[sdiy] Divide by 10^6

[flightofharmony]

Thanks for all the feedback, I'll combine the responses here.

> From: Veronica Merryfield [mailto:veronica.merryfield at shaw.ca]
> What delay element are you using in you unit?

The Sound of Shadows uses the PT2399. I wanted to see what could be done
with this (almost) self-contained chip - a lot more than I expected!

The HEF4521 looks perfect, a one-chip solution! One problem I was having was
finding ICs that could handle a 22MHz clock signal, and the HEF series goes
to 35MHz @ 15Vsupply.

> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of Phillip L. Harbison
>
> You could by 0xF4240 (10^6) using 5 74x161 counters. The
> TC (terminal count) output would be connected to the PL
> (Parallel Load) input and to the clock of a D flip-flop
> configured as a T FF (/Q connected to D). This does not
> save you many chips but gives you a lot of flexibility.
>
> If you are planning to blink an LED, 20 Hz is a bit fast
> for the human eye to recognize. Dividing by 10^7 or 10^8
> (2 Hz to 0.2 Hz) is probably more reasonable. To reduce
> the chip count,
> 
> You could save some chips by using two 74HC4040 to divide
> by 2^N where 1 <= N <= 24. Dividing by 2^23 would give a
> flash rate of about 1 Hz.
> 
> --
> Phil Harbison

I try to keep my designs as compact as possible. The delay circuit itself
uses 6 ICs, so I can't justify doubling the IC count just to add a rate LED.
I would leave it out myself (I don't like LEDs) but the indicator is being
included because several customers requested it, which means I have to use a
design that won't grate too much against my OCD. :P

Flash rate: ~22Mhz is the maximum clock rate, the clock range is
approximately 2MHz-22MHz. I set up a breadboard with 7 DM7490N with an LED
at each decade to see what it looks like. 10^6  is just a little fast at the
high end of the range but the low end seemed about right to convey its
message at a glance, while 10^7 was just too slow at the low range.


> -----Original Message-----
> From: Needham, Alan [mailto:Alan.Needham at centrica.com]
> 
> A tiny microcontroller would eat this job - single chip solution.
> Use the 20MHz as the micro's clock and a simple program could even
> supply a couple of LED flash rates (or 4 LEDs with quadrature drives?).

Heh, I know, I know. But I don't even know where to start with an MCU. No
experience whatsoever, and too many things going on to take time off to
learn (sigh). Hence the "off-the-shelf" requirement.
An MCU would also be the perfect solution for the reefed/recirculate
indicator LED I'm trying to figure out. Not sure yet how I'm going to do
that, or what exactly it would be indicating...
 

Best regards, 

~flight
flight at flightofharmony.com
http://www.flightofharmony.com