kzimmer0817
Well-Known Member
E-Brewers,
From my reading, it appears that a PWM connected to a SSR would be a simple and inexpensive way to control one's heating element manually. I'm thinking that accomplishes the same thing (perhaps not in the same manner) as the knob on the electric stove. This system would be totally manual. If I wanted to progress "gradually" into electric brewing, building/using a PWM might be a good entry point. All it does is electrify what I'm doing manually with my current burner's valve - although I would have much better control using electricity with a PWM than I do with my current propane cooker.
With the PID, I can set the temp I want, and it will power the heating element (thru a SSR) until the set point is reached. My understanding is that the element is fully on during the heating time.
When it's time to boil, it appears that folks shift their PID to manual mode and set it to a certain % of power (exact % found by experimentation). In this manner, it is functioning like a PWM - although I don't know if it accomplishes this by modifying the pulse width, but it shouldn't matter to me.
Someone mentioned that it was somewhat of a pain to set the PID to manual mode - that it took about 30 seconds to do this. If this is so, I was wondering if one might include a PID and a PWM in the same control box. I saw a thread where the idea of having both controls was mentioned, but it appeared that the PID and PWM were being connected in series. The concensus was that this was not a good idea.
My question is considering it from a slightly different angle. I'm suggesting that a DPDT switch be inserted into the circuit between the PID and the SSR where the operator chooses between PID control vs PWM control. The PID and PWM are totally separate.
I'll refer to the schematic for Johnodon's build for purpose of illustration (go to post #6 in the thread):
www.homebrewtalk.com/f170/my-official-e-biab-build-thread-269164/#post3263178
A double-pole A/B selector switch would be placed across the lavender and yellow wires that run from contact # 7 & # 8 to the SSR. I usually think of this kind of switch as a "Y" where power enters the bottom of the Y and one chooses which upper arm to send it out. In this scenario, the "Y" would be turned upside-down such that the 2 contacts from the PID would be connected to one "arm" of the Y and 2 contacts from the PWM could be connected to the other "arm". Two contacts would then go from the "base" of the Y to the SSR. This way, the PID and PWM are not interfering with one another. Of course, I would have to introduce a 9VDC circuit to power the PWM. This PID vs PWM selector switch would be "in addition to" the "Element ON/OFF" switch.
So, with BIAB, during the heating of the strike water, the above-mentioned switch would be set to "PID". During mash, adjustments will be made to the PID. Perhaps, the PID might be used to get just about to boil - perhaps even the alarm go off at 200*F. Then one might flip the switch to "PWM" and control the boil using the potentiometer on the PWM. At the end of the boil, the "Element" switch is turned OFF. With the PID still ON, the temp during cooling can be monitored.
NEVERTHELESS (emphasis), IF it's really quick and easy to get into "Manual Mode" on the PID and adjust the boil this way, then this entire message becomes irrelevant. I won't mind being told so.
Thanks,
Keith
From my reading, it appears that a PWM connected to a SSR would be a simple and inexpensive way to control one's heating element manually. I'm thinking that accomplishes the same thing (perhaps not in the same manner) as the knob on the electric stove. This system would be totally manual. If I wanted to progress "gradually" into electric brewing, building/using a PWM might be a good entry point. All it does is electrify what I'm doing manually with my current burner's valve - although I would have much better control using electricity with a PWM than I do with my current propane cooker.
With the PID, I can set the temp I want, and it will power the heating element (thru a SSR) until the set point is reached. My understanding is that the element is fully on during the heating time.
When it's time to boil, it appears that folks shift their PID to manual mode and set it to a certain % of power (exact % found by experimentation). In this manner, it is functioning like a PWM - although I don't know if it accomplishes this by modifying the pulse width, but it shouldn't matter to me.
Someone mentioned that it was somewhat of a pain to set the PID to manual mode - that it took about 30 seconds to do this. If this is so, I was wondering if one might include a PID and a PWM in the same control box. I saw a thread where the idea of having both controls was mentioned, but it appeared that the PID and PWM were being connected in series. The concensus was that this was not a good idea.
My question is considering it from a slightly different angle. I'm suggesting that a DPDT switch be inserted into the circuit between the PID and the SSR where the operator chooses between PID control vs PWM control. The PID and PWM are totally separate.
I'll refer to the schematic for Johnodon's build for purpose of illustration (go to post #6 in the thread):
www.homebrewtalk.com/f170/my-official-e-biab-build-thread-269164/#post3263178
A double-pole A/B selector switch would be placed across the lavender and yellow wires that run from contact # 7 & # 8 to the SSR. I usually think of this kind of switch as a "Y" where power enters the bottom of the Y and one chooses which upper arm to send it out. In this scenario, the "Y" would be turned upside-down such that the 2 contacts from the PID would be connected to one "arm" of the Y and 2 contacts from the PWM could be connected to the other "arm". Two contacts would then go from the "base" of the Y to the SSR. This way, the PID and PWM are not interfering with one another. Of course, I would have to introduce a 9VDC circuit to power the PWM. This PID vs PWM selector switch would be "in addition to" the "Element ON/OFF" switch.
So, with BIAB, during the heating of the strike water, the above-mentioned switch would be set to "PID". During mash, adjustments will be made to the PID. Perhaps, the PID might be used to get just about to boil - perhaps even the alarm go off at 200*F. Then one might flip the switch to "PWM" and control the boil using the potentiometer on the PWM. At the end of the boil, the "Element" switch is turned OFF. With the PID still ON, the temp during cooling can be monitored.
NEVERTHELESS (emphasis), IF it's really quick and easy to get into "Manual Mode" on the PID and adjust the boil this way, then this entire message becomes irrelevant. I won't mind being told so.
Thanks,
Keith