moisture sensors

[Cybrvanr]

How do the moisture sensors in modern machines work? In the classic dryers, I belive there were metallic contacts in the drum of the dryer. When damp clothes would contact it, they would conduct electricity, and keep the timer from advancing. Once the clothes dried, they would stop conducting electricity, and the timer motor would then advance.

I looked in my newer compact whirlpool dryer though, and I cannot find any sort of contactors in it that would do this. Is the moisture sensor a hydrometer located in the exhaust port? This sounds like a logical place for it?

 

[DADoES]

My 1970 Maytag, 1991 KitchenAid, 1999 GE/Fisher & Paykel, and 2004 Fisher & Paykel have in-drum contact bars.

 

[SactoTeddyBear]

Re: Whirlpool Compact Dryer:

Hi! Steven, if your WP Compact Dryer runs on 220-Volts it does have the Auto-Dry Temp, with a Moisture Sensor Thermostat in the Exhaust. If it runs on 110-Volts as my Kenmore Model does, they do have the Electronic Moisture Sensors on the Lower Right Rear, just below the "Tear-Drop" Lint Screen. They are the older type Sensors, that are set on actually to me what looks like a sideways Tear-Drop Black Plastic Holder and run along the curve of the Drum Rear.

I hope that this helps you with your inquiry.

Peace and Fun Times with WP/Kenmore Compact Dryers, Steve
SactoTeddyBear...

 

[bobbyderegis]

New moisture sensors are just about the same as they were in the late fifties. A positive and negative electrode in the drum or baffle. As before, if your outlet is not properly grounded, the sensors do not work!
Bobby in Boston

 

[bobbyderegis]

Cybfvanr,
Ususally if the machine uses a timer with the sensor, it is because it is an automatic dry cycle, not a sensor. Automatic dry cycles use the temperature of the air in the drum in conjunction with the thermostat to cycle the timer on and off. True sensors use electricity, not temperature. DADoEs and SactoTeddybear, you both could explain this better. Go Maytag Electronic Control!
Bobby in Boston

 

[toggleswitch]

Yup Bobby boy.

Wet clothes keep the drum temperature down. The timer will not advance with that type of automatic cycle while the heater is *ON* As the clothes dry the heater is energized/on less frequently, at which time the timer advances.

The ONE piece of harware upgraded needed? A double-throw temperature limiting thermostat. (has three wire terminals instead of two).

N.O, (normally open~ temp too low)- heater on
when satisfied (temp at set-point) power to timer.

This costs mannies about $2 (if that) and sold at one time for a HUGE markup. Now I believe our Uncle Sam mandates an auto-cycle for energy reasons.

 

[bobbyderegis]

Correct, Toggles. Gov. reg. mandates at least one automatic cycle. My thoughts are that electronic sensors are so much better at sensing moisture, and fairly cheap, why the hell do they still bother with auto dry? I have the auto dry on my Maytag. Can't wait to find it's match w/ electronic control. How have you been?
Bobby in Boston

 

[the7]

The cons of the moisture sensor are:
1) Dryer sheet could make it malfunction.
2) Small laundry will give a false "dry" signal.
3) Some polyester laundry will also give a false signal.

I am still quite happy about my Kenmore (WP) dryer with Auto-Dry Cycle and still using "dryer sheet" in it without any problem.

 

[bobbyderegis]

I agree that small loads and mixed weight fabrics can give a "false read" to electronic dry controls, but they mess up auto dry controls as well. As for dryer sheets, I would make using them in any dryer a Federal offense.
Bobby in Boston

 

[maytagbear]

I've had both

Thermostat-timer ("Autodry"), and sensor. ("Intellidry".)

Sensors are so much better!

Lawrence/Maytagbear

 

[DADoES]

Thermostat-controlled autodry can also be thrown off-kilter by the machine running in extremes of ambient temperature, either hot or cold. Our 1976 Whirlpool dryer with temp autodry was in the garage. Summer could be 100°F+, which would barely run the heating element on the lowest temp setting, which averaged maybe 115°F. I remember sometimes on a VERY hot day after running a load, residual heat would still have the variable thermostat be cut-out at beyond the lowest marked setting for some time after a load ended. Winter could be less than 40°F which caused a much longer run-time trying to hit the 155°F high temp with a heavy load of towels. True moisture-sensing is much more accurate under those conditions.

I've heard that Speed Queen uses only temperature sensing on all of their new domestic line, at which I'm very surprised. Seems like they surely would have moisture-sensing on mid- and/or top-of-line model.

 

[toggleswitch]

Funny other than Maytag, my stuff comes out wet with the electronic sensors.

But then again the flimsy lacey petticoats and slips should not go in with my chaps (....er denims) and heavyweight flannel shirts.

We'll confuse the poor sensors (not to mention the neighbors).

 

[bobbyderegis]

HAHAHAHAHAHA! Maybe only the Maytags have you figured out, Toggles! LOL
Bobby in Boston

 

[Bearpeter]

Oooohhh! Toggle!

Normally you just make me laugh with your fab wit and funny repartee...
Now your technical expertise makes me go all goohey! What a guy!!!
Joking aside, you definitely know your stuff, Nice to understand what I take for granted. Always wanted to know how these dryers work, having one myself.

Thanks!
Peter

 

[repair-man]

I have had two different sensor-dry dryers. A Maytag from 1999 and a new Kenmore Elite. In both machines I get wet clothes unless I set it to the maximum (more dry) setting. I got better results from my first dryer. A 1984 Maytag auto-dry machine.

Ed

 

[toggleswitch]

Thanks boys and girls and undecided.

See, I'm not JUST a dirty mind.

 

[DADoES]

All with moisture sensor --

My 1991 KitchenAid KEYE-760 required maximum-dry for towels and jeans. Perm Press/casuals did OK at normal-dry. It seems oriented toward just barely reaching the point of dryness.

The 1999 GE/F&P was the opposite. It was oriented toward DRYing the clothes. Things came out acceptably-dry even at the less-dry position. Normal or MORE dry were truly *MORE* dry.

The 2004 F&P seems to be a happy medium -- damp dry, less dry, normal dry, etc. are pretty much on target.

 

[toggleswitch]

Glenn:

Good point BTW, I had forgotten about dryers in non-temperature controlled environments!



So in hot dry climates is there any purpose/advantage to a dryer? .... other than:

1- To tumble-fluff and soften
2- To avoid unsightly clothes-lines
3- To avoid the sun bleaching your darks

Is a clothes-line faster in Phoenix, let's say than a dryer?