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PostPosted: 31 Aug 2012, 19:43
by aris

This is the arduino based airflow controller so far.

So I have an Arduino Nano on a mini-breadboard, controlling an external temperature/humidity sensor, a relay (to switch the fan on), an IR proximity sensor (to detect when the UDS lid comes off), the Maveric ET-73 pit probe, and a bluetooth transmitter/receiver which is transmitting all the data to the Android tablet you see in the back. This is all being powered by two 18650 2400MaH lithium ion batteries - these are 3.7v each. I'm hoping this will last for 12-18 hours - if not i'll double up with 4 of these, or look into some power saving techniques on the arduino by putting the processor to sleep when it is not being used.

At the moment the probe is giving some odd readings - i'm guessing because it is not hot enough, it is outside its range and giving these spurious readings. If so, i'll have to take care of that in the code.

Re: UDSflow

PostPosted: 31 Aug 2012, 19:58
by BBQFanatic
Looks like a labour of love that!

Re: UDSflow

PostPosted: 31 Aug 2012, 20:15
by aris
Certainly is fun.

As i'm busy seasoning my UDS - and there were some coals going, I thought i'd take it out and test it. I figured out why i was getting spurious readings from the probe. The ET-73 2.5mm jacks are a few mm longer than a regular audio jack - and the sockets I got were presumably designed for audio. Pulling the jacks out a few mm sorted the problem - saw my probe go to around 400F when inside the UDS.

Now that it is back inside, it is slowly coming down. This probe isn't exactly a Thermapen when it comes to instant readings - but that is fine for the job it is doing.

Might glue or solder a small washer to the jack so that it never goes in too far. A spurious or incorrect reading would be disastrous!

Re: UDSflow

PostPosted: 05 Sep 2012, 14:51
by aris
Did a test (indoors) and the unit ran for 30 hours on one charge. I'm using two 18650 rechargable Lithium Ion batteries in series. These batteries are 2400mAh @ 3.7v - so a total of 7.4v @ 4800mAh. 30 hours should be adequate for a good smoke. This included bluetooth transmission to an android tablet, and switching the relay on and off. The fan has its own power supply - 4 AA batteries. The relay just switches this fan on and off.

After looking at the PID code, I decided against it. I may add it in later, but for now it just looked too complicated and there were just too many input variables affect it. I'm going for a pure thermostat model. If it is below a certain temperature, blow, if not, don't.

In theory I could add 5 food temperature sensors to this unit plus another for the pit itself - making 6 in total. At the moment i'm working with one for the pit and one for the food.

Re: UDSflow

PostPosted: 05 Sep 2012, 14:55
by derekmiller
Hi Aris.
If they are in series then you will have 7.4v @2400mAh. The voltage will double but the current will remain the same.

Re: UDSflow

PostPosted: 05 Sep 2012, 17:20
by aris
Quite right! I'm not an EE and was not thinking straight :-)

Re: UDSflow

PostPosted: 27 Sep 2012, 16:59
by aris
In case you were wondering. Progress has been slow due to other priorities - but it's in a box now.


Basically an Arduino Nano, with a sensor shield to make things a bit easer while testing and plugging things in/out.

Bluetooth module

Humidity/temperature module (the blue thing on the outside)

Two sockets for a pit and food probe - with plenty of scope to add more if needed (about 6 or 7 I should imagine)

And a relay to switch a fan on/off.

Re: UDSflow

PostPosted: 27 Sep 2012, 18:06
by Toby
Looks Smart!

Re: UDSflow

PostPosted: 27 Sep 2012, 18:44
by aris
Thanks - with the cover on it just looks like a box with some connections though :-)

Now onto the UDS itself - if the weather cooperates, i'll hopefully get a bunch done this weekend.

Re: UDSflow

PostPosted: 28 Sep 2012, 05:29
by keith157
You could always go the McClaren route and make a new top of clear acrylic to show off the innards. Great work