We were recently commissioned to design a device to protect the solenoids used as components within a one-man band drum kit. Rather than wearing the drums on the back, this drum kit is made to sit alongside the one-man controlled by foot pedals leaving hands free to play the guitar or a keyboard.
Each foot pedal contains two micro-switches. Rocking the foot backwards and forwards, the heel and toe trigger those switches which activate solenoids which pull a cord which impacts the drumstick on a drum. A bass drum could be connected to the toe switch and a snare drum to the heel switch on one pedal, and a second pedal could control the high hats for example enabling complicated rhythms to be played.
This system all works well except that if the foot is left resting on the pedal so that one of the micro-switches remains closed, the solenoid will burn out. It is also difficult to depress a micro-switch for the correct length of time so that the drumstick hits the drum and bounces immediately off rather than being left pressed against the skin of the drum affecting the sound.
The timer we came up with detects when a drum pedal micro-switch is pressed. It then supplies an output to the solenoid for exactly 0.10 seconds (which has been proven experimentally to be the perfect length of time with this setup). The solenoid will not be activated again until after at least 0.40 seconds has passed and also the micro-switch has been seen to be released before being pressed again. Therefore, if the micro-switch is kept pressed down, the solenoid will not be activated (and not kept activated) and so it will not burn out.
Pictured above is the first prototype unit used for testing purposes with one drum pedal micro-switch and one solenoid only.
Pictured below is the control board for three foot pedal inputs and three solenoid outputs, so heel and toe in one foot pedal and heel or toe in a second foot pedal to control three drums.
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