Grainfather

[atunguyd Senior Member Find all posts View Profile Close atunguyd]

I'm still on my idea of a "CheapFather". Urn with a hot water pump, sommer 12V, some tubing and an STC-1000 and you're there.

Don't think that is going to work too good. Your mash is going to suffer terribly with temperature swings as I don't think a stc1000 is a PID controller.



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[koperaal_koos Junior Member Find all posts View Profile Close koperaal_koos]

I was working towards a a "Cheapfather" also. Do to time constraints was not able to make it work.
PID is a must - slight more expensive that STC1000 but more accurate, have a look on Robotics shop - https://www.robotics.org.za/REX-C100-KIT

[Langchop Senior Member Find all posts View Profile Close Langchop]

Frankly I have grown to prefer the controlled power approach rather than the PID'ing and 'thermostating'. I just think a 2000w+ element is way too hot to control a mash temp well without sensor position being an issue. I somehow think an inline heater on the recirculation line would work a treat.

[Simple Member Find all posts View Profile Close Simple]

Frankly I have grown to prefer the controlled power approach rather than the PID'ing and 'thermostating'. I just think a 2000w+ element is way too hot to control a mash temp well without sensor position being an issue. I somehow think an inline heater on the recirculation line would work a treat.

A PID controller does control the power hence this statement confuses me. The output from the PID is used as a pulse width modulator. Which is just a fancy way of saying how long the element is on for, in a fixed time period. Say you decide to set the time period to 10 seconds. If the PID requests 40% power, then the element will be on for 4 seconds and off for 6 seconds in each 10 second period. If it requests 100% power then it will be on for the full 10 seconds.

To heat 1 litre of water by 1 degree C requires 4200 J. 1 Watt is 1 Joule/s. So going back to the PID if the output is 1% power, then 2000 Watts will be applied for 0.1 seconds or 200 Joules of energy. So this will heat 1 litre of water by 200/4200 = 0.047 degrees. But typically you have about 15 to 20 litres of water in your mash. So then the minimum temp control will be 0.047/15 = 0.003 degrees. Which I am sure you will agree is way fine enough. Hence I dont agree that a 2000W element cannot be controlled to control mash temperature very accurately. You could even make your fixed period 100 seconds and then 1% would be 1 second and you would have a control step of 0.03 degrees.

The Grainfather circulates the water through the grain and has an overflow to ensure that the water is constantly circulated and kept at a constant mash temperature. Apparently lots of users throttle back on the valve to limit the flow through the overflow in a misguided attempt to improve efficiency. But to me this is doff because no more water flows through the grains if you throttle back and the temperature control is worse........

[atunguyd Senior Member Find all posts View Profile Close atunguyd]

What simple said... Although the grain father seems to have about a 1s pulse width which is a lot better than 10s as the power delivery appears to smoother that way.

Lang hop I am not sure what you mean by a controlled power approach?
Short of a variables voltage sine wave invertor there is no other variable power these days (I am excluding variacs here as no one does that any more)

Oh and for the record even a variable sine wave invertor uses pulse width modulation with a circuit to smooth it out to a sine wave

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[groenspookasem Banned Find all posts View Profile Close groenspookasem]

Speaking of which , have you seen that demacraft launched their 65l robobrew clone today?

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[JIGSAW Senior Member Find all posts View Profile Close JIGSAW]

^ Nice

[camsaway Senior Member Find all posts View Profile Close camsaway]

[Langchop Senior Member Find all posts View Profile Close Langchop]

The PID controls power on a feedback loop. It 'pulses' power at varying intervals depending on variance from set point (among other things), but doesnt 'reduce' power per se'

When I brewed smaller scale I would set the oven at ~64deg and let the oven stabilise there, and then I would put the whole pot, at around 64/ 65 deg, in the oven. It worked like a bomb: in one 1.5hr mash (accidental) the mash temp did not deviate in all that time.

When I scaled up my equipment I couldnt do the oven trick anymore, and tried STC1000 and REX100 controls, with a range of different probe positions. Admittedly without a recirculation system, but neither worked very well. The recirculation seemed key.

However I then got a SCR power controller. Yes it 'pulses', but very differently to a PID, and actually effectively allows the element to operate more like a 100W of 500W or 1000W element. Very much like the 'switching mode' cellphone chargers. This was very easy to put some insulation around the tun, 'dial in' a reasonable 'power setting' so it gently 'simmers' in the mash and is sufficient to maintain the mash temp for an extended time. This takes the feedback loop out of the equation, and from my experiences, even though PID control theory may disagree, this means of temperature control has been very simple and very effective.


And onto the grainfatherish stuff... that Robobrew looks quite awesome Groenspook. The big capacity is definately a big plus.

[Simple Member Find all posts View Profile Close Simple]

Without wanting to labour the point, over a fixed time period of say 1 second, there is no difference between having your 2000 W element half on for the full second (using an SCR) or full on for 0.5 seconds and totally off for 0.5 seconds. The amount of energy you need to heat up the water and keep it at a constant temperature can be controlled either way.

There is absolutely no way you can manually eyeball a temperature control to achieve and maintain a temperature set-point as accurately as you can using a properly tuned closed loop control.

[atunguyd Senior Member Find all posts View Profile Close atunguyd]

There is no such thing as half on for half a second with a SCR.

A SCR only switches on or off. I guess if you want to get technical and claim that the SCR is being used to only conduct during half the wave form then yes you ate right but that's pretty much an analogue firm of pwm anyway. So it's just the same thing but now your pulse is period is 20ms

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[Simple Member Find all posts View Profile Close Simple]

There is no such thing as half on for half a second with a SCR.

A SCR only switches on or off. I guess if you want to get technical and claim that the SCR is being used to only conduct during half the wave form then yes you ate right but that's pretty much an analogue firm of pwm anyway. So it's just the same thing but now your pulse is period is 20ms

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I agree 100% with this!

[Langchop Senior Member Find all posts View Profile Close Langchop]

OK so the new Grainfather G70 has been announced, and release date is set for early next year. Price? US$1,800. That's just insane.

Out of interest, any significant improvements on the new one vs the old? (I dont have any hands on GF experience.)

[Toxxyc Senior Member Find all posts View Profile Close Toxxyc]

Out of interest, any significant improvements on the new one vs the old? (I dont have any hands on GF experience.)

No hands-on experience either. There seem to be some changes, but it also seems like GF stuck to some old problems that people hated as well, according to the vid I saw indicating the release info.

[jakeslouw Senior Member Find all posts View Profile Close jakeslouw]

The Dematech 60L looks the biz.