Electromagnets & Coils

Electronic Drivers FAQ

Why do I need a driver to power my coil device?

How do I know what driver to get?

Do I need to add a flyback or freewheeling diode to my circuit?

How many devices can I operate on each driver?

Why do I need a driver to power my coil device?
There are several reasons to use a driver on a coil-based device such as a solenoid or electromagnet

  • The most important reason to use a driver is to prevent circuit damage due to Back EMF. Whenever power is removed from a coil the magnetic field that was being produced collapses which induces a current in the opposite direction that a current was being supplied in. This voltage spike can be many times greater than the voltage that was originally supplied to the coil and can easily damage sensitive electronics. All drivers sold by APW Company have built in protections to prevent back EMF from causing damage.
  • You may want to control a coil device with a digital signal from something like a computer, microcontroller or Arduino. Most coil based devices will require much more energy to operate than a digital signal can provide. Our drivers bridge the gap between the low power levels of digital signals and the comparatively high-power levels that coils require. Our drivers accept digital inputs to control their outputs.
  • Your application may have power consumption or heat constraints. Several of the drivers that we offer at APW Company have adjustable hit and hold functions. This means that they turn on at the full power that is provided to them and then back down to a holding power after a given amount of time. Typically, the greatest magnetic force is needed at the time of initial activation because an armature or strike plate needs to be pulled in over some distance. Once a solenoids armature or an electromagnet’s strike plate is pulled to its activated position it no longer needs that maximum force to hold it there. Dropping to a holding level keeps the heat and power consumption down.

How do I know what driver to get?
There are three styles of drivers that we offer and each is used for different applications. The first style is the Solid State Relay. This is the most basic driver and is used to simply activate a coil with 100% of the power provided to the driver. The second style of driver that we offer is a Hit and Hold type. This driver turns on with 100% of its provided power but then backs down to a holding power after a preset amount of time. These drivers have three user defined settings for the holding strength. This type of driver is used for applications where heat and power consumption are concerns or where an application requires extra magnetic strength at initial activation. The last style of driver is the Fast On Fast Off driver. This product is designed primarily for larger electromagnets. Electromagnets retain some residual magnetism while a magnetic circuit is formed by metal connecting its poles. Even after removing power from an electromagnet it will continue to hold onto a lighter load. This driver functions to reduce or completely remove the residual magnetism allowing it to release more quickly or with less force. These drivers are used when residual magnetism is a concern.

Do I need to add a flyback or freewheeling diode to my circuit?
No, all our drivers are built with electromagnetic protection in mind. They protect sensitive electronics from voltage spikes produced by Back EMF.

How many devices can I operate on each driver?
You can operate several coil devices on one driver, however, they will all activate by the same trigger and their combined voltage and current demands must stay within the limits of the driver being used.

 

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