Thermostat
From UroWiki
A thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The name is derived from the Greek words thermos (hot) and statos (a standing). The thermostat does this by switching heating or cooling devices on or off in order to maintain the correct temperature. It does this with a thermal probe; when the probe registers too low a temperature, the heat source is activated, and when the target temperature range is reached, the heat source is deactivated again. For devices with a secondary connector, a cooling source (such as a fan) may be activated when the temperature exceeds the maximum allowed. Exact specifications and functions vary by model and type.
Use of a thermostat is highly recommended in any reptile enclosure, as it allows more precise control over the temperature range, especially when you are not present to manually adjust the settings.
Contents |
Step-by-step guide
Disclaimer: this guide assumes basic electronics and DIY knowledge.
This section deals with wiring up an All-purpose Temperature Controller (STC-1000), which is easily available from eBay (such as with a casing or without a casing, or other online electronics retailers). Purchasing one complete with a casing is probably best, unless you intend to mount the panel inside a properly-insulated custom-made casing or electronics enclosure. Other models of digital thermostats may be similar or different, and are outwith the scope of this article. You may also enjoy our article on adding a fan to an enclosure.
General notes: it is important to keep wiring colour systems consistent throughout. This not only makes following your wiring a lot easier, but is also safer and reduces the risk of catastrophic accidents such as electrocution and fire hazard.
Wiring colour systems:
- Live (carrying mains voltage, 110-230VAC):
- brown or
- red
- Neutral:
- blue or
- black
- Ground (unused in this example, but any three-pin cable will have ground on the third pin):
- green/yellow striped
Logical arrangements:
- This simply means using an arrangement that makes sense. For example, all of the input terminals on the STC-1000 have two connectors:
- Live input is connected to the left terminal
- Live (switched) output is connected to the right terminal
- Wires are kept in the right order
- Wires are kept in the correct colour scheme at all times
Mains voltage danger
Warning! This device uses mains voltage which, if wired incorrectly, poses a potential electrocution risk. A qualified electrician was present during the construction of this and similar devices. Should you attempt this project on your own, neither the UroWiki nor the author(s) of this article accept any responsibility for fires, electrocution, or any other types of material damage or personal injuries arising from incompetent wiring. If in doubt, always consult a qualified electrician!
How to wire a digital thermostat
| Although cables can be wired directly into the connectors on the STC-1000, for simplicity of wiring and ease of following the connections, they will be routed via connector blocks. The final decision is up to the end user, although the UroWiki recommends use of this convention.
In this image, the live and neutral wires are extended from the mains input on the STC-1000 to the connector block. A link wire is added to bring live current to the third connector, which will later be connected to provide mains voltage power for the heating source. The black cables are the thermal probe, from which the unit gets its temperature readings. |  |
| Another view of the same, showing the wires feeding into the back of the STC-1000. |  |
| Another view of the same, this time showing the wires feeding from the STC-1000 into the connector block, including the link wire from terminal 1 (live input from mains) to terminal 3 (live input for heating device). |  |
| The black thermal probe wires put aside for the moment, more live wires have been added, bringing a live wire into the heating device connector input terminal, and a live wire from the output terminal. When the heating circuit is activated (i.e., the temperature drops below the pre-programmed minimum level and heating is required), the STC-1000 will close this circuit, allowing the mains voltage to continue its journey to the end of this cable, which in this case ends with an Exo-Terra Sun Glo 100W bulb in a properly-wired ceramic socket. |  |
The external sources are added:
It is important at each stage to make sure that your wires are properly twisted at the ends and secured firmly into their respective connectors. Now is also a good time to double-check that all your connections follow a consistent and logical structure, which will not lead to catastrophic and possibly dangerous failure. Make sure that everything is properly insulated and protected - including yourself - before switching it on! |  |
Alternative cooling setup
| This is an alternative cabling setup for the cooling source. Assuming that you are using a low-voltage circuit (such as for a 12V computer fan), you can seperately wire a fan and power source through the cooling switch. In this example, it will require its own power source, as we will not be using mains voltage directly.
As with the examples above, again we have live (red) and neutral (black) coming from our power source, with the neutral terminating in its own connector and the live passing straight through the switch, and returning to the third connector on the connector block. The link wire is only necessary if you are connecting a second fan (and obviously, you could have as many link wires and connector blocks as you want if you are adding more fans, as long as your power source is designed to safely supply sufficient power). |  |
| In the first picture, the first fan is now added to the live output from the switch, and shares a common neutral with the power source. The second picture shows a second fan added into the circuit, again sharing a common neutral. Remember that these fans will all get their power through the cooling device switch, so they will all turn on and off together. |  |
| This picture shows a second fan connected to the first. Remember that if you want heating or cooling elements to go on or off independently (for example, at different ends of the enclosure), you will need to purchase a second STC-1000 and repeat the steps above. It is also worth pointing out that this low-voltage method is less safe than wiring a mains voltage connector out from this circuit, as DC voltage can arc between microswitches, presenting a possible hazard. |  |
