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Magnetic Levitation

Levitation

  1. Introduction
  2. Why
  3. Other Maglev
  4. Hard Drive Maglev
  5. Schematic
  6. Parts List
  7. Buying Parts
  8. Woodworking
  9. Other's
  10. Photographs
  11. Infrared Emitter
  12. Photodetector
  13. Reference Det
  14. Difference Amp
  15. Feedback Loop
  16. Loop Equations
  17. Bode Plot
  18. Phase Lead
  19. Output Amp
  20. Coil Driver
  21. PWM
  22. Lifting Coil
  23. PSPICE
  24. Build Time
  25. PCB
  26. Power Supplies
  27. Setup
  28. Test Power
  29. Test IR Emitter
  30. Test Signal Det
  31. Test Ref Det
  32. Adjust Sensing Res
  33. Test Diff Amp
  34. Test Non-Invert Amp
  35. Test Coil Driver
  36. Test Lifting Coil
  37. Results

Buying the Levitator Parts

How much does it cost? Where do you buy the parts? Is there a printed circuit board?

Total Cost

First the disclaimer: Your mileage will vary! The individual parts aren't very expensive, but if you also have to buy tools (voltmeter, bench power supply, soldering iron, wire stripper, needle-nose pliers, etc) then it quickly adds up to a lot more than I show here. If you have a good parts bin, your price could be a lot less. Substitutions are common (e.g. a different potentiometer, or a fixed resistor instead of a pot), so I encourage you to make your own shopping list starting from this one.

The price is probably under $100, depending on what parts you've got in your scrap box. If you know exactly what you want then buying the few parts you need is as little as $20 total. There are many choices and tradeoffs; it is a little like sewing project where the quality of material and a good-looking visual presentation can run up the prices.

It's a good idea to buy spares. Especially the op-amps, because if they fail then they're certain to die late at night when the stores are closed. :-) It's real hard to get that blue smoke back into the chip; you'll have to buy new parts that contain fresh smoke.

Price List

I don't know if this is a good idea to list prices, but let's see how it works... Although I dislike the prices at Radio Shock, here is the closest part number and price for the parts in my levitator. (Note: This list is current as of December 1999, but will not be kept up to date!) This is merely intended to give you a feeling for the overall cost, and to clearly identify the parts.

Price Part No. Description
US$  Resistors (total = $7.30) 1/4-watt, 5% tolerance carbon-film
0.49 RSU 11344744 300-ohm resistor, pkg of 5
0.49 RSU 11344793 510-ohm resistor, pkg of 5 (need at least 2)
0.49 271-1321 1,000-ohm resistor, pkg of 5
0.49 RSU 11344892 1,500-ohm resistor, pkg of 5
0.49 RSU 11345071 11,000-ohm resistor, pkg of 5
0.49 271-1339 22,000-ohm resistor, pkg of 5
0.49 RSU 11345204 56,000-ohm resistor, pkg of 5
0.49 271-1347 100,000-ohm resistor, pkg of 5
0.49 RSU 11345360 390,000-ohm resistor, pkg of 5
2.89 271-1716 50K ohm potentiometer, linear taper
  Capacitors (total = $2.17)
0.79 272-1053 0.1 uF, 50 volts, mylar film
1.38 272-1027 47 uF, 35 volts, electrolytic, 2@ 0.69
  Semiconductors (total = $11.91)
1.69 276-0143 Infrared LED emitter
1.98 276-0145

Infrared photodetector, 2pkg@ 0.99
(A matched set of emitter/detector is also a good choice as part number 276-142)
2.29 276-1622 Assorted LEDs, pkg of 20
3.16 276-007 LM741 op-amp, 4@ .79
1.99 276-2041 2N3055 NPN power transistor
0.49 276-1101 1N4001 diode, 50v peak inverse voltage, pkg of 2
  Miscellaneous (total = $94.08)
25.98 273-1773 110vac to 12vdc adapter, 500mA, for +/- to control electronics
13.99 273-1770 110vac to 9vdc adapter, 800mA, for coil driver
Note: It is preferred to use a 15v supply, but this is the closest Radio Shark component and will be satisfactory for most people.
21.99 276-169 Solderless breadboard mounted on 4x7" base with non-slip rubber feet. 3 binding posts. 640 plug-in tie-points on 0.1" centers.
9.99 22-402 Dual-scale bench voltmeter, 0-15 or 0-30 vdc
4.49 278-1226 Stranded hook-up wire, 45 feet of 18ga, three spool set in various colors
3.99 278-1215 Solid hook-up wire, 100 feet of 22ga for breadboard jumpers
7.98 278-1345 Magnet wire set, 40' of 22ga, 75' of 26ga, 200' of 30ga (levitator uses about two spools of only 22ga), 2pkg@ 3.99ea
1.49 278-1720 Nylon wire ties, 5-1/4" in various colors, pkg of 20
2.19 278-1638 Spiral wrap, 10 feet, to cover wires to a.c. adapters
1.99 274-659 Barrier strip, 6 terminal, dual row
n/a n/a Wood for base and frame, screws, bolts, washers
  Total $115.46

The parts are non-critical and substitutions can save you money, especially for the power supplies.

Where Did I Buy My Parts?

The cheapest place to shop is a surplus electronics store. I used Radar Electric in Seattle, and Vetco Electronics in Bellevue. Of course, Radio Snack will be the quickest/easiest, but also costs the top $. If it doesn't matter to you if the whole project adds up to $50 vs $100, then you can save a huge amount of time at Radon Shack!

If you know how to build a printed circuit board then skip ahead to PCB plans by Amadeus!

On-line Part Suppliers

There are some large and established parts suppliers on-line:

All these sites are difficult to navigate and hard to find a particular part, but my personal favorite is Digi-Key. Their on-line catalog is in a very nice Acrobat format, and their printed catalog is especially useful with hints and usage notes.

If you have a little experience and know what you want, shopping on-line is excellent. The major drawback of on-line shopping is that the selection is so vast it's hard to decide among all the choices.

Buying a Levitation Kit

Oh yes, you can buy a very nice little kit for $49 US. The kit is from a great article in the February 1996 issue of "Electronics Now". I built their kit and you can read my review. Their contact information is:

   LNS Technologies     www.techkits.com
   PO Box 501
   Vacaville, CA 95687

They updated the kit in May 2006 and lowered the price, so I know they are still in business and eager to sell you the LEV-KIT.
 
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