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I would think the single most efficient control algorithm would be to use an internal humidity sensor to tell the controller that the cloths are dry enough now and to cut the heat source (gas or electric) and start the tumble cooling cycle. I believe that there are dryers that have that control option available all ready?

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most work that way...

but what could improve is variable heat source where most dryers operate on a simple on/off and that will cause some overshoot which is a waste of energy.

adding an arduino also allows for custom cycles. one of my fav's will be a cycle that targets on humidity but use lower temps, this will of course result in a longer cycle but will save on the bill. of course you have to judge time used against heat used... why i included a current sensor so that electricity used can be messured...

again its mostly stitching code together that are my biggest issue in this project.
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most work that way...

but what could improve is variable heat source where most dryers operate on a simple on/off and that will cause some overshoot which is a waste of energy.

Why would overshoot/undershoot be a waste of energy. Is not all the heat energy generated directly going into the drying of the material? As long as you are not continuing to send heat into the material that is already 'dry enough' I don't see where the 'waste' is? Too much heat, time to 'dry enough' shortened, too little heat, time to 'dry enough' takes a little longer, no net change on total heating BTU consumed used to reach the it's 'dry enough' setpoint.

adding an arduino also allows for custom cycles. one of my fav's will be a cycle that targets on humidity but use lower temps, this will of course result in a longer cycle but will save on the bill. Why would this save energy consumed, it should take the same amount of total BTUs to remove xx amount of moisture from the material because it's a heat/time product equation? of course you have to judge time used against heat used... why i included a current sensor so that electricity used can be messured...

again its mostly stitching code together that are my biggest issue in this project.
« Last Edit: September 05, 2012, 04:34:29 pm by retrolefty » Logged

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I'm based in Europe and my dryer is a 1 phase unit so it takes no more than 2300Kw all included (also the rating of the fuse in breaker/fuse panel).

I presume you meant 2300W, not kW. Otherwise, you'd likely have to open a new sub-station in your neighborhood.

I'm surprised that the circuits in the EU are limited to 10A for clothes dryers. In the US, we have to run a different kind of wiring (three or four conductor, heavy duty) to dryer outlets, whose plugs can make standard UK plugs blush with envy. I would not rely on a GFCI to protect you. At least for testing purposes I would have a manual fuse and a disconnect switch. But that's me.

I do have the background, been working 1 year as an electrician and do have about 12 courses in electronics. The Schematics are not included... but that not what worries me, i can draw it in a few hours with the dryer taken apart and a multimeter.

Thanks for re-assuring me that you know what you're doing. Having taken a bunch of these (and many other) appliances apart, I suggest you find a copy of the schematics if you can. Perhaps the OEM can send you a copy. It will make your life a lot easier. Let me give you an example: I recently attached a SSR to a toaster oven circuit and had a diode interfere with it. The diode was not obvious because the OEM had included no diagram with the toaster oven.

For the high loads, in fact both the heating element and motor that rotates the drum its my plan to use solid state relays or triac's. I have in mind those kinds that have either screw terminals or spade connectors depinding on what is used in my unit.

My suggestion would be to use a Triac with 0.25" quick connects. The friction fit is almost impervious to the inevitable vibrations of the dryer as it operates.

40A seems a bit overkill compared to that my system is 10A max.. but maybe go for a 20A would be the choice. since my dryer is a condensing type it has 2 airways.. one internal and one that just takes room air and blows it through the condenser, the output from here is barely any hotter than what it takes in and seems a good place for airflow over the heatsink. i agree to not mess with drum rotation, makes no sense to alter it.

Seems reasonable. For the record, I meant not to alter the drum speed. I agree that changing the drum direction is unlikely to have any benefit either. Hard to do, unless you have the right motor in there to start with.

and the idea with  multiple temp sensors is not bad either, at least i know there has to be a certain difference between room temp and the temp in the drum before the condenser operates, the higher difference the faster you are done but also you use more electricity. i know that my dryer has a resetable thermofuse if it gets to hot. i only need to figure how it detects a full filter.

The thermofuse blows if the temperature near the coils gets too hot. That temperature is a function of air flow. Once the air flow is impeded by a clogged filter, the fuse will hence trip. Down by the actual blower motor (which typically sucks the air through the heater, followed by the drum before exhausting it) you should find at least one more thermal switch or sensor for the less expensive models. Once the exhaust air reaches a certain level, the dryer knows that the clothes are almost dry, runs a bit more, and shuts off.

More expensive dryers will attempt to divine clothing wetness through a variety of additional means.
« Last Edit: September 05, 2012, 06:35:22 pm by Constantin » Logged

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I would think the single most efficient control algorithm would be to use an internal humidity sensor to tell the controller that the cloths are dry enough now and to cut the heat source (gas or electric) and start the tumble cooling cycle. I believe that there are dryers that have that control option available all ready?

Every unit I saw did not measure humidity directly. Either capacitive sensors, temperature, etc. I presume fouling has to do with it. The nice aspect of the "bar" sensors typically found in the back wall of dryers is that they cannot foul easily. How accurate they are is another question. However, you can supplement that info with exit temperature info to hopefully not over- or under-dry too much.
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Why would overshoot/undershoot be a waste of energy. Is not all the heat energy generated directly going into the drying of the material? As long as you are not continuing to send heat into the material that is already 'dry enough' I don't see where the 'waste' is? Too much heat, time to 'dry enough' shortened, too little heat, time to 'dry enough' takes a little longer, no net change on total heating BTU consumed used to reach the it's 'dry enough' setpoint.

Allow me to disagree a bit. This is not a closed system. If you control the input into the dryer by monitoring the exhaust temperature, you can limit the excess heat being exhausted to atmosphere (in the case of dryers with flue pipes) or the house (in the case of condensing dryers). You also have to watch that exit temperature for the dryers typically used in the US to eliminate the chance of condensation inside the flue duct, even if you have a stainless duct that has been designed to drain. In a condensing dryer, you presumably want temperatures closer to condensation to help condense the latent heat out.

Additionally, there are benefits to longer drying cycles per the DOE or IEC test procedure. Since the test procedures prescribe a relatively dry room, you can benefit from the "dry" air being sucked through the appliance carrying off moisture without having to heat the air. Heating simply drives off the water faster.

Over-drying results in clothes that are no drier than they could be (i.e. "bone dry" is the limit) but lots of heat being used. In the US, that usually entails the excess heat being vented to atmosphere, in the EU, that eat is "recycled" into the home when using electric condensing dryers. In the wintertime, there is a marginal benefit, in the summertime, it just adds to the heat load of the house. Additionally, over-drying is bad for clothes.
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Additionally, over-drying is bad for clothes.

That we agree on. I'm just saying if you have an accurate sensing method for when the cloths are actually 'dry enough' then worrying about having more precise temperature control, say a thermostat switch Vs a full P&ID controller, I don't see any benefit in the added complexity and expense. And what drying temperature to operate at Vs the 'best' time duration to dry seems to be a pretty constant product (total BTU consumed per drying cycle needed to dry the cloths to the 'dry enough' state) in my thinking.

 The whole waste heat recovery thing is a different additional animal and is not what I was talking about. Certainly any method of heat recover and recycling will pay off because it would allow the 'dry enough' time to happen faster vs using no waste heat recovery/recycling. If there is other external uses for the waste heat instead of recycling via a air intake heat exchanger, then the possible savings are external, but still real and useful, but doesn't effect what control algorithm the dryer should use.

Bottom line I was trying to make is if one can indeed actually measure accurately when the load has reached a 'dry enough' state then that is the key process variable to used in a closed loop control algorithm.

Under drying the cloths load is a failure of control objective, over drying of cloths is needless waste of energy and hard on the cloths, I suspect we can agree on that?

Lefty  
« Last Edit: September 05, 2012, 07:20:23 pm by retrolefty » Logged

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Retrolefty, based on my experience with the DOE test procedure I do not agree with your position. It is not a closed system. So if you can control the flue exit temperature of the drum, you should be able to reduce the amount of energy needed to dry the clothes.  In the beginning of the cycle, you'll be able to run full bore because the clothes are cold and wet. Beyond a certain temperature, the marginal improvement of full heat vs. modulating will become apparent. Whether that justifies the extra expense of a SSR-based PID-enabled control system is a different question.

Similarly, increasing the drying cycle time will likely reduce your need for heat by using "dry" ambient air - for flue-based dryers, the test procedure does not account for the inherent issues in using air from inside the house and then exhausting it. Yet, in real life, that air has to come from somewhere, i.e. it will cause infiltration. Said infiltration is going to impact the home in one way or the other. BTW, there are no 'balanced' flue-based dryers on the market - i.e. all of them source indoor air and exhaust it outdoors.

As for condensing dryers, all of them are based on electric power and are generally less efficient than their non-condensing platforms. The sole exception here being heat pump dryers marketed by Bosch and others in the EU, but not the US (at least, not yet).

I agree with you that measuring dryness of clothes is the best way to ensure good process control, regardless of the control mechanism being used. However, should you find yourself with not enough to do, have a look at the many different ways that people have tried to figure out clothing dryness inside a dryer.

Now a quick suggestion for the OP: Before you rip out the old control system, etc. may I suggest you install all the sensors we talked about and then log the different behaviors of the control system. That gives you a baseline to compare your dryer performance / algorithms to. Just a thought.
« Last Edit: September 05, 2012, 07:52:37 pm by Constantin » Logged

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most work that way...

but what could improve is variable heat source where most dryers operate on a simple on/off and that will cause some overshoot which is a waste of energy.

Why would overshoot/undershoot be a waste of energy. Is not all the heat energy generated directly going into the drying of the material? As long as you are not continuing to send heat into the material that is already 'dry enough' I don't see where the 'waste' is? Too much heat, time to 'dry enough' shortened, too little heat, time to 'dry enough' takes a little longer, no net change on total heating BTU consumed used to reach the it's 'dry enough' setpoint.

adding an arduino also allows for custom cycles. one of my fav's will be a cycle that targets on humidity but use lower temps, this will of course result in a longer cycle but will save on the bill. Why would this save energy consumed, it should take the same amount of total BTUs to remove xx amount of moisture from the material because it's a heat/time product equation? of course you have to judge time used against heat used... why i included a current sensor so that electricity used can be messured...

again its mostly stitching code together that are my biggest issue in this project.

might just be me, but going over a set temp means waste to me, i agree that i will just get the clothes done more quickly, but i like to go as precise as possible
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might just be me, but going over a set temp means waste to me, i agree that i will just get the clothes done more quickly, but i like to go as precise as possible

OK, but the more pertinent question is do you pants care as much as you do?  smiley-wink

 If we have a simple thermostat sensor controller that might have a control hysteresis or +/- 5 degrees Vs a P&ID control with a nice RTD sensor that might give a +/- 1 degree variation in control. Where is the wasted energy to be found if your drying by either a simple timed cycle or a 'it's dry enough sensor'? Recall that drying cloths is not a 'fast' process, takes 30-60mins normally depending on load size I would think. Having the process variable temperature varying +/- 5 degree Vs varying +/- 1 degree centered on the same setpoint temperature is not going to change the batch size drying length or energy usage. I don't think on my electric dryer there is any attempt to control the temperature at all, just straight 220 AC to the heating element. There are over-temp safety cut-off switches, but that is for malfunction or major air flow blockage protection. Such simple dryer like that are simple open loop control, with just the user selecting a drying timing they think it will take. A closed loop control based on a 'it's dry enough' sensor would be a more beneficial method and I believe some dryers have that optional control mode?

Lefty
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As for condensing dryers, all of them are based on electric power and are generally less efficient than their non-condensing platforms. The sole exception here being heat pump dryers marketed by Bosch and others in the EU, but not the US (at least, not yet).

Now a quick suggestion for the OP: Before you rip out the old control system, etc. may I suggest you install all the sensors we talked about and then log the different behaviors of the control system. That gives you a baseline to compare your dryer performance / algorithms to. Just a thought.

I tend to disagree a bit on condensing dryers, they should be a bit more efficient as they do not just dump the heated air to the outside but recirculate the air inside over the condensing unit and back to the drum. outside air/room air then passes over the condensing unit on the other side and cools it down hence the water in the air on the drum side will start to drip off in a container for my machine, others just let the water run out via a small pipe. i have attached a pic of the condensing unit itself, easy to take out as you need to rinse it once a month or every 3 months, i just take mine with me in a shower.

but yeah placing the sensors before ripping the control was also my plan, at least i can mimic the cycles allready there and then change them to the better.


* P1090446.JPG (771.04 KB, 1600x1200 - viewed 33 times.)

* P1090447.JPG (789.88 KB, 1600x1200 - viewed 37 times.)
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might just be me, but going over a set temp means waste to me, i agree that i will just get the clothes done more quickly, but i like to go as precise as possible

OK, but the more pertinent question is do you pants care as much as you do?  smiley-wink

A closed loop control based on a 'it's dry enough' sensor would be a more beneficial method and I believe some dryers have that optional control mode?

Lefty

I think for a short cycle with high heat it would not matter much, but my goal is to lower the temp and run a bit longer since rotating the drum is not the most expensive part.
Also a pid control is not that expensive, all it takes is a zero cross detection chip and a triac... i have most the idea from this page: http://www.over-engineered.com/projects/sous-vide-pid-controller/
I found a board with all the bits here: http://www.inmojo.com/store/inmojo-market/item/digital-ac-dimmer-module/

My dryer is a closed loop or i would say must be since it does not blow the heated air to the outside, so there must be some way it can detect when the air is dry enough... again i think there could be a bit saved by lower temps and longer cycle...
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forgot to say that on my condensing unit the room air is blown from the back side towards the handle and the hot air from the drum passes over the fins and goes back to the drum.
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might just be me, but going over a set temp means waste to me, i agree that i will just get the clothes done more quickly, but i like to go as precise as possible

OK, but the more pertinent question is do you pants care as much as you do?  smiley-wink

A closed loop control based on a 'it's dry enough' sensor would be a more beneficial method and I believe some dryers have that optional control mode?

Lefty

I think for a short cycle with high heat it would not matter much, but my goal is to lower the temp and run a bit longer since rotating the drum is not the most expensive part.
Also a pid control is not that expensive, all it takes is a zero cross detection chip and a triac... i have most the idea from this page: http://www.over-engineered.com/projects/sous-vide-pid-controller/
I found a board with all the bits here: http://www.inmojo.com/store/inmojo-market/item/digital-ac-dimmer-module/

My dryer is a closed loop or i would say must be since it does not blow the heated air to the outside, so there must be some way it can detect when the air is dry enough... again i think there could be a bit saved by lower temps and longer cycle...

Yes and others have stated that opinion also, but I'm still skeptical of that. I'm of the opinion that it takes a certain total BTU consumption to dry a given load of laundry, and you will pay for the same total amount energy, regardless if you run twice as long at half the temperature vs half the time at twice the temp. There must be some fundamental law of thermodynamics that can prove or disprove that. Plus the constant tumbler motor energy consumption kind of adds a bias against using longer runs. Just because some energy saving idea may seem intuitively better, does not in fact mean it is. It should first be able to be proven mathematically, no?  
« Last Edit: September 06, 2012, 02:06:54 am by retrolefty » Logged

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i just took the idea from the crock pot link and also from my dishwasher, the 45 degree cycle takes 2 hours 55 mins and the 70 degree takes 2 hours and 15 mins. i can reduce the time on the 2 by pushing a button called "vario speed" then the times are 1:30 and 1:27, the difference is water used and the speed on the pump the circulate the water. it do cost more since more water used and you need to heat more water.

of course that can not be used as a direct compare but there is a bit of it, lower temp but run longer, 40 mins in difference but the amount of water is the same... so we lower the temp but run 40 mins longer to get the dishes clean. of course there is a point where the math does not add up any more, ie where the longer run is not justified against electricity used to keep the water at 45 degrees.

of course it raise the need for a google search on how to figure the break even point
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