texts: Safest way to make a high-voltage switch

texts:
First of all, I've dabbled in electronics on and off over the years. I have no formal training.

I'm designing a vacuum tube guitar amplifier (seems like everyone is these days). I want to add a switch to change the voltage of the screen grid of a tetrode (basically to switch it into triode mode. This is in the power amp section.)

The plate voltage is 384V and the screen grid will be somewhere in the vicinity. The current will be a few mA. I don't want to use some big fat gigantic 600V switch to switch it and I don't feel comfortable having almost 400V that close to being touchable. I'd like it to be a little switch in the back of the amp. Either a toggle or a slider.

The leading idea I have at the moment (and this may be a terrible idea, which is why I'm here) is to have two N-Channel MOSFETs, each with the source connected to the screen grid and the drains connected to the two different voltage sources and then an SPDT switch that activates the gate of one of the MOSFETs. (The gates would have pulldown resistors to ground.)

Would this work or is the better way? Would I have to worry about it introducing any sort of noise?

(Incidentally, the switch would be on the back of the amp, probably covered, and meant only to be switched when the amp is powered off).


texts: Not getting enough power to drive a motor while using MOSFET

texts:
I am a complete newbie at electronics. I was trying to drive a motor using MOSFET. It works well, but the motor does not run as fast as it would run if it were directly connected to the battery. I am using Si2300 MOSFET. Is this supposed to happen? If so, then any suggestion to improve this would be really helpful.
Edit: Here is a schematic-


texts:
Is there a lightweight networking framework to facilitate network communications between Ethernet/Wireless enabled Arduinos and Linux/Mac/Windows PCs?

Implementing something like being able to read and write the pins or trigger a function from the PC on the Arduino, or trigger an event on the PC because of some input on the Arduino.

I guess I'm just trying to avoid re-inventing a wheel if possible...


texts: Can we implement LVDS if my supply voltage is 1.2V?

texts:
I am to make output driver for my circuit. In lvds common mode voltage is selected to b3 1.2v.
If my supply voltage is 1.2v, is it possible to implement LVDS?


texts:
I am trying to use rechargeable batteries. If I recharge two of the below batteries via the solar panel below, how many hours will it need to recharge to 100%? Likewise, what if I recharge four batteries?

Batteries:

Rechargable NiMH AA HR6 1.2V 700 mAh

Solar panel:

Related Maximum Power: 3W
Voltage at Pmax: 9V
Current at Pmax: 0.33 A
Open-circuit Voltage: 10.5 V
Short-Circuit Current: 0.43 A
Normal Operating cell Temp: 47 +/- 2 C
Maximum Series Fuse Rating: 10 A
Operating Temperature: -40 C to 85 C
Application Class: Class A
Cell Technology: Ploy-Si
Dimensions: 306 x 148 x 15 mm


texts: How is something level trigger vs edge triggered?

texts:
I understand what they both are, but how exactly is something "made" to be edge triggered? I understand some computer architecture concepts, and while I understand individual components (gates/flip flops/etc...) I don't understand what makes something rising edge/falling edge triggered or level triggered for example?

Im more or less looking for a "Physical" reason that determines why one vs the other.


texts: Accurate frequency output through external speaker

texts:
I'm creating an application where I want to output a constant frequency through a speaker to test the frequency range of a microphone device I've developed. The problem is, my application measures very low frequencies in the range of 2Hz to around 200Hz, where most speakers start at 200Hz!

I've looked into subwoofers but they still seem to begin around the 20Hz range whereas I need it a bit lower.

I'm using MATLAB to output the constant frequency using the built in functionality there. I need a speaker which I can output a very low frequency sound through the 3.5mm port in a laptop/sound card to a speaker which can accurately produce these frequencies.

Is this possible? If so, any recommendations on a speaker which can produce these ranges or anything I need to think about to get as accurate results as possible? Needs to be fairly cheap (~<£50), the cheaper the better.


texts:
It's very rare that I get to design applications in need of cooling so I haven't had the need to study in-depth about that, but now I face an occation where I need cooling for a TO220 and I'm unsure how to calculate what I need.

TRIAC BTA08-600, data sheet: https://www.tme.eu/en/Document/229a1f149ceabe983b1ecaf8c207519b/BTA08-600BRG-STMicroelectronics.pdf

Page 4 tells me the power dissipation relative amps. In my circuit 3A is worst case, but regarding cooling I will calculate for 4A just for the sake of margins. The table tells me 4A => 4W.

Page 3 then tells me Rth(j-a) for TO220 is 60 degrees C per Watt. If I understand this parameter correctly, it would mean that for 4A times 60 degrees, it would go up to 240 degrees C in total. Then, page 2, tells me under "Absolute maximum rating" that Tj is +125 degrees.

If I'm guessing correct here it would mean I would have to use a heatsink that can cool down 240-125 = 115 degrees C.

Question 1: Is this assumption correct?

Question 2: How do I find a TO220-based heatsink that's able to cool 115 degrees? What parameters should I peek on / search for?


texts: Floating charge pump for high side N-channel MOSFET bias

texts:
This question is derived from this one. I'd like to keep gate on for an indefinite period of time (100% Duty cycle) and for that I'd like to use charge pump since idea with relay is not attractive. The problem is that Vin is high (~55VDC) and charge pump circuit has to survive this voltage. If I want to avoid separate floating power supply charge pump has to be floating. I found such solution which is unfortunately obsolete (On Semi NIS6201) and without any successor. Another possibility is to use a cheap hot-swap controller (i.e. LM5069) which comes with such charge pump.

Another possibility is to build charge pump which will survive 50+ VDC.
The question is how to emulate solution which is used in mentioned LM5069 or similar controllers?

EDIT1 (2015-01-29):

I tried on breadboard the circuit proposed by Dwayne Reid and got confusing results. DVM reading is almost 50VDC between "gate" and "source" outputs but in the same time oscilloscope measurement (differential method, Ch1 or A channel is connected to the "gate" and inverted Ch2 or B channel to the "source" output) give me ~22V.

Also when I connect ground of any probe (and differential measurement is not enabled) output voltage on DVM immediately drop to ~13.8V. I hope that is regular behaviour since ground (pin 1) is in that way earthed (hm, but DVM is battery powered and therefore "floating"?). Mentioned 50V DVM reading is present only when probe tip is connected to the "gate" output.

Mosfet was not connected and don't know what will happened if I bring 55VDC to the Drain. NE555 timer is connected to 15V instead of 12V. Frequency is 370KHz.

EDIT2 (2015-01-31):

Here is a tested version of floating charge pump. I found two documents particularly helpful: TI - Discrete Charge Pump Design, slva398a and IR - HV Floating MOS-Gate Driver ICs, an-978.

Two scenarios was tested (Vin=56VDC in both case): R2=3.3K and R2=4.7K.


texts: Troubleshooting why Powerbank Doesn't Charge Cell Phone

texts:
I have powerbank that provides 5v (presumably regulated) power, as typical of most usb interface powerbanks. I have been trying out my powerbank with different phones. It works on all except one. I have tried it with various USB cables, making sure I didn't overlook anything foolish. Then, I looked at the AC adapter of the phone that it didn't seem to be compatible with. The adapter read: 5.4v DC output. The device's official website or manual doesn't tell me what the input voltage should be. So I have the following questions

Is the fact that the device's AC adapter creates a DC 5.4v output enough to assume that, this is the correct voltage for my cell phone?
If 5.4v is the input voltage, then when I attempt to power it with a 5v power bank, am I hurting it? Thus far, it just seems to be non-responsive when I try this.
It seems another explanation is polarity mismatch. I'm aware that laptops have a polarity correction feature, which could explain why I can charge this phone via my laptop. Is there any other way to tell if polarity is an issue, given that I don't have access to detailed product information (unless the official website is updated, or something)

So that's the gist of it, I'm not sure why my powerbank isn't charging my phone. And I'm having difficulty troubleshooting the underlying problem by myself. Any tips big or small will be appreciated.


texts: Trying to understand zener voltage regulator theory

texts:
I'm trying to understand how this circuit operates. For this example lets say "From Battery Stack +" voltage is 42V. This circuit is designed to output about 4V at the source of the n-fet.  I don't understand how that is possible.
I see 42V applied to both the drain of the n-fet and R1. R1 limits the current through the Zener so it can be rated relatively high resistance. The Zener is rated for 5.6V so 5.6V will be applied at the gate of the n-fet. 5.6V is above the threshold gate voltage of the fet which is about 2V so the n-fet will conduct.
Here is were my understanding is lost, if the n-fet is conducting and the voltage on the drain is 42V then wouldn't the source output of the n-fet be 42V as well? How could it be 4V?


texts:
I have a slight problem with logisism concerning d flip flop. Please tell me if this is a bug or not : My d flip flop trigger is high level.

Thank you for any answer you may give


texts:
:)
Is this a capacitor and if it is the sign A4 means ??!]1


texts: Beginner here. I'm trying to read this datasheet, and I'm not sure what Vfb is or how it was obtained. See pages 19-20 in section 8.2. https://www.ti.com/lit/ds/symlink/lm3410.pdf


texts: I have made a rechargeable torch using 4 LEDs in parralel and an 18650 battery. The battery is charged by using a TP4056 module. Due to the fact that I got 10 for 1 pound on ebay it does not have over discharge protection. What is the minimum voltage I can take the battery to. As the 4 LEDs wired in parallel are connected to a 100 ohm resistor will the LEDS switch off when the voltage is too low ?


texts: Where is UNIQUE 125kHz protocol specified?

texts:
I am working on a RFID reader project and I can't find 125kHz UNIQUE tag specification (like listed in this TWN4 reader spec). I could easily find the datasheets for EM4100, EM4200, EM4102 tags.

One tag I've found uses the term "UNIQUE" but has EM4102 chip inside.

Questions:

Is the UNIQUE tag a specific RFID standard or is it only a marketing term?
If it is a standard - where can I find the specification of the UNIQUE tag protocol/data format?


texts:
I have a small aquarium that has been illuminated so far by a 15W fluorescent lamp. The problem is that the ballast has broken (melted) after 2 years of use, and the only replacements I could find on my market (same, 1x18W) break after 1-2 hours of use. By "break" I mean they heat up, start melting, stop working. The melting always happens at the coil, which by the way looks just like a transformer, and probably is one, but only has 2 wires connected to it, while the second pair remains in the air (see attached photo).

So, lacking any viable solution using classical fluorescent tubes, I thought about 2 options:

Find 2 sockets and install them, so they would fit 2 9W compact fluorescent lamps. But:

Are the built-in compact ballasts able to handle a relative humidity of ~70-80%?
Can they work in relatively closed spaces where temperatures might rise to up to 50 degrees Celsius (because of the energy output) during summer?

I have a remarkably rich assortment of LEDs on my market, that is totally lacking fluorescent tube lighting accessories. So I thought about using LED lighting, but:

I've read that they are less efficient than fluorescent tubes, so I'd need then about 20W LED
20W LED would make even more heat, and where would that dissipate? Especially that I've read that LEDs work best below 40 degrees Celsius. I can find lots of single high power LEDs, and combined LED lamps, but the high power LEDs have no accessories to them, no radiator, no nothing.
I'm afraid of the "warm" light spectrum. I have plants that need UV light, and light sources that focus on "warm" light usually cut down on the blue and UV light, while fluorescent lamps peak at UV.

Maybe another option:
Is using a ballast with more power going to help? Or is that only going to fry my tube, while the cheap electronics inside the ballast is as likely to melt as the less powerful one? When I've read what ballasts do, I figured that since they are built for, say, 40W, then they would maintain a higher Voltage*Current for the lamp. Or is it actually a possible solution to my problem?


texts: Why did KiCad merge my pins into one open blob in the solder mask gerber?

texts:
I designed a PCB with an IC that has a pitch of 0.5.  The footprint solder mask looks like this:

However, the gerber came out with one blob that looks like this:

Why did it do that?  Can I stop it?  Should I stop it?

I don't usually answer my own questions (and really probably shouldn't on EE), but I think I have some additional details that are relevant to answering the question fully.  Please provide feedback via comments or votes for the sake of the community.

PCBWay has the following requirements for the solder stop mask:

The TPS612332 Data Sheet recommends a pad width of 0.28mm and solder mask clearance of 0.07mm all around that pad:

If I have a 0.5mm pitch and .28mm of that is occupied by pads with 0.07mm of mask clearance, then I only have 0.08mm for the bridge (which is less than the 0.1mm minimum for PCBWay).

Which is why KiCad didn't put solder mask between the pads for this particular IC.

Can I stop it?  Yes.  Just like @Seth said in his answer, in PCBNew, I can click Setup->Pads to Mask Clearance and change the "Solder mask clearance" and "Solder mask min width" to allow the solder mask to appear.

Should I?  Well, having the solder mask would likely help prevent shorts between pins due to solder issues.  On the other hand, it seems like exceeding the minimum requirements set forth by the manufacturer may also expose risk in the manufacturing process.


texts: When should I use impedence matching resistors in fast signals?

texts:
I've understood why impedence matching resistor terminations are usefull with fast signals in digital electronics, but I'm not sure when I should use them.

My question is, when should I, and really worth, add a termination resistor to a signal line?

I'm looking for a general tip, like: If signal is faster than 200Mhz and line path is longer that 1cm.


texts:
Quite a few decades ago (either late 70's or early 80's), I vaguely remember seeing on TV a demonstration of, what would now be called, mirroring of a CRT screen, that was over 30 meters away, without the use of any cables, fibre optics, wires or what have you - this was "through the air" (as described at the time). Hence, the output of the computer that was connected to the CRT could be seen, even though the "hacker" was not at the actual computer's console.
The TV article raised fears about spying, Soviet espionage, etc. - as was usual in those days.
Irrespective of the geo-politics behind the potential for espionage (involving the misuse of this technology 40 years ago), how was this mirroring actually achieved back in the day1?
I haven't been able to find a recording of the clip yet, but I will update this question when I do.
Addendum
Thanks to Michael's comment, the video in question is this: TEMPEST - Protection from Computer Eavesdropping ~ BBC Tomorrow's World... which sort of has the answer in the video title!

1 Please note that I have no desire to reproduce this effect today, using either CRTs or with flat screen technology. At the risk of repeating myself - I merely wish to know how it was achieved back then.


texts: MOSFETs connected in series forming an H-bridge circuit for switching

texts: I want to develop an H-bridge circuit using 2 MOSFET switches connected such that when the  switch 1 is on (switch 2 off) the output voltage should be +5V and when the switch 2 on (switch 1 off) the output should be -5 V. Can anyone tell me which type of MOSFETs (N channel or P channel) I should use and also, which terminal should be connected to the Vdd (drain or source) and which terminals of the MOSFETs should be connected together/series? I will be using 2 input high side driver to control their gate voltages.


texts: What will happen when the current is too high for a switch?

texts: I powered a 36 volt, 1000 watt motor that is pulling 35 amperes into my wires, but what will happen if I wire up a 36 volt switch with a lower rated-current?


texts: How do I find out whats wrong with my setup of a Bipolar Stepper Motor using L293DNE driver connected to Arduino?

texts:
Using this sheet to an Arduino Uno I am trying to drive a Bipolar Stepper Motor. I have dragged out all the connections 6 times and retried now, but still the  stepper will only do a strange vibration when its connected and I upload the schema. I have checked the pairing of the connections with a multimeter, so I know that that's not the problem, but somewhere in my connection I must have messed something up.  If it can help I have uploaded some screenshots of my setup in the bottom of the post. I am not asking to thoroughly observe them to find my mistake, just for if you want to take a quick look to check if any obvious errors.

Stepper motor datasheet
Stepper motor specs

Any tips on common mistakes when connecting steppers with this kind of driver to Arduino also helpful. Or any other newbie mistakes.

Schema uploading to Arduino I have copied from this page: http://www.tigoe.com/pcomp/code/circuits/motors/stepper-motors/

I have also tried just using the standard Stepper.h library from Arduino.cc and changed the values using two pins. Same result, just random vibrations from the stepper.

Scheme:

Before connecting jumper cables:

Connecting NPN transistors:

All connections done: (here I have connected the jack which is going to battery just to the power source of the 5v in the Arduino, I've tried with a 12v power source, which gives same result)

Don't know if its helpful, but I can provide more images.


texts: What is the nature of the near field at a receiving antenna (excited by a far-away transmitter)?

texts:
Near and far field are usually explained for transmitting antennas, but since antennas are reciprocal, I would expect a receiving antenna to have a near-field phenomenon.
1) Does the impinging field (from a far-away transmitting antenna) cause the receiving antenna to develop its own near field, and what is its "shape" or "quality"?  (I realize it would depend upon how far apart the antennas are.)

2)Continuing with this idea, is there a simulation anywhere such as this one made at MIT: http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/light/dipoleRadiationReversing/DipoleRadiationReversing.htm except it shows two antennas simultaneously, one receiving and one transmitting?  (Preferably, it would be a simulation of a transient broadcast.)

3)If there is a derived near field at the receiver, does the receiving antenna then re-broadcast any energy?

4)Extra credit: Does this touch upon Physics' "Arrow of Time" question?


texts: USB2.0 EH with USB type-C in accordance with USB specifications? Reasoning?

texts:
We would like to implement a slim USB host to
store/retrieve small files to/from an USB-flash-drive (with Type-C Plug).
We would like to implement an embedded (targeted) host according to the
On-the-Go and Embedded Host supplement. We do not want to implement any OTG-functionality, which seems in accordance with the supplement. However, 3.1.3 of that supplement requires Standard-A (to clumsy) and/or Micro AB (needs OTG to implement a host) receptacles. From the type-C specification it seems clear that instead a type-C receptacle may be used (from a technical point of view), as long as CC pins/Vbus are handled properly. However I am missing a clear statement that this supersedes the requirements of the OTG/embedded host supplement. Any hint?

To my understanding, signing an adopters agreement might be possible as long as the product meets the USB specification requirements, even without compliance testing. Does anybody understand if even signing the adopters agreement may be dropped, as long as no copyright protected artwork will be used? Or does using USB-C make mandatory to sign an adopters agreement to avoid patent infringement?

We are talking about a relatively small number of systems. Most real life interoperability issues when using USB flash drives, to my understanding, will be due to the file system (only FAT32 intended, seems to be in accordance with the USB specs), not due to the USB implementation. Therefore, to me, reducing overhead for USB certification testing seems justifiable. Any objections?


texts: How do I make sure my part matches with the eagle part selected?

texts:
I need help matching the part I have with the eagle part.
I'm using a RPX-1.0 data sheet pdf:
https://www.mouser.com/datasheet/2/468/RPX_1_0-1903909.pdf
It is a 3mm by 5mm qfn with 16 pins but it doesn't seem to match up with the qfn options on eagle.
When I try searching for recom, in eagle, I find the following dc-dc converter

but it doesn't seem to match with the footprint on the data sheet

any advice on verifying if the parts match?
Or any advice on how to find the correct part?


texts: PNP transistor switching and inductive load

texts:
I am designing a circuit to control a motorcycle horn (its operating frequency is 490 Hz, its resistance is 3 Ohm, and it consumes 1A on average as indicated by the power supply), and LED lights. The LED must be controlled by a high side switch, while the horn can be controlled by a low side switch.

The LED lights I am testing consist in multiple LEDs encased in a sealed commercially-available stoplight and plate light assembly. Additional components, which are probably present in the assembly, are not included in my schematic. The stoplight and illuminator are specified for 12 V, and at 12 VDC, consume about 100 mA. The plate LED turns on at a voltage of 2.8 V. The stoplight LEDs turn on at a voltage of 6.7 V.

The 12 V is supplied by a power supply (0 - 30 V DC, 0-5 A). I have also tested supplying 12 V with a DC/DC converter (5A, 12V, 50mVp-p ripple) connected to a 52V 40A battery.

When switching the horn on, the LED flickers on the whole time the horn is on. I think the issue is that V1 is spiking down by several volts when the horn is active.
I have tried troubleshooting the issue by:
i) adding a capacitor (470, 47, 0.1 uF) between GND and +12V
ii) adding a snubber with R=10 Ohm and C=10 uF in parallel with the horn

But to no improvement. Can anyone suggest a design that would prevent the LED from flickering when the horn is active?

Thank you!

simulate this circuit – Schematic created using CircuitLab


texts: Voltage division without affecting current

texts: How can I decrease the voltage with voltage division without affecting the current significantly?


texts:
I have this assignment I finished for a vending machine circuit.  Just as some background, there are three inputs for nickels, dimes and a return option.  The return option is for only one nickel/dime at a time (a crappy system I know).  At 25 cents, you get to choose between pepsi and coke.  At 30 cents a nickel is automatically returned and at 35, a dime. As for outputs, there is RN (return nickel), RD (return dime), DC (drop coke), DP (drop pepsi).

I have my state diagram and table attached here.  Now, there is an extra option to implement a next state decoder (which I will not be doing), but just to satisfy my own curiosity, could someone explain to me briefly how I would go about doing that?


texts: Sizing a trace on a PCB to carry 2.5 amps

texts: I need a trace on my PCB to carry up to 2.5 amps (average) current, with 5-6 amp spikes (it's going to a switch mode power supply.) How wide should the traces be? I've got a trade off between reliability and size, as the product is space constrained. Any tips would be appreciated.


texts: Why lines A and B are HIGH when idle (rs485)

texts:
I'm using modbus RTU over RS485 for a project.
I use a RaspberryPI as master and Arduino Pro Mini as slaves.

My problem is the following :
I plug a sensors on the bus and it returs its value.
I plug another sensor, this one returns its value but the first sensor doesn't return its value anymore.
So it looks evident something makes them incompatible.

I tried to diagnose it using a logic analyser and the results are the following :
When idle, the lines A and B from the master are respectively HIGH and LOW.
When idle, the lines A and B from the slave are both HIGH.

I wonder if the line B shouldn't be LOW..
Looking why this line was HIGH, I discovered that the line is pulled HIGH because of the library I use on Arduino. This library pulls DE and RE HIGH when transmitting data, LOW otherwise.
(On the max485 module, I tied DE and RE together. I'm not sure it's a good practice)

Here is the library I use on arduino :
https://platformio.org/lib/show/1727/ModbusSerial

Here is a schema of a modbus slave module :

EDIT :

On logic analyser (1 slave connected to the master) :

I tried with 2 differents usb/rs485 transceivers

Transceiver 1 - 3 seconds record

Transceiver 1 - Zoom on request / response

Transceiver 2 - 3 seconds record

Transceiver 2 - Zoom on request / response

So my question is: Is it normal to get HIGH on both lines A and B ?
And if not, what can I do to correct it ?

Thanks in advance !!


texts: Measure alternating voltage with arduino

texts:
I'm worried about how to measure alternating voltage with Arduino because it measures voltages from 0 to 5.

Please help me with the circuit. What I want is that when:

If Vin = - 5V Vout = 0V

If Vin = 0V Vout = 2.5V

If Vin = 5V Vout =5


texts: I'm designing a circuit that runs on a single cell LiPo battery and I'm trying to choose a proper dc to dc step-up regulator. My circuit needs about 2A maximum. I searched a lot and found so many ICs.A noticeable difference between them is efficiency but not saying clearly in the datasheet for my 3.7 input voltage. For example, I don't know what is exactly different between TI's lm2623 and tps6185. In specs, I almost see the same specs but the packaging is completely different. On the other hand, there are other manufacturers that have ICs with higher efficiency and lower price like MT3608 which says it has almost 97% efficiency. How can I choose which one is good for me? I mean better efficiency and stability on high loads. Actually, I'm getting confused by which parameters I should consider.


texts:
I have used W5500 hardware for my gateway device. It has been implemented in 80-100 locations. But in 4-5 locations I'm getting an unusual issue related to the network connection.
The ethernet mode is static and it is connected to a cisco network switch.

It gets connected to network in 100mbps full duplex mode for an uncertain period and then gets disconnected for which the network configuration is needed to be changed to 10mbps full duplex to connect it again.

The second observation is alternating the port connection. When the network gets disconnected again it gets connected when port is changed in the cisco switch. Also if from the gateway device side the ethernet cable is reinserted it starts connecting to the network.

When configuration of switch is set to the auto mode, it starts working. But, after 2-3 days stops connecting and again configuration changes to 100mbps and full-duplex it starts working fine.

As per the reference design the network mode is set to auto negotiation. I have this much clue on this issue, help me to find out if there is any limitation in firmware or hardware.

Top Layer

Bottom Layer


texts: Successor of VTI's SCP1000 Family of Absolute Pressure Sensors

texts:
VTI's SCP1000 product family is a range of ceramic capacitive pressure sensors that have reached the end of their lifespan. It has been suggested that certain sensors designed by others (like Bosch Sensortec and STMicroelectronics) could be a "suitable substitute, but not a direct replacement."

However, following Murata's acquisition of VTI, has there been an offering from Murata that supersedes the SCP1000 series, in a manner recommended for use by designers who have used SCP1000?

Otherwise, how does the performance of the BMP280 from Bosch Sensortec and the LPS25HBTR from STMicroelectronics compare with that of the SCP1000 for electro-meteorological applications?


texts:
I have 5050 led strip 60 led/m, and I have a power supply I want to use to power it on
Now I got some specs online (not sure if right ones?) for 5050 which say:

150 LED Count: 36W

Now, say I want to have a strip of 50 leds. Does it mean they will draw 12W?
My power supply says PSA15W-120. Does it mean 15 watts at 120V?

How do I know that this power supply will not burn the leds?
Why don't I need a limiting resistor here?

Some other specs for this strip will talk about current consumption, but not sure how to go about it in calculation.

Now if my power supply is 12V and leds draw 12W, will the current be 1A?
Now I have to say that ofcourse I did connect the strip to the supply and it works, but how do I know that neither is get damaged over time?

I know there are a few questions here, but for a seasoned electonicist probably are no-brainer. I appreciate any help or reference to a relevant article.


texts: What's the difference between these two differential mode EMI filters?

texts:
When I search for differential mode input EMI filters (for power supplies), I get two different filter types:

simulate this circuit – Schematic created using CircuitLab
What's the difference between these two differential mode filters?
(The values are random in the schematics.)


texts: Capacitance of short length transmission lines

texts:
I would like to simulate a short length transmission line in MATLAB/Simulink. In the library, there is a block that simulates a transmission line. The parameters that are required are the resistance R, the impedance L and the capacitance C of the line. However,  the capacitance effect is not present in a short transmission line but Simulink does not accept zero (0) as a capacitance value.
So, I am thinking of putting a very small capacitance value (1e-09).
 Do you think that I am going to have an accurate simulation or I should put another capacitance value? What do you propose?


texts: Capacitive sensor as drop-in replacement for mechanical button

texts:
I have a device X (talking toy), which has a jack of two wires for an external button. That is, I can short the two wires and device X accepts it as a press of a button.

Now, I want to use device X for it's function, but replace mechanical button with a capacitive sensor. I have options, but lets assume it's a cheap TTP223 module, with GND, VCC and IO pins, operating at 2 to 5.5 V. When I checked with 3.3 V, it gave about 2.64 V logical "1" on IO pin when touched. At 5 V, gives 3.8 V for "1".

The device X's jack gives about 5 V on it's button jack and even 800 Ohm resistor seems to trigger it. About 210 uA current flows through the button when shorted.

As I see it, the sensor will have it's own power supply (voltage is part of the question).

The main question is, what is the best way to convert logical "1" into "press of the button"? Preferably, without the need for multiple voltage levels. What could be good "relay" for the task?


texts: How to rapidly switch polarity of two plates?

texts: If I have two metal plates, with P1 connected to V+, and P2 connected to GND, how can I alternate the polarity of these two plates? I wish to have P1 connected to GND, and P2 connected to V+. Then swap polarity again, and so forth. Is there such a circuit for this type of polarity switching?


texts:
Oscillator circuit is shown.

a) Calculate frequency of oscillations,

b) Calculate minimum value R1 for which circuit still oscillates,

c) Calculate amplitude of voltage VB, for which voltage VA start cuting off

Vz=6.3V, R1=100K, R2=120K, R3=470, R4=2R6=10K, C1=C2=100nF, Vd=0.7V, R4=R5.

I completed task a) and task b)

I got f_oscillations=232.7Hz and R1_min=250k.

I don't know how to solve task c)

Any idea?

Thanks in advance.


texts: Blowing a Fuse to Permanently Disable Functionality

texts:
Certain electrical designs require permanently disabling hardware functionality on the fly. Sending an overcurrent to a weak fuse may be a method for accomplishing this, breaking the circuit in a particular region of a device. My questions are:

What are the potential risks caused by this process, assuming a fairly weak fuse?
Are there alternatives to this method for disabling functionality permanently?


texts: How to connect an LED indicator with a switch to this device?

texts:
I would like to know how can i add a safety switch with an LED indicator to the input of this device , so that if the safety switch is on then the LED lights , and when i want to use the device , all what i have to do is to press the normally-open switch.

I have attached this schematic and im not sure if it will work correctly ,as i am a very beginner in electronics, so is the design correct?

The device itself is an arc generator with a DC input and th following parameters (Input voltage: DC3.7-7.4V , Input Current: 2A-5A).

I know how to size the LED resistor but not too sure about the switch how can i size it please ?

Thanks


texts: buck regulator strange switching behaviour

texts:
I'm seeing strange voltage at the switch node of my buck regulator.

There is a decaying sine wave of voltage which seems to happen before the switch is enabled. This is a dual channel regulator and I'm only seeing it on channel 1, the switching waveform for channel 2 is nice and square, so I'm expecting it to be an error in the pcb assembly (done by me, with low skill level). But I can't find anything wrong/missing. Any pointers on where to focus investigation would be most welcome.

Note the bottom side FET is not supported by diode (D3), this is not fitted (in either channel).


texts:
Almost certainly a neophyte question. I'm trying to understand the difference between nominal voltage and operation voltage range.  My intuition was that, for a given power supply, it would hold a voltage within a few volts (hence, it would have an operational voltage range within a few volts of it's nominal voltage).

So what I'm trying to understand, is why a device such as this has such a wide operational voltage range:

Image source: http://www.astronautix.com.


texts: This circuit is working inversely on PCB as compare to Proteus Software. In software, when the temperature increases the buzzer is on. This is the desired output, but on PCB this circuit is working inversely when the temperature increases the buzzer is off. How i can solve this problem?


texts: Adjustable LDO post regulator for bench supply design

texts:
I'm designing a small programmable bench power supply (well, I say "small", but the AOT430 FETs will handle 10A+ in their linear region without thermal runaway so...).

A switching regulator provides coarse voltage stepdown (24Vdc to 0-20Vdc isolated) while a MOSFET based LDO handles the fine control, a small DSP oversees everything else.

I want to have both programmable current and voltage limits. As for the control loop, it's probably going to end up as a mix of analog and software controls. I can either regulate the voltage across the load with discretes and handle the current control in software or regulate the current through the load with discretes and handle the voltage regulation in software.

I would like to know what sort of advantages/disadvantages (if any) that either solution would have in the context of a variable bench supply. Or should I try something else altogether? (like all analog or all digital control loops)

At the moment I'm leaning more towards analog voltage control. I'm expecting that analog current control might result in bigger voltage spikes/sags when loads change while the DSP readjusts the current settings to bring the output voltage back under control. But at the same time, I'm thinking that the analog current version would have (much) faster current limiting and short-circuit protection.

simulate this circuit – Schematic created using CircuitLab

(Note: These are only conceptual schematics and have been greatly simplified)


texts: Can I replace all electrolytic capacitors with ceramic?

texts:
I am designing the power supply circuit for a system that needs several supplies, my questions are:

Is it possible to replace all electrolytic caps (Mostly 100uF) by ceramic ones? What are the limitations of ceramic?
Should I use a 2x voltage rating for ceramics as it's done for electrolytic?
What about ripple current rating? Is it an important factor when choosing ceramics as in electrolytic?

Added 1/9/2014: More about ceramic limitations

I found this excellent video submitted by Dave at EEVBlog showing the limitations of different types of ceramic caps and how they are affected by the applied voltage and the bias voltage too. Worth watching!


texts: NPN BJT NOR gate to drive LED. Base resistance problem

texts:
Here's a circuit I'm trying to get working :

I have two digital signals (B and C in the diagram) coming from a CD40174 flipflop.
I use these to light up two LED's.

I also use these as the input for a transistor based NOR gate the output of which I call A.

I also need to be able to drive an LED from A

The problem is that if I calculate R11 (the base resistor for the LED driving transistor) correctly (about 5K) the voltage at A is significantly less than 9V.

I am using A elsewhere and it needs to be as near 9V as possible. Also I'd like to draw as little current as possible from the flipflop outputs.

If I raise R11 to 100K I get a nicer, very nearly 9V at A, but the current through the LED (on pin 8) is significantly less than 20mA

Can someone tell me how to resolve this?


texts:
I am trying to see how I can try the different combinations to change EN1 and EN2.
By soldering the 0 ohm and turning on the device, would I get a high signal to the pin? If I desolder the resistor, would the signal drive down to low to pin?
So, with resistor pin is high and without resistor pin is low.


texts:
I am designing a cheap electric skateboard.

I have played around with various parameters for quite a while until I finally converged towards a specific motor and a specific battery. Lithium batteries are too expensive so I'm going for an AGM motorcycle battery. The problem is that the 0.025Ohm resistance of the motor leads to a huge current (hundreds of amps) up to 10km/hr which is most of my operational range. Other motors do not provide me with sufficient torque, therefore I need to include a current limiter to protect the ESC and maximise the battery capacity. For information, the continuous rating of the ESC I'm using is 60A.

I'm planning on measuring the current with a Hall Effect current sensor such as the Allegro modules out there, and an Arduino. Then map the current to a % of the duty cycle to subtract to the setpoint, before sending it to the ESC. For example, up to 30A => 0 feedback, 60A and above => 100% feedback, varying linearly in between. My gut feeling says it's basically a bang-bang controller which should be converging.

Any better alternatives?


texts: How to to design a PCB lib for components with variable dimensions?

texts:
I'm designing various PCB libraries for components. But sometimes they have variable dimensions:

How should I design the pads for components with fluctuating values?


texts: Op-amp circuit saturates to negative rail and only passes positive side of input

texts:
I've been working on a spring reverb driver circuit, based mostly on figure 5 from this site: https://sound-au.com/articles/reverb.htm. While there's lots of information on the how of the circuit, there's not so much on the why - I'm not entirely sure what the op amp side of the circuit is doing - as far as I can see, C3 decouples, C6 bypasses high frequencies to the inverting input, and R5 and R7 set the level of bypass.  R13 is in the feedback path, making this a current amplifier rather than a voltage amplifier. This arrangement should make it a modified non-inverting amplifier? Past there it's a fairly standard push-pull arrangement, with the reverb input coil connected across the 300R load.

I should note that I copied the circuit from the website onto a breadboard, and it worked fine (albeit noisily, because breadboard). I have a video and scope traces from the output stage, so I wasn't dreaming...

Here's the screenshots of my KiCAD schematic - after the success of the breadboard circuit I felt comfortable ordering some PCBs from Seeed Studio, which arrived a couple of weeks ago.

I built the op amp side of the circuit, omitting the push/pull stage, and hooked my 'scope up to pin 7. I applied a ~1V RMS 1KHz sine wave to the input, and tuned RV1 until I didn't see any clipping on the output. However, the output was saturated to -Vcc, with only the positive side of the sine wave appearing. Assuming I'd made a mistake with the circuit design I re-tested the original circuit from the website on a breadboard, with the same results. I don't recall this happening with my first breadboard circuit.

Can anyone spot where I'm going wrong, or are they able to explain the theory of operation for the circuit better than the website I copied it from, so that I can do some more in depth troubleshooting?


texts: Purpose of a capacitor between op amp inputs in buffer circuit

texts: I have stumbled upon the below circuit. At first I thought it is a voltage follower, but I can't understand why there is a capacitor between the positive and negative inputs. Can anyone please explain to me the purpose of the capacitor in this circuit?


texts: How can a high voltage flyback transformer burn pieces of paper?

texts:
Why is it possible to burn pieces of paper by holding the output of a high-voltage flyback transformer near them? How is the circuit completed if there's no electrical connection between the paper and the flyback's reference?
I would guess the strong electric field at the output tip creates a displacement current in the paper, which is a bad conductor and therefore heats until burning up. So there's no closed circuit. Is this right?
I mean, for example, an old color CRT TV, with the output touching a piece of paper on the table, away from the TV's ground:


texts: Motor choice for quietest (mechanical and electrical) operation

texts: Which types of motor are the most quiet from a mechanical and electrical point of view? To avoid quiet, but weak, suggestions, the motor needs to be capable of about 70 Nm of torque and speed range from 600 to 2400 rpm.


texts: How to wire this “green laser module diode”?

texts:
I am trying to wire a 532 nm, 5 mW green laser module rated at 3 V DC (from ebay).

But how? I would assume the spring is VCC and the housing is GND, but latter is not connected to any of the two wires which go from the PCB to the laser diode, so there seems to be at least one contact missing.

Also, will I have to use a serial resistor to limit the current to 5 mW, or are the on-board device handling that already?

Update – Solved: The laser module was incorrectly labeled as 3VDC, but is in fact 4.2–5 V. As mentioned in Whiskeyjacks answer, GND is connected to the spring and VCC to the housing.


texts: How to connect microphone to an Arduino with an opamp?

texts:
I'm trying to connect a contact microphone to an Arduino.
I got a couple of LM833N audio dual opamps, which I'd like to put to use. I'm still struggling to understand opamps, though.
I've been reading an instructable on audio input on the Arduino. It uses the following circuit:

(source: instructables.com)
However, this is for the TL072 opamp. I'm not really sure if I can use the LM833N in its place. Is this circuit suitable for a contact microphone?
Also, it would be great if someone could point me to a good (easy) introduction to opamps - the wikibooks page is a bit dense for me.


texts:
I know someone who needs a longer version (12ft) of this cable for their TV, but I do not know what type it is. Can someone please identify the ends for me so I know what to shop for?

The cable is has this written on it:

LWC 20-CMR-SD  HDTV SERIAL DIGITAL 20 AWG CMR(UL) C(UL) E113333 ER22211 MADE IN USA

Thanks!


texts: Do Soft Termination Caps Really Increase Reliability?

texts:
I'm managing several designs. At one point I identified a few failures that were caused by 0603 caps failing short. After that I switched to all soft-term caps to hopefully eliminate the problem.

Well it's been several years and the problem has not re-occurred that I know of. So I guess it did work, but keeping these soft term caps adds a lot of cost to every board.

So here's what I'm wondering. To those of you who've produced a lot of boards: is this normal? I'm making products that need to last, but they're not safety critical or anything like that where extreme care is required. They're also not used in a high-shock environment (besides being shipped).

If it's really uncommon to have to do this, I'm considering reviewing the designs for board-flex and switching back to regular caps.


texts: Are there any differences between clamp, twist-on, and crimp coax connectors outside of cost and ease of assembly?

texts:
I have recently started working with software-defined radio, and have replaced some connectors on RG-58 coax in preference to using multiple adapters.

RG-58 BNC connectors seem to come in three flavours:

Clamp (example on Farnell)
Crimp (example on Farnell)
Twist-on (example on Farnell)

I opted for clamp because:

They were cheap on ebay
They didn't require any special tools to assemble
I have found twist-on connectors troublesome

I struggled to find consistent specifications even from the same manufacturer, but all three seem to be available in a range of contact materials and work up to 4GHz. I can't find VSWR information for all three types to compare.

Crimps are quicker to assemble, but I don't have a tool.

So outside of the consideration of cost and east of assembly, are there any differences between the three types?


texts: Lowest power way to latch power supply after input pulse

texts:
Background

Right now I have a circuit consisting of a Adafruit Huzzah Feather (ESP8266 board), an ADXL345 accelerometer, and an ATTiny85 (bare chip).  The circuit is powered by a lipo battery plugged in to the huzzah with the ADXL345 and ATTINy being powered by the VBat pin (so they are always powered).

The INT1 (Interrupt 1) pin of the ADXL345 is connected to ATTiny85 and set to fire on ACTIVITY.  The Tiny wakes on the rising interrupt and turns on the ENABLE pin of the Huzzah (enabling the onboard 3V3 regulator and starting the ESP8266).  When the ESP8266 starts, it clears the interrupt from the ADXL345 (the two are connected via I2C) updates an ePaper display connected via SPI. The Huzzah tells Tiny it is done and ready to shutdown by changing the state on a GPIO pin. Tiny senses this, pulls the ENABLE pin low and then puts itself to sleep.

The LED flashes for 50ms every 2s just so I know if the Tiny is awake or sleeping.

Problem

The problem I am having is that when the Huzzah is disabled and the Tiny is sleeping, the power consumption is still around 900 uA.  Moving the ammeter around, I found that about half of that is current flowing between the sleeping Tiny and disabled huzzah.  The ADXL345 in measurement mode should only consume 23uA.

In the interest of simplifying things, I'd like to replace the Tiny with something simpler and even lower powered.  The three things I've found by googling are:

Low power latching relay (like one of these)
Set-Reset latch/bistable flip-flop (something from here...)
TPL5111 Set-reset timer (Adafruit makes a breakout for it)

Seems like the relay would only consume power while switching but may be overkill (I had difficulty finding a small one since I don't need 10A switching).  The watchdog feature of the TPL5111 chip would be a nice-to-have thing in case the ESP locks up but not required.

Can someone with some EE experience weigh in and help this ME figure out the best way to control power via the enable pin given the above information?  I'm also open to other suggestions too.


texts: Why would a 3-Quadrant Triac NOT be Snubberless/Alternistor/High-Commutation?

texts:
While researching TRIACs, I came across this question: What's the difference between 3 and 4 quadrant triacs?

Ok, straightforward enough, and that matches Wikipedia's explanation.

However, I came across the following Littelfuse datasheets, which seem to include 3-quadrant TRIACs that are listed as standard (not alternistor) TRIA

Datasheet 1 (search for Qxx15L5)
Datasheet 2 (search for Qxx10L5)

So why would a 3-quadrant TRIAC not be snubberless (aka an Alternistor aka high-commutation)? Or am I simply misreading the datasheets?


texts: Energy dissipation of a resistor in an AC circuit

texts:
I am given a resistor of known resistance with a sinusoidal voltage across it, and am asked to calculate the energy dissipation between t=0 and t=1.
Not sure how to do it. Would I

Use P=V^2/R and integrate between the limits to calculate energy dissipation

or

Calculate voltage at t=0 and t=1, then use P=V^2/R?

Thank you for your response.


texts:
I need to power a Zynq-7000 chip from a 28VDC bus. The chip requires a few different voltage rails, 3.3V being the highest and the core voltage of 1.0V being the lowest. Current will be approx. 2.5A for the core, less for the other rails (1.0-1.5A). Due to the large differences in voltage levels, LDOs are not really suitable so I am going to use DC/DC converters.
However, I am not sure whether the best approach is to find a chip that can do the conversion directly from 28VDC (e.g. LTM8051) or to convert down to an intermediate voltage, e.g. 5VDC, and use this voltage to source the rails. This would in turn enable the use of e.g. TPS65218D0, which is specifically made for powering FPGAs. We have also successfully used the LTM4644-1 for powering FPGA’s in the past, but this IC has a max Vin of 14VDC.
Any thoughts?


texts:
I would to know if is possible with simply way ( i'm not electronic expert ) to drive one direction a DC MOTOR ( a little ) from headphone, with power supply of course.

The difficulty is voltage of headphone, is very low 3mvw-6mw, is suppose is not enough to active logical input of L293.

I suppose is possible with transistor with "biais voltage", but how ?

I want to that because, I want to recycle my old android phone, into camera IP, rotate 380°, with eyefish.

I see it exist the IOIO board, but I think it is possible with cheaper parts.

Thanks by advance


texts: PIC pins change state when DC motor connected

texts:
I'm new to PIC programming, and having trouble getting getting it control a DC motor.  It's a PIC18F25K22, and a TI L293D driver.  Power is suppliued by a 5V linear regulator connected to a desktop power supply.  I've setup the PWM correctly, and it drives when I directly connected to the ground and power rails, however I get strange behavior when I connect PIC pins to the control pins of the L293D.  A circuit diagram is shown below.

When unconnected, pin RC1 is low, and pin RC3 is high (0.0V and 5.0V respectively).  When connected, RC1 rises to about 0.25V and RC3 falls significantly to 0.42V, as my multimeter says.  The L293D has internal diodes, and I've put capacitors on either side of the motor to ground.  The pins on the L293D draw a max of half the current a PIC pin can supply.  I'm new to both PICs and motors, so it could be either.

Update

I connected the inputs and enables of the other half of the L293D to ground, and used ground and power to control and enable to half I am using.  This produced expected results.  Leaving the 1,2EN pin connected to 5V, I connected the PIC pins again.  This time, the motor turns, but sluggishly.  I recorded the following voltages

1Y = 1.03V    2Y = 0.34V    1A = 0.84V (PIC pin, set high)    2A = 0.0V (PIC pin, set low)

This is being built on a breadboard currently.


texts: How do I read the state of AC switch, through a microcrontroller?

texts:
I wanted to read the state of an AC switch using a microcontroller.
S1 is an SPST switch and cannot be changed.

What circuit will be required for doing this?

I'm using this for my home automation project where I should have both manual and wireless control. This will also help me find the state of the load (on/off.)


texts: Tactile switch actuator extension methods?

texts:
I am not a 100% sure this is the right place to ask this, but I couldn't figure out another, more appropriate community.

I am designing a PCB for a product, which will have a tactile switch. The PCB will be placed in an enclosure, and I want the button, on the device samples I'm making, to look something like the power button in the image below:

I need a low profile/height switch at right angle, so I will be going with one of these types:
https://www.e-switch.com/product-catalog/tact/product-lines/tl3340-series-smt-sub-miniature-tactile-switch#.V-Mql5MrIck OR
https://www.e-switch.com/product-catalog/tact/product-lines/tl1014-series-micro-miniature-right-angle-smt-tact#.V-MqtJMrIck

Also, I plan to use one of the off-the-shelf button caps available on mouser/digikey. Example:http://www.digikey.com/product-search/en?mpart=1WD30&vendor=882 (image below)

The problem is that I cannot (rather do not want to) commit/finalize to a final enclosure design right now. The final enclosure could have a gap (unknown now) between the tactile switch actuator on the PCB and the side panel/edge. Hence, I need a solution to be able to, reliably, bridge the gap between the switch on the PCB and the button cap one the panel. I would loved it if I could find low height switches that come with add-on accesories for actuator extension or caps. I searched for tactile switch actuator extenders, but none of the results seem suitable for these low profile/height miniature switches.

What are some solutions/suggestions to this?? SHould I use some way other than the cap mentioned above???

I am looking for a solution that is NOT just a flimsy hack. I want something that is kinda sturdy. Also, this is for more than one device, I want to do this for the ~10-15 samples I'm making.
(Also, I understand finalizing my enclosure is the obvious one, but please understand that I do not want to do that right now.)

Also, would like to highlight that I need a 'low height' (less than 4mm tall) switch. And that where the difficulty lies. Otherwise there are tactile switches with long/variable length actuators -- but none that I could find are short (<4mm) with long actuators.


texts:
In particular I'm interested in SMD packages. A DIP package I would assume is simply put into a socket and programmed that way.

Of course you could get around this by designing a programmer header into the final product so the code can be uploaded and/or updated, but I know some companies sell pre-programmed chips (suppliers like Digikey offer this option, and from what I've heard you can sometimes contract with the OEM to supply pre-programmed chips). I'm just curious as to how they do this.

I have a two theories, but I don't think either of these are really practical and/or reliable.

Kind of "hold" the pin in contact with pads on a PCB, perhaps even use some sort of latch to ensure a solid contact. This would be similar to how DIP packages are programmed. Would work for packages with actual leads (QFP, SOIC, etc.), but I have doubts as to how well this works for BGA's or exposed pad type packages.
Solder the part into place, program, then unsolder. Seems like it would subject chipsets to unnecessary thermal stress and would use a ton of solder/other resources.


texts:
I have a signal that gives spikes up to negative 150V. I need to be able to determine these spikes using MCU that can sens 0 to 3.3V.
How can i adjust a signal so that it doesnt fry my MCU. It should be a power friendly method.

Thanks!


texts:
While implementing an RF amplifier circuit, I came across the fact that micro-strip RF chokes are better for narrowband applications and easy to realize than physical inductor.

My question is whether it is possible to implement DC blocks using micro-strip line. If it is possible what are the formulae/relations I can use to implement DC blocks using micro-strip lines?

Thank you!


texts: Is "catch diode" the correct term to use in SMPS context?

texts:
UPDATE: Ok, two good answers, I've chosen the one with more votes as the "right" answer, leaving it to the wisdom of crowds to choose between two fine choices. For anyone who cares, I think I'll settle on the term "catch" diode, mostly because it has fewer syllables and I have a deep abiding respect for Horowitz & Hill. But I'll also adopt the metaphorical view that the switch set the current in motion when open and releases it  ("throws" the current) when it closes, and the diode then "catches" it and delivers it to the output :)

Thanks very much to both respondents and those who commented for informing my choice :)

I've come to the point in my learning about switch-mode power supplies where I find myself referring to the "main" switching diode quite a bit. I'd like to use the most correct name consistently going forward because I'm forming the habit of what I'll be calling it in documentation and conversations like this, etc.

I had pretty much picked up the term "freewheeling" diode, which made some sense to me because the inductor could be thought of as analogous to a physical flywheel that stored energy in it's momentum, and would "freewheel" once energy was no longer added to it (or protest violently on attempts to stop it suddenly :)

However, just lately, I see the term "catch" diode used, as in this TI application note AN-1229.

Is it just one of those terms that never really normalized and everybody chooses between a half-dozen alternatives? Or perhaps is it a "catch" diode in one topology and a "freewheeling" diode in another?

I do note that the term "freewheeling" diode also appears in the context of avoiding turn-off spiking from an inductive load, where one is just looking to dissipate the energy stored in an inductor rather than carefully apply it to a useful load.


texts: Powering mixed 5V and 3.3V circuit from AA batteries

texts:
This my first more-serious project :)

I want to integrate a 5V (air dust) sensor with my ESP8266 IoT gizmo running on 3.3V (we can call it a DIY weather station).

I've bought a sensor with Vin spec between 3V-7V, but later I've noticed the sensor's spec has all data for powering it with 5V, and I assume it will have a better accuracy on 5V than 3.3V.

I have lots of 4xAA battery holders, so the idea I have now is to add additional wire to the holder between the 3rd and 4th AA cell to "steal" a 4.5V power for a 3.3V regulator and use the full 6V to power a 5V regulator.

The ESP8266 could also drive the ENable PIN on the 5.0 voltage regulator powering down entirely the 5V part when it will not be needed (I need to power it only for about 1s every 30minutes).

I think I can use a MOSFET to pull down the sensor's trigger when want to get the measured analog result. So I don't need to have a logic level conversion.

Note: 5V sensor analog output connects through a voltage divider to be in ESP8266 0-1V spec.

It seems the 3.3V regulator will peek at maybe 200mA (worst-case) when ESP82866 radio will push data through WiFi, most of the time it will be <5mA since the ESP82866 will be in a deep sleep. The 5V regulator will have no need provide any current, or 20mA when the measurement is made.

The LDO regulators have very low quiescent current. I hope the batteries will last a few months.

Do you see any flaws in this design? I'm a bit skeptical about using that 3xAA and additional AA for 6V.

Other option I see is to have the 5V regulator output connected to 3.3V regulator input to get the two voltages, but it doesn't make a lot of sense.

I don't think buck (4xAA 6V -> 3.3V) nor boost (from 2xAA 3V -> 5V and 3.3V ??) converter is suitable here.

Cheers!

simulate this circuit – Schematic created using CircuitLab


texts: Induction motor 'droop control' on multi-motor coupled loads

texts:
When using droop control to balance the torque across multiple motors driving a coupled mechanical load such as a chain conveyor, what is the actual variable that is being altered by each drive?  From what I understand, at rated conditions the output of each drive is altered by the selected droop value (i.e. 5%) and scaled linearly to 0% at zero RPM. What I am unsure of is exactly what variable is used to instigate the % droop, is it frequency independent of voltage, or is it the combined V/F signal?
The application in question is a chain conveyor, with 30+ individual induction motors each supplied by a small scalar control converter. The type of VSD specified will depend on what speed control method is appropriate. Most likely Droop control or Speed Trimming. I am attempting to build Simulink model to showcase the use of droop to regulate the motor speeds under variable loading of the conveyor but I am unsure exactly how the output of the drive should be altered when the load torque limit is reached.
Can provide more details if necessary.
Regards


texts: Xilinx clocking wizard - How to connect clkfb_in and clkfb_out

texts: I created a VHDL design which needs a 50 MHz clock input. The Spartan-6 I'm working on gives me a 100 MHz clock signal, so I used the Xilinx Clocking Wizard to get a 50 MHz clock. When I choose "No Buffer" two additional ports will be created - a clkfb_in and a clkfb_out. I don't understand what these ports are good for and how do I connect them?


texts: SMPS Inductor oversized vs properly sized

texts:
I am working on an SMPS for boosting an input voltage to drive a single string of LED's. The input voltage range is from 18 to 32 volts. The output voltage needs to be about 60V and the drive current is around 0.760 Amps. I am working on using the HV9912 as the driver chip. The frequency is set to approximately 200KHz.

The question I have is this:
I have calculated a required inductor rating of 90uH, what happens if I use something significantly larger(as in 2 or 3 times as large)? Will the duty cycle be the only thing affected? What effect does this have on the inductor current?


texts: lightning protection on LAN cables indirect strike crowbar VS isolation

texts:
i am using a crowbar lightning protection system we built 10 years back for LAN on our own devices for the mine industry. it works very well. at that time i decided to use TVS bidirectional 18v , GDS 90v. i added 2 diodes to increase the speed of the port to 100MBPS. the capacitance of the TVS was too high. this worked for me and we did not loose any devices. but we had to replace a lot of lightning protection units, because we blow and are still blowing too many fuses. we are currently using 1/8w 3e3 resistors for fuses.  i considered the TBU as from this site . but 40 volt peak seems too low for me

now i want to see if i can electrically isolate the input from the output by using the lan trf maybe 5000v isolation. may be still protect between the line but not to earth.  will this not be a better solution

my current design looks like this

what is your feel about it.


texts: Please help me solve this electromagnetics problem

texts: A non uniform surface charge density of 5p/(p^2+1) nC/m^2 lies in the plane z=2m whereever p<5m; ps = 0 for p>5m. How much electric flux leaves the circular region p<5m, z=2m.


texts: Relay that detects 240VAC and switches 12V DC

texts:
I'm wishing to detect the loss of AC power (in this case 240V) and when this event occurs have a 12V DC circuit go to earth. This will trigger an alarm for users to react to situation.

Can anyone recommend anything? Voltage sensing relay?

I have a current sensing clip-on transformer, I bought via eBay, but it only provides 3 volts
AC which seems too low for AC/DC relays I have found on Google and Alibaba.


texts: How to test Ethernet PHY's MDI interface through JTAG Boundary scan

texts:
We now use SCANWORKS Boundary Scan Tool from ASSET to make Ethernet SWITCH's manufacturing test. But in almost all PHY chips from broadcom corp, the MDI interfaces are "Linkage" bits. It means that there are no Boundary-Scan Cells(BSC), so we could not access them through JTAG interface. Is there any other method,except function test(because it needs more complicated firmware), to test MDI interfaces between the PHY chips and RJ45 connectors while manufacturing test?
Thanks.


texts: Nodal Analysis - Finding voltage given the network

texts:
My attempt to solve:

I = 10A
i1 = ??
i2 = ??
i3 = ??
ix = ??

Using KCL
@Node 1: I = i1 + i2
@Node 2: i2 + 4ix = ix
@Node 3: i1 = i3 + 4ix

Applying current definitionsf

10 = (v1 - v3)/2 + (v1 - v2)/4 (1)
(v1 - v2)/3 + 4(v2 - 0)/4 = (v2 - 0)/4 (2)
(v1 - v3)/2 = (v3 - 0)/6 + 4(v2 - 0)/4 (3)

Applying cross multiplication

40 = 2(v1 - v3) + (v1 - v2) (1)
4(v1 - v2) + 4v2 = v2  (2)
6(v1 - v3) - 2v3 = 4v2   (3)

Cleaning things up a bit

3v1 - v2 - 2v3 = 40
4v1 - v2            = 0
6v1 - 4v2 - 8v3 = 0

Using a calculator to solve:

v1 = 26.67 V
v2 = 16.67 V
v3 = -33.33 V

My answer was far from being correct. Any help?


texts: Correctly Interfacing to a Bidirectional Signal

texts:
Background

I'm designing an interface in VHDL that connects to a bidirectional signal. However my experience in the dynamics of Hardware Design is limited. What I have at the moment is below:

Within the Red box is what's on the FPGA, outside of that are electrical components.

The RX module looks for a LOW signal for a start bit. To avoid interference between the TX module and the RX module: I placed a Mux controlled by the TX module to pass HIGH whenever it is transmitting.

The external circuitry ensures my TX never drives the line HIGH so to avoid shorts.

The Problem

When the RX and TX modules are separate, they function perfectly. The RX receives and reads the signal properly and the TX transmits (not into the bidirectional line; instead: my oscilloscope) perfectly. However, closing the switch to combine the two is a catastrophe. The RX Module just seems to become non responsive.

The Question

I'm not sure if this is an overall design problem, or something small and stupid with my VHDL.

So is this an acceptable method in interfacing to a bidirectional signal? I have the feeling there is something very wrong in my setup. I'm just looking for suggestions, criticisms, or overall ideas.

If this is indeed an alright setup, then at least I can have confidence in investigating the VHDL for the issue myself, and knowing that my efforts will not be in vain due to an inherently faulty overall design.

Googling: "Interfacing to a bidirectional bus" seems to suggest Tri-State buffers. Is this a better approach?

Extra

I feel obnoxious bugging you guys constantly due to lack in a conceptually understanding, so if I could get a suggestion on books or various research sources for conceptually designing hardware, then that would be fantastic.


texts:
My mouse died recently. Specifically the cord. What ive wanted to do for a while now and have an excuse to do is to try to get the mouse to run via bluetooth. Im a first year engineering student at la tech so i know the basics of some of this. I figured if i wired this:

http://www.robotshop.com/en/usb-ble-link-bluetooth-module.html?gclid=Cj0KEQiAzNfDBRD2xKrO4pSnnOkBEiQAbzzeQXMUou6adLcVWT_23uHjTz-xdh5j--HqDySh0kdAvUkaAuLN8P8HAQ

To the usb wires that i cut and stripped that it could send data to my laptop which has bluetooth in it. The bluetooth part above has a master slave switch and i can just leave it on slave while i use it. What i need help with is connecting a battery to the mouse. How would i do this? Do i need a constant voltage regulator to keep the mouse up to the voltage it needs til the battery dies or can i just use a battery and a resistor and it will work until the battery dies? Will too much voltage or amperage kill the mouse? What batteries do you recommend? Im thinking a AAA (or 2) or a AA since i want to fit everything inside the mouse case. I have a multimeter so i can measure the voltages (and possible amperage idk yet) to see how much power the mouse draws. I figured if i just connected the data wires and power wires from the mouse to the bluetooth slave transmitter and then also connected power to the power wires on the mouse and bluetooth module thing via a battery it would run and the mouse would operate as normal because even if it does have a transformer or something like that in it ive connected power to the same place it takes it in and it wont hurt it. I can deal with the bluetooth thing getting destroyed. Help or ideas with setting this up for use with a battery. If i connect a AAA battery that is 1.5v and a normal usb port operates at 1.5v the theoretically it should power it right? Then all i would need to do is add a resistor for amperage if needed right? Thank you for the help!!

Edit

The mouse is a logitech g300s
Do you think connecting the mouse via bluetooth would change the way it operates? It is still receiving the same data as if it were a usb device right? Or would i have to write a driver for it?


texts: Current division and power delivery to resistors

texts:
I am trying to get the resistor e in this circuit to consume the most power possible by changing its resistance. It seems 100 ohms is just about right, a little less or more and it's power consumption goes down according to the simulations.

However I am wondering if it is a coincidence that the current going along the main loop to the right is the same as the the current that is going through a when the resistor e's power consumption is at it's highest. i.e does diving current evenly through parallel circuit yield maximum power??

I would like to prove mathematically why a 100 ohm is the best choice for resistor e in terms of maximising power consumption however I am not sure where to start.

simulate this circuit – Schematic created using CircuitLab


texts: Why does the mesh current equal for Thevenin's Equivalent

texts:
The question wants us to find the thevenin's equivalent of this circuit. Vth is across R. The 5ohms and 6A was transformed into a series voltage and resistance.
The answer shows that the first loop is : -20 + 3i + Vth + 5i -30 = 0
The Above Loop is 2i - 10 - Vth = 0
My question is why does both mesh share the same current i, shouldn't they have their own respective currents i1 and i2 . Eg,  -20 + 3i1 + Vth + 5i1 -30 = 0 and 2i2 - 10 - Vth = 0


texts: How to switch ON raspberry, arduino, esp32, etc from SQW pin of RTC DS3231

texts:
My issue is how to build the circuit and what is the most efficient one to trigger a MCU from the Alarm of the RTC DS3231.
For the momment I have built the one in the picture bellow (with p-channel mosfet IRF9540):
(The blue rectangle simulates de RTC, the battery with 0v is the SQW pin and the red rectangle is the rRasberry)
The problem is the RDS drop is making that during startup it dies when it reaches a mA peak (cause I imagine it has 4,7 volts instead of 5volts). Is this correct? Can I improve it?
I have tried also to put the P-channel mosfet before the DC-DC, but is not working, the DC does not convert, the red led is OFF, I dont know why.
ps: I know how to trigger the alarm, program the RTC, etc.
pss: I'm taking the circuit from https://www.raspberrypi.org/blog/build-low-power-clock-controlled-devices/


texts: Piezo Film Contact Mic to instrument cable

texts:
I'm trying to attach an instrument cable to the DT4-028K/L w/rivets (Piezo film) and make something exactly like this Large PVDF Film Tab contact microphone. My only issue is I get large amounts of hum when I touch the film.
I am using copper tape w/ conductive adhesive. Is this creating a problem? I have covered both the rivets with electrical tape before the copper tape application as well.

How do I properly replicate 2 and attach this PVDF to an instrument cable. I am currently using this unbalanced cable. I will use a separate Piezo geared pre amp.

I'm sorry but my knowledge is real thin here so please present your answers as if you were talking to a child.


texts: Pullup Rise Time On AVR External Interrupt

texts:
Background

I am designing a simple lamp dimmer using the Atmel ATTiny441 microcontroller.  To this end, I have designed a very basic zero-cross detector which feeds the external interrupt pin (INT0) on the micro.

Unfortunately, I am seeing unreliable triggering of the external interrupt.  Despite having both ISC00 and ISC01 set to enable rising edge triggering I am seeing a trigger on both edges.

Consider the following:

In the above, yellow is mains power, purple is the zero-cross detect signal and teal is an output pin (PA1, in this case) which should invert on every rising edge to form a square wave in phase with the 60Hz from mains.  As you can see, there are spurious triggers which cause an irregular waveform.

Zooming into one of the runt pulses, we see:

Clearly triggering on the falling edge.  I was able to get this behavior by manually clearing the INTF0 flag in the ISR (see code below).  Prior to this enhancement, the triggering was especially flaky:

Notice the tiny pulse on the rising edge.  My suspicion here is that the detect signal is rising too slowly, causing multiple interrupts in the transition region.

Questions

Is there a good way to verify this assumption?
My current pullup is 4.7K however many places online recommend 10K.  Is there a good method to determine suitable pullup values?
The Datasheet doesn't list any minimum rise times (that I can find); What is a good value to shoot for?
The heavy-lifting in my zero-cross detector is done by a 4N25; Am I seeing such a slow rise because of the amplification region of the phototransistor?
If so, should this be addressed in the 7.5K limiting resistor on the HV side or the 4.7K pullup on the LV side?
The catch-all: am I completely off-base and the issue is somewhere else completely?

Additional Information

I have set up the zero-crossing detector circuit as follows:

This is fed into the INT0 pin of the micro.  Note that some currently DNIed components are also powered from the bridge rectifier, hence the lines leading off page.

The code to set up and service the interrupt is pretty basic:

#include <avr/interrupt.h>
#include <avr/io.h>

#define ENA_PROTECTED_IO_REG    0xD8

FUSES =
{
    .low = (LFUSE_DEFAULT & (FUSE_CKOUT)) | ~(FUSE_CKDIV8),
    .high = HFUSE_DEFAULT,
    .extended = EFUSE_DEFAULT,
};

ISR(INT0_vect)
{
    PORTA ^= 0x02;
    GIFR |= _BV(INTF0);    // This solves multiple triggers on the same rising edge
}

int main(){

    // Enable INT0, trigger on rising edge
    CCP = ENA_PROTECTED_IO_REG;              // Required to write to MCUCR
    MCUCR |= (_BV(ISC00) | _BV(ISC01));      // Trigger on rising edge
    GIMSK |= _BV(INT0);                      // Enable INT0 interrupt

    // Global interrupt enable
    sei();

    DDRA = 0x02;
    PORTA = 0x00;

    while (1) { }
}


texts:
I'm trying to find a device that can act as a reference for a thermal camera, but everything I find is always some tens-of-thousands-of-dollars blackbody device that is accurate to within 0.01 K. I have been unable to find anything cheap - for my purposes, I simply need a device that can be accurate to within a quarter of a degree or so. Is it possible to build such a device (or buy one that isn't several thousand dollars)?

Essentially, I'm just trying to get something (i.e. a resistor) to reliably be about 35 degrees Celsius with a .25 degree margin of error or so


texts: Testing camera framerate variability by filming clock time

texts:
I would like to test the framerate variation from nominal value in a range of consumer video cameras.
For this I intend to film some sort of high frequency clock and compare the displayed clock time with the ideal time derived from the selected camera framerate.

Regarding specs, at the moment I'm not looking to measure errors lower than 1ms from the specified frame interval. The framerates I will test for are likely to be within 30 to 300 fps. In the future I might want to measure microseconds errors in 1000Hz cameras.

So I think I just need to be able to film a "clock" display device with a 1000Hz refresh rate and at least 1ms time precision.
My first idea was to use a set of 10 LED, using them as bits, which would allow me to encode 1024 values. The LED pattern would be updated every millisecond with the corresponding value, and I could measure the actual time interval between frames.

However I feel there is probably something already existing doing what I want.

Are there existing devices displaying time down to the millisecond and with a 1000Hz refresh rate ?

I am aware that the results will also depend on the use of a rolling shutter by the camera and the ability to manually change shutter speed.


texts: How to measure resistance/voltage with NHS3152 General Starter Kit?

texts:
I have just started running NHS3152 General Starter Kit, with the LPC-Link 2 debugger and LPCXpresso as IDE.
I have managed to run "App_demo_dp_bLinky" example. However I cannot find an example anywhere of code to measure resistance/voltage.
I am still new at both C and RFID.

Where can I find an example with pin connections setup and code?
Where is a good reference for NHS3152 code, to learn the equivalents of Arduino's analogRead/Write for NHS3152?


texts: About phase margin of inverting amplifiers

texts:
Phase margin is usually defined as how far is the phase of the loop gain from -180:
$$PM = \angle \text({loop \space gain}) +180^{\circ} $$
Let's suppose that we want to compute the maximum phase margin of a single-pole amplifier.
For a non-inverting amplifier, this calculation is straightforward: PM(max) = -90 + 180 = 90. However, when it comes to inverting amplifiers, things can get tricky because of the initial 180 phase delay that already exists at low frequencies between the input and output.
For example, using the previous definition, one can compute PM(max) = (-180 - 90) + 180 = 90 or PM(max) = (+180 - 90) + 180 = 270. Thus, we get different answers depending on how we consider the initial phase delay (+180 or -180).
However, intuition suggests that the correct value should be PM(max) = 90 because it is the amount of phase delay left until the input signal "inverts again".
What is right value of the phase margin in this case ?


texts: Hi guys I'm very new to this field and I'm having a problem with my sound devices 664 recorder. There's a faulty component and it needs to be replaced. I couldn't find the component here in the local market, could you please tell me what brand does it belongs from or the product name/ number ? Below I have attached the picture of the component.


texts: Unstable points in a basic memoryless circuit

texts:
I have been told that there can be more than a single solution to a circuit, and that some of those solutions might be unstable. As a simple example, a resistor with a constant power source, connected to a diac (which, I've also been told, has the "S"-like I vs V characteristic.

The big blue dot I drew was the point that supposedly is unstable. I can't understand why clearly from the explanation attempts I got from the teachers (I don't think the ones I asked understand it clearly either). I wonder if anyone in here can help out


texts: MAX485 Receive Output pin current sufficient for optocoupler LED?

texts:
I want to recreate a project found at this link where an optocoupler's LED is a driven by the receiver output of a MAX485.

Now, my question is, the LED series resistor (R5) value is 470ohms, if my calculation is right the led is taking around 10.6mA however I cant find in MAX485's datasheet, about how much can RO pin sink. The most I got is Vol where it says Io max is 4mA. Does that mean it can only sink 4mA? In that case, how is that shield working? because 6N137 needs at least 5mA to turn ON.


texts: Are Pull Down Resistors too Slow to read Encoder Counts?

texts:
I'm planning on using the LPC1768's QEI module for reading a motor's encoder (which has a high resolution - http://encoder.com/literature/datasheet-770.pdf).

I've read some people have hooked up their encoders to the module using pull down resistors [https://os.mbed.com/users/hexley/notebook/qei_hw-interface-implementation-notes/, however, apparently this is only suitable for reading panel encoders turned by humans because the pull down is too slow for high-speed application.

If this is the case, what would be an alternative to using a pull down/up resistor?

Ultimately I'd like to know the best way to hook up an encoder without losing counts.


texts: What makes these simple circuit diagrams different?

texts:
I'm kind of confused with the behavior changes of these 3 differences of a flip flop.

I made an image to easily show what I'm asking about. I circled the differences in red.. Heres the image:

For 3.) I believe that it just inverts the value going in?

I'm not really sure about the differences in the first two though.

Thanks


texts: Current mirror improvement by adding resistors

texts:
One of the limitations of the current mirror with 2 BJTs is the Early effect. According to the Art of Electronics 2nd Ed., adding emitter resistors should make the circuit "a far better current source" (picture left), but I cannot see any significant difference with the circuit on the right side of the picture in terms of current stability due to Early effect. Is there any better or more formal explanation why the former circuit is preferred?

simulate this circuit – Schematic created using CircuitLab


texts: How to avoid negative voltage on MCU pin from RCV420 converter?

texts:
I am working on a circuit to convert 4-20 mA signal to 0-5 V to finnaly read with an analog input of an MCU (PIC16F886). The IC I'm using to convert the signal is the RCV420K which works fine. On the documentation of the IC it says that it needs to have -1.25 V on the output at 0 mA so at 4 mA can be 0 V.
I am reading the voltage signal with no problems but when I unplug the signal from the IC the voltage goes negative and I suspect it is going to be harmful for the MCU.
The thing is the IC outputs very little current (0.10 mA on my readings) but when the signal source is removed it reads -1.0 mA. Is this safe for my MCU? If not, Is there any way to ground the negative signal so it doesn't affect the MCU?
Thanks in advance!! I'll attach an schematic.


texts:
I have prototyped some DC-DC converter modules, and they work well. However due to size, I don't have a huge amount of copper pour for them to dissipate their heat. I have used 2oz copper but the bottom layer copper pours get really hot at higher current. Even through the solder mask!

I experimented with adding a heatsink to this bottom side of the PCB with some thermal grease and the results were surprisingly good. The heatsinks get hot under heavy load. The buck-boost-inverter went from maxing out at about 1.5A to being stable at 2.5A! This is my current setup:

However I can't help but think that I can improve this. I am thinking of removing the bottom solder mask around the heatsink area for better heat transfer. Also I want to use a Sil-pad instead of thermal grease for easier assembly, and because I don't want to risk shorting different copper pours when the solder mask is gone. Like this:

So my questions are:

Is this a good way to do this? (given my limitations)
is there anything that could affect the long term life of my PCBs with this setup?
Are there any other suggestions people have?

Thanks!


texts: I have some 12 V solenoids and I want to control them via Arduino, but Arduino outputs a maximum 9 V voltage through the Arduino jack input, and the voltage on Arduino pins is only 5 V, so how do I control some solenoids with an Arduino pin which is only 5 V?


texts: What happened with this LM386 Amplifier Output

texts:
yellow channel is from lm386 amp 20 times gain

my circuit is from the lm386 datasheet with 16 V source, what i amplify is 40khz arduino pwm output, is there any explanation why this happened, thanks


texts:
If I have a process which is approximated by a first order system

$$
H(s)\ = \frac{K}{s+a}e^{-sT}
$$

How can I design a PI controller with a rising time < 2 and an overshoot that is less than 10%

I know a typical PI controller is given as

$$
G_{c}(s) = K_{p}+ \frac{K_{I}}{s}
$$

So how do I find KP and KI given my specifications?

I don't need it solved completely just the steps that are needed.


texts: Led matrix 64x64 1/32s HUB75 with only A, B and NC lines

texts:
I am trying to drive a led matrix, a RGB 64x64 with a HUB75 connector, 1/32 scan, with 2 RGB lines (R1G1B1, R2G2B2), a latch pin, a clock pin, an output enabled pin, and 3 pins I don't know how to use it : A, B, NC

Image :
 (also here)

Beside the A, B and NC lines, all other lines (RGB, clock, strobe, OE) behave like other "classical" HUB75 panels.

Does anyone have managed to drive a panel like mine ?


texts: Reflection on SPI Clock Signal, termination or stub issue?

texts:
This is a SPI Clock. 6.25MHz frequency. I see something like a reflection. I don't think it's from cross talk on my board from another signal, not sure.

Added as requested: This is my system diagram (notice I have a stub). Note that the diagram ends at the "Connector". There is a cable to the SPI Slave beyond the "Connector" but that is not even connected when doing the measurement.

What kind of terminations should I try to get rid of this reflection? Should I try to play around with the termination values or try to remove the stub?


texts: It is from a German-made sewing machine pedal. It appears to be 2mm inner diameter, 5mm outer diameter on the metal but has a 6mm plastic molded ring on the end...maybe to assure it stays connected?  I would like to buy this jack and solder to a new wire, or find an affordable cable with this jack on one end to replace a damaged one. Any ideas?  I've not seen this jack before.


texts: The difference between series and parallel LC circuit

texts:
I wanted to know if there is a difference between a series LC circuit and a parallel LC circuit, like these:

I noticed that the tuned circuit is all the time a series LC circuit, and I wondered if it could be a parallel LC circuit.
Also, I wanted to know if the series LC circuit works excatly as a parallel LC circuit (regarding the way they interchange the energy between both of them).


texts: Analysis of BJT transistor - is a linear analysis possible?

texts:
Since semiconductors aren't passive components, can I realistically derive analytic solutions for a circuit with BJTs? I know this may seem like a very naive question, but am I on the right track with this sort of analysis, or do I need more powerful numerical modelling even for basic circuits? e.g., the responses for single transistor amplifiers, etc.

I'm trying to teach myself more about circuit analysis - but after the 'RLC' passives, I don't want to end up on the wrong track. I understand this is bordering on opinions, but I really want to start on the right track.

I should mention, I've used 'rule-of-thumb' stuff for constant current, biasing etc. But I'm not entirely satisfied with this approach.

Thanks for the current (ha ha) feedback. Using some of the 'hobbyist' rules of thumb, I've found it easy to achieve switching (saturation) modes, and biasing giving consistent results with different small-signal transistors - which seemed counter intuitive and really surprised me! I really need something like a first-principles primer that doesn't gloss over the complexity, or the range of uses. My multimeter isn't teaching me much...


texts: Battery powered ionic air pump voltage stepup

texts:
I am working on a proof-of-concept device for medical purposes, but am lacking in the electronics side of the skillset!

I am trying to build a vibration-free wearable air pump, and using an ionic thrust system seems like a potential success, since I don't need huge pressures (0.02-0.25PSI across only about 1/2in^2). There's not a lot of available documentation on ionic air thrust concepts, as the truly lucrative prospects (like transportation) are mostly out of scope for ion drives. However, I have found enough to suggest that I need at least 5.2kV to get the air to ionize enough to get things moving. BUT, a wearable really needs to be cordless and so I need to get some battery source stepped up to that neighborhood somehow.

I'm also curious as to people's theories about what might happen if the air direction is forcibly reversed by backwards pressure.


texts: MLX90616 Infra Red Temperature Sensor problem

texts:
Recently I have been trying to interface with the MLX90616 an infra red temperature sensor by Melexis. After reading the datasheet I have I have written a program to take the object temperature readings via the on board SMBus. Everything on my end seems to be working however the the temperature readings are taking extremely long (greater then 10 minutes) to reach the object temperature. Based on the datasheet the temperature should settle within seconds thanks to the inbuilt thermal gradient compensation. Is there some EPROM setting I have missed to turn on the thermal gradient compensation to acquire fast stable readings?

Further more has anybody had a similar experience with this sensor?
I am unable to find any details of others who have used this particular sensor in the past so some details would be greatly appreciated.

I have attached the main body of my code for your reference:

 I2C1_Init(50000);                   //I2C clock must be in the range of 10kHz to 100kHz for operation according to the SMBus specifications
  //delay_ms(100);                      //Allow time for the SSP module to initialise

  I2C1_Start();
  //Sometimes if I2C read is peformed without an acknologment it can hang the I2C BUS error check on each operation is therefore necessary
  if(I2C1_Wr(0xB4) == 0)           //Address for a write operation to 0x5A
  {
    if(I2C1_Wr(0x07) == 0)         //Address for RAM command to 0x7
    {
      I2C1_Repeated_Start();
      if(I2C1_Wr(0xB5)== 0)        //Address for read operation to 0x5A
      {
        lowerByte = I2C1_Rd(1);
        upperByte = I2C1_Rd(1);
      }
    }
  }
  I2C1_Stop();


texts:
Good day all,

This is my first question on the electronics board, and I have checked for similar queries, but so far no luck.  It is possible that I'm searching for the wrong terms, so I will describe my issue below.

I've recently started working for a company again doing embedded and firmware work (first time in some years), but they do not have an formal 'equipment under test' register or process in place.  By this, I mean keeping track of:

PCBs being tested (with identifying information, ie SN, batch, etc)
History of the PCB (work done, failures, mods, etc)
Current FW versions
Any faults noticed on a particular PCB (or problems found during FW testing)

The last time I worked with such a process, it was a physical (paper) register, but for high value, low volume equipment, in one location.  In this case, volume is higher, and work is spread out somewhat, and I need a way to track the history of boards so that we can see any common issues, or past issues that may be causing a new problem, etc.  It will also be good to know where and with who a given board is at any given time.

I'm not sure at all whether there is software (free or otherwise) that will do this, and what the correct name (or terminology, category, etc) it would be hiding under.

On the software side, we'll be running Git, Jira, and all the related items (pure software development is what I've been doing for the last few years), and ideally I'll be able to link issues from Jira, to specific boards under test.

Any suggestions would be greatly appreciated!

Kind regards,

UPDATE

I should make it clear that this register would be for equipment and boards being used during R&D, and some very basic acceptance testing.  This is not for acceptance testing of boards actually going to customers.  We do, however, still need to track the configurations and history on these boards.  Sorry for any confusion!


texts: How do I introduce impedance in an AC circuit?

texts:
Complete noob here so please bear with me.
I want to know how to and how much impedance to introduce in a single phase AC circuit of 220v and 50hz so that I can bring it down to 100v. My load is an AC single phase motor.
Thanks.


texts:
I am doing an experiment that involves loading an asynchronous 50 HZ generator. For the load to consume current it has to be a capacitive load to cause a phase shift between the current and the voltage. However, what should be the value of the capacitance of the load ?

Thanks


texts: Voltage drops across a Human Body (Set gain of InAmp)

texts:
I'm developing an application that sends an electrical signal to the human body. It is a bioimpedance system.
This signal has approximately 3.2Vpp ranging between + 1.6V and -1.6V, at a frequency ranging from 50KHz to 100KHz, with 1mA of current.

This signal is sent to the Human body and received through an instrumentation amplifier (INA118) as in the following image:

This signal after being amplified by the InAmp goes to a 12bits (0 - 5V) AD converter. I am feeding the InAmp reference pin with a voltage of 2.5V (Vdd / 2) to give an offset gain in the signal.

The current that should circulate in the whole body, right? As in the following image:

My question is:
How do I set the gain of my Instrumentation Amplifier? What is the average voltage drop my signal will have going through the human body? I need to set a value that works for as many people as possible who will use my system.

Thank you!
Regards,


texts: Why do I consider in this circuit diagram that \$I_C = I_E\$ (BJT Transistor)

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Consider follows problem on picture below:
Data diagram:

\$V = 20V \pm 20\%\$

\$I_{Carga} = 5A\$

\$\beta_1=2,\quad\beta_2=50\$

\$V_{diode} = 0.5V\$ (each)

\$V_{zener} = 10V,\quad I_{reserve\cdot zener} = 50mA\$

So find the value \$R\$?

I compute this problem on 2 differents strategies.

One was consider that

\$i_{e1} = (1+\beta_1)\cdot i_{b1}\quad(I)\$

and

\$5 = i_{e2} = (1+\beta_2)\cdot i_{b2}\quad(II)\$

as \$\quad i_{b2} = i_{e1}\$

\$i_{b1} = \dfrac{5}{(1+\beta_1)\cdot (1+\beta_2) }\$

Consider worse case to Voltage source (\$V = 18V\$)

\$i_R = 50mA+i_{b1}\Rightarrow\dfrac{18-(10+2\cdot0.5)}{R} = 50mA + \dfrac{5}{3\cdot 51}\Rightarrow \boxed{R = 85\Omega}\$

(Letter E)

But if I consider \$ i_c = i_e\$ (this problem consider that It is correct strategy)

We got: \$i_R = 50mA+i_{b1}\Rightarrow\dfrac{18-(10+2\cdot0.5)}{R} = 50mA + \dfrac{5}{2\cdot 50}\Rightarrow \boxed{R = 70\Omega}\$

(Letter B)

Like you see the Question 39 answer key show Letter B is correct.

So, Why the first strategy is wrong (or not) and the second is the correct form of resolution?


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My professor gave out this instructions: Use an op amp with to leds connected to the output, one LED needs to turn on (while the other is off) when you have 2v as an input and when you change the input to 1 the other LED needs to turn on.

Those are all the instructions we were given he said we could not use logic gates or anything like that. To be honest I have no idea of how to do it, I'm not asking you to do my homework but if you could point me in the right direction it would be really helpful.


texts: Ratio of two RMS values in recorded audio

texts:
Hey guys quick(ish) question:

I produce music and am having a discussion on the difference between two RMS values in a specific record (Nero-- The Thrill (Porter Robinson Remix)). In the verse, the RMS is -15dB, while in the chorus, the RMS value is -7dB. I would like to find out the value (in terms of a ratio) between these two.

The question is how many times louder is the chorus than the verse.

I have used the equation:

$$20log\Big(\frac{-7}{-15}\Big)$$

Then changed for syntax purposes changed it to:

$$20log\Big(\frac{7}{15}\Big)$$

So finally:

$$20log\Big(\frac{7}{15}\Big)=-6.62$$

I reckon That means that the dynamic range in the chorus has collapsed by 6.62dB, is that correct?

Maybe I'm over doing this, and I really should just set 7:15 up as a ratio (which means it was just over 3dB, or an increase of 2x in sound intensity).

Anyways, I'm really sorry for the word/number salad, as you can see I'm pretty out of me element here!

It should be noted that I posted this topic on the physics site and they said it would be better here. One of the results I got was:

  The dB scale is logarithmic, so when you have two dB levels, their difference is their ratio. Going from -15dB to -7dB is an 8 dB step. It's that simple. --Floris

Is this correct? Do the above equations have any relevance to the problem?


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hope you all are well

The bypass diode is usually connected in parallel with PV cell to avoid hot spot and prevent more PV output power losses.
The bypass diode is connected in opposite direction to the PV cells in such way that it conduct when the PV cell is shaded by (tree).

My question is that what prevent the DC current generated by a string of PV cells in a normal condition ( no shading) from passing through the bypass diode and not through PV cell ?
and why the current can flow through the bypass diode only in the shaded PV cell.

is that because the resistance inside the diode is higher than the PV cell, and the current always prefer to choose the route which has a lower resistance ?
Thank you !


texts:
Whenever I am searching Rf module, I have seen transparent operation on some module.I have searched meaning of transparent operation, but I could not find anything. My questions are

What is the transparent operation ?
Why is it used in RF module ?
What are the drawbacks of the transparent operation?


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I have to amplify or "step up" the voltage of a pulse generator.

I have a pulse generator, which generates 5 volt pulses with on times ranging from 100nano seconds to 1200 nano seconds which repeats itself approximately every 1milisecond .

For design reasons I need to get the same pulse but at 10 or 20 volt in amplitude, without compromising the the pulse times .

My initial thoughts were using an schmitt-trigger as a buffer but It couldn't handle the high frequency of oscillation .

How can I create a pulse from 5V to 10V that lasts 100ns? Can I do this with a capacitor and a mosfet?