texts: Rising/Falling Edge Detection for interrupt generation circuit issues

texts:
I am trying to generate a pulse to trigger an interrupt when the input changes state.
 High->Low & Low->High

 The input is a reed switch.
 I'm using a XOR gate (SN74AHC1G86QDBVRQ1) with an RC delay on one input.
 GPIO2 is used for detecting the state of the input after the MCU wakes from the interrupt.
 The circuit works correctly when changing from Low->High. When changing from high to low, it will only work when a scope probe or another metal object is touching terminal 2 (GPIO2).

 Does anyone have any suggestions on why this is happening?


texts: Single schematic split to multiple PCB in Altium?

texts:
I'm wondering if it is possible to have a single schematic that can create multiple PCBs.

I'm aware of the multi board capability, however this seems to use multiple schematics to create the individual PCBs which are then brought together as modules.

I have a use case that requires splitting an existing schematic into 2 separate PCBs for production. Wondering if this can be achieved without redoing the circuit diagram.


texts: Adding capacitor to model railway 12V motor to keep it going over a dead spot

texts: I have read that you can add a capacitor to a model loco to keep it going over a dead spot on the track - not DCC - just DC. Is this accurate? On one forum someone has been experimenting with 2000mF 12V DC polarised capacitors. However what happens if the power is reversed - I assume a short circuit - can anyone help with advice?


texts: Is there a difference in speaker total excrusion if i using single and dual? Like if single it's just excrused from 0mm to like says, 5mm. and if it was  dual rail i'll go from -5mm to 5mm? If yes then the single rail is actually less useful somehow? (Because inability to reach -5mm, so the power handling are divided by 2?


texts:
Take a look at this schematic, especially on the USB OTG part of it.
It uses a SY6280 "5.5V,  2A  Low  Loss  Power  Distribution  Switch" as a means to control the 5V USB-bus power.
I was wondering if it would be a good idea to implement this sort of thing on all my peripherals, in order to enable them or disable them according to my power requirements e.g SD card, sensors, relays etc.
My design features a 18650 battery to power the device when AC mains is out, like a UPS. Would you consider this approach effective as a means of power management during lost AC mains, in order to power only the necessary blocks of my design?


texts: High stability external crystal for PIC?

texts:
I have a question regarding the external crystal for the PIC
In what application the designer of a circuit should consider a high stability crystal TCXO for the PIC ?
I have seen some PIC have just an expensive regular crystal and some other have a TCXO which cost more.
My appreciation to the answers


texts:
Why is sense the resistor swapped with the load resistor here

and how does this circuit work?
From my understanding of circuit output (node at LED anode) will be at constant 1.25V, and it will change with load I = 1.25/R(load).
What am I missing?


texts: What is the symbol on the supply voltage that looks like a shaded-in capacitor?

texts: I am looking at a datasheet for NJM2073 (dual low-voltage power amplifier). On the fourth page, there is a sample circuit; right at the V+ input there is a symbol that looks like a capacitor. However, it looks like it is shaded in. What is that?


texts: What to do with third contact in DC barrel plug with only two input contacts

texts:
My AC-DC adapter gives output of 12V and GND. I tried to search for suitable DC barrel plugs

and found that most of them have three terminals

So, pin 1 is positive in my case.
1. Which pin should I connect to GND, 2 or 3, in my PCB?
2. What should be done with the remaining pin?
3. Why are there 3 pins for 2 contacts? What is the advantage of this design?


texts: Building a voltage transformer circuit for sensing mains voltage

texts:
I would like to create a safe electrical circuit that measures the voltage from the wall (220vac). And the safest way that i know of so that when something fails there would be a high chance that my electronics could still survive is by using a step down transformer.
The circuit i have came up with looks like this

I have several problems though:

Im having trouble looking for a transformer, since its for voltage sensing only i dont really need highoutput current, but most important of all it must be as small as possible so that i can place it on my pcb. I even opted for smd only to ensure that there will be no arc going onto another pcb on the bottom. But even with that there seems to be a lot type of transformers and dont know which one will work. Here are the three types that i think will likely to work. SMPS, Pulse, Current.
The SMPS seems to be the most likely i will be using having high isolation and its actually stated that it can handle 220VAC. I am having second thoughts on the other tweo because some of them does not say on the datasheet the max voltage the input can handle.

For the value of the voltage divider, to get the desired output voltage that my differential ADC can handle. getting the ratio of the resistor is simple. But i am not sure what the values should be should i go higher or lower? In the circuit above i used 1k and 0.5k but i can also be 10k and 5k. which would be better?

A gut feeling is telling me that my circuit seems to be only good on paper, and in real world there would be more components,? what should i add to this circuit to make more like a proper circuit that can survive in the real world. Heck how do industrial grade equipment do their single phase voltage sensing.


texts: How to MOSFET to drive 12v relay from microcontroller (logic high is 3.3V) using ZXMS6004FF

texts: The above is part of my project design. 'BRAKE_CTL_3' is output pin from uController. It sends 0 or 1 to drive Q4 to turn it on or off. 'BRAKE_LSD_3' connect to one end of Relay. Other end of relay is connected to +12V. I would expect my design to turn relay on or off. However, relay is always turned on(closed). When I measured the pin output at 'BRAKE_LSD_3', the voltage switch from 0 to 3.3V instead of 0V to 12V(ideally). I dont know whats wrong with my design? Can anyone help?


texts: A few of my cables don't work. Is it because they weren't shielded properly?

texts:
I am learning how to build USB cables as a hobby.

For my early attempts, I did not  attempt to shield the cable, I just skipped the bare shield wiring I've seen in other USB cables. However, recently I have found that some of my USB cables don't work properly (the usb device is not recognized on Windows) or some of them only work in a short period of time before the device is disconnected. So, I am now trying to include shielding in my USB cables.

I have tried crimping a bare shield wire to the USB housing at both the devices and host ends of the cable. Is this correct? The wire I use is 24/28awg and I also apply a silicone glue to prevent a short circuit.

What is the correct method of adding shielding into my USB cable builds? Is grounding the shield at both ends of the cable correct? Or should I just crimp the shield on only one side? Or not shield at all?

How I recently do my cables. It works however the connection isn't very good and a few minute later it disconnects.


texts:
simulate this circuit – Schematic created using CircuitLab

This is a minimalist FM transmitter I've found from http://www.talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-1.html

I'm a bit confuse about three things

1)How does this modulates the base input signal to frequency modulation ?
Because I don't see any change happening neither in Inductance nor in Capacitance of that LC tank oscillator. Is that because of C1 somehow ?

2) For what purpose capacitor C5 is used ?


texts: Increase resistance to turn on a light bulb

texts:
I’m wondering if it is possible to use a potentiometer to turn on/off a lightbulb in a binary manner.

I’m thinking high resistance = light on. Low resistance = light off. Is there such a circuit? Does it have a name?


texts:
I am in the case where I read a lot of datasheet and I quite often see some circuit where the chip manufacturer indicate some value for resistors and capacitor but by not indicating any part number, no tolerances, no voltage etc...

How do I select components in this case ?

for example if we look at this simple I2C line:

(source)

We see two pull up resistor of 4.7k. How do I select the tolerance of those resistors, how do i select the part number etc... ?

My question is rather about how to deal with general case rather than with pull up or pull down and it concern indeed the choice of a component who may have different tolerance, package size, power
I am looking at rule of thumb for R, C, L and D :) regarding tolerance % , X5R, 7R, Voltage . Thanks to Peter for his first proposal, if other have their own rule of thumb to propose, I am happy to hear them :)


texts: Someone asked me the other day how an FTDI USB to serial UART works, and I realized I didn't know. I looked at the datasheet for the FT232R and the block diagram didn't really help me. Can anyone explain or link me to a good explanation?


texts:
I am using an STM32F446ZE Nucleo Board which does NOT have an external HSE clock. From CubeMX I set the clock input from the HSE and after in the clock configuration I set the system clock to 180MHz.

and in the clock configuration I set the PLL like this

The code generated by CubeMX seems to be correct also.
My point is that even if I don't have an HSE in the board the uController works in 180MHz. How is this possible? What is the clock input after all?


texts: Does the electrical impedance of a headphone depend more on the cable or on the headphone itself?

texts:
I'm currently considering buying a defect headphone with a built-in broken cable which would be quite expensive otherwise. I'm quite sure I'm able to solder a new cable onto the headphone to fix it.

My question is the following:
Does the impedance of a headphone noticeably change if I use a cheap standard AUX-chord or does it mainly depend on the internal electronics of the headphone?


texts: Drive a 4.8V servo signal line using 3.3V

texts:
I have a servo with an operating voltage of 4.8V.  I want to drive the servo from a MCU running on 3.3V.  I haven't tried it yet, but was wondering if I needed to drive the signal line to 4.8V using a MOSFET or NPN transistor.  Is it possible to drive a 4.8V servo using 3.3V signal?  Will the performance be impacted?

If I need to drive it with 4.8V how should I connect it?  The gate obviously goes to the signal (with the necessary resistance) but how do I connect the servo's signal line?  Should I connect the signal line to 4.8V and the ground to the drain?  I'm guessing this wouldn't work.  Is this even possible?


texts: What's the max current of a power adapter that's rated at 24V Max 7W if I regulate it down to 3.3v?

texts: Does it matter if I regulate it down to 3.3v (probably linear) or will the max current still be 290mAh?


texts: What is the highest pulse rate possible using PIC12F683 measuring the period of a square wave?  In Chapter 3 tip#1 of Microchip Tips and Tricks, it provides a great tip on how measure the period of a square wave, but I need to know then, what is the highest pulse rate possible?


texts: Unwanted property of large electrolytic capacitors?

texts:
Cited article

In the article above, which deals with working with high voltage, there is the statement “Measure the voltage to ensure that the capacitor has safely discharged, and be prepared for a surprise as with some capacitors the voltage will return after discharge due to an unwanted property of large electrolytics. Repeat the discharge until the voltage is gone.”

What is this unwanted property?


texts:
I have an old Weller (around 30 years or more) that still works like a charm, but I need a new tip. The picture of the sticker on the side:

The tip has PTK written on the side:

And also the number 7 on the rear end:

I only found on the web Weller tips from the PT series (for example RS Stock No. 661-649 Mfr. Part No. 4PTO8-1), can anyone let me know if they will work with this soldering station? If not, anyone knows where can I find new tips for it? I'm looking for a thin tip, 0.8mm to 1mm.
And by the way, what does it mean the number on the rear end of the tip?


texts:
For my project, I need to develop a gadget to track if a given book is open or not. Can any one help me what kind of sensor I need to use and the full configuration manual of that sensor. I tried, Proximity sensor from http://popular.ebay.com/business-industrial-k-z/proximity-sensors.htm this page, but I have no idea about how to give power supply to them. Can any one tell me about a sensor that can work with a coin cell (Maxell Batteries)

note : I am a very beginner to sensors.


texts:
I'm designing a PCB that should (among other things) include an M.2 SSD slot and convert that to a SATA slot to be connected to a computer. I considered just soldering a commercial SATA-M.2-adapter onto the board but I'd prefer to integrate it into the PCB design.
Would it be sufficient to directly connect the four SATA data pins to M.2 pins 41, 43, 47, 49 as well as pool all ground and 3.3V pins and connect them to the SATA power connector? (leaving all other pins unconnected)
If something more complex is required is there a commercially available IC to handle the conversion?
(also are the logic voltage levels compatible?)


texts: How to close eletrical circuit (closet lighting on opening the door)

texts:
I bought these (magnetic?) switches from China that open and close the circuit when they touch each other or are close.

My problem is that they work in the current setup in the picture in the opposite. Right now the lights would be on when the door is opened.

I guess I need to wire led to batter directly, but between then I need some kind of component that blocks the circuit when the switch is touching each other.

Am I missing something, is there any other way to build what I want to?
I was trying all sort of keywords but I don't know what component I need.


texts: To use Power banks and DC-DC step up Converter to make Electric Bicycle battery Pack

texts:
Summary of the whole project

I have a small project in mind, just want to find out is this a possible way to make a useful power pack rather then use this normal way
[![enter image description here][2]][2]

to make a traditional E-bike power pack

situation

I will use twelve QC 3.0 capable power banks to constantly supply 20V with around 0.9A, then I parallel them by joining 12 outputs into a thick copper wire.
Because the DC-DC step up converter can only handle 15 Ampere max input (10 Ampere if no cooling, so I choose limit to 10 amp )
step on converter specification: It can take in 16-60 Volt as input      ( with max Current 15 Amp ) output voltage is 18-80 Volt with max current 10 Amp
If need more power, I might make another step up converter group or groups, later join both (or all 3) step up converters output before BMS ( battery management system )

[![enter image description here][3]][3]

500W motor will get electrical power from BMS :)

ok, now come some questions

How do I ground the circuit? Do I need to ground the circuit? Is it necessary??
If I use 2-3 step up converter groups, how should I deal with the grounding circuit problem?
Do I need to put diode ? Especially just outside output of each power banks . If No need Diode , then I can save more energy :)
Do I need to put diode outside the step up converter ? I means in between steps up converter groups and BMS
Any other points that might stop the project from working ?


texts: Upon setting up serial UART between two boards I can only monitor send or receive, not both, Why?

texts: I have an atmega389B talking to a SAMD21 chip over UART and am trying to monitor the data sent by the SAMD21 and 389B chip. The baud rate used to be 9600 8N1 and I was able to observe both the sent and received data between the two boards using an RS485 to USB sniffer with a 120 Ohm resistor between the RX and TX pins. The baud rate has since gone up to 38400 and Now I can only observe the data sent from one board or the other, not both, which I need to do. I can switch the TX and RX pins and get one set of commands or the other but I cannot receive both. The data is flowing between two RS232 chips and for some reason I was still able to reliably get TX and RX data with an RS485 sniffer. Now with a higher speed I cannot. Does anyone know what might be causing this and a solution to this problem? I tried a UART to usb sniffer but got gibberish and I have tried Teraterm and another cheap RS485 terminal program. I've tested the cables as well and they are working. I'm quite confused and could use some help. Here is a drawing of the setup


texts: Are my calculations correct. I used Ohms law to find I1. And then KCL to find the remaining currents. I figured I3 would be a negative answer since the other current source would be supplying power that way.


texts: TJA1048 - Can someone check if my calculation is good about pull-up and pull--down

texts:
I have question about calculating pull-up and pull-down resistors to my CAN transceivers.

I want to my TJ1048 work always on NORMAL mode, so to do that, I need to pull-up STBY high. I know, that resistors with lower resistance will draw more current, than resistors with higher value, but it is important to choose not too high or too low value of resistor, just right for appliaction. Also I know idea of using pull-up or pull-down resistor

I read a lot of information about this topic, but this is still a mystery for me about choosing properly. For most of time, there is common resistors to pull high, like 10k or 4k7 ohm, but I would like to know why.

On SparkFun website I saw, how to calculate pull-up resistor based on Ohm laws.

From Ohm Laws: V = R * I -> R=V/I

So to calculate R, I need to rearrange above equation. But here is a problem for me. From datasheet, Vih min is 0,7VIO and Vih max is Vio+0.3, Iih is from 1 to 10uA. Microcontroller is powered using 3.3V power supply. VIO pin is connected also to 3.3V. In  this case, chip will interpreting high level on STBY pin from range of 2,31V to 3,6V? Is this correct?

Let's assume, that my way of thinking is correct. For V I am taking 3.3V, for I 5uA. After calculation, resistor value is 660k Ohms. Is this correct?

Can someone explain me. how to calculate resistor for pull-down, based on following data: Vil between -0,3 to 0,3Vio, Iil between -1 to 1uA. The same way as above, when I calculated value for pull-up?

Thanks for help!

Best regards


texts: How to terminate a coplanar waveguide with 50 ohm load?

texts:
So I want to structure a coplanar waveguide by lithography, VNA - coaxial - picoprobe - coplanar waveguide transition to measure impedance of the waveguide. As signal and ground lines are on one surface, compared to e.g. a cpw without groundplane, one should be able to terminate the waveguide with 50 Ohm at the end on the wafer?

I found some hinted ways to do this, e.g. different stub geometries, or an antenna or resistor as terminating load. The last one I know from BNC cables, the 50 Ohm ending caps. The correct stub geometry has probably to be found by something like CST Microwave, Sonnet, HFSS? My CPW consists of 100 nm thick gold, width 15 micron, gap 10 micron, 1-2 mm length, 1-2 GHz.

To find a material able to be deposited accurately with resitivity to yield 50 Ohm for this geometrical demands seems tricky like in the upper right of the picture. The lower left is my guess but probably wrong, causing reflections because of the 90° bended ground lines before ending in the stub, so maybe a tapering like in the lower right has to be designed or an antenna-like small coil?

Is there maybe a easier solution for this on-die termination, maybe to use unbalanced or coupled lines (sorry dont know exact name, basically CPW with 1 signal and 1 ground line). Maybe this is easier to design geometrically a terminating stub/antenna/resistor at the end?


texts: Does the inductance change in an LC filter based on frequency?

texts:
I sort of understand the formulas for inductive reactance.  Do they apply to a LC filter?

I have this, inductor at 700nH and caps at 120pF for a 20MHz cutoff emi filter:

simulate this circuit – Schematic created using CircuitLab

The specs for my EMI filter say max 8 ohms DC resistance.  If I solve for inductance in the reactance formula for 8 ohms I get much higher inductance levels than 700nH.  Is this happening, or am I missing a key concept here.


texts: Is it possible to use an NPN transistor to control a 5V power supply from Arduino?

texts:
I am new to EE and have a question. I have an Arduino that I want to control a 5v power supply on and off. Can I use a General NPN Transistor?

Requirements:

The collector is supplied by 5v dc at 1ma
The base will be triggered by the Arduino Pin
The emittor would give a 5 v dc output


texts: Help troubleshooting diy battery charge/protect/step-up circuit

texts:
I am following the schematic below trying to put together the circuit for a battery charger with over/under voltage protection and 3.7 to 5v step up.

I have populated only the battery charger part of the ic, in case it does not work it should be easier to debug.
I expect when I plug in a 5v power supply with a 3.7v li-ion cell connected to the battery terminals that one of the leds would light up and some current will flow to the battery.
The result is, both leds are off and no current flows. I have a current reader connected between the powersupply and the ic.
One of these

I am not sure if the orientation of Q1 and U1 chips is correct, there is no marking on them.
Below how I soldered them.

Picture above is my 12th attempt to mount the smd components, I spent under 1s on each part on this attempt, I am confident I did not thermal damage the components.
I followed the direction of the text as a guide for the chip orientation, that being, text reads from left to right, for Q1 this means bottom left pin is pin 0 and top left pin is pin 0 for U1.
Reference img and link to the pcb layout below.

PCB link
I don't see why the charger ic is not working. I think I followed the schematic correctly.
What series of steps should I take in order to troubleshoot the issue?


texts: Effect on loading a DC motor - load torque

texts:
Could someone give a (detailed) explanation (perhaps with formulas) of how the load (torque) affects the armature current of a DC motor (separately excited or shunt or series)?

As the load torque increases the speed of the motor decreases, and assuming the terminal voltage stays constant, the EMF will become lower and thus the armature current will increase.

But could someone give me the formula that shows the relation between load torque and armature current?

Is it something like:

\$T_\text{developed} = T_\text{shaft} + T_\text{friction windage} + T_\text{load}\$ ,

where \$T_\text{developed} = K \, \text{flux}_\text{pole} \,I_\text{armature}\$ ?

But then you have

\$P_d = P_s + P_{f_w} + P_l   \$

where \$P_d = K \,\text{flux}_\text{pole}\, I_\text{armature}  \,\omega_m\$

In the last formula you can't see that as the increase due to \$P_\text{load }\$ the armature current increases because maybe someone can say the speed \$\omega_m\$ increases.

And how come at no-load the armature current and thus the torque developed is zero? Is it really zero, or do I have to assume there is some current flowing?

Could also explain me the principle of torque developed. Because at no load, the shaft torque is equal to torque developed, right?


texts: The title says it all in signal switching applications - besides choosing a different device, how can I reduce the turn-off delay of (N-channel) MOSFETs? Is there something similar to the Baker Clamp used for BJTs?


texts:
I trying to get EMC certification and stumbled upon problem.

In the above circuit, they will apply ESD to the exposed part of the trim pot, and it permanently changes the value of the trim pot and the resistors R1, and R2. Are there such resistors and Trim pots that are specially designed to withstand ESD?

Trim-pot seems to be affected also by conductive noise injection from the power supply line which is isolated and fed via voltage regulator. Is there specific parameter I have too look for when searching for resistors and trim-pots?


texts:
I would like to set up communication between two Arduinos with a distance of 20 cm, but not more than 40 cm. I looked for an RFID solution, and I found a lot of PCBs which can be used to read and write to the RFID chip.

However I am wondering if it is possible to use such a PCB to exchange information. I need only up to 2 bytes/s transfer rate with a range of 20 cm. Can RFID be used for such communication?


texts: confusion about the stepper motor rating?

texts:
I came across a stepper motor with 10.2kgcm torque, which is ideal for my application. However it says
Voltage rating: 3.3V,
Phase current: 2Amp

If the current rating is the maximum allowed current. Then how come a 3.3V is supposed to provide such a high torque.


texts: Usage of non-linear phase filters in RF receivers

texts:
I'm in the process of designing the analog front end for a RF receiver. The system will use BPSK modulation. I was wondering what effect non-linear phase filters (such as Chebyshev and Butterworth) would have on my system, and front ends in general.

I know that having a variable group delay in the band of interest will distort signals due to a nonlinear phase shift across frequencies (nonlinear in the sense that phase shift is not proportional to frequency). That being said, I also know that filters, such as Chebyshev filters, are commonly used in communication systems. Thus my question is how ordinary communications systems are able to communicate at all with so much variation in group delay? Do receivers perform group delay correction digitally? Note that I'm strictly speaking about analog filters here, not digital FIR filters (which I know can have linear phase).

As an example, I might design a receiver that has a narrow Chebyshev bandpass filter to select our band of interest. But within this band, the phase of the filter undergoes some change that does not linearly follow frequency, thus introducing non-flat group delay. Why doesn't this (or does it?) cause problems in standard communication systems?


texts: Does LTspice peak current for inductors do anything?

texts: LTSpice has a "peak current" parameter for inductors, but it doesn't seem to do anything.  Setting it to near zero or some huge value has no effect. One would expect it to be the saturation current, but it's not. What is that parameter for?


texts: Cyclical output counts from a D Flip Flop, what is this effect called?

texts:
While working on a frequency divider/counter (in this case a frequency subtractor) using flip-flops, I discovered a strange effect in a D flip-flop when I left the clock at a constant frequency, but varied the frequency of the D input.

In this LTSpice sim, the CLK is at a constant 2.88MHz, and the D frequency is stepped through from a range of 0.1MHz to 7MHz

.

After exporting the output of Q and processing the data in Python, I counted the amount of rising edges that took place, with respect to the frequency of the D input.

The relationship looks like the following. X axis is frequency of D in MHz, Y axis is number of rising edges from Q in a 5ms window

First thing of note is that the minimum counts occur at multiples of 2.88MHz (The clock), but what I was surprised to see is that the shape remained the same in both the region where Freq(D) was less than Freq(CLK) as well as greater. Even more surprising is the fact that on a more fine-grained simulation, the results are effectively linear

I set out to create a frequency subtractor which I suppose it is in certain regions, but all-in-all I wouldn't know what effect this is called, or why it produces this output. I would appreciate any speculation or further reading on the uses of flip-flops in ways like this.


texts: Fourier Transform and the Delta Function

texts:
The Fourier transform of cosine is a pair of delta functions. The magnitude of both delta functions have infinite amplitude and infinitesimal width.

What I thought this meant:
The cosine function can be constructed by the sum of two signals of infinite amplitude and corresponding frequencies.

I realised that only if I consider the 'weight' (area) of my delta functions will I obtain the correct result. Why is this?

Does the delta function in the frequency domain refer to it's weight?


texts:
I recently soldered an electret mic. I have never soldered before. How do
I check whether I have damaged the electret mic? If it was a speaker I could have done continuity check but for a mic I don't know. I measured the resistance it comes somewhere around 1.7Kohm. If I blow into mic ,it
comes to 2Kohm. Is this how we check it?

I made a pre-amplifier circuit. It's not working. I am not sure whether it is the problem with the mic or the circuit.


texts: Magnetic coupling between two coils for audio amplifier

texts:
I have a function generator that will emit an audio tone. I have two coils of wire and I'm trying to couple the audio signal from the primary coil to the secondary coil. The output of the secondary coil will be fed to an audio amplifier I bought from jaycar ( https://www.jaycar.com.au/low-cost-mains-powered-stereo-amplifier/p/AA0472 )which I would hear the tone with some headphones. A circuit of what I'm trying to build is shown below with labels and the inductance values of the coils.

A few things I'm unsure about my design.  Will this setup damage my function generator? Should I account for impedance matching? Should I have the two parts of the circuit connected to a common ground?


texts: disabling CSMA/CA protocol in esp8266 or any other wifi ic

texts:
Is there any way to disable or bypass CSMA/CA in esp8266? I don't want my packets to wait for channel to be clear. I want them to be transmitted at predefined time. If it is not possible to completely disable it, can we change random back-off period (so that we can transmit packets sooner rather than waiting for long time)? If not in esp8266 is there such functionality (of disabling CSMA/CA) in any other IC implementing WiFi protocol in 2.4 GHz band?

Edit:
http://www.osbridge.com/download/OSBRiDGE_5G.pdf allows disabling CSMA/CA but it works in 5 GHz band. MikroTik also allows disabling CSMA/CA https://wiki.mikrotik.com/wiki/Manual:Interface/Wireless.


texts:
Why can't the WEMO switch from Belkin be used with sodium discharge lights?

I am investigating the purchase of a switch to remote control some driveway lights which I believe are sodium discharge lights (long time to turn on; amber color).

The Belkin WEMO light switch has ratings for LED, incandescent and halogen lights.  When I contacted customer support, I was told they could NOT control sodium lights, but he did not know why.

Can anyone here enlighten me?

Thanks.


texts: Tektronix's 465B Analog Oscilloscope Volts/DIV's Question

texts:
I just purchased a used Tektronix 465B Oscilloscope and I am having some difficulty with the VOLTS/DIV knobs. Both channels have markings from 5mV up to 50V.

All of the settings work except for the 10, 20 and 50 volt settings. The knob will not physically turn to these settings. Its almost like its locked out or something. Has anyone had experience with this? I feel like I should be able to measure 120V on this hunk of machinery, however I am limited to a max of 20V. :(

Its also worth mentioning there is a x10 mag button located on the front. I don't think its what I am looking for. I have been able to locate a tech manual, but have been unsuccessful with an operational manual. Any experience with this would be greatly appreciated!


texts:
I am taking input from an electret microphone amplified using LM358 amplifier from my PIC16F877A's ADC unit. I am getting the readings in volts from the ADC which ranges from 2.5V to 5V.
How can I convert these readings into dB?


texts: Tuning the "frequency corners" of a PID system (with two integrals)

texts:
I am having some trouble understanding the language used in control theory.
I have a laser that is set up in a "Pound-drever-Hall" lock. This lock basically sets up a feedback loop between the electrical input controlling a piezo in a mechanical system, and an voltage output "error signal" that is sent a PID controller. (For more details on the setup, check out an older question of mine)
My PID controller is made specifically for these kinds of locks. And on the side there is a picture of the "corners" of the gain of the controller.
Here's a picture of the controller:

I can control the "proportional gain" by turning a knob in the front. And there are fixed discrete switches I can turn that let me change the location of the "corners" for the gain response of the controller for the integral and differential parts.
How do I tune such a device? I'm familiar with the Ziegler-Nichols tuning method, but for that you're simply changing the gain values, not the values of the "frequency corners."
Any ideas what I should do?


texts: Nested Vectored Interrupt Controller (NVIC) - Why is it "nested" and "vectored"?

texts:
In ARM microcontrollers there is an peripheral called NVIC
(Nested Vectored Interrupt Controller).

What does the "nested" and "vectored" part refer to, or why is it "nested" and "vectored"?


texts:
I'm not sure, what the current consumption of the CP2102 is, when no USB is connected. In the datasheet it states:
https://www.mouser.de/datasheet/2/368/cp2102n_datasheet-1634912.pdf

And there is this USB pull-up specification. What does this mean? When no USB cable is connected, it draws around 200uA?


texts:
let's consider a simple dipole antenna of length L. The following picture refers to a half-wave dipole:

In general, at different frequencies, it's known that different modes are possible. Precisely, the open circuit at the end of the antenna forces the current to be zero at the antenna end points, which become null point of I(x) (current spatial wave).
Therefore, as shown in the following picture there may be:

a half current wavelength along the dipole
a whole current wavelength along the dipole
1.5 wavelength along the dipole

etc

Obviously, it's a discrete set of wavelengths that follow the equation:
$$L=n\cdot\frac{\lambda}{2}$$
that means a discrete set of frequencies that follow the equation:
$$f=n\cdot\frac{c}{2L}$$
with c = speed of light.
Therefore, only the following frequencies are possible:
$$f=\frac{c}{2L},2\cdot\frac{c}{2L},3\cdot\frac{c}{2L},...$$
Well, what happens if the voltage source of the antenna (i.e. its signal supply) has a different frequency (for instance $$1.5\cdot\frac{c}{2L}$$)?
Such a voltage source forces the current (and voltage) frequency to be such intermediate frequency, but in theory the null points ad the end of the antenna can't allow that frequency to exist...
Which is the solution?
Pictures taken from here and here.


texts: I'm reading the BZX79 datasheet. On page 4 it lists differential resistance at 1mA and 5mA. For instance for the 3V version differential resistance is typical 325\$\Omega\$ at 1mA. Would that mean that a 1mA rise in current would result in a 325mV rise in voltage? That looks wrong to me (much too high). So how should I interpret that?


texts: STM32F030(K6) Systick not triggering (BOOT0 problem)

texts:
I'm trying to write a simple program for a STM32F030K6T6 microcontroller. The problem I am facing is the more common "Systick is not working" problem.

The code is generated using Cube32MX (Firmware 1.9.0) and compiled in Atollic true studio 9.1.0. What I'm trying to do is to toggle a led with a delay of 500ms. The strange part is that I can't get it to work on the STM32F030K6T6 and it works out of the box on the STM32F030R8T8. The systick handler is never called and thus the delay function blocks.

When stepping through the assembly code it is obvious that the microcontroller is in an infinite loop while checking system ticks. However, if the code is executed continuously it jumps further down the program into an other loop (which i can't identify).

What I can't understand is that for two microcontrollers with the same core I obtain very different results. I checked the difference in the two complete project but could not find any differences besides the fact that some peripherals registers differ.

Does anyone has experience with these kind of problems or has any thoughts on what I can do next?


texts: how to control constant current led driver output with pwm?

texts:
i want to control brightness of led series with constant current power supply.
but when i connect the power supply output to pwm controller and led series, i cant control the brightness because power supply has not fix voltage on output.
while pwm output is 255 (high) led work fine, but when the pwm output is 200 or less (low) my led start to blinking.

i think conversion constant current to constant voltage led driver for pwm control, but i haven't any info for this.

my driver detail: input:220-240V AC /output:54-108V DC- 300mA

please help me

thanks for your help

best regards, amin

my schematic:

my driver pic:


texts: Why L6743D MOSFET driver is not working properly?

texts:
I've started to build a brushless driver by using some Power MOSFETs and some MOSFET drivers, in order to drive the Power MOSFETs.

I have connected the chips as shown in the application circuit (page 3) in the datasheet of the L6743D MOSFET driver, in order to drive my couple of N-MOSFET, but I noticed that nothing worked as it should.

After that, I decided to check if the MOSFET Driver (L6743D) is working as it should. Therefore I have powered up the L6743D with 12 V Vcc, set High the EN pin (5 V of the micro) and set the PWM input from my micro (Arduino).

At this point I noticed that the UGATE pin keeps staying HIGH (constant at Vcc = 12 V), while the LGATE is following the PWM signal's shape.

According to the datasheet listed above (page 8), the UGATE pin should be the opposite of the LGATE pin. Hence I should have something similar to my PWM signal given as input and both the signals should turn on/off the Power MOSFETs.

This is not happening and I really don't understand what I'm doing wrong.

Could you help me, please?
Am I missing something about the usage of the L6743D MOSFET Driver?

Thank you in advance for your help!

EDIT

Here you are my circuit, consider the couple of N-MOSFETs into the same package.

When I turn on the power supplier and limit the current to 200mA, the power supplier shows me that there is a CC. I have also tried to set the limit higher without any success.

Hope this is helpful to understand my issue.


texts:
I'm using an external power source to power an MBED module. I have the UART transfer and receive ports connected to a MAX232 level switcher in order to make the signals compatible with RS232. From there the wires go to an RJ-45 connector, which goes to a DB9 connector that is connected to a USB-DB9 converter. This is connected to the laptop.

With this setup, I should be able to program the CPU to write text which will appear in a terminal program like HyperTerminal in Windows? I've tried several things, but haven't been able to get any input in HyperTerminal. I can get it to work if I use a USB connection though.

I've already checked that everything is powered and grounded. I've also checked the connections. What can I do next to figure this out?


texts: Why is the voltage across a Zener diode so dependent on current?

texts:
I was going to use a 3.3V Zener diode to protect the analog inputs of an Arduino Due, but I found that the voltage drop across it was only 2V.

So I tested connecting it to my power source with a series resistor (see diagram) and I found that the voltage seems to vary somewhat widely:

R=15k   1.78V
1.5k    2.44V
150     3.3V

Incidentally, the datasheet for 1N4728A shows a test current of 76mA, which is close to the 58mA current that is obtained via the 150ohm resistor.

simulate this circuit – Schematic created using CircuitLab

I guess I shouldn't be too surprised by my findings, because it just means that the Zener diode has a positive effective resistance, but I was somewhat surprised that the variation was so high.

Also, it's surprising that even when the Zener diode is not "fully conducting" (or whatever the appropriate term is), it shorts out the lower resistor in my resistor network (see below). When I remove the diode, for an input voltage of 12V the voltage at the ADC is 2.89 V, but when I put the diode in, the voltage drops to 1.86V. Should I just choose smaller resistor values, or is the Zener diode useless for this purpose?

simulate this circuit


texts: What is the meaning of "do not populate test points" in a board schematic

texts:
I was finding test points in a schematic of an Analog Devices Evaluation board. In one of the schematic pages, there is a clause mentioned "do not populate test points".

Does anyone knows what it means ?


texts: Is there definitive documentation regarding the reliability of a capacitive touchscreen?

texts:
I'm working with a manufacturer who wants to use a touchscreen (like a mobile phone) to activate the machinery but is afraid the touchscreen could give a false reading.
This would be a touch-and-hold scenario, not just touch-to-activate. Humidity and moisture are not a concern in the given environment, and it's understood that physical objects could register a "touch."
So it becomes a question of whether a hardware failure or software failure in its processing, could cause the touchscreen to return a constant false touch in one region of the screen.
I was reading this answer to Can a water drop do a “fake” touch on a capacitive touchscreen? which seems to imply that the screen would require something in close proximity, but isn't the kind of solid reference that can conclude the discussion.
If possible, I'd like to point them at some documentation describing the reliability or possible failure scenarios of capacitive touchscreen hardware and processing.
Thanks


texts: Converting Headphone-Out to Mic-In Using a Potential Divider

texts:
I need to record audio with a device that only has a mic-in which is heavily amplified. I built a potential divider with R1 = 10 kOhm and R2 = 4.7 kOhm to get a factor of about 30%. I chose the resistors relatively large to prevent blowing the sound card which is signal comes from.

Is it better to use larger resistors not to damage the output device?


texts:
I'm working on designing a board with the RFM22B-S2 SMD Wireless Transceiver - 915MHz. The board module requires a 50 ohm feed line to the antenna. I've been looking at trace impedance calculators and I'm confused. So far every calculator I've found has a micro strip, a single trance on top with a ground plane on the bottom.

Why is there not a ground plane on top as well?

Is there a calculator that accounts for the top ground plane or is there some minimum amount I have to pull the top plane back from the feed line?


texts: Passive LC low pass in combination with series resonant/ band stop stage

texts:
I found this crossover circuit in a construction set and it puzzled me a while. I have absolutely no idea, why I should combine a 2nd order low pass with half a band stop. The low pass alone has a corner frequency of roughly 155Hz. A full scale notch filter would have a center frequency of roughly 73Hz (impedance as shown).

simulate this circuit – Schematic created using CircuitLab
Finally the sub woofer sits in a very small enclosure (<10L) and is itself quite small. The vented cabinet seems to be tuned as expected (Hoge). I'm a bit uncertain about that since the parameters (volume, opening's surface and high channel length) don't differ that much in comparison to tunings over-emphasizing at the lower end (B4).
So I assume this is an additional filter trick to make the small thing sound better at lower frequencies. There is a peak at 34Hz before the band stop takes over, a drop around the mid frequency and the expected cut off now at roughly 210Hz.
Is this correct or did I miss something? There is no additional filter stage for satellite speakers. And my goal is to replace the passive filter network with an active one (before the amplifier).


texts: How to use integration or differentiation to optimize frequency in achieving a specific phase angle?

texts:
Question:

With source voltage kept constant at 8V peak to peak vary the frequency until the phase angle "theta" Vr referenced to Vs is approximately 45degrees. Record the Vpp value across R1 and the frequency at which "theta" is equal to 45degrees.

Situation:

For clarity I will call R1 the resistance in ohms and Theta Vr the phase angle.

I can approach this two ways from what I know. I could use my simulator and increase the frequency step by step. At each time I would have to figure the reactance and perform the following calculation to determine theta. This process would be very long to get an approximate answer for the frequency.

Theta Vr = ARCTAN(Xc/R1)

Xc = Reactance of the capacitor "ohms"

R1 = Resistance "ohms"

Theta Vr = "Theta" Phase angle of Vr referenced to the Source Voltage (VS)

NOTE:
With the source set to 8Vpp and frequency set to 1kHz Theta Vr = 78.27489 degrees.
With the source set to 8Vpp and frequency set to 1kHz Theta Vc = 11.72511 degrees.

The other way I thought would be to derive a formula that resembles a optimization problem. Derivatives will solve for which the slope is zero. So it would seem I could approach this the same way when solving for the frequency.

Finally, lets say we want to change R1's value and repeat this procedure. It would seem that there has to be a generic expression where X is in ohms and Y is in frequency so this calculation is much less tedious.

Any ideas?

Here is a screenshot of the circuit for clarification.

Here are the parameters of which I set my AC source to.


texts:
I've just recently started designing my first PCB using Altium but am confused with the mechanical layers. I have a 4-layer board, and am placing components on both the top and bottom side (Through right-clicking and settings the component layer). This properly assigns the pad, solder, and overlay to the layer I choose, and if I go to 3-d view everything looks right.

However, I've noticed that both the courtyard and the body information (layers 13 & 15 by default) for each side were put on the same mechanical layer. So I enabled their respective pairs (layers 14, and 16), and configured them to be pairs of the already existing layers. But I'm not sure how to actually assign the bottom layer components to have their courtyard/body information on these new layers. I've tried setting them to the top layer, and then back to the bottom layer to see if now that I've configured the new mechanical layers it would just automatically assign them to those, but that was not the case. How do I do this?


texts: How do you connect the pins of a Photomultiplier Tube (PMT) to an Analog to Digital Converter (ADC)?

texts:
I am using a Photomultiplier Tube (PMT) and trying to send a signal to a computer. The PMTs use a voltage and output an analog signal (continuous electrical signal) which cannot be read by a computer. I am planning on using a 16-Bit Analog to Digital Converter (ADC) to convert the analog signal of the PMT to a digital signal which a computer can read.

The problem is that I can't seem to figure how to attach the wires soldered to the output pins of the PMT and the input of the ADC. What color of wires do I need to achieve this task? And what wires should be attached to what pins to get the best results. If possible, please write what the pins on the ADC mean so I can research on this more, if there is no answer. Please provide schematics or sources if you have a potential answer to this question.


texts:
This may be a very quick answer, I had a test that was set up like this. The primary inductance of the transformer was roughly 0.022H and the inductance of the secondary of the transformer was 0.045H. The transformer uses those iron/silicon steel laminations. The resistance of the primary coil is 0.4 Ohms and the same for the secondary coil. I dont know what the leakage inductance is unfortunately. The transformer ratio was 1.35.

simulate this circuit – Schematic created using CircuitLab

I was just experimenting and trying some stuff out as in this experimental set up shown and I basically just swept the frequency from 1Hz to 2kHz and measured the voltage at the point shown on the output side. The graph I got was this:

I was wondering if anyone could tell me what they think about this graph. At first glance to me it looks like an impedance matching curve where the Y-axis is a voltage instead of the impedance, I cant seem to get the simulation to give me the same answers though but I don't normally use circuit lab....

I have a bunch of these transformers I wound a while back and they are all different but they all seems to have a max voltage on that output around the same frequency of around 200Hz on a Squarewave and 400Hz on a sine wave (obviously one is basically double the other), is it a transformer material thing?

Are my results consistent with impedance matching situation?


texts: Theory of operation for a software defined radio

texts:
I've done some reading on software defined radios and while the concept is clear I have yet to grasp how the signaling is actually done. I've researched the Analog to Digital IC's that are involved in the process and they say that the support sampling rates of 500Mhz or more (is that even correct?) My question is: How is the modulation and demodulation acheived in a software deined radio?

EDIT: I was assuming that there was some sort of voltage controlled oscilator involved, however I can't find the literature.


texts: How to test aluminum polymer capacitor for failure?

texts: I'm not electric engineer, so maybe it is obvious, but I would like to know how do I test (in-circuit) aluminum polymer capacitor for failure? Electrolytic capacitor usually fail with easily visible damage to the aluminum case but polymer one (as I understand) look intact even in case of catastrophic failure.


texts: Do you know of software for automatic waveform compliance checking?

texts:
do you know of any software which can be used to automatically check a measured waveform (from a logic analyzer/scope) against some specification? For example I measured some pulse with a logic analyzer and the program can automatically check if this is a single pulse with a length  between 1 ms and 2 ms. It then gives me a pass or fail output.

I would also like to know if there is a special term for what I call "waveform compliance checking".

An ideal program would:

read a textual specification
read a well known waveform format (e.g. vcd)
be open source
run from a terminal such that it can be integrated into an automatic test bench


texts: reverse bias of the gate of an N-channel enhancement mosfet

texts:
So how negative can I drive the Vgs of an N-channel Mosfet before damage occurs?  Datasheets specify BVDSS and BVGSS but these are "forward" breakdown voltages -- ie the absolute maximum Vds before avalanche breakdown of the drain body pn junction, and the maximum gate drive voltage before the electric field breaks down the gate oxide. I can't find the "negative" breakdown voltages in the device specifications.

Does the susceptibility of the gate oxide to an excessive e-field then suggest that the maximum "negative" Vgs is the same as the BVGSS specified but in the opposite polarity?

EDIT:  Here's a portion of the p-channel device I was looking at that prompted the question:


texts: How to predict the output of a solar panel depending upon weather conditions for real time hardware simulation?

texts:
I want to build a system for smart grid which can optimize the grid power, load and battery charging to reduce my costs for grid power. For the optimization problem, I must know the current date to optimize the overall system, so the problem for me is how can I predict the solar power to optimize the system for the next hour. I want to know if there is a controller algorithm that will predict the power from a solar panel and then decide the power to system for optimization.

In my matlab simulation, I implemented a clear-sky model that estimates the solar insolation according to the altitude angle (Chapter 7 of Gilbert Masters' book Renewable and Efficient Electric Power Systems ) . By using this insolation data, I want to predict the power in real hardware and then allow the controller to decide how to operate for the next hour, depending upon the previous hour's values.
This insolation data that I have calculated is not predicted (it is estimated); we don't know the weather condition for the next day, or even the next hour.

What algorithm or controller must I have to  use to predict the solar insolation for use in a real-time hardware simulation depending upon the weather conditions?


texts: Manually triggered variable speed rotating system

texts:
Intro: (okay to skip)

The inspiration for this idea comes from a fidget spinner kind of kinetic desk toy - MezmoGlobe

I bought this recently and fiddle with it regularly, but there is a catch 22 with the toy - its more soothing when spun slowly, but lasts longer when spun fast (just like any other rotating spinner kind of toy)

Challenge

Goal is to be able to kick start (using hands! LOL) a rotating system (mezmoglobe in this case) at any speed and the system understands the speed and starts rotating at that speed until stopped.

More intricate details:

System consists of at least one motor, which acts both as the driver
of the system and the input for the system.
System can sustain any speed between a minimum and a maximum speed.
System is small enough to be hosted in a 3x3x3 inch3 enclosure or smaller.
System is self sufficient. No external power cable or controller wires.
User spins the motor in any direction. System understands the speed and direction and starts the (same) motor at roughly the same speed in the triggered direction.
There can be a switch to stop the motor. Bonus, if stopping the motor by hand actually breaks the circuit and stops the motor.

Few proposals

I have given this some thought and could think of possibly two (incomplete) solutions:

Analog way

System:

The motor is attached to a linear/rotatory actuator of sorts which sets a linear/circular potentiometer to some value.
Rotation of the motor or the movement of the potentiometer also triggers circuit closure of the motor - potentionmeter - battery circuit which then, due to specific setting of the potentionmeter in previous step, starts the motor at a given/desired speed.

TODO tasks
 - Figure out ways to break backward (motor to actuator from step 1) circuit and start forward (battery to motor) circuit.
 - Figure out ways to reset the potentiometer for the next run.

Complications:
 - Too many moving parts.
 - Calibration of speed to match user input speed is tricky.
 - Maybe not possible in the form factor desired?

Micro controller way

System
 - Motor connected to a micro controller.
 - Backward circuit detects any current produced by manual movement of motor.
 - Then sets the direction and speed of movement via a motor driver.

TODO:
 - How to detect kick start of motor by user.
 - Maybe the motor provides feedback and auto stopping can be implemented as well? (user stops the motor by hand, MC detects it)

Challenges
 - I was personally only able to find very few compact single motor drivers, but they all needed some sort of microcontroller setup to run/provide PCM.
 - Is there a compact programmable microcontroller that can fit the size limitations?
 - Generally MC have strict current/voltage requirements to run the MC.


texts: Where to connect GND on keyboard multiplexer circuit?

texts:
Hi all,
I'm making a project to read my old calculator's keyboard with an arduino and I've decided to design a new PCB and change it with the original one, as it's easier than trying to hook into the old circuit.

I'm working in EasyEDA and it's nearly done, but I'm confused about how and where to connect the Ardunio's GND pin to the circuit. I know it has to be connected to the input pins(see below), but I'm not sure if directly... or just how in general. I'm completely new to PCB design and electronics, so if you see anything off, please point it out. I'd be more than happy to hear your thoughts on the design, feel free to share it.

The output pins are where 5v will be applied and the inputs are going to be read. I haven't decided on the diodes' type yet, so the one you see are the default diodes, EasyEDA has in the schematic designer.

My design:

(the yellow circles are the exact positions of the keys on the original PCB)

And one more thing. I saw people use the "Copper Area" option in tutorials many times, but I have no idea what that does, could someone provide any inside on what is it used for?

Ps.: I've got complaints about how I'm not asking a specific question, but please understand that I'm new to this thing. I'm not lazy googleing, but I can't search for something I don't even know about, and I have no other platform to ask these questions.

Thanks in advance!


texts:
I want to make my own kotatsu (a small table with an heating element underneath) and I'm considering using a "heat lamp" as the heat source (one of those aimed at reptiles, fits in a normal light bulb socket) The one I bought supposedly draws 250W at 110-120VAC. Ideally, an Arduino mini pro turns it on/off (SSR) depending on the temperature it reads. My plan would be to screw a small box containing the SSR and the arduino under the table with nothing but insulated wires coming in and out of that box.

This would be my first project dealing so closely with alternating current, so I'm keeping safety in mind... and I have many questions:

Do you see any problems in using a solid-state relay? I have the FOTEK SSR-25DA, which seems to be rated for 25A. If my math is right, it shouldn't be using much more than 2-3A, right? Even considering it might draw more when turned on, it seems reasonable to my (amateur) eyes... Also, I won't be switching it rapidly (minimum time of say, 10 seconds). I don't think it's going to warm up super fast with a single bulb anyway...
I have 22 AWG wires on hand and again, from what I could find on the Internet, they seem to be large enough to handle this kind of current. Still, to my non-electrician eyes, they look small for something carrying 120V and 2-3 amps. Unfounded fears? I'll be using 18AWG stranded wires instead.
How could I connect the arduino and the lamp to the same power source? I'm thinking of simply using a power strip on which I'd plug a wall adapter for the arduino... Makes sense? Is there any problem about having the arduino on the same power line as it controls via SSR? I tried my best to make a schematic of what I have in mind. Do you see problems with this setup?

simulate this circuit – Schematic created using CircuitLab

Anything else you would do differently? Potential safety issues?

Thanks! Sorry for the long question! :)


texts: What kind of external clock is needed for PIC32?

texts:
Nearly all PIC32 errata I have read (Item 41 - page 5) have the same issue -

  A crystal oscillator cannot be used as an input to the Primary Oscillator (OSC1/OSC2 pins).

An internal oscillator will not do, so I will need an external oscillator, but I am unsure what I should be looking for when searching for a suitable part. I am basically looking for an 8MHz clock that I can pump into the internal PLL to boost up.

How can I select a suitable (and near same price as common xtal equiv) external clock for this device ?

Are there any gotcha's for someone who has never used an external clock before that they should be aware of ?


texts: What is the difference between Periodic and Non-Periodic Tx/Rx FIFO in USB?

texts:
I am trying to understand how the USB module works in the very low level on STM32F4 MCUs (ARM Cortex-M4 core). In the reference manual I read often the terms Periodic and Non-Periodic Rx/Tx FIFO (I am not sure if there is periodic and non-periodic RxFIFO), for example:

  Periodic TxFIFO empty interrupt mask
  Nonperiodic TxFIFO empty interrupt mask
  Receive FIFO nonempty interrupt mask

I do not understand what does periodic and non-periodic Tx/Rx FIFO mean (I do know what a FIFO is), I found no really helpful online resources about this. Could someone explain these terms to me please? and are these terms only specific to Tx but not Rx FIFOs?


texts:
I need to power  a 230v bulb off the grid via solar power. Typically, I would have solar panels that charges some 12v dry/wet cells. These cells will have to supply an inverter that would power the bulb for 12 hours.

What are the considerations to achieve this, in terms of solar panel size and type, cell type and quantity and hours of incandescent light?

The area is in a tropical area, where seasons and daylight is not an issue except during monsoon. The relay control has its own cell and is not an issue too. However it sufficient power exists, I would like to connect the switching circuit cell to the solar power source too


texts:
I'll be using a momentary push button, SW1 as shown in the figure. With that, I also decided to make a D flip-flop act like a latch by connecting the switch to the clock.

My question is if my pull-down resistor value is correct. I'll be using 74LS DIP IC gate specifically HD74LS74A. According to the data sheet, the Vil is about 0.8V while the Iil for the clock input is 0.4mA. Based on my readings in forums, I divided the two resulting to 2KΩ.

Should I aim for 2KΩ or should I use a higher or lower value for the pull-down. Sorry I'm not very familiar with this topic.

simulate this circuit – Schematic created using CircuitLab


texts:
I am building a HID device (for flight/space simulators) with an Arduino Micro that will have a 7 column and 4 row matrix plus 4 axes.  I have the matrix working fine with normal buttons and switches but my design calls for 3 switches to have a LED on them to confirm that the switch is active (these have a red toggle guard on them).

I am using 3x 12VDC Toggle Switch with Safety Cover that I purchased from a RadioShack that was going out of business.  These switches have 3 prongs on them labeled: Power, ACC, and Ground.  If I wire the Power and ACC poles the matrix works fine but the LED does not illuminate.  If I connect the ground pole to the ground on the Arduino, the entire row of switches becomes active while in the off state but behaves correctly in the on state.

I have only been working with DIY electronics for about a month now so my skills are rather limited but I have been trying to find an answer to this now for 4 days.  Any assistance is appreciated.


texts: How can cell phones location be detected?

texts:
Specifically: cell phone not connected to internet, not used to talk, just powered
on. What if it's powered off?


texts: Methods for a very low gain audio amplifier?

texts:
I have an audio signal of these characteristics coming out of an instrumentation amplifier:-

Frequency: white

DC offset: 2.5V

Amplitude: 3Vp-p

I also have some 1/4W 8 Ohm and 64 Ohm speakers pilfered from old transistor radios.  I would like to be able to hear the audio component of my signal.  I can just about hear it if I plug the 64 Ohm speaker directly into the in amp output, but of course that's not the proper way.  The speaker is to be mounted permanently to act as a verification device that all the circuitry is working.  It is not a temporary thing.  I also need to maintain the signal levels for further processing down stream so I can't suck all the voltage level out of the in amp.

I've considered a single transistor voltage follower, a simple discrete component class A amplifier and the venerable LM386 audio amp.  I also have a 13.8V power rail.  Is there a simplest option to hear my noise?


texts: I inhaled some solder fumes for a bit of time

texts:
I inhaled some solder fumes while attempting a project last week, and I haven't stopped coughing since. It's getting rather irritating. However, I should mention that prior to my experiment, I had a cold, and strep throat. I'm aware searching the internet for an answer to a personal health concern is rather, quite stupid, but before running to a doctor I want to know if any of you have had a similar incident in which this has simply blown over, or find the incessant coughing to be the initial symptoms of something much larger.
Thanks.


texts:
I'm investigating a bf1105 dual-gate mosfet for use in an rf mixer circuit. I've never used a dg mosfet before so I decided to do a DC sweep of the gates to determine an appropriate bias point. I built the following circuit to sweep g2 with an Arduino, using PWM as a crude DAC. I can adjust the DC voltage on g1 manually via the potentiometer. The sweep range is roughly 0-4.5 volts.

simulate this circuit – Schematic created using CircuitLab

The voltage on g2 drops by up to 20% (a volt or so) as I increase the bias on g1. Aren't the gates supposed to have very high DC resistance, like in the mega-ohm range? Why is this happening? Could ESD or overheating the mosfet during soldering cause this? It seems to be otherwise functional.

When I replace the PWM filter with 1k resistor & 22n capacitor (i.e. similar cutoff frequency but lower impedance) the effect is no longer noticeable.


texts: How to interpret LTspice simulation outputs for improving dual channel boost converter design using LTC3788

texts:
I am working on a boost converter design using the LTC3788. I would like to take advantage of the dual output capabilities of this chip to produce 24 VDC at 4 amps on one output and 48 VDC at 2 amps on the other output.

Linear Technologies provides an example of this circuit in Figure 10 on page 29 of the LTC3788 datasheet.

Figure 10: High Efficiency Dual 24V/48V Boost Converter with Inductor DCR Current Sensing

I was able to simulate this circuit in LTspice but I am having trouble interpreting the simulation output. Some of the components referenced in the figure were substituted with equivalent models that are either defined in the schematic or were found in the LTspice database.

I have read through a lot of the datasheet describing how to choose the external components for a particular design and have chosen components accordingly. I tried specifying models for all diodes, MOSFETs, and capacitors which improved the response of the circuit but the output still fluctuates more than intended.

Other simulations of this boost converter shows a response that reaches steady state in less than 2 mS which make me think there is much to improve on with this design.

What could be causing this circuit to produce the corresponding response? Are there any particular components that could be causing the output to behave in this way?

Circuit design:

Simulation results:

Update (Solved):

It was pointed out to me that the SENSE+ pins on the controller were not properly connected to the inudctors. In addition, the inductors that I originally chose for this design did not specify a DC resistance which is particularly important for this application since DCR sensing is used to measure current to the load. My understanding is that it is important to chose inductors with low DCR values to maintain high efficiency in the controller. A sense resistor could be used to measure current more accurately but, will consume more power in a high current application.

After running a new simulation with an updated schematic the outputs behaved as expected. Using low ESR capacitors also helped with reducing the output ripple voltage.

Updated schematic:

Updated simulation output:


texts:
I need to feed a pair of logic inputs of a DG211 electronic switch with a single logic output from my 3.3V microcontroller.
The two logic inputs on the DG211 need to be one the opposite of the other.
So I can simply connect the microcontroller output to one of them, and then invert that signal to go to the other logic input.
How could I invert that signal without using a whole inverter IC?
would you use a single inverter IC (those that are made of SOT23 package for example) or a simple transistor and resistor would do it just fine?
the frequency of this logic signal is about 100KHz

note: of course I can't use an additional microcontroller output, and I'm aware of the existence of complementary NC/NO analog switch like DG413

edit/update: the PCB with DG211 doesn't have access to 3.3V supply, but only 5V supply. DG211 is fine with 3.3V logic level even if powered by 5V, but any additional IC would be supplied with 5V and not 3.3V


texts: Isolated DC-DC common mode choke without shunt?

texts:
I was reading a page on the Recom site (https://recom-power.com/en/rec-n-very-low-noise-filter-for-isolated-dc!sdc-converters-46.html?3) where they devised a filter setup to achieve very low noise on on of their DC-DC converters. The final circuit is as follows:

But I am trying to understand how the common mode chokes L1 and L2 are actually blocking common mode voltages since in either case there is no connection back to the "ground" to which the common mode voltage is referenced to. I thought C3 might be the path but it is before the choke.
Would these still be operating as common mode chokes in this configuration? (ie. L1 blocks common mode voltages on Vin terminal, L2 blocks common mode voltages on Vout terminals)


texts: What kind of communication protocol is this?

texts:
I'm trying to reverse engineer the communication between two modules, a master and a slave, but I couldn't figure out the used protocol.

All of the signs use 5V.
The blue sign's frequency is 400 kHz.
This sequence is polled periodically, with 100 Hz.

My first guess was SPI, with connected MISO and MOSI (green line on the first picture), but if I disconnect the slave, the master only sends the first 2 or 3 bytes. (I guess 3, because the delay after it is changing back and forth with time). After this the slave should send the result back on the same line, where the MISO would be 0xFF, because without that the SCK wouldn't be there.

My target is to use a microcontroller (STM32F4) to communicate with the slave. When I've tried that, the slave couldn't pull down the data sign.

Any suggestions?

UPDATE:
Some of you've asked for a zoomed in image of the first few bytes.
In my opinion, it's not I2C, because there isn't any ACK sign, and there are only 8 SCK pulses, rather than 9.

The first 3 bytes are always fixed: 0xAA,0xE5,0xFF, after that, the output of the slave changes.
The slave is an unbranded 8-pin SOIC, which probably measures the magnetic field or it's angle.


texts:
Is there a paper that can go into a printer to be used as a pcb? Basically what I'm looking for is a silicon sheet with a thin layer of copper on top that ink can be printed on to be used a resist. Thus removing a lot of steps involved with the conventional method of fabrication.
Stupid man here don't be mean ok?


texts: What will happen if I inject rated output voltage into secondary of a single phase transformer?

texts:
I have a mains rated transformer that takes 220V and gives me 12V. Now what if I connect it to a H-bridge drawing power from a 12V car battery like this?

simulate this circuit – Schematic created using CircuitLab

The gates are connected to two IR2110 drivers which in turn is controlled by an ATmega328P emitting PWM signals for 50Hz sinusoidal wave. Will this fry my IRF540's, my IR2110 driver, the transformer, or would I be pushing out 220V AC?


texts: controlling many LEDs on an individual basis

texts:
Similar to this question here:  Hooking up multiple RGB LEDs while using a minimal number of PWM pins on an Arduino?

I want to control about 800 rgb LEDs (800x red signals, 800x green, 800x blue), but unlike what that question asked,  i need to do it on an individual level. For example, with my design requirements, I could turn 1 led green,  and the rest red, where as the LEDs would be identical in color with the other question.

My first thought was to use i2c addressed LEDs, but i found no such thing on the market.

I then thought to use shift registers to punch in pwm using multiple pins. The down side to this is that its a shift register,  meaning that pwm signal integrity will be compromised as bits shift.

So,  then i came up with the serial input multiplexing arrays. The idea would be that one pin would be the clock pin,  supplementing 300x 8-bit mux chips. These mux chips would each have the universal clock line (CLK), and one data line (D1, D2... Dx) unique to the mux chip.  As the CLK would oscillate 8 times,  the Dx pins would then each put out 1 byte of serial (1 bit per CLK cycle), representing the current state of the 8 LED colors that its controlling.  The idea seems to be better than the first,  because there is no signal compromise, and because there is x times as much theoretical bandwidth as previous. The downfall here is in cost.  300 chips is not cheap.

My eyes then turned to the PCA9685. it has its own pwm controller, is controlled by i2c, and has 16 pwm outputs. The pwm output means that the controller doesn't Have to use that This means that each chip can control 2x as many LEDs, meaning that i would only have to buy half as many chips as i would if i went the mux route (150). This comes with the obvious downside that the chip itself can only be assessed to 64 unique addresses.  This means that i would need 3 i2c busses to support all of my chips. This is still possible,  as it would require 4 pins, 1 universal clock,  and 3 data lines. Much less than the mux route.

Finally,  i noticed that the company adafruit manages to control 1000s of LEDs on a 16 wire interface ( detailed here ) with  "12 16-bit latches". Additionally,  it says that the device is chainable, such that the displays can be expanded via daisy chaining.

What is the ideal way to control many RGB LEDs on an individual level?


texts: What will happen if you supply a higher voltage to a buck converter?

texts:
The title says enough, but let’s give a real life example too. Take one of those LM2596 35V boards. What will happen to it if it gets 50V on the input?

Most likely it will burn, but will this voltage propagate to the load? Will it get damaged too? Is there any kind of protection? Does it make a difference if the over-voltage is a spike or continuous?


texts: My agm battery is completely dead. I got it off of someone who said it was new and uncharged. Is there a way to check if it would accept charge? I brought it to Autozone and they were unable to charge it. it is deeply discharged. Should i hook up a 12v battery and a trickle charger to charge it, or would it risk explosion? Thanks.


texts: Is there a formula to figure out power loss of a power inverter?

texts:
Is there a formula that will give me a ball park idea of how much power I will lose when I run my DC battery bank through a power inverter?  Is this something that varies depending on the inverter?  Are some brands better quality than others with regards to this? Is there anything else I need to factor in or is it just as simple as saying for every V/A being drawn through inverter X you lose n%?

What do I need to know to make a smart decision about the inverter to buy? Without starting a religious war about inverters are there certain things to know about particular brands/inverters that might not otherwise be obvious?


texts:
I'm trying to build a LED panel around my living room, using 10 strips of ~10m packed with WS2812. A rough estimation of the power required with all LEDs at full brightness would be 700 W.

The flexible PCB of the LED strips of course cannot carry that amount of power, so I need to feed power at least once every meter. I'm looking for the sanest way to do that.

My current approach would be two metal pipes along the wall (that would also provide the support), and having individual panels clip onto those, and simple connectors for the signal lines. I'd directly distribute the 5V from the PSUs.

Questions:

is this a good approach, or is there a better way?
if I have two PSUs, each for 350W max, does it make sense to connect one to each end of the rail?
if I assume that most of the time, I'll have a load of ~20W (because brain surgery is my hobby, not my job), is there a way I could make this more efficient?
if I assume that I won't ever need all LEDs on at the same time, can I somehow enforce this (e.g. use three rails, if rail 1 uses more than 175W, power down rail 2 so the entire power consumption will not exceed 350W)?


texts: Why do we prefer zero-crossing optotriacs for driving triacs?

texts:
I usually see a special type of optotriac which has internal zero-crossing detection circuit in it. This type of optotriac is generally used for driving triacs. But, I don't understand its necessity. A normal optotriac can do the same driving job, couldn't it? Why is this zero-crossing triac preferred for driving triacs?

MOC3041


texts: Wiring a multi-speed motor from a tower fan

texts:
I am trying to fix a tower fan from a friend. He found out that the motor was working, but something on the circuit board wasn't. He then took apart the board from the motor without remembering which wire of the motor connected to pads on the circuit board. Now I am trying to find out how this single-phase AC motor works by measuring the resistances across the wires. I did this and found out that some of the wires have some resistance between them (from which I conclude these are the common and speed select wires). There are also two wires (grey and brown) which have infinite resistance to the rest of the wires, but between them have zero resistance. In total I have 7 wires and I will give the resistances down below. Can someone help me with finding out what every wire is supposed to connect to?

I also have a capacitor which was connected before to the circuit board (very large cap). I also already tried to look the motor up on google (Shanhu shm-40), but I can not find anything that looks like a wiring diagram or something like that.

Grey-Brown --> 0 ohms

The other 5 wires seem to be connected in the following way (with resistance from white to black being 1279 ohms):
White-->Blue-->Yellow-->Red-->Black

The following resistances are in between these connections (they add up pretty close to the total of 1279 ohms).
White-Blue --> 332 ohms
Blue-Yellow --> 174 ohms
Yellow-Red --> 204 ohms
Red-Black --> 594 ohms

The fact that brown/grey are not connected at all to the other wires seems very strange to me. If anyone could help me solve this problem I would be very thankful :D.


texts: How to turn off DC-DC step-up converter to run on 3 AA batteries

texts:
simulate this circuit – Schematic created using CircuitLab

I am using this step-up converter :
DC-DC step-up converter
with 3xAA batteries (input voltage for the circuit is ranging from 4.65v down to approx. 3v). The main chip is labeled F193. I would like to take care about current consumption. The first thing I did is to unsolder USB and the LED (so going down from 10mA to 0.8mA). Now, I try to shut down the step-up when not needed. This step-up is used for a stepper motor (28BYJ48 - requiring 5v) that is ON 100ms every minutes.

I am working with an AVR microcontroller that goes to deep sleep when not used consuming about 20uA. I know there is room from improvement on this side but I am trying to fix the problem in order of the more consumption first. This microcontroller runs as low as 1.8v input (far lower than the 3xAA battery depleted around 3v).

I tried with a 2N2222 transitor : base linked to the AVR (with 1K resistor) and in common emitter mode (emitter to ground and the input of the step-up converter from Vcc to collector). This doesn't work as I mesure always a 0.8 mA current even when OFF. I think this is due to the Vce ~ 0.7v.

I also tried with a TIP122 in the same configuration but with the same result (0.7mA still there).

Is there a way to completly shut-down the DC-DC step-up converter ?


texts: I have preamp circuit from an earlier project that is based on TL072 opamps. I have been using it with a 9 V (+-4.5 V) power supply, but now I have the chance to give it a +-9 V supply. The signal that goes through it is a small audio signal, probably never larger than 1 V. Does it make any sense to bother giving it a larger supply voltage? (I know that the minimum supply voltage for this IC is 7 V (+-3.5 V) by the datasheet.)


texts: Identifying VW head-unit connector types

texts:
I've kind of been on a long quest to build an embedded system for working with the head unit of my '04 VW Golf. Others have done some work to detail pin-outs and write source code to send signals to and from the head unit. I'm planning on getting an Arduino Uno and using the RTFM framework in Rust for writing the embedded bit.

I have been using a system called "PhatNoise" (discontinued in 2003) which emulates a CD changer but with a hard drive in the back of the car. Different CD numbers (1-6) have different functionality: 4 is for selecting artists. Suffice it to say that it makes it super easy to navigate through your media collection without taking your eyes off of the road. There's a lot of old stuff involved that I'm tired of dealing with, including only using certain types of IDE hard disks and some weird DRM system with hidden bytes on the disk.

I'm planning on building something that's close to this with a Raspberry Pi communicating with an Arduino Uno over the built-in UART over USB. The Uno will speak the protocol to the head-unit and will allow sending and receiving commands.

I'm having a hard time finding connectors to match what is already present. There are three connectors, the female head-unit cable (which I'll call "FHU"), the male corresponding to the FHU (which I'll call "MHU"), and the unique cable that the PhatNoise has (which I'll call "PHAT").

Here are a smattering of photos, which I will explain and expand on presently.

Here is the FHU female head-unit adapter which goes from the back of the car into the head unit in the front:

Here is the MHU male head-unit adapter which connects the FHU to the PhatNoise device:

Finally, this is the PHAT (PhatNoise input connector) entering the back of the PhatNoise device:

Here is a terribly low quality description of the pin-out:

There's 12V DC from the battery, 12V DC from the accessory (only on when car is on), left/right channel audio, and a ground + MISO + MOSI + SCK for exchanging data with the head-unit.

The general idea here is that there is a "head unit" in the front of the car with media buttons, volume, seek, etc. which drives the controls. Messages are sent to the back of the car via cable terminating in a female connector.

What are these connector types, and is there a place I can purchase them? The most useful one to replace would be the PHAT PhatNoise input connector because it'll save me having to buy multiple parts. Can anyone identify what these connector types are?


texts: Connecting a polygon to a smd pad (Eagle)

texts:
I am attempting to create a polygon that increases the area of an existing smd pad so as to make the area larger in order to hand solder. I am running into an issue removing what I believe is the thermal boundary between the polygon and the pad.

I read through a couple previous posts with similar issues:

 Eagle make copper pour connect to entire smd pad

 Removing pad to polygon space in eagle

the pad in question is only there to adhere the part to the board, it serves no other purpose.

I double checked that I was not using thermals when creating the polygon, then modified the footprint and removed thermals from the pad in question as well. Since then I have completely removed and re-added the part to the board, but the issue still persists.


texts: How to calculate the intrinsic drain voltage (Vk)?

texts:
How to calculate the intrinsic drain voltage (Vk) using TCAD results.
I didn't find a good explanation online, only compact models that doesn't help in TCAD simulation.
I want to plot Vk, which depends on the drain and gate voltages, as shown in the attached image.


texts: I just received some 10K .1% precision resistors from Digikey (part number PTF10KECT-ND). Unlike all their other passive components, which come in a normal plastic bag, these came in a metalized bag with a yellow seal that warns me that they're "electrostatic sensitive devices". They're kidding, aren't they?


texts:
I have a question about the telephone line voltage.
When I make a short for 12 volt I see the spark and heating, my question is why I can’t see anything (spark, heating) when I make short with the live telephone line? Although the voltage for the live telephone line is 48 volts.


texts: MOSFET drain current parametrized to distance

texts: In Id-Vgs Mosfet curves, sometimes, current is parametrized to a distance in micrometers. What is this parameter? Gate length, effective gate length, or width of the transistor.


texts:
To what extent and which components can be salvaged from 5-15 years old electronic devices? In other words, what is feasible to dismantle for hobbyist use and what is not? Especially, is it ok to reuse surface-mounted ICs?

My own experience tells, that resistors, transistors, small capacitors survive quite well, but I am not sure about small diodes, small and surface-mounted electrolytic capacitors, crystals. Also, I have bad experience with recycling connectors (pins get out of plastic case).

Somewhat related, how to check non-trivial components? Do some of them loose precision a lot?

Maybe, there is some specialized web resource on the topic and or guides.

UPDATE: I am really interested in an answer from persons, who had more or less extensive practical experience with recycling different kinds of components. Personally I do not recall anything failed because of thermal impact of desoldering (but I have no experience with SMDs). And this makes this question even more interesting, because answers so far are discouraging the practice.


texts: What is the power / energy of a discrete time constant signal?

texts:
I know that this is a very fundamental (and maybe vague) question.

But I'm not sure what period I should use.
I read somewhere that a constant signal doesn't have a fundamental period but is periodic.
So looking at the formulas for calculating energy and power would that mean that a constant signal is an energy signal?

Thank you for your replies, please let me know if you need more clarification. ( I am new to this topic)


texts:
I want to add a kill switch to my car for the fuel pump relay. The switch I would like to use is one which would need to be pressed/flicked on to start the car but when the car is turned off the power to the switch is lost then the switch automatically turns off without touching it so it would would only be used to turn the car on.
Is there a switch to do this?


texts: Common DC ground with two bridge rectifiers

texts: I have an old AC transformer with many taps off it at different voltages.  Connecting a voltmeter to tap 2 and tap 3 gives 25V and connecting it to 3 and 4 gives 5V.  I connected them to two bridge rectifiers, so the rectifiers now output 25V and 5V DC.  I needed a common ground for the two currents, so I put a wire between the DC grounds of the rectifiers, but now they give the wrong DC voltages (~18V and 33V, if I remember correctly).  What am I doing wrong?


texts: Exclusive execution unit in pipeline stage for execution of memory access instructions

texts: I was studying pipeline concept in microarchitecture. My professor told me that memory read and write operations take longer time to execute since DRAM has a maximum frequency of 1333Mhz. Hence, when a memory i/o operation is executed, the execution takes longer time. This increases the latency of the processor. Other instructions(fetched after memory i/o instructions) get 'delayed'. I was thinking of a vague idea that why cant we have a different execution block for performing all the memory operations. In the fetch hardware itself, once we know that the instruction is a mem instruction, instead of being executed by the main execution unit itself, we could have a different execution unit for such mem instructions. Could someone comment on the thought? Should i propose this idea to my professor? He is a bit grumpy!


texts:
I'm trying to build an ultrasonic transmitter circuit. The datasheet specifies 20V peak-peak for the ultrasonic to operate at its maximum power. However I'm limited to only using a 9V supply. What I thought about doing is making an H-Bridge to switch the polarity of the battery between 9 and -9, giving me  almost 18vpp. Do you think this is a good idea? Do you have anything else to recommend?

This is what the circuit would look like.


texts:
I am using CoolRunnerII CPLD and wish to know what is the I/O Voltage Standard setting in the fitting properties:

I know that Vcc must be 1.8V. I also know that I define the IO bank voltage by providing externally voltages to Vccio1 and Vccio2. So, what exactly is the IO setting in the fitting process configures?


texts: Why would we place an inductor in series with a lamp, rather than just a resistor? I'm sort of thinking it has something to do with being able to control voltage to the lamp, without effecting current? But I'm unsure.


texts: Why would manufacturers use Ni-MH batteries in a robot vacuum cleaner?

texts:
In the late 1990s/early 2000s laptop and cell phone manufacturers started phasing out Ni-MH batteries in favor of Li-Ion. The main reason for this seems to have been that Li-Ion cells do not suffer from memory effect¹, which is the major drawback of Ni-MH cells: if they are frequently charged without having been completely discharged, their capacity drops rapidly.

During the transition period, Li-Ion batteries were mostly reserved for high-end devices, or the costlier option where a device was available in either configuration.

The main obstacle to universal adoption of Li-Ion seems to have been the cell voltage of 3.2–3.6V—in contrast to the 1.2V of Ni-MH cells, which is in the neighborhood of alkaline batteries and led to wide availability of Ni-MH cells in the standard alkaline form factors, whereas no such ”household sizes” ever evolved for Li-Ion.

Today, when I look at the specs of robot vacuum cleaners, I see that most come with Ni-MH batteries. Ariete offers one single model with Li-Ion batteries, which seems to be their low-end model. Also, they have proprietary battery packs—so neither cost nor the standardized form factor seem to have influnced the design decision.

So why are Ni-MH batteries so common in robot vacuum cleaners?

¹ Edit, since there’s some confusion about the term: For the purpose of this question, “memory effect” shall refer to loss of capacity (reversible or not) caused by frequently recharging a battery without fully discharging it first. (If there’s a more accurate, somewhat widely accepted term for this characteristic in Ni-MH cells specifically, a hint will be appreciated.)


texts: Do I need to connect both GND and both VCC on this addressible LED?

texts:
I'm working with APA102-2020 addressable RGB LEDs (datasheet here). Each component has two GND pads and two VCC pads. Testing with a multimeter, I find that each pair of pads is connected (ie GND-GND and VCC-VCC). In the PCB I'm designing, should I connect both GND and both VCC pads, or do I only need to connect one of each? Why/why not?

The datasheet doesn't show these pads, but the datasheet is known to be inaccurate in other ways so I'm not sure if I should fully trust it.

I only know what they are from the KiCAD footprint.

The LEDs look like this:


texts: Continuously log data from an oscilloscope

texts: I have a pin which is being toggled every 100ms by an MCU. I need to plot a graph which consists of the variation from the desired interval . That is the number of times it moved away and was toggled for 101ms or 98 ms and so on. I tried to do it with a scope but the memory seems to be limited. I can capture a maximum of 50000 lines as csv . Even if I reduce the sampling rate , it is nowhere close to the 4 hours of data I need to capture. What kind of an instrument should I be looking for? Is there any easy way to achieve this?


texts: Reverse voltage protection circuit operation

texts:
I have this reverse voltage protection circuit:

Can someone tell me how this circuit protects from very high reverse voltages? I am not able to understand  how the capacitor is connected in such a reverse way and how can it protect the downstream circuit.


texts:
I'm using atmega32 µc with the internal 10-bit ADC. I connected my potentiometer to the ADC 1 and I'm using 5 V Voltage Reference.

using the following code, I did the ADC-config

void ADC_init(void)
{

    //Turn on the ADC
    ADCSRA |= 1<<ADEN;   // Turn On ADC (Enable ADC)

    //ADMUX  |= 1<<ADLAR ;  // Config shifting to the left (10-bit), otherwise it is right adjusted

    ADMUX  |= 1<<REFS0 ;  // Config VRef (external Vref in this case)
    ADMUX  |= 1<<MUX1 ;  // ADC-Channel 1

//  ADCSRA |= 1<<ADIE;   // Enable ADC Interrupt
    ADCSRA |= 3<<ADPS0;  // Assign ADC-prescaler 128

    ADCSRA |= 1<<ADSC;   //start the the measure conversion
}

Then in Main function I am calling the following function each 1000ms and send the data to the USART interface

void ADC_measure(void)
{
    _delay_ms(50);

    // if the ADC right adjusted
    theLow = ADCL;  // ADC Value Low
    _delay_ms(50);

    ADC_TenBit = ADCH<<8 | theLow  ;  // because of lift adjustment of ADC

    _delay_ms(50);

    sprintf( ADCBuffer, "The ADCValue is : %d \n", ADC_TenBit );

    _delay_ms(50);

    usart_pstr(ADCBuffer);

    _delay_ms(50);
    //start the the measure conversion
    ADCSRA |= 1<<ADSC;
}

The problem is : when I open the terminal , I see only the ADC Value = 255 or 248
increasing or decreasing the potentiometer value doesn't change the ADC value.

what can I do now?


texts: How does base resistance affect a transistor?

texts:
I'm not strong with electrical engineering and I have prototyped a circuit which works; however, to my chagrin, I don't understand why.

I'm using an Arduino digital out pin to power a relay.  I have an NPN transistor to switch 5 volts through the relay coil that's 125 ohm.  At first, I just connected the base to the output pin and it worked fine.  Then I noticed people tend to add a base resistor so I stuck a 1K ohm resistor in there and it still worked fine.

I've been trying to learn more about base resistors and I feel like I computed that I should have a larger resistor.  Is the purpose of the base resistor just to lower the current to prevent wasting energy?  Or to prevent generating heat?  I don't fully understand why there's a need for a base resistor, and if there is, why the relay in my circuit worked fine without the resistor and also with a smaller resistor.

This is the datasheet for my transistor: http://pdf1.alldatasheet.com/datasheet-pdf/view/21675/STMICROELECTRONICS/2N2222.html

I don't have a datasheet for the relay (it's part of an old hobby kit . . . you know . . . one of the ones with the breadboard and springs).

Here's my current setup:

simulate this circuit – Schematic created using CircuitLab

Here're my likely incorrect calculations.  I computed the collector current as $$I_{c} = \frac{5V}{125\Omega} = 40mA$$

I felt like, based on the spec, a reasonable \$h_{FE}\$ for 40mA is 75.  Thus, $$I_{b (sat)} = \frac{40mA}{75} \approx .5mA$$

Given that, I felt like the best fit for \$V_{BE (sat)} = 1.3V\$.

Then, I thought I needed to drop 3.7V across the base resistor at .5mA.  Thus, $$R_{base} = \frac{5V - 1.3V}{.5mA \div 1000} = 7,400\Omega$$

So, if that's correct, what am I trying to achieve with this resistor?  Am I trying to prevent energy loss or heat production?  Or, am I trying not to exceed the max base saturation voltage?

Given that 7k4 ohm is not a common resistance, should I drop to a 6k8 ohm resistor or go up to 8k2 ohm resistor?

It seems like 8k2 ohm would keep the base voltage below the saturation max voltage and the 6k8 ohm would keep the base voltage above the max base emitter saturation voltage.  Which am I after?

Or, I suppose, alternatively, am I completely off track?


texts: Why does my LED blink when too much voltage is applied?

texts:
I bought a set of simple light-emmiting diodes. Connecting one to Arduino's full 5V output (without a resistor) causes the diode to blink. However changing the duty cycle to a value below 80% causes the diode to emit constant light.

What causes this behaviour? From my (limited) knowledge of physics I would assume that a diode should either emit constant light or no light at all, regardless of the voltage.


texts: Rogue resistance between Vout and GND in LDO circuit

texts:
I'm currently developing a circuit as seen here:.

I had some suggestions to check my Iout to ensure that I wasn't drawing so much current that I was causing an overheat. After a little checking I believe that my circuit is way under the threshold (~22 mA.)

I've managed to solder up PCBs that have worked, but the vast majority don't. Today when double checking for any strange shorts, I noticed a rogue resistance between Vout on the LDO and GND (~60-100 Ω.) That resistance doesn't exist on the PCBs that do work.

Note: I've tested this circuit with a couple different LDOs and had the same results on each.

Is there a way for me to further troubleshoot this issue? (I don't really know where to start looking for component failure etc.)

Or perhaps any suggestions as to what's causing this strange behaviour?

Is there perhaps an occurrence where the first connection of the circuit is causing something to break?