Posted: Thu Apr 25, 2013 11:19 am
Ok everyone here's the latest updates on my NBTV camera/monitor.
Firstly I replaced the glowing 22k pot, stuck a good 20k pot in and no more glowing which is good. As mentioned the 400Hz clock is working good, on output I'm getting rocksteady 2.5ms square wave!
Then next was to do what Gary suggested, feed a NBTV signal to the monitor to accurately adjust motor speed to 750 RPM so from my MP3 player I fed a some NBTV files to the input of the video sync mixer circuit and up came the the NBTV pictures easy .
After getting the motor to around 750 RPM I then fine tuned the speed control to get as best as possible sync, then I adjusted the encoder disc circuit to see if I could get the sync locked in but no success. Now questions about the encoder disc circuit, the width of the negative pulse part of the wave form on scope, is that meant to be 2.5ms?
So yeah the sync is for some reason not working properly. During testing I have been wondering about some things. Having the encoder disc uncovered and exposed to any light I wonder if stray IR light is coming in from daylight coming into the garage, I know for a fact my 150W lamp emits IR light and was affecting the encoder disc circuit dramatically until I stuck a bit of wood in the way. Also distance of the IR LED/phototransistor from the disc, does it have to be a particular distance? And I am wondering too with the motor/disc spindle, there is a bit of time for readjustment of speed due to the momentum factor, would that upset the sync?
Anyways I have made a video log for you all of what's currently going on with my camera, in the video I have NBTV signal source plugged into the video/sync mixer board and I am demonstrating and talking about what's happening, the video is 15 minutes long so I had to upload it to Depositfiles as it was 118mb, you can download it from this link http://depositfiles.com/files/uyc2wmvz3 .
THOUGHT FLASH: Oh one this just occurred to me, looking at Harry's schematic of the main sync board, I notice there was a connection between pin 3 of the 555 timer and pin 3 of the 4046 but a then a couple of lines drawn over which I "assumed" as an indication of a wiring mistake so I didn't connect the pin 3s together, question for Harry, those 2 lines are they crossout of a wiring mistake or is it meant to be a capacitor? If so then there's at least one of my problems!
Anyways as promised here are all the schematics I used, some are from Harry's circuit sketches and some come from past NBTV club newsletters. Also in the pics below are the waveforms on the scope of what I'm getting in certain key areas of the circuitry:
Firstly I replaced the glowing 22k pot, stuck a good 20k pot in and no more glowing which is good. As mentioned the 400Hz clock is working good, on output I'm getting rocksteady 2.5ms square wave!
Then next was to do what Gary suggested, feed a NBTV signal to the monitor to accurately adjust motor speed to 750 RPM so from my MP3 player I fed a some NBTV files to the input of the video sync mixer circuit and up came the the NBTV pictures easy .
After getting the motor to around 750 RPM I then fine tuned the speed control to get as best as possible sync, then I adjusted the encoder disc circuit to see if I could get the sync locked in but no success. Now questions about the encoder disc circuit, the width of the negative pulse part of the wave form on scope, is that meant to be 2.5ms?
So yeah the sync is for some reason not working properly. During testing I have been wondering about some things. Having the encoder disc uncovered and exposed to any light I wonder if stray IR light is coming in from daylight coming into the garage, I know for a fact my 150W lamp emits IR light and was affecting the encoder disc circuit dramatically until I stuck a bit of wood in the way. Also distance of the IR LED/phototransistor from the disc, does it have to be a particular distance? And I am wondering too with the motor/disc spindle, there is a bit of time for readjustment of speed due to the momentum factor, would that upset the sync?
Anyways I have made a video log for you all of what's currently going on with my camera, in the video I have NBTV signal source plugged into the video/sync mixer board and I am demonstrating and talking about what's happening, the video is 15 minutes long so I had to upload it to Depositfiles as it was 118mb, you can download it from this link http://depositfiles.com/files/uyc2wmvz3 .
THOUGHT FLASH: Oh one this just occurred to me, looking at Harry's schematic of the main sync board, I notice there was a connection between pin 3 of the 555 timer and pin 3 of the 4046 but a then a couple of lines drawn over which I "assumed" as an indication of a wiring mistake so I didn't connect the pin 3s together, question for Harry, those 2 lines are they crossout of a wiring mistake or is it meant to be a capacitor? If so then there's at least one of my problems!
Anyways as promised here are all the schematics I used, some are from Harry's circuit sketches and some come from past NBTV club newsletters. Also in the pics below are the waveforms on the scope of what I'm getting in certain key areas of the circuitry: