How do I build a break beam sensor?
353385
You need some sort of current buffer or relay between the photocell and buzzer. The buzzer operates at a much higher current than the photocell.\n\nA power FET might be useful here with the point which you monitored on the oscilloscope connected to the gate and the buzzer in series with the drain circuit. Many other devices could be used but all will essentially amplify the current available from the photocell circuit. Sorry I can't post a diagram!\n\nAlso, if you need the buzzer to remain activated after the beam continuity is restored you will need to add some sort of timer or latch circuitry.\n\nWK
1160573
e-mail me: intel_knight-at-yahoo-dot-com\n\nAnd I have no clue how to build that EMP thing, or if it is even possible. I just thought it would be a cool thing to have.
243347
There a many commercially availible coin counters out there, check your favorite search engine (or old school phonebook!).  \n\nIf all you want is the sensor I recomend contacting a vending machine supply/repair company for one.\n\nIf you want to make your own from scratch, just use a laser and a photo-detecter.  Have the laser hitting the photodectector and wire your electronics to count up the interuptions of the detector.
1079574
what's the boundary conditions?\nself weight problem? \nthen, what's the material of the beam?\n\npls be clear :)
338528
You can try this one, http://www.xs4all.nl/~smit/asm01001.htm#ready\n\nand contact me for any further help.
1102612
If the antenna is mounted the best way is to use a plumbob and a bubble level gauge. Or just the bubble level gauge with degree increments labeled. another way is to use a compass and a square against the front of the antenna. Hope this helps.
882980
put the counter closer cos alpha raysonly travel a short distance...maybe that will work?... \n\nor get something that will alter with radiation... i think there a material that changes colour when hit with radiation....\n\nOOOOOOOOOrr... get something that emits a longer range radiation ray when the alpha partiles hit it...that way u can get a good approx of the count
943816
i want to make a system that gets mounter to the passenger front bumber of my car, so when im stuck in traffic and some _hole feel he deserves to drive in the emergency lane, the laser will burst a hole in his tire, and give him a reason to be in the emergency lane.  Some issues with this system is the timing of when to fire the laser, how much power the laser would be.  You dont want to accidentally fire at the wrong thing, so these issues must be addressed first.  I think thats pretty innovative.\n\nwhilst working on my M.E. senior design project, my sponsor (an artist) wanted to make a dynamic hologram depicting a full COLOR rainbow..  Yeah, I know...  It made for great jokes the entire year.
981904
Here, found the link below.Wish it is the correct ones. But i suspect since its engineering, u need stronger ones.
748213
Try Edmund Scientific on the web..but if you want to make your own try the link provided.\n\nGood luck!
1128677
If you want to get sharp interference fringes, then yes, you do need a 50/50 beam split.  In order for the beams to exactly cancel out-- they have to be equally bright.  Otherwise, the beams will incompletely cancel, and you'll have bright fringes on a dimmer background, instead of bright fringes on a dark background.\n\nHowever, if you can't get a 50/50 beam split, you could conceivably adjust for that by putting some type of variable attenuator in one arm of the interferometer, and adjusting it 'til you get the intensities of the two beams equal.
38380
hum...not sure you can do that, however, if you want to have to beams (more or less the same as two different lasers, depending on the purpose of your experiment) in phase with each other, you can use something to split the beam (a beam splitter), and, with a coupla mirrors organized in a certain configuration, you should be able to have 2 lasers in phase
419821
must be some kind of a transducer. it could also be a laser as i am not sure whether it is sound or light waves. i think it will use a laser and a sensor to detect the reflaction and hence how near it is to an object.
382475
easy. u need to bias the LDR and have a ammeter to monitor the current. to  detect a wavelength u need to have a monochromator because the LDR will detect everything within its wavelength dependent range.
554109
use ultrasonic machine... the sound waves should shatter it to smithereens
114899
There's a great tutorial/newsletter on using the RAD Video Tools to do just that.  I've included the link below.  It's a free download and the steps are well explained by PapaJohn.
617356
Something about beam misalignment\n\nhttp://www.reference.com/search?db=web&q=jogged%20beam