The quest for caffeine leads many a geek down the road to espresso, as we know all too well. We haven't gotten around to turning a MacBook into an espresso machine... yet, but we just can't resist modifying our stuff. Today's How-To is a bit along the lines of Tim Taylor, but it's all about the espresso.
Today's victim is our prized ECM Giotto. It was misbehaving recently, so we took it apart. While we were visiting her innards, we just couldn't resist making a small upgrade to the pump system.
The original configuration is on the left. The pump supplies pressure on demand, and the OPV (Over Pressure Valve) keeps the pressure from rising too high. The rotary pump has a built-in pressure regulator, and requires a relay to compensate for the higher power draw. Some prefer to leave the OPV in place as a safety relief mechanism. We chose to remove ours completely (of course).
Here's the old Ulka pump, which we decided to replace with this slightly bigger one. Allright, it's way bigger. We're upgrading the puny 41 watt Ulka vibration pump to a new 1/3 horsepower motor with a rebuilt brass rotary ProCon pump.
We're not hooking our machine up to the plumbing, but we wanted a bigger water reservoir. We had a PUR water dispenser handy. The clear container lets us keep an eye on our water levels and if we can tap water from the spout, we can take advantage of gravity to provide constant pressure to the rotary pump.
A quick trip to the hardware store and we found that a piece of 5/8-inch inner diameter vinyl hose fit perfectly over the oval shaped spout. We added a zip tie to secure it and a barb adapter connects it to our 1/2-inch braided PVC supply line.
Rotary pumps are used for lots of applications. When shoping for the right pump, here's what you'll need one that's food grade and won't stall your motor at (or near) 135psi (~9 bar) of pressure. To properly brew espresso you'll need at least 15gph or so. We're using one that's rated for 100gph. It's really far more than we need, but our motor has plenty of power to turn it.
The pump has 3/8-inch pipe fittings, so we added barbed adapters to it. 1/2-inch on the supply side and 1/4-inch on the pressure side. 1/4-inch inner diameter reinforced hose is rated for 250psi, so it will handle our operating pressure.
After the pump, we added a 1/8-inch needle valve, and an inexpensive water pressure gauge ($5 at the hardware store). The valve is used as an adjustable flow restrictor. The gauge allows us to easily adjust the operating pressure. Some sort of gauge is required, otherwise you'll have no idea what your brew pressure is. The zip ties are a bit of a hack, but they work.
The original pump fed the machine via this teflon hose. The fittings are 1/4-inch BSPP. For whatever ungodly reason, Italian espresso machines use British threads. Adapters can be acquired, but we really wanted our espresso machine back so we made our own. Using this hose also provides some temperature isolation between the supply line and the plumbing.
We chopped the 1/4-inch hose and installed a compression fitting on one end. All the parts are available at any hardware store. If it leaks, just tighten the compression nut a bit more and it's good to go.
We added another barbed adapter and use a pair of wire ties to secure the fitting. The teflon hose is quality, but it's a good idea to prevent movement when the job is done. The pressure hose enters through an existing hole in the bottom of the machine.
The OPV is the large brass piece with the silicon hose attached. It's adjustable by dissasembling and adding or removing shims -- a rather annoying process. It can be left in as a safety device or removed if your pump has a by-pass valve like ours does. We removed ours. If we decide to add a group pressure gauge to the machine later on, we can use the T junction that it was attached to.
On the left you can see the teflon hose that we adapted. The blue wire is was the water reservoir sensor. We removed the original water reservoir, so we had to ground this wire to keep the machine working.
To power the giant motor, we picked up a 120v relay from RadioShack (#275-217). For the $9 it cost we probably could have scored a solid state relay. To wire it up, we chopped a spare computer cord, with one grounded set of wires runs to the espresso machine where it connects to the original pump leads. The old pump was running full line current, so use another power cable or something similar. The relay is a double throw, double pole, so when it's not actuated the motor receives no power at all. RadioShack sells a plug in base, but we just soldered the leads right to the relay.
Once everything is rigged up, it's time to adjust the brew pressure. The set screw inside the nut provides the adjustment. Loosen the nut slightly. Put a blank filter basket in the machine (or some sacrificial espresso grinds.) and activate the pump. To prevent over-pressure, we loosened the adjustment a bit before powering up. (Our pump was factory set for 250psi.) We adjusted the screw until we achieved about 135psi on the pressure gauge. Hold the screw in position with a screwdriver and tighten down the acorn nut. Check everything for leaks before buttoning up the machine.
One of the most popular mods is the addition of a PID controller. In essence, the PID is just a high end temperature controller. By replacing the simpler thermostat/pressurestat controllers with a digital PID, we can get not only finer temperature control, but often better temperature stability. The advantages of adding a PID controller to a heat exchanger machine like our Giotto is limited, so we haven't gone that route (yet). If you're interested, go check out Murph's Silvia PID Page
Ahhh, sweet, uh, bitter -- no, no -- delicious success. The monster pump is rockin, the machine is quieter than ever. With the new resevoir, we've got plenty of water for extended hardware hacking sessions. Stay tuned for moremoremoremoremoremore...
Hundreds of espresso beans were sacrificed in the production of this article.