The leader for the Montgomery County Inventors STEM 4-H Club invited me to give a talk and presentation at their Christmas Meeting/Party. Club link (search for inventors) Club Group (need to be member to view).
This was a repeat of demos I was using this year on easier to move hardware.
The STEM phone demo was push a button on a touch tone phone, capture the waveform with the PDP-8, and then do a Fast Fourier transform (FFT) to show the two frequencies the button was encoded with. I brought a XY storage monitor and added mode to connect the waveform sample points with "lines". Without the storage monitor the update rate was too slow for waveform to be usefully visible but with it you could better see the waveform. The Tektronix 611 stores the image in the CRT so it can be displayed without needing digital memory or the computer refreshing it. The PDP-8 can't actually draw lines, it can only draw a sequence of dots that looks like a line. Also had music demo, spacewar graphic game, and various BASIC games.
I intended to use a printing terminal as the console but the paper advance mechanism was too stiff after setting up so it couldn't move to the next line. It may not have liked being in the 30's in the car for an hour. Like always worked fine at home.
The 4-H club members are a wide age range. The younger members were having fun playing with the phone and printing terminal keyboard while I was setting up even though they weren't turned on. That's one of the nice things doing demos to younger kids. They love to try things.
After people got their food and settled down I gave my talk and demoed the signal processing and music. Then let people come up and try the demos.
The following picture links also have descriptions of what is shown in the pictures.
Giving talk ( 73K)
Doing the demo ( 79K)
People looking at my exhibit ( 68K)
another view (104K)
Main display ( 53K)
Printing Terminal & Ephemera ( 85K)
Repairs 1 ( 50K)
Repairs 2 ( 44K)
Feel free to contact me, David Gesswein djg@pdp8online.com with any questions, comments on the web site, or if you have related equipment, documentation, software etc. you are willing to part with. I am interested in anything PDP-8 related, computers, peripherals used with them, DEC or third party, or documentation.
PDP-8 Home Page PDP-8 Site Map PDP-8 Site Search