Mini Pushbutton Power Switch with Reverse Voltage Protection, SV

The Pololu Pushbutton Power Switch is a compact, solid-state power switch that features built-in reverse-voltage protection and is controlled by a momentary pushbutton: one push turns on power and another push turns it off. This is a patented design initially created for use in our own products as an alternative to bulky mechanical switches. Because the switched current does not flow through the mechanical switch, a large variety of small, low-power switches can be used to control a substantial amount of power. The use of momentary switches also allows multiple switches to be used in parallel to control the power to one load.

The board has a small pushbutton already installed and offers convenient points for connecting external pushbutton or tactile switches in parallel. It also offers several alternate pushbutton connection options that result in push-on-only or push-off-only operation, and additional inputs enable further power control options like allowing the load to turn off its own power, which can be beneficial when used with battery chemistries sensitive to over-discharging.

Warning: Do not use this switch as an emergency cutoff or similar safety disconnect in applications where failure to cut power could lead to injury or property damage.

The Pololu Pushbutton Power Switch works well in its intended application as a DC power switch for small robots, but because it is fundamentally different from a mechanical power switch, the benefits and drawbacks of the components must be fully considered.

Benefits over mechanical switches:

• Compact size
• Reverse-voltage protection
• Allows multiple (parallel) switches for improved user interface
• Better turn-on characteristics than a bouncing mechanical switch
• Limited LC spikes for low-resistance loads
• Allows self-shutoff (OFF input)
• Allows external digital device to control the power state (ON and CTRL inputs)
• Breadboard and perfboard compatible (0.1″-pitch)

Drawbacks compared to mechanical switches:

• Switch is one-directional (power applied to VOUT cannot be switched to VIN)
• Limited operating voltage range
• Switch can lose its state when power is disconnected (the switch typically defaults to being off when power is first applied, but it can default to being on near the upper end of the operating range)
• Switches DC only (does not maintain state through power disruptions or excessive noise)
• No complete isolation in off state

WIKI: https://www.pololu.com/product/2809