Glue gun mod...

[nznative]

Hi all. My first post here....



This is a pic of my 18v cordless hot glue gun. It runs at a temp of around 190 degrees centigrade but the material I work with is quite sensitive to those high temps so I have purchased some low temp glue sticks and need to lower the running temp of the gun down to about 120 degrees centigrade. I have run a few tests with a few resistors but it seems my calculations were iut and I did not end up getting the results I had hoped for.



Can anybody offer me any suggestions. Thanks in advance...
[emoji1417][emoji1417][emoji1417]



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[garethw]

Hello,
I would start by measuring the resistance of the heating element with it disconnected. Then I would measure the voltage across the heater during normal operation. Does the IC shown in the first image cycle the heater on and off or does it use PWM to control the temperature.

[ogden]

I would suggest to NOT dissipate extra heat in the resistors, no matter where you put them. You shall investigate possibility of hacking regulator PCB. It does not seem to be complex. Please show close-up pictures of PCB (front and back). Also try to invest some time to reverse-engineer it's schematics.

[Mechatrommer]

yes unnecessary waste of battery energy. if the board in the pic is pwm or buck converter, then maybe you can tweak that to lower output voltage. if not, maybe you can trash that and replace with buck module such as 10¢ click this or better.

[Zero999]

It might not even use a temperature controller. Glue guns often have a PTC element which is self-regulating. It draws a high current, until it reaches a temperature set by the characteristics of the elemnent material itself, then the current falls and it draws the right amount of power to keep itself at that temperature.

If this is the case, there are two ways to accurately reduce the temperature:
1) replace the element
2) add a temperature controller with a temperature sensor.

#1 is probably not viable, as it's unlikely you'll be able to find the correct element and could be expensive.
#2 is more doable but not easy.

[garethw]

What is the intention for the low temperature glue gun? Is it for a one off job or are you intending to use it regularly.
For a one off job, dissipating the excess through a resistor might suffice but it certainly isn't a good permanent solution and could cause a burn if the resistor heats up enough.
Depending on how you want to go, it might be quicker to buy a low temp glue gun; unless you actually want the challenge of building one yourself!

Gareth

[nznative]

Thanks everybody for the feedback. Unfortunately I’ve just blown my power supply for the gun so I’ll need to take a trip to Jaycar ASAP before I’m able to power it up again and record any voltage or resistance at heat data.

Here is a pic of the pcb though...




I agree that resistors will be a waste of battery and a potential problem with the heat they will give out as well.

@Mechatrommer, the link you put up for the buck module looks pretty cool and for 10c I might just splash out and order a few to have a look at.

@Zero999 I may have forgotten to mention that I want the gun to have dual temp options so replacing the element wouldn’t work for me but a temp controller could be an option that would work.

@garethw... the intention for the low temp glue gun is for installing ‘candy glass’. I work in film and television as a SFX technician and the glass we use for stunts etc is no longer made from sugar but is now a brittle styrene material which fractures easily from the temp of a high temp glue gun... I do realise that there are dual temp glue guns available that run on 240v but the advantage of being cordless is HUGE when being on set and replacing breakaway glass between takes... and also yes. I actually relish the challenge of building one myself!!!
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[Brumby]

... and also yes. I actually relish the challenge of building one myself!!!

We can understand that.

[emoji23][emoji23][emoji23]

We can understand that, too!

[Mechatrommer]

Here is a pic of the pcb though...

it looks like PWM generator. when mosfet U1 turned on, it will activate D1 and Q2 to turn the mosfet gate off. the resistors and capacitors network there are probably to provide time constant, changing valuees of those may change PWM duty cycle, but that just a guess. probing those through holes signed TPx with DSO may give some clue, ymmv.

[nznative]

Thanks for the heads up @Mechatrommer...
Forgive my ignorance an my technical understanding of electronics has a long way to come but do you think I could ‘simply’ swap the current board for something like this and hope for success?




https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.au%2Fulk%2Fitm%2F153093882015



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[amyk]

I would try to reverse-engineer that circuit first; it doesn't look like PWM to me, more like a simple linear regulator with D1 (a zener?) setting the voltage.

[garethw]

Here is a pic of the pcb though...

it looks like PWM generator.

I agree with Mechatrommer. The components don’t look large enough for linear regulation.
If it is PWM then it could be a case of replacing a capacitor to lower the temperature. Having said that I think nznative wants both low and high temps.



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[ogden]

I would try to reverse-engineer that circuit first; it doesn't look like PWM to me, more like a simple linear regulator with D1 (a zener?) setting the voltage.

No. It is PWM or just solid state relay. Heater regulation with linear regulator would be insanity.

[Ysjoelfir]

Is that a ryobi glue gun? sure looks like one. If so, I have the same guns at home and could take a look inside when I'm back from work to help you figure out a solution.

[nznative]

If it is PWM then it could be a case of replacing a capacitor to lower the temperature. Having said that I think nznative wants both low and high temps.

Correct @garethw...A dual temp cordless gun is the objective here...!



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[nznative]

Is that a ryobi glue gun? sure looks like one. If so, I have the same guns at home and could take a look inside when I'm back from work to help you figure out a solution.

Correct @Ysjoelfir!
It is a Ryobi indeed. If you could check it out and offer any ideas it would be greatly appreciated!!!



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[garethw]

@nznative, do you have an oscilloscope? If so, some measurements from the Vout terminal would be very useful.


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[nznative]

Not yet @garethw... will check at the workshop tomorrow and see if we have one there...
[emoji1417][emoji1417][emoji1417]


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[Zero999]

I would try to reverse-engineer that circuit first; it doesn't look like PWM to me, more like a simple linear regulator with D1 (a zener?) setting the voltage.

No. It is PWM or just solid state relay. Heater regulation with linear regulator would be insanity.

I suspect that board is purely for battery protections/charging. I doubt that board does any temperature control or PWM. There doesn't appear to be a connection for a temperature sensor.

Start by searching for the part number on the IC.

[nznative]

Thanks @Zero999 will look into it ASAP...


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[Muttley Snickers]

Before making permanent modifications to your gun you might want to check and test that the glue sticks you generally use in that gun will still have the same or similar adhesive properties when used at the lower temperature. The reason I mention this is because some glue sticks don't adhere very well if they don't reach a certain temperature.

[mikerj]

Looks like the circuit is a simple battery undervoltage cut out to me.  C1 turns the PMOS on when power is applied, and the NPN keeps the PMOS switched on as long as the zener D1 is conducting.

[nznative]

Before making permanent modifications to your gun you might want to check and test that the glue sticks you generally use in that gun will still have the same or similar adhesive properties when used at the lower temperature. The reason I mention this is because some glue sticks don't adhere very well if they don't reach a certain temperature.

Hi @Muttley Snickers. I have purchased these ALL temperature sticks from Gorilla. They should do the trick!!

Also hi @mikerj. That is a very helpful schematic! Thank you for your awesome input!


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[Mechatrommer]

I suspect that board is purely for battery protections/charging. I doubt that board does any temperature control or PWM. There doesn't appear to be a connection for a temperature sensor.
Start by searching for the part number on the IC.

do you think I could ‘simply’ swap the current board for something like this and hope for success?

i ignored there is another connection (extra wiring) to the circuit (at U1 or Q1? sink pin, downstream the bat+), looking the big picture in OP, there is one component (heat sensor or PTC?) from the heater coil and black wires into the circuit, not sure what it is (or maybe just connection to the switch? not really clear from here). you may change to buck converter/pwm generator circuit you linked (i'm not 100% sure) but i think you will lose functionality of that extra component. ymmv.

[Raj]

use this -https://www.ebay.com/itm/Digitale-LCD-Temperaturregler-Thermostat-Thermoelement-Industrial/143260092247?hash=item215af78757:g:J8IAAOSw021c4pTm