texts: How to use TMS570 microcontroller UART to communicate to another device

texts:
I am trying to use a TMS570 to communicate to another device through UART. (The pin diagram is here:
http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=SPNU611)
I tried following the following tutorial for how to use the SCI/UART on the microcontroller, but I realized that it only contains instructions for how to communicate between the PC and the microcontroller, not for how to communicate to another device using UART.
I posed this question on the TI E2E forum, and got the following advice:

The TMS570LS1224 has two UARTs, one is a LIN/SCI2 combination and the other is just a plain SCI. In the Launchpad schematic on sheet 12, section A1, you can see that the LIN pins are connected to U7. U7 is the chip that creates the XDS110. The XDS110 is not only a JTAG controller, but also acts as a USB to Serial port for your PC. In the example code from the tutorial SCI2 was writing to the PC and receiving from the PC. The LIN pins are already used on the Launchpad.
If you want to connect two launchpads together by a UART, I suggest you use the plain SCI, pins J2-3 and J2-4.

However, I am not sure how to configure HalCoGen to set up the pins in this way, and what methods to use in Code Composer Studio to communicate through them. Would anyone have any advice?
Thanks!
TMS570 data sheet: http://processors.wiki.ti.com/images/c/c1/LAUNCHXL2_TMS57012_RM46_REVA.pdf


texts: How to determine whether a given transistor is NPN or PNP?

texts: If I have a device which I know is a BJT transistor but I have no other information, how can I determine whether it is NPN or PNP and which pins have C, B & E functionality?


texts: Is it possible to connect a peripheral mouse to the USB side of a USB/UART bridge that is controlled by a CP2103 chip already on an FPGA board?

texts:
As the title states I want to connect a USB mouse to the USB port on a USB/UART bridge. I want to determine if it is possible to communicate with the mouse using serial commands on the FPGA board then converted to USB signals.

In other words, I want the bridge to serve as the host to a peripheral like a mouse/keyboard. Do I need to worry about converting to PS/2 at all when connected?

Is this feasible as I am looking for a viable solution to connect a mouse to my FPGA board without having to create a USB block to handle this from scratch?


texts: Simple pushbutton board acts like its shorted but does't measure shorted

texts:
I have a small simple board with 4 push buttons. The 4 lines are pulled hi in the micro and pushing the PB should pull each low independently. However, On 5 out of 16 new production boards when I push the MENU button the unit acts like I also pressed the ENTER button. I can see the ENTER line drop from 3.3V to 1.4V like there is a short between J4-1 and J4-2 but I don't measure a short. I also see the PLAY line get pulled down to ~3.1V when MENU is pushed. On the working units these lines are steady 3.3V. If I measure from the PB1-1 to J4-1 I see 33 ohms and same for PB2-1 to J4-2 so the resistor network IC seems fine. The good board measures Mohms from J4-1 to J4-2 and the bad boards are measuring about 200k!

The scm section in the dotted box is the push button board. The mating connector and ESD protection is shown for completeness.

I am suspecting board contamination may be the cause but didn't think board flux/residue would so drastically affect such a non-sensitive circuit.


texts: I couldn't find the answer to this anywhere so, how can you tell what the power draw, in amps, of a transformer is knowing the input voltage and turns on primary and secondary.


texts: How to tell if brushless DC motor is wired delta or Y?

texts:
I have a brushless DC motor I'm working with, do not have any spec. sheets for it.  How can I determine if it's wired in delta or Y formation?  There is nothing on the label that indicates this.  Here's a picture of the label.

TY,
Fred


texts:
I have this old power adapter with a rating of 6V 2.4 Amp. I used a voltage divider circuit made of two 1000 ohm and one 10000 ohm resistors. when i measured the voltage across the 10k resistance, I got an exact drop of 1 volt, i.e., it was reading 5 V.
i connected the ends to the micro USB and connected to my windows phone.
The phone was not charging. When i read the voltage with charger, the voltage was only 2.5 V instead of 5 V.
What just happened here? the adapter was a 6 V adapter that was used for a router, why did stepping down voltage result in drop in voltage on connecting load.
thanks for helping me out. How would i get a 5V to charge my cell phone from this adapter?


texts: Connect bus wires to various ports of a channelized subsheet

texts:
I have an 8-line bus chselect[7..0].
I also have a 4x repeated subsheet, each of which has two inputs CSAb and CSBb.
Denote these inputs as CSAb_0, CSBb_0, CSAb_1, CSBb_1,...,CSBb_3 where the number after the underscore indicates which instance the instance of the repeated subsheet.

I want to connect the bus like this:

chselect[0] --> CSAb_0
chselect[1] --> CSBb_0

chselect[2] --> CSAb_1
chselect[3] --> CSBb_1

chselect[4] --> CSAb_2
chselect[5] --> CSBb_2

chselect[6] --> CSAb_3
chselect[7] --> CSBb_3

Here's my attempt in Altium

Is this correct and/or in line with best practice?

I have also asked this on the Altium forum.


texts: PIR motion sensor with MOSFET, optocoupler or Relay to turn on LED ribbon

texts:
I made a small circuit (with a breadboard) which turns a small 12V LED ribbon (a few mA) when the Pir sensor detects a motion.

The circuit is made of:

Velleman PIR motion sensor
Relay
Velleman step down voltage shifter
LED ribbon (12V)

It works like a charm expects the relay makes a "click" sound (I know it normal :) when it's switched on and it needs a 5V power supply (while the LED ribbon and the PIR needs 12V).

Now, I want to optimize the circuit. I searched on the Internet and I found two components that I could use: MOSFET and optocoupler.

The first one, the MOSFET, I know a lot about it now. I read a lot of documentations. I need a logical N MOSFET in my case.

Then I just found today a new component: an optocoupler but I don't know a lot about it.

I need something that can be opened turned on at 3.3v and can provide cope with at least 12V (I know it needs to be higher) and more than 4 Amps.

What would be the "best" between a MOSFET and an optocoupler (in my case)?


texts: Practical differences between putting circuit complexity on the ground side vs the hot side

texts:
I'm wiring some computer fans behind the fridge in my camper-van to help increase ventilation. As part of this circuit, I have a temperature controlling microcontroller plus relay and a series of SPDT switches to control various aspects of this circuit. Originally, I had simply planned to put all the switches and the microcontroller relay on the hot +12V side of the circuit, but it occurs to be that I could put all this on the ground side of the circuit as well.

This is a vehicle, so the body is tied to ground, but I'm not using that fact for this circuit (i.e., nothing in the circuit attaches to the frame, it's all explicitly wired even for the ground return).

So is there any practical difference between say this circuit:

simulate this circuit – Schematic created using CircuitLab

... and this one, which is identical except that the switches and relays are all on the ground side.

simulate this circuit

One potential advantage, I suppose, of putting all the control on the ground side is that keeping the hot side simply (a single return wire) decreases the chance of a short to frame, since all the switches and related wiring are at ground potential.


texts: Altium: make a specific GND pad not to connect to GND pour

texts:
I have a 2 layer board design and I'm using the top layer for traces and ground plane.

Then I have an ADC and the -Vin pin is connected to a connector and both of them to GND but I want the -Vin pin to have one and only connection to GND through the connector pad but Vin- is being connected to the GND plane also. How can this be done?

I know that I could use a cutout but I'm asking for alternatives.


texts: How to assign different pins in Pin Planner in Quartus?

texts:
I am trying to make the 7 segment display of my FPGA work. I found some working code, but I got issues with the pin planner. The FPGA is this, a knockoff Altera Cyclone IV E EP4CE6E22C8.
The code :

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity  seven_segments is
port (
      clk : in std_logic;
        bcd : in std_logic_vector(3 downto 0);  --BCD input
        segment7 : out std_logic_vector(6 downto 0)  -- 7 bit decoded output.
    );
end seven_segments;
--'a' corresponds to MSB of segment7 and g corresponds to LSB of segment7.
architecture Behavioral of seven_segments is

begin
process (clk,bcd)
BEGIN
if (clk'event and clk='1') then
case  bcd is
when "0000"=> segment7 <="0000001";  -- '0'
when "0001"=> segment7 <="1001111";  -- '1'
when "0010"=> segment7 <="0010010";  -- '2'
when "0011"=> segment7 <="0000110";  -- '3'
when "0100"=> segment7 <="1001100";  -- '4'
when "0101"=> segment7 <="0100100";  -- '5'
when "0110"=> segment7 <="0100000";  -- '6'
when "0111"=> segment7 <="0001111";  -- '7'
when "1000"=> segment7 <="0000000";  -- '8'
when "1001"=> segment7 <="0000100";  -- '9'
 --nothing is displayed when a number more than 9 is given as input.
when others=> segment7 <="1111111";
end case;
end if;

end process;

end Behavioral;

The code compiles and I can upload it, I just can't change the pins so that they can match the ones of my FPGA. I was thinking to use the dip switches as inputs. Some screenshots below.

To whoever takes sometime to help, thank you!


texts: Why can't I make an and gate with 1 NPN transistor?

texts: Recently I looked at a schematic for an AND gate and noticed that they used 2 npn transistors.  I was wondering why you would want to use 2 transistors though.  Couldn't you make an AND gate by attaching one input to the collector and one input to the base?  Wouldn't this be better because you would be using half the transistors?


texts: Connecting altium busses with different width

texts:
I have 3 busses in the project:

ADC[16..1],
BUSA[8..1],
BUSB[8..1],

I would like to connect ADC[8..1] to BUSA[8..1] and ADC[16..9] to BUSB[8..1]. Is this possible without adding any series resistors? Whats the cleanest way to accomplish this?

I would really like to avoid dividing the ADC bus on 2 parts, i.e. ADCA[8..1] and ADCB[8..1]...


texts: Different connections on positive and negative pins in PCB design

texts:
I've seen some designs they have connected pins of power components differently.

For example in a buck capacitor at the output of a DC to DC power supply I've seen the positive pin on direct connection and the negative pin on thermal relief connection or with just one via to the ground.

In the picture below you can see a solid state SMD capacitor (both pins have the same size) is directly connected to the positive pin having a much lower impedance but the negative pin is connected to ground with just one via and a thin trace. The pads have the same size.

I'd like to know if there's any good reason behind that or if the engineer did not understand how the current flows.

Isn't that a mistake? Shouldn't both pins have the same impedance path to the power rails?


texts: USB powered Desk Fan vs AC powered Desk Fan

texts:
I would like to convince my employer, a government agency that relies exclusively on battery operated desktop fans, to convert to USB powered desktop fans plugged into employee desktop computers. Employees are restricted from using AC powered fans. All 75 users have desktop computers with 4 USB ports.
How can I calculate how much additional current a 12 volt USB desk fan would add to the load of the desktop computer? Am I correct in assuming that a USB powered desktop fan would be the most energy efficient solution to the problem of 75 users needing desktop fans? Thank you all for your input!


texts:
I am looking for the dimensions of the internal keepout region for a SATA 3.0 receiver eye mask. Anyone have that handy? Not able to find that in specification
Thanks in advance.


texts:
I'm trying to design a buck converter controlled by a PWM signal. The PWM signal and the converter is isolated with a pulse transformer.

My issue is that the pulse transformer behaves differently than expected.

This is the schematics for the pulse transformer part

We use the B82804A0354A110 and the IXDN602SI as driver.

Before we added the pulse transformer to the circuit we measured the output of the IXDN602SI:

This looks good and the pulse are 12V just as specified by the driver.

Now we add the Pulse transformer to the circuit and measured the output of the IXDN602SI again, which is the input to the pulse transformer primary winding:

We also measured the voltage Vgate:

So, the transformer seems to be working as the input is the same as the output (its a 1:1:1 transformer).

The question I have is, why is there a voltage drop? Why is the output voltage of the transformer not 12V pulses?

The pulse frequency is about 1.6 MHz.

Hope you can help.

UPDATE:

As per the answer by @andy aka, I just wanted to show the entire buck converter and explain the reason for my question. The reason I measured the the transformer on its own, is because when I add it to my circuit then the output of the line driver is just 0V and I'm having a hard time understanding why.

This is my schematics and as you can see we do have a gate driver on the secondary side of the pulse transformer.

But my suspection is that there is something wrong with the gate driver, since the entire PWM circuit is driven to 0V. Initially I expected the transformer to be faulty and therefore tested it on its own.


texts: What is this filter switch doing to the AC line that triggers the switching power supply to function and power the rest of the unit?

texts:
This board is identified as a filter power switch and is in is an Akai Sampler. It connects to a switching power supply which outputs the required volts to the rest of the unit.
Intuitively, I thought the switch was only toggling the AC line from open to closed. Now that I discovered the output connecter is always live, I know the switch is only filtering the the AC line. But what exactly does that mean for the switching power supply, causing the unit itself to "turn on"?
Considering the AC line is always live, is there a benefit to this method? Versus, just using the switch to completely cut the power.

Official Schematic for the part.


texts:
In many digital lab PSU designs, designers usually use a thermistor to control the cooling fan speed based on the main regulator actual temperature.

When we have both current and voltage values, is there a reason why they don't control the cooling fan speed based on how much power (in watts) is being drawn from PSU?


texts: Pick and place machine + AAA battery holder?

texts: Say I design a two-sided PCB. I want the bottom side to have just a 2xAAA battery holder. Could a pick and place machine handle this or is it out of the question? What happens when the top side is flipped over - wouldn't the board "wobble" depending on the height of the components on the top side?


texts:
I would like begin a new custom FPGA design and I am considering buying a dev kit for experimentation. When the design has finished, I intend to design a dedicated PCB board. If I change the packaging of the model and instead of a BGA move to QFP, which is easier and cheaper for me to work with, will it drastically affect my timings when I will adjust my design to it? How significant is the packaging of a FPGA related to timing for same models?
I wouldn't like to to invest a fair amount of time and money on dev kit and then find out that I don't meet the timing requirements. I know it's a little vague as a question, but I am looking to get a sense on what to expect. Thank you.


texts:
I know that BME280 measures pressure using the piezoresistive effect, I suppose it uses the thermoresistive effect to measure the temperature. How about humidity? Any advice would be appreciated, even starting points for a little Google-fu.

Datasheet: https://www.bosch-sensortec.com/products/environmental-sensors/humidity-sensors-bme280/#documents


texts:
I was curious about this.  I've searched other similar questions but they weren't quite the same.  One mentioned the use of diodes but I would like to know if this would work first before adding diodes.

Can I hook 1 device (12v) to 2 different power sources supplying 12v each.... Would this fry the device?

Scenario:
I have a 12v led light strip.
It's currently hooked up to a 4.2v li-on battery hooked up to a transformer that outputs 12v.
This circuit has an on/off switch.

Now i want to add a dc input to the light strip also.
The dc adapter will be supply 12v directly to the light strip (bypassing the transformer).

I was wondering, if this dc power source is already supplying the 12v to the light strip, and i turned on the battery power source, would this fry the device? or would it still be a total of 12v going into the device and is safe to use? Which power source would it be pulling from, maybe split between both?  What if both power sources are identical in voltage and amps?

Thank you, i'm afraid to experiment with this to see what happens haha.


texts: I'm currently working on a project that requires me to check if a device is still connected on an RS232 port. Since I do not have access to the code on the connected device(it is a fire alarm panel), I cannot have it transmit a keep alive signal. So I'm just wondering if I could check the voltage of the DCD pins and use that the check if the connection is broken. Thanks.


texts: Storing power from Raspberry Pi 5 V then amping it up to 12 V at 1A

texts:
I recently took part in a challenge called 'Hydrogen Hack' where we have a Raspberry Pi and have to make something controlled by that. The catch is that it has to be powered by a Hydrogen Fuel Cell - each fuel cell has a USB style output of 5 volts at 1 amp.
This is enough to run the Raspberry Pi (we have tested) and draw 5 V off the 5 V GPIO Pin.

However, the minimum voltage our motors can run at is 8 V at 1 A but preferably we need 12 V 1.5 A as the faster the motors spin the better and the H-Bridges we are using draw some power (obviously).

Me and my friends have come up with a few ideas but all of them seem impractical, we need to draw the 8 V 1A (or 12 V 1 A) for around 20 seconds preferably but this could be shrank to 15 seconds again if necessary.

I was wondering if any of you guys could come up with some ideas as to how / if we can do this?

Brief Details:

Pi Input: 5 V 1 A

Pi GPIO 5 V Output: 5 V 200 mA

Power build up: 8 V 1 A for 15 s but preferably 12 V 1 A for 20 seconds

I have googled and cannot really find anything relevant to what we need as it is probably silly to think anyone will of done this and bothered to document it before.

The power loss in the L293D is aprox.: (1.4V + 1.2V) x 0.6A = 1.56W

The motor preferably needs: 12v * 1A = = 12w

Wattage available: 1w

So i firstly need a way of converting the 1w to 13.56 and then storing it

And by the way, You cannot use any other batteries but they did not specifically rule out capacitors.


texts:
I have main device with a 3.3V serial port that has not enough power for the connected ESP. Main device powered by a single LiPo-cell.
I want to power on the ESP (3.3) when the main device is powered on, so I thought using an NPN-transistor, collector to battery +, emmitter to ESP, base powered by serial port + (3.3V).
Will that work? What output voltage will I get from the NPN? Max. current will be 0.5A. Do I need a resistor to the base?


texts: Phase Angles in Series/Parallel networks

texts:
INTRODUCTION:

I've been having a hard time in class trying to understand phase angles. I understand a few concepts which I've stated below for clarity in regards to this discussion.

1.) Inductors-->Current LAGS Voltage by 90 degrees.

I know that current through an inductor induces voltage which acts against current. Therefore, when voltage is at it's maxima or minima current is zero. This is clearly stated in the formula above when we set the slope (change in voltage respect to time) of the tangent line equal to zero.

2.) Capacitors-->Current LEADS Voltage by 90 degrees.

I know that current doesn't travel through a conductor. The electric flux is exchanged "coupled" across the dialectic "insulator" as voltage builds up on one side of the plate. Therefore, when the change of current, respect to time, is at it's greatest voltage is zero.

QUESTIONS:

I cannot get my head around on how to intuitively understand phase angles and more importantly how to analyze a parallel section of a network.

Trying to understand/analyze what the phase angle is for each component as we move down a series/parallel circuit is just plain confusing. Can anyone help me out or provide some educating online resources that could help out? A resource that could help me understand and construct a phasor diagram would even be helpful also.

I have attached an image of a circuit I had to construct and measure the characteristics of in class this week. I am also attaching the table of which includes my calculations and measurements. In the table I highlighted where my phase angles are mixed up. If someone could explain why my phase angles are not lining up that would be a great help also.

My AC source is set to the following parameters.

8 Volts Peak to Peak

10kHz as Frequency


texts: General question about analog and digital signals

texts:
Newbie alert: I am not an electrical engineer, nor have I ever taken electrical engineering, so please bear with me.

Whenever I read about the distinction between digital and analog signals, a graphic like this (or similar to this) is usually attached:

Consider the bottom illustration for a moment (Digital Signal). To my best understanding, electrical current is continuous, so if that is the case, there is no way it will flow in such a manner in any medium.  In other words: there are no "square waves".
So what exactly does that depict?
Is it just interpretation, whenever the voltage passes some barrier or falls under it? Meaning, when the voltage is above some arbitrarily chosen threshold we consider it as "high" but otherwise we consider it "low"?

Please, I know this is not always possible, but try to answer in a way that a layman would understand.


texts:
I'm pretty new in this area so sorry if this question seems foolish.

I have a 12V 20Lpm Diaphragm pump that draws around 18 Amps.  I'm using it on a home built herbicide spray system to help deal with the Spanish Heath that has fully taken over a good portion of my 50 acres.

I am really happy with the pumps performance though it is a little bit of over kill at 20LPM.  I am toying with the idea of making a PWM circuit to control the flow.
I was wondering if anyone has had any experience with this type of idea on a Diaphragm pump?  I'm going to make up a pulse generator circuit out of a couple of 555 timers just to get me started.  I was thinking about making it run from 100Hz to 1Khz with the duty cycle adjustable from 10-100%.  I haven't been able to Google much about controlling flow with this technique and was wondering if anyone had any ideas on the best frequency to drive the pump at or even advise if the idea is viable?  Perhaps I am better off controlling the flow with a valve at the output in which case I have posted to the wrong forum.

Best regards

Adrian.


texts:
I'm trying to understand how mobile phone headsets work. I figured out that the electret mic gets supplied with 2.7V by the phone.

Opening a headset revealed the following PCB:

I looked and measured and came up with the following circuit:

Shouldn't there be at least one cap in series with the mic?


texts: Reasons to use an analog temperature sensor instead of a digital one

texts:
I'm designing a microcontroller-based system that includes a thermostat.

When choosing which temperature sensor to use, I noticed that analog ones have more or less the same power consumption, the same temperature range and the same cost as digital ones.

Aside from possibly having a higher resolution ADC on the MCU than the one included in the digital sensor chip, are there any advantages in using an analog temperature sensor over a digital one?


texts:
Is there any reason for an electronics engineer to go for a professional engineering (PE) license?  My understanding is that becoming a PE is only useful/necessary for architectural electrical engineering, due to government regulations.  Is this correct, or is there any reason that an embedded electronics hardware/software engineer should become a PE?  Also, would this even be possible, as getting a PE usually means years of experience under an existing PE, whom only seem to be working for architectural firms?

One of the main reasons I'm asking is because I was thinking of registering a company name for contract electrical engineering work and I'm wondering if I can even call myself an engineer (legally).  Maybe I should call myself an electronic product designer?  Anyone own a contracting business have any insight here?


texts:
I have a circuit board from a Stratasys UPrint SE filament cartridge, and I'm trying to talk to the EEPROM on it.  This board is unlike other Stratasys boards that I've seen people hacking with, and after a day or two of failed attempts to communicate with it, I'm wondering if I'm even using the correct protocol to interface with the memory chip.

I suspect that it's some sort of 1-wire EEPROM, but beyond that there is very little that I know for sure.

The top of the chip appears to have the markings:

331101
1309B1
442AA

I've Googled all around and can't seem to decipher what these numbers mean.  I've checked two different chips, and they both have the same exact alphanumeric sequence, so it's not a serial number.

The main thing I want to know is -- what particular sort of 1-wire communication protocol do I need to use to talk to this thing?  I've been attempting to use the Raspberry Pi's DS2433 library, but that doesn't seem to recognize this chip.

Thanks for the help!

Edit: Finally was able to initiate communication with the chip via a Raspberry Pi's 1-wire interface.  However, the chip is showing up under family "b3" -- which is very odd, considering that I can't find reference to any sort of "b3" family in any of the w1 family specifications.

w1_master_driver w1_bus_master1: Family b3 for b3.1014d0006d00d.8a is not registered

I wonder if this is perhaps a custom chip of some sort that Stratasys created in an attempt to discourage hackers from accessing the chip?  I'm very puzzled by 0xb3 as the family ID for this device.


texts: Datasheet for XC370696P (Smoke Detector IC)

texts:
I decided on a whim to take apart an old smoke detector that desperately needed replacing, and after some ripping, I got to the guts of the thing.

Neat stuff.

Clearly the brains of the detector is that DIP IC on the right of the board: Motorola XC370696P. Here's a closeup of the part.

The internet is surprisingly quiet about this IC.  Any insight on what this part is, or where the datasheet lives?


texts:
I am currently eyeing installing an electric starter to my pocket bike 49cc engine. This question is purely about the electrical part of it, but I am going to give a little context.
The starter engine is very simple, it has 4 anchors that drive a rotor when powered. There is no one way bearing or disengagement mechanism except cutting power. They are mounted directly onto the crankshaft between the engine and the clutch shoe. For completeness at the bottom is a picture of such a starter.
I have watched several videos where people installed and wired them and (successfully) demonstrated starting the engine. It boiled down to this:

Starter case connected to negative of battery
Positive of starter connected via starter relay/solenoid to positive of battery
Button to close the relay

From an electrical point of view the starting makes sense:

button is pressed
relay is closed
power flows to the starter turning the rotor
engine starts

Now this is where I get confused. Unlike in a car the starter mechanism has no way to disengage when the engine starts (like one way bearing, ratchet, centrifugal, ...) except letting go of the button for the relay. When the engine starts it will also start to drive the starter shaft effectively turning the starter into an inefficient generator. From my understanding that means that until the relay is disconnected current will flow to the starter battery instead of from it. I checked the starter relays used and they don't have any protection for reverse voltage or current.
So my question boils down to: Do these people risk their starter batteries or am I misunderstanding something?


texts: Hand-matching resistors: high-end DMM vs Wheatstone bridge

texts:
I wrote an article dealing with the question of hand-matching resistors to high tolerances using a DMM. The driving purpose behind that article is to show that it's harder to do that than one might naïvely think, rather than to come up with the best possible way to achieve the end goal. So, for the purposes of this question, let us say that my article is unimpeachably correct within that limited scope.

What I want to do here is re-ask a question I got via email: would it be better to use a Wheatstone bridge instead?

From Wikipedia:

The idea behind the question is that a few precision resistors plus an eBay'd galvanometer (VG) would be cheaper than a DMM good enough to achieve the match.

It seems to me there's a serious problem with this idea, which is that to get the benefit from the low-current measuring ability of the galvanometer, you can't make R2 adjustable, as you would in setting up a Wheatstone bridge to measure an unknown resistor. All that does is buy you a new measuring problem, either:

a resistance measurement, the now-unknown value of R2 once you've finished nulling the differential current across VG; or
an angle measurement, if you've made R2 a rotary pot

I initially thought problem #2 would be easier to tackle. You could use a precision pot and an indicator dial knob on it large enough to get the angle measurement accurate to the degree level. For the 1000 ppm sort of measurement I discuss in my article, a 10 turn pot takes care of 1/10 of that, allowing the angle measurement to be accurate to within a few degrees. It seems suitable pots for this range from about $15 to $150, no doubt being a function of repeatability of measurement and such.

The problem is that the pot itself isn't perfect, so all you've done is turn it back into measuring problem #1. You merely get the choice to fully characterize the pot up front or instead treat it as an unknown from the start and measure its value at the end. You therefore still need a high-precision ohmmeter somewhere. I guess it could live at a cal lab somewhere so you don't have to pay for it, but you do still have to "rent" it via the calibration service.

Therefore, instead of making R2 adjustable, I think it would be better to buy three precision resistors instead of two: R1 = R2 = R3. The precision of the resistors has to be at least twice the accuracy you need for the match, so you're talking about at least $20 in parts here, and possibly much higher. On top of that, you now have to build a separate bridge for each resistance value you want to measure.

Yes, I understand that R2 doesn't have to equal Rx, but if they aren't close, you've wasted the potential (ahem) of using a galvanometer, haven't you? Isn't the idea to turn the resistance measurement into a high-precision near-zero current measurement?


texts: Using an inertial measurement unit to compute global motion optical flow of video

texts: I have a camera rigidly mounted together with an IMU that consists of 2-dof gyroscopes and 3-dof accelerometers. My aim is to compute the global optical flow of the image captured by the camera, in order to do global motion compensation when compressing the camera video stream. Instead of doing image processing to compute global optical flow, is it possible to obtain the optical flow based purely on the IMU readings?


texts: Do 0402 chip component need solder mask web between the pads?

texts:
In my board, all 0402 parts are using gang solder mask.

The pad to pad distance is 10 mils. Is there any risk of solder short?

Do I need to suggest applying solder mask web between the pads for all 0402?


texts:
What is known as a common source amplifier is often built with an NMOS, where the bottom channel (source) is connected to ground. What if you switch out the NMOS with a PMOS, and the bottom channel is now really a drain connected to ground, is it still called a "Common Source Amplifier"? And is the gain still negative?

Thank you in advance


texts: Procedure tips for connecting traces between DDR3 SDRAM and FPGA

texts:
This is my first layout connecting two BGAs: DDR3 SDRAM and a Zynq SoC. The design has 4 layers and I'm using Kicad. So far I've understood the following:

1. Focus on signal groups, i.e. ADDR, CTRL, CMD and data bytes.
2. Use the same layer transitions (VIAs) in each group for convenient length/delay control.

General things I keep in mind is to have the traces somewhat short (~25 mm). Looking at various tutorials this seems to be a trivial matter for experienced PCB designers. I do this so that I don't have to worry too much about impedance control.

Starting with the ADDR pins, I have ended up with the layout below. This is perhaps my 5th attempt as I've started over multiple times.

To my not so experienced eyes, this seems like a complete chaos and I have many more pin connections to go. On top of this, all traces will have to be length matched which will introduce even more challenges.

My humble question is: can someone give me a few tips on how to proceed with this?

Is layer increasing the way to go? And/or a larger distance between the components?

To me it seems like Xilinx could've picked better locations for their DDR3 pins in order to simplify the layout work.

Components:

DDR3 SDRAM datasheet - IS43TR16640B-125JBLI

Zynq-7000 Pkg Pinout specs - XC7Z010CLG400


texts: Anti-aliasing filter as notch and lowpass

texts: In order to reach a steep attenuation for an analog antialiasing filter, there are issues if a high Q notch filter is followed by a low order lowpass filter (or vice versa)? The notch resonance could make a brickwall filter near the cutoff frequency while the low pass would handle the higher part of the spectrum.


texts:
I need a help for debugging the error in my 7 segment display based digital clock design. It consist of six 2 inch displays and sixty 1 inch displays. The power supply I am using is 12 V/2 A external SMPS adapter. A 9 V regulator and a 5 V regulator are used in this design. A 7805 is used for providing supply for PIC, RTC and 1 inch display driver circuitry. A 7809 is used for driving 2 inch displays driver circuitry and buzzer. For 1 inch displays BD140 (PNP) is used and for 2 inch displays (ULN2003 + BD140) is used. ULN2003 is used for level shifting pic signals from 5 V to 9 V. Also around 2 meter of 12 V LED strip is driving directly from adapter output.

The clock works fine during testing procedures before sale. After sales, we got many calls from customers with the same complaint. That is, display is fully off, LED strip and adapter is working fine. Then I try to reprogram the IC but failed. There is no specific interval for the damage, sometimes within 1 month, sometimes within one year like that. But whenever this happens, 95% of the complaints will be same.

Actually I don't know where to start. Software problem? Hardware problem? Power supply problem? 2 inch display driving section? We have lots of models with 1 inch displays and almost the same design, and they work satisfactorily).


texts: Hardware required for measuring small weight changes?

texts:
I'm creating my first Arduino project and would appreciate some guidance. I am basically trying to re-create a digital scale that will POST to the internet. I am going to be measuring the coffee levels of a coffee pot and updating our intranet with the info.  The coffee pot will sit on the scale and at regular intervals the data will be submitted. The maximum weight of a full coffee pot will probably be less than 5 lbs (2.2 kg). Since this project is just for fun, I would prefer that the parts would be inexpensive.

I am a professional web developer, so the programming part will be easy for me. However, I have no experience working with electronics/sensors/micro-controllers. What parts do I need in order to measure these small changes in weight to a relatively lightweight object? Where can I buy them? Where can I learn to wire these parts together? Also, any tutorials you can refer me to would be VERY much appreciated.

Update: Here is the parts list that I've compiled so far:

Arduino Uno ($29.95)
Arduino Ethernet Shield ($45.95)
Load Cell (where to find a cheap, small one of these?)


texts:
I am trying to build a simple LED flasher circuit using 555 timer IC. Tried building it on breadboard and simulators several times but that is not working. As I am a beginner I think I am making some mistakes but with a lot of efforts I couldn't find that. Can some one please have a look to the breadboard circuit that I have build on simulator and tell me what is the problem in this circuit and why it is not working.

Here I have used 4k resistors between pin 6 and 7. and used 1k resistor with LED. Also connected pin 2 with pin 6 which is not visible in the image. Thanks


texts: Roland Microcube guitar amp damaged beyond repair?

texts:
My power regulated ac/dc adapter broke the other day and my friend thought it was a good idea to cut the wire from the mains adapter, trim the ends and plug this directly into the mains. he then connected the adapter end to the microcube. the elctricity in the flat tripped out at the circuit breakers. Would the amp be completly wrecked after this happening or is there a part I can replace that will fix it?. I just bought a new ac/dc adapter, plugged it into the amp, but nothing is happening, seems like something has blown(?)

anyone got a suggestion?

UPDATE**..i took it apart and saw that next to the dc input socket there is what appears to be a blown fuse. it says next to it "T800mAL" and i saw this http://cgi.ebay.co.uk/800mA-Amp-T800mA-T800mAL-Fuse-AntiSurge-20x5mm-x-10-/360325684444  I dont have time to go and get one, is there another household device I could steal one from? I really need my amp tonight :(


texts:
I heard somewhere that Fourier transform only works on a signal that contains parts that are harmonic to each other (i.e. f, 2f, 3f etc.).

Can anyone explain me on proof of this? Or if I am mistaken, what is the sufficient condition for Fourier transform?


texts: Why am I getting electric shock from 12V DC Adapter

texts:
May be this is a weird question. But I am little curios to know why my 12V DC adapter is giving shock when the circuit is complete.

I purchased couple of these 1 AMP 200V AC to 12V DC adapter. Unfortunately they didn't come up with a 'data sheet' as such except the specs written on the enclosure of the adpater. It is for sure not a transformer-less adapter. I verified that. When I connect it with as input to my DC to DC converter, the converter parts give electron shock. Well, I must say it never seemed as strong as 220V AC shock. A mild shock, but everytime.

What might be the reason for this? To my knowledge if it's pure 12V DC, I am not supposed to get shock. Is it possible that the DC is not well filtered and some AC components are still left in the adapter's output which is causing the shock. The other day I say a Youtube video where the presenter demonstrated that 12V AC exceeds the comfort level of human being, and one would feel the shock. Is this the case happening here?

If yes, then my last question would be how can I get rid of that? Would a capacitor filter work?


texts: Simulating a Flyback converter using Matlab / Simpowersystems, cannot get it to work, any tips?

texts:
I have created a flyback converter model using Simpowersystems in Simulink/Matlab. But it always gives me the wrong answer! I have simulated the same system using PLECS and Simscape/simulink and got the correct answer. But with my Simpowersystems model, it always gives me the wrong answer here is a link to the model

https://www.dropbox.com/sh/6h6e219x65o6ldk/aKKEgl3Y_D

Any idea what is going on? I tried changing the solver but without luck

Here is a picture of the model


texts:
I need to bias a transistor amplifier operating between 12-15GHz. I will be using a microstrip bias line to connect DC to the collector as well as the base. I came up with the following simple design shown for the bias network

From the results, I need to do a little tuning in CST to get the frequency right
Looking forwards to suggestions/improvements.


texts: I can't add an offset voltage 2.5 V to my analog signal. The circuit is attached.


texts:
I use ferrite N87 cores (datasheet), and I would need losses in the frequency range 50 Hz to 10 kHz. The datasheet on page 5 specifies losses between 25 kHz and 600 kHz. I could try to interpolate with some effort, but I would prefer measured values.

Does anybody know a link to such data? Would you expect a significant slope change if I just interpolate with a straight line to the lower frequencies?


texts: Why do serpentine traces (supposedly) entail decreased ESD immunity?

texts: In an Intel guideline for their 82579 Gigabit Ethernet controller I've read (p. 18) that a side effect of using serpentine traces on the MDI (which carries the actual Ethernet signals) leads to decreased ESD immunity. I'm fairly familiar with the other ills of serpentine traces (cross-talk leading to ladder-like waveforms, increased EMI etc.), but I'm scratching my head trying to figure out how serpentines might affect ESD immunity.


texts: Is it possible to custom program AVR by putting it in the AVR socket of an Arduino?

texts: Is it possible to custom program an AVR chip by putting it in the AVR socket of an Arduino?


texts:
I am trying to simulate an ISERDESE2 component with VIVADO
Networking mode
SDR
8 bits wide.
I emulate the behaviour of the ADC:
CLK and CLKDIV are phase aligned, CLK has its transitions aligned with the center of the data eye.
On the D port of the ISERDESE2 i always send the same word "10101011"
The words that i send for deserialization are equal to "10101011" but in the outputs the result is "10111010".

The result is shifted, i assume i need to use the bitslip signal to barrel shift the result 3 times to get the right word.

But in that case i don't understand the use of CLKDIV it was suppose to be useful to determinate the beggininng and the end of the words, it doesn't seem to be the case.

And when i will use an ADC and try to deserialize the bitstream how can i know how many bitslips will be required as i don't know the content of the words sent by the ADC?

Thank you for your help


texts:
I would like to confirm my understanding.

Suppose I want to have two battery-powered MCUs inside an (unmanned) aircraft communicate with each other via RS-485. If those MCUs are powered from the same battery, or if their grounds are connected, both MCUs should be able to communicate since they are both on (nearly?) the same ground potential. This should especially hold true, when the aircraft is small and interconnecting ground-lines are short and low-impedance. Correct?

Now, suppose one MCU is powered by a separate battery with no ground connection to the others. In my understanding the different between the two battery grounds is arbitrary - could be some mV (in which case communication will be possible) - or much more (in which case the RS-485 transceivers break). Correct?

Provided above points are correct, I figure that I either need an:

isolated RS-485 transceiver on the separate node with the 'outward' ground tied to the ground of the remaining MCUs. However, I then also need to power the outward interface either with an isolated DC/DC converter or from the other nodes.
isolated RS-485 transceivers on all nodes, powered by local isolated DC/DC converters
RS-485 transceiver with high common-mode range like LTC2863

I'm more inclined towards the last option due to the lower part count and complexity. Yet, I'm also interested in other suggestions.

Curiously, while there are many non-isolated DC/DC modules available in any form and power, I've yet to find a small, low-profile isolated DC/DC regulator of ~100mA output current. Can someone suggest a suitable part?

Clarification I'm looking for a small footprint (< 10mm x 10mm), low-profile (<2.5mm) part. All those 5W bricks are way too large for my purpose, considering that the transceivers require <100mA of current. Note that I've no regulatory requirements since we are not dealing with high voltages. Isolation is only needed to protect some components from harm. Therefore we really don't need too large packages that - as I understand - are mostly there to achieve enough distance between isolated pins.


texts: Can I use piezo plate instead of electret mic?

texts:
I am doing a project by following the steps mentioned here.

It provides me the following circuit:

Now, in place of the electret mic can I use a piezo plate?

I need to use the same IC, i.e. LM358.

Kindly provide reasons for your answer.


texts:
I have 3 ICs in my circuit that have active-low reset signals.
By pressing a tactile button I would like to reset all 3 of them.

two of them operates with 3.3V and one of them operates with 1.8V.

How can I achieve this?
Should I put for each RESET signal a pull-up resistor connected to the desired VDD?

Should I consider a simple-reset supervisor IC?

Thank you very much.


texts: Does it matter the order of amplification and rms squaring?

texts: If in a circuit a signal is first amplified and then its rms value is found, would we get the same result if first the signal is rms found and then amplified?


texts: Obtaining O-Scope signals in a AC/DC supply - grounding issues

texts:
I need to check waveforms in the power supply from this design reference by Texas Instruments.

I essentially built the supply, but it is not operating correctly - ie, no output current, but it has around 5,17V at the output.

I've been reading the document back and forth and somewhere it says, that on startup, should everything be operational, one should see a quick 3 pulse signal at the DRV pin - soft-start.

I want to check that out so that I try to figure out what is wrong with my supply.

Now comes the scary part: I can't figure out how to connect the O-scope to my circuit, as I can't figure out were to ground the O-scope's alligator lead(s). Plus, should I need to look at both the primary and secondary in the O-scope at the same time, how should I connect it to my circuit? Would I need to ground alligators from different probes in different places?

The schematic for the circuit uses the notation for ACGND (triangle) in the primary and GND (horizontal lines) in the secondary.

I haven't tried anything yet, because I've been reading around on how to safely use the O-scope (because it's not mine) and I'm feeling scared about blowing it up (or even myself! :)

Any thoughts?

Btw, this is the O-Scope: http://www.hameg.com/710.0.html?L=0

EDIT:
I mistook the link for the design reference and posted the wrong link. The supply I'm working with is actually a 10W (5V@2A max) supply. With @Cornelius' help I validated that the supply is working to some extent. When connected to a LED+resistor load, the supply lights up the LED, so at least 30mA are going through it. I also tried a 4.8 Vdc motor as the load, but I didn't know the rated power for it and it didn't work - after this I realized it was a 35W rated DC motor, which explains its failure to operate.

Right now I'm trying to obtain some DC readings with a multimeter in order to validate the readings I'm obtaining rather than checking out the waveform of the PWM signal at the MOSFET's gate. I'll try to contact TI's FAE to get some more info regarding this subject.

As for the method regarding the O-scope operation, it seems that I need one of two solutions:

either a 1:1 isolated transformer in order to isolate the ACGND and the GND
a differential probe for the O-scope.

Still, I'm having trouble understanding the reasons behind these options, so any insight might come in handy.


texts: How to make sense of the math behind differential opamp

texts:
My first question here!
So, I'm designing a simple fully differential amplifier. The final target will be to implement a low pass filter (but I'm not there yet). Although all seems perfectly fine in my simulation, I have some troubles with the math issue as you'll see below!

So, this amp has a differential gain of 2.35 V/V, which is ~7dB. Each branch (positive and negative outputs) offers a gain of 1.175. So far so good.
Now, when I do AC analysis (as shown in the graph), I get a rather flat gain of ~1.32dB (on the zone of interest). So far so good, since 1.32dB = 1.175 V/V.
Now, my math question comes in: How do I derive the differential gain of 7dB from the individual gain on each + and - branch?
I'm not really interested in all the math behind it, but since I want to interpret the AC response of my filter, I'll find a way to make sense of the plots I'm getting.
EDIT:
I have added a voltmeter to my simulation to be able to plot the difference, and sure enough, the gain is ~7dB, so it's definitely just a math question. It may be obvious, but I'm not able to figure it out!


texts: Using 433 MHz Tx/Rx without encoders/decoders

texts:
I want to use Tx & Rx Modules of 433 MHz standard modules you find everywhere.

I just want Tx module powered up and Rx module should respond (probably key press) on Tx module. I don't have any encoded data to send (by using HT12D, HT12E encoder/decoders).

Any simple solution with few components to use these modules without encoder/decoder support will be sufficient.


texts: Why does SHT21 sensor generate pulses on SDA line?

texts:
I am interfacing a MSP432 microcontroller with a SHT21 sensor. The I2C bus contains only these two devices and has 2k2 pull-ups.

The problem is that the sensor continually generates impulses on SDA line and because of this I cannot communicate correctly with the sensor. I've tried changing the sensor with another one, but it behaves the same.

This is how the pulses look like:

The datasheet and Internet forums do not say anything about this behavior. It is weird that both sensors behaved the same. When I remove the sensor, the SDA line is OK.

The sensor is not PWM type because the frequency is much higher than that described in the datasheet.

Has anybody encountered this? Could it be a hardware-related problem?


texts:
I'm using LM2596 for the power supply of SIM800 GSM module.
LM2596 is stepping down voltage to 3.8V. I have attached schematic diagram of it.

It is working good if I use 12V-5A SMPS as power source. But when I use other supply like 24V-2A, LM2596 burns out while SIM800 is registering on network(during this time SIM800 draws more current). I'm not getting why it is burning out.


texts: How can I implement current source and turn theoretical schematic into schematic with real components?

texts:
I would like to know how can I build some circuit with current source drawn in the "middle of everything" on some theoretical schematic of amplifier or some other circuit.
For example I have choosen this simple schematic (Collpits generator):

Is this current source literally a source and provides energy, or this is just current limiter which I can build with LM117/LM317 and resistor like this:

EDIT:
Another example (current source in "in the middle of everything" - LT3083 regulator block diagram):

I realize that theoretical schematic contains ideal elements and I'm NOT asking about that. I want to know how to replace this with real components:


texts:
Does anybody have experience biasing and pulsing a microwave GaN HEMT?  I've just ordered a 10 Watt S-band transistor.  I know all about bias sequencing.  This application is pulsed.  I've read about pulsing the drain with a high side switch as well as pulsing by pinching the gate (Microsemi, Triquint, etc. white papers and PhD defences).

Has anyone tried either approaches.  In order of importance: (1) rise/fall time, (2) efficiency.  I'm concerned about undocumented effects of more than just series resistance with drain pulsing.

I would like real world experiences.


texts: How do I choose an optocoupler for (19200 baud) serial communication between Arduino and RS422 transceiver?

texts:
I wish to read data from a Fronius solar inverter via the Fronius RS-422 Com Card option (part# 4,240,001).
1000 meter cabling length
The Fronius communication uses a 5-wire RS 422 interface (`RX-`, `RX+`, `TX-`, `TX+`, `GND`). It is based on point-to-point connections which must form a **ring**. It has a selectable baud rate of 2400, 4800, 9600, 14400 or 19200. Fronius documentation specifies a total cable length should not exceed 1000 meters when using termination plugs (`RX+` to `TX+` and `RX-` to `TX-`) or 1000 meters between each device when creating a ring formation without termination plugs.

Galvanic isolation recommendation
Fronius also recommends to galvanically isolate the RS 422
interface of the inverter from external interfaces. This increases the security of the overall system. This is why I am puzzling with choosing an optocoupler.
SP490 line driver
I choose the SP490 as line driver. The driver pin has a specified maximum "input current" of ±10 µA. The IC features a maximum data rate of 10 Mbps (which might be overkill for 19200 baud).
Datasheets
I know that optocoupler datasheets do often try to fool not so knowledgeable readers by supplying Rl values of 100 Ohm, which in real world designs are never used. I also know that at lower input currents the output responds (much) slower.
Bit timing
I know that there is a signal rise and fall time involved in the start and end of the bit time. The EIA RS-422 specification writes that the driver output rise time should max be 10% of the bit width (at condition Rt = 100 Ω). I also know that the bit time can be calculated by dividing 1 second by the baud rate:

.... baud ... bit time ... max rise time
1 ÷ 2400 = 416 µs ⟶ 41,6 µs
1 ÷ 4800 = 208 µs ⟶ 20,8 µs
1 ÷ 9600 = 104 µs ⟶ 10,4 µs
1 ÷ 14400 = 69 µs ⟶  6,9 µs
1 ÷ 19200 = 52 µs ⟶  5,2 µs

source: http://www.vishay.com/docs/49444/sg2129.pdf, page #2.
I also have read about capacitive effect in cabling that affect the transmission rise and fall times.
But which percentage of the signal time is acceptable as fall time, and/or which time is the maximum for total rise and fall time?
Optocoupler output current
I also do know that optocouplers are not equal in the aspect of which amount of current will flow on the output side. The relation of input versus output current seems device (CTR), input current, voltage, temperature and age dependent.
Proposed circuit
I do wish to use the Exar SP490E full duplex RS422 transceiver IC (maximum "input current" ±10 µA). For the microcontroller side I do wish to i/o the signal on a digital input/output of an Arduino Uno. The optocouplers are used to protect the Arduino, not the transceiver. Therefore optocouplers are located between Arduino and the SP490E, not between the line driver and the RS 422 signal. One side of the optocouplers and the SP490E will have isolated 5V supply.
Question
Which datasheet information to look for to make a good choice and archieve minimal current flow (low power)?

Fronius 3th party datalogger cabling documentation


texts: Object identification options, reliability and cost...recommendation

texts:
I'm trying to evaluate options of identifying real world objects. We are creating a product that need to write data and read data based on the object. This would be a consumer product.

Some researched options are:

RFID
barcode (loses some of it's magic if you have to scan a visual bar code)
iButtons by Dallas Semiconductor (I think these are pretty costly)

What are some other ones that are out there?

computer vision is way out there in terms of difficulty and cost

The scanning/identification would be up close...a few centimeters.

UPDATED DETAILS

This would be a consumer handheld device. The objects would be common household objects that can be identified with whatever technology we use...RFID, QR Code, etc. At this point I'm not ruling out touch, but iButtons are expensive.

The MSRP of the reader with some user applied tags should be ~$30 (so if we're using QR codes, we could have them printout QR stickers...if we're using RFID, then the cost of the RFID stickers would need to be considered)

It should be fairly accurate b/c we want a good user experience. We don't the user to be frustrated.


texts: I have a problem with understanding the attached ALU (6 control bits)

texts:
I have an Arithmetic Logic Unit, as shown below (I also included a CircuitJS simulation of it, so it will be much easier to understand the inner working of said ALU).

‘x’ and ‘y’ are the 4-bit input nibbles (operands). (The ALU accepts Natural Binary Code as well as U2 negative numbers [Unfortunately I don’t know why, but “it just works…” – my lecturer has not explained it thoroughly, probably because of the lack of time] ); ‘zx’ basically zeroes the entire ‘x’ nibble regardless of what is currently written to it; ‘nx’ negates the ‘x’ nibble (it, however, may be possible to firstly zero the ‘x’ nibble and then negate it to achieve a nibble consisting of ones – 1111).

The same logic applies to ‘zy’ and ‘ny’. The ‘f’ input controls the operation done by the ALU. If ‘f’ is equal to 0, the ALU performs a logical AND operation. If, however, it is equal to 1, then the ALU performs an arithmetical sum operation (there is a full adder inside the ALU). The ‘no’ input simply negates the output of the ALU.

Below I attached an example table consisting of input values and expected results. Now my question is: How can I work out the combination of the inputs ‘zx’, ‘nx’, ‘zy’, ‘ny’, ‘f’ and ‘no’ that will give me these results: -x, x-y, y-x, x+1, y+1? The answers are shown below, in the after-mentioned table.

I understand the logic behind the other combinations, they are pretty trivial to work out (besides the ‘x OR y’, that requires the De’Morgan’s theorem), but I have no idea, how one could work out the required combinations for the mentioned results. I checked the combinations shown in the attached table, and they all seem to work, but I cannot imagine that someone plugged random combinations, observed the output and, using his/her mind worked out what they must have done… It’s pretty hard to wrap my head around this stuff. Thanks for every, even little bit of help :).

The ALU in-question:

The table with inputs and expected outputs:

Here is the link to a paste that includes the code, which can be used in CircuitJS simulator: ALU simulation code

You can test the ALU by yourself by going to this website: CircuitJS, pressing File → Import From Text... and pasting the copied code.


texts: Z(out) for the BJT emitter-follower configuration

texts:
I have a slight problem trying to understand how to determine the output impedance of a emitter-follower configuration using the re model for small signal analysis. I also added the contribution of \$r_o\$.

From my understanding of circuit theory and analysis theorems, to determine the output impedance, I have to set the input \$V_i = 0\text{ V}\$ (\$R_b\$ has no influence now) and keep \$V_o\$ at a constant value (please correct me if I am wrong, I mostly study on my own without having someone to give me feedback on my understanding). I keep the controlled current source (for there still is a current going though the base node), \$\beta r_e\$, \$r_o\$ and \$R_e\$.

My first instinct would be to calculate $$Zo = \beta r_e \parallel r_o \parallel R_e$$
But I find in the book that $$Zo = \frac{\beta r_e}{\beta + 1} \parallel r_o \parallel R_e$$

What exactly is it that I don't understand?


texts:
I'm designing my first circuit with an ATmega 32u4 processor. Since I read about the BOOTRST and HWBE fuses I'm confused about the programming of the chip.

If

I use a brand new, untouched processor with factory default settings,
my only access point to the built device are the four USB lines (Vcc,D-,D+,GND),
I have access neither to the RESET pin nor to the HWB pin

then will it be possible to upload a program to the device with the help of the built in USB boot loader?


texts: Help understanding combined High/Low Pass filter circuit

texts:
I am a newbie and trying to understand the operation of this White Noise Coloration Filter - I have contacted the original author but at time of writing have bot received a response.
The circuit is as follows (I have retained nomenclature from original post for clarity)
EDIT: Error in original diagram, RV1 should be 10K not 100R

I can't figure out how the bottom half of this is a high pass filter (unless the resistor to ground is R5 and RV1). I can sort of see how the top half is a low pass filter but cant understand how/why the potentiometer and the first 4k7 resistors function.
The OP says

R4/C4/R5 and R6/C5 form low- and high-pass passive filters respectively. The pot pans between them by proportionally grounding one, or the other, or somewhere in between

I've tried to look at this by splitting it into two halves but not sure if that is valid and have made limited progress in my comprehension.
Any pointers on how to go about decomposing this to understand how it works would be gratefully appreciated


texts: Eagle: automatic via creation to different layers?

texts:
I am designing my first PCB using the free edition of Eagle.  This is a simple board, with power and signal lines on the top layer, and ground on the bottom layer.

My question: I have components on the top layer, some which have pins to ground (the ground net is called GND).  When I create the polygon on the bottom layer, and name it GND, all the airwires for GND connections disappear.  Does this mean Eagle has implicitly created the vias for me from the top layer to the bottom layer?

Here is a detail of the schematic, and as you can see, some pins go to ground:

Here is a picture of the same area of the board.  Blue is the bottom layer, i.e. the ground plane (or polygon named GND).  Red is the top layer (power and signals).

For those pins that go to ground, I haven't done anything explicitly.  Will those solder pads automatically have vias to the ground plane?


texts: A question about a current sensing circuit

texts:
While i was searching about accurate circuits to sense currents in high side, i found a very interesting circuit proposed by linear technoloy, but i didn't understand the  role of the NMOS at the output.

What i understood is that the current that flows on the Nmos and the output resistor
is : Vshunt/Rin tthen the output voltage is : Vshunt*Rout/Rin.

The problem is that i thought that the op amp wasn't operating in the linear zone, but when i simulate it i found that the it is operating in the linear zone.

The second problem is that the voltage on the NMOS (VDS) is the same as the common mode and i thought that it would be 0V ( since the current flows into it )

So my question is how this circuit functions generaly ?
Thank you for your help.


texts: When a power supply has multiple stated output parameters, are those discrete output settings or some possible settings along a continuum?

texts:
Let's take my 30W USB-C Apple power supply as an example: https://www.apple.com/shop/product/MR2A2LL/A/30w-usb-c-power-adapter.
Printed on it are 4 outputs:

20V / 1.5A
15V / 2A
9V / 3A
5V / 3A

Are these fundamentally discrete charging profiles between which the power supply can switch or is its output a continuous spectrum of voltage and amperage determined by the device drawing the power and the printed outputs are examples of possible output profiles?


texts:
Where is the best to place resistor in full wave rectifier circuit?
What is the difference in usage of the resistors in these two
circuits?

(values are not precise)

Three side questions:

what about removing one resistor and replacing the left one with bigger value in the first circuit?
is there any disadvantage of relatively big capacitance of the cap (instead of size) or the wave will be just smoother?
when there is the DC fan, do you recommend any snubber or flyback diode in this circuit?

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

Thank you!


texts: Thickness of Depletion region, transistor

texts: I came across a doubt regarding thickness of Depletion region in different regions of transistor while reading an online article. It says that the thickness of Depletion region in collector is more than base, but i think thickness in base should be more because it is lightly doped, am I correct?


texts: I have a little difficulty on my project. Can I calculate Reset Time (Ti) if I just had the value of P gain, I gain, D gain, Process Variable, and Manipulated Variable? Is there any reference about this task?


texts: Is an RF connector required for an NFC Tag?

texts:
I have an NFC tag application that uses an external antenna. The antenna itself has not been properly selected just yet, but my question is with regards to connecting the external antenna to the NFC tag.
NFC Tag is the NXP I2C Plus chip - https://www.nxp.com/docs/en/data-sheet/NT3H2111_2211.pdf
A high-level overview diagram is shown below.

The antenna ports appear to be balanced but I don't know for sure.
Possible options:
Have 2 pads where I can solder some wire to and run up to the external antenna.

Twisted pair vs not?

Add a u.fl connector or similar RF connector and use that to connect to the external antenna.

Would I need a balun or can I connect it straight?


texts: Power 12v DC actuator when 120v @15 amp saw is switched on

texts:
Problem: I want to use a 12v DC actuator to close a blast gate on my dust collecting system when I turn on a 120v 15 amp saw. The actuator can only run for a few seconds until the 6" stroke is reached. If there is a way to close the actuator when the saw is turned off that would be a bonus.  Otherwise I will have to have 2 sets of these controls; one to open and one to close when not needed.
I originally thought I could use a current switch to sense the current at the saw switch. I couldn't find the output info of the current switch to know where to go from there. I then thought I could use a time delay interval relay, but am not finding relays where the input is 120v @15 amp and output is 12v DC. I find them the other way though. I have looked at contactors which seem to be 120v in 120v out and I would lose the time delay function. I believe there has to be a way to do this with minimal devices. I would like to do this with off the shelf devices where I don't have to built a circuit board. Lastly, I would like to do this for $50 or less or so.


texts: Why connect a 35 V decoupling capacitor to stepper motor driver when using only a 9 V DC supply?

texts:
This circuit uses two hybrid stepper motors each connected to a stepper motor driver A4988 and powered by 9 V DC supply to the drivers' MV pins. Both motor drivers have their VDD (logic supply) pins connected to the 5 V output pin from an Arduino UNO R3.The hybrid stepper motor used has a rated current (Amps/Phase): 1.68 and a recommended voltage: 12 - 24 V.

This is the circuit schematic relating to the stepper motors and drivers:

Why is there a 35 V decoupling capacitor? I understand the reasons for using a decoupling capacitor but why this particular value of 35 V? The power supplied to each A4988 motor driver to drive the stepper motors is only 9 V DC. So, why not use a 10 V decoupling capacitor? Or a 50 V for that matter? I did some research and found on some posts that some people are saying that it is a good rule of thumb to use a decoupling capacitor twice the value of the input voltage, to protect the motor driver against voltage spikes. If that's true, then the correct decoupling capacitor would be 9 V x 2 = 18 V? Actually, i'm not sure but maybe there is a mistake on that schematic if it's using 35 V. Any suggestion or advice would be highly appreciated.


texts:
I am running a short (2 m) CAN bus with about 20 nodes. 1 Mbit/s speed, PIC 18F2580s and 18F4580s with MCP2551 transceivers, 10 MHz (with PLL to 40 MHz) crystal oscillators. Both ends are terminated at 120 ohms. Sample point is at 70%.

Nodes are in three groups, each powered from a separate isolated power supply, but the grounds are all commoned along the bus.

I get quite a number of message errors, framing, bit stuffing. Looking at CANH and CANL on an oscilloscope, everything looks beautiful. No ringing, no reflections, and the timing correct. Measuring the oscillators with an accurate frequency measurer shows only a tiny variation.

So far, the only way I have been able to reduce the number of message errors is to beef up the ground wire along the bus until I get the GND difference below about 150 mV. The further above that I go, the more errors I get.

Why? According to the MCP2551 datasheet, they should be able to cope with GND differences up to 7 V!

Am I misunderstanding something?


texts: How to connect the Peltier module to TEC W1209?

texts:
I am trying to control my Peltier module using the W1209 TEC. I set the P0 to H, so that it should provide voltage to my Peltier module until the temperature reaches the set temp. The LED turns on indicating that the load should be turned on, but when I checked there was no voltage between pins K1 and K0, or between either of them and the GND.

I connected 12 VDC supply to pin +12V and GND. I tried different ways to connect my load. I connected it between pins K0 and K1, I also tried using a jumper cable between pins K1 and +12V with the Peltier module attached to K1 and K0, and I also tried the positive of battery being connected to K1 and +12V, its negative connected to ground, and the Peltier module connected to K0 and GND. None of them worked.

Does anyone have any ideas as to what I might be doing wrong? The Peltier module works when connected directly to power supply.


texts: Two of the pins on the l293d are labeled VS and VSS. Apparently they are both power. Here it shows VS being supplied with 12V, while vss is receiving 5V. Here, it shows both receiving 6V from the same source of 4AAs. What are each of these for? Also, in the second link, he shows wiring to the ground on the arduino, why is that? Wouldn't he be able to do the same by wiring to the negative terminals on the batteries?


texts: How to share a digital signal between circuits?

texts:
Please see this :

The Task
I'm trying to create a single module which can safely share a single digital signal.
The idea is that each (identical) module can monitor the status of the signal, and can raise it independently.
For example:
Module one notes that the signal is low (at RX1) and based on some logic decides to indicate to all the other modules that the signal should be high.
So module one raises the signal by applying a 9v pulse to TX1.
Module 2 notices the rising edge of the signal (at RX2) and carries out some operation.
At some point in the future, module N may decide to pulse TXRX etc.
The shared digital signal must not share a ground with any of the modules (modules are audio, wish to avoid ground loops), hence the optoisolators.
QUESTIONS
Is there an accepted pattern for this type of operation?
Perhaps some jellybean IC that I'm unaware of? Possibly some sort of optical system?
What would happen here if several modules tried to raise TXRX at the same time, and how can I safeguard against that (resistors or diodes in some way?)
CONSIDERATION
This design suffers from a few problems in that the LED in a PC817 ideal requires 20ma but may operate at 10ma.
The BJT in the 817 can only supply ~50ma.
This would limit the number of modules I can have in the chain.
I could use an external high power transistor after the 817 transmit but PCB space is limited.
Ideally my solution would require the TXRX bus line to carry minimal current.
I know the old RS485 can handle 32 devices, but that is not isolated.
What sort of connector should I use for these three wires?
I thought about some sort of standard barrel jack, but I don't want any accidents to happen with people
just pushing a 9v DC jack into it.


texts: MicroSim PSPICE - Possible for a component to take on the value of another?

texts:
In MicroSim PSPICE, is there a way I can assign a value to a component such that it is a multiple of another component?
example:  Resistor A = 10K.  I want resistor B to = 20K, but I want to specify it as B=2*A.  This way, I can change A and B will follow.
Thanks.


texts: Transistors - relation between impedance and gain

texts:
In an n-p-n transistor connected in common emitter configuration, I have drawn a graph of the input and output characteristics. Using these two graphs, it is easy to find the input and output impedance - using the slope.
However, I do not know how to relate this to the voltage and current gain. Is there a formula to do so?


texts: Configuring STM32 timer as frequency counter

texts:
I am trying to configuring one of the timer inputs on a STM32 to behave as a frequency counter for an external signal. The STM32 datasheet describes a "input capture mode" in section 17.3.6 (page 342)

My understanding of this mode is that whenever an input comes in on the selected TIMx_CHx input, the processor captures the value of a free-running internal counter. Frequency can then be calculated using the counter value and the frequency of the internal counter.

I am trying to enable this in CubeMX and am having difficulties correlating the datasheet explanation to the settings in CubeMX. This is what I currently have configured. Is is this correct?

Also, can I run multiple independent inputs into separate channels on the same timer to capture timing simultaneously?


texts: I know in IGBTs while operating, parameters Ic (collector current) and Vce (collector-emitter voltage) are Tj (junction temperature) and Vge (gate-emitter voltage) dependent. Is there anything else that Ic and Vce are dependent on them? Is there any formula for these two parameters based on Tj, Vge, ...?


texts: Measuring the electrical performance of a low pass filter

texts:
I built a portion of a loudspeaker crossover circuit. Specifically, a simple 1-st order RC low pass filter. The filter is designed as shown on this page here.

The Resistor is 15.5 Ohms
The capacitor is 15 uF.
This makes the cutoff frequency 684 Hz.

I wanted to test the performance of this low pass filter. So I built it on a breadboard and hooked it up to an amplifier. Instead of using an actual speaker/driver I placed a 7.5 Ohm resistor across the filter outputs. Then I used up an oscilloscope to measure the voltage (Vrms, called Vk on my scope for some reason) at the filter input on channel 1, and measure the voltage at the filter output on channel 2.

I repeated this measurement for each octave of the filter frequency:
21, 42, 86, 171, 342, 684, 1368, 2700, 5470, 10900.

Then I calculated the attenuation (in dB) due to the crossover like so:
dB = 20*log(Vout/Vin)

I then calculate the dB/octave attenuation by taking the dB difference of the current and previous octave. This tells us the slope of the attenuation.

here are my questions:

Is my general procedure correct? Is this a valid way to measure the performance of the low pass filter? Or am I messing something up with the math or the theory?
At 21 Hz we are 5 octaves ahead of the Fc. I would expect almost 0 attenuation yet we are already down 9.6 dB. It looks like a constant 9.6 dB offset. Why is this?
The Fc is supposed to be 684... According to the link above the Fc of this filter is given by:

Fc = 1 / (2*PIRC)
Fc = 1 / (2*3.1415*15.5*0.000015)
Fc = 684 Hz

So we expect the signal to be down 3 dB at 684 Hz. Yet, looking at the data/graph we are only down 0.3 dB at 684 Hz. It is not until 2 full octaves later that we reach approximately 3 dB down. Again, what is wrong here? :) This leads into my final question.
According to theory the slope of the attenuation should be 6 dB/octave. Yet the slope, as seen in my data, starts at 1.2 dB/octave and only reaches 5.4 dB/octave at 10.9 Khz. It should not take 4 octaves to reach a 6 dB/octave slope, and it is not even there yet.


texts: Mitigating noise pickup from contactor turn off

texts:
I am working on an industrial control system that uses a microprocessor to control a bank of 6 contactors.  The contactors have 120V coils.  When all of the contactors turn OFF at the same time, they generate a huge burst of noise which occasionally gets picked up at some GPIO inputs to the MCU.  The inputs are normally high and are set to generate negative edge interrupts.

The inputs are driven by LM339 comparators and it looks like the noise is getting induced into the net that connects the comparator output to the MCU input.  I say it looks like this because lifting the pins on the comparator and MCU and running the net on a twisted pair gets rid of the false triggers.  Also, there are several comparator to MCU connections and the longer nets have more noise pickup issues.  The longest net is about 6" long and the PCB is about 2 feet from the contactors, but about 6" from the mains input.  Adding suppressors to the contactor coils reduced but did not eliminate the noise issues.

While I could just use RC filtering or firmware filtering, I would like to reduce the noise pickup as much as possible first.

My question is what are the best practices for PCB routing that would be similar to a twisted pair as far as reducing pickup from the noise generated when the contactors turn off?


texts:
I had previously posted a question regarding modeling the transfer function of a diode rectifier but it sounds like this not possible.

So I have done some reading on "Average Value Modeling" and it seems like a potentially promising method to model the full bridge rectifier.  Does anyone here have experience working in this area or is familiar with this concept?


texts:
Working on a project where I am wanting to monitor water meter via a magnetic sensor which will detect the spinning magnetic disc. It's very similar to the project this person has accomplished:

http://www.edcheung.com/automa/water.htm

My issue is that my water meter is about 200 feet towards the street. So my plan would be to put the sensor and op-amp in the meter "pit" and then send the pulses back to the pulse counter back at the house. This would be done for two meters (one irrigation and one normal potable water).

My question is will the voltage drop of the 5v output of the op-amp be enough after 200ft of 18AWG irrigation cable which I plan to use?

My plan was to send send 12V down to the meter and use a 7805 to power things down there, or again will the 5V over 200ft be OK?

What about lightening protection? How can I minimize those issues? Would some optoisolator make sense or would that really not offer any protection?

I'm open to other suggestions including the use of a micro controller at the meter "pit", but I think the op-amp is the simplest solution.

In Ed's example he has a variable resistor for the 2V reference, I might want to use some reference IC for that since mine will be exposed to more environmental conditions.

EDIT:

What about some other solutions? Wireless transmitting of the pulse? This way only need to send power down to the meter?

What about some type of fiber solution? The electronics in the meter box pulsing a light?

Given that it seems that the voltage drop will not be a big concern, my biggest concern now is the protection of the devices. I would plan to hook this up to a 1-wire Counter chip and then have a 1-wire <-> Ethernet gateway on the network. My concern is exposing the network and all other equipment to lightning damage via the 1-wire network which will consist of 200ft to one meter, and then 250ft to another meter, all in the ground in Florida.

What about using Shielded Cat5e cable?


texts:
In the question above, are we deriving based on the equation which uses resistors, shown below? Why is it inverted, i.e. $$C_f$$ is below instead of above?

If so, why is $$C_p$$ not factored in the equation? What would the equation be if inductors $$L_f$$ and $$L_s$$ replace the resistors in the diagram above? Would the equation be more similar to the resistor equation, i.e. $$V_\text{out}=V_\text{in}\times(−\frac{L_f}{L_s})$$?
, or the inverted capacitor version, $$V_\text{out}=V_\text{in}\times(−\frac{L_s}{L_f})$$?


texts: Why is my amplifiers frequency response unexpected?

texts:
I am experimenting with moderately high frequency circuits, so decided to analyze, build and test an amplifier. This is the circuit:

Q1 is a CE amplifier, Q2 is Emitter follower to buffer the load. R2-R4 bias the transistors and R4 provides negative feedback. Due to negative feedback, the input impedance of this amplifier is quite low and a strong function of gain. Nonetheless, the 50ohm source is terminated by a 50ohm R6.RLOAD is set to 50.

The transistors in use are the BC547Bs, Ft = 300Mhz, Cbe = 18pf, Cbc = 4pf from the datasheet.

The goal is to build an amplifier that has a reasonably flat response from 1 MHz to about 40 MHz.

Here is the small signal circuit I think applies here and my calculations:

I calculated a gain of about 30 with the Load present and SPICE backs me up. I calculated the -3dB point and that came to about 120 MHz, due to the Miller Impedance of the feedback network, in parallel with R1. SPICE confirms this calculation also.

Here is the circuit all built up:

Here is how I probed everything, the probes are x10, and the scope is a 100 MHz Rigol.

The results are quite perplexing and I’m trying to find out why the theory is not matching with the circuit. At 1 MHz, the gain I measure is about 25, and a theoretical gain of about 30. This isn’t too bad. The trouble is the frequency response is very unexpected. The gain starts to roll off sharply after about 3 MHz, and the -3dB registers at about 16 MHz.

The roll off is at about 15% of the frequency calculated! Possible explanations I have are:

The transistors are not suitable: The transistors are standard BC547s with a transition frequency of about 300 MHz. I have taken into account the junction capacitances so I don’t see why they roll off would happen so early.

The resistors I have used are not suited for high frequency operation: I am not sure about this one, I am using carbon film resistors which should have reasonable low inductances for reliable sub 100 MHz operation (?)

Measurement setup is not correct: This might be possible, as I really don’t have experience measuring high frequency circuits properly. Both input and output measurements are taken with an x10 probe with the standard ground clip. The output is terminated at 50 ohms right at the output. I tried a direct BNC cable to measure the output instead of a probe, but that made things worse in terms of gain loss and distortion. I tried the springy ground tip for the probes, which made no difference.

EDIT:
The physical circuit does not show a capacitor C1, this is because i was trying to eliminate a possible bad output capacitor. The results outlined above are WITH a capacitor C1 in place.

EDIT 2:
After a lot of thought provoking input, i believe i am alot closer to understanding why i am "missing" gain. Ali Chen aptly pointed out the presence of power lead inductance, and after adding that to the sim model, it has bought a smile to my face. Consider the 2 frequency response of gain. The blue trace is with lead inductance, the green without. Most recently i measured a gain of 5 at 40Mhz and the model predicts a gain of about 8 when lead inductance is taken into account!


texts: The Basys 3 advertises "internal clock speeds exceeding 450 MHz," but the default clock pin is connected to a 100MHz oscillator. Is it possible to configure the Basys 3 to use a 450MHz clock?


texts: Since memristors are fundamental two-terminal, passive elements, is memristance a missing contributor that should now be included in distributed element calculations and parasitic extraction?


texts: Dual channel DAC - Combined output mode - Possible downsides

texts:
Can a Dual channel DAC be operated with both output channels tied together to achieve a higher output current?

What would be possible downsides?

Background:

I require an programmable voltage source with up to 25 mA,
and would have liked to do so with minimum required parts. :-)

I have an MCP4822 dual channel DAC with inbuilt op amps for both channels. Each channel typically has a "Short Circuit Current" of 15 mA (25mA is the absolute max. rating for the each output)
http://ww1.microchip.com/downloads/en/devicedoc/20002249b.pdf

I probably could use the Latch DAC Input (LDAC) to keep both outputs in sync.


texts: I know it's used for shielding against magnetic fields but for my homework, it's asking for a diagram and I can't seem to find where the mu-metal is actually used on the transformer


texts: Why don't on board communications like I2C, SPI, etc. have error checking in general?

texts:
Some error checking methods like parity check, checksum, CRC, etc. are used for wired/wireless communications. However, most of the ICs with interfaces like I2C, SPI, etc. don't use an error checking method.

Let's search for "i2c i/o expander" and open a random datasheet. For example, let's consider PCF8574 from TI which is a 8-bit I/O expander. If a bit corresponding to output register is flipped during I2C transmission, the IC will drive the corresponding pin to an undesired level. Why most of these kind of ICs don't have any error checking mechanism at all? My assumption is that even if communication is between ICs, all signals are noisy. Although the probability will be quite low, noise can cause a bit flip.

May this be the reason?: None of error checking mechanism gurantees a completely error free communication. They can only help us to reduce the probability of error. It is obvious that probability of bit error for long range communication is higher than on board communication. Maybe bit error probability for on board communication is in a acceptable range even without any error checking mechanism.

What do you think?


texts: Does current draw of separate pins of a microcontroller affect each other?

texts:
I have a microcontroller with a IR LED and transistor, as well as a RGB LED. If my battery microcontroller is turning on its RGB LED, connecting to cellular, will this mean less current is going to my IR LED while these processes are occurring, even if they are powered by seperate pins?

The microcontroller I am using is the particle electron.


texts: Mid- and lowband frequency response of CE

texts:
I'd like to derive an expression for the small signal voltage gain \$A(s)=V_o/V_{sig}\$ that applies in the mid- and low frequency bands.
I know that for a CE the voltage gain would be:

\$A_v = -g_mR_c/(1+g_mR_E)\$

Does that mean that \$A(s)\$ could easily be found by simply substituting \$R_E=R_e+1/sC_E\$?


texts: I'm using proteus to simulate some schematics, but wheneverI use the dips it doesn't work, I already tried by replacing the dipsw with 3 voltage sources but I need to know how to deal with this kind of problems (in the second image, when I change the position of a switch, the output doesn't change) I also tried by using anoter kind of source and still doesn't work, is there any solution to this problem? thanks


texts:
The picture shows a detail of schematic diagram of the LM555.

I presume the horizontal line is the base, but I'm not sure I understand how the transistor works. What is the effect of connecting base with collector, and what's with the second collector? Is it a current mirror of the other collector?


texts:
I have a motor with a blue, yellow, black, and orangish wire coming out of it and I'm trying to figure out how that should be connected to power based on the wiring diagram on the side of this motor.

Could you point me towards a resource that would help me understand this wiring diagram? Thank you

Edit: I took the motor apart a bit more and have some additional information.

Light blue is connected to the centrifugal switch that turns off the starter winding
Oranges goes though the thermal protection then turns red and goes into the windings
Black turns into blue that goes into the windings
Yellow goes into the windings

Based on this information I decided to connect blue, yellow, and my neutral together and then orange, black, and hot together. This got the motor turning, but it sounded a little funny so I wanted to see if someone else came to a different conclusion from me. I also am attaching  another photo.


texts: Correct use of Flyback or Snubber diode across Motor or Transistor?

texts:
From seeing a few schematics where the flyback or snubber diode has been placed across the transistor C-E terminals (Right Configuration), instead of what I typically seen as the the flyback being placed across the coil terminals (Left Configuration).

Which of these are "correct"? Or does each have a separate purpose?

As a note, the diodes are normally listed as external 1N400x type diodes (on TIP120 Darlingtons), not the internal body diode of the BJT or Mosfet.

Final note, I have seen a few schematics that have both diodes, one across the coil and another across the CE terminals. I assume that one is just redundant without really affecting the circuit in that case, is that a wrong assumption?

simulate this circuit – Schematic created using CircuitLab

The answer to When/why would you use a Zener diode as a flywheel diode (on the coil of a relay)? touches on this slightly, by showing a regular Diode in the above left configuration, while showing a Zener Diode in the right configuration. It doesn't say that the opposite isn't true (or why) So as a second part, can a Zener work in the left configuration, and a regular diode in the right configuration? If so, how does it change how it operates?


texts: Resistive ribbon sensor multiple readings

texts:
I created a resistive ribbon sensor using a resistive strip as follows:

When making contact between A0 and the resistive ribbon (e.g. at the location of the red circle) using a bridge, I can successfully read out the location of this contact on the resistive ribbon strip.

So this all works, but now I want to detect the location of multiple of these bridges (more than 2) on the same resistive strip. For this I use multiple of these bridges. So my Idea is that every "bridge" makes contact with the same resistive strip and a unique analog pin. Essential here is that I want to use the same resisitve strip if possible. I'm not sure how to do this but this is probably not correct I guess?

I don't need all analog readings at the same time, so maybe some kind of multiplexing strategy over time could work as well?

EDIT:
My problem can indeed be seen as a potentiometer with multiple wipers (the red circles in my drawing). Since I do not only want to measure the voltage on the analog input but also want to extract the resistance (which represents the position of the "bridge"), I need to add a fixed resistor (R1) in the design (as seen in the first figure). What still remains unclear to me is how to wire everything up when I have multiple wipers on the same resistive strip (and thus multiple analog pins)? So how can I measure the locations of multiple wipers using a known (fixed) resistor?


texts: does anyone know what is typical life cycle of AD5246 i2c resistor? How many times MCU can write into his register? Any information is welcome


texts: How do I calculate the capacity of a capacitor using measurements of an experiment?

texts:
I build this circuit in an experiment

During the experiment I got these readings:

t (s)   0  10   20   30  40   50   60   70   80   90  100
U (V)   0 0,43 0,86 1,2 1,53 1,84 2,11 2,35 2,58 2,78 2,96

t (s) 110   120  130  140  150 160
U (V) 3,12 3,28 3,41 3,54 3,68 3,76

Can someone show me how to calculate the capacity of the capacitor c using these readings? The power supply is 5,34V.


texts: Unexpected Behavior of a MOSFET Two Stage Differential Op-Amp

texts: Trying to come-up with a basic default MOSFET-transistor amplifier simulation (for educational purposes). I don't get something. In the simulation below "out" is -1.84V while I expect something more like -0.5V. Also the output doesn't change when I sweep R_in. What am I doing wrong?


texts: how do i drive the h bridge to control a motor?

texts:
I am using the ZXMHC3F381N8 MOSFET H-Bridge to drive a motor forwards and backwards. I am using a PIC16F1946. The H bridge is connected to PORTE of the PIC. This is the code I am using to set up the port:

#define MOTOR_STOP      0b11000000
//setup PORTE
PORTE = 0x00 | MOTOR_STOP;
TRISE = 0x00;
ANSELE = 0x00;

So, if I am not mistaken, here is what I need to do turn the motor:

For forward motion: N1G = HIGH P2G = HIGH
For backward motion: N2G = HIGH P1G = HIGH
For stopping: P1G = P2G = HIGH


texts: How to connect RN-131 (wifi module) to RN-SRL-PRO3V-DGL (USB-to-TTLdongle)

texts:
I guess you might think that this question has been asked before, but what I need to ask is something very different.

I have RN-131 which is a wifi module from Roving Networks and also
 RN-SRL-PRO3V-DGL which is a USB to TTL dongle - datasheet here which connects to the wifi module through UART. The connections I made between the wifi module and the dongle are:

TX(dongle) ------ 100ohm resistor ------- RX(wifi module)

RX(dongle) ------ 100ohm resistor ------- TX(wifi module)

GND(dongle) --------------- GND(wifi module)
[here dashes mean wires]

Now I can communicate with the wifi module through TCP by putting the module into ADHOC module. Whatever the module receives over wifi is received by its UART and whatever is written to its UART is transmitted over wifi.

Now when I connect the module to the dongle and plug the dongle into USB port of my laptop, and I use telnet's serial port. Whatever I type on telnet is not displayed. Also to program the module using UART I have to use an escape code which is $ $ $ (i put spaces cauz then text changes). I see that when I type in $$$ into telnet I dont get CMD back from the module which its supposed to when it enteres command mode. Also I receive all sort of rubbish from the module when the USB is plugged in. THere are more strange things happening which I can tell if anyone's interested

Can anyone tell me where I'm going wrong? I have been trying this for past 3 weeks but couldn't get anywhere. What am I supposed to do?


texts: In the paper, "High-Performance Nanostructured Supercapacitors on a Sponge," the author mentions "areal capacitance." What is the physical meaning for areal capacitance? How can it be calculated?


texts:
Is there any single pin AC Male/Female plug is available? What is it called? I tried a lot searching on google but didn't find anything.

I am looking something similar to RCA Cable for transmitting AC Signal (only type from each Cable i.e. Ground/Live/Neutral)

edit:  I found a nice video for AC Connectors. Video explain different kind of available AC connectors.


texts:
Do somebody know why there are large copper strips inside a chopper
transformer that I've hacked and dissembled ?

Does anybody know what is their purpose? What's the mathematical theory behind them?

What will happen if I reassemble that
chopper transformer without those big strips ?

Picture:


texts: I am working with a 50kg load cell. In the datasheet(https://www.sparkfun.com/datasheets/Sensors/loadsensor.pdf), the creep is defined by (3min)%FS. What does it mean?


texts: Solar LiPo battery charger: revision and improvement of the reverse voltage protection circuit for the battery

texts:
I am designing a solar charger with MPPT for a 1-cell lithium polymer battery of approximately 6000 mAh. The solar panel is 10W and 21 Voc.

I am trying to ensure that the charger has protection against reverse voltage for both the solar panel and the battery.

My questions are focused on the protection of the battery against reverse voltage, not on the design of the charger itself.
The complete scheme can be seen below.

The battery protection circuit is extracted from this Analog Devices document but with some modifications.

In summary, the operation is as follows:

Q2 and Q3 provide a reverse voltage detection circuit and Q4 is the one who disables the battery.
If the battery polarity is correct, Q2 and Q3 are cut-off and therefore, Q4 connects the battery.
In the event that the battery is connected in reverse, Q2 and Q3 are activated and then shunt the gate of Q4 to ground, causing Q4 to break and the battery is disabled.
Do you see any fault or something that can be improved?

Datasheets:

Q2 DMN3023L-7
Q3 DMP3099L-7
Q4 PSMN9R8-30MLC

Thanks and best regards.


texts: considerations about little endian processor and opeartions on registers

texts:
Processor is little-endian.
Under followings addresses we have following values (hexdecimal format):

1000: FA
1001: 46
1002: 26
1003: C3

Now, processor is going to do following 16-bits operations:
1. Load to register R1 value of address 1000 (remember that operations are 16-bits).
2.  XOR value of address 1002 with value of register R1.
3. Save result of XOR at address 1010

I show you, how I understand what processor do:
1.  Because of the fact that processor is little-endian it loads to R1 value:  46 FA.
2. xor with value of address 1002 with R1 is:
XOR(C3 26, 46 FA)=85 DC
3. Now, at addresses 1010 and 1011 we have:
1010:DC
1011:85

Tell me please, Am I ok ? If I correctly understand this issue ?


texts: RC Filter measured response differs from calculated transfer function

texts:
I've created a first-order RC filter with R = 68 Ohm, C = 5.0 uF, and I am studying the transfer function of this filter. I have calculated the transfer function to be 1/(1+jwRC), based on the relationship between the output and input voltage (see image): .

I measured the magnitude and phase of the output waveform using an oscilloscope, and plotted it in a Bode diagram against the magnitude and phase of the transfer function above, and this is what I get:

It appears from doing some research that the experimental data is following the curve that is the sum of the Bode pole and Bode zero functions. How do I calculate what the zero and pole equations are from my transfer function, or how do I model the actual response I measured?