Hello!
I am new to arduino. I have been wanting to build an espresso machine for a while now, and today the idea struck me; why don't I use arduino?
Here are the basics:
+I need to be able to switch on/off a heating element based on a temperature sensor
+I need to program some tolerance so it isn't constantly boiling water for a second or so (maybe only have it check temp every 1min or so?)
+I need an indicator of some sort that the machine is ready
+switch to brew (turning on a pump)
Some other things i might do (depending on difficulty)
+Adjust shot size
AGAIN
I am brand new to arduino, I don't even have a chip yet!
Any help y'all could provide would be great!
I'm a caffeine addict and this project really interests me so I'm sure it could be done but, do you know how these machines work? I don't but I thought there was some kind of pressure vessel involved. (pretty dangerous stuff but nothing that can't be handled).
If you have a link or further details of exactly what they do with the water/milk etc.. I'd be more than happy to help.
KenF:
I'm a caffeine addict and this project really interests me so I'm sure it could be done but, do you know how these machines work? I don't but I thought there was some kind of pressure vessel involved. (pretty dangerous stuff but nothing that can't be handled).
The pressure vessel is only if you have a steamer, which I will not be adding to my machine (too complicated!).
So far, I'm thinking:
boiler>pump>(maybe)one way valve>t joint (one port to grouphead)>solenoid
The water meets the coffee at the grouphead, which I will probably make (this is the part that the portafilter connects to).
What I mostly need help with is the componentry and programming. I will also need to read up on some basic wiring, as I will need to power both 120v components (pump and heater), and 12v (arduino and solenoid).
fancycoconut:
The water meets the coffee at the grouphead, which I will probably make (this is the part that the portafilter connects to).
This I shall google
What I mostly need help with is the componentry and programming. I will also need to read up on some basic wiring, as I will need to power both 120v components (pump and heater), and 12v (arduino and solenoid).
This is the easy stuff. Work out how many 120v items you want to be able to switch. So far you've mentioned 2. You can get a 2 relay shield to do the job but I'd suggest going for a slightly bigger board (perhaps 4 relays) In case other features come to mind later.
BTW Is a pump really required. Wouldn't a solenoid valve attached to mains water pressure suffice? (obviously you need to detect water level or have a float valve).
KenF:
BTW Is a pump really required. Wouldn't a solenoid valve attached to mains water pressure suffice? (obviously you need to detect water level or have a float valve).
I need the pump to create the pressure required for the shot. The solenoid is to release excess pressure and water from the line (so you can immediately remove the portafilter without spraying wet grinds everywhere!). This water is released into the drip dish.
Yes I've been busy googling so have a better understanding of the process now. Now here's a suggestion. Rather than using a regular pump and solenoid, you could perahaps use a peristaltic pump powered by a stepper motor. This would have several advantages.
Firstly it would be possible to precisely dose exactly how much water to deliver. It would also be possible to determine how quick to deliver it. The speed of delivery would have no bearing on the accuracy of the amount of water delivered. This would allow you a good deal of control over how the water gets delivered. Another benefit of this type of pump is that there are no mechanical parts of the pump that come into direct contact with the water.
One article I was reading strongly hinted that it's normal for the grouphead to be kept at a high temperature. This is usually achieved by convection, but would it be worth having separate waterways for the sake of maintaining the group head temperature?
Peristalitic Pump; I am interested. Now I am not very familiar with this type of pump, but some quick reading raises a few concerns. Would be the temperature of the water affecting the effectiveness of the system? Also, I'm a bit worried about flow not being smooth. And lastly, I'm having some trouble finding a website that sells them, mind sharing a link (if you have one)?
Oh, and I was considering heating the grouphead. But in order to do so, I need to figure out my design for it first. I suppose the use of a 3 way solenoid could be helpful, since there would be no point in heating the group while pulling the shot.
BTW, for the perfect shot, we will need 106-177 ml/min, with the ideal pressures between 133-142 ml/min.
I'm starting to rethink my worry about the lack of smoothness with the pump. My only remaining worry is the hot water through the tubes. And actually, I started thinking, the constant heating of the group head will mean that there is no worry about the first bit of water in the line is cold (when pulling the shot). This can be achieved by placing a 3-way solenoid right before the grouphead.
Wow, 3 posts in a row, I really should research fully before I post!
The peristaltic pump won't work, pressure for pulling a good shot is 9bar, which is going to mean a very expensive pump!
But I am still interested in heating the grouphead, and I might use a peristaltic pump for that since the vibration pumps are very loud.
My previous post on this thread seems to have completely disappeared. So if it turns up, I'm about to repeat myself.
Peristaltic pumps probably run smoother than any other kind. ESPECIALLY at low delivery rates. Their rate of delivery can be directly calculated by tube diameter and linear speed of the rollers. If you halve the motor speed you halve the rate of delivery. Other pumps do not behave like this. Also when you stop them, it stops the flow dead in it's tracks.
Food grade silicone tubing is easily able to cope with boiling water (assuming it's gravity fed).
The pumps themselves can be found in abundance on ebay, although it's quite difficult to find one that DOESN'T include the motor. This is a shame because I really think you should go for a stepper motor to drive it. It would give you a degree of control that is second to none. Not only would you be able to decide on the rate of delivery, but it would be so consistent that you could determine the amount delivered without having any other sensor to determine levels.
You'd also probably have to change the tubing in any pump you buy online as they're unlikely to be food grade. Any pump sold for food use is likely to be (unjustifyably) overpriced. Since it's only the tube that has any contact with the product, any pump will do.
The pump body is actually a very simple device, it's merely a chamber to hold the tubing in place and a shaft with a few bearings mounted on it, such that the bearings then run along the tube. I wouldn't be surprised if you could build this yourself. I'm half inclined to have a go now
Update:
One of the local universities has allowed to let me use their CNC machine (they were happy to once i told them i was a local high school student!). I will use the machine to make the grouphead, which will be a clamshell design, with a path for the water for brewing, and a path for water to circulate through and heat the group. This is game changing, because having a full metal group will improve heat retention, taste and durability.
Where do you get the figure of 9 bar from? That's pretty darned high high. That would be easily achievable by simply having a sealed vessel and letting the steam do the work, but this isn't the way you want to go is it? To get the same pressure from a pump is not quite so easy.
1/16 inch I.D. Tygon® B-44-3 tubing would be 70 psi x 1.43 = 100.10 psi working pressure.
100 psi = about 6.8 bar. and "working pressure" is calculated as 1/5th of burst pressure. So pushing this to 9 bar would likely still work but with a need to replace the tube more frequently. Even so, I think this would be pushing the bounds of what is possible with a home made device.
Another concept would be to have a separate chamber with a piston (rather like a large syringe). This could be driven by a screw operated by a motor. Using this method you could generate some pretty high pressures.
9 bar is what all of the sites say is the optimal pressure for brewing is. I am going to stick with the vibration pump because I know it will work. And actually, even a true espresso machine doesn't use the steam pressure (except stove-top systems) to brew the coffee, the water just goes through a heat exchanger/coil.
I have had some other ideas also, will probably post some pictures as that will be easier.
That's interesting. I wonder if you're over complicating the arrangement of valves though. I found this image on the net.
I noticed that the heating of the grouphead in this example is gravity fed.
So working on this idea I came up with my own design. The idea being that in the boiler you'd have something like a kettle element in the bottom. Above this would be something like a saucepan lid (but NOT a tight fit). A pipe would then connect into this saucepan lid device and lead the heated water up to the grouphead by simple convection. Any excess pressure can simply pass around the saucepan lid gizmo.
I'm not sure if my idea of putting the vibrator pump BEFORE the heat exchange coil would work though.
I was thinking about that today in school. It may be a better way to go with the coiled copper tubing, the only thing to keep in mind is that magical temperature. Maybe instead of routing water to the group, you have a sealed tank with an output above the max fill line, which you vent to the group, and out some holes at the top (some machines do this and it serves as a cup warmer). My other issue (I thought of mid sentence) is if we switch to a coiled copper tube submerged in the water, we now have a closed line and therefore a pressurized system (cold water enters, heated to 200*...). The pressure may be quite nominal, and I might just be worrying a bit too much.
So if it turns up, I'm about to repeat myself.
