Different approach to solder station, is this a practical idea?
rwgast_logicdesign
Posts: 1,464
Ok so I have been through a string of soldering irons lately and Im getting pretty sick of it! I started looking in to how one could build there own solder station with temperature control. I came across two very informative projects
http://www.pcbheaven.com/projectpages/Homemade_Soldering_Station/?p=0&topic=worklog
http://dangerousprototypes.com/docs/Soldering_Iron_Driver
Originally I had thought about buying this decent Hakko936 clone over at hobby king, http://www.hobbyking.com/hobbyking/store/__19240__Soldering_Station_with_Adjustable_Heat_Range_USA_Warehouse_.html
I figured hey this thing comes with a 5 pin hakko pencil, which has a PCT sensor in it and it has an analog driver board, I could just mod the thing to read the heat sensor and implement a PID loop! Well this 16 dollar station turned in to a 40 dollar station with the cheapest shipping..... so Im ruling that out, I dont understand how this is a deal.
So after a bunch of research I figured I could buy an Elenco SL30 soldering pencil, which has a K type thermocouple and use a Max31855 to help me read the sensors. My biggest issue is the heater control. I dont really understand how triacs work, and a 24v transformer by itself is close to 12 dollars. All I know is that the triac is used to chop the 24v waves down, and this is how the heater is controlled in most soldering stations.
Now what I would like to do is somehow use PWM or a DAC to adjust the voltage of the iron, this would mean I would need to send out the reference voltage signal, and then not only amplify it up to 50W max but also convert it to a standard 60hz AC wave correct? Is it even possible to do something like this? I think if it were using a DAC would be a really accurate way to set the irons heater.
Oh and to get the original power in to the station than blan would be to use a 30v 1 amp power supply, regulated to 25v that is 50watts of DC.
http://www.pcbheaven.com/projectpages/Homemade_Soldering_Station/?p=0&topic=worklog
http://dangerousprototypes.com/docs/Soldering_Iron_Driver
Originally I had thought about buying this decent Hakko936 clone over at hobby king, http://www.hobbyking.com/hobbyking/store/__19240__Soldering_Station_with_Adjustable_Heat_Range_USA_Warehouse_.html
I figured hey this thing comes with a 5 pin hakko pencil, which has a PCT sensor in it and it has an analog driver board, I could just mod the thing to read the heat sensor and implement a PID loop! Well this 16 dollar station turned in to a 40 dollar station with the cheapest shipping..... so Im ruling that out, I dont understand how this is a deal.
So after a bunch of research I figured I could buy an Elenco SL30 soldering pencil, which has a K type thermocouple and use a Max31855 to help me read the sensors. My biggest issue is the heater control. I dont really understand how triacs work, and a 24v transformer by itself is close to 12 dollars. All I know is that the triac is used to chop the 24v waves down, and this is how the heater is controlled in most soldering stations.
Now what I would like to do is somehow use PWM or a DAC to adjust the voltage of the iron, this would mean I would need to send out the reference voltage signal, and then not only amplify it up to 50W max but also convert it to a standard 60hz AC wave correct? Is it even possible to do something like this? I think if it were using a DAC would be a really accurate way to set the irons heater.
Oh and to get the original power in to the station than blan would be to use a 30v 1 amp power supply, regulated to 25v that is 50watts of DC.
Comments
A simpler approach would be to switch the AC waveform on for x out of a number of whole cycles (or half cycles), and it has the advantage of producing much less electrical noise. The thermal inertia of the soldering iron heater and tip would average out the temperature.
Do you mean something like this. You connect a micro to the control line of a relay, then run your specified AC voltage (In the case of a hakko 24v, either full AC, or half wave rectified) to the power side of the relay. You would then switch the relay on and off using the micro for calibrated amounts of time?
It seems to me that a heating element is a resistive component, is there any reason to even bother using AC to run the Irons Heater, wouldnt good old DC work just the same since the heater is resisting the same amount of load regardless of the waveform?
In design work, you just want to pick up the soldering iron and know that it works. You really don't need to spend your design time re-inventing the wheel, wasted time to to better things.
My soldering arsenal:
Radio Shack Digital Soldering Station a bargain at 80 bucks. On it's third year. All tips available on the RS site. It's made by a good manufacturer, but I can't find the link at this moment.
American Beauty 40 Watt Iron, 30 years old. Work Horse for cable.
Radio Shack 150/230 watt gun When you got to bring out the big guns.
Covers the whole gambit.
My 2 cents
Basically I just took a junker $5 wal mart iron apart with a Hak Saw, tested it resistive element with a meter it is 477 ohms which works out to its 25W when 110V is applied. I powered it up with a 30v DC supply and got the expected .06 current draw @ 1.8 watts. This means that the element works just fine at DC voltages.
In theory this idea should work, and im sure most people have all the parts on hand, except an iron meant for a station. Hakko clones can be had for $8 and loaded with genuine Hakko tips though. These station irons all work at 24 volts and put out 50W. This means that you need to dig up a 24v/2.08A or better DC to DC wal wart, I found this little guy http://www.allelectronics.com/make-a-store/item/PS-2460/24-VDC-2.5A-SWITCHING-POWER-SUPPLY/1.html but laptop charge bricjks are readliy available for a dollar at the thrift store! Now you have the full supply to run your 8 dollar hakko, which is better than most 20 dollar irons. At this point you can throw an adjustable regulator on with a pot and get an analog supply, or take it a step further....
Throw a micro in there, pulse a half h bridge connected to your big wal wart, for heat control. Next read the temp sensor on the iron and you can add either full blow PID feed back or simple hysteresis feed back. The hakko irons have a PTC temp sensor, so you would need an analog front end and some math to get accurate reading, BUT if you buy an elenco SL30 iron it uses a K type thermocouple and a MAX31855 which is pricey but can be sampled will convert the thermocouple reading straight to a stable 12 bit digital reading for you, it implements all the algorithms to read these things so you do not have to, If I understand right reading the thermocouple with an ADC will work but the numbers you receive will not be linear and need to be processed through algorithms first. The Hakko Irons use a PTC though, and Maxim does not make a chip for those, so you can save money buy buying Hakko clones but you will end up doing a bit more work if I understand right.
Basically this seems like a cool project for someone who has a lot of parts on hand, the only things that may need to be purchased as I said is a cheap Iron, Fets, and a wal wart or parts for a 24v 2.5 amp supply. I just realized you need to allow some extra amperage for an LDO and Micro so a 2.08 amp supply wont cut it if you want a full 50 Watts.
Considering the cost of a decent mains transformer I wonder why most soldering stations use AS and a Triac still, it also seems to me that you can get much better temperature control using pwm/dac, as it allows for such precise stepping.
The new "p" tips are insane. I use the 101p for 90% of my soldering, and I have a lot of SMD, but 0805s are still in range.
Massimo
It seems as if a 24v power supply is the biggest pain in the butt as far as getting one with enough amperage for cheap, so I started thinking hey... why don't I just use two 12v 3amp supplies, parallel the inputs, and series the outputs. While looking through my wal warts I actually came across a 60W 24v DC transformer I ripped out of an old type writer and forgot about. All I would need to do is add some rectifier diodes and filter caps on the output of this thing and I would have clean DC power correct? I know now that I found this thing I could use the standard method of a triac and AC, to power the Iron but like I said I think the idea of controlling the heater with PWM/DAC is much more precise and I understand it.
When I decide to actually buy a station, it will be a higher end Hakko. I don not plan on buying one right now, and if I did it looks as if metcals are in the 300 plus dollars, that is a lot for someone trying to save by building.
I have to agree with Publison and the other posters comments. Building your own soldering station is not going to provide much reward or saving for the time spent on it, however if you want to tackle it there are several approaches that can be taken. All would need to measure the temperature and control the amount of power going to the heating element.
1 – On/Off (also known as bang-bang) control. Works for DC and AC.
2 – Pulse width modulate power to the tip. Works for DC and rectified AC.
3 – Half/full cycle control. Similar to pulse width modulation, only full/half cycles on/off.
4 – Phase control. See http://en.wikipedia.org/wiki/Dimmer for an explanation.
is an attempt at a lowest cost variable temp solder iron, inspired by the hakaday link listed. $13
Consider - how accurrate does the soldering iron temp have to be? It just has to be hot enough to solder as quick as possible without burning up the part, but not so hot as to burn away all the flux too quickly. Simple is sometimes an advantage.
@Kwinn thank you very much for the reply, when I posted earlier I was thinking of something more along the lines of an SSR if running the heater via AC, but that it pretty pricey compared to using a Triac set up.
I am curious why it seems to be the general opinion to just go out and buy a solder station? Ten or Fifteen years ago it was pretty popular to make your own equipment, there are books on Amazon about building your own lab equipment, function gens, power supplies etc... I do realize that part of the reason more hobbyist are inclined to buy than build these days is because prices are much cheaper. I can find a chinese solder station on e-bay with digital temperature control for about 50 dollars and that is dirt cheap, considering my standard weller iron with no control was $25. The thing is whatever I build may not be as nice as a higher end Hakko station, but with care it should be better than a piece of chinese junk, they want to cut costs so they are going to use the bare minimal parts to build the thing, while I will be using higher quality caps, and fets with bigger capacity than needed. In my case I already have a working iron that will get me through until my station is usable, I also have all the parts on hand I need except the Iron and the Fets. I have an enclosure, plenty of micros, a power supply, LCD screens, pots, rotary encoders, etc. Physically making the station should not be to hard. I can copy and paste a PID loop, so the only software I need to write is the stuff to interface with the sensors and the user. So for 20 buck I can have a digital station that I can expand and upgrade, and have learned quite a bit about how they work, I don't see how this is any different than someone making a clock, or and automatic chicken coop. I am just trying to understand why everyone is always so eager to buy over build when it comes to utilitarian type items.
http://www.testequipmentdepot.com/weller/solder/wlc100.htm
Probably they thought you would have to buy most of the parts, as I did. By the time you add up the cost of all the parts needed it would have been more than the cost of a decent soldering station.
If I would have dropped the $ 30 years ago and went with weller from the beginning I could have saved what I spent for the solder station by simply not buying cheap ones to begin with!
As an alternative, I would mention that I paid for the first three years of college by working on a production line at Hewlett Packard each summer. Even though we were doing quite delicate rework on some boards, we were still using standard irons - no thermostatic control beyond the mere fact that 1) resistance wire increases in resistance as it heats up and 2) the hotter the iron, the greater the free convection. While no one ever explained to me why we used such primitive irons, the fact of the matter is that with proper skill and technique, a hotter iron can solder a joint with less heating of the component than a cooler iron: 700 deg on a lead for 1 second is better than 600 deg on a lead for 5 or 10 seconds. So you might consider just using the Walmart iron and simply improving your skills.
BTW, the biggest irritation I ever had with an iron was cheap tips. The tips really must be iron clad to avoid dissolving in solder. Once a tip starts dissolving, it quickly becomes a PITA to use. The tip of the Weller I use now has lasted for years of heavy use. They really made it right!
My first soldering iron was in a junior high metal shop where you had to heat the iron in a small gas furnance.. not electricity at all. The size of the iron's tip was a thermal mass that allowed you enough heat to get something done before reheating.
If you cannot grasp the concept of a thermal mass, it is somewhat the thermal equivalent of a capacitor. The heat is stored there to later be used.
These days my soldering station is a old dog food can covered with rubber from a motor scooter inner tube, stuffed with pebbles for weight ballast and insulation and supported on its side by a stand made from a twisted brass brazing rod.
I generally use a cheap 30 watt soldering iron as the thermal mass seems about right for what I do, without all the fancy controls.
If I wanted to have further control, I would just wire up a box with a room light dimmer switch to further reduce the power fed to the iron when it seems to get too hot or if it is left on in a stand-by mode.
My feeling is that hand soldering is a craft and one acquires the skills to handle what they are doing without a lot of fancy automation. Generally, I feel there is always a niche for doing something by hand in fabrication and repair. But these days, the craftsman is being pushed out by robotic mass production. I am not sure I like the trend as many of the fundamentals are forgotten along the way.
I think my technique is decent ive been soldering a long time, some may say I use to much solder .. but I think it is kind of called for on protoboard if you want a clean look.
When the weller died I pulled out my wal mart cheapO and the tip lasted 2 days if that. I went to radio shack and bought a switchable 15/30watt iron thinking it would be the last iron I buy for a while. Well the tips burn up at 30 watts, the tips also loosen up while using the iron due to no set screw. I could have went out and bought another 40watt fixed weller like I had but those tips seem to burn up after maybe a month of use. I make sure to keep my tips tinned while stored, and I clean them after every three joints or so. From what I have read even the cheap Hakko clone irons with sensors in them are fairly high quality and the hakko tips last people years. I figured a temperature controlled station would help keep my tips in good shape, as they wouldn't be burning a full 40 watts of power on the tip when not in use.
I had also thought from what I read soldering at lower temperatures for a bit longer than higher temperatures quickly was a better technique... I've read about teachers only using 15 watt hakko fixed irons in their classes. I have to admit since i've tried using this RS iron at 15 watts I have had a much harder time due to the heat capacity and I can definitely feel i'm heating up the components at 15 watts, whereas with the 40 watt weller I basically touched the iro to the board taped the sorder on the copper and let off in under a second. But with a high wattage fixed iron just touching a wires tip will melt its insulation, this hasn't happened to me with the 15watt iron. I'm hoping an iron with feedback will allow me to solder at lower temperatures but with the thermal capacity of a larger iron.
I actually had no idea there was a 35 dollar adjustable weller or I would have bought it this morning before I ordered all the hakko tips and clone iron. If worst comes to worst I can turn off the feedback and have a 50 watt iron with Hakko tips that is probably comparable to my 40 watt weller!
@Loopy, Wow that is amazing! I never knew there was a time when people heated irons in an oven.... what exactly were soldering with no electricity, I would think you would just use butane for bigger metal stuff.
Ever been to a Cracker Barrel Restaurant? Look up on the walls and ceiling and you will see thousands of old tools and kitchen items. Many times you will see non-electric clothes irons which are nothing more than a shaped and smoothed iron mass with a sturdy wooden handle. Grandma used this to press the wrinkles out of your Sunday best by placing this iron on the kitchen wood burning stove until it was hot enough. Any woman that used one of these very long probably had some good sized arms.
Butane or propane torches like you see now were not available then. Blowtorches that used white gas or just plain gasoline were used for the "bigger metal stuff". Getting one of these working took quite a while since the torchhead had to be very hot before it would actually project a usable flame.
A little gas furnace might be used in a shop that has gas supplied to it, but a construction site might use use a coal fire. After all, there wasn't a ready supply of electricity at the time.
and this:
http://www.amazon.com/Weller-WPS18MP-High-Performance-Soldering-Iron/dp/B0013U9R1E/ref=sr_1_10?ie=UTF8&qid=1366198682&sr=8-10&keywords=weller+soldering+iron
Tips of both are eaten away in no time, and 2nd one quit working, after plug'n'play tip (which has 3.5mm audio minijack inside) went loose (I never attached other tip, so this is not the cause).
So may be weller is big name, but quality really stinks.
You're a rather prolific designer and builder of electronic projects. I'm sure you'll get'er done.
CuriousOne, my Weller has been around for a number of years - I must have gotten a good one.
Cooper tools has really let weller become a lesser brand ......
Hakko 888 Its low cost and so far has not let me down ... Its of the best irons i have owned so far ,,,,, the Edysin I had was also Very good .
Peter
[FONT=arial, sans-serif]The weller I had was the same exact 40watt CuriousOne linked too. I was quite surprised it only lasted a year. I use to play with electronics as a kid. My Grandpa gave me a Weller gun he bought in the 70s, The thing still works, and heats up faster than a New Radio Shack iron! From what I have read Wellers quality is pretty dodgy these days and there lower end Irons are just badged OEMs.. It is a shame I thought that 40 watt weller was going to last a lifetime. It really is a shame when you can't support made in America products like Weller because they tossed quality control out the window, what's next a set of Klien dykes snapping? The Weller tips are much better than most cheap irons though, Like I said the reason I think they erode in a month is the fixed 40 watts. The one thing I want out to implement is a feature where the Iron drops down to 250 degrees when I put it in the holder, the higher end Hakko951s do this. [/FONT]
Ok in the next room there is an older DELL laptop that has a 4 amp 19v power brick, the brick is very small, this is because it does not use a transformer, obviously this means it is a switching supply. Now I have been working with DC-DC switching regulation for a while and I understand its concepts, I will say it is pretty hard to find a switching regulator that can handle 4amps or more. How do these bigger AC to DC supplies work? Does one simply rectify the 110/230v in and then build a custom switching unit out of discrete components to step down the voltage?
Now that an AC to DC switching supply is common, and components are cheap to free in quantity what would make a designer use a transformer over a switching supply? In my case I have a transformer and I don't know how to build a high wattage AC to DC converter. But lets take hakko for example, If you tear down there station, including the newer ones like the 88, 888, and 951 you will find a nice hi quality transformer inside. Why is this a transformer cost a lot more money than assorted chips and caps, Is there a difference in quality between the transformer and the AC to DC regulator? Ill tell you one thing, I have the parts for this station all laid out and I can fit it in a pretty small (compared to the size of most stations) radio shack enclosure, It will be nice to have something a bit bigger than a laptop brick that sits between the wall and the iron as compared to a bulky desktop enclosure. The thing is by using a transformer this box is incredibly heavy and unequally weighted, What i'm getting at is with the advent of switching AC to DC regulation there is not only a cost savings but items can be smaller and lighter.
I have never used discrete FETs before but from what I understand I need to buffer there gate in order to keep them switching at fast PWM frequencies. I was hoping some one could help me understand the pros and cons of chosing a FET or a Large transistor, these are what I have on hand
http://www.onsemi.com/pub_link/Collateral/2N3055A-D.PDF
http://www.vishay.com/docs/91047/91047.pdf
I am totally willing to buy something else if neither of those parts are a good fit, but the capacity of both the FET and Power Transistor seem to be overkill for 50W.
The size and weight of a transformer can vary quite a bit.. if you use higher frequencies than 60 0r 50 cycle AC and if you use modern core materials that are found in toroid cores. In other words, there may be a tiny and lighter transfromer doing a bigger and better job than an old iron core 60 cycle dinosaur. Switching supplies use the both the higher frequency approach and new materials for transformer cores.
Soldering is really an old technique.. at least 5000 years or so.
Before electricity and electrical distribution , zinc and copper sheet roofing were very common and some soldering was used in that. It was also a common method in jewelry construction.
http://www.ersa.com/soldering-history-en.html
http://en.wikipedia.org/wiki/Soldering
Oh, and don't forget all those stained glass windows in cathedrals.
Anyways Ill show you guys what I have,
The first pic is just kind of the concept, the mains come out one end, and the other end will have a 5 pin din connector, so it sits inline with the iron like any other power brick would, instead of a clunky station. Of course there will be some sort of controls under the LCD. The second pic is the transformer I want to use, its next to a standard rubix cube so you can gauge the size better. As I said before the thing came out of an old digital typewriter, which I also robbed the rectifier from
I have also thought about scrapping two ATX transformers and then connecting them in series this would give plenty f power and even be a bit lighter from the looks of things.
We have heard here from somone in a HP repair shop that just weilded a cheap iron. That correlates with my experinces as a young student in the "make it right" department of a big military supplier.
For all my hobby work an iron has been sufficient. Never felt the need for temperture control.