Voltage Controlled Pump Pressure (Ulka) - Page 4

#31: Post by **frankmoss** » June 2nd, 2010, 10:52 am

Any more tests with the mod?

I pulled several more doubles last weekend with the mod, and I can say for sure that I'm happy with it. I get full pressure control between 6 and whatever the max on my pump is. Plus I love having the brew pressure gauge on there. While the improvement in taste is not mind-blowing, my espresso has definitely improved. I want to experiment with some different profiles, including a slow ramp up at the beginning of the shot and a slow decline in pressure at the end.

June 6th, 2010, 9:17 pm

For the past week I haven't been making any espresso (and I've been busy with work), but today I made a few shots. Again, this is subjective, but I seem to get more well-rounded flavors using decreased pressure. A bad shot used to be "wow that's really bitter" - now it's more "oh, the dark chocolate is too intense." Does that make sense?

From the long term perspective, I will echo Frank and say that I'm very satisfied with the mod. If you are on the fence about performing this mod, then go do it! Soon I plan on drilling a hole in my case and mounting the rheostat internally. I just got an Arduino board too, so maybe I'll play around with adding a LCD screen to display temperature or shot timing.

Question: does anyone know whether plastic knobs are standardized? The wine cork is sufficient now, but I want a black plastic knob if I mount it. It seems to me that knobs are primarily classified by depth, not internal diameter. The steam knob on my machine now looks like it might fit onto the rheostat. I could keep the look consistent perhaps.

#33: Post by **frankmoss** » June 7th, 2010, 10:42 am

Most knobs are the same diameter. The rheostat has a 1/4" shaft, which is pretty standard. Any of the knobs at RadioShack will fit. You'll have to measure to determine whether the steam knob will fit.

Anyway, I did some more testing this weekend. Just reducing the pressure to 9 bars has helped a lot, and I like the taste produced by declining pressure at the end of the shot. Overall, it's a cheap mod that seems well worth it to me.

#34: Post by **Carneiro** » July 24th, 2011, 4:48 pm

Hi there!

If I want to try a rheostat to my Ulka pump (220V, 48W), should I change the specs? Higher Ohms with similar wattage?

Thanks,

Márcio.

#35: Post by **drgary** » July 25th, 2011, 1:10 am

Hi Folks,

I know this is an old thread that has been revived. Forgive me for asking some very beginner's questions.

Why not plug the whole machine into a box (Variac?) controlled by a rheostat and dim the voltage on the whole machine during a pull with the idea this can avoid all the rewiring and electrical hazard?

Or, could it wreak havoc on a PID or other controls? Yes, it would momentarily reduce power to the heating element, but would that matter much?

#36: Post by **Carneiro** » July 25th, 2011, 5:46 am

How about the 3-way solenoid...?

Márcio.

#37: Post by **allon** » July 25th, 2011, 8:07 am

Dimmers that handle high current are not cheap. Typical consumer grade ones are 500W max, with most rated lower.

And dimmers made for dimming incandescent lights will deal with a purely resistive load, not an inductive load; the inductive load of a solenoid might not be enough to be a problem but...

Dimmers use silicon controlled rectifiers; the diode present on many vibe pumps may have an issue with that; iirc it just won't dim properly with a diode in line.

If you are going to hack your machine without doing any wiring, I'd question how effective you can really be.

Now, put an actuator on an opv, PID controlled by a pressure transducer, and NOW you're talking

#38: Post by **drgary** » July 25th, 2011, 12:15 pm

My questioning was theoretical since I've been able to adjust the pressure downward on my Amica via the OPV. Isn't the easiest way to adjust an OPV downward and if you don't like the pressure profile of your Ulka pump, see if installing a Fluid-O-Tech pump will improve things since these are supposed to have a nearly ideal pressure profile? I know, "notes, notes, notes," but Sherman changed the pump on his Maximatic and really likes the results. He pointed me toward this thread: Olympia Maximatic. Stick to old or change to new?

#39: Post by **Carneiro** » July 25th, 2011, 12:43 pm

My playground is an Elektra Semiautomatica, almost no room for an OPV... But it's just the will to make some experiments, not a final setup.

Márcio.

#40: Post by **indend007** » July 26th, 2011, 10:58 pm

hmmm. ULKA does matters. ^^ Ulka manufactory in Here, south Korea.
So we contacted ulka engineer easy, and ask some questions..

Posting is written korean.. sorry..
maybe, This posting help you solving your matters...

http://cafe.naver.com/coffeemaru/82835