Relay w/ Diode and Switch Wiring

Wiring gurus, request your assitance:

I will be installing a "Painless Cirkit Boss 3-Circuit Ignition Hot Fuse Block" from the battery into the center console of my Avalanche.I plan on running an ignition switched wire to a relay so power only goes to my downstream electrical accessories (PS/2,  DVD, Monitors, Power inverter, etc) when the IGN is on position only.I would like to put a switch in this harness so my accessories only receive power when I activate the switch.Where in line do I place the switch?  I assume on the ignition source power supply prior to it connection to the relay?  I think the relay works in that when it receives IGN power it will close the normally open relay allowing power to flow to the downstream accessories.Also, how do I know what rating (amps) switch to use?And would it be a good idea to install a diode along the ignition switch wire to protect the switch and IGN switched wiring?  If so, I assume the diode would go between the relay and the switch?How do I know what rating diode to get?For those of you who have run wiring from your battery through your firewall, where is a good place to drill the firewall?If you havn't guessed, I am a total wiring rookie.I want to use the "Painless Cirkit Boss 3-Circuit Ignition Hot Fuse Block" so I do not draw to much from my factory wiring.I will be powering a 12v DVD player and (2) headrest monitors and a175 watt power inverter which will power a PS/2. Thanks,SpottyJ

Do not use a diode, you probably won't find a large enough one for your situation. Also if you are using a switch to activate the fuse box, Then you will need a relay and this will isolate the ignition from the circuit.Certified Security Specialist

Always check info with a digital multimeter.

I promise to be good.

Tell Darwin I sent you.

I've been sick lately, sorry I won't be on much.

mobilevt wrote: have you thought of using Power Tamers? Check copelandengineering.com under Power Tamer. I have many units left over from a project, they're awesome timer devices that keeps circuts on for a set time after the ignition is shut off. Sean

Thanks for the rply, looks like a cool product.  However, I am not that interested in having my devices run after vehicle is off.  My 03' Chevy Avalanche does have Retained Acesory Power (RAP), and that would provide 20 minutes of power after vehicle is off.

I have already purchasd the circuit boss 3-way IGN fused harness.  Had I not, I may have jump on your idea.

I am stuck on the need, placement of a diode for protection of the IGN switched wire.