How to set up a temperature profile

[Jane]

For my project I need to set up a temperature profile but the profile should NOT start from ambient temperature ,that can be as low as  20°C , but from a higher temperature, for example from 150°C.
Also it should finish at that temperature 150°C.
Will I need two PID controllers or one will be enough?
And what kind of the controllers_ ALtec P410 or REX C100 or different?
Thank you for help

[billdlv]

I have not used either controller you mention, but I have used many other types of temperature controllers.  I had a look at the instructions for both, and the Altec P410 has profile capability while the REX C100 does not.

I believe you would be able to do what you describe by using an alarm output and the appropriate temperature profile programmed into the controller.  The alarm output would trigger the temperature profile to start, and when finished you can have the controller set point stay at a little higher value than the alarm limit to prevent the profile starting again.  Have a look at the instructions they actually are pretty good for a low cost controller.  This controller also has an autotune facility which will make tuning for the PID constants much easier.

What are you trying to do with your project?  It's a little unusual to run a profile the way you describe. 

I noticed by doing a search for the controller model number you have posted this question to a number of other forums.  Hopefully you get the help you need.  I think you should post your conclusion to all the forums so all can benefit.

[Jane]

Thanks for your reply.
I need to solder items that need only about 10 seconds to be heated and soldered ( no longer)
 The starting temperature can not be ambient (20°C)temperature  because it is not technically possible to heat up ( large) soldering tip to about 220C during those 10 sec. So I must already start from a higher temperature, say 150C. That temperature is lower than melting point of tin but high enough that soldering tip CAN reach the melting point during those 10 sec. After those 10 sec, I need to a soak period to cool down the soldering tip but ONLY to those 150 C from where I started (and  I can solder other items)
Will I need 2 controllers, 2 pcs of TC or only one?
Thank you

[billdlv]

Many SMD devices requires less than 10s in melting zone (240~250/260 deg C), but my experience is just screw it. I have made many boards with sensitive parts, such as high frequency digital, high precision analog and more, they will work perfectly after tens of time of reflow under 250+ deg C. The only real temperature sensitive parts I know are connectors (especially those liquid crystal polymer ones) and RF parts and a few very high precision ADCs.

Another way to get around (for R&D, not mass production) is to use low melt solder paste. I migrated to SnBi a couple years ago, and since then I never fried any connectors.

I don't have much experience soldering SMD devices so I can't comment on the above.  Sounds like bluesskull has some experience and data points to work with.  I know in the soldering videos Dave has posted he does not seem to be concerned too much with getting components too hot when using an iron for the soldering.  I think for doing oven work that is a different story since the profiles are usually for longer durations of time.

You should be able to do what you ask using 1 controller and 1 thermocouple.  With the controller in normal mode you would change the set point to the 150 C and prepare everything.  Once the iron is at the 150 C you would start the profile which would ramp at the rate you desire to the 220 C and run the profile.  When complete, the profile can set the iron back to the 150 C and it will cool down and you can start again.  You will have to perform some tests to see what the cool down rate is and what the maximum transition rate will be with the iron.  It will be tricky to mount the thermocouple in a way to give you an accurate temperature reading.  If you were being very rigorous then you would also mount thermocouples on the parts being soldered and monitor their temperature during the soldering process to ensure they don't exceed the temperature limit.

Whether this is the best thing for what you are trying to do I don't have enough soldering experience to say for sure.

[Seekonk]

I've used PID controllers of that type and have a couple comments.   Autotune is pretty much a joke.  Most uses never get beyond the P proportional unless a large thermal mass is involved.    In P the power starts at 100% at the lower temperature and goes to 0% at the set point.  These controllers are cheap $15 and pretty but I have often felt I could do better with a dozen lines of code in a micro.

[Jane]

Thank you for replies
@billdlv: Yes, it should work as you described but how can I set up a loop, so that the temperature 150C remains regardless of how many soldering cycles I will use ( without heating up from ambient temperature first)?

[tggzzz]

For amateur or one-off boards, consider using a modified skillet method.

I've had success using a saucepan with sand in the bottom and a glass lid, plus a non-contact thermometer. The sand heats the board first (i.e. before the components), acts as a thermal buffer preventing hotspots, and allows controllable temperature rises. The glass lid keeps a little heat in, thus heating the topside components a little, and allows you to see the solder melting so that you can carefully lift the board when it has melted. I've found thin lifting wires hooked through holes on the PCB corner are necessary and sufficient when removing the PCB.

As with any new technique, a little experimentation will enable you to control the rate of temperature rise just by turning the gas up and down.

[billdlv]

Thank you for replies
@billdlv: Yes, it should work as you described but how can I set up a loop, so that the temperature 150C remains regardless of how many soldering cycles I will use ( without heating up from ambient temperature first)?

Once the profile is finished  you have the option  of keeping the last set point  at 150C.  The controller  will keep the iron at that temperature  until  you  start the program  again.  Have a look at the instructions  for the controller  they  explain  the profile  operation  pretty  well.