Category: Technical

Oyster “Clamshell” Idea

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260584878541

I shouldn’t be surprised that the cheapest RFID reader is from China. This might be something to get in the next few months. I’m interested to see if I could create an Oyster Card reader to show current balance and if you’re “touched” in or out.

I’m currently imagining something the size of one of those old credit card sized calculators. The little ones that used to run on solar. The best way would probably to package it like the card holders used on ID lanyards, where the card is slipped into the holder. To my mind this would mean the reader coil would be within a millimetre of the cards aerial, meaning it could get away with extremely low-powered use.

While it came to mind, it would probably be impractical to try and top up the reader’s batteries through induction charging when the bundle was swiped through a terminal.

That said though, there is some small encryption used on the Oyster cards. It’s supposed to take less than a second to crack on a laptop, but this tiny reader idea is not a laptop. I suspect though that the card could capture the key when the bundle is first put through a reader. That is, if the key isn’t already universal and/or the portion of data requested isn’t the bit that’s encrypted.

As a general purpose reader it would fail, but as a single-purpose device it’s at least a plausible concept.

I doubt it would get any support from TFL however, since I imagine they make quite a bit of money from people forgetting to touch out (or finding terminals are broken) and having cards charge the daily maximum fee instead.
And I feel a large number of commuters would appreciate an end to waiting half an hour for a bus only to find their card doesn’t have enough credit on it for them to get on board!

Knocked out in China, I think they’d probably sell well for a fiver. Maybe a tenner, but I feel it’d leave space for someone to undercut you then.

Anyone got any actual RFID experience to tell me if the idea’s feasible?

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Camera diagnostics, part 1

Always knew getting the service manual would be a good move.

Dug out the old JVC GR-S707’s. They’re a pair of SVHS-C semi-professional camcorders I picked up off ebay years back. One worked fine, only needing a new microphone muff. This came with me all the way to the USA to do some filming at a convention, and damn near broke my spine in the process.
The other was acquired a couple of years after that and turned out to be actually broken, as opposed to a little temperamental in high humidity. I set it aside as a parts camera, or something to try and fix later. It now may be “later”.

I still haven’t tested the capture rig, but will be in the next few days. I was actually looking for a lens this evening when I dug out the spares/repair cam. I had a couple of ideas though, and tried them out quickly.

The viewfinder displays a heavily distorted and rolling image when filming or on playback. The spares kit included all the proprietary cables, so I tried hooking it up to the capture card. Same result there, only in colour. Very heavy blue distortion.
Noticed however the viewfinder and AV output share the same connector type. May mean I can fit one or the other with a colour viewfinder from a different camera at some point. I think I have an even more elderly camcorder with a colour tube.
Found a tape to test in camera. Noticeably worse playback than on dedicated playback unit.
So here’s the interesting bit: PLAYBACK on the damaged camera works fine. However recording is badly affected.

A/V board eliminated. Viewfinder eliminated. Playback eliminated.

Now, from the diagrams it APPEARS that the viewfinder connects to the CPU board. Probably since on-screen info can be included on the video and the viewfinder separately, so that’s done there.

Pain the bum is a lot of these block diagrams had sections in green, and they were scanned in black and white for the PDF, so large portions are near-illegible grey smears.

Still, that both outputs from the CPU board are effected, including the portions that should be different for each output, says it’s either the CPU board itself, or the CPU board’s trying to fit the on-screen data to corrupted video. And since I can’t see how the CPU could corrupt the video feed as well, we move further down the line.

The overall wiring block diagram has the CPU connect to the THD (no explanation of abbreviations included for PCBs). Schematic diagrams show this to be motor and sensor control for the optics themselves as well as pass-through for video and character data, to the Video board.
The video board seems to have tonnes of lovely little trim-pots, any of which might have gotten out of whack. Two are named “Sync level” and “1H Delayed sig level”, both of which sound to me like they could be the cause of this odd issue. It does seem to be some sort of timing issue, afterall (and maybe more, if the blue tint isn’t an associated effect).

That said, the grip on the camera has always been.. sticky. As in coated with something. It could be something leaked down inside the camera through the zoom controls and onto the PCBs under it, altering component values.

In any case, opening it up and giving it a clean-out would seem in it’s best interests.

—

Ah, forgot I also bought an original non-PDF copy of the service manual. PCB diagrams are still in greyscale, but in much more detail. Schematics are detailed in colour. Indications of binder-holes though suggest either isn’t (wholly) original itself, or JVC actually sent out service manuals that were photocopied from an original.

Mind you, nice that it even goes into detailing the functions of the pins of each IC used, including part numbers. If I should ever need to make a new CPU board for one of these, it’s nice to know it’s only cost me $300 in processor chips alone. :P

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Power, lathes, wings

Reprap prototype PSU is done and ready for the stepper controllers to arrive now. All boxed up nicely. If memory serves, it didn’t have a fan when it was in the fax machine, so should be fine in the enclosure. At worse I might have to drill it some extra air holes.
Mains lamp, some (vintage) terminal posts, switch and IEC C14 socket.

Even took the engraver to the front panel to mark out the various terminals and added a couple of ferrite beads to the lines to be on the safe side, and used some cable wrap to keep the wires tidy.

Today I also finally removed the piston and cam off the old compressor pump, and filed down a pully to fit. I’ve hooked this up to the 3rd party headstock from the Black and Decker extruded aluminium wood lathe I found last year. It’s meant to be run by a type of drill they no longer make, so the compressor motor should be easily powerful enough. Currently getting a head speed of about 3200rpm, so it’s currently about twice as fast as it needs to be. Will see about swapping the headstock pully for something larger (I have one, but getting the old one off will be a pain).
It’s not urgent, but it’s sitting around and there’s a friend who should be able to use it once it’s basically working.
Also made a control box for it, currently a simple latching safety power switch (see background of first image) from a broken garden shredder and an old RS project box. If I find a spare suitably rated rheostat I may add a limited speed controller.

Also the sewing for the set of “Navi” wings was mostly done today, but one of the blue plastic rods snapped while trying to flex it into it’s “pocket”.
After some considerable swearing and therapeutic angle-grinder time (see above compressor pump), I will tomorrow attempt to construct a coupler out of clear perspex rod and use it to join the two broken ends, as the stress on them will likely be more than any other repair would take. this may mean purposefully breaking and repairing the opposite wing to match.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Paw-pads:
Well, the Shore 75 rubber is now here, the 60 has been returned. I’ve not yet caught up with the orders though. There’s a rare collective motivation going on in the house right now that’s saying “Yes, let’s actually clear stuff out!”

Workshop:
Over the past few days I’ve filled one of the wheelie-bins all by myself just with stuff from the workshop. And there’s more yet to come!
It’s been a really harsh thing to do though. I’m a packrat, and I do tend to use the things I pick up sooner or later. But it’s best not to dwell on it all. The space is far more important atm.

Reprap:
Ordered some more Bonsai prototyping bits, but the aluminium tube was out of stock in the end, so I’m going to have to go with stainless instead.
You see, the first simplification I’m making to the Mendel layout is to use the frame as the runners by wrapping the studding with push-fit tube. It should also have the benefit of making assembly and adjustment easier, if I cut the pipes to the correct lengths. Just assemble and tighten.

Art-bike:
Also stripped down the big bicycle frame someone dumped in the alleyway. The front fork stem is the same diameter as the stem on the unicycle I picked up last year. Will have to do some careful grinding and welding, but fitting the unicycle up as the front wheel should be fine. And the frames pedal cranks look like they’ll swap with the unicycle ones, so I can hopefully get the mechanism I was after working alright.
It should make it all into a nice half-horse and buggy. Eventually.

Blacksmithing:
I’ve got a rough forge assembled, but I still need to line it with refractory. Have fire cement and perlite, but think I need to pick up some dry sand too. Well, and some charcoal.

Video:
Got some footage from the digital camera that needs editing. Also haven’t yet tested the capture machine I assembled last week. It’s on my to-do list.

T-shirts:
Seeing who’s interested in what types and sizes. Think I can afford to get one atm. No reply from supplier atm. Will call them in the morning and make an order for the large blue UKFur shirts.
Also converted the carrying case that came with the shirts into something more like a portable shop by chopping down an Ikea hanging rail and mounting fixings inside the case. Now I can store the rail inside the case and use the case as the base of it.

Art:
Yeah, I’m behind on this. But I am catching up.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Busy busy bee.. or ladybug, since they’re everyfuckingwhere

Old 1.7Ghz machine is out of storage. Running diagnostics to see if I can isolate where the hardware problem is (I suspect the 80Gb boot disk), before installing Win2000 and a capture card on it. And nothing else.
Will also put the old 5.25″ floppy drive in it and see if any old disks still work.

Yesterdays castings are de-moulded. Unfortunately two sets show small areas of unmixed pigment. Will have to double-stage mix it from here on. Still, getting closer to high-resolution shots of all sets, as well as having display sets.

Called TOMPS, still no word yet. Sounds like the boss is out of the office a lot these past few days. Still, have someone wanting a footpad order, and won’t be able to honour it until I have the shore-80. It’s been a week since I emailed them about this.

Up to 9 Mendel brackets cast. Should have the rest needed in an hour or so. I’ll lock up again for a bit after that, get some artwork done, before casting some more pads in the evening.

Had a reply back from the connector company, wanting to know the pitch of the connector image I sent them. I thought I’d included that in my description. Yep. Ugh..

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DorkBot London was very entertaining last night. My main point of confusion had always been that I’d never found where they talked online. Simple answer; they don’t. You go along, meet people and then communicate one-to-one. This seems surprisingly traditional for such a techno-arty field.
I suppose things like the 2600 meets are the same though. It just feels a little upside-down to me though, having mostly gone to groups or forums which then sparked real-world meetings.

EDIT: 5.25″ drive seems to be working intermittently. Will have to strip it down and clean it.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]