With all the back to school sales going on, I decided it was a good time to get a new laptop. I ended up purchasing a Lenovo G505s – an A10 based laptop. One of the first things I loaded on my new laptop was a copy of StarCraft 2. When running StarCraft 2 (on medium settings) I found the fan gets running pretty fast in a very short time. I’m sure the laptop will run fine with its stock cooling hardware but I decided to go ahead with a 1 day project to build a laptop cooler.
My original plan was to build an acrylic wedge shaped box with some holes under the vent holes of my laptop to force air into the laptop heat sink. After making a trip to my favorite plastics store scrap bin I was disappointed to find that the maximum length of most of the 1/4″acrylic scrap was less than 12″ in width. My new laptop is 14.5 inches wide so it was a bit small for what I wanted to put together. While browsing the plastic remnants I came across some 14″x15″ Multi-wall polycarbonate sheet. The width of the sheet was almost perfect for my application and I could use the same tools I had at home for working with acrylic.
Macrolux sheeting after cutting with table saw.
From my computer junk box I sourced a couple of 80mm fans and a fan speed control. I worked a little magic with a router to create a passage through the multi-walled sheet.
Just finished routing holes on one panel with trim router.
Two panels finished Top panel on left, bottom panel on right.
The fans were mounted with some socket head screws through the panel. I used a 12V switching power supply from a surplus store to run the fans and a push on push off switch to control power. With a little help from some packing tape to hold everything together- diy laptop cooler.
Fans mounted to top panel.
Sealing the holes with packing tape.
Adding a fan speed control and power switch.
Profile view of cooler with laptop resting on top.
The airflow path of the laptop cooler becomes a little easier to see from a profile view. The air from the fans enters the passages in the polycarbonate sheet from the top. The passages in the sheet direct the airflow 90 degrees from the fan. The rear edge of the two polycarbonate sheets is sealed with packing tape so that all the airflow exits at the front edge under the laptop. The exit holes in the sheet stop approximately where the bottom cooling holes in my laptop are.
Running a 3D burn in test I measure about a 8.5 degree C drop in GPU temperatures with the laptop cooler fan at 100%. With the fan running in silent mode (about the same noise level as the laptop fan) I get a drop of about 6 degrees.
I’ve been searching for a bigger better battery to power the Raspberry Pi battery board V2. Based on past experience, I’ve found that the least costly sources for Li-Ion batteries to be inconsistent in how well the measured capacity of the battery matches up with what was claimed by the manufacturer. The battery that I have been testing is normally used in a Samsung Galaxy Note 2. The Galaxy Note 2 OEM battery is rated at 3100 mAh. Doing some web research I came across a page called Battery Analysis & Reviews that listed a number of recommended batteries for the Galaxy note 2. One of the batteries recommended on BA&Rs was manufactured by a company called Anker and was available through Amazon. I ordered two of these batteries as a set that included a wall charger for $26 US. The batteries were selling individually for $14.
I haven’t posted any of my battery testing data yet. My testing to this point had shown that all the batteries that I tested were measuring well under the rated capacity. The fact that I had made my own circuit on an Arduino to take the measurements made me question something with my test setup. When I first tested the Anker batteries I couldn’t get a measurement greater than 10500 mWh (milli Watt hours) which for a 3.8V battery works out to be 2763 mAh vs. the rated 3100 mAh. According to the BA&R site, I should be measuring a bit more than the 3100 printed on the label.
My battery tests were run after charging the battery from my home built charger circuit that uses the MCP73831 chip. I repeated the test using the supplied wall charger from Anker and measured 11962 mWh or 3147 mAh. The good news – I finally had some data that showed my Watt hour measurements were believable. The bad news – my homebuilt charger only appears to be charging to about 88% rated capacity of the battery.
There are two reasons that I believe may explain why my circuit is not fully charging the battery. The first possible reason is that the MCP73831 I am using is built for batteries with a 3.7V chemistry so during the constant voltage part of its charge cycle is run at 4.2V vs 4.35V as should be for a 3.8V cell. The 4.2V and 4.35V setting on the MCP73831 is set in the chip itself and I haven’t been able to source the 4.35V version of the chip in a SOT23 package. The second possible reason for the under charge is that (from what I have read) some chargers only charge to 90% of the rated capacity of a battery for the sake of improved charge/discharge cycle life – I will probably have to get my hands on a MCP73831-3 (4.35V version of the chip) to find out.
Raspberry Pi CSI camera
I finally managed to get my hands on a Raspberry Pi camera board. I’ve also wanted to experiment a little with OpenCV. There has to be a awesome application just waiting to be born using the Pi and OpenCV.
I have experimented a little with MJPG-streamer over WiFi on the Raspberry pi but the resoultion was pretty limited – something like 320×280 when using a USB camera. My experiments with MJPG-streamer were done about six months ago so I should probably see how it works with an apt-get update before trying anything with the CSI camera.