Many years ago I bought a kit from smart electronics, it was the 1049 ultrasonic radar kit, which works similar to a car alarm system. After I bought it, it was forgotten in its box for about 10 years until I found it recently. I thought it was a good way to practice soldering after cannibalizing many unfortunate old devices. The smart kit contains all necessary parts and the (labeled) PCB with some very basic instructions. You just have to solder the parts and trim where necessary.---



These are the parts and the pcb of the kit, which as far as I can see from their website it has changed a bit over the years.
The first step is to recognize all the parts (not as easy as it sounds). The most confusing thing is to recognize the resistances, I used the multimeter instead of the color stripes chart, it was much faster.



The soldering was easy, the parts are big and adequately spaced. After the first welds, the soldering became very intuitive and fast.
Unfortunately when I was putting the kit together I hadn't any wire except an old bundle of this thick copper wire so instead of waiting I used that instead (below left). The kit also needs a 9v battery adapter.

The first test showed that all parts were placed correctly and the radar was working! However it has a huge lag and it almost needs constant messing with the trimmers to work correctly.



After replacing the wires and putting the 9v adapter the kit improved significantly. It still needs trimming to work correctly but for its purpose as a proof of concept in soldering I call it a success!



The final touch is the packaging; this little cardboard box holds both the battery and the PCB inside with the sensors placed in the front and the red LED on top.