texts: DC motor. No load current variation with Temperature

texts:
Having a DC motor datasheet where the manufacturer normally provide current consumption and speed Torque for No_load and "Locked rotor".

I have found 3 different ways to calculate the motor current consumption at no load.
Which one is more correct?
Some definitions:

I0 = Current consumption no load.
I0T = Current consumption no load. At a diferent temperature
Is = Current consumption Stall.
W0 = Speed no load.
W0T = Speed no load. At a diferent temperature
K = Motor constant
KT = Motor constant. At a diferent temperature
V = Voltage applied to the mottor.
VT = Voltage applied to the mottor. "At a different temperature" (At diferent conditions of the voltage defined in the datasheet)

Case1. Consider it does not change with the temperature.
This looks really wrong, but I have seen examples, as this one
Case2. Somehow consider that the product No load current and no load speed remains constant over temperature.
$$I0_T=I0*\frac{W0}{W0_T}$$
In that case, W0T was calculated as:
$$W0_T=W0*\frac{K}{K_T}*\frac{V_T}{V} $$
Case3.
Consider that I0 is caused by a friction torque MF which does not change with the temperature and can be defined as:
$$M_F=K*I0$$
So at the new temperature
$$M_F=K_T*I0_T $$
In that case, W0T was calculated as:
$$V_T=Rm_T*I0_T+W0_T*K_T$$

simulate this circuit – Schematic created using CircuitLab
Thanks


texts:
I have a piece of code that I don't understand:

always_ff @(posedge CLK)
state <= RST || ~A[0]===1'bx || ~A[1]===1'bx ? 0 : nextstate;

A is the input. What is this piece of code exactly doing? What is ~A[0]===1'bx or ~A[1]===1'bx?

My guess is that this code is checking if either one of the inputs aren't valid (1'bx). If one of the inputs aren't valid, we jump back to the starting state 0.

But why the negation in ~A[0]===1'bx?


texts: Measuring high voltage low current using a resistor and measuring the amps

texts: Is it possible to measure a voltage beyond what your multimeter is capable of measuring by measuring the amps providing you know the resistance? Just wondering if the voltage would still harm the meter.


texts: I'm currently looking at a new application and found out the customer has no neutral but has a three phase 208v supply, Is there any possibility or any suggestion of how I can get a Neutral?


texts: trying to find or make a very light/small chip (rfid, bluetooth, etc) that can send its location to a cell phone if lost

texts:
I was wondering which technology would be better suited to the goal I am trying to achieve. What I would like to do is embed a chip in an object and by using a cell phone, prompt the chip to send me information on its location.

I know there are chips that are now put in cats to help to track and find them if they are lost. I am trying to find a chip that is very small and light that can help me find it if it gets lost in a maximum 25 foot radius.

Initially I looked into RFID tags for this but cell phones don't have readers in them and the readers are too costly. I have started looking into blue-tooth and have gotten a little befuddled with the details. My education is in medicine, I would very much appreciate any ideas anyone may have.


texts:
After spending too long on the Bluetooth SIG (Special Interest Group) and other websites I still have no idea what is required for selling a Bluetooth enabled product so I'm hoping someone here has more experience.

I'm using a Bluetooth module that is certified and meets all needed regulatory requirements.  I could care less about using the Bluetooth Logo.  Does this mean I don't need to list and declare (e.g. give the Bluetooth SIG a bunch of money)?

Please note this question is purely about Bluetooth SIG compliance and not about regulatory compliance - I am all set there.


texts: Proper method to filter inputs of a (true) differential ADC

texts:
In datasheets of different true differential ADCs I noticed two kinds of  a low pass filter at the inputs. First one with 2 capacitors to the ground

The other with a capacitor between differential inputs:

So what is the proper way to place a filter at the inputs? When each (or perhaps both) of these filters should be used? in general at first ?
And now for my case where I have DC signals as input, so a filter would be used not for antialising, but rather for bandlimiting the input noise? I guess it is not a good idea to try to bypass the inputs of the ADC?


texts: Electronics System Standards Compliance: Certification, Testing & Verification

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Please note: this question has to do with the technical compliance aspects of the consumer electronics indsutry, and as such, I believe is within scope for this site. This question is about compliance, and Compliance is absolutely a qualitative aspect of engineering/design.

An engineer has a great idea for some electronics gadget, say, a "Widget 5000" (W5K). It doesn't really matter what a W5K is or what it does (!).

This engineer designs a prototype for a W5K and forms a startup. He/she obtains funding for the startup and now needs to make sure that the production version of W5K is compliant with all necessary standards so that it is safe for real-world, production usage (the prototype/proof-of-concept is anything but production-grade).

Perhaps W5K is not only an electronics device, but perhaps it uses radio communication. In this case I'm sure the FAA wants to make sure it won't interefere with air conrol traffic, etc. Perhaps the W5K is also used as a medical device, and so it must conform to certain medical technology standard, such as IEC 6061 and/or others.

Companies like UL offer a vast range of services for testing, verifying, validating and certifying electronics.

What I'm hung up on is: how does our engineer know exactly which of these services he/she must utilize in order to safely sell the W5K on retailer shelves?

I would imagine that all sorts of entities want to have a say in the matter:

Retailers/Marketplaces - I would imagine many Retailers won't carry your product unless it is certified by one of the big name companies (again, like UL, etc.)
Insurance Carriers - I would imagine carriers won't even sell our engineer various policies (General Liability, Professional Liability, etc.) unless the W5K meets similar standards
Court Systems - If our engineer's startup gets sued because one W5K caught a customer's house on fire, I'm sure court systems look to see if W5K met certain standards, and take that into heavy consideration when making a ruling
Federal Agencies - I'm sure various agencies (FAA, etc.) want to make sure the W5K is safe and compliant for various obvious reasons
Professional Associations - Perhaps there are Professional Associations or Consumer Electronics Associations that simply won't have anything to do with our engineer's startup if the W5K doesn't meet certain compliances
...and I'm sure I'm missing many more!

After reviewing the play, I think this type of decision comes down to protecting yourself against 3 scenarios:

The startup is sued (by anyone for any reason) and you want to make sure your counsel is armed with the right supporting documentation to prove you did everything in your power to guarantee safety, so as to minimize the chance you lose the suit. Such an effort is made easier if the product's certification(s) cover the nature of the suit; and
The startup is sued (by anyone for any reason) and you lose. In this case you will file a claim with your carrier to pay the amount of the suit, and you need to make sure the carrier can't deny the claim because you didn't have the correct certifications; and
A state and/or federal agency launches an investigation into your product, finds out that you are not legally compliant with a standard that you are required to be compliant with, and fines/sues you.

I know there's no silver/magic bullet here. But what I'm asking is: what is the process by which our engineer can go about determining what standards he/she must make the W5K comply with? I'm sure there are industry-wide best practices for making this type of decision...


texts: Keeping the output of a heated LM317 constant

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I have built a power supply using an LM317:

simulate this circuit – Schematic created using CircuitLab

When the supply is on for a rather long time (several hours) with a respectable load, the output voltage increases in the order of several hundreds of millivolts. I think this is because of the warming up of the LM317. I already have a heatsink, but the IC is still getting hot, especially with a great load and a long on time, of course.

I was wondering if there would be any way to make some kind of protection to make sure the voltage doesn't change too much. I've thought of these options:

Adding a PIC on a separate 5V supply which monitors the supply and beeps when it changes too much. This might be an overkill for such an easy problem.
Adding a PIC and make R2 a digital pot, so that I can digitally set the output voltage, and the PIC takes care of the rest and automatically changes the resistance on the adjust pin when the output voltage changes. Again, an overkill, and I don't want to have a lot of work for this.
Something with a comparator, but that gives a problem with that the supply is variable. I'm not sure how I could work this out with a comparator...
Bigger heatsink, better placement, adding a fan - would probably work indeed, but I feel like there should be an electrical solution (i.e. with adding a circuit) and I'd like to see that solution.

So, what would such a solution with a circuit look like?

Here are two photos of my setup:

First, on the right: the heatsink with the LM317
First, on the left: the board with R2 somewhere
Second, bottom: the two pots (5K and 500) that are R1 together


texts:
I am currently taking the Nand2Tetris course online, where I am in the process of building a virtual computer all from nand gates. I have learned what an ALU is, how it works, and build a simple virtual one myself.

Now I would like to make my own physical 8 bit ALU from simple 74(HC) series IC's. I have experience in building electronics and using the IC's, on a hobby level. My only real problem is that I don't know which functions to choose for my new ALU. In the virtual ALU I build there are input x and y, and 6 functions:
- zero x
- not x (bitwise),
- zero y,
- not y (bitwise),
- f (0: x AND y 1: x + y),
- not(bitwise, on everything).

I am going to build a whole whole computer, so i could of course just for example add multiplication with software later, but I would probably like to have more hardware functions. From my research i found out about in- and decrementers, left/right shifting, other "full" multiplying/dividing circuits and of course more logical implementations. But i have no idea what functions are needed/useful to have in an ALU, and what is a good balance between hardware and software implementations.


texts:
I have an SAR ADC to measure the RMS value of an AC signal. My present method is to use a timer to trigger the conversion and store the conversion result. When I've sampled a whole cycle of points, I subtract the DC level (the average of all points) from the signal then use the well-known RMS algorithm to get the RMS value.

I wonder if there is any method to "distribute" the calculation work to samples. For example, if I need to calculate the mean value of the cycled signal, I can add the conversion result to a global variable "sum" after a conversion is done. When the conversion of the last sample is done, I only need to divide the "sum" by the sample count. In this method, I only need one global variable, there's no need to store all the samples. But for my RMS measurement, what is difficult for me is that I need to subtract the DC level, but the DC level can only be gotten after I've done a whole cycle sampling.

I think you can understand me. Any suggestion is appreciated.

Update:

Thanks for all you who have gave me answers and suggestions. And some answers are acceptable for me. After some searching and thinking, I've an ideal too. But not very sure.

As known,

$$
V_{RMS(total)} = \sqrt{V_{D}^2 + V_{1RMS}^2 + V_{2RMS}^2 + \cdots + V_{nRMS}^2}
$$

Assume a perfect whole cycle sampling, and omit the higher harmonics,

$$
V_{1RMS} = \sqrt{V_{RMS(total)}^2 - V_{D}^2}
$$

So, I can use running-averaging to get \$V_{D}\$, and running-rms to get \$V_{RMS(total)}\$ (without removing the DC), then finally do a subtraction and sqrt to get the RMS value of the fundamental wave signal. Certainly, there will some error when my sampling is not a perfect whole cycle one.

I need someone to confirm this, thanks.


texts: Utility of Node Analysis in Designing Circuits Step-by-Step

texts:
Question: Does node analysis have any utility when designing a circuit step-by-step, or must the entirety of the circuit be known before node analysis is useful? Here's an example to illustrate what I mean.
Suppose that I have a 12V power supply, but I only want to have 6V across my lightbulb. So, when I go to design a circuit, I think through the steps I want the circuit to take:

Reduce the 12V to 6V.
Send those 6V across the lightbulb.

To tackle step 1, I decide that I will use a voltage divider. Thus, I build the following circuit:

If I perform a node analysis on this voltage divider alone, then I will find that I do indeed have the 6V that I was seeking at my output node. However, when I move on to step 2, I'll find that my circuit will not work because I neglected the fact my lightbulb has some resistance. (We'll say 100 ohms.)

Now, when I add my lightbulb, there will only be 4 volts across it. Thus, it seems that my previous node analysis was unfruitful because I had yet to determine all of the components of my circuit.
Yet, it seems that, in most literature, node analysis is performed on "incomplete" circuits. Does this imply that node analysis can still be useful before a full circuit is determined? Or is it just a shortcut taken to avoid wasting time with extraneous information?


texts: Avoiding oscillations in a unity gain voltage buffer circuit

texts:
Assume I have an output stage that is supposed to drive a load about a hundred meters away, connected with a cable.  So what I have is a capacitive load.
My output stage is a simple non-inverting voltage follower, as simple as it gets, but with the resistor R3 on the output to isolate the feedback "network" from the capacitive load (out-of-the-loop compensation).

(1)

Now there's this solution to fight oscillations, an inverting voltage buffer with unity gain and C1 across R2:

(2)

I also found the non-inverting voltage buffer equivalent (but with a gain of 2):

(3)

Just as you need two resistors for an inverting voltage buffer for unity gain, you need them both with the C2 across R2, resulting in (2).
You don't need two resistors for a non-inverting voltage buffer for the unity gain case, resulting in (1).
I've skimmed through dozens of application notes and articles, but haven't found a single example of a non-inverting unity gain voltage buffer that tries to avoid oscillations. How can I modify (1) to avoid oscillations in the same way (2) and (3) work? I need a non-inverting unity gain voltage buffer.

I have also seen the following very simple circuit recently, for driving symmetric lines:

(4)

This has me wondering why the unity gain voltage follower (U1) has only the series resistor at the output (but no capacitor in the feedback path), and the inverting voltage buffer (U2) has a capacitor in the feedback path, although they both drive a capacitive load.

Update:

I found ST's application note AN2653:

http://www.st.com/web/en/resource/technical/document/application_note/CD00176008.pdf

Figure 21 and 22 on page 12 show exactly what I was searching for. Now the problem is that this "solution" doesn't work at all in my ngspice simulations. The result is the same oscillation I get with (1), regardless of the value(s) of \$R_{IL}\$ and \$C_{IL}\$.


texts:
A throwie is a small LED attached to a coin battery and a rare earth magnet.
In quantity, they are used for creating non-destructive graffiti and light displays.
Singly or in small quantities they are just fun.
You use them by throwing individual LEDs onto (ferromagnetic) metallic objects.
By throwing LEDs onto an object, the object itself acts as a canvas.

Throwies usually consist of a CR2032 or pair of CR2016s with an LED held across the battery with tape and a strong magnet.  Very simple, no current limiting resistor, easy for kids to assemble. Lots of fun.

What are the properties for a good throwie LED?

Good things, possibly in order of importance:

Safe (no exploding or burning batteries, LED can withstand being thrown, etc)
Bright
Cheap
Omnidirectional light
Different colors
Lasts a long time (days great, a few hours minimum)

While I know there is no right answer, I'd like to know the properties to look for and a range of the values that would make a good throwie.


texts: How can I test TCP/IP AT-Commands with server?

texts: I'm currently using SIM868 to make a GPS tracker, I wanted to know how  to test tcp/ip protocol with a server. I do not have a server but got a website and a wifi connection(DIR-600M Router) , Is there any way I can use a virtual port listener or something to test the communication?


texts: How to control proportional valve (pvq13-5l-03-m5-a) with arduino

texts:
I would like to know how to control this specific proportional valve with arduino.
The valve operates with a constant 12V and driven by current of a range of 0-170mA.
Could you help me with what components and circuit diagram I would require to operate this valve and
I have tried to PWM a mosfet (IRF520N) in which the output of the mosfet was connected to the valve. I also had 12V coming straight from a power supply however I didn't got it to work.


texts: Controlling DC Motor with stepper driver

texts:
I only have a stepper motor driver TB6600 available at the moment, can I use it for control of a a brushed dc motor? I think it should work as I could use PWM. I also want to be able to reverse direction. I looked through the datasheets and online tutorials but I could not find out how to connect the pins and what mode to select.

My question: Is it possible to control a dc brushed motor with TB6600, and if yes, how?


texts: Can anyone tell me why the control system designers do not prefer pure derivative controller? Instead they use something called a Pseudo derivative controller. What is this Pseudo derivative controller and how does it has an edge over the pure derivative controller?


texts: Need feedback for a PCB design (digital/analog synth)

texts:
Ok so I'm designing a synth using the NES sound chip (AY-3-8910). After poorly designing a PCB for it and testing it, I realized there is noise from the MIDI input bleeding to the audio output.
I read a lot since then and trying to do a somewhat acceptable design this time.
So, different parts of the circuit:
A: Power supply input
B: Analog audio part (EQ and output amp)
C: MIDI input and output (VERY NOISY section!!!)
D: AY-3-89-10. The IC that receives bus data from "1" beneath it and generate audio output to B.
E: Microcontroller (atmega328), buttons, leds, pots, everything digital.
I took a "separate grounds" approach, and I bridged together the ground when there was signals going from one section to another, as you can see in "1", "2" and "3".
One of my concerns is the two traces marked as "2", those are the MIDI input and output signals and are very noisy, I mean they irradiate interference.
The arrows are pointing the power traces directions, all coming from the power section.
There are a lot of connections missing, but wanted to sort this out first.
What do you think??Thanks for your time!!!! :)


texts:
Suppose I have a simple full wave bridge rectifier, with resistive load. Is capacitor ripple current a charging or discharging current? Or maybe it is an avarage/RMS of any current flowing through a capacitor?

On a picture below red is capacitor current, blue - line voltage, yellow - output voltage.


texts:
1000BASE-T uses all 8 wires in a twisted pair to both RX and TX at the same time. It does it using (what seems to me) a complicated process known as echo cancellation. Details here.

1000BASE-TX dedicates two pairs (four wires) in a Twisted Pair to TX only, and the other two pairs to RX only. Conceptually, this seems far simpler to implement and work with than the alternative.

My question is, why did 1000BASE-T become the de facto standard for Gigabit Ethernet? Why not implement the (apparently) simpler standard of 1000BASE-TX? Why didn't 1000BASE-TX gain more popularity than 1000BASE-T?

Wikipedia had this to say about it:

  However, [1000BASE-TX] has been a commercial failure, likely due to the required Category 6 cabling and the rapidly falling cost of 1000BASE-T products.

But I was hoping for a more detailed explanation, or maybe alternative reasons entirely.


texts: How can I increase the base-emitter voltage of an NPN transistor in forward active region?

texts:
For a project which involves amplification, I think I have to increase the base voltage, keeping the emitter voltage the same so that my circuit will not go out of forward active region as the amplitude of my input signal is higher than usual like 5V.
I know that when an NPN is biased in the forward active region, the voltage between base and emitter is like 0.7V which is the turn on voltage, but I need to make it like, let's say, 2V.
Is there any way to do that?
The reason I am asking is that output to base of BJT is so much and base voltage cannot be higher than emitter voltage at all times which is concerning and I would resolve this.
The circuit with beta = 300


texts: With LPC1343 (ARM Cortex M3), how to control the the initial state of the MAT output from the timer?

texts:
I know that when the timer match the M1, I can let the mat pin to be up, down or toggle. But how to control the initial state of the MAT pin?

I'm using LPC1343CodeBase on a port1343 experiment board.

It's a for a simple non blocking servo command. Period is 20ms. Output should be HIGH for 1 or 1.5ms then LOW for the rest of the period.

I use prescale to have ms long duration with the 16 bit timer. M3 is triggering the reset.

I have an imperfect solution: using PWD and being LOW for (20-1)ms and up after that.


texts: Magnetic Monopoles and Magnetic Current Densities

texts:
I see that in electronic engineering the Maxwell equations are written with also some terms which represent the magnetic charge and the magnetic current densities. I was told they are inserted only to get symmetrical equations since they physically do not exist.

enter link description here

But, how can this operation be correct, since it is and arbitrary addition of not physical terms? It is like modifying a correct physical law by adding arbitrary terms to one member: it is a correct operation if and only if these terms are 0.


texts: High voltage drop over output diode sepic converter

texts:
I made a SEPIC converter please see the wiki for the scematic:
https://en.wikipedia.org/wiki/Single-ended_primary-inductor_converter

Observation:
The output is 12V 2A max. When I use a scope I see the diode is conducting for about 2/3 of the time when there is a 20V input voltage.

I reason:
the current trough the diode, when the diode is conducting, would be about 2A/(2/3) this is about 3A.I did try different kind of Schottky diodes like the STPS15L60C. When I take a look at the data-sheet they specify a voltage drop of 0.62V for 7.5A for one diode (there are 2 diodes in the package I use them both parallel).

I measure:
(1) a voltage of 1V across the diode when Voltage in is 20V (diode conducts 2/3 of the time and,
(2) a voltage of 1.2V across the diode when the input voltage is 8V (diode conducts 1/3 of the time).

According to my reasoning, this diode voltage drop seems way too much. I want to get rid of this problem as the diode is getting too hot. Can someone please tell me what's wrong with my reasoning?

Regards.


texts:
I want to remove solder mask in particular area for mount a TO220 package.

As shown in below image I want to mount the 7805 using a M3 nut and need to remove solder mask only in covering area. (like a thermal pad)


texts: Should a TVS be connected from board ground to chassis ground?

texts:
My PCB gets DC power from a connector, let's say the traces coming from the connector are VIN and RTN. I have a TVS (for ESD protection) between VIN and chassis ground. Should I put another TVS between RTN and chassis ground? RTN becomes board ground after it and VIN pass through a common mode choke. If a TVS is needed on RTN, what reverse working voltage should it have? As low as I can find?

Edit: I can make this question simpler. I know I should put ESD protection (like a TVS) on signal lines that exit the enclosure and even on power lines. But what about ground lines? I am using a bleeder circuit between 'ground' and 'chassis ground' so they are not the same. When they ESD gun the ground line, will it cause ripples on the board ground planes without a TVS?


texts:
I have an "interesting" circuit failure. The circuit basically looks like

simulate this circuit – Schematic created using CircuitLab
The left branch works perfectly fine. The right branch turns on and initially works, but after a few seconds flickers unpredictably and then eventually goes out. When this happens, R2 drops most of the voltage and D3 and D4 basically fail short. Turning off the circuit, waiting a bit and trying again produces the same behaviour.
In its failure mode, D3 and D4 always fail together, and D1 and D2 always keep working.
Aside from the LEDs not working, this is a bad thing to happen because U1 is a port driver on a PIC that is only rated to drive up to 100mA. For details on this port see the PIC16F1773 datasheet sections 11.3.8, register 11-17, and electrical limits in 36.1.
When disconnected from the circuit, D3 and D4 present the exact same voltage on a diode tester that new diodes do - a little north of 1.8V, and produce the same dim light that good diodes do when tested.
Why could D3 and D4 be failing-short at the exact same time, and why is it unpredictable? Is it due to some kind of thermal runaway? These LEDs are supposed to be able to handle 50mA and had not been driven up to that current - until of course they fail short, at which point they see more.
Edit: Mystery solved.


texts: My scope detects a 50Hz signal when the probe is not connected to a circuit, is this normal?

texts: Having no prior experience with scopes, it seems strange to me that when the probe is not measuring anything (~ not connected to a circuit) it measures a small 50Hz (~ my mains are running at 230V 50Hz) signal instead of some random noise. Is this normal behaviour (my scope is a Rigol DS1052E)?


texts:
I am currently trying to replace a broken potentiometer in a therapy device ("KMI Hand mentor"). It is a 5k* potentiometer in plastic case/knob and comes in a through-hole version. The length of the shaft is 10mm and the actual package is approximately 90mm x 10mm x 5mm. Any equivalent form factor will work even if the resistance is different. The markings on the PCB just identify KMI and not the potentiometer. The white piece on the top (Figure 1) off the potentiometer can be pulled off (Figure 2).

So far the closest thing I've found is this:
http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK09Y11/RK09Y11_list.html

Any help identifying the manufacturer of this component would be appreciated.

Note: This work is being performed in an academic context, and the device (if fixed) will only be used for prototyping (not re-deployed).


texts:
I have a need to sometimes manually turn the lead screw on a stepper motor controlled CNC system (which I have not purchased yet). So IF I put a switch in the wires of the stepper motor and open the switch manually, is the motor shaft free to turn with out much resistance?

Anyone???

Thanks for the answer.

The "position" of the motor and/or lead screw, is irrelevant to the motor controls. IE:

All I want the motor to do is:

Turn a "lead-screw" clockwise when I press a given button, UNTIL I release the button.
Turn the same "lead-screw counter-clockwise, when I press another button, UNTIL I release the button.
Adjust a "speed" knob, to control the motor's speed when it is moving; from very fast to very slow; and even stop when the control is completely counter-clockwise.
Turn a switch off which will remove all control to the motor; so I can turn the shaft manually without resistance, whenever I do not want the fence to be under control of the motor.

That is ALL I need. (Note: My table saw fence has an electronic "readout"; which tells me exactly where the fence is at all times. I do not need any of the motor's controls to know or show me this.)

I will watch the readout while I am controlling the motor in the above steps; and when the fence gets to the desired distance from the blade: I will stop it. I will do the above every time I want to electrically move the fence to another position.

It is that simple. Hope you understand.

What do I need to purchase? HOW do I connect the required devices (to do the above). And how do I program the Arduino to do same.


texts: Why does my NPN circuit only work with a separate power supply?

texts:
I'm trying to use an NPN transistor to switch a power supply with a proprietary connector on and off.  I can get the supply to turn on by shorting two of the pins.  In stand by one of these pins measures ~4V and the other 0V but the 0V pin does not have continuity with the ground plane.

I bread boarded a simple NPN circuit with the 4V pin on the collector and the 0V pin on the emitter using a bread board powered by a 3.3v external power supply and got it to switch on and off.

simulate this circuit – Schematic created using CircuitLab

The main supply also has a 3.3v rail that is always on I wanted to instead power my switching circuit with that but when I swap out the separate supply for the 3.3VSB power from the supply I'm trying to switch on and off it doesn't work.

What is going on here or what else can I do to diagnose the problem?


texts: With power only on this LCD, will I see anything?

texts:
If I only connect the VSS (pin 1) to ground and VDD (pin 2) to voltage, will I see anything on this LCD screen (as a test)?

Might I expect to see a cursor of some type?

Simple data sheet:
http://www.mouser.com/ds/2/178/08216h3-11837.pdf

Or do I have to send data also?
I apply 5v (up to 6v) and I don't see anything.

Also, what is Vl pin 3?
Does it need voltage on it also?

EDIT

Is there any easy way to test an LCD screen like this in lieu of connecting all data lines to a source?

EDIT 2 - success

All the great help got me there.
Thanks to @Janka and @duskwuff.
Janka, just like you said one dark row and one light row.
DuskWuff - got the pot connected to Vl and adjusting that is what made it show up.


texts: My robot's motor has begun to spin slower, but it works perfectly if I use a different adapter with more voltage.. what does it mean?

texts:
I have the iRobot, a ping pong throwing robot.

I've used it for years without any issues. At one point, my cats chewed out the original AC Adapter but luckily I had another one on hand from another device that had the same specs.

The power specs on the product's website list:

Includes: iPong® Robot, Remote Control, A/C adapter, Setup & Instruction manual
Input: 100-240V ~50/60Hz   0.6A
Output: 9V   2.0A

The label near the power port on the robot lists 6V --- 650mA

Now.. unfortunately I am not sure what the original Power Adapter had in terms of specs because it was a generic brand and I didn't label it. I do have a chewed up cable here which I believe was the one in question. This one lists

Output 12V DC 300mA

Does it make sense that the robot shipped with a power adapter whose specs are not quite the ones of the robot's requirements?

Now.. the replacement adapter that I had been using for ~1-2 year has this output: 6V DC 650mA

But suddenly about a week ago, it still runs but the motor is spinning a lot slower and basically it is now longer flinging ping pong balls.. it just doesn't work anymore. But it worked for a long time.. I got a lot use out of it. So this confused me.

I opened up the robot, cleaned the parts.. removing cat hair and dust.. added a little machine oil and put it back together.. no change. Now I don't have any power meter tools.. or any multi adapters. But today I rummaged through all my existing power supplies for other products.. looking for the ones that had a connector that would fit inside my robot and I came accross only one that made my robot work.

This adapter has this rating: Output 13.5V DC 1000mA

Now this one clerly seems like overkill.. although it makes me wonder since the original adapter I was using.. the one I believe shipped with the robot.. is a 12V adapter.

Using the 13.5 1000mA adapter the robot now works perfectly and is doing a splendid job. I didn't run it for more than 10 minute so far but it seems good as new.

Now I am trying to figure out which replacement power adapter I should be ordering online... one that will please my robot but without sending it to an early death.

Can anyone elaborate please?

Thanks much!!


texts: Output Jitter of jittery bitstream through flipflop

texts:
I have a bitstream of about 10-20 MHz coming out of an FPGA, that is obtained by Delta Sigma modulation. This bitstream is expectedly very jittery and can not be passed directly through an analog filter to restore the desired waveform.
The standard approach seems to be passing the bitstream through a D flip flop that is clocked from a synchronous low jitter clock. There are numerous PLL based clocking chips for a few $ that offer even below 100 fs RMS jitter in e.g. 12kHz-20Mhz. Achieving such low jitter in the bitstream would be wonderful.
But I am concerned that the flip flop itself will add much more random jitter. Googling for fast flipflops, I found e.g. this LVDS Flipflop NB7V52M from OnSemi. It states an RMS jitter spec of almost 1 ps, which is much worse than what some PLL Clocks offer. I suppose fast CMOS based Flipflops like the SN74AUC1G79 from TI would be even worse. On the other hand, ECL flipflops like the MAX9381 have jitter figures that are at least close (albeit still higher) higher than that of PLL Clock sources such as the Si5380A.
So Question 1: Is it possible to achieve well below 1 ps RMS jitter in the bitstream output using Flipflops? Or is it possible in another way?
Question 2: If it turns out that reclocking using flipflops does not yield ultra low jitter, then what are such clocks even useful for ? Aren't they always fed into some logic sooner or later to do actual stuff, at which point their impressively low jitter figure gets deteriorated by the actual device?


texts:
I am puzzling over this schematic, the datasheet just says to follow their recommendations exactly, and doesn't give explanation of the IC actions or circuit functions.

The lower half is easy to understand, it deals with incoming rings, and splitting and directing the signal with the bridge.

I assume that R1 and c4 deal with the received signal.

The upper right part has me perplexed though.  I assume between Q4 and Q3, one is the offhook signal, and the other the output.  R2, Q5, and R11 appear like they could be the output gain, although they tie into Q3 as well??

I really want to up the gain on this circuit, our existing church sound system install has a circuit designed around this schematic, and I find it is not fully saturating the phone system adc, our volume is too low.  The previous system we had based on a transformer had much better volume.

I have punched this into LTspice, its a little unclear at this point. Voltage on DCT gets the best response, as partially predicted by an answer below.  I have use voltage values on pins based on SI AN94.  A sine wave on DCT is the only that outputs a reasonable value.  Not sure if I have telephone line modeled correctly, but ma shown seems reasonable.
LTspice model

Datasheet


texts:
I am having problems trying to design a device with rectangular pads in Eagle:

I tried to model them has a pad enclosed by rectangles on the top and bottom layers, as described in this tutorial Arbitrary Pad Shapes:

Unfortunately I get an overlap error doing the DRC check. What am I doing wrong?


texts: Can a VHDL clocked process be written in single line?

texts:
Is it possible to write either of these in a single line in VHDL?
-- Flip-flop with synchronized reset
process(Clk) is
begin
    if rising_edge(Clk) then
        if nRst = '0' then
            Output <= '0';
        else
            Output <= Input;
        end if;
    end if;
end process;

What if we take the reset out and it becomes:
--
process(Clk) is
begin
    if rising_edge(Clk) then
        Output <= Input;
    end if;
end process;


texts: max output current on 74LS595 - how to read datasheet

texts: Hi i am a newbie and lack experience on how to read datasheet. basically, I want to find out the max current each pin can supply as I need to connect 8 LEDs to the register. any help would be appreciated.


texts: Understanding the authentication with ATSHA204A

texts:
Since there are many Chinese companies that can easily reverse engineer the PCB design and extract the .hex file out of the microcontrollers (even from the secure flash), embedded developers have to add some more protection to their products. In my case I'm using a STM32F103 and I want to add the crypto IC ATSHA204A on my PCB to protect my IP. By doing this, I'm hoping even if they can get the .hex out of the MCU and clone the board, the hex file will refuse to work if it cannot recognize crypto chip on the PCB.
This crypto IC has a unique serial number that was written while being manufactured, and it can always be read. It also has some features such as a secure area to keep some secret data, ability to generate random numbers and send it to the host via I2C or one-wire, ability to calculate SHA-256 hash of some given string and so on.
Now I am trying to understand how I should work with it as I am kind of a noob on the authentication subject. From what I have understood from reading the datasheet is, the workflow will be like this:
Personalization of the crypto IC:

The secure area in the crypto chip will be filled by the host (STM32F103 in my case) with some random secret key for each product, only once.

The secret key will also be present in the hosts flash memory.

Authentication of the board (My understanding, which is probably wrong):

The host requests a random number from the crypto-IC. Then the host generates some concatenated string with the secret key and the random number (nonce?), and calculate the SHA-256 hash of it.

Now the host should send the random key back to the crypto-IC and expect from it to generate the same string with the secret key inside of the crypto-IC and calculate the SHA-256 hash of it.

Crypto-IC sends the calculated hash back to the host and the host compares the hashes.

If the hashes match, validate. If they don't, the host refuses to work.

The workflow is probably wrong, but the main idea should be something close to it. Can anybody explain this?


texts: Eagle: Don't connect pins of the same type on a 40 pin header

texts:
I'm using a RASPBERRYPI-40-PIN-GPIO_PTH_NO_SHROUD_NO_SILK component in Eagle as part of a Hat for a Raspberry Pi. The Raspberry Pi pinout has a number of duplicate pins for GND, 5v and 3.3v. The board layout is requiring that airwires be created between these duplicate pins (e.g. all 3.3v pins must connect to each other). This is a bit redundant and it's making routing of the other airwires difficult.
Is it possible to stop Eagle requiring that pins on the header be connected to eachother?


texts: Better procedure for 'recovering'an STM32F103C8T6?

texts:
I have a STM32F103C8T6 (aka blue pill) and worked with it.

Sometimes - due a reason I don't understand - after debugging it (using Eclipse), the connection is lost and I cannot start a new debug session.

The only thing to do is the following time consuming procedure:

Close Eclipse
Start ST-Link Utility
In the menu ST-LINK/Firmware Update, selecting  button Device Connect (to see if the ST Link stick can connect).
In case of an error, reinsert it (Windows shows Unknown USB Device) and redo the previous step
In case of no error, it shows the version: V2.J27.S6 STM32+STM8 Debugger
Than on the STM32 I have to press and hold the reset button
Select the menu option Target/Erase Chip
Release the button (in time, otherwise repeating the previous step)
Than the chip is erased.
Than start Eclipse again and I can continue

This is already a very tedious operation... is there a better solution?
Or by what reason the debugging session causes the STM32 to lose the ability to start a new debugging session?

And even than in some cases I get the following error when trying to debug:

23:23:02 : Can not connect to target!
                  If you're trying to connect to an STM32W1xx device, please select Normal or HotPlug mode from Target->Settings menu.
                  If you're trying to connect to a low frequency application , please select a lower SWD Frequency mode from Target->Settings menu.
23:23:03 : No target connected

The Eclipse project configuration file fragment:

# use software system reset
reset_config none
set CONNECT_UNDER_RESET 0


texts: My TEC1-12710 peltier cell not cooling enough

texts:
I have a TEC1-12710 Peltier cell which supposedly consumes 10 Amps but when I connected to the power supply (12-15 Vdc 15Amp 180 Watt) the cell only used 4-5 Amp and didn't give me good cooling

the Cold side with sink is 15 degree C, and the hot side with sink and fan is 45 C degree and the Ambient temperature is 24-25 degree C.

I am confused on why the cold sink is not freezing as I saw in some YouTube videos!

do I need to use a PS with more Amperage to get more cold?

The hot side is not bad since the temperature of Hot sink does not exceed 45 C degree, AM I right? or need to be less!

I am feeding 12Vdc for Peltier

Thanks for all and I hope you will be able to help me


texts: Scattering parameters of a phase shifter

texts:
I connected a phase shifter to a VNA and measured S11 and S21. Upon setting the angle (phase) to a 100 degrees and measuring the phase of S11 I obtained the following graph, whereas theoretically S11=S22=0. I am having difficulties explaining this result and would appreciate some help.

As can be seen from the graph, in this waveguide TE10 is active between 6.6 GHz and approx. 13GHz. It appears to be oscillating between -180 deg. and +180 deg., yet with variations (certain angles seem to be far less than 180 deg. for instance).

As said, I'd appreciate your help interpreting these results.


texts: A PCB trace that carries considerable current (~5 Amps) needs to be wide, on the order of 4mm. I am concerned that this wide and thick (70mil) trace may cause problems during hand soldering, but can not figure out a way to make thermal relief for the pads in Kicad. It is easy for copper fills, but that would mean drawing by hand outline for each trace. Is there a less laborious way?


texts: Does this MOSFET datasheet contain missing data?

texts:
This is the datasheet of a mosfet and I have two issues:

http://www.ram-e-shop.com/ds/tr/IRFP150.pdf

First, I can not find the pinout diagram. I don't know where drain, source and gate are. Which pin is gate and which is drain?

Second, Drain-to-Source Breakdown Voltage (VDSS) = 100 V.

When I hear the word "Breakdown", I feel like it is OFF characteristic. I think if I applied more than 100V while the transistor is OFF, A damage will occur.
What I mean by "OFF" is when the gate voltage is zero (no gate signal) or when the MOSFET is reverse-biased (i.e. Drain voltage is 0V and source voltage is +100V).

But I don't know the normal drain-source voltage when the MOSFET is on. What is the maximum supply voltage or the maximum operating voltage? Is It 100V too?

Thank you very much,


texts:
Can a schematic component be created whereby a pin represents a bus (aka multi-bit) signal?

For example consider a case where you want to create a component for a 32-bit 16-to-1 multiplexer. Using a pin for each bit means that the component  will have 516 input pins (32x16 + 4)!

My current approach is to create the component as such but place it inside a hierarchical sheet since the hiearchical sheet pins can take bus inputs. Is this the only approach available in KiCad? How do other programs like Altium and Eagle approach this issue?


texts: What are the ratings of vintage Selenium Rectifier B20/16-2,4?

texts:
Sort-of a follow-up to How to ground a vintage device that was powered without a ground? in that the device is the same.

I finally took the leap and opened up the old charger (depicted in the linked question). The plan is to replace the Selenium rectifier/s by Silicon. The Se rectifiers have two marks as follows

Vertical '15360'
Horizontal 'B20/16-2,4'

Here is what I hope to find out

What is/are the ratings of this/these Selenium Rectifiers?
Should I use 1N4xxx, or 1N58xx in lieu of the Selenium?


texts: Are IR phototransistors always dark, are IR LEDs always clear?

texts:
I've been working through the "Electronic Circuits for the Evil Genius" guide and someone bought me a components kit for the guide specifically. I already have some phototransistors where the plastic is dark in color and I've seen ones before that are dark in color. Also the guide says that they are dark in color. However when I assemble the circuit, its obvious that the components provided by the kit are reversed in color. The dark plastic LED is generating the IR light and the phototransistor is in a clear plastic form that looks like an LED. I can prove this by simply removing the dark LED and pointing an IR remote at the clear part and it will rapidly flash the red notification LED.

So obviously not all phototransistors are dark and not all IR LEDs are clear. Is there a rule or is it just based on the manufacturer's decision?


texts: Reducing ac voltage from 19,2VAC to 18VAC

texts:
My trafo has  a secondary voltage 19,3V and 125 VA. I want to reduce the voltage to 18V. What is the easiest way?
Storm


texts: Why are corresponding USB datalines connected to each other in this USB hub?

texts:
Background: this is (I think) effectively a USB hub, with built in ethernet. This is the circuit as it is being used in the Raspberry Pi B rev. 2

The USB+ from the upstream port (0) is connected to the USB+ on only one of the two downstream ports (3) through a 360R resistor [seen in the very middle of the image]. The USB- is similarly connected to the same downstream port (but the - line).

My questions - why is this being done, and why to that particular port? Could it be done to the other port (2), or both of them, or none?

The datasheet for the LAN controller is here: http://ww1.microchip.com/downloads/en/DeviceDoc/9512.pdf

The whole schematic is here: https://www.raspberrypi.org/wp-content/uploads/2012/10/Raspberry-Pi-R2.0-Schematics-Issue2.2_027.pdf

The part I have taken this image from is on page 3 of the schematic.


texts:
I'm trying to figure out a way to use the Power Good outputs of several stages of voltage regulators to sequence and monitor a board powering several FPGAs. I've done this easily before with a microcontroller, but this is not allowed (!) in this design.

I have setup a primitive sequencing scheme with RC-delays and comparators which turns on the regulators in order. The problem here is I need to monitor several Power Good pins which are tied together.

As I understand it the Power Good pins are open drain pins which are pulled to ground if VOUT of the regulator is below (or over) a certain level. Unfortunately (and obviously) they don't pull to ground if there is no input voltage present at the regulator input. So the input to the comparator needs to be pulled up, possible to parallell and only assert when all Power Good pins are OK.

My current idea of solving this is the below transistor circuit:
When the first regulator turns on, its VOUT pulls the PG pin which should be low until VOUT is OK. The transistors connected to the PG pin are set up so they ground the line which is paralleled to other regulators PG during the startup, and releases the global PG only when the regulator PG is OK. When all Power Goods are released this will trigger the enable pins of the next stage of regulators.

Will it work?

simulate this circuit – Schematic created using CircuitLab


texts: What makes an "rf transistor" different from an ordinary transistor?

texts:
I have been looking at various types of transistors that can switch at higher speeds than my clunky but powerful IGBT, and I came across these things called "rf transistors" or "rf mosfets" which can switch at speeds anywhere from a few mhz to a few ghz. Here is an example datasheet. I was wondering what makes these things so fast. I tried some googling, but all I could find was products--no details on what exactly makes these devices different.

Also, is there anything I should watch out for when driving one of these devices? I have gotten fairly comfortable driving large IGBTs and other power devices, but I definitely experienced a learning curve. For example, it took some time and a fair amount of burned out transistors to realize I had to isolate the voltage that drives the gate from source-drain voltage. I also learned that although a resistor connected to the gate is not necessary, a small one helps get you a cleaner signal (I suspect it prevents ringing between the secondary of a gate drive transformer and the effective capacitance between the gate and source). Finally, I found that for fast switching, it helps to actively pull the gate voltage below zero rather than just let it drain across a diode. So given that these are some things I learned to watch out for when driving power transistors, are there any new caveats I should watch out for when working with rf transistors?


texts: Programming a JN5168-001-Mxx with a USBtinyISP?

texts:
I'm researching different ZigBee implementations for a mesh network application.

I like NXP's JN5168-001-Mxx because it is cheaper than XBee (pricing for 200 units) and has a powerful uC.  Mesh Bee seems to be an open source alternative to the JN5168-001-Mxx, but isn't competitive on price.

The biggest downside to the JN5168-001-Mxx is a lack of community support.

I can't find a specific SPI programmer on NXP's website to use with the JN5168-001-Mxx.  My USBtinyISP is (supposedly) a general-purpose SPI programmer.

Would a USBtinyISP work with the Jennic JN51xx flash programmer (JN-UG-3007)? If not, what would?


texts: Momentary switch power: press to turn on, microcontroller can turn itself off

texts:
So I have this circuit here. Ideally, it allows a momentary switch to connect the power circuit, and when released it would stay on.

Here's what I think this circuit does.

The button is pressed
Power flows and the micro controller begins running it program
Software says to supply voltage on PB3
Transistor turns on connects the circuit to ground
The button is released, and the transistor stays connected.

Here's what it doesn't do yet:

While power is on, hold the button for 1 second (how would I do this?)
micro notices a long press on the button
Software says to remove voltage from pin PB3
Transistor disconnects and the circuit is disconnected

The only part of that I'm not getting is how the chip can detect the button state if both sides are connected to ground.

So two related questions: Will this work to latch power on? And how can the chip know the same button state so it can turn itself off?


texts:
I am using tsc2007 on linux.
The linux kernel has the following configuration to use tsc2007.

https://www.kernel.org/doc/Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt

Required properties:
- compatible: must be "ti,tsc2007".
- reg: I2C address of the chip.
- ti,x-plate-ohms: X-plate resistance in ohms.
...
...
...
        tsc2007@49 {
            compatible = "ti,tsc2007";
            reg = <0x49>;
            interrupt-parent = <&gpio4>;
            interrupts = <0x0 0x8>;
            gpios = <&gpio4 0 0>;
            ti,x-plate-ohms = <180>;
        };

What does x-plate-ohms mean?
Is the value dependent on the hardware?
How should x-plate-ohms be measured?


texts: Hyperterminal, Bluetooth,  Enhanced USART, PIC

texts:
I'm using PIC16F1824, Xtal 8Mhz and bluetooth module with baud rate 9600.
When I sent data using hyperterminal to the BT module, it works fine.
But when I send the same data using Android (Amarino), the data received was corrupted.

What went wrong?

Additional Info:
Corrupted data.
@Kevin: Original Data: 1234567890
But when I sent using Android, it reads as 1234!!0
Some how 56789 was missing.**

Another example: ABCDEF, but it only reads as ABCD!!
Basically it only know how to read the first 4 characters.


texts: How to implement coulomb counter using Sigma Delta ADC for Battery Gauge?

texts:
I am trying to understand working principle of the fuel gauge units of the LiPo batteries.

During my investigation I found that coulomb counting method has been used to calculate energy consumption from the battery.

As to my question, unlike voltage, current highly depends on the load value, especially load is a complex digital circuit, therefore I need to sample current sensing resistor (which is a serial resistor between battery ground and circuit ground) very fast and high linearity. For this reason I think Sigma Delta ADCs are proper solutions.

How can I use Sigma Delta ADC to implement coulomb counter?


texts:
I'm trying to find the output expression of a relaxation oscillator in the Laplace domain, to then convert it to the time domain to be able to trace its output. However, my circuit analysis isn't giving me an expression for
\$V_o\$. Here is the circuit that I am trying to analyze as well as the work I've done so far.

simulate this circuit – Schematic created using CircuitLab

\begin{align}
V^- &= \frac{\frac{0}{\frac{1}{Cs}}+ \frac{V_o}{R}}{\frac{1}{\frac{1}{Cs}}+ \frac{1}{R}} = \frac{V_o}{CRs+1}  \tag{Millmans}\\[0.7em]
V^+ &= \frac{\frac{0}{6k}+ \frac{V_o}{6k}}{\frac{1}{6k}+ \frac{1}{6k}} = \frac{V_o}{2}  \tag{Millmans} \\[0.7em]
V^+ &= V^- \\[0.7em]
\frac{V_o}{2} &= \frac{V_o}{CRs+1} \\[0.7em]
1 &= \frac{2}{CRs+1}\\
\end{align}

As you can see, \$V_o\$ gets canceled.

Could someone please help me find where I am going wrong?

Thanks.


texts:
I wanted to make a DAC (0-80 V) using a PWM input (6 kHz).

You might ask why I did not make it with a single N-MOS. The reason is, I tried a single as well. But power dissipation could be a very big problem, if I need more than 100 DAC channels in a circuit, so I decided to use C-MOS to get away from this problem. Since I need high voltage, I chose PHC2300 and built up the circuit.

The problem starts here. I tried at the beginning with 24 volts. It seems to be working. But afterwards, if I increase the voltage to 80 V, the complimentary MOSFET does not work anymore. I tried several times; it happens again and again. Do you have any idea what the reason could be?


texts: What is the correct order and setup of AC coupling capacitor and line driver?

texts:
When I use an AC coupling cap along with a balance line driver, what is the correct setup? What happens when I omit the resistor in the following schematics? Is it neccessary?

simulate this circuit – Schematic created using CircuitLab

I know the way of calculating the filter cut-off point and resistor values, just wondering what happens when I leave the resistor out?


texts:
I'm looking to replace burned out instrument/indicator lights with LEDs as a project to learn more about electronics. I'm working on an indicator light in a switch now. The LED I have in mind is a 2V/60mA "5730 (5630) Red SMD LED Diode Light Surface Mount Chip 5.7mm x 3.0mm DC 2V 60mA 0.2W, Super Bright Lighting Bulb Lamp".

From what I've learned so far, I should plan on 12-14 volts from the car. My math tells me 14 V / 0.06 A = 233 Ω required, and 14 V * 0.06 A = 0.84 W minimum power rating on that resistor. Am I thinking about this correctly? What power rating can I safely use? Would putting this LED / resistor in place of an incandescent bulb affect the other bulbs on the circuit?


texts: High output impedance from voltage source to a LPF?

texts:
I'm a first year EEE undergrad student. One of my labs was about low-pass filters (simple RC ones). When connecting the voltage source to the LPF circuit, the instructions (of the lab exercise) said to set the function generator to High Output Impedance.

I asked the lab manager and he couldn't answer. Any idea?

simulate this circuit – Schematic created using CircuitLab

Thanks in advance!


texts: Why have the same chip in the same package, but with a different number of pins?

texts:
STMicroelectronics offers the following two accelerometer chips.

The LIS2DW in a 14 pin LGA package
The LIS2DW12 in a 12 pin LGA package

These two chips are functionally equivalent and have the same dimensions (2 mm x2 mm x 0.7 mm), and the two extra pins on the LGA-14 chip offer no additional functionality.  While it makes sense to offer the same chip in different packages to ensure customers are able to place a chip with the equipment they have available (i.e. hand soldering a DIP package vs a BGA package), I don't see how offering a chip in the same package and only changing the number of pins offers any real benefits.

What reasons would there be for offering two functionally equivalent chips in the same form factor, whose only difference is the number of pins?


texts: Charging batteries connected in series as isolated groups

texts:
I put an electric motor into my 30' sailboat to propel it. I'm also using 8x12V Deep Cycle Marine Batteries to create 48V system (4 in series twice, connected in parallel) I have a 24V Wind Generator, 24V Solar Pannel and 24V Hybrid (wind and sollar) Charge Controller. I also purchased a high powered diods, 8 of them, thinking I can isolate batteries as pairs (24V each pair).

I have a whole bunch of switches I think I'll need to use to isolate the batteries. Can it be done outomatically, with out switches and will the batteries charge properly?


texts:
I'm having a little trouble finding the Thevenin resistance equivalent of this circuit. Without the 7.5k resistor, I expect it to be just 15k||15k. Does the 7.5k resistor here act in parallel with the lower 7.5k resistor (to become a 5k resistor) or is it more complicated than that?

simulate this circuit – Schematic created using CircuitLab


texts: High power / high current clamping circuit

texts:
I am looking for ideas on how to clamp high energy surges in the input of a high current / high power system.

The input to the system is 24V. During steady state, the system sources 85A of current from 24V. The supply to this system (a car battery) can have surges of up to 100V, with 100ms duration. During these surges, we need to clamp the surge to ~55V in order to protect downstream electronics.

We have previously designed this type of surge protection, by using integrated circuits such as LTC4366, but for lower current systems. This type of surge protection requires that you have a series MOSFET in the current path, therefore, even during the no-surge steady-state condition, assuming a MOSFET with RdsOn=5mohms, the MOSFET will dissipate ~36W (85A*85A*5). Also, during the surge, the MOSFETs SOA becomes very important as you need to dissipate the surge energy in the MOSFET.

Therefore the clamping method should probably not use anything in series with the supply current. Simply protecting the input with TVSs will likely not suffice, since TVSs are not designed to handle so much energy (in the order of milliseconds).

Are there any other methods that we can use? And, bonus question: Can we handle negative surges as well? (max -200V, max 200us)


texts:
The following lines which works exactly opposite to what i'm expecting, would appreciate correcting my understaing:

Button connected with Pin D2 & Led B2:

    if (PIND & (1 << PD2) )
        {
        (PORTB ^= (1 << PB2));
        _delay_ms(500);
        }
    else
        PORTB |= (1 << PB2);

As far as i understand so far:
when Button pressed [PD2 will high value (1)] which when and'd with the mask (wich is another 1 in location of PD2) then we should get true for the if condition and the LED will keep switching based on the delay value specified.
HOWEVER, what i get is the exact opposite: as lonh as i'm pressing the button  Led goes constantly one, when no button pressed the switching behavior occurs.

i'm kind of lost where i'm wrong


texts: Driving an N Channel MOSFET with Microcontroller

texts:
simulate this circuit – Schematic created using CircuitLab

Dear Group Members,

I have a question which might have been asked before, but I couldn't find the suitable answer for my application, due to which I need more help in my case.

my uC with 3,3V logic is required to turn ON the N-channel Mosfet (as a safety measure, that means Mosfet will operate only in error conditions and not with a certain frequency) which has different reference potential point as compared to uC's Ground (GND). In my Opinion, I cant overload my uC with source and sink currents of Mosfet (might be around 700mA - 1.5A depending on Mosfet), and I think I would need the same reference potential as that of Mosfet to turn it on. The reference potential of Mosfet is shown with small triangle symbol with OpAmp which has same voltage references as that of Mosfet.

In the shown circuit, I have a plan to pull up the GPIO to turn OFF the Mosfet (nearly -5V at Gate of Mosfet, Rail to Rail OpAmp) and pull down the GPIO to turn ON the Mosfet (nearly 0V at Gate of Mosfet).

My question is if this solution is elegant and if it will work as expected or maybe I am missing any detail. In other case, any other more elegant solution will be highly appreciated. Priority is to have a small size and less costly solution.

Note: the microcontroller 3,3V logic is generated with an LDO supplied with reference voltage point of Mosfet (0V) and -5V. That means microcontroller ground (GND) is same as -5V point of Mosfet.

EDIT_1: Resistor R2 moved from Mosfet Source to Gate Side as Pull Down

EDIT_2: 3.3V LDO added


texts: Displaying signals in testbench from counter VHDL

texts: Say I have a count signal in a counter VHDL file and want to display this in my simulation output, what would I have to do to my testbench to output such data?


texts:
I have a question regarding timing analysis for DDR3 and DDR4 signals.
How do we do timing analysis to see if all setup and hold requirements are fulfilled correctly, considering they have write levelling algorithms to take care as well.
Suggeat some method and tools than can assist an engineer to analyse for the timing of the DDR3 and DDR4, specifically where memory device and controller are on two different PCB connected with board to board connectors and not through conventional DIMM or SODIMM


texts: Why isn't the ESP32 used for quadcopter flight control?

texts:
I'm looking for a quadcopter microcontroller to use as a flight controller and am comparing a couple of different ones. Went on this website to see what current boards are using: http://www.rcdronegood.com/flight-controller-board-comparison/

However, I'm looking at the ESP32 microcontroller as well which operates at 240 MHz and performs at up to 600DMIPS. For comparison, the STM32-F3 chip only operates at a clock speed of 72MHz and gets 1.25DMIPS/MHz, but apparently works pretty well as a flight controller. But if the ESP32 has better specs why wouldn't we all just use the ESP32? Am I missing something or comparing wrong things? I guess the real question I have is how can I really compare microcontrollers to make sure I'm using the right one for my application?


texts: Female audio jack connections for PICAXE programmer cable

texts:
I have this 1/8 inline stereo audio jack connector without a datasheet:

I want to use it for connecting a USB programming cable to a PICAXE.

I am unable to identify which pins connect to sleeve, ring, and tip.  Is there standard layout or some easy way to identify? The only clue I can see is that one of the pins is round, and the other is square.


texts: Grounded coplanar waveguide - too wide signal wire - how to handle properly?

texts:
I'm struggling with specifying the convenient signal wire width for the grounded co-planar waveguide for the following parameters:
- PCB: FR4, 1.5mm
- copper thickness: 0.035mm
- pad to pin lenth: 9.8mm
- space between ground and path signal on the same layer: 0.254mm
- frequency: 900/1800MHz (GSM modem)

For these parameters KiCad calculator gives me signal track width of 1.28 mm which is more than the pad width (0.8mm).
The clearance issue I can solve by simply ending the track lower than the bottom edge of the modem pad so that it does not go between pins 46 and 48 disturbing their clearances but will that solution be ok? The image below shows this solution (no ground aside yet)

The only possible ways of making the signal track narrower is to increase the PCB thickness or making the space to the ground planes aside less, but that on the other hand is a PCB making company constraint (they support 10+ mils)


texts: Measuring a voltage that is higher than your reference voltage

texts:
Question: How to measure an input power rail?

Let's say I want to build a circuit that switches in a load that draws 1A from a 5V power rail (that is the supply for the device) and then measures that rail to see if it droops and if so by how much. This seems like a chicken and egg problem as you obviously can't use the 5V as a reference. I have little practical experience with ADCs but suspect that if this is solvable a band gap reference will play a part. Is there any way to do this?


texts:
I have these two reference images:

and

and I'm trying to put a 6-pin header on my circuit so that I can easily reprogram the PIC if needed, without having to resolder. (I'm using the surface mounted version of the PIC, but I assume that makes no difference.)

So far, I have PK-pin1 goes to PIC-pin4, PK-pin2 goes to PIC-pin1, PK-pin3 goes to PIC-pin20, PK-pin4 goes to PIC-pin19, PK-pin5 goes to PIC-pin18, but I'm not sure about PK-6?

First of all, if I do this with the header, I will be able to reprogram the PIC in the circuit, right? Or will I need to put a jumper to isolate the PIC from the rest of the electronic components on the board? I will only have caps, resistors and microswitches. I am otherwise not using the MCLR/PGC/PGD pins at all.

And secondly, do I need to use the PICKit pin6 for anything?

Thanks


texts: Input/output impedance of devices in a circuit simulator

texts:
I have to use a circuit simulator (I'm using Proteus, but can also use Multisim if necessary), to construct and analyse a passive RC filter. The general circuit is shown below:

I need to connect this circuit to a function generator with source impedance \$R_\mathrm{S}\$, and an oscilloscope with load impedance \$R_\mathrm{L}\$, so I've placed the signal generator in the place of \$V_\mathrm{in}\$ and the oscilloscope in place of \$V_\mathrm{out}\$.

Now I have to find the values of the impedances \$R_\mathrm{S}\$ and \$R_\mathrm{L}\$. As this is being done on a circuit simulator, I'm assuming that both impedances will be 'ideal' at 0\$\Omega\$ (or ∞\$\Omega\$, I'm not sure). Can anyone confirm if I'm right in saying this, and if not, how would I go about finding \$R_\mathrm{S}\$ and \$R_\mathrm{L}\$?


texts: Capacitor to limit AC current, block DC current

texts:
I am interested in making a 'life' indicator for my uC, as in, "Is the clock running?". As it has a clock output pin, I was thinking of attaching this schematic to it.

simulate this circuit – Schematic created using CircuitLab

(P1 is clock out)

Theory: P1 goes high, causing C1 to charge to 3V (uC is at 5V) via D1 (2V Vf), it then goes low, causing NODE1 to go to -3V because of the nature of capacitance. This causes D2 to become forward biased, and C1 discharge to 0.65V (D2 has .65Vf), rinse and repeat.

Clock frequency is 16.5MHz. At this frequency, the cap should have an impedance of roughly 965 Ohms, no? Will it act as a ~1k resistor in this circuit for the calculation of led current? And will incresing the size of C1 increase current drawn?


texts: What transistor should I use (I need to control 12v 5a)?

texts:
I am searching for a transistor but I don't know which one I should take and the datasheets are confusing because I'm quite a noob. It needs to be able to control 12v 5a with the circuit from this website. As you can see on the website it is a PWM circuit.

Please help me...


texts:
I need help designing a class ab amplifier to power an 8 ohm 0.2W speaker to create an alarm sound. I'm outputting a sine wave at 150Hz and 5Vpp from a TI microprocessor.

Questions 1: A class AB amplifier amplifies the current not the voltage correct?

I have a couple NPN and PNP transistors, 2N3904 and 2N3906.

Question 2: If Q1 is correct. Will my uP be able to output enough current for these BJT's to amplify? Or do I need some sort of preamplifier or anything before I get to the AB amplifier?

Question 3: How do I figure this out through the BJT's datasheets? What do I look for on them to figure this stuff out for myself? Is it the current gain plot shown below?

Seeking analog help!


texts: Sensing Voltage and Current of an Adjustable Voltage Source

texts:
I am currently working on an Adjustable Voltage Source, the Voltage Source is built by a voltage regulator with an OpAmp with and a Darlington transistor for current amplifying as the following diagram shows.

Vin is the output of the voltage regulator, so we can't know for sure the voltage at Vin. But because of the configuration of the OpAmp (Voltage Follower), we can assure that Node A and Vin are at the same voltage.

Given that Node A is equal to Vin, the OpAmp will compensate for the voltage drop across the Shunt Resistor, thus Node B voltage will be Node A Voltage plus the voltage across the shunt resistor.

I've thought of a Differential amplifier between nodes A and B, to get to know the Voltage across the shunt, thus knowing the current flowing across the load and the shunt.

*Suppose 4 Resistor values are the same

With this configuration a microcontroller con sort out the shunt current with Ohm's Law. But the equation system I tried to solve was missing one variable.

It is possible to figure out the voltage and resistance of the load by knowing the current and voltage across the shunt?

If not, which would be the most part efficient way of sensing the voltage and current across the Load?


texts:
Pretty much all BECs (Battery Eliminator Circuit) are rated to work fine with 12v input but I haven't seen any that mentions lead acid batteries. Almost all datasheets for BEC regulators have write ups such as:

Input voltage: 6V to 33.6v (2s-8s lithium, up to 21 NiMHs)

Is there any concerns using these devices together with a large 100Ah Sealed lead acid (marine) battery?


texts: Does connecting between two series diodes suppress noise?

texts:
I am trying to understand a circuit diagram for a device that I have that has an h-bridge connected to a motor. Each of the wires going to the motor is connected between two diodes in series which are connected to ground and a fixed voltage. The searches that I have done have also shown this same setup connected to a pair of charlie-plexed LEDs.

I am having a hard time understanding the purpose of these diodes. I have two hypotheses.
1) Noise suppression.
2) Circuit protection for when the motor is connected and disconnected from the circuit.


texts: BJT Transconductance Decrease with Increasing Base Voltage

texts:
Hello Everyone!

I am going through transistors and trying to apply it to some RF applications. I am following Sedra and Smith. In the Sine wave generation section (via feedback), it says if the base input amplitude (a in diagram) increases in magnitude, the effective transconductance decreases. I can not figure out why.

The only way I can think of to decrease the transconductance is to reduce the collector current as, $$g_m=\frac{I_c}{V_T}$$But how come increasing the amplitude of input voltage decreases my collector current? Another way I can think of is in terms of from collector-emitter voltage. Say my input voltage is increasing, hence the emitter voltage must increase, hence the emitter current. But then increasing emitter current means increasing collector current. So instead of decreasing collector current I am getting increasing one. What am I missing here??

Thanks in advance.


texts: Finding U2 using superposition for this op-amp

texts:
Using superposition I have found U1 and now I'm finding U2.

To solve U2 I went with this approach

R_2+R_4=2R       because they are in series
R_3//R_5=  R/2        because they are in series

This is the result I came up with, I was hoping for some advice if I tackled this in the right way


texts:
I should apologize if my question is trivial since I did not find a similar question, I decided to specifically ask mine.

I have a microscopic membrane in my lab, this piece which we call it NMS has a variation of voltage caused by its operation. Similiar to the action potential in neurons of a nervous system. We are trying to build an electronic measurement system, which could capture the variation of voltage in -70mV to -55mV range. We want to have an accuracy of at least 1mV or possibly less in our measurements. Since the only electronic guy, we have access to is a bachelor student, we shall be able to help him, So I have decided to seek a community help.

The current SoC he knows how to program and feels confident with is ESP32. As I searched its datasheet, it has some cool functionality which we might use here, I add them here as a reference:

http://espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf

  4.1.2 Analog-to-Digital Converter (ADC)

  ESP32 integrates 12-bit SAR ADCs and supports measurements on 18
  channels (analog-enabled pins).     Some of these pins can be used to
  build a programmable gain amplifier which is used for the measurement
  of small analog signals.  The    ULP-coprocessor in ESP32 is also
  designed to measure the voltages while operating in the sleep mode,
  which enables low-power consumption. The CPU can be woken up by a
  threshold setting and/or via other triggers. With the appropriate
  setting, the ADCs and the amplifier can be configured to measure
  voltage for a maximum of 18 pins.

  4.1.3 Ultra-Low-Noise Analog Pre-Amplifier

  ESP32 integrates an ultra-low-noise analog pre-amplifier that
  amplifies the voltage difference between pins SENSOR_VP and SENSOR_VN
  and outputs the value to the ADC. The amplification ratio is given by
  the size of a    pair of sampling capacitors that are placed off-chip.
  By using a larger capacitor, the sampling noise is reduced, but the
  settling time will be increased. The amplification ratio is also
  limited by the amplifier, which peaks at about 60 dB gain.

  4.1.4 Hall Sensor

  ESP32 integrates a Hall sensor based on an N-carrier resistor. When
  the chip is in the magnetic field, the Hall sensor develops a small
  voltage laterally on the resistor, which can be directly measured by
  the ADC, or amplified by the ultra-low-noise analog pre-amplifier and
  then measured by the ADC.

So, I am basically looking for design suggestions for mentioned measurements with ESP32 chips. We need some advice for building the measurement probe too, specifically, we need a way of connecting our NMS membrane which is sandwiched between a microscope slide and a cover slip to our measurement system.

Thank you all.


texts: How can I plot the voltage across any component by Matlab?

texts:
I want to ask how can I plot the voltage across any component by Matlab?

I have a simple RLC circuit and I want to plot the voltage across the 3 components and I didn't use Matlab before. I found the transfer function here in the site but still can't plot the voltage.

And the voltage source I will use is cosine source but I can't find it in the simulink also.

So this is what I made:

>> L = 0.047;
>> R = 220;
>> C = 0.000001;
>> Num = 1 ;
>> Denum = [L*C R*C 1 ];
>> G = tf(Num , Denum)


texts:
I would like to automatically tune a PID controller. Is there a method that I can use to get the frequency and timing characteristics I want and automatically tune the PID loop?

Concerning industrial controllers,do they use old process data or automate online pid tunning algorithms such as ziegler nichols?


texts: Controlling an electromagnet with Arduino

texts:
I'm just starting up with electronics and looking to control an electromagnet with the Arduino. I'm wondering what hardware setup will make the most sense to use to turn the electromagnet on and off at around 10 times per second. I plan to make the magnets using coiled wire. From what I have read, I need to get a transistor to switch power on and off.

In summary:

Should I use a transistor? If so, what transistor works well with Arduino for this application?
How do I supply power to the electromagnet? A schematic or explanation would be super helpful.

Thanks in advance!


texts:
I don't know whether or not I'll actually build one yet, as to do so properly would require ball bearings, metal working, etc and frankly the fund's just aren't available right now(have yet to purchase the previous circuit I said I'd build, although the design and concepts are as clear as day to me now thanks to your help) That said, I'd like yet more advice from you guys.

I found this excellent resource: http://homepage.cs.uiowa.edu/~jones/step/types.html
and concluded that If I was going to build one I'd build a variable reluctance stepper motor because the rotor wouldn't need to be magnetised and the switching would be 'relatively' simple. Unfortunately, I have absolutely no experience whatsoever with micro-controllers and integrated circuits, though I hear alot of good thing's about Arduino.

It come's down to this: As much googling as I do, fundamentally I know nothing(really) about micro-controller's and integrated circuits and such. While one 'guide' or 'tutorial' uses micro-controller XYZ, with specific code N, another could do it with entirely different code on micro-controller UWN. Worse still some just use discrete components (transistors). Even if I were able to follow the guide to the letter (of those that I've found), I wouldn't know much more than when I'd started and disregarding that I wouldn't even know how to begin to program a micro-controller (interpreter? what's this interpreter you speak of? visual studio 2010, right? I kid, I kid. )

I plan to at least purchase a stepper motor and drive it by myself as a gateway into these kind of components. I'd love to just read a comprehensive guide to these components, but of course no such resource exists. I therefore conclude that I should just decide to build something and build up knowledge that way(It's how I learnt to program and as gruelling as it was, It got the job done).

Some thing's to know: I have 3+ years of experience programming in C++. No experience with coding assembly or other such low-level languages. However it goes without saying I'd be fine coding most program's in C with proper documentation.

Finally, the question: What integrated circuits/micro-controllers, etc, etc would you suggest for me to purchase as a (complete) beginner. I've looked into Arduino but It's obviously not the only solution nor necessarily the best. In terms of number of phases, not sure yet, a controller with room to expand would be great. Also, let me know if this is too much as a 'starting' point. Thanks.


texts: Method or function to determine if pointer is to address in flash or RAM?

texts:
I'm working with an ARM Cortex M4 microcontroller that has a DMA, or peripheral DMA controller. One requirement of the DMA is that it cannot access pointers to addresses that exist in flash, but only pointers to addresses that are in RAM. Is there a way to determine if a particular pointer points to flash or RAM?

If not, I think I need to actually initialize a buffer in RAM then strcpy or something like that to transfer what is in flash into RAM so the DMA can read it. Does anyone know of a better way to do this so as not to waste CPU time if there is no way to tell if the pointer points to flash or RAM?

This is on an Atmel SAM4S.


texts:
I am planning on recycling some cheap low voltage solar panels that came out of a gardening light. I have two of these modules, that soldered in series provide a voltage of around 3.5v (on direct light).

I want to be able to charge two (or at least one) 18650 batteries, the problem is that I've seen some comercial solutions but they all require 5v input.
I wanted to know if there is a way of achieving what I intend to do.

Thanks


texts: Clamper for easy DC-restore in video-composite

texts:
I'm unsure how to properly design a simple clamper in a video circuit like this:

The capacitor should be there to avoid any DC offset flowing into the X1 primary loop. I don't know if I can treat the transformer as "transparent" - like it wouldn't be there for the simple one-diode clamper.


texts: Is 1.4mm Pad Distance at Optocoupler Pins for 230V/50Hz Mains Detector Enough?

texts:
For a project, I use an optocoupler to detect 230V/50Hz AC on a line - if a light switch connected to mains is pressed.

For my calculation, I use 240V as a maximum AC voltage. It will limit the current to 1.2mA for the LEDs of the optocoupler.

My board has a minimum trace distance of 3mm for all traces, except the distance of the pads between the optocoupler:

The shown distance (yellow) is 1.4mm.

I assume, there is only a voltage of 1.4V across these pins, therefore the distance would be enough. Is this correct?


texts: How do SPST neon-indicator-lamp wall switches power their neon indicator?

texts:
I am building a totally overkill electronics repair bench for fun while in quarantine.
Part of this bench build involves wiring up electrical distribution (i.e., a lighting feature to illuminate the work surface, and a bunch of power receptacles). To provide additional safety, I have a GFCI inline with the circuitry, as well as a SPST wall switch wired up to interrupt the live side of the circuit so that I can power off the bench completely when not in use.
Switch product info here:  https://www.legrand.us/~/media/products/resources/peps/pass-and-seymour/lgrp00021v0101en.aspx
At every step of wiring this circuit, I check to ensure there is no continuity between live, neutral, and ground--twice, of course, before plugging it in to live mains. So far, everything is working quite well, with no real issues. However, what puzzles me is the neon indicator lamp included within the switch, which I chose because I wanted the switch to be illuminated due to the circuitry sitting on the underside of the workbench.
The switch works as expected: when tested via multimeter continuity, I found continuity when the switch is closed, and no continuity when the switch is open, and no continuity at all between either switch terminal and the earth bonding screw.
The neon lamp powers on when the switch is opened, illuminating as expected. However, I got to thinking: what is actually powering the neon? I took measurements across live and neutral (see OutletBox1 in the schematic below) and I found

When the switch is closed, the GFCI is closed, and the circuit is powered, there is 120VAC as expected.
When the GFCI is tripped open, the circuit measures 0VAC regardless of the switch state.
When the switch is opened and the GFCI is closed, however, there is 24VAC across live and neutral at the outlet box.

simulate this circuit – Schematic created using CircuitLab
My question is: If the live side is interrupted by the switch being opened, what is actually powering the neon lamp in the switch? Am I correct in assuming the 24VAC measured at the outlet box when the switch is open is a residual voltage from powering neon lamp?
The only two theories I could come up with:

There's some kind of ballast that kickstarts the neon lamp, meaning the continuity test would read negative if the switch was being tested independent of mains (which is how I tested it, for safety), and by extension, this means the circuit isn't actually totally broken by the switch; creating an observable voltage at the receptacles that's too low unable to meaningfully power any mains devices on the other end, or...

The neon lamp is shunting current from live to ground, and because this is happening before the GFCI in the circuit, the GFCI doesn't detect it. This particular option is terrifying!

I'm about 95% sure it's the first one, since it's the only way I can think of how 24 volts would end up across live and neutral. However, before attaching this to the constructed workbench and leaving it plugged in in my office 24/7, I'd rather be completely certain about what's going on under the hood.


texts:
I was looking into I/Q demodulation, and when looking into the equations, I realized that the phase/frequency difference between the carrier and the LO in the receiver had an unwanted effect. The constellation diagram is rotated.
A couple of hours later on google, I read a little about "carrier recovery", which as far as I understand address exactly this problem.

But how is this done in practice?
Especially for high speed data transmission.

I did not find any IC's with carrier recovery build-in.


texts: Do you know how to add VEE and VCC power strips to op-amp in Cadence that will be fit for simulation?

texts:
This is the built in Cadence OPAmp. I need to add A capacitor to the VCC wirep and Ground the VEE wire however, there is clearly not a VEE or VCC on this op amp. Also, I know that I could manually alter the VEE and VCC in the properties but it wont help. I need Those VCC and VEE wires.

Is there a script that I need?


texts:
I'm trying to add a DC offset level to a sine signal through an instrumentation amplifier (as the figure below shows.)

The problem is that, in the simulation, everything works perfectly, however, in reality I can't achieve the DC displacement of the signal.
The input signal parameters are: 0.7Vpp and 100Hz

The image shows the wanted behavior of the circuit, however, I'm not able to obtain that in real life.

What could be the problem? Maybe the AD620 is not the best option to do that?


texts:
How can I calculate if a certain IP will fit into a certain FPGA?
If the unit of measurement of an FPGA size is the LUT, I need that FPGA lut >= core lut
For example, can I put a S1 core (37k look up tables) into a Spartan6 LX9 board (xxx luts)?

Many thanks


texts: employing a series resistor to mitigate an absolute maximum voltage rating

texts: I am trying to run an IC with an absolute maximum voltage spec of 3.6 V. The linear voltage regulator that feeds the whole board specifies a maximum output voltage of 3.63 V. For a given input current range on the said IC, where I shall be mostly using it, I was able to compute the value range for the series resistor that would drop the voltage just enough for both safety and proper IC operation. Is anything wrong with this approach ?


texts: Can I use a voltage regulator to bring high voltage down to 3.3V GPIO input for ESP32?

texts:
I have a button connected to the power rail of my project and I want to know when it's pressed with an ESP32 chip. Since the input voltage (6.5V to 15V) is higher than the maximum rating of the ESP32 I need to bring it down.

Like this video of a power switch circuit,  I used a current limiting resistor of 10K ohm between the button and the chip, relying on the protective diodes of the GPIO pin. But when I measure the voltage it's 4.1V which is still higher then the maximum spec of the ESP32; so I'd like a safer way.

Is this circuit using a 3.3V voltage regulator appropriate? I use a 1k ohm resistor to load the voltage regulator, and 2 10uF caps as suggested in the datasheet. The low response time of the button should be fine.

simulate this circuit – Schematic created using CircuitLab


texts: Buffering Input Signal - Op Amp Alternatives

texts:
I need to buffer a 0-5V signal that is coming from a resistor network and being fed into an IC.  When I feed it directly to the IC there is a loading effect and the value is changed specifically at 0V input the IC will source current out the input pin and produce a ~0.3V value.

My first thought was to use an Op Amp as a voltage follower. I have a TI-082 available and tried to use.  I have a +24V and +5V sources available and using a single 24V supply for the op-amp works great for values from ~1.5-5V but anything under that and the output swings to the 24V supply voltage.  I understand this is due to getting to close to the negative rail.

I next set up a +/-12V supply from my 24V source and everything in the 0-5V range was properly buffered, but the problem was I could no longer input it to the intended IC since the IC is powered by 24V and GND and the input is references to GND so to the IC the 0-5V was appearing as 12-17V.

Is there a way to make the op-amp go to 0V when hitting the negative rail? Forcing the bottom 1.5V to GND would be acceptable but output 24V is not.  Alternatively, is there anyway to configure the +/-12V configuration to work despite the input being referenced to what would be the -12V line from the op-amp's perspective?


texts: What is the exact type of oil used in immersion cooling of electronic devices such as processors?

texts:
I am looking for cooling solutions for a data center with low PUE. I can see that there is an immersion cooling option which uses a very specific oil based liquid that is non conductive but can observe heat efficiently.

I wanna buy this oil from local market but don't know what exactly I should ask for. What is the scientific name of this type of oil? I found "3M Novec Engineered fluid" online, but there is not much details about what type of oil it is and I can not find it in my country (Thailand).

Can I use cooking oil? or something similar?


texts:
I am using a DC/DC converter (buck) in a power distribution board to convert 48V to 12V. Link to the chosen converter is given below. After reading the datasheet, I've concluded with using a 560 μF aluminium electrolytic capacitor at the input pins to keep the voltage stable. At the output I'm thinking of using 2× 10 μF ceramic capacitor to reduce the ripple voltages and noise.

The problem is; I dont have any experience with building boards such as this, so I would like to know if this setup for the DC/DC converter would do okay, or what I have to do different?


texts: Variable Voltage Using PWM and Low Pass Filter

texts:
I am trying to control a steady DC output voltage using a Micro controller with a PWM duty cycle. With the current schematic, the Voltage on Vout is pulsing along with the Mosfet at what ever the duty cycle is.  I know that this is the result of Load being grounded only when Mosfet is "on", but can not figure out how to get around this.  I want a smooth, controllable Vout that uses the same ground as the Fet. I know this is a noob question but any help will be appreciated. Also, I don't want to be picky but for me pictures really do speak a thousand words.

Current Schematic

Simulation

EDIT

What I'm really looking for is a way to use a low-pass filter to smooth a PWM voltage. This smoothed out voltage will then be used to power a 1 ohm load.  I know how to create a PWM voltage and a low pass filter, but not how to implement both to power something.  Since I'm new to circuits, a simple schematic drawing will be very helpful.


texts:
as you can see from the pic, the resistor is burnt out.
It has written on it…
ER G – 74ER – 1R8 – 5% - 7634
This is all I can make out, any help appreciated in choosing a replacement.
It’s from a crossover circuit within a set of speakers.


texts: How does capacitive coupling work for measurements

texts:
The context is the measurement of engine speed on a vintage car that uses a classic Kettering ignition system. Essentially, a voltage pulse of tenths of kV is generated on a high tension (HT) lead. The frequency of the pulses can be used to calculate engine speed.

I have seen two methods of measuring these pulses with instruments:

An oscilloscope with a 1000:1 attenuation probe. The probe tip is a clamp that encloses a segment of the HT lead for measurement

A RPM gauge with a wire wrapped ca. 10 turns around a segment of the HT lead for measurement.

The second type of measurement, in particular, would appear to be inductive, as we're measuring through a coil, but I'm told nevertheless that it's capacitive coupling.

Could someone elaborate on how capacitive coupling works in these two measurement setups?


texts: Use minimum number of half adders for the boolean expression

texts:
I got this question in my exam, and I cannot find the answer to it. My professor also didn't provide a clear solution. Can someone please help me in this?

Design the expression F(A,B,C,D)=AB' + AC' + DC + AD using only half adders. Do it in minimum number of half adders.

My try at the solution-
I converted it into minimal SOP form, which I got is AB' + AC' + CD. I made each complemented literal by passing 1 and the literal to the half adder which gives me both kinds. Then I made the minterms using AND in half adder and then I got stuck how to OR them all together.


texts:
I've read that WiFi b/g/n is using 2.3995 to 2.4845 GHz.

Bluetooth is in between: 2.4000 to 2.4835 GHz.

So what will happen when I put a Bluetooth sending device next to a WiFi sending device?

Will the two devices be aware of each other (like two WiFi devices do)?

Or will they send their data as if they were alone (means interference)?


texts:
I have SMD LEDs of 5 watts each having 6500kelvin with 9-12volts forward voltage with 900-1050 mA operating current and 1100lm@500. I have put 3 LEDs in parallel and connected it parallel to my ACxDC adaptor having input 100-240v at 50/60hz at 0.8A and output of 12volts at 1500mA. I had connected 5 LEDs with a fan in parallel earlier on another adaptor but the adaptor blew off. Now I have connected only 3 LEDs without any fan in the circuit and there are 2 computer fans blowing on the LEDs still the adaptor gets too hot. Will this one also blow out or I need to change the circuit or adaptor?
An earlier circuit with the same 3 LEDs in series is working for almost a year properly!


texts: Substitute a Li-ion Polymer Battery with AA(A)s

texts: My headset broke a few days ago, but the circuit board still functions properly. I want to see if I can re-use it by soldering two 3.5mm female plugs to it, so I can use it with any speaker or headset. The problem is, it used this battery, I don't dare to play with those batteries. So I was wondering if it's possible to replace it with 3 AA, AAA, or another more common battery instead.


texts:
I'm having problem in understanding characteristic of zener diode. In the circuit zener voltage is 5.1V and source voltage is 10V.

When i simulated in a circuit simulator i got the voltage vs time graph (across the resistance) below where the green wave indicates my output. Can anyone please explain me why i have got this kind of graph? Thanks in advance.


texts: Is multiway switching at two locations with SPST switches possible? Normally SPDT switches are used for this, right?


texts: High Capacity Phone Batteries - are they for real or a scam?

texts:
I recently bought a new, allegedly high capacity battery for my Samsung Galaxy S5. It was being sold as a 3800mAh battery whereas original is a 2800mAh battery.
On inspection I read the following from the cases of the 2 batteries;

Original Samsung:-          2800mAh, 3.85V, 10.78Wh

High capacity replacement:- 3800mAh, 3.85V, 10.78Wh

If Watts = Amps x Volts    then...   Watt-hrs = Amp-hrs x Volts

Therefore   Amp-hrs = Watt-hrs / Volts  or 10.78 / 3.85 = 2.8Ah (2800mAh)

This equates to 2800mAh  (2.8Ah) for both batteries so the replacement is wrongly labelled and sold as a 3800mAh Higher Capacity battery to Samsung Galaxy users.

Or have I got something wrong here?


texts: Is there any problem soldering a device while it's powered on?

texts:
I'm frequently tempted to solder to devices that are still powered. Assuming that:

it's a low-voltage device
there's nothing static-sensitive on the board
I'm not going to short anything out (because I'm a ninja)

Is it possible to damage anything (device, myself, soldering iron) by soldering things on the board without powering it off? Are there any hazards that I haven't considered?


texts: Voltage regulator (LM350) gives no current

texts: I am trying to use a Fairchild LM350 to get 8 volt output. I am using basic circuit (page 5 of datasheet) to do that. I get the voltage I want but whenever I try to measure the current (by putting the meter in series with a resistor) it gives me 0 A. I am giving it 8 volt and the resistor is 650kΩ. I tried smaller resistor also but still nothing. Why is this happening?


texts: Can an INA219 current sensor operate with a FET body diode present over the sensing pins?

texts:
I'm designing a board with optional current sensing modules (based on INA219) that can be plugged into it for monitoring the current on some 12V lines that go to peripheral devices.

The schematic for the main board looks like this:

The 12V_INT line is the 12V supply on this board, and the 12V_OUT_1 line goes to a connector that is used by the peripheral whose current load is being monitored.

The idea here is that when the sense module is not present, the CSENSE_PRSNT_1 line is pulled to ground by the 10K resistor, so Q3 is on and Q4 is off. This allows current to flow from 12V_IN directly to 12V_OUT_1, powering the peripheral. The LED is off, indicating that no module is plugged in.

The module board plugs into CONN7 and bridges 12V_INT to CSENSE_PRSNT_1. This raises CSENSE_PRSNT_1 to 12V, switching Q3 off and Q4 on. This turns the LED on, and blocks direct current flow between 12V_INT and 12V_OUT_1. The module board then has a 10mΩ precision resistor across the 12V_INT and 12V_OUT_1 lines, and the INA219's sense pins are connected over it.

As far as I understand, this should work. The body diode of Q3 is pointing in the wrong direction to allow current flow, so it shouldn't affect the reading. The body diode breakdown voltage should not be exceeded, and if it is I have bigger problems. I don't see anything in the INA219 datasheet that indicates there would be a problem. Am I correct here? Did I miss something?