counteracted by a greater distance between them? So, why does simply increasing the difference in how much potential energy a coulomb of charge has between two points increase the amount of charge passing between those two points? I am having a bit of trouble wrapping my head around this, and I would greatly appreciate an intuitive answer to help me fully understand Ohm's law.


texts: How do they make photo lithography lens so accurate?

texts:
How are the lenses and other apparatus required for projecting a miniaturized version of the circuit using photo lithographic technique for IC manfuacture made?

Its known that even the tiniest spec of dust can ruin an entire chip so do you make sure the lens is perfectly clean and devoid of any distortions or scratches that may ruin the projection?


texts:
Do you use any protective gloves while soldering?

It has happened to me a lot that hot solderer touches my fingers.

I am not sure if protective gloves would reduce freedom of my fingers for their right job. Maybe I cannot keep many tiny elements properly.

What type of protective gloves do you use when soldering?


texts: Arduino (STM32) and MOSFET switch with digital pin

texts:
What circuit can I use to switch on a speaker with an arduino (stm32 board)? Ideally the speaker will run longer (automatic off after some time-0.5s)

I have a stopwatch program in STM32 (digitalpinread(low)-when i connect pin to ground=program run) and I need to run speaker-sirene when the push button starts the stopwatch in arduino (sirene ON from start stopwatch with some delay, maybe 0.5s). Is it possible with N-mosfet or what do I need for that?

When momentary push button is ON, the stopwatch will run in arduino software and for some time it should activate the sirene longer (c. 0.5s-1s). Start sound for runners :-)

Explanation example:

simulate this circuit – Schematic created using CircuitLab


texts: Why more, smaller transistors increase power efficiency?

texts:
Transistors, bjt, MOSFETs OK got it.
More transistors = better computing got it.

But compressing the transistors closer to each in my mind only helps reduce the physical dimensions.

So does a CPU or any electronic become more efficient because the transistors use less voltage? Does more computing reduce power usage, thus simply having more transistors the reason?

I am asking because as a newb and soon to graduate engineer, I think basic stuff like this is important to understand. But I always learned this concept as a rule of thumb and not by "first principle" or actual theory of transistor efficiency.

PS I did take a class in where the math of L and W was calculated and compared to new L' and W', reduced on a npn. The theoretical frequency increased but I don't think the math translation well in my head because I don't see how that helps power efficiency, only performance and/or area.


texts: What's wrong with my boost converter math?

texts:
I'm working some equations for a boost converter, and running into a contradiction I don't understand. Assume a steady state, perfect efficiency, and continuous conduction.

Total instantaneous energy stored in the choke is \$\frac{1}{2}LI^2\$

The energy stored in the choke changes as the choke current changes, rising during the on-time, and falling during the off-time. This change in energy is the energy transferred to the load each cycle. Total energy transferred to the load in a given switching cycle is \$\frac{1}{2}L(I_{peak}^2-I_{trough}^2)\$

By difference of squares \$I_{peak}^2-I_{trough}^2 = (I_{peak}-I_{trough})(I_{peak}+I_{trough})\$

The average input current of the converter is the average of the choke current peak and trough, \$I_{peak}+I_{trough} = 2\hat{I}_{in}\$

Define \$\Delta I=(I_{peak}-I_{trough})\$

Total energy transferred per switch is \$\Delta IL\hat{I}_{in}\$

Power transfer \$P=f\Delta IL\hat{I}_{in}\$

Basic choke equation \$V=L\frac{di}{dt}\$

During the "on" part of a switching cycle \$V_{in}=L\frac{\Delta I}{t_{on}}\$

Solve for \$\Delta I=V_{in}\frac{t_{on}}{L}\$

Substitute \$P=ft_{on}V_{in}\hat{I}_{in}\$

On-time times frequency is duty cycle, and input voltage times input current is throughput power \$P=PD\$

\$D=1\$

I've just proved that every boost converter on the planet must, inevitably, explode. I'm reasonably confident this does not occur. But I can't find the flaw in my assumptions or my algebra. Help me?


texts: How to find the best settings for Cyclic voltametery test?

texts:
I am trying to conduct a CV TEST (Cyclic Voltammetry). However, I am unable to get the current peaks on my plot. I tried different ranges of Voltage at different scan rates. However, I could not achieve any meaningful full result. can the test be successful if it is still not showing the current peaks?
The material I am testing right now is Agar (culture gel).
My plots look like:

I am scanning at 100mV/s and starting a potential of -0.1.
is there a way for me to find the correct range to locate my peaks or is it normal for some material not show them


texts: Does slowly charging a battery extend the lifetime? -Why?

texts:
Does slowly charging (like usb: 500mA) a battery of a cellphone/ tablet/ notebook increase the overall lifetime of the battery itself?

If yes: why is it ?
Why do LiIon batteries lose capacity over time (no matter how and when charged)?


texts:
I am trying to determine the feasibility of detecting a cable on the outside of an oilwell casing pipe.  The sensor would be run inside this pipe and the pipe is approximately 1/4" thick.  The cable could be as far as 2 inches from the pipe.

If I applied a current to the cable, is there a sensor that could pick up the current?

The cable, could be 20,000 ft long. Is this possible with today's technology?  What would be my major challenges?


texts: How to determine these resistors in 2-pole 2-zero feedback loop compensation

texts:
I'm trying to build a 2-pole 2-zero feedback loop compensation for controlling a full bridge dc-dc converter. It's my first time doing this and I'm following the book power supply cookbook. Book is not talking about these resistors or I'm mising something about them.

I'm using SG3525 and the error amplifier on it.


texts: How-to migrate from "Blue Pill" STM32F103C8T6 to stand-alone MCU?

texts:
I currently have a working electronic circuit using a "blue pill" STM32F103C8T6 board. It has/uses:

3.3V regulated supply (though if the STM32 could handle the regulation and provide the regulated voltage for the peripherals, I wouldn't mind)
1 SPI bus
2 I2C buses
2 Serial UART TX/DX links
4 digital outputs
And still missing, some way to flash the STM32

I want to migrate it to a PCB design using a stand-alone STM32 MCU, not a dev board.

How should the MCU be wired ? Which parts of the "blue-pill" should be replicated and which ones are not needed ?

Thank you.


texts: Differential gain on BJT differential pair: not symmetric?

texts:
I'm having the following problem. I got to analyze a BJT differential pair with emitter degeneration of both transistors.
I calculated the theoretical expressions of my gain and obtained (since the transistors are equal):

$$A_{d1}=-\frac{βR_{C}}{2(r_{π1}+(1+β)R_{E} )}$$
$$A_{d2}=\frac{βR_{C}}{2(r_{π1}+(1+β)R_{E} )}$$

The numerical values here don't matter for my question I guess.
Then I proceeded to simulate my circuit LTSPICE. As I expected, the values were slightly different from the ones obtained theoretically. What I did not expect was that the values of the gains were slightly different from one another, while that transistor are equal (there should symmetry on the circuit). Why is this happening?

EDIT:
Here is the schematic used

as well as the operating point:

V(n001):     6   voltage
V(vo1):  2.9365  voltage
V(vo2):  2.9365  voltage
V(n003):     -0.746863   voltage
V(n002):     -0.653111   voltage
V(n004):     -0.653111   voltage
V(n005):     -5.32863    voltage
V(n006):     -6  voltage
V(vc):   0   voltage
V(vd):   0   voltage
Ic(Q2):  0.00187503  device_current
Ib(Q2):  1.74223e-005    device_current
Ie(Q2):  -0.00189245     device_current
Ic(Q3):  0.000928333     device_current
Ib(Q3):  9.18252e-006    device_current
Ie(Q3):  -0.000937515    device_current
Ic(Q4):  0.000928333     device_current
Ib(Q4):  9.18252e-006    device_current
Ie(Q4):  -0.000937515    device_current
Ic(Q1):  0.00179235  device_current
Ib(Q1):  1.74223e-005    device_current
Ie(Q1):  -0.00180978     device_current
I(Rref):     0.0018272   device_current
I(Re2):  0.000937515     device_current
I(Re1):  -0.000937515    device_current
I(Rc2):  0.000928333     device_current
I(Rc1):  0.000928333     device_current
I(Vc):   -1.8365e-005    device_current
I(Vd):   -9.18251e-006   device_current
I(Vee):  0.00370223  device_current
I(Vcc):  -0.00368386     device_current

I notice that the current flowing in each of the voltage sources is a little bit different... Could that be the reason? And why are they different?


texts: Finding serial port on generic IP Camera PCB

texts:
Background story is that during firmware update of a generic IP Camera, with great wisdom, I managed to wipe part of the embedded Linux files, and in order to recover it, I need to access the bootloader through serial.

The PCB has no special identification, except for the strings "MP-3.4" and "1238" on the board itself.

Top view:

Bottom view:

First I looked for the J2 label, which from my understanding usually means JTAG or Serial port with this kind of generic camera.

My first suspicion laid upon the 4 connections at the top left corner of the top view:

I measures 3.3v between the two adjacent right pins, but the two to the left did not provide any output, and the Serial to USB adapter I am using remained silent.

I can identify all the chips on the board, as someone else with the same board described here, but could not find any schematics for it that would direct me to the Serial pins.

Do I have a better option other than brute forcing every pin that looks like it's not connected to any component? Is there some kind of best practice to follow when reversing such board? Anyone has any experience with this board?..


texts: Disposable Camera Charging Circuit - Will it transfer a maximum amount of energy?

texts: This may sound naive but I would like to build a toy coil gun. I have seen designs where a charging circuit from a disposable camera is used to charge a capacitor. What if I wanted to use more battery power to charge up a bigger capacitor? Would I encounter problems? Would larger components ruin that type of cheaply priced circuit board?


texts: Which wall charger for Beaglebone Green Wireless?

texts:
I'm trying to find an appropriate wall charger to power my Beaglebone Green Wireless (BBGW) through Micro-USB port.
Wall is 220v 50Hz.
Hardware Overview reveals a TPS65217C Power Management IC (PMIC).
Parameters

Iout (Max) (A) 1.2

Features

2-A Output Current on Power Path
Linear Charger; 700-mA Maximum Charge Current

Confused. How many Amps are enough?
(α) 5V, at least 1.2A
(β)  5V, at least 2A
(γ) 5V, at least 700mA

Seeed Studio BeagleBone® Green Wireless on Seeed Wiki
SeeedStudio BeagleBone Green Wireless on beagleboard.org


texts:
I'm designing an open source USB Type-C Switch (KVM Style), and I started to route the USB 3.x SuperSpeed+ and USB 2.x HighSpeed differential signal pairs on the PCB.
The switch will have 2 input + 1 output USB Type-C ports. The USB 3.x SuperSpeed+ signal are switched by two ON Semi FUSB340-s, while the USB 2.x HighSpeed ones using an ON Semi NL3S588.
As I don't have too much experience with routing high speed signals, I though to post a question here and ask your opinion about my PCB design attempt.
After some research, here is what I came up with:

the PCB will be a 4-layer one, probably with 1 mm thickness. The top and bottom layers will be signal layers, while the two inner layer will be ground planes

the differential signals will be routed on both on the top and bottom layers. According to PCBWay's online calculator, a micro-strip track width of ~0.23 mm with ~0.14 mm spacing should provide about 45 Ω single / 90 Ω differential impedance

the two tracks of each differential pair is length matched

no length matching between multiple differential pairs

clearance between the differential pairs is kept > 1mm (~5x track width)

This is what the USB 3.x and USB 2.x signals would look on the PCB:

(The PCB is about 40 x 50 mm. The two symmetrically places IC-s are the FUSB340-s, while the middle one is the NL3S588. Colors are Top:red, Bottom: green, Inner layers: yellow & magenta)
Now, I have some concerns mainly related to the following areas:

Vias - as there are many track to route, some vias on the differential pairs (2+2 at most) where inevitable - Is 2+2 vias acceptable on a USB 3.x (~5 GHz) differential pair?

Pair swap / flip - in some cases the two signals of the differential pair were in the "wrong order", so I must swap them to be able to route them to their destination. I did this using two vias on one of the singals. - Is this the correct solution?

Top & Bottom layer tracks crossing - I guess is not a problem, as there are two ground layer between them - Is this correct?

Differential pair length matching - when trying to match the length of the tracks in the differential pairs, I observed that KiCad refuses to insert "corrections" if they would be "too small" (but the skew is still > 0.1 mm). I tried to workaround this by adding "corrections" manually. - Is this OK, or there are some special rules I should follow?

(left: KiCAD, right: manual)
What do you think about the above concerns?
Any other thing terribly wrong with my design? Any other observations?
Thanks!

Update:
Here is a new PCB layout with the following changes

re-arranged some signals between the channels of the high-speed mux to better match the layout of the USB Type-C ports
removed pairs swaps / crossings, by swapping the signals in the schematics
re-routed all the signal on the PCB - the layout looks betters, and there are max 2+2 vias on any of the singal pairs
moved all components to the top layer
adjusted the skew tuning parameters to more reasonably sized pattern

What do you think?


texts: Can I convert my old Digital MIDI Keybaord Casio CTK 3000 into a MIDI device, which gives only midi output

texts:
Recently my midi keyboard was damaged and it is not powering on, But now I realize I don't really need many features including speakers of the keyboard. So I thought I can convert into a small portable midi device. So the circuit in the image is the one which is giving midi output. Also this is the only one circuit the keys are connected to. So if I can power that circuit up I think it is going to work as a midi device, How to  Power up only which pin should I connect to GND and power source, also how much voltage, Where can I find these details of a circuit board. The modal of keyboard is CASIO CTK 3000, and what are the precautions I should take. Also How can I power up the circuit with a USB cable from my laptop(if possible)
The 13 pins at the bottom of the image are the one, which is connected to the other board wich takes power input


texts: I am directly connect the Vin to isolation amplifier and observe the output, it clip at 2.5v at output,but we give 3.3v at highside,can anyone explain why this happen? here i am attaching the screenshots of my simulation.


texts:
I am working on a project which is going to have approximately 50 LEDs. These will be status LEDs to show whether an appliance is On/Off. I will also need a brightness control for the LEDs so PWM is a requirement on the pins.

What will be most efficient way (low cost, low PCB area and low component count) to accomplish such a thing?

I had a couple of ideas but then found some issues with all of them:

1) Get a micro-controller with too many GPIO - Controllers with 55 GPIO appeared to give the best GPIO/price ratio. I have selected one with 55 GPIO but even that controller might not be able to handle everything. Putting two micro-controllers complicates things.

2) Use i2c port expanders - These are very costly. I'd rather buy another micro-controller.

3) Use shift out ICs (595) - Lack of PWM. Implementing PWM on code side doesn't seem to be a good idea to me (maybe I am wrong but it feels like I am unnecessarily making things difficult this way).


texts: What are good resistance values for stepper motors?

texts:
I've got some NEMA standard stepper motors, and I've been measuring the resistances of the coils to check if the motors are bad. All 3 yielded the  same result, but that doesn't mean they're right.

The results that I got for the 4 connections (ABCD) I got the following:
AB: 1.9 Ohms
AC: Inf.
AD: Inf.
BC: Inf.
BD: Inf.
CD: 1.9 Ohms

Are these resistance measurements correct for a working stepper motor? If not, what would need to change?


texts: What good is an induction coil in a dimmer switch?

texts:
I asked about a dimmer switch, and was told one has an induction coil. What benefit is an induction coil in a dimmer switch?

  ZE-02S has induction coil built-in on the circuit board, so it is 5/8" longer than ZE-02.

http://www.ebay.com/itm/ZE-02S-Floor-Lamp-Rotary-Dimmer-Switch-500W-120VAC-Part-Replacement-Kit/171396948031


texts: definition of input/output resistance of a circuit

texts: Is input resistance always a small signal parameter or is also defined for large signal model of any circuit? How do we model any circuit after we calculate its input/output resistances?


texts: Looking for Serial-controlled PWM generator

texts:
I'm looking for a chip to generate some PWM signals. Here are my requirements:

Controllable via serial interface (SPI, I2C, or similar)
Outputs 10-20 kHz PWM signals (even better if adjustable)
Outputs should be basic logic level (open-drain, push-pull, etc)

Not constant current, buck, boost, etc. I've found plenty of LED drivers that can do this, but that won't work here.

Should be able to run on 3.3 V supply, but 5 V is OK too.
8 b resolution is good enough, higher is fine.

I've used (and love) the PCA9685. It works really well, and is very flexible and easy to use. Sadly it tops out around 1.5 kHz (or 3 kHz with fastest allowed external clock), so I can't use it here.

I found the LT8500, but it can only do about 6 kHz and isn't nearly as convenient (external PWM clock needed for example).

My end goal is to control 4 H-bridge brushed DC motor controllers from a Raspberry Pi. I need the high frequency to set the motor switching frequency, and I'd like to use a separate chip as the Pi will be doing various other tasks. I don't want to use software PWM, as I don't want to risk the motor going crazy if there is a software hiccup on the Pi.


texts: Reasons for using no conductor finish on PCB

texts:
Some PCB manufacturers, such as Eurocircuits or PCBWay, offer the choice of no conductor finish (vs ENIG, HASL, Immersion Tin, OSP or others). Since this option is not often chosen, it raises the price of small orders since the manufacturer cannot pool multiple orders.

In which conditions would this option make sense?

Could it be for a custom user-applied finish?

Could it be for situations where the surface finish would unpredictably augment the surface roughness, raising the line losses and raising the effective dielectric constant? This does not make sense since the copper will oxidize.


texts:
All of the sudden my ATmega328P stopped responding to flash commands with avrdude.
Here is the output of the attempt:

avrdude -pm328p -P/dev/parport0 -cstk200 -v -F -Uflash:w:./bin/main.hex:i

avrdude: Version 5.11.1, compiled on Oct 30 2011 at 10:41:10
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "/etc/avrdude.conf"
         User configuration file is "/home/darkhan/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/parport0
         Using Programmer              : stk200
         AVR Part                      : ATMEGA328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : PPI
         Description     : STK200
           VCC     =  (not used)
           BUFF    = 4,5
           RESET   = 9
           SCK     = 6
           MOSI    = 7
           MISO    = 10
           ERR LED = 0
           RDY LED = 0
           PGM LED = 0
           VFY LED = 0

avrdude: AVR device not responding
avrdude: initialization failed, rc=-1
avrdude: AVR device initialized and ready to accept instructions
avrdude: Device signature = 0x000000
avrdude: Yikes!  Invalid device signature.
avrdude: Expected signature for ATMEGA328P is 1E 95 0F
avrdude: NOTE: FLASH memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.

avrdude done.  Thank you.

make: *** [program] Error 1

I've used this micro for more than 1 year. But I don't think I've depleted its 10000 flash write/erase cycle count.

Last thing I've done was re-programming fuse with Reset Disable programmed:

avrdude -pm328p -P/dev/parport0 -cstk200 -Ulfuse:w:0x62:m -Uhfuse:w:0x59:m -Uefuse:w:0xff:m -i960

How can I bring my micro to life?


texts: External vs arduino power supply for servo motors?

texts:
I recently built a project that involves the control of three SG90 servo motors. I started off by controlling this through the 5V output pin of the Arduino Uno, with the Arduino powered through the barrel plug with a 9V mains power supply.

However, the servos couldn't perform the full 180° sweep, it would appear to be due to the high torque at the end of the motion for my application.

I then switched to powering the servos separately to the Arduino using four AA batteries in series. I now had no issues with the servos stalling and could perform the full sweep.

I am not sure why this is though.

Four AAs in series will result in 6V, which is not that different to the 5V Arduino output pin, and it seems the current is the issue with servo stalling. Surely the number of batteries makes no difference to this as connected in series it stays the same. Is the current of the AA battery just higher than the 5V Arduino output pin?

Any help would be greatly appreciated, I'd really like to have a better understanding of this.


texts: How to calculate resistor values for a Foot Strap test circuit using a window comparator?

texts:
I'm attempting to create a circuit to test ESD foot straps (and wrist straps). Research has led me to a window comparator circuit for testing power supplies that I've used as a base for the drawing below. I have a basic awareness of Ohm's law and the concepts of calculating resistance in parallel situations, however all of the examples that I've found are much less complex than this and I've been having a difficult time wrapping my brain around the problem.

My main question is:
How can I calculate the resistors needed to set the center of the window and the width of the window such that I can test for a specific Foot Strap/Human resistance? (I believe the resistors I need to change are R6, R8, and R11; and the resistance I want to check for is 1MOhm through 10MOhms)

A few other pieces of info that might help:

I have all of these components assembled on a breadboard and have verified that the original design will light the green/red LEDs depending on the resistors at R6, 8, and 11. This was very much a slightly educated trial-and-error test as I went through a bunch of resistors until I found a combination that lit the green LED.

I haven't wired in the footstrap/human yet; I intend to do so with a metal plate to stand on, and another metal plate to be touched by a finger.

The zener diode at D1 was supposed to be 2.5V but the samples that I have are quite variable; the one I've been using is 2V. This threw off the calculations from the original drawing which assumed 2.5V.

EDIT: Changed a whole bunch of things after reading the response by @Bruce Abbott

This might also be viewable, if I'm linking this correctly, here https://easyeda.com/jsparks/Foot_Strap_Tester-07b6faa6846f4842a7d5b95d6de361e0


texts:
I'm hooking up an LCD to my Teensy 3.2. All the connections are correct, except I had the contrast pin going to ground.

This results in the screen being filled with square blocks. If I tilt the screen I can see the text I entered is visible on the LCD so that confirms everything is working ok.

I tried to hook up a 1k potentiometer. Pin 1 to ground, pin 2 to contrast pin on the LCD and pin 3 to power. It seems that my potentiometers are dead, if I mess with the pins on the pot I get a brief display but nothing consistent.

I don't have any other pots to hand, so for the moment is there anything I can do to get a decent contrast to the display?

This is the LCD I have: https://www.amazon.co.uk/gp/product/B00ALNHTVY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Any help would be much appreciated.

Edit

I got some new potentiometers today, works fine :)


texts: Image position and size controls vs beam alignment in a color CRT

texts:
If you look at a the shadow mask of a color CRT, you can have a pattern like this:

Most TVs were purely analog and had knobs to move the picture horizontally and vertically. How does the green gun stay aligned with the green phosphor in an analog world?
it the deflection done by steps instead of continuously? (if that's the case this is probably not linear on flat screens?)

More confusing to me is that these TVs also have image size settings and then I wonder how it worked since, I remember these knobs beings just pots and I don't understand how the guns' beams could still be aligned with the mask.


texts: How do I provide constant voltage to a load?

texts:
Say, I have 5V supply and I use voltage divider to have 2.5V and 2.5V across each of them. Suppose, I want to power a microcontroller (input impedance of 200Ω) which requires exactly 2.5V but once I connect it   in parallel, the voltage across each component changes.
Is there a way to feed it using the voltage divider at constant voltage?


texts: Could anyone tell me what is the usage of the circuit within the red frame

texts: The whole circuit is used for measuring voltage, but I am wondering what is the usage the circuit of the red section and how to analysis it? could anybody offer me some anlysis? Pleas ignore some notes in this paper…


texts: How to find out Processor GPIO maximum source current and maximum sink current of that pin

texts: How to find out Processor one GPIO pin maximum source current and maximum sink current? In datasheet mentioned IoL and IoH, is it same for GPIO source and sink current also?


texts:
I am trying to make a Raspberry pi Bluetooth receiver. I finally got the raspberry pi to output audio via bluetooth, however the output seems like it is a modulated PWM. The width of the PWM seems to change (The falling edges shakes) when I start playing music. I dont know how to recover the audio.

I tried using a DAC but I have no idea how to even use it.

The Dac I have MAX544

EDIT 1: I have tried using a low pass filter with a cutoff frequency around 40kHz. I noticed something strange. I have put in a buffer for the signal (PWM) and as I checked the output its a triangle wave? Is this due to the op amp slew rate or is there actual filtering happening within the op amp? OP amp in question MCP601 Otherwise the low pass filter seems to work well.


texts:
I got a homework question as follows:

I was able to create triangle wave but I am having problem with the output wave. It is not exactly a square wave. What am I doing wrong ?

Simulate the Schmitt Trigger in the Figure 4 using SPICE. Sweep Vin form 0 to 3.2 and plot Vin
versus Vout when VDD= 3.2V. Determine the threshold voltages Vth- and Vth+ from the plot. Use
the following parameters:

NMOS : vt0=0.48 gamma=0.524 kp=1.02e-4 PMOS : vt0=-0.46 gamma=0.406 kp=5.16e-5

All the transistors have the same L = 60n and
W1 = 1.8u, W2 = 720n, W3 = 180n W4 = 1.2u W5=1.8u W6=180n

Here is my circuit:

Here is my output:


texts: Can I connect a MEMS mic directly to this spectrum analizer chip?

texts:
I have a ICS-40181 MEMS mic and want to do basic spectral analysis using the popular MSGEQ7 chip for the purpose of a sound reactive project.

Can I simply connect one into the other (with cap/res as directed) or do I need an amp between them? Usually the MSGEQ7 takes regular line-level audio. How do I know this based on gain etc?


texts: Safe shutdown circuitry for Raspberry Pi Zero with Adafruit TPL5111

texts:
I have a Raspberry Pi project powered by LiPo via an Adafruit Powerboost 500C.
Trying to maximize battery life without changing platforms (yet).

My solution is to incorporate the Adafruit TPL5111 to wake the device every once in while but shutting it down will be the problem.

The TPL5111 needs a GPIO shutdown signal from the Pi (so obviously the Pi is powered on to do that) but as soon as the TPL5111 receives that signal, power is cut completely.

Mounting the partitions as read-only is one way to minimise SD card corruption but id rather have circuitry that keeps the power flowing long enough after the signal is received for the Pi to shutdown safely.

Are there any (simple and small sized) solutions i could employ?
Maybe a simple capacitor setup or something?

Space is VERY tight as it is so that's issue number 2...

Thanks in advance!


texts: Properly Grounding Analog/mixed ICs from DC-DC Converter

texts:
I am making a PCB with an Array of current DACs, which need ~15V, so I'm using a boost converter followed by an LDO.

I've (tried my best) to layout the dc/dc & LDO per best practices but I'm still unsure about how I should be routing the ground from the analog ICs back to the Power "management" ICs to avoid improper return paths.

Right now, I've got a Ground Plane shared by all the DACs that is separated from the boost converter except through a fill that routes thru the LDO, I tried to highlight my ground plane in the pic.

Is this correct? following the thinking that I want to have the ground return from the DACs go to the LDO instead of to the , accounting for my poor layout techniques
Does it even matter that much??? Is it preferable to just mash the
Power/Analog Grounds together into one big ground plane.
Or am I actually screwing my design? I'm kind of worried i shouldn't have such a long path from the Li-ion (-) terminal to the Analog circuits ground like i have now.

Edit: Here is the annotated board.

Ground plane: Purple
7.4V from battery to VIN of Boost Converter: Light Blue
+15V Vout from Boost Converter to LDO VIN: Dark Blue
+12V Regd output from LDO to Every DAC: Red


texts: Electret Mic preamp for sampling and FFT

texts:
I'm working on a project in which I want to be able to have some light effects based on the ambient music.
I was thinking of sampling a mic and running an FFT, and set effects according to that.

Is that even viable to preform FFT on signal sampled from a mic (after amplification of course) for that purpose ? (quality wise)
Should I even bother with this ? Or just have a line in input instead ?

I will be using this Electret mic.
What kind of amplitude can I expect to get from it ?
How can I model it in LTspice ?

My system is running from a 3.3v regulator which is fed from 12v. The ADC (inside an MCU) would have a 3.3v reference, I would need to bias the signal with VDD/2.
The ADC is 12bit, Should i sacrifice the ADC resolution and have the signal swing less than VDD/2 (elimination the need for rail to rail op amp ?).

How do I choose an op-amp for this application ?
I guess I'll need a low voltage offset op amp (how low ?).
Should I power the opamp from the 12v supply ?
Should I throw in another linear regulator to power the opamp ?
Should I somehow split the supply ?

Thanks in advance,
Mike.


texts:
Consider the following circuit...

simulate this circuit – Schematic created using CircuitLab

Now suppose the resistor has infinite resistance. Then obviously the current through the resistor will be zero. Now if we apply Ohm's law to this situation then the voltage drop across the resistor will be zero (since the current through the resistor is zero). So it means that the points A and B are at the same potential. But that's not possible since a resistor with infinite resistance will drop all the voltage across it. Isn't it? So is Ohm's law violating itself?


texts: I want to check am doing this correctly before I waste a piece o pcb. I exported the image of my pcb then then I copied and pasted the image into a new document. Therefore I have two copies side by side then printed it onto transparencies. I've cut them out and stapled them together. Is the side with the ink (not the smooth side) I want pressed againest the uv coating on the board?


texts:
Originally i asked this question on DSP SE yesterday but untill now couldn't get even a single comment  so I am reproducing my question here as bigger audience is available here and also my question is also related to other subjects of EE such as circuit analysis and electronics
While studying the topic of filter design, I came across the following terms:

Factored form

SOS (second order sections) form

Rational form

Transfer function form

What is the difference between all these terms?
According to my understanding, the first two terms are mutually synonymous and are implemented in the same way in MATLAB, and the last two terms are also mutually synonymous and are implemented in same way in MATLAB.
Is my understanding valid?


texts:
does Arduino Mega2560 (based on ATMega 2560) has an input pull-up on analog inputs? Can I set the input pull-up as usual by software?

The reason is that I need to use the analog pins as extra digital inputs.


texts: Unable to figure out the Voltage levels of LED Strip Controller LPD8806

texts:
For each of the LPD8806, I am unable to figure out what should be the voltage levels of the Data In (DI) and Clock In (CI) pins?

I am trying to use this individually addressable LED Strip here.

I know that VDD has to be 5V but cannot figure out the voltage level of the Data In (DI) and Clock In (CI) on each of the LPD8806s?

Or is anyone aware of a similar product of individually addressable LEDs?


texts:
I want to power up about 2 meters of led strip from a 16.5v dc battery (4s lipo).

I know there are dc-dc converters, but I rather avoid using them due to weight (rc plane)

The lights will not be used very often, probably they will stay on for about 30 minutes.

I have read somewhere that I could plug few diodes in series with the strip, could this be a good idea? Are there any precautions to put in place (do diodes overheat)?

I am basically looking for a solution that works, not for the best practice, performance or top reliability...

Thank you!


texts:
currently i'm trying to interface Alexa LED/Microphone board with Raspberry pi. The big Alexa (1 Gen) has a 0.5mm pitch - I got an 0.1" adapter for this and it's working. Now I'd like to do the same with the Echo Dot, but the Dot has an alternating pitch. Can anyone suggest any kind of adapter for this FPC cable? The width of the whole thing is 11.4mm - nothing I could do by hand... :-)

Alternate source for image: https://de.ifixit.com/Anleitung/Amazon+Echo+Dot+2.+Generation+Flachbandkabel+austauschen/100828#s188942

Thanks in advance!


texts:
I have removed the webcam (Chicony CNF-9157) from an old laptop with the intention of connecting it up to a computer via USB. The webcam and the LCD were connected to the motherboard by LVDS. Supposedly this webcam has a USB interface according to a manual - see bottom of page 17.

I would like to know what I would need to do to connect this board (picture of connector pins) to a computer.


texts: Is this a good layout for a 5A buck converter?

texts:
I have updated this question with the suggestions in comments and answers. Make sure you read everything.

I want to make a PCB for a switching regulator (buck converter). It's a TL5001-based regulator, but this doesn't really matter since the layout is about the power stage, which is common to any regulator of this type.

Here's what I got so far:

The basic idea is to make a star ground. The center of the star is the connector on the right, which is the output connector.
I tried to keep traces away from the inductor (it's a toroid but I'm not sure how it affects nearby traces.
C7 is the input capacitor, placed near the MOSFET, to provide enough current during switching.
The small components (C8/R10 and C9/R12) are snubbers for the catch diode and MOSFET. Previous experiences with this circuit have shown I need a snubber, or else I get a ringing about 15MHz. 10nf+56R solves this. The datasheet only talks about a snubber at the diode, not the MOSFET.

There is no trace between the coil and the diode (thin yellow line) because I couldn't find a way to run a low-impedance trace there, so I'll just solder a thick piece of wire in place.

The rest of the circuit is the PWM controller (TL5001) and the MOSFET driver (2N2222/2N2907).

The feedback pin of the IC is not connected, but it's a solder pad (LSP1 on the left) because I would prefer to run a remote sense wire.

Traces will be rounded once i get a more definitive layout, to reduce EMI (I don't know if that's even necessary)

As you can see, the board is also single-layer, as I don't have the capability to do double layer boards at home, so ground plane layer is out of the question

I would prefer answers to stick to the topic here which is the LAYOUT of the board. I'm not interested in answers regarding:

The converter IC: Yes, I know there are better ones that are faster, cheaper, and every other adjective you can throw at it. But I have a few TL5001s.
The MOSFET driver: Yes, i know there are dedicated MOSFET drivers. But this pair of 2222/2907 does the job I need.
Double layer boards: as I said before I don't have the capability to do double-layer at home.
"But you can have them made for cheap!": Yes, I know. I also know I could just buy a converter, and even save myself the headaches. But I CAN'T have boards made (3 month delays at the post and import restrictions).
Anything unrelated to layout of the board.

EDIT:

Here's a schematic. Vout for me is variable 2-12V, Iout is 0-5A.

EDIT 2:

Here's the schematic corresponding to the layout. There are minimal component changes (addd R13, R14 for slew rate limit, R12, C9 for snubbing mosfet).

Edit 3:

This is the final board I built:

Picture of the finished board:

And here's a video of it in action: http://youtu.be/NXNk-duzGrI


texts: Input and output impedance of a circuit with a BJT

texts:
[The small signal circuit]

Hey, so in this circuit i already figured out the input and output impedance without R1, easy stuff... But now i want to know them with R1 included.

For the input i want the impedance with R1 and R4 , using small signal mode (hybrid-pi model) i'm not sure what to do. For the output R4 is not included.

What advice you guys can give me?


texts: Low power, low performance stepper motor

texts:
I am looking for some small (and cheap) stepper motors that can be driven with <3V and a maximum current draw of 100mA. I'm trying to drive one using a lithium coin battery. Torque can be very low, e.g., 0.01kg/cm.

Any thought appreciated.


texts: Power off detection circuit to close opened latching solenoid valve

texts:
The image above is referred from this SO link. My use case is the following:
A latching solenoid valve, which would be run using 4 AA batteries (6V)
Solenoid Valve (9 Ohm) operates at 6V under 40ms pulse. I'll be running a microcontroller (ESP 12E), which would go into deep sleep to save power. Since this is to be used in remote places, hence latching solenoid powered by AA was chosen.
I don't want a scenario where if battery dies after some weeks or months of operation, one day if the solenoid was turned on, and remained like that, will end up wasting water for a long time (since someone would inspect site only once in a day) before being noticed.
So I looked at the above circuit diagram, and I was thinking how to minimize the power wastage in the voltage divider (R1/R2) circuits. Of course I could increase the R1/R2 such that they are in 100K ranges.
Questions:
Is it possible that due to extremely low input current the GPIO IN would not be able to detect the falling pulse? Is there any minimum current for a GPIO (ESP 12E) to detect the falling voltage?
Also, I'm planning to use AMS1117 to step down 6V to 3.3V needed for ESP 12E. What kind of energy loss can I expect when the ESP is in "Normal" mode and when in "Deep-Sleep" mode?
The reason to use the voltage divider power off detector circuitry is because of its simplicity (I'm no electronics expert) and and cause its cheaper than other solutions.


texts: where do i find max short circuit current of photodiode?

texts:
I'm trying to convert the current signal from a photodiode to voltage through a transimpedence amplifier.

The photodiode is put in photovoltaic mode in order to get the greatest accuracy and lowest possible dark current, which means that the cathode is connected to the invetering input of the amplifier.

Furthermore, in order to get a greater amplification and avoid "minus" voltage on the output, I intend to raise the voltage on the non-inverting input.

I'm now realizing that my photodiode only states a "typical" short circuit current at 100lx, but no maximum current.

http://www.farnell.com/datasheets/8765.pdf?_ga=2.139995315.1420390384.1543406751-57595970.1536135582

I intend to do this in a 5v circuit, and ideally ≈5v from V_Out should resemble the maximum current from the photodiode, and obviously vise-versa ≈0v the lowest.

Since I don't have a minimum and maximum output current of the photodiode in photovoltaic mode, I have a hard time understanding how i should determine the values for hence the offset voltage and the resistance for the feedback resistor?


texts:
Could anybody please help in understading the digital waveforms which are combine with clock and data ?

In the above Picture SCL is normal clock waveform, this can easily readable like High time, Low time.

But here in SDA its like two signals waves merged together seems !! So, Please any one expalin this

Note: this one I2c Waveform


texts: removing the pop noise when amp is switched with passive components only

texts:
I've recently bought this little 2*3W USB-powered amp and it is working pretty well with my old Panasonic boombox speakers (rated 2.7 ohms, 15w peak input).

However when switching off the USB power i hear a "pop" noise from the speakers.

I've seen there are pop-suppression circuits to avoid that, but i'd like to go with a passive solution not requiring any extra power.

So can i just wire 2 slide switches like these in series with the speakers and manually flip them before turning off the amp?

Are the switches better wired on the positive or negative side of the speakers?


texts: I am totally new to LT-spice and i want to simulate a model for PV panel. i followed a youtube video as itas, but my circuit is not working. i have no idea about the errors it's showing. please help. I'll post snapshots below. the main circuit is about pv panel and sub circuit is a simulation model for single solalr cell.


texts: 4-bit synchronous counter IC: Do I need to pre-synchronize the count enables? (Metastability?)

texts:
Using a 74LVC163 synchronous 4-bit binary counter and would like to predicate the counting on an asynchronous signal.  If I apply this signal directly to one of the enables (e.g. CEP), am I assured that the counter will either count or not count when clocked?  Or might it get into a metastable funk if clocked when the enable is neither high nor low? (Possibly resulting in outputs changing long after a clock, for example.)

If metastability is a concern in this scenario, I can synchronize the enable signal through a couple of flip-flops before it reaches the counter.  Not a HUGE deal.  Just wondering if that's truly necessary for reliable operation.  If it isn't, I'd love to save an IC.


texts: How to design a circuit that works on both negedge and posedge

texts:
I have a clock phase bit which decides on which clock edge the design must work. I cannot use an always block inside an if statement. Is it possible to use

`ifdef

statement? will the `ifdef be synthesizable?

Thanks


texts: How can I connect fuel level sender to a gauge and micro-controller simultaneously

texts:
I have a fuel level sender in a tank that ranges from 18 - 180 ohms (standard euro range) and is connected to a standard gauge that measures the resistance.
I'd like to connect it to a micro-controller to feed my on-board data streams.

Removing the gauge I can connect the sender to (say) an Arduino quite trivially using a simple voltage divider circuit, but how can I connect it to the gauge and Arduino simultaneously whilst keeping the resistance (as perceived by the gauge ) as 18 - 180 ohms


texts: Starting with pic programming dspic30f2010

texts:
I'm pretty sure that it's a duplicate in some way but I have to ask anyway. I'm pretty new to chip programming and I got some results using arduino but I still have no idea how to use the pic board my friend gave me.

http://www.futurlec.com/dsPIC30F2010_Board.shtml

It looks good so far. I have 3 cables but I have no idea how to download a program to the board. My question for now isn't that much related to compilation. I have some sample hex files that can be downloaded to the board.

usb -> rs232 (plugs in lights are lighting)
db9 -> rs232
db25 -> 10 female plug (no idea what's the actual name for that plug EMPIC or something)

Since I only have a laptop the only usable cable is usb. I could probably find adapters for the other cables but yeah.

When I plug the usb cable, leds will light and it seems that current is working. On my db9 cable, it's written download rs232 So I kind of assume that downloading a hex file using the rs232 plug should work. But after reading, I believe that this plug might be just for use with the chip and not for programming the chip.

http://www.futurlec.com/Pictures/dsPICBRD4_600.jpg

You can see there that it's just above "download ET-EMPIC"

I can take pictures of my whole set if something isn't clear enough. I'd really love to get working on that chip. I read some of the spec about the chip but couldn't really find anything on how to get started. It's as if people who wrote documentation are assuming that people already know why programmers exists (quite confusing term to be honest), how to use them and how to make things happen.

I'm quite confused and don't understand why it's so hard to actually get something on the board. If someone can help me downloading a hex file to that board I'd be the happiest man on earth for some time.

As far as I understand, this board should be enough to be used without a programmer. But i'm guessing that I have to use the db25 to empic plug. If I have to buy something then I'll probably purchase it. I was also thinking about making my arduino board work as a programmer for my dspic but this isn't really a good option.

Also something I don't understand. The powersupply is requiring 16v while in the docs, I read somewhere that while downloading a program I should supply not less that 14v to the board. I know that my usb cable are providing not more than 5v. Any reason why the programmer would require so much to download the program?

edit

After a bit of research, I found that:

http://www.etteam.com/product/06A07.html

ETT is the actual constructor of the board. Problem is that it's all written in thai. In short I believe it says I have to use winpic800 using ICP plug. It should be possible to program using the ICSP pins but I'd need an external programmer.


texts: Why are tapped transformers needed in RF amplifier circuits?

texts:
I'm not really sure why, but I have seen many different RF circuits in which the input to a transistor is taken from a center tap instead of across the entire secondary, such as this example:

Why is the input taken from the tap instead of across the entire secondary?, I don't understand the need for the tap.

Sometimes also the output might be connected to the tap instead of the bottom side of the primary like this example:

And in some extreme cases, like this IF amplifier, only the tap is used, the outer end of the primary is left disconnected.

What is the logic behind this?


texts:
I would like to make a dimmer for several ikea desktop LED lights. This one is plugged on a LED driver (adapter) with specifications:
Primary:220-240VAC 50/60Mhz, 0.06A
Secondary: constant current: DC 500mA, 2.5...3.5V max 3.8V.

What's is the better? To interact with the DC side and low voltage or with the AC side?

We're going to make a DMX installation so there's a lot of work, and we would like to reuse it, so if it works with AC lights too it's better.

I've searched and would like to use this one:
http://www.instructables.com/id/safe-and-simple-AC-PWM-Dimmer-for-arduino-Raspberr/step3/AC-PWM-dimmer-with-arduino/

Would it dimm the led? I understand that LED are not linearly related it terms of voltage/lumen relation, but would the driver change a lot? can i go from 0V to 3.5v in order to fade in/out it?

Thank you a lot for your help :-)

PH


texts: STM32 Nucleo board, SD card displaying symbols instead of numbers

texts:
Devices: STM32F4

The SD is working and the data is saving on the SD, but the problem is that the integers are displayed as symbols in this SD. So I think that the problem is that the function I used needs char, and the data is int, so is there any way to convert int into char for 2 digits?

Code:

while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
        HAL_RTC_GetTime(&hrtc,&sTime,RTC_FORMAT_BIN);
        HAL_RTC_GetDate(&hrtc, &sDate, RTC_FORMAT_BIN);

char month = sDate.Month;

        /* Mount SD Card */
  if(f_mount(&fs, "", 0) != FR_OK)
Error_Handler();
  /* Open file to write */
  if(f_open(&fil, "second.txt", FA_OPEN_ALWAYS | FA_READ | FA_WRITE) != FR_OK)
Error_Handler();
  /* Check free space */
  if(f_getfree("", &fre_clust, &pfs) != FR_OK)
Error_Handler();
  total = (uint32_t)((pfs->n_fatent - 2) * pfs->csize * 0.5);
  free1 = (uint32_t)(fre_clust * pfs->csize * 0.5);

  /* Free space is less than 1kb */
  if(free1 < 1)
Error_Handler();
  /* Writing text */
    if(freq <=120000 && freq>= 80000){
          f_puts(&month, &fil);
  f_puts("\n", &fil);

    }
  /* Close file */
  if(f_close(&fil) != FR_OK)
Error_Handler();
  /* Open file to read */
  if(f_open(&fil, "second.txt", FA_READ) != FR_OK)
Error_Handler();
  while(f_gets(buffer, sizeof(buffer), &fil))
  {
    //printf("%s", buffer);
  }

  /* Close file */
  if(f_close(&fil) != FR_OK)
Error_Handler();
  /* Unmount SDCARD */
  if(f_mount(NULL, "", 1) != FR_OK)
Error_Handler();

  }
  /* USER CODE END 3 */
}


texts: Overshoots and ringing...Do I need to compensate my probes or is it bad line termination?

texts:
When working with my DSO (Rigol DS2072A) I recently observed that signals have overshoots and showed some ringing as in the image below (it's a 2 MHz digital signal, SPI from a µC).

I use the 10:1 probes that came with it (10MOhm for 1MOhm inputs, 350MHz Bandwidth, type PVP2350, Datasheet of mostly similar probes) and compensated them to show a very clean signal when connected to the inbuilt test signal (1 kHz, 5V) of the DSO. They only have a low frequency compensation screw (6 pF ~ 24 pF).

Now I wonder, if I should compensate my probes when connect to a higher frequency signal (as in this case) or if these are 'real' issues due to bad line termination or whatever ... and compensation would be lying to myself.

AND: How do I actually find out, if the overshoot is real (or caused by probing itself)?

EDIT:

To enable other people learning from it (and serving as an example of what NOT TO DO) here are some photos of my setup. And my changes to the wiring and how this influences the result.

Reconstructed setup for above measurement: Lots of jumper wires and a breadboard to interconnect them. Also the probes are not directly connected to the breadboard/cables, but even more jumper wires! The ground clip is connected to a resistor leg, which is connected to GND-lane of the breadboard (having a connection to the board in the upper left, the signal source). However, the jumper wires and breadboard are not the main issue... as you will see in the next images.

To test my new knowledge, I tried to get as close to signal source as I could. As a next try, I connected the GND-Clip and probes directly at the board pins as shown in the next image:

However, it still didn't look that nice:

I wondered, if these jumper or the breadboard were the issue. But, it turned out that the main issue was the -second- GND-Clip. I did not connect the GND-Clip of the second probe, as I thought there already is a good GND-connection. I connected the other one too... to the resistor leg as shown above. Knowing this was not an optimal choice for the clip (as there is a longer path between the two GND connections) I did not expect much of a change. However, THIS was the main issue in this case:

Doesn't this look MUCH better?! Surely, not perfect... but, if you look at the setup this seems to be a very acceptable outcome. Especially, this explains why the ringing at the data channel (blue/cyan) was much worse than the clock channel (yellow)! BTW, keeping both GND-clips connected to the resistor leg instead of one directly to the GND-Pin at the board, gave approximately the same result.

In case you wonder, what the sole influence of connecting both GND-clips is. I switched back to the setup above... using jumper wires to connect the probes, but connected both GND-Clips to the resistor leg this time.

The result: Yes, both changes had a noticeable influence. However, connecting both GND-clips seemed the more important one. Connecting the probes close to the source reduced ringing even more.

If you wonder how the signal looks like when probing directly at the pins of the receiving board (pin headers not directly at the chip, GND-clips still at the resistor leg):

Looks very similar to probing somewhere in the middle of the cable using jumper wires... So probing there seems to give quite realistic results on how the signal looks when it arrives at the receiver.

Thanks to all your helpful input. I hope this helps others improving their probing!


texts: Typical wavelength range for solar cell measurement

texts: Why is a wavelength range of 300nm-1100nm usually used to investigate the properties of solar cells (EQE, current generated, etc.)? Is it to reduce spectral impact? I also don't understand what is meant by spectral impact...


texts: How do you use Gain Bandwidth Product to estimate bandwidth at different gains?

texts:
I was doing a question related to the dependence of op amps on frequency.This question is from 2nd year electrical engineering micro electronics by sedra smith.

Here is the question:

So there is a non inverting amplifier and it has a gain of 96. it 3db frequency is 8kHz. I can find the unity gain frequency from here from the given quantities. But for what?. Then they mention that the system is required to have a unity gain frequency/bandwidth of 32kHz.
So this is pretty confusing for me. Can some one explain the question please.
Thanks guys!


texts: (Inductor) Low-pass filter for current signal

texts:
I'm using resistors in a series circuit to vary the resistance between a constant 12V supply line and ground.

Using transistors, the current either flow through all resistors, or is routed to ground after one of the resistors.

This creates a current signal in the tens of mA range, corresponding to which transistors are switched on or off.

Per specification, the slew rate of this signal should be between 6 mA / µs and 28 mA / µs.

To limit the slew rate, I previously used high value resistors on the base of the transistors, making them take longer to reach saturation.
It has been brought to my attention that this might not be the cleanest way for the NPN transistors to operate; instead I should simply turn them on and off without such long delays.

Using an inductor in series with the resistors seems to work, but the inductors characteristic curve seems undesirable - the slew rate may exceed the maximum slew rate in the first part, and tapers off to a slew rate far below the minimum slew rate.

Is there a way to low-pass filter a current signal which results in a more linear gradient between two current levels?


texts: Output related to input in diode circuit

texts: I have to find the output voltage Uo related to the input voltage Ui knowing that the input values range from -10V to 30V. I started by assuming that D1 is reversed biased. But then how do i know if D2 is forward or reversed biased? I think i have to take that D2 is forward biased so i can find the Voltage at the node with resistors 10kΩ-10kΩ-10kΩ and then be able to define the range where D1 conducts. However, i am not sure. All diodes are ideal. Any help is appreciated! Thanks in advance!


texts:
The layer stack manager has created a power plane for me on which there is a default polygon pour that is the board size :

For some reason I can't do a polygon pour on that layer... I would like to have multiple power nets on the power plane, but even if I remove some of the automatically placed polygon, I still can't do a polygon pour.

How can I split my power plane to fit multiple power nets?


texts: Chebyshev filter - theoretical vs simulation gain

texts:
Question is about the gain peak (or maybe more suitable would be growth) ocurring in higher frequencies (>20kHz) in Chebyshev filter 4-th order in simulation (simulated using Bode Analyzer in NI Multisim) - what's the reason for this? Theory shows that gain is going still down even up to -150dB, however simulation shows minimum at about -120dB. Is that because of some capacitance effects ocurring in op-amps or something else? I found similar problem to mine, but the grounding there and op-amp was quite different (Unexpected behavior of the Sallen-Key second order filter).
Below theoretical gain based on formula:
$$
A(f)_{dB}=20\log{\left\lvert\frac{k_0}{(1 + a_1(\frac{j(2\pi f)}{\omega_g}) + b_1(\frac{j(2\pi f)}{\omega_g})^2)(1 + a_2(\frac{j(2\pi f)}{\omega_g}) + b_2(\frac{j(2\pi f)}{\omega_g})^2)}\right\rvert}
$$
and chart for this:
The result of the simulation is shown below.

In higher frequencies like 1MHz gain continues to go up. The circuit was constructed based on the Sallen-Key scheme - schematics of the cicuit below.


texts:
Boost converter PTN04050C is used to generate 5.3V from a 3.7V Li battery in a battery powered device. The 5.3V will be used to generate 3.3v (using LDO) for microcontrollers and +- 15v & 5v for ADCs, DACs and opamps.

Question: How much ripple voltage can be allowed to exist in the circuit? The boost conv generates around 15-20mV ripple at 600kHz (best case scenario with a pi-filter) which will pass through the LDOs without much attenuation as they have poor ripple rejection at this frequency.


texts:
I am working with TI's CC2533 SoC Low Power RF

I bought a few chips and assembled a few PCBs.. Using TI's debugger I confirmed that I can send and receive packets using the basic RF using the RFStudio.

Something I have not realised is that TI does not have an IDE for this and uses IAR Workbench 8051 with a TI downloadable SimpliciTI Protocol stack that is supposed to plug into IAR.

The problem is that the software is only 30 day trial and costs nearly 2000 dollars.

Has any body here compiled any firmware using some opensource or free IDE for this series of SoC?

As I jumped off the Arduino band wagon straight onto this.. I assumed there would be an IDE available for general use.. especially because I bought the official dev kit.


texts: Would floating a Lithium battery indefinitely at a lower voltage than max voltage cause any harm?

texts:
As a rule of thumb, charging should be terminated when the charging current drops to 0.1C at constant voltage phase of lithium battery charging. Membranes would have over stressed otherwise, which means "damage" to the battery.

What if we set a lower CV? For example, what if we set 4.1V as CV phase for a Lithium Ion battery and keep it under charge indefinitely? Would it still cause any damage?


texts: What is the difference between relative stability and absolute stability

texts:
Is there any difference between relative stability and absolute stability?
Do all the control system analysis techniques (Root locus, Routh-Hurwitz, Nyquist, Bode plot) are able to find both stabilities?


texts: My school uses HY 3005D-3 but I want to do it myself to save on $. Before opening it, I ask for tips about: not-to-break-it, cheap DC supply and DIY-materials (not that I know them soon). So how to build, to get cheap DC Power supply with such adjusting knobs?


texts: How to solve a a full wave rectifier with two diodes and a ground in the middle?

texts:
This is the problem

I am trying to follow along with the solution but I don't understand what is happening, how do I handle the random ground in the middle?? is the node between d1 and d2 40Vpeek and is the node between r1 and r2 -40V peek. I need some more explanation because I don't know what I'm not seeing?? Any kind of help is greatly appreciated, Thankyou!


texts: Using laptop charger with slightly higher voltage

texts:
I am wondering if it is safe to use a MacBook charger on my Lenovo laptop. Both devices charge via USB C PD. When looking at the voltages I can see that the Lenovo adapter is 20V - 3.25A

The MacBook charger has 20.2V - 4.3A

I am wondering if the .2 increase in voltage with the MacBook charger should be cause for major concern.


texts: can one increase computing power by reducing frequency and increasing transistors count

texts:
I have had the following idea / opinion in a long time, but I am not sure if it is true.

From what I understand, in a processor, coarsely the voltage U required to operate is proportional to the frequency f at which it is run, and the computing power is proportional to the number N of transistors present and the frequency f.

Therefore, one could:

divide the frequency of the processor by k, allowing to divide the voltage by k
increase the number of transistors by k^2

This would in turn give a computing power increased by a factor k (increased by k^2 because of the number of transistors, decreased by k because of the frequency), for an electric power unchanged (power is U^2/ R * N where R is the electric resistance, U is divided by k, N is increased by k^2). If Moore law gives more and more transistors for the same price, then you should have no limit to the computing power you achieve (at the cost of reduced frequency and possibly requiring parallel hardware and algorithms).

Is that reasonable (or even true), or is there an underlying error? Naively / loosely, I think about this as an explication of why the brain is so much powerful while using a bit less energy than a CPU (brain is typically 20 watts and 100Hz, CPUs nowadays often from 35 to 130 watts and 3GHz, some people say ).

Edit 1:

Yes, I know that the energy consumption / power consumption is the wall that processors are meeting. Here I talk in terms of voltage (before converting to power consumption) because it is what predicts (or so I believe?) which frequency one can run at.
The computing power does is proportional to the number of transistors. For example, one can simply build more cores given more transistors. The problem then is power consumption; this is why I consider a decrease of frequency, so that power consumption increase by increasing the number of transistors is zeroed by the power consumption decrease due to running at lower voltage (and, hence, frequency).
I know that this will not increase the one thread execution speed, and will require parallel algorithms, but this is not the question. In the same way, architecture is not the question either. I am aware that manufacturers now add more and more transistors to the caches etc to increase one thread execution speed / reduce latency, but this is not what I ask for here. Here I ask only about whether a very general scaling argument is true, then using this scaling with parallel software is another question.
By the way, we are getting better at using parallel architectures: Artificial Neural Networks on GPUs are all about it. This is exactly the idea behind the brain also: very slow at one thread operation, but incredibly parallel and powerful computing power. What I want to understand really is: given the silicium technology used on current transistors, can we in theory if Moore law holds (i.e., we get more and more transistors for the same cost) build something as powerful as the brain that does not use megawatts or more. For this, it sounds that the solution is to increase parallelism, and reduce frequency (as in the brain). For example, if my scaling argument holds, you can get the frequency of your chip from 3GHz to 100Hz (i.e. divide frequency by alpha = 30 millions) and by adding a LOT of transistors (alpha^2, but if you expect Moore law to hold, we will get it ultimately), and therefore increase the computing power of the chip by the same 30 millions factor. I agree, this is not that straightforward to pack so many transistors, maybe you would need a 3D chip (like the brain) or another architecture change, but I am just interested about the scaling.


texts: Why are complex numbers used in electrical engineering?

texts:
When I was in high school, I asked a physics teacher "Why do we use complex to calculate stuff with electricity?" (something along that line) and he said "Because it just happens to work" without further details on WHY it works.

I'm in CS/IT and am not very well-versed in EE or abstract maths (though I know enough of the basics to make some robots simple.) As I learned about EE basics, I've learnt that complex numbers are VERY useful in EE and complex analysis is a must for students of EE.

I know complex numbers work well for calculating stuff in EE, but WHY does it work? In CS, I've learnt about how logic algebra works and why its maths works and have a pretty good fundamental understanding of it. Complex numbers, however, still seem quite abstract to me. "It just works" doesn't sit quite right with me.

So, how and WHY do imaginary numbers work to calculate stuff in EE?

Edit:

I'm well aware that complex numbers are used in EE like this. However, what I'm asking is, I think, even more mathematically fundamental. Why do complex numbers work here at all?

They only possible answer to this I've seen so far is because of Euler's Formula:
\begin{equation}
\label{Eq:I:22:9}
e^{i\theta}=\cos\theta+i\sin\theta.
\end{equation}

Is that it? Is that the sole reason complex numbers are used?


texts: Project ideas for five hundred AT89C52s?

texts:
I happen to have some 500 old AT89C52 controllers and am looking for ideas how to use them in a project. That's an 8051-based controller with 8K Flash, so you get an idea. And no,  trashing them is not a project! :-)
I remember that in the 80s Steve Ciarcia (of Circuit Cellar fame) wrote in Byte Magazine about a "supercomputer" he built with sixty-four 8048s. Nowadays a quad core Pentium will easily beat five hundred 89C52s, so maybe that's not the way to go. Instead I'm thinking of a series of separate devices, each with its own controller (where a single Pentium would be of little use).
Suggestions?


texts:
I'm a newbie that happened to make a home-made solar panel that outputs 18V and 6A without a load. I'm planning on charging a 12V battery bank through an MPPT or PWM. I've been researching what type of blocking diode I should put on my solar panel and I'm getting confused.

I have a couple Zeners on hand, but I know the reverse voltage on them is far too low. I found out that Schottky diodes are often used as bypass diodes for solar cells, but read that they also have low reverse voltages and high reverse leakage current which didn't sound suitable for a blocking diode. Normal silicon diodes seem workable, but I don't like the voltage drop of ~0.7V compared to the Schottky's ~0.45V.

So what diode should I use? Should I just take the hit and lose 0.7V with the silicon diodes? Or is this a moot point because the MPPT/PWM would take care of this (if so, what if I wasn't using an MMPT/PWM)?

Thanks in advance. Cheers!


texts: what's "wrong" with diesel generator power?

texts:
The electric company was working on the power lines for four days out in the woods, so they put our street on huge diesel generators (each was the size of a small car) that ran constantly to supply us with power. Everything worked fine, but I noticed some anomalies:

My roof solar panels were not working.

The clicking "igniter" on the gas range clicked faster than usual.

The microwave, when cooking, made a louder higher noise than usual.

So my question is: what was "wrong" with the power coming through the lines that distinguished it from what comes in normally? How did these appliances "know" something was odd? Was the Hz too fast?


texts: Impedance discontinuity problem at transmission line?

texts:
I am confused about how the waveform will be to the left of discontinuity. Please help me understand it better.

Here is my understanding:

When the unit step hits the inductive discontinuity, at the discontinuity there is peaking to twice the magnitude of the incident unit step followed up by exponential decay down to input unit step value.

My doubt is :

However i don't understand how the rise time is affected and what happens to the waveform which is reflected off the discontinuity !!


texts:
I am trying to improve my grounding skills

This is a RJ45 connector on one side, a signal transformer, and a pin header on the other side (this is a prototype, and i am splitting the design in parts for simplicity)

The idea is to connect this to a switch ic later.

So, I have a earth ground on the border, and a ground solid place with only 1 point to gnd under the diff pairs.

What do you think?


texts: How do energy harvesting ICs like LTC3106 and LTC3105 safely charge lipos?

texts:
I'm designing a simple device with a single cell LiPo that I want to be chargeable from a single solar power cell. As I start to look through the data sheets, I'm seeing that the battery charging is typically done just by providing a constant voltage output to the battery.

For instance, LTC3106, page 19:

Or LTC3105, front page:

Note position of batteries in line with the load??

These circuits seem to be designed to charge the batteries in question by providing a constant 4.2V power to a single cell battery. Is this really safe? Is this equivalent to trickle charging? Everywhere I've read that a LiPo needs a very specific type of charging discipline, such as MCP73831 (which I use in all of my projects without issue.) For instance, is it actually safe to charge a single cell lipo with a constant-voltage, variable current source and no cut-off?

Can someone more familiar with battery chemistries and charging process help enlighten me? (PS: I am not EE-trained, I am a home hobbyist.)


texts: How to design a circuit to disconnect battery charger automatically?

texts:
I want to use an AC to DC 14.4v adapter to supply both my circuit and its battery.
The circuit works with 12v and I used a battery during power outage(blackout time).
I have prepared the below circuit for switching between adapter and battery but I need to recharge the battery when power comes again.
Assume the dip switch as main power key.

The main problem is that if I use an op-amp as a comparator for battery voltage level, it will shows the adapter output voltage not battery level. So how can i solve it?

And another problem is:
suppose we are in blackout time and battery voltage level decreased to for example 9 volts. How can i disconnect the battery? Is it possible to use a MOSFET transistor something like IRF510 between battery and circuit?

Many thanks.


texts:
I gave a motherboard circuit board to local a repairing professional. He traced and soldered some chips but it is not still working  and advised to show motherboard to manufacturer service center.
But my motherboard now has yellow stains after marks of soldering or maybe soldering flux paste. I am attaching photographs of the soldering marks for your reference.

Before showing to service center I want to clean those yellow marks as   some service center technicians  make excuses  if it has been soldered by local technicians - they may refuse to even touch or find the problem.
I have tried to clean by isopropyl alcohol, but the marks are still there.
Can someone advise or suggest how and by which chemical can I clean the yellow after marks solder or solder flux paste?


texts: Copper weight/thickness current capacity

texts:
i have been reading about how Copper weight/thickness is important in several areas of PCB design. The thickness and width of a trace determines the amount of current (amps) the trace can carry. The thickness is also used in the calculation of trace impedance (ohms) in RF and high speed digital circuits however i have yet to find numbers or at least a simple chart that explains the amount of current per copper weight ( kind of like the 40mils per amp rule)

For example how much more current can my 40mils track carry at 1 oz vs 6 oz copper weight?

also, i have yet to se a track burn itself down by the excess current, i have been using the 40mils rule always, how can i be sure o make my pcb safe enough to carry up to 8 amps without using 320mils tracks? (lets assume im limited to 200mils)


texts: Switching different loads without voltage drop

texts:
I want to switch different loads on my battery (V1 & R1). R1 is internal resistance of the battery. THe battery is a cr2032.

The reason i want to switch different loads is because i want to calculate the internal resistance of the battery under different loads. The problem i am facing is that when i switch the 10ohm battery on, the drain source voltage over M1 is relative high. This means that the voltage on the ADC pin is not its correct value.

Basicly i want to switch the 3 resistors, but without a voltage drop over the mosfet. I have thought of relay's, but i like to avoid mechanical switched because the period of measuring is very short (around 50 ms) and relays have bouncing contacts. I am looking for a good mosfet but i cannot find it. (small RDSon, logic level, no large IDS current rating)

Does anyone have ideas or alternatives?


texts: Assistance required to design a Powerbank

texts:
This is essentially a Q & A tutorial set - as provided for in SE rulez.

I am trying to build a Power Bank* on my own.
Can anyone assist me in designing a circuit or suggest ones which may form a good starting point.

I have tried searching for the circuit online. I have found circuits which use SMD components. For reasons which seem good to me [tm] I'd rather obtain information  on solutions that do not use SMD devices, if possible.

*The name "Power Bank" or "PowerBank" is common parlance amongst those of about Gen-X on - so much so that they may not realise that it may confuse those with Gen-Q brains or before. So,
 The technical name for a "Powerbank" is a boost converter.
A PB is usually a BC designed to operate from a single LiIon (Lithium Ion) cell and to produce 5V output intended to charge a cellphone or similar via a 5V "USB" connection. The target device usually uses a LiIon cell as well so it's essentially part of a LiIon to LiIon charging circuit.


texts:
A lot of people are going thermal sensor crazy right now with the application of screening people for fever. I was asked to research it a bit for my company and I two weeks reading papers, googling, and talking to sensor manufacturers. I've found a range of sensors, from expensive $9k-$5k sensors that show 0.1C real temperature data for every pixel, to $200 sensors that have a +/- 5C accuracy. I was sitting here thinking about if there was a way to get better accuracy on the cheaper sensors. My assumption is the +/-5C comes from sensor noise, so it's not like an offset that drifts with ambient temperature, but more of a it might be 5C low this frame and +5C on the next frame.  Not sure if I'm right there. But then I've seen sensors with more accurate spot meters in the middle and I was wondering if those can be used to correct for the error? I was thinking about trying to use an external accurate spot meter too but I guess it wouldn't be in sync with the noise.

Anyway my real question is, given a sensor like say the sub $200 FLIR lepton 3.5 who has a radiometric accuracy or +/-5C, is there a technique or circuit design to improve that accuracy? I know component questions are off topic but if there is another type of sensor I should be looking at I'd appreciate any suggestions. For context I have some AR glasses and they can let you "see" in thermal vision using external sensors. And I'm looking for an inexpensive solution that would let them be more widely deployed (as opposed to the $9k camera option).

Thanks!


texts: eliminitaing spikes from the circuit input

texts:
Suppose I have a circuit which gets damaged for spikes and high voltages, so that I need to eliminate spikes and high voltages beyond a maximum value, so I have decided for the following two configurations for my circuit. Please tell me which one would act as the best voltage protection for my circuit

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

In the first one, I use an opamp as a voltage buffer and let my max allowable input be Vmax-u, where u is a small tolerance I use for safety, but in the second one I first use a  Low pass filter to get rid of spikes and then I use a transistor circuit which when biased beyond Vmax, would ground the voltages.


texts: stm32 drawing current from 40 outputs at the same time

texts:
I have an hardware question about stm32 family.

I am designing a circuit with STM32F103VB. datasheet mentions that i can draw up to 25 mA current per pin(page 37 table 7). I need to drive 40 npn bjts with mcu. if I draw 15 mA current from 40 pin at the same time, what will happen? same table says that i can draw 150 mA total from power lines.

it is 40*15 = 600 mA total. it's more than half an amp. will it damage the mcu? how much current can i draw per pin for driving bjts at the same time?


texts: Momentary-Pushbutton Latch Switch with off delay?

texts:
I am trying to construct a latching circuit with a 1-2 minute shutdown delay so I can soft start/stop a 240V-5V power supply.

I am looking for a momentary push latching (on-off) circuit to switch the 240V supply that will work like this:

---Push once (irrespective of push duration) the circuit latches and switches the 240V supply to a 240V-5V power transformer.

---Push again (irrespective of push duration), the latching releases but the 240V supply continues running to the 240V-5V transformer for a set time (approximately 1.5 minutes) and then the 240V supply is disconnected.

I have previously used a latching circuit I found online http://www.electronics-lab.com/project/toggle-on-off-switch/ and have found a "Power off delay" thread here How can I add a power-off delay to this circuit.

Because my skill level is low I am thinking about combining the two circuits with the relay in the latching circuit replacing SW1 in one of the options provided by Olin Lathrop and EM Fields.

So my current plan is to simply use a rely to connect the seperate soft start and power off delay circuits.  However I am wondering if there is a simpler way (I am sure there will be) to integrate the latching circuit into one of the Power off delay options? Or is there a better alternative?

Regards


texts: Controlling MOSFET's resistance using negative feedback

texts:
I wanted to use LM317 in a power supply project but wanted to control voltage digitally or with voltage. One possible way was to change one of the voltage divider resistors on the schematic below, with some device used as voltage controlled resistor.

I though of using a MOSFET as voltage controlled resistor, however knowing that the region where it is linear and of suitable "resistance" is quite narrow I thought of using a feedback loop that would automatically control the gate voltage so to provide the resistance needed. I came up with the following configuration:

U2 acts like a buffer while U3 compares the voltage at the adjust pin node with the voltage set by V1, and outputs its own control voltage on the FET's gate. The simulation works perfectly.
Here's output of the lm317 probed while sweeping V1 from 0 to 15 volts.
Here's transient response when V1 is set to 10 volts.

However, predictably it didn't go as smoothly irl. When I built the schematic on a breadboard the circuit oscillated quite a bit. It produced a triangular waveform with frequency of around 15 KHz with Vpp of around 5 volts with approximate offset voltage of the value set by V1.

I understand that there may be a ton of things causing a feedback circuit to oscillate however I'd like to know what can be done to reduce this effect or how to go about solving such a problem.

Even if I don't end up using this circuit in a power supply I still like the idea of controlling non-linear element with a feedback to behave exactly how you want them to.

Edit:
 The circuit works now! However, for reasons I don't completely understand. I removed the unity gain amp and I changed a MOSFET with a BJT (2n2222), and added a 10K resistor to its base. The circuit changed behavior a little bit but still oscillated significantly. I then tried to introduce a capacitor somewhere in the loop. The circuit worked perfectly (500mV ripple at 10 Ohm load) with the capacitor placed between base and collector of the BJT as shown here:

Now, I am happy that the circuit works, however I find it hard to find an explanation as to why? Can anyone provide some insight?


texts: Flexible, flat - and adhesive - connectors for PCB pin pads?

texts:
Apologies in advance that the question is a bit of "does this exist" - but I really cannot remember whether I've actually seen a prototype for something like this; or I've seen an ad for an actual product - or maybe my mind combined images of unrelated ads.
Anyways: I would like to interface with copper pin pads on a PCB that match a, say, 2x5 2.54 mm pin header (basically circular pads, except for the one marking "pin 1", which is typically a square). Typically, the pads have holes, and then male or female pin headers can be inserted in the holes - and that is how I usually interface with them; however this also requires some force when attaching/reattaching. Say, something like this (from here) - just without the holes:

So, I was wondering if there was something like a flexible flat cable, with matching exposed pads, and an adhesive - so you can basically just "stick" the exposed pads of the flexible flat cable, on the copper pin pads of the rigid PCB? And then you could just "unstick" once you're done - and "stick" again once you need to interface?
I guess that would look something like this (taken from here; not sure what this product is supposed to do, though):

The below image is for something completely different (it's from here), but I've edited it, as it shows how I imagine this flexible adhesive connector would be "sticked" on a PCB:

The other end of the connector would presumably be just a normal FFC cable, e.g. like this (taken from here) - except with 10 pins, if the "sticky" end is supposed to interface with a 2x5 pin header pads:

Is there an actual product like this out there, that can be bought (that is, not just a prototype in a lab somewhere)?

Btw, I am aware there are adhesive flat cables for loudspeakers, like Ghost Wire 2.0, Super Flat Adhesive Wire:

... which is a similar concept - however, obviously, these dimensions would not be appropriate for interfacing with a 2x5 2.54mm pads for a pin header.


texts:
I need a 500MHz FIR filter for filtering ADC samples (500MSPS).

After the filtering a few samples needs to be stored in a buffer, for a simple peak detection algorithm.

I have been developing some VHDL code, and used a Xilinx FIR filter library to create the filter.

But after looking into the prices of Xilinx FPGA's that would do a 500MHz FIR filter, well above $100, my jaw hit the desk.

Is there any good and low cost ( less than $50) FPGA for doing this?


texts: Why does touching the capacitor in my buck regulator cause my micrcontroller to start executing code?

texts:
I have an AC powered microcontroller board.  I use a CUI module (VSK-S15-48U) to generate 48V DC from the wall.  That 48V gets bucked down to 3.3V to power a micro (atmega328-mmh) and some other peripherals (the 48V is used for other stuff).  My power connection is pretty ugly -- I took a two prong extension cord/cut the female end off and crimped a connector, which mates to my board (read the connection is probably ugly and I'm definitely getting some transients when I plug in).  The power supplies (48V and 3.3V) looks really nice/clean and there are no oscillations.

For simplicity/prototyping I'm using the arduino IDE.  I've modified the avrdude.conf file such that I'm utilizing the internal RC oscillator at 8 MHz.  I'm able to program the board without issue.  I am, however, noticing that when I initially plug the board into the wall the microcontroller appears to be bricked: a test LED doesn't blink/turn on, another I/O I use appears to be pulled high somewhere, and my I2C lines appear to be tristated (they're pulled high so I read a high voltage).  I tried manually resetting the micro using a push-button, but it seems as though it has zero effect.  Initially it appeared as though it would "randomly" start working and the FW would be executed as expected.  After that, reprogramming/resetting the micro worked as expected until I'd unplug and replug from the wall.  Eventually I noticed that if I touched/tapped the area near the feedback resistor on the buck regulator that the micro would come out of its suspended/bricked state and function appropriately.

Initially I suspected a cold solder joint -- by tapping on the cap I electrically connected it.  Resoldering didn't do the trick.

Looking with a scope, the 3.3V looks good after plugging the device into the wall -- I see nothing to suspect there's anything wrong with it.  The power good output of the buck regulator indicates that the 3.3V is fine.  When I tap on the bypass cap I can see the 3.3V wiggle down to ~2.2V for ~40 mS.  The power good output drops accordingly and then sometimes the micro wakes up and decides to execute the code (occasionally a few taps are required).

I thought maybe the slope rate of vcc was somehow causing the micro to go haywire.  The 48V rises in 10 mS and the 3.3 in roughly 2.5 mS.  The datasheet requires between .01 and 10 V/mS so I'm in the clear there.

I still have some more debugging to do, but at this point I'm unable to find a logical explanation for why the micro doesn't come on initially and why tapping the feedback cap (and therefore causing the buck output to sag for a bit) kicks the micro into gear.

Edit:

I thought it might be beneficial to start the micro in reset by holding the button down and releasing after plugin -- makes no difference.

Schematic of the micro/buck:


texts:
I would like to simulate an induction motor in Matlab/Simulink using the d-q model.

I have found a paper that describes the whole procedure but I have this problem.

I am trying to create this block :

This block defines the following equation.

I can not figure out what the parameter *u in the matrix gain stands for and how this block defines the equation.

Edit: I do not have the Simulink model. The pictures are screenshots taken from the paper that I study.