The 30 Watt 13 Euro soldering iron that i hope i will transfer into an expensive soldering station
Soldering stations comes in a variety of prices and capabilities. The cheaper stations have a power controller, to control the power delivered to the soldering iron. More expensive stations will have a temperature controller near the tip of the soldering iron, and control the temperature using this feedback.
The quality of soldering with a station is much higher than with a simple soldering iron. Especially if the station has a temperature controller on the tip. That is because, the solder has a very specific working temperature. For example, the one i use (60% tin 40% lead), is liquefied at 190oC. Of course, you do not solder at 190oC! The soldering iron i use, exceeds by far this temperature. I measured it up to 410oC! This has negative effect on the soldering quality.
The idea was simple, yet the implementation according to the standards that i had set was much harder to follow as i originally thought. I will use a 30 Watt soldering iron for the job. Somehow, i will measure the temperature as close to the tip as possible. For temperature sensor, i will use a K-type thermocouple pair. I have a complete theory for thermocouples that you may be interested to read. A controller circuit will read the temperature. A potentiometer will be used to set the requested temperature, according to which the controller will turn on or off the soldering iron heater.
An unexpected surprise from Maxim
The chip soldered on the PCB
I got myself a couple of them
If you read the theory of thermocouple pairs, you will see that the controller must compensate the cold junction temperature. Moreover, the temperature acquisition from the thermocouple voltage, is a result of a long polynomial solution. I was just about ready to start the design using a thermistor for the cold junction compensation, when i accidentally came across this:
This chip will do all for you. It has a built-in temperature diode, used to do the cold junction compensation. The thermocouple pair is directly connected to it. It also carries an analog to digital converter, and produces a 12-bit number, with 1/4 of a degree precision. With the simplest protocol ever (3-Wire/SPI), the microcontroller can acquire directly the hot junction temperature in degrees Celsius. The chip comes in a tiny SO package.
There is only one drawback with this chip. It is somehow expensive and cannot be found everywhere... From where i get the PICs, i buy the 16F88 for 3.9 Euro. This chip is sold for over 8 Euro per piece. So, the question here is: Do i buy this expensive chip that will double the price of the controller and avoid all the hard work, or do i go the hard way and save 8 Euro? I was too curious to see how this chip works, therefore i had no time to answer the previous question. My finger followed the checkout procedure by reflects... I got myself a couple of these chips to check them.
And then i got the chips! There is only one word to say: "It works!". With minimum effort and even less programming effort, i got an accurate reading from the thermocouple! The connection and the communication protocol are ridiculously simple.
I got 3 LCD modules, one is already on the workbench
The original idea was to use some 7-segment digits to display set temperature value and tip temperature. But then i decided to give it a more profesional look and feel, by using a 16x2 character LCD module. Surfing the ebay, i found a manufacturer that made a terrible mistake. A whole batch of these displays had a mistake: the backlit connections were not according to standard pinout! Pins 15 and 16 were in reverse order, and therefore he was selling them ridiculously cheap. I got 3 of them, one was for this project.
The first line, will have the set temperature value, and the real temperature value on the tip. The other line, will have a slick bar with the set value. That is subject to change of course.
The thermocouple pair
Some K-type thermocouple pairs
I will use the one size fits all K-type thermocouple pair. I already have some wires. Yet, i am not sure which to use. I still have to solve the problem of the thermocouple mounting. I need to install it as close to the tip as possible.
So, i have a thermocouple pair from a multimeter, some thermocouple extension wires, and some pieces of thermocouple wires. If you are interested, i have run some interesting experiments with K-type thermocouple. You may also like to read the theory of thermocouples.
The triac SSD type control for soldering iron does not work for me. Temperature overshoots and the triac continues to be switched on all the time. I substituted it with an opto-isolated high current 30A mechanical relay and it works fine. I hope some builders who are building this take note of this.
I make the circuit at a breadboard, it have problem, about the T1(BT136D), It does not have a current and voltage. Soldering iron cannot heat. Can you teach me how to connect soldering iron through X2-1 , X2-2 and the supply? can give me a simple image to reference how to connect.
@Giorgos Lazaridis Thanks for your reply, I have other questions to ask:
From your PIC tutorial, your ICD 2.5 programmer has two parts, the ZIF socket and the programmer. If I buy PICkit3(http://www.microchip.com/pickit3), do I need to buy a ZIF socket? Or just simply use the SW1 on the circuit to upload program to PIC?
Also, which part of the source code should be changed if I want to have a different min/max temperature? Will the LCD change the value accordingly?
This is the best DIY project. Hello, my first question here is about the pcb layout, Can you send me a Eagle files of the PCB layout?
Use what layout to do the soldering station is correct? http://www.pcbheaven.com/scripts/imagepresent.php?filename=%2Fprojectpages%2Fimages%2Fhomemadesolderingstation_1273993902.png OR http://www.pcbheaven.com/scripts/imagepresent.php?filename=/userpages/images/Homemade_Soldering_Station_2_AVR_18.png
Can you tell me what layout is correct ?
Really nice work! I'm so impressed i'm doing my own! But i have a few questions:
1- Can I modify this for accepting an arduino board intead of the pic;
2- Can I switch the LCD display for a 7 segment display(call me crazy, but i enjoy a simpler thing over a more complex);
3- Instead of using a simple soldering iron, i was thinking using a weller type, with integrated k-type thermocouple;
4- As i'm not an expert in eletronic(FAR from that, instead i'm a better programmer) can you identify the X1, X2 and X3 pins on the schematic?
I think this is it... I'm sorry for any typos or misspelling errors since i'm not a native speaker. Thanks for the project and bye!
@weazel to control something that is 30-50 watts in terms of less voltage or current, require either a complicated inverter or a lot of power dissipation on the control transistor. Switching is a very efficient solution, and it is not by chance that all PID temperature controllers that i've met and used use this method.
@Kiril I use normal solder paste, i do not remember the brand because i switch the metal bin with a glass one which helps me opening it easier. Nothing special though. To clean, i use isopropyl alcohol.
@jeric3182 hello. a friend of mine built this with AVR:
you can use the replacement of MAX6675 which is the MAX31855K. Has the same pinout as well. As for the temperature, the thermocouple reads the temperature from the iron tip, so you determine the working temperature. The max temperature in the software was just a number almost "random". I strongly recommend you use a higher wattage soldering iron. The operating temperature will still remain the same (controlled by the controller) but the speed of heating will be improved.
I've watched your video on your temperature controlled soldering iron and I was impressed. So impressed that I started building my own! The MAX6675 chip is nowhere to be found from where I live so I devided to make my own thermocouple interface to my AVR. Basically, the thermocouple interface and the AVR chip are the only onces that are different from you design. Got a question though with the setpoint? How'd you determine the max temp for the setpoint? Was this value based on the wattage of you soldering iron? Would the setpoint max temp still be the same if I'm going to choose a higher wattage soldering iron?
@varun i had this question myself when i designed the device and indeed i probed the triac, but it looked resistive. The station works about 2 years now with no problem, but thanks for noticing, since others may have different soldering irons.
Good work. but I think the triac (BT136) will die soon. The soldering Iron works on the induction principle and when handling an inductive load like soldering iron the current legs the voltage by 90 degrees(law of induction). Which means that you can't shut it down like this. you might consider putting a RC snubber network or at the very least a TVS diode for this. you can prob the terminals of the triac to see this effect. It should show you a high voltage glitch when you turn the triac OFF from the ON state. Keep on moving forward. really great work
@GGWL beyond the DIY comes also the quality. The soldering iron i use is priced Euro 15 alone (about 19$), and this is just for the soldering iron. It is not the worst quality, nor an antex or weller of-course. I could use a $3 iron and a drop the price down to half as well.
As always, DIY may be more expensive than getting something ready, but many times it is cheaper in terms of quality/price
Honestly, its clever, but its just for the sake of DIYing your DIY equipment. For the same price (at least, possibly even cheaper), I go this great little soldering station from this little website, for just $20!
@Steve the supply of your circuit must be through a transformer (for galvanic insulation), the tip must be isolated (typical for modern tips) and the iron must be grounded to earth. This way you can safely touch the t/c wire to the tip
thanks for sharing your great project!
I have a quick question: what I understood is that the soldering iron is 30Watt but in the end you used a 9V-1A wall wart adapter which can only supply up to 9Watt...I guess I misunderstood something but I don't know what :D
@Patrick Sawian the circuit works fine except the turn-on glitch. Any other problem you face is something going on with your design. I be using the station for more than a year. Avoid posting problems here. In the forum there are people who already used the station. You can also upload images there, here not.
Oh I fixed up the pot problem. Its ok now. Just a short somewhere. Now there seems to be the serious temperature overshoot problem. The iron is switched on again and the screen loads again repeatedly every 5 seconds or so. And sometimes it doesn't.
There seems to be a serious problem. I noticed that when the soldering iron temperature overshoots a lot more from the set temp, the iron is again switched on. Very strange. Looks like a code problem. Kam your comments awaited.
I used cheap MCT2E opto couplers(collector and emitter) instead of the normal opto-triac driver MOC3021 and works great. I have a few MOC3021.. Its just that I'm saving them for rainy days. They're a lil on the high side where I live and hard to get. ;-)
Errr... just one other glitch. I have a dual board setup one for the soldering the other for the desoldering and I notice that turning the temp set pot for one display causes a change in temp setting of the other too. I'm thinking this might be caused by current drops from the supply to the temp set pots voltage dividers. What do you suggest? Do I use a separate 7805 for the other board as they both share a single regulator as of now. I think there is more current in both boards than the 7805 (though I haven't checked this yet)could handle thus the change of set temps in the displays. Suggestions??
Hey I am very new to this whole micro controller thing but am trying to do similar things with the 16F88 and MAX6675, but cannot figure some things out. I cannot find the BAUD rate required for the MAX6675 and am curious if the MAX6675's 12 bit output and the 16F88 8 bit input caused any problems when using the serial out command. I am using PICBasic Pro.
Thanks for the help!
Its working great, except for the chinese thingie. I hope you can solve that soon. By the way the spelling of Solder Station sometimes comes up with a double S as in "SSolder Station", so prolly you can correct that in the next update. Super project. BY the way will this code work if I burn into a 16F628A??
@Patrick sawian make sure that the LED and the PIC works first. There are some people that tried this project and it works. MrDEB also posted a pcb for this. There is only one bug found: some times, during startup, the LCD does not initialize correctly and instead of normal numbers it shows Chinese characters. Other than that the project works fine.
the LCD connection you post is incorrect. here is the correct:
LCD PIN - PIC PIN
1 - GND
2 - 5V
3 - Pot
4 - RA0 (17)
5 - GND
6 - RB5 (11)
7 - not connected
8 - not connected
9 - not connected
10 - not connected
11 - RB4 (10)
12 - RB0 (6)
13 - RB1 (7)
14 - RB3 (9)
15 - Pot
16 - GND
I tried building this. But the display is blank other than the usual dark squares on normal power up of any text LCD. Of course i have not wired up the PIC to the 6675 and 5K pot yet. I just wanted to check the display. One of the LEDs keep on flashing, but still blank screen. LCD wired this way -
1 - GND
2 - +5V
3 - To contrast adj pot
4 - PIn 17 of PIC
5 - GND
6 - Pin 11 of PIC
7 - PIn 10 of PIC
8 - Pin 6 of PIC
9 - Pin 7 of PIC
10 -Pin 9 of PIC
11 - To +5V via 100 E pot
12 - GND
13 - no connection
14 - no connection
15 - +5V
16 - GND
Going to build similar soon as I have most of the parts but discovered a zero voltage switch that the HAKKO soldering iron uses. Trying to get this schematic to work http://www.n0ss.net/hakko_936_schem-pcb_&_mod_v1r7.pdf but feel the triac and zero voltage switch are not right. Using http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00235248.pdf
for the iron using from Ebay 250865692027.Hopefully using this iron will not need the MAX6675.
Thinking maybe if I use the ADC input of a PIC (the iron sensor goes from 50ohms at room temp to 180 ohms to melt solder. Control the triac using the UAA2016 but need to construct the app circuit on page 3. The math throws me a curve.
If anyone can compute the resistor values using the app circuit and the triac/UAA2016 would be appreciated.
recently posted in element14.com/community/thread/14656
For well over 30 years my Weller TCP 45 soldering iron has been my companion on the bench. Alas all good things come to an end, and so did my Weller. I thought the 'magnestat' control switch contacts had probably failed, but this time the actual element had gone open. I could not find a source for a replacement element. So I priced a new iron: 48W 24V, magnetic temperature control. I eventually searched Farnell Components, and got a shock when I saw the price for a Weller replacement iron is £69.83p.
I don't think my whole Weller kit, inc power supply, cost me that much, but things are more expensive now, so I suppose the price is not all that bad. A bit mor searching in Farnell brought a very interesting item to light: a replacement iron for a Duratool soldering station. This is 24V 50W, and the price, believe it or not, is £5.94p including postage!!! The bits are sold separately, and cost £1.06 inc postage. so I took a chance on buying some cheapo Chinese rubbish, I ordered two irons, ten spare pits, and three spare elements (£1.64p each inc postage). The stuff arrived the next afternoon.
I was very pleasantly surprised at the quality of the iron, bits and elements. Well made, safe, and nice looking. But I was gob smacked when I looked closer at the elements: four wires, not two. The iron is a temperature controlled item! It has a type K thermocouple within the element casing.
I took the old Weller 24V transformer, and a spare pc psu metal case, (the old Weller case was too small) and knocked a simple microcontrolled circuit together to power the new iron. I now have a really cool (to handle) iron which heats up really fast, switches between two setpoints, and even controls the fan which was in the case.
The Duratool iron comes fitted with a four pin free socket which requires a panel mounting socket: the type fitted to CB radios for microphone is the one. I got mine from Maplin Electronics.
A note: the element resistance is approx 3.6 ohms, so beaware of applying 24 volts directly without some form of temperature control. Without you will destroy the element.
The iron is here:
The bits are here:
The spare elements are found here:
In passing, I wrote a little program for a PIC16F628A controller to control my iron. I already had the old 24 volt transformer in the Weller case, so I used that as the power source. It turns out that the iron is in fact a 12 volt item (well, it runs happily on an old PC psu) and I arranged the software to let the iron quickly get to full temp before control comes in. Anyone wnt the circuit diagram and software are welcome to it. By the way, the same iron runs very happily on the 24 volt transformer if a power diode is put in series with the iron, the thermocouple is left unused in this case.
Well while I'm not sure what you mean when you say "not corrected it" what I am sure of is that I just recently started drawing pcb's and schematics with cadsoft eagle, so any help would be great hear. If you don't mind to e-mail what you do have to me ( email@example.com ),maybe it would serve me well as an aid in laying it out.
@Jason Warden i do have a PCB but i never upload PCBs in public, because i am not a pro PCB designer. And it proved (after i gave it to someone else) that the PCB design may have flaws, causing some times failure in initializing the LCD. I can send you the PCB by email though, but i have not correct it.
Hello, my first question here is about the pcb layout, am I on my own with that? or have you got any layouts? I'll be back when I'm far enough along to ask about the firmware when I'm that far along. Oh yeah! does the micro-controller have to be 16f88? I have some 16f87 laying around, could I make do with one of them?
Wow! just got off the phone with maxim, and I've got to say the people with their samples div. are great should have my 6675's in 2-3days ( I live in the states) Free samples ROCK when they cost like this one, make sure you have the whole part number when you call MAX6675ISO+, right now they have that one but not the leaded. I only asked for one, but got 3
Thanks for your reply, the soldering irons that I am talking about are visually the same as the one that you have used for this project, except that it has a 4 wire feed too the plug. Two of these are the element and two are the thermocouple. Not sure if they use a "K2 type thermo sensor?? The irons are somewhere in the £20 region to buy on there own, may be cheaper via E**Y, I will have to check on this.
As far as the other subject that I mentioned, the SMD oven. Your project may just convert with the right programme for the Pic to control a solid state relay that will switch the elements on/off, plus a relay to control a fan that will circulate the hot air inside the oven. I make it sound so easy; maybe I should start to look at your tuition lessons on Pic programming. Start maybe by looking at your program to control the soldering iron. An instructional breakdown of this program may help me to understand how and what goes on inside the program whilst running.
@Alan the soldering iron you mention will work, as long as the thermocouple is K-type, otherwise it will fail. Regarding the SMD oven, i just began switching to SMDs. Maybe in the future i will make one.
What a brilliant article, I have just found this on the web and will be constucting one as soon as possible. We can buy here in the UK the soldering iron on it's own, this already has a thermocouple fitted inside the iron. There should be no problem using this type of iron????
What about constructing a temperature controlled SMD oven? I am not that clever at programming pics.
@Eduardo There is almost no difference in consumption. A 30W @220V draws 30W and a 30W @ 24V draws 30W as well. A very slight difference will exist in the 24V. The current @240V is I=P/U = 0.95A, and @24: I=1.25
So, due to the fact that copper losses are related only to current and resistance, there will be some more copper losses, and also there are also some more losses to the transformer (for the soldering iron).
@wolworein as a matter of fact, i did not construct a dimmer-like controller that needs the zero cross detection. Instead, i used a simpler technique very often used for controlling heaters with AC. I am not sure about its name, it has something to do with "bursts", because it send power in bursts. For example, sending one burst of 500msec each 1 second. This is very commonly used in such applications. Of course, it cannot be used for lighting applications.
Hey great project! Just one thing, as you may be knowing the triac does not commutate by itself, so i guess you have just controlled the firing angle by a pulse from the microcontroller. But how did you get the zero synchronization of the AC mains and the firing angle control pulse??
I've been doing a lot of research into a project like this, and I will say that this is easily the best temp controlled soldering station project I have seen (and i've seen lots). Really hoping to learn lots here, although I am just starting out with this kind of stuff. Just wanted to give props for your work and thank you for sharing the knowledge.
this is my idea only :) im beginner of microcontroller asm language i will try it meybe someone finish that project before me then easy way to understand this 24v solder iron pins heat resistance and ptc with multimeter ohm stage connect to pins and heated by fire solder iron then ohm resistance pickup that pin is ptc ;)
this solder iron so cheap one here is the model number 88-415A 24V 60W
Nice choice erkan, and thanks for sharing. I thought that thermistors are usually used for temperatures bellow 250 Celsius, but obviously i was mistaken... Although i would prefer a 250 V heater (to decrease the current for numerous reasons), i admit that this looks like an excellent choice. I look forward to see your project.
forgot add 24v solder iron link http://cgi.ebay.com/DURATOOL-88-201A-IRON-SOLDERING-
need 24v dc power supply
this 24v solder iron have ptc heat sensor no need add k type thermocouple its possible temperature controlled with pic need add \"rail to rail\" opamp example schematic is here http://www.enocean.com/fileadmin/redaktion/pdf/app_notes/AN305_CLIMATE_SENSOR_Nov09.pdf
best regards from turkey
Tom, you wrote:
"They have internal thermocouple as close as possible to the tip, you can find many different tip sizes and even a replacement heating element."
But this will change the whole project:
The power to this iron handle should be 24Volts (AC or DC i don't know)
Now we have to add a transformer from 110/220 to 24 Volts (about 3A) i think.
Did someone used this alternative?
Hi Robert. BT136 is a popular triac which you can find also in ebay. Just search for BT136 and you will get plenty of results. As for the PIC, there is only one 16F88, unless you talk about something else, and cannot have different I/O. In my BOM (as in every BOM in pcbheaven) i include all the datasheet for the components. Go to the BOM page of this project (http://pcbheaven.com/projectpages/Homemade_Soldering_Station/?p=2&topic=worklog) and find the datasheet directly after the PIC16f88.
For a programmer, if you wish to stay low, then get a USB ICSP programmer from ebay. If you want to get deeper, i strongly suggest ICD3 from microchip, which is rather expensive, around $200. Search in ebay for more products ;) .
great project i am going to mess with this i have been messing with electronics for a wile but never messed with the programing of a chip.
i think this will be a good start to learn i have found almost all the items needed but i cant find a BT136d and been to digikey, newark, radio shak. and they can't find any info yet i found a data sheet online. can someone send me a link please to this part i will add my email address below.
the other question i have is the PIC16F88 when i searched for this i found that ther was at digikey in ther search different I/O memory size
voltage supply rating and Data Converters can someone please send me the correct info as to the chip used as well i would be greatful as to this i need to get in to the micro controler bit of things.
i realy need some help on this guys and gals thank you. oh and what programer do i need to use??? like i stated i am now at this aspect.
my contact email
Thank you for the heads up on the K type thermocoupler, I contacted the seller of the soldering iron on ebay and they did not know what type it has, also they do not sell replacement tips. I will modify one going by your example.
Also thanks for pointing me to futurlec, I found everything I need for the circuit board components plus knobs, ribbon cable, headers. Going to pick up the green lcd and thermocouple from ebay.
Thanks again, you save me some $$, time and frustration.
-Except the MAX 6675, all others should be found in any shop. The MAX is more likely not to exist in all shops. So go backwards. Find the shops that have the MAX, and from there get all others. Doug (read following comments) got this chip from Maxim as free sample!
-1% resistors have better accuracy. In this project, there is no critical point to require such an accuracy. You can use them though with no problem. There will be absolutely no difference
-About the LCD, the pins SHOULD be standard. Yet i found once a Chinese supplier that had the backlit pins different. He stated this with CAPITAL BOLD LETTERS, so i suppose that they are standard. The one you link to, is compartible, yet i would not suggest a blue LCD as they need to have backlit ALWAYS turned on to be visible. I hate this. Green LCDs are visible wven with backlit turned off.
- Regarding Tom's advice, be sure that it uses K-type thermocouple otherwise it will not work.
- For the prototype, you will receive MAX 6675 in a SO package. That is SMD Small Outline. The size of this damn thing is 5x4mm. It cannot be soldered on such a prototype. I suggest you provide yourself an SO adapter for this chip (like this: http://www.futurlec.com/SMD_Adapters.shtml)
Great idea and instructions. Thank you for posting the how-to.
I have been sourcing parts and have a question or three. I know nothing about electronics so want to confirm what I am doing.
I like one stop shopping and have found most of the parts on the Jameco web site. This site had most of the hardware except for a few things. Has anyone found a supplier that has all the circuit board components? I found the Max 6675 at Digi-key.
Would there be any advantage to going with 1% metal film resistors? Doing my web search for parts I found reference to these and that they keep their value longer?
The lcd display I found is a 16x2 HD44780 411Technology Systems. Are the pins on the 16x2 display standard? If this one will not work, a link to one that will would be much appreciated.
I have no experience in making circuit boards so was going to get something like this from Radio Shack or Jameco, I'm hope there will be no problem in placing all the components, even the one that is surface mounted. Please let me know if I am wrong.
I have not make changes. I just want to use it a little bit and experience the upgrades needed myself. After all, i am currently on a new project (the coffee maker). For the MPLAB, you will need to make a directory and paste all the files inside. Then make a project (look my pic pages to explain how) and then add all gthe pasted files to the project. Select a programmer, build the project and upload.
Now I see what your referring to. Your schematic is a little confussing .
I saw the little notes above the LCD connector (I was thinking it is the LCD.
When I get this unit working will post pics.
Have you made any changes?
When it comes to actually programming the 16F88 using a Junebug and MPLAB.
hopefully all goes well. have had no experience using MPLAB and assembly. Would assume just copy n paste the hex into mplab??
any direction would help
Hello, Doug. First of all, the data pins can go to whatever port you like in any series. It is on the software to re-make the data according to the ports you do it. When connected in series (e.g. RB0 through RB3) then it is easier from the programming scope, but the way i do it is more flexible and adaptive.
As for the connector, this is NOT the LCD pinout, is only the connector for the LCD. You may use your own configuration for this. If you follow mine, then i have the pins connected as follows (as i stated on the schematic): The pins of the connector from 1 to 12, are connected to the LCD pins as follows: the first 6 pins goes to LCD 1 through 6, and the other 6 goes to 11 through 16.
I am in the process of designing a PCboard for this soldering station and pretty sure the LCD has the wrong pins connected.Using 16F88
Are not the data outputs supposed to be connected to 4 ports on same (RB0-RB3 or similar. first data pin to first port (RB0 same bus? but in consecutive order for 4 bit data?
also pins 11 &12 on LCD are data pins (unless your using a different LCD?(I need to check your BOM.
You have these connected to Vcc and Vss
15 &16 are back-light adj.
going by this http://digital-diy.com/home/swordfish/code-examples/56-swordfish-tutorial-lcd.html
I just got my FREE samples from Microchip and guess I ordered the wrong chip.
Instead of a 16F88 I ordered a 16F84
not being very knowledgeable about PIC programing etc can I program this chip using the same hex code or ? to build this soldering iron. What do I need to change to make it work right?
Don\\\'t waste your time trying to mount the thermocouple.
Use one of these:
They have internal thermocouple as close as possible to the tip, you can find many diferent tip sizes and even a replacement heating element.
I found a solution for a female socket to plug your thermocouple cold junction plug
A blade type fuse holder
I ordered two, one for the soldering station fuse and one for the thermocouple receptical
Mouser part # 441-R352-GR
Eagle fuseholders, clips & hardware
It mounts on the outside of your enclosure.
Redesigning the PCboard BUT planning on using an 18F452 (have two that I got for FREE)
Was planning on going with the 16F88 as per your schematic and notice that the 16F88 does not have an SPI port.
Would having this port made the code easier to deal with?
I am the last person to ask for advice about PIC programming but was kinda advised on the http://digital-diy.com/ that with a SPI port it would be easier to program with this port?
Hopefully can get some code working using Swordfish as I am familiar with it vers assembly.
also changing some resistor values as IMO the LEDs are drawing too much current?
About the multimeter, reading a thermocouple gives values in millivolts. That is why you need to use the chip (datasheet -> http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3149). It reads the thermocouple and compensates the cold junction temperature as well. You do not need to read it yourself. This would require an accurate ADC with a nice voltage amplifiers. Too complicated. Let the 6675 do the job. It returns (with a very simple 3-wire protocol) a 12-bit value and this value is the exact temperature on the hot junction.
Got ALL the parts now to etch a circuit board but!! and maybe a big BUT?
I discover my DMM only reads down to tenths ( .1 to .9) but using a knowen value like bioling water or ? maybe I can adjust this.
Thinking maybe just do an ADC and see if I can get millivolts?
Then the problem is using a different PIC. Going to use an 18F1320.
For sure will have just enough pins.
Need to write some code in Swordfish as I have no clue of using assembly or other than Swordfish.
Thinking that the max6675 just outputs a digital signal? need to read up on that chip and hopefully understand it (yea right)
use the pot to set desired temp then enable or disable the port that runs the opticoupler.
Any insight on the max 6675? would be helpful.
Yes Tim they work. Any K-type thermocouple will work. After all, it is the cable that you want. So get the cheapest one. Or, get one from a multimeter temperature sensor. I would suggest ebay that you find cheap multimeter k-type thermocouple probes.
Thanks Kammenos, I've read through it (quickly) a few times now. I've also read through the section on experiments with thermocouples and this build log. It is certainly possible that I've missed something, but all I've found is a reference to getting some wire from a friend. I can start looking elsewhere for info to get/make a thermocouple, but I hope to get some direction here. Sorry if I'm being dense.
Doug, i would rather suggest that you do not use PWM for the heating control. Better you make a dimmer circuit (check out the theory http://pcbheaven.com/wikipages/Dimmer_Theory/ and a PIC dimmer circuit http://pcbheaven.com/circuitpages/PIC_DCV_Controlled_AC_Dimmer/). Usually, industrial controllers use bursts to control them. This means that it turns on and off the power on the resistor with long spaces (0.5 to 2 seconds for example). A fast switching PWM will not accurately control the power, as the supply is AC...
If you want to have a very small error, the only way is with PID controller
Hi Tom. I have not worked on this project yet, because i have another project already running. I am making an instant cold coffee maker (AKA frape, very popular in Greece). This is a challenging project and i have given some elegant mechanical solutions. I will post the first page of this long project today (http://pcbheaven.com/projectpages/Instant_Cold_Coffee_Machine/).
Give anymore though to monitoring the current drawn by the element and converting the current to temperature?
This design could be PIC controlled. You would have to calibrate the system but once calibrated, it would be very accurate.
As temperature goes up the element resistance would go up, drawing less current. The trick would be to measure the current across a very small resistor. And the resistance does not change much with nichrome, but it changes enough & the value is stable enough so that once you know the relationship you can use the resistance (current drawn) to give you the tip temperature.
Hopefully etch a board this week?
Will post pics.
Contemplating rewriting the PIC code using an 18F1320 and contemplating using PWM to control the over heating by 4-7 degrees you mentioned.
THINKING - change the duty cycle according to the tip tempeture. Just a thought.
Planning on using Swordfish Basic. More user friendly and easier to read.
Just insert the LCD module,PWM module, An ADC module, add a few bells n whistles and maybe your done?
Presently working on a temperature display for 4 refrigerators using DB18S20 temperature probes.
I have a revised schematic as well as a PCboard design using express pcb.
Not sure where to post it if someone wants to etch a board for this nice soldering station.
Am not real proficient in PIC programming but maybe take a sta at converting to an 18F1320 pic and use Swordfish as programming lang. I find its easier to understand IMO.
If the webmaster Emails me for files then great.
Perplexed about the R8 &R9. Could be an LCD issue?
R1 & R2 at 180 ohms your drawing 25ma. By going to 220 - 330 your drawing 20ma or less. Don't think youll see much difference in the brightness.
Why change the LEDs. In the video it looks great how they operate.
I kinda figured R7 was temp value.
Trying to design a PC board without usaing any jumpers. This is the fun part. Connecting all the dots.
About the LEDs, i am not really sure which is which. After all, i have not yet decide the final operation of the LEDs. It may change. Actually i think of removing one LED.
About R8-R9: I originally had 2.2K, yet it had to change them down to 100 and 500 because did not work correct. I suppose it has to do with the LCD.
R1-R2: I usually use 180.
R7 is the temperature set value.
YES a great starting point.
With input from several different people the project in question will do nothing but improve.
Perhaps "beginner" electronic hobbiest etc can learn from ones so called errors.
I have looked at several of the projects posted on this site with great interest.
Have learned along the way.
Perhaps by pointing out errors may prevent someone from frying a pic (case in point R1 & R2)
Am sure it was a mistype as the author seems to have a vast knowledge of electronics.
We can ALL learn by others mistakes as well as our own.
Presently designing a circuit board and waiting for parts.
Hey guys, give this guy a break. If you've followed any of his projects in the past you would realize that all are works in progress. And this projects like any of the others can be improved upon. At least he's creating and sharing and giving YOU a great starting point!
Back to working on this PCboard and noticed several minor and some major problems. Not to critize but maybe help someone avoid problems.
The posted schematic looks like the earlier version?
R8 and R9 should be 4.7K pots
R1 &R2 should be 220 ohm. with 47 ohm the PIC needs to output 95ma.
what LED is red and which is green?
what does R7 do?
when I am done will post a PDF of PC board.
I have upload the BOM of the project. You should also get the new schematic as i have done some minor changes with the names. C3 is for PIC VCC.
I usually do not upload projects for others to follow line by line. For this reason, i have the circuits section (http://pcbheaven.com/circuitpages/) . The project section is for others to see the solutions i give to some problems, to get ideas etc etc etc. That is why i pay more attention to the construction details rather than the program or the schematic. You may alter the schematic to fit your needs, or change the software.
I am very glad that you will make this project yourself, and i wait to hear the results. I hope that you understand that this is a prototype project and in the future it may present faults and bugs that you may need to correct yourself. In the meanwhile, whatever change i make (hardware or software) i will inform the site calendar (home page left bar or http://pcbheaven.com/sitenews_archive/) but i do NOT send newsletters about project changes. You need to check the news frequently.
CAUTION concerning schematic. The ICSP lay out is wrong.
I looked at the schematic and questioned several points on this forum as well as Elect-Tech.
My concerns are right. If you use the ICSP section as posted in the article the diode will go poof!
Not to be nit picking, but the circuit board layout has 90 degree traces which should not be used.
I plan on building this GREAT project but making corrections. Will post a PCB layout if anyone wishes.
Be really cool if we could get a bunch of boards made professionally.
Hi Doug. First for the thermocouple. You need a K-type to work with the 6675. Check out the theory about thermocouples. I have a photo from one taken from a multimeter. Sold on ebay for less than $5.
About the firmware, download from page 3 of the project worklog (http://pcbheaven.com/projectpages/Homemade_Soldering_Station/?p=2&topic=worklog). R5 can be totally omitted. I have it there because i may want to add a pushbutton. So, i have the pull-up resistor ready. The button will be connected to low, and the input RB6 will be used for the button. During programming, the button must NOT be pressed. I suggest you keep this resistor for upgrade purposes.
I got to build one of these. Contacted Maxium for FREE sample of 6675.
Now to locate thermocoupler.m I wonder if using one for a pilot light would work?
Already has housing etc.
Need to locate the firmware, order 16F88, etch pc boad.
Have question on the schematic- the MCLR, I have only seen where Vcc/20K resistor/diode/PIC connection with the ICSP connected directly to the PIC.
RB6 is tied HIGH via R5? Have never seen this.
NOTE I am a newbi at this PIC stuff.
Tom this sounds really really good! I will test it for sure. I search for a proper 50 Watts soldering iron (weller or antex) with thin tip. Maybe i will get this weller 50watts $50 soldering station and hack it. Excellent idea To!
An alternate way to do this is to not use a thermocouple at all, but to measure the current drawn by the iron when on to calculate the tip temperature. Resistance will go up as the temperature goes up and you would need to map the relationship first.
The firmware is in the worklog pages, in the controller section. The link is:
I have the full assembly listing and the hex file