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Posts by Elleanor Lopez‭

29 posts
80%
+6 −0
Q&A Siglent1104 oscilloscope channels lagging

It was a firmware issue. SDS1xx4X-E Firmware Revision History And Update Instructions The hardware delay between ADC acquisitions was not accounted for. I flashed the scope with new firmware and ...

posted 4y ago by Elleanor Lopez‭

Answer
77%
+5 −0
Q&A Ground pour on outer layers on 4-layer PCB

You have mentioned a few points yourself, so I will try to comment on those points and perhaps suggest some reasons to add or not to add a ground plane. You mentioned twisting (I suppose warping) ...

posted 3y ago by Elleanor Lopez‭  ·  edited 3y ago by Elleanor Lopez‭

Answer
77%
+5 −0
Q&A Siglent1104 oscilloscope channels lagging

First I noticed that clock begins before chipselect gets pulled low on SPI. After eliminating potential sources I started to suspect the scope. I connected all 4 channels to function generator at d...

3 answers  ·  posted 4y ago by Elleanor Lopez‭  ·  last activity 4y ago by Elleanor Lopez‭

Question oscilloscope
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+5 −0
Q&A Unexpected impedance spike when paralleling capacitors

I was watching a video from EEVBLOG about bypass capacitors, and he presented a theory that randomly connecting different values of capacitors in parallel can create unexpected impedance spikes: ...

3 answers  ·  posted 4y ago by Elleanor Lopez‭  ·  last activity 4y ago by Andy aka‭

Question capacitor Impedance bypass-capacitor
75%
+4 −0
Q&A ADE7933 layout guidelines - Lazy Y capacitor?

ADE7933 contains an isolated DC-DC converter (Page 82). The control uses ~1MHz PWM signal with unknown rise time, but assuming something like 10ns, most of the energy would be contained in the 35MH...

1 answer  ·  posted 10mo ago by Elleanor Lopez‭  ·  last activity 10mo ago by Nick Alexeev‭

Question safety
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+4 −0
Q&A Back-EMF in bipolar stepper motor seems inconsistent with torque graph

In the AM2224-1000 datasheet for the '1000' model the following parameters are given: Nominal voltage per phase: 1.4V Back-EMF amplitude: 3.8V/k step/s There is also torque/speed gra...

2 answers  ·  posted 11mo ago by Elleanor Lopez‭  ·  last activity 9mo ago by Elleanor Lopez‭

Question DC-motor
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+4 −0
Q&A Matching network considerations for STM32WB55CEU6

Hi, I am designing a system using STM32WB55CEU6 and I want to use the RF functionality. Looking at evaluation board I see that there is a matching network for the output pin. The datasheet does no...

2 answers  ·  posted 1y ago by Elleanor Lopez‭  ·  last activity 1y ago by Olin Lathrop‭

Question RF
75%
+4 −0
Q&A micro-RF connector crimping options

Do micro-RF connector mating crimp connectors are ever sold separately together with a crimp tool? For example this I have looked through a lot of pages, and can only find PCB connectors + cable a...

1 answer  ·  posted 3y ago by Elleanor Lopez‭  ·  last activity 3y ago by DSI‭

Question RF connector
71%
+3 −0
Q&A Assembly challenges for shared pad between mounting hole and resistor

Hi, I was watching Many EMC Tips to Help You Design Better PCB Boards (with Keith Armstrong) and at 1:01:30 timestamp he talks about bonding reference plane to chassis and emphasizes that the conn...

3 answers  ·  posted 6mo ago by Elleanor Lopez‭  ·  edited 2mo ago by Nick Alexeev‭

Question EMC mounting-holes
71%
+3 −0
Q&A Rigid-Flex vs Flex with stiffeners - What is the practical difference?

Looking at Flex-Rigid PCB technology vs Flex PCB with added stiffeners under sections with components I struggle to see the advantage of Flex-Rigid for low layer counts, as it seems more complex to...

2 answers  ·  posted 8mo ago by Elleanor Lopez‭  ·  edited 8mo ago by Nick Alexeev‭

Question PCB flexible-printed-circuit
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+3 −0
Q&A Is inductor winding insulation rating important for a high-voltage application if the voltage is not across inductor itself?

In many hobby and even commercial designs, people use generic wire-wound inductors or common-mode chokes that do not have a specified insulation or hipot voltage rating. Drum-core inductors are som...

2 answers  ·  posted 9mo ago by Elleanor Lopez‭  ·  last activity 9mo ago by Olin Lathrop‭

Question inductor
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+3 −0
Q&A Current path in GPIOs protected by clamping diodes

The typical GPIO protection circuit can be seen here: In most articles online this type of protection just boils down to 'excess current is dumped into the VDD rail'. However, where does it actu...

1 answer  ·  posted 1y ago by Elleanor Lopez‭  ·  edited 1y ago by Nick Alexeev‭

Question protection GPIO
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+3 −0
Q&A Does preventing CMOS latchup with a diode in VCC path prevents protection diodes from working?

I want to use ADG726 multiplexer for an application where the multiplexer inputs could have potential on them before ADG726 is powered up. Seeing that ADG726 is a CMOS device, it seems it might be ...

1 answer  ·  posted 1y ago by Elleanor Lopez‭  ·  last activity 1y ago by Olin Lathrop‭

Question CMOS
71%
+3 −0
Q&A OPA2211 datasheet discrepancy

Looking at Texas Instruments opamp OPA2211it mentions GBW of 80MHz at a gain of 100, and 45MHz at gain of 1: Looking at the bandwidth graph from Figure 10 in datasheet: It looks like 80MHz is...

2 answers  ·  posted 2y ago by Elleanor Lopez‭  ·  last activity 2y ago by Nick Alexeev‭

Question datasheet opamp
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+3 −0
Q&A Connector rated voltage vs IPC-2221B and IEC 62368

Rosenberger 23C25D-40ML5 specifies 500V RMS rating: Looking at the recommended landing pattern you can see that the distance between the signal landing pad and housing of the connector is 0....

1 answer  ·  posted 2y ago by Elleanor Lopez‭  ·  last activity 2y ago by Olin Lathrop‭

Question safety voltage
71%
+3 −0
Q&A Step voltage 750kV lines

Some gentlemen decided to throw a hook with wire over 750kV lines in Belarus. They survived, however, I find in interesting to find out why. Assuming the connection to Earth was solid, there would...

1 answer  ·  posted 2y ago by Elleanor Lopez‭  ·  last activity 2y ago by Olin Lathrop‭

Question high-voltage safety
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+3 −0
Q&A Cable voltage rating

I was looking for guidelines of how to select appropriate cables for applications (I am interested in DC), I found IEC 183 standard which talks about high voltage cable selection for AC. Also, the ...

1 answer  ·  posted 3y ago by Elleanor Lopez‭  ·  last activity 3y ago by Sclrx‭

Question voltage cable
66%
+2 −0
Q&A Is it allowed to skip a pin to increase creepage distance?

Olin's answer lead me to look for illustrations and I found a reference around creepage definition in IEC 62368 to another IEC norm, namely IEC 60664-1: "Insulation coordination for equipment withi...

posted 3mo ago by Elleanor Lopez‭

Answer
66%
+2 −0
Q&A Back-EMF in bipolar stepper motor seems inconsistent with torque graph

I got an answer regarding the back-EMF number in the datasheet. The back-EMF voltage waveform is a sine and the listed value is the peak value. What this means in practice is that energy can still ...

posted 9mo ago by Elleanor Lopez‭

Answer
66%
+6 −2
Q&A Titanic submarine control considerations

The submarine built by OceanGate went missing on 18th June 2023. A lot of online criticism was directed towards the control hardware of the submarine - Logitech F710 controller. However, why i...

3 answers  ·  posted 3y ago by Elleanor Lopez‭  ·  last activity 3y ago by Pogo‭

Question safety control
62%
+3 −1
Q&A Tesatronic TTD20 DGND AGND unconnected

The TESATRONIC TTD20 is a precision length measuring instrument used in various industrial and laboratory settings. On the backside it provides a 15 pin interface for reading out signals: I want...

2 answers  ·  posted 1y ago by Elleanor Lopez‭  ·  last activity 1y ago by TonyStewart‭

Question Analog equipment
60%
+1 −0
Q&A Is it allowed to skip a pin to increase creepage distance?

From IEC-62368 for signals below 30kHz the creepage distance for pollution degree 2 and material group IIIa,IIIb (FR-4 boards are IIIa) at 40V is specified to be 1.1mm. We have a connector that has...

3 answers  ·  posted 3mo ago by Elleanor Lopez‭  ·  last activity 3mo ago by Elleanor Lopez‭

Question safety
60%
+1 −0
Q&A Missing voltage rating

I am looking at this RF connector. I see that insulation resistance and breakdown voltage are specified, but no voltage rating: I have two questions, one functional and one safety. Functionally...

2 answers  ·  posted 2y ago by Elleanor Lopez‭  ·  last activity 2y ago by Olin Lathrop‭

Question connector
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+1 −0
Q&A Understanding inductive ringing

For my own understanding I tried modelling switching off an inductive load without a freewheeling diode to observe ringing. This is the model I used: 1.) Are the two main components of the reson...

2 answers  ·  posted 2y ago by Elleanor Lopez‭  ·  last activity 2y ago by Olin Lathrop‭

Question inductance
60%
+1 −0
Q&A How to convert dv/dt of noise into frequency for filter capacitor selection?

Noise can be coupled between signal lines through parasitic capacitance formed between these signal lines, as $i = C\frac{dv}{dt}$ where C is the capacitance between the signal lines. Another wa...

1 answer  ·  posted 3y ago by Elleanor Lopez‭  ·  last activity 3y ago by Olin Lathrop‭

Question capacitor filter