Recent Posts

1

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by Gyro on Today at 04:14:55 pm »

This is getting nobody anywhere...

In the real world, semiconductors, including diodes (of all flavors) have datasheets. These specify the typical and worst case voltage / current characteristics under defined conditions. People find these USEFUL in designing them into circuits and products in the real world. Your dogmatic semantic argument that they are all resistors is NOT USEFUL in the real world. See the distinction?

Your dinner tonight will have electrical resistance, which will be determined by its composition temperature etc. as will the plate it is sitting on, the table they are sitting on, the chair you are sitting on (and the arse you're sitting on it with). Will you sit there making semantic arguments that they should all be defined as resistors until it gets cold (or in your case possibly moldy), or in the real world, will you just eat it?

2

Repair / Re: Desoldering advice

« Last post by donlisms on Today at 04:11:27 pm »

The description screams "Need more power!" to me, also. Just because you set your iron to 480 doesn't mean that's what you're getting!

3

Projects, Designs, and Technical Stuff / Re: LTSPice LoopGain2 Circuit Stability example does not make sense.

« Last post by osflores@qdusa.com on Today at 04:09:44 pm »

Yeah I was overlooking the fact that inverting the signal would introduce a 180 degree shift. I was assuming that this method would give me a straight answer. Thanks for the explanation.

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Projects, Designs, and Technical Stuff / Re: Nichicon UPJ for switching power supplies - what's so special about these caps?

« Last post by kimballa on Today at 04:09:07 pm »

I don't think in most cases you need to find the exact same capacitor for a replacement. If it's not super sensitive test equipment, any matching spec usually will do. There's a lot of manufacturers and lots of marketing claims about what applications each model is good / designed for - but I think a lot of that is just SEO so engineers steer their way when looking at a giant catalog of otherwise identical parts.

Capacitance, ESR, Tolerance, max voltage, max temperature, and physical dimensions (especially height).

If it is equal on capacitance and tolerance (virtually all electrolytic are 20%), "similar" esr, and same-or-better voltage and temperature handling and it physically fits on the board / in the enclosure, you're probably good..

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Beginners / Re: XOR gate problem with GND

« Last post by Ian.M on Today at 04:07:01 pm »

Wont work, cant work!
The inputs are effectively paralleled at the base of Q5   so it has no way of discriminating between either input active and both active.  Also with the Vce_sat of Q1 and Q2 in series and at least 0.7V drop across R4, they cant get Q4's base voltage low enough to turn it off.

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Projects, Designs, and Technical Stuff / ESR meter with extended scale.

« Last post by iet on Today at 04:04:18 pm »

Basic information here.
https://electronicsdesignfun.blogspot.com/p/esr-meter.html
The meter is adapted to the tester body.
The front panel contains a zero regulator, a power switch, and a graduated scale. The calibration was done using SMD resistors with low inductance.
Scale: 0.005-5 Ohm.
Some changes have been made to the original scheme.
U1-LM833
Resistors:R4-5.6k,R5,R6-0.1,R8-20k,R11-100k
D1,D2-1N5817
The transformer is wound on a ferrite ring
Supply voltage:9v
Frequency:100 kHz
Vpp:100mV

7

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by Sredni on Today at 04:04:03 pm »

A nonlinear RESISTOR is a RESISTOR.

nonlinear here is an adjective that specifies a particular property of a subset of the general set of resistors.

A bald man is a man.
A one-legged man is still a man, even if in all medicine books the body of a man is shown with two legs.

A nonlinear inductor is still an inductor.
The inductors used in Single Ended Primary Inductor Converters are usually nonlinear but they are called inductors nonetheless. Have you ever read "the nonlinear coil two-port element's current is..." In the description of a switching circuit? No, everybody says "the inductor's current..."

Sheesh...

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Projects, Designs, and Technical Stuff / Re: Powering NeoPixels from 3.3V - Wrong but everyone does it?

« Last post by sebmadgwick on Today at 03:57:59 pm »

Vh_min 0.7*Vdd... and 3.3V logic isn't enough for 5V Vdd

It sounds like you've misinterpreted how logic thresholds are specified.  If Vh_min is specified as a function of VDD then VDD refers to the actual voltage on the VDD pins, not the recommended typical value for VDD.  For example, if VDD was 4V then Vh_min would be 0.7*4V.

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General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by MK14 on Today at 03:57:40 pm »

Bold and font size change, done by me.

I am curious. How many of you people think an LED is a resistor? I should add: from the point of view of circuit theory, not from that of technology and underlying physics.

(This question originates from a question in another forum, where polls are not possible).

You specifically said "resistor", in the poll.

So you can't start changing the "resistor" to other things, such as "non-linear" resistors, later in the thread.

Because it makes the poll (and possibly the thread), relatively meaningless.

10

Microcontrollers / Re: $0.11 PY32F002A: Cortex-M0+ MCU, actually a PY32F030! 32/4KB, 48MHz, PLL, DMA...

« Last post by prosper on Today at 03:55:11 pm »

Thanks for the write up. I was excited about openocd for the PY32.... but there's (still) no source and no linux version. Ah well.

Also may be worth noting: beyond openocd and pyocd, there's also probe-rs which supports the py32. Probe-rs has similar capabilities to openocd and pyocd, but has a much nicer CLI than openocd (more like pyocd). It's also pretty quick (not being python). The only real downside that I've found is that its GDB stub is pretty limited (you can't 'load,' for example), so its not as good as a debug server. [though it does have a vscode extension which supports the microsoft DAP protocol directly, if vscode is your thang]