DIY MIDI 74HC4051/74HCT4051 Question

Title basically says it all

DIY MIDI 74HC4051/74HCT4051 Question

Postby Kate123 » Sat Sep 03, 2016 8:11 am


I am starting a midi controller project.
I'm planning on putting 16 knobs and 9 faders on it = 25 Analog Inputs to manage with a Teensy 3.2.
Which is more than it can handle.

I've read in the USB MIDI Tutorial about the 74HC4051 and 74HCT4051 chips to cope with that.

I'm quite new to electronics and something is driving me crazy.
My problem (may not be a problem):

" For newer Teensy boards with 3.3V signals, 74HCT4051 chips are best. Power the 74HCT4051 from 5V. If 74HC4051 (without the "T") are used, they should be powered by 3.3V when used with a Teensy that has 3.3V signals, or by 5V when used with a Teensy having 5V signals. "

If i'm correct it means that, the powering of the chip and the highest voltage of the signals plugged onto it must be the same. However :

What i underlined here is what i don't understand. How can I power them with 5V (with the board only) if the board outputs only 3.3V.
Will it work with only 3.3V ?
I'm a bit lost. Please guys put me on the right track !
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Joined: Sat Sep 03, 2016 7:58 am

Re: DIY MIDI 74HC4051/74HCT4051 Question

Postby ag » Tue Sep 06, 2016 3:19 pm

Hi Kate,

Since no others have responded, I will give you my best guess answer. Looking at the Teensy specs, I see the term "5.5 volt tolerant". I would therefore tend to interpret the recommendation to suggest running the Teensy with 5 volt supply and powering the HCT from that.

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