Fw: Re: [B9Builders] flasher circuits forthcoming, DIY style

[toblueiis]

Hello,

For my flasher designs,

I was "inspired" by the approach of Mike Loewen's Homebrew
Light Flasher Circuit on the B9 website. He used
separate oscillators whose frequency was set by the timing
resistors and capacitor. For variance, he used
the tolerance values of the components ( the higher the
better, even 20% ), to cause the different flash
rates. Instead of using 555 timers, I used a
CD40106 hex schmidtt inverter. (By the way,
regular inverter chips work lousy as oscillators, trust me.)
That sounds fancy, but it is just 6 inverters that have
specific turn on/off points (percentage wise). They
only need one resistor and capacitor per oscillator, so with
one 14 pin chip, 6 resistors, 6 capacitors, you have 6
independent oscillators. Initially, I thought of them
as random oscillators, but decided that this was probably
not accurate, since each oscillator has its' frequency set
by the resistor and capacitor and that would make it fairly
consistent, so not really random. This setup is really
independent oscillators, since each oscillator has its' own
timing components. If you wanted more inconsistency
between the different oscillators, you can slightly vary the
component values. I did follow Mike's lead
in using ULN2004 as the driver component for the outputs to
drive the lights, whether incandescent or LED. When
using this component, with 7 inputs/outputs, in only a 16
pin chip, where it just grounds the lights which are tied to
their positive lead of what voltage they are operating
under, this allows for different light voltages. For
me, I felt that truly random oscillators COULD mean that you
hardly ever saw some lights flashing, and some might flash
quite often. This flashing could still be accurately
called random. To me, their independent flashing
was more important than being totally random. I was
dependent on their independence, component tolerance, and
possible variance of resistor and/or capacitor values to
give a pseudo random effect. If a person used
flasher bulbs, this would not truly be random, as each bulb
would tend to have a fairly stable flash rate. This
rate could vary, one bulb from another, because of the
materials used in manufacturing the bulb. I think that
it is fair to say that the manufacturer is seeking a fairly
consistent flash rate between bulbs, and he would get it in
an ideal world. Since it has a fairly consistent flash rate,
it doesn't seem proper to call it random. If you can
predict the flash rate, it is not truly random.
Speaking of tolerances, I enjoy a good laugh when I order
zero ohm resistors and they come with a 5% tolerance
value. Hmmmm, 5% of zero..... (since zero times any
number is zero.) If you haven't used
resistors before, think of them as a jumper with a "body"
and no insulation to strip. Also very cheap.
They can give your circuit a nice clean look, compared to a
lot of bare jumpers.

I took advantage of the schmidtt trigger characteristic of
the CD40106 chip to give the circuit a two speed ability.
With a relay, I change the supply voltage of the oscillator
chips on the fly. With an input signal to energize the
relay, the speed changes from slow/normal to faster.
All the independent oscillators change speed at one
time. This is used to give personality, to show
excitement, or increased computing activity.

I have tried to make it simple, inexpensive, and with common
parts. I realize that not everyone wants to attempt
building circuits, but some of us actually enjoy it, so that
is why I am working on this. An ironic thing about the
circuit, is that since it is mostly IC chips, the schematic
is very close to the actually circuit layout. I have
enlarged copies of the circuit board on a copier and hand
draw in the components and work on the configuration.
I have done many different versions, trying to find cleaner,
simpler layouts. One main goal is to eliminate as many
jumpers as possible, since this slows down construction and
increases the chance of wiring errors. I am
trying to use common circuit boards such as Radio Shack
sells. By the way, the name was bought out by someone
else and they have reopened some stores.

Many other people have contributed to the club, which has
benefited me, so I am trying to help show my appreciation by
contributing to the club as I can.

thanks,

David M.

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