Pedro,
If I remember
correctly
The viewing angle should be stated as the
point where the light output is half (they usually quote full angle rather
than half angle).
If you look directly (head on) at the LED, you can move 30
degrees in any direction before the light output drops t half the level
compared t looking head on at it.
You WILL need to limit the current to about 20mA (approx2/3
max) through each diode by using resistors
ie
12v supply- 5.5v across LED = 6.5v dropped across
resistor
R= 6.5v/20mA = 325ohms (330 is close
enough
and an available value)1/4 watt resistors will be OK
You could arrange to feed all LED's in a parallel array
through a single higher wattage resistor, but if(as) any LED fails, the
current through the rest will increase. This would not be a problem if you
have a large array and only one or two fail. But if you only had say 2 in
the array and one failed the current would blow the remaining one
also.
One final point. The light output from these are quite low
so you would need quite a few to illuminate something,
http://uk1.farnell.com/Search/search4-frame.jhtml?_DARGS=%2Fcommon%2Fprodsearchform.jhtml
list some much brighter ones, narrower angle, but if your
using an array...
John
-----Original Message-----
From:
Pedro de Oliveira [mailto:oliveirp@xxxxxxx]
Sent: 25 July 2001 08:53
To: HA
(E-mail)
Subject: [ukha_d] OT - LED's
I thought I would try this question here first since
someone
is always
willing to help with their expert
advice... Anyway....
I am looking at buying some LED's to brighten up a small
area and have been
stumped by their specifications
and their meaning. I understand most of it
but what
does viewing angle mean ? I though an LED emitted light all around
but then I found specs at Maplins and these have a viewing
angle mentioned
http://www.maplin.co.uk/products/frameres.tpl?partcode=JA24B:JA25C:&SKU=12703&cart=943432253&d=f&max=1&Group1=LED%205mm%20blue.
I would like to use a 12v supply but does this mean because
they are rated
at 5.5v max that I would need two
parallel rows of LED's with a resistor and
if so
how
would I wire them so they don't "pop" every week ?
Cheers in advance
pedro
------------------------ Yahoo! Groups Sponsor
---------------------~-->
Small business
owners...
Tell us what you think! http://promo2.yahoo.com/sbin/Yahoo!_BusinessNewsletter/survey.cgi
http://us.click.yahoo.com/vO1FAB/txzCAA/ySSFAA/IBOolB/TM
---------------------------------------------------------------------~->
____________________________________
Automated Home UK
http://www.automatedhome.co.uk
____________________________________
Your use of Yahoo! Groups is subject t http://docs.yahoo.com/info/terms/
____________________________________
Automated
Home UK
http://www.automatedhome.co.uk
____________________________________
Your use of Yahoo! Groups is subject t the Yahoo! Terms of Service.