LFOs

[Jim Johnson]

One detail that you missed is that the counters need to be reset when MIDI
start comes along; otherwise the triggers to the LFO will not be in sync
with the beat.

Jim Johnson 
Metaphoric Software
-------------------
Makers of Techno Toys
Software for Electronic Music
http://www.technotoys.com
info at technotoys.com


*********** REPLY SEPARATOR  ***********

On 6/30/00 at 11:24 PM theinmans at mindspring.com wrote:

>> I would actually be interested in buying such a midi synced lfo module
>> if it came with source code.
>> 
>> fTom.
>> (who some day will sync his vortex to midi clock which should be much
easier)
>
>This may be fairly straightforward.
>
>1)  Get a MIDI to Sequencer Interface Chip from Blacet ($16
>programmed).  
>    This will read MIDI and give you a clock.
>
>2)  a) Use a 555 Timer configured as an ADSR (see TomG's site for
>examples). 
>       Also see Barry Klein's book for examples of this chip used as
>ADSR.
>       Control the speed using a 4040 CMOS divider chip between the MIDI
>to
>       SEQ and 555.  A simple 1 to 12 rotary switch would work.  The
>ADSR
>       configuration would give you a great deal of control over the
>shape 
>       of your LFO.  OR
>    b) Use the PWM idea Harry has been describing for voltage control.  
>       Use the MIDI to SEQ chip to drive a one-shot 555 timer, using a
>pot 
>       to control the 555 pulse width of the "square" wave out.  Use
>this 
>       "square" wave trigger to drive any LFO circuit (one of the simple 
>       transistor / relaxation circuits that provide a sawtooth; 
>       a function generator or oscillator chip like the 8038(?) [see
>current 
>       Nuts and Volts] or 566 [see old Nuts and Volts for T. Henry's use
>of 
>       this as a voltage controlled oscillator]; or any of the many 741 
>       circuits you could find in anything from a Delton Horn / Forrest
>Mims 
>       / Graf Circuit cookbooks.  For a couple of very nice voltage
>controlled 
>       LFO circuits, see Barry Klein's book.
>    c) Skip the 555 timer for pulse width and go straight from the MIDI
>to 
>       SEQ to the LFO circuit through the two diode / one pot pulse
>width 
>       controller to trigger your LFO.  See Barry Klein's book for an
>example 
>       (p. 71 symmetry control). 
>
>To the extent that this is a good idea, I am sure that it is either 
>a) obvious or b) already described completely by another list member a 
>year ago and I have just forgotten who.  :-)  [Probably all from Barry 
>Klein's book].
>
>Elliot (who is counting on better minds to correct me where I am wrong,
>        lest I lead another astray)