Change wordpress default avatar with custom plugin

I’ve used my own custom plugin for custom functions and I’m trying to change the default WordPress avatar to my own custom avatar. My plugin name is “ACh-Toolkit”. I used the following functions but none worked! function ach_avatar( $avatar_defaults ) { $avatar = get_option(‘avatar_default’); $new_avatar_url = plugins_url() . ‘/ACh-Toolkit/images/avatar.png’; if( $avatar != $new_avatar_url ) {…