chasse@ziebmef.uucp (Ken Chasse) (04/27/89)
John H. Lee (johnhlee@cory.Berkely.EDU) has a sound digitizer schematic out and about, and it's now in toronto going all over the boards. Probably off the USENET...I have a slight problem: I need to know which pins I use from the AMPS and the NAND gate chips to get the correct circuit...I wrote to him already, I dont know how fast thre reply will be so I am writing here as well. has anyone else built it? I hear peopl ehave trouble with alot of noise on it.... /kc chasse@ziebmef.UUCP
128a-3cy@e260-1c.berkeley.edu (John Lee) (05/05/89)
In article <1989Apr26.225516.13594@ziebmef.uucp> chasse@ziebmef.UUCP (Ken Chasse) writes: > > >John H. Lee (johnhlee@cory.Berkely.EDU) has a sound digitizer schematic >out and about, and it's now in toronto going all over the boards. Probably >off the USENET...I have a slight problem: I need to know which pins I use >from the AMPS and the NAND gate chips to get the correct circuit...I wrote >to him already, I dont know how fast thre reply will be so I am writing here >as well. > >has anyone else built it? I hear peopl ehave trouble with alot of noise >on it.... > >/kc chasse@ziebmef.UUCP Toronto, eh? Gee, I didn't think it would be that popular. I hope the README file is getting distributed with the schematic. I never got your letter, possible because my e-mail address is johnhlee@cory.Berkeley.EDU (notice the third 'e' in Berkeley.) I hope I didn't misspell Berkeley in the schematic or README. Sorry to reply through the net, but mail bounced from this end for some reason. Besides, it may be of interest to other people. At the moment, I'm busy building my SPARC implementation (my final project for a CS class) but I'll post the pin numbers soon if you still need them. I left the pin numbers out because I figured that whoever builds the circuit would be an experimentor who was mildly curious in using the ADC0809. There are other more appropriate chips for a digitizer. See the README file. My breadboarded implementation of the digitizer works just fine with little/no noise. Since the amp circuit has a gain of about 500, all precautions should be used to shield the circuit from noise. Try these: 1) Use 0.1 uF capacitors across +5 and ground generously. I used one for each chip, wired as close as possible to the chip's power pins. This is a good idea for any digital circuit, especially TTL circuits. 2) Use a 0.05 uF and 1uF capacitor in parallel where the external power enters the circuit board. This helps cut noise from the power supply. 3) Mount the ciruit inside a metal box and ground the box. You'll be surprise how much electrical noise is in the air of an ordinary house, and this ciruit is put right next to one of the loudest sources--a computer. 4) Ground the metal shells of the volume potentiometer(s). This is a major source of noise. Just doing this alone allows me to use the circuit without putting it in a metal box. 5) Separate the amp circuit from the digitizer and clock chips. Don't wire the amp ciruit too close to them as those chips are a source of noise themselves. I hope this helps! --John ------------------------------------------------------------------------------- Raining CATS and DOGS? Try the RATS--The Remote Amiga Teleconferencing System ARPAnet: johnhlee@cory.Berkeley.EDU John Lee, UUCP: ...!ucbvax!cory!johnhlee EECS Student-At-Large