They say Google is ur friend but in this case google gives ****.

I tried for so many hours for a descent iron temp control circuit but it just does not exist. If it did it won't be compatible to my heater type.

This is something everybody wants, right ?
So, why no circuit, even for reference..

See below on the type of heater I have.

I use to have a Hakko temp controlled 50W iron. The tips are interchangeable to any size and ebay has plenty of 'em .

The specs are : 50W Heater, works at 24VAC
Thermistor : PTC, at room temperature the resistance is at 48.3Ω.

Thermistor resistance varies that is increases with temp to around 92Ω reflecting a tip temperature of 450°C.

I have made a table for my reference.

Like I said before, not getting anything to refer, I am making my own, f it works, it works, if not, I guess you guys can guide me from where I got ditched...

For Now I have a circuit drawn and am going to prototype it to see if it works.

NI Simulation works just fine

PS: If any one like to have the works of my iron ( if it worked) just PM me. Always glad to give what I have

Got crappy pictures of the iron, the cam was out of focus throughout. Didn't hit me to check the photos before posting.

Anyways..
I am doing this just so that if anybody else has this type of pencil he too can have it temp controlled with ease. I hope.
For now I managed to find a suitable transformer for my in mind station.

It gives 26VAC. With 2 irons loaded simultaneously, AC drops down to 23V, that is around at 6 to 7 amps loaded.
Plus a spare 12V for the meters...
I am planning to built 2 iron plus a hot gun into a single unit. I have had it with low grades and useless junk.
Can't seem to get a descent piece of iron these days.

I am drawing and building, since I cannot do anything else without these tools, I am going as fast as I can.
Soldered the Triacs and it's opto's.
Now putting together the thermistor amp..........

 

I am not putting this in the thread, 'cuz I already took a cheapshot at something you said in one other You're a good-natured chap.....I hope

Temp. control is so overrated, and unreliable, I take this approach based on the requirements of the job at hand.

I have several soldering irons, acquired hither and yon over the years, and rated by their actual idling temperature in a coil-spring stand w/ a ceramic heat-sink measured by an infrared spot thermometer [ close enough for gov't work ] to establish my point.

Pencil irons rated anywhere from 5 - 40 watts, producing temps anywhere from 200°F -- 900° with expendable tips made from whatever happens to work.

The judgment call comes with what you are soldering.........32 guage wire to a flex-circuit, or spade terminals on 00 stranded...........and which iron will do the deed with adequate heat to finish the task, without incinerating the surrounding components or blistering insulation behind the joint.........

I sweat solder copper plumbing with a mapp-gas torch, 18 - 10 ga. wire w/ my good 'ol Weller 375 watt gun............you get the drift

If you think the thread will benefit from this, be free to cut / copy and paste it in there.

I know what you mean .......and by the way you can pick on me all ya want.

Well !! let me tell u want I want from temp control...
My old gun is worth rebuilding, It has given me years of service u know .

side note : I have plenty of variouse sized tips and I have two broken iron of the same type, so I thought, instead of swapping tips when I am high into a PCB, I should save time and have two irons running. One fine tip at low temp and one with a tip to solder studs and heatsinks at 450°C.
I have seen what no temp control can do to my beautiful tips.

So I still plan on going on with this and infact I have made progress.
Too bad I do not have a n IR temp meter. I have to do with the old thermocouple one.

I have finished and calibrated ( upto some extent) the thermistor amp.
At a 450°C so far I get 4.5V dc output.
Now for the control circuit. The values of the components are changing as I go along. So much for the simulation

Experiment ( my Instinct to be exact) tells me that firing the triac in bursts helps in reducing power consumption and increase the life of the heater as the heat transfer takes time, it is not necessary to keep the heater powered. It can be turned on for a sec and off for a little time so that the heater does not over heat.
( but ofcourse, I like someone to prove me wrong so I can amend it ).

 

try a transformer or a fan speed controler, a shaded pole motor winding. i use these to run motors seems to work prety well like a big resistor with a built in heat sink. i have yet to break one by runing to many A through it eather.

 

Well ! the controller worked flawlessly I must say.

With a fine tip it idles at 200°C tip temperature & with a spade tip I can take it up to 500°C. I can now desolder huge sinks with ease, far better than before I must say...
I do not understand why I thought this was so hard to make, and why there are no sensible temp controllers for irons. This is gonna be a good project.

I am drawing the control schema and will post it later, hope fully with pictures if I find a good camera.

 

Here is the schema for the controller that I build and tested.
Further notes on how I did the adjustment will be added later after a good nights sleep.

I will add pictures later.
Next will be the digital read outs.

PS. The schema will be changed and reposted as work progresses. Basically things will be added rather then a change as I am satisfied with the controller for now.

{ed}

Circuit removed for correction.
New pdf attached in post#17

 

Ok guys. Since work is going on none stop, I will end this thread and continue as a Project and the new circuits will be posted in projects forum with the pictures.

But before that.
Here's the crappy iron I am using right now.

It never gives out the correct tip reading. So opened it and found the crappy control and an ICL7107 voltmeter giving out the temp. Even I am using a typical circuit but atleast it give an accurate reading.

Next is the Hot gun that I am using, it belongs to a friend but it is what is sold here. Notice the logo & model.

Below it is one of my priced possession, the desoldering gun, it's a Hakko original.

I bought it from Bangalore after consulting HMT, it was more than a decade ago. It was on the fritz when the Vacuum pump diaphragm gave up, could not find until recently online but it was too expensive, so I made one with the laser cutter, used a flexible material I found in LCD panels.
Since then it is like new

And here is the one that broke and am remaking, it is a SMD station with a Pencil iron like Hakko.

.

Notice the identical logo & model similarities. I bought it from here and with in months Iron starts giving me trouble and after that the hot gun gave up.

I though I'll show it before rip it to pieces.

The new circuits will be build into this. The vacuum pump works fine, just need to seal the gun.
The transformer is too small, no wonder iron has trouble keeping the temp properly.

A new powerful transformer is already chosen to be used tht can handle two iron without voltage sagging.

Last but not least is the front layout I designed.

It has all the controls and the digital read outs.
2 Iron temp controls and 1 gun control plus it's air flow control.
The temp readout are digit but the air flow rate is indicated by a LED array of 20 leds.

From all the circuits the temp readouts will be difficult for me but I am giving it a go now.
All the components are ready.
@ circuits are built and will be shown in the projects forum with complete details.

I posted my layout in B&W, cause I like to surprise you after it is done. It is gonna be beautiful.
But before engraving I like to open a poll or something and like all of you to give me some idea on the type of name and model no. suitable for you.

My suggestion is already written on top left.
Right side will have my company logo definitely.
Just need a suitable model name and no.
So please throw in ur ideas

 

Warring to any one making this

The circuit woks for me. The heater should have a PTC thermistor in built with around 49Ω at room temperate. Otherwise the sensor circuit (LM358) won't work.
Any thermocouple type will not work. If tried the iron will overheat. I know I melted one. .

As I am doing eagle art work and am at the verge of my firs PCB etching ( break thru for me at least) I will be making the art work for the iron. I will post them. Work is slow since I have to work for living too

One tiny lil'reason is that the clads I ordered from china is still no here.

 

Guilty as charged, R!f@@ I won't pick on you [ or anyone else ] to be mean, just to keep us all honest

I base my judgment of which wattage of iron to use, on the size of component being used, or wire size, and what it is being soldered to...

Actually, your iron has to have enough temp, to heat not only the component, also consider how much heat everything else in the equation is able to sink away from the job at hand... and still keep dwell time under a second...

 

We will see in due time. It's all fun and work and sometimes loss.

I have used a 50W irons all my life and I can do what I want so far.

 

Hi , I have found your thread great , I just tried to retrofit a 907 hakko pencil to a Duratech TS-1390 station , I did as you said turned on but not regulate the temp , my old iron that came with it has had the sensor die , if you don't mind I may also try this idea of yours as the replacement hakko irons are cheap and easy to repair , unlike the Duratech unit there are only retail priced replacement irons , not even spare element assemblies available

Cheers

Allan

 

Hi , I have found your thread great , I just tried to retrofit a 907 hakko pencil to a Duratech TS-1390 station , I did as you said turned on but not regulate the temp , my old iron that came with it has had the sensor die , if you don't mind I may also try this idea of yours as the replacement hakko irons are cheap and easy to repair , unlike the Duratech unit there are only retail priced replacement irons , not even spare element assemblies available

Cheers

Allan

You are most welcome to tr the circuit.
I put this here so others can try and improve it.
Just let us know what you do in this thread.

The Image shown in pots #1 is the heater the circuit is designed for.
The blue sleeves are the sensor wires. It should have ≈50Ω at room temperature. Try any other value heater and the circuit won't work but of course changing the resistor values around the amp LM358 can make it work.
The red sleevs are the heater and it will be around ≈4Ω. It is 24VAC 50W

I believe Hakko 907 pencil uses the same heater cause I have bought a few spares and just checked them. But you too should check them before making the circuit.

 

Before making the circuit I did this test on the heater.

A spade tip should be used inserted in to the heater. Without a tip the heater might melt as it glows red.

I connected the ohmmeter across the blue sleeve wires. Reading was 50Ω

Next I use my thermocouple temp meter. I used heat sink compound and tightly bound the thermocouple to the iron tip with bare copper wire.. The thermocouple sensor should be in good contact with the tip where the solder melts.

Next I applied 24VAC from a transformer (secondary current handling should be at least 2.5A for good regulation---- As 50W = 24VAC X 2.08A )to the red sleeved wires. I used a switch to turn and off the AC voltage.

The temp meter reading rises. Same happens to the resistance reading.

At around 450°C to 500°C I remember getting a reading close to 100Ω.

Based on my table I chose the resistors values around the LM358.

The LM358 is used cause it's what I got laying around and does the job quite well.
The second op amp of LM358 is wired as an Amplifier to amplify the first op-amps DC voltage to the desired value.
The LM393 is used as a window comparator. It compared the sensor reading and the pot reading and switches it's output on and off.
The TL431 and the BC639 forms a precision voltage reference. As I recall output was set at 2.5VDC. I have to find out after building one. But looking at the data sheet of TL431 any one can figure it out as the output is set by R13 & R16. The BC639 is used as a current buffer, just a precaution. The output should be stable no matter what. The circuit needs this reference stable to work.

I will describe the circuit operation in detail later as I am making the art work for the iron. I need a a circuit to do some measurements first.

But please feel free to as and I will explain all I can.

 

Before making the circuit I did this test on the heater.

A spade tip should be used inserted in to the heater. Without a tip the heater might melt as it glows red.

I connected the ohmmeter across the blue sleeve wires. Reading was 50Ω

Next I use my thermocouple temp meter. I used heat sink compound and tightly bound the thermocouple to the iron tip with bare copper wire.. The thermocouple sensor should be in good contact with the tip where the solder melts.

Next I applied 24VAC from a transformer (secondary current handling should be at least 2.5A for good regulation---- As 50W = 24VAC X 2.08A )to the red sleeved wires. I used a switch to turn and off the AC voltage.

The temp meter reading rises. Same happens to the resistance reading.

At around 450°C to 500°C I remember getting a reading close to 100Ω.

Based on my table I chose the resistors values around the LM358.

The LM358 is used cause it's what I got laying around and does the job quite well.
The second op amp of LM358 is wired as an Amplifier to amplify the first op-amps DC voltage to the desired value.
The LM393 is used as a window comparator. It compared the sensor reading and the pot reading and switches it's output on and off.
The TL431 and the BC639 forms a precision voltage reference. As I recall output was set at 2.5VDC. I have to find out after building one. But looking at the data sheet of TL431 any one can figure it out as the output is set by R13 & R16. The BC639 is used as a current buffer, just a precaution. The output should be stable no matter what. The circuit needs this reference stable to work.

I will describe the circuit operation in detail later as I am making the art work for the iron. I need a a circuit to do some measurements first.

But please feel free to as and I will explain all I can.

Check these out

http://eosystems.ro/index.php/projects/esol
Google search
Hakko 936 Schem-pcb & Mod v1r7 -
Also someone on the eevblog built a metcal style diy soldering station.. Found it
http://www.eevblog.com/forum/projects/diy-metcal-13-56-mhz-rf-supply/270/

 

Question:

NEED Recommedation for a soldering iron that doesn't go turn to #### after short duration of use.

I have a gun that puts out super heat and always works but it's too much heat so I use the cheap harbor freight ones.

I try cleaning off the tips, seems to help a bit.....is there a maintenance method for the tips or a better iron ?

Are there better tips to exchange for the ones that go bad ?

Thanks......

I have a weller , it's not much better.

 

Tip will oxidize with too much heat. Temperature regulation will prolong the tip life

 

Hello everyone, hello R!faa

Thanks R!f@@ for this interesting project. I find it very interesting and i wanted to give it a go. I've already built a pcb. i will post some pictures later today of my hakko 907 pencil, heater element and a produced pcb.

Here is a picture of my designed pcb and source file in sprintlayout. I did one change though around triac/optocoupler circuit (yellow square). My problem is that entire circuit refuses to work and i can't have the temperature regulated. Still can't find where the problem is. I examined schematics several times and also the pcb. I found one bug where I reversed pin4 and pin8 at lm358, gnd and vcc. Its fixed in attached picture but still no control.

 

I did some research on the diagram and corrected mistakes, changed / added some resistors.

main issue was the triac opto. It was a mistake on the added part. As I used standard ones in the proto but the schema uses MOC types. The pin 5 of the OC is the substrate and should never be connected. It should be pin 6 instead of 5. The OC led resistor should be changed according to the MOC no. used per datasheet..

My memory did not serve me well. The TL431 voltage reference was not 2.4V but the calculation gave me 4.99V.

Before connecting the iron or the iron drive circuit u should check the emitter of BC639 for proper reference voltage. It should not change when the pot and the amp(LM358) are connected. Changes indicates there is a problem

The new PDF is attached

 

Hello everyone, hello R!faa

Thanks R!f@@ for this interesting project. I find it very interesting and i wanted to give it a go. I've already built a pcb. i will post some pictures later today of my hakko 907 pencil, heater element and a produced pcb.

Here is a picture of my designed pcb and source file in sprintlayout. I did one change though around triac/optocoupler circuit (yellow square). My problem is that entire circuit refuses to work and i can't have the temperature regulated. Still can't find where the problem is. I examined schematics several times and also the pcb. I found one bug where I reversed pin4 and pin8 at lm358, gnd and vcc. Its fixed in attached picture but still no control.

I see u have made all the necessary changes.

I will check ur layout tonight, can you wait till then. I will post tomorrow.

I believe u might need a heatsink for the triac and tell me ur regulator (7812) input AC voltage and the iron AC voltage. Regulator input should not go above 25VDC and the iron needs 24VAC at 3amps

 

Hi R!f@@,

Yes, regarding the triac/opto section if you please look at my pcb, i did that particular change from the very beginning and i replaced it with the moc driving circuit i usually use. I measured my heating element, heater: 4.6 Ohm, sensor: 48.6 Ohm at room temperature. It depends though on the quality of multimeter, mine is not the best one, but that's probably it.

I will measure voltage around tl431 and bc639. Last time i measured voltage on bc639 if i remember correctly (without 10k pot connected) it was ~5v on emitter. I will measure it all again.

Yes, triac is on the heatsink. Actually 7812 is not hot at all. My transformer is 2x12v with central tap (0) so i am driving ~12v AC to the rectifier.

 

The reference should be rock solid. I used a 431 cause I need it to be stable and the BC639 is used cause I designed it to use two irons simultaniuosly and the reference should handle more current.

I will try to rectifier ur issue but I need time as I work most of the part of the day