A lot to think about here Martin! My first go at this used one of these (ht= tp://www.philipharris.co.uk/product/Vibration-Generator-Kit-F4R03088). The = picture is hard to see, but essentially it is a speaker coil type device wi= th no diaphragm. The results were encouraging, but the frequency range over= which the amplitude was useful to me was limited. The amplitude was very i= mpressive at low frequency but the allowable input power is limited & I thi= nk the required input power for getting large amplitude at higher frequenci= es will be too much for it. I just think I need something a bit more 'resea= rch grade'. This unit is a school demo type unit & ideal for what it was de= signed for. Putting a moving magnet in a coil might be analogous to using a HDD voice c= oil drive, so I'm at least going to try that. Joe =20 ________________________________________ From: piclist-bounces@mit.edu [piclist-bounces@mit.edu] On Behalf Of Martin= G. McCormick [martin@server1.shellworld.net] Sent: 01 September 2013 20:20 To: Microcontroller discussion list - Public. Subject: Re: [OT]: Need a fast mechanical linear displacement generator How about a voice coil system? Lots of devices use this idea. I am thinking specifically of loud speakers, of course, old-style telephone ringers, aquarium aireator pumps and other diaphragm pumps and stirring machines. The idea is to place a permanent magnet in to the body of a solenoid such that alternating current will push the magnet towards each end of the coil as the field reverses. Think of a loud speaker. That, by the way, is essentially a diaphragm pump designed to make noise by pushing and pulling on the very air, itself. Make the speaker cone out of rubber and put some valves in the inlets and outlets of the enclosure and you have a diaphragm pump like the kind of pumps used to push air in to acquaria. In your case, the magnet needs to be physically heavy enough to vibrate with the momentum that you need in your project. You would then drive the solenoid with a 1-KHZ tone of sufficient amplitude to drive the solenoid piston back and forth. Old electromechanical telephone ringers and aquarium pumps may have two solenoid coils to help move an arm back and forth to push the diaphragm or tap the bells. You may be able to adapt some cast-off back massager or paint stirrer to this purpose. Running it at 1-KHZ instead of 60 or 50 vibrations per second may be a challenge, but it will probably be easier than finding a 60000 RPM motor. Another term I have heard for these types of devices is "shaker" which is exactly what they do. You may be able to get the 1000-HZ power by feeding a tone through a public-address amplifier and using the 70-volt tap if it has one on its output. Watch what you are doing to make sure you aren't about to burn something up. Coils designed for commercial power operation at 50 or 60 HZ will have much more inductive reactance at 1000 HZ so you will have more phase shift and draw less current but the coils may heat up a lot more. Your amplifier will also be running under continuous duty so you want to be sure you don't burn it up. Old vacuum-tube amplifiers are good for this sort of project as you can get away with more abuse than is possible with solid-state stages. Martin McCormick WB5AGZ Joe McCauley writes: > 60000 rpm for a cam with one 'bump' to get 1KHz (sorry for the non tech > term, but I'm pretty mechanically ignorant). The vibration might be > excessive if the cam were mounted directly on the motor, so two bumps on > the cam might be needed meaning 15000 RPM. Not ideal, but might be doable > if nothing else pans out. -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .