[GreenKeys] Loop supply options

[Steve Garrison]

One of those three folks has built four of those boards!

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net>
On Behalf Of John Nagle
Sent: Tuesday, September 10, 2019 1:28 PM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Loop supply options

> 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-N
D/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
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