Temp Regulator V1.0

Discussion in 'General Electronics Chat' started by R!f@@, Apr 23, 2011.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    See the attached.

    This is a diagram that I manage to cook up by studying a lot of diagrams out there
    Since My Soldering station cum hot gun is on the fritz I decided to upgrade it.

    This is the 2nd stage.
    First stage what I did is strip the whole thing apart. The guns too, renew the heating element and the connectors since it is too loosening. This is going to be a project sort of, but I am not yet documenting much but if any one likes I would take pics from now on.
    This Station will have two soldering irons, with individual temp control and display. The display part is yet to design.
    It will house the hot gun too, which will be also complete circuit make over.

    The aim of this thread is to for u to guys comment on how to improve it. Since this is just a simulation.

    The circuit gave me time step errors on my XP machine, so I tried on win7 and it works.

    The thermistor in the gun is simulated by R5, it is a 50Ω thermistor at room temp and rises as temp rises..
    @ 25°C it is 48Ω and rises to around 100Ω @ temp of about 400°C plus

    Multisim did not have a model.

    I have spent the whole night trying to figure out why the circuit didn't work like I wanted so made some changes.

    The Thermistor inside the heater is a PTC, I checked by heating and noting down the resistance change with temperature. It was really difficult and confusing on how those two behaves.

    You know I did search a lot but I cannot find any circuit that uses a 48Ω Thermistor with a 3Ω Heater which is exactly what I have, A Hakko 926 model iron.
    This Iron is like family, it is been with me like for ever, so I want to upgrade it rather than buy a hefty priced one.

    So now atleast my simulation works the way I want.
    at room temp or OFF state which is shown in pdf 1, gives me a 0V output.
    In pdf 2 shows the heater at max which from my finding gives me around 100Ω, so this temp gives a reading of 5V.

    I used a precision regulator to as the thermistor voltage and is set at 5V. Even though the opamp is at 12V the output never exceeds 5V.

    This circuit is purely my design and the Multisim shows what I wanted.
    Have been changing the circuit and values trying to get a 0 to 5V out.
    Took me 12Hrs to do that. :eek:

    Since there is no circuit on the net that uses the hakko filaments. I have to cook my own. It might not be good cause I am not an expert in circuit design. But it does what I want, so I guess I'll make it.

    The previous attempts failed big time but couldn't give up u know.

    Umm!! the out put will be connected to a ADC pin of a PIC and it will sample the voltage. I believe 0 to 5V is a the safe value for a ADC input. The look up table and the whole mumbo jumbo for the temp and display is yet to be ..well .to tell u the truth I really have no idea yet but I'm learning.. :D

    So guys...what do ya think...Is there any improvement or any tweaking that could be done please throw it here.

    I chose the LM358 after a lot of reading and it seems it was a good idea for me.

    Yaaaaaaawn!! that's it for now....I'll get back after I bread boarded this with hardcore results. Till then .....tooodlooooo..
    Last edited: Apr 24, 2011
  2. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    Version 3 is out...