New answers tagged emc
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You talk about reversing the plug, so it seems it is an ungrounded appliance. In that case reversing the plug should not have any influence, as there is no reference for live and neutral.
However, it is a tv, so it has a third connection being the antenna or cable. I'm going to assume a cable connection, as there are typically grounded. Now this provides a ...
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Background (with a little speculation)
Inside the TV's switch mode power supply will be one or several Y capacitors that connect the internally produced DC voltages to either live or neutral. They are there to reduce the common mode noise produced by the high frequency switching transformer from affecting the DC outputs. Without the Y capacitors, all the ...
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The ethernet cable has an external jacket and you shouldn't be modifying that jacket, so you won't be doing any shield connecting unless you add shielded female-to-female couplers and have two patch cables per segment - a bad idea. So I'm not even sure how "connecting the cable shield option" even came up? How did you plan to actually implement it, ...
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I would highly recommend that you read ETG1600: Guideline for Planning, Assembling and Commissioning
of EtherCAT Networks , a public white sheet that covers the suggestions for system design and covers grounding considerations.
In EtherCAT the signal processing chain is digitized and goes through an EtherCAT slave controller or equivalent on every single ...
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This is one of my favourite topics :) You have to understand where what current flows. I usually divide things into three categories:
DC - you only want to flow on your power lines, hence you will only connect your GND to the shield at one point.
upd: why would you connect it even once? Because the frame is the safe spot to touch, it's grounded to the ...
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How does this not create ground-loops in the shielding?
If the shield is tied to both locations at the "purple" boxes, It does create a ground loop in the shielding (as the red arrows show below). Check to see if the shield on the cable is actually tied to the connector. It would be unlikely that this would be the case, since ethercat or ethernet ...
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When you really get down to it, RF interference, conducted noise, and ground loops are all separate problems which require different solutions.
Ground loops
These occurs when high current devices start raising the ground level locally. It's not an issue within that device, but when it tries to talk to a different device with a lower ground level, the signal ...
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I dont know if this is still relevant, but I would suggest keeping three "ground" lines in mind. Data Ground, Chassis Ground, and Power Supply Negative.
Have these three grounds connect at only one place, and possibly at some (3in-6in min) length from the battery. I would only suggest connecting the CAT shielding to the computer's chassis, nothing ...
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Ground loops cause a voltage differential between two points in the ground system. This can appear as noise on signals that are referenced to this ground. EMF through the loop induces current that must travel through the loop.
The key thing to remember is that the voltage will be equal to this current times the impedance. If your frame is a big hunk of ...
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Even though a ferrite bead only becomes lossy above some frequency, it's still inductive down to DC. The inductance is rarely specified, but you can calculate it from the slope of the impedance graph in the specification.
As it's inductive, you can design a CLC pi filter with one.
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It could be common-mode noise.
You stipulate you have a buck converter, guessing it is a DC/DC converter which implies you have a power supply powering your buck.
120khz is typical from a switched power supply and they generate usually quite a bit of noise and ripple.
Try to add capacitors and also common mode choke at the output of your supply, eventually a ...
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Assuming the device is EMC compliant and legal (which isn't necessarily the case).
It is possible to design a rugged, 3-signal interface using current loops. That is, some proprietary protocol which uses current levels to modulate the digital protocol, rather than voltage levels. You can even do this with 2 signals if you also supply the device through the ...
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For RS485, CAT5 should be just as good as any other shielded twisted pair cable. The impedance should be within tolerance for RS485. What matters most is how you connect the common ground between devices, and how you connect the cable shield, and where you connect the terminators, but that does not depend on if the cable is CAT5 or something else.
The RS485 ...
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The hint referred to your driving the NMOS with 48 V, and grounding both ends of C6. While things don't blow up in SPICE world, they just might not be working as intended.
If you want to see effects of non-idealities, then that's what you have to add to your schematic (see Rohat Kılıç's comment. What you have there is (let's say) a quasi-ideal buck stage. In ...
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Let us consider resonant parasitics.
1uH and 1pF will resonate at 150MHz.
10nanoHenry and 100pF will resonate at 150MHz.
1u and 100pF will resonate at sqrt(100) lower, or 15MHz.
100nanoHenry and 100pF will resonate at 45MHz.
And 4" of PCB trace (not over Ground) will provide about 100nanoHenry.
Thus PCB traces, and power driver junction parasitics, in ...
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If my PCB is not too large (15cm x 5cm) 30-50 MHz emissions are mainly
radiated through power cables?
Yes, that is a general truth and, that means you need to prevent conducted emissions because on a long(ish) cable, conducted emissions become radiated emissions. The good news about conducted emissions is that you can actually simulate the results (with a ...
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If my PCB is not too large (15cm x 5cm) 30-50 MHz emissions are mainly radiated through power cables?
Maybe. Maybe not! Point is, a shorter conductor can still emit – maybe not as efficiently, but will still do. Since we don't know how much energy is not emitted, we can't assume it's not also shorter conductors/components.
If 30-50 MHz 1/4 wavelength is 2....
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