texts: DIY protection for 12V electronics wired directly to a marine 12V battery system

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On my boat I have a number of electronics devices that run on 12V DC and normally get their power from an AC transformer.  They include a media player, a network router, and a portable hard drive.  Since the boat is wired for 12V DC I would like to set these up to run directly off of the boat's DC.  This will free up a lot of power strip space, and eliminate the inefficiency and need to run them through the boat's DC to AC inverter when not connected to shore power.

I've read that this is dangerous territory since the boat's DC system is subject to surges and noise, for example when the starter or the electric windlass are engaged or the VHF radio is in use, and that this can damage electronics directly tied to the boat's DC system.  I've also read that while the marine 12V system's voltage can vary from 12 to 14.4v (depending on whether the alternator and charger are engaged), these devices are not tolerant of these voltage fluctuations and are designed to expect a constant regulated voltage from their AC-DC transformer (wall wart).  There are marine surge and noise suppression products available ranging from $50 - $200 to address this concern.

The marine market is renowned for its high markup.  For safety and navigation applications  where help is far away this is merited, but honestly if any of this equipment I am connecting failed nobody would get hurt or lost.  The price of the commercial products seems high and I suspect the circuit should be relatively simple.  The loads are all less than 5 amps.

I am interested in implementing a custom circuit to accomplish this protection.

Where should I start?

Are there reference designs for such a thing?  What are the critical components:  voltage regulation, surge suppression, noise suppression?

I've done a bunch or Arduino projects and am comfortable soldering, breadboarding, and putting together a custom through-hole project, but I lack a formal EE education and background.  I've also done quite a bit of re-wiring on the boat so am pretty comfortable with the marine DC distribution and circuit protection and the ABYC standards.

A couple examples of commercially available products:

http://www.sto-p.com/pfp/online.htm

http://shop.sailnet.com/charles-1224-volt-suppressor-p-38606.html

edit:  is something like this a good starting point:  http://www.ti.com/product/lm5118 and if so what else should I add?  Ferrite chokes?


texts: Output of a linear system with discrete feedback

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I have this problem here that I had trouble with few years back and I still don't understand
https://imgur.com/At2BbWe

With a T period discretization on the feedback and a first order hold after it.
I believe this is a hybrid system because I imagine its output to have both discrete and continuous behavior.
How do I figure out the output formula for y(t)? or Y(z)?
I have G(p)=1/s if that helps


texts: what does the s-plane response of a system's transfer function describe?

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I am having trouble understanding the s-plane and not sure if I have grasped it from reading the standard signals and systems texts, so hopefully you guys can help me!

Does the z-axis on the s-plane plot the amplitude response of the system's transfer function to the input values of  σ+jω (x+jy)? or does it plot the complex-frequency response (output of the system in terms of σ+jω) of a system to an impulse input signal?

EDIT: Z-axis = axis showing amplitude


texts:
I am challenged with a task of detecting a human from behind the glass. Could you please suggest what kind of sensor will be a good fit for the job?

A sensor can only be mounted on the inside of the glass panel approximately 1 meter above the head or at the knee level.

How do I detect if there is anyone standing in the immediate proximity from the glass panel on the other side?


texts: A fundamental question about crossover distortion

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Following shows the input output waveforms to illustrate crossover distortion:

The supply rails are indicated as if it is a dual supply(+V & -V).

I then tried to simulate this in LTspice as in the below simulation:

As you see above there is no distortion seen in the output voltage.

Am I mistaken that crossover distortion only happens when using single supply, or is my simulation wrong since it doesn't reveal any sort of distortion at the output?


texts: Voltage transition sense - rapid raise or fall

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Which means do we have to sense (relatively) fast voltage transition from one value to another. The exact point of transition start, transition end and the intermediate state. Which schematic gives us indication of these points.
And the special case: how do ICs sense voltage raise or fall?

Edit: Last edit turned question to the wrong direction, so I rolled it back and rephrased.


texts: What are the advantages of a wider bus in comparison to those of a higher clock frequency?

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The aim is to increase data transfer rate.

I understand each may have some drawbacks and advantages. Frankly I'm not knowledgeable enough to know of many so I'd like some input from others. I know that doubling bus width requires making sure memory can handle receiving double the bits at a time. I also know that running things at higher frequency than they're designed for could be damaging. If you can't tell I'm not that aware of the technical details.

As for advantages I understand that a wider bus width may be more advantageous in streaming as you have a greater bandwidth stream and capability to load more bits at a time. I also understand that increasing clock frequency may increase the speed of read operations from memory, so you can load an operand more quickly in that case. I'd like some more tangible input from more knowledgeable people. For example, how do they compare in:

practicality/convenience
cost
Advantages in different uses.
and so on

Thanks.


texts: I am planning to build a grip-release sensor using the foam. I'm pretty interested in the way it works. Does the resistance in circuit increase or decrease when force is applied onto it? And this will be proportional to the force in what manner? I will need to apply a potential difference won't I?


texts: Diode circuit simulation producing strange results

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This is not homework. I was trying to come up with a circuit where the diode's state is not uniquely determined. This is the "on" case. Can you tell me what is the mistake in my analysis?

All resistors are 1 ohm and the source is 0.7 volts.

EDIT: Sorry about the incomplete description, I was posting from my cellphone.

This is the original cicuit. The greek text translates "constant voltage drop model 0.7V":

This is assuming the diode is forward biased:

This is assuming the diode is reverse biased:

Since both assumptions work (do not lead to contradiction) they are equally valid. I was trying to make the point that the constant voltage drop model is insufficient for the analysis of some circuits, i.e. does not admit a unique solution. My professor told me that my calculations in the forward biased circuit are wrong.


texts: Is there anyway to turn on a simple light or motor with no microcontroller via your computer?

texts: Is their a way i can directly turn on things without the use of a micro controller, i feel that for the applications that I am working on I can run whatever I want from the computer alone without going through programing a micro controller.


texts: Efficiency of 2 AA batteries with step-up to 9V vs 9V battery

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I have a device (LEGO PowerFunctions IR receiver to be precise), which operates at 9V, and usually, it's powered with 6AAA batteries. Needless to say, 6AAA batteries fit in quite bulky battery box, so sometimes people just use 9V batteries for it, which, on the other hand - yields much lower performance in terms of capacity (and they're more expensive than AAAs or AAs).

So - how about using 2 AA batteries (NiMH rechargeable, so with voltage of 1.2) with step-up converter to put it up to 9V? Assume the ones capable of 2600mAh, and the efficiency of step-up at 80% level, let's do some calculations:

  2.4V / 9V * 2600mAh * 80% = 554.66mAh

So it would seem it's better than the 9V NiMH batteries on the market can provide. What would be the other considerations that I miss?


texts: Why does a single AND gate need 60 transistors?

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Looking at the datasheet for the MC74VHC1G08, under the features section, it states Chip Complexity: FETs = 62.

Why does this IC need 62 transistors, while an AND gate can be made with only 6 transistors?
What are the other 56 transistors being used for?
My guess would be some sort of protection circuitry, but I am not sure.


texts: What adder does the use of the operator + synthesize to when used in creating an adder module?

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I want to find out what adder(ripple adder, carry look ahead adder etc.) does the operator + in verilog synthesize to when used in design an adder module. For example:
module fulladder(input logic input1, input2, c_in, output logic c_out, sum);
    assign {carry_out, sum} = input1 + input2 + c_in;
endmodule


texts:
I have the following question: I have the characteristic of 2 non linear inductors and i want to find the equivalent for the following connections

my problem is with the series one, i know that the parallel one, I know that the voltage on each one of them is equal so \$v_1=v_2\$ now i wanted to use the fact that \$ v=L\frac{di}{dt}\$ but first i dont know the \$L\$ and second i dont really understand how the time helps me, or how to get rid of it.
the series is i think i understood, since their current is the same then the total flux is the sum of the two fluxes and i will get the following

thanks


texts:
I would like to control a small heat pad using W1209, using a power bank that provides 5V. My circuit is working if I connect step-up voltage controller to the power bank and increase its voltage output to 12V, so that W1209 can be powered as required. But it makes large mount of current to flow through my pad. If I can run at 5V, current can be small. My question is can I bypass the 12V voltage regulator and replace the relay with 5V relay. Please let me know how feasible this is? I didn't find any relevant example or blog post on this. The below is the closest I found, but not much of use
Can I take DC directly from W1209 Thermostat board?


texts: Why does introducing this circuit in cause a higher voltage in existing circuit?

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I have a Trans Control circuit that under normal conditions sends a 5V signal to a 9 ohm solenoid. The TCU controls this solenoid.

I have parallel wired a manually activated 5V supply that I activate using a 12V supply stepped down to 5V using a LM2596 adjustable stepper DC-DC converter.

Ive noticed now the factory TCU output has gone from 5V to 7V when automatically controlled??? After this I fitted a diode in line on my manually activated 5V Supply. The factory control then drops to 6V when automatically activated.

When I take away the manual input it operates as normal at 5V.

Why would this be occurring ??? Below is a poor attempt at a schematic to illustrate my point. and also a picture of the DC DC converter.

Thanks

How can I bring the factory supply back to Stock Specs?


texts: Three-terminal linear regulator output capacitor selection

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SOMEWHERE, SOMEWHEN, I clearly remember reading a very strong recommendation that one put a 1 uF tantalum capacitor between the output pin and ground on a linear 3-terminal fixed voltage regulator, to prevent it from oscillating.
I also remember, back in the late 1970s, seeing a malfunctioning homebrew power supply, that used such a regulator and a 2N3055 pass transistor.  This was a VERY common circuit topology at that time.  Adding the capacitor cured the problem instantly.
Just now, I went digging through old datasheets on the Web, and found that TI says that those parts DON'T need those caps, but they MIGHT help with transient response.
Am I completely nuts?  Or does anyone else remember that seeing that recommendation, and remember where they saw it?


texts: Inrush current limiter for a high power rectifier

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I am designing a 10 kW rectifier (single phase, 230 V, 50 Hz, 44 Arms, 62 App) with power factor correction (a bridgeless boost DC-DC converter working in continuous conduction mode). All works perfectly except the enormous inrush current need to charge the capacitor (1 mF) in the first quarter cycle (>>100 A). I also want to limit capacitor charging current in the case of few cycles power lost, so I need an active solution instead of a passive one, ie. thermistor. What are the most common strategies to deal with this problem?

I am using this topology:


texts:
I'm trying to create a servo drive function on an ATMEL microcontroller without using the built in PWM functions. Basically just with the ISR timer.

My question is... what is the general resolution for Hitec (or Futaba) servos. Is it 10 degrees, 5 degrees, <1 degree? What would be a realistic upper target for my timer's resolution, for it to be robust for most servos?

Assuming a 180 degree rotation servo (1.25ms for 0, 1.5ms at 90, and 1.75ms at 180), I would have 500us for 180 degrees, or 2.779us per degree at 1 degree of resolution. For a 20MHz clock, I would have 50ns per clock cycle or 55.58 clock cycles per degree of resolution.

This would be quite a burden if peripheral processes were running and I'm wondering if I need to increase the CPU speed or if the resolution is even appropriate (too high or low).

For applications, this is rather open ended as I'm trying to build a tool for a myriad of open robotics projects but I would say it should be comparable to the Lynx Motion SSC-32 (http://www.lynxmotion.com/p-395-ssc-32-servo-controller.aspx).


texts: Determine the angle and speed of a rotating platform

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I have a 1 axis (x) spinning platform, that is spinning pretty fast ~300 RPM. I want to be able to detect with a good degree of precision how many degrees it has travailed from its starting position and the speed it is currently trailing at.

For example:
Think of a clock that has a single min hand. The hour hand travels across the face of the clock and I want to measure where it is on the clock face at any given time in degrees.

"3" o-clock it would be 90 degree,
"6" o-clock it would be 180 degree,
"9" o-clock it would be 270 degree,
"12" o-clock it would be 0 degree,

I have both of these sensors

Gyro Breakout Board - LPR530AL Dual 300?/s
Triple Axis Accelerometer Breakout - ADXL345

My questions are:

Can I use a Gyro or Accelerometer to accurately measure how much rotation has occured on a spinning platform?
Is there a better sensor to use to determine rotation in degrees such as a Compass Module - HMC6352
Can you use a Gyro or Accelerometer to measure RPM?


texts: Can your teeth come to harm when using them to strip thin wire?

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When my dad saw I was stripping the insulation off thin tinned copper wire using my teeth he said that this was dangerous because parts of my teeth could break off. I can't believe this because it's generally said that teeth are really strong.

Is there any evidence or research in this area? I couldn't find anything about this on the internet. Did you experience this or have heard of someone else experiencing this?


texts:
I am building a bit of equipment that requires 48DVC @ 2.5A to be brought out of the metal box housing it. I intend to feed it through a piece of plastic tubing along with a sensor wire, which exits via a grommet. It will then be used to control a heater.

What regulations apply to 48VDC wiring etc? What safety issues might arise? In my mind 48VDC is on the edge of being dangerous


texts: Why so many variations of BJT transistors

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Many transistors are very similar to one another, so much so that substitutions are fairly easy to make.  Ft around 300 MHz, gain characteristics very close, etc etc.  Can anyone speak to why so many subtle "flavors" are manufactured?  Not being an engineer, perhaps I simply do not know enough about the tiny differences.  Some are obvious, for example a 2N3355 offers vastly higher Ft than a 2N3904; a 2N2222 handles a little more power, etc.  Noise figure and capacitance are often close, too.

Are these subtleties truly enough to drive the industry to produce the wide variety we see?  Just curious if someone with design manufacturing background can offer some insights, thanks.


texts:
Iam trying to test my mosfet because my project which involved connecting a load to the drain did not work. After some tinkering Iam down to suspecting the mosfet (n-channel, IRF630B). I have connected it this way to test,

+12v -> gate,
ground -> source

Then I switched my multimeter to measure resistance (200 ohm option) and connected the red lead to the drain and black lead to source.

Q1. Am I measuring the Rdson correctly? (it does not need to be accurate, good approx is enough)

Now, with power switched off, I see that the circuit is open. After switching on, the Rdson value is in the range of 10-11 ohms. I have tried 10 different mosfets and all show the same range. According to specs, anything above 10V should bias this mosfet correctly and bring down the Rdson drastically (ideal value is 0.4ohms). I also changed the power source to +19.5v to see if a harder drive makes a difference. I still got similar results.

Q2. What am I doing wrong?


texts: Simple transistor for switching a computer power supply

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I am teaching myself about simple transistor circuit design and have been stumped by the simplest transistor behaviours. The task I have set is to use a transistor to switch on an ATX computer power supply. The principle is the power supply has a wire pulled to 5 V which when grounded causes the supply to switch on.

Ammeter testing shows the current in the grounded circuit is 333 uA so I figured pretty much any transistor could do the job required. Selecting almost at random from a bag of transistors I picked out a BC549B unit and found its datasheet. It appeared to be able to handle this current just fine so I set about making a little circuit that put the 5V wire to the collector and a ground wire to the emitter.

From a separate power supply I used a 2 V supply to the base through at first a large, (147 kOhm) resistor, with the ground of the separate supply coupled to the emitter of the transistor/ground of the ATX supply.

The first observation is interesting and unexpected. Firstly with the base disconnected from the second supply and grounded to zero, the 5 V wire held its full voltage. With the base floating, the 5V was pulled down to about 2.5 V. Is there an obvious explanation for this?

Now with the connected power supply putting out an actual 2.87 V, voltage on the 5V wire was pulled to 446 mV. Incrementally stepping up the input to 12.3 V, the 5 V wire was pulled to 128 mV from ground. Looking at the input currents to the base plotted against collector current, the collector current rose asymptotically toward a value seemingly below the 333 uA current required (about 325 uA.) I figured in this configuration the base resistor was too high and started dropping it's value. I'm at 661 Ohm now, with the full 12.3 V I am pulling the 5 V wire to 30 mV. Even so I am not seeing the supply switch on. I would think surely this is below the switching threshhold of the power supply, am I wrong?

Another strange behaviour is that with the ATX supply connected, if I instantaneously force closed the collector and emitter terminals to force the supply on, the circuit seems to energise itself and the supply stays on until I disconnect one wire from the circuit. Why would this be?

Finally, am I simply using an inadequate transistor for the job or is there some impossibility I am fighting against?

simulate this circuit – Schematic created using CircuitLab


texts: Are there measurements I can take on my server's power supply to estimate its health?

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My server's PSU is about 7 years old, and it's running 24/7 at about 30% load.

While I think that it will last some more years, I would like, if possible, to anticipate its failure, since often it results in further damage to the electronics components.

Are there measurements I can take on its output rails (12 V, 5 V, 3.3 V) to anticipate imminent issues?

I could monitor voltage and ripple, but are they indicative of ageing? Since I have an UPS powering the server, I could in theory correlate the readings with the overall load, if needed.


texts:
The attached image is from a schematic found for Britain's random number generator for Premium Bonds.  I think  that it's for the original equipment.

I'm trying to assess the feasibility of recreating part of ERNIE, but lack the necessary valve design experience.  Can anyone approximate the order of magnitude of voltage levels at the red dot, next to neon bulb V1?  I expect that it's low due to the decoupling capacitor C1, but I can't estimate the effect (if any) coming out of valve V2.  Not sure what all those grids and heaters do.  Am I looking at 200 volts or nearer 1 volt?


texts: Current through diode with zero impurity

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The guiding equation for diode current is

Idiode = Ireverse saturation × (ekV/T – 1)

Now, as far as I know, the reverse saturation current is contributed by minority charge carriers. So, if some day it becomes possible to remove all impurities from a diode, this Is is going to be 0. Then how to calculate the diode current in that case?


texts: what does offline mean in flyback topology

texts:
What off-line means in flyback converter. is there any online also.
if yes please describe


texts: why  does the current in R2 remain always zero regardless the value of other parameters(V1,V2,R1,R3)?)


texts: How do I ensure best signal performance when using a 2.92 mm (K) connector that is compression mounted on my PCB?

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I am concerned that because the recommended PCB layout shows the signal pad completely surrounded by the GND pad, I will need a via in order to route the signal. I am using this K connector instead of a standard SMA connector, because I want the best performance when using 20+ GHz signals. From my understanding, vias are to be avoided when designing RF PCBs. Is it not a big deal as long as the length of the via is considerably less than the effective "wavelength" of the signal? What about the fact that the via introduces a 90 degree bend?

Here is a link to the part's datasheet: 2.92MM JACK 2HOLE FL MT
W/ 0-80 UNF THD

Thanks in advance for everyone's responses!


texts: How to classify devices into photodiodes, photodetectors and photocells?

texts: Is there a clear differentiation between the three? For example in terms of efficiency (induced current/incident power)?


texts:
Here is a schematic of the "Typical Application" for the Maxim MAX1873 -

Can anyone tell me what "To system load" means? Does it mean I can connect this to let's say a 12V door lock (my input is 15V)? And would this device automatically switch to the battery backup when Vin goes down (essentially a power failure)?


texts: Selecting communication between microcontrollers at high temperature

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I have been assigned to a project to find the best possible communication between several PCB boards which have microcontrollers for a specific function. I need to have all microcontrollers communicate with the main board which contains a CPU.

I need to send some information from the mainboard to the controllers and receive a response from the controllers. Each controller board is designed for a specific purpose. I don't need to communicate between the microcontrollers, but even if one microcontroller fails to communicate then it won't effect on others. Presently, I need to have six microcontrollers communicate, but in the future more than that. I want to avoid more wired connections between the mainboard and the other controllers (it should be fewer).

The communication should not be affected by the temperature (250 °F (120 °C)) and pressure (high). The distance between the mainboard to the final controller may be more than one meter. Which type of controllers are best? I need to perform some calculations and sensor readings. Each board having more than two sensors. I need to perform some calculations on sensor readings or send values directly.

I am new to this type of project. I have searched for the best communication, but I am confusing which is best. Some people are suggesting me to use CAN communication. If I choose CAN communication, what type of microcontrollers is best?  I have attached a simple diagram how it is going to look like as shown below.


texts: Direction of current through a circuit with multiple batteries

texts:
So I've got a bit of a problem trying to understand this circuit in my physics book.

If current flows in the direction of the three arrows (I1, I2 and I3, couldn't find a way to name them) how can there be a complete loop? As far as I'm aware current can't travel both ways through the same cable. Are the batteries charging each other up or is there something else going on? Do the currents cancel each other out when they meet after leaving the positive pole?

The reason for me asking this is because I need to know the direction of the three currents "leaving" the
positive sides of the battery in order to do a proper loop equation. Now, I realize that this might be a bit more theoretical than most other problems you answer on this site, but I thought I might as well give it a go.

Thank you in advance to anyone who might want to help me out.

simulate this circuit – Schematic created using CircuitLab


texts: Which household electronics contain or used to contain photo multiplier tubes?

texts: I would like to get my hands on one, but I am unsure where to find them (other than online). Are there any old household electronics that have them, used to have them? I am willing to go scavenge hunting for some.


texts: Is there such thing as a Laser beam detector that returns a non binary result?

texts:
As the title implies , i'm looking for a device that can detect at what point a laser beam has been broken. So idea would be the device to output a certain voltage depending on where someone's finger has broken the beam.

Does such a device exist?


texts: Why aren't decoupling caps built into the IC or IC package?

texts: The title is probably good enough, but I've always wondered why decoupling caps aren't built into the chip or at least the IC packaging?


texts: Switching a divided voltage with transistor or MOSFET

texts:
I have a problem that I cannot solve and need help.

I have an analogue input on a microcontroller and I want to have multiple switches which the micro can see and act on depending on which switch was pressed.
I have 5V that the circuit works on. So I am trying to get different voltages from 0-5 into the analog input of the micro.

The catch however is that I want to control it with a p type transistor or MOSFET so that the user can just short something to ground to activate the divided voltage. I've sat here for days trying to figure this out using MOSFETs and transistors but nothing I do works! The divided values are never correct!

I've been playing with BC327's and BS250 MOSFETs to try and make something work, but everything I try fails.

I realize I need help, so I'm throwing this out there on the chance someone can help me!


texts: Is it possible to fire a spark plug from batteries

texts:
I wanted to create a remote fired trigger for a spud gun so I can trigger it remotely.

Ideally I'd like to use a spark plug to fire because it should work well for gas mixtures but the trigger is pretty small/simple. Basically it's a a little remote box with a push button trigger that runs off of batteries.

It has a light, arm switch, and push button that triggers a relay but I currently don't have anything connected on the relay switch end.

Would it be possible to charge up some caps and get enough juice to bridge a spark plug with a small battery source (4 AAA or AA batteries) or would I need to step it up to something bigger (lipo or lead acid).

Note: I have used caps for filtering before but never for charging/discharging.

Update:

Just wanted to clarify. I know that a gas grill push-button igniter is a viable option but I'm looking for something more reliable. Ie, an igniter that I'm 100% positive it'll fire a good spark when I push the button. Check out "Tater gun Fires a Hunert yards" to see what I mean by unreliable.


texts: Driving a speaker directly through an audio DAC?

texts:
I have a project where I'll need to generate some sound waves. In case it matters, the microcontroller I'll be using is an STM32L476RG which have an internal DAC.
The question I have is related with the output power/sound I'll get. I'm not sure if driving the speaker directly through the DAC will give me         proper volume.

1) What is the main limiting factor of output power / high volume? Is it the speaker?

2) How do I know if the DAC is enough to drive the speaker or if I need an external amplifier? How does the math works on this?

3) I'll be using sampled PCM data contained in a WAV file. Is there any advantage/disadvantage of using a codec (I2S) instead of DAC(+power amplifier)?


texts: How to find new ABCD parameters when reversing 2-port network

texts:
I have an ABCD matrix represenataion which is defined as:

For such a problem, what approach should I follow in order to organize the new ( reversed) network ports voltages and currents properly. I have tried to keep the currents of ports same and making voltages switching places but this did not make any sense in the substituted-general form calculations.


texts: 12V DC power supply - how to make sure it's properly constructed

texts:
I am building a power source for my astro-imaging gear using a 12V marine deep-cycle battery (120 amp-hours) stored in a battery box. The battery is supposed to power the telescope mount (requires 12V DC, 3.5A) and my laptop (requires 19V, 2.4A). Later, I might also add dew heaters for which I would use this controller.

I want to add three 12V cigarette lighter sockets and a fuse.

My main questions are:

Where to add the fuse in the circuit and why?
What rating should the fuse have?
Should I also add a fuse in front of each cigarette lighter socket?

I read that the loads in a circuit will only take the amps the need.

Can a marine deep-cycle battery also actually "push" current into my devices and blow them? Or are voltage fluctuations more of a problem?

For the laptop, I am planning on using a power inverter. I know it's not as efficient as a DC to DC power adapter but I think the battery has enough power to handle this inefficiency no problem and it's also more convenient in case I want to add a different laptop with different power supply specs.


texts: Single Arduino I/O pin driving multiple DVR8834 stepper driver boards

texts:
I working on a project that uses 6 NEMA 8 stepper motors very similar to This One, each stepper will be driven by a DVR8834 and the STEP/DIR logic supplied by a ATmega328P which has a VCC = 2.7V to 5.5V and MAX current per I/O pin of 40mA (page 258 of the datasheet). My question is this can I tie all the STEP inputs of the DVR8834's to a single I/O pin of the ATmega328p to have all the motors step in unison? Am I missing something like drawing too much current on the I/O pin or "cross talk" of the DVR8834's?

Thanks in advance


texts: A simple analog neural network to implement the XOR operation

texts:
I am reading this paper and wanted to replicate some of the results as part of a learning process. I'm more of a digital guy but obviously have had some analog design as part of my studies.
Implementing a neural network model to learn the XOR operation is quite easy in Python, for example. In the analog domain, you have to worry about (1) how to multiply the activations with the weights (2) how to add the result (3) how to apply a non-linear function to the sum (4) how to propagate the errors from the output to the inputs (5) ensure that the amplitude does not degrade as it flows through the network in both directions.
The paper I mentioned above offers a solution to the above problem in the form of the block diagram shown below:

Multiplication and addition is done using a resistive array. This is straight-forward to do (for just the inference).

A sigma non-linearity is applied using a diodes.

Bidirectional amplifiers ensure that the signal quality is maintained in both directions.

A current source at the output injects some current into the network in proportion to the error. This is only done during training.

The author of the paper did the analog simulation for inference in SPICE, read-out the results in Python, computed the error in Python, applied a current in proportion to the error, and allowed the circuit to run again in SPICE.
The result of the implementation of the XOR operation is shown below:

I would like to replicate the results for the system shown above. Even though I have taken a few courses in analog electronics, they have been focused more towards theory and my analog design skills are not great.
My main question is designing the neuron as shown in the first image. How do I design the non-linearity and bidirectional amplifier ?


texts: Connect a micro switch to a PC serial port

texts: How do I connect a micro switch to a PC's serial port and query whether it is open or closed? Which serial pin number(s) do I need to wire up?


texts:
simulate this circuit – Schematic created using CircuitLab

I feel as if I already know the answer to this, but I want a sanity check (I'm working in 0V low, 5V high logic level):

In lieu of a multiplexer (because I had none), I have 32 transistors. The collectors are paired up and hooked to 16 inputs. The emitters are 32 discrete outputs. The bases are hooked up 16 each to the Q and Q' of a toggle.

The voltage of the base signals end up being 1V when "high," and when I would expect an output to be fully high, it is also about 1V.

I tried adding two extra transistors with the bases of each connected to Q and Q', and collectors tied to a small current limiting resistor at the voltage source. This helped a little, but only got me to about 2.5V and these two transistors got very, very hot.

Am I foolish, and this behavior from my hillbilly mux expected? Or should it work, and I likely have something wrong in my soldering?

EDIT: I forgot to mention, the transistors are 2N2222.

EDIT2: Added diagram of 4 resistors as example.

EDIT3: The outputs will be going into the data in / address inputs for a RAM chip, so they do not need to drive very much current. The Q and Q' are coming from a 74LS107 JK flip-flop with J and K tied together so that it acts as a toggle. As stated above, I tried using the Q and Q' signals to switch some other transistors tied almost directly (5V -> 150ohm -> collectors) to the power supply, but that caused them to overheat.

EDIT4: The RAM chips are two 6116P-3. Outputs O1a, O2a, etc are going to one chip, outputs O1b, O2b, etc are going to a second. This is done so that I have two buffers that the inputs can write to. The inputs which will target the I/O lines on the RAM come from a 74HC595 shift register. The inputs which target the address lines come from a CD4040 binary counter.


texts: How to interpret this NTSC color waveform?

texts:
How can the following NTSC video signal be interpreted? Is it using phases or frequencies or amplitudes?

Is this above only the color information of a video broadcast signal?

I have no background on this type of communication. Is H-BLANKING indicating where the data chunk is finished?  I guess the active video period carries color information? chrominance and luminance looks the same frequency. How would the encoder know which one is what? How about peak white?


texts: Why will i calculate the wrong current when i transform part of circuit to Thevenin circuit?

texts:
Here is the circuit in this question

The original circuit is in the left hand side,as we can see,there are two norton circuits in it,so i transform them to the thevenin equivalent circuit,just like the circuit in the right hand side.

Now i can use the KVL to calculate the \$i\$ value

KVL:\$-12=4i+4i+24+4i+12,\$ so \$-48=12i\$,i can know \$i=-4\$

However,the answer for the \$i\$ is \$2\$, i want to ask why?can anyone tell me the reason that why will calculate the wrong answer?

The solution:

\$i_1=\frac{-12-(-24)-(-12)}{4+4+4}=2\$


texts:
I am trying to design and prototype a pressure mapping sensor to measure the force between two surfaces.

I prefer to use piezoresistive materials. I am thinking to use 4x4 cell; also I should try to use flexible material not to be broken under applied force.

Can anyone guide me or inform me of possible references, please?


texts: Connect in-built microphone in webcam through USB

texts:
I recently repurposed a webcam from a HP laptop to make it USB webcam. I was able to connect the webcam to USB. It also has an in-built microphone, and I dont know how to make it usable.
The webcam had 6 connections - D+, D-, Power (5V), GND, L, R. I connected D+, D-, Power & GND to corresponding wires in a USB and got the webcam working. Now I'm left with 2 wires - which is L & R for the mic. I don't know how to connect this to the same USB wire or a different USB. I read somewhere that, these integrated microphones use the same GND as the webcam. Other than that, I have no clue. Seeking help from the experts. The webcam is one of those from Silicon Motion Inc, used in DV4 series of HP Pavilion Notebook PCs.


texts: Looking for a force resistor, but I just want it to act like a switch

texts: I can not for the life of me find something that is a force resistor, so it's flexible, but it acts like a switch.  I could also take just something that recognizes if a baby is sitting in a seat.  I just need something sensitive enough to sense a baby, is flexible, and just asks like a switch.


texts: How to change the volume of one pair of speakers

texts:
I have two speakers outputs on my old technics SU V560 amp that I used for years to drive wharfedale E20 speakers that I use in the living room.
The amp has two stereo outputs, selectable from buttons on the front.
Recently I was given a set of Kef Model 104 AB speakers which sound nicer than the wharfedales so I use the Keff in the living room and the wharfedales in the dining room.
Both sets of speakers are 8 ohm impedance but the wharfedales are much, much louder than the Kefs. So much so that if I set the volume for the wharfedales then the Kefs are very quiet.
There is only one volume control, so I can't change the volume of each speaker set individually.
Both sets of speakers have exactly the same type of speaker cable, all cable are the same length.
How do I reduce the volume of the wharfedales?
I've tried switching the outputs around but this hasn't made any difference. I also bought several 2 ohm 50w resistors in the hope that putting them in series with the wharfedales would quieten them down but they didn't - even linking them in series to a total of 10 ohms seemed to have no effect.
Any ideas out there?


texts:
I have designed a PCB using Autodesk Eagle.

After I routing the PC and check for errors from Tools -> Errors, there are lot of airwires (31) like below. But, I couldn't find any airwire.

How to solve this problem?


texts: Is it possible to use a capacitor and a resistor to keep voltage above 3v and limit current to a certain value?

texts:
I have an RC helicopter and the electronics require a voltage of at least 3v. The electronics also have a certain max amperage which might be around 2 amps.
Under high load on the brushed motor, the voltage drops below 3v and the amperage rises dramatically.
Is it possible to add a capacitor and a resistor to keep voltage above 3v and limit current?
The voltage would not have to be kept above 3v for long, only 3 seconds at a time, for example.
I think what would work is 2 switches:

Opens when the voltage drops below 3V and connects the capacitor
Opens when the amperage goes above 2A and connects the resistor.

What switches meet these requirements?


texts: Detect an IR signal with a photodiode to use it with a microcontroller

texts:
I am trying to detect an IR signal with a photodiode to connect it to my STM32F411 and use it as a trigger signal. The signal I send are two pulses at 500 kHz which looks like this:

I am using a transimpedance amplifier and a bandpass filter to get rid of parasitic signals of the photodiode.

I can detect a rising edge on the receiver side, but it is not fast enough. How can I improve the curcuit to have the same signal I send? That means two pulses with a frequency of 500 kHz.

The measurement was right after the amplifier on V1. So this signal I receive will not pass my bandpass filter. It looks like my circuit is way too slow to reproduce the two amplitudes from the sender.

After receiving answers explaining why the TL074 is a poor choice:
I replaced the TL074CN with an MCP6292 which has the right DC specification. Furthermore I connected the photodiode to ground instead of connecting it directly to VDD.

The rising edge looks pretty good, but now the falling edge isn't fast enough.

Getting closer but not good enough to detect it with my microcontroller.

As recommendet i lowered the Transistor to 10k and removed the capacitor.
Now i have a new behaviour, it depends on the distance from my IR sender
to the photodiode. If the sender is 10cm away fron the photodiode, the graph looks like this:

If the sender moves away from the diode, the two pulses appear.

After 1m the green signal dissapears. How can i increase the range, by using a better photodiode or a different amplification? And how i get rid of the overload/overamplification?


texts: I sometimes see that "A perfect inductor would be with superconductors" and so on. What properties of "Perfect inductors" makes them different from regular and what advantage would they create towards electronic circuits?


texts: How should one switch from using an Arduino as a programmer to an external programmer?

texts:
Part two of a three part series on transitioning from Arduino to a plain AVR microcontroller and minimum supporting components (part one, part three)

I've seen a lot of people ask this on the Internet, so here goes:

I already know how to program and use a barebones ATmega328 with an Arduino as a programmer. I now want to start using an external programmer with the Arduino IDE.

How should I proceed in this transition? What should I learn? (It would be nice if a mini-tutorial for some of the portions was provided as part of the answer)


texts: Protection High side Mosfet driver with less solenoid connection

texts:
I suggest control solenoid. Solenoid will be connected externally via a connector. Steering is via high side MOSFET driver. The requirements are for detecting disconnection, short circuit and current detection. I use the circuit from TI TPS1H100BQ1.
http://www.mouser.com/ds/2/405/tps1h100-q1-558214.pdf

When on switch mode I am disconnecting solenoid induced voltage will destroy the Mosfet. I'm confused with the protection of the mosfet when disconnecting one side of the solenoid. Do you have any advice?

My circuit:


texts: can dropped voltage be greater than forward voltage?

texts:
What I know is:

forward voltage, Vf = The minimum voltage that is required to start current flow across the LED/Diode

dropped voltage, Vd = The voltage that is used/lost across the LED/Diode.

My question is, initially the equation should be Vf>Vd but can Vd>Vf be true at any moment?

Besides, please correct me if I have any misconception.


texts: Comb generator vs. known EMC emitter - different measurements in shielded tent vs. 3 meter chamber

texts:
I've got an EMC testing setup of a 1 meter shielded tent, and a very high gain EMC antenna.

I'm seeing a phenomena that I can't quite explain.

I have a known product that was tested in an accredited 3 meter chamber.

I have a known comb generator that was also tested in a 3 meter chamber.

(dbuV/m are approximate):

In the 3 meter chamber, the comb generator at 100MHz is 40 dbuV/m (that's right at the Part 15 limit).

In the 3 meter chamber, the known emitter at 100MHz is 43 dbuV/m (so it failed by a few dbuV/m)

So now I take the known comb generator, and put it in my 1 meter shielded tent.

In the 1 meter shielded tent, the comb generator at 100MHz is 50 dbuV/m (there are unknown cable losses, scenario not calibrated, etc... but bear with me).

Now I take the known emitter, put it in the 1 meter shielded tent, and at 100MHz the signal is 20 dbuV/m.

From the calibrated chamber readings, we know these should be the same value or very close to each other.

What sort of phenomena could I possibly be seeing?  Could the comb generator, as an intentional transmitter, be reflecting in my tent and somehow increasing the perceived signal strength?


texts: Want LED to stay on once it is triggered

texts:
Have built the Seattle Univ cell phone detector to locate hidden harassment devices around my home, especially the auto tracker presently installed somewhere in my car.

Circuit works well, and LED comes on when it receives a cell signal (don't use the buzzer).  However, I can't drive and keep an eye on the circuit LED at the same time - especially when investigating the trunk, engine area, and under body as possible hiding places.

So, I'd like to insert a flip flop, SCR, etc., in line with the LED so when the circuit receives a cell signal and the LED lights up, it will stay lit until I get a chance to look at it, then I'll pull the power and turn it off.

All help welcome as to what and where to insert!

simulate this circuit – Schematic created using CircuitLab

https://www.youtube.com/watch?v=kXJJauAWrzc

https://seattleu.edu/scieng/ece/LM358_RF_Cell_Phone_Detector.html


texts: Turn STM32F4 Discovery into an HID USB device

texts:
I'm getting an STM32F4 Discovery board delivered this week, and busy snooping around for ways to turn the device into a USB HID device.

I basically want to write a simple application that will allow me to register/configure the board as a HID input device, so my PC can recognise it as a game controller, with one button, connected to the "User Button" on the board.

Does anyone know how to do this?


texts: Is there a limit for voltage a PM generator gets to based on RPMs?

texts: I build different small PM handcrank generators for fun, Recently I built a single phase generator and printed myself a couple transmissions. Now as far as I know 3 things affect voltage, speed of rotation, coil size/#of windings, and magnetic strength. Where I am mentally stuck is that being the same generator (all things equal) when I ran it on my 1-250 transmission, i generated 9 volts with a given load, with the same load and generator, using the 1-400, I got the SAME output, even though I was going faster (i have an rpm reader). Up until now, all the generators I have bought, many of them wye 3 phase, the faster i go, the more voltage. I am certain I am not reaching the limit of my wire, as im using 22 gauge, and only pushing 2.5 amps max. While there is a possibility this was a testing error, I double checked and got the same results. Has anyone ever run into this Voltage wall before? as in no matter how fast you rotate, you hit a wall.


texts: Why in a voltage driven parallel RLC circuit (at resonance), the current of the inductor has a DC component?

texts:
I'm refreshing my knowledge on LC/RLC circuits, and an interesting thing came up that puzzled me.

I'm doing simulation on parallel a RLC circuit (in LTSpice), which is driven with a sine voltage source, at the resonating frequency of the LC tank. The puzzling part is that the current flowing out of the voltage source, as well as the current flowing through the inductor (90 degrees out of phase of corse) have a DC value of Vout,max/R. For the component values that I've chosen - L=100u ; C=10n ; R=100R, the output current of the voltage source has a DC value of 100mA, as well as the current through the inductor. The current through the capacitor, and through the output load resistor swing ±100mA.

Here is a picture of the simulation output :

The same thing happens if I try to simulate just the LC tank. The output current of the voltage source has a DC value of 100mA (with an extremely small AC waveform), and the current of the inductor has a 100mA DC value :

What's the reason behind this ? Regards!


texts: i have two questions about value of adc being changed

texts:
I want to acquire the values movement of two strain gauges attached to dc motor
For example, first strain gauge has values around 10000, the second has 20500 in 0 degree while the first is 10400, the second is 20200 in 5 degrees.
After the motor is returned in 0 degree, the one is back again but the other is not every time.
so i wonder the reason why the value is changed and how to compensate for getting the fixed values in 0 degree
in 0 degree
the first is 10000 the second is 20500
in 5 degrees
the first is 10400 the second is 20200
and then back to 0 degree,
first case
the first is 10000 the second is 20400
second case
the first is 10150 the second is 20500
i'm looking forward to answering my questions


texts: how to connect relay and physical switch to control light

texts:
I am new in this kind of stuff so please excuse me for my lack of knowledge. I have successfully connected blackwidow (wifi + arduino) with a relay to control a 220V light bulb.

Now, I want to embed all this circuitry in my room for each and every socket.
The problem is that I don't want to remove my physical switches from the wall. I want them to be there and always function normally.

How should I connect both elements so that I can control the lighting from both the switches?

Arduino hardware
Physical switch which has been there for a long time

And how can I achieve the following?

Turn on the light with the physical switch, then turn off the same by my android which is connected to the blackwidow via local network
and vice versa

Thanks in advance


texts: Capacitor Current–voltage relations conceptual doubt

texts:
I understand that a capacitor stores energy on the form of voltage. However, looking at the equations for the current and voltage on the capacitor, we have the following:

I was thinking here that if I connect the capacitor to a DC battery, it is going to charge, right?
However, as the voltage is a constant, the current should be 0 according to the second equation. Therefore, according to the first one, the integral value is gonna equal 0, right? If it equals 0, then V(t) = V(t0). Assuming that V(t0) = 0, the voltage is always going to be 0, even though the capacitor charges when you apply a DC voltage to it.

Could someone please explain to me how to link this concept to the mathematical equations?

Thank you very much.


texts: How to simulate a circuit based on dac5578 (I2C TO 8 Channel DAC)

texts:
I designed a circuit based on DAC5578 from TI and I want to simulate it.
Is there a way to do it?
Thanks in Advance


texts: Should I connect metal enclosure to -V or to virtual ground?

texts:
I've built a headphone amplifier powered by a switch-mode 2-pin wall wart power supply. Internally a virtual ground is created by dividing and buffering the supply voltage. Input and output signals are referenced to virtual ground. I/O connector sleeves are isolated from metal enclosure.
If metal enclosure is not grounded, I obviously get 50Hz background hum, so I tried to connect enclosure to -V, then to virtual ground. In both cases the background hum was gone, but which option is "more proper"?


texts: Is it possible to scale +5v : -5v AC to effectively 0:0 with a potentiometer?

texts:
I'm a hobbyist so my theoretical knowledge surrounding electronics is pretty limited.

I'm working on modifying a synthesizer that uses a sine wave control signal whose frequency is in the sub-audio range. The signal peaks at -5v & 5v, and is used to control things like pitch and amplitude of a signal.

I would like to add a potentiometer or some other control to the circuit so that this signal can be attenuated by the person playing the instrument. I would like it so that the potentiometer could allow the signal's amplitude to be changed over time, depending on how the user turns the knob/moves the slider.

To further clarify I've attached an image.

the blue line represents 0v, and the red line is to illustrate the scaling function as it works over time.

My uncertainty is about whether or not a simple circuit can achieve this, and if it is as simple as using ohm's law how I apply it in this situation to pick the proper resistance of a potentiometer.


texts: TEC1-12706 Peltier run from diffirent voltages

texts:
My question relates to a video I saw on youtube. In this video, the user is cascading 3 TEC1-12706 peltier modules to achieve temperatures of -50 on the cold side of the cascaded peltier.

The TEC1-12706 is a 12V 6A unit, but in this video the peltiers are supplied with the following voltages as below:

Peltier 1 on the bottom - 12V

Peltier 2 in the middle - 5V

Peltier 3 on top - 3.3V

Unfortunately I don't really understand how to read the data graphs on data sheets. My question is, how does these lower voltages (5V and 3.3V) affect the performance of the TEC's, and wouldn't it be better to replace the 2 12V peltiers with a 5V and 3.3V version respectively.

EDIT

From the answer from @vindarmagnus, I left the following comment to make it more clear what I'm really after

  I have an idea how cascading work, and you've confirmed what I thought. However, talking specifically about the TEC1-12706 which is a 12V module, how is its performance affected when you run it on 3.3V and 5V. Does the drop in performance justify the use of a 12V module or will it be better to get a 3.3V and 5V module instead whereby I will get better performance.

Just to add, any type of reference as to why would be highly appreciated and would also help future users


texts: What does this power connector look like exposed?

texts:
I'm trying to build a DIN rail power supply enclosure, and not wanting to reinvent the wheel, I did Google Images "din rail mounted power supply".

Many many listed units feature a power connector like the   following image...

I can't quite figure out what it is or find it in an electronics catalogue.  Is it mounted to the internal pcb?  Or is it plugged into another connector as you can see a break that might be another collar /socket.  Is there a wire on the internal side?

I'd appreciate either a verbal description or a link to a supplier's catalogue so that I can see for myself.  There must be loads as many of the images returned from my search featured this exact (down to the colour) connector.

I looked for guidance within this question but it was unfruitful.


texts: Are core and prepreg dielectrics interchangeable?

texts:
This is a followup to an earlier question.

In my experience, PCB fab houses always default to using prepreg and foil on the surface layers.  For example, on a six-layer board, the stackup would be PCPCP:

However, it is possible to use a CPCPC, and one EE.SE user mentioned using PPCPP .

What are the considerations when choosing between these types of stackups?


texts: How can I create a new component using Qucs?

texts: I'm using Qucs for a simulation, but I don't understand how can I create a new component  (E.g. a new LED from a data sheet). How can create it and use it easily in my project?


texts: How to identify the correct power supply for a device

texts:
I imported a lamp from China to the UK, which came with a power supply terminated with a Chinese 2-pin plug. I'd like to use a UK-made power supply, but am not sure what I need to purchase.

I have been browsing for "12V 1A" power supplies on eBay/Amazon, and some mention a Wattage (e.g. 12W). Is this also a factor I need to consider?

The base of the smart lamp mentions "9W":

I can see "0.5A" mentioned on the Chinese power supply, which is obviously not the same as the "1A" written below it, so presumably refers to another variable that I need to consider.

not my pictureAlternatively, I could source a "travel adapter" and use the original power supply through a China to UK plug adapter, however I do not know how safe this is for long term use. I have read many scare stories online about "Chinese" plugs being unsafe and a fire hazard, but without much information as to what makes them "unsafe" so what to look for in a "safe" plug!

(not my picture)


texts: Can a 38kHz IR receiver module (TSOP38238) decode 870Hz pulse modulation IR?

texts:
I'm trying to reverse engineer my A/C remote controller IR.

I've decoded the IR signal as a NEC code with the PJRC IRremote library.
My attempt to retransmit the same code to A/C unit was unsuccessful.

Having a look at the IR code with a logic analyser (with an IR sensor rather than the TSOP38238) revealed the remote uses 870Hz pulse modulation.

How could the TSOP38238 decode that signal? is the decoding reliable?
Is this really a NEC variant with a different modulation?

EDIT: The module isn't a TSOP38238, but something that looks like it with the same pinout (should be compatible). The caption says 084ST


texts: Designing PID controller for 2 servo motor synchronization

texts:
I am trying to use a PID controller to synchronize wheel speeds in an arduino-bot so that I can get it to drive straight. I am unsure how to approach this problem without knowing the physical properties of the servo motors for the disturbance input (i.e., internal friction, moment of inertia, damping ratio). The ultimate goal of the project is to evaluate the gains of the system using transfer functions and then use MATLAB root locus features to evaluate the response & stability.

Could anyone supply me with some direction on how to get started? I have read some information on using step inputs to evaluate different parameters but do not know how exactly to do this. Tools on hand: arduino due, dc servo's with optical encoders and slotted optical wheel, MATLAB, and Simulink. Also have installed the PID & servo libraries for arduino. Thanks.


texts:
Can an induction motor be run safely with a 2:1 step down transformer? They don't work well with triacs because of increased rotor slippage, for example, but if I understand correctly that's because of the chopped up non-sinusoidal power waveform.

What are the implications of undervolting? Would it affect slip or efficiency?


texts: Boolean algebra - dual and self dual functions

texts:
I'm having a problem understanding what influences the dual function has on the original function output.

For example, if I have a self dual function - for the input 11 the function out put will be 1, and the output of the dual function will be the same.

Now for dual function - I saw on the Internet that the dual function always give the opposite output compare to the original function. Im pretty confused because if we look on the function A*B Then the dual function is A+B. now for the input A=1,B=1 they giving the same output.

Some one can explain me what dual function is beside changing the operators?

Thanks!


texts: Reliability of STM HAL driver For Safety Critical Application

texts:
I'm working on a project which must be used in an automotive application and act as a node into the multiplex CAN-BUS network. There are number of I/O that must be actuated and some of them had a level of safety critical attribute.
I developed my code using the STM32 HAL generic driver. And because the overall application and task are simple and latency is in lower priority so I decided not to deal with the register it self and using HAL driver instead, as the matter of speed and optimization of the code.

My question is that although the software seem to be working in prototype device, is it reliable to use HAL driver for safety critical application like automotive?


texts: What battery is lightweight and has a lot of power?

texts:
I'm creating an Arduino project, for that project I'm looking for batteries like the ones used to power scooters or electric wheelchairs, so powerful that they can carry the weight of a human and last for a long time.

I've seen some electric wheelchairs, but the batteries are huge in size and weight. I'm looking for something lighter, that has the same power as an electric wheelchair, and relatively cheap that people like me could buy, the battery has to be rechargeable of course.

maximum potential speed is like 20 km/h maybe less, but the normal speed will be around 5 to 10 km/h, distance around 80 km, i have no problem using some sort of a regenerative brake system or solar power system.

What are my options?

I've been told about Vmax tank and agm batteries, from what I see, it seems too heavy. I need something portable, and don't mind using 2 batteries instead of 1. From what I know, a scooter battery is 12 volts, so I need something like that; or 6 volts and use 2 batteries.

I'm looking for batteries the size of Samsung S4, or an iPad maximum. I know a lot of people who gave me many options but none portable so far.

I'm not going to discuss the project because it's outside this topic, but basically I have 2 problems with my project, finding the right batteries is the first one, I'll discuss the second problem later. Maybe the battery that I'm searching for doesn't exist

I don't care if it's lithium or not.


texts: How to analyze a capacitor in series to a capacitor and resistor in parallel?

texts:
I would like to do a transient analysis on this circuit but I don't know how to use those formulas
$$V(t)=V_0*(1-e^{\frac{-t}{R*C}})$$
$$I(t)=\frac{V_0}{R}*e^{\frac{-t}{R*C}}$$
in this case.

There are no values given for the components as I want to understand the process and not just know the result.

Thank you.


texts: Speaker designed for ultrasound operation

texts:
I've created a transmission protocol in order to transmit information bits between a PC speaker and a smartphone, or between 2 smartphones using ultrasounds. I've implemented a QFSK system which uses 4 frequencies and a 3 kHz bandwidth. Now I would like to build my own Transmitter/Receiver using Rasberry PI or any other SBC. I'm having problems selecting the right speaker for my transmisor because I want the system to operate in the ultrasound region so it won't disturb the users.

I've found some ultrasound 40 kHz transducers but they are mainly used for motion and distance sensing and have a 5.0kHz transmssion bandwidth. Although this devices bandwidth seem to work for me I don't know if you can use them to send a custom made audio signal like the one i want to send. I would also like to have a speaker with greater operation bandwidth, so I could implement a more bandwidth consuming modulation such as 16fsk in order to increase the bit rate.

Are there speakers with a flat frequency response, lets say, between 20 and 48 kHz and could be loud enough for reaching a microphone that is 2 or 3 m away?

It would be appreciated if they were also small and directional. Does such device exist? Maybe all of this features cannot be attained by single device, then one with most of these would do.


texts: Purpose of Cap to Ground in this Circuit?

texts:
I came across this circuit and I am curious about the reason for C2 being where it is. If I am analyzing the circuit correctly, this is effectively just C1 and C2 in parallel. What is the benefit of doing it this way as opposed to just a larger cap for c1? Something with bouncing of the switch perhaps? Any sage wisdom would be greatly appreciated (note that the actual passive values aren't important here; I just knocked this together to make it easier to ask the question).

EDIT: After reading a few answers, I want to post the whole circuit. What I am extracting is the circuit for EN, and SW2 here.
The components I brought together in that simplified diagram have arrows to them. Note I omitted the transistors Q1 and Q2, since I didn't think it changed my core question, but perhaps I am wrong here. So if that's the case, my question still is, what is the purpose of that capacitor? In the full schematic it is C14.


texts:
What type of resistor technology would be best suited for a voltage divider that must be in the 10+ megaohm range that can work at a voltage of 800V+ across one resistor and have low as possible  noise (used as feedback network for high voltage regulator) with a low temperature coefficient?

What techniques would minimize 1/f noise on my high voltage measurement with these resistors?


texts: Toggle between Half-adder and Half-subtractor

texts:
I have constructed a half-adder that looks like this:

And a half-subtractor like this:

It's basically the same circuit except the AND gate at the bottom has a NOT before it for one of the inputs. I would like to combine the two so that I can perform (half-) addition or subtraction based upon a third boolean input. Zero would mean Add and One would mean Subtraction. What would be an example of how I could 'route' the input into an optional NOT gate based upon the type of operation being performed?

One idea I had was to put the operation input into an XOR gate before the AND input.


texts: Dual power supply without center tapped transformer

texts:
I am building a simple bi-polar power supply, that will be capable of -/+12VDC at around 1.25A. I have a mains transformer that brings 230VAC down to ~20VAC, with single windings on both sides. And I was wondering, if its possible to generate a +/- voltage from a  a single winding on the secondary side, so without the center tap. If it is, what is the best/ most efficent or most used way of doing it?

I would really appreciate if you could provide a schematic.

Best regards!

EDIT:

Would it be better if I used a full-wave rectifier getting only a positive voltage and then using a buck/boost or a similar method to invert it to a negative voltage?

What is the advantage/disadvantage of both approaches?


texts:
In class we are designing a few different circuits and it uses some diodes and opamps. Everything is fine on paper and everything makes sense. These are only ever refereed to as a "diode" or "opamp".

So then I made a simulation on pspice. However depending on what diode or opamp I choose the results I got were completely different. There where many opamps and diodes to choose from in the component list.

Until now I just thought a diode is a diode or opamp is an opamp as there's never been any more specifics on them. Nothing like a resistor or capacitor where you have to choose the correct value component to get it all to work.

So I was wondering when people say "use an opamp" is there a standard common / specific opamp that is the general one used.

Same with the diodes. Is there a standard go to diode that is used in all circumstances ..unless otherwise stated.

After thinking about it..what about transistors also?


texts: A 5V @ 1A wifi surveillance camera placed 50ft away (indoor)

texts:
I need to place a Wifi surveillance camera near the entrance of my house where no power outlet is in that area.

I pulled a wire wrapping wire (awg 30) to the target location without thinking about wire resistance.  And as you all expected, it didn't able to power the webcam.

The power the camera uses is 5V @ 1A.

I measured the wire resistance of my awg 30 wire to the location is 11 ohms (to and from) which is 6 ohms one way which is around 50 ft.

So my question is what is the minimum gauge I need to use to be able to power my webcam placed 50ft away from the USB power adapter?

Or how many awg30 wires I need to pull to lower the resistance to allow enough power to pass through?

I assume the common practice is that the voltage drop is less than 5% of the required voltage.

So 5% of 5V is 0.25V

R=V/I so to allow 1A to pass through the resistance should be 0.25V/1A = 0.25ohms.

From the chart:
https://www.cirris.com/learning-center/calculators/133-wire-resistance-calculator-table?

Therefore I need a minimum of one 14 Gauge wire (or a bundle of fifty awg 30 wires LOL) to power the webcam 50ft way?


texts: Augmenting a capacitance base humidity sensing circuit

texts:
Given an electronic device that measures humidity using a capacitance based humidity sensor, how would one alter the circuit to make the humidity reading lower?

From what I can see without taking the device out of service, there is a surface mounted capacitor wired as follows:

simulate this circuit – Schematic created using CircuitLab

Figuring it was worth a try, I removed C1 and it seemed to make no difference in what the device reported as the relative humidity.  Unfortunately, I can not find a schematic for the device.

Here is an article describing humidity sensors, but I am unable to design a circuit alteration based on what I'm finding there.


texts: Oscillating system via negative feed back?

texts:
The Barkhausen criterion for system with positive feedback (being \$B(s)\$ the feedback network transfer function and \$A(s)\$ the gain network transfer function) afirms that for a system to keep oscillating without input signal and without loss, we need the poles of:

\$H(s) = \dfrac{A(s)}{1 - B(s)A(s)}\$

in the imaginary axes at the complex plane.That means there should be a solution to:

\$B(j \omega_o) \cdot A(j \omega_o) = 1\$

and ωo would be the oscillating  frequency.

On the other hand, if i have a system with negative feedback (being B(s) the feedback network transfer function and A(s) the gain network transfer function), the overall transfer function will be:

\$H(s) = \dfrac{A(s)}{1+B(s)A(s)}\$

So, in order to have poles in the imaginary axis (no loss), I need a frequency ωd that solves:

\$B(\omega_d).A(\omega_d) = -1\$

That loop transfer function being -1, should mean that the sinusoidal input with frequency ωd wil be shifted by 180º and will keep the same amplitude after passing through the loop \$A(s).B(s)\$, then will be shifted by 180° again because of the negative feedback and will return to its original form to keep oscillating  indefinitely.

It will also mean that the transfer function \$H(s)\$ will have infinity gain at jωd which is a requirement to keep a system living without any input signal. Isn't it enough to implement a oscillating  system that will keep oscillating any sinusoidal with frequency ωd that enters the loop?

Why do we need positive feedback to implement an oscillating  system ?


texts: Why is D Flip Flop Positive Edge Trigger instead of a Level Trigger

texts:
So i'm trying to understand this D type Positive Edge Flip Flop:

simulate this circuit – Schematic created using CircuitLab

I'm having problem understanding why it's a Positive Edge triggered and not Level triggered.

I understand that when the clock is 0, NAND 2 and 3 will both output 1 locking the current values of the SR latch on the right.

but when the clock value is 1, it stop affecting the circuit , so it can be simplified into something like:

simulate this circuit

where the circuit will start to be affected by the input of D according to the previous state of the circuit.

But if this is how this D type flip flop works, wouldn't it be a level triggered flip flop instead? since the input D will affect the Set and Reset values of the SR latch on the right as long as the clock is 1.

Can someone explain where I've gone wrong in my understanding?


texts:
Ive been reading up on capacitors. But most stuff is over my head. I'm considering a system with the following attributes:

Capacitor: 12 VDC, 0.5 Farad. Power supply: 5 VDC, 1 amp

What will the power output of the capacitor be?

Based on I=C(dV/dT)

C = 0.5 Farad.
dV = 5 VDC.
dT = 1 second.

Then
I = 2.5 amps

So the power output will be 12.5 watts with a 5 watt input.

This doesnt seem right to me. Is this correct?


texts: Bizarre Behavior in a Phototransducer Amplifier

texts:
THE GOAL:

I'm trying to measure light levels with a Hamamatsu S6428-01 photodiode (Blue).

THE CIRCUIT:

Below is the circuit that I have: an Arduino Uno, powered by USB, which is itself powering a ADA 4528-2 op amp. I have marked points p q and r for future reference:

RESULTS:

I ran a general light-responsiveness test with a Tenma 72-7765 multimeter: I waved a blue LED in front of the diode, and saw how certain voltage differences reacted. Here were my observations:

V(q)-V(r) ranged from 0mV to -300mV (saturation), and was negatively correlated with the intensity of the blue light reaching the diode.
V(q)-V(p) was 1.2-1.3mV, and was completely independent of the intensity of the blue light reaching the diode (even with the LED touching the photosensitive area!).

QUESTION:

The first result is perfect, and in line with theory. but for some reason the second result is puzzling: the input pins of an op amp should have the same voltage, and my ADA 4528 has an input offset of <2uV. However, I am getting 1.2mV. What's going on?


texts: Solution to detect key present in door lock?

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What would be a good way to detect whether a door key is present in a door lock (type: pin tumbler lock) at the outside of the house ? The idea is to be alerted when one forgot his keys in the lock.

I am thinking of some electrical/electronic sensor or solution that I can hook up to for example an Arduino (which would then alert me when a key is present in the lock for e.g. more than 5 minutes).

Requirements wishlist:

The most practical solution would not need power and have a simple open/closed contact that I can poll periodically using Arduino. An open/closed contact would have the (marginal) added advantage of being able to put several sensors in series (for multiple doors).
The state of the lock (locked or unlocked) is not relevant.
The actual act of inserting or withdrawing the key is not my primary interest, although it could be used as a stateful (i.e. would require keeping state) workaround solution.

Non-optimal sensor methods considered:

I've considered a light beam sensor monitoring the door entrance at key height (cons: needs power, and requires installation at the outside of the house),
small inductive sensor next to lock (cons: needs power, will be very visible, requires drilling a hole in the door).
Some home made sensor could maybe be a wire wounded round the lock to create a coil (if that would be possible, space-wise) which would presumably have a different inductance based on a key being present or not. However, I am not sure about the required circuitry for the latter.

Any ideas?


texts: Can the voltage regulator from here, Figure 6 be used to supply a negative bias to an APD? Would inverting Vin/GND do the trick or could that damage the IC?


texts:
A circuit was setup to detect obstacle (proximity sensor) using IR transmitter which uses Arduino to generate 40 kHz Frequency (the frequency was checked using a digital oscilloscope and it displays 40 kHz) and TSMP58000 as IR receiver, but the voltage at the output of the IR receiver when an IR pulse gets detected is seen as 3V instead of a value ~0V .What could be the issue?

Receiver used - http://www.vishay.com/docs/82485/tsmp58000.pdf (it receives in 20 kHz - 40 kHz range)

The screen shot of the transmitter and receiver circuits are as below where 4th terminal of IR transmitter is connected to the arduino pin and IR led is connected to the ground. External Power supply is used to power the IR receiver and common ground is used for both.


texts: Calculating the loop gain for an ideal op-amp with time delay

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In the circuit below, \$\tau \$ represents a time delay. We are using a first-order Pade approximation for this time delay. This means that \$\ e^{-s\tau} = (1-s\tau)/(1+s\tau)\$.

Below is the circuit. Does the feedback term, \$\ B = R +  (1-s\tau)/(1+s\tau)\$? What exactly is the loop gain?


texts: How to: Led Dimmer switch to on/off switch

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I have a led strip with a wonderful no touch dimmer on the bottom of the kitchen cabinets. What i would like to do is to "link" the inner lighting of the cabinets to the same switch, in a manner that when the dimmer is turned on, the cabinet lighting is also turned on, but without any dimming.

My first thought was to add a relay in serial to the dimmer, which would turn on the strip directly from the power supply. But the dimmer adjusts the voltage between 7 and 12V. Therefore the voltage would kill a 5v relay, and the 12V relay would only work on Max dimmer brightness.

My question is, is there a good way of making this work (haven't found relays that work with multiple DC trigger voltages), without adding an additional switch.


texts: Television flyback transformer: does it do 2 tasks ie. horizontal flyback and E.H.T.?

texts:
Television EHT transformer is also called Flyback-transformer?

E.H.T. (Extra High Tension) generates the cathode ray; ie. acts in same direction of the main pathway of running electrons, i.e. "normal" projection to centre of screen from cathode. Does-it do something with horizontal movement of electron beam on the screen???

Also, in the terms, "Flyback Transformer", "Horizontal Flyback",  "Flyback-pulse" etc; there is a common-word "Flyback". Are these all flybacks the same thing?


texts:
In the design of an AC servo position flight control surface system, a feedback system compares the output position to the pilot's input command signal.
How is an operational amplifier used as an error detector?


texts: ATTiny IR receiver logging erratic values, but works consitently on Arduino Uno

texts:
I am making a an ATTiny85 IR receiver, programmed with an Arduino Uno.

I'm using a modified version of this code (because the other IR libraries I found weren't compatible).

It's working... sort of. It will respond to anything out of my Universal remote, but I would like it to only respond to one button.

I have the IR sensor connected to 5V, Ground, and ATTiny pin 1 (literally 6), and an LED with capacitor to 4 (literally 3) and ground. 99% percent sure it's not an issue with the components.

If I run the code with the same sensors on my Arduino Uno, it works flawlessly and consistently. The key printed to Serial when I press the power button, for example, is always 2704.

With the ATTiny85, I get values all over the place. From the 0 to thousands. I pressed the power button two dozen times and got 2704 once.

So the variable here is the chip.

I have a hunch it has to do with the ATTiny being unable to measure the times between pulses accurately, but I don't really know how to fix this (calibration? A better external crystal?) and would like some input before I order and then sit around waiting for more components.

It seems possible, because this person built a robot that is controlled with the D-pad on a remote control—but they didn't post their code, schematic, or explain how they made it in very much detail. Other people have asked.

Thank you very much!

Also, here is my code:

int ir_pin = 1;                         //Sensor pin 1 wired through a 220 ohm resistor
int led_pin = 4; //"Ready to Receive" flag, not needed but nice
int start_bit = 2000;                   //Start bit threshold (Microseconds)
int bin_1 = 1000;                           //Binary 1 threshold (Microseconds)
int bin_0 = 400; //Binary 0 threshold (Microseconds)

int led_state = HIGH;

void setup() {
  pinMode(led_pin, OUTPUT);             //This shows when we're ready to receive
  pinMode(ir_pin, INPUT);
  digitalWrite(led_pin, led_state);
  Serial.begin(9600);

}

void loop() {
int key = getIRKey();             //Fetch the key
  if ( key != -1) {
    Serial.println(key);
    //if (key == 2704) {
       led_state = !led_state;
       digitalWrite(led_pin, led_state);
       delay(1000);
    //}
  }
}

int getIRKey() {
int data[12];
while(pulseIn(ir_pin, LOW) < 2200) { //Wait for a start bit
}
data[0] = pulseIn(ir_pin, LOW);       //Start measuring bits, I only want low pulses
data[1] = pulseIn(ir_pin, LOW);
data[2] = pulseIn(ir_pin, LOW);
data[3] = pulseIn(ir_pin, LOW);
data[4] = pulseIn(ir_pin, LOW);
data[5] = pulseIn(ir_pin, LOW);
data[6] = pulseIn(ir_pin, LOW);
data[7] = pulseIn(ir_pin, LOW);
data[8] = pulseIn(ir_pin, LOW);
data[9] = pulseIn(ir_pin, LOW);
data[10] = pulseIn(ir_pin, LOW);
data[11] = pulseIn(ir_pin, LOW);

for(int i=0;i<=11;i++) {                 //Parse them
  if(data[i] > bin_1) {                 //is it a 1?
      data[i] = 1;
  }  else {
      if(data[i] > bin_0) {           //is it a 0?
        data[i] = 0;
      } else {
       data[i] = 2;                     //Flag the data as invalid; I don't know what it is!
      }
  }
}

for(int i=0;i<=11;i++) {                 //Pre-check data for errors
  if(data[i] > 1) {
      return -1;                           //Return -1 on invalid data
  }
}

int result = 0;
int seed = 1;
for(int i=11;i>=0;i--) {                //Convert bits to integer
  if(data[i] == 1) {
      result += seed;
  }
  seed = seed * 2;
}

return result;                             //Return key number
}


texts: How to derive the precise gain of an NPN common emitter amplifier without emitter degeneration?

texts:
As a self imposed exercise, I tried to derive the complete expression of gain in a common emitter amplifier without emitter degeneration. I mean by "complete" that it also takes into account the distortion associated with it. Here is my notations.

simulate this circuit – Schematic created using CircuitLab
And my attempt.
Derivation attempt
Suppose a tiny \$V_{O}\$ nudge \$v_o\$. We know \$V_O = V_{CC} - R_CI_C\$, therefore, as \$V_{CC}\$ and\$R_C\$ are constant, we get :
$$v_o = -R_Ci_C \Rightarrow i_C = - \frac{v_o}{R_C}$$
This will cause a change in the emitter's intrinsic resistance, \$\Delta r_e\$, defined as :
$$\Delta r_e = \frac{V_T}{i_C} = -\frac{V_TR_C}{v_o}$$
By the definition of current gain in a BJT, it will also cause some \$i_B\$ :
$$i_B = \frac{1}{\beta}i_C = -\frac{v_o}{\beta R_C}$$
Because \$I_E = I_B + I_C\$, there will be :
$$i_E = i_B + i_C = -(\frac{v_o}{\beta R_C} + \frac{v_o}{R_C}) = -\frac{(\beta + 1)v_o}{\beta R_C}$$
By Ohm's law and definition, \$v_i = v_B = i_E\cdot(\Delta r_e + r_e(V_O))\$, so :
$$v_i= \frac{(\beta + 1)v_o}{\beta R_C}\cdot(\frac{V_TR_C}{v_o} + \frac{V_TR_C}{\alpha V_O}) = \frac{V_T}{\alpha} + \frac{V_Tv_o}{\alpha^2V_O}$$
From here I am stuck, for I do not know how to handle the "incremental gain" concept. Should I treat it as a gain derivative or as the gain at a particular point ? I do not want this question to exhibit an XY problem, so any pointers toward a solution are appreciated.
I also tried a non-incremental solution, but with it I found \$V_I = V_T/\alpha\$ for all \$V_O\$ which is nonsense.


texts: Using other pic microcontrollers instead of the PIC12C508 (arcade monitor protection circuit

texts:
I want to use another microcontroller because the PIC12C508 isn't available in my country (philippines) I want to use the PIC16f628a or PIC12F510 but I don't know what pins to use and if they're compatible.

edit: I don't have coding knowledge but i know how to program them. The source code is in the site below.

More info on the circuit

The monitor protection circuit protects (cuts off the sync if it's higher than 15Khz) the arcade monitor (which is CGA) from sync frequency being higher than 15Khz when the pc boots. The pc uses VGA with a breakout wire and will run on soft 15Khz.

It also amplifies the VGA signal that is 1 volt peak to peak to 5 volts.

The artcicle is here http://members.optusnet.com.au/eviltim/vga2arc/vga2arc.htm.

here is the circuit: intelligent direct coupled video amplifier

The hex file

:10000000A80C02000C0C0600660061002107060A1D
:100010006C006100AC0261070A0A740C8C000307D3
:0E002000140A020C2600050A210C2600050A0F
:021FFE00EA0FE8
:00000001FF


texts: Power output from a buck boost circuit is too low

texts:
Thanks to all who helped on the earlier part of the circuit - that's now fixed and working.
Now the buck boost circuit to drive the LED is working, but it only puts out a very small fraction of the power that it should.
Here is the circuit:

It is supposed to boost the Vcc from 8V to 12 or 13V to drive the LED at 130-800mA with different R77 resistor values.  Vcc comes from 2 18650 Li ion batteries with sufficient current/power capacity.
With R77 at 4.7ohm, I am supposed to get 130mA across the resistor & through the LEDs, with the feedback voltage at 0.6V.  I actually get a feedback voltage of 0.3V, so 65mA.  (V+ for the led is 10.7V, as indicated.)
When I switch to a lower resistor, V+ and the current stay more or less the same, and the feedback voltage drops to 0.15V (corresponds to roughly 65mA.) (V+ drops slightly to 10.65 or 10.6V.)
I already tried different inductors, but I get more or less similar behavior.
Any ideas what else to try?


texts: STM32F303 Readout Protection Level 1 - programs do not start at all

texts:
I never protect the FLASH memory but this time it is my client requirement. I have my own bootloader and the application ready. Everything works fine if the protection level is zero. But if I switch it (it does not matter if I use ST-LINK utility or it is done from the bootloader) to the Level 1 the program just do not work. I know that is ridiciolus to say "program does not work" - but during the tests I wrote simple LED blinking program. It only enables the GPIO clock and toggles the LED. It works fine on level 0, but stops working on Level1. As I understand switching from level 0 to 1 or 2 does not erase the FLASH (it does in the opposite direction). I cant take a look inside as any debug interfaces are disabled.

Boot 0 is connected via 10k resistor to the GND.


texts:
Ultimately I would like to assemble this simple audio amplifier:

Given my lack of any significant knowledge in the topic I have several problems and questions.

Grounding:

In the thread What is ground and what does it do? it has been said that grounding is basically about creating a reference point and:

  Remember, a complete circuit is required for current to flow. You would need connections to earth ground in two places for current to flow in and out of your circuit from earth ground.

Let's take a lightning. If I am struck by it, how come the circuit is closed? The current certainly flows through me. And also if there was no current flow through grounding wire in any case, what would be a physical reason for attaching it?

In the schematic I showed there are signs of earth ground in multiple places. I saw some video of a man creating this amplifier exactly and it seemed to me (the footage is not that precise) that he created a stand alone device, therefore there could be no physical attachment to actual ground by any external wires. How then should I understand the grounding symbols?

In the LM386 data sheet I found a statement that it features "Ground referenced input". How am I supposed to understand that? Also about pin number 4... Should I attach the pin to the ground (as possibly shown in the schematic) or I could attach all the wires ending with the ground symbol to this pin? If it's the latter how is the pin constructed inside the chip? How come it serves as a ground?

Amplifiers:

I have already assembled some amplifier that looked more or less (rather less) like the one shown. The problem is that it worked with an input from a regular PC jack but it did not work at all with an input from 2.5 mm telephone jack. Someone said that it's because PC audio already has boost and the telephone's port does not. Did he mean a power booster by it? Like "push–pull output"? But what is the general difference between push–pull output and this amplifier? I mean, in this case I am trying to increase voltage of the signal and, as I understand, also a power output (P=UI=U^2/R). So I need a booster to boost my signal so I can boost it again? I don't understand. Someone also said that it could work if I assembled my amplifier correctly. If I assemble this very circuit correctly without any additional parts, will it work with the telephone jack I mentioned (Panasonic KX-DT333)?

Edit:

Also what is the function of the 0.05 mOhm capacitor? What happens if I use 1 mOhm? Also there should be no problems if I use 220 instead of that 250 one, yes?


texts: Find some H Bridge module or build my own?

texts:
I'm doing an RC car with arduino and I got stuck on the H-bridge part.

I'm using an old RC car as a base, so I'm taking advantage of the structure (including the engine and battery) and changing only the electronic part.

I started using a module with an L298N, but after 15 minutes it started to smell burned and stopped working. Every datasheet I find is for the L298 without the N, which tells me they support up to 50v and 2A, but nothing tells me about the L298N exactly.

I need a H-bridge to finish it, I wish it would be possible to control the speed without PWM.

The battery is 9.6V and the motor consumes 2A.

Is there any H-bridge module I can buy?
Or, what components should I use to build a H bridge?

_I'd rather buy some module, because if I need to build my H-bridge, I'll have to do it on boards like this: Board Example

PS: I live in the interior of Brazil and it is difficult to find good electronics stores, even to buy over the internet.


texts: a variable dc power supply with V and I vary independently

texts: checked some variable dc power supply, there is a common problem that when V vary, I following vary, vice versa。 Are there any project overcome this?


texts: VHDL "can't match slice type array type"

texts:
I'm new to VHDL and I'm trying to use code off a teacher's slide that doesn't seem to work as is, and I can't tell what's wrong:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity Add4 is port (
  Data1, Data2 : in std_logic_vector(3 downto 0);
  Cin : in std_logic;
  Cout : out std_logic;
  Sum : out std_logic_vector(3 downto 0) );
end entity Add4;

architecture RTL of Add4 is
  signal Out5bit : unsigned(4 downto 0);
begin
  Out5bit <= ('0' & Data1) + ('0' & Data2) + Cin;
  Sum <= Out5bit(3 downto 0);
  Cout <= Out5bit(4);
end architecture RTL;

The error I'm getting is:

add4.vhd:15:28: no function declarations for operator "+"
add4.vhd:16:17: can't match slice with type array type "std_logic_vector"

The first error goes away if I comment out the assignment of Out5bit and the second goes away if I comment out the assignment of Sum. What am I doing wrong? Would this code have worked without being modified on some older version of VHDL or did my instructor just give me bogus code?


texts: ECG Signal Measurement using Plessey PS25201

texts:
The above said sensor measures the change in the electric field.
Data sheet link :  Click here

When I measure the output from the sensors directly on the CRO with finger placed on the sensor; the output is a pure square wave; blame my CRO for not showing
minor changes in between the transitions.

The typical application of this sensor is to drive them in a differential configuration with sufficient gain (Inferred from Datasheet; Absence of Application notes makes everything harder).

What I've tried is to buffer the input from the individual electrodes with the gain of 13(INA126P) and then INA with gain of 23 (AD620); the output of INA is filtered with 2nd order active LPF and HPF with cutoff of 159Hz, 0.25Hz respectively.  Attached Schematic will give you a better idea.

The above configuration saturates the op-amp (Vcc and -Vee) (R Peak in both directions)

My question is how do I get distinguishable P,Q,S,T,U peaks from these sensors?
Anybody who has used these sensors please guide what circuit to use.

I'm sampling the output at 500Hz with Arduino.
I've also tried sampling MAX1132 ADC with CC3200 Launchpad but with no luck.

EDIT : I'm not using Right Leg Drive as it's a design constraint.


texts: infrared and K-Type temperature sensors badly disagree

texts: They are both cheap. There is a piece of PCB balanced on top of the K-type thermocouple's probe; there is also a red laser light from the infrared thermometer right in the middle of the same PCB where the probe's head can be seen. The difference between the readouts is sometimes larger than 100 degrees C. Which one should I trust more (for the purpose of PCB oven soldering) ?


texts: RaspberryPi + FET LED lighting controller

texts:
I'm attempting to control an LED Lighting Strip from a RasperryPI GPIO pin. I have the following setup:

simulate this circuit – Schematic created using CircuitLab

This is the diagram I have replicated except for only a single channel rather than RGB.

With this setup, the LED strip doesn't light up at all regardless of whether the GPIO pin is powered or not. I feel like I'm using the wrong FET, and if that is the case, what would be a more suitable FET to use in this instance?


texts: How to reduce the data rate?(OV7670 + AL422B(FIFO) Camera Module)

texts:
I bought this module: OV7670 + AL422B(FIFO) Camera Module and I want to send the live video of the camera by this NRF24L01 but I have several questions.

Is the RF module suitable(NRF24L01) for this job?
I think the data rate of the NRF24L01 isn't enough for camera. what's
your opinion?
If you agree with me, in your opinion, how can I solve this problem?(in other word, can I reduce the size of the camera's data(video)?)

I should send the video by NRF24L01 for 1Mbps or more. in addition, I'm using STM32F103RET6 for this job.


texts: How to use/create a real time clock to use with specialized?

texts:
I want an accurate clock that will output a square wave that operates at 1 Hz. I need it to connect to a chain of binary counters. When the right binary number has been achieved the outputs will trigger AND logic gates to advances the count on the display. This would happen once every 86400 seconds (1 Day).

I don't know if this means using an RTC but the ones I have researched are only connected to microcontrollers.

I have tried using a 555 in astable mode but did not receive accurate results (I did not use a crystal).

If anyone knows any way to achieve this, please let me know.

Thank you.


texts: Is there a problem with using delay functions when using internal oscillator in PIC ?

texts:
I am doing a project that requires having the micro-controller to use the delay_ms() functions (compiler CCS C) to wait for a determined period of time.

I am using PIC 16f628A and while the program ran as intended in Proteus but it ran about 85 times faster that that when I tried it on the board .

I did choose to set the internal oscillator to the minimum possible frequency (48khz) to decrease power consumption and I specified that in the wizard and so the .h file have the line    #use delay(internal=48kHz).

What am I doing wrong ?.


texts:
I read about this article about solar lamp. Obviously I can bought the whole thing online by spending $30 something but I want to make it by myself.

I hope this is the right place to look for. I am not sure if this belong to another SE. I have no electrical experience except the little thing I learn from high school. With a proper instruction, I think I can build it by myself from the scratch.

I googled around for "DIY solar lamp" but I cannot find any page which am not using already made $1 solar road lamp, however, I want to bought the things including solar cell, diode, etc and assemble them by myself.

I found this article which seems to be teaching it but it is lacking the
graph.

I've attached an schematic below which I found on the internet. It is about a solar lamp with  a solar cell of size 25x18x5 cm, which I don't think could fit in a jar. I place it here for a reference. It is from Taiwan so it is Chinese. I've made a translation for you.

What I need is a instruction to build a solar lamp from scratch and it could fit in a small jar. Do you have any idea?


texts: Connecting Difference Amplifier to High Impedence Sensor

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I have a high impedance differential sensor (stable 600k impedance Rth, 10mV signal, Fout=1kHz). I need to amplify this signal to about 1V (40dB gain). Due to layout/system constraints only the TLV9061 OpAmp stage can be used. Any suggestions on what topology would enable this? The problem I run into is that any difference amplifier or transimpedence amplifier needs feedback resistors that are unreasonably high (10s or 100s of Megohm) for a real world implementation.

I was looking into T-Network solutions as in this thread but it seems they suffer from high current noise.

Looking for any advice on other topologies to explore or methods to consider. Thanks!


texts: Why most of processor only provide finite number of logic operations (NAND/NOR/XOR) while there are clearly 14 different logic gates available? I understand that we can implement any Boolean logic with only NAND/NOR . But practically, providing less gates make operations such as NIMPLY/IMPLY takes more than 1 cycle to finish as we need to implement them with composition of other gates. It seems to me that if ALU provides the whole set of hardware optimized logic gates we might be able to optimize software performance. Fanout might be an issue if all logic gates' output drive the same bus, but it seems logic operations aren't always the bottleneck of a modern processor because there are much more time consuming operations such as multiplication that limit the clock cycle. So my question is why we seldom see processors provide the full set of logic gates? What are the considerations involved?  How do processor designers reach the optimal number of different logic operations the ALU is going to provide?


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Occasionally I'll get the following errors while programming my SAMD21 chip. Anyone know the reason?

Error: SAMD: NVM programming error
Error: Failed to erase row containing 00000100
Error: SAMD: failed to erase sector 1 at 0x00000100
Error: failed erasing sectors 0 to 10

If I spam sudo openocd then programming will eventually succeed. Below is my script. I'm totally new to this stuff and copied my script with minor modifications from an Adafruit guide.

Script:

source [find interface/raspberrypi2-native.cfg]
transport select swd

set CHIPNAME at91samd21g18
source [find target/at91samdXX.cfg]

# did not yet manage to make a working setup using srst
#reset_config srst_only
reset_config srst_nogate

adapter_nsrst_delay 100
adapter_nsrst_assert_width 100

init
targets
reset halt
at91samd bootloader 0
program image.bin verify
# at91samd bootloader 8192
reset
shutdown

I'm running this on a Raspberry Pi 3B+. I have no need for a bootloader on the SAMD21. I can confirm that my simple "hello world" image works correctly when it's successfully programmed.