[GreenKeys] Loop supply options

[John Nagle]

> Subject: Re: [GreenKeys] Loop supply options

   Here's a nice, simple solution:

https://www.digikey.com/product-detail/en/cui-inc/PDM2-S5-S24-S/102-3007-5-ND/4006975

A tiny 5VDC to 24VDC DC to DC converter.  84mA.
Board mount, and through hole for easy soldering.

5 of those, in series, $28.12.

You'll need a 5V 10W wall wart type power supply to power this,
but those are easy to get.

I once designed a USB powered custom switching power supply
for this application. That's a cool solution (literally,
because it doesn't waste power in a ballast resistor).
Power and data both come from the USB port.
Three people have built that board, but you have to
be able to build up modern surface mount electronics.

(https://github.com/John-Nagle/ttyloopdriver)

I use one of those on my interface board for the
keyboard side power. You need some enough voltage
on the keyboard side to push through an oil film on
the contacts.  5V isn't enough, but 24V seems to be.


			John Nagle