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Activity for Andy aka‭

Type On... Excerpt Status Date
Comment Post #291110 The PLC is meant to be weather protected so there's no way that it should see humidity levels that low.
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7 days ago
Comment Post #291085 Nevertheless, the TVS diodes are offering no protection and, they would likely protect the device if chosen to be the right voltage rating (irrespective of root cause).
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10 days ago
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Answer A: LED driver with feedback through light. Which feedback topology is better?
> Which topology is preferable? The one below because the LED driver is less likely to produce instability and, if it does, you can always tweak C4 (upwards) in order to kill-off the potentially oscillatory pole produced in the response in your first circuit. How to draw schematics that prov...
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12 days ago
Edit Post #291085 Initial revision 12 days ago
Answer A: MAX485 transceivers breaking, Pi filter generating spikes?
What part of the absolute maximum ratings for the A and B data lines do you think would be protected by 33 volt TVS diodes: - Imagealttext If the chip is powered from a 5 volt supply then you use 5.6 volt TVS diodes to ground. Maybe you can raise the TVS to 10 volt if you have a lot of common-m...
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12 days ago
Comment Post #291025 You have to make sure that the op-amp doesn't deliver significantly more than a 90 degrees open loop phase shift at loop gains greater than unity. Most op-amps will be fine but, if you really push things too far to get a rapid response you might come unstuck. Source followers do not have the "only on...
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18 days ago
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Answer A: MOSFET drain current ringing in saturation region
It's got nothing to do with the MOSFET's miller capacitance. Miller capacitance causes problems in common-source circuits but, your circuit is common-drain (or source follower) hence, with a steady DC voltage on the drain (your power supply), there can be no problematic feedback via the miller capaci...
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19 days ago
Edit Post #291004 Initial revision 23 days ago
Answer A: Matched transistors
If the data sheet doesn't indicate that the two devices are matched then sorry, they probably are not and, you should use a matched device like the PMP5201Y that you linked. That data sheet mentions "match" 16 times and 3 times on page 1: - Imagealttext There are zero occurrences of the word "m...
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23 days ago
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Answer A: High voltage transformer design
> When should a transformer core be potted? Should it be potted at all? For this type of job, you would pot the transformer when you can't obtain the necessary creepage and clearance between the secondary (raised externally to 10 kV) and the low-voltage parts of the transformer (including the f...
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2 months ago
Comment Post #290591 You asked about inner layers and, to answer that, the number of layers and secondary voltage need specifying.
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2 months ago
Comment Post #290533 I guess I'm used to isolators for bespoke SMPSs that need tens of kV/us dv/dt withstand capability in their barrier.
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3 months ago
Comment Post #290533 The ADI devices have very small clearance and, no doubt not zero barrier capacitance so, depending what voltage is rattling around on one side of the isolator relative to the other might mean quite significant barrier currents. I'm mentioning this in case you over-looked it. A device may be protected...
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3 months ago
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Answer A: Speed of EM waves from the point of view of an electrical engineer
A loss-less coaxial cable has inductance and capacitance and, their associated formulas introduce \$\epsilon\$ and \$\mu\$. But, to home-in on the velocity of propagation, the characteristic impedance must also be determined. We can avoid the complexity of the telegrapher's equations by looking at a ...
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3 months ago
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Question Speed of EM waves from the point of view of an electrical engineer
An important formula in physics is one that relates the speed of an EM wave (c for instance) with the magnetic permeability and electric permittivity of the medium. In short: - $$c = \dfrac{1}{\sqrt{\epsilon\cdot\mu}}$$ Where \$\epsilon\$ is the absolute value of permittivity of the medium and,...
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Answer A: Transformer design for a Series Resonant Converter
> The website that I mentioned before mentions the max flux density in ferrites at 400 kHz as being close to 0.04 T. Is this correct? No, you have misinterpreted the graph. The graph shown is flux density (not maximum flux density) and is only telling you one thing; that if you increase the frequ...
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3 months ago
Comment Post #290448 The graph on the website you linked doesn't tell you anything other than current reduces in an inductor by a factor of ten when the frequency rises by a factor of ten. In other words it's useless padding by Magnetics to make their page look impressive. When current reduces by ten, flux density reduce...
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3 months ago
Comment Post #290448 **I think this calculation is wrong. The website that I mentioned before mentions the max flux density in ferrites at 400 kHz as being close to 0.04 T. Is this correct?** That is not correct and neither do I see that being mentioned on the link to the magnetics website. Also, why are you using an LLC...
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3 months ago