[sdiy] Doepfer E510 Keyboard Scanner
steve at bendentech.co.uk
Wed Feb 6 11:12:12 CET 2019
On 06/02/2019 03:21, Miles Stevens wrote:
> Poking around the web looking for a polyphonic keyboard scanner to MIDI
> solution and stumbled on the Doepfer E510 IC through an Elektor project
> that utilised it. Seems quite old now but wondering if anyone had
> experience with it?
Ah, a blast from the past!
In the UK, Maplin used to sell the E510 in their shops and catalogue. It
was very expensive for a single IC but did something that was otherwise
much harder to do in those days (late 80s/early 90s).
Yes, they kept their package pin-count down by reading only a single
pair of switch contacts at a time and requiring that the address be
externally decoded. But it is hardly rocket science to interface it to a
standard keybed - in fact, you could argue that by not committing to any
particular matrix arrangement, it is more flexible.
Want an example of how it can be done? Check out the article on p40 of
the August 1992 edition of ETI magazine written by...ahem...me:
I remember sitting in the university library drawing the PCB layout by
hand on acetate - happy days :-)
Please note that there are a couple of minor errors in that article.
First, each keyboard J-wire should have an isolating diode in series
with it, pointing towards the row drive line. I forgot to include them
in the schematic because I was using surplus keyboard mechanisms that
already had them present.
Secondly, the 1Meg pull-up/down resistors on the switch read lines are
too high and should be lower for reliable operation, particularly of the
last key in the matrix.
FWIW, I built a six-octave keyboard by splicing together two surplus
three-octave mechanisms that were originally peripherals for the
Sinclair Spectrum. They only had SPST switch contacts, so I added new
SPDT busbars but kept the original J-wires.
Hope this is of some interest - thanks for the memories!
Benden Sound Technology
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