Thu, 15 Dec 2011

airmiles worth

Airmiles is a canadian rewards point club, where you buy things at participating stores, present your airmiles card, and in turn for you letting them have access to your personal buying habits, they give you points, that you can use to redeem for gift cards or items, trips etc.

One thing that is useful to know is what an airmile is worth, and right now a $20 gift card for groceries or petrol costs 175 points, so 20/175=0.1143, so each point is worth $0.11 cents. So if there is some item offered with 8 bonus points, you can equate that to 8*0.11 or $0.88 cents.

posted at: 14:07 | path: /general | permanent link to this entry


Sat, 10 Dec 2011

fixing a broken power supply

A couple of days ago the lights on my fishtank came on in the morning, but when they did they were flashing on and off like some kind of underwater disco show. I don't think my fish appreciated it much, and so I disconnected the light and started looking into the problem. The lights on the tank are a track of LED lighting that are powered from a 15.2V 1600mA power brick. I figured that was where the problem was and sure enough putting my mutlimeter on it I noticed it fluctuating around a bit. I decided to put my scope on it to see what was going on and got this:

power supply broken

Here we can see the supply is jumping up to 12.5 volts, then dropping down 2 volts every 200 miliseconds or so, which explains why the lights were flashing on and off, but this certainly isn't the desired output. Next up was to open it up and see if anything looked wrong. This proved harder than expected since there wasn't a single screw in the brick design and it was just glued together. I ended up breaking the seal with a screwdriver and finally pried it apart. After some poking about I noticed this one capacitor looks like it had shot its load onto the heatsink.

power supply insides

And here is a not that great picture of the bad cap after it was out, you can see the brown electrolyte that leaked out of the cap

bad cap

And after replacing it we get a steady 15.2V from the supply as it was designed to do (it's not exactly a clean supply, but it does the job for lighting leds)

power supply fixed

Ended up epoxying the plastic case back together and almost as good as new :)

posted at: 00:47 | path: /electronics | permanent link to this entry


2019-Sep
2019-Jul
2019-Jun
2019-May
2018-Dec
2018-Jan
2017-Aug
2017-Jun
2017-May
2016-Nov
2015-Dec
2015-Nov
2015-Oct
2015-Jul
2015-Jun
2014-Dec
2012-Oct
2012-Sep
2012-Jun
2012-Feb
2012-Jan
2011-Dec
2011-Sep
2011-Aug
2011-May
2011-Feb
2010-Jun
2010-Apr
2010-Jan
2009-Sep
2009-Jul
2009-May
2009-Jan
2008-Oct
2008-Sep
2008-Jun
2008-May
2008-Jan
2007-Nov
2007-Oct
2007-Aug
2007-Jun
2007-May
2007-Mar
2007-Feb
2007-Jan
2006-Nov
2006-Oct
2006-Sep
2006-Aug
2006-Jun
2006-Apr
2006-Jan
2005-Dec
2005-Nov
2005-Oct
2005-Sep
2005-Aug
2005-Jul
2005-Jun
2005-May
2005-Apr
2005-Mar
2005-Feb
2005-Jan
2004-Dec
2004-Nov
2004-Oct
2004-Sep
2004-Aug
2004-Jul
2004-Jun
2004-May

Powered by PyBlosxom | RSS 2.0