The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: dansimon@REMOVExmission.com (Daniel Simon)
Subject: Re: 0-100s timer using 555 IC and panel LED
Date: Mon, 16 Sep 2002 18:52:41 GMT
Organization: XMission http://www.xmission.com/
NNTP-Posting-Date: Mon, 16 Sep 2002 18:50:25 +0000 (UTC)
X-Newsreader: Forte Free Agent 1.1/32.230
On 10 Sep 2002 11:27:42 -0700, email@example.com (Jeff
> I am a Physics teacher with a basic understanding of electronic
>circuits. I would like to build an elevated ramp with adjustable
>slope, whereby an object would be allowed to roll down the slope. At
>5 places along the ramp, I would like to incorporate phototransistor -
>LED (focused) pairs, such that when the light beam is interrupted, it
>activates a relay. The main goal would be to time the object at
>different locations, in order to caluculate the velocity at each
>position. I would like to use four digit LED diplays, displaying time
>to the nearest hundredth of a second.
> My questions are as follows:
> a) I was thinking of using a 555 timer in astable mode,
>operating at a frequency of 1000 Hz. This would be coupled to
>appropriate counters and IC chips to convert to 7-segment LED display.
> What is the "real" accuracy of such a circuit in this mode?
> b) Can I use the output of one 555 timer with 4-5 counter
>circuits (one for each group of LED displays)?
> c) Once you remove the input from a counter chip, does that
>"freeze" its output? I need a way of freezing the time at each
>location, once the light beam is interrupted.
>I know this is an ambitious project for me, but the kids would love
>it, I can guarantee!
When I took physics in the prehistoric 70's we attached a
strip of paper to the falling object which would pulll the
paper thru a gizmo that made periodic marks on the paper. we
would measure the increasing gaps in the marks and derive
You could probably solve your problem with a general
purpose frequency/period counter with start and stop inputs.
Construct your apparatus with multiple sensors and repeat
the experiment once for each sensor position (as Mr.Pinnel
suggests). you could build a sensor selector switch into the
ramp to make this quicker.
A good counter is handy for all timing measurements large
and small and should be standard equipment in a physics lab.
I have seen tons of quite servicable ones on eBay and at
surplus instrument sellers for giveaway prices.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup