General > General Technical Chat
The 'Dial-In' jumperless Breadboard, MK14, Nominal Animal, (and buck boost cir)
RJSV:
Well now; This one has to be dedicated, to members here, doing same or similar related posting topics.
My 'project' is maybe very casual, but nevertheless a serious venture into electronics and questions I never encountered, before.
The nebulous idea involves serial strings of various subassembled units, like the ubiquitous Solar Garden lights, I've mentioned on EEVBLOG. (Some was when I used the handle
'haywardcpu'.
Seems I start thinking about the buck voltage doubler used in those garden LED lights, and next thing you know; TWO other posts appear, threads concerning buck boost circuits and inductance.
I figure 6 switches, and 6 modules, can be switched into serial orders of variety somewhere around 1300 permutations.
I have two solar light modules, a resistive CDS light sensor, and a 'Christmas Card' LED moving display. Obviously, many many variations will turn out to be useless.
But I'm curious. Things done 'loosely' like this can have interesting and educational surprises.
Happened before, on various other projects.
Also, other people's threads have things that relate; will try to include those as I go.
Photo showing two garden light circuits, as they are connected in serial form. What that means, is the LED OUTPUT from the first module, connects directly to the Solar Cell input, of the following module.
The results are a bit puzzling, (already, lol)!
More soon...thanks
RJSV:
I kept debating, frivolous, or useful ?
That setup I showed sat for several days, needing simply two wires stripped, for the two conductors running from first LED unit, to the next (via it's own solar cell input). Second unit solar cell, actually, to be a separated, object in the serial switching scheme. That way, you've got an easy natural connection as was original when purchased as complete solar light with self-contained LED.
Right away I've gotten perplexed; the Buck-Boost oscillator waveform coming out WAS capable of driving the next module in line (directly, not optical).
Best I can figure, that first output has enough low or zero voltage signal to cause the following unit to think it's nighttime. These units use zero volts as a sensor would be used, as the photovoltaic cell itself can also be used to sense ambient light levels.
The whole little test, in the bench there is giving indications that the second unit, in line, is thinking that it's dark (and so it lights up). That second unit has its normal LED connected.
Had the scope set up wrong, actually needed to use negative slope for trigger!
Duhuh mm.
RJSV:
The overall scheme relies on 6-position rotary switches; these switches come with two separate levels, for a 2P6T or Two-pole, 6 throw type (also with cute chickaen haed knob).
I figure two switches gives 6 X 6,
three switches gives 36 X 6 or 216 possible (with one option being a null).
Oops; I guess that comes out way higher number of possible configurations, sorry.
Some 40,000 ways. I can always downgrade, to 5 and 5, to have less, uh, testing to deal with.
RJSV:
First decisions involve keeping things intact; that means not shorting two outputs, meanwhile connecting inputs together freely. So each 'stage' would be one device, driving one line on the system bus. That'd be the Wells, so to speak, that each device can connect to. Ironically, I got caught up in auto-debates...as question comes up:
Do you really need to connect, like, unit2 input to the (same) unit2 OUTPUT ? So the compromise is, that specific position would, instead, connect to a push-button. I still do want that option,....so but it will be easy to rewire some so any of the active units (solar light modules, usually) can, yes, be connected to it's own input, later. Ridiculous.
The learning area for me would be gaining the skill to understand that waveform, of the voltage boosting oscillator. As shown, I highlighted the rising edge, of the passive collapse of mag field. I say passive as the 'shorting' transistor has opened, starting the whole field collapse and voltage rise.
What if some student wants to know specifics, about L-R time constants as you can see the LED OUTPUT voltage rise, to about
2.2 V and then a decay curve. I'd be challenged to explain those inductor dynamics, in any academically useful manner!
As to the brief example, running the LED OUTPUT voltage direct into another unit, would be considered a 'Non-Inverting' cascade...would have preferred an 'Inverted' relation, but thats what I get. Have considered including a couple of mid-power NPN transistor, like 2N2222.
If I scoped it properly that oscillator runs at 250 khz, but that doesn't seem right ?
RJSV:
Photo shows the preliminary set that might give useful variety of configurations.
Suppose you wanted to switch these in, keeping a serial order that matches the order of possible elements.
The first 2P6T switch would connect to unit 6 (for circular wrap). Second switch is placed to get it's input from first element. Third switch is placed to get it's input from unit2. All the way to the last switch, sixth switch, which selects element five as input.
I've informally gathered two solar light units, one motor unit, with oscillating lever (from a greeting / birthday card), a couple of LEDs, and a speaker, if I can.
For audio, a speaker is nice, but 8 ohm types need power. Maybe just a piezo style speaker, that doesn't load things down.
One choice of elements would be nice to be open, undedicated, for attaching AN ACTUAL BREADBOARD....(just so as not to hurt anybody's feelings, lol).
That comes out to six elements that can / will select which I put they want.
One irony, the Solar Lights actually present a 'logical high' voltage potential, when sitting passive, by way of the 1.5 V battery cell through the inductor. So the 'binary' states would be:
OFF. =. OUTPUT 1.5 VDC
ON. =. OUTPUT 250 KHZ Square wave.
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