- Finalize your Digital Thermometer Circuit Schematics
You may need a digital thermometer for domestic, commercial, or industrial use. If you are designing its circuit schematics for industrial purposes, then you may need high-temperature tolerance. You may use a microcontroller such as ATmega16 MCU to measure temperature as high as 1024°C.
You may also need to use thermocouples for detecting high temperatures in your digital thermometer. The most common thermocouple is k-type. You may already be using it as it is reliable, accurate, and inexpensive. Moreover, you should also use ICs, such as the MAX6675 IC. It has inherited cold-junction compensation and will convert the K-type signal into digital form.
In digital thermometers, cold-junction compensation offsets the missing thermoelectric voltage because the instrument is cold thermocouple end is not (0°C/32°F). The MAX6675 IC will give you digital signals with a precision of 0.25°C. For getting the display, you may use seven-segment screens. For domestic use, you may use thermistors for the digital thermometers.
2. Make a PCB layout of Digital Thermometer.
Okay, so once you have finalized the circuit schematic and made it in your favourite software, you are all set to begin designing the PCB layout of a digital thermometer. The schema serves as a model for trace layout and components placement on the PCB.
Furthermore, the software for PCB design will import all footprints, wires, and parts into a PCB format, making the design process more efficient.
You should ensure that each schematic symbol in a digital thermometer must associate with a PCB footprint. The PCB footprint defines the physical dimensions of parts and positioning of the through-holes or copper pads. After this, you will start routing the wires of your designed digital thermometer. You can choose auto-routing or do it manually.
Once you complete all the routing, the labelling of the parts or symbols is a good idea. The tags will move to the PCB layout and finally get displayed on the completed PCB. Moreover, you may organize components in every portion of the digital thermometer PCB. It will certify that the conduction traces are small. Lengthy traces can accumulate substantial concentrations of electromagnetic radiation that can cause noise and interference.
3. Etch your PCB
You can use a laser printer to take a print out of digital thermometer PCB on A4 glossy or photo paper. You must take the mirror print out to ensure that it is on the bright side of the article. Also, you must select the black colour of output in both PCB design and printer settings.
After that, cut your copper PCB sheet for the digital thermometer. You may use a cutter or a hacksaw according to PCB layout dimensions. Use abrasive sponge scrubs or steel wool to rub the copper on the PCB. It will remove any photoresist and oxide layer present on the PCB. Next, you will transfer the digital thermometer printed layout to the PCB from the glossy paper.
At this point, it is crucial to keep the board and printout in correct alignment. You may use a tape to keep them in the right position. Finally, you will use an iron to transfer the digital thermometer PCB layout printout to the copper sheet. You will place and press the hot iron on the back of the glossy paper for about 5 to 15 minutes. The heat will transfer the ink to the PCB from the glossy paper.
4. Drill Vias Into your PCB Sheet of Digital Thermometer
You may have used vias while designing your digital thermometer PCB. These are paths that allow the electrical signal to move between different circuit layers. Being a beginner or if you are designing PCBs at home, you may be using through-hole vias. If you have designed buried or blind vias, you may need to contact a PCB manufacturer for drilling purposes.
You cannot drill multiple vias at home. PCB manufacturers have specialized automated drilling machines for such purposes. You will notice that there is an option to export a drill file in all PCB layout software. You need to produce that drill file, and it will contain all the holes specifications for final PCB production.
If you wish to do drilling, there is no unique trick. However, you must obey rules for maximum aspect ratio, minimum diameter, and adjacency of holes. You will get maximum aspect ratio dividing PCB thickness by width of the tunnel. And, adjacency is the minimum permissible distance from hole edge to the closest adjacent hole.