texts: LiPo battery certification standards for EU and US

texts:
We are bringing a wearable product to the market that is powered by a 3.7V LiPo battery. The product will be sold initially only in the EU and US markets. We are currently in the process of performing the necessary tests and assessments with a test lab to certify that the product complies with the necessary Radio, EMC and Safety standards.

As part of this process, I know that certain tests are required for the LiPo battery. The battery supplier has provided the following reports for the battery:

UN38.3 report
1.2M Drop Test report
Report for safe transport of goods
MSDS report
IEC 62133-2: 2017 report

Now the problem:

The test lab says they can accept the IEC 62133 report for the safety requirements in the EU. However, they insist that the above are not sufficient for the US and more testing is needed according to the UL 1642 standard (which also they cannot perform, as they are not accredited to do so, i.e. we need to find another lab to perform that testing).

The battery supplier however is based in the US and sells the same LiPo batteries directly to customers there, without experiencing any problems.

Who is at wrong here? Is the test lab exaggerating a bit here about the need for UL 1642 or is the battery supplier selling products that have not actually passed the safety requirements for the US?

One thing to point out for clarity, that the battery supplier sells standalone batteries, while we are certifying (and intend to sell) the product as a whole (not just the batteries).


texts: What is the syntax for modelling a non-linear element in Spice?

texts: Suppose I have the following circuit. My question is how do I write the net-list in LTSpice such that f(i) = i^2 + 2 (for example) ? I couldn't find the syntax on the internet.


texts:
I had some trouble with home assembly of some PCBAs.  I've got an STM32F411xC (datasheet here).

Anyway, After reworking it a bit, and some issues elsewhere on the board were uncovered (all related to oversights with soldering technique), the first board was toast...Missing pads and so on..

So, I moved to the next clean board, and started fresh...One component at a time, and testing along the way for continuity, resistance, etc.

The first and most technically troublesome part to put down was the STM32F4 in a 64 pin LQFP, so I dropped that thing down and took a reading across the 3.3V rail and GND, and everything looked good...wide open.

So, imagine this...I only have the STM32F4 on the board, that's it...I put 3.3V on the board from an external supply, and it shorts out, 350mA before the current control kicks in.  Now, I've got 26kohm between 3.3V and GND after removing power...

So, after a day of double checking pinout, orientation of the chip (found here), the thing I tried was pulling up the VCAP1 pin and leaving it floating...So, I read a little about it and see that VCAP1 is pretty serious when it says to hang 2x2.2uF or 4.7uF off of it, so I do that...

I get a new IC, desolder the old one, put it down, measure resistance between power and ground, make sure all the pins are really connected to the board well, ring out all the VDD's and VSS's AND slap down two 2.2uF caps on VCAP1.

I turn it on, and still, short circuit.

What the heck is going on here?  This circuit is so simple, it's two components...The STM32F411 and a pair or 2.2uF caps...

I'm tellin' ya...You hook this circuit up, it'll short right out and get real hot, real quick.  What is the GOTCHA here that I'm missing?


texts: Good source to learn about the basics of integrated circuits?

texts:
I would like to learn the basics of integrated circuits and microprocessors. To get an idea of my level of ignorance, here are some question I have:
1. How many "layers" does a microprocessor have? 2, 3, hundreds, thousands? I assume it has to be more than one, since if "wires" cross I assume one must jump to the layer below (or above) for a while and then jump back?
2. I remember reading that distributing the "clock" is a big issue for the power usage and design of a chip. Must all parts of a chip run on the same clock? Can a "communication channel" be self-synchronizing, like I imagine say a USB/ethernet connection is.
3. Is there software where you can design an integrated circuit, simulate it and see if it works?

Anyone know of a good book? My background in math and computer science is very good, my background in electronics is weak.


texts: Micro-controller - Detect If AC Device Plugged In / Drawing Current from a Relay

texts:
So now i have a DC relay being controlled by a microcontroller that turns an AC device on/off using a control line from the microcontroller being fed into a transistor to provide the necessary current for the relay coil.

The relay output is connected to a AC mains plug(female) in which the AC device plugs in(male connector).

I would like to add a status led display with the following states

red (device not plugged in)
yellow (device plugged in + off state / not drawing any current)
green (device plugged in + on state / drawing current)

Any ideas on how would i go detecting these 3 states from the microcontroller?


texts: Understanding this emergency lamp circuit

texts:
I deciphered the circuit below following the tracks of a small PCB. So this is a high level schematic. I'm just trying to grab the idea. B1 is an external battery. The circuit has three 3 states determined by the switches. It's actually a three state slide switch.

Case 1: LED OFF
Case 2: LED will automatically turn on when AC mains goes off.
Case 3: LED turned on manually.

Question 1: How does D7 turn on/ff with the cathode connected to one leg of mains? Does it turn on during the negative cycle of the signal?
Question 2: I don't understand well the arrangement of components around the base of Q2. From a high level, what I understand is that while mains is present there will be a potential at D8 cathode keeping Q2 ON so Q1 OFF.
Quetion 3: What's the purpose of R2?


texts:
I have a question about high-side switching a load using an p-channel MOSFET.

I'm using the following configuration to control the backlight brightness of a LCD panel:

Q1 = N-channel logic level MOSFET so it can control the p-channel MOSFET using a microcontroller.

Q2 = SI2319DS p-channel MOSFET

Now because the backlight has a very specific voltage range (between 29,5V to 30,2V) I want to calculate the voltage drop over the source-drain terminals of Q2.

The datasheet of the SI2319DS states that for a Vgs of -10V Rds(on) is about 65 mΩ. This would mean that my voltage drop would be:
Vds(drop) = 65 mΩ * 120 mA = 8 mV.

Is this really the case? it seems so low.


texts: Why is there no current sharing between neutral and ground?

texts:
In the first system, will lamp1 turn on?

If yes, then why is there no current sharing between neutral and ground as shown in the second system? I always read that neutral is a current carrying conductor but the ground is not. What is the reason behind that? I think current should be shared equally between the two wires of neutral and ground (assuming they have the same resistance).
If no, does that mean earth is not a reference and it does not have "zero" voltage? So there's no need to ground the neutral wire?

Arrows are the direction of currents.

simulate this circuit – Schematic created using CircuitLab


texts: Arduino mega 2560 Analog max reference voltage

texts: Each time I power up the Arduino, the max reference voltage which is represented by 1023 changes. I observed this by measuring the voltage from the Aref pin each time. Is there any internal function or way to find this max voltage? Because, the voltage reading from the analog input pins of a constant voltage source keeps changing every time as a result of varying max reference voltage.


texts:
I'm trying to develop a device that can detect or "watch" an infrared beacon that is freely moving side-to-side anywhere within a 180° field of view (-90° to +90°, with center/forward at 0°); i.e. the sensor should see the beacon if it is directly to the left (-90°), to the right (+90°), or anywhere inbetween, but not if the beacon is anywhere behind the sensor.

I've glued a little IR sensor (TSOP38238) on top of a micro servo (Tower Pro SG92R), and I have these wired up to a Circuit Playground Express with CRICKIT. I'm programming on the board via Arduino, and the software seems to be working great -- the servo will continuously sweep the full field of view, and if the specific IR signal I'm transmitting (38kHz, NEC IR protocol with 32-bit payload data) is received by the sensor, the servo's current position/angle is logged immediately.

However, my problem is restricting the IR sensor's vision. For example, if the servo with IR sensor are facing left (-90°), and the IR signal is being transmitted from front and center (0°), the IR sensor detects that signal and thus determines that the source of the signal came from the left (-90°). This example is real and practical, but the problem is in fact far worse; the sensor is detecting IR transmissions from all 360° -- there is no direction the servo and IR sensor can face that it will not detect the source IR signal being transmitted!

The only thing I know to do is to fabricate blinders to surround the IR sensor. If I can somehow block (reflect, absorb, whatever) any IR signal to which the sensor does not have a direct line-of-sight, then it should help prevent these undesirable signals. Or even if I can't block the signal, perhaps it's possible to corrupt it to cause a change in frequency or payload data.

I've constructed some blinders using craft sticks and super glue, with several layers of aluminum foil (like you use in the kitchen) taped to the outside. I added the aluminum because of this SE thread I found. But still, the IR signals seem to pass right through.

So what other techniques or materials are possible here to restrict IR signals to line-of-sight?

The blinders I constructed look like the following. The wooden side faces the inside (faces the IR sensor), aluminum side faces outward (faces the world):

And the following is how the blinders are mounted onto the servo, with the IR sensor inbetween. The intent is to blind signals coming from the sides, but still allow the signals to reach the sensor if coming from different heights:


texts: I have a motion clock that runs off of two C cell batteries.  One battery runs the movement at 1.5 volts.  That other battery then continues in series to run the motion part delivering 3 volts to it.  I would like to use a 3 volt dc plug in power supply to run the entire clock, but do not know how to separate 1.5 volts from it.  I would not be opposed to using a 4.5 volt power supply if that is what I would need to do - 3V + 1.5V.  The movement is quartz, so I'm sure the amperage draw is small.  The motion part is an electromagnet that pulses and pushes a permanent magnet away from it to move the pendulum.  If possible I would like to put this on a board that would press fit into where one of the batteries go, so it could be returned to battery operation in the future if desired.  I'm also planning to use a jack plug that accepts the power supply/dc transformer, so it could be easily replaced in the future if it burns out.  Thanx in advance for any help.


texts: Why is output equal to non inverting input opamplifier

texts:
I wanted to make a simple current source.
The circuit was build so that the laser would get a constant current.

I bought the opamplifier opa552 from china for 1 euro because it could handle large currents and voltages. But after some measurement I came to the conclusion that the output is equal to the non inverting input and that no current goes through the 3 ohm resistor. I have removed the capacitor in the circuit but that didn't help.

After some time the opamp started to smoke so now it is broken. Is my setup wrong or do you think the opamp pins of my opamp don't correspond with the datasheet of the opa552 or is is just a bad opamp? (all the cables are connected correctly and according to datasheets). Shall I buy new opamp and try it again?

I know I could also build a current source with other methods, by using transistors but I am just curious why this is not working.

By the way, my opamp needs 3 grounds, I have connected all three of them.

Describing the circuit:
Voltage divider so that non inverting input=0.35
Resistance of 3 such that current is=0.35/3 A. THis current will also go through the laser.
For testing I have replaced the laser with 4 resistors.
Capacitors so that when turning on system laser will not get a too high voltage.


texts: Accurately measure high quality factor coils

texts:
What would be the most suitable way to measure the quality factor of high-Q coils under the following conditions?

Specifications

Frequency:  5 MHz to 15 MHz, the target application is wireless charging
Coil type: air core, constructed using hollow copper tubes, size is around 15 cm
Range of the measurements:  Inductance \$L\approx 1 \mu H\$, Quality
factor \$Q> 1000\$ (estimated from the simulations) and resistance \$R=\frac{\omega L}{Q}\approx 30~m \Omega\$ (at \$5 MHz\$)

What I have: VNA, low-frequency LCR meter (only up to 1MHz), other laboratory equipment such as Oscilloscopes, DC supply, etc.
I don't have access to an Impedance analyser working at the target frequency range.

My approach:
I first measure coil inductance at low frequency using the LCR meter and then add series capacitor (NP0 type - resistance of the capacitors is expected to be negligible) to tune the coil to the desired frequency. Next, coil impedance is measured using VNA (impedance parameters). Finally, use curve-fitting to estimate the coil resistance. Currently, estimated resistance is more than three times the expected values.

Identified problems in my approach are 1. Coil resistance is very small and the input impedance is not matched with the VNA at the resonance, therefore, I am not sure how accurate is the reading. 2. In this method, I cannot directly get the frequency response as the resistance is a function of the frequency - This also affects the curve fitting.

The Question: Is there any better way to measure high-Q coils accurately.  I came across a book from Matlab, which I don't have access I am not sure if there is any useful information there.


texts: What options are available for life cycle management and end of life (EOL) tracking of PCB components in a BOM. What are the main free and commercial services that are useful for this task. That is seeing lifecycle status and receiving product change notifications (PCNs) updates.


texts: Can I drive this chip with a signal to drive the output drives?

texts:
This is the datasheet of the chip and I don't speak Chinese. I've tried google translate but with little success.

The chip is used in this car. I am trying to use a raspberry pi to drive it over wifi and I've got the raspberry pi working just fine. If I use a separate motor driver I can drive the motors just fine, but I was wondering if it's possible to use the chip already present to drive the motors. In other words use that as the motor driver. One way would be to "hack" the antenna signal but that's not what I'm after.

This is the motor that I'm trying to drive if that's at all relevant.


texts:
simulate this circuit – Schematic created using CircuitLab

I have faced a problem in understanding, the following circuit. But after deep search, I expect to be Differential Low Pass Filter. If so, why we have make the first Capacitor common with Vin+ and Vin-, and the next two capacitors, we have put a 'ground' between them ?


texts: I'm looking for a resistor which can withstand high power and has a low capacitance and inductance

texts: I'm looking for a resistor about 25 Ohm at 13.56 MHz (this is our operating frequency). The resistor must withstand at least 50 W (100 W is better!) at ~ 1 kV voltage amplitude. As I will use this for compensating the phase difference between the measured voltage and current from our voltage probe and a current transformer, It also must have a low capacitance and inductance. I originally thought a wirewound type resistor would be a good choice due to its strength for high power and high voltage, but I immediately realized that it might have bad inductance and, possbily, capacitance. What type of resistor is the best choice for me?


texts: Trouble with triac driven dimmer circuit

texts:
I have a dimmer circuit that produces the following wave forms.

Red: Triac Gate Signal
Yellow: 120v 60Hz AC Wave (not triac output)

I would assume that given this signal, the triac should flip on and the light and it should be at nearly 100% brighness.  However, this is not what's happening.  Itstead, the light doesn't turn on at all.  Can anyone explain why this might be?  If I change the gate to be always triggered (i.e. always voltage to the gate), the light turns on to 100% brightness as expected.  Is it possible that the resistor sitting before the triac gate is too high (56 Ohms)?

The circuit is essentially the same as this one:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1276992650/0


texts: Adding binary numbers using 2's complement

texts:
I am working on this question:

Add the following signed binary numbers using 2's complement arithmetic:
01110101 + 10111011.
(b) Is there an overflow in this case?

I have got the following answers:

Is this correct?


texts: Design Questions for Dual Tracking Power Supply Using 15 Volt 800mA Secondary Transformer, LM317, LM337, and Op Amp

texts:
I am experimenting with the design for a dual tracking power supply using LM317/LM337. I recall circuit analysis but my design skills have not been used for a while so I have novice level questions. I have two different power sources and want to understand performance expectations for each. I need to understand the circuits better to order parts for further experiment and project build.
Source one is an old ATX power supply that outputs direct current 11.9 volts on yellow wire and -11.2 volts on blue wire with 10 ohm 10 watt load resistor on the 5 volt rail. I would use this source to get +/- 9.5V or more output at whatever current is available with proper heat sinks and relatively small value input filter capacitors in front of the LM317/LM337.
Source two is a wall plug transformer with two secondary outputs at 4 pin mini-DIN connector. Transformer name plate for two outputs (1) 15 Volt 800mA; and (2) 15 Volt 800mA. These outputs each have 1 ampere fuse inside the pet fence which I would replicate in my regulator circuit for short circuit protection. The pet fence circuit uses a common ground node (center tap at the board level but not out of the 4 pin DIN connector) and generates +/- 8 volts for the logic circuits using LM317/LM337 with no heat sinks. It generates +/- 20 volts at the power rails of two 2200uF capacitors. The high voltage rails power two audio driver integrated circuits with giant heat sinks so these power rails are input to the LM317/LM337 regulator substantially as shown in Figure 1 below. I want to estimate how much DC regulated voltage and current could be produced from this circuit with or without heat sinks to decide whether to build a circuit to use this transformer with a bench power supply.
See this link:
https://diyodemag.com/education/the_classroom_part_three_the_linear_power_supply
Figure 1A:

Figure 1B (how does the tracking control loop work with LM337 in the feedback path?):

See also:
https://pe2bz.philpem.me.uk/Power/-%20LV/LV-110-DandyPowerSupply/supply-2.html
Figure 2 (how does this tracking control loop work derived from positive adjust pin?):

My primary questions are:

What are the expected voltage and output current limitations from each source with or without heat sinks on the LM317/LM337 devices?

How do the two different op amp feedback circuits shown respectively in Figures 1B and 2 above provide dual output tracking? Which design is likely to be more accurate or less expensive to use a pot for fine adjustments?

How can I provide lowest cost fine and course adjustment using two or three trim pots where I want to adjust down to zero volts and maybe trim for accurate tracking using two or three adjustment knobs?

So far I have a breadboard working well with LM317, no heat sink, and 1k resistor to LED as the small load on the regulated output. The source is DC 12 volt rails and ground from ATX power supply. The circuit is similar to LM317(2) shown below except I am not using a transistor Q2. Instead I am using a 4k pot for adjust 2 (2k seems to be the range limit for this pot anyway but I don't have one here yet). Also I am using a 1k multiturn trim pot and about 7k resistor in place of Q2 which gives fine adjustment above or below 0 Volt output. This has an op amp voltage follower buffer between the  two diode "regulator" and the LM317 Adjust pin to eliminate resistor loading. I have 3 op amps left to use in the LM324 chip. Maximum voltage output on the positive side is about 10.5 volts with just the LED and 1k resistor load between positive output and ground. I have LM337 on order. Figure 1 depends on LM337 for feedback loop so I can't experiment with that design yet. So next I plan to wire up Figure 2 feedback op amp and see how well it mirrors the positive adjust voltage.


texts: How can I get the viscous coefficient of friction B for a DC motor?

texts: How can I get the value of B for a DC motor when the data sheet has Viscous Damping (F1) like the following?


texts: Extracting ints from a string on Arduino

texts:
I'm trying to extract ints from a String on an Arduino.

I'm using This DCF77 Library (.zip) and I get a date and time in this format:

  DCF77DATA 2012012531819CET

This translates ito

  DCF77DATA YYYYMMDDwhhmmTZ

with Y,M,D being the date, w the day of the week, and h and m being the time. This is always generated at the full minute, so seconds can be expected to be 0.

I've been trying various ways to get the hours and minutes (the date doesn't concern me at the moment) and put them into int variables. The latest method I tried looks like this:

  const char *v = dcf77.getDateTime();
  if (strcmp (v,"DCF77POLL") != 0) {
    Serial.println(v);
    String time = String(v);
    // DCF77DATA 2012012531819CET
    char h_str[3];
    time.substring(19,20).toCharArray(h_str, 2);
    Serial.print("H: ");
    Serial.println(h_str);
    char m_str[2];
    time.substring(21,23).toCharArray(m_str, 2);
    Serial.print("M: ");
    Serial.println(m_str);

    int hours = atoi(h_str);
    int minutes = atoi(m_str);
  }

This produces an interesting result ... I get the first number of the time. When it's "23" minutes I get "2", hence the h_str[3]. I thought it was related to the string being 0-terminated, but it didn't help. Same for the hour.

Additionally, when I try to print out the int I don't get any output at all in the serial console, it seems as if the program just halts.


texts:
my question is about the ACPL-217 Optocoupler, i use it to control P MOSFET transistor.
The ACPL-217 work with the following schema:

I want to leave the pin 1 anode of the diode not connected in my schema.

Is there  any risk to enable the P MOSFET if i leave the PIN 1 not connected ?


texts: Altium designer - Messages panel doesn't show up

texts:
When I compile my project the Messages panel does not appear. Even if I manually try to open it through System -> Messages (bottom right corner) or View -> Workspace Panels -> System -> Messages it doesn't work. I've also tried to close and reopen the project, loading old projects, etc. but none of this has worked. It must be some kind of bug.

Is there any way to solve this or at least to see the errors without this panel?


texts: modifying an existing solenoid to make it less bulky?

texts:
I am only familiar with the applications of a solenoid but never designed one. I was given this task of modifying an existing solenoid used in a device to make it less bulkier. I am not understanding where to start from and what are the control and proportionality factors.

construction:
power supply drives a transient suppressor diode (zener) connected in parallel to a solenoid.the solenoid is enclosed in a steel housing that is closed at one end and opened at the other end. solenoid, when energized sufficient enough, attracts a magnetic plate towards itself through the opened end of the housing.once the power supply is turned off, the coil demagnetizes and the plate is expected to go back to its position as earlier.

specifications:

outer diameter of the bobbin      = .628 inches
operating voltage                 = 18 to 32 vdc (pick-up voltage = 18vdc max)
wire diameter                     = 41 gauge magnet wire
no of turns                       = 7600 minimum
resistance generated by the coils = 1300 to 1400
coil outer diameter after wound
around the bobbin                 = .610 inches max
magnetic holding force            = 2000 to 2500 grams
coil current                      = 25 mA MAX @ 32 VDC
drop out voltage                  = 7 to 8 vdc
length of the coil                = .530 inches

Task: to reduce the size of the solenoid and yet see to that it has the same electrical functionality with same operating values.

my idea: after comparing the existing solenoids in the market i would want to reduce the diameter of the coil & wire and increase the length of the solenoid in a way that the above goal can be achieved. also i understand that the diode is used to ensure that there are no transients in the supply given to the solenoid. i would like to know if we can incorporate any better electronics that are micro sized to perform the same functionality.

but i do not know how to go about it?
kindly help


texts: How to make connection for 220V on this transformer?

texts:
I've a small question regarding how to connect the terminals for 220V output. As per the diagram in below pic my understanding is :

Output terminal H1& H4
Output 220V: H1-H2=shorted & H3-H4= shorted
output 440V: H2&H3 shorted

Is this correct? I don't want to make any wrong connections and blow up things.Also the label says 0.120kVA & 0.150kVA for 220V and 440V respectively. What does that mean? How much max curent can be drawn from this transformer safely?

Thanks.


texts: Battery with 3.7v and 9900mAh , is that enough to know the output current?

texts: I have a battery with those specifications: 3.7 V, and 9900 mAh.  From these figures, can I calculate the maximum output current from the battery? I have 2 batteries with those values; can I use them to power a Raspberry Pi 3b? Thanks :)


texts: RS universal rectifier transformer secondary voltages

texts:
This looks like a good place for some advice on this strange multi tap multi coil transformer, this RS lump of a 40-0-40 @ 1A transformer came to me after an earlier eBay purchase was delivered damaged and the seller sent uninsured, he replaced it with this as I told him I needed 40V 500mA for a filament feed on an old TV PL519 sweep tube I was experimenting with. "I have a great one just what you need" was the answer and this arrived.

After looking at the available voltages I thought yes this will do the job and I began testing all the separate coils and all test good, they are in two identical rails and are 0-1V 0-3V 0-9V 0-27V which I thought would just link in series to 40V per rail with the 0-1V linked on 0V but it seems not?
Here are the secondary tags.

Can anybody advise me the best way to achieve the rated 40-0-40V as I cannot find the datasheet on the internet and I have never seen or used a transformer like this before.


texts: Blinking LED with only 1 capacitor and 1 resistor

texts: wanted to ask if it's possible to make a blinking led using only a capacitor and a resistor, and using a normal 1.5v AA battery as a power supply, like the image, *pd: knowing how my teacher is, it wouldn't surprise me if it's not possible.


texts: Troubleshooting TL071 to TA8207 100 Hertz hum

texts:
I worked out to build a pre-amplifier connected to a power driver in a single setups(a pcb). Problem arises when it's powered up. here are a few questions.

Setup has a TL071CP as preamp with a unity gain. an input impedance of **10meg** through a 100n polyester cap. no mistery here. To notice: we used single star-gnd. Vcc is 12 volt not 17.5 as intended or 35 volts as preferred by the JFET.

Output stage is politely recycled 7W beautiful amplifier device from Toshiba Microelectronics division tagged TA8207K. Actually using 5% resistors at the gain configuration at 100 ohms. All the setup follows guidelines from the schematic.

These are close to original schematics next,

Tests:

I've tested *1meg* and *2meg* input impedance but decided later 10meg as Zin.

For the medium drive Zin tested several passive devices. in general the TA8207 has a 35kohm Ain Z. Ran it using 2.2k resistor to ground and seems to be nice but not completely noise-free at the speakers.

Thus replaced original 47kohms Ain Z at the driver for a 2.2k/2.2k which has a noticeable gain and frequency response along with noise again.

Then finally tried floating Ain to Vcc/2 with no success. In exchange used the voltage divider at TA78207's Ain.

Goals:

My idea is having 3/10 from the actual noise without rebuilding everything. Ideally replacing 5% to 1% bleeder hum noise filter.
Main question:

Do i need matching the output impedance from TL071 which is 120kohm at 10meg input Z to the 35kohm Z in JFET related equation i haven't read?. I've considered a bleeder notch-filter very likely solution to 100hz hum.

If i float using Vcc/2 or add an inductors or add resistors at the different grounds. still need a notch-filter and Vcc/2 at all Ains. ?

Thank you for all your comments. Diego


texts: It's in my syllabus but there's no mention of it in my book. Can someone explain to me what is a Carry Propagate Adder?


texts: Is Saving Through-Hole Components Viable?

texts:
I recently got my hands on some old electronics. After getting some to work and failing to get others to work, I decided to simply desolder some of the through-hole components to possibly use in future project.

After desoldering a few, I realized that resoldering them on to a new board would be difficult considering the tiny amount of remaining wire and that the quality was quite poor.

My Question: Is desoldering and salvaging through-hole and surface-mount PCB components viable, or should I just buy the components online?


texts: Barrier voltage and knee voltage are give same meaning?

texts: Is there any difference between barrier voltage and knee voltage? Could somebody please let me know, if any.


texts: ModelSim: Why can't I see generics in simulation?

texts: When I start simulation, I can see signals and ports in the objects window for what I have selected in the Sim window. Besides this, I can see processes for the same thing in the processes window. However, generics are nowhere to be seen. How do I see, what generics were passed to an entity when it was instantiated during simulation besides looking at the code?


texts: Verilog: Comparison after non-blocking assignment

texts:
I've seen Verilog code which looks something like the following:

...

reg [9:0] count;

always @ (posedge clk)

   count <= count + 1
   if (count == 10'b1000) begin
      ...
   end

   ...

end

I'm wondering how this actually behaves; will the comparison use the new, or the old value of count?

I've been told that all the non-blocking assignments occur in parallel, so if there was the line x <= count further down in the same always block, then this would use the old value of count, which is why I find it ambiguous which value the comparison will use.


texts: K50-HC0CSE25.0000MR Clock signal not being driven to correct logic levels

texts:
I am using a K50-HC0CSE25.0000MR to generate a 25MHz clock for the DDS IC AD9833. I have hooked up the clock output directly to the MCLK input of AD9833 as shown in the diagram..

The data sheet shows the clock signal hitting 0.1VCC and 0.9VCC. However, the clock signal I sense by probing is only ranging from 1.1V to 2.8V (for 5V VCC). With active oscillators such as these, is it necessary to drop the output across a resistor? Their test setup suggests they only dropped it across a 50pF cap. I was hoping the input capacitance of the MCLK pin would be enough(3pF, data sheet says max is 50pF).


texts: Is Back EMF relevant in dynamos, where there is electric generation?

texts: While doing some research about dynamos, I came across a situation wherein there was a question about the validity of my dynamo design. The counter to the design I suggested was that there would be back EMF generated by the design, but the design I have under consideration is that of a dynamo, where we generate electricity. I understand Back EMF is used in cases of motors, and not dynamos, is this the correct picture? The design of the dynamo is briefly described as follows: an outer rotating magnet that has a groove in which a fixed stator can fit in closely, of course, there is an air gap, and so on, as with standard dynamo design, but I did not see how anything like Back EMF, could really destroy the design under consideration, is this the correct?


texts: Adjusting the Potentiometer into Acquired Value

texts: The goal is to find the base current, collector-emitter voltage- and the base-emitter voltage for each of the values.. My problem is, how am I gonna adjust the potentiometer into 0.2 , 0.4 up to 2.0 for me to get the required parameters .. I provided an image for a better view.


texts:
I have a toroidal core which has effective area of .656 cm^2 from magnetics , in magnetics page they say it has 10,500 gauss saturation level (about 1 tesla!).
so.. when designing a flyback "transformer"(or coupled inductor), should I use this value of 1T as the saturation limit?  or should I use less value to decrease the losses?
edit

It seems from this photo that it's okay but considering the imperfection of winding should i use a lower value?


texts: Arduino resets randomly when using a DC motor

texts:
Following a question I posted here a few months ago Using P-Channel mosfet with arduino I'm using pchannel MOSFET for activating a CR02 valve like this one https://es.aliexpress.com/item/1938516987.html?spm=a219c.search0302.3.30.33c06d8djwoxkt&ws_ab_test=searchweb0_0,searchweb201602_0,searchweb201603_0,ppcSwitch_0&algo_pvid=42bb562b-db52-4060-8454-5a31a442a8ec&algo_expid=42bb562b-db52-4060-8454-5a31a442a8ec-4

This valve has 3 wires, one goes to +12V the other goes to GND and the remaning one is used to open/close the valve, if this wire is conected to +12V it opens the valve and if it's unconnected it closes the valve. I'm using the following circuit to operate this valve

VIN = +12V
QD = Arduino PIN
QDV = Valve control wire

It kind of works, I can open and close the valve but once every 6 or 7 times opening or closing it causes the arduino to reset and I don't know why. I'm using a 2A power supply and the specifications of the valve says it consumes 100mA so it should be enough, I'm also using a diode to protect from the spike of voltage when the motor is turned off, any idea what can be causing the problem?


texts: Thermal voltage of a BJT vs. diode voltage drop

texts:
I'm learning about the hydrid-pi model of the BJT transistor:

In this model, the base and the emitter have a resistance \$r_{\pi}\$ in between. The voltage between the base and the emitter is apparently called "thermal voltage" and at room temperature it is approximately \$26mV\$. This voltage divided by the bias current gives the resistance \$r_{\pi}\$.

But normally in circuit analysis it is assumed that a transistors base-emitter junction has the voltage of a diode, approximately \$0.7V\$ across it. Isn't there a contradiction?


texts: High speed data from microcontrollers to pc using daisy chain

texts:
I have STM32F4 discovery boards. I have 30 such boards supporting maximum data of 128Mbps. The max data at any instance in complete system would be 300Mbps.I need to pick this data and send it to PC. All the boards are connected using daisy chain
I am exploring the possibility of using USB3.0, Thunderbolt, Firewire and real time ethernet protocols.

Problems:

1: USB doesnt allow daisy chaining

2: Firewire- Unable to find many off the shelf components

3: Thunderbolt- very few devices can be connected.

4: Real time etherent protocols- Most protocols have data rate of 100mbps with ethercat claimimng to have touched 200mbps.

Can you suggest some protocol which can support such high data rate


texts: openOCD : how do I know if my LPT-JTAG adapter is in sync?

texts:
My openocd config file has the following content

interface parport
gdb_port 3333
gdb_memory_map enable
gdb_flash_program enable

source [find board/mcb1700.cfg]

when I launch openOCD with this config file I get follow

The JTAG adapter is a wiggler clone.

Does this confirms if the JTAG-adapter is in sync with target?

How/Where to reduce the adapter and target communication speed?

I'm unable to program/Erase the LPC1768 target via openOCD.


texts: Can the atmega168 bootloader be installed with arduino uno?

texts: I have an arduino unu (pre-made) with the atmega328 and an atmega168. I am wanting to make a second arduino out of the 168. I don't have a USB programmer. The chip came out of some servo contorller board so I am guessing the arduino bootloader is not already installed. Is it possible to program with my uno, and if so how? Connection to the arduino instead of the computer when sending sketches is fine as long as I can disconnect it from the uno for use.


texts:
We have the circuit in the figure.I have to find I and V.
The solution manual of my book says :

V= 1 V .D1 is conducting and D2 is cut off.

I dont get this,why is V=1 V and not 3 Volt? Also why is D1 conducting and D2 cut off? I know that a diode is conducting when anode voltage>cathode voltage but what are the anode voltages in each diode?


texts:
If we have this circuit:

The diode with the lowest forward voltage drop will conduct and turn on while the other will turn off and not conduct current.
If I have this circuit:

Assuming the 2 diodes have the same voltage drop, R1 can be considered to be in parallel to R2 and that's how we solve those circuits.
However in the same case, what if the 2 diodes have different forward voltage drops? Say Vd1>Vd2 which assumption should I take into account?


texts: What kind of LEDs are typically used in lights?

texts:
Forgive me if "What kind of LED" is technically incorrect. I'm new to electronics and am trying to build a light (reference link attached below) for making videos. I have some LEDs which come standard in Arduino/RPi kits, but I don't believe they are capable of emitting enough light without burning out. I believe they are 3V/20mA 5mm LEDs.

What kind of LEDs are used in lights such as this?


texts: What are SMA connectors and what are they used for?

texts: I have come across these rather big connectors on Altera trasciever boards in particular. I was wondering what is special about them.


texts: Discrete signals: Power and Energy after Up/Downsampling

texts:
I think I have a very simple question, but I am very confused about it right now.

Given is a discrete sequence \$x[n]\$, for simplicity we say its finite and of length \$N\$. Then we know that the energy of this signal is given as
\$E = \sum_{n = 0}^N x[n]^2\$ and its power is given as \$P = \frac 1 N E\$ (since it's finite).

Now here are some things that confused me. Assume we upsample the signal. The energy would be the same, since we only insert 0s. But inserting 0s increases \$N\$, hence we would reduce the power. This cannot make sense... so where is my error here?

Regards


texts:
Can I replace the 1N5395 diode in this diagram with a FR157 diode? Basically I need to lower the heat of my hair dryer and I think the 1N5395 diode in this diagram does exactly this but I have only a FR157 and also I read it's better to use 4 amps or even 6 amps diode like the BY500-400! Care to elaborate? Thanks!

http://www.seekic.com/circuit_diagram/Electrical_Equipment_Circuit/POKO_TD_169C_Hair_dryer_circuit_diagram.html
Edit: So in my dryer I have this heating element (220V, 150W):
Wouldn't a FR157 or a RL205 work to cut the power in half thus reducing the temps?


texts: Does powering both phases (left/right rotation) of an AC motor hurt it?

texts:
I know that one can reverse the direction of an ac motor by powering the different starter windings.
If you power one starter winding, you create a magnetic bias, allowing the motor to rotate to that direction.
Once it is spinning, the main winding will do the heavy lifting.
But what would happen if you were to power both starting windings?
My guess is that when the motor is standing still, you would not create a magnetic bias, so the motor won't start to rotate.
If the motor was running, I think nothing would change. You just remove the magnetic bias. The motor would keeps on running in the same direction at the same speed.
(If the starting windings were connected using centrifugal switches, then it doesn't matter at all, as you would only be powering the main windings.)
I might be completely wrong about this, therefore I would like to know if my reasons is correct.
I've attached an screenshot of the diagram from the installation manual of the motor (Somfy Ilmo 50 WT). I plan to power shutters using two non-zero crossing solid state relays. The software should prevent powering both phases at the same time, but I want to be sure as the motors are expensive. I want to know if I need to add protective circuitry (selecting mux).
The resistors in the diagram are probably used for a slow startup, and I think that they indicate the starter windings.
(B and C are probably internally connected to the main winding as well).
Do you think it will "hurt" the motor if b is powered while c was already powered?


texts: Which isolated ground should I use for an RF can/shield over an optically-isolating component?

texts:
I'm building a PCB that uses an optically-isolated voltage-sensor IC which takes an input voltage of -0.2V to 0.2V on one side and generates an isolated, proportional output that ranges from 0V to VREF (let's say 4V) on the other side, which I feed into a 24-bit ADC.

I have an input which is approximately a 10 KHz sine wave varying from a 10V to 1000V over time, of which I need to measure the voltage accurately.  I am using the IC (labeled "U1" here) as follows in my circuit:

simulate this circuit – Schematic created using CircuitLab

A voltage divider reduces the 1000V input voltage to the IC's 0.2V acceptable range. I also have totally isolated power supplies on each side, with separate grounds. This is all fine and works in my prototype environment.

However, I need the input signal to be as clean as possible. I don't want noise from other things inside my enclosure (and there are a lot of them) to affect the signal going into the IC--all such noise needs to stay below 100 microvolts.

I would like to put an RF can around the sensitive part of this. I've drawn an outline here in green as an example.

However, I cannot (of course) put just half of the IC in the can and the other half not. Therefore, the entire IC will need to be shielded. What I am not sure of is which ground I should use for the shield--whether it should be the input-side ground (indicated in my diagram by the ground symbol with lines, and which is tied to one of the input pins) or the output-side ground (indicated in my diagram with triangle ground) which is completely isolated and floating).

Does anyone have any thoughts on shielding for this situation, where there are two isolated grounds and an opto-isolator in the middle? Which ground should I use for the can? The two grounds could easily be 500V apart from one another.

Edit 1: After writing this, which made me think through the situation more clearly, I realized the solution is likely to use the input-side ground, since I am shielding components on the input side.  If I used the output-side ground, any fluctuations in that could induce noise.

Edit 2: Here is the datasheet for the IC in question, the Avago HCPL-7510. VREF is used to set the range of the output voltages, with VREF/2 out for 0V in, roughly 0V out for -0.2V in, and roughly VREF out for +0.2V in. Shown here with VREF = 4V:

I am using the IC to measure voltage rather than current, by supplying an input voltage directly instead of using a shunt resistor, etc. In addition to current sensing, the manufacturer specifically states that it can also be used for "general analog signal isolation applications." The reference circuits in the datasheet do all tie V- to GND1 and let V+ float around it, but this may not be necessary.

I chose it as it both provides isolation and allows both positive and negative input voltages while converting those to strictly positive voltages.


texts:
I wondered if someone could offer advice here.

I have a 3.3v dc motor.  Obviously, i can change the direction it turns by flipping the + an - leads round.

Can i acheive the same thing but with 2 npn transistors.  Signal to one to turn it one way, and signal 2 for the other.

Can someone advise a simple, safe circuit for this?

Thank you


texts: Why does a multimeter in resistance mode show initial continuity over a diode?

texts:
I originally phrased this question very differently; the original text is retained below in case background information is useful to clarify the context.

When I using this digital multimeter to measure resistance across a diode, it shows 100-some ohms for a second or so (one update of the digital display screen) and then shows 1, for "open circuit".  Why is this?

Original question

Everything that follows was the original body of the question.  It is retained only to provide background information and context.

I have a heat gun that has stopped working.  I don't know why; it wasn't working when I acquired it.  I took it apart to hopefully figure out why.  It looks like the surface reason seems to be that there is a fusible link that has opened because of high temperature.  I'm now trying to find out why that would have happened.

The heat gun consists of two circuits connected in parallel: a heating element and a fan.  I'm testing the fan.  The fan has four electrical contacts, two of which were originally hooked up to the otherwise unmodified (except for a switch) AC in.  They are unmarked.  The other two are indicated + and -.  When I hook up a 9V battery to either pair of contacts, the fan goes.  When I hook up a multimeter in resistance mode to the +/- pair, the multimeter shows about 9 ohms of resistance.

This all seems pretty unexciting.  However: when I hook the multimeter up to the unmarked pair of contacts — the pair that the circuit was hooked up to — the multimeter shows 100-some ohms for a second or so, then shows 1 (open circuit).  Again, hooking up a 9V battery to this pair of contacts will result in a rapidly spinning fan.

Why am I getting this reading from the multimeter?  Could this indicate a problem with the fan that could have caused the heat gun to overheat?

update: Setting the multimeter to diode-check mode — located in the resistance area (on this multimeter) and indicated by an icon of an arrow against a vertical line — gives a consistent reading of 1363±1 for the unmarked pair of contacts.  I don't really understand what this is meant to indicate.  Using diode mode for other circuits, including the +/- circuit on the fan, gives readings similar to those of the 200-ohm-max resistance mode.

update 2: Realized that the mysterious cylinders connecting pairs of unpaired contacts are diodes.  Reassessing.


texts:
I need to convert RGsB (aka SOG or Sync On Green) to VGA. I've built the circuit as shown below:

The circuit works but the output picture looks quite striped, something like this image:

Any help in fixing this problem would be appreciated.


texts: Pulling the power plug => Device damaged

texts:
At work we use a certain type of video conferencing device and recently one broke down because someone pulled the power plug -- without turning off the device first.  (In fact something similar happened half a year ago, after this happened a few times.)

My explanation for this is that 230 V AC abruptly become 0 V, thus high currents might be created.  So it could have happened that the fuse went off.  The video conferencing devices are basically modded PCs, thus having a PC power supply.

So question: is this poor design?  I expect consumer devices to be more fault-tolerant.  (Isn't there a norm for that?)  Could it been prevented by using a surge protector:

Wall Plug <----> Surge protector <----> Device

So in this case pulling the wall plug should have left the device intact probably, right?

Edit: The brand is Vidyo.


texts: Can magnets break LED notification light on phone?

texts:
I'm posting this question here because it's about magnets and electronics. Please tell me if it's better suited to another site!

I've been messing around with some reasonably strong magnets around my Nexus 4 phone (yes, I know that's stupid). Now my LED notification light isn't working. Could the cause of this possibly be interference from the magnets?

The magnets are strongly attracted to each other - but not to my phone - and are like large capsules, about 5cm long and 1cm wide. I don't know exactly which metal they're made of but I'll hazard a guess at iron.

If you want any more details please ask me!


texts: Torque control with H-Bridge via direction pin

texts:
Using the LMD18200 (H-Bridge) and the LM3524D (PWM regulator) I should design
a torque regulation. I've found a circuit in the LMD18200 datasheet which uses the current feedback to adjust the PWM.

The question bothering me is why should I connect the PWM output to the direction
pin and not to the PWM pin itself? Is this only some good practice, doesn't it matter or is it required?

From my point of view connecting to the PWM pin should work fine since the current is always measured the same way.


texts:
I am trying to understand UART synchronization.
In a UART, the default state is high, and it starts the reception process when it receives a start bit (high-to-low transition)

In some scenarios any spike, noise or interrupt may
change the state from high to low, which is enough for the UART to detect it as a start bit. I know that a UART internally handles these
scenarios and avoids the process of receiving a full byyr.

Can anyone explain me how a UART handles these spikes?


texts:
Is it possible to build an RF transmitter final amplifier that can be powered by a single lemon as a battery? (maybe 0.9 Vdc at 1 mA, with suitable electrodes, when fresh)
Desired operating frequency is somewhere in the range of high MF (1 MHz, Part 15) to HF (29 MHz with a U.S amateur license), gain of at least 6 dB over input drive signal, and output to a wire antenna.
If so, what kind of active component (BJT, FET, or IC, silicon or germanium, etc.), and type of circuit should one look into to work under this low voltage, low power and frequency requirement.
The purpose might be to provide a compelling visual demonstration of low voltage low power operation, so any manufactured battery or an adjustable 1 Amp supply won't work nearly as well as a lemon.


texts: Replace CR2032 by li-ion reverse engineering

texts:
I want to replace my Wireless door bell by lithium-ion 3.3 V-4.2 V but I don't know if the circuit is design for that. It work with CR2032 3 V max.

I think I identified Attiny85 on the PCB, I can work up to 5 V. But I don't know if the 433 MHz circuit control by microcontroller can work with 4.3 V max.
Can you help me?

I know I can use LDO regulator (low quiescent) but I can avoid it?

Note: The li-ion battery will 3.9 V- 4.2 V because is charge by Solar.

Regards!

The circuit:


texts: Combine 9V and 1.5V power supplies to make a 7.5V supply

texts: To save on cost, I wish to buy a 9V DC and a 1.5V DC power supply and connect the positive outputs together to create a 7.5V 200mA supply my Plantronics headset needs. That is, 9 - 1.5 = 7.5 across the two negatives at that point. Problems?


texts: Why non linear amplifiers are more battery efficient than linear ones?

texts:
I was going through a document on GMSK modulation where it is specified that it is immune to distortion from non linear amplifiers.Also it was mentioned that non linear amplifiers are more battery efficient.The exact lines are:-

"Non-linear amplifiers are more efficient in terms of the DC power input from the power rails that they convert into a radio frequency signal. This means that the power consumption for a given output is much less, and this results in lower levels of battery consumption; a very important factor for cell phones."

Can anyone explain this concept?


texts: Suitable bias resistor for microphone with higher voltage source than microphone's rating

texts:
I have headset microphone with a rated impedance of 2.2Kohm, that according to the data I've been able to find for it can be powered by 1.5 to 10v.   I do not know what the maximum current is, although I have been able to use this mic on a PC to record audio without any problem.
With some experimentation using various bias resistor values, I have found that running 5v across it in series with a resistor of 4.7K tied to vcc seems to produce the best audio signal for that voltage level (filtered through a capacitor to remove the DC) from the microphone's positive terminal.  I'd like to use a larger power source, however... specifically, the audio amp that I am wanting to hook it up to takes 12v, and I would ideally like to draw the power for the microphone from the same source as for the amp.  I do not, however, want to damage the mic by running more voltage than what it is rated for.
What would I need to change in this configuration  to safely hook up the microphone to 12v without risking damage to it, that would yield an optimal signal?  I'm reluctant to experiment with different bias resistors as I did with the 5v power supply because while 5v was within the allowed voltage for the mic, 12v is not.


texts: Would this isolated boost topology work?

texts:
I've been trying to create an isolated DC/DC converter for cell balancing but I can't seem to get the topology quite right.

In the topology shown in the picture, the cell is on the left and the battery on the right.

The MOSFET with the tag "C1" shorts the inductor, increasing its current. Then it turns off and the inductor current forces the diode to conduct, thus charging the capacitor and increasing the current in the primary of the transformer.

When the MOSFET turns off again, the capacitor would take the decreasing current from the transformer. Since the current in the transformer is always going up and down (but always with the same polarity), this would create magnetic flux in the core of the transformer and transfer energy to the secondary winding, charging the main battery.

The FET with the "BoostON" tag would only turn on when the converter is turned on, and it would be always conducting. When the converter stops the energy transfer between cell and battery, this transistor would be turned off. This is to avoid shorting the cell through the transformer and boost diode when the converter is not working.

So, are there any flaws in this topology? Are there any reasons why this would just outright fail, or would it actually work as intended?

Extra information:

This is just a typical boost converter with an extra transformer and a diode on the secondary side. The bigger circle in the transformer indicates the primary side. The transformer used would be this one, with a 1:4 turn ratio. The objective is to implement PI/PID current control to get an average inductor current of 3 A. The reason I want to avoid the typical fly-back topology is because of the control issues that may arise. The switching frequency is going to be 30kHz, and the inductor used would be somewhere around 70~90uH (calculated for the normal boost topology). The capacitance value in the image is random. Simulations show that the circuit should work as intended.


texts: How can I get 1-10MB/s of debugging data to and from a dev board?

texts:
Here's the fundamental problem I have: I'm looking at a dev board for, say, a TI/AD/Microchip microprocessor or DSP. This is long before a full product design; we're talking proof-of-concept work here. I want to send data from a PC to be processed by my firmware, or have my firmware send data to my PC. And I want the rate to be of the order of 1-10MB/s.

15+ years ago, 1-10MB/s would have been quite niche. kB/s would have been more usual, and the dev board would have had a DB9 connector on it. I could have just plugged a serial cable between the dev board and my PC, perhaps with a USB-to-serial converter, and read and write to COMX or /dev/ttySX.

However, this scheme has a number of limitations that are now starting to show up:

I want MB/s, not kB/s.
The absolute max UART rate a 100MHz device could manage is still only 0.7 MB/s. SPI on the other hand allows up to 3-4 MB/s.
It's incredibly rare for PCs to come with serial ports now, so specialised adaptors are needed to interface with a PC eg. USB to serial cable.

But I'm stumped for what I could use to replace the old serial scheme. The main context for this question is sending serialised debugging data between vendor dev boards and a PC before design is finalised, so anything requiring secondary devices eg. Bluetooth isn't super useful. The µPs I typically work with are in the realm of TI's MSP430, Microchip's PIC32M*, and low power DSPs like the TI C55x or C674. Their dev boards might typically come with headers connected to SPI/I2C/UART peripherals.

Ethernet would require full implementation of a networking stack, which isn't really practical on the constrained DSPs or µPs I often work with. Furthermore most PCs only have one ethernet port, if at all, so you wouldn't be able to use it for wired networking.

Ground-up USB requires getting a vendor ID from a 3rd party, and reinventing all sorts of wheels at the driver and software level just to get data from one device to another.

Ideally I'd like to just be able to dump bytes in a peripheral register on my µP and drain it using Python on the PC or vice versa, using a cable most IT departments would have lying around, and get 1-10 MB/s. A bonus would be not having to poll every available port of whatever kind to find the device on a PC. Is this possible?


texts: How do I protect myself when testing a PCB that involves an AC line?

texts:
I have to test prototype PCBs that convert household AC into several DC voltage levels.

I concern about my safety when working with AC and would like to know how to properly setup a testbench that, for example, will trip a circuit breaker or break a fuse if something goes wrong.

I plan to build a testbox that is located between main AC line, and the test object. The box will probably have the following stuff built into it.

Cable for the connection to the main household AC
Variac (variable transformer)
Emergency stop button (big red button)
Circuit breaker that has a lower rating than the house circuit breaker
Output socket for connecting to the test object
Fuse between the main line and the output socket

What else should I include in this testbox? Or is this testbox thing really helping?


texts:
This is probably a really silly question, but I still want to know...

Given a standard off-the-shelf FM radio alarm clock, what is to stop it from transmitting radio waves when physical motion causes the speaker to move?

The theory is that if FM waves can come in to the antenna, through any tuning circuit, and be spit out as audible noise on a speaker, why not the reverse when I move the speaker, say by flicking it softly a couple of times. In the perfect laboratory scenario, would I see any RF output from doing this? If so, would it be anything more than just RF noise?

Yes, I realize this is not a good setup. No, I'm not trying to implement anything. Thinking theoretically, I just wonder if it's a one-way street or not in a COTS FM clock radio.


texts: Can I have two regulator for wall fan - one default one and second I externally connect at switch board

texts:
I have bought one wall fan with following specification:

Fan speed: 1900 RPM
Voltage: 220-240 V
Frequency: 50 Hz
Power: 125 W

It has inbuilt step type regulator with 3 stage button to either slower or faster the fan speed viz., 1=slow, 2=Medium, 3= Highest. As shown in the image below. Now the problem is that it runs fast at the very 1st stage (i.e 1=slow) and I want it to further slow down.

Hence I bought one another step type electronic regulator as shown with red rectangle in the image below and I am going the connect it in the switching board as is with the ceiling fan. But I have doubt that whether two regulator will work with that fan or not. Can any body help in choosing the best solution for this issue.

Thanks in advance !


texts: Enclosing/Casing Design for electronics (electronic eng. vs industrial designer)

texts: I have been wondering, this since i dont have that much experience in product design, but, who is supposed to do the case design of an electronic product? the industrial engineer or the electronic engineer? i have been trying to find the answer to this question last job i had my boss didnt want to allow me (electronic eng) to participate in the case design (i needed to ground it at least)


texts: Interfacing of 8V hall effect sensor with microcontroller to measure RPM

texts:
I am using a hall effect sensor for measuring the RPM of the engine. The output of this sensor needs to be fed into the ECU (for engine control) and Microcontroller (I am controlling a linear motor based on engine's RPM). The ECU is providing the hall effect sensor 8V supply, therefore the output of sensor will be either 0V (LOW) or ~8V (HIGH) but for my microcontroller digital input, I need 0-5V (I will measure the frequency of digital input using my microcontroller to get sense of RPM).

So basically I need to covert 0-~8V to 0-5V, what's the best method of doing this?


texts: What is this object found on transmission lines?

texts: What are the components, circled in red in the figure, on this transmission line ?


texts: SDRAM on opposite side of board with respect to uC

texts: Just a quick question. Is it advised against to place a high speed memory device on the opposite side of the PCB with respect to the microcontroller? And if it is ill advised, how is it possible to used the same data/address bus for a few different physical memories? There would be no way to route the inner traces that have been sandwiched in by the other address/data lines.


texts: Shutdown Controller for Raspberry Pi in a car

texts:
Following on from my previous question I'm trying to create a shutdown controller for my Raspberry Pi.  The Raspberry Pi needs to be powered from the battery, but should power-down after the Pi detects that the ignition has been turned off.

The Pi will take a 3.3V feed from the ACC line (I have other components that will take 5V from the ACC line via a 7805, so I will step down to 3.3V using a voltage divider unless anyone has a better suggestion - I'll also be driving a uPD6708 which takes 5V CMOS I/O, so will have to step-down from 5V to 3.3V on another 2 lines).

Software running in the RPi will set one of the GPIO pins high, presumably when the RPi shuts down the GPIO pins will all go low.  So Q1 should turn the relay on, keeping the RPi's power on as long as the ignition is on, or the GPIO pin is high.

I have 3 fuse kits with a 1000uF cap and some kind of transformer/inductor, so I may as well use one of them on each the 12V battery and 12V accessory line.

This shut down controller claims to draw only 50uA in standby - if I used a CMOS 4071 OR gate that would be a start, but from what I've read, you'd need more current from the OR gate to saturate the transistor - is that right?

Bearing in mind that I need to level-shift 5 lines from 3.3V to 5V and 2 from 5V to 3.3V in addition to the requirements of this sub-circuit, can anyone recommend components/alternatives for OR1, Q1, RLY1 and/or any modifications?

simulate this circuit – Schematic created using CircuitLab

Here's my attempt at following @Connor Wolf's suggestion.

R1 and C3 need to be be chosen to allow the RPi to shut down properly
I've added C1 because I image that it will take a brief moment before the relay switches after the ignition is turned off - I've got no idea how long that is, but I suppose the RPi is going to be drawing about 700mA from the capacitor, in addition to the 555 and relay

simulate this circuit

@Nick suggests it could be simpler - like this perhaps?  I tried to remove the diodes so that I could just use an off-the-shelf 12V-5V 1A USB power supply (or a pair of them).  The 555 datasheet says that it outputs 3.3V (max source 100mA?  This page says 200mA).  The RPi will take read the ACC line at 3.3V to determine when to shut down.

simulate this circuit


texts:
I am (planning to) use MAX13410E in receive-only mode to convert RS485 differential level to Vo/GND voltage. The chip is outputting Voh=4.6V and Vol=0.4V (relative to GND). The RS485signal will be flipping between 0 and 1 every few seconds, not faster.

This signal will be fed into another device expecting 0...0.15V for low and 0.3...10V for high.

It is a good idea to use voltage divider with e.g. 1:5 ratio to get 4.6/6=.76V high and .4/6=.07V low? Or is there some other standard approach?


texts:
I'm trying to hack a LED fluorescent tube and PWM it with arduino and a TIP120 transistor .
I bought one and disassembled it, basically it's an LED strip connected to a 220v though a LED driver.

I'm trying to bypassing the 220v LED driver, and power the LED strip directly from a DC power supply.
I started measuring the voltage on the LED strip when it's on and i got 18v on 2 points.
however when I'm trying to power those 2 points directly with 18v from an external power source without the 220 LED driver i got nothing...

i attached an image of the LED strip connected to 220 LED driver...

Does anyone have an idea how can I bypass the 220 LED driver ?


texts: Microchip dsPIC33 audio DAC: has anyone succeded using it without noise?

texts:
I am using the 16 bit audio DAC from dsPIC33FJ128GP802 and I am having a lot of noise, even if the output value is held constant.
I have obtained better results in the past using 8 bit PWM from an ATmega328. I have already checked that the power supply is properly filtered, also that the analog circuitry is properly working without adding any noise. Also the PCB was carefully designed and routed. All tests I have made indicate that the noise is coming from the DAC.

Searching on Microchip's forum I found that many people had the same problem in the past, see this link and links therein. I have found no one saying "this was the problem, it is solved". So I came to think that this DAC, although 16 bit, is not useful for audio applications.

Has any one here have used it without getting tons of noise?

EDIT:

Here is the schematic.

Here is the layout (bottom layer). The top layer is a GND plane.

Some tests I have made:

Set the DAC output register to a constant value. There is no audio going out, but the noise remains exactly the same.
Turn off the DAC module. Noise disappears.
Connect things as in this link (while keeping DAC module on), I get good audio quality and noise disappears.

The noise sounds white. Unfortunately I have no instruments to characterize it further. I have an old analog oscilloscope and an audio amplifier.

EDIT 2:

Here there is the waveform, the spectrogram and the FFT of the background noise with and without the audio passing through the MCU. This was recorded using a cellphone recording the line input electrically connected to the output of my circuit.

EDIT 3:

Here is an audio sample of what I am getting. The first half is with the signal passing through the microcontroller, the second half (after the "clak") is without the microcontroller.


texts: What is this IC “30=N26” in Philips hue garden light

texts:
I'm hoping to identify the IC in this Philips Hue garden light controller, in order to replace it.

Suggestions on how to identify what it is, would be greatly appreciated.


texts:
I have a vague recollection that while off, a LED can actually receive light and generate a small current (in uA).
Is that correct? How does that work? What is the best way to prevent this?


texts: What is the connector shown in the photo?

texts: Is the connector marked as CN3 in this photo a standard one? If so what is it called?


texts: How to do Mesh Analysis with Current Sources?

texts:
Basically the circuit below is what my professor gave us and we need to solve for the the voltage across the 8 ohm resistor, the current through the 2 ohm resistor, power absorbed by the 10 ohm resistor, and the power delivered by the 4 a source. I used regular mesh and I got the wrong values(I checked using KCL and KVL). One thing that I think I got wrong is I assumed that I1 = 3A(feedback). I tried to search the web for a solution and I've seen something called "super mesh". Is this helpful? If yes, can anyone assist me on how to work with it?

Other thing is I want to check if my values are correct using MIT's Circuit Sandbox, however I don't know where should I put the ground so that the circuit will simulate in the way I wanted it to be. Every help is very much appreciated Thanks!


texts: Voltage Regulator 317 - Selecting Resistors ( R1, R2 )

texts:
I'm using a 317 Voltage regulator in order to reduce a 12v into 3.7v output.

Using the mathematical relation Vout = 1.25*(1+ R2/R1), A ratio of 2 between R1 and R2 will be suffice for my needs.

Does it matter if I'm using R1=200 [ohm] or R1=10K [ohm] as long as I keep the mentioned ratio ?

I used R1=10K, and I get an error ( Vout ~11.6v ).

Guy


texts: Can you charge a battery to run a device at 5V from the USB port?

texts: Say you had a device that requires 5VDC to operate. It can actually run safely at about 4.8VDC. It normally runs off of USB power but I would like to rig it up to run off of a battery. Would it be possible to design a circuit that would allow the device to run and charge the battery when connected to a usb port and then when unplugged, run off battery power?


texts:
Got a temperature regulated solder iron, always had the temp set to 350C. Used the wet sponge after every solder job to clean the tip. Used a 60/40 rosin core 0.6mm solder.  After week of use, when turning it on again I noticed the stock tip only had few areas where the solder would stick to. The areas were visible, they had dull metallic look, the rest areas were darker. Tried cleaning with wet sponge, made no difference. Finally had to use very fine sandpaper. After that no part of the tip was usable anymore. But the surface was metallic, not copper color so I don't think I sanded away all the tip cover.
Is there any explanation for this?

Replaced the tip with a new one which came with the iron. Solder sticks to it well, but I don't know how long this one will last. Here are pictures of how a 60/40 solder looks on it (wanted to tin the tip). Very odd coloring. Does this give any explanation?

Not a professional, so didn't get an expensive quality solder station, but this one wasn't cheap either and had a iron holder, replaceable tips and temperature knob. The iron itself seems to work fine.


texts: Altium, it is possible to mirror the silk screen?

texts:
I am trying to build a simple PCB at home. It is a single layer PCB, and I would like to transfer the silk screen on the back side, mirrored. But for that, I need to mirror text, etc.

To design the PCB, I place components on my top layer from the library, and they already have the silkscreen on the top layer.

It is possible to do something like cut and paste, mirroring the art?


texts:
I'm having a hard time determining if this mux will work for my application:
https://www.mouser.com/datasheet/2/256/MAX14752-MAX14753-1515255.pdf
I'm trying to use 2 of these together in a PCB I'm designing to be able to switch 16 different voltages (ranging from 2.5v - 58v) from a 16 cell LifePo4 battery bank to a single output (voltage divider) then into an ADS1115 in order to be able to read each individual cell voltage in the battery bank from a raspberry pi.
the datasheet shows:

VDD to VSS .............................................................-0.3V to +72V

From my understanding (correct me if I'm wrong) means from the positive voltage source to the negative or ground?
Since the maximum it looks like the mux can pass is whatever you're feeding it from Vdd, I believe this would fit my requirement of 2.5v - 58v?
Before I commit to this design I would love for someone who actually knows what their doing to confirm or not that this will work.
As an aside, I recently discovered (through another thread on stack exchange) that BMS muxes exist that would fit my criteria as well however they appear to be a little too complicated for my uses at this point and I'm still a little shaky on understanding how to operate those chips via SPI. (If someone has a good reference of one of the Maxim or Ti BMS chips being operated by a raspberry pi it would be greatly appreciated! There doesn't appear to be any write-ups on using these over SPI with the Pi (in python) just with the arduino using C++ which I can somewhat understand but would rather get something simpler going at least at first as I kind of need this up and running ASAP)
Thanks in advance for any help on this!


texts: Stability of input filter in SMPS - Theoretical explanation

texts:
I read the Application note Wurth Electronics ANP008c about negative resistance of a SMPS input and how to avoid oscillation when using an input LC filter. I'm asking for a theorethical clarification on the following:

In the document, it is stated that to avoid oscillation, |Zout| << |Zin|. A real inductor is considered, with a non-ideal frequency response:

The application note states the following:

The  output  impedance  of  the  filter  is  at  its  highest  at
resonance  frequency  and  conflicts  with  the  input impedance of
the switching regulator. To prevent any oscillation, it is recommended
to attenuate the filter [...] to reduce the impedance during
resonance. Therefore, a design tip is to keep the output impedance of
the filter much lower than the input impedance of the switching
regulator.

I cannot understand why this is true. In other words, I don't have any idea on how to demonstrate this statement (e.g. performing a small-signal analysis with the Laplace transform). I tried simply to draw and find the transfer function of a LCR circuit (with ideal Lfilter, Cin with ESR, and -Rin) and I could infer something about the stability of such a 2nd order system; but in that model the inductor is ideal and so I cannot reach the same result of the document. I can add some parasitics to my model but I get a complex fourh-order system. I guess I'm missing some approximations that can simplify the problem without dealing with a high-order system. Can you please suggest me some hints?
Thanks, Alessio


texts:
simulate this circuit – Schematic created using CircuitLab

I am fairly new to electronics. I've been studying it for the last few months and have put together a few circuits. The problem I had was that none of my circuits worked even if I followed a design that i found. I don't know why, but the circuits worked with a 9volt battery rather than using a power adapter (ie, 9v 100ma adapter). As a hobbyist, I have been grabbing old devices around the home, pulled them apart, kept all the resistors,caps, etc and the now empty PCB's.
I wanted to build (probably not the best idea for my first complete circuit design) a box that put out 36, 24, 16 and 12 volts. I had several KA431L IC's and a few 3010KM IC's. I had a transformer that tapped out at 14V, 10.3V and 3.6V and so i used the 3.6v to a ka431L to create a steady 2.5V reference voltage to run the other ka431l and the 3010km. The 2nd ka431l had the 14V across its kathode and was there to give me 36v and 24v (from a switch) and the 10.3 went to the 3010KM.

I can't seem to get more than 6.6Vs from the 2nd ka431l and the 3010km didn't work at all in this circuit. I built each of these circuits before using a prototype board and in that setting they all worked. I just can't figure what I did here (I'll include a picture)
Is this even an acceptable Voltage Regulator circuit? Will I be able to run my DC circuits from this? I wonder if it safe, efficient, could have been done a better way, etc.
I couldn't work out which ground each IC was expecting. ie. i send 14V DC over the 2nd KA431L kathode but I am powering it from the 1st KA431L into the Vref. At the anode, should it be the ground from the 14VDC or from the 1st KA431L?

Legend:
BR - Bridge
SW - Switch
JP - Jumper to a second board
HV1 - connections to the 3010km. each pin corresponds.
TP - Test Point. I have pins that i can attach my multimeter to at various places in the board
SB - The second board. it's shown on the schematic below

All the "c" "r" and other circuit symbology shown on the schematic are only references to where exactly on the up-used PCB i am connecting to or from. These references can be ignored.

I've broken the board into 3 Ground sections which I refer to as PCB Ground. For each IC on the board, there is a corresponding ground area unconnected from other grounds.


texts:
Part 1
What is the standard timing method for bits acquisition for a receiver using Modbus RTU?
For example, for UART: "Communicating UARTs have no shared timing system apart from the communication signal. Typically, UARTs resynchronize their internal clocks on each change of the data line that is not considered a spurious pulse. [...] they resynchronize on the falling edge of the start bit only, and then read the center of each expected data bit, and this system works if the broadcast data rate is accurate enough to allow the stop bits to be sampled reliably." (source wikipeda)
I didn't see that kind of information onto the modbus organization.org website.
Part 2
To go further, here is the issue:
I use a FTDI F232R TTL USB cable (from RS-component) to make a custom sensor (slave with a STM32 uC) communicate (using modbus protocole) with a computer (master), using a terminal (realterm) or a software (ModbusReader or custom) on it. I know I shouldn't do this because I have read that modbus protocole should be used with RS232 or RS485 physical layers, not TTL levels.. (I didn't find yet any explanation about that (?))
Everything works fine at several baud rate speeds (i.e 115200, 19200, 1200) but at 57600 baud rate, it raises error (frame error on Modbus Reader).
So, to know if there is any transmission issue (such as timing ones) on the line, I want to decode my self (using Scilab) the data recorded by an oscilloscope.
Note: strange thing: with an FTDI F232R TTL USB cable from an other (mysterious) source, which I opened to see that it uses same IC, but only 2 capacitors versus 4 capacitors on the RS-component source, I works pretty fine for all baud rate speed.


texts: 8051 interrupt priority level significance

texts:
I am working with P89V51RD2 which is a 80C51 micro-controller. It has Eight Interrupt Sources and Four Priority Levels.

In the above table, there is a column Service Priority which sounds like Fixed-Priority interrupt servicing. And then there are two bits for setting priority of individual interrupts(Interrupt Priority) which makes 4 levels.

I couldn't find the explanation for Priority Bits in the datasheet. What exactly is the purpose of these priority bits?


texts: Origin of a Resolution formula for ADC/DAC

texts:
What is the origin for the forumla:
\$ R= {1\over2}V_{LSB} ={1\over2}*{V_{inMax}\over2^n-1} \$

Where does the \$ {1\over2} \$ comes from?
Shouldn't it be just: \$ R={V_{inMax}\over{2^n-1}}\$ ?


texts: Power to tool vs duration of larger ah batteries

texts: I have a Milwaukee M18 Fuel 18v LI ion cordless impact wrench.  It came with a 18v 2.0 ah 27 Wh battery pack.  They also sell a 18v 5.0 ah battery pack among others. When reading online some people say the 5.0 ah battery will provide more power to the tool from the start while others say it will only provide the same power for a longer period of time.  I tend to think the latter is true, but I am not an electrical engineer.  There was a Youtube video showing that when the guy swapped out the smaller battery for the larger one he was able to break a lug nut loose where the smaller battery was not able to do so.  Was that due to other factors like maybe the age of the batteries, or is there something to the larger battery pack providing more power at the motor from the start as well as for a longer duration?


texts: Clamping Inductive Kickback in AC Circuits

texts:
I want to eliminate/clamp the inductive kickback that would result from turning off a large inductor, such as a relay or a transformer.

In a DC circuit, I would use a diode to flywheel the current. But what do I use in a line voltage AC circuit?

Is an MOV an acceptable device to use? Should I connect it parallel with the inductor or parallel with the switch? MOVs fail closed circuit, so this could be a fire hazard. Fire safety is a very important consideration.

Or should I use a TVS or something else?

Please describe how the suppressor device should be connected to the circuit.


texts: AC power cord different on a laptop and a desktop, other appliances

texts:
If I look at the power cord plugged from the wall socket to desktop computers, monitors, etc. at the office, it looks like (North America):

Now, if I look at the power cord plugged into my laptop's power supply (North America again):

I checked with my colleagues and it seems all the laptops (from many different manufacturers) use the same power cord, while the other appliances (desktop, monitors, etc.) use the first model.

Is there a standard governing this? If yes, what are the electrical reasons for this? Maybe the laptop version fits more snugly in the socket and is thus less prone to being unplugged by accident?

I am eager to improve my knowledge of electronic design so...


texts: TL082 electret preamp and LM386 power amp

texts:
I have spent the last few days trying to prototype a TL082 electret mic preamp (based on this schematic). I swapped the TL071 in the linked example with TL082 (which I understand to be more noise-prone but otherwise similar), made the appropriate changes to the wiring (VCC moved to Pin 8, signal output moved to Pin 1, etc.) and am using 50 Ohm resistors for the Voltage Divider (as opposed to the 62 Ohm used in the example schematic) but otherwise my circuit is identical (this was laid out in EAGLE and the PCB cut via CNC, BTW). See below for my schematic.

As far as I can tell the preamp is sort of working but I am struggling to test and diagnose it. For example: an LM386 power amp will not amplify the signal from this TL082 circuit. The LM386 circuit I use for most things will not amplify the signal from the pre at all (no sound comes out). No idea why, here's a schematic of that circuit below:

If I plug the TL082 into a different amplifier, say a honeytone (which uses the TDA7052A IC), I can kind of hear the signal, whereas I get nothing through the LM386.

Does anyone see anything wrong with my TL082 schematic? Should I not be using LM386 to amplify this preamplified signal? Would something else be better? Any suggestions or reccs would be greatly appreciated!


texts: Is it possible to connect multiple GND with one wire?

texts:
I am making the circuit using Stage and Controller, Power Supply and DAC Card.
As for the system, the power supply provides a 15 V voltage to the controller/amplifier, and a 0 to 10 V control voltage through the DAC. This causes the controller/amplifier to amplify the voltage coming through Control In by 10 times and put it into Stage, and the stage will move depending on the voltage taken.

Finally, not all of them are shown in the figure, but there are four or five lines that need to be connected to the GND from the controller/Amplifier (test GND, Protective GND, for monitoring the voltage on the stage, etc.), all of which are connected to one wire by soldering as shown in the picture.

The wires were all connected by referring to the manual using wires, soldering, and banana jacks.

But It doesn't work, so I'm asking you this question.

Here's what I'm curious about.

Can I connect various GND lines at once as shown in the picture?
Now, there are about five lines that need to be connected to the GND that are connected together.
Will that connect well?
There are two current GND sources. One GND connected to DAC through BNC Cable, and GND terminal present at Power Supply terminal. if there are two GNDs, does GND be properly captured?

Thank you for reading it.


texts:
Hi, in the image below (taken from Design of CMOS Analog Design Circuits by Razavi), a high gain amplifier is used to provide common mode sense and feeback by controlling the current through M3 and M4. The idea is that if both Vout1 and Vout2 rise, then Ve rises, and the current through M3 and M4 rises, which then brings down the output common mode level.

Now I just want to know if my understanding of why exactly this brings the common mode level down is correct. Please correct me if my explanation below is wrong.

Raising Ve will raise the current through M3 and M4, but the transistors stacked on top are biased for a different current (their gate voltages are set). To satisfy KCL at Vout1 and Vout2, the drain voltages move down so that the same currents flow through the cascode PMOS and NMOS transistors and M3 and M4.

In other words, the voltages rise or fall to favor equal currents throughout the branch except for the top PMOS transistors, above the folding node.

I hope my explanation makes sense. Do correct me if I am wrong.


texts: How to connect buttons to gates with status LEDs?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm playing around with 7400 series gates and I wonder what the best way is to connect some buttons as input and how to add some LEDs to make the input visible.

I think I have 3 choices:

positive input and LED in series (SW1)

The LED requires 2-2.4V (depending on make and color) to light up so the gate input should switch between 0V and 2.6-3V. A 74HCxx gates requires an input high voltage of 2.4V so 2.6V should register as high. Is that enough of a safety margin or should I stick with red LEDs that trigger at 2V to get 3V input for the gate? 74AHCTxx gates require an input high voltage of only 2V so they should be even safer, right?
positive input and LED in parallel (SW2)

Or should I connect the LED in parallel to the gate to get a full 5V input? Is 10kOhm a suitable pull-down resistor in this case?
negative input and LED in parallel (SW3)

For an input that should be high when the button isn't pushed it looks like I have no choice but to go for the parallel setup. At least with 74AHCTxx gates the 2-2.4V from the LED would register as high. But with this setup the LED would light up on LOW. Is there something better that doesn't need extra gates or transistors to make the LED go out when I press the button?


texts: drawing too much current out of regulator causing heat, alternative 5v regulation methods?

texts: I am trying to power 5 servo motors from a 5v 7805 regulator with decoupling capacitors. The source is a 9.6v rc battery. Since the servos require 5v I am trying to get 5v to them from the battery hence the regulator but in practice only 3 servos can function at one time and are still causing the regulator to get incredibly hot, connecting any more will stop all of them from working. Since the 7805 can supply little current relative to what I want, What can be an alternative and more efficient way to power these servos with the 9.6v battery I have?


texts: ITS-90 Tempature coefficents for a standard PT100 385 RTD

texts: I'm currently using the ITS-90 formula to convert a resistance of an RTD to a temperature. I got the coefficients from the manufacturers calibration sheet. The problem is I have another probe that I don't have the ITS-90 coefficients for. Is there a standard theoretical set of coefficients that I can use?


texts: How to store audio data for AVR project?

texts:
I see a lot of projects for AVR-based audio players that use an SD card to store the audio data.

In fact, I am currently doing the very same thing on an Arduino and its Wave Shield, which has an SD card reader.

However, I'd like to develop a device that stores the sound on onboard EEPROM or Flash memory rather than a removable medium.

The current files are 16-bit mono 22Khz PCM WAV's and altogether require 620 kilobytes.

I'm not sure what to look for in memory chips. I know I'll need sufficient storage per the above requirements. The device won't record nor alter the data, so additional capacity is unnecessary. Obviously I want to select the lowest-cost solution that will still meet the requirements:

Must store at least 620 KB
Will need to be fast enough to support 16-bit 22Khz 1-channel playback
Compatible with AVR microcontrollers
Can be write-once
Must retain data without power
Preferably SMD package but through-hole is acceptable

Some general tips on adding and using flash (or other types) of memory would be greatly appreciated!


texts: Type "X2" line filtering capacitor failing as short circuit

texts:
I recently plugged in an old Apple IIGS that had been sitting in a basement for almost 15 years and it worked for awhile before blowing up in a smokey mess. The reason for the smoke was easy to diagnose, one of the line filtering film capacitors had exploded and shattered. The fuse was also blown in the process (so I'm assuming the capacitor managed to somehow blow in a short-circuit fashion).

Although it is straightforward for me to buy replacement parts and repair the device, is there a particular reason why a film capacitor would fail in such a spectacular fashion? My understanding is that typical film capacitor failure modes involve a gradual reduction in capacitance, rather than a sudden internal short circuit. Does a capacitor failure in this fashion typically indicate another component has also failed down the circuit? Unfortunately, I do not have schematics for the power supply, but my understanding is that "Type X2" capacitors are "across the line" -- between line and neutral. The exploded (and also the intact capacitor on the other side of the transformer) read: 0.22uF X2 and have a 250V rating.


texts: Optical bandwidth and electrical bandwidth

texts:
I understand the concepts of electrical and optical bandwidths, but I encountered an example problem that used the following formula to calculate the electrical bandwidth:

$$electrical bandwidth = 1/\sqrt{2} * optical bandwidth$$

Can any one explain to me why the equation holds? (I couldn't derive it based on the definitions)
Thanks!

The source is: Example 4.4 page 104 "Biophotonics, Concepts to applications" by Gerd Keiser, 1st ed. 2016 Edition.


texts: Best RFID Technology for long range detection?

texts:
I am considering building an RFID reader system that can monitor runners times in a foot race. I have read that there are three different types of RFID systems. LF, HF, and UHF. Which one would be best for this application? Has anyone had success building an antenna that can read RFID tags from a distance of a meter or more?

EDIT:  Active or Passive? My current thought is to use passive technology. I want to be able to get the tags for as cheap as possible and I don't want there to be a chance of the internal batteries failing.


texts: Can we use long wires with ultrasonic module HC-SR04

texts:
I want to use Ultrasonic module HC-SR04 as ranging sensor but my MCU board is approx 80 ft away from the place where I have to put the US module.

These are its pin-outs and descriptions:

My ranging is from 1 ft (min) to 6 ft (max) and accuracy is +-1 inch (2-3 cm).

Is it possible to run the 4 wires (Vcc, Trig, Echo, Gnd) directly from my MCU board to the US module 80 ft away?


texts:
I bought some very small speakers, but I'm not sure how to solder or connect wires ...

Should I bend the 'butterfly wings' on the left side upwards and connect to both 'wings' (it states a + and - sign on each wing). Since the wings touch the copper color chassis I think it would give a shortcircuit without bending.

The green part is not conductive (checked with multimeter).... so I'm almost sure to just bend the wings up a bit and solder wire to it... but want to be sure (not to blow them) :-)


texts: What is the point of seperating analog ground and digital ground if they are going to meet at the end

texts:
First off, I'm fairly new to electronics, I don't have much knowledge so bear with me. I saw a schematic of an ADC connection to an MCU, and I noticed that the grounds are split into two - Analog and Digital ground. I read up on why they are split. It's to prevent the high frequency noise of the digital signals to interfere with the analog components.

In theory I can understand but practically, if I were to make any product where I use an ADC, then if I were getting power from the mains or a battery, ultimately won't the grounds meet at one point? So then what is the point of separating the ground lines. How does this whole thing work?

Thank you


texts: If you look at the flyback converter circuit above, the current only flows in one of the coils at any instant of time. What stops the magnetic field generated by the coil in series with the MOSFET to induced a current in the coil in series with the diode resulting in a simultaneous flow of current through the diode and the MOSFET at the same time?


texts: What processor architecture is in a 230GMULps KPU design?

texts:
While AI products are becoming popular recently, when looking at the "Seeed Studio Grove AI HAT for Edge Computing Artificial Intelligence Board" it mentions a RISC-V, a 230GMULps 16-bit KPU (Neural Network Processor), a FPU, etc.
What is this "230GMULps"? What could be the processor architecture in it if it can be illustrated by an example?
Update: I initially thought of a specific model. As comments indicated that it is the number of multiplications, so I updated the question to ask for an example architecture.


texts:
How can I choose a ferrite bead if on schematics it's marked as 100uH? On Mouser all ferrites have only Impedance value. How can it be compared to inductance in Henry?

JIC, in BOM it also commented that it can be replaced with 100 Ohm resistor.

Here is a schematics:


texts: How does a 120VAC neon indicator lamp respond to a leading-edge triac dimmer?

texts:
I bought a dirt cheap toaster oven to convert to a solder reflow station, and I noticed in the teardown that it apparently has a neon power indicator.  It goes out instantly when it loses power instead of fading like an incandescent, and it measures open-circuit when off.

I'm not opposed to cutting it out of circuit, but I also thought it might be nice to have a rough indicator of what it's actually doing, if it actually works that way.

Here's the circuit:

simulate this circuit – Schematic created using CircuitLab

So:

Does it "just work" and produce an incandescent-like end result?
Can it confuse the triac?  (probably not because it's in parallel with the resistive heater and my software is going to hold the opto on anyway)
Is there something else I ought to know about using neons and triac dimmers together?


texts: Spectrum Analyzer vs. numerical FFT-based methods?

texts:
We sample a signal over time (e.g. voltage fluctuations of a resistor). Then do a FFT-based Power Spectral Density in a PC.

What advantage would a physical spectrum analyzer provide over doing the spectral analysis numerically in a PC? (I am NOT interested in a real-time analysis, I only do post-analysis)


texts: Is this way of sizing the series resistor for Zener regulator correct?

texts:
This is a completely made up imaginary question to ask the question easier. Let's say I have a 0.1W 5V Zener diode. And I want to use this to regulate from 9V to a 10k load. I draw this as in the below diagram:

So above if I want to set Rs. I do the following:

First calculate zener current as 01W/5V =  20mA.
The load current Iload = 5V/10K = 0.5mA.

So the current passing through Rs = 20+0.5 = 20.5mA.

The voltage drop across Rs = 9-5 = 4V.

Rs = 4V / 20.5mA = 195k.

Is my way of sizing Rs correct?


texts: Recording motion/movement sequence efficiently & accurately

texts:
We have a motion platform (camera - pan & tilt) that is controlled by a user using a joystick (so the demand inputs are pan & tilt velocities).

The platform itself uses stepper motors, so we have a control loop in our micro which handles the movement. It can either run towards the demanded speed (joystick) or move to absolute positions, in both cases taking into account accel/decel curves, speed limits/targets and movement limits (end stops).

What we want to implement is a record-and-playback of a sequence of movements executed by the user under joystick control. This presents a problem, as the user is giving us velocities (pan right 50% speed) at irregular time intervals and will expect the camera to smoothly replay the movement whilst also hitting the same positional targets they hit during the "recording" - at 50x zoom you have to be very accurate, a few steps off and you're pointing an entire screen away from what you're supposed to be looking at.

I believe this puts basic algorithms such as just recording changes in demand velocity & the time they occur as the potential for errors (especially cumulative errors on complex sequences) is too high.

There are a number of ways I can think of of achieving this, but they all seem quite cumbersome / inelegant and potentially memory-intensive for a small embedded environment (imagine recording position and speed 10 times per second for 60 seconds) and I have the feeling I'm missing something or going over old ground solving a problem that's already been solved 100x before, for example in industrial robotics.

Any thoughts, links, reading recommendations welcome!


texts: How to protecting stepper drivers from manual motion?

texts: I am trying to figure out a way to protect my stepper drivers from manual motion of the motor. To make this more clear, the system which these steppers are being built into allows for both computer controlled or manual controlled motion. I am concerned that if the manual motion is too quick, damage will result to the drivers. Is this something I should be worried about, and if so, is there a recommended way to electrically isolate the motor from the driver when under manual control? Thank you!