Three-speaker Chladni Patterns - Revision history

Lingyu Xie: /* Main frequency sweep code */

2009-03-20T06:38:46Z

Main frequency sweep code

← Older revision		Revision as of 01:38, 20 March 2009
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	After this, the analog port pin is set up and the lcd_init() function is called to set up the LCD display. The LCD displays the current frequency that the AD9833 is currently outputting and the target frequency that the chip is supposed to sweep up/down to. See [[C Example: Parallel Interfacing with LCDs]] to learn about how to interface and send information to the LCD.		After this, the analog port pin is set up and the lcd_init() function is called to set up the LCD display. The LCD displays the current frequency that the AD9833 is currently outputting and the target frequency that the chip is supposed to sweep up/down to. See [[C Example: Parallel Interfacing with LCDs]] to learn about how to interface and send information to the LCD.

	Once the initial set up information is finished, the code sends the first frequency command to the AD9833, starting it at a frequency of 298 Hz by giving it the target_freq_reg register value (initialized at 298 Hz). This allows the speakers to sweep up to the first resonant frequency and oscillate the salt into the first resonant shape when the system is turned on. The register values are then converted to Hz and displayed on the LCD. From there, the code goes into a while() loop which continuously checks the input from the user interface knob which indicates the target frequency that the AD9833 should go to. After getting the target frequency from check_input(), the code compares this new frequency information to the old frequency information (old_freq_reg). If they are different, then the knob was switched to a new frequency and the AD9833 needs to sweep up or down to the new frequency. Depending on whether the new frequency is above or below the old frequency, a for-loop will keep sending new frequency register commands to the AD9833, ~~shifting~~ up or down by 1 Hz every 100 ms, constantly ~~updating~~ the LCD to display the current and target frequency, until the actual frequency is equal to the target frequency. The function check_input() is called for each iteration of the for-loop to check if the target frequency was changed. The old_target_freq_reg is then set equal to the target_freq_reg and the program then holds at this one resonant frequency until the knob sends a different target_freq_reg.		Once the initial set up information is finished, the code sends the first frequency command to the AD9833, starting it at a frequency of 298 Hz by giving it the target_freq_reg register value (initialized at 298 Hz). This allows the speakers to sweep up to the first resonant frequency and oscillate the salt into the first resonant shape when the system is turned on. The register values are then converted to Hz and displayed on the LCD. From there, the code goes into a while() loop which continuously checks the input from the user interface knob which indicates the target frequency that the AD9833 should go to. After getting the target frequency from check_input(), the code compares this new frequency information to the old frequency information (old_freq_reg). If they are different, then the knob was switched to a new frequency and the AD9833 needs to sweep up or down to the new frequency. Depending on whether the new frequency is above or below the old frequency, a for-loop will keep sending new frequency register commands to the AD9833 by calling send_freq(), which is a function that shifts the frequency up or down by 1 Hz every 100 ms, and constantly updates the LCD to display the current and target frequency until the actual frequency is equal to the target frequency. The function check_input() is called for each iteration of the for-loop to check if the target frequency was changed. The old_target_freq_reg is then set equal to the target_freq_reg and the program then holds at this one resonant frequency until the knob sends a different target_freq_reg.

	<pre>		<pre>

Lingyu Xie: /* Main frequency sweep code */

2009-03-20T06:36:30Z

Main frequency sweep code

@@ Line 176: / Line 176: @@
 void check_input();
 void main()
@@ Line 216: / Line 217: @@
             for(ct=old_target_freq_reg; ct<=target_freq_reg; ct=ct+7) //ct+7 approximate increases frequency by 1 Hz
+            {
                check_input(); //see if knob position has selected different target freq
@@ Line 242: / Line 230: @@
             for(ct=old_target_freq_reg; ct>=target_freq_reg; ct=ct-7) //ct+7 approximate decreases frequency by 1 Hz
+            {
                check_input(); //see if knob position has selected different target freq
@@ Line 266: / Line 240: @@
+      }
+   }
+}
 </pre>
 <br>
 === Checking user input ===
 This function is used to check the knob/potentiometer position at certain points during the changing of frequencies in the main function. It sets the ADC channel to 0 and takes the analog input from pin A0 on the PIC using read_adc(). This input, set to the variable knob_val, is an integer between 0-255 which corresponds to the voltage coming out of the knob/potentiometer, which is 0 if the output is at 0V and 255 if the output is at 5V. By checking if knob_val is between a certain integer range corresponding to the different numbers on the knob (numbered 0-10), the target frequency can be set by the user. Nine target resonant frequencies were programmed in this function based on the good clarity of the shapes they produced on the plate, but more resonant frequencies exist and can be added to the if-statement in this function. The target frequency registers should be adjusted depending on the plate shape and size.

Lingyu Xie at 06:17, 20 March 2009

2009-03-20T06:17:30Z

← Older revision		Revision as of 01:17, 20 March 2009
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	[[Image:chladni_complete_system\|right\|thumb\|500px]]		[[Image:chladni_complete_system\|right\|Three-Speaker Chladni Setup with User Interface Box\|thumb\|500px]]

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Lingyu Xie at 06:16, 20 March 2009

2009-03-20T06:16:44Z

← Older revision		Revision as of 01:16, 20 March 2009
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	[[Image:chladni_complete_system\|right\|thumb\|~~300px~~]]		[[Image:chladni_complete_system\|right\|thumb\|500px]]

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Lingyu Xie at 06:16, 20 March 2009

2009-03-20T06:16:33Z

← Older revision		Revision as of 01:16, 20 March 2009
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	[[Image:chladni_complete_system\|right\|thumb\|~~1000px~~]]		[[Image:chladni_complete_system\|right\|thumb\|300px]]

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Lingyu Xie at 06:16, 20 March 2009

2009-03-20T06:16:04Z

← Older revision		Revision as of 01:16, 20 March 2009
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	[[Image:~~chladni_660hz~~\|right\|thumb\|1000px]]		[[Image:chladni_complete_system\|right\|thumb\|1000px]]

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Lingyu Xie: /* Circuit Diagram */

2009-03-20T06:13:15Z

Circuit Diagram

← Older revision		Revision as of 01:13, 20 March 2009
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	[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]		[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]
	<br clear=all>		<br clear=all>
	Note: If the TDA2040 is to be used, connect the output of the unity gain buffer amps to the Vi input of the TDA2040 chip. The load at pin 4 of the TDA2040 chip is then the speaker.		Note: If the TDA2040 is to be used, connect the output of the unity gain buffer amps to the Vi input of the TDA2040 chip. The load at pin 4 of the TDA2040 chip is then the speaker. +Vs is +12V and -Vs is -12V for the TDA2040 circuit.
	<br clear=all>		<br clear=all>

Lingyu Xie: /* Circuit Diagram */

2009-03-20T06:12:08Z

Circuit Diagram

← Older revision		Revision as of 01:12, 20 March 2009
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	[[image:chladni_circuit_actual\|left\|Circuit schematic of circuit used for demonstration 3-speaker Chladni\|thumb\|500px]]		[[image:chladni_circuit_actual\|left\|Circuit schematic of circuit used for demonstration 3-speaker Chladni\|thumb\|500px]]
	[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]		[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]
	<br>		<br clear=all>
	Note: If the TDA2040 is to be used, connect the output of the unity gain buffer amps to the Vi input of the TDA2040 chip. The load at pin 4 of the TDA2040 chip is then the speaker.		Note: If the TDA2040 is to be used, connect the output of the unity gain buffer amps to the Vi input of the TDA2040 chip. The load at pin 4 of the TDA2040 chip is then the speaker.
	<br clear=all>		<br clear=all>

Lingyu Xie: /* Circuit Diagram */

2009-03-20T06:11:55Z

Circuit Diagram

← Older revision		Revision as of 01:11, 20 March 2009
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	[[image:chladni_circuit_actual\|left\|Circuit schematic of circuit used for demonstration 3-speaker Chladni\|thumb\|500px]]		[[image:chladni_circuit_actual\|left\|Circuit schematic of circuit used for demonstration 3-speaker Chladni\|thumb\|500px]]
	[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]		[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]
			<br>
			Note: If the TDA2040 is to be used, connect the output of the unity gain buffer amps to the Vi input of the TDA2040 chip. The load at pin 4 of the TDA2040 chip is then the speaker.
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Lingyu Xie: /* Circuit Diagram */

2009-03-20T06:09:14Z

Circuit Diagram

← Older revision		Revision as of 01:09, 20 March 2009
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	[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]		[[image:tda2040_circuit\|left\|TDA-2040 Audio Amp Circuit[http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf']\|thumb\|300px]]
	<br clear=all>		<br clear=all>

	<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>

	== Code ==		== Code ==