Bootloader-less Programming Arduino Pro Mini

Recently I was creating a configurable timer circuit based Arduino Pro Mini. The circuit has a momentary push button which user can press to turn ON the device. The device will turn OFF itself once the time is elapsed. On starting, Arduino has to turn on a relay to get permanent connection to power source, so it will get power when user released the push button. One issue I faced was that Arduino takes around 3 seconds to start executing the program because of the presence of the bootloader.

One Channel Relay Module

Here is the schematic and details for creating one channel relay module. It would be capable of driving both DC and AC current when appropriate relay is used. We can connect output pin of most of microcontrollers including Arduino to control it. Components Required 817 Optocoupler 470Ω Resistor - 2 nos. 2N2222 Transistor 1N4148 Diode 5V Relay (SRD-05VDC-SL-C) Schematic One channel relay module schematic