texts: Tranmission line equations when initial conditions are not zero

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A high voltage DC line is in steady state sufficiently long time after applying 1 MV at the input terminals through a DC voltage source of 30 ohm impedance with an open circuit at the load end. The characterstic impedance of the line is 20 ohms. The line length is 1000 Km. The line capacitance is 0.2 nF/m. The line may be treated as lossless.
To this charged line a 30 ohm load is connected at t=0 . Find an expression for the voltage on the line after t = 0 at various points on the line with usual labeling : position of sending end is –L and load end position is 0 and any arbitrary location is –
I cam across this question my college assignment, I couldn't solve it any suggestions how to solve it? Any reference material?


texts: How to check Leakage LEDs in a LED Matrix

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Is there any method to check the leakage LEDs in a LED matrix?

I’m building my own matrix by using unbranded cheap Chinese OVAL LEDs. They have no datasheet/specs.

*Some LEDs lights up but take lots of current (like a short circuit).

*Some LEDs current passes when they are reverse biased.

Due to the above scenarios, when my matrix working I see inactive LEDs lights up slightly.
I tested individual LEDs by using an analog multi-meter(X1K range).

*When I see the pointer moving both sides, then the particular LED has a problem. I replace them.

*Some LEDs I see the pointer moves more than others, means it takes more current than other LEDs. I replace them as well.

Now the problem vanished & I get a nice display.

I have 512 LEDs in each matrix block, Is there any easy method to check those leakage LEDs in a matrix?


texts:
I've got one of these cabinets, which I intend to use for storing electronic components:

It has 24 drawers (each 175 x 69 x 37mm).

Every drawer can be subdivided into up to six compartments by installing dividers.

Can you suggest a good system for organizing resistors, capacitors and suchlike into the limited number of drawers that's available?


texts: Using a boost or buck converter for a transient load?

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I have a 12V 270mA electric strike door lock that will only act as a load when unlocking.
The control system for this is a 5V Raspberry Pi zero

Which would be more prudent to use?
5V supply and a boost converter to supply the lock
or
12V supply and a buck converter to supply the Pi

My current thinking is to use the buck as the boost will try to run even with no load


texts: circuit boards, what are the numbers next to the component e.g. C156 next to SMD. capacitor

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I'm trying to buy replacement smd capacitor on a tablet circuit board. I don't know the value of it, can the number next to it on the board help. The number on the circuit board next to the one I need is C156.
Any help would be great. Thanks.


texts:
I usually buy electronics components at an online surplus store and they usually throw in the box some more goodies to pack what you order.

I bought a multi section plastic container and it was filled with all sort of components, and this one in particular intrigues me. Here is a photo:

They seem to be transistors, maybe their odd shape is because they are RF or something...

Some "old school" guy that has used them?


texts:
I am attempting to built this circuit here:

It is used by an LED manufacturer to provide pulses to a high-power LED. In my case, I'm using an ARDUINO to provide the TTL signal. I haven't sourced the other parts yet as I'm trying to understand the system first.

I'm a bit confused as to how to calculate the current through the LED. I assume I can change it by varying the resistance (R) and the LED voltage source (V-LED) but I'm not sure what the relationship is, I was wondering if it was dependent on the drain-source current? I've been reading up on MOSFETs/drivers but I don't know how/if it relates to the current through my LED.


texts: hacking a flash light - what's the resistance required for this group of LEDs?

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We have a bank of LEDs from a flashlight that plug directly into 4.5v. There's 8 LEDs on a circuit. I'm trying to get them to run off a 9v battery by just connecting the wires from the circuit board (it works fine when connected to 4.5v battery pack). So basically I just need to put a resistor in between the 9v battery and the circuit, but I'm not sure which one to use and I don't want to blow the LEDs.

I tried a 270ohm resistor, but they would not light up. I'm thinking that I probably need to add the diode forward current of 20mA together, which would be 160mA, (as there are 8 LEDs in the circuit) this would mean I should use a 33ohm resistor? Is this the right way to think about it?

Can anyone confirm that a 33ohm resistor would make sense in this case, or do I need a different one? It's for a child's project and I don't want to just test it and risk blowing them.

Thank you!

Here's some photos.


texts:
I want to design on-chip antenna (that is, antenna on PCB itself). Is it also called microchip antenna ?
Can anyone provide me details and/or steps as to how to design on-chip antenna? How to proceed designing it? (Question 1)
I want to design my own PCB having an on-chip antenna for GPS module. It is possible, right ? (Question 2)
See below image of sample on-chip antenna design in EAGLE:


texts: Altium Short Circuit Undetected Between Layer

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I designed a PCB a few months ago, and after prototyping we have found a short circuit between a via and an internal power track. For an unknown reason I didn't see this problem earlier and when I reopen the PCB layout file I still don't see any mark from Altium indicating this short circuit. What I have done to see this short is to un-tent the via which was tented.

Does anybody know why Altium didn't indicate this short circuit to me before? Normally I run the design rule check so I am a bit amazed that I didn't catch this one. I attached two screenshots of the issue I had. One screenshot is taken immediately after reopening the layout file, and the other shows the violation I got after un-tenting the via. I didn't touch any design rules between the two pictures (I just un-tented the via)


texts:
As a homework assignment, I was given to design a simple vending machine circuit as follows

Receives 5 cent, and 10 cent one at at time.
20 cent per snack, gives change when necessary (IE, 25 cents, gives 5 cents back with a snack)
Once snack is given, it goes back to it's original state.
Requires asynchronous reset. Resets at active low (back to initial state), and forces to give out any change. At active high, operates normally.
3 Inputs (D, N, R) 2 outputs (Snack, Change)
DN (00) specifies no coins, (01) specifies a nickel and (11) specifies a dime

I have completed everything from state tables to drawings but it's VERY complicated and I don't think this is the best way of doing it. Here's what I did

State Diagram

State Table

The circuit was designed using a JK flip flop, D flip flop and T flip flop. (Had to use these because said so) and I end up with 32 situations that I have to account for which made the circuit very complicated (Could not use k-maps T_T). If anyone can give me an idea on how to simplify (not for the sake of homework, for my own knowledge as well), or rather reduce the amount of material in the truth table, would be great. Also I don't know how to integrate the asynchronous reset properly. If anyone needs any more information I'd be glad to give it to you.


texts: Converting parallel printer switch into USB KVM switch

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cable and switch http://ibb.co/dDctkk

http://ibb.co/dDOAWQ)

Quick preface, I have nothing but rudimentary EE education, only what I may call "common sense" sort of knowledge.

I have 3x serial (or parallel, actually) switches, used for printers at a now defunct call center, the entire centers' equipment which I inherited via Craigslist last summer.

Two switches are 25PDT switches in a big box and the third switch is a fancy PCB switch, shown in pictures.

I have an FTP server running in Windows 7 on one PC and Debian Jessie on a separate system, and I am getting tired of switching the USB plug when I want to switch systems, so I thought I could use the parallel switch with USB wired in to accomplish this task. All wires and all circuits have shown connections, as tested with a *-rigged circuit tester I made - - the Led lights up.

The problem is that there is no connection when I put the switch into the loop. Is anyone able and willing to help me troubleshoot?

That is about all I know to inform you with. If there is any further pertinent information, please allow me to update my question with said information.

Thank you if you have read this far, as I know I can be verbose to put it


texts: 12V DC to 5V DC with an output current of 2A

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I'm trying to convert 12V to 5V using cheap parts; zener and transistor.

Now I want to gain the output current to 1A or 2A, I want to use this circuit to make mobile charger

Any ideas and if there any improvement to this circuit?


texts: What kind of material is this and what is the purpose of this?

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In 500 GB or higher capacity HDD's, you can frequently find these black things (see photo below). It is made from a very weird feeling material. It is not made of plastic, it has a dull glass sound when hitting something, it is not painted black iron/steel/aluminium, it is not ferrite (a magnet cannot pick it up), it is very strong, very light and very conductive.

What is this kind of material and what is it used for, shielding? I ask this because this part is not described anywhere. It seems a latest addition, does not exists in earlier lower capacity drives.

Any ideas?


texts: Is it possible to derive a custom boolean function from a truth table in terms of known boolean operators?

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And how would one do so?

I'm doing a programming project that requires me to propagate input signals through a circuit consisting of different types of logic gates. One of the gates I need to implement is a custom one whose truth table is:

+---------+---------+---------+--------+
| Input 1 | Input 2 | Input 3 | Output |
+---------+---------+---------+--------+
|       0 |       0 |       0 |      1 |
|       0 |       0 |       1 |      1 |
|       0 |       1 |       0 |      0 |
|       0 |       1 |       1 |      0 |
|       1 |       0 |       0 |      1 |
|       1 |       0 |       1 |      0 |
|       1 |       1 |       0 |      0 |
|       1 |       1 |       1 |      0 |
+---------+---------+---------+--------+

I'm not terribly familiar with boolean functions, digital logic, etc. so any help or insight is greatly appreciated.


texts: (Ultra)capacitor Series vs. Parallel with (Buck-)boost converter

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I've seen that many online schematics for using ultracapacitors as power sources place the ultracaps in series in order to increase the voltage that they can be charged to, lowering the capacitance of the circuit drastically while preserving the total energy. For example, 5 pieces of 2.7v 100F capacitors might be placed in series, bringing the voltage rating up to about 13.5v and the capacitance down to 20F. Now, ultracaps can't be used as direct replacements for batteries since their voltage drops quickly. So they'd need a buck, boost, or buck-boost converter to utilize the full capacity. For this example, let's try to get 12 volts at 750mA. Would it be more efficient / get more energy out using a buck-boost converter with a 13.5v, 20F setup, or using a boost converter with a 2.7v, 600F setup, or a 5.4v, 300F setup, etc?

Edit: Sorry, I meant for these setups to include balancing systems.


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I'm designing a circuit in Eagle and I need to have fixed dimensions on certain holes. I can of course use the dimension tool to measure the distance but I don't see a way to make the dimension "stick" to the hole I'm designing.

Is this possible? So that I can make the dimension tool measure from the hole to the side of the board and then when I move the hole the dimension follows?


texts: How to design inductor for non-isolated boost converter?

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I am trying to design an inductor of 500uH for non-isolated boost converter from following data.
Input voltage Vin=330V DC,
Maximum duty ratio Dmax=63%,
Switching frequency Fsw=30kHz,
Saturation flux density=0.4 T,
Maximum flux density Bmax=0.2 T,
Peak current Ipeak=70 A,
RMS current Irms=50 A,
Current density J=5A/mm^2,
Min conductor area required Acond=Irms/J=10 mm^2.

I have selected 4 stacks of  EE80/38/20 core (N27 material),
So Core area Ae= 1552 mm^2,
Window area Aw=1080 mm^2.

1.
I know

L=NBmaxAe/Ipeak,

N(turns)=LIpeak/(BmaxAe).

I am getting approximately 112 turns.

So total bare conductor area=N*Acond=112*10=1120 mm^2

Excluding Window area utilization factor (Kw)

So winding is going out of a window.

2.
I know one more relation of calculating the minimum number of turns.

N=1000*SQRT(L/AL)

If I consider AL=0.5 mH/turn  (Am I considering this wrong?)

then, N=1000*SQRT(500u/0.5) =32 turns

And now required bare conductor area =N*Acond=32*10=320 mm^2

By including Kw and increasing awg of winding it can fit into a core.

I am not getting where I am going wrong here?

link to Datasheet of core is Datasheet of core


texts: How to measure the current of a high voltage CO2 Laser?

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The manufacturer of the CO2 Laser tube instructs to put an amp meter on the low side of the laser tube for calibration. While I understand the amp meter will only see a few milli volts above ground; the tube will be at 19kV @ 26mA.

Will any amp meter work for this?Is it safe to leave the current meter in the system after calibration for monitoring?

Should I put a zener diode or some sort of protect around my amp meter? If I used a hall effect current sensor and attached the output to a controller board would I need optical isolation?


texts: Led strips power supply , consumation and contorller

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Hello everyone  i am really bad at this stuff, i tried reading a few articles but i can't seems to understand anything.

So basically i bought the LED strips from aliexpress that came without power supply or remote, which i didn't know is the way the guy sells them.

So i wanna buy the controller and power supply, but i don't know what and which one.

I also read the feedbacks and they say so many different things

https://www.aliexpress.com/item/Free-Shipping-SMD5050-12V-flexible-light-60-leds-m-LED-strips-5m-lot-White-Blue-Green/1599651146.html?spm=a2g0s.9042311.0.0.11b34c4dcaUpUC

here is the link of ones i bought, what i know from the name, and what you can know is that they re 5050, they have 12vDC. but i don't know how strong power supply i need for them

I bought RGB ones with 4 pins. and i have 10 meteres of them.

Also for the controller does that also need to be different W or A , or i can buy any ?

From what i also saw on other people post is that the small black things on the strips are important. on them it says 151. and i don't know if that is 331. or it's E letter, but you can take a look .


texts: Low power temperature logging to an SD card

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I want a make a low-power data logger, for now just to read a digital temperature sensor (DS18B20) and write the data to an SD card. The device will be asleep most of the time and just wake up from time to time (once every minute or every five minutes) to do a reading.

I thought of using the MCP1640 boost converter and an ATmega328P like this:

The idea is to keep the sleeping AVR powered directly from two alkaline batteries and then, when I need to take a reading, power up the MCP1640 to boost the Vcc to 3.3 V and also power up (via the PNP transistor) the SD card and temperature sensor.

After reading and storing the temperature, the AVR should power everything back down and go to sleep (I got the idea from Microchip's AN1337. At some point in the document they show a microcontroller boosting its own voltage up and using a capacitor to power itself while in sleep mode with MCP1640 disabled).
In my drawing, only one PNP transistor is shown, but I might use two (one for the temperature sensor and one for the SD card) and do buffering of the reads (to reduce the number of writes to the SD card).

I also plan on using the internal ATmega oscillator at 1 MHz and an external 32768 kHz clock crystal for time keeping.

What is not clear to me (and I'd like to find more before ordering the parts and start prototyping it):

Are there any potential issues with the AVR switching its own power? Basically Vcc will be fluctuating between the Vin (3.4 V with fresh batteries down to 1.9 V when discharged) and 3.3 V for a short while. That means the voltage at the reset pin (tied to Vcc via a 10 kΩ resistor) will do the same. Can that cause a reset? How about the clock crystal, will the cc fluctuation influence it in any way?
MCP1640 is rated for 350 mA maximum output current. Will that be enough for the SD card?
Also, another thing which isn't clear to me: right after powering off the SD card, it will still have 3.3 V at its Vcc pin for a short while (since I plan on having 100 nF + 100 µF decoupling capacitors there). During this time, the AVR is powered from, let's say, 2.2 V (not new batteries), so at the AVR pins connected to the SD card there might be a voltage higher than the microcontroller's Vcc... I thought to keep the MCP1640 still powered on for a short period after shutting down the power to the SD card, to allow the capacitors to discharge. Or, discharge the capacitors (via a resistor) through one of the AVR pins. Will that be enough? Or do I worry too much about a small voltage difference?


texts: Loop Controlled v. Full Swing Pierce Oscillator

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I am going to be working with the Freescale MC9S12XE processor and trying to figure out the oscillator configuration. They offer the following options:

Loop Controlled Pierce Oscillator

Full Swing Pierce Oscillator

They recommend the Loop Controlled for most situations but suggest the Full Swing for high frequency crystal operation.

The documentation states the following about the general Pierce Oscillator and noise immunity:

  The XOSC will contain circuitry to dynamically control current gain in the output amplitude. This ensures
  a signal with low harmonic distortion, low power and good noise immunity.

  • High noise immunity due to input hysteresis

But it does not say if one configuration offers more noise immunity over the other.

My question is, would one of these configurations offer more noise immunity than the other? Why or why not?


texts: changing 12v halogen lighting to 12v LED

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i have an old project that is causing the client current problems. installed was 12v halogen lighting 10w bulbs,G4 base, multiple lights, buried cabling, multiple transformers from 120v to 12v. client is interested in swapping to LEDs and i understand the halogen transformers will not successfully run the LEDs due to flickering and burn-out issues. there are 7 different lines, in two distribution blocks, run by 2 transformers, 4 and 3...
i am at a loss on how many transformers, resisters, etc. to use to power the "new" LED lighting...


texts: When to factor duty cycle into power consumption calculations?

texts:
This is probably a simple question for most of you.

I am calculating the power consumption of a device. The load is driven using a square PWM signal. At what point do I factor in the duty cycle? For now let's assume a 50% duty cycle with a starting voltage of 10 V, resistance of 1 ohm (for simple maths).

Currently the calcs look like.

Effective Volts = 10 * 0.5 = 5 V.
Watts = 52 / 1 = 25 watts.

Instead should I be doing:

Watts = 102/ 1 = 100 watts
Effective watts = 100 * 0.5 = 50 watts


texts: TI MAX3237 TTL / RS232 transciever, transmission not working

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I've got a TI MAX3237 5 TX / 3 RX transceiver (TI datasheet, Maxim datasheet) set up as follows:

The supply is 3V3 from a BeagleBone Black, measured at 3.35v. The CMOS level inputs and outputs (T1IN, T2IN, R1OUT, R2OUT) are taken out to headers, where I can connect them as desired.

The receive part of the transceiver is working great. I can put an RS232 level signal on R1IN / R2IN and receive a level shifted version on R1OUT / R2OUT. I've confirmed this both by looking at it with a scope, and by actually hooking the outputs up to a UART and receiving data.

The problem is transmission. Putting a signal on T1IN results in nothing on T1OUT - literally. The signal level is at 0V. Channel 1 (yellow) is the UART output, and channel 2 (green) is T1OUT. (this is with the output also connected to a RS232 receiver - with the receiver disconnected the result looks the same)

I've measured V+ and V-, which seem to be at 2.37V and -2.37V respectively; while the datasheet claims they should be 5.5V and -5.5V. Could this be the problem? If so, what could be causing it? I'm using non-polarized ceramics as my capacitors.


texts: Are there any dedicated chips for measuring logic supply voltages?

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If I reboot into my PC's BIOS/UEFI I can get "instantaneous" readouts of its 12/5/3V3 voltages to 3 decimal places.

How is this classically done? Is this just a classic resistor divider into an ADC on a chip like the PCH, or is there a dedicated power-bus-checker IC? I'm working on a design and I can't seem to find anything that does this as an all-in-one chip.


texts: system and properties of linearity,causality, time invariance, stability, invertibility

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I have a system and I want to find which properties hold for this system

$$
  y(t) = \left.\begin{cases}  x(t)
& t \geq 1 \\ \\ 0 & -1 < t < 1 \\ \\
  -x(t) & t \leq -1 \end{cases} \right\} \\ \\
$$

is the system linear, time invariant, causal , invertible, stable?

My problem is that I don't know how to work, because the function is piecewise defined.If I try to prove for example that each piece of function is linear then the whole function is linear ? With this methodology I found that the system is linear, causal and stable.Am I right?


texts: How do I store and transport microcontroller boards safely?

texts: I'm looking for a carrying case for my various electronics components, mostly various microcontroller boards (Arduino, Teensy, etc). I've seen a lot of people use plastic tool boxes, sometimes with foam inserts. Do these present a problem with ESD? Is there a particular type of plastic I should look for that has lower static buildup?


texts:
Hello there I am trying to solve a question and in the question I have a system with two complex conjugate poles. The question asks me to analyse the Maximum % Overshoot, Settling-Peak-Rise Time and Damping ratio if those poles were moved to the left. Here are my conclusions:

Natural frequency (wn) increases since the radial distance of the poles are going to be greater. Angle theta is going to decrease.
Since theta decreases damping ratio (zeta) is going to increase since it is equal to cos(theta).
Maximum percent overshoot is going to decrease.
Settling time is going to decrease.

I could not reach to a certain conclusion about the Peak Time and Rise Time. I know that Peak time is equal to pi/wn.(sqrt(1-zeta^2)). And I also know that Rise time cannot be calculated directly.

Can you help me with that?

Here is the question:

I am of course not trying to get the answer. I am just trying to get some feedback.


texts: Shown in the image are the solder points corresponding to the two terminals of a JST-PH connector. (Jumper is there as a size reference). They are way too close for comfort for me, especially with potentially catastrophic consequences of shorting a LiPo. How can I reliably insulate them?


texts:
I'm trying to make a 7 to 3 priority encoder for a circuit diagram for a class.  The problem is that we have to take in a 7 bit number and output a 3 bit answer representing the maximum number of consecutive ones in the input.

Example:

0011100 = 011 (3)
1111111 = 111 (7)
0000000 = 000 (0)

The issue at the moment is that regardless of the input, it is always outputting 111 (7).

I have circuits for handling every possible combination of consecutive ones in the input, and am then piping that into a 7 to 3 priority encoder, but for some reason the encoder is not working the way it should.  What am I doing wrong?  Or is there a better way that I should be doing this?

Original Circuit diagram:

Attempt 2:


texts:
I recently found a dead laptop battery and disassembled it, found 6 batteries of CGR18650. So when I checked with them my multimeter, they had quite bit of voltage. So I decided to charge them, since I didn't want to spend money for a charger, I decided to make one. found This, I made it and now I'm able to charge my batteries. I'm watching charging current using my multimeter. So I found LM339N voltage comparator IC inside a broken power-supply and the IC is working.

Here's the sketch of charging circuit,

So how do I modify my charging circuit with LM339N, I'm not an expert in electronics. So my knowledge is limited. Since I don't want my multimeter to be connected with the battery to measure current, I want to make some led bulbs glow when the charging is completed.


texts: Measuring direction of a three phase motor (400VAC, 50 Hz) within a 5V-circuit

texts:
I've got a lot of motor controller boards, without the actual motor, and I'm interested in measuring at the output terminals (U,V, W) to see if there's any voltage. This to just check rudimentally if the boards work.

Since it's three phase output, I also need to check the phase order: U-V-W = forward, W-V-U = backward.

The actual direction is simple to test with a small PIC, but how can I reduce the dangerous voltages to a 5V compatible level? I don't think relays will work due to the fast switching (and tremendous amount of noise), so is there any other safe way?


texts: Does solder stick to tin? (not aluminum)

texts:
Will regular leaded(or non-leaded) solder stick to actual tin or tin foil? Does the tin have a low enough melting point that it'd melt along with the solder? Has anyone actually tried soldering copper to tin using regular solder?

(I tried googling, but everything I found seemed to be about tinning a soldering iron)

Edit: Note I was talking about the actual metal Tin. I realize that most "tin foil" is actually aluminum and you've given me some useful information about aluminum but what about actual tin?


texts:
I'm implementing a radio in Verilog. the time taken for bit reversal while computing the FFT is more. it is almost equal to a symbol time (OFDM system). Can I use a FFT library in C, which can be integrated to the code, to speed up my simulation?

If so, can these codes be used for an FPGA in real time?


texts:
I'm using the ADS1675 ADC in a project of mine. It has a differential input which is +/- 3V. I'm confused by the datasheet that says the recommended common mode voltage is 2.5V. Why would you want a common mode voltage in a differential signal? And this is essentially just a DC offset right, so the actual input range relative to the ADC ground will be between -.5V and +5.5V?

So essentially I will need to add a 2.5V supply or reference and use that as ground for the input stage as in the picture below?

Also they use -4V and 9V as the amplifier rails. I get that this is like +/- 6.5V raised by 2.5V.. So would I just use the 2.5V reference as ground for a +/- 6.5V supply?


texts: Help me add outputs from a two 3 to 8 decoders

texts:
I have built two 3 to 8 decoders, so that I can get an octal output 0-7 from each.
Now, I need to be able to add these outputs to determine wether a number is greater than 7 or not.

I have tried to come up with several solutions but I am just stuck. Can someone give me some directions please. Also I can only use the basic logic gates (OR, AND, NOT). I am using logisim to test.


texts:
I'm hoping there's an HDMI guru in EE.SE. I'm having some difficulty getting an HDMI 2:1 switch working. I'm using TI's TS3DV642, which is made for muxing HDMI and DVI signals. My project needs to be able switch between two HDMI sources and display the selected source on one HDMI sink. Both sources will be consumer electronic-grade HDMI cameras. For simplicity, let's just say I've got two GoPros and I want to be able to switch between them to display one of them on an HDTV screen.

I made a test PCB and it failed. I get no video on the display or any indication that the display even realizes there's something plugged in. Unfortunately, I don't have access to a high-speed oscilloscope right now, so I can't directly probe the HDMI TMDS lines.

Here's my schematic and PCB layout for visual reference. Also, here are the Eagle .sch and .brd files to download directly from my dropbox:
https://www.dropbox.com/s/0p61i8b9muy42pb/Vid_Switch_QuickTest.brd?dl=0
https://www.dropbox.com/s/7ax6id4ko8cnw1n/Vid_Switch_QuickTest.sch?dl=0

The left-most and right-most components in the schematic are the HDMI connectors (labeled "GoPro1", "GoPro2", and "HDTV"). Of the two IC's in the middle, the taller one is the 2:1 mux. The other one is a TPD12S016, which provides ESD protection and level shifting for the HDMI signal lines.

Since I don't have the right oscilloscope for the job right now, I'm focusing on the signals that I can see, namely, the HPD and I2C lines. I'm hoping someone that has a deep working understanding of the HDMI spec can point out an error in my design. Here's my considerations, troubleshooting steps I've taken so far, and questions:

I connected the GoPros I'm using directly into the HDTV to verify the HDMI cables are good and the display is compatible with the source. I've also tried several different kinds of HDMI displays and they all exhibit the same behavior.
I designed the schematic to have pull-up/down resistors on the SEL1/SEL2 pins of the mux so that it defaults to input A, which is "GoPro1" in my schematic.
I verified that the HPD pin of the GoPro1 connector goes high (~4V) when I plug in the HDTV connector and low when the HDTV is unplugged.
I verified the HDMI connectors on both sides have a steady 5V power source on the appropriate pin when everything is plugged in.
I initially found a weird problem with the SDA line of the DDC I2C port. At the HDTV connector side, the SDA signal looked good. Nice square waves that went from 0V to 5V. On the GoPro connector side, however, the signal achieved 3 different voltages: 0V, 2.5V, and 4V. The yellow line is the HDTV side and the blue line is the GoPro side.

It looks to me like a resistor divider is happening in there somehow. Since the TPD12S016 buffers the I2C lines, I suspected it was the problem. I lifted the relevant pin off the board and green-wired the SDA line directly between the GoPro1 and the HDTV connectors. Now the signal looks clean across the board. Can anyone suggest why it occasionally floated at 2.5V like that?
Is it correct to assume that an integrated consumer video device (like a GoPro) would take care of the pull-up resistors on the DDC I2C port?
I understand the DDC I2C port is used by the sink to tell the source about itself and vice versa. When I have a GoPro and the HDTV all connected, I see a continuous stream of I2C communication on the SDA line. Is it typical for the source and sink to continuously talk to each on the DDC port while connected? Or is that a sign that one of the devices is trying over and over to communicate but the other side isn't responding? I'm wondering if maybe the HDTV is waiting until successful DDC comms before it allows the video to be displayed.
Assuming the TMDS signals themselves are getting through (which I have no way of verifying right now), are there other common reasons that the HDMI sink will refuse to show the video stream?


texts:
I have an electromagnet (just a nail and wire).  I linked the nail/wire to 1.5 AA battery, nothing.  9V and 12V, nothing.  I then linked the nail/wire to a 6V lantern battery and it picked up the filings.

My question is, why did it fry the copper wire?  The other, higher voltage batteries (new) did not.


texts: How to reset / clear IRQ requests in AX5043

texts:
Has anyone gained experience with Onsemi's RF Transceiver AX5043?! I'm not able to clear the interrupt request Bits. For example my XTALREADY interrupt is fired immediately after reset and fired again and again when I activate the related interrupt mask. There are some interrupt inversion registers but they do not take effect.

http://www.onsemi.com/pub/Collateral/AND9347-D.PDF

Thanks in advance!


texts:
I have used MAX232 as UART serial line driver using 5V power supply. Now I have come across TRS202 chip in a circuit. It also run with 5V power supply. Does this chip has some special difference or is it replaceable by MAX232 chip?

Edit: correction in above info.


texts: Designing Or Customizing A HDD/SSD Logic Controller

texts:
I read this post which answered most of my questions, but was a bit disheartening. So, this one may need to be deleted. I have also done my other research looking through articles like this.

Is it possible for a single person to design (or at least partially design/customize) a hard drive?

This may have been off the table for rotating drives since there was lot more physics and precision measurements involved, but I am thinking that with an SSD, the design of a customized logic controller for solid-state memory may not be as difficult.
If it is not possible for a single person to design a complete SSD logic controller, are there any types of programmable controllers, or something similary, available that may take care of most of the memory management, but allow for additional modification/customization? This would be the way to go, since I prefer to use a HDD with good performance, and will be better than anything a one-man shop will cook up.

This post offered some hope, but I am far from understanding all of it, and is probably doctorate-level work(?).


texts:
I'm trying to use a BTS7710G as a h-bridge to swap voltage on load. this is from datasheet:

what i'm doing is turning on IH2 and IL1 pins at once . and another time turning on IH1 and IL2 to swap voltage on load  ( micro supply voltage is 5V).

but i see driver ic get to hot and output voltage without load is 5.5V and under load is 3 volt (supply voltage is 7V and load current is about 3A) . I'm wondering if i am doing something wrong


texts:
For a fun project I've been trying to create some sort of circuit that behaves as follows:

Two outputs, Vout1 and Vout2.
One Input Vin
1 Controlling potentiometer Rpot from 0-MAX.
Any combination (and amount) of BJTs, MOSFETs, capacitors, inductors, and   resistors.

What I'm trying to accomplish is this: An AC signal enters the circuit. When Rpot is at some middle value say Rpot = .5MAX, both outputs are essentially in parallel and connected to the source Vin. Vout1 and Vout1 must receive the same signal (or very very close, 1-5mV off), and also must have at least 90% of the magnitude that Vin has (so if Vin has an amplitude of 1V, Vout1 and Vout2 must have an amplitude of ~.8V or better).

As Rpot is increased to its MAX value, I want to decrease the amount of the signal that Vout1 or Vout2 receives.

For Example:
As Rpot increases to MAX, Vout1 = 1V amplitude while Vout2 = .5V And if Rpot approaches its 0 value then Vout2 = 1V amplitude while Vout1 = .5V

While the amplitudes I'm using are arbituary I think it gets what I'm trying to accomplish across. As I either increase or decrease the resistance of Rpot, I only want one output to attenuate at a time.

I've tried numerous voltage divider circuits and tried to use some BJTs to create some logical feedback but I'm running into  wall. The closest I've gotten is using a voltage regulator that turns on when one channel is attenuating but I can't quite get it to work. Any help would be appreciated.

Thanks in advance!


texts:
I have a 12 volt power supply rated at 250 amps for my landscape lights.
If I switch to led's with little current draw will the power supply still draw 250 amps or only what is required of the connected led's?


texts: Optocoupler works with led but not with camera shutter

texts:
I'm trying to take photos with my arduino and a 4n25 opto. To trigger my camera you only need to close the circuit of the shutter cable, however the below simple circuit is not working. I've tried to change the shutter cable with a led and 3v and it works perfectly. I added a switch(SW3) to make sure it worked as expected when closing the circuit, which it does.
I've tried also changing the R2 resistor to 330, 220 and 84 Ohms, all of them work nice lighting a led but no luck with the camera.
Is there something I'm missing? Maybe a reason which makes impossible to close the shutter circuit with a transistor?
Any help would be greatly appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: TWO 3.5mm AUX sockets to ONE 3.5 AUX plug - Car Audio Application

texts:
I am putting together a car audio system and replacing the factory stereo with a new aftermarket head unit that has a single aux input. The vehicle comes with a single OEM aux input jack in the dash. We’re looking to add a second aux input jack in the rear passanger area so passangers can play and control the vehicles music from their device (iPhone/iPad/Android/MP3 player/etc.).

In regard to the exist OEM aux input jack in the dash, the factory harness that sends the signal through the cars wiring to the OEM stereo will be bypassed and only the physical plugs will be used so that we can send the signal through our own route.

Essentially, I need to be able to combine both inputs from the OEM aux jack and the NEW aux jack (being installed in the rear passamger area) in to ONE 3.5mm plug that will go to the single input on the new aftermarket head unit.

In my initial research, I’ve found that there are “mixers” I can buy but all the ones I’ve found have manual switches that need to be switched to change sources. We need both inputs to be active so that we don’t need to flip a switch between the sources.

Also, it needs to either be a “passive” solution OR an “active” solution that can be powered by 12v DC, given that this will be installed in a vehicle.

Is there any product that I can purchase to accomplish what I have described here?

OR

I am also willing to build my own custom wiring harness to accomplish what I need. I can purchase wiring, plugs, etc., and solder everything together to create a custom solution.

EDIT:
So I decided to just purchase a mixer (Behringer MicroMIX MX400). The power spec for the mixer is: 12v DC/150mA. It comes with a power supply that plugs into a wall outlet. I need to power it in a vehicle. Since it’s already 12V DC, I was thinking just connecting it to an unused/open circuit the interior fuse box, that is 5A switched (only active when key is in the ignition). The power will be connected to the fuse box circuit and I’ll just ground it to an exiting ground point.

Will that work?


texts: Can a faraday cage cell phone case protect wearer against possibly harmful signals?

texts: I don't know much about harm a cell phone can cause if worn close to human body for prolonged periods of time, but I'd like to know if the phone's signals can be dissipated from the side of wearer's body by a small faraday cage.


texts:
I plan on designing a variable power supply (1-50V, isolated), able to provide a power of about 50W. For efficiency's sake, linear regulation is out of the question. The natural thing would be to design a flyback AC-DC supply, but there are a number of problems raised:

The fact that it is variable complicates things:  for example, the aux winding will not provide a fixed voltage. Also, will the flyback topology be appropriate for a large range of duty cycles ?
I did not find any off-the-shelf flyback transformer that would be appropriate. Either the output voltage is not right, or the power, or the aux voltage, or they are not in stock anywhere. So I'd certainly have to design my own transformer, but I don't feel confident about this part (neither regarding the core choice, the design, or the DIY construction of this).
Even the other parts of the flyback supply design seems risky: the snubber across the primary winding (which seems to consume a lot of power, by the way), the optocoupler feedback (which seems to require some tuning), etc ...

On the other hand, I feel confident about designing an appropriate DC-DC buck converter. There are a lot of tools from various manufacturers to help in designing them (TI, Linear Technology, ...), and it seems there are a lot less parameters that could lead to a non-functioning design.

So, I plan on using a simple toroidal transformer (much more easily available) to do the isolation and an initial stepping-down of the AC voltage, then the usual diode bridge + filtering capacitor, and then the appropriate DC-DC conversion step.

Apart from the fact that the transformer will be a lot bigger (and more expensive) than for a flyback design, are there some drawbacks of using this topology ? It seems nobody really does this, but I can't think of any reason that would make this a bad idea. The efficiency should still be pretty high, right ?


texts: Design considerations when combining multiple DC DC converter with the same input, but different output

texts: I've used TI Webench to implement single DC DC converters in a circuit, so I'm always confident in using whatever TI generates for me. But what are some design considerations or modifications required when combining two or more DC DC converters with different rated load? I was thinking this may need a change in the CIN, CINX components of the circuit. Or just leave as is? Here is a schematic with labels highlighting my concerns.


texts: How can I use an Arduino to simulate button presses on this Remote Control PCB

texts:
I read with interest here this post: How can I use an Arduino to simulate button presses on this PCB

I am a beginner in this and I am trying to learn how to do this based on a small remote control I would like to simulate a fake press using an arduino.

I am also not sure if I need to use a MOSFET as it is a very small device requiring little amperage so I think a small transistor will do ?

Basically, I would like Arduino to send a signal to the 2 red points here that will simulate a fake button press.

Hope I am making sense here. I appreciate any guidance or pointers on what I need to make this happen. Thanks !

More details to share:
With COM on Battery-Negative and the other lead:

on the right side of the button = 12V. When button is pressed = 12V
on the left side of the button = 0V. When the button is pressed = 12V.

I will just focus on one button. Disregard the other button.

@Dave Tweed
https://electronics.stackexchange.com/users/11683/dave-tweed
If you are listening, I would really appreciate if you can share some advice.

Thanks all


texts: A way to determine a symmetric connector's position

texts:
I have an old, custom pair of connectors in use by what will be a large number of systems. The connectors are mother/father and symmetrical, as in they don't have a mechanical guide to have the user plug it in in the "right" position.

I cannot alter the father device and connector in any way.

The 4 pins are: VCC GND Rx Tx. I have a high voltage on the power pin and Rx/Tx logic is at 5V. Rx/Tx clock is pre-set at a particular value.

Therefore, the father connector can be plugged in in 4 possible ways.

Mother supplies father with VCC under 1000V and under 100A if and when the pins are "aligned". Until then, the devices can talk through Rx and Tx @ 5V (there is a small rechargeable battery on the father connector end device).

Connectors' and devices' case(s) are non-conductive.

I need to be able to detect the orientation / how the father connector is inserted so I can relay current and signals properly, so that the devices will connect and talk regardless how the connectors are plugged in.

What is the best way to accomplish this? By "best way" I mean least number of components/FETs/relays/diodes. I can use any type of MCU on my end, was looking at a L0-class from STM.

NB: an electro-mechanical device behind the mother connector, in the form of a disk is rotated by a motor in steps of 90' clockwise (basically up to 4 "tries" are made until the signals are properly aligned) has been proposed through another channel, I am not looking for this kind of solution, need something solid state, without moving parts.


texts:
I'm looking at the Adafruit Feather 32u4 schematic.

It auto-switches between battery and USB power. From looking at the schematic, when the USB power is not connected, the battery power VBAT goes through a MBR120 Shottky diode, then a SPX3819 regulator to power the Atmega32u4.

From looking at the datasheets, the MBR120 has a 0.45V drop, and the SPX3819 has a 0.25V dropout at 50mA. This would be a total voltage drop of 0.7V. Since the regulator outputs 3.3V, the minimum input voltage would have to be 4V.

Since a LiPo battery runs down to about 3.5V when getting low, that would mean that the circuit could not be powered except when the battery was very full.

Am I missing something, or is this how it works? It would seem strange that you would be unable to use most of the battery power.


texts: Can't find circuit example for a solenoid valve 2W025-08

texts:
I recently bought this solenoid valve for an Arduino project where I need to flow liquid between 50 and 100 degrees Celsius.

I didn't find a circuit example or a technical sheet specific to this component. Based on a circuit I found for a different solenoid valve, I know I need a transistor and a rectifier diode in order to make it work but I'm not sure if I can use the very same components : A TIP120 Darlington Transistor and a 1N4001 Diode ( from this circuit example ).

Thanks for any help


texts: Need help with troubleshooting an H bridge circuit

texts:
I designed an H bridge using the DGD0506A gate drivers.
https://www.diodes.com/assets/Datasheets/DGD0506A.pdf

I used the FDMC7696 for both high side and low side mosfets.
I went with the suggested circuit as provided in the gate driver datasheet

I just used a transistor to invert the IN signal to the second chip, so the opposite mosfets turn on (e.g. HO on the U1 and LO on the U2)

and this is the arrangement of H bridge itself

after ordering the parts and the PCB, I started testing it, but I had no luck and it wouldn't work.
I checked everything and found out I'm missing a connection here:

I just botched a few wires to make that connection but it still wouldn't work.

I have tried it with a DC motor and a 5k resistor connected to the load, no chance with either of them. I checked a few volrages and the Vs is sitting at around 9.5v with respect to ground (drops quickly to 7.8 volts when measured by a multimeter or oscilloscope) but the voltage across both tantalum capacitors is 0. I've created this exact same circuit 3 times and I'm running out of them but I've had no luck finding what the problem is.
(both EN1 and DIR1 are 3.3v signals,DIR1 is digital High/Low, but EN1 is a PWM @25KHz. VCC is 12v and VDD is not being utilized here but it would be 3.3)

I was wondering if you guys can help me troubleshoot this issue and perhaps get this board working. I have enough parts to make 1 new board but that's pretty much it.Thank you very much.


texts: Is there a buffered/high impedance voltage monitoring circuit with voltage limiting?

texts:
I have a 10 mA circuit that I would like to monitor. I'm only interested in the values between 0 V and 3.3 V and only have a 3.3 V supply. But the circuit can end up as high as 18 V. I cannot load the original circuit very much. Can anyone suggest what to use?
I've looked at op-amps but the ones I've seen with over-voltage protection seem to use diodes to drop the voltage back down, which seems like it would load the circuit.
I've looked at the LM321 as the input voltage can go up to 32 V. It seems like it might work but it looks like it can't go anywhere near the rails for output.
I've considered a BJT common collector but when the input goes higher than the source, current flows from base to collector. I've tried adding another NPN with the base tied to source. While that prevents the current flow, it also clips the top voltage at 1.4 V below input.
I've considered a MOSFET but the threshold voltage seems like it would kill the low-end.
Other circuits I see online commonly show using a fractional gain to scale the input down. But I don't want to scale it, just clip.
Am I missing some easy solution?


texts: Looking for some help in calculating air gap patch antenna dimensions. There are several air gap designs online (eg https://www.youtube.com/watch?v=OY0hvWsH-mg&feature=youtu.be&ab_channel=Adam9A4QV for 1495MHz or https://www.rc-cam.com/imagepat/cad/gp_patch.pdf for 2.4GHz) but if I try to scale them to 1622MHz I get different sizes, so looking to calculate dimensions from scratch.


texts: Can I use a Zener diode to convert 14 V into 5 V in a small-current circuit?

texts:
I'm working on a microcontroller-based device, and I need it to detect an input voltage (distinguish between zero and non-zero). When it's not zero, it can be anything between 10 V DC and 14.6V with some added noise of various frequencies. When it is zero, it will either be at GND or floating, I'm not sure yet.

Can I use a 5V Zener diode to stabilize this voltage and connect to the 5V-tolerant MCU's input? The current consumed will be however much the MCU requires, I expect it to be in the range of 1-3 mA (but I should probably see if I can find input current in the MCU's datasheet, which I couldn't so far but I'm sure it's there).


texts:
I'm having an oven that is heating a specific element. I have cascaded P/PI loops.
I have two thermo elements as sensors.

I would like to know how would I implement a thermal runaway protection.

For example If I'm heating and I removed the second thermocouple, it will heat forever, how would I know If specific element is burnt or the wire is cut or the wire is not there at all.

FOLLOW UP:

IF (rInputPWM = 1 ) THEN
    timerPWMDetection(IN :=TRUE, PT:= T#1S);

    IF(timerPWMDetection.Q) THEN
        counter := counter + 1;

        IF(rPreviousTemp < rTemperature AND counter = 60) THEN
            bRelay := FALSE;
         END_IF

        timerPWMDetection(IN:=FALSE);
    END_IF
ELSE
    timerPWMDetection(IN:= FALSE);
    counter := 0;
END_IF

rPreviousTemp := rTemperature;


texts: Can a L293D H-bridge be used for this application?

texts:
I'm building a circuit that is needed for a logging device we have. With some of our sensors the current is going in one direction and with others the other way around. That means that we have a polarity mistake (minus sign) on some of out sensors when we log. We log the voltage drop over a resistor when the current passes through it.

I tried to solve this using a L293D H-bridge (http://www.ti.com/product/L293D/support). I could then change the polarity of the meassured voltage drop over the resistor by enabling 1A and 2A respectively. This worked in principle. However, because of the internal voltage drop the L293D introduced a error in the measurements we could not live with. Are there other H-bridges that introduces almost no voltage drop I could use, or maybe a completely different component?

As you probably can see I'm no electronics expert.


texts:
I am currently building a line-following robot for a competition this summer. I have figured out everything except the power.

I expect my robot to draw 7.5 amps in the worst case. now, I've selected a 2S LiPo battery for this, as 7.4 volts is enough for my system. However, I am not sure which capacity to select:

300 mAh is more compact, but gives about 2.5 minutes battery life under full load. The course should be covered by my robot in much less than a minute, so from the first glance it is not a problem. However, the battery will need more recharging.
1000 mAh and above give much more battery life, which means more recharging, but they are less compact, which is not particularly good.

I fear that the low-capacity batteries will experience quicker voltage drops, which will decrease performance of the robot. In your poinion, which is the better option regarding the batteries?

Thanks for your time!


texts: Power measurement in star three phase balanced load

texts:
I had a doubt, in a balanced star three phase arrangement:
Using two wattmeter method, we obtain power readings as W1 and W2. (which may be unequal).
Let us take W1=5 watt and W2= 6 watt for instance and phase current to be 10 ampere.
However from the definition of real power, we know that power will be dissipated in resistor only.
So if I use power= i^2 *r,
In the first case, when power is 5 watt,
r=5/100 ohm while in second case it is 6/100 ohm
However, we said that it is a balanced arrangement, then how come the value of resistances is different.
Any help is appreciated.


texts: What does % of Population mean in a datasheet graphic about voltage output

texts:
I was checking a 3-axis accelerometer sensor an I found out this one https://www.digikey.it/it/datasheets/analogdevicesinc/analog-devices-inc-adxl335

Reading the datasheet, on page 6 under TYPICAL PERFORMANCE CHARACTERISTICS, all the graphics have on the Y the % of Population.

I can't understand what it refers to... Is it a statistic about the possible output of the sensor?

Below a screen for reference


texts: How do I detect what kinds of signal(s) this device receives/sends

texts:
Xcortech 3300w - Component board

So I have a somewhat hopefully simple question. I'm a bit of an amateur with on-board components and am trying to figure out what kind of signals this board receives. This device is an Xcortech 3300w. Documentation is sparse outside of youtube videos that just go over basic function if that helps.

Here is how it works:
This board combines with an inline mosfet unit and a separate high accuracy speed measurement device that attaches to the muzzle of electronic bb guns to do three things

It measures the velocity of each shot fired and displays it on the board shown when in the right mode
It tracks each shot, and has some flash memory so it can store how many rounds have been fired along with a counter up or down(tracks through reboots and keeps memory)
It "pairs" with the inline mosfet so that it can SEND the mosfet a signal to cut off the battery when the bb gun is "out of ammo" according to the shot counter mentioned in #2. It appears as if this"pairing" is NOT bluetooth, or wifi.

It does all of this wirelessly, which is quite handy. I don't like the design of the box and the digital LED readout. It feels very 90s.

What I want to do:
My goal was to redesign the tracker to use a micro sized TFT LCD and an ESP32 or Arduino to intercept the signals and function as the brain of the unit. The problem is that I can't seem to detect what kind of signal it's sending at all. I'm fairly certain its not bluetooth (I sometimes see a null bluetooth ID with a mac address when im at home and this thing is on, but i cant connect to it and i dont sniff any signal being sent ever so its probably not that), it's definitely not Wifi, and if it IS RF, i can't detect what frequency it's sending at (using the low-grade detection of my phone)

My question to you guys is, does anything on this board stand out as a particular kind of receiver for any kind of signal you might know about? Or even if not, do you know of any way I can sniff or even detect intermittent wireless signals of various varieties? I don't necessarily even need to read and decode them, even the fact that a signal of a particular frequency was sent is enough for me to track the information I want (namely just the shot counter functionality)

Bonus points:
Links on how to decode wireless signals once I do manage to detect the signal. I know it's at least sending a 3 digit numeric value (Feet per second value). So if I can just take the binary output and brute force it in to an int somehow that would be fine. I suspect the can ONLY sends this 3 digit int value, and the computer pictured decodes that signal as "i've shot a bb, its going this fast, you can keep track of how many shots have been fired and how many per second i'm shooting"


texts: Why is the Inductive reactance formula (XL=2πfL) not working for me?

texts:
I have an inductor labeled as "222" which I believe its means that its inductance value is equal to 2200 Microhenries. I double checked by measuring the inductor with and LCR meter and the value matched the label.

According to the inductor reactance formula "XL=2πfL", a frequency of around 3620 Hz impressed into a 2200 Microhenries inductor should yield around 50 ohms of inductance reactance.

To test this, I fired up my signal generator configured to output 4 volts peak to peak with a frequency of 3620 Hz. Given that my signal generator has a built in 50 ohms resistance I was expecting the voltage drop across the inductor to be 2 volts (2 volts dropped across the signal generator built in 50 ohms resistor and 2 volts dropped across the inductor 50 ohms reactance). However, the voltage drop across the inductor turned out to be 3 volts.

This means (according to me) that the impedance / reactance generated by the inductor is more like 150 ohms. Basically, 1 volts dropped across the signal generator built in resistor and and 3 volts dropped across the inductor.

Why is this happening? What am I doing wrong? Why is the formula not working for me?

Thanks.


texts: Arduino triggering a TRIAC for EL Wire, no optoisolator

texts:
I have been researching and looking up how to control EL wire online and I will be using the same layout as the EL Escudo shield from Sparkfun but just for one strand.

Basically: Arduino (+ resistor) -> Triac Gate -> EL Wire.
http://www.sparkfun.com/datasheets/DevTools/Arduino/EL%20Escudo-v02.pdf

In recent research I have noticed some people using Optoisolators in their EL wire circuits to control the gate and provide safety from AC.

So my question is: Is it safe to use a TRIAC without an optoisolator just like the EL Escudo circuit?

My main worry is zapping the Arduino or my laptop over USB with the 110V AC from the inverter.

Details: Arduino Pro Mini 3.3v, TRIAC MAC 97A4, Sparkfun 3v EL Inverter, Sparkfun EL wire.

Here's what it will be installed on once its all done (sans tape): http://dl.dropbox.com/u/6039877/IMG_0433.jpg


texts: A different way for converting to 2's complement

texts: One way to convert any number to 2's complement is by adding the number to 256, if the number can be represented by 8 bit number. For example if we want to convert -100 to 2's complement we do addition with 256 to get 156, which has a binary value of 10011100, but if we do binary conversion while considering this as a 2's complement number we will get -128+16+8+4 = -100. If seems to be working as I am getting wring answers, but I am not able to figure out why this works, what the math/logic behind the adding a 8 bit number. Any help/direction will be appreciated.


texts: Finding equivalent impedance with ideal transformer

texts:
I'm working on finding the equivalent impedance of an ideal transformer. I want to derive the formula they are using in the book and lecture.

Unfortunately when I try and get this equation by hand the third term comes out negative (I know that my example has the second dot on the opposite side compared to the example that derived the equation above). It mentioned in the book that "M" is always positive because it is being squared but there is a j squared in the equation that would mathematically make it negative.

Is there an engineering or math principle that I'm missing that would clear this up?


texts: Op amp circuit stability in linear regulator circuit

texts:
I am trying to design a stable linear regulator using MOSFET and op amp. Schematics is shown below:

I am using LTSpice for simulations. This circuit is mostly for educational purpose: I want to understand how to use bode plots to design a stable op amp circuit with feedback. I have studied a bunch of theory on this topic but I don't have any practice regarding op amp circuits.

So first of all I broke the feedback loop, grounded inverting input of the opamp, ran ac analysis measuring node "out". I put DC offset of the V5 to 0V and results are shown below:

!!See fig 1!! (sorry I had to put figures in one image because my reputation is lower than 10 and I can't attach more than 2 images)

Gain is not going higher than 0dB.

Afterwards, I have used V4 for injecting AC into the feedback loop (DC value = 0, I have restored the feedback loop). Plot of V(out)/V(vn) is show below:

!!See fig 2!!

Phase margin might be not that good but anyways...

Also I have done a plot of V5 with AC 1 and without using V4 in the loop:

!!See fig 3!!

Here I actually see the peak near 200 kHz but... Transient analysis is showing the following:

!!See fig 4!!

A bit closer...

!!See fig 5!!

So the circuit is oscillating and frequency is 1.8 MHz. I don't understand why. Obviously I am laking some knowledge concerning AC analysis... I understand that I should just increase capacitance C1 to 40uF and it will solve the problem but I want to know why I should do that (i.e. how can I see it on the bode plot). The only plot which showed some problems was the transient plot to step response.

Figures:

I will really appreciate your help! Thank you for your time!

UPDATED:

The reason I am trying to use an op-amp in this circuit is that I already have a following linear regulator in my device and I want to upgrade it:

It works fine but sometimes it is not charging the capacitor C1 fast enough so I thought about using op-amp to make the response faster. And the most important characteristic here is to make the C1 charge from 8V to 10V as fast as possible.

R1 is 2 km long cable.


texts: Are there any circuits to get output as a sum of a set of current sources?

texts:
I have 3 current sources (I1, I2 and I3) and I need to get an output of linear summation of the current of these sources.

Iout = aI1+bI2+cI3

where a,b and c are gain factors (like 1 to 10 and are constants). I1, I2 and I3 ranges from tens of uAs to hundreds of mAs.

I need to drive a Laser LED, target is to keep its voltage constant and vary the current depending on the light power required. Therefore I think converting current into voltage and back to current using a resistor is not an option I have. Required bandwidth is about 10MHz (This bandwidth will be applied to one of the input current components, say I1).

Are there any circuits to do this job.


texts: Understanding the sensitivity of an L3G4200D gyroscope

texts:
I'm hoping someone can help me interpret the meaning of the sensitivity values for the L3G4200D gyroscope. Two small extracts of the datasheet are below:

So my question is this. If the gyroscope is configured in the +/- 250dps (degrees per second) range how is it that the sensitivity is only 8.75 mdps/digit?
I would expect that the sensitivity would be 0.00762939453125dps or 7.629mdps/digit.
I calculate this as follows:
16bits = provides a scale of 2^16=65536 unique combinations;
Because the gyro is + and - 250 dps we have a range of 500.
500/65536=0.00762939453125 dps or 7.629mdps/digit

How do you calculate the mdps/digit? and where am I going wrong?


texts:
I'm running an Atmega32u4 on a 5V circuit. However, I'm also using a Bluetooth IC [MDBT40] on a 3.3V circuit that I'm setting down from 5V with a linear regulator. I'm turning both SCK and MOSI to 3.3V using 74LVC2G34.
However, I'm a little bit stuck on the MISO line to the Atmega. From Adafruit's schematic here, it seems like MISO [despite being 3.3V] is passed off directly. Can I connect this 3.3V signal wire to my 5V Atmega and have it function?


texts: Relation between current and used energy

texts:
Thinking about a dc motor and a constant voltage battery, if you slow down the motor by resisting it physically without stopping it, its resistance increases, right? Therefore reducing the current in the circuit, since the voltage is constant.

In a similar way, when you benchmark a computer, compared to idle, it should increase the resistance, therefore reducing current. But, I also know that using the computer uses more electricity.

And how about the example above, does the slower spinning motor equal lower battery drain?

I think I am totally misunderstanding things, which is why I need a little bit of redirection.


texts: Multiple voltages and currents required in one circuit

texts:
I have a circuit with the following components:

microcontroller - 7-12V, v.low current
2x Servo - 6V, 250mA
Solenoid - 18V, 14 Ohm coil
Geared motor - 9V, 6A stall current
Power supply - 19V, 3A DC

From my research I have the following options on how to supply each component with the correct voltage and allowing them to draw enough current for the job.

Linear voltage regulators - my current set up - horribly inefficient, low current capability (<1.5A) & thermal shutdown.
Switching voltage regulators - fairly complex, (I don't know about the current capability).
Voltage dividers - seems ideal except that, from what I understand, as soon as any substantial current is drawn the divider rule goes out the window...  Also high current resistors need to be used.
Other?

My query is - are there any other options I have overlooked and what do people think is the best solution to my set up?

All answers welcome,
many thanks!


texts: Why is my seconds counter in verilog jumping values behaviour?

texts:
I am implementing a seconds counter on the Altera DE-1 Educational Board powered by the old Cyclone 2 FPGA. My plan is to make a 'down-clocker' that takes the on-board 50 MHz clock and produces a 1 Hz clock signal (referred to as the 'pulse'), which will then be used to drive the normal counter. The down clocker module is as follows:

module downClockerTest(pulse, clk, reset);
    output reg pulse;
    reg [25:0] count;
    input clk, reset;

    always @(posedge clk or negedge reset) begin
        if(~reset) begin
            count <= 26'h0;
            pulse <= 1'd0;
        end
        else if(count == 26'd49999999)
            count <= 26'd0;
        else begin
            count <= count + 26'h1;
            pulse <= (count > 26'd24999999);
        end
    end
endmodule

With the following RTL:

Notice that the output 'pulse' is registered. This design works fine; the counter counts as it should. However, if I try and remove the register at end by attempting to drive the 'pulse' output by a single assign statement, the seconds-counter seems to begin jumping by 1 and then 4 in 1 second, indicating 5 pos-edges from the down-clocker, where there should only be one.

The slightly modded down-clocker is as follows:

module downClockerTest(pulse, clk, reset);
    output pulse;
    reg [25:0] count;
    input clk, reset;

    assign pulse = (count > 26'd24999999);  // The counter seems to increment by 1 and then 4 in quick succession (1 second).

    always @(posedge clk or negedge reset) begin
        if(~reset) begin
            count <= 26'h0;
        end
        else if(count == 26'd49999999)
            count <= 26'd0;
        else begin
            count <= count + 26'h1;
        end
    end
endmodule

The changed RTL without the register is:

Why is it that the down-clocker only works right when there is a register at the end? Is the register performing some king of 'debouncing'? Does 'bouncing' occur in non-mechanical switching circuits as well? What could be the possible reason from an electronics point of view?

It might be prudent to add that the TimeQuest Timing analysis fails in both cases with critical warning: 'Timing Requirements are not met'. But still, one works where other does not.

I am guessing this bizarre behavior has to do with a race condition caused when a sequence of bits drastically changes its 1's and 0's after an increment. For instance, 110111 becoming 111000 after increment-by-1. Since there is no telling which of the flip-flops - storing the individual bit positions in the sequence - will update their values first, the number (read: bit sequence) might fluctuate for an instant before attaining a stable value. There might exist numbers (bit-sequences) that, while tending towards their stable values, fluctuate through the value being compared (24999999, in our case) and cause the comparator to output Logic-HI.
A register at the end would certainly solve this issue. However, all this is guess work, with bases in little experimentation. Any learned opinion would be welcome.


texts: Fuzzy digits when driving with TPIC6B595

texts:
I designed a schematic and PCB of a simple Nixie clock and I hope that someone will be able to explain what's happening.

The problem is that when I'm driving the cathodes with TPIC6B595 shift register, some of the digits are not readable/fuzzy. It's worth noticing that on different tubes different digits get fuzzy, eg. cathode 0 and 7, the rest is okay.

Example of a bad/fuzzy digit

Example of a well displayed digit

HV is 180 V DC, series resistors are 2x10k, I'm switching on the anode voltage using a pair of MPSA42 and 92.

I checked individual tubes with a resistor and HV power supply - they're all ok.
I checked the TPIC6B595 outputs with a LED and series resistor - they're all ok, I'm driving one cathode at a time, one of them is always lit, I'm filling the registers first, then turning on the anode supply.

The displayed sequence is 0-3-4-5-6-7-8-9-0-..., because cathodes 1 and 2 are connected to the next register, which is always filled with 0's. This is for test purpose only, as I have only two shift registers soldered to the PCB for now.

Here is the code:

void test_load_and_latch_two_registers(uint8_t output_number){
uint8_t value_to_load, j;
if(output_number > 7) return;
value_to_load = (1 << output_number);

// second register fill with 0
for(j = 0; j < 8; j++)
{
    set_shift_register_clock(GPIO_PIN_RESET);
    HAL_Delay(1);
    set_data(GPIO_PIN_RESET);
    HAL_Delay(1);
    set_shift_register_clock(GPIO_PIN_SET);
    HAL_Delay(1);
}

set_shift_register_clock(GPIO_PIN_RESET);

// first register fill with data
for(j = 0; j < 8; j++)
{
    set_shift_register_clock(GPIO_PIN_RESET);
    HAL_Delay(1);
    if(value_to_load & (1 << j)) set_data(GPIO_PIN_SET);
    else set_data(GPIO_PIN_RESET);
    HAL_Delay(1);
    set_shift_register_clock(GPIO_PIN_SET);
    HAL_Delay(1);
}

set_shift_register_clock(GPIO_PIN_RESET);

latch_shift_register();

HAL_Delay(1000);}

I would be grateful for any hints on this.
I suppose there's a problem with floating cathodes voltage, but have no idea what is happening in this circuit.

Edit 1:
Video: https://youtu.be/ibOdviAl_b4
Digit 7 is not displayed correctly. If I check this tube directly with a resistor and HV power supply, digit 7 lights up correctly.
Replacing tubes result in a different digit being blurry.

Edit 2:
I measured voltages when a single digit is displayed in two cases.

Digit 5 displayed correctly:

A  - 135 V
C0 - 123 V
C1 - 66 V
C2 - 124 V
C3 - 54 V
C4 - 102 V
C5 - 0 V
C6 - 54 V
C7 - 103 V
C8 - 54 V
C9 - 54 V

Digit 0 displayed incorrectly:

A  - 169 V
C0 - 0 V
C1 - 58 V
C2 - 82 V
C3 - 54 V
C4 - 54 V
C5 - 54 V
C6 - 53 V
C7 - 53 V
C8 - 54 V
C9 - 54 V

As far as I understand, the off cathodes voltages in ideal case should be equal around anode voltage, but the internal clamping of TPIC6B595 should drop this floating voltage to around 50-55 V. But it seems that it doesn't work like that.

EDIT:
I was able to solve the problem - some nixie pins didn't make a contact with PCB pads and were left floating. Now everything works as expected.


texts:
I have 3-pin current sensor  honeywell csnf661

the pins are +V, -V, O/P or I+

I wanted to interface this on arduino and I followed the instruction at openenergymonitor.org

I am not sure if I am doing it right because the tutorial is using different current sensor

  YHDC SCT-013-000 CT

Base on the datasheet, does it mean that I need to supply 12-15V?

After supplying voltage on current sensor, I'm still confuse where to connect them since there are only 2 lines (I highlighted them with red lines).

Do I need to connect the +V and -V, or -V and I+?


texts: When were tantalum capacitors first used in computing?

texts:
I know that nowadays tantalum is very common in computer components, specifically capacitors, due to its desirable electrical properties. I'm curious when it was first used specifically in the context of computing, and for what purpose.

Bonus: did the computer spur the use of tantalum (that is, was tantalum useless before computers took off) or were computer engineers looking for something that had desirable properties and found that tantalum, being used elsewhere, would do the job?

This question is migrated from retro-computing here.

Some research I've done tells me that Bell Labs required a new type of capacitor for their new transistor, but it was Sprague Electric who made them into something commercially viable somewhere around 1956.  However, I don't know when the merger of the tantalum cap and the computer happened, which is what I'm looking for.


texts: Is it a good idea to design a real time system on a multicore processor? Task's execution time isn't determinist in these kind of processor because of core management. This makes scheduler's elaboration hard to do.


texts:
I am trying to figure out how to run a device that requires 1 AA battery (1.5v?) Using a mains adapter.
All the adapters seem to be 3v minimum.
Can anyone help please?
Product details: https://www.amazon.co.uk/dp/B074HY3MKC/ref=cm_sw_r_cp_apa_i_9UNKFbZA0ET4N?_encoding=UTF8&psc=1


texts: How can I wire a microusb to a MIMXRT1062DVL6A?

texts: I've never touched a barebones microcontroller before. I've been toying around with an Arduino and Teensy for a few years now. Recently I've been itching to ditch the comfort of those buttercup modules and begin using standalone MCUs. The chip I'm looking at is NXP's ARM Cortex-M7 MIMXRT1062DVL6A. I know there are chips in the market that are less complex, but my question depending on if I'm able to phrase it properly could be generalized to any MCU. I want to know how I can upload code I've written into the device's memory. Specifically via MicroUSB. I've tried looking through the datasheet, but frankly, I don't know where to start. I was wondering if there's a programmer that needs to be installed between the MicroUSB and MCU. Also, I'm curious if when working with MCUs is the datasheet and manual the best documentation for understanding the MCU or are there additional sources I should look into?


texts: I learned about shift registers a few weeks ago but I don't know why it is very important and everyone said that it is necessary for microcontroller, etc. Please make sense for me.


texts: How to identify different LDR photoresistors that have been mixed together?

texts:
I purchased a variety pack of LDR photoresistors from eBay which includes GL5506, GL5516, GL5528, GL5537, GL5539.

The problem is that they all came in the same little bag and are visually identical. How can I sort them into their individual model numbers?


texts: Common-emitter amplifier simulation is giving me the wrong result

texts:
I'm trying to simulate a common-emitter amplifier with a BJT and check that the results match with the equations I have.
The circuit I have is basically this:

This is the simulation: https://easyeda.com/editor#mode=sim,id=e10ea3e41e3d46f0b3a0bdef250a14ac. (you can simulate it by pressing F8)
I input 1.2 V and I'm expecting an output of 6.33 V, but I'm getting 0.1 mV approx. according to the simulator. I suspect that I have misinterpreted the BJT datasheet, let me explain:
The BJT that is supposed to be used by the simulator is 2N2222 whose datasheet is here: https://datasheet.lcsc.com/szlcsc/1809200018_ST-Semtech-2N2222A_C118536.pdf
According to the above, the expected DC gain (beta) for this BJT is 75 when iC is 10 mA. So I have found an RI that causes iC to be 11 mA just in case:
iC = 11 mA
Vi = 1.2 V
iC = beta * (Vi - 0.6) / RI

which gives me RI = 4k ohms approx.
I calculate the expected output voltage with the following formula:
vOUT = Vd - ( ((vIN - 0.6) / RIN) * beta * RL )

Given that RI = 4k ohms, Vd = 10 V, vIN = 1.2 V beta = 75, and choosing an RL = 500 ohms, the above equation gives 6.3325 V.
However, as explained, the simulator gives me 0.1 mV approx. What am I doing wrong?
PD.: you can check my formulas here


texts: Understanding voltage and current - is there voltage without current flow?

texts:
I'm trying to increase my knowledge of electric circuits and their major components.  My current understanding is very basic, which will explain why my question may seem laughable to most people on here.  Regardless, I'm hoping someone can water down an explanation for me regarding operational amplifiers.  After a bit of reading and looking for explanations, the common thread is that:

In an ideal amplifier, current does not flow into or out of the inputs (there is 0 input bias current).  However, I keep hearing that you essentially "put in" a voltage.  I'm unclear as to how one can input a voltage while supplying no current.

I understand how there can be voltage without current flow (say, if a point charge is present but not moving in space).  But in amplifier inputs, the important part seems to be "inputing" a voltage.  I just don't understand how you can supply or input a voltage without moving some charge through the input (at least initially).

If my understanding is so far gone that you do not understand my question, please let me know (and perhaps provide a few resources that you feel describe amplifiers or electronics in an easily digestible way).


texts: Can silicon temperature sensor (e.g. KTY84)'s polarity be inferred if it's inaccesible - polarity band cannot be visually checked?

texts:
I have two electric motors at my disposal, both equipped with KTY84-130 silicon temperature sensors (PTC thermistors).
The sensors themselves are buried deep within the innards of the motors and I don't want to meddle there if not absolutely required.

I always thought these type of sensors are just temperature-dependent resistors, so polarity does not matter. Indeed, when measured with a DMM, they show the same resistance (around 620 ohms at room temp) in both directions.

However, the Curtis controller manual warns about observing proper polarity:

Moreover, after some digging in the datasheet of the KTY84 it seems they are non-symmetrical, but only above 150°C:

Question

I'm looking for some minor tell-tale sign to infer the polarity (like how you can discern between the B-E and B-C junction of a NPN - the diode drop is slightly lower for the B-E). All I have is:

the two motors with coloured wires sticking out of them¹
two more sensors (as through-hole parts)
DMM/bench PSU/etc. (normal lab equipment)

How (if it's possible) can I identify the polarity?

One method (which I don't like)

I can pass current to self-heat the thermistors, but I'll have to cook them over 150°C for this method to work, and I'll very likely need to exceed the absolute maximum rating for current to achieve sufficient heating. I'll keep this as a last-resort method.

¹ and those wires don't help either; they are not even consistent between the two motors. I asked the guys who made the motors, they don't know how they installed them, they too were thinking the sensors don't have polarity.


texts: What's the use of neutral wire in single phase home supply?

texts:
I am aware that the neurtal wire provides a return path for the current to the power source. But that neutral wire too, is connected to the ground at somewhere between the load and the source.
My question is: Why use three wires Live, Neutral and Ground? Instead we can use two wires Live and Ground which does the same work, as Neutral and Ground are joined.
Another question: Does two grounds of different localities have same potential?
If they have different potentials, is this the reason why we use neutral as the common reference for both the load and the supply?


texts: Optocoupler with phototransistor base lead

texts: I'm thinking about using 4N25 optocoupler - it has a separate lead for base of phototransistor. How do I use it? I suppose I can't leave it floating?


texts: Looking for High Speed Parallel DAC IC without data latch

texts:
I have designed a FPGA based DDS that creates digital signals between 0-70MHz. Now I want to convert my digital data into analog. As the base frequency is 200MHz, I need a high performance parallel DAC with minimum 200MSPS. As I widely searched, such DACs are plentiful but I couldn't find one without a latch. All I found work like this: data is sent to D0-Dx -> a clock latches the data -> conversion is done.

If I want to have a DAC with this system, my output frequency will be reduced to 1/2 ( one clock for D0-Dx + one clock for the data latch).

Anyone knows a part with such properties ( something that works like DAC80xx , but in high frequencies, something like this:) ?


texts: Which force moves the armature of an electric motor?

texts:
As I understood the tangential force F on a current-carrying conductor in a magnetic field makes the armature of a electric motor move. But actually the groove where the conductor is located in is (almost) field-free.

The field of the current-carrying conductor, however, influences the magnetic field in the tooth flanks (is that right?) which leads to an unbalance of the field forces so that the effective tangential forces in electrical machines mainly arise by Maxwell's tensile stresses on the tooth flanks (it's a machine translation).

I'm confused about this.

Is this explanation correct?
Is there a more simple explanation how it works?
Is this valid for all electric motors?
Any good online source about this?


texts: Create breakout for small FPGA in BGA package

texts:
I'm going to buy a MachXO3 FPGA by Lattice, famous for the low cost, in order to create a bridge between an HDMI input and a MIPI DSI output for low cost/high res display.

Lattice lets you buy only the FPGA without the breakout (link) and I have no idea how to obtain a dev board (no one seems to produce something with the machxo3) or how to create it.

Is it reasonably possible to create a DIY PCB (instructions?) or buy a breakout for the BGA package that seems to be a FBGA-256?

PS: I'm quite new in electronic development, and I'm not able to use any EDA software (yet).


texts:
I'm trying to be sure I'm computing the values for this circuit right. Here's an example of the circuit I'm trying to build (it's going in a 12 V DC system, so I filled that in already).

I have a textbook from electronics class several years ago (which is where the circuit design came from), and it has these formulas:

\$
V_{h}=hysteresis~width
\$

\$
V_{ut}=upper~threshold~voltage
\$

\$
V_{ctr}=center~of~threshold~voltages
\$

\$
V_{lt}=lower~threshold~voltage
\$

\$
V{ref}=comparator~reference~voltage
\$

\$
n=resistor~multiplier~for~the~hysteresis~divider
\$

\$
V_{h} = V_{ut}-V_{lt}
\$

\$
V_{ctr}=\dfrac{V_{ut}+V_{lt}}{2}
\$

\$
n=\dfrac{+V_{sat} -(-V_{sat})}{V_{h}}-1
\$

\$
V_{ref}=\dfrac{n+1}{n}V_{ctr}
\$

So according to this, if I want the comparator that has Vut = 7 V and Vlt = 6 V I should have n=11 and Vref = 7.09 V to match my Vsat+ = 12 V and Vsat- = 0 V.

In ngspice (using an LF411 model from National Semiconductor) these values simulate an output that is more like Vut = 7.5 V, Vlt = 6.5 V. I even used exact resistor values (R = 10 kohm, nR = 110 kohm) instead of closest-available.

Is this a good circuit to use for my purpose? Should I normally have to tweak these values for real life? I've found that R = 10 kohm, nR = 75 kohm, and Vref = 6.5 V get me closer to the Vut = 7 V and Vlt = 6 V that I wanted, but those values are pretty far off from expected.


texts: What is a good way to in-circuit update the program on a SyncMOS 5964?

texts:
I want something that can re-program a PQFP SyncMOS SM5964 chip already soldered to the target circuit board.
I picture a ribbon cable that I plug between some sort of 2x8 or so header connector soldered on the target circuit board, and a 2x8 or so header connector on a chip programmer, with the chip programmer plugging into a standard PC serial port or USB port.

Is there a standard connector and pinout I should design onto the target board for in-circuit programming a completely blank SM5964 chip soldered to the board? (For older boards, I can temporarily connect such a connector with a bunch of wires from that connector to pins on the chip).
Is there such a standard in-circuit programming connector for other 8051 and 8052 chips?
Is there a reasonably-priced programmer that can program such a blank SM5964 chip already soldered to the target board?
Is there a standard bootloader firmware for this chip?

So far, my web searches have turned up a few chip programmers such as the
$295 XPRO-5000
that can program the SyncMOS SM5964
using a big ZIF socket and a PQFP adapter.
I suppose I could solder some wires between a DIP socket and a female header, insert the DIP socket into the ZIF socket on such a programmer, and plug the female header into a in-circuit programming header on the target board. But it seems unnecessarily complicated.

I expected to find answers to some of these questions at http://8052.com/ ; perhaps I am looking in the wrong place.


texts:
Hi I am facing some problem with Reading the input from a PIC18f4550 , for a simple arrangement where when a switch on (switch = 1), few led should glow., and on releasing the switch the led should go off (switch = 0),. On providing some volts across a pin (RA0 or RA1)- the leds should glow but I am getting no success in doing so.
I am using MPLAB IDE AND C18 compiler. tried with MPLABX and XC8 compiler too.

I wanted to take input from RA0 and RA1 , with a two push switch. And glow leds on RD7-RD4.
I made a simple if then else statement, inside a while(1) loop to do so.

    #include <p18f4550.h>
    #define switch1  PORTAbits.RA0   // two switches
    #define switch2  PORTAbits.RA1
    #define led1    LATDbits.LATD7   // defining led’s for making life easy
    #define led2    LATDbits.LATD6
    #define led3    LATDbits.LATD5
    #define led4    LATDbits.LATD4

    void main (void)
            {
                    // IO settings
                    /* tired both ways*/

            TRISbits.RA0=1   //making input for switch 1
            TRISbits.TRISA1=1  //making input for switch 2

            TRISDbits.TRISD7 = 0;   // RD7 to RD4 set to output for led.
            TRISDbits.TRISD6 = 0;
            TRISDbits.TRISD5= 0;
            TRISDbits.TRISD4 = 0;

            ADCON1bits.PCFG0 = 1;        // making all pins digital.
            ADCON1bits.PCFG1 = 1;
            ADCON1bits.PCFG2 = 1;     // referred Data Sheet Page:262
            ADCON1bits.PCFG3 = 1;

              while(1)
                {      if(switch1 == 1)
                            {    led1 = 1;
                                 led2 = 1;
                                 led3 = 1;
                                 led4 = 1;          }

         else if (switch1 == 0)  // on reading no voltage
                            {     led1 =  0;
                                  led2 =  0;
                                  led3 =  0;
                                  led4 =  0;  }
                               else { }
                          }
   }

It did not work out well.. the leds on RD7-RD4 keeps glowing all the time no matter what I do.

I tried to change the

        PORTAbits.RA0   to  LATAbits.LATA0  but still no help.

I did little bit of research and someone recommended me to turn the ADC value off and after looking up datasheet setting. I turned the adc off

        ADCON0bits.ADON = 0;  //turn off the ADC

Checked with the circuit on breadboard. Everything but still situation same.
Someone further recommended that , it’s a better idea to turn off the comparator. Hence I turned off the comparator again.

     CMCON = 0x07;     // comparator off.

     ADCON1=0x0F;  //All pins digital

I built entire thing again from scratch but still no success. I push the switch on or off. The leds on RD7-RD4 only of port D keeps glowing all the time :’( .. Here I am please help me.

PS: [Just to add up, I also thought may be my pic18f4550 has gone bad. Hence I tested a code to blink led on pic18f4550 http://goo.gl/PosRgg from a website it worked fine… hence I am sure my pic184550 is has not gone bad.] Please help and recommend where I gone wrong, i have been trying since 3 days now :'(


texts:
1) How do I choose the resistor for a triac?
I saw this design in the opto-isolator datasheet that I'm using. I thought I'll just change the resistor value based on the gate characteristics of my Triac. I referred a few other circuits that had similar resistor values, irrespective of the triac. I'm using a 3Q triac, Q6012LH5, which is a 600V, 12A,3Q triac.

Related question 1,
Related question 2
In one of the questions, a member specified that the value of the resistor is based on the Absolute max of the optocoupler. I still didn't understand, why max  gate current is not taken into account.

2) In the triac datasheet, it is mentioned that max gate current Igt = 50mA. And Igtm(Abs Max Rating) = 2A(10us). Do they mean that 50mA is the max current that is required to trigger the triac in all conditions?

3) I understand that holding current Ih is the minimum current that a triac needs to keep itself On, after the gate pulse is removed. Right? Then why do they specify Ih = 50mA when It = 100mA. Is doesn't make sense to me! Am I missing something here?


texts: Power supply and PWM for brushed 24V DC motor

texts:
I've got a 24V motor with these characteristics:

-voltage: 24VDC
- rated speed 2750rpm
- Output: 200w
Rated current: 10.9A

I want to use it for a watchmater lathe, so I need to control the speed, while keeping the torque. I think that PWM can be the solution.

Which are the carachteristics for the power supply and the pwm control that I need to look for?
Do you have a suggestion for the rcheap power supply/pwm I can buy?


texts:
I am planing to upgrade the radiator fans on my car and I would like to do some modifications to reduce the noise and have them run at lower speed when a curtain temperature is reached and run at full speed only when it reaches the maximum temperature.
I have already figured out the relay setup to trigger each circuit but I need a way to reduce the speed.

I have already made a circuit with a voltage regulate that was intended for car LED lights but then I have found out that dropping voltage can damage LEDs and I cannot afford damaging them so I replaced it with a PMW circuit. Now I am planing to use that circuit for the fans instead. Here is the schematic for the voltage regulator (12v to 8v)

simulate this circuit – Schematic created using CircuitLab

Can I use this for the fans? I am going to install two fans and each one draws maximum of 10Amps so 20Amps in total.
The reason why I have chosen this over a PWM circuit is for the simplicity of this one and the availability of those parts in my area.


texts: How to determine what transistor is needed

texts:
I created a circuit that uses a transistor to run a small (1.5 - 3v) motor. The transistor I used was a 2n3904 NPN. I calculated Beta to be about 11 when it's hooked up to an Arduino the base resistor I used was 47 Ohms and it worked well.

Given that I moved the circuit from the Arduino to a HiTechnic prototyping board, It's digital pins only put out 3.3v and from what I can tell (they don't say this online or in any documentation) the current is really tiny, about 8mA. Because of that it seems like I need use a different transistor - at least that is my guess, because even when I put a base resistor with 0 Ohms of resistance the motor barley turns and the current into the collector is barley 170mA.

To get a better idea of what I am doing. I have essentially taken this video tutorial and migrated it to this setup and I am using the Arduino to turn it on and off using the wire library and bitWrite.

The motor I am using is a Radio Shack Model: 273-258. It says it is .18amps to .25amps at no load, it will start spinning at just over .21amps.


texts: Triode - how come grid is "more negative" than cathode?

texts:
This is probably the most lame question of all the time here, but... I cannot understad grid-cathode "negative" polarization. For me, grid is always positive to the cathode. I mean, in practice, cathode is just GND or 0V, while grid gets voltage larger than zero and never goes below zero. So how come it has negative voltage comparing to cathode?

Let me show you how I understand a triode operating.

This is the most basic grid-cathode polarisation example and it does make some sense for me. We have reference 0V and this is cathode electron emitter, but we also have a battery connected below zero:

This example "seems legit" - cathode is connected to 0V but grid has own battery that provides voltage which is (theoretically) below zero*.

However, in real life no such battery exists, and there's just one 0V/GND point, common both for cathode and input signal.

What's more, the input voltage changes from 0 to 1V (not from -1V to 0V) in my example, so... how does the tube even work? It should not pass possitive voltages through the grid at all and the tube shouldn't work. But it does:

The resistor is of course the key, however it never drops input voltage BELOW 0V because there is no "below zero" point in the circuit. The ultimate zero is just zero, the same 0V point cathode emitts electrons from.

Or is it and I'm just unable to see it?

*) for me in this example grid voltage is stil positive over the cathode :/


texts:
I am using a camera module of our custom application. The camera module started consuming more current when compared to a previous board which has all the same settings, chipsets and modules.

In our conversation with a support engineer, we got this answer:

  VCAMD power supply in previous board is driven by a 1.27V DCDC, in
  present board it is driven by LDO. In a dark environment, DCDC will save
  about 14mA and in a light environment, DCDC will save about 25mA. So test
  results of both are different.

How can using a DCDC save power, the module would consume the power that it needs?


texts: Transimpedance amplifier with inverted output

texts:
In a little hobby project I am trying to send data from one Arduino to another using a modulated laser and a photodiode.

On the sender side, the laser has a dedicated modulation input for up to 100kHz. The input is low-active and I connect it directly to the TX pin of the sender-Arduino serial port. Since the UART is low-active too, the laser is turned off, if the UART is idle, which is nice.

On the receiver side I have a photo diode and a transimpedance amplifier with an LM385 opamp. The output is wired to the RX of the receiver-Arduino.

Here is the problem: If the sender pulls TX to low (1), this causes the laser turn on (2). On the receiver side the photo diode is illuminated causing a current to flow (3) and the transimpedance amplifier to output a high signal at RX (4). In short: Sender TX low -> Receiver RX high.

I clearly need an inversion of the transimpedance amplifier's output: 5V -> 0V and 0V -> 5V. The inversion cannot be done in software in the receiver, since the UART of the Arduino cannot be configured to do that. Of couse I could add a 7404 with a NOT gate to the schematics. But would it be possible to change the transimpedance amplifier in a way that the output is inverted but it still stays a transimpedance amplifier with the performance advantages for my application?

Careful with the word "inverted" in the world of opamps. You have "inverting opamps" but that is something different. And I do not want to "invert" by making 5V -> -5V or something like that.


texts: I have an active buzzer connected to an Arduino and everything works fine but the buzzer is just not loud enough. I don't know any specs about the buzzer but I've tried connecting it to a 9v battery using a transistor with the collector connected to +9v, the base connected to the digital output pin of the Arduino, and the emitter connected to the buzzer. This did not seem to do anything different. I tried using a passive buzzer as well using a PWM pin, but I was not able to achieve the same results so I'd like to stick with the active buzzer. Thank you.


texts: Vibration Detection bronze keyed instrument

texts:
I want to be able to detect when a bronze key (Balinese Gamelan) gets struck by a mallet (hard wood) without effecting the keys vibration, so a piezo is likely out.

Example of the instrument:

Is there a cheap optical vibration sensor that could go under the key and detect when the key has been struck?


texts: How to read whole data sent to USART with interrupt?

texts:
I am currently able to read byte by byte from USART with this code

ISR(USART_RX_vect)
{
    cli();
    while(!(UCSR0A&(1<<RXC0))){};
    // clear the USART interrupt
    received = UDR0;

    if(pinState == 0)
    {
        OCR2A = received;
        pinState = 1;
    }
    else if(pinState == 1)
    {
        OCR2B = received;
        pinState = 2;
    }
    else
    {
        OCR0A = received;
        pinState = 0;
    }
    sei();
}

But now I will send 4 bytes of data which is solely necessary for my application. I could not figure out how to read 4 bytes at once since the interrupt is triggered for every byte. Thank you for any effort in advance.

To make it clearer I will briefly explain what that pinState is. I am sending 3 bytes of data and I want the 1. byte to go pin 3 pwm 2. byte pin 11 pwm and 3. byte to pin6 pwm. As you see in every interrupt I am not gettin 3 bytes, but 1 byte instead. So that pinState thing is only standing for that purpose.


texts: Is symmetrical current perfectly symmetrical beyond analysis?

texts: Lets suppose that a circuit was constructed with almost identical components and wires to a ridiculous accuracy. When we say that a current is equal due to symmetry after a branch in a node with circuit analysis, would a real circuit built with the specifications above actually contain an equal distribution of the current between both paths? It seems logical that they would vary slightly, how slight is that and how dependent on the components that you used is the difference in current? What is the magnitude of the variation (milli-amps, nano-amps, single electrons)?


texts: Help to ID this little Transistor/Diode with proper markings SOT-89

texts:
I've been looking for the proper resources in order to find out what component this is.

The manufacturer wouldn't provide any schematics or technical information.

The inscriptions on it are :  KE with an X printed sideways.

edit:
Unfortunately, this device ( whatever it is ) is shorted on one side.