The honorable relay vs technology

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
User avatar
Lenp
Posts: 1371
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

The honorable relay vs technology

Post by Lenp » Tue Jul 02, 2019 8:05 pm

We have a console dehumidifier in the basement of our house. We also have two new cats...! Their litter box is in the basement. The cat's don't like, and are scared of, the dehumidifier. ....Are you getting the picture yet?

To keep peace it was decided to let the humidifier run all day, since cats tend to sleep most of the day time, and around midnight shut the dehumidifier off for several hours to give them, and us, a much needed break.

So since nobody remembers things like turning stuff on and off, a timer was to be the answer. The dehumidifier does have a timer but it only offers a delay start or timed run time but does not cycle.

An external timer was connected to the power and here comes the technology part... It didn't work. Oh the dehumidifier came on, it's internal computer initialized and then it went to sleep, waiting for a finger push on the on/off button. Holding the button down while powering it up did nothing different.

The solution was to box up a line voltage relay to be operated by the timer and then connect it's contacts to the keyboard switch in the dehumidifier. A pound of screws and half the tools I own later the PCB was out, the wires were soldered, and the out of warranty unit was reassembled.

Since the on/off switch needs to be cycled I set the timer to go on at 12:00AM then off at 12:01 then on again at 06:00 AM and off at 06:01. So, the relay is energized twice a day for one minute each time. Understand that the switch is momentary switch, press on-press off so every press alternates the run/stop. The external timer doesn't know, or does it care a whit , if the dehumidifier is running or not, it just makes and breaks it's relay contacts twice a day.

So, unless someone operates the power switch on the dehumidifier all should be well. If they do, then the timer won't know it, the on/off times will be reversed, and the cats will probably have a really bad day!
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
Joseph
Posts: 653
Joined: Mon Dec 10, 2001 1:01 am
Location: USA,World
Contact:

Re: The honorable relay vs technology

Post by Joseph » Wed Jul 03, 2019 7:44 am

Oh that was a bummer how only cycling the power to the unit couldn't turn it on and off. I'm glad the ones I have can be turned on/off remotely by means of the AC going to the power cord.

User avatar
haklesup
Posts: 2934
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: The honorable relay vs technology

Post by haklesup » Mon Jul 08, 2019 1:00 pm

At least you got it working. You probably could have rigged a 555 timer and a wall wart to press the button soon after power up since the button was probably looking for a rising or falling edge rather than a fixed voltage level. A capacitor coupling interface to the switch may have been enough to disturb the button pulse and cause it to detect a press and may not have had to go through the trouble of paralleling the power button contacts with a secondary switch. If the button is capacitively coupled, then the 555 output to a pad of aluminum foil might be enough

User avatar
Lenp
Posts: 1371
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: The honorable relay vs technology

Post by Lenp » Mon Jul 08, 2019 3:38 pm

Update...
The dehumidifier takes about 10 seconds after power up to initialize then it goes to into standby. During that time no button input is accepted.
Then the button input will turn it on, but, if the button is depressed too long, it looks like a failure, or stuck button, and it it shuts down again...Bummer, since It looks like the timing is about 1 minute and that's what the external timer does so its operation has been hit or miss!

So now it's game on again and three attacks are being considered!

First...
I'll just plug the dehumidifier into the normal outlet and add a relay controlled by the timer, to turn off the compressor and fan, leaving the smart CPU to believe it is really doing something useful. Unless it has smarter-than-me diagnostics then that should work.

Or...
If it is too smart, I'll plug the dehumidifier into the timer, as would be conventional, but, inside the dehumidifier, powered from the unit's power, I'll use a micro, with a wait loop starting at power up to allow enough time for the initialization period. Then I'll fire a single one or two second pulse to an opto-isolator to turn it on. Turning it off will be the job of the external timer since it controls the power. A bonus is that this will also serve to auto-start the unit after a power failure or glitch, which has happened, and adding a switch makes it a 'user option'.

And last
Sell the cats to a Chinese buffet !!!

(I may have these out of logical order for some people :smile: )

I SHALL PREVAIL !
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
haklesup
Posts: 2934
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: The honorable relay vs technology

Post by haklesup » Mon Jul 08, 2019 5:29 pm

Here are a couple things to think about

Humidity controller you can outright replace the one in the dehumidifier
https://www.omega.com/en-us/control-and ... /RHCN-7002



Humidity and temperature controlled power strip:
https://www.amazon.com/Inkbird-Temperat ... 4092512877

User avatar
Lenp
Posts: 1371
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: The honorable relay vs technology

Post by Lenp » Mon Jul 08, 2019 5:37 pm

There is absolutely nothing wrong with the humidifier's controls. It is all about the time of day that it runs!
And with a controlled power strip, as said previously, the unit still would not start!

Good shot though!
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
haklesup
Posts: 2934
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: The honorable relay vs technology

Post by haklesup » Tue Jul 09, 2019 11:11 am

I understand that the OEM controls are working correctly but in this time is money world, perhaps replacing the controls with one with specs that fit is more cost effective than reverse engineering, designing, procuring, building, testing, installing and hoping (OTOH, I do understand how much fun those steps can be and why the long road is one I would choose). I'm not trying to change your design, I'm just commenting on alternate solutions.

Your uController solution is likely to work as long as you can parallel the button switch easily enough, it's equivalent to logic and a timer like the 555 but with perhaps lower parts count and operating voltage and more configurability, now you can integrate the clock directly if you wanted. I think you have a different implementation in mind but if I were going to program a uController I would simply leave it plugged in and try to operate the buttons using the micro IO pins and a macro.

User avatar
Joseph
Posts: 653
Joined: Mon Dec 10, 2001 1:01 am
Location: USA,World
Contact:

Re: The honorable relay vs technology

Post by Joseph » Tue Jul 09, 2019 8:26 pm

I control the compressor of my window A/C externally to get better results than stock performance. But I have to attend to it or the evaporator will ice up. Once I fell asleep and the ice on the evaporator got thick and stopped the fan. It was straining and overheating when I woke up.

User avatar
Lenp
Posts: 1371
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: The honorable relay vs technology

Post by Lenp » Wed Jul 10, 2019 6:31 am

Regarding replacing the intetnal controls, there is more than simple on/off based on humidiity.
Some items the units processor handles are humidity monitoring, ambient temperature monitoring, fan speeds, defrost control, internal drain pump control,, full collection bin shutoff.....
Not a two wire swap out.
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

Post Reply

Who is online

Users browsing this forum: No registered users and 18 guests