texts:
I'm buying a LM317 and it comes in 3 different packages. Which is the best for attaching a heat sink? The options are:

TO-3
TO-220
TO-92


texts:
I'm trying to use Kirchhoff's voltage law to find the bias point of a bjt amplifier circuit, as shown below:

I begin with switching off the signal and opening all capacitors

simulate this circuit – Schematic created using CircuitLab

The transistors are identical, both with beta of 150.

I then assume Q1 and Q2 are in forward active mode, and arrive at the following:

Vc - VBE2 + r4* ix = 0 ---> (1)

Vc - VBE2 -iy* R6 - VBE2 - R3* ix = 0 --- >(2)

ix = 151*iy ---> (3)

Solving the above in Wolfram, I find that both ix and iy are negative. What do I do then? Does it mean Q1 is not forward active, and all the assumptions are wrong?

I hate to ask a "please check my calculations" sort of question, but I've verified the steps again and again for hours and am getting nowhere.

Please enlighten me!


texts: Logic Synthesis Synthesis - Consensus property?

texts:
OK, I'm working on a synthesis problem that doesn't quite make sense. I start with the equation \$f = x_1x_2'x_3' + x_1x_2x_4 + x_1x_2'x_3x_4'\$ and have to reduce it but I keep going in loops. I tried the solution from the solution from the Solutions Manual but one line doesn't make sense. They go from

\$x_1x_2'x_3'x_4' + x_1x_2'x_3'x_4 + x_1x_2x_4 + x_1x_2'x_3x_4'\$

to

\$x_1x_2'x_3' + x_1x_2'(x_3' + x_3)x_4' + x_1x_2x_4\$

I understand what they've done to combine the 1st and 4th products (and moved the 3rd product to the end), but what happened to the \$x_4'\$ on the second term?


texts: Activating a relay when certain voltage received (Water injection system)

texts:
I decided to build a simple water/methanol injection system for my car and now I'm thinking about a simple way to activate the water pump only from certain boost level. For the boost reading I'm planning to use map sensor. The map sensor has +12v supply, ground and output pin (5v max). The output voltage varies depending on the boost pressure.

What would be the easiest way to activate a relay which turns on the pump when certain voltage (or more) is received at the output from the map sensor? Ideally with a potentiometer for the boost level adjustment but that would be just a nice to have option.


texts: Understanding the role of a pull-up resistor

texts:
I am trying to understand the role of the transistor R11 in the following schematic:

The schematic simply generates a pulse at R5 when the switch is pressed.
If I understand correctly R11 is what one calls a "pull-up resistor" and it ensures that we can reliably switch on and switch off the circuit using the transistor. More precisely the presence of R11 (at a smaller resistance) allows us to reliably connect R4 + C2 to the ground. It makes sense that this is helpful.
But I don't understand why this is necessary. For instance is it possible to remove R11 from the schematic and connect directly R4 + C2 as the collector of the transistor?
Is it correct for me to assume that this will not work because the voltage across the capacitor will be sometimes negative? And as a result the transistor would not act like a switch but more like an amplifier?.
I'm sorry if these questions are trivial, I'm still learning about transistors...


texts:
I have to communicate between a sensor module and micro-controller board. The sensor module uses UART at 230400 bps. I have used a MAX3227 on sensor module as well as micro-controller board. So, the signal levels will be +5V and -5V. The distance between the two circuits will be 3 meters.

The baud rate and distance are fixed and cannot be changed.

I am confused about what cable should I use. I read that twisted pair for Rx-Tx will cause crosstalk. Please suggest me what cable I should select. Thanks!


texts: Low power timer circuit for solar tracking

texts:
I'm making a solar based device but it needs to be aligned according to sun's position in sky , the whole assembly needs to move around 11 degree/hr.
So I was thinking of using a timer circuit (low power) to power motor (stepper) after short time period.
Now for powering the batteries I'm thinking of using wind energy as my project will be placed in open space (terrace etc).
I need your help in suggesting switching circuit with low power consumption which remains in dead state when inactive.


texts: Battery management system circuit validation. Is my rough circuit design correct? Am I on the right path?

texts:
After referring to several pieces of literature, websites and several questions on Stack Exchange, I have designed the circuit of a battery management system and roughly sketched it for a 10s, 36 V, 2.5 Ah battery pack.

I would like to get my circuit validated whether I am going on correct path or not. I think it is correct because I referred to many papers following the same exact method and circuit, but still I need a validation. If is there anything that I need to change, please tell me.

Once it is validated I will proceed to create schematics.

Here is the rough BMS circuit:

Battery pack: 36 V, 2.5 Ah
Battery monitoring IC: LTC60811-2
Microcontroller: STM32F401RCT6
Current sensing amplifier: AD8205
Buck converter (42 V to 3.3 V): LTC3638
MOSFETs: IPD088N06N3 G

I have already validated the internal circuits of each IC and also I have validated the power consumption.

I would like to get my whole circuit validated and need to know whether I am on the right path.


texts:
After all that has been learned about electricity - if the grid and removing financial considerations and adoption feasibility. Imagine you're constructing for Mars or some post apocalyptic environment where sufficient technology exists to adopt a perfectly optimized solution - it needs only to be identified.

I appreciate the input and I am interested in the entire grid from production through distribution to commercial and consumer consumption. If you have additional input as it pertains to devices on battery power, I'm interested in that as well.

As far as removing


texts: How were values of Vc(0+) and i(1.5ms) found?

texts:
I get that by applying source transformation, we get a (0.1*200=20 V) source but shouldn't 0.1 A current be divided into 50 ohm and 100 ohm resistance?
Also why i=0 at t=1.5ms?


texts: High voltage to low voltage buck converter for(60V IN 5V 3A out) making noises?

texts:
I've been trying to convert a high voltage input to a lower voltage (5V at around 3A) with no luck using these Modules

and all of the LM2596HV iteretions of modules out there and all seem to make some audioable noises with their inductors even with lower loads.

Now I'm looking for either a solution + explanation for it and or a better module product with quite a small form factor that can withstand these specs:

60V+ Input voltage

5-12V 3A output


texts: How do I make a 12 LED grid USB powered?

texts:
I want to make a grid of 12 LEDS which is powered by a USB cable... I know that the voltage is too high for one LED..the cpu stops the voltage after 2 sec.

So what is the setup i need to use to do so..

I thought connecting 4 rows (parallel) of 3 serial LEDS to the usb cable? Is it ok?

The LEDs are of default type.
USB gives 5v so 3 serialed leds will get 1.66v each (which is close to 1.5v when testing leds)
4 parallel rows won't change the voltage but what about the current? does it matter?

If possible a solution without resistors will be great..

thanks, Eli.


texts: How to implement a BLDC for variable torque in its phase (InstaSPIN, TI)

texts:
By chance I read this patented method to control the rotor pitch without a swash plate usually a helicopter, by adding two parallel hinges on each blade root. When add torque to spin it the pitch would change so you can generate a vector force against the rotor axis:

http://modlabupenn.org/underactuated-rotor/

This is a very useful control technique for control a miniature indoor drone, although it's patented (https://www.google.ch/patents/WO2014160526A3?cl=en).
I still want to try it at home by building an ESC (hobby model naming for brushless motor controller).

A good starting place may be to buy a cheap TI FOC InstalSPIN controller demo board by hacking some code on:
http://www.ti.com/tool/launchxl-f28027f
with a driver board to drive a 2213 dji phantom motor.

The question is:

I don't have any experience, would this board/code base could implement this function directly?
If not, any starting point for other FOC controller will do

I want to make a ESC with 3 120 angled position input to tell the motor controller where I want the positive pitch to go.


texts: THAT4315 audio analyzer - capacitors getting hot

texts:
I have designed a audio spectrum analyzer circuit with THAT4315 and a drivers for IN-13 bar graph nixie tube to visualize the signal level.

To supply +-12V to the opamps, the Meanwell NSD15 module is used. At the moment, no additional input/output voltage filtering (other than the caps on the module) is used.

Here's the schematic for one frequency band.

The problem is that the electrolytic capacitors are getting too hot. I measured around 55 deg.C using an infrared thermometer. It's hard to pinpoint the exact caps, which are getting hottest, but it looks like the ones encircled in the schematic are slightly hotter than others.

These are the caps I used:
EEE-FK1H220SR, EEE-1HA100WR, EEE-1HA4R7SR

Any ideas about what might be causing the caps to get hot in this circuit?


texts:
I am struggling to come to term with how negative feedback helps widen the scope of input signals coming into FETs (or OpAmps for that matter, but I am using J201 JFETs).

I am aware that the largest input into a FET can be equal or less than the value of \$V_P\$ (\$V_{GSoff}\$) before clipping. I am also aware that \$V_S\$ acts as negative feedback allowing an initially larger signal to control the FET without clipping and (potentially) creating distortion.

Can somebody explain how this works and how I am able to ascertain what maths need to be used to work out what amplitude signal can be used on the input with a \$V_P\$ as a limit cleanly?

Image is just for an example. The values are not what I'm using.


texts:
I am having issue with my OLIMEX PIC18F4550
(link).

I am not able to view any tools in my IPE.

I am using PICkit 3 from Microchip. I think the issue might be that OLIMEX isn't powering up. I have connected it to my PC via USB. But I don't understand why its not powering up. I have attached the connection of PICkit 3 and OLIMEX.

Kindly tell me what is it what I am doing wrong here.


texts: 455 kHz intermediate Frequency transformer windings

texts: While repairing an old radio with no AM reception, I found on my multimeter that there is continuity between the primary and secondary windings of the first 455 kHz IF transformer in the circuit. I desoldered it and found that the windings are still reading 0.6 ohms between primary and secondary. Is this normal? I checked for shorts between the can and IFT coil but there are none so I am not sure why the windings would appear to be connected.


texts: Raspberry pi with two USB 2.5 inch Hard drives and powering them in parallel via one 5V PSU

texts:
I'm a hobbyist/tinkerer and want to make sure I don't fry my equipment by doing it wrong.

I'm trying to connect two/three 2.5 in USB HDD's to a Raspberry Pi 3. The power supply I have is 5V 2.5A and I plan to upgrade that to a 5V 4A or 5A whichever is available/needed. (At startup each drive can take between 600 to 1100 mA and then falls back down to 400 mA during normal operation.)

I imagine that just by providing higher PSU to Pi will not suffice and I should look into separating the Data and power of my HDD's so that the Data is still connecting to Pi, but the power is provided by the PSU directly.

To oversimplify - I'm thinking of taking the 5V 4A PSU and using a Y connector splitting it into two.
1. goes to Power the Pi.
2. goes to power the HDDs.

My question is:
- Is this the correct way to do it ?
- What kind of circuitry do I need to build so I can power these reliably?

Thanks in advance.


texts: Is it true that  +5v & +12v can not share the -12v ground on a NPN BJT being used as a switch controlled by a MCU signal? If so why?


texts: Is there a good reason why TO-220 5-lead components have bent leads?

texts:
I've recently acquired some LM2596T-5.0 3A buck converters. They are TO-220-5L packages with bent leads similar to this image:

I have seen other TO-220-5L components with straight leads like this:

My question is whether there is a good reason why they are bent (arcing, magnetic interference, etc) or is it just to make mounting easier, or some other reason. The bent lead don't work very well on breadboards or prototype boards so I have straightened them and then fanned them out a bit so they will fit but I just wondered if this would cause me a problem at some point.


texts: SMD Electronics Part that could be used for hanging

texts:
I'm working on a decorative PCB and I want the ability to hang it up on a wall conveniently. I was trying to think of something that would work similar to the saw tooth looking piece in this example

One requirement is that is has to be a surface mounted part. Something I thought of was a test point ( https://www.digikey.ca/product-detail/en/harwin-inc/S1751-46R/952-1478-1-ND/2264564 ), but they don't seem to come in a large enough size to work. The other thing I thought of was using a battery holder ( https://www.digikey.ca/product-detail/en/linx-technologies-inc/BAT-HLD-001-TR/BAT-HLD-001-TRCT-ND/5803803 ), which could work alright but is still a bit small.

I wanted to see if anyone had any ideas for common SMD electronics parts that could work with a household nail or screw.


texts: Use microcontroller to measure the microcontrollers voltage

texts:
When using an Analog to Digital Converter (ADC) I want to convert to millivolts (mV) afterwards. My microcontroller is running on 3.3V, but I want to measure more accurately to get better result.

$$mV = \frac{adcData}{2^{12}} * V_{cc} * \frac{1}{1000}$$

Vcc is ideally 3.3V, but I want to measure it.

Is there any way to do this, except measuring the voltage with a multimeter on the board directly?


texts: Why is this power cable sometimes polarized and sometimes not?

texts:
I have a handful of power cables like this:

Some have polarized male plugs, while others are not polarized.

Given that the female end appears to be reversible, why are some of them polarized?

I have an LED television that came with a polarized version of one of these cables.  But I have a longer non-polarized version.  Would it harm either myself or the TV to use a non-polarized version of the cable?

(Bonus: Do these cables have a name?)


texts: Can an ordinary transformer be used for coupling the speaker with a transistor amplifier

texts:
Audio transformers are not available in my locality. However, I have bought an ordinary transformer. It has the following specifications:
Primary voltage: 230 V
Secondary voltage: 6 V
Current rating: 300 mA

Apart from these, I measured the impedance using multimeter. For the primary side it is 2 kilo-ohms and for the secondary, it is 11 ohms. These impedance kind of match with what I require for my amplifier load.

Now my question is whether I can use the ordinary transformer or not. I googled and some sites said that these transformers are safe to use in the audio frequency range. At the same time some sites said the opposite. I just want to clarify before I end up messing my transformer.

Also please provide any other means for impedance matching. I tried an emitter follower, but its not very pleasing.


texts: Very high temperature (>500C) IC packages

texts: I was looking for IC packages where I can mount a small wafer (3mmx3mm) wire bond to the leads of the package and conduct operation at 500C. I have contacted couple of companies which do ceramic IC packages but they only guarantee operation till 250C. Would these ceramic packages hold till 500C? Also, is there any conductive thermal paste to mount the wafer which can sustain 500C? Any help would be very useful!


texts:
I'm building a small light system for an RC car, this is the schematic:

The power source is 5.5 V. These are the LEDs that I am using, KKHMF 100個 3mm LED 発光ダイオード LED電子部品バッグ 5種類 各20個 - two white, three red and one green.

I've used an online resistor simulator for calculate them, I hope that they are right

I would like to add a blinking capability to four of them, and I've understood that I need a microcontroller.

Here my questions:

Are the resistors correct?
What microcontroller can I use and how I can connect it?

The car is very small (1/30 scale) so all the parts have to be at very low consumption and very small, able to resist to mild vibration and some shocks.


texts:
[![enter image description here][2]][2]everybody, I have a project which is to dim 1000 W halogen light connected to Arduino. I used this circuit which is working fine with 100 W halogen light but when I connect 1000 W light the transistor burns once I on the circuit I am a beginner so forgive me.

This is the components I used

Bridge rectifier: 6 amp 400 Volt
Transistor: IRF740
Optocoupler: 4n35
resistor 4.7k
resistor 100k 1 Watt
resistor 6k8 1/4 Watt
Capacitor 100uF 400 Volt
Zener 15 Volt 0.5 Watt
diode 10A10


texts: Why does I²C only have pull-up resistors (interview question)?

texts: The interviewer wanted to know why pull-up resistors are used on SDA and SCL when the opposite logic can also be implemented. Is there an explanation for why pull-up resistor usage is the chosen design?


texts: PNP high-side switching with logic reverse

texts:
I am trying to design a High side switch(24V,10A) using a PNP Transistor, the switch control signal is PNP or NPN from the PLC output.
How to select the control signal type (NPN or PNP) using a selectable switch?


texts: Electronics in high temperature environments

texts:
I'm relatively (ok, very) new to electronics.  I'm trying to find where to buy parts (or even just more information on what sort of materials I should be looking for) to build a circuit board with a micro controller and RF transmitter that can withstand being exposed to a hot, dry environment.  The upper end of the temperature range would be 200C (~392F), and would be need to be able to operate under constant exposure to this temperature for 8-12 hours.  Ultimately, it would need to be fairly small (we're hoping to keep it smaller than the size of a couple 9V batteries stacked together)

Not being a traditionally educated EE or material scientist, I'm very much out of my element here - referrals to other sources of information, web sites, etc., so that I can at least get an idea of direction would be tremendously helpful.

I would also be interested to hear more information about thermal protection methods - would there be a way that I could build an enclosure to protect the internal electronics from the same environment.  I would think that no matter the sort of "housing" I could build, without an active cooling system (which is all but prohibited given the target form factor), then the electronics themselves would need to be able to tolerate the temperature - but I would certainly love it if someone could correct my naive assumptions here.

Thanks for any advice/help.


texts: Why to disconnect the negative/ground terminal, not positive?

texts:
To break off any circuit, the common way is to disconnect the negative and or ground terminal. I rarely see people disconnecting the positive and if so, they're not well educated in electrical engineering most of the times.

Well, I've no electrical degree either and to me, breaking the circuit off at the negative side seems counter intuitive.

In my intuition, breaking the input makes more sense than breaking the output, due this is the side where the energy is coming from.

Why to disconnect the negative/ground terminal, not the positive?


texts: With a HDL design how/when do we know that we need multi_cycle path, how do we implement it

texts:
I understand that we use the multi_cycle path when the delay between launch and latch register shall be more than 1 clock cycle. With a HDL design how can one predict that the combinational logic between two registers shall be more than clock cycle and thus there is need to use the multi_cycle path constraint? Besides this, for a HDL design where we may not know exactly which registers we are talking about, how can we put in a multi_cycle path constraint? Is it important that this delay be more than 1 clock cycle under best as well as worst conditions?

As far as I understand. We first synthesize our design and if the propagation delay of the gates is big enough between two registers than we know we need this constraint. This shall happen before the fitter as after fitting the routing delay shall add up as well. Is this correct?

Can we also force the fitter to fit logic in such a way that it takes 2 clock cycles for data to reach the latch register? My confusion exists because when we have a HDL design we are at a higher level of abstraction and don't know about all the physical registers that exist in the design, that is unless and until we do a STA on the post-synthesis netlist.


texts: Problem testing an ADC with a DAC and voltage divider

texts:
I am testing a self-made ADC shield for Arduino Due based on the ADS1299, a 24-bit ADC with a 24x programmable gain amplifier.

I have a signal generator sketch running on another Arduino Due that can output waveforms via the Due's DAC0 output. I can connect an oscilloscope to the signal generator, and see the waveforms. When I connect the ADS1299 to the DAC directly (at 1x or 24x gain) it can see the waveforms perfectly too.

The problem: I want to use a voltage divider to test the DAC at lower output voltages. To start with, I constructed a voltage divider that reduces the output voltage by a factor of 2. But when I connect the ADS1299 to the voltage divider, it reads 0v (well, noise around 0v).

However, the oscilloscope can see the waveform perfectly when connected to the voltage divider.

What's going on?

Here's the voltage divider circuit I'm using:

Z1 and Z2 are 3.3kΩ. Vin is connected to the DAC output. Vout is connected to either the scope or the ADS1299 (with appropriate grounding in both cases). I've tried the circuit with 2 47Ω resistors too, with the same results.

(I've checked the questions Voltage dividers and ADC's, How to Convert 0 to 10V analog signal to 0 to 2.5V for ADC input?, and Shrinking an input signal for the ADC and some others - it seems like the voltage divider's impedance may be interfering with the ADS1299 sample-and-hold, and the scope's probes may have a way of adjusting for that, but I am not sure. The datasheet says the ADC's DC input impedance is 1000MΩ, and the dividers I tried are not anywhere near that.)


texts:
I'm having a bit of trouble with my Feather HUZZAH ESP8266 and a airsoft DC motor (similar to this one).

This is my circuit:

I want to use Pin 4 on the ESP8266 to turn the DC motor on and off at 0.5 second intervals through the IRL40B209 MOSFET. Acknowledging that the MCU can only output 3.3V the GPIO pin, I am using a TC4427 MOSFET Driver to bring the signal up to Vcc (7.5V at 2A). The MCU is on a 7805CT voltage regulator, while M1 pulls directly from the power supply. The power supply is a Philmore Multivoltage regulated power supply set to 7.5V.

Unfortunately, once M1 turns on, it won't turn off, even with the pulldown resistor at R2. Once it's turned on, it goes full power and nothing short of pulling the gate wire out or shutting off the power will stop it. On my multimeter it shows that the data pin doesn't go logic low after M1 turns on. I think the motor is interfering with the MCU when it turns on.

What can I do to make sure that the motor turns off when the MCU goes low?

(P.S. Note that the above behavior does NOT occur while the MCU is plugged into my computer. The code is written in Micropython and I originally tested it while the MCU was plugged in and the code run through the webREPL. The circuit works exactly as intended while plugged in USB. A test with my multimeter also showed that the logic low voltage was lower while plugged into my computer (0.055V) vs when it's running off the power supply through the MCU's voltage regulator (0.885V).

EDIT: While on the Philmore power supply, once the motor is turned on, the ESP8266 stays at logic high 3.3V even though it is programmed to go low after 0.5 seconds, as measured by multimeter at the output for pin 4 between the resistor and the MOSFET driver. This behavior does NOT occur while the ESP8266 is connected to my PC by USB cable.


texts: Basic operation of a bipolar junction transistor

texts:
I've tried really hard to understand the basic operational principle of a transistor. I've referred to many books and been to forums but have never got a convincing answer.

Here are the things I want to understand:

A transistor is similar to a reverse biased diode unless a voltage is applied to the Base.  Since the Emitter-Base junction is forward-biased, there will be conduction of - say - electrons (npn). What happens then? Is it true that these electrons from the Base break the barrier of the Collector-Base junction and then the combined current passes to the Emitter? (IB + IC = IE)

And why is that we are getting more current? Where is amplification? It can't be like creating something out of nothing. I know I'm missing some crucial point here. Can somebody explain me clearly in simple terms?

It has been a week I'm tryin to understand this. :(


texts:
I am an absolute beginner to PIC microcontrollers. I am using PICKit3 to program a PIC18F4550 and MPLABX-IDE / MPLAB IPE version 5.20.
The problem I'm not able to solve is that the connection to pickit3 always fails and I don't know why. I looked at countless similar questions but none could solve the problem. Here are the complete details:
PICKit3 Programmer
PIC ICD2 PICKit2 PICKIT3 Universal Programming Adapter Programmer Board
MPLAB-X IDE / MPLAB IPE v5.20
OS: Ubuntu 16.04
The first problem I was getting was that my USB port was supplying 4.750000 volts instead of the required 5V. So I used an Arduino as an external power source.
Connection diagram:

And the MPLAB IPE Screen:


texts: VHDL: couldn't implement registers for assignments on this clock edge

texts:
I'm getting the following errors:
Error (10822): HDL error at pwm.vhd(15): couldn't implement registers for assignments on this clock edge
Error (10822): HDL error at pwm.vhd(18): couldn't implement registers for assignments on this clock edge

Obviously the problem is the two rising edges that both change 'output'. How could I fix this problem?
code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
entity PWM is
port(
button1, button2 : in STD_LOGIC;
output : inout STD_LOGIC_VECTOR(7 downto 0) := "00000000"
);
end PWM;
architecture behavioral of PWM is
begin
process(button1, button2)
begin
if rising_edge(button1) then
    output <= output + 1;
end if;
if rising_edge(button2) then
    output <= output - 1;
end if;
end process;
end behavioral;


texts: Is there a difference between measuring the resistance using a multimeter ohm function and using the voltage / current relation?

texts:
I need to measure the electrical resistivity of a concrete sample following the procedure described in ASTM C-1760.

The procedure requires a 60V DC potential to be applied across the concrete sample (cylinder with 10cm diameter and 10cm length) and the current measured to obtain the bulk resistivity of the sample.

The problem is that I don't have a power supply capable of delivering 60V.

I was wondering if a regular multimeter can produce the same result using the ohm function. The expected sample resistivity should range 50 - 500 Ohm.m


texts: How to choose the right MOSFET for this circuit

texts: I am very new to EE and have a question. In this circuit, below a MOSFET is used. Based on the schematic, how would I know how to choose the right equivalent MOSFET?


texts: How to route a specific resistance differential pair?

texts:
I've done a few basic boards and I've decided to try my hand at a basic Raspberry Pi Compute Module board. From the Compute Module Datasheet/Design Guide:

  The USB port (Pins USB DP and USB DM) must be routed as 90 ohm differential PCB traces

Similar notes exist for other devices but USB is the one I'm most interested in. I understand how routing a matched impedance differential pair works but I've never encountered the need for a specific resistance value for the traces. So my question is...

Considering there is a relatively short distance between the pin and the USB transceiver chip, how do I design for a specific resistance? Is it acceptable to add a resistor in line with the PCB trace to tune this, or must it be done in copper? Is the impedance value supposed to be derived solely by adjusting the trace width/length?


texts: I have a HJR-4102E-L-05 relay that is has a contact rating of 3A/120VAC. I was curious if it would be able to switch a 100 watt 120VAC lamp. I know that the relay is rated to 360 watts. My concern is that the voltage is at the 120VAC rating and the 'C' terminal on the relay will be connected to my brand new Arduino.


texts: How to have 256 bit input for micro-controllers like Arduino?

texts:
I want to read 256 digital input, each of which is driven by a switch. I don't need to read state of all 256 switches more than 5 times a second (or may be even less). Multiple switches can be ON and OFF at any point in time. Obviously that's too much of wiring if I want to do it naively. So I want to do it as simply as possible without using loads of components or wires. My first thought is to have have 16X16 matrix with diodes. But that's too many diodes to add on to breadboard. So essentially I'm looking for some chip that will have 16+16 input pins that I can use it to feed in rows and columns of the matrix. That chip then will have (may be) 8 output pins that I can read somehow 16 times in succession to get all of 256 bits.

Questions I have...

Does this kind of chip exists?
Is this the best, cheapest and least messiest way to do it?
Can it be done without chip with something like Arduno Mega that already have 56 bit input? I do want to reduce component count.
Should I be using may be combination of chips which does only 8 rows and columns?

If you have any pointer to tutorial/guide to implement this, that had be great as well!


texts: Overvoltage protection when going from 24V AC to 3.3V DC

texts:
I'm trying to wrap my head around transient voltage protection and how to implement it when also trying to rectify a AC source to DC then step it down to 3.3V for a microcontroller. I understand that MOVs are great for high voltage and AC, where as Zener diodes are good for low power DC overvoltage protection.
My problem is that I have an 24V AC source which tends to be rather noisy and can spike due to solenoids and motors sharing the same rail. This is unfortunately out of my control. Obviously, surge protection is required, but how to implement it escapes me. I haven't been able to measure how high these surges get but I assume they are higher then the 40V max of the LM2596.
My current thinking, as illustrated by the diagram, is to take the 24V AC in then have a MOV to take any major spikes out. Once this is done then rectify the AC current to DC and have a second transient voltage suppressor in the form of a Zener diode. This diode has a reverse voltage of 39V which is lower then the max input of the LM2596 which is 40V. I have read that I might need to add a resistor to this Zener to reduce the load, but what load would be on the diode in a surge event? I know my max load on the 3.3V side of the regulator is 1A, however nominally around 400mA.
My real question is then, is my thinking correct or have I miss understood how to protect the circuit? If so, what do I need to look at/change to achieve my goal?


texts: Why do linear differential equations governing a circuit mean that each circuit element has same angular frequency?

texts:
I was seeing this video from khan academy about linear circuit systems(linear system with a single input), at  3:24  Willy McAllister says that if it is a linear circuit, then we can assume all components have the same 'omega'. I don't get why this is true and some searching on SE led me to this post. In the answer by jramsay, it is said that it is because linear system corresponds to a linear differential equation with the following relation between input x(t) and output y(t):
$$
a_0 + a_1(t)y(t) + a_2(t)\frac{dy(t)}{dt}+a_3(t)\frac{d^2y(t)}{dt^2} + ... = b_0 + b_1(t)x(t) + b_2(t)\frac{dx(t)}{dt}+b_3(t)\frac{d^2x(t)}{dt^2} + ...
$$
They state that if \$x(t)=\sin(\omega t)\$ then RHS can only contain sine and cosine term to first power, and then he says that this implies LHS must contain similar terms with the same frequency. The premise is intuitive for me but I don't get how the conclusion follows (The statements on LHS)
Tl;dr: I want to understand why linear differential equations governing a circuit imply each component has the same frequency.
Edit: I found this link helpful see pg-6 and 7


texts: Termination resistors using bipolar transistors for RS-485?

texts:
I am planning to use RS-485 on a network and I do not have too much experience on the standard but I understand that termination resistance must be provided for considerable lengths and transmission speeds. For CAT5e the impedance matching value is typically 120 ohms. If the impedance varies depending on the cable length, then:

Does the impedance matching resistor's value needs to be adjusted depending on the length of wire/speed of transmission, or can this be "activated" as a fixed value (120 ohms) whenever the length of cable increases or the user desires to increase the transmission speed?

Is it possible to provide electronic activation of the IM resistor using bipolar transistors? I have in mind something like this:

As the activation of the transistor may depend on how the polarity is present at the A/B lines of the RS-485, I figure it could be possible to activate a set of resistors via transistors managed by a microcontroller GPIO. Is this correct? if not, can you share a specific circuit arrangement for this?

If the resistance needs to be controlled dynamically (i.e. depending on length, wire type CAT5e = 120 ohms and CAT6 typically 100 ohms) then depending on a command, I figure I can program the 100 ohm IM resistor set or the 120 ohm set if I can use a controllable termination.
I am planning on using MAX3081 with low bias for communications. The recommendation on their diagrams is to use terminators across A/B lines, not from signal to ground (in case someone asks).

Let me know your thoughts/recommendations on this.


texts: Kirchhoff's Current Law at the ground node?

texts:
Can one do KCL at the ground node? Does any current go into the ground?

I think not, but I am not sure.

Bonus Question:

If yes, then how does grounding buildings drain the current into the Earth?


texts:
I am trying to identify an IC that can sit in proximity to an appliance power cord (120VAC) and simply detect if current is flowing or not. On-off output is fine; no need to actually measure the current flow.

I thought this would be a trivial exercise, but it seems not so simple. I have seen a number of examples using Arduino, or similar, but this seems like overkill for this application.

Can someone please point me in the right direction for a simple non-contact integrated circuit that outputs on/off, depending on AC current flow in a nearby conductor?

I have been looking at current sensors, like ACS712). But these seem to need current flowing through, rather than just proximity.

So then I looked at standard Hall effect sensors. I thought a unipolar version would provide an output signal proportional to average current, which should work in my application. But reading the spec sheet on US5881 seems to indicate the output depends on polarity of the field. I think this will fluctuate constantly for AC, rather than giving an average current value output.


texts: Best Option for converting & processing multiple analog data lines

texts: I am looking for a good Microcontroller (or DSP or other device if they are more applicable) option that has a reasonably large amount of analog input data lines (preferably > 10 analog input lines) and an on-chip ADC.  The clock speed shoudl probably also be equal to or greater than 1 MHz.  Any suggestions?


texts: How do you test SMD ICs that are not soldered to a PCB?

texts:
To be more specific, let's say I have SOP16 SMD chips that have been purchased from overseas.  I have several PCBs that they need to be soldered to, but I don't want to risk paying for assembly and also wasting a PCB if the chip (for whatever reason, pretend that I am overly paranoid) is faulty.

I have seen those SMD test clips, but they look like they are intended to attach to a chip that's already soldered in.  I want to use something like that, but also something that prevents damage to the leads.  I can think of a custom solution, like a jig that holds the ICs in place and allows me to clip onto their leads, but was hoping for something OTS.

Can anyone here please provide me with some suggestions?


texts: Voltage jump in time series data acquisition

texts:
This might be a basic question, but I am a Mechanical Engineer and hence stumped. I am acquiring (output) time series data from Strain gauge (excited by amplifiers). Attached plot is the output (ADC voltage time series) recorded by my data acquisition hardware/software (X-time, Y-voltage). I don't understand the source of these jumps. I installed an APC to eliminate the irregular power supply, but it did not help.
I can provide more details about the setup if required.


texts:
I am having troubles with some push buttons, such that some of them work, some of them sometimes works, and some of them just do not work.

In an attempt to find the cause of the issue, I took one of the faulty buttons apart to see if anything had broken internally. I found nothing to be broken, but was surprised at the mechanism used to make the contact when pressed and it did not strike me as the best way to make to contact so wondered what other mechanisms were about. Alas, my searching on the interweb has not prevailed with an answer, probably because of my incorrect terminology.

The type I currently have, looks like this button and mechanism:

So, as the button is depressed, it bends the 'dome' of metal to make contact between the two pins. So, to me, this doesn't seem the most reliable method, what are the other options for the internal mechanism of a push to make button?


texts:
I'm building an analog audio VU meter just for fun (no microcontroller). I already have the basic functionality of the circuit working. However, I would like the LEDs that I'm using to have a sharp, almost digital turn on.

I know how I could accomplish this using a comparator. Since I'm going to be using a lot of LEDs, I was trying to think of alternate ways of turning the LEDs all the way when a specific threshold voltage has been reached and completely off when it hasn't.

Anyone out there have any clever ways of doing this, maybe using zeners and/or some cheap BJTs? I can include a quick schematic of what I currently have, but it really isn't too important to the brunt of the question.


texts: Is there a limit to the number of inputs that can be summed with an op-amp summing circuit?

texts:
I'm interested in the limits you encounter if you try to add many inputs into an op amp summing circuit. I've read that the inverting configuration is more natural for adding many inputs since the gain for an input is just determined by the feedback resistor and the resistor on that particular branch. Is there a maximum number of inputs you can get away with?

This answer maximun number of inputs on a opamp adder circuit (dealing with a non-inverting amplifier) says that noise is a limiting factor as you add each input. I guess I would assume that the noise would add in quadrature so that the noise would go as sqrt(N) for N inputs. Is this right - and are there any other factors that would limit you from adding inputs indefinitely? Thanks!


texts: Voltage Fluctuations in Arduino-opamp-thermistor circuit

texts:
I'm working on a board that takes measurements of voltage off a thermistor through an Arduino and amplified by an opamp (really an instrumentation amp AD623), also there are two potentiometers. See schematic below:

I've been receiving some very strange voltage fluctuations that I can't seem to isolate to any particular component. I've tested both the voltage source and the thermistor independently of the circuit and they are both stable.

Below is a graph

..and on the bottom of the pic you can see the fluctuations over time with no change implemented in the system. At times they look almost oscillatory, but then stabilize at a random voltage before jumping around again. example, would go from 0.01-0.06 volts, jump around 0.3-0.4 volts, and occasionally go as high as 1-2 volts (With no change to the thermistor!)

I was wondering if anyone had any ideas for what is causing the noise/fluctuations. Also, I've heard of a floating ground (not sure what that is), and I was wondering if that was an issue here.


texts: What are the UART voltage levels for the RN4020?

texts: I've recently bought an RN4020 BLE module, but I'm having figuring out how to make it work. In the datasheet some pins are listed as 1.65V input, 1.35V out, while for the rest of them, there's no indication whatsoever. How can I figure out what voltage levels the pins specifically the TX, RX, WAKE_SW and WAKE_HW use?


texts:
I'm in the midst of prototyping my circuit. However during testing, the psu led light keep flickering and there was no output observed. Subsequent investigation revealed that the mosfet have actually short circuited. I have short circuited 3 pieces of mosfet so far. Please refer to the image for reference.

You might be wondering why I did not implement an ac/dc flyback. The area that I live in do not have customable flyback transformer and the epcos tdk was the best I could find. Is there any advice on how to modify my circuit.
I am using an Arduino max to act as my pwm which output less than 5v. I have not connected any sorts of load as I would like to observe the no load voltage first.

Thanks in advance.


texts: Finding the overall transfer function and plotting root locus of a digital control system

texts:
I have started to learn about digital control theory and struggling with a particular diagram of a digital control system. The system is presented below:

\$D(z)\$ is a digital compensator, \$G_{h0}\$ is a zero order hold circuit with adjustable gain \$k_2\$. The blocks \$G_{p1}\$ and \$G_{p2}\$ are part of the DC motor model. The sampling time is \$0.1\$s.

Given the motor parameters, \$G_{p1}\$ is found to be:

$$ G_{p1}(s) = \frac{K_t}{JLs^2 + (JR+bL)s +bR + K_e K_t} $$

and \$G_{p2}\$:

$$G_{p2}(s) = \frac{1}{s} $$

The motor parameters are:

% DC motor constants
J=0.01; % Rotor momentum of inertia
b=0.01; % viscous friction
kt=0.01; % torque constant
ke=0.01; % electromotive force constant
k2 = 1; % ZOH gain
R=1;    % rotor resistance
L=0.5;  % inductor resistance
T = 0.1; % sampling time
s = tf('s');
z = tf('z');

Step 1: Open Loop subsystem \$k_2 * G_ho * G_p1\$

num=kt*k2;
den=[J*L J*R+b*L b*R+ke*kt];
ol_cont=tf(num,den);

ol_discrete = c2d(ol_cont,0.1)

ol_discrete =

  0.009056 z + 0.008194
  ----------------------
  z^2 - 1.723 z + 0.7408

Step 2: Closed Loop subsystem

cl_discrete = feedback(ol_discrete,-1)

cl_discrete =

  0.009056 z + 0.008194
  ----------------------
  z^2 - 1.732 z + 0.7326

Step 3: Overall Open Loop Excluding compensator

overall_ol_discrete = cl_discrete*(z/(z-1))

overall_ol_discrete =

      0.009056 z^2 + 0.008194 z
  ----------------------------------
  z^3 - 2.732 z^2 + 2.465 z - 0.7326

overall_ol_discrete_zpk =

    0.0090558 z (z+0.9048)
  ---------------------------
  (z-1) (z-0.9994) (z-0.7331)

Step 4: Overall Closed Loop

overall_cl_discrete = feedback(overall_ol_discrete,-1)
overall_cl_discrete =

      0.009056 z^2 + 0.008194 z
  ----------------------------------
  z^3 - 2.742 z^2 + 2.457 z - 0.7326

I am then asked to design a compensator that ensures system dynamic behavior defined by the dynamic ratio of gzita = 0.7 and \$ w_n = 3rad/s\$.

If I use overall_ol_discrete found above, this is not possible via Matlab ControlSystemDesigner. Since Matlab fails to solve for this compensator, it means that either (1) the design paramaters are incorrect or more likely, (2) the plant I have found as described above is incorrect.

Therefore, is the working above to achieve the overall closed loop transfer function correct?

Any suggestions would be appreciated.

As per the suggesion below.

rlocus(overall_ol_discrete* D_z)

This is the closest I have managed to come unfortunately, I cannot find a compensator to get to the required specs.

Step response:


texts: Should I drive control lines of an IC at voltages higher than VCC

texts:
I am designing a circuit that will be running from a single cell LiPo battery. The battery will provide the input voltage to a boost converter that will output 5V, which will power a microcontroller.

There are some control pins on the boost converter, such as PS, which enables power saving mode, as such I would like to be able to set PS high or low using my microcontroller, however, the micro will be providing 5v, and the boost converter is only running on the power supplied by the LiPo cell (~3.7v).

Does the voltage on PS need to be <= the voltage powering the boost converter, or can I safely push 5v into it without need needing to add a voltage level converter?


texts: Single-ended analog signal to differential

texts:
I need to transmit 2 analog signals over a cable in a noisy environment.
How to transmit them as differential ?
Given that :

Each signal can be used to inject and receive current (< 130 kHz, < 100 uA, bidirectional)
Each signal can be used to measure potential difference
My system works at 3 VDC

The main problem being : I need the transmission to be bidirectionnal.
What component or circuitry should I use ? I am a beginner at analog signals transmission...
Thanks


texts: VHDL structural vs Behavioural implementation vs data flow

texts:
I was wondering what would be the benefits of structural vs behavioural vs data flow implementation of a code. I know behavioural is easy since its close to C++ and it doesn't have hardware concerns, data flow is good because we see how the data is flows in the hardware. The structural is in terms of logic gates and thus is very good for area and time optimization.
Can someone provide more information on that topic. Thanks,


texts:
We use a 1650 mAh capacity LiPo battery.

It has a 2.5volt undercurrent protection cutoff set.
Our device uses a CONSTANT 5mA of draw UNTIL the battery
drops down to 3.2V, at which time the system cuts its power draw in half.

Can someone help me write a FORMULA for calculating how many TOTAL hours of run time
our device has?

Formula is what I'm looking for here because I want to create a
spreadsheet from this formula so that we can use it to predict
run times with different capacity batteries and different draw currents.

Thanks!


texts: Powering SN75176 for RS485/UART communications over long distances

texts:
I have an application where a master/transmitter system communicates with a slave/receiver subsystem over an arbitrary distance. The two systems each consists of a microcontroller and some analog and digital circuitry. For communications between the two systems, a UART signal from the transmitter system is sent to a SN75176 differential bus transceiver to convert the UART signal to RS485. Similarly, on the receiver side, the RS485 signal is converted back to UART by another SN75176 for the receiver system's microcontroller to receive data/instructions from the transmitter system. A CAT-5e cable is used for this communication.

A particular requirement for the design is that the two systems are powered from completely separate power sources. Thus, the two systems' power interfaces may have nothing in common with one another (not even a shared ground). A proposed solution for this is to power both SN75176 ICs from the transmitter system's power supply and to optically isolate the final UART output at the receiver side. One of the wires in the CAT-5e cable can be used as a power supply line and another as the ground line for powering the receiver side's SN75176 IC. The idea is that the communications can be made to work while having two independent/isolated power supplies for the two systems. The following two circuit diagrams illustrate the setup.

For the transmitter system:

For the receiver system:

From the SN75176's datasheet, the supply voltage must be between 4.75 V and 7 V (with 5-5.25 V being the ideal choice). Wikipedia indicates that CAT-5e cable has a resistance of 0.188 ohm/meter. If it is assumed that a max of 200 mA of current can flow in the cable (for the RS485 comms, receiver SN75176 power and optical isolation), then the voltage drop per meter of cable is:

$$
V_{drop} = I * R = (0.2 A)*(0.188 ohm) = 0.0376 [V/m].
$$

For a cable length of 80 m, the voltage drop is thus:
$$
V_{drop} = (80 m)*(0.0376 V/m) = 3.008 V
$$

If VCC in the transmitter circuit diagram is 12 V, then the power supply to the receiver SN75176 via the CAT-5e cable would be \$12 V - 3 V = 9 V\$, which would still be fine for the voltage regulator to regulate down to the suitable voltage level for the receiver SN75176 IC. By using the potentiometer (R25 in the receiver circuit), the output voltage of the regulator can be tuned to the desired supply voltage for the receiver SN75176 IC. The reason for using the voltage regulator, and not just a direct 5 V connection from the transmitter side to the receiver side's SN75176 power supply, is that the losses over the cable would drop the receiver side's SN75176 supply voltage to below the specified minimum. Conversely, a direct 12 V connection would provide a supply voltage that is too high.

The following questions now arise:

Should the distance/length of the cable be much longer, the input voltage to the voltage regulator could drop to below the drop-out voltage of the regulator (due to losses over the long cable), rendering it unusable for supplying power to the receiver SN75176 IC. Could a higher input voltage (higher than 12 V as indicated in the schematic) solve this problem?
Would the concept of optically isolating the UART RX signal at the receiver side be feasible?
Is the concept of using the voltage regulator feasible?
Would this setup work in the first place?

Is there any other method that would be better to use than the prescribed method?


texts: How to sense the two magnet attracting each other

texts:
I have a cube that has four side sticked with magnet sheet and I have other boxes like this and I want to know how could I sense each time a cube is connected to to another and other and other
I have read about magnetometer but I am not sure if it works with this situation


texts: Bootstrapped Transimpedance Amplifier (TIA) - High Frequency Instability

texts:
I have constructed transimpedance amplifier in the hopes to achieve both high-gain (5kΩ) and high-bandwidth (50MHz) performance using the FGA21 photodiode, the OPA657 Op-Amp and the 2N2369 Transistor. Key specifications include:

Gain Bandwidth Product: GBW = 1.6GHz
Photodiode Capacitance: Cd > 100pF

To extend the amplifier bandwidth I have implemented the bootstrap architecture, as illustrated in the figure below:

Here the photodiode is replaced by the equivalent circuit. This circuit has been constructed and to confirm stable operation a voltage noise measurement was recorded:

This shows a bright noise feature at 50MHz which is problematic as it is near the frequency band of interest for our application. To explore this behaviour further the detector output was measured on an oscilliscope and a clean +120mV DC output was observed, which is consistent with the base current provided by the transistor. When the photodiode is illuminated the output starts decreasing as expected from an inverting amplifier, however, as it approaches 0V the output begins oscillating dramatically (+-500mV amplitude) at the resonance frequency of 50MHz. Suggesting this resonance feature is being excited.

My only explanations are the following:

The 2N2369 transistor is not fast enough to ensure stability at 50MHz
And/or when the photodiode is illuminated the photodiode current counteracts the base current and switches the transistor off when it reaches an appropriate level, reducing the gain at 50MHz even further and causing dramatic oscillations.

However, I am not convinced about either of these answers as the SPICE model of this circuit does not predict resonances at these frequencies. Any ideas on the cause of/ solution to these problems would be greatly appreciated.

(EDIT: Please find the board layout below for reference)


texts: Can I extrapolate the rated overload spec of a wirewound resistor to a joule rating?

texts:
I'm considering using a Vishay FVT series resistor for precharging some capacitors.

Capacitance: 3300uF
Voltage: 730V
Resistance: 500 ohms
Resistor continuous wattage: 25W

This series, like many wirewound resistors I've seen, have a spec'd overload rating of 10x for five seconds. So my 25W resistor can handle 250W for five seconds, or 1250 joules.

In my precharge configuration, the peak power dissipation in the resistor will be 1080 watts, 43x the continuous rating. Obviously the resistor can't survive that indefinitely, but the power dissipation will decay exponentially. My reasoning is that if the total energy dissipated in the resistor is under 1250 joules, it should be safe.

The total energy dissipated in the resistor is the same as the total energy stored in the caps, giving me ~880 joules, less than my 1250-joule limit. Is my analysis valid? Should my resistor be safe? Or will the high instantaneous peak power break something even though I'm within my computed joule limit?


texts: Is there an IC that works like the PL2303 for TTL TO USB?

texts:
Is there an IC that works like the PL2303 for TTL TO USB and can connect to android device with driver?
I have search a lot but I did not find such a thing.


texts: Why does the position of the resistor matter here? (Arduino)

texts:
I made a small circuit that when someone push a button a servo rotates to 90° and go back to his initial position after a certain amount of time.
My issue was with the resistor. I needed it to be in a particular position for my small project to work, which confuses me because in the small inner circuit (ground → resistor → input pin → button → source) I thought it was a good idea to get rid of what seem at first a useless cable, so I removed the cable that connects the button to the source and placed the resistor. I connected the input pin directly to the button, but it did not work as I expected.
To make things clearer, I made a picture of the circuit in a different shape.

I learned that in a circuit the position of the resistor has no impact (Ohm's law).
Why is it like this?
PS: The picture of my Arduino breadboard.


texts: How to determine proper stepper polarity?

texts:
In one of the answers to this question, it is stated that wiring one of the coils on a bipolar stepper backwards can cause the motor to step improperly, or not at all. I've salvaged several steppers from discarded electronics (printers, scanners, typewriters), and I'm curious, is there a better method than trial and error for determining the proper polarity of the coils?

If I reverse both coils, does the motor simply run in reverse?


texts:
I come from mechanical engineering background and have little hands-on experience with Arduino and electronics.
I would like to connect a pressure sensor SX01DN with Arduino for reading the values.
But as the datasheet mentions, output voltage in FS is 20mV, therefore an OP-amp is needed.
There is a circuit on pg 7 but to me, it's complicated to understand.

I will very much appriciate if anyone can assist me in this project and also help me understand this amplifier circuit (or suggest a simpler version).

Thanks,

Z


texts:
Important note: You are not helping me do my homework. This is for a competition for engineering students, that encourages you to "use your network" ;)

I've got this pattern for a frequency divider that divides the clock by 5. It's supposed to have one major problem, but I can't seem to figure out exactly what it is.

The options I have to fix this problem is:

X==(000|001|100), Y==(001)
X==(000|001|010|011), Y==(010|011)
X==(001|010|011), Y==(000)
Both a) and c) are correct!

I've taken the time to map out the signals in the original design and in option number 3, as I thought that was the answer.

I've shifted the clock one half clock cycle, whoops. Shouldn't change anything though.
The rest is done by hand.

Does anyone here have any good suggestions?


texts: State based vs State-less design (in verilog)

texts:
Recently, I have been carrying out some beginner to lower moderate level designs, from starting to all the way to HDL coding in verilog. I thought that FSM based design, either Mealy or Moore is the only option. However, while actually translating the design in verilog HDL, I had lots of trouble. Many times, the design would just not work the way it should because of timing related problems. Plus it took good amount of typing efforts as well.

Contrary to this approach, it took me quite less time and effort following a state-less approach for same designs, and , produced results. But maybe this could be because my designs are not too big at this stage.

So how do you decide whether to use a state based FSM model or stateless model in design ?

Is there some pattern while following any approach ? Or maybe some specific group of problems which should be solved only by state based approach ?

By state-less design, I mean creating / connecting already designed modules, alongwith some more new logic. Not quite structural modelling, combination of structural and behavioural modelling you can say.

I'm not asking about pros and cons of Mealy vs Moore.

Thank you


texts: Why does voltage drop across a resistor?

texts: I don't get why there would be a voltage across a resistor as that would mean electrons pile up on 1 side of the resistor and as far as I know, that's not the case. My assumption is that voltage is dropping all over the circuit and the resistor just happened to be between a potential difference in the circuit. Someone please explain me!


texts: ULN2003 based stepper driver not driving 28BYJ-48, and nothing coming up on the indicator lights

texts:
I recently received five of the ULN2003/28BYJ combos, as described on the below link:
http://www.4tronix.co.uk/arduino/Stepper-Motors.php

I am powering the stepper controller with a 5v supply from the YwRobot breadboard power supply, which in turn is powered by a 12v wall wart. I have tried to use both the breadboard output pins and the 5v jumpers directly on the YwRobot PSU.

I am using an Arduino Nano to run the controller, and I am using digital pins 8,9,10 and 11, which are connected to cables IN1, IN2, IN3 and IN4 respectively.

Pretty much everything is stock standard as described on the 4tronix site, I am even just running their sample code, and have nothing else fancy going on.

I am not seeing any LEDs come up on the driver controller, and the motor does not turn. I have tried three of the units, and double and triple checked my wiring, but it seems for all intents and purposes that the controllers are just not getting any input.

I have tested the Arduino ports with LEDs and temperature sensors, and tested another Nano as well, to no avail.

How can I best trouble shoot the controller, or else figure out how to get these to work?


texts: Comparison of energy storage density of inductive and capacitive systems

texts:
In the paper A Review of Short Pulse Generator Technology by John Mankowski (IEEE Transactions on Plasma Science, Vol. 28, No. 1, 2000, pp 102-108) I found that "energy density of inductive storage systems is two orders of magnitude greater than that of capacitive systems". The author first showed equations for energy density:

Then he claimed to choose "reasonable" parameters:

Could anyone please explain why these parameters are reasonable. Is this really a valid comparison?


texts: How to calculate the dead time to incorporate in the complementay PWM input to an H-Bridge designed using MOSFETs?

texts:
I am working on making an autonomous robot. Right now,  I am involved in designing an H-Bridge using discrete components for my robot. I am almost done with the H-Bridge design, and want to test it now. However, I am not being able to decide a dead time for the input complementary PWM I will provide as an input to the H-Bridge. I know that to prevent overshoot, you have to delay the turn-on of the low-side FET by at least as much as the turn-off time of the high-side FET. The same goes of course for the other transition, when you switch from low-side to the high-side.

I have searched about finding the dead time online and I haven't found any useful information. The information I found was for H-Bridges who have gate driver circuitry designed discretely, and use formulas to find the actual turn on and turn off times of the MOSFET. Whereas, I am using IR2112 to drive the MOSFETs (IRFZ44N in my case).

I am attaching the schematic of my H-Bridge circuit. Please view it and tell me how should I calculate the dead time. I do know the turn on/off delays of both the gate driver IC and the MOSFET. Should I add the turn off delay of both these to get my dead time?


texts: Can any one say which Schematic Software is used for this Circuit diagram

texts: Can any one say which Schematic Software is used for this circuit diagram. I know Eagle and Pspice


texts: 555 ticks at different frequency than calculated

texts:
I'm trying to get a 250kHz signal with 58% duty cycle from an NE555, i'm using values calculated by an online calculator but the circuit clocks at 168kHz when viewed in an oscilloscope.
I'm feeding the circuit with a 9v battery. Am i doing something wrong?

simulate this circuit – Schematic created using CircuitLab


texts: Question regarding the LM7810 voltage regulator

texts: Is there a simple way I can hook up this regulator to reduce the maximum output current from the 1A rating down to a 500mA maximum output without affecting the 10vdc output?


texts: What is the crystal range for a dsPIC30F5016 to get max MIPS?

texts:
I'm slightly confused on what my xtal limit is.

I'm looking at a dsPIC30F5016 and it says that it can go up to 30MIPS and with an oscillator input between 4Mhz-10Mhz with PLL active (4x,8x and 16x)

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en024210#1

But looking at Section 7: Oscillator of the Ref Man 1 (pg 7-11), it shows that I can go up to 25Mhz in HS mode.

http://ww1.microchip.com/downloads/en/DeviceDoc/70054e.pdf

Can I use a 15Mhz xtal ( with a HS/2 and w/PLL 16x) to give me 120Mhz or am I limited to 7.37Mhz w/ PLL 16x to give me 118Mhz?

If I can use the 15Mhz, is there an advantage or disadvantage to using the freq divder or /2 or /3 ?

Thanks!


texts: is a hardware registar the same as a processor registar?

texts: I have tried searching for the difference between these two terms but everything i find gives ambiguous results. can anyone explain to me what is the difference between a harware registar and a processor registar, if there is any?


texts: Why does the condition -(t_setup)<t_hold has to stand

texts: I was given this inequality in logical circuits class and I can't figure out the reason behind it, and how can t_hold be negative. Is the condition relevant when t_hold is positive?


texts: Calculating LCD display horizontal and vertical porch values

texts:
How should I set the porch and sync values given an LCD display?

For example, say my FHD (1920x1080) display datasheet says its has a total vertical cycle of 1125. I have 45 clocks remaining (subtract 1080 clocks of visible period). Can I rather randomly set the front porch, back porch and the sync to 20, 20, and 5 respectively?


texts:
I am an Electrical Engineering student.
I'm in my final year and doing a thesis about soft switching.

I am trying to grasp the calculation of diode switching losses. I'm having the impression that only the turn-off losses are calculated (which are related to the reverse recovery charge of the diode). In a book I have, Power Electronics from Mohan, Undeland and Robbins they show the voltage waveforms of power diodes (page 535 if you are interested, I don't succeed in uploading a picture). You can clearly see that at turn-on, an overshoot of the voltage occurs. During this phase, the current already builds up. How is this turn-on loss calculated? I can't really find it in diode datasheets where they only mention the parameters to calculate the reverse recovery losses.

So could anyone explain me how the turn-on losses can be calculated from the diode datasheet?

If it is negligible, could anyone explain me why?


texts:
Consider the following (incomplete) instruction schedule for a MIPS pipeline where loads and stores take three cycles:

               0 1 2 3 4 5 6
...
ADDI R1,R1,#1  F D E M W
SUB R4,R3,R2     F D E M W
SW  R1,0(R3)       F D E M W
...

This is part of a solution to homework problem where we were told that there is only forwarding hardware for ex->ex and mem->ex.

My question is: how does the SW get the correct value for R1? It clearly depends upon the result of the ADDI. But when SW attempts to read R1 from the register file, ADDI has not yet  written the result to the register file.

I think this is a fundamental misunderstanding of mine in regards to pipeline registers and forwarding. My guess is that the ADDI could forward the value of R1 via mem->ex forwarding to SW, and it would "hang around", being pushed forward through the pipeline registers until it is needed in the mem stage. But every description I have seen of forwarding to the ex stage involves pushing the result into the ALU, which would be useless here.


texts: Experimental loss measurement of simple wireless link

texts:
I connect a simple SDR to a spectrum analyzer (SA) and measure the output power. The SDR outputs a single tone at 1 GHz; between SDR and SA is a lowpass filter:

With gain setting GTX1 I measure -53.2dBm. With GTX2, -7.2dBm and with GTX3 I measure 12.8dBm.

Now I add a wireless link:

The two antennas are directional antennas with 10dBi gain (these: https://www.amazon.ca/APOHALO-800-2500MHz-Mobile-signal-antenna/dp/B07C91TFWP). They are placed exactly 1.2m apart, have full line-of-sight and are mounted on a tripod (Fresnel zone is clear).
I measure again the signal powers for the same three gain settings on the SDR GTX1, GTX2 and GTX3 and measure: -80.2dBm, -32.2dBm, -14.2dBm.

The difference in gain between these two setups is 27dB, 25dB and 27dB, respectively. So adding the 1.2m wireless link in between gives me 25-27dB measured attenuation.

Now the path loss is 34dB (https://en.wikipedia.org/wiki/Free-space_path_loss). The two antennas have 10dBi gain each, so I would expect a total loss of only 34-10-10=14dB.

This is more than 10dB difference from what I measure.

What could the discrepancy come from?

(I am aware that the antennas themselves have losses but to my understanding they are factored into the gain: Gain=efficiency x directivity). And 13dB would be pretty large).


texts: Can someone help me to explain why LED have better response time when compare with other light source (ex:fluorescent lightbulb). Because their structure or anything else? Thanks everyone so much.


texts: Brushed DC motor braking with speed controller

texts:
I've been getting some amazing info on this site so thanks for all the info so far!

Onto my question.

I know I can brake a dc motor by shorting the terminals but I also know how much current that can generate. I need to be able to disconnect my speed controller before shorting the terminals as i'll probably cause a failure or worse, a fire!

I've attached 2 drawings...one of my current setup and one with a DPDT switch that will disconnect the motor and at the same time, short the terminals. (I think I've got the wiring right?!) My concern is that the current generated by the braking will still damage my SPDT relays that are used for polarity switching. Is there another way around this?

It's for an electric car. Motors are 12vdc pulling approx 4a no load. SPDT relays rated at 40a.


texts: How can I make an OR gate out of two sockets

texts:
I have some lights that go into the wall, that I've plugged into this smart outlet so I can control these through my phone. I want to also be able to power them through a movement activated sensor.

So it would either be a button on my phone telling it to be always on, or someone being present in the garden activating it while it's off.

Is such design possible?


texts: Good method to remove tenting on vias after assembly for debugging?

texts:
This is a question about modifying an assembled board to make it easier to debug.

In a perfect world, I would have left the bottoms of these vias un-tented. Whoops.

I have two BGA parts on a PCB, with a 32 bit wide bus with a few control lines and a clock line connecting them. Almost all of these traces are only on internal layers. There looks like a signal integrity problem on the bus.

The good news is that the board only has parts on one side, and all the vias are through-all.

Can anyone suggest good ways to remove the tenting over the vias so they could be probed with an oscilloscope, or at least be able to solder 30 gauge wire to them?

The connection needs to be pretty good – the bus runs at about 100 MHz.

There are also some traces on the bottom layer, which I need to avoid damaging.

My current ideas:

use x-acto knife to scrape off solder mask, first with a side to side scraping motion and then swivel the blade in a circular fashion.
Use fine grit sand paper and remove the solder mask from the local area (covering several other vias, and maybe a few traces)

This article has a little more information too:
http://www.edn.com/electronics-blogs/signal-integrity/4327009/Scrape-it-How-to-probe-a-microstrip-trace-with-no-accessible-test-points-or-vias

However I am hoping someone has a method that they consider a "joy to use."

I don’t want to just dive in; this prototype costs more than my car and I just have the one.


texts: Alternative Wheatstone bridge for thermistor - Interpretation needed

texts:
I have a problem understanding the following Wheatstone bridge circuit. It originates from a temperature controller, the voltage V_out is supplied to a PID regulator and hence can be seen as an error signal. V_out is zero when the thermistor resistance matches the value of the reference resistor.

I'd like to understand the purpose of the OP-AMP in the Wheatstone bridge and how I can model it on paper. Additionally, what is the (dis-)advantage to the more common way of e.g. this circuit?

Thank you!


texts: What is the effect on lithium ion batteries from long term storage in sub-freezing temperatures?

texts:
I am designing an off-grid power system for a mountain cabin that is not used in the winter.  The ambient temperature can get as low as -20deg F (-29deg C) during the winter.   Due to snow and other environmental factors the system will be totally shut down during the winter months.   I hope to use lithium ion batteries. I know I cannot charge the batteries at these temperatures, but can lithium ion batteries be totally disconnected and stored at -20deg F (-29deg C) without damage?

Note: I can set the charge level to whatever is appropriate before storage.


texts: Altium Designer: Polygon does not connect to the pads on the same Net

texts:
I'm trying to put a plane shield using polygon pour and I realized that some object is not connected to my polygon.

In the picture below it is clearly seen that the GND through hole is not connected to my polygon that is declared as "GND"

I can't understand the reason because I ckecked all possible causes and I wasn't able to find anything.

Can anyone give me a hint?

I don't know what to say. I did a program restart and everything is fine.


texts: Reactive power in single phase controlled full wave bridge rectifier

texts: How to calculate the reactive power,Q (VAR) in single phase controlled full wave bridge rectifier with only R-load? The sample observations of the experiment are given in the image. But I am wondering how does reactive power exist in case of pure resistive load!


texts:
I have an Arduino UNO board with a ATMEGA328-PU and am trying to control the LED on output 13 that is on the processor pin B5.

I have a switch connected on the Arduino port 7, which is on the processor pin D8.
This is the program I am running on the Arduino IDE like this:

    #include <util/delay.h>

   void setup() {

   DDRB = DDRB | 0xff;
   DDRD = DDRD & 0x7f;
   PORTD=PORTD | 0x80;
   }

   void loop() {
         ReadSwitch();
              }

   void ReadSwitch()
   {
    PORTB= PORTB | 0xff;
     _delay_ms(500);
     if(PIND & 0x80)
        {
        PORTB=0x00;
        }
     else
       {
        PORTB= 0xff;
        }
     _delay_ms(500);

   }

My question is: when I set the PORTB to all 0's it switches on the LED, but when I set it to all 1, it switches off the LED. How is that possible? Should not the LED switch off when the PORTB is set to 0? Is this normal or something is broken somewhere?

For a bit of background: I have been programming.NET for many years but have never written programs for the microprocessors directly. So I am really new, if this question is inappropriate for this forum, kindly re-direct me to the correct place.


texts: This PCB is from a old Sharp 1999 TV I have been reverse engineering lately; also sorry for any bad images.  I have noticed that there are some "missing" components in the holes of: D4002, D4003, D4001, D4004, and C4002.  Are there certain components that were once in those holes as part of the design?


texts: Building an 8 to 4 Encoder from a 8 to 4 Multiplexer?

texts:
I have a a 8-to-4 Multiplexer ICs (MM74hC4052N) and I want to use it as a 8-to-4 encoder or 8-to-3 encoder.

Is that possible? If it is, can drop me some hints on how to do that?

At one glance, I thought this 8-to-4 Mux works by taking inputs (in this case, 8 inputs) and using the select signal, it channels the inputs simultaneously into the 4 outputs.However, after reading the data sheet, I was getting confused. The truth table does not follow what I thought.

Practically, I have 8 switches representing 8 bits of a binary number, and I need to send a 4 bits signal to a microcontroller, representing the 8 bits binary number, using this 8-to-4 IC.

Link to datasheet : http://www.farnell.com/datasheets/89046.pdf


texts: Why do series combinations of Batteries not increase Capacity?

texts:
I've come to realize that batteries connected in series does not increase the capacity. But why is this so?

This question explains that it doesnt Adding mAh when wiring battery cells in series?,
but does not get into why this is the case.

It seems like it would have something to do with the Current not increasing over a series combination either, but why would the total useable charge not add?

For example: Why when connecting two 12V batteries of 20Ah capacity do we not have a total usable capacity of 40Ah?


texts: Controlling SMD-LEDs using a 74HC595 & NPN-transistor as switch

texts:
I want to control several SMD-LEDs (0603) 3.5V - 25mA, using a voltage source of 4V. Each LED needs a resistor of ~20 Ω to work fine, like shown in the circuit below:

simulate this circuit – Schematic created using CircuitLab
But I would like to switch and control the LEDs pairwise. So in this example LED1 & LED2 should light together and in a next step LED1, LED2, LED3 & LED4 should all light together. In my real project I have 16 LEDs in total. I got to know that the 74HC595 must not exceed 70mA, but each LED needs 25, so I need to have a separate source for all LEDs and a PNP-transistor for each state to be able to switch my LEDs using the 74HC595.

Is that correct?
Will the following circuit work? (Note: I simplified the 74HC595 in this circuit)

Please be fair, I'm a beginner in electrical engineering.
Thanks for your help!


texts: What modifications can I do in my simulation so Vg must not exceed 20V?

texts: I have implemented gate driver of Buck Converter. But when input voltage exceeds 20V then Vg also exceeds 20V wich is threshold value of transistor. What modifications should I do so that my gate voltage don't exceed 20V and circuit runs properly about 20V.


texts: Can an ATtiny with RSTDISBL programmed be reprogrammed over ISP?

texts:
The ATtiny85 datasheet, on page 152, seems pretty clear on this:

  After this fuse has been programmed device can be programmed via
  high-voltage serial mode, only.

But elsewhere, on page 28, it says:

  If the RSTDISBL fuse is programmed, this start-up time will be
  increased to 14CK + 4 ms to ensure programming mode can be entered.

Can an ATtiny be reprogrammed over ISP by entering programming mode within a short interval after powering it on? If not, why is the startup delay increased as described in the second quote?


texts: Equalization of Square Pulse in Visible Light Communication

texts: I am currently working on a VLC project to build a VLC receiver. I attached a schematic of the circuit I have designed. The circuit on the left is the transmitter sending a square signal at 1 MHz using the CREE RGB LED. I am receiving the signal at the other end using a OSRAM photo-diode and passing it through front end amplifier to amplify the received signal. Later its sent through a 1st order equalization circuit, to fix my distorted square wave signal. I amunsure whether my equalization circuit is correct since I do not see any change in the signal when I implement this circuit. I also experience a ringing (overshoot and oscillations to settle down) in the output waveform. Could you please help me understand the how I can equalize to get a better response to get a cleaner square wave and also to reduce the ringing in my circuit. Any response is much appreciated.


texts:
I have a LDR circuit here:

I'm using it to turn on a relay that is connected to an electromagnet lock. When there is light the lock unlocks and when there isn't the lock goes back to locked.

Everything works perfectly when i'm running the LDR circuit on a 9v battery and the relay and lock on a different 12v power supply running on the same ground as the 9v battery.

However I want to run everything off of the same 12v power supply and ditch the 9v battery. When I try to remove the 9v battery and run the LDR circuit off of the same 12v power supply the lock unlocks when light hits the LDR and then when the light is gone it never locks again. I have to move the pot all the way down in order to get it to lock. Any idea whats going on here?


texts: Can I requst data too quickly from an I²C ADC?

texts:
I'm getting some pretty noisy data from a 12-bit I²C ADC (MAX11617 to be precise). Though it's most likely some very sub-optimal board layout that's introducing a lot of noise to the analog signal, I'd like to rule out a one particular thing first.
When I write software for a µC there's usually some bit in some ADC control register that indicates, that the ADC is done sampling, so it's safe to go on and read the data. In this particular case, it's a TI sitara processor running Linux so the readout is done over the I²C bus by just grabbing the data off of /dev/i2c-* like so:

read(m_fd,tmpBuf,24)

Since I have very limited control over the I²C bus in this case, is it possible that I'm requesting data while the ADC is still sampling? The datasheet only says

  Once all conversions are complete, the MAX11617 release SCL, allowing
  it to be pulled high. The master can now clock the results out of the
  memory in the same order the scan conversion has been done at a clock
  rate of up to 1.7MHz.

Can I safely assume that the Linux I²C driver is taking care of this?

(I wasn't sure whether electronics.stackexchange.com or stackoverflow.com was the proper place for this question so please excuse me if I'm off-topic here.)

Any input or pointer are greatly appreciated!


texts: Choosing the values for this magnetostriction oscillator circuit

texts:
I'm working with the following magnetostriction oscillator, and I need helping to set the values for L1, C1, L2, and V (my BJT is a 2N2222) such that the length of my iron rod (labeled as ferromagnetic rod) is less than equal to 25 cm and its diameter is in a range of 3 to 6 mm.

If l is the length of the iron rod then-->

Where Y is the Young's modulus (208 x 10^9 PA from what I know) and P is the density (7860 kg/m^3)
The permeability is 6.3 *10^-3 and ideally, I'd like the magnetic field B1 created by L1 to be equal to 0.63 tesla (so that I can use a 0.1 mm thick copper wire for it.)
I'm not sure how to do the beta and alpha calculations to set the voltage and find out the collector and emitter currents, and I'm also not sure how to do the calculations for the current/voltage induced in L2.
Could someone please share a schematic for how the transistor becomes a current source when there is an EMF induced in L2? I can’t seem to understand that properly.


texts: Common-drain complementary MOSFET pair to produce zero-crossing AC PWM

texts:
My goal is to generate microcontroller-driven PWM from -10V (low) to 50V (high).

The load is 50Ohm resistive and sensitive to voltage, reverse voltage -50V (even on PWM) can cause dielectric breakdown.

Single MOSFET does not allow this. After some searching I found this diagram:

Image source: Electronics Tutorials - Complementary MOSFET Motor Controller
However I have some doubts about this configuration:

My driving MCU output is 2kHz with extremely low duty (<1us high time). So one MOSFET will work much harder than the other MOSFET.
The gate is floating At some point on rising or falling edge, both MOSFET will be on, shorting V+ and V-.

simulate this circuit – Schematic created using CircuitLab
Will something like this work ? (with deadtime) ?
Thanks in advance.


texts: Collector current decreases with the increase of base current in saturation mode of bjt

texts:
I'm new to BJT and i'm trying to understand the characteristics of bjt in different modes of it. In my book they explained that in saturation mode of bjt the collector current decreases even if i increase the base current.

but i don't understand why it should decrease. Because in the saturation mode base-collector works as a forward bias, so there should be breakdown of collector current. But instead of that collector current decreases with the increase of base current. Please help me to make my concept clear and correct.


texts: LEDs in Parallel; Which Transistor, and do I Need Resistors?

texts:
perhaps you can help out.

So, I'm making a prop replica and light is a big part of it. To this end, I picked up three cheap LED torches, which have arrays of 9 LEDs in each. Cheaper than I could buy the LEDs separately!

Firstly, to power them I was thinking I'd use a transistor to switch them on and off, as the microcontroller couldn't handle the load if it was to switch them directly. Can you recommend a transistor that'll happily switch enough current for the 27 white LEDs when I give it a low-level signal from the microcontroller?

Secondly, as I dismantle the torches I notice they don't have any resistors in series with the LEDs. The LEDs themselves are connected in parallel, and run from three batteries (providing 4.5V) and I was thinking I'd connect the three arrays also in parallel -- so 27 LEDs in parallel, effectively.

I'm using a 5V power supply for all this, and I'm thinking the extra half volt shouldn't worry the LEDs too much, right? But do I need to add any series resistors in here, given that there weren't any in the torches?

Thanks in advance for all your advice!


texts: Solution to interface SD card with microcontroller using only 2 pins (I2C/SPI)

texts:
So I am trying to add an SD card to my circuit and unfortunately, all I have left are 4 GPIOs, but I was asked to try and find a solution to only use 2. So using 4 is a worst case scenario.
I thought about bit-banging SPI so that is one solution but ideally, I want to use 2 pins only so my guess is SPI is not possible and all is left is I2C bit-banging. I considered using an I2C-SPI bridge (speed is not a problem here), but memory is written in blocks of 512 bytes whereas the bridge sends 200 bytes at a time max.
Any solutions? If a 2-pin solution is not possible, what is the best solution using 4 pins?


texts: PCB Trace Impedance Matching on microcontroller

texts:
I'm doing research for the best antenna for a 2.4 GHz connection from our device to a local router. The problem is that our device will have varying loads connected to the other pins of the micro controller.

My question is will the varying loads on other pins of a micro controller will effect the impedance matching for the antenna?

I have tried searching this with no avail. I have no experience with antennas so pardon if this is a trivial question.


texts: Connect 240v PIR motion detector to Raspberry Pi

texts:
I want to connect a 240V PIR motion detector directly to my Raspberry Pi 3.

Inside its plastic case I found 2 PCBs. One is the power supply board which has a 24VDC relay, a S9013 NPN transistor, some blue resistors, 2 small zener diodes and 1 bigger one, a big red film capacitor (CBB22/630V334J), a smaller one (CBB22/630V223J), a gray film capacitor (222/1200V), 4 1N4007 diodes, 2 electrolytic caps (220uF/35V, 100uF/25V), 1 small ceramic capacitor, 2 big gray resistors??? and 3 wires (RED, BLUE, BROWN). The other board contains the PIR sensor, a S9013 NPN transistor, a lot of blue resistors ??? , a UTC324D IC, 5 electrolytic caps (1uF/50v, 10uF/50V, 100uF/16v, 100uF/25V, 47uF/25V), 4 small ceramic capacitors, 3 zener diodes, 3 potentiometers for adjusting "SENS, TIME, LUX" and a photoresistor (which i removed for another purpose and I can't find it, but I think it works without it).

The board with the PIR sensor is connected to the power supply board with 3 wires. How i should connect these 3 wires to my Raspberry Pi 3 in order to get the PIR sensor working? Do i have to remove something from the PCB? Is it going to work on 3.3v as it is?
The UTC324D datasheet says that it can work with supply voltages between 3-32VDC so this is not a problem.

If i can't connect it to my Raspberry Pi, can you tell me how I can make this work on 12v? I have seen a tutorial about wiring an external motion detector to 12v, but the author of the article had a 4 pin board and I don't know how to wire it.

Some photos:


texts:
I've been working through a Nixie Clock schematic, to understand how the clocks function as a whole, and am stuck on how timing works for the PIC microcontroller.
The schematic can be found here: http://www.nixieuhren.de/downloads/108b-6.pdf

Why does the microcontroller need both a crystal (in the OSC Pins) and a frequency from the power source (in the T0CKI pin)? Couldn't the microcontroller keep time simply from the oscillator?

Is the frequency from the power source necessary? And if so, why?


texts: how to rectify/amplify voltage across current sensing resistor?

texts:
Say a mains AC (120v, 60hz) 10 amp load with a 0.003 ohm current sense resistor in series with it. The voltage across the resistor is roughly 30mv. How do you rectify such a small voltage (I read precision rectifier, but haven't been able to make the circuit work in Circuit Simulator Applet), or amplify it?
Basically, how do you get a usable signal out of that tiny voltage?


texts: Trying to understand this table - comparator with carry

texts:
Create a circuit-table which compares two (signless) 4-bit binary numbers. The result is output signal c_i which is 1 if we have A≥B.

Given is A=0100 and B=0010. Fill the table whereby you choose c_-1 bit yourself so it makes all sense..

I believe this compare is done by subtraction and so we can use adder for this

(this is now for 1 bit:)

        3   2   1   0
----------------------
Ai      0   1   0   0
Bi      0   0   1   0
~Bi     1   1   0   1

Ci-1    1   0   0   1

Ci      1   1   0   1

We need to negate B, so negation of B is ~Bi in the table.

Then we add A and negation of B and if we see that Ci is 1 then we need to make sure that we get a carry when we add A and not B. I thought this is done like that.

Please can you tell me if this is right?


texts: Does resistance affect a capacitor charging from another capacitor?

texts:
Consider two capacitors connected to each other, where one is charged (5.0V) and the other has no charge stored:

When they are connected, current flows to even out the charge and the resulting voltages can easily be determined from the ratio of the two capacitances. My question is: when a resistor is added between them (diagram below), does that affect the conservation of charge and result in lower final voltages?


texts: Are bound current and eddy current independent of each other

texts:
I know that bound currents are due to magnetization of any material while eddy current is due to rate of change of flux through a metal so I wanted to know whether both currents are
are independent of each other i.e let's say if a metal of iron is placed in a time varying magnetic field then do both currents affect each other or not?


texts: Stepper motor stalling when ramping down and then back up?

texts:
I'm driving a NEMA34 bipolar geared stepper motor with the following specifications: Rated Current 4A, Voltage 24-60V. It is being driven by a MA860H driver with output current of 2.6-7.2A 24-80VAC. I have the driver configured for a peak current of 4.45A, and using a microstep of 5 (1000 pulses / rev). This is connected to a gearbox that results in an input of around ~4000 steps / rev.

(http://www.leadshine.com/UploadFile/Down/MA860m.pdf)

The driver is being controlled by a PLC that drives the stepper motor to a desired position. The motion control allows for a desired position, steps/second, and a ramp up/down time (ms).

This particular use case requires a new motion command to be issued while the motor may be in travel. There are no issues if i move the motor from standstill, or issue a new move command while the motor has reached its max steps/second.

However, if the motor is moving, and is nearing its desired position, it will begin to ramp down, if during this ramp a new move command is issued with an increased desired position, the motor should ramp back up and continue to move. Instead, the motor will seize up and makes a high pitch squeal. The longer i set the ramp-up/down time the easier this condition is to reproduce. Oddly enough if i perform the same function but the new move command tells the motor to reverse, this condition does not occur.

I'm not sure what the exact issue i am facing, or how to narrow it down to a particular component. Could it be counter EMF from the motor that is causing the strange behavior, or have i sized the motor incorrectly?


texts:
Here is the datasheet of the crystal (32 MHz) that I use for a MCU.

The right layout is an older version of my board which totally works fine. The left one is the newer version where I placed the components closer to each others (as well as the crystal). However, the 32 MHz crystal does not work properly on the new board ( I carefully assembled three of them).

I measured the pins of crystal by an oscillator, and I see the logic level of pins goes a  higher, but don't oscillate. In addition, my code gets stuck on clock initialization.

Basically everything is the same, apart from the distance of the components.

What I did so far to debug the problem is that:

I replaced the crystal and load caps with the new ones and the ones from the old board that works for sure. It didn't help
pins of the crystals are measured by an oscillator, but there is no oscillation on the pins (the board has a 32k crystal as well, that one works fine).
I tested the same SW on different designs that the SW works correctly and it should be HW problem.
The orientation of the crystal is assembled correctly for sure, I use known brand capacitors (Murata and Kemet).
I inspected crystal's path to the MCU by a microscope and the solder on the pins looks fine.

Left side of CC321 bypass cap belongs to VCC path, and it might be too close to the crystal's In/Out pin (>0.2 mm). I wonder if it could be the problem that high frequency signal couples with the VCC path?

I removed the C321 but did not observe anything different.

Does anyone see any possible problem or have any suspicion or have any suggestion to debug/solve the problem?

Additional information about the Crystal:

And related-schematic view of the layout


texts:
Consider the following transfer function

$$
G(s)=\frac{1\times 10^6\, s}{s+1}
$$

If I evaluate the dB magnitude analytically at frequency 0.1 rad/s, we have

$$
\text{Mag. at 0.1 rad/s} = 20\, \log \frac{1\times 10^5}{1.1} \simeq 99 \, \text{dB}
$$

and dB magnitude analytically at frequency 1 rad/s, we have

$$
\text{Mag. at 1 rad/s} = 20\, \log \frac{1\times 10^6}{2} \simeq 114 \, \text{dB}
$$

If we start at 0.1 rad/s with a 99 dB we can say that at 1 decade later i.e. 1 rad/s we will get about 119 dB due to the zero term. But we are getting 114 dB  with the analytical calculation. Why about 6 dB down from 119 or 120 dB and not just 3 dB down to reach about 117 dB?

The actual dB magnitude plot is below:

My question would be why I am getting 114 dB with the analytical calculation. This value seems too low.


texts:
I was reading this simple description of magnetron working principle.

Can you explain me why when electrons go near the cavities, they start to resonate at microwave frequency? I do not see the link between these two phenomena.


texts: Ground/Earth connection missing on power strip?

texts:
I purchased a power strip with no cable from the hardware store, so that I could wire it up myself with some spare cable that I had lying around.
When I opened the power strip, I noticed that it does not have a connector for the ground (earth) wire.

Does this mean that if I want to have the ground connection work I have to solder the earth wire to the center piece of metal? Is this common for power strips to not have the earth connected but have the conductors on the plugs for it?
Thanks for the help in advance!
Note: I live in Europe


texts:
In the circuit below (schematic diagram), the command from a microcontroller allow to send the 5V to the output through two transistors command Q1 and Q2.

simulate this circuit – Schematic created using CircuitLab

My question is: what happen if the transistor Q1 is short circuit, the output can be energized even if the command from the microcontroller is off ?


texts:
I am attempting to replace an old PLCC32 part that was directly soldered to the board with a new part of undecided form. We will definitely need an adapter as we have not been able to find a PLCC32 part that does what we need. I cannot use a PLCC adapter plug because there are also height restrictions. We are considering building a two-sided adapter board that has pads on the bottom side that match the PLCC32 layout on the current board, with the new layout on top. Theoretically, the adapter board would be soldered directly to the old board and the new chip on top of the adapter.

However, I have not seen any examples of soldering two PCBs directly together in this manner, which makes me think it is a likely to be a bad idea. Can anyone comment on this sort of custom adapter?


texts:
I'm new in electronic and I want to know the exact definition of equivlant circuit. My trouble is that we know for example that a resistance equivalence has same current of the resistances in series for a same tension. If we substitute the resistance in series with the equivalent resistance we obtain another circuit and then we calculate the tension in to the poles of the equivlent resistance. At this point we use this voltage in original circuit, but how we know that in the orginal circuit the tension is the same? I don't see explanation maybe it follows from linearity but textbooks I had read don't say anything about this question.

Update

Suppose we have a circuit C and a subcircuit A and let be K the complement circuit of A in C so C=K+A. Now I say that A' is equivalent to A if we consider C'=K+A' calculate the currents and voltages of K in this case and they are the same of K in the original circuit C.
If my definition is correct then we must proof that proposition in all cases we want to show an equivlant circuit such as equivalent resistance.
Correct me if I'm wrong.
I gave that definition because it is what we do in exercises.

New update

I have these two circuits:

I solve the second circuit and I find the voltage on R23, then usually in exercises I use that voltage in first circuit to compute current in R2 and R3 in first circuit. My question is: why the volatage in the second circuit can be used for the first (I want a rigorous proof)? Is there a theorem concerning equivalent circuits (in this case R23 is quivalent of R2, R3 in parallel) embedded in other circuits?


texts: Turning switch state at two different voltage

texts:
I have a requirement to change the transistor/mosfet switch state at two different voltages.

Below is a small graphical representation.  3.3 v (red) to 4.5 (green). switch should be open when the voltage is between red line and Green. once the voltage reaches green switch should be close as long as it has not reached the red line level. Once the voltage had reached the red line switch should immediately open and should not close unless it has gone back to the green level.

i was thinking of schmitt trigger with transistor but could not get it. voltage can vary between 3.3 v (red) to 4.5 (green)

Edit:

I managed to get what is needed with the following circuit, it is powered 4v power supply. following is the schematic. but could not get the upper and lower threshold voltage. currently i am getting 1.5v to 1.8v as threshold. Any suggestion for change in resistance value to shift the threshold to desired value between 3.3v and 3.9v (upper)