Volume 1, Issue 2, February 2015 - Page 16

16

February, 2015

For my application I use low voltage Category 5 (CAT 5)communications cable (twisted pairs). One cable contains 4 pairs of wires in a neat and tidy bundle. I ran multiple cables throughout my boat to provide me with plenty of options.

The wires are easily spliced together using a plastic device called a 3M Scotchlok that are available at home improvement stores like Home Depot, or the wires can be soldered together.

A momentary switch works only when pressure is applied. It will

stop and return to an inactive

position when pressure is removed. It is important when using an actuator that power is removed when the actuator reaches its limits (either extended or retracted), or it will overheat the actuator’s motor and possibly break internal components. Look for actuators with built in limit switches to prevent this from happening.

There are two circuits for each relay in the diagram above. When the remote switches (not pic-tured) are activated, voltage will

flow between 85 and 86, activ-ating the high-voltage circuit between 87 and 30. Make sure that the wires on 87 and 30 are large enough to carry the load for the actuator. Using two relays in this way reverses the polarity of the circuit and allows the actuator to extend and retract (see video on next page).

The great thing about relays is that they can be installed close to the load, as well as the battery, to keep the runs of heavy wire as short as possible.

The actuator you select will depend on its intended purpose. Large, powerful actuators with stroke lengths of 6-8 inches and dynamic loads of 250-500 lbs are often used to control steering on a pusher fan. We touched on this in last month's issue.

Smaller actuators can control finer functions, like the throttle on a kicker, or fan motor. Firgelli's miniature linear actuators come

(continued on next page)

Tools of the trade

Clockwise from top left:

A scotchlok is a handy device for splicing solid copper, low voltage cable like CAT 5, plus it has a gel filling to prevent corrosion.

Scotchlok pliers only close enough to fully seal a Scotchlok. Regular pliers work in a pinch, but are not as trusty.

CAT 5 cable contains 4 pairs of wires that are color-coded for easy identification.

Deciphering the code below:

Model L16, featuring a 50mm stroke (2 inches), 150:1 gear ratio (speed) at 12 volts with built-in limit switches (S)