texts: How can I get rid of interference between two signals in this timing circuit?

texts:
I have designed a small circuit to perform the following functional purpose as illustrated below. The circuit takes a PWM signal as input from a microcontroller and outputs two smaller pulses (ideally between 0.5\$\mu\$s and 10\$\mu\$s) - In practice I can achieve a minimum of 1\$\mu\$s. The pulse widths and delay between the two pulses are adjustable via potentiometers such that TA,TD and TB are adjustable independently.

I originally designed this circuit around some 555 timers however quickly realised that this choice of IC was a bad one because the minimum pulse width I could get was around 7\$\mu\$s. I've now designed the circuit using the DM74LS123 as shown below:

The circuit above is based on the delay circuit in this application note (page 14). It uses two ICs with only the first half being used on the first IC.
I've constructed the circuit on veroboard. Shown below is the PWM input signal (top) and the first output pulse from the timer IC below it on channel 2 labelled "pulse 1" in the schematic above.

The first output pulse (width around 13\$\mu\$s) is shown relative to the rising edge of the PWM pulse:

Lastly the first output pulse and second output pulse are shown top and bottom respectively. At the rising edge of pulse 1 there is a small spike on the second channel as well as a larger spike where the falling edge of pulse 1 is on the second channel. There are also some spikes at the pulse edges. I've highlighted these "trouble regions" in red below. Ordinarily this wouldn't be a problem however these pulses are fed into an H-bridge circuit and used to switch high voltages (I suspect that these pulses may be too small to drive such large voltages but that is another story) and so I need the pulses to be as square as possible and transition from low to high without any spikes before the rising edges. Using the second pulse from this timing circuit into my H-bridge amplifies this spike before the rising edge. This is undesirable for my application as I'm trying to use two consecutive small high voltage pulses to flex a piezo buzzer in one direction and then in another. This small pulse before the rising edge may cause the buzzer to flex in one direction, return to its nominal position and then flex again more strongly which I do not want:

My questions:

What could be causing these small spikes before the rising edges?
How can I remove those spikes and make these pulses as square as possible? (Schmitt trigger maybe?)

edit
One user suggested monitoring the supply rails. Below is the 5V rail on channel 1 and on channel 2 the second output pulse from the timer. It looks like the +5V rail peaks and dips substantially (nearly 1V from nominal 5V) at the falling edge of the second pulse. On the veroboard I already have two 0.1uF caps from the VCC pin of each of the chips to ground. They're ceramic capacitors. The datasheet for this IC states:

VCC and ground wiring should conform to good high-frequency standards and practices so that switching transients on the VCC and ground return leads do not cause
interaction between one-shots. A 0.01 mF to 0.10 mF
bypass capacitor (disk ceramic or monolithic type) from
VCC to ground is necessary on each device. Furthermore, the bypass capacitor should be located as close
to the VCC-pin as space permits

Tried changing the 0.01uF caps I had in there to 100uF but that made no difference to the spikes.


texts: Eagle - 6 Layer Via pairing error + bga fanout

texts:
I'm trying to manually fanout 5 bga's on my 6 layer board. Tried using Eagle's default Auto BGA router and kept coming up with problems regarding my additional layers being used but not enabled, I managed to fix this problem for my bottom ground layer but wasn't able to fix this for my power, middle signal & top ground layers however, so I just ended up doing this manually.

My 1st problem I'm encountering is the via pairing within the DRC layers tab.
I've got it set to 6 layers and want to be use the following pairings:

1-2
1-3
14-16
15-16
1-14
3-16

I can add everything perfectly fine except the 2 last pairings (1-14 & 3-16). I can add one or the other; however if I add the other then I get an error either for invalid blind via or unexpected ':'

For example if I add the 3-16 pairing I will get the following setup string:  ([3:[2:[1*2*3*14*15*16:3]:15]:14])
However if I then add 1-14 I get the following below error:

If anyone knows how to get around this error and allow me to use all of the above pairings in one go, would be most appreciated.

My board stackup is as follow:

Top     (1)
TGround (2)
Middle  (3)
Power   (14)
BGround (15)
Bottom  (16)

Where Top, Middle and Bottom are signal layers whilst all signal lines relating to power will be located on the Power layer.

My 2nd problem I'm faced with is that out of the 5 bga's I'm working on 2 of them are completely different pitches for their ball arrays.

With one being 0.5mm & the other being 0.42mm (The other 3 bga's being 0.65mm)
Which settings within DRC do I need to change so I can fanout the smallest bga?

An sub-question to this I'd like to ask how I would be able to manually place micro-via's? The auto bga router apparently does it but after scouring the web/autodesk eagle forums I've found no posts on how to manually place them.

Thank you for help @Tom Carpenter. I did manage to get a hold of a product specialise from AutoDesk who provided me with the following setup string: [14:[3:[2:(1+2+3+14+15+16):15]:14]:3]

My question to ask regarding this string as its purely 5 cores. Would it be possible at all to incorporate prepreg into 1:2, 3:14 & 15:16 or would this create an impossible to build design?


texts: Correct calculation of conductance/susceptane and from there to admittance, impedance, resistance and reactance.

texts:
I am sending a sine wave through a unknown RC circuit. At the other side I have a current-to-voltage converter (transimpedance amplifier) measuring the current indirectly as voltage.

I am using IQ demodulation technique and get the Real and Imaginary part of the voltage representing the current.

I want to calculate the admittance, impedance, conductance, resistance, susceptance and reactance.

First of all the values Iv and Qv (Iv and Qv is the voltage representing current) need to be converted to current:

Ii = Iv / Rf
Qi = Qv / Rf

where Rf is the transimpedance amplifier feedback resistor.

Since I am exciting with voltage and reading the current I assume I have a ratio of current to voltage which is admittance.

If the excitation voltage is Vex admittance Y is then given as:

Y = G + jB = (Ii/Vex) + (jQi/Vex)

The amplitude is given as:

|Y| = sqrt(G^2 + B^2)

By using complex number one can derive the relationship between conductance and resistance:

R = ( G / (G^2 + B^2) )

and reactance and susceptance:

X = -j * ( B / (G^2 + B^2) )

Impedance is then:

Z = R + jX

and amplitude:

|Z| = sqrt(R^2 + X^2)

Do I convert to current correctly? Do I find conductance and susceptance correctly? Did I understand correctly that the values I measure is admittance? Is the Z, R, X conversions correct?

Lets say that the unknown RC circuit was only a 1000 Ohm resistor. I would then find out that Z = R = 1000 right?


texts:
I'm currently trying to build a circuit on a breadboard that, through a temperature sensor,
gives off a voltage which I need to amplify. I'm using a Pt100 sensor with 3 wires (red, blue and yellow) connected in a Wheatstone bridge that I in turn connect to an instrumental amplifier and get an output voltage. I have built pretty much the entire circuit; the schematic is this:

The negative voltage input to the amplifier goes in pin 2 and the positive in pin 3.
I'm using 100 Ohm resistors for the Bridge and a potentiometer for the Gain Resistance, but that's not the problem. I don't know how to connect the Pt100 wires in order to get my Wheatstone Bridge. I have thus far built the following circuit in my breadboard:

I have wracked my brains over this and although I'm sure the answer is right in front of me I can't for the life of me see it. My head hurts. I wouldn't know if you need any further information. I figure with the 100 Ohm resistances further up on the breadboard I'm getting the lower 2 that show up in the schematic. I'm not sure anymore though. Everything got messed up in my head somewhere along building it.

I greatly appreciate your help. I looked up how the wires work but didn't understand much. I guess the answer I'm looking for is an explanation of why there are 3 wires, how to connect them and breadboard-related, where exactly (row number, letter) to connect them. Or any corrections to the bridge.


texts: Antenna Diversity: two Yagi antennas to the Rx and Rx/Tx u.fl-male points on the wifi-NIC?

texts:
I looked at the BCM4312 file - available as as doc or a pdf - and it says:

  BCM4312 has 2 radio chains, one is a dedicated Rx chain, the other is shared by TX and > RX chain using an RF switch
  Support Antenna Diversity

  RF Output Power
             802.11b: 16.5 dBm ± 1.5 dBm
             802.11g: 15.5 dBm ±1.5 dBm

Can I hook up two Yagi antennas to each u.fl connector (it has 2 u.fl male connectors) and will "diversity" work? How exactly does all this work?

Wiki says:

  Spatial diversity employs multiple antennas, usually with the same
  characteristics, that are physically separated from one another.
  Depending upon the expected incidence of the incoming signal,
  sometimes a space on the order of a wavelength is sufficient. Other
  times much larger distances are needed

  Transmit/Receive diversity uses two separate, collocated antennas for
  transmit and receive functions. Such a configuration eliminates the
  need for a duplexer and can protect sensitive receiver components from
  the high power used in transmit.

  All of the above techniques require some sort of post processing to recover the
  desired message
  - Switching – In a switching receiver, the signal from only one antenna is fed to the receiver for as long as the quality of that signal remains above some prescribed threshold. If and when the signal degrades, another antenna is switched in. Switching is the easiest and least power consuming of the antenna diversity processing techniques but periods of fading and desynchronization may occur while the quality of one antenna degrades and another antenna link is established.


texts:
I'm building a small laptop-ish device in a briefcase. Imagine the green wires aren't there. The LCD half lies somewhat deeper in its case than the keyboard part.

For now, testing and programming, I'm using four wires (2x I2C, ground, 5V) to connect the both parts. However, that isn't that neat. When closing the case for example, you should look after the wires in order for them to stay in the case. First solution of course is shorter wires, but that wouldn't be that neat either.

So what I'm looking for is a neat way to do the inter-board communication. It should be easy to handle and robust.

The normal way to do this in a laptop is to wire it through the hinges. This isn't a possibility with this case, unfortunately.


texts:
Assume we have a full-wave rectifier bridge circuit connected to a load made of a resistor with resistance R and a capacitor with capacitance C in parallel to each other.

In the first quarter-period, the capacitor is obviously charging with the diode from the rectifier on (We assume it is ideal and that the connecting wires are ideal as well.). However, from the quarter period to the half of the period, I have no idea how to get an analytical formula and derive whether the capacitor charges or discharges.

How do we get an exact equation governing the capacitor and when exactly does it start discharging? Does it do so exactly at the quarter period or does it start discharging after a certain angle?


texts: How to determine class of these amplifiers?

texts:
Is there a way to figure out the class of the following IC amplifiers from their datasheets?

https://www.st.com/resource/en/datasheet/cd00000134.pdf

http://www.unisonic.com.tw/datasheet/MC3419.pdf


texts: How are DC offset square wave transmission waveforms generated?

texts:
The balanced serial transmission shown in the picture is similar to rs485 except that the square wave has a DC offset (e.g. 24VDC) with an alternating offset.

The transceiver chip "drives" the bus using capacitors that are in series with the bus.

How does one generate plus-minus ~3Volt offsets with a 1uF series capacitor? Blue and Purple signals are created this way.
Edit: Clarifying the DC offset part.  The bus is powered by a DC power supply (e.g. 24VDC) and an "AC blocking" inductor (which looks like a transformer).


texts: Opamp Burn up in constant current circuit

texts:
I designed a programmable constant current power supply to control two solenoids(electromagnetic).For the solenoid to open and close proportionally(it can move between fully open to fully closed and in between)  i need to change the current from 0 Amps to 0.5 Amps under 24V. My problem is after few runs the opamp tend to heat up and it malfunctions(sometimes one valve stop working) and once the op-amp burnt up(literally smoke came out and was split in the middle)

What am I doing wrong and how to fix it ?

FYI: the Arduino and 24V power supply grounds are connected even though its not clear in this diagram.

MOSFET data sheet : https://www.jaycar.com.au/medias/sys_master/images/9346270003230/ZT2468-dataSheetMain.pdf

Opamp data sheet : http://www.ti.com/lit/ds/symlink/lm358.pdf


texts:
I want to know how can I choose stepper driver, once I have decided on the stepper motor that I wish to use.

This is how I understand it: If a motor can draw a current of say 0.5 amps and operates on 6.5 volts, I should choose a driver that's capable of providing at least 1.4 times more current than 0.5A. (Let me know if my understanding is correct). Also will I damage the motor by using a driver that itself works on voltage of 8-35V (voltage higher than that of motor)?

Let me know if my understanding is correct that if the stepper can provide more current it's good and will not damage the motor?

I conducted an experiment recently and used a L293D board to run a stepper taken out of DVD drive. I found the chip got way too hot (chip could provide current only of about 600mA), but motor was a little toy. I wonder where I went wrong. Perhaps the operating voltage of the driver was high (4.5V-32V). I did not have datasheet for the motor unfortunately. I need help with choosing driver so that I don't burn something and could succeed in building my own CNC.

I do not wish to go with kits that come from China and want to make informed decision. :-)

Thanks.


texts: Can't power controller and LEDs with chosen power supply (works in one project but not in other)

texts:
I'm currently running into a rather confusing problem...

I'm trying to power a strip of 60 WS2812 Leds and an NodeMcu/ESP8266 board.

The supply I chose is a 5V/4A supply.

This one to be precise:
Meanwell GST25e05-P1J

I got myself some sockets to connect the supply to my circuit.

I already built a similar project here and it works flawlessly.

But in my current project I just can't seem to power the LEDs with that supply. I already tested it on the other circuit and there it works. So it isn't faulty.

But then when I power the current project with the USB from the NodeMcu-Board or with this 5V/10A power supply it works as intended.

I also ordered another batch of power supplies using the same connector but they also don't work.

So I rebuilt the whole circuit on a breadboard and used another of the sockets I had to power it with the same supply and it works without any problems.

So I thought it might be a problem with the socket I built into my case. But when I soldered another socket in there I still get the same result. It just doesn't seem to work.

I will attach a poorly drawn circuit diagram and a picture of the circuit in its case.
(Yes I know it's ugly :/)

Is there anything I can do to fix that? I just can't think of any other reason why this should not work.
Especially when everything works fine when I don't use the socket i added.

I already measured the voltage with an oscilloscope but it seems stable to me. So no drop because of the load or any weird interference on the output.

I really need help here :/

If you need any other info or better clarification or whatnot please tell me and I will try to update as soon as possible.

Or if you know a better place to ask this I also welcome any suggestion on that part :)


texts:
So, this is where I am at currently( no pun intended). I am assuming that with an inverter for both components and 3 - 4-18650 cells in series - in parallel rated at 4800mAh would be good enough?
Ill have to look at the controller again but I think the data and power are delivered in the same ribbon.


texts:
back at it again with a problem that I am stuck on and need some clear explanation of.

1/2: I was wondering How those Bass controls work, for example the ones in the car you allow to change the bass from -10 to 0 to 10 and the bass would increase to barely hearing the drums. Is this due to a gain change or a Fc(Cut off frequency) change?

2/2 I been having a problem on a filter, and I am sure I am over thinking it, however in the picture below using an Input source of 1.92Vpk @ 1kHz. The Fc of the High pass filter is ~250Hz however the 1kHz is not at 0dB which means I am losing some sound on this common frequency in audio which isn't good. I was wondering to over come this problem would a higher order filter would work? Essentially making the roll off more sharper ?


texts:
I am building a H-Bridge controller dor DC motors, and I want to add some current limiting on it. Does anyone knows a good algorithm for doing so?
I am planning to read the current, and if it goes beyond a limit, I start a PI loop until it drops under the limit.
Thanks!


texts: Relationship between capacitance and capacitor voltage rating?

texts:
I recently went to buy a capacitor of 10 microfarad and I was told by the shop that 10microfarad 67 volt is available.

The confusion for me is that will I be able to charge the full 10microfarad only if the potential difference across plates is 67 volt or is 67 volt the maximum voltage it can safely bear or both?

When I searched the web i was getting both answers sort of? All I need to know is if i use this capacitor in 9v circuit, then i get 10microfarad or something like 1-2 microfarad?


texts: What is difference between choosing OCRnA and ICRn in timer/counter CTC mode in ATMega2560?

texts: I can't find any difference since both function the same role: define the top value so that timer will reset when reach this value. Both have its interrupt flag and interrupt service routine.


texts:
I want to accurately measure the resistance of a single strain gauge, unaffected by lead wire resistance and with ratiometric ADC conversion to compensate for excitation drifts.
I know for RTD measurements its common to use a simple circuit like below:

simulate this circuit – Schematic created using CircuitLab
Unfortunately this works poorly for strain gauges, since the full swing of the signal is very low, on the order of V_exc/2 +- 10 mV, so a lot of the usable signal vanishes into ADC noise.
Naturally a bridge configuation + instrumentation amplifier comes to mind, but after trying for quite some time I just cannot come up with a decent 4-wire connection. Best I can find is a 3-wire one like this:

Since there a a lot of 4-wire strain gauge setups available commercially, there must be solution to this that I cannot find. Can someone point me in the right direction here?


texts:
As a disclaimer, I'm a novice when it comes to electrical engineering and I am looking for assistance in order to complete my endeavor. I have spent the past few weeks teaching myself concepts and have designed the following circuit, but still have a few questions.

=====================================================

I am building a project with a goal of having on-board electronics (ESC, motor, receiver, etc.) get power from solar cells when there is enough sunlight, and get power from both solar and battery when there is not enough sunlight. Additionally, if there is excess power from solar, the extra power should trickle charge the battery, since the battery and solar cells are connected in parallel and the energy flow is decided by Kirchhoff’s current law. A receiver controlled switch will be used to connect/disconnect the solar cells depending on need.

Below I have attached the circuit I designed and the questions I have about it.

My questions regarding the circuit design are the following:

How can overcharging the battery be avoided?
I am thinking that an MPPT is not needed since the battery and solar panels are well adjusted in parallel. Is this a good idea to not have a MPPT because of that and because a MPPT is a heavy device with some power dissipation?
Is the Schottky diode necessary in the setup (since the solar cells themselves act as a diode and would only be damaged if there is much higher voltage)?
Would my current setup achieve my goal?
Do you have any other recommendations?
Is there any small electronic device that I can add that will help me monitor the voltage of battery from a far away distance?
I think that LiPo balancing is not an issue since the LiPo will not be too deeply discharged or with high current. Is my thinking correct and if not how would the battery be balanced while charging through solar?

Thank you very much for your time and help! Have a great day.


texts: Which potentiometer to chose for LCD screen contrast?

texts: I recently obtained DEM 16217 SYH-PY 2x16 character screen. Here's the datasheet. As far as I can see, its contrast pin should be connected to voltage source over a potentiometer. How do I pick correct resistance of the potentiometer for this use?


texts: Comparing two negative LDOs One has a Ishutdown rating of 3uA and the other 17uA. Was wondering what exactly Ishutdown is? I can't seem to find any explanation.


texts:
I have a RS flip flop made out of 2 NOR gates right now. However the problem is, the output voltage of this circuit is too weak for my LED. I tried to decrease the resistance of the resistor but the current proved to be too strong. I will show you the schematics of my circuit below. It is pretty messy but I hope you can read it. (source = 5v DC)

The power source is 5V. The red light is the LED. It has 50 mA of current going through but only 100mV. How am I supposed to increase this voltage to 5V? I am very new to this so sorry if I am a bit slow. My LED has forward voltage of 3.3V and max forward current of 75mA. Thanks!


texts: Is using a 125VAC Kill-A-Watt (Power meter) on a 220VAC network possible?

texts:
A 125VAC Kill-A-Watt has come to my hands, but in my country, the grid operates at 220VAC.

I know I can't use it as-is, but is it possible to modify it to be usable?


texts: Basic insulation level for a 22 kV system

texts:
In the lab we tested a surge arrestor bracket for a 22 kV system with a 1.2/50 impulse. It was found that U10 for the bracket is 102 kV. I found this table for IEC standard of a 22 kV system

I read up about Basic Insulation Levels and to my understanding is that the system from the table for 22 kV should be able to handle 125 kV surge. Which means that the arrestor bracket must have a BIL lower than that in order to absorb the surge. Am I correct ?, or can someone help me understand this more clearly ?, thanks


texts: Piezo contact mic into iMac - avoid signal spikes

texts:
I've wired an external piezo as contact mic to the TRRS 3.5 jack of an iMac and it is working fine - BUT the signal will just randomly stop after hitting the contact mic several times too hard, so I suspect the iMac kills the connection after it gets too high voltage spikes from the mic...?

How can I avoid/dampen these signal spikes?

This is the way it's wired (needs to have that 10k in parallel for the mac to recognise it as a mic and the 33ohms are there to fake the speakers on L/R channels)


texts: Capacitive touch sense problem with battery powered laptop

texts:
I designed a PCB that includes capacitive touch. The circuit works with 5V powered from USB.
When Laptop is connected to 220V line, the PIC can sense capacitance variation.
When Laptop is not connected to 220V line(self battery powered), the PIC can't sense any capacitance variation.

I only add 2 bypass capacitors to the input. I did not do the ground design of the PCB very carefully.
Is the source of the problem PCB ground design? Is it error in the 5V input circuit design? or what else?
What would you suggest me for solving the problem? Can I fix the problem by adding some components to the 5V line?


texts: What is the signal-noise model of laser induced fluorescence?

texts:
The following image is an example of a fluorescence signal trace from the photomultiplier tube detector (PMT). Each spike represents one fluorescently labeled cell.

This signal model is definitely not additive white Gaussian, although the noise term is Gaussian. The signals are low variance but the point is that when the signal amplitude increases, the noise variance rapidly decreases. In the given example, above the intensity value of \$0.6\$ all three Gaussian signals are almost noise free. Around \$0.4-0.5\$ intensity of the noise is reduced but can be seen if zoomed. Below \$0.4\$ the noise is significantly apparent.

  How can this signal-noise relation be properly modeled? For example for additive noise we have $$x[n]=s[n]+w[n]$$ where \$x\$ is the received signal \$s\$ is the error free signal and \$w\$ is the Gaussian noise.

My aim is to simulate such signals in Matlab using a theoretical model. However, I was not able to see and/or find any model via google search or on some related books.

The physics behind this is due to detection of laser signal via photodiodes or PMTs. I was thinking that the noise source was probably the quantum noise but I am not sure because for the quantum noise, the noise variance does not decrease when the total number of photons \$N\$ increases. Instead it increases as \$\sqrt N\$.

What I tried was dividing the noise values by \$k+s[n]^2\$ before adding to the signal, where \$k\$ is some constant. I did this over additive Gaussian noise model. The results were okay. But I am not able to justify this theoretically. It is just my intuitive understanding.

Sources:

https://www.cut.ac.cy/faculties/fet/mem/research/research-units-and-laboratories/biolisys/research/imaging/cytometry/?languageId=1

https://en.wikipedia.org/wiki/Laser-induced_fluorescence


texts: PDM signal demodulator CIC filter input bit width

texts:
In order to convert the PDM stream into PCM samples, the PDM stream needs to be decimated.
Bits in PDM stream can be encoded as 1=> +1 and 0=>-1 and this corresponds 2bits signed number(S2.0). I use CIC decimation filter. I'm confused at this point: What should be the data type in the filter input?

I saw the following on the internet: Sign extension the PDM bits to a 8bits number before CIC or counting 1s in 8bits/16bits in PDM stream and applying this to CIC filter. Which one is reasonable?


texts: Clarification on the usage of Semaphores vs task notifcations vs queues

texts:
I'm trying to understand the basic concepts of FreeRTOS.

When do you use queues vs task notifications? I see queues are used for task-task, task-interrupt synchronization i.e one task waiting on a queue via xQueueReceive() while the ISR is populating the queue. So in an ISR, you'd call xQueueSendToBackFromISR().
You could get around the same behaviour via task notifications by using ulTaskNotifyTake() in the blocked task and xTaskNotifyFromISR() in the task that's supposed to unblock the other task, except you aren't writing/reading from a queue. Or is it that when you want to send data or something to a task, queues should be used and otherwise notifications?

When do you use task notifications vs semaphore? I see task notifications can act as a semaphore...


texts: How do I connect a 555 timer to a CMOS Input?

texts:
I designed the following circuit, using a 555 timer, to supply a single trigger pulse with the same width to digital circuits, no matter how long the button is pressed. The actual pulse output works perfectly. I was  just wondering if there was a special way to connect a 555 timer output to CMOS and/or TTL inputs.

Here's the schematic:

[Edit by OP]

In my original schematic I used a 7555 timer, but when I built the circuit I used a standard 555. Also, when I built it, I did use a base resistor!

Here is what I really built:

[Another Edit By OP]

So, I went back to my bench and tried out the circuit again and and realized that the switch was bouncing! I then added a switch debouncer(See below schematic). I was wondering if there is a simpler way to get rid of the bouncing.

Here is the schematic with the switch debouncer:


texts: How to use ESP-WROOM-32 to send wireless TX and RX commands from a PIC?

texts:
I want to have the possibility to send the commands of a PIC in a way that it's wireless and I thought it would be a good idea to use a ESP WROOM 32.

In the datasheet it has the following schematic:

I came up with what I think is needed for my case:

But probably would it be good to have the JTAG included in my board? That way I can program the ESP anytime.


texts: FPGA doesn't seem to work the way I imagined

texts:
A couple of years ago I read an interesting Wikipedia article about something called a "field-programmable gate array". The article made it sound like it's a box of logic gets which you can arbitrarily wire together to implement any kind of logic you want (but without needing thousands of discrete components).

Now, I had assumed this works something like a PROM. As in, you buy a die which has all the gates on it, with everything connected to everything, and then there's a glass window to the die, and you use one of those extremely expensive UV-laser writers to "burn" through the connections you don't want, resulting in the logic circuit you designed. (And maybe there's a version that's erasable too, like how CD-RW is somehow erasable.) Once you've "burned" your program into the chip, it behaves as if it were that actual combination of logic gates. (Because now it is that combination of logic gates!)

However, more recently I've been reading about this, and it appears this isn't how the technology works at all. A lot of recent articles talk about needing to send a "bitstream" to the FPGA at system power-up (and even the possibility of encrypting this bitstream to stop your competitors reading it). This makes it sound alarmingly like a FPGA isn't a hardware construct at all; it makes it sound like really it's just an ordinary microprocessor that's simulating your design in software.

In particular, that means a design programmed into an FPGA can never run any faster than the underlying microprocessor that's simulating it. Which kind of makes the entire endeavour sound... kinda pointless. I thought the whole point of an FPGA was to make custom logic that does stuff faster than you can do it in software. But all this "bitstream" stuff makes it sound like it is still software...

I'm a little confused here. How does an FPGA actually work?


texts: XC32 optimizes vaiable used for register reading

texts:
I am facing a problem with XC32 compiler's optimization. Whenever I write a function to read something from register, XC32 optimizes (read: Removes) the variable which holds the return value.

I have a wrapper function which reads a perticular pin of perticular port:

uint8_t u8INT_DIO_ReadRangeSelect(void)
{
    uint8_t u8pinstatus = 0;

    // Read pin assigned to Range Select input
    u8pinstatus = (uint8_t) SYS_PORTS_PinRead(PORTS_ID_0,
            RANGE_SELECT_PORT, RANGE_SELECT_PIN);

    return u8pinstatus;
}

Here SYS_PORTS_PinRead is a harmony (PIC's code generating tool) generated code and it just reads the port pin.
Code for that is:

return( _SFR_BIT_READ( _PORTS_READ_B_VREG(index) + ((channel-1) * 0x40), bitPos ) );

Note that, it's an inline function.

Now, when I set Optimization level to 1, XC32 removes u8pinstatus variable and always returns 0.

But if I declare u8pinstatus as volatile, everything works fine (which was expected).

But then I need to declare all the variables volatile because all my wrapper functions are always returning 0. That's not a good way.

Is it that XC32 gone bonks or am I doing something wrong?

Additional Info:

Assembly code with optimization:

!uint8_t u8INT_DIO_ReadRangeSelect(void)
!{
0x9D00AA8C: ADDIU SP, SP, -24
0x9D00AA90: SW RA, 20(SP)
!    uint8_t u8pinstatus = 0;
!
!    // Read pin assigned to Range Select input
!    u8pinstatus = (uint8_t) SYS_PORTS_PinRead(PORTS_ID_0,
0x9D00AA94: ADDU A0, ZERO, ZERO
0x9D00AA98: ADDIU A1, ZERO, 3
0x9D00AA9C: JAL SYS_PORTS_PinRead
0x9D00AAA0: ADDIU A2, ZERO, 8
!            RANGE_SELECT_PORT, RANGE_SELECT_PIN);
!    return u8pinstatus;
!}
0x9D00AAA4: LW RA, 20(SP)
0x9D00AAA8: JR RA
0x9D00AAAC: ADDIU SP, SP, 24

Assembly code without optimization:

!uint8_t u8INT_DIO_ReadRangeSelect(void)
!{
0x9D00F998: ADDIU SP, SP, -32
0x9D00F99C: SW RA, 28(SP)
0x9D00F9A0: SW S8, 24(SP)
0x9D00F9A4: ADDU S8, SP, ZERO
!    uint8_t u8pinstatus = 0;
0x9D00F9A8: SB ZERO, 16(S8)
!
!    // Read pin assigned to Range Select input
!    u8pinstatus = (uint8_t) SYS_PORTS_PinRead(PORTS_ID_0,
0x9D00F9AC: ADDU A0, ZERO, ZERO
0x9D00F9B0: ADDIU A1, ZERO, 3
0x9D00F9B4: ADDIU A2, ZERO, 8
0x9D00F9B8: JAL SYS_PORTS_PinRead
0x9D00F9BC: NOP
0x9D00F9C0: SB V0, 16(S8)
!            RANGE_SELECT_PORT, RANGE_SELECT_PIN);
!    return u8pinstatus;
0x9D00F9C4: LBU V0, 16(S8)
!}
0x9D00F9C8: ADDU SP, S8, ZERO
0x9D00F9CC: LW RA, 28(SP)
0x9D00F9D0: LW S8, 24(SP)
0x9D00F9D4: ADDIU SP, SP, 32
0x9D00F9D8: JR RA
0x9D00F9DC: NOP


texts: LNA design question - series drain inductor

texts:
I am designing an LNA in Cadence that follows the schematic below very closely. This is taken directly from TH Lee's book on RF integrated circuit design.

The book says that \$L_d\$ and \$C_L\$ should be tuned to resonate at the center frequency of the design. So in terms of small signals, the drain of M2 should see a very high impedance.

I am trying to understand how the DC levels in this circuit work. Because \$L_d\$ is essentially a short circuit to Vdd, the drain of M2 sits right at VDD. How is there any headroom for voltage gain when the DC drain voltage of M2 is equal to Vdd?


texts:
First of all, I'm a biologist, so please let me know if this question is being asked in the wrong place.  I regularly perform operations on rats and recently stumbled upon the following paper (http://ar.in.tum.de/pub/padoy2008IAAI/padoy2008IAAI.pdf) where surgical activity is classified primarily based on the use of specific surgical tools.  I thought this would be a very interesting thing for me to do with my own work and may help me be more efficient with my time.  I have a good CS background so the use of the required computational models is not problematic.  What is a problem though is the fact that the authors of this paper use manual tagging to identify whether a given tool is being used or not.  This seems inefficient; the authors admit this, saying automatic tagging is possible.

I am wondering if anyone can suggest a good way to tag the tools being used?  My instinct is to use a simple RFID system, where each tool is tagged and the tool tray could contain a reader.  This would allow me to collect a binary signal vector from each tool across the duration of an operation (successful read indicates tool is not being used, failed read indicates that it is).  Is this a good approach to my problem?  If so, could someone recommend a specific tagging system to use?  If not, could someone recommend another approach?

As an aside, this project is for my own edification and enjoyment: it is not a part of my funded research, I am not going to publish on it, and I am not going to sell anything I put together.

UPDATE:

Assume that the cost of the sensing system is not a constraint when offering suggestions.


texts:
i want to make 2 to 4 level converter for 8-QAM modulation, i'm going to use two digital input to get +/- voltage level, i want the output approximately like this,,

when the input 00=-3 V , 01=-5 V , 10=+3 , 11=+5.

i already have one circuit  reference, but i'm still confuse, how do i can get a - voltage ?, because the circuit only can make + voltage, take a look this circuit

simulate this circuit – Schematic created using CircuitLab

Any help would be appreciated :)


texts: How can you estimate the final position of a gyroscope graphically?

texts:
A Smartphone is initially in the position indicated as follow

We move it, and get the next gyro reading.

How can you estimate your final position graphically?


texts: Pico ITX Power Supply and AC-DC Inverter

texts:
So I have four computers all using these little pico itx power supplies and was wondering rather than have 4 power bricks attached to these power supplies could I just use an Power-Bright-PW900-12-Inverter.

To me it seems like a better and more power efficient solution unless I am missing something. Also if I were to do this what is the best way to slap DC wires from four different power supplies into this thing?


texts:
I have the next situation:

I've got two microcontrollers that should drive 4 motors. It's either microcontroller1 or microcontroller2 that is driving the motors.And 4 motors means that each microcontroller has 4 outputs. So I'm searching for a system that could choose(depending on a extern variable) which microcontroller is driving the motors.

So basically it's something like a selective switch, but with 8 inputs (comming from microcontroller1 and microcontroller2, and 4 outputs that go to the motors)

Thanks in advance


texts:
I am working on a boost converter with analogue PI control. I want to make the PI controller using a separate Op-amp IC and giving its output to the PWM controller to generate proportional PWM signal. I also thought of using TL494 and giving PI controller's output directly to its feedback pin but I am not sure whether this method will work or not. As in TL494, I am not using the internal opamps, it's wastage so is there an IC without any internal opamp?
Please suggest me a PWM controller IC that fulfils the need, I will be using a separate gate driver to drive the MOSFET.


texts: Rocker switch & Electronic Relay switch circuit (240v)

texts:
I have an already existing circuit between the mains wall supply and a window shutter (see image), it has a gewiss rocker switch for opening and closing the shutter when you press and hold one of the two-buttons. I want to add another switch that will be operated remotely/automatically. I plan to add this using the pink wiring on the diagram below.

My question is: is this a legitimate circuit? In terms of, what happens if both switches are closed at the same time #1 for alternate directions, and #2 for the same direction (say UP)? Or any other faults you can see?


texts: Safety of designing / using a plug that connects between two different wall outlets for increased voltage?

texts:
In North America we use 120V wall outlets, but sometimes 240V is needed for an application.

Usually in a residential house in order to reduce load on the circuits they either run two different phases of AC into the house for different outlets, or with single phase they use one line in the circuit connected to neutral for one outlet, and another line in the circuit (the return) connected to neutral to another outlet, giving a 240V potential difference across the live wires of two different outlets in your house. Assuming your house has these two different outlets right next to each other, as often occurs in kitchens and bathrooms, how safe would it be to have a plug that rather than plugging into the neutral and live of a single outlet, plugs into the live of two different outlets to harvest this 240V potential difference? I know you would have the disadvantage of not being able to polarize your plug, but aside from that would there be any safety concerns for running a device with this method?


texts: I'm looking for a power amplifier that can drive water pumps (this system) at variable speeds in order to control water levels in tanks. This is for an engineering teaching lab. The amp should output up to 24 V at 100 W, with a voltage gain of 3 (relative to the input voltage). The supplier is recommending a power amp but I'm looking for off-the-shelf alternatives to that amp. As I look around online, I'm having trouble finding something that isn't an audio amplifier. What is the name for what I'm looking for? What should I Google?


texts: Would it be possible to make a solid state transistor by hand?

texts:
I am curious, would it be possible to fabricate a modern BJT/FET transistor with hobby/garage tools only if size and aesthetics was not important?

Which materials would one use and how would one acquire them?


texts:
I got a 4D systems Serial uLCD and been messing with- pretty awesome kit. But when i got round  to reading files of a FAT16 partition, wave, graphics nothing was happening. I was getting ACK/NACK randomly and just did not make sence.

I got to this article on the forum.

How can i prevent this voltage "dip" from happening on the 5v. i suspect it happens because it has to power up the SD card and gets corrupt bits from the start.. but that is not my issue. This guy said if he uses batteries it works for him (and its only Arduino Mega with this problem)


texts:
I am using 2 interrupts on LPC1778.
One for CAN and one for timer.
The CAN interrupts whenever a new message is received.
The timer interrupts every 200uS.
The priority for timer interrupt is the highest(i.e NVIC Priority=0).
My doubt is, if a CAN message arrives, and im in the ISR, suppose a timer interrupt occurs while in CAN ISR, will the timer interrupt ISR be executed and then return back to CAN ISR?
Or,will CAN interrupt be completed before timer interrupt is executed.
Does priority apply only if both interrupts occur at same time or does priority apply for setting which interrupts cant be masked under any circumstance.
Because,its very critical that timer interrupt has to execute every 200uS under any circumstance.


texts:
This is my first proper circuit I've designed and I'm after some advice.

I need a 16 bit DAC, output 0-5V and I need to measure the resistance of a thermistor to 0.1mk accuracy. At the moment, I am using this circuit (left hand component is the AD5667R (DAC) in a MSOP package and the right is a ADS1252U (24 Bit ADC) in a SOIC 8 package):
,

However, I have read that a Wheatstone bridge is better than my design, why? How? What problems might I encounter?:

I would like some advice on the whole circuit. Ideally I need to replace the AD5667R with a chip with a larger package, SOIC 8 or larger, because it needs to be hand soldered by undergraduate physicists. I'm hoping some alternative design ideas might avoid the need to use that particular part.

The circuit is part of a high accuracy temperature stabilisation unit based on an Arduino, designed for optical clocks, if anyone is interested in this I've placed a link to a report I wrote on the first version in a code block below.

https://aaronwjones.com/pdf/Aaron_Y4_Project_Final_Report.pdf


texts: Driving state machine in FPGA directly from input

texts:
I'm learning verilog and in the process trying to implement some simple logic circuits (and as everybody, a simple SOC)

I implemented a simple UART, and it worked well during simulation and the test-benches, but after synthesis in an actual FPGA (an ice40, using Yosys), I run into problems in about 2% of the received characters.

Using a logic analyzer, I captured te following trace:

D2 is the RX data, D3 is the TX data (should be an echo of the received data), D0 is the sampling pulses of the UART, D1 is a "uart receiving" signal.

The problem was that the UART was ending before the current byte has ended.

After a lot of testing, I realized that when the High to Low transition at the start bit was at a time near enough to the internal FPGA clock, the initial state in verilog was not set to the correct value.

The verilog code was:

    always @(posedge clk)
    begin
         // Main RX processing
         if (!rx_active)
         begin
             if (!rx)
             begin
                 rx_shift <= 0;
                 rx_state <= 19;
             end
         end

I changed the code to:

    always @(posedge clk)
    begin
         // Latches RX signal, prevents glitches
         rx_latch <= rx;

         // Main RX processing
         if (!rx_active)
         begin
             if (!rx_latch)
             begin
                 rx_shift <= 0;
                 rx_state <= 19;
             end
         end

After that change, the UART worked always ok, this means that the combinatorial logic generating the state transition was setting only some of the bits in rx_state, as probably the clock signal did not reached all FF at the same time.

My questions are:

Is this expected behavior in Verilog?
How I can test if this race conditions are possible in my code?


texts: How to connect USB barcode scanner to a PIC?

texts:
I've got a bog standard barcode scanner with a USB output and I'm trying to figure out how to connect it to a PIC.

Basically, the idea is that I use the scanner to scan a barcode and the barcode is then passed to the PIC which in turn uses the barcode to do either lock or unlock a solenoid lock (the lock is something I'm going to work on later).

So I've been looking at ways to try and connect the barcode scanner to the PIC with somewhat limited success. So far it seems like one way might be to convert the USB output to an RS232 output and then connect it to the PIC and try to interpret the output but I'm not entirely sure whether that will work, or even how to do it.

So I was wondering if anyone had any ideas on a simple way I could go about connecting the scanner to the PIC please. Is the idea I have so far any good and, if so, are there any good ways to go about doing it? Or is it just needlessly complicated and is there a better way of doing it?

Thanks very much.


texts: What happens to the semiconductor in an LED when it is given voltage that it cannot handle?

texts: Let us suppose we have an LED with the allowed voltage range of 1.5V to 4.5V and we gave it somewhat 12V. Now we know that the LED will instantly stop forever. But I want to know what will happen to the material (the semiconductor, etc) when this happens.


texts:
I'm currently working on this circuit and it appears that my output voltage is not showing the correct values for the positive half wave .
For starters I have these values below  - \$U_{CE} = 5 V\$

\$R_1 = 6.1kΩ\$
\$ R_2 = 1.35kΩ\$
\$ R_E = 1kΩ \$
\$ R_3 = 1.5kΩ\$
\$V_1 = 15 V \$
\$ I_C = 2mA \$
\$ U_{BE} = 0.4V \$
\$ B = 180 \$

Given formula \$r_{BE} \approx \frac {40 mV}{I_B}\$

First I calculated CE with the use of this formula \$τE ≈ (r_{BE}·C_E ) / β =  1/(2 \pi f) \$
These are my calculations:
$$ I_C = B . I_B $$
$$  rBE = 40mV/ I_B  =  40mV . B / I_C  = 40 . 180 / 2 mA ≈ 4kΩ $$
Let's say the frequency of this amplifier is 1kHz
$$ => τE = 1/(2 \pi f) = 1/(2 \pi 1000)  = 1.519 . 10^{-4} s    $$
Which makes
$$ => C_E = B.τE  / rBE  = 1.519.10^{-4} . 180 / 3600 = 7.6 uF $$
And also
$$τE = (r_E / B ). C1 $$
$$ τE  = (R_E / B )* C1  $$
$$ r_E  = (rBE + B Re) || R1 || R2
       = (4kΩ + 180 * 1kΩ) || 6.1kΩ || 1.35kΩ
       = 1100 Ω
       = 1.1 kΩ  $$
$$ C1 = τE  . B / r_E =>
C1 = ( 1.519 . 10^{-4} s . 180 ) / ( 1.1 * 10^{3} )
      =  0.26 uF $$
Then with this question I could calculate C_2.
What is the minimum size of capacitor C2 if the lower limit frequency should be approx.imately 1000 Hz when the output is loaded with 100 kΩ?
$$τE = R * C2 => C2 = τE / R = 1.519 * 10^{-4}  / 100kΩ = 1.519 nF $$
$$Ue =√( (1+ω²(R1*C1)²) * (1+ω²(R2*C2)²) . (1+ω²(RE*CE)² ))   = 8.5 V  $$
Summary :

\$C_E = 7.6   uF \$
\$C_1 = 0.26  uF \$
\$C_2 = 1.519 nF \$

And with these calculations I can simulate my circuit .
Output in red, input in blue:

Shouldn't the positive wave of the output voltage be bigger than the positive wave of the input voltage?


texts: Sending analog signal over twisted pair in noisy enviroment

texts:
I need to transmit several analog signals from one board to another (maximum 1m distance) in a very noisy environment (power electronics converter operating at 20kHz). The range of frequencies of the analog signals is [0,20 MHz]. Presently I opted for differential signals, and designed a differential driver AD8132 on the transmit side. The signal from the sensor is 300mV p-p (current shunt if it matters).
On the receiver side, I am using a difference amplifier AD8270. I expect this to do sufficiently well since the common mode signal will be small (grounds of both boards are tied at single point)
The circuit is illustrated in the image below (i simulated it in spice with different components earlier but the circuit layout is the same. In the meantime i changed the amplifiers but the functionality should stay the same).

I opted for simple difference amplifier. The rationale is that the common mode voltage is expected to be low which in combination with matched resistor network of AD8270 should give decent performance.I plan to use a twisted pair to transmit the signals.

Should I be worried about reflections on the cable?
Would a coaxial cable be a better/simpler solution in this situation?

Any thoughts/suggestions are appreciated.


texts: What can be the consequences of a smaller airgap in a induction motor for the efficiency and rotor current?

texts:
Last year I bought 3 motors from a junkyward, and one of them was a 1/4 hp, 4 pole single-phase induction motor made by WEG for an Electrolux washing machine.
Or at least it was supposed to be, cause most were disassembled and thrown in a pit, so I had to go around matching rotors and stators.
One was already complete, another was the correct match and this one I'm talking about I thought to be correct, turns out it wasn't.
Firstly the rotor is about 7 mm shorter than the stator (the stator is taller). The bearings aren't fully sitting in their sockets either.
But, most notably, the airgap is absurdly small. The rotor isn't scraping the stator by a miracle, cause the airgap is literally invisible. If I put the motor against a white screen or against the Sun I can't see light passing by any angle.
I've never seen such a small airgap, most are pretty visible and specially if you put against a light source.
I've run it by some minutes to see if thermal expansion would cause it to scrape, and it didn't, but it also heat a hell lot more than it was supposed. it reached 80 ºC in about 6 minutes, and most notably the rotor heated too much.
Could the reduced gap be increasing the rotor current?
The overall operating current seems to be close to normal from my measures.
It could also be that the rotor properties aren't the same of the original design, but from pictures it seem to be mostly identical and I counted the same amount of aluminum bars.


texts:
Consider we have QPSK signal with carrier frequency 10kHz. Generally, we demodulate  or use matched filter on the the QPSK signal and recover the transmitted bit or the symbols. If the QPSk signal is noisy can we use band pass filter before demodulation, where the pass band  is around 10 kHz? The QPSK signal has discontinuity when the bit/symbol changes, so are we going to loose valuable information if we band pass the signal before matched filter? Is there an appropriate band width of the band pass filter which can be applied so that matched filter still works after the band pass filter?

EDIT: More importantly can a band pass filter prior to matched filter show better results? If so under what conditions?
This question is also asked in:
https://dsp.stackexchange.com/questions/59079/can-we-band-pass-filter-qpsk-signal


texts: Correct way to measure circuit power consumption before or after LDO

texts:
I have created a low power MCU project, and I want to measure the power consumption.
I am confused with:
a) the correct way to place the ammeter, before (picture A) or after (picture B) my voltage regulator (LDO)?
I measure the same current, which is strange, as the voltage is slightly different.
b) which option is in general the correct? If I place the ammeter BEFORE LDO, the battery voltage will vary, so I will have to measure both current AND voltage in order to measure Power. If I place the ammeter AFTER LDO, i will have to just measure current, as the voltage is stable (3.3V).
c) is it better to present Watts or Amperes in such projects in order to demonstrate the power management? I have seen both used..


texts:
This is the circuit I have designed. I want to be sure whether I have designed it properly or not.
Here is the Purpose:
I am trying to power a Network device 24 hours which requires 9v (600ma). I have a 12 Volts 9AH (SLA) battery and a 12-0-12 (2 ampere) center tapped transformer. When there is mains available this circuit should charge the battery, auto cut off when full charge state is achieved and protect the battery from over discharging.
Circuit:

When battery voltage reaches 13.8 V then the T1 (Transistor BC547) goes on, making relay K1 on so the default connection between point 'a' and 'b' breaks and the charging stops. Similarly when battery voltage drops below 10.8v then T2 goes off so is the relay, Hence the over discharge is prevented.
Problem: This circuit is working to some extent, but as mains go off this circuit will provide power for only 50-55 minutes. I don't have any idea why this battery drains so fast. Also the relay bounces back and forth for a while near to the cut-off voltages.
So my point is how do I stop this battery from draining so fast. I am using a brand new battery and there is no problem with the battery. Is relay drawing so many power or may be the linear regulator 7809. Also how do I make it more efficient. Any suggestion would be appreciated.
EDIT:
This is what is written on battery:
Cycle use: 14.4-15 Volts
Stand By use: 11.5-13.8 Volts
Initial Current not less than 2.7 ampere
Questions
1. Moreover, At what current and voltage should I charge this battery?
2. Suppose I am charging the battery at 2 ampere current and lets say, I do not apply any current regulator (meaning, Once I have started charging I do not regulate the current there after) , does current gradually decrease as the battery charges up or do I have to reduce the charging current after 70% charge of state?
3. How important is the float charge in my case? Battery is frequently drained lets say once in a two day period.
4. How can I cut down the components and ultimately the price?


texts:
I did a small simulation for a RLC circuit as here :

How does one compute the maximal voltage attained for this resonance?


texts: Why do LCR meter manufacturers give the details of measurement frequency to us?

texts:
When you want to purchase a DMM, more probably you don't see at what frequency the DMM you considered would work, but in the situation you're considering to purchase an LCR meter, manufacturers give you big details on the frequency of the LCR meter.

Why do they give us the details on the frequency of their LCR meter?
It seems that they gives us the measurement frequency for all of three components. Resistors, inductors, and capacitors. Okay, but how the best frequency be chosen for each one of these components?

Here is several links to some LCR manufacturers:

IET/QuadTech 7600 Plus Precision LCR Meter

Lutron LCR-9184

HIOKI IM3536

CEM DT-9935

MS5308


texts:
We have now got Altium 17 installed and set up, and I've used it to make various schematics.

One feature of the software is the Symbol Wizard for creating our own symbols for different components. It's great for labelling up the component pins and so on. However, when I make the component, it is all aligned on an imperial gird, despite all of the pages being set to metric.

This isn't noticeable until I try and use it in a schematic, and none of my metric wires can match up to the imperially aligned pins.

Is there a setting for units for the symbol wizard?


texts:
I have recently been working on a project in which a material, whose ignition temperature is 500 °C, is to be ignited.

So, what type of nichrome wire would be suitable for me, if I am using a 5 V power supply capable of 5-10 A and length of wire is about 1 cm?


texts:
When the manufacturer recommends some capacitors with specific values, can I choose caps with more capacitance? Will it give any advantage? For example decoupling caps at MCU power pins. Or LDO input and output caps.

Thanks


texts: know the parameter of common mode choke for power adapter

texts:
How to choose right common mode choke in my power supply design?
What are the parameters we have to consider during selection?

Thanks
Deep


texts: Efficient high amplitude current regulation, so I don't end up being sad

texts:
I have an unstable power source 0-10V (I don't actually know if it can drop to 0) from solar panels and I want to boost and stabilize it to charge 19V 2.1A laptop and a 12V 12Ah battery. I've already asked a question about this and got an answer that I need a boost converter. So I was thinking about getting a boost converter IC, then searched, found and bought TL499ACP. But I've made a foolish mistake... I forgot to check if it handles the current that I need...

When I bought solar cells for building the panels, per cell specification was 0.5V 8A 4W. So to get maximum power out of it, I need a current of 8 amps. As far as I know, to charge a 12V 12Ah battery I need current of 1 amp. The input of TL499ACP can be up to 500mA and output up to 100mA.

So is there any way to decrease the input current (8A from solar panels) for the booster and then increase its output externally (because more than 100mA is deadly for the booster) without loosing too much efficiency (balance between efficiency and letting the booster go)?


texts:
There is a corporate phone system that uses multi-line phones.

The idea is to connect a cheap 2 line phone only for answering calls without adding a line.

Can this be done?

Just connecting in parallel doesn't work.

Edit
The 4 line phone is Northern Telecom Meridian.


texts: Best Way to Solder/Desolder Surface Mount Components

texts: I recently got my hands on some old motherboards/PCB's, and even though I know reusing parts from old PCB's is not as good as using new parts, I was wondering what the best way is to solder/Desolder small surface mount components such as this:


texts: I often see something like this void UART2_IRQHandler(void) __irq, and I wonder why __irq is used when declaring interrupt handler, is it required or handler can work without it?


texts: I am trying to create a simple SMA connector footprint in Kicad but whenever I try to save the footprint to a library, Kicad generates a "validation conflict" error. I have no visibility into the nature of the error. Can anyone suggest how I can figure out what's going on?


texts: Is it safe to drive I/O pins of an unpowered AVR ATmega328P?

texts:
Is it safe to drive the pins of this AVR chip while it's unpowered?

For example, if I were to share a motor driver such that it can be driven by two microcontrollers, would either microcontroller be damaged while the other is unpowered, but is seeing the signal voltages on its pins from the other microcontroller?

EDIT: Because this was marked as a duplicate, here is some clarification. The MCU specified here is different from a different manufacturer. Though I'm not sure, their operation and limits would most certainly differ. This question was not about wether it'll 'weaken' the MCU but about if its safe to do so in the first place. IMO weaken would mean that it is possible but over time it'll degrade the performance of the MCU.


texts: I have a TTL signal of 1 V, and I need to drive an LED by amplifying the TTL to 3 V. I used the following voltage amplifier circuit with Rc = 10 KOhm and Re = 1 kOhm. The DC input I use is 3 V. However the LED does not light up. Does anybody have a better idea for a configuration that might work?


texts:
I would like to confirm if the implementation of my 74LS191 counter is correct. Here is a diagram of my circuit:

The purpose of the circuit is to count from binary 0011 to binary 1111. However, the circuit above only counts from 0011 to 1110. After 1110 it recycles back to 0011. My expectation is that it would reach 1111 and then recycle back to 0011. Is this the normal operation of the 74LS191, or am I missing something?


texts: SMPS design, requirement of generating High Frequency

texts:
Question:
Is that requirement of converting 50Hz to a higher frequency in SMPS (Switched Mode Power Supply) is just to reduce the transformer/inductor core size?

Background:

Since as we all know that in a typical SMPS design, the AC input is first converted into
DC and then it is chopped and converted to a higher frequency (100KHz to several MHz). There are problems on this approach, such as bad power factor correction, etc.

Why isn't is possible to just use the 50Hz as it is and using a traic and a optocoupler we could do the same thing at 50Hz.  I mean turning off cycles when optocoupler is on through the traic and otherwise turning it off.  Why is that design not used in power supply designs?

Off topic, but curious readers will fire this one soon, then why we are using such a low frequency in transmission lines.  Can't we make power plant rated transformers into a size similar to a television?

[ I originally stolen this idea from one Amstrong oscillator based SMPS].


texts:
I've been reading over amplifier output stage design and hoped someone might be able to advise if my circuit has any fundamental flaws - or if there are any tweaks I should make that would bring significant improvement?
Design:

Constant Current source sufficient to drive 1W into a 4ohm load (~ 18mA)
Vbe Multiplier to bias the push-pull emitter follower transistors
Input signal of max 6Vpp

Observations:

Output isn't overly distorted (No crossover distortion)
Quiescent current (lowering R4 to 1.4k has reduced this significantly!)

In particular, is it sensible to be setting the DC output voltage via R11 or is there a better way?

Input/Output Signals:

Many Thanks


texts: Translating 16-bit digital counts on a CD to voltage on the output RCA connector

texts: CDs use 16-bit signed integers to represent each sample.  So each sample is an integer between -2^15 and 2^15-1.  A typical consumer CD player has two RCA outputs coming out the back of it, one for the right channel, one for the left, and no volume control.  If the right channel on a CD track is simply a (discretized) 1 kHz sine wave with an amplitude of 2^14 "counts", what will be the amplitude (in volts) of the signal on the RCA output?  (Just to be clear, when I say "amplitude", I mean one half the peak-to-peak amplitude.  So the maximum of my digital sine wave is 2^14 counts, and the minimum is -2^14 counts.)


texts: Using CD4093 as Schmitt trigger oscillator. How to measure high and low trigger thresholds?

texts:
Based on the suggestion of answerer in another post (this one: Adding Diodes to Transistor Astable Multivibrator; 1N5818 Schottky diodes work but 1N4148 diodes don't; can't figure out why), I built an audio frequency Schmitt trigger inverter oscillator out of a TI CD4093BE chip.

I built the TI datasheet circuit which uses pin 1 as an "enable/disable" pin for the oscillator.  See page 4 of the datasheet.  The datasheet can be viewed at this web page at TI's website:  http://www.ti.com/lit/ds/symlink/cd4093b.pdf

Here is the schematic of my circuit (as an image):

I powered the circuit with 9V DC from my workbench power supply.

I used a .1 microfarad mylar capacitor.

I used a 100K ohms potentiometer as a variable resistor to make the output frequency variable.

A .1 microfarad ceramic capacitor from the power supply pin (14) to ground was necessary for stability.

Here is what I measured:

*Pot set to 10.7K ohms

*Output frequency: 1.029 kHz

*Capacitor charge/discharge frequency:  1.030 kHz

*V out, from looking at oscilloscope, appears to be 8.8 volts, peak-to-peak

*The peak-to-peak voltage of the capacitor's triangle/sawtooth charging and
discharging wave was about 2.2 volts

*Oscilloscope set to .5 volts per vertical division

*Oscilloscope set to .2 mS per horizontal division

Here are pictures of the setup:

The datasheet has a (hard to read) chart showing the high and low threshold for the schmitt trigger inputs (Vp and Vn).  See page 3 of the datasheet.

The datasheet also provides minimum, typical, and maximum trigger thresholds for 5, 10, and 15 volts VDD (power supply) to the circuit.  See page 2 of the datassheet.

The datasheet also specifies the hysterisis voltage, minimum, typical, and maximum, for the 5, 10, and 15 volts level of VDD.  See page 2 of the datasheet.

OK, so far so good.

I can see from the datasheet that, at 10 volts, the typical hysterisis voltage is 2.3 volts.  This is close to my measurement of 2.2 volts.

But I wanted to actually measure the Vp (high) and Vn (low) trigger thresholds.

:-(

I have only my old BK Precision Model 2120 analog oscilloscope (20 mHz).

I can see the triangle/sawtooth wave of the capacitor as it charges and discharges.  I can see the that the total voltage swing, peak-to-peak, is about 2.2 volts.

BUT, how can I see what the voltage is at the top peak and the bottom peak (the high and low trigger voltage?

Do I need a digital oscilloscope?

Can I set my dials and switches on the analog scope to show this?

Can I derive the Vn and Vp values from my measurements?

* Update of March 16, 2019: *

Well, thanks to the answerer, Spehro Pefhany!  Putting the oscilloscope into DC coupling mode was the answer!  I need to "read the fine manual" for the old, analog oscilloscope.  It does more than I have been using it for.

As you can see from the pics, the low Schmitt trigger threshold looks like about 3.2 volts and the high Schmitt trigger threshold looks like about 5.8 volts.  This is close to the "typical" values specified on page 2 of the datasheet.

Another problem solved thanks to the helpful and generous people on StackExchange.  Gracias!


texts: Can the 741's offset null pins be grounded?

texts:
... Or should I leave them not connected if I'm not going to trim them?

I think I fried an LM741 when it's output was only connected to a single MOSFET's gate (and the single supply was <12V). The only thing I can figure is it's bad to ground those offset null pins, but I can't tell from its datasheet.


texts: Why SS pin must be set to OUTPUT for SPI master?

texts:
In SPI, SS pin is used as latch, which means that it must be set as OUTPUT.

The matter is that on arduino micro a LED is attached to the SS pin (aka PB0), so I cannot use it for the latch in SPI.

But it is required to be set as OUTPUT anyway, otherwise SPI will work in slave mode. Does this mean that the latch is handled automatically by the AVR when data is transmitted by writing to SPDR register?
Otherwise I see no reason that this one specific pin is demanded to be always set to OUTPUT mode for SPI master.

In other words: if I use the latch on SS pin, will writing to SPDR register do everything automatically, or I have to handle SS pin manually anyway? And if the latter is true, why require it to be set to OUTPUT?


texts: What is the difference between Micro-controller and Micro-Processor?

texts:
Possible Duplicate:
  What's the difference between a microcontroller and a microprocessor?

I am new to the micro-controllers and yet I don’t know much about that. While reading a book about micro controllers I come the Question that "What is the fundamental difference between Micro-Controllers and Micro-Processors?”, because AFAIK both can do the same job. And Intel micro processor series starts form Intel 8086, which is a microcontroller.


texts:
I have a regulated power source supplying +/-48 VDC that I would like drop to +/- 24 VDC. I think linear regulators are the way to go here since they are powering an audio circuit. I would like to use a pair of regulators, such as 7824 and 7924, but those particular ones have a max input voltage of +40 VDC and -40 VDC.

Are there similar regulators with higher maximum inputs? Nothing shows up on Mouser. If not, am I correct in thinking the best option would be to use transformers?

Alternatively, the device to be powered also has regulators at the input (can't quite see their model numbers, which are obscured by heatsinks), so maybe some sort of resistor-based solution would work?

edit: Since there were some questions about the power supply: it's not a standard power supply. The whole system is a guitar combo amp that was essentially built from a rackmount preamp installed into a powered speaker. The power amp had a +/-48V tap that was powering the preamp. I wanted the option to use the preamp separately, so I converted the preamp to use a separate +/-24V power supply, which had the added benefit of removing some resistors that were overheating and burning the circuit board. However, when using the whole system as it was originally designed, I'd like the option to power the preamp from the 48V power tap.

The designer recommended jumpering those resistors to convert the preamp to 24VDC. I can't tell how those resistors were originally dropping the voltage, but I'd rather not use a similar solution to convert the power amp's output to 24V. Some commenters already pointed out how inefficient that is.


texts: How would I convert a 4.1(ish) volt li ion battery to 240v ac?

texts:
I'm fairly interested in electronics but not very educated in it.

I was wondering how I would go about safely converting your average li ion battery pack to a usuable voltage (240v ac) for things like bulbs and such.

I've so far got multiple packs I charge them using 5v usb chips of various kinds and run them all in series. I have a 5v solar panel which in the summer can trickle them and ive created a charging bridge from 12v dc to the 5 v dc and thus the batterys themselves and a small solar panel trickle charge (unfortunatly right now the battery is not deep cycle I know thats bad)

if you were to wire them in paralel would the voltage step up like with conventional batterys?

I was hoping I could run a 5v transformer in reverse ? but have yet to figure out the maths on how many amps I would have. I know I would need 2 diodes to make a rectifying bridge and then hoping to put it threw a 5v to 240v transformer

this is all just a spiral off my hydro / sterling engine 5v generator to battery bank for off grid basic gadgetry.


texts: help need in driving high side nmos without bootstrap circuit

texts:
I am currently planning to upgrade an existing circuit which charges a lead acid battery using a non-synchronous buck topology.
The NMOS which i have used is IRFP4768PbF.Currently my driver is the IR2110 which uses a bootstrap capacitor.

I would like to remove the IR2110 and replace it with an opto isolated gate drive(TLP5701) with a dedicated dc/dc converter.
I have drawn up a shematic and i have a few quiries in it ,regarding he dc/dc converter.

1.I am going to use the  MEU1S1212ZC(12v/83mA).The input to this module will be referenced to the system groung(solar-) and the output will be referenced to the source of the MOSFET.
The the current sufficient enough to grive the MOSFET?

2.What should be the values of R1 and R2.Is 10 ohm(R1) and 3k(R2) sufficient enough?

Edit:
I have sketched the DC/DC converter section also to avoid any confusion.


texts: Do you need multiple instrumental amplifiers and filters for multichannel EEG systems?

texts: I've created a 1 channel EEG using the AD620 instrumental amplifier and various active band filters. To add more channels, would I need one instrumental amp and series of filters per channel? or can I use one instrumental amplifier to amplify multiple signals?


texts: Batteries in series capacity considerations

texts:
Let´s say I have a 2 AA 1,5V 1000mAh Alkaline battery cells in series.

The circuit it´s connected to consumes 500mA, works at 3V and it´s powered on always, and taking into account other electrical specs as ideal, the time it would take to last would be:

1000mAh / 500mA = 2h

Is this correct?

I´ve checked this question and it confuses me.


texts: Trouble Detecting pF capacitance with Arduino

texts:
Im working with an EAP (electroactive polymer) thats capacitance changes when deformed. It varies between the ranges of around 0.5 - 3 nF. Im trying to connect it to an arduino to take readings that I can then do something useful with.

I managed to alter the CapacitanceMeter tutorial too to get things working a bit better, but it doesnt seem to be accurate enough as Im getting values that swing by around 500pF when un-stretched.

Im using a 10M Ohm resistor, and realise I could go to a G ohm but surely that will increase noise?


texts: why recieved ASCI contradicts scope waveform

texts:
I have written the following code,Which using USART,where in case we send 'a' to the controller  it sends back in a loop 0F which is 00001111,In case we send 'b' to the controller it send back 2F which is 00101111.
In case we send 'c' to the controller the controller sends back 4F which is 01001111.Waveforms of every case shown bellow.
The problem Is when i use PCOM or MATLAB i get a stream of the ASCII 'O'
No matter what command i send to the controller.
Where did i go wrong?
Thanks.

#include "em_device.h"
#include "em_cmu.h"
#include "em_gpio.h"
#include "em_usart.h"
#include "em_chip.h"
#include <stdint.h>
#include <stdbool.h>
#include "em_emu.h"
#include "bsp.h"
#include "bsp_trace.h"

uint8_t received_flag=0;//
// Receive data buffer
uint8_t buffer;
uint8_t tx_buffer=0x6F;
uint8_t tx_buffer_new=0x06;

void USART0_RX_IRQHandler(void)
{
    received_flag=1;
  // Get the character just received
  buffer = USART0->RXDATA;

  switch (buffer)
      {
        case 'a':

            tx_buffer_new=0x0F;
        break;

        case 'b':
            tx_buffer_new=0x2F;
        break;

        case 'c':
                    tx_buffer_new=0x4F;
         break;

        default:

        break;

      }//end switch
  // Clear the requesting interrupt before exiting the handler
  USART_IntClear(USART0, USART_IF_RXDATAV);
}

int main(void)
{
  uint32_t i;

  // Chip errata
  CHIP_Init();
  CMU_ClockEnable(cmuClock_GPIO, true);
  CMU_ClockEnable(cmuClock_USART0, true);

  //EFR32fg14 LOC2 page 157 data sheet TX P0
  GPIO_PinModeSet(gpioPortA,2, gpioModePushPull, 1);

//EFR32fg14 LOC2 page 157 data sheet RX P2
  GPIO_PinModeSet(gpioPortA,3, gpioModeInput, 0);

  GPIO_PinModeSet(gpioPortA, 5, gpioModePushPull, 1);

  // Default asynchronous initializer (115.2 Kbps, 8N1, no flow control)
  USART_InitAsync_TypeDef init = USART_INITASYNC_DEFAULT;

  // Configure and enable USART0
  USART_InitAsync(USART0, &init);
  //datasheet page 157 location2  rx portA pin3(P2) ,tx port A pin2(P0)
  USART0->ROUTELOC0 = USART_ROUTELOC0_RXLOC_LOC2 | USART_ROUTELOC0_TXLOC_LOC2;
  USART0->ROUTEPEN |= USART_ROUTEPEN_TXPEN | USART_ROUTEPEN_RXPEN;

  // Enable NVIC USART sources
  NVIC_ClearPendingIRQ(USART0_RX_IRQn);
  NVIC_EnableIRQ(USART0_RX_IRQn);
  NVIC_ClearPendingIRQ(USART0_TX_IRQn);
  NVIC_EnableIRQ(USART0_TX_IRQn);

  while (1)
  {

      if (received_flag==1)
      {
          USART_Tx(USART0,tx_buffer_new);
          USART_Tx(USART0,'\n');
          tx_buffer=tx_buffer_new;
          received_flag=0;
      }
      else
      {
          USART_Tx(USART0,tx_buffer);
                  USART_Tx(USART0,'\n');
      }
      for(i=0;i<115;i++)
      {
           GPIO_PinOutSet(gpioPortA,5);
           GPIO_PinOutClear(gpioPortA,5);
       }

    // Enable receive data valid interrupt
    USART_IntEnable(USART0, USART_IEN_RXDATAV);

  }
}


texts: Shorting the output ports which have nominal bandgap voltages of 1.24V

texts:
I am using LED drivers (TLC5940) which allow one to fix the operating current \$I_c\$ flowing through LEDs. This is accomplished by connecting a resistor (of the desired value) between an output port, driven by a bandgap reference of 1.24V, and ground. The chip then amplifies the current flowing out of the reference port by a fixed factor to give \$I_c\$.

The situation is that I have several of such chips on a PCB board. To reduce component usage, I am thinking of shorting all the bandgap referenced ports and use a resistor to bias all chips in one go. The issue is that if the references on different chips happen to be slightly different, shorting the outputs may be unwise.

In that case, is shorting advisable?


texts: What is the best low power wireless transmitter?

texts:
I would like to send a sensor signal (e.g. Temperature) wirelessly to a computer for a short distance (e.g.3~5 meters). The challenge is I have a very low power source (3V 50mV).
I am thinking of using a

Bluetooth chip: (Good quality signal, but I feel that the chips that I found online are power-draining)

Antenna: with the amount of power I am delivering noise might be an issue if I am it is impossible to operate of high frequencies.

What is the best way to transmit my signal from the sensor wirelessly with as low power as possible?


texts: What condition may cause the plug or the power adapter to become very warm or hot?

texts:
I know that using a power adapter for very long hours (probably more than 24 hours) can cause the plug of a power adapter (or even the power adapter itself) very warm or hot.

However, I am interested to know what other situation(s) can cause the plug and/or its power adapter to become very warm or hot? (and would appreciate if answer can include on how to prevent or solve the situation)


texts: Which way do the white and green wires go in a usb connection?

texts: I am making a system that requires the white wires and the green wires (in usb cables) need to kind of be on a diode. Which one goes to the computer and which goes to the USB device?


texts:
I'm building a parallel isolated DC/DC converter setup, using the Murata
DBE0125V2NBSC (datasheet here). The datasheet recommends the following for parallel current sharing:

Turn all units off before configuring the output voltage via PMBus
commands; all units must have the same output voltage configuration.
It is recommended to turn on one unit first and then turn other unit
(s) on after the output for the first one has settled. Turn on the
next unit (s) after the previous unit reaches its regulated output
voltage for at l

I have control logic on the isolated side, but what is the most common way to control the primary on/off on these converters? Would I use relays? If so, how would I best choose one (try to match the isolation ratings, etc.)?
Thanks for your input.


texts: How to adapt a string of 10 LEDs powered by 3 AA batteries to work off a USB port?

texts:
I have a string of Christmas lights made up of 10 warm white LEDs. The lights are connected in parallel (not in series). The string works with 3 AA batteries (that is, 4.5 VDC). And all that stands between the power source and the lights is one 200 Ohm resistor (this is a photo of the resistor, in case I read it incorrectly):

Now, that's all I know/understand of the string of lights. What I want to do is change the power source: I would like it to work off the 5 VDC that come from a USB output.

My basic knowledge of electronics tells me that there's basically 2 things I have to worry about here:

1) How do I drop that 0.5 volt I don't need? (Although, playing around with LEDs, I think they'll have no problem working with half a volt over what they were originally working with); and

2) Is the current coming out of a normal USB outlet (such as from a telephone charger, 0.8-1.2 amps) going to be too much and, if so, how can I drop it to the current needed? (If I'm not very much mistaken, the current will be too much because a normal LED takes 15-20mA, right?)

I understand this issue is very basic but so is my knowledge of electronics. I would really appreciate any help you can afford. I think that if I could "fix" this issue, find a way to get it to work, I would be able to understand a little more about how it works. So far, reading theory... well, it's all mixed up in my head; perhaps if I could solve this real-life situation, the little I understand could start falling into place and organising itself.

So thanks a lot in advance!


texts:
I'm currently working on a project that contains a battery pack and consists of 10 nimh batteries each at 1.2v 2400mAh running in series (12v @ 2.4amps). Because I don't want to keep opening and closing my external case to get access to the battery, I'm looking into having a way to easily charge this using a power adapter via a charging circuit.

This charging circuit is where I stumble. Because I've got 10 cells, should I provide a constant current source of 240mA @ 12v (10%) which will take 10 hours to charge my pack (I can have a microcontroller to isolate the charging after 10 hours)? Because each cell might different between one and another, I don't know how I would go about providing a balanced charging current for each of these, as they are in series.


texts: Harmonic distortion in sub threshold 2 stage opamp

texts:
I have designed an 2 stage opamp with all MOSFETs in subthreshold region as shown in the figure below,

I have gain of 48 dB, GBW of 60KHz, Slew rate of 0.014 V/us and Power dissipation of just 0.6 micro Watts.

Here is the Frequency response ,

I have a appreciable Phase margin of 60 degrees from the frequency response.
I am a little down on noise and harmonic distortion analysis in LT spice..
But i do know that FFT of the output gives an idea of the THD.But how to calculate the percentage harmonic distortion ?

Here is a picture of FFT of the output, (Note :i am operating at 400Hz sine input)

What does this values in db mean and i do see peak at 800Hz which is an harmonic of fundamental frequency 400Hz , what should i conclude from it and how is the THD evaluated?

I would also like to know about the stability analysis of the same.


texts: Precise multi-point over-temperature control using comparator

texts:
This circuit will (hopefully) send a signal to MCU if over-temperature is observed in any of the NTCs.

Using LM339 as comparator, and a reference voltage (from TL431), assuming high precision for NTC and resistors, does this circuit use the LM339 correctly? (It's my first time setting up comparator, mostly modifying datasheet example circuits.)
My doubts are about the 5.00 V supplied to LM339 (should it be higher?)
The voltage divider which feeds IN- of LM339 is made of constant 3.3k resistor and NTC.
[providing 1.24 V @25C and 3.11 V @75C (which is considered high-temp condition)]
Somewhere in the op-amp datasheet it states conditions for IN+, IN-, and the supply voltage (pins 3, 12) and different op-amp working modes, which I honestly couldn't understand fully. (Or I have, if the circuit is correctly working, at least on paper/simulation)
LM339 datasheet


texts: Increasing TPS63001 Under Voltage lockout from 1.8V to 2.5V for use with LiFePO4 cell

texts:
The Under Voltage Lockout threshold for this chip ranges from 1.5 V to 1.8 V. I want to use this with a LiFePO4 cell, whose minimum voltage is 2.5 V.

With reference to the datasheet here, the VINA pin is responsible for monitoring the input voltage.

As such Will it be effective to connect a schottky diode with 800mV forward voltage dropt between VIN and VINA pins, to shutdown the chip when VIN reaches 2.5 V?

Any better ways to solve this? Kindly suggest.


texts: Would a silicone mat (not anti-static) placed on a truly ESD anti-static mat become anti-static?

texts:
It's just like another component placed on the anti-static mat, right? This should work at providing an inexpensive heat-resistant and anti-static workbench area?
All the 'anti-static' heat resistant mats I found explain in the comments about how they are not really anti-static. And all the inexpensive, true EDS, anti-static mats are not heat resistant. (I'm sure there is one out there that has both, but it's likely out of my price range.)
Therefore, placing a $20 heat resistant mat on a $20 EDS anti-static mat would be the ideal choice? Is there something I'm not considering?


texts: How does System Generator for DSP actually works?

texts:
I'm developing control algorithms on FPGAs. By now, we use hand-written VHDL code for our fundamental entities we combine to more complex IPs, all done manually. In my opinion, this is not satisfying.

Reviewing the literature it seems that System Generator for DSP by Xilinx is quiet popular at the moment for automated FPGA implementation out of Simulink.

My question is: How does XSG actually works? Does it only combine pre-defined IP cores according to model scheme or does it really compile VHDL code of the system? Is there any chance to at least "have a look" to the inner HDL description of the blocks?


texts:
I'm trying to controll 4 parallel 12V DC LED strips with an speedcontroller. I am able to dim the lights from 100% lit to about 5% lit, but it never turns them off completely. My multimeter can't detect the phases that the speed controller is generating, so it reads 2.0V at 0.0A when all the way dimmed. When fully turned up, its at 11.5V and 2.0A.

The speedcontroller has a 100k omh potentiometer on it and is specified for 12V DC up to 2A. The LED strips are 12V too, and should consume about 10W in total. What are my options to get it working as intented, so that it's turned off completely?

Help is much appreciated!


texts: Using two momentary switches to toggle LED

texts:
So, this circuit should (in theory, at least) turn the diode on when ON button is pressed, and turn it off when OFF button is pressed. It doesn't though. The diode is powered on at the moment where I connect the circuit to power, and it switches off only for the time when OFF button is pressed, and turns on immediately after OFF button is released.
I'm kinda new, so it's very possible that I've made some dumb mistakes :p
Thanks in advance

Here's the schematic:
And datasheets:
2n2222
S9012


texts: How to calculate the voltage at the OUT point in this PWM creator

texts: This is a Circuit for creating a PWM signal,I have the results but I wanted to know how I come to this results,because I dont really know!Thank you!Here DC=50%,what about DC=75%.Please help!!


texts: Why isn't atmega8 using the internal oscillator at 8MHz by default?

texts:
I've been using the atmega8 for some time and encountered a problem related to timers that require higher clock speeds. I missed the part in the datasheet and thought that the default clock speed of 1MHz is the maximum internal frequency I can get. However, it is quite trivial to fuse the bits and get frequency of 8MHz or even overclock.

What are the drawbacks of using 8MHz clock speed by default?


texts: NFET As Voltage Controlled Switch Question

texts:
See pic

EDIT: The original youtube video link: https://www.youtube.com/watch?v=3XpzgvUDVDQ
What is a signaling node?
Why do I have four nodes? I thought MOSFET's had 3 pins
Why does connecting the signaling node to ground give us the switch behavior we want?


texts: What is the use of two n mosfets with their sources tied together?

texts:
The circuit I'm looking at recommends two n-channel mosfets in series with their sources tied together between it's output and the power input.

pin description:

  High voltage open-drain gate driver, which may be used to drive an NMOS/PMOS power  switch.  This  pin  is  connected  to  the  gate  of  the  power  switch.

But why two mosfets? Why not only the right mosfet?


texts: vhdl synthesis optimization: counters in statemachines

texts:
I have a general question about the efficiency of a synthesizable state machine.

The first version uses the same counter for each state.
The second uses one own counter for each state.
Which version of the two is more efficient (logic area, speed...)??

How much area of the FPGA is occupied by the routing of the count1 signal when i use the same counter for each state.
Is it better to user one counter for each state??

I'hope somebody with more experience can explain which solution is the best (maybe a third version) and why.

Thank you!

Kind Regards,

Oliver

-- 1. Version ===============================================================

signal count1: integer range 0 to 1000 := 1000;
type mystates is (s1, s2, s3, s4);
signal mymode: mystates := s1;

BEGIN

MyProcess: process(clk)

BEGIN

    IF (clk'event and clk = '1') THEN

        case mymode is
        when s1 =>
            If (count1 = 0) then
            mymode <= s2;
            count1 <= 555;
            -- (stuff)
            else
            count1 <= count1 - 1;
            end if;
        when s2 =>
            If (count1 = 0) then
            mymode <= s3;
            count1 <= 666;
            -- (stuff)
            else
            count1 <= count1 - 1;
            end if;
        when s3 =>
            If (count1 = 0) then
            mymode <= s4;
            count1 <= 784;
            -- (stuff)
            else
            count1 <= count1 - 1;
            end if;
        when s4 =>
            If (count1 = 0) then
            mymode <= s1;
            count1 <= 1000;
            -- (stuff)
            else
            count1 <= count1 - 1;
            end if;
        when others =>
            Null;
        end case;

    END IF;

end process;

-- 2. Version ===============================================================

signal count1, count2, count3, count4: integer range 0 to 1000 := 1000;
type mystates is (s1, s2, s3, s4);
signal mymode: mystates := s1;

BEGIN

MyProcess: process(clk)

BEGIN

    IF (clk'event and clk = '1') THEN

        case mymode is
        when s1 =>
            If (count1 = 0) then
            mymode <= s2;
            count1 <= 555;
            -- (stuff)
            else
            count1 <= count1 - 1;
            end if;
        when s2 =>
            If (count2 = 0) then
            mymode <= s3;
            count2 <= 666;
            -- (stuff)
            else
            count2 <= count2 - 1;
            end if;
        when s3 =>
            If (count3 = 0) then
            mymode <= s4;
            count3 <= 784;
            -- (stuff)
            else
            count3 <= count3 - 1;
            end if;
        when s4 =>
            If (count4 = 0) then
            mymode <= s1;
            count4 <= 1000;
            -- (stuff)
            else
            count4 <= count4 - 1;
            end if;
        when others =>
            Null;
        end case;

    END IF;

end process;


texts: Does the Resistor have an impact to the electric charge of the capacitors?

texts:
I have this circuit (picture below) and at first I had to calculate the eletric charge of the capacitors without the resistor which is parallel to C1. Which was not a problem at all.
After that the resistor came up parallel to the C1 and I should calculate the electric charge again for both capacitors.
The voltage is DC and the electric charge for t -> infinity.

I'm not sure how to calculate it because I think the resistor does not change anything.

Here the circuit:


texts: Antenna preamplifier design for ELF Schumann resonances receiver

texts:
I'm interested in listening to extremely low frequency band below 100Hz, where the famous Schumann resonances reside. I will use a large T shape antenna together with a very low noise, very high impedance preamplifier. This is my current draft of the preamplifier:

C2 is the SA102A100JARC 10pF ceramic through-hole capacitor. R2 is the SM102035007FE 5GOhm through-hole resistor. C3 is an SMD ALU electrolythic capacitor. The goal is to have a -3dB LP cutoff at 100Hz and as low as possible HP -3dB cutoff (~ 1Hz). VCC is 5 volts. The next stage would probably be a 50Hz twin T notch filter. I would appreciate if you guys can do a quick check of the circuit and maybe suggest some enchancements :) Thanks !

P.S.: R2 and C2 are through-hole because of the guard ring and easier control of the leakage current.


texts:
This is related to an earlier question of mine, but I have a different follow-up question that I wanted to make a new post for.

I'm trying to understand more about how the below circuit works, specifically the amplifier:

Taken from here with some extra details added.  EDIT:  Was able to find the source document here, in case that's useful to anybody.

I've tried implementing something similar with an instrumentation amp, but was told that an opamp would be a much better choice.  However, I'm not totally clear about how the opamp is functioning in this context.  This doesn't appear to be set up like a difference amplifier with gain-limiting feedback resistors, and it was suggested that large gain is actually beneficial here.  So here's what I don't understand:

Is this opamp configured to act as a comparator here?  I.e., is the amplifier output primarily going to be saturated near 5V or ground most of the time, and avoid intermediate output voltages?
If it's acting as a comparator, what happens when the bridge is balanced?  The thermistor should be held at an elevated temp when this happens, so would we essentially see a square wave at the opamp output?
If this isn't acting as a comparator, how is the gain being set?

Sorry for what might be a simple misunderstanding - I'm just having a hard time wrapping my head around the intended operation as I'm used to simpler opamp circuits.

TLV2434 data sheet

2N2222 data sheet of sorts.


texts: Criteria for gyroscope export restrictions

texts:
Recently I tried to purchase a gyro for a GPS car tracking device I'm designing and Digi-Key refused to sell me since I'm outside US and that specific part (L3G4200D from STMicro) is export-restricted.
I imagined that it was due to its precision (maybe high enough to be used in a weapon guidance system) but every alternative I found was restricted too.

Anyone knows what are the specific criteria for making gyros export-controlled, and if that really affects all of them? If not, what would be the maximum allowed for the relevant parameters (precision & etc.)?


texts: Grounding apparently causes volume increase in speaker

texts:
I have a pair of speakers connected to a subwoofer. The second speaker is barely audible, until I touch (but without necessarily turning) the volume control knob on the first speaker. As long as I am touching the knob, it emits sound. This is the exact oppoiste of my experience with speakers and amps, when touching the wiring usually silences background hum.

I'm not looking for a fix, I'll repair it like I do most electronics, by tinkering until it works, I'm just wondering what would cause grounding to end up making the speaker louder?


texts: Discriminating between aluminum and other metals

texts:
I am looking at being able to detect aluminium (or other cheap metal if suggested) with ultra high specificity and sensitivity in the presence of steel, and possibly titanium.

The piece of aluminium would be a cord of around 3mm by 5cm.

Would a metal detector be able to be tuned for this purpose?


texts:
I am learning about VLSI static timing analysis (STA) and some applications of SDC commands. I'm probably still missing some big picture concepts, but my question is about "why" when it comes to using set_clock_latency.

I see from the command there is an option to specify the latency from -source (the originating point of the clock such as a PLL) to the point where the clock is defined (like a port pin), and then there is a different set of options to specify network latency (from the point where the clock is defined to the final clock pin of a flop).

What's a good use for this? When do you care about the latency between the source and port pin? Wouldn't caring about timing relative to the pin be good enough? I can see the -min/-max/-early/-late being useful, but couldn't these values get rolled up into a "set_clock_uncertainty" command?

And for network latency, isn't this something the tools should worry about since it's handling the clock tree synthesis? What is gained by me directing the tools, and what value would I even put?


texts:
How would I go about making a push button to act as a toggle switch. A switch would just stay in the active state until "un-switched". I need my button to toggle something.

Example:

Button down (active)   -> output active
Button up (not active) -> output active
Button down (active)   -> output not active
Button up (not active) -> output not active

It should'nt matter how long the button is pressed for, it should only be able to deactivate once the button has been released once.

Currently I'm using a PROM to check for all these states but I feel like there should be an easier way, perhaps with a T-flip-flop, but if you hold the button for more than one clock pulse it messes up.


texts: Wiring in Thermostat (Rittal 31100) as a 24V Temperature Switch

texts:
I want to wire in the following thermostat.
https://proax.ca/en/product/205417/RIT3110000
And am having a hard time understanding the wiring diagram

I think I get that 5 is L and can be connected to your heater (3) or cooling (4). So pins 3,4,5 are just a single pole double throw switch? I would be able to connect 24V to pin 5 and probe pins 3 and 4 to determine if the thermostat was above/below the set point? Or does the switch need power and is that incorrect?
Maybe instead pin 5 needs to be 120VAC or 240VAC depending on location, and then what would 1 and 2 be?
I'm missing something - any help would be greatly appreciated!


texts: Single H Bridge to control multiple DC motors

texts: I am looking to control multiple DC motors off of a single H bridge.  I only need one active at any given time I need direction but not speed control.  I'm not looking for a product recommendation, but I guess asking is it possible to use an analog mux or shift register on the output of the H bridge to act as a switch? I am a software guy just getting into hardware so if I'm missing something obvious please forgive me!


texts: Taping down cord with duct tape fire hazard?

texts:
Curious as to if taping down a cord is a fire hazard. Some cords have very thick insulation and rubber so I do not see how it would be the case. I will try to find the article and update the post if ai find it.

For scenario Is it a fire hazard to tape down a cable that pulls 1500 watts and belongs to a space heater? What are your thoughts. 120V region


texts: Using Adafruit Stepper controller to control 1A/phase stepper

texts:
I'm trying to control a stepper motor with Adafruit Motor/Stepper/Servo Shield V1, Arduino UNO and a 19V/5A power supply.
The motor uses 1A/phase making the driver overheat.
Is it possible to use the two stepper controls from the driver in parallel to control only one stepper and avoid overheating?

(source: prometec.net)