![[Diagrams]](bump.gif)
One of the "frills" almost never a feature of older portable, and most non-portable lighting controllers is bump buttons. For the unintiated, these are push buttons which instantly bring a dimmer to "full" when pressed. They are a great feature for rock music, musicals, and occasionally for a special effect. A set of bump buttons gives the operator the opportunity to "play" the lights along with the music. As with my previous articles, I will detail how to add this feature to a portable dimmer system external to the actual controller and without making any permanent modifications to the system.
Remembering that an analog dimmer, the older ones, always operates from a control voltage of 0 volts dc for off and some voltage other than 0 for 10 (or 100 or full). This voltage is usually positive and more often than not 10 or 12 volts. Before you try this verify the exact voltage and polarity on which your system is based!! A mistake here cause damage. For those of you with the newer multiplexed (amx or dmx) dimmer signals, this can't be done. Analog only!!!
The method that I will use to achieve bump buttons is to superimpose a voltage on the control line on top of the one supplied by the controller. The best place to do this is in the control cable between the controller and the dimmer pack.
At this point, I suggest that to implement this or any like modifications the following device be constructed. Purchase a male and a female connector of the type used by the system in question. Also, sufficient terminal strips to connect a wire from all utilized pins on each connector to a terminal on the strip and for our additions (Three times as manny terminal connections as channels plus 3 for common connections). For a 6 pack this is 21 connection points. Note any other wires in the connectors should feed straight from one connector to the other as they are used for other purposes. Build this into a convenient box to protect the connections. There is no danger of lethal electrical shock but the connections need to be protected and strain reliefed so that the connections cannot be easily pulled out or (worse) shorted together which could damage the controller. The modification can then be simply taken out of the circuit when not desired.
For this project, the input pin will be connected to the output pin for each channel with one diode with the addition of a second diode carrying the current from the bump button. (see Figure 1).
The first diode is to protect the controller and may reduce the full on level of the dimmer slightly. This can sometimes be adjusted at the dimmer. The second diode is to provide separation on the channels so that they will not interact with one another. The project in now quite simple. Provide a power supply of the appropriate voltage plus 0.7 volts (the voltage loss across the diode), a momentary push button for each dimmer to be controlled, the same number of diodes, a board, some wire, and a little elbox grease.
The voltage supplied must be pure DC and of a reasonably precise value. A 12 volt transformer is adequate for 10 or 12 volts. Above this move to a 24 volt transformer. The easiest to use are the plug in "battery eliminator" type power supply available at most electronics stores. Assuming that a DC power supply is purchased, build Figure 3, if a discreet transformer is used (AC) add Figure 2 to Figure 3. The potentiometer is adjusted to provide the proper voltage output. The voltage output is then connected to each switch/diode combination and then to the terminal box.
This modification can also be accomplished in permanent installation consoles but since most of these do not use plug-in connectors for connections different mechanical means are necessary to accomplish the connections.