Wednesday, December 30, 2015

Building a Model Train Power Supply - Part 2

Incase you got here from Google and missed it, Part 1 of this build is here.

So I needed to get 1/4" material that would take laser engraving well and not be expensive. I took a chance on using Sande Plywood. It's a material sold at Home Depot in 4' x 8' sheets. After cutting the 4x8 sheet lengthwise, then ripping that into 12" strips using a table saw, I was ready to put the strips into this:


This Epilog Mini is available for use in the basement of the Cleveland Public Library in their maker space called Tech Central. I scheduled a time to use the machine, made sure my drawings fit onto the 12" x 20" sheets (the maximum "printable" area of the laser engraver), and got started. About 90 minutes later, I had not only cut the parts of the power supply box, but also was able to engrave some signs to put on the doors of my daughter's bedrooms as Christmas gifts.

So, here are the pieces cut out of the Sande Ply:


Next I stained the plywood with a Minwax Natural Stain:


Then apply a Minwax Quick Drying Polyurethane:


Now, assembly! I modified the buck converter that I bought from Amazon by removing the 50K trim pot (I removed it to measure it's resistance) and soldering a wire jumper to a panel mountable 50K pot I got from my local MicroCenter.


Now solder on the 3 wire voltage meter powering it with the 24v coming into the DC-DC converter and measuring the output:


Then install the power switch/fuse/jack and the neon light:


After doing some soldering and hot gluing the voltage meter in, here is where we're at:


You'll notice that I have 2 binding posts that aren't hooked up. I mean for them to be 5v & 12v respectively but I didn't have enough time to build the regulator circuit for the posts just yet. That will be resolved soon.

Since some of the parts I needed to solder were rather large (compared to soldering parts on a PCB) I had to use a much larger soldering iron to get the volume of heat I needed. So, I busted out an old school soldering iron that is certainly much older than me:


So after installing the knob for the speed control pot, here is the "finished" product:






And here it is hooked up to the train set, but after I already removed the live Christmas tree.


My girls enjoyed playing with it which is all I could hope for. I suppose, I could use the power supply as a makeshift bench power supply in the off season...

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