Freewheeling Friday

What a totally random Friday I just had. If you’re a fan of Ross Noble then you might have seen his series Freewheeling where he responds to random stuff on Twitter and heads off round the country on his motorbike. Well, he’s currently busy filming for series 2 and when he tweeted this I thought I’d mention my NFC implant.

I am looking to feature the following on freewheeling.
Ventriloquism
Taxidermy
Alternative people(tattoos body mods etc)
Can u help

The film crew in my garden

The film crew in my garden

A few messages back and forth with his production team and he turns up with a film crew to have a chat. We spent about 20 minutes or so in my back garden chatting about the back door to my garage / workshop which has an NFC-enabled lock. My wife also had a chat about how she wanted nothing to do with implanting it for me. She pretended to be all aloof about having a celebrity popping round, but when it looked like she’d be out before they turned up, she managed to cancel her other engagement!

Me, and a firmly shut garage door

Me, and a firmly shut garage door

I also showed him the Fisher Price records and the laser. We chatted for a bit about motorbikes while the crew sorted out the next destination – a taxidemist who stuff mice in positions reading the newspaper, etc.

Adam (two and a half) was too shy to join us.

Adam (two and a half) was too shy to join us.

He seemed to be a really nice genuine guy. And whilst it looks like a bit of fun it seems like really hard work to make it look that way. They do 2 weeks solid filming morning to night 3 times. Each week turns out to be a single episode. My older boy Adam is motorbike obsessed and loved his KTM SuperDuke. Ross even said he could sit on the bike, but a bout of shyness meant that he wouldn’t.

All in all, a fairly unusual day. Then off for a stag weekend…

Oh yeah – it should be on around the end of the year. I’ve no idea how much footage they take or how likely I am to make the final cut. It’s a great series though. Watch it anyway.

CNC controller enclosure

Laser cut acrylic enclosure

Laser cut acrylic enclosure

I converted my Proxxon MF70 mill to CNC quite a while ago. When I was testing things out I wired up the PSU and controller board and just threw them in a Tupperware container so that nobody got electrocuted. It even had the lid open to allow the cables (including 240V mains supply) in. A temporary hack if ever there was one. You know how temporary hacks are though – they tend to stick around longer than intended.

Close up of the connectors for the axes, e-stop and LED

Close up of the connectors for the axes, e-stop and LED

Well, I finally got round to making a proper acrylic enclosure. I attempted to mill one ages ago, but struggled with the small working area on the MF70 and abandoned it. This one is laser cut. It’s held together with machine screw’s and has two shelves – one for the PSU and one for the TB6560 based stepper controller. I particularly like the rounded piece for the power LED and the hexagonal grid for venting.

I’d be happy to share the design files if anyone is interested, but I doubt anyone has exactly the same setup as me. I also altered things as I went, so I don’t have any “final” versions.

Laser improvements – coolant monitoring

One of the quickest ways to destroy a CO2 laser tube is to let it overheat. My laser has a very simple system – just a plastic breakfast cereal container of water with a small aquarium pump. It works well enough, but is easy to forget.

My first modification was to power the pump from the laser so that it’s running when the laser is switched on at the mains. That gets around the “oops, I forgot” problem, but doesn’t cover a pipe coming loose or the temperature creeping up. I really wanted to actually check cold(ish) water was flowing through the glass laser tube.

The water and temp sensor

The water and temp sensor

To check the flow, I started with a LM35DZ temperature sensor and a cheap water flow sensor from eBay. For neatness I carefully milled the flow sensor to embed the temperature sensor in it. This was then attached to the output of the laser. I intend to check that enough water is coming out and that it’s below a temperature threshold.

I etched a board with a MSP430G2533 microcontroller that counted the pulses from the flow sensor over a fixed timer period and used the onboard ADC to read the temperature. I set the threshold at 40C and 75% of the normal flow.

PCB with logic error

First PCB with logic error

My initial attempt used a MOSFET to pull the last signal down to GND if things were awry. Unfortunately this fired rather than disabled the laser! This was replaced with a 74LSxxx AND gate so I could force it to 5V and disable the active low signal. Some connectors to match the controller board meant I could drop it in with no rewiring.

The finshed PCB - with a fix for a lifted trace

The finshed PCB – with a fix for a lifted trace

So far it has been working well. (I actually finished this months ago but didn’t document it.) It’s not actually been needed to save my tube yet, but it’s nice to know it’s there. I might later and another sensor on the input and also flag if the difference between the two is too high. I could also add a cheap LCD display but that seems a little over the top.

Coolant monitor in the laser

Coolant monitor in the laser

As it’s a single sided board with some through hole pin headers, when it’s in place you only see the “boring” side of it with not tracks or components. Oh well – there’s no need for it to look pretty. Here it is in place. It’s a drop-in addition on the 6 pin cable to the controller board. It’s powered from the existing 5V line and simply forces the signal to fire the laser high (as it’s active low) when it senses trouble. From teh top you can see:
  • The connector to the sensor
  • A debugging / programming header
  • A currently unused connector for a screen
  • The connectors to patch into existing power and signals

If anyone wants a copy of the PCB layout or code, just ask.

My NFC implant

For quite a few years now I’ve wanted to get a RFID implant. The main use for one I suppose is as a key that you can’t lose. RFID readers are readily available and it’s not too hard to add a microcontroller and get it doing what ever you want. The main reason I didn’t get one is that the last few places I’ve worked (and a friend’s holiday house) have used the proprietary Paxton RFID entry system. Whilst this works using a 125kHz carrier like most standard systems, it’s deliberately incompatible with the standard EM4100/EM4200 125kHz tags that are available in implantable form. Very annoying. I did contact Paxton to see if it would be possible ot create an implantable Paxton tag, but unsurprisingly they said it wasn’t. It would be annoying having a RFID implant that I could almost use every day!

Well, everything changed when I spotted a crowdfunded campaign for a NFC based implantable tag. It was run by someone I recognised from his work with EM4200 tags – Amal Graafstra. NFC is similar, but it works using a high frequency 13.56MHz frequency. It’s pretty much high frequency RFID with a few protocols on top. The big plus is that reading NFC is supported by things like smart phones. I decided to go for it. Here it is.

It was a particularly well run campaign. (Much better that the Agent watch I’m still waiting for.) A few months later and my ready to implant tag arrived!

Ready to implant

Ready to implant

On to the next step – getting it implanted. This proved a little trickier. Some people have done it themselves and I’m not too squeamish about these things, but you really need two hands and as it’s going to be stuck into one of them, you only have one free! My wife’s a GP and would definitely be capable of doing it, but she refused. Not for any medical or ethical reason – just because she said it was “weird, geeky and creepy and if I wanted something daft like that done she wouldn’t help”. Fair enough I suppose. I went to a few piercing / tattoing studios but they all felt it was outside of what they were comfortable with. Eventually Kalima were recommended and I popped along. They were really friendly, helpful and professional. I can’t recommend them highly enough. It wasn’t cheap (£100) but I’d checked out the quality of their other work and was impressed – especially with things like ear reconstruction which must be far more complicated that this!

Anyway, with detailed instructions from Dangerous Things and Quentin’s experience with implanting neodymium magnets and stuff, it al went well. Anyway, enough of the waffle. You probably just wanted to see some gory photos!

X marks the spot

X marks the spot

In it goes

In it goes

Just checking the position is right

Just checking the position is right

A bit of bleeding

A bit of bleeding

I’m also glad to say it works really well unlocking both my Nexus 5 phone and the Samsung Ezon SHS-2320 lock on my workshop. I’ve currently got my contact vCard on it so can give my details to someone just by touching their (NFC enabled) phone against my hand. That would have been much more useful before I was married!

Further PCB improvements

I’m glad to report I’m getting even better result with my PCB etching. Results do seem a bit up and down each time I get back to it but I feel I’m narrowing it down and getting more polished.

One. I’ve started using Ziplock vacuum bags to evenly press the transparency against the PCB. A really nice cheap substitute for a vacuum light box! I can thoroughly recommend them.

Etching underway

Etching underway

Two. I’m now able to get even better exposure with 3.5 minutes under the UV box rather than using the fluorescent tube. Maybe my developer solution used to be too strong. Maybe ditching the glass in favour of the Ziplock helped. Regardless, I’m getting a really good result. Here’s the partially etched board showing great definition.

Three. I got some Tin plating solution. No idea why I didn’t do this before, as it’s really easy and gives a great finish. The instruction say to carefully clean the copper with an abrasive. However, I assumed that as I’d just removed the etch resist from the copper with acetone and it had to be just about as clean as it could be. I popped it straight in the tinning solution before I got fingerprints all over it.

Etched and soldermasked board

Etched and soldermasked board

Milled, drilled and populated

Milled, drilled and populated

I had to mess something up and I removed the protective layer on the soldermask before exposing. Some of it dulled a little on contact with the transparency. Oh well. Otherwise I’m very happy. The ridiculously small negative text even came out a little. Here’s the board before drilling and populating. It a simple MSP430 based alarm for when my two year old son opens the front door. He can now just reach the handle.

When I’ve got it all sorted (and have tried the via rivets too) I think I might do a proper write-up.

CNC mill alignment camera (version 1.0)

Since switching from milling PCBs to etching them, one of the most awkward steps is getting accurate alignment for drilling and cutting out the boards. Mounting a camera on the spindle isn’t an original idea, but after sporting some tiny endoscope cameras on eBay (10mm dia, 40mm long) I thought I’d give it a go. A good excuse to use the new lathe too.

image

The design is pretty simple. I drilled out some  aluminium bar stock to 12mm, with one end slightly narrower and tapped to M12. Then I turned down a M12 bolt to for in the 3mm collet I use with my end mills. A slot at the top is for the USB cable and two sets of three nylon screws allow for accurate alignment.

image

As you can see, a Mach3 video plug in makes it very easy to set the origin on a PCB or other work. Unfortunately it’s a bit long so there’s only just enough room to use with flat stock. I considered mounting it to the side of the spindle (with a known offset) but that didn’t seem right. A more compact version 2.0 is already planned using just the guts of the camera.

A lathe for the workshop

image

My workshop is starting to look a little crowded, but it is certainly becoming more of a workshop! I’ve wanted a lathe for a while although I’m not exactly sure why. Maybe as much to “complete the set” with the CNC mill, 3D printer and laser as having a pressing need for it. Sure there are things I’m making on the lathe, but I could probably have managed without or done them on the mill.

Anyway, a saved eBay search found me a nice Sieg C3 with some tools for what I felt was a bargain but it now price. I bought it only a couple of hours after it was listed before someone beat me to it. Life (and a second kid) meant it was about a month before I even got to use it!

No surprise that the first things in making are bits to improve the other tools. I’ve started on a combined spacer and Oldham coupler for the mill. It’s all a bit circular and sometimes you can start wondering if you’re actually producing anything. As a friend once pointed out – of it’s your hobby then the end result of an enjoyable way to spend your time is all that’s required.

Whilst it would definitely be fun to convert it to CNC, I think that might be going just a bit too far. I’ll hold of for now and just use it manually. It’s been about 20 years since I used a lathe, so nice just to get used to it again.