Heating Element: A Creative Electronics Project
For my Creative Electronics course at the TU/e, we were asked to create a heating system with basic electronic components. So that means, no programming the Arduino, Teensy or Atmel to handle everything. This makes the whole thing a totally new experience and lets us learn a lot more about electronics.
In this course a few basic components were covered, 3 of which were the transistor, OPAMPs and capacitors. These components are quite difficult to handle if you haven’t worked with them, but are very handy when building circuits. If you want to read my report on some assignments and the heating system, just scroll down and click on that download link, but if you want to stick around, that’s fine too.
I will be going over my design process and will show my calculations and thought process. I will go somewhat more indev in things like, specific models of components, differences between these, and what I can add to the system to make it more interesting.
The design fase is quite a long fase, but it can also be done in parts. For example, if we are designing a car, we can design the wheels first, prototype those and so on. Then, would could move on to the engine. The same goes for a lot of other projects, but in the end, it all must work together. So, with designing this is an important aspect (No wonder that there are standards in engineering and science).
Thinking and Drawing
To start building something, I always start with some plain old sitting down and thinking. How do I want to start? What do I want do first? Can I divide this in parts? And so on…
For the heating system there were some resources we could use out of the box, so this was quite nice. One of the things I always do first, was also already made. This is a system diagram or block diagram. Here you can see how the system must function and what parts the system needs.
Here we can clearly see what the project needs and how to connect them. We have the main control system with a OPAMP (the triangle) as the main logic unit and two inputs, being the temperature sensor and the reference setting (user input.). Also a heating element must be connect to heat up a room. Lastly we need a power supply.
A list of parts was already made, but I changed some parts out for price or performance reasons:
- Temperature Sensor – NTC 10 kΩ
- Reference Setting – Potentiometer 10 kΩ
- OPAMP (Comparator) – LM324 Quad OPAMP
- Heating Element – 10 Ω resistor, power rated at 3W
- Transistor – n channel MOSFET STP16NF06
You may have noticed the last part wasn’t on the system sheet, so why use it? Well, the heating element needs to be switched on and we want that the happen electronically. The MOSFET has a gate pin, where we can provide a voltage. When this voltage is higher than the gate threshold voltage, it will activate and current can flow through the other two pins.
Of course every part of the circuit must be thought about and be calculated. I’m not going to bore you with these calculations, as these are quite easy to do if you have done some electronics before. If you do want to see these, you can always download my full report and look at them there.
Now, lets actually look at creating a circuit!
When I start drawing circuits, it starts being a mess at first. A lot of separate parts, making no sense at all. But when I combine them and draw them in one circuit, it starts coming together.
My drawings are getting more neat with the next iteration, but if you look closely it can also be seen, that some parts of the circuit changed entirely, this is because I tested out some parts and it didn’t work and so, I changed that part to work.
Beginning to prototype is always a fun thing to do. When prototyping with electronics, a tool that is definitely necessary is a breadboard. This is a small board were we can easily insert pins and cables to test stuff.
This is an example of such a board. And this example happens to be my prototype of the heating system! If you already know electronics you can easily identify all the different parts and you will scream about my cable management and component placement. Also the NTC is placement nowhere near the heating element, so it wouldn’t work as expected.
Failing and Iterating
That’s why iterating is a good thing. When you fail, you don’t just lie down and cry, but you look at what you did wrong, why it happened, and how to improve and prevent this next time. So, now identifying the problems.
The NTC is too far from the heating element. This way, the NTC will take a long time to sense the heat from the heating element, and the system won’t work that well, if at all.
When is the system on and does it have power? I will make an LED for this just to be sure.
Advancing and additions
With these problems fixed, we can draw a final circuit and make the circuit itself. This time, I’m not going to make the circuit on a breadboard, but solder it onto a PCB or a Printed Circuit Board. Mine isn’t printed, but I have template to work with. The PCB ended up being far too large for this project, but that is something to think about next time. I added a global on and off button just to be sure, as well as a battery pack to make it more mobile.
Finally, I can show the final result and the whole system working. This process didn’t need too many iterations, so that was quite nice. There is still a lot to improve, if I want to make this a real product, but for this project it is fine.
For the full project click on this link! Final Report