Heat gun mod question

[RokGoblin]

I am not an electrician but I like to tinker. I am just getting started with DIY type electronics kits and I have decent soldering skills. I cant say I am an expert at reading prints, but I can usually build a simple schmatic.

I wish to disassemble a heat gun for parts and add in a potentiometer to vary the heat, another potentiometer to control the airflow, and a digital temperature probe with temp display.

I am attempting to build a heat generating device with precise control of the temperature and airflow. I dont really want to spend $150 on a fancy LED digital display heat gun with variable heat dial, so this is my next option and potentially a heck of a lot more fun.

Initially I just want to get the variable heat and airflow control(potentiometers) hooked up, and if it will be easy enough I can later install the temp display. I could always just use a cheap "laser" temp probe to check the temp and ensure it is fairly stable.

The heat gun I am looking at is a piece of junk and it only has 2 temp settings. How easy is it to install a potentiometer for varying the heat and one for the airflow? I assume I can just install the one for heat control inline after the circuit that sets the maximum heat level and dial in the temp I want. As for the airflow control I assume I could do the same thing, but instead put it before the power lead feeding the fan. I am not an electrical engineer so I want to make sure this will work first before I fry my cheapo $20 heat gun.

Would it be bettter to just gut the entire thing and work with the naked parts and install my own circuit to control and display the temp or could I keep the basic unit intact and mod from there? Any ideas, or a basic schematic that would satisfy this requirement would be greatly appreciated.

 

[Boncuk]

Hi,

what you want to do sounds a bit weird. Adjusting temperature can be done easily using a phase control circuit for the heater, which doesn't even require a zero voltage detector (similar to lamp dimmers).

Using a second one to control motor rpm, hence air flow, will mess up the temperature setting you've already done adjusting the amount of heat.

With increasing/decreasing air flow you'll have to adapt the heat control automatically, which is not achieved easily and calls for data processing using a microcontroller.

Using a microcontroller to shrink a hose around a piece of cable is certainly something which costs a lot without a better effect than just controlling temperature.

Well designed heat guns develop a final temperature of 1,300deg/C and you might ruin the heatgun, decreasing air flow while increasing heater power.

Best and most effective solution would be employing a temperature element directly in the air stream and use the exhaust temperature to compare with the desired temperature and just regulate the amount of heat.

Boncuk

 

[RokGoblin]

Boncuck,

Thanks for the input and comments. I see what you mean about the airflow situation. What about setting my airflow first until I have the gentle stream I desire (or a stronger blast if needed), then manually setting the heater to the desired temp using a temp probe in the exiting airstream(as you mentioned)? Would it maintain that temp, or would I need to install some kind of controller to monitor and maintain whatever temp I set?

This is not going to be used to shrink or mold plastic, but I want to be able to have relatively precise (+/- 10deg or tighter) temperature control. If it gets too complicated or expensive I could always break down and buy the bosch heat gun I found here (**broken link removed**) but I would hate to gut something so nice and new.

I think I just want to gut a Wal Mart heat gun and scavange the parts and reassemble it into what I need.

Would I be better off just buying a small 1200w heating element and incorporate the phase control circuit you mentioned and making my own PCB? I have no idea what to use in my design if I do that, so I thought I could cheat and use an existing heat gun. How could I limit the temp output in the event I dont want the full 1200w power the heating element is capable of producing?

 

[Menticol]

RokGoblin, I think you didn't get the Boncuck's point: At low motor RPM (low airflow), is fine to select a low temperature setting for the heating element.

But there is always a chance to select the powerful setting and cause a catastrophic failure. The only way to do it right is using a PIC, that would be always controlling the heat and the airflow, maintaining them into the limits, and also meeting the user requeriments. It gets too complex when cheaper and better-built alternatives are present.

I'm also a "modder" (ugly name I think) and I share your point about the DIY fun. As Boncuck said, use a light dimmer to control the heating element, and attach a simple digital termometer on the barrel of the gun to get the desired temp. If you need less airflow, put the gun far from the target.

 

[be80be]

Just buy you a 1500watt dimmer if you slow down the fan to much you'll burn out the
element the dimmer would lower the fan and the heat thats what is in the bosch it's probably no better then the wall mart 1 . The bosch just lowers the power with a dimmer you could do the same

 

[audioguru]

Stores don't sell a 1200W lamp dimmer for homes. They are only 600W max.
You need a store that specializes in a powerful lamp dimmer for restaurants.

 

[Menticol]

That's true, didn't remember that fact what about replacing the internal TRIAC, with a poweful one?

 

[be80be]

Where I buy thay do But I don't work on house's I play with 480 volt motors and building with a lot of light in them when you have 20 60watt bulbs you use a 1500watt dimmer so it don't get to hot. And no home depot don't sell them but Granger has them.

 

[audioguru]

A home lamp dimmer is small. A restaurant lamp dimmer has a pretty big heatsink on it. They are completely different.

 

[be80be]

here

Lutron T-1500 Athena Single-Pole Incandescent Rotary Dimmer, 1500 Watts

Specification:
Description: Lutron T-1500 Athena Single-Pole, 1500 Watt Incandescent Rotary Dimmer.
Colors:

Gold Anodized Aluminum ONLY
Voltage:

120 Volts
Wattage:

1500 Watt Maximum Load
Installation: Uses standard Single Pole wiring.
Size:

4.56" H x 4.56" W x 0.65 D
Features:

* Cost -effective rotary dimmers
* Heavy duty components for surge protection and long product life
* Exclusive gold-anodized aluminum wallplate for sophisticated appearance
* Voltage compensation
* Power failure memory
* Superior RFI suppression

Special Features: Athena exclusive single-gang wallplate provided with product.
Certification: UL Listed to U.S. and Canadian safety standards.

maybe this will help

 

[be80be]

And the bottom Line heat gun $20.00 dimmer $30.00 total $50.00 you can get them that will fit in a single-gang box

 

[RokGoblin]

Thanks guys, I will try the quoted dimmer and use a cheap laser thermometer to check the temp.

A big thanks to Boncuk for raising the safety issue. This is a prototype and will only be used to test the concept. The later design will incorporate a PIC once I get some help designing a circuit.

 

[Boncuk]

Stores don't sell a 1200W lamp dimmer for homes. They are only 600W max.
You need a store that specializes in a powerful lamp dimmer for restaurants.

They are made in Japan and sold here in Thailand - 1500W, and very small. I tested one of those and it is absolutely reliable controlling my desoldering pot having a total power of 1400W.

They also fit in a standard USA wall outlet occupying just the room for one socket.