texts: Replace capacitor with open circuit or short circuit?

texts: We have this circuit,  where potential difference between capacitor plates is zero, and no current flow through it too. So I want to draw a simplified version of this circuit where is composed of just resistors and eliminate capacitor. Now I wonder whether I should replace capacitor  with open circuit or short circuit?


texts: Must this switch be turned on and off periodically?

texts:
Imagine that the AC1-2 is 170VAC at 150kHz~.

I simply want to turn the MOSFETs on, and let the AC flow through a inductive-capacitive load.

1) If I can turn the MOSFETs on to saturation by applying a control voltage, is it okay just to leave them in saturation for however long I want to have the load active?

2) If I cannot turn the MOSFETs on to saturation by applying a control voltage, is it okay to use a bootstrap setup switching at the same frequency as the AC flowing through AC1-2 for however long I want to have the load active?

3) If all of this ends up being kind of shitty, what would you recommend I do? I kind of just want to have something that can pass 150kHz 170VAC as if it was a 'wire' i could 'turn on'. It's all just to add capacitance to a high voltage inductor.

At this point, any help would be appreciated, and I hope I've been clear.


texts: What kind of RS232 protocol uses just pin 2 and 4 on a DB-9 connector. This is what is sent from a Tenma model 72-6870 Digital Multimeter.

texts:
I have several Tenma model 72-6870 DMMs in our physics lab that use a 2 wire data transfer set up. Does anyone have any information that could leed me to understanding this type of data protocol?
Also, is there any information on the 5 wire Tenma model 72-7755 DMM RS232 Protocol that anyone could share with me? This meter interfaces with a computer via the RS232 connector on a PC. Software is supplied by Tenma to log readings from the DMM.
My problem is "how to interface the latter 72-7755 DMM to our 4 1/2 digital  display units that have been working with former 72-6870 DMM"


texts: why there is a need to define temporary reg and only then assign to the output in verilog?

texts:
Following is the Verilog code for a 4-bit unsigned up counter with asynchronous clear as shown in ASIC.CO.IN:
module counter (clk, clr, q);
input        clk, clr;
output [3:0] q;
reg    [3:0] tmp;
always @(posedge clk or posedge clr)
begin
   if (clr)
      tmp <= 4’b0000;
   else
      tmp <= tmp + 1’b1;
end
   assign q = tmp;
endmodule

Can I define the output as reg and write the verilog as following?:
module counter (clk, clr, q);
input        clk, clr;
output [3:0] q;
reg    [3:0] q;
always @(posedge clk or posedge clr)
begin
   if (clr)
      q<= 4’b0000;
   else
      q<= q+ 1’b1;
end

endmodule

As I see this, there is no difference between those two codes, am I wrong?


texts: SC18IM700 operation (RS485 to UART to I2C)

texts:
I need to create a circuit to talk to a piece of equipment using the I2C bus.  I'm on a PC that has an NI serial card with RS485 ports(I'm not sure of the model number off the top of my head).  I found the NXP SC18IM700 IC that seems like it would be perfect for my application, but I can't seem to get it communicating properly.  I started out using the PC's RS232 port as the UART connection to the SC18IM700, but the voltage levels on the RS232 are very high at around 12.5V, and the SC18IM700 seems to only accept inputs up to 5V.
I think I found a way around that problem for the moment using a USB FTDI cable, but I can't use USB in my final project.  I'm also still having an issue with proper communication using the FTDI cable.  What I found is that using the default baud rate of 9600 I would receive a framing error when trying to just read the "OK" message the SC18IM700 outputs when it is powered on/reset.  I fixed that by lowering the baud rate of my serial port to something less than 9300, so now I'm getting the OK message with no problem.
However, now I'm unable to send/receive messages to the I2C bus.  I'm using a circuit setup provided by NXP to test the operation of the SC18IM700 to control some LED's using the AN10397 document.  I've set up the circuit exactly as described, and am using the commands as written, as well as sending the entire command in HEX values, but I can't seem to get any 2 way communication.  I can see on my oscilloscope that when I send a message to the SC18IM700 that the I2C clock and I2C data line have some reaction, but I'm not sure what messages are being sent across the I2C line.  I'm unsure how to proceed on this right now though.  What I'm thinking right now is that I need to bring the logic levels down on the UART side to something less than 5V.  I believe I can use the MAX3062 to convert RS485 to RS232, then use the MAX3232 to level shift the RS232 to <5V, which should provide the proper communications.  My problem is that even with the proper logic levels on the UART, the SC18IM700 is still not providing that bi-directional communication with the I2C bus.
I know this is a long read, I've tried to be as descriptive as possible.  Has anyone conquered this problem before?  Anyone have any experience with the SC18IM700 IC?  It's pretty frustrating as it seems from the data sheet of the SC18IM700 that it really should just be plug and play.
EDIT (SCHEMATIC CLARIFICATION):
I believe the circuit schematic is shown in the AN10397 application note that I linked to.  It's a simple circuit though.  The Vdd on both chips are set to 3.6V on the same bus.  Each has a 0.1uF cap between Vdd and Vss.  Vss is tied directly to GND.  WAKEUP! has a 1k resistor to Vdd.  The SCL/SDA lines are connected to the same pin on each chip with a 4.7k resistor pulling each line to Vdd.  the RESET! pins on each chip are connected together and have a 100k resistor pulling up to Vdd.  Tx/Rx and GND from the FTDI cable are connected to Rx/Tx and Vss on the SC18IM700.  All GPIO on the SC18IM700 are left floating.  The Vdd on the FTDI cable is left unconnected.  The 3 address pins on the LED Driver chip are tied to Vss/GND.  The LED anodes are tied to Pins 5-12, with a 200ohm resistor to Vdd.
I have the communication working now.  I don't know what the problem was, but it did start working, albeit still at 9300 baud (I also have several IC's on hand to use and abuse.  I probably did ruin the first chip with the 12V RS232).  I'd like to change the baud, or at least verify the register settings on the chip for baud rate, but I can't figure out the equation they give to set the values of the BGR0 and BGR1 registers.  The equation used is:
Baud Rate = 7,372,800 / [16 + (BRG1 , BRG0)
The default values in the registers from the data sheet, and verified by my own reads of those registers, are BRG0 = 02 (02h) & BRG1 = 240 (or F0h).  I can't for the life of me figure out how 240 and 02 equate to 9600 baud.  If (BRG1,BRG0) = 752, then it works to set the baud to 9600, but how does (240,02) equat to 752?


texts: Producing AC excitation current from microcontroller

texts:
See the current transformer below. Primary to secondary turns ratio is 1000:1, and Test winding to secondary turns ratio is 1:1. The burden resistor across the secondary is 10 ohms. I'm trying to produce a 60Hz AC current for the test winding. This winding is only used when one wants to test the proper functioning of the secondary circuit. The resistance of both the test and secondary winding is 80 ohms.

As the ratio between test and secondary winding is 1:1, I would happy producing just 1 mA current. But I'm not sure how to do this from a 3.3V microcontroller.

The idea I have is to generate a square wave from the micro, and feed that to an amplifier as shown below. I think I don't need that amplifier though, because I only need 1 mA. The switch S4 is an analog switch to open the test winding when not testing. C8 is the coupling cap, and L3 would limit the current provided that it has higher impedance than the test coil.

Do you think this approach is okay? Can it be simplified by removing the amplifier? How do I choose the components to ensure 1 mA through the test coil?


texts: Questions on acquiring signals in Peak Detect mode in an oscilloscope

texts:
I just learned that one must set the Acquire feature of a scope to "Peak Detect" to see the possible glitches of pulses.

But in the following document it also mentions that:

"This mode is effective when at the horizontal scale setting of 5 ms/division or slower." Here is the source:
http://www.tek.com/manual-topic/acquire

How reliable is this information?
Do one really needs to set the horizontal scale to 5 ms/division or more to make use of the peak detect mode? Why is that?


texts:
I am a beginner hobbyist, trying to understand a circuit from an old Radio Shack electronic snap kits game (the game variant I have is "electronics 303", and the circuit is project #202 : Oscillator 0.5 - 30Hz, in case you ever owned a copy).
When I build the circuit, the LED does indeed blink once every 2 seconds or so for a certain potentiometer setting. However, I can't see any oscillation when I try to simulate it: I used ngspice, my own simulator, as well as the variant from this website. To be fair, I don't know all the simulator parameters for the transistors and LED involved, so I used a lot of defaults. In the game I have, the transistors were 8050 and 8055 (I don't know about the LED), but most posts I've read suggested that the exact values for the parameters shouldn't matter.
Does anyone know:

How to estimate the oscillation frequency? (that is, without building the circuit and doing measurements, hopefully using only pen and paper, if possible)

Why is it oscillating? (I tried a very simplistic analysis, using the linear approximation of the transistor equations, but -maybe a made a mistake? - the capacitor C2 seems to be charging all the time)

Why aren't the simulators showing any oscillation? Are their models too simplistic? Does it only oscillate for very specific transistors/diode?

simulate this circuit – Schematic created using CircuitLab


texts: LED circuit stopped working when expanded

texts:
I built a small prototype as shown in my diagram with the Si926 n-FET, 250 ohm pull up resistor. In my prototype board I have only 4 channels connected (only two shown). Only one LED is ever turned on at a time. When I set 3 outputs off (ground) and only 1 on, the FET turns on and I am able to supply current close to my max of 100mA for specific LEDs. I can do this for any of 4 channels, one at a time with the other channels off.  However, I had a pcb made with 32 channels, 32 FETS and 32 LEDs (only 16 pull ups) and 2 decoder chips.  Now my circuit behaves oddly.  If I turn on only one channel and others, as described, then slowly turn up the current source, the current supply drops out at 1ma.  Drop out, is when the current source detects an open circuit or extremely high impedance and subsequently disables its output.

NOTE: I am not using the PWM of max6964. The brightness of the LEDS is controlled by the current source. The constant current source is part of a design restriction. It is supplied by a constant current supply that is controlled elsewhere. It is a bench top current source. One source for all LEDs.

MAX6964 Data Sheet

Si926dl Data Sheet

Is it possible that having 32 of these output circuits is somehow effecting (lowering) the FET gate voltage with the decoder chip output low (ground) and thus causing the FET to not switch on?

Do I need a different pull up resistor? I wanted to keep it small so the voltage drop would be in the range of Vgs 1 to 2.5v.

Would changing the FET to Toshiba SSM6N43FU with Vgs 0.35v to 1V do the trick?
Toshiba SSM6N43FU


texts:
I know that measuring amperage in a circuit, makes sense when you have load, but what if you have an ic component?

I want to power supply operational amplifier LM741 (http://www.ti.com/lit/ds/symlink/lm741.pdf) from a Ni-Cd 9.6 V, 700mAh battery. Datasheet doesn't refer about input current, however it refers about overload protection. Am I ok with this?

Moreover, it refers Input Offset Current: 200 nA (Max). Is there a problem if I have greater current input?

I 'm in the beginning of figuring out datasheets and I want to be sure about my next steps.


texts: Is it possible to use a coil to create sustained displacement/preasure? without a permanent magnet?

texts:
So, as far as I understand, speakers are basically coils coupled with permanent magnets, then when a current is run through the coil it creates a magnetic field, pushing out against the permanent magnet, moving the diaphragm that's attached to the permanent magnet and creating sound waves.

What I'm interested in is using a coil to do something similar but instead create human perceivable pressure. For example, something to lightly but noticeably push against your finger at a constant rate (not something that constantly moves back and forth like a speaker diaphragm).

If I just make a small coil out of some magnet wire and hook it up to a battery, I think that the magnetic field created by the wire would create a constant pressure against the magnet with the current being proportional to displacement. Is this correct?

If that's right then my real question is if this is possible to do without using a permanent magnet? I know you can create an attractive force to metal with a coil but is there a way to create a repulsive force?


texts: Carry look ahead adder/subtractor & Overflow, Negative Bits

texts:
I am suppose to design a carry look ahead adder with ...

Input flag bits

E (Enable)
S (Subtraction)

Output

The usual sum & carry out
O (Overflow)
N (Negative)
Z (Zero)

But the question is vague ... It says if

E = 0, S = 1, do subtraction
E = 0, S = 0, do addition
then if E = 1? What do I do? What do usual circuits do? I suppose if 0 is enable, 1 is disable, then I put all outputs 0?
For overflow bit, I suppose the below, where \$C_{in}, C_{out}\$ are carry in/out of MSB/Sign Bit and \$S\$ is subtract bit. The 1st half checks if Cin is different from Cout (of MSB), when doing subtraction. And the 2nd half checks if theres a carry out when doing addition. Is my implementation correct?

For negative bit I also check if doing subtraction using \$S \cdot MSB\$?


texts:
I'm having a little confusion with a question on JFET amplifiers. This is the Q.

You are required to design an audio amplifier using an n-channel JFET which has a pinch off voltage of -16V and a saturation drain current of 32mA. Your design should meet the following criteria.

Self bias method must be used
Source is not bypassed by a source bypass capacitor
Bias voltage of the gate with respect to source terminal of JFET should be -4V
Peak-to-Peak AC voltage variation of 6V should be achieved on the drain terminal

Following components are available to make the audio amplifier

Drain resistance having a resistance of 200
20V DC supply
Variable resistor of 0-100 Ohms
1 M fixed resistor
Two coupling capacitors

a) Draw your circuit diagram with proper labeling of all components

b) Calculate the drain current.
$$I_D = I_{Dss} \left(1-\frac{V}{V_{GS}}\right)^2 $$
$$I_D = 32 \left(1-\frac{-4}{-16}\right)^2$$
This gives Drain current 18 mA.

c) Find the voltage across drain resistance
$$V = I_DR$$
$$V = 18 mA . 200 \Omega = 3.6 V$$

d) Find the resistance value that should be set in the variable resistance
$$V_{GS} + I_D R_v = 0$$
$$-V_{GS} = I_D R_v$$
$$-(-4V) = 18 mA. R_v$$
which gives 222.22 Ohms which is way above the given ratings of the variable resistor. Where did I go wrong?


texts: Find the transfer function and determine the type of this filter

texts:
I am learning basic circuits and I got stuck at this question:

This is what I got:
$$V_{o}=(\frac{sC_{1}V_{o}R_{2}+V_{o}-V_{in}}{R_{1}}-sC_{1}V_{o})\cdot \frac{-1}{sC_{2}}+sC_{1}V_{o}R_{2}+V_{o} $$
And this is how:
For the ideal op amp, V_+ = V_- = V_o, so I got the current passes through C_1, and R_2, hence got the voltage after R_1, and use this to form the formula above.
I kept checking but I don't see where I got wrong, but this seems too messy to be the answer. To get H(s), I need to divide it by V_in, and make it even messier. Could you give me some hints to get a simpler form to determine the type of this filter?
I know this is not a Helpdesk, I hope this could be an example for all who are studying the same thing. Thank!


texts: I'd like to know whether flame retardant epoxy resins, the FR-4 brominated type for instance, are used in the outer molding for integrated circuits or whether it's just a plain epoxy resin. Additionally, if anyone can direct me to any literature or textbooks that rigorously cover materials of construction for circuit boards I would greatly appreciate it!


texts: Can't seem to determine quadrature encoder resolution

texts:
I'm currently working on an autonomous terrain-mapping rover, and I've run into problems in the seemingly most straight-forward area: processing quadrature encoder data.

For any unfamiliar, a quadrature encoder is a rotary incremental encoder with 2 output channels which fire pulses 90 degrees out of sync. I.e. if ChnA's pulse leads ChnB's, you're moving forward and vice versa. And if you know the resolution of the encoder (pulses/revolution) you can easily determine the distance you've traveled.

I'm specifically using this encoder: http://www.lynxmotion.com/p-448-quadrature-motor-encoder-wcable.aspx

Now according to the encoder's specs, 400 pulses = 1 revolution.

Ok great! I'll just hook up ChnA to the input of a digital counter module, and preload the module to 400 less than its interrupt point, and every interrupt will be a rotation!

WRONG!

The wheel barely moves an eighth of a revolution.

Looking at the output of ChnA on my logic analyzer reveals that in one full rotation of the wheel, there are over 2400 pulses. I have no idea where that's coming from.

Does it have something to do with the gear ratio (it is attached to a motor shaft with a 30:1 gear ratio)? If that's what it was, it would be 400*30 which is way more pulses than I'm actually getting per rotation. Or am I missing some other glaringly obvious piece of information?

Thank you!


texts: Unknown TI microcontroller identification

texts:
80-pin QFP package, has JTAG, UART, connected LCD. Powered by 3V Li battery.
Package marking: 80AGL 10A2K.

Can't find anything similar on TI's site and google.


texts:
Background

I'm working on a fairly dense mixed PTH/SMD (plated through hole / surface mount) component PCB design. I'm using Eagle CAD for it for the schematic capture / layout and I'm using the auto-router function to route. It's a two-layer board, and I'm trying to keep all the SMD components on the same side of the board for ease of manufacture.

Experience

I usually place my components in what I think are sensible locations from a point of view of interface proximity, rotate QFP packages 45 degrees where it looks like it might be useful, set the routing grid to 1mil (i.e. the minimum?), set the DRC minimum trace width to the minimum allowed by my manufacturer, click Go, catch some shuteye and see how it turns out in the morning (or that it failed). There are a lot of settings in the auto-router and DRC that I frankly never mess with because I don't understand how they impact routability (is that a word?), which may contribute to my frustrations with it.

Question

I've used Eagle a lot at this point, and I'm very happy with it, but it often seems like a real challenge to get the auto-route to complete, and routability seems to be very sensitive to component placement. It will often times get up to 98+% routed and then give up. What are some rules of thumb / guidelines / advice for how to help the auto-router get the job done?


texts: Looking for microcontroller for computer project

texts:
I'm planing to build a small 80's "home computer" style computer, something with the following spec:s

8-12 Mhz
256 / 512 KB external memory
128 KB eprom
320 x 200 x 32 colors (VGA interface)
SD card for storage (cant find any tape hardware ;) )
I would prefer a development environment with a live debugger and fast rebuild process, for a stream lined development process.

I havnt found anything that matches this description, AVR is out, Zilog seem to be out since I cant find a reasonable development environ (as described above) and PIC was never an alternative (for the same reason as AVR)

So do you guys have any tips ?


texts: Silkscreen labels for components - what could Y?? be?

texts:
Components on PCBs are usually labelled using silkscreen markings and most of the markings seem to be quite intuitive:

C?? - capacitor
D?? - diode
FB?? - ferrite bead
J?? - jumper wire
L?? - inductor
LED?? - light emitting diode
Q?? - transistor
R?? - resistor
RJ?? - RJxx connectors
SW?? - switch
T?? - magnetics (ex. for RJ45 connectors)
TP?? - testpoint
U?? - packaged integrated circuit

What could be the component marked as 'Y??' be? Unfortunately the board where I have this marking does not have this place populated.

[Edit] Wikipedia has a page about reference designators.


texts: Effective time constant of an RC circuit

texts:
I have read in some books that to determine the equivalent time constant of charging of a capacitor in any RC circuit containing either only one capacitor and any number of resistors arranged in any way or any number of capacitors arranged in any way and one resistor, we follow the follow the following steps:

1)Short circuit all the batteries.

2)In case of many resistors, the product of equivalent resistance across the capacitor and the capacitance of the capacitor will give the time constant of the circuit.

3)In case of many capacitors, the product of equivalent capacitance across the resistance and the resistance of the resistor will give the equivanent time constant.

I have given a lot of thought on this but I am not able to figure out why that method works. Can someone please help? Can't this method be somehow extended to the general case containing any number of capacitors and resistors?


texts: How to use Voltage Supervisor and MOSFET to switch off ESP32 supply?

texts:
I am planning a solar project using following components:

Solar cells
18650 battery
TP4056
MCP1700-3302E
TC54VN2902EZB Voltage Supervisor
IRLZ44N
and an ESP32

I have only seen a block diagram for using the voltage supervisor and the IRLZ44N.  I want to protect the 18650 from discharge below the threshold of the voltage supervisor.
Any changes to ensure safe charging of 18650 battery?


texts:
I have a DC measuring digital voltmeter. The power for the voltmeter is coming out of a charging rectifier. The frequency out of the charging rectifier is anywhere between 20 and 60Hz. Operating voltage of the voltmeter is about 12V.

The voltmeter consumes max 30mA. What capacity is required for the decoupling capacitor to supply the voltmeter to continue working during power dropouts?


texts: Implementing a sine wave inverter with an oscillation circuit

texts:
I was thinking today about a whether it would be feasible to implement an inverter using a simple sine wave oscillator (perhaps op amp based or a Wien bridge implementation), a power amplifier stage and a step-up transformer. The more common simple circuits online use a 555 or a 4047 and as such the inverter has a square wave output as well.

However I'm sure I'm missing something here because an implementation would surely exist if it were plausible. So what are the limitations of using the the setup I mentioned earlier?

PS: I understand that buying an inverter would be more efficient and more cost effective. Just wondering if what I'm talking about would actually work at all.


texts:
I'm trying to build a full-bridge dc-dc converter, PWM signals are ok but drain-source waveform has some problems. Here is drain-source waveform with a proper pwm signal on gate.

Then I decided to add a C snubber(100nF) across drain-source and waveform turned into this:

Is the voltage waveform in 2.pic is acceptable? or do I need to make changes?
I'm very weak about snubbers, even I don't know which snubber to use or should I use a snubber? Or is there any other way to make this better?


texts: Avoid voltage drop on DC motor start-up with h-bridge

texts:
I'm trying to control a 12V DC brushed motor (4A with load ) with an H-bridge , TLE5205 datasheet ( 5A , 6A peak , 40V , integrated free-Wheeling diodes ), but when using a 3S1P lipo battery ( 11.1V , 3.5Ah , 25C ), on motor start-up , a voltage drop occour and the h-bridge automatically goes in Undervoltage lockout ( Vs < 6 Volts ), switching off the motor

Actually this is my test circuit ( the same of datasheet )

I tried both single 4700uF capacitor and two 4700uF in parallel

Using a 11V ni-mh battery everything works fine. So I guess it's related only on lipo batteries.

If the motor is connected directly to lipo battery , it runs without any problem.

How could I smooth voltage drop , and avoid the h-bridge to go in UVLO ?

I know the h-bridge is going in UVLO because I compared outputs ( which are in tristate ) and Vef with the error table in datasheet  :  IN1 = IN2 = 0V  , OUT1 = Vs/2 , OUT2 = Vs/2 , Vef = 0 ( Error flag circuit is not shown in the picture above )


texts: How to switch between a solar panel and battery?

texts: A 12v battery is being charged from a solar panel. When battery is 12v solar panel is disconnected from battery and connect the load with battery. And again solar panel is connected with battery when battery voltage is say 10v. How to switch simply? Which one is preferable, optocoupler or mosfet? and how they are interconnected for proper switching?


texts: Silk screen layer over pad resist cutouts on pcb

texts: I am designing a SMD PCB and have noticed that some component silk screen outlines extend over the pad resist cutouts. Is this acceptable? If the resist cutouts are made after the silkscreen process I can see this working.


texts: Output voltage of powerbank circuit is the same as the battery voltage

texts:
I'm trying to use this small (and awesome?) unit as a boost/step-up converter for my project. I need to give my ESP8266 12-E NodeMCU a 5v input from a 18650 battery. Since this powerbank already had 1x 18650 battery in it, I assumed doing this would be easy. I was wrong.

The circuit looks like this:

On the far right, you can see the micro USB input, which charges the battery (B+ and B-) at 4.2v. In the middle, you can see 4 solder pads. That is a regular female USB connector, which I desoldered.

Here's the weird issue: If I take my battery, which is at 3.8v at the moment, and I check the voltage on the USB in the middle (which would normally charge your phone), it will be at 3.8v as well.

Am I doing something wrong? Shouldn't it be 5v, so it would charge my other devices at 5v? You can see the complete unit here: https://imgur.com/a/7almr


texts: Splitting/y'ing a thermocouple amongst 2+ inputs

texts:
The system in question has just one type K thermocouple.

Is it a bad practice to Y a thermocouple into 2+ thermocouple inputs?

For example, Y a thermocouple into:

DAC thermocouple input card
Limit controller (for over temperature safe shutdown)

The temperatures I work at are between 0°C and 42°C, with a tolerance of +/- 0.1°C.

Y'ing Method

Using type K thermocouple extension wire
Soldering (63% Sn, 37% Pb) the two Y's together
Individually heat shrinking the connections afterwards, so they won't touch

I think this works because:

Solder beads are at the same atmospheric temperature as each other
Solder beads are at the same atmospheric temperature as the electronics
The solder beads aren't touching --> no thermocouple junction is formed there
The same dissimilar metal is used in each solder bead

From what I have read on thermocouples, this seems to indicate that it should be fine.

Assumptions

Cannot add more thermocouples or replace with dual element thermocouples
Do not want to replace control devices to work with temperature transmitter
If the thermocouple were a probe, it would be ungrounded

Possible Solutions

Just to address these two solutions (outside of the scope of this question) up front.

From How do you split a thermocouple signal?

Dual element thermocouple (only relevant if thermocouple is a probe)

Pros:

Doesn't rely on Y'ing small mV signal to several inputs

Cons:

Higher cost
Probably not readily available in your local factory
I have observed them to be more fragile in bending

Thermocouple transmitters

Pros:

Doesn't rely on Y'ing small mV signal to several inputs

Cons:

Added system cost/complexity
Usually requires swapping out pre-existing hardware as analogkid2digitalman did in this thread

**Edit**: Other Relevant Information

NTC to multiple inputs

  One or both controllers might not even have one end of the thermister
  connected to ground (or any other shareable reference node), further
  complicating matters.

  In other words, you need to know a lot about how both controllers work
  internally before you can consider how to get them to share a sensor.

As @KevinWhite brings up in the comments, knowing the internals of the input hardware is relevant, as grounding is an important parameter.


texts: Why is magnetic field not accounted for in the theory of CRO

texts:
I’m reading the chapter on Oscilloscopes in Cooper’s Electronic Instrumentation and Measurement Techniques.

Nowhere in the theory of the working of CRO (like deflection sensitivity) does he take into account the effect of magnetic field that should definitely be present due to rapidly changing very high voltages (~1000 V) applied on the vertical plates (~10 MHz or more).

But I’m aware that the speed of electrons in CRO is huge (~1/10th the speed of light). So even small magnetic fields should affect the motion greatly. (Magnetic force has a cross product of velocity and field.)

So why is neglecting it reasonable?


texts:
Atmel Studio started asking me this morning to repair itself:

After 15 minutes, the repair is done:

Running the application, it shows again the first image:

I've done this loop three times, so far. How can I exit this loop?

I use Windows 8.1.


texts:
I've been brushing up on my analog design, and have some questions regarding improving the design of a simple comparator. It's been a while since I got this deep into it. I'm trying to implement it based around a differential amplifier.

I've been experimenting with how the different parameters affect the output of the system. I realize I could improve the performance using FETs instead, however I want to do this exercise with BJTs for the added challenge. I do also realize that the ideal components here don't take into account real world variations between parts which would require other steps to correct. I'm using a norton equivalent for the non-ideal current source at the emitters. I chose the parallel resistance somewhat empirically.

I have a couple of questions to start with.

I'm wondering how I can best go about increasing the input impedance. Doing a darlington array seems like the most common solution for this, however that does degrade the input bandwidth, and requires a larger signal. Is this an unavoidable tradeoff or are there methods I can use to achieve higher input impedance without degrading frequency response?
I'm wondering how to manage the tradeoff between the emitter bias level, and the transition range (Not sure about the proper term for that). Sweeping a range from 0-40mA in 10mA steps, the output range increases, at the cost of a much larger input response being required to adequately drive the output to its full level. This plot is only showing the output of VOut2.

The 0mA and 10mA currents have fairly acceptable behavior. I know this is going to require some output conditioning to achieve a 0-VCC response, however I was wondering if there's anything else to be done with the differential amplifier that could improve this. I'm also considering adding in emitter degeneration resistors to see how that improves the input response.
In another experiment, I held IBias constant at 10mA, and swept the reference voltage from 0-5V in 1V increments. As the reference voltage increases the output signal at VOut2 winds up being compressed further and further until it practically vanishes. What can I do with the input signals before they reach the differential amplifier to help correct this behavior?
The output has when measuring between VOut2 and VOut1 is very nonlinear. This plot shows the output with the reference voltage stepped from 0-5V in 1V increments.  The nicer stepped behavior only occurs when the reference signal is up at 5V. I'm wondering how I can go about improving this. The book I have describes emitter degradation as one method for widening the linear range, but what I'm seeing in this plot just seems excessively bad. VOut2 shows much nicer behavior, for a comparator application should I just be using that alone? This plot shows VOut2 with VRef being stepped as before:

I'm working with Bipolar and MOS Analog Integrated Circuit Design by Alan Grebene, I would appreciate any other useful references I could look up.

Thanks!

EDIT: Plot of Q1 base current and collector current with swept reference levels:


texts: Is it good general practice to avoid powering components from the 5v pin on an arduino?

texts:
Most examples and tutorials have you power small components by connecting them to the 5v pin on the Arduino. As part of my learning process, I've messed up an arduino or two by not considering the amount of power a component would draw or by expecting that it would be drawing less power than it actually did.

Is it - in general - a good idea to be on the safe side and virtually never power any components from the 5v pin, instead using a separate 5v power supply (or at least, a separate line to the same power supply that is powering the arduino)? It seems to me that this way, you'd at least never ruin the arduino itself should you make a mistake, just the power supply (if it's not up to the task), although it might be overcomplicating things.

What are people's best practices in this regard?


texts: FOG Yaw Gyro, transformation to remove earths rotation based on attitude (roll,pitch,yaw,latitude)

texts:
I'm trying to use an accurate FOG gryo for tracking heading in a moving platform.  The FOG gyro has two rate errors, Faraday (fixed amount regardless of alignment to the earth) and the 15.04 degrees per hour of the earths rotation (function of my alligmnet to the rotation).

I know the attitude of the gyro ring..  Roll,Pitch,Yaw and Latitude,Longitude..  If the gyro is exactly aligned with the rotation I will see all of the 15.04 deg/hr superimposed, none of it if I'm perpendicular to the rotation.     Now I need mapping/function that will give me a number between -1 to 1 giving me the amount of the earths rotation imparted at a given roll,pitch and yaw on the surface of the earth..  Where roll=pitch=0 level with the surface, yaw=0 pointing true north.  The gyro (yaw axis) is mounted flat in the plane of the earth.

This will allow me to remove the Faraday drift (constant) and then calculate the amount of the earths rotation projected into this gyro at this roll,pitch, yaw, latitude.

Can someone help with this transformation or point me to a document that can help?


texts:
on the raspberry PI 3 computer IO boards datasheet it has on page 10 (first sheet) is has the option to connect jumper 13-14 to wake up the computer module by connecting global_en to run_pg
run_pg is high when awake and low when halted and pulling global_en low for >1ms wakes the compute module
on page 11(second sheet) it has the rtc setup to reset the module (this appears to reset even if awake)
im looking to be able to wake the module in two situations
periodically if halted and if external power returned when on battery power (separate battery management IC)

Would this circuit work for the RTC of is there a better way?

wake via RTC

simulate this circuit – Schematic created using CircuitLab

I think i need a IC/circuit that on a rising edge on Power_Good connects Global_en to RUN_PG for > 1ms, the circuit for the RTC should generate the low pulse but im not sure about rising edge detection
of the Power_Good signal from the regulator for external power


texts: How can one calculate Load Regulation for a temperature sensor?

texts:
I am wondering how to calculate the Load Regulation of a temperature sensor. For example ADI's TMP37?

I know how to calculate % Load Regulation from Wiki, but not sure how to get to the mC/uA units?

Thank you for your help.


texts: How does the ft2232h read/write work in cpu-style FIFO interface mode?

texts:
I'm thinking of making the following circuitry:
PC <-> Ft2232h <-> MCU
(I'm using the MCU just for an initial test to see if I can get the ft2232 working. An FPGA will be used later)

Have I understood the following read/write procedures correctly?
In order to read from the MCU to the PC:
 1. Set the pins (on my MCU) connected to D7-D0 (channel A or B), to the required logic level representing the data to be read.
 2. Set CS# = 0, A0 = 0.
 3. Toggle RD# from high to low and then high again.

In order to write to the MCU from the PC:
 1. Set CS# = 0, A0 = 0.
 2. Toggle WR# from high to low and then high again.
 3. Read from the pins (on my MCU) connected to D7-D0 (channel A or B)


texts: Is it dangerous to continue to remove a slightly punctured phone battery?

texts:
I have been trying to replace the phone screen on a Galaxy S7, and therefore had to remove the battery in the process. While doing so, I saw a tiny spark and felt a weird smell. I can't see any damage on the battery, but obviously it is no longer safe to use, and I am going to have to replace it, and dispose of the old battery properly. My problem is: the battery is still glued to my phone. Is it dangerous to continue to remove the battery now, or should I just trash the entire phone? If not; is it safe to use a heat gun to loosen up the glue?

Also; could it be dangerous to leave it on the kitchen table over night?
Should I wear gloves when doing this now?

I have looked for answers on the internet for over an hour now, but I still haven't found anything on removing an already damaged battery or the dangers of leaving it unattended.


texts:
What I already know is that they are used as a frequency generator when they are stimulated at their own resonance frequency.
But when I have to tune the applied voltage to that certain frequency, why can't I use this voltage directly. What's the crystal for?
I've already seen How does a Crystal work? but I think the question or at least the answers live more on a low level why I'd need a high level answer first to dive deeper.


texts: Op-Amp + MOSFET = Constant Current Power Source (?)

texts:
I'm trying to make my first circuit from Horowitz and Hill- a constant current source that sits above the load, and can (hopefully) source 1A.

I decided to use the components I had on hand- an LMP2231 as the op-amp, a p-channel MOSFET NDS356A as the switch, a 0.5 \$\Omega\$ resistor to act as the sense resistor, and a voltage divider that provides the reference for the Op-amp. I've attached a schematic that also has the component labels.

The problem is, when I connect a resistor from the MOSFET drain to ground, no current flows through the circuit. I'm not sure what I've done wrong here, but I am wondering if maybe it has to do with the Op-Amp not being able to pull the gate on the MOSFET? If this is the case, What are the criteria for matching an Op-amp with a mosfet so it will work?

simulate this circuit – Schematic created using CircuitLab

=========== EDITS ==========

EDIT: So in response to the well-thought out replies below I've gone and repicked some (all) of the components to get a circuit that looks like it will work:

selected an Op-Amp (AD8605) that has a maximum differential input voltage of 6V
altered the values of \$R_1\$, \$R_2\$, and \$R_3\$ such that the operating voltage is now 3 V @ 1 A
selected a MOSFET (STD26P3LLH6) that is rated to 20 W of power dissipation, and whose on-state characteristics are such that it would appear to be able to provide 1 A at \$I_d\$ for a \$V_{GS}\$ of 3V

I will order these components and report back, but am I missing anything? Any obvious gotchas?

simulate this circuit


texts:
I'm using KiCad 5.1.7 and have created a simple circuit just to see what happens.
It contains a fan, an unpolarized capacitor (110u) and a VSource.  [Just wondering
what happens..]
When I try to simulate it using the simulator, I'm getting the following error:
Error on line 4 :
m1 net-_m1-pad1_ net-_c1-pad1_ fan
could not find a valid modelname
Error: circuit not parsed.

Looking through [1], it seems that I need to find the right model; but [1]
applies only to the opamp ic and not some generic fan.   What is the
right model for a fan?
Thanks
[1] - http://ngspice.sourceforge.net/ngspice-eeschema.html#BipAmp


texts: Time calculation in SVPWM switching of 3 phase inverter

texts:
This is a code I found from microchip's website.

void CalcRefVec( void )
;{
;    if( Vr1 >= 0 )
;        {
;        // (xx1)
;        if( Vr2 >= 0 )
;            {
;            // (x11)
;            // Must be Sector 3 since Sector 7 not allowed
;            // Sector 3: (0,1,1)  0-60 degrees
;            T1 = Vr2
;            T2 = Vr1
;            CalcTimes();
;            dPWM1 = Ta
;            dPWM2 = Tb
;            dPWM3 = Tc
;            }
;        else
;            {
;            // (x01)
;            if( Vr3 >= 0 )
;                {
;                // Sector 5: (1,0,1)  120-180 degrees
;                T1 = Vr1
;                T2 = Vr3
;                CalcTimes();
;                dPWM1 = Tc
;                dPWM2 = Ta
;                dPWM3 = Tb
;
;                }
;            else
;                {
;                // Sector 1: (0,0,1)  60-120 degrees
;                T1 = -Vr2;
;                T2 = -Vr3;
;                CalcTimes();
;                dPWM1 = Tb
;                dPWM2 = Ta
;                dPWM3 = Tc
;                }
;            }
;        }
;    else
;        {
;        // (xx0)
;        if( Vr2 >= 0 )
;            {
;            // (x10)
;            if( Vr3 >= 0 )
;                {
;                // Sector 6: (1,1,0)  240-300 degrees
;                T1 = Vr3
;                T2 = Vr2
;                CalcTimes();
;                dPWM1 = Tb
;                dPWM2 = Tc
;                dPWM3 = Ta
;                }
;            else
;                {
;                // Sector 2: (0,1,0)  300-0 degrees
;                T1 = -Vr3
;                T2 = -Vr1
;                CalcTimes();
;                dPWM1 = Ta
;                dPWM2 = Tc
;                dPWM3 = Tb
;                }
;            }
;        else
;            {
;            // (x00)
;            // Must be Sector 4 since Sector 0 not allowed
;            // Sector 4: (1,0,0)  180-240 degrees
;            T1 = -Vr1
;            T2 = -Vr2
;            CalcTimes();
;            dPWM1 = Tc
;            dPWM2 = Tb
;            dPWM3 = Ta
;
;            }
;        }
;}
;
;
;void CalcTimes(void)
;{
;    T1 = PWM*T1
;    T2 = PWM*T2
;    Tc = (PWM-T1-T2)/2
;    Tb = Ta + T1
;    Ta = Tb + T2
;}

Code was originally from AN1162 from Microchip, Sensorless FOC of ACIM.

Vr1,Vr2,Vr3 are the reference voltages from inverse Clarke transform. But how are they calculating time here?

I've been trying to understand this for a while now.


texts: How can I find the voltage across individual capacitors in a circuit?

texts:
I was able to find the total current in the following circuit (.145 mA). I also was able to find the voltage across the first capacitor (7.71 V) and also across the second capacitor (2.29 V). But I can't figure out the voltage across the rest of the capacitors.

I know that conservation of current does not apply to circuits like these.


texts: Power cables for speakers, how much difference it makes

texts:
I have some Audioengine A5+ speakers, and I've been reading from a number of sources that the out-of-the-box power cable is of inadequate quality, and that a $75 cable like the Wireworld Stratus would do wonders for my speakers. My questions are:

Barring pretty substantial resistance, which I assume is absurd for a power cable, how can it make a difference? Isn't the power output determined way more by the wall output than the cable?
What is this notion of "clean power"? I see it all over the place and I don't understand it.


texts: Will reverse voltage on the "set" pins of a DUAL COIL latching relay "unset it"?

texts:
I am repairing a device that uses an HFD2/005-S-L1-D single-coil latching relay (datasheet) and needs a replacement part.
However, it seems extremely hard to source single-coil latching relays with all the same specifications (i.e. physical dimensions like relay height are critical in this device, as is pin spacing).
I can easily find replacement HFD2/005-S-L2-D parts, which is a dual-coil variation of the same latching relay.
My question is -- if I were to cut pins 2 and 15 on this dual-coil latching relay, would it effectively work like a single-coil latching relay? Meaning would reverse voltage applied to pins 1 and 16 unset it?
Thanks.


texts: I'm looking for a sensor to sense impact, let's say the sensor is placed behind a thick metal/wood casing, the impact depending on the amount of force could either deform the casing or only causes vibrations. Every path have led me to strain gauge sensors and I was wondering if these types of sensors can sense a force that only cause vibrations ? I am not interested in calculating the force but only a sensor that's triggered by a force, is there a better option than strain gauge ? how much surface do one strain gauge sensor normally cover in terms of sensing ?


texts: Connecting a LED directly to a GPIO Pin of ESP32 board?

texts:
I would like to connect and power a LED directly by using a GPIO pin of the ESP32 board (I am using the ESP32 NodeMCU WiFi Dev Kit C). As far as I know the GPIO pins provide 3.3V. I found some LEDs with 5V blocking voltage and 2.8V max. supply voltage. If I understand it right, it needs a resistor.
If the max. forward current are 20mA. So the resistors needs to be (3.3V - 2.8V) / 0.02mA = 25 ohm, is that right?
Is there a way to use a built-in resistor so that I do not need to add a resistor? Or how can I connect a resistor so that I can also connect the LED directly to the GPIO pin? What is the recommended way? I only worked with breadboards.
Thanks in advance.


texts: Using MCP1700-3302E LDO for Arduino/ ESP32 Solar projects

texts:
I'm using Solar-powered projects ( including batteries ), for remote sensing/ reporting.
When Battery drains below a certain voltage (~ 2.7-3.0v) due to lack of sun, MCU gets into "zombie" mode, which will not bootup correctly even if power in battery will suffice.
So, I'm looking for a cut-off circuit ( let say below 2.7v).
Can the MCP1700-3302E will do it ?
Most Solar Projects shared on-line, don't take this problem into considerationSolar Project.
For those who think that choosing a better / bigger battery will solve it, you are right, this is one way, but I think that when a device comes down... must have the ability to wake up ( and notify a re-boot, or battery deficiency ).
Guy


texts:
I am after an RGB controller or amp capable of powering 8 x strips of the RGB lights that come on 5 meter reels, which are 36W each.
The problem T have is the client has supplied the lights which come with their own controller, but are only designed to run 1 strip and I need 8 of them to run at the same time. The client has bought an amp, but after a lot of messing around it will not work. So after whipping the lid off the controller I have noticed the terminals are   - R G B and on one of the other controllers the terminals are + R G B so it seems I have two batches of lights, but I don't know the difference. The amp we have will work with the lights and controller marked + R G B but the client has just bought ten new sets of lights for this display and the controller is the - R G B. Is there a way I can run these through an amp with the +RGB terminals?

Thanks in advance.


texts: How i fix this PSPICE orCAD problem? - Model D1N747 used by D_D1 is undefined

texts:
From [PSPICE NETLIST] section of C:\SPB_DATA\cdssetup\OrCAD_PSpice\17.0.0\PSpice.ini file:
.lib "nomd.lib"

Analysis directives:
.TRAN  0 500ms 0
.OPTIONS ADVCONV
.PROBE64 V(alias()) I(alias()) W(alias()) D(alias()) NOISE(alias())
.INC "..\SCHEMATIC1.net"

**** INCLUDING SCHEMATIC1.net ****
* source ELECTRICAI_LAB_2_PUNTO_1
D_D1         0 N00392 D1N747
D_D2         N00346 N00392 D1N747
R_R1         N00148 N00346  1k TC=0,0
V_V1         N00148 0  AC 0
+SIN 0 10 60 0 0 0

**** RESUMING ElectronicaI_Lab_2_Punto_1.cir ****
.END

ERROR(ORPSIM-15113): Model D1N747 used by D_D1 is undefined

ERROR(ORPSIM-15113): Model D1N747 used by D_D2 is undefined


texts:
I have an old Apple keyboard that I would like to use but it uses the ADB bus instead of the newer USB bus. Griffin used to produce a product called the iMate which was an ADB-to-USB converter but have since discontinued it.

So I've decided to build one. It shouldn't be that difficult right?

pinouts.ru has the bus specs.

The pinouts are pretty straight forward:

Pin   Name  Description
-----------------------------
 1    ADB   Apple Desktop Bus
 2    PSW   Power Switch
 3    +5V   Power +5V
 4    GND   Ground

How would I go about building something like this? Would I need to get a FTDI chip to do the interface?


texts: Error: can't resolve multiple constant driver (VHDL)

texts:
trying to solve this error but none of it work. It says
Error (10028): Can't resolve multiple constant drivers for net "current_state.S4" at wood_detector.vhd(23)

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity wood_detector is
port(clk,rst: in std_logic;
AB: in std_logic_vector( 1 downto 0) ;
z: out std_logic);
end wood_detector;

architecture fsm of wood_detector is
type t_state is (S0, S1, S2, S3, S4);
signal current_state, next_state: t_state;

begin
process(clk,rst)
begin
    if(rst = '1') then current_state<= S0;
    elsif(clk'event and clk = '1') then current_state <= next_state;
end if;
end process;

process(current_state,AB)
begin
case(current_state) is
when S0 => if(AB="10") then next_state<=S1;
                else next_state<=S0;
                end if;
when S1 => if(AB="00") then next_state <= S2;
                    elsif(AB="11") then next_state <= S3;
                else current_state <= S1;
                end if;
when S2 => if(AB="01") then next_state <= S4;
                else next_state <= S2;
                end if;
when S3 => if(AB="01") then next_state <= S4;
                else next_state <= S3;
                end if;

when others=>NULL;
end case;
end process;

z <= '1' when (current_state <= S2 and AB="00") else '0';

end fsm;


texts:
So I am pretty new to soldering and have recently started modding controllers. When I was trying to resolder a stick box back to the board, the solder was not sticking to a few pins. On those pins I noticed they were missing some metal on the board

I was basically wondering what type of metal that is to get the solder to stick, and if I can repair the parts missing said metal.

Thanks so so much for looking at my post!

-back ground information-
During my attempts my solder pen was on the hottest setting and I was also using Flux. Every open spot that does have the metal ring I have 0 issues to get the solder to stick so I am pretty sure that's what's wrong.


texts:
Here is the expression I am trying to represent in the Karnaugh Map:

This is what I have done: Can somebody confirm if this is right? I have done the truth table right, however I am having doubts on whether the map has been done correctly.

Any help would be appreciated


texts: USB to Serial Disappears from Windows 7 Device Manager when Tx of board connects to Rx of usb-to-serial converter

texts:
I have two different usb to serial converters.
Both have 5 pins with 3v3, txd, rxd, gnd, 5v. In the past I have used them to connect to raspberry pis and arduinos successfully.

I have a board developed by my work that I can connect to using a pci card in my computer at work. All I do is connect the ground and tx from the board to the gnd and rx going to the pci card on the computer. I can then see the board output.

At home when I plug the usb-to-serial adapter into my computer the device manager recognizes it fine. I can connect the ground pin of the adapter to the ground pin of the board but when I connect the tx of the board to the rx of the adapter windows give the usb disconnect sound and the device manager refreshes and the com port is gone.

Any one have any idea on what is going on? I have never had to connect the 5v or 3v3 pins before. Anyone run into this and have a solution?


texts: What is the name of the IC that runs a low-harmonic power supply?

texts: I'm interested in building an AC/DC converter for low-harmonic applications. Single-phase AC input, followed by a rectifier and a PWM-controlled boost converter. I know there are ICs which are designed specifically to run converters of this type, but I'm not seeing any obvious keywords. What should I be looking for?


texts:
I am using one of these Side LED's on the edge of a PCB to illuminate it through the light guide.

http://www.digikey.com/product-detail/en/osram-opto-semiconductors-inc/LB%20A67C-P2R1-35-Z/475-1163-2-ND/808879

These side LEDs were oriented wrong on my PCB design (placed inwards instead of outwards).

I can't think of a way to solve the problem on the board.

Can anyone think of a temporary short term fix for this?

I can solve the the design issue long term on the board.


texts: DIY Ring Light: Grounding Bulbs in Series

texts:
I'm looking at making a DIY ring light using multiple fluorescent light bulbs. I'm in New Zealand and we get 230-240V and an current of 10A. I know from this I could rig up to 24 100W bulbs in series onto the ring. Although it is likely I won't have more than 10-15.

Here is an example ring light.

My question is this, how should I go about grounding this circuit? I've done some physics and am happy with power and voltage equations but was always a bit fuzzy on the concept of grounding and how it should properly be carried out.

Thanks in advance!


texts:
This question is related to part with part number PJ-102AH (CUI Devices).

Digikey link: https://www.digikey.com/products/en?keywords=PJ-102AH

Datasheet: https://www.cuidevices.com/product/resource/pj-102ah.pdf

The datasheet shows this:

For this, I understand that pin 1 is positive.

What is really the negative? 2 or 3?

And how the remaining pin work? Does it connected to negative when the cable is plugged-in?


texts:
Are there any low-cost (<50$USD) wireless ambient temperature sensors available?

I would like a simple to interface to the sensor i.e. IP over Wifi if at all possible.


texts: Box header to individually crimped wires

texts:
I've got an amplifier board that has a 2x10 keyed box header with a pitch of 2.54mm (black connector in photo below). It's designed to take the IDC type connector. I want to connect a few channels of my balanced audio source to this box header.

I think the design of the amplifier board is expecting me to make up a daughter board with another 2x10 keyed box header which is connected by a standard ribbon cable. I don't want to make a PCB up for this, and instead would rather take the balanced audio sources and connect it directly to the box header with some crimped connections that work well with a gauge wire that is larger than typically found in the fragile IDC ribbons. I know I can do this using what is commonly referred to as 'dupont' connectors (like the Harwin M20 series), but the ones I can find aren't keyed (they don't have the little notch that stops the cable being inserted the wrong way).
Is there another connector series that is compatible with this box header (including the key for the notch), that I can use to neatly crimp individual wires?


texts:
I'm trying to understand how timers work in this board.
I want to make a simple led blink after X amount of microseconds and then keep the led on for X amount of microseconds

stimer_t _timer;

void setup() {

    _timer.timer = TIM3; //84Mhz

    TimerHandleInit(&_timer, 60000, ??);
    attachIntHandle(&_timer,TimerTestIsr);
}

volatile bool isOn = false;

static void TimerTestIsr(stimer_t *timer) {

    UNUSED(timer);

    //just to mesure time
    previusTime = nowTime;
    nowTime = micros();

    if (isOn == false) {
        digitalWrite(LedPin, HIGH);
        isOn = true;
        setTimerCounter(&_timer,(65535 - 1234)); //so the counter will start from 64301 till 65535 is 1234
    }
    else {
        //on the next trigger it will shutdown the led
        digitalWrite(LedPin, LOW);
        isOn == false;
    }
}

As I understand the timer can go up to 65535 and then overflows to trigger the interrupt. But I'm strugling to understand how to set the prescaler for 1us or 1ms or 1sec. So what I want to do exactly is set the prescaler so every time the counter increase its 1us or what ever time I want. So if the counter is 50000 I want this to be a delay of 50000us.


texts:
Question is weird but it's about something that I really want to try.
AC power here in India has 50Hz frequency. What I really want to try is to make a series path with two continuous conversions. In start, I want to convert 50Hz AC 230V signal to 100Hz 230V AC signal and at the end of this path I want it to became the same signal of 50Hz AC 230V.  That is,  I want to convert the frequency of the signal at both ends.  At one end multiply it by double and at the other end devide by half. How can I do this?
I tried the cyclo converter circuit but couldn't find the proper result. Is there any modification required in the cyclo converter or any other method available?


texts: Question about an Intel USB Host Controller power supplied per USB port

texts:
I had a general question regarding the Intel(R) 82801FB/FBM USB Universal Host Controller (ICH6). The ICH6 has five USB Host controllers in it, with (I'm assuming) two physical USB ports per controller.

My Question is, does the ICH6 or any Intel SouthBridge supply up to 500mA per physical USB port, or does it share the 500mA per Host controller between the two USB ports on each controller?


texts: How to combine two LED indicators (one to VCC, one to GND)

texts:
I have two seperate sub-circuits that each have an indicator LED and only one circuit will have power at a time.  So far so good, however I would much prefer to have only a single indicator light.

My Problem is that one LED comes out of a 555 IC to VCC and the other comes out of the emitter pin of a 2N2222A transitor and runs to GND.

If they both went to VCC or both went to GND it would be easy.

I tried adding a 2N2222A transistor to the 555 IC (Base to pin), collector to 9VCC and running the LED out of the emitter to GND. I also tried a few resistor values between the collector and the 9VCC.

The subcircuit still worked, but the indicator LED would not turn on.

Is there any simple way this can be done?


texts: Protective insulation for magnet installed in earth

texts:
My this question is a part of a question I earlier asked sensor to detect magnetism. So please don't refer it as non-engineering question.

I had to install some neodymium magnets in the earth. Their top is going to be exposed for detection by sensor. I am looking for any solution like insulation OR cape that can protect those from corrosion but I have not find any good result. Can someone tell me a solution that is commercially available for this situation.


texts: Temperature drift on volatge divider built with resistors from the same series

texts:
I am in the process of designing a data acquisition device that will be used outdoors, with temperature swings of around 30 degrees.
For this i need to scale the input to a voltage suitable to the adc and reference i am using, the initial offset of the circuit is a non issue as it will be calibrated out, however what concerns me is the temperature drift.
One way to be sure the drift won't be a problem would be to use resistors with a very low Tc, these usually are pretty expensive if i want a drift of less than 0.02% over the temperature range, so i was wondering if it was reasonable to assume that by using resistors of the same series and keeping them at the same temperature one could assume the drift will be reasonably equal in both hence canceling out or if that assumption is completely erroneous.
Thanks


texts: Connect 2 SMALL Perpendicular PCBs - Need your creativity!

texts:
I'm looking to connect 2 small PCBs. I have up to 10 signals that need to be passed from 1 PCB to the other. The 2 PCBs sit perpendicular to each other, and need to be detachable; 1 PCB is an 8 layer, while the other can be anything (doesn't exist yet). Consumer device, so the speed of the signal and all that can be neglected for now; as long as the 2 boards are electrically connected and can be disconnected, it is okay.

The easiest solution would be to use an edge card connector. However, I have less than 6.5mm in width, and need the height to be minimal. I was thinking some gimmicky way to use slots in order to connect the PCBs in a puzzle like fashion, but I feel the connectivity reliability would be questionable.

I'm open to any crazy ideas; or if anyone has found really small connectors, or done something similar, please feel free to share your experience.


texts: Problem with switches on a toy circuit board

texts: I am trying to find out what's wrong with a toy train. There are two 4 pin switches on the board - one to start the train and another for a sound effect. The problem is that when I press one of the switches nothing happens. When I press the sound switch and keep it pressed, then press the motor switch, I hear the sound and vice versa - when I press the motor switch and hold it, then press the sound switch, the motor starts. My question is, how do I diagnose what's wrong - is it one of the solder joints, one of the switches, or something else?


texts: How to correctly connect a USB shield on a PCB

texts:
I have designed a simple PCB on EasyEDA; I am using USB 3.0 as a convenient means of providing power, ground and taking outputs from the magnet sensors (connected to the PCB) which will be routed to the corresponding pins on an Arduino microcontroller.

I would like to know whether I have correctly connected the two pins of the USB shield/shell (through a decoupling 100nF capacitor, through a 330ohm resistor to ground) following the advice of other threads on here.

Image is shown below

Have I done this correctly?

The package size used for the resistors is 0603 and for the capacitors they are 0402 (chosen due to stock on LCSC) Will those package sizes work fine for this use case (because one user mentioned a 0603 package may be ideal due to certain frequencies)?

I have connected them in series, is that correct or do one both or either of them need to be in parallel?

Any other advice, best practices?

Edit:

Thank you guys for your responses. @JYelton I have followed your example (Figure 1) of connecting the PCB to chassis ground. This is shown in the images below:

Image 1: Chassis ground schematic

Image 2: EasyEDA PCB implementation

Can you please check if I have correctly implemented the 'chassis ground' on my PCB. I have done this by exposing the copper trace around the mounting holes where the PCB will be bolted to the aluminium chassis via steel fasteners.

EasyEDA colour guide:

Red - Copper trace covered by silk mask

Pink - Board outline

Yellow - Markings

Purple - Exposed Copper (can be hard to see, labeled on image 2)


texts: STM32 - Fastest way to change ADC channels after each conversion

texts:
I'm using the STSPIN32F0 (edit: I'm using the STPIN32F0 6-step control evaluation board from ST called STEVAL-SPIN3202) to develop a 6-step speed controller for brushless DC motors. The STSPIN has an integrated STM32F031C6 microcontroller. I've set up my system to trigger ADC conversions on TIM1 update events, where TIM1 is configured as a center-aligned waveform.

Here's a diagram of what I'm trying to do. On the PWM off-time, I want to sample an ADC channel corresponding to the phase on which BEMF is being measured for the current step. On the PWM on-time, I want to sample an ADC channel corresponding to the current sense network.

The BEMF reads must correspond to the TIM1 update events that happen on the counter up->down transition, and the current reads must happen on the TIM1 update events that happen on the counter down->up transition.

To achieve this synchronization, I decided to structure my firmware so that on each ADC conversion, the conversion-complete callback toggles the ADC channel.

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
   /* This is called after the conversion is completed */
   if(__HAL_TIM_IS_TIM_COUNTING_DOWN(&htim1))
   {
      //read bemf
      SM_sampleBEMF();
   }
   else
   {
      //read current
      SM_sampleCurrent();
   }
}

void SM_sampleBEMF()
{
   bemf = HAL_ADC_GetValue(&hadc);
   if(bemf < BEMF_thresh)
   {
      HAL_TIM_SET_AUTORELOAD(&htim2, __HAL_TIM_GET_COUNTER(&htim2) << 1);
   }
   num_bemfs++;
   ADC_Channel(ADC_CURRENT_CHANNEL);
}

void SM_sampleCurrent()
{
   current_error = HAL_ADC_GetValue(&hadc) - current_reference;
   current_error_acc += current_error;
   num_currents++;
   ADC_Channel(currentBemfAdcChannel);
}

inline void ADC_Channel(uint32_t adc_ch)
{
   hadc.Instance->CR |= ADC_CR_ADSTP;
   while(hadc.Instance->CR & ADC_CR_ADSTP);
   hadc.Instance->CHSELR = ADC_CHSELR_CHANNEL(adc_ch);
   hadc.Instance->CR |= ADC_CR_ADSTART;
}

I'm observing is that the entire cycle of converting a channel, processing the conversion complete callback, and changing the ADC channel does not happen quickly enough. I'm running TIM1 at 30 kHz, which means the update events happen at 60kHz. Wondering if there's a way to speed up the ADC Channel toggling compared to how I've implemented it? Or is my only option to slow down the PWM frequency.

The BEMF data must be processed at as high a speed as possible because the controller needs to detect BEMF zero-crossing. I decided therefore that slowing the update event generation or buffering multiple ADC reads with some sort of DMA setup was not an option.

Appreciate any suggestions on alternate approaches to my goal as well.


texts: Is a Difference Equation causal, anti causal, or non causal?

texts:
A stable discrete-time LTI system is described by the following difference equation:

$$
  y[n] - y[n-1] + Cy[n-2] = x[n]
$$

where C is a real number. Determine the range of C so that

(a) the system is causal;

(b) the system is anti-causal;

(c) the system is non-causal (i.e., it has a two-sided impulse response).

It is straight forward to calculate the transfer function:

\begin{align*}
  Y(z) - z^{-1}Y(z) + Cz^{-2}Y(z) &= X(z) \\
  H(Z) = \frac{Y(z)}{X(z)} &= \frac{1}{1 - z^{-1} + Cz^{-2}} \\
\end{align*}

We are given that the system is stable so the ROC must include the unit circle. Therefore there can not be a pole with magnitude \$1\$.

With \$C=0\$, \$H(z)= \frac{1}{1 - z^{-1}}\$, there is a pole at \$1\$ so that is not possible.

With \$C=-2\$, \$H(z)= \frac{1}{1 - z^{-1} - 2z^{-2}} = \frac{\frac{1}{3}}{1+z^{-1}} + \frac{\frac{2}{3}}{1-2z^{-1}}\$, there is a pole at \$-1\$ so that is not possible.

From there, where do I go?

Ultimately this may factor into the form:

$$
  \frac{k_1}{1 + a_1 z^{-1}} + \frac{k_2}{1 + a_2 z^{-1}}
$$

Is that a causal transfer function or not? The inverse Z transform can yield both a causal and anti-causal impulse response function.


texts:
I'm attempting to simulate a circuit that is intended to take a 5V/GND input and make split +/- 2.5V rails with a virtual ground.

When I try to simulate, LTSpice complains about "unknown subcircuit" as shown in the screenshot.  I have placed red arrows to indicate the wires that are mentioned in the error dialog.

What does this error mean and how may I fix it?

Note: I'm using sine wave voltage and current sources to simulate noisy rails and loads.


texts:
Basically, I'm looking to program a PIC16F917, so that a particular int will increment by one every time I press a button.

Now I got the ADC up and running, I got loops to count, but I seem to be lacking the knowledge and experience to put it altogether, and latch the input back to zero before the int increases by a number greater than one.

The following code is what I have written so far. The problem with it is that it increments multiple times per push (as many delay cycles that the button was held for), and I'd love to make it only count by one. I was thinking of creating a new function and int but I just can't seem to put it together - much help needed.

Thanks for helping, Ezra

#include <xc.h>
#include "config-bits.h"

#define _XTAL_FREQ 4000000

int result;
int output;

void delay()
{
    int i;

    for(i=0; i<100; i++)
    {
        /*Timer Stuff*/
    }
}

int main()
{
    TRISA=1;                    //Set all pins to input
    TRISB=1;
    TRISC=1;
    TRISD=1;
    TRISE=1;

    TRISDbits.TRISD0 = 0;       //LED output
    ANSELbits.ANS0 = 1;         //Select ADC input

    ADCON0bits.ADFM = 1;        //ADC result is right justified
    ADCON0bits.VCFG = 0;        //Vdd is the +ve reference
    ADCON1bits.ADCS = 0b001;    //Fosc/8 is the conversion clock
                                //This is selected because the conversion
                                //clock period (Tad) must be greater than 1.5us.
                                //With a Fosc of 4MHz, Fosc/8 results in a Tad
                                //of 2us.
    ADCON0bits.CHS =  0;        //select analog input, AN2
    ADCON0bits.ADON = 1;        //Turn on the ADC

    while(1)
    {
        delay();                        //Wait the acquisition time (about 5us).

        ADCON0bits.GO = 1;              //start the conversion
        while(ADCON0bits.GO==1){};      //wait for the conversion to end

        result = (ADRESH<<8)+ADRESL;    //combine the 10 bits of the conversion

        if(result > 512)
        {
            PORTD=output++;
            delay();
        }
        else
        {
            NOP();
        }
    }
}


texts: Issues related to Bit-banging transceiver modules

texts:
I have two Infrared Transceiver modules from TFDU4101-TR3 on two separate boards each interfaced to ATMega164PA microcontroller. To drive these transceivers an endec is needed which I have not used in my design due to budget constraints.

So what I am trying to do is bit-banging. The RX and TX follow normal standard, RX is active low and TX is active high. I am toggling the TxD pin one 'Board A' 50 times at 5 Khz to send 50 pulses to the receiver. On 'Board B' I have implemented a PIN change interrupt which should technically receive 100 pulses (2 pulses for each transmit pulse that it receives). This is not the final design, I just learning and experimenting how to transmit data from one board to another.

Now the problem is that when I send 50 pulses from Board A to Board B, I do not get 100 pulses, but instead I sometimes get 90 or 81 or 98. In short I don't get the intended number of pulses. Is there something wrong with my approach?

Please let me know if any further information is needed.


texts: Half Bridge Low Side Mosfet vs. Flyback Diode

texts:
I intend to use this high side switch in a PWM application with a brushed 12V motor drawing 8A steady state max: https://www.nxp.com/docs/en/data-sheet/MC33981.pdf
The switch allows for a half bridge configuration, where an external low side MOSFET is placed across the load as show in the diagram below:

The document states the following:

I do not understand why decreased power dissipation is desirable in this application, other than for thermal reasons.
Using a diode, the energy stored in the inductive load would be dissipated more quickly when the high side is removed. I'm not sure how having residual current flowing through the inductor before the next on cycle of the PWM would affect the system, but I assumed it was not desirable.
So why, in this case, would a mosfet be a desirable substitute?


texts: What is the exact principle of this circuit? (PNP transistors and P-channel MOSFET)

texts:
I have this given circuit:

I can see by the look of it that this is a power rail "choosing" circuit. When VBUS is applied and there is no +5V, then the body diode of Q1 simply conducts.

I am trying to understand what the logic behind this circuit is, when VBUS and +5V are supplied externally at the same time. I think that Q1 is being turned off when +5V is higher than VBUS, but I can't explain it.

I would appreciate some hints, as I cannot really follow the scenario here with the Q2 and Q3 transistors.


texts: How to boost current through encoder/decoder IC's?

texts:
This is my first electronics project in 15 years and I have clearly forgotten everything I learned in all my electrical engineering courses in college. Hope this question isn't too ignorant..

I'm building a pretty simple but very large (25'x15') array of LED's to show a bitmap. Probably will end up 40x25 LED's given the spacing we have. Currently looking at using 20-30ma blue (~4.5V) LED's.

I'm doing what I guess is a typical setup where LED's sit at grid intersections and along the edges I drive a horizontal line and sink a vertical line in pairs in a fast scanning algorithm from a cheap processor to render the bitmap. To reduce wiring I'll be putting decoders (3-8 demultipliers) every 8 lines. Easy stuff.

The problem is this: all the decoders I can find (74*138 / 74*238) can handle 5-8mA of current.

Am I just looking at the wrong parts? Or do I need to add an additional part at each 8-line module to boost the output, like a buffer? I barely even know the right words to use, so long since I've done this..

Many thanks in advance. Ideas, suggestions at different directions are very welcome. This is just my first stab at this.


texts: How to sense a control voltage without pulling it down?

texts:
I am working on a project in a photonics teachings lab. In the lab, we perform a demonstration for the students using a \$\mathrm{CO}_2\$ gas laser. The output of the laser is terminated in a wattmeter. The other end of the optical cavity is formed by a reflection grating mounted to a stepper motor. The angle the grating forms with the optical axis determines which wavelength of light is reflected back into the cavity. This allows us to effectively scan the spectrum of the laser (i.e. to plot power against wavelength).

For control, we have a slider which controls the scanrate, and a three-position switch which controls the scan direction.

For data acquisition, I have an RPi and Arduino Nano. The RPi is running a small GUI with a plot window. When the GUI is started, the RPi establishes serial communications with the Arduino. When ready to collect data, the user will press start on the GUI. The RPi then begins to query the Arduino on A1 (where the control voltage is connected). When it detects the necessary condition, the RPi starts to instead query on A0 (where the wattmeter output is connected) and plot in real time.

This all works quite well, except for a few problems relating to the control signal. The signal is a voltage between -5 V and +5 V. The magnitude of the voltage encodes the scanrate, and the polarity the direction. The slowest speed corresponds to a magnitude of 1 V.

We scan in the reverse direction at the slowest speed, which means we need to be able to detect the -1 V signal on A1. However, the Arduino cannot sense negative voltages. I have tried the typical methods here. Voltage divider, inverting amplifier. These "work" in the sense that the script executes as expected. They do not work in the sense that these methods seem to actually change the operation of the stepper motor, which is a critical failure.

My last solution attempt was to capacitively couple the signal in an attempt to extract the edges (the only critical information), but I could not get this to work either.

My experience with electronics comes from personal hobby. I apologize if this is an extremely simple question.

How can I isolate the necessary transformation I need to do to the control voltage without modifying what the stepper controller sees?


texts: Remotely control power supply with adjustable voltage

texts:
I have a power supply unit with adjustable output voltage. The output voltage is adjusted using a potentiometer. However, I need to change output voltage remotely and dynamically.

What kind of circuit should I use to substitute the potentiometer in the power supply unit to control it remotely (30-50 cm) by the micro-controller?

Both analog and digital control of the modified PSU is acceptable.
Cost and low wire count are also important factors.
However, the most important factor is how reliable the system is (isolation between PSU and MCU in case of a lightning strike etc).

Thank you in advance.


texts:
The ideal op-amp is connected to a power source \$V_s\$ at t = 0. Initial charge on the capacitor is 0.
Then it is given that \$V_{OUT}\$ swings to positive value and \$V^-\$ starts increasing. \$V^-\$ increases till \$V_{TH}\$  and then starts decreasing, till it reaches \$-V_{TH}\$ and starts increasing again. Thus it is a periodic cycle with oscillations between \$V_{TH}\$  and \$-V_{TH}\$. \$V_{TH}\$ is to be determined along with the oscillation period.\
I wrote the following two equation for the op-amp terminals
$$V^+ = \frac{R_3V_{OUT}}{R_2+R_3} \; \; \; \; \; \; \; \; \; V^- = V_C \; \; \; \; \; \; \; \; \; \dot{V_C} = \frac{1}{R_1C}(V_{OUT}-V_C)$$
And since op amp is ideal \$V^- = V^+\$ at all times.
What I could not understand was how would \$V^-\$ reach to a threshold voltage? Because after the capacitor voltage reaches \$V_{TH}\$, when it starts to decrease, the current across \$R_1\$ will become 0 momentarily, before switching direction. At that moment \$V^- = V_{OUT}\$; which will violate the equation of positive terminal.


texts: Why is Zener reverse based on relay circuit?

texts:
In a common relay circuit a zener diode, or other diode, is used to shunt the spiked that the relay could cause.

Now, why is the zener's cathode connected to the battery (or other source)'s positive terminal, and the anode to negative?

Should it not be the other way around?


texts: What do you call the little black nub on the end of a scanner's USB cable?

texts: This a scanner's USB cable , I'm wondering what's the little black nub on the end of the cable and what's it for ?


texts: Determining the Maximum Output Current of a Switch Mode Power Supply

texts:
I'm looking into building a simple 5 Volt DC Switch Mode Power Supply, and I've been looking at a few schematics, but I can't seem to figure out how you determine the (Maximum) output current of a Power Supply.

Specs of Power Supply I'm Looking to Build:
86-240 VAC Input
5 VDC Output
2 Amp Output


texts: Sending data from PC to micro-controller

texts:
In my Graduation project I need to send data from computer to microcontroller to control the position of a stepper motor

Most of the examples I have seen use the legacy parallel port. unfortunately parallel port is not available anymore.

My Question is what are the alternatives that available nowadays and compare between them from the following perspectives: hardware needed, complexity, ability to use with C++ and PIC microcontroller.

I am Using C++, Windows 7, PIC  microcontroller.

If you point me to any reference I will appreciate it very much


texts:
I have two voltage regulator which works on ac. They are both the same model and provide a maximum power of 3000w.

I would like to plug their outputs together to make a 6000w total voltage regulator. It doesn't matter if one works harder than the other. I know it's easy to achieve this with diodes when the voltage regulator output direct current.

To be short, I think I need to isolate both regulator from each other while both being able to output the current on one source. (Although I'm not even sure if they really need to be isolated.)

I've been trying to do it with diodes but without success. I keep facing the problem of alternating current which needs to go in both ways.

Thank you for your help. I have a little knowledge in electronics and still beginning.

Here is the model of the voltage regulator:
LiteFuze LR-3000


texts: Tradeoffs between transmitting and listening with low-power 2.4GHz

texts:
On a number of 2.4GHz chips, listening for a signal is actually more expensive than transmitting.  If one is trying to minimize power consumption with such devices, to what extent should one strive to minimize transmissions, and to what extent should one be willing to make extra transmissions in an effort to minimize listening time?  Is there an "etiquette" when using low-power unregulated transmissions?

For example, suppose one wishes to have two devices remain 'in sync' with each other, but one doesn't need them to exchange much data.  Both devices have agreed on a time, +/- 1ms each, when one will send the other a packet.  Assume that transmitting a packet takes 100us; assume further that powering the transmitter for 100us costs as much as powering the receiver for 100us, so power may be measured in terms of active transmit+listen time.

One approach would be to have a receiver switch on for 2.1ms, and have the sender send one packet.  Total active time would be 2.2ms.  Another approach would be to have the transmitter blindly send five packets at 0.5ms intervals, and have the receiver listen for 0.6ms.  Total active time would be only 1.1ms--a 50% savings.  On the other hand, the latter approach would generate five times as much radio traffic as the former approach, thus creating more potential conflicts with other devices' packets.

Should devices try to minimize unnecessary transmissions, or is it acceptable to give priority toward minimizing battery usage?

EDIT/clarification

My question is not how best to minimize power usage, but to what extent one should factor in the negative externalities (social costs) of unnecessary transmissions.  If many devices in the 2.4GHz band blindly transmit much more data than needed, in the hope that some will get through, that will greatly impair the utility of that band.  On the other hand, it would be silly for the designer of a device to accept an extra 10% power drain so that it will cause only 0.1 percentage points of congestion in the 2.4GHz band instead of 0.2, if the designers of other devices that use more bandwidth don't make similar efforts.  My intuition would be that trying to avoid causing 10% congestion at a frequency if one could get by almost as well causing only 5% would be good, even if it increased power consumption slightly, but reducing congestion from 0.01% to 0.00001%--even though it would be a thousand-fold reduction in congestion, would not be worth even a 1% increase in power draw.  On the other hand, I don't know where the trade-offs should lie, or on what time scales congestion should be measured.  A device which transmits solidly for one minute each hour, or one which transmitted for 2us every 120us, would seem more "obnoxious" than one which transmitted for 100us every 5ms, even though the first two would have a 1/60 duty cycle and the latter would have a 1/50 duty cycle.


texts: Making a electronic alphabet locker that lock gift to friends

texts:
Imagine you are giving a gift to someone, but you want them to solve your question and enter your secrete password.

You want the password to be entered in order and if touch any other will fail.
For example if you want enter "dog", then we can use:

*from "make: electronics"

the user have to press button E,F,G,H in sequence without touching button B,C,D to get output from the last logic gate.

But what about when you want him enter a password like "hook"?
(with 2 same letter)

*In the current circuit if you push "hok" instead of "hook" it will also work.

but we only want the user press "hook"

I designed a circuit, but seems missing something:

anyone have any idea?


texts:
I have an PC audio amplifier using TDA8947. One 30W subwoofer and two satellites.
It produces a lot of background noise and I would like to cut it down a bit. The noise is all in the subwoofer. It was always there since I purchased the system.

I supposed the source of the noise is:
1. poor filtered power supply (it already has a 4700uF/35V capacitor)
2. noise in the input cable (which in my case is pretty long)

To test 1) I removed the power supply and hooked the amplifier to batteries. Yes people, you are reading this right! I put together nine 1.2V rechargeable cells and one 9V battery and I got close to 21V, while the DC voltage from the transformer was 24V.
Results: the noise didn't changed a bit! So it is not a power supply filter problem.

To test point 2) I shorcuted the input, right on PCB.
Result: the noise didn't changed a bit! So, it is not a noise on the input cable problem.

The upper part of the circuit board is shielded by ICs heat sink which is really thick. The lower part (where the connections are) is not shielded. I will try some aluminum foil.

What else should I try?


texts: How is the equation for Compliance voltage?

texts:
Here is the link for a current mirror discussion. I am trying to understand the meaning of compliance voltage equation and how it can be dervied:
https://wiki.analog.com/university/courses/electronics/text/chapter-11

Attached the same relevant section screen-shot:

Please advice.

Thanks
VT


texts: How to use MATLAB to observe the effect of multiple damping factors?

texts:
I want to use MATLAB to observe the effect of changing zeta (damping factor) on system response?

Here is a m-file code that plots three responses: underdamped, overdamped and critically damped.

clc
clear all
close all
num1=[16]
den1=[1 4 16]
num2=[16]
den2=[1 8 16]
num3=[16]
den3=[1 10 16]
sys1=tf(num1,den1)

I have also attached a snapshot of the response:

I want to do something that allows me to change the value of zeta directly and according to that zeta value the response changes, instead of writing a new transfer function or changing original transfer function.


texts: How to set output voltage on this dual output buck converter board?

texts:
I guess this board's dual output voltage is configured by the EN terminal?
Resistance to ground? (Link to the eBay listing: 20W DC-DC Step UP & Down 5V-35V 12V 24V to ±5V ±9V ±12V ±15V Dual Power Supply.)

These are cheap on eBay, but I bet they arrive undocumented and there is no indication of how to set the voltage on the listing. I've asked the seller and had no reply as yet. I would be very grateful for advice, it looks a very good solution for powering a graphic EQ module.


texts: Determine state of MOSFET transistor - trouble identifying Q-point

texts:
Problem

Determine the state (cutoff, linear, saturation) of both transistors in the following circuit.
\$K = 0.4 \frac{\text{mA}}{\text{V}^2}, \: R_{D1}= 1\text{k}\Omega, \: \:  R_{D2}=0.6 \text{k}\Omega, \: \: V_{DD}=5\text{V}, V_{to}=2\text{V}\$.

My attempt
From the schematic it's easy to see that \$V_{GS1} = V_{GS2}\$. My idea was to use load line analysis to analyze the transistor current and voltage behavior. I intend to find the operating point, or Q-point for both transistors, and see what region they operate in. Here is my work so far with my calculations on the left and my graph on the right of the paper.

However, I realized I don't know how to identify the Q-point at all. The definition of the Q-point is just the operating point for the circuit with zero input signal, but that doesn't help me in this case.
Can anyone help me out and tell me how to find the Q-point? And also if my idea of solving this problem is okay?
Maple calculation in response to Andy aka's answer


texts: Chosing a suitable switch mode power supply

texts:
I have an application where I have to drive 40 high-power LED's in short pulses using a LED light controller. I got the part after the light controller dimensioned, so now I just need to choose a suitable PSU to supply the light controller. The PSU output voltage has to be in the range of 35-48Vdc and be able to supply around 550W of power within 20us.

I found a couple of 48Vdc 600W PSU's that will meet the first two requirements, but what parameter should I look after to be sure that the PSU can deliver the needed power within just 20us?

Clarification:
A single pulse starts with a 20us delay (low), then there is a 300us period where the pulse is high followed by a 19700us delay (low). My main concern is to make sure that the PSU can deliver the power needed immediately after the initial 20us delay.


texts: A push button switch before or after a PWM DC motor speed controller

texts:
What is the difference of putting a push button switch between a switching power supply and a PWM speed controller (dial on 100%) or it between PWM controller and a 12V DC motor (to turn it on and off repeteadly)?
If the motor has huge initial current, will be any harm for the motor, power supply or speed controller by numerous on and offs operated with the switch?


texts: Why do fuses burn at a specific current?

texts:
We usually specify the maximum current that a conductor (such as a fuse) can handle without burning. But doesn't the conductor really fail when a certain amount of energy/heat has been dissipated in the conductor? Then the conductor is at a too high temperature and burns/melts.

Let's say I have a fuse that's rated for 10A. Why is it then that I can operate the fuse continuously at a lower current like 9A without the fuse burning too, but just a bit later?

We also know that power, voltage and current are related by Ohm's law. So if we have a 10A fuse, and it has some arbitrary resistance such as 100 ohms, why don't we instead call it 1kV fuse (10A * 100 ohms), or 10kW fuse (10A * 10A * 100 ohms)? These numbers are completely arbitrary so I know they don't reflect reality but they make my point clear.


texts: "One way" level shifter for PWM 4PIN fan control

texts:
I'd like to make a 4 pin pwm fan control using 3v3 uC. Fan is 12v powered and I have a 12v to 3v3 converter to power uC (VCC gate is 3v3 uC power). I want to isolate 3v3 VCC and 12v as much as possible, but without using optocouplers, just with FETs. This fan has a PWM input that shall be used to control it's speed. I need to make some kind of "repeater" for uC 3v3 logical level PWM signal. The output level shall not exceed 5V, so I made the following schematics:

The "highlighted" part is the "repeater". My questions are:

Is it ok to use such a repeater?
Is it possible to simplify it, for example to make it using just one FET?


texts: How large is the percentage of non silicon materials in overall production capacity for semiconductors?

texts:
Most of all semiconductors produced these days are made from silicon, as it is easy and cheap to manufacture in very well researched bulk processes. But some electronic devices require the physical properties of other materials, like some high speed transistors or light emitting diodes. Depending on the wavelength you want to emit, you use materials with an according band gap, like AlGaAs, GaAsP or InGaN.

But my question is: How large is the percentage of these non silicon materials in overall production capacity for semiconductors?

I guess it will be difficult to give an exact number, but I would like to know at least an educated guess. Is the non silicon part vanishing in the x-th decimal place, because microchips are absolutly dominating the semiconductor market? Or is maybe the raising production of LEDs increasing to percentage to several percent?

EDIT: I'm mainly refering to the produced chip area, but if this information is even less available than e.g. the volume of used material, then this might also be an interesting information.
I'm aware that manufactures will not give detailed numbers about this, if any at all, but there are always some analyists, making guesses at least about the order of magnitude we are talking about.


texts: Why should the primary winding of the transformer not be grounded?

texts:
I've been wondering what would happen if you grounded both star points of a Y/Y connected transformer. This shouldn't affect the voltages,  so why really is it not advised to earth both the primary and secondary star points of a transformer?

Any information on this will be appreciated.


texts: MPLAB X IDE : Can we get "console like" output using dsPic?

texts:
I was wondering, can we get console like output using command like "printf" on MPLAB X IDE ???

Console Output just like standard C ??

example : if i want to get the value/data of the variable on output screen. How to display it ??

If not, What can be alternate options to get the debug output ???

I am using dsPic33E on MPLAB X IDE v3.00

Thanks in advance


texts:
I'm trying to build a portable screen so that I can watch movies around my apartment if I need to move away from my TV screen (think a WiiU gamepad or a tablet). I have many raw components and I think I will be able to succeed as long as I can solve all of the little problems (classic statement, I know).

My system contains a Raspberry Pi along with a wifi dongle, some button/joystick inputs, and a 7" touch screen. My background is mostly in CS/programming, so I don't know exactly how to deal with powering the system. I have a relatively large battery supply that has two outputs of 5V/2.1 A and 5V/1A so I know I can power the RPi along with the simple components directly connected to it, but I'm having trouble figuring out how to power the screen/driver. I can make the system work if I plug a 12V/1A power supply into the board but with my 5V battery supply that clearly does not work on its own. Attached is a picture of the power regulator.

Is there any way to convert my 5V battery (either the 2.1A or 1A port) to work with this board? I'd be willing to purchase other parts and/or deconstruct the video driver board if needed. (I know Watt-wise I can /almost/ make it, so I'm hopeful that someone out there has a creative solution!)

The markings of the regulator on the board (if you're having trouble reading it):

  AA20 C
HY2576 S
-ADJ  P+

I can't find anything on Google about the regulator, but my google-fu may just be off.


texts: If Contact Rating of switch is 5A 240V AC & 0.25A 240 DC, Then is this switch can be used for contact rating of 220V (+10, -15% voltage variation) AC & 127V (+10, -15% voltage variation)


texts: what does `x` mean in PIC opcode format?

texts:
I hope this is right place to ask
In PIC mid-range micro controller instruction set
I found this strange formatted op code for the instruction

CLRW  00010xxxxxxx
It doesn't make any sense what these x(s) refer to ?


texts: Can items in Microsemi Libero SmartDesign canvas be rotated?

texts: I am sure there is a way to rotate or flip the things we put into the canvas of the Microsemi Libero SmartDesign Canvas but it is not clear how to do this.


texts:
I'm sure I've seen something like this before, but I can't find it now, or even find any appropriate names to call it to search for it.

I'm looking for a small momentary pushbutton switch similar to this:

The switch is approximately 12.7mm by 6.35mm.  But the ones I'm looking for can also be twisted 90 degrees to lock them in place while in the unpressed position so they can't be accidentally pushed.

The closest I've been able to find are huge ones at are used as emergency switches for machinery (push in to disconnect, twist to turn back on), but that's not quite what I'm looking for, and way too big.

Is there a special name for such a switch?  Am I just imagining that they exist?  Or do I just fail at searching?


texts: Controlled supercapacitor charging with buck converter

texts: I'm building a charging circuit for two supercaps (2.7V, 3000F each) in series. I've got a 12V supply and a buck converter rated to 15A, which I've set to provide 4.8V. I'm using balance resistors to evenly distribute the voltage between the two caps. I'm using an Arduino to monitor and display the charge across the capacitor bank  through another potential divider, and the current with a 20A ACS712 module. I can charge the capacitors by using a current limiting ~0.5 Ohm resistor (actually quite a few power resistors in parallel) in series with the capacitor but this is quite inefficient in terms of both volume and power. Can I use a PWM signal from the Arduino to control a power MOSFET in place of the resistor to limit the current to the capacitor, basing the duty cycle on the ACS712 current signal? I'm guessing I'd need to smooth the input signal to the Arduino to get an average current reading, but my question is would this rapid switching of current damage the buck converter or capacitor?


texts:
I am attempting to regulate the temperature inside a not so small (maybe 0.5m^3) box above the ambient. Currently the design is using a bathroom heater spare parts heating element. 230VAC are passed via a triac.

Because the box needs to be opened sometimes, I would like to avoid the risk of electric shock. Furthermore, the design is already using a computer PSU, so 5VDC supply is abundant.

Can I get a combination of heating element and control element (mosfet?), which runs at 5V? The power needs to be at the very least 200W and the price not much higher than 10BGN.


texts:
Could you please help me out here. What would this component be? It's marked YA.

Thank you


texts: I have an application with a BLE stack and I'd like to figure out how much space that stack uses up (more or less) in order to figure out if I have enough flash available to write an additional BLE bootloader. How would I figure out the size of a specific block of code?


texts: Footprint panel is grayed on Altium Designer PCB

texts:
This is a project I imported from Eagle (not so bad by the way). I resolved all schematic compilation errors. But now I am facing some small issues in the PCB part:

On the properties panel when I select any component, footprint is grayed. See picture. Not a big issue because I can still update my footprints by the menu option (all, or one by one).

Do you know why all my components seem locked? Could I revert this to a "normal" situation where footprint name and library could be modified? This way I could push to schematics modification of footprint done in PCB.

I tried to "update all component footprint" - did nothing.

This is Altium Designer 18.1.8

EDIT:

Ok, new components that I added since the conversion seems to work as usual. But old one are still locked.


texts: Question about 4-bit binary adder on 7 segment display and subtraction

texts:
In my lab, we successfully built a 4-bit binary parallel adder and were able to display the results of some tests on the 7 segment display.

But our TA asked us to try something: subtract 1-9, and we got 7. Why is that?