Many Analog Inputs

[mister_e]

yup 4051 was the one i used too. Few I2C i/o expander were used to control those 4051 lines... well i had 27 of them on-board after all

[Darrel Taylor]

I went the 4051 route before too, but had several problems.

There are 2 different versions. CD4051 and the 74HC4051.

The CD4051, was completely useless. Very high ON resistance (~300 ohms), and very high cross-talk between channels.

The 74HC4051 was better, lower ON resistance (~80 ohms), but the crosstalk was still unacceptable. Readings were still affected by the input from the other channels.

Ended up using a MAX4617 instead. 10 ohm ON resistance and very good crosstalk rejection. (pin compatable with 4051)

A bit more expensive, but it was worth it.

They also have a couple 16 channel multiplexers. Might help with the POT count.
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[mister_e]

So i had to be lucky... done since 1 year 1/2, no problem, about 1000 unit sold as now....mmm.

[Darrel Taylor]

I suppose it depends on the application. If being 5-10 counts off (10-bit) doesn't matter to your program, then no one will complain.

In mine, it was too much error.

And, only 400 sold (so far).
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[mister_e]

Yup, you're right. In fact the whole 10bit accuracy wasn't really needed. 8 bit was enough to do the job (motorized fader and pots position). longer ones 100mm /256 steps = 0.4mm or so... not a human will see it.

But i'll keep in mind the one you sugested.

[Ioannis]

Thanks to all for the replies.

I found another multiplexer, 74HC(T)4067, 16 to 1 analog. I think it is the one to go (will support 8x16=128 pots maximum!).

Darrel, in your case I suppose that you had AC signals? That's why crosstalk was important. In my case and maybe Steve's DC or low freq does not need any good crosstalk parameter. A HC series might be just fine.

Again thanks to all (and Steve for the files, I got them).

Ioannis