texts:
I am going to make a solenoid that will only be required to lift a small metal rod for a couple of seconds - and not very often.
It has to run of a standard 9V battery and the small rod should be as big as possible. So - which wire gauge should I use to get the most lift? I am getting 100 grams of lacquered copper wire but can choose the gauge - from 0,15 to 2,00 mm. thick.
So longer but thin wire with a lot of turns or thicker but short wire with few turns?
Edit to clarify:
This is for a sort of puzzlebox.
The 9V is not my choice - that is what it has to be.
Different people will come and open it - each will have a "new" battery with them - so how long it will last is of no interest for me - as long as it can open the lock for a few seconds.
The small rod should be as big as possible because it is a lock - but I am aware that a 9V will probably not lift anything too big - therefore "small". I therefore do not have the measurements of it as I will chose it based on the solenoids capability.
I have next to no knowledge of the calculations regarding this project - it is pretty much trial and error. I just need to know which gauge will probably give me the best chances ;-)
Edited to further clarify:
When I write "as big as possible" I am not really looking for the max - I am looking for something long enough to penetrate the sides of the box sufficiently to be secure and something thick enough to not just snap if forced.
The rod will probably penetrate about 5-7 mm. and will have to be moved that distance.
The box is to commemorate the 200 year of the first lecture proving electromagnetism. This is also the reason that I want it as simple as possible with as few parts as possible as it will be made of plexiglass so that the opener can see that it is only electromagnetism doing the work. This is also why I want gravity to work as the locking-mechanism and the rod has to be lifted.


texts: Do power plants supply their own electricity?

texts:
I tried looking it up but there's no answer for this. This is mainly concerning nuclear power plants or natural gas plants, where they would have other buildings attached on site to operate the plants.
When they run the plants does it go to the grid and then back to the facilities? Or are the building circuits directly powered by the plant electricity, then the remaining electricity goes to the grid?
I also assume wind farms and solar PV farms don't have this concern, but I could be wrong.


texts:
I would like to use NXP NVT20XX as bidirectional voltage-level translator in my system (I2C at 100kHz, 6 slaves) and I only don't understand one thing. I am little bit confused.
In the datasheet they said:

  Bit widths ranging from 1-bit or 2-bit are offered for level translation application with transmission speeds < 33 MHz for an open-drain system with a 50 pF capacitance and a pull-up of 197 Ω

And my question is what does it mean this 50pF? Does it say that I can use ony 1 slave (SCL, SDA Input Capacitance (CBIN) = 60oF)?


texts: How to electrically brake a brushless motor

texts:
I'm sorry if this question is too stupid, unfortunately I have a very low experience with BLDC motors.
I would like to use 4 x 350W, 24VDC brushless motor hubs for my wheeled robot (they are usually used for ATVs or hover boards).
Each motor is geared and comes with an encoder with 1024 pulses/rev.
The problem is that when the robot isn't moving, the wheels/motors can still move since they act like free wheels when no power is applied and this is bad if the robot stops in slope or if someone tries to pull/push the robot because it can be easily moved.
I never had this problem with other robots since I always used brushed DC motors with angled gearbox with high output torque so it was very hard to move the wheels when the robot is stopped.
The brushless motors come with U,V,W wires, three wires for Hall sensor, two wires for encoder, two wires for +5VDC and GND.
I was reading a discussion on researchgate about braking by shorting motor terminals.
Few days ago, I've read a very interesting discussion on this forum about the difference between brushless and stepper motors. I think what I need should be the holding torque like it happens for stepepr motors.
I was thinking to try to implement something like that via software:

the robot is not moving
check if encoder pulses are changing and their direction
if they are changing, then the robot is moving in free wheel
if moving, try to apply power in opposite direction till encoder pulses are NULL.

This procedure looks complex for me so I would like to know if there is any smarter electronic solution.
Thank you!
P.S. I forgot to mention that obviously the controller can store the energy produced during the braking into the batteries.


texts:
So I'm trying to design a sawtooth wave generator that goes from 2.5V to 3.25V. I'm using this design:

I'm getting a voltage range from around -4V to 4V. Is there any way for me to get 2.5 to 3.25 by editing the values in this circuit? If not is there any other configuration that will help me achieve this, preferably using op amps and/or mosfets.

Edit:
Thank you for the quick responses I was able to work something out.


texts: Why must some HDMI repeaters know the cable length?

texts:
I just bought an HDMI repeater and had connectivity issues until I realized the repeater had to know the cable length. It has (1,2,4,8) dip switches that you have to use (binary coded) to set the cable length.

What I'm wondering is: How is the cable length important? If it was just a question of power/loss over the cable, wouldn't the stronger setting always be the best? I assume that since the length is required it either has to do with capacity or signal echo bouncing back the cable end.

Technical details would be enlighting.


texts: Help understanding onboard power supply measurement test connections

texts:
I recently came across this circuit for measuring the output of a TPS54620 switching regulator (12V->3.3V).  I'm not a power engineer, so I'd like some help understanding the parts in red boxes (presumably used by the power engineer to measure the power supply?)

1) Is this Hirose U.FL coax connection (J4) used for measuring the output ripple and/or noise on the regulated 3.3V output?  I think the 49.9 ohm resistor is used to provide a 50-ohm source impedance to match a 50-ohm coax cable, which is presumably terminated via a 50-ohm BNC pass-through (or the 50-ohm setting on a scope).  Is 49.9-ohm used instead of 50-ohm to ensure that the resistance is precise to within 0.1-ohm?  (just curious why you'd use a 49.9 ohm...)

If the designer was just concerned with ripple/noise, why wouldn't they add a DC blocking capacitor in series before the 49.9 ohm resistor?  Since there is no DC blocking, this presents a 100-ohm DC load (49.9-ohm + 50-ohm), which results in a static current draw.  For 3.3V output, this is probably ok (3.3V * (3.3V / 100-ohm) = 0.1W), but if the output was 12V, you'd get 12V * (12V / 100-ohm) = 1.44W, which I think is too much power for the 50-ohm input on my scope.  Do people normally put some kind of DC block inline with the coax cable?  What is the best practice for putting an onboard coax connection like this?  What tests is this connection typically used for?

2) I believe R134 (the 10-ohm resistor) is for loop stability measurements (see http://www.tij.co.jp/jp/lit/an/snva364a/snva364a.pdf)  TI recommends adding a 20-ohm resistor into the feedback loop of the power supply for bode measurements, and I think the 10-ohm resistor is for the same purpose here.  Is this correct?  Any other reason for this resistor?

3) Why have another large resistance (R137) in parallel with the upper half of the feedback divider?  The TI reference design uses 31.6k/10k resistors in the feedback loop, so 3.16k/1k seem like they should be the correct value without R137.  I'm not sure why you'd want this resistor?


texts: External Oscillator charging RST Cap when chip is not powered on

texts:
I have a chip (Hub USB) with an external oscillator. Chip is powered with 5V and external oscillator is powered with 12V.

When I have power on the oscillator but not on the chip, the Reset pin charges a bit (through XI - internal circuitry) and if I power the 5V after that, the chip fails to initialize properly. It works if I only enable the 12V after the 5V.

My question is, there are a passive way (without a mcu, ampop or smith trigger) to drive the Reset Pin to Low if I only have the 12V On?

Edit: Somehow the board worked on the client assembly with current configuration. But already implementing a voltage supervisor circuit to make sure RESET pin is low if chip VDD is not stable for next version.


texts:
I am using Oriental's PK-243-03A stepper motor in bipolar series configuration. The driver I am using is TI's DRV8825. I want to measure my motor's current in order to plot a Speed - Current graph. I have figured out a way to measure speed using photo - interrupter, but I am a little confused on how I should measure the motor's current. I have a couple of questions.

The driver IC I am using has an Isense pin in it which uses an Rsense resistor to set current threshold value for my motor, maybe I can measure the current from there somehow, but how?

Or can I attach an ammeter in series with the VMx pin of the driver and measure current?

Is there any tested or proven method for measuring current? I can really use the help.

Thanks in advance!


texts: Wiring a switching regulator, two relays, and a LED…

texts:
Currently I’m working on a small portable amp which will be run either with 17 to 24 volts, depending if I drive it with a battery or a wall wart. It’s my first electronics project, so I have some fairly basic questions...

To power two single coil non latching relays (G6K-2P DC12 by Omron Electronics, coil current: 9.1 mA, coil voltage: 12 V, used as input selector, and stereo-to-mono switch) and an LED, I plan to use a voltage regulator. After reading an input by Russell McMahon on the Electrical Engineering Stack Exchange, it seems to me that in my situation (voltage drop of up to 12 volts) it would be the best to use a switching regulator, like the OKI-78SR-12/1.0-W36-C by Murata (input: 15 - 36 V, output: 12 V).

I want to design a little PCB with the regulator, the relays, a power output for the LED, and all the circuits and resistors needed for the input selector, and the stereo-to-mono switch). I got the audio part all figured out, but I’m not sure if I got the power part right.

Here is my schematic (just the power part), showing how I would connect the regulator the relays, and the LED:

I already tried to sketch out, how I would put this on a PCB in the size that would fit into my amp case. I will not solder the LED and the SPST switches to control the relays directly on the PCB therefore on the PCB you see the footprints of JST connectors at their place (SW1 = P2, SW2 = P3, LE1 = P7).

Now, I have the following questions:

Is is a good choice to use a switching regulator, as the one linked
from Murata?
Is my schematic correct?
Is the routing in my PCB correct, and supposed to work?


texts: Circuit analysis - determine the voltage and current on branches

texts:
I am working on a cardiovascular model that uses circuit diagram as an approximation and this is the circuit of a bifurcation but I got troubles determining the voltage on the capacitors and the current through the branches.

I got a following diagram  where the parameter of the elements are known and a time-varying input current is defined

After I applied the KVL, I end up with the following differential equations:

$$\frac{di_2}{dt}=-\frac{(R_2+R_3)}{L_2} i_2-\frac{V_{C1}}{L_2}-\frac{R_1}{L_2} i_1 - \frac{L_1}{L_2} \frac{di_1}{dt} + V_I$$
$$\frac{dV_{C1}}{dt} = \frac{i_2}{C_1} - \frac{V_{C1}}{C_1 R_4}$$
$$\frac{di_3}{dt}=-\frac{(R_5+R_6)}{L_3} i_3-\frac{V_{C2}}{L_3}-\frac{R_1}{L_3} i_1 - \frac{L_1}{L_3} \frac{di_1}{dt} + V_I$$
$$\frac{dV_{C2}}{dt} = \frac{i_3}{C_2} - \frac{V_{C2}}{C_2 R_7}$$

where \$i_2\$ and \$i_3\$ are currents on the branches, \$V_I\$ is the voltage on the source. However that's where I am stuck and don't know how to proceed as I am a bit confused about the \$V_I\$ term how to determine it.

Am I missing anything information or did I forgot a step? Thank you very much for help.


texts: Did I choose the correct fuse for my USB powered circuit?

texts:
I need to drive a circuit (operational current 150mA) with a USB port. I would like to protect the port with a fuse and from
this question I concluded, that what I want is a PTC fuse. Is that the correct conclusion?

I would choose the MF-PSMF035X, but I am somewhat confused by all the different currents provided in the data sheet and can not really tell, if this fuse would "blow" (how do you say that for a resettable fuse?) earlier than the fuse on my motherboard, which I would want to not blow, of course.

So here is my interpretation of the different currents:

\$I_{MAX}\$ = current at which the fuse gets destroyed
\$I_{HOLD}\$ = normal operational current
\$I_{TRIP}\$ = max current through "blown" fuse
Max. time to trip [Amperes @ 23 C] = max. current it takes for the fuse to "blow"

Now the USB fuse of my motherboard should blow at 1.5A according to the USB specs. If my PTC "blows" at 8A, as it says in the sheet, then it would effectively NOT protect my MB, would it? And also \$I_{TRIP}\$ of 750mA is larger than the 500mA one can continuously draw from a USB port. Is that a problem?

Oh and additionally: what is the best thing to do with the data pins of a USB port, if I only need the power pins? I read somewhere, that you are supposed to short them, but that does not seem like a good idea to me.


texts: Differences between thermistors and thermocouples

texts:
As I understand it, both thermistors and thermocouples are temperature sensors. So what are the advantages/disadvantages of using one over the other to measure the temperature?
What are the specific applications for either of the sensors?


texts: Single Phase Induction Motor Wiring help

texts:
I have purchased a Single Phase Induction Motor that runs anti-clockwise, I require it to run clockwise however I am unable to figure how to change the wiring to do this, any help would be appreciated.

https://imgur.com/a/popMb

Worth noting, if I fully remove the starting capacitor, the motor starts in anti-clockwise even if I give it a spin clockwise before switching it on.


texts: Back to Back and Ladder Protection Diodes

texts:
I'm considering replicating this schematic from a paper (https://ieeexplore.ieee.org/document/5062317).  The idea of the circuit is to measure the capacitance of a transistor between the Drain and the Source at different Drain voltages (Vds).  But the trick is to not inject the high Vds voltages or currents into the sensitive impedance analyzer. C1 and C2 help keep DC current and voltage out of Hcur and Hpot while L1 shorts DC current away from Lcur and Lpot.

However, I'm not entirely sure what the different sets of protection diodes are suppose to accomplish.  Here is my understanding so far:

ZD1/ZD2 - clamps Hcur to +-10V
D1/ZD4/ZD3/D2 - the zeners clamp Hpot to +-10V but not sure what the 1N4004 diodes do
D3/D4 - diodes to ensure there is no voltage difference between C1 and C2 if one changes suddenly
Ladder of Diodes connected to Lcur and Lpot - no idea what this layout is used for

Could someone explain the point of each of these protection diodes layouts?


texts: Inverter constructed using LDMOS transistors

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I have the following question: is it possible to construct an inverter using LDMOS transistors when HV power supply is equal to 30 V and maximum VGS for LDMOS transistors is 5 V? Moreover, lower MV domain is 5 V.

See the attachment for visualization - problem section.

I can do following solution - see the attachment (solution section). However, doing it means constant current consumption and problems to turn on PMOS (apply 25 V on its gate). PMOS is turned on through 5R resistor.

Do you know if it is possible to construct such an inverter?

EDIT: IT MUST BE AN INTEGRATED CIRCUIT SOLUTION.


texts: Finding voltage difference in a resistance temperature device

texts:
I would like to know if I am on the right track on this question
The way I approached this question is as follows.

$$ R = 500[1+0.005(100-30)]\\R = 675\Omega \\$$
Then I find $$R_{eq} = 540.23 \Omega$$
I found the total current going into the branches
$$I = \frac{10}{R_{eq}} = 18.5 mA$$

I applied the current division and found the current going through RT
$$I_2 = 8.13mA$$

Then the Voltage at B

$$I_2 = \frac{10-V_b}{675} = 8.13mA\\V_b = 4.51V$$

I just want to know if I am doing this question correctly. Any help would be appreciated it.

EDIT: After fixing my mistake, I found $$I_2 = 8.5 mA\\ V_b = 5.74V$$ And as others pointed out $$V_a = 5V$$


texts:
I am currently looking at a 4017B Decade Counter Data Sheet.

As I look at the Logic Schematic for this IC (http://www.ti.com/lit/ds/symlink/cd4017b.pdf) I can see several sqaure boxes label D, C, Q(bar), Q.

Am I correct in assuming that these square boxes are a variant of the 'Flip Flop' in order to store the value that the counter is on and would I be right in assuming if I replicated this schematic with my own flip flop I could create my own Decade Counter?

Thanks.


texts:
I found the Req of the whole circuit at first, then tried re-assembling the circuit and still I couldn't get the right answer.

Any idea on how I should proceed in this exercise?

I'm not looking for any answers, just a walkthrough.

Step 1:

simulate this circuit – Schematic created using CircuitLab

Step 2:

simulate this circuit

Step 3:

simulate this circuit


texts: PL9823 data line corruption when using 3v3

texts:
This is my schematic:

The PL9823 uses the same protocol as WS1012 (NeoPixel)

When using 5V MCU and 5V to power the LED everything works OK.

When using 3v3 MCU and 3v3 to power the LED everything works OK.

When using 3v3 MCU and 5V to power the LED it does not work. The led is not set to a desired color and changes to a random one.

After reading up on the diode it was suggested that I place a capacitor between data line and ground on the first diode. After I did that the signal didn't do anything and the diode didn't change color.

Next thing I did was add a resistor in RC low-pass filter configuration and the signal did change the LED to a desired color. But sometimes the signal did get corrupted and the LED didn't show the correct value. I tried different resistor and capacitor values and the LED still on some occasions showed the wrong color.

What am I doing wrong?


texts: How does this power supply (resistor/capacitor) divider filter work?

texts:
I've been looking at various valve guitar amplifier circuits and in specific, the power supply section.

I've been seeing a particular circuit that's repeating itself here and there in the power supply stage of various amplifier schematics.

simulate this circuit – Schematic created using CircuitLab

Am I on the right lines by guessing that node X is some sort of virtual ground which is held constant by the voltage divider formed by the identically sized resistors? As in node X will be held at ~275V and any noise/variation/ripple to upset that will be "soaked up" by the capacitors?

I still don't understand why they wouldn't simply use a single big capacitor instead of this circuitry? The node X is not used anywhere and it seems to be there simply to aid filtering of the output of the bridge rectifier. Not to mention power losses due to the resistors. Atleast around 1W.

How about tolerances, obviously the resistors are not identical in real life, and such the voltage can't be half of B+. What implications does this have on the behaviour? Similarly capacitors have variance too.


texts: How to assert multiple concurrent assertions in system verilog?

texts:
I want to do something like this using concurrent assertions (I want to check that when from_clk changes to_clk must change and when to_clk changes from_clk must change):

($changed(from_clk) |-> $changed(to_clk)) &&
  ($changed(to_clk) |-> $changed(from_clk))

I have written the below assertions but it is not giving correct result in simulation.

property check_clock;
@(from_clk or to_clk) disable iff(reset || ~enable)
($changed(from_clk) |-> $changed(to_clk)) &&
 ($changed(to_clk) |-> $changed(from_clk));
endproperty

ASSERT_CHECK_CLOCK : assert property(check_clock)
                     else $error();

Please suggest how to achieve this.


texts:
I am an ancient old pensioner (92) and I recently collapsed in my bungalow where I live alone and stayed on the floor until discovered. In hospital the Red Cross suggested an electronic emergency service which consists of a wrist band transmitter and shelf receiver which sends an alarm to a monitoring station.  Works fine but I now discover it costs an initial £25.00 then £15.96 per month.

There are thousands in need out there who cannot afford this but who live alone and do need a rescue system. We need a simple low cost automatic " person down" alarm that costs a little and is a one-off purchase.  I think I have the idea for a solution but it will need a simple electronic circuit.

The circuit needs to flash a very bright bulb when triggered until manually stopped. This circuit does absolutely NOTHING for a pre-determined time - say 24 hours.  If an obvious button is pressed it continues to do NOTHING for another 24 hours.  If the button is NOT pressed then after the allotted time it goes into action and the strong bright light goes into full flashing mode.  A second button would stop the action if it was accidentally triggered and a third button would activate the device if the lonely person was in trouble and could reach it before the device went automatic. Mains operated with an automatic battery back-up if the mains connection failed, with automatic trickle charging when mains connected.

Housing would be a simple box shape about 12 inches square and a depth of about four inches to sit on a windowsill, perhaps simple legs if height was needed. The front 12" square would have a cut-out board with large HELP.  The powerful light, red bulb or coloured film over cut-out would illuminate the HELP.  If the lonely person was in good shape and always remembered to press the " I'M OK" button then the device would never come to life.

If the lonely person was forgetful and allowed the device to go to alarm when nothing was wrong - then so-what! At least their loneliness would be broken by visitors; and the visitors should not care about the slight inconvenience of helping an old lonely person.  Might trigger some good Samaritan to check every day.

I belong to a local "MensShed" and we could knock up a prototype if somebody could work out a circuit.  If we could produce a working prototype then it might not be difficult to find a manufacturer and perhaps the Red Cross and AGE to distribute it.

I am a life member of the RAF Association and the top brass at the RAF Benevolent fund have show interest to supply to RAF veterans who are in need.  Any help available?


texts:
Suppose I have a signal that consists of a sine plus noise. Is it possible to measure the SNR with an oscilloscope?

Is the following procedure correct?

Check the noise floor in the FFT mode of the oscilloscope (green FFT in picture).
Connect the DUT and measure the SNR as indicated (red FFT in picture).


texts: I'm looking for a D-punch/die set for SMA bulkhead cut-outs into 1mm thick plastic. Coax connector manufacturers don't seem to offer such tools (even though there are many manufacturers offering such widely used connectors)... I'm wondering if anything like this even exists ? Has anybody heard of anything that may be used for cutting out SMA coaxial holes into thin panels ?


texts:
I was looking at two ADCs, the ADS8568 and AD7606B and came by a rather curious design decision for both.

ADS8568

AD7606B

800ksps per channel

There's quite a mismatch between the sample rate and the bandwidth of each ADC. The ADS8568 has a bandwidth wildly larger than its sample rate, whereas the AD7606B goes in the other direction where it's sample rate is wildly larger than its bandwidth.

Isn't this kind of a waste? I understand sampling up to (a somewhat arbitrary) 32x times faster than the bandwidth, but these two ADC swing farther than that (and do so in both directions).

The only intentional reason I can think of the bandwidth of the ADS8568 being so much larger than its sample rate is for undersampling but is undersampling really common enough for the ADC to be designed with that in mind? This seems unlikely to me though. It seems much more likely to me that SARs ADCs in general just have really high bandwidths relative to their sample rates with little effort since the sampling capacitor just grabs whatever is on the line. I saw this with another SARs ADC but have not checked too many though.

Then there's the AD7606B where it seems like a pretty big restriction just to permanently throw in an anti-aliasing filter to clamp its bandwidth to 32x slower than its sample rate. This one is the bigger mystery to me.


texts: Unable to compile (build) code with MPLAB for PIC with CCS C compiler

texts:
I'm a newbie  trying to lean PIC, i downloaded MPLAB and MPLAB X ide .
Ihave done this around 100 times and looked over web enough before asking this question, but my code is not compiled  and it is failed always.
Here is what i did:-

Created a  new project using PROJECT WIZARD
Edited the code
Copied the  "16F871.H" library in both folder (i created the project in) and added it to the header files in MPLAB IDE.

Here's my code

*> // IFIN.C Tests an input
#include " 16F877A.h "
void main()
{
int x; // Declare variable
output_D(0); // Clear all outputs
while(1) //
{
x = input(PIN_C0); // Get input state
if(x = = 1)output_high(PIN_D0); // Change output
}
}*

  But on compiling the code  i'm getting error a this  Executing:

  "C:\Program Files\PICC\Ccsc.exe" +FM "NEW.c" #_DEBUG=1 +ICD +DF +LN
  +T +A +M +Z +Y=9 +EA  #_16F877A=TRUE

  * Error 18 "NEW.c" Line 2(10,23): File can not be opened

Not in project "C:\Users\jatin\Desktop\DHAKKAN PIC\ 16F877A.h "

Not in "C:\Program Files\PICC\devices\ 16F877A.h "

Not in "C:\Program Files\PICC\drivers\ 16F877A.h "

  * Error 128 "NEW.c" Line 2(10,17): A #DEVICE required before this line

  * Error 12 "NEW.c" Line 6(9,10): Undefined identifier  -- output_D

  * Error 12 "NEW.c" Line 9(10,11): Undefined identifier  -- input

  * Error 51 "NEW.c" Line 10(8,9): A numeric expression must appear here

  5 Errors,  0 Warnings. Build Failed. Halting build on first failure as requested. BUILD FAILED: Mon Jul 08 15:09:17 2013

I would be grateful to you if you could help me.


texts: Confusion on sensor resolution specification

texts:
This sensor has resolution +0.001% F.R. , and output noise of Output Noise 0.02% F.R.
If full range is 10V, according to the datasheet the resolution becomes 0.1mV and the output noise becomes 2mV.
Neglect the accuracy and any other noise sources, does that mean that the output noise already lowering the resolution from 0.1mV to 2mV? If so, what is the point to mention the resolution lower as in the datasheet?


texts: Automatically distinguish between various two terminal components

texts:
I would like to distinguish in the easiest and safest way possible between the following kinds of components attached to my circuit:

resistor
diode
zener diode
capacitor
polarized capacitor (electrolytic)
inductor

Safe because I do not want to e.g. exceed the voltage rating of components. Also the electrolytics polarity should be detected properly. Basically you should be able to put the component on the device and it tells you what you put on there.

Since resistors have an inductance, and inductors have a resistance I would be fine with restrictions for useful values; that is something with 10Ω and 500nH should probably be qualified as a resistor and not a tiny inductor.

The circuit should not need any extremely sophisticated parts that e.g. amount to an internal high class oscilloscope. It should probably use some average PIC.

Note that I am not asking for a complete circuit but some rough ideas, if graphical maybe as blocks.

The main points that I am having problems with is:

detecting polarity of a capacitor without applying reverse voltage
First idea for a zener was (after detecting it is a diode) that I detect the breakdown voltage, but what if it is just a normal diode that gets destroyed this way because it has a rather low breakdown? That would limit the breakdown voltage that I could detect in zeners.


texts:
I find it hard to find on the internet a simplified explanation of the principle of operation of the CDMA system. Could you give me an example of how it works and how a receiver can correctly identify a user's message?

Precisely, as I understand it, each user sends a certain message, often called spreading code, which is composed of a series of pulses called chips.

For example, the spreading codes of two users may be:

User 1: 1, 1, -1, -1

User 2: -1, -1.1, -1

I read on the internet that each user has a personal code, which is chosen to ensure orthogonality to avoid interference. However it is not specified which sequences must be orthogonal: orthogonality between the spreading codes, orthogonality between the personal code of a user and those of the other users, orthogonality between the personal code of a user and the spreading codes of other users?


texts: Logomatic v2 serial SD Datalogger issues

texts:
Hi i bought this data logger a few weeks ago, http://www.littlebirdelectronics.com/products/Logomatic-v2-Serial-SD-Datalogger.html

I've been having some trouble with it. I read the data sheet and I've powered it up (using a 2Gb Sandisk micro sd card formatted to FAT16 512 allocation size and powered by 2 AA batteries). The data sheet says that on initial startup the leds should blink rapidly and then stop. What I'm having happen is that the usb light will go on and after about 30 seconds the stat1 and stat0 will also light up and they will all stay on. When I turn the unit off and then connect it to the usb, my computer (Windows 7 64bit, also tried 32bit) says that the device has malfunctioned and it cannot install the drivers. I then tried uninstalling the SD card and connecting it to my computer but it shows that the SD card is empty and there are no log files contained on it.

I really need to get this working in the next week for my uni major project so any help would be greatly appreciated.

Thanks heaps,


texts: Trying to understand how to design the gate of a frequency counter

texts:
I´m trying to design a frequency counter for my physics class. My teacher demanded that we build it using a 32768 Hz crystal and 4060 ic. In my research i stumbled across this design:

I don´t have a good knowledge on digital electronics and i have no idea on how i can fisically build the main gate and gate/flip-flop blocks (which ics to use and stuff). I deeply appreciate any help.


texts: Guessing power line voltage from the number of disc insulator

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Is there a good way to guess the power line voltage based on the number of insulator discs that attach the line to the transmission tower?

Wikipedia seems to suggest that there is a "Typical number of disc insulator units for standard line voltages".

Is this a good ball park upper bound to the voltage on the power line?
Is there a better way of guessing line voltages?
Is it possible to further refine this guess based on the type of insulator discs?


texts: PIC/ICSP - Protect circuit from VPP voltage?

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I'm more of a software engineer, but I've done a fair amount of toying with components and microcontrollers. That said, this has me concerned, and my searches so far seem to indicate that no one's ever had an issue with this.

I have a PIC12F675 - it has 6 I/O pins, and I need all of them. One will be an analog input, the rest LED outputs. And since I'll likely be soldering this to the board, I think the potential for ICSP would be of great use, to add features or fix bugs later. The only problem, as I have recently discovered, is that the VPP is something around 13 volts. On a pin that's connected to an LED. I'm not much of an electrical engineer, but I'm thinking the 220-ohm resistor isn't going to stop things from exploding.

What can I use to protect the LED, or other circuitry in general? I've got several of these chips, so I'm sure the issue will come up again, with components of varying sensitivity.


texts:
Typically in the block scheme of a spectrum analyzer a video filter, with a bandwidth VBW, is located after the envelope detector and before the screen.

As pointed out in this document, the VBW may (and sometimes should) be less than RBW (Resolution BandWidth, that is the bandwith of the IF filter): the resulting signal will be less affected by noise (page 28). But if the VBW is smaller than RBW, this means that part of the RBW output is "wasted", which is undesirable.

1) Isn't it?

The envelope detector itself is a low-pass filter applied after the RBW and before VBW, so (even without the VBW) the signal displayed on the screen has a lower bandwidth than RBW. But the bandwidth of the envelope detector is nowhere specified. So:

2) How can I become sure that no useful signals are cut off by a VBW < RBW? Should I display the signal with VBW > RBW and then lower VBW till all the harmonics are still preserved and stop when a harmonic is cancelled, in a trial-and-error procedure?

Note: the document was just an example, the only useful I found so far. I am not referring to a particular model, but to the (theoretical) reason why a video filter is used in a spectrum analyzer.


texts: Why MII interface needs two clock TXCLK and RXCLK where as RMII needs only one clock REFCLK

texts: I was reading this article and Learned that MII interface needs two clocks TXCLK and RXCLK whereas RMII interface needs only one clock. Is there any benefit of having two clocks? If yes what is the limitation of RMII interface then?


texts:
I am making a switch to control a desk light using this pilot relay. My module is plugged into a half-hot wall outlet that's controlled by a wall switch.

The module uses a momentary-on switch to energize the relay, which then holds itself closed until a momentary-off switch breaks the connection. Additionally, removing power from the module (turning off the wall switch) resets the relay so I can turn my lamp on or off from either the wall or the desk.

My question is: what is an appropriate safety feature for such a module, since the switches will be conducting 120 VAC, and my shock-intolerant fingers will be using the switches?

The switches are in an insulated housing, and there is a 3-conductor 28 AWG insulated cable connecting the switch housing to my module. Assume I am paranoid about liquid spill onto the switches or damage to the connecting cable.

Fusing the entire module wouldn't work, since it's driving up to a 10 A lighting load. I could conceivably fuse all three wires in the cable.


texts: Finding component values of bandpass filter with load?

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I have to find the components of a bandpass filter given only the two corner frequencies. The only components are \$C_1\$ and \$R_1\$ for the high pass, and \$R_2\$, \$C_2\$, and Load resistance (\$5\$M\$\Omega\$) on the low pass.

I set \$R_1\$ to \$10\$k\$\Omega\$ and got \$C_1 = 53.05\$nF when corner frequency for high pass is \$300\$Hz using \$C=1/2\pi fR_1\$.

However, for the low pass... I can't figure it out. I combined \$C_2\$ and the load into equivalent impedance \$Z\$ (they are in parallel), then plugged \$Z\$ into the transfer equation for a low pass filter where ever a \$C\$ would have normally appeared, and get \$C_2 = 1.588\$nF while \$R_2 = 10\$k\$\Omega\$ (setting transfer of low pass filter equal to \$1/\sqrt{2}\$). Also corner frequency of low pass filter is 10kHz. But the graph of the output voltage looks like a high pass filter only, and is in the micro volts and the -3db frequencies are nowhere even close... I don't get what is going wrong with the low pass filter

So was wondering if anyone can show me how to calculate the \$R\$ and \$C\$ values of the low pass filter part of a bandpass filter when it is connected to a load?

It is quite a basic bandpass filter, but imagine a 5Mohm load where Vout is.


texts: Including a short in a real-world circuit

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In theory, the voltage across a wire is zero, so any components bypassed by a short circuit can be ignored when analyzing the circuit.

A real wire, however, is not an ideal conductor.  Is there any real-world situation where you would have a circuit where a component is deliberately short-circuited?


texts: Making a plastic card that looks like a credit card with a long-range module inside

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Does anyone know how I could make a card the size of a credit card with something like a GPS/bluettoth/RFID module that could be detected from a relatively long range. The purpose is to see where this card is on a map for example.

Are there GPS modules that are that small?

If someone could direct me to some tutorials or help.

EDIT: Really the idea is, If I ever lost my wallet for example, I could track where in the house I lost this wallet. A lame example but this is the basic idea.

Thank you.


texts: Increasing Overdischarge Protection Voltage in DW01A

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I am working on a academic project which requires TP4056 along with battery protection circuit (DW01A).

The ciruit uses a 1S LiPo 500mAh battery.

I want to keep the Overdischarge Protection Voltage (VODP) to 3.2v. Looking at the datasheet of DW01A-G, it mentions that VODP is typically 2.4v.

https://www.ic-fortune.com/upload/Download/DW01x-DS-17_EN_53550.pdf

Can i increase the VODP by simply increasing the resisor value R2 which is shown in the typical application circuit?

I did search for other posts in SE but didn't find any convincing answers. Please let me know.


texts:
I have a question about power good connections.
In my circuit design I'm using a LDO linear regulator (TPS79401,) an USB 3.0 controller (TUSB7320) and a Raspberry Compute Module 4. I have seen on a TI forum one schematic where the GRST pin was connected to RUN_PG by a resistor, but the GRST pin of TUSB7320 datasheet says that if this pin is high, the device doesn't work.
Furthermore, TI recommends this: "It is highly recommended that the GRST# input be connected to a power good output from a power supply", and on their schematics and recommended design they connect PG of power supply TPS74401 (I'm using 79401 because there is not stock and are almost the same) to GRST.
How should I connect these pins? GRST_TUSB7320 to PG_TPS79401? GRST_TUSB7320 to Rasp_RUN_PG? All of them connected by the same wire?
PG pin TPS79401

TUSB7320 GRST

Raspberry Compute Module 4


texts: Reverse Engineering of a AC speed controller

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Recently I've bought one of these AC speed controllers AC Speed controller from china. After a few tests the BTA16-600BW Triac blew up, so I tried to reverse engineer this controller.

Here are the Images of the top and bottom

This is the circuit which I got from reverse engineering

simulate this circuit – Schematic created using CircuitLab

Actually I dont understand how this circuit works.
As far as I know, the C2, R4,R1 andf R2 network is used to genarate the pulses to turn on the triac. but how exactly does it work?


texts: Voltage follower with antique lm308 op amp

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I'm playing with an antique LM308 http://web.mit.edu/6.301/www/LM108.pdf
For some simple tests I've wired it as a voltage follower.

simulate this circuit – Schematic created using CircuitLab

Now I'm trying to understand my measures :

0V <= Vin <= 600mV       Vout = 600mV
600mV < Vin <= 4.57V     Vout = Vin
Vin > 4.57V              Vout ~ 4.6V

One important thing is that I got Vout(peak-peak) at an high level, for these antique op amp, adding a compensating capacitor between 1 and 8 pin is needed.

From datasheet with Vs=+-15

common mode min input range = +-14V
Min output swing            = +-13V

So with 0-5V supply, does that mean :

input range = 1-4V
output range = 2-3V
?
Why is 600mV measured?

An another op amp http://www.analog.com/media/en/technical-documentation/data-sheets/OP270.pdf, I've these results :

0V <= Vin <= 750mV        Vout = 0V
750mV < Vin <= 5V         Vout = Vin + 900mV
How can I explain results?

After this first experiment, I wired a non inverting amplifier with 2 gain (R1 = R2 = 1k)

0V <= Vin <= 600mV  \ Vout = 600mV
600mV < Vin <= 1.9V  Vout = 2 x Vin
Vin > 1.9V           Vout = 3.8V

As in previous setup, op amp not active when Vin <=600mV.
When Vin > 1.9V Vout reaches a max value of 3.8V, why does this value differ from previous setup?

Thanks for your explanations.
lah


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Problem : BTA16 triac is always on with using MOC3043 as driver
Facts: BTA16 working correct when moc3043 is disconnected from it's gate pin.
Atmega8 output pin is connected to 330ohm resistor and it's output is working correct.
MOC3043 output is always on regardless of it's input state.
Question: According to MOC3043 datasheet, the maximum input current is 5 mA, is it possible that 330 ohm resistor with 5 volt cause MOC3043 input LED to burn out and it's output becoming always on?


texts:
Is it possible to make a 20 MHz radio with this

by creating a circuit consisting of a battery, that crystal oscillator and an antenna?


texts: How is Q for surface acoustic wave devices measured?

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I do not have a good understanding of Q, the quality factor.
I get the basic concept that it has to do with energy losses within a system, particularly oscillating systems like resonators. Higher Q has less damping and will ring a longer time, while lower Q are the opposite.

I would like to know how is Q determined for SAW resonators typically? I came across something about the frequency to bandwidth ratio being used to determine Q. Is that it or am I missing something else?
Will devices with increasingly narrower bandwidths (for the same frequency) have higher Qs and oscillate for longer and more efficiently? If so, why? I would like to understand the reasoning behind it.


texts: How do I attach an IC chip to a DIN rail?

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I am using a 74AHCT125N to shift up voltage of pwm signal. The problem we are having is how to attach this chip to DIN rail. We were thinking of using a DIN rail mounted PCB. I am looking for solutions, suggestions other than that?

Thank you very much for your help!

74AHCT125N:
https://www.digikey.ca/product-detail/en/texas-instruments/SN74AHCT125N/296-4655-5-ND/375798


texts: what is an affordable indoor 3D positioning sensor setup?

texts:
I have a question regarding a problem that seems easy, but after already doing some internet searches, seems not to be that easy to solve. I have a non-moving test setup in a large room where I have to measure the 3D coordinates of some sensors, and I need a fast and easy way of measuring their 3D position coordinates - without having to use a ruler. The sensors are quite small and mostly installed inside a machine. Because of the installation inside a machine, typically visual methods are not possible. The location has to be determined only once, and the reason to automate this is because there are quite a lot of sensors on locations that are not always easy to measure.

The required precision would be in the order of 1 cm. The solution should be fast, but does not have to be wireless. The size of the test setup itself could be several meters.

Does someone have an idea what type of sensors would be suitable for this kind of application? Is a dead-reckoning solution with accelerometers that have suitable low-frequent sensitity a good and cost-effective solution, regarding the given precision? And if so, should I use some noise filters?


texts: Why are the mosfet gate tunneling currents disappearing in a bsim4 simulation under a width and/or length of 10µm? (TSMC65)

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I am trying to simulate the current from the gate of a mosfet to its body (drain, source and bulk are shorted). But with a downscaling of the transistor the current disappears abruptly and fully under 10µm, although the igcmod and igbmod flags are set to 1 in the model (tunnel current simulation is on). The purpuse of this is the design of a floating gate memory cell in standard TSMC65 process; something like this.
I tried remodeling the behaviour in an external element, defined by a verilogA file which contains all the necessary formulas from the BSIM4 documentation, but the resulting current (above 10µm) doesn't match the original simulation. While reading through the technology parameters i noticed though that single transistor models are defined multiple times, usually prefaced with  something like "1:ptype ..." then again "2:ptype" and so on. Could my problem have something to do with the simulator using different models of the transistor for different voltages or sizes? And how can I make sure the tunneling current will be calculated at all times?
Thank you in advance!


texts: Crazy homebrew 500 MHz 1 Gs/s oscilloscope possible?

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I was reading USB scope probe - request for comments and ideas, and it got me thinking. What I'd really like is a very high performance oscilloscope, one which would cost $10000 or so. Surely many other people would like one too. And surely, with the expertise available on this site, it should be possible to design and open-source one.

Here's my idea:

It would be a hand-held 'scope probe with a USB lead coming out.
Battery operated to isolate it from USB power.
Input stage is a high speed op-amp, like THS3201DBVT?
ADC is something like ASD5010, which is 1 Gs/s and 650 MHz input bandwidth.
FPGA to handle the 32-bit data coming out, do the triggering, and package it into the USB.
Open-source software to run on the PC.

Is this a fool's errand? What am I missing?

Added, more details in response to the answers:

This 'scope would not be able to compete with the fancy expensive scopes out there. The main aim is to have something which would make it possible to examine high speed signals, while costing less than $200 for someone to make themselves.
USB bandwidth: This is not an analog scope, nor is it a fancy LeCroy. However, USB is quite capable of transfering 2k samples at 60 Hz. This still makes it extremely useful, even though it might not be capable of capturing transient events in between those frames.
A clear responsive display. Well, a PC's monitor is certainly clear. Better than almost all scopes on the market. So clarity and size are no problems. Responsive? As long as the screen can be updated at 60 Hz, I think that's pretty responsive.
Triggering: I was imagining simple level triggering happening on the device. Again, it would not be able to compete with fancy scopes, but remember: this is supposed to be a $200 device.
It's not supposed to have 1 GHz bandwidth. Where did I say that? But surely it could have more than 100 MHz bandwidth?

Take home points:

It's a $200 device.
The main aim of the device is to make it possible to see high speed signals without spending $10000.
There would be many things that it would be unable to do.
Surely something like this would be fairly useful to people here.
Surely, with the expertise available on this site, we could make it happen?


texts: EAGLE CAD: Push aside traces by DRC clearance

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Does anyone know of a script or tool which makes it easier to 'push aside' traces when routing by the specified DRC spacing? For example, if I have 2 traces which should be parallel and are 6 mils wide and 6 mils apart it is fine to route on a 12 mil grid if I am strictly routing horizontally or vertically. However, if I try to route on the same grid diagonally, they will be too close together, just due to geometry.

Some PCB layout programs have a push aside or 'shove' command which does exactly this. Is there a native command or script which performs this function in EAGLE?


texts:
So I have two daisychained 74HC595 Shift Registers driving 16 low current LEDs, and the shift registers are wired to an Arduino Mega.

Initially the ciruit worked perfectly, the test code scanned left to right toggling one LED, a few weeks later it suddenly began to toggle random leds.
Also, when you firmly press the cables together it becomes more stable.

I have tried adding more decoupling capacitors (100nF as per datasheet) directly onto the VCC and GND of each Shift Register, I've switched out the cables for a sheilded cable with twisted pairs and the measured current is within the Reccomended specs. Still no change.

I borrowed an osiliscope and the data/clock/latch seem to be fine, but it's a pretty old model that I am not too familar with and I could've made an error.

What could cause this 'noise' and how would you prevent it?
Thanks!

EDIT: Quick Schematic

EDIT: After buying a new set of decoupling capacitors, everything worked.


texts: What does "Run Power and Ground wires back to the Arduino" mean?

texts:
An Adafruit article showing people how to wire up an RGB LED to an Arduino UNO has the warning shown below on its page.

  For longer strips requiring more than 1 Amp, wire the power directly to the strip, then run power and ground wires back to the Arduino.

I understand that you can connect ground wires together, however, it's advising us to run power wires back to the Arduino. I don't know what this would mean as I don't think a +12 Volt line will do the Arduino any good as it runs at 5 volts. Is this a typo on their end or is there something I'm missing here?


texts: Li-Ion Charging - Constant Voltage Stage

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The charging curve for Li-Ion batteries (explained here) has a final constant voltage stage where the charge voltage plateaus and the charge controller slowly shuts off the current until it reaches some threshold (10% in the video's example) and charger considers the battery full.

I can take a battery and measure the voltage. But here the voltage is constant, so how does the charge controller know when to cut off the current?


texts: Why do some pins have `~` signs next to their numbers?

texts: I was looking at my Arduino Uno and I noticed that symbol by digital pins 11, 10, 9, 6, 5, and 3. What do these mean? Does this affect the way it works? Can I not use these pins for certain situations?


texts: Specifying the address range of each memory block

texts:
Four 16x4bit blocks are interconnected to form a 64-bit memory as shown below

First of all why is a block here called 16x4bit ; 4 bits are related to the input gates but what's with 16 here ?
I also specified the address-range of each block but it seems that my answer was incorrect : This is what I did :
Memory MA => 0x00 - 0x0F (Since it has only 4 bits = half of a byte = 16 Adresses)
Memory MB => 0x10 - 0x1F
Memory MC => 0x20 - 0x2F
Memory MD => 0x30 - 0x3F
What am I doing wrong here ?


texts: Series reactance of inductor and capacitor

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Series LC circuit, connected across a constant voltage AC source.
If the capacitor had the greatest reactance, could the circuit be simplified to simply a capacitor (by resolving the reactances)? How would this all work with the relevant phasors?

Thanks!


texts: Microcontroller shutting down in etched circuit, but works as expected in breadboard circuit

texts:
I have a computer fan controller circuit which uses an microcontroller to convert an analog signal from a potentiometer to control the speed of an computer fan (PWM controlled) and indicate the rough speed percentage with 4 LEDs.

When I use my circuit on the breadboard it works perfectly, but when I use the etched circuit it flickers for a second or two then shuts down completely.

Background

Here is the circuit:

As you can see it's using a 12V supply and then a voltage regulator to supply the microcontroller with the needed 5V. Then I have the fan hooked up to the 12V supply and the control cable hooked up to the microcontroller.

When I'm using the circuit in the breadboard I connect the resistors and the potentiometer to the breadboard via the IC holder on the etched circuit to make sure there isn't something wrong with the components or soldering. Then I supply the microcontroller with 5V from a stabilized DC power supply.

Then I measure the 5V PWM signal that should go to the fan with a multimeter. Everything works like expected, the LEDs light up when I turn the potentiometer and the voltage measured goes up.

Here is what the circuit looks like in action from the breadboard. (I'm measuring the PWM output with the potentiometer on these images) 0 percent:

Around 50 percent (Yes, the code that lights the LEDs needs to be fine tuned :P)

100 percent!

So the only difference is essentially the supply. When I put my microcontroller on the circuit and connect my DC power supply with 12V it flickers and stops working after a second or two.

Here is what the circuit looks like in action in the circuit itself with 12V applied across the supply. It stays like this even if I turn the potentiometer. I have checked that the regulator is regulating successfully and that the microcontroller VCC pin has 5V applied.

What could be the problem?

This is the first circuit I have designed and etched, so no need to tell you that I'm a novice. The only thing I can come up with that would be a problem is that different supplies share the same ground. Is there something else that could be the problem?


texts: PWMing the output of a constant current driver

texts:
I have a set of LED panels that come with AC-DC constant current drivers. Is it acceptable to use a MOSFET to PWM the LED (MOSFET goes between the driver and the LED)?
Also the microcontroller that will be producing the PWM will use a different AC-DC power supply. Is it OK to common the ground rails from the LED driver and the microcontroller PSU, or is it advisable to use an optocoupler?


texts: Basic transistor audio amplifier bias question

texts:
I'm just learning about transistor biasing for ac signal gains, and while I have many questions about setting Q points, I'll ask one which is not familiar to me. In the schematic below it's teaching how to bias a transistor with voltage dividers. I follow most of it until they say to set collector current by base current of .1ma. Fine, I understand HFE gains, but then proceeds to say the voltage divider across r3/r4 needs to have current approx .9ma plus the .1ma of base current. If there's no base resistor setting .1 from voltage divider, wouldn't base current be .9? If they are referring to the ac signal from coupling capacitor, how do ac voltages and currents combine with DC voltage divider bias? I can't seem to find visual descriptions to explain this interaction in principle. Any help would be appreciated.

http://www.rason.org/Projects/bipolamp/bipolamp.htm


texts: Does anyone knows the SmartGen LINK Port protocol?

texts:
I need to replace an SG72A controller in a machine, I would like to make a cable or small component to It, because I have no time to wait for this to came from China to Brazil.

I didn't found any information about the protocol used by this LINK port, the only thing is that it´s a TTL level port, witch doesn't say to much for me. Can anyone help me with some link or any information?


texts: Does an LED TV that is displaying "black" emit enough light to trigger an LDR?

texts:
I would like to monitor a digital sign to make sure it stays 'online' - the setup is a Raspberry Pi connected via HDMI to an LED TV. I have seen some general linux discussion about polling HDMI-attached devices but have not not yet been able to get this working. Since the GPIO pins exist can I just use a "physical" solution and check to see if the TV is on and producing output by taping a small LDR to the corner of the screen?

One caveat is that the slideshow has a black background, and so I'm wondering if there will be enough "light" from this to definitively register the difference between "on" and "off" with the LDR.

I just ordered some cheap LDR's and am planning to taking some readings when they arrive, but am I headed in the right direction? If not, what are some options I could use instead of an LDR?


texts: How to mix High-Z and Low-Z audio signals? (Sum should be High-Z)

texts:
I'm trying to inject additional sound into a phone call. Therefore i modified a basic cable headset to use audio from my iPod.

This is my current prototype circuit:

That circuit is already working, but has some disadvantages due to the very basic passive mixing. When i turn up the iPod's volume it get louder and louder, but it also starts to decrease the mic volume.

Basically I'd like to be able to increase the iPod's volume without affecting the microphone level.

I think it has something to do with the iPod being a low impedance device (around 32Ω i think) and the electret mic being a high-Z device (around 1.5 k – 10 kΩ). Maybe there's also a problem with the power? The mic will only produce several millivolts, where as the iPod can supply more than 1 volts?

How could i improve my circuit, but still keet the headset recognized as a high impedance device. (if it's low-Z, the phone won't detect it properly).

Thanks in advance & bye!
Hans


texts:
I am working on a Tiva launchpad board and want to use the GPIO. I have successfully enabled the clock on PORTF using this line of code:

SYSCTL_RCGCGPIO_R = 0x20U;

So I tried changing the above line to the one shown below:

SYSCTL_RCGCGPIO_R |= (5 << 1U);

This did not work. Will someone explain the difference between the two.


texts: Why do we need a bootloader separate from our application program in microcontrollers?

texts:
Why do we need a separate program in the same flash program memory of a microcontroller, specifically STM32F103, which is called a bootloader?

What is special about it to keep it separate from the main application program?

Generally speaking, does a bootloader of a microprocessor-based system (say PowerPC MPC8270) do the same job as that of a microcontroller (say ARM STM32F103) or are they doing fundamentally different jobs from each other and yet both are called a 'bootloader'?


texts:
I built the schematic from this link: http://www.learningelectronics.net/extremecircuits/led-torch-uses-blocking-oscillator_13.html

It is working, but the LED is not illuminating at full brightness. I used a 5 mm white led. I know that the current is controlled from the inductor value. I powered the circuit using a 1.5V LM317 power supply and using a AA battery.

What value should I use for the inductor in order to make the LED to light at full brightness and not to destroy the LED ?
Can I use series inductors ?

The voltage across the LED is 2.79V.
The current through the LED si 3.12mA.
The power supply voltage is 1.49V.

Circuit diagram:


texts: I am looking for a low power way to mimic the ticking sound of a cars blinker. I had an LED flasher that made a ticking sound, but now with the setup I am using the flasher no longer will work with the system. Any ideas of a device (not a relay) that will produce this sound?


texts: Can anybody tell me what these three white boxes are at the bottom of the power pole?

texts: Can anybody tell me what these three white boxes are at the bottom of the pole? And how can I tell the number of the circuits on the electrical power pole and what voltages they have? Also, can I see what kind of three phase transformer it is? A delta star?


texts: AC Induction motors use an internal squirrel cage with skewed bars for the stator... However no matter how hard I look around on the internet I cannot find an external-cage AC induction motor design, except for a mention about ceiling fans using them. How would the wiring differentiate--if any--if you utilize an external cage vs an internal cage? How would torque output change with a larger cage as an outer rotor?


texts: What are these coaxial connectors called?

texts:
I know these are coaxial and probably SMB, however, I'd like to know how each particular type of connector is called.

Moreover, I was wondering if these colors mean anything in particular (i.e. if there is a specific color-coding convention).

Edit: Some context. The device is a car infotainment system. The device for #1 is a GPS antenna, and 1 through 5 are the adaptors I currently have to be able to connect the GPS antenna to the system (dark-yellow-ish connector & port). Thing is I need to get more GPS antennas and I don't think I'd really need all these cables (2 through 4) if I just had #5 instead of #1 directly in the GPS antenna.


texts:
Why can't we light an LED with a single positive wire on the anode, leaving the cathode unconnected?

Let's suppose I connect a wire with a positive voltage to the anode of the LED.  Now, I think, current will flow past the light emitting diode.  This should, by my understanding, make it glow, even though the cathode isn't connected to anything.  However, experimental evidence and common knowledge show that this isn't the case.

Is it possible in any situation(IDEAL) that we calculate current and voltage value so that this circuit will work, and automatically flow to ground after passing through the circuit?  If so, do we need a connection to ground in the real world?

Please point out my mistake if you notice a simple error I've made, and let me know what is right.


texts:
Simple question: I want to connect my geophone to an Arduino input. The geophone I have is actually output to a microphone jack and I can plug it directly into my computer. I'm pretty sure I can treat it like a microphone, but not positive.

The purpose of this project is to detect footsteps, which I have determined to be in the 7-30 Hz range on my bedroom floor. (While I'm here, anyone know of any easy, low-frequency low-pass and possibly high pass filter to write in the software?)


texts: Multilateration with TOA using lowcost transceivers (like NRF24L01) and uCs

texts:
My problem is the following, I would like to localize an object (main node) via multilateration using a wireless sensor network of 4 nodes with less than half a meter accuracy. The equations are already worked out and what is left is to obtain distance measurements from the network nodes to the main node using TOA method (this is what I am working on right now). My hardware specifications are the as follows:

5 NRF24L01+ transceivers (2.4GHz, 2Mbps, GFSK, 16MHz inner clock)
4 ATTiny85 uC (for the wireless sensor network) (8MHz clock)
PIC16f877A (main node) (16MHz clock)

Specifically, what I want to know is: can I measure the time of arrival of a signal (in less than a meter), with this hardware? If not, point some way out for me, either acquire new hardware (not too expensive) or change the method implemented.

PD: If possible look at the basic idea I have in mind before answering (and give me feedback on it): Narrowing down the problem time of flight between two nodes only (N1 and N2), the total time for a bit of data to go from N1 to N2 and back is:
$$t = 2(t_b + t_c) = 2\left ( \frac{1}{R} + \frac{1}{c}\times d  \right ),$$
where \$t\$ corresponds to bit transfer rate (\$R\$ = 2Mbps for NRF24L01+), or the time the transceiver takes to send that one bit to the channel; \$t_c\$ is the time in the channel that is approximately, the length of the channel over the speed of light.

The NRF24L01+ can send up to 32 bits in one go, this implies:
$$t = 64(t_b + t_c) = 2\left ( \frac{1}{R} + \frac{1}{c}\times d  \right ).$$
However, for \$d=0.5\$ (as I want) this yields \$t_c = 0.106\mu s \$, with a 8MHz MCU this time is invisible (1/8MHz = 0.125\$\mu s\$). A posibility is to resend the message to increase \$t_c\$ to a visible value.
Is the previous reasoning accurate?


texts: When a load draws more current than a source can give

texts:
I'm planning to use the LM2623 to boost a single AA for a 5V load that draws 400mA. This graph seems useful

The graph seems to suggest that at Vin=1.5V, there's no way 400mA could be drawn without a large voltage drop. At 200mA, Vout can be kept at 5V. I'm guessing that the load (if USB) will refuse to draw if the voltage is too low (<4.4V).

Is there a way to let it draw as much as it can from the input source? Could two DC/DC converters be used so that the first boosts the input from 1.5V to, e.g., 3V, and the second boosts the 3V to 5V. This way, at Vin=3V, the load could draw higher current (not for very long though).


texts: Are there any methods by which one could measure the current being drawn by an FPGA in real time i.e., when it is actually deployed in a working system? Where can I get some information about them?


texts: Please give me some advices for below schematic. Why is the need of bridge rectifier if both sources are at the same voltage?


texts: what voltage will 7805 deliver as output if input is lower than 5 volts, lets say 3 volts

texts:
I am looking at the 7805 specs sheet and there is one chart I find missing. It is the relationship between output voltage with input voltage, specifically when input voltage is lower that 5 volts, the "nominal" output voltage.

I think it would be desirable to have 0 volts on output until 7805 can provide 5 volts, but I think this is not the real situation.

So, my question is : what voltage will 7805 deliver as output if the input voltage is 3 volts ?

Any pointer is welcome. Thanks.


texts: Does quaternion data become inaccurate when the gyroscope spins at a rate faster than the maximum rotation it can measure?

texts:
I am currently using an invensense MPU9250 sensor board. The gyroscope measures a maximum of 2000dps. I record the quaternion value at an initial position which is <1,0,0,0> and then I rotate the board really fast. When the board returns to this initial position, the quaternion is not the same.
Is it because the spin rate was more than the gyro could measure?


texts: What is the purpose of the brown pads on this PCB?

texts:
This PCB has wire connections to external coils that are soldered to pads on the board. Each of the connections has a patch of brown material carefully placed in between the two pads. What is the brown stuff and what function does it serve?

Guesses:

The brown stuff is an extra heavy duty resist to ensure that no solder bridges form between the pads when the wires are soldered on. This is plausible, but the pads are far enough apart that bridging seems unlikely.
There are versions of the board that have connectors for the coil connections rather than having the wires directly soldered to the pads. The brown stuff is a heat activated adhesive that is laid down to bond these connectors. The version of the board that I have does not have connectors, so the adhesive is unused.
Some kind of spark suppression for flyback kick from the coils?  Like a poor man's spark barrier?
Exclude condensation or dirt from that spot?
Physically prevent a short from errant metal falling on top of the pads? The blob acts like a little fulcrum so that a flat piece can't touch both at once?

Here is the whole board with 6 of these blobbed connections:


texts:
I'm trying to understand the effect of ripple rejection in linear regulators since I'm using 2 LDO's in designing a linear power supply, however I'm unsure about something. A lot of datasheets have values that range from 50dB to 90dB, however they're dependent on the ripple frequency, load current, and other variables.

For example the LT3090 http://cds.linear.com/docs/en/datasheet/3090fa.pdf has the following Ripple Rejection characteristics:

So going by this, my understanding is that the Ripple Rejection capability of an LDO decreases with an increasing ripple frequency, and increasing load current?

Does anyone know how much of a significant impact a 50dB ripple rejection would have on the operation of an LDO? Are there 'common' or 'typical' ripple rejection values that are acceptable? My linear power supply should be able to deliver maximum of ~700mA, so I need to consider the ripple. It's the first time I'm dealing with this so I'm unsure.

For the record, the power supply I'm designing will have a 21.6V Li-Ion battery as input, which will then power a dual rail supply, so I can get anywhere between +/-8V - +/-10V. I'm currently going with the LM337 and LM317 regulators, which both have ripple rejection values of 75/77dB, but they're also rated at 120Hz.


texts: What is the best abstraction for HDL code?

texts: I have recently started seriously coding in Verilog HDL. Although I am still to get a grip of FPGAs and CPLDs, I am curious about the levels of abstractions used in these codes. I understand I have 3 options right now, Behavioral, Register Transfer and Gate level modeling. But I cannot decide which is the most suited for good synthesis. For example, when making smaller circuits I dabbled in Gate level modeling, but later on when I moved to describing my own ALUs I used behavioral level modeling. But Behavioral modeling feels like just concurrent programming and not exactly hardware description. So what is the best way to write code which will ensure proper synthesis?


texts: Monitoring circuit for the switching voltage

texts:
I would like to monitor the switching voltage which is switching between 24V and ground at a frequency of 100kHz. If the voltage is below 21V, then generate a reset signal. The lines are the differential lines with a different ground than the monitoring circuit. Some more info: the lines are the outputs of the half bridge circuit.
For example, using this device.


texts:
Hi everyone I'm studying Op-Amp but I can't understand this point in the AC circuit :

In the first picture it says Vo = Ic * Rc,
and in the second picture I have the value of Ic,
when I try to apply this in the given formula before the answer is wrong. Why?

This second formula is used instead of the first one?

Is there is a difference ?


texts: Simulating a specific circuit on LTspice

texts:
Because I wanted to find the Voc and the Isc (of the load) for the circuit to calculate Rth, I decided to put the resistance as 99999999 to find Voc, and then 0 to find Isc.

The problem here is I have no idea how to edit the current controlled voltage source to reflect current passing through the resistor. The Youtube tutorials I found online only teach the methods to connect the CCVS to a current source, but not to a resistor.

I tried to put the Value of the dependent source as R1 and Value2 as 3 but LTspice tells me that R1 is an unknown value.


texts: This is my solution,but i have a problem with doing a node analysis for node 2 and 3.In my textbook the solution is like this: (2+i1+i1)V1 -2VO -i1V2=0 and(1-i2+i1)V2-i1V1=5


texts:
I'm using this Stepper Motor from TI.
This is the first time I am working with Stepper Motor.
I need to calculate the load current or the current that the Motor takes.
The Stepper is rated at 0.6A/phase.
The application of the stepper is to move up and down an object. So, in this case, what are the factors that determine the current through a stepper motor?
I feel my question is very incomplete. Since, this is my first attempt at working with Stepper Motors, please tell me what should I look for and what are the parameters that I should focus on while working with stepper motors.


texts: Issue using TCC3 of microchip SAMD21J in variant file

texts:
I am writing variant files for SAMD21J/G/E.
I am unable to use TCC3 of SAMD21J/G/E in Variant.cpp for arduino IDE. If it is used Arduino IDE shows error TCC3 undeclared variable whereas, all other timers are working perfectly.
Can somebody tell me solution of using TCC3 for PWM/Timer pin. What variant modifications do I need to use it?


texts: How can I pass a 10 bit value to a module that needs a 12 bit input in verilog?

texts:
I have a module declared as:

module bin2BCD(
    input [11:0] bin12_in],
    output reg [3:0] thousands,
    output reg [3:0] hundreds,
    output reg [3:0] tens,
    output reg [3:0] ones,
);

I have another module which generates a 10 bit binary output (call it M) whose maximum value is 861 base 10.

Because of this, I would like instantiate this module with the first two bits of bin12_in set to 0, followed by the binary value of M (to make 12 bits).

How can I pass a 10 bit value to a module that needs a 12 bit input?


texts: Purpose of the diode and capacitor in this motor circuit

texts:
I'm hooking up a small DC motor to an arduino using an NPN transistor using the following diagrams I found online:

The circuit works, and I'm successfully able to make the motor run.  Now, I'm seeking to understand why it works the way it does.  In particular, I'd like to understand:

Why are the diode and capacitor hooked up in parallel to the motor?  What role do they serve here?
Why is a resistor needed between the transistor and the digital PWM pin on the arduino?  Would it be safe to run the circuit without it?


texts:
This question could also be labelled, "can you demystify noise and ground loops for a clueless physicist?"

Our laboratory has an endemic problem with ground loops, unterminated signals and all the things that people do when you give them 30 minutes, a soldering iron and Wikipedia. One of the less home-brew but still confusing problems I've found is the one I'm using as an example here.

We have a laser which is attached to a laser controller. This controller is a rack of electronics that sends various signals to the laser. It also receives signals from photodiodes in the lab. These are powered by floating supplies so I have left them off the diagram below since (I think) they shouldn't affect things.

When I want to monitor a signal from the laser, I plug a cable from the controller into an oscilloscope. However, making contact just with the shields of the cable (cable 1) results in greatly increased noise on the error signal the controller produces (as diagnosed by an LED on the controller).

This behaviour I attributed to the ground loop formed by the mains connections of the controller and scope, and the cable shield.

However, when I then connect the grounds of the scope and the controller together with another cable (cable 2) from a different rack in the controller, the noise goes away again.

Can you suggest why this would happen? I ask mostly from an educational point of view.


texts: Does a server put in a 19-inch rack require CE marking?

texts:
If I sell to a european customer a simple 1U rack-mount server in a 19-inch rack, do I need to test the conformity of the whole "thing"?
The server itself has CE mark, not sure about the 19-inch rack (as I don't know whether CE marking is mandatory for this kind of product).
What if the 19-inch rack includes PDUs (which are CE marked)?


texts:
Let's say I have a computer running at 4 GHz.

I would say it means I need a way to measure increments of time of about 0.25 ns.

How does a computer do that? My question is both:

Technological: what is the "physical" technology of the raw sensor (is it quartz? What are its defining characteristics ?)
Practical: based on this raw sensor, what methods are put in place to actually be able to measure such a small increment of time somewhat correctly? E.g. if you tell me the clock uses a quartz whose frequency is about 32768 Hz, how do you use that to measure a 0.25ns increment? Do you amplify the quartz signal so massively that you can actually measure a 0.001% variation of amplitude in the resulting signal? in which case, what about noise in the amplification procedure?


texts: How would parasitic capacitance changes happen in a crystal oscillator?

texts:
This article about crystal oscillators talks about the trade-offs of different crystal load capacitance values (crystal load capacitance parameter, not load capacitor values)
It says “a crystal with a lower CL is going to have a faster startup time” and “lower CL means that the negative resistance provided by the oscillator transistor is higher so that the oscillation can be sustained with lower power” … “Given these power advantages, why would anyone choose a higher CL crystal?  The answer is frequency stability.”
Then says “if parasitic capacitance changes, which can be modeled as part of Co, the resulting frequency change will be less if CL is large. If a crystal with a low CL is used, small changes in parasitics will cause larger changes in frequency.”
My question is, why would parasitic capacitance change unless you make physical changes to the board?
Additionally, would you say that it is best to always select the crystal with lowest CL if the  parasitic capacitance is not expected to change? Or do you have any other thoughts on the matter?


texts:
I am having some issues with what I think to be good code. This is for a uni assignment but this is not the code I'm submitting. This is a test file to understand how it all works. Some of this code was given in the assignment: the snum & binary sections.

I need to get each number in snum in turn and display the equivalent binary number on a 7 segment for a few seconds. It runs in the debugger until 'call binary', then it jumps back to start (after that instructino).

I don't know what I am doing wrong. Any ideas?

; Directive sets processor type .............................

        list  p=16F84A
        #include "P16F84A.INC"

; Set configuration fuses ...................................

        __CONFIG _CP_OFF & _WDT_OFF &_PWRTE_ON & _RC_OSC

; Code protection off, watchdog timer off, power up timer on, RC Clock

        errorlevel  -302        ;No warnings, register not in Bank 0
PCL         EQU     02  ; Program Counter Low
PORTB       EQU     06  ; Port B Data Register
TRISB   EQU 86  ; Port B Data direction register
STATUS  EQU 03  ; Status register
RP0 EQU 05  ; Bank select bit
timer       EQU     0C  ; GPR1 used as delay counter
point       EQU     0D  ; GPR2 used as table pointer

    org 000
    goto    start

snum    addwf   PCL,F
    dt  "0001035020"    ;Substitute your student number
                        ;(10 ASCII digits)

;       Pattern table for seven segment display on Port B ..

binary  addwf   PCL,F
    retlw   b'00111111' ;Set display to 0
    retlw   b'00000110' ;Set display to 1
    retlw   b'01011011' ;Set display to 2
    retlw   b'01001111' ;Set display to 3
    retlw   b'01100110' ;Set display to 4
    retlw   b'01101101' ;Set display to 5
    retlw   b'01111111' ;Set display to 6
    retlw   b'00000111' ;Set display to 7
    retlw   b'01111111' ;Set display to 8
    retlw   b'01101111' ;Set display to 9

; Initialise Port B (Port A defaults to inputs)........

start   bcf STATUS,RP0  ;Bank select 0
    clrf    PORTB   ;Clear Port B data latches
    bsf STATUS,RP0  ;Bank select 1
    movlw   0x00    ;
    movwf   TRISB   ;Set port B lines to output
    bcf STATUS,RP0  ;Bank select 0

; MAIN LOOP
nextdigit   movlw   d'10'
    subwf   point,W
    btfsc   3,2
    goto    nextdigit
    movf    point,W
    call    snum
    call    binary
    movwf   PORTB
    NOP
    NOP
    incf    point
    goto    nextdigit

    end


texts: positive and negative voltages from power supply

texts: How to get +ve and -ve voltages from the single power supply which doesn't have the functionality of +ve and -ve voltages. I have tries with the voltage divider circuits with two 10 Kilo Ohm resistor with the 10V supply because i want to have the +5V and -5V but after having this circuit the voltage fluctuating constantly.


texts: Behavior of frequency in a sinusoidal circuit

texts: My question is in regards to a circuit like this with a sinusoidal voltage source Vin. When I try to figure out the voltage ratio between Vin and Vout I get ωCR/(ωCR - j). I then try to figure out what the Vout becomes when ω >> cutoff-frequency(1/RC) AND ω << frequency(1/RC). For the first instance, I get that Vout will be 1 because as the frequency becomes bigger, the capacitor acts like a short circuit. But what happens when the frequency becomes smaller than the cutoff frequency?


texts: Servo motor and EMI noise on peripheral devices (microcontroller)

texts:
I have 6 servo motors (DELTA  ASD-A2-0121). Peripheral devices are affected by EMI noise (When motors are in on state and have no movement). I have changed the ground system from series mode to parallel as Pic1, although noise is slightly reduced but still affects microcontrollers. What else should I do to remove noise? Is isolation transformer effective?
Update 1:
Pic2, 3, 4, 5 are voltages of a microcontroller pin, when it's pulldown (Pic 2, 3) and when it has a PWM signal as output (Pic4, 5).
Motor power supply: 220-230 VAC, 1 ph, 1.6 A, 100 W
Microcontroller supply: 5 VDC, 3 W, supplied via USB 3 port.
Update 2:
1. Oscilloscope probe link.

Grounding system is under 7 ohm.

servo drives are connected to ethernet motion control and motion control is connected to PC via ethernet cable and communication protocol is mode bus (Pic 6.)

Update 3:
Microcontroller is This camera and it's block diagram is shown in Pic 7. Camera (microcontroller) provides some output control signals.
Image of probe setup is added as Pic 8.
Update 4:
I used a 220v  1KW isolation transformer and there is less noise now. See  Pic 9, Pic 10.
update 5:
System connection image added.

Pic 1. Serial and parallel ground connection.

Pic 2. EMI noise using series ground connection on a microcontroller pin (pulldown) when motor is in ON state.

Pic 3. EMI noise using parallel ground connection on a microcontroller pin (pulldown)  when motor is in ON state.

Pic 4. A microcontroller pin voltage (PWM signal as output) when motor is in ON state.

Pic 5. A microcontroller voltage (PWM signal as output) when motor is in OFF state.

Pic 6. servo drivers are connected to X,Y,Z AXIS of motion control and motion control is connected to PC via ethernet cable(mode bus communication).

Pic 7. Camera (microcontroller) block diagram.

Pic 8. How probe is connected to camera outputs.

I used a 1KW isolation transformer on main power of servo drivers and now there is less noise than before. It's shown in below pictures.

Pic 9. Camera/microcontroller output (output port is pull down) with isolation transformer (up) and without it (down).

Pic 10. Camera/microcontroller output (pulses as output) with isolation transformer (up) and without it (down).

Pic 11. System connection.


texts: How can you design a frequency divider circuit?

texts:
I have been trying to design a frequency multiplier circuit which can translate frequencies from Mhz range to a few Ghz range using PLL.
But I am not able to figure out how to create the frequency divider block, as the value of the n by which it has to be divided is in the factor of 100's.

Simple divide by 2 frequencies can be done using Flip flops, but I guess cascading these in the order of 10's may not be the solution to this problem.

After looking up some more places online I have found that there were these programmable divider blocks, but I cannot figure out how these work or how to design them.

So is the programmable divider blocks the only option(if so how do you design them?) or is there any other alternative solution?


texts: What IC is good for driving an array of smaller solenoids?

texts:
I have a 7 segment display where all segments are driven with a solenoid. In order to switch each segment I have to pulse a short current on the solenoid. To change the segment I have to pulse it in reverse polarity. This means that I have to use something like a "full H-Bridge" for each segment which can switch 12volts, 300mA for 100 microseconds.

I'm looking for a suitable IC that I can do this with. I'd like to end up with as few components as possible while maintaining the cost low (don't we all).

Since I don't need PWM I don't know what IC to get. Ideally something that works similar to a shift register where I can cascade to drive an array of solenoids. Alternatively an H-Bridge that can drive 7 solenoids.

I'm driving this with 3.3v logic from a microcontroller.


texts: What is the meaning of output of an accelerometer

texts:
I know this question is not fully related to aviation, but I assume the people on this subsection will also have some idea.

Suppose I have an accelerometer resting on a table(flat surface, horizontal). When I look from directly above, I see its reference coordinate system(it is labeled on it) as follows:

(from this site)

When I monitor the accelerometer readings (Ax, Ay, Az) ,

X and Y values are 0 initially(as they should be), and when I push the accelerometer(well, I am pushing the entire breakout board indeed) in the +x direction let's say, there happens an increase first and a decrease when I stop pushing it( I guess because of inertial acceleration ) in the Ax value(in terms of g) which is not surprising. Same for the y axis movements.

So this makes me conclude that the g in here is pure 9.8 m/s^2 without the sign.

But when it comes to z axis I am getting confused. In the above setup  - in which positive z axis is pointing through the ground - when horizontal and no external force is applied(other than gravitational); Az value is -1, i.e -g or -9.8 m/s^2.

There the question, what does this accelerometer output actually? In such a standing on a surface scenario, there is only a gravitational force on the device and it is pointing towards +z direction. So should not the sensor give + 1g instead of - 1g ?

I guess I have misunderstood some concepts about these sensors(accelerometers).

Please explain me, thanks.


texts: Pachislo Token Sensor Optical sensor replacement part#?

texts:
Pachislo Token Sensor Optical sensor

As shown above I have a Pachislo Mazya Dynamite Kid's Machine which has a bad Token Sensor Booard. Can someone please advise on what a suitable replacement part can be used for the 2 Optical Sensors? I haven't been able to find the depicted part# P1018 00: or the Manufacture symbol it has.


texts: What's a good plastic for self-cutting solder paste stencils on a laser?

texts:
I've tried making my own solder paste stencil using 4 mil polyester (for overhead projection slides) on a 45W Epilog laser cutter at the local TechShop maker space.
I could not "cut" the stencil cleanly, because the edges charred and became uneven.
I had some more success with "etching" the stencil, but the solder paste application still had a lot of slop around a 0.5mm TQFP footprint (generating several solder bridges.)
Meanwhile, when I used a stainless steel stencil from Advanced Circuits, for the same footprint and paste/applicator, the imprint was super crisp and no solder bridges.

I know that others are successfully applying solder paste with polyester/mylar based stencils from places like Pololu or OSH Stencils. Given that I have access to a laser cutter, I'm thinking there's got to be a way to make them on my own, and probably the problem I had was that I used an inappropriate film/material.
However, researching online, I can't find any material specifically billed as being good for this kind of work -- so, does anyone have experience to share on particular materials for laser-cut stencils? Part numbers or at least specific brand/model names would be great!

EDIT in October 2016: OSH Stencils now offers affordable steel stencils, so making my own is much less desirable. I highly recommend steel over plastic!


texts:
I need to find node voltage at A. This seems like a trivial question, but when I set up the resistive voltage divider equations they are not equal to each other. Am I doing something wrong?

My equations are \$V_A = V_1(R3/(R3+R1)) = V_2(R3/(R3+R2))\$

I tried solving this problem with an LTSpice simulation and with the superposition method, but my answers did not match (although very close to each other). Is this because the simulator uses an approximation? Can someone compare results?


texts: is it a photodiode or a phototransistor?

texts:
I have been working on a circuit which involves a photosensitive element soldered on a PCB. I am confused whether it is a photodiode or a phototransistor. Is there any means by which I can figure out whether its a photodiode or phototransistor without desoldering it?
its a two terminal device.
I am attaching its picture.


texts: Negative input, negative output switching regulator?

texts:
I've got a component within a larger device that requires both +15 and -15V, drawing about 100mA per rail.

In addition, the main power supply of the larger device is providing +/- 28V, with a common ground.

My initial thought was to use good old linear regulators - 7815 for +15 and 7915 for -15. However I want something a little more efficient...

...and it just so happens I have a bunch of these fancy R-7815-0.5 switching regulators (PDF) by Recom. They accept 18-35V on the input, and produce +15V on the output (500mA). In addition, they can be used to convert positive to negative, albeit at a lower output current (200mA).

I want the +28V from my supply to step down to +15... no problem there, one of the Recom devices will work perfectly. In addition, it makes sense to me that the -28V be stepped down to -15V.

However, I can't determine whether a switching regulator like this can be wired up to accept a negative voltage input, and thus produce my desired negative output voltage. To be clear, I don't want to do any voltage conversion - I want to my input +28V to produce my +15V, and my -28V to produce my -15V, to ensure that approximately the same load is being placed on both my + and - supply evenly.

In the world of compact, all-in-one switching regulators, there don't seem to be "79xx" equivalents which would make this easy!

Is it possible to do this with the devices I have - i.e. wire the
R-7815-0.5 to accept a negative input?
If not, what would be the best way to efficiently produce +/-15V from my supply, placing an even burden on each +/-28V rail?


texts: Altium: Connecting routes through different layers

texts: I know how to route and create vias to connect the track from one layer to the next (i.e. layer A to B then to C). But is it possible to connect tracks from one layer to a specified layer directly without having to go through the intermediate layers (i.e. layer A to C)? If so how?


texts:
I'm currently investigating the SAP-1 to build in order to grasp a really good understanding of simple 8 bit computers.

There are a few questions that I would like clearing up.

What exactly is the WBUS? Looking at the logical diagram attached below I'm struggling to understand what the WBUS is, I'm presuming it may possibly be the inputs to the computer but cannot be certain.

Am I right in assuming all a register is is a place to store a value and each value the shift register is storing is put into context by the clock cycle?


texts:
Can someone explain this IC? It seems to be a two-way n-mos (has two circuits in one).
I have a master device that runs on 5V and multiple slaves that run at 3V3 and they communicate via i2c.

Why is this necessary? Why, for example, it would not be possible to use the 3V3 signals for i2c bus where the master runs at 5V? What are the dangers/problems associated with that?

Datasheet:
https://www.mouser.co.uk/datasheet/2/308/2N7002DW-D-1658850.pdf

Now let's assume I will run both the master and the slaves at 3V3. Is this the correct way to pull the i2c lines up?


texts:
I have build a welding inverter using two switch forward (reference based http://danyk.cz). But I used Irgpc40u igbt(single each side) and sg3525 pwm. I test it at 900watt power line, 1.6mm electrode. Circuit breaker tripped when I increased output current. As result, metal object not cooked well.
Is 900 watt power line enough for welding?
And I also want to build one more, cz I still have many components at home. But I still doubt about better topology used. Which the better about 4 igbt for full bridge (with single igbt each side), compared with two switch forward (with double/paralelled igbt each side)?


texts: How to design a non inverting op amp adder for my circuit?

texts:
I am trying to implement an adder for my circuit using 4 resistors.
From what I read, I understood that so long as you have R1 = R2 and
R3 = R4 it really does not matter what value you use. The ultimate
result would be V1 + V2.

Now, what my problem is that I have a signal which goes to 1.2 - 1.8 V on the +Ve side and till -800 mV on the -Ve.
I want to scale up the signal to the positive level and tried the same thing as given here.

Am I doing something wrong? If yes, is there a better way to do it?


texts: Im building a LM317 based power supply and the output range must be 0.3V-21V. I've used a 2 diodes in series and a resistor supplied by a negative voltage and take the node between resistor and diode to be a negative reference to be fed to the adjust pin of LM317 to reduce its reference voltage. Now, I found other people saying TL431 is much better reference voltage but I dont know how to reduce its reference voltage. Can someone help me?


texts:
I am working on a project for development of load cell amplifier circuit. I want to rationalize the output of the load cell to fix counts like 20000 counts at full range capacity.

I have 5 Kg load cell with output of 1.7576 mV/V and excitation voltage is 5.0986 V. Any guidance or any documents on rationalizing the output of the load cell will be of great help.


texts:
Ok - total newbie question here.  I'm trying to work out the size or number of solar panels required to run a DC pump for use as a solar heating system for a swimming pool.

I've located what looks like a suitable pump with the following specs

Voltage: 8V-24V DC (Standard:12V DC), 4.5amps
Max Flow Rate for 15W model : 11.5 L/Min - Max Water Head: 3M
Min start-up power consumption less than 2 Watt

The aim is to direct connect the pump to the solar panel allowing for it to operate whilst sufficient sunlight in order to pump water into the heating elements of the pool (think black plastic tubes on roof of house).

Now the question.  Given 24v, 4.5amps I think it equates to approximately 100watts.  The solar panels from a local supplier give specs such as:

Maximum power: 120W
Rated voltage: 12V
Open circuit voltage: 21.8V
Short circuit current: 7.14A

The other alternative is the 200w panel which has specs like:

Maximum power: 200W
Rated voltage: 24V
Open circuit voltage: 45.3V
Short circuit current: 6.15A
Voltage at max power: 37.8V
Current at max power: 5.31A

Thus which panel would work; 120W or 200W ?   Also do I need to worry about the open circuit voltage and short circuit current ?

thanks for you help
grant


texts:
Given the following circuit, what ways there are to calculate its total capacitance?

Thing is this is not a simple case, and I can't really decide which part is parallel and which is a series, since this all seems to be rather intertwined, and nor do I see the order in which this should be solved.


texts:
I have the nRF52832, connected via FT232RL FTDI and it fails when I try to upload a firmware file to it. I'm using PlatformIO in Atom. Following instructions at
Get started with Arduino and Nordic nRF52-DK.

platform.ini

[env:nrf52_dk]
platform = nordicnrf52
board = nrf52_dk
framework = arduino
build_flags = -DNRF52_S132
lib_deps =
  BLEPeripheral
upload_protocol = blackmagic

Code builds fine, but the upload to the Nordic fails.

Output

Configuring upload protocol...
AVAILABLE: blackmagic, cmsis-dap, jlink, mbed, nrfjprog, stlink
CURRENT: upload_protocol = blackmagic
MethodWrapper(["upload"], [".pioenvs/nrf52_dk/firmware.hex"])
Auto-detected: /dev/cu.usbserial-00000000
arm-none-eabi-gdb -nx --batch -ex "target extended-remote /dev/cu.usbserial-00000000" -ex "monitor swdp_scan" -ex "attach 1" -ex load -ex compare-sections -ex kill /Users/thomas/workspace/Arduino/ble-blink/.pioenvs/nrf52_dk/firmware.elf
Ignoring packet error, continuing...
warning: unrecognized item "timeout" in "qSupported" response
Ignoring packet error, continuing...
Remote replied unexpectedly to 'vMustReplyEmpty': timeout
"monitor" command not supported by this target.
Don't know how to attach.  Try "help target".
You can't do that when your target is `exec'
Section .text, range 0x1c000 -- 0x1cbdc: matched.
Section .ARM.exidx, range 0x1cbdc -- 0x1cbe4: matched.
warning: One or more sections of the target image does not match
the loaded file
The program is not being run.
Section .data, range 0x1cbe4 -- 0x1d020: MIS-MATCHED!


texts:
I am working on a project which requires me to create some sinusoidal signals at specific frequencies using a DC battery as the only power input. And I also want to tune the amplitude of the output sine wave lets say minimum -5/+5 Volts. To achieve that, I made some research and found that Wien-Bridge oscillator might be the solution. However, I cannot be sure that whether it can accomplish given requirements I mentioned above or not.

Does it take its input as DC?
Can I tune its output amplitude easily?

And if it is not the solution I was looking, how can I get sinusoidal signals only using DC sources?