FPS Weapons has built this DIY EMP Generator. It uses some off the shelf components to generate some large EMP pulses with the push of a button. The device runs off a rechargeable lithium ion battery, a high voltage converter goes through a spark gap and then through a coil. The coil was made using some varnished wire. Hot glue was used liberally to keep everything in place. Use this device with caution since permanent electronic damage can occur with this type of device.