texts: Finding a replacement voltage regulator... what do the codes mean?

texts:
So I need to replace the following voltage regulator in an old Atari as it's registering 0.5V between output and ground and 24V on the input, but it's supposed to be providing 12V on the output side of things.

I'm trying to establish whether either of the following (locally available) parts are suitable replacements:
http://www.jaycar.com.au/productView.asp?ID=ZV1634
http://www.jaycar.com.au/productView.asp?ID=ZV1642
I'm a complete newbie to electronics (I'm a software guy) but I've read on here that the M is for Medium current, so I'm guessing that the 3A regulator I linked to would be capable of the job, but figured it'd be better to ask than to burn out some other component.
Question
What do the parts of the component code mean? I guess the 12 in UA85M12UC means 12V, but I have no idea about the UA78 and UC!


texts: Interfacing coin cell back up for internal RTC of ESP32

texts:
In esp wroom-32 all the VDD pins has a common connection. It includes VDD_RTC too. So in case of power failure if I switch the power between main DC source and coin cell using a mosfet, will it create any interrupt on updating the RTC time?

I haven't done any practical on this topic. I got this doubt while going through the internal connection of wroom-32. So please share if there is any proper solution.


texts: A question about differential ended settings for single ended inputs

texts:
Reading this documentation, what could be the reason to use 10k if one uses differential ended input settings for signal sources?:

I dont know why they recommend 10k but I had 6 channels going to this board from single ended 6-axis force transducer system and the signals measured were very clean. But when I added some other transducers to rest of the channels such as temperature, humidity ect. transducers, I started to have more noise and 50Hz noise. All inputs to the daq are single ended( the transducers' grounds are not earthed so no ground loops expected) and BNC coax cables used.

In my case I had shorted all channels' CHLow to LLGND but they recommend 10k resistor, could that be the reason? What could be the 10k resistor's function?

edit:

I tried to make a simulation regarding Spehro Pefhany's answer:

(left click to enlarge)

I couple EMF to both lines, and Rx is the recommended 10k.

If I dont use 10k and short CHLow to LLGND I obtain noisy output(red plot):

If I use 10k the 10k develops a common-mode and the output(red plot) doesn't have the noise:

I haven't tried this 10k in practice yet though.


texts: Help figuring out an op amp circuit with two loudspeaker outputs

texts:
I have to design a circuit that amplifies a sine wave with either a AD8616 or a LTC6256 (currently using the AD8616) to a 50 ohm loudspeaker and a rated power of 0.5 W. I'm a novice when it comes to analog electronics and I'm getting very confused trying to design a circuit for my needs. I'm not a native English speaker too, so please correct me when I use the wrong terms.

The circuit:
I am really trying to figure out if this design is correct and what it actually does. I got the gist of how non-inverting configurations work, but I'm not sure how the input sine signal is transmitted.
First there's the input voltage at 3.3 V that gets divided evenly, so at Pin 3 (non-inverting input) there should be 1.6 V. I read that through a feedback loop the voltage at both inputs (inverting/Pin 2 and non-inverting/Pin 3) should be the same (1.6 V). Therefore there should be a gain of 11 (with R3 and R4) at output 1 right? I am able to measure the 1.6 V with a multimeter, but at the loudspeaker outputs the voltage seems to drop with time (probably because of the capacitors?).
I'm slightly more confused at what's going on at pin 5-7 because I don't understand how the sine signal is transmitted. I don't know what voltage there is at the non-inverting Pin 5, is it the voltage from the sine signal? Shouldn't it also get 3.3 V like Pin 3? When I try to measure it with a multimeter, there's little to no voltage and I can't seem to power the loudspeaker. I think it's because the sine wave measures only about 150 mV.
The op amps:
Currently I'm using the AD8616 because of its high output current. The data sheet reads 150 mA at 5 V, so I'm thinking of switching the 3.3 V input to 5 V because of the loudspeakers high impedance of 50 ohms, so it can get more power.
I'm sorry if I'm all over the place, I'm stuck at what I should do or switch up to get the loudspeaker to work.
Edit:

simulate this circuit – Schematic created using CircuitLab


texts: Can I input a square wave LO into a mixer?

texts:
I would like to downconvert a signal at 169.55MHz (10khz bandwidth) into an IF of 20.4MHz.
For that purpose, I need a local oscillator of 149.15MHz or 189.95MHz.

But... of course, I cannot find a crystal at these frequencies (at least I think I don't have the budget for a custom Xtal. But I might be wrong on that point. I have no idea.) and I have to find another way.

I decided to try to generate one of my LO frequencies from a PLL. But most of the PLL have a CMOS or other kind of logic output, not sine waves. This is especially true when the output of the PLL IC is post scaled. This approach is convenient, because it's easy and low cost to design such a PLL with an integrated, high speed, VCO (such as the ADF4351).  That VCO runs at frequencies around 1GHz, is divided and output using a logic driver (here differential at 0dBm).

My question is: can I inject the logic signal from the PLL at the input of my mixer? That signal has a lot of harmonics (only the odd harmonics, in theory.. right?) Or do I need to low pass filter that LO at the input of the mixer?

I have computed that none of the LO harmonics, mixed with the input signal (or harmonics of it) falls into my 20.4 IF band pass filter. But is it enough? Do I have to expect another issue related to this?

I would feel very confident to inject a "as clean as possible" sine into my mixer, but not a square wave...


texts: Determining Number of states in State Space Modeling

texts:
I want to use state space modeling for representing the following circuit system. However, I am unable to decide the number of states. I am able to describe the system with a set of three equations. However, I am unable to form the matrix A with three states. Is the number of states three or more and how do I determine the number of states for circuits in general? (By the way, my outputs are currents through inductors and the voltage across the capacitor.)

simulate this circuit – Schematic created using CircuitLab


texts: How to Indicate Bridged Solder Jumper for Production PCBA

texts:
If I would like to indicate to the PCBA manufacturer that a solder jumper position is to be "bridged" with a solder blob, what is the preferred way to indicate this? I have thought of the following options

Paste Layer Data - indicate coverage (conversely, no paste if no jumper)
In Component BOM - Indicate population of position and let PCBA figure it out.
Manually or specifically indicate, e.g. in engineering drawing.

A second question is if this is something that would normally be done during smt processing or manually afterwards.


texts:
I'm looking for some advice as to the best way to achieve wireless
video streaming from an OSLess embedded system we are building.

I have never done any work with WiFi before so all the help I can get would
be appreciated.

Since we are looking to stream video we will need a high throughput connection
on both the WiFi and interface ends of the device (we are looking for an add on
module type solution). I have been researching on the web for a week or so now
and haven't really had much luck.

our system is based on a Freescale i.mx 233 processor (USB and SDIO interfaces)

The possible solutions we have come up with would be:

an SDIO Wifi N module (as SDIO seems to be the only interface fast enough (excluding USB), am I correct?)
a USB stack with WiFi over USB class drivers allowing the use of a WiFi dongle.
using a minimal RTOS that has support for WiFi over USB dongles

Whiznet provides SDIO modules that suit our need
Jungo USBWare has an OSLess WiFi over USB stack and class driver
Freescale provides the MQX RTOS that has an optional USB stack with the CDC USB class driver (as well as a few other minimal RTOS that provide this kind of support)

Whiznet has been very slow getting back to me with information (I don't even know there prices yet and they don't seem to sell through distributors which makes me think I won't have much luck with them)

I haven't even heard back from Jungo and I would rather stay away from USB if possible as it seems like an unnecessary complication.

I would like to avoid an RTOS as much as possible as we're doing some image processing and I would like to be in control of as much of the overhead as possible, though if there are no other solutions we will probably go down this path.

Does anyone have any experience doing a similar thing?
What do you think, what's my best option and have I missed any?

It feels a lot harder than it seems it should be.

edit

We are looking at streaming video with an absolute minimum resolution and frame-rate of 320x480 @ 15FPS


texts: Help understanding BJT voltage comparator

texts:
I'm trying to understand how a transistor voltage comparator works. For example I've been studying this LM339:

comparator circuit diagram http://lc.fie.umich.mx/~a0686696c/Materias_files/Lab.Elect.Analog_files/Voltmetro/Comparators_files/ComparatorGuts.GIF

My questions are:

What are the current sources for and how would those actually be implemented if for example I wanted to bread board this circuit
How can the circuit differentiate between inputs of say 1.5V or 2V? I must be wrong but my understanding is that if the voltage on a transistor exceeds a certain threshold the transistor will turn on. So I don't understand how inputs of (3V, 4V) and (4V, 3V) for example are any different.
If INPUT+ is at 0V and V+ is at say 12V then wouldn't 12V be shorted to 0V at the base of Q2?

Basically a walk-through of what happens with this circuit for different inputs would be great.


texts: RFC realization for bias of microwave transistor circuits

texts:
I saw the following configuration for the bias circuit of some microwave amplifier circuits.

I think in the left figure the RFC is realized using a quarter wavelength short circuited stub (because of the capacitors), but there is no by-pass cap in the right figure. How RFC is realized in this configuration?

Also there is an extra stub at the end of the short circuited stub. What is the purpose of this additional part?

Link to the references: see
page 4 and
page 8

Also there are a few examples in the book "Microwave Transistor Amplifiers: Analysis and Design" by Guillermo Gonzalez, Prentice Hall, 1997, chapter 4.


texts:
I'm designing a keyboard and I want to be able to daisy chain another USB device through it. I have a Drop ALT that does this and I really like it. It has two USB C ports and you can connect either one to the computer and use the other as a pass through. It uses a USB2422 as the hub and I've read the data sheet several times but I can't figure out how it's working. The USB2422 has one upstream port and two downstream. I thought the upstream would go to the computer but then why doesn't it matter which port you use?
Edit to add pictures.


texts:
I am trying to design a dc-dc converter using the UC3844 IC. The working is clear to me. But the datasheet has an application circuit that is a bit confusing for me. The datasheet.

The circuit in question is the one shown below -

.

Pin2 is the error amplifier and should be connected to the Vout. How is this connected in this application circuit ? Which secondary should it be connected precisely ?


texts: PCB footprint recommendations for FPC soldering

texts:
I'm considering making a PCB to which I would directly solder an OLED display like this; it has a 30-pin, 0.7 mm-pitch FPC connector (a link to the datasheet is on the page).

What's the right way to design a footprint for this kind of connection? Are there any resources that provide a recommended footprint or at least some general guidelines for the geometry and positioning? (For example, how long should the pads be? Should they be bigger than the FPC contacts, and in which directions?)


texts: implementing direct addressing mode for a load instruction on a mips archtitecture

texts:
Given a Mips machine with 26 bit addresses and 32 bits data-paths, where the load instruction is as follows

|OPT code|rs|rd|immediate|

|6 bits  |5 bits|5 bits|16 bits|

The OPT code is the instruction type(lw), rd is where the value will be loaded to, rs is the base register and immediate is the offset. Mips support only displacement mode meaning:

 lw $t9, ($t7)60

is the same as

 Reg[$t9]<-M[Reg[$t7]+60]

This is a typical mips load but what if i wanted to implement address indirect load in the control unit, writing the misconstructions for address indirect mode similar to a basic cisc computer. Where the the address of the value is in memory. is this possible to do in one instruction?

Edit:

This is what i am looking for  in one instruction:

Reg[$t9]<-M[Addrs]

or better yet

Reg[$t9]<-M[M[Addrs]]


texts: Reprogrammable Remote Power Supply Raspberry Pi Monitor and Control

texts:
I currently have a reprogrammable power supply (HCS-3400) hooked up to be controlled remotely from an control/monitor app provided by the power supply company, Manson. The supply is connected via USB to a Raspberry Pi B+ which is connected to the internet network (Ethernt), thus can be accessed from the App.

I am looking for a way i can track the voltage, current and power coming from the supply to the Raspberry and hopefully create some code which could stop the Supply from reaching a threshold level/s or from varying abruptly.

Does anyone have any ideas for this? I was thinking either finding some kind of Watchdog software or see if Python on the Pi can control USB input/outputs

HELP


texts: would i need a fuse when experimenting with transformers?

texts:
I have a 0.7A center tapped 12v/15v transformer(i dont know details about it). However i dont know which pin is which among the output pins, so I have to jump them in many ways and measure with multimeters.

would i need a fuse about 250V 1A(the only fuse I have) to safely do some experiments with the transformers? or is it okay because the current is low?


texts: Securing a PCB board to a plastic casing - can I just glue the bottom?

texts:
I have an inertial measurement unit PCB that picks up changes in acceleration. I want to secure it inside a plastic box/casing. The products (and pictures) I want to use are below:

https://www.sparkfun.com/products/13303

https://www.aliexpress.com/item/1-piece-plastic-standard-box-76-35-20mm-2-99-1-38-0-79-inch-box/1439035089.html
(The PCB fits inside easily, it measures about 2.5cm x 2.3cm)

Now it's incredibly important that the PCB - which has the sensor - is very rigid to the plastic box/casing. I want to measure motion of the box as precisely as possible. I'm not sure if using the 2 corner holes with screws/nuts is sufficient as it's only on one side and therefore provides some leeway for the other side to flex slightly.

So I was thinking why not just glue the damn thing? Glue doesn't conduct electrical signals (as far as I know) so that's not an issue. And the part being glued, the PCB, is extremely light, so the holding force need not be too high.

Will this work? If so, what glue/adhesive product should I use? Are there better solutions? This is a hacked-together project, so professionalism isn't the highest priority. Just the requirement that the PCB is very rigidly attached to the bottom half of the plastic case. Thanks for any help!


texts:
I'm looking for advice in making sure the FET driver I've chosen is capable of driving the FETs I've chosen with turn on time as low as possible.

I'm going to use the LMG1210 and EPC2020 with 12V rails switching at \$500kHz\$. The datasheet says the gate charge (\$Q_g\$) is \$16nC\$ typ. The peak current of the LMG1210 is \$3A\$. Am I correct in saying the minimum turn on time of this FET can be calculated using:

\$T_{on} = \frac{Q_g}{I_g} = \frac{16nC}{3} = 5.3nS\$


texts:
My building recently installed a CCTV camera system. Anyone with cable TV is able to tune into channel XX and watch the CCTV stream live.

I want to get a cheap and small LCD (≤7") and build a dedicated "television" that would be tuned to channel XX. Eventually, the plan is to hook this up to a caller-id circuit and have the "TV" turn on when I get a call from downstairs.

I'm a programmer by trade and don't have much experience with building circuits.
I'd just like a ballpark figure of what I'll need and how difficult it would be to make a primitive TV these days.


texts:
I'm currently trying to use EAGLE software and I'm trying to import a part called 'LT3022' which is a voltage regulator from Linear Technology.

I've found a CAD library of LT products from element14 and downloaded and added the library.

But in the library the par that I'm looking for is called 'LT3022EMSE'.

It does look like the one I'm looking for but I'm not sure what the EMSE means.

The pin numbers matches the the datasheet so I guess this is the same but I would like to know what the EMSE means anyway.

The image below is a screenshot that mentions EMSE. Looks like there's a lot of variations of EMSE too...


texts: how to copy the value of a register into another (Logisim)

texts:
how to design the circuit that copy the value of register into the other? I only know the register can be written or loaded, but how is it possible that after loaded the value of 1 register and still keep it?

for example: MOVE Rb, Rc // copies the contents if Rc into Rb


texts: Why does the voltage gain of a transistor-based amplifier vary with input frequency?

texts:
Why does the gain of a MOSFET-based common-source amplifier depend on the frequency, and why does it vary the way it does?

I did an experiment with a common source amplifier and recorded the gain at different input signal frequencies, and noticed that if the frequency was low/high, the gain would be low, but in a few central frequencies, the gain was peaked and was flatlining, much like the picture above.

I tried researching this, and a site said something about the internal capacitances in the transistor causing this effect, but the descriptions were too complex for my level of knowledge, as they started discussing BJTs and I am only really familiar with FETs.

Can someone explain the reasoning behind the fact that lower band and higher band of frequencies experience less gain than the midband frequencies?

Thanks

The following is a diagram of the circuit:

The model of the transistor used is CD4007UBE from Texas Instruments, using only pins 6,7, and 8.

Here is some data:
For f = 1 kHz, G = 7.26 dB
For f = 10 kHz, G = 7.41 dB
For f = 100 kHz, G = 7.38 dB
For f = 1000 kHz, G = 6.88 dB


texts: Can IPv6 be implemented on a mcf52259 demo board?

texts:
I heard that there is a possibility of IPv4 being implemented on a mc52259demo coldfire board. Can IPv6 be implemented too? It is a Coldfire processor board developed by Freescale and it uses MQX OS.

Even Embedded Access Inc (as seen in Mark's answer) does not provide IPv6 on the MCF52259demo board.

I am implementing this myself and not depending on any RTOS vendor's support, so the actual problem in implementation is this: What changes need to occur in the code in IPv6 from IPv4 that is to be loaded onto the board?


texts: I want to regulate 52 volt to 44 volt with applying different pwm signal

texts: I just want to regulate 52 volt to 44 volt with different pwm signal from arduino through a optocoupler 4n35.I just use this circuit in which i used 6 pmos and 6 optocoupler...i applied 52 volt and 45 amp to get voltage between 52 to 44 but when i try to regulate the circuit it failed all the MOSFET have burnt.The output of this circuit is going to connect to motor driver circuit please help to find...is there any alternative circuit to control if then please post here


texts: How to test the voltage of a speed sensor and identify the +ve, ground and signal wires using a DMM?

texts:
I am a novice and would like to identify each of the wires going to a speed sensor.

Below is a photo of the connector from the mainboard (left) to the sensor (right):

Is it possible to identify the signal wire from the colours? How can each of the wires be identified using a DMM?

That is, should I "intercept" the wires between the connectors and look to find a steady voltage between two wires?

What about the signal wire, what should I be looking for? Will a DMM be able to identify the signal wire?

This is what the service manual wiring diagram shows:


texts: How to maintain gpio state if esp8266 get reset or crash

texts:
I am really new to electronic and wish to learn more. Pardon me if the question is inappropriate.

I am trying to turn a led on, off or dim over the Internet. My question is how can i maintain the state of the led if something happens to the Esp8266, for example the unit get reset or crash. So that the led doesnt go off if it was previous turn on when the Esp8266 rebooting.

My guess is that this might involve some external chip or circuit. When the esp8266 receives a command to turn the led on. it will then forward the state to a chip which powered separately. And so, the chip can power the led even if the esp8266 is rebooting.

I am wondering what the chip or circuit would be? (shift register or etc).

Thanks for the advice.


texts: How can I test the amount of power I can draw out of a USB charger?

texts:
I've got several USB chargers where the labeling has worn off. I'm interested in using some of these with a Raspberry Pi Model B, which needs at least 700 mA, as well as other devices with varying current requirements.

Is there any way for me to empirically test exactly how much current I can safely draw from these unlabeled chargers? I've got access to a desktop multimeter, breadboards, components, etc.


texts: Frequency response of dual vs single op amp: OPA2890 vs OPA890

texts:
I am looking for an op amp to use as a unity gain buffer with a disable feature. The OPAx890 looks like a good candidate because it is unity gain stable.

I have noticed that some op amps labeled as unity gain stable have worse stability than others (e.g. OPA690 claims unity gain stability, but its stability is poor. The G=+1 small-signal frequency response shows >3dB of peaking in the datasheet).

The OPA2890 has a very nice looking small-signal frequency response in a unity gain configuration:

I do not need a dual op amp. I was glad to find that there is also the OPA890 which looks like a single version of the OPA2890. It looks like the OPA890 has worse stability with some peaking at G=+1:

Does this make any sense? I would think the same op amp would have the same frequency response, or for the single to have better properties than the dual. Of course I can just get the dual and use 1, but is this an actual difference between op amps or just an error in the datasheet?


texts: Alternative to a potentiometer to regulate 50 W

texts: I want to regulate the input current into an ultrasound transducer (40 kHz, 50W). The signal is being generated by PCB. I read that regular potentiometers are usually employed up to a power of 1 Watt. I have found potentiometers that could be used, but they seem a bit bulky and expensive (ca. 80 EUR). Is there an alternative to a standard potentiometer to regulate the current up to 50W?


texts: How to specify a motor driver H-bridge (3v motor)

texts:
I am trying to choose an H-bridge to allow the use of logic for basic directional control of a three volt brushed DC motor (not PWM signals), however they all seem to have minimum voltages above what I need.

Am I thinking of this wrong? I was thinking of the L293 series drivers, however they have minimum voltages around 4.5v which is too high and also low current limits (0.6-1A). This is the motor I have http://uk.rs-online.com/web/p/dc-geared-motors/4130600/

Would I have to build one using MOSFETS to allow operation at this voltage, because obviously it is easier to use a pre-built IC? Or would the L293 series be lenient and allow me to supply them with 3v so that they run at this level.

Thanks for any responses and I'm sorry if I've missed anything.


texts: I have a question about the YouTube video Raspberry Pi Controls Relay. It's about controlling a SainSmart 4-Channel 5V Relay Module. Is it driven directly off the 3.3V GPIO?


texts: Because on a short the voltage goes down while the current goes up, and a resistance of the line would be nill and remain unchanged. Does the formula fail or am I misunderstanding something?


texts: Determine the resistance of electric transmission lines

texts:
How could I determine the resistance of electric transmission lines?

I face a lot of problems in determining the resistance of electric transmission lines, for example:

"if we need to deliver an amount of power from a power station to a factory to be used there, and the distance between them is 1000km, and we would use transmission lines, and the resistance per km is 0.25Ω.......etc."

When I start to solve the problem and try to determine the whole resistance of the transmission lines, I do this:

  R(tot.)= 0.25*1000 = 250Ω.

But what I find is that this step is wrong, and the total resistance will be determined as this:

  R(tot.)= 2*0.25*1000 = 500Ω.

That is what I find in my text book, and that confused me, and I would like if someone helped me and explains this. Are there always two lines to connect power stations and the consumers, because I find that "2" used in the equation, in every solution to a problem like the one above?


texts: Measuring battery voltage, capacitor on drain (nMOSFET switching load)

texts:
I've got a schematic to measure a battery voltage using a nMosfet (triggered by a GPIO high level). The voltage is measured at the Probe (see picture).

Can you tell me the purpose of Capacitor C1 on drain and how its value is determined?

edit:

(here's a quick answer before I take more time to check in deep your analysis)

Well yes I forgot to mention:

the Probe is actually a MCU PIN (nrf52 / 3.3V) so yes to ADC
the nMOSFET is NTK3134N (datasheet)
the battery is a Lipo (like 3.7 V)

I know putting capacitors like this is to prevent AC and spikes but I wondered if there were other reasons for that.


texts: Is there a pattern to where various industrial AC voltages are used?

texts:
AC voltages in the "low voltage" class vary quite a bit. I've seen nominal voltages of 208, 220-240, 277, 380-415, 460-480, 575-600, and 690 VAC. Past that I don't see anything until medium voltage and 2.2 kVAC. I have the vague idea that 575-600 VAC is common in Canada, 460-480 VAC and 220-240 VAC are common in the US, and 380-415 VAC are common the rest of the world. But that's just a vague idea, and doesn't cover 690 VAC at all.

Are there standards defining which voltage is used where or under what circumstances? Does it really vary with country or region that clearly? Is it more application-based?


texts:
I am confused by this question for a long time. Let's say the initial states are R=1,S=0,Q=1,Q'=0, and both NOR gates are ideal (no propagation delay). Then both gates should change their states simultaneously, and we get R=1,S=0,Q=0,Q'=0.

But as the figure below shows, it contains two steps change, firstly R=1,Q'=0 and we get Q=0. Then S=0,Q=0 and we get Q'=1. This is the result in all contexts. I don't understand why it is two steps change.

Thanks


texts:
I want to generate a software PWM signal for 5 millisecond. using GPIO with 50 percent duty cycle and 100 KHz.

While(5ms)
{
 PIN = 1;
 delay_micro(10);
 PIN = 0;
 delay_micro(5);
 PIN = 1;
}

Is this correct or I want to do any thing else.


texts: I have an Atari 1040ST with a half-bad power supply - Along with two 5v Red wires that Are good, there is a Blue wire that requires 12v .9A (aka 9mA??) - With A/c on, it's measuring at 10.73v (on the Blue wire, if you also have an Atari) causing my machine to cycle the Floppy drive when powered up to a beat of "we will rock you" steady clicking so, I'm pretty sure 10.73v is causing that - I have an external adapter that is 12v but 1.25A and another one that is 12v but .41A - I was reading one of the contributors here, Insta's answer which leads me to think I should use the 1.25A and definitely Not the .41A adapter - I will be splicing in to the Black Ground wire (there are 3 of these, I'll just pick one) and I will Cut the Blue and Splice the + going to that pin, bypassing the Atari PS altogether - I will then have the A/C AND the DC adapter on a Surge suppressor so that they power up at the same time - Should/Can I use the 1.25A adapter is my long question (sorry 'bout that!)


texts: Instantaneous DC output using Laplace transform

texts:
I am testing a feedback system in which a feedback signal from sensor is applied to a correction network and then compared with threshold values.

I need some clue on how to get around this task, I will be applying DC voltage to the network and will compare its output obtained with the one I calculated theoretically. Here is the transfer function of the network with a natural frequency of 90Hz

$$H(s)=\dfrac{1+0.145s+0.0019s^2}{1+\dfrac{0.8}{150 }s+\dfrac{1}{150²}s²}×\dfrac{1}{1+0.0012s}×\dfrac{1}{1+0.008s}$$

I calculated the output of the network by finding its inverse Laplace with step function as its input. The issue is that the output voltage obtained from solving this is a non-linear function hence changes it at every instant so how am I supposed to test the output for a particular DC input?

Any ideas?

Here is the step response I plotted using Matlab


texts:
What is the meaning behind different AC input levels such as AC120, AC135, AC175 etc? I understand that AC_X means the level is Vref + X mV. And I also understand that the setup time is defined with respect to the AC(ih) or AC(il) to the DQS strobe crossing in the case of DQ data signals.
But...

What is the reason these different levels are defined?

Which AC level must be crossed to register a High/Low?

How to tell which level you design is suited for given data rate? For instance a dram I’m using specifies both AC135 and AC160 for 800/1066 speeds.


texts: Why do most battery protection circuits have 2.5V discharge cap?

texts:
I was looking for a battery charge- discharge circuit from ebay, and most if not all, state to have overdischarge protection voltage at ~2,5V. Isn't this way too low? By my knowledge Lithium batteries (LiPos in this case) can only be brought to around 3.5V before riskin damage to the cell? Certainly no lower than 3.0V.
Here are some examples of the boards I found:

https://www.ebay.com/itm/5-10-20Pcs-TP4056-5V-1A-Micro-USB-Lithium-Battery-Charging-Module-Charger-Board/172856541571?hash=item283f0d8183:m:m1YzA8TerE_cywHj69klcVA

https://www.ebay.com/itm/10x-3A-Protection-Board-for-1S-3-7V-18650-Li-ion-lithium-Battery-W-Solder-Belt/282474147244?hash=item41c4c56dac:g:hu4AAOSwY3BZFV3A

Am I missing something? Would it be safe to connect these to a bare lithium polymer cell?


texts: How to protect ADC input from reverse polarity?

texts:
I want to use an AD7124-8 ADC in a project:

I was wondering how to protect the analogue inputs from reverse polarity. According to the datasheet inputs can tolerate at most 0.05/0.1 volts of reverse voltage:

Thus, clamp diodes cannot offer any protection here. Any suggestions on how to resolve this issue?

P.S. Reverse voltage is at most 15 volts.

Thanks


texts: Isolating and instrumentation Amplifiers, does the order matter?

texts:
I've been reading up on the concepts of properly isolating sensitive signals in applications like analog front ends.
For small signals, it is appropriate to use an in-amp. I understand that. But what about isolation?
It seems (see figure below) most flow-charts and lectures show the in-amp being the first stage of input, cascading into an isolation amplifier or barrier of some type.

Practically speaking, looking at isolation amplifiers it seems their topology outputs a differential signal to mitigate noise. However, what if you are only interested in observing the positive wave cycle? In this instance is it appropriate to leave the naught output floating? Pull down resistor? Or cascade into a differential amp?
TI Isolation Amp

From this line of thought, why is it important to first feed the signal to an inamp before isolation? If an isolation amp outputs a fully differential signal wouldn't it make sense to first isolate the signal, feeding the differential output to the difference amp and reduce the component count?


texts:
With help of this site, I have redeveloped my voltage alarm circuit (see my previous question for the history). I started off with an 741 Opamp and it did not work as I wanted it to work (Thanks for your input here). So I did some research and found a LT1017 comparator.

Based on the data sheet, I assumed that I can drive a LED with the output (it says in the datasheet that it can source 70 mA). But it does not work. The output voltage collapses under load.

Anyway, I switched it around and used a PNP transistor (2N2907) to drive a relay, LED and buzzer (See schematics).

So I still have issues and I don't understand why. The 2N2907 has a hfe of around 250 (measured with my multimeter). The buzzer, relay and LED use about 70 mA. Let's keep it simple and use a hfe of 100. This means I need 0.7mA as ib and with 14V Vcc we are at 14-0.7 at 13.3V/0.7mA, that would be 20k.

My problem: With this calculated Rb nothing happens. Even with Rb = 1k only the relay and LED works, the buzzer does not produce sound.

If I play with Rb and measure ib and ic, I get ib of around 10mA and a ic of 50mA. So the transistor has a hfe of 5 according to this.

I know that I must be making a massive error, but where is it? I learned that stuff 30 years ago and I am going back into it now a little. Of course I forgot many many things from back then, but what am I doing wrong?

Thanks in advance for your input.


texts: Creating a coupled inductor with two discrete inductors

texts: Is it possible to create a coupled inductor (with high coupling coefficient) by just placing two inductors very close to each other on the PCB? (Even as far as placing them on top of each other.)


texts: Strange output with a LM7171 opamp (non-inverser amplifier)

texts:
I have a continuous input signal with a very high impedance and I need an output signal with a low impedance of 50Ω. That's why I've considered the LM7171 (High Output Current: 100 mA).
I've tried to make the following non-inverser amplifier using a LM7171 (the datasheet suggests to make an amplifier rather than just a voltage follower):

simulate this circuit – Schematic created using CircuitLab
Unfortunately, I've enormous and fast oscillations of the output (*10):
Without any input:

With an input of 3V:

Why and what could I do ?
Thanks !

EDIT (16/01)
The input signal comes from a NI BNC 2110.
|V+|=|V-|=15V

EDIT (17/01)
I've made some changes to my circuit according to Neil_UK recommendations (from the datasheet), plus I've tried a resistor 10kΩ between the ground and the output.

simulate this circuit
However, the problem still remains... I'll say you if I succeed in solving this.


texts: How can I make contact with the material if soldering is not possible?

texts:
Sorry for the title, I have problems putting it to words in English.

I ordered some small and cheap Chinese solar panels. I thought it was fun to tinker with them and learn about electricity. After my horrible soldering I found out I want them in series, not parallel and during the resoldering I ruined two of them. Too much heat... and no skills.

Please take a look at the picture. I was wondering is there any way to make a contact again with these empty holes? If I stick my multimeter in the hole, I still get voltage. Probably I didn't break them for good.

I tried to Google the problem, but haven't found answers. Is there some kind of paste or liguid? I cant just stick a wire inside the whole, it doesn't stick.


texts: Looking for a 74LS "friendly" decimal counter or BCD to decimal decoder (similar to CD4017)

texts: Without getting into too much detail: For my project I've been provided exclusively 74LS chips, but I need either a BCD to decimal decoder, or a decimal counter like the CD4017 for control signals. The 4017 is very convenient because it already has decoded outputs which can be used as signals for other input pins on a circuit. Is there a similar  chip that can fan out to at least 2 to 3 74LS input pins? I don't want to run into current issues mixing 4000 and 74LS.


texts: Can you load Gerber files back into a PCB layout designer such as Eagle?

texts: There's a PCB I may need to change a solder pad, but the schematic and layout are gone and were not added to source control. Is it possible to load the Gerber files back into a designer to change the pads so that I don't have to try to draw out the entire schematic and layout again?


texts:
I am currently trying to build a package for a through hole potentiometer in Eagle Cad and I wanted to incorporate holes in my PCB for the metal tabs on the side of the pot. I determined that these holes should be at least 1.8 mm in diameter. However, the moment I select a diameter greater than 1.0 mm I get this weird forward slash through my drill hole icon and I'm not sure if this is okay or what it means (see figure below). Here is the datasheet: https://www.bourns.com/docs/Product-Datasheets/PTV09.pdf. I am using PTV09A-4
(Horizontal/Rear Mount, Bushingless)

Thank you!


texts: FTDI USB Chip in UART Mode and Bitbanging at same time

texts:
Using a FTDI FT2232D (Datasheet) in UART Mode for a dual RS-485 application I like to use some of the pins (e.g. not used handshake signals) as GPIOs (e.g. for switching on/of a termination resistor).

Does anybody know if this is supported in parallel to the VCP Driver for Linux? How would I access the pins separately?


texts: Alternatives to FT232H for USB to SPI communcation

texts:
For my current use case, I am using FT232H as a general purpose device that changes my USB packets into SPI information as an SPI controller for my SPI peripheral. My SPI peripheral can support upto 50Mhz clock speed.

FT232H has a max clock speed of 30Mhz
The libMPSSEengine that is written by FTDI is quite ancient and seems to have a INFRA_DELAY(2) which causes significant delays when I am toggling the CS pin as described here FT232HL FTDI consecutive SPI bytes delay problem
USB 2 Buffering and general performance

Given these 3 concerns, I can hack 2 and 3 by interesting buffering solutions. Is there any alternative chips i should consider that is as simple as FT232H to use that can give me the full 50Mhz signal. The reason I feel it is important is that extra 66% speed boost for each data transfer can improve my buffering system. And preferably that uses USB 3/3.1 specification for a plausibly lower latencies.
I have googled several chips and am not able to find a suitable alternative. Suggestions like Raspberry Pi has all been tested (it has an Max SPI speed of 500 Khz, and i get a practical 300 Khz).


texts: How Is Context Switching Done In Hardware?

texts:
I have a question about how process state would be saved during a context switch.

Given a relatively simple design for a CPU using von Neumann style architecture, how is the process image saved without overriding some of that state in the process?

For example, if I want to save the current state of all registers including the program and memory address registers, how can I write them to a memory location without overriding the stack and base pointers in the process?

Is there auxiliary hardware that holds intermediate values, and if so what does it look like in a more simple sense compared to the industry standard?


texts: Direction of E1 and E2 in phasor diagram of transformer

texts: The phasor diagram of transformer is a bit confusing. Is E1 and E2 have same direction? Different books mention it differently. Please clarify!!


texts:
Sorry if my question is stupid but I'm an electronic passionate only during the weekend.

I had a talk with a friend, we want to bring the power supply to a box containing a microcontroller inside a garden. The cable that has to bring the electricity will be 20 meters long.

Both me and my friend do agree on the fact that we need to bring the 220V AC to the box and over there use a power adapter for transforming 220V AC to 5V DC in place.

But I think that the distance is difficult to cover with DC, he thought that the distance is difficult to cover with 5V (and if the voltage is 5V at the head of the cable could be 3V or less in the tail of the cable if the cable is too long).

What is the reality? Why is difficult to bring 5V DC in a 20 meter long cable? Well.. is it really difficult or not?

PS: the microcontroller is an Arduino, it has to read some sensors (light, temperature, humidity) and swhitch on some actuators (few LED and two or three servo motors mainly). It has to run all day long for all the summer.


texts:
module averager(
    clk,
    rst,
    n,
    sum,
    cnt,
    out,
    avg
 );

input  [9:0] n;
input clk;
input rst;
output reg [19:0] out;
output reg [9:0] cnt;
output reg [19:0] sum;
output reg [9:0] avg;

integer i = 0;

always @(posedge clk )
    if (rst == 1) begin
        sum = 20'b0;
        cnt = 10'b0;
        out = 20'b0;
        avg = 10'b0;
    end else if (rst == 0) begin
        sum = sum + n;
        out = sum;
        cnt = cnt + 1;
        avg = 0;

        for (i=0; i<641; i=i+1) begin
            if(out >= cnt) begin
                out = out - cnt;
                avg = avg + 1;
            end
        end
    end
endmodule

The above is the code to implement a cumulative moving average filter. The for loop is used for division to find the average and involves repeated subtraction. However I am getting the following warning and error:

WARNING:Xst:2254 - Area constraint could not be met for block <averager>, final ratio is 509.
WARNING:Xst:1336 -  (*) More than 100% of Device resources are used
ERROR:Pack:18 - The design is too large for the given device and package.
  Please check the Design Summary section to see which resource requirement for
  your design exceeds the resources available in the device.

This must be because I am using large values in the for loop and thus am getting a large circuit that can't be implemented. I am looking for an alternative of the for loop, which could find the average for me. I just need the quotient value.

Design Properties:
Family: Spartan3E
Device: XC3S500E


texts:
Image is from Fundamentals of Electric Circuits 6th Edition, Alexander and Sadiku. Page 314.

a) i(0+) = 42/(10+2) = 3.5 A
   v(0+) = (10/12)*42 = 35 V

b) di(0+)/dt = v/L = 35/0.4 = 87.5 A/s
   dv(0+)/dt = ic(0+)/C = 0 V/s

c) v(infinity) = 42 V
   i(infinity) = 42/12 = 3.5 A

From my understanding when t-> infinity the circuit still remains in the dc steady state, right? Shouldn't the i(infinity) be 3.5A instead of 21A?


texts:
I need to transfer almost all kinds of data (arrays, video/audio stream, control signals) between mcu and an Android smartphone. MCU will accumulate data from smartphone and further send it by other abstract communication channel. It will also bring data from this channel to smartphone. Host is located very close to device so the distance does not matter.
I thought it was obvious that wired bus better, but I started to doubt when found BLE chip DA14531 with the lowest current consumption of 1,5 mA in TX (20 dBm) and 2,3 mА in RX. Declared speed is 1 Mbps in this mode.
What I did not find was the current consumption of USB work in different data rates (e.g. Full Speed). In specification there is no parameters which describe exactly Tx/Rx current of the bus. There is only magnitude of max current that the host provides to device, but that's not what I need.
Could you explain me which interface is worth using to achieve the lowest power consumption in this case, for example with the required data rate of 500-600 kbps?


texts:
Can anyone please suggest a circuit to convert 16 bit TTL (3.3V) RGB signal to a VGA signal. I used a resistor network, it works but I think some active component is necessary for load matching purpose.

Edit..

I am using r/2r ladder with an output voltage divider. I know it is not a good method, but it was fine for testing. The brightness of the display is too low with the circuit, and color quality is too low.


texts: Is possible to put a PFET before a DCDC step up converter?

texts:
I have the following schematic:
3.7V battery --> DCDC step up converter to regulated 5V USB --> Raspberry Pi Zero.
I want to be able to cut the power supply with a MOSFET, I have to use a P-channel. When I put it after the DCDC converter, no issues, all works fine except for the voltage drop due to RDS resitance.
When I try to put the MOSFET before the DCDC and I plug in the Raspberry Pi, then the DCDC goes off and nothing works.
Why is this happening? How could I solve this? What is the best approach? Is the choice of this P-channel OK?
Please find the circuit attached:


texts:
Below was my setup:

The moment I connected the probe the RCD tripped.

My scope was earth grounded. Does that mean I shorted the neutral and the earth ground? I know that neutral and earth are connected somewhere outside the building or at the utility transformer. But I completely forgot about it.

And what can I do to prevent that that? Which one is a safe solution: using an unearthed plug for the scope or a 1:1 isolation transformer? Any ideas?

1:1 isolation transformer might not be okay for all cases and might corrupt the original waveform?


texts:
I try to find the formula for resonance frequence in a circuit
in series R-L-C1 and parallel to that C2.

simulate this circuit – Schematic created using CircuitLab

I know only the formula for normal RLC-circuits its
$$
\frac{1}{2\pi*\sqrt{L*C}}
$$

My derivation so far(maybe someone could say something to it):

$$
Z_E = R+j\omega*L-\frac{j}{\omega*C} = R + j(\frac{\omega^2LC-1}{\omega * C})\\
Z_{C_2} = - \frac{j}{\omega C_2} \\
Z_G = \frac{Z_{C_2} * Z_E}{Z_{C_2} + Z_E} = \frac{-\frac{j}{\omega C_2} * (R + j(\frac{\omega^2LC-1}{\omega * C}))}{-\frac{j}{\omega C_2} + R + j(\frac{\omega^2LC-1}{\omega * C})}
$$
 From here I think I have to split up the imaginary part from real part and than I can set it to 0?


texts: What are some common/popular/go-to switching voltage regulators?

texts:
So I've used the popular linear regulators (7805, LM317, LD1117, etc), but I'd like to learn more about switching regulators.

Are there any "must have" switching regulators out there that are as popular, as ubiquitous as those common linear ones?


texts: I'm trying to amplify my PWM signal from 0-5V to 0-10V. As the nature of my project is a flyback converter, I thought that using a logic level mosfet with gate inputs from Arduino was enough to switch it but I was proven wrong. I've got a pwm from china on the way but it is only able to go 0-5V 100khz. I've learn from the kind users here that the mosfet requires 0-10v for the mosfet to be able to do fast switching. Is anyone able to point me the right direction in pulling up the amplitude perhaps recommend a solution? I read about D amplifiers but I have a square wave output already. Thanks in advance !


texts: Which way to draw diode in a circuit diagram

texts:
Im having a bit of trouble drawing a circuit with a diode in. I know the current flows from negative to positive, but convention says that current goes from positive to negative.

When drawing a circuit with a diode do you draw the arrow pointing to the positive (matching the actual flow of electrons) or towards the negative terminal (matching conventional current)?

If you follow convention then surely when building circuits from the diagram the diode will not allow current as it is actually facing the incorrect way?


texts: I am doing the link budget for a device several hundred meters away from the typical cell tower. I have already found out how much antenna gain for that device. I am wondering how much antenna gain should I assume for a typical cell tower?


texts:
There, in a high lighted area, are elements named "3 port, 0402 package, zero ohm resistor". Could anyone tell me what it is and how can I implement it in my design? But it has 2 terminal in the datasheet. Thanks for your help!
(Manufacturer: Koa , Part Number: RK73Z1ETTP )


texts: How can I fix a dry solder pin in a BGA package?

texts:
I am facing problem in a 16-bit transceiver chip, 74LVCHR16245AZQLR, which is a 56-pin BGA package.

Its one data pin is not working as expected while all other pins are working OK. The problem pin is only sinking 6 mA of current while all other data pins, which are working OK, are sinking 12 mA of current.

I suspect it is a dry-soldering issue. But I don't how to fix this as the chip package is a 56-pin BGA. Is there an easy way to fix this?


texts: Current source with multiple "taps" for driving different LEDs

texts:
I'm building a light source for a (one-off, hobby) 8mm film scanner that will be taking several exposures of each frame with different color (R, G, B, and possibly IR) light.  I'd started with high-CRI white (Yuji) LEDs and was planning to use color filters to get the colors I needed.

The Yuji LED datasheet showed that the light quality (CRI) depended on using a forward current as close to \$120\:\text{mA}\$ as possible.

I'm just a hobbyist and had a lot of fun designing my first resistor network where the power rating of each component actually mattered.  After much longer than it should have taken, I eventually came up with this:

simulate this circuit – Schematic created using CircuitLab

It lets me dial in the forward current precisely. \$\:\text{R1}\$ does the heavy lifting, so I don't overload the lower current rated \$\:\text{R3}\$.  Sweeping the pot its full range gave 110 through 130mA, neatly centered on the desired current.  (In the final application, these will have a ~3% duty cycle, so I'm less worried about thermal effects on the current.)  Overall, I was happy with this solution.

Since then, I've learned that much narrower, specific wavelengths of light will (counter-intuitively) aid in color reproduction.  (PDF reference, section 2.3)  So, I've gone back to the drawing board with some very specific R, G, and B LEDs.  For a separate dirt/debris removal step, I'd also like to capture an IR channel.  (Here's a nice video showing how "Digital ICE" works.)  And for a couple (less vital) reasons I was thinking of leaving the white LEDs in the design, too.

All the channels will be captured separately (using a monochrome image sensor), so no two colors of LED need to be lit at once.  I'd been considering reusing as much of this design as possible, simply adding new output "legs" that could each be controlled by separate microcontroller lines (which are in ready supply; no need to demux).

Finally, the trouble: the best parts I've been able to find with the closest wavelengths use a variety of forward currents.  The R, G, and B LEDs are all \$350\:\text{mA}\$ (with what appears to be some wiggle room with the data sheet graphs showing pulse currents all the way up to \$1.5\:\text{A}\$).  The IR LEDs are all lower current, around \$70\:\text{mA}\$.  And if I leave the white LEDs in there, I'll still need \$120\:\text{mA}\$, too.

I'd considered adjusting the resistor network so the LM317 outputs \$350\:\text{mA}\$ and then running the IR and W legs of the circuit with the LEDs in parallel (5x parallel for IR and 3x parallel for W).  But everywhere I've read about "LEDs in parallel" basically says "don't do it".

There isn't any hard requirement on the part count, but I was hoping--for aesthetic reasons mostly--to avoid just stamping out a bunch of copies of the circuit and having all these LM317's hanging off the board.  (I'm right at the skill level to appreciate the beauty of a minimal design that solves a problem well, while continuing to struggle to find it myself!)  If parallel LEDs are a bad idea, maybe the microcontroller could also switch parts of the resistor network to affect the LM317's adjustment pin instead so that each color leg will simply get the current it wants?

Signing up to CircuitLab just to post this question, even the voltage divider-based current source tutorial caught my eye as a more graceful solution than just repeating things three times.

I'm not too worried about their forward voltages.  This will be running off a bench-top power supply (so that 18V is variable), and I'll just string as many of each color in series until their voltage drops are close enough on each leg, then adjust the voltage source down until the LM317 doesn't have to work very hard.

Are there any obvious solutions I'm missing?  The R, G, and B channels don't need to be nearly as precisely controlled, which leaves a lot of design space wide open.  Thanks!


texts: Using LEDs in a bridge rectifier circuit

texts:
How would I wire 4 LEDs so they would serve as their own bridge rectifier? I have a limited space (the interior of a bicycle taillight fixture) so I would like to use the LEDs themselves to rectify the A.C. coming from a bicycle wheel generator.

Also, to limit the current so as not to exceed the forward current to each LED, how would I calculate the resistor(s) value?


texts:
Hybrid electric vehicles use 12 V for most purposes (other than traction and aircon), and they generally come with a 12 V ‘auxiliary’ battery (lead-acid, about 45 Ah) charged from the vehicle DC-DC converter. For some owners, it would make more sense to use LFP chemistry for the auxiliary battery (which does not crank an engine). The vehicle that I have tested (a 2019 rav4 hybrid) does seem to sense and send appropriate voltage to a 50 Ah LFP battery (14.2 V bulk stage, dropping to 13.6 V once the battery is charged). But at low SOC, an unregulated LFP battery can draw too much current for either the battery (1C) or the vehicle circuitry (~100 A). There is a single cable to deliver charge to and from the battery. Interposing a DC-DC charger would limit current to the battery, but these are generally unidirectional, so the battery can no longer provide power as needed. Bidirectional DC-DC converters exist, but currently they seem to be very expensive. Is it as simple as adding something like a Schottky power diode back from the battery to the vehicle circuit? Is there a better solution?
I have looked at this thread using-lifepo4-battery-as-car-battery but it does not answer my question.


texts: I have little experience with AC motors since I'm majoring in Mech.E. My team is setting up an AC motor with a VFD to control the movement of an airfoil inside a metal cage we built. I understand the basic wiring principles to hook up the power supply to a circuit breaker to a VFD and then to a motor using the right fuses and wire gauge. Now I'm a little confused about PES. I know it is there for shielding, but can someone explain the attached schematic for me? I'm confused about the horizontal lines in the schematic with the PES labels in the 2nd pic. Am I supposed to ground the braided shield of the cable to ground? And then to an earth plane/metal chassis? Am I supposed to have a wire connection to the metal cage we built or the chassis of the motor?


texts: Powering externally a 3v a 2 relay module

texts:
I'm using an ESP8266 to control a dual relay module. As a good practice, and a longer life for the MCU, I wish to power it not using its vcc and gnd pins, but using its JDVcc.
Appreciate explanation whether a 5v input into JDVcc is valid and won't damage the module.


texts: Low volt LED signage ( two separate signs)

texts:
We are installing a sign in front of our building the top one says spine pro, and the bottom says accident and injury center. They are all 12 volt led and worked while on the ground. Now that it’s installed and wires are pulled through the wall we are having some issues. 110v to dc 12v transformer. 16 awg. The transformer is about a foot away from the sign itself. We want to power both signs from the single power. Each hooked up separately work fine. But when both hooked up the transformer blinks and acts as if there was a short. However if both are working separately how could a short be possible? This sign worked on the ground before installation so we know there is enough power. All contacts seem legitimate and stable. Let me know if you have any ideas! Thanks

Aaron


texts: Help identifying an IC - Motorola SC42604P

texts:
I found an old board in my stash which seems to be from a smoke detector. Trying to convert it into a doorbell I can hear way out in the yard. I tried Googling the numbers marked on the IC but I can't find anything. What I know so far is that the IC seems to be in a DIP-14 package, top is marked with a Motorola logo although the manufacturer prefix tend to indicate it is from Phillips. Pins 1, 3, 10, and 13 are not connected. Pin 2 is raised upwards as if there used to be another connection to another board at some point. Does anyone know what this IC is? A datasheet would help a lot.
Thanks


texts: 200 LED through arduino via SN74HC595N shift register

texts:
I'm very new to any forms of multiplexing let alone electronics itself. From what I have researched, I can add more inputs/outputs to an Arduino via a shift register. I bought 10 SN74HC595N shift registers that have 10 outputs each (I think). I need to control two main strips of LEDs, that branch off in certain segments.

I know very basic electronics, and I think using multiplexing will give me more inputs/outputs. If I have 10 shift registers that give me 10 inputs each that gives me 100 extra inputs/outputs. ideally, I would only need to try to get two LEDs per input, so I could technically use charlieplexing. Can someone please explain what to do to connect 2 individual strips of LEDs (100 each) to a shift register using multiplexing.


texts: surge limiting resistors for full-wave bridge rectifiers

texts: I'm an electrician going back to school online to get my electrical engineering degree. I am having a hard time with some of the homework, as the book is extremely confusing, and does not always go into detail as to how the math is done. I need to calculate the minimum value of the surge limiting resistor required for a full bridge rectifier with a peak output of 50 volts. The rectifier is using 1N4933 diodes. I'm not asking for the answer-just the math formula to calculate. I would appreciate any and all help. Thanks!


texts: Angles and measurement - PCB design help

texts:
I have started doing PCB design from last month and very new to this. I have done tiny bits on eagle cad and Altium cad but still learning things everyday. Now I got a challenging board to do.  Though board is not complex but the measurements and angles has to be exact and not sure how to approach it.

Please see the pic which got spiral pads. All are circular and has to be with correct measurements as mentioned on it. Also let me know which tool is best for doing these type of custom stuff.

Hope some of you guys have experience here and might help me with good advice


texts: what is the disadvantage in using mosfet at input stage?

texts: In a cascade connection of mos transistor and Bipolar junction transistor ,what are the cons of using MOS transistor at input stage of the connection??


texts: How do we realize the design of a simple Op-amp with Bipolar Junction Transistors or MOS Field Effect Transistors alone? I mean I understand the need for differential amplifiers for providing a differential mode gain and I understand the requirement of Darlington pair as voltage amplifiers of the differential gain, but what about the others, how do they integrate the common mode gain into the equation as well.


texts: If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

texts: If an FM signal has different frequencies according to the modulation, how does the radio receive the signal in a fixed frequency like 103.2 MHz?


texts: I have an LLC converter controlled by L6699 and I want to add a current controller. It means I want to limit the current at 8 amps and it can't be done with the shunt resistor which is for short circuit protection. Any Idea how I can do it?


texts: Timer1 not working with external crystal (PIC16F628A)

texts:
I am unable to get the external 32.768kHz crystal (on RB6 and RB7) / timer1 to function (PIC16F628A / Mikro C). The crystal never starts. The same circuit has been reproduced twice (with short crystal connections, correct value capacitors etc) and the issue is the same.

The code I currently have working (running on the internal 4MHz), changing TMR1CS to 1 results in no timer function, no crsytal start.

TMR1L = 0;
TMR1H = 0;

T1CON.T1CKPS0 = 1;        // Set Timer 1 prescaler
T1CON.T1CKPS1 = 1;        // TICKPS0 & TICKPS1 set to 1 (for /8 prescale), not 0
//T1CON.TMR1CS  = 1;
T1CON.TMR1CS  = 0;        //Use internal OSC for testing
T1CON.T1OSCEN = 1;
//T1CON = 0b00001111;

CCP1CON = 0b00001011;            // Timer 1 compare mode, Special Event mode
CCPR1L = (16383 & 0x00FF);       // Preset compare register low/high bytes
CCPR1H = (16383 & 0xFF00)>>8;

This, not working

 TMR1L = 0;
      TMR1H = 0x80;

      T1CON.T1CKPS0 = 0;        // Set Timer 1 prescaler
      T1CON.T1CKPS1 = 0;        // RJ TICKPS0 & TICKPS1 set to 1 (for /8 prescale), not 0
      T1CON.TMR1CS  = 1;
      //T1CON.TMR1CS  = 0;      //RJ Use internal OSC for testing
      T1CON.T1OSCEN = 1;
      //T1CON = 0b00001111;

      CCP1CON = 0b00001011;            // Timer 1 compare mode, Special Event mode
      CCPR1L = (16383 & 0x00FF);       // Preset compare register low/high bytes
      CCPR1H = (16383 & 0xFF00)>>8;

Does anyone have a tested / working scenario from which they can provide the precise settings for T1CON and the config bits? I have followed the Microchip timer1 sheet to the letter and this is still not working.

Regards
Active


texts: Relation between Digital frequency counter and temperature

texts:
This is a homework question, I can normally solve the problems on freqeuncy counter but I never did with temperature related frequency counter problems.

A digital frequency counter has these properties.

Display 10 Digits.
Timebase-oscillator:(Ftbu=10MHz)
Mode:Frequency-measurement
High-precision-input-signal(Finp)=200MHz +- 0.0002Hz
Measurement time: 1sec

Room-temperature:40 centigrade. The display shows the value 200001000. What is the actual frequency of the time base oscillator.

2.Which accuracy has the local time-base-oscillator?

3.The room-temperature changes to 0 degree Centigrade. Now the display shows the value 200002000. Which temperatur-drift has the local time-base-unit. Derive the temperatur-coefficent of time base unit. Which value will be visible on the display at a temperature of 20 Centigrade.


texts: RTC circuit supercapacitor charge/discharge doubts

texts:
This is my current RTC circuit...

Supercapacitor = DXJ-5R5V334U (ELNA)...
DXJ-5R5V334U = 0.33F, 5.5V, ESR = 150 Ohms
Resistor = 150 ohms 0603 100mW 1%
If I consider only the resistor, I have a RC constant of 0.33 * 150 = 49.5 (~50) seconds... 50 seconds x 3 = 150 seconds (3x RC = capacitor very well charged, 95%...). That is 150 seconds... divided by 60 = 2,5 minutes...

But if I consider also the ESR of the supercapacitor, I will have 300 Ohms in total, so that the charging time would be 5 minutes, double the time...
What value of resistance should I consider in practice? 150 ohms (2.5 minutes)? Or 300 ohms (5 minutes)?
Another question related to that, is: the VBAT pin consumption is 1.2uA (@ 3.3V)... If the supercapacitor is fully charged (like 95%) and the circuit loss the power supply of 3.3V (shutdown/off), the RTC will continue to operate from the VBAT pin (supercapacitor), so how much time the RTC would stay working from VBAT? (1 month? more?). As I said, consumption is 1.2uA (@ 3.3V) and the capacitor is 0.33F charged with something like 3 to 3.1V, how much time the RTC IC would stay working if the 3.3V rail keeps off "foreve"r? According the the datasheet of RTC chip, the "Backup supply voltage" minimum voltage is 1.3V. Do you know some online calculator where I could estimate that time of operating from VBAT pin after power-off of the board and capacitor being 95% charged? Could you calculate these things to me please? Or maybe an online calculator would be great also...
Thanks and Best Regards...


texts: What fedex paper to use for toner transfer

texts: I am very new to creating PCBs and I am planning to make my first one in the upcoming weeks.  I noticed that all the instructions and tutorials called for using a laser printer which I do not have easy access to.  I decided that I would print my design using FedEx office.  I am unsure what paper would be the best to use.  I was wondering if "Laser" paper or "Gloss Text" would likely work for the purpose of transferring toner to a pcb.


texts:
The communication would be used for communicating between a computer and a Raspberry Pi/arduino board. The range should be about 500m in city area, and the data rate some kB/s.

In the RF segment there is the xbee pro which would be perfect, but is a bit too pricy for this project.

On the other hand there is the GSM network. Which has a much higher range than RF and higher data rate. But the data is expensive.

What would be good communication solution?

EDIT1:

The location of the devices is not fixed.

EDIT2:

It seems that at that price range it is not possible to get a suitable communication system.

Making a custom RF system would probably cut down the costs, but how much work is it and what should one be aware when building/projecting it?


texts: Is it realistic to expect full Spectre fix in branch predictors of future CPUs?

texts:
Recently, it has been observed that two branches sharing the same branch predictor state in the same process or even across processes allows certain side channel exploits (Spectre).

Let's consider a basic branch predictor. It has 2^14 slots, and each slot consists of two bits (strongly taken, weakly taken, weakly not taken, strongly not taken). The 14 index bits are the low-order bits of the branch instruction. Thus, the branch predictor has 2*2^14 = 32768 bits or 4 kilobytes.

Now, there's a problem: when switching between user space processes, the branch predictor state is not flushed. This can be fixed by adding a branch predictor flush instruction that is actively used when doing context switches.

There's another problem: two branches in the same process address space can share the same slot. If one of these branches is untrusted JITed code and the other is branching on one bit of a secret password, we're in trouble. This could presumably be fixed by flushing the branch predictor state before running untrusted JITed code. However, if the process flushes the branch predictor too often, its benefits are lost.

However, there's a more general solution (proposed in https://security.stackexchange.com/questions/176678/is-branch-predictor-flush-instruction-a-complete-spectre-fix): store in addition to 2 bits the remaining address bits as a tag. On 32-bit architecture, it would be 32-14 = 18 bits, on 48-bit address space in a 64-bit architecture, it would be 48-14 = 34 bits. This would make the branch predictor state 20 bits or 36 bits instead of 2 bits, multiplying its size by 10 or 18.

Is this kind of general solution realistic? It would certainly require more transistors in the branch predictor. But is the branch predictor already too large, or is it so small that its size can easily be multiplied by the required factor? There could be other benefits as well, such as the possibility to make the branch predictor easily 2-way, 4-way or 8-way set associative like CPU caches are these days. Perhaps the benefits of set associativity are so great that this kind of more general solution could be deployed?

P.S. There really should be a CPU Microarchitecture Stack Exchange. I considered Information Security Stack Exchange, Stack Overflow, Computer Science Stack Exchange and Electronics Stack Exchange and decided to post here.


texts: Substitute 12v Lead Acid Battery with Nominal 10.8v Lithium Ion Battery?

texts:
I am looking to replace an existing 12v Lead Acid battery configuration (two 7.5Ah batteries in parallel) for an old practice tennis ball machine. The machine consists of 12v dc motors and sensors to deliver overall speed, spin, height, etc., with some electronic circuitry to control the motors in tandem after receiving adjustments from analog dials.

Might a Lithium Ion battery be a viable replacement? The attractive qualities are the decreased weight and increased capacity.
My understanding is that most Lithium Ion batteries come in roughly 3.6v cell configurations which are then connected in series, generating 10.8v for a group of 3 cells. Some sellers call the resulting battery a "12v" and indicate the 10.8v is a "nominal charge". My impression is that the cells can also be slightly overcharged to exceed the 3.6v individual capacity. Is all this correct? Could a 10.8v Lithium Ion battery be used to replace a 12v dual 7.5Ah battery setup?
The dual 7.5 Ah setup powers the machine for approximately 3-4hrs; what would a good recommendation for that or, preferably, a longer period be?
Are there any potential drawbacks of foregoing Lead Acid and using Lithium Ion in this application?
Any recommendations on what would be a good lithium ion battery and charger configuration for this, or any other alternatives?

I really appreciate the help! Thanks!


texts:
\$H(s)\$ is the transfer function and we're looking for its magnitude gain. I went from the Laplace domain to the frequency domain by replacing \$s\$ with \$j\omega\$. However, the solution didn't match what I did.

They looked at the poles and zeroes. Please explain their process to me. Thanks.


texts:
Behzad Razavi in his book mentions

  It is important to bear in mind that small signal analysis deals with only (small) changes in voltages and currents around their quiescent values.... If the signal perturbs the bias point of the device only negligibly, we say the circuit operates in the small signal regime. So the change in Icq due to the signal must remain small.

However when we study about maximum symmetrical swing we look to bias it by the middle of the ac load line.. So the if the collector bias current is Icq then the maximum swing too is Icq. But.. How then is the change in Icq, small, due to application of signal?????  How do we specify the small signal regime of operation?


texts: GPIO failing to drive 2N2222 & LED simultaneously

texts:
I've had a PCB manufactured, which is doing a whole bunch of things, all working flawlessly, using EEPROM, MAX232, Voltage Conversion etc etc.

Part of the circuit is supposed to use a 2N2222 as a switch for a low current 24v output, it is also supposed to have an indicator LED to show when this is active. I can't seem to light the LED and power the transistor at the same time (Both work fine independently) I've tried many combinations of resistor values/jumpers.

Can anyone suggest a way to solve the problem without changing the design such that new PCBs need to be manufactured? (Bodge wires totally fine though)

It's a 'standard' 3mm red LED

Output voltage from GPIO pin is 3V3

Output current from GPIO is around 50mA


texts: Controlling more relays than the no. of free IO pins a uC has - Low-cost options

texts:
While I understand that moving up to a high pin-count uC might be the simplest option, I am looking for Low-cost options to do the same with low pin-count uC.

Would like to control a maximum of 8 relays, using an ATtiny85, which has 5 available GPIO pins, of which I definitely need to set aside 2 for some other purpose, leaving me 3. One obvious approach that comes to my mind is a Mux. Given 3 pins, 2^3 = 8, fits nicely. However I was wondering if the relays (which control the power-supply socket for servers), would de-energise, while changing mux values ?

Are there other gotchas with this approach ? Are there any alternative methods available ? I've heard about IO expanders, but would it be a worthwhile approach from complexity / cost standpoint ?


texts:
Previous question here

In Linear Instruments LT3652 DC-DC buck battery charger datasheet (pag 14) there is a formula to determinate the inductor saturation current in order to select the inductor for your design:

$$I_{SAT} = \left(1+ {\frac{\Delta I_{(MAX)}}{2}}\right) \cdot I_{CHG(MAX)}$$

But anywhere is described what \$\Delta I_{(MAX)}\$is.

\$\Delta I_{L}\$ is the peak-to-peak inductor ripple current.


texts: Cascading Common-Emitter Common-Collector for maximum power transfer

texts:
Hi Am trying to understand what am doing wrong, I connected CE to CC with a small Rload am designing it so Zout of the second stage equal Rload to get Maximum output.

From what i read in CC-amp Zout = RE||(r'e+ ((R1||R2||RS)/Bac)) were RS is the source resistance, i figured since CC-amp is connected to CE-amp then RC takes place of RS.

I reedited the calculation and obviously it came out wrong.

Bac = 100
Rload = 30
RS= RC = 1800
(R3 || R4 || RS) / Bac = 18 since RS << R3||R4
r'e + 18 = 30 => r'e = 12
IE = 25mV /r'e = 2.08mA
RE = 100*Rload = 3000
VE = 6.24V

Zout = RE||(r'e+ ((R3||R4||RS)/Bac)) = 29.7
Zout = Rload

Recalculate DC for final result

Vth = VE +VBE + Delta= 7.2V
Rth = Bdc(Vth - VBE / IE - RE) = 12500
R3 = Rth * (VCC / Vth ) = 15625
R4 =1/ (1/Rth - 1/R3) = 62500

Tried different ways but nothing, is the cutoff caused by first stage i tried to keep Q1 in midpoint and without CC it Amplifies signal without distortion, is it a cap problem or is it cause the current is to high

thank you for the help


texts: Running Microwave Oven interupts Wifi connection. Should I worry about it?

texts: Every time I turn on microwave oven, Wifi connection to my computer is disconnected. When the oven's done, Wifi recovers. This means the microwave somehow floats in my home when it's running. Should I worry about this? I am sure contacting microwave is not good at all.


texts: I2C bus arbitration - communication layer

texts:
I want to understand about the communication layer on which I2C Bus arbitration is done.
My question is based on this question which was previously asked here.

The accepted answer states that

  Bus arbitration is not part of several of the protocols you mention.
  RS422, RS485 and SPI can have bus arbitration but it is not part of
  the protocol, rather must be implemented on a different communications
  layer.

I understand the I2C arbitration procedure but I want to understand that on which communication layer is I2C bus arbitration done ?

Can someone brief on the communication layer regarding the bus arbitration for I2C protocol and other protocols which have bus arbitration


texts:
Requirement: Need to use only accelerometer in LSM6DS3 at 104 Hz in 2g full-scale mode and FIFO in Continuous mode. Interrupt should be generated every 320 msec.

Understanding: For every 1 sec there are 104 samples (104 "X" samples, 104 "Y" samples and 104 "Z" samples, 2 bytes each) i.e. 624 bytes per second. So to generate interrupt at 320 msec, I need to set FIFO threshold as 210 bytes. INT1 pin is configured as interrupt. I2C protocol is used.

Register Settings:

CTRL1_XL = 0x10; //operating at 2g mode and ODR is 104Hz
CTRL3_C = 0x64; // BDU=1,H_LACTIVE=1,IF_INC=1
CTRL4_C = 0x29 //STOP_ON_FTH =1 and INT2_on_INT1=1 and SLEEP_G=1
CTRL6_C = 0x10 //XL_HM_MODE =1
MASTER_CONFIG = 0x80 //DRDY_ON_INT1=1
INT1_CTRL = 0x08
FIFO_CTRL1 =210 bytes as threslod
FIFO_CTRL5 = 0x23 //FIFO ODR is set to 104 Hz and FIFO Continuous mode selected

Problem: No interrupt is generated.

Please let me know if anything is missing or anything needs to be added/modified.
Any help greatly appreciated.


texts: Philips 26PF5321 backlight mod, dim backlight

texts:
Got this older Philips 26PF5321 LCD-TV, like it because it is not a smart-tv.

What I dislike about this TV is the fixed backlight setting (cannot change it via software menu and there is no update for that setting). It doesn't change when you change the brightness for example. Watching a movie or playing a game in a dark room is not a pleasure (very, very bright and black is very soft gray) so I want to do something about it.

There is an inverter board inside that drives the background light bulbs. Do you think it is possible to control the voltage to this board to make it possible to control the brightness or is this, in basic, just a silly/stupid idea?

Didn't open the TV yet so I don't know how it is exactly organized. I expect that it is controlled by one or two boards that drive an array of bulbs, like many LED TV's of that era (2006).

I think, the easiest way to do this is to 'manage' the input voltage to the inverter (expecting it is a lower voltage than the high voltage output to the bulbs) but don't know how the inverter will react by doing that. Some people got any experience with this?

Here is the specs of the TV:

http://www.p4c.philips.com/cgi-bin/cpindex.pl?scy=PL&slg=EN&ctn=26PF5321/12

https://www.scribd.com/doc/17746102/Philips-Chassis-Lc4-31-ET


texts: How has solar panel power density improved recently

texts: Im interested in how watt per kg has advanced over the past 10-20 years for consumer solar panels. Can anyone shed some light on this? A table would be great.


texts:
There's a audio 3.5mm to pigtail cable on sell at Adafruit:
https://www.adafruit.com/product/1700

It looks like what I need as I could connect one side to an old phone, play some music and the loose wires to a breadboard\oscilloscope etc.

But what I don't understand is why it has 3 wires coming out of it and not just 2?

One wire is for ground - check
Another should be for signal I believe and that's it.

But it has 3, and it says
"Ground ring is black, middle ring is white and tip is red."

Why are there white and red and just one or the other?
If I want the audio signal w/o caring if it's stereo, can I just pick say the red one and ignore the white one (or vice versa)?

Thanks kindly for your help..


texts:
I'd like as an end state of my project for sound to activate a relay and then either

a) the relay to stay on for a limited amount of time (~15 seconds) or
b) ideally - the relay to be triggered off with another sound

I understand that either of these can be achieved with a 555 timer chip, I am loathe to use option a) because I hear that they can be fairly inaccurate when it comes to lower time limits (e.g. 15 seconds)

Here is what I have currently

Microphone can be found here https://www.sparkfun.com/products/9964

The LED flickers pleasantly in time to music. This seems problematic for a bistable switch - because I can imagine that the sound activation (ideally a shout, or a knock) will have to many pauses and lilts for it to trigger the bistable switch only once - I think this is a phenomena called bounce.

ACTUAL QUESTIONS:

Is this circuit dangerous?
How could it be improved?
How do I fulfil option a) or b)?
Why if I put a capcitator (I've tried a range of capacitances and ceramic and electrolytic types) before the LED and after the resistor the LED will no longer turn on.


texts: DC-DC converter/regulator lead-acid battery charger design question

texts:
I am trying to build a DC-DC voltage converter/regulator for a bicycle generator (dynamo). Expected unregulated input voltage range will vary with the speed of the bicycle (about 0 - 120Vdc) and want a constant output of about 15Vdc and output current of 3A

Can I use buck-boost converter? or something else? Thanks in advance for any input.


texts: Strategy for approximating an FIR Filter with analog RLC components from Impulse Response

texts:
I have a measured digital/discrete finite impulse response from a system. As known from signal theory, this is in essence the sequence of filter coefficients of the corresponding FIR filter.
I think in practice it should be possible to approximate the impulse response with resistors, capacitors and inductors alone. Gain can be made up after the filter chain. Noise can be neglected. Realization with ideal components in e.g. SPICE would be enough for my purposes.
I'm wondering what the best strategy would be to design such an analog filter "backwards" from digital into analog again with respect to accuracy. What I mean with the last point is that I'm aware that a more accurate filter would need more components, but assuming I want n stages at most in my filter (I'm thinking of a ladder-type filter when I say "stages", but any kind of filter structure would be acceptable as long as it's only RLC), how do I find the optimal one (approximations within reason are acceptable)?
Impulse response as requested.


texts: Finding an analog switch IC (BBM & SPDT) for video signal

texts:
I'm looking for a SPDT analog switch IC with Break-before-make to switch between video signals. However, the amount of options available leaves me overwhelmed with no clear option in sight.

I've found this PDF from TI and a switch like TS3A44159 seems to fill my requirements, with the caveat of being surface mount (I'd prefer to have through-hole to tinker more easily, but it's not a strict requirement).

Would an IC like that be a good option for video signals like HDMI/DP? Is there a better way or a better place to look for components like these? Thanks!


texts:
This circuit creates a delay of 200 ms, the driver is POL power good signal.

My question is why do I need 47.5 kΩ, is this resistor part of RC delay? What is it doing?


texts: Transformer coils in series, switching for 12/24V. EMF killing my circuit?

texts:
I'm making a little linear PSU for my lab. Based on the good ol' LM338K. I fried one last night and I'm still trying to figure out why. I think it might be EMF from my transformer.

I have a transformer, a toroidal 220V to 12V 200W. I noticed it was built as two coils in parallel, so I figured i could connect the coils in series to make it 24V 100W. Indeed, this seems to work (when they're in the right phase, of course).

Now, to reduce dissipation on the LM338K, I decided to add a small relay and connect it like this (let's call the point where the two coils are joined together the "center tap").

"Right" transformer leg: Diode Bridge ~ input.
Relay common contact: Diode bridge ~ input.
"Left" Transformer leg: Relay NO.
"Center tap":   Relay NC.

This allows my PSU to start at 12VAC -> diode bridge + capacitor -> LM338K (I added all the suggested external components, especially the discharge diodes from Vout to Vin).

To control the relay, I have a PIC (which also serves as voltmeter and current meter). I programmed the PIC so that when the output is over 9V, it switches to the full 24V. When it's below 8V, it switches back to 12V coil.

To recap: here's the schematic for the relevant part.

Now, I was testing this last night. Something weird happened. I dialed my pot to 12V, I heard the clicking of the relay and I had effectively 12VDC at the output. When I loaded it with a 120R resistor, all was fine. Then I used a 12V 50W lamp. I gave it 6V. it was working good, regulated excellent. So i started dialing the voltage up to 12V and it started clicking like crazy (I suppose the hysteresis on my program was too quick), it switched 12/24 a few tens of times and then the voltage output went to 0.3V. I quickly shut everything down. Discharged the 2x4700uF caps at the diode bridge output, and turned it back on. It was working again. Then I noticed the voltage was a little off and smelled of "heat": it was the potentiometer glowing inside! The voltage output was = Vin. My LM338K was dead (this is not a fake 338K as the autopsy revealed the component is genuine: i took the cap off and it had a proper copper heatsink and several bond wires for high current pins).

I'm thinking I didn't do anything wrong with this. All current and voltages were within spec of the regulator. The 338 has enough protections (my dad's 30 year old power supply has seen worse and the 338 never burned. Only that time when he accidentally hit a TV's B+ ..60V).

The only thing I can think went wrong is that, when the coil is switched over, I have an open circuit on the transformer for a few milliseconds. Then the other coil is connected. I think what could have happened is EMF from the coil switching making a very high voltage spike appear on the 338 and frying it.

Does this make sense? If EMF could be the problem, how could I solve this? I suppose a snubber network somewhere should do the work, but I'm not sure where. In my schematic, should a snubber network go between:
 - A and C?
 - A-B and B-C
 - AB, BC and AC?

Also: how would I calculate the value for an RC network of this type? The relay specs 10mS "Operate time" and 5mS "release time".


texts: How do I exactly calculate the amount of heat generated in MOSFET?

texts:
I am using two IRFP260N MOSFETs (datasheet) in parallel for my application. I am using it to drive a motor rated at 24VDC and consumes 8 to 10 Amps. I found some answers here and calculated the temperature accordingly using the formula:

Id^2.Rds.Rθja

4^2 x 0.055 x 40 = 35.2'C

The result would be 60.2'C considering an ambient temperature of 25'C.

But when practically using the circuit produces no heat at all, maybe a couple of deg. C.
Before using IRFP260, I used 3xIRFP450 (datasheet) with heatsink which produced decent amount(70+'C) of heat for 4 minutes of operation. Am I missing something?


texts: I am interfacing MAX232 with STM32F030k6. I have very recently found out that Max3232 would be a better choice, because it works with 3,3 volt. But I am eager to know if UART reciever pin of the mentioned MCU is 5 Volt tolerant. On the other side, I know that MAX232 recognizes any voltage higher that 2V as 5V. Therefore That wouldn't become a trouble. I have took a look at my MCU user manual but didn't find anything. I appreciate your ideas on this issue.


texts:
If I have a boolean expression made up of ANDs and XORs in algebraic normal form, are there any algorithms which can minimize the circuit further?

I'm looking to minimize AND gates specifically.

I'm building ANF from a truth table, so if there's a different way to go about getting a circuit made from XORs and ANDs starting with a truth table that has a minimal number of ANDs that'd be helpful too.

Thank you for any help you can provide!!

Edit: to be more explicit, I'm limited to using xor and and gates.


texts: How to specify throttle range of RC ESC?

texts:
I've bought some cheap ESC's off banggood in order to build a drone. Now I'm trying  controlling them using an Arduino. I just can't figure out how to use them properly.

The ESC is called XXD HW30. No datasheet was attached to it, so I had to look around on the internet, most of them seem to work similarly. On the banggood website, one customer linked to this paper: here. One thing written on there, as on many others:

  Because different transmitter has different throttle range, we strongly suggest you using the “Throttle Range Setting Function” to calibrate throttle range.

And the Throttle range setting then most of the time

Turn transceiver on
Push throttle to high
Wait until a signal, often "beep-beep", after about 2s
Push throttle to low
One long beep confirms new range
So I'm trying to put this into practice.

I'm experimenting with this short sketch:

#include <Servo.h>
Servo servo;
void setup() {
  servo.attach(9);
  servo.writeMicroseconds(1999);
}

void loop() {
  // put your main code here, to run repeatedly:

}

Now here's what I've gathered, and I can't make sense of it:

If I set the pulse width to 1800, 1900, 2000, short beeps with long pauses are emitted - "Throttle signal is irregular ". I've read that this can be emitted when the pulse width is out of range.
If I lower it to something like 1200, 1300, the error code is now beeps with an interval of .25s, indicating "The throttle stick is not in the
bottom (lowest) position "
If I lower the pulse width even more, to 700 or less, the ESC emits "beep-beep- beep----", which sounds like neither the initiation sequence nor the throttle range sequence. After that sequence, the motor can be turned on by increasing the pulse width.

What am I doing wrong? Do I have the wrong datasheet? Is my board fried? How does the esc determine whether my throttle stick is at the top, or in the middle anyway, if different transceivers have different ranges? The behavior seems so unpredictable. Sometimes, switching port makes it work. Sometimes, it just starts working out of the blue. And it stops working again.


texts: Read some (unknown?) RFID tags with a chinese reader / writer (125kHZ)

texts:
Some months ago I bought this 125kHz RFID Reader / Writer from eBay.

I was wondering how can I actually read or write an RFID Tag with it.
So I attached it by usb to my computer (running Linux) and saw just this:

[786026.932028] usb 3-1: new full-speed USB device number 3 using uhci_hcd
[786027.092100] usb 3-1: New USB device found, idVendor=10c4, idProduct=ea60
[786027.092107] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[786027.092111] usb 3-1: Product: CP2102 USB to UART Bridge Controller
[786027.092115] usb 3-1: Manufacturer: Silicon Labs
[786027.092122] usb 3-1: SerialNumber: 0001
[786027.262224] usbcore: registered new interface driver usbserial
[786027.262243] usbcore: registered new interface driver usbserial_generic
[786027.262257] usbserial: USB Serial support registered for generic
[786027.267525] usbcore: registered new interface driver cp210x
[786027.267546] usbserial: USB Serial support registered for cp210x
[786027.267583] cp210x 3-1:1.0: cp210x converter detected
[786027.376029] usb 3-1: reset full-speed USB device number 3 using uhci_hcd
[786027.522286] usb 3-1: cp210x converter now attached to ttyUSB0

I tried to print characters to serial port echo "blah" > /dev/ttyS0 but nothing is answered by the RFID reader ( with cat /dev/ttyS0 ).

Since it's a chinese RFID Reader not much infos could be retrieved from internet. No usage specifics. Nothing.

I tried to search over internet the model name: HL-208 but I haven't found anything that could help me reading / writing my RFID tags.

I also looked for that cp210x and undercovered that is actually an USB to UART Bridge.

"Bonus" Question:
How can I actually determinate which type of RFID tags are these?
Is there anything I can do, except trying it with every single RFID Reader specific to the model, to determine which frequency and type they are?


texts: Why a newer TOP value in the Atmega328p Timer1 has to be greater than the values in all The compare registers?

texts:
The datasheet mentioned the following on p.167

When changing the TOP value the program must ensure that the new TOP value is higher or equal to the
value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a
compare match will never occur between the TCNT1 and the OCR1x.

I have no clue what does that mean actually. Does that mean that once I defined a top value in OCRnx registers the next one must be greater in value? (Although. this How I got it, I really doubt it)


texts: Who said, "all sensors are temperature sensors, but some are better than others"?

texts: One of my favorite electrical quotes goes something like "all sensors are temperature sensors, but some are better than others". Unfortunately, I don't remember where I read this. What is the origin of the quote?


texts: Does turning off an appliance (e.g. vacuum cleaner) at the power socket have any negative affect?

texts: Does turning off an appliance (e.g. vacuum cleaner) at the power socket, rather than from the appliance itself; have any negative affect?


texts:
I am designing a high voltage motor controller and I want to validate the switching circuitry to ensure there's no excessive ringing behavior.

I had an idea to use something like an SMA or u.FL connector with an adapter to a BNC cable that I could plug into my scope, but couldn't figure out how to safely attenuate the signal. The voltage I'm measuring can exceed 500V and if I used a simple resistor divider, I'm concerned with the source impedance being too high and causing reflections in the measurement cable which would completely invalidate any overshoot/pre-shoot measurements. The best solution I had was to use an attenuator composed of 1M resistors and a high-speed unity buffer to generate the output signal at a known impedance but this is expensive in terms of board area.

This white paper from TI seems to suggest what I was talking about above but I was hoping there was something simpler that wasn't created to sell a product.

EDIT: Could I perhaps design this system with high impedance circuitry only and operate the scope in high impedance mode? I am concerned about retaining a high enough bandwidth with such a design


texts: How would one go about using a 46V DC power source to power something which needs 36V DC using resistors?

texts: How would one go about using a 42V DC power source to power something which needs 36 V DC using resistors?


texts: Possible to calculate forward voltage of LED

texts:
I'm wondering if it's possible to calculate the forward voltage of some LEDs I have, given that I have their other specifications:

Base type Aluminum
Power consumption 1W
Voltage 12V <- I believe this is the power supply this calls for, not a forward voltage.
Lumens 11.7-84.2 lumens
Beam angle 25 degree narrow spot beam
Color temperature 3300-6500K
LED working temperature -20 to 60 degree (around 54 degree)
IP Class IP68
Lifespan 50,000+ hours

Would anyone be able to provide some advice for the calculation I'm looking to make? Thanks!


texts: Linear voltage regulator with a solar panel?

texts:
I'm wondering how to go about reasoning about the losses in a linear voltage regulator connected to a solar panel.

The OC voltage of the panel is around 22V, the maximum power voltage is around 18V, and I'd down-regulate it to 12V for a battery pack.

So far, I got this:

The more current I draw from the panel, the lower its voltage will be. Since the battery can sink in as much current as I can provide it (it's a tiny panel, let's say 0.5A), the voltage will probably drop significantly. The current will be maximal in this phase but the voltage drop across the LDO will be minimal (let's say 0.5A * 2V = 1W dissipation).
As the battery gets charged, it will draw less and less current, and the solar panel voltage will rise. When it rises above the LDO voltage, the LDO will start dissipating more power as heat, however, at that point the current will be minimal.
When the battery is charged at a steady voltage (let's say it's 12V), the voltage on the input of the LDO will be near the OC voltage, but the current through it and into the battery will be negligible.

Does this make sense? Am I missing something?

Edit: I'm not asking about exact calculations, just a confirmation about is this line of reasoning ok.


texts:
I am working through Razavi mircroelectronics and regarding BJT resistances, there are three master rules:
Rule # 1:  looking into the base, the impedance is r_π if emitter is (ac) grounded.
Rule # 2:  looking into the collector, the impedance is r_ο if emitter is (ac) grounded.
Rule # 3:  looking into the emitter, the impedance is 1/gm if base is (ac) grounded and Early effect is neglected.
But in the circuit below, the Resistance looking into emitter2 is show to be r_π || r_o || 1 / gm (and not just 1/gm).
Why is that?

simulate this circuit – Schematic created using CircuitLab


texts: Isolating 220V AC from low voltage DC on the PCB

texts:
Below picture is the rectifier section of design on the PCB:

The space between AC and DC voltage is ~2 cm, except at the bottom that I put four M3 holes which I'm going to drill and connect them to each other.

The relay control part is going to connect to an opto-isolator and from there to the MCU.

Is the taken precaution steps enough for isolating AC from DC? any tips for improvement?


texts: Required timer count for a number of same frequency different duty cycle PWM signal

texts:
Ok, it may look a bit confusing. I am specifically talking about STM32 MCUs, or even more specific, STM32F103C8T6. I did some amount of reading, but could not find the answer to this.

Let's say I want 4 PWM signals each at 50 Hz but all with different duty cycles. In such a case will I need 4 distinct timers, or can I use one timer with 4 channels? I mean can each channel of same timer be configured with different duty cycle?


texts: How to split 2 audio signals and then mix them?

texts:
I'm working on a simple audio circuit which takes two different signals from mp3 players (earphones output), mix them up and outputs to an amplifier/speaker. But before mixing the signals, I need to measure the onset of Signal 1 with a microcontroller, in the case an Atmega328. I have little experience with audio and amplifiers so I don't know how to split Signal 1 from Signal 2 in order to read Signal 1 only.

I have also added a simple voltage divider for DC offset so the Atmega328 won't read negative voltages. Below a simple schematic of what I have so far:

simulate this circuit – Schematic created using CircuitLab


texts: How far can I wire a Sensor or an electrical component that it would work?

texts:
I had this doubt in my mind. I wanted to know the range till which a sensor could be attached so that it works. Suppose I have a setup, in which my main circuit is in a room and I have a PIR sensor or a fingerprint scanner near the door. Will it work at a distance of say 20-30m from the room? I am asking this because there will be a voltage drop due to the wire. If suppose it doesn't, how can I make it work? Do I need to provide extra voltage externally? I'll  be using an Arduino.

Thanks a lot!!


texts: I have searched for hours trying to find stack structures for cortex m and cortex a devices.  I am attempting to add freertos debugging support for the cortex a5 to eclipse via the jlink SDK.  The code for the jlink and the code for openocd are similar, and both show the same offsets for the cortex M, which show a non contiguous arrangement.  All the data sheets I can find for the a5 and the M don’t show in what order these are pushed and popped into stack ram, but obviously the writers of that code found it somewhere.  Perhaps I just don’t know what to google, or maybe I have a misunderstanding here, but where could I find this information?