Electronic Relays/Solenoids

[Feetwet]

I have never had much luck with mechanical solenoids, either in marine applications or in aircraft. They always seem to pit and go intermittant after a year or two's use. My RV-4 starter solenoid went out the end of last year, and now the master is intermittently chattering. Has anyone considered or tried the Cole Hersee electronic solenoid as either a master relay or start solenoid? It appears to cost about $112 and handle 85 amps.

[breister]

I researched high-amperage solenoids for my gear retraction system (off subject, but same types of solenoids). They are much more expensive; most are not truly rated for continuous amperage, few are for high voltage DC current, and from what I have come to understand they consume a measurable portion of what they control.

Thus, you will end up losing range (e.g. they act a bit like a resistor). They can also fail, but I don't know how much more or less likely that is.

I would recommend simply having multiply redundant systems (like we do in the airplane world). Many inexpensive redundant components configured in a "system" tend to be more reliable than a single expensive component.

[w1curtis]

Spruce has a Lamar version for $115

http://www.aircraftspruce.com/catalo...uperSwitch.php
http://www.aircraftspruce.com/catalo...ationlamar.pdf

[breister]

Nice - Any idea what the continuous use power drain is compared to a "normal" contactor?

[Feetwet]

Very interesting! The Lamar unit as advertised seems to be able to replace both the master relay and the starter solenoid. When you view the Cole Hersee unit, (Part No. 48785), it looks very different and the most common application seems to be Marine. With all the cooling fins it would seem to be more designed for continuous use. I have e-mailed customer service at Cole Hersee to see if they believe 48785 is a substitute for the 24115 master relay, and the 24021 starter solenoid. I will post the reply if I get one.

The price for both Lamar and Hersee units is about five times that for the mechanical solenoids, but if the eSolenoids truly provide trouble free service for the life of the aircraft, the extra $80 is probably well spent.

[Rick_A]

I came across these electronic solenoids. I don't know anything about them personally.

From a previous thread on this topic: http://relays.tycoelectronics.com/datasheets/ev200.pdf

and this one, that looks like the same device but with a different brand name: http://www.jamestowndistributors.com...olenoid+Switch

[breister]

That partially answers the power question - it lists 1.7 watt "hold power", which equates to only about 0.15 amps at 12 volts. If there are no transmission losses in addition to that (no internal resistance to the power flow) then I'd say these have matured to prime time use.

[Mike S]

Read the specs carefully, the units Rick has linked to appear to be a mechanical unit-----solenoid and contact points.

Not to mention it costs close to $200

Re read the first line of the OP, he is looking for a non mechanical setup, as I read this.

Something solid state. No contact points. Like what William Curtis posted, but the unit in his post is not rated enough amps for a starter.

I am afraid that if a solid state unit exists that will handle starter load, it is going to really scare folks with the price, and possibly the physical size.

[MCA]

We have several of the Lamar units that we are looking at in the lab here. You can buy them in several variations: unidirectional current flow (starter solenoid) or bi-directional current flow (master relay or cross-tie). You can also get positive trigger (starter) or negative (master).

The hold current draw is negligible, whereas mechanical contactors are about 0.7A at 14v.

Now just need to find time to put 'em on my RV...

[Feetwet]

Very Helpful MCA, thanks. It looks like the Lamar superswitch is a good option for my Master relay. I presume a diode isn't necessary, and understand the ground switching, but why is bidirectional necessary for a Master?