The pump dimmer mod - can I dim the entire espresso machine?

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#1: Post by BaristaMcBob »

I read that some people wire up a dimmer switch to the ULKA pump in order to achieve flow control. That's cool - assuming it works, but I'm thinking - why open up the machine? Why not just plug the entire espresso machine into an outlet box which has a dimmer in it? So yes, you'd be applying 'dimmed' power to the entire machine, but so what? Other than some incandescent lights and a heater coil, nothing seems to be voltage / current sensitive. I have a BZ10 by the way.

I'm assuming that the GICAR controller doesn't have any sensitive electronics. Obviously, I wouldn't suggest this for a machine which has digital controls.

What do y'all think? Is this nuts?

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Randy G.

#2: Post by Randy G. »

Because it will also affect the heating element...?
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#3: Post by Jeff »

As well as the solenoids in the valves

(Recent Gicar controllers also have more than just a couple transistors in them for the level sensor.)


#4: Post by boren »

Randy G. wrote:Because it will also affect the heating element...?
If you only change voltage during extraction I don't see how it would matter. Just make sure to change it back to the standard voltage once extraction ends.

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#5: Post by ira »

The power supplies in the Gicar boxes I've looked at are quite crude. If you drop the voltage enough you may find the processor resetting or the relays that control the solenoids dropping out.


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#6: Post by cafeIKE »

Assuming you mean a triac lamp style dimmer, it's a poor idea for a vibe pump. The pumps are designed for a symmetric on/off cycle. A lamp dimmer creates an asymmetric waveform and will not resonate as intended.

If I wanted to do it on the cheap, I'd add a valve to 6mm hole in the front of the e61 group. It would work about as well and be a heck of a lot more entertaining. :roll:

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BaristaBoy E61

#7: Post by BaristaBoy E61 »

BaristaMcBob wrote:What do y'all think? Is this nuts?

Solenoids don't respond well to lower voltages.
Not a good all-around idea.
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BaristaMcBob (original poster)

#8: Post by BaristaMcBob (original poster) »

It's a misconception that dimmers change the voltage. They clip the shape of the sine wave and therefore the amount of power being delivered. This video illustrates the effect:

Nonetheless, it might still wreak havoc on valves and controls.

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BaristaBoy E61

#9: Post by BaristaBoy E61 »

Bob's linked to the YouTube video also illustrates why a 'True RMS' digital voltmeter is necessary, as only a 'True RMS' AC voltmeter can accurately measure these 'distorted' AC wave forms. Non 'True RMS' digital voltmeters can only measure non distorted symmetrical AC wave forms.

If your meter does not say, 'True RMS' then it cannot be relied upon to accurately measure any complex wave form.
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BaristaMcBob (original poster)

#10: Post by BaristaMcBob (original poster) »

I've concluded that it's a bad idea. I think conceptually it would work, but the problem is that I'd have to be very careful that the heating element does not come on. Big dimmers are only rated for 600w. The heater is 1200w. I'd have to keep my eye on the boiler pressure at all times. That's sort of a buzz kill.