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Manually control Behmor power with 555 timer/SSR combo?

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  • Manually control Behmor power with 555 timer/SSR combo?

    I'm getting better at controlling ROR by quickly flicking between power levels but it's hard to do consistently.

    After much googling and even grave digger here, seems using a 555 timer in astable mode as a PWM triggering a SSR direct to the heating elements could be a simple solution. So rather than be restricted to just 25/50/75/100% power, I could have it infinitely variable.

    I've already got some 555 based circuits kicking around I could potentially re-purpose. Just need an appropriate SSR.

    Basically I just want to be able to control the power more precisely. Even 10% increments would probably be sufficient.

    Thoughts?

  • #2
    Sounds very interesting and worth a shot however,
    I think the fact you already have control of the power is a massive advantage over no power control so being able to break it down into 10% increments, personally I don't see it as much of a gain.
    Not sure that consistency will be greatly improved also as you're effectively still manually controlling the roast.
    If you're looking at creating a closed loop system where the power adjustments are auto controlled based on the current temp and profile, then that's another story.

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    • #3
      Auto control would be the holy grail though I don't know any simply DIY solutions to achieve this. Even computer controlled solutions (eg arduino) are still based on user input.

      Essentially after FC, 100% is too high and 75% is too low.

      I've tried playing about with bean mass as some have suggested but you can't obviously change that on the fly and ambient temp, humidity and bean type also affect it.

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      • #4
        An ssvr will do what you want. A pot controls the output 0-100% infinitely variable. Use P5 and then the pot will give full control.

        You could manually log the power % on roast monitor to aid repeatability.

        Cheers

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        • #5
          Originally posted by MrFreddofrog View Post
          Even computer controlled solutions (eg arduino) are still based on user input.
          Sometimes yes but it can be done automatically. My Arduino configuration uses PID from within the RoastLogger software to automatically adjust the heat output based on the input temperature and were it needs to be according to the profile.

          Originally posted by MrFreddofrog View Post
          Essentially after FC, 100% is too high and 75% is too low.
          In this case, the ability to further vary the output would certainly help

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          • #6
            Originally posted by MrFreddofrog View Post
            Auto control would be the holy grail though I don't know any simply DIY solutions to achieve this.
            I've done it with my Huky, it was actually pretty easy using artisan. Artisan can set alarms at specific events, e.g. "When BT gets to 150°C turn fan to 20% and gas to 80%" and so on. Events can be time or temperature based (very configurable, e.g. "time since turning point" or "time since charge etc.). Artisan can run an external program at these alarms, I have mine setup to run a program which tells the arduino to set the fan/gas to the appropriate settings.

            Trying to follow replicated a saved profile wouldn't be too hard, however I haven't found I've needed to do that since the above artisan alarms are configurable enough and work well enough for me.

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            • #7
              I use an osPID, which is an open hardware/firmware PID controller based on Arduino. It has the ability to do pretty much any ramp/soak profile you want (I use up to 11 steps).

              I modified the firmware to talk to RoastLogger and experimented with writing my own application too.

              Write a profile, upload it and hit go. No other manual input required.

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              • #8
                Another site has mentioned SSVRs and it certainly is simpler but I'm not sure if anything else may be affected by varying the voltage. As the Behmor regulates power through simply cycling the heater on and off (rather than reducing voltage through it), I thought it safer to use that same control logic. Not saying I'm against the SSVR idea, I just need more confidence it's not going to harm the unit.

                Thanks guys on the options for full auto control. I do use Artisan (and manually log power) but I hadn't twigged you can use the alarms for that purpose (duh!). I've only briefly looked into PIDs but for now I think full manual control should suffice. That said, now that I conceptually know how to do full auto control, that will most likely be the next step.

                If anyone could shed light on how suitable a SSVR would be that would be great otherwise the 555 Timer/SSR combo looks viable.

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                • #9
                  You leave the behmor on 100% and reduce power as needed with the ssvr.

                  Would be best to have a two way setup. Behmor standard and then full power controlled by ssvr.

                  Be mindful if you exceed the wall temp max (166 degrees from memory) it will cut out as a safety precaution.

                  Cheers

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                  • #10
                    Yeah that's the plan, leave on P5 and reduce power as needed.

                    How do SSRVs work? I actually don't have any experience with them and google is producing just voltage regulators.

                    I thought they were like glorified dimmer switches, ie variable resistors but new dimmer switches work by "chopping" or essentially pulse modulating the waveform in which case it should work?

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                    • #11
                      Not sure how they do it but I thought it's like a high powered resistor? Not expensive to give it a bash, search for item 140553987088 on the bay for an example.

                      Leaving the toaster on p5 still gives you the safeguards eg over temp, hitting stop etc. and you could easily bypass it with a switch or similar to return the behmor to standard operation easily and switch the ssvr on/off.

                      Cheers

                      Comment


                      • #12
                        Originally posted by artman View Post
                        Not sure how they do it but I thought it's like a high powered resistor? Not expensive to give it a bash, search for item 140553987088 on the bay for an example.

                        Leaving the toaster on p5 still gives you the safeguards eg over temp, hitting stop etc. and you could easily bypass it with a switch or similar to return the behmor to standard operation easily and switch the ssvr on/off.

                        Cheers
                        Yep, can easily bypass the SSVR but I'm more concerned about the affects on the electrical components down stream. They (assuming there are any which there may not be) are expecting to see a certain voltage and if I change it, that could be problematic. Then again I might be worried about nothing and it may simply flow straight to earth. As simple as a SSVR solution is, I'd rather be 100% sure before going down this route.

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                        • #13
                          You would wire it up so the ssvr only controls the heating elements. I don't see any dramas with these seeing less voltage. Obviously do at your own risk, 240 can kill, use an electrician etc...

                          If you examine the board and roaster you will see the way the elements are wired and you can easily have a ssvr/bypass.

                          Cheers

                          Comment


                          • #14
                            I use a heat sink mounted 25amp Solid State Voltage Regulator + 500K ohm Potentiometer with my Behmor 1600. Just tap it between the lead that connects the heating element and the control board. Pretty simple and it works well. I just use P1 Auto and control heat manually. Behmor Plus will have an advantage of higher heat using P5 manual with this mod.

                            Comment


                            • #15
                              Originally posted by JojoS View Post
                              I use a heat sink mounted 25amp Solid State Voltage Regulator + 500K ohm Potentiometer ....
                              Great, sounds like SSVR is the choice then. Couple of questions if I may:

                              1. Where did you get the SSVR? Doesn't seem to be a component that even Jaycar or Altronics stock
                              2. Is your potentiometer linear or log?
                              3. What size is your heat sink?
                              4. Possible to get any photos of your set up?

                              I have a 1600+ so will use manual P5 and adjust heat down from there.

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