Recently in Bodging Category

I've been spending the past couple of months in Tokyo. Worried about the radiation, I brought my DRGB-90 russian geiger counter /dosimeter that I had bought a couple of years ago. Unfortunately, the DRGB is a rather old analogue design and the readings at low (natural background radiation) are rather imprecise. There's an application on iOS called Geigerbot that is a sophisticated click-counter. Set up correctly, it can give you precise microsievert per hour readings. It also interfaces with Pachube which allows historical readings. Now Geigerbot can use the microphone on your iPad/iPhone to detect the geiger counter's audible clicks, but it will of course also pick extraneous external noise. I wanted to directly interface my DRGB-90 with my iPhone so I could have more precise readings. Unfortunately, the DRGB doesn't have an external speaker jack or any other outputs. Here's how I hacked it.

Step 1: Take it apart

It's very important to note that geiger counters produce very high voltages (400 volts in the case of DRGB-90). Before opening the case, remove the batteries. This is what it looks like on the inside. The long cylinder is the SBM-20 geiger-muller tube. It came wrapped in aluminum foil from the factory in order to give it better shielding against beta radiation (in order to emphasize gamma radiation).

I was disappointed to not see the speaker when I opened it up. Hmm, it must be on the back side of the printed circuit board. The board didn't up easily, it took some wrenching

Step 2: Under the PCB

Lifting up the PCB (with the help of a sharp scoring knife to break the PCB conformal coating). The piezo speaker becomes visible. I wanted to patch into the speaker. Using my multimeter, it becomes clear that the piezo speaker frame is grounded to ground and there's a small (almost invisible in the photo) lead to the piezo.

Step 3: Patching into the speaker output

I cut the speaker output lead and soldered in my own lead.

Step 4: The speaker jack

I then hacked in my own headphone jack using the lead from the piezo speaker as the positive terminal and the battery ground as the ground. On the headphone jack end, I used the necessary bypass capacitor and voltage dividing resistors that the iPhone needs to recognize a microphone input, as noted on the Geigerbot homepage. I could have built this into the unit itself if I had thought a bit more about it. In order to reduce the output to iPhone mic-in levels, I used the 100:1 voltage divider circuit on Higuchi's page, but the volume levels were a bit low in Geigerbot, so I later changed it to 40:1 by swapping out the 100K resister.

Step 5: Putting it all together

Here it is all put together and hooked into my old iPhone 3G which had been previously destined for the dust box.

The iPhone then connects into my Pachube account for a real-time and historical data feed.

From the "I wouldn't believe the physics even if I saw the youtube video" department, a sail car that can go faster downwind than the wind itself. While it's possible to go faster than the wind when tacking against it, it was long thought to be impossible to faster directly downwind. These folks prove it's not so:

Some links to enjoy:

• http://blueplanettimes.com/?page_id=4116
• http://dansdata.blogsome.com/2011/05/04/common-sense-versus-reality/
• http://www.nalsa.org/DownWind.html
• http://www.wired.com/autopia/2010/08/ddwfttw/all/1

I burnt out the original brushless motor and installed a new one, here's the new revised bill of materials (BOM) (dated 2011.5):

Base Unit	Piaggio Boxer (1971) - 50 cc 2-stroke internal combustion engine (removed)
Electric Motor	Turnigy 80-100-A 180Kv Brushless Outrunner from Hobby King - Tachs: 7700 rpm @ 43.2v nominal (6500 rpm @ 36v) - Max amps drawn: 140A @ 43V - Max watts drawn: ~ 6 kilowatts - Geared with 250A front pulley and notched V-belt - Speed: 50 kph top speed (at current gearing)
Electronic Speed Controller	Castle Creations Phoenix HV-110 (link) - 110 amps @ 50 volts limit - Force air cooled
Throttle	Magura 0-5K Potentiometer motorcycle twist grip throttle
Servo Tester (Pot to ESC)	Boman Industries Polar-Matic PC-50 (ebay) -modified for use with Magura pot and HV-110
Power Monitor	Cycle Analyst (link)
Batteries	Prius Gen 2 NiMH - 6S2P packs (12 in total) - 43.2 volts nominal @ 6.5 Ah each - 43.2 volts nominal @ 13 Ah combined - 330 watt-hours (conservative) - Range: unknown but estimated 7 km based on 45 Wh/km and 330 watt-h calculation
Power Connectors	- Anderson PowerPole 75A on main connections - link - Anderson PowerPole 30A on sub connections - link
Wiring	- 8 gauge stranded copper on main power lines and motor leads - 12 gauge stranded copper on sub power lines
Lighting	- Front lighting using 10-Watt LED (driven at 12v @ 750ma; specced at 500~600 lumens @ 6500K ) - Rear lighting using high-power red LEDs
Low Voltage (48VDC to 12/5 VDC) DC:DC Converters	Twin 12VDC @ 3A DC:DC converters using the National Semiconductor LM2576HVT-12-ND buck-converter Unit 1: Front and rear lighting, motor cooling fan Unit 2: ESC controller cooling 12 volt to 5VDC converter using MC34063 Based Switching Regulator for front lighting (currently bypassed) Quark Pro BEC 3A 5V UBEC for servo tester / RC components
Things I burned out/destroyed	E-Sky EK2-0907 Servo Tester Doc Wattson power monitor ELF 100 ESC speed controller Castle Creations Phoenix HV-110 HXT 80-100-B 130Kv Brushless Outrunner motor Right index finger on burnt out ESC Power diodes for battery tap Various burns and scrapes My pride :-)

Please leave comments and questions on this post!

Yesterday I went to  the Maker Faire in New York City, the first time it's been here.  It was held at the New York Hall of Science, which is actually the old expo fairgrounds in Brooklyn, made famous as the scene of the final battle in Men in Black.

The Faire was nothing what I expected. I thought it would be something more akin to the MIT Flea Market, which I attend regularly: a bunch of old and young, mostly male, geeks.  But instead, it was a very strange blend of families, kids doing cool projects, craft people, and just general strangeness.

At the Sparkfun booth, they were showing kids how to solder.  Sparkfun is one of my favorite companies so I'm really glad to see them help grow the community this way.

(more after the jump)

One of my best purchases last year was a little MIG welder from HarborFreight. It was around $100 with coupons. It doesn't come with any accessories, so I bought an auto-darkening welding helmet for around $40, leather welding gloves, slag chipper, etc. also at HF.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=98871

The MIG welder is flux core only with no gas option. This means you get a lot of splatter and slag, but you can always grind those off. I'm happy with the increasing quality of my welds on iron and steel. I used it to make the rear carrier on my scooter EV -- and most recently, a firewood rack for 1/2 cord of firewood. The little MIG welder runs on 120 VAC which is very handy since I can just use the current power outlet in my back yard.

Unfortunately a flux core MIG welder means that I can't weld aluminium (which needs gas), which is a bummer since the weight/strength ratio of AL is ideal for EV use. I need to upgrade to a gas MIG welder -- or a TIG welder. I'm leaning towards the latter but I really need to ge a 240/220 volt outlet installed since it's not worth trying to buy a 120 VAC TIG. But getting a TIG welder would be great. I could even weld titanium if I wanted to. :-) Maybe Santa will get me a Lincoln TIG welder for Christmas....

I use steel from a local steel reseller, Logan Steel. They sell surplus steel bar and sheet for $1 a pound, which is quite reasonable. Their billboards are ubiquitous in southern CT.

The other useful tools I'm using are an offset grinder to prep my welding stock. Also, I converted my HarborFreight compound sliding miter saw to be a metal cutting saw by putting in a 10" metal cutting disk. Very useful, especially when I'm cutting a lot of stock. What I like about my miter saw conversion is that I retained the ability to do 45° cuts (or any arbitrary degree) as well as relatively long cross-cuts, which a lot of dedicated metal chopsaws can't do.

I didn't like the wooden saddlebag style racks on my Piaggio that I had originally made. The problem was that the Piaggio didn't have adequate mounting brackets for them, which meant they were putting strain on the rear fender. Also, they interfered with the pedal action.

I decided to change the mounting system to a rear rack style. I removed the elongated double seat and replaced it with a bicycle seat. I used my MIG welder to bodge up a rear carrier, seen below. I think it looks pretty good.

More postings to follow re: the decision to change batteries and the actual battery carrier itself.