texts: Working with LCD Optrex F-51684 without datasheet

texts:
I have a display from Panasonic car stereo (Toyota Corolla), but can't determine how to work it. It's called Optrex F-51684, and there is no datasheet for that LCD. Is it possible to find how to work with it without datasheet? This is screenshot of the connector pins from main board:

So it has a serial interface, i can select a chip here (CS1 and CS2), but also there is an unknown pin LCD-DET.

I thought it has S1D15605 (like nearest Optrex LCD-s) controller but pins seem different. Also there is chip on the module, marked as EF766102 B01 R ,without any information about it on the internet. Same time it has a name IC2 so it should be second chip, but there is no sign of IC1. Can it be hidden somehow?


texts:
I've been working on a project to build a microphone in DIY after finishing my audio engineering internship, but it seems like my knowledge in electronic isn't good enough to fully understand what i'm doing here.

The microphone is working great after the build, but the constructor gave no informations on the PCB schematic and what they are intended to do in the circuit.
I would like to know what both PCB are doing in just few words, any tips would be very helpfull as it is quite hard to find precise informations on microphone PCBs, especially for a frenchie!

    PCB B

https://imgur.com/a/8tJhO    PCB A

I have been told from an electronic store guy that they are intended to take the extremely small charge variation from the capsule and convert it to a voltage, but that is all the informations he gave me.
I also believe this are originated from Schoeps circuit.

Any help would be great, i would really like to understand what's goind on in there!

Thanks,

Cheers


texts: Pads very close together, no space for guard ring? What should I do?

texts:
Introduction to the problem

I use an OpAmp to buffer the output of an InAmp and to drive the input of an ADC, so the signal path looks basically like this: InAmp -> OpAmp -> ADC

The device of interest is the ADA4805-1 Operational Amplifier. This OpAmp comes in a 6-pin SC-70 package (dimensions and pinout are shown in the image below).

In my particular application, the pins are connected as follows:

Pin 1 : connected to ADC input (max. 3.3V)
Pin 2 : connected to GND (0V, single-supply)
Pin 3 : connected to InAmp output via an anti-aliasing filter (max. 3.3V)
Pin 4 : connected to Pin 1 (unity gain buffer configuration)
Pin 5 : connected to 5V (shutdown functionality not used)
Pin 6 : connected to 5V

Please also refer to the schematic below (only the relevant part is shown, A13 is the OpAmp).

The input of the OpAmp is a high impedance node. Thus, I want to utilize a guard ring to prevent any relevant leakage currents. I already utilized this technique for the inputs of the instrumentation amplifier A11. The instrumentation amplifier is an AD8422. Its pinout makes the routing of the guard ring very easy (pins 1-4 are all on a very similar potential, so simply encircle the whole input with a single guard ring).
The pinout of the OpAmp on the other hand makes it very difficult to route the guard ring. I want to use the guard ring to encircle the positive input (pin 3) of the OpAmp, which is a high impedance node, and drive the guard ring with the output of the OpAmp, which is a low impedance node and on the same potential.

The actual question

The problem with the guard ring is, that there is not enough space to route it between two pads of the ADA4805-1 OpAmp. The picture below shows that there is not enough space between two pads of the ADA4805-1 OpAmp, even if I only use a 3mil wide guard ring trace (which is ridiculously narrow, usually I prefer  traces > 6mil). The grid shown in the picture is a 2mil-grid. Please note: The picture does not show a finished layout, it is just there to illustrate the problem. Nothing else is routed on that picture and the guard ring is not connected to the output of the OpAmp yet.

So, what should I do about this? I could simply omit the guard ring, but that would probably cause leakage currents. However, I am not sure how serious the leakage-current-problem is, since the maximum voltage is only 3.3V. The PCB will have a ground plane, but there will be no ground plane below the ADA4805-1 OpAmp to reduce leakage. So my main concern is any leakage to / from the supply pins of the OpAmp.

This is my first question on Stackexchange. Please notify me, if there is anything I can change to improve the question.
I am sorry, if there are any language errors, I am not a native speaker of the English language.


texts: Clarification about AC and DC coupling on oscilloscope

texts:
I was measuring voltage on zener diode and found unclear behavior of oscilloscope.
So I have function generator which puts saw wave(or sine, doesn't matter) of 20 Vpp. It goes through 1k resistor to 5.1 zener diode. Like on the picture.

If I probe the diode with DC coupling set on oscilloscope channel - I get expected waveform i.e. voltage cuts on around -0.8 Volt when forward biased and around 5.1 when reverse biased.
But when I use AC coupling on the channel, the waveform looks weird and doesn't maen anything useful at all - now it swings from -2.4 to 3.8 - which is not what you expect from this circuit.
So I get that the waveform we got is not the AC, but rather DC biased AC(though we still have -0.8 volts). But what happens with AC coupled measurement on oscilloscope? Why does it take such a weird shape? Where -2.4V and 3.8V came from?

P.S. Should stop asking silly questions in the middle of the night... AC coupling just dropped the "DC bias" to zero... duh...


texts: I'm going to use this AC Dimmer Module with an inductive load, so I plan to help it by adding an RC Snubber Module. Most of the schemes show that the best way to use an RC snubber is to connect it across the TRIAC terminals (Option 1), but what if I connect it to the module terminals (Option 2)... will it operate properly?


texts: Why can't circuit breakers close across a large phase angle difference?

texts: In power systems I understand that breakers have mechanisms preventing their closing if they detect the phase angle (and voltage) across them to be too large. This is usually called a 'sync check'. But assuming the voltage magnitude was the same and only the phase was different why is this required?


texts:
I am using an STM32F405 based board (OpenPilot revo) to receive PWM signals from a joystick receiver.

I have to capture five PWM signals using only two timers, timer 8 and timer 12. I've already succeeded capturing a PWM signal and computing the duty cycle on only a channel for each timer using the example provided with the standard library (PWM INPUT).

But I couldn't use multiple channels for each timer. How do I configure the channels? It would be great if someone has an example with more than a channel used for PWM input.


texts: "To ground" or "not to ground" a coax to prevent RF ingress?

texts:
I have a communications system that connects a self-powered sensor circuit to a wall-powered processing/analyzing circuit by coax cable
The coax reaches out about 60m, and it is matched/terminated at the far end. When I measure the noise/interference spectrum on the line at the near end, I see a significant amount of RF ingress from AM stations. When the cable's shield is grounded at the near end, the ingress seems to be worse than when there is no cable grounding.
If I uncouple the shield from earth-ground, the ingress is still notable, but it drops by 15 to 20dB.
There is no grounding possible at the far end, but at the near end I have the option of earth-grounding to the mains, or not. Of course, at the near end it is also matched/terminated.

Is the shield acting as a 60m antenna, and is the signal possibly coupling into the core along the length of the coax?

My understanding is that it is best practice to ground at the receiving end, which in my case is the near end, but the above observation seems to be going against it.
In my measurement set-up the analyzer/scope is not grounded, but in the communication system where the coax is to be deployed, the circuit ground is (for now) earth grounded.
The chassis and power supply of the system on the near end must be grounded for safety reasons.

Am I correct to conclude that the comms circuit ground should be decoupled from the earth/chassis ground?

Upon request, a crude drawing (sorry, won't use this drawing tool again)
A: the communications system
B: the measurement set up observing AM ingress with coax shield grounded


texts:
I have a 9V powered multimeter (Voltcraft VC165) where the 5V LDO is broken.
When I apply 5V manually, the functions I checked so far work fine, so I'd like to repair it.
The LDO is a SOT23-5 SMD part, the mark says "PAW", there is no logo visible.
Here a picture of the circuit:

And one picture with U3 removed (I also removed and resoldered C17, and my soldering tip is... not the best ;-)

The circuit looks like this:

The switch is closed when the multimeter switch is in "OFF" position.
I checked about 100 datasheets of LDOs, but could only find two where Pin 1 is GND and Pin 2 is V_in - but for those Pin 3 is V_out, Pin 4 and 5 are not connected (JRC NJU7231 and OnSemi MC78LC00).
Is my analysis correct?
Is there a chance to find out which type was mounted here?
What replacement type would you recommend?
Thank you very much for any helpful input!
EDIT: As @Unimportant assumed, my schematic is wrong! Capacitor's GND/logic GND and battery GND are not connected.


texts: 120vac to 24vac transformer for sprinkler/irrigation solenoids - lightweight solutions?

texts:
I am putting together a DIY IOT relay to control my sprinkler system.  My relay controller requires 5VDC, the sprinkler solenoids are the standard 24VAC.   I'm planning on a single plug (120VAC) in, then splitting the 120 to separate 5VDC (for the relay controller) and 24VAC (for the solenoids).

My question is in regards to the proper 120VAC->24VAC transformer to use.

I believe sprinkler solenoids don't use more than a few hundred mA.  My issue is finding a transformer for this project.

Regular (industrial?) transformers like this one:
https://www.amazon.com/Packard-Control-Transformer-Class-Mount/dp/B01HPJT7C0/ref=sr_1_19?keywords=120vac+to+24vac&qid=1583520933&sr=8-19

Weigh almost a pound and a half, whereas wallwarts such as this:
https://www.amazon.com/Apas-Sprinkler-Adapter-Transformer-Irrigation/dp/B0784S9358/ref=sr_1_5?keywords=120vac+to+24vac+power+adapter&qid=1583519910&sr=8-5

are rated for lower amperage, but also weigh less than half a pound.  If I bought a wall wart, I'd have to try to extract the transformer, which I don't want to have to deal with if possible.

Are there any 120VAC->24VAC transformers readily available that aren't as heavy as paperweights?

My goal is to fit everything (PCB, 2 transformers) in a plastic enclosure that is hopefully lightweight.

Edit: The unit will be indoors, along with all the power sources.


texts: In closed loop (negative feedback) configuration of a OP AMP the input voltages are same that means the differential voltage is zero Vd=(V1-V2)=0 ,then how we obtain the gain? where the output is come from?


texts: FCT guy thrust into the ICT world. We build our fixtures using only 100mil and 75mil sockets. What are the smallest test points I can hit with a spear probe reliably? Also using the previous sockets what is the smallest via I can use for a test point using a crown probe?


texts:
I saw the following question online

I knew that while Vbe was less than 0.6v, there would be no current and the collector voltage would be Vcc. At 0.6V, I knew that the transistor would turn on, and there would be a voltage drop across the resistor, but I did not know how much. After 0.6v, I did not know

Here is the answer, but I cannot explain it- Why does he say that it goes into saturation? Why does the voltage go up?


texts: Effect of source output impedance on reflections in a transmission line

texts:
For preventing reflections when the frequencies are higher or close to the transmission line length, for a 50 Ohm coaxial cable a 50 Ohm termination resistor is recommended.

simulate this circuit – Schematic created using CircuitLab

I also used to think/know that source output impedance Rs also needs to be 50 Ohm. But recently I have read in a forum or a text(I'm sorry that I cannot find it at the moment where), someone was mentioning that the source output impedance Rs doesn't have to be 50 Ohm and it is enough only coax characteristic impedance and the Rin are equal/matched.

Is that correct? Can Rs be anything other than 50 Ohm safely?


texts: What causes a thorn like feeling when your put your hand in water in electronic appliances?

texts:
I live in India, the voltage supply in houses is 220V.

Sometimes, for example in my washing machine, when it is full of water and I put my hand in it, I get a feeling like a thorn/tiny nail is piercing my finger near nails. Same happens if some liquid is touch inside freezer.

Sometimes it happens when I even touch the body of fridge.

It doesn't give a shock, but I'm serious about it. Is it a low level of shock or is it something else?

It happens when the appliances are plugged in.


texts: Configure GPIO pin for infrared interface (IRTIM) of STM32F030x4/x6/x8

texts:
I have a problem for use infrared interface (IRTIM) of my MCU. When I saw in Reference manual I could find this:

Now, when I search for find GPIOx_AFRx register, I cannot find this register in reference manual.

Where is it?


texts: What's the difference between bluetooth-soc chips and bluetooth modules?

texts:
I'm currently shopping for a Bluetooth transceiver to play around with.
After doing some research, I think there's a bit of crucial terminology that I'm missing.

Specifically, there's two products that I'm looking at:

- BC127
- Csr8675

Are they intended for different purposes?

From what I can tell, they're pretty similar in functionality and both have mass production in mind.
Yet the BC127 is 2 times the physical size of the Csr chip, as well as being 2 times the price for a single unit.

And on their respective webpages, the Bc127 is referred to as a module while Csr chips are referred to as 'audio system-on-chip' or 'audio platform'?

Is there any intrinsic difference between the two?


texts: Can I measure resistance of an inductor on a bridge?

texts:
I designed a circuit to have a Q-factor of 15, knowing the inductor value I rearranged the equation \$\omega_o=\frac{1}{\sqrt{LC}}\$ to give me a capacitor value for a certain resonant frequency. When I built the final RCL circuit, the Q factor was found to be way out (using \$\frac{\omega}{\Delta\omega}\$) with a Q factor <7.

I am told this is due to the resistance in say the signal generator, cabling etc and also the inductor. Is it ok to measure the inductor on a bridge using the resistor setting so it gives a value in ohms? Or am I going about this Q factor error the wrong way?


texts:
I'm designing a diode limiter for audio use where the signal is high passed through a discrete transistor circuit. After the diode stage the signal would need its low end restored and I'm struggling to find a way to archieve a flat response at the output.
I initially had three opamp LPFs configured so that frequencies above fc will be at unity gain. That's the only way I could remove the low end slope, though it seemed a bit sketchy and unprecise as it would create quite a hearable bump (5db) at around 200Hz.
Now I thought to copy the same exact HPF circuit that I use at the input and put it in the negative feedback of the opamp. Theoretically in that way the opamp will have a frequency response that will be exact opposite of the one in the feedback loop HPF?
Anyway it doesn't seem to work, somehow the low end it's still not flat but a slope going to -30dB.
Before I go crazy trying to make it work, does anybody know if I made any wrong assumptions/ or know of a better way to solve the freq response drama?
Cheers!


texts: Data Sheets or Power Output ratings for Cisco Power Supplies

texts: I have 2 used Cisco power supply units that I would like to re-purpose into bench power supplies. The first is a Astec AA20270, Cisco part # 34-0850-01. The second is a Computer Products NFN40-7632E, Cisco part # 34-0625-02. I can not find any data sheets for these 2 supplies. I need to find out the maximum current draw they can handle first. I used a meter and determined that the voltage outputs on both supplies are the same, with +12v, 5v, and -12v.  Thanks for any help on how to locate this information or figuring it out.


texts:
How do I determine the minimum and maximum humidity allowed for a PCB mounted with IC's?
(Without having to use some sort of humidity chamber)
EDIT: During operation.


texts:
I want to make a power DC supply with voltage rating 0-200V.
I want it to be a variable power supply with voltage from 1V to 200v.
What should be my approach?


texts: Over voltage protection for a buck controller 24V in. 4-5V out

texts:
Please see Image below, if the output votlage here is 4-5V with current out 3A-15A(depending on LOAD).

Could I stick a Zener diode to clamp any over voltages to protect the load from over voltages?

for example something like this https://www.littelfuse.com/~/media/electronics/product_specifications/polyzen_devices/littelfuse_polyzen_zen056v115a24ls_product_specification.pdf.pdf


texts: Some questions about power supply noise and transducer wiring

texts:
A 24V SMPS power supply is used to create a +/-12V bipolar supply.
This bipolar supply then powers this accelerometer transducer which converts small mechanical vibrations to amplified voltages.

The circuit on the top is the discrete bipolar supply. I made the biploar converter interface by soldering the discrete components on a strip board. The bottom circuit represents the transducer and it is just a theoretical simplistic model of the transducer. Since I don't know the inner circuitry, and since the data-sheet talks about excitation voltage, I decided to model this transducer as Wheatstone bridge and a differential amplifier with gain.

My worry was about noise coming through the 24V power supply and the bipolar converter wires; and I was thinking this might be an issue for the output. So I added a noise source to the power supply to see the effects in simulation.

As you see the noise can be seen between the biploar rails on the first plot. In the second plot noise can still be seen at each output terminals of the Wheatstone bridge. But at the output the noise disappears.

I have two questions. one is theoretical another is practical:

1) I concluded that the power supply related noise should not be an issue because the Wheatstone bridge's differential behavior makes this noise appear as common-mode at the differential ended amplifier input terminals. Is my model for power supply noise and the conclusion is correct? I heard some use batteries to obtain clean +/-12V voltages for the supply signals but in this case I cannot see any benefit of it.

2) This bipolar supply powers four of these transducers. I made a box including all inputs outputs, the power supply and cable shield ends ect. All the shields go to earth ground at in the box end. All four transducers are around 30 meters far away from this box by FTP CAT6 cables. An the outputs go to very high input impedance ADC device(like a data acq. device). For the moment the SNR for the output signals is not a problem. But now I need max 300 meters long cables at min -20°C temperature. I know the best way is to test but I wanted to know whether there is fundamental problem with the practice?


texts:
So, how should I proceed to find U_ab (or V_ab)?

I have found I = -0.5mA, U_1=-2.5V, U_2 = -0.5V, U_3 = 2.0V.

How would I even find U_a and U_b separately so I can apply U_ab = U_a - U_b?

Also, does the 10v source receive or deliver power?


texts: Confusion about calculating inductance of a coil

texts: I'm a little confused about how to calculate the inductance of a wire coil.  While I thought this would be really clear, what is confusing me is that there seems to be different ways to calculate it.  In this question, the result of the inductance formula is dependent on cross sectional area, number of turns, permeability and the length of the coil.  For the calculator on EEWeb, the inputs are the diameter (and hence the cross sectional area), the number of turns, permeability and the wire diameter, and the wire diameter, rather than the length of the coil.  I'm unclear how the formulas are related or which one to use.  My guess is that the 2nd calculation determines the inductance for a coil one meter long and I have to divide by the length of the coil I'd want to find the inductance of, but I'm not sure.


texts: How to measure AC voltage without a voltage divider using microcontroller

texts:
I have to measure AC voltage of the mains supply 180-220 VAC through a microcontroller. I have been wondering how to measure it without using a voltage divider. Since the resistance may wear out with time, doesn't sound like a good design.

I can use a transformer but that design would be too bulky. Isn't there any other way? Even the voltage sensing IC's use a resistive network to divide the voltage.


texts: Why use a step-down transformer for soldering gun?

texts:
As I understand it, some devices that heat up to a high temperature, like soldering gun, use a step-down transformer, in order to increase the current flowing through the heating element. An alternative option would be to use no transformer, and a heating element with a higher resistance. For the right value of resistor, this would result in the same power dissipation, and therefore the same heat, in the heating element. Why is this not done? What benefit does the step-down transformer have?

Note: This question is not specifically about soldering guns, just any device where a step-down transformer is used with a heating element.


texts: LED and lamp in series - why does the bulb not light?

texts:
My 6 year old son has just started experimenting with a Snap Circuits style kit and already we have a very basic question.

If we arrange an LED and lamp in parallel powered by batteries then both LED and lamp light up brightly.

However, if we arrange the LED and lamp in series then only the LED comes on.

Obviously current is passing through the lamp (if I unscrew the bulb the LED goes off).

So why does the bulb not light?

I'm a bit of a cheapskate so rather than buy proper Snap Circuits I bought a similar generic set from China on eBay (See: Electronic Blocks Kit W-58)

(Apologies if this is too basic for this forum but I haven't yet found the answer via Google)


texts: ATTiny85 wont turn on, not sure how to debug

texts:
The ATTiny85 in the below circuit refuses to do anything.

$ avrdude -c usbtiny -p attiny85
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.
avrdude done.  Thank you.

My setup:

Programmer: USBTiny ISP (Verified it works with an ATTiny with 0.1" pins in a breadboard that I could program just fine)
Environment: avrdude via OSX
Programmer interface: 6 header pins shoved into 6 pin ISP plug and inserted into offset programmer holes

I've verified:

ATTiny chip is mounted in the correct orientation, the dot lines up where it should.
Positive voltage (~4V from LiPo) exists between VCC and GND pins on the chip.
All traces from the ISP holes to the chip pins are connected where they should be.
Ceramic oscillator contacts connect with correct pins, and it's GND is grounded.
I can't find any shorts between discreet traces.

I've done everything I can think of and everything checks out. Except that my USBTinyISP programmer cannot talk to this chip. It acts as the programmer pins are not connected to anything.

Lastly, a previous iteration of this board seemed to work fine. That older board didn't include the LiPo charging circuit and it connected the ISP 5V+ pin to the power line (which shouldn't be required if the battery is powering the circuit).

Could my chip be bad?
What are the chances the ATTiny85 cap was put on backwards?

I'm out of troubleshooting ideas. What am I missing?


texts: Filter Q factor with 4 pole filter question

texts:
I am designing something related to a vocoder and I need 10 filters with certain specifications and I am confused about the required Q factor.
The specifications of the 10 filters that are needed are 2 slightly overlapping 2-pole filters with a required Q of 10 or higher.
So I am confused over what does Q of 10 really mean in this case?  I know what Q factor is, but I am wondering if a Q of 10 means each filter section has a Q of 10 , or if they add the Q factor of each section to make 10 as in if each filter section had a Q of 5 and they added each up to get 10.
I know with when you calculate filters there is something called maximum Q which is the highest Q for any of the stages, in which a Q of 10 could mean just one of the sections could be a Q of 10 but not the others.


texts: why smartphones don't cause noise on the around speakers

texts: Before the smartphones (or maybe before the some new tech) when a cell phone rings, the speakers around it made noises. Hovewer, nowadays they do not. Why? What changed?


texts: Does it matter if the shunt resister in an audio Line Out L-Pad attenuator is 6 feet away from the series resister?

texts:
I am designing a 14dB L-Pad attenuator to be buried in a guitar instrument cable as per below.
The placement of the 22K ohm series resister is to go inline inside the amplifier side of the 1/4" mono plug. I would like to place the 5.6K shunt resister parallel inside the other cable end.
I could try to get them both at the amp side of the cable but that is a tight squeeze in the small small space inside the plug.
Does the placement of the shunt at the other end of the 6 foot cable change the tone or have any other detrimental impact?

Specifications
Pad = -13.89dB
R1 = 22K, R2 = 5.6K
Circuit impedance = 27.569K ohms
Vout = 1.223V rms, Vin = 0.247V rms
Cable: 6' instrument shielded. Two parallel for stereo.
Amplifier Line Out Z= 600 ohms.
Effects pedal input is 1M ohms.
There will be two cables since this is a stereo in/out setup.


texts: What could be the reason that this transistor gets too hot unexpectedly?

texts:
In the following circuit, for the transistor it can be calculated that: Vce=4.5V and Ic=170mA. I also implemented this on breadboard and measured almost the same quantities.

The opamp is an LM324 and the NPN transistor datasheet is here.

Here is the photo of the transistor:

The transistor power in the circuit above must be P=VcexIc.  This becomes 4.5V x 0.18A which is less than 1W power.

In the transistor datasheet the thermal resistance is given as 10 degrees per Watt. So in my case I expect not more than 10 C increase. The room temperature is 25 C and I expect 35 C for the tansistor surface.

But when I touch with my finger it feels like it is very hot like 100 C. Is my interpretation of the temperature wrong or is my expectation is wrong? Why does it get hot that much?


texts:
My apologies in advance if this has already been asked

I have a MCU (esp8266 or esp32) which will primarily live off mains power with transformer 110VAC -> DC 3.3V

Occasionally USB is plugged into the device for programming and diagnostic.  Expect a CP210x, FTDI or similar connected to the esp.

I'd prefer not to 'cut' the USB +5V power line to the device, or in other words, I'd like both power sources to be able to coexist.  What would you recommend?

Additional consideration: some of the boards considered (like Wemos D1) already have the CP210x hard wired to power the device

UPDATE:

The design will have a 5V -> 3.3V regulator onhand for powering from USB.

I am interested in powering the device from USB for the programming and diagnostic portion.  I'd prefer not to have to unplug the mains -> 3.3V supply at that time, and would also like the option of powering the device solely from USB occasionally.


texts:
I'm having some trouble with a "cheap and cheerful" bench power supply that I become an owner of. When scoping the outputs I'm seeing some really high noise peaks (see attached photos) in the region of +/- 5V  at around 66MHz when outputting 3.8V! Now interestingly when I connect the scope probes to the ground terminal on the scope and switch the power supply on, the same sort of noise appears on the scope, which leads me to think that the power supply is kicking out some noise down the 230V power input neutral which is then throwing the scope off. I also get a crackling sound from my speakers when the power supply is on! Are there any modifications that I could do to the power supply to reduce this noise?

Any input would be much appreciated!

Update:
I've run the scope with a 10ohm load across the power supply running at ~4V and this seems reduce those massive noise peaks across the neutral. However, when scoping the actually supply this is the result I get (and that's with a decoupling cap in parallel with the load!):

So another thing I've noticed, when turning voltage on the power supply down with an open load, a (quite noisy volume wise) transformer turns off (I assume to let the smoothing capacitors discharge a bit). During this time there is no electrical noise at all, however when the noisy transformer kicks back it the electrical noise comes back.


texts: Interactive Art with Wooden Mirrors - How are the pixels controlled?

texts:
http://www.youtube.com/watch?v=BZysu9QcceM

This video shows a mirror made up of moving wooden pieces. Please have a look. He achieves different intensity levels by motion of the wooden pieces and placing different light sources on the top.

But how did he achieve this motion? Did he really used 1 motor for every pixel? In any case how much energy does this thing consume?


texts:
Noob question here.  I'm new to Microchip devices

I have a dsPIC33 series chip and a PICKit2 programmer.

I have a BIN file I would like to flash the chip with but not sure how to go about it.

The MPLAB IDE and PICKet2 software will load HEX files but they don't seem to recognize BIN files.  Both MPLAB and PICKit2 recognize the dsPIC33 chip when connected to the appropriate pins.

I don't have a HEX or source code of the BIN file.  Just have a BIN file.


texts: How slowly can a brushless DC motor spin?

texts:
Obviously dependent on the internal design of the bearings and the rolling friction.
Otherwise, is the slowest rpm for a brushless motor related to the number of poles the motor is designed with?


texts: High voltage LED indicator 40-1000 VDC without additional power supply

texts:
I would like to make an indicator to show that DC bus (700VDC) capacitors are charged (be careful!).

What is the best way to make a LED indicator, which will work for a long time from 40VDC to 1000VDC without additional power supply and with minimum power losses?


texts:
According to this link, the following schematic is equivalent to an inductance R1*R2*C placed between input and ground. Under which conditions is this true? As a guideline, we assume Vcc=9V. See this post for the context of the question.

simulate this circuit – Schematic created using CircuitLab

Application with R1=390 Ohm, R2=22 kOhm, R3=2.2 kOhm, R4=70 kOhm, C1=100 nF, C2=200 uF.


texts:
I've been tearing my hair out at this for a while.
I have a dsPIC33FJ16GS502 and I've been trying to get it to transmit a single character to my computer but so far, I have been getting absolute garbage:

The uC should be sending 'b' instead of 0x89.  I have a gist of my code available here.

I have a 16 Mhz crystal connected to OSC1 and OSC2 with two 27 pF capacitors attached.  I also have a 10 uF electrolytic cap at Vcap (datasheet says I should really use tantalum but I don't have any at the moment).  I'm using a pickit 2 to program the uC.  The TX pin is connected to a FTDI FT232 usb-serial converter.  Baud rate is 9600.

Maybe I'm missing something really basic.  Any help would be greatly appreciated!

Edit:  Here's a photo of my setup:

Edit 2:  Measurements from a logic analyzer.  There seems to be a fluctuation between 0x89 and a comma:


texts: Low pass filter to remove noise from signal

texts: I am working with an inductive proximity sensor. In the ideal condition, it gives 5V as a high signal when metal is sensed and gives 0 as a low signal when metal is not in proximity. But due to electrical noise low signal is not exactly at 0. It contains noise which makes low voltage level around 0.9V. I want to make this 0.9V to exact 0V so that my microcontroller can perfectly detect 0 or 1. I have tried RC low pass filter but still noise level is the same. Any other method to remove noise from the signal?


texts: What makes smartphones tilt-sensitive? Will they retain this ability in zero-gravity conditions?

texts:
Most smartphones are tilt-sensitive, but what device makes this possible? Additionally, how does it (and the sensors associated with it) work?

Also, since the working of these sensors seem, almost certainly, based on the presence of an external gravitational field (for instance, the earth's), this begs the second question: Do smartphones retain their tilt-sensitivity under zero-gravity (hypothetical) conditions?

(Recently played an aircraft simulator game on my phone...the fact that the plane responded so well to tilting took me aback; hence the urge to ask this question)

Extras:

I put some thought into this myself, so I'll be putting that up here too. For all intents and purposes, my question ended after the second paragraph, but what I've added after this might help tailor an answer that fits my current understanding of physics.

I'm currently in high-school, and if I recall correctly, there are six degrees of freedom for a particle in a 3D Cartesian system. From my experience with the aircraft simulator app, smartphones seem to detect motion in only three degrees of freedom: pitch, roll and yaw

Speaking of tilt-sensitive sensors: The way I assume these sensors/transducers work, is by detecting the minute changes in gravitational potential energy (which may manifest itself as small-scale motion of some tiny components of the sensor)  that is associated with the phone's change in spatial orientation.

The way I see it, such a sensor would require moving parts, and cannot simply be another chip on a circuit board.

Under these circumstances, if I were tasked with building a tilt-sensitive device that perceives minute changes in gravitational potential energy, I would probably require at least 3 pairs of sensors (a pair in each of the three coordinate axes). Also, seeing how very sensitive my smartphone appears to be to tilting, I'd have to build a ridiculously large device, with each sensor in a pair placed several meters apart to achieve tilt-sensitivity comparable to that of my phone.

However, smartphones have dimensions smaller than that of a typical sandwich, so having "sensors in a pair placed several meters apart", apart from being impractical, is clearly not the case.

^ I went ranting about this, so that you can get a feel of my genuine perplexity in the sub-question that follows:

How come these sensors are so sensitive, despite their small size?


texts: PNP/NPN - Why do we not just use one of the two types?

texts: Using PNP instead of NPN merely requires one to make circuit upside down and reverse current direction, if this is true then why don't we just do everything with NPN transistors? Are there any applications where we can only use one of the two types? Why?


texts: Low-sampling rate scope with high-frequency chips? How to bring the frequency down?

texts:
Kortuk instructed me with my new handheld scope DSO201:

  You can use very high end chips and high working ranges, just at the end you will need a
  filter to bring it down to what your o-scope can handle, which is
  roughly 1/2.1 the bandwidth of your scope. (Chat
  discussion)

I did not understand this. Does this mean that it is possible to measure high-frequency samples with a handheld scope having "1MHz analogue bandwidth -- but -- 200kHz (1 Msps)"? What does it mean to "bring it down"? By which chip I can bring the frequency down to make it visible with a small scope?


texts:
I thought I could read schematics, but I have this problem: sometimes there are unnamed signals connected to buses and I don't know where they are supposed to be connected.

Example:

IC3 pis 14...23
IC1 pins 12...19

How to read those?

Link to the project


texts: Frame size range calculation for stop-and-wait protocol

texts:
I have a question and answer below. The answer seems to show less working on how it derived.

My question is if the efficiency of at least is changed to say 60%? Will it still be the same answer?

Question
A channel has a data rate of 4 kbps and a propagation delay of 20 ms. For what range of frame sizes does stop-and-wait give an efficiency of at least 50%?

Answer

$$a = \frac{Propagation\,Delay}{Transmission\,Time}
    = \frac{20 \times 10^{-3}}{\frac{L}{4 \times 10^{3}}}$$

Using the maximum possible utilization expression:

$$ U = \frac{1}{1+2a} = \frac{1}{1 + \frac{160}{L}} \ge 0.5$$

$$ L \ge 160$$

Therefore, an efficiency of at least 50% requires a frame size of at least 160 bits.


texts: Induction coil interference from an electromagnet?

texts: If I have a nail three dividers on it to keep the coils on the nail, and wrap an induction coil between the head of the nail and the middle, then wrap an electromagnetic coil between the tip of the nail and the middle, would the electromagnetic coil interfere too much with the induction coil?  Would this turn into a transformer, or would the induction coil be able to still function?  The reason for this is I am looking to make guitar pickups, and have a bit of wire, but not many magnets.  I thought this may work, but I am unsure whether the electromagnetic coil would interfere too much.


texts:
The application notes of several boost-converters, e.g. from TI (TPS61070, p.18) or LT (LT3464, p.14), show similar unregulated auxiliary output circuits for doubling or inverting the (regular) regulated output.

The following schematic shows how the invertingg auxiliary amplifier topology is combined with the boost converter. Diodes should be schottkies.

simulate this circuit – Schematic created using CircuitLab

Do these circuits have a specific name? I could not find them in literature about switch-mode-power-supplies, but would like to learn more about it.

As far as I can tell, the auxiliary output is mainly practical for supplying small loads e.g. for operation amplifiers or logic-level-conversion ics.
Are there any noteworthy trapdoors or design considerations when using this auxiliary output for such applications? E.g. can this introduce a negative impact on the boost stage or overall efficiency?


texts:
I am trying make a Gimbal BLDC motor spin slowly (~0.2Hz).

For some reason I have problems with the motor stuttering, as shown in this video. At the end of the video I also show PWM signal from the MCU (yellow), and what goes to the motor (light blue).

The driver circuit is based around an ST L6234 (see picture), with the Enable-pins bound to high. The motor is an iPower GBM2804H-100T (12N14P) with a winding resistance of 6.5 Ohm.

[][3]

The input-pins on the L6243 is driven with a PWM-signal at 42kHz, so that the motor is unaudible. The stuttering disappears if I reduce the frequency to 5kHz, but this causes the motor to make a terrible whining noise. The stuttering also reduces a bit if I increase the driving voltage from 12V to 20V. However I have only 12V available in the final application, so I would prefer to use that.

What causes this stuttering - and is there any way to remove the stuttering without increasing the voltage/decreasing PWM frequency?

Edit: Added additional info below.

The Sense-resistor I am using is 0.47 Ohm.
The power supply to the L6234 is decoupled according to an ST application note (Google "AN1088 L6234", first page. My rep is too low to add more links). Basically I have two capacitors totalling 200uF on the main input. The power supply to the microcontroller is separate, and does not have additional decoupling except what was provided in the kit I am using (MikroElektronika Mini-M4).
The waveform I am using to drive the motor is a normal sine wave. I have also tried space vector modulation (see berryjam.eu spinning BLDC at super slow speeds). The result is that the stuttering has two "stutters" in close succession where there only used to be one. To give a stupid image, it goes zzzzz dok dok zzzzz dok dok instead of zzzzz dok zzzzz dok.


texts: Circuit seems to use mains AC to trigger triac?

texts:
I'm trying to modify the following circuit to switch a mains load using a sparkfun esp8266 thing:

Credit: https://hristoborisov.com/index.php/projects/switcher-a-wifi-open-source-power-switch/

I've modified it like this (I know the symbol inside the optoisolator is wrong - sorry about that. The hi-link is a solid state mains to 5V DC PSU):

It looks like, when triggered, the OI allows the mains to trigger the triac, which switches the main load. Is that OK?


texts:
I am describing a system in VHDL. This system already contains a
processor, a DDR SDRAM controller and a VGA controller. VGA reads pixels
from SDRAM (already validated and proven in FPGA).

Although VGA and SDRAM are already communicating with each other, I still need
to implement the connection between the processor and SDRAM. In the end, what I
intend to have is a processor that draws in the framebuffer stored in SDRAM. Then, a page flip occurs and VGA starts to fetch the new picture that was drawn by the processor.

To instruct the VGA to fetch from the new location, I would like to inform
the VGA controller (using memory mapped io) the new address of the new image.
A simple strategy that I though was to put a mux and verify if the
address range falls on the VGA controller's registers or in the
cache's address range. Also, would I need to care about different clock
domains? If yes, what possible problems should I care about?

For example, sometime in the past I saw code from x86 that writes (using
outb instruction) and the next instruction was a inb to the same and/or a related location. In this case, would I need to modify the processor logic
to stall on such operations? If yes, how many cases to implement? How many
interfaces to care about?

Also, at bootup, how cache is used if all entries are invalidated? I believe
there is a ROM image with the startup code. Could it also exist a temporary local RAM for writings made by code stored in ROM (sw instructions)?

Resume: I need information on how to implement memory hierarchy
circuitry: caches, memory mapped io, TLBs, virtual memory etc.
And how all this communicate together with each other. I know how to implement
caches and TLBs, for instance. But I am not sure on how to connect them
together. I could just use something that works (like the mux idea). But I want
to follow designs that are established in industry.

What I've already studied:
- how to run mips
- computer architecture (Patterson)
- MIPS manuals
- ARM's manuals
- Intel's manuals

But none explains in detail.

If there are many ways to implement, just show me one that you know of, please.
Even if it is source code or a block diagram. Again, I don't need the
explanation of how it works internally. I just need to know the interfaces
between the modules.

Thank you all


texts:
I used lan cable for light LED up on my bread board
power source is PC's power supply.

without any resistor, the lan cable melt!

I reallize I have to keep OHM's law in my mind
and use proper resistor for safety.

on lan cable's jacket,

it says

"0270M LS Cable UTP 4PR 24AWG CM CAT . 5E 75C KS Verified KS C 3342 HDPE 2009 V8"

how much current do this 24AWG cable tolerate?

and
could somebody tell me the relationship between temperture, current, thickness, and material?

linking website, simple hint also welcome.

thanks.


texts: I stripped the ends of a 14v DC power supply to power a small 6-12v DC motor. I first measured the voltage coming from the supply and found an actual 17 volts coming out, but then when I connect the motor to the supply I find the voltage across the motor to be 21v. What happened here? How does the motor have a larger potential difference across it than was supplied?


texts: Amplifying Sinusoid From Microcontroller to ~40V 3-5A

texts:
I’m investigating transient switch arcing that occurs in a 3 phase switching unit.

I am planning on generating the phase signals with an STM32F4 using DAC and DMA with timing separation for the phase difference.

I need to boost this signal to around 40 V peak with around 3-5A with the ability to provide or than that for short periods.

I was considering a power opamp like the LM675 but I’m not sure if this would be the best or feasible approach.

Is there a typical way of accomplishing this kind of amplification?

I can purchase basic components as required and have lab bench power supplies available.

Thanks


texts: Schematics of PIN Photodiode interfacing with an ADC

texts:
This question is in continuation of my previous question.

I am moving forward with PCB designing now. I have selected low input-bias current op-amp AD8616 for converting current signal into voltage. I have used another AD8616 op-amp as a buffer. I am using internal ADC of my microcontroller (PIC24EP256GP204).

The PIN diode is IG22x250S4i and works in photovoltaic mode. The specifications are:

Capacitance (@0V): 40pF
Forward Voltage: 0.56 V
Reverse Voltage Max: 5V
Forward Current: 1 mA Max
Reverse Current: 0.5 mA (Max)
Dark Current: 0.5 uA (at 5 V reverse voltage)
Shunt Impedance: 400 - 500 k ohm
Wavelength: 1150 - 2200 nm

The datasheet of the sensor is over here. The application notes and reference circuit is over here.

The schematics is given below:

My questions are:

What can I do with ground/case pin of PIN photodiode to improve performance? Currently, I have just grounded it.
I am using second op-amp as buffer. Is there any possibility of buffer getting unstable? What measures I can take?
I am included a capacitor in parallel with feedback resistor to compensate the pole included by capacitance of PIN diode. What other measures I can take to stabilize my interface circuit if I found any instability after I get my PCB done?


texts:
I am able to successfully send strings and numbers between two STM32F407VG Discovery boards and between two Arduino Uno boards but I am unable to do it between an STM32F4 and an Arduino Uno.

Here is what I did:

Arduino Uno RX --> PA2
Arduino Uno TX --> PA3
A pin from the STM32F4 ground to the arduino ground.

I use the default configuration 9600 baudrate, 8 bit data size, 1 stop bit and no parity. Output type of the gpios on the stm32f4 is push pull and they are pulled up.

Is there something I am missing?


texts: WEMOS D1 R1 Interrupt repeats continuously, when triggered, Is it bouncing? How to fix it?

texts:
I am having such a nightmare to make it work, I am using a WEMOS D1R1 to handle the movement of an encoder via external interrupts.
Instead if detecting the edge (L to H), it detects the status, so the interrupt function repeats continuously if the state is H, so its behaving like a  while(state==H){...}, instead of triggering once per H to L .
Here is my code so far:
void ICACHE_RAM_ATTR ISRC();
void setup() {
  Serial.begin(115200);
  pinMode(D9,OUTPUT);
  pinMode(D8, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(D8), ISRC, RISING);
  Serial.println("Started");
}

void loop()
{}

//This function is supposed to get executed when interrupt happens, instead it happens looply while D8 is HIGH
 void ISRC() {
 Serial.println("Interrupt Detected");
}

I dont know what else to try here is what the monitor says, please, note the time marks:
20:41:49.935 -> Interrupt Detected
20:41:49.935 -> Interrupt Detected
20:41:49.935 -> Interrupt Detected
[...]
I have readed here that setting the input as INPUT_PULLUP fixes the issue, but it didnt happen with me.
I had tried wiring the interrupt input (D8), to a "clean" source, as it is the BUILTIN_LED (D9) pin, and then it does work perfectly.
The problem comes when I connect it to the encoder or a button.
I guess its a bouncing problem...
How can I avoid this supposed bouncing?
Is it really a bouncing problem?
How can I make it work?
Thanks everyoune in advance.
Here is a pic of the encoder schematic, i just added a pullup resistor to the Output (O)
Here is a link to the datasheet
https://www.digchip.com/datasheets/parts/datasheet/000/EE-SX460-P1-pdf.php


texts: Cleaning up a 5V Switching DC-DC converter for low noise 5V output

texts:
I have a project that I have to hook to a 5V bus coming from this DC-DC switching converter.

I need to clean this up to use with a logamp (LOG114), photodiode, and ADC (ADS8519). I would also like this circuit to work on future projects with similar power supplies.


texts:
I recently purchased a step-up converter, the specifications state that it can boost 5 V to 30 V with varying input voltages.

The reason I purchased it was because the charger for my handheld vacuum cleaner stopped working, and the charger has very specific specifications that are hard to replace: 27 VDC 85 mA.

I'm currently using 12 VDC 1000 mA as an input and stepping it up to 27 V, my question is is this safe, and will it work correctly?

TLDR: I have a step-up voltage converter/regulator that works within 5-30 V, I have a 12 VDC 1000 mA power supply that I want to step-up (boost) to 27 VDC 85 mA and I'm wondering if it will work correctly.

PS: I have a higher current 12 VDC power supplies at 2000 mA, and one have a 19 VDC 2000 mA also. Would they be better to use instead?

PS2: This is the one I purchased: https://www.amazon.de/gp/product/B075SXMXN9/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1


texts: Comparator hysteresis input signal filter

texts:
I need to heavily low pass filter an input to a hysteresis comparator, but due to the fact that R1 is one of the components setting the hysteresis, I can't add additional RC-circuits in series with it.
My question is if it is suitable to double-up the function of the R1 resistor as in circuit below? The resistor is now also intended to function as a part of the low-pass filter.
The circuit displayed below is a basic comparator with noninverting hysteresis where I have added a sizable capacitor marked by the red circle.


texts: Shut down engine when temp to high, oil pressure to low or RPM's too high

texts:
We do stationary dock testing on boats and would like to set up some safeties on the engine to shut it down. The engine is a 5.7L gm running a 12 volt system.

We have done it in the past using a mechanical latching relay, and maybe that is the best way, or maybe there is a better solution out there.

We use an oil pressure dummy switch sensor and also one for temperature. For RPM we use a MSD rpm window switch. All of these devices provide the ground for the latching relay so if any one of them is triggered it will shut down the engine. The way we shut down the engine is by putting ground to the negative (tach) side of the coil via the latching relay.

The dummy sensors can be hooked directly to the negative side of the coil, but the rpm window switch causes an issue because when the rpm limit is hit, it puts out a ground killing spark to the engine and then when the rpm falls back below the limit it takes away the ground, so it acts like a rev limiter.

Does anyone have a better ideas for a solution? Ideally it would just be a box that i hook all my wires from the safeties to, and if it sees a ground it outputs a ground. and then I click a reset switch to reset it, or just turn the ignition off and on.

Thanks,

Justin


texts: T460P Whining when not connected to charger

texts: I have a Thinkpad T460P that whines when performing tasks. This happens mostly when it is not connected to the charger. Has anyone else had this problem, and fixed it (e.g. desolder coils/capacitors on the motherboard?)


texts: Run code once in lifetime of an embedded C program

texts:
How can I make a code snippet run only once in the lifetime of a program? It can be turned off and turned on many times. The only option to run the code snippet again must be flashing the board again.

The code is a Calibration Section which I don't want to run again. If I use EEPROM or Flash we will be setting a Flag to true or False. So When we first read that memory location what would be the random value in that memory area?

What is the best method to implement this in embedded C?


texts:
I am using a 5 Watt PCB mount AC/DC power module with universal input(85-264 V) and output as 12 V. The cost of the module is very high so thought if we could replace the module with a PCB mount transformer which will convert 230 VAC to 12 VAC and then a rectifier with a linear regulator can be used for 12 VDC output. I cannot decide the VA rating of the PCB mount transformer size. I did some search and found that I need power factor for getting VA rating. How can I get power factor?
I have space constraint on my PCB so I cannot go for a very big transformer. Please suggest a solution.
I am new to electronics so please excuse me for my ignorance.


texts: What will happened to the electric/electronic equipment if we supply with different Cos Phi?

texts:
In some part of our country, the cos phi is 0.9 while in some other is still 0.8. The higher the cos phi the better. The power is belong to government (say the name is MAINS). Different cos phi is possible as the they are on a a different network, in a different island.

I would like to install 150KVA ON-GRID solar panel using a 330 Watt output power of each panel (output of a single independent panel theoretically is 330 watt. By connecting some panels parallel and invert it to AC from DC, expected will meet the requirement). The output of the panels we will use internally. But as no guaranty that the power the panel produce will be enough for our need (as could be cloud, rain, etc), the solar panel system will still be (inter)-connected to the MAINS. Once the power produced by the solar panel is not enough, than system will draw from MAINS by the ON GRID inverter. Means, there will be two electric sources for us. From MAINS and from solar panel.

Then my question is, what will happened to all the electric equipment or to our network if the cos phi are not same? Say, the MAINS' cos phi is 0.9 while our cos phi is 0.8 or something like that.


texts: Using two isolated secondaries of different voltages to power one device

texts:
I'm making a simple 555 timer circuit to drive a flyback transformer. The 555 circuit controls an N-Channel mosfet which is what drives the flyback. I have an old receiver mains transformer that I wish to use to power the entire device. It has multiple isolated secondary taps. One of these taps is 12v and the other is a 50v supply.

I want the 12v supply to drive the 555 circuitry and the 50v supply to drive the flyback. I was going to use two full wave rectifiers, one for each supply. But then I figured without some sort of common the mosfet wouldn't work (no voltage potential right?). So can I simply connect the two taps in parallel or series and then that would work fine? I've read other places that this is acceptable to do but I have to then do half wave rectifiers as a full wave causes issues. Is this true? How would this impact the ripple on my rectified DC supplies?


texts:
I built this very simple SAW transmitter, with a simple "spring" antenna for the right frequency. To test it, I tuned a portable receiver to around 433.92Mhz and fine tuned it until I heard silence. But I noticed that when tapped the board, the antenna would vibrate and I could hear the "boing!" in the receiver.

Why does this happen?


texts: Reducing ground level fluctuations when Multiplexing 7-Segment Displays

texts:
I am using a microcontroller to multiplex 6x 7-segment displays. Segments are driven by 2N3906’s and displays by a ULN2003. Average segment current is around 9mA, so instantaneous LED current pulses are around 53mA per segment.

My code is currently setup to do the following:

1)  Display n is on for 1.9ms

2)  When 1.9ms has elapsed, switch off all segments

3)  Reset timer

4)  Select Display n+1

5)  Turn On correct segments for Display n+1

The delay between switching on and off (step 2 & 5) is around 150usec. The code works perfectly fine, but my issue is noise. I’m using an ADC to measure an input voltage and the reference isn’t even close to stable despite filtering and separate grounds due to the massive switching currents. This is compounded by the fact that I am switching the segments completely off, then completely on when switching displays, but this is the only way I have found to prevent bleedover between displays (similarly described in this post: Multiplexing two 7-Segment displays (Ghosting issues)) … if I keep the segments on, then switch displays, there is a bleedover of the previous digit into the next digit. The reverse is true if I switch displays first.  The scope traces look somewhat better (significantly fewer spikes) if I don’t switch segments completely off first.

Does anyone have any suggestions on how I might reduce this bleedover in the code without having to completely turn segments on/off?

With regard to the noise, this is currently being done on a breadboard so ground separation isn’t great, but different strips are used for switching and chip/reference power. I’m also considering switching to MOSFETs as opposed to the 2N3906’s to reduce uC port switching currents a bit.

UPDATE:

Display Drive Schematic (there are only 2x 2200uF caps total)

ADC Reference Schematic, Reference is just TL431A

Reference Output with Microcontroller Disconnected

Reference Output with Segments Switched On-Off

While I didn't post the reference out with segments switched on-off vs on all the time, there actually isn't a significant difference between them. The real difference seems to be that the large spikes are slightly lower in amplitude, but not significant. However it can be clearly seen that the reference out is extremely noisy. The spikes are located at about 310kHz, 2x the DC-DC converter frequency (generating the 5.3V).

Any other tips to improve the noise behavior? Would MOSFETs like BSS84 replacing the 2N3906s help?


texts:
I would like to build an underwater mammal detector to take videos of seals when they get in and out of their cave (the entrance of their cave is underwater).

It will be a waterproof sealed box with a camera in it, fixed on the rocks (underwater, in front of a cave), which will record video whenever a seal is swimming in front of it, probably connected to a solar panel placed on the ground (on the shore, not underwater). The device should be autonomous for about a week.

I can think of a few solutions:

Just use a regular smartphone with a waterproof case (connected to a solar panel), with an app which process the video and record it when something is moving,
Same thing with a Raspberry PI and a webcam (infrared?),
Use a Raspberry PI, a webcam and PIR sensor to trigger the video recording,
Same thing with a laser trigger (probably not the best solution)

I would emphasize on simplicity and robustness.
So I have a few questions:

What solar panel would I need to power an iPhone processing/recording video non-stop (it will be in Greece with good sunlight conditions) (which power/specs, not which brand/model)? How will the battery evolve? Will a Raspberry PI consume less power?
Would a PIR sensor work underwater? Which one should I get (which specs)? How will it react to ambient light changes (day/night)?

The smartphone solution is attractive because of its simplicity, the PIR sensor solution might be better because it will consume less power.

Edit: Seals are mammals, they have warm blood (37°C), but it does not mean their skin is warmed than water. "Seals keep their skin at just 34°F (1°C) when lying on ice" Mammal Anatomy: An Illustrated Guide.

I don't know if they would be detected by PIR sensor + infrared is quickly absorbed by water.


texts:
I read in few places, one of them is this, that one of the main differences between UART and SPI is that the former is a type of hardware and the latter is a protocol.
I'm having hard time to fully grasp this notion. This is briefly what I got so far from the reading material I found googling, embedded with some questions:
UART
UART is a piece of hardware used to communicate between two components. The UART converts parallel data that it receives from a data bus into a serial stream of bits that are transferred across only one wire and vice versa. A UART uses only 2 wires - one for receiving and one for transmitting. The rest of the details aren't important for the manner of this discussion.
SPI
SPI is a synchronous (since it uses a clock) communication protocol used between devices.
This protocol uses 4 wired (if only one slave is present):

MOSI (Master Out/Slave In) - used to transmit data from master to slave
MISO (Master In/Slave Out) - used to transmit data from slave to master
SCLK - (Clock) - used to synchronize the data transmission.
SS/CS - (Slave Select/Chip Select) - When pulled low, signals the chip to communicate.

Unlike UART, it transfers bits in a stream not divided to packets (Here confusion begins - it's compared to UART). Devices communicating via SPI are in master-slave relationship. Master is the controlling device - usually a microcontroller -  while the slave - usually something like a display, sensor or memory chip - takes instructions from the master. (Sanity check - When we say that the master controls the slave, we merely mean the selection of the slave by the SS/CS wire and the clock signaling?)
Differences between UART and SPI

Number of wires - UART uses 2, SPI uses at least 4
No start/stop bits - data is sent continuously without interruptions.
Number of devices - UART can have only 2, SPI can virtually connect unlimited number of slaves to one master
Hardware vs Protocol - UART is a type of hardware while SPI is a protocol.

Finally - the question
What I'm mainly confused about is this last difference - Hardware vs Protocol. It seems that these two communication schemes are compared side-to-side in the same parameters (Number of pins, start/stop bits, Speed, etc.) - you can't compare 2 essentially different entities based on the same parameters right?
Is the difference is that UART is a dedicated piece of hardware and SPI uses general GPIOs of the microcontroller?


texts: Cutting female-to-female jumper wires to create female-to-male

texts: So I have a female-to-female jumper wire, but no female-to-male. Would I be able to create one from the female-to-female that is as reliable as a shop bought one, or is it best to just buy them? Thanks


texts: Choosing the right PTC Resettable Fuse for a protection circuit

texts:
Power shield protection circuit specs
Hello! Iv'e been creating an ESP32 power shield and started designing the protection circuit for the power supply with the following features:

Reverse polarity protection.
Overvoltage protection.
Overcurrent protection.

However, it is important to note that the design I'm using is based on this
Input
Supplied through either a 9V 2.5A power source to a screw terminal or a 9V 2.5A power charger to a barrel jack.
Output
The output of the protection circuit will be connected to 3 different regulators:

Vin (Connected to internal ESP32 regulator that takes 3.3v 500ma at load).
3.3V 1A regulator.
5V 1A regulator.

Component links
I Chose the following components for the circuit:

D3 (Schottky Barrier Diode)
F2 (PTC Resettable Fuse)
D4 (Zener Diode)

The PTC Resettable Fuse was chosen after reading this
Schematic

The Questions

Do I need to put a series resistor with D4 or is the PTC Resettable Fuse sufficient ?
Did i choose the correct PTC Resettable Fuse ?

P.S.
I'm new to electronics so please go easy on me if I miss obvious stuff.


texts: gold finger plating needed on prototype board edge connector?

texts:
I am making a PCIe card and will be ordering prototypes.

I know that in my production cards I should order hard gold plating on the edge connector.

Can I skip this plating on my prototype cards to save expense and production time?  I understand that the default plating (tin?) may be damaged by repeated insertions, but will a few insertions be an issue?

Helping the situation is that my card will be attached to a PCIe flexible riser cable, and could theoretically stay attached to that riser cable most of the time during testing, so most of the insertion cycles would wear on the riser cable and not my card.


texts: What happens when both sides of a bi-directional MOSFET logic level shifter try to drive it and how to make sure terrible things don't happen?

texts:
I understand the principle of operation of a simple MOSFET logic level shifter like the one described in this question. However, the answer to that question only states what happens when we apply logic levels to one of the sides leaving the other floating. I'm about to need a logic level converter for a bi-directional data line, so I'm interested in what we would expect to happen if both sides accidentally try to drive the circuit (e.g. by either side malfunctioning).

And then, how can the circuit be enhanced to ensure that we don't try to sink/source more than we can on either side? What about a situation where either or both sides aren't open drains but rather have internal pull-ups?


texts: How to express a logic sequence of a control circuit operation for a motor control center?

texts:
I have a customer to which I need to explain the logic sequence of the operation of the motor control centre's control schematics. The MCC has a complex RVSS unit for which the logic sequence has a moderate difficulty level. However, I tried every possible way in form of excel worksheet and pictorial representation. By pictorial representation I mean this :-

Ofcourse the above logic is simple and is shown for example.
Using the excel worksheet, I use textual form for every logical sequence (or rung) Example,

When the START push button is depressed, the coil M is energized and is latched through M XIC TRUE.
When the STOP push button in depressed, the coil M is denergized, thus the M XIC is turned FALSE

This becomes a tedious task for vast control schematics, including RVSS, VFDs and smart overload relays. Is there any specific way to express the control sequence algorithm the easier way (other than these) ?


texts:
I know it's needed to connect a capacitor from Vdd to Vss on 40XX IC's. Is it also useful on a CD4026 counter to connect the reset pin to one end of the capacitor to reset the IC to zero when powered on?

I used the same type of circuit for the CD4060 1 Hz quartz crystal which i'm using for my digital clock. I referred to this guide

This schematic is not complete, but notice how I have resistors connected to the ends of the capacitors.. Am I even using these correctly? I will also be using AND gates to reset these CD4026's at different times so really, not having these resistors would simplify my circuit a bit. Would rather not have them if they aren't needed.

I found another guide here with another reset circuit. It's slightly different than the first guide.

And from the First guide I posted.

Are either of these incorrect and why?

Update: The first guide was confirmed incorrect in the comments. I’m going to test with the second since I don’t have a diode.


texts:
I'm a hobbyist and I'm trying to place a 0.5mm pitch BGA with tweezers. I've yet to land the chip properly on 3 attempts. At ~$30/board, I need a better way.

What are my options?

I've seen some DIY manual pick and place rigs, but I don't really feel like spending 2 weeks to rig a frame that's only marginally better than placing it by hand. Professional rigs seem to start at ~$4,000, and I just don't have that to burn.

I'm using a SiLabs EFM32 part, and the only variant that has both USB and all 16 cap touch channels comes in a 0.5mm pitch BGA. I have a "plab B" board that uses an external cap touch chip so I can use a TQFP part instead, but I'd really like to at least try and see what I can do with this: I have a solder stencil and boards printed for the BGA: All I need to do is land the thing properly.

Using 1 chip will be simpler, smaller, have lower power consumption and a lower total cost. Most importantly, I have everything ready to go except rock-steady hands. Any advice is appreciated! I'd love to be able to drop this thing in and go!


texts: Reverse polarity protection non-isolated power supply

texts:
I'm trying to design a circuit with reverse polarity protection.
I have found numerous of examples but I can't get it to work for me with a non-isolated power supply. I'm open for suggestions.

I changed the circuit to this

I'm working on a school project and i thought it was smart to include a reverse polarity protection.
I need +20 and -20 Volt and these are not isolated. Here is what i come up with.

I use the following MOSFETS:
SI4825DY-T1-E3
IRFI4410ZPBF

Can anyone confirm if i choose the right MOSFETS?


texts: Lead Acid battery trickle charger sizing

texts:
I have a couple of lead acid batteries that need to be stored so I though up of a simple trickle charger with the following objectives in mind:
Objectives:

Should waste least amount of power so that power could be applied to the batteries as long as possible
Should be simple as it will be operated manually (voltage will be checked with a multimeter and connected and disconnected manually)

Schematic:

Components:

AC-DC power module from Hi-Link (part#:HLK-20M15) which outputs 15V with a max of 1.33A (20W) which has output short circuit and over current protection and self-recovery.
The diode for reverse polarity protection as well as a drop 1.1V which will allow the max output voltage to be 13.9V and
The 1ohm resistor is added as a current limiting resistor which can drop 1.33V at max output current.

Reasoning:
A total voltage drop of 2.4V (diode + resistor) from a 15V supply should allow me to charge the battery from 12.6V. I will be using a proper tested and certified charger for bulk charging if the voltage drops below 12.6V.
Question:
All that said I wanted to know if:

This should suffice from a safety point of view or any changes are required
Does charging to 13.9V for storage good enough for long term storage since I won't be drawing any current from it because I've seen some batteries require boost voltages of about 14.4-14.6V and some people suggested boost upto 16V.


texts: Y-Δ transform with generators. Equivalence of three-terminal devices

texts:
So my book asks me to find \$i_a, i_b, i_c\$ (as functions of \$v_1, v_2, v_3\$) as well as \$G_a, G_b, G_c\$ such that the circuit on the right picture (shown below) is equivalent to the circuit on the left. First he suggests to use Y-Δ transform to find \$G_a, G_b, G_c\$ with equivalent resitances \$R_1, R_2, R_3\$.

This is what I tried (note that this exercise is about so-called shift properties, where you duplicate generators in order to transform them into an equivalent form):

As you can see I duplicated each current source adding a short circuit (which it can be shown not to invalidate Kirchhoff's laws, thus obtaining parallel of the current source and resistance, which ultimately can be transformed to a voltage source). However, the resulting linear system has 0 determinant: what is wrong with my reasoning? How would you solve this exercise?


texts: design of compensator type 2 for current mode control of boost converter?

texts:
I have designed boost converter with Peak current mode control in PLECS. I have used the method of k factor approach to design the compensator. the bode plot transfer function of the power stage is used to select the crossover frequency of 40KHz as I am using a switching frequency of 2.2MHz and from this, I defined my compensator which shows a good bode plot(). the bode plot of the complete system is perfectly matching my expectation as you can see in the figure.
however, when I run the same circuit in PLECS with the compensator I get a huge oscillation and non-stable system and the compensator() is meant to stabilize my system ( I could not upload the file in stackoverflow). my question how can the frequency domain analysis works perfectly but when it comes to time domain( circuit) the system is completely wrong?
I have used a crossover frequency of 5KHz and shows the good result which means that my  control  loop does not show good behavior when it comes to higher crossover frequency which goes against my understanding that says I Can choose any crossover frequency as long as it is tenth less than the switching frequency.
the  bode plot of the compensated circuit(circuit with the compensator) is :
the circuit:
the cross over freqquency where it is unstable is 40KHz, I have chosen phase margin 60 and with the k factor approach I calculated the pole zeros and gain of the comensator


texts:
I am having a galvanic cell with the following half cell equations:

Anode--> 2Al(s) + 6OH --> 2Al(OH)3 + 6e-

Cathode--> 6H+ + 6e- --> 3H2(g)

So my cell is producing 6 electrons. Is there a way to calculate the current (ampere) generated using 6 electrons, theoretically?

P.S. sorry for the bad formatting but when I tried OH$^-$, it did not give me OH superscript - as shown.


texts: Reducing long term unpredictability in pairs of crystal oscillators?

texts:
We want to keep two physically separated units in sync with each other with the least drift between them possible. Absolute timekeeping accuracy is not important, only the relative drift between the two units.

Using off-the-shelf temperature compensated crystals (example), it is possible to get to about 2ppm over time periods greater than months.

I'd like to try to reduce that by characterizing and canceling the differences between the two crystals that contribute to that 2ppm drift.

Only one part I've found specifies the unit-to-unit variability in the data sheet, and interestingly that variability increases significantly after exposure to reflow temperatures...

So apparently exposure to high temps increases part-to-part variability, but why?

What are the other root sources of the drift between two temp compensated crystals? How can they be measured and (hopefully) canceled? Is it possible to buy or make crystals in pairs that minimize these sources of variation? Is there any other ultra low power (<10uA) oscillator types with lower unit-to-unit drift?

Note that in our case the units not subject to any acceleration except for constant G downwards.

This problem seems like something that would also come up in ultra low power communications systems where you want to receiver to wake up the instant before a transmission is expected and no sooner. Kind of like BLE power save RX windows, but on the order of months and years rather than milliseconds.


texts:
I'm building an interactive disco dance floor. Like the light up dance floors from the 70's, but each floor panel should be able to detect when it's being stepped on and possibly light up to show this. I'm trying to figure out the best method of step detection.

Each panel will be about 12" x 12".
Since people will be dancing, the panels should not move (a little bit of give is okay)
Optical detection from above will detect the person blob, but not which panel is being stepped on (not accurate enough).
Optical detection from below is expensive and could be troublesome if trash is on the floor.

What is the best approach here? Ideally the panel wouldn't move at all and could just detect that someone is standing on it. Although, I'm okay with the panel having a bit of give, if needed. The important thing is that people can dance normally without feeling like the floor is unstable.

Here are some of the ideas that I have come across:

Piezo Sensor: I believe the voltage spike with these sensors is momentary and wouldn't let the system know if the person is still standing on the panel.

Custom Foam Pressure Sensor: Based on this instructable, an analog pressure sensor made from foam. It is cheap, but probably not well calibrated or consistent between panels.

Accelerometer Tap/Click Detection: Would require a heavy enough stomp to detect and the feedback would be momentary, like the piezo sensor, and not let me know the person is still standing on it.

Air Pressure sensor: A sealed rubber tube with a barometric pressure sensor under the panel. This would require me to build the sealed tube and could be susceptible to damage or leaks over time.

Capacitance Detection: Would it be possible to detect capacitance change over the panel? Even if the person is wearing rubber or leather soled shoes?

Load Cell:
Like this one from SparkFun. Would report when someone is standing on it and how much of their weight is applied. Currently my favorite option.

Ideally I want to go with something that will work consistently and will last.


texts:
I have used the following circuit to for the purpose of reverse voltage protection. But, I am a little bit confuse about the working of the zener diode in combination of the 100k resistor in this circuit.

So, what is the need of the zener diode in combination of the resistor in this circuit? How they are exactly working here?


texts: How do I use 5V PWM from PIC to control 12V fan?

texts:
I'm not sure if that title explains it well enough, but I have a 12V PWM PC fan which I want to drive using a 5V PIC.

The fan has 4 pins, GND, +12V, PWM and TACH. The TACH is a speed sense pulse from a Hall effect sensor, and I won't be using that.

The PWM is pulled up internally in the fan so that it will run at full speed if that pin is not connected (e.g. for motherboards that only support 3-pin fans). Therefore, to control the speed, I need to drive the fan's PWM pin from the PWM output of the PIC.

When testing with a couple of spare fans, I just applied +12V to get the fan running at full speed and then measured the voltage between the fan's PWM pin and GND. On some fans, it seems to be pulled up internally to 3.3V but on the fan I want to use, it's pulled up to 12V. (So I'm glad I measured it rather than assuming they were all the same).

According to the specifications I've found, the fan's PWM should not source more than 5mA (I measured it at only 0.68mA) but having said that the spec also says that the PWM should be pulled up to a maximum of 5.25V within the fan and I measured 12V. The fan manufacturer gives minimal information.

Can I just drive the gate of a MOSFET directly from the PIC's PWM output and connect the drain to the fan's PWM and source to common ground? Is that the "right" way to do it? Is it appropriate to use a MOSFET rather than a BJT? (I'm thinking of 2N7000, just because I have some handy).


texts:
For my new PCB, I want to use a 7-series XILINX FPGA. I was a little bit unsure of the JTAG interface so I looked up some schematics of XILINX evaluation boards.
I found the Arty S7 50 schematic.
The JTAG interface of the Arty S7 50 is depicted below (can be found on page 6 in the schematic).

I think the Zener diodes have the purpose to protect the I/Os of a voltage that would be too big. Zener diodes have different breakdown voltages. I guess the depicted Zener diodes have a breakdown voltage that is bigger than 3.3V.
Is this correct? So when I use Zener diodes with a breakdown voltage of around 5V I should be good.


texts: Encoder vs Hall Effect for FOC control of BLDC

texts:
I've been reading into field orientation control a bit (specifically I want to design a position controller), and it seems that there are three ways to get to position feedback

Hall effect
Encoder
Sliding mode estimator using current measurements

The sensorless option is complex, and I'm still trying to wrap my head around that. It seems I'm missing something, however in understanding the sensored options. From my understanding, a hall effect sensor will give an absolute rotor position; an encoder on the other hand will only give a relative position. When using an encoder, is there some sort of calibration step to get the initial rotor position?
Are there any specific reasons to use one type of sensor over the other?


texts:
I want to control the power consumption and intensity of a IR LED which is fed by a 38kHz signal.
Can I add mosfets in series with different resistors (25/250) like in my schematic? Application is a battery powered beam brake.

IRLML2502PBF MOSFET datasheet here

Do I need additional resistor in gate and between gate and source?
Driven by 5V Atmega328P or maybe 3.3V to lower the power consumption.
Also, am I right that using mosfets instead of  bipolar transistors is more energy-saving?

Version 2


texts: Will a car battery break small electronic equipment?

texts:
I have a 12V car battery. I'd like to run a small wireless router type device on it for a couple of hours. The wireless router has "12V 1A max" written on it.

Will the car battery damage the router, or will it just draw the current it needs and work okay?


texts: Killswitch: switchable high voltage path/shunt to ground without any additional power supply

texts:
I have a circuit with a high voltage source (rectifet 400VAC) (part of a
capacitor discharge ignition.)
High voltage should only be available if normal power (low voltage DC power supply for the rest of the circuit) is connected.
That means if power is off there has to be a way to shunt/dissipate the power of the high voltage source.
Turn circuit off --> kill high voltage.
I have developed a circuit that should do the trick
Maybe someone has feedback, a better idea or sees a failure point.
Circuit description:
The gate voltage of the MOSFET Q1 to the left should always be 1,8V below the source (high voltage) so it is conducting even if power is off connecting the high voltage to a resistor connected to ground for power dissipation.
Now if the second MOSFET Q2 is conducting it is shorting the three diodes to the right which would be after circuit powerup if the MCU switches Q3 over the optocoupler.
The resistors in series to the diodes are picked very high so in normal “on” operation there is close to no high voltage supply power loss.
This is because (in normal “on” operation) the high voltage is used to charge a capacitor and every bit of change is needed.


texts: Can I measure large force using series FSR?

texts:
Is it possible to measure large force using multiple Force Sensitive Resistors in a series? Will I have to stack the resistors up? Will the measurement be reliable if I place them side by side?

I want to measure the pressure applied by a standing human on a surface. I do not expect the entire weight of a human on the sensor, but whatever part of the foot that touches the FSR. Any suggestions?


texts:
With an example for data with a hexadecimal value of 0xda and a polynomial 0x07, I would find the CRC as follows (using the methodology from Wikipedia)

0xda = 11011010

11011010|00000000
111
00111010|00000000
  111
00000010|00000000
      11 1
00000001|10000000
       1 11
00000000|01000000

But the answer should be 0x08 according to this calculator.

I need the answer to be correct for the IEEE standard Ethernet. I've found that some sources pad the data and some don't. IEEE seem to suggest padding is required if the data is less than the CRC width.

Note: I know that the CRC is not strictly the remainder of the data divided by the polynomial either.

0xda = 11011010 = 218
0x07 = 00000111 = 7
218/7 = 31 r 1

As you can see below, the IEEE outlines a lot more steps than suggested on Wikipedia. How can I be certain that the CRC calculators online give the correct values for Ethernet?

For my attempt at following the standard (with the 8 bit CRC example)
a.) First 8 bits of the frame are complemented

11011010 -> 00100101

c.) Multiply by x^8 is equivalent to shifting by 8 bits (padded with zeros)

00100101 -> 00100101 00000000 = 18688

d.) Divide by G(x) and get remainder  R(x)

18688/7 = 2669 r 5

Update: I have since got an 8 bit vhdl implementation using a 256 entry lookup table working. Or at least it gives the same results as the calculator online.


texts:
What is the correct voltage terminology for VDD and VSS?

I've been installing a Winstar WEH001602D OLED and was struggling until I realised that it appears to have pins 1 and 2 reversed compared to the usual convention. It requires +5 V DC on pin 1 and 0 V on pin2.

However in the abbreviated data sheet it says "pin 1, VDD, Ground Pin" and "pin 2, VSS, Voltage for logic" whilst the website says "pin 1, VDD, Supply Voltage for logic" and "pin 2, Vss, Ground Pin".

The WEH001602D's that I have definitely have the two pins reversed, though.


texts: How do I make the Fairchild FSA9280/FSA9480/FSA880 BOOT pin trigger? (Samsung Galaxy S)

texts:
this is a bit of a long shot but I'm hoping someone has access to the full data sheet for one of the chips listed in the title, and can tell me what combination of VBUS_IN and resistors on ID_CON will make it trigger the BOOT pin on the chip. Unfortunately Fairchild will not release the full data sheet for these chips (I have asked), and only an abbreviated version (PDF link) is available on the web.

Long story: the FSA9480 chip is used on some Samsung phones to detect various accessories using sensing resistors on the ID pin of the USB port. We've already made a lot of progress through info from the phone's Android kernel source. Now we're trying to force the phone's CPU into a boot recovery mode that will make it load an external bootloader from the serial port, and it looks like the BOOT pin on the FSA9480 might do this, but we can't figure out how to trigger it.

So far I've tried all the resistors on the known list without power connected to the USB port, and all of the resistor values that produced serial output again with power on the USB port.

Update: We're working on the theory that this schematic from the service manual shows a signal going from the FSA9480 BOOT pin to a signal named BOOT_MODE, which in any sane world would go the the application processor chip's OM5 pin. But we don't have the full schematic to prove it, and we don't have the internal details of the FSA9480 to show how that pin gets triggered. You would think it would be the resistors with BOOT_ON in their names (like RID_FM_BOOT_ON_UART), but apparently not. Or maybe it is, but the BOOT_MODE signal doesn't go to the right place. Either way the FSAx80 data sheet would confirm it.

I've reverse-engineered the startup and bootloader download code in the application processor's (Samsung S5PC110) internal ROM, and worked out that if we succeed we should see the first byte of the bootloader download protocol on the serial port. Instead we are getting the output of the primary bootloader which is being loaded from NAND, which indicates a normal boot.


texts:
I want to measure the impedance of a speaker (by different frequencies). The idea to test it was the following, I have the follow circuit:

Now, in order to find the impedance I measured the voltage across the speaker and over the potentiometer, if they are different then I turn the potentiometer as much that it will read the same voltage that is standing over the speaker. Then I get (using formula's):

$$\underline{\text{U}_\text{sp}}=\underline{\text{U}_\text{R}}=\underline{\text{I}_\text{sp}}\cdot\underline{\text{Z}_\text{sp}}=\underline{\text{I}_\text{R}}\cdot\underline{\text{Z}_\text{R}}=\underline{\text{I}_\text{in}}\cdot\underline{\text{Z}_\text{sp}}=\underline{\text{I}_\text{in}}\cdot\text{R}\space\Longleftrightarrow\space\underline{\text{Z}_\text{sp}}=\text{R}$$

But I think I'm measuring the absolute value of \$\underline{\text{Z}_\text{sp}}\$.

  Question: Can I use this method? And if I can am I measuring \$\left|\underline{\text{Z}_\text{sp}}\right|\$?


texts:
I would like to know how can I measure or calculate the junction capacitance of an oxygen sensor(or photodiode or any current source sensor).

The manufacturer does not have this information on their datasheet.
http://www.teledyne-ai.com/pdf/schem_a59452.pdf


texts: high voltage DC biasing on top of low voltage AC with floating load

texts:
I am in process of designing a power supply for heating a filament in an electron gun. The AC heating current has to float on top of DC high voltage acceleration voltage. The following circuit seems to work (at least simulated..) such that I get about 2 A of current onto the filament. Yet I have seen circuits that includes a capacitor C1 in series with the AC source. Is this capacitor necessary in real world application and if so, then why?
thanks!


texts:
I know there is clock gating method that xor-ing the input and output of FF, and use that signal as clock enable. (figure 1, i'll call it xor-ing from now)

I'm now studying sequential clock gating. I can't understand why sequential clock gating such as using STC or ODC condition is useful.

I think clock gating some serial FFs through STC condition gets the same result of gating them by xor-ing each input and output of FFs. In case of ODC condition, i think it could be effective because clk of FFs can be gated while input/output of FFs are not equal, which cannot be gated by xor-ing.

In case of STC condition, however, i cannot understand why it is useful. Let's say there are three serial FFs,  FF1, FF2 and FF3. When FF1 is stable, FF2 can be clock gated in the next timeframe, and then FF3 can be clock gated next, as sequential clock gating through STC conditioin says. My question is, does it get more power reduction than just xor-ing three FFs respectively?
I studied this problem for a few days, but still I didn't get answer.

figure1: XOR-ing the input/output of FF, generate clock enable signal


texts: Do I need >5V power supply to adequately protect against overvoltage >5V? Seems contradictory

texts:
My circuit requires 5 volts and roughly 4 amps. I am using a 5V/10A power supply. I would like to protect against overcurrent and overvoltage (>5V).
Protecting against overcurrent seems straightforward using a polyfuse. My circuit should never require > 5A, so I am sizing my polyfuse accordingly.
But, protecting against overvoltage seems almost impossible while using a 5 volt supply. Nearly all the overvoltage protection methods use Zener diodes, which typically have a 0.6V voltage drop, which would provide less than the 5 volts I need downstream.
Increasing the voltage of my power supply (>5V) to ensure a safer lower voltage (5V) seems wrong to me. It's like increasing the danger in order to decrease the danger. Am I missing something?
I am pairing a 5V power supply with my 5 volt circuit. I'm just worried than someone else could accidently plug in a 12V (or worse) supply and cause damage.


texts: Maximum current for a single-core cable?

texts:
I want to connect the cables of a LiPo 7.4 V 2200 mAh battery, to a breadboard. However, the only way to make this happens is to solder the ends of the battery cables with a single-core cable with solid conductor.

Is this a safe option or there is the risk of damaging the single-core cable? As far as I know, the current draw will be about 700 mA.


texts:
I have a square-shaped plastic plate (3 cm length X 3 cm width X 1.5 cm height) attached to a motor that rotates it at 500 Hz:

I would like to have an interrupt fired on my microcontroller every time Point X (on rotating plate) reaches Position Y (fixed).

What would be an accurate way of accomplishing this such that the interrupt fires as exactly at that location as possible?

__

My notes: I would prefer not to modify the square plate with any additional material (so I'm guessing magnetic encoding is out). Therefore, I'm thinking some sort of optical interruption/reflectance sensor would do the job, but for greater accuracy perhaps the system might benefit from using an infrared laser diode placed above the plate, and a photodiode with matching wavelength range under the plate?

__

EDIT 1: I should mention that the square-plate is permanently fixed to the motor shaft, and cannot be removed to, e.g., insert an optical encoder disk in between.

EDIT 2: Detecting any/all of the four X corners of the square is OK; it doesn't have to be one particular X.

EDIT 3: Accuracy desired: +/- 0.1 mm radial travel.


texts:
I want to do a MIDI Controller which uses 15 MHz SPI between a Teensy 3.6 and 74HC595 / 74HC165 Shift Registers to read a button Matrix. The code is finished and the PCB would be the next step. I have read a lot about 50 Ohm controlled impedance transmission lines, return paths on ground planes, etc.
However, as I am completely new to this I have some simple (noob) questions:

Does the return path really matter this much? I have attached a picture of my breadboard layout. Wires are going very chaotic and just to test stability I used 60 cm wires for the SPI. It just works fine. Do I have to be so much more careful when using a PCB? I would like to stick to two layers because it is much cheaper. My general Sketch runs with 4 kHz and I have some PWM at 29 kHz. There is nothing going on in parallel during the SPI transfer. I propably will not have space for a proper ground plane as I also use motor faders, encoders and stuff and they will become a lot more than on the prototype  and therefore, will need lot's of connections.

Does crosstalk to other signal matter if I don't need to evaluate them at the same time?

If you say it won't work without a good return path, can I replace the ground plane with a ground track running close to the SPI signal line? Unforunately I found nothing about that.

According the Saturn PCB Toolikit even with 75 MHz (I considered that because I was not sure if 15 Mhz would mean a bandwith of 75 MHz)  and a Lambda of 1/10 I can go approx. 15 Inches without considering it to be a transmission line. I think I just can't run clock and signal in parallel to avoid cross talk in between them. Perhaps running a ground track in between them & keeping them approx. the same length will be good.
Thanks.


texts: Need advice on microcontroller to switch relay on/off

texts:
I am trying to connect an OMRON G2RL-2A DPST 12 VDC relay (G2RL relay datasheet) to my PICAXE 20x2 microcontroller. I also have a ULN2803A relay driver (ULN2803A datasheet).

I managed to get the microcontroller to work quite well, so I don't have a problem with it.

The question is this: The ULN2803 does not have a V+ pin, so does that mean it does not require power? It only has a GND pin, which I believe should be connected to a GND (probably the GND of the microcontroller?)

Now, I think I have to connect an output of the PICAXE 20x2 to an input of ULN2803. After this, where should I connect the respective output of the ULN2803 on the relay?

Also do I have to use a 12 VDC power for my relay? Or maybe I can use the same 5 V power of my microcontroller? If not, where should I connect this 12 V on the relay?

Sorry for total noob questions, I hope you can guide me.

UPDATE

I can not still make this circuit to work properly. Here is the work I have done so far, please have a look. The problem is, if I connect ULN2803 pin 10 to +12 V or GND, the relays either dont work or just lock the current state. Where should I connect ULN2803 pin 10?


texts:
I am trying to confirm the right orientation for all the packages I am using in Eagle before sending for pick and place assembly. After reading a bit, I understand that there is no standard from one chip company to another.

My question is simple: can I know for sure the proper orientation based on the way the chip is positioned in the reel ?

Looking at the way leds are packaged, and knowing that rotation 0 for leds is cathode on the left and anode on the right, I would tend to think that I can get the rotation 0 orientation by looking at chip with the holes on the left: is that correct ?


texts:
When designing a QFN footprint, I've read from (reputation limited, only 2) sources...

http://www.freescale.com/files/analog/doc/app_note/AN1902.pdf
http://www.atmel.com/images/doc8583.pdf

...that the QFN should sit approximately 50-75um (2-3 mil) high off the board for reliable solder joints. I assume that this "standoff" height is created by the solder joints themselves.

So far I have gathered:

Use ENIG or OSP finish. This provides the most flat surface (necessary for applying the stencil, paste and placing the package).
For the center pad (a.k.a. exposed pad, EP, thermal pad), use a SMD (solder mask defined) pad.
For outside (a.k.a perimeter) pads, use non-SMD pads. NSMD pads will result in a pad that is most accurate to your design because copper etching has a tighter tolerance than solder mask.
Extend perimeter pads towards center of package 0.05mm and away from package ~0.2-0.6mm. This provides a more reliable solder joint and potentially allows for easy rework since the pad will extend outside the package.
For QFNs at a pitch of 0.5mm and below, keep PCB footprint pad width equal to package pad width. For 0.65mm and above.
For QFNs at a pitch of 0.5mm and above, you can define the solder mask between pads. For QFNs at a pitch of 0.4mm and below, define an area that keeps mask out for each row of pads on the QFN.

There are many variables here.
The answer I am looking for would define a stencil thickness and aperture opening relative to pad size and pitch. Does the center pad or do the perimeter pads have the most effect on standoff height?
How important is the standoff height?  Are the datasheets simply warning us not to float the part with too much solder in the middle?
Past experiences in production environments as well as prototype (DIY, applying stencil and paste by hand) would be incredible.

What design parameters influence the "standoff" (or solder joint) height?


texts: How can I tell if a serial connection is sending bytes okay?

texts:
I have a Teensy connected to a Pololu motor controller. If I send bytes over USB (using Pololu Serial Transmitter v1.3) I can get it to work (For instance, 0x85 0x00 0x20 makes the motor run at slow speed). However when I attempt the same thing in my sketch I cannot get it to work. This leads me to the conclusion that there may be a problem with my serial wires or with the motor control board itself.

So I'd like to be able to test that the serial connection is working, can I accomplish this with a multimeter or something?

My code, just in case there's something wrong with that is:

#define rxPin 10
#define txPin 9
SoftwareSerial smcSerial = SoftwareSerial(rxPin, txPin);

loop:

smcSerial.write(0x85);
smcSerial.write((byte) 0x00);
smcSerial.write(0x20);