Just two quick questions for people with more electrical knowledge than me: When wiring up a solenoid/relay to a solid-state switch, does it matter what diode you use to prevent a flyback spike? Does the end with the line go to + or ground? Thanks!
Here's a link ot the Wikipedia article on flyback diodes, also called a freewheeling diode. There is a simple example circuit image given in the article. Your solenoid is the inductor. The diode is placed with the cathode (the side with the line) is on the positive side of the solenoid, and the anode is on the negative side. This can be called antiparallel. When the solenoid is energized, the cathode feels a more positive voltage than the anode, which feels a more negative voltage, thus the diode is reverse biased and does not conduct. When the solid state switch opens, the inductor opposes a change in current flow and acts as a voltage source. This inductive kick will forward bias the diode, which is now conductive and completes a path for current to flow. The current freewheels through the solenoid and diode rather than damage the solid state switch. So in answer to your question, the cathode (marked with a thin band or bar) goes on the positive side of the solenoid. The anode goes on the negative side of the solenoid. Don't forget to take a look at the ratings of the diode you're going to use (at least a glance). Compare the current capacity to the current of the solenoid. Also look at the reverse breakdown voltage, although I doubt a boat's battery will be much concern there.
Thanks Gascan! The Bitondo brothers always come through it seems The solenoid is rated at 1 watt, or 0.151515A at 6V, so it should be pretty easy for me to find an acceptable unit...
Please note that some recommend placing the diode as close to the load as possible. Engineers I have talked to indicated that while this may be a "best practices" thought, it is not really necessary. I note that Pololu and some other manufacturers mount the flyback diodes on the boards themselves, making hookups easier and perhaps a bit more fool proof. Cheers,
