So there comes a time in life where one feels alone, and they decide to…

Oh who am I kidding, I got tired of photographing/filming in the basement lab with next to no lighting, so I went out and spent $56 on a 2×500W work light rig light cannon with tripod.

Update Nov 3, 2009: almost ready for some fun things…

1L and 500mL round bottom flasks, plus all the other bits for distillation. Enough to do reflux and workup. I have also gotten a separatory funnel (not shown) and other bits of glassware.

Upcoming soon will be a procedure for hydrolysis of vegetable based oils to obtain oleic acid, which amongst other uses will be for a ferrofluid procedure.

My distillation glassware has finally arrived!

Just as a teaser, but perhaps down the road things like essential oil steam extraction and simple distillations will be posted.

In the realm of intelligent battery chargers, there are far too many choices. Prices range from about $50USD to some in the $300 range and come with a whole variety of features. The problem is that the new emerging market is for cheap products that don’t perform, or don’t have the durability and quality expected for a complex device.

Most new intelligent battery chargers can charge, discharge, and cycle Pb, NiCd, NiMH, Li-ion, LiPo, and more recently LiFePO4. These chargers feature control over charging/discharging current. Contrast this to your ‘dumb’ chargers that are essentially trickle charge wall warts that push in around 0.5C that can overcharge NiCd/NiMH, or slow LiPo balance trickle chargers that come with RC helis sometimes.

The GT Power A8 charger sells for about $80USD + S&H, I got mine from HobbyCity.com. It features:

• NiCd and NiMH charging, discharging, multiple cycling
• Pb charge/discharge
• Lithium battery mode: charging, balance, fast charge, storage charge, discharge
• Settings menu: lithium battery type, NiMH/NiCd sensitivity (to detect dV/dt peak), temperature cutoff, timer cutoff, etc (more settings exist, but those are the only noteworthy ones)

The first thing out of the box, was the charger, followed by the instruction manual, CD, and several cables with Deans ultra connectors on them that even had little grips moulded (for anyone that uses deans connectors, you know how hard it is to connect/disconnect). The charger also includes a temperature sensor, and a short USB A to USB mini cable. My first impression of the charger is that it seems to be built solidly and has a few useful accessories, but my opinion will wait until I see what it can do.

One useful feature that this charger has is that it features a USB connection and allows for software monitoring of charging/discharging, etc. Most of the really cheap crappy intelligent chargers (in the $50-70 range) have a USB port, but because of incorrect design and lack of testing, it actually ended up being a serial UART port on a USB connector.

USB to serial UART IC

The GT Power A8 charger has a proper serial UART to USB adapter IC inside, and works properly. Unfortunately the supplied software does not work, however a different software called Logview does work (requires that you select the e-Station BC8). For the most part alot of these cheap Chinese chargers are electrically identical in design, with minor variations in component quality, assembly, and firmware (the moral of the story is you get what you pay for).

LiFePO4 Discharge & Charge

NiCd Discharge & Charge

So I ran the charger through its paces and did a discharge/charge cycle on a 900mAh NiCd and a 1350mAh (probably closer to 800mAh) LiFePO4 battery. You can see from the discharge curve (only relevant traces shown) that the batteries have different characteristic curves, but more importantly that the charger can monitor the voltage and prevent over-discharge. Also the temperature sensor shows the charger how hot the battery is, and you can set a cutoff point for the device to prevent overheating. During the charge cycle the charger seems to be programmed to turn off at intervals to check charge state, and recognizes the negative dV/dt value as the end of the charge cycle for NiCd cells.

So for a quick summary:

Pros:

• Its somewhat cheap, you get good features for a affordable price, but its not *too* cheap.
• Comes with different adapter cables, and a temperature sensor.
• Cooling fan and multiple transistors with proper heatsinking inside mean that it is unlikely to fry

Cons:

• The software doesn’t work (fortunately you can use Logview)
• Temperature sensor only works for batteries with ferromagnetic materials (ie: steel battery cases), a separate battery sensor meant for LiPo batteries that could strap on would be better.
• The input power leads aren’t the same length because a snap on ferrite bead was added, and they wrap one of the leads around it to get more supression.

This last weekend I had the chance to go up to the University of Toronto Survey Camp as part of my freshwater ecology course with Dr. Nick Collins. The camp is normally used by Civil engineers to practice their survey skills in the field, but it is also situated on Gull Lake which like most freshwater lakes, supports a diverse ecosystem.

The whole trip started out with a bit of a rough start, mainly because of some confusion over the pick-up location for the bus driver, he came, left, and we eventually got another bus 4 hours later. Because we arrived late, we missed a segment of activities, but regardless we went to sleep for the night while the two TAs tirelessly did stuff in the middle of the night (echosounding runs and buoy deployment).

So once we actually arrived on site and unloaded, one of the first things we noticed was that apparently, civil engineers are anything but civil…

Civil engineers, anything but civil.

That aside, the next morning we woke up bright and early for breakfast, the morning briefing, and beginning activities. I learned that our prof can make some pretty awesome bacon, and overall everyone can cook well.

Breakfast!

At 6AM, you can get some pretty beautiful pictures, and because of the temperature differences, the lake (around 17degC) fogs up the air (around 4degC) and creates this nice surreal look as the cool air from the ground flows out onto the lake. Another beautiful picture was the panorama I assembled (warning, 10mb image!)

A beautiful 6AM sunrise

For some more details, here are some of the things that all the different groups did during our time at Gull Lake:

• Seineing: fishing with a seine net near-shore with hip waders, followed by collecting, measuring (length & weight) and classifying by species all the fish collected.
• Stream sampling: off-site sampling using kick and sweep (essentially stirring up sediment and rocks, sweeping with a net, washing away sediment).
• Echosounding: using a device which uses sound echos to determine depth to the bottom of the lake, or the nearest object (such as fish). Trends were found between different times of day for fish schooling habits
• Water chemistry tests using a YSI 6600 V2 multifunction sonde at different depths for pH, dissolved oxygen, conductivity, temperature, and chlorophyll content.
• Dissolved oxygen tests: sampling water from varying depths using a Kemmerer bottle for dissolved oxygen and conductivity tests.
• Plankton sampling: deploying nets down to depth and gathering a sample of plankton representative of the water column, or using traps to gather from a specific depth.
• Plant sampling: near shore aquatic plant sampling to assess diversity and provide a cross section of plant life
• Benthic sampling: using pole dredges for shallow water, or free-fall dredges for deep water to sample sediment for organisms.

Sadly I don’t have any photos of these activities, we were all too busy gathering data from the lake to worry about photos (plus dragging my camera along on the lake seemed too risky). You can view all the photos from the trip here, but sadly most of the trip I was without my camera. Regardless, everyone thought the trip was very fun and educational, and since we were doing real work on a lake and seeing trends show up from concepts learned in the classroom, we really gained a perspective for our course material.

If anyone reads this and is considering a field course in ecology, think about how willing you are to get your hands a little dirty and experience real work in the field. If you are willing, you won’t regret it; not only did everyone learn, but our entire class feels like one big family and we have gained friends from this.

So my last post about an alternator to brushless motor conversion seemed to draw some interest, but people were asking some details so I drew up a quick diagram in inkscape last night.

So again, essentially what I did to modify the alternator was:

1. Remove the 3 phase rectifier module and voltage regulator module
2. Connect the brushes to an external set of wires
3. Connect the 3 phase windings to an external set of wires

Readers were also wondering how fast the motor was actually spinning as well. Since I don’t have a tachometer at the moment, I scoped one leg of the 3 phase windings (warning: because the 3 phase windings are floating, and the driver may push-pull, do not connect the ground of the scope to one of the 3 phase windings under any circumstance, only connect it to the electrical ground of the speed controller) and found at maximum speed with my power supply at its limit, there was 1ms on, 2 ms off of switching time, and I knew from counting turns that the stator had 12 electrical poles, thus 36ms per revolution, working out to 1620RPM. I need a bigger power supply, and a test stand with some sort of load to give it a real test…

So for now at least, a few interested parties have enough information to try this themselves. I do plan on developing this further and doing a full writeup with pictures and all, so stay tuned.

So I’ve been tinkering with the idea of using a car alternator as a motor, and got it to work yesterday. Here is the result:

Exploding capacitor Co. ensures that your product fails at the precise moment when user need is greatest using our patented failinite technology.

So I promised a review of this little bad boy, and here it is! Essentially the two products are the same, minus the labelling as Canadian Tire has a deal to rebrand a few Xantrex products including smaller and larger power packs.

In a nutshell, its main features are:

1. 12V, 20Ah sealed lead acid battery
2. 400W AC inverter (square wave)
3. Air compressor with short hose and fittings
4. Separate jumper cable for boosting low car batteries

My first impressions on this pack is that the weight is acceptable, it has enough features, and a powerful enough inverter for things like a small drill, or a sump pump. Handy in a pinch.

So starting from the outside, on the front from left to right we can see:

1. 12V outlet
2. The main display panel (button displays battery charge %, and displays inverter wattage during use)
3. Inverter with switch

Moving around to the side, we can see a small light with a switch below, somewhat handy although I haven’t used it as of yet. Just below the light and switch is a connector for the jumper cables, which I believe is a Anderson powerpole, SB series, but I’m not sure exactly what size.

The jumper cables are about 1-2ft long, enough to balance the pack ontop of the edge of your hood and hook up the jumper cables, although I would have liked to see longer cables for proper hookup to avoid connecting both to the battery (instead of the more usual positive to battery, negative to chassis/engine block), and avoid awkward situations where the battery is located in the rear of the hood, instead of close to the front bumper.

On the other side we see the compressor with pressure gauge, good enough to inflate a tire.

In the back, we can see lots of warning labels, and a small compartment.

Opening the compartment, we can see a small number of accessories for the compressor (needles and nozzles), a small barrel connector for charging, and the fuse for the battery.

Also in the back, you can just make out the shape of a small DC fan to cool the inverter under heavy loads.

Last but not least, removing the 4 screws of the battery compartment, we can get to the sealed lead acid battery compartment. The simplicity of getting to the battery means that through heavy use, or abuse, you can still replace the battery with a standard sized battery.

Closing thoughts

• The supplied charger is a 13.5VDC wall wart, unregulated, and very inefficient. Even with low charging current the plug pack heats up way too much, I would strongly advise that anyone interested, try to use a bigger power supply and a good charge controller to avoid overcharging, or overheating the charger.
• The display is a little misleading, claiming 100% at only 12.7V, when full charge is much higher. Perhaps the two units I have are a little off, however I think that the calibration is off entirely and could lead to people under-charging and sulfating their batteries.

All in all the power pack is a useful piece of kit, I’ve used it only twice now, once during a blackout, once during a test, and found that its been handy, to the point where I bought a second one and keep both float charged via the 12V outlet and a solar panel.

So this somewhat amused me today, I came across this paper by 4 students from the University of Ottawa and Carleton modelling zombie outbreaks from a math perspective.

What amused me more is that the matlab code is included. But most of all, section 6 – impulsive eradication made me smile. Being a fan of zombie films, I’m going to save this PDF for the inevitable zombie outbreak.

So recently I put together a small 3W solar array of cheap amorphous solar panels, and I have since given the small charge controller to my parents who have 3x 15W solar panels (also amorphous). Currently I’m running a test, but from the looks of it there was a modest amount of unharnessed energy (ie: the panels are there, but they weren’t being used to their full potential without a proper charge controller for automation.

My current charge controller schematic is here, but I have a future plan to add a extra stage which cuts out when the battery voltage drops below a set level (so that the load will be disconnected when the battery voltage drops too low).

Essentially what happens is that the opamp compares the battery voltage (through a divider) against a voltage reference, and as the voltage of the battery approaches the reference, the output rises (which in turn increases the current flow through the shunt, decreasing voltage that reaches the battery). The equilibrium is reached fairly quickly in fact once the battery reaches the set voltage.

One point to note is that with this charge controller, most of the power is actually dissipated in the transistor, and while I may have just used a TIP122, choosing a transistor over a darlington, and using a schottky diode will decrease the heatsink requirements.  With a 3W array, no heating occurs (in fact probably no heatsink would be needed), and with a 15W panel, the small heatsink actually gets quite warm to the touch, but with either panel, almost no heating can be registered from the resistors.

The charge controller in all its glory. Note the omitted second transistor.

While this charge controller is good for keeping batteries at float charge, it is not the most efficient. When a battery is very ‘hungry’, the solar panel voltage drops to that of the battery, typically out of the maximum efficiency range of the panel. A better type of charge controller for very large solar arrays is called a MPPT or maximum power point tracker charge controller that acts as a dc-dc converter (buck boost I would imagine) to get the most power out of your panels in varying sunlight inputs.

Some ideas I have for a better version:

• Low Rds(on) MOSFET to disable load (or inversely to connect load) to prevent over-discharge
• LED indicators to display charge or ‘full’ status
• LM3915 based voltage gauge
• Modular approach to charge multiple independent batteries (fleet maintainance  of 12V lanterns, flashlights, radios, or other devices)

Hopefully I will get around to building a nice regulator for a 45W solar panel array for my parents as a nice little gift, assuming I can keep a 60AH battery topped off, one could use maybe 20-30AH of power from the battery per day, maybe something like a nice fan.