Diodes should be installed as close as possible to the solenoid. Soldering a diode directly across the 2 solenoid terminals is ideal.Use a diode with a voltage rating of at least 10 times the circuit voltage and a current rating at least as big as the current flowing through the solenoid. In practice, diodes rates at 200 volts and 1 amp are readily available for a few cents and are appropriate for most applications. Diodes have a stripe on one end of the case (Cathode). On equipment wired with negative ground.
Diodes have a stripe on one end of the case (Cathode). On equipment wired with negative grounds, the end with the stripe should be installed on the most positive side of the solenoid. This is usually the side that has the wire from the switch. Sure Grip manufactures a diode pack which can be used to provide surge suppression.
Wire Routing Tips
Wire breakage inside the cable can be one of the most difficult and frustrating problems to find. Almost all wire breakage problems can be traced to two common installation mistakes.
1. Crushing the wire Nylon tie wraps are very useful in giving the wiring harness a neat and finished appearance, but applying them too tightly can crush the wire insulation and pinch the wires. When the cable is pinched, it doesn't allow the wire to slide inside the cable jacket and creates a stress point.
2. Forcing the wire to flex at one point If the wire from the control handle is routed down the joystick shaft with little slack, the wire will tend to flex over a small area. Eventually the repeated flexing will cause the wire strands to break. The solution is to provide enough slack in the cable so that the flexing motion is distributed over a longer section of wire.
Ideally, a loop should be left around the mounting stud to spread the flexing point over a larger area. The loop can be created either inside or outside the rubber boot.
Surge Suppression Explained
Inductive kick (surge) occurs any time an electrically generated field collapses. A voltage, opposite in polarity to the original applied voltage is generated by the collapsing magnetic field. A good example of this is in an automobile ignition system. When the breaker points open, the current flowing to the ignition coil is shut off and the magnetic field built up in the coil collapses. The resulting inductive kick voltage is high enough to jump the gap at the spark plug.
The same effect also happens whenever solenoid used on a hydraulic valve is shut off. The voltage surge can reach several hundred volts which will arc across the switch contacts and quickly destroy them. Switch life can be reduced to one-tenth of normal. The solution is to add a diode in parallel across the solenoid terminals (See Fig.1). A diode acts as a one-way valve for electricity. In normal operation, the electric current can't flow through the diode, so it flows through the solenoid coil. When the operator releases the switch, the current is shut off to the solenoid and the inductive kick flows backwards through the diode rather than through the switch contacts, bleeding off the high voltage spike.
Typical Switch Life
Sure Grip Handles use reliable snap action micro switches that have proven to give the longest life and greatest reliability of any switch on the market.While the switches are rated for up to 10 million cycles, switch life is dependent on several factors that can greatly influence the number of on/off cycles that a switch can perform before it fails. The load (in amps) and proper diode protection are two of the greatest factors that will determine the life of a switch.
The switching capacity of the switch depends on the type of load that the switch is switching and the contact material. Sure Grip Handles use switches with silver plating on the contacts for maximum load capacity and long life. If the handles will be switching logic level signals (under 20 mA), the best performance will be obtained using switches with gold plated contacts. Consult factory for special switch options.