NBTV Camera Question

[Harry Dalek]

Heres a few pictures of the project today .

Heres the reflective sensor as is adjusted where it is for my encoder .

This is the new one on the dvd plastic protector.

[gary]

Your reflective sensor is horizontal to the horizontal slot .
Mine is horizontal but my slot would be sort of angled vertical.

I don't think that will make a difference.

Yours is close looks at 5mm mines more looking more like 20mm but using it as is thats what worked .

Well that is definitely wrong as the optimum distance is 5mm (refer data sheet) - mine wouldn't work at 20mm, but yours may - and it does support the theory that your output is way higher than mine - are you absolutely sure that the resistor is really 22k and that the connections to the HOA1405 are correct? A close up photo would be good (peer review ).

The reflective sensor you sent has this written on it HOA1405-2 8839 Mexeco

and that is correct.

[Harry Dalek]

Just an update on using the crystal oscillator in the video mixer .
As is it sort of works but i think because the pulse width is to wide only getting half screen and effecting the video modulation...also the video rolls very slowly from right to left .

Perhaps i need another monostable to adjust the pulse width i recall i was getting the same screen results just using the output from the LM311 when i started in the video mixer screen size wise .

My biggest problem at the moment is i have gone backwards in noise so another laptop swap to see if this causing it .

[Harry Dalek]

Well that is definitely wrong as the optimum distance is 5mm (refer data sheet) - mine wouldn't work at 20mm, but yours may - and it does support the theory that your output is way higher than mine - are you absolutely sure that the resistor is really 22k and that the connections to the HOA1405 are correct? A close up photo would be good (peer review ).

Gary i will have a look at this today i will double check for sure i will tell you where the pin connections are going take a snap ...hope there will be an oh thats what i did wrong

As you are thinking there has to be a reason most of the time its simple mistake ...i don't think it would be faulty as these things either work or don't

[Harry Dalek]

Heres the resistor check Gary on the reflective sensor...
I have looked at the sensor again and and did this messy schematic ..
The 2 resistors together are the ones in the drawing 22k red red orange
330 ohm orange orange brown.

I don't think it would work the wrong way around but could be wrong if i have hooked the ir and photo trany with the wrong resistors..

Any case what do you think .

[gary]

That looks fine Harry - I'm out of ideas I'm afraid.

[Harry Dalek]

That looks fine Harry - I'm out of ideas I'm afraid.

I haven't tried the high quality printout to make sure ..
If its nothing to do with the electronics your idea on the paper type or how black the black is on the print out must be the cause....

[gary]

I must admit I was sort of hoping you had swapped the 2 resistors around, although at 12V that might have zapped the phototransistor - my BIG theory was going to be that you were picking up IR from some other source and that was why it was working at 20mm.

Trouble is:

a) There MUST be enough contrast difference between ANY printer black and pure white to be at least detectable, I would have thought.

b) I can't come up with a reasonable theory as to how it is working at 20mm.

Well, I suppose the last hope of the side is that the black you are currently using reflects well enough to saturate the phototransistor - I don't hold out any great hopes however.

I suppose I should unpack the CRO and fire up the beast and see for myself - however my recollections are that it only worked within a small range of distance and 20mm is well out of that.

Good luck anyhow.

[AncientBrit]

Harry,

"Black is Black"

I don't know whether this is relevant to your camera but I did find that ordinary ink jet 'blacks' are transparent to Infra red light.

A few years ago I built a Nipkow disc camera using the Club's dome sensor and to check out the HF response I printed out a 'fan shaped' resolution chart.

The results were very disappointing with poor contrast range.

I made a photo copy of the test chart and the results were markedly improved.

I assumed that the fused toner employed in the photocopy were opaque to IR.

A better solution would have course been to add an IR filter to the optical path in the camera, thereby improving flesh tone renditions.

Cheers,

Graham

[Harry Dalek]

Harry,

"Black is Black"

Yes just next to the cd black its greyer ..black is black there are shades to it i suppose .

I don't know whether this is relevant to your camera but I did find that ordinary ink jet 'blacks' are transparent to Infra red light.

Oh I think gary would be interested in this to..well that would be the reason we are both scratching our heads !:shock:

A few years ago I built a Nipkow disc camera using the Club's dome sensor and to check out the HF response I printed out a 'fan shaped' resolution chart.

The results were very disappointing with poor contrast range.

I made a photo copy of the test chart and the results were markedly improved.

This is a very important bit of information for any one else making one gary and i might have the same type of printer but the brand and type of ink might be the reason hes works and mine diddly squat !

I assumed that the fused toner employed in the photocopy were opaque to IR.

MMMMM very interesting i will keep this in my head !

A better solution would have course been to add an IR filter to the optical path in the camera, thereby improving flesh tone renditions.

Cheers,

Graham

Thanks for that graham is your camera still going ?

[AncientBrit]

Hi Harry,

Yes the camera is still operational.

I locked the disc motor to 50Hz to 'freeze' any hum bars.

The locking circuit is a little temperamental though.

Speed control pot needs handling gently to achieve lock with a bit of hunting.

It was written up in one of the earlier Newsletters.

Cheers,

Graham

[Harry Dalek]

Hi Graham

Hi Harry,

Yes the camera is still operational.

I locked the disc motor to 50Hz to 'freeze' any hum bars.

So you use the strobe disk for motor control ?..

The locking circuit is a little temperamental though.

I think they all are and have there moments .

Speed control pot needs handling gently to achieve lock with a bit of hunting.

I have been slack on this side of motor control till of late but tried a few times now so of going all out on this one,i not only want the motor controlled but that feed back loop to control my sync to the pc as a monitor or recoder works for the mechanical clock doing the sync but i want the sync crystal controlled ..sort of worked when i tried the other day pulse widths to wide picture was half size,i have wacked in a monostable to try again..

It was written up in one of the earlier Newsletters.

Cheers,

Graham

Is it in the first dvd ,i have the paper issues only back 2 years i will see if i can track it down.

[gary]

I don't know whether this is relevant to your camera but I did find that ordinary ink jet 'blacks' are transparent to Infra red light.

Well that is good to hear Graham, I now feel slightly less like I'm going insane.

Harry, buy yourself a Brother laser printer $80 - worth every cent...

Actually I should check that because my encoders were printed off a Konica-Minolta - I bought the Brother specifically for producing PCBs (toner method) but have read recently that the Brother is the only laser printer known to not work for that method d'oh!

Harry it seems that I have inadvertently given you a bum steer in recommending the reflective encoder method - sorry about that - I had no idea about the IR properties of ink jet ink - who'd have guessed?

I suppose your best bet is to follow Graham's lead and get a photo copy of the encoder.

[gary]

Is it in the first dvd ,i have the paper issues only back 2 years i will see if i can track it down.

Yes it is - V25-4

[AncientBrit]

Harry,

re the sync pickup I'll have to dig out the circuit and the actual camera.

I've a feeling I used an opto detector looking through a single hole, with a 4046 PLL to generate 31 pulses per revolution, then another PLL locked to that.

A bit convoluted but it worked.

Not sure that I would recommend this 'solution' to you though.

It was early days with my NBTV experimentation and I'd probably do it differently if I re-visited the design, maybe a PIC.

The motor control is not ideal.

As I say it's a bit touchy to set up and drive.

Cheers,

Graham