LiPo Battery Ruggedized Power Module

A while back, we decided that we needed a 24v power source for various “testing” applications. This source needed to be durable enough for daily use by a wide variety of people without becoming damaged. It also needed to protect the device being powered, and be easy to maintain.

Given that tall list, Ben suggested a HobbyKing LiPo pack, 6S, 5Ah. With that start, we decided that it should have volt and amp meters for monitoring, as well as a circuit breaker to provide positive power disconnect, and protect the battery (easily capable of 150A into a dead short).Meters were ordered from Ebay and the breaker was something out of an old UPS.

The blue enclosure is a waterproof storage box from Walmart, modified to pass through various connectors.  It’s not waterproof at this point, but we’re more after the durability of the polycarbonate than the waterproof aspect anyhow.

Internally, there’s quite a bit going on.  The battery is packed into a foamed-off area, while the other side contains the electronics, including the circuit breaker,ammeter shunt and all the connectors.

Charging is accomplished via a modified ATX connector (which re-presents the balance plug and main power leads), with a fuse to protect against abuse. The idea is that it’s virtually impossible to charge the battery improperly, or to break a relatively fragile balance connector.

Overall, it was a pretty straight-forward build, and cost around $90, including the battery and all the connectors.

Microscope Photography – Integrated Circuits

On Tuesday night, we were disassembling some old printers, and salvaged some large ROM chips. Patrick got the idea to use the mill to remove the top layer of the case, and expose the IC inside.  Here are some photos we took of the chip’s insides with a microscope. Magnifications range between 4x and 40x, thought the 40x were pretty difficult to illuminate properly, because the lens obscures most of the light. As for the cameras, we  used a little point and shoot and a cell phone camera, both just held up to the microscope’s eyepiece.

Easier Vacuforming with Sintra

One of the other projects enhanced by the Variac is the vacuformer.  It consists of two parts: a box with a heating element that melts plastic (background) and a perforated box which sucks the softened plastic down over a heat-resistant form (foreground).  Prior to the Variac, we’d had problems damaging the plastic sheet, because it was heated too rapidly.  Now, we can adjust the heat very precisely and results are much better.

Note: The reason for the incomplete formations in the black plastic (Sintra) is that both the objects used as forms were heavy, metal and cold; The plastic cooled too rapidly, before a good impression could be achieved.

The vacuforming equipment (both the heater box and vacuum bed) are stored in the “TOOLS” cabinet.  There are several shop vacs to be had, typically stored below one of the benches in the “less clean” area.

Acrylic Bender

The Makery’s recent acquisition of a Variac has rekindled interest in a few projects that had been on hold.  One of those projects was the Acrylic Bender that James had been working on. At it’s core, the bender is just a halogen bulb between two aluminum tubes full of circulating water. The idea is to create a line of focused heat to allow plastics to be bent accurately.  We found that it works equally well for acrylic and Sintra (Foamed PVC).  The Bender (along with the Variac) is currently stored in the “TOOLS” cabinet.

Home-made Hobbed Gears

At the Makery lately, Brandon and I [with some help] have been working on a CNC Hot-wire Foam cutter quite a bit like this one.  Ours is going to be a bit larger, capable of slicing up a 2×4 foot piece of foam (actually, the X is more like 5 feet than 4). For our Z axis, we are using a salvaged set of rails including a rack and pinion setup, but our X axis is entirely homebrew.

I’d initially lobbied for a belt setup similar to the X-axis on a Prusa Mendel, but Brandon objected on grounds of the cost for a 10 foot piece of belting.  He proposed instead using a piece of all-thread as a rack, and a curved gear as the pinion.  That was fine, but seemed like the gear would cost more than the belting. In the end, we decided to try making a gear, in the same way that extruder rollers are made for the 3d printers: Hobbing.

Tonight, I got around to trying to make the gear.  We’d settled on 3/8-16 all-thread, as it’d be sufficiently beefy as to not bend with a gear pressing against it, and to not sag under the weight of a mostly unsupported 5 foot span.  I grabbed a piece of (approximately) 1″ round aluminum from the scrap bin, and drilled a 3/16″ hole through.  I bolted the cylinder to a bearing I had lying around, and chucked it into a V-jaw in the mill vise, with one end floating free.  I chucked up a 3/8-16 tap in the spindle, and set the speed as low as it goes (I around 500rpm, I think).

From there, I aligned the tap so that the centermost full thread was parallel to the bolt through the work, so that I’d be cutting only on full threads. I used the Y-axis of the mill table to position the tap along the length of the work, and advanced the work onto the spinning tap by slowly feeding the X axis as the work turned. (The work spun freely in the bearing, powered by the tap cutting into the aluminum, like when a board lifts as a wood screw is driven.)

I initially had a bit of trouble with the work flexing in the chuck (as I was only supported from one end), but I overcame this by grabbing the outboard end of the bolt with my hand and keeping the bolt parallel to the vise jaws manually.

Overall, the process worked really well.  The tap cut nice, deep, uniform teeth into the aluminum. If I were going to do it again, I’d find a better way to hold the work (supported by both ends) in the vise; I’d also pick a better piece of material, as I didn’t bother turning the surface imperfections of out this one before I started.

Handlebar Camera Bracket

Tonight, I finally got around to finishing up the Handlebar Camera Mount project.  The mount consists of a hunk of printed PLA, sawed in half, and bolted back together around the handlebars. At the moment, I have a piece of rubber tape wrapped around the bar, under the mount, to keep it from slipping, but my Canon S5 is pretty heavy and it needs a bit more wrapping underneath.

The printed portion of the mount weighs around 60 grams, and took about 90 minutes to print on the Makery Mendel.  On the side facing the camera, you can see where we lost a bit of blue tape.  The part has an inner diameter of an inch, and is about 2″ wide, to provide good stability for the camera.

The hardware is 4 1.5″,1/4-20 stainless steel hex head cap screws. I opted for stainless because “It’s a bike, and it’s going to be outside”… The bolts were around a buck a piece, which wasn’t really any more money than the regular steel ones.  Hex-keyed is sorta like metric: It just costs more, and no one knows why.

All this puts total materials cost (including the PLA for printing) at just under $10.  The model for the printed version is available here.

 

In the Making: Player Guitar

Kevin’s been busy lately. All hail the hypnoguitar!

So far it plays 1 string and can play simple songs. The idea is to make a slide guitar that can play complex music from a program, much like “player” pianos read from sheet music. This is a demo video showing the progress so far.

Its coming together, don’t you think?

Read more on the project at the Player Guitar Wiki

Print heads for the Makery Mendel

Tonight, I was on assignment for Brandon and the Makery Mendel again, this time drilling some really really tiny holes.

These acorn nuts will be used as print heads to extrude the molten plastic on the almost-done Makery Mendel 3D printer. I started the process by holding the piece of allthread (Which has a shallow hole in the end) in the lathe chuck and threading a nut onto the end.  I know that generally a bolt thread isn’t true enough to rely on for machining, but in this case, I want the operations all true to the bolt, as that’s how it’s going to be held in use.

Next, I faced off the rounded end of the nut, being careful not to get too deep (which is what happened on the rightmost unit). I then used a tiny drill bit in the tailstock chuck to ever-so-gently drill the hole.  On the 0.3mm unit, you can see where the drill bit had a slight bend in it, and wanted to drag around the part instead of start drilling in the center.  I was able to change the orientation of the bit in the chuck to correct this.

Finally, I cut a bit of an angle on the side of the nut, making it more conical than round.  Sort of like a cut-off funnel.  Hopefully it works well. One of the nuts turned out to be plated (which, sadly, is one of the sizes I didn’t make a duplicate for)

Stepping Up…

Tonight, I did some prep work on a new EasyDriver (on breadboard) that I ordered for an upcoming project. I mounted a 4-pin Molex Floppy connector for the motor output, and pin-headers reversed for breadboard mounting.

I also milled the gear off of a scrap stepper motor and built a coupler to a fancy leadscrew I had laying around. The leadscrew in question (pictured foreground) is about 9″ long, has 5 starts (5 parallel sets of threads) and has a twist-rate of 1 inch per turn (one TPI).  The screw is further teflon-coated and uses a (probably Delrin) plastic nut.

Brandon questions if “that wimpy stepper” can drive such an aggressive leadscrew, but I don’t think it’ll be a problem.  If it does become a problem, building a new coupler (or finding a motor that has the same shaft size) shouldn’t be hard.