Controlling the RPM of a DF64 with a VFD

Grinders are one of the keys to exceptional espresso. Discuss them here.
ltanzil

#1: Post by ltanzil »

Moderator's note: split from Hacking the DF64 exit chute
spopinski wrote:Haven't found a single phase VFD anywhere.. For speed controller your grinder will lose so much torque it will stall often.
I have used df64 with VFD. i use panasonic VF0 series 0.75 kw. it also has low rpm torque boost feature. i can drop the rpm up to 650 rpm reliably with out stalling.
GDM528 wrote:LOL - good catch!

How about a crappy motor speed controller with dubious specifications. I found one on Amazon - one of its specifications listed was the color: "blue"...
i found this VFD second hand. and it cost about 50$ US.

GDM528

#2: Post by GDM528 »

ltanzil wrote:I have used df64 with VFD. i use panasonic VF0 series 0.75 kw. it also has low rpm torque boost feature. i can drop the rpm up to 650 rpm reliably with out stalling.

i found this VFD second hand. and it cost about 50$ US.
image
Nice find! Can you post the manufacturer's model number?

Speaking of 650 rpm, is that the speed you've settled on? I'm researching a DIY speed reducer, and dropping from 60Hz to 30Hz would dramatically simplify the circuit design.

ltanzil (original poster)

#3: Post by ltanzil (original poster) » replying to GDM528 »



My unit type Panasonic Vf0 BFV0072GK-E
since i live in indonesia this unit is 220v and my df64 is also 220v

if you unit is 110v the better option is Invertek 110v single phase
https://www.invertekdrives.com/variable ... e/features
https://www.invertekdrives.com/variable ... 70-1F12-01

it is available new for about 300$
https://www.wolfautomation.com/ac-drive ... v-1-phase/

a slightly older model available second hand for 198$ at ebay
https://www.ebay.com/itm/353606261529?m ... media=COPY

Still a lot cheaper than lagom p64 :D

one caveat though. you have to bypass the df64 control pcd and switch. it does not like high frequency switching. so wire direct motor to vfd.

most of the time i settled at 700 hz. that is about 25hz, since my base frequency is 50hz. halving the rpm from stock 1480 rpm give higher clarity in my experience. i am still playing around with the rpm because i just changed my burr to ssp Lab sweet.

spopinski

#4: Post by spopinski »

Nice find! I also lives in Indonesia and very intrigued :D

ltanzil (original poster)

#5: Post by ltanzil (original poster) » replying to spopinski »

you can find it here if you are in indonesia

https://tokopedia.link/Iy4bGIWqmrb

it is about 50 usd while it last

GDM528

#6: Post by GDM528 »

ltanzil wrote:
one caveat though. you have to bypass the df64 control pcd and switch. it does not like high frequency switching. so wire direct motor to vfd.

Interesting... I would have figured the external VFD already has a motor start function built in, making the start circuit built into the DF64 redundant.

So this is a know-what-you're-doing sort of hack, given the voltages and currents involved.

Dunno if this warrants a new thread, but I wonder if it might be simpler to swap in a different motor...

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Paul_Pratt

#7: Post by Paul_Pratt »

I use Invertek VFD's on old 3ph grinders. I can highly recommend them. Very easy to set up.

spopinski

#8: Post by spopinski »

ltanzil wrote:you can find it here if you are in indonesia

https://tokopedia.link/Iy4bGIWqmrb

it is about 50 usd while it last
Do you also bypass the capacitor and use all 3 output wires to drive the motor? Effectively remove all the grinder electronics?

Giampiero

#9: Post by Giampiero »

GDM528 wrote:Dunno if this warrants a new thread, but I wonder if it might be simpler to swap in a different motor...
Definitely, yes IMHO, the use of a VFD will generate a lot of new field to explore, with the DF64, and even many comments, i hope, if not in a dedicate thread we could possibly lost useful shared info lost in others gigantic threads.
Swap in a different motor does not seems to me a "simpler" solution, unless i misunderstood your comment.

ltanzil (original poster)

#10: Post by ltanzil (original poster) »

GDM528 wrote: Interesting... I would have figured the external VFD already has a motor start function built in, making the start circuit built into the DF64 redundant.

So this is a know-what-you're-doing sort of hack, given the voltages and currents involved.

Dunno if this warrants a new thread, but I wonder if it might be simpler to swap in a different motor...
i agree with giampiero. swapping the motor is ten times more hassle. i have thought of it. the motor shaft is directly attached to the burr. and stator is press to the grinder body. it is going to be a nightmare.

the PcB inside df64 is just a glorify relay timer that cut power after 45 second and profiding latching for the power switch.

does not protect the motor what so ever. it does not even have a fuse. it also doing nothing when the motor
start.


the vfd is way more advanced in starting, controlling and protecting the motor. it also can start the motor gently and ramping up to the dersired rpm

bypassing the PCB is very straightforward. connect two wire that come out from the motor directly to two wire from power cord. leave ground wire from the powercord connected to the grinder body. that's it. leave the big white capacitor. i will take picture of my connection

the know how part is actually more on the programing the vfd. that is the true challenge.

another thing that i might consider is actually rewinding the motor to 3 phase if desired more torque. it is also a nightmare :x slightly less though compared to swapping motor