Electronics question please.

[Interlude]

Just remembered the MOSFET relay I suggested advises you put a fast recovery schottky diode in series if you have an inductive load (like an autopilot motor!), so you will lose another 0.5 volts or thereabouts. This may apply to the other ss relays/darlingtons/etc.

 

[GHA]

Putting two directly in parallel may not help - they will have (small) differences in "on" resistance, which will result in unequal sharing of current -

Is that read a problem with mos fets having a positive temperature coefficient? If one takes more current it will warm up a bit and self regulate?

 

[tjbrace]

The Garmin AP that I have has a black box that distributes power to the AP units, heading sensor, ram, rudder position sensor, and control display. The black box takes the high power feed to then do its distribution. I think that will have built in protection from the ram pump motor. Maybe.......

 

[lw395]

These can take 16a (subject to temperature) and draw next to nothing -

http://www.st.com/web/en/resource/technical/document/datasheet/CD00002501.pdf

You could parallel up a few in a row....?

http://uk.rs-online.com/web/p/mosfet-transistors/4857901/

P Channel is easier for switching the +ve supply.
80 Amps and 0.018 ohms RDSon is respectable.
There is something to be said for paralleling, as the wiring/connections can be easier with multiple wires/traces?

 

[tjbrace]

http://uk.rs-online.com/web/p/mosfet-transistors/4857901/

P Channel is easier for switching the +ve supply.
80 Amps and 0.018 ohms RDSon is respectable.
There is something to be said for paralleling, as the wiring/connections can be easier with multiple wires/traces?

Thanks for this link. I have read that p channel should be used in the positive side when switching. With this component can I simply replace my relay with it, using the switched feed from the distribution board connected to the gate and the positive feed from the battery connected through the source/ drain terminals. Would it need protecting components too? Eg resistors, diodes etc.