Misting system for lizard enclosure - Page 1
Forum section: electronics / projects

author: Legion
author_rank: Frequent Contributor
timestamp: April 06, 2014, 05:19:54 pm
content: I've got an Argentinean Red Tegu. Her environment needs to be kept fairly humid, 70% - 90%. Right now I have manual hand pump sprayers that I use everyday to wet the enclosure. It works, but it isn't very well controlled and you end up with high humidity for a couple hours after spraying but it can drop down to < 20% after a while.I figure a microcontrolled misting system that uses hygrometer sensors to determine when to spray could keep things a little more even and provide a little automation.The uC will be connected to the two sensors and average their values. If the humidity reading drops below a certain value the uC will switch a relay controlling a mains outlet that the misting pump is plugged into causing the misting system to engage. I also thought it'd be useful to have a seven segment display showing the current humidity level.Here's the equipment list:Misting system: MistKing standard pump, 3x Premium double T nozzles, 1/4" tubinguC: Arduino UnoHumidity sensors: Honeywell HIH-8120 HumidIconRelay circuit: Built according to this design from sparkfun:https://www.sparkfun.com/tutorials/1197-Segment Display: Arduino shield from sparkfun -https://www.sparkfun.com/products/11846I've made some progress already. I got the uC talking to the sensors and averaging the values. I also tested the relay circuit and it works. Both of these circuits are on breadboards right now and will have to be transferred to something more permanent.The misting system should arrive this week, so I should be able to test turning it on and off from the uC.My biggest challenge right now is figuring out how to package the sensors. They are really small and come in a SIP with a pin pitch much smaller than the regular 0.1" breadboard standard. You can see a picture of the sensor in this datasheet here:https://dl.dropboxusercontent.com/u/91808950/Honeywell%20HIH8000%20HumidIcon%20Sensor%20Datasheet.pdfWhat I'd like to have is a sensor enclosure as small as possible with an opening for the sensor face to take readings. The circuit board and enclosure will only have the sensor, 2 resistors and a capacitor. It will also need 4 wires to come in for V+, GND, SCL and SDA.It'd be awesome if you guys had some suggestions for the sensor housing and PCB. Below are some pictures of the enclosure and tegu.

author: Niklas
author_rank: Frequent Contributor
timestamp: April 06, 2014, 05:36:44 pm
content: As you seem to know Sparkfun, have a look at this adaptor PCB:https://www.sparkfun.com/products/494

author: SeanB
author_rank: Super Contributor
timestamp: April 06, 2014, 05:39:37 pm
content: You should have ordered the HIH8121 devices, as they have the filter that will allow them to keep working even when misted. A small plastic tube with a gauze cover top and bottom attached near the top of the tank out of the heat from the lights and away from the spray mister will work the best. Place the sensor so that it is vertical and have the tubing vertical so convection will move air through it. Keep it about 10cm from the top of the tank.You will definitely have to average the sensor reading over a long period, like a half hour or so, and operate the pump to give a minimum amount of water so that you do not drown them. If you add in a few extra mains control relays you could also have the lighting and heating done via the sensor temperature value. It might be best to have 2 sensors and average the values and have a warning if they differ by more than 10% for more than 2 averaging cycles.

author: Legion
author_rank: Frequent Contributor
timestamp: April 06, 2014, 05:40:00 pm
content: Quote from: Niklas on April 06, 2014, 05:36:44 pmThanks, but I think you're looking at the wrong sensor in the datasheet. I have the 4-pin SIP, not the 8-pin DIP.

author: Legion
author_rank: Frequent Contributor
timestamp: April 06, 2014, 05:47:02 pm
content: Quote from: SeanB on April 06, 2014, 05:39:37 pmIf you're saying what I think you're saying, we're on the same page. A small tube over the sensor face should prevent errant water droplets from hitting it. I was also going to have the nozzles medium high up, angled down. I have to be careful that no water directly hits the heating lamps, otherwise I could have a mess of shattered glass.I noticed the filter on the 8121 only after I purchased the 8120's. At $20 each I'm going to keep the unfiltered for now. If it proves impossible to keep the sensor from being hit directly I guess I'll do the upgrade.Temperature and lights already sit at a proper equilibrium and are controlled by a timer. For now I'm going to leave them alone.

author: SeanB
author_rank: Super Contributor
timestamp: April 06, 2014, 05:51:15 pm
content: Just use half the pins, and it will then fit as an adaptor board. Solder it to the board and it then can be used to connect the wiring and the added components. You can place the capacitor there, and add the pull up resistors on the control board, no need to have them at the sensor end. Use shielded cable to connect the sensor, Cat5 cable works well.

author: calexanian
author_rank: Super Contributor
timestamp: April 07, 2014, 02:45:19 am
content: Hydroponic and greenhouse controllers will do everything you need. I would think you could readily find something.

author: Legion
author_rank: Frequent Contributor
timestamp: April 07, 2014, 03:29:41 am
content: Quote from: calexanian on April 07, 2014, 02:45:19 amTrue, but then I wouldn't learn anything.

author: made2hack
author_rank: Frequent Contributor
timestamp: April 07, 2014, 05:10:16 pm
content: What about ultra sonic foggers? They are used extensively in thehydroponicagriculture industry?What happens is that instead of a fine mist, ultra micro particles of water are created, like fog. Thus, the humidity is much better maintained, in that the water is always suspended in a way.I don't know anything about lizards so I don't know whether this might affect the tegu, but it is apparently far superior to misting.I meant to say in aeroponics.

author: pickle9000
author_rank: Super Contributor
timestamp: April 07, 2014, 05:24:43 pm
content: - The ultrasonics could bother the lizard.- I'd probably pot the assembly an not use a box. The pcb can be extended and mounting holes put on it.- If you do use a box and because this is a hobby paraffin wax used for canning could be used as a potting compound and you can remove it without much effort.

author: Legion
author_rank: Frequent Contributor
timestamp: April 07, 2014, 06:48:12 pm
content: Quote from: pickle9000 on April 07, 2014, 05:24:43 pmI've heard of potting but I don't really understand it's purpose. Can you explain what it would do in the context of this project?

author: poorchava
author_rank: Super Contributor
timestamp: April 08, 2014, 08:04:36 am
content: However you mount the sensor to the pcb, and wires, drown it in something water resistant like silicon, epoxy, parafine etc, leaving opening only for the sensor area. This will prevent moisture from damaging sensor leads and other electronic parts on the pcb.

author: Legion
author_rank: Frequent Contributor
timestamp: April 09, 2014, 03:30:13 am
content: Got the 7 segment display working. Also soldered together the relay circuit.

author: jeremy
author_rank: Super Contributor
timestamp: April 09, 2014, 05:30:16 am
content: nice lizard!I perhaps wouldn't even bother with a PCB. Just get a 220nF 0805 SMD resistor and pop it between pins one and two. Then just run some wire to each of the pins, solder it on and gloop the whole thing up with hot glue except for the sensing hole. Where I live is 70-90% humidity pretty much all the time and hot glue seems to be fine. You can put the pullup resistors on the other end of the cable at the micro assuming the cable is not too long. How long are the wires that connect your sensor to the micro going to be? You may have issues with bus capacitance.

author: pickle9000
author_rank: Super Contributor
timestamp: April 09, 2014, 06:25:10 am
content: Quote from: Legion on April 07, 2014, 06:48:12 pmIn this case potting is a way of waterproofing, conformal coatings are also used for this purpose.The environment you are putting the sensor in is harsh. You could use a waterproof box seal joints and such but that is expensive. Paraffin, in this case the type used for canning will do a good job weatherproofing the sensor.The housing for the sensor could be as simple as a screw cap off a pop bottle. Drill a hole in the back connect the wires up place the sensor, cork the tube and make sure to uncork before use. If you don't cork / protect the sensor the potting will ruin it. Melt a bit of wax (don't use a microwave) and fill up the cap, allow to set and your done.Things to be aware of, make sure you don't trap moisture or any corrosive materials on the surface of the pcb. Clean and dry the pcb before potting. Test your board before potting.You will need a good quality wire to attach your sensor. If you have any old mice the wire from one will work well. Keep the wire as short as possible. If you are using led or florescent lighting that can completely screw up the signal. The wires running to the relay board can be long so consider that.You may want to have a look at a gas sensor, maybe you could detect the level of methane. That could be an indication of how dirty it is. A simple LDR (light detector) could be used to warn you if the light didn't come on when expected.

author: pickle9000
author_rank: Super Contributor
timestamp: April 09, 2014, 06:28:55 am
content: Here is a gas sensor to look at.http://www.ebay.ca/itm/1X-MQ-4-Methane-Gas-Sensor-Natural-Coal-Co-methane-detector-module-for-Arduino-/171179611149?pt=LH_DefaultDomain_0&hash=item27db19940d

author: Legion
author_rank: Frequent Contributor
timestamp: May 12, 2014, 12:23:43 am
content: Been a while since the last update. Unfortunately, my bearded dragon passed away April 10th. Kinda took the wind outta my sails for a while and I didn't make any progress.Anyway, finished up the sensors today and rigged up a test to make sure the uC could read them. Seems to work. The relay controlled outlet isn't working though. The relay works fine, but the GFCI outlet always has the fault light on. It won't reset while the power is off, but I'm not sure I want to touch it live. The outlet isn't housed and it'd be real easy to brush up against 120V.

author: echen1024
author_rank: Super Contributor
timestamp: May 12, 2014, 02:38:40 am
content: Have you considered an SSR like the sharp 216:http://www.digikey.com/product-detail/en/S216S02F/425-2414-ND/720364

author: rexxar
author_rank: Frequent Contributor
timestamp: May 12, 2014, 03:51:15 am
content: Quote from: echen1024 on May 12, 2014, 02:38:40 amMechanical relays are probably not the reason the GFCI is showing a fault.Are you sure you've got your mains wired up correctly? You may want to check your wall outlet just in case the wiring there is messed up. If you put your multimeter between hot (the small slot) and ground, you should see 120V, and if you put it between neutral and ground, you should see close to 0.

author: echen1024
author_rank: Super Contributor
timestamp: May 12, 2014, 04:38:50 am
content: Quote from: rexxar on May 12, 2014, 03:51:15 amI understand. I just stated that it might make more sense from a reliability standpoint to use a SSR.

author: Legion
author_rank: Frequent Contributor
timestamp: May 21, 2014, 02:06:50 am
content: I got the GFCI outlet working. Hadn't wired it quite correctly the first time. Working fine now though. At this point pretty much everything is done. Just have to wait for a friend of mine to build the enclosures.