Humidor control with self-developed HumiCon-Shield

[AlexOk]

Since 2 years I have been running my humidor cabinet with a self-developed Arduino based humidifier. And I'm very happy with it. But for some time already annoyed me that the used Relay Shield clacks minimal and the flying wired Protoshield, although you can not see, looked like a permanent provisional arrangement.

The resulting solution is a self-developed and professionally produced control board, which combines both Shields and works with electronic transistors instead of mechanical relays. In order to have more options for the future, the circuit was designed somewhat universally.

The photo was taken from my cigar-blog.

Here are the new main features:

• 12V input voltage
• Power supply for all 5V Arduino models (Uno, Leonardo, Mega, Yun)
• Up to 4 independently readable hygrometer
• Up to 4 independently controllable fans (convection and/or humidifier)
• Display via I²C bus connectable

The specific setup for my humidor is:

• 2 LED-stripes for lighing
• 1 self-monitoring hygrometer (consisting of 3 hygrometer type AM2303)
• 1 humidifier
• 1 convection fan
• Display 2x16

The photo was taken from my cigar-blog.

The accompanying blog articles:

• April 28, 2013: New Humidor with "HumidorControl F"
• May 17, 2015: Humidor control with HumiCon-Shield

And if the question comes up: I do not sell these shields.

Cheers

Don

[PigFish]

Bravo mate. Making cigar keeping better is a passion! Cheers and thanks for sharing. -the Pig

[jimsta10]

You must be impressed as I am Piggy...

Hey Don,

would love to see this in action. Im always keen on new technology in action.

Cheers

[AlexOk]

Hi Mate,

the problem with electronics in action is, that you actually see...

...nothing.

It does not blink, it is not noisy, it just works fine and quietly. And filming a running fan is rather pointless.

Cheers!

[PigFish]

Do you run AC or DC fans?

I personally prefer mechanical relays myself. I have used a number of different SSRs and the only relays that have ever failed in one of my systems were in fact SSRs. Additionally, SSRs create quite a bit of heat and should be attached to a heat sink as well as back EMF protected or snubbed in inductive DC circuits. I found that I spent more time trying to protect an expensive SSR than anything else and finally quit using them.

While the audible 'click' of mechanical relays can be somewhat annoying, I have found the cost, availability and lack of buffering requirement in DC applications to be a significant benefit. I have 100s of dollars of the damn SSRs around the shop, collecting dust in some corner somewhere. This is a case where I have chosen historical reliability to the newer technology.

I typically run a well overrated relay to run my coolers fans etc. (significant overkill). I can sell these quite reasonably as a part of a system, and they last forever, don't need a heat sink and will clip to a DIN rail... They take up less than half the space of an SSR rated at 25% their amperage. Sometimes the tried and true, the older technology is the best option (at least for me).

I will be curious as to what kind of mean time to failure you get on the SSRs that you use and what kind of loads you are putting on them. With small resistive loads they could last for a very long time, but I would be careful with inductive, DC loads on them.

Cheers! -Piggy

[AlexOk]

I work exclusively with low voltage DC. 12V in maximum. The fans are normal, speed-controlled PC fans. Not the cheapest ones, but quite normal.

So far I have also used mostly mechanical relays. However, I find SSDs as something "elegant" as an archaic mechanism. Although I also appreciate the historical reliability.

To protect the SSRs I oversized them and use additional flyback diodes. The cooling is also not necessary since the SSRs remain cold even without heatsinks. But if the heatsinks are there, they are also screwed on...

All in all, I hope that the SSRs are made to last. However, at least long enough. I'm not an electrician, therefore I am a bit proud that I made it at all.

How it behaves with the inductive DC-loads due to the fans in future, I will see. I hope the best.

Cheers!

[PigFish]

Looks like a great project mate. Thanks for sharing! -R