Electrical Engineering

PlasmaHH

07:52

@Asmyldof I haven't seen it powered that way, especially not when there is a transformer and a12v rail elsewhere. Probably wanted no risks of getting 220 into there

Bartek Banachewicz

09:46

hmm, this seems to be a quite nice price

seems to be not much worse than the DS1054Z spec-wise

PlasmaHH

2 channel 60mhzs 500ms/s vs. 4 channel 100mhz 1gs/s ?

2mV vs 1mV?

Bartek Banachewicz

@PlasmaHH accurate to the order of magnitude :D I'm trying to find counter arguments to buying the Rigol, but I found a video that shows how to hack and unlock it making it effectively the same as the 2x more expensive unit

PlasmaHH

a video? why these days people distribute all their information in videos? 2kb text vs 200mb video... 2s reading vs 2 minutes looking at someone doing it and still not getting because it is all blurred out of focus noisy and shaky

Bartek Banachewicz

10:03

@PlasmaHH I wasn't looking for a video, but this was the medium that popped up first. I also think videos are overused.

For electronics this still kinda makes sense; the worst of all are coding videos

PlasmaHH

For teardowns and fun stuff it kinda makes sense, but for transferring information or even looking it up, videos are totally unsuable. one little thing you wanted to know, have to waste 20 minutes of your life sifting tghrough a video where it is explained somewhere

Bartek Banachewicz

true

Bartek Banachewicz

10:25

@PlasmaHH welp, should arive around friday ;)

Bartek Banachewicz

10:52

that should give me enough time to actually educate myself

Anonymous

11:42

0

Q: Resource Recommendation: Controlling/Tuning Antennas and Rectenna

I'm looking for resources to learn about controlling/tuning antennas (using microcontrollers like Rasberry Pi/Arduino) for power transfer using microwaves, radio waves and other EM waves. I looked on the net but could not find much reference on this topic. I'd be grateful if someone could give m...

Anonymous

Could someone give me suggestions ? ^

Anonymous

Books/Websites/Documents etc will do

Bartek Banachewicz

12:20

I can't really recommend any books, as all books I have on this topic required the reader to have an in-depth understanding of topics such as transmission lines and EM-waves. In addition, buying-suggestion questions are unwanted. Instead, you could change your question to ask about the topics you need to master in order to solve/design a system, and then find resources on these topics yourself. — Joren Vaes 27 mins ago

I think your question is awfully vague tbh

maybe you should just state out what you wanted to build

Anonymous

@BartekBanachewicz I modified my question after Joren commented. At the moment I just want to learn how to tune antennas using a microcontroller. I'm looking for books on that topic.

PlasmaHH

recommendations are always a good question to vtc as primarily opinion based

Bartek Banachewicz

or off-topic on Stack Overflow

Anonymous

Is it off topic in chat, too?

Anonymous

I hope not

PlasmaHH

12:24

not at all

Anonymous

If you wish I could delete the question from the main site

Anonymous

I'm just looking for some books to get started. I learnt basic Arduino coding from the book by Massimo.

Anonymous

My project is to build a small scale wireless power transfer system

PlasmaHH

I don't even get if you want a single antenna tuned or use a µC or an RPi/Arduino to tune them

Anonymous

@PlasmaHH The latter

PlasmaHH

12:27

that sounds really weird, why would you want to do that? Does your communication frequency change so much all the time?

Anonymous

@PlasmaHH I just want to learn how to tune using RPi/Arduino. It's not really a technical issue I'm facing. I'm just going through the necessary theory to enable me to do the project.

PlasmaHH

hmk. did it occur to you that for things that are not very practical in reality there will be little material to read about?

Anonymous

You're right. I agree

PlasmaHH

You could start by learning about how antenna tuners and their matching networks with variable caps and inductors work, and why

Anonymous

@PlasmaHH I see. Does this seem like a good book to get started with that ?

Asmyldof

12:35

No.

PlasmaHH

The (broken) antenna tuner I have lying around is bigger than my lab PSUs ...

@Blue I dn't know, I haven't read it, but I highly doubt its a good book at all

Asmyldof

If the title of a book about antennas and/or radio contains Ardiuno or Raspberry it's EXTREMELY unlikely to actually go into the how and why of things and will likely in stead just chew out a couple of designs and haphazzardly force some broad assumptions to allow you to modify them

Anonymous

Antenna tuner

An antenna tuner, a matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, or feedline coupler is a device connected between a radio transmitter or receiver and its antenna to improve power transfer between them by matching the impedance of the radio to the antenna's feedline. Similar matching networks are used in other equipment (such as linear amplifiers) to transform impedance. An antenna's impedance is different at different frequencies. An antenna tuner matches a radio with a fixed impedance (typically 50 Ohms for modern transceivers) to the combination of the feedline and the antenna...

Anonymous

I think I should just get started with Antenna Theory

Anonymous

There are some books on that

bwDraco

13:11

@Asmyldof, a bit of a technical question: I just got one of these DC load testers:

amazon.com/DROK-Portable-Intelligent-Discharge-Resistance/dp/…

They claim the device dissipating the power is a MOSFET, but I apparently got a different revision product than the one shown in the picture because the PCB layout is different.

I took the bottom plastic cover off and found that it's not a MOSFET but a Darlington transistor:

in Root Access, 7 hours ago, by bwDraco

On the load tester... The transistor is a Fairchild TIP122, which isn't even a MOSFET but a Darlington transistor. The microcontroller is a Holtek HT66F018 (why am I not surprised they're using Holtek?). An ON Semiconductor MC34063A powers the fan, up to 24V.

PlasmaHH

it gets hot, who cares what kind of transistor this si...

bwDraco

So how does one use a transistor to dissipate arbitrary amounts of power in a circuit like this?

The device I have can go anywhere from <0.1A to >4.4A.

PlasmaHH

slap a shunt resistor in and configure an opamp to regulate the tranny according to the desired voltage drop

bwDraco

Oh, okay. So they're basically using the transistor to control the ~~power~~ current that gets fed through the resistor.

PlasmaHH

current

bwDraco

13:20

Yeah. It's constant-current.

PlasmaHH

the shunt resistor has no idea on how much power is routed through that system, it only sees current

Asmyldof

Basically that's what happens

Used to be a 1st year sub-project

The main project being accurate thermal control of a block through controlling the heating power and fan speed using a VHDL home-made microcontroller

You have a 0.1 Ohm resistor, for example, by forcing a voltage over that, through Ohm's law of I = V/R you get a current

given accurate enough components and measurements it's very easy to control that current for constant current or constant power

bwDraco

Hmm. Now that's interesting.

Asmyldof

Any voltage not burned by the resistor is burned in the transistor set up to be a voltage follower

With a modern MOSFET you can very easily build an electronic load on those principles and it's just Firmware work to make it present as constant resistance, constant current, constant voltage or constant power

Down to tenths of volts

bwDraco

Wow.

I suppose the microcontroller is just there to monitor the unit, control the fan, drive the LCD, and calculate things like the total energy, etc.

PlasmaHH

13:26

I personally like it more to have the µC set a current by outputting a voltage and let an opamp drive the transistor than it trying to do it itself.

Asmyldof

Probably they included it in the loop of controlling the transistor, but strictly it doesn't need to be

bwDraco

So how do they get the thing to maintain constant current even when the source voltage falls off a cliff?

PlasmaHH

they dont

bwDraco

3-21V. I actually tried a 20V source last night and the behavior was pretty much the same.

PlasmaHH

you can't go below RDSon

bwDraco

13:31

That imposes a floor on the voltage, right?

PlasmaHH

for a given current

bwDraco

Hmm...

Also, what happens if the wattage is too high? Is this device entirely thermally limited?

I was wrong about some of the assumptions earlier.

PlasmaHH

it might undergo a sudden unplanned diassembly

bwDraco

lol

It's rated for 35W. Again, is this thermally-limited?

The load tester beeps warnings at me if the power exceeds 35W.

PlasmaHH

read the specs. it may or may not be. unlikely for cheap chinese crap

bwDraco

13:35

> unlikely for cheap chinese crap

explain?

PlasmaHH

thermal protection costs money

bwDraco

It doesn't seem to have a thermal shutdown, though it does have a temperature sensor for fan control.

PlasmaHH

it may still overheat

bwDraco

I was thinking that the device would just let out the magic smoke because you've exceeded the cooling capacity.

PlasmaHH

thats what it likely does, though I would not call that thermally limited

bwDraco

13:38

Oddly, the temperature sensor tops out at 80 °C, at which the fan runs at full speed.

PlasmaHH

it better does

though I personally would make it run at full speed at anything over 35°C or so

point?

I have one of these cheap chinese battery tester loads, replaced the fet with a beafier one and slapped it onto a cpu heatsink...

bwDraco

Heh.

Anyway, it was nice talking to you - see you soon.

Giskard42

14:01

I took a Hyper 212 EVO processor cooler, slapped a huge darlington on it, hooked up a dac, and now I have a 200w load for $30

It strikes me as unbelievable how much BK et al charge for theirs

pingOfDoom

hello again all

Im back with another vhdl question

Im trying to run a simulation with isim on xilinx ise

and I get some weird error where it says something to do with a zero delay oscillation

on a full adder

any ideas?

PlasmaHH

"something to do". quite precise error message.

pingOfDoom

14:19

ERROR: at 60 ns(10000): Iteration limit 10000 is reached. Possible zero delay oscillation detected where simulation can not advance in time because signals can not resolve to a stable value in File

verbatim

Followed by the file path

that links me to the Sum line on a full adder

W5VO

14:50

@pingOfDoom Sounds like you may have the SUM feeding back

somewhere the result of the adder gets fed back to the inputs?

(without going through a register)

Asmyldof

15:02

@Giskard42 Because they actually specify noise and ripple figures and curvature guarantees and have spent ages on getting all of the operation modes stable in their control system

PlasmaHH

15:13

plus measurement accuracy ofa darn good multimeter

Giskard42

18:23

@PlasmaHH @Asmyldof -g3 -Os compiler flags. That's all it was.

Oh, actually, no.

Giskard42

19:15

For some reason, if I click Atmel studio's run button, some register gets set, and permanently fixes the board.

GPNVM bit 0.

SAM-BA.

I'm such an idiot.

Thanks everyone for your help over the last week. Sorry to constantly bother you guys :>

Giskard42

19:46

Still don't know why the GPNVM0 bit would specifically prevent the PLL from starting, but nothing else.

PlasmaHH

20:19

@Giskard42 your code is then wrong somewhere and invoking undefined behaviour

Anyways

These doors that switch from transparent to translucent, are they available as sliding doors?

Giskard42

@PlasmaHH smarttint.com

Asmyldof

@Giskard42 Which is exactly what the earlier post you linked said....

Giskard42

@Asmyldof Wait, really? Which one?

Asmyldof

@PlasmaHH I have had several offers from Chinese manufacturers for foil that does that, as well as sample offers. You looking?

@Giskard42 One them AVRFreaks or EEVBlog discussions about the SAM with newest FW version ICE

Giskard42

@Asmyldof Hmm, yeah. you're right

Oh, but that hard fault in reset handler was unrelated

I'd already solved that problem

Anyhow, I'll stop making excuses for my apparent lack of intelligence.

PlasmaHH

20:46

@Asmyldof we (wife mostly) have a customer renovating 220qm apartment and we are looking for some options and highlights to offer, and my concerns are about the durability when you do this as a sliding door, no idea about the actual cabling there

Asmyldof

@PlasmaHH Should be solvable

There's 3-axis systems with motors that make 100k strokes with no broken wires

Don't know if it already exists, but should be doable if it doesn't

Maybe even a copper-tungsten type sliding contact situation

PlasmaHH

@Asmyldof any idea about the power they need? I think the lowest voltages you get are 50 or 70 or so, with little actual power and a voltage boost battery might be feasible

Asmyldof

@PlasmaHH I believe it's mostly charge systems rather than actual drain, but no idea

Transcript for

Electrical Engineering