Steve, as usual, you are correct! I did not take the full-wave rectifier into account, which I should have after staring at the waveform on the oscilloscope. The math makes more sense if the dynamo output AC frequency is doubled. I probably won't even mess with the values then.
Standlight vs Voltage Doubler
- Thread starter mbanzi
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Steve K
Flashlight Enthusiast
well, I forgot all about it too. 
One of the early things I learned when designing or troubleshooting was to document everything you do. It's as much for the benefit of others as for myself. I know that if I have to go back and look at something 6 months or a year later, I won't remember much at all. I've had various times at work where someone has asked "do you remember that project 8 years ago? Any idea why we did <blank>?", and I've usually been able to find my files and give them an answer. Who needs a memory when you have a good filing system?
One of the early things I learned when designing or troubleshooting was to document everything you do. It's as much for the benefit of others as for myself. I know that if I have to go back and look at something 6 months or a year later, I won't remember much at all. I've had various times at work where someone has asked "do you remember that project 8 years ago? Any idea why we did <blank>?", and I've usually been able to find my files and give them an answer. Who needs a memory when you have a good filing system?
Hi mbanzi
I have a recollection that I designed that circuit - I may be wrong - I certainly used it in my old incandescent one-or-two-bulbs-in-series switch.
the monostables are re-triggerable, and edge-triggered
It is the period of the first monostable that sets the rotational speed at which the switch triggers.
At low speed, it output is a train of pulses, keeping the second mono triggered.
Once the first mono receives input edges above a certain rate, its output pulses meet, they become a solid logic level with no edges. So the second mono no longer receives edges, so its output becomes a solid 1 (or 0, I can't remember).
The second mono timing is not critical, but gives a handy delay to stop flickering near the transition - so a second or so is good.
The other Steve
Thanks Steve! Once I drew a timing diagram it all made sense to me - I would have never thought of that. I guess that's why my my EE friends say microprocessors make you lazy.
You are welcome. After I posted, I noticed Steve k had already explained it.
Even though I was a hardware eng (and therefore cannot be trusted to write object-oriented code
, I have done two microcontroller-controlled dynamo light circuits. I went the software route because it cuts the number of components down - generally to one chip and a handful of other components. MCU timing does a great job of removing the need for monostables - BTW - that circuit above is a common one, it has the disadvantage (in some circumstances) that it also gives the high-speed output state at 0mph.
That said, if you go entirely MCU, you do have to write lines of code to cope with situations that a single capacitor would cure in the hardware realm!
I am very happy to be as helpful to you as I can.
For example, I did a nice one-transistor interface circuit to get safe timing pulses into the MCU from the nasty world of dynamo voltages, and a few other bits and pieces.
Sadly, I cannot post diagrams - I don't know how and don't want to spend time learning, but I can always email them to someone who has learned.
I could design hardware for you if you like - as could Steve K, who is probably a better bet for selecting inductors as he has more switching power experience than me.
The other Steve
Steve K
Flashlight Enthusiast
Mr Bandgap can correct me, but I think the circuit is an evolution of the "missing pulse detector" circuit that is found in the datasheet or application notes for one-shot circuits.
Back in the day... databooks were a treasured resource, containing lots of helpful circuit ideas and application ideas. Many common problems had already been solved in the past and a solution could be found in the databook.
there are still some circuits where some basic logic IC's provide the most cost effective solution. They are certainly a good thing in terms of not going obsolete or having software issues. I recall seeing some small parts for earthmoving equipment that were designed around a LM556 IC or a hex inverter package. These parts have been in production for decades and will likely be around for another decade or two.
For more complex functions, however, a little uC makes a lot of sense.
Hi Mr K
You were up early!
Indeed, I still have shelves full - and what a lovely resource they are for tricky little circuit issues.
For anyone reading this, flick through a Jim Williams application note to see a master at work
Indeed, and in the case of HC and HCT cmos logic, an almost unbeatable solution.
My favourite bit is the input protection structure, which enables the chip inputs to interface to many volts, even hundreds of volts, with only a single resistor per input.
I also like the negligible quiescent current in static state - who needs a power switch
The Other Steve
You were up early!
Or 'speed switch' as I remember. I may have copied your design Steve.
Indeed, I still have shelves full - and what a lovely resource they are for tricky little circuit issues.
For anyone reading this, flick through a Jim Williams application note to see a master at work
Indeed, and in the case of HC and HCT cmos logic, an almost unbeatable solution.
My favourite bit is the input protection structure, which enables the chip inputs to interface to many volts, even hundreds of volts, with only a single resistor per input.
I also like the negligible quiescent current in static state - who needs a power switch
The Other Steve
