Hi everyone,

A couple of weeks ago I responded in Major refurbishing thread with a video of a small grinder controller that I was working on. It's now finished and connected to my Macap (in the future I plan to use it with my Major) so I've decided to start a new topic to describe it a little bit (didn't want to hijack the original thread).

The 'brain' of the unit is a PIC16F628 uC from Microchip which was programmed using a JDM-style based programmer via RS232. It uses it's built in 48kHz timer and a simple 7805 5V power supply, all placed together on a small piece of switchboard, connected using a few cables. The o/i elements that were used are an LCD - 2x16 chars, 6 tictile switches and an SSR (together with a transistor). Because I wanted to create something that's similar to the original Mazzer E grinders control I've decided on some basic requirements

- timer settings with 0.1s precision

- programming for single and double dose

- auto/manual mode

Of course to make life easier additonal requirements appeared when working and fault testing the unit:

- fast +, - adjustment for inc/dec timer buttons to easily change the setpoint (holding the button down for more than 1s activates fast change mode)

- EEPROM read/write to store single/double timer setpoints after turning the unit off

The original idea was to mount all the electronics in the doser lid, just like it's done on Mazzer Electronic models and install it all on my rebuilt Major. This however changed a bit because I still haven't converted the grinder to doserless (something I was working on with BradS...) and it still hasn't got new burrs, not to mention that I still haven't got a doser lid. In addition I didn't want to modify my current grinder - Macap, so I decided to use a small box and simply use it like an external controller. Can't say that cutting out all the holes for switches was a pleasent thing to do, but in the end it works and looks quite good, so I guess I can't complain. Below you can find photos of the finished unit, external and internal shots:







I will try to post a short clip to show how it works sometime soon.

It certainly makes life a bit easier and simplyfies the whole preparation process. I'm pretty sure that with the doserless Major it will work even better, but it does it's job even with the 'clumping-holding-a-lot-of-coffee-in-the-chute' doserless Macap. I was surprised to see how slow the Macap grinds though, the weight-time ratio is 0.65g - 1s which compared to Mini-E (I believe it's somewhere around 2.5g per 1s) is quite bad. The good thing is that the pours are completely different than before when weighing beans per shot. It doesn't blond so fast, it's slow and looks like it's going to run forever. Whether this is caused by the beans in the hopper pushing the ones at the bottom down I don't know but I know that it tastes bloody amazing:)

Cheers,
dsc.

Since I am also an engineer, I appreciate what you have done with your control circuit. Do you control only the on-time or do you try to vary the motor speed as well? I know that variable speed control is really best for either DC motors or for 3-phase motors but I have been successful with variable frequency drive on single phase motors although the torque suffers.

Question for all espresso fanatics:
I am really considering getting yet another grinder to try the effect of conical burrs on espresso. Several different posts including yours referred to a common problem of clumping. Is this owing to the doserless chute or is it related to the conical grinder?
Have you or any readers compared this grinder to the Cimbali Dual MAX?

Regards,

Jeffrey Pawlan

Hi Jeffrey,

it's only the time that's being changed since the whole unit is pretty much a programable timer with 0.1s precision.

As for clumping I believe that most grinders suffer from it (except for grinder with outlets directly under the burrs, some conicals and probably some flat burrs as well), although they might have elements which break the clumps, ie. dosers, grids on outlets etc. In my Macap there's no such thing so I use a BBQ stick to break the clumps in the basket during grinding. Works well and isn't that much annoying. I would love to have a clumpless grinder though, that's why I'm trying to convert my Major into a doserless funnel design model.

Regards,
dsc.