texts: Multiple slave I2C on different power rails

texts:
I read following threads, but still there are some unclear parts for me.
Multiple I2C devices with the same address
I2C Pull-ups with Multiple Power Supplies
Design for Multiple I2C slave devices

I have two slave I2C devices (sensors) to connect to one master MCU. They are not modules on breakout boards with preset PU resistors.

The first slave I2C device is on the same power rail as MCU is.
I put the other slave I2C device on another power rail due to following reasons:

I want to make a PCB for it, so that the second sensor could be attached through a terminal connector.
Not always the second I2C will be connected (in case I don't want to use it).
To lower power consumption. I want to put MCU on power down mode. So, periodically it can turn on sensors and read their values and turn them off again and go to power down.

I was thinking to do as following schematic. But I would like to know your recommendations, if there are issues with it, or if there are better ways to do it.

simulate this circuit – Schematic created using CircuitLab

If I use this schematic, do I have to add diodes to prevent current draw from second slave sensor when it is off?

More details:

I2C device will not be hot plugged/ how swapped.
I have a sensor that could be used as second I2C sensor. But it does not have sleep mode. That's why I'm thinking to turn it off.
I2C sensors and MCU are working on 3.3V.
The first sensor is BME280 (always connected).
Second sensor could be this one.

What do you think about adding a buffer, like PCA9306, in this schematic2?

What do you think about using I2C mux e.g. PI4MSD5V9540B? In case of using mux, I can use two sensors with same address.


texts:
I'm having trouble analysing this circuit and was hoping someone could help me. The circuit in question is below.

I want to find the voltage drop and current across each of the parts. So far I've found the thevenin equivalent:

I'm a little confused as to how to find the current. Would I simply use $$\frac{11.2V}{13.33k\Omega}?$$

Or does the diode subtract 0.6 or so volts from the total voltage to be $$\frac{10.6V}{13.33k\Omega}?$$


texts: LPF and AMP for ADC with op amp not giving sufficient gain

texts:
I have a project where I need to have audio input into atmega168PA. I've decided to implement it by using an electret microphone which will feed into op amplifier for low-pass filtering and amplification.

I'v implemented a simple non-inverting amplifier ciruit shown below:

Design is not mine, I found it from another thread.

Total gain of the circuit should be around 900 and output should be nicely centered around 2.5VDC. Problem is that measuring with an oscilloscope I see that it doesn't give nearly enough amplification. By tapping pretty strongly on the mic I get only about 500-600mV (shown below) of peak-to-peak amplitude around 2.5V. With a loud clap I get little more than volt. Not nearly enough to register normal voice.

Scope view:

I understand that microphones need a lot of amplification so I added another stage (shown below) with amplification gain of 15 which should have produced gain more than 15000 in total, but still the peak-to-peak amplitude was little under a volt.

Circuit with added stage:

So, what am I doing wrong? I used TL074ACN op amps and I also tried LM324N op amp, but the results where same. Is it possible that neither of those amps are suitable for this application?

I also tried a simple circuit (shown below) with a transistor 2N3904 with schematic found from some other thread, which produced very good results allthough as I didn't have correct bias the signal was very distorted. But peak-to-peak amplitude was okay (around 3.6V).

Circuit:

Scope view:

As I said I want to actually feed the output into ADC so I've designed a Sallen-key low-pass filter with cut-off frequency around 5kHz and verified that it works (I'm going to use the same one for DAC output). So my final schematic should look something like this:

Final circuit:

Can someone point out whats wrong with my circuit or how to troubleshoot the problem? Or should I just go with transistor for amplification?


texts: Why put capacitor between ground and chassis?

texts:
In the product I analyse (an optical fork sensor, rated 10V-35V), there is a sizewise big capacitor between ground and chassis.

I measured its value with an LCR meter, it is 60nF. I also broke one by accident, which revealed a liquid from inside. Looking at its size and considering the liquid inside, I think it is a film capacitor.

Questions:

1) Why is there a capacitor between ground and chassis? For EMI purposes? (Note: the cables used for this product are usually not shielded - chassis is floating if there is no capacitor)

2) Why is the capacitor a metallized film type? (if it is) It seemed to me like a ceramic capacitor may also have been used in this scenario - it has a smaller footprint.


texts:
I need a power supply for a device that contains a bluetooth chip and antenna and a relay. The input voltage ranges from 12AC or 12 DC to 24AC or 24DC, because it need to be powered from diferent sources in different situations. The output voltage needs to be 3.3V and the output current around 200mA for the bluetooth consumption peaks and the relay actuation.

Because it needs to be powered form AC and DC, i was thinking the input cam be a bridge rectifier and a bulk capacitor.

The next stage is where i need help. First of all, i'm learning and i'd like to learn how a real product engineer would design a real solution for this problem. I thought two different solutions:

The most simple solution: Regulator. The maximun input voltage for a regulator for this desing is with 24v AC, 34V DC after rectifier. So a regulator with max input > 34V and 3.3V output will do the job. But it can get really hot because at 200mA it disipates 6W!
Buck converter. Much more efficient, better solution than the regulator. But i was worried about how it affects (noise of the switching frecuency) the RF circuit (bluetooth) or EMC certification.

Witch one is the best solution?, is another one better?, how a real product engineer would solve it?


texts: How to connect a sensor via I2C on an OSX computer?

texts:
I am growing a sort of interest for hardware projects; and lately I started to experiment with BeagleBone and various types of sensor.

Now I realize that, to reduce the size of your hardware (and costs of course), you can't always have an Arduino or a BeagleBone attached to your sensors, to drive the I2C chain. So I am looking for alternatives, that allows me to have a I2C chain of sensors, without using the beagle bone or the Arduino.

The first idea would be to use a computer to drive the sensors (after all, the hardware would run in conjunction with an application that is running on a computer). I have done a search for USB to I2C, but seems that most of these adapters are not simple translators but they have a ton of features that I don't need (hence the high cost).

Either via USB or via wireless would be fine; all that I need is to drive these sensors, gather the data and then send it out for processing. At the moment I can do it with the beagle bone, but I would like to explore alternatives. My sensors works either with I2C and with SPI, I have 5 of them.

I am new to the world of hardware hacking; I barely was able to connect a temperature sensor to the BeagleBone, and write a console app to process the data from it; so I am not even sure if this is possible with normal means, or if I need more experience and skills to make my own interfaces and boards. Although it seems quite strange to reinvent the wheel every time :) If hardware development is similar to software development; there must be someone else that already had that issue and made a solution, so you don't have to write the same thing over and over.


texts: Why is green the default solder mask color?

texts: Solder masks can be had in many different colors. I have personally gotten white, black, red, and blue. But green is, by far, the most prevalent color on printed circuit boards, and the default at every fab house I've seen. Why green?


texts: Running Bus at Low Speed- I2C bit banging

texts:
I am implementing I2C using Bit bang. The slave can accept maximum baud rate of 400kbps. Iam not using external pull up, which is required because of which the fall/rise are not accordingly. I read somewhere fall/rise time can corrected by using external pull up or by running bus at very low speed. Can someone please tell what does running the bus slow means.
Please guide me on this.

Thanks


texts: Two independent current sources with one opamp?

texts:
simulate this circuit – Schematic created using CircuitLab
The above circuit delivers a predetermined current to the load:
$$i_L=-\frac{u_s}{2R}$$
Is it possible to extend it, so that it does the same thing, but for two diffrent loads, while using only one opamp (and resistors)?
Basically, I am looking for a way to create two independent current sources.


texts: Burning arduino bootloader with avrdude and AVR dragon on ATmega32U4 failing

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I am attempting to burn a bootloader on a ATmega32U4 aka. Arduino Micro which is not succeeding. I am using a AVR Dragon with ISP interface.

avrdude -c dragon_isp -p m32u4 -P usb -U flash:w:Caterina-Micro.hex -U lfuse:w:0xff:m -U hfuse:w:0xd8:m -U efuse:w:0xcb:m -U lock:w:0x2f:m

When this commando is executed i get bunch of following errors:

savrdude: stk500v2_jtagmkII_recv(): failed

OS: OSX Mavericks

avrdude: v6.1

UPDATE

When i set the -B flag with 200 it clearly starts burning the bootloader, but is this due to a hardware flaw? It takes more than 3 minutes to burn.

avrdude -c dragon_isp -p m32u4 -P usb -U flash:w:Caterina-Micro.hex -U lfuse:w:0xff:m -U hfuse:w:0xd8:m -U efuse:w:0xcb:m -U lock:w:0x2f:m -v -B 1000
avrdude: Device signature = 0x000100
avrdude: Expected signature for ATmega32U4 is 1E 95 87
         Double check chip, or use -F to override this check.

Or:

avrdude -c dragon_isp -p m32u4 -B 1000

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.26s

avrdude: Device signature = 0x1e9587
avrdude: safemode: Verify error - unable to read efuse properly. Programmer may not be reliable.
avrdude: safemode: To protect your AVR the programming will be aborted

And:

avrdude -c dragon_isp -p m32u4 -B 200000

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 2.46s

avrdude: Device signature = 0x1e9587
avrdude: safemode: Fuses OK (E:CB, H:D8, L:FF)
avrdude done.  Thank you.


texts:
What's the definition of the undamped natural frequency?  I've looked and I cannot find it.

A second order system has the following transfer function
$$
H(s) = \frac{A_o \omega_n^2}{s^2 + 2 \zeta \omega_n s + \omega_n^2}
$$
where \$\zeta\$ and \$\omega_n\$ are the damping coefficients and the undamped natural frequency respectively.

Let's suppose I have a transfer function as follows
$$
T(s) = \frac{200}{s^2 + 10s - 50}
$$
What would the undamped natural frequency be?  I don't know if it'd be \$\sqrt{50}\$ or \$j\sqrt{50}\$ or something else...  If \$\omega_n\$ were complex, this would also imply that \$\zeta\$ be complex.  Is it even possible to have a complex valued damping coefficient?  Also, since it's \$\omega_n^2\$, does this imply that there are always two undamped natural frequencies?  A positive and a negative one?


texts: How can I gate the output of this phase detector?

texts:
I want to make a PLL which will lock to the subcarrier of a composite video signal during colourburst. The colourburst is present for about 2.25uS of each scanline which is 64uS long. So during that 2.25uS I need the phase detector to apply a control voltage to the VCXO. The rest of the time, the VCXO needs to coast. The control voltage during this period should remain at what it was during the last colourburst interval.

During colourburst, the voltage at Gate will be low and the phase detector should be connected to the loop filter (R2 / C1). Other times the gate voltage will be high, the circuit between the phase detector and loop filter will be open, and C1 will maintain its charge.

Can I use 2 P-channel mosfets back to back in this way to gate the output of the phase detector? Is there a better way to achieve this?

simulate this circuit – Schematic created using CircuitLab


texts: Balance charging battery pack one-half at a time?

texts:
I'm trying to wrap my head around how I need to go about balancing charging a few NiMh battery packs.

I'm using a HiTec x4 charger, which supports balancing charging up to 6 cells at a time. However, the battery packs I'm working with have 12 cells welded together in series. 12 x 1.2v cells, for a total of 14.4v (actually ~17v fully charged).

I attempted to connect the 6 charging leads to the positive ends of the last 6 cells (closest to overall negative), and the 1 negative lead to the overall negative of the pack. However, this causes the charger to throw a 'Connection break' error, which I'm assuming is caused by the other 6 cells, even though they 'sit behind' the cells I'm attempting to balance charge?

How should I go about balance charging these 12 cell packs with a 6 cell balance charger, given I'm not able to break the weld without damaging them? Should I connect the positives leads to every other cell, and balance charge them as 6 x 2.4v "cells" instead? My worry with that is the charger might damage the cells, as it's expecting 1.2v NiMh cells, and I'm giving it 2.4v cells instead.

Any ideas?

Thanks in advance.


texts:
I'm looking into building a temperature monitoring system, and I want the sensor to have the ability to be submersed into boiling water. Can a thermocouple handle this?  I'm looking into this one now, but I'm not sure if it's waterproof.

My other idea would be to drop a small temperature sensor into an aluminum tube and seal it off.

Any ideas or suggestions?

EDIT:  Sorry, I should have provided more context with my question. To clarify some things, the sensor will be used to monitor and control water temperatures ranging from 30F to 230F, not just to test when water is boiling :).  Also, the water being monitored is consumable, so the sensor needs to be food safe as well, and since this is a hobby project, I'm trying to keep the sensor as cheap as possible.


texts: If there are different packages for the same component, which one you should consider?

texts:
I am designing a small PCB for mass production, and I am trying to keep costs low. One of the components is available in several different packages: 24QFN, 32QFN and LP (TSSOP 24 Pin). There is a significant difference in price and size.

So, what should I consider for this? I guess that some are harder to mount than others. What I found is that most of PCB assemblers will tell you "Yes, we can do it!", but later, we will see if the board comes with the component well connected or not.

I am also concerned about temperature, it is a stepper driver (the Allegro Micro A4984), and it can get really hot. I am sure that bigger ones are better for dissipation, but also more expensive.

Ideas?


texts:
I am doing the derivation of the Shannon Limit, and I think I ran into a snag, and am in need of a bit of assistance:

Background:

From information theory, we know that the Shannon Limit is:
$$C = W *log_2(1 + SNR)$$
Where W represents the bandwidth and C is the capacity of the channel. It can be found that (assuming that data rate is equal to the theoretical capacity):

$$SNR = E_b/N_0 * C/W$$

Plugging the SNR in, and doing a bit of algebra we get the equation:
$$E_b/N_0 = \frac{2^\frac{c}{W} - 1}{\frac{c}{w}}$$

Computing the value of $$\frac{Eb}{N_0}$$ in the limit as C/W  -> 0, we get the Shannon Limit.
However, when I take the limit of the above equation, I get that the limit is $$ln(\frac{c}{w})$$.

Question:

From Wikipedia (https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem) and other internet sources, the "Ultimate Shannon Limit" is ln(2). My question is, am I correct with my mathematics and the work that I have done? How can I derive an expression for the required Eb/N0 as a function of capacity and bandwidth (assuming that data rate is equal to the theoretical capacity), to achieve the Shannon limit?

Thanks in advanced for your help!


texts: Why is chassis connected to earth ground but not neutral?

texts: My question arose from my previous questions. Here depicts how electricity is distributed to houses:http://www.epanorama.net/documents/groundloop/feed_1phase.gif It seems like the earth ground and neutral are connected at the end. If so why we not just ground the chassis to neutral instead of earth?


texts: How to amplify signal for driving a more powerful motor

texts:
I have a 0-12V signal supplying max. 10A, which drives the 12V DC motor with peak consumption of 10A. I'd like to replace this motor with a more powerful 12V DC motor with the peak consumption of 30A.

The new control signal has to replicate the original one and obviously be able to drive the new motor. I have access to the external 12V, 50A power supply.

So far I came up with three possible options.

Option 1

My first guess is to convert my signal to 0-5V PWM and use it as an input for  a driver chip such as BTN8982TA.

In that case my qeustion is how to convert my signal to PWM?

Option 2

Another solution that I've found is to use op-amp together with MOSET tansistor. I took the circuit design from this question

Does it make sense to use the amplifier here?
Won't the MOSFET overheat?

Which of the proposed solutions would be more sutiable for my task?


texts: Why are Arduino peripherals called shields?

texts:
When looking up electronics shields the only useful information I could find pertained to Electromagnetic shielding. But when inspecting Arduino shield schematics most offer no protection to the Arduino.

So it begs the question, why are Arduino peripherals called shields?

https://en.m.wikipedia.org/wiki/Electromagnetic_shielding

http://m.instructables.com/id/ATtiny-Programming-Shield-for-Arduino-1/


texts:
I found this circuit for a relay driver.  It is similar to others I have seen, though it appears to have two extra parts that others do not have.

I mostly understand how it works, but I would like to understand it thoroughly, so I have some questions in my attempt to analyze it.  This is not homework for a class.  Rather, I am attempting to educate myself.  My questions come after studying tutorials online, but I still have questions.

I usually see an input-base resistor around 4K7.  I think it determines the current flowing from base to emitter when an input is applied.  I think it needs to be high enough for the transistor to saturate, and no more than the maximum CMOS load, which I think is 20mA.

I want to understand why the resistor  is 4K7.  My analysis: The Vbe(sat) for the 2N3904 is about 0.7v.  If the input voltage is 12v, the load on the input voltage is (12 - 0.7) / 4700, or about 2.3mA, ok for CMOS.  I have a 12v relay that has a DC coil resistance measuring 392R, so at (12 - 0.7)v, that means about 29mA to actuate it (too much for a CMOS load without a driver).  The 2N3904 has a beta / hFE of 300 (max), so the minimum Ib I need for saturation is 29mA / 300, or  96uA, though it should be higher to be reliable.  I think the input base resistor could be as high as (12 - 0.7)v / 150uA, or about 75K, but a lower value would be more reliable for a wider range of loads.

With the 4K7 resistor, 2.3mA is the load at 12v input, so a load of (300 * 2.3mA) or 67mA is possible.  The 2N3904 can dissipate 200mADC, but for a load that high, the 4K7 resistor would be more like 1K5.

Is my analysis correct?

This circuit adds a 2K2 resistor from base to emitter (ground), something I do not usually see in other circuits. I think this may change the bias voltage for the transistor, but I don't know why you would do that here.  What is the purpose of this resistor, i.e. what problem does it solve?
For relay control, I always see a  "flywheel diode" across the relay, with anode at transistor collector and cathode at Vcc, as shown in this diagram.  I understand that the inductive effect of the relay coil causes a backward voltage spike to occur as the magnetic field collapses, and the diode protects the transistor from too large a reverse spike.

I think if I connect a diode across a power supply with anode at Vcc and no current limiting resistor, it will burn out.  The backward spike would seem to do the same.  Can you explain why it does not?  Is it because the spike is too brief to burn out the diode?

Most circuits have only the one diode across the relay, but some also have one from the emitter to the collector.  This circuit has one (it is not certain that it is actually connected to the collector, as there is no junction dot in the diagram there).  I have a feeling there is another spike, perhaps on power on, but I don't know why that would happen, and I would like to understand.  What problem does this second diode solve?
I have a new oscilloscope, but I don't know how to apply it to this circuit.  In particular, if there is a transient across the relay when it turns off, do I simply connect the scope across the relay to see it?  If the answer to #4 is "another spike," where do I connect the scope to see it, across C and E?  Do I have to remove the second diode to see it?
Do you think that this is a suitable circuit using best practices?  If not, please critique.


texts: Is there a difference between the blocking voltage and the.breakdown.voltage in mosfet transistor ? Or the two are the same?


texts: Why do fiber-optic interfaces have much higher bandwidth than optocouplers?

texts: I've noticed that optocouplers typically have a bandwidth in the kHz range (i.e 200 kHz). Fiber-optic interfaces can reach speeds of 100 gigabits / sec. What's so different about these two technologies that gives fiber-optics such a high bandwidth?


texts: What is the definition of interference vs. noise in radio communication?

texts:
Is it defined by the source or by the nature of the waves?

Can one with some instrument make a reading like "In this room we have this level of interference and this level of noise"?


texts:
I'm starting my first scratch design FM receiver. I pulled the S parameters from an RF amplifier datasheet and designed an input matching circuit. A new question popped up when I looked at the spice outputs:

The matching circuit is showing that the signal is maxed out around -11.6 dB. The amplifier has a gain of 26 dB. Does this mean that the effective gain will only be 14.4 dB? I know this is probably a very basic question but I can't seem to find any explanations that show gain of each stage including matching losses. Obviously a 12 dB lower output than expected is a pretty big difference. I don't want to over amplify and blow out the next component in the chain.


texts:
I have an application which uses a PCB to control a big AC fan (approx 1300VA) and a cartridge heating element. Since the application will be operated on regular mains, there needs to be some form of Line filtering, considering the motor is a big inductive load. Note that it is designed for 230v 50Hz european mains.

Searching the internet i found a few methods of filtering:

A common mode choke filter
A balanced LC filter

The common mode choke: Farnell To be used directly at the mains. And possibly a smaller one only before the control PCB to prevent the motor from releasing its voltage spikes in the control circuit. Though what worries me is that the Farnell page only lists DC current and not AC.

The balanced LC filter, to be used in the same locations, for the same reasons.

As for specifications: it doesn't need to be perfect, it should just prevent the device from misbehaving and from terrorizing other devices in the vicinity

The question is: will these work/ which one is better?

EDIT: i should have mentions that the motor is being switched by a TRIAC + RC snubber circuit. The heating element is switched using a relay.


texts: Best/cheapest way to cheaply get a 5-bit DAC: R-2R, or R = 2^N

texts:
I can either use an R-2R divider or a R = 2^N divider to get a 5-bit DAC.

Which will be more accurate? R = 2^N I suspect, but;
Which will be cheaper? I think R-2R because it can use standard values, but...
I've heard R-2R have issues with monotonicity, when the output doesn't change for the same amount with each count. Would this be an isuse with 5-bit DAC - would any such monotonicity simply be overwhelmed by divider error?
There's also the trade off of size, R = 2^N will be larger.
Also there's the possibility of using an IC to do this. I'd be open to doing this as well, if it wasn't very big and could be interfaced over I2C.

The DAC is going to be used to feed a comparator. The comparator will use this reference to compare against an incoming video signal.


texts: Inverter ICs for (5v DC -> 5v AC) and (9v DC -> 9v AC)

texts:
What are some ICs that can turn 5v DC into 5v AC? How about 9v DC into 9v AC?

I'm wiring up the liquid-crystal lenses from active shutter 3D glasses to be electric-powered sunglasses. Depending on the lens model, they need either 5v or 9v to go fully dark.

They can work when powered by DC (which is what I'm currently doing), but this biases the crystal and dramatically lowers its lifespan. Instead, they should be driven by AC with a frequency between 30 Hz - 100 Hz (see: http://www.pacificdisplay.com/lcd_static_drive.htm).


texts: Can somone please put into layman's terms how a TF affects a Bode diagram?

texts:
I'm given the TF of a system, and I can figure out the magnitude for the Bode plot (just switch to jw and grind out for the requested w), but I don't understand in layman's terms how a transfer function affects the phase.
Not an electrical person (mechanical engineer major), but hoping someone can put this stuff into something I can understand.

Can you explain this, or link something? I'm really just trying to understand how to plot out a phase diagram based solely on a TF, which before I was always given copious amounts of data, but none of my 2 semester notes mention how to deal with not being given that copious amount.

(Please feel free to roast me, but this is the TF: \$\frac{.1(s+1)}{(s+10)(s+1000)}\$. I have Matlab and can see the results, so I'm not asking for the answer. I'm asking for why it's the answer.)


texts: How to draw a gate diagram for F = w'x'y' + w'yz + wxz' + y'z' + wy' using only NOR gates, and w', x', y', z' inputs are not possible?

texts: I optimized F(w,x,y,z) =  M(2,5,6,10,11,15) this and got F = w'x'y' + w'yz + wxz' + y'z' + wy'. I was asked to build the gate diagram of the equation using only NOR gates, and w', x', y', z' inputs are not possible. I have tried, but ended up using NOT gate several times.


texts: Why is kerosene stopping my red LEDs from illuminating?

texts:
I initially posted this on chemistry.stackexchange but didn't get any answers, so I'm reposting it here.

Long story short - we have an electronic product that is submerged in fuels (kerosene being one of them) and uses an RGB LED (click here for datasheet). Due to a sealing problem in the enclosure, kerosene has managed to get in and cover the PCBs. What's interesting is the effect that has had on the PCB. The PCB's functionality has been completely unaffected, apart from the fact that the red LED in the RGB LED module has completely stopped illuminating. We've replicated this ourselves manually by submerging 2 new PCBs in kerosene for a day and then taking them out and powering them up and seeing that the red LED stops illuminating entirely. The green and blue LEDs continue to illuminate just fine.

Examination of the failed boards shows that there are no other electrical faults. It is just the red LED that completely stops illuminating. We measured the forward voltage across each of the LEDs in the failure condition, but didn't notice any significant difference that would explain the fault.

After leaving the PCBs to dry, the red LED starts working again. So the problem is not permanent.

Looking at the last page on the datasheet, the LED material is listed as AlGaInP / GaAs. Is there any obvious reaction between kerosene and these materials that would explain why just the red LED stops working?

Update 1: I've carried out the following experiments:

Dripping kerosene on to the LED.
Submerging the PCB+LED in kerosene while running.

(Videos to follow up later on today, hopefully)

In both cases, there was no perceived effect on the LED - it continued to operate just fine. This would seem to indicate that the problem is not purely an optical problem between the kerosene and the LED. So far, the problem has only occurred after soaking the LED in kerosene for some time.

Update 2: I've taken a fresh PCB with LED on it (haven't done any tests yet with just the LED) and soaked it in kerosene. I've taken some close up photographs of the LED before soaking, after soaking while it's not working and after it resumes working after it's been left to dry.

What the photos show is that there is a very obvious bulge in the LED lens during the period when it's not working. Once the bulge recedes, the LED illuminates again.

Unfortunately, I don't have a camera set up on the PCB to see the exact moment that it stops working. I'd let it soak for about an hour before it stopped working. I checked on the LED every now and then and noticed no change in the LED brightness. I came to check it once and it was just off. My suspicion is that the change is sudden.

Judging by the swelling, I'm going to guess that there is some mechanical damage internally that's moving something and once the swelling recedes it springs back to position.

Left: Kerosene-soaked LED; Right: Normal LED

LED in failed state after soaking

Normal LED

Left: Kerosene-soaked LED after being left to dry and in the working condition; Right: Normal LED

Kerosene-soaked LED after being left to dry and in the working condition


texts: Bulk capacitors/charge reservoir for large pulse current/current exceeding supply?

texts:
Say I have a battery that can provide 150-200mA of current continuously, but I have a module which is active periodically, and requires a large pulse current as well as a continuous current that exceeds what the battery provides.

For argument's sake lets say the module is a GSM modem, with a pulse of 2A for 200us, and continuous current of 300mA for 5s.

What is the best way to utilise some sort of bulk capacitor or charge reservoir to power the module?
How might I do this without exceeding the battery's max output current to provide the charge?

Here's an example of a battery that illustrates the supply: http://www.farnell.com/datasheets/1445889.pdf


texts: Intel 8259A: mysterious T bit doesn't fit the pattern

texts:
I'm implementing a driver for the Intel 8259A PIC for x86. To do this properly, I am reading the Intel 8259A PIC Datasheet. It is halfway comprehensible even for someone who approaches controller chips exclusively from the software perspective like me but there is this diagram I don't get:

It is the 8-bit pointer sent from the controller to the CPU in response to the second #INTA (interrupt acknowledgement) raise.
IR is an abbreviation for "interrupt request," the D bits denote the data lines of the 8-bit data buffer of the controller.

What are these T3, T4, ..., T7? The datasheet does not mention them ever again, they are just there. I already wrote a driver for the Intel 8042 (guided by the IBM 5170 (PC AT) Technical Reference) and the T0 and T1 bits were called "test inputs" there (p. 1-44).

Is that related to the T bits from the description of the Intel 8042 controller? What other meaning could these names have?


texts:
I'm trying to get a grip on this circuit, I'd like to clip a signal with this circuit. I want it to clip anything above 5v. Taking into account 0.7v voltage drop of the diode, than Vbias would be 4.3v right? But how do I (without a battery..) get this 4.3 volts. I tried a voltage divider at the cathode of the diode, no good results.

My question is probably an easy one; how does one replace Vbias with REAL components? Iow: how can I build this circuit on my breadboard? (in this drawing it's drawn as a battery but I'm not using batteries in my circuit....not even considering..) (i'm guessing it's reaaaaaal simple, but I do not seem to get it...)

Please help understand this puzzle...


texts:
I am using 3 of these Mighty Max 12V 12Ah batteries on my Razor MX650 electric bike and they are connected with 12 gauge wire. I would like to tap into the power on one of the batteries with a 20 gauge wire. Is it ok for me to tap into the 12 gauge wire with a 20 gauge wire to pull power? I am actually just going to use it to power a voltmeter on the bike.
UPDATE:
@Cubic273.15
Here is an actual diagram of the wiring for the bike, I added what I am trying to do with the voltmeter. I just want to make sure you are saying it's ok to tap into the 12ga wire with the 20ga wire.


texts:
Input and output Structures
A logic family should provide features for effective interfacing both at the input and output. Interfacing at the input requires facility to accept different voltage levels for the two logic states, and to accept signals with rise and fall times very different from those of the signals associated with that logic family. At the output we require larger current driving capability, facility to increase the voltages associated with the two logic levels, and the ability to tie the outputs of gates to have wired logic operations.

here what is the meaning of large current driving capability?


texts: What kind of options are there for very high bandwidth long distance data links?

texts: I'm considering a future product. A high definition (720p) video transmitter. Ideally a compressed MPEG link would be used but this would still require at least 80 Mbit/s. I'm not looking at a simple solution, and I don't even think it's possible without high cost and big transmitting gear, but what is everyone's opinions? What about sending component video over long distances? I'm talking about 10km or so and the link must be wireless. The nodes may move, one would likely be an RC plane.


texts: Transient analysis with differential equation

texts:
Anyone may help with the differential equation for vC?

I write the Nodal analysis equations and find equation for vC but roots of characteristic equation is incorrect! v1 – the node where current source enters the top of schema


texts: What part do I need to increase current output

texts:
I am working on a mobile robotics personal project with a Raspberry Pi 3 Model B. The 4.5 VDC motor controllers on the rover has a no load current of 190 mA and a max load current of 250 mA. (I am using this rover here https://www.amazon.com/gp/product/B00UAXEHCO/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1).
The voltage output of a gpio pin on the raspberry pi is 3.3 V, which with my power supply is enough to get the motors running (not at full speed of course), but the current output of the gpio pin isn't nearly enough to get the motors on the rover to run. Would I need some sort of boost voltage regulator?


texts: Why connectors become smaller as frequency increases

texts: Why connectors size get smaller as frequency increases? For ex: 1.85mm connector is smaller compared to 2.4mm and 2.4mm is smaller compared to 3.5 mm. I think skin effect maybe one reason but I believe there are other reasons.. can somebody advice..


texts:
I'm just trying to understand the communication protocol with the HV5623. Here is the Function table:

I want to be able to hold the HV output while I shift in the new states into the shift register, then enable the HV output then rinse and repeat. My understanding is that I should send the data with LE Low, BL high, and POL high and then pulse LE in order to set the shift register values to the HV output.
For sending data am I able to use I2C where Data->SDA and CLK->SCL? Does I2C continuously pulse the clock or does it only pulse the clock when there is a bit to send? My understanding is that if the clock only pulses when data is being sent then after the data is shifted in, then this set up will work, but if the clock is always running, then the LE pulled high will have to be timed fairly precisely.
Any confirmation (or explanation of why I'm wrong) that using I2C with a switching LE and BL/POL held high would be appreciated


texts: RF output matching using baluns: LTC6946

texts:
The datasheet that I refer to below can be found here:
https://www.analog.com/media/en/technical-documentation/data-sheets/6946fb.pdf
I have a question about baluns. In the datasheet for LTC6946 integer-N synthesizer, the manufacturer recommends that the RF+/RF- output port be driven differentially. However, they also include the option to drive it single ended. They then include a table (on page 26) titled "single-ended RF output impedance." Why do they specifically say single-ended? If I wanted to transform the RF+/RF- differential ports to single ended using a balun, would I still need to do the impedance matching? If so, how would I do  that?
As a side note, I would like to get RF frequencies of approx 400 MHz and 900 MHz out of the device, but it only mentions output impedance for 500 and 1000 ohms. If I was to design a matching circuit, would I just use the matching for 500 and 1000 and say "close enough, good enough"?
Thanks for any help in advance.


texts: What are some "professional" arduino alternatives?

texts: I've been working with arduinos for quite some time now and finished some cool projects. The problem I have with arduino boards is that programming them is extremely simple and I have virtually no idea what is happening on the inside (you don't learn much about microelectronics while using them). I am pretty fluent in C and C++, however the arduino's version of these languages is very basic. I was wondering what microcontrollers/microprocessors are being used in the industry and how to implement them in my projects? I've heard about AVR, ARM, ATMEGA (on it's own), etc. Are those the ones that are being integrated in professional (commercial) projects? I've seen the MIT's video about autonomous robotic plane - https://www.youtube.com/watch?v=kYs215TgI7c, where they have used an "Intel Atom Processor". How can you use an Intel Processor to control electronics? Obviously an Intel processor is overkill for my electronics projects, however I am still curious how it can be used.


texts:
I have a 28c256-25 EEPROM that I have created a breadboard circuit to program. The datasheet says after the address is set and the data is put on the I/O pins, a low pulse on /WE while /OE and /CE are tied high should write that data into the provided address.
I have tried (using an RC circuit) giving a 33 nanosecond, 100 nanosecond, and 500 nanosecond negative pulse on /WE, but I could not get the data on the I/O pins to get written into memory. Here is the datasheet: https://www.jameco.com/Jameco/Products/ProdDS/74878XICOR.pdf
There is a short description of the Write cycle on page 4 and a timing diagram on page 14.Am I supposed to send the data on the I/O pins during or after the /WE pulse or something? What am I doing wrong?


texts: ESP32S: More than two SPI channels possible?

texts:
In a test with an ESP32-CAM, I was successfully able to use SPI with pins 2, 12, 14, and 15:

#define GPIO_MOSI 2
#define GPIO_MISO 12
#define GPIO_SCLK 14
#define GPIO_CS 15

However, I cannot run the camera in parallel with my additional SPI communication. The problem are not the pins. Pins 2, 12, 14, and 15 are not used by the camera. The problem is the following line in my code:

spi_slave_initialize(HSPI_HOST, &buscfg, &slvcfg, 1);

If I switch to HSPI_HOST, then again the camera won't start. The camera on the ESP32-CAM uses both SPI channels, HSPI and VSPI. The module is built around an ESP32S.

On the ESP32S, is there a third channel that I can use?

Notes:

The ESP-EYE, another ESP32 based board with a camera, can do SPI communication while the camera is running. This I have tested. The ESP-EYE is more expensive, though, and it is hard to connect to a board. I will need a few dozen ESP32 based camera modules.
Communication speed can be low, 1200 baud would be more than enough.


texts:
I am overwhelmed with the variety of switching devices. MOSFETS/BJTS Relays(mechanical/solidstate),optoisolated solutions, etc..

I need to support 15V, 60A bursts, should be high efficiency, and switching time is not important since it wont be changing very often.  Noise is also not a large issue.
This will serve the function of a battery cut off in a circuit.

Based on these requirements, what would you guys recommend?


texts: Feedback requested for my circuit (automated brewery)

texts:
I am building an automated fermentation controller for a brewery which integrates 110V and runs an Arduino with respective sensors and other valves.
Can you offer any feedback on my overall schematic below? New to working with high voltage (left side)


texts: Is it possible to use the HX711 as an amplifier without using its ADC capabilities?

texts:
For my embedded systems project, I decided that I wanted to create a weight scale. Naturally, I found the HX711 amplifier that would be perfect for this application. My question is, is it possible to use the HX711 as an instrumentation amplifier without using its built in ADC? The specifications of my project make it so that it's highly preferred if I could use the ADC built into the micro-controller that I'm using (KL43Z).

Thanks for any responses.


texts: Measure current through H-bridge using shunt

texts:
I am trying to measure the current through the H-bridge and brushed DC motor and shut it off if it exceeds a pre-set limit. This is how I have it currently set up:

simulate this circuit – Schematic created using CircuitLab

OA1 acts as a non-inverting amplifier to amplify the signal that can then be compared by OA2 to a pre-set limit. And if it equals or bigger it outputs 5V signal to microconctroller, which then disables the H-bridge.

The problem is that the output from OA1 saturates at 5V. Which according to my calculations shouldn't be. If I disconnect the wire from OA1 and connects it to oscilloscope I can see a thick sine-like wave from -50mV to +200mV on the shunt resistor. Which is rather weird... The measured current only through the motor with no load is around 2A. So \$U=R\times I=0.01\times 2=20mV\$.

Whats going on?


texts: How can I design a high speed RF peak detector?

texts: The diode-capacitor solution would not work in my application because the operating frequency of my circuit is about 1.4GHz. So what is an alternative solution that would work in such high frequencies?


texts: Reverse Engineering a Tamura Inverter Board

texts:
This is about the pin-out of 9-pin connector 1 of inverter board
Tamura HBL-0291, part of a Toshiba Tecra M2 laptop from the early
2000s (see images).  The controller chip on the inverter board is
labeled TH12A 4625.

Here is what I have done already:

Googled for specs, to no avail.
Contacted Tamura for specs, to no avail.
Identified pins 1-3 (5V0), 4-6 (GND), 7 (ADJ: voltage-based,
max. brightness at 1V).
Operated the inverter board and backlight connected to the laptop
mainboard:

Measured the voltage at pins 8 and 9 on the main board connector
when the backlight/display is on (4.6V) and when it is off (0V).

But this does not mean that pins 8 or 9 are some kind of ENA pins:
To switch off the backlight, the laptop completely switches off the
voltage on pins 1-3 using a high-side MOS-FET.

When changing brightness on the laptop, only the voltage on ADJ
changes, nothing changes on pins 8 or 9.

Checked pins 8 and 9 with a scope as well, nothing interesting going
on, all DC.  No equipment available to check what exactly happens on
these pins and in what order when the laptop switches on or off the
backlight.
Operated the inverter board and backlight stand-alone on a
breadboard:

The backlight operates fine both with 0V and 5V on pins 8 and 9.
There is a small increase of backlight brightness when switching
pins 8 and 9 from 0V to 5V.
Traced the circuitry as far as possible of pins 8 and 9, both on the
main board and on the inverter board (see sketch).  Q5 and Q6 are
labelled G25, but I have not found any specs matching these clearly
transistor-ish parts: With voltage of about 2V applied across 1-2
the connection 3-2 drops resistance.

I would like to understand what these mysterious pins 8 and 9 are good
for to operate the backlight and inverter board as "originally as
possible" from a microcontroller.  (Using another inverter board is
not an option due to size restrictions.)

The best conclusion I could come to as a beginner is that these are
for "soft-startup" or "soft-shutdown" of the CCFL.  So to switch on
the backlight I would:

Apply 5V to pins 1-3 also using some high-side MOS-FET.
Wait for 5ms
Apply 3.3V to pin 9 using a GPIO pin
Wait for 5ms
Apply 3.3V to pin 8 using a GPIO pin

and to switch it off I would process above sequence in opposite order.

What do you think?


texts:
I am designing a guitar pedal using OpAmps, and i need to feed them with +6V and -6V (beucase the musical signal is senoidal centered in 0V). I need to use a 12V DC PSU for the pedal, and i need to convert to positive and negative voltage. If possible it would be better if it was +12V and -12V but if its not possible i can work with +-6V. I also need this to be reasonably simple and cheap.
Thanks!


texts: I've ordered fabrication and assembly of small PCB batches (~100) a couple of times already. Each time, the assembly factory asked me if I wanted to do testing on the boards. Since I'm not a professional, I didn't know what to do about it, so I tested the boards myself when I got them back... finding unacceptable percentages (>10~20%) of soldering problems. Although my boards were fairy complex (+100 components), I hadn't designed any testing procedures on them or even know how to do it. So I'm wondering, what are the usual test capabilities for a low volume production like this, and what kinds of test can be asked to the factory without going overboard? Is that usually costly? I'm talking about testing the assembled board, not the bare PCB. Thanks in advance.


texts:
I never had to deal with sound and I am pretty sure some of you guys have some experience in that kind of application.

My question is more about getting some tips on the different ways to implement an embedded system based on an AVR that plays sounds. More precisely:

What library should I use?
Which sound format should I choose? Do I necessarily need a dedicated memory chip aside the MCU? If yes, which one would you recommend?
Do you have some code sample to share?

As always, I know that everything depends on the target application. Here are a few precisions:

I want to make a toy for the kids of a friend of mine, the idea is to have a short sound lasting no more than 30[s]
I am not interested in high fidelity sound
Power consumption matters


texts: Help Trobleshooting my first solderless circuit on a breadboard

texts:
I'm working on my first project from the book "Electronics All in One for dummies", chapter 6, book 1. I work through all the instruction but I cannot make the LED blinks. The circuit diagram is:

Here is an image of my breadboard circuit:

I have no clue on how to start troubleshooting it. What steps should I take to start troubleshooting a problem like this?

Appreciate all the help you can lend me. Thanks


texts: Modeling MOSFET Pole and Transconductance for use in Larger Overall Control System

texts:
Recently I began a project involving some active current limiting using a MOSFET and an Op Amp. It is part of a larger overall circuit involving other Amplifiers.
I would like to perform a block-diagram-style analysis on my circuit in order to investigate loop gain and stability. However, I was stuck when it came time for me to analyze the MOSFET's transconductance behavior. The simplified example below illustrates my problem:

The circled block in the above diagram is what I'm trying to unpack. As stated in the diagram, since this is part of a stability analysis, I really only need the RC pole location and the transconductance.
Is there a way to model any MOSFET Trans conductance amplifier as a single-pole Transfer Function?
Furthermore:
How would I go about extracting the necessary parameters from I-V curves within the MOSFET datasheet?
EDIT:
More details on what I'm looking for:
I understand my dummy example has stability concerns due to the OA's dominant pole and the additional pole from the series R and the MOSFET's Ciss. Of course this leads to instability in some scenarios.
I want to know how to pull out the MOSFET's behavior into its own "block" as seen in the block diagram in my post. I assume its "block" looks something like gm*{Something}/(1+s{Some_Tau}). I'm wondering how to extract the "something" and "some_tau" from datasheets within some reasonable tolerance. I know Ciss varies somewhat, but I'm fine with some reasonable accuracy.


texts: DC Op-Amp Output at an unexpected voltage?

texts:
For some reason Op-Amps are impossible for me. I'm experimenting with them a little bit. I have the following circuit...

simulate this circuit – Schematic created using CircuitLab

This is the circuit I have on my breadboard. I was just trying to see the "infinite gain" I would expect from this configuration.

The inverting input is around 4.5v, while the non-inverting input is at ground. I should be achieving my maximum potential (Limited by the power rail.) I.E. around 9V at the output, but I'm recieving .6v?


texts: breakpoints in baremetal code for arm stm32

texts:
I am writing a simple baremetal code for STM32. I wrote the linker and the startup code similar to this . My understanding is that the .text section will be placed in the flash memory of the controller.
Question:
In such a case, it is not possible to use software breakpoints right? From what I've read sw bp replace in memory the optocode with the break optcode (and keep the real optocode in some table, etc. ) in order to halt the processor. This cannot be done on non-writable memories like flash, where my code is, and hence where the program counter points to.


texts: Circuit to protect against undervoltage?

texts:
What is the simplest way to regulate the min DC voltage in a circuit?
Is it possible to do with zener diodes?

Desired performance:

Input > 3.3 VDC     Output = Input
Input = 3.3 VDC     Output = Input
Input < 3.3 VDC     Output = 0.


texts: Op-Amp Datasheet: Open Loop Gain vs Phase

texts:
I am attempting to decipher the datasheet for TI's LM6171 op-amp.

Here is the open loop frequency response from the datasheet:

How can I tell which curve is the gain and which curve is the phase? They're not labeled. I would guess that the top curve at 10 kHz is the gain and the bottom is the phase, but I don't know how to confirm this.


texts:
I have been made my first digital clock circuit, but it still not working. After I test many ways, I find the problem on the crystal.

The waveform graph of XTAL from my pcb

And this is the correct waveform.

This is my designed circuit

This is my pcb layout

I use Kicadv4.07 IDE to develop my project.
Can anybody can solve this?
I will appreciate your kindness.


texts:
Specifically, using the GPIO pins of a Raspberry Pi, which PICPgm does explicitly support, but I think that's irrelevant unless it's an XY problem.
PICPgm's home page lists a bunch of devices that it's explicitly compatible with, but my relatively new one isn't in that list.  There's a way to add a new programmer by editing a config file, but adding a new device is glaringly absent from any documentation that I can find.  PICPgm's forum is 404, and Microchip's forum isn't very helpful either.
Microchip's Programming Specification for my device suggests that the hardware is okay, in that the Pi's GPIO pins are capable of providing and accepting the right signals for Low-Voltage-Programming (LVP).  So before I dive into this ratsnest of hardware again and bury another new module into it, how can I be sure that I won't have to dig it back out again just to put my PICkit on it?
(I'll just leave the programming interface permanently connected to the GPIO's, which are normally configured to let the chip run.)


texts:
I have read that for transformers operating at low frequencies, a larger core is needed.
I am trying to calculate the core size for a single phase transformer operating at 2Hz.

I do not have a physical example of a transformer, but I have done a simulation of a transformer using Femm that gives me a value for the flux in Telsa.

I would appreciate it if anyone could comment on, or correct my method for finding the ideal core size of the transformer.
I thought this formula for finding the induced voltage in the secondary coil would apply:

induced voltage = 4.44fNAB

Where

f= frequency in Hz
N= number of turns in the secondary coil
A= cross section of the core area in Meters
B= flux in the core in Tesla

My primary coil is 0.5mm diameter wire with 400 turns

P coil resistance: 5.3695271 Ohms
P coil current: 1.5 Amps
P coil voltage: 8.05429 Volts
P coil power: 12.08144 Watts

I would like to assume for the moment that the transformer is a “perfect” transformer with no core losses, just make my understanding easier for the time being.
My questions -

Is this the correct formula to use?

and

If the above formula gives me a value for the induced voltage in the secondary coil that equals a lower Watts value in the secondary coil than in the primary coil, does this mean that the transformer core is too small for the frequency?


texts: Inverter output frequency is 46 Hz but it should be 50 Hz, will it cause any problem?

texts:
I bought a car inverter (150W.) The inverter output should be 220V 50Hz (in Turkey) but the output is 227V  46Hz.  I think the voltage is at a reasonable value but is the frequency OK?
I measured the values with the power meter. When I measured the normal home socket with the same power meter, I saw 222.5V 50Hz.


texts: Can LM339 comparator inputs go way above Vcc?

texts:
The datasheet for the LM339 quad open-drain comparator shows the absolute max values:

\$V_{cc} \le 36V\$ (Supply voltage)
\$V_{I} \le 36V\$ (Input voltage range (either input))

I want to compare a (fairly weak, 100k impedance) \$0V\$ to \$+15V\$ input signal against a \$+3V\$ reference, while powering the device from a \$+5V\$ supply. According to the spec, that should be fine.

However, I'm surprised and wary, because it's common that device inputs can't go much above the supply rail. Then again, I can imagine comparators being unusual in this respect, and if that were the case here, I'd expect to see the input defined as \$V_{I} \le V_{cc}+0.6V\$, or similar.

Have you used an LM339 like this, and was it fine? I've been looking for a circuit diagram of the internals of the device, but I'm struggling to find anything that makes it crystal clear. I don't want to find out in a year's time that we're gently destroying them!


texts: I'm developing a current source based on NPN Wilson modified current mirror. There's a restriction that cannot be used opamps, so i'm using only transistors. However, it's fundamental that doesn't appear voltage at the output if there is no load connected, so this is my question: how can I develop an output stage which doesn't produces voltage without load? Sorry for my bad english.


texts: Differential to single ended digital signal

texts: i have a 8GHz differential clock to convert to single ended. Is taking one end of the clock enough? what are the risks of doing so?


texts: Ceramic Capacitor 10uF NP0 Cold Temperatures

texts:
For my pcb which will be used at very low temperatures, say 50 K, I am searching appropriate Bypass Caps. Many papers stated that NP0(C0G) Caps are especially good because of their constant temperature behaviour.
But now the problem is that I need a 10 uF Bypass, which does not exist with NP0 dielectricum.. What alternatives do I have?

Till now I have a 1 nF (size 0603), 10 nF (0603), 100 nF (1203) all NP0 Ceramics.

Appreciate any help

Many thanks


texts: Will this motor controller take more motors?

texts:
If I was to connect two motors in parallel instead of just the one motor it currently has on each H-Bridge,, would the transistors on the motor controller blow?

I have this motor controller - here is a schematic & table as well:

The lowest pin on the connector is pin 7  --------  The lowest on this connector is pin 1

I am controlling this using my Raspberry Pi, connected to the first 4 pins and last pin of the 7 pin socket - this is not relevant as such, but this outputs 3V3, and controls the H-Bridge.

An individual motor draws less than 0.1A at 6VDC, but on startup and stop can draw up 0.48A These measurements are from a multimeter, which will only take an average anyway.

Each motor has one of these already attached as well:

Here are the transistors:

Q7 - Q10 are 2SC3279 - NPN, can take 2Amps DC, 5Amps 1/100th  of a second

Q11 - Q14 are 2SA1300 - PNP, can -2A DC, -5A also for 1/100th  of a second

For more info on the controller see here

Here are some data sheets of the relevant transistors:
2SC3270
2SA1300


texts:
People often talk about noise in circuits. Cheap op-amps are noisy, running a motor can create noise on the supply, and a lot of analog circuits deal with the signal-to-noise ratio (ie: trying to keep the noise floor low).

My intuition is that noise is the presence of signals at frequencies we're not interested in. (This may or may not be right.) However, I don't know where this noise comes from.

How does electrical noise appear? What generates it? How do I get rid of it?


texts:
I am coding a display control for the Spartan 3E. It has 8 LEDs. When the ALU's state signal (from other block) is "00" the MSBs and LSBs are time-multiplexed for one second each byte. When state is not "00" then a LED is rotated to right every 125 ms. The FPGA clock is 100 MHz. I have the following code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity display_control is

  port (
    clk        : in  std_logic;
    rst        : in  std_logic;
    state      : in  std_logic_vector(1 downto 0);
    MSB_result : in  std_logic_vector(7 downto 0);
    LSB_result : in  std_logic_vector(7 downto 0);
    leds       : out std_logic_vector(7 downto 0));

end display_control;

architecture rtl of display_control is
  signal en_1Hz                    : std_logic;
  signal en_8Hz                    : std_logic;
  signal cnt0_next, cnt0_reg       : integer;
  signal cnt1_next, cnt1_reg       : integer;
  signal ror_next, ror_reg, x      : std_logic_vector(7 downto 0);
  signal muxctrl_reg, muxctrl_next : std_logic;

  constant PRESCALER0_DIV_FACTOR : integer := 100;  --000000;  -- 100M = (100MHz/0.5MHz)
  constant PRESCALER1_DIV_FACTOR : integer := 12;  --500000;  -- 12.5M = (100MHz/8MHz)

begin

  -- registers
  process (clk, rst, en_8Hz, en_1Hz)
  begin
    if rst = '1' then
      cnt0_reg    <= 0;
      cnt1_reg    <= 0;
      muxctrl_reg <= '0';
      ror_reg     <= (others => '0');
    elsif clk'event and clk = '1' then
      cnt0_reg <= cnt0_next;
      cnt1_reg <= cnt1_next;
      if en_1Hz = '1' then
        muxctrl_reg <= muxctrl_next;
      end if;
      if en_8Hz = '1' then
        ror_reg <= ror_next;
      end if;
    end if;
  end process;

  -- register's next state
  cnt0_next    <= cnt0_reg +1 when cnt0_reg /= PRESCALER0_DIV_FACTOR -1 else 0;
  cnt1_next    <= cnt1_reg +1 when cnt1_reg /= PRESCALER1_DIV_FACTOR -1 else 0;
  muxctrl_next <= not muxctrl_reg;
  ror_next     <= ror_reg(0) & ror_reg(6 downto 0);
  -- prescalers output
  en_1Hz       <= '1'         when cnt0_reg = PRESCALER0_DIV_FACTOR -1  else '0';
  en_8Hz       <= '1'         when cnt1_reg = PRESCALER1_DIV_FACTOR -1  else '0';

  -- output logic
  x <= LSB_result when  muxctrl_reg = '0' else MSB_result;
  leds <= x when state = "00" else ror_reg;

end rtl;

But when I synthesize the code I obtain the following warnings:

WARNING:Xst:3002 - This design contains one or more registers/latches that are directly
   incompatible with the Spartan6 architecture. The two primary causes of this is
   either a register or latch described with both an asynchronous set and
   asynchronous reset, or a register or latch described with an asynchronous
   set or reset which however has an initialization value of the opposite
   polarity (i.e. asynchronous reset with an initialization value of 1).

and

WARNING:Xst:1426 - The value init of the FF/Latch cnt0_reg_31_LD hinder the constant cleaning in the block display_control.
   You should achieve better results by setting this init to 0.

How can I fix it?


texts: Precise sampling rate for data acquisition with Arduino and Python

texts:
I built a simple data logger with Arduino and Python (Accelerometer --SPI--> ESP32 --USBSerial--> RPi). I used the timer interrupt to control the output data rate, which is set to 300Hz. But I noticed that the sampling rate is not stable. I let the sensor sit still for some time. As you can see in the graph below, it has some sample rate drift, probably caused by the change in clock frequency of ESP32.

Now comes the question: How can I achieve an accurate sample rate without using expensive DAQ equipment and possibly also reduce random jitter? It would also be good to know what is the technically correct way to do it.

Maybe if I increase the data rate to 3.2Khz (as recommended by the sensor manufacturer) and down-sample it in a more controlled environment on the PC in Python? But for Raspberry it will probably be a rather too recourse intensive task.

P.S. For a reason I am not connection the sensor directly to RPi SPI interface.

Edit: You are all right. The drift cannot be caused by an uneven data rate as it does not affect the amplitude of the signal. But it affects the measured frequency. When I perform an FFT, it shows a significantly different result than it actually is. I have adjusted the data rate with interrupt counter timer. But it is still not a proper solution and does not help with jitter.


texts:
I am using this linear regulator and the application circuit looks like this:

Is the above circuit good enough?

I have a habit of putting a series ferrite bead on the input side but after reading a couple of answers about the topic, I feel that ferrite bead is not useful for such cases.

In most of the cases, the Vin will come from a ac to DC offline switching power supply which work around 100 kHz switching frequency.

1) Does it make sense to use a series ferrite bead or an inductor at the input side?

2) Is 1 uF and 2.2 uF capacitor good enough or should I increase the values? My load will be an MCU drawing roughly 10 mA and RF module drawing 50 mA during transmits.

3) To manage my inventory well, is it acceptable if I purchase 50 V rated X5R ceramic capacitors and use the same for all voltage ranges up to 24 VDC? Is ceramic capacitors good for this purpose?


texts:
I would like to implement multiple receivers/senders with CC1101[1] from TI.
Idea is that all receivers are listening for specific commands and do their job, after that if some specific receiver reads ID inside msg, that specific one performs else all do the same.
Also request for specific listener/or few of them could be made to report back, will collision detection be done automatically?
[1] https://www.ti.com/lit/ds/symlink/cc1101.pdf?ts=1594302116526&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FCC1101
Tnx for help!


texts:
To make printf kind of debugging possible, I planned to use variable arguments to pass to the USB device as serial device.

Code to print a test string:

Debug::Print("Auto toggle 2 %d %s", 12, "!");

With implementation:

void Debug::Print(const char* format, ...)
{
    va_list args;
    va_start(args, format);
    char buffer[256];
    vsprintf(buffer, format, args);
    Debug::Print(buffer);
    va_end(args);
}

I would expect:

 Auto toggle 2 12!

However, the device does not respond. When I use the OCD, at line Debug::Print, the buffer contains:

"Auto toggle 2 134229731 !\0§ª\232KÖ-çPä(\215õ\221º=\23   ... (continued with unreadable characters)

This is probably the reason the device does not respond. However, what should I use to make the buffer be filled correctly?

I tried it as a Windows console C++ program and there I get the correct output.
Initially I used a sprintf instead of vsprintf and got also a big number (lik e134229731 above). However, I did not get the additional 'rubbish'.


texts: Strange behaviour of TP4056 when charging complete

texts: I am using a TP4056 to charge a 18650 LiIon cell as shown in the circuit below. The BAT output is connected to the 18650 cell through a BQ29700 protection IC. According to the datasheet of the TP4056, the green LED should light up when the cell is fully charged. However, what happens is that when the green LED is on, the red LED also comes on. Why could this be the case? Theoretically, there shouldn't be any interaction between the TP4056 and BQ29700 since the float voltage output of the TP4056 is 4.26V max and the overvoltage threshold of the BQ29700 is 4.275V.


texts:
I was doing an experiment for finding the radiation pattern of Pyramidal Horn Antennas at RF frequencies(as part of my course curriculum). There I came across the Friis Transmission Equation

What I don't understand here is the two terms Gt and Gr. What does these gain terms refer to? Gain is something associated with active devices like amplifiers. But how come antennas have gain? They don't have any source of energy so that they can amplify the power, they are transmitting or receiving.


texts: What soldering kit for tiny electronics?

texts:
This is a my first foray into building electronics.
I am building a project that uses chip/SMD LEDs and resistors. What type of soldering kit should I be using for those devices?


texts: Effect of decreasing input voltage of transformer on output voltage

texts:
I have designed a device which is controlled with a PIC micro controller.This micro's power is +5 volt. I have used a transformer for converting +220 volt to lower voltage +15 volt. Then a 7805 regulator generate +5 volt which is used by micro and other components. Now i want to know what happens if input voltage drop down very high. For example in bad situation maybe accidentally city voltage +220 drop down very high and goes up.
If input voltage drop down output voltage of transformer will drop down consequently and in high current +5 volt does not generate. This affect on micro and micro will be turn off.
This is very bad situation for my device. How could this be protected? is it true using transformer? Is there another solution for protecting from decreasing input voltage?


texts:
If I remove C5 I am able to use ISP. However, with C5 on board ISP programming fails... Capacitor is for button debouncing.

What is the quick workaround to have debouncing routine and use ISP? I can't change the board because it's already on PCB, just can make a patch.


texts: How can I size the components of a square wave generator in order to obtain a 7kHz frequency?

texts: I used this circuit to generate a triangle wave that comes from the - input of the square wave generator. This is part of a circuit that generates a PWM signal. I need to have a frequency of 7kHz and to size the resistors and capacitors in order to get that. Can anyone help we with a formula for the frequency for this circuit?


texts: How is the location of a finger or more detected on a capacitive touch panel?

texts: I think I understand the basics of capacitive touch screen, i.e. when one or more fingers touches the panel it creates a potential difference at that location drawing current. But how do you go about locating the position of contact? From what I have gathered, there are wires thinner than human hair that forms a grid on the panel. I was looking at the wiring grid on my keyboard recently, and considering the accuracy of the touch screen on my phone there must be thousands of these wires for both x and y. But obviously ICs only have so many input pins. So how does it work?


texts: MPU6050 data go crazy while transmitting via HC-12 radio

texts:
I'm building a project based on the raspberry pi 3 (written in NodeJS & python) which uses the following modules: a bmp180 barometer, an mpu6050 imu, a hc-12 radio, a ublox-neo7m GPS, an LCD with an i2c converter & a qmc5883l magnetometer.

I supply the rpi and LCD with 5v from a power distribution board powered from a 3-cell 12V LiPo. The LCD's i2c lines are connected to the rpi's via a dual-channel bidirectional logic level shifter. The GPS, barometer, magnetometer & mpu6050 modules are powered from the rpi's 3V and the HC-12 radio is powered from a separate power converter, which takes 5V from the power distribution board and outputs 3V (max 800mA), because the radio takes about 300mA while transmitting.

Everything works perfectly as long as the radio is not transmitting. When I start the transmission (and my project transmits continuously after first data is sent, so it sends data and in about 350ms there is an answer, which triggers next data to be sent, etc.), mpu data start to go crazy, e.g. a stable (I mean the mpu6050 imu is in the same position all the time) roll of 30 can start going to -30 or to any other values after the radio starts transmitting.
Also, after I start transmitting data, I get a message "Failed to write data register: I/O error" once per a few i2c data polls to the mpu, though the data is read anyway, but, as I already said, the values are unreliable. If I stop the transmission and restart the program (which reinitializes all the modules), everything works fine until I transmit data with the radio again.

What can be the solution to this problem? And is it possible that just the i2c communication draws too much current from the rpi, so the values go crazy, because the rpi is overloaded?

Thanks in advance


texts: Is there a name for that moving blank space on an oscilloscope?

texts: On most oscilloscopes, there is a blank space that moves along as the data is sampled. Is there a name or phrase that described what that thing is? When you put the oscilloscope on a lower time/division, you can see it moving across the screen. In case I'm unclear, here's a picture where the waveform is not completed and the scope is in the middle of capturing:


texts: Very low temperature (-25C) on ds18b20 precision

texts:
I'm busy building a multi-probe temperature sensor and log system using a couple of ds18b20 probes on a Raspberry Pi.

They will be monitoring freezer temperatures that should be between -23°C and -18°C.

I'm a little concerned about the precision of the probes though as the datasheets only give the precision between the -10°C to +85°C Range (±0.5°C).

There's an error curve on page 18 here, and another almost identical one on page 20 here. Both of them however start a 0°C and only go up.

As I'll be operating outside of this range, how/where can I find the expected accuracy?

The freezers that the probes will be monitoring are used for storing human tissue, and I'll need this before I can put forward a tender/proposal. Any Ideas?


texts: Changing the duration of a pulse in PSPICE

texts:
I am trying to simulate lightning in PSpice using an exponential voltage source (VEXP). The duration of the lightning pulse is required to be in the 110-120 microseconds range with peak voltage = 400V. The one that I am getting, however, reaches nearly 800 microseconds. I've been randomly changing parameters on the source but they don't seem to affect pulse duration. Any input from you guys would be much appreciated?
Rise time (time till peak) = 40 microseconds (measured from 0)
Decay time (50% of peak) = 120 microseconds (measured from 0)


texts: Why do square waves have this spectrum response?

texts:
Below shows my makeshift spectrum analyser, where a 2V, 66Hz square wave on the input. Why do square have have this response (where every harmonic has some amplitude attached to it)? I read somewhere vaguely they have an unlimited spectrum which causes this. The spectrum analyser is using a trapezium window for reference.

The image below is the input signal on my makeshift oscilloscope.


texts: Controlling for ambient temperature changes in a transimpedance amplifier

texts:
I'll start by saying I'm new to electronics, and have only minor working knowledge. I am designing a transimpedance amplifier to measure the opacity of a surface that is changing over time. The resulting voltage is sent into an ADC for me to record. My circuit is below:

I am seeing a lot of voltage variation due to the ambient temperature of the room (I've put a temperature sensor next to my TIA, and noted a strong correlation between a rise in temperature and a decrease in voltage). This variation is relatively large, and causes my measurements to have long cyclic behaviour (due to room heating turning on and off). FYI the ambient temperature changes by ~0.5std. Below is an example of the relationship I'm seeing (Blue is temperature, green is voltage):

(Blue is temperature, green is voltage)
My questions are:

Is the variation in output caused by

the LED warming up, causing a decrease in light output?
the feedback resistor changing due to temperature changes?
both? maybe the photodiode?

What are some possible solutions to correct for this, assuming I'll never have perfectly stable ambient temperature?

I could add a thermsistor to the diagram, and use an input on the ADC to record the variation in temperature and use software to correct the op-amp output voltage. This makes sense to me, but I've can't seem to find ppl doing this after some searching.
Measure temperature and use a calibration curve to "correct" the reading back to 20C - is this going to be robust though?
Some electronic solution? Not sure what that looks like.
A PID controller that tries to stabilize the LED output (assuming it's the LED that is causing the variation).

Thanks for any suggestions!


texts: What is this? Identifying Proximity Sensor Chip (IR)

texts:
I am in a bit of a pickle.  If anyone could help/has any ideas I will be very grateful - am aware this post is pretty long but thought if anyone was clever enough to know it would be you guys.  If anyone needs more information/has ideas then I'm also listening!  Thank you.

Have a specialist bit of kit which uses proximity sensors and would dearly like to be able to replace sensors on it with the same model.  However, I am unable to ID the chip and manufacturer of product will not help.  Therefore - does anyone know what chip this might be?  The chip senses reflectance from a person from about 1cm to closer.

Visually inspecting the chip it consists of an LED and a sensor, separated by some dividing plastic.  On the underside, it has 4 pads, with 4 microvias.

Initially it looks like the chip was mounted on a small PCB but I think this is an integral part of the chip - or at least I have been unable to separate it with hot air.  No markings anywhere other than an arrow of copper to indicate direction, on underside, as well as a slightly larger pad on the top layer of the "pcb" to again indicate LED.

On PCB layout it is measured as shown.

Pad layout on the chip is pretty similar.  I was unable to measure the microvias so haven't included dimensions.

Pin layout is (from pin1 marked on PCB layout moving clockwise):

Phototransistor/diode Anode
IR LED Anode
IR LED Cathode
Phototransistor/diode Cathode

The phototransistor/diode is operating in reverse bias.  Vcc is connected to pins 2 + 4.  Pin 3 connected via current limiting resistor (100 ohm) to digital ground.  Pin 4 is run to analog ground via 1k resistor w cap in parallel for noise reduction (standard voltage divider). It (pin 4) also runs to an ADC where measurement is taken. Vcc is approx 3.6V.

I don't have a spectrometre so am unable to confirm what wavelength of light is but I assume it's IR as it is not visible.

I have sketched the dimensions here -

I modelled it in fusion though my calipers are fairly budget so the accuracy may be slightly off(+-0.1mm).  https://a360.co/2Kkbv5k

Thanks for the help!


texts: Camera rig with multiple AC transformers

texts: I have 10 cameras in a rig each hooked up to a separate AC transformer.  I am looking for a way to decrease the bulk of having 10 separate transformers.  What would I have to do to achieve this?  Ideally I would like a single plug and a single box, with 10 feeds going to the various cameras.


texts: Choosing Vds and id values for a Power MOSFET

texts:
I have a question regarding the choice of an appropiate power MOSFET in relation to the circuit below. What are the safety margins that I need to look for.

For example, Vdd = 100V and I = 5A. Obviously, buying a transistor with Vds = 100V and id = 5A is not a good ideea. What do you suggest the % safety margin is? And just a quick stupid question, Vds has to be greater than 100V, not 50V, right?

MOSFET is in saturation region, acting as a switch. (output is either Vdd or GND).

simulate this circuit – Schematic created using CircuitLab


texts: Lower impedance for AC coupled darlington amplifier?

texts:
I have a problem I can't quite figure out.

I essentially want to "buffer" a 50mVpp audio signal to drive a 16 ohm load.

I preferably want to use primitive components so I thought that maybe a Darlington emitter follower might be used.

The problem is that AC coupling, the way I do it, makes the Darlington amplifiers output distort the waveform and massively shrinks the voltage amplitude.

Like this:

But there is no distortion and no shrinking of amplitude when disabling the AC coupling:

Altough AC coupling works for with a bigger load:

But since I want to drive smaller loads, I tried to see if a Darlington quadruple would work. And the waveform and the amplitude actually looks a little bit better, but it's still far from perfect:

I wonder why the AC coupling creates this problem for me?

Correction:
Actually, the Darlington quadruple was not better in any way. The better wave form was only a result of a higher bias voltage (before the transistors).


texts: I want to use the Nxperia BUK6213-30A transistor on my PCB board, but I noticed that only two pins can actually touch the PCB. The pin in the center is raised above the PCB and cannot be mounted. Is there a trick that I'm missing for mounting the second pin? (I'm completely new to this so sorry for stupid questions)


texts: Splitting power from usb type c charging brick

texts:
I did a DIY a portable monitor from a salvaged laptop LCD screen using a controller board I ordered online. Managed to make it work with a power adapter and an HDMI cable. I want to use it with my laptop but here's the thing. My laptop has a USB type C charging port with a 12V 3A brick. I'm trying to figure out a way to power both laptop and DIY monitor with just that one brick.

My initial plan was to look for a Y-cable with USB-C female split into USB-C male and USB-A male (or micro), and splice the DC jack to the USB-A for the DIY monitor, but I cannot find such a cable anywhere online or in stores. So I thought maybe I can use a short USB-C male to USB-C female extension cable and splice the DC jack to the wires in the extension cable.

Before I do any purchasing, I'd like to know would it be possible to accomplish this? Will there be enough current to power both devices? Is there another or better way to go about this issue?

Thanks!


texts: how to find Vout/Vin in this circuit? BJT frequency response

texts: I have been struggling for 1 hour trying to relate Vout to Vin. However, I truly cannot. I tried KVL, node analysis etc everything that I could. Can you help me pls? The topic is frequency response of BJT amplifiers. I found and draw small signal model. The circuit has 1 capacitor. I drown in equations and unknown variables. Can you guide me in the right direction so that I can easily solve such questions? I do not want to make use of Rin as it is comlicated. I all the time get devastated by questions involving emitter resistor.


texts:
I want to dim a led in a circuit if there's less light.
However, the Photoresistor I'm working with reduces the resistance when there's more light.
How can I achieve the opposite effect on resistance ?


texts:
Suppose we have a residential lighting dimmer switch circuit, where the output power across the load is controlled by the phase (alpha) of SCRs. Depending on the phase, the SCRs will essentially chop the input voltage, so that only part of it will appear across the load.

From what I'v been told, this chopping of the voltage will affect the power factor of the system. However, I don't quite understand why.
I'v watched countless Youtube videos on power factor and every one of them explains how the power factor is simply dependent on the phase difference between the voltage and current. Essentially poor power factor is a result of an inductive or capacitive load, which either shifts the phase of the voltage or current. Because of this phase shift, when the voltage and current sinusoids are multiplied together to obtain the average power, some of the area under the curve of the integral will become negative. From my understanding, this essentially means that the load is feeding back some of the power to the source for part of the cycle.
In this circuit, however, there is no phase difference between the voltage and current. The current and voltage follow each other exactly when the switches are on.
In general, for a circuit where the output is switched on and off, how can we analyze the power factor?  How do we calculate the real power, the reactive power, and the apparent power? Even the name "reactive power" points towards the power due to reactive components, such as inductors and capacitors. If there are no reactive components, how is there reactive power?


texts: What will happen if I initially set J=K=Clk=1 in this circuit?

texts:
Will it remain in the state \$Q = Q-bar = 0\$ as the feedback given back will always be zero?

Will this lock the JK in this state as long as the \$V_cc\$ is connected?

Note: I have used the word initially, because doing it on a later stage probably won't affect the internal SR latch.


texts: How to safely increase power consumption on purpose

texts:
I have an esp32 nodemcu hooked up to a powerbank. My issue is that the power consumption is so low, that the powerbank thinks there's nothing connected to it and some electronics inside then tell it after a few minutes to stop delivering power to that port.

It's running a Bluetooth GATT server, so my next attempt is to make it try to constantly connect to an WiFi AP in parallel, but I'd like to know if there is another way, ie by using a variable resistor, but I'm not sure where to put it.

It should be as compact as possible, so no adapter between the USB plugs.


texts: Help me debug: flash programming successful and verified; program does not run

texts:
I am trying to put together a simple bootloader in the high end of the flash of an atmega8. The loader communicates with minicom via the XMODEM protocol, checks for errors, writes the corresponding flash pages and verifies them. All this is tested and working.

What is not working is executing the application after it has been flashed. I have 4 test cases.

If the input file is 1kB of 0x00 or 0x01 bytes, after cold reboot, program execution seems to start at the bootloader, although the BOOTSEL bit is set to start at flash address 0x0000 and the loader is at 0x1800.

If the input file is a binary file of an actual program, the chip hangs and no communication is possible. I have tried with a very simple and a quite complex applications, and the result is the same.

avr-gcc app.c -o app.out
avr-objcopy -j .text -j .data -O binary app.out app.bin  # doesn't work
avr-objcopy -j .text -j .data -O ihex app.out app.hex  # works via an isp

While both programs have been verified to work by uploading the .hex file via an in system programmer, uploading the .bin biles resuts in the explained hanging.

For example, here are the first several bytes of the very simple application:

00000000  12 c0 24 c0 23 c0 22 c0  21 c0 20 c0 1f c0 1e c0  |..$.#.".!. .....|

This is big-endian, being converted to small-endian by the bootloader. The opticode of an RJMP is 1100 kkkk kkkk kkkk where k is an up to 2kB offset. Thus 12 c0 becomes c0 12, which becomes 1100 0000 0001 0010. So the vector table is there.

What could be wrong? I am out of ideas. And my only debugging aids are printf() over uart and blinking a led - no JTAG available. Where shall I investigate for the solution?


texts:
I'm (Trying) to build a trigger timer for an air cannon to launch ham radio antennas. This is an attempt to only allow the valve to stay open by a consistent interval to get max distance without wasting air and hopefully getting multiple launches out of a tank of air.

For some reason I keep blowing the 2STN1550 NPN Transistor.
You'll see in the design that there is a voltage regulator that knocks down the 12V to 5V for the 555 timer (monostable multivibrator) and to feed the 2STN1550 transistor for a period of time set by the resistor/cap combo on the 555 timer. I've cut this circuit board and it seems ok, but after one launch I fried another 2STN1550. For the life of me I can't figure out why. Maybe someone else with more experience will have an explanation.

NOTE: the Flyback Diode is shown backward from the way I have it in reality. the valve is a sprinkler valve actuated by a solenoid that came with a 1" inline Orbit sprinkler valve.

Here is a simplified version of the part of my circuit that I'm concerned about.

simulate this circuit – Schematic created using CircuitLab


texts:
I have been trying to simulate high voltage regulator LR8 on the MINDI software.
I first ran this circuit which came as is in the "examples" folder, and just changed the input to our need. It worked properly and gave a constant 5V output as expected.
We want a 60V/10V/18V output, however, so we tried manipulating the resistors R1 and R2 to get our required Vout= 60V (as stated by the formula in the data sheet of LR8) but the software refused to simulate this iteration. We tried several such iterations, but none worked.
Please guide me on how we can get our required output voltage of 60V/10V/18V.


texts: OBD II Female connector with datasheet and measurements

texts:
I need an OBD II J1962 female port with 90 degree angled pins for pcb mount.

I am struggling to find a part which has a data sheet or enough info so I can create a pcb footprint for it.

Do you know where can I find one ?

So far I could only find these,

https://www.alibaba.com/product-detail/J1962-OBD-Female-Plug-with-90_60786542032.html?spm=a2700.7724857.normalList.1.7048675a0b9stC
https://www.alibaba.com/product-detail/J1962-OBD-Female-Plug-with-90_60791426891.html?spm=a2700.details.deiletai6.1.3dc247fcjMT6mG


texts: Wireless power transfer through stainless steel

texts:
The SS in question is 316, and is only weakly magnetic.
Does anyone know whether this is possible?


texts: Can an induction motor be used to generate power?

texts:
Induction motors do not have magnets in them, instead the magnetic field the outer coils generate creates electricity, and subsequently magnetic field, in the inner coil. This means those motors need no brushes as the inner coil is not connected to anything.

I was wondering, purely academically, if you could prime the motor with field first, by putting current through the outer coil and then spin it to generate electricity. Assuming you'd spin it correctly, I imagine the magnetic fields would maintain themselves using power absorbed from the motion until the system came to a halt.

Is this possible or nonsense?


texts:
When looking at PCBs in consumer products or PCBs I have ordered from manufacturers myself, I notice that, while many of the vias are covered in soldermask, it seems like a few random vias are missing it for no apparent reason.  This is true even if I specify soldermask to cover all of the vias.

Why is this?  Does the soldermask get wicked down inside the vias during manufacturing?  Is there a way to prevent this?

All of the vias on my projects are a minimum of 15 mils.  If I used smaller vias would this not happen?


texts: Multiple Analog input for one channel ADC with Amplifier drivers?

texts:
I have a concept of using a one channel ADC for three differents analog inputs sources.
My question is: should I worry if the the analog inputs have differents inputs impedance, one is very high internal impedance, the second is very low internal impedance and the third is zero internal impedance? ( OpAmp buffer between the ADC and the source analog  inputs)
If I only wanted to select one analog inputs at once, I thought of having a mosfest switch between the analog inputs and the OpAmp?
Below is the circuit with voltage controller switch used as Analog swich in LTspice.


texts: Getting more information about PH brand transistor manufacturer

texts:
I have several transistors marked as:

PH
331XN
m9249

The package is SOT-82 and here is the photo:

But can not find any information about the brand PH...
Some says it is equivalent of BD331 transistor. Perhaps "PH" is abbreviation for PHILIPS?


texts: Microwave starts working when door opens - how dangerous is it?

texts: I've just rented a house that came with an equipped kitchen, and I've found that the microwave has a rather weird behavior - opening the doors seems to trigger it to start working, which the owners claim "has always been like that". Yet, I've been placing anything I want to heat as fast as possible and without completely opening the door for fear of exposure to microwaves - and I'm curious, assuming there is something wrong with the device, how dangerous is this type of short exposure?


texts:
I am looking at Figure 13.119 in The Art of Electronics, which shows a psuedo random bit sequence generator using shift registers. I understand how this functions. It then takes taps off of the shift registers, using various resistor values to feed into an op amp circuit which then outputs the noise... The book mentions that the values are derived from sin(x) / x [I think?].

What I am asking is, how and why the resistor values used were chosen? And why this works with the op amp configuration shown?

Here is the figure for reference:


texts: How gain is changed in this Op-AMP integrator?

texts:
Hi, I am simulating this circuit for personal development. The gain of the integrator can be calculated using the following formula:
Gain = -Rf/R1 (1/(1+(2 x pi x f x C1 x Rf)))
But, how to calculate the gain of this circuit when diodes are introduced for rectification.
I tried for some time. But couldn't get the result I see on simulation. How to calculate the gain of this circuit and output voltage(both Vrms and Vdc) with that gain?
Also, if anybody explains how this circuit works, it will be helpful for me.


texts: What could be the reason for these bands in this data acquisition measurement?

texts:
Here is zoomed view of 16 channel

The first plot looks very peculiar to me hence there are like two forbidden bands(looks like white lines as you see). This also appears if I plot any individual channel(again without any filter). For example this is for channel 7:

One can only see these white bands if the plot us plotted with dots.

What could be the reason for these white bands?

will be updated..


texts:
In the last few months I have been working on this project and now the next stage is to make a PCB for this circuit.

I know this PCB is very far from perfect (my first PCB), but I would like to know if this may work properly or if it does not even make sense to send to the manufacturer for production.

This circuit on the breadboard is working without problems.

I am using a microcontroller to receive GPS (will be connected to the GPS headers) coordinates from a Neo 6M module. The microcontroller will process those coordinates and will activate a relay if needed. Every 10 seconds I will read the GPS and send data from the DB9 connector (serial) over UART. The uC has a 16 MHz external crystal.

I am on a budget and I need to make this into a two layer PCB. I know that the best approach is to make a ground plane and make the data tracks on the other layer however without ground plane will this work in theory?

Can I connect the 16 MHz crystal this way or will it cause electrical noise?

By the way, any more obvious mistakes that I am making?

Thanks very much and sorry for the noob questions!

EDIT:
First of all thank you for all the help! Made some new changes to the design:

Changed footprint of 20pf and 100nf capacitors to non-polarized.
Added 100nF bypass cap.
Switched position of crystal caps and the crystal itself.
I managed to get a bottom ground plane to improve stability.

A few considerations:

Design rule check shows no errors.
There is really no need for mounting holes yet.
I use THT because this is my first PCB and to not get over my head with SMD components.

Now that I got all the GND stuff out of the way, can you tell me if I am on the right way or is it missing something ? I will optimize the board as suggested, I am just making sure I am not doing anything foolish without realizing it :)


texts: Isolated vs non-isolated dc/dc in multi-rail design

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I want to build a efficient, small and lightweight multi rail dc/dc power supply. I've been thinking about several topologies and ideas. However, the main question of "isolated vs non-isolated" still stands. I am working with a 3cell lipo (11.1V nom. 9.2V min, 12.6V max). So the input voltage will vary over time. I need atleast 12V @ 5A output, 5V @ 5A, 3V3 and perhaps some other specific voltage levels I yet have to receive info about. So my initial thought was quite biased for my love of isolated power supplies: With the following block scheme as my idea:

The idea behind this was to have a single core with multiple output windings. So I thought, since N1:N2:N3:Nn will always remain constant, any offset in the voltage on a single rail will also be present on the other rail. Correction would be done via a microcontroller. This simplifies the circuit to a single switching stage that corrects itself and a sense circuit. I have no idea how well this works, if it does. A problem with this would be that accuracy of the voltage outputs will be crude, since the amount of turns rarely turn out to give perfect 5000 mVDC for example. The lack of regulation on each output can be problematic with some sensors which this converter will power.

My other idea was to have a non-isolated dc/dc converter for every single output. Like this:

For the buck-boost I would use the SEPIC topology and for the buck I would consider a synchronous buck converter. The advantage of this is that it won't use a heavy transformer and all the outputs are properly regulated. A problem would be that it requires multiple dc/dc converters.

Which concept is more suited for building a DC/DC power supply?


texts: Analog multiplier using logarithmic and anti-logarithmic opamp output problem

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I'm trying to build a analog multiplier that takes in two voltages and produces the product of them. I have tried to simulate a circuit. Simulation with this methods is part of the objectives in the project. However the output doesn't even go as I expected. This is the basic layout of the circuit:

As you can see, I got 1 V on the both V1 and V2 input, but the output shows 9.23 mV. Is there any suggestion how to fix it?


texts: Identify components on computer motherboard - cylindrical and cube shapes

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I'd like to know what components are the ones with blue numbers and the big ones behind them:

The latter components I'm talking about:


texts: What is an easy way to program an ATtiny microcontroller in C without an ISP?

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I understand the "most raw" method to program an AVR microcontroller is probably with an ISP such as the AVRISP mkII.

However, I'm after a method that doesn't involve me having to purchase a $40 tool for a one-off project.

I have at my disposal a computer, an Arduino Uno, and a Raspberry Pi.

I'm not really interested in using the Arduino IDE and writing sketches. I want to get down into the low level code which is possible in C, preferably using an IDE such as Atmel Studio.

As I understand the Arduino Uno has an ATmega16U2 which connects to a computer via USB, which is used to program the ATmega328P.

Is the ATmega16U2 acting as a ISP here? If so, can I use it to program the ATtiny? I've gone through the schematic, and it shows the mega16u2 has an ICSP header, but it's connected to the mega328 via TX/RX lines.


texts: What is dropping all this voltage in a circuit with just a heating coil?

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I have a heating coil (actually an e-cigarette vaporizer) that I soldered two 10cm wires to. If I hook it up to a regulated 5V power source and measure the voltage over the coil, it measures about 4.07V. I find this puzzling because I can't figure out where the remaining 0.93 volts went. I'm measuring straight on the point where the wires connect to the power source leads. If I take away the coil, the leads measure exactly 5V.

I also have a 9V battery that, when measured, still has about 7.47V. If I connect the coil to that and, again, measure on the point where the wires connect to the battery leads, I measure only 2.39V over the coil, meaning 5,08V has somehow disappeared.

How is this happening? Is a heating element like this some sort of non-ohmic resistor? What exactly is going on here?


texts: How to make a switching source for voltage converters

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I would like to make a automatic switching of source for my buck converter when the  input voltage is below 5v.

In the very simplified circuit image above as you can see the input voltage can be 3.3V or 6V or 8.4V. The buck converter that outputs 3.3V has a minimum input voltage of 4.5V, this is a problem when the source voltage is 3.3V. So instead if the source voltage is 3.3V (or anything below 4.5V) it must get its power from the buck-boost converter that constantly output 7.5V.

How do i create a switch that switches when the voltage is at a certain threshold. Also it would be nice to create a hysteresis to prevent it from going crazy


texts: How to pull Triac gate to ground with an NPN transistor with AC present

texts: I am trying to figure out in this circuit, which lets the Triac 170 to conduct normally, which prevents an engine from firing, how to use an NPN transistor to replace the seat switch 154, but I assume there is AC voltage on the 112a line, and I know that AC would not play nicely with the transistor.