Subject: AS-1 Type Sensor =20 I would appreciate any comments regarding my AS-1 type sensor. It's close t= o the original design. I did not like the knife edge aluminum boom attached= to a score mark in the aluminum mast, so I modified the boom to mast attac= hment. I am using two razor blades. One on the boom and one on the mast. Ha= rdened steel on steel. Friction is much less. Free running oscillations hav= e a much longer duration. Does anyone have a better suggestion? I would lik= e to hear from you. =20 See my pic's here: http://picasaweb.google.com/cfi2fly/MyPictures# =20 Also, Chris, if you read this, if I reversed the coil and magnet, would the= effort be worth the results? =20 Hi Richard, =20 I agree about the original design, The arm needs to be held fairly rigi= dly to prevent it from rotating about it's long axis, or swinging from side= to side. You can use a twin wire suspension in tension as shown on http://= www.oregonshakes.com/temp/DesignDrawings4.pdf or an old type double edged s= afety razor blade, in compression. This involves clamping one blade to the = beam and the other to the vertical post. I blunt the blades on an emery sto= ne first to avoid handling accidents. The two loop ends of the blade do the= flexing. I have broken the ends of blades. The edges are fairly sharp, but= I have never observed a section 'flying off'. You can only use this suspen= sion for a vertical sensor. =20 The horizontal arm on the AS-1 is a very hard non magnetic alloy, nol a= n Aluminum alloy. The ends of the spring should ideally be straightened and clamped. Loop= ends fixed by an eyelet tend to be noisy. You could also try gluing the lo= op ends in position? Two component Acrylic glues are much better structural= glues than Epoxies. They set strong and tough and have a short setting tim= e, rather than strong but brittle with a long setting time. =20 The benefits of reversing the coil and the magnet depend on how much n= oise you are picking up. The Alnico U magnets do not have a very strong fie= ld, the coil is a bit bulky and the output is not very high. You would do m= uch better to use a quad NdFeB magnet block. See the designs at www.jclahr.= com/science/psn/chapman/lehman/index.html You can get 10x the voltage outpu= t this way without any difficulty. Also, the 1/4" mild steel backing plates= provide an effective electrostatic and magnetic screen for the pickup coil= .. I suggest that you use a brass mass. There is also a design for an AS-1 m= agnetic damper on the website. =20 I hope that these comments are helpful. Regards, =20 Chris Chapman= Subject: AS-1 Type Sensor=
I would appreciate any comments regarding my AS-1 type sensor. It's cl= ose to the original design. I did not like the knife edge aluminu= m boom attached to a score mark in the aluminum mast, so I modifi= ed the boom to mast attachment. I am using two razor blades. One on th= e boom and one on the mast. Hardened steel on steel. Friction is much less.= Free running oscillations have a much longer duration. Does anyone have a = better suggestion? I would like to hear from you.See my pic's here: http://picasaweb.google.com/cfi2fly/MyPicture= s#Also, Chris, if you read this, if I reversed the coil and magnet,= would the effort be worth the results?Hi Richard,I agree about the original design, The arm needs to= be held fairly rigidly to prevent it from rotating about it's long axis, o= r swinging from side to side. You can use a twin wire suspension in te= nsion as shown on http://www.oregonshake= s.com/temp/DesignDrawings4.pdf or an old type double edged = safety razor blade, in compression. This involves clamping one blade t= o the beam and the other to the vertical post. I blunt the blades on an eme= ry stone first to avoid handling accidents. The two loop ends of the b= lade do the flexing. I have broken the ends of blades. The edges are f= airly sharp, but I have never observed a section 'flying off'. You can only= use this suspension for a vertical sensor.The horizontal arm on the AS-1 is a very hard non m= agnetic alloy, nol an Aluminum alloy.The ends of the spring should ideally be straighten= ed and clamped. Loop ends fixed by an eyelet tend to be noisy. You could al= so try gluing the loop ends in position? Two component Acrylic glues a= re much better structural glues than Epoxies. They set strong and toug= h and have a short setting time, rather than strong but brittle with a long= setting time.The benefits of reversing the coil and the ma= gnet depend on how much noise you are picking up. The Alnico U magnets do n= ot have a very strong field, the coil is a bit bulky and the output is= not very high. You would do much better to use a quad NdFeB magnet block. = See the designs at www.jclahr.com/science/psn/chapman/lehman/index.html&nb= sp;You can get 10x the voltage output this way without any difficulty. Also= , the 1/4" mild steel backing plates provide an effective electrostatic and= magnetic screen for the pickup coil. I suggest that you use a brass mass. = There is also a design for an AS-1 magnetic damper on the website.I hope that these comments are helpful.Regards,Chris Chapman[ Top ] [ Back ] [ Home Page ]