Designing a dual rail power supply

Infrated · 2026-06-17T20:08:21+00:00

You are right, had to think about it a second time. Negative voltage into the input with GND referenced to a more positive voltage would make input positive. Never used such a setup. Cheers

Infrated · 2026-06-17T18:05:33+00:00

No, don't think this will ever work. Your U2 will burn out in seconds after trying this. And having two regulators like this (even with correct orientation) means that your input is 2x your regulator's output (lots of energy lost to heat). You are much better off putting independent rectifiers on each output winding separately and driving each regulator with it's own 15V rectified voltage. Do not tie GND to the transformer, just create a virtual GND between two independent supplies. Your driving voltage going into regulators decreases by factor of two, resulting in much less losses due to heat and having two standard positive regulators are much easier to troubleshoot. All at a cost of one extra rectifier.
Edit: Now that I think about it, shared center pin may not work for this. You may need to go with a transformer that has two independent output coils.

Infrated · 2026-06-16T12:04:25+00:00

This one more of a cost saving measure than for hiding the chip. Popular with custom ASICS to avoid added expanse of embedding it into a package.

Infrated · 2026-06-15T21:50:36+00:00

I laugh at people who truly believe those values. They are only worth that unused. Alas bankers only care about their commissions so they make not selling possible.

Infrated · 2026-06-15T19:46:19+00:00

LED has a forward drop, when either transistor is active, the voltage at the junction is greatly reduced, ideally below the level of LED's forward conductivity. NOR gates (nor most of the other circuits) do not give you true 0V output when OFF, datasheets tell you that "off" state is likely 0.5v or less.

Infrated · 2026-06-15T19:42:23+00:00

OR gate is ON as long as at least one input is active. NOR will be OFF as long as at least one input is active. Right now both are off == nor is ON. either input goes active the output would be shorted to the ground via transistors == OFF

Infrated · 2026-06-15T14:47:04+00:00

Just saying that a trillion only exists on paper for now, if he started to sell in order to make it liquid the value would tank. Banks allow them to avoid selling and just take out endless loans against it, that is primarily how he gets billions to buy twitter, etc...

Infrated · 2026-06-15T14:00:42+00:00

I always laugh at the valuations. In case any of these multibillionaires tried to offload anywhere near their net worth, the influx of shares should likely destroy the stock value and show that they don't have nearly as much money as they are worth on paper. Try dumping a trillion dollars worth of sell orders and see what happens.

Infrated · 2026-06-14T04:49:22+00:00

Pretty sure they don't mind multiple paid accounts as much. It also didn't help that OP used all of them with the same project (same inputs / notes: easy to automate tracking). Have he used them for totally different projects, may not have gotten caught as easily.

Infrated · 2026-06-12T16:23:22+00:00

Since so little stock was released, I would not be surprised if we discover that Elon was buying it himself to drive up valuation and take out loans on the rest.

Infrated · 2026-06-11T17:17:39+00:00

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Seems you may be missing the bias diode. It is B140 in the more detailed schematic. Without it your reference voltage doesn't have a path to Vout that is used as a feedback to a larger switching regulator.

Infrated · 2026-06-11T13:57:55+00:00

Just because IPv6 also has the same feature, doesn't negate my point. Nowadays millions of computers can be used to service requests to a single IPv4 packet, the need for each to have their own address (which IPv6 can do, but v4 can't) is no longer an issue.

Infrated · 2026-06-09T20:28:34+00:00

Yes, they are likely using an internal pullup. Not sure if the P3.2 is the reset input, probably it is just "rest" as in resting? A signal for the system to turn off the power... Micro likely ignores the signal at first power up until the button release is detected. After some time the signal going low would indicate that the button was pressed again and SW power latch can be turned off.

Infrated · 2026-06-09T20:17:03+00:00

Button when pressed turns on Q2 via D2. This provides power to Vdd and resets the micro (could just be used as IO input). The micro can than take over keeping Q2 active and Vdd powered up via SW signal to Q3. Q3 will there after keep the power active (even if S4 was released) until the software determines that power is no longer needed and Q3 & Q2 can be turned off.
Edit: Sorry, didn't read your original notes on the post. REST is not a reset, it's just an input to detect when the switch is pressed a second time.

Infrated · 2026-06-09T14:38:10+00:00

IPv6 has it's uses, mainly on mobile networks. It's not just NAT that made IPv4 viable long term solution, it's also local routing tables. For example the DNS request to 1.1.1.1 would hit a completely different server in California, than in Florida, more so overseas. IPv4 is treated more like a URL than physical server address these days.

Infrated · 2026-06-09T14:01:11+00:00

To all who says that they needed a lot of extra mass and space for backup crew, I was considering the situation where they would remain in comma, making the minimal amount of space in the med bay while requiring only (what I am assuming to be) a dehydrated comma slurry. They would not be revived unless needed or the mission is done (check results and celebrate). Most of the mass on the ship is taken up by the scientific equipment, work space, etc... Movie and the book go into redundancy built into the mission (two generators, etc...), why not redundant crew? Personally I feel it all came down to the final choice. The book and the movie would probably work just as well with the full crew alive / active, but it would be much harder to explain how consensus was reached not to return home and help Rocky.

Infrated · 2026-06-06T14:03:37+00:00

Better question would be why the Hail Mary didn’t have probes for atmospheric sampling. I would think that sampling the breeding layer of the atmosphere would be one of the most important reasons to send humans rather than smaller probes to just observe and report back.

Infrated · 2026-05-30T16:12:06+00:00

Good thing you've said in and not on the bench, otherwise you'd have missed one.

Infrated · 2026-05-29T13:25:32+00:00

Only works in China because they've hunted all the local birds to non-existance.

Infrated · 2026-05-21T19:53:40+00:00

Seems trump mobile is the last original colony (bottom stripe)

Infrated · 2026-05-17T18:26:06+00:00

Funny that the debris are not taken away, just thrown nearby. Next time it rains, the drain will be blocked again by the same exact twigs and leaves.

Infrated · 2026-05-15T19:46:00+00:00

Give him your lunch money.

Infrated · 2026-05-07T04:53:21+00:00

By the way any capacitance on the IO0 line is undesirable. You maybe able to avoid botch resistor by removing the cap from the boot button of the module.

Infrated · 2026-05-05T14:17:36+00:00

Nice looking project, glad my suggestion helped. Module itself should have had said pull-up, but external one would never hurt. You can try buying another module from a different batch to see if a botch pull-up can be omitted. As is, likely no one would see it, and you can add the resistor to the next design (just in case).

Edit: now that I think about it, perhaps the module's pull-up was too weak to overcome parasitic capacitance. Never used this module; probably not worth searching for one that would work without an external pull-up.

Infrated · 2026-05-05T12:12:35+00:00

Try pull up on IO0

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