texts: nodemcu/esp8266 reads lower than expected on A0

texts:
I got a NodeMCU/ESP8266 development board and am trying to utilise the A0 (10-bit ADC) input to read the voltage from a voltage divider on the 3.3V pin. So I have the following:

simulate this circuit – Schematic created using CircuitLab

However when I read A0, it's not the ~512 value that I'd expect for the 1.65V (as measured with a multimeter) that is on A0. It's rather somewhere around 450.

If I swap out the 100K resistors for 1M resistors (which is my target because I have a 1M thermister), the reading is even more off, around 200 where the voltage on A0 reads about 1.55V with a multimeter.

Even with 3.3V on A0, it's only reading 1016-1017 and with nothing on A0 it reads 9 which isn't hugely out, but it's still not hugely accurate either.

Is there something I am not understanding and not taking into account? I'd be interested in any insight.


texts: Small PSU with 110-240 Vac 50-60 Hz input and 12 V @ 1 A output

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I spent my day trying to find a functional schematic featuring those specifications:

AC input voltage range of 100 to 240 V
AC input frequency range of 50 to 60 Hz
output is the easiest part, I can use either a LM317 or LM7812

I guess I can do something similar to (after calculating values of course)

simulate this circuit – Schematic created using CircuitLab
My main question is about accepting the input voltage and frequency ranges mentioned above. How do I do that and build something quite small?
Any other concept can be accepted too, instead of my schematic if you feel this not optimized.
OK, so let's select a AC-to-DC converter module then. It should be the best solution for me - at those prices, I won't hesitate :)


texts:
I have been looking into IQ-modulation and found myself a little confused.

"Traditionally" IQ-Modulation schemes goes something like this:

IQ_Data -> 2 x DAC -> IQ_Modulator -> RF

But I have seen some DACs with internal digital Modulator, which then generates the complete complex IQ-signal.

IQ_Data -> DAC (Digital Mixing/Modulation) -> Mixer -> RF

Texas got one: http://www.ti.com/lit/ds/symlink/dac5687.pdf

What are the pros. and cons. of analog vs. digital IQ-modulation?

And does one have limits regarding high-speed communication >100Mbit?


texts: I would like to replace my broken earphone's 3.5mm audio jack. However, I am not able to indicate which wire is the right (red) and which is the left (green). I see the red and green wires but they are twisted with cooper. Please help me to identify each of them. I believe the gold one is the ground. Thank you.


texts: Building power/control interface for RGB LED strips

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I am attempting to build/create/design/whatever a way to control my RGB LED strips via a USB or ethernet interface. These strips consume a lot of power and the mass produced controllers suck. I would also like independently controllable "zones" if you will, so ideally this device could power 1 or more strips.

Since a picture is worth 1,000 words I've attached an image of what I am trying to accomplish. Does anyone know of something like this commercially available, or how I can practically create something that will power this many LEDs? At a minimum I would really like each device to power 3 strips at a time which is quite a bit of power. I'm am very new to EE, so this is all kind of overwhelming to me.


texts:
So I have have an equation and I need to do laplace inverse transformation  $$ I(s)=\frac{s}{7s+6} $$ and then for partial fractions I got $$ I(s)=1/7-\frac{6}{49s+42}$$ and now for inverse transform I have $$I(t)=\frac{-6}{49}*e^{-(6t/7)}+\frac{1}{7}$$
I can't get the right answers with this so can somebody tell me is the transformation done wrong
                                                                          or is just my starting values wrong


texts: What is a 'quiet ground' / 'Ground plane'

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I really don't expect an analytic answer.  I'm sure there are far too many variables to consider.

I'm working with a fairly simple circuit (Precision voltage, Instrument amplifier) but need to really an output signal that has have noise a low as possible.  I suspect I have a ground loop problem but I'm not sure.  Here's the background.

I have a multi-channel 24 bit DAC (data acquisition system_)  -- differential or single ended.  My approach to measuring the 'ground'/'current loop' voltage is to  connect the 'ground'/ common return lead to the to both inputs for a differential input while the circuit is powered and collect the data over an extended time (an hour or so).  Data is collected once per second so I have lots of data.   I expect there to be noise on the 'ground' wire but I don't know what is reasonable.   The data shows that there is a mean voltage of 450 microvolts with a max excursions about the mean of +/- 15 microvolts.  A 25 sample running average of the data gives the same 450 microvolts with an average deviation for the data (an 3600 + points) of 7 microvolts.

These values are the maximum resolution advertised by the DAC equipment.  The basic question is "Is this a Quiet ground or is more expensive equipment required"???

If this is not a quiet ground, can you point to design documents (circuit/PCB) to further reduce the noise.


texts:
I have been working on a 1953 Zenith TV; I can get raster on the top half of the screen only. If I reverse the leads on the Vertical deflection coil, I get raster on the bottom half only.  So far, in addition to replacing all caps. & tubes, I have replaced the deflection yoke, vertical output transformer, and Flyback transformer. Nothing has changed as far as the raster goes. Moving the ion trap around does not help.  I'm stumped.....

Any suggestions.


texts:
I found the following transformer model in the AN1679/D written by ON SEMICONDUCTOR. The document is really interesting and very well explained.
Nevertheless, I do not understand this point, how the two model are equivalent :

If I try to put Ll2 which is at the secondary to the primary, I do not find the relation given :( Here are my calculs :
$$
\mathrm{
L_{l2}*\frac{dI_{0}}{dt} = \frac{N_{p}}{N_{s}}(V_{p}-V_{L1}) -V_{0}
}
$$
and
$$
\mathrm{
L_{l2'}*\frac{N_{s}*dI_{0}}{N_{p}*dt} = V_{p}-V_{L1} -V_{0}
}
$$
We then express each relation equal to
$$
\mathrm{
\frac{dI_{0}}{dt} = \frac{dI_{0}}{dt}
}
$$
For express Ll2 in function of Ll2', and we get the correct relation only if Ns = 1 and Np = 1...
Did I do an error ? I m really interested by this subject !
For informations :

Thank you very much and have a nice day !


texts: In a circuit diagram were capacitance value of an electrolytic capacitor is given, how do you know the capacitor voltage to use?


texts: Powering a ESP8226 via supplied breakout board

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I have brought a couple of ESP8226s from ebay to have a go at making some fancy wi-fi controlled projects and i'm having some trouble, i cant get anything out of them!
With the chips I got breakout boards, (see pictures), i have dutifully soldered them up so i can put everything on a breadboard. When i plug it into my 3.3v power supply i don't get anything (the onboard LED does nothing and i don't get any response via serial).

Putting a meter on it I don't have any connection between the VCC of the breakout and the VCC of the chip.

Has anyone use one of these boards before? There are 3 small holes that could be needing a component/jumper in them but i have no idea what and don't want to start soldering stuff willy-nilly. What do i need to do to get my chips powered?

Thanks


texts: Three-phase inverter simulation - incorrect result

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while simulating a three-phase inverter circuit with a three-phase load circuit. the simulation result seems incorrect. here is my circuit and simulation result. the input voltage is 300v the output voltage is in the order of 12kv. I really wondered why this is so?
NB. when the load is disconnected the result is 300v as expected. the problem comes when the load is connected.


texts: Is there an easier way to signal this active low relay module for the pi?

texts:
Two parts to this question:

Part 1:

I am planning on setting up this relay module with my pi (which afaik has gpio pins set to LOW at startup).

1.) Does this mean if I hook it up as the picture suggests on that page, that all the relay sub-modules will be on at startup?

2.) Does this mean if I want the relays to be off at startup, I need some sort of transistor outside the relay module to provide the HIGH signal constantly so that I can use a HIGH GPIO to turn on the relay (by making the transistor go from HIGH to LOW)? Is there an easier way to do this than to use an external transistor?

Part 2:

After briefly looking for other relay modules, many seem to have this active low behavior. What is the reasoning behind this? Especially if they are meant for microcontroller usage (being a module and not just a relay), wouldn't it make more sense to have the modules be active high?


texts:
I'm thinking of using a supercapacitor to power a device with low power consumption. I have one 1 F capacitor rated at 5.5 V and I plan to charge it using input voltage of 5 V.

What precautions should I take when charging it? I'm afraid that it will overload my power supply if I just connect it directly.

Any other tips would be appreciated too.


texts: I am trying to understand the behavior of a pulse

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I have this pulse
This is the observed data. I have a LTSPice model that needs to be matched as close as possible to the observed data I need to match the e area of from 350 to 500 ns, because the pulse is not returning to zero. The thought is that there is a parasitic element behaving as a cap or inductor.  in this close up, the circles are the observed data the blue line is the LTSpice data and the red line is the curve generated in R  from the lm () function for a third order polynomial.
I am not sure that is the correct model for this part of the curve. as it gives me this information when I run the coefficients. At this point I am kind of lost because I have been asked to give the equation to describe it
Call:
lm(formula = y_100 ~ poly(x_100, 3, raw = TRUE))

Residuals:
     Min       1Q   Median       3Q      Max
-2080.10  -372.44   -40.37   342.17  1412.65

Coefficients:
                              Estimate Std. Error t value Pr(>|t|)
(Intercept)                 -2.030e+06  7.050e+04  -28.79   <2e-16 ***
poly(x_100, 3, raw = TRUE)1  1.424e+04  5.196e+02   27.40   <2e-16 ***
poly(x_100, 3, raw = TRUE)2 -3.327e+01  1.272e+00  -26.17   <2e-16 ***
poly(x_100, 3, raw = TRUE)3  2.590e-02  1.034e-03   25.06   <2e-16 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 584.6 on 296 degrees of freedom
Multiple R-squared:  0.9627,    Adjusted R-squared:  0.9623
F-statistic:  2547 on 3 and 296 DF,  p-value: < 2.2e-16

> coef(fit3_df_200)
                (Intercept) poly(x_200, 3, raw = TRUE)1
              -2.733113e+06                1.914600e+04
poly(x_200, 3, raw = TRUE)2 poly(x_200, 3, raw = TRUE)3
              -4.467164e+01                3.469908e-02

I am a data analyst who is assigned to give a mathematical representation of that part of the graph. I use R to model it and zoom in on the area. If I can give the engineers an equation that represents that area they can use that to eliminate the parasitic. I have asked the people in data science if they had thoughts but they get hung up on that its happening over time. Time series is for events that happen repeatedly anyway I digress.


texts:
I have a flashlight that seems to use the inside of the metal body to conduct the negative terminal of the LiPo battery inside. The outside isn't conductive - likely anodized.
Would there be adverse effects if the whole body was conductive, i.e. make both the inside and outside conduct the negative terminal? I'm guessing the user wouldn't receive shocks given the low voltage.
The flashlight looks like the following

(source: opticsplanet.com)


texts: What is a suitable candela for a status led?

texts:
What is a suitable candela value for a LED to have that doesn't blind you if you stare at it, and will still allow you to view silkscreen markings on the PCB but not to dim that you can see the internal workings of the LED ?

I suppose this question is more of an experience question.

This question originally had "lumens" in the text but what I was really asking was for candela. The question has been edited with candela.


texts: Motorola telephone-style handset audio to 3.5mm jack

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I retrieved a Motorola Telephone-Style handset wich was in service with a Motorola radio GM380. It is the same as https://shop.motorolasolutions.com/rln4756-telephone-style-handset/product/RLN4756A but with two additionnal keys (F1 and F2).

I would like to get the mic output of the handset to a 3.5mm jack for a computer. I already managed to make the speaker work, but I can't get the mic to work.

The connection is an RJ50, and I didn't find the pinout for the GM380. So I did some reverse engineering and the pinout seems similar to this one (from the GM300), if you take pin 1 as pin 2, pin 2 as pin 3, ... :

Here is the circuit in my handset (both wires red and black at the bottom go to the mic) :

For the RJ50 at the top, corresponding pinout to the RJ45 with the previous scheme (the RJ50 is only 8-pin on this side because 2 pin are not wired on the other side) :

WHITE - pin 1 "PB1"
BROWN - NC
BLUE - pin 3 "HOOK"
BLACK - pin 4 GND
RED - pin 5 MIC AUDIO
GREEN - pin 6 PTT
PURPLE - NC
YELLOW - pin 8 HANDSET AUDIO

I only did some basic electronics and never any audio thing before, so I don't get how can I make the mic work. Can someone help me please?


texts:
I've been trying to figure out how this PMOS circuit is functioning.

B_VCC is 5V coming from a USB port on the board, while VCC5V is used elsewhere in a regulator to create 3.3V but otherwise does not exist anywhere else. PSELF is effectively grounded as nothing is being plugged into the DC Jack.

When USB is plugged in and nothing is plugged into the DC jack, B_VCC goes to 5V which is understandable but VCC5V goes to 5V as well, which means the transistor must be on. For it to turn on, the conditions are that the PMOS is either in Linear or Saturation.

\$V_{sd}\$=floating-5V ; \$V_{sg}\$ = floating-0V ; \$V_t\$ = -0.8V (from datasheet)

\$V_{sd} < V_{sg} – \vert V_t\vert\$ LINEAR

TRUE

\$V_{sd} > V_{sg} – \vert V_t\vert\$ SATURATION

FALSE

Is it okay to assume that the floating VCC5V is 0V?

Also after VCC5V goes to 5V, then \$V_{sd}=0\$, \$V_{sg}\$=-5V and \$V_t\$ = -0.8V so it would then move to Saturation mode?


texts: Interference from high voltage power supply (EHT power supply)

texts:
In class today our physics teacher was demonstrating how ionic fluids move when a high voltage exists between them. A USB microscope was placed above the test rig, and the image was projected onto the virtual board. He used a 500V-5kV supply, limited to 60µA. The demonstration was interesting, but more interesting was what happened when he turned the supply voltage up: the image on the board began to flicker, then broke up completely and eventually "no signal" popped up. It also caused the USB microscope to reset.

I'm thinking it was interference, but how could a high voltage but low current supply cause such problems for the projector?

I think it might be related to my digital clock having difficulties (resetting, alarm going off randomly, time skipping several seconds at a time) when it is within about 10 cm of my plasma ball, because both use high voltages.

Any ideas?


texts: Identifying 8051 garbage microcontrollers (updated)

texts:
Here I am with another question about the 8051.

After researching various resources, I read in the datasheet that the ALE pin is enabled by default but can be disabled in code however I did not use code to disable the pin. It also states that the ALE is emitted at a constant rate of 1/6th the oscillator frequency.

What I want to do is identify if the microcontroller itself is garbage (by testing pins) before even trying to program it. The one I'm using is AT89C51-24PC.

I tried the reset to see if my code will execute with the micro on a breadboard to no avail. In the tests I tried an 8Mhz crystal with each leg grounded through 10pF caps without success. I then replaced that arrangement with just a 32Khz crystal and I still get the same result.

Now I tried hooking ALE to ground through an LED+ 1K resistor in series and the LED stays off. If I hooked ALE to VCC through LED + 1K resistor, the LED stays on.

Because I havent explicitly told the micro to disable ALE, I would expect the LED to blink at a high-speed but it is not.

In all tests, the reset pin is grounded through a 10K resistor.

Is my test of ALE sufficient enough or do I need to do something else hardware wise to check if the chip is internally damaged? (and no I'm not going to hook the pins to a high voltage source)

UPDATE

I fixed my programmer code so that the correct signals are sent to the chip yet I still have no luck.

My code is this:

mov R6,#0h
mov R7,#0h
l3:
l2:
l:
djnz R7,l
djnz R6,l2
dec P1
ljmp l3
END

When I tested the LED on the ALE pin now with 8Mhz crystal rammed into the breadboard with 10pF caps, the light seems to be running normally, however the output to P1 stays all logic high when it should be decrementing from 255 to 0 over and over again. when I connected the Led+Resistor from +ve to random pins (one at a time), I noticed PSEN made the led not light right after the reset was issued  but then I waited in hopes that it would come on because if the chip was literally never programmed, then FFh or 00h would be stored on the chip which from one source represents "Mov R7,A" and "nop" respectively. Neither instruction causes a loop so I figured if that's the case then when the chip wants the 4097th or later byte, wouldn't PSEN change state? (aka light up in my case)?

Now I feel I need to waste a circuit board just to test a chip, but are there other options here?

update 2

I don't get it. Now on the breadboard I decided to add a SIP resistor pack (so that all P0 pins are individually connected to VCC through 4.7K resistors), and when I connected the PSEN to VCC through the LED and 1K resistor, the LED was off at first then after a few seconds, it endlessly was blinking. I guess this tells me my program never entered the chip in the first place. I'm starting to think the EPROM in my chip is broken before I ever received it. I'm going to try other 8051 chips and see what happens.


texts: Substituting an inductor - cannot find any pieces containing inductance needed

texts:
I am a beginner electronics hobbyist trying to follow an old schematic / instructions to build a theremin.

I have all of the pieces except one. This piece (Toko 154ANS-T1019Z) calls for a "68 µH, hi-Q, variable inductor". However I cannot find a 68 uh variable inductor at all (See link, all options are discontinued pieces which cannot be purchased).

Note: Octopart shows the part may be available when it is not. The websites Octopart uses show the part is unavailable. In other words I cannot find this part or any variable inductor with 68 uh inductance

See the potion of the schematic below:

How could I substitute this piece?


texts:
I came across few different ground names (digital, analog, signal, power, mecca, EM, shield, etc).

I do understand most of them - but mecca is a new one for me. Can someone please explain this mecca ground?


texts: Finding the Analog Bandwidth of a Voltage Controlled Oscillator

texts:
We've built a current starved voltage controlled oscillator

And tuned it so it works only in the linear region, which means it oscillations between 720-840 mV, and outputs 3.6-4.4 GHz. In order to calculate the SQNR, we need the ABW. How is it possible to find the analog bandwidth of the Vco?

I've tried taking the output of the ring oscillator and using a fourier transform of it, and we get a series of pulses at different amplitudes from 25Mhz to 675 Mhz. Do I need to take the two 3dB values from here?

Thanks!


texts: In a receiver blocking test, I always see the description that "the test is peformed at a signal level 3dB above the required sensitivity". So what is meant by testing the receiver at "3dB above the required sensitivity"? And why this 3dB is the benchmark for the blocking test?


texts: CAN Problems with MCP2515, MCP2561 and Rpi

texts:
I work with some devices which used STM32 MCU and MCP2561.
Theses devices talks on a CAN Bus.
Everything is ok.

But when i plug a Raspberry Pi with a MCP2515(Spi) and a MCP2561.
I see a lot of invalid frames on my scope like this :

A valid CAN Frame is like :

A zoom on the problem :

I don't understand why there is a problem at the ACK/ACK Delimiter.

Thank You for your help.


texts: Convert a NO push button into an On/Off button

texts:
I'm building a boombox, and it needs a couple of switches for main on/off, voltmeter on/off and LED lights on/off. Since I don't have any metalworking tools I am going to buy a premade front panel, this one. It has room for an on/off switch, and two NO push buttons  These push buttons are momentary, so they will only let electricity flow while the button is pressed. This is ok for the voltmeter, but it gets a bit tiring to hold down the button when you want the LED lights to turn on!

I've looked at some JK relays such as this 74107 relay. However, looking at the datasheet, it only supports voltages ranging from 4.75V to 5.25V, and the boombox is 12V. And even if it worked for higher voltages, I'm confused about what pins to connect where.

Can someone please point me in the direction of a relay that supports higher voltages, or perhaps another, easier solution? Thank you!


texts: Altium: Surface Mount Test Pad Passing Through PCB

texts:
I'm working on a PCB in Altium that will sit inside an assembly above another board. The board on the bottom has a test pad, but once everything is assembled it will be inaccessible. Therefore, I am attempting to add two pads to the top PCB (one on the bottom layer, one on the top) that are connected through vias around the edge (No, I cannot simply use a through-hole pad). The issue is this: In order to connect the vias to the top and bottom pads, they must all be connected to the same net. However, there is not a designated net for these pads, as they are simply fed through the PCB and are not used by it. It is a PCB-only feature and is not part of the circuit, so I don't want to add it to the schematic. How might I go about connecting these top and bottom layer pads through vias? Here's an image showing the top side of the PCB:

The bottom layer pad is directly beneath the one shown in the image.


texts: Are there any convenient "bus keeper" or "bus hold" chips?

texts:
Many CPLDs have a handy feature which will weakly drive pins toward their present state, so that a pin which is weakly pulled high will pull high and one which is weakly pulled low will pull low.  Are there any convenient ICs which will perform that function without needing a CPLD or a bunch of resistors?  A possible design for a 14-pin part would be to have eight "bus" pins with "weak" drivers, VDD and VSS, and two pairs of mode pins controlling four bus pins each.  The mode pins would select one of four bus modes:

00 - Open-circuit (no pull-up or pull-down)
01 - Unconditional weak pull-down
10 - Unconditional weak pull-up
11 - Pull-up or pull-down based upon current pin state

Such a part could be used for bus-keeper applications, and also for things like low-power polling of switches (with the pull-up/pull-down modes).  Does anything like that exist?


texts: Why is the noise gain of an op amp always constant at $$1+\frac{R_1}{R_2}$$ and independent of configuration, unlike signal gain?


texts: Is the Raspberry Pi polarity protected on the USB?

texts:
I am building a Pi into some equipment just to drive a display. Now this is normally powered by a USB lead with the usual 5VDC. So I will have to cut the USB cable and put ferrules on the leads (omitting the data lines) to connect to the 5VDC supply on the DIN rail.

The question being, if someone gets the polarity wrong in production, will it destroy the Pi, or is there internal protection? Is there typically internal polarity protection on other devices that take power from USB eg phones? Is putting in such protection feasible given (say) the voltage drop produced by a simple diode? What other protection circuits exist that do not drop voltage (if this is even possible)?


texts:
I am building a watering system with an Arduino. Basically it runs on a track with a hose that drips water down on plants a couple of times every day. Its outside, and water might sometimes get from the leaves of the plants down to the Arduino controller.

What is the best way to protect my Arduino against weather and water from the watering system?


texts: In SPI rom, we configure both Normal and Fast Speed, how can we confirm if SPI clock is using fast speed or normal speed?

texts:
In SPI rom, we configure both Normal Speed i.e. 33Mhz and Fast Speed that is 66Mhz.
How can we confirm if SPI clock frequency is fast speed or normal speed?
Does SPI clock frequency changes based on type of spi read commands like 0xB and 0x3?
Do different SPI commands/instruction are based on which spimode (dual/quad) is set ?
SPI quad instruction/commands:
“Fast Read Quad Output(6Bh)”,
“Fast Read Quad I/O (EBh)
SPI dual instruction/commands:
“Fast Read Dual Output (3Bh)”
“Fast Read Dual I/O (BBh)”


texts: What is the difference between these two battery setups in parallel?

texts:
I have a couple of batteries with original main feeds connected to them. I want to add another battery in parallel, without touching the main feeds.

Setup 1 in the image below shows the current setup, with the exception of the single battery on the right to be added. This battery is a little further than the couple of batteries on the left.

I'm not sure if setup 1 (which requires less work) will compare to setup 2 which is something I'd see recommended. Will I get more resistance with setup 1?

Edit (for dimension): Let's say the distance between the old batteries and new battery is 2 meters: Setup 1 will use 5 meters of cable; Setup 2 will use 8 meters of cable.


texts: May I power atmega32a-pu microcontroller from AA batteries?

texts:
I need to provide +-4.5V to the microcontroller. That would be fine by having 4x rechargable batteries, but how is it with current? On each AA battery is written min.2550mAh. I am not sure but I think that max what I can put to the microcontroller is around 500mA.

Could you please advice me how to do it? Should I use resistors? Am I right about the 500mA?


texts: Where can I buy or how can I make high quality jumper cables?

texts:
The jumper cables in my possession are all so stiff and seem cheaply made.  The connectors fall apart and its frustrating.  The jumper cable is such a simple but critical component - how/where can I make the time or money investment to get nice cables?  I do have one example (in my minimal experience) of a set of nice cables, and these come off of my Saleae Logic analyzer.  They seem rugged, not stiff, well made and built to last.  Any way to get jumper cables for prototyping that resemble these?
 There is no doubt that the engineers who created the Saleae Logic Analyzer were aware of the components out there for making good jumper cables, and chose to make or provide ones of high quality.


texts:
I want to use this slide switch SL13-213C (DP3T) (Datasheet), but I'm not sure about how the connector work.
The first image on the left comes from the datasheet. The rest is my understanding. Is it correct?


texts:
I am trying to understand how the CDI module in my RC airplane engine works. Unlike newer engines, the engine I have is still using a "magneto style" ignition, which does not require a DC source to operate.
Googling around, I found an old post with the schematic attached:

The coil on the left side is energized by the passage of three magnets (+-+ configuration) mounted on the flywheel. This is already different from most of the small engine ignitions I have seen, which use two magnets.
If I read the schematic correctly, the AC voltage generated on the left coil is rectified by D2 and used to charge the 0.39 uF C1 capacitor. The 5 Ohm resistor and D1 then would clamp the negative pulse.
At the right time, the TRIAC goes into conduction, and the capacitor discharges via the coil on the right. At this point, D3 C1 and the grey coil form a LC circuit where the voltage should oscillate until dissipated.
I have attached a scope to the black wire on the left of the diagram when the engine is running, but what I observe are only positive peaks. This suggests that either a diode is missing from the circuit or else the black wire connects to the right of D2. But my real question is what triggers the TRIAC? Normally, I would expect the gate of the TRIAC to be connected to a triggering circuit, which I do not see in this diagram.
Also, I know that the ignition fires when the second and third magnets are almost directly under the "legs" of the ferric core, over which the coil on the left must be wound. Therefore, I think that the negative pulse must somehow act as a trigger. Yet, I do not see how this would happen based on this circuit.
Finally, if I wanted to build a small testing rig where I use a drill to provide rotation to the flywheel, can I safely use a resistor in place of the grey coil? And if so, what value would be appropriate?


texts: Issue with ESP32 programming circuit using CP2102N

texts:
I've designed a custom PCB that uses a ESP32. At first I was using a CP2104 as USB to serial IC to program the ESP32, that worked without issues (I was able to program the ESP32 using the arduino IDE).
I then designed a new version with several improvements. One of the things I changed was that I swapped out the CP2104 for a CP2102N, since the CP2104 is not Recommended for New Designs according to Silicon labs. The CP2102N is pin compatible with the CP2104, so I did not expect any issues with this change.
The circuit basically looks like this:

Unfortunately, the board doesn't seem to go into program mode. I am able to get output from the esp32
Any idea why this might not work?


texts:
I am with EE background and recently I had question in interview regarding “How to sense/know when device needs power?”.
So, basically I had a good interview on different topics and one of them was MOSFET.
I answered mostly all questions properly until this question comes up.
Interviewer asked me: “If you are making power supply for a laptop and when laptop goes in to sleep that time your supply should not provide full power (may be negligible). And when you on the laptop or started working on it at that time your supply should provide required power.”
How can you design circuit which sense/detects when device needs power?
Can any one of you help me on this? I would really appreciated any input.


texts: I can't derive a differential equation from this complex RLC network

texts:
So I was drawing arbitrary RLC networks and solving them as an exercise. But I came across this one and it seems impossible.

Specifically, I want to derive a differential equation that solves for \$i_2\$ (an equation with \$i_2\$ and its derivatives).

simulate this circuit – Schematic created using CircuitLab

And here's my attempt. The voltages and currents are defined such that: $$v_2=L\frac{d(i_1-i_2)}{dt}, v_3=i_2R_1, v_4=\frac{1}{C_1}\int{i_2dt}, v_5=(i_2-i_3)R_2,$$ $$v_6=(i_1-i_3)R_3, v_7=i_3R_4, v_8=\frac{1}{C_2}\int{i_3dt}$$ Applying Kirchhoff's voltage law to all loops gives us: $$v_2=v_3+v_4+v_5=L\frac{d(i_1-i_2)}{dt}=i_2R_1+\frac{1}{C_1}\int{i_2dt}+(i_2-i_3)R_2$$ $$v_6=v_7+v_8-v_5=(i_1-i_3)R_3=i_3R_4+\frac{1}{C_2}\int{i_3dt}-(i_2-i_3)R_2$$ $$v_1=v_2+v_6=L\frac{d(i_1-i_2)}{dt}+(i_1-i_3)R_3$$ $$v_1=v_3+v_4+v_5+v_6=i_2R_1+\frac{1}{C_1}\int{i_2dt}+(i_2-i_3)R_2+(i_1-i_3)R_3$$ $$v_1=v_2-v_5+v_7+v_8=L\frac{d(i_1-i_2)}{dt}-(i_2-i_3)R_2+i_3R_4+\frac{1}{C_2}\int{i_3dt}$$ $$v_1=v_3+v_4+v_7+v_8=i_2R_1+\frac{1}{C_1}\int{i_2dt}+i_3R_4+\frac{1}{C_2}\int{i_3dt}$$ $$v_2+v_6=v_3+v_4+v_7+v_8$$ $$=L\frac{d(i_1-i_2)}{dt}+(i_1-i_3)R_3=i_2R_1+\frac{1}{C_1}\int{i_2dt}+i_3R_4+\frac{1}{C_2}\int{i_3dt}$$ Now all I need to do is somehow write \$i_1\$ and \$i_3\$ in terms of \$i_2\$, and if the above clues aren't enough to do just that, I don't know what else. But it seemingly cannot be done!..as far as I have tried! Here are a few definitions of \$i_3\$ and \$i_1\$ that I've picked up using above clues (which you can hopefully build up on): $$i_3=\frac{1}{R_2C_1}\int{i_2dt}+\left(\frac{R_1}{R_2}+1\right)i_2-\frac{L}{R_2}\frac{d(i_1-i_2)}{dt}$$ $$i_3=\frac{L}{R_3}\frac{d(i_1-i_2)}{dt}+i_1-\frac{v_1}{R_3}$$ $$i_3=\frac{1}{R_2+R_3}\left(\frac{1}{C_1}\int{i_2dt}+(R_1+R_2)i_2+i_1R_3-v_1\right)$$ $$\frac{di_1}{dt}=\frac{di_2}{dt}+\frac{R_1}{L}i_2+\frac{1}{LC_1}\int{i_2dt}+\frac{R_2}{L}(i_2-i_3)$$ $$i_1=\left(\frac{R_2+R_4}{R_3}+1\right)i_3+\frac{1}{R_3C_2}\int{i_3dt}-\frac{R_2}{R_3}i_2$$ $$i_1=\frac{1}{R_3}\left(v_1-i_2R_1-\frac{1}{C_1}\int{i_2dt}-i_2R_2+(R_2+R_3)i_3\right)$$ $$\frac{di_1}{dt}=\frac{v_1}{L}+\frac{di_2}{dt}+\frac{R_2}{L}i_2-\frac{R_2+R_4}{L}i_3-\frac{1}{LC_2}\int{i_3dt}$$


texts: How could I put an Enable pin on a standard two-stage CMOS op-amp?

texts:
I need to design an LDO regulator that only sources supply voltage and current to the load whenever it receives a logic-1 signal. Since the main element used in the LDO regulator is a differential amplifier, I would like to know how I can take the standard two-stage op-amp design and attach an Enable pin to it so that it works as I've described. See the image below for the CMOS op-amp I'm using.

I had a difficult time trying to word this question, so please let me know if more details are required.


texts: We are in the process of developing network storage with integrated Wi-Fi. Here we are facing problem. We have checked various solutions from Texas instruments and Microchip. But CC3000 from Texas instrument only supports speed of upto 11 MBPS and it doesnt support the N standard. Similar story with microchip module. If anyone has experience with high speed Wi-Fi module.do share your experience. Any solution has Wi-Fi + Bluetooth combination will be added advantage.


texts: Wiring on-off switch with resistor to SoC

texts:
Please note: although this question involves a Raspberry Pi (hereafter RPi), it is really a pure electronics question at heart!

I am trying to connect my RPi 1 Model A to a breadboard with a single, simple on-off-on-off switch on it. The kicker here is that although I'm using an on-off-on-off switch, I really just want it to function like a normal (on-off) switch. That is: push it once, the circuit is closed and sending an input signal on to my RPi. Push it again, and the circuit open. Rinse and repeat.

I was given this diagram to follow for wiring things up:

I then subsequently  inferred my own rendition of this, which more clearly shows the joining of the switch's left and right pins together (giving it the desired on-off behavior) as well as how to wire the 3.3V power on the RPi to the GPIO input pin:

So to behin with if anything above looks incorrect or awry to you, please begin by correcting me!

Assuming I'm on track, I'm now trying to actually wire this up in real life, between my RPi and my breadboard. Here's my best attempt:

Nevermind the LED and resistors in the bottom right corner of the breadboard, they're leftover from another experiment and aren't connected to anything else.

So at the top-left we have the 3.3V power source from the RPi connected to the top-most rail on the breadboard via a red jumper; then
A smaller red jumper wire forwards the power onto a column that is then connected to a 10-kOhm resistor; more on this in a second

On the left-side of the above photo we have the switch, here's a better look at the wiring/setup:

Notice the small orange jumper connecting the left and right switch pins; I believe this is what accomplishes the on-off-on-off -> on-off behavior I'm looking for
The same column that joins left and right pins (via orange jumper) is also connected to a red jumper which is also connected to the same 10-kOhm resistor we talked about up above
Finally, the switch's middle pin is connected to the GND rail via a black jumper

This brings us to the center of the beadboard, where that big fat 10-kOhm resistor is hanging out:

The resistor is connecting the RPi's power to the switch (both pins at the same time)
The resistor is also connecting back to the GPIO's input pin via gray jumper wire

Finally, my question!

Remember, at the end of the day, all I want to do is:

Convert this on-off-on-off switch to a on-off switch
When the user presses the switch (closing it), an appropriate signal is sent on to the GPIO input pin, which is then handled at the software layer

So I ask: will my circuit accomplish the following behavior? Is it wired correctly (correct junctions of wires, correct usage of resistor, etc.)? Or will it "fry my pi"?! If anything is incorrect, what's the fix/solution?

Update

Several users have pointed out to me that my wiring around the switch is incorrect, here's a Fritzing diagram of what I think the solution is:

Final update

Wiring when I set the internal pin resistor at the software layer, and omit the breadboard resistor:


texts:
The circuit given below is typical pH meter op-amp circuit. But here LMC6001 is not configured as unity gain.

My question is this, I want to make this circuit with unity-gain buffer op-amp. What about R2, R4, C1 and R9 in here? What do they do? Are they useful to make signal stable?

What about making LMC6001 unity-gain by removing R1,R2,R3 and moving C1 R9 shunt to LMC6001's feedback loop?

And what I understand yet: R1, R3 are gain resistors. LMC6041's function is adding reference voltage (adjusted by R8 // R6,R7,R8 resistor divider) offset to ADC's input (or pH signal).


texts: Relation between group delay, pole frequency and quality factor

texts:
So I'm solving some problems on filters and came up with an apparent contradiction that I would like to get clear.
Considering a low-pass biquadratic section:
$$T(s)=\frac{V_o(s)}{V_i(s)}=\frac{K_0\omega_0^2}{s^2+\frac{\omega_0}{Q_0}s+\omega_0^2}$$
So in the first problem that this appeared I was expected to calculate the group-delay at pole frequency.
I considered the phase being given by (because in this exercise the gain is negative)
$$\phi(\omega)=\pi-\arctan(\frac{\frac{\omega\omega_0}{Q_0}}{\omega_0^2-\omega^2})$$
and the group delay calculated with
$$\tau_g(\omega)=-\frac{d\phi}{d\omega}$$
I come up with
$$\tau_g(\omega)=\frac{Q_0\omega_0(\omega_0^2+\omega^2)}{Q_0^2(\omega_0^2-\omega^2)^2+\omega_0^2\omega^2}$$
Finally at \$ \omega_0 \$:
$$\tau_g(\omega_0)=\frac{2Q_0}{\omega_0}$$
Done!
Now off with the second exercise, I have to consider the same biquadratic section but now it is a Bessel filter with constant group delay \$\tau_0 \$. Now the author calculates the group delay as a function of the pole frequency and the quality factor and comes up with.
$$\tau_0=\frac{1}{Q_0\omega_0}$$
I have no idea where this expression comes from and why it contradicts my answer of the previous exercise. Is this because this a Bessel filter now? How do we arrive with this new expression? What are the math steps? Thank you in advance


texts: Why the current in X ray tube is in milli amps

texts: If we see a X ray generating tube the voltage applying to tube is in kV, but the tube current is in milliamps. Why this current is in mAs not in amps?


texts: Cirrus Logic CS4334 DAC Low Pass Filter?

texts:
I have a Cirrus Logic CS4334 audio DAC chip working (datasheet here).  One thing that confuses me is the "typical connection diagram" circuitry from the datasheet shown below.
In my experience with audio DACs, the R and C values on the output lines are for a typical resistor/capacitor (RC) low pass filter where part of the calculation is the cutoff frequency (F sub S).  However, I'm used to the circuit and calculation used for the RC filter being different than what is used in the circuit diagram below.
I'm used to an RC low pass filter circuit being like this where the signal being filtered first goes through a resistor and then there is a capacitor to ground following the resistor.  However, in the circuit below the signal first has the capacitor to ground then the resistor to ground (???).  Maybe this is a different kind of low pass filter I'm not aware of?
Also, note the equation for the C value in the diagram below.  Say I was a low pass filter with frequency cutoff of 20KHz and I'm going to use a 22 ohm resistor.  I take it I should use a capacitor around 188 nanofarads as shown in my math below, agree?
C = (22 + 560) / (4π * 20000 * 22 * 560) = 1.879e-7 = 188nF

Any insights anyone might have to help me understand this better would be much appreciated.  Thank you.


texts: How do you fill this circuit-table correctly (digital comparator)?

texts:
The following task is from an old exam and because the new exam will be similar to this one, I'm trying to understand it. Unfortunately there are no solutions or hints given and I got nothing to understand it really (I can provide source that this is really from an old exam and NOT homework.)

Task:

Given is a comparator that compares 4-bit binary numbers A[3...0] and B[3...0] (aka A_3, A_2, A_1, A_0 ..). The result is the output signal C_i which has the value 1 if A > B.

The arithmetic-circuit is supposed to be made up by connecting 4 identical 1-bit arithmetic-modules. Each of these 1-bit modules have the inputs A_i, B_i and C_i-1 and the output C_i with i= 0, 1, 2, 3. So, the carry outputs will be taken of the less significant digit i-1.

Given is A=0100 and B=0010. Fill the following table whereby C_-1-bit is supposed to be chosen by you in a reasonable way. The carry C_i is 1 exactly when A > B

I have filled the table as good as I could but I have no idea how to do it with C_i-1. The fields I have filled, are they correct at all?

I also hope I have explained clear enough please do tell me if I did not. You guys are really my last chance, got no one and nothing else to understand this I'm totally serious : /

**Edit: I would fill C(i-1) in table like that: 0 0 1 0 it's right now?


texts:
I have a board which has a CON1 connector being currently used for a battery. Are all CON1 ports serial? Why would a battery need a CON1 port?

My guess is, this port can be used to interface and debug the board. Where can I buy a suitable cable?

photo http://img145.imageshack.us/img145/5756/serialb.png

EDIT: Sorry, the port is called CON1. The print was really small.


texts: How to protect the ADC GPIO PIN [Battery monitor] from reverse polarity?

texts:
I have a circuit which uses a battery boost converter to power the MCU.  I use the ADC on the MCU to measure the actual battery voltage to display how much charge is left in the battery.
The power side is protected from reverse polarity since the boost converter won't power up if the batteries are inserted backwards.
The ADC PIN of the un-powered MCU, however, will see negative -3 Volts between VBAT and GND. MCU pins handle -0.3V max, not -3V.
Adding additional components either mess up the measuring of the battery voltage or in the case of a reverse protection diode possibly short the batteries (not user friendly).
What's the solution here? Pretty sure I'm not the first person with this issue.  How is this commonly dealt with?
thanks!

simulate this circuit – Schematic created using CircuitLab


texts: DC-to-DC voltage booster mosfet heat problem

texts:
I'm tying to understand boost and buck converter designs. Recently I made a prototype of a simple boost converter, used this as a reference. Used parts are as follows:

Transistor - IRF3205
Diode - STPS1545CT
Inductor - T80-6 core with 25 windings of 1mm wire.
PWM Source - Arduino Leonardo

PWM Duty cycle is set to 60%, frequency 70kHz.

It boost 12V input up to 40V. But transistor dissipates to much heat. Are there any issue I have to take into account? What is the reason for such power dissipation?


texts: How to recalibrate a cheap hygrometer module?

texts:
Some time ago I purchased one of these very cheap hygrometer/temp modules made in China. They come for less than 5 EUR. I know, the precision is not very good, but I thought, why not give it a try. Somewhere I read they have an accuracy of +/- 5% for humidity which would be acceptable for some use cases.

The device seemed to work well enough for some time but then it unfortunately got wet. The display went blank so I immediately removed the batteries and disassembled the module. To my surprise there's very few parts and they are not glued or anything. The display's pink contact bar is simply pressed against the contacts on the little board when put into the case.

I've dried all the parts and put them back together and it still works! But now the humidity is way off. Before it was in a range of 40-60% which are reasonable values. Now it only shows between 20%-40% which is far from realistic values. I've also done the calibration test using wet salt in a sealed bag. It should give 75% after some hours. The module only showed 40%.

The humidity sensor looks fine. I can hardly imagine how some drops of water could seriously damage it. I've bent it up a little on the image below:

So given the very simple board it made me curious how it works. I guess that there's a small microcontroller under the black pad. My assumption is, that it may use some autocalibration algorithm, which somehow got messed up. If that's correct then there should be a way to recalibrate the device.

Does someone have an idea, how these modules usually work and how they are calibrated during production? And is there maybe some trick to recalibrate this module?

Maybe someone can also identify the sensor and whether they don't like direct contact with water.

UPDATE: As answered below, the sensor could be a HR202L. If you compare the sensor image above to a HR202L you'll notice, that my sensor has a little black spot, right on the top of the black winding tracks, that connects both tracks. I've had a closer look and thought, it might be some dirt - so I removed it with a scalpel. This was a bad idea, as now the display shows even lower values < 20%. So probably time to buy a new module.


texts:
I'm using LTSpice XVII to try and simulate a circuit.

I've created a schematic which uses a Pulse voltage source to simulate a rotary encoder as follows:

As you can see in the PULSE component, I'm trying to specify the delay as a variable that can be set. I'd also prefer to be able to set the frequency via the period and timing values, but I'll start with baby steps.

Is this completely impossible, or am I just doing it wrongly?

If I replace 'tdel' with 0 directly, the component works 'correctly', but all copies of the component will be the same, which makes it difficult to test offsets or vary the frequency to check response when adding capacitors or similar.


texts: How to determine if battery tabbing nickel strip is steel or pure nickel?

texts:
I'm not sure if this Stack Exchange section is the most appropriate for this question.  Please provide guidance if I need to move to a different section.
I am about to start building some Li-Ion battery packs that do not have solder tabs.  The standard method for doing this is to use a spot welder and nickel strip.
I ordered some strip that is described as "pure nickel".  However, it is not welding as I expect it to.  Cutting the strip with either side cutters or tin snips feels exactly like cutting steel.  I expected the nickel to be softer.
I am looking for a method or technique that I can use to determine if what I was shipped is in fact pure nickel or if it is nickel-plated steel.


texts: Eagle routing gate swap and abitrary connectible pins

texts: Is it possible to have the Eagle autorouter swap gates or pins on parts allowing such exchanges to untangle traces ?


texts: Most ideal wire termination for round screw terminals

texts:
My '60 Volkswagen Beetle uses a number of electrical components that are equipped with round screw terminals, like you can see in the picture below:

What is the most ideal wire termination for these type of terminals?

So far, I've been considering the followings options:

Soldering the end of the wire

Although it will keep the wires from fraying, it takes a lot of practice to deliver a consistent job each and every time. Also, soldering inside a car is far from ideal, especially in awkward spaces. Wire terminations are also almost never soldered in aircraft and motorsport applications, same goes for automotive manufacturers. Must be a good reason for that.

Crimping ferrule onto the wire

This seems like a good option and I believe the VW factory did this. However, the tools they used made a rather small indentation which doesn't seem very reliable to me. I can find proper crimping tools that make a square or hexagonal compression, but I worry about the contact area and possible resistance with these ferrules in those round screw terminals. Is this something to be concerned about?

Soldering ferrule onto the wire

This leaves the round shape of the ferrule intact, but, as said, there are many reasons not to prefer soldering for automotive applications.

Are there better options out there?


texts: Matching network for complex source and load

texts: I'm trying to match a complex source to a complex load with an LC network at 10 kHz only. For instance a 1626 + j2280 Ω source at 10 kHz to a 122k - j3.5*10^6 Ω load. Can someone provide or document the process for going about this?


texts: Can several bluetooth devices be seen as one unique device from the point of view of an Android smartphone?

texts:
I need to put multiple bluetooth modules in various places so that they trigger something on a smartphone.

Of course the smartphone has to grant access to the bluetooth device at some point, but I would like to avoid this by stating that every bluetooth module that is broadcasting "my secret key" must be handled as virtually the same device. That way the user does not have to accept the pairing each time he/she encounters one of my devices.

Does the bluetooth specification allow me to do so, or is the authentication based on the unique address of each chip ?

EDIT :
From a pure design point of view, I plan to use this chip together with an ATMega and all the usual stuff that are needed to power up the board (battery holder + DC/DC regulator + buffer capacitors, pullup resistors, etc.), but that is not relevant for this question as I am still considering the feasibility of the project.


texts:
If a DC-DC converter (say 48V input to a 5V device) fails, is it possible for it to send the raw input voltage (48V) into the 5V device? And, if warranted, could anyone elaborate further as to common failure modes for DC-DC converters and how those might impact the output side? I'm not an electrical engineer, so please understand I'm a noob at all this and have no expertise whatsoever. Thanks in advance for understanding.

Background: I'm powering an Android tablet (5V) with a 48V->5V DC-DC converter. I've seen a couple tablets eventually get fried with no warning (just running for several months). They literally smoke and burn a hole in the case near a transistor where the power comes into the tablet. I've examined a less-than-ideal scope plot with the converter in question's output side... the amplitude on the output is nearly 500mV, and there's even an oscillation to the amplitude (there isn't with some other converters I've tested)... it varies from 200mV to 500mV. The other "good" converter I've tested is pretty steady at about 200-250mV amplitude.

My guess is that either the tablet's charging circuitry is getting worn out by the dirty power of the DC-DC converter, or the converter itself is failing and shunting through 48V to the tablet. Curious what others more knowledgeable might think.

Note: I tried researching before posting (and found the following posts), but these are way over my head, and probably not really what my situation is...

Not getting stable voltage output with DC-DC Buck Converter
What is causing large oscillations in my DC/DC boost converter? Is this ground bounce or some other effect?


texts: Understanding layers in Eagle schematic window?

texts:
Eagle schematic editor is having the following default layers:

91 Nets: Nets
92 Busses: Buses
93 Pins: Connection points for component symbols
         with additional information
94 Symbols: Shapes of component symbols
95 Names: Names of component symbols
96 Values: Values/component types
97 Info: General information
98 Guide: Guide lines

What is the purpose of the last 2 layers, info and guide in a schematic? Is it possible to have an example? Thanks.


texts: How to get a serial reading from an Ultrasonic Rangefinder on a Raspberry 3 B+?

texts:
I'm trying to set up a Maxbotix Ultrasonic Rangefinder (LV-EZ0) with a Raspberry Pi 3 B+.

I've tried all the tips I could find:

raspi-config

disable serial interfacing for shell, but keep it on for port hardware

/boot/config.txt

I made sure that those lines were there or I added them myself:

enable_uart=1
dtoverlay=disable-bt (also tried dtoverlay=pi3-miniuart-bt)

# services
Stopped / Disabled bluetooth, serial-getty@ttyAMA0

I also tried to: sudo cat /dev/serial0 > catReading.txtin one ssh window and sudo echo -en "test\n" > /dev/serial0in another one, but catReading.txt stays empty because I get a "Permission denied" to write anything to serial0.

Command outputs

sudo dmesg | grep tty =>
   [    0.000901] console [tty1] enabled
   [    1.023127] 3f201000.serial: ttyAMA0 at MMIO 0x3f201000 (irq = 81, base_baud = 0) is a PL011 rev2

ls -l /dev/* =>

lrwxrwxrwx  1 root root           7 Jan 31 16:57 serial0 -> ttyAMA0
lrwxrwxrwx  1 root root           5 Jan 31 16:57 serial1 -> ttyS0

cat /boot/cmdline.txt =>
console=tty1 root=/dev/mmcblk0p7 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

Wiring

Sensor VCC to 5V pin on raspi
Sensor GND to GND on raspi
Sensor TX to TX on raspi (I tried to plug it to Raspi's RX as well, because I simply don't know what I'm doing here . When I did that, I can read a few bytes, none of them starting with 'R' once decoded to utf-8, so probably not data sent by the sensor).

I looked up to see if there was any way to read a PWM input on the Raspi 3, but it's apparently not possible unless I add extra hardware.

Any suggestion from there?


texts: Charge Lithium-Ion batteries using a solar panel in parallel

texts:
I want to charge some Lithium-Ion batteries using a solar panel with this loading circuit found on ebay here. Apparently it works fine with just one Li-Ion battery, but I would like to extend the capacity for some more battery life. Can i just connect 2 or 3 cells in parallel to this charger without worrying? Would there be a balancing issue? How do I balance them? Am I doing any risky stuff by putting them in parallel? Also I want to charge them using a 5.5V 2.5W solar panel using the charging board. Would that be enough? Should I buy a second solar panel?

The batteries I was looking @ are some panasonic ones. Are they good quality?


texts:
I'd like to connect my logic analyzer to the address and data lines of a 6264 parallel SRAM chip on a PCB I'm working on. It's a 28-pin, .600 mil DIP package.

I have a 3M test clip for a .300 mil DIP28, but it won't fit, and new ones are very expensive. I don't have any minigrabbers either.

Does anyone have an interesting hack for piggybacking wires to a DIP in-circuit? I was thinking about soldering some wires to a DIP socket, or 2 rows of header pins on a piece of perfboard, then wedging it on top of the chip. Not sure either will have the strength to stay in place and maintain all connections though.


texts: Understanding capacitors and pre-amp configuration in this tone decoder circuit

texts:
I found the following circuit from http://www.talkingelectronics.com/ChipDataEbook-1d/html/567.html :

I'm confused as to why a 1uF and 10uF capacitor is connected between a 1K resistor and a 10K or 15K resistor. Also, it looks as if some filter is present with the 470k and 100pF in parallel.

More importantly, how are the values I just mentioned calculated?

I ask because I want to adapt this circuit to the output of a receiver that makes a lot of white noise along with the tone I want to detect.


texts: I am doing repairs on a monitor of mine and I have to replace a thermistor. I cannot quite read the values of the thermistor on the schematic for the monitor. Can someone see the image and help me to understand this?


texts: Can I solder a wire between two leads on a PCB to make up for a trace that isn't wide enough?

texts:
I have a PCB that has 2 traces on one corner who's width only supports a ~10a load. I need support for a 20a load. Actually, it really only needs to support a 15amp load but I'm trying to build in some healthy breathing room.

Can I just solder a wire between the two leads in parallel with the trace? The terminal block and the relay both support 20amps and these are the only parts touched by the load. I know it's messy but I figure it's not as messy as having to wire all of this up off the PCB.


texts:
A bit of background: I'm doing some research with Doppler cooling and I need to design a new electronics package to tune a set of lasers to stimulate various two photon transitions.

At the moment, the laser locking package makes use of the ADF4350, (it's the eval kit). However, for this new application I need to use something in the 10GHz range. The closest thing I could find was this series:

https://www.hittite.com/products/view.html/view/HMC778LP6CE

A perusal of popular suppliers: TI, AD again, SiLabs, Lattice Semi, etc, has yielded little outside of 3GHz (makes sense I guess, for 6Gbps video?). Also, while I wouldnt mind designing the board, I would prefer a dev kit as it would save time.

Just wondering if anyone has any suggestions.

Thanks.

EDIT: someone made a good point, I'm looking for an oscillator and not a clock. I need it to be fairly close to a delta function around the fundamental. I've found some good ones at RFMD.


texts:
I am designing a custom circuit board for a CG scale test instrument to find the centre of gravity for model airplanes. My design is based on the model here: https://github.com/olkal/CG_scale and it uses the same circuit except that my one uses an I2C display and has a regulator and lithium charge module and the ATmega328p chip is built into the board.
The problem is, when I power the board with the I2C screen plugged in, nothing happens but if I unplug the screen, D2 lights up. (board design files and schemas attached here*) I have tried powering off a lithium battery and using the regulator I put in the design.
I was wondering if you could see something wrong that I couldn't. (Hopefully it's not something glaringly obvious :-) ) I hope I have given enough information but if I haven't, let me know so I can add extra details, images, etc.
*Edit: A PDF version of the schematic is now available in the github repo but you can open the full project with KiCad EDA.
Edit: I have tried flipping the LCD connector and it does not seem to be the problem.
Edit The display I'm using is an LCD 16x2 with an I2C adapter on it


texts: Thevenin's theorem in transistor circuit

texts:
When analyzing this transistor circuit it was suggested that I simplify the left side by using Thevenin's theorem with the points A and B as follow. Before I jump in let me apologize the lenght of the question and my english. But I would really appreciate any insight because my professor told me Thevenin is important in the electronics course, I would like to learn it well. The actual questions are in bold (1) and (2).

simulate this circuit – Schematic created using CircuitLab

The simpified circuit after using Thevenin's theorem is the following:

simulate this circuit

What I couldn't understand is why the voltage source of 22V still appears in the simplified circit. By my what I understand of Thevenin, the 22V source should not appear in the final circuit, since Vth's calculations involved the 22V source. This is what it would look if I were to do it (the simplified circuit below):

simulate this circuit

Now, calculating Vth and Rth I get the same results, but when plugging again the dead network, here's what mine would look like:

simulate this circuit

I tried to make the most of the "name nodes" feature to explain myself better, especially because my questions are messy sometimes. Back to business. Obviously, I would not know where to "plug" "Wire X" terminals. It could not be at point A because R3 was connected between R1 and the 22V source, and it could not be between Vth and Rth because it also doesn't make sense and is probably wrong.

(1) I think that, maybe, the 22V source was plugged in the final circuit because this is the voltage in R3 even before we simplify it and it is like it is there, is this correct? But in case there is a resistance between V1 and R1 in the original I would run into trouble because I would first need to known what is the voltage drop between that resistor. (2) How do we deal when our points of analysis A and B are in the middle of the circuit?


texts: Implementing a continuous time transfer function in PC code

texts:
I have a transfer function like this:

\$ H(s) = \frac{1}{Ts + 1} \$

I converted it into a difference equation to solve it iteratively:

\$
H(s) = \frac{Y(s)}{X(s)} = \frac{1}{Ts + 1} \\
TsY(s) + Y(s) = X(s) \\
\mbox{Assuming the initial conditions are zero,} \\
T\frac{dy(t)}{dt} + y(t) = x(t) \\
y(t) = x(t) - Ty'(t)
\$

I wrote a code like this;

const double dt = 0.001;
double x;       // Input
double y;       // Output
double yp=0;    // Previous output value
double yd;      // Derivative of output
for(double t=0; t<TIMEMAX; t+=dt)
{
    // ...
    x = ReadNewInput();
    yd = (y - yp) / dt;
    yp = y;
    y = x - T*yd;       // y(t) = x(t) - Ty'(t)
    StoreNewOutput(y);
    //...
}

T symbolizes sensor delay (the sensor which reads x(t)) in my code. If T=0 (no sensor delay) my code runs very good. But if I set even a very small sensor delay (e.g.; T=0.1s) output becomes unstable (y approaches to infinity after a few iterations).

Am I doing something wrong? This is my first time implementing a transfer function in a computer algorithm like this. Are realization of continuous time transfer functions done like this, or do people use a different method? Please, can you confirm validity of my method, or make corrections on it?


texts:
I am looking for suggestions for wireless transmitter/receiver chips/circuitry. I have the following system in mind:

Multiple transmitters to one receiver
Transmitters do not have access to microcontroller and have to run off batteries that can only supply a few mAmp.
Bi-directional communication not a must, but a nice to have
I only need to send a byte or two of data to and from
System needs to be as miniature as possible, thus SMD IC's and chips are a must
System requires 50m or more transmission range

I have developed a solution that uses simple 433MHz transmitters with HT12 encoders and the corresponding receiver system on the other side. The downfall of this system is that while one transmitter is transmitting it will jam any other transmitter, and its one directional.
Does anyone have suggestions for the above? Bluetooth, BLE, RF, etc?


texts: what are these components under cpu chip?


texts: How to correctly read the nameplate of a Bitzer motor

texts:
This is the first time I have dealt with a BITZER compressor and the concept of part winding start. I have searched for meaning of all the information on the nameplate of a compressor motor. I want to make sure my information are correct

Nominal voltage = 380-420.
Frequency = 50.
Maximal operating current = 37.
A(Y) = 97 is starting current using the connexion part winding start Y/YY.
A(YY) = 158 is starting current using the connexion direct on line start YY.
The thing that confuses me the most is :
In nameplate of the compressor, the part winding start connexion it is indicated by (Y) but in cover of the motor terminal board by (Y/YY), while the direct on line start connexion it is indicated by (YY) and the same in the motor terminal board.
According to what I understood, the indication to Part winding start is Y=Y/YY while YY refers to direct on line start.
Correct to me if I am wrong
Thanks in advance


texts:
I was trying to find the stepper motor speed and the datasheet shows that it has a gear ratio of 10(the data circled with red). I assume this means that the stepper motor has an attached gear head. My question is when I am calculating the speed should I include the gear ratio, meaning the speed will undergo a reduction of 10?
If include gear ratio factor, my motor speed is 6rpm

Or I should just refer to this graph to get my motor speed(rpm)?
my pulse speed is 2000Hz. If i straight away use the data in graph , I get speed around 60rpm.
Sorry if this is an obvious question and I appreciate any inputs. Thanks!


texts:
I have a simple question. How many amperes can an AA battery draw? I'm studying electronics and looking at the Ohms law: V=IR and taking as an example a 1.5V AA alkaline battery, and considering the battery has an internal resistance in the order of 0.1 then it could be capable of delivering up to 15 Amperes?

Reading I see these can deliver up to 2 Amperes in real life so I'm a bit confused. What else is playing here that I'm missing?

Thank you,

Matias.


texts:
I have seen many times on the Internet how a boost converter can be used to step up the voltage of a low voltage battery (like 1.5 volts) to a higher level to light up an LED which normally wouldn't operate (it would not emit any light we can see) at this lower voltage.

I understand that the current-voltage relationship of an LED is exponential since an LED is essentially a diode.

But what confuses me is this: To conserve energy, if we step up the voltage with a boost converter, the current must decrease. So if we connect an LED to the boost converter, why do we see it light up? I mean, the LED says that if the voltage across it increases, the current through it increases exponentially (and it lights up). But on the other hand, the converter says that if the voltage on the output increases, the available current output decreases. To me this seems that the LED and the converter "contradict" each other, for the lack of a better word.

I would much appreciate if somebody could clarify this situation for me. The type of converter I'm talking about if pictured below. I'm imagining the LED in place of "load" in this picture.


texts: Calculate thermal noise power of receiver

texts:
My primary question (addressed at the end of this post) is that I have a voltage noise at the input to an ADC that I'd like to convert to a noise power. The remainder of this post details how I arrived at this voltage noise and why I'm having trouble converting it to a power level.
I'm attempting to calculate the thermal noise power of a receiver (at the input to an ADC). This is for a radar application where I'll use this noise power plus a minimum SNR to calculate the minimum detectable signal power, which I can use in turn to calculate the maximum range of the radar using the radar range equation. To calculate the noise power at the antenna, I use \$P=kTB\$. To determine the bandwidth, I take the frequency bin resolution of my downstream FFT, which is \$1.953\,\text{kHz}\$. I've used \$T=300\,\text{K}\$, which gives me a thermal noise (per FFT bin) of \$P=-141\,\text{dBm}\$.
The next 3 components in the receiver are an LNA, an RF amplifier and a mixer, which have reported noise figure (NF) and gains (G) of (all in dB):
LNA: NF=1, G=13
RF amp: NF=5.5, G=12
mixer: NF=14, G=-3
This gives me a cumulative NF of 1.7dB. I believe all of this is correct so far. Here's where it gets a bit trickier though. All inputs and outputs prior to the mixer output were matched to \$50\,\Omega\$. The mixer output has a differential impedance of \$200\,\Omega\$ and the IF amplifier that follows it has a high input impedance, and low output impedance as would be expected. The mixer output is AC-coupled to the IF amplifier input. So, I believe the next step is to take the cumulative noise power so far (at the mixer output), which is \$-139.3\,\text{dBm}\$ (\$1.17\times 10^{-17}\,\text{W}\$) and convert it to a voltage noise. \$V=\sqrt{PR}\$, which gives me a voltage of \$48.5\,\text{nV}\$ (\$R=200\,\Omega\$).
The IF amplifier datasheet contains a section detailing how to estimate the output noise voltage. I've followed these instructions (and checked it against their calculator mentioned in the datasheet) and got a output differential voltage noise density of \$90.8\,\text{nV}/\sqrt{\text{Hz}}\$. I multiply this by the square root of my FFT bin bandwidth (stated earlier) to get about \$4\,\text{$\mu$V}\$ of noise voltage added by the IF amp. Then I apply the gain to the mixer output voltage noise (48.5nV) and add that to the \$4\,\text{$\mu$V}\$ I just found. \$23.5\,\text{dB}\$ as a linear voltage gain is \$15\$, which amplifies the mixer output noise to about \$0.7\,\text{$\mu$V}\$. Add that to the 4 gives me \$5\,\text{$\mu$V}\$ thermal noise at the ADC input. I'm slightly less certain about this 2nd part, but I still feel everything is correct. Now here's where I'm stuck. Normally I'd convert this back to a power level using the ADC input resistance. However, it doesn't appear that the ADC I'm using listed the analog input resistance anywhere. At least I can't find it in the datasheet. Is this typical? How can I convert this back to a power level? Do I assume a differential input impedance? For instance, if I were to use \$1\,\text{M$\Omega$}\$, I would have a noise power of \$-136\,\text{dBm}\$. I guess this seems reasonable, but assuming the ADC input impedance doesn't feel very precise. Conversely, if I assume a larger input impedance at some point the noise falls below the initial value of -141dBm. This, of course, can't be correct.


texts:
I was just wondering out of curiosity... In the following circuit, if I were to supply a steady DC voltage to Vin and another to the Offset input, would this be true:

Vout = Vin - Offset


texts:
I've found several answers on switching between an Adapter and a Battery.
But I need to autmoatically switch between two batteries. One of them is 'hotplugable'.

Problem:
I've got a Solarcell which charges a ~16000mAh Li-Ion battery (BATa). Once in a while, the Solarcell doesn't manage to charge the battery enough. It's crucial that I have 3.0 to 4.1 Volts on my VSYS but the voltage will drop below this value if the Solarcell wasn't able to do its job (cloudy weather, vulcano eruption [joke], dirty cells, etc).

My Plan: I've come up with the idea to feed the VSYS with a additional, hotplugable backup battery (BATb) which does get connected to VSYS if BATa drops below ~3.1v.

So basically I need a Low-Voltage-Cutoff (using a Z-Diode with a Mosfet?) which, when cutoff happens, opens another Mosfet..?

simulate this circuit – Schematic created using CircuitLab

I'm not sure about the selection of M2 and how to wire it, so it will be conductive if M1 won't forward power anymore.

And I know about another electrical problem: Just using a Z-Diode (D1) with M1 will render M1 to something like a resistor, not a switch.
I've read, that I could use something like a Shut Reference (i.e. TI's TL43xx). Again I'm not sure how to chose the correct one and how to wire it.


texts: What is Power Supply Rejection Ratio and how does a high PSRR help me?

texts:
A lot of regulator datasheets give a figure of Power Supply Rejection Ration in decibals. I understand that a high PSRR is good, but how and where does it help me?

For instance, suppose I have a regulated wall-wart power supply that outputs 5V but with about 20 mV noise imposed upon it - let's further assume that the noise is most significant at around 50 kHz.

Would a regulator with 90 db PSRR from 20kHz to 1MHz help me reject that noise?

Let's further assume that I'm measuring voltage with an Instrumenation Amp + ADC (i.e. the In. Amp is driving the ADC). Would a high PSRR generally help me? (I know it probably depends upon a lot of factors but I'm talking about the general situation).


texts:
In the country were I live the mains electricity voltage is 230Vac. When I measure the mains voltage using an Uni-t UT52 multimeter, the multimeter measures about 247Vac.
It is safe to power the oscilloscope (model GDS 1052 U) at this voltage (247Vac)?
In the manual it is wrote that it can be powered at up to maximum 240Vac. Also in the manual it says "the power supply voltage should not fluctuate more than 10%".

It is safe to use the scope at 247Vac without any damage?
The oscilloscope could be damaged in time (after a few years or months of use) because of the high mains voltage?


texts: How does this overcurrent detection circuit work?

texts:
This is a overcurrent protection circuit. It'll triggered when it's more than 2Amps. I'm wondering how does that LM339 works related to the circuit. On the datasheet of LM339 page 11-13, it says:

– If IN– is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking
current

– If IN– is lower than IN+ and the offset voltage, the output is high impedance and the output transistor is
not conducting.

I'm trying to figure out how does the output go to short detection when IN- is higher than IN+, and the output will go to 3.3V when IN- is lower than IN+ (based on my spice simulation). Like how does the current flow in the high impedance mode and how does the current flow to the short detection node? The short detection node is a digital input to a microcontroller.


texts: Programming a UART for PIC24F, can't write the character into the Transmit Buffer

texts:
I want to create a simple program that transmits a signal from my UART module of my PIC24FJ1024GB610 microcontroller from Microchip.

I am using UART1, 8 bits, No parity, and one Stop bit.

According to the Datasheet and the dsPIC33/PIC24 Family Reference Manual, UART, in order to start a transmission, we should perform the following steps:

Configure the Clock Signal source (4MHz from FRC)

I would like Fcy = 4MHz, CS is sourced from FRC (Fast Internal RC) which have a frequency of 8MHz, after passing through the postscalar the frequency gets divided by 2. Section 9.0 of the Datasheet

#pragma config FNOSC = FRC

Configure the Baud Rate Generator Time Period.

This formula is from the Datasheet, Section 19.1, I use this formula to get the Baud Rate Generator period (UxBRG). My Fcy = 4MHz, Baud Rate = 9600

U1BRG = ((4000000)/(16*9600)) - 1

U1BRG = 25

Configure the UART, I would like the UART data format to have 8 bits, No Parity, and one Stop bit

U1MODEbits.PDSEL = 0;//8 bits, No Parity
U1MODEbits.STSEL = 0;//1 stop bit
U1MODEbits.UEN = 0;//only use UxRX and UxTX pins

Configure UART TX ISR source, I want a TXIF to be set when a write is performed on UART1 Transmit Buffer (U1TXREG) U1STAbits.TXISEL0 = 0 U1STAbits.TXISEL0 = 0

Enable the UART U1MODEbits.UARTEN = 1 and enable the Transmitter U1STAbits.UTXEN = 1
write a value at the TX Buffer U1TXREG

As soon as there is a write on the TX Register, the data is transferred to the Transmit Shift Register, and it will stream the data one bit at a time.

In order to ensure a successful transmission at first, there should be a delay between Enabling the UART and writing to Transmit Buffer, the delay = 1/BaudRate, in our case it is 1/9600 = 105 us

Since my application isn't time critical I decided to make a simple for loop as a delay it will count from 0 to 0xFFFE for(i = 0;i<0xFFFF;++i);

There is the full code for reference:

#pragma config FWDTEN = OFF
#pragma config ICS = PGD2

#pragma config FNOSC = FRC

#include "xc.h"

int main(void)
{
    U1BRG = 25;//U1BRG = (4000000)/(16*9600) - 1

    //UART SETUP
    U1MODEbits.PDSEL = 0;//No parity, 8 bits
    U1MODEbits.STSEL = 0;//One Stop Bit
    U1MODEbits.UEN = 0;//only U1TX and U1RX
    U1MODEbits.BRGH = 0;

    U1STAbits.UTXISEL1 = 0;//tx isr when a write occurs to TX BUF
    U1STAbits.UTXISEL0 = 0;

    //U1TX pin
    RPOR5bits.RP10R = 3;//U1TX -> RP10

    U1MODEbits.UARTEN = 1;//enable UART

    U1STAbits.UTXEN = 1;//enable transmission

    unsigned int i;

    for(i = 0; i < 0xFFFF;++i);

    U1TXREG = 'a';

    while(1);

    return 0;
}

When I debug and step into the U1TXREG = 'a', I am supposed to get an 'a' at the U1TXREG, but instead, it is 0, I even changed the to a 2 and it is still 0.

I even tried debugging and capturing the UART signal using an oscilloscope, I mapped U1TX pin to a Peripheral Pin Select pin (RP10) which is Pin 49 on my development board (Explorer 16/32), I only see a High State (3.3V) at the pin.

Your help is appreciated.


texts: Non-reentrant Functions as Macros for utilities used in both Main and Interrupts

texts:
When compiling software with xc8 for a PIC which has functions which are called in both interrupts and in the main function the compiler gives an advisory:

non-reentrant function "foo" appears in multiple call graphs and has been duplicated by the compiler

Although this is not necessarily an issue, I understand from some reading that it is bad practice to call functions from both an interrupt and main.

Does this extend to pre-processor macros?

Most of the functions that I implement and are used in both are simple aliases for some simple maths, for example:

uint16_t timer3_get_value(void)
{
    return (uint16_t) (TMR3H << 8) | TMR3L;
}

Would making this function inline or changing it to a macro make a difference and/or be better practice?

#define TIMER3_GET_VALUE() (uint16_t) (TMR3H << 8) | TMR3L


texts: Figuring out transmission protocol in cheap wireless door bell

texts:
Due to boredom I've tried some reverse engineering of simple cheap wireless ring bell which uses 433.92MHz transmitter and receiver via OOK modulation. It sends several times the same information. On the transmitter side there is AD1614AT chip (which seems to be this one). On the receiver side there is CMT2210LC chip (this one).
I've recorded data on DOUT pin on the receiver side, it looks like following:

I'm not very familiar with such coding protocol(?) so I need help from more experienced guys here.
Data from record looks like that (assuming that 200us is our "clock period"):
1110 1000 1000 1000 1000 1000 1110 1110 1000 1110 1110 1000 1110 1000 1110 1000 1000 1110 1000 1000 1110 1000 1000 1000 1000
I've noticed also that short impulse takes about 200us and long one about 600us. It looks like data is encoded as pair of long and short states, for example 600us H + 200us L -> binary "1". If we do such decoding we get following data:
10000 01101 10101 00100 10000
or if we decode data other way we have:
01111 10010 01010 11011 01111
I've grouped data into 5 "bits" because we got 25 bits in total. From that point I'm lost. Do you guys know such coding/decoding method? I saw something similar (long/short impulses) some time ago in some old IR remote control but I don't know anything more. I've checked transmitter's datasheet and in ODS_TIMING register description (page 42) I've found following "serializer" description:
ODS_GROUP_WIDTH[2:0] - Controls Symbol Group width, from 2–8 Symbols. Set to 4 to transmit 5 symbol groups obtained from 4/5 encoding. Or set to 7 to send 8 symbol group obtained from Manchester encoding of 4 bits.
With 4/5 encoding we would decode it to:
10000 01101 10101 00100 10000 -> no '10000' symbol in the table :(
01111 10010 01010 11011 01111 -> 0x07 0x08 0x04 0x0D 0x07
I'm not sure is that data has any meanings, but it would be nice to know if I decoded it correctly. One more thing what I've found in the meantime that similar coding(?) is in remote controls, for example NEC1 protocol (burst for 562.5us, 562.5us space -> "0" etc.). Here I have the same time for single "symbol".
Edit:
As @Mattman944 suggested, protocol codes symbols ("1" and "0") by long and short pulses. After every pulse there is a change in signal state. Therefore message would look like this (assume long pulse as "1"):
10010101010110100110100110011001011001011001010101
50 bits, let's say first 2 bits is header, then we have:
10 01010101 01101001 10100110 01100101 10010110 01010101 ->
HDR 0x55 0x69 0xA6 0x65 0x96 0x55 ->
frame header, marker, val_1, val_2, ((val_2<<4 & 0xF0)| (~(val_2>>4)) & 0x0F), ~val_1, marker
Which seems to be that message. To make sure I would need to dump code from transmitter and disassemble its code but it's too much for such simple device.
Anyway new question is:  what is the name of such coding when symbols are coded by length of pulses (long/short) and after every pulse there is a change in signal's state? It look similar to some barcode coding but I don't know which one.
For any hint and help thanks in advance!


texts: Can multiple looper ICs (ISD1820) share one single electret microphone?

texts: I'm using multiple of these ICs to create a simple audio looper. Can they share the same single electret microphone, or should they each have their own? Multiple ICs may have brief overlap of use of the microphone.


texts: have real data types in vhdl and want to convert std_logic_vector;

texts:
I have trouble understanding conversion between different data types in VHDL and needed help with conversion to `STD_LOGIC_VECTOR' type in VHDL.

I want the code below to be synthesized such that it can be used on real hardware.

This is my code:

LIBRARY  ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.numeric_std.ALL;

ENTITY sfixed IS
  port( N1 : in integer := 15;
            N2 : in integer := 23;
            Ni : inout integer;
            Nii : inout integer;
            N : inout integer;
            Y : inout integer;
          SIG_A  : out STD_LOGIC_VECTOR(31 DOWNTO 0));

END ENTITY sfixed;

ARCHITECTURE behavioral OF sfixed is
  constant  W1  : real := 0.4992;
  constant  W2 : real := 0.4992;
  constant b : real := 0.0099297;
  constant N1max : integer := 35;
  constant N1min : integer := 0;
  constant N2max : integer := 56;
  constant N2min : integer := 0;
  constant Nbmax : integer :=90;
  constant Nbmin : integer := 0;
  signal W3: unsigned(31 DOWNTO 0);
  signal W4: unsigned(31 DOWNTO 0);
  signal b1 : unsigned(31 DOWNTO 0);

BEGIN
    W3 <= to_unsigned(natural(W1),32);
    W4 <= to_unsigned(natural(W2),32);
    Ni <= ((N1-N1min)/(N1max-N1min));
    Nii <= ((N2-N2min)/(N2max-N2min));
    Y <= (Ni*W1)+(Nii*W2)+b;
    N <= (Y*(Nbmax-Nbmin))+Nbmin;
  SIG_A <= STD_LOGIC_VECTOR(Y(31 DOWNTO 0));

END behavioral;

and i get many error like this:

ERROR:HDLCompiler:1731 -  Line 54: found '0' definitions of operator "*", cannot determine exact overloaded matching definition for "*"

ERROR:HDLCompiler:541 -  Line 56: Type integer is not an array type and cannot be indexed.
ERROR:HDLCompiler:622 -  Line 56: Near std_logic_vector ; type conversion expression type cannot be determined uniquely
ERROR:HDLCompiler:854 -  Line 34: Unit <behavioral> ignored due to previous errors.

Thanks


texts: Why are CT's(Current Transformers) on an ammeter / energy meter connected to ground?

texts:
It's understandable that a CT, needs to be shorted (or a burden resistor) if there's nothing connected to its output, otherwise it would work as a step-up transformer.

But why is it that energy meters (example) show in their datasheets(p.9, fig1-8) that the CT's should be connected to earth?

As they state in the user manual:

  Current measuring input terminals must be connected through a
  R/C Measuring transformer with one lead connected to Earth.
  Direct connection to the line voltage is not allowed.

I wonder what is the technical/scientific reason behind this.


texts: I have a piece of old instrument circa 1988 that uses +-12V in its serial port. According to the manual, DTR pin (Data Terminal Ready) must be held at +8V in order for the instrument to recognize that it is being connected to from the serial port. I have tried CH340 USB to serial dongles to no avail before I discovered this DTR voltage requirement. Do I have to build a voltage booster for this? I see numerous USB or PCI to serial dongles and cards, but none specifically mentions having an adjustable voltage level.  Is there a simple solution for this situation?


texts: How to create tag type of label in Cad Eagle?

texts:
I can't get my copy of cad eagle to create tag type of label for a wire or a net. Instead I get simple text type of label. GND label is what I am trying to get.

I have tried turning xref on and off, and changing size or font. In the end, all I get is simple plain text label. So, how do I get the fancy tag type of label?


texts:
I'm building a small circuit to power a heater at 380mA using a 3.7V battery.  I'm using an AMC7135 to regulate the current to 380mA.  Without the AMC7135 the heater would typically draw ~500mA, so the AMC7135 should have no trouble regulating it.  This is the circuit I currently have:

simulate this circuit – Schematic created using CircuitLab
The problem is that it always regulates the current to just 30mA, instead of the expected 380mA.  I assumed this was some sort of inrush current problem, so I tried putting capacitors between GND and OUT, and GND and VDD, and OUT and VDD as well.  But that didn't work either.
Interestingly, if I hold the switch down then connect the battery, it goes to 380mA as expected.  But pushing the switch alone just gives 30mA.
In the final product, the switch will be replaced with a microcontroller. So it can't be attached directly between the battery and load (otherwise it would be fried by the 380mA).
How can this circuit be modified to get the 380mA regulation as expected?
EDIT:
My inspiration for this circuit comes from this webpage:
http://www.pratikpanda.com/amc7135-pwm-led-control-max-frequency-speed/
I'm assuming that if PWM works, then turning it on and off manually should work too.


texts: Coaxial Conducter Diameter for Antenna Tuning VNA Small Trace IoT

texts:
I have a very small IoT type board, and have been asked to tune the antenna on the system.  The antennas traces are very small and I'm wondering what inner size conductor diameter folks are using on these boards with coax pigtails?

I don't have the gerbers of the board, so I'm not certain quite how on the diameter of the trace but it's tiny.

Once you get past RG405 (0.086"), it gets really expensive for SMA terminated cabling like I want for my VNA.   I've ordered some 0.086" coax just to confirm, but I think it'll be too big.

Is there anyone with experience tuning tiny antenna traces, if so, what size coax did you end up using?


texts: Monostable Multivibrator One Shot - action with input held indefinitely

texts:
Looking for a one shot IC, that will produce and complete the predetermined output pulse (about 15ms) despite the input, that gave rise to said pulse, held constant.  The reset needs to be accomplished once the input changes its state again. The input is a footswitch that may remain actuated beyond the pulse duration.  Retriggering during the pulse is not allowed.

I found a chip that in the data sheet perfectly describes the desired action in, for example, Maxim's Microprocessor Supervisory chips (with manual reset capability), but the SMD package is too small.

There are at least two PDIP chips named Monostable Multivibrator but mention nothing of the case where the input is held throughout the pulse duration, or whether changing the input state back to where it was will prepare the chip for the next event.  They are:

CD54HC4538, CD74HC4538,
CD54HCT4538, CD74HCT4538

SN54121, SN74121

Any pointers will be greatly appreciated.


texts: Transimpedance Amplifier Behavior With Supply Voltage

texts:
Below is a transimpedance amplifier (OPA380) that I'm using to convert a pulsing current signal from a photodiode in (SFH7050).

Everything works as expected when I was using 2.5V and -2.5V as supply, eg. output voltage and frequency response.

When I change the supply voltage to 3.3V and GND as supply, everything just changed. In this case, the frequency response slide downwards from 1kHz onwards and the output voltage is not the same as before. The output voltage drop from V to mV.

I can't figured out what's wrong as the datasheet mentioned it could operate in a single supply from 2.7V - 5.5V. I can't post more than 2 links currently, so I'll try to provide more info in the comments.


texts:
The ATtiny85 datasheet specifies an absolute maximum negative voltage for any pin of -0.5 volts relative to ground.

Consider this partial schematic:

MOSI and MISO are the respective ATtiny85 pins and the CLOCK terminal is connected to the coil of a lavet stepper motor - which means it's just an electromagnet coil.

It works, but when I had the outputs on a scope to examine some of the timing, I happened to notice a negative going spike as the output is turned off, despite the presence of the flyback diode. I quickly realized that the magnitude of the spike is the forward voltage of the diode - in this case, 1 volt.

The question I have now is, does that absolute maximum (actually, absolute minimum in this case) rating apply to pins configured as outputs set to LOW?

I can replace the 1N4148s with Schottky diodes with a forward voltage of only 0.5 volts... but is it worth bothering with?


texts: How to access Altium Content Vault component libraries in CircuitStudio 1.5?

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Note that I am on the 30 day trial of circuit studio; not sure if they limited access to this feature because of the trial. Older forums indicate that this is not the issue, but FYI.
I followed this Altium youtube video as well as this CircuitStudio documentation.
Added the content vault without issue:

However when I open the "Vault Explorer" I only see half of the menu the documentation/youtube video sees. There is no way to search or select components. The right click menu has some structure tree options but does not have the option to select or add parts. Thoughts??

The search tab has even less info:


texts: Charging capacitor to power LED with a low current source

texts: I have a 10000uF 6.3V capacitor, and my source is generating 3.3V and 15uA of current. How long will it take to charge it enough so i can pulse a standard 5mm LED for lets say 1 second?.


texts: Calculating dissipation of a CCR powered via a full bridge rectifier

texts:
I'm putting together a string of UV/purple LEDs for photoetching purposes.

The idea is the following:

simulate this circuit – Schematic created using CircuitLab

The 80 LEDs are in series, and have a typical Vf=3,5 V. Since the maximum Vak across the CCR is 45 V, I'm also adding a resistor (ideally 1,45 KOhm, I will check later an appropriate standard value), just in case the supply voltage reaches the full 253 V.

This is the CCR I'm using: NSI45020AT1G

This is the application note I'm following: AND8433/D

Now to my problem: I wanted to check how much power the CCR should dissipate and I tried to follow the application note.

Quoting page 3:

  Thermal Analysis of Design Example 1
  (120 VAC, 38 LEDs)
  The power dissipation of the CCR for Figure 3 is determined by:

  (Vak rms) x (IREG*Duty Cycle )

  Vak rms = Vbridge rms - LED string VFrms

  (120 Vbr rms-(38 x 3.3 V LED x 0.707 ) x (30 mA x 50%)

  = 31 V rms x 15 mA = 465 mW

I'm confused by the calculation for Vak rms, in particular by the 0,707 factor. And wh

This is how I would have calculated the Vakrms:

$$Vbridge =Vpk*sin(2\pi f t)$$

where Vpk is 350 V for a 230*1,1 V supply, f=50 Hz.

Most of the current flows when

Vbridge > 1,8 V [the CCR overhead] + 80*(3,5 V) + R1*20 mA

So,

$$\left |\sin (314  t)\right | > \frac{1,8 V + 80\, (3,5 V) + R1\; 20 mA}{Vpk}$$

I plug the whole thing in Wolfram|Alpha and find that the on time is 6 ms.

6 ms * 50 Hz = 0,3

So the duty rate is more or less 30%.

Vak rms = (Vbridgerms - 80*Vf -R1*20 mA)*0,3

and Vbridgerms is 230 V (or 250 V at most)

Am I doing something wrong here? And what the idea behind the calculation on the paper is? In particular, what is the 0,707 ($ \frac{\sqrt{2}}{2} $ ?) factor for?

Thanks


texts: What would be involved in rectifying electricity from a faulty car alternator?

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Disclaimer: Newbe

As I understand things:

a car "alternator" generates a/c current
the alternator contains diodes that rectify the current to d/c current
if one or more diodes fail then the alternator sends a/c current into the wiring causing all kinds of grief

Rather than replacing the alternator what would be involved in wiring a rectifier inline (external to the alternator on the output side) to get rid of the a/c?


texts: driving LEDs via a PI a attiny and TLC5940 (validation) and possible powering issues

texts:
at the moment I am planning my first real (big) electronics project. I want to build a LED lamp, that can be controlled by a RaspberryPi (for e.g. programming a binary clock or changing the brightness according time of day).
I built this schematic for the project (also at the end of the question as a image, as this is a .pdf).

There are two main problems giving me headaches:

I wonder if the LEDs will be a) faded/animated smoothly and b) provided constant/non-fluctuating power, because there are a Pi, a AtTiny, five TLC5940 and far too many other LEDs. I currently want to use a fairly standard switching power supply
I have no experience at all with µControllers except a little bit of arduino testing, so, will my idea of using the Pi to write the PWM data (at inconsistent timings) while using the attiny for clocking the TLC5940s (at consistent timings) work? I intended to send a READY signal from the Pi to the attiny so it knows it can BLANK and restart the PWM counters and maybe can slow down a bit (it has a too high clock speed for this application anyway, doesn't it), though I have no idea how to the latter program at this point.

so, yeah, I would greatly appreciate it if someone has any ideas for these two issues

as a little more information here is a "blueprint" like drawing of the lamp :D

thanks in advance!

EDIT: Just noticed I confused the XLAT and XERR ... I want to read the error flags and have an output to the latches, not the other way around. I'll leave as it is for the time being though


texts: Why does 802.11 use the same modulation for each subcarrier?

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In Wireless Communications, Dr. Molisch writes that the 802.11 standard "does not foresee truly adaptive modulation in the sense that the modulation alphabet can differ from subcarrier to subcarrier."

Why did the 802.11 standards committee not design towards allowing different data rates on different subcarriers?


texts: I connected the oscilloscope probe to the mains supply but i find its waveform not excactly pure sine wave, So im wondering if there are problem in my scope or something else.


texts: Can I power TTL chips with an USB-powered MB102 board?

texts:
I am adapting the digital electronics lab assignments I teach so they can be done at home with inexpensive supplies rather than with the equipment in the hardware lab. I have breadboards, TTL chips, and LEDs and will want students to build full-adders out of AND, OR, and NOT gates, so I don't need much current. I am looking at MB102 power supply modules, most of which have USB inputs. I understand that I won't get 5V out with 5V input through the USB port. Will I get a high enough voltage to use TTL chips without flakiness? I am trying to avoid the expense of buying and shipping wall warts (but can do so if necessary).
To answer some questions, soldering is not an option. The unit is only on digital electronics, not analog. I'd like something quick and easy for students that just works, especially because it will be hard to debug circuits remotely.


texts: What tasks does Graphics hardware perform and what steps does it follow to do so

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I am not intending to go into high end GPUs here. That is too advanced. What tasks does a basic graphics hardward perform? By basic perhaps we can go back in time and see what it did in the early days before we got into all this 3D graphics and pixel shaders world. I understand that it should be able to draw lines and write text and "rotate things", but that is layman's language. For engineers that work with these things, how would they describe the functions of a basic graphics hardware in technical terms?

Now usually in digital circuits there is some state machine based controller which implements the hardware functionality. I curious about how a basic graphics hardware works and would be good to see a basic example of it.

And finally, have people had to write a graphics hardware to implement on FPGA for an application which has a rather complex LCD display?


texts: 9-volt battery connected to transistor controlling LEDs with Arduino

texts:
I am trying to add a custom LED lighting setup to my desktop gaming computer. In this setup I want small sets of LEDs to be able to be turned on separate of other sets. This is so that I can turn on different sets at different times to make a "light show".

I am using an Arduino's digital I/O pins to control a transistor (BC547B) which will supply power from a 9-volt battery to the LEDs. The LEDs are rated at 1.9v and I have multiple sets of 5 LEDs (5 * 1.9 = 9.5 -- no need for a resistor... right?) connected in series and those "multiple sets" are to be connected in parallel.

However, due to a simple lack of transistors, I am temperarily (until I get more transistors) connecting 2 sets of the 5 LEDs per transistor. Confused? Let me put this together in a schematic using only 1 transistor (in the final version there will be more):

simulate this circuit – Schematic created using CircuitLab

So, basically the problem is, when I turn on pin 5 on my Arduino, the LEDs do not light up. Why is this?. I may be doing something wrong here, but, if I am, I cannot figure it out.

Here is the temporary code for the Arduino I am using, just in case someone wants to see it:

void setup() {
    pinMode(5, OUTPUT);
}

void loop() {
    digitalWrite(5, HIGH);
    delay(1000);
    digitalWrite(5, LOW);
    delay(1000);
}

All it does is turn pin 5 on, wait a second, turn it off, wait a second, and repeat.

Thanks in advance.

P.S. Apologies for awkward title.

EDIT:

I should also note that I'm very new to this kind of stuff. I'm doing this for a sort of learning project (and so my computer can look cool).