Monthly Archives: June 2014

The Yearly Cost of Running Networking Gear

Posted on 24-June-2014 by mathscinotes

Figure 1 shows how the power conversion for this particular ONT is performed. There actually are two power conversion stages involved: (1) 120 V AC to -48 V, and (2) -48 V to 12 V. Two conversion stages were required because no off-the-shelf, 12 V UPS exists that had sufficient battery capacity to meet the customer's backup time requirements. However, a -48 V UPS is available with a large enough battery to meet their needs. This type of problem is common in real-world deployments. Continue reading →

Posted in Electronics | 1 Comment

Interesting Folding Bed

Posted on 22-June-2014 by mathscinotes

I am an amateur woodworker and I find clever, geometric constructions in wood very interesting. Here is an interesting collapsible bed design. Check out their web page. Continue reading →

Posted in Construction, Geometry | 1 Comment

Engineering Origami

Posted on 21-June-2014 by mathscinotes

I have always been a big fan of origami -- especially rigid origami. I saw two articles in the engineering press that are definitely worth taking a look at. Continue reading →

Posted in Geometry, Origami, Paper Machines | Comments Off on Engineering Origami

It's Warm Out and the PVC is Getting Longer ...

Posted on 20-June-2014 by mathscinotes

I live in Minnesota -- where winter temperatures can be as low as -36 °C (-33 °F) and summer temperatures can be as hot as 38 °C (100 °F). Because most things expand when our days get hotter, we occasionally have things like doors and windows that are too tight in the summer and too loose in the winter. Today, I encountered a PVC pipe that was installed during the heat of last summer and it had ripped itself free of its mounting brackets during the cold of winter. Of course, it is summer now and the pipe is back to its installed length. I was asked by an electrical equipment installer today how much length variation should he plan for when using PVC pipe outdoors. It turns out the National Electrical Code (NEC) actually has a table that addresses this question and I will discuss in this post how that table was generated. Let's discuss the answer I gave this installer. Continue reading →

Posted in Construction, General Science | 2 Comments