texts: Calculating phase currents and neutral phase current

texts:
I am doing a homework that I got yesterday and it concerns calculating phase currents and a neutral phase current. 3 phase it is. Three individual charges, each on their own phase and a shared 3-phase charge. L2 phase charge has a power factor of cosΦ 0,90.

Homework goes like this:

  We have a house with 400/230V grid and in a certain point of time it has charges like these:

  L1 - Lightning and heating 3kW L2 - Lightning, heating and motors 4,5kW, power factor cos Φ =0,90 L3 - Lightning and heating 1,5kW.

  Additional to those we have a 3-phased boiler that charges our grid with 6,0kW. Calculate phase currents and neutral phase current.

I tried to calculate this over 10 hours now, but for some reason I didn´t "get" the idea of it. This is what i have thought of it this far:

P1 = 3kW + 2kW (latter is 1/3 of that 3-phased boiler) = 5kW

P3 = 1,5kW + 2kW (latter is 1/3 of that 3-phased boiler) = 3,5kW

P2 seems like the "trap" of this task. As far as I have understanding, active powers can´t be summed together in this case. I will get back to this later, first I calculate currents of P1 and P3:

I1 = P1/Uv = 5000W/230V = 21,74A

I2 = P3/Uv = 3500W/230V = 15,22A

Two out of four currents calculated. Now we need the I3, so we could make vectors on paper and solve neutral phase current In.

If I calculate I2 like this, would it be right?

First I name both charges, so I don´t mix them up. P2x is the 4500W charge and P2y is the 2000W charge (1/3 of that 3-phased boilers power)

I2 = (P2x/Uv*cosΦ 0,9) + (P2y/Uv)

= (4500W/(230V*cosΦ 0,9)) + (2000W/230V)

= 21,74A + 8,695A

= 30,435A

Now I have all three currents that I need to solve neutral phase current.

I1= 21,74A

I2= 30,435A

I3= 15,22A

I decided to make an vector drawing out of it.

First vector is the I1 and it goes along L1, because power factor of it is 1.
Second vector will be drawn continuing from L1 toward L2.

If there would be no difference in power factor, the angle would be 60°. This time we have it, and it is as much as cosΦ 0,90, as a degrees, it is 25,84°. We will subtract it from that basic angle 60°.

60° - 25,84°= 34,16°

Last current left, until we can measure the neutral phase current.
We draw it in an angle of 60°, because once again power factor is 1.

Phew... Now I measure, with shaking hands. And I get 4,5A for a neutral phase current.

Somehow I just feel I didn´t get the exact right answer out of it. There is something that I don´t understand and I think it concerns calculating Phase L2:s active powers.

At first I thought that I could calculate current powers together and solve current out of it. Like this:

P2 = 4500w+2000w = 6500W

I2 = P2/(Uv*cosΦ0,90)

= 6500W/(230V*cosΦ0,90)

= 31,4A

I just felt it can´t be right, because there is kind of two different idle and active powers and from those I should get apparent power. S² = P² + Q² wouldn´t apply straight and true. From combined apparent power I could solve the phase current of I2.

I know that I am not stupid, but a slow learner. Half of our class won´t even try to do this, because they have given up, even if they want to learn. Our teacher rush things forward and he won´t be interested to explain things better.

Yesterday I tried to think of this homework like 6 hours and approximately the same amount today too. If and when I learn this, then I will surely teach it to other people in our class too.


texts: How to drive a load that draws 1 A with a sinusoidal voltage?

texts:
As a hobby project I'm trying to drive a small RL load which should draw about 1A pp using a sinusoidal voltage coming out of a series of op amp stages. The signal should be applied directly to the load. How can I do that?

With BJT it is pretty easy to do that when using a DC voltage drive and output such as below:

simulate this circuit – Schematic created using CircuitLab

The schematic is just for reference, to show you the simple driver I've been using for dc loads. In the case of this question you might as well substiture the load with a constant current source at 1A.

However, suppose my signal is a sinusoidal 1V pp wave coming from an op amp. The op amp cannot supply 1A and the transistor will be under stress with 0.3Vce and 1A pp current. This "issue" however can be solved by choosing a transistor that can handle 400mW and a 1.5 A max collector current. The bigger problem is that this circuit is going to reproduce only the positive half of the driving sinusoidal wave since the load is grounded.

A possible solution is to change the ground voltage to -1V but that solution has two main disadvantages:

During the upper part of the sine wave, the voltage across the load becomes 2V drawing which is not acceptable.
The load draws more current making the transistor dissipating even more power and probably exceeding the maximum ratings.

What other simple options do I have? Maybe using n channel mosfets?

EDIT:
The sine wave signal frequency is in the range 10 to 50Hz.


texts:
Background and clarifications:

I've never developed/written a single piece of hardware before, but I'm currently using Verilog to develop a huge project for a FPGA as my final graduation project.

I've got some questions on how to write verilog code efficiently. (Assume that, when I say "efficient", I mean "the way that uses less area and pins of the board").

Within the problems I'll suggest possible solutions, but, if none of them is right, feel free to negate them and add your correct solution.

In a certain way, problem 1 is the same as problem 3, so feel free to answer only one of them. I've written both to provide another example of the problem, just in case one feels more comfortable in answering one than the other.

In case you don't know how to answer problem 2, don't worry, as it's not the main problem here.

Thank you for your help.

Problems:

1 - Let's assume we have a module X that controls if modules A, B, ... N are logically on/off, that is, it sends signals to them to signal if they should be enabled or disabled. I see two ways of doing this:

Option 1: Send, to each destination module, a pair of enable/disable wires, wasting space with wires. i.e.:

module X(o_enable1, o_enable2, o_disable1, o_disable2);

assign i_enable1 = o_enable1;
assign i_disable1 = o_disable1;
module A(i_enable1, i_disable1);

assign i_enable2 = o_enable2;
assign i_disable2 = o_disable2;
module B(i_enable2, i_disable2);

Option 2: Create a bus, and each destination module would be responsible to mask it and verify if the enable/disable signal was sent to it, saving wire space, but creating a demux for every module. i.e.:

// o_enableDisable -> 0 = `ENABLE, 1 = `DISABLE
module X(o_enableDisable, o_enableDisable_bus);

assign i_enDis1 = o_enableDisable;
assign i_enDis_bus1 = o_enableDisable;
module A(i_enDis1, i_enDis_bus1);

assign i_enDis2 = o_enableDisable2;
assign i_enDis_bus2 = o_enableDisable2;
module B(i_enDis2, i_enDis_bus2);

// ... Inside A
if ((if i_enDis1 == `ENABLE)&&(i_enDis_bus1 == ENABLE_FOO1)) // Do something
if ((if i_enDis1 == `DISABLE)&&(i_enDis_bus1 == DISABLE_FOO1)) // Do something

2 - In the previous problem, we assumed that we were going to enable/disable modules logically. In case we wanted to turn them on/off physically to save power, is there a way to do that, or do we just have an if statement inside the module? i.e:

if (enabled) begin
  // Contents of module while on
end else begin
  // Contents of module while off
end

3 - Let's assume we have a decoder module X that sends commands to modules A, B, ..., N. I see 3 ways to do this:

Option 1: Commands as single wires, loosing pins, but saving the space of a demux. i.e.:

module X(o_com1, ..., o_com_m, ..., o_com_n);

assign i_com1 = o_com1;
// ...
assign i_com_m = o_com_m;
module A(i_com1, ... , i_com_m);

module B(i_com_m_plus_1, ..., i_com_n);

Option 2: Logarithmic input to be decoded inside destination module, wasting space with a demux. (Note that X decodes an instruction, decides which module it should send a command to and then sends a command to it)

module X(o_command_A, o_command_B, ...);

assign i_command_A = o_command_A;
module A(i_command_A);

assign i_command_B = o_command_B;
module B(i_command_B);

// Inside A
case (i_command_A)
  `COMMAND_1: begin /* ... */ end
  // ...
  `COMMAND_n: begin /* ... */end
endcase

Option 3: A mix of both.


texts:
One of my son's toys stopped working and I decided to jump in to see what was causing the problem.  I found that a number of the smaller detector microswitches had their tabs broken off.  Therefore they were unable to respond to the inputs when certain parts were inserted into the vehicle.  (The toy is the Little Tike Construct 'n Learn Workbench, great toy BTW...).

Here is an image of the circuitboard with the failed components.

I have taken the switch at position S12 off the board (the black plastic protrusion has been broken off this one) to get a better look at it.  It is here (Sorry for the blur):

I have been unable to locate a suitable substitute (or the original part) for this switch.  I have looked at Digikey and Mouser and have come up fairly empty.  I thought that somebody here might just be better at this than me and would know where to look.  The dimensions of the switch housing (less the black plastic profusion) are 3.43mm X 6.4mm X 2.7mm.

Can anybody help me to find this part so I can order some and replace the bad switches?  Thanks.


texts:
What is pass transistor?. How does it work?.

while reading about the DC-DC converter, I came across Pass Transistor.


texts:
I have two corded phone lines that I want to connect both of them to one telephone device. The phone must be connected to line 1 by default, and it switches to line 2 when it rings. I made a simple circuit to detect line 2 ring signal that turns on a 2-contact relay to switch lines. It works well when the relay powered from an external supply, But I want it to be a small box beside the telephone device and I don't want to uses an external power supply. The problem is that powering the relay from the phone line draws about 35mA that causes the phone to be answered immediately as it rings. Is there any idea to solve this problem? Like electronic switch replacement for the relay. Note that I don't want to get power from line 1.(I will add a timer and end-of-call detection circuit to this circuit to avoid switching back to line 1 while using line 2 later.)

simulate this circuit – Schematic created using CircuitLab


texts:
I hate to say it, but I am an electronics noob. Well, I've had some successes, so I probably know enough to that there's a lot I don't know.

I'm having problems with, I think, noise.

I have keypad at my gate which I would like to use to open the gate for people who have a valid PIN. Elementary.

There is a nifty little Arduino library that drives a PIN pad, and got that to work under controlled circumstances: I plugged a test PIN pad directly into the arduino, and, everything worked as anticipated. The documentation is here: http://playground.arduino.cc//Code/Keypad

However, when I connect the gate keypad to the Arduino over a 50m Ethernet cable, things don't work as I expect. The Arduino senses closures on the wire. Dozens, in the space of a few seconds (I think the libraries debounce mechanism may act as a rate limiter).

The closures result in readings as follows:

222222222222112222221
222222222112222212222
212222222221222222222
221321222222222212222
222132222222222221322

So, in general, the centre colum of keys, with a few closures from the first and last columns. If I remove the connector from the first row, a similar, seemingly random pattern repeats, but this time reflecting closures on the second row:

556565555555555555555
555555555555555555555
565555556555555555555
555655555555555565555
556555555555555555554

I conclude that the Arduino is sensing random closures (and that the library scans the first row before it scans the second). Which is interesting as I understood the pullup resistor on the Arduino should have dealt with this ("You won't need external resistors or diodes because the library uses the internal pullup resistors and additonally ensures that all unused column pins are high-impedance").

The keypad is about 50m away from the Arduino, and the connections are made over Ethernet, twisted pair cable (which does not carry current). The cable runs past a pool pump and parrell to (although in seperate conduit) the electrical feed to that pool pump. Somebody ran an angle grinder through the Ethernet wire and consequently the keypad is connected to the Ethernet cable in a junction box that also includes a small 240V to 1A DC transformer, and a slew of other wires.

If I methodically test all the closures from the keyboard over the 50m ethernet run, my tests are positive in that I see the resistance fall to near zero whenever a button is pressed on the keypad.

Software is my game. So, in theory, I could pile into the library and apply myself to improving it. But, I sense that the problem is an electronics one.

I would really value any input as to how to correct this situation (short of moving the Arduino to the keypad). If it is even possible to reliably measure a closure to at 50m.


texts:
electronics noob here. Just looking for some advice on replacing a part for a ebike motor controller. I think I may have shorted one of the schottky diodes (part) by running current through the circuit without the piece of metal the mosfet & schottky barrier rectifiers contact.

Anyway, I tested a diode (sorry if this terminology is incorrect) by touching the red lede of multimeter to the middle pin and black lede to outer pin. The voltage steadily climbed to 1.9 and then read O.L. I flipped the ledes and it read .2 V, I guess some voltage leakage. I also tested the schottky diodes with power running through the circuit and did not get voltage drop on my multimeter.

Would replacing these schottky diodes fix the problem? My bike motor doesn't run anymore. First, it wasn't too bad, the motor would turn off in the middle of the ride. But finally it just quit. I attached a schematic for the motor controller I bought off ebay. I am hoping I didnt damage the motor through my folly. Your help is much appreciated!


texts: Why does DMA send the first byte as soon as it is enabled?

texts:
I'm using DMA to send data to GPIOF which is configured as a parallel bus. DMA is being driven by update events on TIM8. TIM8 is configured in slave mode and starts on an output compare event from TIM1. And TIM1 runs in input mode, being reset by a falling edge on pin A9, and capturing the width and duty cycle of the pulse on A9.

TIM1 also raises an interrupt on input capture events. Then I check the width and duty cycle of the last pulse to determine whether I am currently in active video or not, and re-enable DMA for the next scanline if I am.

For context, this is for a video graphics application. GPIOF outputs pixels driven by a pixel clock (TIM8), in time with sync pulses from an external composite video source (pin A9).

Mostly this all works like clockwork. But I noticed that when I enable DMA in the interrupt, a single byte gets sent to GPIOF by DMA immediately. The rest of the bytes in the scanline buffer are sent at the expected time, when TIM8 starts running.

Here is a logic analyzer session showing what happens. CSYNC is the pulse going to pin A9. PCLK is a pin being toggled by TIM8. PIXEL0 is pin 0 on GPIOF. The first black band is (roughly) the time when the interrupt occurs and DMA is enabled. The second black band is when TIM8 is gated on by an output compare on TIM1.

What is the reason that PIXEL0 turns on shortly after DMA is enabled, causing a very wide pulse which continues until PCLK starts?


texts: Can a rocket igniter rated for 12v and 3 amps be powered with a 4v battery at 9 amps?

texts: I have a rocket motor igniter that says it requires a 12 volt battery at 3 amps. Since power is I x V, and power is really what heats up the wire that starts the igniter, is it possible that I could use a lower voltage battery, but use a much larger current to compensate, and have the same power?


texts: Calculate Voltage Seen at High Impedance Pin

texts:
Background

I am designing a simple lamp dimmer circuit for use with a 450W bulb for the purpose of heat fusing various synthetic materials.  I have the basic dimming functional but now I am attempting to measure the actual power used for finer control.  To this end I have selected the Allegro ACS71020 (datasheet) to do all of the heavy lifting.

Unfortunately, I am having trouble calculating the proper value for Rsense as seen on the first page of the datasheet and reproduced below:

simulate this circuit – Schematic created using CircuitLab

Questions

1)  In general, how should I calculate the voltage at either terminal of Rsense and, by extension, the inputs to the IC?

I feel like this should fall straight out of Ohm's law however the high impedance input throws me for a loop.  The functional block diagram on page 4 of the datasheet indicates that the two sense inputs (VINP and VINN) are buffered.  As I understand it, this should mean that practically no current flows which means the voltage (E=IR) is practically zero.  Now, in reality, there will be some small leakage current however the datasheet doesn't list it (or calls it by a name I don't understand) so I have difficulty believing it will be significant.

The datasheet does list the maximal input voltage as +/- 275mV.  I know that I need to select Rsense such that the maximal input voltage (115V but call in 130V for safety margin) reads as +275mV.  I simply can't figure out what the voltage will be at the other end of the second 1M resistor.

I think that I need to look at all five resistors in a chain and figure the voltage drop across Rsense for the maximal voltage input, acting as if the high impedance connections are nonexistent.  I am not sure of this, however.

2)  Why use two separate 1M resistors instead of a single 2M resistor?

I got nothing on this one.  According to good old Ohm's law, each of these resistors should drop half of the total voltage in this system but I don't see how that is beneficial to the overall design.  Better thermal dissipation?  Minimization of skew due to tolerances?  The guy who wrote the datasheet has stock in a resistor manufacturing company?


texts: TPS3619-33 (Backup-Battery Supervisor) overdrawing current at the VBAT path after a few runs

texts:
I've been having a few problems in integrating the TPS3619-33(Backup-Battery Supervisor) into a product that I've been working on for quite a while. After installing a new TPS3619 into the board after a few hook-ups at the VBAT input with a variable bench linear power supply the IC starts to over draw current, bearing in mind that if the current was not limited by the power supply the IC would definitely burnout ( right now limited to 10mA and unfortunately it is maxed out) and I've disconnected the load and it is clear now the TPS3619 is the one drawing the current. At this state the IC can still switch between Vbat and VDD automatically, but it is clear that it is not advised to continue using the IC in this state and a replacement is required, but I would really appreciate if someone would advise what would cause this behaviour.
VBAT : 3.0-3.6V
VDD : 3.2-3.3V

What i have in mind of possible suspects ,

ESD , maybe VBAT needs an ESD diode ?.

PFO is directly connected to the MCU GPIO (0 - 3.3V) , I'm not sure maybe some condition that may fry the IC ?

The bench power supply connectors arcing or overshooting maybe during power on/off at the VBAT input ? (Siglent  SPD3303X-E ).

I would really appreciate if someone would share his experience and/or thoughts on this subject.
BR


texts:
I am creating a led grid with 176 cells. Details:

The size of each cell is 30cm x 30cm.
Each cell contains two WS2812 LEDs that work under 5 volts.
The power supply unit has to be placed 10~20 meters away from the led grid.
To minimize the current value and voltage drop, I decided to use a 350W, 24V power supply unit.

Power management proposal:

Each led @ full brightness consumes about 0.5W, one row has 16 cells, each row consumes about 0.5w x 2leds/cell x 16 cells = 16W
At the location of the PSU, split the power into 12 channels: 11 channels to 11 rows and 1 channel to MCU. Each channel is protected by a 2A PTC resettable fuse.
Each row consumes 16W which is going to be about 16w/24v = 0.66A. Considering the power consumption through the wire. I assume each row uses 24V/1A~0A (Sometimes one row can be all off and another row is on full brightness)
Each channel feeds the power to one row.
24V channels are stepped down to 5V by a buck converter. This is to ensure every LED has the same brightness without voltage drop.

Questions:

How can I ensure that each signal shares the same ground reference? How should I connect the grounds properly?
How can I improve the design?


texts:
What kind of transformer is this?

Which side is Primary and which side is secondary?


texts: I'm trying to design an LC low pass filter to attenuate 30-35kHz noise on a 3.3V power rail. It's preferable to attenuate higher frequencies as well. So I designed an LC filter with L=10u, C=1u (which is wrong, but this is just an example) - and I found it boosted frequencies near the cut-off point. Is there any way to avoid this? The boost of 22dB corresponded to an increase in 12.5x the voltage. The rail will be powering a microcontroller, which draws 100mA, so this increase in voltage would likely damage it.


texts: Is using electrolytic polarised capacitor this way wrong?

texts:
Maybe this was asked before, but I have a capacitor set with electrolytics and ceramics. And all the capacitors which has capacitance equal or bigger than 1uF are polarized electrolytic capacitors.

Imagine I have a +/-5V sine wave input swing(coming e.g. from a strain gauge amplifier); and if I were to use an electrolytic polarized capacitor as below:

It seems that the capacitor voltage at its positive lead goes below ground when the input becomes negative swing. Does that mean electrolytic capacitor should never be used for such filter application? And will it not work at all if used?


texts: 12v load doesn't turn on with boost converter

texts:
I'm trying to build a power source for my router during load shedding. But the router doesn't turns on while connected to any sort of boost converter. I have tried 5 more different routers from different brands. All the routers turns off after they are connected to any boost converter. They run well with wall adapter, other 12v input etc. Here are the diagram 2 setups.
Set-up 1:

Set-up 2:

Here's the boost converters I'm using.
Boost converter 1:

Boost converter 2:

Note: all my boost converters are working with other 12v to 24v applications, yet the router doesn't get any power. Also the female barrel connector and boost converter connector are same. Also, my primary router is a tp link router with 12v input.


texts:
I couldn't figure out the maximum amount of continuous current can a 4 meter 0.085 Ohm wire carry? Also, for 300 milliseconds can it handle 100Amps? Provided a powerful fan cooling it?

What about 100A continuous current with a cooling unit(industrial fans)?


texts:
The output of buck regulator is the average value of the output across the regulator.
So below are my questions.

1) How the average value is coming across the load resistor practically ?

2) Whether the switching action (ON/OFF) leads to create the average value at the output ? If so, how ?

3) The average value is coming across the resistor because of what force or impact (practical perspective)?


texts:
I designed a Clapp VFO to aid in my Ham Radio projects (Non-superhet SSB and CW recievers for 80M and hopefuly 40M).
I chose the clapp topology for it's frequency stability. I want it to tune at least from 3.2MHz to 4.2MHz and have low harmonics. It'd be nice to be able to tune for 7MHz as well.
Is my circut good, are the C2 and C3 values? I know values are diffrent in the sim and schematic. Q2 is to buffer the oscilator.


texts:
I recently bought a MAXWELL RS-150-12 switching power supply but I can't find any documentation on how to select the ac input voltage (115V or 230V).
Here is a picture of the switch: (I want to select 230V to be the input voltage)

I dont know which position sets which input voltage. My guess is: the voltage that is visible on the switch is the selected one.
But I'm not sure and I dont want to damage the supply.
BTW: I only have 230V avaiable so I cannot test the setting with a lower voltage.


texts: Issue with the AMIS42700 CAN bus extender

texts:
I am currently setting up a CAN network of 16 nodes. For future extension of the network, the nodes are distributed on 4 different branches. These branches are bonded together by two CAN bus extenders (more specifically, two AMIS42700 chips) and supervised by a master CAN node (even if there is no such a thing in CAN). The AMIS42700 acts as both a CAN extender and transceiver for the master node. The schematic of the CAN bus extender part is showed below:

The issue with the AMIS42700 chip is that when trying to broadcast a message to all nodes, it seems to keep sending the same message repeatedly. This does not occur when transmitting messages between slave nodes (I checked this on the oscilloscope).

Where this is not a problem in itself when broadcasting messages from master to slaves, the CAN nodes receive multiple replicas of the same message, and eventually the network becomes saturated with messages from the master node. This affects the overall quality of the communication and is rather problematic in my case.

Can anybody shed some light on this peculiar behavior? Is it specific to CAN bus extenders?

For completeness, here is a list of things that I already tested:

Modify the value of the termination resistor on all branches (from 0 to 170 ohm)
Change the broadcast message. I could see the change at the oscilloscope, therefore I am assuming that this is not an error frame, but rather a replica of my message. Is it a reasonable assumption?
Remove the termination resistors: in this case, the CAN nodes could not communicate with each other anymore, and the behavior was similar to the one experienced with the AMIS42700 (they were trying to re-send the message, and the internal buffers could never be emptied).
Check the transmit buffers of the CAN controller on the master node: they are never full. It seems that the CAN controller on the master is insensitive to the value of the termination resistor.
Strangely, when disconnecting one of the CAN lines (CANH or CANL) at a time, the communication could be established between nodes. In that case though I did not check CANH and CANL at the oscilloscope.

All advices on the testing method and on the CAN bus extenders and CAN in general will be more than appreciated!


texts:
I have the schematic below.

It works fine and has done so for a few months. However, today, it seems the PIC USB module has died when I powered off/on the board.

Is there more input protection needed? Is the VBUS need some protection as well ?

The board is externally powered through an isolated AC/DC supply.

The USBLC6:


texts: I can not find any information about the type of load of neon lamps, for example neon probe or wall contact plug or extension cord with switch with small red lamp. I think this is a passive capacitive load, but in the workplace we measured an extension cord and the meter showed it is a purely active load. How does it work?


texts: Current distribution via current mirrors

texts:
I tried to distribute a current via pmos and nmos current mirrors (see the schematic below).

While the pmos and nmos mirros itself work fine, the distribution from a nmos to a pmos mirror yields an error.
The undermost red curve is the current through M9 (The first pmos mirror). This works fine. The other red curve is the current through M18 and M21 (The mirrored nmos current). Here I get a differnce.
The mirroring in pmos mirror M18, M19 then works fine again (blue curve).

My suggestion is that the mirroring depends on the Vds of the transistors but actually I'm not sure.
Can someone explain why this isn't working properly and how to fix it?

Edit: I'm aware of the channel-length issue. Therefore I have used large transistors with a W/L ratio of 1u/8u (schematic). Vdd is set to 1.2V


texts: hamonics and sidebands in dc-dc converter

texts:
The lecture (page 8) shows output voltage spectrum with sinusoidal modulation of duty cycle of a dc-dc converter.

I am wondering where the hamonics and sidebands come from.

For hamonics, I read somewhere that because converter power stage is non-linear
so it generates hamonics. I can see it from the nonlinear static control-to-output characteristic of buck-boost converter below.

However, I don't see where switching hamonics and sidebands come from.

Could anyone explain why these hamonics and sidebands exist here.


texts: Constructing a medical model: logic gates with feedback?

texts:
I'm a third-year medical student from Sweden.

I am attempting to simulate a specific chain of proteins in a cell using logic gates - specifically, I seek to construct a representation of the RTK-Ras-MAPK-pathway. In this pathway, there is a protein called Ras, which is important for regulating cellular proliferation, specialization and self-destruction.

Ras is interesting because it functions like a switch: it can be either on or off. When Ras is activated, it stays active for a short time and then automatically falls back to its off-state by intrinsic mechanisms.

I have read enough about logic gates to know that a gate cannot simply feed back into itself. What I would ideally like to do is something like below:

simulate this circuit – Schematic created using CircuitLab

However, I've understood from several sources that this isn't feasible, and that connecting a gate to itself like this would create something of a "paradox"?

I've thought about using switch-controlled inputs from additional voltage sources as the second input for Ras (the XOR gate), but it seems to hinge on the fact that input 2 is undetermined until a signal comes from the XOR gate, and that the signal cannot be determined until the XOR gate gives some logical output.

My question is this: would it be possible to design a logic circuit that can take input from itself? If it isn't possible, are there ways to achieve similar results using other means?

Please note that I am not fluent in the language of electronics. If I have misunderstood something or am unclear I apologize.


texts:
Assume that we have a circuit that is connected with components that have positive resistance. At this point the effective resistance between every two node is positive. (below is an example of such circuit)

simulate this circuit – Schematic created using CircuitLab

Now, if we add components with negative resistance, we can have negative effective resistance between two nodes. (Here the effective resistance between node 1 and node 3, has become -2).

simulate this circuit
At this point, is it possible to make the effective resistance between every two nodes positive by adding more negative resistance components?


texts: The variation of the DAC output is abnormal

texts:
Description of the situation

I want to output the data from the ADC to the DAC.

I use an ADC from Microchip dsPIC33EV128GM104-E / PT and I am using 12 bits.

Microchip MCP4922T-E / ST is used and 12bit is used.

I created the driver code using mcc code generator and it works fine.

I am using 1 DAC and Vref is using 5V.

The gain of the DAC is used as 1.

We tested that the data received from the ADC comes in normally.

Used chipset

ADC : Microchip dsPIC33EV128GM104-E/PT
DAC : Microchip MCP4922T-E/ST

The problem

The DAC output data goes up and down and then suddenly increases significantly.

When the output value of the DAC is confirmed by the oscilloscope, it suddenly increases from 600mv to 900mv. It also increases from 1.1v to 1.8v.

Also, the output value decreases and increases.

I wrote a code that raises 0 ~ 4095 as a test code and the same symptom appears.

The question

I wonder about three points.

When does this happen?
The value of the DAC increases like a staircase, but can this be the same thing?
Does the DAC's SDO, SCK, and CS have 22R resistors that could be a problem?

Resources

dsPIC33 https://www.microchip.com/wwwproducts/en/dsPIC33EV128GM104

DAC
http://ww1.microchip.com/downloads/en/devicedoc/22250a.pdf

Edited

When we checked with the oscilloscope we found that the value increased significantly when the first bit changed.

0000 1111 1111 -> 0001 0000 0000

When the lower bit changes, the value is incremented and descended.


texts: Electrostatics - Calculating the vector of electric field

texts:
Most of the problems I run into while studying electrostatics are ones regarding a charged thread for which I need to calculate the vector of the electric field. The thing that is confusing me is how to integrate dE.

For example, I need to find E for this long angled thing with two sides of length a each. The solution says that I should separate it into two parts so I could apply superposition. I figured that out, but the second picture confuses me. Why did they put the first side on the negative part of the x-axis?

Can someone describe how to solve this problem? I don't know where to start from.


texts: Automatic transfer switch or some such solution

texts:
I have only rudimentary knowledge of electronics.

I live in South Africa, where we are now experiencing rolling blackouts. (Euphemistically called "Load Shedding" here.) During the day it's just a matter of waiting for the blackout to end after about 2 & half hours. But, as you can imagine, at night it becomes more of a problem.

To lessen the impact, I have installed a parallel 12 V DC lighting circuit. I have run solid 20 A copper wires to each regular AC light fitting (isolated from the AC power of course) and stuck 3 W LED lights in each. These run from a 12 Ah sealed 12 V battery located on top of a kitchen cabinet, which, when there is power is kept on a float charger.

Although the LEDs don't provide enough illumination for general lighting, they do at least keep us from walking into the furniture.

At the moment, when necessary, I walk to the kitchen in the dark with a torch (flashlight) and turn on the emergency lights.

I would like to have the emergency lights come on automatically when the power fails but am not sure how to achieve this. I did manage to achieve an automatic switch-over when experimenting on the bench. I used a regular AC/DC relay and this seems to work OK but I have some concerns.

For instance, in my experiments, I used the interruption of the power to the float charger to trigger the relay. I'm concerned that I am playing around with 220 VAC current and that, on the DC side, the relays has to be powered full time, in order to keep the Normally Closed switch open. I'm worried that this may eventually lead to contact corrosion and eventually arcing with the resultant fire hazard.

I think there must be a simpler and safer solution.

Edit: -

Thanks for the comments so far and thanks to AnalogKid for setting my mind at ease regarding power relays.

I'm sorry, but I am not sufficiently knowledgable regarding electronics notation to use Cicuitlab, which I have never heard of before now.

It's been a while since I played around with the relay, so I don't remember exactly what I did at the time. (We have had various bouts of blackouts over the last few years.)

I will have to try the relay again and let you all know.

I have had a thought though that never occurred to me before: The wire running to the battery from the float charger, has to be DC and probably a bit over 12 Volts. So, I don't have to deal with AC power at all, as I did in the past.

The relay could be located between the wall wart of the charger and the battery terminals. When the charging current is interrupted, it could trigger the relay.

I'll give that a try and let ya'll know

Regards


texts: Is a cosmetic logotype on an outer copper layer a bad idea?

texts:
I've seen many people add logotypes and other graphics in the copper layers of PCBs, often also removing the solder mask in these places to expose the bare (or rather plated) copper.

Is there anything electrically, mechanically or chemically that makes this a bad idea?


texts: I've been reading more about how oscillators work and one of the more simple ones is the Colpitts oscillator.  My understanding is that two capacitors in combination with the inductor can produce oscillations at a given frequency, and the transistor ensures that the oscillations persist.  Other schematics use additional capacitors which I'm unclear about, but which I don't think affect the frequency unless they're part of the tank circuit.  I'm definitely confused about what the values of the capacitors should be relative to each other, because some schematics suggest using capacitors with the same values or two different values, and I'm unclear on how or if that affects the output of the circuit (if you had two capacitors with the same value or two with different values but their combined capacitance was the same).  Also, what part of the oscillator is generally used for the output?  Should it be the collector and emitter to get a full AC waveform?


texts:
I am designing a series of heaters. One of them, actually, is designed for 220V and uses two resistors on series to achieve the power desired. The total current is, on peak, almost 20A. To keep the compatibility with others machines, and based on a lot of other things, the TRIAC which will drive the load will be the BT139-600E. But the maximum current its allow it's 16A.
To solve this problem I have two possibilities. First of them is to separate both resistors(doubling the effective value) and drive them on parallel (each resistor on a different TRIAC, which will limit the current on each to rough 10A).
Another possibility is to keep the connection of resistor as it has been done and put the TRIACs on parallel nor the resistors. In this scheme two TRIACs will drive the same load.
The point is:
If I use two TRIACs on parallel to drive the same load, will the system keep the currents drained by each balanced? On other words, have the TRIACs almost the same impedance at conduction? Are there any other disadvantages of the second solution compared with the first?


texts: Separating the AM and QAM components in PAL signal demodulation

texts:
I'm attempting to emulate the modulation and demodulation of a PAL video frame in software, but I'm having trouble understanding how the AM (luma) and QAM (UV) components of the signal are separated during the demodulation process.

Background:

The software I'm writing takes an RGB bitmap, translates it to Y'UV using the BT.601 standard, generates (modulates) a signal as a series of samples, then saves those samples to a wave file. Those samples can then be loaded back in and demodulated back into a bitmap, with the H-sync pulses honoured against the H-pos ramp generator as an old CRT TV would do, and finally translated back into an RGB bitmap.

There are two motivations behind this project: first, to create some cool looking analog fuzz in software; and second, to better understand the TV standards and basic modulation / demodulation techniques in a domain (software) where I am more comfortable.

What I've got so far:

The code performs the modulation fine, and when the result is viewed in Audacity (with a sample rate faked at 1/1000th the real frequency) it shows a signal that I recognise to be a series of PAL picture lines. The full process works if I put it in black-and-white mode, thus omitting the QAM signal from the modulation step and leaving only the amplitude modulated luma channel. I've also tested the QAM modulation and demodulation code against a simple audio file, and it works great. The only bit I haven't got working is the image demodulation with both the AM luma and QAM colour components included.

The confusion:

Given a pure untouched QAM signal, it seems relatively trivial to demodulate the signal back to its original composite signals, by multiplying with the carrier sine and its cosine individually:

$$I_t = s_t \cos(2\pi f_c t)$$
$$Q_t = s_t \sin(2\pi f_c t)$$

The two components are then low-passed at the carrier frequency to remove high-frequency terms. This seems to work great, and as I noted above my implementation of QAM demodulation works just fine.

Similarly, I can implement simple AM demodulation, even when the signal is accompanied by other signals in separate parts of the frequency domain - it's just a case of high-pass and/or low-pass until you've got the bit you want.

However, from what I can see, the QAM modulated UV component is added to the base AM luma signal, with both parts overlapping in the frequency domain, as the following diagram from Wikipedia appears to show:

At this point I'm a little stumped. It doesn't look like I can low-pass to get the AM luma signal due to the overlap, and I can't see how I'd subtract the QAM signal from the underlying AM.

What am I missing? What are the logical steps that should be taken to separate the luma and UV components?


texts:
I had an issue using an Arduino Nano to investigate simple RC circuits. The capacitor would not fully charge to the supply voltage. I assumed it was something to do with the digital pin circuit on the Arduino so I set up the RC circuit with a 1.5V battery. Same issue.

Here's what I found. Caps are ceramic non-polarised.

100 ohm + 10nf = charged to 1.2 Volts
100 ohm + 100nf = charged to 1.2 Volts
110K ohm + 100nf = charged to 900 mV
1M ohm + 100nf = charged to 650 mV (this was the original circuit
analysed with a 1-second pulse from the Arduino) 650 mV charge after
400ms, which is about right for the time period.

I am using a standard breadboard and a 6022 Hantek PC oscilloscope. My voltmeter confirms the same charged voltage results.

Why does the capacitor not charge to supply voltage with high resistance values? Any clues?


texts: Synchronous vs asynchronous PWM modulation

texts:
According to Mohan/Power Electronics, asynchronous PWM modulation results in subharmonics that are very undesirable in most applications. We can use this type of modulation only if we choose a large number of mf. (mf stands for the frequency modulation ratio).

Are there any reasons to choose asynchronous PWM modulation over synchronous?


texts: Why do some audio amplifiers connect the power ground to the signal ground?

texts:
Trying to add a MIDI synthesizer & speakers to a keyboard here. Here's the schematic:

simulate this circuit – Schematic created using CircuitLab

But I was getting annoying crackling and popping noise. I did some debugging and found my problem is very similar to the one in this question:

Ground loop? Switch mode power supply noise

The problem is the amplifier board connects the negative inputs to the power ground. These are then connected to the headphone ground, which is really 1.5V*, causing the worst possible ground loop! I guess there's another coupling capacitor inside the computer to protect the headphone ground from being shorted. It seems in theory if the headphone ground stays perfectly constant, then there will be no ground loop current and therefore, no noise. But in reality, there will be current flowing from the headphone ground.

So, I cut the traces on the amplifier board that connected the negative inputs to ground. The noise went away finally.

But I'm still utterly at a loss at why would an amplifier connect the negative inputs to ground? That would only work if you plan on powering it from another isolated power supply.

*I measured HPCOM @ 1.5V without load. The Allwinner A10 datasheet (22.1) says, "Support to automatic change from Virtual Ground to True Ground to protect headphone amplifier"


texts: i am making a motorized slider(nema 23 stepper motor), where i have also included a power supply of(12V 20A SMPS - 240W) i also need to include a 15watt bulb in it, is there anyway to do it or do i have to completely use another connection and switch to connect that bulb.THANKS


texts: Restoring deleted designators on Altium PCB

texts:
Is there a way to restore component designators on the PCB without having to delete and re-add the component in the schematic? I deleted quite a few designators while I was laying out the design and now they're not showing up on the Assembly drawing.

Thanks


texts:
The modular 5V-powered design's module is having two output clocks (21 MHz and 3.5 MHz) to other modules in the system. I am looking for the best way for buffering these signals so that they would be enough fanout / strength and least distortion for several distant wires attached within the system. Length can be considerable, up to 60 cm (25 inches).

The choices are: use LVC1GU04 unbuffered inverter (the same type used in the Pierce oscillation circuit), use buffer like LVC1G126, or LVC1G14 Schmitt trigger.

During investigation I found out several pieces of information making me a little stuck with making the conclusions.

The functional difference between LVC1GU04 and LVC1G126. Comparing the datasheets I see no much difference. Historically, I would expect 1G126 to be more load-capable, but here it looks like just buffer with enable. Thus is there any rationale on using 1G126?
This document called Use of the CMOS Unbuffered Inverter in Oscillator Circuits says:

  An unbuffered inverter itself may not have enough drive for a high-capacitive load. As a result, the output voltage swing may not be rail to rail. This also will slow down the edge rate of the output signal. To solve these problems, a buffer or inverter with a Schmitt-trigger input can be used at the output of the oscillator.

But I do not see proof of this in the datasheets of 1GU04 and 1G126, both circuits are being tested by the 30 pF and 50 pF loads.

The starting, general clock buffering circuit I obtained looks like the follwing:

simulate this circuit – Schematic created using CircuitLab

It uses standard DIP packaged 74LS04, series resistor to match impedance (and I guess limit output current), and pull up to ensure high level is maximally close to 5V as LS04 is TTL and is not rail-to-rail. Is there any better buffering circuit for the LVC1G(U)04 or other related small logic 1G chips in this family? What would be the frequency limit of the input clock?

I am looking for guidance. I can not change design and length of the traces in other modules, thus the effort is only about designing proper buffering/redriver circuit.


texts: Effects of Pulsed vs Direct Current on Battery Depletion

texts: I'm doing some work with a portable, cell-battery-based electronics and someone on the design team mentioned that pulsed current will more quickly deplete a battery than constant current, even if both have the same total energy consumed. Is this true?  What is the reasoning behind it if it is true?


texts: Interfacing a button to a microcontroller (and PC) with a 50 m long cable

texts:
I am designing a board that will be plugged into a computer and will read the status of a button ~50 m away in an office environment (it's actually a lot closer, but the cable is long).

I think it's a good idea to galvanically isolate the button wiring from the computer, since the PC will be grounded. I don't want any faults on the wiring to be able to damage the computer.

I'm assuming less than 100 ohm resistance for the cable, and while a simple series resistor would work, I think having a constant current sink for the opto LED is safer (i.e. if the cable has to be a lot longer, or shorter, etc.).

Is this a sensible approach to it? Cost/space is not much an issue, so I could add some protection/filtering circuitry, but I'm not entirely sure where/how to do it, so I'd be happy to hear some suggestions.

simulate this circuit – Schematic created using CircuitLab


texts:
I was looking at a Diagram, and I saw that a relay uses a Zener diode and a common diode in series between the coil ends. In the past I've seen a common diode being used in order to protect the voltage from going to the X1 end (ground), but in this case I don't know what is the purpose. I would really appreciate if someone could help me please.

Thanks.


texts: Will a 0.5V difference in output damage the device?

texts:
I have a speaker adapter, with an output rating of AC 11.5V ~ 1600mA, which I am looking to replace and the only replacement I can find has a rated output of 12V ~ 2000mA.

I've read somewhere that a higher current is okay since the speakers will only draw what it needs, but I'm wary if the 0.5 difference in voltage will overload/damage it.


texts: How do I get multiple voltage lines from a single PSU output?

texts: Suppose I have a regulated power supply that has +20V and -20V outputs, and an amplifier circuit that uses them. I also have a push-button (not momentary) power switch with an integrated LED which requires 12V to run. What is a simple way for me to adapt the existing PSU rails to also light the LED?


texts: How do voltages at outputs drop as current increases?

texts:
As I looked at some 74xxTxx ICs, such as this simple NAND gate, I noticed that the minimum \$V_{OH}\$ decrease as current flowing from the outputs increase.

But, from my understanding of Ohm's law, \$U = RI\$ implies \$\frac {dU}{dI} = R * dI\$, and as \$R \gt 0\$, the more current flows, the greater should tension be at the pin relative to the ground.

I think, because this behavior affect only \$V_{OH}\$ and not \$V_{OL}\$, that it is because when an output is high, it sources current, hence negative current.

But it contradicts my intuitive understanding of electricity, as I believe sense of current doesn't act on resistances, intuitively (else AC circuits would go crazy).

As I'm just a beginner in electronics and electrical fiddling, I'm sure that I must have made a mistake somewhere, but where ? And, if my reasoning is oddly enough correct, how does the 74xxTxx ICs do to achieve this lowering in tension ?


texts:
i am looking at getting a solenoid bolt like this for a project but the problem is alot of solenoid bolts that i have ordered can be retracted by pushing the bolt in manually so for example with your finger

i need a solenoid bolt which can only be retracted when power is supplied

Are all solenoids built like this or are there specific solenoids which can only be retracted with power on/off?


texts: Current Sensing on positive and negative voltage rails

texts:
I'm working on a design that uses two separate buck regulators to generate a positive and negative voltage, and I'm trying to implement current limiting with a current sensor. However, I am running into issues with the way the sense resistor is integrated into the feedback loop as shown in my block diagram below:

simulate this circuit – Schematic created using CircuitLab

With the way the regulators are set up, the current sense resistors have to be included in the appropriate feedback loops in order to maintain the correct output voltage. Otherwise, the regulator won't take into account the voltage drop, and the output voltages will be less than what is expected.

The issue is with the way the two regulators are configured. When you add the sense resistor to the negative voltage circuit, it seems to create a different 'return node' for the negative voltage. If it wasn't there, both regulators can be tied to the ground node at their returns. What other methods of current sensing can be used for the negative voltage circuit such that the appropriate returns can be tied together?

EDIT: As Hacktastical said, there is a way to have a buck regulator output a negative voltage. I based the reference circuit off of an app note from TI:

Positive to Negative Buck-Boost Converter


texts: Reason for voltage between grounds on Oscilloscope and Function Generator?

texts:
I was using one of the little XR2206 Function Generator kits with my analog oscilloscope.  It displayed a sine wave no problem - but I noticed that as I connected the ground strap of my oscilloscope probe to the ground terminal on the XR2206 board - there was a little bit of sparking visible like when you short a 9V battery.  I pulled out the multimeter to measure the voltage across the two grounds and it showed a reading of 4V DC between them and just under 21V AC.

I was powering the XR2206 with a 9V DC wall plug power supply, no ground pin.

Is there a simple explanation for what is likely taking place?  Where would this voltage potential between the two grounds be coming from?

Thank you!


texts: 2-Layer PCB Through-Hole Layout/Soldering

texts:
So I'm designing a 2-layer PCB consisting of a bunch of ICs (op-amps, OTAs) and passive components. I would like to have my decoupling caps (little 100nF axial) as close to my op-amps as possible, so I've have the following thoughts.
My op-amp sockets are mounted on the front-layer of the board and will be soldered from the back layer, as per normal. My first thought was to mount the decoupling caps directly under the op-amp socket, but on the back layer (with pins poking through the front-layer), then solder them from the front layer.
But after some more thinking I don't think this will work, since the soldered pins of the caps would be sticking up directly under the op-amp socket, and might not make the header sit flush or flat on the front-layer, depending on the final soldered pin height.
Here's my solution to this. Mount the caps on the back layer and solder them from the back layer, then just pre-cut the cap pins so they don't poke through into the front layer. Two questions about this however:

Do PCB makers (JLCPCB in my case) put soldering pads on both sides of a through-hole board or just the opposite side of where a component is mounted?

Is it good practice to solder passive components on the same side they are mounted?

For reference, here's a Kicad pic of what I was thinking, in terms of mounting (TL074 on front side, caps on back side):


texts: What can be soldered with a hot air rework station?

texts:
)I'm considering buying a rework station (Aoyue AO968A+220V). What could I expect to solder consistently using hot air that's not "possible" with solder iron?
What I've been avoiding from a soldering point of view is packages with less than 0.8mm pitch, and no-lead packages. Obviously BGAs has been totally out of the question.
The purpose of the soldering is prototyping and the alternative would of course be to get the PCB manufacturer to also assemble the board, but that might be less flexible solution.


texts: How can I detect HIGH or LOW input on a NXP microcontroller?

texts:
I am using NXP micro-controller P89V51RD2. I need to detect HIGH or LOW from 2 single bits. How do I store input state to a pre-defined address so that my functions can detect it as data?

I need to use 2 transistors coupled emitter to base to detect change in resistance(indirectly by measuring current and voltage) in a load cell. The coupling is an attempt for a rudimentary type of switching. This I need to give to a bit in e.g. port P1 for detection. I have trouble getting the right code ( H/L bit identification) for this AND connection configuration (buffer or another signal conditioner needed?) for this.

The code compiling is done in Keil μVision v4.

The official website for Keil says it can be done by code : sbit b1 = P1^0. However, I don't know how to proceed afterwards as this code doesn't give required results.


texts:
I am looking for an operational amplifier which will fit my requirements.
My circuit consists of two cascaded non-inverting amplifiers.I have a classical non-inverting setup.The minus pin of both stages is at ground potential. My positive input to the first stage is a voltage that can be in uV region, therefore the op-amp needs to be able to operate as expected at this level.
I have a single supply voltage of +3.3v, no split rail, my input is always a positive voltage.
I need the amp to have the following characteristics:
Low noise,
Ultra low offset,
Low power,
True Rail/Rail IO,
Should work in a single supply of 3.3V
Any suggestions for an op-amp for my requirements? I have tried a MAX4239 but it seems not to work as expected when the positive input is only a few uV, the output load is a comparator input and an ADC input. VGND in schematic is GND


texts: STM32 UART character encoding issues (can't decode using either ASCII or UTF-8)

texts:
first some specifics:

STM32F411 Nucleo board,
Atollic TrueSTUDIO v9.1.0,
Debian linux 9.6.

I am sending a telemetry string over the UART using the HAL.  I am using the following code to construct and transmit the data:

sprintf(str, "#, %d, %d, %s\n", csvString.range, csvString.lux, csvString.time);
HAL_UART_Transmit(&huart2, str, strlen(str), 100);

where '#' is the telemetry sentence start character, and the data follows a pre-formatted CSV type structure for easy manipulation on the receiving side.  If I do a simple

cat /dev/ttyACM0

I can see the output, which looks like:

#, 21, 114, 01:58:001

so that looks like it's working well.  However when I attempt to use a simple python script to parse this information in, I get a mess.  It appears to be an encoding problem.  The python that I'm using looks (as an excerpt) like this:

ser = serial.Serial('/dev/ttyACM0', 115200, timeout=2, parity = serial.PARITY_EVEN, bytesize = serial.EIGHTBITS, stopbits = serial.STOPBITS_ONE)

if ser.isOpen():
    ser.close()

ser.open()
ser.flushInput()
ser.flushOutput()
line = ser.readline(100)

ser.close()

and the result I get out of this reading of 100 bytes off the UART (just a sniff to see if things are working properly) looks like:

#\t\x920\t\x8a1\x13\t\xa22\xa7\xb2:\x820\xe1#\t\x922\t\x8a1\x13\t\xa22\xa7\xba:\x821\xe1#\t\x921\t\x8a1&\t\xa22\xa7\xba:\x821\xe1#\t\x923\t\x8a1&\t\xa22\xa7\xba:\x821\xe1#\t\x921\t\x8a1&\t\xa22\xa7\xba:\x821\xe1#\t\x920\t\x8a1\x13\t\xa22\xa7\xba:\x82

There is an obvious repeating pattern in this, which looks like it lines up with the telemetry sentences.  I can't use some of the other methods in python to read off the UART easily because they can't detect newline characters in this.

It's obviously an encoding problem, but I'm not sure how to solve this as:

I do not know how to (even after searching) verify the transmit encoding used by the STM32 HAL/Compiler
I am not a talented software person

Could the community please:

Help me determine what the encoding being sent is
Give an example of how to decode it so that I can then write code to parse things as I need to

Thanks!

EDIT:
To address a comment suggesting evaluating the UART data using an oscilloscope, I can not do this as I am using the UART bridge on the STLink part of the STM32 Nucleo board.  I am not currently able to switch to the other UART as those pins are in use.  It would also not account for why I can see the data properly formatted if I display the output of the device in a terminal session (the above mentioned cat /dev/ttyACM0).  Thank you for your suggestion.


texts: How to add a reset after 4 clock cycles in LTSpice

texts:
I am trying to verify the output for 4 bit SAR logic.  So far this is my schematic:

These are my resullts so far:

I am trying to add more to the PWL, which is what I assume I have to do, but the outputs aren't resetting after 4 clock cycles.

EDIT:I now changed the PWL at the CLK to a pulse

These are now the results, where the first and last bit aren't showing the expected results:

These are the values on each component:


texts: Programming methods for detecting liquid drops with phototransistor

texts:
I have a simple circuit with an LED pointing at a phototransistor. There is a tube in between them that drops of liquid will drip through at random times. I am reading the voltage with an Arduino at the emitter as it drops when the LED is occluded.

I have tried a few methods of my own (e.g. averages last some number of values and checking for different averages) but they seem to be pretty unstable. I'm not an expert at signal processing or anything, but I was wondering what some good methods/algorithms would be for this kind of thing. Any help would be appreciated. Thanks!


texts: Arduino-powered silent relay needed. Will AQV210E work?

texts:
I'm trying to find a small, affordable, solid-state SPST relay that I can use for an Arduino project.  I've made an analog clock using regular electromechanical relays, and it works fine.  But the clicks (once every 15 seconds) are driving (especially) my wife and me crazy!
I have found a 6-pin DIP SSR, a Panasonic chip called "AQV210E" (https://www.digikey.com/product-detail/en/panasonic-electric-works/AQV210E/255-1143-5-ND/251915), with a detailed description that reads:
Solid State SPST-NO (1 Form A) 6-DIP (0.300", 7.62mm)
It looks to me as if the AQV210E will work, as long as I use appropriate resistance for its input (Arduino uses +5v or 0v digital pin output signal, and this chip's input is rated for only 1.14vdc).  It seems to me (I admit I'm a novice/hobbyist) that the input of this chip should behave just like any LED being powered by a 5vdc signal... correct resistance between Arduino digital pin output and AQV210E chip input should allow successful On/Off behavior without frying the AQV210E.
Output-wise, I'll be making and breaking a ground connection for one or two LEDs at a time, so very little current is involved.  The AQV201E isn't a zero-crossing relay, and it appears to be useful for a DC in / DC out application.
Can someone tell me if this AQV210E chip might work for me?


texts: Can Brushless DC Motor (BLDC) be used as Stepper Motor?

texts: I have a BLDC motor and I am keen to know if there is a controller out there that can allow BLDC to be used as stepper motors with (holding torque and accuracy in step size) I know BLDC motors are built for smooth drive experience while stepper motors are built to perform accurate steps (however is there a way to make BLDC motor perform with with the accuracy of stepper motor?


texts:
So I'm trying to figure out how I can analyze S-parameter matrices.

The i. should be pretty straightforward, though I'm not 100% sure if I am correct with what it means. I'm assuming that there's only one active, ideal part.

For ii. and iii. I'm a lot more clueless, though I can definitely see the consistences of the values.

Parts i. and ii. have two ports whereas iii. has 3 ports. iii. has only 3 different values for the real/imaginary values and the cross-section is consistent (\$S_{11}\$, \$S_{22}\$, \$S_{33}\$).

I'm not exactly sure what kind of conclusion I'm even supposed to arrive to or what I should do to approach this analysis.


texts: How to turn analog audio into analog cable signal for radio receiver?

texts:
Because I have several good (but older) sound systems in my apartment I am looking for a way to play audio from an iPhone or computer (anything with a headphone jack) synchronously on all of them. All the receivers are hooked up to Analog Cable Radio (Not over the air antenna). So I thought it might be clever to send the music over the existing wiring on a specific carrier frequency which I would set the receiver to.

Does anybody know how to do this? Is there maybe a little gadget or a not-to-complicated way to build it?

Hope you guys get my point and thanks in advance!


texts: I had the luck to have someone who could explain everything to me, but most starting hobbyists don't have someone like that. Is there a guide available which covers all the basics, like formulas, parallel / series, etc.?


texts: Are typical computer power supply units leading or lagging power?

texts: Computer power supplies often have "power factor correction" features which raise the power factor in use to levels close to resistive loads (1). I'm curious what, in the absence of power factor correction, power supply loads would be. (Switching-mode power supplies use both inductors and capacitors; I'm not sure what their load looks like on the AC side though)


texts: Device Descriptors in Serial Communication

texts: I was wondering if there was any Descriptor part in the data packets during RS 232 based Serial Communication. If not (apparently) then how does the computer decide regarding the type of device connected.?


texts:
I have a rotary 5 V potentiometer with a center point of 2.5 V, that only reads a max of 3.8 V and a min of 1.2 V due to mechanical restrictions I can not give the pot and more movement.

Is there a way I can scope this up to 4.5 V max and a of 0.5 V min? I have a very good 5 V input.

Please give it to me in simple terms as I don't fully understand diagram terminology.


texts: AC servo position flight surface control system

texts: So if a control transmitter is used to set the Pilot's input command signal and a control transformer is used to compare this desired position to the current position and produce an error signal. My question is how does the feedback system work for this? How does the control transformer get the current position? Does it have something to do with its shaft? Quite unsure about this


texts: External quality factor of an RLC circuit capacitively coupled to a feedline

texts:
I have an inductor coupled via coupling capacitance C_c to a transmission line with impedance Z_L. Given that the inductor has some internal losses and a capacitance, I imagine that for all intents and purposes it can be modeled as an RLC circuit. This gives a simple circuit shown below:

What I am interested in here is an analytic expression for the external quality factor of the circuit in terms of C_c, C, L, Z_L, and perhaps R but I imagine that only goes into the internal quality factor.
Now, from the definition of the quality factor, we can write that
$$Q_E = \omega \frac{E}{P}$$
where omega is the frequency, E is the energy stored in the RLC circuit, and P is the power lost in the transmission line, essentially due to the coupling. But I have to admit, at this point I'm already starting to get stuck in relating it to C_c, C, L, Z_L. Could someone help me get started on how to continue?
Coplanar Waveguide Resonators for Circuit Quantum Electrodynamics by Goppl et al from 2008  looks at something along these lines, but this is not an identical system. They transform their circuit using Norton equivalences, but I don't think that is the way to go. However, if one were to take their figure 5c and make some adjustments, perhaps that helps?

Taking the above with R* = R_L, C* = 0, and replacing C by the series capacitance of C_c and C, would that not be identical? In that case the external quality factor is given in the paper to be Z_L/2 times C_c C / (C_c + C) times the resonant frequency of the RLC circuit. I am not 100% sure this is correct; could someone help me out there?


texts: Selecting wiring hardware for CAN network

texts:
I'm having trouble selecting wire, jack and plug for small (up to 6 nodes, 3-4 m) CAN network. Each node will have 2 jacks wired for pass-through and short patch cables will be used to daisy-chain them together.

Previously, we were using CAT5e hardware with 100 Ohm termination for wiring CAN and 26V power. While not exactly up to 120 Ohm CAN spec, it worked just fine for such a short network and was really on a budget.

Right now we are trying to reduce the dimensions of some components and those RJ45 jacks come out as too big. So, the idea is to use 6p6c RJ25 connectors and 3 pair twisted cables. This gives us the same twisted pair for CAN and two pairs for power as before, but in much more compact package.

The problem:

Unlike CAT5e hardware, there is next to zero impedance data on alternative components. For example, here are some parts I've found on digikey: jack, plug, cable. I might be able to calculate wire impedance using one of the online twisted pair calculators and approximate dielectric constant for polypropylene, but this seems to be rather guesswork. I have no idea how to even approach the same question for jack and plug.

The question(s):

Is there a way to find out impedance for those components? Do such components even exist in the desired impedance range (100-120 Ohm)?

And more generic: how do you approach a task like this? I don't believe every engineer who needs to establish communication between two devices bothers with such low level details. Most likely they would use off-shelf components and focus on the software/device functionality.

Unfortunately, unlike Ethernet, the CAN networking solutions seem to be overpriced and oriented on industrial shoppers buying in bulk. Way out of our price range.

Update:

I've decided to go with CAT3 hardware (cables, jacks and plugs). It is not optimal, but all parts usually have rating clearly indicated and there is no need in guesswork.


texts: Common Base Amplifier - Hybrid-Pi vs. T Model

texts:
I have a common base amplifier with a source resistance and a load resistor.  I am trying to solve for the system gain including the source resistor with both the hybrid-pi and T model but seem to be getting different answers.

When solving the hybrid-pi model for Vbe by looking at the currents at the emitter I end up with an extra gm term due to the voltage controlled current source.  I do not get this term when I solve for the same circuit with the T-model.  Any help?  Its probably something simple I am missing.


texts:
I have worked with PIC16 and PIC18s for over three years now and would like to get to know AVR as well. I have no specific project in mind, but would like to try around with the different architectures. I'd like to get a compatibility report on PIC and AVR.

uC's software
I am familiar with Assembly and C for PIC16 and PIC18. How do the Assembly and C variants for AVR microcontrollers vary from the PIC variants? Are there a lot differences?

PC's software
What software would I need to compile and assemble my programs for AVR chips? Is it free and where can I download it?

Programming hardware
I've used VOTI's Wisp648 to program PICs, but that board can't program AVRs. Do I have to buy a programmer or are there any circuits available on the web that I can build myself?

uC's hardware
For PICs, I have used the PIC18F4620 a lot. I'm looking for an AVR with similar features. The features I like are:

Internal Oscillator
Timers
5V and 3.3V version
ADC
MSSP with I2C and SPI support
(E)USART
PWM
Much I/O pins
>= 32kB program memory, >= 2kB RAM
DIP package

What AVR chip would have the same features? The package is a deal breaker, I really want DIP, PDIP or SPDIP. What would an AVR with comparable features be?

SPI and I2C variants
I was told that Microchip has its own variants on the SPI and I2C protocol. I often use SPI and I2C slave devices from microchip in combination with a PIC. Would I be able to use these chips (23K256, RTC, ENC28J60, ...), in combination with an AVR? In addition to that, would it be possible to link an AVR and a PIC chip using I2C or SPI?


texts: FPGA/SoC - System Architecture: Independent Block Enables/Resets

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For low power design, clock enables can be used to turn off a block, thus reducing dynamic power. For example, if raw ADC data is being obtained and not FFT processed data, then that FFT module could be shut down using the clock enable.

My question is this:

Does anyone have any resources (papers, white papers, app notes) that discuss separate block resets, where those resets are (a) secondary to the global reset and (b) are tied to a uProc's register map? Is this even good design practice?
The design intent would be for run-time debug. Let's say we have a FIFO filled with data that is being transferred to uProc working memory via DMA. Now, if the DMA engine flags up that it has an issue, it would be useful to reset the DMA engine separately to the FIFO. Obviously global reset would reset everything including the FIFO and the uProc, meaning the data and processor status that was obtained during the fault is lost.
For a uProc controlled FPGA design (SoC), there may be SPI/I2C peripherals, there may be DMA engines, memory banks, Ethernet controllers, DSP IP cores etc. If there was an issue with an SPI controller for example, I want to be able to reset this without a full global reset.

Has anyone seen any white papers or application notes for this strategy?

Many thanks.


texts:
I am developing an IoT product for a company.

The product runs off of two alkaline batteries at a max of 3.2V. It is fully enclosed in a solid plastic case, with small panel openings for a switch and LED. It broadcasts cellular data.

I will test until the case is able to contain a short on the batteries without damaging/excessively heating its surroundings. This is the worst-case fault I can imagine for the product, under any normal conditions.

If the company and I are satisfied that the product is safe, does it need certification to be deployed to a customer's house unattended? My region is Ontario, Canada. If it needs certification, what is the lowest cost that could be expected?


texts: Is there such a thing as ground "quality"?

texts:
I recently bought a surge-protected outlet which has a light showing when it is not grounded.
At my appartment the light indicating "not grounded" is always on, but when I tested it at work (where I'm certain the very expensive hardware is grounded) it wasn't on.
I had a professionnal come and check my electrical installation at home and he told me that everything was grounded. As for the discrepancy between home and work, he told me that the ground at work was of "better quality".

Does that mean anything? and if it does what does it mean (to a layman)?

Edit: This is in France.


texts:
I want to switch AC load by LBA110 because it has NC switch pole and tiny side. I tried to read datasheet, but with my bad knowledge about electric, I can not find out how to make it work. Is it work with 3.3v from output pin of esp8266? Datasheet not provide clearly information about input voltage, it give max on resistance is 35 Ohm and current max is 50mA, is it mean max voltage is 1,75V and normally working voltage is 1 - 1.2v, 20 - 30mA? I read some informations from Mouser here that say

Input Current: 50 mA
Output Type: MOSFET
Package / Case: DIP-8
Series: LBA110
Packaging: Tube
Contact Form: SPST (1 Form A), SPST (1 Form B)
Input Voltage: 5 V

So my question: is this IC working like another Opto, connect esp pin -> resistor -> LBA110 input pin -> esp's GND? If not, please help me a solution.

Thanks

Here datasheet of LBA110 LBA 110 Datasheet


texts: Idealized characteristic of power transistors

texts:
The idealized BJT characteristic it's represented as:

Meaning that the transistor  is able to conduct current from + to - when is turned on, and when is off it will block positive voltages. I found the same images in both books, Fundamentals of Power Electronics by Robert Erickson, and in Power Electronics by Need Mohan.

In the case of Mosfet transistors,  Mohan's book  shows this characteristic:

Same behavior as the BJT.

But in the book  of Robert Erickson this image is shown:

Meaning that Mosfet is able to conduct current positive and negative currents. Drain to source and Source to Drain. Why this discrepancy in the behavior of the Mosfet?

And also why is not shown the behavior for negative voltages? Can't those transistors allow negative voltages when are off?


texts: BS170 Mosfet equivalent for PWM application

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I'm currently using a Mosfet BS170 to drive LEDs from a 3.3V 1Khz PWM output.
The problem is I would like to use more current (something around 2A max at 12V Max) than the 500mA allowed by the BS170. Which Mosfet could I use ?

There is tons of models available, and I must admit I'm pretty confused by all the specs.
But if I understand well, I should choose one with a Max Gate Threshold Voltage below 3.3V am I right ?

Something like.

(max of 2.35V)

Or should I use a cheaper one, like.
(max of 4V) and use another mosfet (BS170/2N7000) and connect it to the gate of the power mosfet in order to reach the requested 4V?


texts: Adding DC offset control to a function generator

texts:
I recently bought the following small hand-held function generator: http://www.velleman.co.uk/contents/en-uk/p371_hpg1.html

But unfortunately it doesn't have a DC offset control. What is the easy way to add a DC offset control (for example from -10V to +10V range) at the output of this function generator? How to implement it?


texts: Noisy rising and falling edges at the output of a schmitt trigger circuit

texts:
I wanted to replicate a comparator circuit to PCB and I later noticed that I mistakenly swapped the inverting and non-inverting inputs. The comparator used is LM2903. Surprisingly the board was still outputting normal besides with a lot of noise in rising and falling edges. The complete initial working circuit on a euroboard is as shown in below schematics:

To make the question more clear I simplified the original board as following:

And here its plots you can see hysteresis as well:

So after that I replicated the board on a PCB but unfortunately swapped the inputs pin numbers 2 and 3.
So below when the board is on PCB with swapped inputs:

And here its plots:

The thing is the above LTspice simulations do not show big differences. But for the PCB version(inputs swapped version) when I check the rising and falling edges with a scope I see something like in below hand drawn plot:

It is like some oscillation is superimposed only during rising and falling edges.

Should I definitely swap back the inputs? Can the nosiy rising and falling edges be the result of such swapped inputs?

Edit:

I swapped back to the original one and the issue disparaged.
It was not easy to do on the PCB though it look ugly:


texts: Using PWM output from ATMega to provide external clock to external 3.3V device

texts:
I am creating an ultrasound time of flight system and am currently in the testing phase. I am using a TDC1000-TDC7200EVM board from TI for testing.

Currently, I have a 40 kHz ultrasonic transducer. My test board comes with a 8 MHz clock preinstalled. Given the divider values available (powers of 2), the closest output frequency I can get for the transducer is 31.25 kHz.

My idea is to use the PWM output from ATmega chip on an Arduino to generate an external clock source for the TDC board. I can generate 2.67 MHz PWM, then the TI board can divide that by 64 to get 41.7 kHz output.

My question is: How can I connect the PWM to the TI boards external clock pin?

Since the ATMega operates at 5V and the TI chips are 3.3V, I tried using a voltage divider to get a 3.3V PWM signal. However, this behaves in an unexpected way. I am using 330kΩ and 680kΩ in series. After the 330 kΩ resistor, by signal drops to ~30 mV peak-peak.

If I use smaller resistors, 3.3 kΩ and 6.8 kΩ, I get ~640 mV peak-peak, but the signal looks like a triangle wave instead of square wave.


texts:
I have this problem and I'm wondering if using the Supermesh method is the right way to go?
When assigning how the currents are flowing they should be clockwise, but how should I think when the current is flowing the other way?

Could someone lead me into the right direction?

Thank you!


texts: Reverse recovery method for carrier lifetime measurement

texts:
I have used reverse recovery method for measurement of carrier lifetime. I have used a simple setup consisting of a function generator, a resistance and DUT

(design under test). In a conventional transient response, there is a constant current phase and a recovery phase and effective carrier lifetime can be determined from

these equations in this link.

But transient response which I have measured, has not constant current phase and after switching, begins decaying to reverse saturation current.

My question is, why there is not constant current phase in transient response? Is it related to If/Ir ratio? Is there any consideration about If/Ir ratio in reverse recovery method?
Thank you.


texts: Will the schematic I created for my project work?

texts:
Edit: I made it and it works like a charm :D . Only had to connect the switch -ve to the -ve lane and the switch +ve to the +ve lane (not shown in schematic!!) and the circuit works like a chram. I also found that removing the resistors connected to the LEDs helps by makeing them glow brighter. I guess the ICs take the voltage down a fair bit)
thank you all for helping!
This is my physics project for this term, and I want to know if my schematic would work.

However, I'd like to supply a little background first - I'm an 11th grader who doesn't know much about circuits, and definitely nothing about ICs (our sessions start in April and we have a summer break in MAY so, we haven't covered electricity as part of our syllabus.) I decided to do my project on logic gates, despite it really being a 12th grade topic, and I need a little help putting together the demonstration. This also says I won't understand any fancy terms you might throw my way. Im familiar with BASIC circuits and Ohm's law and a few of the relations (that don't really matter here) but I don't know network theorems and so on.

I've failed 3 times so this time, I'm planning properly, with a proper schematic. I haven't yet put any of it together, since I don't want to screw it up - it's really hard de-soldering a board. I somehow managed once, don't wan't to go through the hell again. Here is an inventory of all I have at my disposal. I really can't get anything else, unless its really cheap, it takes me forever to get to the shop and I have a lot of tests coming up.

A soldering iron
Solder
Soldering flux
Several 100ohm resistors (about 15, I think)
Several LEDs (again around 10)
One 9V battery
One 6V (4 AA's in series) battery
ICs (NOT, AND, OR, NOR, XOR, XNOR, NAND, NOT) and their datasheets.
A "multipurpose" IC board (a protoboard?)
Wire (NOT insulated, the insulated stuff is just TOO thick for the circuit)
IC sockets (so I can make basic circuits and change the IC in just their holders to demonstrate different ones without having to make a lot of circuits, only the minimum 3 as all gates except NOT and NOR have the same input and output pins)
2x 3-state switches (logic 1, logic 0 and off). Model - 25139 NAB

As stated above, I have to make this work with only this stuff.

So here is the schematic, and it has one question and I think all of the necessary data.

All I need to do is show the output (but the glowing or not glowing LEDs) depending on the A and B input.

If the photo isn't visible, here is a better one.
EDIT #1: at any given point of time, only ONE logic gate will be plugged in.
EDIT #2: The schematic will feature a wire running from the switch to the ground(battery -ve).(Not shown in current schematic)


texts: Same z transformed function, but different answers of inverse z transform?

texts:
Given z transformed function is
E(z)=1/(z+4)

I know there are several ways to get the inverse z transform of this function.

use partial fraction

E(z)=1/(z+4)

E(z)/z=1/z(z+4) apply partial fraction here,

E(z)/z=(1/4)*((1/z)-(1/(z+4)) so E(z) is,

E(z)=(1/4)*(1-(z/(z+4)) as you know, it is easy to use inverse z transform here.

e(k)=(1/4)*(delta(k)-(-4)^k)

inversion formula method

E(z) has simple pole at z=-4, the residue is evaluated as

{(residue)|z=-4} = {(z+4)*E(z)*z^(k-1)|z=-4

             = {1*z^(k-1)|z=-4}

             = (-4)^(k-1)

             = -(1/4)*(-4)^k

The problem is that inverse z transform of the same function E(z)

has 2 different answers. As you see, there is no delta function when I used

inversion formula method.

At first, I thought it was because a simple pole,z=-4, is outside of the unit

circle, but same things happen when I used a simple which is inside of the unit circle.

Why does this difference happen?

What is the real answer?


texts: (Electrical Misconduct) Two phases connected as three

texts:
I'm trying to be brief as best as I can, There are only two phases working (Red & Yellow), so the electrician shared Yellow phase between two terminals (as seen in the image), and of course will make 380v potential difference with the red phase, so my question is what happens if we connected a motor or a 3 phase tool to the 380 V plug? Feel free to share your opinion upon anything about the post.
Thanks.


texts: How much input voltage is required to get 12V from an LM2596?

texts:
I am trying to run a WiFi router from a 12V lead acid UPS battery.

To get a stable 12V output from the battery I used an LM2596.

The problem is that the output is always 8.28V-8.50V. No matter how many times I spin the potentiometer the output is 8.28V.

Is this a wrong approach to get stable 12V DC from a 12V lead acid battery?


texts:
Vcc=5V, Vin= a noisy input voltag
I'm designing a non-inverting schmitt trigger using voltage divider. As shown from the image, I designed it on LTSpice and I got the desired results but from the waveform, however, I'm only seeing one threshold which is my reference voltage at 2.143V. I thought for a schmitt trigger it generate two threshold values? Is there something wrong with this circuit?

I'm having trouble analyzing this waveform. Vreference is the threshold, how come I don't see two of them where there should be a high threshold and a low threshold.


texts:
An analog input card can convert a -10V to +10V signal into a digital value of 0-27648.
What is the digital value if the input signal is 0V?
digital output = (2^N * analog input voltage) / (reference voltage)
Will this formula work for this application?


texts: How to light LEDs with Arduino without having any resistors

texts:
I've got a silly situation. I have an Arduino board (2009). There's just one inbuilt LED but can't do much with it beyond blinking. I have five LEDs (3 yellow, 2 green), breadboards, jumper wires but not resistors. (And there is a total lockdown here) I wish to play with these LEDs but can't risk it putting it directly. I tried using them in series but that did not light them up.
I know each LED needs a 330ohm resistor but that I don't have. I even have a 2x 7 segment display too but the same problem.
Any way to use them?
Thanks.
Update:
On suggestions, we have got two resistors from a faulty solder gun (blue-grey-orange-gold = 68k) and a (brown-black-brown-gold = 100) and 1 IN4000 diode.


texts: Why doesn't Graphic LCD (128x64) automatically changes line

texts: I am using a 128x64 graphic LCD (Model: JHD12864E) for my college project. I want to print a sentence. But the problem is that it automatically increases the 'Y' value and once it reaches the value 64 (in the selected display chip) it resets it to 0 (zero) and overlaps whatever I have written there before. Is there any way to ensure that it doesn't overlap and breaks the line automatically? Can I read the current values of x,y and z?


texts:
So I am looking for a way to switch three signal lines between 1 source and another, the idea being I want to switch a MIDI Port on my device between thru and out modes, but also can't have any delay in the line when in one mode or the other. I have been looking at using some low voltage relays (My device is Arduino Based) as no part of the design is higher than 5v, however I am now looking to see if there is a better solution, specifically, less space consuming (For a pocket device) and that can stand many switches over a long period of time without a potential failure. Any ideas?

EDIT

Hi again, sorry for the confusion. Hopefully this edit will explain it all a bit better.

End Goal

The end goal is for my device to sit in a theatrical show control system and show me the status of the show control system, which will be running MIDI Show Control, basically a specification build on top of MIDI to tell lights, pyro and automation what to do, or what the time into the show is (MIDI Timecode), and the device (Lighting Controller for example) decides what to do. When I press a button, it stops the control system from passing messages to my device so that I can do things separate to the show as a whole.

Control Lines Info

So, when I say three signal lines I mean that in MIDI there are three lines:

Positive (The actual signal, +5v or 0v)
Negative
Shield

When in 'Mode 1', my device will pass all of these lines thru the device onto devices further down the chain. When in 'Mode 2', my device will be the terminating device for those lines and will instead pass a second set of those lines from its self. The idea being that when in 'Mode 2', my device stops signals and can send its own. I have attached a schematic below to show this idea.

Orange arrows are control signals from the original device (Device 1). In Mode 1, these must pass through the device with no delay (I will explain that in a moment), my device will see them but that is all. In Mode 2, these signals stop at my device and I will make new signals to continue onto device 2 (Blue arrows).

simulate this circuit – Schematic created using CircuitLab

No Delay

What I mean by no delay is that there can be no real world delay introduced by my device. As this device is part of a show control system, timings are very important. The system may for example trigger two cues, 0.1s apart, so while I understand that electronics add some delay, it needs to be minimal. This is also because the device may be removed (For example, once I have finished programming the show).

Hope this makes a bit more sense than the first post that was a bit rushed.


texts: Circuit to measure current in high voltage, high frequency transformer

texts:
Next it is a simplified circuit diagram for high frequency transformer (50 kHz) which supplies a cathode-ray tube:

Colored parts are intended to measure load current by ADC of microcontroller; magnitude of load current is around 3mA (maximum).
As electronic hobbyist I am familiar with some blocks, but I am lacking knowledge about diode circuits, so these are my questions:

Blue block. C55 stabilize signal and Z5 protect ADC input from over voltage. Right?
Red block. R55 and R4 make a voltage divider but, What is the function of diode D4?
Green block. I do not really understand at all function of these components. I am familiar with zener diodes used as voltage reference or clamp element but this way of connection is new for me.
Yellow block. R1, R2 and R3 form a voltage divider. Right?

Schematics and values were obtained from a very old design. I will simplify circuit merging some components. I have already run some simulations in Proteus changing RL value, and ADC-MCU probe always shows same value (~2.82V).
If anybody has expertise in this type of circuits I will appreciate the help and guidance in this topic, or if there is any suggestion to measure load current it will be welcome. My biggest doubt is how is it possible this circuit works? I had have a hard time looking information on internet and I have found nothing similar to points me in the right direction.


texts: Is it possible to use a non-Leonardo board to act as a keyboard or other device?

texts:
I have been seeing lots of reports about the brand new Leonardo and it's capabilities, cheapness, and most popular, it's USB features. However, I look down at the ol' Arduino Uno and sigh. I don't mind not having the new features besides the USB reprogrammibility. I have read reports that there are ways to do this on the Uno, but they never said how. Someone else hinted that the ICSP headers for the USB port could reprogram the TX/RX to USB chip somehow. So how do I do this if this is possible?

Edit: Please don't have any posts that I have to solder anything to my board because I don't like modifying my boards; I don't know why, but I mostly don't like the unprofessional look of some SMD and some through hole parts and I don't want to resolder anything every time I want to do a different project, etc.


texts: Torque Ripple for PMSM with sinusoidal flux for 1-SPP and 2-SPP machine

texts:
Conditions:

Machine 1: 3-phase 1SPP (6-slots)
Machine 2: 3-phase-2-spp(12-slots)
Rotor flux: Sinusoidal shape

Questions:

For any given pole-arc of the magnet of the rotor, which machine has low torque ripple (Cogging torque)?
Does this behavior is also the same for other pole-arc angles?
Keeping other parameters the same, do 2-SPP machines ALWAYS have less Torque-Ripple (Cogging torque) as compared to the 1-SPP machine?

If possible, kindly point me towards some relevant material/research papers.


texts: Select Phase Detector Cutoff Frequency? Phase Locked Loop FM Demodulation

texts:
I'm studying a Phase Locked Loop used for FM demodulation, obviously a phase detector is used in the system.

A basic implementation of a phase detector is a multiplier followed by a lowpass filter. I am a bit confused on how to select the cutoff frequency of this lowpass filter.

I know that the multiplication of the two signals will produce two signal components:

1) A component where the carrier frequency has been doubled.

2) A component where the carrier frequency has been eliminated. This produces a "phase error" component.

I know that the purpose of the lowpass filter is to isolate the "phase error" component but I am confused at what frequencies the "phase error" contains.

I'll setup an example with relatively simple numbers to illustrate my confusion:

Carrier Frequency : 1MHz

Peak Frequency Deviation : 75kHz (I believe this is common for U.S. radio stations?)

Max Frequency of Original Unmodulated Message : 25kHz

FM Modulation Transmission Bandwidth : Carsons Rule: 2*(peak frequency deviation) + 2*(Max message frequency) = 200kHz

This would mean that the incoming modulated signal would have a frequency range from 800kHz to 1200kHz. This means that after the multiplier in the phase detector, the double frequency component would change to a range of 1600kHz to 2400kHz. In this case, would I select the cutoff frequency of the lowpass filter to be below 1600kHz so as to eliminate these higher frequencies?

Or is it that without the carrier frequency, the remaining frequencies are centered around 200kHz so that the "phase error" component contains frequencies from 0Hz to 400kHz? This would be because the frequency needs to be able to deviate 200kHz +- from the center point as this is the transmission bandwidth? In this case the cutoff frequency would be ~400kHz.

Or at this point in the phase locked loop, would the message already be demodulated so that the maximum cutoff frequency would be near 25kHz?

I suppose my confusion is rooted in what frequencies remain in the "phase error" component that has the carrier frequency removed.

edit:

So I'm still a bit confused on the lowpass behavior of the loop as referred to in an answer below. I understand that the integrator has a laplace transformation of 1/s but when I actually find the loop transfer function it appears to have high pass behavior instead. Below is a photo of what I mean.

To me this looks like a high pass behavior?

edit2:

Confusion lied in that I was viewing the system from an output/input relationship rather than an input/output relationship in which the lowpass behavior is indeed present.


texts: How Does One Handle Heat Dissipation in a TO92 Package?

texts:
I've experimented with LM7805 analogs from NTE (the NTE960), and the large tab on top makes it obvious how to dissipate generated heat.

However, NTE also makes an LM7805 analog in a TO92 package (the NTE950). I'm a sometimes hobbyist, and I don't really know how one goes about handling the heat when inputting, say, 7 volts to such a packaged chip. Can someone point me to a good discussion or tutorial on this topic? Thanks.


texts: just had an Arduino UNO bootloader replacement. Computer still won't recognize it

texts:
Before I get any thumb-downs, I would like to mention that I have read all the questions posted regarding the issue I have, but none of them had a working answer to my problem.
Here's my problem:
I have recently plugged in an DC motor directly to my Arduino UNO, and it resulted in the atmega328p being completely fried. So, I went ahead and purchased a new ATMEGA328P-PU and replaced it with the toast one. The computer, however, still won't recognize my chip.
My questions are:
Why is my microcontroller not being recognized?
Is there a chance that what I've done have completely fried the microcontroller, not only the bootloader?

Things I have tried/observed:
I have noticed that the new bootloader blinks the 'L' LED. My assumption here is that the bootloader comes pre-compiled with the 'Blink' project.
I own 7 computers (with the three major OSs on them). None of my computers was able to recognize the microcontroller (so at least now I know it's not an issue with the USB connection).

I am considering buying a new Arduino UNO, but before I do so, I really need to know what exactly is wrong with this one, just to avoid encountering similar issues in the future.

I know I'm desperate and slightly out of options when I end up posting on stackoverflow. So, I'd highly appreciate any contribution to solve my problem.