It’s definitely an AC pump (first of all because it says so on the pump label and in the Olab site, and secondly because it’s how vibration pumps work) - however, it’s not quite what the electronic forum guy seems to think it is: the pump only uses one half of the sinewave to activate the magned, the spring provides the force for the return stroke. The ‘negative’ half of the sinewave is discarded/blocked by the rectifier, not used to provide a reverse force.


(note the ~ symbol for AC power)

This is why a PWM approach could work (the duty cycle would need to start at 50%, i.e. all the “positive half” of the sine, and go down from there), but there is a question as to whether mechanically the pump would react as designed to a square(r) wave shape, and using a high frequency PWM is out of the question because of the slow response time of the membrane-piston/spring system.

    CoyoteOldMan The proper way to do it might be by pulsed DC. Rectify the AC using a 100W bridge rectifier chip, then add a circuit that can fire a power Mosfet (100W rating) from 1 HZ to 60Hz. I would think that would do it. Presumably that’s what Decent do.

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        DavecUK Yep. Easy and cheap to build with a 555 and a handful of passive components. Or go complicated, and attach an Arduino or Raspberry to it.

            CoyoteOldMan DavecUK

            You gents sure do know your electrical engineering. 🙇 This is well beyond my pay grade. 🤯

            Subject to my hearing anything back from Olab, it sounds like the PWM approach won’t work, without substantial electrical modifications. I was hoping to just buy something simple off the shelf, but I guess (from your replies) that neither a low frequency or high frequency PWM will work without substantial modifications. And I’d need to find someone here to do these electrical enhancements for me, which will be challenging.

            So, on to Plan B, which is further investigating the needle valve idea. If that starts to also look unduly complicated, then I may simply move on to Plan C, which is the rheostat (single pole dimmer).

                DavecUK CoyoteOldMan

                Unless you think that a Triac is a better option than a rheostat or a variac, to avoid pump stalling below 6 BAR ?? If a triac is compatible with the pump and the Lelit?

                Just looking for off the shelf installation solutions for flow control, while I save for a Lelit B 🤑

                      JHCCoffee A dimmer would work ‘as fine as it can be’ (without getting into the pulsed DC/PWM faff) and work better than a rheostat or a variac - plus it would be more energy efficient than a rheostat, and smaller than a variac.

                      Depending on how the circuit is built, it may generate some EM spikes (it shouldn’t, but…), which can be ‘interesting’ in an electronic-rich machine like the Elizabeth - I’d pick a leading-edge dimmer, “LED compatible” or whatever they are called in Canada nowadays - less likely to be trouble with the electronics.

                          a month later

                          DavecUK CoyoteOldMan
                          @hornbyben
                          @Inspector

                          I just bought a dosing colour from CoffeeSensor (Tudor Petriman) via his Etsy site and have been chatting with him about flow control mods, as he sells some valves. As they will not work for the Lelit E (he is a Gagia guy), he (as do you) has floated the idea of a light dimmer mod, but (also as you) expressed concerns about pump motor control (stalling and uneven control). So he suggests buying an ARS - CP3 model pump, which he thinks might work on Lelit machines since “they are too SBDU machines and work with (usually) a ULKA pump”.

                          I am on the fence about a Slayer type mod vs dimmer mod (I’ve just barely begun to look into the Slayer mod), but thought I’d run this ARS pump idea by you. I will look up ARS - CP3. I am guessing that it is some kind of a variable speed pump?

                          Anyway any thoughts, knowledge or ideas on the ARS - CP3 or alternatives?

                          PS
                          I have asked Tudor for specs

                                This looks like the pump that is used in the Gaggia Jura. I’m not sure of the benefit of swapping out the LE pump for this. Will let you know if I learn anything different.

                                  JHCCoffee Just looking at this eBay ad, it seems there is a membrane regulator that is adapted to/developed for it. Quite how the regulator is governed (if it can be!), and whether that is a useable method for the Elizabeth… still no clues. I would bet it is going to be significantly more complex than working with the default Lelit/Olab pump.

                                  https://www.ebay.co.uk/itm/122887244554

                                    JHCCoffee I don’t have an experience of an ARS pump, from a look on the internet it just looks another manufacturer of vibratory pump. I don’t see how this would be any different from a standard ULKA pump, or the OLAB silent pump you already have.

                                    The silent pump does have slightly less power (35 vs 41W), but I’m not sure it makes much difference.

                                    While I obviously can’t guarantee it, I can’t see how the dimmer mod could damage a vibe pump. The electricity is charging a coil which makes a magnet move and hence the attached piston. Should it destroy the pump (I can’t think how it could) its £69 for a new one (obviously you’d need to find one in Canada), so in the grand scheme of coffee paraphernalia it’s not that much.

                                    If I was you I’d stop theorising and just give the dimmer mod a go. As long as you don’t drill your case it’s fully reversible. You could mock it up in a project box, obviously ensuring you take suitable precautions not to electrocute yourself. You should soon find out whether it works or not

                                      Personally I’d just take a step back (given you haven’t had the machine for very long, if memory doesn’t fail me) and would just explore its features and enjoy it within the realms of its capabilities.

                                      After a year or two, think about modding it.

                                        4 months later

                                        While I had the top off today, I looked for the wire that I would connect an impending dimmer switch to, for a dimmer mod. The red wire on the top right of the below photo appears to come from below (possibly the power feed-in). The red wire on the left heads over to a multiple connector junction on the top right side of the machine (near the water tank). I am thinking that I should tap into the red wire on the top right, but obviously don’t want to be wrong.

                                        MediumRoastSteam or @DavecUK Which wire should I tap into?

                                        Here are the pictures, which are taken looking down, facing from machine front to back.

                                            @DavecUK
                                            If and when you have a moment might you be able to identify which wire to connect to, from the preceding pictures. Most appreciated!

                                              JHCCoffee @DavecUK
                                              If and when you have a moment might you be able to identify which wire to connect to, from the preceding pictures. Most appreciated!

                                              I’m with MRS, I think I know what wire it is…but you never know if they changed the wiring. The photos below was when I was doing an engineering review for Lelit and asked them to make all the changes to Elizabeth (software/hardware), including putting the Quiet pump in rather than the normal ULKA they were using. You should be able to work it out from these. be careful because the mauve thinner wire goes into the Gicar and a thicker pale bluey mauve wire (switched) comes from the Gicar (the Gicar box doing the switching on/off) to the pump…the yellow wire is the other side of the pump and is attached to the thermal trip. That should be on the “common” (non switched side)

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                                                  DavecUK I’m with MRS, I think I know what wire it is…but you never know if they changed the wiring

                                                  Thanks and will do.

                                                  Just curious: in the photos that you provided, which wire would I connect to? That will give me a beginning clue.

                                                  Once my Lelit is back from steam valve repair (at the retailer) I will open it up and take an updated picture.

                                                      JHCCoffee Just curious: in the photos that you provided, which wire would I connect to? That will give me a beginning clue.

                                                      I don’t know what colours the wires are in yours (it’s why the word photo keeps being mentioned), or how they are laid out. Mine was converted to almost the current spec by me, they made some big changes based on my feedback back in the day.

                                                      I also have no idea what connections your dimmer has, what it looks like, it it’s meant to be wired in and how you want it wired up?

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