'Pressure Profiling' With The Fluid-O-Tech TMFR Pump - Or, Wholesale Copying Greg Scace's Ideas - Page 28

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GlennV

#271: Post by GlennV »

To answer to own question, there are 9 teeth on each of the main and idler gears (the parts diagram is online). So, my 450Hz at 24V into a 0.6 gicleur corresponds to 3000rpm. The speed drops about 130rpm into a blind filter (with the internal bypass set at 9.5bar). This is the MGCF11S motor, which I believe the Strada uses.
4000ft wrote:I did have it hooked up to cheapy pwm and 24v supply, it worked fine but some pressure feedback + pid type calculations would be better.
I'm not sure it would be better. As the puck resistance drops then, if you hold pump speed constant, pressure drops (whether measured before or after the gicleur) and flow rate increases. If you use control to stop the pressure dropping then the flow will speed up even more. According to the LM literature, the Strada EP gives you control over pump speed in manual mode - although maybe it's actually motor voltage/PWM duty cycle. Does anyone here know if the note of the pump changes on the Strada if you put a blind filter in with the paddle left in a fixed position, or whether it really does keep the motor speed constant?

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4000ft

#272: Post by 4000ft »

My first try with arduino :D

McGyvered arduino enclosure



Temp setup



Busy action shot, few little programing things happening, initial pump speed is programmed to be 60% (first 400ms, not enough...), ssr opening the 3way after 100ms, and a smooth ramp down at the very end 400ms before 3way closes, and someone making omelets in the background.
Everything works as expected except I need a check valve between the pump and boiler, steam is pushed back through the pump when the silvias heating.

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Dan Bollinger

#273: Post by Dan Bollinger »

Nice video of the action. Seeing the pressure change is inspiring. Yes, a check valve is a must. Some carbonator pumps have a built-in check valve in lieu of the bypass valve. Since I imagine you are defeating the bypass valve , or setting it higher than necessary, this is an option to consider in the future. I don't know if this is an option for this series of pumps or not. See the photo in the OP, it shows an external brass check valve mounted on the outlet of the pump.

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FotonDrv

#274: Post by FotonDrv »

Great Thread on Pressure Profiling and MOD's for the GS/3.
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4000ft

#275: Post by 4000ft »

LCD + Pressure transducer arrived, the video is just showing pressure measurement with a bicycle pump and the shot timer, I dont know where to put the LCD in my setup so I can see it while pulling a shot :oops:

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4000ft

#276: Post by 4000ft »

Sorry about the quality, the screen is readable (half of it) if you goto youtube to watch it

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FotonDrv

#277: Post by FotonDrv »

Can I assume that you were watching the pressure rise and fall as you adjusted the potentiometer?
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4000ft

#278: Post by 4000ft »

Yes, keeping it at or under 8bar seems to work for this SO Guatemalan

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FotonDrv

#279: Post by FotonDrv »

That is pretty nice, being able to adjust pressures on the fly as you change bean/grinds. Very impressive!! Kudos :D
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4000ft

#280: Post by 4000ft »

I will be away for a while so quickly grabbed some data before my flight tonight, to see what can be inferred for automated profiling or calculating shot volumes, these are all 30ml shots from an LM single basket and I attempted to keep the flow rate reasonably even between them

L = light, LD = medium and D = dark roast, all 3 weeks old
Numbers correspond to grind setting, large conical with mazzer style collar adjustment
Solid lines are pressure and dotted lines are voltage



Something has gone very wrong with either D1 or D2, the finer grind of D1 should have required a higher pressure

My thoughts:
Calculating shot volumes might not be possible with only this information, the changes in times and pressures dont follow a pattern as far as I can see
Voltage control is close enough to direct pressure control once the puck is saturated and void space pressurised that I think pressure profiles can be made by recording and playing back voltage with only minimal corrections from pressure feedback