Forums

Nightlight problems.

Started by bitrex April 25, 2014
 
My new nightlight has a cds cell feeding a comparator with a time
 constant,  so it doesn't turn on immediately when the cell is
 covered.  Only problem is that if you put it too close to
 something, you get a relaxation oscillator:

 http://youtu.be/er44GoUs5Wc
-- 




----Android NewsGroup Reader----
http://www.piaohong.tk/newsgroup
On Fri, 25 Apr 2014 18:34:04 -0400 (EDT), bitrex
<bitrex@de.lete.earthlink.net> wrote:

> My new nightlight has a cds cell feeding a comparator with a time > constant, so it doesn't turn on immediately when the cell is > covered. Only problem is that if you put it too close to > something, you get a relaxation oscillator: > > http://youtu.be/er44GoUs5Wc
Patent it ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
"bitrex"
> > My new nightlight has a cds cell feeding a comparator with a time > constant, so it doesn't turn on immediately when the cell is > covered. Only problem is that if you put it too close to > something, you get a relaxation oscillator: > > http://youtu.be/er44GoUs5Wc > --
** Yeah - the light sensor must not be illuminated by the same light it controls. Just as dumb is putting the sensor in direct sun light and then controlling a hallway light that is in deep shade. That *was* the case in the block where I live, the natural light level in the hallways fell to near darkness (about 0.5lux) before the sensor brought the fluoro lighting on. Similarly in the mornings, the lighting went off long before there was any daylight in the halls. The sensor unit has no accessible adjustment, so I painted several coats of white acrylic over the window until it worked as desired. .... Phil
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote 
in message news:i0ull99dt5nhmt0kebuqn7gfhjn767h4bo@4ax.com...
> On Fri, 25 Apr 2014 18:34:04 -0400 (EDT), bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> My new nightlight has a cds cell feeding a comparator with a time >> constant, so it doesn't turn on immediately when the cell is >> covered. Only problem is that if you put it too close to >> something, you get a relaxation oscillator: >> >> http://youtu.be/er44GoUs5Wc > > Patent it ;-)
Already exists, it's called a UJT :^) https://www.youtube.com/watch?v=Iscf6UJF3MY Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
On Fri, 25 Apr 2014 15:34:04 -0700, bitrex <bitrex@de.lete.earthlink.net>  
wrote:

> My new nightlight has a cds cell feeding a comparator with a time > constant, so it doesn't turn on immediately when the cell is > covered. Only problem is that if you put it too close to > something, you get a relaxation oscillator: > > http://youtu.be/er44GoUs5Wc
that's just irritating. seems incredibly stupid to NOT use hysteresis instead of time constant. Perhaps, what you're seeing is an 'integration' effect that appears to look like a time constant. ...just food for thought.