Hi all! Considering this project. Opinions and help needed :)

Discussion in 'The Projects Forum' started by johnyelland1234, Mar 17, 2012.

  1. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
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    Hello all i'm new to the forum but have been reading all of the interesting projects that members have been making.

    I'm based over seas and in the HM forces, when I move back to the UK I plan to buy a large dog house and run. It basically has a run area with a sheltered and enclosed area for my dog to sleep, lie down in or plot against mankind.

    Now, I plan on buying 2 tubular heaters:
    http://www.amazon.co.uk/WHITE-TUBUL...UTF8&coliid=IDZOA87M8HELT&colid=2E2YM1JAY0RNK

    I plan on installing them inside his enclosed area and then fitting a temperature sensor and fire alarm.

    These will go back to a IP66 rated enclosure on the outside of the building, which will have a LED screen and keypad to set the inside temperature. Switches to activate/deactivate the systems and a float sensor on his water bowl which will report that the water is low and top it up.

    There will be a piezo (sp?) buzzer inside the enclosure which will go off on a fire alarm trip or if the system loses power (by backup square battery).

    Now, although this all sounds extravagant and a waste of resources, it's purely a project that when completed will hopefully of taught me about electronics and look pretty cool.

    I've attached a rough sketch of what I hope it to look like:

    [​IMG]


    I already have:

    Good Soldering iron
    Good Multimeter
    Buzzer (12v)
    Square battery connector
    LCD Screen
    3x Switches
    4x Lights
    1x LED Light strip (to illuminate box)
    Plenty of copper plated/fiberglass PCB
    Breadboard
    Lots of jump wires
    Flux pens
    IP66 Rated Enclosure
    Keypad

    Limited knowledge of electronics, I have rewired a motorbike and fixed a couple of things but that is as far as i've been.

    ----------------------

    So, I ask you the knowing community, how 'do-able' is this project and what elements are required? Such as EPROM and chips etc.

    Can anyone give me advice on where to start?

    Your ideas, thoughts and suggestions are greatly appreciated.

    Thanks
    John
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,157
    3,064
    I think this is definitely doable. Me, I'd build a thermostat based on the LM35 sensor and a comparator such as the LM339. The LM35 produces a voltage proportional to temperature, and the comparator can be set to trigger on or off at some voltage. I'd use an old laptop power supply or desktop PSU to power the control system, which would run at, say, 12v DC. I'd use a relay to switch the heaters on and off. The comparator output would switch a MOSFET to energize the relay coils. The LM339 is a quad comparator - and maybe you would find other tasks for the remaining 3. Once you gain familiarity with comparators, you'll think up all kinds of ways to light up indicator lights and so on.

    Take a look at this related project to see some of these ideas in action.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,157
    3,064
    Oops, I missed that you want to have a digital system (LCD readout, keypad programming and such). My suggestion is pure old-school analog. One simple way to go digital would be to get a digital thermostat available at any hardware store for under $20. This would also give you time-of-day and day-of-week programming.
     
  4. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
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    Awesome, I never thought of a laptop charger.

    I'm at work at the moment, but will look into everything you said when I get back in :)
     
  5. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
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    Hi Wayne,

    So alot of those numbers like LM35 etc made no sense to me:) I really am a simpleton.

    I have seen this on dhgate:
    http://www.dhgate.com/220v-digital-...132c6b7b50132e272d2741154.html?recinfo=8,32,6

    Would this be suitable for my setup?

    It's rated at 220V, but obviously mains power in the uk is 240v. Can I still use it or is it going to go pop?

    I have ordered a 12v power supply for this, to power the alarms, piezo buzzer and water bowl system.

    Thanks for pointing me in this direction, it has saved me a fair bit of work and is still a pretty big electronics project for a first one.
     
  6. evilclem

    Member

    Dec 20, 2011
    118
    16
    First and foremost, ensure that the earth wire is well secured to the IP66 enclosure, baseplate and door.

    The digital thermostat you linked to will work fine. 220V and 240V are pretty much the same thing for all intents and purposes. Be very careful however as the relay contact is only rated at 5A (1200W), if you buy the tubular heaters you linked to originally then you'll be fine as they are 180W each. Read the manual carefully before use, the thermostat will likely have options for PID or Hysteresis control, stick with Hysteresis for now, also make sure you set it to heat mode and not refrigeration mode.
     
  7. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
    0
    Evil, thank you very much for your response.

    I've now ordered the controller and a 12v wired smoke detector for the inside of the house.

    There seems to be a couple of 12v sources inside the unit. Would I be able to safely run a wire from one of them to run the remainder of the system?
    (LED strip, LED lightsx2, 2 switches, buzzer and fire alarm?)

    All low current stuff but safety would be paramount.

    I'll revise my plan and put a new sketch up. Thank you very much for the help :)
     
    Last edited: Mar 18, 2012
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I've thought of doing something similar, glad to see someone biting the bullet.

    The heaters do need to be low voltage, as Fido will do things you may not have expected, such as peeing on important electronics.

    Any high voltage devices should be interfaced via low voltage to the dog house. I'm not too sure of the heaters, they look to be high voltage items to me.

    You can buy screw on resistors such as these...

    [​IMG]

    mounting them under a metal plate that serves as a floor to provide a warm bed. They could be feed with 12V or less to keep it safe. There are huge numbers of ways to do this, this is just one suggestion.

    The LM35 is a sensor circuit (a component). From what you've said you want to go off the shelf as much as possible. It will be a bit more expensive (which is actually unusual, as off the shelf is usually cheaper), but if you value the pooches life I would not have high voltage any where near him.
     
  9. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
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    Ok, before I go to work I thought i'd have a play with expressPCB and this is what I have so far:

    [​IMG]

    Now that a controller is doing all of the heating side, this circuit should be pretty simple.

    Basically a 12v source from the controller is soldered to the board to power the other systems. It passes over the top and on the bottom to power a small LED strip for lighting, and a LED light in the bottom right corner to tell me the power is on.

    It then goes passed the LED strip and into 2 switches (as the third is no longer needed).

    Each switch then goes to its own LED and then outputs to whatever system it is. Like the float switch requires a 12v to work, so a 12v output is on the float system to power that. (The float switch will then go straight to the hose pipe activator rather than back to the board).

    The fire alarm and power off alarm is a little more complicated, the fire alarm system outputs 12v to the fire alarm inside the doghouse, then, the fire alarm is outputted back to the box to fire off the internal buzzer/alarm if a fire is detected (with the original fire alarm still activated for added loudness).

    What I need help with (especially the complete noobness of this curcuit system) is that I have a 9v battery that I want to connect to the alarm system, that will activate the same buzzer if the power to the system is cut off.

    I think I need a reverse relay that is off when power is applied and on when it's not, which will then connect the battery to the buzzer and sound the buzzer to tell me the system (and heaters) have lost power.

    Any ideas on how to rig up the 9v battery to the alarm?

    Or even any tips on the board itself?

    This is turning out to be quite a fun project!
    Thanks
    John
     
  10. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
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    Hi Bill thanks for responding, I want to thank you for your excellent thread on making PCB. It was that thread that inspired me to start this project.

    The heaters are IP55 rated which if it's anything like my GPS is waterproof for up to 5 minutes at .5m (or something can't remember).

    They are enclosed units and I originally saw them on ebay from a pet seller, although I can't find them now.

    I was going to buy the cages that go around them and silicone seal any threads or places where he can pee on. I think it's pretty safe.
     
  11. evilclem

    Member

    Dec 20, 2011
    118
    16
    IP55 means that it is dust resistant and resistant to a 6.3mm nozzle water jet. http://en.wikipedia.org/wiki/IP_Code

    You are chasing a normally closed relay for the 9V battery. That is the 12V system power will hold the relay open and when the power is removed the relay will reset to the normally closed position connecting the 9V to the buzzer/warning system through its poles. Just make sure that the coil voltage is 12Vdc and the contact voltage and current ratings are adequate for your buzzer/alarm and that the relay is NOT latching. You really can't go wrong with a standard DPDT relay.
     
  12. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
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    Thanks again Evilclem :)

    Would this be sufficient for a relay?

    http://www.maplin.co.uk/dpdt-1a-miniature-relay-37494

    It will only be powering a buzzer when closed and current passing through it when open will be a 12v fire alarm.

    On the questions part it says it not latching. Is there a easy way to confirm this?
     
  13. evilclem

    Member

    Dec 20, 2011
    118
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    I'd lean towards something like this: http://www.maplin.co.uk/5a-miniature-relay-37515

    Seeing the insides is good for anyone new to electronics as it can easily be seen how they work and what connects to where when power is supplied and removed.

    If it doesn't say latching, then it's likely to be non-latching.
     
  14. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
    0
    Ok so I have now ordered a 12v version of the relay you linked.

    I have the board designed to be wired up like this:

    [​IMG]

    I'm going to build it on my breadboard soon to see if it works.

    But will I need a GND on the board?

    I thought components had to go in circuit loops and no ground was required for DC?

    Also if I do need a ground and have everything + and -, could I use 1 side of the board as + and the other as -?

    Hope i'm not confusing!
    Thanks
    John
     
  15. evilclem

    Member

    Dec 20, 2011
    118
    16
    When making PCB's at work we use the spare space on the board as a ground plane.

    GND and - are the same thing when working with DC. The power has to flow through each component from the positive to the negative (conventionally).

    You may need a resistor in series with your LED's as well to limit their current. I'd recommend at least 520 Ohms for a 12V system.
     
  16. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
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  17. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
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    Actually the resisters are really cheap, I got 100x 560 ohms and 100x 510 ohms. Which one would be best? The 510 ohms?
     
  18. evilclem

    Member

    Dec 20, 2011
    118
    16
    560 ohms will work fine and use a little less power (slightly lower current).
     
  19. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    George's house, abt. 15 cubic feet, kept toasty with 100 W heater- series parallel resistors, but Tucson nights seldom drop below 32 deg F.
     
  20. johnyelland1234

    Thread Starter New Member

    Mar 17, 2012
    11
    0
    Excellent, i've factored them into my PCB design.

    I've been to Tucson (Davis Montham AB) and really enjoyed it, spent 5 weeks there.

    We had our dinner at Risky Business almost everynight!
     
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