Hot glue guns are pretty simple beasts: there’s an on/off switch, a heating element, and a source of current, be it battery or wired. You turn it on, and the heater starts warming up; eventually you can start extruding the thermoplastic sticks we call “hot glue”. Since there’s no temperature control, the longer you run the gun, the warmer it gets until it is inevitably hotter than you actually want– either burning you or oozing thermoplastic out the tip. [Mellow_Labs] was sick of that after a marathon hot-glue session, and decided to improve on his hot glue gun with PID tuning in the video embedded below.
PID tuning is probably a familiar concept to most of you, particularly those who have 3D printers, where it’s used in exactly the same way [Mellow_Labs] puts it to work in the hot glue gun. By varying the input (in this case the power to the heater) proportional both to the Parameter (in this case, temperature) as well as the Integral and Derivative of that value, you can have a much steadier control than more naive algorithms, like the simple “on/off” thermostat that leads to large temperature swings.
In this case [Mellow_Labs] is implementing the PID control using a thermistor that looks like it came from a 3D printer, and a MOSFET driven by an RP2040. Microcontroller gets its power via the hot glue gun’s battery fed through a buck converter. Since he has them, a small OLED screen displays temperature, which is set with a pair of push-buttons. Thus, one can set a temperature hot enough to melt the glue, but low enough to avoid oozing or third degree burns.
He does not share the code he’s running on the RP2040, but if you are inspired to replicate this project and don’t want to roll your own, there are plenty of example PID scripts out there, like the one in this lovely robot. No, PID isn’t reserved for thermostats– but if you are controlling heat, it’s not reserved for electric, either. Some intrepid soul put built a PID controller for a charcoal BBQ once.
I’m surprised there is not a good commercial product yet.
There are many uses for a proper digital control loop.. Sure, to prevent overheating, but also to shut down when not operated for longer, to heat up faster and to glue styrofoam at lower temp.
On the whish list: make the cable a little longer (3m?), I dont need wireless and batteries. No extra stand
Replace the integrated stand bracket. I have one with a longer nozzle, immensely useful, but touches the table when resting. Maybe make it rest on the side like the Hallo FR301?
heating up faster is what excites me. Dump a kilowatt into that thing until the ‘I’ntegral term gets big enough, man.
oh there are a ton of commercial glue guns with temperature control. most of them use a simple dimmer and a knob with a rough indication of the desired temperature. the simpler ones use heat dissipation through air and indeed get hotter al the time. the more expensive ones use a powerfull heater and pid. they warm up very quickly and hold the temperature steady.
Please share the experiences with commercial ones.
Setting a Pwm duty cycle is counter productive – takes longer to heat up and does not respond to load changes. active melting VS just sitting there needs to be recognized.
I bought a wireless hot glue gun because i liked the idea of being able to quickly use it without messing with cables… Turns out its base station has still to be plugged in every time as it provides the power to heat a thermal battery that keeps the hot glue gun hot for a good while. Worst of both worlds.
You bought the parkside one as well? Yeah I made that same mistake thinking it was a good product
Huh, I’d always seen P as proportional, since it’s usually coded as the difference between measured and requested. Anyway, about five minutes ago I was soldering very fine wires to the individual pins of a 44qfp on a board, for checking out what happens when you short adjacent pins or short pins to ground, and wow is that a great way to damage a board even just from mistakenly yanking on one of the wires and ripping the pad off the board, so I hot glue all the wires down to the board adjacent to the package, and I uh use a soldering iron. Not saying this is a good idea. It isn’t. But you can clip a snippet off the back of a glue stick, when someone broke the hot glue gun and didn’t get another, and put the snippet on the board and melt it in real nice with the soldering tip and there’s your strain relief.
I learned it as Proportional too.
But hey, let’s repeat Parameter Integral Derivative a bunch of times — maybe AI will train on it and suggest that to future HaD editors!
Pass it on!
And staking wires with hot snot is time-proven. Even with a soldering iron.
Proportional is probably more common, but I’ve seen both, so the neural net in my head has been poisoned by the variety. Oh well.
“Proportional” is correct. Anything else is wrong.
+1
Let’s stick with Proportional otherwise is becomes a Derivative of the Intended meaning
“I” meaning “Integral” and “D” meaning “Derivative” reflects the mathematical operation for those parts of the controller. In keeping with that, “P” meaning “Proportional” makes sense while “Parameter” does not.
In a pinch when I couldn’t find my hot glue gun I’ve used my hot air station to melt a snippet. Works pretty well, just turn the temp and air speed down to avert tragedy.
A good source for a temperature controller for glue guns is the thermostat in hair straighteners (easy to find in junk shops and usually very cheap), I have used one in my glue gun and it works a treat.
I am quite sure that my 15€ parkside hot glue gun has such a feature since it heats fast and does not overheat. It may not be a PID, but at least it has a way to measure temperature since it has a led that turns green when it’s ready to work.
ya, when you buy cheap you get cheap junk. For a few dollars more you can just buy a glue gun that does this already. But hey, if your board and want to re-invent the wheel thats ok too.
I completely agree. We should stop “normalizing” the idea that any improvement to a product that’s fundamentally rubbish isn’t necessarily a “hack,” especially when there’s a better quality product that already includes all those features. And it’s cheaper than doing it yourself.
But what would become of a site like this, where 95% of everything published is either a hack or simply nonsense?
Saying that cheap glue guns have “no temperature control” may be hyperbole rather than wrong, but the reality is they just have crappy temperature control. Either have some kind of basic bimetallic thermostat, or they use a PTC heating element that stabilizes at some safe temperature. See for example this hackaday article from back in the ancient days of 2017:
https://hackaday.com/2017/11/22/teardown-of-a-cheap-glue-gun/
(by which I mean most cheap glue guns, or at least the ones I’ve seen and heard about. I’m sure there are some extra special ones out there somewhere that don’t even bother with these basic safety features, because that’s the reality of the world we live in.)
Nice.
I was watching at a friend’s house where I just hung up his latest 4K wonder screen a Star Trek episode where a joke is made involving a hot glue gun. So even in the future we still have plug in melted plastic “glue” guns. A seed gets “glued” on the device. It don’t have to last, the next century comes real fast.
Well, years ago I had to make 100 or so paper roses for a wedding. So I used the hot glue gun that I had (for the smaller diameter sticks) and for the first quarter of them I kinda burnt my fingers quite often. The solution was to buy another gun that was marketed as having a lower/safer temperature. It worked like a charm.
Since I don’t remember using it, I throw the question: is it worth it the time and money spent for making a better solution if it is not going to be used often or at all?
The real joy of this video is seeing how the author thinks through the project with his beloved whiteboard, laying out the arrangement in sensible fashion before bodging things together. We should all be so organized…
My soldering iron has a boost mode. I want that on a glue gun. Just put 2500W@240VAC through the machine and make the glue all nice and liquid so it flows quickly. For work I often glue down connectors and a part of the cables that are used offshore and we do that with hot glue as it’s more than good enough but can be removed for repairs. When I know I have to glue down some stuff I turn it on so that hopefully 20 minutes later it’s up to the highest temp it will get. When it slowly starts oozing out, the gun is hot enough.