Wednesday, June 15, 2011

DIY Heat Gun!!

Need a Tool, well i always say if you don't have build it.
Recently i have started on a new project that requires me to solder alot of SMDs on PCBs. so a few test boards destroyed, and money lost because of over heating the PCB. I had to stop until i had a reliable way of doing it without destroying the PCB. well first thing that came to mind was a heat gun. since i am limited on money i can spend. it tends to make getting tools a little difficult. so in good old school hacker fashion i started to learn how to build a heat gun.

Google be your friend. I started off by finding out many different ways of going about doing this.

Many people tend to go the simplest route by buying a cheap desoldering tools from RaidoShack.
and then add a small air pump too it.

This would not work because of the issues of overheating. so i continued to hunt.
i soon came across this one. using old parts from paint heat guns he was able to make a high temp.
but again controlling temp was a issue. while adjusting the voltage would produce the right temp.

Now i know the basics of building the heat gun. i went hunting down specs required to solder SMDs.
this was very simple wikipedia was the first and last stop i had to make.
this tells me that the highiest temp would be around 300 °C (572 °F). e So with the required temp known and
basic build down.

So here is a list a basics of what is needed.
1) One heating element with high enough temp
2) Some form of air mover
3) Control unit for the temp
4) Case

So time to scrounge around for parts. The first most important part is the heating element. most people doing anything similar is use a soldering iron. so found my old broken soldering iron and began to take it apart. as i had to make sure that i could retrieve the parts needed. This ended in a bust. as i found out the hard way way , that most cheap soldering irons do not use soled ceramic elements. they tend to have a ceramic film that is wraped around and around to make the element. so this means that they are almost impossible to remove to the bare element as it seems to fall apart very easily.

At this point i almost gave up as i had no money to purchase  any thing. Luck has it i was about to goto bed and rembered a old device i might have from my teenage days. ya'll might remember it was one of the first vaporizers ever sold. So i sat for a moment and day dreamed oof yesteryear ( insert The Wonder Years Theme ) and began to take it apart.

Now WOW, i really hit the jackpot with this relic. The heating element was a nice size, self contained, and free at least at this point in time. The real treasure is that it had came with a control board with led display and knob, and semi self-contained   this little board save me days of work as now i have a stable temp control with out the hard work of designing it my self. ( witch i had already designed mostly, I will post a small tutorial at a later date. )

With the hard part out of the way, because of my laziness years ago. ROFL. now came to design a stable case for the unit. i had played with about 5-6 ideas on unit design. one was make a small variation to the case it was in and run a metal hose. most of them where along that route.But i had remembered a problem with the high powered DIY was air leakage. so i took a break and deiced to clean my house. while cleaning i used up the last of  two canned cleaning products. so i put those aside and finished up cleaning real quick.

I began to rework the design around one signal can. ( had one for backup ) The can was perfect for air tight seal. so at this point i had to work on the air system to work with can. again i went to the DIY groups and dug up an old reference to making a turbine. it seemed simple enough. again went hunting around the house for parts came up with two deadbolts. i fell in love with them because they had nice protective steal covers that slide right off. and they made a perfect shape for a holding a few fans. and made a real  nice tight seal on the inside of the can.

now the tip where the air comes out. many people use the easy design and that leads the a very small nozzle. Or buying a heat gun most likely has a huge opening and needs to purchase tips to work with smaller parts.  so i got to thinking . How big? will it need adapters ? how much air will flow through ? so back in my parts pile i came up with a nozzle that is used in plumbing with water heaters. ( never know when those stupid things breaks )  it was a real nice fit right where and plastic tube in the can enters with some small amount of coxing. this gave me almost  a 1/4 inch hole with a good flow.

on to the heating element part. now this posed a problem with it directly touching the can. so i came up with a spoke type system to hold it straight. and then salvaged the cover from my old soldering iron. this allowed me to cover the element and still let air pass over. as the cover is not as hot when touching the can. with this part of the design posed on more serious problem.

Where do i put the controls? that was simple. the other can i just plan and simply ran out of room with the first can. but that solved the fear about heat on the unit controls. so now we through together a control box.
i decided to salvage the plastic face plate that held the control board together. and one switch, one fuse, and one small wall-wart. right now you are probably going huh? you have power already. yes i do but the element runs on strictly ac and i had lacked the components to make the change to DC. so i found a small adapter with the right voltage and a little higher mA.

now that the design part is out of the way lets put the sucker together YaY. well i thought it would be that easy. The heating element and turbine unit fit nice and snug. it did take me a a good minute as i had to work the nozzle in, cut the spoke to hold the element straight. the fan was easy too, again the longest part was shaping the high heat Styrofoam i had laying around. ( i'm hoping high enough but it will be shield also)

the control can was pretty straight forward after some circuit design and breadboard testing. cut some holes that the switch, fuse, power cord,  and control board would fit into. the first power adapter fit right into the bottom making the can squarish. but apparently i had grabbed a fairly old adapter as it had failed after i finished putting it together. some testing with a multimeter showed that the transformer had failed completely. so i had replaced it with a newer smaller adapter. and closed the bottom of the can off with the main part of a deadbolt for weight. with both cans finished a cable with wires inside roughly the same gauge as the original wires running the heating element, and fans.

And it's done kinda. every thing works and gets the right voltage. but i have a few drawbacks the can does get really hot, so i have to use a oven mit. right now the max temp is not quite where i would like it to be. i hoping to bumb it up about 150 °F more to make 550 °F. i need a better stand. and the control case could be better looking ! when i do get the extra cash i want to build my own control unit from the ground up and still use the same gun part and add fan speed control.  but it does heat up nicely. and fans stay warm to the touch after 30 mins at 400 °F. it's pretty darn quite. the fans stay on even if the heating element is off. at this time i have not tested on soldering as it was way to late when i finished. here is a small video and some pictures and hope you enjoy. because i had hela fun making it!!


120v AC in
12v DC to FANS
PWM of 120v AC to heating element for temp control
200 °F ~ 400 °F

2 clean aerosol cans
2 deadbolts
1 switch
1 fuse
1 12v dc adapter
1 old broken vaporizer
some styrofoam

screwdriver set
soldering iron
sand paper

28 hours Start to finish (4 hour nap in there some where ROFL)

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