Slow Scan Television Experiments
Posted: Sun Oct 05, 2014 8:57 pm
Slow scan television the original System is always enjoyable to try out with a mechanical twist .
I am trying a camera idea out using mirrors or mirror ,i know an easier way would be a rotating drum on a long screw with a photo wrapped around the drum in the way old fax imaging systems used but with a laser .
But due to the problems i had on the NBTV mirror camera version i am going to try some thing similar here to see and work out problems i had hopefully ,it should be a little more adaptable to different experiments .
For a start i could just not use the frame mirror and mechanically move the sensor and just have the line mirror ,could do a flying spot SSTV camera but my heart is set on a direct light version but any case succeed or fail just show here what i have been up to of late.
My original idea on the mechanical side of things was use some dc motors and pulleys but due to the slow speeds i found it a little sloppy so redesigned it with bipolar steppers see both versions in photos posted here .
The electronic side I have a crystal clock feeding a 4040 which gives me the 15 hz line pulse and some 7490s for the frame pulse , i have put in a opto switch at the mirror corners as the mirrors are where the line control sync should be coming from in a mechanical system .
So i have used a similar system to the last project opto switch to LM311 to a 555 bistable switch so the line mirror is in sync with my clock and the opto switch and LM311 part are used for the line pulse .
SSTV cameras need a Voltage controlled oscillator so my head amp needs vary the frequency of the VCO from 1500 to 2300 from black to white .
Just going to use one of the Free SSTV programs when i get to the point of testing view on PC
I am trying a camera idea out using mirrors or mirror ,i know an easier way would be a rotating drum on a long screw with a photo wrapped around the drum in the way old fax imaging systems used but with a laser .
But due to the problems i had on the NBTV mirror camera version i am going to try some thing similar here to see and work out problems i had hopefully ,it should be a little more adaptable to different experiments .
For a start i could just not use the frame mirror and mechanically move the sensor and just have the line mirror ,could do a flying spot SSTV camera but my heart is set on a direct light version but any case succeed or fail just show here what i have been up to of late.
My original idea on the mechanical side of things was use some dc motors and pulleys but due to the slow speeds i found it a little sloppy so redesigned it with bipolar steppers see both versions in photos posted here .
The electronic side I have a crystal clock feeding a 4040 which gives me the 15 hz line pulse and some 7490s for the frame pulse , i have put in a opto switch at the mirror corners as the mirrors are where the line control sync should be coming from in a mechanical system .
So i have used a similar system to the last project opto switch to LM311 to a 555 bistable switch so the line mirror is in sync with my clock and the opto switch and LM311 part are used for the line pulse .
SSTV cameras need a Voltage controlled oscillator so my head amp needs vary the frequency of the VCO from 1500 to 2300 from black to white .
Just going to use one of the Free SSTV programs when i get to the point of testing view on PC