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Thread: Any electrical engineers out there?

  1. #1
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    Any electrical engineers out there?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hey guys,

    Im looking to build a shot timer with LED 7 segmented display to add to my machine.

    I wouldnt have a clue where to start, how to build the circuit etc. My electrical engineering experience is about 2 units worth in a bachelor of mechanical engineering.

    Basically the requirements of the timer are:

    1) 2x 7 segmented display to display 00 to 99
    2) Real time count up while brew is engaged
    3) Continuous display of the shot time until brew switch is activated again for the next shot at which requirement (2) will be occur.

    Any kits that exist already? Pointers...tips?

    Cheers,

    Dave :D

  2. #2
    A_M
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    Re: Any electrical engineers out there?

    You need to give us more of the FUNCTIONAL specs and what your looking to archive..

    As it stands you have already defined the technical outcome... Yet there could be many others..

    In addition... Stand alone dual mode counters that give the dif and overall time are available... Some use a single display and depending on how you run it... You then scroll through to look at the different times etc... A trip timer in effect.. Rally car drivers know all about them.


    If you want it built in *and *auto triggered etc... *Then depending on what inputs are available (every machine / model could be different) this will add to the level of complexity...

  3. #3
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    Re: Any electrical engineers out there?

    the timer is definately going to be built into the facia of the machine.

    Im thinking about using the voltage from pump, step down the voltage to create a suitable input. Flow meter would be unsuitable because it outputs pulses I believe.

    I can modify my ANLY H5CLR timers which I have used to build grinder timers for barista comps to display the time for now. Looking for an elegant solution.

    EDIT: Now that I think about it, taking the line to the pump as an input would not work because of the autofill circuit. hmmm

  4. #4
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    Re: Any electrical engineers out there?

    Your still in Technical mode...

    Please explain the intended functionality, step by step...

    A: To time ???? and ???? and to do what ???
    B: First trigger is by ???
    C: Second trigger is by ???
    D: Display is to enable WHAT ??

    In addition how much real estate is available including depth...

    Further more, what $$$ are you looking at ?

    555 timers are great and simple... It is the inputs and outputs that will be the pain to drive / manage and they will also cost the most.

  5. #5
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    Re: Any electrical engineers out there?

    The timer is intended to time how long the brew pump is engaged for...i.e. shot time. So the display is to output the shot time.

    Triggers I will still have to figure out by poking my head through my machine tomorrow after work.

    Cost is not a problem...hoping it wont cost more than $100 though.

  6. #6
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    Re: Any electrical engineers out there?

    Quote Originally Posted by 577573686F6573000 link=1232276136/4#4 date=1232278748
    The timer is intended to time how long the brew pump is engaged for...i.e. shot time. So the display is to output the shot time.

    Triggers I will still have to figure out by poking my head through my machine tomorrow after work.

    Cost is not a problem...hoping it wont cost more than $100 though.
    So its a single timer to count the shot time in whole or part Seconds ?

    Input can be directly off the pump or what ever (240 or 110) as it can drive opto isolators to trigger the count cct. * LCD dicplay could then start to count on the signal and stop and hold at the loss of signal... Positivet and negative triggers..

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    Re: Any electrical engineers out there?

    whole seconds. Not interested in milliseconds. Maybe 1/2 second resolution would be nice though...but not essential.

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    Re: Any electrical engineers out there?

    How about using the 3 way solenoid power as the timer start signal?

    Damian.

  9. #9
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    Re: Any electrical engineers out there?

    Radio Spares and others have off the shelf LCD Counters; that run from 240/110 an will take AC (including 240 / 110) or DC inputs.

    May be above the $100 limit you set... However very professional and a finished product.

    JayCar and others may have some kits....

    Mark

  10. #10
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    Re: Any electrical engineers out there?

    Hi David

    Still on the triggering, from what I understand you need to Start, Stop and Reset [display] the timer.

    Is the intended machine semiautomatic?
    If so, Stop and Start could be derived from the brew switch via contacts on a 240VAC DPDT relay.

    The brew switch AC supply drives the relay coil.
    [You need NC/NO contacts, so that one closes when the brew switch is activated and the other closes when it is switched off]

    This will give you all the triggering you need except for reset of the timer display.
    Can you put up with a manual reset button?

    If thats all you require a $4 Vic market stopwatch timer and a suitable relay would be a simple [but not elegant solution]
    You just need to "tap" into its start/stop pushbuttons.

    To build a simple cct yourself you could start with a 555 timer circuit to generate 1 sec pulses and and combine this to drive a 0-99 led counter/display driver.

    You can get multiple 555 timers in one package so you could set another 555 circuit up as a dwell timer [delayed dropoff] to give you automated reset of the display.
    The dwell time could be set to say 30sec and and would be triggered by the Stop [brew off] signal.
    The output from the dwell time could be used to reset the display.

    check out these links but there a millions of other helpul sites:
    http://www.uoguelph.ca/~antoon/gadgets/555/555.html
    http://www.angelfire.com/electronic/beausalector/7segmentcounter.
    http://www.ecelab.com/circuit-astable-555.htm
    http://www.electronics-lab.com/projects/oscillators_timers/014/

    I reckon the above application is pretty common so with some prudent googling there should be a few circuits around to do exactly what you want.

    Cheers Reuben

  11. #11
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    Re: Any electrical engineers out there?

    Thanks Reuben. It would have been simple if my machine was semi-auto, but it is not :( Any idea where I can pull the triggers off an automatic machine?

    I was actually just thinking about hacking a kitchen timer..the kind that you use at barista comps and hacking in to the start stop buttons. Would like to have the time reset on the start of a new brew. What I actually want is an illuminated display.


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    Re: Any electrical engineers out there?

    I found a suitable timer in kit 148T2

    See attached PDF for technical information.

    The guy who sells it is willing to modify the firmware for me. This is what he has said:

    It will work as follows:

    1. On power up or reset it will display zero.
    2. When START input is low it starts counting up.
    3. When START input goes high it stops counting and displays current time.
    4. When START goes low again it resets the display and starts counting up again.
    etc, etc.
    Now, considering all the inputs and outputs to the brainbox of the machine are 240v ac, where would I be able to find a suitable input?

    Thanks,

    Dave





  13. #13
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    Re: Any electrical engineers out there?

    Any number of opto isolators or Solid state relays that will take a 240 In and give either a NO or NC output. In addition, some will provide a voltage out if there is a separate DC low voltage supply.

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    Re: Any electrical engineers out there?

    Cant I just take the output of one of the relays already in the brain box that controls the pump and connect it to the input of the timer kit? Time to go hunting tomorrow to decypher the Italian brain box.

    OR alternatively

    have a suitable 240v ac/18v dc normally open relay/ssr in line with the brew solenoid/flowmeter and take the output contacts of the relay and attach them to the start pins on the timer which will cause it to short and thus causing it to trigger the timer to start.

    Thinking about the brew solenoid and flowmeters because the only time they operate is when the brew is engaged. The pump can kick on at any moment like autofill.

    Thoughts?

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    Re: Any electrical engineers out there?

    Quote Originally Posted by 765452494E4452210 link=1232276136/13#13 date=1232364043
    Cant I just take the output of one of the relays already in the brain box that controls the pump and connect it to the input of the timer kit? Time to go hunting tomorrow to decypher the Italian brain box.
    An opto from the feed to the 3-Way Solenoid Coil would be the best and simplest, surely... :-?

    Mal.

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    Re: Any electrical engineers out there?

    Call me stupid, wat the hell is an opto?

    I think this is what Im going to do. Have an ac input solid state relay in series with the brew solenoid. Have the output terminals of the relay connected to the brew solenoid as well as connected to the start and earth terminals of the timer kit to short circuit and hence trigger timing. Im finding it quite hard to find AC input solid state relays....I only have a few DC input ones at home which means I need to stepdown the 240v ac brew solenoid line to maximum 32v dc. A needless step?

    i.e.
    + brew solenoid and start pin of timer
    240v AC ------------ SSR
    - brew solenoid and ground pin of timer

    Does anyone see anything wrong with this?

  17. #17
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    Re: Any electrical engineers out there?

    Quote Originally Posted by 4B696F7473796F1C0 link=1232276137/15#15 date=1232543522
    Call me stupid, what the hell is an opto?
    An Optoisolator..... Basically converts an input voltage to a preferred and more friendly, usable voltage with an intermediary optical element that completely isolates the Input Voltage from the Output Voltage. Most SSRs have this feature. If you approach any industrial controls supplier they would have a wide range of suitable components.

    WRT 240V AC Input SSR.... These are also relatively easy to acquire as well, from the same sort of vendor referred to above. Like these, for example.... http://www.ecefast.com.au/ProductDet...=455&catid=230

    Mal.

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    Re: Any electrical engineers out there?

    Got home today and received a surprise package. My timer kit in 1 million components...yay! *:o Wasnt expecting it until next week.

    I did a bit of competition practice...got bored and then thought I should get around to soldering the thing together.

    Here is the timer in test mode connected to a 9v battery. Works perfectly and all I really wanted was 1/10 resolution on the time. Anything more would have been overkill.

    All I have to do is figure out how to wire the damn thing in to my machine now. *AC input SSR on the way from Ocean Controls in Melbourne. Ill simply add the SSR in parallel to the brew solenoid which will cause the SSR to switch and thus short circuit the terminals (which are connected to the output of the SSR) on the timer to trigger timing. :D

    The voltage requirements of this unit is 9 to 12 V dc. I was thinking about powering this unit from the 18 V dc line from the flow meter and adding a 20 or 30 ohm resistor or something appropriate in series with it or should I just power this unit separately through a plug pack? What do you guys think? *:D




  19. #19
    A_M
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    Re: Any electrical engineers out there?

    Power from a plug pack... Safe and constant...

    Adding a R in series is assuming that I is constant and it also means heat... Depending on I draw this may or may not be an issue but is in-efficient.

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    Do I have a faulty SSR?

    Finally found the time to wire this baby in.

    wired the SSR in parallel with the brew solenoid. when I press a brew button, the SSR immediately turns on and short circuits the terminals on the timer to activate timing. When the brew solenoid is deactivated (i.e. stopped pouring espresso) the SSR turns off, but the timer doesnt stop like it should.

    I know there is nothing wrong with the timer. It works perfectly when I simulate a short circuit on the terminals, then make it an open circuit again. It starts and stops as intended. This leads me to think the when the SSR is turned off the relay doesnt open circuit the output terminals of the SSR.

    Is my SSR faulty? Thoughts...opinions?

  21. #21
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    Re: Any electrical engineers out there?

    What is teh specs on the SSR ?

    Some are triggered differently and not just about performing a Latching function...

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    Re: Any electrical engineers out there?

    This is the SSR I have

    http://www.ecefast.com.au/ProductDetail.aspx?prodid=455&catid=230

    Part Number Description
    CH-SSR10-AC 10 amp 240V AC - AC trigger

    PDF specification file: http://www.ecefast.com.au/download.asp?filename=20061210185847593.pdf&folder =Specification


  23. #23
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    Re: Any electrical engineers out there?

    Quote Originally Posted by 5173756E696375060 link=1232276137/20#20 date=1233653457
    This leads me to think the when the SSR is turned off the relay doesnt open circuit the output terminals of the SSR. *
    This is called working Live and should only be done by a Qualified Electrician...

    1: Check of input signals on Activation and end of shot... Looking for stray signals

    2: Check output *operation of the SSR when not connected to teh timer.

    Soz... All I can think *of quickly..

    NOTE: Your working around 240AC (680ptp V) it is dangerous...

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    Re: Any electrical engineers out there?

    Im not sure a SSR is suitable for your purpose....

    It is designed to switch a large AC load..... the beauty of AC is that it drops to 0 volts 100 times a second.... and at that point (assuming the trigger is off) it disconnects the load.

    I suspect you are switching a DC level to trigger your counter..... and that doesnt fall to zero - but is permanently applied....

    So the trigger (brew switch) switches on the SSR.... which then remains on until the polarity of the voltage to the load reverses.... which it never does! So it remains on even when the trigger is removed.....

    There is a minimum holding current (current through the SSR) below which it can no longer stay latched on (once the trigger is removed....) but it looks like the current is exceeding that.

    Id go a low tech solution.... a relay (the old mechanical ones!!!!) with a 240V coil... (assuming your brew switch is on a 240V circuit).... and with a set of normally open contacts switching your counter....

    Not as fancy as an SSR approach - but will work. The better solution would be to use an opto isolator..... drop the brew switch voltage via the capacitive reactance of a suitable sized capacitor.... voltage limit the output with two zener diodes.... rectify the resultant low voltage AC, smooth it to a dc level (filter capacitor) and apply it to the opto via a suitable resistor...... the output of the opto will then drive the timer....

    If the last para sounds like double dutch.... use a mechanical relay ::) ;D ;D ;D

  25. #25
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    Re: Any electrical engineers out there?

    Quote Originally Posted by 654E594E6D2F0 link=1232276137/24#24 date=1233657106
    Im not sure a SSR is suitable for your purpose....

    It is designed to switch a large AC load..... the beauty of AC is that it drops to 0 volts 100 times a second.... and at that point (assuming the trigger is off) it disconnects the load.

    I suspect you are switching a DC level to trigger your counter..... and that doesnt fall to zero - but is permanently applied....

    So the trigger (brew switch) switches on the SSR.... which then remains on until the polarity of the voltage to the load reverses.... which it never does! So it remains on even when the trigger is removed.....

    There is a minimum holding current (current through the SSR) below which it can no longer stay latched on (once the trigger is removed....) but it looks like the current is exceeding that.

    Id go a low tech solution.... a relay (the old mechanical ones!!!!) with a 240V coil... (assuming your brew switch is on a 240V circuit).... and with a set of normally open contacts switching your counter....

    Not as fancy as an SSR approach - but will work. The better solution would be to use an opto isolator..... drop the brew switch voltage via the capacitive reactance of a suitable sized capacitor.... voltage limit the output with two zener diodes.... rectify the resultant low voltage AC, smooth it to a dc level (filter capacitor) and apply it to the opto via a suitable resistor...... the output of the opto will then drive the timer....

    If the last para sounds like double dutch.... use a mechanical relay ::) ;D ;D ;D
    Having never seeing the cct I assumed the output of the SSR was nothing more than trying to act as a switch.. Relay with NO / NC would do teh job.

    I know there is nothing wrong with the timer. It works perfectly when I simulate a short circuit on the terminals, then make it an open circuit again. It starts and stops as intended

  26. #26
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    Re: Any electrical engineers out there?

    Quote Originally Posted by 69464F4D5A654946494F4D454D465C280 link=1232276137/25#25 date=1233660382
    Having never seeing the cct I assumed the output of the SSR was nothing more than trying to act as a switch..Relay with NO / NC would do teh job.
    Yep, and the SSR would work fine if it was switching AC..... but the timer input will be DC.... once on it wont turn off... They are "zero crossing" switches.... they switch off when current flowing through them drops to zero (thus when switching large loads - like motors - they dont generate radio frequency interference which they would if they switched like a relay - at any point of the AC cycle)

    However in a low current DC circuit a relay I feel is the go!

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    Re: Any electrical engineers out there?

    Thanks for your help guys.

    I ended up going for the simplest solution. I threw away the SSR and went with a 240v ac coil DPDT relay and shoved it right behind the volumetric pad. The unit is powered by a small external transformer. I will be fully integrating the power for the chronos with the machine rather than having an external transformer.

    The project is finished.....almost. Just going to find a more elegant way to attach the chronos with the machine. I will probably end up getting the front fascia cut to fit the display.

    Heres the final setup.






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    Re: Any electrical engineers out there?

    Nice one David!
    Would look great cut into the facia, but there are other options.
    Keep your eyes open for a suitable chrome box, places like Ikea, bunnings, $2 shops can have very useful things....one mans soap holder is anothers timer housing.



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