How much does it cost? Where do you buy the parts? Is there a printed circuit board?
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 $20 total. There are many choices and tradeoffs; it is a little like sewing project where the quality of material and a good-looking visual presentation can run up the prices.
It's a good idea to buy spares. Especially the op-amps, because if they fail then they're certain to die late at night when the stores are closed. :-) It's real hard to get that blue smoke back into the chip; you'll have to buy new parts that contain fresh smoke.
I don't know if this is a good idea to list prices, but let's see how it works... Although I dislike the prices at Radio Shock, here is the closest part number and price for the parts in my levitator. (Note: This list is current as of December 1999, but will not be kept up to date!) This is merely intended to give you a feeling for the overall cost, and to clearly identify the parts.
| Price | Part No. | Description |
| US$ | 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 |
| 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.
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!
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.
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.
Last update November 26, 2007 by Barry Hansen ©1998-2007