Cadbury's drum monitor

[AncientBrit]

Cadbury's drum monitor

Issue 39/2 of the NBTVA newsletter contained my write-up of my drum monitor based on a redundant Cadbury's biscuit tin.
I've attached a few pix of the monitor in action.

The avi's of drum interior and exterior were shot on my 'phone, hence the slight camera shake.

The 3rd movie is the drum being braked by finger to show the action of the motor servo.
Although the line lock recovery is good what is not apparent is that initial lock can be in any frame phase, not just +/- 1 line as is usual.
I suspect that the large inertia of the drum and the belt gearing may be responsible for this.

This last avi was shot on a web camera which had the unusual property that frame rate depended on incident light.
By allowing a small controlled 'bleed' of sunlight to left of frame I was able to approach 12 fps and minimise rolling frame bars.
However this upset auto colour balance, hence the blue tinge to the displayed image.


Kind regards,


Graham

[gary]

Thanks for that Graham - great work as usual. The rock solid line lock is very impressive.

[Harry Dalek]

Yes very nice monitor Graham ! i like the use of the old floppy drive,now thats one thing i don't have the old 5 inch ones are very rare now .

It was good seeing it in the newsletter i was wondering if you had finished it i recall you saying a while back you were busy with it.

Thanks for posting the video and pictures very inspirational seeing it work , well balanced drum i know that not easy to do sitting on the side ! .

[Panrock]

Impressive work as ever Graham. The ability to adapt everyday objects for NBTV use seems to be an essential part of our hobby. Maybe see you at the Convention this year?

Steve O

[AncientBrit]

Hi gents,

Thanks for the kind feedback.

Not sure if I'll make the Convention, family commitments etc.

Cheers,

Graham

[Harry Dalek]

I notice the pictures are saying not yet downloaded but i have and i am sure others have mmmm wonder why .

[gary]

I notice the pictures are saying not yet downloaded but i have and i am sure others have mmmm wonder why .

Sorry Harry I don't quite get you - are you saying you can't download the pictures (jpgs)? I have them downloaded and can send them to you if needs be.

[Steve Anderson]

Harry's correct, I've noticed this. A jpg/gif etc shows how many have viewed the file, but if it requires a download it doesn't seem to update the 'Number of downloads' field. No big deal as long as people can download it I guess, a bug probably.

Although in this case it seems the other way around...

Steve A.

[gary]

Harry's correct, I've noticed this. A jpg/gif etc shows how many have viewed the file, but if it requires a download it doesn't seem to update the 'Number of downloads' field. No big deal as long as people can download it I guess, a bug probably.

Although in this case it seems the other way around...

Steve A.

Aaah, It wasn't obvious to me that that was what he meant, however I both viewed (first) and (then) downloaded so, strange.

[Harry Dalek]

I just wanted Graham to know that i think people are interested in hes monitor just not showing up in the photo down loads .

I am gad he posted them much easier to see the details and we get to see it work in a video .

[gary]

Aaaah a very meritorious sentiment Harry, and I am very glad he posted them as well.

[dominicbeesley]

That looks very good - how did you drill the tin. I tried something similar a while back but my line registration was very poor!

D

[AncientBrit]

Hi Dom,

The main scanning holes are punched in a strip of thin black card.

I made a punch using a base board and a lead screw to advance the punch head.
The head uses a ground down sewing needle of just over 0.5 mm diameter.

The strip of card is supported on the surface of the biscuit tin which is punched below with an oversized holes of around 3mm diameter to allow fine positioning of the scanning strip.
The strip is held to the surface using pieces of tape.
(Not very permanent I know)
Surprisingly you can 'cheat' the line spacing by pulling the strip left or right using the tape.
Remember we are talking of very small distances here.

Ideally each hole would be provide with X and Y adjustments.
I couldn't think of a lightweight but accurate way of providing this.

The oversized holes were achieved by initially laying on the drum another punched strip and spot marking through with a bradawl.
The steel was thin enough to allow the hole to be achieved by pushing the tapered bradawl through the surface and continuing until the approx diameter of 3mm was achieved.
The interior of the drum was supported on a block of wood next to the hole so distortion was minimised.
I removed most of the jagged edges with a hand held 10mm diameter drill bit used as a crude countersink.

(Perhaps I should write up this part of the project as well)

Harry, thanks for the feedback on 'head count' of those viewing the images.

Kind regards,

Graham

[Harry Dalek]

Hi Graham ,i was thinking you had used a template on the flat to do drums scanning holes but didn't think of using large holes in the tin drum after ,thats a good idea i will pinch that idea if i ever get around to something similar and the rotating mirrors don't do me in first

Yes a lot of the ideas you used are well worth writing up here or the newsletter .

[AncientBrit]

Thanks Harry.

When I have time I'll write up the hole punch apparatus.

Cheers,

Graham