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| digitally controlled potentiometer? I got this! |
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| VK3DRB:
I think we have the next Steve Wozniak here. Can't wait for iPot 2.0 :D. The production volume world wide in the first year is forecast at 1. Seriously, you could put in a closed loop control algorithm and you could get an accurate resistance, but mechanical hysteresis could present a problem, making it not too different to the resolution of a digital pot IC. |
| retrolefty:
Whatever it takes to move the project on is what I say. :-+ The fundamental concept is valid. For a more professional rendition for this concept one can look here: http://jimmyauw.com/wp-datajim/audio/119_alps1.jpg Another advantage of this kind of arrangement is that one can both manually manipulate the pot as well as electrically. That is something you couldn't do with the hobby servo drive unless you power off servo when not changing values. IC volume chips are very handy but as already stated there are real limitations that the chip solution can't meet for some applications. |
| SeanB:
Problem with the ALPS motorised pots is that they invariably are a log law ( typically audio taper using 2 track segments) and also are limited to a few low power rated resistance values. Servo upgraded one will work and you are free to use any pot in any power rating with only needing a shaft that is adjustable via a knob. If it needs 200Nm to turn you just get a big enough servo driver to move it. |
| Galenbo:
--- Quote from: German_EE on September 04, 2015, 09:23:12 pm ---A few observations: 1) Your average digital potentiometer on a chip will only work to the chip supply voltage, feed anything more than this and you let the magic smoke out. 2) Your average digital potentiometer on a chip is a low current device, this method could be used with a wirewound resistor in medium current applications. 3) Most digital potentiometers use either I2C or SPI which means a microchip somewhere, this technique could use a simple 555 chip. 4) Isolation between the control signals and the variable resistor is very good, useful for high voltage applications. So, this particular implementation may not be too neat but the idea is sound, --- End quote --- I used an optocoupler for that in the past. All potentiometers I saw are used as variable resistor or voltage divider. A simple schematic with some resistors can do that. It isn't digitally controlled, an additional D/A or reconfiguring an output pin can do that. also from me: --- Quote from: Melt-O-Tronic on September 04, 2015, 05:26:13 pm ---Facepalm + high five! :clap: --- End quote --- |
| canibalimao:
--- Quote from: rx8pilot on September 04, 2015, 05:50:54 pm ---You do know that there are many i2c and SPI digital pots on the market right? One that I have used before.... http://www.digikey.com/product-search/en?KeyWords=MCP4661T-503E%2FMLCT-ND&WT.z_header=search_go --- End quote --- Yes, but using this packages in DIY projects is not very handy... About the motorized pots, they are a bit expensive and run it on a low power environment could be a bit tricky... I know that a servo isn't better than this, this was just a funny project. |
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