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Microcontrollers & FPGAs / Re: I2C to Wifi or UART for ESP32
« Last post by Quarlo Klobrigney on Today at 01:32:13 am »
Have you seen this fellow's page yet? Lots of examples here.
Andreas Spiess - YouTube
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I forgot to mention that the diode check on the meter can charge up the gate and turn on the mosfet, which then apears to have a D-S short. You can short G-D together for a moment to discharge and turn it off.
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Test Equipment / Re: EEVblog 121GW Multimeter Issues
« Last post by Candid on Today at 01:29:05 am »
I only did a quick test. But let me see... shit no tape eraser around  :D.

What I did was DMMCheck Plus with 1mAdc and the 121GW with my Fluke 28II in series. Then I used a strong neodymium magnet and the 121GW reacts on it (not as much as to the electrical field of your tape eraser but noticeable) and the Fluke 28II does not. I did not do any further or deep testing and did not check other DMMs.
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Be quick!

https://www.ebay-kleinanzeigen.de/s-anzeige/oszilloskop-oszillograph-agilent-mso6054a-4-kanal/924081002-168-9104

Thanks for the linking, it's tempting!

Not sure if I am being a drama queen, but is this not a bit TOO cheap? Or have the prices of these things fallen this far now? if it was an ebay sale, with Ebay protection I'd feel a bit more secure, but it is just a private ad in a country too far away to go door knocking if it's not what it purports to be ;)
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Beginners / Re: Current sensing Optocoupler
« Last post by Ian.M on Today at 01:25:56 am »
Its worse than that - depending on how much the "18V 1A+ pulse" goes over 1A.  e.g. if it reaches 1.5A, the voltage drop with a 2Ω current sense resistor will reach 3V which only leaves 15V for the load, and results in 4.5W dissipation in the resistor.

If this circuit is unsuitable, the first question to ask is: Does the output need to be isolated, or can it share a common ground with the 18V load?
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General PCB/EDA/CAD Discussions / Re: Do you start in a simulator?
« Last post by free_electron on Today at 01:24:51 am »
for anything io , digital , microcontroller and simple analog : straight to board.

Only for simple stuff.

It is highly educational to simulate a multi-output digital system driving a moderate load. To pick a few figures:
  • a digital output, say 3V, with a series 100ohm resistor, 1ns risetime
  • one side of that digital output is connected to an inductor to ground. That inductor represents the inductance of the ic's ground lead, 1nH/mm so say 5nH
  • that resistor is connected to a transmission line, 100ohms, 1ns, and the other end of the transmission line is connected to a 5pF capacitor representing another ic's input capacitance

Do a transient analysis and look at both ends of the transmission line.

Then simulate eight such outputs switching simultaneously, by reducing the resistor to 12.5ohms.

If you think that is academic, I suggest you look at and understand the IBIS models published for digital ics - and why they need to exist.
Why would you want to do that ? That is bad design practice to begin with.
The driving IC output is already in the order of 20 to 25 ohms. So you are  mismatching your transmission line.
1nS rise time is NOT a GPIO of a microcontroller anymore. Your run of the mill micrcontroller can't even go there. Besides those are current limited and slope controlled these days.

If i need to make a controller for let's say a reflow oven or a plant watering system : there is no need to grab a simulator. that's straight to board.

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General Chat / Re: Is it me or Netflix content is awful
« Last post by james_s on Today at 01:22:24 am »
Also, when there is a series, which only gets released months after television - > not good enough. You cannot release Mr Robot later, half the experience is reddit. Even if it is not even distributed in the country I'm watching it.

Reddit? I cannot even imagine why I would want to discuss something I was watching on there. I want to watch what I want to watch, when I want to watch it, I don't want to discuss it with a bunch of opinionated people. Then again, with the exception of animated sitcoms I can't think of a single TV series made in the last decade that I'd want to watch at all, IMHO most of the good stuff was made in the 70s-90s.
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Microcontrollers & FPGAs / Re: Issue with STM32L432KC Nucleo and ADC
« Last post by newbrain on Today at 01:15:13 am »
Not that specific Nucleo, but many others, with and without HAL or LL...

The HAL is "a bit" bloated and has some bugs (much less than other vendor provided libraries I have seen, though) but it generally works.
It gets some time to get used to its conventions, though CubeMX is good help in generating complete initialization code.

Did you try debugging to see where your code gets stuck?
Are you enabling interrupts but not servicing them?

Without your code, it's next to impossible to give a meaningful answer  :-//, so help us help you!
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Beginners / Re: Current sensing Optocoupler
« Last post by Paul Moir on Today at 01:13:09 am »
As Ian.M said, Vf of the LED drives the design, and to a place that might not be acceptable to you.  To light the LED you must exceed it's Vf by the voltage dropped across R2.  For example, say you want the LED on at 750mA:
V=IR
1.3V=0.750A x R2
R2 = 1.7\$\Omega\$
Now you can't get a 1.7\$\Omega\$ resistor and like Ian.M said you'll need some extra voltage headroom for R4, so you select a R2 to be 2 \$\Omega\$.  And while you want the LED to be on for sure below 1A, 1A is what you typically draw.  So the actual drop across R2 is:
V=1A x 2 \$\Omega\$
V=2V. 
Since those 2V of your 18V supply are going away in R2, your load is now only going to see 16V.  Is this OK?   Also R2 is going to be burning:
P=VI
P=2V * 1A
P=2W
Is it acceptable in your application to be burning away 2 watts of power?
If the answer to either question is "No", then this circuit won't work for you.   
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1kW is going to be plenty for 2 liter oven.

For comparison electric kitchen ovens are about 70 liters of volume, have about 3kW of power and really lousy glass door and yet reach ~300C temperature.
YMMV but based on some measurements I did with kitchen ovens they run at less than 50% duty cycle even at 300c setting once they reach the temperature.  (models with pyrolytic cleaning can get up to 500 celsius during burn-off)
Do you know how fast they heat up?

JS


some of the newer ovens with "fast heating" claims 180'C in 5 minutes


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