counter circuit help needed
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From: Silvester on 7 Mar 2006 08:40 Electronics is not my field, so I scoured the internet to find counter circuits, but none of what I found really hits my exact needs. I'm looking for a 2 or 3 digit counter that will count down from a predefined number to zero - with a RESET switch to send the count back to the max number. >From what little I know of binary, I firgure I could use DIP switches to set the maximum number that the count starts at - a bank of 8 DIP switches gives me a max of 255. I need to count objects passing a certain point and I figured I use a LED emitter and receiver pair, probably IR. Can any one offer me some help? Silvester
From: default on 7 Mar 2006 10:39 On 7 Mar 2006 05:40:22 -0800, "Silvester" <professor03(a)hotmail.com> wrote: >Electronics is not my field, so I scoured the internet to find counter >circuits, but none of what I found really hits my exact needs. > > >I'm looking for a 2 or 3 digit counter that will count down from a >predefined number to zero - with a RESET switch to send the count back >to >the max number. > >>From what little I know of binary, I firgure I could use DIP switches >to set >the maximum number that the count starts at - a bank of 8 DIP switches >gives me a max of 255. > >I need to count objects passing a certain point and I figured I use a >LED emitter and receiver pair, probably IR. > > >Can any one offer me some help? > >Silvester Do you want to build it or buy it? There's some simple to implement IC's that contain presettable up/down counters used with BCD encoded switches that contain most of what you need like the counters, digital comparators, and latched display drivers. Plenty of "robot" sites on the web with fairly easy to implement TV remote control style circuitry for break beam or reflective detectors. If you don't need a display and never intend to change the count it may be less costly to build a discrete logic counter - but if it were me, I'd use one of the Intersil counters. Likewise you can get a hold of an industrial controls catalog and buy a multifunction counter with display and optical sensor. First option is inexpensive (in terms of money) time consuming, educational and personally rewarding. Second option is fast, expensive and easy. Check a Graingers catalog for relatively cheap, ready made controls. Build it for ~$50, buy it for ~$200 If you want to build it, look at http://wwww.ges.cz/sheet/i/icm7217.pdf The ICM7217 does it all in one IC and they show an LED example and LCD adaptation. I had an application that required a presettable count down timer to switch a valve then start a second timer. (Intersil makes a modulus 60 counter as well as decade counters) Wiring and debugging took me two days with the intersil parts, and another day to package it for the lab to use. It was a breeze. Doing the same thing with discrete logic elements would have taken me a week or two. I could send you schematics of my timers - but the data sheet gives you what you need - my timer had a crystal controlled time base and some logic circuits to stop one counter and start the second one. Likewise I have some schematics of break beam and retro reflective sensors. -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
From: John Fields on 7 Mar 2006 11:19 On 7 Mar 2006 05:40:22 -0800, "Silvester" <professor03(a)hotmail.com> wrote: >Electronics is not my field, so I scoured the internet to find counter >circuits, but none of what I found really hits my exact needs. > > >I'm looking for a 2 or 3 digit counter that will count down from a >predefined number to zero - with a RESET switch to send the count back >to >the max number. > >>From what little I know of binary, I firgure I could use DIP switches >to set >the maximum number that the count starts at - a bank of 8 DIP switches >gives me a max of 255. > >I need to count objects passing a certain point and I figured I use a >LED emitter and receiver pair, probably IR. > > >Can any one offer me some help? --- If you only need to count and reset and don't want a numerical display, you could use: http://www.semiconductors.philips.com/acrobat_download/datasheets/74HC40103_3.pdf with, perhaps, an LED to signal that the counter had reached zero? -- John Fields Professional Circuit Designer
From: John_H on 7 Mar 2006 12:08 "Silvester" <professor03(a)hotmail.com> wrote in message news:1141738822.448393.96950(a)p10g2000cwp.googlegroups.com... > Electronics is not my field, so I scoured the internet to find counter > circuits, but none of what I found really hits my exact needs. > > > I'm looking for a 2 or 3 digit counter that will count down from a > predefined number to zero - with a RESET switch to send the count back > to > the max number. > >>From what little I know of binary, I firgure I could use DIP switches > to set > the maximum number that the count starts at - a bank of 8 DIP switches > gives me a max of 255. > > I need to count objects passing a certain point and I figured I use a > LED emitter and receiver pair, probably IR. > > > Can any one offer me some help? > > Silvester You could use a simple CPLD - programmable logic - to implement your function to even include a 7-segment display driver if you need. The $49 development board from Xilinx http://www.xilinx.com/xlnx/xil_prodcat_product.jsp?title=design_kit should include everything you need to get a chip that does what you want. If you wanted to buy the kit but not get into the details of logic design, there are plenty of folks that could help, particularly at comp.arch.fpga (even if it is a cpld). You could use dip switches, 0-9 rotary swiches, even a "set" mode like on your alarm clock though that method would lose its memory on power-cycle. Logic design is fun these days.
From: Michael on 7 Mar 2006 12:33
Silvester wrote: > > Electronics is not my field, so I scoured the internet to find counter > circuits, but none of what I found really hits my exact needs. > > I'm looking for a 2 or 3 digit counter that will count down from a > predefined number to zero - with a RESET switch to send the count back > to > the max number. > > >From what little I know of binary, I firgure I could use DIP switches > to set > the maximum number that the count starts at - a bank of 8 DIP switches > gives me a max of 255. > > I need to count objects passing a certain point and I figured I use a > LED emitter and receiver pair, probably IR. > > Can any one offer me some help? > > Silvester Your project takes me back to the early 70's, when I designed and built such a thing for my sister (and for my pleasure, of course). My circuit was a kitchen timer. As I recall, I used TTL Up/Down decade counter chips, wired for Down operation. Number of minutes was set by two thumbwheel switches. BCD of each switch was latched into the respective counters upon power ON; counters were decremented by 1 minute pulses from a counter driven by the AC line. When both decade counters reached "0", decrement was disabled and a Sonalert was switched on. Sis could hear that thing scream even when she was out in the back yard mowing the grass. -- Michael |