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Solid State Timer | Solid State Relay Timer

Solid State Timer

Solid State Timers come in many shapes and sizes. The most common timers used in industry: ON delay solid-state timers and the OFF delay solid-state timers.

ON Delay Timer Connection

The on delay solid-state timer relay is a two-piece device in which one part of the device is the base and the other is the time relay. The base of the on delay timer is interchangeably used with control relays. The base has eight pin holes, see figure 1, and a keyhole to ensure proper placement.

ON Delay Pin Layout

Fig.1: ON Delay Pin Layout

The pin layout, shown in figure 1, of the ON delay timer, works as follows:

  • Pin 7 and 2 are the coil terminals
  • Pin 8 and 1 are the common terminals for the two sets of contacts
  • Pin 3 is normally open contact and common to pin one.
  • Pin 4 is a normally closed contact and common to pin one
  • Pin 6 is a normally open contact and is common and to pin eight
  • Pin 5 is a normally closed contact and common to pin eight

OFF Delay Timer Connection

The off delay timer is much like the on delay timer relay except it has 11 pins instead of the eight pins as shown in figure 2. The base of the off delay timer has 11 terminals to connect the control wires of the control system. It also contains 11 female pin holes and a female keyhole to ensure the device is seated properly. The off delay unit has a dial to adjust and set the preset time and 11 male pins and a male key way for proper connection to the base.

OFF Delay Pin Layout

Fig.2: OFF Delay Pin Layout

The off delay relay pin layout, as shown in figure 2 (b), operates as follows:

  • Pin 2 and 10 are the coil terminals.
  • Pin 1 and 11 are the common terminals to the two sets of contacts
  • Pin 3 is a normally open contact that is common to pin 1
  • Pin 4 is a normally closed contact, and to pin 1
  • Pin 9 is a normally open contact common to pin 11
  • Pin 8 is a normally closed contact common to pin 11
  • Pins 5 and 6 is the internal circuit used to trigger the off delay timer.
  • Pin 7 is not used

When working with any type of relay or timer coil it is important to always match the coil voltage to the supply voltage to ensure proper operation.

Programmable Timers

One of the most widely used timers in the industry is the programmable timer. Programmable timers offer a greater advantage over the traditional solid-state timers.

  1. Programmable timers are accurate because they can be set to operate within the millisecond range.
  2. Programmable timers also contain instantaneous contacts which reduce the need for control relays.
  3. Programmable timers also can be used for more than one timing function.
  4. At the press of a button or click of the mouse, the programmable timer can go from operating as an ON-delay timer to an off-delay timer, retentive timer, or a one-shot timer.
  5. Programmable timers are incorporated into many of the PLR (programmable logic relays) and PLCs (programmable logic controllers) used in process manufacturing.

Programmable timers include retentive and non-retentive timers. A retentive timer is a timer that maintains its current accumulated time value when power is removed from the coil or power to the timer is removed. A non-retentive timer is a timer that does not maintain its accumulated time when power to the timer is removed.

About Ahmad Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.