texts: How safe is it to supply power to a linear regulator output?

texts:
I have a number of early-80s era microcomputers that are missing their external power supplies, or in some cases have internal power supplies that are dodgy or broken. These take various (and sometimes unusual or even unknown) external voltages from the PSUs for which they were designed and almost invariably regulate them down to no more than four standard voltages: +5, +12, -12 and -5. Most often this is done with linear regulators, typically 7805 and suchlike, which are frequently on the motherboard itself.
I'm thinking that rather than trying to replicate the various missing external power supplies (or fix the internal ones), it would be convenient just to use a modern +5/+12/-5/-12 switching power supply to directly supply the voltage rails on the motherboard, ignoring (as much as possible) the original power supply circuitry. For machines where the original PSU can be completely disconnected from the motherboard there's obviously no problem: just unplug the original PSU's cables and in its place connect my modern PSU.
But for many machines only part of the PSU can be easily disconnected. (This part being the external "wall wart" or internal transformer, often including the rectifier and other related circuitry.) Thus, if I clip my modern PSU to the power rails, the remaining part of the PSU circuitry on the board, such as the regulator output, would be seeing the rail voltage with no voltage at its input.
What I'd like to know is what sort of issues I should be looking at to try to do this safely (i.e., without damage to the microcomputer) and minimally intrusively. From questions like this and threads like this I gather that it's sometimes safe to leave the input of a voltage regulator unconnected when supplying power to a circuit via alternate means, but in other cases a protection diode is needed to ensure that the regulator input is at the same level as the output.
Obviously I could simply cut off the regulator's output pin, but I'd rather avoid making such drastic changes to vintage equipment, especially if it would make it unusable with the original PSU. Soldering in a diode would be a lot less drastic, but still a modification, which I'd like to avoid if possible.
So how do I tell how safe it is to supply any particular board in this way, what should I be looking for that might cause problems with doing this, and what can I do to mitigate them?
(I'm aware that some computers use their PSUs for more than just power: for example the 9 VAC from the Commodore 64 external PSU is used not only to generate +12 VDC but also as a frequency source for timers. To keep things simple, you can ignore any considerations of this nature in your answer.)
In case it helps, here's one example of an external power supply (which I do not have) and the regulator circuitry on the microcomputer's motherboard that the external PSU feeds. I am guessing that pin 2 is actually -8 VDC, as marked on the diagram, not +8 VDC as it might appear from the text at the top. These are from a National (Panasonic) JR-100, released in 1981.


texts:
I remember a while ago , i saw some Digital based Theremins circuits from glasgow university...

http://www.theremin.info/-/viewpub/tid/10/pid/65

would it be possible to make a theremin by using an FPGA ?


texts: Coupling electret microphone input to linear audio output

texts:
I have two SIM900D module which have linear audio output and electret microphone input, and I want to connect audio output of one module to audio input of other module and vice-versa. The input and output parameters are at page 43 of the datasheet.

How should I do that correctly?


texts: In what way is a Craft Port different from a conventional RS-232 Port? It seems to be similar. Are there any interface or other important differences? Does craft port imply a higher level protocol on top of RS-232 as well?


texts:
I seek to design an USB device or UFP, using a USB-C connector and do not wish to use power delivery (PD) of USB-C as my application would be a big underuse of this feature. The device would use a STM32 microcontroller with USB Full Speed (FS) capability which I already found, and the max current would be 1.5A@5V. I seek it to be able to be powered by a varitety of USB ports, including wall chargers. USB is quite a complicated norm, but here's my understanding so far of how the device should be designed:

The device would not draw more than 100mA upon connecting.

The device would include an IC (This for example) whose goal would be, in compliance to the USB Battery Charging (BC) norm, to determine if what is powering the board is a dummy wall charger (~DCP) or something more intelligent (SDP), eventually with BC compliance (CDP)

If what's powering the board is a DCP, I must assume that it either have the current capability or that (if the user wasn't wise enough and picked a DCP with not enough power) it has current limiting capabilities (that will result in the shutting-off without explosion of the power output) and therefore enable the high current (1.4A) draw of my device.

If what's powering the board is an SDP or a CDP, the device would, using the STM32 USB FS capabilities, start the USB communication, enumerate itself and announce its wish to get 1.4A of current, and if accepted by the SDP/CDP enable the high current draw of the device. In the other case, the device would still be able to function (but without exceeding the 100mA limit) and for example could be reprogrammed, communicate data, etc.

Both CC pins of the USB-C connector should have Rd pull-down resistors with a value of 5.1kΩ ± 10% so that if a true USB-c DFP is connected, the DFP enables Vbus to +5V and accepts to communicate.

I don't know if the other unused pins of the USB-C connector should be connected to ground or left unconnected.

I should use an IC for ESD-handling on the D- and D+ line, and also clamp the voltage on Vbus although not mandatory.

The device should present a 1.5k pullup resistor on D+ to identify itself as a FS device, although I'm unsure if this should be enabled with the GPIOs of the MCU after the BC IC did its magic, or if it doesn't matter.

Can you confirm my understanding, and if not indicate what I got wrong or forgot ?
I would be very thankful.


texts: What will be minimum number of states / state variables for these control systems in state-space model?

texts:
Consider the systems as LTI and SISO with transfer functions given below:

I have read that minimum number of states for an LTI SISO system required to represent in state space analysis for any transfer function is maximum number of power in denominator of transfer function.I am confused that can I violate this rule.For correct me for state-space diagram for first transfer function

I am getting 4 states but if I see  degree of numerator is 15 then accordingly number of states should be minimum 15

Also please mention State matrix for each case.


texts: fundamental difference between a metal and a semiconductor?

texts:
A fundamental difference between a metal and a semiconductor is that
  the former is unipolar, whereas a semiconductor is bipolar.

[Section 2.5, Millmans Integrated electronics]

Can somebody explain why is it considered so, as after all electrons are responsible for the current which leave the one end(-) of voltage source and enter the another end(+) in same quantity. I am unable to figure out holes shifting into the -ve terminal  and thus act as bipolar current.


texts: A logic 0 can be a non-zero value (say upto 0.5volts), wouldn't that cause a current to flow through a device connected to output and then ground?

texts:
A current or no-current situation seems ideal to distinguish between a logic 1 and 0. But since logic 0 can be a non-zero volt, wouldn't that cause a current to flow through an external load connected to ground through a low value resistor or say, glow a low-current LED in both cases (0 and 1) as it will be forward-biased in both cases? If yes, then should we be aware of this fact and adjust circuits accordingly to distinguish precisely between a 0 and 1 logic (say, by making sure that LED doesnt light-up when output state is 0)? How exactly we should see a logic 0 compared to a logic 1?

Sorry if my question sounds too noob.


texts: could anybody help me resolve this error?

texts:
library IEEE;
use IEEE.STD_logic_1164.all;
entity select_assignment is
port(x1,x2,x3,x4:in std_logic;
f1,f2:out std_logic);
end select_assignment; --CREATE ENTITY
architecture Behavior of select_assignment is --CREATE ARCHITECTURE
signal s:std_logic_vector(1 downto 0); --Create Signal to access output
signal x:std_logic_vector(3 downto 0);
begin
x<=x1 & x2 & x3 & x4;
WITH x SELECT --define system with SELECT statement
s <= "10" when "0000"|"0001"|"0100"|"0101", --define inputs to get out put as f1=1 and f2=0
"00" when "0110"|"1000"|"1001"|"1100"|"1101"|"1110", --define inputs to get out put as f1=0 and f2=0
"01" when "0010"|"0011"|"1010"|"1011", --define inputs to get out put as f1=0 and f2=1
"11" when "0111"|"1111",-- define inputs to get output as f1=1 and f2=1
"00" when others;
f1<=s(1);
f2<=s(0);
end Behavior;


texts: How to add a Linear and Logarithmic Potentiometer in Circuit Wizard

texts:
I'm new in this kind of thing and I'm using Circuit Wizard (Circuit Simulation Software). I was trying to simulate an overdrive pedal circuit (https://www.instructables.com/id/Overdrive-Pedal/) in Circuit Wizard, but I found some problems...

Some notes that can help somehow:

The 50k Potentiometer in this picture ("Gain"), it's a 100k Linear Potentiometer;
The 100k Potentiometer ("Volume"), it's a 100k Logarithmic Potentiometer;
The 10k Potentiometer ("Tone"), it's a 10k Linear Potentiometer.

For Circuit Wizard Website click on this link

I would like an answer for these questions:

Visualy (in a schematic), can you distinguish a Linear Potentiometer from a Logarithmic Potentiometer?
How do you add both Linear and Logarithmic Potentiometers to a circuit in Circuit Wizard?

Thank you.


texts:
This is a follow-up question to this one.

I am trying to modify a transimpedance amplifier in a way that its TTL output is inverted: 0V instead of 5V and 5V instead of 0V (like adding a NOT gate to its output).

I will first describe the original circuit and then switch to the inverted one with the question.

Original circuit

This is the basic schematic diagram of the original transimpedance amplifier. I know a capacitor is missing in parallel to Rf to avoid oscillation, but that is not the problem I am dealing with here.

Those are the original data sheets for the main components:

Opamp LM358
Photo diode Everlight PD333

I point a laser diode (1mW) to the photo diode that is pulsed with UART data. The laser pointer is just millimeters away causing significant changes in light intensity.

At the kathode of the photo diode we can measure this signal. The pulse width of the narrow pulses is around 833ms which fits the UART speed of 1200bauds. When the laser is OFF ("Idle"), the voltage level is 620mV and it drops when the laser is ON to -260mV.

At the output of the circuit we measure this signal. A very well-behaved signal between 920mV (OFF) and 5080mV (ON), ready to be fed as a TTL signal into a micro-controller.

Inverted circuit

In the original question, Olin Lathrop suggested this circuit (I hope I interpreted his suggestion correctly). We basically flip the photo diode and connect (+) of the opamp to 5V instead of 0V.

At the anode of the photo diode we measure this signal. When idle (laser OFF), we measure 4.64V. When the laser is turned ON, we measure 5.41V. Makes sense regarding the schematics.

But on the output of the opamp we just measure fixed 5V, no matter if the laser is ON or OFF. Changing the size of the resistor Rf does not change anything. What am I doing wrong?


texts:
I try to get a grasp on the IO-Link protocol but the Interface Specification seems to be horribly bad.
Has someone ever used IO-Link on a FPGA? Is it feasable to implement a small master (I only have to support one specific sensor) or is the protocol to complex to have it in hardware? Do I really need all the different layers? The whole protocol is pretty blown up and I haven't found any reference project.


texts: Using lower frequency signals to transfer data

texts:
I am working on a system that should transfer some integer data on a distance of couple of kilometers in a mountainous area and should be as cheap as possible. I've read about LoRa modules and the like but they are quite expensive and also tend to be much less effective when surrounded by obstacles, much like any other transceiver that uses UHF frequencies.

However lower frequencies have much easier time reaching long distances. So I thought if it is feasible to make a transceiver with frequency range of let's say 10 Mhz (The number is arbitrary, the point is lowering the frequency), and transmitting data at extremely low bit rate with ASK modulation. If the antenna size would be 1/20 of the wavelength would such a device be feasible or are there some considerations that make the idea impossible?


texts:
For my internship, I am tasked to design a power supply whose main purpose will be to power a 90 Vdc motor. The motor is used for a short amount of time (roughly 30 seconds), pulling about 1 A during most of this time, but towards the end of its use as torque increases it can pull up to about 3.1 A for a few seconds. Since the operation time is very short and the motor will not be used very frequently, efficiency is not a key issue. Additionally, since the load is a motor not much regulation is required and quite a bit of ripple is tolerated.

To accomplish this, I have decided to use a simple series pass transistor with a 91 V zener diode as a reference. Input will come from mains 120 Vac, 60 Hz, with a rated output of 90 Vdc, 4 A. The design will also be transformerless in order to reduce cost and size. My design right now uses a full bridge rectifier to convert 120 Vac to 170 Vdc, with a capacitor to reduce the amount of ripple. I am wanting to use a npn Darlington configuration for the series pass transistor but this is where I have questions.

When looking at transistor power ratings, is this average power or instantaneous power? Going from 170 V to 90 V requires a Vce of 80 V, so at rated current instantaneous power will be over 300 W. Due to the amount of ripple, average power will be much less than this. Either way, the Darlington will have to have a very high power rating and a large heat sink. The highest power rating Darlington that I have been able to find is the MJ11032 (300W) but I do not know if this is suitable for this application. Are there any other transistors out there that are better suited for this or do you have any suggestions on other ways to go about this?

Lastly, I know there will be concerns about safety, but all of my designing right now is on the computer and when I get to the prototyping stage this will be done with the help of an experienced engineer. Also the power supply will be completely enclosed in the final product, and all interface will be done via a separate 24V side that has already been designed.


texts: What to do with transformer's unused center taps?

texts:
I want to use a 1:1 audio transformer for galvanic isolation of an audio output. I have some 1:1 transformers left that match my requirements, however they have a center tap on both the primary and secondary. I don't "need" these center taps.
What should I do with these CT pins ? Can I leave these pins unused ? should I connect them to ground (what about the isolation then) ? If I use such a transformer with a CT, will it have an impact from a noise/hum perspective ?
Thank you for your help!


texts: Every time I connect ADE measuring chip , it blows up

texts:
My current system:-

I'm working on a electricity metering system ,

I'm using shunt resistor configured in high side mode (a current sensor ) ,

I'm also using ADE7755 measuring chip ,

A schematic of the current circuit :-

A higher resolution schematic here

The problem:-
When connecting the circuit as shown in the above schematic , R1, R2 , R3 & R4 blow up with some fire .

This isn't the first time happens , it happened before 3 times .

My initial guess it's that Analog & Digital ground are connected some how ..

I'm ready for any questions to clear the problem , thanks .

UPDATE#1 :-

I connected the PIN AGND in ADE 7755 chip to the Digital ground


texts:
I am trying to understand the hex file generated by the AVR Studio. I wrote a code in assembly. The code is as follows:

#include "m328pdef.inc"
.org 33
rjmp reset
reset:
        add r16,r17
main:
        out DDRB,r16
        rjmp main

The .org is to hard code my code into the memory location 33. Then I checked the generated hex file. That is as follows:

:020000020000FC
:0800420000C0010F04B9FECF5C
:00000001FF

The 2nd line should be of interest. The address where this is stored is 0042. How so?
Can you kindly clarify my understanding please.


texts: Difference between parallel and standard form pid controller in simulink?

texts: What is the difference between parallel and standard form of pid controller that is provided by pidtool in Matlab  simulink? In terms of block diagram?


texts:
An LT-spice simulation suggests that the output is always near -15V, that is, saturation. Assuming linearity, I come up with only two linearly independent equations:   $$I_{in}=\frac{Vin}{R}$$
$$I_{R3}=\frac{-Vout}{R3}$$


texts:
I was watching my oscilloscope as I was holding a very short wire attached to the probe. It was showing about 0 voltage (small spikes) until I touched the metal. When I touched the metal, the scope immediately showed a 60.0Hz (peroid of 16.66ms), approximately sinusoidal (very noisy) waveform. Considering that the power in my area is a 60Hz AC, I think it most likely that it was picking up coupling from the power lines. This sine wave was immediately replaced with a flat, -200mV line when I touched an electrical ground, but resumed when I let go.

Was I acting as an antenna for electrical noise from the mains line? I was wearing rubber shoes on a concrete floor and touching nothing but the probe.


texts: Using only certain pins on a sensor board

texts:
First of all I have to apologize if this has been answered before. I'm such a noob when it comes to electronics, I don't even know how to find an answer. I've tried, trust me.

So, I have bought XloBorg (https://www.piborg.org/xloborg) to attach to my GoPiGo 2 robokit. But as it went, it doesn't attach directly to the GoPiGo but to the Raspberry Pi. But it takes basically all of the pins in the Raspberry board, so I can't really attach it there.

So, ultimately I only need the magnetometer part of the XloBorg, I don't really care of the accelerometer. I checked the schematics and I can see which of the pins are for the magnetometer. So my question is, can I just use jumper wires, put them to the correct slots and get the magnetometer data? Or are these boards built so that I need to attach the whole thing for anything to work?

Cheers!


texts: Constant current MOSFET circuit oscillating, how to get it to stop?

texts:
simulate this circuit – Schematic created using CircuitLab
I have a constant current load circuit using a sense resistor and discrete quad op-amp set up as a 3 op-amp instrumentation amplifier and using the 4th to drive the gate of a MOSFET. The circuit oscillated for a long time until I dropped the gate driving op-amp feedback resistors to fairly low values and then  it worked fine for a while. I did some load testing of the MOSFET itself (controlling the gate with a POT) to see how well it could handle heat and if the heatsink would do any good. It got crazy hot (starting melting it's own solder) but it still works and isn't shorted. I could try replacing the MOSFET with a new and less abused one but I'd like to have this circuit be less vulnerable to oscillating in general so if I can get it working with this one I'd prefer.


texts: Will a 4 Ah 12 V battery be fine for a 2 A 12 V diaphragm pump + a Raspberry Pi?

texts:
I've got a 4 Ah 12 V lead acid battery which currently runs a Raspberry PI. I'd like to connect a diaphragm pump to this battery as well. The pump has a max. rating of 2 A.

Assuming a fully charged battery : when the pump starts working, will this (a 4 Ah 12 V lead acid battery) be able to provide a steady voltage, or will the additional load (caused by the pump) cause undesired results? The pump will typically run for 10 - 15 minutes a day.

The Raspberry PI is apparantly notorious for being picky about the power supply.

If a 12 V 4 Ah battery is not enough; will it help if I replace the current battery with a larger one?

______________

Added:

Extra information:

The context of this question is that it is asked by someone who knows software development, but not electronics.

I used a RPi because that's what I had lying around and it runs Linux and Java. Easy to get started with.

The battery gets charged up every day via solar cells.


texts:
Okay, I have mini coreless motor drone. I want to make a bigger drone by replacing the corless motor with 180 motor. For that, I need to control 4 MOSFETs to drive four 180 motors. Here comes my question - how can I drive those FETs?  I've tried connecting the gate signals which are already fed to the gate of the internal MOSFETs (9926a Dual MOSFET) for driving the coreless motors to my IRFZ44N (I only have these) MOSFETs gate. But the signal voltage is too low for my MOSFETs. So then I tried connecting the signals to an arduino and tried to map them from 0 to 5v which is suitable for IRFZ44N, but it didn’t work. I don't know why.
Any idea how I can drive my MOSFETs with the signal. When I pull the throttle a little bit the signal read 0.5v and 2.7v at maximum throttle.


texts: What is the best location of a (damped) LC network here?

texts:
I'm using this circuit to create the analog supply in my usb-device:

After the high-side switch, the incoming 5V is boosted to 5.5V and then regulated back down to 5 volts. The entire analog part does not draw more than 200 mA.
I'm still experiencing between 8 and 30 mV of ripple at +5VA, depending on the quality of the usb power supply.
In the next iteration I will change the boost converter to one that outputs 6V to give the regulator some more headroom.
I'd like to put a LC network in there as well, without adding too much capacitance to limit current draw when the supply is enabled. Where would this be placed most effectively? I'm doubting if the bulk of C134 is not better put to use before the regulator; I could break it into multiple caps to form the network.
Is there a rule of thumb for a generally ok network (using 100uH chokes and 33uF caps), or do I need to go into output and input impedances?


texts:
I'm looking to start on my first microcontroller project-- a midi controller that (hopefully) will connect to an android device via ADK as part of a touch interface.  I've never worked with this lower level hardware type stuff, so before I start investing cash and time I want to make sure I've got a board that's capable enough for the project.

I'm eyeing the mbed LPC1768 because it has usb host functionality and what look to be fairly flexible libraries for usb and usb-midi. My rough plan is to do 12 -16 pots/faders, 6 on the analog io and the rest on a multichannel adc, and about as many buttons on the digital side. The mbed will have to run to some sort of usb hub that can "route" the signal to the correct endpoint: android ADK -> mbed to change midi function (lower timing priority), mbed -> host pc to transmit the data (higher timing priority).

Will the LPC1768 (100 MHz ARM Cortex-M3, 64 KB SRAM, 512 KB Flash) accommodate the above functions at a perceptibly instantaneous time scale? (ie midi latency ideally < 1ms)?
If so, how do I go about it? What interface(s) to use (mbed offers i2c and SSP), how to handle data sampling of the inputs, how to solve the data routing problem, etc.


texts:
Intro: My Colleague and I have been using altium Designer for Sometime now . Currently AD 17.1.6 (build 538) . The PCB we draw are 3d 4 layer maximum . the only difference between us is that the smallest grid I use is 0.1mm , while he uses the finest Grid 0.025mm.

Problem: when my Colleague is using Design Rule check it is taking for every to be done ( about 30 minutes ) . while my PCB which is comparable in number of components nad size takes about 30 seconds on the same Computer !!

My thoughts: I am trying to analyze the problem and i have come up with 2 possible causes :

The Fine Grid is causing the program to make more calculations causing it to take more time , can anyone confirm/comment on that ??
The 3D objects placement and clearance is causing the software to consume the extra time (unlikely) , but does anyone know  a way to prevent the DRC from looking for violations in certain rules ? so i can go one by one and eliminate until i find most time consuming rule.

If anyone is wondering about the PC : it is a core i5 processor, with 8Gb ram and GTX 660Ti VGA.


texts: How would you go about testing a USB cable for a short?

texts:
I have had an issue with a USB cable blowing up a device when plugging it in (pop, burning smell) assuming a resistor blew. I'm trying to figure out if this was caused by the cable or the port.

If I use a multi meter to test the USB cable from a different power source, should I expect to see 5v been pwr and gnd, and nothing been d+ / d- and gnd?

I'm assuming a short from the power wire to either data wire could cause something like this to happen?


texts: Lithium ion (Li-ion) vs. Lithium thionyl chloride (LTC) battery?

texts:
I need some consultation on which battery of the two to use for the GPS trackers I'm designing. My trackers wakeup when there's movement only so they're not on all the time and they have low power consumption.

I need something with long battery life and to maintain a constant voltage of at least 3.4V. The LTC is more capacity efficient where a C size can have capacity of 8.5Ah compared to Li-ion where it's only 5.2Ah for the same size. But is either of them better than the other in keeping the voltage constant over discharge?

I would guess there's not much difference between the two since they are lithium based.


texts: I have a old battery charge, which says its output is 6 - 12 Volt 4 Amps R.M.S. Does this mean the output is AC?

texts: The battery charger is an HC45 which I could not find any information online about. As stated in the question does the 4 Amps R.M.S mean the output is AC or is the peak of the input equal to 4 Amps?


texts:
So, I have hooked up a ATtiny88, and am programming it with the Dragon AVR using ISP. I have also set up the build toolchain, using avrdude, and the gnu avr tools. Everything is working great.

Now I would like to do in-circuit debugging using the advertised debugwire which is also connected to the ISP and which the dragon supports. But which tools do I use? I see there is a avr-gdb, but it seems that I needs some kind of simulator, however I would like to debug in-circuit on the real MCU. Is this possible?

Thanks in advance.


texts: What is the utility of the reference clock in PCI express?

texts:
I understand that PCI express is a serial connection with clock embedded with the signals. So, what is the utility of the reference clock signal? What is it used for?

Does the reference clock have to be matched and routed with the data lanes? Is there a possibility of reference clock being skewed?


texts:
Hello everyone,
                         I'm currently involved in a project of measuring distance beyond 50m and upto 100m. Here is my setup, transmitter and receiver at one end and prism(reflector) on the other end. I'm using PIC18F45K22 microcontroller with red laser and BPW34 as photodiode. I tried with CTMU unit in pic with receiver circuit being switched ON using transistor BC547. Readings I got through this is not satisfactory as readings keep on changing depending on intensity of light falling on photodiode. I'm stuck in this one and can't able to move further. Is there any alternative solutions to this or how can I implement this overall ?? And is it possible to use counters in pic ???


texts: What's the right way to connect two exposed pins from a board to BNC?

texts:
For an ADC evaluation board like this one, where signals go in through exposed pins, I'd like to have the signals come from a BNC cable (or SMA). However, I'm concerned about noise. What's the right way to do this connection? There doesn't seem to be commercial solutions that go from jumper cables/pins to BNC/SMA cables.

EDIT:

So to be clearer, here's what I need to connect to (which is another board for the same ADC). I need to connect to the J2 part on the left, I need to get two adjacent pins (AIN0 + AIN1, for example) connected to BNC.


texts: Do parallel LNAs at 90-degrees to eachother reduce the noise floor more than side-by-side?

texts:
Wiring amplifiers in parallel in a summing configuration improves the signal to noise ratio because amplifier noise in each LNA is uncorrulated.  However, external noise sources will still be a factor because both LNAs receive those noise sources, thus the external noise sources are correlated.
With 2 LNAs, would any of these be useful to reduce the correlation of external noise sources? If so, what might be best?

Physically rotate LNA1 90-degrees from LNA2
Physically rotate LNA1 180-degrees from LNA2
Mount one LNA flat on the board and one vertical or on its side (think horizontal vs vertical polarization)

-Eric, KJ7LNW


texts:
Two identical three-phase, Y-connected, synchronous generators are connected in parallel to equally share a load of 900 kW at 11 kV and 0.8 pf lagging. The synchronous impedance of each generator is 0.5 + jl0 R/phase. The field current of one generator is adjusted so that its armature current is 25 A at a lagging power factor. Determine (a)the armature current of the other generator, (b) the power factor of each generator, (c) the per-phase generated voltage, and (d) the power angle of each generator. What is the circulating current under no load?

My question is, how do I find the complex phasor angle of the phasor current with magnitude 25 A? I tried expressing the unknown current angle as theta and then I did a KCL to express the other generator current in terms of the 25 A phasor current and then 2 KVL equations involving the generator phasor voltages plus a power balance equation to complete the number of equations needed to solve all the unknowns. My reference phasor is the terminal voltage which is $$
\frac{11000}{\sqrt{3}}V$$.


texts: I was told to add an emitter resistor to the transistor T1. I'ver been researching the subject and could only find vague info about the E resistor and now I'm utterly confused. The transistor here converts linear voltage change (from the DC mixer) to non-linear. How does the emitter resistor change it? Would it change the range, the linearity or what? I've been even trying to simulate it Circuitlab with no success.


texts: Is it possible to build an in-line stereo amplifier for piezo contact mics (stereo pair) with 2.5v plug-in power?

texts:
From one idea to the next, here's the back story:
I'm currently taking an interest in sound design, and read an article about making sound effects from recording via contact microphones. I already have a portable stereo recorder which is the Zoom H2n, which has a line/mic input (which is stereo), which has 2.5v plug-in power which I can switch on if required.

Now I want to make my own stereo piezo mic and plug it into my recorder, but do you think I need a pre-amp when the Zoom h2N has it's own mic gain control? I gather the impedence of piezos is as much as 50KOhm and would be too quiet if wired directly to a line/mic input. The ones at Maplin (where I might source my components) are 450Ohm-800Ohm.  If I need the extra preamp then I'd like to see if I can use the plug-in power from my recorder to power a home-made stereo preamp. I've seen the Alex Rice preamp circuit design, but this is made for 48v Phantom power not 2.5v. I presume I will need a complete exchange of components as well as adapt it for stereo if don't just make two of them....so, is 2.5v enough to amplify a piezo contact mic signal?

For the record I'm no good at designing circuits, I'm just good at assembling them.


texts: Why is the damping RC used in these accelerometers?

texts:
What is the damping capacitor resistor couple used for at force balance accelerometers?:

Can you explain what happens as a malfunction if it doesn't exist?


texts:
I just received my first PCB back from the manufacturer. After soldering on the SMT components I found that the board works absolutely fine. The only thing I'm puzzled about is that both the ground pour and the traces are a brown color and not the green I would expect it to be since I specified a green solder mask. This is what it looks like:

I've tested the resistance of the ground pour between two points and it is not conductive, so this does not appear to be pure copper. However, since this is my first PCB I am really puzzled about the brown color. Does anyone have an explanation?


texts: Is a capacitor considered a solid state device?

texts:
Based on a description I read here.

Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material.

I was thinking Caps are usually built of "layers" of "stuff" (paper, plastic, glass, mica), but they can also have fluid in them (electrolytic), which is not solid. The article I was reading mentioned that vacuum tubes aren't solid state because they contain/use gas, so would that be the same for a capacitor? or are they generally considered solid state devices anyway?


texts: Lack of data when performing hand calculations

texts:
This question refers to BJTs, FETs, MOSFETs, etc.

When I am designing a one or more staged BJT transistor circuit I am often considering differential base-emitter resistance aka "rπ" and finite collector-emitter resistance aka "ro", whereas both of them are often neglected. I prefer not to ignore them in hand calculations.

Calculating those extra equations isn't a big deal. Things get more complicated, for example, when I need to calculate "ro", where Va or Early Voltage parameter is not given by any transistor data sheet.

In some cases "ro" is totally irrelevant, but in others it can't be ignored especially if some parameter is strongly dependent on it.

I know there are some ways of calculating "ro", and this is done only by measurement. But don't you think measuring every transistor before putting it into a circuit is a bit waste of time?

How does each one of you deal with this parameter or parameters, which value is not given by manufacturers?

Also, I am interested about this (green-lined) h-parameter:

Can "hoe" aka "gm" be used in the calculus of "ro" -> ro = 1/gm?


texts: How does a DC-AC inverter's DC input current change with time?

texts:
Newbie question, would really appreciate some help.

I am modelling a simple full-bridge inverter in Matlab. I've used the supplied example file of a full-bridge inverter that was developed by the Matlab engineers.

The DC current appears to be wildly fluctuating / inverting. (see image below)

I have always thought that DC-AC inverters had (by definition) a DC and an AC side and that thus naturally the current on the DC side could only flow in one direction. Also, when I look at the DC input voltage, it is constant and positive.

My questions:
1. How does a DC-AC inverter's input current change with time? (ie. Is this actually how DC-AC inverters behave?)
2. Is it at all possible to have a positive voltage and a negative current, as we see in the model? (or does that break physics....)
3. If this model is insufficient, any suggestions on how I can model a DC-AC inverter?

The matlab model, straight from the built in examples but with a couple of extra scopes for monitoring:

The strange-looking DC input current and voltage:

The inverter AC output current and voltage:

Thanks!


texts:
How do i minimize error due to Offset voltage, Bias Current, Offset Voltage,
Frequency response etc.
For an µa741.

I have no idea on how i can cancel or just minimize the effect of these errors.
I would be very glad if someone could help me :(.

I am actually using in a negative feedback circuit.. So as far as i Understand.. Bias current can be compensated by setting the impedance at the input to be the sane, any values preferable?.. Bias offset I won't  be able to change,minimize or compensate. Offset voltage same as bias offset... Frequensy response is just the fact that Aol chances in frequency..Could someone explain me about domaint poles and single poles, and what it has to do with frequency compensation and how it has something to do ringing with the op.amp and what it means.. ?


texts: Measuring Voltage drop across MOSFET 2N7000

texts:
My setup is 2.1V on the gate.
A 330 Ohm load between Vdd and drain.
And Source to ground.

I stepped Vdd from 0V to 9V in small increments and measured the current through Vdd to ground. Got currents in the 2mA range and saturated around 1.8V.

I'm trying to compare current against the Voltage drop across JUST the MOSFET but there's voltage drop across the 330 Ohm resistor too. How do I isolate just the Vds drop without measuring the drop across the resistor and PLEASE give an example calculation.  I've already captured the current through the system at each increment AND the voltage on VDD (0-9V).  I know that once I get to saturation voltage the voltage drop across the MOSFET will be minimal.  Just trying to understand (also trying to understand Q-point but I suppose that's another question).


texts:
I am planning to install series of APA102 addressable RGB LED strips along the perimeter of my garage (just below the ceiling, not visible directly but illuminating the area where the ceiling and wall meets). The total length of the run (interrupted by some doors and other objects) is about 36 meters.

I am looking how to power it. It comes in reels of 5m, it appears that at full brightness it is still not enough to be powered just at both ends, as the white brightness starts turning amber after about 2 meters, returning back to white at the 4th meter. So, I plan to supply power at every 2.5 meters.

Regarding the APA102 clock and data lines, there should be no problem, as the signal is fresh at every output. But I am afraid if just running a 5V power line along the strip, supplying it at 2.5 meter periods, will be enough, as the voltage would drop along the power line that goes up to 20 meters (assuming I have the power adapter somewhere in the middle). How I can ensure stable 5V supply along the whole route? Just throw more adapters at it, connecting, say, 3 of them them in parallel, at 6th, 12th, and 30th meter?


texts: LED reverse voltage and LED supply issue

texts:
I am using LED part number 17-215/BHC-AN1P2/3T which has 5V reverse voltage and 3.3 V forward voltage ratings.
I have two questions:

As I am applying only positive voltage to the anode and negative to the cathode, the LED is only forward biased. So is there any need to verify and consider the reverse voltage?

As I am working on 3.3V supply and the LED forward voltage = 3.3V, will it work normally or do I need to use any specific circuit for this case?


texts: How can you reduce the amount of noise in an environment?

texts:
Are there any ways to reduce electrical noise coming from outside the circuit by changing the environment the circuit is in?

If so, would these changes be significant enough to qualitatively improve mV-scale readings on oscilloscope hooked to a circuit on a 5in x 8in breadboard with 50kOhm equivalent impedance? (With this example I am just trying to come up with a fairly general use case.)


texts: Why CCVS feedback amplifiers are popular as RF buffers

texts:
I've been attempting to build a VCO recently (around 50Mhz) and I've reached the part where I need a solid buffer for my oscillator.  Looking around at various options I can't help noticing that many of the buffer amplifiers used in designs are actually of the CCVS type.  Take a look at these:

G3PDMs Vackar circuit with CCVS style feedback buffer

Wideband MMIC configuration with collector feedback style CCVS buffer amp

Taken from here

RF buffer taken from mid-80's copy of the ARRL handbook featuring a collector feedback style buffer amp with impedance transforming pi-filter

What's intriguing about all of these configurations is that they have an intrinsically low input impedance.  If you take the 2nd circuit (MMIC) as an example.  The circuit aims for a high trans-conductance, that makes the trans-impedance close to 560.  This gives a gain of approx 11 with a 50 ohm source.  But, it has a very low input impedance and the higher you make the open-loop gain, the lower it gets.  Even with a 50 ohm source, the impedance is very low, I think.

So, what am I missing here?  Why are these shunt type configurations so attractive in RF circles?  Does it have something to do with standing wave reflection?


texts: LCD contrast - is there a way to control the variation in contrast during production of a consumer product?

texts:
I'm working on a product with a vendor/factory and they've sourced two difference LCD's. One has a darker contrast. We chose the one with the darker contrast because it is easier to read.

However, according to the vendor, they said that variation in production will give us different darkness for the same LCD.

So, today, I received 3 pre-production samples and indeed there was variation in the darkness.
One was too dark so that at certain angles the digits were a little hard to read.

Is there a way for them to adjust this? Can they just change a resistor somewhere or put an adjustable potentiometer somewhere? (I read that the bias voltage or the contrast voltage can be adjusted)

Are there LCD's out there where adjustment is not possible?


texts: multi microcontrolers and one ram for use like a circular buffer for intercomunication, how do and select?

texts:
I'm studying the development of a hardware composed of modules, I initially thought of a serial bus like ICSP, I2C or even CAM to communicate between modules, but I wonder if it could not use a ram in common between processes to build circular buffers for Each module and its serialized data structures, so the modules would be present through reserved spaces to identify them and each circular buffer would be defined according to the presence of the module.

These modules would be, for example, a GPS controlled by a Cortex-M0 (there being an alternative to an ESP8266 A7), an ESP8266 A6 would be used for cellular communication and another for WiFi communication, thus the GPS module would be depositing in its circular buffer the collected data And preprocessed GPS, the other Wireless modules would also maintain communication through their circular buffers in this ram memory, with pinnacles connected to the central cortex-M triggering ISR alerts when hearing emergency cases that need to be prioritized.

Well the big question is how to use a ram memory shared between these modules, I know there are Cortex-M line chips that allow such features, but would there be such a possibility with the ESP8266?

Assuming two scenarios:

A first one where all the modules would be based on Cortex-M, choosing the most suitable to work respectively GPS data collection, GSM / GPRS Communication and WiFi / BlueTooth Communication, and finally a central processing and logger module via SDCard.

And a second module has this mix between Cortex-M and ESP8266, with ESP8266 being responsible for Wireless and GPS communication, and Cortex-M for central processing and datalogger.

What would then be the Cortex-M models available for use with external ram memory, how to adapt the ESP8266 for such use? And Of course what external RAM could be used?


texts: Protecting BJT base-emitter junction from breakdown voltage

texts:
I was playing with a BJT based circuit and I learned about the breakdown voltage of BE junction.

I came out with a solution of connecting a diode in series, with higher breakdown voltage. But I am not sure if connecting in the bottom and top are both same

where the zener BE is the model of the base-emitter junction.
If I connect the protection diode in the emitter (D2) I will certainly avoid the stress in BE junction. Does it act in same way if I connect the dioe to the base? (D3)?

The bjt has a breakdown of 6V. so if I apply like 12V (limited with a high resistor) I see a voltage of around 7V, which makes sense since 6V is just the minimum specified. The current through the gate is very low, since I work with 12V and limiting resistors of 270k. when I breakdown the junction and 47k as pullup. The BJT in the bench is a BC846ALT1G.

EDIT: since the complete circuit could depends on the collector state, here is a sketch of the circuit:

The emitter of Q2 is the one which I try to connect to 12V (VCC) with 270k, while the collector of Q2 is always connected to 12V. Basically I want to bypass a resistor with a BJT where the OUTPUT goes to another circuitry which uses a  pull down of the same size. The load driven by the Q2 emitter is 270k/2 Ohm, since the other pulldown is 270k as well, there is nothing else.

I was trying to understand the situation more deeply in order to apply less changes as possible.

Q1 is kept conducting or open (applying a current limited voltage on base, like 5V or 0V) and works as it is supposed to work.

The reverse junction which I am referring to is on the Q2 BE junction.


texts:
I use Eagle Cad 6.4 to prepare PCB layouts then manufacture them at home. As I use amateurish equipment and  method, I would like to have bigger pads as much as possible so that when I drill the pad holes, I will have a very large ring of copper around the hole to solder. It would be convenient to have bigger pads (when it is possible on the layout). I can do it on photoshop for sure or maybe by redefining each component's packet description on the library, but it is a little bit time consuming. I wonder if there is an easy tool like change tool to enlarge the pads I want.

The pads I'd like to enlarge are the green circles below image. For example, the diode (the most left circle ) has a bigger pad area, where as the resistors (the closest two green circles) have thinner circles.

When I drill these holes, sometime the drill takes the copper away and I'm left with rings that are too thin. For example, please see the below photo. These pins are not important but in some cases, it would be better to have a larger copper area. Is it possible to do it on Eagle Cad 6.4?


texts:
I was trying to make an LED lamp with 16 series 3528  SMD LED chips.  I am planning to use a transformerless capacitive power supply to step down 230V.
As per my calculation 16 led will require the voltage of 56V and each LED can take 20mA.
So how to calculate series capacitor values for stepping down 230V to 56V.


texts: voltage cutoff for very low voltage (0.5v)

texts:
I have a circuit that I want to not allow any voltage to go over 0.5v.
I read the voltage with ADC and the input can go from 0v to 0.5v and what I want is a circuit that will keep the voltage 0.5 even if it goes over 0.5v.
i have  looked for 0.5v zener diode but I didn't find any.
Thanks for your help


texts: Arriving at a wrong output impedance for a BJT Emitter Follower Configuration Circuit

texts:
We've to calculate output impedance of the circuit (figure 1). Although i understood the textbook solution (figure 2, figure 3), I took a different approach and arrived at a wrong answer.

step 1: I shorted the input voltage sources. (since, Zout is being calculated)
step 2: since there is no power anywhere in circuit, Ib will definitely be 0.
step 3: the dependent source is opened. (since, Ib = 0)
step 4: also RB is shorted by the source
step 5: thus, when seen b/w emitter terminal and ground, βre and RE are parallel
but equation 8.42 says otherwise!

please point where the mistake was in my approach.


texts: RPM Gauge Arduino.... Need the explanation of the Zener diode, what is the fuction on this circuit

texts: Hello everybody... I need the electronic explanation of Zener diode.... I researched the Zener Diode I understand how it work .... But still don't understand the relationship with the zener with tip120, what is the function of the zener diode in this circuit with the TIP120? Thanks!


texts: Output characteristics of power transistors

texts: The book about electronics that I'm currently reading only briefly mentions IGBTs and power mosfets(such as the VMOS, or the HEXFET), and gives no depiction of the output characteristics. The image above is the one I found online. Is it even correct? It seems to me that they are essentially the same as for ordinary mosfets, only the gate voltages being substantially higher here since these are power devices.


texts: Digital Clock Manager on FPGA - Boundary Problem

texts: I am working on BASYS3 and using Vivado. I have a 3 MHz signal and I have to make it close to 190 MHz. BASYS3 can increase the frequency by 64 times; however my problem is that BASYS3 takes at least 10 MHz as an DCM input frequency, so 3 is not enough. Is there anything that I can do to solve this problem?


texts: can ouput of a 120V AC triac fan speed controller also keep energized a 120VAC relay coil at any setting

texts:
I want to actuate a light simultaneously whenever a triac based fan controller switch is on at any setting.
One idea I had was to use a 120VAC coil relay connected to the fan controller output.  I only scrath my head cause I don't know if the modified waveform from the triac controller will keep the coil energized no matter the setting?  If I had to guess I'd say yes because the max voltage remains 120v at 50/60hz, even if the rms voltage changes.
I suppose I could just buy a relay and give it try but thought I would ask here b4 I go to the effort.
As a clear example I would use this controller with this relay.
https://www.amazon.com/Broan-72W-Electronic-Variable-Control/dp/B000UVWWGO
https://www.amazon.com/American-Zettler-Power-120VAC-AZ2280-1C-120A/dp/B07587NZTC
the relay contacts at 30amps is overkill for a led light power supply but couldn't find a cheaper one with lower rated contacts (probably only need an amp at most)
alternatively maybe I can just hook up the controller output right to the led light power supply.  Maybe the modified wave form won't affect the DC output voltage (12VDC I think) of that power supply.


texts: mimicking DVM 10 to 11MΩ input impedance on microcontroller analogue input

texts:
I'd like to mimic a digital volt meter's high input impedance (10 to 11MΩ) at an analogue input (ADC) on a microcontroller.  Currently I'm using an ATmega32U4-based Kookye Pro Micro.
Specifically, I've rigged up a simple voltage monitoring loop, very similar to this one.  I currently have a voltage divider (10KΩ and 90KΩ) feeding into an analogue pin, with 5V powering the microcontroller (a reference voltage).  So I'm able to measure up to 50V, and the values I'm getting for known power sources correspond to what I expect.
The reason I'd like to mimic DVM-like high input impedance is because I'd like to be able to monitor the voltage off on an RF dummy load that has a tap for measuring input power via voltage.  The designers of the dummy load have confirmed to me that "the dummy load is designed to give accurate power readings with a 10-11 megohm input resistance digital voltmeter."
The voltage monitoring circuit gives erratic readings when attached to the dummy load (with input applied).  With a low-power load (~5V), it mostly reads 0(V), but with higher a power load (over 10W), it reports other readings too—all low, never going above 1.5V or so (the expected measurement for that amount of power is over 30V).
So the question is whether something can be rigged up so that the microcontroller's ADC can be made to measure voltage similarly to a DVM with high input impedance.  If so, what sorts of options are there?  If not, what is the limitation?


texts:
Is it a good idea to place the usual 100nF decoupling capacitor on a power-on-reset chip? Mightn't that influence its behavior on brown-out or power dips?

What is the best approach here?

The power-on-reset IC is a Micrel MIC803. I could not find any info on this on SE or in the datasheet. The reference circuit does not show a decoupling capacitor, but many reference circuits don't even if it is advisable to put one in.


texts:
Cant identify what is this ...SMD
The only thing i can understand is that is Motorola.
Any help appreciated.


texts:
I have a 12v solar panel which gives 500mah most of the time...
I have two microprocessors with onboard 3.3v voltage regulator, which consumes around 400-500mah.
Can I connect the microprocessors in SERIES to the solar panel without any problem?

If your answer is no, any alternatives?

thanks.


texts:
I am having problems with simulation for this particular counter. below are all my diagram including truth table and multisim simulation. the problem is its only going from 0-4 and vice versa. It should go like 0,1,2,3,4,0,1,2,3,4. Any help will be much appreciated.

My Kc is equal to 1 and ka is also equal to 1
A=m
b=Qa
c=Qb
d=Qc


texts:
what is this distortion?

This is the circuit where it is derived

http://puu.sh/1xdew

As you can see, it looks like there is a problem in the negative half cycle, its not really a straight clip. The waveform is taken at the 8 ohm resistor


texts: Can 12V 130 Watts/7A Solar Panel power 500 Watts inverter

texts: I had an inverter of 500 Watts that I use with my car batteries and recently purchased two 130w/7A solar panels that is yet to arrive. Is it a good practice to use the two panels directly to the 500 Watts inverter without batteries or do I purchase extra two panels of 130w/7A?


texts: Possibility of SMBus/PMBus device with I2C Master?

texts: Can I communicate with a SMBus/PMBus device with I2C? I've been reading the specs and getting quite confused. It seems to me the only difference is the voltage levels and the need to have a restart condition. Am I correct or I'm missing something?


texts: Verilog: Warning (13410): Pin "pin_name2" is stuck at GND

texts:
I cannot understand why g and b are stuck. It is my understanding that always@(posedge clock) will execute any time clock input goes from 0 to 1. I have the clock pin connected to a pll that is driven by the FPGA's clock. My variable count should increment with each clock, and then color should increment every time that count wraps around. Can someone help explain what I am missing.

module state_machine ( clock, r, g, b );
input clock;
output reg r;
output reg g;
output reg b;

reg count;

reg color;

always@(posedge clock)
begin

if(count == 50000000) count = 0;
else count = count + 1;

if(count == 0) color = color + 1;

if(color > 1'o7) color = 1'o0;

r = color & 1'o1;
g = color & 1'o2;
b = color & 1'o4;

end
endmodule

Here is the error message from Quartus:

Warning (10230): Verilog HDL assignment warning at state_machine.v(15): truncated value with size 32 to match size of target (1)
Warning (10230): Verilog HDL assignment warning at state_machine.v(17): truncated value with size 32 to match size of target (1)
Warning (13024): Output pins are stuck at VCC or GND
    Warning (13410): Pin "pin_name2" is stuck at GND
    Warning (13410): Pin "pin_name3" is stuck at GND

EDIT: Thanks for the help. I now have this and it works.

module state_machine ( clock, rgb );
input clock;
output reg[2:0] rgb;

reg[31:0] count;
reg[2:0] color;

always@(posedge clock)
begin

if(count == 50000000) count = 0;
else count = count + 1;

if(count == 0) rgb = rgb + 1'o1;

end
endmodule


texts: USB OTG device that always supplies +5V, any issues?

texts:
I recently came across an USB device that seems to have a broken USB OTG implementation. The device always provides +5V on its micro-USB port, and using the appropriate adapter, you can use other USB clients (storage etc.). It's not powered through the USB port, but rather with a proprietary charger. So far, so good.

However, even if you plug in a regular micro-USB cable with a plain old USB-A plug for connecting to a host, it still provides +5V. This is obviously wrong according to the spec, but will it actually cause any issues?

AFAICT it should be fine: both the host and the device drive the supply line to +5V, but since neither side actually draws power from the connection, it will basically just stay there. I'm guessing that the voltages won't be exactly equal (maybe +4.98V and +5.03V or so), therefore a few mA might flow from one side to the other, but this is something that the protection circuit inside the port should be able to handle?


texts: CAN Bus - Is bit stuffing required at EOF and INT?

texts:
In a CAN Bus, to ensure enough transitions to maintain synchronization, bit stuffing is used after five consecutive bits of the same polarity.

But we see that the End of Frame EOF (7 consecutive high bits) and the Intermission Int (3 consecutive high bits) make a total of 10 consecutive high bits( or also called recessive bits).

Clearly this is at the end of the message and looks like we don't need bit stuffing. But I want to know for sure that is bit stuffing used here or not.

If not, is there any possibility ever, that there could be a problem due to loss of synchronization.


texts: How a signal is transfered with only one connection in a simple circuit

texts:
I need some explanation to something i experience.
I use an Arduino (DUE) to create some audio waveforms, and a laptop as an oscilloscope to watch the waveforms (and for programming - powering the Arduino).

I measured the voltage of the mic jack and the multi-meter displayed 3.2 V.

When i connected the signal terminal and the ground of the mic input to the DAC0 (and ground accordingly) of Arduino DUE it burned the DAC0 pin.
I guess it provided current, beneath the rating the DAC pin allowed. (provided or sinking current?)

After this i use the DAC1, and i connect my earphone to the DAC1 pin and to the ground of the Arduino.

Now if i have connected the earphone to the DAC1 pin and to the ground of Arduino -so to hear the audio- and i also connect only the positive cable of the mic input of the laptop/oscilloscope to the ground of the Arduino I get the signal displayed, so it passes through the mic input with only one cable connected.

So i have 2 questions:

a. why the signal appears in the ground and how it gets transferred to the mic input with only 1 cable connected (and no ground). Is it because as i' m powering the circuit from the laptop a complete circuit is created? Does it works with a common ground?

b. why the mic input of my laptop
provided or sunk current to the DAC and it fried it? (is it because it provides current to power a mic? Is it because it acts as an amplifier also? Or it provides current anyway just because it "exists" as a circuit?)


texts: Unable to charge at current 500mA with TP4054

texts:
Hi I have a PCB which is operating a 5V Fan running on 500mAh 3.7v battery. The PCB uses a booster and a charging circuit. I am using TP4054 for charging module:
https://lcsc.com/product-detail/PMIC-Battery-Management_TOPPOWER-Nanjing-Extension-Microelectronics-TP4054_C32574.html
Want to charge the battery in 1 hour so I am using 1K resistor but it seems nothing is working for me because the charging time is 2 hours(tested with 560 Ohms as well). I tested and found that the charging starts at 500mA but immediately drops to 200mA and then charges continuously on it for sometime and than again drops slowly.
I am attaching a Altium design files kindly help!!
Altium files: https://1drv.ms/u/s!AtZEMlINNL5Njy1TaQ9GLlR1iWO1?e=hJ4MU5
Schematics: https://1drv.ms/b/s!AtZEMlINNL5Njzf8aaUusIrz9zoV?e=vB9Hwa


texts: How do digital potentiometer data sheets define maxmimum power disipation?

texts:
I am new to digital potsentiometers, but I would like to use one in a design.
I have been looking at several digital potetiometer datasheets and I kind of expected to see some kind of maximum power dissipation value that needed to be respected for all settings.
Is that parameter described in a digital potentiometer data sheet in another fashion?  Can anyone explain how to understand the upper limit of power dissipation in a digital potentiometer?


texts: Can a bilateral switch block transmitter interference and can my board still produce great audio?

texts:
I made a circuit in which an ISD1760 chip outputs music via an LM386 IC and I like the quality and volume of sound, however, when I run an HM-TRP transmitter on the same circuit board and the transmitter is sending data out at 38kbps, I get the oscillation sound on the speaker (fast motorboat), yet I didn't ask the ISD1760 to play anything. I don't get the sound when the transmitter stops sending data. The transmitter runs on a 915Mhz frequency.

I consulted other forums and I was told its because my gain is too high, so I feel my only options are as follows:

Waste the board, build circuits so the transmitter and audio amplifier don't share the same board. (messy)
Lower the volume of the audio, but if I do that, I might not hear the sound. (not cool)
Make it where the audio and transmissions occur at different times.

Now I may be happy with #3 and I can program a microcontroller to cause #3 to occur but I have two questions on that:

Instead of placing more demands on the micro, could I get away with a bilateral switch and a one-shot timer (like one in the CD4538 cmos IC) and connect the input of the timer to the radio transmit pin so when data is activated, the bilateral switch shuts off the speaker until a byte of data is transmitted and turn the speaker back on?

and

If idea #3 is doable, will my sound significantly improve or will I still get those oscillations to a worse degree than before?


texts: Arduino gets false triggers due to compressor switching on/off?

texts:
I'm working on controlling a rotating arm with a mounted camera through a DC motor and limit switches inside a proofing chamber.

Whenever the compressor of the chamber turns on/off, false limit switch triggers occur to the Arduino.
The limit switches are connected normally-opened through a pull-up circuit.
The arm rotation works totally fine according to my code except for the moments when the compressor switches on or off.

What's causing this and how could it be solved?


texts: What is the name / Part Number for PCIE 6+2 Power Connectors (Specifically the +2 connector without a retention clip)

texts:
This is the part I'm trying to find:

I can find the 6 pin connector (I think), but I can't seem to find the +2 pin connector. I'm attempting to make some cable assemblies for a weird but fun project and need to find a way to get these parts.
Thank you in advance.


texts: Australia–ASEAN Power Link - why not build the solar farm near Singapore?

texts:
World's Largest Solar Farm to Be Built in Australia

The 10GW, 120 square km solar farm in Australia is connected to Singapore via a 4,500-kilometre high-voltage direct current (HVDC) network.
The Australian desert might be a good location for the solar farm, but how does that justify the 4,500-kilometre HVDC? Does Singapore have cloudy weather, perhaps? (It is closer to the equator.)
Wikipedia, Guardian


texts:
I am trying to interface SIM900 with PIC18F2520. I need to send SMS to a particular cell number. According to AT commands, AT+CMGS="number" is used to send SMS. After sending this command, we have to write our message and then press Ctrl+Z to terminate it. SIM 900 will then send the SMS.

I am doing the same thing as above but not able to send SMS. Following is the code:

putrsUSART("AT+CMGS=\"96********\"\r);   //command with number
putrsUSART("Hello");    //message content
putrsUSART("0x1A");     /to terminate it

but after sending these commands I am not receiving any SMS. I am confused with how to send 0x1A to SIM900. How to actually send hex numbers via UART?

Edit:

I am able to send sms but the sms is empty. I have attached a image of the response:


texts: What is the logic of running a NiMH battery in charge-discharge cycles everyday?

texts:
I have an 1500 mAh NiMH battery for powering a 2250 kV motor and four 9g servos for my radio controlled plane.

I had bought the battery 8 months back and I had used it to fly my plane which drained my battery after 20 minutes and 8 months hence when I drain it, it runs for like 9 minutes. So I haven't used it during that span of 8 months nor have I charged it.

After a lot of googling and research as to why that happened, the reason I got was that I should be running my battery on charge - discharge cycles everyday but didn't get any answer as to why we have to run it.


texts: IMPACT : Can't open /dev/parport0: No such file or directory

texts:
Why the following IMPACT log with JTAG ?

Can't open /dev/parport0: No such file or directory
Can't open /dev/parport1: No such file or directory
Can't open /dev/parport2: No such file or directory
Can't open /dev/parport3: No such file or directory

GUI --- Auto connect to cable...
// *** BATCH CMD : setCable -port auto
AutoDetecting cable. Please wait.
*** WARNING ***: When port is set to auto detect mode, cable speed is set to default 6 MHz regardless of explicit arguments supplied for setting the baud rates
PROGRESS_START - Starting Operation.
 Using windrvr6 driver.
Connecting to cable (Usb Port - USB21).
Checking cable driver.
File version of /opt/Xilinx/14.7/ISE_DS/ISE/bin/lin64/xusbdfwu.hex = 1030.
File version of /usr/share/xusbdfwu.hex = 1030.
 libusb-driver.so version: 2021-04-18 11:44:26.
Cable connection failed.
Connecting to cable (Parallel Port - parport0).
 libusb-driver.so version: 2021-04-18 11:44:26.
 LPT1 Base Address set from env variable = 0.
 LPT base address = 0000h.
 LPT1 Ecp Address set from env variable = 400.
 ECP base address = 0400h.
LPT port is already in use. rc = FFFFFFFFh
Cable connection failed.
Connecting to cable (Parallel Port - parport1).
 libusb-driver.so version: 2021-04-18 11:44:26.
 LPT2 Base Address set from env variable = 10.
 LPT base address = 0010h.
 LPT2 Ecp Address set from env variable = 410.
 ECP base address = 0410h.
LPT port is already in use. rc = FFFFFFFFh
Cable connection failed.
Connecting to cable (Parallel Port - parport2).
 libusb-driver.so version: 2021-04-18 11:44:26.
 LPT3 Base Address set from env variable = 20.
 LPT base address = 0020h.
 LPT3 Ecp Address set from env variable = 420.
 ECP base address = 0420h.
LPT port is already in use. rc = FFFFFFFFh
Cable connection failed.
Connecting to cable (Parallel Port - parport3).
 libusb-driver.so version: 2021-04-18 11:44:26.
 LPT4 Base Address set from env variable = 30.
 LPT base address = 0030h.
 LPT4 Ecp Address set from env variable = 430.
 ECP base address = 0430h.
LPT port is already in use. rc = FFFFFFFFh
Cable connection failed.
PROGRESS_END - End Operation.
Elapsed time =      2 sec.
Cable autodetection failed.
WARNING:iMPACT:923 - Can not find cable, check cable setup !


texts: Current Theshold Pin of Flyback Converter controller

texts:
I am designing a PoE PD with integrated flyback converter controller based on LT4295. I understand most of it but the ITHB Pin (current threshold pin for primary MOSFET) gives me headache. I do not fully understand how to design its external components.

In the datasheet, page 6, it states that the voltage of this pin corresponds to the peak voltage of primary MOSFET. So far so good, this means the max. peak current of the FET can be set via this pin. On page 15 it can be seen, that there is an RC network connected to the pin. The capacitor get charged up via the feedback pin, which sets the output voltage of the converter. The ITHB voltage is than sent through a linear amplifier to get VSENSE. VSENSE is then compared with the current sensed by a sense resistor and if the current sensed is greater than VSENSE, the FET will turn off.

This is what I don't understand: How are the RC components chosen to set the threshold voltage?

Any help on this topic would be appreciated.


texts: Does the lm317TG require a load resistor in the final design or just for testing?

texts:
I'm building variable voltage regulator, the regulator has levels of 9, 12, 15 and 18 volts and a potentiometer that allows for incremental adjustment between the levels, so at level 18v you can drop down close to 15V.
My circuit works fine when testing, but I need to connect it to a load resistor. I've been using a 5k potentiometer and varying the resistance to make sure the voltage stays steady, which it does.
However without a load resistor the voltage regulation does not work, which brings up a question.
Do I need to implement a load resistor in the actual design?
The device I'm building will be used as a power supply for guitar effect pedals, which usually have a current output of 10mA to 450mA, so the device should work fine when connected to a pedal.
But my device also has to pass a test, so how do I check the voltage output when a load isn't attached?
Here is the data sheet for the chip I'm using and below is my schematic in three pictures to make it easier to see.
All the pins starting with an "S" will go to a dp4t switch and the pins starting with a "P" will go to a potentiometer.


texts: Should I add a resistor between _every_ WS2812b pixel?

texts:
I have some strings of WS2812b 'Neopixel' LEDs. Some are individual pixels separated by short lengths of cable; others are clusters of six or twelve pixels separated by slightly longer cables. The cable will be fairly chunky (up to 1.5mm²).
Adafruit's best practices for their Neopixel LED strings say:

Place a 300 to 500 Ohm resistor between the Arduino data output pin and the input to the first NeoPixel.

And this question gives some insight into why this is valuable.  My question is: is it a Good Idea, Bad Idea, or an It Depends Idea, to include a resistor between the pixels, or at the start of each pixel cluster?  Does it depend on how long/thick the connecting cable is?


texts:
I am trying to get some practice on the basics, but i am having some issues with the following question:

Find Currents I(1) and I(2) and show them on a phasor diagram.
Find the total current, I(total).
Find the Voltage across each component.
Calculate the total circuit impedance, Z(total).

Find the total current I(total).
Find the voltage across each component.
Calculate the total circuit impedance Z(total).

For #1, I have worked out the answer for I(1) to be 3.88 A and I(2) to be 2.26 A. Does this seem correct?

For #2, I have worked out an answer of 2.59 A for I(total). But, this cannot be correct, right?

I have looked online for guidance and it seems it may be useful to use complex numbers for working it out, but I do not know where this would fit in, or even if this is required to answer it.

Any help or point in the right direction would be appreciated. Thanks


texts: Grid like footprint on kicad for RPM5-3 component

texts:
I'm developing a PCB in KiCAD which uses the RPM5-3 DC power module from Recom. (Link to datasheet)

I created my schematic symbol and now I'm creating the footprint according to the datasheet specifications.

I created the following footprint in KiCAD:

The thing is, I don't have 25 pins on the chip, it has only 9 and several pads are connected to one another. How can I tell KiCAD which pad is connected to which? How can I translate what is shown in the datasheet as "pinning information" to KiCAD?


texts:
From my understanding of mathematics, the mode is the value that appears the most in a set of data.  As such, how does this translate to "common-mode" voltage?

I understand how the cancelling out works, for example in instrumentation amplifiers (at least as far as the math is concerned), but what I am confused on is what is meant by MODE?

Why would cancelling the commonly most appearing voltage have an effect on something?  Does voltage interfere, and thus this is the only way to cancel any voltage whatsoever?  I am lacking basic concepts it may seem, so pardon my bewilderment if it is unwarranted.


texts: Get current gear from rpm and speed through OBD2

texts:
I would like to modify my car with the help of Arduino to display the current gear. I wasn't quite sure where should I post this question as it is a car topic, as well as an electric engineering and mathematics topic.

I want to get the engine rpm and current speed (and any additional information I need) via the OBD2 port of my car. The best solution would be with a small cable adapter so I could simply hide the cable behind the dashboard. The OBD2 for Arduino adapter is just too big, unfortunately the connector in my car is under the steering wheel so it should be as compact as possible as I don't want to accidentally kick it. For the Arduino part I would like to use an ATtiny85 (since it is so compact) and a small display, 7 segment or LED matrix.

The math part is to calculate the current gear from the OBD data. How should I do it? Is it even possible? There is an extension for the Torque app (RacingMeter) that shows the current gear, I am not sure how, but that is where the idea came from.


texts: Measuring pitch under dynamic acceleration: better to use 6DOF sensor or 9DOF?

texts:
I am working on a project that is challenging me. I've researched on the subject as best I can, but would like additional opinions.

I have a 4' long aluminum c-channel (essentially, a metal rod) with a 9DOF sensor on the end of it (FXOS8700 + FXAS21002, accel & mag + gyro). The sensor is under constant acceleration as it rotates in a circle of radius 4'. This "rod" rests on a small castor wheel that lets it move along the ground. The base that the rod is fixed to does not move laterally. Thus, the sensor moves in a 4' circle, and rises and falls with changes in elevation.

Here is our goal: to measure the pitch of the sensor as it moves at regular intervals

First of all, because the sensor is under constant acceleration, am I correct in understanding that the equation of pitch using arctan (used for static applications) will not be correct?

I believe we need to use an IMU in this case. I have tried using the the Mahony and a Kalman filter (written for our particular sensor, based on NXP's Sensor Fusion algorithm, but is not hardware-dependent like NXP's algorithm is).

Both algorithms are 9DOF, incorporating all three sensors. However, I am wondering if this isn't a good idea for us. When we used the same sensor to get the yaw, our results tended to vary terribly. I attributed this to soft-iron errors from fluctuating magnetic fields. The algorithms would function better when we calibrated (using MotionCal software) for hard and soft iron errors, but as soon as we moved the system elsewhere we would get terrible accuracy problems. So my thought is to ignore input from the magnetometer, since we aren't looking to get a heading, just a pitch.

Now, would this mean using a 6DOF algorithm instead, if we wanted to ignore our magnetometer? I am not sure that it's possible to tell either algorithm to "ignore" the magnetometer.

I am also aware about drift error from the gyro. I have tried following the instructions from this post: AHRS algorithm under continuous linear accelerations by taking several readings from the gyro for a few seconds before each run, and then averaging them and subtracting them from subsequent readings.

Here is our problem at the moment: when we read the pitch from either algorithm, even with the sensor not rotating in a circle, the values are constantly falling. They will fall to zero, and then wrap around. Occasionally, they seem to be stable, and respond very quickly and accurately to changes in actual sensor pitch, but other times, they simply fall without stopping.

Other members of my team believe that I am way over complicating things, and all we really need is the y-component of the accelerations. But I believe that we are not looking for accelerations due to gravity exactly, but rather a dynamic pitch, which is complicated slightly by a radial acceleration.

Am I incorrect in my line of thinking somewhere? If so, please correct me.


texts: Ultra Sonic coverage angle problem in Cylinder

texts:
I have 2.5 meter long height, 5cm radius cylinder. This cylinder can be used as a trashcan and I want to install an Ultra Sonic Ranger like SRF05 to see how much space left in it.

Cylinder has long height compared to radius and SRF sensor will be installed on the top of cylinder. And I read these sensors have a coverage angle of 15degrees.

Would it be possible if sensor's beam angle produce a false distance by hitting Cylinder walls before actually reaching the bottom of the object?
I mean Cylinder is really slender and I'm worried about the surface around since SRF sends beam in a 15degree circular angle instead of linear straight line.

More about Ultrasonics:

http://www.sensorsmag.com/sensors/acoustic-ultrasound/choosing-ultrasonic-sensor-proximity-or-distance-measurement-838

It would be great if it could detect in a straight line.


texts: Controlling positive and negative voltage rail

texts: I need to control and switch between positive and negative voltage rail at about 400 kHz with PWM signal at 50% duty cycle(Square wave). The positive rail is at about 150V and negative at -50V. It is possible to switch just positive rail but I'm not able to do for the negative rail. I've tried to use MOSFETs with gate drivers but I can't seem to get it work. Can any one suggest a schematic for this?


texts:
Im trying to understand the source of ringing at the termination point of a PCB traces before i delve into actually designing a PCB. For example, by 'termination point', I mean a clock signal terminating at the input of an IC.

Some online sources point to ringing caused by reflections due to an impedance mismatch at the termination point of a PCB trace.
Other sources point to the parasitic inductive and capactive nature of the lines causing ringing if there is not enough resistive damping.

Are they both manifestations of the same thing, or are they two seperate sources of ringing?

If they are two seperate sources and both are present on a line, is it common for a termination resistor to be unable satisfy both the impedance matching and damping requirements?


texts: Creating a small scale bumper car ground power grid

texts:
I'd like to build a tiny RC car that can run indefinitely without the need to charge. Bumper cars have strips of power on the ground and according to Wikipedia this is how they work:

  "Uses alternating strips of metal across the floor separated by
  insulating spacers. The alternating strips carry the supply current,
  and the cars are large enough so that the vehicle body can always
  cover at least two strips at any one time. An array of brushes under
  each car make random contact with whatever strip is below, and the
  voltage polarity on each contact is sorted out to always provide a
  correct and complete circuit to operate the vehicle."

Has anyone attempted this before on a smaller scale? I'm not quite sure the circuit required to achieve this on a 5V~ scale, and the type of "brushes" that would be required. Any links or direction would be greatly appreciated thank you!

Edit: Alternatively I'd love if anyone had any ideas on how to keep a power cable directly above a car as it moves around a closed space (so if there were multiple cars they couldn't tangle on each other's wires).


texts: Can resistors be used to bring a heating element within range?

texts:
I have a replacement 24V/60W desoldering gun I would like to modify for use on my Aoyue Int958A+ soldering station. My 968A+ has a smoke absorber which has enough suction to double as a solder vacuum. Mapping the pins is relatively straightforward.

During my measurements, however, I found the desoldering gun's heat sensor resistance was significantly lower than my soldering iron's (see table below). When I briefly heated the tip of the gun with a torch lighter, I noticed the resistance steadily climb to around 6 ohms. Could this be a thermistor instead of a thermocouple? Also, is it possible to correct the resistance range by adding a ~50 ohm resistor in series with the heat sensor?

Desoldering Gun Pinouts

PIN WIRE    PURPOSE
1   Black   Heat Sensor
2   Blue    Heat Sensor
3   Red     Heating Element
4   Red     Heating Element
5   White   Trigger switch
6   White   Trigger switch
7   CENTER  Vibration sensor (unused)

Resistance Measurements

Pins 1 & 2              1 to 2  Ω
Pins 4 & 5              1 to 2  Ω
Pin 3 & solder tip      Below 2  Ω

Soldering Iron Port Pinouts

PIN WIRE    PURPOSE
1   Blue    Heating element
2   Green   Heating element
3   Yellow  Case ground
4   Red     Heat Sensor
5   Black   Heat Sensor
6   Unused

Resistance Measurements

Pins 1 & 2              2.3 to 3.5  Ω
Pins 4 & 5              43 to 58  Ω
Pin 3 & solder tip      Below 2  Ω


texts: Solenoid doesn't actuate when driven through MOSFET

texts:
I'm trying to drive a solenoid with a GPIO on a Raspberry Pi.  Here's the schematic:

The current through the solenoid and MOSFET should be:

So the voltage drop across the MOSFET should be:

leaving us with 13.8V across the solenoid, which should be enough to actuate the 12V solenoid.

Naturally I've tried actuating it directly:

This works just fine.

Suspecting that maybe the MOSFET wasn't fully switched on, I took the Raspi out of the mix and tried applying 4V directly to the gate:

but it doesn't actuate...

I've also tried replacing the solenoid/diode with a simple LED/resistor combo and it lights up as expected in both the Raspi/non-Raspi configurations, so the MOSFET appears to be switching as expected...

What am I missing here??  Why won't the solenoid actuate when I have the MOSFET in the mix?

Parts:

IRF510 MOSFET (from Radioshack)
1N4148 Diode
DC 12V Solenoid (amazon)

Solution

As pointed out by Respawned Fluff and The Photon, I was fundamentally confused about some of the parameters of my MOSFET.  Specifically, \$V_{gs(threshold)}\$ is not the point at which \$R_{ds}\$ becomes \$R_{ds(on)}\$.  \$V_{gs(threshold)}\$ on this MOSFET is 2-4V, so I thought I could switch it on with 3.3V.  However, the value I needed to switch this guy on is actually 10V (read from the \$R_{ds(on)}\$ row on the datasheet).

Per Respawned Fluff's suggestion, I added a MOSFET driver between my logic output and the MOSFET and, sure enough, things started working perfectly.  I probably also could have swapped out my MOSFET for a logic-level one.  Here's the final working circuit:

The MOSFET driver is MIC4452YN.


texts: Is there any way to use the saturation harmonics to determine the rated voltage of a induction motor?

texts: When the motor is running at no-load, the core eventually saturates as the AC supply voltage is increased. Therefore, harmonics will be present in the AC supply current waveform . I suspect that the harmonic content will be low at the rated AC supply voltage and increase greatly above the rated voltage     . With these harmonics, mostly 3rd,5th,7th, can the rated voltage be estimated ? Would looking at the magnitude of the third harmonic give a reliable indication ?


texts: Adding voltage cutoff to a circuit? 3s li-po

texts:
Possible Duplicate:
  Adding voltage cutoff to a circuit?

Adding voltage cutoff to a circuit?

I'm powering a project with a 3-cell 11.1V LiPo battery. What circuit do I add to make the unit stop drawing power when the voltage from the battery drops below 9V? The goal is to protect the LiPo battery from discharging below 3V/cell. my battery is: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=6501
by the way, i looking do draw max if 2 ampere from it, hope it wont change nothing...


texts: In which way could this noise be coupling?

texts:
In a data acquisition system, a single ended earth grounded daq board has inputs from many force transducers and some transducers types.

Daq basically has a common ground for all inputs and multiplexes the inputs.

Below is a simplistic model od this application:

My question is only about a peculiar observation.

If you look at the diagram above, when any of the force transducer's shield(T1  as an example in the diagram) touches a large floating metallic frame nearby(an aluminum frame where many servos mounted on it but the system is OFF);
when any of the transducer's shield touches to this frame, that particular channel picks up large amount of 50Hz and its harmonics noise. But not the other channels. I observe this from the daq software.

I thought if it were a ground loop this noise would appear on all channels, but since it appears only on the channels which is in contact with the frame I thought it cant be ground loop? Does that mean the frame picks up the 50Hz noise through the air?

What can be said about the coupling way of the noise knowing that it only appears on the channel which is in contact with the frame even though all channel grounds are common at the daq side?

Edit:


texts: Use crystal or oscillator for a Ethernet PHY?

texts:
I've saw so many reference designs use just a crystal to generate the clock for ethernet phys, though they can be generated with a crystal oscillator too. Such as KSZ9021's 'XI' and 'XO' pin.

Are there some special reason that a crystal is better than a oscillator here? Or just because crystal is cheaper than a oscillator?


texts: How can I build a receiver to draw power from an alternating electrical field?

texts:
Yes, that is a vague question. Here are the specifics: the normal operation of human cerebral cortex generates a detectable alternating current at the cortical surface. The existence of this current allows for the recording of electroencephalography and electrocorticography. In theory, one should be able to construct some kind of receiver that could sit on the cortical surface and when properly oriented, extract electrical power from the field being generated. Yes, the amount of energy obtained would likely be very small - but for the uses I have in mind the power requirements are minimal.

So my specific question is: what would the circuit design of such a receiver look like? Thank you for your attention.


texts: GPIO speed in LPC812 Cortex-M0 MCU from NXP

texts:
Based on datasheet page 17:

  GPIO registers are located on the ARM Cortex M0+ IO bus for fastest possible single-cycle I/O timing, allowing GPIO toggling with rates of up to 15 MHz.

And I used a tiny code (based on the LPCOPEN library) to test its speed:

Chip_GPIO_SetPinDIROutput(LPC_GPIO_PORT, 0, 12);

while(1)
{
    Chip_GPIO_SetPinState(LPC_GPIO_PORT, 0, 12, true);
    Chip_GPIO_SetPinState(LPC_GPIO_PORT, 0, 12, false);

}

When I trace this GPIO pin by logic analyzer, it's toggling around 250 kHz which is far from the mentioned value in datasheet.

I also used PLL to increase main clock and system clock for achieving better speed:

Chip_IRC_SetFreq(96000000, 24000000);

but even for different values 250 kHz is the highest frequency which I can achieve. Decreasing PLL speed cause decrements on output frequency of GPIO and also I know I can achieve better speed with assembly code but 250 kHz is so far away from datasheet, and it seems the MCU are not able to exceed this limit (there are same substance for 60 MHz/30MHz – 60MHz/15MHz and so) Also 250 kHz is maximum speed which pins in the SPI peripheral state can toggled.

EDIT:
I'm aware that for full speed test, needed to code in assembly directly with registers, but as I said before the problem is after increasing the 12 MHz main clock, GPIO cannot toggle faster, and also toggling speed for SPI CLOCK pin is limited to this speed too.


texts: Altium - Defining top or bottom layers as a plane layer

texts:
I have four layer PCB stack up but wish to use the bottom layer as a 'plane' layer instead of a signal layer. Is it possible to configure Altium like this through layer stackup manager?

L1 Top - Signal
L2 Mid - Plane
L3 Mid - Signal
L4 Bottom - Plane

I can use multiple polygons but for my design a negative plane definition with splits would be easier to work with.


texts: Connecting CAN transceivers for devwork /home prototyping

texts:
I'm doing some home project, and would like to use this CAN transceiver (note just in case, not selecting CAN controller+transceiver chip, that's how I need it).
I would like to use this transceiver from PIC (high speed, and can get it now in DIP..)
MCP2561/2FD, link to the device webpage

I want to connect 2, 3 of these, for higher speed communication for my nodes - I hope above 2Mbps (transceivers support upto 8Mbps). My nodes will be basically on different bread boards, and I'm trying to figure out simplest or most essential connection I need.

Looking at Sec. 1.8 in that reference - Typical applications. Can I just use one 5V supply for both - my MCU and the transceiver - and the bus, using the 2 120 resistors, and ignore that SPLIT line? (sort of combining those 2 cases they have into one ..). Could I skip the 0.1 uF diode, using 1 power supply / Vdd ?

Do I need LDO's at all, can't I just connect to my power supply 5V?


texts: Getting 12Amps of 0-12VDC from relatively low frequency PWM

texts:
I am trying to drive 4 parallel TEC elements. (TEC1-12706) I intend to run them together up to 12A (or 3A each.)

I am using an ATMega328p (in the form of an Arduino Uno Board) to control the system, but it's only means of variable output is a low frequency PWM.
Do to their nature, TEC elements are unsuited to PWM. The efficiency is inversely proportional to the square of the current. In addition, apparently they wear out quickly if voltage swings too much, so a relatively smooth DC voltage is required. (Probably around around 1%, or 0.12V)

I found this similar question, and it appears a buck-converter could work for this purpose, however...
My required current is higher and the control frequency is lower, which seems to result in the need for impractically large components.

Something like this: (The resistors represent the 4 TEC Elements)

simulate this circuit – Schematic created using CircuitLab

Ignoring the MOSFET and diode currents for a moment, I am more worried about L1 and C1, since those seem ridiculously large.

My question is: What can I do to avoid needing such high rated components, other than increasing control frequency? Alternatively, is there another approach that might work better? Possibly an RC filter to form a DAC, and then use a power op-amp?

I am thinking there must be some way to add additional stages, or maybe attach multiple of these converters in parallel, but I'm not sure exactly how to do  that. If I understand correctly, adding capacitors in parralel increases both capacitance and max allowed ripple current, totals sum together.
However, for inductors, they apparently loose inductance in parallel, but still gain max safe current, as the load is distributed. Seems like a catch-22.

Any help (or even just advice) is appreciated!


texts:
Function:  Σ a,b,c,d(2,5,6,7,8,12) + D a,b,c,d(1,10,13,15)

My attempt at solution

Prime Implicates :

BD
AC’D’
A’CD’
A’BC
B’CD’
AB’D’
ABC’

Essential Prime Implicates : BD

Minimal SOP: BD + AC’D’+A’CD’

Am I including too many implicates for the prime implicates? When do I know that the prime implicate is not needed? For example the implicate A'C'D was not included because the "1" in question was already apart of an implicate that was larger (4 as opposed to 2). Is it true that I include all possible combinations of an implicate if it belongs to an implicate of the same size?


texts: Why does there have to be a load in MOS inverters?

texts:
I have been studying about inverters for a while. In the book that I was reading, inverters have been explained according to the type of load connected to the drain of the driving transistors ie. resistive load, e-type nMOS load and d-type NMOS load.

In both of the above circuits, if a low input voltage is fed to the gate of the driving transistor the o/p will be high because current does not pass through the load or driving transistor and the o/p is simply Vdd.

When the input voltage is high current passes through the load and driving transistor and a low o/p is obtained because minimal voltage drop occurs in this case.
In neither of the above cases does having a load seems to be of any benefit.The loads seem to be simply contributing to power dissipation during linear mode operation and area . Why then are they connected in the first place?


texts: Can I use electrolytic capacitors in an oscillator?

texts:
I'm trying to learn about oscillators so I thought I'd put together something like one of the colpitts oscillator circuits I've seen and play around with it. I'm pulling scavanged parts from my junk box and realized As far as matched pairs, I have almost entirely electrolytic capacitors. Is it even possible to use these to build an oscillator since they are polarized?

If I can and orientation matters, how would I orient the cathode and anode? Are there other things I should consider?

Please excuse what I'm sure is a simple question.


texts: Can a PWM with 1% resolution in a PID heater loop achieve better than 1% temperature accuracy?

texts: I need to set a temperature between 20 °C and 300 °C. I am using a PWM output with a resolution of 1% duty cycle. Can the overall PWM period, and PID loop timing, get better than 1% accuracy of the temperature span in the load?


texts: Programming issue when uploading bootloader to samd11 via OpenOCD on RPI

texts:
I'm attempting to flash a bootloader on to an atsamd11c14a using openocd on an rpi model 3b+ but encountering some trouble.

No issues on installing openocd (following adafruit's guide) and I believe my wiring is correct (was following some other guides). Reset pin is currently not connected.

Where I'm running in to issues is during the actual upload. The output I'm getting is:

Open On-Chip Debugger 0.10.0+dev-01151-gd9ffe75e-dirty (2020-03-26-09:28)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : BCM2835 GPIO JTAG/SWD bitbang driver
Info : JTAG and SWD modes enabled
Info : clock speed 400 kHz
Info : SWD DPIDR 0x0bc11477
Info : at91samd11c14a.cpu: hardware has 4 breakpoints, 2 watchpoints
Info : Listening on port 3333 for gdb connections
Error: at91samd11c14a.cpu -- clearing lockup after double fault
target halted due to debug-request, current mode: Handler HardFault
xPSR: 0xd1000003 pc: 0xfffffffe msp: 0xffffffd8
target halted due to debug-request, current mode: Thread
xPSR: 0xd1000000 pc: 0xfffffffe msp: 0xfffffffc
target halted due to debug-request, current mode: Thread
xPSR: 0xd1000000 pc: 0xfffffffe msp: 0xfffffffc
** Programming Started **
Info : SAMD MCU: SAMD11C14A (16KB Flash, 4KB RAM)
Error: SAMD: NVM programming error
Error: Failed to erase row containing 00000100
Error: SAMD: failed to erase sector 1 at 0x00000100
Error: failed erasing sectors 0 to 15
embedded:startup.tcl:522: Error: ** Programming Failed **
in procedure 'script'
at file "embedded:startup.tcl", line 26
in procedure 'program' called at file "openocd.cfg", line 33
in procedure 'program_error' called at file "embedded:startup.tcl", line 587
at file "embedded:startup.tcl", line 522
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections

I've attempted looking up the first few error lines but not having any luck.  My openocd config file is as follows:

source [find interface/raspberrypi2-native.cfg]
transport select swd

set CHIPNAME at91samd11c14a
source [find target/at91samdXX.cfg]

# did not yet manage to make a working setup using srst
#reset_config srst_only
reset_config srst_nogate

# says next two lines are deprecated
#adapter_nsrst_delay 100
#adapter_nsrst_assert_width 100
adapter srst delay 100
adapter srst pulse_width 100

init
targets
reset halt

at91samd bootloader
program sam_ba_Generic_D11C14A_SAMD11C14A.bin verify
at91samd bootloader 4096
reset
shutdown

I've also tried adding at91samd chip-erase just before programming (was suggested somewhere as a way to clear a lock if there was one), but didn't have any real effect aside from saying '''chip erase started''' before the programming attempt. The chips themselves are brand new, so I believe (not sure how to verify) that they should already be empty.


texts: getting STM32F4 working as USB audio/video device

texts:
I have a project to implement a simple webcam on an STM32F4 dev board. My start point is the STM32 middleware libraries. From these I could build an example project which functions as a USB audio output.
My game plan is as follows:

modify the project so the dev board becomes an audio input (to the HOST, a windows/linux PC)
write a simple routine to make the dev board become an audio tone generator
add code to sample from a microphone to fill the buffer (also addressing need to sync)
add USB interface and endpoints so the board becomes a UVC device
fill a bugger with video data and capture it on the host
capture frames from a camera and use then to fill the buffer

At the moment the board is recognised as a microphone source on the PC - this by changing the descriptors in the middleware header files (I used an example in the USB 1.0 spec as a guide). Device Manager shows it as working correctly and I can select it as an audio source although of course I cannot record from it.
Now I am looking for the place in the code where I need to fill a buffer, but I don't find it. There are some likely looking routines in the middleware but they don't seem to run. I have found what looks like some config handler for EP0 which needs to be implemented, but I am not sure how.
Next I intend to connect the board to a laptop with wireshark and see what transfers are taking place when the dev board is plugged in.
My question is just to ask whether anyone has any useful tips or references on how to get this going. I am making progress but it is slow going. Anything that would help me understand the STM32 middleware and USB configuration process would be helpful.
(I have downloaded another STM32 extension library which claims to support recording, but when I look into the code, some critical routines do not seem to be implemented, so it seems less than helpful.)


texts:
I just bought a package of 100 laser diodes on eBay:

http://www.ebay.com/itm/110887381932?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

My first question is: Will they need a driver? Can't I just hook two of them up in series to a 9V battery, and be done?

Secondly, I plan to attach them all to a Halloween costume and fire them all at the same time. My initial thought was that I could solder two and two in series, and then create one giant 50-in-parallel circuit of these sets of two laser diodes. Then I was hoping to run the caboodle from the aforementioned 9V battery. Is this a proper way of doing this?