Mirror Camera project

[gary]

Oh that looks very plausible except you have the wrong monostable output - we want positive going pulses (because that's what comes out of PD1).

[Harry Dalek]

Yes but what I was trying to do was get to the bottom of why the syncs are so long - pretty hard to do when they are not there! LOL

True True ,i think i have been more worried about distortion side ,Taking to you about the video sync mixer i didn't realise how much one effected the other.

basically what I am trying to do is get to a stage where we have a black picture - i.e. no video signal - but even a black picture needs syncs.

OK i have taken that in thats a good thing to try and remember .

The trick is we are trying to get the output of the mixer at 1vpp - with the sync portion being .3V - so a black picture will be .3vpp - once we have that we can add video - step by step, inch by inch.

This is a good standard procedure Gary i can come back to this and review .

yes but it will be useful if we have to look at other parts of the cct besides the output.

Ok i hope the last post helped

Anyway you can inject the sync pulses is fine for these tests Harry - no need to use my suggestion if you have an easier way.

I had it AC coupled first but with no signal it looked noisy much cleaner DC coupled

BTW I just want you to realise that the height of the sync pulses from your monostable will have nothing to do with the height of the pulses coming out of the mixer - they need only be enough to saturate Q1 on and off (like a switch).

OK well theres enough of that there for sure ,if its just switching i see what you mean ...

[Harry Dalek]

Oh that looks very plausible except you have the wrong monostable output - we want positive going pulses (because that's what comes out of PD1).

Thats an easy fix will do .

[gary]

The scope grabs were good but when you invert the syncs I would like to see a wave file as well if possible.

[Harry Dalek]

The scope grabs were good but when you invert the syncs I would like to see a wave file as well if possible.

Its 1.2 volts pin 6 ic2

and for some reason the other pulse has noise between the pulses

I will do a wav and up load after this posting

[Harry Dalek]

Heres the 400 hz out of the sync mixer video output R9 R10

[gary]

Re: noise:

That's odd isn't it?

Questions:

It appears your scope is set to AC input is that so? If so could you swap to DC so we can see the "real" voltages please?

is the supply now 12V?

is VR1 set fully down?

and the big one...

Is your supply fully decoupled?

[gary]

Ok that's looking better (except the noise) - please be aware that you are recording inverted now that the syncs are the right way up - oh well that's fairly normal - you always have to be aware that the recording can be inverted when recording into a pc.

It appears that you have your volume control for recording ratcheted up to a spine tapping 11 - you should back that off to about a Lawrence Welkian 6-7.

[Harry Dalek]

Ok that's looking better (except the noise) - please be aware that you are recording inverted now that the syncs are the right way up - oh well that's fairly normal - you always have to be aware that the recording can be inverted when recording into a pc.

It appears that you have your volume control for recording ratcheted up to a spine tapping 11 - you should back that off to about a Lawrence Welkian 6-7.

If it looks ok thats fine with me >
If you have any next steps you can think of just post if they come to mind and i will get to them when i can Monday i might be to busy but rest of the week might be ok ...happy with the testing results puts my mind at rest !

No it doesn't have a good range for recording adjustment this thing its easier knocking back something to it than it its self,so sorry about that .

[gary]

You are using windows right? All Windows Os's have a mixer (or one that can be installed) and that's all you need - let me know if you want me to walk you through it.

[Harry Dalek]

You are using windows right? All Windows Os's have a mixer (or one that can be installed) and that's all you need - let me know if you want me to walk you through it.

Sorry again Gary i just looked and it was on full my fault again .

Thanks for the help today i am happier with the electronics side ....the testing we have done is one less problem .

Done a few things i would not of thought of .

I am going to let you knock off early for the night

[Harry Dalek]

Still working on my project Gary has been helping me with some tests and advice so i think its time to resume posting here .

Now i have changed the 400 hz 4060 oscillator into a cyrstal version to see if can get better motor control all the tests posted below are out of the video output of the video sync mixer .

Black is sync only

Black to white a 400hz sawtooth gary sent me to test my levels

crystal test is 2 test cards with my sync added .

The wavy look on the last i think is due to the pulley rubber band more than anything ,i think i'd rather direct drive for motors.

[gary]

That's an odd thing Harry your video is drifting even faster than the sync - so something appears to be awry with your video source.

But you have me confused now because I thought that both your test video AND your sync pulse are generated electronically - so how could the pulley belt affect things?

[Harry Dalek]

That's an odd thing Harry your video is drifting even faster than the sync - so something appears to be awry with your video source.

But you have me confused now because I thought that both your test video AND your sync pulse are generated electronically - so how could the pulley belt affect things?

Hi Gary

Confused me too !...

First see if i have got any thing wrong in the design......generating the sync is the opto switch on the polygon mirror( edges <) then to the lm311 schmitt trigger then to the 4528 monostable with pulse width adjustment then to Q1 of the video sync mixer club hand book circuit .

I use the 4060 ic generating the 400hz now converted to a crystal clock out put to one side of the 555 bistable pin 2 trigger and the output of the lm311 schitt trigger to pin 4 reset so the bistable controls the polygons motor which pulley drives the polygon mirror via a rubber belt .

I can see in that last video the belt movement in the video slight shake perhaps a slight vibration is being picked up in the opto switch,

When i was fixing the loose belt and motor last night and before i fixed it in place i noticed how critical the belt tension was to speed control and picture shake when i added those nbtv videos to my sync .

Should i just be using the crystal clocks pulse it would be cleaner and let the opto switch part of the circuit just control the motor or is it much of muchness ,i can only think the drift in the video is the mechanical feed back delay in the motor control system .

The clock circuit is now changed as i said so pin 2 is 400hz should i be feeding this to the 4528 instead of LM311's output.

[gary]

Ok, I am with you now - you are using the xtal to control the motor speed and the syncs are being generated (correctly) from the line scanner opto sensor - that's the arrangement you definitely would want when it is working as a camera as it will also align the sync with the start (or end) of each video line.

Yes belt drives can be problematical if you get slippage, which is why many go for a direct drive. None-the-less your signals seem very serviceable - it looks like you are nearly ready to start testing as a camera?