LED Dimming & Flashing information
You may sometimes want to create flashing or dimmed displays with LEDs. This is not quite as simple to do as you might think! But we have solutions to make sure you are successful.
To start with, we will consider flashing the more common parallel connected 12V-DC and 24V-DC types of LED that run on constant voltage power supply units (PSU). If you tried to flash these by simply switching the mains supply to the PSU you would have problems: the PSU usually take a moment or two to energise and light the LEDs. Switching them means that the LEDs may not light when you want and there may be damage to the PSU. The LEDs themselves do not like being switched rapidly also. The safer, more effective way of achieving flashing LEDs is to feed them with a Pulse Width Modulated (PWM) signal. This picture shows how this works:
These pulses are very rapid, so the eye isn't aware of them. We have flashers with PWM outputs - you feed the low voltage supply from the PSU into the flasher and the output from the flasher goes to the LEDs. Like this: