Okay, a few changes:

After thinking about it, I decided that, instead of using the smaller RTD sensor and mounting it on the outside of the boiler (which would probably work, but wouldn't be as accurate), I would order a probe type RTD sensor, which would stick into the actual water inside the boiler.

Here's the one I decided to go with:



http://www.auberins.com/index.php?main_ ... cts_id=136

My plan is to drill a hole into the boiler element plate, then put this through and capture the inside with a stainless steel 1/8 NPT locking nut and copper sealing washer. That should provide plenty of clamping force and accomplish a water tight seal. The probe will stick directly into the boiler water and should provide a more accurate temperature reading.

I'm also going to incorporate a SSR (solid state relay). I ended up ordering this 40 amp one (see link below), which will provide more than enough of a safety margin when it comes to switching the 1000W heating element. This will also take some stress and wear/tear off the relay contacts inside the PID controller, which should help to extend the life. And, as pointed out correctly by Eric, the switching time when using the SSR will likely be much faster.

http://www.auberins.com/index.php?main_ ... ucts_id=30

As far as fitting the PID controller inside the base... that's still up in the air. The base is .065" thick, which is a little beyond the nibble capacity of my nibbler. Also, in the front, where I want to mount the PID controller, the base curves, which could be a problem. I may be able to flatten things out a bit (if needed) after making a cut, but I am not 100% yet. I still need to make some measurements and see how radical the curve is.

As far as ambient air temperature issues, I'm just thinking about cutting out some vent holes in the bottom plate that attaches to the base. That should allow for enough air flow to keep things relatively cool around the PID controller.

So we'll see.

Ray

Re : SSR : You need specs on it's current capability. None are included in SSR spec.

cafeIKE wrote:NO increase in load capacity will take the place of a proper heat sink. A 40A device has a current rating of 6A and a 90A device only 7A without heatsink @ 40°C, half that @ 60°C. Heatsink location plays an important part in its effectiveness. Ideally, outside the machine and mounted so convective air currents have free air flow.
from Help switching to solid state contactor for steam boiler on 2003 La Marzocco Linea 2av

cafeIKE wrote:Re : SSR : You need specs on it's current capability. None are included in SSR spec.

You lost me a little bit there Ian. Are you saying that a 40 amp SSR won't be able to handle switching the 10 amp circuit without a heat sink?

Let me contact Auber and find out what the specs for the 40 amp SSR (without a heat sink) is.

Ray

I contacted Auber and you are correct, the "40 amp" SSR will only be able to handle about 8 amps without additional cooling. I canceled my order and upgraded to a 100 amp model. It's the same size, but uses copper internally, in place of aluminum. It's still the same situation - largely - but I feel like the 100 amp rating may provide enough of an additional buffer to work with my application.

Also, Auber indicated that as long as you aren't running current through the SSR for 10 or 15 minutes straight, then you will probably be okay drawing 10 amps on the 40 amp or 100 amp model without a cooling heat sink.

Here is the spec sheet for the 100 amp SSR I ordered:

http://www.auberins.com/RMSSRb.pdf

From what I can see, it appears the 100 amp model is rated for 30 amps (RMS) at 25C. I may be reading that incorrectly, but that is what it appears to be.

I also ordered an project box, since I'm starting to lean towards mounting the PID controller outside of the base of the La Pavoni. This wasn't my first choice, but I think it may be a good option until I'm able to determine the ambient temperature inside the base (in other words, I can always mount the PID controller inside the base of the La Pavoni down the road).

Thanks to Ian for bringing this issue to light!

Ray

RayJohns wrote: I may be reading that incorrectly...

Yup. That spec is for controlling a motor. The AC51 and AC53a are part of IEC specs :
AC51 indicates a resistive load. For details, refer to IEC 60947-4-3.
AC53a indicates an inductive (motor) load. For details, refer to IEC 60947-4-2.

Note the table at the bottom left of pg 3: "No heatsink required -- N/A"
That means you need a heat sink.

From the table at the bottom of pg 4, for 10A @ 40°C, you need a heatsink with a MAXIMUM Thermal resistance of 7.5 K/W.

See this for an RHS 300
The RHS300 is mounted in FREE AIR and attached to a DIN rail which forms part of the heat sink.

Without a heatsink, the maximum safe current is about 7A @ 40°C

Thanks very much for the run down Ian - that's very helpful.

I'm wondering if I can attach the SSR to the bottom plate that screws into the base and have it act as enough of a heat sink. If not, I can probably mill up an aluminum one or something.

I'll study the information available here and see if I can get a better handle on all of it.

Ray

Hopefully this might help : SSR Heatsink Basics

Stardate: minus 311,724.10

19 days without espresso... we now go where no man has gone before...

Both the RTD sensor and SSR have arrived. Everything looks pretty good and I'm looking forward to wiring things up soon to see how it all functions.

It won't be much longer until it's time to drill & tap the boiler element. However, right now, I'm in the middle of building my Taig lathe and restoring my drill press (new spindle bearings, etc.), so that might delay things a bit. Once the drill press is back on-line, then I will probably drill the boiler element and tap it.



Some of the remaining parts for the PID project should be arriving tomorrow or on Wednesday. As soon as they show up, I'll post more photos. This includes the pressure gauge also and I'm really I'm looking forward to seeing that in the flesh. I am not sure when the brass adapters from the UK are going to show up, but hopefully soon. Modifying the brass adapter (for the gauge & pressure inlet, etc.) depends quite a bit on the Taig lathe, which is currently sitting in a bunch of parts on my dining room table:



I'm guessing the lathe won't be operational for a few weeks, as I need to build a bracket to hold the DC motor in place and also wire up the PWM DC motor controller (just to name a couple of things on the huge lathe "todo" list).

Anyway, at some point here, I hope to rig everything up on the counter: the PID controller, the SSR, La Pavoni, etc. This will allow me to do some bench testing and see how hot the SSR becomes, etc. It will also allow me to have a shot of espresso for a change!

As far as the SSR issue: my thinking, after talking with Ian on the SSR thread, is that I may mill up a very large heatsink; I'm thinking sort of a finned monolithic 2001 sort of thing. Something fitting of having Apes hurl bones at it in a panic - yes, that big.



Can you picture it? A huge monolithic heatsink next to the La Pavoni, with the SSR sitting proudly on top for all the world to see? Then the PID controller can mount in the middle-bottom. I'll name the heatsink "Ian" and maybe buy some scale Apes to place around it in awe. Espresso will never be the same...

In any event, here's a photo of the SSR:





On the RTD sensor, it had some crazy spring coil on it (which was a bit much I thought). I ended up removing it and cutting it down to make it a little smaller, then re-epoxying it in place. It's drying right now. I think having a bit fewer coils of spring will make installation a little easier (as far as room goes). Here's the modification on that:


The RTD sensor and wiring harness as delivered from Auber


Size comparison / You can see the amount of spring here also


Here is the spring they have on the controller. When stretched open, you can see it's just wires inside


Here's a shot after I have cut away some of the unneeded spring/wire. I've also removed the epoxy they used to hold it in place.


Mixing up some JB Weld, in order to put everything back together and secure the spring again


Here is the RTD sensor after chipping out the factory epoxy and pulling the spring out. Getting the spring out was quite a job; I ended up cutting myself in the process of unwinding it and pulling it out - thus the sporty Bandaid there.


JB weld being applied. I used a toothpick to pack it down into the groove, until it started to over flow


Here it is after a little clean up & prior to re-seating the coil spring sheathing


Here it is with the spring back in place


"I'm ready for my close-up"

And here are the final results. Now it just needs about 24 hours to cure and the RTD sensor should be much easier to install into the base and have a bit more clearance, etc. Also, making that right angle turn will be a bit easier now I think.

Ray

Well, some more parts arrived from McMaster.com today... here's a run down for anyone interested


This is the 1/8 NPT 316 stainless steel sealing nut. It will go inside the boiler to seal the RTD sensor. It looks like it has a nice ring machined into it also, which I can put a copper sealing washer into.


Another shot of the RTD sensor and sealing nut


Here they are - together at last


Here is a possible candidate for the spacer which will go into the groove where the pressure gauge / pressure inlet will mount (on top of the upper sight tube boss). It will require turning down a bit on the lathe (and opening the center hole to ~ 12mm). It's 8-18 stainless steel.


This is a bronze bushing, which may also be used for the groove mentioned above. It will require parting off on the lathe in order to fit correctly on the La Pavoni


Here is the stainless steel pressure gauge from McMaster - part # 4066K211


Oh oh.. looks like someone didn't center the dial very well when assembling the gauge at the factory.


Here is a side shot of the gauge. I'm loving the small size of this gauge!


And the back of the gauge


Here's a view showing the 1/8 NPT adapter. It's a little different than the picture on the McMaster website (as I recall), but I like the look of this better actually.


Here is the gauge with the face removed. I wanted to see how bad the dial was off center. Yup, it's pretty off center; that's disappointing for a nearly $70 gauge


Luckily, it appears the dial can be fixed by loosening the two screws on the back


Here is the gauge after I adjusted the face. Much better now!


Here it is with the dial cover back on. As you can see, the dial looks a lot more suiting of the La Pavoni, now that the gauge face plate has been properly centered.

Here is the link for the product information on Ashcroft's website for this gauge (just in case anyone ever needs is in the future):

http://www.ashcroft.com/products/pressu ... Gauges.cfm

Okay, that's all for now. Still awaiting the arrival of the brass adapters from the UK. As far as actually machining some of the parts, I'm just waiting on new spindle bearings to show up for the drill press. Those should be here this week and once the drill press is back together, then I will set about drilling the boiler element / plate. Once the RTD sensor is installed, then I can maybe wire things up and see how the PID controller functions.

I'll probably get around to all that this weekend if all goes well. I'll see about taking a video also.

More to come...

Ray

Well, as the old saying goes, "I have good news and bad news".

The good news is that the M12 x 1.00 brass adapters from the UK arrived today. The bad news, however, is that I don't think they are going to be of much help as far as the La Pavoni project goes.

Here's a photo:



The problem is that the diameter of the major thread and the top part of the fitting are very close in size. As a result, anything which has a large enough hole for the adapter to fit through, isn't going to end up leaving much of a "sealing lip" once everything is torqued down.

So, plan B: I'm going to have to sell the adapters on ebay and buy myself a M12 x 1.00 die. Once I get the lathe up and running, then I'll machine my own custom adapter and thread the end that goes into the La Pavoni.

In other news, the spindle bearings for the drill press also arrived today, so hopefully I can get the boiler element assembly drilled shortly here.

Ray