texts: Is a Power Distribution Unit safe for home use?

texts:
I got my hands on a Power Distribution Units (Dynamode 8WS-V-SP-1U 13A) and
Examples ca be seen here and here.

I was hoping to use it at home like a power strip. However, it has a big warning message that states it is "exclusively for cabinet use".

Is it safe to use? Why would it be for cabinet use only?


texts: Tube transmitter plate current meter question

texts:
Can I install the mA meter in this schematic directly in the circuit?

This is the high voltage plate supply and there is RF on it.

The diagram doesn't specify if there is any circuitry to adapt the meter to RF, if that is even needed?

The ammeter I purchased is just a square face, sweep meter, 200mA.


texts: Is there a way to plot differentiation of frequency in LTSpice?

texts: I'm simulating a circuit and I obtained the AC simulation (bode plot) of it. However, now I want to plot the group delay, meaning, the negative derivative of the phase in terms of frequency. Is there a way to do that?


texts: Stencil at home with extremely small parts?

texts:
I was amazed lately to find out about solder paste - so we can assemble our PCB prototypes at home relatively easily.

The process seems easy, but now I started to suspect I am going to have a problem with small 0402 and 0603 parts.  I also have the main part which is QFN-48 (no pins, only pads underneath).

To make the stencil with such small sizes that you can't even print seems like a real problem - e.g for 0603 is less then 1 mm so most printers will not do it, even laser.
If I do these parts by hand, can I make a stencil for the QFN-48 pins (600x600)? or is it too small for that? 12 pins per 6 mm is one pin for 0.5mm!

How do you do these things? Can I just splash all pins with the paste without stencil fixture?  Assembly for 2-5 parts can cost more than $350, and some parts such as QFN can't be assembled by hand.


texts: Choice of state variables in circuit theory

texts:
I have been trying to get a more fundamental grasp on what a circuit is, mathematically speaking. I have read about the lumped element model, constitutive equations, and the memristor. However, I still have some doubts about what the conceptual framework is.

When talking about memristors, people say that the state variables are voltage, current, charge and magnetic flux (or flux linkage, not sure about the distinction). Then there are 6 possible pairings of state variables, two of which are definitions, and from the rest the basic circuit elements would arise:
$$
\dot q=i, \ \
\dot \Phi = v \\
v = R i, \ \
\Phi = L i, \ \
q = C v, \ \
\Phi = M q
$$

However, it seems to me charge and flux linkage don't add much to the picture, since they are related to v and i by their definitions. One could say that only v and i are state variables, and the circuit elements are the usual:

$$
v = L \dot i, \ \
v = i R \iff i = Gv, \ \
i = C \dot v
$$

Do these two models differ in any significant way? I guess the status of the memristor within the model is a distinction. Or is it just a matter of personal preference?

More broadly: I've also been wondering about obtaining the minimal set of equations for a circuit, and in general trying to fit things like dependent sources, nullors (norators and nullators), mutual inductances and multi-port elements into a series of gradually more complex models, and in general about the mapping to a series of linear equations. I have found some fancy math which is probably related but I don't understand, so I guess this questions are not so trivial. Nevertheless I'd be content with some guiding principles, or any pointers to accessible material that takes a more principled approach than the usual descriptive stuff. Thanks.

Edit: Just for clarification, I'm talking about an axiomatic approach to the subject. Circuits as an abstraction: what mathematical structure remains of Maxwell's equations when certain assumptions are made.


texts: How do computers execute instructions spanning multiple clock cycles?

texts: There are some(or most) instructions in a computer that simply cannot be executed in a single clock cycle. But there lies a problem. How does the program counter in the computer know when an instruction is completed, considering that one instruction might take 2 clock cycles vs another being 3 clock cycles. How do program counters(or more importantly, the machinery that detects that an instruction is complete) work?


texts:
I have an L298 Dual H-Bridge DC Motor Controller which comes with an LM1117-5 voltage regulator. I want to use this regulator for a logic level converter to go from 3.3v to 5v.

I have one board that outputs 3.3v which is connected with its own power supply and I have the L298 connected to another power supply where I get the 12v that it requires.

I tested their respective outputs individually and I got 3.3v and 5v. The thing was when I connected 3.3v to the logic converter and the 5v from the L298, I connected gnds coming from different power supplies to have the same voltage reference. When I was testing the output of the logic level converter I noticed that the high voltage was 12v rather than 5.

I disconnected everything and now I can see that the output from the LM1117 that it is on the L298 is the same as the input (12v) rather than 5v.

Could it be the cause of this that I connected grounds from different power supplies?. I believe I must do that, right?

Thanks for the help.

EDIT 1: Here is a schematic. Control board is a development board which comes with its own 12v@1A power supply. It has multiple digital outputs (pmods) which also includes 3.3v and GND pins. On the other side it is the L298 which I connect to a 12v power supply which the board contains a 5v voltage regulator and I connected grounds of both boards via the logic level converter.
From this thread I can confirm that it was correct to connect all GNDs so I don't get what might have happened with the voltage regulator on the L298 board.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm doing some project and I'm using Arduino to prototype, I have to use 10 pushbuttons (along with more things) and I don't have enough pins.

One solution I could think of is to use the analog pins and use each of them for two push buttons, something like this:

simulate this circuit – Schematic created using CircuitLab

That way I can read the pin A0 and know which of them is being pushed by looking if the voltage is 5V or half of that.

Is this a good idea? The different push buttons are NEVER supposed to be pushed at the same time, which is the only problem I can think off.

Are there better ways?


texts:
I want to make an introduction to "ARM programming" without using Atmel Software Framework (ASF). That is what I don't know: the definitions of the chip peripherals.

For example: How can I refer to a PORT or to a PIN or to UART's data register or to Status Register?

In AVR we use DDRx to specify the x port direction, and PORTx to change the logic level of an Output port or to setup Pull-Up or Pull-Down resistors, and PINx to read the buffer register of a port which is defined as input.

ADCH to get the eight MSBytes of ADC controller and ADCL for LSBytes respectively
How can I see these defines which I can use for programming?

I am referring to C Programming using Atmel Studio 6.2.


texts:
The capacitor C is fully charged by the battery while the switch is in position A.  The switch is then thrown to position B. Compute the charge on the capacitors and the resulting voltages.  The battery is 100 volts.

I tried to compute $$15 \space \mu F*100\space V=0.0015 \space C$$ to find out how much charge was available for the resulting situation. But reverse engineering the answer, even this is wrong.  It it trivial to find the voltage on each capacitor (it has to add up to 100, right?) if we know the charge, but clearly I am failing to do that.

Initially, I assumed the charge would be divided evenly.  But then I realized that since not all capacitors have the same internal field, this is probably not the case - each wire will have a (potentially) unique potential difference across of it!

I must admit, this problem has me stumped.  If anyone could explain just the method for how to approach this, I can check the answer myself.

Thanks!


texts: Switched capacitor sample and hold circuit as as mixer

texts:
I am trying to find out how important the "hold " level in a sample and hold down-conversion mixer is.
If the level is decreased, will it lead to any loss?
Out of these three subfigures, which one is correct?
Please justify.


texts: Pass USB 3.0 connection through D-SUB connector

texts:
I need to pass a USB cable through a vacuum chamber wall, for which we have only D-SUB passthrough flanges available. So I cut a USB cable in half and soldered a D-SUB connector to each half. For USB 2.0 connections, this works without any issues, but I've had troubles getting a USB 3.0 connection to work.

Specifically, the computer emits the connect/disconnect sound repeatedly every few seconds when the cable is plugged in. The only workaround is to push the connector in slowly, until the device is recognised, essentially forcing a USB 2.0 connection.

I assume this is due to insufficient shielding to get a USB 3.0 link?

The individual connections seem to be fine, with <3Ω resistance for each one and no shorts. Below is a diagram of how I routed the cables through the connector:

As shown in the figure, the shield is connected to the shell of the connector to connect the shield on both sides together. I tried to keep the amount of destroyed shielding low, with around 3cm on either side removed.

What is the most likely cause for this failure, and how to avoid it in the future, if possible?


texts: Is it safe to charge a device with only slightly different voltage and amperage?

texts:
My Asus tablet charger has 5.2V and 1.25A.

But my new Micromax phone's charger has 5.0V and 2A.

I am tired of carrying two different chargers everywhere. Is it OK to use either charger to charge both the devices? Both are android devices and both chargers are Micro USB.


texts: Do I need extra components for SAI with PCM?

texts: I'm in the very early stages of designing a low cost audio device. I will be using PCM (probably 16-bit 44.1khz) audio. I haven't settled on a microcontroller yet, but the stm32f74 arm cortex m7 looks promising because it has audio capabilities built in like SAI, I2S, etc. My question is, do I need external components, other than maybe an amplifier and obviously a speaker when using SAI and PCM? Or can I output directly to a speaker from the stm32?


texts: Parking Light And Signal light with same LED using MOSFETS

texts:
I have a project where I have an existing 12v parking light and I want to also have the turn signal use the same light. I've constructed a circuit using 2x NMOS and 1x PMOS. I think it will work and will basically function as such:

When parking light is on and signal is off, the LED will light for the parking light
When parking light if off and signal is on, the LED will flash with the signal
When parking light is on and signal is on, the parking light will be on, and it will cut out (turn off) each time the turn signal 'flashes'.

Does this circuit look like it will work? The mosfet model numbers and ratings of the resistors, etc. are just dummy values as a proof of concept. Im pretty new to circuit involving MOSFETs so im hoping ive got this right.


texts: Measuring the activation time of a solenoid

texts:
I'm trying to measure the activation time of a pull-type solenoid.

When the solenoid doesn't have a load connected to it, you can measure its activation time through the current it consumes.
At first, the solenoid will consume current until the magnetic field is strong enough to move the armature, at which point the current consumption decreases until the armature has reached its holding position. At that point the current will rise a bit more until it stabilizes.

However, if there is a load attached to the armature, the curve of current consumption never dips, which means that you can't quite tell at what point the armature is fully pulled in.

I'm wondering what technique could be used or is standard for measuring the time it takes the armature to reach the end position with a load.

I've thought of making the load close a circuit so you could measure the time between activation of the solenoid and the closing of the measuring circuit but I'm wondering if there are other approaches which I haven't thought of.

(p.s. if this is off-topic let me know and I'll remove the question)

Edit: Preferably the solution can be embedded in a machine with up to 1000 solenoids. This means that the added hardware (cost for example) needs to be somewhat realistic (i.e. no 200$ camera per solenoid ;) )


texts: Low impedance complementary negative level shifter for a BBD

texts:
I'm trying to clock a BBD (Bucket Brigade Device) circuit (for example the MN3007) from a microcontroller output. However, the circuit requires a complementary negative clock, i.e. CP1 is \$-12V\$ to \$0V\$ and CP2 is \$0V\$ to \$-12V\$ (for \$\mathrm{VDD} = -12V\$). The transition time for the clock is specified as less than 500ns, although I'd prefer to be well below that since apparently the clock signal directly drives the BBD transistors, so a slow transition increases non-linearities. Further, apparently the output should have reasonably low impedance, as the clock IC usually used with these types of BBD's (such as the MN3101) advertises about \$2mA\$ output current. Yet worse, the datasheet specifies that the clock cross point, i.e. where the the two complementary clock signals cross, should be between 0V and -3V, so a perfectly symmetrical drive won't do. One last technical requirement is that the that the clock voltages should be as close as possible to the rails, since those limit the signal swing (looking at the datasheet, the clock directly drives the gates of the switching transistors).
So, to summarize, your mission, should you choose to accept it, is to
point me to the right direction for designing a circuit that:

Given an input clock signal 0V - 3.3V, generates a complementary pair of clock outputs with levels 0 and -12V
transition time is less than 500ns
The clock outputs are able to provide at least 2 mA of output current
The levels are as close as possible to the rails (this disqualifies the most standard BJT circuit, such as discussed in this question)
The clock signals cross between 0 and -3V: alternatively: instead of providing the complementary outputs, I'll just design a good level shifter, and I'll use two channels of MCU PWM outputs for the complementary clocks and time them to adjust the crossing level. This requires that the level shifter edge shape is predictable in production and over varying environmental circumstances.
Price is important, 1$ per clock is already a lot (I'll be needing two of these per device, production numbers will probably be in the hundreds so parts pricing at hundreds is the correct quantity to consider)
PCB real estate is even more important

Bonus goals:

Using only components that can be wave soldered (due to some inevitable through hole components, we have to wave solder one side of the board, so this would give me a chance to keep all components on one side), while still keeping 5. and 6. in mind.
Transition time is much less than 500ns.

Possible trick to use:
One way that could make life a bit easier is that I could just as well hang the BBD between the +12V and 0V rails, instead of 0 and -12V. This would mean that the clock levels would instead be +12V and 0V, and the crossing point would be between +12V and +9V.


texts: I am currently studying solid state electronic devices and want to build my concept in this subject. Can anyone explain to me what is E-k Diagram and what is its significance?


texts: How to connect the transistor if I have to use it before the load?

texts:
I'm pretty much a newbie in the transistors stuff. I have an arduino and I want to read the engine RPM on it. The RPM signal is a square wave with amplitude of 12V and the frequency rises with the RPMs. I want to use a transistor as a switch. The base would be connected to the RPM signal, and I want it to act as a switch between arduino 5V output, and input so that the arduino would get a signal of the same frequency but amplitude of 5 volts.
Now:
I know that in NPN transistors, the emitter should be connected to GND, and the load should be between the source and the collector. I guess you could say in my case: the source is the 5V output, the load is the input pin on arduino. How do I connect a transistor if it has to be 5V output and input? Connecting emmiter to GND is impossible in this configuration


texts:
I'm trying to build an ESC (electronic speed controller) for three phase brushless motor. I found some intresting circuits but I am trying to build something very easy to do, with mosfet and pc817 and an Arduino.

I am using the DAC of the mcu to sense the voltage of the motor in each coil. So far I had used a resistor divider and worked, but motors vary a lot in voltage range (some are of 11.1V, others even of 22V and more,) so using a resistor divider limitsit to a certain family of motors.

I want to know if it is posible to divide whatever the voltage enter to the DAC pin (40v max)  to 0 (or -5v) and 5v without losing the sine wave form.


texts:
Let's say I have a n level tree, where n starts from 0. Each level of the tree has 2^n elements. For the sake of an example, let's say n=4. Since we have 4 levels, we need 4 bits to hold the index of any element in the tree. Suppose we are in level 2 (so, 1 level above the last level). Level 2 has 2^2 = 4 elements. Let's take one element from this level, say element with index 3. In binary, that is 0011. Since we are one level above the last level, I want to shift this value leftwards by 1. So, 0011 should become 0110. To make things clear. Let's take level 1. It has 2 elements. Lets take the second element: 0001. Since level 1 is 2 levels above level 0, we shift 0001 two places to the left to get 0100.
At the moment, the only way I'm thinking of accomplishing such a task is to use a barrel shifter. However, a variable width barrel-shifter might seem like an overkill (and might occupy a lot of area) for something as simple as this. Is there a better way to do this ?


texts:
I have a pocket flashlight (27 Leds) that runs on 3 aaa batts. I would like to use this item to replace my bulbs in my "emergency lighting. The bulbs exhaust the battery too quickly (90 minutes). The master lead acid cell(standby) is 6volt at 4.5 amps.

WHAT do I need to convert to these units? It would be two flashlight heads for each "emergency lite".

This is the lighting for exit doors and hallway lighting during "power" outages.


texts:
To start, I have no experience with electronics except what I've been googling the past week. What I'm having issues with is finding a way to make a voltmeter that functions like an led vu-meter would.

What I'm making is a gear driven dynamo and I want to make a visual representation to show the user that a faster spin produces more voltage by using LED's as user feedback. It is not important that it is accurate just that a faster spin makes more lights come on.

How can I make a volt-meter show that a dynamo is producing more voltage?

additional note: The intention is to make the dynamo the only source of power as well as what is being metered.


texts:
I'm looking to design a game where players fire a gun at a target using LASERS or IR.  The target only registers a hit when a certain amount of players (say 3) are hitting the target consistantly for 5 seconds. The target has got to be around 6" square. The range will be about 3 meters.

The problem i have with this project is that I'm not sure what I can use for a target? I have looked on this site and found solar panels don't seem to work that well.

Im considering an array of photodiodes/transistors to detect the lasers/IR. But as the target is big i'll need a lot of them!

Any ideas anyone?


texts: AC mains wire finder + live wire equivalent circuit

texts:
I'm talking about devices for tracing hidden AC mains wires in walls like this one: https://www.ebay.com/itm/3-in-1-LCD-Wall-Detector-Stud-Center-Finder-AC-Live-Wire-Metal-Detector-Scanner-/322510160930

Is it correct that it uses capacitive coupling and can be approximated by the following circuit?

SPICE tools require a common ground between the mains side and the device side (resistance in this case) but it reality the device is isolated from the mains, so I'm not sure if this is still a valid approximation because of this.


texts:
I was reading about why we need active filters even when we have passive filters with us.
I got to know that one of the main reasons for doing so, is that at lower frequencies the size of the inductor is large and it becomes bulky so it can not be fabricated on IC.

So can anyone please tell me how the size of inductor is related to the frequency of operation.


texts: Calculate voltage in a alternating voltage circuit

texts:
Im trying to calculate the voltage through C2 in this circuit but i am unsure how to.

e(t) = 0.3 sin(ωt + 18°)V , C1= 10μF , C2= 5μF , R = 5 Ohm , ω=3*10^3 rad/s

This is what i got so far:
frequency = 477.5 Hz

I put 0.3 sin(ωt + 18) in my calculator and got that one period takes 0.1057s so t = 0.1057s

then i put that in e(0.1057) = 0.3 sin(3000*0-1057 + 18) = -0.1263V

I calculated Xc1 and Xc2 and got them to be: Xc1 = 33.32 ohm and Xc2 = 66.67 ohm.

I then used these and calculated the impedance of R and C2 (4.9853ohm) and got the total resistance to be RT = 34.068 with 81.7 degrees.

I then used that to calculate the voltage in Uc2 with the following equation: (4.9853/34.068)*-0.1263 = -0.018482V

I did not get the correct answer though. I didnt know how to calculate this before i started so i gave it a shot, what ive done is probably completely wrong. All help would be appreciated.


texts: Power efficiency with Boost vs Buck-Boost using same regulator

texts:
I'm doing a few tests and figuring out what will be the best option for what will eventually be part of a battery powered circuit. I have both a boost and buck-boost converter, both using the XLSEMI XL6009 regulator. I have both set to 12V output and connected to an 8ohm power resistor to simulate a 1.5A load.
Using a lab bench power supply to simulate different voltages, I noticed with sub 12V inputs, the power consumption stays very close to 20W using the boost converter. But with the buck-boost, I'm seeing 24W starting at 12V with increasing power consumption as voltage decreases.
Is it normal for buck-boost converters to be less efficient? I imagined it would have been roughly the same power efficiency, since it uses the same regulator.
I included a link to the XL6009 datasheet here


texts: Opto-isolator output from collector vs. emitter

texts:
I have an Isocom ISQ2X quad opto-isolator (datasheet) that I will use to drive a logic input. The opto-isolator's simplified model given by the datasheet is pictured below. The transistor base pin is not brought out.

I have two possible configurations, pictured below:

Config1 where the logic output is taken from the transistor's collector
Config2 where the logic output is taken from the transistor's emitter

My question is: Aside from the inverted logic, are there any differences between these configurations? For example: does raising the collector voltage (when the transistor in Config2 is activated) have any effect on things like current-transfer-ratio or saturation voltages?

Additional, unnecessary, information:

If both configuration are equal I will go with Config2 because it is preferential for my application to have a logic low output if the diode driver is accidentally disconnected.
The logic input belongs to Intersil HIP4081A H-bridge driver which is powered by the +12V rail in the picture (Logic low threshold: 1V max, Logic high threshold: 2.5V min, Logic absolute maximum: VDD+0.3V).
The diode current will be controlled by a series resistor, probably to around 10 mA.
I could consider adding a buffering transistor/FET/IC if it is beneficial to my application.
I have these opto-isolators on hand and would therefore prefer to use them.
My intuition tells me that there isn't any difference between the configurations, since the phototransistor is effectively just series connected with a resistor and doesn't even "know" which configuration it is in. I ask because two colleagues prefer and recommend Config1, but that might be because they are thinking of Config2 as a standard NPN BJT common-collector circuit where they base pin would need to be raised as the collector is driven higher. Some literature I've looked at present both options without mentioning any differences.

Edit: I guess I was hoping for an explanation involving some sort of a phototransistor model and/or an answer citing some book/literature. As I don't think this question will pickup steam I've marked Olin's answer as accepted since he elaborated a bit on his answer - but I'm still open to more people weighing in on this.


texts: Current "jumps" from one wire to the other

texts:
I have cable with two 1.5mm wires in it. Why does my test light show voltage in both wires even though only one of them is connected to 220V AC grid.

// Also there are old cables with metal jacket with the same problem when testing the jacket.


texts: measuring current to 100uA accuracy in a battery powered circuit

texts:
I'm trying to figure out the best way to measure and log current consumption in my circuit, which houses an ATMega2560 and a number of sensors and servos. Using a DMM, I see about 100mA draw when running at full power (with servos off), and <1mA when sleeping.

An (albeit cursory) search through hall effect current sensors is giving me ICs meant to measure 10s of amps or more at hundreds of volts. The smallest I can find is this batch of Allegro sensors that go as low as 5A. I assume that means that my option is a resistor-based approach, and I'm trying to wrap my head around how that would work.

As I understand it, the idea is to pass all current through a small resistor and effectively measure the voltage drop across it to determine the I in V=IR. That's great, but doing some basic math shows that with the ATMega's 10 bit ADC, running against a 3.3V Vref, I get roughly 3.2mV / LSB. To get 100uA to be visible to the ADC, I would need my shunt to be 30 Ohms, which would of course not work.

Is this a dead end? Is it possible to measure current at that resolution with an ATMega?


texts: Synchronous 4-Bit Up/Down Counters preset

texts: I have a synchronous 4-bit up/down counter, and in the data sheet it stands that there are 4 pins where I can enter a 4 bit preset number, but it doesn't say what this number represents. I believe that it is the first number in the counting sequence (e.g. if preset is 0001, the counter will start from 0010), am I right?


texts: Circuit with two voltage dividers in parallel

texts:
I have the below circuit.

I'm solving for Vx. Vx is just Vout for another voltage divider. So, the top left R is R1 the bottom is R2. Therefore shouldn't Vx be R/3R (Vs) = 1/3 Vs?

But it's actually


texts: Is this a proper way to find the derivate of a 12-bit ADC?

texts:
I'm seeking a solution to find the derivative of an 12-bit ADC. It's for STM32 but let's say it's for likely for an arbitrary micro controller.
while(1){

  uint16_t a1 = adc(0); // Read the analog value first time

  uint32_t t1 = time(); // Get the time

  uint16_t a2 = adc(0); // Read the analog value second time

  uint32_t delta = time() - t1; // Update the time difference

  uint16_t d = (a2-a1)/(delta); // Find the derivative of adc(0)

}

Are they any better solutions rather than this solution if I'm using FreeRTOS?
What if I have noise in my measurements? What can I do to prevent that?


texts: Can the base voltage (say 5V) be lower than the collector voltage (say 12V)?

texts:
I am new to electronics so sorry if this question sounds stupid. I want to control a 2N222 transistor (the normal gain kinda way) and wanted to ask if the base voltage can be lower than the collector voltage. Will the transistor function normally?
Sorry for my poor English. I am not a native speaker.
Thanks.


texts: What is the name of this common metal tubing?

texts: I see tubing used all over the place in machines, but I do not know what it is called. The cross section looks somewhat like this drawn picture. Can someone clue me in on it?


texts:
i am looking for sensor supply circuit for a sensor. The sensor requires bipolar +-6V to -15V DC and 10 mA power consumption at 6V DC (6V*10mA=0.06mW). Also power supply of this sensor requires less than 100Vrms/root(Hz) noise level. So i can use a low noise adjustable regulator for it (for example lt1763 adj) but i want to know what is the best way for it? Is there any better or sensible idea? Also i want to add a current limiting curcuit not to exceed to 10 mA. I thought a 10 mA polyfuse can be useful for protection. But you can advice better way to me. Finally How a sensor supply circuit should be? Can anyone tell me the method of this design?
King regards,
Cem


texts:
I have come across the Salcone-Bond paper Selecting Film Bus Link Capacitors
For High Performance Inverter Applications (PDF), which shows equations for single-phase inverters. But I can't seem to find any guide or paper on how to size DC link capacitors for 3-phase PWM controlled inverters.

How can I size the DC link capacitor of a 3 phase inverter?


texts: Is there anything better that a SSR when working with audio signals?

texts:
I'm using the output of an op amp (LM308) with a low pass filter (R=4700Ohm C= .01 uF if that helps) to control a SSR (D2w203F) which is controlling a string of Christmas lights. I was wondering if there is anything better than a relay that I could use. I've heard SSR are bad when working with audio signals.

The goal is the make the string of christmas lights pulse to the bass of a song. The input is from an audio cable plug into an iPod.

PLEASE provide datasheet references to components used - RM.

ie

Datasheet D2W203F 280 VAc, 3.5A, zero crossing SSR

Datasheet: LM308 opamp


texts:
I am thinking about an automatic blind opener/closer. In this idea I need to detect the end of blind while opening or closing to stop the motor. I don't want to use mechanical sensors on both side (for simplicity sake).

Is there a way to detect reaching to the end with motor's behavior (ie: looking for more current drawing with increased load)?


texts: Using Raspberry Pi to read open collector outputs from tally connector

texts:
Please forgive my ignorance, I'm a software programmer who is new to the electrical and hardware side.

Our Panasonic HS300G video switcher has a Tally connector.
Below is the pin diagram and circuit diagram.

Pin 1-6 are for telling me which Camera input is active (Camera 1-6).

Using a Raspberry Pi 3, I need to be able to detect which pin is "active", and my software will then use that to run a software-based tally system.

I've been trying to research as much as possible myself to understand how "open collector outputs" work, but I'm still confused, and I don't want to fry anything on this video mixer by sending 3.3V to a wrong pin.

Would this design work as follows?

Attach Pin 9 to GROUND on the Raspberry Pi.
Attached Pin 1-6 to 6 individual GPIO pins set as "input" on Raspberry Pi
Send 3.3V from a Raspberry Pi GPIO to Pin 7.
Result: My GPIO "input" pins (1-6) will receive 3.3V whenever the corresponding camera input is selected. This will give the GPIO a "high" reading and my software will know that camera is active.

I would like to test this theory but I can't afford to send too high voltage and mess something up on this mixer! Please help me understand what is going on here, really appreciate it.

EDIT: How do I wire up the 3.3V into the circuit properly? What am I missing?


texts: Wave soldering of PCB with Through hole and test points. Masking test points

texts:
I want to do wave soldering for the through hole components. All through hole components are top side of PCB. Bottom side of PCB has only test points.
How do the assembly house mask the test points ? Can he do wave solder the through hole parts without masking it ?
As per our assembly house input, adding masks on test points and removing the masks after soldering is same as manual soldering effort, in terms of cost.

Can any one explain the process.
Just trying to understand the process and cost involved.


texts: OpAmp with slightly negative supply for ADC input

texts:
I would like to discuss a design idea around the supply of OpAmps that drive a ADC cannels of a microcontroller or DSP. Let the ADC be supplied by 3.3V and 0V ("analog" supplies separated from similar "digital" supplies), with an internal or external reference of 3.0V, that defines the full-scale input.

simulate this circuit – Schematic created using CircuitLab
If the OpAmp is supplied by the same 3.3V - 0V, even if it is a rail-to-rail model, there is always a "footroom" limit of at least some tents of milliVolts. Therefore, my idea is to use a "Single Supply OpAmp" where its negative supply is connected to a slightly negative voltage, in order to use its complete voltage swing compensating for its rail-to-output difference both on the positive and the negative side of the amplifier.
What do you think about?


texts: Eagle >Label attribute (in some Adafruit parts)

texts:
I'm using an SMA edge launch connector from Adafruit's part library. Alongside the usual >NAME and >VALUE text it also has >LABEL which I've not seen before. I can't see an obvious way of assigning the text and I can't remove it from the footprint like a name/value as it's baked into tplace. I've just removed it from the footprint.

The question is simply - does >LABEL mean something in Eagle?

For example (here WIFI_1 is the part value)


texts: Can I connect a smart charger to a lithium battery with a BMS

texts:
I have several tools with NiCad batteries which are failing due to the age of the batteries. I refuse to throw these perfectly good tools away and wish to convert the batteries to lithium.
I HAVE LEARNED ABOUT THE DANGERS OF HANDLING LITHIUM BATTERIES.
I have a Sky B6ACV2 charger which states that it shouldn't be connected to a BMS.
If I do not incorperate a BMS into my batteries how do I avoid an over discharge and also excessive amperage draw when in use?
I apologise for my ignorance.


texts: Adapting an older schematic for use with recent components: How might this circuit need to change?

texts:
The schematic below is a bidirectional bluetooth-to-infrared serial device.

Computer sends bits to device via bluetooth virtual COM port.
Device re-transmits bits via 950nm IR w/ 38khz carrier frequency.
Device can also receive IR signal, transmitting back to the computer via BT.

U1 is this, which creates the 38kHz freqency.
U2 is this, which receives an IR signal.
U3 is this, which regulates a 5V supply for the IR receiver.
My problem is that the SparkFun BluesmiRF module is no longer a 9V device: it now operates on 3.3V to 6V, and the TX pin outputs at the same voltage as PWR. So my questions are:

Should I connect C to D to power the BT module with the regulator U3, or just use a voltage divider? I believe U3 can handle the extra current.
In the original circuit, TX was likely 9V; it is now 5V. Does R7 or transistor A need to change to compensate?
U1's RST pin calls for 0.3V to 1V. If TX is at 5V instead of 9V, will voltage divider B still output 0.3V to 1V?
I'm fairly new to electronics. Anything else I should consider before attempting this build?


texts:
I am new to electrical engineering and the usage of microcontrollers. I am trying to build a custom circuit board using parts bought separately, but I'm not sure how this should be done.

Some things aren't clear to me. For example, I want my chip to control a LED that turns on and off at a specified interval. My questions are:

How this things should be linked? I mean the microchip has some input and output pins. The output pins should be linked to the part that controls the flow of electricity trough the LED. But what output pin, cause there are more than one.
If I have a USB connection connected to an input pin(or more, I'm not sure). How should I load the program in the microchip's memory? Is a boot loader needed? Do I need a special program to write the code in. I assume that I can load the code and if I want to use another code I just load the new one and overwrite the memory.
If I want to turn on 3 LEDs at different moments, how should the wires be linked? I guess that I can specify in the code what pin to output to but what if I want to control a lot of LEDs ?

I don't know if my questions are wrong. I'm in high school and I try to learn on myself but google can't find me everything I need.


texts: Is this figure a correct (O)QPSK waveform?

texts:
I am currently reading Pasupathy, Subbarayan. "Minimum shift keying: A spectrally efficient modulation." IEEE Communications Magazine 17.4 (1979): 14-22.

The paper explains MSK as a form of OQPSK with a half sinusoid instead of rectangular weighting with a figure below:

But in my opinion, this figures seems incorrect. Because  figure 5(a) shows a bit stream +1, -1, -1 and +1 inside a waveform, but the actual waveform is drawn as if its corresponding bit stream is +1, +1, -1, -1.

Am I missing something?

Edit

Maybe I learned that the original problem is solved by taking a phase into account.

Another problem is, a waveform in the IEEE 802.15.4 standard differs from the original one.

It seems that a direction (upward/downward) of a waveform indicates a bit.

Are both acceptable? Is 802.15.4's O-QPSK a variant of the original one?


texts: Interpreting Zero sequence impedance of YNyn0 Transformer

texts:
I have a transformer test report in which the zero sequence impedance has measured according to IEEE standard.
YNyn0 Transformer has rating of 132/11kV, 45MVA, 28% impedance with no delta winding.
In the test report there is no single value for zero sequence impedance but have three derived impedance values. They have measured Z1no, Z1ns and Z2no.
That is impedance measured from primary side while secondary open and short, and impedance measured from secondary side while primary opened. Eventually calculated Z1, Z2, and Z3.
These are the steps of deriving.

I assume this Z3 is phantom/ tank delta impedance. My question is what should I used as zero sequence impedance? is it Z3 or any combination of Z1,Z2 & Z3?

Again in DIgSILENT, this winding configuration requires following data.
Zero sequence impedance and zero sequence magnetizing impedance.
Are those values respectively Z3 and Z1+Z2?

quite similar question!
What is the zero-sequence equivalent of a YNy0 transformer?


texts: How to put a delay timer on a micro motor small Area

texts: I am trying to put a micro motor  basically as small as I can inside of a 1"or so wide tube like a long fishing plug, I am going to put a small prop or propeller on one end. What I need is to be able to have that motor to run that prop maybe run on a 3v battery, I need the motor to run on a delay to kick on run the prop for 1 or 2 seconds shut off then in about 3 seconds kick on and continue do the same thing,  any suggestions on what I would have to do to make a motor do that cheaply Don


texts: Triac misfires because of noise from inductive loads

texts:
The product is a wifi enabled smart switching device. One device has 4 different channel for four different appliances to be connected to the product. Each channel has a pair of optocoupler and triac for switching and dimming. The gate of the triacs are controlled by a microcontroller through a optocoupler.

The issue is misfiring of triacs. The circuit has a common line(220v) for all four triacs and whenever there is noise on any of the triacs, some of the other misfire for a fraction of second. As an example, if I connect a fan to one of the triacs, the fan being an inductive load, passes noise on the common line. Sometimes, one of the other triacs connected to LED lights misfire and a flash of light is seen on the LED lights. My assumption is that this is due to the power supply picking up even the smallest wave and converting it dc for the LED. This also happens if the fan, for example, also has a regulator in series. When the speed of the fan is changed on the regulator, for the brief split second for which the regulator knob is floating between steps, there are flashes of light on the LEDs. Sometimes these noises are so severe that the triacs are damaged.

How to remove this noise from the circuit?


texts: How to split mono signal to sterio siginal of AD9833 Sin wave generator?

texts:
I am sorry that I am not well aware in audio amplifiers, that's why I am asking this question maybe it's my stupidity. I have an AD9833 sin wave generator, I need to connect the AD9833's output to TPA6100 Low power stereo headphone amplifier.I am confused about how I use the mono signal coming from AD9833 to the TPA6100 because it is a stereo amplifier. If anyone can help me.

Appreciate your help, thanks!


texts:
I am in the 6th week in Navy school and we are on voltage regulators or circuits that have components that maintain a constant voltage output. I need an explanation on how to work out this problem here:

Find \$V_o\$ and the zener current where \$R_L = 1 k\Omega\$:

The answer is 11.3 v for the output voltage and 36 mA for the zener current. This is my attempt:

\$I_e = I_b + I_c = (1 + \beta)I_c\$ and \$V_o = I_e \times R_L\$

I wanted to say that the base voltage is 12 volts but that doesn't seem to work out with this problem.


texts: What is this three pin, cyclindrical component?

texts:
I'm curious as to what the component is on this PCB. It is surrounded by a polyfuse / zener arrangement (for overvolt / fusing) - I believe it is something to do with the AC input but am not completely sure. It appears to be polarized.

What is it and what might it be used for?


texts:
I have edited the question to make it easier to explain what I am asking for.To make it clear, I have deleted the part with the 555 timer.
I have a question regarding the following:

simulate this circuit – Schematic created using CircuitLab

I know that once the battery is connected, the capacitor is going to have a varying voltage across it until it will be fully charged, reaching 7 volts. During this time, what will happen to the other two branches (the ones with the two resistors) ? According to the law of parallel connections, the voltage measured across any component will be the same, equal with the one of the battery. As the cap. charges, will the other branches have a varying voltage across them too, or will they have a potential difference of 7 volts from the beginning across them, as the capacitor?


texts: Actel ProASIC3 FPGA all IO pins are getting active high after programming

texts:
I am kind new to Microsemi FPGA environment. I am using ProASIC3 FPGA with Libero SoC 11.9 tool. I am simply assigning inputs to outputs but the real trouble is having 3.3 volts on input channels by default.

input i1;
input i2;

output reg o1 = 0;
output reg o2 = 0;

always @ (*) begin
//<statements>
    o1 <= i1;
    o2 <= i2;

I have assigned pins using I/O attributes editor. Here what I am expecting is 0 volts by default on i1 by default and changing it to 3.3 volts by external circuit when needed. Is this common to have all IOs at 3.3volts (including unused)? Or am I missing something in Libero SoC tool?

Thanks.


texts:
How may I determine an amplifier's class given its schematic?

Based on the schematic I think it would be class F, but I am not sure.

Z elements are microstrips.


texts: Does higher dBi mean further range, for an antenna?

texts:
I recently purchased this (ridiculously expensive) Bluetooth module for my Arduino from SparkFun.  On the item's page it says that it has been tested at 100 m.  I contacted SparkFun for info about their setup and they said to achieve the 100 m range they used this 2.2 dBi antenna.

I presume any (2.4GHz) 2.2 dBi antenna will yield similar, 100m, results: is that correct?

However, I have this 7 dBi antenna on it's way.  If I use that will I be able to get further range than from the 2.2 dBi antenna?


texts:
The PIC is supplied at 3.3V and clocked at 16kHz. For this part of the design I need the external interrupt to trigger on the falling edge of a 100Hz square wave signal on RB0 and toggle the state of RD7.

In the figure below we can see that the interrupt works as intended when I'm testing it with an SPST switch. The following image is the schematic when using the SPST switch (ignore the LM324 and attached components)

For Trace 1:

Channel B (Blue) - SPST Input

For both traces:

Channel C (pink) - RD7 Voltage Level

However in  when I attach the square wave (shown in the figure below), it seems to be triggered on the rising edge of the square wave.
For Trace 2:

Channel B (Blue) - 100Hz Signal

At first I thought that for some reason the NE555 was loading the input of RB0 so I added a buffer but that didn't help. I also tried pulling up RB0 but that failed as well. I dug around in the manual and found this:

  For external interrupt events, such as the INT pin or PORTB change interrupt, the latency will be three or four instruction cycles.

So it might be that the interrupt is being triggered too quickly? Even at 16kHz however 4 instruction cycles will be 0.001s and the signal period is 0.01s. Does anyone know what might be causing this and how to fix it?

Software used: Proteus Professional 8

EDIT: Code and image Added

                        LIST    p=16f877
                    INCLUDE <P16F877.INC>

W_TEMP              EQU     0x20
STATUS_TEMP         EQU     0x21
time_hi             EQU     0x22
time_lo             EQU     0x23
time_cp             EQU     0x24
timerCount          EQU     0x25

                    ORG     0x00
                    goto    main
                    ORG     0x04
                    goto    ISR
                    ORG     0x20

main
                    BANKSEL TRISD
                    bcf     TRISD,RD7
                    call    interruptSetup

loop
                    goto    loop

;--------------------------------Configure Interrupts-------------------------------

interruptSetup
                    call    rb0FallingEdgeInt

                    call    enableInterrupts

                    return

rb0FallingEdgeInt
                    bsf     STATUS,RP0
                    bcf     STATUS,RP1

                    bsf     TRISB,RB0
                    bcf     OPTION_REG,INTEDG
                    bsf     INTCON,INTE

                    return

enableInterrupts

                    bsf     INTCON,PEIE
                    bsf     INTCON,GIE

                    return

;------------------------------ISR---------------------------------
ISR
                    movwf   W_TEMP      ; SAVE  W AND STATUS REGISTERS
                    swapf   STATUS,W
                    movwf   STATUS_TEMP
                    bcf     INTCON,GIE

                    btfsc   INTCON,INTF
                    call    fallEdgeIntHandler

                    bsf     INTCON,GIE
                    swapf   STATUS_TEMP,W   ; RESTORE W AND STATUS REGISTERS
                    movwf   STATUS
                    swapf   W_TEMP,F
                    swapf   W_TEMP,W

                    retfie

;---------------------------ISR HANDLERS------------------------------
fallEdgeIntHandler
                    BANKSEL PORTD
                    movlw   B'10000000'
                    xorwf   PORTD,W
                    movwf   PORTD
                    bcf     INTCON,INTF
                    return

                    END


texts: Are there any micro-controllers which support writing data to large sized SATA disks?


texts: How to find RS485 UART pins are inverted in the data sheet?

texts:
I want to know, how we identify the RS485 pins are inverted. I am using at91 microcontroller?

This sam9260 board has four rs485 in which two of them are inverted. How to know which ports are inverted, I didn't find such information in the datasheet also?

This is the simple code:

rs485ctrl.inverted = 1;
rs485ctrl.pin = -1;

EDIT: other serial device configuration:

rs485ctrl.inverted = 1;
rs485ctrl.pin = 0x40 + 2;

I didn't understand where this 0x40 +2 magic number came from? I interpreted if the pin is inverted it set as -1, perhaps what I understood is wrong?

I used the multimeter to verify the positive wire is greater than negative wire during idle but don't know if there any other way to find the polarity of RS485?

Don't know, is this the right forum to ask such a question.


texts: How to identify when a pulsed rf supply is active

texts:
I have a signal that consists of a 13MHz RF signal inside a pulse envelope (around 100ms on, 300ms off). I want to convert this to a 0-5V pulse that will just tell me when the primary RF signal is active ( i.e. ignoring the RF component, just taking the pulse).

I was thinking of using a bridge rectifier and then and averaging this with an earth (using an op-amp, I guess?) and then subsequently using a relay to turn this signal into a 0-5V signal. Does that sound feasible? Am I missing an easier way?

Many thanks for your help.


texts:
My question is in reference to the circuit above. (An EE non-graded assignment.)

What is the purpose of R1 in this circuit? My feeling is it's providing bias and/or feedback to act as a current limit to the transistors (MJ2955) but I'm struggling to say exactly how or why.

Any better insight would be greatly appreciated.


texts: Transfer data from computer through USB to digital potentiometer and back

texts:
I have a robotic device manually controlled by several digital potentiometers. I am also manually taking readings from my potentiometers. Now I want to control my device from computer through USB port. What is the best way to transfer digital data from digital potentiometer(s) to computer using USB and back? Where do I start?
Thank you,
Andrew

PS
I am very new in electronics. Please give me an answer “for dummies.”
Andrew


texts:
I actually need to communication between my pc and a device using serial protocol through USB.

I'm looking for some guidances and best practices and messaging architecture.

Do you know any reference books or authors on the topic ?


texts:
I have a question about the need of the use of the X2 capacitor. I have a simple design which can be connected to AC line and I not use an X2 class capacitor but I m using an SMD capacitor from Murata (GA255DR7E2104MW01L) (size much more compact than THT X2 capacitor). However somedays, I discover that the SMD capacitor C1 is damaged (cc) which cause the damage of the two resistors (R1 and R2). For this circuit I use also a unidirectionnal TVS diode which is the P4SMA400A, to avoid overvoltage. So is there any need to use an X2 capacitor for my case? Otherwise what can be the real cause of the failure of this capacitor. I thank you for your help.

Best regards


texts: CE# pin pulsed low by ARM when configured

texts:
I have an STM32F2 that has a "Flexible Static Memory Controller" (FSMC). For some reason, when I configure the Chip Enable (CE#) pin of my PSRAM as a FSMC pin, the STM32 will pull the pin low (by default the pin is pulled high with an external pull-up).

The reason I ask is because this CE# pulse maybe explain why the very first read/write operation fails on my PSRAM.

Why is there such a pulse? Does STM have detailed documentation for it's Flexible Static Memory Controller explaining this behaviour?


texts:
I see that there're vibration sensors and that piezo can detect vibrations. Which is better (more sensitive) for detecting knocks over a piece of wood? I'm looking for a small package, so I'm only looking at small piezo. I've tried tap-enabled accelerometers, but they don't seem to be very sensitive. Should piezo or vibration sensors have higher sensitivity than accelerometers?

Thanks


texts: KiCAD - plethora of errors when performing ERC

texts:
I finally finished my first schematic and everything looked great.
I went ahead to perform Electrical Rules Check.
There were many errors.
Most of them were:

Pin connected to other pins, but not driven by any pin.

Pin not connected (use a "No-connection" flag to suppress this error).

I used bi-directional pins exclusively.
Also note that I used the Arduino shield template. Maybe I had to declare all pins not used as NC?
If you want, I can upload the schematic file somewhere.
EDIT: Here is a picture of the schematic.


texts: Can generator of a thermal power plant be used by binary cycle geo thermal power plant?

texts:
The thermal power plant will be operating on a Rankin cycle and the binary cycle geothermal power plant on an organic Rankin cycle.
I was just curious that in case the thermal power plant shuts down will its generator be used by the geothermal power plant.
Please do mention if any other parts of thermal power plant could be used in the making of a geothermal power plant.


texts:
The picture below shows a pin on a voltage regulator that must be connected to the ground, so I am wondering why not connected this pin directly to ground without using the circuit shown in the picture. However, there is no recommendation in the datasheet of the regulator for connecting this pin.

Edit 1: The following is the complete schematic. It is from AWR1642BOOST datasheet.


texts: Questions regarding eliminating hysteresis in ac dimmer

texts:
In the following circuit it says:

“This hysteresis effect can be eliminated however, using the circuit from a detailed application note from Littelfuse shown in Fig. 6.4.4. Here the capacitor C1 is fully discharged every time VS passes through zero. If the charge on the top plate of C1 is positive and point X is at zero volts, C1 will discharge to 0V via D3 and R4. If the charge on C1 is negative when X = 0V, C1 will be discharged via D1 and R3. When point X is either positive or negative C1 cannot be charged via D1 or D3 as the voltages at the bottom of R3 and R4 will be held within about +/-0.6V of zero due to the forward conducting voltage of either D2 (during the positive half cycle) or D4 (during the negative half cycle). C1 is therefore always charged via R1 and R2.”

My questions:

Where does C1 discharge to via D3/R4 and D1/R3? Does it discharge into the load?
Why can’t the capacitor be charged through D1/D3 when X is either positive or negative if to me it looks like they’re connected similar to a bridge rectifier to the cap? Does the voltage just go back to Vs?
Do the diodes convert ac to dc at the capacitor?

I’m sure I’m missing something simple here


texts: Wide Input Voltage Range Constant Current Source

texts: I would like to design a Constant Current Source of 25mA, With Input varying from 2V to 50V. Please provide just an idea how to get about this.


texts: What power supply do I need for my LED light strips?

texts:
My set up is this: Power supply > RGB LED WiFi controller > 1 to 3 cable splitter > 2M cable (x3) > 132.5cm 120leds/m 5050 RGB strip (x3)

I contacted the eBay seller about what power supply I would need to power the 5M cable they provided. They told me 12V 5A. After a little research it seems that this is wrong.

I read that 5050 LEDs draw 60mA per segment (3 LEDs per segment). There are 200 segments in this 5M strip, so 60mA x 200 = 12,000mA. Which would mean I would actually need a 12V 12A power supply. Unless the current draw from 5050 LEDs differ from different manufacturers?

I won't need this much current since I'm cutting off 3 individual 132.5cm strips from mine. Each strip has 159 LEDs, which equates to 53 segments (159 / 3). 60mA x 53 gives a current of 3180mA for one strip. The total current of all three is 9,540mA (3180mA x 3). So I guess this means I need a 12V 10A adapter? This is expensive though, so I am wandering, if I'm not powering them to white all the time, I could manage with less current?

I've already tested a 12V 5A adapter on the strips and it seems to work fine. It doesn't get hot or anything. I even tried a smaller section of strip to see if it was any brighter and it's seems to be the same brightness. Surely it should be brighter than using a longer strip??


texts:
Could someone explain how HLS treats arrays that are declared constants? I declare an array as:

const uint8 myArray [100][100] = {....};

and then access the array by element in the loop. According to the UG902 on p.328, such array is implemented as a ROM and consequently I need to partition it to get more reads in the clock cycle. Why would HLS implement this array as a ROM and use resources instead of converting it to ties of VCCs and GNDs? Do I need to explicitly tell HLS to implement it as ties to VCC and GND?


texts: What is this connector called and how do I open it?

texts: And how do I open it to put in a wire? And can I use stranded wire or should i crimp (it's so small ferrule connectors dont fit)


texts: Power Supply Design 240VAC to 12VDC, what value smoothing capacitor do I need?

texts:
I am designing a power supply for a docking station, however I'm struggling to determine what value capacitor I will need? The transformer I am going to use is:http://uk.farnell.com/carel/tra12un100/transformer-240vac-in-12vac-out/dp/645400

I need a voltage regulator of 12V also and a current of 5A to power 2 separate circuits?

If you need some more information please don't hesitate to ask :)


texts:
I've got a project I want to work on, which involves an LCD, MAX232, and MSP430.  The LCD requires 5V for logic and 3V for the backlight.  The MAX232 will work from 3VDC to 5.5VDC.  The MSP430G2231 will handle 1.8VDC to 3.6VDC.

The main power source is going to be the 12V accessory power circuit in a car.  It seems logical to regulate the ~12VDC to 5VDC, and then use the regulated 5V to create the 3.3V needed for the MSP430.  I was thinking about trying 3.3V on the backlight -- the specs state 3V typical, but don't specify a min or max value.  I plan to see if I can just measure Vf of the backlight and add a current-limiting resistor to the circuit so I can safely use the 3.3V.

Anyhow, since I need two voltage regulators, does anyone have any recommendations for an ideal configuration?  It looks like the LCD uses a max of 1.5mA @ 5V, and the backlight takes a max of 45mA.  The MAX232 clone uses a max of 1mA @ 3.3V with no load (I have no idea what it would be under load), and the MSP430 looks like it uses about 4.2mA @ 3.3V and 16MHz.  I think these are worst-case conditions.

Would you use a switching regulator to go from 12V to 5V, and then a linear regulator to go from 5V to 3.3V?  Or one of the really low-count options as in the 3V Tips 'n Tricks from Microchip like a single zener or multiple diodes?  I picked up some MC34063s to play with, but am open to anything else with a lower / smaller part count.

LCD specs I used:

MSP430 specs:

MAX232 specs:

I would sure appreciate any comments, like recommended approaches, or if I have flaws in my interpretation of the specs.


texts:
A car starter circuit pulls around 500A to start a car.
Does this mean the resistance of this circuit is around 12 / 500 = 0.024 ohms? (Assuming the battery is ideal)


texts: A Single Antenna for Multiple Sub-GHz Receivers

texts:
I am thinking about making an inexpensive LoRa geteway by combining eight single-channel RFM95W 915 MHz transceivers. These would just work as receivers, and I would have a 9th one working separately as a transmitter. The point is that these modules are available cheaply.

I am wondering if it's possible to connect all eight to a single antenna. The ninth (transmitter) would be on a separate antenna, so there would be two antennas. This question is similar but is concerned about MIMO, which is not the case for me. I have also seen this question, where a power divider is suggested.

However, I am not sure that a power divider is appropriate. I have not seen an eight-channel one in IC form. The first question I referenced mentioned doing a microstrip Wilkinson power divider, but I am not sure if this is feasible for 8 receivers.

Is what I am thinking about doing reasonable/feasible?

I also thought about just laying out nine PCB antennas or using 9 chip antennas. Would placing these side-by-side on the PCB be reasonable?


texts: What is wrong with my KVL approach on a really simple circuit?

texts:
Hello, so this is a really simple circuit question that has been bothering me. I know that by simply looking at the circuit and using logic it makes sense that the voltage drop across the resistor(as pointed in the picture) should be 0.6V. But when I actually write the Kirchoff Voltage Law(KVL) around the loop as shown in the picture, I somehow get -1.8V. I am probably messing up my convention. Would someone please explain how I would get the same 0.6V using KVL as well?

Edit: found the answer from my class notes for your refernce. Is the solution assuming opposite convention for how the current flows in the circuit so as opposed to positive to minus terminal is it assuming minus to positive?


texts:
I've created the circuit shown. I'm using a 9V battery (actually throwing out 9.53V) and 5V coming from an Arduino to test with both 9 and 5 volts. The transistor is a BC 548B (datasheet I'm using is here).

simulate this circuit – Schematic created using CircuitLab

I've conducted a number tests changing the values of Rb and Rc with the following results, no idea if they're actually right though.

9V
Ref  Rb     Rc     Ib (μA)   Ic (mA)   Beta
1    160k   560    50        15.6      312
2    470k   1.2k   18        6.15      342
3    220k   1.2k   41        7.5       183
4    180k   1.2k   51        7.5       147

5V
Ref  Rb     Rc     Ib (μA)   Ic (mA)   Beta
1    160k   560    24        7.7       321
2    82k    330    52        14.1      271
3    470k   1.2k   9         2.89      321

My questions are as follows;

I understand that from the datasheet, the range for this transistor can range from 200 to 450. I think that the reason that there are values less than 200 in 9V table ref 3 and 4 is because the collector emitter circuit has saturated, and can't rise any higher, causing the beta to drop as the Ib current increases. Is that correct?
In all the textbooks I've looked at, the beta is a static value. "If the beta is X, work out the resister in the base needed to create a current of Y in the collector". I've since read that the beta will fluctuate with temperature and collector current (I think it's collector current). Where do I actually find this data? Where is the table the tells me the beta vs Ic? If the beta is constantly varying, how do you actually select a resister that will always work, and/or have too much current in the what would be load on the collector?
Figure 1 from the datasheet, shows that with a 50μA current in the base, the collector current shouldn't exceed about 11mA REGARDLESS of the voltage between the collector and the emitter. But given 9V ref 1 and 5V ref 2, which both have Ib ~ 50μA I have a higher Ic than stated. Why is this? What is Figure 1 actually telling me?
Figure 3 from the datasheet shows that the hFE is 200 for Ic < 40mA given Vce = 5V. That is obviously not happening given all the results in the 5V table in this post. So again, what is this graph?
I tried to connect the circuit up so that I would have my 9V battery running from the collector to the emitter, and my 5V Arduino powering the base, essentially what a transistor switch is for. I think that's going to short out the Arduino. How do I have the 9V battery running from C to E and 5V on the end of the base? How do I actually wire this?


texts:
I have a signal that varies between 3 volts and 4 volts. Now I want to amplify that 1 volt difference to a range from 0 volt to 5 volts.

I tried to find a solution with an opamp or a transistor, but hopeless. What can do the trick in place of the question mark?

simulate this circuit – Schematic created using CircuitLab


texts: Series RLC Max Voltage calculation Problem

texts:
I am confused on how to calculate frequency for VLmax and VCmax.

Is there a better way to find other than d(VC)/df = 0 and d(VL)/df = 0 ?


texts: Which reasons are behind analog synthesizers creating less "perfect" or "defined" waveforms, when compared to their digital counterparts?

texts:
While doing some tests for this music stack exchange question regarding differences in the waveforms of different synthesizers, I noticed that a digital synthesizer sawtooth waveform tends to look something like this:

While an analog (or virtual analog) synthesizer waveform tends to look more like this:

What's the difference between analog and digital oscillators that is inducing this distinction? Why are analog synthesizers implementations of sawtooth (and maybe other waveforms) not so "well defined", when compared to digitally generated sawtooth waveforms?


texts: Higher Voltage = Improved Signal Strength

texts:
I'm using a reed switch to detect the state of my garage door. It's connected to an ESP8266 via twisted cables of 1.5m and each line has a pull-up as the signal floats too much otherwise.

Well it still floats and I've been wondering whether it would've been wiser to use the 5V for the pull-up instead of the 3.3V I used. The ESP is 5V-tolerant so that should be no problem.

As far as I know, the higher the voltage the stronger the signal, but I may be spoiled by landlines with high voltage. :-)

Thanks for clarifying.


texts: PWM phase voltage and current measurement for power consumption calculation for a BLDC MOTOR

texts: I have been trying to log both voltage and current from the battery of an electric two wheeler for finding out efficiency at inverter, battery level.


texts:
I'm using a msp430g2553 and setting the clock to 1Mhz:

BCSCTL1 = CALBC1_1MHZ;
DCOCTL = CALDCO_1MHZ;

I've timed a 5 million cycles and it unexpectedly takes around 6 seconds (I was expecting 5).
The loop I've used is:

int i;
for(i=0;i<5000;i++)
    __delay_cycles(1000);

I've read about using interrupts (probably based on Timer_A, etc) but I'd like to avoid that for now.

So my question is: how can I implement a constant argument sleep based on __delay_cycles?

Later edit

Assembly for:

void delay1000() {
        __delay_cycles(1000);
}

is:

delay1000:
    0c3b4: 04 12                     PUSH    R4
    0c3b6: 04 41                     MOV     SP,      R4
    0c3b8: 24 53                     INCD    R4
    0c3ba: 3f 40 4c 01               MOV     #0x014c, R15    // 332 decimal (1000/3 -> DEC, TST and JNZ)
    0c3be: 1f 83                     DEC     R15
    0c3c0: 0f 93                     TST     R15
    0c3c2: fd 23                     JNZ     delay1000+0xa
    0c3c4: 03 43                     NOP
    0c3c6: 03 43                     NOP
    0c3c8: 34 41                     POP     R4
    0c3ca: 30 41                     RET


texts:
Looking at the data sheet of the MAX4410 headphone driver, lower impedance headphones will get more power.

Is this true in general for laptop headphone drivers? especially with regards to 8-32 ohm impedance ?


texts: Can I use a Quarz Oszilator instead of a Standard quartz?

texts: I want to complete this tutorial on burning a bootloader onto a atmega328. There a Standard quartz is used, but called a Quarz oszilator. Now I bought this Oszilator. Can I use the oszilator as well and how can I connect it?


texts:
I am very new to electronics as a whole and this is my first somewhat advanced circuit using transistors. (Also I am new to this community, so if I messed up somewhere in this post feel free to ask me to clarify). Here is my sketch:

This is supposed to control a motor for an airsoft gun. The gun always needs to stay on a whole cycle. The end of the cycle is indicated by a short 5V signal that runs into a NOT gate. This is supposed to cut off the "feedback loop" from the 12V rail to the main transistor in order to stop the firing (if the signal below is still high, another cycle will be initiated.) The 5V is provided by a power supply connected to the 12V batteries.
Here are the issues I experience whentrying to build this circuit on a breadboard (with buttons as inputs for the signals):

The motor gets basically no current and the voltage at the motor is not the expected 12V but 1.2V. I thought that could be because the motor might split the voltage with the voltage going in the back of Q1, but that does not make sense at all since Q2 is not even on.
The NOT gate works, but the output cannot turn on the feedback line (into the base of Q1).
Q2 is off all the time.

I really don't know if I messed up with the components I selected or the basic laws of physics (or both.)
Help would really be appreciated.
Of course if you could explain your solution it would be great, but right now I just want it to work.


texts: In my house there is a wall outlet with 2 coaxial cables coming out. Why 2? I saw there some sort of service that needs double bandwidth?


texts: Understanding and Changing Transistor Oscillator Circuit

texts:
I am using a EAST EFM-290ED Buzzer Alarm. It needs to be oscillated to work.

I found a simple one transistor setup that makes it work, but I am not sure if it is working well for this buzzer.

Update: I found that this type of oscillator is called a Hartley oscillator?

simulate this circuit – Schematic created using CircuitLab

When the pot is below 25Ω, the buzzer is off and 3mA. When its ~30Ω the buzzer is on, and I get about 3.1mA. The buzzer and current peaks around 500Ω, 3.45mA. And at the high end, 1k, I get 2.9mA and a softer buzzer than the 500Ω point.

But its not nearly enough compared to what it should be (4.5v (3xAA) but pretty ear piercingly loud at close quarters, it was used in a Carbon Monoxide alarm).

Seems the buzzer needs a 3.4khz oscillation. I am not sure if the FB pin provides that oscillation, or if the transistor can keep up.

Does anyone have a little insight into this? Should I change the pullup r2 or the base resistor r4? Is a 2n3904 suited for this? (The original diagram suggested 20k for R4, I tried 10k and 33k. I also tried 33k for R2).

Secondly if I wanted to control this through a microcontroller, could I use a second npn transistor, where the Ammeter is?

Update: This Murata procedure note (Page 5 Self Drive Method) for the same type of piezo with feedback shows:

While stating:

Phase difference between νo and νf shown in Fig. 9
must be 180 degrees.
The following conditions must be satisfied: νf / νo >= (R2+hie)/(hfe · R3)
where hie: Input impedance of transistor and hfe: Current amplification
Set R1 so that the D.C. bias point of transistor, VCE is half of supply voltage.
Adjust R2 so that spurious oscillation is not applied to oscillating waves.

Hie for the 2n3904 is 1k min to 10k max. hfe at Ic 1mA is 100 to 300. I am not sure if my existing values meet these conditions, (unsure of how to calculate R1 so VCE is half of V, or how to figure Vo and Vf)


texts: Design an interfacing circuit/address decoding circuit to interface one 4KB EPROM and two 2KB R/W memory for 8085 microprocessor?

texts:
I don't know if this question is a good question to get answers or not but I am trying to honestly explain my situation.

I am studying 8085 microprocessor, so I am stumbled upon address decoding circuits. As I was looking over past year questions, I saw many questions like the one I asked above are being asked in exams.

Then, I started to read books and pdfs all over the internet and knew the uses of address decoding, and other basic concepts such as memory mapped i/0...etc

Now, my confusions are

1) How to find the ending address for these 2 devices?
 2) How to design a proper circuit for it?

This may be too broad, but I believe that many students are facing similar problems.
Though this is not the place for homework solving but due to lack of good materials around the web, I am here and I am optimistic to get a complete solution.


texts: Designing circuits with a longer lifetime

texts:
I have learned about the pic microcontroler for a period of time and have a reasonable amount of knowledge about handling digital electronics. I have worked on basic electronic projects and now I need to work on some commercial applications.

My question is about how to design and build reliable and long lasting circuits. I built a automatic light controller circuit which takes the input from a LDR and displays the value of the analogue reading on a seven segment panel. Then it does some calculations and controls a light through a relay. This circuit needs to be switched on permanently(24 hours a day). The first few months the circuit worked perfectly ,but after about 6 months it started malfunctioning. It showed senseless things on the 7 segment display(it showed just parts of numbers), then it lights the bulb on the indicator LED but it's not switching on the relay.This is not the expected behaviour. The thing is it won't always work that way. Sometimes it works perfectly. Then it starts again to malfunction. There is no exact order in which it works.

Now my question is why do these circuits behave this way. I assume this may be because it works all day without any intervals.This kind of application needs to work all the day. I use PIC because I know about pic only. Is atmal more reliable than pic? (I asked because atmal is used in most of automation applications,more frequently than the pic is used)
   I need some advice from an expert in digital electronics. How is this kind of industrial applications built? Are there any special rules to follow?  How to design more reliable circuits?
   Any advice or guidance from an expert will be highly appreciated.
Thank you...

EDIT

As it's suggested in the answers,I'll edit my answer by providing additional resources to help figure out the bugs in the design.

Below is an image describing how the circuit looks like after it was built. It's a 12V center tapped transformer which supplies power to the circuit.It's rectified using a half wave rectifier, then regulated using a 7805 IC.

Below is the schematic design.

If any additional information is needed I will provide everything needed. If the program is needed I'll add it. The program is somewhat long.It uses interrupts.


texts: How do smaller capacitors filter out higher frequencies than larger values?

texts:
I commonly see 0.1 µF used on IC pins for decoupling. I occasionally see 0.01 µF and 0.001 µF capacitors used for filtering out higher frequencies. Is that incorrect, because I thought the impedance would increase at a fixed frequency if my capacitance decreased?
Meaning the higher frequencies would go into the IC or device you are filtering.


texts:
Most sources on the internet discuss routing signals over a split power plane and how to do this properly. The main solution here is to create a short return current path.
I'm wondering whether routing signals over a split power supply plane (not ground plane) will have any noticeable effect on the signal integrity and if i should take measures.

My situation:

4-layer PCB:

Top layer: signal
Internal plane:
splitted ground (analog/digital)
Internal Plane: splitted power supply
plane (3.3V digital and 3.3V analog
are relevant in this case)
Bottom layer: signal

I'm routing a few clock signals at the bottom layer starting from the digital section to the analog section. The signals will cross the power plane split between the digital and analog section (gap is 0.5mm wide). I will provide a solid current return path on the ground plane (bridge between digital and analog) so return currents shouldn't be an issue.

The clock signal is just above 12MHz, the traces are 0.2mm wide and a maximum length of 13.4cm. The traces are terminated with a series resistor.


texts: Determine voltage of old brushed DC motor

texts:
I have salvaged a DC motor from an old (10-15 years) food processor and would like to use it for a project. However, in the process of taking it apart the controller board was broken so I can't measure the output to find out what voltage it needs. Are there any ways I can determine what voltage was used to drive it in the first place?

These are the things I know:

It is definitely a brushed DC motor.
The circuitry of the food processor is - Input from the mains (240V AC) goes through what I believe is an isolating transformer board (240V AC -> 240V AC, measured with a multimeter) which then goes immediately into a rectifier on the main board, followed by some components whose purpose I don't know, then to the motor.
The resistance of the motor (across the motor terminals) is about 15 Ohms.
The food processor is rated for 500W.
When driven at 5V from a PSU, it turns quite slowly and can easily be stopped. Same for 12V. 24V drives it faster but it still doesn't have enough torque, and I can't get any higher voltages from the PSU.
The motor is 7cm in diameter and weighs about 1kg.
The motor has no identifying markings.

From the second point, it would seem that because the transformer doesn't step down the voltage and 240V AC gets rectified into 240V DC, the max voltage of the motor is 240V DC but this seems much too high. The other circuitry probably used PWN to reduce the effective voltage but still... Does this assumption seem correct?

The project I want to use it in is a tabletop disc sander. For this purpose I guess the motor doesn't need to run at full speed but maybe ~60V? I'm interested in building my own DC motor controller circuit to just supply a constant voltage, nothing too fancy. Does this seem achievable? Could anyone point me in the right direction? What do I need in the circuit other than a transformer, rectifier & flyback diode?

I have some experience with digital electronics but this is my first time using high voltage.

Thanks


texts: Which end is host in a USB-C to USB-C charging/power cable?

texts:
I have two different kinds of DIY USB-C connectors...one kind that is rigged to be a "host" USB-C connector (pulled-up with a 56k resistor per spec), and the other is rigged to be a "device" USB-C connector (pulled-down with a 51k resistor per spec).

My question is: when assembling a charging cable that is used to charge a device (e.g. phone) via a wall outlet puck...which end should be "host"? The phone end, or the power outlet end? Just want to make sure I understand this. Thank you so much in advance!


texts: Best way to turn off switching regulator and conserve power

texts:
I am trying to figure out one of two ways to switch off the power in my circuit using an LM2596-5.0 switching regulator.

Option 1: In the datasheet it says you can pull the regulator ON/OFF pin to VCC to turn it off, with a loss of 80uA.

I'm using an SPDT switch, so if I choose the above option, the regular's input capacitor will remain charged, and won't the battery drain?

Option 2 is a more traditional way, leave the regulator ON/OFF pin tied to ground (datasheet says this will turn the regulator on), and the SPDT switches all of the power to the circuit, which charges the capacitor up and I'm sure eventually this might wear out the switch's contacts, despite it being rated for 5 Amps. The circuit consumes less than 50mA average, but I'm assuming that capacitor wants to charge quickly, hence my concern.

In either Option 1 or 2, I'm avoiding a parasitic loss on a voltage divider as shown in my schematic. Option 2 would avoid the 80uA loss if I use the regulator's shutdown feature, but in my application I don't need to worry about 80uA loss.

I see in the datasheet for the LM2596 that if I choose my Option 1 it would truly be a 'soft' start, which would extend the switch life? (not really an issue I'm thinking, due to the switch's rating, but I may be wrong?)

Can someone help me decide what would work best? Thank you.

BVCC is battery voltage which is connected to the common/center pin of the SPDT switch, the top pin of the switch is connected to the common/center pin when the switch actuator points downwards.

1st schematic showing Option 1:

1nd schematic showing Option 2:


texts: i plan on doing a SC test on a power supply that the output is switched on with a p-mosfet i was just wondering if there is defined recovery time for the pmos to cool down before you can do another short circuit test.


texts: 24-30pin connector for digital picture frame

texts:
Hey all I have 3 27" lcd panels that I will be making digital picture frames out of and I am looking for advice on what i can use in order to use only 1 cable going to the digital picture frame since it will be on the wall. The less wires the better.

Currently I will be purchasing the lcd controller boards for these lcd panels. These boards requires a 12vdc @ 4a to power it.

There is also the lvds cable that connects to the back of the panel itself. This usually has 5/3.3vdc going to it.

So does anyone have any possible suggestions for a type of cable that has enough pins for the lvds and power? I was thinking of using a HDMI-I cable but I am unsure if it could handle the 12vdc @4a? And keep in mind I would like to find a cable that's not very expensive since ill need about 15-25ft of it per digital picture frame.


texts: Changing Music on a Cuckoo Clock Movement

texts:
A band has asked me to design a cuckoo clock for them that plays a piece of their music, to sell to their fans. Movements that just cuckoo and also movements that play music in addition are readily available.
The basic movement sounds a cuckoo call on the hour and half hour as the cuckoo goes in and out. A musical movement has the addition of a carousel (the dancers you see on the front) going round as the music is played. So all of the triggers are there.
Here's the movement.
Here's a clock in action (scroll down a little for the video)
Rather than having to order these custom in thousands from China via Germany, could it be that the chip in the movement could be swapped out on this end for one with the band's music?
Thanks for any light anyone can shed on this,

Jodie

Edit: Added an image of the board.


texts:
I'm using a Teensy 3.0 which outputs 3.3v 100mA. I would like to connect many leds (probably 100…). Obviously I fear that the brightness of all the leds will be lower than I like to. I'm using the STP16CP05, a constant-current led driver.
Do you think it is possible to maybe connect 5v to the vss of the STP16CP05s (I have 5v available on my board) or will it cause problems with the Teensy?
Do you may have any other suggestions?

Also: Would the led brightness sink from each led to led or would each led have the same (low?) brightness?


texts: Safely testing a DC supply with an unknown output configuration

texts:
This picture shows the connector for the DC end of a power supply I extracted from a dead HP MFD (Multi Function Device):

As you can see it consists of 4 pins in a 2x2 configuration. The sockets across the ascending diagonal are hexagonal, whereas the ones on the descending diagonal are square. What is the best way to test the pins without killing the supply and/or my meter?


texts: confused about pnp transistor current flow

texts:
I am new to electronics and this question might seem silly.

I do not understand why in the transistor below current seems to flow from collector to emitter, because based on what I have read, I'd say this is a PNP transistor — isn't current meant to flow from emitter to collector in a PNP transistor?

Also, isn't a small current meant to go from the emitter into the base? It does not seem like it's happening here.


texts: How can I simulate/create a unit ramp signal by netlist or in schematic in TopSpice?

texts:
I have some circuits in schematic form. I want to see the circuits' response to a unit ramp signal but I can't out find how to implement this signal in the schematic.
I would like to know how could create this signal in netlist form for a circuit as simple as a resistor in parallel with the unit ramp source.
I´m a little stuck in how to create circuits by netlist in TopSpice and I would like to learn this topic.


texts: Powering microcontroller off USB, load off wall-wart

texts:
I'm developing a light display thing using a Teensy 2 and a digitally addressable LED string that draws quite a bit of power, more than can be provided over USB. I have ordered a switched wall-wart style power supply that more than adequately meets the power needs of the system, and should serve me well in production.

During firmware development however the Teensy will be connected over USB to the host computer. The methods recommended by the manufacturer are a bit invasive. I like that the Teensy is powered over USB, and I plan to keep using that function after this project is done. Also, I don't really feel comfortable taking a razor to my Teensy, let alone soldering an additional component to those tiny tiny pads.

Question:

Is it possible to power the Teensy off the USB connection and the load off a separate power supply if I make sure they share a common ground potential? Do I need to take any special precautions? Is this just a really really bad idea?

I can't shake the feeling that I should not be doing this, but I can't think of a reason why. Can anyone settle this one way or the other?

UPDATE

Thanks to your excellent answers, I now have 50 individually addressable 24-bit color RGB LEDs in my Christmas tree. Read more about it here and here!


texts: Adding Bass and Treble control to existing schematic

texts:
I have a little project in mind that I want to try.
This picture below is a stereo amplifier circuit. For more info about it, you can see this page. Stereo Amp

The circuit above only has Gain and Volume control, how do I add Bass and Treble control?
Where do I add them?
How's the circuit layout/schematic?

Thank you.


texts: Identify this component on a DYP-ME007Y ultrasonic sensor

texts:
I'm working with the DYP-ME007Y ultrasonic sensor for a project and I bought two off eBay. Both seem to work however they have this 'unknown' twistable part which is in a different position of rotation on both. I have a suspicion it is a trim pot of some description, but I would like to make sure. It could possibly be a method of tuning.

The part in question is the tall silver component with the black circle on top. The only writing on it is 7708, on the other side.


texts: How to configure the internal oscillator in a PIC16F616?

texts:
I want to use the internal oscillator in PIC16F616 in 8 MHz configuration and have the I/O function on RA4 and RA5. I've read through the datasheet, and I cannot find what I am doing wrong.

As far as I understand from the below information, TMR0 should increment every 500 ns, and it should create an interrupt when it overflows from "0xFF" to "0x00".
However, RA4 pin toggles about every 20 us.

From the datasheet:

  5.1.1

  8-BIT TIMER MODE

  When used as a timer, the Timer0 module will
  increment every instruction cycle (without prescaler).

  Timer mode is selected by clearing the T0CS bit of the
  OPTION register to ‘0’.

Also;

  Note: The value written to the TMR0 register can
  be adjusted, in order to account for the two
  instruction cycle delay when TMR0 is
  written.

Here is my code, my compiler is MPLAB XC8. :

#include <xc.h>
__CONFIG(FOSC_INTOSCIO & WDTE_OFF & PWRTE_ON & MCLRE_OFF & CP_OFF & IOSCFS_8MHZ & BOREN_ON);

void interrupt myInterrupt(void)
{
    if (T0IE && T0IF)
    {
        RA4 = ~RA4;
        TMR0 = 254;
        T0IF = 0;
    }
}

void main()
{
    TRISA = 0;
    ANSEL = 0;

    PSA = 1; // Prescaler Assignment bit : 1 = Prescaler is assigned to the WDT, 0 = Prescaler is assigned to the Timer0 module
    T0CS = 0; // T0CS: TMR0 Clock Source Select bit : 0 = Internal instruction cycle clock (FOSC/4), 1 = Transition on T0CKI pin
    T0IE = 1; //T0IE: Timer0 Overflow Interrupt Enable bit
    GIE = 1; //GIE: Global Interrupt Enable bit

    while (1);
}


texts: Designing a Light/Dark Sensor for motors, using Transistor and and LDR

texts:
I am working on some project for which I need to turn off a motor whenever it's dark. I looked around and found some light/dark sensing circuits. However, most of these circuits use an LED that switches on whenever is light or dark, depending upon application. I was wondering if someone could help me to modify the circuit(resistor values) to replace the LED with a motor, as shown in the figure below.

It would be helpful if you can show the respective calculations :)


texts: I am struggling with this problem: I have a fan whose output tacho signal is a square wave when it is running properly. If the fan stops the signal remains at its last value (either high or low). I need to a simple circuit to lignt up a red led if the fan stops and a green one if is running properly. Do you have any suggestion? I thought about using a monostable IC but I am quite unexperienced.


texts: How to calculate capacitance and resistance for this simple A.M. radio?

texts:
\$v_i\$ is the A.M. signal, \$v_o\$ is the modulation wave. How do I calculate the optimal capacitance and resistance, for a given carrier wave frequency? If there isn't necessarily an "optimal" configuration,  then how should I go about selecting them? (In actual A.M. radios, how do they tune to different frequencies?)

Here is what I have so far: falstad

I have calculus experience, so I could appreciate a mathematical explanation (as opposed to just saying "this is the answer", although that also works).


texts: Should I be worried about electro-static discharge?

texts:
Doing mostly micro-controller work, I have never bothered with grounding myself with a wrist-strap or any other implementation.
Should I be worried about this?
How serious is ESD when working at my workbench on projects?


texts:
I'm studying the following two-stages class AB amplifier:

Basically it is a standard two-stages op-amp (i.e. the cascade of a differential pair with active current mirror followed by an inverter with active load) to which the source follower M8-M9 has been added in order to provide the single-ended output signal of the differential pair to the gates of both M5 and M6.
I have doubts about some sentences of my book.

1st question

The book says that the gain of the second stage (i.e. the inverter with active load given by M5-M6) is:

Shouldn't the gain be negative? M5 and M6 give raise indeed to an inverter.

2nd question

I think that the book has an error: the gate of M1 should be in-, while the gate of M2 should be in+.

3rd question

Since the book does not provide the expression of the total low frequency gain, I surmise that it is given by the product of the gains of the three stages. Is it correct to assume the gain of the source follower equal to 1 for semplicity?


texts: Is this a good layout for BQ40Z60-based battery management unit?

texts:
Could you please take a look at board layout and tell is there some stupid mistakes.

I tried to accomplish the following characteristics:

Max discharge current: 10A
Max charge current: 5A
Charge voltage: 19-24V
3S or 4S Li-ion pack
Small board dimensions

Board is 2-layer, 70μm (2oz), 50x23mm (1968x906mil). On the Layout.jpg image I've shown battery, load and charger connection points.

Dataheet: BQ40Z60
Application notes: sluua04c, sluub71

(schematics, layout and datasheets originally from here: https://yadi.sk/d/cAIporoBtRDc9)


texts: Need guidance on simulating my control project

texts:
I've got Uni project in which I will have a small enclosure with a nichrome wire inside as a heating element, I am supposed to implement a PID controller using a microcontroller to maintain the temperature inside the enclosure at 50c by turning on/off the voltage supplied (using MOSFET) to the heating element, also a fan to speed up getting rid of extra heat introduced by outside sources.
Now I have to wait for quite a while until I receive the parts, was wondering what sort of software I can use to first try to simulate this project as closely as possible to try to come up with a PID controller, this will help me to learn about PID itself and my project before I start the practical part.
Thanks.


texts:
I'm trying to design a current source that can be adjusted from 0mA to 25mA (for an input voltage of 0V to 3V) using a dual P-Channel FET (NTZD3152P).

I've based my design on some PMOS current mirror circuits I've found online but with the addition of the adjustable input voltage. Will the attached circuit work? If not, why and how can I fix/improve it?

I've built this circuit using the LMV931 for my opamp. I've also added a 150nF capacitor between the gates and my non-inverting input, however I'm seeing a lot of oscillation on the non-inverting input and output still. I can increase the cap the further reduce the oscillation but I don't want to mask a fundamental design issue. Any ideas on how to fix this? I've included a quick sketch of what I observed.


texts: How would I make an Arduino Due recieve RS-232/422 signals?

texts:
Background on this question is here: What can I do to decrease the latency from these serial ports which are attached to a PC via a Serial to USB adapter?

I'm looking at purchasing an Arduino Due to take in 3 (well, ultimately 5, but currently 3) serial signals, one rs-232 and two rs-422. The point would be to get accurate time stamps before sending them on to a real computer for processing.

The due has a USB port, but I'd presumably have to put something together that could let the microcontroller access the serial signals.

I happen to know bupkis about hardware, though. This isn't a plea for someone to draw me up wiring diagrams (I don't actually know if wiring diagrams are relevant to this problem, and I couldn't read them [yet] if you did). I just don't have the language to research this. I would presumably have to solder things together? A serial port (x5) to a circuit board of some sort? Would the Due let me do three serial inputs? Could it support five? More importantly, how can you tell? (I'm kind of guessing that since the Due has 54 pins, and a serial port has 9 each, and 5 * 9 = 45, that the Due could support all five devices. Am I on the right track?)


texts:
I'm trying to build a simple IOT push-button with the ESP-01. My goal is to have it powered by 2 coin-cell batteries (3v), so I want it to power up when I push the button, and then power itself down.

I was advised on reddit to use a P-channel mosfet to allow the ESP to power itself by holding the gate low via a GPI0 pin, then setting it high to power it down. I'm struggling to get this working. I have it wired up like so:

But as soon as I release the button, the ESP shuts off immediately (it doesn't seem to draw any power through the mosfet). I tested my code by hooking ESP's 3v3 pin directly to battery+, and used a voltmeter to measure at the mosfet's drain pin. When it boots up, the voltmeter almost immediately reads ~3.3v, my code makes a successful HTTP request, and then voltmeter drops ~0v, as expected.

However, when I wire the ESP's 3v3 pin back where the voltmeter was (on the drain pin), the ESP shuts off as soon as I release the button.

What am I missing? I've seen other schematics for "soft-latching" circuits that include an additional NPN transistor, but I'm not sure whether or not that applies to my situation.


texts:
Is it 5 // ((1//2) + 3)?

So the 5 is parallel with 3, which is in series with a 1 parallel with 2?

Right or wrong?


texts: Strange voltage tracking problem with regulated power supply build

texts:
I'm building my own regulated linear DC power supply based on the Farnell L30 (service manual and circuit diagram here) and I'm sticking mainly to the original design with some modifications for parts and improvements.

The section of interest for this problem is shown below:

For completeness, I'm using some nice old 2.5k pots (course and fine) and I'm driving the Howland current source (via the pots) with a steady, TL431 based 5V supply.  Also, instead of 15V and -5V rails, I have +/-12V rails.

I haven't included a schematic of these changes because they aren't relevant to this issue, as I'll explain shortly.

The problem I'm having is that the voltage output is very non-linear as I adjust the pots.  Ignoring the fine adjustment (set to 0), if I divide the course pot adjustment into 9 segments, roughly half the 30V output is delivered in the first 2 segments, with the remainder forming a linear ramp to 30V.

Here's a plot of what I'm talking about:

It took quite a bit of debugging, but I've concluded that the issue lies with the voltage comparator op amp (IC2 in the schematic).  In my circuit, this is a FET input TL082 and it seems this has something to do with bias currents.

When I had the 10k resistors at the inputs, I got the plot above.  If I change R14 to 20k, I get the following plot:

Not exactly linear, but the rate of change at the start is less.

It's extremely difficult to debug this issue properly because any attempt to measure voltages at the op amp inputs causes the op amp to rail with the loss of control causing the pass transistors to saturate (not desirable).  Obviously, the voltmeter draws current and this will affect the reading and I need the control loop in place to make effective measurements - so a bit of a pain really.

However, I can conform the following:

The pots are linear

The current source is linear (to test this I tied the current source to the 0V reference rail through a 1k resistor and tracked the changes - all perfect)

The supply rails to the control section and the 5V current source driving voltage are all steady.

So, after all that, would you agree that this may be the cause of the issue I'm seeing (I have experimental evidence, but I still don't grasp the theory)?

Can somebody provide a good theoretical explanation as to the effect I'm seeing?

UPDATE:

Some pictures to give you an idea of the layout:

FURTHER UPDATE:

Looks like @PlasmaHH was on the money.  I have quite a bit of oscillation at the voltage comparator and the output.  Below I've included some pictures (excuse the poor image quality!).  At 5V (as read erroneously from my DMM at a DC setting) the oscillation frequency is about 142 kHz and I have a 1V pp oscillation at the inverting pin of the voltage comparator op amp (image#1) and a staggering 36V pp at the supply output (image#2).

Looks like I'll need to sort out these oscillations before going any further.  Any ideas about which components to tweak to kill these?