Arduino CO2 Sensor Controls PCM Fans in HRV

[NiHaoMike]

Attach a resistor (heater) to the sensor that turns on when it registers a way high so it never sees any condensation.

[kostas]

Uhm, I guess I was wrong about the DHT11 as we used a DHT22, which is more precise.
I attach the code we used with the arduino mega2560, but it may not work properly with the DHT11. It seems that you can easily find it's code on the net, though..
Sorry about the misunderstanding

[AC_Hacker]

Originally Posted by NiHaoMike

Attach a resistor (heater) to the sensor that turns on when it registers a way high so it never sees any condensation.

Have you actually tried this with this sensor?

Is this blue sky brainstorming or do you know from your own experience that this actually is a useful idea?

-AC

[AC_Hacker]

Originally Posted by kostas

Uhm, I guess I was wrong about the DHT11 as we used a DHT22, which is more precise.
I attach the code we used with the arduino mega2560, but it may not work properly with the DHT11. It seems that you can easily find it's code on the net, though..
Sorry about the misunderstanding

Thanks for the update.

I've been thinking how interesting it would be to have temp/humidity sensors at the in-ports and also out-ports of the HRV I'm working on. It would be very useful.

But I have to monitor myself so that I don't fall prey to 'project creep' and continue to add features until nothing gets done.

However, in my thinking & searching, I came across this amazing site that has Arduino add-ons that are useful and affordable and of incredible variety.

Best,

-AC

[NiHaoMike]

Originally Posted by AC_Hacker

Have you actually tried this with this sensor?

Is this blue sky brainstorming or do you know from your own experience that this actually is a useful idea?

-AC

Just a common solution to the problem. Heating up an object makes it less likely for the moisture to condense.

[kostas]

Indeed, I have recently installed a rain sensor for closing my motorized roof windows in case of rain or snow and I discovered that it's heated by a resistor in order to avoid false closings when it's only humid outside...

[AC_Hacker]

Originally Posted by kostas

Indeed, I have recently installed a rain sensor for closing my motorized roof windows in case of rain or snow and I discovered that it's heated by a resistor in order to avoid false closings when it's only humid outside...

Indeed, but you're not expecting accurate, proportional data from your sensor... your sensor's only job is to let you know that point at which rain is imminent and to trigger a window closing event.

It may be that the way I'm using the temperature and humidity sensors is not clear...

I am NOT using them to detect a set-point at which the fan will go on, and when the fan's job has been done, to turn the fan OFF. I am using the continuous stream of data from the sensors to continuously change the duty-cycle of a PWM wave, so for the most part, the fans always will be running. The idea is that if there are very few people in the house, the fans will run slowly, but if there are several, or if bathing or cooking is detected, the fans can ramp up to appropriately meet the demand.

-AC

[AC_Hacker]

The Humidity/Temperature sensors have arrived and they are pretty much what I expected.

A quick search on "Arduino DHT11" took me to an abundance of great resources.

The very first link on that page took me to a tutorial with sample code, DHT11 librarys, and answers to questions I hadn't even thought to ask.

So I plugged the sensor into my proto-board, hooked up three wires, volts, ground and data. A quick look at the sketch told me that the DHT11 data wire was supposed to go to Arduino pin #2, so I found the Teensy pin that corresponded to the Arduino pin.

I copied and saved the libraries to my Arduino folder, as directed in the tutorial.

Then I copied the sketch to the program page, compiled and ran the code un-altered, and the Teensy started burping out data, just like it was supposed to do.

Life is good!

The sketch does lots more than I actually need, so the next step will be to strip out the parts of the code that I don't need, and cautiously merge this code with my previous code.

NOTE: Already, I am seeing that the temperature and humidity readings of this sensor are not as close to the readings of a factory-made humidity & temperature device that I have come to trust. I bought two of these DHT11 sensors, so I'll check out the other one, too. I may even go with some Honeywell units that are a fair bit more expensive.

But, keeping this all in perspective... for regulating the speed of a HRV fan, great accuracy is probably not so very important.

Best,

-AC

[Mikesolar]

What are the specs for the one you bought? I saw a few that looked the same but the min temp on one was 0C and depending on what you want to measure, you might need much colder. I just ordered some good for -40C at about $5 ea.

[AC_Hacker]

Originally Posted by Mikesolar

What are the specs for the one you bought? I saw a few that looked the same but the min temp on one was 0C and depending on what you want to measure, you might need much colder. I just ordered some good for -40C at about $5 ea.

Yeah, the one I have is for a more limited range. Since I want to use in inside the house, the range was not so important.

I think yours uses a different library, but everything else is pretty much the same.

If it's temperature only that you want, I really like the 1-wire sensors. They have a pretty good range of temperatures, and they're accurate.

But I also found some interesting honeywell temperature and humidity sensors that are more expensive, but I'm pretty sure they're more accurate.

I'm gonna continue on with the DHT11, until I see a definite reason to go another direction.

Best,

-AC