Re: Mini version of Scophony - its do-able
Posted: Tue Jan 26, 2021 9:02 am
Harry,
I have looked through your post on scope modulation, you got very good results, especially the syncing on both line and frame scans.
Although Steve is right, most of this can be done using just a single pic microcontroller, my thoughts are also to go for a simpler way by using similar circuits to the Klass sync and NBTV circuits, and add to this the additional logic electronics to be able to drive the stepper motors. When I complete this project, successfully I hope, it would be interesting to do a pic version of this.
The first part which I am currently building, the sync separator is very similar to the NBTV televisor and Klass circuits as previously shown. As for the missing pulse restorer, I have now re-designed this as shown below, to use 4098 dual monostable instead of the 4001 gates, as this may be more accurate.
To simplify things for different line resolutions the first monostable makes the sync pulse width standard at 500 usecs for all resolutions (32 lines 400 hz, 60 lines 750 hz, 120 lines (1500 hz) Etc at 12.5 frames. Although this pulse width is much higher than the standard sync pulse width, the sync pulse here is only required to drive the stepper motor and even at 1500 hz it will operate.
The second monostable provides a delay of exactly one line scan interval with selection of line/frequency resolution by manual switching . The final monostable again provides a pulse with 500 usecs width from the delayed output of the second monostable.
By mixing the 500 sync pulse from the output of monostable 1 with the delayed output of monostable 3 by using an OR circuit consisting of the 2 diodes and resistor, the missing pulse is replaced, without any phase change.
I have looked through your post on scope modulation, you got very good results, especially the syncing on both line and frame scans.
Although Steve is right, most of this can be done using just a single pic microcontroller, my thoughts are also to go for a simpler way by using similar circuits to the Klass sync and NBTV circuits, and add to this the additional logic electronics to be able to drive the stepper motors. When I complete this project, successfully I hope, it would be interesting to do a pic version of this.
The first part which I am currently building, the sync separator is very similar to the NBTV televisor and Klass circuits as previously shown. As for the missing pulse restorer, I have now re-designed this as shown below, to use 4098 dual monostable instead of the 4001 gates, as this may be more accurate.
To simplify things for different line resolutions the first monostable makes the sync pulse width standard at 500 usecs for all resolutions (32 lines 400 hz, 60 lines 750 hz, 120 lines (1500 hz) Etc at 12.5 frames. Although this pulse width is much higher than the standard sync pulse width, the sync pulse here is only required to drive the stepper motor and even at 1500 hz it will operate.
The second monostable provides a delay of exactly one line scan interval with selection of line/frequency resolution by manual switching . The final monostable again provides a pulse with 500 usecs width from the delayed output of the second monostable.
By mixing the 500 sync pulse from the output of monostable 1 with the delayed output of monostable 3 by using an OR circuit consisting of the 2 diodes and resistor, the missing pulse is replaced, without any phase change.