So a few friends from Hacklab.to gave me a set of homemade lockpicks and turned me loose on a few locks (easy ones) earlier this week. I took the picks home, bought a few padlocks from Walmart, and I’ve been poking at them on and off during my breaks. I *just* picked a 4 pin lock for the first time, whee.
And yes, that is a journal article in the background. Specifically:
Sabourin, L., Beck, A., Duenk, PW., et al. 2009 Runoff of pharmaceuticals and personal care products following application of dewatered municipal biosolids to an agricultural field. Science of the Total Environment. 407:4596-4604.
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.
Just to begin, this guide is not a fix-all solution to dead uninterruptable power supply (UPS) batteries, I will describe what the cause of one particular, common failure mode for sealed lead acid batteries is, and the solution.
So I’ve been busy over the last few days on a few projects.
First, a quick and simple wood frame for 3x 1W solar panels I purchased for $9 a piece. I plan to add a shunt controller, or at the very least a simple LM317 regulator set for 13.7-13.8V, because the solar panels are happy putting out a unloaded 23V!.
Yet another quick and dirty project, during my post-exam cleanup I decided I wanted to build a stand for my printer to sit on so that I can store stuff (ie: paper) underneeth it. Just old spare MDF from Ikea furniture. Always a good hack for anyone with flat pack furniture that they can’t be bothered to sell.
Another project that is unfortunately a bit of a failure is a big rackmount power supply I built. Using a beefy transformer it supplies 13.8VDC regulated, at high current (20-40A). Unfortunately the transformer I used was a microwave oven transformer, re-wound for low voltage. The transformer contains a shunt, and the laminations are welded together, shorting them and creating a ton of wasted power, and high idle current. Testing with a proper meter, I found out that the idle current is 6A, with a power factor of 0.12! Once I replace the transformer, the power supply should be rock solid and reliable.
Enough of that rant, the technical details:
The power supply uses 42000uF in the smoothing filter, 2x ISOTOP/SOT-227 dual diode modules for rectification, and 4x 2n3055 pass transistors with a LM723 regulator. The inside is a bit of a rats nest, however it works well and even *with* the voltage sag due to the transformer being very lossy, I can push at least 20A within a range of 12-14V. Note that using fuses is a very good idea with a power supply that has a very large short current, and the fuse block is mounted behind the front panel (those 2 screws on the right).
Future additions include: more binding posts, and a volt/current meter setup, along with the replacement transformer.
Last but not least, new gear! I’m studying for my amateurs license, and I’ve already picked up my radio, and a cheap (as in free) tuner.
