HI All,
Any solution to the "bean on probe" problem?
Two out of three roasts this weekend ended with a bean stuck on the probe requiring "tugging" to remove.
What impact, if any, does the "bean on probe" have on the roast? The two roasts completed at the expected time. Cool down was prolonged with the temperature hovering at about 40C. Had to end manually and dump the beans. Ambient temperature was "high". So, this may have been unrelated.
When does the bean get stuck? I presume its after first crack.
Does the probe need a redesign?
Sam
Bean stuck on probe
-
kaffelogic
- Site Admin
- Posts: 514
- Joined: Thu 18 Oct, 2018 9:38 am
- x 74
- Contact:
Re: Bean stuck on probe
Protecting the probe from contact with the beans changes the thermodynamic behaviour significantly and leads to major re-design of the control algorithm. This is a potential future development, but as so many things are interrelated it is not going to be just a matter of change to the probe by itself so it is a R&D branch all of its own.
As for what we know about the phenomenon, it is rare enough that it is difficult for us to observe. We can do hundreds of roasts without a single incidence of a bean stuck to a probe, or alternatively, sometimes you get two out of three. As far as we know, the roast itself it not adversely affected by the bean stuck on the probe, although you can expect it to be different from a roast without a stuck bean as the relationship between probe temperature and bean surface temperature will have changed. I am assuming that the bean becomes stuck during first crack, with the central crack of the bean closing like a vice when the bean 'cracks'.
Cooldown will automatically end when the probe temperature gets below 40 deg C. However, cooldown will not bring the temperature below ambient plus 10 deg C (the roaster uses the cooling air to cool its electronics before it puts it into the roast chamber - this warms the air above ambient by the time it enters the roast chamber). If ambient temperatures approach 30 deg C expect prolonged cooldown. The cooldown will time out after 10 minutes. If ambient temperatures exceed 30 deg C you can either let it run for 10 mins, or stop it manually around the ambient plus 10 deg point. Nice short 2-minute cooling requires ambient temperatures in the low twenties.
As for what we know about the phenomenon, it is rare enough that it is difficult for us to observe. We can do hundreds of roasts without a single incidence of a bean stuck to a probe, or alternatively, sometimes you get two out of three. As far as we know, the roast itself it not adversely affected by the bean stuck on the probe, although you can expect it to be different from a roast without a stuck bean as the relationship between probe temperature and bean surface temperature will have changed. I am assuming that the bean becomes stuck during first crack, with the central crack of the bean closing like a vice when the bean 'cracks'.
Cooldown will automatically end when the probe temperature gets below 40 deg C. However, cooldown will not bring the temperature below ambient plus 10 deg C (the roaster uses the cooling air to cool its electronics before it puts it into the roast chamber - this warms the air above ambient by the time it enters the roast chamber). If ambient temperatures approach 30 deg C expect prolonged cooldown. The cooldown will time out after 10 minutes. If ambient temperatures exceed 30 deg C you can either let it run for 10 mins, or stop it manually around the ambient plus 10 deg point. Nice short 2-minute cooling requires ambient temperatures in the low twenties.