Abate Holding Your Breath...Thompson's Design

Here you go...

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I figure, if you had a mind to, you could add regulation by running this dude in burst mode, by stopping the 555 via its RESETbar input.

Diode D7 prevents some really weird behavior from back conduction. If there were a need to tighten up the efficiency, I'd replace it with another P-channel, body in the opposite direction from MP1 (for lack of finding a suitable transistor, modeled as a 0.3 Ohm device extrapolated from my vast CMOS device library :-). Then I'd use a comparator to make the drop like a near ideal diode as in...

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My experiments with using an auto-transformer would indicate that the current capability of the hub dynamo (at least as presently modeled... I'm suspicious of its accuracy)) falls off rapidly, almost acting like a (near) constant power device.

I'd ask one of the local "pansies in spandex" to make experiments with their hub dynamos, but I'm their enemy for suggesting publicly that they should be required to be licensed, and be fined when they go riding three-abreast down the middle of a thoroughfare, rather than single-file in the bicycle lane :-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson
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Good grief, this is just a fixed-duty-cycle nonregulating buck switcher. I suggested this architecture days ago.

The 555 drains the battery all the time. If it doesn't, it won't start up. And there's probably ways to blow out the gate of the p-fet, which would take out the n-fet as a bonus. Amateur stuff.

You spent four days on *this* ?

John

Reply to
John Larkin

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Component values included!

Cheers

Reply to
Martin Riddle

My thoughts are along the lines; a couple of comparators flipping a bistable with a 3rd comparator as a UVLO, that's to prevent the buck from latchin up in 100% MSR when it draws enough current to drag the generator voltage below its optimum load curve.

Not put pen to paper yet, I'd rather find time to fully study the tables & graphs from the link Marcell posted first.

Reply to
Ian Field

Of course: "design" by Spice fiddling.

John

Reply to
John Larkin

I always do that. I had that info the very first day, as I alluded in an early post (I verbally provided the results, same as the sims now posted... which got me "naa, naa, naa poo poo"), so I just let Larkin run off at the mouth, just for the sport of it ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

You might impress a few simple people, but it certainly won't do what I set out to achieve.

I wasn't holding my breath, I wasn't expecting a useful result and I wasn't disappointed.

Reply to
Ian Field

JF will love it, since it has a 555.

John

Reply to
John Larkin

[snip]

Ian Field would best get what he "set out to achieve" by stuffing his head up his own arse. However, the circuit I presented _will_ charge the battery _and_ run the lamp. But Ian clearly has not the competency to apply it to his bicycle. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

It may have been possible to achieve something aproximating to regulation by externally pulling the 5k/5k/5k divider, but it would be a huge comromise.

There's a schematic taking shape and tempting me to put pen to paper.

But I'm inclined not to do it all for the 2 principle knowitalls that in reality don't know a fraction of what they'd like us to believe.

Reply to
Ian Field

I don't think the problem has been clearly stated. What is this circuit supposed to do, and what is the user interface? Jim's circuit leaves the lights on all the time, runs the 555 all the time, and loads the alternator whenever it can, and probably blows out the fets now and then. That doesn't sound like what anybody would want on their bicycle.

And who wants to lug around a 20 mH power inductor that dissipates a couple of watts?

John

Reply to
John Larkin

I'm thinking maximise the minimalist.

A window comparator wired-or'ed to a bistable to switch the pass transistor, a 3rd comparator also wired-or'ed to the bistable as UVLO so it can't go

100% at times of high demand. .

Eh! - that's more than the rated output of the 'dynamo'.

I'm increasingly convinced the 2 trolls are playing the mischievious misinformation game (even they can't be that thick)!

Reply to
Ian Field

How many switches do you want? What do they do?

Yes. Let's build a sophisticated impedance matcher/current multiplier to get more power out of the hub, then waste a bunch of that power in the inductor.

John

Reply to
John Larkin

As few as I can get away with.

As much as I can coax them into.

Reply to
Ian Field

OK, be that way.

John

Reply to
John Larkin

Eh!

Reply to
Ian Field

Ian, Take note-------^^^^^^^^^^

Really? It supports the lamp load AND charges the battery.

Why would it "be a huge com[p]romise" ? But you might have stability issues.

So show us... don't be a reductive Larkin replication :-)

What a bull-shit artist!

The only "user interface" would be to pedal the bike. Add a switch for daytime use.

I thought the object was to have the battery provide power when the bicycle stops at an intersection, or do you prefer to be rear-ended by a car when your tail-light goes out? Here in AZ a moonless night can have you unable to see your own hand in front of your eyes.

You have some problem installing a switch where RBAT is in the drawing? Maybe use a DPDT switch and disconnect the dynamo during daylight, though I'd opt to charge the battery during the day.

I don't know what you're harping about... it loads the alternator whenever the dynamo voltage exceeds the battery voltage. (I'd regulate using burst mode myself... easier to make completely stable.)

"Probably" ??

Here's what the dynamo looks like open and shorted....

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50s time point is same as 50kmph bicycle speed. PDF shows ramp up from zero speed. Protecting gates is trivial.

Here's a 5mH, 5 AMP, yes AMPERES, inductor for my CDI ignition, 20mH at 0.5 Amp would be substantially smaller...

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Tell us, John, how did you calculate that "couple of watts"? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

OK, disconnect the battery, forget you flipped that switch, and ride off. That will blow out the lights.

Suppose you don't want the drag, or don't want to overcharge the battery?

That depends on how you solve the problems above. Any switching that unloads the thing but leaves the alternator connected can put lots of voltage on the input. If you decide to switch the lights on (or off?) blasting down a hill with 100 volts at the input, you could get lucky and blow out the fets *and* the lights. When you design something with hazards, they tend to manifest.

And it still doesn't regulate, so can overcharge the battery.

Which is what Marcel posted a week ago.

Then why didn't you do it?

Start with the 0.7 amp alternator, double that with the switcher, dump into a 1 ohm inductor. 2 watts. But 20 mH is silly anyhow.

This thing hasn't been thought through and isn't practical. It was an act of desperation, and not a very good one. How many hours did this take?

John

Reply to
John Larkin

Barely an hour to proof of concept... but with reservations... read the thread.

But hey, John! You win! You're the Obama of electronics, lord of the

99% who can't flip a light switch without an assistant.

You and Ian have dragged SED down to below SEB. Enjoy.

I give up. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

by

Naturally.

John

Reply to
John Larkin

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