texts: Understanding the IR Emitter / Detector I pulled off of an inkjet printer

texts:
Long Story Short

It's a "linear/rotary optical encoder," or, "incremental encoder," like this one, which costs about \$6:

http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10

You use it with "optical encoder strips," or "codestrips," like this one, which costs about \$.30:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G15602

It uses a single LED with 2 photodetectors. These are exposed as pins labeled Channel A and Channel B. The pins will output either 0 or Vcc V, which is 5V in my case. Since there are 4 distinct states for A and B, you get 4 times the resolution of your codestrip. Since it can handle up to 150 lines per inch on a codestrip, you get 1 600th of an inch resolution. When monitoring the A and B channels, you can determine which direction you are moving by comparing your current state to your last state. For example if A and B are both high, and then A goes low, you've moved up 1 600th of an inch.

It is a great, accurate, affordable system for determining precise linear position.

Original Post

The red arrow points to the ir emitter / detector. The blue arrow points to where I got it. The printed circuit board under the blue arrow would slide back and forth under that gray band, which is transparent plastic with lots and lots of very skinny black lines. That was probably how the inkjet printer kept track of the position of the print head.

The 2 ir diode pins were easy enough to figure out. That's being powered by the fat white wire on the far left. I can't figure out the additional 4 pins on the detector part though. Notice, that's a total of 6 pins. I pulled the cover off the part to get a closer look, and those pins look like this, with the skinny white wire attached to the pin on the far right:

The black cover on the ir e/d has tiny white letters:

9981
C526

and tiny black letters

Agilent
18

I tried Googling around for datasheets, but I didn't manage to find anything. I tried calling Agilent but just got lost in the phone tree, and they hung up on me at some point, haha.

Does anybody have a datasheet for this or a similar component, or have any idea how this 4 pin detector works, or know where to look for a datasheet or who to call, or know a component I could substitute, or anything really?

This is all part of a bigger thing I'm trying to get a handle on, which is precise 1 dimensional movement, and then ultimately precise 2 dimensional movement.

Edit

To be clear, there are 6 pins total. 2 for the diode, and 4 for the detector. I don't understand what all 4 pins on just the detector are for.

Edit 2

I found a very promising blog post about this kind of problem. http://benkrasnow.blogspot.com/2010/02/linear-position-tracking-with.html

Here's a 6 pin linear optical encoder with data sheet which I found from this blog post.

http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10


texts: Why must resistors be on the respective anode terminals instead of the common cathode terminal of a RGB LED?

texts:
Different from the best answer of this one: Why does a resistor need to be on the anode of an LED?
But well, I'm also an electronics noob ^.^

Recently I bought the official Arduino starter kit and played around with the common cathode RGB LED that came with this kit. In the project book, the instructions for the colour mixing lamp is to use separate 220ohm resistor for each of the RGB legs. But I thought, why can't I put the resistor on just the cathode of the LED?

I tried that by plugging the LED into the breadboard and connecting the cathode through a 220ohm resistor to the ground of Arduino UNO. When I touched any one of the R, G or B anode legs with a jumper wire connected to +5V, the respective colour lights up alright. However, when I bridge the G and B pins together, only the green LED lights up. When I bridge all three anodes together, only the red LED lights up. But if I connect the anodes to +5V through their separate 220ohm resistors(according to the instruction), the colours will combine.

Why is it so?


texts: What kind of output / DC side protection is recommended when using an AC-DC converter?

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Using a CUI AC-DC converter, http://www.cui.com/product/power/ac-dc-power-supplies/board-mount/vof-6b-series.

What kind of output protection is recommended in order to handle CE testing events like surges, ESD hits on the input, radiated emissions etc, to protect the DC circuit?


texts:
I was recently reminded that BJTs can be used in reverse active mode.

Can somebody enlighten me whether and to what extent the same is true for optocouplers? Do the same limitations apply to reverse active mode as for BJTs?

Edit 1:

Of course I only mean reverse polarity on the "transistor side" of the optocoupler, not on the "LED side"...


texts: Using a high resistance pull down resistor

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I'm trying to make a circuit where closing a switch will change a GPIO from low to high, and I want to minimize current as much as possible to increase battery life. The chip I will be using is Nordic Semiconductors nRF51422 (https://www.nordicsemi.com/eng/Products/ANT/nRF51422).

My understanding of pull up and pull down resistors is that they limit current, protecting the chip and decreasing power usage, while still keeping the GPIO either pulled up or pulled down. Having too large of a pull up/down resistor increases the time constant of the circuit making transitions from high to low slower and 'pushes' the GPIO out of the range where it is recognized high or low.

The exact set up I was envisioning was this. I use a very large pull down resistor (on the order of mega Ohms). The voltage drop across this resistor will be so large that it will essentially behave as a pull up resistor with the added benefit of exceptionally small power usage. I then have a switch that when closed connects the GPIO to ground across the recommended size resistor (13 kOhms). The circuit diagram would then resemble a GPIO connected to ground across two parallel resistors, one very large and one much smaller, which will behave like a single smaller resistor  Thus, when the switch is closed the digital value of the GPIO changes from high to low, and when open there is only a small trickle of current which saves battery life immensely.

Would that work? In particular, does my idea with the large resistor even make sense?

EDIT:

I'm gonna rephrase my question and add a schematic.

So my understanding is that GPIO's have high input impedance hence a very small leakage current when connected to ground. If I were to connect a resistor that had a impedance of, say, 10 times the input impedance of the GPIO between the pin of the GPIO and ground would the GPIO pin be at 0.9*VDD? I'm assuming the input impedance of the GPIO is independent of what is connected to it.

I've made a schematic that illustrates what I'm thinking by simplifying the GPIO as a black box resistor. Schematic

Would this work? Is my schematic just straight up wrong?


texts: What does this mean in datasheet : 2k: Ipgm/10 for term; Ipgm/5 for precharge

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I was referencing the datasheet for BQ24040 Texas Instrument IC and could not understand the following statement and what does it actually mean. I am new to this. Can some one explain what does it mean.

This is on page '4' in the datasheet. Reference datasheet can be found here: http://www.ti.com/lit/ds/symlink/bq24040.pdf


texts:
I would like to make a circuit that can heat up an object to a very high temperature, similar to an electric griddle or coffee cup warmer. What kind of heating elements do they typically use and where can I buy them? They should be pretty easy to power with 120VAC right? I just need to be able to switch it on and off from an MCU.

Target temperature is ~200°C


texts: Writing unused areas of a page on a NAND flash

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I'm working on a project based on the ESP32 that uses a NAND chip from the GD5F1 family (link to the datasheet). Sorry for the long question, but it's a bit convoluted, and it's driving me nuts for the last week.

I managed to write consistently and without issue for a long time. Now, I had an idea about signing some pages after a certain process, so I can keep track of the pages processed and in case of power loss, restart from the first unprocessed page.

As I have a bit of extra memory on each page, I thought, "why not add a certain pattern, e.g 0x11223344, on the last 4B, as they are always 0xFFFFFFFF". As far as I know, and based on some preliminary tests, I can write on a page that has data. If the sector of the page that I'm writing is still 0xFF, I get whatever I want and if it's not, I get the AND of what I wanted to write and whatever was there first. So far so good, and all working as expected.

As I said, I did some tests, and all worked as expected, but now, on my app, the behaviour is very erratic. In my application, I use the first page of the NAND to store some metadata (60B), and then I write a variable number of pages with 2016B (the page size is 2048B). When I try to write something on the header page, I get garbage written if I write on a position below 2016, and what I wanted to get if I write after the 2016B mark.

If I change the amount of data on pages 1 and onwards, to let's say 1500B, and then try to write on the metadata page, I get garbage before the 1500B and whatever I wanted to write after the 1500B.

I'm really puzzled by this behaviour. Can somebody shed some light?

The most relevant test that I've done so far is writing 4 bytes on the first 4 blocks (256 pages) at position 0, then repeat at position 4, 8, ... 2048. Result: all the pages are correctly written, proving that I can write on a page as long as it's content are 1's. Tried also with other sizes, no problem whatsoever in going back and forth writing on unused areas of the flash.

What doesn't work: Write 60B on page 0, then write 2016B on the next pages, and try to write back on page 0 again, on any location < than 2016. There are no other references in my code to that 2016 other than the "write 2016B" commands.

The code that I'm using is quite a big chunk split in several libraries. I think it will take quite a while to review. It's quite a complex problem I'm struggling even to try to explain it, so I'm looking more for ideas of things to try than really somebody auditing my code.

Thanks!


texts:
I recently installed a solar ups and it has been charging the batteries all the time.
I have two 12v 230ah Batteries (lead acid tubular) in series and my solar charger software says that it is charging (c.v) at 29.2 volts.
My batteries are brand new and even after a week they are still charging all the time during day time.
Battery percentage in the software is always 95% and never reaches 100% so it never stops.

What should be correct charging voltage for a flooded lead acid battery to achive 100% charge and then stop charging?


texts: Say someone has a large array of solar panels or a wind turbine or two. They produce all the electricity they need for their house and then some. I always hear that, "The extra electricity can be sold back to the power company. They will pay you." How does this actually work? I know I cannot run my neighbors house off of my power line without disconnecting them from the power grid because it will short circuit. How does one push power back up the grid to receive credit with the power company? Is this some hoax from the power companies to get us to buy renewable power? I'm all for renewable energy, but this 'selling power back" thing sounds fishy.


texts:
I have been told that passing DC current through two probes in water will lead to corrosion on the terminals.

Apparently AC does not cause corrosion. Preventing corrosion is of high importance to me.

I am using a microcontroller in this design. What is the best way to generate and measure the AC signal?

Or otherwise, how do say dive watches detect water?


texts:
I've built a nice programmable switch basing on Raspberry and a relay board. It's fine for driving common 230V appliances but the relays seem rather flimsy; I wouldn't trust them to run 10A of current through them. I'd like to connect devices that potentially take about much - heaters for my home etc. The obvious solution is next stage relay rated for currents of that order; 230V input from my switch, 230V over some thick wire from a rated socket, the load on output of the relay.

simulate this circuit – Schematic created using CircuitLab

What I'd like to ask - is that enough? I know driving the relay driven by logic pin requires quite a bit of "glue electronics", an optocoupler, a transistor to amplify signal from the optocoupler, protecting diodes, resistors regulating the levels etc. Is anything of that kind required when driving one 230V relay from another? Any extra electronics between them, or can I safely connect them directly like in the schematics above?


texts: A Bare Bones Internet Connected Microcontroller < $10?

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These days businesses are all talking about the Internet of Things and how Cisco predicts 25 billion devices will be connected by 2015.

All around the hobbyist community various internet shields and internet ready devices like the Raspberry Pi cost somewhere around $35. The ENC28J60 is $21. The Electric Imp is $30. The Nanode Classic is $40.

When I check out PICs and AVRs chips with built-in ethernet, they all seem to cost something like $6. Toss in an RJ-45, various other components, a PCB and a lot of time and I seem to be back to something almost as expensive as the hobby grade systems.

With all this talk of the Internet of Things, and the cheapest 32-bit PICs around $1, it just feels out of place that I haven't encountered any complete ethernet solutions for under $3. I can't imagine any designers willing to equip an alarm clock with internet connectivity for $25.

As a CS student about to graduate, I am trying to create a small volume product with the electronics costing under $10 that will send very simple analog data by ethernet to my web service. I have built the web app and prototyped with a Raspberry Pi, but $60 for an internet connected sensor is just too expensive.

Can anyone shed some light as to whether web connected sensors under $10 are possible for a guy like me to develop or use? Maybe they exist and I just haven't found them?


texts: Arduino (ATmega328) in-circuit programming

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I am designing a circuit/software for some guy...

I am using an ATmega328 surface-mounted microcontroller in the design and am just supplying the schematic and code. He is going to build it (make a PCB) and use it for his business.

I was going to program it using the Arduino IDE since I have more experience with that and was going to add in an ISP header and suggest using this http://docs-europe.electrocomponents.com/webdocs/0dba/0900766b80dba9b4.pdf to program it..

However I noticed that the 328 is not listed under the supported devices for that programmer?? And even if it was I am unsure if that would work using the regular Arduino program?

What is the best way for me to do this? I need to be able to test the code on my Arduino Uno, and also provide the means for him to easily program the code onto a new chip on the PCB.

I don't mind programming it outside of the Arduino IDE if I need to as long as I can test that code with my Arduino Uno.

I tried looking around for answers, but I didn't find anything satisfactory. Here is the schematic I have so far, with an ISP header (that apparently isn't supported?)


texts: Would a battery be considered an independent or dependent voltage source?

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This is a very trivial question in my opinion, but I was thinking about what a battery would be classified as. In the physics world, batteries are often used to represent a voltage source.

I feel like that a battery should be considered a dependent voltage source since a batteries voltage is dependent on the amount of current the load draws within a certain amount of time. An ideal battery wouldn't have this issue. But to me, batteries aren't independent sources like power supplies, which will always supply a fixed voltage (as long as it is CV mode).

The question is do you think batteries are independent voltage sources or dependent voltage sources?


texts: What is the difference in RISCV between JAL and JALR?

texts: I'm kinda confused on what the difference is between the two instructions and would love a comparison of the two!


texts: Can I use a toroidal inductor as part of a tuning circuit for medium waves?

texts: Toroidal inductors can have very high inductances. So is it possible use a toroid as the tuning coil for a AM radio? If so, what are the drawbacks?


texts: Having a problem using TRIAC in my project:

texts:
I’m having a problem working with TRIAC (BT-131) in my project. I’m trying to switch a low power LED with a 5V DC output from a sensor. I’ve used an Opto-coupler (MOC3021) in between the TRIAC and the sensor. When the sensor gives a 5V output (through a 470ohm resistor) to the Opto-coupler, it triggers the Gate of the TRIAC (through a resistor, R6). When R6 is 100k, the LEDs glows at the moment of switching, then turns off. If I use 10k or 470ohm resistor as R6, the LED glows continuously, but very soon R6 burns out and LED goes off.

simulate this circuit – Schematic created using CircuitLab

I don’t understand why is it happening and what is the remedy for this. I searched about the characteristics of the TRIAC in Datasheet, searched YouTube for similar projects, but didn’t understand the reason behind the phenomena.

Can anyone help me in this ?


texts: Best way to power an Arduino with externals modules?

texts:
For my current project I have a Arduino wired to 5 externals modules that requires a precise 5V input (CT measurement). The cable between the Arduino and theses modules will be a 4x0.22 mm² of about 1.5 meters long.

My questions are the following :

Can I create a clean 5v from a 9v AC to DC transformer inside my Arduino case (regulator + capacitor) and power up the Arduino and all modules from there without having loose in my modules voltages ?
Or should I transport 9v to each module and create the 5v current onto each module board ?
Also, which type of regulator should I use ? They will be enclosed in a small box, I don't know how much heat 9v to 5v are going to generate.

I only have a bit of electronic experience on bread board, I have never deployed a project in real world situation, so I am bit confused about the best practice to use.

Additional information:

I would like a voltage precision of +/- 0.1v
My externals modules are also homemade, they are basically composed of a AC relay and a CT. My precision need is for the CT voltage measurement.
The only component drawing current in my modules is the relay, so at the maximum 5x 90mA + the arduino consumption (with Ethernet Shield).


texts: USB NiMH charger keeps drawing same power forever?

texts:
If my USB charger for AA/AAA NiMH batteries by BTY charges a NiMH battery, the current (ampèrage) of charge only depends on the USB input voltage (usually 5V) and the battery manufacturer (input current at 5V USB varies between 0.12A and 0.17A).

It keeps drawing the same power forever, even if the NiMH battery is full. The only difference is that the NiMH battery gets warm if charged completely.

I measured it with an USB multimeter (KW203).

That BTY charger has no charging controller.

Why does the charger keep drawing the same power forever?


texts: How do I identify a what kind of power connector for AC mains is on a product?

texts: I see an AC mains input but I have no idea what kind of cable it goes to, how do I find the cable type so I can design around that? (Or conversely I have a cable and I don't know what type it is)


texts: Cooling buck converter mosfets by placing on bottom layer of PCB - a problem?

texts:
I have a design and layout for a buck converter which currently sits on one layer of a 2 layer PCB. I would like to force-cool the heat generating components of the board by placing them directly onto a flat heatsink.

Because there are multiple identical buck converters for different applications, having the entire board bolt to a heatsink would be ideal. I therefore wish to place the FETs on the bottom layer of the PCB. (they are SMD and not the tallest components on the board- the inductor is.

I have heard that placing the FETs on the bottom layer of the PCB (the other side to the inductor) might introduce issues into the board. Can anybody tell me if this is true, and if so, how can I mitigate these issues? Can I simply use enough vias to mitigate?


texts: Clearance and creepage for AC Optocoupler for 230V line detection

texts:
I was wondering how I need to handle clearance and creepage in this scenario.
It's AC mains line detection circuit.
I need to achieve around 2.5mm creepage.


texts: How, could hardware write protect be implemented for flash media?

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I come from a software background, but feel this is a hardware/electronics question.

Looking for a way to hardware-write-protect on flash media, I bought an SDHC card   (with a tiny switch labelled "lock") and a cheap USB card reader.  I wanted to create a 'read-only' device that I can be certain will not be modified - without having to consider the software on the hosts to which I connect it.

Inserted directly into my Dell laptop, the card can only be written when unlocked... I assumed this meant that the write protect is implemented by the SD card... When I put the SD card into the USB reader, however, the same laptop allows me to write to the locked card.  I've now read this question, and this confirmation that I was wrong to assume that the 'lock' switch would provide hardware write protect.  I now know that the 'lock' is not a feature of the card in isolation - and that standard 'locked' depends upon OS drivers (which I don't want to be forced to trust.)

I would like to know:  What would be a straightforward, simple, reliable, neat and cheap way to implement a hardware write protect switch for flash media? Ideally, I would like to access this media over USB.  I assume that I will need a device that can intercept the blocks of data exchanged over the serial interface to either USB or the SD card?


texts:
A company that is looking to add equipment in their facility informed me that they have an IT ground. The ground can actually result in damage to electronic components if they aren't compatible. About the only thing I have come up with is this Wikipedia article that mentions it:

Earthing system - IT network

  In an IT network, the electrical distribution system has no connection to earth at all, or it has only a high impedance connection.

Of course you have to take Wikipedia with a grain of salt but the information supplied isn't very in depth. I want to make certain I have a clear understanding of this.

What makes electronics such as servo drives and PLCs I.T. ground compatible?


texts: How does BA6220 motor speed controller actually work?

texts:
The BA6220 is a chip that performs speed stabilization of small motors by means of back EMF. However, the datasheet is very scarce on the details and has no explanation for its workings.

If I understand it correctly, the chip has no PWM and performs linear regulation with a transistor. How would it measure back EMF while driving the motor, then?
What RPM stability can be expected wrt. supply voltage and mechanical load? Are there similar contemporary chips?


texts: self guided electronics text recommendations

texts:
Can anyone recommend a good text or texts that they have experience with for someone learning electronics on their own. I have taken some very basic college courses, but I want to know more. There are so many books out there that claim to be geared toward this, but I'd love to hear from some of the more experienced people with higher knowledge levels about what they would personally recommend. I have done a lot of searching and was going to base my selection on online user reviews, but I thought some input from people on here would be valuable. I have a lot of experience with DC electrical systems, and some with AC electrical systems, but only a small bit with electronics.

As I work through some self learning and project using online resources, I am quickly deciding that I need some actual text reference material.

I apologize if this is an inappropriate place for this question.

Thank you for any info!


texts: Replacing a tactile switch with an ultrasonic ranger

texts:
I'd like to have a switch activated when something gets near it. Today it's just a pushbutton, that's active as long as it's depressed.

I'm going to use an analog ultrasonic ranger, using its analog output. What I'd like to do is have an analog circuit activate a mosfet when a certain range threshold is hit. My question is - how do I make this "binary?" How do I have Vgs applied to the mosfet when the analog voltage on the ranger crosses a specific value? I thought about using a zener diode with the breakdown voltage at the distance that I need (the threshold I'm looking for is about 10" away from the device, which translates to ~100mV on the analog pin). Given the low voltage the sensor will output at that distance, I assume a zener won't work.

I'd like to not involve an MCU if possible, because I'd like this to be a simple drop-in.


texts: Interrupt generating circuit: 0 ~ +3.3 V

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For the purpose of testing a MCU and it's interrupt handling I want to design a circuit to generate interrupts. Ideally I would use a relaxation oscillator, but my supply is constrained to 0V and +3.3V and the output signal should also be close to 0V / 3.3C.

What would be a good possibility to overcome the problem of not having (and not wanting to have) a negative voltage supply?


texts: Arduino analogReference() switching during run time

texts: I'm trying to read ADC value off two sensors one that uses 5V as VREF and one that uses the INTERNAL  2.54V as VREF so I use analogReference(); between the reading and it seems to affect the measured values even after a 10mS delay after each analogReference(); Is there a way to use it properly with the code or do you have to choose a single reference in the setup() and that's it?


texts:
I have started the book The Elements of Computing Systems. I am at the point where I am making an OR gate, although I'm not getting the proper results.

I am using one NAND and one NOT gate for my OR gate. It goes like this:

simulate this circuit – Schematic created using CircuitLab

Why will my NOT1 gate not reverse the digital signal? Why does the below example work, even though it seems like the same logic? Which fundamental rule of electricity am I unaware of that makes my first design non-functional?

simulate this circuit


texts:
I am trying to come up with the equation for testing electronic capacitors by discharging them with a test pulse using a known resistor value.

A known value resistor is switched in circuit for a test pulse period to discharge the capacitor voltage by 10% over a test period time (T2-T1). Because a known value resistor was used to discharge the capacitor by 10%, it is possible to calculate the actual true capacitance of the capacitor, the equation below is using capacitor voltage and time:

E = 0.5 * C * V^2 ( Energy stored in a capacitor in joules )

Delta_E = ((((((V1 – V2) / 2)+V2) / R) ^2)* R) * (T2-T1) ( Change in capacitor stored energy )

And (0.5 * C * V2^2) + Delta_E = (0.5 * C * V1^2)

C = -1 * (Delta_E / ((0.707*V2+0.707*V1)*(0.707*V2-0.707*V1))

For example, the capacitor was charged up to 50 Volts, a discharge resistor of 475 Ohms was used to reduce the capacitor voltage to 45 Volts, during the test, it took 16.66 milliseconds to discharge the capacitor.

V1 = 50 Volts, V2 = 45 Volts, R = 475 Ohms, T2-T1 = 16.66ms

Delta_E = 0.079135 Joules

C = 333uF

The electronic circuit simulator used a capacitor of 330uF so the result for C is very close.

1) The above equation does not consider that the capacitor discharges exponentially, what is the equation for using exponential voltage decay?

2) The capacitor could have a unknown series resistance called ESR, what would be the equation if ESR is also considered?


texts: Effect of wire gauge change on thermocouple measurement

texts:
I'm working on attaching to a thermocouple harness that had six 16AWG chromel wires and one 12AWG Alumel. The alumel would T off with each of the chromel wires to make a pairing and so the common was the same for each to give six measurements around the engine. I need to make a cable that will hook into this and go off to my box to do measurements. I'm having a hell of a time finding 12AWG of any flavor of type k thermocouple wire and 16AWG is possible but rare so expensive.

My question is would dropping the gauge to 16AWG or 20AWG for my cable affect the measurement significantly? It's only about 10ft of cable that I need and from what I've read the change in gauge adds about less than 10ohms/1000ft so that shouldn't be affected too much. Is there anything else to consider or avoid for this setup?


texts:
I've created the following simulation on LTSpice and I'm running a DC sweep for V1, I1: .dc V1 0 5 5m I1 0 100u 10u.

After the simulation is finished, I get those two graphs for \$ V_c=f(V_b)\$ and \$I_c=f(I_{b})\$.

simulate this circuit – Schematic created using CircuitLab

Can someone help me understand what I am seeing in those graphs? I was expecting that the voltage on the collector would start at the max value \$V_1\$ as the transistor is in saturation mode and then it would drop to \$ \approx 0V\$ as the transistor is getting into the cutoff region. I am not seeing that here and I'm confused about what equations describe that problem. How can I calculate the voltage and current gain using those graphs?

Thank you in advance.


texts:
My project involves a number of components. Some are 3.3v and some are 5v

The project must be powered by 8 AA batteries.

Most of the time the components will be in a low power state.  But they will all turn on at the same time and then off again at the same time. With the exception of 2 servos. One 5v and 1 3v. They will be on almost all the time.

My plan is to combine the batteries to make a reliable 6v supply. 4 x 1.5 x 2.
Then use a 5v regulator to get a 5v rail and use a 3.3v regulator from the 5v to get a 3.3v rail.

I know there is not much detail about the circuit here but my question is really about the battery formation.

Should I instead create two seperate power sources to match my reails. Should I create a separate power source for my servos and have 4 rails (2 of each) Should I group the batteries to get a heigher voltage like 7.5 or 9

Ideally I would want all batteries to drain at the same rate so it's easy to replace them as they will all be dead at the same time

The number and size of batteries is fixed but most other things are up for grabs. I can provide more detail on anything if needed.


texts: Why solar cells have a wind speed meter?

texts:
I saw some solar cells in rooftop of a governmental office that were there for providing 220V Ac current for the office's lights and low consuming electrical devices.
one of the cells had a wind speed meter like the image below:(it only had a speed meter , not a wind direction sensor in the right side of the image)

And a fuse box was installed on that cell.
also there was an astronomical clock in the way of wires that were connecting the cells output to the office.

My question is why solar cells need astronomical clock and a wind speed meter?


texts:
So I currently have a 9 pin switch, that looks like this:

And the project I'm doing calls for a 6 pin switch like this:

I'm kind of an electronics newbie and I was wondering if I could just use the 9 pin switch instead of the 6 pin. Would it be a massive problem and is not possible at all or could it work out?

All advice is appreciated, thanks for everything. :D

Here's the schematic:


texts: Is there a way I can power this circuit without a +- 15V power supply?

texts:
Simple Amplifier Kit

I built this audio amplifier for my circuits lab course. In the lab I had access to a benchtop power supply for the necessary +- 15V. Now I'd like to give the completed amp and speaker to a friend as a Christmas gift, but I need some way of powering it without the power supplies we had in school.

I intend to build it inside a tin lunchbox and I'm considering just using the necessary batteries. However, I'd also like to know if there is a simple way to get the +- 15V I need through a standard 120V wall outlet.

Thanks!


texts: Using a breadboard power supply along with USB to Serial chip

texts:
This is a very niche question but I'm wondering if there is a general princinal that can be applied to help answer it.

Here is my prediciment.  I am making an Arduino on a breadboard.  For the power supply, I am using this Breadboard Power Supply Stick.  For the USB to serial I am using  Board for RL USB to Serial.  I have got everything working, sort of.

The issue is, that when the breadboard power supply is at all attached to the board, even if it is not plugged in, it makes the USB to serial connection unable to upload programs to the ATMEGA328P.  If the power supply is switched off and even unplugged from the wall, the USB to serial connection does not work.  The only way that the USB to serial connection works is if the power supply is physically removed from the board.

Why is this?  How can I fix it?  Ideally, what I would like to do is be able to power the mC and a few servos using the breadboard power supply(the USB alone can't power much), while still being able to program and read serial out from the chip on my computer while the program is running.

Thank you.

Related Documents

Here is the schematic for the USB to serial connection
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/FT232R-Breakout-v36.pdf

Here is the underside of the USB to serial board http://arduino.cc/en/uploads/Main/arduinobb_usbback.jpg

Here is the schematic for the bread board power supply
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/Breadboard%20Power%20Supply%20-%20SMD%20v13.pdf


texts:
I have an FPGA clocked at 20 MHz and receiving an input sync signal clocked at 1 MHz. I would like to test that the sync signal has clean edges, so that if the FPGA was to use the sync signal as a clock, that clock would be a reliable one.

What is my best approach to "programmatically" test the cleanness such a 1 MHz signal without using an oscilloscope?


texts: Currently I use a USB-6501 DIO and inexpensive Sansmart 8x1 SPDT relays to switch on/off numerous inexpensive fixed DC power supplies for a flash programming process. Every 20,000 to 50,000 parts i have to replace the relay board. Is there a better way to switch DC voltages and get higher switch reliability?


texts:
Question asks to work out the potential drop across each resistor and the current going through each resistor.

For R1 I got a current of 0.5A and a voltage drop of 3V.
For R2 I got a current of 0.3A and a voltage drop of 6V.
For R3 I got a current of 0.2A and a voltage drop of 6V.

Just not sure if I have done it properly, could someone please let me know if these answers are wrong.


texts:
I'm trying to configure a Maxon ECX BLDC motor.  During the configuration step where they ask you to choose the step count for the incremental encoder there's this "information on resolution" note box that says to follow this basic rule: "As high resolution as necessary"

Given that the price for the sensor is the same for different step counts, why do they say this?

Wouldn't higher step count always be better since it provides better resolution (degrees/step) thereby allowing for finer position/speed/force control?
What are the disadvantages of having way higher encoder resolution than is needed?


texts: How to calculate the maximum output current of a flyback design?

texts:
I've searched and researched but to no avail. I understand how to calculate the turner ratio, the output voltage, but it seems that no one cares about how to calculate the current as both this site and various other sites literally do not have ANYTHING related to this aspect of flyback design, those which touched this issue simply skimmed through it without putting any emphasis at all. So please indulge me a bit if I asked a completely illegitimate question(as in, no one should care about what the Iomax is).

I just want to calculate the maximum output current and if possible, the average one but since this is SE, I'll stick to only one question .

More specifically, I want to know how can you calculate the max output current of this particular design:

Please note that I'm not trying to get you to do my homework, so feel free to link me to pages dealing specifically with such a problem, but I doubt you'll show me something I haven't read and gave up before.

Also, the reason I want to know this is because I want to tweak both the voltage and current a bit to tune the output power to what I want, as you can see, this design supports an output of up to 50W, I want to tune it all the way up to 90W with sink.

Please help, thank you!


texts:
I have a pellet burning stove and the manufacturer provides for two options for battery backups. One is an inverter and deep cycle battery that can run the device for a few hours, the other is a UPS that will basically run it until it the fire stops.
I couldn't find the specified UPS, and the replacement version had a bit more oomph so I thought I was safe. I checked the wattage/amperage against the old version and it looked ok. Stove uses 150W at full load and up to 5-6A while igniting. The UPS was rated up to 800W and 7.1A output.
I charged the UPS for nearly a month it just sat there plugged in. It started to get cold so I got the stove running and went to simulate a power outage by pulling the plug of the UPS out of the wall. The stove made some clicking and buzzing noise, and within seconds the UPS was dead. It should have lasted ~20 min, per the calculations given by the mfg.
So I plugged the ups back into the wall, and there was a flash of light. Everything was dead. The 9A fuse on the board was gone and there was a small red disc that I thought was a ceramic capacitor next to it that also was split open and charred. I called the vendor, they told me it was a '150W surge protector' but I think the term is actually a varistor, but those look like they deal in voltages, not wattage...so maybe it's 150V.
I think I can re-solider the component on the cheap, I'm a hobbyist at best with these things but something blew this up. I suspect the UPS, but I need more than
a hunch.
What I know

The stove ran fine for 2 years on straight plugged wall power.
The stove ran fine while the UPS was plugged into the wall.
The stove did not function as expected when only running on UPS.
When reconnected to wall power, there was an electrical malfunction. Spontaneous exothermic event.
The UPS still has some functionality, as it will power a floor lamp. 6-11W LED.
The power is run directly back to its own breaker.

The MFG does not, nor do the recommended battery solutions, specify anything about pure sine wave, however I wondered if going from pure sine/wall to modified sine/UPS was ok, but going back from modified sine/UPS to pure sine/wall caused the issue? The pure sine thing has come up on forums.
What other things can I look at for this malfunction? I'm going to be on the hook for a control board repair if I can't make the repair work.


texts: Oscillation between the inverting input and output of opamp

texts:
I am looking into a circuit simlar to what is attached here, when I place a probe between the opamp's output and the inverting input - I see oscillation when V1 = 0V. But when voltage is applied to V1 (i.e 10V), the oscillation is gone. Is it normal? Or something is going wrong with my circuit and I need to compensate for it?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm using an IRFZ44N power MOSFET to drive a DC motor (24v, 4kgcm, 2A, FLRPM 500.) I found from the datasheet that the IRFZ44N has an ampere rating of 49A and still it is getting very hot.
Here is the schematic:

The IRFZ44N is driven from a PWM of 244 Hz. I found that it only gets hot at low duty cyclex.  At higher duty cycles the MOSFET is not heated at all.
What might be the possible reasons?


texts: Reroute existing wires with autorouter eagle

texts: I created a board in Eagle, autorouted it and then moved components around. Is it possible to autoroute again, because now the wires are not straight. If I autoroute it just ignores existing wires.


texts: Is it OK to use the USB 5v pin as power source?

texts:
I am doing some stuff in my case and I need a power source for one LED from inside my case.

I looked up and there are two +5v pins on a USB header inside my case. Is it OK to use them as power source? Can it handle sustained usage?


texts: Can I use a car battery as input for a solar charging controller?

texts:
I have the following setup

30W 12V solar panel
connected to
260W solar charging controller
connected to
12V 7Ah AGM battery

I would now like to use my 60Ah car battery to charge the 7Ah AGM battery.
Can I just connect it to the charging controllers input instead of the solar panel?

spec sheet of the controller:

Rated voltage: 12 V/24 V car identify
Rated Current: 20 A
Max. PV Voltage: 50 V
Max. PV input power: 260 W (12 V)/520 W (24 V)
Working temperature: -35 °C to + 60 °C  Standby current: < 10mA
Float charge: 13.7 V (Standard, adjustable)
Discharge: 10.7 V (Standard, adjustable)
Discharge plug: 12.6 V (Standard, adjustable)


texts: Putting two sallen key filters in series

texts:
Can I put two sallen key filters in series without putting a buffer in between them (in order to analyse it mathematically correct)?

I know that when the output impedance of the first sallen key filter is much lower than the input impedance of the first sallen key filter.


texts: chip resistor/capacitor size vs performance for analog circuits

texts:
I am designing one four layer ADS1298 (TI) based analog PCB. Signal frequency is about 1.5Hz to 3.79kHz. It is a four layer board with most of the components and traces on top layer and the ground plane/power plane on the second and third layer.

Since the board needs to be small, i am thinking about using small package resistors and capacitors, such as 0402. I know that for resistors, the smaller size leads to lower power. However, it is not a big issue in my case.

My question is whether there are some other things I need to pay attention to for using smaller package passive components.

Edit 2: found this link talking about capacitor selection. Still looking for the resistor related articles.....

What parameters to look at when comparing capacitors of same value but different package size

Thanks


texts:
We were given the following problem. We spent a night but could not even get close to solve it. It would be great if you could help us solve it.

Three identical 10 kVA, 19920/220 transformers are used to build a three-phase transformer
in Y-Δ connection. An open-circuit test is performed on the low-voltage side of this threephase transformer: Vline (line-to-line)=220 V, Iline=5 A, P3ϕ(total power in three
phases)=430 W. A short-circuit test is performed on the high-voltage side: Vline=500V,
Iline=0.5 A, P3ϕ=86 W.
a. Determine the equivalent circuit of the three-phase transformer bank.
b. Find the efficiency of the transformer bank with a three-phase full-load for a power
factor of 0.8 (lagging).


texts: Level Shifting Circuit to output 0.2V-4.8V

texts: Having a sensor's dynamic range from 4V - 10V, I am looking for a level shifting circuit using op-amp that gives me an output of 0.2V - 4.8V.  I have been looking through many design yet I could not get what I am looking for. Through hand calculation, I got a reference voltage of -12.286V but I am unsure whether it is correct or not. Can anyone help me out?


texts: Understanding this Mean Well Power Supply

texts:
I purchased, I believe, the wrong power supply for my purposes, but I'd like to understand a few aspects of its specs: https://www.meanwell.com/webapp/product/search.aspx?prod=ELG-200&mws=8519DC592A6AAA18

This unit appears to have no way to adjust the constant voltage aspect - so am I correct that this will never output above 24V, even if I were to hook up several LED strips in series (each one with an operating range of 23-24v) - so what is the purpose? I can hook up my LEDs in parallel, but then the constant current aspect seems wasted?

In the INPUT section, it says lists 142 ~ 431VDC - what does this mean? This power supply can handle both AC and DC input?


texts: What is the impedance limit for using 10X probes with oscilloscopes?

texts:
I thought 10X probes are only used for impedance matching at high freq. circuits.

But I read in a text that they are also used in high impedance circuits to prevent loading. But isn't a scope's input impedance already huge? I mean what is high impedance in this case and how can 10X help the situation?


texts: Books on Bypassing, decoupling and Grounding

texts: I am really sorry to ask this question but I am new to PCB designing and Its pretty challenging for me. The layout works in LAB but does not work well outside. I observe glitches in system. I am a beginner and i want to follow the best practices and industry standards. So I would be grateful if someone can suggest be a good book on these topics. Thanks.


texts:
Does this mean that the battery only outputs current equal to the amount of current draw? I always thought that batteries outputted a constant output, but apparently after some research I found this to be false. Can someone help explain?

UPDATE
What I mean is that if I have a load that requires 100ma and then I get a battery that releases 150mAh, what does that mean? Does the battery always give 150mA or does that mean that the load only draws 100mA from the 150mA battery


texts: Increase USB 2.0 power by adding buck converter to motherboard?

texts:
I'm thinking about adding more power to my laptops USB 2.0 ports, by hooking it up to a buck converter witch takes its input directly from the power connector of my laptop.

The voltage and current supplied by the charger are 19V ~4A and this is the voltage i would supply the buck converter to and then get 5V out of it and as much current as possible (i don't think the current is going to be an issue though since i wont need more than 2A anyway) and then connect these 5V to the USB power lines, i hope you get the picture!

I don't want to use a powered USB hub because its not practical and i need another power supply for no real reason as it seems.

Did anyone do something similar and do i need to pay attention to something while doing this (i don't want to mess up the ports since they are kind of custom and harder to find, and that applies to the on board hub also), thanks.


texts:
Sanity check: I need to measure the junction temperature (or as close as possible) of an SMD LED. Can I solder the tip of a thermocouple to a leg of the part? Assuming there is no ground loop (the meter is battery operated, standalone), is there anything I should be aware of?

I am assuming that the thermocouple being in connection with the circuit will not influence the reading, is that a correct assumption? The LED is driven by a 25kHz PWM signal.
I'll also be connecting another thermocouple to the metal enclosure by drilling a hole and pinching the tip in the hole.

I have tried thermal glue previously and that was a unreliable so I would want to avoid glue.


texts: Arduino project: ultrasonic sensor + 5M 5050 RGB LED strip lights

texts:
I'm relatively new to electronics, and as a newbie, I am seeking advice.

I'm my current project, I would like to test out the combination of RGB LED strip controlled by one ultrasonic sensor. I am starting to gather my materials and components, however I am having some trouble to determine which type of resistors I should use for the circuit. I'm not too familiar with how to find or work out the Forward Current \$I_f\$ (mA) and Forward Voltage \$V_f\$ (Volts).

I bought my LED strip package from eBay. The components included in the 5MT LED Kit were:

one 5050 5MT RGB LED Flex Strip Waterproof IR Controller;
44 Key Remote controller; and
a power supply adapter.

According to the information from the seller it should be 150pcs of LED/5M.

Power Supply Specification:

Input Voltage: 100-240V 1.5A
Output Voltage: 12V DC
Output Current: 0 - 5A
Output Power: 60W
Safety Compliance:  CCC/ FCC / CE / UL / GS
Working Temperature: 0°C-40°
Storage Temperature: -20°C-60°C

My next inquiry is: has anyone been able to find an Arduino project example combining an ultrasonic sensor with an RGB LED strip such as the one I bought?

I've found some youtube videos, however, aside from the video, there are no extra information I could use as reference.


texts: AVR or Arduino Profibus interface project?

texts:
Is there an open source solution to interface any profibus slave or master chips?

EDIT1: These are the latest finds for a Profibus slave AVR solution:

AVR GCC with up to 187.5Kbps profibus slave in software
AVR GCC with up to 12Mbps profibus slave in hardware
AVR ASM with up to 187.5Kbps profibus slave in software

EDIT2: As suggested by moderator I have put these new links as separate answers.


texts:
I'm about to embark on my first (actually useful) Arduino project. I have a Kinect setup to detect when I get close to my PC, and I can send a message to my Arduino board to switch on a LED when I get close, and turn it off when I get far away.

Now, I want to make a full lamp, rather than just 1 LED, however, I have a limited knowledge of electronics.

What will I need to read up on before I start buying parts and building this lamp to make sure I don't blow the board/mess anything else up?


texts:
I designed a motherboard for RPi Compute Module (v1). The compute module is flashed with Raspbian and I confirm that I can see the root console on its pins (GPIO14 and GPIO15) when plugged into its official motherboard (CMIO).

Now when it is plugged into mine it does not do anything.

Things I have checked so far:

3.3V, 2.5V and 1.8V are super precious and they are generated by the same components as it was on the CMIO board and the original RPi version 1.
When powered there is no power consumption from the main source which is 5V.
On the serial console there is no activity at all.

My motherboard is very simple, but at the moment there is only the power supplies and the RPi CM header are soldered.
In the datasheet of the CM it looks that it only needs power.

Now what would you recommend me to investigate? I'm quite stuck on this issue now.

Datasheet: https://www.raspberrypi.org/documentation/hardware/computemodule/RPI-CM-DATASHEET-V1_0.pdf


texts: Isolated DC-DC coupling capacitor location?

texts:
For a coupling capacitor across the isolation barrier of a DC-DC converter to provide a return path due to the parasitic capacitance in the transformer, there seems to be many different configuration suggestions floating around online.

A cap between the two grounds and two outputs
Just the grounds on each side coupled
The ground on the iso side coupled to the high side on the non-iso side

Can anyone enlighten me as to what each of these different configurations achieve? Or is there not a lot of difference?


texts: Simplest ATmega328P / Arduino PCB schematic for PC serial communication

texts:
I'm a little bit new to electronics. For a project, I needed the simplest possible form of Arduino board. The board will recieve data from the PC via serial connection, run some basic computations (using an Arduino library) on this data, and return the output to PC with serial connection. There are two basic things that I need from this board.

Should be Arduino bootloader burnable (If yes, how will I do it?)
Should be able to do serial communication via USB.

I have used ATmega 328P-MU (the SMD version) as the microcontroller and FT232RL for USB to UART conversion.

And this is my design (I'm using easyeda.com):

Since I'm new to electronics, I wanted to check if the design is correct and the board will run as I want, before I send the design to online PCB assembly.

Should I change anything in my design, or will it work as I wanted?

Thanks in advance :)


texts:
Ive installed LED downlights in my room, these :
https://www.screwfix.com/p/lap-fixed-led-downlight-contractor-pack-white-370lm-5w-220-240v-10-pack/728fj
they are controller via a smart dimmer switch, this :
https://www.amazon.co.uk/gp/product/B07BKXMS6C/
they work fine, dim up and down but the lowest brightness is 10% (is still super bright), using the smart app you can set them to 1% which is much better
as the lights are all wired one to the next, to the next, i just wondered if i could permently reduce the current flow by using an inline resistor or an inline dimmer to lower the effective brightness? Basically so when the switch thinks the lights are at 10%, the power they are actually recieveing is more like under 5% brightness?
Im not an electricial so please dont shout at me if im asking for the impossible!!!
Thanks,


texts: The diagram of the photodiode is shown below. Why is the p+ layer very thin here? Could we have used a n+p configuration instead?


texts: Strange problem with Teensy 4.0 connected to external power only running code when serial connection is introduced

texts:
I am working on a project with an accelerometer and some LEDs, and I have encountered a strange problem getting everything to function while powered via battery.

When I plug in the battery, the code doesn't run (the led's are supposed to be triggered by the accelerometer moving). When I plug the USB in to look into the Serial monitor to debug, everything suddenly works correctly. And when I unplug the usb, it continues to work!

Does anyone know why this may be? Everything seems to be functional as long as it has serial communication with the computer? The battery is connected to Vin and ground with Vin seperated from Vusb (cut), so the USB shouldn't be supplying additional power?

simulate this circuit – Schematic created using CircuitLab


texts: Toggle between 1.5V and 5V Supply for MQ7 CO Sensor

texts:
I am interfacing MQ7 gas sensor https://www.sparkfun.com/products/9403 with esp32. MQ7 is a carbon monoxide sensor which requires two cycles to work.

It requires 90 seconds cycle to release absorbed gas (by powering it with 5V) and 60 seconds cycle to start absorbing CO (by powering it with 1.5V). I have written code to achieve this toggle on a GPIO of esp32.

I have designed following circuit to achieve the toggle.

In this circuit, RH is the resistance of the MQ7 sensor.
If I apply 0V on Base, VRH = 1.5V (precise)
If I apply 3.3V on Base, VRH = 4.84V (instead of 5V)

Fore time being, I am using Powerbank for 5V Vcc supply.

The problem I am facing is that due to large VCE saturation of pn2222 (max=1V), I am unable to get 5V during saturation phase.

I think I can use a Transistor with small VCE saturation to resolve this issue? Should I do it?
Or there is better alternative available?

Thanks


texts:
I've been looking at getting a Test Socket as of late to try and test out a bunch of old micro controllers on dead boards. However, these test sockets are very expensive when compared to their PCB-Breakout brothers which require soldering. Specifically note the LQFP 100+ test sockets where there are many pins. I'm not especially keen to soldering, because my current setup consists of a 25$ Weller soldering gun, and a toaster oven. I'm afraid that I would ruin my MCUs If I tried soldering with my setup.

That said, I'm still interested in making some prototypes with micro controllers.
My question then is; are test sockets practical for hobbyist use? At what point is it practical to buy one?


texts: Why does a non contact AC voltage detector detect voltage on a DC line that is not flowing

texts: I have two non contact voltage detectors (Klein and Greenlee) ..both are rated to detect AC voltage with a sensitivity range from 50 to 1000 V. I used these detectors on 9 different cell phone power adapters with only the USB cable attached to the adapter (so no current is flowing). On 5 of the power adapters it states that the output is DC at about 5 V with a range from 0.3 to 1.0 amps.  Everything I have researched says that these non contact detectors will only detect AC voltage; not DC.  On four of these adapters I detect voltage and on one I do not.  The results are the same for both detectors and are repeatable.  Can anyone explain why these detectors that are rated for AC use at 50 to 1000V apparently can detect voltage on a DC supply at about 5 V??  ...and why voltage is not detected on one (1) of the power adapters??


texts:
I was looking at the AOZ1280CI DC-DC buck converter, and I'm having trouble properly interpreting the datasheet concerning the enable pin.

In the pinout description, it states:

  Enable pin. The enable pin is active high. Connect EN pin to VIN through current limiting
  resistor. Do not leave the EN pin floating.

However, they don't offer any way to calculate the value of the current-limiting resistor or what an acceptable value is. The upper limit I figured is (12V - 1.4V) / 3 uA = 3.5 Mohms, but between a short and this limit are a ton of different possible values.

Later on in the datasheet, they state:

  The EN pin of the AOZ1280 is active high. Connect the
  EN pin to VIN if the enable function is not used. Pulling
  EN to ground will disable the AOZ1280. Do not leave EN
  open.

Somehow I interpret this as being that the EN pin can be shorted to VIN to have the output always enabled. I am misinterpreting this? Can I short the EN pin to GND/VIN without a current-limit resistor and expect safe operation?


texts: I have difficulty connecting smaller plastic rocker switches. With these switches the metal contacts can be pretty small, so it is not like you can attach a big heat sink in there. When I go to solder wires onto the switch, if I get the whole system (connector and wire) hot enough to melt solder, then the switch melts. In one case I was soldering and the contact just came right out of the switch because the plastic that was holding it in melted.


texts:
As someone starting with electronics I keep hearing, "Check the datasheet!"

Why are datasheets so important and what information can I expect to find in them? It seems like a large amount of information would come from experience and know how, not reading a long dry document the chip manufacturer publishes.

Also, is it really worth reading the entire thing?

edit
When is it OK to work at Absolute Maximum Ratings (AMR)?


texts: How to calculate battery lifetime from datasheet

texts:
I wanted to understand how one can model the lifetime of a cell when it supplies power to a step-up converter.

For this question, I want to focus on two products. Tadiran TL-4930 cell and Adafruit PowerBoost. Assume that a constant power load is connected to the output node of the step-up converter and consumes 1W continuously. Also, assume that the power efficiency of the converter is 90%.

In this case I should expect that the input power to the converter is 1.25W. But I have no idea how to calculate the terminal voltage and the output current of the TL-4830 at the room temperature. Is there a reliable way of estimating the voltage and current under a certain condition? Let's assume the cell has the full capacity.

Another question is, if the cell temperature is -40 degrees Celsius, how do you estimate the voltage and current?

The last question is, is it possible to estimate the voltage, current as function of T and Q?


texts: Using Multiple Power Supplies with RGB Leds and Arduino

texts:
I'm trying to control 3x 5m RGB LED strips using an Arduino Mega's PWM pins.  Building off ladyada's tutorial: http://www.ladyada.net/products/rgbledstrip/.  I created a 3x3 bank of N-channel mosfets, each being supplied by a seperate 12V, 5a power supply.  As a diagram if each P is its own 12V DC power supply (P1 powering led strip 1, etc.) , and M is a mosfet:

    R  G  B

P1  - M -M -M    (per mosfet: left leg pwm, middle leg to led rgb power strip,  right leg ground)
  P2   -M -M -M
  P3   -M -M -M

I can't seem to get each row to be controlled by pwm when supplying power directing to the mosfets.

To test, I powered P1 with DC power and had the arduino plugged into USB.  The colors remained fixed blue despite a script that was to cycle colors.  When I powered the same row through the Vin and ground through the arduino, everything worked fine.

Why is this?  Is there any way to power each row without utilizing the arduino Vin?  Can I use 3 seperate power supplies and one Arduino Mega to do this?  Or do I need to get 3 arduino unos or equivalents?

Thanks,
Michael

Here are two schematics.  The first the arduino is plugged into a USB, and each bank of mosfets is connected to its own power source.  The second the arduino Vin is powering one of the banks but not the other two.

(Because I'm a new user I can't upload photos, but they can be found here:
http://www.flickr.com/photos/80053489@N06/7165312673/
http://www.flickr.com/photos/80053489@N06/7165313015/


texts: How do I make this electronics system of circuits and batteries work?

texts:
I have this:

where Battery #2 will connect with pins (like wireless earbuds) to Battery #1 so Battery #2 can get charged (from Battery #1). So Battery #2 can be easily disconnected and connected to Battery #1 just like wireless earbuds with their case.

My question is, how do I make it so that when Battery #2 is disconnected from Battery #1, Battery #2 and Circuit #2 are connected. But when Battery #2 is connected to Battery #1, the connection between Battery #2 and Circuit #2 is determined by the switch (or the state of the connection) between Battery #1 and Circuit #1? In that way, when Circuit #1 is on and Battery #2 is connected to Battery #1, Circuit #2 is also on. When Circuit #1 is off and Battery #2 is connected to Battery #1, Circuit #2 is also off. And when Battery #2 is not connected to Battery #1, Circuit #2 is on. What's the easiest way to do this with least components?


texts: Clock synchronization between Cortex-A9 and Cortex-M3

texts:
I'm working on the synchronization between a Cortex-A9 and Cortex-M3 microcontroller. The Cortex-A9 is the master and is connected to the Cortex-M3 via SPI.

How can the Cortex-A9 (master) and the Cortex-M3 (slave) have a synchronized clock? Should we use the PPS GPS signal? If so, how?
Is it correct that when they are communicating via SPI, it makes it difficult to do clock synchronization?


texts: Why does my TSAL6200 Infrared diode have a short range

texts:
I am using a Vishay TSAL6200 Infrared diode to control a Dakin AC unit. It worked fine as long as the controller is within 4 – 6 ft of the AC unit. I would think it would have a longer range. I must have done something wrong with my design or implementation. The IR LED is driven by a 2N2222 transistor. Here is the circuit diagram.

According to the TSAL6200 datasheet the max current is .1a. I calculated the value of R2 as 5v / .1a = 50 ohm resistor.
I would have expected a range of at least 15 ft. Have I done something wrong?


texts: 6-pin SMD identification - top marking B7 AP

texts:
I am trying to repair a Garmin Echo fishfinder after moisture got into it, I have replaced the op amp but it seems the 6-pin device above it is also faulty. The trouble is I can't identify what it is. I'm guessing it's some kind of optocoupler to protect the digital processing from spikes from the transducer signals. It only has top marking B7 AP and a dot near the bottom left pin.

Can anyone suggest what it might be?

I'm sorry, I seem to have transgressed the rules, I saw that other people had asked about identifying components and thought I'd do the same.
Thanks to those who replied to the question, I'll try and look it up with the information you gave.
Apologies again.


texts: Why is such amplifier configuration chosen for HB100 microwave sensor?

texts:
For HB100 microwave sensor module, I don't quite understand how this amplifier works and why it's been chosen instead of something simpler, such as two inverting or non-inverting op-amps. What can see for the diagram is that they are feeding integrator's output into an inverting differentiator's input. One friend suggested that a differentiator forms a band-pass filter and an integrator+differentiator combination cancels each other out, leaving you with a linear amplifier with a band-pass filter.

If that's that case, why would we want that?
How does that work, briefly described, and why has this circuit been chosen as an amplifier for this module (I am ignoring all the passive filters and coupling/bypass capacitors).

I and my co-worker are going to build it tomorrow and if anyone could shed some light I'd really appreciate it.

Datasheet (diagram at Annex 1): http://www.theorycircuit.com/wp-content/uploads/2016/09/HB100_Microwave_Sensor_datasheet.pdf


texts: Arduino Negative Voltage Reading with Positive Ground

texts:
I am trying to measure voltage & current off a solar charge controller from panel, battery & load simultaneously with my arduino. I have managed to achieve this by tying all the negatives together and using it as GND, however, when I do that the charge controller doesn't function properly and when I switch to off-mode the loads still run. After checking the instruction manual further, I found out that the positives are shared common between Pan, Bat, Load. This was confirmed with a multimeter.

So now what I am thinking of doing is using the positive from the battery as the GND reference and then measuring all other voltages (through voltage dividers with respect to the GND). The voltages should then range between -17V to 0V.

However, I have read that the analog input pins are not able to read negative voltages, and with respect to the positive GND, the Analog inputs will all be negative.

EDIT: I was thinking of using an amplifier to invert positive ground to a negative ground, meaning I could measure all the positive sides of the voltages. But after getting answers from you guys it seems I may not have to use an amplifier and a voltage divider may suffice. I have currently included a 2 resistor voltage divider between each analog input, +5V source, Vmeasure which you can see in the diagram below.

According to my calculations, if this works, @-17V I should see 0.6V @ analog input. @0V I should see 4V at analog input.

I'd appreciate feedback on this circuit, and below in the second image I've also included a piece of another method suggested by @jonk (thanks), and would be interested in knowing what the benefits are of method B) over method A)

Thanks!

Ps. the ameters are there in place of ACS712 current sensors which also go into analog input pins.

Method A)

simulate this circuit – Schematic created using CircuitLab

Method B (EDIT: This method has worked, I am still yet to test method A) thanks @Jonk))

simulate this circuit


texts: 5th order low pass filter transfer function

texts:
It is a complete mystery to me how one would write down the transfer function of a generic 5th order low pass filter.

I find it inherently confusing because the question doesn't give any hint or indication as to what the constraints are.

All I can come up with is a five-fold coupled RC low pass filter where we assume that they do no load each other.

Since I've seen examples of a 5th order Chebyshev- and a 5th order Butterworth filter, which are seen to differ in their Bode plots, I sense that the question at hand is simply ill posed.


texts: Alternative to high Watt resistor terminating resistor

texts:
In the following circuit a 120 ohm termination resistor is placed across the Rx+ and Rx- data lines connected to a RS485/422 transceiver. The transceiver is protected up +/- 60V.

simulate this circuit – Schematic created using CircuitLab

I want voltage protection on these lines up to 24V. This would mean a user could possibly connect 24V directly across the 120 ohm resistor resulting in 4.8 Watts power disapation. Safe design practice would be to add at least around 50% tolerance to my resistor meaning a need a resistor rated around 7W.

Based on my searching a 7W resistor means moving to a large through hole part. The board space I have is very limited and this is undesirable.

Is there any alternatives to this problem?


texts: On a PCB, what does an Earth Ground prong (from a 3-prong plug) connect to?

texts:
I feel like this is a ridiculous question, but I constantly see examples of projects which are USB-powered, or from a DC power supply, OR using a transformer plug to DC barrel jack. If I am designing a device which handles its own power and I want it to use a 3-prong plug, what does the grounding line connect to?
My understanding is that it would just connect to wherever the GND symbol is, but on simple circuits, that's essentially just the power return. Is that right?
So for example (and I know this is a ridiculous/non-workable schematic, but ignore the load for a minute), would it be connected something like this?


texts: Problem when connect ProPIC2 and USB to Parallel port adapter

texts:
I have a ProPIC 2 programmer which needs parallel port (DB25) to work but I don't have in my notebook that port (SO: Windows 8), so I'm using a USB-Parallel adapter.

When I connect the device it installs the driver correctly but not recognize the programmer.
If I go to "Manage devices" my adapter is shown as an USB connection and not as parallel port.
Here appears a little message : "No printer connected".

Could you tell me if it's possible to connect the programmer with an adapter?
Thank you.


texts:
I'm encountering problems flashing my LPCxpresso1769 with FlashMagic.

I had previously been able to get it to work using a USB to UART lead (TTL-234X-3V3) and powering the device externally (i.e. not via the USB debug probe).

I've since lost the USB to UART lead so have tried using a USB to RS232 instead (https://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_USB_RS232_CABLES.pdf). Is this the reason for my problems? Do I need to use UART?


texts: What happens if you manually turn a moving DC motor the opposite way

texts:
If I have a brushed DC motor moving at a slow speed, and I apply a force to it in the opposite direction, enough for it to rotate the other way, does this damage the motor?

I have a steering wheel connected to the shaft of the motor.

I'm trying add resistance to the steering wheel when it turns, and this was one idea.


texts: Switching multiple outputs with a single input

texts:
Here's my problem. I need a way to switch between two inputs of four signals each (four 5V lines and 4 3V3 lines). They need to be switched together, and ideally with a single jumper or an electrical signal. I know there are many ways to accomplish this (e.g. by 4-sets of 3-pole jumpers), but I'm wondering what you think the most efficient way is.

To put it in the context of the image below: depending on whether S is on or off, the outputs O1..3 should be connected with A1..3 or B1..3. What part does this most efficiently?

simulate this circuit – Schematic created using CircuitLab


texts: Is there an alternative to using a 9V alkaline or lithium battery to power LEDs

texts: I'm looking for an alternative power source to illuminate several LEDs. I'm using a 9V battery to power between 12 and 20 3mm/20mA white LEDs. They are wired in series parallel, everything works fine but a 9V battery will only last approx 2 hours. I'm looking for a rechargeable option that would last 3-4 or 6 hours. Any suggestions?


texts:
I have a circuit with 3 op amps who require dual +- 5 volt supplies.
 The datasheets mention their supply currents at 19 mA ,19 mA and ~5 mA.
 I intend to provide the -5 volts from a  charge pump IC .
 Do the supply currents splits in half for the positive and negative supplies ? What output current the charge pump should be able to provide ?


texts:
I am currently in France on an exchange and me and my lab partner have to do an assignment where the goal is to design the lock part of the circuit in an RFID-circuit. Everything here is in French, and we don't speak the language very well yet, hence we have a hard time asking questions to the professors and so on. Now we're beginning to fear that we might not pass this course, and I hope that someone might be able to help.

This is the circuit for what comes after the terminal in the RFID circuit.

The circuit is divided into six parts, as shown in the picture (we think).

Oscillator, generates a sine wave with \$f = 3.2768MHz\$.
Power unit, transistors that transforms the signal to a square wave signal.
RF-filter, bandpass with \$f_c = 3MHz\$, another purpose, if i understand the French in the assignment correctly, is that it "adapts the impedance from the power unit, which is \$8\Omega\$ to the impedance of the terminal which is \$50\Omega\$". Very uncertain of the last purpose..
Comparator, figures out if incoming signal differs from the normal signal. This meaning that it detects wether or not the RFID-card is near the terminal. If it is, the signal will be different, and the comparator will detect it.
Decoder, checks if the card has the right code to open the door.
A circuit element which remembers the state of the door (open/closed), a latch of some sort I guess.

This is what we think so far, but there might be errors.

Our problem now is to find the values of some of the circuit elements (the ones we have to find are marked with xxx where their values should be).

And it is in box 3, 4 and 5 we have trouble. We're not really sure where we should begin.

In box 3 we think that this is some kind of impedance matching between two parts of the circuit, the first part being C3 and L1, and the second part being C4, C5 and L2. \$f_c\$ here would be equal to \$\frac{1}{\sqrt{LC}}\$. But we are not sure how to calculate this impedance matching to get this right.

In box 4 and 5 we are clueless, and don't really know where to begin.


texts: Where does the current in a Dickson Charge Pump come from? Does the oscillator/PWM pin of a microcontroller also source current?

texts:
Well, I am making a small circuit which looks like this:

When simulated, the load current gets up to about 200-280 mA no problem, so I want to implement this circuit in real life. My only problem is, I want to use either an oscillator, a microcontroller or a 555 timer as the source of the PWM signal V1, but such a device can only source about 20mA, so I am wondering, where does the current through the load come from? The constant 3V source V2? Or does it also come from V1? And if V1 also sources current, how much does it source? Is it under 20mA?


texts: Using supercapacitors on DC-DC converter output for high in-rush current

texts:
I have a motor that draws a max continuous current of 60A, but has a peak in-rush draw over 120A for a few milliseconds. I want to power the motor using a DC-DC converter.
I purchased a converter that has a peak output of 60A and tested it with the motor. It worked, but there was a long wind-up before the motor achieved its required torque. Turns out the converter has a built-in mechanism to prevent in-rush current so we were not getting the instantaneous torque we wanted.
I was thinking of purchasing a supercapacitor bank and connecting it in parallel to the converter's output. My understanding is that the converter will slowly charge up the caps initially, and as the motors start-up, it will draw the in-rush current from  the capacitor bank. Once the motor reaches its steady-state current draw, the DC-DC converter will be able to supply that and top-up the capacitors.
I am asking to see if my thought process is correct or is there something I am missing or have to be careful when designing/testing. With regards to the details, I will make sure that the capacitors and DC-DC converter are spec'ed properly to be able to handle the voltage and current draw.
Any advice will be appreciated!


texts:
I want to read the armature current of a brushed DC motor. I am using the current sensor ACS712 20A. How can I feed the output of the sensor to an Arduino Due analogue input pin (A0) to read its digital value using the analogRead() function?

The Arduino Due operates at only 3.3V, but the sensor output is 5V as it operates on a 5V supply.


texts: Discrete MOSFET driver, limiting voltage

texts:
I would like to use the example circuit, from TL5001's guide, for a wider voltage range. I need it to work with almost 50V input.

Here's the circuit:

Now, the problem with this is that Q3 pulls the MOSFET's gate to GND. While the source voltage is around 40-50V, and this would destroy the gate. How can I limit this voltage?

As a secondary question: TL5001 max input voltage is 40V. Will a simple shunt regulator, with a zener diode, be enough to supply it?

I know this isn't the ideal IC to do this job, and I know that there are easier ways to drive a MOSFET gate nowadays, but please, I'd like to avoid answers suggesting the use os MOSFET driver ICs or other controller chips. There are reasons why I need to work with this particular IC.


texts: PIC microcontroller bit specific adressing beginner question.. PORTBbits.RB0 or just RB0?

texts:
In a PIC microcontroller,
people use PORTB to access all pins of the PORTB at once and PORTBbits.RB0 for bit specific addressing, for me RB0 itself is working, why not I use that instead of PORTBbits.RB0
I use the latest XC8 compiler
Thank You


texts: How to minimize the effect of threshold voltage mismatch of a current mirror?

texts:
Consider the current mirror below. As you can see, the circuit is affected by a threshold voltage mismatch, modelled by \$ V_{mm} \$. I want to minimize the effect of the mismatch and dimension the circuit accordingly.

So from my point of view, what needs to be done is adjusting the length of the MOSFETs, because of the short-channel effect, which causes a decrease of threshold voltage by lowering the length. Since \$ V_{mm} \$ is unknown, it is impossible to design the length in a way that the mismatch would be compensated. Therefore, the best thing would be to increase the length of both transistors to increase their threshold voltage, until the short-channel effect is not noticeable anymore. Then, a mismatch would have the smallest effect on the circuit.

Is my above reasoning correct? Is there anything else I can do to diminish the effect of mismatch?

simulate this circuit – Schematic created using CircuitLab

EDIT: Concerning the influence of the effective channel length on the threshold voltage:

  An interesting phenomenon observed in scaled transistors is the dependence of the threshold voltage
  on the channel length. As shown in Fig. 17.5, transistors fabricated on the same wafer but with different
  lengths yield lower V
  TH
  as L decreases. This is because the depletion regions associated with the source
  and drain junctions protrude into the channel area considerably, thereby reducing the immobile charge
  that must be imaged by the charge on the gate (Fig. 17.6). In other words, part of the immobile charge in
  the substrate is now imaged by the charge inside the source and drain areas rather than by the charge on
  the gate. As a result, the gate voltage required to create an inversion layer decreases. Since the channel
  length cannot be controlled accurately during fabrication, this effect introduces additional variations in
  V
  . The implication of this phenomenon in analog design is that if the length of a device is increased
  so as to achieve a higher output impedance, then the threshold voltage also increases by as much as 100
  to 200 mV. [Razavi]


texts: If a record turntable's base is made from a 2" think piece of acrylic (for instance polycarbonate or Plexiglas) can it be successfully grounded to eliminate any static charge that it would build up in normal use?


texts: What happens when we write delay instruction twice continuously in an MSP430?

texts:
What happens when we write a delay instruction twice continuously in MSP430 code as follows:

void delay();
{
    __delay_cycles(1000);
    __delay_cycles(1000);
}

For 1  cycle delay time is 1ms if we add another what happens?


texts:
On the DE1-SoC (from Terasic) schematic, I found 47 Ohm series resistors connected to GPIOs, they are using 3.3V VCCIO.
The cyclone V datasheet show that no external termination is required as shown in the attached picture.
What will happen if we don't use those resistors, as I found a document for cyclone III and IV interface with 3.3 LVTTL and LVCMOS but didn't found such guide for cyclone V??


texts: Matching SPI Wire Length for Multiple Devices

texts:
I have a main PCB write to 5 different flash memory chips. Four of them are on their own PCBs and are connected by 6 inches of wire from the main PCB. One flash chip is on the main PCB itself and very close to the microcontroller. Each of the four external PCBs also has an accelerometer on it on the same SPI bus.
I can read/write to the external flash chips just fine, but when I have everything connected I can't read/write anything to the onboard flash chip. On the scope I see that the onboard flash chip just never responds on the MISO line(clock, chip select, and MOSI are all correct). If I remove any of the external PCBs, then I will be able to write to the onboard flash chip.
I found the solution that if I unsolder the onboard flash chip and set it up 6" of wire away on a breadboard with all of the same connections it will work. Does SPI need some type of length matching for the wires? Otherwise why does the onboard flash only work when it is further away?


texts: Can an electric resonator (like a microwave) be used to effectively heat things other than water at different frequencies?

texts: For example, could you determine the resonant frequency of slag in an ore sample and melt it by putting it in an electric resonator at the appropriate frequency?


texts:
I was just trying to lift a toy motor off the ground so mounted a toy propeller and tested it, i think it would have lifted(without battery weight) but i didn't bothered balancing it.

Final result was that it became a very nice little fan.

Coming to the point, winter is coming so i decided to make a heater out of it. i got 8x 2500mAh 3.7v lithium ion batteries (similar to those found in laptops). i use them as a powerbank. that makes about 20Amp.
As a heat sources, i decided to use nichrome wire out of soldering iron(rated 25W) and tested it using about 8" piece of it. It worked fine.
This is not my field so please bear with my calculations.

Power source : 3.7V lithium ion batteries 8x2500=20000mAh(20Amp), 74 Watt
Motor consumption : 11 Watt (1.3 Ohm)
4 pieces of nichrome wire each with 3.5 Ohm resistence = 4 Watt

My questions are

can i use nichrome wire for this purpose?
should i use resistor to control heat?
can i produce enough heat using nichrome wire at around 16 Watt (4x 4 Watt pieces) for this purpose?
will my batteries last 2 hours of time?

And finally, is it a good idea?

Edit: i am not trying to raise room temperature, just trying to make it portable to make my hands or mostly feet warm using hot air.


texts: Synopsys Synthesis with underlying modules as gate libraries

texts:
I am trying to synthesize my Verilog modules into 1 top module which contains all the modules extracted into 1 top module.

With setting -hierarchy option in write_file, I get all the modules separately.
I am not really sure if I explained it properly as I am quite new to this.


texts:
Hi, I faced an LC topology that I haven't seen before. (above pic)
Unlike a standard LC tank circuit, L is divided and connected to GND.
To understand it, I have studied many article about LC oscillators.
But, I was not able to find out any hint about this topology. :(
Could anyone help me analyze this circuit?

And I'm also curious about C1,C2(270 pF).
I guess it is to block DC current.
Can they influence the capacitance of LC circuit?

Thanks in advance.


texts: Need help with a vertical mount, male A USB connector

texts:
I need to figure out a way to get a Male A USB connector to vertically attach to a PCB. Ideally, we wouldn't use a surface mount right angle connector.

Any help would be greatly appreciated! Most of the male connectors are right angle SMT which would require an extra step in our assembly (and more labor).


texts: What is rd and gm in oscillator circuits and how to set them up in LT Spice

texts:
I have a lab experiment about Oscillator Circuits, we were given a phase-shift oscillator circuit. In the given variables are: rd(r sub d) = 40k and gm (g sub m) = 6000mS. We are supposed to use a 2n5458 transistor in the amplifier part of the circuit. My question is, how, where or what component do I assign the values of gm and rd in LT Spice

I searched around and found out that rd and Rd is different. So i'm confused now. thank you

EDIT:

2n5458 is a n-channel JFET

Here is the Schematic diagram of the circuit

We were only given powerpoint presentations about Feedback Concepts and Oscillator Concepts and it does not explain in depth about what gm and rd is. All I know is that gm is a factor of Voltage Gain (A) in feedback concepts and I know that Rd is Drain Resistance.

  A = (rd)(RL) where RL is load resistance

EDIT2:

I'm so sorry for the mix up, here is the Schematic diagram.


texts: Identify component in old West German flip clock

texts:
I recently got hold of three nice vintage flip clocks. No time keeping mechanism is present but there is something to advance the time on the clock. This mechanism has one major component labelled BT1200 Type 5. Nothing else. I can't phantom what this thing does.

The very thin wiring going in (extreme left) suggests it is not a mains component (I think).

More images can be found on [my G+ account].(https://plus.google.com/102458454375959628481/posts/Yh4YQhrHnXU)


texts:
While repairing a Marantz amplifier using the service manual, I came across resistors with odd symbols (see page 18).
They are trapped between two parallel lines (for example, 3297).

Is this linked to the fact that this is a 0.33W resistor? A comment suggested it could be related to the way it's mounted to the board for heat dissipation, but I don't see any mounting difference between 3297 and 3283 (see picture below).

Furthermore, what's the difference between the "R" and "E" letters for 3293 & 3305. Don't they both mean "Ohm" ? Is there any reason for Marantz to use both notations in this diagram or is it just an inconsistency?


texts:
I would like to modulate a UART output with a PWM signal. I think the following schematics should work. Can you see any mistake?

The result I'm expecting:

PWM  = GND and UART = VCC -> LED is on

PWM  = GND and UART = GND -> LED is off

PWM  = VCC and UART = VCC -> LED is off

PWM  = VCC and UART = GND -> LED is off

Is this correct?

simulate this circuit – Schematic created using CircuitLab


texts:
I am currently designing a PoE device with IC Si3402B Isolated refer and circuit my design:

I use an RJ45 port with an internal diode bridge:

I bought the RJ45 but not yet. I tested the external power supply from the 51VDC-1.25A adapter to supply directly to the PWR+ and PWR- power sources. But the circuit does not work and the Si3402B chips heat up very fast.

As far as I understand, the power from the RJ45 will be the same DC voltage as the adapter. Is it true ?

I do not know where I was wrong. Please help me find the wrong point in the circuit I design?

I am a new member, if anything is not accurate, please help me know about it.

Thank you.


texts:
I've been research metal detector designs for a few days now and I can't quite wrap my head around the amplification they are using for the first stage right out of the coil. Below is an example schematic from one of the paper explaining how to build a pulse induction metal detector:

I understand the most of the circuit, the problem I am having is understanding what the inputs and outputs should look like on IC4. As far as I understand it the amplifier is essentially amplifying the difference between the coil and the 9V rail. As far as I can tell the coil voltage should fly highly positive when TR4 opens. This voltage is clamped by D3 and D4 until it gets below the forward voltage threshold. At this point it is then amplified by IC4. The part I don't get is why they made it an inverting amplifier, because from what I can tell the output of IC4 should be pegged at 0 the entire time the coil is discharging since the voltage will always be higher than the 9V rail.

If anyone has insight as to what I am missing or how that section of the circuit works I would really appreciate it.

Here is the link to the full pdf paper which contains an explanation for most of the circuit: PI Metal Detector - Mark Stuart (1989)


texts:
Is it possible to make a simple dimmer thats operated just with the flick of the regular wall switch on and off? just like what Philips sceneswitch bulb does?

My requirement is 100%, 50% and 10% brightness settings. These have to cycle each time I flick the switch on and off. There is no need for a time limit ( eg: like flick the switch withing 3 seconds to change the brightness mode). Also there is no need for memory to remember the brightness next time I turn the light on.

The light in question is a 12v 500mA Led panel. It uses an AC to DC driver so I guess I can install the dimmer between the DC out of that driver and the DC in of the led panel.

What all components will I need for this and how can I do it?

Thanks in advance.

Edit-
Modes I want are going to be like this
-Switch on -> 100% brightness
-Switch off
-Switch on -> 50% brightness
-Switch off
-Switch on -> 10% brightness
-Switch off
-process repeats

By 'memory' I meant that the dimmer doesn't have to remember my brightness preference each time I turn the light back on. Instead the dimmer can simply switch to the next mode.


texts: Need a processor to be able to turn off its own power

texts:
I have a processor that is powered by a mains 5V power from a wall adapter, and has a short term battery backup.

I need the processor to turn on automatically and immediately when 5V mains supply is present. 5V power, processor turns on.

But, if mains power is removed, the processor needs to stay powered from the battery, save to memory, and then it can assert a signal saying it is ready to turn off, which should then turn off the power.

Power can then not turn on again until the 5V mains supply is present again.

How can this be possible to do, without it entering an unstable state where the processor tries to turn off and then can't hold it off and turns back on in a loop...


texts: Can a fast blow fuse with higher current rating affect motor's performance?

texts:
I have an old blender that I wanted to use after a couple of years. When I turned it on, it was functional for about half a minute and then stopped working.

When I took it apart, I found that the fuse was blown (slow T 500 mA, 250 V) so I took it out and because I thought that perhaps the fuse was just old and went when it shouldn't have, I wanted to try it with another one. Since I only had a fast one at hand and its rated current was much higher (1.6 A), I put it in there and turned the blender on, however the motor didn't appear to be working and instead produced low noise. The second fuse wasn't damaged.

My question is whether a fast fuse in place of a slow one can affect a motor's performance based on speed or higher rated current. If not, what could be the source of the problem?

Could there be an unrelated electrical problem that had caused the first fuse to blow but since the second can take much higher current, it now only overloads the motor?

Thank you.

(Note that I wasn't planning on using the 1.6 A fuse long-term; it was just to test if the rest was working correctly.)


texts: Ethernet communications bypass Relay specs question

texts:
EDIT: Added another diagram to help understand that if a daisy chained device looses power, that the signal relay with power would use the normally open contacts with the device still being able to communicate normally. When power is lost, the Relay contacts go to there default un-powered state, normally closed, and bypass the device that lost power, so other devices can still function and communicate on the network without being blocked.
Want to use a Relay to bypass Ethernet communications with a dual Ethernet port device
I'm creating a dual ethernet device with dual ethernet jacks for daisy chaining. I've researched and seen how others either use STP or RSTP if a device loses power to keep communications going with a daisy chain of devices.
I have a device that currently uses the Microchip ENC28J60 microcontroller and works perfect.
I want to add another ethernet port for dual ports and researched and found the most simple way is to use a Relay powered on with normally closed connections being open with power as shown in picture.
When power is lost, the relay loses power, and the contacts close keeping ethernet communication going.
I've searched and have not found a "Ethernet Bypass Relay" and only generic relays keep showing up.
I'm looking for relay specs that would be required to keep 10/100mbs going in case of power loss of device.
I need it to be a small micro relay so as not to consume PCB board space.
What would the electrical specs for having ethernet signals pass thru the relay be ?
Or are there relays specifically made already for this application, and if so, can anyone provide some part numbers and or manufactures or feedback or direction on what terms to look for for searching to weed out generic relays so signal integrity is kept intact ? I can't filter google feedback enough to be specific on my search.
Thanks for any feedback.


texts:
Typically, is the likelihood higher for a chip/module with Vcc = 3.3V to break if it gets switched on and off frequently over a prolonged period? For instance, on for 3s and off for 3s, continuously. That's almost 30k switches a day.

Are there (subtle) technical properties that could render the chip/module less durable, e.g., the silicon, the metalisation (if any)?

I'm asking because I wonder if it's a good idea to switch off a module whenever the MCU goes to sleep; the MCU can sleep and wake frequently.

EDIT: The part in question is CC2504.


texts: Connecting LEDs to 4.5 volts in parallel

texts:
I'm trying to mod a NERF gun to add LEDs onto it, and I'm trying to wire them in parallel. Unfortunately, when I try to wire them, it doesn't work. I have it wired like this:

The only issue I could possibly see is that I soldered the two wires together and then connected the LEDs to them, but I figured that that shouldn't be an issue because I figured that's how parallel works. The first LED lights up fine, but the second doesn't, and I'm not sure what I'm doing wrong. I was wondering if it was because I was doing it with 4.5 volts, I was going to add some resistors later but I just wanted it working first. Any help would be appreciated.


texts: Why am I getting the error: "`WDRT' was not declared in this scope" trying to turn of the WDT on my AVR?

texts:
I am clearing the Watchdog System Reset Flag on my ATMEGA168 after a WDT reset...

...using the code...

MCUSR &= ~_BV(WDRT);

...but the compiler complains...

  `WDRT' was not declared in this scope

What am I doing wrong?


texts:
Bit of background, we have an open office and there are toilet blocks in the office, sometimes you can hear sounds coming from the toilets, not to pleasant !

So I want to play the radio/music to drown out the unpleasant noises (powered ON inline with the lights) only problem is there are male and female toilets so I need to sense is the men’s light on or is the ladies lights on,I want to use a common music player

Is there an off the self solution for a high voltage logic OR gate ? Or do I need to do some custom engineering ?

Thanks


texts:
I am a beginner of the micro-controller and I have the kit for AVR. I am currently using an ATMega16 to learn the basics. I have tried a few simple experiments with this micro-controller using LED's. Now I wanted to do some hardware interfacing and I found an interesting project.

I want to use 6 push buttons for counting to 2500 and display it on the multiplexed seven segment LED's. 3 buttons for counting upwards, i.e., (100's, 10's and 1's). For instance, if I have to display 1532, I will press 100's button 15 times, 10's button 3 times and 1's button twice. Similarly, for counting down, I want to use 3 buttons. I have tried some code that makes use of conditional statements for checking the pin status but none of them seem to work.

Please help me out with this as I have been stuck on this for quite a while. It seems to be the issue with "debouncing" but I am not entirely sure about that concept.

I am trying to count the number of times the switch has been pressed (PB0) and when it reaches 5, I want to turn ON an LED(PD0). The below code does not work.

int main(void)
{
 unsigned char count=0;

TCCR0 = (1<<WGM01)|(1<<CS02)|(1<<CS00); // Timer0 Mode 2: CTC-Prescaler 1024
TCNT0 = 0;
OCR0 = (((XTAL / 1024.0)*10e-3)-1); // For 10ms
TIMSK = 1<<OCIE0;           // enable T0 interrupt

DDRB = 0x00;                // PB0 input
PORTB = 0x00;               // external pullup

DDRD = 0x01;                // PD0 LED output
PORTD = 0x00;               // LEDs off

sei();

while(1)
{                               // main loop
    if(!(PINB & _BV(PB0)))
    {
        count++;

        if(count>=5)
        {
            PORTD|= (1<<PD0);   // SET LED on keypress
            _delay_ms(10);
            count = 0;
        }

    }

   }

}


texts: Bosch Glue Pen: Bypassing automatic timeout

texts:
I have this Bosch hot glue pen. It has an annoying habit of turning itself off. I guess it's probably intended to be a safety feature or a battery saver, but really it's just a nuisance.

Can I modify the circuit to bypass this functionality? I want it to stay on, until I switch it off manually/by hand.

(Images from: Electro Bob - Bosch GluePen teardown)