texts:
Is it possible to send/recieve on RS485 without flow control. I am working on stm32f4 platform with a MAX3160 multiprotocol transceiver(supports RS232 and RS485). The UART lines form STM32F4 are connected to the MAX3160. When the MAX3160 is configured to RS232 it works fine. But when configured to RS485(only 1 pin toggle on MAX3160, input/output lines are same) i am not able to send/receive data. The devices connected to RS485 are using modbus protocol. I am not using RTS/CTS and have configured NO_FLOWCONTROL on UART. My modbus devices also has just 2 wires A+ and B-.

Could the RS485 data enable or not configuring CTS/RTS causing this issue.

I am not very experienced in hardware. So any pointers will help.

EDIT:
Yes. I am not too sure about the basics as this is the first time I am working on any hardware boards. I have a board with stm32f427. The USART1 lines are connected to a MAX3160 transreciever which supports both Rs232 and Rs 485, although not simultaneously. It can be configured with one pin. The input and output lines for both rs232 and Rs 485 are same.  I connect the rx tx from these to the modbus device. I configure the uart with no flow control, 9600 baud rate, stopbit 1, no parity and enable Rs 232 pin on MAX3160. I use a rs232 to Rs 485 converter connector and connect the modbus device. It works fine. So i am sure the pi configuration is fine. Now I just enable pull the rs232/rs485 pin high to enable Rs 485. I remove the rs232 to Rs 485 converter and connect the modbus device directly.  I am guessing it should work without any changes. But I hooked up a oasicalltor and I cannot detect anything. MAX3160 data sheet has some pin called DE485(data enable). Should this be set. Or some other change specific to Rs 485. Currently I have not set this data enable pin. If it needs to be set, when should it be set. My modbus device has only 2 wires A+ and B- which I have connected to Rx and Tx respectively.


texts: For a nerve-teste circuit, what causes the shock at low voltage?

texts:
As a bit of a weird test for my new 555 IC, I have been thinking of stepping down a 9V PP3 battery to five or so volts and creating a square wave @ ~100Hz and shocking my finger.

I understand that a possible breakdown voltage of dry skin is fairly high, in respect to five volts, so my question is: Would the sensation of shock of a non-DC current be across the surface layers of the skin? Would I need to put an "easy" path to ground partly up the finger for it to work at such a lower voltage? I assume related (in terms of contact), how would those silly prank shocking devices achieve this?

I will attempt to limit everything to the lowest currents, the main intent is just to "feel" wave forms and frequencies, likely not that different, an interest of mine however.


texts: DC-DC 12V converter using switching voltage regulators: heatsink dimensioning and board design

texts:
To replace my overheating linear regulator DC-DC converter, I've designed this new board. This time I used a couple of switching 12V regulators (LM2575-12V). I'm using two 1 amp regulators because my local supplier doesn't have a 2 amp version.

Here are the schematics.

Here's the board.

There are no pictures of the board because it doesn't exist yet. This time, I did the math first and didn't blindly built the thing.

The red arrows highlight the single-point grounding I tried to make, as recommended in the datasheet. Is that design correct?.

Here is my math for calculating the temperature rise from ambient temperature. According to the LM2575 datasheet, the power dissipation is calculated as follows:

$$PowerDissipated = V_{in} .I_q + (V_o/V_{in}).I_{load}.V_{sat}$$
$$V_o = 12V, V_{in} = 18V, V_{sat} = 1.4V, I_q = 10mA, I_{load} = 1A $$
$$PowerDissipated = 0.18W + 0.93W = 1.11W$$

Again, from the LM2575 datasheet, its termal resistance (junction to ambient, in worst case) is 65°C/W, which would keep the regulators just below 100°C considering a ambient temperature of 25°C. If I use my heatsinks with 20°C/W and the regulator thermal resistance (junction to case) of 2°, that would keep the regulators under 50°C

My questions are:

1. Is my heat dissipation calculations correct?

2. Is my board designed correctly, especially regarding the required single-point grounding for the regulator pins? These points are marked by the red arrows on the board image.


texts:
For the circuit given in Figure Q6, calculate the total current and power of
the voltage supply, and the voltages V1 and V2. All resistors are of 1 kΩ

I have tried applying the Kirchhoff's law like this.

But i couldn't get to answer. I found the Voltage Drop between V1 1,6 Volts but i couldn't find V2.

Thanks


texts: Can I pull up a 5V logic line to 12V without damaging anything?

texts:
What happens if I pull a 5V logic line (from a µC via a 74HCT245 level shifter) up to 12V with a, say, 10KΩ resistor? Is this going to damage anything?

My goal is to have the logic line at the same potential as the 12V rail when the µC and level shifter are not powered, but to "obey" the 0V and 5V logic level output of the level shifter when they are.


texts:
I've seen microcontrollers which claim to drive LCD segments.

For example, the CC430 can drive 96 segments. But, it's a 64 pin chip.

So, it must be providing signals for some kind of mux, what is this interface called?

For dot matrix LCDs, could a microcontroller like this drive more than 96 segments by scanning? I want to drive a small (eg. 32x32 pixel display).


texts: Which components for flat waterproof buttons controller

texts:
I'm trying to build a waterproof controller to mount on a motorcycle, to interact with a Raspberry PI Zero. I'm looking for the best way to build something flat (it has to be mounted on the handlebar), sort of like this controller for heated grips:

I'm thinking about a PCB with small push buttons (the surface mounted ones), but what I'm struggling with is finding those rubber caps to go on top of the switches. Do they exist for consumer sale, and if yes what are they called? Can anyone recommend a better method?

Cheers


texts:
I need some help identifying the connector on the photos. The pitch is 2mm and looks very similar to a JST PA, but I'm not really sure it's one of those as it doesn't look exactly the official photos I can find (JST PA seems to have two "fins" on each side, but my connector has a single one, plus the latch design is different).
My Connector:

Board end:

JST PA:


texts: Modifying a CE transistor Amp to a Single Ended Class B Amp

texts:
I've designed the above amplifier to give an Av=10 and be mid point bias. I simulated it and it's all working well. But I need to modify the bias (so only changing resistor values, not adding or removing components) in order for Vout to look like a Class B amplifier. By this I mean the output should only change with input for half the ac signal.
I think I should move the Q point on the DC load line to either Ic=Ic(sat) or Vce=Vcc to only allow half the AC signal to be outputted, but I don't understand how to mathematically choose the resistors needed to do this. Any help would be appreciated. Only set conditions are Vcc=10, use all 4 resistors, use BC107 (no additional transistors) and have a Class B output.
Please note I'll be doing the same with class Ab and C afterwards, so I'm more interested in methods or techniques than just values


texts:
I'm trying to build a bench test in order to measure the torque required to put and keep in rotation a brake which function with friction. The rotational speed for this test is slow (15 RPM) to be sure not to cause any damages to the brake.
The idea was to drive the current within the servo drive to calculate the torque. However as I need to be precise on my torque estimation I don't want to use directly the torque constant given by the motor manufacturer. I would like to calibrate the motor with a known torque and then read my current value to establish a link between torque and current.
Do you have any idea?
I tried to use a hysteresis dynamometer but it only function with higher rotational speeds. And I'm not sure at all that the constant linking torque and current will remains valid at lower frequencies.
Thanks for your help!


texts:
I have managed to output 500kHz PWM at 50% duty cycle on PA2 TOCC1 of ATTiny841.

DDRA = (1 << PA2);//PA2 pin as an output
TOCPMSA0 = (1 << TOCC1S0);//TOCC1 linkage
TOCPMCOE = (1 << TOCC1OE);//Enable PWM
TCCR1A = (1 << COM1A1) | (1 << WGM11);//Fast PWM 1110
TCCR1B = (1 << CS10) | (1 << WGM12) | (1 << WGM13);//Fast PWM 1110
ICR1 = 1;//Not sure how clock is calculated but this gives me 500kHz on scope

I would like now to generate a 450kHz PWM on that same pin. 444.44kHz = 8MHz/18 would be acceptable. How can I do that?

The datasheet of ATTiny 841 is available here: http://www.atmel.com/Images/Atmel-8495-8-bit-AVR-Microcontrollers-ATtiny441-ATtiny841_Datasheet.pdf


texts:
I have designed a Xilinx Spartan-6 PCI card with SPI configuration interface (please check Figure 2-12 of ug380.pdf user guide). I can program the serial flash through JTAG cable, I can also modify/program the serial flash through the PCI bridge chip, for field upgrade purposes. Unfortunately I forgot to connect one of the GPIO pins from the PCI chip to the FPGA's PROGRAM_B pin, now I have to power cycle the computer to restart the configuration.

Is there a way that FPGA firmware can "FORCE" the configuration process without external assertion?


texts:
Can you identify any inherent problems with the following LED driver circuit?

simulate this circuit – Schematic created using CircuitLab

Ignore the part numbers as they are just for symbolic purposes. Assuming that the n-channel MOSFET in question can handle the 60mA called for by the LEDs, is this a sound LED drive circuit?

It's not typical in my experience to put an n-Channel MOSFET on the high side, but I'm hoping that's just my inexperience talking. I'm willing to lose some efficiency in exchange for not having to use inverse logic on the control point. What type of n-channel MOSFET is appropriate in this context? One that I'm considering using is NXP 2N7002, will it do the job?

Update #1

To make this clearer, I am interested in using a circuit like this as part of the topology for an LED matrix. My thought was something like this (where the current sinks are implemented by, e.g. TLC5916) for a 3x3 configuration:

simulate this circuit


texts:
I saw in a video that the person was using something he called bridge wire to solder a pcb with.
I was wondering what kind if wire is used as a bridge to do the connection between components?

Here are 2 screenshots of what I was thinking of.


texts: Finding the current in a parallel circuit

texts: How could we find the current that passes through each resistor in this circuit? The problem is that we don't have the voltage of each resistor to find the current, because the voltages of the resistors are not equal to the voltage of the source.


texts: Addressing 45 Inputs Down to 6 pin Output

texts:
I'm looking for a chip which could minimize ~45 button inputs down to an 6 pin input for use with Raspberry Pi.

I know this is a simple problem and it has likely been solved before, but as an absolute beginner, most of the responses were either too theoretical or too high-level for me to utilize effectively.

The cheaper the chip/easier the process, the better.

Thanks you for any help!


texts: Most energy efficient and very small volume way to produce motion

texts: I'm looking to make motion (may be 100g) using very small, and very energy efficient component, and prefereably very cheap, i've found some nano servomotors which satisfy my criteria, but i wonder if there is any simple piece of hardware that acts like the old door bell.


texts:
I’m  hoping someone can clear up some confusion.I understand how an earth reference transformer works and how if there was an earth fault there would be a large rush of current through ground and back to loop causing a fuse to melt or MCB to trip and a residual circuit device. I understand how the ac works where you would have +230 with electrons flowing towards higher potential and then on the negative part of cycle electrons flow the opposite direction again to higher potential with neutral having no voltage. Now my confusion lies with isolation transformers with floating leads.

Can someone  explain to me what voltage is where on the two hot leads on an isolation transformer? Is it +230 through one and -230 through the other at same time. Is it shared? I’m confused.
The diagram included (taken from another post) illustrates an isolation transformer with no reference to ground. I know that in order to get a shock I would have to (and foolishly) make contact with both leads on some part of my body to create a loop and get a shock, touching one and ground wouldn’t shock me. So how does electricity flow on floating sensors? With no loop created back to source how is current flowing through those lamps?
Clearly I’m missing something and hope someone can explain.

Thanks


texts: Can I swap active/neutral on an isolated 240V power supply?

texts:
I'm looking at using a Meanwell IRM-03 isolated switchmode power supply (datasheet) in a project but the active/neutral pins are arranged in an inconvenient way for the PCB tracks. It would be a heap easier to route the board if I swapped those connections.

Is there any reason I shouldn't just swap them? Most of the discussion I can find around the topic refers to equipment where swapping them means the neutral is switched, making it dangerous.

Similar power supplies are used in countries with non-polarised 2 pin power sockets (eg USA) - in that case I imagine it could get plugged in either way with no ill effects.


texts:
I've been building a light based alarm system, using an LDR, Op Amp, AND gate, some resistors, and an output of buzzers..

Here's my circuit so far... It beeps when it senses light as well as being 'armed' with a toggle switch.

http://i.stack.imgur.com/7UOm6.png

Now I've got to breadboard that circuit, and I'm so hopeless, that it took me 25 minutes to get an LED to work :\ Is there any way I could get help breadboarding this circuit, or asking for help with a drawing on how to do it? :\

Could anyone help me put the components on this diagram? I'm really stuck, I've been failing for about 3 weeks now! :S

http://i.stack.imgur.com/ttoj5.png

The 741 is an 8pin and the IC2b 4081 AND gate is a 14 pin :S I have no clue, at all how I could get this to work on a breadboard, and I'd really appreciate the help!

Thank you very much!


texts:
I have an easy question that I feel I might be overlooking.

The question I was given was:

A 15V power supply is used to power a 6V, 500mA device. The device draws 500mA at the rated voltage, but will operate properly with +/- 20% voltage variation.  Design the appropriate voltage divider. Note that the load current requirement is variable and not always 500mA (edited again for clarity on what I was told about the question).

simulate this circuit – Schematic created using CircuitLab

My question is: What do I take into consideration when designing the circuit?

Do I design the circuit such that the "Ohm's Law \$V_t/R_t = I\$ current" is at least 500mA and also make sure that the device receives 4.8 - 7.2V at the same time by choosing the right resistor values?
Or, can I design the circuit (ignoring the current, but making sure the overall current in the circuit is greater that 500mA) taking just voltage in consideration? By that I mean I assume that at 500mA in the circuit, there will be a voltage drop of so and so much based on the resistor values?

If this is the case, do I ignore the "Ohm's Law \$V_t/R_t = I\$ current" ?

As a follow up question: Do I have to consider the "unloaded voltage divider equation" i.e. \$V_{out} = V_{in} \left(\frac{R2}{R1+R2}\right)\$ or can I just work with the voltage drops at 100mA and 500mA, making sure that the voltage drop on \$R2 / RL\$ is at between 4.8 and 7.2V?


texts: Allegro ACS71020 problem interpreting I2C data

texts:
I've added an Allegro ACS71020 to my Arduino project to measure power usage (circuit shown below).

I can connect to I2C on 0x63 and I get response (check the image below) - but the values do not change if I have AC connected or not, nor if I connect some load.

And ZC is working even if mains is not connected.

What am I doing incorrectly?
Is there some initialization that I need to do before I start using it?

I used reference design with R_sense=1.8k (for 240VAC).

Thank you in advance.


texts: Are common and differential mode chokes interchangeable?

texts:
Is it possible to use a common mode choke as a differential mode by switching around one pair of wires and v.v. as shown on the drawing?
Intuitively it seems that this should work.

I need a power differential choke so that I can send signals and provide power on the same bus.
It should be roughly 30mH and while there is a plethora of common mode chokes in this range, there are almost no differential ones ...

Thanks :)


texts: Would this be the correct way to wire this breakout board sensor with an ADC?

texts:
I have a Raspberry Pi 3 Model B. It is going to be wired to an ADC  called the MCP3008 like this:

I also have a breakout board, called the ML8511 UV Sensor which I am going to solder to the breadboard.

Could someone explain where to solder the breakout board to the breadboard and which wires should be placed where.


texts: Soft Toggle Circuit with T-Flip Flop not working

texts:
I'm trying to design an electronically toggled switch(one single switch turning an LED on and off) using a T-Flip Flop(a 74HC73, to be precise). I believe I've connected all the inputs and outputs properly, yet, when I'm sending a clock pulse, the output is not getting toggled.

Please take a look at the circuit and try to figure out the problem:

Here's what the circuit is like on paper:

simulate this circuit – Schematic created using CircuitLab

I think it is worthy to mention here that I haven't tried the circuit in reality yet, but, the Autodesk Simulator(which is pretty accurate) is not giving appropriate results. So, I believe the problem is with the circuit only.

Thank you for your time!


texts:
I have a wireless GSM module located inside a metallic enclosure. The module has an SMA connector to be connected to an antenna. I need a way to connect the external antenna to the module. The enclosure is to be used outdoor so the connector should be weather proof. That is protected from heavy rain, so IP65 is good.

I first saw this connector which probably do the job nicely:
http://www.aliexpress.com/item/1pce-Adapter-SMA-female-to-jack-nut-panel-mount-O-ring-waterproof-connector-F-F/32619043048.html

There is an O-ring that should prevent water from entering the enclosure. Also I suppose that the white material inside the SMA connector (fluorcarbon) acts as an inner seal so water can't escape from there neither. So this connector is supposed to be weather-proof. I will then have to use an SMA to SMA cable to connect the connector to the module (inside the enclosure) and just connect the external antenna to the outside of the connector. The problem is that... this connector has no datasheet or drawing and its probably a very low quality product. I searched for something similar from molex or amphenol but with no luck.

I then came across this connector from molex:

http://www.digikey.com/product-detail/en/molex-llc/0732510360/WM9355-ND/3468821

but it has no O-ring. So the question is, Can I apply some silicone between this connector and the metallic enclosure or an O-ring and consider this connector to be weather proof?

Similarly, there is something like this:
http://www.digikey.com/product-detail/en/linx-technologies-inc/CSA-SMAM-216-SAFB/CSA-SMAM-216-SAFB-ND/1962867

Same question, Can I just use Silicone or an O-ring and consider the whole system rain-proof?


texts: Effect of Isat on inductor when connecting four inductors in a combination

texts:
In my circuit I want to use inductor having value 330uH. So instead of connecting a single inductor, I prefer to connect 4 inductors, two of them in series two make it 660uH and another two in parallel with the last two of them to make it again 330uH. This is it if we are talking about only inductance but waht about saturation current. Using this connection how it would affect the saturation current of the indductors? Will I actually get 2 x 4amp = 8amp Isat?
For a little bit of time, consider this one as a cheaper than using a single inductor. What are the pros and cons for doing this??


texts: Irregular common emitter amplifier design

texts:
Would anyone know of any merits (or demerits) to the common emitter amplifier represented in Figure 1 in comparison to one of a regular pattern (Figure 2)? Thanks.
(The 'DS548' transistor in Figure 1 is just a BC548.)
(The diode in Figure 1 is just a 1N4004 power diode that's there in case someone connects the power source the wrong way round.)

(Source: S. Voron, R. Tester and M. Middleton, Funway into Electronics Volume 1. Chullora, NSW: Dick Smith Electronics, 2008)

Figure 2 (Source: Electronics Tutorials - Common Emitter Amplifier)


texts: Non-inverting and inverting gain of differential amplifier

texts:
simulate this circuit – Schematic created using CircuitLab

From what I understand, the diagram above is of a differential amplifier and I understand them and how they work. But the question I have been given is to find the non-inverting gain and the inverting gain for the op-amp above. I'm struggling to understand how it can have two different gains so I would really appreciate it if someone could shed some light on this please. Going from what I have currently, I think the inverting gain is just the regular -Rf/Rg but I don't even have a guess for the non-inverting gain. This is my first time posting so sorry if did something incorrectly.


texts:
I configured a pin on my micro-controller(STM32F4-discovery) as an open drain and I wanted to connect it to a 5V pull-up network and drive an LED. The output of my pin is 3V so hence I wanted to pull up the pin to another voltage if I have another device that requires 5V. I am using an LED as an example to test the proof of concept, but I am confused that why it wouldn't work:

I have also been reading about Logic Level Converter recently where it can "convert" your 3V to 5V. Should I be using that instead?


texts: Reduce voltage from 220V DC to 30 - 50V DC without transformer

texts:
I am trying search something which I can use to convert 220V-DC to about 30-50V DC. I don't want it to be a transformer. I found some voltage regulators providing required output but not having the required input, so all useless, but there may be some available which escaped me.
You can also suggest something, which I can make at home but not too advanced for a Senior High School student. Thanks.

Edit (Thanks to @Transistor, @Asmyldof)
I am trying to make a air cleaner, so trying to power an electric motor having the given range requirement, ie, 30-50V DC.
I am converting the 220v AC mains supply to 220v DC(slightly lower) using 'bridge rectifier', which I had already made and tested.
I will also use 'filter capacitor' in the circuit (parallel) before the regulator.


texts: Electrical Requirements and Current/Voltage Ratings

texts:
Good afternoon everyone.

I need to purchase PCB components and I need to make sure I have the right idea.  A little background.  I will have a socket connector embedded in plastic, running from end to end.  These sockets will be in parallel, one for + and another for -.  They will be around 24 inches long.  I need them to potentially carry 250 Watts.  I will have pins attached to pcb boards to connect to these sockets, powering what is in between.

The sockets I am looking at state Current Rating of 1.0A and Voltage rating of 250V ac/dc.  Is it safe to assume that I could use a power supply of 48V and 5A, or are these specific ratings?


texts:
Hello I am in need of some advices, I am planning on placing a power switch for my circuit that uses 12v 2A DC. But unfortunately i could not find a switch with the form factor needed that is rated for that power. So what i initially planned is to use a N - channel mosfet along with the switch. This make lower rated switch be able to switch the load. As shown

simulate this circuit – Schematic created using CircuitLab
But I already have a reverse voltage protection IC LM74610 that utilizes a N-channel mostfet to switch to the load.

It would be kind of redundant if i use 2 mostfet switches, So i was thinking if anybody can help me modify the example circuit of the LM74610 to combine with a switch.
I would logically assume that it would be placed at the gate drive pin but before gate pull down. It is my first time dealing with ic that are not referenced to ground so im not really sure.


texts: What company and/or government permits/licenses are required when selling an electrical device in the United States?

texts:
Are there specific licenses that need to be on hand, or any permits that need to be signed by various parties, in the United States, when an electronic device is sold?  If it's easier, if the device is sold in a specific state only (Wisconsin), what is needed?  I read something about obtaining a commerce license.  How about anything for e-commerce, if selling online?  I've read about UL (under writers laboratory?) on some devices.  Is that relevant?

By the way, this product has almost all open source hardware, except wiring (probably doesn't count) and a switch.

Hope this isn't a loaded question.


texts: How can I calculate knee current for this foldback current limiter

texts:
So as the title says, I'm trying to calculate the knee current for this schematic. I know Veb(Q2)/R1 is approximately the maximum current through the emitter of Q1 if R4 wasn't there and this was a normal current limiting scheme. I also know R2 is there for limiting the current through the base of Q2. R3 is the current limiting resistor for the base of Q1. but how can I calculate the knee current point? (Rload is just a dummy value)

simulate this circuit – Schematic created using CircuitLab


texts:
I'm building myown galvo motors and for that I need some coils that I'll have to build myself to fit into the dimensions I need.
Is there any technique for winding the wire or is it just straight forward hand winding? Any trick or detail that you could share would be very useful as well.

Thank you.


texts: How to power a low consumption Computer On Module from noisy industrial power sources

texts:
I am thinking about using a small Linux Computer On Module in an industrial environment. The specific application I need to use it for is in a panel that has limited power source options.

The only source that is semi conditioned is ~24 volts that comes off a DC to DC converter in the panel. I was thiking about using the TI PTN78020 that has a high current output (6A)and wide input range of 7v to 36 v and a wide output range of 2.5v to 22v. I was going to just design a small board that has the minimum required circuitry (filtering caps, resisters, etc).

The problem is my boss doesn't want me to design this simple power supply and instead wants to find one pre made. I tried to explain the incredibly amount of variability and the specific constraints that limit us.

So fellow EE enthusiasts, I ask you what are my alternatives. Should I just tell him I am going to have to make this and it isn't a big deal or is there a premade example that is cheap?

Must have wide input range (because it is in a system with
automotive-esqe power needs and spikes)
Must need to be robust and have a semi good operating temp range (it
gets quite hot in industrial panels on location)
A good price for possible volume purchasing


texts: Generate a voltage that is 7 volts below the input voltage for at least 250 mA in the range of 20-26 volts

texts:
For programming bipolar ROMs I need a programming voltage of U=27V,30V,33V and an input voltage of U-7V. My first idea was to use a Zener diode in series to drop 7V at the diode. However, the needed current of at least 230 mA is too high for usual Zener diodes.
Is there a simple way to get the 2nd voltage with a transistor?

simulate this circuit – Schematic created using CircuitLab
Might it also work with a negative voltage regulator like the 7905, with a zener somehow to generate -7V with respect to the U rail and then use this negative voltage but with respect to the real ground?

simulate this circuit


texts: confused about power rating for washing machine in datasheet

texts:
I am interested in purchasing a Primus washing machine but I get confused about the power rating that is recorded in the data sheet (link below). On page 2 of the data sheet, the manufacturer states that the machine consumes 27 kW. Is this not too high for a washing machine? I searched on the internet for what the average power consumed by a dishwasher would be and its typically around 700 W so I got confused when I saw that this one consumes 27 kW. Please advice.

http://www.primuslaundry.com/_media/primus-2a2f5bfe85cfb8271fb3eb5bac192566/techspecs_rx350_520_eng.pdf


texts: Buck Boost Battery 3.6V (Lithium-thionyl Chloride) to 5V

texts:
I hope this question has not been asked and it's not as far as I have seen.

I am developing an IoT project which uses almost no current (< 100uA) when sleeping and up to 80mA when running. The problem is I need to power this with a battery which has to last quite a long time (1-2 years) and it doesn't have to be rechargeable. In particular I have found Lithium-thionyl Chloride to be pretty good at this and usually have a voltage of 3.6V at full charge.

My project runs on an ARM processor and the whole system works with an input from 3.6V to 6V and I'd like to input 5V. So I need to use a very efficient buck boost converter to go from 2/3.6V to 5V. This is how I am thinking to go about it.

If anyone knows a better way to power up this type of system I'd appreciate suggestions.

I'd prefer buying the complete circuit/product instead of building it but I can't find a good one on eBay. I can build one but I would really like to do that only in the worst case scenario.

Does anyone here know how to move about this?

Thanks everyone.


texts: Amplifying an ionization current with an op amp

texts:
My observation:
Previously at my work I was assigned a project in which I needed to amplify an AC signal from a piezoelectric electric sensor. I simply made an inverted op amp circuit to accomplish this. I now have been assigned a project involving a mass spectrometer (RGA). In the spectrometer there is an electron multiplier to amplify the partial pressures. The fact that an op amp was not used to provide gain for the ionization current perplexed me.

My question:
Why can't one use an op amp to amplifier the current from the output of the quadruple mass spectrometer? My suspicion is that the reason is something to do with ion current being in a vacuum. I understand that inside the RGA is a electron multiplier, I just want to know why an op amp would not accomplish the same result.

Notes:
My background is in Computer Science and my knowledge in physics is elementary, so sorry in advance if my question is based off of a misconception.

Links:
https://www.mksinst.com/docs/ur/hpq3-ds.pdf (The RGA that the mass spectrometer will be hooked up to. - Could not get my hands on the data sheet for the actual mass spectometer.)


texts: Determing when lead acid battery is parallel through embedded systems

texts:
I have browsed my fingers out but I just can't get close to what my needs are.

I am trying to work out a solution whereby my charger should charge a 200ah lead acid battery at a specific current, but once the battery is paralleled with another 200ah making it 400ah, my charger should know and increase the charging Current by 2.

Can someone help out with some stunt, I would really be grateful.


texts:
I got a faulty Tektronix 2213 analog oscilloscope and am hoping to repair it. When it should be showing a straight line, it shows this crazy waveform instead. This results in severe distortion when viewing any signal.

That picture should be a straight line, the input coupling is set to GND. Here is a picture of the settings:

The trace looks different on different settings, it gets bigger at smaller volts/division and gets wider with smaller seconds/division, exactly how a real signal would respond. It can even trigger off of this "signal". It looks the same on channel 2 as well. It looks like it might even be affecting the Z-axis, notice the varying intensity, although it does not seem to correlate with the amplitude of the signal the way you would expect if it were indeed being modulated by the same signal.

I checked the voltages inside and they are all slightly high (except for the regulated 5V line), out of tolerance according to the service manual. I think this is due to my power line being 120V instead of the 115V the manual specifies for testing. Unfortunately I do not have a variac to test this theory.

Any ideas would be greatly appreciated, I'm about to start just trying each test point from the manual and seeing if the waveforms match, but knowing what area to focus on would be a big help. Here is the service manual: http://w140.com/tektronix_2213_service.pdf

I do have another good oscilloscope to troubleshoot this with. I've hooked up a function generator and am trying to trace the signal to see where the distortion begins but it is very difficult to probe the front end from all the stuff in the way. I would need to remove the attenuator board to reach most of the points and it plugs straight into the front panel board- I don't see a way to probe most of it while it is operating... but I'll keep trying!

Something is definitely also affecting the 1KHz calibration output. The trace will not stay still on the scope I'm using to measure it and it is triggering at around 45KHz and the top and bottom of the square wave look incredibly noisy. I can't tell if it is exactly the same noise modulating it...

I've taken some noise measurements of the power rails- they look reasonable except for the -8.6V line having 700mV of ripple at 50kHz, and the 5V line having 1.2V of ripple at 50kHz!! I think this severe ripple could be the source of the problem and I'm going to investigate the power supply now.

Thanks!


texts: Get signal from apartment intercom to know when someone ring

texts:
In my apartment I have an old intercom to know when someone is at the entrance of the building and to unlock the door. I waned to connect it to an esp8266 to let me know remotely if someone ring and to open.
The opening part is ok, I used a relay for that.
But the tricky part is to be notified when someone ring.The intercom is running with 12v but when someone ring the current is going to 0v.

The intercom as only to cable. I tried to get signal by using this circuit. The idea is to detect current drop :

problem is: when nobody is ringing and 12v is present in the intercom wire, GPIO is going high and low constantly. Is there any reason for that ? Is there something wrong with this circuit ?


texts:
I'm working on a design that is susceptible to ESD.  The product is handheld and powered by a 5V wall-wart via a barrel jack connector.  The 5V supplies a few ICs with power.  Additionally there are a few push buttons, which interface with different ICs.  I'd like to protect both the barrel jack input as well as the button inputs from ESD transients, but I'm having trouble finding an appropriate TVS and left wondering if my approach is incorrect.  Ultimately I plan on having one TVS for the 5V supply and one for each pushbutton.

Of the ICs in the design the most sensitive has an absolute max Vcc and Vin (from push buttons) of 6V.  Here's what I've done so far:

Select Vstandoff for the TVS. Since the nominal operating voltage of the circuit is 5V I need a standoff that's equal to or slightly greater than 5V (absolute max of ICs is 6V).
Select Breakdown voltage of TVS.  Since the min absolute max V of the ICs is 6V I need my breakdown voltage to be between the standoff voltage and 6V.  It strikes me that the particular value here isn't so critical.
Select Vclamp of the TVS.  This seems to be the most critical parameter.  As I understand it Vclamp of the TVS is the max voltage drop across the TVS at a specified current pulse.  If I'd like my device to be compliant with various ESD standards (e.g. +/-8 kV 8x20uS pulse per IEC61000-4-2) then I need a clamping voltage that will be less than the absolute max of my ICs -- e.g. less than or equal to 6V (but obviously greater than 5V).  After all the clamping voltage is the voltage that will be seen by the ICs.
Make sure peak pulse power requirements for TVS are satisfactory.

Assuming the above is true I'm having a heck of time finding a TVS which meets requirements for my design.  In particular the clamping voltages of the TVSs I'm looking at exceed the maximum 6V requirement.  In general clamping voltages appear to be ~60% higher than the breakdown voltages, which in turn appear to be ~20% greater than the standoff voltage.  There are several parts, which have Vclamp on the order of 9V (this is just one example).

The absence of an obviously suitable part leads me to wonder whether I'm missing something in my TVS selection (e.g. perhaps it's actually OK for vclamp to be 9V since it's such a short pulse?) or whether I'm supposed to be using a TVS in tandem with something else.  How should I handle ESD protection for my circuit given the "tight" tolerance between my Vsupply/Absolute Max V and Vclamp of the TVSs I'm seeing out there?


texts: What is the best way to combine multiple batteries (flooded lead acid)?

texts:
I wish to know the best way to connect four 12V 150Ah lead acid batteries to make it 24V 150Ah battery bank. I currently have connected 1 and 2 and 3 and 4 serially to make two 24V 150Ah volt banks, and then both banks connected in parallel to make a 24V 300Ah system.

But I feel that a better system would be to first connect 1 and 2 and 3 and 4 in parallel to make 12V 300Ah banks, and then connect them in serial to make 24 300Ah.

The battery bank is charged by  24V solar panels, charged during the day and used at night.

Is there any difference between the two connection systems?


texts: What is asked by this question re cache memory?

texts:
I've a difficulty understanding what is asked by this questions:

Can you explain in more detail? AFAIK the associativity determines the number of sets and the size of the set determines the number of bits that is not the tag. Is that correct? Then the block size determines the number of bytes per row of each set.

Here we got block size 4 words i.e. 4*4 bytes = 16 bytes. Which is 2^4 so there are 4 bytes per row of each set. Since there is only one set, the size of the set is 16 KB = 2^4 * 2^10 * 2^2 = 2^16 = 16 KB data. But I don't understand the third sentence "Each block has 4 X 32 or 128 bits of data plus a tag." Why is the number of bits an other than the size of the data?


texts:
How can I change the sheet size in Eagle? I want to do this both for board schematics and the package design area. The latter is especially annoying.  I'm inputting a BGA part and I can't zoom in and scroll to the outer edges of the package, although I've been able to input it all through a script.

edit: I'm using Eagle Hobbyist 6.4.0 on a 13" MacBook Air OS X 10.8.3 with touchpad.


texts: Why use 2.048V and 4.096 as a reference?

texts:
On many voltage reference ICs (As an example a MAX610x) there seems to be various different reference voltages available (1.25, 1.8, 2.5, 3.3 etc).

What strikes me as odd are the 2.048V and 4.096V references. Why do we use references at those voltages instead of just simply 2V and 4V which would surely be easier to use mathematically?


texts: audio mixer - is ground isolation needed for each channel?

texts:
In every audio mixer schematic that I have found, the signal circuit is described extensively.  Here are a few examples:

However, these diagrams do not show any considerations for the ground connections or isolation for the input's grounds.  Is this required?  Can all of the grounds for all of the inputs be connected together without creating any signal contamination, or should there be some resistance (or other element) added?


texts:
I have purchased a 300W Modified Sine Wave Inverter. I am also connecting a 12V 18A/hr SLA battery to it.

I am using it to power an RFID reader. The input power characteristics of the power block are: 100-250V, 50-60Hz, 0.5A.

The output characteristics are: +48V DC, 0.4A. Please note the power block connects to the RFID reader via an ethernet cable only. Hence I cannot just connect a DC supply directly to the RFID reader.

How would I calculate how long the battery will last before I need to charge it, do I use the input or output characteristics of the power block? (Is there an equation I could also use).

Also, I would also like to connect my laptop charger to the inverter while the inverter is powering the RFID reader. The input characteristics for the laptop charger is: 100-240V, 50-60Hz, 1.2A

Output characteristics are for the laptop charger are 19V DC, 2.73A.

Will it be okay to connect the laptop charger and the RFID reader at the same time, or will this exceed the limitations of the battery and the inverter?

I know how to calculate the duration of a battery given a DC to DC setup. But know I am going from DC to AC to DC again. Do I use the input characteristics of the power supply blocks i.e. the currents or the output characteristics of the power blocks?


texts: Multiple Hall Effect sensors to one input

texts:
I've done some work in the past with hooking up Hall Effect sensors, e.g. OH090U up to an Arduino. Please note, I do have limited electronics knowledge.

What I would like to know is if it is possible to wire up multiple OH090U components to increase the coverage of detecting a magnetic field over a larger area. Is there a way to tie the digital output across multiple sensors, so that if one or many sensors trigger it just sends one digital output?


texts:
i don't want to lose time on understanding it's theory, i just wanna know what kind of input does it take in, does it take a PWM input like the class D (the one below) ?

or just a ON/OFF signal with the frequency of the output and a duty cycle of 50% and a frequency near it's resonating frequency. since it's a switchmode amp i believe it wouldn't take a sinusuidal input.

here is the class E circuit


texts: Why there is reduction in voltage after diode?

texts:
I have used simple resistor divider with the diode whose forward voltage drop is 0.617V as shown in figure. I am reading voltage in voltmeter as seen figure. Can anyone explain me why it is like this?

I am expecting no drop across diode.


texts: Daisy chaining a large number (20) of TLC5940 in serial. Bolstering signals?

texts:
Working with shift registers (tlc5940 and Library) on Sparkfun breakout boards driving individual LEDs.

The boards are designed to connect VPRG, GSCLOCK, BLANK, XLATCH, SIN/OUT, SCLK,VCC, GND in serial. Everything works perfectly on Board #1-10.  However, I need quite a few more boards/chips (up to 28) and the signals get crazy from Board 11 onwards.

I was hoping to find some options to increase the signal strengths to and past board #11, all while keeping the timing correct.. Any help with possible solutions/specific schematics is GREATLY appreciated.

The TLC breakout boards are spaced every three inches. LEDs, chips and Arduino all are powered from a 5V regulated, 40amp source (MeanWell). Power is getting to last board and it's Leds. The connections/soldering are solid and not shorting. Each led and board has been tested individually.

I understand that this is a tall order, impedance, connections, conductance, the board, etc are in play here but I very much need to keep the boards in this lengthy configuration (necessary for art installation).  Even if this boost doesn’t get all 28 chips working, I’d like to understand more how the various clock, latch, data signals can work through an extended serial bus and what I can do to clean up, bolster and push them further.

Chip Datasheet: https://www.sparkfun.com/datasheets/Components/General/tlc5940.pdf
Spark fun Board: https://www.sparkfun.com/products/10616

EDIT: ROUND TWO

Hoping the break from this project doesn't bury it, but I've got a few more questions based on trying to use the above suggestions.

I've redesigned the art installation so that I could get the chip/boards centralized and next to each other/Arduino rather than separated out to the 4 grids of LEDs. I am going to run a much, much thicker solid straight line for connections, ground and power (which I will increase to 6v). Main question I have is about the difference between a Buffer Amp and the clock driver. Since the TLC5940 boards are designed to run in serial, and since I need so many (approx30), It's been suggested that I run a 74HC7014 Non-invert amp every three-ish boards. I can do that, but should I drive all of the signals from the same Buffer? Data, VPRG, Blank, and both clock signals (GSclock, Sclk)?

Or should I push both clock signals in parallel from a "robust" clock driver (any suggestions as to which one?) and the rest of the signals in serial through the boards and Buffers?

I was also wondering how and if I need to do anything to terminate any of the signals/ground? Would it help keep everything working as supposed? Right now, all signals/power and ground are just in a long line, from the Arduino straight through all boards and drivers (It does bend in half, though, to keep it compact) Is there anything that should be done after the last board? Or can they just end?

Could use a little more suggestion on the schematic before I solder this up and try it out. @oldfart ?


texts: Looking for a 15kV Zener - or equivalent circuitry

texts:
I have a high frequency high voltage module that puts out about 15kV (not the stun gun modules sold on eBay). Because of the circuit design the transformer is damaged if it does not arc over. I am looking for a method to limit the voltage when I feed it into a capacitance, with no arcover. I want a 15kV HF voltage on that rather tiny capacitance which is formed by a microscope slide with foil on both sides

One obvious thought is a resistor, but not sure how viable. The other is of course the Zener above, but I don't think anyone makes such a device, and certainly not cheaply. OTOH, would the capacitor itself act as a suitable sink?

Before anyone asks, I do not yet know the frequencies involved. However, the device itself that I am considering using is this


texts: Why are parasitic capacitances the main factor for limiting high frequency performance of active devices such as transistors?

texts:
According to the Wikipedia article, the reason for the limit of frequencies in which transistors operate is the parasitic capacitance. But I don't understand why this is so.
Wikipedia article:
Parasitic capacitance.


texts:
I am planning on powering a set of RGB LED strips (I am leading towards APA102 https://cdn-shop.adafruit.com/datasheets/APA102.pdf).  I know that, at full brightness, each LED requires 60mA.  So, at 30LEDs/m, that is 1.8A/m, or (5V x 1.8A =) 9W/m.

I will be using 13m, and so I need a (13*9W=) 117W power supply that can provide 23.4A at 5V.

My question is this.  Can I use a 12V 10A (=120W) power supply, and 5 LM1084 voltage regulators in parallel to covert the 12V to 5V?  Each LM1084 is rated for 5A output. http://www.ti.com/lit/an/snva558/snva558.pdf

Please excuse my ignorance.  Perhaps my reasoning is off, or thee is a glaring safety hazard here.  Please feel free to offer any helpful advice at all.

Thanks in advance.


texts:
I was thinking about inserting some lights in postcards. But classic leds would increase the thickness too much.

Is it easy enough to use this kind of component for a simple circuit(just one or two leds and a battery)? Is it in reach for a soldering beginner?
Would it work without a stable PCB?

I am asking about your opinion on feasability; not especially how to do it. The answers would lead me to go deeper in this way or go for flat "classic" leds.

Inspiration: http://www.blackbookgallery.com/prints/hari-deepti/


texts: any way to boost data transmission in GPIB?

texts: I have a pretty old device connected to computer with GPIB (IEEE 488 standard), the bandwidth is limited so it is pretty slow to transmission 1MB data. I wonder if it is possible to boost the transmission speed.


texts:
I am studying Intel speed shift. I see a slide:

Reference

I don't understand, why the green line 1/f means system energy, I think more performance should need more energy as the red line (compute energy).

Original site: The Intel Skylake Mobile and Desktop Launch, with Architecture Analysis


texts:
pulled a load cell from a small scale that I bought from amazon. I read online about how to use a INA125P to amplify the signal from the load cell, but when i examined the load cell i pulled from the scale, I found the wire coloring did not match that of the tutorials I read. I even found some lists that show wiring colors by manufacturer and all of them seem to at least have a green wire, whereas my wires are red, white, yellow and blue. Here is a picture of my load cell. I've tried Googling the text on the cell as seen in this picture, with no luck.

Perhaps an understanding of how a load cell works on a more fundamental level could allow me to reverse engineer the wiring with a multimeter. Or is there some other way of determining the wiring of this load cell?


texts: So ive been doing some research on how overshoot can be reduced in an AC servo position system. I found out that tacho generators are used connected from the load to the motor that drives this load. However I found out that it may cause velocity lag and error. I found out this can be overcome by replacing the tachogenerator with an RC network error rate damping but im not too sure about its operation, can someone explain it to me?


texts: Is there a difference in the meaning of power and current amplifier terms?

texts:
I understand the difference between voltage amplifier and power or current amplifier. For example in an audio amplifier there are usually three stages: two voltage amplifiers and a power amplifier at the last stage. Okay they call the first two amplifiers here voltage amplifiers since they increase/amplify the input voltages with driving very little current from the power supply.

But at the last stage the current is amplified, hence the power. I understand that power is related with current's square but my question is about naming.

Does "power amplifier" and "current amplifier" mean the same thing? Or power amplifier term is used when an amplifier amplifies both current and voltage; but "current amplifier" is only used when there is unity voltage gain with high current gain?


texts:
I'm having a problem with finding out the value of resistor that has 5 band color code but matches 4 band color code. I'm presuming its 0.47 5%, but I could be wrong.

Resistor is blown and there is no similar resistor anywhere on board to match measure ratings.

Device is Samsung HT-F4200, an DVD player and smart box.

I appreciate any help offered. I really don't wanna see this device going in junk for what it seems one faulty resistor.


texts: Digitally selectable filter for the ST7580

texts:
For the ST7580, it uses PSK or FSK to send a signal over power lines. In the design guide the example is designed for an FSK or PSK signal to be transmitted at 80 kHz see page 23 for reference to the RX filter calculations below.

For my design I would like to send and receive signals across multiple bands. As this is industry related, I will have to stay away from CENELEC Band A. So I would like to make use of CENELEC Band B (102.5 kHz and 117.5 kHz), C (132.5 kHz), D and a part of the FCC Band (147.5 kHz); As the ST7580 can modulate up to 250 kHz but the RX filter need select these frequencies.

I would like to find out if the following sketch is a viable option:

This is just a crude drawing, the final design will only use one inductor and the capacitor will be selected with transistors rather than all the filter components.

The two main components of the filter is C3 and L2. I would like to know if I "take" GND away from the filter via a NPN transistor, will this lead to the effect that I am going for? (Which is to have four RX filters on the same board and simply flick between them with a few pins on my microchip). Only one transistor will be on at one time.

EDIT: To clarify I am just focusing on the reception filter, as shown in the figure below boxed in red, for now. This does not have the R5 resistor included, but it is a part of the circuit.

I eventually wish to make this a selectable BPF with a few transistors. Is this a valid method of performing this by changing L2 and C3?


texts: Handling cyclic and acyclic UART messages

texts:
I'm looking into designing an IO-Link slave on page 35 of the IO-Link spec they mention Communication Channels. I have received an IO-Link device stack from TEConcept (ST/STM IO-Link partner), I cannot link to it, as it is given by request only. When I run through their stack I don't see this communication type being handled anywhere, just a single UART being utilized without any operating system or threads etc. controlling the flow.

As far as I know the UART protocol doesn't differentiate between cyclic and acyclic communication, only synchronous and asynchronous.

So the design question is how do I handle this ? I'm thinking of using freeRTOS to set up these "Communication channels" / RTOS tasks.

Could it just be that the IO-Link Master handles all this?

Does anyone have experience with designing their own IO-Link device ? My research on the web hasn't been very succesful.


texts:
guys. I'm trying to evalute received signals from a transceiver. I'm a rookie in wireless communication. So I hope that you guys can help me out. I want to make a threshold of received signal so that we can say some signals are meaningless. I have learnt something about Signal-to-Noise-Ratio (SNR) and Reveived-Signal-Strength (RSS). But I found that symbols can still be decoded even in low SNR (<= 0dB).

Here are my questions:

If I choose SNR as my metrics, will my threshold be relavant to modulation or coding schemes?
Will RSS be suitable for theoritic analysis as metrics?

Thanks!


texts:
I am building a portable device with Raspberry Pi and powered by 3 AAA batteries in series. I am trying to create a battery indicator with a LED:

Green = Full power
Orange = Half power
Red = Low power

This is not an indicator for charging the battery, since I am not doing that. The purpose of this is to let me know when I have to change the batteries.The Raspberry Pi has an ADC that I can use. The device works from 6V to 3.3V (3xAAA cells that I usually use gives me 3.6V, but depending on the cells I get 4.5V).

Is there a simple way for me to do that?

Thank you.


texts: 16 Cree XM-L2 LEDs on one Mean Well driver

texts:
My friend's father has a small supermarket and he has a cold room that he likes to light up with as many lumens per watt as possible so the heat will be minimal.

I would like to make this for him and connect 16 pieces of Cree XM-l2 in each lamp fixture then hook it up with a suitable driver.

I am not good at this but I would like to learn much more. Can I just put the LEDs in series and get the 48V driver? My friend's father wants as little heat and as much lm/W as possible from this fixture. He needs 4 fixtures and I am keen on doing a perfect job for him.


texts: Unable to read correct value from ADC10MEM

texts:
I am currently attempting to read a value from ADC10MEM and convert it to a usable value to process. However, the value I am receiving (random value) is not what was anticipated (approx. 0.1 volts). The error may be in my conversion from ADC10MEM to my value. Any help is greatly appreciated!

unsigned int value = 0;
double accurateValue = 0;

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD; // Stop WDT
  ADC10CTL0 = ADC10SHT_2 + ADC10ON + ADC10IE + REFON;
  /*
   *    ADC10CTL0:
   *
   *    ADC10SHT_3  =>  SampleHoldTime: "64 x ADC10CLKs"
   *    ADC10ON     =>  ADC10:          "ADC10 On/Enable"
   *    ADC10IE     =>  Interrupts:     "ADC10 Interrupt Enabled"
   *    REFON       =>  Internal Ref:   "ADC10 Internal Ref On"
   *    REF2_5V     =>  Ref Volt:       "ADC10 Ref 0: 1.5V"
   *
   */

  ADC10AE0 |= 0x01;
  /*
   *    ADC10AE0    =>  Channel:    "P2.0" (board pin 3)
   */

  for (;;)
  {
    ADC10CTL0 |= ENC + ADC10SC;
    /*
     *  ENC     =>  "ADC10 Enable Conversion"
     *  ADC10SC =>  "ADC10 Start Conversion"
     */

    __bis_SR_register(CPUOFF + GIE);        // LPM0, ADC10_ISR will force exit

    /*
     *  ADC10MEM:
     *
     *  Conversion:
     *
     *  Nadc = 1023 * (Vin - Vr-) / ( Vr+ - Vr- )
     *
     *  Vin = ( Nadc * (Vr+ - Vr-) / 1023 ) + Vr-
     *
     *  Assuming Vr- == 0;
     *
     *  Vin = Nadc * 1.5 / 1023
     *
     */

    value = ADC10MEM * 15 / 1023; // 15 instead of 1.5 (using integers)

    accurateValue = ( (float)value ) / 10; // actual value (type double)
  }
}

Additional Requirements
The input should be between 0.1 mV and 1 V

Additional Information
Devices: MSP430F2274, eZ430-rf2500, eZ430-rf2500T
IDE: CCS V6.1
MSP430F22x4 Datasheet
MSP430x2xx Family User's Guide
TI Example Code: http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slac123&fileType=zip


texts: How to create block diagrams efficiently?

texts:
TL;DR: Need good block diagram schematic drawing process.

Table of Contents

Topicality and Relevance
Question

Topicality and Relevance

Topicality: John F. Wakerly, in his book Digital Design: Principles and Practice, Fourth Edition, (Amazon, book site) devotes an entire section, 6.1, to "Documentation Standards." He says "Good documentation is essential for correct design and efficient maintenance of digital systems" (p342; emphasis is mine). He then outlines six major components of good documentation, of which block diagrams are the second.

The next section, 6.1.1, is devoted to block diagrams, their features and their use. For example, he lets us know that "important control signals and buses should have names, usually the same names that appear in the more detailed schematic." (p346) I will note that this is the only subsection devoted specifically to any of the six types of documentation he describes.

Relevance: Clearly, any large project will be composed of a number of components. These components are shown in a block diagram. There may be several levels of block diagrams, which in turn describe the higher level blocks using lower level blocks in a mostly hierarchial fashion. To keep a project comprehensible to both the creator (over time) and others, block diagrams are essential. Hence, good digital design includes the creation of these diagrams.

If the diagram takes more time and effort to create than other stages of the design process, it is more likely to be skipped, short-circuited, or otherwise not given the proper attention. I'm a new digital designer and I have spent one full week (of several hours an evening) creating a block diagram of my MIPS processor's data path. To me, this seems like an excessive amount of time to have spent creating a block diagram, especially when I could have created the same diagram in under an hour with paper and pencil.

There are many layers to digital design, from concept to diagram to schematic to HDL to synthesis or tape-out or whatever happens next (I'm a novice so I can't say for sure). The ability to create this block diagram form of documentation efficiently seems to be highly relevant to digital design. After all, the about site for this Stack Exchange states to ask about "an actual problem you have faced"
that deals with "a specific electronics design problem."

Well, here's my problem: How do I efficiently create (and maintain) block diagrams? I would love to know about procedures, processes, tools, and the like, because what I am doing so far as a novice clearly is untenable.

Question

I'm working on building a full pipelined-architecture MIPS-style CPU in SystemVerilog, extending the concepts in Digital Design and Computer Architecture, 2e. This is being done with Quartus II running in BootCamp.

To keep things straight as it gets more complex, I want to keep the processor's block diagram up to date with my SV code. So far I have been using print outs of the diagrams in the book, generally starting from this one but sometimes using others from the published (odd) answer key (see book link for this and other PDF versions).

So, I recreated much of the diagram in Omnigraffle Pro 5, which I have used for years. (Edit: I have since completed the block diagram for the processor's datapath.) However, this incomplete result has so far taken me almost 10 hours, which is completely unacceptable, given that I could draw the whole thing in probably 20 minutes and modify the pre-generated diagrams (although with more messiness as complexity increases) in five. It's very difficult to label lines, to connect lines to other lines, make sure lines don't cross in bad locations, and even connect lines to objects in this program. I never noticed this in the past as I never had to do diagrams of such complexity.

I'm clearly in need of a better process, method and/or tools. I welcome suggestions. Thanks!


texts: How to improve the performance of subwoofer made with a TDA2030?

texts:
I have built a subwoofer amplifier with the IC TDA2030, it works well with my 8Ohm 30W woofer.

How can I increase the bass? It is not much as expected, is it possible to improve the bass by altering the circuit or do I have to design a bass filter for this?

I have seen the datasheet and tried to do it myself, but I don't know how to change the filter configuration in this circuit.


texts: How deep underwater can Bluetooth reliably transmit?

texts:
I know that Bluetooth operating at the standard 2.4GHz has a hard time penetrating water (I guess the water "absorbs" the signal). However, at what depth does this really start? In my case I am thinking about a device that operates within 1 meter of the surface and would transmit to someone nearby on land. Is a reliable pairing possible to attain and maintain? If so, is it doable with standard transmitters? That is, would there need to be any special signal amplifiers or the like?

Furthermore, if this is possible, is it only possible with Bluetooth classic or would BLE fare similarly?


texts:
I am a bit confused on a few things regarding photodiodes. Here are two circuits that I am referring to:

or

For the second circuit the capacitor is not of importance.

Here are my fundamental questions:

Why do we need an external voltage?
Why do we need a resistor?
What is exactly happening to the resistor when light hits the photodiode?
Why is the voltage measured between the photodiode and the resistor?
Why doesn't the external voltage influence the voltage from the photodiode (assuming the voltage from the photodiode is relatively low compared to the external voltage)?
For the second photo: what would be the need for a capacitor here? What would it change?

I don't expect all the questions from one user to be answered but I would definitely appreciate some insight or perhaps some recommendations what I should read to fill in some of the gaps. I know the questions seem rudimentary but I need those "Aha!" moments right about now.


texts: Can I accidentally create a coil with a bunch of isolated cables?

texts: I just finished rearranging furniture in my room and I ended up with a lot of cables next to each other, some of them powering electronics that draw a few hundred watts. Is it any risky - for example, can I create a coil this way? I am aware that this way I can probably cause some powerful interference.


texts: Charging a big battery with small solar panels very very slowly

texts:
I have a 6V, .7amp solar panel that typically puts out 2-5V under normal conditions.

I would like to charge a 12V 5 amp hr lead acid battery over a few days to weeks.

The device that I want to power is a lock that needs 12v at about .8 amps for a fraction of a second. The lock is used only once or twice a week. There is also a 3-5V microcontroller that needs to run for maybe 5min. to prime the lock.

Space and weight aren't an issue so I thought lead acid would be simpler.

Now I'm wondering if it'd make more sense to have a 3.7V lipo battery, use a charging board designed for solar and then boost it to open the lock?

When I looked up the charging info for this battery it says to charge it at 14v. It also says that lower voltages may be needed to trickle charge it if it's totally dead (which I don't see happening if this is set up correctly)

What I can't tell is if I can trickle charge it when it's at about 11.85-11.95V. I suspect that if I try to boost my sad little 6V solar panel to 14V the amperage will be so low what will be the point?

Furthermore, when I tried an out-of-the-box adjustable boost board with the solar panel it only turned on at all in direct sunlight. I need to capitalize on the indirect light too.

Are there any application examples of smaller, lower voltage solar panels being used over a long period of time to slowly build up a larger battery? Or do the loss factors make this unlikely?


texts: Adding a relay to stop motorcycle engine

texts:
I have a Honda CG125 - kickstart CDI motor cycle and I am adding a security system in it which has a relay to cut off the engine remotely.

The ignition coil has two cables coming to it, one green and other black/light green.
one of the cable is coming from CDI and the other is ground.

I am planning to install relay to one of these wires. I connected the Voltmeter to find out the voltage, when I kick the starter the voltage seems to go very high like 10,000 V etc.

Is this OK to install relay to one of these cable to stop engine - the relay 12 V / 40 A ?


texts:
I have some problems about programming my ATMEGA328 with USBasp programmer.

I have found different schematics for the connections and I do not know which I have to use (and I'm afraid to break something if I choose the wrong one):

First one:

The problem of this schematic is that I do not know which is the "verse" of the connector, and it is in contrast with the following other configurations.

Second one

The verse of the connector is specified, but this schematic is different from the previous one: Pin 3 is not more NC but is grounded.

Third one

The verse of the connector is specified, but this schematic is different from others: Pin 3 is  is grounded and 4 and 6 are not grounded.

My seller did not provide the datasheet for my programmer, so I have to consider the schematic of this generic USBasp programmer (it is identical to that of the previous picture).


texts: How to effectively generate random number with PICAXE 08M2?

texts:
I'm wondering how to effectively generate random numbers with my PICAXE 08M2. The following is my code:

; Inputs
symbol push_red = C.1 ; In 1
symbol push_buzzer = C.3; In 3

; Outputs
symbol buzzer = C.2; Out 2
symbol led_red = C.4;

symbol action = b0
symbol randnum = w5;
symbol randbit = w6;

main:

    FOR action = 1 TO 5
        RANDOM randnum
        LET randbit = randnum // 10
        IF randnum > 4 THEN
            PAUSE 500
            low led_red
            pause 500
            high led_red
        ELSE
            SOUND buzzer,(100, 100)
        ENDIF
    NEXT action

    SOUND buzzer,(120, 200)

Even though I'm generating a new random number with every loop, the result is always the same: LEDs light up, no sound generated. I've read some articles about dividing randnum by an appropriate number, but not sure how that works.


texts: Twisted triple wires when current is balanced

texts: Twisted pair cables are supposed to be effective for differential signals since the current flow is equal and opposite. If I have three wires such that the total current is also zero (say, +5V, GND, -5V), is twisting similarly effective to attenuate noise coupling?


texts: What are the differences between line tree decoder and matrix decoder?

texts:
Here's the reference material which has me confused.

After reviewing these 2 images I am confused about the differences between the 2 as the 6 to 64 decoder looks remarkably like a matrix decoder albeit with additional and gates.

Are there any conventional size (eg 2-4 decoders only) or structure restrictions?

Or is a matrix decoder just 2 line tree decoders laid at 90 degree angles of one another?


texts: How can I connect an Xbee to FPGA to transmit data.


texts: What is the minimum freqeuncy required to transmit 2400 bits per second?

texts: Yes we can use diiferent symbols and modulation sechemes for example QAM ,DPSK,QPSK etc... you can use any modulation secheme. What will be or can be the minimum frequency to transmit information equals to 2400 bits per second over a channel.


texts: Where to leave the test leads on a Fluke multimeter

texts:
I think this is somewhat of a "trade secret".

Being a software engineer for embedded devices myself, I often find myself using oscilloscopes and multimeters. I have always wondered about my Fluke 87-V and all flukes before that.

They have these slots in the back that perfectly fit your test probes/leads, protecting their points. However: I have -never- been able to find a way to properly wrap/fold the leads around the multimeter, and still be able to use the slots nicely.

Is there some secret to this, or should I just disconnect my leads after use?


texts: If current produces a magnetic field, how can the current be known?

texts: If the flow of electrons (i.e. current) produces a magnetic field, how can the actual flow be calculated? You cannot know if some external magnetism interferes and affects the velocity of the electrons, right?


texts: Does a longer stator equal more torque in a BLDC setup?

texts:
I'm interested in making something like this:
http://www.vivax-assist.com/en/produkte/vivax-assist-4-0/vivax-assist_4-0.php

Because it looks awesome, but for the price i could buy a motorcycle and the needed driver's license(!).

I think i remember reading somewhere that a longer stator = more torque, while more windings = more speed. I could not find anything to back up this theory though, so now I'm asking here.

So, smart people of this forum, does this theory hold up? Or is it just something I've been telling myself and mistakenly taken as something i read once?

Cheers


texts:
I wanted to connect a USB HID Controller to an Arduino and use it to control a Remote Controlled car.

But I'm unable to find what bit sequence is sent when a button is pressed on the joystick. I would like to find what that sequence is.

I'm running a dual-boot system with both Linux and Windows, so software that works on either one is fine.


texts: Proper Way of Powering a Circuit with 2 AA Batteries

texts:
That is a real primitive question.

a) Many MCUs and SOCs are able to work @3V (-/+ 0.3V)

b) This is voltage of 2 AA (or AAA) batteries

And the real question is:

What is the legitimate way to power a circuit with a MCU @3V with 2AA batteries?

Details:

Do you have to use a step up (boost) converter? Why?
Or would you prefer any other topology?
What is the drawbacks of powering directly from battery without boost converter?


texts: How do I calculate the unknowns of the current equation for a RLC series circuit?

texts:
Suppose I was dealing with the following voltage equation for the RLC series circuit:

\$ v(t) = Ae^{m_1t} + Be^{m_2t} + V_s \$

To know the values of A and B I would do the two initial conditions:

voltage at t=0 (I would solve the equation for t=0)
dv/dt at t=0 (I would derivate the equation and solve for t=0)

Now suppose that I want to do the particular conditions for the current case to discover A and B.

\$ i(t) = Ae^{m_1t} + Be^{m_2t} \$

What should I do? I suppose the conditions are the same, so, if I have the current equation, I have to integrate that to get voltage's but doing so, I will generate a constant of integration that will be a third unknown (I suppose it will be V0).

The whole thing is sounding a little strange.

In resume: I give you the i(t) equation of a series RLC circuit in the form

\$ i(t) = Ae^{m_1t} + Be^{m_2t} \$

How do you get, for example, the values of A and B in the form of variables, I mean in terms of formula that can be used for any case?

How is that really solved?


texts: Why DRAM costs much more than flash memory?

texts:
Comparing prices at a local store, I calculated prices 0.36 USD/GB for SSD NAND flash memory and 5.41 USD/GB for DRAM memory. The difference is 15 times. Why so big difference?

Both are semiconductor devices. Memory cells of both types occupy approximately the same die area: 4 F^2 for NAND flash memory, 6 F^2 for DRAM. (I can't give a good source; this information is scattered over the internet.) MLC of flash memory gives 2 times improvement. (BTW, is the same technology possible for DRAM?) I can't blame market forces because both markets seem similar to me in terms of competition, maturity, and size. For example, DRAM revenue 35.74e9 USD, SSD revenue 10.9e9 USD in 2013.


texts:
I want to use a STM32F3 GPIO (3.6V) to drive another device using 5V input.  Which is the correct way to do so?

I know that is possible to use the open drain mode on the GPIO, but I'm not sure if I need to connect an external 10K resistor with 5V power supply or the system is already included in the board for this purpose.


texts: What's the third wire on a piezo buzzer?

texts:
Most piezos I've seen have just two connections, but this type has three.

What's the third wire for?


texts: Will a buck converter drain 2 X 9v batteries with no output load

texts:
I'm currently building a circuit used in a personal portable cooling system.

The fan is a 12v turbine fan (0.1A)

My plan is to use 2 9v batteries in series to give me 18v then use a buck-converter to step the voltage down to 12v.

My question is, if I have a switch between the turbine fan and the output of the buck converter, and turn the switch off, will the buck converter its self still slowly drain the batteries?

Or would it be best to have the power switch between the batteries and the buck converter?

Ideally due to the way the product will be implemented and used, it would be more user friendly to have the switch between the buck-converter and the turbine fan however if this would drain the batteries even when turned off, then I will need to have a little re-think.


texts: How to power a 12V fan simply using a PV panel?

texts:
I am an electronics noob and I'd like to create some air circulation through my friends cellar using a salvaged 12V 0,8A brushless DC computer fan and a suitable PV panel. I have searched Ebay for 12V solar panels but their V-maximum is mostly in the 17-18V range and that worries me.

What PV rated wattage would be ideal, how would I calculate?
Will 17-18Vmax kill my 12V fan?
If yes, then do I need a step-down buck converter or should continue looking for a 12Vmax panel?
Does a step-down converter help? Does it help or hinder in cloudy weather?

Id like to keep it cheap and simple but any suggestions to make it better are very very welome. Thank you in advance!

This is the fan: Delta Electronics AFB1212SH-F00

These are two PV panels that I am considering, a 10W Eco-worthy and a 20W GWL/Sunny mono (not enough reputation for link).


texts: Using active BPF to convert a square wave into a sine

texts:
I have an inverter that converts 24 V DC to a 48 VAC peak-to-peak square wave with a frequency of 55 Hz. I am then going to use a step-up transformer to output 120 VAC to power some rocket valves that take maximum 150 VA.

We are not sure which ones we are using yet, but I want to provide 150 VA to make sure.

My approach was to use an active wide band pass filter to convert the square wave into a sine wave. The schematic has a first order high pass filter, a non-inverting amplifier that controls the gain, and a low pass filter.

I set the HPF's cutoff frequency to be 50 Hz (\$f_o = 1/(2*\pi*R*C) \$ for a first order filter) and the LPF to be 60 Hz. I also set the gain to be 1 by setting \$ R_4 = 1M\$ and \$R_3=100 \$.

What is wrong in this setup? Why is the output sine not a perfect wave? And if this op-amp cannot provide the inrush current needed, what circuit is capable of preserving power while converting this square into a sine?


texts: Design recomendations for Mosfet H-Bridge

texts:
I'm trying to build my first Mosfet H Bridge, the goal is to build a bridge with Vin = 5 - 12 V, Imax = 30 A, managed by microcontroller.

I have read about functional principle and Mosfet parameters, but I have some doubts about the implementation.

I have seen that many people use Half bridge drivers like in this answer but I have not seen that galvanic isolation is implemented in any design, furthermore in most of these chips that I have seen just have one Ground or Reference Point, with exception of IRS21844, so I supposed that these IC's don't have isolation.

I know in advance of the IGBT Gate Drive Optocoupler existence. So my questions are:

Is enough safe to use only chips like IRS21844 to drive the bridge and if not which optocoupler you recommend?.

What security precautions should I take into account in addition to TVS diodes, Pull Down resistors and Zener diodes in the gates?

Which is the best method to control the bridge, Optocoupler + Anti shoot through circuit + float power supply, Half bridge driver + optocouplers?

Which is the best way to get a float power supply?

Excuse me for so many questions, but is the first time I work with Mosfets and my intention is to learn the right way to build H bridge with these :).


texts: Send and "read" a tone over the AC power lines

texts:
I would like to use this circuit to send a signal over the a live wire;

Assuming the live wire on the right carry the signal;

simulate this circuit – Schematic created using CircuitLab

This would work? The signal can be between 1 kHz to 12 kHz.

PS. I have an electrician background, installing and maintaining equipment on 127/220/380/440V, so I understand the safety issues. I'm careful.


texts: Rule of thumb to select MOSFET transistors based on conmutation frequncy

texts:
In a power circuit once the power requirements of the transistor are meet , which is a dump of thumb rule to select or discard a MOSFET transistor based on the switching frequency?

For example for the IRF540, what are the  frequency bounds to work  with this transistor?

I guess the switching losses emerges as the more relevant factor if a specific efficiency requirements have to be achieved, but I'm looking for a simpler general rule, something like:

The cutoff freq of the LC filter should be 10 times smaller that the switching frequency in a DC - DC converter


texts:
I need to place components in a circle of a certain diameter, with a certain pitch, and angled evenly.

Is possible to do it in KiCAD automatically?


texts: Inverse Laplace Transform of RLC Circuit

texts:
The voltage across the power source equals the summed voltage across the resistor, capacitor, and inductor at any time (t). This is shown in the equation below:

$$Ri(t)+\frac{1}{C}\int_0^ti(t)+L\frac{d\:i(t)}{d\:t} = v_s(t)$$

for this example let: $$v_s(t) = 6$$

The laplace transform of this is:

$$RI(s)+\frac{1}{Cs}I(s)+LsI(s)=\frac{6}{s}$$

Rearrange it to make I(s) the subject:

$$I(s)=\frac{(\frac{6}{s})}{R+\frac{1}{Cs}+Ls}$$

Do some algebra to put it in a form that is easy to do an inverse laplace transform (ie. a form that represents an example in a laplace transform table)

$$I(s) = \frac{6}{Ls^2+Rs+\frac{1}{C}}$$

But I get stuck at this part. How would I do the algebra and inverse laplace transform so I can find what i(t) equals?

I expect that the answer will have the exponation e^-at in it, as the current will decay because of the energy dissipated in the resistor. I also expect it will have a sin, cos, both, or an imaginary number in it as the current will oscillate. According to wolfram alpha the answer is this. From this you can see that if 4L > CR^2 then the discriminant (the square root in the numerator of exponent) will be an imaginary number. You could then use eulers formula to get an equations with sin and cos in it.

simulate this circuit – Schematic created using CircuitLab


texts: What are the construction differences between a 1% transformer and a 5% transformer?

texts: I'm told that a 1% transformer costs more than a 5% transformer of the same power rating. I understand that the 5% transformer has higher output impedance, which seems to imply more windings and thinner wire. Is this the only construction difference between a 1% and 5% transformer of the same power rating? Or are there more considerations?


texts: Final transistor in VOX circuit design is saturated even when no audio is supplied

texts:
Background: I have a μBITx v6 HF transceiver. It has an audio input and output, and a mechanism where the transmitter is keyed up when the ring connector (called PTT, push-to-talk) from the audio input is shorted to ground.
In the radio hobby, there are methods of communicating called digital modes. In essence, you connect the radio to a computer, which acts as a modem that decodes and encodes digital signals into audio, that are fed into the radio. However, it's not as simple as just plugging two aux cords into the radio, I need some control circuit to tell the transmitter when to key up.
The simplest and cheapest method of doing this is to create a VOX circuit. When the circuit detects audio at the input, the PTT is shorted to ground and the transmitter is turned on. When the audio is not there anymore, after a short delay of a few milliseconds, PTT is no longer shorted to ground, and the transmitter stops, allowing the transceiver to receive audio from the airwaves again.
Steps I tried:
I had a breadboard handy, and prototyped a VOX circuit according to this design.
Using a bench DC supply at 9V (switched mode), I powered up the VOX circuit. I also had a 12V lead acid battery, which I used to power the radio. I used an alligator clip to connect both grounds together.
When I connected the audio input of the radio to the VOX circuit, it immediately keyed up regardless of what setting I had at the potentiometer (R6). This happened with no audio source connected. When I disconnected the base of Q1 from the rest of the circuit, the transmitter stopped keying up, but immediately started when I reconnected the base to the circuit. This tells me that something is causing Q1 to saturate when it shouldn't be saturated.
Can anyone provide other insights into what the problem could be? Again, the issue is that Q1 is allowing PTT to short to ground when I did not expect that to happen. No audio was applied to the input.
Just to make sure that my transistor wasn't faulty, I used a multimeter in diode mode to test the transistor. Everything looked normal. I don't think that's enough to rule out a problem with the transistor, but I tried substituting that transistor with other ones of the same part number. The same issue occurred.
I also tried to use the battery for both the radio and the VOX circuit, skipping the power supply altogether. This did not fix the issue.
I noticed that my diode, which has part number 1N4007, does not match what the schematic specified (1N914). Could that be an issue?
EDIT 1: I tried jumping R5 according to a comment, so Vcc is directly connected to the potentiometer. This did something, but not exactly what I was looking for. Now, if I connect the radio to the circuit, PTT does not trigger, but the moment I connect the computer to the circuit, it triggers. It also caused some RF feedback, which I solved with some ferrite chokes on the line. I'm going to try powering this with a 9V battery instead to see if the RF feedback problem disappears entirely.
EDIT 2: Using the 9V battery worked. However, the circuit still keys up. I tried connecting this ground loop isolator I purchased online a while back, and that caused the PTT to trigger as well. This means that any audio device will cause a short to ground when it is undesired. To counteract this, I will have to access the PTT line on the radio itself and add another coupling capacitor similar to C1 for the connection to the radio. I will post another edit on the results.


texts: Is Ohm's Law always exactly true even at the microscopic level?

texts:
My probability textbook introduction just mentioned that Ohm's Law is not always precisely true at the microscopic level.

How is this possible? What is causing this to happen?


texts: Using schottky diode near reverse breakdown region

texts:
I am currently using a 1N7070 schottky diode as the output rectifier for a flyback converter. The designed reverse blocking voltage is 70V. However, due to leakage elements I am seeing a transient spike(upto 98V) in the voltage when the primary MOSFET turns ON. This is after I had used a secondary RC snubber element over the diode.

I face two issues now.

1) How would one go about reducing this spike (other than using a proper RC snubber)

2) Does operating the diode with these characteristics result in failure
(A Microsemi note says that the breakdown voltage of these diodes is typically 20-30% above the rated value (and that too with some guard ring?))

Edit: Rated reverse voltage  = 100V


texts: Altium: Rectangular clearance around rectangular pads

texts: I am designing a high voltage PCB so I have created clearance rules between nets equal to the pad spacing on the high voltage capacitors (4.5 mm). When I pour polygons, Altium appears to produce rectangular clearances around the pads for the capacitors. This probably does not matter with small clearances but with larger clearances I get large notches in polygons. Is there a way round this?


texts:
I am working on MatLab simulation software to plot a Bode plot in the Matlab Environment. The open loop transfer function is $$a(s) = \frac{a_0}{(1+s/\omega_1)(1+s/\omega_2)}$$

Where \$\omega_1\$ and \$\omega_2\$ are pole frequencies (on the assumption that the op amp has 2 pole) and \$a_0\$ is the open loop DC gain of the op-amp.

To plot a bode plot for general purpose op-amp 741 we know that \$a_0=2\times 10^5\$.

But what are the pole frequencies (\$\omega\$) for op-amp 741?

Datasheet is attached in this link.


texts: How to connect two traces nearby on a PCB

texts:
I make a mistake in my design before getting several PCBs printed and I now need to fix it.

I missed a connection between two areas. Connection needs to carry 3amps peak at a low duty cycle.

Board is 2 layer, 2oz copper.

I can either connect pads about 10mm away, or I’m wondering about connecting traces. I have a 2mm gap between the two areas that’s about 5mm long with nothing between.

Is there an easy way to remove the solder mask, expose the copper on both sides and make a good connection? Would scraping away the mask and getting a blob of solder on there work?


texts: How to get a better square wave out of ne555

texts:
I built a basic astable circuit for the 555 and I'm using an oscilloscope to view the output.

I know this IC is supposed to output a square wave but instead I get these slopes (I don't know what to call them) in the wave. Is there a way I can get better waveforms out of the circuits like putting more capacitors or others?


texts:
I am learning hardware form a software background (playing with Arduino) and I am having difficulty remembering absolute wiring basics.

Bu board has a 5v and gnd pin, whilst my component has + & - terminals; which way round do I connect these?

Thanks


texts: Arduino Atmega328 sleep mode with internal timer interrupt

texts:
I am trying to reduce the current consumption of my Atmega328 -Arduino- by using the sleep modes. In my code, I want to wake-up every 10ms, read the value from ADC, and go to the sleep mode again.

There are some useful instructions (here and here), but most of them are either based on Watch Dog Timre or external interrupt from pins.

Here is the simplified code of mine, but doesn't work (it doesn't go to the interrupt handler function):

In the setup, I take care of the Timer and its handler:

void setup() {
   Serial.begin(19200);

   Timer1.initialize(10000);  //10ms sampling rate
   Timer1.attachInterrupt(ReadMyADC,10000);

   power_spi_disable(); // SPI
   power_timer0_disable();// Timer 0
}

The rest of the code including loop() is as follows:

void ReadMyADC(){
    sleep_disable();
    PRR = PRR & 0b00000000;
    Serial.print("sth");
    power_adc_enable(); // ebable ADC converter
    //Read ADC
    power_adc_disable();
}
void loop() {
    // ----------------low power ---------------
    PRR = PRR | 0b00100000;
    sleep_enable();
    set_sleep_mode(SLEEP_MODE_STANDBY);
    EIMSK |= _BV(INT0);            //enable INT0
    ADCSRA = 0;                    //disable ADC
    cli();
    mcucr1 = MCUCR | _BV(BODS) | _BV(BODSE);  //turn off the brown-out detector
    mcucr2 = mcucr1 & ~_BV(BODSE);
    MCUCR = mcucr1;
    MCUCR = mcucr2;
    sei();                         //ensure interrupts enabled so we can wake up again
    sleep_cpu();                   //go to sleep
    sleep_disable();               //wake up here
    Serial.print("Wake\n");
}

Apparently, Timer1 is not able to exit the cpu from sleep mode.
Do you have any idea how to manage that, or where the problem is?


texts:
What value resistor should I use for the base resistor for a transistor in front of a shutdown pin that uses virtually no current? If I do the math myself I get a crazy high number.

I am trying to control a shutdown pin that's pulled high to 5v via a 10k pullup resistor from a 3.3v signal. The shutdown pin is probably implemented as something like a mosfet that uses virtually no current.

Update:

The 5v 10k pullup resistor is tiny smd on a breakout board for the device I'm trying to interface with and I can't change it easily. And that pullup is why I can't drive the pin directly as I have a 3.3v MCU, it would presumably damage the 3.3v-only GPIO pin.

I just need a logic level shift to drive a small 5V signal low. I only have BJT transistors laying around and don't have any small signal mosfets. As I understand it the base resistor is (I think?) inversely proportional to the amount of current you expect to consume, and the shutdown pin will use virtually no current.

Update #2:

This is how I'm simulating what I'm trying to do (below). I assume that the shutdown pin is like a mosfet gate.

I found that making the base resistor very low (~100Ω) made driving the BJT consume about 30ma of current, which seems like a bit much. I found that 1kΩ-10kΩ base seemed to function exactly the same, and consumed about 1ma. Which I think is exactly what you would expect through the 10kΩ pullup. 100kΩ and it was not able to drive the mosfet fully. The logic is inverted of course but I don't care about that.

So I think this is what I'm going to go with unless I can find something else wrong with it.


texts: Setting manual thermal voltage for a diode in LTSPICE

texts:
I want to simulate some series and parallel connected solar cells with the same reference temperature but different operation temperature for each cell. To do so, I need to configure the thermal voltage of the diodes which I use in my circuit.

The problem is that it is not possible to change the operating temperature (.Temp) for each element of the circuit. Therefore, I want to calculate the diode properties manually. For the diode model, I do not know how can I specify the thermal voltage manually and I need your help.

Vt=kT/q is the thermal voltage that I want to configure it to a specific value.


texts: Can't get 2-relay module to work through JD-Vcc

texts:
I bought this 2-relay module: https://www.amazon.de/gp/product/B00E0NTPP4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I'm testing it out using a 5v 1 amp power supply.
If the JD-Vcc jumper is set and I power the relay board via the Vcc and ground pins next to the input pins, everything works fine. When I pull an input pin to ground, the relay actuates.
Anyway, I want to power the relay board through JD-Vcc. Here, I can't get anything to work. I removed the JD-Vcc jumper and connected the power supply's 5v to the JDVcc pin and ground to the ground pin on the separate connector set. If I touch the input pins to ground of the power supply, the relays don't actuate.
I've searched through a few posts her and I can't see what I'm missing. Any clues out there?


texts:
I'm getting stuck at the problem 2.16 in Art of Electronics.

"Design a tuned common emitter amplifier stage to operate at 100kHz. Use a bypassed emitter resistor, and set the quiescent current at 1mA. Assume Vcc is 15V, L = 1mH, and put a 6.2k resistor across LC to set Q = 10. Use capacitive input coupling."

simulate this circuit – Schematic created using CircuitLab

Is this a correct design? I found two way to find C:

1) f = 1/(2*pi*sqrt(LC)) ( and I know f = 100kHz, L = 1mH)

2) Q = w0 RC ( Q is 10, R is 6.2k, and w is based on f = 100kHz)

And they give different results. How could I solve this problem?


texts: How do I convert S-parameters for impedance matching?

texts:
How do I derive the Z-parameters to calculate a matching network for a device? I'm not sure what terms to even search for as I get all sorts of information I am not familiar with.
My task is to construct a matching network for the MRF1535NT1 FET from the provided S-parameters in the datasheet [PDF].

Frequency: 150MHz, |S11|:0.91 Θ:-175, |S21|:2.429 Θ:63, |S12|:0.011 Θ:-23, |S22|:0.82 Θ:-170

I started off by realizing that the given impedance data is for their already developed networks and not for the device itself so the only data I have is the S-parameters.
What I have gathered so far is that S-parameters cannot be directly converted to impedance since the ports differ from input to output impedance. [ref]
I tried out the formula given by biff44 - EDA Board

Zin = 50*(1 + S11)/(1 - S11)
Zout = 50*(1 + S22)/(1 - S22)
Where Zin and Zout are the impedances looking INTO the device. You have to multiply by 50 to convert the normalized impedance into ohms (assuming your S parameters were measured on a 50 ohm network analyzer).

However utilizing this formula I get very weird results. ~573-j598 after converting the polar form to rectangular and then performing the operation for Zin.
I'm not sure if I'm even doing this right, or if using the Z-parameters for this match will be helpful. Utilizing the Z-parameters for matching such as an L-match[4] are the only method I am aware of how to calculate. I am aware there is smith chart matching but I don't understand how to get there utilizing S-Parameters. I've tried reading some application notes such as those by Maxim, but they are a bit over my head.
The steps that I think I need to perform to make this match would be the following:
Covert S-parameters to Z domain for Zin and Zout -> Calculate L-Match given formulas in [Bowick] -> Simulate and test network in ADS.
References:

[1] MRF1535NT1 Datasheet

[2] StackExchange - Converting S Parameters to Z Parameters - Divergence

[3]  EDA Board - How to Convert S11 and S22 to Complex Impedance

[4] RF Circuit Design 2nd Ed. [Chris Bowick] - Chapter 4: Impedance Matching

[5] Maxim - Impedance Matching and the Smith Chart: The Fundamentals


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I am new to electronics and creating my first big project but I am stumped on figuring out the value of the base resistor (R2 in diagram) of an NPN 2n3904 transistor. All of the LED are rated for 20mA. I have done a lot of research but the more look in to it, the more I am confused. Any help on this issue would be greatly appreciated!

simulate this circuit – Schematic created using CircuitLab


texts: DC DC converter control design, PID vs compensators

texts:
I have to make a dc dc converter to power a resistive load, and I have reviewed various applications notes,  and applications reports like SLVA633 and SLVA662

They make uses of an compensator design approach, a type II or type III compensator whether is a current control or a voltage control,  then I have the doubt about the use of the pid control instead of the compensator approach, in the reports states that type II compensators is the industry standard for current mode control and I haven't found the same amount of information if any  about an analog pid design/analysis for dc dc conventers


texts: Finding Loop Gain (Aβ) of Transimpedance Amplifier

texts:
I have been having trouble finding the loop gain (Aβ) of the following transimpedance amplifier:

simulate this circuit – Schematic created using CircuitLab

To find Aβ, the books I have looked at (Sedra&Smith as well as Razavi CMOS ICs), the following method is used:

Break the feedback loop at any point (preferably at a point of infinite  impedance)
Place a test voltage at one side
At the other side reconstruct impedance seen from the test voltage
Eliminate the input source
Loop gain Aβ will be the ratio Vreturn/Vtest where Vreturn is the voltage at the other side of the break point

I have tried the break point above for this circuit and as you can see above it doesn't give the right answer. For example, using that break point Aβ would be found to be:

\$ Vreturn/Vtest = \mu \$

However using method of finding separate A and β circuits:

\$ Vreturn/Vtest = \mu (R_f/(R_f+r_o)) \$

I find it easy to find loop gain Aβ using method of finding seperate A and β circuits, but would like to know how to apply the described method here. I have found the method successful in other amplifiers such as voltage, and transconductance amplifiers, but can't seem to figure out how to apply it here.


texts: Voltage holder circuit configuration circuit

texts:
hi I didn't studies all the circuit configurations  and also I'm a newbie to EE.
My question is I need to design something like a voltage holder.

The idea is two emitter followers.
One is NPN one and other is PNP one and it will balance the threshold voltage across
junctions. Circuit diagram looks like this.

The functional requirement is that when I press the 5V switch , the outuput voltage
should go to 5V and hold  it 5V no matter I released the switch.
And when I give a 2V pluse , it should again come back to 2V.

The problem is, circuit simulator does not output it's expected functionality.
Any reasons why is that? It came back to OV, and sometimes it give me a
convergent error.Any workaround on this?

--Thanks in Advance--