gene cafe not heating up fully

[Dimal]

Re: gene cafe not heating up fully

Thanks for the info and charts "hazbean"....

Helps a lot to engender an understanding of what might be going on. The Sawtooth" pattern of the rising gradient is indicative of On/Off Control through, not PID but it may use a basic Proportional design to generate the error to form the basis of control. As you say, there definitely seems to be plenty of thermal capacity available as there is no flattening off occurring on that steadily rising ramp.

Given all that, and the unfortunate usage of different specd RTD/Thermistor devices (most likely Thermistors as RTDs are considerably more expensive than $20), it should be possible to adjust the error voltage, or in code on the PIC to bring the unit back into within standard operating tolerances. One would think that this should be possible.

Also, is the Air Speed a controlled variable or fixed? As Kevin mentions above, thermal energy and air speed are intrinsically coupled and I was wondering if the management of this is more complex than just control of the element output alone? Would be great to grab hold of a Service Manual as well as a look at the PIC code - I wonder if there is one out in the wild somewhere.... :

Mal.

[KJM]

Re: gene cafe not heating up fully

Also, is the Air Speed a controlled variable or fixed?

Its fixed. The control is basically simple PWM in a PID loop (in so far as I can tell).

Jigging with the sensors is likely to be troublesome - the thing has been through that last phase of engineering. The bit that removes every last component from the board.

Ive not pulled the PIC out and tried to suck the code out - I suspect theyve probably blown the protection fuses. Also given how some of it works, I suspect they have the code memory quite full... which would make reverse engineering a pain.

Id love it if there was a service manual!

/Kevin

[KJM]

Re: gene cafe not heating up fully

Hey Greenbe - any joy?

/Kevin

[greenbe]

Re: gene cafe not heating up fully

Hi kev,
Thanks for all the info it has been great.
l took the fan apart and cleaned it with a tooth brush which got most of it out we are talking 98 % clean.Did the time test it hit 250 but it is taking about 10 min.It is roasting a lot better now l think that is about all l can do . My chaff collector is a bit melted and shitty l was thinking of maybe getting a new one .One thing l have learned from this exercise is that small things make a difference and carnt be under estimated.
greenbe

[KJM]

Re: gene cafe not heating up fully

Hey - if the chaff box is a bit tired, have you checked the screens inside it??

I would like to think I keep mine reasonably clean, but I did a bunch of roasts a couple of years back during the summer during which I did dump the chaff after each group of 3 back-to-back roasts, but didnt clean out the screen.

At the end of the 3 x 3-back-to-backs, it was short cycling. I thought I had fatally wounded the thing, but when I held the chaff box up to the light it was pretty blocked. Cleaning totally fixed the problem, so Im hot on keeping it clean ever since.

Having said it was pretty blocked, you could still see daylight, but the "holes" were small in the middle and bigger to the edges. So even partial blockage is a no-no.

Glad to hear it is getting to 250C now. 10 minutes is longer than mine - last weekend it was 8 minutes from cold to 250C. That seems to me to be about 2:30 longer than when it was "new"!

Cheers
/Kevin

[hazbean]

Re: gene cafe not heating up fully

Yes, if the inner screen is clogged, heating becomes severely limited.

Here is a pic of mine taken a while ago when I first made this discovery:
  http://tinyurl.com/3b45z54

Since then, I have kept it spotless (and eventually picked up a large collector, which is much easier to keep clean).

10 minutes is slow but workable. How is it going with real roasting?

[rong]

Re: gene cafe not heating up fully

Dont suppose there has been any further progress on this??? My Gene is suffering the same problem even after replacing the heater, cleaning fan and chaff filter. It takes about 10 min to get to 250 with no beans. With beans, it struggles to get to 235. I now get 1st cracks about 14min

[KJM]

Re: gene cafe not heating up fully

rong - Im still using mine, but it has started to marginally mis-behave like hazbeans did.

The symptoms are pretty simple: as the temperature climbs, it reaches a point where you hear a click (the relay dropping out to the heater) and maybe 1 second later, it clicks back on. This behaviour arises when the temperature on the RHS and LHS of the machine are too different.

Since Hazbean and I both have Genes - we did a series of component swaps when his was playing up and mine wasnt. The only things we didnt swap (because it was just a tiny bit too much work ) were the temperature sensors themselves. It made no difference to his machine.

So I reckon it must be some kind of degradation of the sensors that is happening.

But on the other hand, I perceive that my Gene takes longer to get to temperature than it used to (when it doesnt click on and off). When I replaced the heater, I took the old one apart - and it is clear that a couple times the heating element has busted and re-fused itself taking out a turn of the element.

So I dont know what to suggest. The Gene is a lovely piece of work, but I wish there was a bit more on-line expertise available on debugging faults.

I might see what happens if I replace the temperature probes..

Cheers
/Kevin

[TC]

Re: gene cafe not heating up fully

Perhaps it might be worth contacting Avacuppa?

They are the importers and will be able to advise on any technical issue.

Chris

[rong]

Re: gene cafe not heating up fully

rong - Im still using mine, but it has started to marginally mis-behave like hazbeans did.

The symptoms are pretty simple: as the temperature climbs, it reaches a point where you hear a click (the relay dropping out to the heater) and maybe 1 second later, it clicks back on.  This behaviour arises when the temperature on the RHS and LHS of the machine are too different. 

Since Hazbean and I both have Genes - we did a series of component swaps when his was playing up and mine wasnt.  The only things we didnt swap (because it was just a tiny bit too much work  ) were the temperature sensors themselves.    It made no difference to his machine.

So I reckon it must be some kind of degradation of the sensors that is happening.

But on the other hand, I perceive that my Gene takes longer to get to temperature than it used to (when it doesnt click on and off).  When I replaced the heater, I took the old one apart - and it is clear that a couple times the heating element has busted and re-fused itself taking out a turn of the element.

So I dont know what to suggest.  The Gene is a lovely piece of work, but I wish there was a bit more on-line expertise available on debugging faults. 

I might see what happens if I replace the temperature probes..

Cheers
/Kevin

Kevin, it sounds very much like the temperature sensors are at fault. The reason for that suspicion is that I have noticed that 1st crack appears to occur at a lower temp than before - i.e. about 231 instead of 238 - so I wonder if the outlet sensor is gummed up a bit or just reading low. That might account for the fact that the thermal cutout starts to kick in around 210 and really drags out the temp gradient.

I will have a look to see if the sensor is impeded in any way :-?

[KJM]

Re: gene cafe not heating up fully

I will have a look to see if the sensor is impeded in any way 

Well - either the output or input > You cant really tell... The output sensor is "finger reachable" and on mine looks clean (well, it is now). It pretty much agrees with a K-type thermocouple suffed up the chaff box outlet 8-) The input sensor Im not 100% sure about - it could be the problem - I can just get a finger on it.

Interesting your observation of the displayed temps seeming a bit low though. Ive not observed that, but will keep my eyes on the temp this weekend.

If that is all it is, then the fix seems pretty simple (and cheap!).

Cheers
/Kevin

[rong]

Re: gene cafe not heating up fully

I assume the sensors are easy to come by. Havent looked.

[KJM]

Re: gene cafe not heating up fully

I assume the sensors are easy to come by. Havent looked.

Sorry rong - have been away from CS for a bit. The sensors are somewhat unknown... I dont know if you can source them directly from a supplier (you could, if only we knew exactly what they are..). You probably need to get genuine bits from the importer..

/Kevin