PID Controlled Glue Gun

Internals of a glue gun controlled with a PID controller

Hot glue falls into the same category of duct tape and zip ties as a versatile┬ámaterial for fixing anything that needs to be stuck together. [Ed]’s Bosch glue gun served him well, but after a couple of years the temperature regulation stopped working. Rather than buying a new one, he decided to rip it apart.

With the old temperature regulation circuit cooked, [Ed] looked around for something better on eBay. He came across a cheap PID temperature controller, and the Frankengluegun was born.

A thermocouple, affixed with some kapton tape and thermal paste, was used to measure the temperature of the barrel. Power for the glue gun was routed through the PID controller, which uses PWM to accurately controller the temperature. All the wiring could even be routed through the original cord grips for a clean build.

Quality glue guns with accurate temperature control are quite pricey. This solution can be added on to a glue gun for less than $30, and the final product looks just as good.

21 thoughts on “PID Controlled Glue Gun

      1. no worries, you just need a bigger flame for reflow. I recommend a propane torch. puts a zippo to shame. (note: the stronger the fumes, the better it’s working!)

        1. It is *a* point, but not *the* point. And said point also lacks vision, and passing a negative judgement before bothering to understand its merits. Kind of like saying soldering irons are $5, why bother upgrading it so it’s as nice as an $80 solder station?

          This glue gun now has a settable temperature, something that is not available unless you put far more money into it. Normal cheap glue guns have one or two, if you’re lucky, and they don’t say what temps they are. Also, normal glue guns warm up very slowly. I’m willing to bet this thing heats up several times faster than any of the cheap replacements.

          1. Since he used the pre-existing heater, I doubt it heats faster. It will just be more precise.

          2. As That-one-guy says the improvement may not be noticeable without replacing the heating element. The one in the device has been designed to give enough heat to melt the glue and not burn the unit at (I assume) 100% duty cycle and an open control loop. PID might help if there was some spare power.

            However, all that said, there is a detail this hack may help with. With the duty cycle set to a little less than 100% the glue gun may stop dripping and that “little less” may be enough for PID to work with when a user presses the trigger and needs some more heat to melt new glue.

    1. But, those really suck. When used constantly, they typically only last a few weeks before the trigger, feed mechanism, or heater break. They also have a limited availability of stick sizes and types. The more expensive ones last a long time. I have one I use at work for demoing hot melt for customers. It’s lasted 15 years so far. The more expensive ones usually have replaceable nozzles depending on the application. The el-cheapos don’t. There is also a huge variety of sizes and types.

  1. This is a pretty clean build. I noticed the same effect on another gun some years back. I solved it with a simple thermostat, but i don’t remember the temperature setting.

    I did not know PIC controllers could be had for such little money from ebay.

  2. I think the temperature control still works in my hot glue gun. Heck the gun itself still works pretty good so I’m going to assume it is OK. How do we tell if the PID is broken? Like what does the gun do then?

  3. I should point out for those who haven’t spotted the important detail:
    My gluegun had got far too hot – it was always about 200W even when at operating temperature – this is why the PID controller was a good hack to add. Cold, it should be 200W, once warmed up it should be about 15W.

    The heating element in most glue guns is self-regulating. Not like a thermostat but a PTC resistor, as it gets hotter it draws less current, hence modulating it’s own power appropriately.

    Left unchecked, my gluegun now runs 100% power, 100% of the time. Great for PID control, not so great for being wired directly into the plug. This seemed an ideal opportunity to make it temperature controlled since the PID controller would work far better with a heater with a sensible mostly linear behaviour.

    A 200W cartridge heater would be perfect if one could be found to fit the existing heater barrel – then the gluegun would have ample power to heat up and the PTC nature of the original heater can be forgotten about.

    Since this gluegun can be used for about 8 hours on the run and we pump 3-4 trigger squeezes of glue each time it is picked up, it gets a fair amount of cyclic use and the PID is great for compensating for the sudden fresh cold glue arriving in the barrel.

    The glue gun is a bosch, it’s really well made and I’d far rather fix it like this and improve it beyond it’s original spec than buy another. Also, the whole thing probably took about 20 mins – I had everything on hand already.

    :) happy hacking!

    1. My company sells adhesive application machinery, so we get a lot of calls from the average DIYer who receive severe “sticker shock” when we tell them how much a glue gun with precision control will cost them. I don’t blame you one bit for trying to find an alternate homebrew solution.

      All of the equipment we sell, be it thermostat control or PID, will have an overtemp thermostat to help prevent fires from the adhesive boiling and flashing over. The typical overtemp switch is set at 425F. There are special applications that will require higher (usually butyl) or lower (wax or pressure sensitive) temperature ranges. That being said, I would highly recommend putting in some type of thermal fuse to protect from runaway heating. It would just have to be inline with one of the power leads of the heater.

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