Re: temperature for roasting in corretto
Hi Peter,
Im glad Belinda and I were able to help.
The heat gun adjustments required around and after FC are very fine... and I doubt you will be able to make them with a standard heatgun - well not without a lot of pain.
Part of the problem is the thermal lag... the effect of any change isnt visible on the probes for 20-30 seconds (in my corretto) so you firstly need to get a feel for what is required that far in advance or you will overshoot or undershoot the correction.
Ive modified my heatgun for finer control - if you have a friend who is an electrician you could do the same.
Firstly I opened the heatgun (voids the warranty) and identified the heating circuit. I then built a 16 amp triac "light dimmer" with 12 switched stages of output between full and about 60 deg C output.... (using 11 equal resistors to set the output of the triac) and connected it externally to the heating circuit.
That improved the control of output a lot - but I still found it a bit coarse.
I then installed a potentiometer (variable resistor) of the same value as each resistor.... so one complete turn of the potentiometer gave 1/12 of the heat range...
Now I control the temperature from first into second crack with the variable control (temperature up to just before first crack with the switched control). I find the variation required to be about half a turn of the knob on the potentiometer - or about 4%...... and you wont get that with any standard heatgun.
I can even maintain the temp at a constant setting by fine adjustment of the potentiometer - and providing I allow for the thermal lag of the roaster.
Total cost of the mod was about $20 .... and I think it will also extend the like of the heatgun heaps - it is hardly ever "flat out" and at the end of the roast I can turn it right down to cool down the gun.
I even used the lowest setting (60C) to cool the beans in the corretto once. It worked well - took a little time to cool them down- but is possible. You just have to start the cooling a little earlier as the beans will continue to roast a bit.
So if you have a mate who is an electrician ..........
Hi Peter,
Im glad Belinda and I were able to help.
The heat gun adjustments required around and after FC are very fine... and I doubt you will be able to make them with a standard heatgun - well not without a lot of pain.
Part of the problem is the thermal lag... the effect of any change isnt visible on the probes for 20-30 seconds (in my corretto) so you firstly need to get a feel for what is required that far in advance or you will overshoot or undershoot the correction.
Ive modified my heatgun for finer control - if you have a friend who is an electrician you could do the same.
Firstly I opened the heatgun (voids the warranty) and identified the heating circuit. I then built a 16 amp triac "light dimmer" with 12 switched stages of output between full and about 60 deg C output.... (using 11 equal resistors to set the output of the triac) and connected it externally to the heating circuit.
That improved the control of output a lot - but I still found it a bit coarse.
I then installed a potentiometer (variable resistor) of the same value as each resistor.... so one complete turn of the potentiometer gave 1/12 of the heat range...
Now I control the temperature from first into second crack with the variable control (temperature up to just before first crack with the switched control). I find the variation required to be about half a turn of the knob on the potentiometer - or about 4%...... and you wont get that with any standard heatgun.
I can even maintain the temp at a constant setting by fine adjustment of the potentiometer - and providing I allow for the thermal lag of the roaster.
Total cost of the mod was about $20 .... and I think it will also extend the like of the heatgun heaps - it is hardly ever "flat out" and at the end of the roast I can turn it right down to cool down the gun.
I even used the lowest setting (60C) to cool the beans in the corretto once. It worked well - took a little time to cool them down- but is possible. You just have to start the cooling a little earlier as the beans will continue to roast a bit.
So if you have a mate who is an electrician ..........



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