[GreenKeys] GreenKeys Digest, Vol 74, Issue 41

[gil at baudot.net]

Hi John:

Wow, I love the brass-and-glass case you made for your M15:
http://www.aetherltd.com/aesthetic.html

Beautiful workmanship, and a great way to show off the mechanism.

I am also intrigued by your BaudotRSS stuff -- texting to a tty, or
polling an rss feed is pretty cool.

fun stuff,

gil smith
greenkeys moderator
gil at baudot.net
www.baudot.net
Vaux Electronics:  480-354-5556



> -------- Original Message --------
> Subject: Re: [GreenKeys] GreenKeys Digest, Vol 74, Issue 41
> From: John Nagle <nagle at animats.com>
> Date: Sat, March 27, 2010 10:18 am
> To: greenkeys at mailman.qth.net
> 
>      I have a board design available at
> 
> 	http://www.aetherltd.com/connecting.html
> 
> Schematics, board artwork, parts list, etc. are all freely available.
> This is for 60mA current loop Teletypes.  You can still buy 20mA current
> loop interfaces commercially, so I didn't bother supporting that.  An
> external 120VDC supply is required.  I've bought 120VDC 200mA open frame
> linear supplies commercially.  I included a motor control relay circuit;
> I use a solid-state power relay for motor control.
> 
>      I don't sell parts, boards, kits, or assembled units.  Just send
> the board design to PCBexpress and the parts list to DigiKey.
> 
>      For connecting to a computer, I use the Silicon Labs CP2102, a common
> USB to serial converter part which can be configured for 45 baud.  See
> 
> 	http://www.aetherltd.com/connectingusb.html
> 
> This runs with Windows, Linux, desktops, and laptops.  I normally use
> an EeePC 2G Surf, a tiny subnotebook, to run a Teletype Model 15.
> 
>      This is packaged in a brass and wood case.
> 
> 	http://www.aetherltd.com/aesthetic.html
> 
> (I'm into steampunk, not amateur radio.  I only do nostalgia for stuff
> older than I am.)
> 
>       For software, I've written "BaudotRSS", which connects a Baudot
> Teletype to RSS feeds and SMS messaging (via Google Voice).  That
> software is available at
> 
> 	http://www.aetherltd.com/communicating.html
> 
> with the source on SourceForge.
> 
>       The heat dissipation in the ballast resistor remains
> annoying.  I have a simulated design for a solution to that at
> 
> 	http://www.aetherltd.com/public/flashsupply6.asc
> 
> which needs the free version of LTSpice to run.
> 
> 	http://www.linear.com/designtools/software/
> 
> This is an attempt to design a 60mA 120V current loop supply to drive one
> Model 15 selector magnet from a USB port, without external power.  You
> really only need 120V for the first millisecond after a SPACE to MARK
> transition.  The steady-state voltage needed, once the 4H inductance
> has been overcome, is only 55 ohms * 60 mA = 3.3V.  So this design
> uses a photoflash IC as a switching power supply, to step up the 4.8V from
> the USB port to 120V and charge a capacitor.  When the input changes to
> MARK, the capacitor dumps into the selector magnet.  There's also a 3.3V
> regulator to provide the sustain current, which takes over when the
> capacitor has discharged.  Only 250mA is required from the USB port,
> and you can take up to 500mA from a USB port.
> 
> This is just a proof of concept simulation, to demonstrate that such
> a device could be driven from a USB port.  The energy budget works.
> (At least at 60WPM; at 100WPM, there isn't enough SPACE time to
> charge the capacitor.)
> 
> So there are some more modern designs.
> 
> 				John Nagle
> 
> 
> 
> 
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html