texts: Stepper motor shaft vibrating and vibrates the load

texts:
I am new to the electronics hobby so any hep is appreciated. For my application I need a quiet motor that can provide high torque at low speed. I purchased a NEMA 17 stepper motor (model is 17HS4401s) and I am using the DRV8825 driver chip and PIC microcontroller to drive it. I've connected the circuit like as the diagram below with a 12 volts 2 Amps motor power supply.

Now, after getting the motor to work, mounting it using screws and attaching the load, the motor itself is stable, yet the shaft vibrates and causes the causing the load to vibrate with it. I've tried the following:

Microstepping the motor to 1/32 steps -> Reduced the vibrations a lot but the load still vibrates
Limiting the current to 1.4 Amps -> Did not make a difference
Limiting the current to 1 Amp -> Again reduced the vibration a bit but the load still vibrates
Different step frequency values (0.5 ms, 1 ms and 2 ms) but no significant change happened

Is there a way to get a smooth stable motion from the motor and stop the shaft from vibrating? Would switching to a different driver the TMC2100 SilentStepStick make a difference?


texts: I am developing a project for ECG detection using PVDF (Piezo Film) sensor. I have already managed to detect my heart rate but since the sensor used produces voltage corresponding to vibrations, sometimes the signal of interest has lower amplitude than the "noise" (movement of the arm for example) and after amplification the output swings to the rails (filtering doesn't help at all as both signals are of close/matching frequencies). I know that my input should not exceed the limits but is it bad for an op-amp if its output periodically hits the rails? According to comparator circuits operation, I think it should not be a problem but I would like to hear more experienced opinion.


texts: Which type of RF harvested device is used now?

texts:
I want to do some research about energy harvesting optimization, and I want to ask which type of RF energy harvested device is used now?

first,one transmitter will transmit one signal to the energy harvester

I have A type and B type.

If the RF energy harvester device has five antennas,then type A just feeds the received signal to the RF-DC converter directly, then sums the DC power and charges the battery.

Type B is different from type A. Type B will use some method to let all the phase of received signals be the same, then sum them to be one signal wave, then feed this signal to the RF-DC converter, then charge the battery.

Because I am not the researcher in the electrical, but communication engineering, so I don't really know which RF energy harvest device is used in the real world. Hoping someone can tell me about this information.

            fig(1) typeA

 fig(2) typeB

In my thinking,if i have 5 antenna,i need five RF-DC converter in type A ,however, i need one combining and just one RF-DC converter in type B.So should the power consumption of one combining be larger than the sum power consumption of RF-DC converter?

Or the size of that combining is very large,larger than the size of four RF-DC converter,because i search the internet,and find the RF-DC converter :https://www.youtube.com/watch?v=k807J2JRp_M is very "tiny"


texts: 100K potentiometer reading 26K at lowest seting

texts: I have a 100K potentiometer that reads 104K maximum, but reads 26K at minimum.  Is there something wrong with it? I sprayed some contact cleaner to ensure it wasn't due to contamination, but got the same reading. The knob turned smoother though.


texts: NPN circuit to switch 12v 1A DC load by 3.3v 1A DC using PIR

texts:
I am trying to switch on a circuit using PIR motion detection.

I have a PIR module which outputs 3.3v 1A DC when it detects a motion. I want to switch on a circuit rated at 12v 1A DC. I read some articles that we can use NPN transistor to switch on the load.

But I am not able to figure out the value of transistor to use and resistors if required. Can someone please help.

A complete circuit diagram will be really helpful.

Regards

Not new but still learner *


texts: Use 3.5V power LED connection on motherboard to control a 12V lighting accessory in a computer case?

texts:
Background for the problem:

I rebuilt my computer in a new case where the components fit a bit better. Everything is great, and I have no issues with it. However, because of the way they engineered the front panel LEDs, I don't have an LED indicator of computer sleep status. The power light is powered off their control board, which is powered from the PSU directly, so I don't have a sleep indicator.

Now, I could easily just get an LED and extension cable for a simple power LED installation, but I got to thinking that I'd like to try something a bit more elaborate. That is, instead of a single 3.5V LED, I want to use a 12V light source (such as a LED spotlight or cold cathode) and install that to have something that could indicate sleep/power status with a bit more style. I have a mesh grill on the front of my case, so I figure something that illuminates under the mesh would be cool looking and noticeable but also not be disruptive in a dark room (like if I'm sleeping). There's some hurdles to this, though. For one, I obviously can't power one of these straight from the motherboard connector. It doesn't provide enough voltage. For another, the PSU shuts off my case lighting when in sleep mode.

Proposed solution:

So, I'd like to make something to do what I want. I'm a programmer but I have tinkered with electronics kits as a child, so I'm familiar with some (very) basics, and have assembled circuits before (at least, from pre-written designs). It has been a while though and my efforts in designing my own analog circuitry are best not to be spoken of, so I hope I can do something simple, here. :)

What I figure I would have to do is build a simple circuit that uses the power output from the power LED connection on the motherboard to power a switch (of some sort) that would provide power to the 12V light source from a battery, which could be recharged from the PSU. I believe the 3.5V connection on the motherboard just provides straight power to a LED (if one is connected). But instead of a LED, I want to make it so that while the computer is powered on, it would close the circuit for the 12V light so it would illuminate, while simultaneously charging the battery. When in standby mode, it would light the LED (my motherboard causes it to blink) by drawing power from the now-charged battery.

Question:

I think that a simple relay switch would probably be adequate for controlling the 12V circuit, but they're noisy. :) Is there a solid-state alternative? Since I'm dealing with two power sources, I'm not sure if it's possible for me to isolate them easily in a single circuit without physical separation (as a relay switch would provide). As I said, I only tinkered with electronics kits as a child. I didn't take electrical engineering in college, as I got into computer programming instead. But if it is and is simple enough to implement, I'd prefer it.

Also, I'm sure that dealing with a rechargeable battery brings with it its own set of caveats and things to worry about (like worries of overcharging). Is there anything else that I'd have to take into account?


texts: How to sense voltage of 48 V 600 Ah VRLA battery bank for Arduino

texts: How to check the battery terminal voltage across 48 V (2* 24 V cells) of VRLA battery bank (600 Ah). I am not sure whether a voltage divider serves the purpose. Please give me the advice to convert it to 5 V (Arduino compatible).


texts:
Below is a latch made up of two transistors:

When the base current of Q2 is increased this also increases the base current of Q1 which in turn increases the base current of Q2 more. By such positive feedback, both transistors go into saturation and establish an ON switch.
I have two questions regarding this latch:

When this latch is saturated by applying voltage at B1, what happens if B1 is left floating just after that. Will the switch remain saturated?
If the latch is ON i.e saturated, how can it be turned OFF indefinitely besides turning off the Vcc? Would grounding B1 work for that?


texts: What is the transfer function of an LCL filter?

texts:
simulate this circuit – Schematic created using CircuitLab

I read that for grid-tied inverters it is common to use a LCL filter like above, to turn the PWM output from the H-bridge into a sine. But I'm having trouble designing something like this.

If you'd calculate the voltage at the right end without the resistor, L2 doesn't do anything and it's just an LC filter.

If you connect it to the grid by placing another voltage source there, the question what the voltage is is moot, because it's always the voltage over the voltage source.

So I decided to place a resistive load there and find the voltage over that. But this lead to some horrible mess.

$$Z_t=\frac{j\omega L_2 R_1}{1+(j\omega)^2 L_2 C_1 + j\omega R_1 C_1}$$

$$V_{C1}=V_1 \frac{Z_t}{j\omega L_1+Z_t}$$

$$V_{R1}=V_{C1} \frac{R_1}{j\omega L_1+R_l}$$

$$V_{R1}=V_{1} \frac{j\omega L_2 R_1 + R_1^2}{(j\omega L_1)^2+(j\omega)^4 L_1^2 L_2 C_1 +(j\omega)^3 L_1^2 R_1 C_2 + j\omega L_1 R_1 + (j\omega)^3 L_1 L_2 R_1 C_1 + (j\omega)^2 L_1 R_1^2 C_1}$$

I feel like I'm missing something obvious here. Or I made some stupid mistake. Or this stuff is just hard.

[edit]
I worked out the transfer function for current, as seen below. The transfer function matches the one given in equation 9 in http://inside.mines.edu/~mSimoes/documents/paper_54.pdf and Figure 5 also matches what I get, for some arbitrary values.

$$\begin{align}
I_2&=\frac{V_s}{j\omega L_1} \cdot \frac{\frac{j\omega L_1}{1+(j\omega)^2 L_1 C_4}}{j\omega L_2 + \frac{j\omega L_1}{1+(j\omega)^2 L_1 C_4}} \\
\frac{I_2}{V_s}&=\frac{1}{j\omega(L_1+L_2) + (j\omega)^3L_1L_2C_4}\\
H(j\omega)&=\frac{1}{\frac{j\omega}{\omega_0}+\left(\frac{j\omega}{\omega_1}\right)^3}\\
\omega_0&=\frac{1}{L_1+L_2}\\
\omega_1&=\frac{1}{\sqrt[3]{L_1L_2C_4}}\\
\left|H(j\omega)\right|&=\frac{|1|}{\left|\frac{j\omega}{\omega_0}+\left(\frac{j\omega}{\omega_1}\right)^3\right|}\\
&=\frac{1}{\frac{\omega}{\omega_0}-\left(\frac{\omega}{\omega_1}\right)^3}\\
arg(H(j\omega))&=arg(1)-arg\left(\frac{j\omega}{\omega_0}+\left(\frac{j\omega}{\omega_1}\right)^3\right) \\
&=0-arctan\left(\frac{\frac{\omega}{\omega_0}-\left(\frac{\omega}{\omega_1}\right)^3}{0}\right)\\
&=\pm \frac{\pi}{2}
\end{align}$$

(The omega stuff is wrong, they never taught us to actually rewrite to standard form, but Matlab does't care. It just means I can't find the resonance frequency or draw a straight line approximation, sadly.)


texts: As I cannot manage to find it done on internet, I wonder if it is possible to program a CAN controller in a CPLD ? It's look like it is going to require a least an FPGA.


texts: Is it time to move from a 2 layer board to a 4 layer board

texts:
Below are two pictures of a portion of a PCB layout I did. The first shows the signal traces and the second shows the ground pour. U1 is an 8 MHz MCU, U3 an I2C sensor, U4 a RTC, and U2 a boosting power supply. The PCB is limited in size.

I don't have much experience in PCB layout, so there are probably a few fundamental flaws in the routing. It functions fine, though I can't comment on EMI. For VCC and GND I tried to use a gridded layout as much as possible, and add bypass caps as close as possible to the pins.

Now I'm trying to learn better PCB layout, e.g. signal return paths, reducing EMI, MCU having it's own little ground plane (Olin's answer), etc.

Can I achieve best practice layout on this fixed size PCB with 2 layers, or should I move to 4 layers?


texts:
Please I need a bit of your help. Do you know what IC is this marked IA89G or 1A89G perhaps? I've tried Googling but to no avail. I'm really wondering why this is such a hard nut to crack.

Here are a few snapshots of the IC:

Thanks a lot!

Joemill


texts: Why would I use triangular solder jumper pads?

texts:
My PCB layout program of choice - Kicad - has footprints for normal rounded solder jumpers; but also triangular ones.

What benefits, if any, do the triangular ones offer? Or is it a purely aesthetic choice? Seems to me that the triangular ones would be more annoying; that they would be more difficult to clear of solder.


texts: analog and digital ground connection point selection

texts:
I've read some articles that say the connection point of digital ground and analog ground should be at the power supply output port. However, when there are two or more power supplies which are physically far away from each other, I have no idea where should the connection point put.

My design is as bellow, there are three supplies which are Vcc for the digital circuit, Vcmos for CMOS camera and Vad for A/D chip. The Vcmos is generated from the DCDC while Vad is from the LDO. The ground plane is separated into two parts for GND and AGND. The distance between LDO and DCDC is around 2500mil. Now I want to put a ferrite to connect the GND and AGND. The question is should I put the ferrite near the LDO or DCDC, and why?


texts: How to read/understand Bode plot of Insertion loss in EMI Filter

texts:
I am designing a noise filter with a Target frequency for noise reduction =100KHz and with the help of Murata Noise Filter Designer website.

Recommended circuit from Murata with component value is as below,

But first I want to understand or read the Bode plot of a Common Mode Insertion Loss.

I have selected the followng settings in website,

Rated Current(ldc) of L/Bead/CMCC  = 3A
Rated Voltage(Vdc) of IWCC/CMCC = 50V
Temperature characteristics of MLCC = 125°C
Target frequency range for noise reduction =0.15MHz-10MHz (LWMW/SW band, etc.)

and the bode plot for Common mode Insertion loss is generated as seen below

To be frank, I have not understand this bode or how to read this.

How does this bode help to design filter for 100KHz?
Which points in Plot are good?
The plot is declining until 100MHz, is this good? Why is it declining? Why does it rise after 100MHz ?

I have gone through some of the available documents online. But I have not get an Idea how to read this bode plot for my use!

edit: I have added a second ciruit below with a New Bode plot. How does it differ from the First plot? Is this a good or bad while comparing with the first plot?

Many thanks in advance.


texts: Circuit for measuring low current output from a high voltage input

texts:
I am trying to design a DC circuit that allows a high input voltage of about 1 to 20kV and I can measure a low current output of about 1nA to 10mA.

This is my approach but I need feedbacks. I want to use the Thevenin's theorem.
I want to set up a chain of resistors (Thevenin equivalent). The input voltage is the thevenin voltage. Then I introduce a load resistor in series with the thevenin resistance. The voltage across the resistor would then be measured. I am thinking of using Phidget's bridge to measure it. The output current is then gotten using the ohm's law formula.

This is just my basic knowledge. Are there more efficient ways to create a circuit the allows high voltage supply and measure low output current?  What are the real life challenges to consider and how can I solve these challenges e.g clamping, isolation etc.

Thank you.


texts: How to build a voltage-controlled current sink / voltage-controlled resistor

texts:
I am trying to control a current through several current-mirror device (specifically the IREF pin on the TLC5940) using a single potentiometer.  I've tried using a modified Howland current souce as in the following schematic:

simulate this circuit – Schematic created using CircuitLab

While this works OK with resistor values as shown for dimming a LED, it doesn't work as a current sink given a 1.24V voltage source at the node marked sink.  I am using an LM324 quad op-amp. If someone can suggest some avenues to explore for a voltage controlled I-sink, or voltage-controlled resistor (VCR), or an R-controlled resistor, etc. I would appreciate it. I'd like a minimalist circuit, if possible, as I'll need to control at least six current mirrors (TLC5940s) for my application, with a single pot/trimmer, and accuracy is not really critical in this application.

Some relevant links

The question on voltage-controlled potentiometers is relevant, however, I would like to avoid buying a specialized part, if possible.
People seem to have built VCRs out of photocells + LEDs, however, this seems a bit cludgey. I suppose an optocoupler is an option, however, I think linearity will be an (admitedly not huge) issue.


texts:
Hi want to charge my 4000 mAh 1.2V nimh cell battery simply, I do not use them very often.
So I wanted to plug this kind of voltage regulator

which I think is like that : https://en.wikipedia.org/wiki/LM317#/media/File:LM317_typical_schematic.svg

I setup the Vout at 1.45V and plug it on my battery (Vout on the +)
as the Usb should deliver 500mA@5v I would expect to have at least 500mA@1.45V.

but when I test it I have only 100mA for charging. The LM317 is hot (near 50°C). To test another way, I plug a power bank which can deliver 2A@5V but same thing current is near 100mA@1.45V.

Any idea to boost this current?


texts: Is using a register chain feeding into a LFSR sufficient to generate "true random numbers" inside an FPGA?

texts:
One way to generate random numbers is to pseudo-random numbers. Otherwise, one would need a special mechanism to generate them using dedicated hardware. However, (For FPGAs specifically) why not just rely on delay chains and register their output while perhaps feed it into an LFSR to generate true random numbers?

EDIT:
The delay between a delay chain made up of logic gates depends on temperature and some other factors. Why not use this to create true random numbers? The randomness shall rely on temperature to an extent.


texts:
I'm in the process of designing an inductor for a boost converter, and I'm having a hard time finding exactly what I need for this project. I have found a core size/shape that appears to work except I can only get the core in the material I want (N49) in an ungapped core (s = 0 in the image below). Running the calculations for this core, it looks like with the \$A_L\$ value listed, I will saturate the core before reaching my target design current. However, the core is large enough that if I could decrease the \$A_L\$ I would have a viable design. So I think I want to add a gap to the pre-existing core.

How can I add a gap to the core without compromising performance? I've come up with a few methods listed below, but I'm unsure what is "best".

Place a thin film (e.g. Kapton tape) as a gap material on both the inner post and outer legs. Easy, but the coil is supposed to be centered on the gap (right?) and it won't be centered on the outside legs.
Sand down one of the center posts carefully. I'm concerned about being able to estimate the required turn count as the gap size determines the effective \$A_L\$. Also, I am unsure how critical it is that the two center posts are planar when there is a gap.
I'm doing something "weird" and there's a good reason why I can't find what I'm looking for.

For the background, I'm trying to make an energy storage inductor for a boost converter operating at higher frequencies (500 kHz), higher current (>12A), and higher inductance (>200µH).


texts:
I am trying to wire up a DSP controller. It has 2 limit switches, and the instructions say to connect the "COM" on both switches together and the "NO" to y- and x-. There is an indicator light on the controller to show when the switch(es) are activated. When the switch(es) is/are activated, the light on the controller does light; However, the stepper motors do NOT stop moving when the switch is activated.

Wouldn't "Common" and "Ground" be the same thing? Any ideas?


texts: Can Peltier devices be cascaded to create a bigger temperature difference? Like mounting one on top of anther one to increase the maximum difference from 60 degrees C to 120 degrees.


texts: How much current can a CAT6 cable reliably handle? I want to use 3 of the cores for +5V and 3 cores for GND. I'm wondering at what current I need to think of another power solution.


texts:
I have tested a new part number (as replacement) for an LED backlight for an LCD. The LED tested is SML-D15MWT86. We have followed a physical arrangement similar to the original pcb (2 parallel rows, with 4 LEDs per row distributed symmetrically throughout the front pcb.
The layers are something like this (top to bottom):
-lcd
-diffusion film
-light splitter + elastomeric connectors (pcb to lcd)
-LEDs on the front pcb)
The problem is that even with the diffusion film, the new backlight LEDs exhibit some hotspots (uneven distribution of light). I have tried searching about "datasheets" of diffusion films but found none. Most manufacturer websites only ask the user the physical dimension (l x w x thickness). I wanted to start fixing the hotspot by checking if there are specs I need to see in the diffusion film used.
The original backlight (no hotspots) is white color (intensity is ~200-500 millicandela (mcd), wide beam angle of ~120 degrees, lens type is clear), while new one is green with ~50-70 mcd, wide beam angle of ~180 degrees and diffused lens type as well. I believe it's not the best option for trial and error method (try different diffusion film/LED part no's) to find an LED backlight replacement.
On comparing the old and new backlight, the old one has a clear lens type but the one we tested is diffused. (1) Does it matter that if we're using a diffusion film, the LED to be used should be clear type lens?
I have read LEDs datasheets and found that LEDs have differing beam angles (which appear to be inversely proportional to intensity). On mouser, higher intensity LEDs tend to have lower beam angles (more focused?). (2) If using a diffuser film, is better to actually use LEDs with narrow beam angle and let the diffuser film do the "spreading of light" compared to using LEDs with wide beam angle?
So far, the only way I can eliminate the hotspot is by increasing the distance between diffusion film and LEDs. This is consistent with what I've read on a couple of websites but this is not the best fix I am  hoping for, since I would need to re-design other parts of the product (front panel, elastomeric connector height, etc).
Another thing I've done is to try to place the LEDs closer to each other (more concentrated on center). The result was that the edges were considerably darker, and the hotspots were reduced (but not eliminated).
I have not yet tested other diffusion film since we have no other available ones. I have tried other LED as well (SML-D12M8WT86) which has lower intensity. The result is the same (hotspots present).
Another thing I've tested is vary the intensities by varying the current limiting resistors (swept from 5 to 20 mA). The hotspots remain regardless.
Lastly, I tried SML-D15MWT86 in a 5x2 arrangement (instead of 4x2) to increase the overall light output. The hotspots remain, but they don't seem to be as obvious compared to 4x2. This led me to thinking that (3) higher intensity LEDs could help eliminate hotspots given the same diffusion film?


texts:
Background

For a while now I've been trying to come up with a simple module to handle modulated light detection for part of a laser trip sensor. Initial attempts I wanted to use a dual op-amp as an RC Oscillator and a comparator but could never get the circuit to work. Now while reading up on logic gates and flip flops I thought I could use those to accomplish the same this. Initially I thought it would use two JK flip flops and several logic gates but ended up finding something far more simple.

Question

Can I use nothing more than a D flip-flop to detect if the pulse I'm receiving is that same as the one emitted? Here is the circuit simulated in CircuitJS. A little bit of hand waving is required do to simplification and shortcomings in the sim but assume that clk is the PWM being fed into a MOSFET powering the laser diode and the switch represents a phototransitor either receiving the laser light while closed or the beam being broken when opened. The inverter is to trigger an interrupt on break.


texts: Balanced three phase circuit Y-Y with neutral

texts:
Here is my equivalent balanced three phase circuit Y-Y with neutral:

Rla + jXla is my line impedance by phase. L1 and L2 are my loads. The exercise is saying that L1 absorbs 180 W and 240 VAr, L2 absorbs 600 VAr and has 0.6 lagging power factor. The line impedance is 5 + j8. The line voltage is 240 V. Its asking me what is the voltage VAN across the loads.

LOOK WHAT I HAVE TRIED:

VAN.IL1* = SL1 = 180 + j240 VA
VAN.IL2* = SL2 = 450 + j600 VA
VAN.IL* = SL = SL1 + SL2 = 630 + j840 VA
IL = IL1 + IL2
VaA = IL.(Ra+jXLa)
VAN = Van - VaA
Van = 240/sqrt(3) with angle of -30 degrees
SL/IL* = Van - IL.(Ra+jXLa)
(630 + j840)/IL* = (120 - j69.282) - IL(5 + j8)

When I throw this equation at wolfram alpha, It says there's no solution:

Link for wolfram alpha's analysis

What am I doing wrong?


texts: Considerations for powering solenoid and arduino from the same power supply

texts:
I'm working on a project where I will need to power a small solenoid (probably 12V) and an Arduino Pro Mini 3.3V (3.3-12V input, onboard circuitry regulates to 3.3V). I'm thinking about using an H-bridge, relay, or MOSFET for controlling the solenoid, depending on the type of solenoid that is needed.

There will be a single power supply supplying power (most likely 12V) for both the Arduino and the solenoid. What should I do to ensure that the solenoid doesn't interfere with the Arduino's power while it is switching?

(Any input on H-Bridge vs. relay vs. MOSFET (or vs. Darlington if you want) would also be welcome.)

Thanks!


texts: How to convert high impedance / ground output to 24V / ground output

texts:
My background is from software development so please forgive my ignorance.  I have an Adam 6156EI device I can control via Ethernet, it has 16 digital outputs.  When I programmatically set an output to "true", the respective output becomes "ground".  When I send "false", the output becomes what I would call "High Z" (disconnected, neither power nor ground).  If I connect the positive side of a test lamp to +24V power, and the negative side of the lamp to the output, I can switch the light on and off.  I think the output operates like a single pole/single throw switch connected to ground.

My problem is that the downstream device I'm trying to control wants to receive either 24V or 0V in order for it to go on or off (I believe the currents are just a few milliamps, it handles its own amplification).

What can I put in front of this output to convert it from High-Z / Ground to +24V / Ground?  Or have I done something else wrong?


texts: Method for rechargeable batteries in Parallel

texts:
I have several Sealed Lead Acid batteries (12v 100Ah). The batteries are from a commercial UPS and they are not brand new. I wish to connect them to my home DC solar system to store solar energy for night time use. I would like the batteries to last for as many years as possible.

If I connect them in parallel, I am concerned that when no load is connected, the strongest battery will continuously "charge" the weakest one as soon as the sun goes down and the lifetime of the batteries will be reduced, as well as wasting energy.

The benefit of having them in parallel is that the load on each battery will be distributed and the depth of discharge will be less, leading to longer service life.

So there would be three states:

Charging from the solar system (current going into each battery),
DC load at night (all batteries contributing to the load), and
no load at night (batteries discharging into each other).

I have come up with a scheme using diodes to reduce battery damage from State 3.

Is this a good idea or is there a better way to deal with State 3?

simulate this circuit – Schematic created using CircuitLab

Another idea is to have 2 relays per battery (where the diodes are) and a current sensing system which would connect/disconnect each relay optimally.

And a third idea would be to have a low-current, 12.8v, float-charger connecting the batteries to mains power in State 3 in an effort to prevent batteries discharging.


texts: Power planes splits effect on differential pairs routing

texts: I'm routing a differential pair (rs485), and I'm wondering if I should avoid routing it above a power plane split. I read about the undesired effects that a ground plane split can have over those signals, but I'm unsure if this also applies on a power plane.


texts: Using AC fuse for DC & DC fuse for AC...!

texts:
Recently I visited a site where I saw that in an  inverter AC fuse are use for DC..it is quit odd for me..!!!
Is it ok to use the same?
What are the factors to be considered when we use AC fuse in DC and DC fuse in AC?


texts: Why is the voltage drop being added to the voltage source instead of getting subtracted on the left ? Shouldnt it be 24-3io = 4io?

texts: This is a circuit with a dependent source which is the current aross the 3 ohm resistor.


texts:
We are planning on using Cat7A twisted pair cable for an application with which high bandwidth (~800MHz) analogue signals are being transferred over around about 3 metres.

At the moment the cable uses ARJ45 connectors (they are premade cables), so we have been using those on our prototype designs. However as we have four of these cables feeding in to a very small space, the connectors are simply too bulky. I've been looking for other ways of attaching the cable, however things like PCB mount splice terminals are not acceptable as they are not really designed for such high frequencies.

The best solution I can come up with at the moment is to solder the cables directly to a small well designed PCB which can then plug on to the main board using a decent edge connector (e.g. Samtec MEC1-EM or the like).

The trouble with doing this is that the cable is fully shielded with each pair having an individual foil shield which is made of Aluminium - in other words not easy to solder without nasty fluxes. The outer shield is a braided copper screen, so that is relatively easy to attach for mechanical strength.

So to my question - what would be the best method to go about attaching the cable to a PCB?

For reference, this is the internals of the cable with the foil stripped away in a couple of places to get an idea of what it looks like inside:

Soldering the twisted pair would be the cleanest method, but soldering the foil shields is not really possible. I wonder though if I even need to solder the shield as it will be attached at one end by the connectors, so it may actually perform better to leave the other end floating to minimise ground loops.

Alternatively, has anyone come across some alternate connectors for attaching either shielded twisted pair cables, or just their shields?


texts: Trouble with first part of Experiment 11 (Make: Electronics)

texts:
Experiment 11 from Make: Electronics

Hi, this'd be my first forum post. I'm really out of options here. Let me get straight to the point. I bought the book "Make: Electronics by Charles Platt" a while back, and I'm currently stuck on the very first part of Experiment 11. It is where you build the oscillator part of the circuit. I'm going to include the parts used, a couple images of my circuit (As I don't have a camera, I had to take them with my webcam), and what I threw together on Fritzing. Be aware that I'm a bit of noob, so I tried to make the Fritzing circuit look as best as I could in the time that I had to post this question. The problem is that the LED is not blinking, it is suppose to blink very rapidly due to the discharges of the electrolytic capacitor in the circuit. But for some reason, the capacitor is not building up voltage to do this. I have a feeling it has something to do with the 2N6027 transistor and how its placed. But I'll let you guys have a look.

2N6027 data sheet - it's a "PUT" - a programmable unijunction transistor.

What I've tried

Different layouts like thisenter link description here
Rotating the LED to observe polarity
Ordered from a different seller, at Digikey
I rotated the transistor, every time I did, the LED would light up, but wouldn't blink.

Parts

Resistors: 470K, 15K, 27K
Capacitors: 2.2uF electrolytic capacitor
Output: Red LED
Transistors: 2N6027 ordered here
---> http://www.amazon.com/gp/product/B0002ZPTN6/ref=oh_aui_detailpage_o04_s00ie=UTF8&psc=1

I'd appreciate any help I could get! Thank you so much!


texts: How to eliminate the noise that is generated after the A\D conversion?

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I have built a Ultrasonic range sensor using a ultrasonic (250ST/R160) speaker, which emits a 25kHz square wave with a Vpp of 12V for 1ms. The microphone (SPU0410LR5H-QB) is powered with 3.3V and its SGN pin is connected to the ADC input pin of the microcontroller. The ADC is sampling at 250kHz (at 10 points). ADC turns ON 1ms after the speaker turns OFF and stays ON for 8ms. Then this process is repeated.

I am monitoring the ADC output by outputting the signal using a DAC. The problem is that the readings that the DAC is outputting are noisy. (Initially I thought I was sampling too frequently that I was picking up the noise instead of the actual signal. But I believe sampling 10 times faster is the rule of thumb.)

I am also monitoring the SGN pin of the microphone (the signal that is fed into the ADC), and although there is little amount of noise it is no where near to what I am seeing at the DAC output.

It appears that the level of the noise is constant and the Signal-to-Noise ratio can be increased by increasing the Vpp of the square wave to 30V. But I cannot supply such a high voltage onboard without a power supply. Therefore, I need to find a way to alleviate the noise without increasing the Vpp.

I am waiting for your recommendations, thank you.

Please see the diagram below:


texts: Will a 2000w Step Down Transformer be enough to safely power a Japanese Oven Toaster?

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I recently acquired a Japanese oven toaster, with a maximum power consumption of 1000w at 100v, and I would like to use this appliance in USA.

I was told that for safety reasons I should get a step-down transformer with wattage at least double the appliance's wattage.

Another source told me that if the appliance generates heat, I should get a step-down transformer with wattage at least 4 times the appliance's wattage.

Do I really need 4 times the appliance's power consumption? For example, can I get away with using a 2400w or 3000w step-down transformer?


texts:
So I have been trying to solve this BJT problem for the last 20 min with no luck so far.

My question is, in this circuit, is \$I_B = I_E\$?

I have tried solving the problem with this consideration and without, but still can't do it.

Btw, the hint basically gives us \$V_{BE} = 0.8 \$ and \$V_{CE} = 0.2\$

EDIT:

I have tried solving it using KVL:
$$5 - 2{I_B} - V_{BE} - 3{I_E} = 0$$

That got me no where. I then thought \$I_B\$ may be equal to \$I_E\$ but the answer I got was wrong.


texts: LC oscillator V.S. LC oscillator deactivation

texts:
I read a paper,and it said using the LC oscillator to start-up will have a very low peak efficiency,about 1%,so they use the LC oscillator deactivation to let the peak efficiency become 33%.And i see their schematic,i think they still use a LC oscillator to start-up.

At first,i thought the meaning of LC oscillator deactivation is that i don't use the LC oscillator,but now it seems not,so i am confused now.

What does  LC oscillator deactivation mean?

What is difference between LC oscillator and LC oscillator deactivation?

The picture below is their schematic for start-up circuit,and i think the left one is a  LC oscillator deactivation they said.

Paper is from :ieeexplore.ieee.org/document/7479575/


texts:
I'm new to the whole electronic circuit scene, I've been trying to work out for hours how to design a 3-bit synchronous counter using D-Flip Flops to count in a given sequence.

So say for instances that the counters sequence is 111->010->011->001, what is the best approach to this problem?

any help much appreciated.


texts: Draw circuit diagrams with custom shapes?

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I want all the benefits of dedicated schematic drawing software but I often don't like the way the diagrams actually look. I know it sounds trivial, but I find it easier to read nicely hand drawn diagrams than all-red wireframe type ones.

Is there a decent piece of software where for example I can customise the shape or colour of opamps/wires/transistors etc?


texts: How to prevent MPLABX and XC16 from polluting my assembly program on 16-bit PIC24?

texts:
I recently started programming PIC microcontrollers after AVR and I wrote a small, do-nothing program just to see what the assembler produces in the HEX file:

;File:  main.s

.include    "p24FJ64GA202.inc"
.global     __reset
.global     __INT1Interrupt
.text

__reset:
    nop
    goto    infinite

__INT1Interrupt:
    nop
    retfie

infinite:
    nop
    nop
    nop
    bra     infinite

.end

After building and disassembling, I found that the assembler puts these unnecessary blocks in my code, that I did not write:

and

How can I prevent this from happening?


texts: Best cable to carry 3 DP (differential pairs), power, ground and 4 signals

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i need to carry the signals from a Raspberry compute module to a camera module and vice versa. Since I need to place the camera around 4 foot away from the microComputer, and i want the connection to be sturdy, and I need to be able to connect and deconnect the camera hundreds of time, the flat ribbon cable that is "native" to Raspberry is not viable.
The signals/power that need to travel are:

three differential pairs (For data and clock)
3V3 and GND
4 logic signals

All logic signals and differential pairs are bidirectional. Power goes from the compute module to the camera module, which is totally passive.
I've experimented with an HDMI cable, printing custom PCB connector adapters on both ends and it works perfectly even for longer distances (3m or so). It has been working for months, so the idea is working. They even sell commercial adapters for this.
I've also experimented with HDMI <-> miniHDMI and it works also, but the connectors are too bulky and moreover I've not found a cable with both endings miniHDMI.
Now I am looking for a similar, commercially available cable, with small connectors and able to carry the data I need.
I've tried with a miniDP but, because of my ignorance, I've overlooked the problem of power on pin20, so I have to discard it.
Now I've thought about USB-C, but it seems too complicated, with much logic in the connectors, I don't know if they are suitable. And moreover it seems that there are 3 differential pairs, but not enough signals for my use (I could work with just 3 control signals instead of 4, or at the very worst I think I could make do even with 2)
It puzzles me the thing that pins are replicated top and bottom (so inserting either way is unimportant)..
Any idea?
Thanks
Z
P.S. At the moment I've experimented with using one of the "signal" channels to route 3V3. I've jury rigged the PCB at the end of the cable to pass the power to the 3V3 tracks. It seems to work. I just hope internally the signal strand is able to carry the power (even if amperage is quite low)


texts: What's the best way to add USB support to a project

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It just so happened that I need to add a usb communication for my next project that I am working on.What's the best/cheapest way to do this.

Should I be using a microcontroller with USB support like maybe the ATMEGA32U2 or use a ftdi chip,or maybe something else.

I have never really worked with USB before,so any help would be nice.


texts:
I have this circuit design with an Arduino nano and a Nokia 5110 LCD that needs 3.3v. The circuit should work from 12v when connected to JP1.
I added to regulators and 2 rails one with an 7805 and another with 78l33. When the arduino is plugged in the USB it gives voltage to the 5v rail and the 7805 lets 4v pass from output to in. Then across the 78l33 2.5v appears on the display and the display turns on.
Is this a problem? If a put a diode on the output there will be a voltage drop so the output will not be exactly 5v volts. Also what happens when the 12v power is connected to JP1 and also the USB is plugged in will something fry? How can I protect this circuit or is it not a problem? One of the display was not working when powering it with the 12v rail and I don't know if the display is faulty or I made something.
Thank You


texts: Should the PLL pins be decoupled on an MCU?

texts:
Literature covers very well the decoupling of many pin types on a microcontroller, such as from muRata and E2V. The currents in are decoupled from the ground plane. PLL's are also grounded, however I have not read anything about decoupling them. Do PLL pins need decoupling in the same way as power pins?

For instance, Atmel detail the decoupling of VDD and VDDGND pins and describe the clock circuits for one of their MCU's. They do not detail any decoupling of their GNDPLL at all.


texts: Does using a electrical device that is connecting to a series of power extension safe?

texts:
I have a 4-way power extension connecting from a power outlet. I connect a 3-way plug on top of the power extension and following by a timer on the 3-way plug.

Is it safe if I connect a electrical device on the timer?

Timer

3-way Adapter

4-way extension


texts: why does sources with same voltage drive different current through same load?

texts:
I have three mobile phone chargers with rating 5V 500mAh, 5V 1Ah , 5V 2Ah. When I charge my phone Mi 4i with these chargers , the charging time is different. It means all these chargers drive different current through my phone's charging circuit.

So my question is, how can same voltage sources(5V) drive different current ( here 500mA , 1A and 2A) through same load(my phone)??


texts: Capacitor's voltage dropping instantaneously

texts:
I've got a fairly large capacitor (hundred mF's) that has a low voltage rating (10V). And, when I charge it to that value, as soon as I remove power supply (same voltage) the capacitor drops to around 6V (60%).

Is this possibly a capacitor electrolyte leak? I've subjected the capacitor to fairly harsh conditions.

EDIT:
I forgot to mention, when I reconnect the power supply, the 6V suddenly jumps back to 10V, and when I disconnect, again, down to 6V... Perhaps, the capacitor never actually reaches 10V?? But it's weird as I observed the charging from nearly 0V to 10V, in a logarithmic way (or is it right shifted upside down exponentiation??).


texts: Common mode choke in circuit with multiple ground connections

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I'm designing an automotive circuit where I'm using a reference power design from TI. Together with protection circuitry, this design includes a common mode choke.

The same circuit has an antenna input, and this antenna is grounded to the car chassis. This means that the circuit has two ground connections when the antenna is connected.

My understanding of a common mode choke is that it only works as expected when the same amount of current flows in each direction of the choke. (correct me if I'm wrong)

I'm then wondering how this second ground connection through the antenna cable will impact the performance of the common mode choke? Can it still be used?

update: Added schematics. The output of the choke goes to a TI LM53601 switching regulator and a TI TPS7B7701 antenna LDO for supplying phantom power to the antenna. IN GND and GND are separate nets. GND is also the ground connection for the antenna.

All the antennas I've investigated have 0 ohm resistance between the fixture that connects the antenna to the car and the shield around the antenna signal (inside the cable). Example of one such antenna is the Antennensysteme  3785.01 as shown below. When tightened to the car roof, the antenna will certainly be grounded to the chassis.


texts: How do I select transistors for logarithmic amplifier?

texts:
I need a logarithmic amplifier and found this equivalent schematic in the datasheet for the LOG104:

The LOG104 is rather expensive, so I want to build this myself. What are the requirements for the transistors? (I guess they have to be matched.)

I want to use this with a phototransistor to measure light levels.


texts: I wonder if it is possible to use the TinyOS-nesC environment to program a Basys2 card? Digilent has developed a driver for this card under Linux but their technical department says that it utilizes Xilinx-VHDL programs for Basys2. Does anyone have an idea?


texts: Electrical Standards - Earth Wire at Low Voltages?

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I got a question about safety standards:

I'm designing a consumer device and I'm not sure whether I need an earth wire.

I have an AC-DC converter plug that outputs 5 V and up-to a maximum of 1 A current. This plug goes from NEMA 5-15P to a barrel plug.

The main device is made out of (exposed) metal.

At this level of voltage/current do safety standards require that I ground the enclosure to earth ground?


texts:
I have been looking into making a voltage controlled oscillator using varicap diodes, however I have had hard time simulating the diodes in spice.

Would anyone here have an idea how this would be done?

Thanks in advance


texts:
I've looked through both the datasheet and the reference manual, but I can't figure out which pins can be used with the USART.
I don't want to use the STM32CubeMX for this.


texts: Does impedance balancing in the far end make no sense?

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Below shows a conversion of unbalanced line to a balanced one:

My question is about: if the unbalanced line is very long which means the signal source and the isolation amplifier is apart from each other 100 meters for instance.

In that case, if the balancing isolation transformer is at the far end i.e. right before the difference amplifier, and the unbalanced line is very long what happens to the CM noise coupled on the unbalanced line?

Will it be rejected at the isolation amplifier? If no, does that mean the isolation amplifier should be right after the signal source?


texts:
I am trying to tune/tweak/repair this transmitter for a friend of mine. It is oscillating, and it has rf power on the antenna, but it just doesn't seem as "strong" as it should be.

The diagram says 35-40 watt carrier. Now its a class A final amp, so I should be expecting half (or less) of that carrier wattage, correct?
It came to me with a VFO, Hartley oscillator which was very unstable, so I replaced it with a Colpitts crystal for testing purposes. (I changed the diagram as well.) The only other thing I have added is a 40uH RF choke in the plate supply line to the 807s. I could not get a clean carrier without this choke.

As far as I can tell, everything is working. It oscillates, has RF at the buffer EL84 stage, and has RF at the 807s.

I tune for the "dip" in 807 plate current, which then has the highest RF on my diy field strength meter, and here are the 807 measurements:
Plate voltage: 500-525v
Plate current: 90mA No signal
Screen voltage: 115v No signal <-- this seems low to me.
Grid voltage: -14.7v No signal <-- also seems low. (not negative enough)

The antenna is a 1 wave long wire. 25AWG magnet wire, about 10ft off the ground, no counterpoise. RF ground is a foundation stake pounded into the earth about 4 ft. (and it's raining here. ground is wet.)
I was using an antenna matching large variable inductor with multiple taps and fine tuning, but it seems to be "robbing" RF. It has a large neon bulb that glows brightly when it's hooked up though.

Is there anything fundamentally wrong with this circuit? Any red flags looking at the schematic? Lack of RF chokes? RF feeding back into the power transformer? Does the EL84 oscillator buffer need a tank circuit on the plate to tune to resonance?

Any help would be appreciated! Thanks.

Here's a link to the 807 class A specs I've been using:

Dwayne Reid: Thanks for your help. When I pull the audio EL84, the 807 plate current shoots up to 160mA, screen voltage increases to 204v, grid voltage stays the same, -14ish. The field strength of the antenna increases as well.


texts: Understanding analog frontend for PIR sensor

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I read this application note from Texas Instruments to learn something about the design of an analog frontend for PIR sensors, but I don´t know the function of the first OpAmp circuit.
What is the purpose of the two diodes in the feedback loop of the OPAmp?


texts: Noise mitigation in +/-5mV instrumentation amplifier?

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I am building a differential amplifier to boost a 0-5mV (delta) signal off a load cell wheatstone bridge.

In simulation, the design works here (falstad):

(for those who have not used falstad circuit simulator, the "2.53V" line are just voltage readings).

However, when factoring ambient noise, as observed in experimentation, the amplifier is essentially useless. I built the circuit in our lab yesterday to confirm this and unfortunately forgot to capture any scope screenshots. However, it appears that the noise off the wheatstone bridge is not from any direct source (eg 60Hz).

Apart from keeping wires short and ensuring consistent grounding, what else can I do to get rid of this noise? The very small delta of 5mV is observable on the scope when loading the load cell via an "up and down" translation on the scope. However, the channel itself has about +/-50mV of noise in the signal.

Any advice?

EDIT And I should finally add in case it is not clear, this is a DC circuit. Thus, frequency is ideally <1Hz.


texts: Why is this small signal model incorrect?

texts:
Here is the model I was told to redraw by replacing the transistors with their mid frequency small signal model:

And here is my attempt at doing so:

Upon receiving feedback, I was informed that the Rb resistors are missing. I think I made the mistake of not short circuiting the capacitors but where would the Rb resistors go and why?


texts: How is the Collector-Base region reverse biased in Common Collector configuration of BJT?

texts:
This is the circuit diagram of an n-p-n BJT in Common Collector configuration, taken from the book :-

I know that for the transistor to operate in active mode :-

the Emitter-Base junction should be forward biased.
the Collector-Base junction should be reverse biased.

By looking at the diagram, I can see that the Emitter-Base junction is forward biased. But I am unable to understand how the Collector-Base junction is reverse biased, since the Base is connected to the +ve terminal of VBB and the collector is at zero potential ( looks like forward biased to me ) .


texts:
I attached a tiny electric motor and battery to a small balsa wood glider. I'd like to add a tiny remote kill switch, with a range roughly around 20-40 meters. A switch that requires line-of-sight would be fine. Reliability is not vital (75% reliable would be fine).

I don't want full RC control, just a simple kill switch to shut off the motor remotely.

It needs to be tiny and lightweight and will run off a 3v or 5v battery. Preferably cheap as well, since my whole project has cost about $3 so far.

What wireless technology should I be looking for? Bluetooth? Infrared? 2.4 GHz? Something else?


texts:
Please need help in:

Do somebody have a a working code that writes to sd card via sdio using FatFs and DMA?( data logger)
In a poling mode (without DMA) I am writing to .bin file and getting error when the file is 4096 bytes. Do you know how and where can I remove this limit?


texts:
I have 8 LED's and I am trying to turn 2 on at a time.  My voltage source is 5V and the LED's require up to 200 mA current.  I am finding quite a few demultiplex chips that are 2x4:1 but most of them do not operate in this range of voltage and current.  Does anyone have a suggestion for a higher current Demultiplex chip or a switch.  The reason demultiplex is appealing is because it has control inputs, which I need something similar to control the switch itself.  A chip I found that would be ideal, if the voltage and current maximums were larger, is the TS3A5017

These LED's are BJT driven, which I won't go in to, but in order to turn them OFF the voltage source has to be off.


texts: I want a continuous and highly stable light from an LED for around a couple of hours, for which I need a highly constant and highly stable current source. I prefer an opamp-based circuit for the same. What should I use?


texts: Can someone help me understand DIACs and TRIACs

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These are something that has confused me for quite some time. Just like a lot of you, I'm sure, I'm a tinkerer. I like to take things apart, salvage parts, etc. A lot of stuff I take apart have a triac for AC control (a good example is a broken heater fan I'm trying to fix, but the triac isn't the issue there).

I know (or I think I know) that a triac is used for phase control of AC circuits, but I always see them used with a diac in schematics, and that's where the main confusion comes in. In almost everything I've taken apart with a triac in it, there's no specific component that comes up as a diac (when I look up part numbers).

My understanding is that a diac can simply be two regular schottky diodes in parallel with reverse polarities, is this true? I'm not overly fond of the idea of trying it with live AC without understanding it a little better. I'd like to phase-control a 120V resistive heating element (or more than one, if possible) and I just want to be more comfortable with what I'm doing. The internet keeps contradicting itself with the information I find.


texts:
I am in India. We have 3 phase power coming in from the grid. They don't do single phase for anything over 3 kVA. 4 wires from the pole to a fuse box. 415V, 3 wires each going to a separate fuse and neutral. All appliances are single phase. They are distributed across all 3 phases. All sockets have a ground, neutral and live. Is this a 3 phase wye? That would mean 240V at each socket which sounds correct.
Now if you were to get a generator would you do a single phase or 3 phase generator? 3 phase is slightly cheaper. How would the single phase generator be connected in this scenario?


texts:
I have been trying to repair an old 14 transistor radio from the mid-60's and have no sign of any image of the radio or schematics for it online.

One step I'm taking is to replace old caps (mostly the electrolytics) and I found a capacitor that appears to take the common form factor of an electrolytic capacitor, but has no clear marking for any kind of polarity.

The picture I have included shows the only marking on the capacitor and I would like to know if anyone can identify what types of capacitor it could be (electrolytic, tantalum, etc). In addition, an ID of the polarity could be useful as well. (One leg is longer than the other, but it was mounted with one hole further from the base) (Red coloring is my doing as well)

Another possibility is a test to determine polarity?

I know this is a tough ask, but I would appreciate if anyone could offer suggestions based off experience.

Thanks so much!


texts: Pull up/down a pin on a PCA9536 does not register?

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Quite a obscure question here, concerning a very specific I2C expander IC, however I believe that this example can be replicated with most expander bus ICs.

I am using a PCA9536 to switch the 4 pins on and off and read the states of inputs.

PCA9536 Datasheet here

When using the PCA9536, a command register can be used to determine, pin direction, state and even inverse the incoming logic.

My application requires the ability to read the electrical state of any given pin at any given moment, regardless of whether its an input or output.

This IC supposedly does this (page 16):

  7.3.2.3 Register Descriptions

  The Input Port register (register 0) reflects the incoming logic levels of the pins, regardless of whether
  the pin is defined as an input or an output by the Configuration
  register.

So, to test this, I conducted the following two tests:

Test A

I have set a pin to be an output and made it LOW, then pulled it HIGH

Reading the value of the pin, using I2C Register 0, returns a value of HIGH.

GREAT!

Test B

I have set a pin to be an output and made it HIGH, then pulled it LOW

Reading the value of the pin using I2C Register 0, returns a value of HIGH.

NOT GREAT!

This is my problem, as I need to detect a short HIGH or LOW.

What are the possible reasons for this and is there a workaround please?
Thank you in advance for any help you can offer me.


texts: Required creepage distance & clearance in high temp. (600~1000℃) for high voltage DC system (400V)

texts:
We have a high voltage battery pack. During abuse test, the Li-ion cells will eject lots of hot gas and graphite. These ejection will cause short circuit which is definitely not wanted. I want to know what's the required creepage distance & clearance in this circumstance. But the standards and handbook I found only have Room Temp. information. Is there some handbook for high temp. design?
Voltage: 400V max.
Temp.: 600-1000℃
Thanks.


texts: What device controls whether a signal is high or low

texts:
In circuitry, there is always inputs in circuits (for example: input A and B into an AND gate), but what exactly allows these inputs to switch states?
I think the best way to illustrate what I have in mind is the following:

Where basic is the input to the device

I can see how a person can switch the pivot between high and low but clearly that is not the case for electronics. In essence I am curious what the Basic (the most fundamental device possible) is. At the moment my best guess is it has something to do with the clock but I cannot expand on that idea.
I believe what I am describing is a device that takes in no physical input signals but outputs either a high or low depending on what is asked of it. And yes I understand that is an input in it's own sense.
I have experience with coding down to assembly language and the basics of computer architecture just for reference.
EDIT:
changing my notation of "base" to "Basic" to avoid confusion with transistors.
Also the command to change high or low is coming from code (for example digitalWrite(pin1, HIGH) in arduino)
EDIT 2:
My metaphor to what I am thinking. A person is using an old school computer with mechanical switches to manually enter any signals that are needed for the computer to do something. The person in this case is the switch in figure 2 and I am curious what is the modern day equivalent for this person


texts:
This schematic is part of a fan controller.

simulate this circuit – Schematic created using CircuitLab

FAN_POWER: 3.3 V (or 5 V for higher loads)

PW_FAN: goes to the fan

What kind of filter is this on the right hand side of the PNP-BJT? I'm not very familiar with LC  circuits in this way.


texts: Schottky diode / Rectifier Diode difference and how to test them?

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I have 3 diodes that I would like to test

1x USD935
2x USD2009

USD935 is identified by its datasheets as a "Power Schottky Rectifier Diode". I cannot find the datasheet of the USD2009 but they have similar test readings. So I'm assuming they are also a "Power Schottky Rectifier Diodes"

I am a bit confused by the name, as I thought a Schottky diode and Rectifier Diode were 2 different things. (different symbols).
Some make a distinction between the 2 , others say that a Schottky diode can be used as a rectifier.

To add to the confusion, I have them out of circuit and read that they can be tested using a multimeter in Ohms mode, as well as using the Diode function of the multimeter.

I tested them and got the following results

Diode test

black lead kathode /  red lead anode : 0.18v (beep)
Black lead anide / red lead kathode : OLD

Resistanse test

black lead kathode /  red lead anode : 170k ohm
Black lead anide / red lead kathode : 1k ohm

In terms of interpreting the results I found the following :

In How to Test a Diode Rectifier a forward voltage of 0.5 to 0.8 volts is mentioned when using the diode function of the multimeter. (mine is only 0.18v).
They also say that with the resistance test (black lead on the anode and the red lead on the kathode) there should be an OL  where instead I have 1k ohm.
In How to Test a Schottky Diode it is mentioned that Shottky diodes can be tested using the continuity test on the diode. Is that the case ? With mine there is no continuity between the anode and kathode.

Are my diodes bad, or am I misinterpreting the test-results / executing the test in the wrong way?


texts: Is there a standard way to implement desat protection on high-current FETs?

texts:
To implement desaturation protection on a switching transistor, one typically sets some manner of comparator to watch the voltage across the current flow terminals of the device. If that voltage exceeds a set level, a fault is thrown and the driver shuts down.

For high-current FETs, carrying hundreds of amps, this poses an interesting challenge. Since Rds(on) in this case is 1.3 mOhm, the difference between the voltages where the device is okay and where the device detonates is relatively small. We're talking about reliably and quickly sensing a ~.2V difference in an environment with very high currents flowing nearby, possibly within an inch on the same circuit board.

Are there any standard techniques for implementing a reliable desat circuit in such a situation? Noise reduction, component selection, shielding, component spacing, PCB design?


texts: SPI programming flash chip(s) - connecting HOLD and WP pins

texts:
I am trying to learn with SPI programming and have started with this guide using a Beaglebone Black.

I have one DIP8 package connected via breadboard for testing, and another SOIC8 package on-board a working system that I would eventually like to flash via clip.

The guide says when flashing a chip that isn't connected to a board, I'll almost certainly have to connect them. Why does it matter whether the chip is connected to a board or not? I'm powering the chip from an external source and the system in question won't be powered on, so I would expect I'd need to connect these pins to VDD regardless.


texts: How to turn an LM741 op amp into a distorted portable guitar amplifier?

texts:
Here is my circuit (to the best of my recollection):

simulate this circuit – Schematic created using CircuitLab

NOTE: The voltages and resistance values are not known to me and what you see in the schematic is just default.

Features:

Reverse feedback loop (I may mean "inverting" here)
LM741 opamp from Texas Instruments
Only two resistors used
This is a clipping circuit

My question is two-fold:

What is the simplest configuration for building a headphone guitar amp using only an LM741 op amp and two resistors?
Any idea why mine died after only 2 days of use?


texts: Cube IDE : Error: unknown type name 'HAL_StatusTypeDef'

texts:
I am taking code from a stm32f0 series and trying to convert it to a stm32l4 series dev kit. I have already changed the necessary addresses and include files that I needed to migrate, but I keep on getting the following errors in the stm32l4xx_hal_uart Files:

../Drivers/STM32L4xx_HAL_Driver/Inc/stm32l4xx_hal.h:610:1: error: unknown type name 'HAL_StatusTypeDef'; did you mean 'HAL_RTCStateTypeDef'?
 HAL_StatusTypeDef HAL_DeInit(void);
 ^~~~~~~~~~~~~~~~~

The error appears by this segment of code:

HAL_StatusTypeDef HAL_HalfDuplex_Init(UART_HandleTypeDef *huart);

I have already defined the HAL_UART_MODULE_ENABLED in the stm32l4xx_hal_conf.h and nothing has changed.

What is the cause of this and how can I fix it?


texts: lpc1343 upload firmware via UART bluetooth module from linux

texts:
I am a novice to BT so I am looking for some advice. My LPC1314 has a bluetooth module soldered to its UART.

I believe the BT module is a HC-06.

I want to use BT to flash the firmware.bin to the device (later also for debugging). Unfortunately I do not have a manual and I could not get it to work.

the BT module / connection works (I can remote control the device using an android app)

I can BT scan the device (it shows the MAC address):
hcitool scan

I tried different tools to send the file (no luck):

bluetooth-sendto
coax-software pybootloader.SerialLoader.py

Any ideas about the right tools to send the firmware.bin file from Linux?

Here my attempt to use the suggested LPC21ISP tool:

mark@ichikawa:~$ sudo rfcomm bind rfcomm0 00:19:MY:MA:xx:yy 1
mark@ichikawa:~$ rfcomm
rfcomm0: 00:19:MY:MA:xx:yy channel 1 clean
mark@ichikawa:~$ ls -l /dev/rfcomm0
crw-rw---- 1 root dialout 216, 0 Feb  3 09:07 /dev/rfcomm0

I resolved the permission issue and lpc21isp stopped complain about the com port...

mark@ichikawa:~$ sudo lpc21isp -control -verify -bin firmware.bin /dev/rfcomm0 115200 12000
Verify after copy RAM to Flash.
lpc21isp version 1.94
File firmware.bin:
loaded...
image size : 1952
Image size : 1952
Synchronizing (ESC to abort)..............................................
............. no answer on '?'

I also pressed the ISP button on the device but still the firmware is not uploaded.
I tried using LPC21ISP on Windows7 and it shows me the same synchronizing issue.


texts:
I'm writing a bootloader for ATXMEGA256A3U. At page 14, Table 7.1 of the datasheet I know the bootloader address start at 0x20000.

Using AtmelStudio I set in the linker option the following relocation:

.text=0x20000

and my bootloader work fine.
Now in MPLAB IDE X, I tried to do the same inside Project properties > Avr GCC > avr-ld > MemorySettings > FLASH segment.

But the whole generated hex is empty (all 0xFF). I also tried to lower the start address, i.e. .text=0x800 but it's the same.

To be sure, I inspected the generated command line and seems correct to me:

"libm";"libm" -Wl,--gc-sections  -Wl,-section-start=.text=0x20000

How to relocate the base address of my firmware to 0x20000?
By the way, the actual byte address is 0x40000.


texts: Extra negative battery cable when charging outside car?

texts:
If you go to: http://www.battery-chargers.com/charging_instructions.htm

...Under "Operating Instructions" part "B: Charging battery outside of vehicle", it says you have to attach an extra jumper cable to the negative battery post, that is then clamped to the charger's actual negative cable. See below:

Both my charger's instructions and these look identical on this point (Indeed, they might be the same instruction sheet).

Why is this extra cable needed?

(Not like I don't have one, just rather curious...)

Thanks!


texts: Is not it too much memory consumption for a simple thing?

texts:
I was trying to lower the memory consumption in my project and realized that a simple change of "uint8_t" value to the "define" shows effect much more and I thought. It seems I'm lacking some knowledge of this subject and want to ask this to the community.
MCU = STM32F072
Using HAL Library...
uint8_t msg_LengthWithoutCrc = 16;

// Check the CRC of the Info Message
if (check_CRC(start_info.msgBuffer, MSG_LENGTH_WITHOUT_CRC, start_info.msgValues.crc_val))
{
    xxxxxxx;
}

If I use "#define MSG_LENGTH_WITHOUT_CRC 16U" instead of  "uint8_t msg_LengthWithoutCrc = 16;" then my memory consumption goes down by 12 bytes. That seems strange to me.


texts: How to match gate driver with Power MOSFET?

texts:
I have a HB power  MOSFET , and I need to check if the driver  that I choose  drive the Half Bridge MOSFET  by a good way

Here the schematic  and Specification of  the driver and MOSFET

  Switching frequency  : 100Khz
  Vbus = 400V
  Iload =15A
  Ambiant temperature Ta= 85°C

Specification of driver IR2110

  Isource: 2A
  Isink : 2A
  ton/off (typ.) 120 & 94 ns
  Driver gate supply  Vdd= 15V
  Rthja = 75°C/W
  Tjunction = 150W

Specification of MOSFET

VDS @ TJ=25°C 900 V
Rdson @ TJ=25°C   : 0.12ohm
Qg = 270nC
Rg_MOSFET =0.9 Ohm
http://www.infineon.com/dgdl/Infineon-IPW90R120C3-DS-v01_00-en.pdf?fileId=db3a3043183a955501185000e1d254f2

the power needed to  drive the Mosfet is:

P= 2*Vdd*Fsw*Qg =0.810 W Per  2 MOSFET

the maximun gate current is

Igmax= Vdd/(Rg_ext+Rg_MOSFET)= 1.37A

My question is : How to define PROPRELY the  capabilty of gate driver regarding Source/Sink current and Igmax to driving the HB Mosfet correctly, or  I need  to calculate the power dissipation of  driver  based on RThJa?

Thank you in advance


texts:
I am having problems with getting certain pins on my microcontroller (PIC16F1933) working as outputs. I have been simulating the code in Proteus Design Suite by Labcenter Electronics and it doesn't toggle all of the pins correctly which I am assuming is a problem with the code. The pins I am mostly having an issue with are PB1, PC0 & PC3. I have been through the datasheet and have tried to turn off all the peripherals that could be causing the problem but nothing seems to have solved it.

    LIST    p=16F1933           ; Tell assembler what chip we are using
include "P16F1933.inc"      ; Include the defaults for the chip

__CONFIG _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _MCLRE_ON & _CP_OFF & _CPD_OFF & _BOREN_OFF & _CLKOUTEN_ON & _IESO_OFF & _FCMEN_OFF
__CONFIG _CONFIG2, _WRT_OFF & _VCAPEN_OFF & _PLLEN_OFF & _STVREN_ON & _BORV_19 & _LVP_ON

    ORG     0x0000           ; Processor reset vector
    PAGESEL START
    GOTO    START            ; When using debug header, first inst.

ORG 0x0005

START                            ; Turn on 16MHz OSC and select 8MHz
    banksel OSCCON
    bsf     OSCCON, IRCF3    ; 1110 = 8MHz HF
    bsf     OSCCON, IRCF2
    bsf     OSCCON, IRCF1
    bcf     OSCCON, IRCF0
    bsf     OSCCON, SCS1    ; Internal osc block

                            ; Wait for the internal oscillator to stablise

    btfss   OSCSTAT, HFIOFS ; HFIOFS: stable (0.5%)
    goto    OSCWAIT

                            ; Initialize I/O pins
INITPIC

    movlw   b'00000000'     ; Least significant bits [3..0] to be set as outputs
    movwf   TRISA           ; Set as Port A lower four pins as output for L198 - 1
    movwf   TRISB           ; Set as Port B lower four pins as output for L198 - 2
    movwf   TRISC           ; Set as Port C lower four pins as output for LEDs
    movlw   b'00000000'     ; Set all pins to not be analogue inputs
    movwf   ANSELA          ; Set PORTA pins not be analogue input
    movwf   ANSELB          ; Set PORTB pins not be analogue input
    clrf    PORTA           ; Clear port A house keeping
    clrf    PORTB           ; Clear port B house keeping
    clrf    PORTC           ; Clear port C house keeping

    movlw   b'11111111'     ; Default OUTPUT
    movwf   LATA            ; Set intial output values of pins on port A to 0
    movwf   LATB            ; Set intial output values of pins on port B to 0
    movwf   LATC            ; Set intial output values of pins on port C to 0

LOOP
    movlw   b'11111111'     ; Output set one used to test port C
    movwf   LATA            ; Move test value to Port C output pins
    movwf   LATB            ; Move test value to Port C output pins
    movwf   LATC            ; Move test value to Port C output pins
    movlw   b'00000000'     ; Output set two used to test port C
    movwf   LATA            ; Move test value to Port C output pins
    movwf   LATB            ; Move test value to Port C output pins
    movwf   LATC            ; Move test value to Port C output pins
    goto    LOOP

END

All I am trying to do at the moment is get the pins to high/low with the relevant LAT register for each port.


texts: Confirming the use of a RIFA snubbing component across 120V relay switch

texts: I have a mains relay switch (Packard C230B 2 Pole 30 Amp Contactor 120 Volt Coil) which allows me to turn on my pre-amp based on the existence of AC voltage on the amplifiers AC output plug (which is not sufficiently rated to drive the pre-amp). It's been working fine for quite a while, but generates a noticeable "PLONK" sound when switched off, which I know is because of the lack of flyback suppression on the circuit. I want to eliminate this and bought a RIFA PMR205 RC snubbing unit a while ago. Before I install this across the relay, I'd like to confirm that this is the right way to go about this (and yes, I should have never put the relay in without something like this in the first place, but I didn't know better at the time and it worked).


texts: Choosing a MOSFET driver - calculating gate drive current requirement

texts:
I am trying to understand how to select an appropriate MOSFET driver for controlling a DC motor. I went through quite a lot of literature from Texas Instruments and Microchip, but I am still not able to completely understand how to exactly calculate the gate driver current. Microchip has an application note on how to calculate the gate drive current which notes that the gate drive current (I_G) = Q_G/t, where Q_G is the total gate charge and t is the rise time.

While looking at some drivers on the TI website, I found the DRV8701 and the corresponding EVM module. Going through the schematic the GH and GL pins are connected through a 0 Ohm resistor to the gate of the transistors CSD18532Q5B. The maximum series gate resistance of MOSFET is 2.4 Ohm. According to the DRV8701 datasheet, I_DRIVE is 6 mA when the R_IDRIVE is <1KOhm to the ground ( I am assuming this the R_IDRIVE I should be looking at ). When I do the math for required Gate current as per the Microchip Application note, it comes out to be 8.05 A (=58 nC/7.2 ns). Even if I look at the maximum I_DRIVE current of the DRV8701 (150 mA), this requirement will not be satisfied.

I am not sure what I am doing wrong. When I use a PWM signal does the I_G value reduce depending on the  duty cycle? Is this why the 8701EVM is capable of driving the said FET


texts: Circuit Design: Momentary switch long press ON, short press OFF

texts:
I'm trying to create an accessory controller for my 2001 BMW motorcycle.  To those who aren't familiar with the older BMWs, there is a separate "turn signal cancel switch" on the handle bars that when pressed, grounds an input on the flasher relay and stops the lights from flashing.

I would like to use this ground signal as a trigger to turn on/off some auxiliary lights. .

I want to make it so that:

You hold down the turn signal cancel button for 3-5 seconds to turn on the aux lights.
You tap the turn signal cancel button to turn the lights off.

I've looked at some examples using a 555 chip LIKE THIS however this example uses a constant trigger voltage source.  I would like to keep the footprint a small as possible. Ideally, I would like the footprint of the entire circuit to be the size of a typical automobile relay.

There is an aftermarket controller already available that does this however I have additional ideas that will incorporate this controller into a fuse block/accessory all-in-one to keep the footprint small.  Plus I want to LEARN!

Any help you can provide will be greatly appreciated! Thanks in advance!


texts: Water level detection, where water is somewhat polluted and has significant dissolved salts

texts:
Found this excellent QnA here which provides several options for measuring or detection water-level. For my case, it is enough to differentiate 4 levels of water (very low, low, middle, full), of the tank.

I need to do the same, but in my case, I am having to deal with a concern, that this is not exactly clean potable water. The water, which is pumped out from a deep tube-well, appears to be somewhat polluted with silt (the rusty dark brown/blackish kinds) and lot of dissolved salts. While the silt is filtered by a 5 micron felt/microfiber based sediment pre-filter, in the post-pump section, it is present in the ground-level sump. The salt is a big concern too, because it stains (salt deposits) metal, plastic and pretty-much any surface. Any metal / plastic part left submerged for long-enough, gets a rather significant deposit of salt, which needs to be scrapped off (with difficulty).

Given these operating environment characteristics, I was wondering which ones of the following methods (all from the previous QnA cited above) of detecting water level, can be expected to work most reliably, and with minimum maintenance required over time.

Differential Pressure Transducer at the bottom of tank. What's the chance that the sensing surface or it's edges might get choked by the salt/silt deposit, and stop functioning in a few months. The salt/silt deposit itself may introduce errors in pressure reading over time.
Float switch - As this has moving parts, I wonder if they can be rendered immobile (lose mobility of the float) by the salt/silt deposit ?
Capacitive sensing - This is not explained in great detail in the cited QnA, but I've read elsewhere that it depends on an average dielectric coefficient of water, where-in 2 insulated probes are placed along the depth of tank / sump, in fairly close proximity. The capacitance of this, varies with water level, which is measured. The exact mechanism is not clear. Also, apparently, low voltage AC current is apparently used for this, but again, how part is not clear. Also, what roles the salt/silt deposits may play in change in capacitance over time, isn't clear to me.
Conductivity testing at multiple levels - Electrodes are placed at various levels, which are supposed to operate as closed circuits when water reaches the particular circuit placed at certain levels. Electrical current (say something like 24VDC) is passed through the circuits, periodically, for a short period to determine which all circuits are closed, and infer water level from such information. Now again, does salt/silt change the conductivity ? And can they corrode the electrodes ? Can I use aluminum or copper electrode ?
Ultrasonic, proximity sensing - Placing such a sensor face-down i.e. looking straight at the bottom of tank, and use the standard proximity sensing mechanism to detect water levels. To me, this seems most promising, as the sensor is rarely (if at all ever) in contact with water. Also, it's installation should be easiest. Of all of these, this however, is probably the most expensive approach, and possibly less robust (i.e. might not do well under the extreme humidity and temperature variation of a closed water tank/sump).


texts: What's this substance looking like glass cloth in an electrolytic cap?

texts:
This epic image of a blown electrolytic cap is from this question.

It looks like the cap is made of something that looks like glass fiber cloth inside.

What is that material that the inside of the cap is made of?


texts: What type of paper is good for the toner transfer PCB process?

texts:
I've been using magazines and it works about half of the time. Thick sheets work better but they are hard to find and I must cut them to size.

I'd rather just have something that works so I bought glossy yellow paper meant for toner transfer on Amazon.

It didn't work at all, my printer can hardly get the toner to stick. Magazines are better, but they still are not good.

Is there a type of paper that works consistently?


texts: Where did j go in the underdamped response of an RLC circuit?

texts:
I was following the derivation of the solution to the underdamped case for a series RLC circuit in my textbook, and ran into a roadblock. The derivation goes like this:

$$
\because \text{The general solution is } i(t)=A_1e^{s_1t}+A_2e^{s_2t}\\
\because s_{1,2} = -\alpha \pm \sqrt{\alpha^2 - \omega_0^2} \text{ and } \alpha<\omega_0\\
\therefore s_{1,2} = -\alpha \pm j\omega_d \text{ where } \omega_d=\sqrt{\omega_0^2-\alpha^2}
$$

Plugging these roots into the general solution we have:

$$
i(t)=A_1e^{(-\alpha+j\omega_d)t}+A_2e^{(-\alpha-j\omega_d)t}=A_1e^{-\alpha t}e^{j\omega_d t}+A_2e^{-\alpha t}e^{-j\omega_d t}\\
\implies i(t)=e^{-\alpha t}(A_1e^{j\omega_d t}+A_2e^{-j\omega_d t})
$$

Then, using Euler's formula, we can write:

$$
i(t)=e^{-\alpha t}[A_1(\cos(\omega_d t)+j\sin(\omega_d t))+A_2(\cos(\omega_d t)-j\sin(\omega_d t))]\\
\implies i(t)=e^{-\alpha t}[(A_1+A_2)\cos(\omega_d t) + j(A_1-A_2)\sin(\omega_d t)]
$$

Now, here is where I get lost. The book goes on and says:

$$
\text{Let } B_1=A_1+A_2 \text{ and } B_2=j(A_1-A_2)\\
\therefore i(t)=e^{-\alpha t}(B_1\cos(\omega_dt)+B_2\sin(\omega_dt))
$$

It then presents the above equation as the natural, underdamped response of an RLC circuit.

But how can this be true? It seems to me as if they just all of a sudden decided that the imaginary part \$j(A_1-A_2)\sin(\omega_dt)\$ was actually real. Shouldn't the actual solution be:
$$
i(t)=\text{Re}[e^{-\alpha t}(B_1\cos(\omega_dt)+jB_2\sin(\omega_dt))] \text{ where } B_2=A_1-A_2
$$

To me, it just appears as if they are ignoring the fact that the second sinusoid in the solution is imaginary, and therefore cannot be treated as if it were part of the 'real' response.

Can anyone elaborate on this?


texts: Removing high impedance ground pours parallel to signal traces in Altium

texts:
whenever I route parallel traces on Altium, I get those narrow ground pours between my signal traces when I fill my ground planes. A collegue told me: since these pours are narrow and thus high impedance compared to a ground plane, they would pair with the signal lines, and I should avoid this and remove those narrow pours (I thought parallel ground was good, though?). I wanted to remove these small pours in Altium, but since they don't fit as islands or dead copper, they are still filled. I cannot find a sleek way to do this except by placing awkward shaped polygon cutouts over my traces

Is there a clean way to cutout these "partial islands" of ground pour  on Altium? Thanks!


texts: What Transfer Protocol for "Streaming over USB"

texts:
I'm programming the FPGA on the Red Pitaya and I'm using it for gathering datas and generating images with those datas. Then, I need to transfer the images to an Android device.
I so need to use the USB port (for connecting the board to an Android device) and I was wondering what transfer protocol I should use for the image transfer. UDP over USB? Serial over USB? Other?

Or maybe something already exists on the Red Pitaya?

Thanks for your answers.


texts:
I'm just starting to work with KiCAD. One of the video tutorial shows that 3D view should incorporate components placed on the board:

However in my case I can see only the board with pads:

Looks like I need to tune up my KiCAD installation (I'm using Windows 7, KiCAD version 4.0.0).

Could anyone give me any advize for that?

EDIT 1

As @Robert Stiffler mentioned I verified if the component 3D view is enabled. As I can treat the follwoing screen - everything should be OK. However the option name is differ from suggested ("Show component 3D shape" VS "Show 3D footprints"). So it is possible that I picked the wrong setting.

And the libraries are mostly standard.


texts: Why is my LED flickering when it is connected to a variable resistor, and it's resistance is at the minimum value

texts:
I am doing a simple breadboard circuit, with an LED, 3.3V power supply (a microcontroller connected to the PC will be the voltage source), a potentiometer, and a Voltmeter connected across the LED.

This is the schematic of the circuit

When I put the slider at the bottom, the LED's brightness is dim, and the voltage across it will be (Voltmeter reading): 1.791 V

When I put the slider just below the top, the LED lights very bright, and the Voltage across it will be: 2.103 V

but when I put the slider at the top position, the Voltage across the LED decreases to 1.962 V, and the LED starts to flicker.

Can someone help me with this issue?

EDIT

I hope the picture is clear, I am connecting the Launch Pad to the PC, and using its 3V3 pin, and GND pin as a voltage source to my circuit, there is no code, or digital output pin involved (launch pad is just a fancy battery)


texts: Electronics to Measure Impact / Pressure

texts:
I am looking to setup device(s) that measures levels of impact / pressure and which then can be transferred via cable back to a computer for analysis. Ideally I want to buy a premade solution that is modifiable and can handle input from more than one device.

Can anyone suggest something like this or what a certain type of electronic may be called?

Ideally the electronics should be small, no larger than a thumb size. Realistically I know this chance is small, but free software to go with the paid devices would be a bonus.

Any ideas welcome

Thanks


texts: 12 V PWM fan and Wemos D1 Mini - ground loop?

texts:
Newbie here.

I'm trying to power a 12 V 4-wire fan and a Wemos D1 Mini from the same power source. The aim is to use a Dallas DS18B20 temp sensor and increase/decrease the fan speed as per the temp range.

Everything works fine when I power the Wemos separately (i.e. via the USB connector) and the fan by a 12 V source, but as soon as I try and run the two from the same power source, I start burning the 18B20 temp sensor.

I suspect a ground loop or something like that - here's a diagram of how I've wired things up:

simulate this circuit – Schematic created using CircuitLab


texts: Can someone explain me from the following table on how to get the DAC output.


texts: Cascading an Op Amp at a desired frequency question

texts:
So I have a lab practical with the instructions

"Demonstrate an operational amplifier circuit which may consist of one or two op amps with a gain of X (±10%) and a -3dB frequency exceeding Y kHz. The sign of gain can be + or -. "

I understand the operation and build of an amp and this is actually the second time doing this lab as I screwed it up the first time. The first time I was asked to design an amplifier with a gain of 80 with a frequency of around 1kHz. I used a circuit similar to the one depicted below to do this. Obviously my resistor values were different because I required a different gain.

As my understanding, depending on the sign of the gain dictates whether I used the noninverting (-R2/R1) or the inverting equation (1+R2/R1). Using these equations and the desired gain I can choose resistor values that give my desired gain. I also understand that if the desired gain is high enough I will have to cascade op amps. What I'm confused about is designing around the desired -3dB frequency. I guess I would like someone to explain where the -3dB frequency comes in to play in designing an op amp circuit.


texts: Transfomation of impedance using a balun

texts: I need to convert 75 ohms balanced impedance to 50 ohms unbalanced impedance using a balun. How do I do that? I am new to this and don't really understand the concept of a:1 voltage and current baluns.


texts: Is it technologically possible for IVR systems to recognize and support pulse dialing

texts:
I understand all the concepts behind IVR systems.

I've never been able to quite understand why pulse dialing can't be used with IVR systems. Tones are obviously sent to the other party, but a pulse is essentially a quick disconnect and connect of the circuit, so wouldn't the other party be able to somehow sense that disruption? Today, most phone companies don't use Strowger switches - they use digital switches meaning they are already using computers to "read" the pulses being sent down the line, so I don't understand why they couldn't just 'pass' those pulses on to the called party. The only answers I've seen online is "it costs too much" which is just ridiculous because pulse dialing can be done with purely mechanical equipment and there is no reason a computer cannot listen for pulses the same way it listens for tones.

Am I missing something else here? I am assuming that pulses are detectable by the called party and that the equipment reading pulses is digital (basically a computer of some sort). I'm not sure why pulses can't be passed on from the central office in the same manner as DTMF tones, especially since my understanding is that the other part can hear audible clicks on the line if you spin the dial or rapidly depress the switchhook when on a call.

In fact, I have just confirmed this. I can hear VERY LOUD pulses through the receiver when the calling telephone's dial is released, just as one would expect.

Note: I am not referring to the use of the * and # keys, which you obviously can't emulate when pulse dialing; but rather how any digit cannot be pulse dialed and used with IVR systems.

IVR = Interactive Voice Response (i.e. Press 1 for X, Press 2 for Y, Press 3 for Z, etc...)

I have two Panasonic PBX systems at home and they both automatically convert pulses to tones when an outgoing call is made. So the telephone company could easily do the SAME thing with absolutely NO additional cost. My PBXs make it seem like pulses and tones are equally easy to forward to the caller (I've tested and tones and pulses can both be heard by the caller) so systems should be smart enough to recognize simple pulses in addition to tones.

Obviously, * and # could not be simulated using pulses but you can't have everything...

From previous comments, I've gotten the vibe that companies just choose not to support it. But given the telephone company can recognize pulses using the same equipment, I am not sure why the same cannot be said for customer premises equipment that listens to keypad input. Regardless of whether or not it is or should be supported, is this feasible and possible??


texts: How to program USB RFID reader/writer module?

texts:
I bought an USB RFID reader/writer module from local store, it is not well known and branded, It connect to computer with USB port , and i want to write a program for it in Linux Ubuntu.

I find out (from CD with module) it use:

Silicon Laboratories CP210x USB to RS232 serial adaptor

I install the Driver from CD on Ubuntu and i compiled and run the example C++ file is in this link.

Now i want to send charachter message to it and receive proper massage from it but the example just send HEX value and if i put char in ioctl, it wont work, i tried this:

static const char HELLO3[] = "Howdy";
ret_val = ioctl(fd, HELLO3, &gpio);
cout << ret_val ;

It(ioctl) only get long unsigned int, I guess this integers should be in library but i don't know how to use them. How can i send massage to device and receive massage like response from it ?

The datasheet is not in English but it have some example for c# it is like :

serialport.writeline("W0abcdef65\r\n");

It mean write abcdef65 on Block 0 and it receive Msg0000001 which means the command run perfectly. How can i get same functionality in C or C++ in Linux.

PS :

1-The library or driver is in the same folder as example link in github which i mentioned before.

2-The device works properly with the application carried with its package in Windows but i want to program it in Linux with C++ or C.


texts: How do I implement F using one 4-16 Decoder and a NOR gate?

texts:
I currently have more than 50% of question done I believe, but what I don't get is that why does the question ask me to use a NOR gate. Doesn't that change the value of F. For example, if I have 0000 my output F should be 0, but a nor gate would make it 1. I do recall my professor saying that 0000 actually gives 1 and we NOR it to get 0. How did he know it outputs 1?

(Original)

I am just confused why he said 0000 would give 1 on output. Or am I misinterpreting the question?


texts: Selecting diodes for HV full bridge rectifier

texts:
I'm using a current-fed Royer self resonant circuit to generate 1kV DC output voltage. The transformer is producing a sine wave of 100kHz/2kVpp (Cap-Royer = 100nF). At the output of the transformer I added a full bridge rectifier consisting of four BY203 HV diodes (2kV, <300ns), now I see that after adding the bridge rectifier the idle supply current of the Royer converter doubled from 25mA to 50mA, without adding a load!

By coincidence I found that adding a 20pF capacitor in parallel to one of the diodes is reducing the idle current to 27~30mA, but adding capacitors to two diodes (U$15, U$17) brings it back to the high current.

Is the problem here maybe that the diodes are not fast enough? I couldn't find diodes with lower recovery time for the high voltage >1.5kV.

What effect is causing the parallel capacitor to reduce the idle current?


texts:
I have the following transistor, whose I have calculated the parameters that were not given.

Now, I want to draw the corresponding AC circuit.
Can someone help me with this or give me any source where I can learn more about it.

Does C2 need to be included when drawing the AC circuit ?


texts:
I am making a transformer-less AC to Dc power supply and the best design that I have got till now is this:-

For better understanding you can download this PDF:-
www.nxp.com/documents/user_manual/UM10522.pdf

This circuit uses a TEA1721 ic to convert AC Mains voltage to DC voltage. This design claims to have a 77% efficiency without a transformer and is non-isolated, both of which are fine by me.

The output of this converter is 12V 200mA and I desire 5V 450mA (or greater amperage). Please suggest any changes that I can make in this circuit to get a 5V 450mA output.

If there is a better circuit (without any transformer) which has a better efficiency and an output of 5V 500mA (or greater amperage), then please do suggest me that as well.


texts: Does some components search by specs encyclopedia exist?

texts:
I'm wondering if exists some comprehensive search resource where I could find electrical components parts (resistances, inductors, diodes, capacitors, transistors etc. etc.) of most producers and related specs.
For example, consider that you need a 1 farad capacitor, you may just start to google "1 farad capacitors" and start to check the detailed specs of each producer, and this is time consuming.

Would be better if you can have a service where you can search "1 farad capacitor" check (almost) all the models present on the market to choose the one with desired thermal tolerance and better shelf life, a specific material etc. using a detailed contextually parametrized search.

Something similar would be very useful also to do comparison based on average price to design products with a better quality\price ratio.

I'm doing this question because I'm considering to create a similar service.


texts: In my internship, I get to use Cadence (Allegro/OrCad) for PCB designing. I was seriously shocked how complicated it is (very specific on each components). At the same time, it feels like a very outdated software as well (even though the one I was using was updated in 2016). However, I have used Altium for my school projects before which is very easy to use and convenient, and the UI of the software is beautiful. Therefore, I wonder what EDA software people normally use in the industries.


texts:
I have made a lipo battery pack with 2 identical 3.7V 1400mAh battery packs connected in series.

This pack is being used in a wearable project where I wear this pack on my wrist.

Now to charge it up, I have a TP4056 1A single cell lipo charger. Now my charger allows me to charge one cell at a time. I was thinking that if I wire individual cells to the charger in parallel, I could use the same charger for both the cells and could keep my battery pack compact and would have a simple plug-in solution for charging it up.

Will this method work?


texts: Precise capacitor in parallel to power supply

texts:
I found this schematic in ADNS-2610 datasheet.

There are two capacitors in parallel between pins 6 and 7 (GND and  VDD.) One is 4.7 uF and the another is 0.1 uF, so the parallel result is 4.8 uF.
Why is the 0.1 uF capacitor needed? It doesn't seem to be a precision-critical component, because it's just in parallel to the power supply (I think just to stabilize the voltage.) Isn't just the 4.7 uF one sufficient?
Maybe the fact that one is polarized and the other isn't makes some constructive/technical difference? I can't see any reasonable motivation.


texts: What is this device included in my Arduino parts Kit?

texts: It was included with the light emitting LEDs so I assume it also gives off light? I understand the the shorter prong goes to negative/ground and the positive prong is longer, but this little thing has 4 prongs! How do I properly wire it?


texts: How do I model the optical coupling between two optoelectronic devices?

texts: I'm building a circuit composed by two parts that are electrically isolating. One part has a LED (model: SIR333) and a phototransistor (model: SFH309FA). I basically have to model the optical coupling between this two optoelectronic devices, using a linear relation between the currents, with proportional constant dependent on the distance between this devices. I have no idea where to start, and if there is any info on the datasheets of this devices that can help me. How can I correctly measeure this? Thank you in advance!


texts:
I'm trying to generate a square wave at 21kHz (+13V,0V) using this schematic:

I used formulas and this website to find the correct values for my components but it doesn't seem to work on Simetrix.

Do you see any problem?


texts: Does it make sense to only mention amp requirements and not voltage requirement, or vice versa?

texts:
When reading about the electrical needs of various electronic devices and/or appliances, I often see a requirement for only one of the various measures related to electricity. For example, it will say "requires 120 volts" and not mention anything about amps. Or it will say "takes 10 amps" but not mention anything about volts.

Here is just one example from Lifehacker, in an article about the Raspberry Pi:

  A power supply: The Raspberry Pi is powered by a micro USB, much like
  the one you’ve likely used for your phone. Since the Pi 3 has four USB
  ports, it’s best to use a good power supply that can provide at least
  2.5A of juice.

Isn't a statement like that useless? There is no mention of required voltage. 2.5 amps can be delivered in many different ways - i.e. by 5 volt pressure, or 240 volt pressure. I suspect this can produce very different outcomes.

So why are volts and amps often given as though they are completely independent? Why would there be an explicit requirement for one and not the other?


texts: What components are needed for a 20MHz square wave clock?

texts:
I would like to create a 20Mhz clock that generates a square wave for the home-brew Z80 computer I' making. I already have several 20MHz crystal oscillators but am at a loss when it comes to circuit diagrams and other components needed. I have looked around but I haven't found any diagrams with all of the details that I need.

Thanks!