texts: How would cutting this heated bed in half affect the current draw?

texts:
I'm working on a project in which I need a small heater pad. I'm limited to a 12V supply which can provide 12.5A and I am drawing about 3.5A of that with my other electronics.
I have an old AnyCubic I3 Mega heated bed shown below which I thought I might be able to use. Based on this which is not exactly the same bed but I assume probably has similar specs, at 12V and 145W this will draw around 12A.
Looking at the tracks on the underside of the bed I can see that the bed has two heater elements connected up in parallel. I'd like to know what would happen if I were to cut the bed in half right between the two elements? If I could do so neatly enough without damaging the tracks on one half am I correct in thinking that the 'half' heater will draw 6A?


texts: Current to voltage converter with signal at non inverting terminal

texts:
I'm studying the following current to voltage converter:

The output should be:

$$V_{ADC2}=-Z \, I_Z - V_{WE2}$$

with \$Z=\frac{R}{RCs+1}\$.
Why there is the input \$V_{WE2}\$? What is its role?

The whole circuit in which there is the above I-V convert (and there is also another I-V converter, always with voltage at non inverting terminal) is:

Thank you so much for your time.


texts: PSpice Bipolar Junction Transistors Modeling

texts:
i want to simulate the circuit AmpopTBH2, on PSpice.
On image 1hbt.png we can see that Draft4 is working fine, on image 2hbt_pardif.png is the same circuit as Draft4 but on PSpice that circuit won't work right, because on Green voltage marker the same point as vpardif on LTspice, the voltage is always 3V (3vpardif_pspice.png)
The transistor i am using is BFR92A/PLP, because on PHILRF.lib the BFR92 is not there, no model available, but BFR92A is still the complementary of BFT92 so i thought it would work on PSpice, but unfortunately yet no.

The only circuit of HBT on PSpice is working right now for me is Class B Amplifier: HBTclassB.png & HBTclassB_vout_graph.png .

I also checked the SIEMENS.lib, but i didn't find any PNP/NPN complementary transistors, i have to use both types. I need a Transition Frequency about 5GHz.

I have physically (brought) the transistors  BFR92 and BFT92.

Edit: My question is what reason might be that the Differential Amplifier work well on LTSpice but on PSpice not ?
(On PSpice the voltage on nodes is always 3 Volts, and the current on this nodes is in the range of 1 pico Ampere pA, and it should be in the range of micro Ampere uA).


texts:
I am soldering using lead-free solder for about 1 hour a day with a solder fume extractor that has a carbon filter that looks like the image below. The place of soldering is in a building with commercial-grade ventilation, but without the ability to open windows.
This source claims solder fumes to consist of 95% particulates and 5% gases,
while this other source claims 99.5% particulates and 0.5% gases.
Considering the effectiveness of the carbon filter, the possible composition of the fumes, and location, would this setup be considered safe?


texts: What is the effect of very small AC frequency deviations from the grid on invertors and transformers for normal comsumer objects?

texts: What additional wear or inefficiencies are there from inverting a AC signal  to DC from say, 59.99 hertz instead of 60.00 hertz? And is there additional wear on transformers?  How do small deviations from 60 hertz negatively affect equipment?


texts: Net name requirement for PCB design on upverter

texts:
I am using Upverter to do my PCB design. Whenever I have 3 or more connections on a net, it shows me a warning saying that I need to explicitly name it.

I would like to know if this is just a quirk of Upverter or it is some industry standard to name nets with 3 or more connections. In addition to that, is there an industry convention on how to name nets?


texts: IC Pins with adjacent same net need to be made as common shape?

texts:
Attached is the layout I am working on.

Please see the yellow circled area. It is a common net. I have kept it as separate trace in the layout for each pin. Is there any advantage by providing shape at the pins instead individual trace. I am considering this as a generic question though this chip is a transistor array used to drive relay circuitry.


texts:
I have these two batteries, 18350 form factor, without any label.
As far as I know they are rechargeable because I've salvaged them and put in my salvaged "li-ion to be cecked" box. Now I've completely forgot where I took them and they doesn't seem to be li-ion.

They were at 2.7V more or less, then not too low to be used if li-ion,but then I've tried to charge them with my li-ion charger at 0.1A and the charger blocked the charge because no current were delivered.
I thought they were already fully charged (quite strange, since they were in this box since january) and in fact after 24h they show 2.85V.

There's a way to understand which kind of batteries are them?
PS: I can charge/discharge under constant load/voltage and log the current/tension. (in a safe container, of course)


texts:
I wish to expose a usb flash drive and read it as raw binary data, particularly read each byte & simultaneously writing it to another flash drive.

Given that I am working with an 8085 microprocessor, & I am in a position to program it & read data from secondary memory device, how can I start working with the usb.

I have tried to understand USB from this:

http://www.beyondlogic.org/usbnutshell/usb1.shtml

But I still have no idea how I would be writing my program to host flash drives.


texts: Connecting LEDs to 220v without using a power supply

texts:
I'm designing a backlit custom picture frame, and I want to include the power supply (or the lack of one) inside the body of the frame.

The problem is, since the frame design is more or less thin, I don't have space to place a power supply, so I ran into this doubt, can I make a circuit to use a LED strip that connects directly to 220v without using a power supply?.

My knowledge of electronic is almost null, I ran into several links explaining how to power LEDs strips directly to 200v, but, I have honestly no idea what problems, advantages or disadvantages I could find, and the language used was kind of advanced for me.

Basically, I want to know if this is possible, and what is required to do so.

Please explain to me like If I'm 6 years old, thanks!.


texts: Why doesn't my 555 + MOSFET setup drive my motor?

texts:
I have a 3v motor driven by a MOSFET that gets its input off an inverter circuit that comes off the output of a 555:

The idea is that when you press the button, it waits for about 20 seconds and then starts the motor.  (It's for a rotating banner that goes under a drone, I need it to start spinning after the drone lifts off from the ground and not before!)

So it seems to work if I put an LED instead of the motor, but with a motor it makes a mess and becomes flaky.  Sometimes the motor turns on, sometimes it doesn't, sometimes it runs for a few seconds and then turns off.

Motor is supposed to run on 3v, but I think it's not getting the full 3 volts.  It's hard to measure as the voltage seems to change when I put the voltmeter on!  When I replace it with an LED it seems dimmer than it would be if I hooked it up to straight 3v.

(The "GDS" circle thing is an IRFZ34N N-Type Power MOSFET, sorry I didn't know how to draw it.)

I tried replacing the 9v with 3v and 16v, still doesn't really work.  Also tried replacing the 1k resisters with 100, they just got really hot.

Any ideas what I might be doing wrong and how I can get this to work?  (Thanks for your patience, I'm a bit of a noob)


texts: Need to fixate current of motor connected to a battery

texts:
I have a gadget which includes a small 80mAh DC vibration motor connected to a CR2032 3V coin battery. The motor needs to keep running as long as the battery has juice, but instead of having it run at full speed and slow down gradually as the battery drains I prefer to have it running at constant speed more or less as long as the battery can provide enough power.

What would be the simplest (cheapest) way to implement such a solution in a small form factor?

Thank you.


texts:
I am looking for a component which can help me controlling the pressure in a tube.

I explain :

I have a compressor which blow some air in a tube. The compressor blow up to 8 bar and the tube is really small. I need a pressure between 1.5 and 2 bar in the tube. Then I am looking for a component, that I can drive electronicaly, which can do that for me.

Does anyone know about this type of component?

I don't know if I am clear, if you need othr information I'll edit my question.


texts: Show that adding a series capacitor of value C = 1/(w x L) makes the power factor equal 1 in a series RL circuit

texts:
Show that the power factor is equal to 1 when C = 1/WL in an RLC circuit.
I've had some problems finding out how to prove this, and I found a similiar solution online.

I have some problems understanding most of the steps. When the person finds the phasor current, I understand that he multiplies the complex conjugate on nominator and deminator.
As far as I can understand, after that he multiplies V with the phasor current, and he finds the real numbers of V*I. What I don't understand is what the person does after that.
For me it seems like he doesn't do anything wit the real number he found out of V*I, instead he takes the square root of complex conjugate in the nominator, and it just a mess after that.
Does anyone understand the steps after that, or do someone have an easier way to solve this probem? Worst case scenario, can someone provide me with the resources so I can understand the math behind this? My math is a bit rusty.


texts:
I'm using the P-Channel MOSFET IRF5305 (Datasheet: http://docs-asia.electrocomponents.com/webdocs/0791/0900766b807910f6.pdf) as an 'ideal diode.' However, it is not behaving like an ideal diode.

To better understand what is going on, I have connected two different multimeters between the Drain(D) and Source(S) of the MOSFET at different times. They indicate large resistance between D and S when V_GS is equal to zero.
This particular MOSFET has a threshold of V_GS somewhere between -2V and -4V (from datasheet).

In my operation, I have grounded the Gate through a pull-down resistor to discharge any gate capacitance between switching. I have connected a 5V DC power source to the Drain of the MOSFET, and there is a larger than expected voltage drop between Drain and Source of the MOSFET. The multimeters indicate R_DS is about 200 Ohms (the datasheet for this MOSFET indicates R_DSON as low as 0.06 Ohms). Is there something I'm doing wrong or some factor I have not considered?

For clarity: The MOSFET has 1 Ohm or less resistance when I have the output (from the Source) open-circuited. But when I connected a 5W 22 Ohm resistor as the load, there was a significant voltage drop at the MOSFET.

EDIT: schematic included. I intend to use some control at the Gate of the MOSFET. The resistor is there to discharge any voltage at the gate that accumulates whilst the gate is HIGH due to the gate capacitance.

EDIT: The voltage drop I observed when I connected the 5W 22Ohm resistor was about 0.4V. The multimeter is being used in a 'resistance' mode and I am connecting it directly to the Drain and Source legs of the MOSFET. I am not calculating the resistance from a Voltage or Current measurement.

simulate this circuit – Schematic created using CircuitLab


texts: Tested MCP1700-3300E dropout voltage doesn't match datasheet

texts:
I have several MCP1700-3300E LDO regulators that I plan to use. The datasheet claims that this LDO has:

Low Dropout (LDO) Voltage-  178 mV Typical @ 250 mA for VOUT=2.8V

And the dropout plot for 2.8V:

Actually, I am using 3.3V variant, not the 2.8V one, but unfortunately the datasheet doesn't provide dropout plot for 3.3V variant. Nevertheless, dropout should be similar, right?
So, I rigged up a simple schematic. My PSU feeding 3.7V to the MCP, and a 22 ohm resistor between the output of the MCP and the ground to give it a load. Running, my PSU says the current is 128 mA, around half of the maximum this LDO can handle. But measuring the voltage between the output and the ground of the MCP gives 2.97V, which is a 0.73V drop - far more than the datasheet suggests. This is a schematic of the exact setup I have for testing:

So, what am I missing here? According to the datasheet, I should be getting ~ 0.1V dropout, so the output should still be 3.3V. But the actual dropout is way more than that. I tried several different MCP's, thinking this one might be defected, but all of them show the same behavior. Can anyone help?


texts:
I've an unsolved exercise to ask.
The circuit is shown below:

The first question ask to find a value of R2 for which  Vout = 0 with Vin = 0.

I think this question is referred to the small signal model of the amplifier. So I've writed down the small signal model.

simulate this circuit – Schematic created using CircuitLab

Since the Re is shorted by Ce, I find a short circuit between the emitter of T2 and the collector of T1.
It looks like (to me) that Vout doesn't depend on R2.
Where is my mistake?
Thanks a lot!


texts:
I have a door bell that uses 2 AA batteries.

I want to use a 18650 — would it work in such an application?

It was recommended to use a 18650 in series with a Si diode, such as a 1N4001? The 0.6V drop should reduce the voltage sufficient to be considered safe.

How would I hook that up? A diagram if possible would help.


texts:
I want to make current pulses, the intensity of the pulses must go up slowly during a period of time until it reaches a maximum value...
I have thought of using a microcontroller to make voltage pulses using pwm then by using a voltage to current converter i can get current pulses.. I understand the meaning of pwm that we're changing the off-on time but i need to know what do i get as the output? I mean do i get values between 0 and 5 v?
*I don't know if the whole thought is correct tho... I appreciate any other thoughts


texts: what is bootstrap capacitor in this circuit how does it improve linearity and how does divide the collector resisitance?


texts: Calculating capacitance on breadboard vs PCB tracks

texts:
Is there an equation I can use to calculate:

the actual capacitance between two PCB tracks close together and
the actual capacitance between two adjacent holes of a breadboard

I believe such capacitance is called stray capacitance but I'm not 100% sure.

The reason why I ask is because I make super-regenerative receivers and the results are different when I transfer the circuit to PCB from a breadboard, most notably capacitance values, and I verify this because the reception frequency (station) is different even though I haven't change any values of any components.

The rest of the parts that form the circuit in both cases are exactly the same including the wall wart 5VDC power supply.

I also would like equations in order to make successful tests on the breadboard, so then I don't have to waste solder, or PCB material over failed attempts, and yes I removed and re-soldered components in the past which can be a pain so I want to avoid that route.

Any ideas on how to calculate the capacitance?


texts: Filter USB Power noise after Voltage Regulator?

texts:
I have designed a product which will be powered from USB 5V power supply. My product has two PCB. One PCB has USB connector, FTDI FT234XD, Voltage regulator (LM11173V3) and few passive components (Ferrite bead, capacitors and resistors). This circuit connects to other PCB which has sensitive analog sensor and PIC24E. After doing some experiments, I found out if I use my first PCB (PCB with usb) alone and check 3.3V output of Voltage regulator with a Digital Oscilloscope, then it has 92mV Peak-to-Peak noise. I want to reduce that noise and noise frequency.

The screenshot of oscillator is (without ferrite bead):

The schematic of PCB with USB connector is:

I have observed that if I solder ferrite bead (BLM18AG121SN1), then peak-to-peak noise increases to 200mV.

The layout of USB PCB is:

My questions are:

Can I reduce noise further?
How can ferrite bead in my circuit increase the noise?

EDIT:
My PCB has two layers with solid copper pour on both layers.


texts: Is it possible to use Kinetic energy to power small devices?

texts:
I've tried looking around for as much information as I could gather to build really small wearable electronics that could power themselves by generating energy with movement.

I know that the technology already exists in watches. There are watches that produce their own energy using a small generator that spins when the wearer moves its arm around. The energy is stored in a capacitor to make the watch work quasi-infinitely as long as the wearer moves enough throughout the day so that enough energy is generated. (some info here : http://en.wikipedia.org/wiki/Automatic_quartz )

I have trouble finding information about just how much current can this technique output for practical uses and if this technique can be adapted to work with other electronics.

In spirit of actually having real questions and not just vague stuff, here's a couple of questions I hope can get answered

How much energy can these devices produce / store?
Is there any other devices aside from watches that are powered using only kinetic energy?
Is there any schematics on how to create a kinetic generator for low-power devices?

Edit : Some people have said that it is hard to determine if it's possible since I didn't mention exactly what I would be doing. I don't have any project right now but I want to play around with wearable electronics that are motion-powered instead of battery-powered that you need to replace or recharge.

I'm thinking of using the lowest-power MCU I can find (something like the IT MSP430 microcontrollers) and reduce the current usage to the maximum by using standy mode as much as possible and doing very little active work, maybe just for logging multiple sensor data every couple seconds.


texts: I need a non-voltile serial memory chip that I can clock random bits(about 500 bits) into one at a time by hand using toggle switch to clock them in . This stored bitstream is then clocked out at 20K bits/second at the push of a button, every time you push this button the chip outputs the same bitstream. Can I do this without having to write any programs? Thank you!


texts: Do surface charges exist when EM wave gets reflected by dielectric boundary?

texts: If both the materials on a boundary are dielectric then do surface charge exists. I was solving using pillbox it showed that there should be surface charge on boundary to satisfy change in normal component of Electric flux density vector. But I am confused how so can happen.


texts:
I have an AC signal that is isolated after a transformer and is an input to inverting summing op amp, and a DC circuit which supplies voltage as an offset to the same summing op amp.

The AC is 1 VAC, 400 hz, while the DC is 1V.

To create a common potential point, is it possible to connect the AC neutral after the transformer to the DC COM or should we keep them separate?

Would combining these two compromise the isolation of the AC and DC circuits?

I personally thought AC neutral was also hot and would damage the DC com port if connected, but I am not entirely sure.

Thanks for the help!


texts: Good resources for learning about my STK500

texts:
I have a Atmel STK500. And I can't get my head around what half of the board does. Does any one know of any good resources for learning about it. I have the following books:

The primer book is good with the STK500 but only talks about the mega16(I think I maybe wrong on that don't have it to hand). But then stops after the first couple of pages and tells you how to only program the one microcontroller with it. Is there anything else I can look at to use my STK500 to its full potential? And configuring the jumpers as they confuse me being a novice. I would like to program other microcontrollers from atmel with it.


texts: Are there Multi-Turn Absolute Encoders that Store the Number of Turns in Non-Volatile Manner?

texts:
I have been learning about absolute encoders, and am testing a multi-turn absolute encoder (link to datasheet is here). During testing, I realized that after shutting down the power, although the encoder position is saved, the number of turns is not, which means the encoder position is non-volatile, but the number of turns is volatile.

So, forgive me for a lack of fundamental knowledge, but: does there exist a type of absolute encoder that saves the number of turns, even after power is turned off and on again?

I have tried searching for this on stackexchange and on Google, using the search terms "non-volatile" and "multi turn absolute encoder", but I could not find an answer.

EDIT: while searching more about different types of multi-turn encoders, I found a type of encoder that uses what is called the "Wiegand Effect". Wikipedia states "As the encoder revolves, the Wiegand wire core coil generates a pulse of electricity sufficient to power the encoder and write the turns count to non-volatile memory". I have also found an example of this encoder, and this example's datasheet is here. So, I guess I should modify my question as, "Are there any other types of absolute encoders that saves the number of turns, even after power is turned off and on again (other than Wiegand-based encoders)?" I am interested in learning all the different types, if there are any others.


texts: How much amperage can pass through a current limiter

texts:
I just completed an FAA required recurrent course for the aircraft I fly.  The Power Point program & instructor teach that a wire with 75 amp rated current limiters at each end will provide 150 amps of load before one or both current limiters melts and opens the circuit.  The use of the current limiters is a modification to  replace a single 450 amp rated reverse current circuit breaker.  Instead of one line with a 450 amp RCCB between the main battery and the main bus, three parallel lines are used with current limiters at each end of each line.  The advantage of the three parallel lines is to not lose all power to the bus if only one or two of the three parallel lines opens.

The explanation given is that total resistance in a series circuit is the sum of the individual resistances; therefore, six 75 amp current limiters (one at each end of the three parallel lines) will allow the same sustained current as the single 450 amp reverse current circuit breaker.

I disagree and I've read that each current limiter is rated at 150 amps and each of the parallel lines will allow a sustained current of 150 amps.  By analogy, if a line has current limiters at each end, one rated at 75 amps and one rated at 50 amps, the circuit will open with a sustained current in excess of 50 amps, not a total of 125 amps.


texts: Finding Equivalent Resistance - does order matter?

texts:
Conceptual question:
When you have a super complicated circuit, does it matter which node you start at when finding equivalent resistance? How about capacitance?


texts: What is a good way to add a programable offset to a diffential signal?

texts:
I have an AC coupled, ~10 MHz to 1 GHz, differential signal, with a programmable gain, coming from a detector. The signal contain pulses, and the DC-balance is poor but constant (even if my hand drawings don't show it that well...). I would like to add a programmable offset to my signal to optimize its amplitude:

A Differential op-amp is already in the circuit to adjust common mode:

simulate this circuit – Schematic created using CircuitLab

How can I add the offset without changing the common mode?


texts: Is there a practical way to convert a log potentiometer to an inverse log one?

texts:
I want to convert a log poti to an inverse log poti. The difference is shown below:

Let's say we have a 10k log poti, is there a practical way to inverse the output so that we can obtain something similar to the green plot above?


texts: Does the paint colour matter on a heat sink?

texts:
Heat leaves a heat sink via conduction, convection and radiation.  I was taught that black surfaces are best at radiating heat and correspondingly a lot of heat sinks are black.  But they also have fins for convection.  And large heat sinks have lots of large fins.  Convection therefore seems important.

So what happens if for aesthetic reasons I have to paint a heat sink brilliant white? White of course is the best colour for reflecting thermal radiation. Would that then reflect the heat back inside like a foil wrapped turkey? Can some one guesstimate a loss of efficiency or a necessary compensatory increase in rating?

P.S. Domestic radiators are white.

P.P.S. What does "material finish" imply in heat-sink terminology? doesn't quite answer it.


texts: Battery for ESP32 + Capacitive Soil Moisture Sensor 1.2

texts:
I have got a very beginner question.
I am planning to use the ESP32 microcontroller wired up with some sensors, such as this one
The sensor has an Operating Voltage: DC 3.3-5.5V, so I was planning to use a battery for running the ESP32, possibly at 3.3 V. Said that, do you think the sensor is going to have a huge impact in the battery life or it is the micro itself that is going to draw the most current?
Please note that my process will be to get the sensor value, send it through wifi and then going in deep sleep mode for half a day or so.
Has anyone experience in using this device with battery (and sensors) and able to make it last at least 1 month?


texts:
I am an engineering undergrad trying to build one gps tracking device with features like live streaming, current position, average speed, etc. (and if possible then sound etc.) from some computer located somewhere else.

I know coding very well and i am good in mechanical part, but i guess it will require more of electrical part.

Can any expert in this field just help me get started? I read few tutorials which suggested approaches like rfid, etc. But i am not sure how to "actually" do it, like configure internet to device and what all parts do i need to buy/make, I am just looking to make this device, in the best possible way i can.
Any help to get me started?


texts: How can a IC (or transistors or diodes) design make it difficult for a malicious manufacturer to subvert it undetected?

texts:
Introduction

This is a spin of from my question on security.se. To give more context:

  If I have a threat model where

  the adversary

  wants to corrupt computation or steal information
  does not want to be noticed at all (or at least until I made sensitive computation)
  knows the software I use
  does lie about and modify higher hardware such as CPUs before handing it out
  can not access the hardware directly later

  I

  want to compute correctly and secretly (or and at least prevent theft of sensitive information)
  want to exchange information with the outside
  have access to mathematically verified software (and additionally have access to clean hardware for Bootstrapping only)
  can check lower hardware such as wires for manipulation and can repair or rewire
  can not check higher hardware for manipulation

  In brackets (...) are some weakened circumstances.

Manipulation of hardware by malicious manufacturers is problematic attack vector in the chain of trust. My idea is to use simple verifiable parts to control the smart complex parts (e.g. compare output of confused CPUs). You can read it if you are interested. It is my main question. It links to the spin-offs and is updated.

Question

Before the edit of the question I thought that it is simple to make an corrupt IC act intelligently (e.g. a corrupt XOR gate could output 0 at certain times. That says the input is the same. This could be triggered after it sees a certain pattern.) But user The Photon explains that you would need on the order 10x as many gates as you need for just the XOR and that would be visible in the midst of 2 or 3 gates. But there seem to be different opinions by other users. It would be useful if I could use IC for a design.

After many edits the question is now specific:  It asks about designs that can be used to make it difficult to subvert IC (or transistors or diodes) for a malicious manufacturer undetected.  State of the art methods would be good information.

Please consider answering for the method: In what ways could the malicious manufacturer hide a modification? How can you detect that?


texts: Significance of ARM SysTick Timer vs. Other Timers?

texts:
I'm coming from 8 bit MCUs, and I've used a system timer to generate a periodic interrupt that seems to be the motivation behind the Cortex M SysTick timer?

Is there some kind of architectural significance to using the SysTick timer versus any other timer on the Cortex M MCUs?

Is it just a matter of coding preference, that programmers have used the SysTick timer as the primary every few ms timer?

The 800 page reference manual is pretty silent on SysTick other than how you apply post/prescalars.

I see it is a default high priority interrupt, so it kind of the path of least resistance for the system tick. But the interrupt priority is settable.

(The origin of this question is that I am using the STM32CubeMX to generate a project template, and when you go to add FreeRTOS, the Cube generates a warning that FreeRTOS should use a separate timer from SysTick... what makes me wonder if there something else at play here?  I has just assumed you would the SysTick because that is "how things are done"...).


texts: Multi cell lipo charging or boost converter

texts:
I'm working on a prototype for a project that needs to drive a stepper motor at 12V and 2A.  It needs to be powered by lipo batteries, have all of the charging circuitry in the device, charge through a DC jack, and everything needs to fit in a fairly small space.  I've been doing a lot of research, but I'm a bit of an EE noob.  Originally I was thinking I would have 3 3.7v lipo cells, but after tons of research, I can't find any off the shelf board to do balance charging of a 3S pack.

It appears there are lots of cheap single cell charger boards.  Does it make more since to just use a large cell (8000mah), and then use a boost converter to get to 12V/2A?  The problem I ran into there is that it looks like most of the boost converters I found don't go up to 2A when going from 3.7 to 12v.  (The efficiency loss is another concern, though for the prototype, I will take simplicity and a larger battery over complexity)

I'm sort of out of ideas at this point.  I'm looking for something I can use off the shelf.  Preferably something that costs under $30.  Does anyone have any ideas on the best approach here?

Update: just to clarify.  Ideally I would like the batteries to be self contained inside of the device and not need to be changed out.  (The actual amount of time the device gets used will be very minimal, so battery life expectancy is not a big concern)

Thanks!


texts: why power is lower if memory accesses are spread over a longer time?

texts:
I am studying Intel speed shift, I saw a sentence:

"If these memory accesses are spread over a longer time, the power is lower but the energy is equal"

My understanding is that when longer runtime, we need more energy even platform power is constant.

I think power = V x I at a testing moment.

Why power became lower if memory accesses are spread over a longer time ?

ref:
http://webee.technion.ac.il/~ran/papers/IEEE-Computer-H-EARtH-2016.pdf

page.35,

"Fixed energy (not shown in Figure 2): During workload execution, a fixed amount of data is transferred to and from memory, disk drives, and so on. This activity is a function of the application footprint and the devices’ physical characteristics; it does not depend on CPU frequency and therefore translates to fixed energy. If these memory accesses are spread over a longer time, the power is lower but the energy is equal"


texts: Why does (my) NUC/Laptop use odd (19V) power supply voltages?

texts: Nothing comes to mind that really needs exactly 19V, with USB-C on board which can provide 20V it seems even a bit of a drawback to step up the voltage rather than increasing the PSU voltage.


texts: IP Camera and USB data transmission over Ethernet Cable

texts:
Currently I am working on a project that requires connection of the Arduino and IP Camera over single Ethernet cable to a laptop and additionally supply power to a robot.

The goal is to stream Video from camera and communicate with Arduino board.

4 wires from Ethernet cable are required for the camera.
2 wires are needed for power supply.
That leaves me with 2 spare wires for USB connection Rx/Tx but no wires left for USB ground.

My question is: Do I need to run a separate GND wire for USB connection? Or will the GND be shared over RJ45 IP camera connector? And is it safe to operate?

I am not sure how camera data transmission works, but it's logical for me to assume that camera and laptop share GND.

simulate this circuit – Schematic created using CircuitLab


texts: N-MOSFET switching behavior when turning off

texts:
I am switching a 1 Ohm load with an N-channel MOSFET, which is driven by a TC4420 driver. The load is three Arcol HS50 330 mOhm resistors in series, the power supply is a 3S LiPo battery. The switching frequency is 1kHz with 10% duty.

I am trying to understand what is happening in the circuit when the FET is switching off.
I started with this:

This is the waveform in this case. Channel 2 (blue) is just the signal generator output, Channel 1 (yellow) is Vds, channel 4 (green) is the battery voltage, measured on the main battery wires (if I measure it through the balancer connector, the shape of the waveform is still the same, with smaller amplitude):

First I thought the huge peak around 55V is the avalanche breakdown of the FET, due to the load and the wiring having some inductance, followed by some ringing for the same reason plus the FET output capacitance. But then why is there that big rise on the battery voltage? This implies to me that current is flowing into the battery, which I really do not understand.

Then I tried adding a flyback diode:

Which resulted in a bigger battery voltage rise, but not much otherwise:

To eliminate the ringing, I added a snubber circuit (without the previous flywheel diode):

This was quite effective regarding the ringing:

So I tried with both the snubber and the diode:

With the same additional results as before (bigger battery voltage rise, and nothing else):

So my question is basically what is happening here? More specifically:

What causes the voltage rise on the battery, when I do not expect the current flowing back into the battery?
Why does the avalance happen regardless the presence of the flywheel diode? (Maybe this is some other phenomenon, not avalanche?)


texts: Theory Question: Speakers don't work unless I poke soldered points with screwdriver

texts:
In case you couldn't tell by the title, I don't really have any idea what I'm doing with electronics. Something happened though, and I am really curious about it. Don't know how to ask it specifically, so here's the backstory.
I brought out some old speakers from storage. I plugged them in, and they didn't work. However, if I turned, twisted, and pulled the volume turner just right, the speakers would start working. Usually only one worked, and the other was staticy, but which one was working would switch back and forth. After using them like that for about a month, I decided I had enough and took it apart to see if there was a loose part with the volume knob. Everything was soldered down tight, and nothing was loose with the knob. With everything on, I poked around at the soldered points with my screwdriver and heard some loud pops from the speakers. Just like that, they started working again (not perfectly, but 100x better).
This leads to a few questions. Why does poking at soldered points make them work again? Does static build up overtime or something? Also, is this dangerous to do again? The screwdriver is insulated, and I'm not touching any metal with either hand, so why is there any effect at all?
The speakers started acting up again recently, and the same solution worked once more.


texts: When a bench power supply is rated for 0-30V, 0-5A, does that mean that it can supply more than 5A at voltages below 30V while keeping the max power constant, or is there a hard cap on the current?


texts: How to use most GPIOs of ESP12e for simple push button inputs and led outputs?

texts: I'm using esp12e for my project and encountered difficulty in using more than 5 GPIOs. I have connected GPIO15 to Ground, GPIO0 to VCC, Enable to VCC (Connections as as per attached image). I'm able to use only GPIO4,5,12,13 & 14 (5 IOs) as normal IOs. How can I use more pins as IOs?


texts: Step up converter (3.7V to 5V) that will also charge battery!

texts:
As a picture often speaks better than words, here is what I'm looking for (the yellow circuit on this picture):

i.e. :

a circuit that converts 3.7 V to 5 V when a 18650 battery (3.7V) is connected
and that both outputs 5 V and charges the battery if a phone charger is connected

Optionnally, it would be great if the circuit could send a "low battery" trigger to some other chip.

Such circuit is probably quite common (in many everyday-use devices that can run in battery or with adapter), do you know where to find one? (either the schematics or even ready-to-use circuits)


texts: SMPS Transformer Primary Winding Ringing

texts:
We are working on a 24V 4A flyback SMPS design. But when we analyze the primary winding of SMPS transformer, we are determining very high voltage oscillations(ringing) up to 350V. But our DC bus is 150V. We have snubber circuit for primary side. ( f(switching)=100kHz )

When we analyze another 24V 4A SMPS from market and when we remove the snubber circuit of this SMPS, their SMPS primary winding oscillations is 10 % of our primary side oscillations of SMPS that is designed by us.
Why we are getting too much oscillation/ringing voltage?


texts: STM32 MCU - Temp sensor gives weird values

texts:
I'm fooling around with a Nucleo-F103RB STM32 board and I'm trying to measure the ambient temperature using its internal sensor. I activate the ADC and get data normally via the HAL_ADC_GetValue() function (the value is around 1700 - 1800 and varies with temperature as it should) but the problem is that I get really weird numbers when converting to Celsius using the formula given in the manual, namely: $$\frac{V_{25} - V_{ADC}}{AvgSlope} + 25$$ (about 70-80 degrees when the real temperature is no more than 25).

I suspect that has to do with the way I'm converting the ADC value into volts, but I can't see something obviously wrong, so I came to ask here.

Code is here :

#include "TempMsr.h"

volatile uint32_t sensorData = 0;
volatile uint32_t temp = 0;

uint32_t getTemp(ADC_HandleTypeDef* ADCHandle)
{
    sensorData = HAL_ADC_GetValue(ADCHandle);
    temp = ((V25 * 1000 - sensorData * 0.8) / AVGSLOPE) + 25;

    //V25 and sensorData must be in mV for this formula to work, as the
    //AVGSLOPE value is given in mV/oC

    //the 0.8 multiplication comes from dividing the max ADC voltage (3.3V) with its resolution (12 bits => 4096) which is 0.8mV/ADC unit

    return temp;
}

Its header file:

#ifndef TEMPMSR_H_
#define TEMPMSR_H_

#include "stm32f1xx_hal.h"

#define AVGSLOPE 4.3
//average slope of T-V chart according to datasheet pg 79
//(min is 4 mV/C, max 4.6, default (4.3): typical)

#define V25 1.43
//voltage of temperature sensor at 25C according to datasheet pg 79 (in V)
//(min is 1.34, max is 1.52, default(1.43): typical)

uint32_t getTemp(ADC_HandleTypeDef* ADCHandle);

#endif /* TEMPMSR_H_ */

Thanks in advance!

EDIT: I just noticed in the reference manual that the sensor has a bias (of up to +- 45 degrees) due to the manufacturing process, which is different on every chip and I have neither calculated it for my particular MCU nor included it in the formula. Could this be the problem?


texts:
just asking for some reassurance really, probably a novice question. Thank you in advance for any advice.

I am building this project:

https://github.com/brianmarkpeters/CHIP_BASED_SYNTHESIZERS/tree/master/SID%20SYNTH

to control a SID audio chip from a Commodore 64 via a Teensy microcontroller.
I have the project working and can control the chip via usb midi.
Next I would like to add some flashing lights in the form of some LEDS to visually demonstrate it functioning.

I have the data sheet for the IC:
http://archive.6502.org/datasheets/mos_6582_sid.pdf

I intend to add power LEDs for the two power supplies (5v and 9v)

my thinking is that I can also add eight LEDs (and resistors) for pins d0-7 on the chip which will light as data is being sent to these pinsr. In theory I would connect the anodes to the pins, and cathodes via a resistor to ground.

My concern is that the LEDs may themselves interfere with the data being transferred.
Some my questions are really; Is there any way to be sure of this other than experimenting with resistor values? Am I missing something and am actually likely to destroy the IC?
Would pins A0-A4 be any different?

the doc has this to say about pins D0-D7.

"D0-D7 (Pins 15-22) — These bidirectional lines are used
to transfer data between SID and the microprocessor.
They are TTL compatible in the output mode and capable
of driving 2 TTL loads in the output mode. The data
buffers are usually in the high-impedance off state.
During a Write operation, the data buffers remain in the
off (input) state and the microprocessor supplies data to
SID over these lines. During a Read operation, the data
buffers turn on and SID supplies data to the
microprocessor over these lines. The pins are normally
connected to the corresponding data lines of the
microprocessor."


texts:
I just got the TENMA 72-8700A bench power supply. A link to the manual is here. I have read it, but I am a bit confused by the wording. I cannot figure out under what circumstances the device is in constant voltage or constant current mode, and when I am able to adjust the current or voltage. Can anyone who has some experience with these things help me out? I want to know when I can adjust the output current, and when I can adjust the output voltage.

I have figured this out. The thing I was confused about was the fact that the readout only shows the current flowing, not the set maximum current. I was expecting the readout to show the set max current, not the flowing current


texts: What are the (mathematical) restrictions of a TMS320C6713 DSP?

texts:
I have a function that computes the sum of even numbers in a Fibonacci sequence less than a boundary.

Should I be worried about this calculation? Can the TMS320C6713 handle it?

When I run the following code on Visual Studio on my 64-bit computer with a value of 4294967295 (232 -1), it returns 4611685999100035072.

unsigned long long int sum = 0;
unsigned int f_n0 = 0;
unsigned int f_n1 = 1;
unsigned long long int f_n2 = 0;

unsigned long long int list_fibonacci(unsigned long long int boundary)
{
   while ((f_n2 = f_n0 + f_n1) < boundary)
   {
       if (f_n2 % 2 == 0)
          sum += f_n2;
       f_n0 = f_n1;
       f_n1 = f_n2;
   }
   return sum;
}

Thank you.


texts: How BJT Collector current behave in common base saturation mode?

texts: I'm trying to understand the characteristics of bjt in different modes of operation . .when it comes to the saturation mode of operation in common base configuration ,some books says that the collector current becomes zero and some say it increase rapidly independent of the emitter current.so, which is correct


texts:
I've been trying to build up certain Embedded systems and i wonder how people make them secure. Or else it would have been reproduced well. I know there is an extent to provide security if you are using Controllers like PIC/AVR and well known chips from established companies like ATMEL/MICROCHIP/TI  EEPROM. But Still i don't have any clue how they secure their Code and Hardware. I'm asking from the perspective of a Product Developer and what methods he/she normally opts for.

Or Is it like that people don't make things secure which i trust is a No.

I would extremely happy if you input some suggestions through which you make your PCB/Software not reproducible so easily...By reverse engineering enthusiasts.

All tried or tested methods or Nerdy methods would be welcome.


texts: Shield grounding location for an STP cable in a balanced system

texts:
If a balanced source or driver is coupled to a differential balanced receiver via a balanced STP cable as shown in the hand drawn illustration below:

in such case I have read that grounding the shield of the STP cable at both receiver and source side might cause ground loops.

Is there a difference between using |AA’| and |BB’| for grounding the shield? In other words is there a consensus about whether the shield must be grounded at receiver end or the source end? And what happens if the shield is not grounded at all?


texts: How does this continuity/mains tester detect microwave RF?

texts:
This tester can detect leakage from microwave oven above a certain value (among its other uses). It has only resistor, transistor (darlington), LED and two batteries.
As far as I understand, it can detect hot wire without making a contact with the wire thanks to the capacitive coupling effect.

But, how does this continuity/mains tester detect microwave oven RF?


texts:
This is an IP Camera circuit and after i put accidentally 12vDC instead of 5vDC this component has died with smoking. I want to replace this component with new one but i didnt figurate it out what is this component and have a closer look under magnifier find some clues as u can see pictures below.
This component have 5 lead
Barely seen a write "A14P" maybe, but not sure
U10 sign left side of component.
Please help what is this component so i can order new one and replace it.

This is the full size circuit if it helps


texts: What does this circuit do? Reed switch debounce?

texts: I'm trying to reverse engineer a pcb and I'm stuck on this circuit. I believe the capacitors maybe for debounce. The switch is a reed switch. Can anyone shed any light on it?


texts: Help with multiple receiver channels and single storage architecture

texts:
I want to build a datalogger that has multiple receiver channels that run on serial communication protocol RS232 and then collect the information from the channels in a single storage that would be accessed by another controller whenever it gets full.

I'm using Spartan-6 for the job. I figured I could use Ken Chapman's ultra compact uart to use as receivers and then deploy glue logic to store the data in a FIFO of depth equal to \$noofchannels \cdot (\frac{1}{2}.receiverbufferdepth)+ 4\$
assuming the width to be 8 in all the buffers.
Now I have three fillstate signals available from this UART:

Data Present
Buffer full
Buffer half full

and I have to attach a channel ID every time I read data from the receiver-buffer so that the controller reading my FIFO would know which data was from which channel-this thing introduces overhead. I want my algorithm to have lowest overhead as possible as in I want it to attach an appropriate chunk of data (bytes) with each identifier. My baud rate is 115.200 kBd and my clock is 16 MHz. I'm thinking of having 4 receiver channels.

At first I decided to run an FSM that would start every time a half-full signal goes high and read from that particular buffer till its data-present signal goes zero. Also I calculated that if I keep the buffer depth 4 at each receiver channels and if reading every byte took 2 cycles then I would still have appropriate clock cycles left to read all of the buffers, write it to a single FIFO and ask the controller to read all of it.

Problem with this approach is that I might lose data in case a channel doesn't send more than 7 bytes ( because kcuart6 has a FIFO of depth 16 which I can't change to 4).

Guys I want suggestions for a fool proof architecture that would ensure that no bytes are lost while my glue logic is reading from receiver buffers and also while the controller is accessing my storage memory (because I can't write while the controller is reading my FIFO).


texts: Why h-parameters of BJT are no longer popular?

texts:
I realized that most modern textbooks (see Sedra Smith, Razavi, Franco, even AoE) analyze BJTs using parameters such as \$g_m\$, \$ \beta\$, \$r_{\pi}\$, while old books tend to use two-port parameters such as \$h_{ie}\$, \$h_{fe}\$, \$h_{re}\$, \$h_{oe}\$.

So, apparently h-parameters of BJT are no longer popular. Why?


texts: Where do the oscillations in a GaN half-bridge design exactly come from?

texts:
I'm working on a inverter pcb for a PMSM with GaN switches and I'm wondering:

where exactly do the oscillations come from, when the high-side GaN goes high and the low-side GaN goes low.
Why don't these oscillations also occur when the high-side GaN goes low and the low-side GaN goes high?
Are these internal capacitances or charges of the GaN in combination with the motor winding (~4uH) which create these oscillations? If so, which ones exactly?

Notes:

VDC- is connected to GND at one single point at the PCB
GaNs are Infineon ###
Please disregard the values of the low-pass filter at the inputs of the
driver.


texts: Proper grounding in a battery powered AGV

texts:
I have a few general-grounding-technique questions for an AGV IO & control PCB. Some context:
The power input pins VIn+ and VIn0 of the board will be connected to the 48V battery terminals. The battery voltage is then converted into a clean 5V logic voltage by an on-board isolated DC/DC.
The PCB connector houses IO (7 24V logic level digital inputs, 7 24V logic level digital outputs and 2 10V logic level analog inputs) and communication (CAN, RS-232, RS-485) used to read and control sensors, actuators and CAN-slaves. All pins on the connector are isolated from the logic side of the PCB via purpose-built isolated transcievers, optocouplers, SSR inputs and a moat between the PCB signal ground and the connector-side ground. A visual representation:

What I still struggle with is:

Should the chassis ground and the connector-side signal reference ground be the same net?
Should the isolated PCB ground be connected to chassis? I seem to have read that it should; this seems strange to me as it would void the benefits of galvanic isolation.
Is connecting the chassis to ground through metal-plated mounting holes enough in this scenario?
Is it perhaps best to leave the logic ground alone and floating compared to the chassis and focus on the connector-side reference signals?


texts:
This circuit is n-EMOSFET circuit, VTH=3V, K=1mA/V2, find VGS, ID and VD.

Vo = 15-3300ID

ID = (15 -Vo)/3300

VD = 3300ID

Since IG=0, VGS=VDS=Vo

ID = (15 -Vo)/3300 = 1mA/V2 (VGS- VTH)/2

ID = (15 -Vo)/3300 = 1mA/V2 (Vo- VTH)/2

From this equation, I got Vo , then I can find VGS, VD and ID.

Please correct me whether I got it right?


texts:
I have an LED (5mm, 2V 20mA) which is always on from a 12V supply. (I assume it has some resistors to drop the voltage.)
I need to turn this LED off when another power supply line gets a 3V input, and when the 3V is not there the LED has to stay on. What is the simplest circuit to achieve this? The input battery will be like a 12V 7.5A one. Please help.
An image of the current setup is as below.


texts: Questions about signal and logic circuit

texts:
I just learned about basic logic and logic circuit from a Discrete Math book and I have a few questions:

What exactly is a signal in Engineering? From Wikipedia, a signal is defined as a time-varying quantity, but I don't really understand what that means. Does the definition mean that anything that can change in a circuit is a signal?

From my understanding of what signal is, in a switch circuit, the input signals are the states of the component switches and the output signal is the state of the whole circuit itself while in a logic circuit, the input signals are the voltage at points that are not behind any gates(and also behind a switch? I'm still not sure about this) and the output signal is the voltage at the point behind all logic gates, with respect to the Ground. Is my understanding correct?

In a circuit that contains both switches and logic gates (not like just a few switches followed immediately by logic gates but maybe a bunch of switches connected in series and parallel and then is connected with a combinational logic circuit), what exactly are the input signals and output signal? I mean, is it possible for the input signals and output signals to be of different types?


texts: How do I set up both CAN modules on the PIC DSPIC33EP128GM604?

texts:
So I am in the midst of my first proper PIC project, and it has been interesting to say the least. The problem I'm having is setting up the CAN modules. The PIC I'm using has two ECAN modules. Using the code examples provided, I set up CAN1 (module 1) to transmit a message, and it works absolutely fine. I can see the signal on the designated I/O pin.

The problem is when I try to use the same code with CAN2 (the second module on the PIC). It transmits some data, but not the one I set up in the buffer; all I see is 0x0000 throughout the package.

My code is mostly from the the ECAN application notes, with my few configuration tweeks. CAN1 works just fine, but CAN2 does not. When I ask both modules to transmit (CAN1 first then CAN2), only CAN1 works, but CAN2 doesn't budge at all (I have no idea why). When I turn off CAN1 and only ask CAN2 to transmit, as mentioned above, it works, but only transmits 0's (it seems like it's not talking to the DMA properly, even though I'm using the same tried-and-tested code that I used for CAN1).

Set up DMA1 for CAN transmit:

DMA1CONbits.SIZE = 0x0;
DMA1CONbits.DIR = 0x1; //From peripheral to DMA
DMA1CONbits.AMODE = 0x2;
DMA1CONbits.MODE = 0x0;
DMA1REQ = 70;
DMA1CNT = 7; //Data length
DMA1PAD = (volatile unsigned int) &C1TXD; //Point to peripheral register
DMA1STAL = (unsigned int) &CAN1MsgBuf; //Point to buffer
DMA1STAH = (unsigned int) &CAN1MsgBuf; //Point to buffer
DMA1CONbits.CHEN = 0x1; //Enable

Set CAN bus speed (This is a peripheral Library function):

CAN1Initialize(CAN_SYNC_JUMP_WIDTH2 &
               CAN_BAUD_PRE_SCALE(4),
               CAN_WAKEUP_BY_FILTER_DIS &
               CAN_PHASE_SEG2_TQ(3) &
               CAN_PHASE_SEG1_TQ(3) &
               CAN_PROPAGATIONTIME_SEG_TQ(3) &
               CAN_SEG2_FREE_PROG &
               CAN_SAMPLE1TIME); //CAN-IN

Send the Data:

    C1TR01CONbits.TXEN0 = 0x1;
    C1TR01CONbits.TX0PRI = 0x3;

    /* At this point the ECAN1 module is ready to transmit a message. Place the ECAN module in
       Normal mode. */
    C1CTRL1bits.REQOP = 0;
    while (C1CTRL1bits.OPMODE != 0)
        ;

    /* Write to message buffer 0. */
    /* CiTRBnSID = 0bxxx1 0010 0011 1100
       IDE = 0b0
       SRR = 0b0
       SID<10:0>= 0b100 1000 1111 */

    unsigned int ID = 0xB1;
    CAN1MsgBuf[0][0] = ID<<2;
    /* CiTRBnEID = 0bxxxx 0000 0000 0000
       EID<17:6> = 0b0000 0000 0000 */

    CAN1MsgBuf[0][1] = 0x0000;
    /* CiTRBnDLC = 0b0000 0000 xxx0 1111
       EID<17:6> = 0b000000
       RTR = 0b0
       RB1 = 0b0
       RB0 = 0b0
       DLC = 0b1111 */
    CAN1MsgBuf[0][2] = 0x0008;

    /* Write message data bytes */
    CAN1MsgBuf[0][3] = 0xabcd;
    CAN1MsgBuf[0][4] = 0xabcd;
    CAN1MsgBuf[0][5] = 0xabcd;
    CAN1MsgBuf[0][6] = 0xabcd;

    /* Request message buffer 0 transmission */
    C1TR01CONbits.TXREQ0 = 0x1;

    /* The following shows an example of how the TXREQ bit
       can be polled to check if transmission is complete. */
    while (C1TR01CONbits.TXREQ0 == 1)
        ;

    /* Message was placed successfully on the bus. */

I am using the same code for both modules. I only switch the 1's to the 2's for the address names. For example, C1TR01CON for CAN1 becomes C2TR01CON for CAN2, etc.


texts:
I'm following the idea that it could be helpful to have a feedback of a servo. There are already servos on the market plus self-made-tutorials, but all of them provide only the actual position. What I want is the force (energy) which is currently applied to the motors because I believe this could much better be interpreted by an AI as external forces and as positioning support than the actual position does.

Are there such servos on the market and/or what's the keyword to search for them?


texts: Relationship between FFT in dB and spectrum analyser output in dBm

texts:
I am trying to calibrate my RF daughter board in USRP software defined radio. I am trying to measure transmitted power for different frequencies at a certain set gain and transmitter amplitude. When I use a spectrum analyser, I get some voltage in dBm, so as dBm is an absolute scale I can measure the power by converting to normal MilliWatt units.

Now I connected a receiver USRP(software defined radio) and ran FFT script which is inside GNURadio. But I see that it shows a plot of frequency vs power in dB. Now I am unable to correlate between power value in  spectrum analyser and power in dB given by GNURadio FFT script. I am of the opinion that you can't convert the dB value of FFT to normal watt because you don't know the reference by which the FFT is calculated. For example if there is a graph or spec which says 3 dB it means to say that when you give any input in the range specified, the output will be half of that value. So converting dB to normal units of power is dependent on what reference you divide it by. Am I right? In that case I need to know the reference that gnuradio script of FFT is calculated by. I would like to know other ways of correlating these two graphs that i am having.


texts: Homemade ethernet hub not working with three computers

texts:
I am trying to connect three computers in one network. I have connected the wires like the photo.

I works with two computers but not three computers at the same time.

For example, let's name the ports: A, B, C:

A+B works if C is empty.
A+C works if B is empty.
B+C works if A is empty.
A+B+C does not work.

What can be the problem (or, should this work)?


texts: How to measure impedance of sensor's traces?

texts:
I'm designing a humidity sensor as a semester project and I want to measure impedance of these traces:

I don't have specialized impedance measuring instruments for this.
As I'm thinking, this should be done using Arduino Uno i.e Some hardware and a bit of code. Help me find a solution to this.


texts: The Resonant Choke filter in its traditional form looks like an orthodox choke input filter but it has a cap across the choke tuning it to twice the power frequency. This means 100 or 120 Hz depending on what part of the world. Intuitively you can get lower output ripple for a given output cap value compared to the normal choke input filter. In fact old audiophiles would sometimes "tune the choke" to reduce hum. Quite simply the choke and resonant cap form a high impedence parallel tuned circuit that blocks the 2F ripple. The higher order terms of the full wave rectified sine wave are of much lower amplitude and are dealt with by the output cap. An interesting aspect of this postwar circuit is that it has the potential for a good power factor but the old choke input filter can have a power factor that beats the cap input filter anyway. Could the choke in a resonant choke be smaller than the choke in a traditional choke input filter because less inductance is needed          ? What would be a sensible L/C ratio? Would the power factor compete with the valley fill? When this was originally done loads tended to have less variation. How would the resonant choke perform under changing loading?Is this circuit easy on the diode recovery making it a contender in a sine wave SMPS? How would it perform if it was slightly off resonance ? Would the component tolerances be reasonably broad for easy production ? Would the low THD input current waveform be useful for a quiet SMPS ?


texts: Voltage level in an open drain bus (I2C)

texts:
I have a setup as seen in this image:

The question is what will the voltage at the line on the left size (marked with [Volt ??] ) be when the open-drain logic is active? The goal is to have a logic zero but I am not sure how the diode D1 is going to affect this.  Will it depend of its forward voltage or some other characteristics? How can I estimate the voltage at [Volt??] to make sure it will be low enough to register as logic zero?

For clarifications: this is an I2C bus connecting a Raspberry Pi to an Atmel ATTiny13 micro-controller. The 3.3v and R1 are the RPi side, and the open-drain side is one of the ATTiny I/O pins. The diode D1 is added to protect the RPi from miss configuration on the ATTiny side that might pull the line high to 5v which might damage the RPi.


texts: AC source resistance problem while simulating transformer in LTSpice

texts: I am trying to build a Voltage quadruple circuit. But as per my requirement ,the source I will be using has a resistance of 25 ohms.As the input signal to too small I need to use a transformer to boost up the signal. while simulating the circuit in LT spice , if I give 25 Ohm as series resistance of the source.. the circuit is not working and showing very negligible output voltage. Please suggest me how to solve this problem?


texts: How to pick the right plug/socket pair for my application?

texts:
I could ask for my specific application, but then I'd need to re-ask every time I need one, plus you frown upon "hardware recommendation" requests, so instead, I'm asking to teach me a method I can use and reuse whenever the need arises.

I'm developing a device and need a connector. I have a number of lines - some of them signal (analog (say, thermistor, speaker), or trivial binary, like a switch), some run power of known max amperage and voltage. These lines must be disconnectable from the board in a way more convenient than unscrewing them from a terminal block. I know how frequently the socket would be used, whether it would be hot-pluggable or not, and what's the required lifetime of the device. There might be data lines that require shielding, or an antenna line, though if considering these in the answer would make it too complex, feel free to ignore that part.

One thing I know is it's non-standard, so using any popular socket standard like DE15 (VGA connector) is asking for trouble, as some idiot is bound to try to connect a VGA monitor to it and destroy it.

I'm entering a catalogue... and I'm swamped.

I narrow it down to number of pins > min, < min+delta, similarly for voltage and I'm still getting at least 50 results to choose from, differing by parameters I have no clue about. I narrow it down to my precise needs and I have only one, a 4 kilogram plug+socket for under-sea applications, $15000/piece. Not something for a home workshop appliance.

What's the right approach?


texts: Altium Designer - How to make chamfer on 90 degrees tracks?

texts:
My need, is what you can read in the title: how can I make chamfer in 90° tracks connections? I've found a way to do that but works only with auto-routing. I want to do it manually.

I have Altium Designer 10 and i don't understand how to do it in a simple way.

Currently:

What I want to achieve:


texts:
I have a buzzer circuit.

Waveform :

My questions :

I have marked the points in the circuit where I am measuring the voltage and the current. PWM pulse is given to the base of the transistor.
I want to understand why the voltage waveform is like that and the current waveform is like that?
Why is the voltage waveform Flat and the current waveform like spiked?
I would like to understand, only what will happen if I keep increasing the PWM pulse width at the base of the transistor. Please help me understand. (I don't write codes which is why I would not be able to check this by varying the PWM output coming from the Microcontroller to the base of the transistor)


texts:
Can I replace the potentiometer in this AC dimmer circuit with a fixed resistor so that I can get a permanent dim setting?. If yes then how.

Components in this circuit are
The parts used are

WH149-500k potentiometer
DB3 bidirectional diode
2k resistance 0.25W
MAC97A6
104 630V CBB capacitor

Edit.
here is the picture of the pcb kit. The pot has 4 legs??

Edit.
I'm adding another circuit which should be clearer.


texts:
I'm setting up a playful coding challenge for our programmers. It's about coding theory. There are source, channel and sink. The task will be to implement an encoder for the source and a decoder for the sink. The encoded information will be transmitted over a channel with simulated garbling.

Now my question:

What common noise patterns do we encounter in real settings and how would their transformations look like?

What people talk about are for example:

band tapes (stressed at start and end)
defect memory (some bits are always off)
lightning strike
meteor shower

But they never mention how these patterns would look like.


texts:
I am using Relay OJE series SPST and I want to drive the relay with V=5v and the resistance through the coil is 125 ohm. From microcontroller 3.3v and 1k resistor. The NPN type is BC817-25 and the max hfe/B is 400.

What is Ib, Ic? And how much current goes through the coil? To make sure my relay type is ok and can handle the current!


texts: How to control AXI DMA and/or BRAM cores in a ZYNQ

texts:
I am trying to produce a sine wave using the DAC of a ZYNQ board (red pitaya). It is important that I have accurate control over the phase of the signal that I am producing.

I would like to do this as follows:

Generate the signal (samples) with a program that runs on the CPU.
Transfer the samples to a block ram in the logical part of my design.
Clock the samples out of the block ram and into the DAC.
Repeat the above.

My current setup is based on Anton Potočnik's tutorial:

The heirarchy "dac_side" contains some IP cores for memory management and a signal generator:

and the following memory addresses have been assigned:

I have no problem controlling the LEDs via the GPIO port at address 0x42000000.

Writing the samples of a sine wave into 0x42400000 results in short bursts of 20 MHz sine waves that completely fade away within a few cycles (possibly some kind of impulse response).

Writing the samples to 0x42430000 results in the following error message:

Unhandled fault: external abort on non-linefetch (0x818) at 0xb6f42000
pgd = d84bc000
[b6f42000] *pgd=18a09831, *pte=42430743, *ppte=42430c33
Bus error

The fact that I have the choice between two addresses is already a sign that I haven't configured the IP cores for memory management correctly. Also, I currently don't have any control signals in order to specify when the processing system is writing to the BRAM and when the DAC should read out the values from the BRAM. Maybe these kind of tasks are handled by the AXI BRAM Controller, or maybe my Block Memory Generator should have two ports and I should be connecting a second AXI Bram Controller.

My question:

How should I be connecting the Block Memory Generator in order to achieve the sequency (1, 2, 3, 4) described above?


texts: I want to read 8 PWM inputs (standard servo PWM, 1ms to 2ms) without an input capture module (my module only has 7 channels.) Could I use a capacitor and the ADC on my MCU? Does anyone know of any successful implementation of this, or have any references for this?


texts:
I want to build a circuit to switch a 1 1/2hp pump ON and OFF. ON to fill a large tank. OFF when the tank is full. I want to use a mechanical start (push the button) with a switch to cut the power. I see this as a mechanical latching relay application. I prefer to have a 24vac coil to match other devices in the system.

I want latching so that the coil is not powered during the 3 hour fill time but only gets momentary power when the full float completes the coil circuit. After that, the coil and the pump lose power  until a finger pushes button.

The catalogs I have read suggest the mechanical portion of the relay is an accessory. How do I spec this relay? I know I need to have contacts for two hot legs to the pump and contacts to control the power to the step down transformer for the coil.
I am a hobbyist. Thank you for any clues.


texts: i am using Max232 and max485 to convert the RS232 pc data to RS485. I got a circuit using these ICs with a transistor and some resitor. circuit is such that RE and DE are short together and tied to collector of NPN transitor. Base of the transistor is connected to Rout of Max232. now when PC is receiving data from RS485, then Rout is high, and after inverting through transistor turns low and RE enables the RO. this is understandible. but when PC starts transmitting, RO turn low initially due to start bit, which through transistor inverts and turn high, which turn DE high and hence DI pass data to 485. but after start bit RO will be changing its state, then what will happen. changing RO state will ultimately switch RE and DE controlling pin on each bit of packet. My Question, how does pulsating RE DE works for this circuit when pc is transmitting RS232 to 485. I know i am thinking all this in some wrong pattern, please help me in to know this circuit. (i have attach picture of ckt). just want to know the operation, as this circuit is working fine.


texts: What are the differences between NAND and NOR flash?

texts: What are the differences and where would you use each?


texts: How to find out if a binary number is zero or not using logic gates?

texts:
I'm trying to put some logic gates together which would perform a task of finding out whether a number is zero or not. I came across a thread like this on here already (How to find out if a binary number is zero) and it says to "or every bit in the bus and then apply a not gate" but i'm not quite sure how this works.

I've tried drawing out the logic gates and their inputs/outputs, and what I've got is 4 OR gates which have inputs going from in[0] to in[7], so the first and second OR gates are:

Or(a=in[0], b=in[1], out=out0);
Or(a=in[2], b=in[3], out=out1);

And so on for the next two gates. I then get 4 outputs and i'm not entirely sure what to do with them now. I was thinking of somehow combining them into one input and then applying a single NOT gate to it, but i'm not sure if that would work, as well as applying 4 NOT gates to each of the outputs, but then i'd end up with 4 outputs after the NOT gate anyway, just inverted.

Anyone got any advice/tips on how I could do this?


texts: It occurred to me that since single-phase AC induction motors can act as generators, it might be possible to brake an induction motor with a resistive load. The basic idea is that when you want to stop the motor, you would disconnect the motor from the AC power source, and connect a resistive load to the motor. Well, I just bought a radial arm saw which takes a long time to coast down, so I thought I would try it. Here is the plan. If anyone knows whether this will work at all, or can help suggest what the load should be, it would be much appreciated.


texts:
I have looked at multiple datasheets of multiple radio modules including one I'm using (HM-TRP) and none of them specify a ramp-up or a ramp-down time. According to research, this is known as the guard time.

Through my own experimentation with data radios, one must wait a certain amount of time after the last transmitter has finished before the next transmitter can begin, otherwise data will be lost.

I could go on and on and experiment with 65,536+ different values and waiting 10 minutes to try each value but that I feel is a waste.

Since I do want to exchange data at high speed on the modules, I'm trying to avoid a ridiculous guard time. Hopefully I can get away with less than 15mS guard time.

Given that no datasheet I read so far has made any indication about ramp or guard times, My question then is, after the last bit has been transmitted by the remote radio, how long should I make the local radio wait before beginning to transmit data?

All radios in question are the same models (HM-TRP fsk radios) use the exact same settings.
The radios are currently 1 meter apart in distance and there is nothing causing interference in-between
The radios are also half-duplex.


texts: How feasible is creating a plug in -out hardware system ? is it possible ??

texts:
I'm making a hardware system that uses both analog and digital :
The system will have the following components ,
RF ID module
GSM/GPRS
Bluetooth
LCD
Micro-controller
..... etc of several modules that have their own embedded software to run them in a proper way

I was thinking as I can apply Software engineering to make the software in a modular way , can I do this in hardware ??
i.e if I don't need the "bluetooth" in my design I will simply remove the hardware and the software >

Here's my imagination :


texts: Can someone help me in getting to know what is wrong with my Frequency multiplier circuit using 565?

texts:
I just learned the working of NE565 and I tried to simulate a Frequency as multiplier using 565 in Proteus , but I don't know why PIN 4 of my NE565 is not giving any output . Its coming plane blank in output waveform in the oscilloscope . Please can someone help me in getting to know where I have gone wrong ?
I have attached my circuit diagram with my post.


texts: How do i go about finding the transfer function of this system with two inputs?

texts:
This was how i tried to formulate the answer but ive been told its incorrect.

$$R(t)=u(t)$$
$$D(t)=u(t)=1/s$$
$$K=10$$
$$H=1$$

$$G=\frac{K}{s(s+1)(s+2)}
=\frac{K}{s^3+3s^2+2s}
$$

If someone could help me understand how i tackle this system that would be appreciated.


texts: Two BJT as Switch for 24V problem with LED always on

texts:
Circuit
This is the simulation on Falstad that works:

Where it is being done that way for tests purposes, but the objective is to use a TTL signal from the encoder to send a 24V signal to a PLC or Data Aquisition Board.
Problem
There are two transistors:

A PNP (BC558)
And a NPN (BC337)

The moment when the 24V source is turned on and the 5V switch is off, the LED lights on. Is it a problem from the transistor specs? Or It is to work that way and another thing is wrong...
Is it possible to make a TTL encoder signal conversion to 24V just with two transistors?
EDIT:
It worked with an optocoupler:

However, when testing with an encoder for the 5V input, the optocoupler couldn't switch on the required frequency. So a new NPN transistor was used and the circuit worked:

And the PLC read the encoder pulses correctly.
So I got rid of the 24V at the base of PNP. It is working, however, any noise on the circuit can make it send pulses incorrectly.


texts: Why do KiCad's library footprints for 0402 resistors and capacitors have different pad sizes?

texts: KiCad's default library footprint for C_0402 is longer than R_0402.  Why?


texts: How does an ohmmeter measure different resistances?

texts:
An ohmmeter has set of range settings for the resistances to be measured.
When we switch to any range, what behavior of the test reference is being adjusted?

In other words; I'm wondering if we change lets say from a 200 to 1k ohm range, what exactly are we changing? Are we adjusting the voltage applied to the resistance under test or are we adjusting the current flowing through the resistance under test?

(If we want to measure a diode's bulk resistance I may need to know what is applied to the ends of the diode not to damage it)


texts:
I am part of a hobby project where we have a pair of fat, insulated #4 AWG stranded copper wires carrying +5V and ground. I want to tap into these wires every few inches to draw power off it (max draw of around 4A per tap), for a total of 24 tap pairs.

The 'best' idea I've had so far is sketchy: Drive some steel metal screws in through the insulation and into the center of the wire strands. Solder the connecting wires off of the heads of those screws, and eventually cover the heads in electrical tape or similar (to prevent people accidentally shorting across two posts).

How much electrical loss would you expect from this connection? I'd prefer it if these were copper screws instead of steel, but the local hardware store does not have those. Is the resistance of steel negligible given the short travel distance?

Do you have a better suggestion for tapping into this wire? The best 'correct' solution I've found for an insulation-piercing tap that will handle #4 AWG appears to cost $15 for each tap. Since I need 48 taps, this path would be prohibitively expensive.


texts:
So, there's a tape with width of 2a, -a on the -y and a on the y, and it very long, penetrating the the plane of picture, it's charge density (dQ/dS) is

σ=σ0 * y /a , σ0 is a constant.

What is the electric field in point A(a.0)?

I tried solving this using charged disk, expressing electric field over polar coordinates etc., that is when there's a uniform charge. But I have no idea how to express y using shapes. What to do?


texts: Am working for a private organisation. We have one hot air oven for curing application. Here we are using 15kw heaters(1.5kw x 10nos). My question is, shall I use 15kw Variable frequency drive for temp controller. Bcoz I need PID logic to maint the exact temperature in oven. Please guide me.


texts: Un-masked Copper Boundary across RF section

texts: I have seen so many PCB which has an un-masked (without solder mask), copper boundary across RF sections. The boundary has via-stitching and there are also few openings in the boundary. Can someone explain their purpose? Please have a look at the picture below:


texts: Does using a push only plug for and F connector in a coaxial cable decreases the signal or adds noise?

texts:
I'm intending to find a replacement cable for my cablemodem unit. The existing cable that the phone company installed is a screw in terminal on both ends of the coaxial cable with one end connected to the modem and the other connected to a splitter.
What I intend to do is to replace the cable with another one which has a non screw F terminal, something which can be plugged by only pressing it against the female terminal either the modem or the splitter.
Upon browsing online I found these and also this.
The reason for why I intend to use these instead of the regular screw in type F connector is because my cablemodem is in a temporary place (as I have recently moved) and I have to disconnect it from time to time to take the unit to other part of the house.
And I noticed after unplugging it a couple of times the screw indents on the edges of the female and male terminals seem to be wearing off. In order to avoid further worsening the situation (other than obviously finding for them a more permanent place, which I cannot do for the time being) I considered to use these friendly pushing in alternatives for a type F connector.
However, neither of these indicate if the signal will be affected by using this?. Will it make any noticeable difference?. Back in the 90s my tv cable provider installed the cable to a wall in my house and I noticed the socket in the wall had much noise, so when I replaced the F terminal and connected it directly to the tv it improved a lot the quality of the image, hence my question.
I do not have an oscilloscope neither any other sophisticated equipment to verify this. But does it exist any reason to believe such?
Has anyone used these cables?. I remember using them on my VCR equipment back in the 90s as well and I had good experience using these push only F terminals, never had any sort of diminishing the quality. But since I intend to use these for a cablemodem which transfers data, will that make any difference?. If I buy the cable on amazon which I had referenced earlier will it be a safe choice?. Does the influx of information on a coaxial cable will it make it get hot or something? Does it exist better alternatives along the options which I have mentioned above?.
AS mentioned I also found this but I have no idea if it will be safe, does it exist some specification or some group of cables which say specifically only for tv use or not for internet use. Does it exist some standard for this? Can someone guide me with this matter?.


texts:
There is touch sense circuit that controls a SMPS circuit drives a power LED at output.  When disconnect the energy while LED ON, if I reconnect the energy LED must start be as ON state. I need a cheap, logic circuit. Thank you for your help.

simulate this circuit – Schematic created using CircuitLab
Here is a simple referance design. Touch IC'output state is initially active high, because of them there is a NOT circuit made by NPN.
Circuit should save ON state at least 30 minutes.
U2 is IQS127D


texts: What is the role of the Op-Amp integrator in this circuit?

texts:
Helo dier community! I got a 400 Hz broken Power Inverter and reverse-engineered the circuit just for the simplicity of repairing it.
Then I got deeper in and started to understand the engineering principle of the circuit. But I em stuck on this Op-Amp integrator build in and his role in this circuit. It would be nice if you could help me to understand his role. If you need some Voltage references I can provide it. The circuit is a simulation in Multisim and fully running.


texts: Why does an OpAmp with negative Feedback not amplify the potential difference on his inputs?

texts:
An OpAmp without any feedback just takes the potential difference between his 2 inputs and amplifies it by a certain factor. I know that in an OpAmp Circuit with negative feedback, we can make the assumption that the potential difference between his 2 inputs is ideally zero. I know this is just an ideal assumption, in reality there will be a small potential difference remaining. I also know that when we have an inverting amplifier-circuit, we can basically "adjust" the amplification to a value we want by the ratio of the 2 resistors.

However I'm wondering: Once we have that circuit, what gets amplified is the Input Voltage and NOT the differential-voltage between his 2 inputs anymore. Why is that? The OpAmp doesn't "know" about the feedback surrounding him, so why does he not amplify that really small remaining potential difference between his inputs?


texts: Does an AC wave running through a wire produce EM waves?

texts:
I understand that current from a DC source running through a wire produces a magnetic field. However, is the changing magnetic field produced via current from an AC source, technically a part of a EM or radio wave?

If so, do transmission lines produce EM waves at 50-60 Hz?


texts: Handling of temporary signals in concurrent environment

texts:
I am learing VHDL and wrote the code for Full Adder as :

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity FA1 is
port (
A: in std_logic;
B: in std_logic;
Cin: in std_logic;
Cout: out std_logic;
Sum: out std_logic
);
end FA1;

architecture Behavioral of FA1 is
signal s1,c1,c2 : std_logic :='0';

begin

HA1: entity work.HA1 port map(A,B,c1,s1);
HA2: entity work.HA1 port map(s1,Cin,c2,Sum);
Cout  = c1 OR c2;

end Behavioral;

My doubt is as all the statements are going to be executed concurrently, how are the signals in the architecture of FA1 handled, e.g how are the values of s1 and c2 cordinated between these two statements? In this example it is must that that HA1 must be executed before HA2. So how is this handled without using "process"?

Also in the line HA1: entity work.HA1 port map(A,B,c1,s1);  work is referred to as the directory in which we are files will be compiled. However I couldn't find any folder named "work" in the  workspace.


texts: Historical: I am trying to get a handle on when output voltage was used to protect from faulty LEDs

texts: I am interested in when a simple over voltage detector was first used to protect LED arrays from damage caused by one faulty unit. I have a reference from 1999 but am sure I saw something first implemented in the mid 90's - memory not helping!


texts: What are the limits to connecting batteries in parallel?

texts:
i've been researching components for a solar project and have been struggling to find an answer to this general question:

how do you determine how many batteries, or series of batteries (lead acid in this case), in parallel a charge controller can safely charge?

i've read that for lead acid charge current should be 0.05C but that quality chargers can greatly exceed this in the bulk charging stage


texts: Drive 4 small DC motors with servo controller via PWM

texts:
I need to drive 4 small traction DC motors on a 4WD robotic platform from my C++ code which runs on x86 only. I already use the Tinkerforge Servo Brick (it has C++ API) for one servo and I wonder whether this board is capable of driving the 4 small traction motors of the robot with PWM.

If this is not possible, then Tinkerforge has a dedicated DC Brick that drives a single motor. Could I use 2 of these bricks then - one for the 2 motors on each side of the robot? Alternatively I could only use 2 motors for propulsion (one on each side) which should make things a bit simpler.


texts: Why does capacitor never fully discharge in this circuit?

texts:
I've found in the following circuit, when the value of RPD is very high (say 10MΩ), sometimes the capacitor actually never fully discharges and the mosfet stays partially on. The LED dims but never completely turns off.

For lower values of that resistor (say 100kΩ) it fades off completely as expected.

What's going on here?


texts: What is the difference between a nonretriggerable and retriggerable One Shot?

texts:
One shot is a monostable multivibrator, it is normally in a stable state but once triggered it changes to an unstable state.

But I can't understand the difference between a nonretriggerable and a retriggerable One shot.

Can somebody please help me understand it ?


texts: 3 pins digital switch component for an Arduino project

texts:
I am trying to use a digital switch component to switch on/off SCL lines of some I2C sensors. On proteus, I can perfectly simulate that with a component name DSWITCH as shown on the attached picture.

Now, when it comes to physically building this circuit, what component can I use to achieve this switching programmatically just like in my simulation?


texts: What is the most cost effective way to produce a custom circuit board?

texts:
UPDATE June 21, 2012:
I purchased a Ferric Chloride, Positive Developer, and positive PCB boards from MG Chemicals and used the photo-etching process.  The results were OUTSTANDING!  You don't need their sparge tank or exposure kit.  I simply exposed my pcb underneath a 20W compact florescent bulb for 10 minutes, developed the pcb in a tupperware dish according to the instructions, and then etched in the same (rinsed out) tupperware dish for 15 minutes while agitating occaisionally with a foam brush.
Also, I used an inkjet printer.  The instructions say only to use a laser printer, but I found that if I set my printer to print the transparency using very dark, rich dpi settings that I had sufficient contrast.
The results were great--super fine and detailed thin traces!!
Background
I recently purchased some Syma brand indoor RC helicopters for my nephews.  Well, I had so much fun enjoying these with the boys that I have since started a small collection of my own.
Although loads of fun and durable, these toys use cheap electronics:

An infrared transmitter/receiver that seems to lose signal quality in a brightly lit room
Single channel so that you and someone else can't fly at the same time without interfering with one another.

About me:

Not an electronic engineer, though I am technically minded.
I am very much a novice with soldering and wouldn't be capable of soldering the tiny board inside these little birds.

What I would like to do:
In an ideal world, I would like to have a custom circuit board made for these little birds that

Accepts a non-infrared signal (2.4 GHz? Bluetooth? Wi-Fi? --Remember these are "living room" flyers).
Allows for you to choose between 2-3 channels on both the transmitter and receiver so that 2-3 people can fly concurrently.

I realize that this might already be available for bigger outdoor birds, but I need the circuit board to be small.
Is there a cost-effective way of prototyping this? Is there perhaps a place where I can send them the specifications and they would "print" up the circuit? Software that a semi-layman like myself could use to design it? I realize that the first run would be expensive, but I can see this being an after-market item that those of us bitten by the indoor heli-bug would buy enough of to bring the cost down.


texts: Transistor amplifier circuit for triangular wave

texts:
I've made triangular wave oscilator as shown in Fig. 1 and it works perfectly at frequancy 10 kHz with peak voltage +3 Volt to -3 Volt.

I intend to generate SPWM. But when I feed this circuit to comparator, the output drops to 0 Volt. How can this happen?

I assume that output current of op-amp IC TL-082 is very small, not enough to feed comparator. If my assumption is correct, can I use transistor amplifier to produce enough current?


texts: Replace zener diode of 14v with two in series of 6.8v in power supply board of kenwood kr9940-9040 receiver board shorted

texts:
I am trying to repair a Kenwood quad receiver KR9940.
This receiver has been given to me, hoping that I could give it a new life.
It didn't power on, after first inspection I found a group of four power transistors (it sports eight transistors) NEC 2SD287 faulty which I replaced with four MJ15015 also the four matching wire wound 0.47 resistors where broken in half, and in the power supply board the two transistors 2SC1000 (QK2-QK3) faulty plus one other resistor and zener diode dk1, which I replaced with onother zener of unknown specifications (silly of me).
After this first intervention I powered it up and the fuse R2 of 2 A blown plus the zener shorted and transistor QK2 broken.
The Zener diode (DK1) YZ140 is of 14 V 500 mW as I could not find the exact one I used a 13 V instead.
Previously I replaced the following faulty transistors QK1 2SC789, QK2 and QK3 2SC1000 with QK1 BD243c and QK2 Qkr with BC550 and BC 414.
When I powered up the receiver  smoke came from QK2 and  the zener diode was shorted again.
Is it possible that 1V for the Zener diode made the difference and blew the transistor?
Also in this case as I cannot find the 14 V Zener diode could I possibly replaced it with two in series of 6.8 V each?
I apologise for my knowledge of electronics which is basic level hopefully someone can help, I really appreciate it.
Many thanks.
PS I checked the four power transistors which I replaced and they are still ok.


texts: ADC Stimulus file with MPLAB SIM (Simulation with MPLAB SIM)

texts:
I'm trying to simulate my project using MPLAB SIM but I get the following message:

  ADC-W0008: No stimulus file attached to ADRESL for A/D.

How do I create an ADC Stimulus file?

Info that might be useful:

MPLAB 8.30.00.00
PIC18F4520
PicKit2 programmer.


texts: Are these LEDs glowing due to leakage current? How to prevent it?

texts:
I've been trying to develop this circuit for a multiplexed display with two seven segment digits and five SMD LEDs.

For simplicity, I've only shown one digit (LEDS 1 through 7) and two SMD LEDs (8 and 9). I have the code to write the appropriate data on PORT B and switch on the corresponding LED bank using PORT A.

Although the display works okay, the LEDs and segments seem to glow dimly even when they are OFF (logic LOW on PORT B).

I have tried reducing the value of R3 and increasing R2 but it doesn't seem to help.

Datasheets: 9012, 9013, ULN2003A


texts:
I'm using a PIC12F675 for a project, and everything works fine except one thing. GP4 does not work as digital IO. I've looked at the configs and the code a lot, but couldn't find anything.

Config:

#pragma config FOSC = INTRCCLK
#pragma config WDTE = OFF
#pragma config PWRTE = OFF
#pragma config MCLRE = OFF
#pragma config BOREN = ON
#pragma config CP = OFF
#pragma config CPD = OFF

Code:

#include <xc.h>
#include <math.h>
#include "config.h"
#define _XTAL_FREQ 4000000

void delay(unsigned int freq){
    for(int i = 0; i < (int)freq; i++){
        __delay_ms(1);
    }
}

void dClock(unsigned int freq){
    GPIO1 = 1;
    delay(freq);
    GPIO1 = 0;
    delay(freq);
}

void InitADC(){
    ANSEL = 0x11;
    ADCON0 = 0b10000001;
    CMCON = 0x7;
    VRCON = 0;
}

unsigned int GetADCValue(){
    ADCON0 = 0b10000011;
    while(GO_nDONE);
    return (ADRESH << 8) + ADRESL;
}

void main(void) {
    TRISIO0 = 1; //analog input
    TRISIO1 = 0; //output
    TRISIO2 = 0; //indication
    TRISIO3 = 1; //mode
    TRISIO4 = 0; //halt
    TRISIO5 = 1; //pulse_button

    char pressed = 0;
    GPIO1 = 0;

    InitADC();

    while(1){
        if(GPIO4 == 0){
            if(GPIO3 == 0){
                GPIO2 = 1;
                unsigned int freq = GetADCValue();
                dClock(freq);
            }
            else{
                GPIO2 = 0;
                if(GPIO5 == 1 && pressed == 0){
                    GPIO1 = 1;
                    __delay_ms(50);
                    GPIO1 = 0;
                    pressed = 1;
                }
                else if(GPIO5 == 0 && pressed == 1){
                    pressed = 0;
                }
            }

        }
    }
    return;
}


texts: Does PCB positive photoresist and related chimistry deteriorate over time (without usage)?

texts:
For creating PCBs, I use the following process:

Project the layout on a PCB (with a pre-applied positive photoresist layer)
Reveal the mask with sodium metasilicate pentahydrate saturated solution
Etching with Na2Si2O8 solution
Clean the mask with acetone

This process has been successful tens of times until last usage (like 3 years ago)(yes, long time).
Now, trying to reveal the mask with the already prepared sodium metasilicate (3 years old solution) does not seem to have any effect on the photoresist (same box, 3 years old).
My hypotheses are:

The photoresist has degradated over time, making it less sensitive to light.
The sodium metasilicate has degradated over time (maybe absorbing some substance from air, as the bottle was not well closed and water evaporated).

Is this deterioration of PCB photoresist or sodium metasilicate known? Which? (or should I look into some other direction)


texts: Can I Use Current Sensing Transformer Instead of Power Transformer

texts:
This is a follow-up on this question:

How to Design Arduino Voltage and Current Sensing Shield

Thanks to user bigjosh, I read the article:

http://openenergymonitor.org/emon/buildingblocks/measuring-voltage-with-an-acac-power-adapter

and I started designing my own board for sensing current/voltage.

Now the question I have is the following. In the above-mentioned article they use simple power-transformer for decreasing the grid voltage to a reasonable value. Can I use a current-sense transformer such as the one in

http://www.farnell.com/datasheets/1872311.pdf

instead of a power-transformer.

In my opinion, it would be even better as due to the small number of primary coils the distortion in the EMF would be smaller and the distortion in the resulting signal would be smaller.


texts: How can I sweep duty cycle of a pulse train in PSPICE?

texts:
I have found some solution in LTspice but Im wondering if anybody could achieve to sweep duty cycle of a fixed freq. pulse in PSpice.

Is that possible?

I tried the following but it didnt work:


texts:
I have someone else's design that I have been asked to choose matching components for.

The antenna is a chip antenna and the filter is a band pass SAW filter in a single package.  The SAW filter is a DC short to ground, so at DC, all the components are tied to ground, but at it's operating frequency, it acts like a proper transmission line network.

My question is, since this is on a PCB and I've got an Agilent/HP 8753 VNA with S11 only, what is the proper way to measure and select matching components for this?

More specifically, I have read from some App notes from TI that the way to calibrate the 8753 is to do OPEN, SHORT, and LOAD measurements on the actual board itself...But, what do you remove from the board to test the load?  Where should the VNA measurement point be?  Do I have to do each filter separately?  Can I leave the SAW filter in or should I replace it with a 0ohm resistor?

I've made some component changes (namely only using L1, L2 and C2) and have got a reasonable match by measuring at the L1,C2,BPFilter node and ground (~-27dB@fo), but my range of my antenna is still spotty.  I'm not sure what to compare it to or if I'm doing this measurement right.

Thanks!


texts: Will two identical antennas next to each other pickup the exact same noise?

texts:
If you had two exact same antennas next to each other, say 10cm, or even wound together. Would they see the exact same noise?

I'm thinking whether it would be possible to amplify a signal by amplifying the common signal and removing the noise in the case the input signal is of unknown frequency and amplitude.

The reason I ask is that types of noise are inherently random such that an antenna with an unknown signal on it would have a hard or impossible time differentiating the desired signal from noise, whereas dual antennas could see a common signal and be able to remove/cancel the noise out by differntial signal rejection methods if said noise was random or different in each antenna.


texts: Can I use this circuit for a 15V voltage inverter using TC962 charge pump controller?

texts:
I need a +/-15V, 45mA source to power some current sensors.
I think Microchip's TC962 (datasheet) would be suitable to provide a -15V rail.
I had a look at the datasheet but they don't specifically show a voltage inverter circuit, only a 'Combined Negative Converter and Positive Multiplier' on page 5. I think I can just leave out part of this circuit, like in the attached screenshot, but I just wanted to make sure.


texts:
I once saw somewhere that it is possible to control 3 LEDs with 2 IOs and only using LEDs and resistors. The high state is 5v and low state is 0v.

With 2 digital IOs, we can have 4 different possible situations for LEDs.

00 -> all off
01 -> LED1 on, others off
10 -> LED2 on, others off
11 -> LED3 on, others off

So it is logically possible using logical gates and mixing them. but How could it be done only with resistors and LEDs? and I am sure this method exists.

If they were 2 It was so easy. we connected them the in opposite to each other in parallel with a series resistor and 01 would light the first one and 10 would light the other one. like this :