Rotax 912iS Switch Voltage

[PaulSS]

Hi guys,

I put this post on the Rotax Forum but, thus far, no takers, so I thought I'd pop it on here just in case there are any sage-like opinions that I can draw on.

Cheers

In the installation manual the voltage recommendation/requirement for the switches is 28V and various currents. I've had some fancy rocker switches manufactured (I know, I know, far too soon) and they can handle 28V but the LEDs in the switches are rated for 14V. Now, it's not a huge deal to put in a resistor so the LEDs don't burn out but I just wanted to confirm whether 28V is actually flowing through those switches or just 14V. The switches in question are the LANE, BACKUP BATTERY & FUEL PUMP switches. If it's 28V then a resistor it is; if it's 14V then no resistor.

Also, does anyone have any idea of the current that is drawn when the backup battery switch is in use? The circuit diagram has a 30A CB and the switch requirement is 20A. The rocker switches I have can handle 20A but I was just wondering if the CB 'let through' 29A and then that went through the switch (no relay, obviously) then that would not necessarily be a good thing. I've read the forum regarding relays for this switch and I think it would be a good idea if I could avoid using one but that really depends on what the actual current draw is. If it's actually comfortably below 20A then no snags.

Thank you for your time in considering my beginner's questions and I'll no doubt have a million more when I finally get the toy and its power plant.

[neville]

A little electric theory: voltage does not flow. Voltage is a pressure. Electrons flow in the form of current . Excessive current is stopped by fuses or circuit breakers. Excessive current damages components. The amount of current in a circuit depends on the how high the the pressure is and how much resistance is present int the circuit. The voltage rating of a switch refer to the ability of the components in a switch, such as contacts and insulators (which all have a resistance of some value) to withstand the potential current flow produced by a given voltage being applied to the switch. That is, if a switch were rated at 28 volts the installation of the switch in a 50 volt circuit could cause excessive current through the contacts or through the insulation to ground thereby damaging components inside the switch.

The basis of all this is found in OHMS LAW E=IXR or I+E/R or R+E/I, where E is the voltage, I is the current, and R is the resistance.

As current flows through a component heat is generated so the issue is how much heat can the component (which has a given amount of resistance) withstand before it burns up.