Really old projects that I just found pictures of

So I made a new years resolution to go through and organize the mess of photos I have laying around my computer. I stumbled upon a pile achient photos from projects I did some time ago while in high school

Linear Induction Knex coaster:

This was for a high school physics class, the idea was to demonstrate on a small scale the use of a linear electromagnetic induction system for launching a vehicle.

I wanted to discharge a capacitor bank through the coils by triggering an SCR when a infrared beam is broken. The beam is at the entrance to each coil / stage and the SCR would dump the capacitor bank through the coil. It was basically a large solenoid.

I built a launch stage that held the coils around a suspended T rail that the knex coaster would ride along on. It looked really cool even though it never worked. After several coil designs I was still not able to generate enough force to accelerate the vehicle fast enough.

I decided to present a system using a modified trunk pop solenoid from a car instead. Dumping the capacitor bank through it to shoot 0.5″ steel rods through shaken soda cans across the room and make a huge mess.

This would be a fun project to re attempt now that I know a bit more about the topic ;-)

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Desktop CNC Machine – Part 3: Computer Control

It was a lot of fun building the mechanics of my machine, but I feel much more in my element tangled in a sea of wires. If you are unfamiliar with how this type of system works, what components are involved, or just have no clue what’s going on. I highly recommend reading the Mach3 users guide, Mach3 is a very popular CNC control program by ArtSoft.

The manual actually goes way beyond the scope of the software and discusses many different aspects of the electrical design and layout of a machine. Even if you don’t plan on using Mach3 to drive your machine it really is a worth while read, if you do plan on using Mach3 its a required read. Hit the link below to get started.

Mach3Mill Users Guide

Computer:

I decided to use my old desktop PC for a control system, A AMD Athalon XP3000+ with 1GB DDR400 and an ATI X800GTO. Its probably a little overkill for this application but its the most stable machine I found and I cant think of a better use for the computer right now. Running the Mach3 driver test even in 100Khz mode results an amazingly consistent system response time even while monkeying around a bit.  I would very highly recommend formatting whatever computer you choose to test and install a fresh OS before testing. Do not connect the network interface or install any windows updates, just format, install necessary drivers, mach3 and test. If you have good results proceed with configuration of the computer, installing antivirus, updates, networking, etc. However keep in mind the more services your computer is running the more likely you are going to get variations in system response time, this will be more noticeable on older computers. The secret (its not really a secret) to a good stable CNC computer is a clean CNC computer.

Mach3 does has a driver watchdog that will send an E-stop command to the system if it detects the response time becoming unstable. However this is still not something you want to have to deal with in the middle of a job. After I got my system properly setup  and tuned I made a ghost image of the hard drive, so as to make for easy fixing when I mess something up.

Most hobby CNC setups involve a remote enclosure that houses a DC power supply and drivers for whatever stepper or servo motors are installed on the machine. This enclosure then connects to the controlling PC via DB25 parallel and to the machine via a separate wiring harness. I wanted to integrate the two systems as much as possible, installing the DC power supply and motor drivers in the PC case. I chose a used(beaten) cooler master computer case because of its heavy construction, removable motherboard tray, and because its all aluminum :) . Lets go over what has to fit inside.

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Desktop CNC Machine – Part 2 : Machine Construction

I set out to build the frame of my machine during the last week of my 08-09 winter break, about 9 Days.  As of writing this I would estimate I have about 200 hours into the design and build of my machine.

Shopping for build supplies consumed a good amount of time. I ended up purchasing my metal stock from a local Rochester supplier; metal supermarkets. I was able to get all of the 6061-T6 aluminum I needed from end cuts and saved a bundle, the service was great too. I was also able to purchase four 1000mmx45mmx90mm Bosch aluminum extrusions for $40 from a local machine builder.

I purchased all needed fasteners from Herbs Fastener Supply a local Rochester business, again great service and price. No more $1/pc nuts and bolts from Home Depot and Lowes! Most other components were sourced online and I will list a few major ones below, however Ebay and my scrap bin made some serious contributions so there will be some missing links.

McMastercarr – ACME leadscrews

DumpsterCNC - leadnuts

Misumi USA - Bearings

Hubbard cnc – pullys and timing belts

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All the parts that needed to be made had been modeled in Inventor. Each part was pushed down to a 2D drawing and dimensioned for machining.

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Ford Siemens EV Motor

I picked up a Ford Siemens PV5133-4WS20 W11 EV traction motor today, Let the EV project begin!

Ballards Ratings:

· AC Induction Motor
· 67 kW Peak Power
· 32 kW Continuous Power
· 190Nm Peak Torque
· 0-14,000 rpm

Power / Torque Curve

Ballard Brag Sheet

Mechanical drawing

The motors main drawback and reason for its low price is that there are no controllers / inverters available for it. Because of this you wont see many being used in DIY conversions right now.

Eric Tischer has done some great work finding ways to work with this motor in his conversion. He is using a modified industrial VFD to run the motor, as well as a taper-lock adapter for the motors odd output shaft.

These motors are surplus from the Ford EV rangers and US Postal vehicles, they have been available from Electro Mavin for around $1000-$2000 for the past couple years.

I was upset to find that Mavins stock had recently depleted, and scrambled to find a motor. Mavin informed me that they originally had 300 of these motors!

I was very fortunate to be able to somewhat locally buy one from Gregg Witmer who had purchased it with intentions of building a controller for it. However after realizing the amount of time it would take to develop the controller, opted for a Azure Dynamics setup and had no use for the Ford Siemens motor.

Gregg was kind enough to sell me his motor and even provide me with all the parts he had collected for building the drive. It was great being able to meet with Gregg and see his EV conversion in the works its very well done and was inspirational, keep up the good work!

I am planning on developing a controller for the Ford Siemens motor this fall for use in a spring 2010 EV project.

I should have time to start digging into this in a week or two. Going to try blogging this project as I move along vs. a write-up at the end, so stay tuned!

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DIY Vending Machine

The final assignment for one of my fall courses was to code the logic behind a Red Bull vending machine. The assignment required that when a drink was dispensed a single LED was to be lit until the dispense button was released. For some reason that sounded really lame to me and l had an official Red Bull mini fridge sitting behind me.

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Desktop CNC Machine – Part 1 : Design

So I have really wanted to do some sort of CNC machine project for a long time now, lacking money and a real use has always kept this project a dream. However with the apparent death of my HP plotter I have decided to make the jump to a CNC milling process. Even with when the pen plotter was working I was not able to successfully “plot” etch resist on a small enough scale for most surface mount components. Moving to a CNC milling process can greatly increase my resolution and repeatability, as well as eliminate the need for nasty etchants, drill all holes, cut out enclosures, etch panels, make pizza, etc…

Having a hobby CNC routing setup at home is not that exotic anymore and there is a sea of knowledge online. Forums like cnczone are a great place for beginners to professionals to communicate and share information, designs, etc. Having watched and drooled over many other machine builds over the years had already given me some good background knowledge for starting my design.

I originally started thinking about MDF based designs using drawer slides I had laying around as linear guides and timing belts with steppers for movement. The idea here being cheep is good and I already had a box full of heavy duty drawer slides, tools to work with MDF, and timing belts are much cheaper than ballscrews.

I had planned on using a moving table and fixed gantry design similar to most large mills and similar to the one pictured below. It did not take long for me to realize that although it would be fun to build, this scale machine was not what I needed. At this point I started to think about exactly what it was that I needed.

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HP 7475A Plotter [Part 2]

It has been quite some while since I made my first post on the 7475a, it has been sitting in my closet neglected for months because of my move and I am back in classes now. But in need of several pcb’s for current projects I made a point to dust it off last weekend and see if we could etch some copper.

I had already done quite a bit of experimentation before I had packed it away over the summer and was expecting to be able to get it up and running quite easily. I had scoured the internet for some time as for software to drive the device with really no luck. This process is a little bit more difficult that just finding a driver for your old Epson inkjet, the 7475a is a vector graphics “printer” and thus a driver for one is quite different. There are commercial products such as winLINE, however I found them expensive and the trial prints with a large watermark.

I had been printing using the eagle CAM tool and a command line, the HPGL text file generated from eagle can be simply copied to the plotter via command prompt. I found this to be by far the best method, there are no crazy old drivers needed and the process should work regardless of operating system.

It is important to first ensure you have your serial communication settings correctly set. I have successfully used the following port settings:
Bits per second – 9600
Data bits – 8
Parity – None
Stop bits – 1
Flow control – None
The picture below also shows the corresponding dip switch settings on the plotter, now using your null modem cable that we talked about some time ago in my first post we are ready to communicate.
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My Pong Clock

This was one of those things that made me feel like a little kid again, I saw it and I wasn’t leaving the store without it. The best part is that unlike Ferrari go-carts and personal hovercraft this was within the reach of my penny-pinching monthly allowance.

The pong clock was featured on hack a day on September 14th and what really got me excited about this seeming random and totally useless project, was that I could do something with one of my old laptops. In all honesty I really don’t care much for the game pong and have plenty of clocks around the house, I did this because it looked cool and got an old laptop out of my closet.

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Starting my LM4780 Chip Amp

This is one of those things that has been sitting on my to do list for some time now, having just moved from an apartment to a house i finally have a need for a bigger stereo.

I chose National Semiconductors overture audio power amplifier series because of the great reviews from the DIY audio community and free samples are available. The LM4780 is the biggest of the family and can supply 60watts to a 4ohm load with a +-35v supply, and 120watts when its bridged. I plan on using two bridged chips for this two channel design.

Allot of the lure of building a chip amp for me, other than getting to build it, is a high quality amplifier at low cost. I am going to try to use as many recycled components as possible in my build to minimize cost and waste. Usually the most expensive component in a deign is the transformer (the price of copper doesn’t help), followed by the case / heat sink, large capacitors, and the chip itself.

I begin by cannibalizing an old Kenwood KR-5600 stereo tuner i had around, you can probably find something like this at goodwill for $15. The tuner had a 25v center tapped secondary (25*1.4=35) assuming the transformer is big enough it could be perfect for the chip amp. Unfortunately the transformer has no markings so i will have to research and test it first.

IMGP5520phpfNh1yI I salvaged the rest of the power supply from the Kenwood as well however i plan on replacing the caps and possibly the rectifier as well because of there age. I will also try to reuse the heat sink assuming it is an adequate size, and the tuning dial for a volume knob because its big and shiny.

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HP 7475a Plotter [First look]

IMGP5215 I picked up a HP 7475a pen plotter from the bay for $15, my intension’s are to use it for PCB etching. By skipping the whole toner transfer / photo sensitive board process i can save a lot of money, time and cut the general mess associated with diy PCB manufacturing. I want to be able to finish my project in p-spice, dump it into eagle for board layout, plot the etch resist on a board and drop in etchant. Sounds easy enough right?

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