texts:
I am driving a 9V DC (5 PINS) Relay from darlington array ULQ2003.
The ULQ2003 COM pin is connected to 9V power supply while the Relay coil is connected to +12V supply. The Ground of both are connected together.

When 'OUT1' is at LOW then the Relay is operated and its 'NO' contact is connected with the 'C' pin.
When 'OUT1' is open-circuit (floating) the Relay remains latched and its 'NO' contact remain connected with 'C' pin. If I check voltage at 'AB' points then I get positive voltage there.

V(AB) = 2.3V --> that is VA is 2.3V higher than VB.

My understanding is that after the Relay power is turned-off then a reverse polarity voltage will appear across its coil, and for that we put a reverse diode in parallel with the Relay coil.

I cannot understand why the Relay is not able to de-energize completely when its circuit is break?


texts: SIM800C GSM module works via PC but not on battery

texts:
Before giving the specifications of my project, I'd like to say that I'm a total beginner in electronics but I do have a background in IT development.

I also want to apologize if this question has been answered already but I can't find any thread that answers this specific question.

I am trying to power a SIM800C GSM module via Li-Ion battery but it doesn't seem to work. The module is powering-up fine and SEEMS to work since it blinks every 3 seconds after a short period (seems it's connected to the network) but when I send the AT command via my PC (going through a NodeMCU), I got no response.

In the meantime, if I power up the module via my PC, it works just fine, the module is able to answer the AT command.

The SIM800C works in an 3.3-4.4 Volts DC input range and on 400mA up to 2A.
My battery outputs 10.8 up to 12.6 Volts DC and 4800mAh.

The amps seemed high to me so I unbuilt the battery and discovered 3 little batteries in series, each outputing 3.7 to 4.2 Volts and 1500mAh.

I then proceeded to power the module with a single little battery and by the led blinking 1 time every 3 seconds I could tell the module was powered-up and theorically working, but still no response on the console.

I also tried to power-it up via the charger of my phone and the same effect goes : The module is powered-up but doesn't take AT commands.

To sum up what works and what doesn't, I'll link two schemas, one is a "working" one and the other isn't.

Below is the working one :

And then, the non-working one :

I read here and there that I should use capacitors or resistors, but I am totally lost under all the information.

Do you know how should I proceed to get the answer from AT commands ?

Thanks in advance and once again, sorry for my noobyness

Edit: Here is a photo of the montage. We can see the NodeMCU being powered by USB in the center, the battery in the bottom left as well as the GSM Module (SIM800C) in the bottom right of the picture.


texts: How to map 10-bit ADC value to a range with restrictions

texts:
I need to map a 10-bit ADC i.e. [0-1023] to a range [1-100]. The mapping formula itself is the direct "y=(x-a)/(b-a)*(d-c)+c" to map x in [a-b] to y in [c-d].

Input x is calculated as the average of say 1000 ADC readings.

My problem is this. The input to ADC is a potentiometer and i need to calculate x ONLY when the potentiometer is stationary. How do you detect this? The way i am currently doing it is to read sets of 1000 ADC values (on a timer), calculate their average and compare the "current avg" with the "previous avg". If "current avg - previous avg" is some "+-delta" i assume the potentiometer is stationary and do the calculation.

Is there a better way of doing this?

Edit: To provide some more data;

I am using a C8051F850 MCU from SiLabs running at 24.5MHz
ADC samples are collected every 100us
Avg of 2500 samples ~ 250ms is calculated per set. Thus two avgs are compared every 500ms.
My "delta" is 10 units (approx of 1024/100)
Integer arithmetic so rounding errors


texts: How to get force gate to ground if pwm is low

texts:
I built a simple 555 motor controller with a mosfet. I use a the 555 to send a pwm signal to the mosfet to control the speed of the motor.

However when i slow down the motor to 0 the motor makes a noise. I believe this is happening because it is sending a slow pwm signal to the mosfet.

I'm using this:

My motor is 230v DC. Is there anyway to tune the 555 to send a constant negative volatge to keep the mosfet off when the pot is on a low speed?


texts: Vibration coupling through clothes as function of frequency

texts:
Serious question. Trying to figure out if there is any research/guidelines on selecting the frequency of a vibrator for a portable electronic device. This is safety related wearble device for first responders/cops/etc. I know lower frequency is better but is there a frequency that really starts to fall off when it comes to coupling vibrations though a belt or jacket/vest?

I've googled around a bit but all I'm finding is things related to measureing vibrations from heavy machinery and such.

Also, maybe this is more of a biology question?


texts: Truth table to transistor diagram and Boolean experssion to transistor diagram

texts:
I'm having a little trouble, making transistor level diagrams based off truth tables and Boolean expressions.

I was doing a problem to which I understand the first part, but I am unsure on how to do the second part.

Given the truth table

ABC| Output

0 0 0  |  0
0 0 1  |  0
0 1 0  |  1
0 1  1 |  1
1 0 0 |  0
1 0 1  |  0
1 1 0  |  1
1 1  1 |  0

I constructed the transistor level diagram

I feel fairly comfortable with this, however the next part I am perplexed

I am given the expression AB'C'+A'B'C+A'BC'+AB'C to which I simplified to

AB'+B'C+A'BC'
Now how would I construct the transistor level diagram from here? the only thing I can think of is constructing a truth table, but is there an easier/quicker way?


texts:
I am trying to synthesis system verilog (.sv) file in vivado. The file uses defines from another verilog (.v) file. This combination is not working. I tried renaming define file into *.sv then the error got resolved.
Is there such constraint that all defines for system verilog should be in another system verilog file ?
If no, what is the best way to resolved this issue ? I dont want to rename the file since it is part of release from different team. Please help.
Let know if you need further info on this.
Regards,
Tollin


texts: How do true wireless earbuds perform inter-ear communication?

texts:
What protocol, frequency band and messaging style is used by typical popular true wireless earbuds between the two ears? Is it another Bluetooth connection? Bluetooth LE, or something proprietary to the chipset?

In typical popular true wireless earbuds, I understand in stereo mode only one bud communicates with the source device, and relays audio data to the other earbud over a secondary connection. Is my understanding correct? How do they deal with the challenge of transmitting through the wearer's head (or around)?

Thanks in advance for any pointers to a technical description. If there is no commonality between different devices, feel free to describe the model for a particular popular device eg AirPods, Jabra 65t, etc or chipset manufacturer (Qualcomm, Realtek etc)


texts: Compatibility of an LCD module and a connector

texts:
I want to realize i2c communication myself using Raspberry Pi and a LCD module.
I am reading documentations to find an appropriate connector but I am a bit confused and I need help.

Here is the LCD module that I want to use.
https://www.digikey.com/product-detail/en/COG-C144MVGI-08/153-1146-ND/2523706
Data sheet : https://media.digikey.com/pdf/Data%20Sheets/Varitronix%20PDFs/COG-C144MVGI-08.pdf

Here is the connector that I found :
https://www.digikey.com/product-detail/en/te-connectivity-amp-connectors/A9CAG-1202F/A9CAG-1202F-ND/470099
http://www.johnsonelectric.com/en/resources-for-engineers/ffc-flat-flexible-cables/ffc-inquiry-form-and-distribution-availability/~/media/68341462F8C24422B092CABF67385811.ashx
(The FFC used is PSR1635-12.)

Are they compatible? The pitch is 0.100", so that should be find, but I am not exactly sure if the cable width corresponds to that of the LCD module.
I want to solder the LCD module and the connector so that I can use it more easily afterward.
Thank you.


texts: How do I calculate the transfer function of this basic terminated RC filter?

texts:
I'm reading through an electronics book to teach myself, and I'm in the section about filters. I've been following along so far, but now I'm confused about how the author came to a conclusion in his math. Here is an excerpt from the book (Practical Electronics for Inventors, 4th edition, page 213):

He is computing the transfer function for the circuit in the image, and he says that:
$$
H=\frac{V_{out}}{V_{in}}=\frac{1/(j\omega C)||R_L}{R+[1/(j\omega C)||R_L]}
$$
This makes sense to me, since this is just computing \$V_{out}\$ using the voltage divider equation. The next step is what confuses me, where he says that the equation above is equivalent to:
$$
= \frac{R'}{1+j(\omega R'C)}V_{in} \text{  where  } R'=R||R_L
$$
How do I come to this conclusion? I've tried simplifying the circuit using Thevenin's theorem by combining \$R\$ and \$C\$, which gives me:
$$
R_{THEV} = R||\frac{1}{j\omega C} = \frac{R/(j\omega C)}{R+1/(j\omega C)} = \frac{R}{1+j\omega RC}
$$
That's pretty close to the author's answer, except I have \$R\$ instead of \$R'\$. I've searched around and haven't found other resources making this leap. I'm a little lost! The book continues making use of this throughout the filters section, so I really want to understand it. Any help here would be greatly appreciated.
Edit: The answer by Paul below solved the problem. The numerator of the equation in red should be \$R'/R\$ and not \$R\$. I expanded both the green equation and the corrected red equation and got a matching result.
Expansion of green equation:
$$
H=\frac{V_{out}}{V_{in}}=\frac{1/(j\omega C)||R_L}{R+[1/(j\omega C)||R_L]}V_{in}
= \frac{(R_L/(j\omega C))/(R_L + 1/(j\omega C))}{R+(R_L/(j\omega C))/(R_L + 1/(j\omega C))}\\
= \frac{R_L/(R_L j\omega C+1)}{R+R_L/(R_L j\omega C+1)}
= \frac{R_L}{R(R_L j\omega C+1)+R_L}
= \frac{R_L}{R+R_L+j\omega CRR_L}
$$
Expansion of corrected red equation (with \$R'\$ replaced with \$R||R_L\$):
$$
\frac{(R||R_L)/R}{1+j\omega (R||R_L)C}
= \frac{\frac{RR_L}{R+R_L}/R}{1+j\omega C(\frac{RR_L}{R+R_L})}
= \frac{R_L}{(R+R_L)(1+j\omega C\frac{RR_L}{R+R_L})}
= \frac{R_L}{R+R_L+j\omega CRR_L}
$$


texts: Are ultrasonic Tx/Rx pairs really just the same sensor?

texts:
I want to retool the classic HC SR04 rangefinder to be able to do ToF gas flow sensing. I need to be able to do ToF on a column of air in both directions, so it benefits me to be able to use the transceiver as both transmit and receive.

TxR>[=====]>TxR

Otherwise, I either need a larger diameter tube with a pair of Tx/Rx on either side, or two tubes, neither is optimal.

Is there any reason why I can't just use a mux and alternately use one module as Tx and other as Rx, then switch roles?

Here's a datasheet of what I think is a representative transducer.

How could I even go about telling if the two components are different? They are likely piezoelectric, so resistance won't tell me much.


texts: Hello I am troubleshooting a voltage divider circuit in which I know the output going to U28 pin 3 should be around 700mv. What I am measuring however is around 7.5v. How do I calculate the v out for this circuit. I know I have to account for R83 because it is a potentiometer but still I should be able to math this out and get close to 700mv but I can’t seem to calculate it right even after watching YouTube. The top photo is the actual schematic drawing but I redrew it to in the way in which I thought it works because I noticed r85 and r86 share the same ground therefore r83 and r85 must be in parallel to r114. So did I draw this out right and how do I solve for vout?


texts:
I built an 2nd order active highpass filter with cut-off frequency at 800Hz using an OPA847 (and R18=39.2k, R19=16.9k, R16=11.3k, R17=11.3k, C7=20nF, C8=20nF). Simulation works fine. In real life however, the active filter didn't work with these values. My assumption was, that OPA847 has a too low input impedance (2.7k), so I divided all resistors by 1k and multiplied the capacitors with 1k.

Now the oscillator shows me a square wave with frequency 450 KHz. It seems that the active filter is an oscillator now. How can I remove oscillation? Where do I have to look at?


texts: Control of a Permanent Magnet Synchronous Machine (PMSM)

texts:
I'm trying to control the speed of a PMSM in the simulation software PSIM.

Now, I have learned that in a Synchronous Machine the steady-state speed is directly proportional to the frequency of the source, independently of the load (assuming it is in a supported range).

Therefore, I was hoping to be able to control the speed in a open-loop, by just changing the frequency using a inverter (and the voltage accordingly, to avoid flux saturation). But I have not been succesful and every article I've found so far uses Current Control to achieve speed control, which increases the complexity.

Is it not possible to control the speed of a PMSM without caring about the current?


texts:
I'm currently learning electronics and right now, I'm trying to use a relays... without success. Here is a picture of my circuit:

First of all, don't mind the 2 cables on the top right and the relay on the bottom right, they are not used.

So, from what I understood about relays, here are my thoughts about this circuit.

When the button is not pressed, the relay does not receive any tension, so the pins connected to the lightning LED are active, which is why the LED on the top is lightning... That I get...

Now, when I press the button, a 12V DC tension is going inside the relay, so I was kind of hoping that it would make it switch and then the second LED would be lightning but... no...

The relay is an AXICOM IM26, you can find the datasheet of this one in here: http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Specification+Or+Standard%7F108-98001%7FV%7Fpdf%7FEnglish%7FENG_SS_108-98001_V_IM_0614_v1.pdf%7F4-1462039-1

However, a friend made me notice that this datasheet "talks about" a switching current of 2/5A but I have trouble to imagine that this small relay really requires that amount of current to switch, especially because it is writing "12 V DC" on it, which, for me, tend to indicate that it switches at 12V. But it would explain why it is not switching when I press the button.

Can someone explain me what is wrong with my circuit ?

Thanks


texts: How to calculate or show in matlab/pspice the DC component from a circuit simulation?

texts:
Based on Pspice I'm simulating this RL full wave rectifier

That gives the next voltage and current output at the showed probe point

The idea is to extract the DC component of the current or voltage, but I don't know how to this (be in pspice or matlab).
From the matlab approach, I export the simulation as csv, open inside matlab launch the pid tuner program and load the data, then fit and get this one

and the next model of the plant

But whats next? I don't know if the FFT apply here since this is not a frequency analysis.


texts: Is my understanding of how this amplifier circuit works correct?

texts:
Hello.  This is the amp that I'm trying to wrap my head around.

This is how I understand how it works and I'd love your input if what I say makes sense:

The input voltage is a sine-wave of increasing and decreasing voltage.  Let's say that the highest voltage is 4 and the lowest is 3.  When this input hits the initial capacitor, this voltage drops down to 1 to 0.  Basically, the power is either on or off.

When current is flowing, this causes the NPN transistor to allow power to flow through it and the electrons from the ground to link up with the electrons flowing through R2 and R4 to create an amplification.  However, when the voltage drops to 0, then the NPN stops the transfer of power entirely and the output is whatever the electrons coming across from the input signal.

Does this make sense or am I totally off-base?


texts: Sensing 240V and converting to CMOS logic levels

texts:
I lab tested the circuit below, which Olin Lathrop designed in this answer.

The problem is, on OUT (pin 4) of the optocoupler I get 1.7 volts when 240 V is applied to the high voltage (HV) side of the circuit, I'd like the voltage on OUT to be lower (less than 0.8V) to represent a logic 0. How can this be achieved?

The AC current on the HV side of circuit measured 1.1mA.


texts: What is differences of WV and V for Capacitors

texts: Units can differ in the volt values above the capacitors I use. thera are two capacitors one of them is 400V another is 400WV. If the farads were the same, could I use 400wv instead of 400v? In addition, I sometimes encounter VAC or VDC units on capacitors (generally small ones). Please tell me what is differences of V/WV/VDC/VAC. if there are differences where to use?


texts: What is the output voltage and current necessary to operate the MEMS mirror?

texts: I am trying to develop a driver to control a MEMS mirror by Mirrorcle. The specific component is A8L2.2-5000AU-TINY48.4. The data sheet only includes VdifferenceMax and and frequency information, but no where on it can I find the specifications for the required current and voltage needed to operate the device. Would I have to calculate that on my own? I've looked all over the web for this info, but got nothing.


texts: BJT Active Region - Biasing of BE and BC junction

texts: I am having trouble understanding why the BC junction is considered to be reversed biased in these two models. The way I see it, the base looks to be in a higher potential than the collector junction given the polarity in the PNP model.


texts: What effects limit throughput of a short channel?

texts:
In a short channel, e.g. a 1" long Ethernet cable, which effects are most likely to reduce throughput and why? What would the nature of the throughput reduction be? Specifically, I am wondering about 100/1000 Mbps Ethernet over standard cables like CAT5/5e/6/etc. My assumption is the error rate will jump significantly as the transmission line crosses a threshold that we could colloquially call "too short," but I am unable to quantify that in a meaningful way.

I've been researching this and I'm not finding a lot of relevant information. This paper has some interesting information, but the low-level dive into signals and EM fields is beyond the scope of the topic it seems.

I'm thinking there are a few potential issues:

Fractional wavelength issues due to the transmission line length
Timing (min time violations if such a thing exists in this context)
Power (saturating the receiver)
ISI (reflections)

I'm sure there are others and maybe the issues I've listed aren't relevant. Any information would be greatly appreciated.


texts: How to automatically switch to backup outlet if power goes away?

texts:
So I have two 220V outlets side by side. One of them has power all the time, the other is unreliable but has cheaper power. I'd like a device that uses the unreliable when power is present but switches to the normal when it's not. What is this called?

Maybe some kind of failover switch I could just buy?
Relay switch cotrolled by a Raspberry Pi via GPIO?
UPS with dual power inputs?

Load is ~1700w and it's not a problem if the failover happens in an interrupted way. I would prefer something inexpensive.


texts:
I have a question regarding RC filter designs.  I have a system that picks up an analog signal at 200Hz and I'm passing the signal through a two stage low pass filter and then a two stage high pass filter.  Currently I'm using a 0.1 µF capacitor and a 4.6k resistor for the low pass stages (346Hz) and a 0.1 µF and a 10k resistor for the high pass stages (159Hz).

I'm losing a lot of my actual signal and I'm wondering if I need to be considering some different components.

The signal coming directly out of the amplifier chip (INA128) reads a peak to peak swing of about 3.5volts. It is powered by a true split supply rail +/-9V.  The signal after the filtering is somewhere in the neighborhood of 300mV.  So what am I doing wrong on the filtering?  Any ideas?

EDIT: Filter Design image added.  Pin 6 at the top is the output pin from the INA128.  The left trace to the capacitors and resistors are the Common rail.  You'll notice that there are two 4.7 zeners on the output (to protect against over-voltage to the ADC chip downstream) and the final signal is getting passed to an ADS1015 analog to digital chip.  (I know, I'm losing my negative signal on the ADS1015, but that's not really important data in my circuit.  I'll tackle that later with a true split rail ADC chip.)


texts: Input AC current of a mains power supply - how is defined

texts:
My question is about definition, measurement and documentation.

Let's look at a random datasheet of a switch-mode power supply.
Here is the datasheet of Delta PMT-5V35W1AA.

It's input current is given as <0.50A @ 230Vac.

Its output power is 35W, efficiency is about 81%. This gives an input power of about 44W.

This PSU does not have PFC, so its input current has large spikes on every half-cycle while charging input capacitors. However there isn't a significant phase shift, as it would be with an inductive load. Power factor is not stated, but I don't think it would be so small (lass than 40%).

Where comes the big difference from?

How can I measure this input current to declare it in the datasheet of a new PSU?


texts:
I'm new to Arduino so baby language for me please :)
Problem: I'm trying to power 2 servos (https://www.amazon.co.uk/gp/product/B07DQFXDC9/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1)
but there's only 1 5v pin on my Uno.
The project involves making two servos move when I hold down a button (also coming from the 5V and has a resistor in series).
I've tried two things to make this work:

Powering both servos from the 5v pin. The motors are slightly weaker than I'd like and if I hold down the button for a few seconds, the motors glitch, the computer makes the disconnect sound and the arduino restarts.
Powering both servos from an external 9v battery. Both motors are MUCH weaker than when just one was plugged into the 5v and theyre unusable like that for this project.

Any help is massively appreciated and feel free to dumb it down for me haha


texts: Adjustable non-inverting Buck-Boost converter failing right after starting in boost-mode

texts:
I am designing an adjustable non-inverting buck-boost converter based on LM5176 chip. Adjusting is done by DAC via feedback network, more on that technique can be found here.
The input voltage is 32V and is been sourced from bench power supply unit.
At the start, the DAC output is 0V, the converter should reach 50.6V at the output. It does that and then goes down to ~1.5V and never starts up again.
The same happens with 17.8k resistor connected to GND instead of DAC output, so I ruled out any spikes on DAC output causing the problem. With 17.8k resistor removed it works perfectly and reaches 42V at the output. The feedback loop is working fine since the load transitions from 0A to 0.9A are fast and without ringing in both buck and boost modes. I did increased capacitance of CS-CSG filter, because it was quite polluted with ringing (~160MHz) from switch nodes. Both instant and average current limiters are working as expected.

On most of burned LM5176 chips I found that COMP (error amp output) pin was shorted to GND. And in some the FB pin was also shorted to GND.
The max output voltage according datasheet can be 55V on this converter, so I need at least 50V.
At lower starting voltage (up to 42V) I can measure and paste here voltage or waveforms at any point in the schematic, so don't hesitate to ask for them. Values of the parts are written and if some part number is required, I can write it down.
So, any ideas for debugging or upgrading this converter?

Update 2018-12-04:

COMP pin during start-up sampled (17.8k resistor on FB and 470pF from COMP pin removed):

Chan1- COMP
Chan2- VOUT
Chan3- FB


texts:
IR light is the mainstay frequency for optical communication systems.
How could I experiment with UV frequencies doing the same thing?
Ideally I want to set up a serial link just as is often done with IR.

Thanks you all for your help on this matter.


texts: How do I convert AC current at 110v to Watts?

texts:
So I'm trying to measure the power consumption of my home PC. I used to have a kill-a-watt meter which I can't find, so I wired up my multimeter to measure the current.

Now I'm not sure what to do next.

Is it just .6Ax110v = 66W? Or do I have to do one of those sqrt(2) adjustments?

Seems like a silly question to ask.


texts: Why are two transistors or one transistor and a resistor used for a NOT gate?

texts: We use one n-type and one p-type MOS transistor for a NOT gate or one transistor and one resistor. Why can't we use one transistor only without a resistor?


texts: Combine protocols on a U/FTP Cat 6a cable (USB 2.0/I2C)

texts:
Main question
Can I use a Cat 6a cable for USB communication? On the cable it says 650 MHz, is this sufficient for USB 2.0? The length of the cable would be about 6 meters (about 19 ft).
If so, would the following be the correct way to wire this?

Follow-up question
If the answer to the first question is yes, would it then also be possible to combine it with I2C like below? Is my assumption correct that the pair-shielding will prevent either protocol from interfering with the other? (this way of wiring I2C with twisted pairs I got from NXP's AN255, see figure 30)

I also assume the capacitance from the shielding is not too much for 6 meters of cable for I2C's standard 100 KHz clock? (I don't know how to calculate/measure this)

Background / Extra info
The reason I'm asking this is because I need to pass I2C and USB through a tube of small diameter (inner 16mm), which has several inconvenient bends in it (and it's inside a plaster/concrete wall). This limits the amount (and diameter) of cables I can get through without damaging them.


texts: Understanding portable music player's power specs

texts:
Right now I'm looking at the specs of two portable music players. The specs of the first player describe the power provied to the headphones, depending on their impedance:

Output into 16 Ohm - > 436 mW
Output into 32 Ohm - > 255 mW
Output into 300 Ohm - > 27 mW
Max output voltage - >8.2 Vp-p
Max output current - >250 mA

and the second one:

Output into 16 Ohm - > 460 mW
Output into 32 Ohm - > 255 mW
Output into 300 Ohm - > 28 mW
Max output voltage - >8 Vp-p
Max output current - >150 mA

Is it physically possible for both these specs to be true? What might be a possible logical explanation of this?

For me it pretty much conflicts with the Ohm law. Look at the first player - it has both higher maximum voltage and current (limited by battery source), but somehow it produces less power than the second one. Power is not something that magically appears on a cable, but it's directly dependent on the voltage and load - impedance of headphones in this case (and maximum output current the battery can handle).

I know that my question is not related to circuit deisgning, but I guess it can give a better understanding of certain aspects for beginners.


texts: How to calculate time for NiMH batteries to discharge?

texts:
I want to use 4 battery cells AA NiMH (or NiCd) 1.2 V, 2600 mAh in order to power up circuit that requires 5 V, 300 mA.

I know that fully charged NiMH can provide 1.35 V each, which means 5.4 V in this case. Circuit's electrical specification is Min: 4.8 V, Typ: 5 V, Max: 5.2 V. However, it refers Max voltage without damage: 12 V.

My question is:

Can I calculate time that batteries will be able to power up the circuit, before voltage drops under 4.8 V, if we assume that provided amperage from batteries is 300mA?


texts: What are these wiry protrusions on a TV antenna?

texts:
This photo shows part of a large antenna assembly which has a series of thin wire protrusions:

(Source)

This antenna is apparently used for TV transmission.

What are those protrusions for? I'm guessing something to do with lightning or static? The photo is from near the antenna's base, it was hard to tell how far up they go.

(Interesting video, BTW as the giant antenna has to be replaced by helicopter at the top of a 1500 ft tower)


texts: Understanding common mode vs output voltage graph for instrumentation amps

texts:
What are limitations on the design imposed by this graph? Say, if I want my output to span 0V - 3.3V, does this mean that I should position my input signal at 2.5V?

edit:  InAmp in question is AD8226


texts: At the first fig. there is a basic common emitter amplifier circuit where signal source v_i is "superimposed" on the dc bias voltage V_BE. At the second fig. a  biasing scheme (poor, nevertheless sufficient for my purpose) is shown where V_BE is fixed using a voltage divider across the power supply V_CC. Now, on numerous occasions, I have seen the signal source v_i is applied at node X (colored blue). Does this actually "superimpose" v_i on V_BE? How? Thanks.


texts: I want to measure how much power my PIC is using. At the output of my 3.3V regulator I put a 1 ohm resistor in series with the rest of the circuit. I was going to measure the voltage drop across that resistor to get the current and so on. With the 1 ohm resistor installed the circuit works just fine but when I put the probe of my o'scope across it it my 3.3V goes to zero. It seems as though the scope is creating a short to ground or something. Does anyone know why this happens or how to make it stop?


texts:
I was reading stuff on NTC self heating and I was thinking if the thermal runaway  is something that could really affect a measurement. So, not an offset, but actually a drift on the resistance.
So I tried to think what happens in a circuit like this:

The maximum power absorbed by the thermistor is when has the same resistance as Rref due to the maximum power transfer theorem. Plotting this power absorbed versus temperature (i.e. resistance) and facing the graphs, I obtain something like this:

where of course at 25°C both resistance are at the same value. Now, for temperatures higher than 25°C, I can see that there is some negative feedback that keeps the sensor from drifting: as temperature increases, the power dissipated decrease and temperature decrease again, and I expect that it will stay in one balance point lower than the offset without this negative feedback.
On the other hand, for temperatures lower than 25°C, as the sensor increase its temperature, it will increase the dissipated power, increasing further, up to arrive at stationary point of 25°C.
Now, if those assumptions are correct, how this is taken into account in the design? Is this effect dumped out somehow?
This question I think applies also on some "fixed" resistors, but with significant parasitic thermal dependence.


texts: Circuit Diagrams - 2 Input/Output Current Source

texts:
I have encountered a situation where I need to draw 1 controlled current source on a circuit diagram with 2 inputs and 2 outputs but I'm not sure what is the proper way to convey this idea. I can't seem to find anything online either.

Here is what I came up with (doesn't seem proper to me):

How can I draw a current source with two outputs?


texts: Long supply line and capacitor to prevent voltage drop

texts:
I have a 30 feet line with DC supply 12 V. A motor on the end draws about 0.5 Amps initially (100 ms). It's logic shuts down because of the line's voltage drop caused by inrush current.
A capacitor of 1000 uF prevents the shutdown.

However, if I calculate the size of the capacitor that prevents a drop of more than 1 V, a much larger (x50) value comes out (0.5 A * 0.1 s / 1 V = 0.05 Farad).

I figure this is because the supply isn't disconnected but continues to supply power, so the capacitor does not have to provide the current alone.

How can I improve my model so the calculation is closer to the real thing?


texts: Calculate input impedance of transmission line without knowing L or C

texts:
I have the following problem:

  A TV antenna lead-in wire 10 cm long has a characteristic impedance of 250 ohms and is open-circuited at its end. If the line operates at 400 MHz, determine its input impedance.

I know the following formula for input impedance \$Z_{in}\$:

\begin{equation}
Z_{in} = \frac{Z_0}{j\tan(\beta L)}
\end{equation}

where \$\beta\$ is the phase constant, \$L\$ the length of the line, \$Z_0\$ the characteristic impedance an \$j=\sqrt{-1}\$. The question is, how do I find beta? The only formulas I can find for beta involve both the capacitance and inductance per length of the transmission line, neither of which are given in the problem.


texts: What is the largest inductance value ever attained(in Henries)?

texts: For example, are there inductors with values in terms of kilo-henries or even mega-henries? 1 Henry inductors are not all that easy to find.


texts: Can I use a 220v AC rated switch for 220v 120Hz DC?

texts:
so I have this setup:

Bridge Rectifier has no Capacitors! So it outputs 120Hz DC

I had this without the bridge rectifier, but then, since it's AC and you only break one side
the current would jump to the ground and short out the fuse.

The Question is, will the relay slowly get fried or will it do just fine?
Is there something else I should be concerned about?


texts: Is it possible to find out the W/L ratio and process transconductance parameters of a mosfet from it's datasheet when it is not directly given ? If yes, how ?


texts:
I have a group project that requires us to use three flip flops with the following requirements.
If x = 0 and y = 0, the counter remains the same.

If x = 0 and y = 1, the circuit through the state transition from 000, 001,...,111, back to 000 and repeats.

If x = 1 and y = 0, state transitions from 111, 110, ..., 000 back to 111, and repeats.

If x = 1 and y = 1, the counter resets to 000.

I have created the state table to determine the functin of the circuit and constructed the circuit in Multisim. I've tried connecting the lcd display to the Q outputs of the JK's, but my output does not make any sense. It does not count through the cycles.


texts: DC motor and encoder for pendulum with low static friction

texts:
I would like to build a pendulum from scratch and model/control via Matlab. I don't know what DC motor should I use that has low friction (low static friction), so the pendulum can rotate by its self. Moreover, I would like to have an encode with "good" precision, less then 1^o.
I want to control the position of the pendulum by using the motor to put energy in the system. It will be a closed loop control and the controlled variable is the voltage drop on the motor.

How to check in a technical specification if the motor has low static friction?

Eg. the technical specification for a motor include:

  Values at nominal voltage: Nominal voltage; No load speed; No load
  current; Nominal speed; Nominal torque (max. continuous torque);
  Nominal current (max. continuous current); Stall torque; Starting
  current; Max. efficiency; Terminal resistance; Terminal inductance;
  Torque constant; Speed constant; Speed / torque gradient; Mechanical
  time constant; Rotor inertia.


texts: Why isn't this active rectifier circuit working?

texts:
I built the following active rectifier schematic on a breadboard, and inputted a 15 KHz 1V peak to peak sine wave from my signal generator.

The output looked like a sine wave and I have no idea why. Attached is the oscilloscope picture. I ran a simulation that said it would work (also attached). I know the signal was amplified correctly (on the positive swing), I could read that on the o-scope....but why wasn't it rectified?

The negative swing on the output was from 0 to -700 mV, which is the forward voltage of my diodes. Is that just a coincidence? The positive swing is from 0 to 1V. Maybe it has something to do with the simulation not accounting for real world characteristics?? Any help would be greatly appreciated.

Attached is another o-scope capture showing the input (blue) and the output (yellow). I think the phase shift is due to the amplifiers.

simulate this circuit – Schematic created using CircuitLab


texts: What part number is this 20-pin connector?

texts: Pin pitch is 1mm, row spacing 2.5mm. DigiKey filter search turns up empty. Two of these are used on a MiTAC motherboard, one for custom MiAPI and one as (probably) for a parallel port. Nothing helpful is silk-screened on the motherboard around this connector.


texts: Simple op amp question, finding gain and input resistance

texts: Why is the gain -10 for the following op amp? Isn't there a voltage divider between the 100k and the leftmost 10k yielding -11 as gain? And why aren't these resistors playing any role in evaluating the input resistance? Why would Rin be merely 10k?


texts:
I have a syringe of solder paste that is leaded, no clean.

I've had it a while and don't use it very often.  But I usually keep it in the refrigerator.  Is that necessary? Or, can I just leave it my utility drawer with everything else?

Thanks.


texts: CMOS Camera Module - Question regarding power supply

texts:
I have a question regarding the choice of some components for a CMOS camera module.

The camera IC is the OV7670. The module PCB contains a pin header and power regulation circuitry to convert 3V3 voltage to 2V8 and 1V8, required by the OV7670.

My question is why are the two 10 ohm resistors, R1 and R2. Are they used just so there are two separate paths for AVDD and DOVDD? Thank you!


texts: Filter passband amplitude ripple and group delay ripple (group delay variation)

texts: Are they completely independent? or does one lead at least partially to the other?


texts:
I wanted to control a RGB-LED with my RaspberryPi. The Problem is that my LED is a bit strange. The long lead is positive and the shorter leads are as usual for red, green and blue but have to be connected to ground (with a resistor in series).
Therefore I can't just control every single color with a PWM-signal.

I thought about connecting the three negative leads to a transistor which I then could control with my RaspberryPi.
If this could work, what transistor should I use?

Edit:
My LED only needs 3V for blue, 2.2V for green and 2V for red at a current of 20mA.


texts: What does the reference designator NT mean?

texts:
I found NT1 in a Microchip demo board schematic (103-00419-R1.pdf) but can't figure out what it means.

There is a box with a note saying "Default connection between 1-2. User to cut the trace if 5V VDD is needed.", with NT1 as a little box with wires going to pins 1 and 2 on the header.

I can't find the refdes on Wikipedia or Google in general, so I'm out of ideas. Here's a screenshot of the part in question (on the right side):


texts: Design of Wiring Harness Tester for Automobiles

texts:
I've been given a task to design a wiring harness tester for automobiles. The tester's job is to test wiring harnesses which can contain upto 300 wires. My initial design was quite simple. Feed the wires 5V and connect them to multiplexers. The AVR can address the mux and test each line to see if its high. If its high, the wire is good to go. In my "back of the envelope" design I chose to use 10 32-channel mux.

Of course, addressing each would also take 50 pins in itself - not practical. But I could address each using the same pins - that is, I could wire them in parallel. So if I set mux 1 to select line 12, the rest of the 9 mux also do that. The uC can then check to see if all these 10 lines are high - if so, they are all good to go.

However, I also need to check to see if two lines (or more) are short circuited. Obviously, this means that I'll need to make sure that the only the line being addressed is high. How can I ensure this? To my understanding, I'm going to need some sort of device which can switch voltages for lines.

I thought of using a demultiplexer to switch the 5V onto the wire being tested. So suppose wire 'B' is being tested - the uC would switch 5V onto wire 'B' and then run through all wires to see if they are high. If only the other end of wire 'B' (i.e. B`) are high, then the wire is good.

What would be the best way to approach this problem? My ultimate goal is to test the entire wiring harness and then display the errors (or lack of) on a 20 x 4 LCD.


texts: When should the AC resistance of a diode be taken into account in a practical circuit?

texts:
In many circuit design examples I see the diode drop is taken constant value such as 700mV. And I also know that for amplification and small signals transistors are used as discrete components.

Here AC resistance is explained under the name of "Small-Signal Diode Model and Its Application". Yes I can understand the math behind the AC resistance of the diode here. But what is the application here? I mean maybe SPICE programs take care of the AC resistance of diodes, but when one designs a circuit does he really take this into account?

I'm wondering when can the knowledge of AC resistance of a diode comes into scene in a practical circuit design. When would you need to consider this when you have pen and paper and a circuit in mind? What can be the examples?

edit:


texts:
I want to prove that a voltage signal I apply in the primary of an ideal transformer(or 2 coupled coils) will produce the same voltage signal in the secondary, e.g. a square wave(+- V) in the primary yielding a square wave in the secondary by using the fact that V=L*(di/dt).

So let´s suppose I have a square wave generator. At the moment the square wave reaches +V then V=L1* (di1/dt) and the current I1 in the primary ramps up linearly, causing then V/(L1)*t = i(t), and that means (di1/dt) = V/L1.

This increasing current will then create a magnetic field B= k1 * i(t), where k1 is a constant and the induced voltage in the secondary is going to be V2= -(d(phi)/dt) = - k1 * (di1/dt) = -k1 * (V/L1).

The outcome shows the secondary is going to have the same wave shape signal as the primary, which in this case is a square wave. So assuming I have a V(t) applied to this ideal transformer, the secondary signal is going to be the proportional to this V(t).

Finally, my question is: Can I prove the secondary signal will be alike the the primary by the way I did above? Which is by using the inductor formula V=L*(di/dt)?


texts: Why voltage drops when I short a battery?

texts:
When I short an AA battery, I have observed that it's voltage drops a couple hundred millivolts and when I break the short, its voltage starts to "replenish" at a decreasing speed.

What is the reason for this behavior?


texts: Question about magnetic field induction and AC generator

texts:
Since electromagnetic induction (faraday's law) is described as inducing a current why then would you need to be grounded to receive an electric shock? Since current is already present?

If say (use your imagination) a giant copper coil being spun in a magnetic field (an AC generator) was floating in the air, and had small copper lead attached also floating in the air, and then you were holding onto this (you are also floating) would you not get fried by the induced current? If the magnetic field and spin were fast and strong enough?


texts: How to determine sinusoidal steady state response from bode plot

texts:
I'm given a problem by the following:

Find the sinusoidal steady state response (in the time domain) of the following systems modeled by transfer function, P(s), to the input u(t). Use the Bode plot (in Matlab bode.m) of the frequency response as opposed to solving the convolution integral of the inverse Laplace transform.

$$
P(S) = 11.4/(s+1.4), u(t) = cos(5t)
$$

I'm a bit confused by the question because I thought bode plot is the definition of steady state response, but it's asking me to find it in time domain. Is such thing possible? Anyways plotting this in matlab gives me the following:

$$
Y(S) = P(S)U(S)
$$

where from laplace transform

$$
U(S) = s/(s^2+25)
$$

Y =

           11.4 s
  -------------------------
  s^3 + 1.4 s^2 + 25 s + 35

Continuous-time transfer function.

>> bode(Y), grid

This doesn't look like a typical bode plot either (Maybe because output is third order?) What can I infer from this representation of bode plot?

Edit: So this is a bode plot for just P(s)

At w = 5, it seems like the phase of -75 degrees and magnitude of 7db

Since magnitude in db, the final steady state response in time domain is

$$
Y_sss(t) = 2.24cos(5t - 75^{\circ})
$$

Really? This simple?


texts: Is an unenclosed cable modem circuit board a fire hazard?

texts:
I've come up with a clever hack to save space and reduce # power adapter eye sores by bolting my cable modem (Netgear CM500) under the Wifi router (WRT 3200ACM).

The heat sink over the Broadcom baseband processor is very hot to touch. I measured ~70C for the processor and ~55C for the RF (de)modulator enclosure (had to set mode to glossy or else readings for shiny surfaces are wildly underestimated). Modem consumes 8W max.

As clever as it seems, I was worried if there's any fire hazard or other problems if I were to let the heatsink lie on top of a a wood surface or carpet.

I had a read some of this guide,

https://incompliancemag.com/article/electrically-caused-fire-in-multilayer-circuit-boards/

and the main take away was that for fire, it had to generate a temperature beyond the ignition temperature. But I didn't see any way to calculate the
 temperature. That would be a function of the power density and thermal resistance of the heating element.

Also, it said to distinguish between normal conditions and fault conditions.
Normal condition of ~70C already feels worrisome.

But most developer boards for embedded platforms are unenclosed. I guess they would've thought about fire hazards also?


texts: What form for Transfer Functions to use for filters and Bode plots?

texts:
I've seen some different forms for the equation of a transfer function and wonder which one is most correct and why? Does it depend on type of filter etc.?

Let's take an example and its transfer function: $$H(w)=\frac{V_o(w)}{V_i(w)}=\frac{R_2jwL}{R_1(R_2+jwL)+R_2jwL}$$

With some algebra you can get it on two different forms:

\$H_1(w)=\bigl(\frac{R_2}{R_1+R_2}\bigr)\frac{jw}{jw+\bigl(\frac{R_1R_2}{L(R_1+R_2}\bigl)}\$ where \$\frac{R_1R_2}{L(R_1+R_2)}\$ is the pole (and \$jw\$ is a zero?).

\$H_2(w)=\bigl(\frac{L}{R_1}\bigr)\frac{jw}{1+j\Biggl(\frac{w}{\bigl(\frac{R_1R_2}{L(R_1+R_2)}\bigl)}\Biggr)}\$ where \$\frac{R_1R_2}{L(R_1+R_2)}\$ is the pole (and \$jw\$ is a zero?).

\$H_1(0)=0\$, \$H_2(0)=0\$, \$H_1(\infty)=\frac{R_2}{R_1+R_2}\$ and \$H_2(\infty)=\frac{R_2}{R_1+R_2}\$.

Questions:

They are clearly the same (if I've calculated it all right), but which form is most correct and standard to use? Does it differ from type of filter, i.e low vs. high pass etc.? It seems easier to use \$H_1\$ to read of the constant \$\frac{R_2}{R_1+R_2}\$ as \$w\$ approach \$\infty\$, although I've seen the form av \$H_2\$ more often and it seems standard two try to get a "\$1+...\$" in the denominator?

Thank you!


texts:
I want to know total noise I am feeding into ADC and I have learnt about Opamp Noise and resistor noise thanks to this forum.
Now I want to know the contribution of resistor in my overall noise due to 'current noise' of Opamp and for that I need to find equivalent source resistance which I can just multiply with Current noise to get voltage noise (am I right) and also the equivalent feedback resistance through which this noise current is flowing to get voltage noise due to it.
I read somewhere that equivalent resistance in a wheatstone bridge is nothing but the value of a single resistor but only if all resistor are of same value and my case doesn't seem to fit the criteria, the wheatstone bridge I am using is SM5652 pressure sensor.
what will the equivalent source and feedback resistances in this case?


texts:
I try to design a board with an ARTIX-7 FPGA. There is a big question that which pin of FPGA should I put an oscillator?
I inspected a document about clocking the 7 series xilinx FPGA (7 Series FPGAs
Clocking Resources
) but I still don't know what should I do, because I saw a design of a kintex-7 and is had been put various oscillator with different frequancy.

What is the difference between MRCC and SRCC pins?

I'm thankful if someone can help me!


texts:
I have an +- 10V/1A sawtooth signal that needs to be clamped to gnd when a trigger pulse is received.

The signal is supposed to stay clamped until the next zero crossing, upon which the circuit is supposed to reset.

I thyristor would be ideal, if it did not have an on state voltage of typically 1.2V.

The voltage needs to be clamped below 400 mV, less is better.

The transition open -> clamped needs to be faster than 500 ns, preferably much less.

simulate this circuit – Schematic created using CircuitLab

Is there anything like a thyristor/triac (or a drop in replacement circuit), but with a much lower on-state voltage (below 400 mV)?

Edit:
I came across a few devices I wasn't aware of. Doesn't help with my problem, but might be useful for someone else:

Programmable unijunction transistor (Von voltage not clear from datasheet, maybe 500 mV + IR, obscure component)
Silicon bilateral switch
http://www.farnell.com/datasheets/239125.pdf
(IC version of a triac, Von = 1.7V, Main advantage is very precise switching voltage)


texts: is it posssible to make a 4-bit up/down asychronous counter using jk flip flops, xnor gates and nothing else?

texts:
the image below is supposed to represent the last segment of the circuit, where the 'updown' input would change the direction of the counting: when updown=0 it counts backwards (f,e,d,...1,0,f...) when =1, it counts upwards (0,1,2,...e,f,0...)

yet i am even strugling to design one with two bits. i have tried different variations of the circuit below but none seem to work the way it has to

note that i am only allowed to use j-k flip-flops (74LS112) and XNOR gates (TTL 74266)
could someone give me a hint or something because i am in severe pain


texts: Reed switch sensitivity/Strong magnets for 6 ft detection

texts: Can I detect magnetic field from 6 feet distance using Reed switch ? Do I require very strong magnet for it ? I can have low AT Reed switch for more sensitivity but detecting distance of 6 feet should I have strong magnets ??


texts:
We installed some TVs in the main floor of our facility. We have personnel here from 8am until 12am, and the TVs have been set to turn on at 7am and off at 1am. Sometime during the day, YouTubeTV asks "Are You Still There?", and the video is paused during this prompt. Suspecting the remotes are bound to get lost, they aren't left out for someone to acknowledge the prompt, and eventually the app stops and the TV screensaver takes over.

Can I record, on an oscilloscope, some key presses from the remote with a photoresistor, and play those back with a small circuit? We have sections of drop ceiling in our facility. I could place the circuitry above the ceiling tiles close enough to the TVs, and still maintain line of sight.

Pressing the up arrow shows the video progress bar. Without any interaction, that goes away after ten seconds or so. I think replaying the up arrow once an hour would be sufficient.

The IR blasters I've seen only replay incoming signals from a remote, not pre-recorded signals.

If a device like I describe already exists, can someone tell me the terminology to google?


texts: combinations of binary digits for decimal numbers

texts:
Four bits are required to represent the ten decimal digits, and since there
are 2^4 combinations of four binary digits, six combinations are not used and the code is
said to contain redundancy.
The four binary digits can be allocated to ten decimal digits in a purely arbitrary
manner and it is possible to generate 2.9 • 10^10 four-bit codes, only a few of which
have any practical application.

Can anyone explain the second point?


texts: How to simulate adjustable 'negative resistance' with active components?

texts:
I'm building a decade resistance box using 2W resistors, from 10x1M ohm to 10x0.1 ohm. However, due to some contact resistance, the 0.1 to 1 ohm resistance will likely turn out to be ~1.1 ohm to 2 ohms (the rest of which will be in a tolerable margin of error). Is there a way I can 'offset' the ~1 ohm of wiper and contact resistance with some active components, with an adjustable potentiometer for fine tuning?

I'm thinking -1 ohm +/- 0.5 ohms ought to do, and ideally it would handle up to 2W just like the other resistors. Is such a circuit possible?


texts: Why is my buck regulator based on LM22679 limiting current way under the set limit?

texts:
I have a LM22679-ADJ based buck converter. The output voltage is set to 24V. The input voltage may vary from 28-40V DC. The current limit is set to above 5A according to the graph given in the datasheet. Here's the schematic:

*The values of R1,R2,R3,R4 were incorrect. Actual values used were 47k,47k,5.1k,1.8k.
The R7 resistor is set to 6.8k to set load limit at just above 5A. And one of the inductors is shorted. Diodes used were Schottky type as advised in the datasheet.
Significant observations:

With a load of 25 ohms the waveform across D1 becomes distorted, and the device starts limiting current, when measured across the diode D1 only when the input voltage is above 31V.
When I add another inductor in parallel to the one in the circuit thereby reducing the inductance to ~2.3uH, the input voltage at which the output voltage drops out of regulation increases, however, it is not completely gone.

The following are the images of the DSO under different circumstances, all measured across the diode D1 and load resistance fixed at 25 ohms.
Case 1: Inductance 4.7uH. The max input voltage at which output is not distorted(~31V). Output voltage is regulated and current is not limited. This is whats supposed to happen.

Case 2: Inductance 4.7uH. But input voltage increased to 35V. Although output voltage is very close to set voltage, the waveform doesn't make sense. What is supposed to happen is the square wave is supposed to reduce its duty cycle. But this happens instead.

Case 3: Inductance halved to 2.3uH. Input voltage at 35V. Note the change in waveform. The output voltage is still being regulated at 24V.

Case 4: Inductance 4.7uH. Input voltage increased further to 37.5V. The output voltage completely drops out of regulation to about 17V. To reset the IC from this state, either the load must be removed or it must be reset at lower input voltage. Simply reducing the input voltage to where it previously used to regulate output does not make the IC regulate output again. There is a hysteresis of some sort.

Case 5: Inductance halved to 2.3uH and input voltage at 37.5V. This time, the output does not drop out of regulation. But the waveform is still weird.

I have calculated the output inductor value as per the datasheet and it came out to be 9.6uH for max input of 40V and output of 24V. But, with both inductors in series, the output dropped out of regulation much sooner than in the above mentioned cases.
This is the datasheet.
Questions:

Why is the wave form like this and not a square wave like the first case at higher input voltages? (and what is the role of the output inductor in this)
What can I do do that my regulator does not drop out of regulation for the max input of 40V?

Thank You.
EDIT:
@csabahu I had the chance to take some measurements today.
At 10uH,200uF,25Ω the IC drops out of regulation at input of 32.2V
At 4.7uH,200uF,25Ω the IC drops out of regulation at input of 36.2V
At 2.3uH,200uF,25Ω the IC drops out of regulation didn't drop out of regulation for 40V. But I tried a load of 16.7Ω and it certainly did drop out of regulation.
Halving output capacitor value had no significant effect on above measurements.
I also tried increasing the inductance value to about 24uH. At 100uF and 25Ω there was no dropping out of regulation. Further, the ringing due to what I'd presume was discontinuous mode operation was completely gone even at 40V.(Which is to be expected I suppose) This also holds for 16uH at similar conditions. However, at increasing the load to 16.7Ω the IC immediately goes into current limit. What was interesting to note here was that the IC seemed like it was skipping cycles. And the waveform did not resemble the DCM operation. The frequency was lower than the standard 500Khz.
I removed the 6.8k R7 current limit resistor, but this had no effect on any of the above measurements.


texts: How do I calculate battery life allowing for duty cycle?

texts:
I have a battery rated at 2610mAh.
The device it's powering transmits to the network for 35ms during this time it uses 1.95mA of power. the rest of the time the device draws 0mA. I want to workout how long the battery would last in seconds.

Here's what I've done to calculate this. I'm not too sure if I've done it right. First I converted the 2610mAh (battery rating) into mA seconds:

$$2610 \cdot 60 \cdot 60 = 9396000\ mA \cdot s$$

Then I calculated how many mA the device uses each second:

$$\frac{1.95}{35} = 0.055714 mA/ms \cdot 1000 = 55.714 mA/s$$

Now I use the formula \$t=\frac{C}{I}\$:

$$\frac{9396000}{55.714} = 168647s$$

Is this the correct way to do this?


texts: I am building a circuit that has 5, analogue output, temperature sensors(LMT85LP) connected to an AD converter (MCP3208-CI/P), two of the sensors are located aprox. 50 meters(164 feet) away from the AD converter and the rest of the circuit (raspberry pi 3, etc). The cable is Cat5. Sensors output current is ~7mA. All will be powered by raspberry power out 3v3 pins. Note that the AD converter will be located next to raspberry, only the sensors will be away. Such distance is viable? And if so the readings are reliable?


texts: Read the state from an LED in a MCP23017

texts:
I read already this 2 questions:

Read state from LED in another circuit

Read the state of a 12v illuminated switch from an Arduino Uno

and I can read the state in a MCP23017 controlled by an NodeMCU V1

I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

And I need to get a reading of a 1 or a 0 for each LED that its ON or OFF , This is my code:

#include <Wire.h>
#include "Adafruit_MCP23017.h"

Adafruit_MCP23017 mcp;

int value = 0;
int total = 0;

void setup() {
  mcp.begin(0,D2,D1);

  for (int a = 0 ; a <= 15; a++) {
  mcp.pinMode(a, INPUT);
  mcp.pullUp(a, LOW);  // 100K pullup internally <- I tried commenting it out and changing it to HIGH
  }

}

void loop() {
  total = 0;
  for (int a = 0 ; a <= 15; a++) {
    value =  mcp.digitalRead(a);
    Serial.print(value);
    total += value;
  }
  Serial.println();
  Serial.println(total);
  delay(200);
}

All I get is either: LED on and off but the reading is 0 (or 1 if I use the pullup option)  or I get the LED light but the reading is always 0.

Is there any difference on having an arduinio or nodeMCU directly or is there something I need to do to make it work?


texts: Can I safely put a 9 volt battery across 12 volt auto battery

texts: To change out my automobile battery some sites say, to save auto memory devices, I should procure a gadget using a 9 volt battery which you hook up to the auto battery cables just before you undo them -- so there I no interruption to the computer and auto accessories when you take out the 12 volt auto battery. At the moment of the disconnect of the 12 volt battery there is for a short time a 9 v0lt battery across the terminals. Is this a safe situation?


texts: I am attempting to have an Arduino interpret an AFSK signal, this is very vague but can anyone just point me in the right direction for detecting the frequency of the AFSK signal with an arduino?


texts: How to switch 220 VAC? (Magnetic relay, SSR relay or triac)?

texts:
I want to switch 220V AC with a microcontroller. Before I used magnetic relays or SSR relays, but now I want to use a triac for this function (like in this circuit) and my load can be any 220 V AC object. The reason is, triacs are cheaper, smaller and have more ability for high currents than magnetic or SSR relays.

1) Please guide me at the choice between magnetic relay, SSR and triac.
2) Someone told me that triacs for switching AC current creates noise. Is this correct? And what is the solution?


texts: How to increase a transformer's primary voltage rating?

texts:
I want to know if there's a way to operate a normal (250 VAC primary rating) transformer at higher primary voltage levels, as I have an AC voltmeter project using a microcontroller (currently using Arduino Uno), with over voltage detection.
The controller will perform a specific task for undervoltage case, a specific task for normal voltage case, and a specific task for high voltage case (>250 VAC rms).
I have accomplished the voltage detection using a simple circuit shown below, in which, the output DC voltage has a certain mathematical relation with the input AC voltage.
But my only concern is whether the 250 VAC (rms) primary rated transformer will survive high voltages (upto 400 VAC rms). If not, what are the ways that can help increase the primary voltage rating. For example, combining 2 transformers, or anything?


texts:
I've build this circuit (that will be part of a more complex circuit):

All works as expected and on the zener I have exactly 15 V rectified.
Later, one day after, I've discovered that even with the AC power (230V) disconnected on the C1 capacitor there were about 5 residuals Volts.
For this reason I've short-circuited the capacitor with the purpose of completly discharge it.
This, probably, was my big mistake because after that the circuit stops working and I've discovered that the bridge rectifier was irrimediably broken and shot-circuited.
Frankly I don't understand why this it happened and how to improve my circuit to prevent a similar event in the future.
Any idea?
Thanks in advance.
ADD: Reading all replays an comment I suspect that the circuit is not so good. Neverthless, I've forgetted to say that before that the bridge rectifier broke down, I've connected an oscilloscope probe across the zener and by this way I could see that there was a residual 5V voltage on the capacitor. I don't know if that can explain what is happen...

I've a significant update to my issue.
After I've added the bleed resistor and replaced the fried bridge rectifier, than I've replugged the AC power and all seemed to works fine too.
I've connected the multimeter and all measures are right.
At this point I've connected the oscilloscope probe and puff... the bridge rectifier was fried too.
The oscilloscope is a Tektronix TBS1000C Series, brand new, just purchased and works fine even after the issue described.
Nevertheless I've a suspect.
The circuit that mount the bridge rectifier is connected to the power wall outlet (230V) while the oscilloscope is connected to an APC Smart UPS.
All like the following layout:

I don't know if this could be the reason of the issue and, especially, why.
Any other idea?


texts: Does it looks like a bandpass matching network?

texts:
I am trying to understand this receiver and figure out what does this L-C network is.

I read about matching networks and found this example, I am curious if it is the same thing. is it?

In the datasheet of SYN531R it says
two components for the matching network, and two components for the pre-selector band pass filter, what is the
matching network made of (C2, L2?) and what is the pre-selector band pass filter made of (C1, L1?) ?


texts: what is the German/Austrian nomenclature(Voltage and current direction) in electronic circuit?

texts:
AS I came from a country where we use the french system in defining the voltage current arrows in electronic circuit, I am confused about the German/Austrian system where I see the voltage arrow is directed from positive to negative and this makes me confused when it comes to analyse complex circuit especially with diodes and mosfet. any clarification is more than welcome

here one of the circuit if I use the German Terminology


texts: I have a schematic in kicad that I have finished working on and would like to begin laying out the PCB. I attempt to generate the netlist for PCBnew, I click generate, I select an output directory, then the annotation window pops up and I select to keep the current annotations. Then nothing happens. There is no netlist file in the output directory, nor do I get any errors that would indicate that something wrong has happened.


texts: Correct location of header file for arduino sketches

texts:
I have NewSoftSerial.h and NewSoftSerial.cpp in the same folder as my sketch.

The sketch is thus.

#include <NewSoftSerial.h>

int incomingByte = 0;   // for incoming serial data
NewSoftSerial bluetooth(2, 3);

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);   // opens serial port, sets data rate to 9600 bps
  Serial.flush();
  //enter command mode
  Serial.println("$$$");
}

void loop() {
  // send data only when you receive data:
  if (Serial.available() > 0) {
    //read the incoming byte:
    incomingByte = Serial.read();

    //say what you got:
    Serial.print("I received: ");
    Serial.println(incomingByte, BYTE);
  }
}

What am I doing wrong that I get these errors?

  trainremotesketch.cpp:1:27: error:
  NewSoftSerial.h: No such file or
  directory trainremotesketch:3: error:
  'NewSoftSerial' does not name a type


texts:
I recently started to play with online circuit simulator and in a very simple circuit I can't understand the behavior

I have a voltage source connected through a current limiting resistor to a diode and an inductor in parallel. As far as I know, a diode should behave like a short circuit when its anode is connected to the positive terminal of the voltage source. In this simulator something very strange happens: as I close the switch, a lot of current passes through the diode (and very small amount through the inductor) and after couple of seconds no there is significant drop of the current through the diode until it stops completely. Why is that?

link for my circuit in the simulator: Link (click on the swtich to close it and watch the simulation)


texts: Why is power reflected when there is an impedance mismatch?

texts: I understand that when there is an impedance mismatch between an output stage, for example from an amplifier, and an input stage, for example, a transducer; power is reflected. I would like to know why this occurs, and what happens to that reflected power?


texts:
What is exactly meant by output compliance of a current source? I've read that it's the range of voltage over which the current source behaves well. What exactly does behaving well mean?

I've got a little problem based on this concept, but Im not sure how to go about it.

You have +5 and +15 volt regulated supplies available in a circuit. Design a 5mA npn circuit source(sink) using the +5 volts on the base. What is the output compliance?

How would you do this?


texts:
I have to do a project involving a common emitter amplifier. The only given data is: the amplitude of the input signal is 100u, and offset voltage is 0.

I need that signal to be amplified. But my circuit won't amplify the signal, instead it will add offset voltage or even attenuate it.

What have i done wrong? Any ideas how to dimensionate the elements ( if that's the problem ) ?

Circuit was made in OrCAD Lite 16.6.


texts: Is it possible to control DC-DC boost convertor by N-ch MOSFET @ Vin-?

texts:
With the widely available DC-DC boost ready built modules based on MT3608 chip can I control it by adding the N-ch MOSFET to the Vin- line like this:

The module itself are pretty reference in design similar to this:

Module load are COB LED +12V light. +Vbat are Li-Ion power which also powers the MCU through 3.3V LDO and I want to enable/disable module & LED from MCU.

PS: I know the DC-DC IC has the ENABLE pin, but it's hard wired to the Vin+ on board and I don't want to deal with cutting traces.

I'm also aware it's possible to control LED by adding MOSFET to the LED GND line but this way the module will be always powered up and I want to save battery power by turning it off completely when not used.


texts: I want to know can I take two opposite directions of current in mesh analysis or I am bounded to take the direction of current same in mesh analysis

texts: I want to know that in mesh analysis can we take the direction of current in different ways means in two meshes can we take on current direction in clockwise but other will be in anticlockwise.


texts:
I have a rigid PCB and a flex (4 layer) PCB. I want to bond them instead of using a connector (although if what I am expecting is impossible I will use a connector).

What methods are available for bonding a flex to the surface of a rigid PCB? Can we back them with solder like an SMT component and then bake them?


texts:
I'm going to use ethernet cable as a long range cable for serial (5v) and power (5V and 16V, almost no A) and I remember reading that because of the loops in the wire and the impedance effect some pairs were best for data and others for power. I doubt it would make much a difference for my case, but i'm still curious :)

I'm searching the heck of it but can't find anything useful on that end.


texts: Connecting wall power supply (primary) in parallel with alkaline/NiMH batteries (backup)

texts:
Interested to learn if this is a bad idea and why.

Specific case...

I have battery powered wireless doorbell receivers.
They run on 2 AA batteries (e.g. ~3VDC with alkaline or 2.4VDC with NiMH).
The problem is that every time the batteries run out I have to do a little "reprogramming" dance after inserting the new batteries.

Since these receivers are stationary and near outlets I figured I could just take the batteries out and solder in a 3VDC wall-wart supply.

However anytime these are unplugged or there is a power outage, they would need to be reprogrammed.

So I was thinking...if I leave the Alkaline (or NiMH) batteries in there then theoretically the wall supply (3VDC) being higher...the batteries wouldn't discharge unless unplugged...then they would function as a backup so I don't have to reprogram the bell if I unplug it temporarily.

Originally I was thinking of just leaving the NiMH in there since they are rechargeable anyway...but with a constant 3VDC applied to them it might kill them in short order (would require some type of charging management circuit I guess)?

Then I was wondering what the consequence would be if I left alkalines in there (low self-discharge compared to NiMH).  Their full voltage should be around 3VDC...but if they discharge a bit then their voltage drops off pretty quickly and I am not sure what happens at that point if they have 3VDC applied across them.

Interested to learn as well as have recommendations about what to do or not do here.  Thanks.


texts: How to make LTSpice sub-circuits available globally?

texts:
LTSpice Hierachy block can not be found if it is not in current working directory.

I am using this tutorial to create sub-circuits in LTSpice:

http://www.audio-perfection.com/spice-ltspice/hierarchical-blocks-in-ltspice.html

Everything is fine except that the sub-circuit that I make can not be used globally. Every time that I have a new design I must copy my sub-circuits to the directory that my top-level design resides.

I even moved my sub-circuit (both .asc and .asy files) into a folder under E:\Program Files (x86)\LTC\LTspiceIV\lib\sym but LTSpice can not find it. I suspect there must be a directive such that includes a folder into the global search path (or top-level search path) but I can't locate the option.

I appreciate if you tell me how to make LTSpice sub-circuits available globally?

Update:

This is my inverter_035_1.asc:

Version 4
SHEET 1 880 680
WIRE 208 -96 208 -160
WIRE 272 -96 208 -96
WIRE 208 -80 208 -96
WIRE 160 -32 80 -32
WIRE 272 -32 272 -96
WIRE 272 -32 208 -32
WIRE 80 32 80 -32
WIRE 80 32 -16 32
WIRE 208 32 208 16
WIRE 448 32 208 32
WIRE 208 48 208 32
WIRE 80 96 80 32
WIRE 160 96 80 96
WIRE 400 96 208 96
WIRE 208 176 208 144
WIRE 400 176 400 96
WIRE 400 176 208 176
WIRE 208 240 208 176
FLAG 448 32 out
IOPIN 448 32 Out
FLAG 208 -160 VDD
IOPIN 208 -160 BiDir
FLAG 208 240 GND
IOPIN 208 240 BiDir
FLAG -16 32 in
IOPIN -16 32 In
SYMBOL nmos_035 160 48 R0
SYMATTR InstName M1
SYMATTR Prefix X
SYMATTR Value2 W=1u L=0.35u
SYMATTR SpiceLine ""
SYMBOL pmos_035 160 -80 R0
SYMATTR InstName M2
SYMATTR Value2 W=3u L=0.35u
SYMATTR Prefix X
SYMATTR SpiceLine ""

And this is my inverter_035_1.asy:

Version 4
SymbolType BLOCK
LINE Normal -16 32 -16 -32
LINE Normal 33 0 -16 32
LINE Normal -16 -32 33 0
LINE Normal 64 0 44 0
LINE Normal 0 -48 0 -21
LINE Normal 0 48 0 22
LINE Normal -16 0 -48 0
CIRCLE Normal 44 5 33 -5
PIN -48 0 NONE 8
PINATTR PinName in
PINATTR SpiceOrder 1
PIN 64 0 NONE 8
PINATTR PinName out
PINATTR SpiceOrder 2
PIN 0 -48 NONE 8
PINATTR PinName VDD
PINATTR SpiceOrder 3
PIN 0 48 NONE 8
PINATTR PinName GND
PINATTR SpiceOrder 4

Both files reside in a sub-folder under E:\Program Files (x86)\LTC\LTspiceIV\lib\sym\


texts: Fan speed switch: why OFF :: HIGH :: MED :: LOW?

texts:
Many AC fans, including inexpensive floor models, have a rotary speed control which rotates from OFF to HIGH to MED to LOW.  Since the switch does not rotate 360°, you have to rotate it backwards to shut it off.  This has always slightly annoyed me, because it appears to make no logical sense to have to speed the fan up to turn it off.

Why are the speed settings from fastest to slowest? This design seems counter-intuitive, but I assume there is a good reason because the design is so common.


texts: What is the maximum current that can pass through my pcb?

texts:
As I been learning electronics I been creating custom PCBs instead of using solderable breadboard like this one.
On my design I am planing to turn on and off a motor with a a relay that uses 12 volts @ 15 amps. (180 Watts). My PCB looks like this:

The thick (0.11 inches of width) blue pads is where I plan to pass 15 amps of current. That is the reason why I made them extra thick. Will it be safe to use this thick pads @ 180 watts? Where can I find a rule that states how thik the pads are and how much current they can use?
Edit
I should had done more research sorry. Your comments answer the question. I need 2 oz of copper when building my pcb. That increases the price by more than double though. I will solder cables on the back of the pcb instead of using 2 oz of copper as I am only using one relay in my whole PCB. The blue thick pads will also have wires soldered on the back I will just have to solder 3 cables.


texts: Why does lumped discipline not hold as dimension approaches operating signal wavelength?

texts:
I'm studying some basic introduction to the lumped matter discipline on my own. I completely understand where the first two constraints come from (i.e. lumped matter can only interact through their terminals, which is consistent with KVL and KCL), however, while  I do understand what is meant by the last constraint, I don't feel like I get the full picture!

Here is a quote from the book I'm reading:

  The signal timescales must be much larger than the propagation delay of electromagnetic waves through the circuit.

This part is pretty trivial, since the propagation of em waves is finite we have to agree to choose a large enough timescale to allow propagation to happen. (right?)

Then the author states this rule in another way. This is where I loose it:

  Put another way, the size of our lumped elements must be much smaller than the wavelength associated with the V and I signals.

My question is, if all electromagnetic wave travel at the same speed, then why does wavelength matter? Said another way, why is it that as circuit or component dimension approaches wavelength this rule does not hold? (I'm  really keen on knowing the why, the underlying logic, and physics behind it.)

My best guess at the moment is that because if the circuit is smaller than wavelength it will be in the first cycle of the wave and thus can be treated as equal along all point on that circuit. Am I correct?


texts: Batteries connected both in series and in parallel

texts:
I am confused.
Some sources say that connecting batteries in series also doubles the amperage (not only voltage) while maintaining the same mAh rating, while connecting them in parallel only increases the capacity mAh, while other sources say the amperage remains the same.

To put it simple, say I want to power an electrical motor that is 48V/1000W.
I will first need to connect 12 (3.7 hi-drain 20A 3000mAh li-ions) in series output 44.4V / 3000 mAh.
But since the motor drains 20.8Amps and 3000mAh means the battery can provide 3 Amps per hour, this essentially means the battery will get drained for what. 7 minutes? On max power.

This means I will also need to connect some batteries in parallel, to provide more capacity. So if I connect those 12 batteries in parallel with another battery.. does this make 14 minutes?

Edit, according to this, two batteries connected like that output 6A.
If measured separately they are 3A.


texts: Sharing a single ground wire across multiple RTDs

texts:
Consider the following, simplified schematic for a single, two-wire RTD sensor:

simulate this circuit – Schematic created using CircuitLab

The two wires from the RTD sensor plug into pins 1 and 2 on J1. A bridge is used, consisting of resistors R1, R2, and R3. U1 is an LTC2418 24-bit low-latency ∆Σ ADC (but the specific ADC should not actually matter for the purposes of this question).

There is nothing strange about pin 1 on J1: that connects to the positive (+) wire from the two-wire RTD (RTD1_P). However, pin 2 on J2—the negative (−) wire from the RTD—connects straight to ground, instead of to RTD1_N.

I am told that this circuit works properly. Is that claim correct?

If so, it implies that multiple RTD sensors can be added (using additional channels on the ADC), with all RTDs connected to a shared ground (pin 2 on J1). Thus, for n RTDs, only n+1 wires are required on the external connector, rather than n×2. This is a significant advantage for my application. Again, is this correct and feasible? And if it is, what are the limitations (if any) involved in doing it this way, as opposed to a more standard configuration that is fully differential, requiring n×2 wires?

(Nota bene: I understand that RTDs can also be connected in three-wire and four-wire configurations, as described here and/or on Wikipedia. I understand the limitations/compromises involved in selecting a two-wire configuration. For the purposes of this question, please assume a two-wire configuration.)


texts: Example of stable non minimum phase system with negative gain or phase margin

texts:
I read in a particular book that the fact that gain margin and phase margin are positive implies stability is only true for minimum phase systems. But, for non-minimum phase systems, system can be stable even with negative gain and phase margins

Can you please given an example of a non-minimum phase system, which is stable but has a negative gain margin or phase margin


texts: Selecting AVR microcontroller with or without PicoPower?

texts:
I have been using ATTiny13 DIP AVR's for a few years, for very simple projects. I'm now expanding and switching to surface mount devices.

I'm a little confused about some of Atmel's offerings; let's take one example, the ATTINY26.

Specifically there are so many variants of this that I have no idea what to select. If I select non-reel SOIC, I'm left with three choices:

ATTINY261-20SU: 20MHz, 2.7-5.5V
ATTINY261V-10SU: 10MHz, 1.8-5.5V
ATTINY261A-SU: 20MHz, 1.8-5.5V (PicoPower)

Based on these, is there any reason I would not want to select the newer "PicoPower" (1.8V) capable AVR? I realize that the clock speed decreases with less power. In my application, I do not need to take advantage of the lower power operation. Since the cost for small quantities is similar, there's no real advantage that I can see to selecting the slower 10MHz version.

Bottom line, is there any reason to opt for the older and/or slower (first two listed) rather than the newer low-power version?

Edit:

PicoPower on this device is 1.8V, not 0.7V. (I must have misread part of the datasheet.)


texts: What is application of latch in VLSI design?

texts:
I went through the documents stating difference between latch and flip flop. I even came across the scenarios where unintentional latches are created in RTL designs.

My doubt is there any real application for latch?


texts: Issues with using higher capacitance than required

texts:
http://www.digikey.ca/product-detail/en/stmicroelectronics/LD1117V33/497-1491-5-ND/586012

I am planning on using this regulator for a home project. I noticed on the datasheet that a minimum 10uF capacitance can be used. On the design diagram, they also have a 10uF listed.

What is the downfall of using a 22uF capacitor instead of the 10uF recommended capacitor? Is there a downfall at all? It is just a minimum recommending but I can go higher if I wanted to?

Thank you!


texts:
How to put all components in schematic sub-sheets in higher level sheet room in Altium Designer?
I want a few channels of my mulit-channel design to go into the same room to ease parts placement and layout.  Basically, I've got 48 channels of LED drivers and I want to put them into 12 rooms of 4 channels each.  I jumped through a bunch of hoops to have a repeat block on the highest level schematic that repeats 12 times.  Then the sub-sheet has 4 sheet symbols with links to the lowest-level driver sheet.
No amount of messing with the Project Options/ Class Generation tab gives me 12 rooms with 4 channels each.  I can get 48 individual channels each in a room or no rooms at all depending on if the 'Generate Rooms' box is checked for the lowest level schematic.  Checking the generate rooms box for the sheet with the 4 sheet symbols in it doesn't do anything.
Copy/ Pasting 4 identical versions into the 4 channel sheet seems terrible (even before having to manually change the reference designators).  Is there a way to do this?
Here's a link to some of my thoughts on rooms from a previous SE post.


texts:
I'm stuck with an exercise and would appreciate any hints.

I have to calculate the impedance between the points A and B:

So what I got is (starting from the right):

2L + (2R || R) + (3C || 3C)

but I don't know how to deal with this bridge-like 2C and C capacitors.

I don't expect a solution from you guys, just a hint how to do it.

Thanks!


texts:
I'm trying to control my headlights with my Arduino and a LDR. For this I will use the Arduino as a middle man between the lights switch and the actual lights.
The switch has three positions OFF / DAYTIME LIGHTS / HEADLIGHTS.
The switch itself is a potentiometer and has 3 cables: 12V, GND and the signal one.
The Arduino then would read which setting is chosen in the switch, decide what to to do, and send the signal thru this cable.

The problem comes here. The Arduino, as far as I know, can  only handle <= 5V. So how am I supposed to read the switch, and then send a signal back to the car?
(I suppose that these signals would be around 12V or so).

Sorry if I'm not explaining so well. Not very experienced in electronics.

EDIT

I have measured the voltages across the three cables (WHITE/GREEN/BLACK), assuming black as ground.

When engine is off:

White = 23-25V

When engine is on:

Switch == off

White = 28.5V

Green = 30.3V

Switch = daylights

White = 0V
Green = 30.3V

Switch = headlights

White and green = 0V

From this I wouldn't know what to do. Thought the switch worked like a potentiometer but I think I am wrong.

Also I am trying to find a logic answer of why both white and green have 0V when the lights are switched on.

EDIT 2

I found the part online, and its name is "WELLS SW6250", a combination switch. I thought that, because of the white and green cables going 0V when the lights are turned off, that there might be another cable coming from the square part of the knob, where there are other connections.


texts: Protect a micro controller even on mistakenly connected

texts:
I am basically a computer engineer and having only basics in electronics and electrical field. I have also searched for the solution but it looks, it would be better if i ask it to experts here...

Micro-Controllers are designed to work only if the input characteristics are met. If wrongly connected, it may damage the board.

What i am trying to achieve is ( OUTPUT ) :

Say i want to accept Point A as Positive Pole, Which goes to VCC
Say i want to accept Point B as Ground Pole, Which goes to GND
Say i want to accept Voltage accross A and B should be 5V

As to the INPUT :

User has two wires coming from DC Battery 12V
User has two points : Point X and Point Y for connecting these two wires
No matter, however user connects two wires coming from DC Battery 12V to Point X and Point Y ( May be + or - to Point X and remaining to the Point Y)

How should i design a circuit which takes above X and Y as input and Produce A and B as output 5v across, So that i can save the micro-controller even if end user mistakenly connects positive and negative wires. Thanking you so much in advance.


texts: How do I make the document parameters in Altium visible?

texts:
I am currently using a student license for Altium and I am trying to edit the "title" and "drawn by" parameters in my schematics. However, I am unable to do so due to a locked visible option when editing a document parameter.
Does anybody know how to unlock this so I can make my parameters visible?


texts: What is the expected output of an LVDS IO cell of an FPGA (or just simulation) when the P and N pad inputs are both the same logical value?

texts:
I am curious what, in general, the output would be of an LVDS signal when both inputs are the same voltage level.

So if the truth table is:

P  N | Y
0  0 | ?
0  1 | 0
1  0 | 1
1  1 | ?

What would be 00 or 11 in terms of logic output? My assumption would be X (undefined) in sim and either no change or 0 in the real-world depending on the chip.

The reason I ask is because there is a tool I am using (logic equivalence checking which randomizes inputs and flags this as an issue in LEC). However, this a case I would not worry about because its LVDS and I would expect the chip to operate normally when powered on. Also, the issue occurs in RTL and not the gate-level output from PNR, so it seems to me the issue would not propagate X's throughout the system. I may be able to disposition this or dig into the tool's options to constrain the LVDS inputs as differential to perhaps skip this case.


texts: DDR4 differential pair routing guideline

texts:
I have a question about the DDR4 trace routing on the server main board.

For clock and DQS signals, are they both considered differential signals?

I checked the Intel PDG; it shows that two specs for the impedance control on these signals.

In one table, it specifies the single-ended impedance spec.
In another table, it defines the trace spacing between P/N trace. Does anyone know why the spec defines the single-ended impedance for the differential pair?
Why not just define the differential impedance?

I also saw a spec for clock and DQS in another layout guideline. It says that the trace of these signals should be routed as a "pseudo differential pair",
which means that we should first consider one trace as single-ended (here the spec defines 50 Ohm), and then try to meet the spacing as in the spec.

Again, why should we define the single-ended impedance for a differential pair?


texts: Should I connect a cable's shield to the ground layer of board when it's isolated from earth?

texts:
I have a controller board powered by DC that may or may not be isolated from earth ground. The chassis of the device is non-metallic.
This board connects through a long (30-40m), shielded cable to a small sensor board. The sensor board does not electrically connect to anything else, and is also housed in a non-metallic enclosure.

I know the usual "best practice" recommendation is to connect the cable shield to ground at only one end, and this recommendation makes sense when that grounding would be to a conductive, earthed chassis. Any noise induced on the shield would be shorted to earth and be kept away from my sensitive circuits.

However, in my case there is no conductive chassis, no separate earth wire connection to the system, and even the ground return of the DC input to the system may be earth-grounded or it may be battery powered (and thus completely isolated from earth). Does it still make sense to connect the shield to the ground of my circuit in this case? that would mean connecting it to the signal-ground layer (as there is nothing else)... I worry that any noise induced on the shield would just couple more effectively to my circuit through the suggested connection to ground. I'm essentially connecting a huge antenna to my circuit...

On the other hand, I heard everywhere that a completely unconnected shield is as bad or even worse than no shield at all.

So, what would be a good grounding scheme in such a situation?


texts: Custom HDMI-to-( TFT or LVDS ) decoder/driver

texts:
I am working on a custom-made handheld PCB based around a PI Compute Module 3+ and one of the hardest steps I have found is how to include an HDMI-to-50pin-TTL driver on my PCB to run an LCD TFT 7" 1024x600 IPS panel. First I have not found any available open-source driver board, either TTL, LVDS, or parallel RGB. The only alternative I have found is the Adafruit TFP401 board, but it is only compatible with Adafruit's low-resolution 40pin TTL screens. Higher resolutions TTL screens often come with 50 pin connectors. Also, I know the pi's MIPI display connector is closed-sourced and only works with pi's expensive and low-resolution screens.
In summary, do you know any open-source HDMI-to-TTL or LVDS driver PCB design I can use for my project? If so, could you also share the schematics and compatible list of screens available for this driver? Thank you.
Maybe I am looking at it from the wrong perspective. If you would have to add an LCD driver to your custom PCB, how would you do it?


texts: Constant Current Led Driver (non dimmable) to work with PWM

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I have 18W lamps that came with non dimmable led drivers. Ive found datasheet for the main chip (ws3441), which included schematics:

and internal block scheme of the chip:

I'd like to add dimming controlled with PWM - 1024 levels. I already have PWM part ready - used 6W lamps before successully. They also came with non dimable led drivers but I replaced power adapters to one one 20V with enogh power, which was not sensitive to the shorts in the circuit made by MOSFETs controled by microchip. For 18W lamps I cannot find right power adapter - 70V / >2A. Anyways, I plan to mount those lamps in different rooms so one adapter will not be enough. The best solution would be to make use of those drivers that came with lamps.
I've read a bit and searched over internet for solution, found few interesting topics, two of them below:

link 1
link 2

but I dont know how to get use of that information to resolve my problem.
Basically Im taking following solutions into account:

somehow disable current sensing and make it fixed (led driver will only be used with this one kind of lamp) so PWM can work properly,
maybe using additional transformer like shown here would be solution?

Here are photos of the driver:


texts: Will this shottky diode circuit protect my ADC, and if so, are there options with more than 2x channels?

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I am trying to read 8x 12VDC digital inputs and 4x 5VDC analog inputs with my 3v3 Teensy 4.0 Microcontroller. In V1 of my design, I used a voltage divider circuit to drop down to 3v3.
I would like to ensure that if my input sees more voltage than intended I do not damage the inputs on the Teensy, especially as this is an automotive application and power is notoriously bad. I have come up with this design based on Analog's application note and using the BAT54TW Shottky array and was wondering a few things.

will this work as I think, and protect any input from higher than 3v3?
If so, is there any additional protection/filtering I should add that I don't have?
Would this same design work with my 5VDC analog inputs as well?
Are there larger Shottky arrays that I could use? I'll just use 6x BAT54s if I need to, but would prefer a denser solution.
It appears as though the RuggedDuino uses single zener diodes per input and is rated up to 30V input, would that work just as well in this circumstance?

Edit: the inputs I am dealing with are as follows:

1x RPM input, digital only, 300Hz signal, read with interrupts
5x digital 12V inputs for things like ignition status, fans being on, etc. Not timing critical at all.
4x analog 5VDC pressure sensors. Only need to sample every ~250ms max.
2x 12VDC analog battery inputs. Needs to be able to take a max of 18VDC and be able to read it, then clamp anything over that. Also not timing critical, same 250ms max is fine.

Right now I am using 12x voltage dividers for these signals and it's functioning, but I know it's not safe, and the RPM needs a lot of cleanup on it as well.
Edit 2: Based on the answer from @Jeffrey, below is the revised schematic using zener diodes instead of shottky, as well as re-integrating the voltage dividers. Here is the schematic:
However, according to CircuitLabs the values of the passives don't seem to do what we want.

With only a 10nF cap and 17kΩ resistor for R2 we get a little closer, but I feel like that defeats the low-pass filter.


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Hi guys i have a very simple question, im very new to electronics so keep that in mind.

I got an off brand  lm2596(eboot brand from amazon), and could not find the datasheet for it. I found datasheet from TI and it looks like the "lm2596" is only a simple 5 pin chip. They also show a typical use circuit on that datasheet requiring more external components.

Now my lm2596 came on a board with all those components, so my question is: Am i good to go and hook up the lm2596 to an arduino and a 12v battery or do i need any extra components?

This is the module i have:

This is the link for the datasheet, the first circuit is what i am referring to:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.ti.com/lit/ds/symlink/lm2596.pdf&ved=2ahUKEwiEkcn7-OvYAhUEWK0KHbURA2gQFjAAegQIFRAB&usg=AOvVaw3AmyKYZtlGT_fs-tvh6iL2

Thank you.


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I was porting Arduino library ps/2 mouse to pic and I wondered why pull high works when declaring the pin as an input and then making it high and that worked for pic and Arduino alike, but when I declare the pin as an output then write high, I didn't get the acknowledgment right.

Why does pull high require being an input?and why software writing to an input work?


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Consider the following circuit:

(notice the 20 diodes in the feedback loop). If I analysed this correctly, the output from the common-emitter amplifier is just the input signal but inverted and with a gain of (10/1) = 10. In order to forward bias the diodes, I would need 20*0.6=12 V of output from the op amp, but it is connected to a 10V supply.

From this, the feedback loop must be cut off and so the output signal is just directly connected to the output of the common-emitter amplifier. Therefore, I immediately guessed that the output is just an inverted signal with a gain of 10 but the answer sheet to this problem says that the output is 0. Can someone point me in the right direction on why my analysis was flawed?


texts: Microcontroller internal Clock frequency tolerances

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I am having this microcontroller - S32K142 64 Pin 5V Core voltage
Microcontroller Reference Manual
I want to use the FIRC and want to see the frequency tolerance of the FIRC.
Can someone help to find how to find the frequency tolerances of the internal clocks? Like SIRC, FIRC and the clock that can obtained after the PLL?
I couldn't find the frequency tolerances of the internal clocks


texts: Is a N-Channel Mosfet save/reliable for level shifting UART from 3V3 to 5V?

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I am busy with a design that needs to connect a Raspberry Pi to an Arduino via UART.
Previously I have designed a circuit that worked okay.

(source: protoneer.co.nz)

But now I want start using SMD components and is planing on using the following component: BSS138BKS + 10k Resistor Bank.

I am not an expert at these things and I am usually use designs from other circuits in my new designs.

My question is, will the BSS138BKS used like in the original setup with the 2N7000 be able to run continuously without issues.

And is this the right way to do level shifting between the two devices? (I don't want to damaging the boards).

Edit: Updated circuit


texts: I'm working with the Amphenol ZTP-101T thermopile to get IR temperature measurements and I'm confused since the thermopile voltage seems to range between -1 and 5 mV at ambient temperature of 25C (page 3 of datasheet). What would the output voltage range be if the ambient temperature dropped? Would the whole sensitivity graph just shift left until the ambient temperature corresponds to 0mV thermopile output? I'm guessing that if the ambient temperature is 0C, a 0V reading would no longer mean 25C object temperature.


texts: Using a voltage divider and an N-channel MOSFET to switch an Arduino input pin from a EL2008 Beckhoff digital output module

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I need to switch an Arduino input pin (0-5 V, max current is 40 mA) from an EL2008 Beckhoff digital output module (+24 V HIGH, 0V LOW, max output current of 0.5 A) using the circuit depicted below. I have not tested the circuit outside of simulations.
Would it work as desired?
That is, if I connect the source to the Arduino's pin would it

Switch the pin
Not damage the Arduino
Will the resistors burn up from the power being dissipated?

Please note: I am using Vcc from the Arduino as the drain-to-source voltage. Additionally, I've used a battery of 24 V and 48 ohm internal resistance to mimic the HIGH state (@ 0.5 A) of the EL2008 Beckhoff module.

N-Channel MOSFET: IRL520N
Resistors: 1.5K Ohm and 390 Ohm (both 1/4 W)


texts:
I have circuit as below,

*

Because the input source for D1 is ground, I for D1 is zero. Both diode have forward bias of 0.7V. The equation to find I for D2 is 10V - 5(I for D2) - 0.7V - 10 ( I for D1 + I for D2) = -10V . Am I right? Thanks.