texts: turning YM T8 SMD2835 110V led light tube into USB or Battery lamp

texts:
A few days ago the electric circuit of a T8 led tube broke, but when I measured the led all were ok. Then I came up with the idea of using them in an experiment and turning them into a usb or battery lamp.

The tube consists of 30 smd led 2835 connected, two lines of 30 leds connected in series, and they connected in parallel with each other. So I have had to change this and connect all the leds in parallel, one by one. And I have managed to light the lamp well, so far, I still have 30 LEDs to connect.

My question is if I need any resistance or capacitor, because when I connect them with a usb these will warm up a bit, and I do not want them to get lost.

Here I leave a picture of how they are staying, lit with an old tablet battery.


texts: SMD resistor maximum voltage: is 200V really a limiting factor?

texts:
I need a resistor to work with 230 VAC voltage. So 400V rating would be appreciated.

However most of the chip resistor with size 1206 and above has only 200 Volts of maximum working voltage. Main of my concern is: why this voltage doesn't rise up with resistor size?

This table taken from Rohms datasheet:

And the similar situation appears in different suppliers.

It looks very weird as 2512 is more than twice as long as 1206 but it has same voltage rating.

This is a bit frustrating... What shoud I use in a circuits working under power line voltages?


texts: How do computers power so many lights on a keyboard?

texts:
Beginner here. I am working on building my own keyboard PCB, and I wanted to add a backlight for my keys. However, I've been reading methods of powering teensy little 3mm LEDs and it seems like an impossible task to get 77 powered by anything less than a billion volt power supply with them in series or somehow get a billion amps pumped out to run them in parallel. (I know I'm exaggerating, but still...)

I'm looking at using white 3mm LEDs with a max current of 20 mA and a forward voltage of 3-3.4v. If I put all of the LEDs in series, I'd need 77*3.4V = 261V power supply, and if I put all of the LEDs in parallel I'd need to supply 77*20mA = 1540 mA of current. The teensy microcontroller that will process the keyboard inputs and that I plug into my computer is what I would like to power my LEDs, but its pins can only supply 3.3V at 250mA. (and I've only got 2 to use).

How do everyday computers power so many little key backlights without running out of battery immediately?

The only way I could think of getting this to work would be to have a separate power supply of a million AA batteries taped to the bottom of the keyboard separately powering just the LEDs.

Is there a better solution out there?

Thank you for your time.


texts: Logic Conversion 3.3V to 5V (Current Related) 74HC 74HCT

texts:
A beginner style question.
I'm attempting to perform some logic level conversions on 3.3V signals to 5V using the 74HC4050D powered at 3.3V and 74HC541 powered at 5V. Is it OK to directly connect the outputs of the 74HC4050 to the inputs of the 74HC541 ? or do I need pull up/Pull down resistors from the output of the 74HC4050D to the input of the 74HC541 for each pin?

What should I be looking for in terms of the datasheets when determining these things (in my case I don't really aim to source or sink current to other devices.I just aim to do the voltage conversion. Is it only leakage current that would be output in this instance?
If one didn't add a pull up/down resistors or a series resistor would the only risk be that of an unkown logic state if VCC were to change abruptly or signal noise was present?

PS I'm aware of that the maximum current into these devices Icc is about 50ma and a max output of a particular pin Io is around 4-5ma.

Links for you reference:
74HC4050D
74HC541


texts: Unsure if motor starter (contactor + overload) is needed instead of normal solid state relay

texts: I am designing a system with several pumps ranging from 0.5 to 1.5 HP (all single phase) and am unsure of what kind of circuitry I need. I researched different motor contactors and overloads I could use, but I also have found relays that provide up to 40A, which is more than enough for my highest load of 30A. I mostly read that contactors are better at handling three phase and for inrush currents. I would appreciate any help on this topic.


texts:
Hey people, I need to program the ATmega8 chips via serial. I understand that for doing that I would need to install a bootloader on the chip. And to install a bootloader, I would need a parallel port programmer. Am I right? Or can I just hookup the chip with an MAX232 to make a programmer? I am really confused right now. The best answer here would be a circuit.

UPDATE

He people I just found this http://www.qubbeks.puslapiai.lt/images/articles/AVR_programmer/avr_programatorius_schema.jpg. Do you think this is the kind of circuit which won't require any bootloading?


texts:
Our car sharing club is working to implement a smart system in our vehicles which will allow access via RFID-cards, and which will record milage for the booking and billing system.

We are using a tracker unit (http://flextrack.dk/en/products/tracking-devices/lommy-pro-ii.html which has a relatively low power consumption, but unfortunately not low enough.

We have found that if a car is left unused for 4-6 days the car battery is drained such that we cannot start the engine. This is not acceptable.

The tracker is in contact with our server over GSM/GPRS and we cannot switch it off since it must be available to receive information about new reservations and to act on RFID signals from users.

The tracker has a an internal 1.1Ah 3.7V Lithium-ion battery which will keep the unit running for around 5-6 hrs, so I suspect that our main problem has to do with the charging circuit being "greedy" and not energy saving.

Without trying to hack into the tracker, my plan is to put a timer switch on the external power supply from the car battery to the tracker. I would like a simple circuit which, when the ignition is turned off, would connect/disconnect power for e.g. 10min/60min.

I will do some tests to establish the actual on/off durations required to keep the tracker alive. My expectation is that this will reduce the overhead consumption of the tracker charging circuit, and ensure that it feed most of the power from the car battery into the internal battery in the tracker.

If possible, I would prefer to use simple discrete components tuned to the on/off periods instead of a microcontroller.


texts: Do Schmitt-trigger specs give requirements to avoid metastability?

texts:
Although Schmitt triggers are not usually regarded as latches with setup/hold constraints, a Schmitt trigger is functionally a sort of latch which is forced one way when the input is above a certain threshold, forced the other way when the input is below a certain threshold, and is expected to hold its value when the input is between the upper and lower thresholds.  While the thresholds may or may not be specified in such fashion as to have a non-overlapping region between them, the fact that a device doesn't switch at a particular voltage but switches at a voltage near that would imply that the former voltage should be within the "hold" zone.  For example, given http://www.ti.com/lit/ds/symlink/sn74ahct14.pdf

Table 7.5 Electrical Characteristics
![enter image description here][1]

which guarantees 0.4V hysteresis, if device outputs high while the input sits at 1.2 volts, then goes low when the input rises to 1.3 volts and sits there awhile, it must remain low until the input goes below 0.9 volts.  If the output hadn't gone low until the input rose to 1.5 volts, it could go back high as soon as the input went back down to 1.1 volts.

Because the Schmitt trigger is a latching device, it will necessarily be, like all latching devices, susceptible to being placed in a metastable condition.  While an ideal Schmitt trigger would switch exactly once if given a signal which never deviates by more than +/- 0.2V (half the hysteresis voltage) from a monotonically rising or falling waveform, it must like any latch have input conditions which would induce metastability. Most latches and latching devices have designated setup/hold timings and promise that they will not go metastable unless those timings are violated.  Do Schmitt triggers offer any guarantees, e.g. promising that a signal that crosses the upper threshold for less than some maximum "reject" time will not cause the output to switch at all, and any signal which crosses the threshold for more than some "capture" time will be guaranteed to cause the output to switch and stay switched?  Are such guarantees documented anywhere?


texts: LDR circuit does not change sound frequency

texts:
I am a complete beginner in the field of electrical engineering. In the Arduino cookbook, there is this circuit:

I have been trying to reproduce it, and I do hear a sound after uploading the software, but it does not change at all regardless of the light intensity. I think I got buildup right, but I did not have a 4.7k resistor, so I used one with 3.3k (problem here?).

Here is a schematic of how I put the lower part together (I assume the upper part is not the problem, otherwise I probably would not be hearing anything); please excuse my poor drawing skills.

I would appreciate a hint on why this is not working as expected. Thanks in advance.


texts: Can a dc generator / dynamo be used as a dc motor? If so is this realistic without causing meltdown?


texts:
What kind of memory does the device memory of modern smartphones belong to? Is it SRAM or DRAM, or some other kinds of memory? I think the device memory of smartphones is an analogy to RAM in personal computers (in terms of usage), except the former cannot be easily added or installed by user, while SD card of smartphones is an analogy to hard disks in PCs. So, is the device memory the same type of memory as the RAM in PCs?

p.s. Sorry if this question is off-topic. I think this is a question about computer organization and architecture, so it seems best suited to electronic engineering.


texts:
I'm trying to linearize the output of an audio tapered potentiometer. Right now, I'm using ADC on a Beaglebone to read the value of a 250k potentiometer with 3.3V. I get a value between 0 and 1, but it is scaled such that the rate of change of the potentiometer's value increases dramatically as the knob is turned to the right - it looks something like an exponential curve.

I was wondering how I could convert the value of the audio tapered potentiometer to that resembling a linear one. Can I just do something with logarithms?


texts:
I would like to use SIM800L for M2M. I have power of 5V 2A for powering uC board and would like to add gsm module. It seems that SIM800L has rather strange voltage input rating: 3.4V - 4.4V.
What would be proper way to power it up with this configuration?

One proposal was to use zener diode with VF 1V, is this viable solution?


texts:
I am totally new to soldering. But I tried to gather as much information on this topic as possible (e.g the guides by CuriousInventor).

My soldering iron is a simple, unregulated Weller SP 25. For cleaning I used a brass sponge and a standard wet sponge. I always tinned the tip before putting it back in the stand and cleaned it before soldering. I soldered maybe 20 - 30 hours in total.

The tip was a conical, but now one side is flat. (I did not use a file.)
I hope you can see the flat tip on the picture properly.

What can damage a tip like that? How can I prevent such damage? I dont want to ruin another tip that fast.


texts: Wide voltage supply for PIC microcontroller

texts:
I am looking to power a PIC with a supply voltage that ranges from 4.5 V to 18 V.

This will be a battery powered device so I would like to conserve power, i.e. linear regulators like the 7805 is less desirable.

Also the application will be producing quite a bit of heat in an enclosed space so no need to add to heat generation with the linear regulator dissipating excess voltage.

After some hunting I suppose I am after a switch mode DC-DC converter, a step down one.

I have been looking at an LM2575 based circuit, but wondering what Vout would be if my supply Vin drops below the minimum 7 V for regulation. The PIC I am working with have an operating range of 2 V to 5.5 V so I am OK with Vout being equal to Vin when Vin < regulation threshold.

So my question is, what happens to Vout when Vin < regulation threshold?

Also are there any additional things/circuits I should be considering?


texts:
I've dealt with multiple electrical cables both 120 extension cords and laptop low voltage cords that when the cable is new it's straight (as in you can reasonably pull it fairly straight without trouble)
but over time it forms this weird coiling shape almost as if it's wrapped around the length of a thin rod with roughly a turn of wire around said rod being every few inches ... come to think of it maybe the shape would better be called a spiral? or helix? anyways does anyone know why this seems to happen with so many electrical cables?


texts: Arduino PSU with battery backup (SLA) and mains/battery monitoring

texts:
Please could somebody review my following schematic, as it is my first attempt at a PSU circuit. The aim of this circuit is as follows:
I am using a 15V (150W) PSU to power an Arduino, 2 separate 12V circuits and trickle (float) charge a 7Ah SLA battery which takes over in event of mains failure. It should also be able to monitor the mains (PSU) supply via an Arduino pin and also check the battery is OK periodically.
Regarding the charging, there is a current-limiting resistor of 1k8 to provide 0.7Ah to the battery.
Regarding the monitoring, the PSU has a 12V relay (15V applied to coil is OK) in parallel to switch a contact from/to Ground, so I can monitor the Arduino pin to see if it is reading ground or not (PSU output is OK or not).
The current-limiting resistor is also connected via a 5V relay (controlled by Arduino pin) so when the Arduino pin is switched, the current-limiting resistor is no longer in the circuit. During this time while there is no trickle charge, if the battery is OK (suitable voltage present) another relay will be energised by the battery voltage which switches another Arduino pin to ground.
I have a voltage regulator to provide 12V to the parts that need 12V and another voltage regulator to provide 5V to the Arduino (building Arduino from components).
I've attached a picture of the schematic. If someone more experienced could have a quick look and tell me if it's OK or not (and if so where) that would be great, as I know battery charging done wrongly can have pretty nasty results...
The high current from the PSU is needed to run several more Arduinos at the end of an RS485 line, as well as some addressable RGB LEDs and some other 12V components.
The battery monitoring doesn't have to indicate charge or condition, just whether it is connected and have enough voltage to run things for at least a few seconds (so it can log it) preferably longer as required, but not essential.
Thanks in advance.
EDIT: changed 2 relays to DPDT which will mean when the mains is on and the battery is not being tested the battery has no load. Also added a capacitor to cope with PSU/battery switchover (during relay operation)

simulate this circuit – Schematic created using CircuitLab
OP's schematic tidied up by @Transistor.
EDIT: Updated schematic to indicate 12v and 5v outputs and switched the erroneous wiring of the capacitor C1 to parallel (non-blocking)
From Battery manufacturers spec sheet:

Charge Current
Float charge current limit (A): No limit
Cyclic (or Boost) charge current limit (A): 1.75

From powerstream.com

Sealed lead acid batteries can recycle the generated gasses as long as they are being overcharged at less than C/3.

From mpoweruk.com

Trickle charging is designed to compensate for the self discharge of the battery. Continuous charge. Long term constant current charging for standby use.


texts: ESP32 and moisture sensor transistor switch

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I'm doing the classic water moisture sensor project with my ESP32, but I want to be able to switch the sensor on and off since that will reduce the amount of corrosion that occurs.  Can I use a BC547 transistor as suggested below to achieve turning using GPIO18?

I've also wired an LED in series to show when it's reading/not reading. Would I need the resistor if I didn't have this LED?
Please be easy on me - I'm a beginner to all of this.
CORRECTIONS (and removed the led):


texts:
I need help to understand this circuit and calculate voltage \$V_o\$

First what will \$V_o\$ be if \$V_2=1v\$ and \$v_1=0.5v\$

I do not understand how to think here. The voltage at both terminals of the amp should be the same and if we see the voltage at positive terminal as from the voltage from potential divider then it should be 0.25 V.


texts: Quality Factor and Cut-off Frequency Defintion

texts:
Suppose we have

$$ H(s) = \dfrac{ k \frac{\omega_o}{Q}s}{s^2 + \frac{\omega_o}{Q}s + \omega_n^2}$$

What is the definition of the quality factor? My understanding is that it is the gain at the cut-off frequency. I know how to find this from a bode plot by extending a line from the band pass gain and extending a line when there is a drop off in gain and finding their intersection. This gives us the cut-off frequency and hence we can find the gain at the cut-off frequency, which is the quality factor.

Also, if I had a transfer function as above, how would I find the cut-off frequency mathematically without a bode plot? If I set \$ |{H(\omega_o j)}| = \dfrac{1}{\sqrt{2}} \$, I can find the cut off frequency, but doesn't that assume that the quality factor is \$\dfrac{1}{\sqrt{2}}\$? Also, to do this, doesn't the gain have to be 1?

Thanks.


texts: Can i use a slower clock rate for a CPU or a Microcontroller than the one it is supposed to use?

texts: Say i have a CPU or a Microcontroller with a clock rate of 1 GHz, can i use a 1 kHz instead?


texts: If an MCB protects from overcurrent, which device protects from overvoltage?

texts:
In the context of whole house protection devices used in distribution panel, if an MCB protects from overcurrent, which device protects from overvoltage?

Surge Protection Devices (SPD) can only protect from transient overvoltages before failing. Temporary overvoltage (TOV/Ut) withstand capacity for an SPD with rated voltage of 230V is often 330-440V for 5s.

Is there a circuit breaker that trips from overvoltage?


texts: Is ULPI the only protocol for interfacing with USB devices?

texts: At work I was told to look for a USB 3.0 transceiver that interfaces to ULPI. I'm not able to find transceivers which fit this description. Is there some other "lingo", or feature I should be looking for?


texts: How does a microwave oven-leakage detector work?

texts: What type of sensor or circuitry is inside one of these devices that allows measurement of microwave radiation strength? I've never opened one but I'm assuming it's similar to measuring RSSI on a wireless receiver module, e.g. an Xbee.


texts: Universal series motor control using relays

texts:
I have a 220AC universal series wound motor I am trying to connect to a RF Remote Switch using relays and full bridge rectifiers.
I have come up with the following schematic:

The RF Remote Switch takes 220AC through the P-N connection and outputs it through L-N (UP) or L1-N (DOWN) depending on the selected direction on the remote control and it also has a stop button where no output is enabled. The switch seems to be correctly designed and has a small delay when changing from L-N to L1-N or vice versa.
The full bridge rectifiers are KBPC5010 (50A, 500V) and the DPDT relays are LY2NJ or LY2J.
R1 relay is used to control polarity when the L1 output is selected, and the R2 relay is used for dynamic braking through the R resistor.
The problem I encounter is that dynamic breaking seems to work fine when only operating the motor in the UP direction (L-N) and stopping, as the R resistor heats up; but it does not work when operating in the DOWN direction (L1-N). When the motor is receiving voltage through the L1 line and it is stopped, a visible spark comes out of the motor housing.
I think this is because deactivation of the L1 line causes the R1 relay to switch before the R2 relay (R1 activation is caused by L1, while R2 activation comes from the dual bridge assembly) and causes a change in polarity to the input of the motor before the dynamic breaking resistor path can be activated. What would be the correct way to avoid this from happening?


texts:
I have a project involving audio on a Xilinx Spartan6 FPGA. The goal of the project is to make an audio processor using HDL (mostly educative and for fun). It's basically a pipeline of audio effects that can be configured using SPI. I wanted to use this project to get an introduction to Matlab HDL coder.

I design the audio effects in Simulink then implements them in Verilog. I would like to improve my work method and hopefully use the Simulink design to implement directly in my FPGA, which HDL coder is supposed to do.

My audio signal is sampled at 48KHz, but my FPGA is clocked at 96MHz. When I design the effects in Simulink, I set my sampling frequency to 48KHz, then uses blocs like adders/multiplier,etc that all execute within a single step. In my verilog code, the implementation I do are not always executed in a single clock cycle. For example, I use a custom module for scaling samples that is optimized in space but takes as much clock cycle as there is bits in the operand.

When comes to simulate in Matlab, setting my sampling frequency at 96MHz is too slow to get a real gain in efficacity. The time I save by not writing Verilog is lost waiting for the simulation to process few audio samples.

How do people uses HDL coder to overcome this very obvious problem?
Do professionals have very powerful simulation machines? Do they wait? Do they uses FPGA powerful enough not to need to worry about saving some elements like DSP slices?

Is there a way to have 2 versions of the same bloc, like a simulation v.s. an implementation one?

Thank you


texts: Does anyone know how to create a cf controller in order to read data from cf card?


texts: Component identification, on USB 2.0 data lines

texts:
The component i'm trying to identify is on the usb 2.0 D+ and D- lines of a nintendo switch, its got two ground connections and has the letters DUG on it.

Can anyone identify this component?


texts: Current Sensing with Op-Amp, do I need a shunt resistor in series with the load on the output?

texts:
Hi I am building a circuit to measure current draw from a load, I opted for a voltage follower with a transistor and a shunt in between, The transistor is needed to allow higher currents to flow through the load, here is my schematic:

The Op-Amp is configured with Negative Feedback, So as long as the Input Voltage plus the shunt voltage plus the transistor Vce is lower than the Collector Voltage, the transistor would be in saturation mode (I'm actually not sure).
If the BJT is in saturation mode, the voltage across the load would be exactly the same as the Input Voltage, also the current across the shunt is the same as the current across the load, allowing to sense the current with a differential amplifier across the shunt.
What I am not really sure is if I need to place a resistor between the Op-Amp Output and the base of the BJT, I think that the Op-Amp would compensate by itself, but idk.
So the actual question is if a resistor needed between the base of the BJT and the Op-Amp output.
EDIT:
This is the second stage for a DC Variable Voltage source.
This stage has three purposes:

-The first, to keep the voltage across the load equal to the input voltage.
-The second is to be able to measure the load current with a differential amplifier across the load
-The third to increase me maximum current that can be supplied to the load. Since the first stage is 1.5 Amps max, I would like to make this at least 3 Amp max


texts: Effect of swapping positive and negative traces in a LVDS differential pair, for both clock lines and data lines?

texts:
For an LVDS signal, I am trying to understand what will happen if the transmitter's positive and negative sides of the differential pair get swapped on their way to the receiver. In other words you have two output pins on a transmitter, LVDS_Positive and LVDS_Negative. A receiver has two pins, LVDS_+ and LVDS_-. The LVDS_Positive gets routed to LVDS_- and vice-verse.

My intuition tells me that for a standalone clock (perhaps a clock buffer or an LVDS mux with selectable clock inputs) this will work perfectly fine the same as if it were routed + to + and - to -. This is because the polarity only swaps which edge is rising and which is falling, the clock is still propagated to the chip just fine, that skew is irrelevant I would think (unless there's a specific application where you are trying to align clock edges to bring in data or something like that.)

However for a data signal, example shown below, this would NOT work because it does not switch polarity every period as a clock does (depending on what bits the data contains), so transmitted 1's would be received as 0's and vice versa so the data would be corrupted.

I also know that certain standards, like PCIE, have built in that they can accept polarity differences in differential data signals which confounds this further.

Any help to understand this would be appreciated.


texts: When is it appropriate to galvanically isolate components/subsytems?

texts:
As the question implies, how do you determine when it is appropriate to galvanically isolate parts of the same electrical system from one another?

For example, I'm currently constructing a tube amplifier that has a significant amount of digital electronics in it. Currently, the digital part and tube part are powered off of separate windings from the same transformer - However, they are both referenced to the chassis earth (as in each respective circuit has a single wire running from their respective power supply ground to a single point on the chassis - does this even count as galvanically isolated?).

My mongrel amplifier also houses a digitally controlled high voltage regulator section, so I can adjust the voltage to my tubes. For no specific reasons in mind, other than "I don't want my lowly digital signals interfacing with potentially 400 volts!", I decided to stick a cheap isolated DC/DC brick with 1000v internal insulation into the design, as well as a digital isolator, to isolate the onboard DAC from my other digital crap. Attached is an eagle board design view of the offending area, so you can see what I'm ranting about. (sorry, not enough rep for inline images).

The poorly drawn black-dotted line indicates the intended 'isolated' area.

I think my justification for doing this at the time, is that in the likelihood that a component fails on the HV regulator and HV is placed upon any of my poor low voltage components, my digital components on other boards (and there are a LOT of them), would remain safe, rather than be obliterated as the surge propagated through. I don't actually know how true this is, hence the question. Would you consider it appropriate to isolate these two systems in this manner, would you do something different, or would you not even consider isolation necessary at all? In what situations would you consider isolation mandatory?


texts:
The Android AOA specification states that

  When the Android-powered device is in host mode, it acts as the USB host and powers the bus.

and

  When the Android-powered device is in USB accessory mode, the connected USB hardware (an Android USB accessory in this case) acts as the host and powers the bus.

As a consequence, all of the Android Accessory documentation or examples are for circuits/programs that provide USB Host to communicate with the Android in device mode. The particular Android accessory I want to develop needs to draw power from the device, and I know this is possible with On-the-Go technology, but using an OTG device puts the Android in Host mode.

How can an HID device (AVR device using LUFA, to be specific) act as an Android Accessory AND pull power from the Android phone?


texts: Why can't certain isolated DC/DC converters operate at over 50% duty cycle?

texts:
I am currently studying two switch isolated DC/DC converters, more specifically the Push-Pull, the Half-Bridge and the Full-Bridge DC/DC converters. Several books say that these converters cannot operate at over 50% duty cycle because, if that's the case, you would be shorting the transformer. My question is why? Why can't you operate at over 50% duty cycle?
Thanks in advance.


texts:
It is possibile to power on a single led (in a led panel) using wireless powering?
I know the possibility to transfer power by wireless, but, is there a way to transfer power with high precision (1mm) ?


texts:
I'm looking at coupling the output of two computer PSUs, driving a fairly stable high power project (around 300-400W peak) most likely using all output rails (12V, 5V, 3.3V) all well within the rated limits of a single PSU. Ignoring issues balancing load between rails on a single PSU, I want to use a second supply as a backup to take the load if the first one fails.

I have two questions for the electrical engineers out there:

1) can I simply use two high current power diodes as simple backflow prevention to allow failover to occur reasonably transparently, by using a common ground and tapping off +12V between the diodes below?

+Vin (1)   ~ o----->|----o----|<-----o ~   +Vin (2)
                         +Vout

I'm thinking of using one or more bridge rectifiers to do this, purely from a cost perspective - they're cheap and ready to use (rated ~50A, maybe more). I'd be applying +V from each PSU to the each of the two AC inputs and taking the output off the + terminal. Is there any problem inherently with this design?

2) I'm having trouble understanding the datasheets, I'm trying to work out (a) what the forward voltage drop will be if I feed in 12V, 5V or 3.3V, hence what the heart dissipation requirements will be, and (b) determine if the voltage drop or heat dissipation requirements are going to be too high for my requirements, in which case I'll work out a relay-based solution instead. Take this one for example:

http://www.farnell.com/datasheets/2341003.pdf

It lists "Forward voltage per leg" as 1.2V, is this the voltage drop? At what temperature? Or is it the minimum forward voltage?

Should I be looking at Schottky diodes instead, as a 1.2V drop is significant on a 3.3V line?  Are there any other options I could consider?


texts:
I'm trying to debug a incorrect output voltage from a boost regulator (TPS61220). The schematic is below. Pointed colors represent the measuring points in graphs underneath:

The graphs show the circuit behavior.

The graph below is the input voltage and the L voltage captured with an oscilloscope:

According to the datasheet, the ratio of R1 and R2 should result in an output voltage of cca. 2.8V. However the output (green) is never higher than the input and is rather unstable. The current coming from the source is a constant 15mA even though there is nothing connected to the output.

The prototype board was assembled on a breadboard.

The power source is expected to be unstable, vary in voltage between 0.8-2.5.

Questions:

How would one approach debugging this circuit?
Should the current be observed on the induct and it makes no sense to check the voltage (green)?
Would 15mA of current without a consumer imply an assembly problem?


texts: Benifits of using Breadboard instead of PCB

texts: What are the main advantages of using breadboard instead of PCB?


texts: Dependent source while calculating Thevenin's voltage

texts: In this case how and why while calculating the thevenin's voltage a dependent source plays a part but a resistor in its place have no contributions?


texts: What is in/out traction frequency in a stepper motor?

texts:
I'm referring to this spec sheet for a stepper motor.
EDIT Just to be clear, this is not an "I want advice on what motor to use" type of question. I just want to know what "in-traction frequency" and "out-traction frequency" on the linked spec sheet mean.


texts:
I'm developing a fully graphical on screen display (OSD) for RC aircraft and other RC things. The project is almost complete, with a working prototype and PCBs made. The OSD is based around a dsPIC33F clocked at 36.85 MHz and works with PAL and NTSC video sources. The video sync is sliced by an LM1881 sync separator. On the CSYNC rising edge, an interrupt fires, checks VSYNC, checks ODDEVEN, and then outputs a scan line if required. The output stage is assembler code, and it works by controlling an IO port. Making a black pixel is accomplished by setting the output low, making a white pixel is accomplished by setting the output high, and no pixel is handled by tristating the pin. Everything about this is open sourced here: http://code.google.com/p/super-osd/

Now, as it stands, there is one minor problem with this. The image has ringing on it. The resolution of the OSD is 208 pixels horizontally and the ringing can sometimes extend to two or three pixels, which is quite a lot! It doesn't make the OSD look as good as it should and reduces visibility. (Which is very important on an RC aircraft. If you are miles from home, you need to know exactly where you are, in case your plane goes down or you get lost.)

Below is an image capture of the OSD. Look near the edges of the test lines, and near the text. Ignore the chroma noise, that is an unavoidable effect of composite video. (The OSD firmware still has some bugs, and I'm still squashing them, like the horizontal lines being one pixel too long and wrapping to the next line. Ignore them for now...)

Now, I have few ideas why the image has so much ringing on it. I suspect it might be due to poorly terminated video signals but I have no idea on how to terminate them correctly, as my video card has already got a built in 75 ohm termination and my camera has matching termination (I hope.)

You can see how much ringing the video has in the scope trace below (bottom trace, 70mV/div):

I suspect the ringing comes down to the capacitance of the IO pin, the termination resistance, and reflections in my... uh... transmission line which is currently a small piece of wire.

The ringing matches the image - about 2-3 pixel clocks. (One pixel clock is 40µs / 208 = 192 ns.)

So, any ideas?


texts:
I am implementing a Linear Feedback Shift Register (LFSR) in Pspice A/D with a new logic family. Anyways, to initiate the random number generation I am required to feed in some value to the circuit, to be specific, the output of all the D-latches can not be zero initially so I am trying to make the output of any D-latch '1' initially. It should be done such that after the initialization the circuit works by itself. I tried using a fixed voltage source but that does not work, quite obviously.
Please suggest anything you may find applicable to this.

Below is the circuit I am trying to make:

And just in case it may help, I am trying to get results like these:


texts: can I use a choke 150uH inductor for my AM transmitter circuit?

texts:
I am trying to develop an AM transmitter but I am having problems with getting a variable capacitor and inductor (for the rf circuit) in my location. I was able to find a choke coil with an inductance of 150uH but most of the circuits I was able to find in the net have 200uH inductors. Is it possible to use this inductor?

edit:

Here is the link to where I am going to base my circuit on:
http://www.zen22142.zen.co.uk/Circuits/rf/amtx.htm

and here is the link to the inductor I am planning to use:
http://www.e-gizmo.net/oc/index.php?route=product/product&product_id=45861&search=150uH

for the capacitor of the rf amplifier, only 75pF trimmer capacitors are available in our nearby shop
so can I use constant capacitors in parallel so I could still control the capacitance?


texts: Does calculation of resistances in parallel apply to magnetic circuits too?

texts:
Like the title says.

Is 1/Rges = 1/R1 + 1/R2.... for magnetic resistances true aswell?

E.g. can we say that Rpar = R1*R2/(R1+R2) with magnetic resistances in parallel?


texts:
I'm trying to make a dot matrix message board -type thing work,

The dot matrix IC's are the DL-57 Alpha Numeric Dot Matrix Display [Data Sheet] : https://drive.google.com/file/d/0B6Pibr6_2jwcQ2xmRUIwTjFBZ0k/edit?usp=sharing

Which is pretty simple as you can see, hwoever the hard part comes in where I want the message to be configurable, not on the fly though.

I know I need some kind of ROM, and the one I have right now is the M27C256B, it's a UV EPROM (Data sheet shown here : http://pdf.datasheetarchive.com/datasheetsmain/Datasheets-20/DSA-394559.pdf)

Erasing it is no problem, obviously, but programmers are mega expensive, I did google for some DIY programmers, but the only ones that I could find were in a google cache.

Is there any other way to make a sort-of-ROM-thing with other IC's?
Or maybe I overlooked some DIY EPROM programmer?

Any help would be appreciated.

(I also have a UV EPLD : EP900 DC-3 3F19007 (datasheet available but I already have two links in here) , but again the problem is programming the thing....)

Any help would be welcomed, I do have a large stock room of TONS of parts, so please, if you have some kind of schematic for building a programmer, that would be much appreciated.


texts:
I am developing a board that will need both USB and battery power options, non switched. I put this schematic together that I think is right, but I want to make sure I'm not going to blow the chip. I'm using an STM32F405 100 pin.
The nets in the Power Schematic are VIN (From USB), up to VUSB (goes to PA09 on MCU) and then 3.3V output after the LDO regulator

Is this the proper schematic for a USB / Battery powered MCU? I think with this design I can use either 3, or 4 AAs without having to worry about the excess voltage on the VUSB net. The 3.3v should be protected by the LDO, and each power input from each other by the diodes.

I just want to make sure my placement of the components is correct and will not blow my chip if it's being powered by either, and often times both if I'm programming via USB.

*EDIT
Something like this?

*EDIT 2
Here are the updates after comments.

*EDIT 3
VBus directly to VIN. Is this what you meant?

*EDIT 4
This looks a little better I think


texts: How can I determine what type of logic structure this circuit represents?

texts:
I have the following circuit:

How can I determine which one of the following functions it represents:

F = (AB+CD)'
F = ((A+B)(C+D))'
F = AB+CD


texts: Switching 1 BT Module between 4 Arduino devices

texts:
I have a design for an electronics workbench that has 2 Arduino's (a Mega and an Uno), and several component testers that have Atmega328 MCU's at their core, and I was wondering if there is a way to have one BT HC-05 module that I can switch between the devices to program them individually one at a time (rather than having 4 BT modules ie. one for each).

They can share a common 3.3V rail, ground, and LED indicator pins as all the devices share the same power and ground.  AFAICT the only 3 bus lines that need to be switched between the devices are the RST (using the HC-05 pin 32 & 100nF Capacitor), TX & RX lines.  What components & circuit can I use to select and switch these three bus lines to the devices I wish to program?

The basic circuit for one device with one BT module is here: ->
Arduino BT programming circuit

Though I will be using the bare module, not the version on a 5V adapter board.

Could I use 3 quad optocouplers (one each for the 3 lines that need to be swiched between the 4 devices) and some mechanism to select when to turn the one I want in each OC package on? I understand how to turn on the OC (probably with the ATMEGA328 or a latching logic gate triggered by a push button, but would I need any components around the OC on the data line side (the EC side of the OC) or would it be pretty much a simple placement of the quad OC transistor side into the circuit? I'm stretching my knowledge here a bit, but you have to learn somehow I guess.


texts: Can a transistor transistion between cut-off and active without going through the linear region?

texts:
So it is operated in either saturation or cut off region but in between these two there is linear region (the intermediate region between the LOW and HIGH states of the transistor) and the transistor will obviously pass through that going from cut off to saturation and vice versa.

Can a transistor switch between cut-off and saturation without going through the linear region?


texts:
First of all, this question is not a duplicate of this or this.

I'm making an adjustable switching power supply (0-60VDC, 7A) with a panel  in front of it which contains a display and some buttons so that the user can adjust output voltage and current limit by "typing" manually (i.e. there's no potentiometer and the user does not want any). Expected resolutions are, 0.1VDC for voltage and 1mA for current (e.g. the user wants to type 23.4V & 1.234A). Of course, the same display will also be used for showing current drawn and actual output voltage.

Since there's no potentiometer for adjustments, I'm sure I need to use a microcontroller, a few ADCs for voltage/current measurements and DACs for generating reference voltages.

Without further ado, here's my question:

I'll go for high-side current measurement approach. Since the resolution is 1mA for current, I should be able to measure from 1mA to 7A but the problem is, I think I cannot measure 1mA with the same shunt resistor chosen for 7A. So, my solution is like this:

simulate this circuit – Schematic created using CircuitLab

(RELAY is from SHRACK with a current carrying capacity of 8A per contact. Both shunt resistors are 3W through hole resistors with low temp coeffs.)

My idea is to drive the relay on when the current exceeds 1A and off when the current is less than 1A. But I cannot foresee the effect(s) of relay's switch on and off action during operation.

What do you think? Do you see any problem with this? Any suggestions?


texts: Do it yourself operational transconductance amp?

texts:
While quickly prototyping some of diy-synth circuits I realized that I don't have OTA at hand, but I wanted to continue fiddling with the circuit. Is there a way to make OTA out of op-amps and transistors at hand? Quick googling couldn't find me any solutions.
If I understand correctly, OTA is OP-amp with current-controlled gain. Well, a differential amp with controlled current source should do the trick, right? Or there is something more to it?


texts: problem with fixed point butterworth implementation

texts:
I have designed a 2nd order Butterworth filter with MATLAB fdatool for VHDL implementation. the cuttoff frequency is less than Fs/10, which should be okay since fdatool uses prewarping.
Indeed, the floating point implementation works fine. However, after quantization to fixed point, even with very large word lengths (64 bit), the filter does not work as expected. Is there a way of fixing this? or is there another way of approximating a butterwoth response which will work with fixed point ?


texts: PWM square wave to DC voltage simple conversion

texts: How do I convert a PWM square signal into a stable DC voltage (0V - 3.3V) in easiest and reliable way possible? (preferably in programming- microcontroller)


texts:
I'm trying to understand the options when setting up an interrupt in a pic24fj128ga010. There in an attribute option for either auto_psv or no_auto_psv.

I understand that PSV stands for program space visibility. This a window through which program memory can be accessed through the RAM address space. This is very useful when accessing, often used constant variables. By declaring them constant they only reside in program memory and don't waist RAM space.

All that being said, what do these two options actually do?


texts: what does pull-up resistor and pull-down resistor mean? How do I implement them in my circuit?

texts:
I am trying to understand the basics of electronics and I often come across the terms pull-up and pull-down resistors. From what I understand these resistors help the switching logic devices like transistors.

Could you help understand the basics of these components in simple terms.

Edit 1:

I am trying to build a small feed back system that uses a transistor as switch. The system uses a buzzer that makes a sound when the yellow and gray components meet. The problem that I am facing is that the buzzer keeps making a low volume sound even when the components are not touching. I was reading about pull up and pull down resistors and would like to know how to implement it here

Figure 1. Buzzer schematic.

simulate this circuit – Schematic created using CircuitLab

Figure 2. The OP's schematic redrawn by @Transistor using the CircuitLab schematic editor. (There's a button on the toolbar.)


texts:
How can I query the system clock on an STM32F3xx to make sure it is what I intended to set it as?  It appears that I suddenly am operating much slower than before.

It looks like the HAL API (V1.5.2 via HAL_Driver/Src/stm323xx_hal.c) changed and I can no longer:

#include "stm32f3xx_hal_rcc.h"
...
RCC_ClocksTypeDef clocks;
RCC_GetClocksFreq(&clocks);
__NOP(); // <- Breakpoint here and inspect local variable


texts: Compiler error when using HAL functions for I2C communication

texts:
I am using the board STM32F3 and I am trying to establish I2C communication between the microcontroller and the accelerometer LSM303DLHC by using the HAL functions. This is the code:

uint8_t IC[4];

#define acc 0b0011001

IC[0] = 0x20;           // register adress

IC[1] = 0x87;          // data to write

HAL_I2C_Master_Transmit(&hi2c1, acc<<1, IC, 2, 10);

When I compile, I obtain the following errors:

error: #165: too few arguments in function call

error: #18: expected a ")"

I have no idea how to debug this code, can someone help me?


texts: Controlling a ring oscillator with a signal

texts:
So for example if you have a very simple oscillator such as:

How could I control this so that the oscillator is only in operation when a signal (x) is high. And not in operation when it is low?


texts: NodeMCU + PIC16F877A IoT Project Problem

texts:
I've searched the internet for my specific use-case but had no solution.
I have a circuit set up with PIC16F877A which perfectly displays a hard-coded text on a 16x2 LCD.
But I want to change that text via the internet from a website (or a Flutter developed app).
For example, The user enters some text in a text box and that is displayed on the LCD.
My main concern is that I cannot use Arduino since this is for a college project and it is not allowed.
I'm still learning this stuff and I would be really grateful if someone can give me some help.


texts: How voltage and power transfer in cascaded amplifiers work?

texts:
When there are three amplifiers that are cascaded to produce higher gain:

The source resistance should be lower than input impedance of first amplifier
The output impedance of first amplifier should be lower than input impedance of second amplifier
The output impedance of second amplifier should be lower than input impedance of the last amplifier
Then the output impedance of last amplifier should be matched/equal to load resistance for max power transfer

In short,am I correct to conclude that: On the way to the load resistance, we maximize voltage transferred but when in front of the load resistance, we maximize power transferred by matching the impedances, but this means the output voltage will then be half of what the last amplifier should have gained.
I also wonder why we don't match impedance between two amplifiers(just like how we match impedance of the last amplifier to load resistance) to also transfer max power?


texts: Do I still need tweaking after using gm/Id method if some of the MOSFETs are not in saturation?

texts:
gm/Id method links the design spec to gm, width, Id of each MOSFETs. There are some design examples that show how gm/Id is used in the circuit designs. They show the sizes of the MOSFETs and how it meets the design spec.
My questions:

Does gm/Id method guarantee the MOSFETs are in the saturation? I don't think so, but I need some confirmation since the design examples always show that the design meets the spec which means all the MOSFETs are in the saturation.

What should I adjust after using gm/Id method if some of the MOSFETs are not in the saturation?

assume that the circuits are the ones which require all the MOSFETs work in saturation (either weak or strong inversion).
edit2:
Let's say M6(and M5) and Mtail(showen as Iss) are not in saturation when I give a certain input VCM. I want to have a determined DC voltage on the output. let's say at mid point, half VDD. Before, I did it by doing so many trial and error as well as the precomputed LUT method and prefer not to that method again. I know that I need to find correct W and Vgs for each MOSFET, I also do not mind changing VCM, but do not know the efficient way to do that. I also want to make sure I understand what gm/Id method can do and cannot do, so I do not chase a ghost.


texts: Modifying an automotive 12V power outlet to disable power when car is off?

texts: Recently, on a business trip, I had a rental car. Now, in my car, all of my 12V power outlets are always on. On the rental car, some of them were always on, some of them were only on when the car was on. Is there a way that I could hack my existing 12V outlets to either have some of them only be active when the car is on, or better, add a simple toggle switch that will toggle them between running always or only when the car is on?


texts: Does the depth that you plug in an appliance have an effect?

texts: Let us assume that we have an outlet that is a bit into the wall(receptacle is set behind cover, so difficult to plug in larger plugs). If an appliance - lets us say a phone charger - were plugged in but only about 5/6 or 7/8 (essentially small difference) the way in, would that affect charging or draw of current? Or would current be consistent as long as the prongs are in contact with the wire?


texts:
I would like to benchmark my ADC.

I can calculate a sensitivity value based on the information in the datasheet. However, I would like to measure/benchmark this figure.

Is there a standard method for doing this?
How would you go about measuring accuracy of any ADC?

Considering this is a 24bit chip that can measure down to few µV, it is not very straight  forward to plug in a signal generator.

Would high ratios of voltage divider help to generate a low noise low voltage signal in µV range to feed into the ADC?
Wouldn't Johnson noise stop one from using high value resister in this case?


texts: Using cheap RF module encoding with UART in a commercial product

texts:
For my graduation project, I need to design a system that transmits several different data packets to the computer wirelessly. It needs to have a potential to be commercial product, so both functional and inexpensive. It doesn't have to be bi-directional.

I found cheap modules RFM110W and RFM210W, transmitter and receiver, respectively. Since I am trying to write whole firmware in AVR Assembly, to make it fast and easy (to not write encoding part of code), I ended up like this:

Edit: (in the picture, it is not 443 Mhz it is 433 Mhz)

With a little bit data handling, It works well at 1200 baudrate and data can be easily captured on serial monitor.

Because the UART is not for encoding RF signals, using it for encoding data seems like a little bit tricky. And I have concerns about using it in potentially commercial product.

Is it reliable for simple data transmission in the aspect of engineering?

If it's not, what are the potential problems I should be expecting to face with?

Edit:

FT232 USB to UART bridge datasheet

RFM110W Transmitter Module

RFM210W Receiver Module

Example romanblack.com


texts: How do mobile phone chargers produce regulated voltage?

texts:
I have come across many mobile phone chargers/power supplies that produce a regulated 5 volt output but I don't see any voltage regulator or a Zener diode inside. I want to know how these power supplies produce the regulated output.
Moreover, why can't we simply provide a 4.1 volts input to batteries instead of using 5 volts power supply with an overcharge protection circuit?


texts: How to go about testing which pins to short to turn on Daly BMS?

texts:
I have a 7S DALY BMS, but I forgot to buy the 'SOC (state of charge) display board', which has LEDs that display the state of charge, and crucially, a switch to turn on the battery itself.  The board connects to the BMS with a 7 pin connector.   For an example, see:
https://www.aliexpress.com/item/1005001339044095.html
I could order the 'SOC Display board', but it will take months to ship, and I don't actually want that functionality.  I just want a way to turn on the BMS.  I suspect that if I short two of those pins together, the BMS will turn on.  My question is, is there a safe way to try all the combinations, while protecting the BMS?
I guess, more generally, is there a safe way to approach this type of problem? I am often trying to recycle things, and I'd like to improve my skillset.
Thanks


texts: EMI: CFLs vs Incandescent Lights in Your Lab?

texts: Being a green-oriented treehugger, I've put in all CFL lights in my house.  Just as much light for about 1/4 or 1/3 the power.   Nice, but flourescent lights put out a lot of EMI.  Does this cause trouble for anyone?  What are your experiences of CFL or other flourescents versus incandescent bulbs  in the room or house where you do sensitive electronics work?   Does anyone stick with ol' tungsten just to keep EMI down?


texts:
So I have STM32F4 board and long story short - I am stuck at putting a user defined number (0 - 60) in FLASH memory, so after restarting, I could use last-used-settings.
How do I allocate correct space in flash memory, so it doesn't interfere with my code? How to I store it?


texts: Options for dual-role USB on an embedded device supporting serial connections

texts:
I am new to USB and working on an USB-capable embedded device for a customer who has designed the hardware. The target is an STM32F4.

The use case is that this device A) When connected to a computer, should appear as a COM port. B) When connected to a peripheral device be able act as host to talk to it over a COM port. For example, the initial peripheral will provide a DB9 connection so there would probably be a USB to RS232 dongle between my embedded device and the peripheral. So, in this case our peripheral would be the dongle, I think. C) Longer-term goals would be to support other peripherals for example flash drives and user input devices.

Item A) above has already been implemented using ST's CDC class driver. I have lots of questions regarding how to approach this.

My understanding of the On The Go Supplement is that there are basically two ways to approach this- either as an embedded host or using OTG.

1) The spec seems to indicate that if using the embedded host model, one will have to support at least two USB connections, presumably going to multiple ports on the micro, one configured as a host connection, one configured as a peripheral connection. Is this correct?

2) The customer had planned to use OTG and hardwire the ID signal to ground (Host) at the micro with the plan being to switch roles (maybe via HNP, if both support OTG?) as needed. I don't believe this will work given that when connecting to a PC the PC will assume it is a host, correct?

3) I'm a little confused by the relationship between CDC(ACP) and VCP. It seems like VCP is a specific type of CDC but is not clear to me how it extends it. Given that the customer has already implemented A) above using the ST CDC driver, it seems odd to me that this works without VCP?

4) If I wanted to implement B) above (let's say using OTG) what is needed on my side given that the device already acts as a peripheral CDC? I.e. what is needed to act as a host of a CDC connection beyond what is already in the driver when acting as a peripheral?


texts:
I would like to create an Magsafe 1 to USB C adapter to re-use my macbook magsafe charger on my usb-c macbook.

I have these components below and already tried to connect both V+ and Ground with no luck, it does not work. I guess I should connect the charge control pin somewhere but on which usb-c pin ? Or maybe it's a bit more complicated than just re-mapping pins ?


texts: How to measure output voltage and current of a VFD?

texts:
Is it possible to measure the output of a Variable Frequency Drive without relying on it's display data? I tried to measure the line voltage with a DMM and current with a clamp meter but it shows inaccurate results. I'm running the motor at 50Hz and the carrier frequency is 6kHz if that matters.

Thank you in advance!


texts:
I am using an LT1630 as a buffer...

I know its not the greatest OPAMP for the job because it has fairly Hi input current, but It has good DC characteristic, HI current drive, and rail to rail capabilities which is what I need for this circuit.

Its unity-gains stable as far as know. The Datasheet does not explicitly say it but the example circuits don't show a capacitor in the feedback.

I'm buffering a Hi-Z resistor divider circuit.

The top circuit shows an equivalent resistor in the FB and a 10pF cap. The Datasheet says to use a 10pF cap in the FB to counteract instability caused by the input capacitance.

The Bottom circuit has no additional components...

My question is: Will the top circuit operate as needed even though FB resistor is fairly Hi?

Thanks
Tony


texts:
I have a rowing machine that I'm trying to replace the computer on.  It uses a phototransistor switch to detect flywheel rotation speed.  The phototransistor is an Optek OPB365T55.

Here is the datasheet.

TT electronics provides an App Bulletin showing a sample circuit and formulas for calculating the values for R1 and R2. Here is the link.

When I examine the existing computer's circuit board it seems they are using a value of 5.6K for R2.  This seems to be in line with all of my research on this type of circuit.  Usually, I find most similar circuits are using values from 4.7K to 10K.

My application uses the circuit config from Figure 1 in the App Bulletin.  The formula given for R2 is R2 = (VCC - VCEsat)/Ic(on).  Using the values from the datasheet (Ic(on) 3.5mA to 14mA) and with VCC = to 3.3V I calculate a value of between 207 Ohm and 828 Ohm.  This doesn't seem in line with what the observed circuit is using or with any of my research.  Please educate me on what I am missing.  This is fairly new to me.

By the way, my calculation for R1 would seem to be 100 Ohm.  Does this seem correct?

Thank you for your help.


texts: Reading the status of 48v connection with arduino

texts:
I have an arcade crane machine that has 3 DC motors that all run at 48v, i would like to connect an Arduino in parallel with the motor that lifts the claw up and down so i can see which direction the motor is going in so it will update a strip of WS2815 addressable leds that serve as the attract mode lights. The machine's main control PCB has 7 relays, one for each direction and for the claw solenoid, it basically flips the polarity when it needs to go the other way.
I was thinking about using resistors to lower the 48V to 5v and then connecting both wires to the Arduino's digital pins, then i could read them as HIGH or LOW, but I'm not sure.
Thanks in advance.


texts: Getting bad clipping issues with this 3 stage amplifier

texts:
What am I using? 3 stages of amplification. An input voltage of 10mV peak or 20mV pkpk into the first stage.

1st stage: NJFET Common Source. Using a voltage gain of 3.

2nd stage: NPN BJT Emitter Resister. Using a voltage gain of 30.

3rd stage: NPN BJT Emitter Resister. Using a voltage gain of 30.

What is my problem? I am getting bad clipping on my final output in multisim simulations. The first two stages simulated great. I got a voltage gain of around 68 from the first two stages with no clipping. I know these two stages work correctly. The last stage is where I'm getting my clipping.

Below I will include images of my circuit, my output/input values, as well as my calculations.

Why I need your help I need to get rid of this voltage clipping. Any suggestions would be great. Thanks!


texts: Is this the correct way to use this Audio AD Converter?

texts:
I have a PCM1804 -- and I want to use it convert the stereo audio signal from RCA/SCART to a TosLink Optical output - outputting a PCM signal.

I have been using its datasheet found here : PCM1804 datasheet

This is the proposed circuit as my starting point. I know there will be  mistakes, and missing components in here - this is exactly what I hope to identify and understand. Any advice would be very much appreciated:

simulate this circuit – Schematic created using CircuitLab

I have never used a chip like the PCM1804 - so am fully aware I have got this wrong, and this is really where I am looking for some guidance.

Please offer constructive support in building the approproiate circuit around the PCM1804. Explaining why each mistake, or missing component is necessary will really help me to understand what is going on! Thank you!


texts:
The Arduino Uno has one main controller and one controller serving as USB-to-serial interface. The RX/TX pins of the main controller are directly connected, via 1k resistors, to some pins of the "communication controller".
RX/TX pins are also on one of the pin headers.

I'm wondering whether the TX pin of the "communication controller" (connected to the RX pin of the main controller) goes into high state (or is switched to input state) when no USB cable is connected and whether I could use the RX/TX pins on the header to connect some other stuff on a homegrown shield and perform serial communication through this shield.


texts: 555 Timer Stops working after a few seconds

texts:
I'm building a LED dimmer using a 555 timer (yeah, lame I know). I'm using it to produce photographic flat frames which require perfect illuminated fields even with shutter speeds as low as 1/1000 of a second. I wanted to build a variable light dimmer which operates on a PWM frequency higher than 10kHz. I've built everything on a breadboard and it was working nicely. Now I've soldered everything to a prototyping PCB and things get weird. Not sure if something got lost in translation but I remember running this circuit for almost 1 hour, testing currents and voltage drops.

simulate this circuit – Schematic created using CircuitLab

Simulation with circuitjs: Run Simulation

The Setup

I'm driving a LED system which is kind of a black box for me. All I know officially is that it's a 12V system. I've measured the load and there's 350mA of current flowing through my power supply when I connect the LED system with 12V. This indicates a total resistance of ~ 34.3 Ohm.

Now I'm driving the LED with an NPN darlington BJT with an hFE of ~ 1000. It's a TIP212 transistor. Maybe not the perfect choice? That's what I have, along with the PNP TIP version and some low current BJTs. The 555 timer drops my voltage down to 9.86V on the output and as far as I understood, to keep forward bias, Vc cannot be greater than Vb - 0.7(?!). Since this is a darlington setup, I guess that's why I only measure 8.66V at Vc, although connected straight to the 12V supply.

I decided, due to the sufficient quality I get with 8.66V (I need a really dim light), I'll just go with that. I naively estimated the load of the LED to be around 252mA. As per the theory, I should, therefore, have 0.25mA at Ib, right? That would mean a resistor Rb of ~40kOhm right? I tried that, but the current Ib was limited and I couldn't figure out why. I started trial and error exercises and landed at 10kOhm. My testing method during trial and error was rather scientific, but I just gauged the light intensity and compared it to direct 8.66V brightness.

Problem and Symptoms:

After I soldered everything to a prototyping PCB (Schema is attached), my system started to show symptoms. There was a flickering that started to get worse and then the dimming function was gone. The LED was the same brightness even at the lowest variable resistance. I measured the output of the 555 timer using my oscilloscope and there was just straight current without any modulation. If I disconnect the circuit for some time and reconnect it, the PWM is showing for about 3 seconds, before it flattens out again. Also, the flattening is immediate.

I know a lot of you guys probably already see 10 things I'm doing wrong, and I'm so much looking forward to hearing what it is :-)

Happy new year!!!!

Update 01.01.2019

Meanwhile, I've done some more testing and thanks to the Q&A on this question I've been running some simulations with circuitjs. I've also tested to switch from the darlington NPN BJT to a power MOSFET (HEXFET from IR). Running some tests in simulation made me realize a problem which can occur if the variable resistance (potentiometer) is turned all the way down to have only minimal resistance. The circuitjs simulator must have a potentiometer with very low resistance min/max values. I've noticed that in combination with the 10nF capacitor, there was a negative voltage spike on the trigger and threshold path in the circuit everytime the cap got discharged. To prevent that, I've introduced a 150 Ohm resistor in series with the potentiometer. I've resoldered my PCB and the problem seems to be gone. I will also apply this change to the previous PCB board wich is the one I've posted this question and verify if the negative voltage spike is causing the issue there too. Does anyone know is what I observed could be the root of my problem and the symptoms I'm seeing?


texts: im reading a arm based mcu board schematic and there is 100R resistor (R30) at external 25MHz oscillator source. What is the main reason of using serial resistor at clock line ?


texts: Calulating the total thermal power in three phase system

texts:
In my book I have following task that actually has a solution. However I do not understand the solution idea and that's why I'm asking you guys to help me understand that if possible.

Why I do not understand are following:

Why do we have a \$U_a'\$, \$U_b'\$...?
Do we in the end use \$U_a\$,\$U_b\$,.... or \$U_0\$?
How they calculate the \$I_1\$ or \$I_2\$? Why do they use \$U_0\$ when
calculating the current but do not use \$Z_{L0}\$.


texts: LED driver: how to choose current and voltage?

texts:
In my project I have a microcontroller which has to light 3 groups of LED. Group A has 3 LED, Group B has 2 LED, Group C has 1 LED. There are all the same LED. In each group the LED are in series.

Let's consider group A :

VCC is obtained from a positive voltage regulator. The lighting of the group is controlled by an MOSFET which acts as a switch. The microcontroller is driving this transistor open or close.

I have never done this before so I have questions :

How do I know which voltage I have to appply with the regulator for each group? Is it the sum of each forward voltage ? Let's consider each LED has a forward voltage of 3 V. I would then need to apply 9 V, 6 V and 3 V?
Do I need a series resistor in each group?
How do I know the current which will be drawn by the LED in each group? How do I set the current to 1 A in each group for example?


texts:
My input signal is a sine of amplitude 1 so the input ranges from -1 to 1 so the range is 2 (pk-pk.)
On the other hand, the flash voltage divider ladder goes from 0 to Vref.
Which one of the two options is considered full scale for SQNR?
In the SQNR formula shown below we see they take a range and divide it by 2, so it may say that we take peak to peak value of the input and divide it by 2 (to get the amplitude ) of the signal.
Why can't the flash ladder voltage range be considered as full scale voltage?


texts: Dual mosfet 8205A - lithium battery protection circuit

texts: This is a basic lithium battery protection circuit, but looking at the dual mos-fet part of the circuit, It doesn't make sense to me. It's a 8205A dual mos-fet, with its drain connected together and each of its source connected to the negative of the input and output. Normally, the drain of a mosfet is connected to the positive. in this case both are connected to the negative if they are turned-on. I don't understand! what voltage will be the drain with respect to the ground?


texts: Configuration settings for programming flash memory

texts:
I need to specify a memory addresses settings in the configuration file for programming flash memory with Macraigor Flash programmer utility. The device is BCM3360 (MIPS32) chip and flash memory is 640P30T. The full  marking on flash chip is 640P30T A9027310 Z9022040B, I think its Intel flash chip 28F640P30T, but I'm not 100% sure though, it can be also Micron NOR Flash.
I've selected 28F640P30T on  'Flash' tab of OCD Flash programmer, but I don't know about specific memory addresses I need to specify.
In the 'Configuration' > 'Program' tab:

Target RAM starts at: $0000
Starts at: 0x00000000
Width: 16 x 1

The flash configuration file includes settings:

[SETUP]
CpuVendor=BroadCom
CpuChip=MIPS32
CpuEndian=BIG
FlashVendor=Intel
FlashChip=28F640P30T
RamAddress=$0000
FlashAddress=0x00000000
FlashWidth=16
FlashChipsPerSector=1
LittleEndian=0
SimCount=0
MemoryCount=0
TLBCount=0
ScanChainCount=0

Can anyone tell me what is an actual memory map for BCM3360 and Intel 28F640P30T flash memory? I need to specify the base address of RAM, the base address of Flash Memory, the bus width of Flash device.

RamAddress=$0000
FlashAddress=0x00000000
FlashWidth=16
FlashChipsPerSector=1

Since this hardware have no serial interface which usually displays the full configuration details during booting process, I can't get that info. Can anyone advice about mentioned settings?


texts:
The question is basically: why use capacitor in this particular DC circuit? Generally, as I read in the thread below, using a capacitor in DC circuit may have different reasons and purposes. Given my lack on knowledge in the topic I do not know what is the reason for using it here.

What is the role of capacitors in DC circuits like motherboard, graphic card etc?

Here I am talking about the 10nF capacitor right after USB GND. Basically it connects USB GND with USB VCC. Given that USB is DC isn't it just a break in the circuit? Or, if we assume that some significant current can actually flow there, wouldn't we be causing s/c?

I understand that that this partial circuit shown at the bottom of the picture is something we could use instead of this 10nF and ferrite bead setup. So my thinking is that all these capacitors are here only for some EMI filtration. Is that correct? If yes, why is it so important to filter it here on the power terminals rather than maybe data terminals? Will it cause problems if we skip it completely? And why we are doing nothing with the data terminals? Thanks.

The picture comes from
http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf


texts: How can I troubleshoot/use a 14 wire motor encoder from Harmonic Drive?

texts:
I have an AC Servo from Harmonic Drive (type RSS-20-6006S) that I have no information on.

I am used to encoders with several leads, including differential A B and Z wires, but I have never seen 14!  They each have a unique color in a rainbow spectrum.

I can't seem to find much documentation about such 14 wire encoders, but I saw them mentioned as "a standard" somewhere in Harmonic Drives website, but can't seem to find any specification.  Any suggestions on how to troubleshoot this encoder?  Is this an industry or Harmonic Drive standard that maybe was "phased out"?


texts: Can I keep Li-Ion battery 'charging' continuously at 3.7 V?

texts:
I have built a Raspberry Pi NAS and it is powered by a lithium-ion battery through a 5 V step-up module - the one used in powerbanks. The battery is a 18650 Li-Ion battery which is kept continuously at 3.7 V by an adjusted LM2596 module.

I am not directly powering the Pi through a 5 V mobile charger because of two reasons - brownouts and blackouts will cause the NAS to reboot. Second, no cheap-ish mobile charger's output is free from AC ripples and Y-cap leakages, which might shorten the life of the Pi. And it'll be overkill to buy a well-constructed Apple charger that's fairly foolproof.

Now, I was wondering, is it harmful for the lithium-ion battery to be kept at 3.7 V? Does it cause continuous trickle charging, that is harmful for lithium-ion batteries? Or does the battery take zero current once it's at 3.7 V?

The circuit is like this:

!


texts: how to pass parameter variable to module in verilog

texts:
I need some help changing dynamically parameters of one module

I'm trying to extract part of network data that it comes from the top module  and goes to the internal modules

In specific I have one internal module (field_extract) that receives 4 inputs:
the clock, data(network data from the top module), a signal that indicates  the start of frame (sof), vld (indicates that the data is valid)
and two parameters one of them is how many bytes I want to extract from data and the OFFSET of these bytes from the start of frame, the parameter that I want to modify in execution time is the OFFSET

Also, this module has two outputs, one is field(the value extracted from the data) and vld(asserts when the data it was extracted)

Instantiation of this module looks like this:

field_extract
#
(
  .BYTES(1),
  .OFFSET(TYPE_OFFSET)
)
Type_extract
(
  .clk(clk),
  .data(data),
  .sof(sof),
  .vld(vld),

  .field(Type),
  .field_vld(Type_vld)
);

my question is how can I change "TYPE_OFFSET" depending on a variable parameters

What I mean with this is: I want to extract "Type" in certain OFFSET depending on certain values extracted from the frame in the past, so "Type" is not at the same position of the frame if the first part of the frame contains certain values something like this:

always @ (posedge clk) begin
   if (First_Message_Type == MESSAGE_TYPE_X) TYPE_OFFSET <= 50;
end

I know that the last code is not possible because TYPE_OFFSET is a constant but here is the question again... there is any way to modify this constant in a time of execution?

I hope this has been clear Thanks for your time and help.


texts: Why does the potentiometer burn up in my setup?

texts:
I connected a potentiometer to my DC power supply (max 1A, 12V), and then connected a motor to the variable voltage side of potentiometer as well.

The potentiometer is just 1K.

When I tried using some China-made motor (RS-545) there appeared sparks and red light and subsequently burning smell coming from potentiometer as it near the 12V range.  Why is it so?

Is it caused by back EMF?


texts: Error with phase noise to jitter calculation

texts:
I'm trying to get the jitter for an oscillator. The nominal frequency \$f_0\$ is 10 MHz, I'm integrating from 1 Hz to 100 kHz.
The specifications are given as "RF Output Phase Noise (SSB)", in dBc/Hz.

The formula I'm using is:

\$x_{RMS}=\frac{1}{2 \pi f_0} \sqrt{\int_{1 Hz}^{10^5 Hz} 2 \mathscr{L} (f) df}\$

The corresponding python code is:

import numpy as np

f  = np.array([1e0,1e1, 1e2, 1e3, 1e4, 1e5])
Lf = np.array([-50,-70,-113,-128,-135,-140])
f0 = 10e6

Sphi = 2*10.0**(Lf/10.0)

jitter = 1.0/2/np.pi/f0 * np.sqrt(np.trapz(Sphi,f))

print jitter * 1e12,
print 'ps'

raw_input('done')

The result is:

159.083754236 ps
done

Two different online tools gave me an identical results of 68.66 ps, and this is also closer to what I'm expecting from lab data.

Am I using the formula incorrectly? Or maybe I made a mistake in my code?


texts: Voltage Gain decreases when load resistance included

texts:
Why does the voltage gain of a  (voltage divider) common emitter bypassed emitter bias bjt amplifier decreases when putting a load resistance on the output Vo?
I mean Vo should remain the same because resistances in parallel have the same voltage across them.
Link below provides the image for the circuit diagram:

https://www.google.mu/search?q=voltage+divider+bias+bjt+amplifier&newwindow=1&espv=2&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMIksf_me-UyAIVRlwaCh3x6w9j&biw=1366&bih=667#imgrc=ZAlOvfkzwcITRM%3A


texts: Electrolytic Capacitors damaged while Soldering

texts:
While adding a new lead to a pcb board by soldering iron touched one of the electrolytic Capacitors, and melted the plastic casing of the Cap.

Should I replace this Cap?


texts:
Lets say I want to realize a logic function in CMOS gates.

I have a function like this
$$Y = (¬A *¬B) + ¬C + ¬D$$

If I had a function without inverted inputs:  $$ Y = ( A*B) +C +D $$ it does not present a challenge to me but with the inverted inputs this is much harder for me.

What do I have to do to model these functions with CMOS gates ?


texts: e2 studio undefined reference to 'posix_memalign'

texts:
I need some help to solve this error. I am new to use e2 studio of Renesas. I started to import and build a project, which used for GR-Peach board. Then I got this error:

My toolchain version is 8.3.1.20190703.
And the file definition is stdlib.h in directory C:\Program Files (x86)\GNU Tools ARM Embedded\8 2019-q3-update\arm-none-eabi\include

#if __POSIX_VISIBLE >= 200112
int posix_memalign (void **, size_t, size_t) __nonnull((1))
        __result_use_check;
#endif

I also tried changing -std=gnu99 and using aligned_alloc instead for posix_memalign but they not worked.

// definition in stdlib.h
/*
 * If we're in a mode greater than C99, expose C11 functions.
 */
#if __ISO_C_VISIBLE >= 2011
void *  aligned_alloc(size_t, size_t) __malloc_like __alloc_align(1)
        __alloc_size(2) __result_use_check;
int at_quick_exit(void (*)(void));
_Noreturn void
    quick_exit(int);
#endif /* __ISO_C_VISIBLE >= 2011 */


texts:
Is there a way to make an ungrounded simulated inductor?
The figure below shows a grounded simulated inductor. I was wondering if this circuit could be altered to simulate an ungrounded inductor.


texts: How does a junction-less transistors work?

texts:
I have recently read in a book that in 2010,junction-less transistors were developed.

I can't understand how a junction-less transistor can be used to amplify current or voltage with having any junction in it or rather how does it work?

Can someone explain me it's working?

I read about the construction in google's links, but the working given there doesn't help me a lot.


texts: SIM card power supply design, from 3V/50mA into 2.7V/10..100mA

texts:
I am designing a SIM card with RF radio included. The radio with its CPU needs minimum 2.7V to run. The current consumption is my problem:
- for a period of 50msec (during transmission), it requires 100mA or more
- for the same period afterwards, there is an idle period where it needs less than 10mA

The SIM card is plugged into any cell phone, which supplies on the SIM connector 3V/50mA guaranteed.

My idea is to take advantage of my radio idle period, charge something up, and add that charge to my high demand period.

In short:
- supply to SIM card from the phone is 3V / 50mA (no more current allowed)
- the SIM circuit requires 2.7V minimum, but the consumption needs to alternate between 10/100mA (50mA supply is not sufficient)

Sound like 'just add a capacitor'... but here is my last obstacle: SIM card is TINY, we have a total of about 8 x 10mm

We have tried to use a charge-pump to hold the 2.7V for as long as possible, but unless we are wrong, the capacitance needed is 1mF which we do not see how to do in the small size we have available.

Anybody has any smart idea how to solve this?


texts: Looking for ideas for a 5V power supply with 12V battery backup

texts:
I'm looking for ideas for a 5V power supply that will run from either 220V or 110V and have a battery backup. I want to use a standard 7AHr 12V sealed led acid battery.

I was looking at capacitive transformerless power supply but the unit I use pulls about 1.2Amps every now and then. Capacitive transformerless power supply can only supply low current outputs. It looks like I will have to use a transformer.

Is there a battery monitoring and charging chip, that say works with 12V. I can always use a DC/DC convertor to convert the 12V to 5V DC. I found it uses much less power that a 7805.


texts:
I've been looking at creating a simple circuit to slowly turn a halogen daylight bulb on over about 30 minutes as soon as power is supplied to simulate dawn.

I've got a 240VAC 42W halogen bulb that will be used in conjunction with a 7 day timer socket. I've been looking at various triac and triac opto driver (MOC3020) circuits to try and find one that will do this but they all want to be really fancy and use microcontrollers or other such things to do far more than I need. I just want a simple circuit that will brighten the bulb over a set time (30m) when it is turned on by the timer socket.

Help with values and component ratings would also be greatly appreciated.

Thanks for the responses.
Further to this; size and heat dissapation are factors for this circuit as it will need to fit within some sort of lamp holder, also when I have looked at the triac solutions they all talk about chopping the ac waveform and doing from the zero crossing point to provide a smoother operation which made me think of the following:

Is it feasible to chop the ac waveform with a pwm at a higher frequency (5kHz)?
Would this make it buzzier of lessen the buzzing or is it just totally unnecessary?


texts:
The following circuit modulates the SIG wave with a 1kHz CLK signal and produces the OUT resulting wave.

I have read that the superimposed wave has an amplitude of the sum of the original waves. If two waves are ASIN(wt) and BSIN(wt) then the superimposed wave has an amplitude of A+B.

What I don't understand is why the OUT wave has less amplitude than then the SIG wave, when the SIG and the CLK are in phases!

If we zoom in we can see some detail:

The amplitude of SIG wave is = 2V
The amplitude of CLK wave is = 1V

How to calculate the amplitude of the OUT wave?


texts: What options for 16 bit audio sampling to low cost microcontroller

texts:
We have a platform based around the LPC1313 -- 72Mhz M3. This, and many other microcontrollers with similar specs look limited to 10 or 12 bit A2D.

If I want to sample single channel 16 bit (16kHz) audio, what are my design options?


texts: Why simulink step response differs from matlab's step function?

texts:
step response is different in simulink showing oscillatory behavior unlike in matlab step function

Transfer function

Step response

Block diagram in simulink

Simulink scope


texts:
I am currently involved in developing a resonant-converter for research purposes. One idea was to have two separate boards for each side of the involved transformer, while the heavy transformer could be independently fixed to the case. Connecting those parts could mean using connectors/plugs or soldering the wiring directly on the PCBs.

What I am unsure off:
To my knowledge connectors behave differently at higher frequencies, usually showing increased impedance. Obviously this would impact efficiency. So far I only know HF connectors for communication/RF or similar which address this. Would we need special connectors for this application?

The resonance frequency will be some hundreds of kHz and the working frequency will max out below 500 kHz. The desired signal formed by the resonance circuit is sinusoidal. The wiring would see about 400 V, 16 A (rms).


texts: If a PIC MCU provides multiple Vdd/Vss should you provide power to them all?

texts:
Take a look at this example schematic:

The chip in question is the PIC18F4550 and as you can see power is provided on both sides (with a 100nF cap to smooth noise I guess). Is this strictly required or could you put power into one side and just ignore the other? I know that I have just put power in one side and everything still seems to work fine but I feel uneasy with doing that. I feel that they would not waste pins that could be doing something useful by having an extra pair of power in/out pins.
For what purpose does this PIC MCU (and others like it) have multiple power pins?


texts:
The on/off button of my radio is not working.

Pushing the button (on top of the board) has no effect.
Short-circuiting the two solder pads (in the red oval) does turn the radio on and off.
What should I do next?
What I tried (with no luck):

WD-40.
Pressing the button very hard.


texts: need advice with LM317T current limiting circuit ,new alternative

texts:
i am using  an LM317 as a Current Regulator  for series LED similar to protecting LEDs From over current ( in time of short circuiting) for my LEDs and Mosfets, similar to this picture:

the problem is that i need bigger voltage source ( up t0 20V) and momre cost fo voltage source and LM317 IC, because of dropping voltage on the LM317 ( in range of 4.5v to 5.5V) so if i found another eleman ( similar to fuse or ...) for protecting LEDs AND MOSFETs at the time of over currenting. so is there any alternative (for protecting LED ANd MOSFETS) and is it OK i use one fuse instead of current regulator ( which one is first to burning : MOSFET or Fuse).
Thanks a lot.


texts: SD Card Trace Inductance and Capacitance

texts:
Most (if not all) SD card datasheets contain the following requirements, which I gather are copied from the standard:

16nH max trace inductance for f < 20 MHz
40pF max line capacitance

Two questions:

Why does the SD standard and/or datasheet need to "micromanage" the amount of trace capacitance and inductance? Can we just meet the timing requirements and be fine? I understand the relationship between too much L-C on the line and signal integrity, and that they go hand-in-hand, but am confused why the standard requires specific L-C values.
Is there an explanation for the "f < 20MHz" condition on the inductance requirement? It seems vague what is required at higher frequencies (our system is clocking the SD card at 50 MHz). Also, why would this be a 'less-than' spec, and not a 'greater-than' spec?

Miscellaneous Background: we built our PCB with an Altera Cyclone V SoC driving a MicroSD card. It wasn't until after the first proto we realized the L-C requirements of the SD card interface. We currently do not meet the L-C requirements given the length of our traces (2.12in for the clock trace). The inductance is 7.8 nH/in, plus three vias at ~1.2 nH a pop brings us to a solid 20 nH, not including the inductance of the SoC's BGA at 8.3nH. We will try to shorten up the traces in Proto 2, but would like to understand the requirements of the SD standard (which we don't have access to directly) before spending considerable effort trying to meet the specs.


texts: How do multimeters measure capacitance of polarized capacitors?

texts:
On my multimeter it doesnt matter in which polarity I put polarized capacitor.

How is it made?

If it is just simple rc circuit that measures charging time, how does it not damage capacitor in reverse voltage?


texts: What's the best method to responsibly dispose of used alkaline batteries?

texts:
Years ago, I would have typically tossed typical, Alkaline batteries in the trash.  I have been reading more and more on this topic, and while I see that rechargeable batteries should be recycled, I'm finding conflicting evidence on how best to dispose of Alkaline batteries.

For example, Duracell claims that since they removed the mercury from batteries, they're safe for disposal.  But others claim (see Disqus comments at the bottom) that since all batteries contain various kinds of heavy heavy metals and should thus be recycled.


texts: I would like to set up something where I use a miniature solar cell (like this) to power a push solenoid (something like this), so that when light hits the cell, the solenoid pushes. I know basically nothing about engineering, but I know that the 4 watts produced by the solar cell are not enough to push a 7 watt solenoid. How could I accomplish something like this?


texts: How to setup a development network for the ENC28J60 on XP?

texts:
I'm working on an ethernet connection with the ENC28J60. During development, I'd like to connect the chip to my computer directly (i.e. not via a gateway). This computer is running XP, has a primary network interface over WLAN (local IP 192.168.1.69 (DHCP assigned), default gateway 192.168.1.254, subnet mask 255.255.255.0) and I do not use the ethernet for other connections.

How should I setup the network? Normally, you'd use the default settings with DHCP to get an IP address assigned, however now, I think I have to set this up manually. Is this correct? How should I setup the ethernet configuration on my computer?

The ENC28J60 and its PIC's configuration use the IP address 192.168.0.140 for themselves, and 192.168.0.1 for the default gateway.


texts: What's the use of ground coupling on digital oscilloscopes?

texts:
What's the practical use of ground coupling on modern DSOs? I know that it can be useful on analog oscilloscopes to adjust the ground exactly to a graticule line, but from what I've seen, most of the digital scopes have a sort of marker which shows exactly where the ground is on the screen, which removes the need for ground coupling.

Is there any other use for that option that I'm not aware of?


texts:
IPC-7351 gives a pin out and a 0 degree rotation for SOT23-3 packages; but, IC vendors use many different pin numberings.

When I make my library component should I use the IPC pin numbering for all of my parts or use the datasheet pin numbering for each part?

I can put functional labels and put the part body outline in the schematic symbol to reduce confusion there.

I am most concerned about confusion at the board assembly house. It seems to me that they would prefer consistent IPC numbering and rotation.  But they might look at the datasheet or some other info from the manufacturer resulting in confusion.


texts:
I have a 3-phase bridge rectifier which uses IGBT's shown in the image below. The circuit works perfectly and the voltage on the output (unfiltered) is exactly as expected. However the gates are referenced to the collector. Now in order to turn on an IGBT the gate voltage must be greater than gate-emitter voltage.

When I reference them to the emitter the circuit does not work but does work when referenced to collector.

Can anyone clarify why this is??

Thanks.


texts: Terminating unused unity-gain Unstable op-amp

texts: I am trying to terminate the unused unity-gain unstable op-amp. I have tried to terminate it with the typical unity-gain stable configuration (http://www.maximintegrated.com/en/app-notes/index.mvp/id/1957) and so far in the lab, it seemed to work and gave stable output. However, I am still concerned about it as it is unstable at unity-gain region mentioned in datasheet. I want to learn if there is anything more robust than using unity-gain termination configuration. The amplifier I am using is OPA2614 from TI. So far I have tried this to stabilize the output at 12V but don't know if this is the best way.:


texts:
I want to study the bandgap voltage reference and use it in somewhere. But first I would like to learn more about the basics of generating and using voltage references (mostly for operational amplifiers). What course of studies should I take?

I have worked on operational amplifiers, but I have usually used a ready-made reference from different lab devices. It is the first time I have encountered a situation where I want to add a voltage reference of my own. What kind of things should I study and what should be the approach to learn about this stuff?


texts: What is the alternative for BYW98 diode?

texts:
We are using a driver circuit (L6203), however though, the diode in the device is broken, and we can not find the exact diode on the market. Would any body please, suggest an alternative diode for BYW98 diode?
I would appreciate any comments.
My datasheet is
here.


texts: Difficulty in calculating output impedance for the emitter follower

texts:
This is the pic for the emitter follower using BJT.

Is there a direct way of calculating output impedance instead of the way proceeded in the text book?

Textbook procedure:

Ps: The images are of >2mb and couldn't be uploaded directly. excuse me for any inconvenience.


texts:
I'm trying to make a boost converter, from a 9V battery, but I'm not sure if understand the schematic entirely:

.

The load appears to be a resistor, leading me to my question: how does the voltage even get stepped up? As you begin to charge the capacitor, would it not discharge, through the resistor, immediately?


texts: What is the off-white powdery material found at the base of GU5.3 light bulbs?

texts:
I've noticed most GU5.3 light bulbs, both halogen and LED, contain a granular material at the base.
There seems to be considerable variation in how much of this powder is present, even within the same brand and type of lamp. Sometimes, the base is filled with the powder. Sometimes there are large gaps or empty spaces with only a small quantity of the powder near the connectors.
A small amount usually extrudes through the holes where the pins pass through casing, and I occasionally note slight discoloration on some pins where this occurs more than usual.

What could this powder be? Could it be cement, perhaps, or for heat dissipation?
Is there a higher failure rate with those bulbs that have less of this powder?


texts: AC analysis from a DC fresh grad/point of view

texts:
So i was finished taking DC circuits and im adept at basic laws like KCL, KVL and Ohms. But today im taking AC circuits and i wondered why things dont work well as before. Lets take this  example

A series RL circuit is connected to a 110-V ac
source. If the voltage across the resistor is 85 V, ﬁnd
the voltage across the inductor.

So i solve it using phasors, using phytagoras for Vl, Vs and Vr, and I get the correct answer. Now when i try applying KVL around the loop, it doesnt give the correct answer (I just use KVL in a loop, Vs = Vr + Vl)

from the KVL perspective, everything in my equation seems valid, and so why it didn't end up the way phasors do?

PS: on the left part, youll see the phasors method, and right part is my so called KVL from DC circuits


texts: 5-12v ~15w simple class a audio amp & build to 2.1 pc speaker

texts: is there any IC that take 5-12v input and 15 w output class A amplifier for 2.1 ch pc speaker?(can be mono amp) because i've search google and found ic that only take more than 15v DC power supply, and how to connect subwoofer in 2.0?


texts: Power consumption of a Fluorescent choke

texts:
We had 4 x 36W Fluorescent lamps (120cm) in a kitchen.

We replaced them with 4 x 18W LED lamps.

This was the Fluorescent choke for the old lamps:

Question: how much power did the original Fluorescent lamps consume?

My hint: 4 x 36W = 144W + does the choke consume some watts? I read that it could easily consume 4 x 30W. So could it be that the original setup costed them 264W/hour?

UPDATE: we just want the power consumption of the old "ballast and the starter" and the old fluorescent lamps together, so we can know how much less does a LED operation costs.


texts:
I took a flyback transformer out of an old CRT television.

This is how it looks like on the top:

And this is how it looks like on the bottom:
http://i.imgur.com/8QYwPhQ.png

W1 is a thick red wire that ends with a suction cup;
W2 is another red wire similar to W1, but thinner and without suction cup;
P# are the pins.

In order to identify the 0 V pin of the secondary coil, I connected the + input of a voltmeter to W1, the - input of the voltmeter to the 0 V output of a power supply, and I tried touching each pin of the transformer with the 24 V output of the power supply.

I read +0.03 V on P0, +1.79 V on P4, 0.00 V on the others. However, I saw on the internet that by using this method I should read something between +5 V and +10 V on the 0 V pin of the secondary of the transformer. I couldn't get that voltage on any of the pins: am I doing something wrong? Is probably P4 the pin I'm looking for? How can I be sure? Thanks.


texts: Interpreting alphanumeric code on power resistor

texts: I'm reverse engineering a circuit board for a 180V dc motor driver and one of the components which is presumably a power resistor (white rectangular with two leads) is marked "N5W0Ω03J" is there a standard or at least best guess for interpreting the value for this component? Google is no help in this circumstance due to the Ω character and any attempt to find a resistor code key just comes back with the color codes.


texts:
This is a mouthful! I have a copper pipe fixed with zink coated (galvanised) saddles.

I want to ascertain what the voltage would be in the dissimilar metal galvanic reaction between zinc and copper? Looking at the tables is confusing to me because the values given for copper is +0.34V but 0.34V in relation to what? is that the voltage relation between copper and Stainless steel or Copper - Tinanium or Copper - Zinc, I dont know?
Would the surface area influence the voltage or potential difference between the metals?
If so, how would I determine the voltage produced per square surface of the metal faces. I have 10 sq cm surfaces of the metals in contact with each other.
How would I then calculate the current strength between the two metal surfaces?

Thank you for any help with this!