texts:
I know that if I use vias on high speed traces that I need to reduce the inductance effect of the via. So I will put ground vias next to these vias to help returning current. I have seen a picture about using ground vias that has confused me. Here is the first picture:

Everything seems OK on the left one, returning current turns from the reference layer ground. On the right image the vias between the two ground planes seems OK too.

But in this picture:

Which I desire to use for my design one layer is ground and one layer is the power plane. When I saw the picture, it uses two vias and a bypass between them. Do I have to use it like this, or any other advice?


texts: High voltage, low current and vice versa

texts:
Can someone please explain to me in simple terms how is it possible to have high voltage and low current and low voltage and high current and what actually does harm to human body.

Here is what I don't understand:

12V / 1000 Ohm = 0.012A (12mA)

300V / 1000 Ohm = 0.3A (300mA)

So if I go and touch 12V battery terminals, my body is 1000 Ohms 12mA of current flow through me and it is safe.

Then if I go and touch 300V battery terminals and 300mA of current flow through me it is fatal.

Yet 12V battery vehicles have fuses rated for 30A and more. Well, that means if there is a short etc. 30A will flow through a wire and break the fuse.

30A in a short circuit wire with a 12V is safe and 0.3A is a 300V is not? How is this possible?


texts: How to find a transfer function when an \$\omega\$ is not paired with \$j\$?

texts:
With the standard transfer function of:

$$H(s) = \frac{N(s)}{D(s)} =  \frac{(s-z_1)(s-z_2)...(s-z_{m-1})(s-z_m)}{(s-p_1)(s-p_2)...(s-p_{n-1})(s-p_n)}$$

and defining: \$s = \sigma + j\omega\$

Can you put a transfer function into this form if you have an \$\omega\$ not multiplied by a \$j\$?

To give some context, you can run into this scenario when finding the impedance of a  capacitor using a series R,L,C model.

simulate this circuit – Schematic created using CircuitLab

$$\hat{Z} = R + j\omega L + \frac{1}{j\omega C}$$

$$\hat{Z} = \frac{j\omega RC - \omega^2LC + 1}{j\omega C}$$

If you treat \$\omega\$ as your input variable and \$\hat{Z}\$ as your output variable, then the complex impedance can be seen as a transfer function. For the equation shown, can you put this into the pole-zero format?

Edit:

What I was not seeing here is that in \$s = \sigma + j\omega\$, \$\sigma==0\$ for sinusoidal inputs, as there is no real (decaying) part to the input (See Why do we use \$s=j\omega\$ in AC analysis instead of \$s=\sigma+j\omega\$?). This means that \$s^2 = -\omega^2\$. Thus my previous equation can be changed to look like:

$$\hat{Z} = L\frac{-\omega^2 + j\omega \frac{R}{L} + \frac{1}{LC}}{j\omega}$$
$$\hat{Z} = L\frac{s^2 + s\frac{R}{L} + \frac{1}{LC}}{s}$$

See Matt L.'s answer for the rest.


texts: Is a toy's remote controller interchangeable?

texts:
This Christmas I'm buying a couple people remote controlled quadcopters. Then it hits me. Is there a possibility that the different remote controllers will crosstalk and wind up controlling a robot that it is not meant to control?

How do electronic engineers ensure that electronic toys will be controlled over via one remote controller and not the other?

Some thoughts:

each RF circuit is only tuned to listen to a single frequency, but how to create so many variants of the circuits?
each quadcopter has a unique identifier and is sent through the wireless controller before each instruction so that the receiver can identify signal through only one set of controller

Any ideas?


texts: In a real-world op-amp, how does it make sure Vn and Vp differs and don't equal each other?

texts:
I was confused about op-amps and asked this question: In an op-amp, why does Vn approach Vp until the difference is delta V / A? Why doesn't Vn just equal Vp? and received really helpful answers.

I now know why in a real-world op-amp, Vn has to differ from Vp; Vn can't just equal Vp or else the output voltage will equal 0. However, how does a real-world op-amp ensure that Vp and Vn differ by a small amount? How does it make sure that Vn doesn't increase to equal Vp? How does it ensure that the difference between Vp and Vn is Vp - (Vp - Vn) / A instead of 0?


texts: What is the connection of this synchronous motor?

texts: so yeah I took this picture of the terminal box of the synchronous motor we're cleaning. I can't distinguish what is wye or delta when it's shown like this. what are the indications that a connection is wye/delta?


texts:
I'm debugging a code for the Microchip PIC18F4520 using the PROTEUS ISIS. The code was compiled with the C18 compiler.
There is a very crazy bug in the code that I don't know whether it is my fault or an ISIS/PIC problem.
The imagem below shows the problem.

At the function 'free', before the statement at address 1004 is executed the variable 'i' has the value 0. When the instruction is executed, the variable 'i' magically receives the value 125.

The 'heap_status' is a global variable that has no binding with the variable 'i'.

Why assigning a value to 'heap_status' affects the variable 'i'?

PS.: When the function is executed for the first time, this doesn't happen. The problem arises when the function executes for the second time.


texts: Computer arithmetic algorithm: what might I be doing wrong?

texts:
So I'm working with the following differences equation:
$$y_n=\alpha y_{n-1}+(1-\alpha)x_n$$
I know this works with 16-fixed point arithmetic, and given some samples I'm trying to figure out how the operation is working. The data given to me is: ´
$$-13559=23528\times(-23528)+(1-23528)\times 12539$$
So my attempt was to do the multiplications, then shift one bit to the left (to eliminate the repeated sign bit) and then shift 16 bits to the right so that result is kept in Q15.
I obtain:
$$-13559=-16893-9002$$
Now the result is divided by 2 to put the result in Q14 (I know this is not needed here but since this needs to be general for any pair of numbers we need to guarantee there is no overflow).
So now I get:
$$-13559=-12947$$
Which is way off.
Any idea about what I might be doing wrong? I can provide more pairs of samples if needed.
Thank you!
EDIT:
I was pointed out that my samples might be wrong but I don't think they are I provide here the respective values:
$$\alpha=23528$$
Sequence of values
yn=-32767
xn=0 -> yn=-23528
xn=12539 -> yn=-13359
xn=23170 -> yn=-3060
xn=30273 -> yn=6338
xn=32767 -> yn=13789
EDIT2: Ok so now I seem to be achieving more consistent things. However I still can't achieve the exact values of the samples given. Below are my results:
Sequence of values
yn=-32767
xn=0 -> yn=-23528  -> ynOBTAINED=-23528
xn=12539 -> yn=-13359 -> ynOBTAINED=-13359
xn=23170 -> yn=-3060 -> ynOBTAINED=-3059
xn=30273 -> yn=6338 -> ynOBTAINED=6339
xn=32767 -> yn=13789 -> ynOBTAINED=13790
So it is quite similar but there seems to be an offset. I unfortunately noticed later samples have a deviation of 3 or more so there is something wrong with the way I am computing this.
I've tried two different approaches but with the same results
output_filt=((((output_filt*alpha)<<1)>>16)+(((input_filt*(32767-alpha))<<1)>>16));

OR
output_filt=((output_filt*alpha + input_filt*(32767-alpha))<<1)>>16;

Can someone please help me?


texts: I’m new to electricity, and I’ve got a question about electrons flow inside a Li-on battery. A lot of articles and videos show us only Li+ ion flows from anode to cathode through electrolyte during discharging of battery. But there is no info about e- flow from cathode to anode inside battery. As I know, there must be closed loop of electrons flow, but also there is conception that separator doesn’t let e- to flow through electrolyte. So how electrons pass through Li-on battery to comply with close loop conception?


texts:
I designed a robot. It consists of an actuator, linkage and a camera. the actuator is considered as a dc motor in this problem. I need to identify this system. how can I find a model for actuator and loads on it(camera and linkage have mass)?

I used this actuator

edited:
It is a 2 Dof robot. camera rotates about y and movies up and down (z-axis). The camera and linkage are attached to the Stroke. When the camera is lifting up, the actuator is retracting and when it moves down, the actuator is expanding.


texts:
One component on this board has eluded me.  It is marked S447 horizontally at top,  the letters MEX down the right an J6 at the bottom.  The T logo is stylized with a swooping top.  Searching for the manufacturer has eluded me as well.

I appreciate any assistance identifying this component.


texts:
is there a way to build a log amplifier using vacuum tubes? I would like to have a VU meter (with the proper log response), but do not want to use solid state components. The output would be to a IN-13 neon indicator which has a linear response between the current and the length of the light bar.

I know that I could build an opamp out of tubes and then use any of the opamp circuits available to get what I want, but I am wondering maybe there is an easier way to do it using less tubes.

I also know that I could use a magic eye tube (EM84 or similar) because they have a log response already, however, the tubes are smaller and would not look as good from further away than the IN-13.

As this is for a VU meter and not for some scientific purpose or an analog computer, the response does not need to be perfectly accurate, just accurate enough to not look that much different on the output.


texts: Is this mains switch on the Neutral or on the Live wire?

texts:
I'm changing the chandelier in my living room and I would like to double check whether its switch is on the live or on the neutral wire.

I have a test lamp which is rated to measure 125-250V. There are 2 wires coming from the ceiling. When I turn the switch on and test wires with the test lamp, there is light on one of the wires. When I turn the switch off and test again, there is no light.

Does that mean that the switch is on the live wire, as it should be? And does that mean that there is no current in it and it's safe to work on it?

I'm asking this mostly because I would like to work with the wires, without turning off the main fuse.

Thanks.


texts: Is this power supply suitable for powering these chip on board (COB) LEDs?

texts:
I have an LED project using 100 Citizen CLU048-1212C4 LEDs.
I need to run each LED at 70W, and I want to run every 5 LEDs on 1 power supply.
I was thinking of using the MEAN WELL LSR-350-35 (it takes a long time to show PDF)
Video review of the power supply.
This screenshot is from the LED datasheet

I saw in the power supply datasheet:

INPUT Voltage Range : 90 ~ 132VAC / 180 ~ 264VAC by switch 240 ~ 370VDC (switch on 230VAC)

This screenshot is from the power supply datasheet

Where I live, the electrical power 220V and 50Hz.
I think if I connect the LEDs parallel it'll be good because the current of the power supply (9.7A) will be divided on the LEDs count so every LED will take 9.7A/5 = 1.94A for each LED DC voltage 36V.
I think that means 1.94*36=69.84W ~ 70W (automatically.)

Is that power supply good for this project?

I feel confused from this screenshot from the LED datasheet.
I think I need to drive the LEDs at ~38V to reach 1.9A, I'm not sure about that.
This screenshot is from the from the LED datasheet


texts: Optimal sensor for measuring object velocity in an open area?

texts:
I am trying to measure vertical and horizontal speed of an object attached to a parachute. It will be launched from a low altitude and in an open area, allowing satellite GPS lock.

Data treatment will be post flight, so no real-time or processing power requirements.

Up to now, I have identified two solutions:

9-DOF IMU, sensor fusion to get absolute orientation, accelerometer integration to get the velocity vector.
GPS, ground speed for horizontal speed and elevation for vertical speed. I would probably fuse GPS elevation with a barometer relative altitude to maximize precision.

I have explored the IMU solution up to now, but I have encountered some problems:

accelerometer integration is very prone to error, since it depends on the absolute orientation, gravity offset removal, numerical integration methods, noise attenuation, drift correction, etc.
sensor fusion SDKs are pessimistic about inertial navigation performance, which leads me to think that getting velocities from it is easier said than done.

After reading some GPS datasheets, and I have also identified some problems:

Weather may block GPS satellite signals and accuracy depends highly on the locked number of satellites.
Update rates are pretty slow, I should not rely on something faster than 2 Hz.

I have the following questions:

Am I missing another type of sensor that would be easier to implement and get accurate velocity vectors?
Would the GPS be a more reliable solution than the IMU?
Am I correct on the assumption the ground speed I get from the GPS is the horizontal speed of the object?


texts:
Incoming Noob question alert!

So, I am new to this platform and I have a few questions.

What happens when I upload a new sketch to the Arduino from the Arduino IDE, the older sketch gets deleted?  or older one still survives in the Arduino memory somehow?  if it does.. what happens when it runs out of memory? and how do you go about choosing which one to run?I have a feeling that the old one gets deleted, but I want someone to confirm it.
I understand that the there is a void setup () part and void loop () part, the void loop part keeps the thing going indefinitely. Regardless, is there a way to start/stop the program? without cutting the power to the board?


texts: TIP127 + TL074 power supply doesn't work until I touch it

texts:
I have such a schematic based on the TL074 opamp and the TIP127 PNP darlington transistor to control the fan voltage (shown as motor near the D3 diode). VCC = 12V, VDIG = 5V generated by a LM7805. The problem is that this schematic works perfectly in the simulation, yet it resists to work on the breadboard until I touch the opamp's positive input. After that, the schematic works perfectly until I try to turn it off and on again - it turns off fluently (using the pot), yet it does not turn on until I touch that positive input.

I don't understand what is going on. My guess is that I should put a capacitor somewhere, but I don't understand where and - more imporantly - why to make it work.

I am using a 12V 0.3A fan as a load.


texts:
I have the following schematic:

Vcc can vary from 12 to 15 volts, so the design was intended to switch on the relay through a MOSFET when the input voltage is over 13.4 volts. The actual Zener I've used has a Zener voltage of 6.9 volts, so the comparator output should turn on at 13.8 V. However, two things are happening that I cannot explain:

There is some hysteresis in the circuit. The relay turns on at 13.8V, and switches off at 13.4. I've checked with a DMM at the comparator output: when below 13.4V it is almost 0, when in between 13.4 - 13.8 it is turning to ~7 volts, then increases as I increase the input voltage. How can I explain this hysteresis, and how can I control it?
Once I forgot to put flyback diode D2 in place. The scheme worked OK, but hysteresis narrowed to 0.1V, from 13.7 to 13.8V. Then I decided to use an LED instead of a regular diode, so I replaced D2 with an LED (1.8V forward drop). So with the LED, hysteresis is back to 13.4 - 13.8 volts, and the LED is lighting in this interval, going from dim to bright, then turning dark over 13.8. If I switch off the power supply, the LED produces a flash as the relay clicks.

I guess these two facts are somehow connected. Please help me explain how and why?

EDIT:

So the suggested scheme is as below?

I should swap the inputs, connect the open Emitter to GND, and use a pull-up resistor between Vcc and open Collector/MOSFET Gate?

My second question is still in place - how to add and control a hysteresis to this scheme?


texts: Single Supply Class-A-Amplifier circuit to amplify voltage signal alternating around ground

texts:
I have a sensor which outputs a voltage signal alternating a few millivolts around zero volts and want to design a circuit which prepares this signal for processing by a microcontroller like in the picture below:

Now the problem is that i only have a supply voltage range between 0V and 3.3V  and therefore need to add some DC offset to my signal and then amplify the alternating part.

I think that op amps are not suited for my application because they amplify the DC signal as well as the AC Signal and so I thought of a class-A-amplifier circuit like this:

simulate this circuit – Schematic created using CircuitLab

Now the question:
Is it possible with the class-A-amplifier to process my millivolt input signal to the larger one in the picture at the top or are there any better methods?


texts: Does a bit in Flash memory store net charge

texts:
This is with regards to the discussion in the comments in my answer to this question with regards to the charge stored in a Flash.

The way a Flash memory works is that it either stores a small charge (signifying logical 0) on the gate of a floating gate transistor, or doesn't store it (signifying logical 1).

Capacitors, batteries etc are often said to store charge, but in reality they store energy but no net charge since there is always the same number of positive and negative charges on opposite plates.

Now, the question is: is there ever net electric charge stored on any transistor in a Flash chip, such that Kirchoff's current law is temporarily breached? (Presumably charge conservation holds, so electrons from the programming current trapped on the gates are later balanced when erasing that memory cell). Or are the charges of the trapped electrons balanced internally to the transistor by, for example, holes (in the sense of semiconductor theory, an absence of an electron in the valence band) in the substrate?

References to credible sources on the matter are highly appreciated.


texts: In earlier tape recorders, how was tape spool angular velocity adjusted?

texts:
Tape recorders that use spools of magnetic tape transfer the tape from one spool to another as the tape plays/records. The spool with less tape must be rotated faster than the other. Here is such a tape recorder/player. This is the Craig Model 212.

At start, the spool with all tape rotates slowly and the empty spool rotates quickly. As the tape plays and tape transfers to the initially empty spool, the situation is reversed. In order to prevent tape from breaking and play/record at constant rate, we must finely adjust the angular velocity of each spool in real time. The angular velocity of each is a function of the amount of tape on the spool.

Tape recorders have existed since before transistor was invented, before microprocessor was invented. What type of circuit/electronics was used to control the speed of the tape and how?


texts:
I would need to control 4 relays (300 mA each) with an esp32.
Relay will open and close at the same time so i not need a dedicated control.
As I'm not expert I would like to ask you if you can propose a solution (I'm thinking of a MOSFET) to drive the 4 relays.
Many thanks


texts: dry contact control relay - Am I on the right path

texts:
Need help understanding a dry contact control relay.

My goal is to cut power to an electronics module ( 100 mA max ) with a contact closure input to the relay.  By "contact closure" I mean simply the equivalent of mechanical toggle switch closing.

I would need a NC output on the relay to maintain power to the electronics module until the contact closure occurs on the input to the dry contact control relay.

Am I correct that a "dry contact control relay" would accomplish this?


texts: How do I find a replacement for this SMD Zener diode?

texts:
I am attempting to repair a circuit board where this particular Zener Diode is fried.  I have attempted to search for any references to Zener diodes that are marked 8•9 (and 6•8) without success.

How can I identify a suitable replacement?

The approximate dimensions are 0.8mm x 1mm x 2mm.


texts: VHDL: Architecture naming and interpretation

texts:
Note: I am using Xilinx's ISE and have an FPGA board to work with (with switches and lights and so on), and I've hacked together some simple projects so far. At the same time I'm reading several tutorials to build a foundation for what I'm doing.

I've seen various entities and their architectures mentioned in the reference materials I've been going through, but the naming is often confusing. Often instead of "architecture rtl of.." or "architecture structural of..." I'll see "architecture foo of..." or even "architecture arch of..."

I realize (belatedly) that the architecture name is just as arbitrary as the entity naming, though there are style guides that suggest more consistent naming conventions can be used to avoid this issue. This leads me to a few questions:

Looking at an entity, how can one determine the actual architectural
model being used without hints from the architecture name? RTL,
behavioral, structural... they appear to be quite similar to my
learner's eye (assuming the examples I've seen were actually named
correctly). A simple but obvious example would be helpful here (or a
pointer to one).
If specifying multiple architectures for a single entity (which I
understand is possible) do you simply give the architectures
different names in the same file or...?
Are the architecture names confined to a given entity (that is, is
there any problem with "namespaces" by using the same architecture
name over multiple entities)?

Edit: and one more:

It seems there is a distinction between RTL and behavioral, but as mentioned above I'm not really seeing it in the examples I've seen (often I only see one architecture being defined). Is one architecture more common than the others?

What I've been looking for is a comprehensive yet simple multi-component project (little components), written using best practices (proper naming, not all crammed into one file, etc.) but I've yet to find one. I find properly crafted sample projects very useful for illuminating basic principles and best practices. If you know of such an example project I'd be grateful for a pointer to that as well. (If nothing else, perhaps once I figure this out I can share one of my own...)


texts: Passive bandpass filter simulation gives wrong cutoff values

texts:
I'm simulating the following passive bandpass filter in LTSPICE, and can't figure out why my calculated cutoff values don't match the -3db values in the simulation. Here's the circuit I'm simulating:

Here are my calculations:

\$f_{cutoff, HPF} = {\frac 1{2π(20k)(100p)}= 80kHz}\$

\$f_{cutoff, LPF} = {\frac 1{2π(1k)(1n)}= 160kHz}\$

Here are the simulation results (See the values in the lower left for Freq and dB):

Maximum value of plot is about -0.4dB @ 106kHZ:

Measured HPF cutoff is around 6kHz @ -3.4dB:

Measured LPF cutoff is around 1.8MHz @ -3.4dB:

So what gives? Why are my calculated cutoff values so much different than my simulated cutoff values?


texts: MPU6050 (ACCEL_YOUT_H , ACCEL_YOUT_L) register , have constant value

texts:
every one
I have problem with reading data of (ACCEL_YOUT_H , ACCEL_YOUT_L) registers , I wanted to stabilize quadcopter with this sensor , I already read data from these register correctly with stm32f103 until a problem occurred , this problem was an -Instability- in the system , since then these registers have a constant value  , while all another data register have correct value and change .
with this condition my question is that : can I fix this problem in software with change configuration or reset sensor and how can do this , or my hardware damaged I must change sensor and use another one .
this is my module config :
Single_WriteI2C(0xD2,PWR_MGMT_1  , 0x08);disable temp sensor and enable 8mhz internal crystal[![enter image description here][1]][1]
Single_WriteI2C(0xD2,MPU_CONFIG  , 0x04);   //21HZ accelerometer bandwidth and 20HZ gyro bandwidth digital filter, input signal is off
Single_WriteI2C(0xD2,SMPLRT_DIV  , 0x04); //1khz/5= 200hz---digital low pass filter is on
Single_WriteI2C(0xD2,GYRO_CONFIG , 0x18); //set on +-2000 degree/sec
Single_WriteI2C(0xD2,ACCEL_CONFIG, 0x08); // set on +-4 g/s


texts: Control 220V stepper motor with arduino?

texts:
Is that possible?

It is an Saia UFR1 motor running on 220V.
https://oc.kosmospora.de/index.php/s/gp3szJXgk3P0SMP

Can I simply use a double relais shield?

EDIT:
The motor is part of a valve actuator of my heating at home, so I simply need to move the valve now and then for a few seconds.
datasheet: https://oc.kosmospora.de/index.php/s/IKvxI8rzKuATTsC

The existing control circuit board is burnt at two places, transistors it seems. Fotos https://ksmspr.uber.space/nextcloud/index.php/s/JwuCxtRpQlVAnWm
Maybe I could try to replace the transistor!?

When I run the motor directly on 220V (one pair, red and yellow wire), it seems it goes a sec CW and then CCW and CW again and so on!?


texts: Can I use aluminum foil for a heat gun as a nozzle?

texts:
Wanted to desolder a small chip with 48 pins on a PCB.

Since my heat gun didn't come with a small nozzle included, can I use aluminum foil to create a ghetto nozzle for it?

What can I do as an alternative option?


texts:
For a pet project I am doing (trying to fly a kite using my computer) I need to move and reverse an electro motor to my liking (I took the motor from an old hand-held vacuum cleaner). I need to control this movement from a Raspberry Pi.

From what I understand there are 3 basic types of electro motors: DC, Single phase AC and 3 phase AC. From these three only the DC motor reverses when you switch polarity (which I guess means switching positive and negative). On this page however, I read that "for a DC motor which has a wound field winding instead of a permanent magnet you have to reverse the connections either to the field winding or to the armature.". And here I'm lost.

So I thought to simply try it out: I hooked up the + of the battery to the - of the motor and vice versa. The motor did in fact move, but still in the same direction and a lot slower. Unfortunately, after a few seconds it smelled like something was burning. So I quickly took the load of the motor. Luckily it still works..

The things I now wonder about are:

What kind of motor do I have (see pics below)?
How do I reverse this motor?
Can I reverse this motor from the Raspberry Pi using the Gertboard's on board motorcontroller (as far as I understand the motorcontroller on the Gertboard simply reverses the positive and negative when it wants to reverse the motor)?
If this motor cannot be reversed using the Gertboard, where would I be able to get a motor that can actually be reversed using the Gertboard (preferably by getting it from an old home appliance)?

All tips are welcome!


texts: Altium: Access Database Library - Only "Library Ref" Appears In Lib Panel

texts:
Over the past couple of days I have been experimenting with Altium's Access database library feature and have run into an issue. I have a test database and Altium seems to be reading from it without a problem, but in the Libraries panel when I try to go add a part, the part number field does not show up. Only the Library Ref column appears:

The tutorial I am following shows other fields (namely "Part Number"):

The above image is what I am expecting (except I would like to be able to choose which fields appear). What am I missing here? What tells Altium which fields to show in that panel?


texts:
I have the question "Two resistors of resistance, 3 ohms and 6 ohms, are connected in parallel across a battery having a voltage of 12V."

I am asked to determine the total circuit resistance. Here is my attempt is this correct ?

It then asks me to find the current flowing in the 3 ohm resistor using the answer above. For which I got:

V = IR

Therefore , I = V/R

Therefore,

I = 12/2 = 6A

Is this correct also ?


texts: large voltage spike over shunt resistor even at no load

texts:
I'm trying to build a stepper-motor driver. Each windig is driven as shown:

at the moment, im feeding this with PWNM signals of constant duty cycle, just to see how everything response. (PWMs are complementary to drive current in only one direcion) So i'm not using the OPAMP and MCU to measure any currents. What i see is that when a Mosfet gets turned on or off i see a spike over the shunt resistor, even with no load attached.

CH1 = voltage over shunt resistor
CH2 = voltage at switching node

output voltage looks ok, same under load (testet with up to 3A). But im not shure where these spikes are comming from. I used a Ground-clip to measure this.

Any idea how i can get rid of this? Or is there anythin obvios wrong with my schematic. My current prototype uses a 4-Layer pcb with an (almost) solid GND-plane and seperate supply-planes under each H-bridge.

Update:

Dead-time of PWM signal is 460ns. I changed the gate resistors to 10R to allow for faster rise/fall of each gate voltage. but no improvment on the shunt signal

Output signal of the gate driver:

Gate voltages with RG = 22R

Gate voltages with RG = 10R

Better Measurement of gate voltages, might this peak be the problem?

Update 2:

i've been testing and probing around to see if i can narrow it down. Wiring C49 and C54 directly to GND (as mentioned by peufeu) improved the signal over all, but it did not affect the spikes. But the signal is much cleaner right befor the spike, during dead time.

I found out that this Spike/swing is also present on the supply voltage. I changed C47 to 1000uF and still the supply voltage swings about +/-5V and more. Under no load, and there is no current drawn form the power supply. Wouldn't i take quite some current to cause such fast voltage change over an Elko? The swing on the supply voltage looks basically like the one over the shunt, but inverted.


texts: Driving a LED high current / high speed (>= 200nsec pulse width, >=10us delay)

texts:
I have a project for which I need to pulse a LED at pulse times starting at 200ns followed by a delay time typically >10us. I want to achieve high current in this pulse period to emit enough light. The LED acts as a background light source for a microscopic camera.

The pulse/delay times are generated by a uProcessor running at 200Mhz, so instruction cycle is 50Mhz.

I have NO idea how to design the power electronics part for this LED driver.

Thank you very much for any advice


texts: Can I safely trickle charge a 24v garage actuator battery with a pair of 12v solar panels?

texts:
I have a Hormann Promatic Akku Garage door actuator, since my garage doesn't have mains electricity. Generally speaking I'm very impressed with how well it works. Unfortunately while it lasts around two months between charging, it gives almost no notice about when battery charge is getting low.

I would like it to last longer between charges, so a while ago I bought some low power solar chargers. My concern is that there may be something I've missed in the naive way I'm intending to wire them up.

Background

The Hormann battery unit (lower right in the picture) has a pair of XLR sockets, so you can plug the actuator power lead into either one. I presume that Hormanns own (ridiculously expensive and not available in the UK) solar charger plugs into the other socket. Internally, there are a couple of deep discharge 12v batteries wired in series.

 Attrib. Hormann.

When fully charged, the battery module measures 26.3v and the actuator refuses to work when the voltage drops to 23.3v.

The solar panels I have are just 1w, but are have an integral diode. They were sold as solar 12v battery re-chargers, and the research I did at the time suggested that such a small wattage should count as trickle charging the batteries, so over charging shouldn't be an issue. I note though that open circuit voltage under bright sunlight can reach 18v though.

On one of the panels the diode is blown, so any advice on replacing it would also be useful (I removed the old diode, but it was hot glued to the panel and removing it scratched off some of the ID, I'm guessing it's a 1N4007 though).

How I intend to wire them up

So, naively, I was just going to wire up both panels in series, just as the batteries are wired up, through an XLR plug and leave them connected permanently.

I'm also considering whether it might be better to leave the diode off the second panel and just wire the two panels together with a single diode between them.

My concerns

Assuming a rare British summers day, I know that at just 1w @ 18v means a pretty low current to the battery, but might 36v from a pair of panels damage the actuator circuitry? I'm guessing that being connected to the battery will drop that voltage to just above the battery voltage, but it would be nice to know for sure.

Also, when the actuator is actually drawing current, it is drawing quite a few watts for 20-30 seconds. Could the solar cells be in any way damaged? Looking at the diode datasheet, it looks like each of the diodes would be more than capable of coping with the current and voltages we are talking about.

I've reviewed the relevant solar-cell tagged and battery-charging questions, but non that I can find seem to address my concerns.


texts:
I am using 4 IRF840 N-channel mosfet,converting 325VDC to 230VAC with SPWM and H-bridge.I have no problem with resistive load,but when I connect inductive load or a device with capacitor power supply,mosfets of one side burn.here is m circuit:
M question is:Would placing 350V TVS diode on source-drain of each 4 mosfet,solve this problem?

I mean placing diodes like this:


texts: Can a CM choke saturate due to the leakage inductance?

texts:
On a 3-phase common-mode choke, if the three currents sum to zero, then it will theoretically never saturate.

I understand that the leakage inductance stores energy in the core.

Can the three phases have different leakage inductance?
If so, can that imbalance contribute to core saturation?
E.g., if phase A has more leakage inductance than B and C, then when current A is at its peak, the energy stored in the core is not zero. Is this true?


texts: What determines a load's current requirements?

texts:
Apologies if this question has been asked before. I'm sure it has but hard to find as wording of question may not bring up the duplicate question.

Let us say we have a 10 ohm resistor as a load. Under a power source of 5V, it will draw a 500mA current. In this scenario, we had two "givens": the resistance and the voltage.

Now here is what I am wondering. Does a 10 ohm load think (using the above resistor as a figurative character)

"Ok, I never know how much current I need. For me to know how much current I need, I need to know what the voltage is since I already know my resistance. If your voltage is 5V, then I will take 500mA. If your voltage is 10V, I will need 1A. But don't give me more than 20V because I won't be able to handle that much of a voltage drop and 2A of current!"

So does this mean a load in series will always draw what it needs to comply with Ohm's law rather than preserve itself from taking on too much current? (i.e. taking the above example, "Load sees that the voltage is 30V "Uh oh, I need to take on 3A. This will destroy me but I must draw it anyway to comply with Ohm's law. So long!"?"


texts: MOSFET relay as an alternative for TRIAC relay

texts:
I use a 2 A TRIAC relay with non zero crossing from sharp in one application.
Unfortunately I couldn't find this type of relay, and I want to use another relay (MOSFET relay 2A from TWOARD). Theses two relays are exactly the same, but one TRIAC and the other MOSFET.

Is it possible to use MOSFET as an alternative?
With MOSFET relay is there also zero crossing and non zero crossing?


texts:
I am using a Pro Micro, which the Arduino software for sketches identifies as Arduino Micro.
When I plugged it into power the LED lights were too bright for my eyes to handle, so I verified and then uploaded this sketch:
void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:
  exit(0);
}

The problem is now the board immediately disconnects when plugged into my computer, before I can upload a new sketch onto it removing that exit(0); line of code above.
How can I reset this chip? :-( This was my first and favourite chip, so this is a painful experience.
Picture of the chip since I cannot remember where I bought it, but it was most likely a cheap Chinese one:


texts:
I am attempting to design an envelope detector, however, I'm having problems with regards to diagonal clipping and negative peak clipping of a certain input.

While trying to follow this video's simulation file, without modifying its input, I noticed that there isn't a lot of hassle when picking for the RC values since the modulation index was okay for the input wave.
Input:

(modulation index: 0.5)
Output:

However, I am unsure of what RC values to choose when my input is:
$$f_m = 10kHz\quad f_c=600kHz \quad \text{amplitude}=1V \quad \text{modulation index}=0.5$$
I first tried getting the geometric mean of my messenger frequency and my carrier frequency but the plot shows that these values large
Input:

Output:

I then tried lowering my RC value in an attempt to fix the diagonal clipping, but as seen on the plot, the output still isn't a clean sine wave (compared to the very first output. Decreasing the RC values further would then result to negative clipping and ripples on the upper portion of the output.
Some questions I want to ask are:

How do I get the RC values that would still maintain the shape of the envelope given the input? Is it possible to do so without adding components to the envelope detector?
If it is not possible to get the optimal RC values, is it still possible to retrieve the message in later stages? (i.e. inputting the output to a high pass filter/low pass filter or amplifier)


texts: How to check continuity or shorting using arduino

texts:
I was trying to build a multimeter using an arduino (just for learning purpose). I am able to measure voltages directly using analogRead() and for measuring currents I am using a o.o1ohm shunt resistor. However, I cannot figure ot how to built a circuit to check shorting (i.e the buzzer would beep if there is a short just like in a DMM). Can anyone help me please?

Thank you.


texts: Simple parallel SMD LED circuit(need help)

texts:
I'm going to make some LED circuits, but I'm not sure if it will work.
The problem is that I want to use Red and Blue leds, but they have different drop voltage. Will this circuit work?


texts: Nichrome wire not heating up with a 9v battery

texts:
I have a 42 gauge nichrome wire. When I pass current through it from a 9v battery, it does not heat up. I have checked the circuit properly and also the battery.

Wire resistance: 5.8533 ohms

Wire length: 1 inch


texts:
I am designing an active high function in my MCU program and I need a jumper to activate/deactivate the function by placing it between Vcc and one input pin of the MCU. I have came up with two connections

Which connection is better and what is the reason behind?


texts:
I am designing a product (prototype) that consists of many RS485 networked nodes. They will share a common bus.
My network will be small on size and doesn't need a very high baud rate. RS485 recommends termination resistors, which I want to add. Now, I wouldn't like to request the user to add these resistors at the ends of the bus, because the user is not expected to be tech-savyy. I was planning to add a termination resistor inside each module in the bus, thus making redundant resistors. In my prototype, I want it to seem that you can "just plug them in"

Standard setup:

simulate this circuit – Schematic created using CircuitLab

intended setup:

simulate this circuit

This means each module has two jacks: one to connect to the bus, and other jack to chain the following module into the bus aswell.

So maybe a higher value resistor could result in a sort of progressive terminator resistor? More modules-->lower overall resistance between A and B.

I have also heard that you can use this standard with only one terminal, if you don't expect noise. Is that true?


texts: Voltage and current calculations, Resistor and inductor in parallel

texts:
Im trying to solve a problem in a book which goes as follows:

A 100mH inductor is connected in paralel with a 2k ohm resistor. The current through the inductor is given by:

Compute:

a) Whats the voltage across the inductor Vl(t) ?

b) Whats the voltage across the resistor Vr(t)?

c) Is Vl+Vr=0?

That is all the data that is given, it doesnt mention a voltage or current source, so I figured that an inductor in paralel with a resistor in such configuration would be this:

simulate this circuit – Schematic created using CircuitLab

In which case they are actually in series with each other, thus the current of the inductor should be the same current through the resistor.

Thus: il(t)=ir(t)

Now, I calculate the voltage across the inductor:

And the Voltage across the resistor using ohms law:

The problem is that according to Kirchhoff's law, Vl + Vr should be zero, and they are clearly not. However as time goes by, it is true that Vl + Vr will tend to zero due to the exponential function (time (t) approaching infinity).

What troubles me is that Kirchhoffs law is not valid for short values of time, like t=1, or t=2, etc...

What am I doing wrong? what is going on here?


texts:
I have the following setup;
20v solar panel -->> MPPT chagre controller (sparkfun sunny buddy) -->> battery(3.7v 7000mAh & 5v microcontroller in parallel, see diagram below.

In full sunlight and approx. 19v input to the charge controller from the solar panel;

Should there be power applied to both the battery and the microcontroller?
If the battery is low ( i.e. charging ) will the microcontroller still get power?

Thank you.

simulate this circuit – Schematic created using CircuitLab


texts:
The following circuit is what am using to make a volt meter using an arduino for my psu. It's a 30v psu hence I'll be measuring up to 30v. I don't know why I keep getting random values on the ADC. One minute it's 245 next it's 1024 then it's 0 for some time. Just jumps all over the place. I was told I would only need to supply 1mA to the analogue pin.

Avcc and vcc all decoupled to gnd using 0.1uf non polarised cap.

Here's the sketch code I am using to read the value of the adc

 ![void setup()
    {
      // begin the serial communication
      Serial.begin(19200);
    }

    // variable to hold the analog input value
    int analogValue = 0;

    void loop()
    {
      // read the analog input on pin 0
      analogValue = analogRead(0);

      // print as an ASCII-encoded decimal
      Serial.print(analogValue);

      // print a terminal newline character so the AVR Voltmeter
      // will know that it has received the full string
      Serial.print('\n');

      // delay 1 second before the next reading:
      delay(1000);
    }][1]


texts: L298 high side driver: how does this actually work?

texts:
I recently took another look at the L298 since some students were having problems (due to the commonly discussed high V_CE-on of the combined high side and low side drivers). One thing that struck me as weird is that the L298 uses NPN transistors as both high side and low-side drivers.

How does the high-side driver actually switch when VB < VE < VC? For example, if Vs is 40V and Vss is only 5V, the base (as the diagram is drawn) is lower than both collector and emitter voltages, so I don't see how the high-side transistors are doing anything (other than maybe pulling the load up to ~4V and getting hot). Is there some base-drive logic that's not drawn in the diagram? I was thinking that it's possible the high side AND gates are actually open-collector, so that normally they would be pulled up to Vs through an internal resistor which is not drawn. That would sort of work - but in that case, the current gain is still limited by the inherent diode drop in the transistor, which also would change depending on the load current...

Is there a good analysis of the actual operation of the L298 h-bridge? It seems to be more complicated than it looks.

I've attached the diagram from the datasheet for convenience.


texts:
I'm puzzled in understanding how the P-channel enhancement MOSFET in figure is activated.

The role of the MOSFET is to disable the VBAT supply when VUSB is provided (a usb cable is plugged).
I kind of understood that when VUSB is provided, 5V are both at gate and source, turning off the MOSFET, which is fine.

From the datasheet Vgs=-0.55V, so for the MOSFET to turn on and let VBAT power the U1 voltage regulator, there should be a difference in voltage between gate and source.
Let's assume VUSB is disconnected (usb cable unplugged), the MOSFET is off and VBAT is connected to a 3.7V battery, where does the Vgs of at least -0.55V comes from?

Mosfet datasheet

Thanks!


texts:
I'm fairly new to electronics and am having some issues with soldering and could do with some advice:

from what I have read the solder shouldn't directly touch the soldering iron when solding the component. However, I find the component I.e. a diode, gets incredibly hot before the solder has melted and I'm worries this will damage the component.
the solder won't stick to the circuit board material (I'm using a brown board which has lots of holes already in place (I'm sorry I don't know what it's called) the other issue with this is the board also looks like it starts to melt or discolour a bit when I'm soldering.
the soldering iron I'm using is a kit from Maplin, it is 40w and includes a lead free solder.

I also have a 12w iron which appears to be useless.

I seem to get a big blob of solder off which just bonds the wires together and doesn't bind to the board!

Any advice, tips or tricks or if you could signpost me to a video etc about how to best get started is me most greatful as I'm really struggling to get off the ground and it's very disheartening.

Many thanks,

James


texts: Please explain LIN Parameter, bit quantization

texts:
We are using number of Local Interconnect Network(LIN) channels from Renesas RH850 / U2A16 Microcontroller in our embedded system.  All LIN channels in our embedded system are Master.
What is LIN Parameter called bit quantization?  I didn't find explanation of this parameter in LIN Controller user's manual.


texts:
I have a Sony A7R camera and i want to make a power supply that runs of a 12v lead acid and has a output of 4.2v so i can take long time lapses, i don't know much about electronics so i came here to ask for some help.

I was thinking of using a 12v to 5v converter and a LT3083 to adjust the voltage from 5v to 4.2v, this would also mean i could use a 5v battery bank to power the voltage regulator, do you think this will work?

Because the camera is quite expensive i want to add over voltage protection and a display that shows the estimated battery life, for the voltage protection i could use a MCU and a voltage divider to measure the voltage on the LT3083 output, if the voltage is correct the MCU can turn on a transistor that goes from the voltage regulator to the camera,
and i could use another voltage divider to measure the voltage of the 12v lead acid to give a estimated battery life.

If you could give me your thoughts and any improvements i would greatly appreciate it.


texts: Question about function generator's arbitrary waveform generation ability

texts: I want to buy a function generator with arbitrary waveform generation ability for lab use. My question is, can arbitrary waveform generation's capability generate one sine wave(act as noise) rides on a different frequency sine wave(act as signal). I want to use this capability to study filters.


texts: Unknown identifier error, new to VHDL and having trouble with this error. I use model sim

texts:
Compiler log:

67): (vcom-1136) Unknown identifier "cin".
67): (vcom-1136) Unknown identifier "cout1".
67): (vcom-1454) Formal "cout" of mode OUT cannot be associated with an expression.
68): (vcom-1436) Actual expression (indexed name) of formal "A" is not globally static.
68): (vcom-1136) Unknown identifier "cout1".
68): (vcom-1454) Formal "cout" of mode OUT cannot be associated with an expression.
68): (vcom-1136) Unknown identifier "cout1".
69): (vcom-1436) Actual expression (indexed name) of formal "A" is not globally static.
69): (vcom-1136) Unknown identifier "cout1".
69): (vcom-1454) Formal "cout" of mode OUT cannot be associated with an expression.

Source code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
--entity declaration
entity multi is
port(
 A: in std_logic_vector (3 downto 0);
 B: in std_logic_vector (3 downto 0);
 P: out std_logic_vector (7 downto 0)
 );

end entity multi;
--architecture declaration
architecture multiple_4bit of multi is

signal AB0, AB1, AB2,AB3: std_logic_vector (3 downto 0);
--B Inputs (B0 has three bits of AND product)
signal add1,add2, add3: std_logic_vector (3 downto 0);
signal cout0: std_logic_vector (3 downto 0);
--component declaration
component AND_gate is
    port( X: in std_logic;
         Y: in std_logic;
         F: out std_logic
         );

end component;
--component declaration
component full_adder
port(
A:in std_logic;
B:in std_logic;
cin: in std_logic;
sum: out std_logic;
cout1: out std_logic;
cout2: out std_logic;
cout3: out std_logic

);

end component;

signal temp: std_logic_vector (3 downto 0);
begin
U0: AND_gate port map (A(0), B(0),AB0(0));
U1: AND_gate port map (A(1), B(0),AB0(1));
U2: AND_gate port map (A(2), B(0),AB0(2));
U3: AND_gate port map (A(3), B(0),AB0(3));
U4: AND_gate port map (A(4), B(0),AB0(4));

U5: AND_gate port map (A(0), B(1),AB0(0));
U6: AND_gate port map (A(1), B(1),AB0(1));
U7: AND_gate port map (A(2), B(1),AB0(2));
U8: AND_gate port map (A(3), B(1),AB0(3));

U9: AND_gate port map (A(0), B(2),AB0(0));
U10:AND_gate port map (A(1), B(2),AB0(1));
U11:AND_gate port map (A(2), B(2),AB0(2));
U12:AND_gate port map (A(3), B(2),AB0(3));

U13:AND_gate port map (A(0), B(3),AB0(0));
U14:AND_gate port map (A(1), B(3),AB0(1));
U15:AND_gate port map (A(2), B(3),AB0(2));
U16:AND_gate port map (A(3), B(3),AB0(3));

U17: full_adder port map (cin, AB0(1), AB1(0), add1(0), cout1(0));
U18: full_adder port map (cout1(0), AB0(2), AB1(1), add1(1), cout1(1));
U19: full_adder port map (cout1(1), AB0(3), AB1(2), add1(2), cout1(2));
U20: full_adder port map (cout1(2), cinZ, AB1(3), add1(3), cout1(3));

U21: full_adder port map (cin, AB2(0) add1(1), add2(0), cout2(0));
U22: full_adder port map (cout2(0), AB2(1), add1(2), add2(1), cout2(1));
U23: full_adder port map (cout2(1), AB2(2), add1(3), add2(2), cout2(2));
U24: full_adder port map (cout2(2), AB2(3), cout1(3), add2(3), cout2(3));

U25: full_adder port map (cin, AB3(0), add2(1), add3(0), cout3(0));
U26: full_adder port map (cout3(0), AB3(1), add2(2), add3(1), cout3(1));
U27: full_adder port map (cout3(1), AB3(2), add2(3), add3(2), cout3(2));
U28: full_adder port map (cout3(2), AB3(3), cout2(3), add3(3), cout3(3));

-- output definitions P
p(0) <= AB0(0);
p(1) <= add1(0);
p(2) <= add2(0);
p(3) <= add3(0);
p(4) <= add3(1);
p(5) <= add3(2);
p(6) <= add3(3);
p(7) <= cout3(3);

end multiple_4bit;


texts:
I have a switching regulator that operates at switching frequency of 260Khz that steps down a 28vdc to 3.3Vdc.
The switching regulator output will supply current as high as 1 amp for the initial 5 minutes on power up then it falls off to several mAs.
Can you suggest any addition or modification to the circuit to improve the radiated & conducted EMI at the input?
I have followed Ti's/national semicondutor layout to lessen EMI generation and improve the ripple at the input in the datasheet. Any other suggestions is appreciated.
Little bit more about the circuit:
At the input I am using TVS diode to clamp down large voltage spikes. DS1 is for reverse polarity protection. The combination of( Q1,R0, DZ1) clamps down the voltage to around 30V for large input voltage spikes.

0.1uF added


texts:
In a paper about radiation hard FPGAs I came across this sentence:

  "Another concern regarding Virtex devices is half latches. Half
  latches are sometimes used within these devices for internal
  constants, as this is more efficient than using logic".

I have never heard about an FPGA device primitive called a "half latch".
As far as I understand, it sounds like a hidden mechanism to "source" a constant '0' or '1' in the backend tools...
Can anyone explain what exactly a "half latch" is, especially in the context of FPGAs, and how they can be used to save logic?

EDIT: The paper were I found this was A Comparison of Radiation-Hard and Radiation-Tolerant FPGAs for Space Applications


texts: Projects that require 2 power supply voltages (Raspberry Pi)

texts:
I'm looking for some help building a circuit to supply a Raspberry Pi Zero, as well as a 1W RGB LED driven through a Picobuck driver. The Picobuck needs 12V and the Pi Zero just needs 5V (from a USB power).

I tried using a 12V to 5V buck converter board, connecting the 12V to the Picobuck and the 5V to the Pi. This is fine until I switch on the LED, which causes the Pi to either reboot or shutdown. I presume there is a voltage drop, or not enough current to keep the Pi running stable?

So right now my project has 2 wall adapters (one USB AC->5V DC, and one AC->12V DC). The project is working well! But I want to eliminate the second power supply.

What do I need / what is a good circuit option to have a single AC power source, and then 2 outputs -> 12V and 5V without a current draw from the 12V causing a ripple or voltage drop on the 5V?

Is there such a circuit design? I can build something if its not too complicated, but I am still a beginner and wouldn't know where to start designing a circuit like this. Preferably I would like to just use my existing AC wall adapter that outputs 12V @ 1A. Is this enough power?

Thanks


texts:
I've designed a 1.25W buck converter which is fed by 220VAC(85-265) and has a 5V output. Now I'm trying to design a EMI input filter for it. I don't have a PE connection so I didn't use a CM filter so I only go for DM filter.
My switching frequency is kinda low(30kHz) because of IC I use and build a filter like:

simulate this circuit – Schematic created using CircuitLab
filter has 3.5kHz cutoff(I calculated required cutoff according to my input ripple)
I know 1uF cap is pretty big but if I decrease it I need to increase the inductor value to keep my cutoff same you know.
problem here is; this filter need to stand between the grid and the rectifier. Since my filter cap is 1uF and we have 50Hz frequency in grid, because of the impedence of capacitor, the cap will draw much more current than SMPS(since the SMPS is 1.25W).
Question is:
Can I put the filter after the rectifier instead of putting before it?
Or
Is there any other way to design a proper filter for such a low power SMPS


texts: Can a FELV circuit be connected to a SELV circuit?

texts:
This might be a very very simple question, but I'm unsure how to interpret the rules.

I have a circuit which switches 230V using relays. The circuit is a motor controller for a motor control box attached to Modbus RTU over RS485. I may not be able to achieve the required creepage distance to separate the low-voltage parts of the circuit from the 230V parts in accordance with the rules for SELV ( http://en.wikipedia.org/wiki/Extra-low_voltage ) . This means the motor controller may possibly be rated only FELV.

Does this mean that anything else connected to the same MODBUS bus is now also only FELV? (Since, potentially, if the motor controller fails it could in principle put 230V out on the modbus wires)

If the whole system is to be considered FELV, would it still be okay to use CAT6 cable to implement the MODBUS bus? I believe CAT6 cable can probably withstand 230V easily, but it isn't usually rated for this I think?


texts: How to calculate capacitor and resistors on virtual ground circuit?

texts:
How do I calculate the resistors and the capacitor on this circuit, which has ground and virtual ground as you can see?

In the second image, how do I find the current I2?


texts: Are my calculations for flyback diode/s corret?

texts:
I have looked up some existing questions and did my own calculations for my own problem.

I am switching a relay with a BJT transistor and would like to protect the transistor from voltage spike on relay coil, after the transistor stops conducting.

Circuit:

I decided to connect two diodes in parallel with my relay. A schottky and a zener diode.

First I determined/checked up the relay datasheet. My relay has nominal coil voltage of 5V (this is what I will be using for switching my relay minus the Vce voltage drop) and 35mA coil current (I used 40mA in my calculations).

I then searched for a BJT. I found one with Vce_max equal to 40V and Vcb_max equal to 60V. Maximum power dissipation is 200mW.

Next I picked a schottky diode with Vf_max equal to 0.3V, repetitive reverse peak voltage 30V and Iforward 1A and a zener diode with 2V Vz @ 5mA Iz. I looked at the graph in the datasheet which shows current/voltage curve and at the coil current which is 40mA voltage drop across zener diode is 2.7V.

In my opinion these chosen elements are okay, can anyone confirm this?

The circuit is not meant to switch relay with high frequency. It's meant for opening/closing garage doors.

From the diodes I have chosen is my assumption correct that voltage drop across coil will be around 3V (sum of both voltages of zener and schottky) after the transistor stops conducting and coil starts to discharge through diodes?

Thanks in advance.


texts: using the PS2 keyboard library with Arduino Leonardo

texts:
I'm having difficulties getting the PJRC PS2 keyboard library working reliably with the Arduino Leonardo.  I'm relatively new to using the Arduino, but this library seems to be the recommended way to read PS2 keystrokes.

When I run the example sketch to echo keystrokes to the serial terminal, I get about 50% of the characters echoed correctly.  The other half typically consists of random characters.  In addition, I'd say only 30% of the keystrokes are actually detected at all.  I tested many keys on the keyboard to see if there was a mechanical fault but this mis-identification and detection lag happened to all of them.

I get very different results using  code from this blog which just implements the PS2 protocol in a barebones way.  All of the scan codes echoed from this program are consistent (and correct after I manually looked them up) and there is no lag in detection.

So I could implement my own lookup tables with the second example but I'm curious if there is a known fix for the PJRC lib.  There are more features in that library that I would like to make use of.


texts: What is supposed to happen in Verilog if a signal of one width is assigned to another signal of a different width?

texts:
As in these two cases:

wire [3:0] A, B;
wire [4:0] C, D;

assign A = C;  // larger width to smaller width
assign D = B;  // smaller width to larger width

What should A and D look like in terms of C and B respectively?


texts: At what frequency will the reactance of a 1μF capacitor equal to the resistance of a 2kΩ resistor?

texts:
Here is my work:

\$ R = 2000 \Omega\$

\$ X_L = 2 \pi f L = 2 \pi (1 \mu F) f = 6.28\mu F(f)\$

\$f = \dfrac{2000 \Omega}{6.28 \mu F} = 318.471MHz \$

Does this look right to everyone?


texts: Activate motor on speaker sound using speaker wire

texts:
I have a mission: I want to put the board of a Google Home Mini inside the Nabaztag Smart Rabbit, an old iot device that doesn't work anymore because they shutdown the server.

Nabaztag has two motorized ears and some lights: I want to move the ears when Google Home Mini reproduce a sound. How can I detect the passage of current on the speaker wire (with arduino maybe?) so I can activate ears and lights?


texts: What are the differences between raw tin and the tin used for soldering through hole and SMD components?

texts: What are the key differences between raw tin and the tin used for soldering electronic components?


texts: Can I solve this relay output issue by using a resistor?

texts:
For an enclosure, I will control the power at the terminals of a panel mount AC socket by using an SSR. The AC mains socket will have this indicator lamp in parallel to indicate whether the socket is live/powered. The indicator lamp according to the datasheet draws only 3mA current at 230V AC.

Below is the diagram of the system:

As shown above the system worked but the lamp was extremely dimmed when the relay was ON. Then I connected a voltmeter across it(across A and B) and nothing changed. Except I saw 230V AC even relay is OFF due to capacitive coupling.

But when I set the voltmeter to low impedance setting, the indicator started to glow as it supposed to. And the fake ghost voltage at OFF times also disappeared.

So I went back to the SSR’s datasheet and at its output characteristics it says “Min. Load current to maintain on: 50mA”

My conclusion was the problem is: if the load draws less than 50mA I will have problem; either with the indicator lamp or any such weak load.

To solve this issue can I connect a resistor across the node A and B in my diagram which draws 50mA current. To make sure the weak loads like the lamp would work fine when the SSR is ON.

If I use a resistor across A and B for 50mA the minimum resistor becomes 1000*(230/50) around 47k.
And power for such resistor is 1.25 Watt.

I never used a resistor for such purpose for AC power application. Can any 3W 47k resistor be used? Do I need any heatsink? The relay might be ON more than six months. Can this be a solution or what else can be done?

edit:


texts:
I have been dealing with these differential amplifiers for weeks now and still don't understand the basic principles of its operation and how should it be used inside an audio amplifier.

I understand everything to the point when input (say AC) signal is applied to circuit. I completely do not understand how should negative feedback from output of amplifier back to non-inverting input do anything at all. All that distortion canceling within diff-amplifier pair negative feedback is totally unclear to me (in practical way mostly).

How do the two transistors improve amplifier's THD (Total Harmonic Distortion)? How is a part of that distortion being canceled by diff-amp? Does there have to be 180 degree phase shift back to negative feedback for distortion to get canceled (If yes, why)?

Any answer to one of this question with practical example would certainly improve my understanding of this "wonder".


texts: Help Finding Transfer Function Of Circuit

texts: What would be the transfer function of the following circuit, assuming an ideal op-amp?


texts: Trouble with Schematic Diagram - Distance measurement using radio waves

texts:
I am working on a project to find out the distance with 2 objects using radio waves.
On one end we have a transmitter/receiver than sends a signal to another transmitter/receiver which spontaneously sends it back to the transmitting end. The first transmitter/receiver finds out the time it took for the signal to go and come back and uses that to calculate the distance between both of them.

The diagram below shows how it has been implemented by someone named Jones here. He uses counters, oscillators, dirty radios and a bunch of leds to show the results.

Not coming from a electronics background I am having trouble understanding parts labeled A,B,C of the Schematic Diagram which I have circled below.

Thanks for your help.


texts: I have to use a 28V DC power supply for a certain design I am doing. But I only need 12V DC to power up this device. How would I design this in a schematic? What would I need? I have been searching up DC/DC converters...but I am not sure if I am on the right track. Thank you.


texts: Signal distortion in simulation of a current to voltage converter

texts:
I'm trying to simulate a current-to-voltage preamplifier as part of a circuit I'm building. The current signals I'm working with range from pico-amps to nano-amps. With a gain of \$10^8\$ ohms, a 50 pA signal will be -5 mV, and a 50 nA signal will be -5 V. The reference 'schematic' is below:

Using an ideal op-amp model in my simulation, I'm trying to see what diodes will be appropriate in the circuit. They seem to just act as input protection diodes to protect the op-amp from stray voltages, but when I use a common diode like the 1N4148, the output gets distorted shown below. Other diodes I'm considering, like the BAV45, seem to keep the signal relatively the same as the ideal model in green. What diode parameters would cause such a distortion to occur?

EDIT: Thanks to some comments, I added a feedback capacitor, and you can see the results below. It really did the trick.


texts:
I have a battery charger on which a resistor is damaged and I don't know how much resistance was that.
Is there any way to check damaged resistor's value?
And also please let know that if a resistor has "100" written on it what does it means?


texts: Relay coil set and reset with momentary switch

texts:
I am having trouble with the activation of a set-and-reset coil of a relay which is dual coil-latching.
The datasheet mentions that to set or reset the coil I need to apply the rated voltage for max. 20ms (in the coil data specifications section) and also mentions a min. 100ms pulse length to set and reset in the Notes section.
I am not sure which one to consider. I would like to know the minimum and maximum time length I can apply to the relay coil to set or reset.
I am thinking of doing it with a momentary SPDT toggle switch (I am not sure if can go with it). Do I absolutely need a control circuit to set or reset the coil? Or will an other method which is not necessarily cheap do the job? If anyone has any experience with dual coil latching please help me with this.
PS: Supply for the coil is coming from a DC supply


texts: using stm8s003f3p6 for frequency counter

texts:
I want to use Sm8s003f3p6 as a frequency counter ,  My program is as  described in stm8s reference manual  17.4.3 External clock source mode 1
and pulse counting is done in pin PC7  using HSI 16 Mhz   , but the speed of counting is very low , for example for a 10 mhz pulse in 1 ms  TIM1_CNTRL counts to 60 .
I want to know is this speed of counting correct ?
Is it possible to have faster counting ?
what is the maximum counting frequency of stm8s003f3p6?
I  want to make a frequency counter and need to have more speed to
count high frequency wave .
As I said for 10 mhz pulse ,  counter is 60  so each increment of counter is equal to 10Mhz/60 = 167 khz that is not a good resolution .  .
my code for timer counter is as follows
#include <iostm8S003f3.h>
#include <intrinsics.h>
unsigned long int fr=0,f=0;  // fr increment in timer1 overflow , f is number of final pulse counting
unsigned char h; //dummy variable
int main(void)
{
  __disable_interrupt();
  InitialiseSystemClock();
  InitialisePorts();
  config_counter();
  TIM1_IER_UIE = 1;  // enable timer 1 interrupt
  __enable_interrupt();
  while (1)
  {
    fr=0;
    TIM1_CNTRH = 0; //reset counter
    TIM1_CNTRL = 0;
    TIM1_CR1_CEN=1; // start counter
    delayms(1);
    TIM1_CR1_CEN=0; // stop counting
    // calculate counter as a number = TIM1_CNTRH*256 + TIM1_CNTRL + fr*65536
    // fr will increment whenever tim1 counter overflows
    h=TIM1_CNTRH ;
    f=h*256;
    h=TIM1_CNTRL;
    f=f+h;
    f=fr*65536+f;
  }
}

void delayms(int t)
{
 int d;
 while(t--)
 for (d = 0; d < 2020; ++d) ; //approximately 1 ms delay with 16 mhz clock
}

#pragma vector = TIM1_OVR_UIF_vector
__interrupt void TIM1_UPD_OVF_IRQHandler(void)
{
 fr++;
 TIM1_SR1_UIF = 0;
}

void InitialisePorts()
{
  PC_DDR_DDR7=0;  // pc7 as input
  PC_CR1_C17 = 0; // no pullup
  PC_CR2_C27 = 0; // no interrupt
}

void InitialiseSystemClock()
{
  CLK_ICKR = 0;            // Reset the Internal Clock Register.
  CLK_ICKR_HSIEN = 1;         // Enable the HSI.
  CLK_ECKR = 0;            // Disable the external clock.
  while (CLK_ICKR_HSIRDY == 0);    // Wait for the HSI to be ready for use.
  CLK_CKDIVR = 0;           // Ensure the clocks are running at full speed.
  CLK_PCKENR1 = 0xff;         // Enable all peripheral clocks.
  CLK_PCKENR2 = 0xff;
  CLK_CCOR = 0;            // Turn off CCO.
  CLK_HSITRIMR = 0;          // Turn off any HSIU trimming.
  CLK_SWIMCCR = 0;          // Set SWIM to run at clock / 2.
  CLK_SWR = 0xe1;           // Use HSI as the clock source.
  CLK_SWCR = 0;            // Reset the clock switch control register.
  CLK_SWCR_SWEN = 1;         // Enable switching.
  while (CLK_SWCR_SWBSY != 0);    // Pause while the clock switch is busy.
}

void config_counter()
{
 TIM1_CNTRH = 0;
 TIM1_CNTRL = 0; //Reset counter
 TIM1_IER = 0; //Interrupt disabled
 TIM1_SR1 = 0; //Clear Interrupt
 TIM1_CCMR2 |= 1<<0; //External pulse source T1C2
 TIM1_CCER1 &= ~(1<<5); //Rising edge
 TIM1_SMCR |= (7<<0); //External Clock Source
 TIM1_SMCR |= (6<<4); //T1C2 Input Source
 TIM1_CR1 &= ~(1<<0); //Counter disabled
 return;
}


texts: Electromagnet stays energized after being switched off

texts:
I've designed a circuit to turn on/off a 12V electromagnet but when I turn off power to the magnet it still has a magnetic force.  The magnetic force when OFF is not as strong as when it is ON but it still has more magnetic force than desired.  The electromagnet has no magnetic force before the circuit is powered up and current is applied to the magnet.  Is there a modification I can make to my circuit that will eliminate the magnetic force when the magnet is switched off.

The 100nF capacitor is to absorb flyback current caused by the coil into the switch which is actually a digital I/O pin of an Atmel 328p

simulate this circuit – Schematic created using CircuitLab


texts: Driving 7 segment displays through Raspberry Pi's GPIO

texts:
So I was thinking of wiring up four 7-Segment displays through the Raspberry PI.
I'd do that by multiplexing each of them, and came across this:
http://hackyourmind.org/public/images/display7seg_anim.gif

The thing is, I'm aware that I can draw (and sink) a max of 16 mA per GPIO pin. Therefore I can only have a max draw of 16mA for each segment correct? (assuming I don't use a transistor for each segment to draw power from the 5v rail).
So, if I'm only drawing less than 16mA at any given time, do I need those transistors to switch the multiple displays on and off? Can't I wire each of the common anodes/cathodes directly from the GPIO pins and just switch them high and low to turn them on and off?

EDIT: I'm also pulsing each of the segments of each display so I don't need 7 resistors per diplay and can get along with just using one resistor on the common anode/cathode and keep the brightness across different digits (is there a better way to do this?)


texts:
I'm designing a circuit board for a large industrial product which is intended to be UL certified, so the boss wants as many individual submodules to be UL certified as possible, including mine. The problem is, certification seems to be an impenetrable maze for someone who isn't an expert or doesn't have significant experience; every standard is locked behind a paywall, and there are no clear guides to which standards a given product even needs to meet in the first place. CE isn't quite as bad, a bit of googling tells me as long as my board is safe and doesn't put out much EMI, I should be good.

The board is a Power-over-Ethernet PD, the sole function of which is driving some stepper motors. I'm just trying to get some idea of what I need to take into account when designing the thing to give it a decent chance of passing certification.

In general, how is someone starting any new design supposed to find out what they need to take into account without paying large sums of money?


texts: analog ground and digital ground question

texts:
I'm designing a CCD control circuit and have some questions.

1.Should the ground in the 1st and 2nd position in the oval be analog ground or digital ground?

2.If they should be the DGND, whether the AGND and DGND should be connected through a passage or they can be isolated?


texts: Does it take/cost power when supplying in 3v to a "5v to 3v" regulator

texts:
I have a boost converter that converts 1.5v to 3v, and I have a ESP32 that takes a USB input of 5V and uses a regulator to convert it down to 3v.

If I provide 3v to the 5v input that goes via the regulator, is it the same as skipping the regulator and connecting it directly.


texts:
Background:

I'm trying to connect a Compact Logix PLC -> MAX232CPE Maxium chip -> arduino.
Currently my PLC does communicate modbus RS232 with a request for data from the arduino. I can see this by tapping into the serial connection and reading the output from a custom C program. The arduino has a RS232 library that should handle the request and send the reply back to the PLC. The MAX232CPE chip is intended to turn the RS232 signal from the compact logix to that in the format of TTL serial signal for the arduino by changing the voltages. The MAX232 chip is given a 5V source from the Arduino Uno with 1uF aluminum Electrolytic capacitors (i've made sure the polarity is correct). Additionally I have another MAX232 chip set up with .1uF ceramic capacitors. Both capacitors are rated for 50V. My setup follows the picture below:

Max232 datasheet link: http://datasheets.maximintegrated.com/en/ds/MAX220-MAX249.pdf

Problem:

The voltage levels for the 1uF capacitor set up goes as follows

 1uF capacitor voltages                       .1uF capacitor voltages
 Pin 1: 5.56V             Pin 16: 5.00V       Pin 1: 6.48V             Pin 16: 5.00V
 Pin 2: 6.16V             Pin 15: 0.00V       Pin 2: 7.67V             Pin 15: 0.00V
 Pin 3: 4.36V                                 Pin 3: 3.72V
 Pin 4: 4.78V                                 Pin 4: 4.43V
 Pin 5: 2.42V                                 Pin 5: -1.12V
 Pin 6: .937V                                 Pin 6: -3.65V

 Expected Values for pins 2 and pins 6
 pin 2: 10.00V
 pin 6: -10.00V

While the PLC sends out RS232 modbus the signal seems to get lost in the MAX232 chip. I've tried going directly to the Arduino but once it heads through the Rx Terminal on the Arduino, the values coming in completely change. I've changed out all my capacitors, flipped polarities, and tried changing out the MAX232 chip with the other 2 I have so this is not an issue of a bad part. Also when I connect the PLC and Arduino to the .1uF set up Pin 2 sometimes changes to 4.06V and Pin 6 changes to 3.64V. This happens when sending and receiving data. The set up for the .1uF is shown below

The Red wire is a 5V source produced by the Arduino Uno. - on the board is my common ground.

Questions:

How do I go about getting the pins 2 and 6 close to correct voltage levels?

Is there an easier way than using the MAX232 chip that is cheap and effective for this project?

Even with the .1uF set up being the closest Signal is completely dropped at the MAX232 chip

EDIT/SOLUTION:
Instead of using an LED I connected pin 15 directly to ground but this created another problem of the chip overheating. This overheating causes pin 2 to decrease while pin 6 becomes positive in voltage. To alleviate this problem I added a 200k Resistor to pins 10 and 8 as pull down resistors. This caused the voltage on pin 2 and 6 to be the expected value and prevent the chip from frying.


texts: Can I use GPS to synchronise two pieces of hardware?

texts:
I'm working on a project with multiple sensors. These sensors need to be synchronised with eachother as precisely as possible without a physical connection.
I need to make sure that if I tell them to start measuring that they start at the same point. If one starts 1 microsecond later than the other then all the measurements  will    be no use.

Im planning on using GPS to make synchronise the clock rates as being demonstrated here https://pdfs.semanticscholar.org/0529/00a69bbb3db6a615bfb14843a5bcf54292d5.pdf
So my GPS synchronises the relative time of the sensors, but can I also use it to synchronise the absolute time? so I can set a t(0) at the exact same time?


texts: Transfer functions with constant voltage sources in them?

texts:
I am trying to get the transfer function:
$$H(s)=\frac{V_o}{I_i}$$
For the following circuit:

simulate this circuit – Schematic created using CircuitLab

I think I can get it without \$V_2+R_3\$ by transforming \$V_1+R_1\$ into its Norton equivalent and summing the current sources together before retransforming them into the Thevenin equivalent and use standard RC blocks but even then I'm not sure: 1) whether the RC blocks can be done regardless of the impedance of \$R_2+C_2\$ compared to \$C_1\$ 2) if it's actually a transfer function (enabled me to wire it in Simulink at least).

And in the end, I do need \$V_2+R_3\$... Either way, I don't know what to do with those voltage sources to get the transfer function of the circuit.

Please advise?

Update

In the comments it's been suggested to use the superposition theorem. I tried that:

Converted both \$V_1+R_1\$ and \$V_2+R_2\$ into their Norton equivalent
Defined \$X_1=R_1||C_1\$ and \$X_2=R_3||C_3\$
Calculated \$V_o\$ for \$I_i\$ open and \$V_1\$ shorted:

$$V_{o1}=\frac{X_2 \cdot (R_2+X_1)}{R_2+X_1+X_2} \cdot \frac{V_2}{R_3}$$

Calculated \$V_o\$ for \$I_i\$ open and \$V_2\$ shorted:

$$V_{o2}=\frac{X_2 \cdot X_1}{R_2+X_1+X_2}\cdot\frac{V_1}{R_1}$$

Calculated \$V_o\$ for \$V_1\$ and \$V_2\$ shorted:

$$V_{o3}=\frac{X_2 \cdot X_1}{R_2+X_1+X_2} \cdot I_i$$

However summing all that up does not enable me to isolate \$I_i\$ to calculate \$H\$...


texts:
The club I am a part of at my school is currently trying to host a variety/dating show in which contestants will have the capability of controlling a button. There should be about 12 buttons to make in total, and these buttons serve to input a keystroke to a nearby computer (preferably wirelessly) to produce certain results in the show.

Specifically, there will be 12 contestants sitting on one side of a rectangular table, with a button in front of each contestant. Initially, there will be an "on" state for all of the buttons (maybe indicated by a physical light/lamp connected to the button or graphically on the computer).

Some ideas I had for this could be to take the IC chip of a cheap wireless keyboard, and soldering a Staples button's leads on to the wireless keyboard IC in such a way that it would send a certain keystroke when the button is pressed. Then I would have 12 bluetooth receivers connected to a USB hub, receiving the keystrokes. I have seen the wireless buttons that people have made, and are selling online, but they are expensive and require extra software, which also costs a lot of money. Is there any simpler solution to this? Will my idea be viable?

I got my idea from this youtube video https://www.youtube.com/watch?v=T2JCNLgubU0, but 12 of those keyboards sounds quite expensive, not to mention that they are discontinued and a newer model may not work for this idea. Is it possible to just buy the IC chip somewhere, or something that could produce the results I want?

I was thinking that in the video, the guy's idea is to use 5 keyboard IC chips to modify 5 separate buttons, but would it be possible to have one keyboard IC, and the buttons each soldered to different leads for certain keystrokes, that way eliminating the need for 12 IC chips in my case?..

Sorry if this is the wrong place to ask a question like this, but I am not sure where else to ask.


texts: How to protect electrical parts from heating coil

texts:
I'm trying to diy an electric lighter with a 3.7v lithium battery, an on\off switch, and a micro lipo usb charger.

Already connected the coil and everything works as expected.

The only problem I have is creating an enclosure for this thing. I want to try and make it the size of a USB stick or a key.

But I have no idea of what materials to use to protect the electronics from the heat. How far away do I need to mount the lithium battery?

Is there some coating or isolation I can add to dissipate the heat better ?

Am I over thinking it? (As an electric lighter is on for just a second or two and the heat generated is very short time wise)

Would making the enclosure metal help dissipate the heat? Or will the casing just heat up to an unpleasant temperature?

Help would be appreciated :-)


texts:
I have the following datasheet for a thermisistor:
http://make-documents.s3.amazonaws.com/UGulDNLaIajWgPom.pdf

I am trying to use the formula (found here http:// iwantmyreal.name/blog/2012/09/23/measuring-the-temperature-with-an-arduino-and-a-thermistor/):
$$
1/T=1/T_0+1/B*ln(R/R_0)
$$
I am not sure I'm using the correct values, my understanding is that the values provided in the datasheet are as follow: $$R_0=20,000 ohm,$$ $$T_0=25 C,$$ $$Beta=4300$$ Can anyone confirm that this is correct?

I'm trying to get a temperature reading out of that sensor using an Arduino UNO microcontroller using the following found at http://playground.arduino.cc//ComponentLib/Thermistor2 at the bottom where it says example #2 using numbers instead of episco k164 definition .... (substituting with the above values)

The results are ~41.96 degrees F, and the room is between 75-80 degrees F so that means the temperatures readings are way off, I don't understand why unless I got the wrong values from the datasheet. Also I have two of these sensors and both give about the same value.

Code currently using:

// Code obtained from http://playground.arduino.cc//ComponentLib/Thermistor2
#include <math.h>
// enumarating 3 major temperature scales
enum {
  T_KELVIN=0,
  T_CELSIUS,
  T_FAHRENHEIT
};

// manufacturer data for episco k164 10k thermistor
// simply delete this if you don't need it
// or use this idea to define your own thermistors
#define EPISCO_K164_10k 4300.0f,298.15f,10000.0f  // B,T0,R0

// Temperature function outputs float , the actual
// temperature
// Temperature function inputs
// 1.AnalogInputNumber - analog input to read from
// 2.OuputUnit - output in celsius, kelvin or fahrenheit
// 3.Thermistor B parameter - found in datasheet
// 4.Manufacturer T0 parameter - found in datasheet (kelvin)
// 5. Manufacturer R0 parameter - found in datasheet (ohms)
// 6. Your balance resistor resistance in ohms

float Temperature(int AnalogInputNumber,int OutputUnit,float B,float T0,float R0,float     R_Balance)
{
  float R,T;

  R=(1024.0f*R_Balance/float(analogRead(AnalogInputNumber)))-R_Balance;
  T=1.0f/(1.0f/T0+(1.0f/B)*log(R/R0));

  switch(OutputUnit) {
    case T_CELSIUS :
      T-=273.15f;
    break;
    case T_FAHRENHEIT :
      T=9.0f*(T-273.15f)/5.0f+32.0f;
    break;
    default:
    break;
  };

  return T;
}

void setup() {
 Serial.begin(9600);
}

void loop() {

 Serial.println("*************************");
 Serial.println("10k Balance");
 Serial.println(Temperature(0,T_FAHRENHEIT,4300.0f,298.15f,20000.0f,9770.0f));
 //Serial.println(Temperature(1,T_FAHRENHEIT,4300.0f,298.15f,20000.0f,9770.0f));
 Serial.println("*************************");

 delay(500);
}


texts: How is impedance matching for chip antennas practically done?

texts:
I designed a PCB for a GPS tracking device and i want to further develop it to have a smd gps antenna mounted on the board. I know that for optimal signal transfer i need to design a matching circuit, that generally depend on the design and geometry of the PCB.

So how would one actually do this matching? Is it done by a rule of thumb, simulations or trial and error?


texts:
For LCD, I have to make back-light voltage provision.
As per below image, LEDK1 to LEDK4 pins are internally grounded in LCD module itself.
But I have to add series resistor to limit current.

LED specification in LCD is as follows:

Is it good option to have common resistor to all LED's? What value should I choose if VF=3.2V (typ), IF-25 mA (max) for each LED.

What value of If should I consider to put it in below equation:
Rs= Vs-Vf/(If)?
Is it for single LED (25mA) or for 4 LED's (100mA)?


texts:
I'm working on 2000W furnace controlling with Atmega32a and an optocoupler with BTA40600 triac, my program is designed to heat up the furnace to 850 degree Celsius in one shot (always ON state til temperature reaches) and wait on 850 for 40 minutes, then heat up to 920 degree Celsius. everything is fine but after 10 cycles of working, triac eventually burns out and the furnace is lost control (after burning out, the triac is short-circuited and the furnace is connected directly to the main). I think the reason for triac fault is to remains ON state for 40 minutes at least, is it true? the alternative is to control the triac with slow PWM which means tells it to stay ON for 2 seconds and after that OFF for 500 ms.
if you have a different experience please share with me
by the way I use a large heatsink for cooling purpose of the triac

IGPIR.jpg

Actually, the best way to get over this problem to replace the triac and relative component with industrial SSR, I think 40 to 50 amps SSR is enough !!


texts: Serial Data Input through Microcontroller to Output Voltage

texts:
I am new here and new to programming, so I thought maybe some of you might be able to help me in the right direction.

I am looking to design a circuit that receives serial data from an RS232 port on my CPU, and input that into what I would imagine would be a microcontroller of sorts, containing a Digital-to-Analog converter. From there, based on the specific data from serial, output voltages to drive a Bar Graph LED meter.

In more detail, there is an audio recording program I am using that outputs MIDI metering data in groups of 8. I am able to convert those MIDI messages to serial messages, outputting via one RS232 cable. I would like to send this serial data to a microchip, and program that data to output specific voltages, per channel.

Lets say I have Meter 1 outputting serial data to a microcontroller. I would want to use the microchip to convert that data to a voltage, out of one pin of the micro chip. Since there are 8 channels of metering, I hope it's possible to have 8 separate pins, outputting 8 specific voltages based on its serial data input programming, to drive 8 separate LED Bar Meters.

The reason I am looking to convert to analog, is because it gives the meter a finer resolution. After lots of research on LED matrices (digital meters), this seems like a better solution. The serial data should have specific levels outputting, as does the converted MIDI data. I will be monitoring this in the near future to confirm. The LED meter circuits do accept analog input.

The initial plan to design a 'Midi Meter bridge', staying in the digital realm didn't seem possible after lots of talking and research. This is why I am exploring this route. Ultimately I am looking to have a meter 32 LED's tall, 32 channels across total... but using a digital led matrix, I haven't found that to be an option.

My apologies, when I refer to resolution, I mean this... designing a meter bridge via an LED matrix, the most resolution I can get is 16 LEDs. Even though, the MIDI protocol is 8-bit, allowing 128 steps for the meter. If it were possible to program a Microchip to output a specific voltage for every 4 steps, the resolution on the analog LED bar meter would look better than the MIDI matrix. Additionally, using my analog LED bar graph, I can add many more segments than I could with the matrix.

As an alternative, (noob here) looking at the analog schematic above, would it make more sense (or even be possible) for the PIC16f88 to accept the 'serial data' instead of the audio to control the LED meters??


texts:
I am building a project that uses a MCU to read data from various sensors every hour, and I'm aiming to use a RTC to wake it up.

The circuit uses two transistors that are controlled with the alarm flag of the RTC and a pin from the MCU respectively and when activated, both enable another transistor that powers up the MCU. It looks like this:

R3 is the load where the MCU would be.

This circuit works like this:

The RTC activates the switch that powers the MCU
The now powered MCU enables it's conroll pin to hold the switch open
The MCU tells the RTC to toggle the alarm flag

The circuit works as it stands, I put a resistor in Vout and the voltage is stable. The problems come when i plug the MCU to Vout, because when I do it the voltage starts to tremble and go up and down a bit which causes the microcontroller to reset every 2 or 3 seconds.

Have you had any issues like that? how could I solve it?


texts: What separates a "good" eye diagram from a "bad" one?

texts:
I'm running some USB verification testing at work, and the Agilent oscilloscope I'm working with returns a nice summary of pass/fail statistics along with a pretty eye diagram. Since the pass/fail is indicated within the scope, I don't need to do a ton of analysis on these diagrams.

I've looked at quite a few of these in the past few days and it's made me curious:In general, what separates a"good" eye diagrams from a"bad" one? In a lot of the tests I've run, the device failed, but the eye diagram looked very similar to one that passed.

I can understand a diagram where there are blatant crossings through the eye, but what other factors are taken into account when looking at these diagrams?


texts:
Has anyone come across a real manufacturer-supplied device model that I can use for testing an I2C master, in VHDL or Verilog?

I've had a look through the Opencores slave models, and the testbenches for masters, but there's nothing obvious - too many reported bugs, too little functionality, not documented, and so on.

EDIT

To clarify, what I'm looking for is a device model for a slave, which conforms to the I2C specification, ie. NXP UM10204. It would be nice if it contained R/W registers, as this will simplify testing. It would be nice if it could stretch the clock.


texts: I want to build a robot that will navigate over every spot it can in a room. But i thought some kind of a laser to map the room would be best or maybe a ultra sonic sensor. Could anyone guide me in a direction to learn how to do this or is there a better way to do this?


texts: How can we convert multi-input NOR gate diagram to a 2-input NOR gate diagram?

texts:
The question asks us to simplify the Boolean expression and implement it using 2-input NOR gates. I used a K-map and got the POS and drew the diagram without nor gates at first then replaced every OR with and OR-invert and the AND with invert-AND.Then I replaced the invert-AND with NOR. Lastly, I compensated the NOR bubble by complementing the output literal.

Problem: My diagram doesn't work since I used a 3-input NOR, I should use 2 input NOR.

Note:
W=A
X=B
Y=C
Z=C

My diagram:

Solution Manual:


texts: When routing power how is a safe current-carrying wire configuration determined with multiple wires?

texts:
I've been looking at a device/power-supply pair I was sent recently for a project.

The device specs say it needs 24V and will draw 10A max.

The power supply provides 24V @ 9A (14A peak).

The power supply has 3 posts for V+ and 3 posts for GND (call them V0, V1, V2, G0, G1, and G2 respectively).

The cable that was supplied bundles 14 24 AWG wires, connected into a molex receptacle such that 2 wires go to V0, 2 to V1, 3 to V2, 2 to G0, 2 to G1, and 3 to G2.

I looked at a load-limit table for 24 AWG wire and it says that for chassis wiring, the wire is rated for 3.5A max and for power transmission 0.577A max.

Since the device can draw up to 10A, clearly a single piece of 24 AWG would be too small to be safe in this configuration.

The only conclusion I can draw from this is that using 7 wires across 3 terminals spreads the current load out such that 24 AWG is safe.

My questions, if you've managed to get this far are:

1) What is the calculation to determine the correct minimum number of smaller gauge wires to use in such a setup (i.e. where you're replacing a single larger wire)?  Is it simply max current draw / number of wires?

2) How is the voltage drop due to the wire length calculated when using multiple wires (I know how to do it with one wire)?

Thank you!


texts:
I am writing some RTL for IPs for personal learning. Right now, they don't implement any bus interfaces for communicating between each other. I was looking around and thought about implementing the Wishbone bus protocol as it is doesn't look to complicated.

I have a question regarding what exactly master/slaves means in the context of bus interface. Is it fair to say master makes request for data and slave responds to the request? Can slave make a request?

Also if I have 1 master and say 5 slaves, the master IP can communicate with ALL of the slave IP, but the slaves can only communicate with the master and not between each other (unless they go through the master?)? Thanks.


texts: I have attached the problem together with the solution I have with me. I am facing problem deciding status of 2 BJT's. Please give me a generalised approach to tackle such problems.


texts: Trying to choose a high current DC/DC step-down converter

texts:
I'm working on a project that will drive a long length of LED strips, the WS2811 kind built into 5050 LEDs on a flexible strip. I've got most of the project worked out, except for power. Since it needs to be completely mobile, I'm trying to figure out how to run the strips at full power off of a large battery (probably from an RC car or something).

My problem here is that the strips I want to use run at about 3.6A @ 5V max per 1 meter (All LEDs showing full brightness white). I'm hoping to use as much as 10 meters for this project... so you can see where this is going :P

Mind... It's obviously NOT going to be running at full current all the time, but I kind of what the option to run it at full for a few seconds if I want to.
I've used these strips before and under normal use they were drawing maybe 25% of max on average. But I will probably have 10 roughly 1 meter lengths, so I would either need a really big 36A DC/DC converter or like 10 4A converters.

Is there any decent component out there that:

has minimal component count - some switching converters I've used also require all sorts of other stuff - inductors, caps, etc. I'd like to keep my part count per converter low
can do at least 3A each, preferably 4-5A
won't completely kill my budget (I'd prefer less than $100 for the power conversion system - not including batteries).

Also, in doing something like this I know that a linear regulator is going to be more efficient if input V is closer to output V, but with a switching regulator does that matter as much. Like would I be better off going with a 7.4V RC battery than a 12V version?

Any suggestions on a component?


texts: Does anyone know what it is about each logic gate that makes it "and, or not xand, etc." like, is it a different shape, therefore causing electrons to go different places when a charge is applied through it? As in I'd like to know what they look like under a microscope to know why a gate is what it is. Thanks


texts: Op. Amp instead of Push pull stage as power amplifier

texts:
I have been going through the push pull stage as power amplifier. Even though the gain in this topology is less than 1, still people use it. I am assuming this is because in emitter-follower OR source-follower topology the input impedance is high and output impedance is low, that is why we are using these stages as power amplifiers.

BUT, operational amplifiers also depict the same characteristics, and hence I believe can be used as power amplifiers.

So why the book does not discuss op-amp as power amplifiers? Does op-amp lack something to act as power amplifier?

Can anyone be kind enough to throw some light in the above thinking.


texts:
This photo output from Mentor Graphic layout pdf output, when I click to component, there is information about component. But in altium, I can not make that.
Do you have any idea?


texts: Starting the 5.5kva Kipor diesel generator from a distance

texts: How can I start my kipor 5.5kva diesel engine generator from a distance of about 30m? I would like to avoid going outside my house to access the ignition key panel but just start from the comfort of my house.


texts:
This assignment we have been given has been causing me major headaches. I feel like I'm finally close to getting this amp to work after hours of fiddling around, but now I've found the output is clipping at a very low voltage. It must have a differential input and a class AB output. Minimum of 1500 voltage gain. Stability and wasted power aren't a concern, as long as I can write up where power is lost.

I'm sure there's enough base current, and don't think there's any loading, but there is no voltage swing available at the output.

What is causing this clipping?

I'll buy a pint for anyone who can get this thing to work. I want to understand where I'm going wrong, I just can't work it out for the life of me.

Thanks for looking!

EDIT:

Scope with DC coupling shows the following waveforms. The left hand one is the base of Q11, and the right hand side one is the load output (before cap). It seems like together they make a full sine wave.. What is going on???

Edit 2: Here are both waveforms on the same scope: red output, blue input to Q11.


texts:
I just started circuit analysis today and learn't about Kirchhoff's Laws.

Its pretty straightforward, but in all the examples my book gives they already specify the direction of the current and the end of the branch with the higher voltage.

For example,

there arrows everywhere indicating the direction of the current at each node and  +/- signs indicating the end of the branch with a higher voltage.

Obviously, when actually designing stuff the direction of the current and the side of the branch with the higher voltage wouldn't be indicated.

So what I'm asking is:

1) Can Kirchhoff's Law be used to figure out the direction of the current and side with higher voltage?

2) If not, do techniques exist to find the directions?

Please note that I'm not talking about convention. (i.e. currents flowing into the node are positive and currents flowing out are negative etc.) You can't just have a convention because you can't differentiate which direction the currents or voltages are going.