texts:
I am building a circuit with two AD8495 thermocouple amplifiers. I chose them because they are simple to get and quite cheap - there's basically no other reason. Now I need to create an interface between the amplifiers and a microcontroller (AVR). The AVR's ADC has 10 bits resolution, and I'd like to use as much of that as I can.
The temperature I am expecting at the thermocouples is up to 300°C. As the AD8495 gives 5mV/°C, the maximum output should be somewhere around 1.4V. I could supply a suitable reference voltage to the ADC to resolve that range, but when the AD8495 has no thermocouple connected (or something else goes wrong), the signal will rise to 5V (supply voltage), which would be too much for the ADC with a low reference voltage.
I see two basic options:
I can clamp the signal to the reference voltage (or some "compatible" voltage using a resistor and a Z diode:

This is simple and cheap, but I think I might mess up the whole measurement with this.
I can also use an OpAmp to amplify the AD8495's output to the full 5V range:

Connected with these options are two equivalent problems:

I have never build a clamping circuit with a Z diode,
I have never used an OpAmp before. I picked the TS912 because it's a rail-to-rail, single supply type (and I can easily get it)

While I know how the ideal devices are supposed to work, I also know that the real devices will mess with my measurement a lot.
I would like to achive +/- 5°C accuracy at 280°C. I have not yet done calculations on that, but given the ADC, reference, and AD8495 accuracies, this might be a bit too optimistic. I am aware of that.
Link to datasheet download page

Edit 1: The AVR has an internal 2.56V reference which I could use. Unfortunately, it is not very precise (2.4 ... 2.8 V) and I'm not sure how much current it can sink or source. So even if the ADC channels have internal clamping diodes (which would have to clamp to Aref), I need some extra protection or conditioning. Using an external reference will not really solve that problem either.
Edit 2: This is my solution, more or less:

The two AD8495 outputs are connected to an ADC (MCP3426), which has an internal 2.048V reference. That is much more accurate than the AVR's internal reference and tolerates the AD8495's 5V output when no thermocouple is connected. I've added screw terminals for the thermocouples and a 0.1" header. All pin holes are on a 0.1" grid. Layout and routing was quite easy:

There are two short SCL and SDA traces on the bottom side, everything else is ground. I've made the thermocouple traces (left) a bit wider for lower thermal resistance.


texts: Single ended to differential amplifier workings

texts:
Hello electronics experts,

I do not yet have enough reputation to post more then two images. For the images please see: http://imgur.com/a/dizis

I have a single ended signal that i want to convert to be differential so that I can use the full scale of the differential ADC (ADS1278).

The single ended signal that i want to use is 0V - 2.5V. The ADC input range goes from +Vref to -Vref, i have the Vrefp tied to 2.5V and the Vrefn tied to ground. To convert the signal a THS4521 differential amplifier is used.

Now from what I know, when the single ended signal looks like image 1 the differential signal should look like image 2.

But when I use the single ended to differential schematic from the amplifiers datasheet image 3 (Vocm is set to 1.25V), The output of the amplifier gives me the signal of image 4.

I can see that the pk-pk voltage of this resulting differential signal is the same as the single ended signal (2.5V). But is is different from what I thought that was going to happen (image 2). Can anyone explain to me why this happens or what I am not understanding about differential signals?

Thank you,
Sisco


texts: Simplest way to turn on a LED controlled from a 0v control signal?

texts:
Simplest way to turn on a LED controlled from a gnd or 0v signal and to turn the led off when voltage is added?
Thanks !!


texts: Eagle help- vias won't connect to GND plane

texts:
I'm trying to place some 100W wire wound resistors on my board and I'm going to be using my ground plane and some vias as my heat sink. I have a polygon labelled "GND" on both sides enclosed by a stop mask so the copper will be exposed. There is also a GND polygon filling the entire board on both sides, not just near the resistors.

Most of my vias connected to the ground plane without issue but a bunch of them won't connect and I'm unsure why. You can see the airwires in the screenshot below.

I've seen a few other people have issues getting things to connect to the ground plane but the solution usually had something to do with a specific package.

All of these vias are right next to each other on top of the ground plane with no traces between so I'm not sure why only a few won't connect.

Any thoughts?


texts:
I apologise for the attached picture, I just made sure everything is readable so you can assist.
So I'm wondering if this is a logical idea, if 12 volts is supplied, to the circuit, as the capacitor reaches the zener 5.1v + 0.65v of the transistor Vbe, it will switch off the p channel MOSFET, and thus stop the current flow from supply, until the voltage in the capacitor drops below 5v1 + 0.65v again, which in turn will allow the p channel MOSFET to be switched on again.
Is this possible? Please feel free to correct me, thank you.


texts: Resistor Divider Circuit with Voltage Bias

texts:
Could someone please help me to calculate the output voltage across the voltmeter of a resistor divider network as shown in below schematic whose input can vary from -20V to +20V, R1 = 43K, R2 = 5.1K and Bias Voltage on R2 is 2.5V.

simulate this circuit – Schematic created using CircuitLab


texts:
I am reading some specs about Intel CPU. The word bank appears in the following contexts. I am not a native English speaker. Please help me understand its meaning. Thanks.

From the Intel Manual Vol. 3B Chapter 15.1:

  The Pentium 4, Intel Xeon, Intel Atom, and P6 family processors
  implement a machine-check architecture that provides a mechanism for
  detecting and reporting hardware (machine) errors, such as: system bus
  errors, ECC errors, parity errors, cache errors, and TLB errors. It
  consists of a set of model-specific registers (MSRs) that are used to
  set up machine checking and additional banks of MSRs used for
  recording errors that are detected.

And... 15.3.1.1 IA32_MCG_CAP MSR:

  MCG_CMCI_P (Corrected MC error counting/signaling extension present)
  flag, bit 10 — Indicates (when set) that extended state and associated
  MSRs necessary to support the reporting of an interrupt on a corrected
  MC error event and/or count threshold of corrected MC errors, is
  present. When this bit is set, it does not imply this feature is
  supported across all banks. Software should check the availability of
  the necessary logic on a bank by bank basis when using this signaling
  capability (i.e. bit 30 settable in individual IA32_MCi_CTL2
  register).

I understand the bank in first quotation just means a bunch of MSR (Model Specific Registers). But what does the bank in the second quotation mean?


texts: resonator or Crystal Oscillator for atmega2560

texts:
I've received the PCB that I have designed.

This PCB has an atmega2560 on it.

I have designed it to use a Crystal Oscillator such as this figure shows :

Is this designed supposed to work on an atmega2560 ?

Because, when I look at the schematic of the arduino mega, I see that they don't use a crystal oscillator, but they use a resonator with a 1M resistor :


texts: Simple Impedance/Admittance based Transmission/Reflection Simulation

texts:
TL;DR: Why does the (pseudo-)code below produce a different output than a proper simulation software?
Edit: -> Answer: The program (RFSim99) displays only abs, not squared (which is what I plotted). Hadn't even considered that as an option.

Full problem description:
I want to be able to simulate simple (idealized) RF circuits, such as resonators, filters etc, in a self-written program (I currently use python).
The first circuit I attempted the simplest example of just a capacitor:

The way I implemented this is the following (pseudocode):

Z0 = 50
func YC(f,C) = 1j*2*f*C
func ZR(f) = 1/YC(C=27e-12) + Z0
func s11(f) = (ZR(f) - Z0)/(ZR(f) + Z0)
func s21(f) = ZR(f)/Z0
plot(abs(s21(x))^2, abs(s11(x))^2, x={1,...,10e9})

This gave me something which is very similar to what I'd expect:

But if I compare that with a very simple software (RFsim99, all ideal models)

This small, but not negligible discrepancy can also be seen in slightly more complicated circuits, like a simple resonator circuit (see below). I am wondering where the discrepancy could come from.

What I've tried so far: I tried several things like adding series 50 'resistors' to emulate the admittance of the ports; I checked weather my chosen language (python) handles the inversion of complex numbers well and it does. I checked time and again if the RFsim-Software has some 'more physical' model for it's components, but since you can explicitly turn these off and on (and I have them turned off) and the manual doesn't say anything, I strongly believe, that it should be an 'ideal' model. I tried using more physical models for the capacitor (by adding inductive and resistive elements), but to no avail.

Question: Does anyone have any new (see above) ideas or suggestions?

Here are the 5GHz resonator's results:

P.S.: If you have a more accurate title, please feel free to change it!


texts: Interpret the arrows in a circuit diagram of an OP-amp

texts:
I have the following diagram of an ideal OP and
$$
y=-Ae \tag 1
$$

simulate this circuit – Schematic created using CircuitLab

I'm not used of using arrows for voltages, so I don't grasp the meaning of the arrow \$e\$. I tried to redraw the diagram below. Is \$e\$ the voltage difference between the inputs \$+\$ and \$- \$? I call them \$v_2\$ and \$v_1\$ below, so is \$e=v_2-v_1\$?.

Is the following diagram equal to the one above?

simulate this circuit

And also, why the negative sign in equation \$(1)\$?
Using my diagram we have \$e=v_2-v_1\$ and \$v_2=0\$ so
\$
y=Ae=A(v_2-v_1)=-Av_1.
\$
But this is not equal to equation \$(1)\$...


texts: Driving a 3v Latching Relay with an 1.8v logic MCU Not Working

texts:
I have a battery powered device with an 8051-base MCU running off a 3v coin cell (with a DC/DC converter down to ~2.1v).
I'm attempting to drive a 3v dual-coil latching relay using two GPIO pins of the MCU with the following schematic:

simulate this circuit – Schematic created using CircuitLab

However, when running off the battery, the above does not work. It does work when powered off the debugger, which supplies 3.3v, without the DC/DC converter.

The parts in question are:

CC2541 MCU
DMG6968U N-Channel MOSFETs
RT314F03 Latching Relay:
1N4148W Diode

Is there something inherently wrong with the design? Is there something I'm missing? Something else I can test?

Perhaps there's a better way to drive this (or another) relay from a battery powered device?

Thanks in advance!


texts: Distributed parameters of an unknown conductor

texts:
I have been asked in my assignment to find the values of the four distributed parameters R, L, G, and C for the following transmission line:

  A 790 m length of 50 Hz power transmission line is represented by a
  symmetrical 'nominal PI' equivalent circuit. The series impedance Z
  consists of a resistance of 12.3 ohms in series with an inductance of
  1.49 mH, and the parallel branches at each end consist of 1.8 nF capacitors.

Now I think there there is something missing in the line description. Shouldn't I be given the conductor material i.e. its conductivity, permeability, etc.?


texts: Is energy consumption of the 3kw kettle lower than 2kw kettle?

texts:
On the market there are 2kw 1.7 liter kettles and also 3kw 1.7 liter kettles.
I understand that bringing the same quantity of water to the same temperature require same amount of energy, but from the engineering perspective could it be that one or the other have better efficiency etc.


texts: Impedance matching: is coaxial cable Z important?

texts:
I am working between 1-5 MHz, pure sine wave from signal generator.

I have been using transformer to match the impedance of source (50 ohm) to load (2-10 Ohm).

My question is does it matter that I need to match the characteristic impedance of the coaxial cable on primary (connect from source to primary coil) and, specifically, secondary transmission (connect from secondary to load)?

Edit: the cable is about 1 metre or less


texts: Data Centre Rack Power Connector options

texts:
I am tying to educate myself on the options I have for Data Centre power connectivity in our racks, for both UK and USA Data Centres.  I am UK based so have a better understanding of the UK options, and have minimal experience with US Data Centres.  I am confused by the US Equivalents, as there seems to be many different options.  I know their domestic power is typically 110V, but they also seem to use higher in some circumstances.  All My DC's are in NY, so I am interested primarily from their perspective, if there are many state differences, but also good to understand the differences incase we have a presense elsewhere.

I usually use PDUs from APC.  I am trying to choose from the Rack PDU Selector

In the UK, I have typically used 230/240v 16A or 32A single Phase delivered to my Rack PDU via a Blue IEC 60309 32A P+N+E or 2P+E.  This is fairly simple.  It seems there is a 60A version of this as well, but my DC's don't support it.

Q1.  Is P+N+E The same as 2P+E?  I am assuming P is Pin or Pole, not Phase. Or is the 2P+E doing something different?

My racks are starting to need more power than a single phase can deliver, and this is where my knowledge starts to reach it's limits.  The kit in the racks is still all single Phase 230V on IEC C13/14 or C19/20 connectors. There is just more of it, and each socket is drawing more.

As I understand it in the UK, 3 phase power for racks is usually a Red 63A 3P+N+E. Which is Three Phases (L1,L2,L3), Neutral and Earth.  The Voltage Between Phases is ~400V (Hence the red Plug) and the Voltage Between N and any single Phase is ~230V.  The Rack PDU's present three banks of outlets one for each Phase, L1,L2&L3.  This gives a total of ~25KW

Now that's all well and Good for the UK.  How does it work in the US?  I can see they often use the NEMA connectors, and the L6-30P seems to be roughly equivalent to the Blue 309 2P+E 230V.

Q2. Does the Data Centre kit in the US still run on 230v, or is it 110V?

Q3. What is the USA Equivalent or similar of the UK 3P+N+E 63A feed Connector, that would give me that would give me the similar total Power in the rack of around 25KW?

Q4. Why is it 63A and not 64A?  64 seems to be the logical progression from 16-32-64.  I'm a data network engineer,  I like numbers that are 2^n.

Q5. Is it ok if a device with dual PSU is plugged into different phases?  Would bad things happen if someone accidentally plugged one side into L1 and the other into L2?

Q5. What are the most common power connectors in the USA for different levels of Power delivery?


texts: Op-amp voltage on output during connection to constant current source

texts:
I'm looking to use an op-amp to control the voltage across a constant-current loop. To simplify things I think we can consider it a voltage follower. The constant current source provides 10mA, which is more than fine for the op-amp to sink. My concern is what happens when I plug it in.
If left in open-circuit the constant-current source appears to float to 18v. This exceeds the maximum 5v that I'm supposed to apply to the output of the op-amp, and through the feedback to the inputs. I'm not sure if this is a concern or not though because it seems as soon as the op-amp was to sink any current it would end up in the acceptable 0v-5v range.
Is this a concern? And if it's a concern how would I address it? I've considered maybe a zener between the output and ground, but would that work or would the op-amp still see higher voltages temporarily?

Example circuit where the switch substitutes for plugging it in, and the zener is used to simulate the existing max voltage of the constant-current source. Link to simulation
Edit: Okay, background on what I'm doing. The constant current source if from a garage door opener (GDO). It puts out 10mA on two wires that run to a wall console. That console has two buttons and an LED. Normally there's around 4v across the circuit. Either button will put a resistance across the wires. One button is 82.5Ω, the other is 203.5Ω.
I'm looking to use a microcontroller hooked up to the same two wires. I'd like to be able to set the same resistance across the wires programmatically while keeping the existing functionality of the wall console.
My first solution was using 3 signal relays and 2 resistors. This seems like it would work, but is kind of bulky and I'd rather avoid mechanical relays if there's a small ic solution.
My second solution was using transistors/mosfet with resistors. In that case I'd have to disconnect the existing load and maybe need one relay for that anyway, and by the time I add 3 mosfets and 2 resistors the cost wasn't really cheaper than a cheap DAC.
On my previous question someone suggested a voltage source instead, so my third solution is a DAC with buffered output (op-amp). The existing circuit is pulled to around 2v from 1 button, and 850mV from the other. From playing around in that simulator it seems I should be able to pull the same using the output of the DAC.
In normal operation this seems like it should be fine. The op-amp would sink 10mA and the correct resistance to set the other side of the circuit to the correct voltage.
The issue I'm having is figuring out the error cases. For example if the wall console is disconnected for some reason (eg during hookup) then sticking a multimeter between the GDO pins shows ~18v. It seems it can't push harder than that. Once everything is hooked together the op-amp should easily be able to keep things in the 0v-5v range by just sinking that 10mA. I just don't know what happens when I plug an 18v wire with no current to back up that 18v in to a 5v op-amp.
If there's better solutions to this problem them I'm all for hearing them. Ideally whatever I put across here should put a minimal load on the existing circuit and I'd like the existing circuit to work if the mcu is off.


texts: Capacitor in parallel decrease my power factor

texts:
I made a DIY solar system including a batteries and a pure sine-wave inverter, and I wanted to increase the power factor (which is typically 0.6 ~ 0.8) with a laptop power adapter load.
After calculating the right capacitor value, I tried to connect a 1.5µF in parallel to increase the power factor; unfortunately the power factor was actually decreased.
On the other hand, when I connect a fan containing an induction motor, the power factor goes above 0.9!
I don't get why this happens.
By the way, I don't have an oscilloscope.
My meter reads:

The calculations I made:


texts: I'm building a portable charger for my phone using a large 2.7v supercapacitor, which uses a very simple boost converter to create 5v. I am not concerned about input current, however, when a load (my phone) is connected, the voltage falls to 4.53v, regardless of any changes I make to the duty cycle, frequency, or inductance. My best guess is that my phone only begins charging when the voltage increases over this point, but this causes the voltage to fall again and oscillate. My question is, how can I increase the amount of current that the boost converter can source, so that the output voltage will be nearer to 5v?


texts: What is this schematic symbol that is a circled capacitor?

texts:
I am trying to determine what this symbol is that looks like a circled capacitor and is labeled as "Z1" that I circled in blue below.

Here is the full schematic with this component being near the top left at the input.

In my search I found this question with a circled capacitor and a dot but I'm not sure if its the same. I also found websites saying Z is for zener diodes which this obviously is not or this website that says Z could be for  a balun, general network, or phase shifter but I did not find circuit symbols that match this one when googling those.


texts: usb drive EEPROM IC how is memory read-only blocked and unblocked?

texts:
I notice ofteen free give-away usb thumb drive come with a certain memory space locked and unwritable so that a 4 GB flash drive for instance has 1GB of advert which cannot be format.
Given that thumb drives are quite standardized, for instance they have a IC SK6211 to interface a EEPROM IC to the computer and a crystal oscillator, I wonder where they hardwire the information to lock a certain space of the drive.
Is it a pin pulled to ground or something? any example available online or some common design in EEPROM IC?


texts:
[![enter image description here][1]][1]I am trying to build a simple circuit to power a load with two different power supplies (5 V and 0.7 V).

When one is active the other one is not and it's disconnected from the load. I know that this would be straightforward with a manual switch but I need this application to be automatic, maybe using a MOSFET as a switch controlled by a uC but it's not clear to me how I can achieve that. I wouldn't use a relay since I have constraints on cost and size of the footprint.
Thanks.
Claudio


texts:
I recently started developing an interest for electronics (doing mods for my car, Delayed lights etc...) so I decided to sign up here.

I have some questions about capacitors (which are very new to me).

My question is since they have got +/- sides, do I need to ground them or does this work on hot side only like the image, say the bulb in the image is car park lights. As far as I know, this should take about 1.5 sec to reach 12V.


texts:
I am planning to buy an LCD display which has been customised as per my needs and it will comprise of 128 segment.
I was planning to buy a stm  MCU which will contain an LCD driver inside it while keeping the total cost of such a unit to less than $2 in a quantity of more than 50.
I came across STM8L052R8 which suggests it has built in lcd controller for 4x28 or 8x24 options.
So that means, my custom lcd should be designed such that it can be driven by this particular stm, so I'll need to choose 8 com+16 fp pins.
I'm unable to get any directions where the RAM to LCD pin mapping is kept. Any help would be welcome. Also, if my thought process is okay.


texts:
Sparkfun sell a module with the INMP401 module on (Datasheet), it has a small amplifier circuit and I have been using it in a project.

I am creating my own PCB for this and I've just noticed that the module is obsolete and I can't seem to identify a replacement.

What would be a good replacement for this microphone?


texts:
On my other question I asked about how could I regulate a TEG like this:

for a 12 V, 10 W load I have. My first idea was to use some resistors, a zener diode and a linear voltage regulator. But people said that a buck converter would be better.
The problem was that I could not find a buck converter that could handle the 96 V max input from the TEG, at least where I live.
After thinking for a while, I remembered that this TEG curve I showed is actually for 20 peltier modules connected in series so I could instead connect two strings of 10 in parallel for a resulting IxV curve like this:

That should mean something like this:

And now I can use an adjustable  LM2576HV module to regulate the 12 V and allow at least the 10 W from the TEG.
The only detail I saw is that maybe the voltage from the TEG won’t be exactly the same and some reverse current might occur, my idea was to add simple blocking diodes to the output of each string to avoid reverse current, so my final circuit looks like this:

What do you say? Any room for improvement? for me it seems pretty ok.
Thanks in advance!


texts: Temperature degradation of ferrite cores

texts:
While building smps halfbridge (old ATX similar) recently I went to a problem:
When I use working transformer as a base drive one - it works good, but when I heat it up, unwind, and wind the same - it doesn't;
To disassemble the core I use this tehnic: https://www.youtube.com/watch?v=IOwT8GkvIjs, which works well, but unfortunately I think it degrades core properties:
I made a test - I wound 4 additional 4 turns on the factory working transformer, inductance I measured was 18 uH, then i coocked it up, and mesured it one more - only 2-3 uH!!. Why does this happen? Is it normal? Is it possible to disassemble this cores without this happening? Can I somehow restore core properties?

Photos after boiling (core is glued with hot glue, so there is not visible gap):

Please, help!


texts: What is an instrumentation amplifier and how does the AD524 work?

texts:
I am struggling with instrumentation amplifiers. Particularly, I would like to know

what defines an instrumentation amplifier
what kind of circuit configuration could be classified as an instrumentation amplifier
how does an AD524 work.

In fact, firstly I've seen the so-called INA111, the circuit of which, available in its datasheet, is reported in the following picture

Where \$R_{\text{gain}}\$ is an external resistance to be connected to two proper leads of the integrated circuit and it's used to adjust the gain.
Later on I've noticed that even Wikipedia provides a page named "instrumentation amplifier" which also shows the some gain and the some circuital configuration of the INA111.
So I thought "this circuit is an instrumentation amplifier". But later I realized that something is wrong with this...
By the way, I also figured out how to calculate its gain, by calculating separately each one of its parts, as reported here

"blue part" gain

$$
\qquad V_{o1} = \left( 1 + \frac{2R_1}{R_{\text{gain}}} \right)V_1 - V_{m}\frac{2R_1}{G_{gain}}\\
$$

"green part" gain

$$
\qquad V_{o2} = \left( 1 + \frac{2R_1}{R_{\text{gain}}} \right)V_2 - V_{m}\frac{2R_1}{G_{\text{gain}}}
$$

"red part" gain

$$
\qquad V_+ = \frac{R_3}{R_2}V_{o2}
$$

"orange part" gain

$$
\qquad V_{\text{out}} = \left( 1 + \frac{R_3}{R_2} \right)V_+ - V_{o1}\frac{R_3}{G_2}
$$
subtracting the "blue part" with the "green part" and using the other two equations to eliminate \$V_{o1}\$ and \$V_{o2}\$ the total gain I get is
$$
G = \left(1 + \frac{2R_1}{R_{\text{gain}}}\right)\frac{R_3}{R_2}
$$
which is in agreement both with Wikipedia and the INA111 datasheet.
But afterwards I faced the AD524, which still is classified as an instrumentation amplifier, but its internal structure is

Not only is it not the previous circuit configuration anymore, but also I do not recognize inverting, non inverting or differential configurations. I don't know how to calculate its gain neither I do not know how does it work. Furthermore, I do not properly understand how to connect many of its leads.
So now, how do I understand its behavior? How do I calculate its gain?


texts:
I'm trying to interface a 3.3V I2C device to a 5V Arduino.

I don't have any problem with SCL line.
I can use a simple voltage divider but I have an issue with the SDA line as this is bi-directional.

I'm not at all sure how to handle this. I have though of adding a pair of diodes, with a voltage divider on the slave input side and nothing extra on the master input.

Are there any other solutions?


texts: troubleshooting GEOFEX guitar effect panner

texts:
I'm building a circuit that allows me to blend a guitar effect in and out, based on >this< (page 2, bottom circuit). I have, however, replaced the 10k pot and the 15k and 51k resistors with 100k, 150k and 510k.

The blending works fine, however the volume is too low, and the blend pot is prone to noise when in the middle position, which makes me think of an impedance problem. Do I have to replace the 1M resistors at FX in and FX out with 10M ones?

Also, the circuit clips quite early. I checked the voltages at the opamp's pins, and, while the second half is OK, the first half has 3.5 at the non-inverting input and 4.5 at the inverting one and at the output. Those should all be within 10mV from each other, right? Try as I might, I couldn't make it right.

I'm in kind of a hurry, and this pedal has already taken me more time than I could possibly give. I'll be immensely thankful if somebody pointed me in the right direction.

Here's my schematic. Right click and choose "view image" to see it in full.


texts: How to drive a P-channel MOSFET with a MCP1407

texts:
I'm designing a buck converter with an input voltage of 30V. For this I'm using a IRF9540 P-channel MOSFET which I need to drive from 0V to 30V relative to ground to fully turn it on and off respectively.

I always used a MC1407 to drive my N-channel MOSFET but now I can't use it because the maximum supply voltage is 18V, far from 30V. I tried the classic push-pull with BJT transistors and it works kind of well until I approximate to 20% duty cycle (I'm working at 150kHz).

My question is, can I put 15V in the GND pin of the MCP1407 and 30V on Vdd? On this way I wouldn't be exceeding the maximum operating voltage and I could drive the P Channel MOSFET perfectly.

I also thought about using gate driver transformers but my duty cycle can exceed 50% so they are not an option unfortunately.


texts: Why doesn't the leakage currents automatically turn on thyristor?

texts:
I understand that when \$TR_1\$ and \$TR_2\$ are ideal transistors, we need an initial \$I_G\$ current pulse signal in \$G\$ to turn on the thyristor. This \$I_G\$ will turn on \$TR_2\$ and the collector will current of \$TR_2\$ will turn on \$TR_1\$ and the overall system (the thyristor) will conduct.

However, when we work with realistic electronic parts, there will be a a tiny leakage current through \$TR_1\$ (from emitter to collector). This tiny current will create a collector current through \$TR_2\$ which is \$h_{FE}\$ times multiplied. And this collector current will further increase the current through \$TR_1\$. So on, this loop of events will cause an avalanche effect and finally, in a very short time, both transistors will saturate and the thyristor structure will conduct.

But it doesn't happen so.

Once I tested a thyristor on bread board. Initially I didn't connect anything to its gate; I left it open. The thyristor didn't conduct until I touched its gate with a cable which had some positive voltage on it.

Why doesn't leakage currents turn on thyristor automatically?


texts: Stray Input Capacltance Compensatlon with constant-GBP OpAmp

texts:
In the book: Design with operational amplifiers and analog integrated circuits, section 8.2, it shows a circuit as below:

And give:

$$f_{z} = \frac{1}{2\pi(R_{1}||R_{2})(C_{n}+C_{f})},\:f_{p}=\frac{1}{2\pi R_{2} C_{f}}
$$

And the locations of fz and fp are shown at right. Apparently, it assumes fz is lower than fp.

Actually, because this is a amplifier circuit, so R2 may much greater than R1, and we may choose a Cf much greater than Cn (Cn is the stray capacitance at the inverting input terminal, usually small). Then the zero can be approximated as:

$$f_{z} \approx \frac{1}{2\pi R_{1}C_{f}} $$

Because R2 is bigger than R1, so we can choose a R2 big enought to get a fz greater than fp. Is it stable or not in this situation? The textbook don't mention this. Or simply, can I choose a much bigger Cf to move fp lower than fz, what's the cons and pros?


texts: Transistor input and output characteristics

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Why do we change output voltage for plotting input characteristic of a transistor and change input current for plotting output characteristics of the transistor?

I am self reading the material and I have no teacher.


texts:
I am currently working with software for a safety relay and during my work I started to think about how much time it takes for a relay to switch.

The relay and it's data sheet I am using can be found here:
http://www.digikey.com/catalog/en/partgroup/sr2m-schrack-series/960

Can somebody help me understand how to calculate the time for this relay to toggle when it has maximum current load (6A)? Considering the worst case scenario.

I suspect that the parameter "Frequency of operation, with/without load 6/300min-1" have something to do with my question but I can't understand it.


texts: Portable power supply for over 300 ws2812 LEDs (similar to youtube video)

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I have an idea fro a project which requires a few hundred ws2812 LEDs to be powered using relatively small battery which can be carried. I was wondering how you could power over 300 ws2812 LEDs similar the dress in this Creators Project Video on Youtube:

https://www.youtube.com/watch?v=oo_7s4TrL28

The dress looks like it has atleast over 250 LEDs (assumed to be ws2812s) , and they are all powered with a single rechargeable Li-Ion battery.

My calculations show that

300 LEDs × 60 mA ÷ 1,000 = 12 Amps minimum

How did she managed to power all those LEDs with a single battery one could carry?

Please forgive me for being a noob.


texts: current limiter / short circuit indicator for a variable power supply

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I am building a variable power supply circuit and I am wanting to add a current limiter or a short circuit protector to its output. I feature that I'm attempting to add to the protector is an indicator of load resistance that falls below a certain threshold. To be more specific, the power supply is run from a 12VDC power source and has an LM350 voltage regulator. The output is narrowed between 3-5VDC. The load will vary between 1.8 to 2.5 ohms. The load on average will be 2.2 ohms. The load on the power supply will be 3 amps. It is to run between 1.7 - 2.4 amps normally. I am having trouble searching for a circuit to handle this without having to use HUGE transistors or resistors due to space constraints. It would have a green LED and a red LED. If the load on the circuit is within 1.8 to 2.5 ohms then the operation is normal and the green LED is lit. If the load falls below 1.8 ohms, the load is either cut or is used to have the red LED lit. I first felt that it would look similar to the circuit found at:
Power supply short circuit protection
but finding an SK100 transistor apparently is not easy or I have to substitute it with a physically large transistor. I am currently using gEDA to design the circuit but can't seem to make heads or tail of NGSpice or GNUCap to test and adjust the circuit (or I simply don't know how to use them properly) and have only contemplate almost having to learn another programming language to use them. Some of the free online graphical simulators have given either vague or inconclusive results.  One of the schematics that I have put together is the same PS with a different circuit protector. At this time, I'm sure it's calculations may be off. Can anyone point me in the right direction to help solve this or suggest a better protector circuit? Many thanks in advance.


texts:
I am planning to create a mobile application that scans a NFC tag and performs an action based on the unique scan (tap). Because Apple iPhone do not support NFC I am forced to look for an alternate option i.e BLE 4.0 (at least works for iPhone and android)

MY NEEDS

I just need to trigger the action when the user is very close (like a Tap). Not looking for a geo-fencing or location-sensing use case.
Had iPhone supported NFC, I would not have needed BLE Tag. A cheap NFC tag would have solved my need.
Pairing is absolutely not possible for my app. User case just does not fit. User should be able to tap any Tag without pairing

BUILD OR BUY

The are plenty for BLE Tag providers in market (BlueCats, Estimote, Sonic notify etc), but they are turning out to be a bit expensive for me (all in the range of $15-20 in bulk). If I have to install 50 beacons per location and may be 1000s of locations, that's a big cost.
There are few chip makes like TI and Nordicsemi. Would it be cheaper to get it manufactured with help of an OEM manufacturer?
Any tips/best practices if I decided to Build instead of Buy?
Should I even think of Building one?


texts: Anyone know why the TP4056 shuts down in this config?  If I bypass it, everything works and the measured current does not exceed the limit of the TP4056.


texts: Is there a good overview to find connector types?

texts:
While taking a look into my overheating B&O speakers, I unfortunately ripped off a connector. Now I need an exact matching replacement, but I did not find it in any online-shop by filtering.
So my more general question is: Do you know a good website/database to find out the type of a connector?
If there is none, can you help me to find the type of the connector in the image below? There are 2x10 rectangular pins with a rough 1mm pitch.

Edited: It is an DF50-20DP-1V by Hirose


texts:
Possible Duplicate:
  Choosing power supply, how to get the voltage and current ratings?

Can I replace the power adapter of 12V/0.8A with one of 12V/2A?

I have a Digital device that uses a power adapter to 12V/0.8A, and it stopped working.
Can I replace it with other adapter that is 2A? Would this work? And what effect would it have?


texts: how to resolve LM358's huge error as a current sense differential amplifier

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I've built a current sense differential amplifier that measures the voltage across a 1 Ohm resistor, to give me a reading for the current through it.

I've connected it as follows, all resistors are matched 10k to give a gain of 1:

(Image source: Electronics Tutorials)

I am powering it from a single rail 12 volt source. The problem is even though this is a rail to rail opamp (Output Low swing from 5-20mV) I'm getting a constant error of 0.62V and it seems the opamp is not able to go below this value.

I have tried to resolve this by connected Vout to ground using a 10k resistor, but that makes no difference whatsoever.

I tried it with dual supply configuration (+8V, -8V) and that seems to resolve the issue. However I want to run this off a single supply rail, so this is not a viable option.

How can I resolve this? I'm trying to measure the voltage drop across a 1 ohm resistor to give me a reading for current through the circuit (0-1V represents 0-1 A) so I can set up a current limit. A better way (or practice) to doing this is also welcomed. The initial (but not ideal) fix I can think of, is to offset the readings by a few volts?

Edit:

Changed R1-R4 from 10k to 100k and I'm down to about 30-50mV!


texts: I am not sure if it is the right place to ask this kind of question, but I wasn't able to find anything specific on this subject. In OCPP 1.6/2.0 documentation, there is a part about stacking charging profiles and specific example of charging profile of purpose TxDefaultProfile with a duration and recurrence of one week that allows full power or current charging on weekdays from 23:00h to 06:00h and from 00:00h to 24:00h in weekends and reduced power or current charging at other times. I can think how to make charging profiles for 'Daily' recurrencyKind, but I have no idea how to implement profiles with 'Weekly' recurrencyKind, let alone combine one with multiple other profiles. Has anybody dealt with stacked charging profiles before?


texts: How to implement Quartus IP cores using ALMs?

texts:
This is a follow-up question on this, where I had asked about how one can implement multiplications without using any DSPs of the FPGA.

Now, I would like to know whether one can implement Quartus IP cores such as floating-point multiplier using ALMs (LUTs) instead of DSPs. I tried applying the answer to my previous question (i.e. (* multstyle = "logic" *)), but it did not work.

Is there a method for implementing the multipliers, adders, and MACs in the IP library using logic blocks rather than DSPs?


texts:
The LIS3DH 3-axis accelerometer specifies that it's supply voltage should be between 1.71 V and 3.6 V. For most applications, this just means you are using either 1.8 V or 3.3 V as your main rail. However, page 12 of the datasheet also mentions that the absolute maximum for the supply voltage is -0.3 V to 4.8 V. Given that it includes a negative voltage, I'm going to assume that this rating is the safe voltage range that can be applied to the VDD pins.
It does specifically mention that "functional operation of the device under these conditions is not implied", but could I safely operate this device directly and exclusively from a LiPo battery? 2.7 V to 4.2 V is well within the absolute ratings, but what exactly am I risking at this point? I'm also not the first one to be using these kinds of voltages (ST Forums Thread).
Before you ask, using an LDO doesn't make a lot of sense for my application due to the extra circuitry to facilitate a multi-voltage I2C bus and limited PCB real-estate. I didn't feel like it was strictly necessary to include detailed info about my application for my specific questions, but I'd be happy to provide it if needed.
LIS3DH Datasheet


texts: TP4054 Battery Charging IC - Weak Pulldown / TriState Output

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I'm playing around with a TP4054, which is battery charging IC -- and I didn't know what I was doing when I added it to a sample board.  The CHRG pin is similiar to the Microchip MCP battery charging ICs, I think they call it the STATUS pin on the PIC parts.

I didn't read the datasheet in English, and I assumed it was not a tristate output for the CHRG pin (which basically goes high, low, or high impedance).  I thought it was just a AC present high signal, or no AC present low signal.

I'm confused about one state in the datasheet.  With no AC present, the chip is high impedance.  With AC present and charging, drives low.

With AC present and battery charged -- I don't get it what is happening...

TP4054 Datasheet translated to English

Here is the description of the CHRG pin:

"Open-Drain Charge Status
Output. When the battery is charging, the
 pin is pulled low by an internal
N-channel MOSFET. When the charge cycle
is completed, a weak pull-down of
approximately 20µA is connected to the
pin, indicating an “AC present” condition.
When the TP4054 detects an under voltage
lockout condition, is forced high
impedance."

Two questions:

1)
What exactly is the "weak pull-down of approximately 20µA"?  What does that mean?  How is that different from being pulled to ground when it is fully charging?

I originally had an internal pull-up on this CHRG pin, assuming it just pulls low when it is charging but this weak pull-down is monkeying with my MCU logic levels as it no longer reads as a low.  What exactly is happening here?

2)
When no voltage is detected, the CHRG pin goes high impedance -- meaning it becomes an input.  I've seen people recommend you built a voltage divider from VCC, and use an ADC which will read whatever voltage the divider makes when the CHRG pin is high impedance.  But what happens with this weak pull-down condition with the divider network?


texts: generating a 10mVpp signal from computer

texts:
I have an input to a system that requires a 10mVpp max signal.  I have to use my computer to input it due to constraints out of my control.  I am well aware an audio card cannot go down that low.
I have several attunators, one active and one passive (just a potentiometer and some resistors).

no matter what I do I cannot get the signal to go that low.  I have also tried introducing a digital amplifier (just some high quality digital speakers with an audio out) into the system between the computer and the attenuators but had no success.

Where can I go next?  what other information can I provide to help.

I am running audacity on a dell optiplex 760 (my computer) and it has the manufacturers audio card in it.  I did some quick research and it seems most built in audio cards have about 46Ohm impedence.  I couldn't find info on my exact card.  It maxes out its output at about 3Vpp and starts to struggle keeping its output stable below 150mVpp.

I am also using a probe master 20:1/200:1 active attenuator (model 4231) and a homemade potentiometer attenuator.. about as simple as it sounds.

ANY help is appriciated.. this is stumping several of us and we are unsure of where to go next.

thanks in advance!


texts: How do I quantitatively describe a system with 2 parallel diodes and a current source

texts:
What would happen in this system? How can I find the bias point of a circuit like this:

Considering the LEDs are not perfectly matched. The 35mA are generated by a high precision stablizied current source.

I tried to find the voltage over the LEDs, but I can't seem to find an expression that makes sense. I thought that the voltage depends on the current that flows through the LED, but the current also depends on the resistance of the LEDs in their bias point. That bias point might be different for the two LEDs, so the voltage might be different as well, but that makes no sense as the terminals are connected on both sides.

I'm not getting anywhere with my thoughts. Any ideas? Also, considering those are LEDs, wouldn't the generated heat effectively shut down one of the LEDs in a chain reaction after a short while?


texts: How to charge multiple 3.7V LiPo batteries in parallel?

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let's say I have 4x 3.7V LiPo batteries connected parallel.
I want to use TP4056 charger boards to charge them. (see picture)
As a power supply, I use a 5V 15A adapter, so there is plenty of power available.

So why it's charging with only less than 2A?
TP4056 is 1A charger, so with empty batteries, I assume it should take 4A from power supply right?
But it doesn't...

If I use 4 separate power supplies, then it works. But I want to use only one. What am I doing wrong?

Thanks


texts: AC motor turning a certain turns and stop, then can turns reverse only for certain turns

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I bought this motor from some one who said it was used in an automatic recliner armchair sofa.

The motor can turn only certain turns [set N] and stop, then can turns reverse only. It can resume the same direction turning if manually stop it before it reached N, till got N and stop.

Any suggestions?

OK, here comes the result feedback. I opened the motor and found that there is a sets of gear group in the back end, which drives a drum wheel that can trig a limit switch after certain turns.


texts: Determining maximum current through 18 gauge wire in robot arm

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For a robotics application, I'd like to power some external electronics and sensors off the logic circuit in a robot arm.

The components are a computer (19V, 65W => 5A), 2 cameras (1.2A), 1 light (0.35A), USB2.0 I/O board, and power board. All this on top of current draw from the motor logic, which runs off a 4.3A power supply atm. Therefore, I estimate the upper bound to be 12A.

The logic power runs through an 18 gauge wire. According to this table, 18 gauge permits either 16A as chassis wiring, or 2.3A as power transmission.

Note the robot arm is roughly 0.6m long; obviously, because the logic power runs internally, the wire length is greater than 0.6m.

Will I be able to power my electronics from logic power?

I am willing to test my system empirically.

(BTW, as a CS major, I have zero experience with electronics.)


texts: Bluetooth low energy digital thermometer approvals

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We have developed a bluetooth low energy digital thermometer and need to know what certification processes we need to go through to be able to sell it in the USA.  I am happy about the EU and the UK with the CE self certification but unsure of the USA process.

The unit uses an approved BLE Module and an approved plug in PSU (for charging).  Do I need to go through independent testing of the finished product or will the already approved certification be enough?


texts: How do I actually verify that a flux is made for electronics and not plumbing?

texts:
After seeing a question about soldering flux and in particular flux paste which I'm interested in trying, I was reminded that there is a lot of confusion and scare about solder flux. I'm one of the confused.
Plumbing flux is bad

Tom Carpenter learns the hard way, from his answer.
There are two basic things people ask about: No-clean and Plumbing flux. My question now is only about plumbing flux, which we all know not to use on electronics. If you accidentally use plumbing flux it must be cleaned. A few random quotes from high-rep users:
Majenko, Nov 18 '16:

Fluxes designed for metalwork, such as soldering pipes, is generally an acidic flux and must never be used on PCBs or it will corrode things horribly.

WhatRoughBeast, Jul 8 '17:

In general, though, solder pastes are acid-based, and much more aggressive than rosin-based. You can use such fluxes, but intense care in washing off the residue is required to avoid corrosion later.

Just buy the good stuff!
With the influx (get it?) of large international marketplaces it can be difficult to know for sure what you are buying. Translation errors, different brands in different regions, different regulations on what has to be printed on the label, the possibility of the sender to stock or ship the wrong thing, counterfeit products, etc. Since the internet still is pretty U.S.-centric (for natural reasons), a lot of recommendations are for U.S.-based products not readily available in other parts of the world, or are much more expensive.
But how do you know?
Sometimes they tell you straight up on the package: "Not applicable to PC boards", but you're not always that lucky. The user in the question that prompted me to ask here thought that his flux was corrosive because it had warning labels, but here is a quality U.S. made flux paste (SRA #135) that is obviously rosin-based and designed for electronics repair, and still warns against being "irritating to eyes, respiratory system, and skin".

Illustrations for the previous paragraph, click to enlarge
There are some questions and answers about the different types, and what the chemical composition is, etc, but I'm asking a much more practical question:
How can I verify or test at home that a solder flux I have bought is suitable for electronics?
Can I do it in a way that does not take 3 months? In a way that does not require a chemistry lab? What am I actually looking for? From what I understand there are degrees of corrosiveness so maybe it's not even possible to say for sure?


texts:
There are some devices that look like ordinary light dimmers, but are sold expressly for ceiling fan speed control. For example: Lutron Diva Quiet 3-speed control. Unlike an ordinary dimmer, this has a three-position switch for low, medium, and high speeds, instead of a continuously variable knob. The manual shows typical wiring, which is like an ordinary dimmer:

(the unconnected red/white wire is for an optional 3-way circuit)

I've heard people say "don't run a fan on a dimmer; you will start a fire", but don't say why. Yet, that Lutron sells this device expressly for fans suggests it is something other than an ordinary triac light dimmer, and that it's totally safe, but they also don't say why.

I also know when I bought this house, a different, uglier fan controller of a similar type was installed. Could it be that this ceiling fan is designed for this type of control, where others are not?

Can someone tell me, as an electrical engineer, exactly what these fan speed controllers do, electrically? How are they different from ordinary triac light dimmers?


texts: Controlling high voltage/current signals with a Pi function generator

texts:
YES, I understand corona, arcing, safety, and Ohm's law...

I am building a high power AC/DC variable power supply: Microwave oven transformers, CW voltage multipliers, flyback transformer, variac... Yes, the bits are potted, and in a massive heat sink with active air-flow. Adequate grounding, etc...

My question is: I would like to use a Raspberry Pi2 as a function generator/oscilloscope. I would use the analog GPIO for the function out, a bitscope for the imaging.

Do I control the upstream supply? The downstream power, or somewhere in between?

What is the best way to use the Pi to generate the signal (sine, square, etc.. vari freq from <1Hz to <1 GHz) then match that signal with the enormous values I get from the supply - a HVLC side, and a HCLV side isolated, and read the output on the scope image

I have a guy who will be coding the function generator, and the scope, so that I have preset wave forms, and display will be one period of the signal. The frequency change will be done via pot, the voltage with a Variac, and the current.. maybe a rheostat.

NOTE: The DC side will have signals: ON/Pulse - the pulse with variable dwell and delay, I thought to drive that with a simple relay.

Using 5vdc to control 0-1MvAC/DC (Not at the same time, and not necessarily that value for each mode)

It runs on 115vAC @ 60Hz. I had considered an LC for the variable freq, but this does nothing for different wave forms, and I do not believe that I can get the frequency range I am looking for with this method.

Thanks!!


texts: Maximum deliverable angular acceleration and torque of motor due to a load

texts:
I am currently in the process of sizing my flywheel for a reaction wheel that I intend to build as part of a project. I was wondering how to calculate the maximum acceleration and torque deliverable by my motor after I attach the flywheel to it.
The motor I am currently using is this Faulhaber 2610T006B, shown below:

https://fmcc.faulhaber.com/details/overview/PGR_4563_13825/PGR_13825_13814/en/SG/

I am guessing that the mass of my flywheel plays a part, but I am unsure how to do the calculations.

I am aware of the equation \$\tau\$ = \$I\$/\$\alpha\$ , I current have the \$\tau\$ that I require, so I would need \$\alpha\$ to find the moment of inertia required by my flywheel, so that I can size it to meet that requirement.

Thanks.


texts: Is this optocoupler driving relay circuit reliable and works great?

texts:
This is the circuit that I have, the optocoupler is an EL817 and the transistor is a BC817, the 24V relay is an  Omron g2r_1_e, a 24V coil relay.

But when the optocoupler input is floating (not connected to any thing,) VBE on Q1 is floating.

This circuit should be reliable, so I added a 10k pulldown resistor to Q1 base pin, therefore when the EL817 input is floating the Q1 base is always 0V and the relay always off.

This is a kind of darlington but I add a pulldown to it, and I don't if it will work well.

Will this circuit work reliably?

Are the values correct?

Update:

First the R2=1kohm,when i power the circuit on ,R2 is warm and draw current,its base limiting resistor ,it should not get hot!so i change it to 10k .

this is my calculation for R2 : I suppose Ibase Q2=2ma (relay coil current is about 30ma,relay coil is 24V) , 24v-0.7v(EL817 Vce)-0.7v(Q2 Vce) =22.6V ,R2=22.6v/2ma=11.3Kohm.=>R2=10kohm is good. Pr2=V*I -> Pr2=22.6*2ma=45.2mw so i select 0805 package.

1-Is my calculation right? 2-Is it ok i connect the EL817 collector directly to 24v without any resistor?(i think R2 is limit the current)


texts: I have doubt that can Li-ion batteries in a non-turbo charging  smartphone be charged with turbo charge? In a nutshell, can we apply more current than a rated current in li-ion batteries? What will be the consequences of this scenario? How it affects li-ion battery? Thanks in advance!


texts:
I am building a DIY laptop, and I need a battery pack that will allow me to use and charge my device as you would any modern laptop, i.e. by connecting a regular 12-19V DC power brick to a panel mounted barrel jack. Specifically, I don't want to have to stop using the laptop in order to charge the batteries.

But with Lithium-Ion and LiPo batteries having a habit of venting with flame when you mistreat them, I figure I could use some advice on how to build a safe and solid charging circuitry for a DIY laptop.

--

The project specifics:

My DIY laptop contains an ODROID XU4 single board computer and an iPad2 replacement LCD panel. From a power perspective, the needs are:

Single board computer: 5V @ 1A continuous, spiking briefly to 3A during startup
LCD + controller: 12V @ 1A (it technically accepts 5-24V, though I've read that it's unstable at 5V)

To power the 5V rail I have a buck converter which accepts 9-35V and outputs a nice stable 5V (up to 5A) for the ODROID. So my power source should be between 9V-24V. I've found that a 12V/4A power brick works perfectly fine.

For the best safety-to-power-density profile, I would like to use LiFePO4 cells, and I figure a 4S configuration is ideal, yielding a total voltage of 11.2V-14.4V.

Assuming around 1200mAh per cell, I would need 8 cells in a 2P4S configuration to achieve 2400mAh, which by my math should give me up to 2 hours of use between charges, which I think is adequate for a 'show pony' device like this.

--

Now for the question:

How would you go about charging a 4S configuration of LiFePO4 cells while the device was in use?

So far, the best idea I've come up with involves this batteryspace.com listing for a combined charging / protection PCB:

http://www.batteryspace.com/cmb-for-12-8v-lifepo4-battery-pack-4a-limited-with-dc-charging-fuel-gauge-and-full-protection.aspx

or alternatively, this one for 3S (11.1V) Li-Ion packs:

http://www.batteryspace.com/CMB-for-11.1V-Li-Ion-Battery-Pack-10A-limit-RoHS-Compliant-with-DC-char.aspx

If I read the listing correctly, that PCB would allow me to do 'pass-through charging' and it would keep the cells balanced and protected from overcharge, overdischarge, etc.

I would hook it up to my 2P4S cells, add a fuse between the PCB and my panel mounted DC jack for a bit of extra safety, and possibly another buck converter to allow me to use a wider variety of power bricks and still feed the correct voltage to the PCB.

But would that work? Would it actually balance the cells? Or am I missing something?

And for a bonus question: With a protection PCB like that, I assume I should be using cells that don't have their own built-in protection circuits - is that correct?

Sincerely, Jens


texts:
I am trying to familiarize myself with operational amplifiers by going through this book by Sergio Franco.

This is a basic question regarding the example given on page 16, which I am struggling to understand.

According to the explanation, V3 is equal to -6V.

I know that when operated with negative feedback, an ideal op amp will output whatever voltage and current it takes to drive VD to zero, or equivalently, to force VN to track VP.

The top half of the circuit looks like an inverting amplifier circuit, with the bottom half leaving Vp (Voltage at positive input) at 0:

What am I doing wrong here?


texts: Electronics Circuits Simulator Framework?

texts:
Is there a framework for circuits simulation that I can use through easy APIs? and return me an array of results for each component?

I want to build an android based simulator, so a java framework would be perfect, is there any advice?


texts: How is underground electrical infrastructure insulated

texts:
I know that overhead power lines use ceramic power-line "holders" to insulate the high voltage current from grounding itself from the poles.

But how do underground power lines avoid grounding? What insulates them?

I hope the question is easy to understand!


texts: Heating a 1km long wire to 110 C using a 12v supply from a car cigarette lighter

texts:
I am a complete newbie to anything electrical/electronics. I am doing a project where I need to heat a 1 km long (Nichrome/Kanthal) wire to up to 110 degree Celcius. The only power supply available is 12V from car cigarette lighter. Can someone explain what is the best way to attain this using the available resources please.

Thanks for your replies.

Thanks for your replies. I am intending to weave the wire onto a fabric which can easily withstand over 200 C. The wire will be in a continuous forms and the purpose of the wire is to heat all of the fabric. Imagine a blanket that is covering the back seat. something similar to heated car seats, but much hotter. It will only be used inside the car.

I could possibly connect the wires in parallel, but is not preferred due to the work involved. The thickness of the wire can be anywhere from 0.3 to 0.6 mm. Any thicker or thinner is not practical to lay into fabric. The 1 km of wire will be laid with in a 2-3 square meter of fabric.

By the way, this is to heat the whole car (atleast passenger area) so that the kids can sit in a warm car, rather than a cold car.


texts:
I'm doing the exercises from Wisc-Online. This one

I think they are really great to learn and practice and have already done a bunch of their practical trainings. But here I'm starting to be crazy. I need to calculate \$I_{r1}\$

Here's the schema :

simulate this circuit – Schematic created using CircuitLab

According to their lesson :

\$I_{Rx} = \dfrac{R_{T}}{R_{x}} \times I_{T}\$

So :

\$I_{R1} = \dfrac{R_{1} \parallel R_{2}}{R_{1}} \times I_{T}\$

With values :

\$I_{R1} = \dfrac{\dfrac{1}{\cfrac{1}{5000}+\cfrac{1}{10000}}}{\dfrac{1}{5000}} \times 3mA\$

\$I_{R1} = 50000mA\$

But the answer should be 2mA

What's wrong in my formula ? :'(


texts:
I am designing high-speed TTL-based processor.

I will be using only fast AC, ACT and LVC series, so switching frequencies will be in 100Mhz range with 1-3ns fronts.

I plan to use homemade 2-sided PCB (4-layer commercial-grade PCB is not an option). 'Bottom' will be VCC, 'top' will be GND with high-speed traces on it. Low-speed signals will be just soldered wires on top of the PCB. I plan to drill lots of holes across PCB and solder bunch of 1uF ceramic caps there to get some distributed capacitance.

Here are the questions:

1) What is optimal FR4 thickness for such high-speed schemes? I have both 1.5mm and 0.5mm FR4. I guess 0.5mm FR4-based PCB would allow some distributed capacitance between VCC & GND...

2) What is the optimal trace width for high-speed digital signals? As I don't know input/output impedance of all TTL devices I have, I can't do impedance matching. What is the optimal clearance between trace & surrounding GND? I guess it's hard to get even 1pf trace to GND capacitance...

3) Do I need any termination for 5-10cm traces with 1-3ns fronts? If so, what it should be (220 ohm to GND?)?


texts: How to know if the li-ion batteries are fully charged?

texts:
As much as I know if your li-ion cell is providing 4.20V then it is fully charged one. But when I bought a pair of new ones they were at 3.9V each and then I charged both using TP4056 module and they both started showing fully charged after a few hours and then I measured the voltage and found to be 4.11V and 4.16V but when I plugged them again in the module for further charging they are not charging and the module also indicating they are fully charged.
So is it possible that a fully charged li-ion can give these voltages or are they not fully charged?


texts: Trace impedance for two signal layers between ground planes

texts:
When watching a few videos about stackup, EMI and impedance (especially this video from Fedevel Academy: https://youtu.be/52fxuRGifLU), I got confused how to compute trace impedance in the case of two signal layers between ground planes.
Considering a stackup including at least 4 successive inner layers such as:

L2: ground (GND)
L3: Signal layer, it could have no copper pour (option A), ground pour (option B), power pour (option C).
L4: Signal layer, it could have no copper pour (option A), ground pour (option B), power pour (option C).
L5: ground (GND)

The stackup is represented below. Some layers exist above L2 and below L5 but are considered out of the scope. Signal traces on L2 and L3 are orthogonal as shown. Distance between layers is assumed to be the same between all these layers.

In the following, we will focus on signal tracks on L3 only.
Option A - without copper pour on L3 and L4.
It seems to me that the impedance for L3 traces can be computed using standard calculations for striplines: reference layers for L3 traces are L2 and L5 (reference layers for L4 would be also L2 and L5). Equidistance between layers implies that 80% of the electromagnetic field for signal traces on L3 will be between L2 and L3 since the fields are proportional to the inverse of distance squared. Since signal traces on L3 and L4 are also orthogonal to each other, it should limit cross coupling between signals.
This option A seems to be a decent solution to me up to some frequencies as described in this video (reference: https://youtu.be/52fxuRGifLU?t=1774 [29:34])
Option B - With power pour on L3 and L4. This option comes from a 12 layer board stackup suggested by Rick Hartley (reference: similar video to above https://youtu.be/52fxuRGifLU?t=3698 [1:01:38]).I assume that signal traces on L3 can only "see" L2 and L4 (L5 being hidden behind power pour on L4). It seems to me that it does not exist a continuous return path on L4 for L3 traces. Even though L4 is not a continuous plane, should it actually be considered as a solid reference plane when calculating the impedance for L3 traces? Is it possible that L3 is only referencing to L2 which is the lowest impedance path for return current? If so, what to tell the PCB manufacturer for controlled impedance calculations (since striplines are supposed to be between two planes and microstrips on the PCB top or bottom)? Moreover, it is then unclear if the power pour on L4 needs to be power actually used to generate signals on L3 or if it does not matter in that case.
Option C: with ground pour on L3 and L4. I assume that signal traces on L3 can only "see" L2 and L4 again. As for option B, it seems to me that it does not exist a continuous return path on L4 for L3 traces. The current would then go through some ground vias connecting L2 and L3 but that would add quite a bit of inductance for this path... Similarly to option B, can we then consider that the current will follow the path of lowest inductance and flow mostly through L2? If so, how to work with the PCB manufacturer for this design again since it is does not look like microstrip?
Questions:

Feel free to comment and discuss any points/questions above. I may misunderstand some basic concepts.
For option B and C, how does L4 come into play when calculating the trace impedance for L3 traces?
For option B and C, if L4 cannot be considered as a solid reference plane, what to do to estimate the required trace width for controlled impedance, and how do we work with the PCB manufacturer?
Does option B have any advantages over option C except that it allows to carry some power "tracks" which may not fit anywhere else in the PCB?

Thank you !


texts: What should I use as a test load to calibrate a UPS?

texts:
I have a 1440VA (980W) Uninterruptable Power Supply (UPS) which I bought a while back to protect my computers from power fluctuations and possible outages.  Recently the battery failed and so I acquired a replacement.  The replacement battery came with instructions saying that after installing the battery I need to recalibrate the UPS so that it learns the total discharge time of the new battery.  The procedure for doing this involves:

allowing the battery to charge for 24 hours,
applying a 30% load to the UPS,
unplugging the UPS from the wall, and
allowing the battery to completely discharge while powering the load.

Performing this procedure is apparently a condition of the warranty on the battery.  I'd like to perform the procedure, but the problem is I do not know what to use as the test load.  I obviously do not want to have my computers plugged in because when the battery runs out at the end of the test, they will crash hard, the same as if there were no UPS and the power failed.  So I guess I need something that will consume about 300 watts of power that will not harm the UPS electronics and is not itself harmed by a power failure scenario.

What would be suitable to use for a test load?

My first thought was maybe a small heater of some sort, but I think most heaters draw too much current and I think that might be bad for the UPS.  However, I think I might have a couple of halogen construction lamps in my basement; is that safe to use as a load?  Anything else I should consider?


texts:
I have this schematic, an invert Schmitt trigger attached to the RC component to create a triangle wave.
It's an oscillator.
The two oscillators go in to the amplifier, but I don't understand why I need another capacitor and 2 resistors ( the red part ).

Someone can help me?


texts: Why to use 50/60 Hz Frequency and Not other Higher/Lower Values?

texts:
At our homes and utilities, the frequency is 50/60 Hz. Why not use any other value such as 500 Hz, 200 Hz or a small value 40 Hz, 30 Hz.
Previously I searched it over the StackExchange but I want to know the technical and logical reason.


texts: VHDL: How to create a memory block with some elements being constant?

texts:
I have created a 2D RAM block, it is an array of 32 bit std_logic_vectors:
subtype TEST_MEM_DATA_WORD is std_logic_vector(31 downto 0);
type TEST_MEM_DATA_MEM_ARRAY is array (natural range <>) of TEST_MEM_DATA_WORD;
signal TEST_DATA_MEM : TEST_MEM_DATA_MEM_ARRAY (63 downto 0);

Here is the process that is used to read and write it:
  TEST_DATA_MEM_PROC: process(CLK) is
    variable address_int: natural;
  begin
    if rising_edge(CLK) then
      if RESET = '0' then
        TEST_DATA_MEM <= (others=>(others=>'0'));
        TEST_MEMORY_RDATA_OUT <= (others=>'0');
        address_int := 0;
      else
          address_int := to_integer(unsigned(TEST_MEMORY_ADDR_IN));
          if TEST_MEMORY_WR_IN = '1' then
            TEST_DATA_MEM (address_int) <= TEST_MEMORY_WDATA_IN;
          end if;
          if TEST_MEMORY_RD_IN = '1' then
            TEST_MEMORY_RDATA_OUT <= TEST_DATA_MEM (address_int);
          end if;
      end if;
    end if;
  end process;

I want to achieve a scenario where the few address locations of the TEST_DATA_MEM have constant values assigned to them. We are able to read these locations but not able to write these locations. How should this process be changed to achieve this end? There are certainly multiple ways but I want to know the proper way. I think this would be where no registers would have to be synthesized since the value shall remain constant forever.
Putting constant assignment outside the process will clash since there will be 2 drivers into the process. Putting assignment at end of the clocked process is one way to do this. However, I suspect that this shall infer registers since the constant values shall get assigned on the first rising edge of clock and not from time zero.
Using an if statement to check the address value before writing into the memory as another way to ensure that only the value assigned in the process remains. However, as per syntax of VHDL and the typical synthesis tool rules, there must be a way to achieve this without involving an if statement that checks the address value when TEST_MEMORY_WR_IN is '1'.


texts: Why does this circuit use a transistor buffer even though there is an high input impedance op amp afterwards?

texts:
Regarding this circuit I found on www.geofex.com detailing the famous Tube Screamer guitar pedal

(source: geofex.com)

I don't understand the purpose of the BJT input emitter follower transistor. If it was to increase the input resistance of the pedal then the TL072 would have much greater input impedance than a BJT no? (I read approximately 10^12 in the datasheet for TL07x)


texts: Reprogram a calculator to a cash register

texts: due to the "high cost" (at least from my point of view) of a thermal printer I was wondering whether it was possible/worth the effort to buy a compared cheaper device with it integrated already (a calculator for example). I was thinking of buying a "P1-DTSC, Canon" calculator for my "misuse". So would it be easier to replace/reprogram the microcontroller or just take the needed printer and control it with an arduino bord.


texts:
simulate this circuit – Schematic created using CircuitLab

This circuit has a bandwidth of 0.9Hz but I want even lower bandwidth.

I have this RC tuning circuit. If i had an RLC tuning circuit I could play with the resistance to increase the quality factor-> increasing the selectivity.

Can I do something similar to this circuit?


texts: Sources for cheap/free electronics for students?

texts:
I've just recently discovered an incredible interest in building my own circuits and my own logic. I'm in a computer architecture class and we're learning how to make ALUs based on a set of instructions.

Last year, we would create logic circuits on a breadboard using NAND and NOR chips. This year, we're using Altera to download circuits we build in software to download to a circuit board. This stuff gets me so excited, it's not even funny.

I've been collecting certain parts (some logic gates and LEDs) and I have a breadboard. I'm also thinking of buying an (or a couple) Arduino(s). However I want to build more complicated circuits with other components (variable resistors, sensors, etc). Is there a good online source where I can buy these on the cheap (maybe even bulk)? I've also heard of companies giving parts for free (as long as it is for education purposes, which I believe it is).

I'm a student and I can't afford to spend significant amounts of money on a part collection, but I do want to learn and explore.\

(On a side note, I've read Which electronics components should I always have on hand?. Does this apply to a student as well? Any advice on WHAT components I would benefit from?)


texts: Automotive Sensor - Excessive Ripple Noise

texts:
I'm designing an automotive oil temperature sensor based around a 3-wire RTD. This is my analog circuitry:

U1 and U2 provide a 1mA bias on the RTD which is measured by U3 and gained up by U4. R5, R10, D1 and D2 are for input protection on the op amps. Op amps are a quad package MCP604 single supply and are properly bypassed with a 0.1u cap.

I have the whole thing prototyped out and it works perfectly if Vin to the 7805 circuit is powered by my 12V bench supply, but as soon as I connect it to 12V battery power in my car, I get some sort of ripple voltage or oscillation in the RTD that throws the ADC readings way off.

I don't have access to a scope at home to really see what's going on, but there's a small ~10mV ripple voltage on the RTD which is being amplified by the gain stage. I added the 1uF caps in the feedback path to try and remove it, which helped, but the ripple is still bad enough to render the measurements useless.

If I disconnect Vin from the vehicle 12V and power it with my bench supply (with GND remaining through the vehicle chassis) the ripple disappears and the temperature reading is spot on.

Powering it with a 9V battery also works just fine.

This is with the vehicle ignition off, so there shouldn't be any crazy noise present.

Also, if I leave it powered by vehicle 12V and replace the RTD with a 100 ohm resistor, it works fine. So it looks like some sort of interaction with either the platinum resistance element or the sensor leads.

Is there some sort of interaction I'm not accounting for with vehicle power vs. my bench supply or 9V battery? Or is there a potential stability issue with my circuit that is being pushed over the edge when connected to vehicle power?

EDIT: I'm fairly certain this is a ground loop issue. Rewiring the circuit into a star-ground configuration improved the situation, but there are still measurable stray ground currents through the RTD causing unpredictable results.


texts: Can I damage a hall effect sensor with too much current?

texts: I'm sensing the output current of a transformer which can get up to 250A. However, I'm only interested in turning on a separate circuit if this current exceeds 10A. If I use a 0-15A hall effect sensor and the current goes to 250A, will the sensor be damaged? I can't find any info on the max amount of current through a sensor before damage, only the max amount it can read accurately. I haven't chose a sensor yet, but it does need to be the type where it clamps around an existing wire.


texts: Component for covering a very tiny hole (pinhole camera aperture)

texts:
I am experimenting with a pinhole camera - it is basically a camera with a very small hole (only 0,2 mm in diameter) instead of a lens (Wikipedia)

I am trying to design the shutter - something that I could control to cover/uncover the pinhole (so light passes through only when intended). How would you design such a thing? The following solutions have crossed my mind:

Mechanically cover the hole using a lid. I guess a solenoid or linear actuator could be used, but the hole is so small (only 0,2mm!) so it seems a bit overkill?
I could put a "smart film" on top of the pinhole - the ones that turn transparent when you put current through them and are opaque otherwise. However, that may not be such a good idea to use in a camera since it might impact the imaging quality...

Do you know of any other solutions? If there is a component that could move a small object just a half millimeter forward/backward (and is also reasonably cheap), that would probably suffer.


texts: calculate current nodal voltage method problem

texts:
I don't know how he calculated the current and get this result.
any help please??

my try


texts: Identification of Bluetooth IC marked TED8402818

texts:
Today I opened a Bluetooth headset (from HCWY company) and saw this circuit:

So I try to read the IC number on it and found something like TED8402818, but didn't found anything using Google. Also there is one steel coated IC and I cannot read its number. It seems simple and only has two ICs with Rx, Tx pins which I think is for programming it.

So I would like to know about the circuit and those ICs.


texts: Eagle PCB supply symbols in a multi-voltage system

texts:
Supply symbols signify vdd and gnd and perhaps vdd, gnd and vss in dual supply system.

However, in a situation where one has +5V, -5V, +3.3V, 1.8V, Analogue ground and Digital ground, what should one do about the symbols? There do seem to be 2 ground symbols so ground is not an issue but not many other symbols for nonground supply rails.

Expanding on this question if I am creating a "multi design" PCB with multiple +5V rails, +3.3V rails and grounds where every design has its own area on the PCB with no interaction with other designs, how does one use supply symbols in that case?


texts: ESP8266 fails to work when connected to sdcard reader

texts:
I have a simple blink LED program running on the ESP8266:
#include <Arduino.h>

void setup() {
  // put your setup code here, to run once:
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(LED_BUILTIN, HIGH);
  delay(1000);
  digitalWrite(LED_BUILTIN, LOW);
  delay(1000);
}

This runs fine but when I hook up an sdcard reader to it the light stops blinking. If I try to upload the same blink led script as above while the sd card reader is connected I get:
A fatal error occurred: Timed out waiting for packet header

In troubleshooting, I hooked up:

VCC on the SD reader ->  VIN NodeMCU
GND SD reader-> GND NodeMCU
MISO on the SD reader -> MISO NodeMCU

with the blink led script still running and the led sticks (the led stays in whatever state it's in) until I remove the wire connected to SD0 (MISO). So just like the diagram below, with only the red, black and blue wires and the blue wire is connected to SD0. Those are the only connections present.

I've tried adding a 10uF cap between EN and GND to no avail. Also, I know that some GPIOs should be kept low/high during boot. But the fact that this happens while the blink led script is running baffles me even more. How can I get the ESP to still run loop with the sdcard reader connected?


texts: How to get consistent yaw and pitch angular velocity measurements in a moving frame of reference

texts:
I am using a BNO055 sensor with a ESP32 development board to control my mouse cursor. I'm able to get data from the sensor as angular velocity, or as absolute orientation in quaternions and use that to control the cursor movement on screen.
My aim is to be able to get yaw and pitch angular velocity measurements, which align to the movement of the hand in space, with the device attached to the hand. I'm able to do this when the device is straight. But I'm facing issues, if the device is rotated on its frame's roll axis. This results in a movement of the hand registering angular velocity on both the yaw and pitch axis. I have made a short video to demonstrate the issue, which hopefully makes more sense than the written explanation.
If you would like to view the current project code that is available here.
I understand this is very specific, and potentially time-consuming to answer so no expectations! Still, I would appreciate any guidance on how to approach solving this.
PS. Sorry for bad video quality, I have RSI and can't spend too long on touchy stuff like this.


texts: Why are so many wires coming out from a 3-phase transformer?

texts:
I want to make an arc welder from this stripped transformer. As far as I know it is a 3 phase transformer that could transform 380V to 12,24,40. I know how a regular 2 coil transformer works, but I don't understand the need of these many wires.

The 4 on the back were cut, the top 3 on the front go into the voltage switcher, bottom 4 on the front go into another switch(which I guess is for amps). There are lots of loose wires and missing parts. I want to make something useful out of this. Do I have to rewire the transformer to be useful for me?

I was thinking to make the 2 outside coils the primary and hook it up to 230V. The middle to be the secondary and use less winding. I don't know if this would work at all.

Any help?

Update:
So I mesaured the 3*4 wires on the back side each 4 are linked which I guess means 3 phase + neutral and that should mean star topology.
The problem is I only mesaured 1.6 ohm on these wires that's very low isn't it?
The 3*10 wires mesaured 0.9-1.3 ohm, but all of them are linked when I tested it with continuity and resistance. Does that mean that all of the wires are melted/corroded?
I have also noticed the remains of a blue and red wire and 3 white, the 3 white colored wires are much thinner.


texts: is multipath the real cause of small-scale fading?

texts:
Since I was a student I've been told that small-scale fading is due to multipath propagation.
With multipath you get constructive and destructive interference making the signal received power fade. Well that makes sense.

But here is my question: If you are in a completely static environment, say, locked on a room where nothing moves, you place your receiver at a point where you get constructive interference from multipath. Does your signal fade? If not, then small-scale fading is not due to multipath: is it due to movement and multipath. Movement between Tx or Rx or movement from the environment where the signal travels.

Since multipath is always there, it should be said that small-scale fading is due to movement and not due to multipath. Am I right or wrong?


texts: Options for a simple over-temperature cut-off?

texts:
I am designing a heater circuit that will be used in a product to be produced in small to medium quantities (hundreds to thousands of units, not tens of thousands).  This heater will be PWM controlled to maintain a set temperature in the heated medium, however as an additional safety measure I would like to include a separate over temperature cut-out to prevent fires or high surface temperatures in case of a fault in the control loop (failed sensor, switching FET shorts out, load is removed from the heater element etc. etc.).

The cut-off should return to an operating state once the over-temperature condition is resolved (ie. normal, trip-once thermal fuses are not appropriate).  Ideally the solution would be as simple as possible and contain few parts, the device would be used in remote locations so reliability is a concern.

The heater would be driven from 12V, maximum power would be 40W  (ie 3.3A).  The cut-off should operate at 50 to 60 degC.

The options I am considering and their relative merits are below:

a. Normally-Closed Bi-metallic Switches, placed in series with the heater element (eg. Klixon 7AM):

For:
          + Simple, single component.
          + Seems to be the most common solution for this application.
          + Significantly more expensive than PTC (>$3.00/pc).
Against:
          - I have not been able to find any surface   mountable options.
          - Has moving parts which raises reliability concerns in my mind although
          they do seem to have quite acceptable lifetime ratings.

b. Positive Temperature Coefficient (PTC) Resistors, placed in series with the heater element:

For:
          + Simple, single component.
          + No moving parts.
          + Surface mountable.
          + Cheap (less than $0.40/pc).
Against:
          - Generally designed for use in over-current protection and data is given to suit
          eg. available data does not give resistance vs temperature curves.
          - Temperature trip point would be dependant on current through the resistor.
          - Few options available for use over 3A.

c. Temperature Switch IC (eg. Analog ADT650x Series) driving a FET:

For:
          + No moving parts.
          + Surface mountable.
Against:
          - Multiple parts (reliability).
          - Additional design work (ok, it's negligible but I'm lazy).
          - Requires additional power supply (5v).
          - Total BOM cost is similar to bi-metallic switch.

My questions are:

Any feedback on the merits of these options?
Can anyone suggest alternative options for implementing this cut-off?
Is anyone aware of any PTC resistors designed for this usage or higher current applications?


texts: Help with the use of STM32 peripheral library, error definition with for example GPIO_Typedef

texts:
I really need help here because I'm trying to make a project for stm32f10x microcontrollers, I've found in the following thread of Keil forum
Libray forum
that the best way to add the library to a project is to add the needed files to the project folder and use them.
The problem here is that I did that and right now the compiler is giving me a lot of errors of the type
./stm32f10x_gpio.h(349): error: unknown type name 'GPIO_TypeDef'

The previous is one of the 76 errors that the compiler gave me on definitions. I have the ST document about how to migrate projects from the old library to the newest one and the say that those definitions are for legacy projects in stm32f10x.h which I verified is true so I included in the file with the definition problem by doing this
/* Includes ------------------------------------------------------------------*/
#include "stm32f10x.h"

and still is giving me those error, I'm new to this so right now I don't have any idea of what to do make those errors disappear.
Previous to ask this question I tried to copy those definitions inside the header of the file with definition problems, after compiled it then said that there are several definitions of the same type and gives me a warning or an error (I don't remember), to me this means that the compiler is seeing the file stm32f10x.h but for some unknown reason is not getting the definitions to make it work.
How can this problem be solved?. I'm blocked here right now.


texts: Is it possible to control distance of RF Transmitter

texts:
Noob question here, is it possible to control the distance range of RF transmitter.

I need a RF transmitter application where i can control its distance with pot.


texts: 16X16 matrix, analog sensors, VDD, GND, comon OUT to Arduino UNO A0. How to operate the GND MUX?

texts:
I have 256 analog sensors that have VDD (5V), GND, OUT ( analog output that goes to A0 of my arduino uno).
i was hopping to controll them by turning them on or off individualy and take readings in A0 that they all connect.
To do so i was thinking of connecting their suplly to a matrix and control the matrix with 2 16:1 multiplexers.
and now my question is :

A CD74HM4067M multiplexer has a common pin. i will provide the 5v by conecting it to a digital pin on my arduino and setting it to HIGH. When i change my multiplexer to go to 2nd channel of the 16 the rest of the channels will stay at their previus condition or will the go Low?

If this is the case how do i operate tha GND MUX ? should i use transistors to triger with my Multiplexer in order to connect the right gnd collumn to GND ?

if so , should i do the same with the 5v rows as well ?


texts:
I have recently built a board using an ATSAMD09D14A-MUT, today it came the time to test it, however problems arose in a strangely annoying manner, when trying to connect to the device i get error 4109 (no device detected),

As you can see in the following schematics the setup is quite standard, the only things that can be considered somewhat odd are the pull up resistors (they are quite high in value) and the absence of an oscillator, since it the timing precision required for this application didn't require one.

the steps i took to try solving this issue are the following:

1: reduce the swd frequency down to 32khz

2: change the resistors from 100k down to 50k

3: change the reset resistor to 10k assuming there may be noise in the line

4: build a second programming cable to eliminate that possibility

the result was the same after these steps
also, the device was externally powered (i know ice doesn't supply power)

i would really appreciate any help with this since i pretty much eliminated all the possibilities i could think of

Edit:
The cable used to connect the device is as follows

Header    ICE

pin 1 <-> pin 2

pin 2 <-> pin 4

pin 3 <-> pin 3

pin 4 <-> pin 1

pin 5 <-> pin 10


texts: Matrix-Vector equation for active and reactive power in a transmission line

texts:
Suppose that we know vtilde (the complex voltage phasor vector at all buses), C the incidence matrix for a network, b (susceptance vector containing each line's susceptance), and the admittance matrix Y (where Y = C' * b * C).

I can compute any branch l's current magnitude by looking at the lth index of

b_l^2 [ abs(C * vtilde)^2 ]_l

Is there a "vectorized" way that I can compute the active power of the lth branch using b, C, vtilde, and b?


texts: Choosing Altera Quartus II clock rate for stopper

texts: I'm using Altera Quartus II to built a stopper. I'm using 2 counters and I need to choose the right clock rate to get pulse every 1 sec. There are only two options in Quartus for the clock: 27Mhz and 50Mhz. Which one should I use?


texts: How does a zero in transfer function affect the bandwidth of a system

texts:
Suppose we have a system with the closed-loop gain:

\$\displaystyle G(s) = \frac{\omega_n^2}{s^2 + 2\zeta\omega_n+\omega_n^2}\$

Which is the default two-pole system closed-loop gain. Let's also assume that bandwith \$\omega_0\$ is defined with \$|G(j\omega_0)| = \frac{1}{\sqrt{2}}|G(j0)|\$ (standard 3dB definition).

Through substitution of these two expressions we end up with:

\$ \omega_0 = \omega_n\sqrt{1-2\zeta^2+\sqrt{4\zeta^4 - 4\zeta^2 + 2}}\$.

-> My question is: If we add a finite zero to the transfer function, such as:

\$\displaystyle G(s) = \frac{(s+z)\omega_n^2}{s^2 + 2\zeta\omega_n+\omega_n^2}\$

what will happen to the bandwidth? Will it change? I know that the finite zero only affects the system in transient phase, and in stable phase (when t \$\rightarrow \infty\$) the zero doesn't affect it. However, I'm not sure about the bandwidth.

Of course, I could substitute G(s) into the bandwidth expression, but I won't get a normal result.

Help :)


texts: What is the name of this "plastic wire loop"?

texts:
Someone told me that it is called wire loop.
I want to buy it, but I could not find it using wire loop as keyword


texts: Computing capacitor voltage through series connected diode

texts:
I have been trying to analyze this circuit and calculate the maximum voltage across the capacitor. Here is the diagram:

And, here are the graphs for various inputs and the resultant outputs:

VG1(peak): 300mV
VM2: 157mV

Even though the diode is not conducting(in cutoff region), the capacitor is getting charged. I don't know why.

VG1(peak): 1V
VM2: 769mV

VG1(peak): 30V
VM2: 29.61V

What decides the maximum voltage on the capacitor?


texts:
I have just had a conversation with a friend who studied quantum computing. Sadly I have forgotten most of the conversation as it was far beyond my knowledge threshold.

Essentially he was saying was that current tradition computer chips are getting smaller and faster but soon we will hit the limit because as the chips shrink we have to pass less current through them. Here, there will be a trade off of chip performance against size.

So as these don't already exist, there must be a good reason why microprocessors can't be build that run on 3 phase AC rather than traditional single phase. Is this because as I understand it, microprocessors have oscillators inside them to generate their clock cycles, these oscillators wouldn't be changing state, but always be fixed, because of the constant flow of electrons? Without the peaks and troughs of single phase, I would assume an oscillator can not oscillate, is that correct?

My knowledge if electronics is pitiful at best, so there is likely some fundamental reason why this isn't mainstream because in my head, this would allow for potentially three times the computing power compared to a traditional microchip.

Thank you.


texts: Will covering ring on male 1/4 TRS jack with tape work?

texts: I plan to connect balanced TRS output with unbalanced TS  input and I wonder if instead of cutting the cable and leaving ring floating I could just cover the male jack itself (the ring part that goes to the unbalanced input) with insulation tape. My guess is it should prevent the signal from the ring connect with the sleeve of the unbalanced, TS input.


texts:
I am working on a project that uses a Ulka water pump rated at about 0.5A. I will ultimately want to control the pump using an Arduino, however before I attempt that to start with I am just using a push button switch wired up as the schematic diagram shows:

From what I have read here, an inductive load (which I believe the Ulka pump to be) requires a random switching Solid State Relay (SSR).

So first I tried a random switching SSR rated for 5A, which didn't work, but I could hear the pump humming all the time.

Just in case, I then tried using a zero-crossing SSR rated for 10A to switch the active (hot) wire, which worked, except the pump hummed when not in use. This made me think maybe I need to switch both active (hot) and neutral wires, but I thought that since its a single phase switching just the active (hot) would be sufficient.

Should I be switching both wires?

I also tried using an electromechanical relay rated for 15A, I heard the relay switch, but the pump did not turn on.

Could I potentially use a zero-crossong triac driver to accomplish this?


texts:
Consider an isolated Flyback SMPS with RCD snubber on the primary side MOSFET's drain. As the drain voltage rises above the sum of input voltage and snubber capacitor voltage, the diode opens and conducts the leakage energy into the capacitor.

The same happens with an active clamp circuit, the only difference is that the diode is replaced with a MOSFET. But where is the resistor? Why is it needed in the RCD version and not in the active clamp?


texts:
I recently designed my first 2 PCBs. Both have a 5v copper plane on the top layer and a ground plane on the bottom layer. I use short traces and vias to connect top components to the ground plane.

As you can see in my image, the bottom PCB was manufactured as expected. The top PCB was not. The vias in the top PCB have rings around them where there is no copper (thermal relief?) which means nothing connects to ground and my board does not work.

I designed these using EasyEDA and have viewed them in Eagle. I don't see any difference in my two designs, even though they came out differently.

Is there a term for the vias seen in my top board ( the ones that don't connect)? I obviously need to order these again, but I'm not 100% sure I won't get the same faulty vias.


texts: What kind of WiFi Antenna is that Iphone uses?

texts:
I dig up on WiFi antennas. What researchers design on their articles looks complex PIFAs, however, this's from Iphone 6. It just looks a rectangular patch to me. I m not sure, what kind of antenna is that ?

Thanks in advance


texts: Can several CS pins be multiplexed with a shift register?

texts: When sharing a SPI data line between several ICs and an Arduino, what exactly are the frequency constrains of the CS pin? Can I use a shift register to multiplex the CS pins (thus only requiring one I/O pin, the Shift Register CS, out of the Arduino)? Or does CS must be synced carefully with SCK (in order to avoid garbage if CS is pulled high too "late")


texts:
I just started to working with proteus and I want to implement and test some simple circuits.
I made subcircuit and tested it with logic state and logic probes.
first picture is my main sheet and second picture is the circuit inside subcircuit
why I don't get any output from bottom circuit while I get output from top circuit Since they are the same subcircuit?


texts: Help to identify middle click microswitch in Razer Naga mouse

texts:
Can someone please identify microswitch used for mouse wheel click (sw3 on the pcb)? Here is an Imgur album with Naga disassembly.

Recently my Razer Naga middle click became less responsive. It requires more force to respond. Since mouse's warranty has expired I decided to fix it myself.
I looked up teardowns and fixes on the internet, but did not find exact model of microswitch used in the mouse.

Thanks in advance!


texts: Encoding version or configuration on PCB

texts:
I need to encode information about either version or configuration on the board/electrically, so the firmware can detect which board layout is used.

What options are possible and what are their pro/cons?


texts:
I was reading the Lpc2148 Manual and in the Static Ram section I came across

  Write back buffer

The SRAM controller incorporates a write-back buffer in order to prevent CPU stalls
during back-to-back writes. The write-back buffer always holds the last data sent by
software to the SRAM. This data is only written to the SRAM when another write is
requested by software.(the data is only written to the SRAM when software does another
write). If a chip reset occurs, actual SRAM contents will not reflect the most recent write
request (i.e. after a "warm" chip reset, the SRAM does not reflect the last write operation).
Any software that checks SRAM contents after reset must take this into account. Two
identical writes to a location guarantee that the data will be present after a Reset.

What does it mean. and what did he mean by CPU stalls and back to back writes