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is there a way to increase the light of an LED with a dial?

R

Ron(UK)

Jan 1, 1970
0
Victory said:
At the highschool it was on one of those 'tester' boards with
different voltages and such.
Top post clipped for clarity<

Possibly the 12 volt output was current limited and the 5 v not so

Ron(UK)
 
A

Arfa Daily

Jan 1, 1970
0
Ron(UK) said:
Possibly the 12 volt output was current limited and the 5 v not so

Ron(UK)

Hmmm. It's a thought, Ron, but we're only talking a pretty small current
draw here, and I'd be surprised if any current limiting on a schools type
power supply would have the 'delicacy of touch' required to be able to limit
the current to something tha would not burn out a white LED i.e. less than
30mA perhaps ?

Arfa
 
I

Ian Malcolm

Jan 1, 1970
0
Arfa said:
Hmmm. It's a thought, Ron, but we're only talking a pretty small current
draw here, and I'd be surprised if any current limiting on a schools type
power supply would have the 'delicacy of touch' required to be able to limit
the current to something tha would not burn out a white LED i.e. less than
30mA perhaps ?

Arfa
I suspect 78L12 & 79L12 for powering the board's 'opamp' module and 7805
(or maybe 78M05) for logic. What is a 78L series good for when its gone
into foldback limiting?

Now a *proper* school lab PSU is probably good for something like 25V
adjustable at well over 10A. I have fond memories of cutting tin plate
with a carbon arc using a 3B pencil, two such lab PSUs strapped in
parallel and a whopping great inductor wound with silk covered wire with
a bundle of soft iron wire as its core, mounted on a beautifull piece of
varnished mahogany, with *massive* brass thumbscrew terminals in series
to stabilise the arc. *AHH...* the joys of a physics lab supervised by
a newly qualified substitute teacher . . . . :)

Didn't pay to get a 74xx logic chip in the breadboard backwards, the 5V
bench supply was rated for something like 200A (it was a 4 foot high
cabinet with fan cooling at the front of the room and each row of
benches had a 30A thermal circuit breaker). A dead short would melt
your hookup wire quite easily before the breaker tripped and a reversed
chip would melt itself into the breadboard. SMELL that smoldering PVC
insulation . . .
 
V

Victory

Jan 1, 1970
0
Ok, I hope someone can help me out with this. I went out and bought a
1k variable resistor. I took a picture of the setup and I would love
it if someone could take photoshop or paint and connect the dots for
me and therefore I will know where to put the wires. The LED doesn't
have any specs and the batteries are TWO 3V button batteries in
series. I have tried connecting it myself and all I can get is the
light "on and off", but it doesn't dim or get brighter.
I have also bought a bunch of trim pots (really really small) - these
radio shack trim pots aren't a problem - I have tested and hooked them
up to the LED. Turning the turning the dial to dims and brightened
the LED.
BUT when I try the 1k resistor, because it has the EXTRA hooks up (5
instead of 3 that are in the trim pots), I am not sure how to make it
work.
Here is the picture :

http://davidd.250free.com/resistor.gif

Thanks again. I know that I am probably asking rudimentary questions,
but I am learning along the way. Thanks for the patience.
 
BUT when I try the 1k resistor, because it has the EXTRA hooks up (5
instead of 3 that are in the trim pots), I am not sure how to make it
work.
Here is the picture :

http://davidd.250free.com/resistor.gif

Thanks again. I know that I am probably asking rudimentary questions,
but I am learning along the way. Thanks for the patience.

Are you sure those two extra ones on the side are not connected to the
metal case? In other words, just a place to attach grounds. Is the
metal part of the housing connected right to those two. I see no
other reason for them.

As far as the others, the center is the variable contact or output.
The left and right go across the source, whereas one is generally
grounded, and the other would be positive voltage or audio input
signal (input from source). I forget which is which. If it turns the
wrong direction, jsut reverse the wires to those two outer ones.
 
A

Arfa Daily

Jan 1, 1970
0
Victory said:
Ok, I hope someone can help me out with this. I went out and bought a
1k variable resistor. I took a picture of the setup and I would love
it if someone could take photoshop or paint and connect the dots for
me and therefore I will know where to put the wires. The LED doesn't
have any specs and the batteries are TWO 3V button batteries in
series. I have tried connecting it myself and all I can get is the
light "on and off", but it doesn't dim or get brighter.
I have also bought a bunch of trim pots (really really small) - these
radio shack trim pots aren't a problem - I have tested and hooked them
up to the LED. Turning the turning the dial to dims and brightened
the LED.
BUT when I try the 1k resistor, because it has the EXTRA hooks up (5
instead of 3 that are in the trim pots), I am not sure how to make it
work.
Here is the picture :

http://davidd.250free.com/resistor.gif

Thanks again. I know that I am probably asking rudimentary questions,
but I am learning along the way. Thanks for the patience.

OK. Assuming that the wire to the left of your battery pack is "-" and the
one to the right is "+", then it connects pretty much as you have it lying
there. The short leg of the LED goes straight to battery "-". The battery
"+" wire goes to the right-hand tag of the three that are together on the
pot, as we are looking at it on the picture. The centre and left tags should
be joined together. You then need a fixed resistor of say 22 ohms connected
between the joined-together pot tags, and the long lead on the LED. This
resistor is important, as it will limit the maximum current that the LED can
draw with the pot turned right up. Without it, the LED will burn out.

Can I just ask that you post replies to the bottom of any text that you are
replying to, rather than the top, as you would when replying to a personal
e-mail. It makes the thread a lot easier to follow, and whilst there are a
few that vociferously defend newsgroup top-posting, the accepted convention
is to bottom post, with top snipping if needed to aid clarity.

Thanks.

Arfa
 
V

Victory

Jan 1, 1970
0
OK. Assuming that the wire to the left of your battery pack is "-" and the
one to the right is "+", then it connects pretty much as you have it lying
there. The short leg of the LED goes straight to battery "-". The battery
"+" wire goes to the right-hand tag of the three that are together on the
pot, as we are looking at it on the picture. The centre and left tags should
be joined together. You then need a fixed resistor of say 22 ohms connected
between the joined-together pot tags, and the long lead on the LED. This
resistor is important, as it will limit the maximum current that the LED can
draw with the pot turned right up. Without it, the LED will burn out.

http://davidd.250free.com/resistor2.gif

Ok, I have two wire setups here.
1) The first one in light GREEN is the one that works great for
turning the LED off and on, but does NOT dim or brighten it. I have
tried this setup and it works.
2) The second setup in RED is one that works great for dimming and
brightening of the LED - but does NOT turn off/on

The trouble now is getting them to work in combination so I can have
it dim and turn off/on. As I said, I have tried both of these setup
and then tried to mix and match the setup to see if I could get both
the bright/dim and the off/on to work at the SAME TIME, but to no
avail.

I have not used a resistor for either of these setup because when I
connect the TWO batteries directly to the LED (the way I have been
using it before the variable resistor), it has never been a problem
and doesn't get hot or burn out.
 
V

Victory

Jan 1, 1970
0
OK. Assuming that the wire to the left of your battery pack is "-" and the
one to the right is "+", then it connects pretty much as you have it lying
there. The short leg of the LED goes straight to battery "-". The battery
"+" wire goes to the right-hand tag of the three that are together on the
pot, as we are looking at it on the picture. The centre and left tags should
be joined together. You then need a fixed resistor of say 22 ohms connected
between the joined-together pot tags, and the long lead on the LED. This
resistor is important, as it will limit the maximum current that the LED can
draw with the pot turned right up. Without it, the LED will burn out.

http://davidd.250free.com/resistor2.gif

Ok, I have two wire setups here.
1) The first one in light GREEN is the one that works great for
turning the LED off and on, but does NOT dim or brighten it. I have
tried this setup and it works.
2) The second setup in RED is one that works great for dimming and
brightening of the LED - but does NOT turn off/on

The trouble now is getting them to work in combination so I can have
it dim and turn off/on. As I said, I have tried both of these setup
and then tried to mix and match the setup to see if I could get both
the bright/dim and the off/on to work at the SAME TIME, but to no
avail.

I have not used a resistor for either of these setup because when I
connect the TWO batteries directly to the LED (the way I have been
using it before the variable resistor), it has never been a problem
and doesn't get hot or burn out.
 
V

Victory

Jan 1, 1970
0
OK. Assuming that the wire to the left of your battery pack is "-" and the
one to the right is "+", then it connects pretty much as you have it lying
there. The short leg of the LED goes straight to battery "-". The battery
"+" wire goes to the right-hand tag of the three that are together on the
pot, as we are looking at it on the picture. The centre and left tags should
be joined together. You then need a fixed resistor of say 22 ohms connected
between the joined-together pot tags, and the long lead on the LED. This
resistor is important, as it will limit the maximum current that the LED can
draw with the pot turned right up. Without it, the LED will burn out.

http://davidd.250free.com/resistor2.gif

Ok, I have two wire setups here.
1) The first one in light GREEN is the one that works great for
turning the LED off and on, but does NOT dim or brighten it. I have
tried this setup and it works.
2) The second setup in RED is one that works great for dimming and
brightening of the LED - but does NOT turn off/on

The trouble now is getting them to work in combination so I can have
it dim and turn off/on. As I said, I have tried both of these setup
and then tried to mix and match the setup to see if I could get both
the bright/dim and the off/on to work at the SAME TIME, but to no
avail.

I have not used a resistor for either of these setup because when I
connect the TWO batteries directly to the LED (the way I have been
using it before the variable resistor), it has never been a problem
and doesn't get hot or burn out.
 
V

Victory

Jan 1, 1970
0
OK. Assuming that the wire to the left of your battery pack is "-" and the
one to the right is "+", then it connects pretty much as you have it lying
there. The short leg of the LED goes straight to battery "-". The battery
"+" wire goes to the right-hand tag of the three that are together on the
pot, as we are looking at it on the picture. The centre and left tags should
be joined together. You then need a fixed resistor of say 22 ohms connected
between the joined-together pot tags, and the long lead on the LED. This
resistor is important, as it will limit the maximum current that the LED can
draw with the pot turned right up. Without it, the LED will burn out.

http://davidd.250free.com/resistor2.gif

Ok, I have two wire setups here.
1) The first one in light GREEN is the one that works great for
turning the LED off and on, but does NOT dim or brighten it. I have
tried this setup and it works.
2) The second setup in RED is one that works great for dimming and
brightening of the LED - but does NOT turn off/on

The trouble now is getting them to work in combination so I can have
it dim and turn off/on. As I said, I have tried both of these setup
and then tried to mix and match the setup to see if I could get both
the bright/dim and the off/on to work at the SAME TIME, but to no
avail.

I have not used a resistor for either of these setup because when I
connect the TWO batteries directly to the LED (the way I have been
using it before the variable resistor), it has never been a problem
and doesn't get hot or burn out.
 
V

Victory

Jan 1, 1970
0
OK. Assuming that the wire to the left of your battery pack is "-" and the
one to the right is "+", then it connects pretty much as you have it lying
there. The short leg of the LED goes straight to battery "-". The battery
"+" wire goes to the right-hand tag of the three that are together on the
pot, as we are looking at it on the picture. The centre and left tags should
be joined together. You then need a fixed resistor of say 22 ohms connected
between the joined-together pot tags, and the long lead on the LED. This
resistor is important, as it will limit the maximum current that the LED can
draw with the pot turned right up. Without it, the LED will burn out.

http://davidd.250free.com/resistor2.gif

Ok, I have two wire setups here.
1) The first one in light GREEN is the one that works great for
turning the LED off and on, but does NOT dim or brighten it. I have
tried this setup and it works.
2) The second setup in RED is one that works great for dimming and
brightening of the LED - but does NOT turn off/on

The trouble now is getting them to work in combination so I can have
it dim and turn off/on. As I said, I have tried both of these setup
and then tried to mix and match the setup to see if I could get both
the bright/dim and the off/on to work at the SAME TIME, but to no
avail.

I have not used a resistor for either of these setup because when I
connect the TWO batteries directly to the LED (the way I have been
using it before the variable resistor), it has never been a problem
and doesn't get hot or burn out.
 
A

Arfa Daily

Jan 1, 1970
0
Victory said:
http://davidd.250free.com/resistor2.gif

Ok, I have two wire setups here.
1) The first one in light GREEN is the one that works great for
turning the LED off and on, but does NOT dim or brighten it. I have
tried this setup and it works.
2) The second setup in RED is one that works great for dimming and
brightening of the LED - but does NOT turn off/on

The trouble now is getting them to work in combination so I can have
it dim and turn off/on. As I said, I have tried both of these setup
and then tried to mix and match the setup to see if I could get both
the bright/dim and the off/on to work at the SAME TIME, but to no
avail.

I have not used a resistor for either of these setup because when I
connect the TWO batteries directly to the LED (the way I have been
using it before the variable resistor), it has never been a problem
and doesn't get hot or burn out.

Ah! OK. Now I can see what the two additional terminals on the pot are. They
are a switch, which presumably goes "click" when you go fully anticlockwise,
yes ?

Assuming yes, then the correct hookup will be right hand side yellow to mid
body righthand tag, as shown. New wire from left hand mid body tag to
righthand tag of the block of three tags, ie the tag where you are currently
showing a red wire on the right. Lefthand red wire where it is currently
shown ie to the centre and left tags that are joined together. Lefthand
yellow wire now irrelevant. Bottom red or yellow wire as currently
indicated.

Now, when the pot is clicked fully anticlockwise, the feed from the battery
to the righthand pot tag, will be broken by the switch, so no current will
flow through the LED, and it will extinguish. Once the switch has clicked
back on, as you rotate clockwise, you will be returned to the 'red' circuit
that worked ok to dim the LED. Do you follow that OK ?

As far as not having any additional series resistor, if that's the way it
was done in the original unit that you canibalised it from, then that's
fine. I would however suggest that you do not use any other battery type
than the originals, as it probably gets away with current limiting by the
internal resistance of this type of cell. Whilst the LED may have its own
internal current limiting, from the photo, it looks like a pretty
bog-standard type, which if you do allow it to draw too much current, will
destroy itself.

Incidentally, your post appeared multiple times on my news server, separated
by a couple of minutes each, so I'm not too sure what happened there.

Arfa
 
V

Victory

Jan 1, 1970
0
I did notice the replication of the posts. I deleted them, but I
don't know why google repeated them so.

To make it easier on me to understand, I have updated the image with
numbers, so now it is a matter of matching numbers (I hope). I think
this is always the difficulties with tech support on the phone or
online because it is really hard to visualize with words sometimes.

http://davidd.250free.com/resistor3.gif

I tried to read through what you had written and got a little
confused, so this might make it easier.
Ah! OK. Now I can see what the two additional terminals on the pot are. They
are a switch, which presumably goes "click" when you go fully anticlockwise,
yes ?

Yes, it clicks off/on
 
A

Arfa Daily

Jan 1, 1970
0
Victory said:
I did notice the replication of the posts. I deleted them, but I
don't know why google repeated them so.

To make it easier on me to understand, I have updated the image with
numbers, so now it is a matter of matching numbers (I hope). I think
this is always the difficulties with tech support on the phone or
online because it is really hard to visualize with words sometimes.

Hmm. I thought that I pretty much covered all the bases with unambiguous
wording ...
http://davidd.250free.com/resistor3.gif

I tried to read through what you had written and got a little
confused, so this might make it easier.

Right then.

9 to 8. New wire 4 to 7. 5/6 to 3. 1 to 2. Hows about that then ? Follow OK
?

Arfa
 
J

James Sweet

Jan 1, 1970
0
Arfa Daily said:
Hmm. I thought that I pretty much covered all the bases with unambiguous
wording ...


Right then.

9 to 8. New wire 4 to 7. 5/6 to 3. 1 to 2. Hows about that then ? Follow
OK ?

Arfa

Seems like he really needs to get a book, or read up on basic electronics
online. It would be beneficial to have the slightest clue how each of the
components works. It's a very simple circuit, anyone with any interest in
electronics should soak up enough to be able to make it work on their own.
Little is learned through such extensive handholding.
 
V

Victory

Jan 1, 1970
0
No you were perfect in your other explanation - I just didn't want to
get it wrong since I have tried a dozen combination and couldn't get
it right. This way is great and I understand it completely. As you
can tell, I don't have a electronic background of any sort (obvious),
but I have experiments myself. I got a regular 3-prong pot to work,
it is just these extra prongs that were throwing me. I would love to
take a course in this stuff, but unfortunately, it is not offered in
my area (yes, I have checked).

I will let you know how it turns out once it is all connected.
 
V

Victory

Jan 1, 1970
0
Sweet success! Thank you so much. It goes pretty much through the
entire cycle of bright to dim as it turns.

I was going to put an ON/OFF switch with another 3-prong POT when I
couldn't get this 5 prong POT going, but this is great.

Now, since you have been so completely helpful, I am going ask one
more favor - I want to find a source for a 5-prong pots like this
online - but I want to make sure it is smaller and lighter than what I
have, (which is about 1 inch high) - any suggestions?
 
S

Smitty Two

Jan 1, 1970
0
James Sweet said:
Seems like he really needs to get a book, or read up on basic electronics
online. It would be beneficial to have the slightest clue how each of the
components works. It's a very simple circuit, anyone with any interest in
electronics should soak up enough to be able to make it work on their own.
Little is learned through such extensive handholding.

No shit. I was the first respondent to this guy, and the only thing I
told him was to get a book. It was clear from the outset that he hadn't
a speck of basic knowledge and no interest in obtaining any. Arfa's
patience is exemplary but sometimes misguided, I think. OK, so the
circuit works now, but the OP isn't one step closer to understanding
anything about how or why it works.

Give a man a fish...
 
A

Arfa Daily

Jan 1, 1970
0
Victory said:
Sweet success! Thank you so much. It goes pretty much through the
entire cycle of bright to dim as it turns.

I was going to put an ON/OFF switch with another 3-prong POT when I
couldn't get this 5 prong POT going, but this is great.

Now, since you have been so completely helpful, I am going ask one
more favor - I want to find a source for a 5-prong pots like this
online - but I want to make sure it is smaller and lighter than what I
have, (which is about 1 inch high) - any suggestions?

Dunno. Wherabouts in the world are you ? If in the UK, Maplins do quite a
range. Probably Farnell and RS as well. You can now order from them without
being 'trade'. If in the US, Digikey or Mouser, perhaps ? I would suggest
that Google is your friend here ... Look for "pot with switch" and you
probably are looking for ones with a linear rather than logarithmic taper.
(Google that for a better understanding). Wiki have some very good sections
on basic electronics. Try typing into their search box for articles that you
might understand ok. The 'prongs' are called tags, or pins if it's a printed
circuit mounting component. Be careful with going any 'lighter' duty on the
component, as its (relatively) delicate guts may not be able to stand the
current that the LED draws at high brightness. These days, pots tend to all
be of the 'Japanese' variety that you show in your pictures, so you will
probably struggle a bit to get a smaller one with a switch, in any case.
Anyway, glad you got it going in the end, and hope you learnt something
along the way

(even if it is just about top and bottom posting conventions ... d;~} )

Arfa
 
A

Arfa Daily

Jan 1, 1970
0
Smitty Two said:
No shit. I was the first respondent to this guy, and the only thing I
told him was to get a book. It was clear from the outset that he hadn't
a speck of basic knowledge and no interest in obtaining any. Arfa's
patience is exemplary but sometimes misguided, I think. OK, so the
circuit works now, but the OP isn't one step closer to understanding
anything about how or why it works.

Give a man a fish...


Hi Smiddy, how goes it ? Well, gotta do ya bit, you know ? I guess we were
all electronically 'dumb' at one time. Hopefully, by giving the guy this one
fish supper, I'll have encouraged him to go out and buy a rod ...

I would like to think that he understands at least a bit about it now, and
at least he seems appreciative of the help he's received, unlike some on
here. Like the one that I took the trouble to send schematics to a couple of
weeks or so ago, who hasn't even had the courtesy to acknowledge the effort,
let alone offer any thanks ...

Misguided ? Yeah, I've been that all my life. That's why I've got me a GPS
now ... :)

Arfa
 
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