Hardware

120VAC Circuit Board

The 120V enclosure contains a PCB with the following major circuits

1. 120VAC – 3.3VDC Converter
2. 1x Relay circuit for 3-Way Valve Control
3. 1x Relay circuit for Pump Control
4. 3x 120VAC – 3.3VDC control circuits to detect Brew, Hot Water and Steam Toggle Switches
   • Each switch circuit uses an optical logic switch to achieve 120VAC isolation

Board Inputs and Outputs are as follows:

1. 7x 120VAC Inputs / Outputs via 0.25″ Quick Connectors – consistent with the rest of the Silvia’s wiring connectors
2. 1x 8P8C RJ45 Connector for 3.3VDC power and logic signals to/from the Control Board
3. 1x 2P Screw Terminal Connector for SSR 3.3VDC Control Signal Output

 

120V Enclosure

For the 120V Enclosure I started with a 1411CU Aluminum Enclosure from Hammond Manufacturing.  This worked out to be just about perfect (another 2mm shorter and it would have been perfect).  Here are the modifications I made to the enclosure:

Step 1: Add PCB standoffs to the bottom half of the enclosure with JB Weld Epoxy (or equivalent)

1. Attach the standoffs to the PCB with the M4 screws; just snug enough so they don’t move.
2. Test fit to make sure all looks good.
3. Rough up the bottom of the Standoffs as well as the inside of the enclosure where the standoffs will be epoxied in place to ensure good adhesion; also make sure they are free from dirt and grease.
4. Apply just a little JB Weld to the bottoms of the standoffs.  Be careful not to get any on the PCB or to apply too much to the standoffs as it may get into the threads and glue your screw in place permanently!
5. Let the JB Weld fully cure as per the instructions (I can’t remember, but I believe it’s 16 – 24 hrs).
6. Take the screws out and you should be able to remove the PCB and have 4 standoffs attached!
7. (Optional) To make sure everything is good and strong, I mixed a bit more JB Weld and applied it like a small fillet weld around the outside of each standoff for a bit of extra insurance.

Step 2: Drill Mounting Hole in Bottom of Enclosure

Unfortunately I didn’t take specific pictures for this step.  The pictures below are of the final product.  I’ve used them here to give a better idea of enclosure placement inside the machine.

1. First note that there are a number of existing holes in the bottom plate at the back of the machine.
2. Place the bottom half of the enclosure in it’s final destination at the back of the espresso machine; it will cover some of these holes noted in step one.
3. Tip the espresso machine over so that you can access the bottom of the machine.
4. Make sure that your enclosure is still in the proper place, and use a marker from the bottom to mark a center mark through one of the existing holes in the bottom of the machine.
5. Make sure you choose a hole that does not interfere with the standoffs.
6. Drill a hole in the bottom of the enclosure as marked; I used a #10 machine screw and nut, but use whatever you have laying around that works and drill the hole accordingly.
7. Test fit mounting the bottom half of the enclosure; if you’re a bit off you may be able to drill your hole large for some extra tolerance.

Step 3: Cut Openings in the Top Half of the Enclosure to Provide Access to the Connectors

I had taken measurements when laying out my openings; unfortunately I can’t find them now.  When / if I build another one of these I will try to take some more measurements and include them here.  For now, I don’t think it’s a big deal.  You can lay these out easy enough.

1. Mount your PCB in the bottom half.
2. Set the top half on top and make the marks for opening widths on both sides.
3. Set the top half next to the bottom half and make the marks for the opening height on both sides; leave extra room for height and width to allow room for the connectors.
4. Use a square to “connect the dots” and form your cut lines
5. You can use snips, a jigsaw or a die grinder to cut out the openings.  I chose the latter; not sure if it’s the best method.  Definitely not the cleanest!  If you do use a die grinder, use cutting oil, or a WD40 liberally to avoid clogging your cutting tool.  By the way, don’t try use a cutting disk on aluminum.
6. If you go the die grinder route, you end up with something like this.
7. Use a file to square out any edges as required; again, use cutting oil or WD40 liberally to minimize aluminum gumming up your file.

 

Step 4: Mount the PCB and Enclosure

1. All the parts are complete, now we just need to assemble!
2. Before installing the PCB, mount the bottom half of the enclosure into the back of the espresso machine
3. Install the PCB into the enclosure with the M4 screws
4. BEFORE installing the top half, make sure to complete your wiring.  You will need the top off to install your SSR wires into the screw terminals.
5. Once ready, to install the top half of the enclosure, I removed the pump screws to get better access to the enclosure side screws

NOTE: To ensure continuity, remove the plastic film that is on the enclosure BEFORE you mount the new ground lug that is part of the new wiring.  See more on the new ground wire in the Wiring Section below.

 

To ensure accurate temperature readings with minimal lag, I decided to make a fit for purpose RTD sensor for the Silvia Boiler.  The RTD sensor design I came up with screws into one of the mounting holes and uses commonly available components.  Essentially I’ve mounted a small PT100 probe inside of a brass PCB standoff that can then be screwed into the boiler.

My choice of a SATA cable for the RTD may seem odd, but it was the best I could come up with that met the following criteria:

• Low Profile 90degree or very short connector dimensions (for plugging into the control board and to keep overall install streamlined)
• Shielded Cable
• Minimum of 3 conductors (not including shield grounds)
• Readily available
• Thin – ideally flat – cable type to fit between small gap in Silvia body panels to avoid drilling any holes

RJ10 cable was my first choice, but I had trouble finding shielded versions and if the shielded RJ45 connectors and cable are any indicator, the connector dimensions and cables become quite bulky.

Before getting to the step by step instructions, here are the materials you will need; note that the components are listed in the control board BOM as well along with Part # references where applicable:

Components:

1. 1x M3 Brass Male x Female PCB Stand-off, Overall Length = 16mm, Board – Board Height = 10mm
2. 1x PT100 RTD Sensor
3. 1x SATA Cable, Right Angle Connector, 24″ Length
4. 1′ Heat Shrink, Flexible, 0.236″ Inner Dia, 3:1 Shrinkag
5. 1′ Heat Shrink, Flexible, 0.092″ Innder Dia, 2:1 Shrinkage

Consumables:

1. Thermal Grease
2. Silicon (Rated for 200°C or higher)

 

Step 1: RTD Probe

1. Secure PT100 sensor in a slit of cardboard or similar; careful not to damage it.
2. Separate the leads enough to ensure we can get silicone in between and achieve isolation but keep them within the width of the sensor head so that we can fit everything into the standoff.
3. Using a toothpick or other small applicator, apply silicon (I used high temp silicone) to the bottom 3/4 of both leads.  A good check to perform before applying silicon is to insert the probe into the standoff; the length of the leads that extend out of the standoff should be left uncovered as we will need to solder to them later.  DO NOT apply silicone to the sensor head!
4. Allow the silicone to fully cure ( 8 – 24 hrs) before proceeding.
5. Take the brass standoff and inject some of the thermal grease inside.  Ideally with a small syringe to avoid mixing with silicone in the coming steps.  If all else fails, after injecting the thermal grease, try to wipe the inside of the stand off as best as possible near the top with a toothpick and some cloth.
6. Insert the PT100 probe into the brass standoff.
7. Apply silicone into the standoff to secure the RTD sensor; remember to leave the exposed leads clean and bare so we can solder to them.
8. Allow silicone to full cure (8 – 24hrs)
9. The final two steps here confirm that the installation went as planned.  Take a multi meter and check the resistance between the two leads.  You should see 100 – 110 ohms.  If you have zero, unfortunately you have a short and likely need to start over.
10. Take a multi meter and hold one of the meter leads so it’s touching both RTD leads, and the touch the other multi meter lead to the brass standoff.  You should not have any continuity if everything is insulated properly.

 

Step 2: Cable Preparation

 

1. Cut off one end of the cable; make sure you leave the Right Angle 90deg connector intact.
2. Cut a ~6″ or longer piece of the larger heat shrink and slide it onto the SATA cable; slide it up and out of the way for now.
3. Using Quick Strippers, or a utility knife, strip back the SATA cable outer insulation 2 – 3″ to reveal the shielding.
4. Unwind the shielding around all 4 wires; leave the shielding and the bare ground wires intact.
5. You will know have 4 white conductor wires, cut about 1/4″ off each conductor (we’ll see why during assembly), and then strip a small amount off each end of each conductor.  Do not cut the 4 bare wires – ground wires – shorter; leave them as is.
6. Using a multi meter, identify and mark the two -RTD and one +RTD wires as per the PCB connector diagram below.  Remember, the layout below is of the connector on the PCB and is what you will plug into. 
7. Triple check you have your wiring identified correctly, you don’t want to mess this part up.
8. Cut two pieces of the smaller heat shrink; about 1″.  Enough to cover the bare RTD leads, but short enough that you can still physically assemble everything.
9. Cut the unused white conductor short to get it out of the way.

Step 3: Assemble the RTD Probe and Cable

1. We now need to solder the RTD leads to the cable leads; use some rigging to minimize strain on the RTD leads as they are delicate.  The RTD leads are interchangeable, but we need to make sure the cable conductors are properly identified as per the steps above.
2. Solder both -RTD conductors to one of the RTD leads using some liquid flux and solder.  Be careful not to hold your solder iron on the lead for too long as you could overheat the RTD and damage the probe. 
3. Solder the +RTD conductor to the other RTD lead.
4. Slide the small heat shrink sleeves over both solder joints and use a heat gun to shrink them.
5. Re-wrap the shielding foil that we had pull back previously, and position the 4 ground wires over top of the brass standoff (this is why we cut the conductors 1/4″ shorter when prepping the cable).  Having the shield ground wires grounded to the machine will ensure the shielding is effective.
6. Making sure the foil shielding is in place, and the 4 ground wires are over top the brass standoff, slide the large sleeve into place and heat shrink to complete the cable.
7. As a final check, take a multi meter again and check continuity is as expected at the connector end:
   1. -RTD to -RTD should be close to zero
   2. -RTD (either wire) to +RTD should be 100 – 130 ohm
   3. Any of the 4 ground contacts to the brass standoff should be close to zero
8. One final step that I did was that I did add a small tie-wrap around the heat shrink and brass standoff as seen in the picture below.  Although the heat shrink is rated for 135C, it becomes soft at 100C and the small ground wires loose contact with the brass.  The tie wrap keeps everything in place during operation.