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April 01, 2015, 08:26:41 AM
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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  a/b/c/d - select one or sequence - logic for switching 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: a/b/c/d - select one or sequence - logic for switching  (Read 648 times)
Posts: 3384

I couldn't resist

a/b/c/d - select one or sequence - logic for switching
« on: March 14, 2014, 08:37:18 AM »

shown is the formunkys dual-mode data select logic. using a 6pole/2pos rotary and 4 momentary switches, the user can, in select mode, choose any one of 4 outputs. in the sequence mode, the user can step through each of the four outputs, using one switch. "on" outputs can be "added" one at a time, up to the full four shown, and stepped in sequence. all four outputs can be muted at once.

but there's more. invert outputs, !Qn (I can't find a bar to put over Q on my keyboard) are also available, so the on/off-sequence compliment can be utilised, instead or as well. the four outputs can be used to drive anything, logic gates, bjt's, mosfets, jfets, indicator leds as indicated, buffered relays or cmos switches. and the 4 can be expanded, by adding a flip/flop with the right (clear or !clear) logic, a diode (or a proper OR gate) and a mom switch for each channel extra.

parts values are not critical. the ic's themselves are not critical, they can be 4000 series at 5 to 15 volts, vegulator or not, or mixed 74HC/4000 with a 5V reg. the seq mode can be hardwired, saving a mom switch and the rotary; the sel mode can be hardwired, saving just the rotary. the circuit shown includes mode indicators (there was some switch spare) and Q status leds, which can also be un/driven from V+ and the !Q outputs.

in use: in the select mode, the user presses the switch s/he want "on". that is all this mode does, one (Qn) output selected at a time. the !Qn outputs will be one output "off" at a time, logic is like that. the initial state may be all Q's off, but selecting 1-4 overcomes this.

the sequence mode is a bit tricky. step on either "sw1" or "sw2" to shift the "on" output (and the corresponding "off" !Q output) by one place. 1-2-3-4-1-2 and so on, in ring fashion. because logic gates can't be guaranteed to power-up in a particular state without a power-on reset, "sw3" will reset all Q outputs to "off", or mute. as there is now no data to step through the ring, pressing "sw4" will "add one" "on" Q output. this is always "Q4", as you would expect by pressing the button so marked.

and yes, to answer your question, it does. press 3 to reset, press 4 to add one on, press 4 again and you have 2 outputs on, "Q1" and "Q4". this is because "add one" also steps "Q4", then turns "on" "Q4". and yes, you can have 3 or 4 outputs on at a time, that's another good reason to have a reset. and if you clear, add one, step, then add one, you get "Q2" and "Q4" on, and stepping then shifts both around the ring by 1. now you have the start of a chaser. add another, and step a single "off" around the "Q" ring.

so there is the logic, or at least how to do the logic. I don't know how you want control your signal flows, so there is no output controlling elements included. there is not much you can't tack onto this, expand or contract. I may have re-invented something again, but I only have 4 monkeys and 4 typewriters, and I don't like shakespeare.


"In computer jargon, my plans have all gone tits-up" - Holly. s8, e3
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