Experimenting with Hot Glue..

[evahle]

Has anyone experimented with hot glue? There are so many things that I've seen people doing with this stuff.

An idea occurred to me while working on a clock circuit. Since I'm always needing a way to diffuse an LED(the bright ones are more like a laser), I thought maybe making a few different molds, then pouring in some hot glue to make different sizes and shapes to put my LEDs in.

The "HOUR" display I'm making, may look a lot better if I could take both colored LEDs and put them inside one of these molds and then pour hot glue all around them. I thought maybe, with a little practice, I could make some interesting projects with this.

Has anyone done anything like this? If so, what kind of experiments have you done?

Thanks.

evahle

[psycho]

The only thing like that that I have done is embed a DS1820 One-Wire Temp Sensor in it. I had an old prescription pill bottle filled with glue and just the wires coming out. This worked well for use outdoors.

[MrAl]

Hi there evahle,


Interesting that you should bring this up, because i use hot glue for
all kinds of things on a regular basis, probably at least once a week.

Perhaps we can start a list where everyone can add their own
uses to the list as time goes on. I never thought of using it for
display purposes and i guess you could make just about any
shape object and "light it up" with LEDs, that's a good idea.

What i use it for can be classed into two different catagories:
A. Permanent Use
B. Temporary Use

A good example of temporary use is when gluing or epoxying some
objects together and cant quite get them to stay together in the right
position while the 'normal' glue or epoxy hardens. I first set up
the objects and glue them with hot glue, which only takes about 2
minutes to harden. I try not to get hot glue where i want permanent
glue when doing this. Once the hot glue hardens, i then apply the
'real' glue or epoxy. While it's hardening the hot glue keeps it
perfectly in place. Once that hardens, i can peel the hot glue off
if it will interfere with the end application or simply leave it there
if not.
Another semi-temporary use is for weather stripping. Gluing that
with hot glue means i can either leave it there or take it off in the
summer.
Another semi-temp use is for electrical isolation. You have to be
careful here but i find that it makes a decent electrical insulator,
so you can cover up bare wires to prevent touching them at
least temporarily.

For permanent long term use there are a few precautions:
Some glues yellow with age.
Even worse, hot glue cracks when under too much stress.
It will of course melt if subject to high temps, or bend if mild temps.

Taking these things into account i guess it's good for quite a few things.
I've used it for speaker connections (insulation), even a make shift
tool handle once, feet for a small (non heating) appliance.
In fact, you can make some pretty nice feet by quickly putting four
dabs on the bottom of your (say) alarm clock, then turning it right
side up and placing on top of some clear plastic wrap over a smooth
flat surface. After the glue cools you've got some good feet that
could even be different sizes depending on the shape of the bottom
of the device (as an alarm clock for example).

I think my biggest use though is to hold things together or in place
while i wait for the normal glue or epoxy to set.

A craft store about 8 miles from here had a sale on glue sticks
one time for 2 cents per stick (the short ones) i went down and
bought 200 of them. That was several years ago, but i still have
about 50 sticks left.

Oh yeah, another temporary use was when my modem kept sliding off
the top of the computer box. I like to keep it there so i applied a little
hot glue (not too much). It holds it there just fine and if i ever want
to move it all i have to do is peel the hot glue off.

[evahle]

WOW! Fantastic ideas guys. I think I see a book coming out this. Maybe we could call it "1001 uses of Hot Glue in Electronics" LOL.

I plan on printing this thread out, so I can try some of these ideas. I did use hot glue once for feet on the bottom of a PC board, because I didn't want to put it in a case and I couldn't find the right size rubber feet to fit. I forgot about that.

I wonder which hot glue to use to keep it from yellowing over time. That wouldn't be too good for displays.

I really like the idea of putting sensors into hot glue for outdoors. I wonder how long it would last under extreme conditions.

evahle

[Janitor Tzap]

Hey there evahle,

I wouldn't use Hot Glue for your application.
It's melting point is to low.

If your planning on using those Ultra Bright 1W LEDs.
You will end up with a melted mess.

I suggest instead some 5 minute epoxy.
Add some colored dye to the mixture of epoxy before you pore it into the mold.

If you look at some of the new LED Light strings.
They embed the LED into a colored plastic bulb shaped lense.

Thou, that may be easier, to just get a string of colored LED's.
And use them in your project.


Signed: Janitor Tzap

[evahle]

1W huh? Well actually I wasn't going to get that carried away.
I'm just using the standard 1.7 - 3.5v LEDs (5mm), but they are around 4000-5000mcd types with about a 25deg angle. I really want to make the hot glue sort of glow, if possible. I'm not sure it will work until I actually try it.

Do they make different color glue sticks? That may work better.
evahle

[CeaSaR]

...and placing on top of some clear plastic wrap over a smooth flat surface.

Does the glue stick to the plastic wrap or melt it? Have you ever tried
either wax paper or parchment paper? I would think that parchment
paper would be the best to use in that situation. Hmm, maybe a few tests
are in order...

As for what uses it can be put to, the craft community has been using the
stuff for years. I've seen it used in so many different applications that to
describe them all would wear my fingers down to the knuckles. So, yes,
you can use it to pot your LED's for diffusion. Just make sure you use
the "frosted/milky" style of glue, not the clear stuff. You just have to
make sure that you can remove your glue shapes from the molds. I
would check some craft sights on how to do this.

CeaSaR

BTW, they make different melting point glues for different wattage glue
guns, and they also have non-yellowing types of glue.

[Janitor Tzap]

1W huh? Well actually I wasn't going to get that carried away.
I'm just using the standard 1.7 - 3.5v LEDs (5mm), but they are around 4000-5000mcd types with about a 25deg angle. I really want to make the hot glue sort of glow, if possible. I'm not sure it will work until I actually try it.

Do they make different color glue sticks? That may work better.
evahle

Ok,

Well, you can get the hot glue sticks in several colors.
But, try to find light colored sticks, not dark colored ones.
You want to defuse the light through the hot glue, not block it out.


Signed: Janitor Tzap

[MrAl]

Ceasar:
Well actually i just suggested that, your idea may be better.
I have used a counter top lamination in the past and this makes
a nice rough bottom for the feet so they are non slide.

I really like the idea of putting sensors into hot glue for outdoors.
I wonder how long it would last under extreme conditions.
evahle

That's a good question and you reminded me of a use i almost
forget entirely about. That is, for tubes of OTHER glue
or silicone you can use it to block the top to prevent air
from getting into the glue. This works much better than
the standard tops that come with various glues and silicone
rubber tubes. I used this on a big tube of silicone and
it didnt dry out after two years time.
The standard tube tops usually allow some air to get to
the glue or silicone, even a little is no good because
over long periods of time the glue or silicone dries out
anyway. With a cover of hot glue it takes years.
I also did one tube where i made a small ball of hot glue
and then put it into the top of the glue, then when i
put the top on the glue tube it squeezed the hot glue
ball (cooled) into the tip of the glue tube and that made
a good air seal too to prevent drying out.

Too much sunlight will probably deteriorate the hot glue
and if the temperature gets too high it will cause it to soften.
This could be a problem so the effectiveness probably
varies from application to application.

[CeaSaR]

I have used a counter top lamination in the past and this
makes a nice rough bottom for the feet so they are non slide.

True. The parchment paper is actually a tad rough, but still very slippery
so it is mostly nonstick. You could even go to a kitchen / cooking type of
store (even the big craft stores) and look for a textured silicone baking
sheet to give a certain type of facing to the glue. Just make sure the wife
doesn't try to claim it!

CeaSaR

[psycho]

I would use aluminum foil. I know that won't melt with the glue gun I have. And, if you look at it, there is a shiny side and a dull side. The shiny side is very smooth. (for molding different things).

I had a thought... Instead of a project box, encase the whole circuit board of a project in a "case of glue". Have the connectors/buttons/etc stick out and have everything else encased in glue (as long as heat would not be an issue). The problem with that would be melting enough glue at once and not making a major mess. Alos, making the form to do it would be a challenge. Of coarse, debugging afterwards would not be an option

Kevin

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typos
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[MrAl]

I have used a counter top lamination in the past and this
makes a nice rough bottom for the feet so they are non slide.

True. The parchment paper is actually a tad rough, but still very slippery
so it is mostly nonstick. You could even go to a kitchen / cooking type of
store (even the big craft stores) and look for a textured silicone baking
sheet to give a certain type of facing to the glue. Just make sure the wife
doesn't try to claim it!

CeaSaR

Not a bad idea for the bottom 'mold' texture which would make a nice
non slip bottom. I think i may have something like that laying around
(the 'baking sheet', not the 'wife' he he he).

I would use aluminum foil. I know that won't melt with the glue gun I have. And, if
you look at it, there is a shiny side and a dull side. The shiny side is very smooth. (for molding
different things).
I had a thought... Instead of a project box, encase the whole circuit board of a project in
a "case of glue". Have the connectors/buttons/etc stick out and have everything else encased
in glue (as long as heat would not be an issue). The problem with that would be melting enough
glue at once and not making a major mess. Alos, making the form to do it would be a challenge.
Of coarse, debugging afterwards would not be an option

Kevin

That's actually a very decent idea too i believe. Right, if heat is not an issue
then the entire circuit would be protected from moisture to a very high degree, from
what i know about the protective qualities of hot glue. Since i have found in the past
that hot glue is a very good material to keep out air, i dont see why it wouldnt work
even better to keep out moisture.
The neat thing about hot glue though is that it can be torn off, ie
broken up a little and peeled off, so actual repair might still be an
option where with say epoxy it would be very hard to do.

[dacflyer]

evahle >> what i usually do, (takes time!) i use the sanding drum for a dremmel, or i use the edge of a saw off blade, and lightly sand the LED.
it makes it nice and frosty looking. but it is time consuming, especially if you do bunches of them..not to mention the dust

[psycho]

I wasn't thinking of keeping out moisture in the glue box. But, I would think that you could make some cool effects. You could use different colored sticks and make letters and embed the letters into the clear glue. I would think that the letters would have to be high temp and the clear would need to be low temp so that the clear didn't obliterate the letters.

Though, for kicks, I looked at the prices of bulk glue (only on ebay) and it seems expensive. One guy has a 25# box of it for 35 bux or so but its another $22 in shipping.

As for melting large quantities, anyone know if you can put it in a microwave or toaster oven without it breaking down or, more importantly, fuming the oven with toxins?

[Lenp]

Here's another thought,

I do tech support for a large bindery and they use lots of hot glue for binding. It has different melting and clarity properties than the craft store glue sticks, comes as small beads or shapes and melts easily so it can be poured. Maybe a local bindery shop would part with, or would order some for you. They get it in large boxes or drums.

Also a few years ago a friend wanted really small LED's for a model train project. The physical size was not an issue, just the lens. Since the top of the LED is only the lens/diffuser, I turned some standard LED's on a lathe so they had a small cylinder, about 1mm diameter at the end instead of the domed top, faced them square and he used them as lights on a caboose!.

Len