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Projects, Designs, and Technical Stuff / Re: Estimating time spent on Miller Plateau (maths)
« Last post by iMo on Today at 02:29:31 pm »I do not have your exact BUK model handy, but basically the LTspice shows some results..
Recent Posts
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General Technical Chat / Re: Will AC power distribution become obsolete?
« Last post by IanB on Today at 02:29:31 pm »So why do we need AC in our homes? We don't. A house could be supplied with DC power from the mains, and converted to any type of power we could require. Imagine a future where DC power receptacles are installed in a house, at a safe voltage, where electrocution is impossible, and converters simply transform the safe current into anything that is required. Synchronization between solar power and grid power will be much simpler than it is now. It takes some sophisticated equipment to synchronize AC circuits together. With DC, it's a much simpler matter.
This is obviously impractical and will never happen.
You would have DC power supplied to a home at a voltage like 240 V (necessary for efficient power delivery), and then every outlet in the home would have a DC/DC converter stepping it down to something like 24 V DC. (There are over 100 outlets in my house, so that would be dozens of DC/DC converters required.) And on the supply side, every distribution transformer would have to be replaced by a DC/DC converter to change ~10 kV to ~240 V. This would change a simple, robust, transformer with a complex, failure-prone electronic converter at millions and millions of locations around the country. No way is this sensible.
That is not to mention appliances that consume 1.5 to 3 kW that are common. At 24 V that would require up to 125 A in the appliance cord. It's never going to happen.
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Manufacturing & Assembly / Re: What is LOT number and Batch number
« Last post by coromonadalix on Today at 02:28:37 pm »https://www.linkedin.com/advice/0/how-do-you-train-your-staff-importance-use-batch
to give some ideas
or this text:
Generally, batch numbers should be assigned at the point of production or processing, with a format indicating date, time, location, and sequence.
Lot numbers should be assigned at the point of shipment or receipt, with a format indicating order number, customer number, supplier number, or other relevant information.
Electronic pcb's have or may have revisions too ...
But same answers as @Ataradov too Electronics, phamaceuticals, etc ... it change
to give some ideas
or this text:
Generally, batch numbers should be assigned at the point of production or processing, with a format indicating date, time, location, and sequence.
Lot numbers should be assigned at the point of shipment or receipt, with a format indicating order number, customer number, supplier number, or other relevant information.
Electronic pcb's have or may have revisions too ...
But same answers as @Ataradov too Electronics, phamaceuticals, etc ... it change
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Projects, Designs, and Technical Stuff / Re: Linear power supply project
« Last post by pqass on Today at 02:28:04 pm »A few more questions if you don't mind.
1) I can have a good design and good craftsmanship but if I have poor quality components I will not have a good device. How do I assure quality components? Which manufacturers do I look to?
2) The attached section of the schematic shows all the components that are deleted in the 3610a. It seems as though the section needs a complete redesign with the TIP147. Is there a reference somewhere I can use to help with that?
3) Also in this section Q1,2 will be the Darlingtons. It shows two components next to them D6,7 that look identical to Q1,2. These are not listed in the parts list and Have me a bit confused. What are they? Edit: I have uploaded a PDF of the schematic in the original post. It is much more clear and D6,7 are actually Q6,7. Still not listed parts, so still confused.
See attached refactor of the Series Pass and Driver transistors for an E3610A implementation.
The non-applicable components (those for the E3612A) were removed or replaced with a short if they were in-series. Also, only one series pass transistor + emitter resistor is shown since it's the minimum required. You can add as many as you need depending on the output current desired; needing more current means hotter transistor so double,quadruple-up to keep any one from exceeding its spec.
1) Quality of components:
If obtained from a reliable source any manufacturer equivalent part would do. The design isn't demanding; no high-speed switching requiring low ESR caps, Q1, Q2, CR4,5,8 can have many alternatives, etc.
Mini rant: HP seems to use odd valued components (non E12 series) and precision (< 5%) in the most mundane of places like pullup resistors; no BOM consolidation at all. No wonder even their simplest products are so expensive.
2) Redesign schematic for darlingtons:
The HP schematic is generic for three implementations (E3610,11,12A) but as is, it's hard to see the core within the clutter. Just re-writing it without the clutter helps (see attached).
3) Diodes across MOSFETs (I think you're referring to):
These are the "body" diodes[url] inside every MOSFET.
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Buy/Sell/Wanted / FS: [EU] MSP-FET MSP430 programmer
« Last post by samofab on Today at 02:27:33 pm »Selling my MSP-FET MSP430 programmer with a bunch of MSP430 devices.
Price: 5€ + shipping (typical price to EU: 15€).
Price: 5€ + shipping (typical price to EU: 15€).
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Projects, Designs, and Technical Stuff / Re: Estimating time spent on Miller Plateau (maths)
« Last post by Lomax on Today at 02:25:58 pm »Gate is driven directly from an MCU, which can deliver 40 mA (at 5 V). Hence 100 Ω gate resistor. The gate is pulled down with a 10k Ω resistor, to keep it from floating during start-up. While switching losses mainly occur during the plateau, I need the time from cycle start to know how large a percentage of the PWM pulse will be spent before the MOSFET is fully on, so I will use QGS + QGD to estimate the capacitance that needs to be satisfied before the end of the Miller Plateau (instead of QG(tot)). To convert this to time I will use Vgp (2.3 V) rather than VGS(on). With these changes I get:
This is actually a slightly better result than my initial attempt.
It might not be to others, but yes, to me it is. I'm happy with a an estimated "worst case", which I think the above gives. I'm also happy with 10% of the pulse width at 10% duty being spent before the MOSFET is fully on. Seems low enough that I shouldn't need to worry too much about switching losses?
- Effective gate capacitance CG(eff) = (QGS + QGD) / Vgp = (1.6n + 4.6n) / 2.3 = 2.7 nF
- Gate resistance RG = 1 Ω (guesstimate)
- External gate resistor RG(ext) = 100 Ω
- MCU pin resistance RG(drv) = 25 Ω (guesstimate)
- Total gate resistance RG(tot) = RG + RG(ext) + RG(drv) = 126 Ω
- Gate charge time TG(on) = CG(eff) × RG(tot) = 339 ns
- Tpwm = 1/30 kHz = 33.3 us
- % Miller T @ 100% duty = (TG(on) / Tpwm) x 100 = 1.02%
- % Miller T @ 50% duty = (TG(on) / Tpwm) x 200 = 2.04%
- % Miller T @ 25% duty = (TG(on) / Tpwm) x 400 = 4.08%
- % Miller T @ 12.5% duty = (TG(on) / Tpwm) x 800 = 8.16%
This is actually a slightly better result than my initial attempt.
If that's too much trouble, just guard-banding the design (design for at worst so-and-so performance, and make everything else handle the best-case result) is fine.
It might not be to others, but yes, to me it is. I'm happy with a an estimated "worst case", which I think the above gives. I'm also happy with 10% of the pulse width at 10% duty being spent before the MOSFET is fully on. Seems low enough that I shouldn't need to worry too much about switching losses?
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Manufacturing & Assembly / Re: Panelized PCBs - DIY or let the fab do it
« Last post by level6 on Today at 02:25:24 pm »Thank you everyone for the replies.
I discovered KiKit and I'm now using it to make my own panels. As stated above, there are some good advantages to creating your own, one of them is placing stenciling fiducials on the rails.
I discovered KiKit and I'm now using it to make my own panels. As stated above, there are some good advantages to creating your own, one of them is placing stenciling fiducials on the rails.
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General Technical Chat / Re: Will AC power distribution become obsolete?
« Last post by Connecteur on Today at 02:22:07 pm »Seems to me, all the more reason to abandon AC distribution all the way down the line.inefficient transformers.This one has to be proved.
From what I was able to find by doing a brief search, typical efficiency of an AC transformer is well over 95%. This is a level that few DC-DC converters can reach, and only when the load matches the operating conditions they were optimized for.
Feasibility of high-voltage switch mode DC-DC converters is another intersting topic. You mentioned a 500 kV DC line, which implies that it should be possible, yet it sounds like a much more challenging task than a good old buzzing bulky AC transformer.
I tend to think that if transformers were more efficient than DC converters, the power companies wouldn't be building so many DC transmission lines.
There are considerably more sources of loss than just transformers. The primary benefit of HVDC is in the transmission e.g. no capacitive loss, no skin effect, no need for three phases, no reactive power issues, lower peak voltages meaning smaller/cheaper insulators etc. You can have more losses in the conversion stages and still end up with better efficiency over long distances.
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Repair / Re: Terminal block screws
« Last post by gaminn on Today at 02:22:05 pm »Yes, if the screw are impossible to buy, I will replace the whole terminals. But to be honest, the terminals are OK, only the screws are missing or damaged because someone can't use the right screwdriver....
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General Technical Chat / Re: engineeringly complex problem: how to put this bike wheelset on the plane?!?
« Last post by coromonadalix on Today at 02:21:19 pm »it is not possible ? to make some mods on the frame by specialist to get fast release wheels
to make slots instead of holes and use the illustrated quick connect skew levers ? you only need one more hole for the curved washer / lock ----
attached image
why going to complicate ways and loose time and $, a friend in our Canadian race teams, has made this mod on his 10k $ carbon frame .... even i have it on a basic mountain bike
to make slots instead of holes and use the illustrated quick connect skew levers ? you only need one more hole for the curved washer / lock ----
attached image
why going to complicate ways and loose time and $, a friend in our Canadian race teams, has made this mod on his 10k $ carbon frame .... even i have it on a basic mountain bike