# Controlling Vibe pump with a dimmer switch



## tribs (Feb 21, 2012)

Having read this thread on coffeegeek some time ago, I decided to have a go at this mod. So I bought a cheap 250w dimmer switch from Screwfix and wired it up to the Ulka pump on my Classic.

It sort of works, in that the pump still pumps and with the dimmer fully on I get full ~9bar pressure. But, at the bottom end of the dimmer, I am still getting ~7.5bar so it doesn't really make it practical for using as a preinfuse for example.

Anyone know why this might be the case? I am guessing it might have something to do with the minimum rating of the dimmer (40W). Do you think using a low load dimmer say 0-120W, would give a more usable range, or is the range something that is different and not released by the manufacturer and the only way to find out is to try it?

Also, in the thread above it is mentioned that it does not matter on which side of the pump the dimmer is wired (in series). Can anyone confirm if this is true?

Pulling shots with the current limited range, it does appear that it could be very useful, especially if I could increase the range a little more.


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## garydyke1 (Mar 9, 2011)

anything of help here? http://www.home-barista.com/espresso-machines/voltage-control-of-vibratory-pump-t12665.html


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## tribs (Feb 21, 2012)

Not really. I think most people who have tried it have found the dimmer will reduce the speed of the pump, but at a certain point the pump is no longer able to push the water at all. I can't even get that low.

Like, I say its still pretty useful though. It means I can grind a little bit coarser and if I think the shot is flowing too fast, I can slow it (a smidgen). The pump actually sounds a lot smoother with the dimmer on its lowest setting.


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## MWJB (Feb 28, 2012)

Can you explain how you have connected the dimmer?


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## tribs (Feb 21, 2012)

In series on the neutral (I think) side of the pump.


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## MWJB (Feb 28, 2012)

I don't know much about household wiring & dimmers (or any electrical devices designed after about 1959! :-o), but it would strike me that the dimmer would be best placed between the brew switch (9) & pump (10), live side? There's a reverse polarity diode after the pump that may affect the dimmer's performance and/or the pump's ability to see the dimmer?


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## tribs (Feb 21, 2012)

Thanks MWJB. I did wonder about that, it was just easier to get to the other terminal, but will try swapping it. It's easy enough. Will report back.


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## tribs (Feb 21, 2012)

They were right! It makes no difference.


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## MWJB (Feb 28, 2012)

Ha ha...oh well!


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## MWJB (Feb 28, 2012)

Your pump is a 48W pump, you say your dimmer is rated 40W min? 40W/48W = .83

.83 * 9bar = 7.5bar. Seems more than coincidental?


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## tribs (Feb 21, 2012)

MWJB said:


> Your pump is a 48W pump, you say your dimmer is rated 40W min? 40W/48W = .83
> 
> .83 * 9bar = 7.5bar. Seems more than coincidental?


That's what I was thinking.

I was hoping someone could confirm before I fork out £12 on a low load dimmer.


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## tribs (Feb 21, 2012)

Sod it. I've taken a punt on a low load dimmer.

Will let you know how I get on when it arrives.


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## MWJB (Feb 28, 2012)

if that doesn't work you could always try a 2kW variac...it'll weigh as much as an anvil and kill you if you get it wet! ;-)


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## tribs (Feb 21, 2012)

I received the low load dimmer









And it's not much better









I can get down to maybe 6.5bar at the lowest end of the range, but it also has a tendency to stop the pump completely, so it's not a good idea to go that low.

On the plus side, I discovered that I can do a preinfuse with this setup, probably with either dimmer. If I run the pump and then activate the off switch of the dimmer, I have the solenoid open, but the pump is not running. If there is some pressure in the boiler then a little water runs out. Unfortunately only a max of about 10ml which I doubt is enough for preinfuse. If I pulse the pump, however (switch on and off with the dimmer) I can push water through without building any kind of pressure and as the solenoid is open all the time you do not get any puck cracking pressure build up. I've only tried it a couple of times, but it seems to work.


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## majnu (Jan 31, 2014)

MWJB said:


> Your pump is a 48W pump, you say your dimmer is rated 40W min? 40W/48W = .83
> 
> .83 * 9bar = 7.5bar. Seems more than coincidental?


Sorry to resurrect but would a 10watt min 100watt max trailing edge dimmer be better to acheive low pressure preinfusion? From the threads I've read people can acheive 3bar from 600watt dimmers which then contradicts your formula.


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