Arduino Hellschreiber

I have had the idea for a while about whether one of the Color TFT displays for an Arduino could display Hellschreiber. Well I got some encouraging initial results when I attempted it on one of these displays.






A friend had told me about these displays that Radio Shack is closing out in their stores now. They are the Seeed 1.0 2.8 inch TFT displays selling for around 15 bucks! The newer models else where are 35 bucks.






Since it is a shield that plugs directly on top of the Arduino Uno I had to "tether it" via jumper wires so I could access the analog ports.






The display does use some of the analog ports if you want to use the touch screen part, but there is two unused ports even if you do, I left them all unconnected with my tether.

I constructed the following 2N3904 circuit with an electret mic to acoustically couple the Hellschreiber signals for my initial tests.






I am still working on the code and trying to develop some simple image processing methods to make it easier to use, but I have a long "to do" list.

1.) Modify the input circuit with an isolation transformer for direct connection to receiver/transceiver (e.g. PFR-3A).
2.) Code the contrast image controls in software
3.) Code the transmit Hellschrieber
4.) Build a keying circuit interface
5.) Build a shield that plugs between the Arduino and the Display to make it a clean package.

The idea is to have a small standalone Hellschrieber terminal that can connect to any standard CW transceiver. The Arduino makes this a nearly instant "on" system requiring no computer and ready for portable or field use.