Comparing old and new Bullet

After installation of the new IBTS sensor and the new power board in my originally V1 Bullet (at 240V), I am now able to compare the roasting results. Using the same coffee a Guatemala Antigua, and after a period of seeking and exploring, I now have the feeling that we have found the best control actions to get out our most preferred profile. We set out for a roasting duration of about 10:30 minutes seeking for a slowly decreasing ROR to get to an espresso roast which you might typify as nicely balanced, with sweetness in the cup, a slightly bitter touch together with a hunch of citrus. The beans are evenly colored with a slightly silky shine.

We start with a temperature of 230C (IBTS) and power at P8. Our ROR climbs directly to a level around or slightly over 20. In the bread phase, around 170C, power goes down to P7. At the start of FC Power to P6 and then slowly back to P5 and P4 depending on your observations. ROR wil ideally be between 8 and 3 in that period. After 10:30 roast will be ended at 219C. For filter roasts we stop at 215C.
It is very clear that the new power board is a bit more powerful, as we used to start at P9. I think that the IBTS sensor is a bit more realistic. FC and dumping temps correspond with my experiences with a bigger machine, a Probat 5 kg.

I look forward to the RoR based on IBTS as well as a levelling algorithm. But in the meantime, I feel the Bullet performs excellent. I will soon also compare the roasts with batches of around 900 grams.


How big is the batch that you’ve perfected? Smaller than 900g, I assume, but I didn’t see it mentioned. Maybe I’m missing it.

The batch that Cees is referring to is in the online database.
Guatemala espresso roast

It is showing as 601gms which would not be a power challenge even for 1.5 roasters with the V1 heater. I’d love to see that V2 heater tested on larger batch sizes to see if that new heater has :muscle:.

Yes as indicated a full batch will be the next step, probably next week. I first wanted to consolidate this level. It is true, 600 gram has never been a big deal, but It seems easier with the v2 power board.

Many thanks Cees for posting since you are an early-adopter of the V2 with the new Power board. I would have done the same thing that you did in testing with a smaller qty to start. We’re “all ears” to hear how it goes with a future larger roast. :sunglasses: