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PID Temp Control for less than $50

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  • nikko.the.scorpio
    replied
    Sorry to exhume such an old thread but fascinating read and such a shame there wasn't able to be a few more pix or general instructions for folks to follow as I'd imagine a LOT of people would definitely be interested in doing something like this given the low cost vs high reward ratio of the exercise.

    Great post by the OP and love to see more from him or anyone who's done anything similar.

    Leave a comment:


  • Macropin
    replied
    Hi Guys, I dug up this thread, as I'm looking at sourcing a C100 (or maybe C700) from dx.com to mod my Silvia. For those of you who've installed a C100 (or similar), did you manage to wire it up to automatically change the temp depending on the active function? or do you manually dial in the temp on the controller, and wait until the thermocouple reads the right temp, then use whatever machine function you require (eg hot water/steam/brew)?

    Leave a comment:


  • Tanke
    replied
    Originally posted by Tanke View Post
    Hi Wilki,

    I had just received my REX-C100 with relay output. I wish to modify the pid to SSR output as you did. I have the required electronics knowledge for the jib, but not sure the proper way of opening up the PID casing (without demaging the plastic casing).

    Thus I would appreciate very much if you show me the way to do it.

    Regards.
    Tanke
    I managed to open up the casing with ease. No "cracking" is necessary. The modification is straight forward.

    Thanks.

    Leave a comment:


  • Tanke
    replied
    Modification of REX-C100 PID

    Hi Wilki,

    I had just received my REX-C100 with relay output. I wish to modify the pid to SSR output as you did. I have the required electronics knowledge for the jib, but not sure the proper way of opening up the PID casing (without demaging the plastic casing).

    Thus I would appreciate very much if you show me the way to do it.

    Regards.
    Tanke

    Leave a comment:


  • jbrewster
    replied
    Originally posted by Javaphile View Post
    While I would agree with this for cheap Chinese parts these relays were made in Switzerland.
    Ahh, yeah, fair enough, the Swiss know how to engineer stuff (refer to earler comment about over-engineering)

    Leave a comment:


  • Javaphile
    replied
    Originally posted by jbrewster View Post
    Heh, at what percentage of maximum ratings? I generally divide MTBF/other reliability figures by 5-10 to get something more reflective of reality ;P

    If it's worth engineering it's worth over-engineering ;D
    While I would agree with this for cheap Chinese parts these relays were made in Switzerland.

    The original relay was rated for 1,000,000 cycles. The machine was in a commercial setting for ~14 years where it was left on 24/7 year-round and then ran here 24/7 for 8 months out of the year for 7 years. Using the avg cycle time as measured here that means the relay had almost 2,000,000 cycles on it when it died. I'd say it's fair to say the relay was over-built and that their stated duty life was pretty fair reflection of what to expect in reality.


    Java "Very happy with the accuracy of the manufactures specs" phile

    Leave a comment:


  • jbrewster
    replied
    Originally posted by blend52 View Post
    To clarify further,..the PID, i used was the small (din 32) XMT7100 unit that has 3A ( 7A actual) relay, AND SSR outputs. (for $20)
    So i didnt need remove the relay, run extra wires, or mess with anything internally on the PID.!
    Ahh, must've been somebody else who commented about bypassing the relay.

    the XMT7100 isn't a bad unit actually, I use two of them (one for boiler control the other is a group temperature display), I bypassed the alarm relay in the boiler control unit so I could direcly drive my steam control SSR.

    Leave a comment:


  • jbrewster
    replied
    Originally posted by Javaphile View Post
    700,000 cycles or even more on the good non-Chinese ones: http://coffeesnobs.com.au/showthread...l=1#post279955
    Heh, at what percentage of maximum ratings? I generally divide MTBF/other reliability figures by 5-10 to get something more reflective of reality ;P

    If it's worth engineering it's worth over-engineering ;D

    Leave a comment:


  • Javaphile
    replied
    Originally posted by jbrewster View Post
    Barring the bit where the electromechanical relay dies after about 10,000 cycles (100,000 for better relays)
    700,000 cycles or even more on the good non-Chinese ones: http://coffeesnobs.com.au/showthread...l=1#post279955


    Java "You want to relay what?!?" phile

    Leave a comment:


  • blend52
    replied
    Originally posted by jbrewster View Post
    No, he removed the internal relay and ran the lines which were driving that out to the SSR (I've done this myself on several PIDs) but initially he was running the element directly off the internal relay.
    I think there is some confusion between posts here ..
    To clarify further,..the PID, i used was the small (din 32) XMT7100 unit that has 3A ( 7A actual) relay, AND SSR outputs. (for $20)
    So i didnt need remove the relay, run extra wires, or mess with anything internally on the PID.

    FYI : there are simpler, cheaper electronic temp controllers available ( ebay..$10) with 30A internal relays .
    They are not ideal, but they will hold a temp much closer than the stock bi-metal T'stats fitted as standard, and give a digital temp display.
    The display itself is a huge help in getting consistent shot quality, and reducing a temp variation from 30 C,... to 5 C , is a bonus !

    Leave a comment:


  • jbrewster
    replied
    Originally posted by Wilki View Post
    If the tracks did burn out and you still wanted to use the relay, you could always open her up and solder wires directly to the relay
    Considering 25A SSRs (not that I'd trust them for more than ~10A) go for ~$7 on evilbay I wouldn't bother, bringing the drive out (or better yet getting a PID controller with SSR outputs to begin with) is a better option, to say nothing of the potential fire hazard if the tracks should burn out...

    Leave a comment:


  • Wilki
    replied
    Originally posted by jbrewster View Post
    No, he removed the internal relay and ran the lines which were driving that out to the SSR (I've done this myself on several PIDs) but initially he was running the element directly off the internal relay.



    Whilst this is true, people with less experience in these matters might think "awesome I can run 7A through this" because they are not aware of the other considerations here. Also, good engineering practise dictates an 80% derating (5.6A in this case), i.e. you don't run things close to the rating on the spec sheet.



    On dirt-cheap chinese mass-production? Highly doubtful. I'd be surprised if the tracks are even appropriate for the rating on the box, copper is expensive and given the space constraints the way you'd get extra current handling is to use 2oz copper instead of 1oz, which means the whole board becomes more expensive.

    A relevant anecdote, Jeri Ellsworth replicated the Commodore 64 in a joystick for some toy company or other, when the designs got shipped to the factory in China they couldn't get the prototypes to work, when she went over there to check it out she found that they'd removed a large number of essential components like bypass capacitors in order to reduce costs, high-speed digital systems don't work without proper bypassing.

    The 7A relay would be because it fit and they could buy a few hundred thousand of them at a few cents a pop, the current rating has little bearing on the cost of such relay when you're buying in those sorts of quantities.



    Valid point, the main concern would be the initial warm up period.



    Barring the bit where the electromechanical relay dies after about 10,000 cycles (100,000 for better relays)
    If the tracks did burn out and you still wanted to use the relay, you could always open her up and solder wires directly to the relay

    Leave a comment:


  • jbrewster
    replied
    Originally posted by brettchris View Post
    I read it he brought out the ss control wires to the ssr mounted external to the control
    No, he removed the internal relay and ran the lines which were driving that out to the SSR (I've done this myself on several PIDs) but initially he was running the element directly off the internal relay.

    Originally posted by blend52 View Post
    1) I was not running 7 A through it...the Silvia element pulls little over 4 A max
    Whilst this is true, people with less experience in these matters might think "awesome I can run 7A through this" because they are not aware of the other considerations here. Also, good engineering practise dictates an 80% derating (5.6A in this case), i.e. you don't run things close to the rating on the spec sheet.

    Originally posted by blend52 View Post
    2) I expect most elec designers build in a little safety margin ? ( maybe thats why they used a 7A relay !)
    On dirt-cheap chinese mass-production? Highly doubtful. I'd be surprised if the tracks are even appropriate for the rating on the box, copper is expensive and given the space constraints the way you'd get extra current handling is to use 2oz copper instead of 1oz, which means the whole board becomes more expensive.

    A relevant anecdote, Jeri Ellsworth replicated the Commodore 64 in a joystick for some toy company or other, when the designs got shipped to the factory in China they couldn't get the prototypes to work, when she went over there to check it out she found that they'd removed a large number of essential components like bypass capacitors in order to reduce costs, high-speed digital systems don't work without proper bypassing.

    The 7A relay would be because it fit and they could buy a few hundred thousand of them at a few cents a pop, the current rating has little bearing on the cost of such relay when you're buying in those sorts of quantities.

    Originally posted by blend52 View Post
    3) the current draw is not continuous. 5 mins to initial heat from cold, then cycling for a few seconds at a time.
    Valid point, the main concern would be the initial warm up period.

    Originally posted by blend52 View Post
    4) It was a test..never intended to be permanent. ( Though i believe it is perfectly viable if you can tolerate the solenoid clicking !)
    Barring the bit where the electromechanical relay dies after about 10,000 cycles (100,000 for better relays)

    Leave a comment:


  • Wilki
    replied
    Originally posted by MrJack View Post
    So, the milion dollar question; how is the coffee?
    For me? Very hard to say. I have too many inconsistencies to be able to tell sadly.
    I mostly just enjoy hacking things

    Leave a comment:


  • blend52
    replied
    Originally posted by jbrewster View Post
    Oh and I wouldn't recommend running a 7A load through a PID rated for 3A regardless of what the relay rating is .
    Fair comment,..but to be clear.....
    1) I was not running 7 A through it...the Silvia element pulls little over 4 A max
    2) I expect most elec designers build in a little safety margin ? ( maybe thats why they used a 7A relay !)
    3) the current draw is not continuous. 5 mins to initial heat from cold, then cycling for a few seconds at a time.
    4) It was a test..never intended to be permanent. ( Though i believe it is perfectly viable if you can tolerate the solenoid clicking !)

    Leave a comment:

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