texts: How to make amplifier (almost) Beta independent?

texts:
There are several ways to bias the quiescent point of transistor, when used as an amplifier. Among which voltage divider is best known for its improvements (improved temperature drift and beta variation). But as we use different transistors, even voltage divider cannot make amplifier beta independent.

I am specially interested in the biasing of differential transistor pair (amplifier), where biasing is done only by replacing emitter resistor with active device known as constant current source, or should be done; as stated in Wikipedia and many other sites:

"...the differential pair is directly biased from the side of the emitters by sinking/injecting the total quiescent current. The series negative feedback (the emitter degeneration) makes the transistors act as voltage stabilizers; it forces them to adjust their VBE voltages (base currents) to pass the quiescent current through their collector-emitter junctions..."

I somehow still don't understand how a transistor could conduct any current without Vbe connected between the base and emitter of transistor. But by forcing the Vbe to "occur" and conduct current, whereas Vbe is forced by the current source...

Can anyone explain me what is actually happening here? Or at least show a practical example, where this kind of biasing is put into use.


texts: How do receivers know what to output to radio speaker or TV screen?

texts: I understand that receivers are often used with mixers which take the sum and difference of two signals to make an output signal.  How does a radio signal of say 102.5 MHz know to tell the speakers to output a person singing, a guitar with distortion, and a drums all at the same time in the range of 20-20,000 Hz?  In the same vein, whenever a TV receives a signal for a channel of 150 MHz, how does it know what pixels to light up on the screen?  This may be an obvious question and I'm just not making a connection, but any further explanation would be appreciated.


texts: Using the same switch for two devices of different signal voltage levels

texts:
When I press an ON-OFF type switch (SPST), I would like to have a corresponding HIGH or LOW registered on the inputs of both a 5V-level microcontroller as well as a 10V-level device, without damaging either one obviously.

How would I go about achieving this -- should I use a resistive divider?


texts:
I'm trying to generate a combination of 2 waves with different frequencies. For example 1Khz and 5Khz - so I could recognize it on my PC using FFT.
It seems that feat is not possible using arduino.

Any one succeeded? is it possible with any other way? physically possible?

Thanks!


texts: How do you get a program onto an eZdsp board?

texts: I'm using an eZdsp board which has a TMS320f2812 chip on it. The board has a parallel port on it which is used to program it. I'm experienced with software but not at using microcontrollers or DSPs and don't know wher to begin with getting a simple program on, like to flash the built in LED on the board. I'm using windows 7 and have downloaded the latest code composer studio and have a parallel to parallel cable to connect from computer to board. So now what to get a program on there? Thanks


texts: Is phase angle a important thing to consider when designing filters?

texts: Whenever I was choosing values for filters I always ignored the phase angle plots, but should I be taking it into consideration when for example designing a high-pass filter for the input of an amplifier or a low-pass filter in the feedback network? What are the situations where it's important to know the phase angle and take it into consideration in the design?


texts: Difference between torque and speed in dc motor?

texts: I have knowledge about the definitions about both speed as well as of the torque. But I am unable to think dc motors in terms of speed and torque. When the armature of a dc motor rotates , we call it torque because of rotational movement about the fixed axis. So where is speed?


texts:
Does the product on USA market with inactive transmitter (2,24 GHz) need the FCC certification?

We are going to use Tx/Rx module, but the transmitting function will be software disabled.


texts: I want to generate sinewave by using Ad9833 and an amplifier on LT Spice IV but this Ic is not available,so how i can make this schematic to get sinwave? It would be great if anybody can help!


texts:
I have a gizmo im trying to build and am running into some problems. I need to power a time punch clock 24 hrs a day drawing 1.2 Amps. I am trying to run this from a deep cycle agm battery with a solar panel to charge and keep this a maintenance free, working device. Is this even possible? I have tried everything my very limited brain can come up with to solve the problem.
 In short i guess Im asking, can i charge at a higher amp than my draw and have the excess go to the battery for storage?


texts:
I have created an mif file in Quartus and I am working with cyclone 2 Altera. My query is "How can I use this mif file to initialize a variable in my top level design architecture"?
Let me elaborate. My aim is to produce a sine wave using FPGA storing the values in look up tables and accessing it from a VHDL program. I calculated the look up table values myself using MATLAB. I have put them in a mif file. Now I think I should write a program that takes in these LUT values and feed it to the DAC.

For this I am trying to write a vhdl program with a variable that is initialised with my LUT values. I will then assign the values to an output vector variable(should it be a two dimensional array?) and then use the DAC.

I heard there are no direct DACs in cyclone 2?


texts: What is bus hold LOW or HIGH current refer to in the data sheet?  (Specifically looking at this data sheet for a translator buffer): http://www.nxp.com/documents/data_sheet/74LVC_LVCH2T45.pdf


texts: Where to begin with programming an audio interface driver?

texts:
I'm designing my own mic/line preamp (the analog portions) and would like to have it interface with a computer in a send-return fashion as well (like any typical audio interface).

I've noticed that Texas Instruments and other manufacturers sell A/D/A converter chips for dirt cheap.  However, the missing link would be the driver code to actually have the computer read and interpret the sent bits, as well as send bits back to the device via USB (having the correct USB topology would also be important).  I know a bit of C programming, and I've heard that is the language audio drivers are typically created in.

Here are my questions: are there pre-programmed microcontrollers that include all the necessary I/O and driver code for audio-to-computer interfacing?  Or can generic driver code be found on  a site like GitHub?  If not, where do I begin with programming such software?  i.e. what to research, what to focus on, etc.

Thanks a lot for your help!


texts: How to make a device in miniSD or microSD form factor?

texts:
I would like to design and get produced a device in miniSD or microSD card form factor.  This is not actually a memory card, it just uses that connector.  There are other devices like that, for example Electric Imp.  I'm wondering what type of circuit board and what type of outside packaging is used in devices like that?

microSD thickness is only 1mm.  There are plenty of chips which are thicker than that, even in the thinnest possible package they come in.  Typical circuit boards are 62 mil (1.62mm), the thinnest I have seen is 10 mil (0.25mm).  I'm not sure if a multi-layer board can be made in 10 mil in any case.  Are microSD memory cards usually made as system in package (SIP) or do they have a board inside?  In non-memory devices, what type of board is used (if any) and how do they solve the device height problem?

In a device like this, are the contact fingers on the circuit board or on the case?  If on the case, then how does the board connect to them?  How is the case made?

EDIT Bounty started.  Please describe: How are such devices built?  (wire-bond, PoP, encapsulated in epoxy, WLCSP on thin or flex board, etc ...)  If a board is used, what kind exactly?  Who can manufacture these?  (board, assembly, encapsulation, ...)  Any example whitepaper explaining the design or different designs?  How to deal with over-thick chips? (for which no thin replacement exists)  Thanks!

EDIT The answer below had some good ideas, but I am still looking for a definitive answer.  I want a "design guide/white paper" for small form factor encapsulated devices like this, and some pointers to manufacturers.  Any good answer will get a bounty.


texts: Is there a standard way to load an image into VHDL testbench so image processing logic output can be tested? Obviously there will be an output from the testbench, also an image that must be possible to open and view.


texts: Why is the amplitude of ringing in square wave independent of frequency of square wave?

texts:
Reflections in a transmission line is causing ringing in square wave because certain frequencies are getting enhanced, but when frequency of the square wave changes won't the amplitude of those enhanced frequency decrease or increase because the amplitude of higher harmonics decrease or increase when we change the frequency of square wave according to Fourier series expansion? Still we don't see any change in amplitude of ringing in square wave. Why is that so?

I understand why the frequency won't change but I don't understand why the amplitude of ringing won't change with the change in frequency of square wave. Please help me understand.


texts: Finding current over controllable voltage source using nodal analysis

texts:
I have the following circuit:

Let me explain the diagram a bit first: I0 is current in that direction, V0 is voltage and 2 V0 is also voltage times two. V1, V2, and V3 are my nodes. The 'S' by the resistor values stand for Siemens or conductance (reciprocal of Ohm).

What I want to do is find the current I0 and the voltage V0. I have found the voltage V0 to be $$V_0=6.29V$$ and the other voltages to be $$V_1=18.86, \;\;\;V_2=6.3V, \;\;\;V_3=13V$$
Which also means:
$$2*V_0=12.58V$$

Where I'm stuck is what will be the value for I0? I really do not know how to go about finding it. I'm using nodal analysis on this problem.

Thank you for any help, I'm very stuck and would like to learn how to go about this problem.


texts: How can an LED have more than 100 percent efficiency

texts: I saw this little article that said people from MIT were able to have an LED consume 30pW and emmit 70pW. How is this possible knowing the law of conservation?


texts: I am working on surface mount circuit boards and having trouble removing components (through hole) due to the power and ground planes sucking away all of the heat from the soldering iron.  Do you have a suggestion on what wattage iron I should be using?


texts: FPGA project sanity check, PCIE and video processeing

texts:
I have an Altera DE4 education FPGA that I'd like to use for video processing... But the thing doesn't have many ports to work with, and I don't have the funds to purchase any daughter boards.

My plan is to plug the FPGA into my computer via the PCIE port, and then send video to the board that way.

Will this work?  Or am I just grasping at straws here?  Was it much trouble to interface with the board in this way.


texts:
Seeing as there are more and more mutli-core processors systems. I'd like to learn more about them.

What mutli-core microcontroller eval boards exist, if any?

Thanks


texts:
I salvaged this breaker unit from the scrape yard. Compared to every other breakers i have seen before, this is very different. It has 5 terminals.

The labels are very clear but there is no information about the usage of its terminals. The terminals are labelled A, B and C. Its not even labelled clearly which side is load and which side is line.

The greatest mystery is the terminal C. What is it's purpose and how is it used?


texts: What is it called when a WiFi chip advertises its own SSID so users can connect

texts:
I am not sure which stack should I post this, but here is my question:
when you buys these WiFi-enabled gadgets, when they turn on they advertise a SSID where you can connect to it and enter your homes network detail in them.
What is this mode called? Access Point? Hot spot? Is this possible to be done on a raspberry pi zero?


texts:
I am trying to design a circuit with power supply for a microcontroller with a li-ion cell depending on whether a charger is connected or not.
I tried it first in the Falstad simulator. "USB 5V" with the switch acts as a USB plug (connected/disconnected), 1k resistor acts as the charger IC (to manage the voltage for a cell, for ex. MCP73831 from the Microchip Technology), capacitor acts as Li-Ion cell and 100 ohms resistor acts as a converter from 5V to 3.3V for uC (and next the current flows to the uC etc.). The p-channel MOSFET and Schottky diode are "real", 10k resistor is a pull down added to set 0V on the G of the MOSFET when the USB is disconnected.
- My needs are:

when USB plug is disconnected (or switch on the schematic is open), 0V is on G of the MOSFET, so MOSFET can pass the current between S and D, so the current is drained from the cell and flows through the MOSFET, from S to D and to the converter IC (so the uC will be powered from Li-Ion cell).

when USB plug is connected, the MOSFET cannot pass the current from S to D now. So it's time for charging Li-Ion cell and the cell itself will not power the microcontroller at this point. BUT the microcontroller will be powered by USB itself through the Schottky diode.

So all in all, USB connection would not be of much importance for the microcontroller (Either way, it would be powered either from Li-Ion cell or from USB).
But I'm worried about the Ix current flowing the other way than through the converter IC when the charger is plugged in. This current flowing through the Schottky diode will bypass the Charger IC and flow between D and S of the MOSFET, and eventually destroy the cell. How can I fix it?

My inspiration:
https://www.youtube.com/watch?v=GRd9uTwg7r4&t=614s&ab_channel=MicroTypeEngineering


texts:
I'm currently working on a project about I/O with FPGA. I am using TTL-232R-3v3 cable for serial communication between my laptop and DE0-nano. I want to know if it is possible to send a signal on RX wire to FPGA and light up LEDs with that signal or is UART needed?

Any advice or guidance would be greatly appreciated, thanks for your time.

edit-

I'm using usb cable for power supply and I'm using only RX, TX and GND wires of TTL cable. Here's my clash code

module Blinker where

import CLaSH.Prelude

{-# ANN topEntity
  (defTop
    { t_name     = "blinker"
    , t_inputs   = ["GPIO_IN"]
    , t_outputs  = ["LED"]
    , t_extraIn  = [ ("CLOCK_50", 1)
                   , ("KEY0"    , 1)
                   ]
    , t_clocks   = [ (altpll "altpll50"
                             "CLOCK_50(0)"
                             "not KEY0(0)")
                   ]
    }) #-}
topEntity :: Signal Bit -> Signal (BitVector 8)
topEntity gpio_in = mealy blinkerT 0 gpio_in
blinkerT :: Int -> Bit -> (Int,BitVector 8)
blinkerT a bit = (a,pack bits)
    where bits = repeat $ bit == high


texts: Homemade shielding of a wire to a capacitive sensor

texts:
I'm using a capacitive sensor CAP1188 with Arduino, connecting 8 of its touch sensor inputs to 8 copper boards that I want to be the actual touch surfaces.

The wires to the sensor are quite long (100 to 500mm depending on the location of the copper board in the system) and approaching them also triggers the sensor, which I do not want.

How to remove the noise on these wires?

To fit the setup the wires need to stay thin (2mm of external diameter max). I am currently using phone wires (from R11 male - RJ male cable)

I've already tested surrounding the wire with a large piece of aluminium foil connected to the sensor's GND, but the detection seems even more noisy. For simplicity I grouped the wires together when possible (i.e. protected with a single aluminium foil), but I presume this is a bad idea?


texts: Should a PAM8403 be directly fed from a CHIP GPIO audio signal?

texts:
I am building an internet radio (I somehow know how to develop and am an absolute beginner in electronics), for which I wanted to use a C.H.I.P computer and a PAM8403-based audio amplifier.

This has already been done and I followed the instructions from the C.H.I.P blog, to essentially build this

simulate this circuit – Schematic created using CircuitLab

Upon connecting the L/G signal from the C.H.I.P. and without streaming anything, the loudspeaker was issuing a continous hiss, sort of white noise, rather high-frequency.

When sending some audio signal, the signal was very distorded.

Plugging the spekaers directly on the audio outputs of the C.H.I.P. gave a nice sound, although very weak (this is the reason I wanted to amplify it in the first place).

I assume therefore that something is wrong in the way this output signal is processed by the amplifier chip.

I went on reading and articles about how to deal with such nuisances revolve around a low-pass filter. So I added one.

simulate this circuit

When turning the potentiometer (high resistance to low) I get an almost inaudible sound (I have to put the loudspeaker to my ear) and then suddenly the signal is all distorted again. But the hissing sound is gone.

Sioce I find these hind of hardware hacks fascinating I am ready to jump in to understand everything, and my main question would be: is the approach I have correct, that is: is the output signal of GPIO pins of devices such as the C.H.I.P. or a RPi intended to be used with amplifiers such as the PAM8403?

Another possibility would be a faulty element - I will look for another PAM8403 amplifier to discard that as the article I was basing my hack on is clear with the the connections.


texts: Weird polarity switching in home inverter wiring

texts:
So I have a Backup Inverter installed in my house, it was installed when I wasn't around. Now I need to add an inverter line to a board that didn't had it before. To do this I generally tap the (live/phase) wire from the inverter output and run a wire to that board. But the problem is when the mains supply is ON the inverter's output along with the neutral wire of mains are working (those two wires are making the bulb glow) but when the mains is OFF then the inverter's live coupled with the live of mains works. What i don't understand is why is the polarity switching like this? And how should I connect the board so that I would get continues power in that board irrespective of mains being present or not?

What I'd guess is that this Inverter configuration is not simply a common neutral one but something else.


texts: How to do a simple overcurrent protection/circuit breaker circuit for 12V 1-2A?

texts:
We're developing an I/O shield for Arduino (sort of) and having four FET controlled output connectors with approximated 12V 1-2A load each. I need all these four outputs to be short-circuit protected and such incidents detected by another input pin on the Arduino.

Since we're using the Olimexino-STM32 Arduino clone, we've only got 3v3 on the CPU pins. Therefore we've attached an 12V driven LM339 between the CPU pin and the P-channel FET driving the 1-2A output. Pretty much like this, but with LM339 instead of transistor:

But since these four 1-2A outputs will drive four loads individually, we don't want the whole circuit to burn out in case of short-circuit. Ideally, short-circuit on one single output would not cause and disturbance on the other outputs, but report back to the CPU (using another input pin) it's lost, and the CPU could then alert higher-level system of the short-circuit.

The board is driven by a 12V source and the outputs will also need 12V so the solution will have to be have a low dropout voltage.

I've found some simple solutions using JFET with bound Gate and Source, but I'm not sure what's the actual current limit level, or even if it's applicable in our project since it's mostly used as constant-current driver for LEDs:

EDIT:

Thanks alot for all the anwers! We made some changes to our original design, but your suggestions is really helpful in other cases. This is how we've done:

To keep it both simple and cheap we've changed the overall supply voltage to 24v and implemented a first-stage high-effective switch regulator which brings the voltage to ~14.5V and then we've added a simple linear regulator (LM7812 derivate) for each output stabilising it to 12V and makes each one independent from the others. The linear regulator has short circuit and over current protection built-in.


texts: How do I properly calculate the requirements for an on/off switch?

texts:
I'm building an arc lighter to learn more about electronics and I'm not certain how to calculate what I need given the components I have. Do I go off the rating for the battery or the combination of battery and parts?

I want to buy the correct on/off switch.
So far I have an 18650 battery 3.7v 3000mah, a charging board 5v 1A, a momentary push button switch 3A 120VAC, a high voltage transformer kit and a rubberized altoids case. I've put the links below if you're interested.

Any help with how I can calculate the requirements for an on/off switch would be great. If you see something I might be doing wrong off the bat I'd also appreciate the info.

Links

https://www.ebay.com/itm/171933254204
5V 1A Micro USB 18650 Lithium Battery Charging Board Charger Module+ Protection

https://www.ebay.com/itm/222083901779
DIY kit DC High voltage Generator Inverter Electric Ignitor for 18650 Battery


texts: The best mode to drive an LCD Display to get noise immunity

texts:
Which one of these modes is the best for get noise immunity when driving a LCD Display 16x02? (or 16x04 etc.)

-I2C module using PCF8574 I/O expansion.

-8 bit Parallel

-4 bit Parallel

I had a PCB which drives an LCD Display 16x02 and drives 4 dc motors (80mA each - no load).
When a used to use this pcb I got some problems with noise from the motors and sometimes I got strange characters printed by LCD. I used to use Parallel 4 bit mode.
But now I'm designing a new PCB which will drive 4 motors with H-Bridge and 1 LCD Display 16x02 and will have 2 UART and 1 I2C communications using a PIC16F1947 MCU.

I'm going to be sure for have a great ground plane on my PCB (4 layers) and I'm going to increase noise protection too.

Should I still using 4 bit Parallel mode and do something to decrease the noise?
Should I change for 8 bit Parallel mode? or Doesn't it make sense?
Should I change to use I2C module?
I know I2C is for communications between ICs in the same PCB but I think Could be better because 2 wires is less than 8 wires so Could be more difficult to get noise using i2c mode.

The distance between the pcb and the LCD Display is like 20 cm.
Should I do somethings on the cables? Like Twist the cables?

I think could be good for all of us know the safest way to drive an LCD Display.

Sorry for my bad English.


texts: Sallen-Key - how opamp input bias current changes cutoff frequency?

texts:
As in the title: what exactly is the impact of input bias current in Sallen-Key topology, for example the one below:

I read that it can matter significantly, however I did not find anything more on this matter.


texts: Protective-Earthing the chassis with the earthing point being the star-point - How does it keep the Chassis at Earth potential?

texts:
I always understood that one of the two purposes of protective earthing is keeping the electric potential difference between the chassis of a devide and the ground (the ground I am standing uppon while using this device) at a  low rate, preferably lower than what is considered harmful to the human body. However, looking at this particular realisation of the protective grounding (TN-Net)

there is something I don't understand:

The PE-Connection will keep the chassis at the same Potential as the ground located at the star point of the system. However (as this question indicates), the ground I am standing on in the moment I am touching the device may have a different potential than the one that exists at the point where the network is grounded. How will this help me not being shocked?

EDIT: I know that there are other protective measures, like the RCD shutting down when it detects a difference between the L1 current and the N current. I'd still like to know wether the difference in potentials do have an effect (or why they don't have an effect).


texts: Connected ground planes from different power sources not working

texts:
I made a simple uC (8266) based schematic that controls some peripherals. It is powered via 12v ac-dc power supply connected to the lm2596:

PCB1:

The uC has uart connector like that:

PCB1:

This is the first device made on separate pcb.

I also made a second device on another pcb - it’s an usb/uart converter to connect the uC to the computer:

PCB2:

And 3v3 power source on this converter's board:

PCB2:

Physically both devices connected via 5pins pgm/prg connector.

And here the magic starts. When I connect 12v to the uC board and usb to the usb/uart adapter and them both to each other, my computer simply reboots almost immediately. But when I disconnect 12v from the uC, and power it from the usb-attached 3v3 power source, everything is working just fine. Please help - what I missed and what is my mistake? The only thing I suspect could influence, is the connected ground planes of the 12v power source and computer's usb port. Is it related to the ground plane at all? Have no idea what could it be.

Thank you.

One more update: just did a check, thanks to comments here. Connected the ground wire of the prg/pgm connector only. So, both devices shares the ground line only. Computer rebooted.
So, basically all this schematic is irrelevant.

The question can be simplified (thanx to @Swedgin): why computer reboots when I connect USB ground to the 12v external power source ground?


texts: How to calculate the gain of a RLC tank filter?

texts:
I'm supposed to create a passive bandpass filter to select a reasonably sinusoidal 750 Hz signal from a 250 Hz square wave.

Since we have very limited choices for the inductor (0.03 H) and capacitor (0.22, 0.47 and 1 uF) in the lab, and also very limited space to put those components on, I would need a really low resistance for a small bandwidth if I were to use a series RLC circuit. So I decided to use a parallel circuit instead, which I simulated on qucs

and went on to the lab and measured the gain as a function of input frequency. And it worked, kinda of, but I don't know how to fit the data I gathered.

Also, the gain was really low, and the filtered signal needs to have an amplitude of at least 10% of the original wave. Is the parallel RLC filter not the answer?


texts: Transmission Lines:Standaing Wave Voltage Characteristic at Half Wavelength

texts:
The voltage equation for lossless transmission line that my professor has given me is :
$$V(l)=V^+ e^{j\beta l} +V^- e^{-j\beta l}$$
and he says that when singals transits by half the wavelength the characteristics seem to repeat:
but considering that $$\beta =\frac{ 2\pi}{\lambda}$$
if $$l=l+\frac{\lambda}{2},\beta(l+\frac{\lambda}{2})=\beta l+\pi$$ and
$$V(l+\frac{\lambda}{2})=V^+ e^{j\beta l}e^{j\pi} +V^- e^{-j\beta l}e^{-j\pi}=-V(l)$$
So I don't know how he can say that the characteristics repeat or maybe I'am missing something. I'm not sure.


texts:
I am looking to detect the amount of light coming from a specific direction that lands in a specific area on a PCB. In my research, I have only found ambient light sensors and never any kind of directional light sensor. I want to confirm that there is no kind of existing IC package for sensing directional light.

My idea is therefore to take an ambient light sensor and shroud it to shrink the field of view. My sensor will be on a PCB. I am thinking about 3D printing a tube in matte black and attaching it to the PCB over the ambient light sensor IC. However, I'm not sure what the most durable way to attach the shroud around the sensor would be -- I'd like something better than glue. I was wondering if there is some kind of PCB component I could include in my design so that the shroud could be soldered or screwed on.

Is there such a component as a directional light sensor?
What are good methods for fabricating a shroud for an ambient light sensor?
What are good methods for attaching the shroud around an ambient light sensor on a PCB?


texts: How to control the amplification of a Transistor?

texts:
I'm currently building a very simple overdrive/distortion pedal using a 2N5089 transistor.

I want to be able to have a potentiometer control the "drive" which I assume is the voltage amplification. Do I do this by changing the base current?

Hopefully this isn't a stupid question and I appreciate all responses and any guidance in learning more and more about electronics in this area.

Thank you in advance


texts: What does it mean for an input impedance to be "differential"?

texts:
In a specs of a data acq. device the input impedance is shown as "20 MΩ differential". Does that mean the measured impedance in diff input case? If so how can I calculate the input impedance for single input case? Here is the device:
http://www.mccdaq.com/PDFs/manuals/USB-1616HS-BNC.pdf


texts:
I have a typical NPN phototransistor.  I have it working in a common-collector configuration; see figure 2 of this app note.

Increasing Re will increase the sensitivity, but decrease the speed.  I have been studying phototransistors for a few days now, and I think that a transimpedance amplifier can give me additional sensitivity without sacrificing speed, since I won't have Re loading the emitter anymore.

However, I can't seem to find straightforward implementations.  The vast majority of app notes describe photodiodes.  Unlike a photodiode, a phototransistor needs to be biased, and the few application notes that discuss using phototransistors assume the presence of a negative biasing voltage in their transimpedance amplifiers.  I need a solution that works with a single-supply op-amp.

Would a virtual ground on the non-inverting input of the transimpedance amplifier correctly bias the phototransistor?  Usually virtual ground is half-way between VCC and GND, but I don't think it has to be.  My phototransistor saturation voltage is 0.15V; given VCC=3.3V, does that mean my virtual ground could be at ~3V?

Is there a better way to design this circuit?  I would like the output to get as close to GND as possible, because there will probably be a second-stage amplifier.

EDIT:

More details on the application.  I'm sensing light levels; low, very low, and off.  There are no problems with ambient light, so I'd rather not focus on the phototransistor aspect of this question too much.  The bandwidth of interest is around 1-10 kHz.  The common-collector almost works; I've raised Re as high as it can go while maintaining the bandwidth I want, but I'd still like Re about 2x larger which results in a signal that's too slow.


texts: Common Source JFET small signal equivalent circuit

texts:
This circuit is equivalent to small-signal common source JFET amplifier:

If you look at the input and output impedance you can see that Zin = R1 || R2 and Zout = rd || Rd || Rl. It can be seen from the small-signal model.

But shouldn't small-signal model look like this?

I just want to understand these models and maybe derivate input and output impedance myself.


texts: What are the tools to identify ICs by marking?

texts:
I have two ICs and I need to discover them. I've searched for the marking on top of them, but I didn't have success. I've tried some tools on the internet (this forum included), also nothing. I used google advanced search tools, combining packages and nothing.
Infos that i got from IC 1:
IB2 or 1B2 (it's not clear)
D0E0
On the pin 1 circle it has a "33J" engraved

Infos that i got from IC 2:
CG6865 PHI
1819 616
857
   □C


texts: CE and FCC for MCU boards/Raspberry Pi HATs/Arduino shields etc

texts:
There doesn't seem to be a great deal of information on the internet about this (and the information that there is is usually contradicted somewhere else), so I'm going to ask this here, in the hope that somebody has experience with it.

Are there exceptions from CE, or FCC compliance for boards such as HATS/Arduino shields etc... which are unintentional radiators? Most boards like this that are sold seem to not be tested, and basically, I'm asking whether this is just a case of the rules not being enforced for small quantities, or if there are genuine exceptions (such as if they count as subassemblies).


texts: How to identify this SMD device from the code on top of the component?

texts:
I'm having a problem.

I need to know what kind of smd this is.
there is RC39 written on it but i can't find anything about it on the internet.
maybe someone can help me?


texts: Handheld oscilloscope for saving waveform in memory

texts:
I am looking for an handheld oscilloscope which can save some single frozen waveforms on memory and transfer it later to a computer. The saved waveform should have a lot of points so that I can process it on the computer with FFT for spectrum.
I want it to be a handheld oscilloscope instead of a USB oscilloscope are numerous:
More lightweight, less boot time,...

I wonder why I have found none with this capability, some difficulties with this approach?


texts:
In the example below:

ldi ZL, low(2*label)
ldi ZH, high(2*label)

label:
.db "Hello world", 0
lpm

Why multiplication label with 2 is needed? I understand that program memory is word addressed, and I guess label: it self is 16bit long(!?).

Here is quoted text from author of the example:

  "If the address is not multiplied by two and label is at byte address 0x60 (word address 0x30), Z will point at the code stored there. I hope this clarified the addressing problem. Other versions are..."

Can you clarify.


texts:
We do have couple of old Valves Pharmacia IMV-8 but just a few controllers lying around in our labs. I would like to control these valves either via an Arduino or Raspberry. The manual states following protocol for external control:

I would like to buy a programmable power supply because I do not have time to dig into this topic and make myself one. But I had no success with searching the web. Probably, because I do not know the proper terminology.

Do you know some solutions/devices ? If there exist a simple amplifier/controller which just have to be soldered onto a board, that would be fine too.

To be more precice: I do need 24 V DC power supply and would like to be able to provide variable current to pin 2 (>30 mA) and 6 (1 A and 300 mA). Ideally, it is some kind of board which is programmable and can be connected to an Arduino or Pi.

I do not really know how the valve operates. I guess I have to try what happens If I provide a current of ~ 50 mA to pin 2 and 1 A to pin 6 (probably a pulse followed by a period of 300 mA). I am used to provide Voltage signals but not currents. So I do not really know how to start. The motor moves the slit from position to position (radial flow)


texts: DYI USB Hub - It is possible to just connect ports in parallel?

texts:
I want to make device what is similar to KVM switch.

I have mouse + keyboard connected to my table PC and I want to use it for my notebook as well.

I decided to make USB HUB with 2 USB input (for mouse and keyboard) and 2x 1 USB for output. Those two outputs will be switchable by switch.

My question is: Can I just connect two input USB in parallel to make HUB? Or it will not work and mouse+keyboard will not be recognized? If it will not work what do I need to make it work?


texts: What could this scammy "magic whole-house electronic powersaving surge protector box" have actually done?

texts:
My parents had good intentions, I guess, but the company that sold them this bad boy probably didn't. After blowing a fuse at their place, I noticed this box hooked up to the breaker panel. It was hooked up to a 50 amp breaker which led to the stove. I removed it shortly after I explained that there is no magic box to cut power bills, and they received a full chargeback through their credit card company when the installer of this device didn't even dispute that it was a scam. Not to mention, the way it was tied into the panel was not even close to being up to code - 2 wires into one breaker, one was stranded. They also charged just under a hundred bucks to wrap our hot water tank in bubble wrap. Sigh. The total was somewhere near $1500. I feel terrible for the folks who bought this and didn't know any better.

Anyways, that doesn't stop the curiosity. Obviously nothing useful, but what could this thing have possibly done? I think I see diodes, caps and resistors.. so I'm thinking maybe there's a transformer in that cylinder and maybe this is a power supply for the light on the box? Or maybe that's not an LED and none of this stuff does anything at all. I'm a little scared to open up the large cylinder. If you guys give me the go-ahead, I'll cut that open too. The company was called SolarTEK, and no, they don't do solar. Gotta hand it to them though, pretty decent production quality.

EDIT: Below it was suggested that this could be a power factor correction unit. Regardless of the usefulness of that at all in this context, this makes me wonder:

Would such a device have functioned, being hooked up to only one circuit in the breaker?
I saw an image while researching these capacitors that suggests on physical expansion of the capacitor, it breaks a fuse. Is that a type of surge protection? What would it take to trigger that? And if so, with this literally hooked up in-line with a stove, that couldn't possibly have protected the entire house from an actual surge, could it?


texts:
I'm spending a lot time figuring out which microcontroller I should choose for my projects.

For example, for one project I have the following requirements, in order of importance:

I2S interface (for connecting at least 2 digital microphones, 4 preferred)
At least 32kB RAM
At least 40MHz clock
Low power. Has to work for at least 24 hours on an 900mAh battery
Should come in some kind of a board that I can work with by hand
The board should be small, not much larger than a mobile phone
This is a one-off project, so cost is not a major issue

How does one go about finding a short-list of candidates that meet or exceed a given set of requirements (such as the above), and be sure that they haven't missed anything?

Currently, I'm browsing through the element-14 catalogue and opening up datasheets at random. This is a very slow process. Ideally, there would be some table where I could select what columns to display (such as RAM, clock speed, power consumption) and sort MCUs that match my criteria. Things may not be ideal, but surely people have smarter ways to browse the MCU market?


texts: Capacitor does not hold charge when switching power

texts:
I'm trying to create a power source switch using a relay. This's supposedly will be used for my Raspberry Pi. So what I want to do here is :

Create a backup power source with battery that will replace the main power if it's failed/off
Add a capacitor to holds charge, so when the relay is switching, the power will not completely cut off

Here's my schematic:

I already tried to create this, but the problem is when the main power is cut off, the output still drops and then backs up to 5V. So I've assumed the capacitor is not doing its job.

But strangely, if I cut both of the power, the output still shows 5V (and slowly going down), so this means the capacitor actually holds a charge, right? Then why when the relay switching, the power still temporary went down? Do I did this incorrectly?


texts: Why is this high amperage metal melter making an electric arc?

texts:
There is a video on youtube with a device for melting metal (video below). It's a step-down transformer that transforms 120VAC in primary coil to ~3VAC in secondary coil, therefore stepping up the current 40x.

However, I don't understand why it makes electric arc you can see in the video at time 0.10-0.14. Until today I was under impression that arcs are only formed from very high VOLTAGE, not amperage. Is this assumption wrong?

In my mind, this device should simply heat up metal on contact, without the arc.

https://www.youtube.com/watch?v=JIlZsuRc9jQ


texts: how the LIFX or Hue generate millions of colors?

texts:
I see the Philips Hue and LIFX led bulb can generate the millions of colors, I can find .

can anyone tell me how this light works to generate millions of colors, what is the yellow LED light and white LED light, are they all the RGB led lights ? is each LED individually controlled by the circuit, and use all of them to make a color combination and is each LED controlled by simply opening/closing or dimming in different levels.

Thank you


texts: Low voltage DC to High Voltage DC Circuit Explanation

texts:
This is a circuit for switching the transformer at high frequency and so that we get ac on the secondary side. A voltage multiplier circuit is connected to the secondary of the transformer which will give a high voltage dc at the output. That dc voltage is then fedback which is shown in the figure as OUTPUT FEEDBACK.
In this circuit i am not able to understand

the use of 220microFarad capacitor which is connected with the centre tap of the transformer
How is feedback circuit working, Is it a window comparator circuit?
Use of transistor, I mean the Square wave which we are getting can be directly fed to the Mosfet but why have we used transistors?

I have uploaded a photo in reference to my 3rd question. I have simply removed transistors in this and i did its simulation in proteus and is working. I am unable to understand the use of transistor in this??


texts: I want to be able to measure weight (typical range of human weight), what sensor can I use?

texts:
I've seen this force plate from Vernier and it requires another USB interface device. They have an SDK that will they allow us to communicate with the force plate.

Is there something that I can create on my own that also measures weight?
I think that I've seen a strain gauge thread on this forum.

There's this load sensor from Sparkfun (mentioned in thread) but it maxes out at 125lbs.

I essentially want to create a plate for someone to step onto and be able to measure their weight.


texts: I have virtually no understanding of how batteries work and charge, and have various questions on them

texts:
I'm doing research into portable power generators for a university class and need help understanding how charging a device works. From my research, I've found certain methods of harvesting energy can yield an output of about .5mW of electricity. If you were to try to charge a device with this output, what would happen? For examples sake, lets say we were trying to charge my phone's battery. The battery is a 3200mAh, 3.8 V Li-Ion battery, and the default charger is a 5.3V, 2A charger.

On such a device, how does the amount of wattage being inputted affect charging? Is there a minimum amount of watts needed before the device will charge at all? What do the battery and charger voltage requirements mean?


texts: Voltage follower/Buffer circuit as summing amp

texts:
Is that possible to use a voltage follower/buffer circuit as summing amp?
In history, what kind of circuit was used for summing amp before people started to use those inverting summing amp circuit?

-ref buffer circuit
http://www.learningaboutelectronics.com/Articles/Voltage-follower

Thanks for your help


texts: Problems with peripheral control of a LED on an AT91SAM7X chip

texts:
I'm using an AT91SAM7 chip on the MakingThings board for some custom work. To better understand the peripheral driver, I'm trying to directly call/control an output pin (PA12) to turn on the status LED.

main()
{
    AT91C_BASE_PIOA->PIO_PER = AT91C_PIO_PA12; //Enable Pin PA12
    AT91C_BASE_PIOA->PIO_OER = AT91C_PIO_PA12; // Enable Pin PA12 as 'peripheral manager' controlled pin
    AT91C_BASE_PIOA->PIO_PPUDR = AT91C_PIO_PA12; //Disable Pull Up resistors
    AT91C_BASE_PIOA->PIO_SODR =  AT91C_PIO_PA12; // Set pin state to 'high'
}

That code builds fine.  When I burn the firmware and test it, that does not turn on the LED on pin A 12. The peripheral controller is a bit complex, so I'm concerned I'm doing something in a wrong order, or that I am missing some other register that must be set. Does anyone have feedback or info on why that might be wrong?

(I can run other code, do other examples, run USB data, etc. It's just the simple flicking on an LED that is weird).


texts: Connecting equipment modules without cables

texts:
I develop a system with a lot of small mechatronic modules which need to be connected to the equipment base both mechanically and electrically (usually AC mains and CAN bus).  Often I need to mount and dismount these modules for debugging and replacement. I like reliable cables with circular connectors, but they take too much space, cables tend to clutter up  the work zone, and it is annoying to connect them many times in not-so-convenient places.

I am looking for electrical connectors which can self-center and reliably connect when I need to care just about mechanical connection. I even made one from teapot connectors :) But I hope there are more conventional ways to do it. What are them? What is the right term for this type of connection and what parts are usually used to do it?

Here is connector I found in the transport card validator. Unfortunately I could not find its suppliers and even specification on the Internet.


texts: Is it possible to obtain a sine wave with a 3 phase inverter?

texts:
In several pages, I have read that it is possible to obtain a sine wave (maybe with harmonics) from a three-phase inverter, with six transistors or thyristors, like this:

I have seen some techniques, like SPWM, but I am not sure about the correct working of those techniques.
I would like to know if it's possible to obtain sine waves from such inverter.
Thank you in advance.


texts: LIN diagnostic frames: Request continuation-frames

texts:
I have a question about LIN communication. To be sure my current knowledge is correct, I'll start here:

LIN 2.1 diagnostic basics:

The communication in a LIN diagnostics session uses frames with 8bytes payload, and in general looks like this:

TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
RX:  <NAD> 10  08  <D1> <D2> <D3> <D4> <D5>
RX:  <NAD> 21 <D6> <D7> <D8>  FF   FF  FF

The master sends to device <NAD> a single frame (0)  containing 3 data bytes <D1>...<D3>
The slave <NAD> replies with a first frame (1) and will send a total of 0 08 data bytes. This message holds the first data bytes <D1>...<D5>.
The slave <NAD> sends a continuation frame (2) numbered 1 and the last 3 data bytes <D6>...<D8>.

Now, simply speaking, both devices have two 8 byte buffers, one for TX and one for RX, and the data is transferred at predefined intervals.
Since the interval can be very fast, the same message can be transmitted several times, before the TX buffer is filled with new content. Vice versa, the same message might be received multiple times.  So a real communication  might look like this:

TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
RX:  <NAD> 10  08  <D1> <D2> <D3> <D4> <D5> <- slave starts response
TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF <- Master still sending
RX:  <NAD> 10  08  <D1> <D2> <D3> <D4> <D5> <- slave still sending
TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
RX:  <NAD> 10  08  <D1> <D2> <D3> <D4> <D5>
TX:  <NAD> 03 <D1> <D2> <D3>  FF   FF  FF
RX:  <NAD> 10  08  <D1> <D2> <D3> <D4> <D5>

Question:

The master knows due to the 10 08 reply that there will be a single continuation frame, but how does it request that one? It must somehow signal the slave that the first frame was processed and it can now receive the second one.


texts: mesh current discrepancy in demystified circuit analysis book

texts:
Find I1, I2, I3.

So I setup the mess equations:

$$\begin{aligned}\text{mesh1: } & -20 + 10I_1 + 4(I_1-I_3) + 8 +6(I_1-I_2) + 6 = 0  \\ \\ \text{mesh2: } & -6 + 6(I_2-I_1) + 2(I_2-I_3) + 2 + 6I_2 + 2= 0 \\ \\ \text{mesh3: } &~ 2I_3 + 6 -2 + 2(I_3-I_2) - 8 + 4(I_3-I_1)=0\end{aligned}$$

Then I simplify them to this system of equations:

$$\begin{bmatrix}20 & -6 & -4 \\ -6 & 14 & -2 \\ -4 & -2 & 8 \end{bmatrix}\begin{bmatrix}I_1 \\ I_2 \\ I_3\end{bmatrix} = \begin{bmatrix}6 \\ 2 \\ 4 \end{bmatrix}$$

then using "system-solve" button on my calculator I find that solution for 3x3 system is:

$$\begin{matrix}I_1 = 664~mA & I_2 = 567~mA & I_3 = 994~mA\end{matrix}$$

I double checked the above exercise 3 times....

Here's the part I don't get... when i simulate this circuit online I get a discrepancy on current $I_3$ see below:

Then, I look at the key in the back of the book it has a discripency on a different current (ignoring that they only save 2 significant digits).   Book key says:

$$\begin{matrix}I_1 = 660~mA & I_2 = 550~mA & I_3 = 970~mA\end{matrix}$$

So who's wrong and who's right?


texts:
So I am trying to create a calculator program in arduino using this codes.

void loop()
{
    char keypressed = myKeypad.getKey();
    if (keypressed != NO_KEY)
    {
        //Serial.print(keypressed - 48);
        Serial.print(keypressed);

        if(keypressed > 47 && keypressed < 58)
        {
              if(!mySwitch)
              {
                  num1 = (num1*10) + (keypressed - 48);
              }else{
                  num2 = (num2*10) + (keypressed - 48);
              }
         }

         if(keypressed == 61)
         {
             answer = num1 + num2;
             Serial.println(answer);
             num1 = 0;
             num2 = 0;
             mySwitch = false;
         }else if (keypressed == 43)
         {
             mySwitch = true;
         }
    }
}

This code is for adding the numbers. I do a nested loop

if(keypressed == 61)
{
    if(keypressed == 43){
        answer = num1 + num2;
        Serial.println(answer);
        num1 = 0;
        num2 = 0;
        mySwitch = false;
    }else if (keypressed == 43){
        mySwitch = true;
    }

    if(keypressed == 45){
        answer = num1 - num2;
        Serial.println(answer);
        num1 = 0;
        num2 = 0;
        mySwitch = false;
    }else if (keypressed == 45){
        mySwitch = true;
    }
}

it will only accepts the value and not compute it after pressing the "="sign
btw "61", "43", "45" is the ASCII value of "=", "+", "-"


texts:
I'm very newbie in electronics, so, I kindly asking the community to review my schematic. This is my most advanced project I ever did and I'm really unsure about particular points in my scheme and about overall design.

What I'm doing is a multi-channel DC-motor controller with external powering. The motors will be small 5v or so DC motors with current draw about few hundreds mA.

Here what about I'm unsure:

Is it correct to connect ULN2803 in parallel to achieve more max current per channel? Is it correct in my particular scheme?
Is it enough to just put capacitor in parallel to each motor to perform low-pass filtering? Or I should add extra resistors for explicit RC-filter? If resistors required, then where I should put them: to Vcc line to ULN2803's pin?
Maybe I should put RC-filter between MCU and input of Darlington pair?
Do I need extra fly-back diode or ULN2803's internal diode would be enough?
How well the "USB part"? Won't it burn my PC's port? Will it even work o_O? Do I need to put resistors in between tx-rx and rx-tx lines? Will it work fine with external power source?
I added rectifier to make polarity-agnostic board. How lame it is?
How to make over-current protection? Do I even need to do it?
Is it fine that there no resistors near J1 port (ISP programming)?
Should I pull-down (pull-up?) unused MCU's pins or it will be fine to left them in air?
How critical for USART reliability to use crystal frequency 11.0592Mhz or multiple? Will it work fine with 16Mhz?


texts: How to represent the variation of electrical resistance with frequency for ideal circuit elements?

texts:
Can anyone please help me a little and guide me through representing the variation of electrical resistance with frequency for an ideal resistor, coil and capacitor.

I will do all the work I can myself, I just need some guidance on how to start here.

SO far I only found connections between frequency and impedance on the web, so I'm really stuck, theoretically-wise.


texts: IRFZ44N with Arduino works fine on breadboard but not when directly connected with wire

texts:
I have a circuit that looks like this in the picture below.

I am getting 5V to power Arduino Nano BLE 33 from the powerboost 500 module that is connected to the 450mAh lipo battery and the wireless charger receiver. The photodiode module (veml7700 from adafruit) is being powered by the Arduino 3.3V. Also the laser is being controlled by Arduino pin D3 which is being connected to the IRFZ44N MOSFET with pull down resistor. The laser seems to have a constant current driver with working voltage from 3V to 4.5V although it is still working with 5V. I am also using Arduino Nano BLE 33 to have a Bluetooth connection to my phone to read and show the photodiode readings in real time. In order for me to get the readings, I am using the MOSFET to turn the laser on 1 sec before the photodiode reading and to turn off 1 sec after the photodiode reading.
Everything seems to work find when I test the circuit on the breadboard. However, the problem occurs when I try to put everything together by directly wiring them together.
The photodiode reading starts to fluctuate like the picture below.

There is no problem with the Bluetooth connection and the conversion of the data between the Arduino and the Android App. I know this because the app correctly converts the transmitted data from the Arduino. The problem is that the photodiode reading itself isn't consistent when directly connected with wires instead of using the breadboard.
I tried to troubleshoot and found out that the MOSFET is not completely shutting down fast enough but instead have a little voltage carrying over to the next cycle like the picture below.

To trouble shoot, I replaced the laser with LED and tested the MOSFET. It is shutting down and on perfectly like below.

I know that it is not the battery issue since when I was testing with breadboard, I also used the same battery to power all the circuit. Using the breadboard, it was working perfectly fine, so fluctuation in photodiode reading. I also checked every wiring to make sure that the grounds are all connected. They all seem to have a good connection.
I desperately need some help to figure out why my circuit doesn't work when directly wired instead of using the breadboard.


texts: Multimeter can't measure current. Maybe broken?

texts:
So basically when I put red jack to 10A mode it shows amperage fine, but when I switch to other, it shows 00.0 eveywhere, even when I set to micro amperage it doesn't react to my tongue and skin. It shows Voltage and Resistance fine. The only problem is that it doean't react with smaller currents. Maybe the reason is that I've tried to measure 0.5A in 200mA mode?

Edit: Never mind, the fuse is actually destroyed.


texts: Why can't I read the ATmega328P from an Arduino board using USBasp?

texts:
I have been using a USBasp board and AVRDUDE to successfully program ATtiny13 chips. I thought I'd have a look at the chip from my Arduino (ATmega328P), but AVRDUDE can't seem to read the chip.

$ ./avrdude -p m328p -c usbasp

avrdude.exe: warning: cannot set sck period. please check for usbasp firmware update.
avrdude.exe: error: programm enable: target doesn't answer. 1
avrdude.exe: initialization failed, rc=-1
             Double check connections and try again, or use -F to override
             this check.

avrdude.exe done.  Thank you.

I have checked the connections on the breadboard several times (I took the chip off the Uno and connected the pinout of the USBasp to the chip directly). Does the ATmega328P need an external oscillator to be programmed (there is one on the USBasp board)?


texts: Oscilloscope ground-probe causing test circuit to malfunction

texts:
Today I was trying to measure the rectified SMPS incoming power supply ( 315VDC) using a tektronix TDS 3932C oscilloscope with P6139A  probe. Every time the ground-probe touches the ground of the supply, the power supply rectifier diode is getting damaged. I assumed it may be related to earth fault current, but both equipment supplies are properly earthed.

I need some advice here.

Eqpt :Tektronix TDS 3932C Digital Phosphor Oscilloscope 300 MHz
Probe used: P6139A , 500MHz, 8 pF ,10 MOhms, 10x

Edited I want to check the pwm controller IC O/p waveform with the oscilloscope, the Vcc of the IC itself is tapped from the rectifier supply, and I am unable to use the oscilloscope.


texts: I'm trying to understand the above circuit . iDE- is a ceramic sensing element and can be thought of as resistance with voltage across it , and this circuit is to measure the current through the IDE , what is the function of the Opamp in the above circuit . The output is connected to an ADC pin of a microcontroller . Is the opamp acting as a voltage buffer ?


texts: Safe to ground feedback loop of voltage follower

texts:
I have a simple voltage follower with an AD822 Op amp feeding its output to VIN of an AD637

The AD822 is setup standard like so:

I want to temporarily ground the feedback loop of the AD822 to inject a failure to keep the incoming signal low. Is this safe? I assume the high impedance of the Op amp will protect it, but would I need a current limiting resistor?


texts:
If I have, for example, 4-8 (or more) inputs that I need to AND together (or even NAND or OR) should I look for larger input devices like the 7430 NAND or is common practice to daisy chain multiple quad 2-inputs together?

I'm reading the ZX Spectrum ULA book and a lot of the circuits seem to have up to 8 inputs going through to one OR/NOR/AND/NAND.

I didn't know if those schematic symbols were just shortcuts to represent multiple IC's or if it was/is common to use the higher input devices.

Hope that makes sense.

Thanks


texts: Explaining the need for two transistors in Not Gate

texts:
I was reading:

http://www.cs.bu.edu/~best/courses/modules/Transistors2Gates/

To teach myself transistor logic, but I have some questions on what I believe are unnecessary strucutres (most likely since I don't understand their physical need).

In the construction of the not gate, the site gives a combination of our input being split and connected to a $N$ transistor and $N^{-1}$ transistor such that the sink of $N^{-1}$ is the sourceo f $N$ and the output Z flows from between the two transistors

(The book didn't give a notation for specifying the normal and complementary transistors so I made my own, the behavior of N is if the input is 1, then it doesn't let the current flow,and $N^{-1}$ is complementary behavior)

Now I'm curious as to why we can't just have a single $N^{-1}$ transistor, with X as the input, and we take its sink to be the output. The sink will only have current flowing if X doesn't have charge, other wise it won't have current flowing if X does have charge.

Thats exactly the behavior of the not gate, so I guess the question reduces to: physically why do we need two transistors there?


texts:
I'm working on plugin for simulation software (digital IC only).
For example there is 8 bit bus.
User wants to read it's value. On plugin side I check each pin's state. It can be 1, 0 or undefined. At the moment if at least one bit is floating, I return nil as bus value. Is it right at all? May be better return value replacing floating bits with random [1-0] and warn user in log about it?


texts: How do I use multiple GY-521, I2C sensor with Arduino?

texts:
I'm working on an Arduino robotics project that requires I find the position of 12 different angles (I'm making a walking scale model of the Star Wars AT-AT and need to measure the angle of three different parts of the four legs). I'm currently going to use GY-521 Gyroscope sensor, however, I need 12 (3 angles, 4 legs) and each sensor has the same I2C address. Any possible solution?

My knowledge of Arduino is moderate; knowledge of programming is basic/moderate; my knowledge of electronics is moderate/advanced.

Would you recommend using something else to find the position of the leg?
ALL advice is welcome!!!


texts:
On the wiki page of 'Duty Cycle' there is a nice animation that shows the frequency spectrum of PWM wave as its duty cycle is modulated from 0 to 100%.

The animation shows the 'spectral lines' as well as the 'envelope' of the spectrum.

What I understand is that the 'spectral lines' are the individual frequency components starting from its DC value, and 1st 2nd 3rd.. harmonic components.

What I don't understand is the meaning of 'envelope'? What does that signify practically? are there infinitely many sub-harmonic components
of the waveform whose limiting values gives the 'envelope' of the spectrum or is it just the mathematical function that join together all the harmonic components?


texts: Can an operational amplifier circuit be made entirely out of diode Nand and Nor gates?

texts: I'm not sure whether this question has been asked before, but in researching my question, I came across this user's post (at If-else decision structure using op amps or any other non-programmable electronic device), which appears to ask my question in reverse. This user seems to be asking (effectively) whether OP Amp circuitry can be constructed in such a way as to mimic or "emulate" logical operations (or by extension, logic gates). My question, which is precisely the reverse of that, is can a circuit, consisting entirely of particular combinations of NAND and NOR diode logic gates, be constructed to function like an Operational Amplifier? (I recently asked an electrical engineer that question, and his brief answer was "no". But he never explained why he believed that it could not be done. If it cannot be done, there should be a rational reason why that is the case.) I suppose that an equivalent alternative way of phrasing my question might be, can there exist an algorithm for simulating all of the operations of an Operational Amplifier? --John


texts: Fuse on Primary Side of Transformer keeps blowing

texts:
I have a HVAC which is having a 24V 40VAC transformer. I might have shorted the output of the transformer while working on the wires.

I noticed that the fuses on the input side of transformer blew off and I replaced them with time delay 2A fuses. I unloaded the output of transformer (open circuit) to test if transformer is providing the right volts. Here the fuses blew off again.

Is it because the transformer is bad or I am using wrong fuses here ?

Transformer: Input: 240V
Output: 24V 40VAC


texts: AD5933 Feedback and Calibration Resistance

texts:
I'm making an AD5933-based circuit where I'm measuring the change of impedance. Based on the application note on how to calibrate the device for different impedance ranges, I see the formula is the following:

Since I am only interested in the change of capacitance (that is my unknown impedance), would it be possible to replace RFB with a capacitor? If so, what would the formula be? How do they arrive at the formula for RFB? I see in the circuit diagram its just a feedback placed after the unknown impedance. So in principle it should be possible to use a capacitor, right?
And would it also be possible to replace RCAL with a capacitor? I know the datasheet mentions "Do Not Calibrate the System with a Complex Impedance", so perhaps RCAL has to remain?


texts: Triggering a capacitive sensor electronically?

texts:
I'm working on a little project I call my "Green Box". Basically, I'm trying to drop my electric usage as low as possible, without losing the convenience of my gadgetry.

So far, I'm incorporating a passive IR sensor for motion detection, an ambient light sensor, and using [hopefully] a small SNMP subset to an ethernet shield to determine the state of activity. Based on these factors, I want to turn on/off various devices (PWM for fans speed of laptop cooler, IR to power on/off a few components, wireless X-10 for controlling lights), etc. I'll admit, I'm lazy; I could just do all of this myself, but with 6 kids running around, it's easy to forget to hit a power switch (let alone 5 or 6).

I have 2 Samsung monitors which have capacitive touch controls on the front. I would like to trigger these with the Arduino in the box to turn the monitors on/off, without having to rip them apart and hack them. I'm a perpetual upgrader, and I'd like to sell them in "like new" condition when I decide to.

So, from googling, I've found a few people mention that I could put a small metal plate over the sensor, and use a transistor to ground that plate to trigger the touch. I know nothing but theory of how capacitive touch works so:

This seems plausible to me; is it?

If so, can it be ANY gound (the one from the Arduino), or does it have to be the ground from the monitor?

Based on answers from the previous questions; could I run a single lead to a PNP transistors base and collector, and connect the emitter to the plate? Would this work?


texts: PIC24f16KL402 skipping values at serial port

texts:
I am trying to write the values of a counter on the serial interface, just to test the interface.
The problem is that only every second value (2,4,6,8,...) is received by the desktop. I use port PORTA to verify the values of the counter. A trace of the port shows that the odd values of the counter are present on the port only for a much shorter time, as if it does not have to wait until the value has been written through the relatively slow serial interface (9600 baud). It seems that every second value is never written into the serial port.

If I uncomment the second call of UART1PutChar(a); (last statement in the code below) it all works fine. I receive all the values as expected (1,2,3,4,...), but I cannot expain this behaviour.

void UART1Init(int bautrate)
{
   U1BRG = bautrate;
   U1MODE   =   0x8000;
   U1STA    =   0x8400;
   IFS0bits.U1RXIF = 0;
}

void UART1PutChar(char Ch)
{
   while(U1STAbits.UTXBF == 1);
   U1TXREG = Ch;
}

int16_t main(void)
{

    UART1Init(51);

    TRISA = TRISA & 0xFF00;
    PORTA = 0;
    unsigned char a = 0;
    int i;
    while(1)
    {
        a = a+1;
        PORTA = a;
        UART1PutChar(a);
        //UART1PutChar(a);
    }
}

Setup:

PIC24f16KL402
Compiler C30
MPLAB X 1.60 with PICKIT 3


texts: BQ24650 or BQ24620 for LiFePO battery charger | Solar powered + Grid powered

texts:
I am designing a Battery Charge controller for our 12V LiFePo battery.

Power input is:

a. Solar Panel 80W @ 12V (Vopencircuit=21.33V, Vmaxpower=17.78V) OR

b. 18VDC grid power.

Either one power input will be selected at time of deployment, so PCB should be able to handle both cases.

Question: Which of the following IC is better for the application, BQ24650 or BQ24620? What is the difference between these ICs?

Battery specs: Charge Voltage=14.3V, 4 cell Lithium Iron Phosphate, Vout=12V

This is my first time design a Solar panel powered circuit. Thank you.


texts: Looking to build signal level converter to reduce 20V input to 3.3v out. Am I on the right track?

texts:
I'm working on a small pet project with my RaspberryPi and I'm looking hook it up to some sensors.  The output from the sensors is normally at 0v but when the sensor is triggered, goes high to 20v. The RaspberryPi's gpio ports will only accept a maximum voltage of 3.3v, so I've been researching how best to drop the input voltage from 20v to 3.3v, so it won't fry my Pi's gpio ports.  The Pi doesn't need to send anything back, it's strictly one-way into the Pi, and the line will only go to 20v when the sensor is triggered.

In my research, I read about a circuit comprising of an LM317 Variable Regulator, and 2 resistors, which could give me the 20v to 3.3v that I need.  However, I'm worried about the kind of heat that could be given off with such a large difference in voltage.

I've tried to be as clear as possible, and have also included a handy dandy schematic of what I mean.

simulate this circuit – Schematic created using CircuitLab

To add to things, I'm likely to be adding more 20v connections to other io ports on the Pi, probably up to 15, so I'm also considering what the combined heat could be like...

Am I on the right track, and is the heat just something that I'm going to have to work with? Or is there a better solution out there?


texts: Correctly Using ACS712 hooked to a microcontroller

texts:
I am making a project that involves AC current measurement from the Mains. I have done a bit of research and have found that the ACS712 can do this.

I would like to know the correct way of using this module so that it outputs analog data that my microcontroller can read(I would like to get the total WATTS) .

I will use THIS. I am assuming that incoming current will go to one of the screws, and the wire connected to the load , to the other one(correct me if i am wrong)

I read somewhere that capacitors are needed. Please tell me how, and why.
Also tell me if the ground pin needs to be connected from the ground of the mains


texts: Using a watchdog in low power application?

texts:
Most low-power applications operate in burst mode, where the system is asleep most of the time.
I don't understand how to use a watchdog (WD) in those kinds of systems.
The perfect scenario would be to wake up periodically to reset my MCU's internal WD.
The problem: internal WDs are too energy expensive (usually more than 1uA) to use while sleeping. (Assuming a CR2032 coin cell battery as a power source).
What are the strategies to use a WD in a low power system?
Use a specialized IC?
Enable WD at wakeup?


texts: If someone catches an overhead railway power line while standing on top of a train, why wouldn't others in the train be electrocuted also?

texts:
I recently came upon a video where a man catches a 25kV power line on top of a train.

BEWARE!!! Video is not safe for the weak hearted.
https://www.youtube.com/watch?v=7Vt9OLL2bkQ

Why didn't others on the train get electrocuted too? I understand that due to effect of Faraday cage everyone completely inside the train would be unharmed.
But in the video there are several people at the doors holding the door handle with their feet on the platform. Shouldn't they get the shock too?


texts: Can you explain the 3 terminals that PTC thermistors have

texts:
Okay, so I found from Amazon a cheap PTC thermistor with a fan, just search "Zerodis PTC" and you find it from there. I see it has 3 terminals, also other PTC elements do. Since it's a semiconductor component I'm assuming some gate-drain-source type of stuff of FETs, with the middle terminal voltage basically setting up the operating point. Am I right or wrong? It's been a long while since I studied any electronics so if you can explain from basics what those 3 terminals roles actually are, since it ought to be a resistor (2 terminals) with positive thermal coefficient of resistance. So, between which terminals is it actually a resistor, and how do I (if anyhow) have to setup the "operating point".

Though, I've also seen some other similar 3 terminal thermistors and many seem to have the two outer terminals shunted to each other. Is that how I should indeed operate thermistors and simply apply voltage from the middle to two outsides, and why?


texts:
I have to calculate the voltage across R5 using the voltage divider formula but the problem is the answer is V5=2.23V (Here V5 is the voltage across R5) but according to my solution,

Solution:
R234567=1.80Ω
On Applying Voltage Divider Formula on R234567,
(Other resistor in series with R234567 is R1)
V234567=6.428V

So this voltage will be same across R2345 and R7. Since these two resistors are in series with one another we can apply voltage divider formula on R2345 to get the voltage across R5.
(R2345=1.528Ω when it's solved)
On Applying Voltage Divider Formula on R2345 we get,
V2345=2.16V
Also V5=V2345
Therefore, V5=2.16VBut according the the given answer V5=2.23V.I want to know that the answer given with the question is correct or not?


texts: Switching a current with an NPN transistor and a P-MOSFET

texts:
Just learning about transistors and I'm trying to clearly understand how to apply them for basic switching, in terms of the two standard cases, i.e., Active HIGH behavior and Active LOW behavior. For the Active LOW case, I am still having some trouble.

Assume a simple circuit where I want to switch an arbitrary 1-Amp current based on the status of a Digital signal, and I want Active LOW behavior (i.e., current should flow when digital signal LOW).

I'd be interested in brief feedback in terms of whether my circuit drawn below would accomplish the above, or if it can be improved/simplified further.

Notes: Q1 is an NPN transistor, and M1 is a P-MOSFET. And I chose a 10K value resistor for R2 because fast switching is not critical, but I'd also welcome opinions on that.

EDIT: Below circuits are 1st revision based on @ThePhoton's suggestions.

Method A:

Method B:

(Below is my original, erroneous method prior to 1st revision:)


texts:
I want to use an ISERDESE2 to deserialize a bitstream from an ADC, but the clock of the ADC that samples the bits is discontinuous, it remains at '0' between two words sent.
Is this a problem if a try to use this clock as the CLK entry of the ISERDESE2?


texts: Two-way voltage limiting circuit to protect microcontroller

texts:
I am making a device with a micro controller that has a single exposed pin that needs to be able to function as either an input or an output based on the software. When in OUTPUT mode, there has to be at least 1kΩ impedance so it can't get shorted. When in input mode, I have to limit the incoming voltage. The external voltage could be ±10 V but the micro controller can only handle 0 - 5 V. This port will carry a digital signal so it does not need to care about the analog value. It just needs to transmit HIGH and LOW states effectively (around 0 V and 5 V).
My current solution looks like this:

simulate this circuit – Schematic created using CircuitLab
It works perfectly in OUTPUT mode, and it is almost perfect in INPUT mode, as long as the input is capable of sinking current. But, if I leave the input floating, the micro controller's side is pulled HIGH (I want it to be LOW by default).
My first thought was to add a pulldown resistor on the input, but it then works as a voltage divider in OUTPUT mode, reducing the voltage. If I put a small enough pulldown resistor to counteract the pullup force on the microcontroller side, then the output is reduced enough to no longer register as "HIGH".
Is there any relatively simple way I can fix this problem? Or is there a better type of circuit to use for this purpose? Maybe something based on diodes would be simpler?
Thanks for your help!


texts: I will be needing a 1.25V PWM input into an LED driver (AP8802) and will have to interface it with a 5v PWM output from a micro-controller (ATMEGA328). Would a simple potential divider do the job, or is there a better option?


texts: Measured voltage and current different from the calculated value

texts:
I am learning a simple LED and resistor circuit. I have the following components:

One 5mm blue LED
5V USB power source

From what I've learned so far, I am using the following forward voltage 3V and 20mA of the blue LED. Therefore, the R = (5-3)/0.02 = 100ohm. I think this is the correct calculation. I am also able to put them all together and light up the LED without issue.
However when I use the multimeter to verify my calculation, both current and the voltage reading are completely different from my calculation. From the multimeter reading, here is the schematic and the measurements.

simulate this circuit – Schematic created using CircuitLab
Can someone point me out what have I done wrong and point me to the right way?


texts: Replacing an AC drive in my mill and the use of a magnetic contactor in the power supply line

texts:
I have a small mill in my shop that I converted from single phase 110V 1hp motor to a 220V 3phase 2hp motor using a Teco Jnev 202. When I did that about 10 years ago I just wired it off a 30 A breaker and used a control box that had an on/off, fwd/rev and a shutoff switch. That drive failed last month and I bought a Fuji FRN0010C2S-7U to replace it.
When I install this new drive I am adding a braking resistor and I also want to ensure I wire it in correctly. I am trying to decide if I need to use a magnetic contactor along with a molded case circuit breaker in place of just using a 30 A breaker to supply power. I am coming into the drive with 220V single phase. I've read that in some cases a mag contactor is not needed, so I am looking for recommendations that explain what the best way to correctly wire this drive's power supply.


texts: Dual slope converter vs. delta-sigma converter?

texts: I'm curious as to why dual-slope analog to digital converters are used in most digital voltmeters, like one of these when a delta-sigma converter like one of these easily exceeds the specifications of any of the other dual-slope converters sold by Microchip, and in fact many other suppliers, especially given the low price point of the chip (about $4 in low quantities.) Is there a reason I am missing?


texts:
I was listening to a local FM station from my smartphone using a headset.

While I was surfing over the available bands I saw that few FM stations can broadcast the name of the song/music details (song name, movie, release year) while playing.

While a few stations broadcast their FM brand name using the same.

What features or signal manipulators are they using? Since frequency modulation is for wide or narrow band signals, do they use any special keying methods? If they can broadcast along with FM, how is it done for each song?


texts: Differential Voltage Range vs. Clipping Level

texts:
The data sheet for the AD835 analog multiplier mentions that its inputs have a "Differential Voltage Range" of ±1V and a "Differential Clipping Level" of at least ±1.2V (typ. ±1.4V).

What is the difference in meaning between the two figures? Is ±1V simply the "design" input range, but the chip is actually guaranteed to handle a bit more without distortion?

In my actual circuit, two of the chips seem to indeed perform fine (i.e. no clipping/distortion on the output) above ±1V (actually, up to about ±1.6V), but of course I'd rather not take a bet on that…


texts: What is the change in voltage across an inductor, or change in current through a capacitor?

texts:
The formula for voltage on an inductor is stated as

v = L (inductance) x (di / dt)

and current for a capacitor is

i = C (capacitance) x (dv / dt)

But I don't understand what the (dv/dt) part of this equation should be.

For example

simulate this circuit – Schematic created using CircuitLab

In this circuit, if I wanted to know the current on the capacitor at some point in time, how would this be calculated. Would we count the "change in voltage" as going from 0v to the supply voltage in one unit of time? Or would it happen more slowly? How do we know how slowly?

What if there was a switch in this circuit, so there was 0v and then the voltage changed to 1v?


texts:
I am a chemical engineering student. I need to control a valve and pump system using an Arduino Uno.

I was testing out my 12V DC solenoid valve with a variable DC power supply, and noticed that the solenoid valve would not open, I hear a clicking noise though.

In another question posted on this forum, a user stated that a minimum pressure is required to open the valve. Pressure should not be an issue according to the data sheet provided here:

https://www.mantech.co.za/datasheets/products/91741-R0.pdf

Thank you in advance.

Edit: The question is why isn't the solenoid valve opening when the required voltage and current is applied across the terminals?

Edit2: Thank you Drew! Despite it not being on the data sheet it does require an operating pressure higher than I was delivering. Simply applying the pressure using my mouth opened the valve.


texts: Ways to build a speedometer for a bike or skateboard

texts:
I'm trying to think of different ways to build a device that will allow me to mount it to any moving object so that the moving object will be able to discern it's speed (It DOES NOT have to be very accurate)

Requirements:

I just need to know a few levels of speed: not moving, slow, medium, fast, etc.
I want to be able to mount it on a bike, maybe a scooter, maybe a skateboard, etc.
Cheap - I want to be able to make this thing for

Bike computers work with a magnet mounted on a wheel and a hall effect sensor to pick up each rotation.

A velocity can be calculated by discerning the distance traveled given time. (the bike computer method is great, but it doesn't allow me to use it on a skateboard, for example)

Are there optical sensors that can be pointed at the ground?

An infrared distance sensor won't work (right?) because it is always the same distance from the ground.

What about a sound sensor? Can it measure some sort of doppler shift?

GPS is too expensive

I potentially can use an accelerometer. How would I know the difference between a stand still vs. no acceleration.


texts:
I created a circuit using a keypad, a servo and a few LED's. This was connected to my Arduino Uno. Now I tried putting everything onto a single PCB and thus building my own custom "Arduino" into it.

I made the mistake of etching and assembling the new circuit without testing it on a breadboard.

The problem will most probably be within the "custom arduino" part of the sketch.

Can you please take a look and help me out (Click for full-size):

I tested the power source and found it at 5.47V and the voltage on the output side of the 5V-regulator is ~4V.

Edit

I disconnected the reset pin from anything, but the board still reacts the same. I tried bypassing the voltage regulator, but it did not do anything.

The red LED is supposed to shine and the servo must move to a certain position upon startup, but it does not happen - the servo does get power and keeps it reacts in two ways:

1) When power goes through regulator, it jumps, step by step to the one side
2) when I skip the regulator, it goes straight all the way to the opposite side.

Is there any other thing I might have forgotten? It would be very difficult to add those capacitors.


texts: How to properly model an linear power supply with LDO in LTspice?

texts:
I've build the following linear power supply:

Before building it I tried to model it in LTspice. I couldn't find an LTspice model of L4941BV LDO (datasheet [PDF]) or a suitable replacement. Thus I used the following "naive" model:

R1, R2, L1 and L2 are measured resistance and inductance of a transformer windings. V1 is 50Hz, amplitude: 310 V. Here is Vout:

My idea was following. Let's say that all extra voltage turns into heat, and also account for ~10 mA quiescent current  of LDO itself. In other words assume that this circuit's output power is ~0.95W.
Naturally this model turns out to be inadequate. It predicts PF 0.442 and efficiency 32%. The real device can produce up to 217 mA before a noticeable ripple (60 mV) will be observed. Under these circumstances it's measured PF is 0.925, consumed power - 2.75 W and efficiency - about 39.5%.
I tried to play with values used in the model but didn't come even close to observed PF and efficiency. Thus it looks like a less naive model is required.
The problem is I have no clue how to make an accurate model of an LDO. Could you please explain how it can be done or at least suggest some literature on the subject.


texts:
I have a circuit which drives capacitve loads (they vary from around 800pf to 1600pf) and because of circumanstances like air polution and dust it can come to electrical contact to the surroundings or even short circuits.

The circuit uses a MP104 to drive the load and when something happens, this is the part which is destroyed.

The output is driving 150V with a 50V/µs slew rate for falling and rising and holds the voltage for about 1µs. Between 2 Pulses there is a minimum of 1 µs pause. The Input of the amplifier is controlled by a DAC to control slew rate and so on.

Where +VS is 150V and -VS the 0V potential for +VS.

I am searching for a circuit protection.

Conventional fuses are too slow for the driver.
Currently I am exploring OCP possibilities like using a LMG3411 to control +VS of the driver. It can even be a replacement for the MP104.

I can't tell the exact circumstances where the driver breaks because I just get feedback when it's too late. Also I am able to destroy the driver by making a short as load but wasn't able to determine an exact current where it breaks.


texts: Locating and Adding Arduino Due Schematic/Footprint to Altium

texts:
I am working on the design of a PCB that is being used to allow for quick/modular swapping of sensors with specific types of connectors to various pins on an Arduino Due board. I have looked but I am having trouble finding a schematic symbol with all of the connections that I can use to create the schematic for the PCB. I would also need a footprint for the Arduino for the layout after. I have tried looking for info about this straight from the Altium website but it is horrible from what I can tell.
I have designed some PCBs in the past but never one that incorporates a microcontroller like this. Because of this, I am also wondering what is the best/recommended way to fully connect the Arduino to the PCB itself?
Thanks in advance!


texts: Arduino serial communication protocol design

texts:
I make a drum sequencer interface for electronic music.

It uses an arduino mega as it's microprocessor, and currently it interfaces to a Processing program that I wrote for serial communication. From there, OSC messages are sent out to a Max/MSP program that my collaborating partner wrote to create a midi data stream.

So:

My physical interface -> Arduino Mega -> serial I/O -> Processing -> OSC -> Max/MSP -> Midi ( -> music app)

I chose this path partly out of not being clever enough to remove any of the steps yet, but also to accommodate being able to update the physical interface the way we want, being able to make the physical interface multi-purpose (multiple modes for the faders, knobs, and voice select buttons), and be able to ensure mission critical timing and rhythm modification (aka "swing").

My serial messages are set up like this:

PL,1;        // transport control: play
PL,0;        // transport control: stop
SW,30;       // swing value 30
TM,130;      // tempo value 130
SD,1,8,04,0; // Step sequencer data, pattern 1, voice 8 (of 8), step 04 (of 16), off
MU,8,1;      // Mute, voice 8 (of 8), on
SO,4,0;      // Solo, voice 4 (of 8), off
VL,3,127;    // Velocity, voice 3 (of 8), value 127
CC,1,127;    // Midi CC, controller 1, value 127
NN,1,36;     // Note number, voice 1 (of 8), value 36 (usually a kick drum)

So, you can see that based on the number of commas per semicolon, I can determine how to parse the serial data from the arduino in the processing program.  From Processing, these kinds of messages are transformed into OSC like this:

/beatseqr/play 1
/beatseqr/play 0
/beatseqr/swing 30
/beatseqr/tempo 130
/beatseqr/matrix/1/8/04 0
/beatseqr/mute/8 1
/beatseqr/solo/4 0
/beatseqr/velocity/3 127
/beatseqr/midicc/1 127
/beatseqr/midinn/1 36

And it all works ok, but it feels inefficient. Do I really need the processing app in the middle?

Now, I had tried to chop Processing and the OSC parts out of the equation, but I'm missing some knowledge in regard to serial data protocol design.

I'm aware that there is a udpreceive object in Max. And that works ok I guess? Maybe I'm using it wrong.

At one point I had switched all of my arduino code to not send newlines at the end of every serial message since that didn't mean anything special to Max's udpreceive object. In fact, if I recall correctly, it would only accept the first message up to the first newline and then it would stop processing data. So to get around that, I took out all the newline characters and then it would spew into max/msp continuously.

Then the next problem with this method is that the udpreceive object only accepts one character at a time. So I was trying to use a js javascript object to concatenate the incoming characters, and then parse them on the semicolons and commas.  The problem I ran into there was that it was unpredictable and unstable. Characters would drop out and the message would be unprocessable. So it's really making me wonder if I should change my serial data protocol to something more robust? Or if I'm just doing it wrong entirely?

Should I just scrap it all and start over from scratch using a firmata firmware? I've seen some tutorials for using the firmata with Max/MSP, and I guess I could take a fresh look at what the code on the box is doing and if it needs to do it at all.  Can the firmata accept string data on a pin to send to the on-board serial LCD? if I can control the LCD from max/msp, that might work out ok.

Got any advice?


texts: LTspice: Vary a resistor's value over time

texts: I want to simulate the load regulation of a power-supply.  I'm sure I remember being able to vary the value of a resistor over the course of a simulation in LTspice, but I can't remember how. Anyone?


texts: SystemVerilog FIFO problem with 6 bits in and 4 bits out

texts:
I was trying to induce the following functionality into SystemVerilog but i cant think of any efficient ways:

So above is a picture of two 6-bit input packets that come one after the other (triggered by a clock edge). Out of that i need to deliver three 4-bit output packets.

These output packets need to be sent next after the other. So from the first input packet i need to send out 4-bit output packet, store the last 2 bits of the packet and concatenate it with the first 2 bits from the next package. Finally, the last 4-bits are then sent as one 4-bit packet.

N.B: This is an example. The Input packets number can go upto like 1000 and its width can change which would mean the 'residue' or left out bits would change.

So please if anyone can guide me how to approach this problem, i'll be really grateful.

Edit: I think i've confused everyone. The problem is quite complex so i didn't include everything for the sake of simplicity. Here it goes:

The module i'm trying to make has a higher input parallelism as compared to the output which means that the data going inside the module is greater than data coming out. This would mean an accumulation of more data inside the module with every transaction.

The input packets would be arriving continuously. Each input packets lasts one clock cycle. The requirement is to push output packets (smaller than input packets) continuously aswell. The output packet should also last one clock cycle. The N.B sentence i've added is related to parameterization in which i can choose an arbitrary number of input and output parallelism. This is just to inform you the 6-bit input and 4-bit output packets are just an illustration. It could clearly be 16 bits input and 10-bit output.

This would clearly be done through a state machine but i don't know how i can concatenate the bits from the previous messages with the incoming messages and maintain a continuous flow of output packets with each clock cycle. Hopefully this clears everything.


texts: microSD Class 4 card in SPI mode returns 0x000000021F after `CMD8`

texts:
I am trying to read an microSD card through an unbranded SD slot and a Basys3 FPGA. The microSD card, Kingston microSD HC 8GB Class 4, is used via an SD card adapter, also Kingston.

I am having trouble with getting past CMD8 of the initialization process. After I sent CMD0 it responded with 0x01 which is normal. After CMD0 I sent the CMD8 command; it responded with 0x000000021F. I wasn't able to find anything related to this code in any documentation.

To test, I tried using a SanDisk Ultra SDHC 32GB Class 10 with the same code. It successfully initialized.

Other things I have tried:

Sending Dummy Clocks before and after command with CS HIGH .
Always / Not Always Sending SCLK.

Please help.

Waveforms

The first one shows all of the initialization process. SD_CD is Card Detect (Active Low) and SD_WP is Write Protect (Active Low). SD_CLK is running at 390 kHz, 256 times slower than _cpuClock. Please note that the SD_MISO, SD_CD, SD_WP and _cpuClock are all simulated manually (i.e. doesn't receive any signal from the SD module). After card is detected, 1 millisecond is waited, followed by 74 SD_CLK's.

The second image is a zoom in of CMD0 and its response.

The third image is a zoom in of CMD8 and its response.

The final image is a zoom in of CMD55 and its response.

Update 1 (Prior to @Annoymous Answer) I managed to get my hands on a couple more cards. After testing it seems that only SanDisk Class 10 SDHC (both SD and microSD) returns an initialization finished state. The Kingston Class 4 SDHC SD returns a timeout after CMD0 while the Kingston Class 4 SDHC microSD returns a 0x000000021F. Changing the adapter made no difference in all cases. In the image below, the successful ones are in green and the unsuccessful ones are in red.

Update 2 (Response to @Annoymous Answer) After changing MOSI from posedge to negedge, the Kingston Class 4 SD card seems to initialized (which was previously timeouted). However, the Kingston Class 4 microSD card still respondsed with 0x000000021F.


texts: What is the proper placement of VCC and GND copper pours in 4-layer PCB?

texts:
This is my first PCB design and I'm struggling with proper copper pour usage.

I would like to copper pour VCC and GND.

From what I understand, a copper pour will net multilayer plated through holes automatically.  When properly done, it is helpful for most boards.
(I just love the fact that I can connect VCC and GND without traces)

Please help me understand the best placement of VCC and GND copper pours in 4-layer PCB.

I think, Top (GND), layer2 (VCC), layer3 (GND), layer4 (GND)?

Added Info: All components on top layer, 5MHz using SPI w/ Mode0, board is large (35cm X 35cm), 4 layers.


texts: Encode and decode SPDT switch over single wire

texts:
I'm trying to devise a way to connect a device to a SPDT switch using only one wire. Specifically, I want to connect a wall switch to some kind of smart home thingy, and I only have a single switching wire and a neutral lead at the site of the switch.
One obvious way of encoding this would be to have one side of the switch connect via a resistor, and the other one directly. The other side would then see either no resistance, some kind of resistance I get to pick, and infinite resistance.

simulate this circuit – Schematic created using CircuitLab
Basically, what to put in the box?
My limited knowledge suggests that I am going to at least need two transistors to pull the wires down to ground. I could then fiddle around with resistors in such a way that when R1 is connected to the box, one of them turns on, and when it's directly connected to ground, the other transistor turns on. But: how to get the first transistor to switch off in this case?


texts:
I'm working on an IR contact-less thermometer. I am using Diana Friedman's paper as a general guide. I'm planning on using a circuit similar to the one presented in figure 10.

I'm planning on using the SFH 203 FA photodiode which senses in the near infrared range and has a fairly small half angle. It also has a built-in light filter.

I'm expecting very small leakage currents (on the order of nA's) that I'll have to measure. In Diana's design, she's using the OPA380 amplifier which is marketed as a "transimpedance amplifier" ideally suited for this type of application. Unfortunately, this is only sold in SMD packages and what I'd really like is a through-hole component.

I'm considering using the TC7650 chopper amplifier instead. It has better current input bias and voltage input offset characteristics than the OPA380, but also has a significantly smaller gain-bandwidth product (2MHz vs. 90MHz).

I expect this means that my maximum sampling frequency will be 1/45 that of the original circuit, but I'm not sure how to calculate the gain for the circuit so I have no idea if this is an acceptable sacrifice for my uses.

How do I calculate the gain of the circuit in figure 10, or more directly the maximum sampling rate for the same circuit?
Are there other parameters about the amplifiers I need to take into consideration? As far as I can tell I've mentioned the 3 big ones already.


texts: Led Ballast using Flyback Converter Topology

texts:
I have a question regarding flyback converter control.
I am currently trying to create a LED ballast using flyback converter topology, however, I am unable to produce the voltage 10V and current 1A that I would like to get. I suspect that the problem is with the control system that I have designed but i cannot figure out what went wrong.
The given parameters are Vin = 240Vac 50Hz, Po = 20W, fsw = 200kHz.

I have attached a photo of the circuit diagram created using PSIM and I would appreciate it if you guys can help me with this.
Thank you.


texts: Help identifying 2 capacitors in a Synology DS415+

texts: I am hoping to get a little help in confirming the blue and red aluminium electrolytic capacitors in the attached image.  I think the red one is a 100uF 16V and the blue is a 560uF 6.3V but I just want to be sure, as I am not familiar with the other markings.  TIA


texts: Is that a center tap tranformer just labelled differently?

texts:
my transformer has a secondary winding of 0 - 12v - 24v

Is it just labelled differently and is it really a center tap where 12v would be the center, 0 would be -12v and 24 would be 12v?

Thanks!


texts: Given a fixed area on a solar panel, at what point does adding cells in parallel not increase voltage?

texts:
Given a fixed space on a solar panel, all else equal, adding multiple cells in series increases the voltage (while current remains the same). For example, two cells equals 0.5v + 0.5v = 1v total output. Three cells equals 0.5v + 0.5v + 0.5v = 1.5v, etc.
My question is, why wouldn't solar panel manufacturers create infinitely small cells (that are still workable) in parallel in order to maximize voltage? For example, on a solar panel, wouldn't reducing the size of solar cells to half the size (effectively doubling the number of cells on the panel while keeping the same area) double the voltage?