http://www.layerone.org our awesome hacker conference in Anaheim, CA on 5/26/2012!
This year for our electronic badges we wanted something that people could maybe get some more interaction out of than is usual. So I figured lets make the badges into RC cars. The idea being the badge itself was the chassis for the car.
First off I thought buy some wheels, motors, gears from some hobby/robot store and use those to build up the cars, well that didn’t go well unless our budget was $100’s per car, its crazy how much people charge for the little wheels and motors kits.
We looked at the usual Tamiya kits which aren’t terribly priced, strangely even though Tamiya is about 10 miles from us, it was cheaper to buy them from abroad and ship back, but still very costly. Also I wanted tanks, but sadly no.
These are about $18 ish, it varies. It does have more parts though but the gearbox though a sheer master of Japanese ingenuity and design, won’t work for us.
Next was the usual hobby and robotic online stores, waaaaaaaaaaay more expensive, motors alone were crazy priced, especially the geared ones. So plan C, China.. Remember we need motors, mounting hardware, hearing, wheels, axels, steering mechanism, remote control parts.
I live on the edge of the Toy District in Downtown Los Angeles, so I wandered around and looked through the various stores for suitable donors.
We pulled apart a bunch of these figuring we could just take all the motors and wheels off and re-use them, and we could at a massive saving the FX Race car I picked up for $3.50
Pulling the cars apart we found they all used the RX-2B/TX-2B chips, I contacted the OEM in China for some of the chips and we brought in a bundle of them. Silan Electronics. http://www.silan.com.cn/english/product/ProductItemDetail.aspx?id=18&pid=2859&c=%E9%81%A5%E6%8E%A7%E7%8E%A9%E5%85%B7%E8%BD%A6%E7%94%B5%E8%B7%AF
Of course its such a popular chip, others have come across it too
krs did a way more awesome schematic though
We didn’t manage to source the SMD version which some cars had, some of which are a knock off of the Silan. For a very simple short range RF setup with 5 functions its not bad at all. The (RX-2B/TX-2B) chips themselves has nothing to do with the RF stage, it just encodes or decodes the pulse train into an on/off for each of the 5 outputs.
So I started working on a prototype car I used the electronics out of the car, and the wheels and motors, the top part of the PCB we reverse engineered the remote control and added it to the badge pcb, it was designed to snap off so you could drive the car part around and it’d still identify you as a conference attendee.
Paper aeroplane with wheels. Back to the drawing board.
Note to self, check wear on router bit first…..
But now we’re getting to the basic shape, the rear and front are both measured up to fit.
Here it is compared to our cheapest car and the most expensive (at the toy market and its still only $12!!) Geared motor and motorised steering. Yes they’re cheap motors and they’ll wear out but the kits are $3.50 – $4.50 ish and you get two motors.
Its drivable at this point, the front wheels get stuck the maximum turning angles.
Back to eagle, to refine it a ‘tad’. Add three batteries, remote and the car. We’re using CR123a’s
Cut it out. Basically Model T to well a Model T really..
This is how Ferrari started BTW
Add some more bits, to hold the rear drive motor we had to go around the wheels rather than sleek, this isn’t great but not really an easy way to hold the rear on.
this one only has one battery, and so its running at 3V, a bit less since its an old battery. Adding two batteries its a lot faster. Of course all the video we shot of the nicer cars and other driving, seem to have disappeared..
The tuneable inductor was going to be the tricky part, krs and mmca sat and tried out different settings, a resistor is used to set speed of the encode/decode time allowing multiple cars on the same frequency. See page 6 of the data sheet
The nicer cars have a 27.145Mhz carrier frequency crystal, the cheapest cars didn’t use crystals at all.. The FCC has been informed obviously. However they are surprisingly accurate.
The crystals were ‘hard’ to get , read unpossible in the USA. eBay as usual came through, one seller agreed to DHL them to me and I got them in a few days from again China, which is great, of course all the others I bought that had ‘30 day’ delivery times also turned up the next week. So I have quite a lot of 24.145Mhz crystals for you know all those things that I use 24.145Mhz for, don’t be surprised to see us selling them on eBay
We built a test harness for the chips to see how it works, it mixes a a frequency with a pulse train, sends that out, strips out just the pulses and the chip decodes it into a single pin on the ic, left, right up down etc.
Everything was going pretty well, it wasn’t going to break the bank for us and we had a pretty good car running around. It was zippy and as easy to control as the normal ones.
So I think ok better buy all the cars, head back to the same store, with one of the cars, the business card and quote from the first few we bought. The guy swears he’s never sold them, even though I have pictures of us in the store buying them. So that’s a problem the next cheapest car is $5.50 I haggle him down to $4.50 and knowing I have some of this newer type at NSL, I head back to take it apart and see how it goes together so we can mod the PCB chassis.
I take apart all of the other cars, not one of them is suitable for mounting as easily (of course) I find the distributor, they’ve either gone under or changed names, I find the new supplier in the same address but they don’t carry that line…
So what do we do, time is getting short.. OK I think, we’ll just give people a finished car and a remote, but that’s not much on the badge. So of course what do we add to it, yes everyone’s favourite “open source/hardware” begins with an A ends with ‘sounds terrible to the average Italian’.
We can still use the parts from the slightly more expensive cars as bases for PCB cars and robots but we’d need some more standoffs and bits to mount the motors, much easier when you’re building a few of them at the space, but the idea is to get people up and running as quickly as possible at the conference so they can hack on them and enjoy the rest of conference.
I redesign the badge and have them sent out for quick turn PCB at Pentalogix.
A few minutes later and here it is. We stripped off everything not needed and made it able to run off 3V or less and 5V USB with magical jumpers. I forgot one of the power traces, so a quick wire jumper after the old, why isn’t it booting up! We’re using the slowduino boot loader (page is down) so it can run at 3V albeit at a slower clock rate of up to 8Mhz. We left the pads for the xtals too though so it can function as a full speed device.
So now instead of it being car, it’s a remote control that has the inputs wired to the ATMega CPU so that it can be controlled via USB, autonomous, strapped to the car, add sensors , switches etc. We left in the blink LED well because LEDs and the duino..
The QRCODE came from an eagle script on a forum post from honken http://dangerousprototypes.com/2011/10/01/qr-code-generator-script-for-eagle/ on Ian Lesnet’s dangerous prototypes forum, which is a great place btw
The top part you can cut off and the two parts still work, like everyone thinks worms can do. Though if you cut it off badly, neither will work…
New donor car, sadly not as awesome. I did try!
mmca and krs further tune and identify the parts we need. Spec Ana time, looking great.
Tuning the antenna lengths, by (A) doing the maths, (B) guessing and cutting lengths. The peak is the 27.145Mhz the blips are the encoded data for the remote
Guessing worked better,, science!! oh wait!
Also you can see our spindle for the mini CNC PCB we’re building, its been sitting there since late last year…never enough time…
This actually worked for the proxmark, just a spool of wire. I think our best antenna was around a metre
OK so now that’s working back to the store and pick up cars and hoping the guy still sells cars, that lady is the one who originally sold me the other cars, and she remembers but its all too late now.
This left side is pretty much all helicopters and cars. As I wait for krs to come pick me up they try to sell me helicopters and all sorts of other things, those ones are IR LED based for the remote control, but that’s another story.
Cheap $4.50 crap you say? Well consider this
Those ‘drift’ cars come with one on/off led headlights, tail lights, motors, spare wheels, rechargeable batteries, aa batteries, remote and some other stuff, I picked them up for $8 for staff and other volunteers. the other boxes have the $4.50 cars. Also they drift awesome since they have shiny plastic wheels, lots of fun and great donor parts.For $8 ! Granted we’re limited on what we can do with it as a robotic base, but for lots of cheap steerable bots its great.
For that price its really well made too. its got a can style electrolytic cap!, actual connectors and lots of screws holding things together.
Our pile of donor cars gets bigger along the way.. The engrish on these is great btw. It is all FAST YOU GO and SPEED BECOMING etc
And our neat pile of cars gets reduced
krs making the test boards.
With a prep sheets to help people build them at the conference.
I redesign the badge and send it in to Pentalogix’s off shore PCB fab. We got them today (Wednesday), the conference is on Saturday.
Looks ok right? Granted I admit I didn’t spent as much time on the graphics this time…. The QRCode works great but I did waver on changing the URL to a bit.ly or something so we could have changed the link during the conference.. Ahh well. I also have a QR code for NSL with the URL as a graphic inside it but I didn’t want to push my luck on how well it read. I spent a more time drawing the L1 logo, rather than stick with the BMP to eagle conversion, I did that the over drew it with rectangles and a circle, since its more of an even finish and easier to scale. the www box was meant to be place holder.. We used the standard 2×3 ICSP header instead of usual 6×1 which was a hassle since all our 2×3 to 2×3 cables had been converted into 2×3 to 1×6 adapters.. But easier for others. Which reminds me to go place an order for 2×3 IDC crimped headers..
But wait what??? The PCB is twice as thick!! its .125 vs .0602ish. I check the email order and sure enough I ordered .125 , I talked to Pentalogix and sure enough I did order that, the quick turns were .060s . I thought ‘oops’ so after some investigating I found a slight bug in the element14 to Pentalogix Eagle PCB quote web page, which Pentalogix are now aware of, it doesn’t properly transfer the thickness of the board and changes it to .125” you can change it here, but to be honest ‘finish thickness’ I didn’t notice as being 0.125” as the thickness of the PCB, plus defaults, It’s my fault though, I should have spotted it.
Anyways no biggie, it can probably stop bullets now. Its solid…
Blink ! krs built this while I was writing this post. One nice thing about the thick board is that the pins don’t protrude out the other side, so for a badge that’s great! since no pins to mess up fabric
We also get to break out Pickobear for the speaker add on, it’s a shield that plugs in and it’s a remix of the last years badge, but designed as a quick build with a few days turnaround.
Getting crazy! (still have to write the code for it!) its 11:17PM Wednesday….. Plenty of time.. It has a TI TPS61040 boost convertor on it too. Also we have to test it… yes hackerspace….
Batteries and holders arrived today as well, AA’s and CR123as and the battery holders .. super cheap too! from www.batteryspace.com luckily paypal screwed something up, I’d ordered them from elsewhere and batteryspace had them cheaper, so I was able to reorder.
We’re giving away some prizes to people who do the best car/badge hack at layerone , they’re not awesome prizes but hopefully someone likes them, they’ll still have a RC car and a ATMega based controller board.
There’s a lot more I’m going to add to this post, especially technical details. All our projects are open source and are available in our SVN in 032.la including all the screw-ups right from the start.. I’m exhausted after this project, and we haven’t even got to the conference yet ! We’ve also got out PCB CNC we’re designing too.
It’s a shame we didn’t get the PCB car thing, I wish we had but it was just time and uncertainty and these are much more hackable with the CPU added.
Packing all the stuff for layerOne, as usual we’ll have an awesome HHV with scopes, Metcal irons , hot air guns and hot plates, and we’ll be teaching as well as building kits. Hope to see some of you there.
If we’re using shoelaces as lanyards, the lanyard supplier let us down and they didn’t turn up on Friday morning…. the parts from Digikey are supposed to be in on Thursday PM.. Talk about cutting it tight, this is why Joe Grand did an awesome job at Defcon a much larger conference.
Also our 90W laser cutter we imported from China decided to clear port on Wednesday as well, so that is fabulous it would have been really useful to have it earlier and now it gets to sit in a box in a warehouse til after layerOne.
next years badge ?
Fuses (when I get to the conference, and think OMG what are the fuses, even though we’re preprograming)