The Clapper

To create Harold "Doc" Edgerton's strobe experiment, I used the piezo as a microphone instead of a beeper. I connected the peizo from the UML dev board to Portc 0 of the Logo chip with a 10k resistor pulling it to ground. I wired eight LED’s to Portb 6. The basic circuit can be seen below in Fig 1.

This circuit, when hearing a loud noise, causes the LED’s to flash. The way I have it wired above is not enough. It will only light the LED’s when I flick the piezo. I believe that this is due to the fact that clapping does not create enough of an output signal from the piezo to light the LED’s, a few hundredths of a volt. By including an amplifier between the piezo and the input pin C0, the signal generated by the piezo will be made greater allowing the LED’s to light when a noise is made. The amplifier would allow a wider range of noises to be seen through the LED’s. A circuit diagram of an amplifier that could be used can be seen below:

Above is a picture of the circuit I created. The code to cause the lights to flash when a sound is heard is the following:

Constants

[[portb 6][portb-ddr $86]

[portc 7]]

to blink

setbit 6 portb

wait 3

clearbit 6 portb

end

to init

write portb-ddr 0

end

to clap

waituntil [touch] blink

end clap

to touch

output testbit 0 portc

end touch

to slave

waituntil [newbus?]

if brcv = $180 [clap]

slave

end slave

to start

init

slave

start

end start

Then on the command line beep was used to execute the program. When the PIC chip receives a signal from the piezo, it sets the pin B6 to a one, which lights the LED’s. Placing this code in an infinite loop allows it to light the LED’s whenever it hears something loud enough.

The code that I used on the Cricket was the simple command line: bsend $180 beep. Hooking up the Logo Chip as a slave on the bus and adding a few lines of code allowed the Cricket to control the clapper. The clapper would only respond to a clap if the Cricket told it that it could. The Cricket would send a signal to the Logo chip to tell it that it could do what it wanted. As long as the Logo chip did not receive this signal, it would sit idle. Below is a picture of the Logo chip hooked up to the Cricket via a bus:

Only two wires are required to hook up the Logo chip to the Cricket. The black one is wired to ground and the white one is wired to Port B0. Everything else is the same as in Figure 1. In addition to having the Cricket tell the clapper when to respond, I was thinking of having the Logo chip send back a single bit telling the Cricket that it had completed successfully. Upon receiving this bit, I was thinking of making the cricket display a random message on a 4 digit 7-segment LED display.