Opensource DIY clothes dryer

retrolefty:
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.

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

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.

retrolefty:

boelle:
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

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? :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

Constantin:
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.

retrolefty:

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? :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...

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.

boelle:

retrolefty:

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? :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? **

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

The mathematics are quite simple.

  1. For a non-condensing dryer (i.e. one with a flue pipe)
    The hotter the exhaust gas, the more you're heating the exterior vs. heating the clothes.

  2. For a condensing dryer
    The hotter the exhaust gas, the more you have to cool the flue gases before you can extract the latent heat.

Either dryer uses ambient air to its advantage - the condensing type may recirculate air internally but it is also running external air over the condenser HX continuously - otherwise it wouldn't condense. The non-condensing dryer derives a benefit from more ambient dry air being pumped through the machine and hence absorbing some of the moisture at the very low cost of drum rotation and blower use. In either application, the heat is the primary 'cost' of operation. So to the extent that you can maximize the heat being absorbed by the clothes vs. blowing it out to atmosphere (or into the house) you will benefit.

hmm... so if both drum and both airflows are driven by the same motor there is not much point in doing anything advanced...

but if i could adjust both airflows individualy there would be some benefit... ie let the internal flow be slow and the external high so that the internal is cooled as much as possible hence is would condense more..

am i total off?

just been fooling arround with my simple "setup" sketch so now i can update wifi config...

have tried to figure how i could add a single cycle so that i could start it remotely, later i would add local start of the cycle...

a guy made a dishwasher controlled by arduino and its very logic to me how it runs, but how could i do it over wifi?

i can redo the main page no problem with that.. what i would like is at the main page i click a cycle... it should then draw a page that says what cycle its running and sensor values and target vaules... temp reading could be done with a one wire dallas chip and heat control could simply be on/off for now. for moisture sensing i found this http://www.digikey.com/product-detail/en/CHS-GSS/445-2575-ND/931221?cur=USD it puts out 10 mv per % so 100% is 1V and it can be driven from 5V supply

so what i need is pointers on how to make a cycle... i have a mega so there should be enough pins. for now lets just say 1 pin for drum rotation and airflow. another pin for heat control. and 1 pin for moisture sensor and another pin for the dallas chip.

my dryer do reverse the drum direction every now and then for about 5 secs. i guess its to keep the clothes from going in to one big ball.. would like to keep that and guess it requires another pin

my code is taken from here, i have only added "back" links to each page

http://notebook.kulchenko.com/embedded/storing-wifi-configuration-in-eeprom-on-arduino

nobody able to help me stitching the code together?

so i tried to add 2 one wire temp probes... only trouble is figureing out how to display them and in the end make a simple cycle out of it....

i would like to have a /cycle1 page and display the 2 dallas chip temps and maybe one of the analog pins and keep it in that loop until the analog pin has a set value... i was thinking of a while statement so that i could step through the cycle...

ie first step is to heat up and keep temp with simple on/off (might make it more advanced later on)
after temp is reached step forward and target humidity while keeping the temp
next step is to shut off heat and only turn the drum once in a while (cooldown)

after cooldown return to the mainpage...

add on top that if one user starts a cycle and others wants to look in they should be directed to the cycle1 part as long its active

my sketch so far: #include <DHCPLite.h>#include <RedFly.h>#include <EEPROM.h>#include <OneWi - Pastebin.com

the define section now look like this:

#define LEDPIN 13 // LED simulating heating element
#define LEDPIN 14 // LED simulating motor turning drum
#define LEDPIN 15 // LED simulating indicating drum turning reverse (used to distribute clothes)

#define ONE_WIRE_BUS 16 // Data wire from dallas chips
#define humidpin 17 // humidity sensor
#define waterpin 18 // watertank full
#define currentpin 19 // analog voltage input from current clamp
#define airflowpin 20 // analog voltage from airflow sensor

and part where i set if pin is output/input has changed to:

pinMode(13, OUTPUT); // heating element
pinMode(14, OUTPUT); // drum motor
pinMode(15, OUTPUT); // drum reverse

pinMode(16, INPUT); // DS18B20 one wire bus
pinMode(17, INPUT); // humidity sensor
pinMode(18, INPUT); // watertank full
pinMode(19, INPUT); // current clamp
pinMode(20, INPUT); // airflow

damm XD

even a simple thing as jumping from one loop to another is causing trouble... ie if i write /cycle1 after the ip the code should take it to another loop i also call cycle1

the idea is to create a loop that simply displays what cycle is running and status... it should then refresh every x sec's and when done it will/should return it to the main loop

on line 194 i try to jump to the cycle1 loop (line 283)...

but nothing happens... other than that the code works

some able to help me?

made a menu and place where target values can be entered... settings form just there still need to figure how to store settings... in danish thou but you should be able to understand or else just ask:

anybody that can give a hint on how to store a table cell in eeprom?

reading is easy enough, just do do eprom read in to a variable and then set the cell value to that or am i mistaken?

then change whatever cells needed and hit save....

been look at this on/off for weeks but not sure, many examples use for next loop etc and i cant figure it

EDIT: my table starts at line 410 in the above paste bin, what i would like is a SIMPLE example on how to store the cell c1temp