Gaggia Classic PID

stimpson

Well it has arrived and it only took a week from the US. I'm still waiting on my ebay pressure gauge from the UK...



As you can see it consists of the PID, a relay, a bag of stuff (including wires and funky coloured cable ties) and a CD of instructions. The instructions come as a set of PDF's and seem to be very comprehensive. Fitting the thermocouple look like it's going to be nearly impossible as it's at the bottom of the boiler...

I also think it will be possible to put the machine back to an unmodified state, as there seems to be no splicing of wires or anything.

Anyway, if I can resist the temptation to crack open the Gaggia tonight, I'll definitely fit it tomorrow night when the other half is at college. And I'll make sure to get pictures up.

Mr Magnolia

I was wondering when it would arrive alright. The post from the UK can be a disaster sometimes.

stimpson

Well now I'm pissed off... the install was pretty straightforward, but the results were a little disappointing to say the least...


(Disclaimer - these are not instructions - do not do this if you have no electronics training. Electricity + water = death. You're on your own. Don't come running to me if you kill yourself)


Anyway, first thing to do is read the instructions, then read them again. They are pretty good, with a couple of exceptions which I'll cover below.

First, wire up the relay as described in the instructions...



Shoddy....


Anyone who's ever built a PC will be familiar with this...



Apply thermal paste to relay..



Mount on back of machine

Now the fun part - replacing the thermostat. This is mounted at the bottom of the boiler. Easy to remove - nearly impossible to replace...



It's that little black thing. Remove the connectors. Use a 17mm spanner - it's not that tight - once it's loose, you can ease it off with your fingers. When it falls on the bottom of the machine, fish it out with a long nose pliers, magnet on a string or a trained mouse.

Replacing with the temperature sensor is the hardest part of the install. You need to thread it into a hole that you can't see. I used a little of the thermal compound in it even though it wasn't in the instructions. The original thermostat had some on so I figured it's probably a good idea.

Try it a few times. Swear. Try it again. Swear like a docker. Apologise to your girlfriend. Agree it's not the kind of language that an unborn should hear in the womb. Hug. Tell her you love her. Take a deep breath.



BRAINWAVE! use and elastic band to wrap around wire loom and attach other end to the steam wand. Now you have room to work!

With a great deal of patience and care, thread sensor into hole you can't see, turning half a turn at a time. Make sure to keep sensor leads tied up, and keep wire bundle turning too - it's really delicate and I'm sure it's easy to break off wires.



Slowly slowly catchy monkey!

Tighten this hand tight. Breath a sigh of relief. Hard part is now over. Yay!

Now - Wiring



Groovy piggyback connectors so you don't have to splice anything. One goes on to the middle connector of the power switch (forgot to take photo). Notice how the 2 thick red wires from the relay are now connected to the thermostat connectors?? Yes - I forgot a step.



Other one goes to brown wire on power socket on back of machine.



Max just can't stay awake without espresso. He turns his nose up at instant (good boy!)



Wire up PID as per instructions



Smoke test. Behold! It lives!!



Tidy up cables and and use cable ties for strain relief.



IMPORTANT Reconnect earth connection to chassis. This is NOT in the instructions and is SUPER important.



Looking good...



Mounted with supplied 3M pad

Now for the down side...

I swich it on. The temp rises, hits 100 degrees. Keeps rising. Weird - soem kind of self test??? Temp hits 150 degrees and thermostat kicks in, light goes off. Temp drops to 125, light turns on. Temp hits 150 again. Not good.

Swearing starts again, but by this time girlfriend is in bed and can't hear.

I double check wiring. All seems fine.

I check the resistance on the sensor - fine.

I check voltages on the PID. As temperature passes 100, voltage to relay drops from 6.5 V to 5.5 V. Surely that not enough to close the realy... So I do some digging and find a data sheet for the relay, and sure enough it need voltage to drop past 1.5V to turn off. PID is FUBAR...

Now auberins.com want me to return PID at my own cost before they will replace, and I can't return my machine to original without replacing the thermostat (noooooooo!!!!)

So I had to dig out my old school stove top espresso pot this morning. Considering it cost me €10 on a trip to rome a couple of years ago, and allowign for the lack of crema, it makes really tasty coffee. Dare I say it, better than an unmodded Gaggia.

Have I been wastiing my money??

Victor_M

In fairness great write up, that's a pain in the hole all right, if it's any consolation you'll probably be able to drop the replacement one in place in a fraction of the time.

stoopid question time - What exactly are the benefits of the PID upgrade, you set a specific temp set point? So the boiler never goes above a certain point, thus never burning the coffee? is the stock thermostat not up to the job? Or does the PID do something else?

Dero

Victor_M wrote: »

What exactly are the benefits of the PID?

As far as I understand it, the PID does pretty much what the thermostat does, but with much more accuracy, stability and control. The idea is that you can set a temperature point, and the PID will effectively "learn" the temperature response of your machine and adjust the element accordingly to provide a much more stable temperature with minimal variation. Stability is the key.

Clicky here for more info.

Edit: Good summary of espresso temperature control.

stimpson

I'm not sure it does any learning. As I understand it, it has been programmed specifically for the thermal characteristics of the Gaggia grouphead.

It is for temp stability though. The standard thermostat has a gap of about 20-30 degrees between on and off, so it's in or around the correct temp. The Sensor with the PID kit can measure temperatures to 0.1 of a degree.

The PID is essentially a computer programmed to monitor the sensor and turn the heater on and off at just the right time to accurately ensure a consistent temp.

It also has a a red seven segment display, so it's got that 80's retro chic, which in itself is worth the money

Dero

This thread is giving me the PID bug. Not sure it's worth it though. Normally, I love to mod stuff, but as I only have a Coffee Deluxe, I never bothered beyond a couple of simple repairs. I wonder how well that PID could be adapted to any future machine upgrade? Actually, maybe I should just keep an eye out for a good 2nd hand Classic and mod the life out of it...

stimpson

If it's the same as the US Gaggia Coffee then the internals are exactly the same, and the instructions provided have photos of the Coffee. In fact the page on their website has a picture of a Coffee Deluxe:

http://auberins.com/index.php?main_page=product_info&cPath=6&products_id=35

Pop the top off it and compare to the photo's in this thread. If you can see the thermostat down the side of the boiler then you're in business.

Gran Hermano

Dero wrote: »

This thread is giving me the PID bug. Not sure it's worth it though. Normally, I love to mod stuff, but as I only have a Coffee Deluxe, I never bothered beyond a couple of simple repairs. I wonder how well that PID could be adapted to any future machine upgrade? Actually, maybe I should just keep an eye out for a good 2nd hand Classic and mod the life out of it...

You could do worse than have a look here - (factory reconditioned)
http://www.gaggia.uk.com/onlineshopindex.htm

Dero

stimpson wrote: »

If it's the same as the US Gaggia Coffee then the internals are exactly the same, and the instructions provided have photos of the Coffee. In fact the page on their website has a picture of a Coffee Deluxe.

Yeah, It'll work fine on my current machine. My only concern is that it wouldn't be worth the cost/effort because I'm not planning to keep this machine any longer than I can afford (that could be forever though ). I never considered a Classic as a worthwhile upgrade from a Coffee before, but now that I consider the OPV mod & the ability to backflush on top of the PID mod & a Silvia steam wand (both of which will work on the Coffee too), it seems like a better proposition.

Suffice to say this thread has given me much food for thought...

stimpson

Of course it's worth the effort!

OPV is a no-cost, no brainer. Even doing a blind 3/4 turn gives an improvement.

Silvia wand is an excellent mod if you like the odd cappuccino.

Wait and see what the PID holds in store. I believe it will make a big difference (it better or I will be very angry!)

I've been warned against backflushing a domestic Gaggia - not sure why, but it's not recommended by some people.

I do want a bottomless filter, so if you're thinking of buying a Silvia wand, I'd be happy to split postage from happydonkey with you.

Victor_M

Same here actually, if anyone is ordering from Happydonkey I'll gladly split shipping too on a the Silvia upgrade kit (live in Castleknock work in Leixlip if that's near any of you lads by any chance)

I have a pressure gauge on order from Ebay once I get it up and running if anyone needs a lend to calibrate they will be welcome to it.

stimpson

My replacement PID arrived this morning. Fair play to auberins.com - it was postmarked 3/10/08 so he didn't wait to receive the faulty one. Will fit it tonight- watch this space!

stimpson

Well I finally got my PID fitted this weekend and it works perfectly. Looks like it was just an incorrectly programmed controller. Wired it up, flicked the switch and it hit 102 degrees and it switched off the element. I let it warm up for about 15 minutes and pulled a shot. It only dropped by an indicated 3 degrees during the shot and had settled back to shot temperature within a minute.

It's obviously far more accurate than the original setup as it flicks the element on and off for less than a second at a time when it's around the brew temp. Temperature surfing while steaming is much easier as you can see the temp. I find that if I start steaming at about 147 degrees it keeps the heat on and you can steam enough for 2 cappuccinos in one go (when steaming, the steam thermostat is still doing it's job but the temp display still works).

All the coffee made over the weekend was tamped with the crappy plastic tamper as my steel one has been packed away (I have builders in...). Nevertheless, there is a noticeable difference in taste - espresso is far less acidic, much smoother - a little sweet even. I'll have to wait until I get into my new kitchen in a couple of weeks before I can give it a proper workout, but so far I'm really impressed - looks like it was worth the wait.

Mr Magnolia

Well done on the mod. Do you know what value is was at before you programmed the 102? That seems a lot more stable than I would have expected. The coffee from my classic is always too hot too drink straight after pouring which may mean that the brew temp is also too high?

stimpson

It was set at 102, but you can change it to suit the bean, which I will do when I've played with it for a bit.

102 is the temp at the thermocouple which is quite near to the heating element. I believe it has been calculated that this ensures a temp of 98 at the grouphead.

If you saw how often it flicks the juice on and off to maintain the temp you'd realise how wide a variation in temp is allowed by the stock thermal switch which takes ~30 sec between on and off.

GRINDER*MAN

Hi Stimpson, well done on the mod - I've also fitted an auberins pid to my classic - it definitely takes some of the guesswork out of things re starting temp, but I still find that you get over extraction at the start and under extraction at the end of the pour due to a lack of temp stability throughout the pour. The high temp start point (102 c) compensates for the low temp at the end of the pour, (though the heat in the grouphead further compensates/stabilizes the water temp as it hits the coffee). Anyhow, i think it would be pretty cool if you could preheat the water coming into the small boiler - this would mean you could set the pid to a lower temp (maybe as low as 96c) and be sure of temp stability throughout the pour, thus improving extractions. I have found this link on the web, http://www.home-barista.com/forums/preheating-incoming-water-on-gaggia-classic-t2794.html , but it looks pretty hard to do. Might be possible to something similar with coiled copper pipe. Any thoughts?! I guess I think it would be last piece in the jigsaw.

stimpson

There was a PDF provided with the kit that details a Temperature performance study. I won't go into the details here, but it maintains that a 102 degree Set Value results in an average Brew temp of 92 degrees, with a peak of 96. He does say that the shot temperature can vary by up to 10 degrees during the shot due to the size of the boiler. He also maintains that you should allow 20 mins warm up time and 4 mins between shots to stabilise temp which will all help to minimise temp variation.

I saw that very page when I was planning mods and his temp graphs are pretty impressive. I'm a bit surprised at his success though, as it's bolted directly to the boiler which creates a thermal load. I would have thought that this would pull the temperature down when it is filled with cold water - essentially it's the same as increasing the size of the boiler.

I'm not sure about using copper piping as you need surface area contact to ensure heat transfer.

Anyway, one thing at a time. A bottomless portafilter is next on the list.

Mr Magnolia

Thanks for the info, interesting.

stimpson wrote: »

Anyway, one thing at a time. A bottomless portafilter is next on the list.

Great to check for channeling and the like. Looks dead sexeh too.