Idea for crude digipot presets

[MrStab]

hi guys,

sometimes i get bored and blazed and try to think of circuits totally alien to what i'm working on at the moment. you may want to bear the "blazed" part in mind. i currently have zero interest in this sort of project, but maybe it could at least be food for thought for someone else. i love computers and tweaking those but i'm definitely not a programmer, either.

so i was reading various stuff and i came across this page, which shows you how to use a CMOS NAND gate (74HC132) to operate certain kinds of digital pot: http://www.nutsvolts.com/questions-and-answers/digital-potentiometer-manual-control (is this BS to begin with?)

then, for some reason, i was looking over datasheets for digital pots (eg. the DS1804), and i noticed quite a few had a built-in EEPROM save feature. i decided to read more in order to maybe teach myself something. all these NVM pot ICs, with the same pinout, seem to follow this condition: "Storage of the wiper position takes place whenever the CS input transitions from low-to-high while the INC is high."

So in the absence of a microcontroller, i thought maybe a switch to send V+ to the INC line immediately, but delayed to the CS input via. an RC network, could work to save the wiper position. could it? would this be too crude and unpredictable? i haven't considered discharging that RC cap or anything post-cycle yet.

Next up, a "load" or "restore" feature would be needed. turns out the wiper position is loaded on power-up, so i crudely just put a SPST between V+ and the pot's Vcc pin. no doubt that part needs more work, because it would cause problems in the signal path to just switch it off like that, but in terms of overall concept, would that work?



no resistor values as it's all just an idea. one i had yesterday, and i'm too worn out from a gig to error-check. i'm curious to hear what you guys think - even if a microcontroller could do it 10 times better, maybe this could be handy for the DIYer who doesn't wanna delve too deep into digital for some presets. things can definitely be improved upon, if it does work.

cheers!