Music

Ghost Pedal lets guitarists wander the stage and wah

Ghost Pedal lets guitarists wa...
A team of Purdue University students has developed a device that uses sensors at a guitarist's ankle to wirelessly control a virtual wah distortion effect
A team of Purdue University students has developed a device that uses sensors at a guitarist's ankle to wirelessly control a virtual wah distortion effect
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The Ghost Pedal gives a guitarist the freedom to roam the stage area and wirelessly control a virtual wah distortion effect whenever and wherever the mood grabs
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The Ghost Pedal gives a guitarist the freedom to roam the stage area and wirelessly control a virtual wah distortion effect whenever and wherever the mood grabs
A team of Purdue University students has developed a device that uses sensors at a guitarist's ankle to wirelessly control a virtual wah distortion effect
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A team of Purdue University students has developed a device that uses sensors at a guitarist's ankle to wirelessly control a virtual wah distortion effect
The Ghost Pedal is strapped to a player's ankle and operated in much the same fashion as a physical wah, expect there's no physical pedal
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The Ghost Pedal is strapped to a player's ankle and operated in much the same fashion as a physical wah, expect there's no physical pedal
When the unit is first switched on, there's a ten second calibration period where a wearer's ability to flex the ankle is determined and stored
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When the unit is first switched on, there's a ten second calibration period where a wearer's ability to flex the ankle is determined and stored
If a player wants to deactivate the wah effect, a tap to the sustain sensor on the side of the device will bypass or sustain the signal
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If a player wants to deactivate the wah effect, a tap to the sustain sensor on the side of the device will bypass or sustain the signal
The ankle unit is made up of a variable resistor sensor that tracks the movement of the ankle and a sustain sensor which either accepts the virtual wah feed or ignores/sustains it
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The ankle unit is made up of a variable resistor sensor that tracks the movement of the ankle and a sustain sensor which either accepts the virtual wah feed or ignores/sustains it
Team member Will Black demonstrating the Ghost Pedal, which is hidden from view by the player's trousers
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Team member Will Black demonstrating the Ghost Pedal, which is hidden from view by the player's trousers

No matter the size of the stage, most gigging guitar players are likely to have to return to the same spot from time to time to change the tone, increase the volume, check tuning or to operate the wah effect. Thanks to a team of students from Purdue University's School of Mechanical Engineering, the last of those has now been liberated from the pedal board and strapped to the player's ankle. This doesn't involve attaching a large brick-shaped wah pedal to one leg, as one's imagination might suggest, but wearing a small wireless transmitter and a couple of sensors instead. Players operate the Ghost Pedal in much the same fashion as a physical pedal, the sensors registering the rocking motion of the foot and feeding data to a base station connected to the amplifier.

The ankle unit is made up of a variable resistor sensor that tracks the movement of the ankle and a sustain sensor which either accepts the virtual wah feed or ignores/sustains it. When the unit is first switched on, there's a ten second calibration period where a wearer's ability to flex the ankle is determined and stored. After that the device goes into free-play mode which allows the user to virtually control the amount of wah by changing the angle of the foot from the floor, in much the same motion used with an actual wah pedal.

When the unit is first switched on, there's a ten second calibration period where a wearer's ability to flex the ankle is determined and stored
When the unit is first switched on, there's a ten second calibration period where a wearer's ability to flex the ankle is determined and stored

If the player wants to bypass the wah effect to move position, the sustain sensor is positioned at the inner ankle and is tapped with the other foot to activate. When the guitarist has climbed atop the Marshall stack or simply moved to another part of the stage, another tap will bring back the wah. The signals from the ankle unit are sent wirelessly to a micro-controller that translates them into instructions for the wah circuit's resistors. The analog nature of the signal is maintained by using a digital potentiometer to marry the digital and analog circuitry.

Although virtual pedal control is currently limited to the wah effect, the team says that there's no reason why such a device can't be adapted to wirelessly control other effects - such as pitch, volume, distortion and so on. The calibration mode also means that one unit can be easily used by different players - a very useful feature.

Team member Will Black demonstrating the Ghost Pedal, which is hidden from view by the player's trousers
Team member Will Black demonstrating the Ghost Pedal, which is hidden from view by the player's trousers

The team includes Garrett Baker, Will Black (pictured above), Matthew Boyle, Brett Hartnagel, Christine Labelle, Adam Pflugshaupt, Nick Sannella and Robbie Hoye, who all graduated from Purdue last year and created the patent-pending Ghost Pedal as a senior project. Licensing of the Ghost Pedal technology is currently in the hands of Purdue's Office of Technology Commercialization.

Purdue students' device creates "wah" effect without physical pedal

Source: Purdue University Office of Technology Commercialization

All images courtesy of the Purdue Research Foundation

2 comments
Ross Mcewen-Page
Awesome!
Bradley Donaldson
Would have been nice to hear more of the pedal. Hard to believe you're pushing a Wah pedal and the guy didn't throw in a little Voodoo Chile Slight Return, Ya Know?