texts: Connecting balanced low impedance output with unbalanced high impedance input

texts:
I want to send the signal form my audio interface to the guitar pedal effect. I'll use interface's line out balanced output and plan to plug it in to the effect pedal which has high impedance unbalanced input.

Which cable should I use? TS, unbalanced jack, or TRS balanced jack?


texts: Trouble visualizing voltage-shunt mixing

texts:
I'm trying to understand how voltage-shunt feedback works in an inverting op-amp circuit.  I can't seem to visualize how the feedback gets mixed in shunt with the input.
NB: Before I tried this, I was able to understand voltage-series feedback in a similar non-inverting op-amp circuit.  I redrew the circuit until I could "see" that the feedback network was in parallel with the output voltage and in series with the input voltage.  Here is the circuit I'm working on now.

simulate this circuit – Schematic created using CircuitLab
I redrew it (below) to help me visualize that the feedback network is in shunt, and I am suitably convinced that the feedback network is actually sampling the voltage.

simulate this circuit
But I can't for the life of me visualize how the feedback is applying itself in shunt on the input side.  R1 sure looks like it's sitting in series with the input to me, but I know that's not correct.  Somehow, it's in shunt and capable of applying a current in a manner different from how the voltage-series feedback worked.  Can anyone redraw what I have to help me see it?
EDIT - Put another way, I'm trying to reconcile the differences above with block diagrams I see like this (below), which clearly show the feedback being applied in shunt.  source


texts: In HLW8012 schematic, where should the Referenced ground be connected

texts:
In the datasheet of HLW8012, the both 33nF capacitors , 1K resistor and 0.1uF capacitor are connected to GND. I'm not sure where should I connect those ends of components marked with GND symbol, (To Live, To Natural). I can't read Chinese, I don't really know what everything mean there.

I see most of schematic on the internet have mixed the GND of IC on the Bottom Right with the Natural Line , I don't know why.

I want to play with this cheap power metering IC.

Can someone explain me / Redraw this schematic with everything connected ?


texts: Solid State Relay Capacitance Bad for Audio?

texts:
Regarding MOSFET optocoupler relays like the Panasonic AQW212, am I correct in understanding that the capcitance between the terminals and ground when the switch is open ("off") is around 100pF when the potential across the terminals is small?

If you look at the datasheet for AQW212 it says it has low Coff but if you look at the chart that seems to not be the case. With a small voltage the capacitance rises sharply.

Consider the following example where the audio signal may be routed through a SS relay driven stepped potential divider like a volume control in the nearly off position:

I've been searching for a good pro-audio signal routing method that could work with somewhat arbitrary circuits like old mic preamps running on 24V or maybe even guitar tube amps that might switch 70V signals.

simulate this circuit – Schematic created using CircuitLab

In this example, it so happens the circuit calls for a large resistance so as not to load the collector of a transistor amplifier perhaps. This arrangement conspires to produce high series resistance and low signal level which when coupled with the multiple drain / source capacitances of each device could result in high frequency loss.

Is this understanding correct? Or could a MOSFET based device be used to build something like a stepped attenuator?

I have also looked at devices like the Analog Devices iCMOS analog switches but these too have high junction capacitance. It seems the lower the on resistance, the higher the capacitance.

If only there were a mechanical relay with many positions like an old telephone exchange stepper switch but the size of a regular relay. Meaning a SP12T relay that can ratchet in either direction.


texts:
The only switches I have every worked with are basic switches with on/off state, but I want to be able to add a power button to my project that is just like the power button on a cell phone. (hold for x seconds to power on, hold for x seconds to power off). It should also obviously act similarly to a momentary switch that doesn't depress or change levels when it is clicked.

I know this requires specific programming within the controller; I'm just confused about the best switch setup to accomplish this.

Do I accomplish this with a certain type of momentary switch? I am getting confused by the different types on digikey, such as this one: https://www.digikey.com/product-detail/en/e-switch/TL3315NF100Q/EG4620CT-ND/1870400


texts:
What is the best way of generating strong, steady, electric fields (E) using the tools and voltages available to the home hobbyist? Is it better to using electrostatic sources like a Van de Graaff generator, or can high strength fields be obtained using electrical circuits in some way?

In addition, is there a way of generating such strong field while still making them "accessible"? That is, having a strong field which instruments and equipment can be brought close to to take advantage of the field strength?


texts:
Can someone please explain to me the following. For the last part, why did they use the Van to find Vab( secondary line voltage of the delta).

I did it and my magnitude matches the solution but the phase angle doesnt. I used the VAB which is 1732 angle of 0 (reference) and the wye to delta formula which stated VL(secondary delta) = VL(primary wye)/(sqrt3 * A). where A is the transformer ratio . Please explain.


texts: Why are there so many resistors in a typical schematic?

texts:
I know that some resistors cause pull-up or pull-down or work as a voltage divider and/or current divider.

But sometimes I cannot understand their function in some simple circuits:

Take this motor driver (L9110) for an example. Why are there 2x4.7k resistors?
The L9110 is rated to be able to recieve 2.5v-12v according to the datasheet

Or take this zener diode voltage regulator, The 40Ω resistor, ohm's law says that V = I x R, increasing the resistance lowers the current. But why is that 40Ω resistor needed at all? Why not let it flow straight through (~0Ω)?

Or lastly this RS232 level shifter, I understand the 10kΩ resistors. But why is there a 4.7kΩ resistor between RX(Device) and TX(Device)? (Should they even be connected?)


texts: What are the voltage & current ratings of output contacts of optocouplers ? whether they can withstand ac voltage or not?

texts: Currently I'm designing Voltage Stabilizer and I'm using three DC relays at the output of my AVR Controller, at the output of relays I have connected ac sources which is in the range of 190V to 280V and current ranges from 0.9A to 2A, whether I can use opto-coupler (opto-isolator) instead of relays or not ?


texts:
I am trying to make a very simple AND Logic gate with the help of a breadboard. This is my first time using all this. I have referred to the video
http://www.youtube.com/watch?v=x9R9KAtTyWA

It said that IC 7408 is for AND Gate and I bought that only. The code on this chip that I bought is PO148SD
           MM74HC08N
           MC74HC08N

So I did everything that was in that video but still my LED didn't lit on 1 1 output. What am I doing wrong?


texts:
So according to a book example (See Digital Integrated Circuits by J. M. Rabaey example 3.9) I'm trying to determine the Gate capacitance using the following schematics scetch:

This comes directly from the book, however, a simulation gives me the error of a floating point.

What am I doing wrong or should I do different?
I tried replacing this source with a voltage source what gave me no errors and a way to plot the current floating into the gate. This remains zero however.
This making it look like it is a ideal transistor. (what it shouldn't be?)


texts: 2 NPN configuration that apparently works by small Recombination Currents

texts:
simulate this circuit – Schematic created using CircuitLab

In this configuration of 2 NPNs, how is V_OUT following V_IN? Ignoring recombination current:

Assuming conventional current, current flows from Node_A to Q1 collector  and Q2 base, but is somehow replenished by a voltage source that we can't see.
Assuming electron flow, current from Q1 collector and Q2 base are drained in Node_A which is a constant voltage source or ground that we can't see.

Now if we were to assume recombination current, we have an exception. But even after reading through some Recombination Current articles, I still can't see why this would be behaving like this.

Can somebody give an explanation?

I'm sure this isn't Reverse Mode, as V_IN causes Q1 to be forward biased and the emitter of Q2 is pulled to ground.

EDIT:

Dave answered that Q1 is acting like a dual diode. So I thought of testing if it was with this simplification:

simulate this circuit

I've actually had to ramp up the resistor to ground to 100k from the previous 10k to obtain a full swing. The collector still follows the emitter. Perhaps there's resistance at the emitter, so there's feedback in the collector? I checked the Gummel-Poon model and it seems to agree with this assertion. Just adding this little bit.

EDIT:

Something that I want to correct is that the the base-emitter of Q1 forms a closed loop of voltage source V2. The base of Q2 (on the first figure) and 100k R2 (of the second) only taps onto this. So it's following.


texts: What are AT commands ? When to use them?

texts:
I read some articles about the AT commands but I am still unable to understand something. As the article says "AT commands are instructions used to control a modem."
I used a while ago an Bluetooth module(HC-05) to control a RC car and I saw that the module recognise AT commands. I could control the car using only UART communication and at that moment I just ignored the AT commands.
 So, why does the Bluetooth uses AT commands ?


texts: Lithium Ion in series+parallel, is this right?

texts:
I have 3 identical lithium ion batteries, i want to connect two in series for about 8 volts, and then the last one in parallel for more capacity, and then I'm going to wire this to a 5v regulator and charge my phone (which i use as a wireless security camera). Since i don't want the lithium ion blowing up on me, i just wanted to make sure that i have wired it correctly:

Does this seem right? Thanks!


texts:
I am asking you for a help with following boolean expression that i can't solve by myself. I can minimize expression in Karnaugh map but i have to use boolean algebra too.

Expression:

!(C + !D) * !(B + D) + !!(C + !D) * !!(B + D)

(!C * D) * (!B * !D) + (C + !D) * (B+D) - De Morgan law
(!C * D) * (!B * !D) equals 0 because of A * 0 = 0
(C + !D) * (B + D) - multiplying everything
BC + B!D  + CD + !DD
!DD equals 0
BC + B!D + CD - that what remains

So i'm stucked and i don't know how should i continue.

Expression after simplification should be:
CD + B!D - (SoP - Sum of Products)

Can you help me, please?

Thank you very much for your time.


texts:
below I have the following problem along with the circuit's picture

My analysis is as follows:

for G and D open

\begin{equation}
I_{D1}=I_{D2}\hspace{10mm}therefore\hspace{10mm}V_{ov1}=\:V_{ov2}
\end{equation}
\begin{equation}
V_G+0.5=0.5-V_G\hspace{5mm}therefore\hspace{5mm}V_G=0
\end{equation}
using the this equation:
\begin{equation}
I_D=\frac{1}{2}k_nV_{ov}^2
\end{equation}
we see that:
\begin{equation}
I_{D1}=I_{D2} = 0.125mA
\end{equation}

My problem is that my analytical results don't agree with my simulation results below

We see from the simulation that V_G = 0.4375 which is not zero according to my analytical work. Also, the current I_D = 0.000439453 which is not 0.125mA according to my calculations. Can somebody please tell me what am I doing wrong. Thanks in advance for all the help.


texts:
To me it is a very complicated transform in terms of math and my question is not about the math side but the practical use.

How is wavelet transform in practice handled for electrical signals? Are circuit simulators like LTspice able to perform such transform for a given data samples? I read that if the signal is non-stationary, FFT is not good as wavelet transform.

I have DAQ board where I can couple an electrical signal and sample and log it. Later I want to do first FFT and then wavelet transform of that logged signal and see the differences. But I only have Python and LTspice as tools. My purpose is to make a setup and observe the differences for the sake of learning. Does anybody have experience  with that?

(I couldn't find any straightforward example. And most articles are about image processing.)


texts: Small inductor coil in VCC, why did it help?

texts:
I have two devices - I know nothing about their internal circuits - and they  communicate with each other.
The communication between them is made by four wires, VCC, GND and two communication wires.
One of the devices supplies power to the other.  For communication to occur it is necessary to place a coiled wire in the VCC between the two.
I do 3 turns on the VCC wire and a diameter of about 5mm as shown in the picture.
After that the communication between them occurs without problems.
Could anyone explain why it worked when I do the coil with the VCC wire? Is it a noise matter?


texts: How can one compare resonant and non resonant antenna based on parameters like Directivity, Radiation resistance, Cross polarisation, Efficiency?

texts:
Basically I want to make a choice between two antennas when ample space is given objectively based on parameters
1.Directivity
2.Radiation Resistance
3.Cross Polarization ratio
4.Loss resistance
I'll consider both antennas to be of nearly same length i.e. the difference between length is only such that one is (a)exactly resonant
and other is
(b)just short or
(c)just long
to be called resonant all are operating at same wave length.


texts: Can I use a different transistor or mosfet?

texts:
I want to make an amplifier for my speaker.
Here is the link for the circuit.

Can I use a different transistor instead the 13007 MOSFET?
I have a LM35 transistor.


texts: Which protocol specifies the meaning of each bit in a CAN message?

texts:
A lot of books and articles describe the basic idea of CAN (controller area network) and the requirements to the physical layer as well as the data link layer.
But I didn't find any description how the bits of the payload gets assigned to some specific information like a wheel speed.
Is there a special protocol? Is there a basic database that describes the assignments of every bit to an information?
example:
ECU1 sends the following payload to ECU2: 1111 0000 1111 0000
How does ECU2 know which bit describes what information?


texts: Safely shutting down 19V mini PC when power fails

texts:
I am adding an Intel NUC (4"x4" i5 PC, 12-19V, 10A@19V) to my guitar effect pedalboard for all kinds of fun signal processing with Ableton Live and Max/Msp. I'm building a 12V 20A power supply using this for all the pedalboard's 5,9,12V electronics.

My goal is to get the PC to safely shut down when I unplug the pedal board from the wall using this. I assume this shutdown sequence will take about 5-7 seconds, and will no doubt need some sort of supplemental power source (battery? capacitor?) to keep it running during that time.

I was looking at universal 19V laptop batteries but then I have to take charging into account, source switching, added weight and space, etc. I'm am interested but inexperienced circuit designer, for example having just learned how to regulate those 5&9V circuits with regulators and capacitors. Of course it would be great if there was a simple product available that could take care of some or all of this task.

Thanks!


texts: Connecting DB25 socket to protoboard/breadboard

texts:
I need to connect a DB25 connector to a breadboard. One way I can think of is buying a solder-cup connector (e.g. http://www.digikey.ca/product-detail/en/171-025-103L001/225ME-ND/858135) and wiring it to the breadboard, but I would like a cleaner and more trusty solution. (e.g. discontinued: https://www.sparkfun.com/products/retired/8552)

Does anyone have experience?

Thanks,
S


texts: Voltage and current sensing hardware on chip

texts:
I have an external R C circuit excited by a step voltage source ( to be present inside a chip) to find the values of components R and C through transient analysis. Since we need to know voltage and current across the network to achieve this purpose, I am wondering how can we design a hardware using MOSFET and other passive components (may be through a differential or instrumentation amplifier), which will be present inside the same integrated chip, to measure voltage and current across the network at different instants of time. Is this done before to have the voltage and current measuring hardware in an integrated circuit? Any help would be appreciated.
Thanks!


texts: Building a simple PC - looking for a CPU

texts:
I would like to build a computer. It is a child's dream that I had and now that I am at college, I finally gain the knowledge I need.

I want it to be simple. I admire the early designs of 1990's notebooks and I imagine building something like that myself. I think it could be interesting to build a device with limited computational power, yet gain the advantage of using highly-integrated components available today (instead of hundreds of single purpose ICs).

I would write a very simple operating system myself, firmly tied to the actual design to run efficiently, as well as few other programs I cannot live without (vi clone for start).

When I wanted to buy a new notebook eight months ago, I did not find anything that would make me happy. Here's what I want from a notebook to have fun:

60 MHz CPU
8 MB RAM
256 MB non-volatile storage space
monochrome VGA resolution display
10 hr battery life

Only high-end notebooks or simple netbooks have the required battery life. Small netbooks kill ergonomy (I really love large keyboard), high-end models are expensive (Lenovo is close to what I need). I decided to keep my old SONY VAIO VGN-FW21Z and gave up on buying a new notebook.

(Note: The moment I start xorg, the fan gets a little loud. I always think: why do I feed the CPU with so much energy and keep it cool all the time, if I only need a fraction of its actual power? It is my strong belief that a vast amount of the power of today's PCs is totally wasted for nothing while having super-fancy logos and trademarks all over the damn shiny chassis.)

Designing my own computer from beginning to end would be partially a great exercise, partially I would like to build something that fits my precise needs. It would be great fun of course.

Recently, I have been through discussions on the topic of CPU selection.

ARM processors seem to be way more powerful than I need
Texas Instruments offer MCUs that seem to be designated for real-time control and floating-point performance
Atmel MCUs (AT32UC3C0512C in particular) seem to be the best fit

What confuses me is this. The AT32UC3C0512C is SoC device that itself incorporates main memory (68 KB SRAM), A/D converters etc. I would really like to wire my own RAM modules and drive them myself rather than having them on the chip already. The same applies to most of the other peripherals already contained in the package.

It seems I would need the sole UC32 CPU. My question is - is there a simple CPU operating around 60 MHz with solid architecture that I would use in this project? I am not looking for legacy components.

By the way, if you have any experience you can share, I kindly ask you to post a link to it.

Nice hacking!


texts: Wiring a BJT differential amplifier in a circuit

texts:
I need to switch a 12V relay when an input signal passes a certain voltage threshold. I use this popular BJT amplifier:

In my case:

VCC = 5V
RC1 = RC2 = 2.2k
RE = 1k
Q1 = Q2 = BC547
VIN1 and VIN2 are DC voltages set by potentiometers.

The ideea is that one input(with voktages ranging from 0-5v) will be compared to the second(same range). Based on which is bigger  a relay will be opened or closed.
The current circuit's precision is good enough with 0.04V threshold before a big enough voltage appears on the outputs.
At this moment approximately 1.8V are between VO1 and VO2 which is perfect. The only problem is that this voltage is not referenced to ground. This means I can't use a transistor with the base and emitter connected to the two outputs and the collector to the 12v rail. One solution would be to have an isolated source between the collector and emitter of this transistor for powering the relay but this it's not convenient.
Another solution which I tested was to connect the two outputs to a optocoupler which then provided power for a Darlington transistor and finally for the relay and 12V.
The reality is that I couldn't find a circuit that used such an amplifier so I don't know how I should use it.
NOTE: I don't have any opamp laying around just BJTs, mosfets , diodes and resistors.


texts:
I'd like to use Flash Magic to load programs onto my LPCXpresso1769 development board (https://www.embeddedartists.com/wp-content/uploads/2018/06/LPCXpresso1769_CD_revD.pdf), via ISP.

I purchased a USB to Serial data converter - TTLl-232R-3v3(https://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf), and wired it up to the board as follows:

1) GND (FTDI Black) goes to J2-1.

2) TXD (FTDI Orange) goes to J2-22.

3) RXD (FTDI Yellow) goes to J2-21.

The board is powered via the USB debugger probe

I enter ISP mode in the typical way, although it appears that the RESET button on the board is actually the ISP button, and vice versa (can anyone confirm this?), so I tried both combinations to make sure I was entering ISP mode.

In Flash Magic, I tried all available COM ports, and a range of baud rates, with the clock set to 12Mhz. I tried to establish a connection by using Read Signature, and on all occasions, a "Failed to transmit or receive", or, "Auto-baud" error was displayed. Is there anything glaringly obvious I'm doing wrong?


texts: What is the relation between efficiency of solar cella and incident light power \$\eta(P_{inc})\$?

texts:
What mathematical relation, if there is one usually valid, describes the variation of efficiency \$\eta\$ of a solar cell (i.e. the ratio of produced electrical power \$P_{el}\$ and incident light power \$P_{inc}\$) and incident light power \$P_{inc}\$ itself?

In other words, what is the typical form of the relation \$\eta(P_{inc})=f(P_{inc})\$
?


texts: PIC16: Out of Data Space - Make use all available banks

texts:
I'm using a Microchip PIC16F1825 with the XC8 (v1.12) compiler and defining some arrays (size between 16 and 64 bytes). I was able to declare them (linker output below). However, as soon as I try to access a few of them in a for-loop, I get an error on build:

error: could not find space (32 bytes) for variable _tempMeasurements
(908) exit status = 1

The more arrays I try to access the more Data Space usage goes up. How can I avoid running out of memory? Clearly, not all banks are used.

Memory Class Usage:

Program space:
    CONST                used     0h (     0) of  2000h words   (  0.0%)
    CODE                 used   B8Dh (  2957) of  2000h words   ( 36.1%)
    STRCODE              used     0h (     0) of  2000h words   (  0.0%)
    ENTRY                used     0h (     0) of  2000h words   (  0.0%)
    STRING               used     5h (     5) of  2000h words   (  0.1%)

Data space:
    COMMON               used     Eh (    14) of    10h bytes   ( 87.5%)
    BANK0                used    4Fh (    79) of    50h bytes   ( 98.8%)
    BANK1                used    4Eh (    78) of    50h bytes   ( 97.5%)
    BANK2                used    4Ah (    74) of    50h bytes   ( 92.5%)
    BANK3                used    50h (    80) of    50h bytes   (100.0%)
    BANK4                used    40h (    64) of    50h bytes   ( 80.0%)
    BANK5                used    40h (    64) of    50h bytes   ( 80.0%)
    BANK6                used    40h (    64) of    50h bytes   ( 80.0%)
    BANK7                used    40h (    64) of    50h bytes   ( 80.0%)
    BANK8                used     0h (     0) of    50h bytes   (  0.0%)
    BANK9                used     0h (     0) of    50h bytes   (  0.0%)
    BANK10               used     0h (     0) of    50h bytes   (  0.0%)
    BANK11               used     0h (     0) of    50h bytes   (  0.0%)
    BANK12               used     0h (     0) of    30h bytes   (  0.0%)
    ABS1                 used   16Ah (   362) of   400h bytes   ( 35.4%)

EEPROM space:
    EEDATA               used     0h (     0) of   100h bytes   (  0.0%)

Configuration bits:
    CONFIG               used     2h (     2) of     2h words   (100.0%)

ID Location space:
    IDLOC                used     0h (     0) of     4h words   (  0.0%)

Memory Summary:
    Program space        used   B92h (  2962) of  2000h words   ( 36.2%)
    Data space           used   3AFh (   943) of   400h bytes   ( 92.1%)
    EEPROM space         used     0h (     0) of   100h bytes   (  0.0%)
    Configuration bits   used     2h (     2) of     2h words   (100.0%)
    ID Location space    used     0h (     0) of     4h bytes   (  0.0%)


texts:
My original question was put on hold because a number of people found it confusing. Drew figured it out, however, and set me down the right path with relays (not diodes). There is still one issue outstanding, so I'm updating my question based on my newfound understanding of relays.
THE BASICS

I'm wiring a vintage traffic light for novelty use in my home.
I purchased a controller that sends load to the G-Y-R lights in
sequence, same as you see on the street.
I'm trying to customize the behavior of the lights a bit.

Instead of:

Phase 1 (G)
Phase 2 (Y)
Phase 3 (R)

I want this:

Phase 1 (G and Y simultaneously)
Phase 2 (Y and R simultaneously)
Phase 3 (R)

The solution that Drew provided — a relay — works perfectly for Phase 3. Meaning when R gets juice from the controller, the current can't also advance to the Y through the relay.
Originally I didn't describe the desired output of each phase because I didn't think it necessary. However, now I see that without two additional relays, during Phase 1 (G and Y), current will advance to the R through the relay. And during Phase 2 (Y and R), current will advance to the G through the push-in wire connector.
QUESTION: even if that last paragraph isn't clear, as illustrated below will the three relays succeed in channeling the current to only the colors indicated during the active phase?


texts: Why doesn't Class C modulator operate in saturation?

texts:
The following circuit is a class C (actually class B) amplifier used in AM modulator in my previous question.

According to the textbooks, the transistor is driven into saturation in this class. A practical design has an additional resistor in the base. However, the results of simulation shows that collector-Emitter voltage is always above 0.2v and the transistor never operates in saturation.

  Why doesn't the transistor operate in saturation by inserting the resistor R6?

simulate this circuit – Schematic created using CircuitLab

EDIT:

Simulation with different time steps give different results. the question was asked based on timestep=0.1us.

Here is the results of time domain analysis with timestep=0.01us:

EDIT:

It's somehow confusing for me. The above plots are achieved with time step 0.01us with circuit lab (since I haven't a simulation program on my desktop). but the previous results (before edits) were obtained with time step 0.1us. I don't know which one is correct!

Time domain analysis with timestep=0.1us:

Also the base voltage is continuously decreasing.

I've also placed a FET instead of BJT. here is the result for
collector voltage and
collector current.


texts:
I need to connect an input signal from a function generator to a circuit I made on a breadboard.

If I use a BNC to Banana cable, then would the "ground" of the function generator (the ground on the banana clip) be the ground for the entire circuit?
I suppose my question is, is the ground voltage just something I choose so long as I keep it consistent, or is there a literal ground on the breadboard somewhere?

The breadboard looks like this:


texts: Powering dual 5VDC, 2.4A USB ports via a switch in vehicle

texts:
I have an illuminated 2 port usb charger that plugs into a cigarette lighter/accessory socket in a car. The face of the charger is flat and sits flush when inserted into the cigarette lighter/accessory socket. I’d like to install this “permanently” in the rear passanger area of a car so that two passangers can charger their devices. I did not want to install a second accessory socket so I’ve opened the charger and now have the internal circuitry to which I can connect my own wiring.

Since it is illuminated, and since I don’t always have passangers in the rear, like to be able to control this with a switch. Here are the specs for the devices involved:

Power supply from car:
12v, 5A or 10A max from fuse box are both available (switched power)

Switch:
5 pin (NO, NC, C, +, -), max 3A

USB charger:

• Input
10-16VDC 2.9A

• Output
5v, 2.4A max X 2 ports = 5v, 4.8A if both are used at the same time.

QUESTION:
It appears the switch I have will not be able to handle current draw if both ports are being used at their max draw (2.4A x 2 = 4.8A). Is this statement correct?

If I still want to use this switch, I will need a relay that can handle up to 5A. Is this statement correct?

Lastly, is it even worth doing all this? Should I just connect the charger directly to power from my fuse box on the 5A circuit with a 5A fuse?


texts: Can I cut off a thermocouple's metal head?

texts:
I want to attach a thermocouple to my 40Watt soldering iron in order to make it temperature controlled. The thermocouple I'm going to buy is a K type MAX6675 thermocouple that looks like this:

But the thing is it has this bulky metal head attached to it which doesn't seem to be detachable. Since I want to attach the thermocouple to my soldering iron the smaller it is the better for my application.

I was wondering if I could just cut off the metal head of the MAX6675, twist the heads of the wires together and turn it into something like this:

Will the thermocopule stay intact if I do such thing?

And if not, is there any other way I can get rid of that bulky head? (Buying another thermocopule is not an option)


texts: I set up an amplifier (LF351) for a gain of 5.7, but it is saturating. Do I have to utilize the offset null pins?

texts:
simulate this circuit – Schematic created using CircuitLab

The feedback network I am using is a voltage divider with 4.7K and a 1K resistor. The node after the 4.7K resistor is connected to the inverting input of the amp. The node after the 1K is grounded. Attached is the hyperlink to the LF351 datasheet.

LF351 datasheet


texts: I want to use the diode 1N4571 (Vbrkdn=6.4V) and 1N4761 (Vbrkdn= 75V) in my circuit. Please help me design these zener diodes in LTSPICE.


texts: How can I set the condition code in assembly language?

texts:
I want test the variable sign. In other words, I want know answer to the whether a variable is positive or negative. How can I write following if-then-else conditions in assembly language ?

  if X > 0
      goto A
  else
      goto B

I am using PİC16f87x

To do my question to be more general, if you know can you give answer to below questions?

i.)

    if X > Y
        goto A
    else
        goto B

ii.)

    if X >= Y
        goto A
    else
        goto B

iii.)

    if X != Y
        goto A
    else
        goto B


texts: U16 takes more time than my U32 for sine operation

texts:
I was doing a performance monitoring for my sine function and interestingly when I use the variable a in the sine as 16 bit unsigned types it takes more time to calculate than when I use the same variable as a 32 bit unsigned. Could this be because inside the sine algorithm in math.h/.c it takes more time to type caste the 16 bit type ??

This is how my operation looks like,
start_performance,
for(50 times)
{ a=sin(a*3.14/180); }
stop_performance_and_read values

My performance monitoring unit works fine , its just that I dont understand why the result is odd.


texts: Find the Range of Rs for which the transistor is in saturation

texts:
I have been trying to solve this question but I am getting messy eqyuations.

My Attempt:

For saturation mode of NMOS transistor , the following conditions should be satisfied;

  $$v_{gs}\ge v_t $$
  $$ v_d \ge v_g-v_t$$

Where v_d is drain voltage, v_gs is gate to source voltage, v_t is thershold voltage and v_g is the gate potential.

From the first equation,

$$5-I_d\times 1 \ge v_g-v_t$$
$$\implies 5-I_d \ge 0-v_t$$
$$\implies 5-I_d \ge 0-1$$
$$\implies I_d \le 6$$

Now I tried to express I_d as a function of R_s by using the current equations for drain and source current,but the equations kept getting messier and messier, eventually I gave up.

I think either the question is incorrect, this transistor always remains in saturation independent of R_s, or I have commited errors.

Help would be appreciatec either way.


texts:
I have recently designed a four-layer PCB in KiCad. It is a spectrometer having PIC24EP and a CCD linear image sensor (TCD1304). The layer stack up is as follows:

Signal (no copper pour)
Ground
3.3 V power plane
Signal (copper pour connected to ground)

The TOP layer is of RED color and the bottom layer is of GREEN color. The middle layers are completely copper pour (no trace in them). Below is the picture of my layout:

I have read over here about three types of coupling, and I have been trying to reduce as much noise as possible (not even µV, if it is possible to achieve). I have mentioned below how I think my board should be avoiding each type of coupling. However, I am not sure if I understood the concept correctly and maybe I have missed a few things which I don't know yet. That's why I have posted this question. Please review my board and my explanation and help me.

Common Impedance Coupling:

The ground plane behind the TOP signal layer helps in reducing the impedance of the ground (as it has widest area). I have used two pins for GROUND in header J1 to reduce the common impedance coupling.

Electrical Field Coupling:

I have taken care of distance between critical tracks. The analog pin of TCD1304 is far away from the clocks of TCD1304 and oscillator.

Magnetic Field Coupling:

I know that magnetic field coupling can be reduced if there is a large distance between loops and they are aligned at 90 degree to each other. There is a wide distance between TCD1304 clock lines and the ADC pin. However, I can't run horizontal/vertical tracks on top/bottom layers as I think it is not possible (please suggest to each that if I am wrong).

Regarding Return current path:

The return current path of the top layer will be ground plane (as it is just below it) and of the bottom layer will be 3.3 V plane. I think the return current path for oscillator and crystal will be ground plane and as you can see it in layout, it is not interrupted. The return current path of TCD clock lines and analog output line will be just below the signal and hence, it is not interrupted as well.

I am not quite sure about voltage references (LM4041). I want to have very low coupling to them for stable references. I think there is no such problem with my references in my board, but I can consider to place them at the bottom layer if it helps to achieve good performance.

I am not sure about position (at what layer) of the decoupling capacitors. Please tell me best placement for them.

The clock frequency of TCD is 2 MHz. The PIC24EP has 12 MHz SMD crystal. The Fosc of the PIC is 64 MHz. I know maybe most of the things won't matter at this frequency, but I am an undergraduate trying to learn and build things. Please point me towards the right direction.

EDIT 2:

I have modified my layout as suggested by others (just solved the pads issue). I am working on reducing noise by understanding what others has suggested.


texts: PCI-Express on SATA or SATA on PCI-Express damaging?

texts:
OK, at first this sounds like an obvious and serious design error. But I'm trying to figure out muxing the SERDES signals on a PCI-Express Mini card, such as WiFi cards in laptops and mSATA cards in laptops, to make a dual-purpose autodetecting slot. While I haven't yet got the spec to see if there's a detect pin to control the mux, I'm pondering an audomatic software solution if no mode detect pin exists.

Do PCI-Express enumeration with the SERDES mux set to PCI-Express. If something is found in this slot, then we're done.

If nothing is found in this slot, it's either empty or an mSATA, as I don't expect a SATA device to respond to a PCI-Express scan, at least not in an understandable fashion, so the PCI-Express root controller will ignore it. So use a GPIO to swap the SERDES mux over to the SATA signals, and try to enumerate it from a SATA controller. If something is found, great, we're done.

If at this point, nothing was found by the SATA controller, then the slot is empty.

If one of the two controllers found a usable device, then it should be working fine.

Of course this depends on neither signalling type being damaging to the other kind of device, and so I am here with my question. Does one of these two things run at a higher voltage that would damage the other? Or use packets which would confuse and somehow damage a device of the other type by doing something not part of it's standard and very unexpected from being designed to that other standard?

Or would everything be OK, perhaps confusing the chip but in a non-damaging fashion, and things would work great again when the mux goes over to the correct connection for that device?

I am of course ignoring the other similar shape/same connector things such as the eeebook cards and whatever else is not at all close, but it seems the PCI-Express and mSATA may be close enough to do this autodetect/switch/autodetect sequence.

I'm looking at SERDES muxes such as TI HD3SS3415 or TI HD3SS3412 or Pericom PI2USB3212 signal switches. These are rated for higher than USB3 Superspeed and PCI-Express Gen2 signalling, and I'd imagine that'd be fine for mSATA 3Gbps as well.


texts: How to create/optimize a matching circuit in the middle of a PCB with a network analyzer?

texts:
I have a PCB with an SMA connector as only input. The block diagram of the circuit looks like:

I would like to update the L-match for optimum matching (L, C1, C2 at 915 MHz).
I connect a VNA to the SMA and measure Ztot=26-j17. Then I disconnect L and C1 (=L-match and "B" are disconnected) and I measure only Za.

With this information, how can I redesign the L-match? (The first instinct is Ztot=Za+Zl+Zb or Ztot=Za//Zl//Zb. But it doesn't seem so trivial)
When measuring Za, instead of removing C1 and L, should I short C1 instead? I would like to avoid putting 50 Ohm there because a) I don't have precise 50 Ohm resistors, b) I would need to consider the package and parasitics as well.

PS: A is "ideally" a short: It consists of ac coupling caps, RF switches, PCB traces and artificial transmission lines (delay lines). B is mainly an LNA input (but also has lots of PCB traces, lumped components etc).


texts:
I need to do a project where I mix up to 8 to 10 audio channels together to play through a speaker. This needs to be done on a low cost microcontroller such as an ARM cortex M0 and I am thinking about how to do it.

The audio will be placed in an SPI FLASH memory chip in raw mono format (bit depth should 12-16).

The only way I can see to do it is to add the samples together - but for this I need a much higher dynamic range than 16 bits. So I think I would need a 24 bit DAC.

Is there anything else I am missing? Any other ways to mix audio or to do it without an expensive DAC? Is it even achievable?


texts: Control two DC brushed motors with two wires in common

texts:
I'm working on a retrofitting project. I need to control 3 DC brushed motors with full H-bridge drivers. In most scenarios the 3 motors have independent connections:

simulate this circuit – Schematic created using CircuitLab
But in few cases the actual connections are the followings:

simulate this circuit
The X motor has independent connections for both wires, while motors Y and Z have two wires in common.
I cannot change the wirings but I can modify the driver circuits. Of course, I'm trying to avoid to make a completely different driver just for few systems.
The circuit for each axis is this one:

If I connect the motors to the control board, Y and Z axis move together due to the shared wire.
I guess the original board (that I don't have, by the way) uses a dual power supply: the common wire goes to GND and a positive or negative voltage is applied to the other side of the motor.
Do you see any solution to fit two full-bridge drivers like the ones above to this wiring?


texts:
I am trying to understand the SDRAM and in the datasheet I am not able to understand the geometry. The SDRAM is a Samsung K4S561632N 32MB. http://www.samsung.com/global/business/semiconductor/product/consumer-dram/detail?productId=7147&iaId=742

In the datasheet http://www.samsung.com/global/business/semiconductor/file/2011/product/2010/5/6/135616ds_k4s56xx32n_rev10.pdf it is given that "The K4S560432N / K4S560832N / K4S561632N is 268,435,456 bits synchronous high data rate Dynamic RAM organized as 4 x 16,777,216 words by 4
bits / 4 x 8,388,608 words by 8bits / 4 x 4,194,304 words by 16bits, fabricated with SAMSUNG's high performance CMOS technology."

The last numbers i.e. 4x4,194,304 words by 16bits I am able to understand that the first number is bank. I am not able to understand the second and third numbers. What does a 'word' mean there (1 byte or 2 bytes??)? Is it the number of rows by columns?


texts: The datasheet of TRI-T D22-5002 C6 display screen

texts:
does anyone have any idea on where I can find the data sheet of the D22-5002 C6 display screen?
It has 22 pins on 2 opposite sides (11 on each).  I searched everywhere but I can't find it.
I have the data sheet of the D22-5003 display screen but it have 18 pins, so I don't think it can help me.


texts: What does the tamper button on my STM3220G-EVAL board do?

texts:
Reading through the reference manual of the STM3220G-EVAL development board (an ARM Cortex-M3 dev/eval board) I see that it has a "tamper button", also weirdly referred to as an "anti-tamper button".

What is this tamper/anti-tamper button?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to design a simple switch for a electric valve. I'm using a 2N4033, and I'm providing 12.3V between the emitter and the collector. For the base, I have a voltage divider of a 100k and a 1k, which provides the base with about 12V. This should cause Vce to be 0, as the voltage difference between Vce and Vbe is under 0.7V. However, when everything is powered on, the Vce is 12V, when it should be zero. Can anyone help with what I'm doing wrong?

Edit: Added circuit diagram. The SPST is the control mechanism for turning the circuit on and off. The valve is represented by the inductor. The current draw from the valve is 540 mA at 12V. My power supply can supply 2A at 12V.


texts:
I'm new to CAN and currently having problem with a setup.

The image shows how my devices are connected to each other. I'm using the canutils Linux package to send messages (Linux uses its network layer to register and operate the CAN interfaces). So I start up the devices, bring up a terminal and type the following configuration commands on them:

ip link set can0 type can bitrate 125000 //This one registers an interface for can0 and sets the bit rate to 125000 bit/s.

ifconfig can0 up //Switches on the interface

At start, both devices' IDs are full null. Now, on one of the devices I switch on the listening state, which is:

candump can0

On the other one, I send out a message, something like this:

cansend 123#0x01 0x02 0x30 //123 specifies the ID, after "#" comes the data

Now, when this happens, the sender interface goes from error-active (normal state) to error-passive (error state). The "receiver" doesn't receive anything at all; it stays at error-active state. No messages are processed or catched, the log is clear (ip -d -s link show can0) and on the oscilloscope I can see the diff signal, and the sender is sending the message periodically, non-stop.

Maybe it's waiting for a response? I don't know if it's the whole message or just a fraction of it, but it sure changes with the given data, so I guess it's the whole message. And after that, if I try to send out another message with different data, the program just loads it into a buffer (I know this because after, like, 10 new cansends, it writes out that the buffer is full) and continues to broadcast the same old message. So I have to type canconfig stop -> canconfig start to restart the interface into error-active mode.

I'm sure that I'm messing up something fundamental, but I can't figure it out.

How can I fix this problem? Could it be a software or hardware issue, or maybe both?


texts:
So I’m trying to design an AC/DC convertor for a test unit that will go inside of an environmental chamber, but I’m also trying to build in a battery backup charger and switcher circuit, in the event I lose power from the AC/DC power convertor. I’m currently planning on using TI’s LM3420 to deal with the Battery charging. A big drawback is it wants 13-20V to power the charging circuitry. And the Battery will be approximately 8.4V Volts.

Almost all of my remaining electronics will be running on 5V, MCU, LCD display, LEDS, etc. So I don’t necessarily want to use a 7805 5V voltage regulator coming off the battery or Convertor because I’ll be losing a lot of energy and converting it to heat, both of which I’m trying to avoid. Does anyone have any suggestions or a different way to go about reducing my power dissipation or a better way to reduce my voltage loss for both the AC/DC convertor and the battery.

Below is a link to the Battery Charger Controller I'm trying to use, pg 14, is the current design I'm considering implementing.

http://www.ti.com/lit/ds/symlink/lm3420.pdf

Above is a rough block diagram of how I'm seeing this system interacting with the various components.

Thanks for any advice or design considerations I have mentioned


texts: Strange Waveform Using FPGA with NI myDAQ

texts:
I am testing my Microsemi FPGA with a NI myDAQ and am getting some strange waveforms. All that I am doing is inputting a 3Vpp square wave at 10kHz and expecting the same output since my code is just setting the output to the input (shown below). I've also included a picture of my input waveform before it is connected to the myDAQ and what it looks like after the myDAQ is connected.
module test( in_1, clk, out_1 );
input in_1, clk;
output out_1;

reg out_1;

//<statements>
always @(posedge clk)
begin
    out_1 <= in_1;
end

endmodule

Here is the input waveform when the myDAQ is not connected:

Here is the waveform when the myDAQ is connected. The top wave (green) is the input while the bottom wave (blue) is the output. Why is the input voltage dropping by almost 1V when the myDAQ is connected and why is the output wave dropping even lower than that? The original signal was 3Vpp so shouldn't the output be the same?

I know I should be using a real function generator with a real oscilloscope instead of a myDAQ, but I am not allowed in my lab right now because of the pandemic.


texts: How to calculate the switching loss of an OR Gate?

texts:
This is the datasheet of the OR gate. Current consumption as per the datasheet is 25 uA. (Electrical Characteristics table - Page 4
Input current Icc = 25 uA).

I am wondering how power consumption will change if the gate is working, for example Assume OR gate is switching a clock of 3.3 V at 24.576 MHz.

Intention is find extra power consumption, if there is any. I have gone through the datasheet, but not found such any information.


texts: the implementaion of communication systems

texts: I wonder , Why when we study communications systems , we just study the theoretical part(Math) , and we never touch the electrical circuits that used to implements this systems , I have asked my DR. that teaching me a communication course , and he told me "know theory , then you simply know the electronic circuits" , then i asked another DR. that given me another course  and he told me that is a advanced topics , So Im confused about this , could any one give me a clear answer ?


texts: When an LED has a "light degredation" specification, does that means it's an OLED?

texts:
I was reading a datasheet for an LED panel, and I saw a spec for "Light Degradation" after 1000 hours.  Can I assume this means it's an OLED (Organic LED), and that the organic materials will decay over time, reducing the brightness of the light?

I prefer the "inorganic" LED materials, where lifetimes were measured in 100,000s of hours, so I need a way to determine the answer to this question.
YSM-1288CR3G2C is the specific part number.


texts: Why is the gain of this amplifier so small?

texts:
Consider the following circuit:

I want to find the gain of this configuration, with and without the bypass capacitor (the 47uF capacitor).

Vx will be taken as the input voltage and Vout as the output.

Part 1: using the bypass capacitor

Using the small signal pi model, we obtain the following circuit.

Therefore:

Vout = -(ro || 4.7k || 10k) * gm * Vin

Av = Vout / Vin = -(ro || 4.7k || 10k) * gm

I built this circuit and measured and found that the current through the drain is 1.8074 mA. This would give ro = VA/ID = 25/1.8074 = 13.86 ohms. If we consider gm to be equal to 0.5 * 10^(-3) Siemens and we calculate Av, we get -6.90 * 10^(-3) V/V.

Question:

Why is the gain so low?

Part 2: without the bypass capacitor

Using the T-model, we get the following circuit.

Analyzing this circuit, we get:

Vout = - gm * Vgs * (4.7k || 10k)

Vin = (1/gm + 1k) * gm * Vgs

Therefore, Av = Vout/Vin = -1.067 after plugging in the values.

Question:
This gain makes more sense. Is this because ro was ignored in the T-model?


texts:
This seems like a very common voltage.
I remember older batteries used more round numbers like 1.5V or 3V or 9V.
3.7V seems very arbitrary but seems to be everywhere.


texts:
I have a couple of cheap prefabricated 1m 50 Ohm cables terminated with male BNC connectors. These connect to a device in an environmental test chamber which is cycling between 5 degC and 60 degC.

I suspect there may be problems with signal integrity - is this likely? The signals of interest are at 120kHz with a typical peak to peak value of 100mV feeding into a 10K input impedance. Nothing visible on the scope, but the changes I am looking at are timing related in the nS.


texts:
Today, while drinking some water from a \$500mL\$ bottle, I started reading the info about the water and found out that the conductivity (\$\sigma\$) at \$25°\$C is \$147.9\mu S/cm\$. So it came to my attention that maybe I could calculate the resistance of the water bottle, from top to bottom. After some measuring, I found out that the bottle can be approximated as a cylinder with \$18cm\$ height and \$3cm\$ base radius.

So we can do the following: \$R_{eq} = \frac{\rho L}{A}\$, where \$\rho = \frac{1}{\sigma}\$ is the resistivity, \$L\$ is the bottle's height and \$A\$ is the base area. By doing this, I got \$R_{eq} \simeq 4.3k\Omega\$.

Then, I bought a new full bottle, made a hole on it's bottom (of course avoiding leakages) and measured the resistance (with a digital multimeter) from this hole to the "mouth", at first making it so that only the tip of the probes touches water. The measured resistance was really high, ranging from \$180k\Omega\$ to even \$1M\Omega\$ depending on how deep in water I positioned the probes.

Why is the measured resistance so different from what I calculated? Am I missing something? Is it possible at all to use a bottle of water as a resistor?

Edit #1:
Jippie pointed out that I should use electrodes with the same shape as the bottle. I used some aluminum foil and it actually worked! Except this time I measured ~\$10k\Omega\$ and not the \$4.3k\Omega\$ I calculated. One thing I was able to notice while lighting a LED with water as a resistor was that the resistance was slowly growing over time. May this phenomenon be explained by the electrolysis that happens while DC current travels through water (the electrodes slowly get worse because of ion accumulation at their surfaces)?
This would not happen for AC current, right?


texts:
There are two clocks of the same frequency, but one has a phase shift. So we have two clocks, one leading and one lagging. How can we determine which clock has arrived first?

One way would be to use another faster clock in the design to sample these two clocks and make a decision.

Is there any simpler way to achieve this in RTL?


texts: Arduino MKR analog maximum frequency input

texts:
I know the Arduino ATMega based boards’ maximum reading rate of analog pin is 10kHz but what about MKR Family SAMD21 based boards?
I couldn’t find any info for it. I will appreciate your responses


texts:
I am designing a vibration sensor in enclosure to be placed on vertical surfaces, like windows, doors, etc.

My first try was with ready made sw420 module, but looks like it is to sensitive for my purposes (when adjusted to lower sensitivity, it reacts to light knocking, when i need it to detect "slamming").

Then i decided to try Piezo Disks. I found nice article about it.
It looks promising.

The one thing is worrying me is positioning of disk.
In article it is placed horizontally and there is some "weight" on it (as explained - to increase sensitivity). In my case it will be positioned vertically in plastic enclosure. So i cannot use any "weight".

Should it works if i just stick disk to enclosure with epoxy.

I will redesign extension/tamper board (right one in top enclosure) to fit op-amp and other components. So i was thinking, maybe i can solder bottom part of disk to bottom layer of board, and top(ceramic) with wire to the pad on top. Basically disk will be floating in air soldered to left side of board.

So in which case the element will be more sensitive? Fixed to enclosure or floating with board?
     Or may be other solutions (combined)? (i can redesign board and enclosure).

Currently i don't have components and pcb to experiment. And i want to gather more information before ordering new board.


texts: I have noticed many PCBs with solder mask free regions/areas on the edges. I am attaching an image with this. What is the purpose of such areas ? What I can think of is heat transfer to the ambient region around the PCB. In that case what is the need to remove Solder mask ? Does Solder mask trap the heat from escaping into the surrounding ?


texts: How should I design a schematic component for a component library?

texts:
This is my first time making schematic components, of which I will then be making the footprints for PCB designs. I'm using KiCad.

I don't know the best "layout" for the components I'm making. For example, some component libraries seem to bunch different connections together logically (e.g. Power and ground pins are next to each other, microcontroller ports are placed next to each other in order etc.) and then you get components where they have just randomly drawn any old shape and put the connections anywhere.

For example, these two components I've picked, the connections are in groups (note that this is a direct screenshot of one schematic page, I haven't resized either image):

My questions are:

Firstly, what shape should I use? I see some components as rectangles, other one as squares.
Is there a industry standard or something similar that states where the connections/pins should be displayed on the components (e.g. "put power and ground on the bottom side", that type of thing.)
What size should I make the schematic components? As can be seen above, there is quite a large difference between the size of the component, it's text, and the font used.
What colours/fonts should I use? Above one uses white one uses yellow as the filler colour.


texts:
I have a Huawei internet router with 12 volt 2 ampere input power.  I bought a solar panel 18V 10 watt with direct connection plug which I'm to use for the router but it seem to not working.

Please I need solution on how to make this to device work because I'm using this where there is AC power at all typically sun base device is what is needed there, I thought of connecting the 12 volt adapter direct to the panel then to router but I don't just know how well it will work.


texts: I read that steel/iron/metal/conducting cages, with gaps less than the wavelength of electro magnetic waves, shield whatever is inside from that radiation. But when I put my mobile inside a cooker and called it, it rang. Why isn't this working? Please explain Faraday cage working more in detail.


texts: Why there are data bit lower than 8 data bit of uart

texts:
Our group are creating a UART IP Soft Core with Wishbone Wrapper and we are using 5,6,7 and 8 data bit. I just want to know what are the use of the 5, 6 and 7 data bit?

In addition to my question above, what are the possible applications of the customizable uart? any suggetion please?


texts: Below is the efficiency curve for the TI TPS53513(datasheet). Can someone explain what causes this characteristic efficiency curve? It seems to be similar to the one for other regulators as well. Why is the curve parabolic with a peak efficiency? Why is there a "discontinuity" in the curve at the low current ratings around 750mA where the curve jumps up and then down?


texts: Connecting LED to a microcontroller powered with CR2032 with discharge voltage range 3.3V to 2V

texts:
For my project I'm using a nRF51822 SoC with a CR2032 powering it. I'm using an LED with 1.5mA consumption to signal a rare event. The LED has to have 2 V to work.

As the battery discharges, the voltage drops from 3.3V down to 2V when its empty. For the majority of time its voltage is around 3V.

When the Battery is close to empty, the microcontroller still works, but the LED doesn't.

What would be the best way (the simplest) to power that LED, even when the battery voltage falls?

Currently its just connected to a microcontroller with a 510 ohm resistor in series, since it's ok for the led to get 2V to 2.4V.


texts: Clarification required on DALI Standard 101,103

texts:
I want to develop a complete DALI Control Device with two important features, one being "3 DALI buses on the device" and other being the "RGB colour control feature"! Already, I have successfully designed a DALI Master-Slave prototype system using two STM32s.

As my next step, I want to make my DALI Master compatible with the available commercial products(DALI Gears). Also in parallel, I would like to buy essential DALI standards.

Q1. What are the essential DALI standards for my purpose?

I was going through these two (System Components- Part 101, Control Device- part 103) standards and I could not find any info related to RGB colour control! Rather it is noted that part 101 works in conjunction with part 102 and part 209 describe the colour control!  I certainly cannot afford to buy 4 standards(101,102,103 and 209) now!!

Q2: What are the designated commands for RGB colour control?? or Can I just use some random un-allocated(reserved) commands for this purpose?

Q3: Are 102, 209 required for my purpose? I will not be developing DALI Gear rather just DALI control device! I am assuming these two define how the DALI Gear should be designed!!

Essentially, I cannot afford to buy 4 DALI standards rather at max 3! In general, any suggestions regarding this project will be appreciated.

EDIT: What are the essential standards for me to get started? Maybe over some time, I could purchase all 4 but I am on the tight budget constraint. I could only ask for more money when I show some practical results with the above two features. Is there any workaround?

PS: I am not interested in getting the product certified anytime soon! I want to test it first for various practical scenarios.


texts:
I am using stm32f103c8t6 discovery board and I was doing a practise by using ADC peripherals. While using keil debugger I have realized something so strange to me.If discovery board is not connected to voltage source or ground, It is giving like 1900-2200.
The adc is configured as 12 bit read mode.It came so strange to me. I will leave my code ıf you want to check it.

#include "main.h"
#include "stm32f1xx_hal.h"

ADC_HandleTypeDef hadc1;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_ADC1_Init(void);
uint16_t adc_voltage;
int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_ADC1_Init();
  while (1)
  {
HAL_ADC_Start(&hadc1);
while(HAL_ADC_PollForConversion(&hadc1,500));
adc_voltage = HAL_ADC_GetValue(&hadc1);
HAL_ADC_Stop(&hadc1);
HAL_Delay(500);
  }

}

void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
  RCC_PeriphCLKInitTypeDef PeriphClkInit;

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = 16;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV8;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC;
  PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV8;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}

static void MX_ADC1_Init(void)
{
  ADC_ChannelConfTypeDef sConfig;

  hadc1.Instance = ADC1;
  hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  HAL_ADC_Init(&hadc1);

  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_41CYCLES_5;
  HAL_ADC_ConfigChannel(&hadc1, &sConfig);

}

static void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);

  GPIO_InitStruct.Pin = GPIO_PIN_13;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

}

void _Error_Handler(char *file, int line)
{

  while(1)
  {
  }

}

#ifdef  USE_FULL_ASSERT

void assert_failed(uint8_t* file, uint32_t line)
{

}
#endif


texts: Arduino Ethernet shield: it just won't work!

texts:
I have an Arduino Ethernet shield on top of an Arduino Mega2560 and have connected the Mega2560 through serial to my laptop and through the UTP port on the Ethernet shield to my router.

I've tried the "search Arduino on Google" example (where I corrected Google's IP address, the example was old), and it doesn't work (it doesn't seem to connect to the Internet. On the serial, I get: "connecting... /connection failed / disconnecting.").

My UTP cable is working fine... I've tested it on my laptop.

The Mega2560 is connected to my router (which has everything disabled so that's not the problem ) and when I ping from my laptop the IP address I gave the Arduino assembly, it doesn't ping back.

Why? Maybe there is something I'm missing? Here is my code:

Code:

#include <SPI.h>
#include <Ethernet.h>

// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = {  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
byte ip[] = { 192,168,1,177 };
byte server[] = { 209,85,148,147 }; // Google

// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
Client client(server, 80);

void setup() {
  // Start the Ethernet connection:
  Ethernet.begin(mac, ip);
  // Start the serial library:
  Serial.begin(9600);
  // Give the Ethernet shield a second to initialize:
  delay(1000);
  Serial.println("connecting...");

  // If you get a connection, report back via serial:
  if (client.connect()) {
    Serial.println("connected");
    // Make a HTTP request:
    client.println("GET /search?q=arduino HTTP/1.0");
    client.println();
  }
  else {
    // If you didn't get a connection to the server:
    Serial.println("connection failed");
  }
}

void loop()
{
  // If there are incoming bytes available
  // from the server, read them and print them:
  if (client.available()) {
    char c = client.read();
    Serial.print(c);
  }

  // If the server's disconnected, stop the client:
  if (!client.connected()) {
    Serial.println();
    Serial.println("disconnecting.");
    client.stop();

    // Do nothing forevermore:
    for(;;)
      ;
  }
}


texts: I need some help understanding overshoot and ringing in MOSFET half bridges

texts:
From FDA75N28 datasheet:

What I am having difficulty understanding are the reasons behind overshoot and ringing in V_DS.

Now, to what I already know:

The current that passes in an inductor cannot change abruptly, but has to change gradually.
Initially current is flowing through the Driver FET, but then this transistor turns off.
The current has to keep going somewhere, and the easiest way is to flow through the freewheeling diode of DUT transistor. This makes V_DS negative, as the drain pin has a higher potential than the source pin, thus forward biasing the body diode.
Before all the excess current is dissipated in whatever parasitic resistances the circuit has, the driver transistor turns on again.

(I need help undestanding what happens between these two steps and am not 100% sure of the next)

The body diode of DUT transistor becomes reverse biased right after it was forward biased. Because the depletion region takes some time to reestablish, current starts flowing in opposite direction to what is normal in the diode. From the datasheet, this phenomenon does not take too much long, 320ns which is the reverse recovery time. The current passing in the inductor keeps flowing in the same direction but this time through the driver transistor instead of through the body diode of the DUT transistor.

Additional remark:

As far as I can tell, the potential of the positive probe, V_D, never changes, so for an overshoot to happen, the negative probe has to go below the negative pin of the power supply. I cannot see what can cause this.

Why the ringing after overshoot? I have talked with a teacher that only has a general knowledge in electronics and he suggested that it could be a parasitic capacitance somewhere that was auto-oscillating with the inductance. I would like to know what exactly causes this.


texts: What external sensor could detect if a cd-tray had opened?

texts:
What would be a sensor that I could use to detect if my desktop's CD tray has opened?

There are so many sensors to choose from in the Digikey catalog.

Should I use a mechanical component?

A light beam interference component?

Which one would allow me to detect if my CD tray is open such that the information can be fed into a PIC MCU?

I know I can do a system call for this sort of question, but I would prefer some sort of external sensor.


texts: Attenuation and Insertion Loss for a 2 port network

texts:
in my university lectures the insertion loss and the attenuation of a 2 port network have been defined in the following way (and I have an extremely basic question about them):

the Lnsertion Loss L is the ratio between the power transferred from a voltage generator to a load when directly connected (figure 1) and the power transferred from a source to a load when connected through a two port network (figure 2):

By solving some equations with S parameters, this is the final expression of L:

As you can easily see, it depends not only on the network S parameters, but also on the load and source properties.

Attenuation is defined as the Insertion Loss evaluated when the reflection coefficients of the source and of the load are zero:

My question is: which is the meaning of defining the attenuation when \$\Gamma_{g} = 0\$? This condition means that \$b_{g} = 0\$, so no power is trasmitted to the two port network (and so to the load).

My book says that \$\Gamma_{g}\$ takes into account of the reflection of the power coming from the network (which is generated through the reflection of the source power at port 1 and port 2). I may understand this, but I think that globally \$b_{g}\$ is the direct traveling wave from the source to the network, and so if it is 0, no power is transmitted.


texts: 2xAA + 5V Boost Converter: Unexpectedly Low Current Output

texts:
I'm quite new to electronics, and decided to make a mobile powerbank for my Raspberry Pi Zero / Phone out of 2xAA Batteries and a 5V, 600mA boost converter with USB output. However, I'm getting an unexpectedly low output of only 0.08~0.10mA @ 4.5~5V when charging! I'm trying to figure out why this is.

My components are:

2x Panasonic AA Batteries at full charge. I'm having a very hard time researching the amount of current these are able to provide, but as far as I understand from the datasheet and a bit of googling, they should be able to output 1000mA above 1.2V

1x 0.9~5V 5V 600mA Boost Converter

2x Small Alligator Clips soldered on to the positive and negative through-holes of the boost converter.

1x AA box where I mount the batteries in series.

By my reckoning, my two batteries should output roughly 1A @ 3V, which equates to 3 Watts. But I'm getting only 0.08A @ 5V, amounting to a mere 0.4 Watts! Even given room for generous inefficiency, something doesn't seem to be adding up. I know that 3xAA chargers can output 500mA @ 5V, so in the real world, I would expect to get at least 1.5~2 Watts output with 2xAA's.

I've also tried some rechargeable NiMH batteries that I have, and had even worse results; only 0.2 Watts.

Why am I only getting a tenth of my expected output?
How can I go about debugging this?


texts: Given only a gerber file how do I automatically find out the number of pads that are there on the PCB

texts:
I am building a website right now , and am trying to automatically calculate the number of PCB pads that are there given only a gerber file. One way is to manually review this. Is there any other way to determine how many pads a gerber file has?
From a BOM one can easily find it. However, from the gerber is there anyway to find it?


texts: Why does 555 timer output change based on load?

texts:
I have a 555 timer setup in astable mode, with a frequency of about 1Hz which I measured and verified without load.  Out of curiosity, I connected an 8 ohm speaker, expecting not to hear anything.  However, I heard a tone, and when I looked at the signal on a scope, the frequency was about 1.4KHz.  How can the frequency change like this when I have a load?

Update:

@s3c: I added a 47 ohm series resistor at the output of the 555, and re-measured the signals.  I no longer see the strange 1.4KHz output.  The 555 output looks normal (yellow scope trace).  Should the speaker input (blue trace) be an AC coupled, reduced voltage version of the 555 output?


texts: How does one compute the ripple currents seen by a rectifier filter capacitor?

texts:
Suppose one is designing a full-wave rectifier bridge, with a known maximum current load, and a known input inductance. Assume three-phase for this example, though the same concept applies to single-phase:

The ripple current seen by the output capacitor is critical. If that current is too high, the capacitor will heat up, and its lifespan will be reduced. But how does one compute the ripple seen by this capacitor?


texts: Electrical current on machine and power socket

texts: I would like to check if my machine is 220V and drawing a max current of 16A . My power socket is producing 220V with a 13 A fuse in it . Will this cause the machine to trip or cause any fire hazard to the power socket ?


texts: Control of electric hoist motor based on variable load

texts: Is it possible to control the power of a hoist motor based on the specific load that will be lifted? What if the load is known by using a weight sensor?


texts: What is shunt field resistance in a DC Generator?

texts:
Is the "shunt field resistance" the resistance of the  coils in a shunt generator?

Googling https://www.google.com/search?q=%22shunt+field+resistance%22&oq=%22shunt+field+resistance%22&sourceid=chrome&ie=UTF-8 didn't give any helpful results.


texts:
I'm designing an alarm clock with an ESP8266 (Nodemcu) and a RTC module (DS3231). My system doesn't have any battery, it will be constantly powered through USB. I'd like to keep my ESP866 in deepsleep and waking it up at a specific time thanks to the RTC.

I first created a software alarm with the TimeAlarms library and it works fine. Now I'm trying to do the same thing directly with the hardware. My idea is that the RTC would send an impulse to the ESP8266 at a specific time set in one of the two alarms available on the DS3231 that would wake it up.

I'm using RCTlib.h, the RTC library from Adafruit that works perfectly but there isn't any example of alarm setting.

How do I use an RTC to wake up an ESP8266?


texts: Is it safe to use a TVS diode with StandOff voltage 3.3v on the output of a 3.3v regulator ?


texts: Combine two DPDT relays to make a 4PDT relay

texts:
I'm trying to come up with a replacement for the obsolete OMRON G6A-434P 4PDT relay for a replacement PCB I'm building.  I've got a bunch of OMRON G5V DPDT relays and I'm thinking wiring two of these up together with the coil polarities matched, it should work...right?  I've looked all over Google trying to find an example circuit, but I cannot find anything.  I was hoping you guys could help me out?

Thanks in advance.


texts: Output changing electrical currents from a PC

texts:
I need to send fast-changing electrical current from a computer to electrodes connected to muscle (Not the point).

I need to send multiple different currents simultaneously, and that the current could be changed on command from the PC.

I don't need something like an Arduino, I need the component IN the Arduino that allows this.

The main problem is that I need the change to be fast, less then a second.

I don't know many of the technical terms so I might have missed a similar question.


texts: Microcontroller driver the gate of a mosfet with a pull up resistor to 12V

texts:
I designed a PCB to drive mosfets with a ESP32 micro-controller. The ESP32 will be connected to the PCB with wires from a separate PCB. When there is no micro-controller connected to the input of the Mosfet PCB all Mosfets should be turned on. So I connected a pull-up resistor to their gate. The only onboard voltage is 12V so the pull-up is connected to the 12V as well.
When nothing is connected the voltage at the input pins will be 12V because of the ESP32. this doesn't seem a safe scenario to me for connecting a micro-controller. I worked out a few possible solutions.

Default scenario
Using a voltage divider
Using a 3V zener diode at the input
Creating a separate 3V source with a zener diode, and use this source to connect the pull-up.
(UPDATE) instead of option 4 use a voltage regulator to connect a pull-up to

For each scenario I've written my thoughts next to it. I'm not sure which one I should pick.
What is the best practice in this scenario? Opto-couplers might be but they slow down my switching time to much.

Thanks in advance

Link to simulation in falstad

UPDATE
This is my actual schematic I'm using at the moment. R7 Needs to be changed to a pull-up that's the one I was talking about.

A little bit more info on my circuit.

Q4 is the power-mosfet that will get a voltage of 0V or 12V at its gate. From Mosfet driver U2.
U2 is a mostfet driver with the internal schematic of a totem pole transistor configuration. To get around 12V at it's output we need 12V at it's input.
To to make a 12V to 0V input voltage at U2 controller by only a 0-3.3V control voltage I use Q3 a N-CH Mosfet with a pull-up resistor.

The reason I'm using this mosfet driver and I'm not controlling it directly is because I need a very high switching speed. At the moment when I measured this I only have a 33ns delay between input and output. And I'm afraid that adding an extra transistor or mosfet will slow down the propagation time even more.

If a transistor is faster than a mosfet which I guess it is I would gladly change Q3 for a transistor. But then I'm in the same situation as before with the pull-up at the gate/base.


texts:
Hi I have a generator with a 3 phase brushless motor acting as a generator rectified and smoothed to produce 0-12 volts however theoretically 2hp is approximately 1.5kw and at 12 volts before losses would give you a maximum current of 125 amps.

I have not load tested yet and voltage is dependent upon engine speed using pulleys to rotate it to get 12 volts at 10, 000 rpm, I wish to regulate this using a boost converter however I have not seen any for such high currents is there a reason for this.

I am assuming I cannot just build the standard boost circuit with high current components?


texts: What voltage does a laptop provide over USB C?

texts:
I have read a bit already about USB C specification. One thing is not clear for me though. Please take a look at this picture:

A device with profile from 1 to 5 can provide a higher voltage on the Vbus. From profile 4 to 5 it is specified that up to 20 V. The question is:

Can the Vbus voltage vary from 12 to 20 V freely or is it always 12V or 20V for profiles 4 and 5? I am not certain about this especially because even the AC adapters for laptops provide 19.5V, meaning that it would be hard (from the power electronics point of view) for a laptop to provide 20 V.
Note: take under consideration only USB C to USB C cable connection, not USB A to USB C, as this one clearly can provide only 5V.

When designing a device that would like to be charged from USB C, should it have the ability to be charged from 5V and 12 - 20 V? I would appreciate all help.


texts: Can Opening a Switch Cause a Short Circuit?

texts: Is it possible to construct a simple circuit (sans transistors) that would cause a short circuit between two points when a switch is opened? My intuition says no, but I don't have any proof for such a claim.


texts: Cheap alternative to limit inrush current (eg. relay bypassing a fixed resistor or MOSFET)

texts:
I'm editing the question because several (great) answers focus on the fact that the LTC3780 module (inside ajustable my power supply) can handle the inrush current (maybe, maybe not). I'm glad to know, but it doesn't answer my main question which is more global: how would you limit inrush current, in a cheap manner?
I apologized, my question wasn't clear.
(So the circuit I'm talking about below is just an example, let's say I use another power supply than the LTC3780 that deliver 12V-80W but can't handle the inrush current― but please keep the precious information provided in your answer about it).

The situation:
I want to power 5 fans in parallel (12V 0.80A, each) using an LTC 3780 (it's (DIY adjustable power supply)

Because my fan are brushless, I will have a high inrush current. My LTC 3780 can't handle more than 80W so I need to limit the current to about 6A (=80W/12V)

The possible solution:
I am looking for a simple/cheap solution (so no NTC thermistors*)

One cheap/simple solution would be to use a fixed resistor (R1) to limit inrush current to 6A, and a switch to bypass it. After a couple of second as the fans speed up, counter-electromotive force starts to limit the current. So the resistor R1 becomes useless and even inefficient as it consumes voltage/limits current that I need for my fans. The switch then allow to bypass R1.

The question is  which switch : a relay, or even better, a  MOSFET ? But how can I switch it? Could it work with a capacitor (or 555 timer ?)

Here is a working circuit with a relay (the fans are replaced by resistors with inductors).

How to choose the components ?
If this is a good solution,  how can I determine the value for R1, R2, C1?
- If my understanding is right, R1 would need to be more than 2 ohms (= 12V/6A), so I guess a 4,7 Ohms would be right for R1.
- I guess I need a R2, but how to choose it's value.
- And what about C1? I guess the bigger it is the longer, it will take to switch on the relay.

And also how to choose the relay so that it doesn't switch on too early (before my fans reach their steady-state or C1 is full) : is there a way to know the minimum voltage/current needed to activate it? Would something like  this MOFSET (or this relay) works ?

Better solutions ?
I also found this dirt cheap Time Delay Relay. If I use one with a fixed time like 5-10 seconds, would it work with my 12V/6A power supply and my five 12V, 0.8A fans?

Also is using a relay the best solution ? Couldn't I use a MOSFET as they consume less then a relay.
Here is my try at making a circuit with a MOSFET (but I can't find a way to use the capacitor to switch on the MOSFET):

(* Thermistors are expensive and I prefer to invest in components that I can re-use in other circuits.)


texts: Beginner question regarding batteries' voltage/amperage

texts:
I want to use two batteries rated 6v, 4A with a 9v,1A device. I figured that connecting the batteries in parallel would give 12v and connecting a 3ohm resistor in series with the device would give the device 9v(law of potential dividers). Now, to get the required current, do I connect a resistor(~8 ohm) in parallel to the device? Would that do the trick?

Also, how do I set up the circuit to charge these batteries up?


texts: how to reduce turn-off delay time of PNP transistor

texts:
I am having tough time while driving PNP transistor with optocoupler to generate 1KHZ PWM signal. my circuit consists of micro controller which will generate 1KHZ pwm signal which will go to base of PNP transistor(Q2) and the collector terminal of PNP transistor(Q2) will go to optocoupler input. and the optocoupler collector terminal is going to base of PNP transistor(Q1). the collector terminal of PNP transistor(Q1) is going to microcontroller pin. when i probe at micro pin or Q1 transistor collector the turn off time i am seeing 400ms. because of this i am getting error in PWM signal measurement which is 1KHZ.
output of R4 is connected to micro controller in the below circuit but not grounded like below


texts:
I am using an XR2206 IC to make a simple oscillator module. The documentation shows that it has a VCO as a part of the IC, and uses a variable resistor loop and a capacitor loop to control frequency.

My question is: How could I make a toggle, such that I can switch the IC between being controlled by the pots and caps and being controlled by a CV out device, e.g. keyboard? I would appreciate simple wording, as I'm not comprehensively educated on EE.


texts:
I'm working on the wiring harness for a PC build that's going to include a bunch of (5050) LED strip lights.

The strips will be wired to fan connectors (more details at end). For testing, I've been running them off of a SATA to fan splitter (e.g. this) connected to a stock SATA power cable. However, I'm going to have a lot of wires to cram under the PSU shroud and the splitter and stock SATA power cable are adding a bunch of bulk (and TBH, the splitter feels a little sketchy). Since I don't need 5V anywhere, I'd like to build some cables that don't have unused wires.

My initial thought was to build a peripheral cable that would run PSU → SATA (for some case fans) and somehow chain fan connectors off the end of that. (Or maybe with the SATA at the end.) However, to do this I would have to double-crimp a bunch of fan pins, or build a 2x SATA cable and keep the splitter. And in either case, I would also need fan extension cables, and 100% of the total load is being carried by a single pair of wires.

Then it occurred to me... I'm almost certainly never going to be using more than 4 out of 6 of my EPS/PCI ports otherwise... and an 8-pin EPS connector is 4x 12V pairs (compared to a peripheral connector which has only 1x 12V pair). AFAICT, although the pin pairing is a little screwy, there are no paired wires in the EPS cables, and the PSU end is also 4x 12V pairs. Physically, I could wire up a custom cable that plugs into an EPS/PCI port and has 4 separate 22/2 stranded 12V pairs coming off of it. This would add a little bit of extra wire right by the PSU, but each pair can be made to length (no extensions!) with a fan connector on the end (no SATA → fan adapters!), and each pair is only carrying the load of one set of LEDs.

Practically... Is this a good idea, or a terrible, terrible idea that will turn my Corsair AX1000 into an expensive paperweight?

All that said, I have already run the entire 5 meter strip off the stock SATA power cable → fan splitter → 4" 22AWG adapter, so the PSU does seem able to take the load on a single 12V pair (nothing caught fire, not did I notice any melting... aside from the LEDs themselves which put out much more heat than I would have expected). However this was only for maybe 30 minutes, where the completed harness is probably going to run 24/7.

In any case, the strips themselves are going to be connected with 22AWG solderless connectors (e.g. these) that have had fan pins crimped to the other end. Strips will be connected with either similar connectors (where possible; the pre-made connectors are only about 10cm long) or soldered with 22/2 between strips. The longest connected run will be about 1 M - 1½ M. Total lighting will be less than the 5 M reel (but possibly a significant portion thereof). Allegedly (read: according to the product description), the entire reel draws 38W, but what I have left of the reel (about 80-90%) only pulls about 2.3A (measured), so probably closer to 30W. Thus, each of the four runs, individually, will not exceed 1.5A, and probably closer to 0.6A each.

p.s. This is sort of very, very loosely related to Is it electrically safe to use an ATX PSU's PCI output for SATA/MOLEX instead of graphics cards?. Unlike that question, however, I'm powering LEDs, not HDDs, and only need 12V.


texts: What lens/reflector when bouncing off ceiling

texts:
"I'd like to fill a room with ambient daylight by bouncing LED light off the ceiling."

EDIT: Poor wording, but by "fill", "ambient" and "daylight", I'm not considering the intensity, but just how to focus and direct whatever light output I have, to achieve a "general brightness from above" similar to being under a bright sky, avoiding direct glare. For instance, should I try to cover most of the ceiling with a wide beam, or direct a narrower beam towards its center? And ultimately, how to choose lens/reflector components for COB LEDs.

"Initially I would test with 15x10W LEDs aimed diagonally upwards from the top of a shelf."

EDIT: I'm not expecting to simulate sunlight with 150W, it's just seems like a reasonable place to start in terms of cost and managing the cooling requirements. There is an article about DIY SAD treatment by bouncing 150W directional light off the ceiling, using a ceramic metal-halide bulb. In 2017 it seems possible to achieve 100 lm/W and CRI: 95 with LEDs at a similar cost. The author finally suggests using 25,000-50,000 lm, which would be 2-4 times more than 150W.

"If the LEDs' emission angle is 120°, how important are lenses and/or reflectors for this kind of setup, and what do I need to consider when choosing them?"

EDIT: I understand that this question might not be appropriate here, what I'm looking for is the big picture of how to find and select a lens for COB LEDs. I don't think the Physics SE would be suitable for that, either. I apologize and respect any decision by the mods. :)

Thank you for the detailed and insightful answers!


texts: Is this negative resistor model valid for any type of LC self oscillating circuit?

texts:
Is the following negative resistance model valid for any type of LC oscillator? If not, what are the exceptions?

Image Source is from here


texts: How to infer equivalent PID controller coefficients from an existing black box ccontroller?

texts:
I have a 2 input, 2 output system that I have recorded in response to 1. steps (actually quasi-steps, with 50 ms rise time + some overshoot), and 2. sine waves from 0.5 to 50 Hz, in both open and closed loop. In the open loop configuration, I can infer the internal parameters based on knowledge of the system's structure. In the closed loop configuration, a controller with ~60 ms delay brings the output close to a given target (which is separate from the input signal), but I can't figure out what the controller parameters are. I've attempted to model it as a PID controller using numerical (euler) simulations, but it seems to quickly become unstable when either I or D components are increased. In contrast, I can create the model in transfer function form and predict the frequency response, but I don't know howto then predict the response to arbitrary inputs (such as the quasi-steps, or sine waves where the control signal might differ from the input).

The system (u2 is the "goal/setpoint", F is the controller feedback with 60 ms delay, y2 is just a second output that I use to compare to data to infer H):

For example, here is the output from the transfer function (solid) v. numerical simulation (dashed) of the entire model in closed loop, for a 0.5 Hz input:

My question is:
1. Is there a better way to infer the PID parameters of F than using a numerical simulation +  fminsearch (matlab) approach?

(Maybe this is a separate question, sorry). If not, how to think about the discrepancy between the implicitly stable TF response and the oscillating numerical response? How can I avoid the oscillations in the numerical response?


texts: TM4C129EXL: Read UART data form RX TX pins and display on console in Code Composer Studio

texts:
I am using a TM4C129EXL Tiva-C launchpad and I am facing difficulty in reading the data from the RX and TX pins which are connected to a NEO-6M GPS module.
The NEO-6M led indication shows that Position has been fixed, but I am not able to display the data in Code composer Studio(CCS) console.

Pin connection:
NEO6M RX -----> PA7 UART2 TX of MCU
NEO6M TX -----> PA6 UART2 RX of MCU
NEO6M Vcc -----> +5v of MCU
NEO6M GND ------> GND of MCU
Code:
#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/gpio.h"
#include "drivers/pinout.h"
#include "driverlib/pin_map.h"
#include "driverlib/rom.h"
#include "driverlib/rom_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"

uint32_t g_ui32SysClock;
char charBuffer[128];
uint8_t *charHolder;

#ifdef DEBUG
void
__error__(char *pcFilename, uint32_t ui32Line)
{
}
#endif

void
ConfigureUART(void)
{
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
    // wait till port A is ready.
    while(!ROM_SysCtlPeripheralReady){}

    // setting the pins
    ROM_GPIOPinConfigure(GPIO_PA6_U2RX);
    ROM_GPIOPinConfigure(GPIO_PA7_U2TX);
    ROM_GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_6 | GPIO_PIN_7);

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_UART2);
    // wait till the peripheral is ready
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_UART2)){}

    // configuring the UART with baud rate 9600
    ROM_UARTConfigSetExpClk(UART2_BASE,g_ui32SysClock,9600,(UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE | UART_CONFIG_PAR_NONE));
    ROM_UARTEnable(UART2_BASE);

}

void UARTIntHandler(void){

}
int
main(void)
{
    //
    // Run from the PLL at 120 MHz.
    //
    g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
                SYSCTL_OSC_MAIN | SYSCTL_USE_PLL |
                SYSCTL_CFG_VCO_480), 120000000);

    //
    // Configure the device pins.
    //
    PinoutSet(false, false);
    ConfigureUART();

    while(1)
    {

        if(UARTCharsAvail(UART2_BASE)){
          UARTprintf((char*)UARTCharGetNonBlocking(UART2_BASE));

        }else{
            UARTprintf("hello world\n");
        }

    }
}


texts: Does position of resistor matter in this schematic?

texts:
This is the schematic:

Above picture is the crystal resonator part of Arduino ATMEGA328P micro-controller, in the green rectangle they placed the resistor in parallel before the crystal and in Arduino UNO also it's before the crystal.

What does this resistor do?
Does the position of the resistor matter? can i place it after the crystal?
Why crystal is so close to the chip in Arduino UNO?


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I have 8 identical infrared LEDs (datasheet as shown below) connected like so:

I am trying to determine the correct R1 and R2 values to achieve 80 mA current in each of the LEDs. Help


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texts:
I tried replacing a no-brand FFC cable marked "AWM 20624 80C 60V VW-1" with a 3 times longer one from WE marked "AWM 20706 105C 60V VW-1". It's not working, and I'm faulting length.

However is it possible those are two different cable standards and that is interfering with the signal propagation? I'm guessing not, since that I didn't find any such information in the cable datasheet, but I still find it worth asking. Thank you.


texts: opt101 (photodiode) adjust voltage output

texts:
I'm using the popular OPT101 photodiode with 5V. How can I scale the output between 0 and 5V (or as close to that range as possible)? Now the output is ca 0-400mV (maximum is room light here).
I'm a noob, and if I had more experience, I would be able to figure out with >the datasheet< what Pin would lead to the desired 'amplification', but I have no clue where to start. I did follow the instructions outlined in the datasheet (pinned below), i.e. all recommended Pins are connected (Vs has 5V in that diagram, V- is connected to ground).
As far as I know, the circuit contains an opamp, that is probably usable to scale the output to the desired range, but I find no instructions about how to adjust it - I have a strong suspicion exactly one resistor or pin connection is needed to achieve this...
I should add, I was hoping I can achieve this without applying any negative voltage, since that seems a bit more complicated, and I avoided it wherever possible here

Circuit schematic from datasheet:


texts: Is it possible to plot Voltage vs Current in ngspice?

texts:
I need to plot the voltage in the Y axis and the current in the X axis in ngspice, like X-Y mode in an oscilloscope.
I could not find anything regarding this in the manual.
Can this be done? If so, how?
found solution:
Fortunatelly ngspice has the 'vs' operator.
So if I want to plot let say, voltage at node "in" versus current at resistor R1,
I do:
plot v(in) vs @r1[i]
assuming both v(in) and @r1[i] are saved vectors.
The operands could also be any voltage or current in the circuit, so you could also plot VxV, IxI, etc.


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texts:
I have designed multiple small PCBs for personal projects, and have used USB ports many times for an output.  I have always wondered if it is a good idea to connect the two mounting holes for the USB port together via traces.

Is this a good idea or does it even matter?

Picture of USB footprint:


texts:
Can someone please explain how to find the pin-out of a 5M80Z CPLD device.
The documentation on this page shows the names of the pins but does not indicate the pin numbers.

I have not encountered this naming scheme before:
http://www.altera.com/literature/lit-dp.jsp?category=MAX%205

Also I do not have ORCAD installed so using the .obj files is out of the question.

EDIT:

I just installed the demo version of ORCAD and I see this which is completely confusing:

So which is true now, the rightmost column on the pdf or the .olb file


texts:
I want to use one button for set and reset. With a hex-inverter (because of falling edge), when I press the button, set works fine, but I need another button to reset the 74HC73.
Is there some possibility to make a 74HC73 reset automaticallt when I release the same button? I will upload schematic later to provide you logic.
Thank you in advance.


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