i. How to make a self-powered protoboard with a microcontroller tester?

Protoboard is commonly used to test new ideas and create innovative IC circuits. Many protoboards have their own power supplies. Any high frequency digital circuit like a microcontroller requires high power connections. Though the average power consumption is small, the chips may still require a lot of instant power when they are fast changing logical states. This produces electrical current spikes. It is possible to mitigate them by using a large capacitor with 10,000 µF or more and some small capacitors at each chip. However, power lines must also be able to instantly carry enough current from the capacitor to the protoboard. High power at low voltage spells high current, so it is not a bad idea to use 10 A or more power lines from a 230 V~ power cord to deliver power from the large capacitor to protoboard contacts. It is also important not to use too long wires to connect the chips to the power contacts, because thinner wires have much less conductivity than ticker ones.

The next step is to integrate a microcontroller IC circuit tester (see Custom projects section for ideas on how to make one), or to use an external basic microcontroller circuit. Though PIC18F2xJ50 microcontrollers typically operate on 3.3 V (or at most 3.6 V) and most of the digital ICs use 5 V, they still have a number of up to 5.5 V capable and TTL compatible digital inputs. All the outputs are nevertheless TTL compatible. The only concern is about the other inputs that allow only up to 3.3 V (or up to the power supply voltage). You can use 2:3 voltage dividers (see subsection 3.a. on how to make a voltage divider), or a microcontroller from the PIC18 family that is designed to work on 5 V, like PIC18F2550. However, you should take into account that more and more ICs are working on lover voltage and it might not be a bad idea to integrate a 3.3 V microcontroller anyway. The advantage of PIC18FxxJxx microcontrollers is also almost twice as large SRAM and the maximum of 64 kB of flash RAM, which give you much more programming options.