NU32: Using the MAX9918 current sensor - Revision history

Lynch at 11:37, 16 January 2016

2016-01-16T11:37:14Z

NickMarchuk: /* Wiring */

2012-03-06T22:14:47Z

Wiring

NickMarchuk: /* Wiring */

2012-03-03T20:20:28Z

Wiring

NickMarchuk: /* Details */

2012-03-01T17:13:33Z

Details

NickMarchuk: /* Details */

2012-03-01T17:11:37Z

Details

NickMarchuk at 16:38, 1 March 2012

2012-03-01T16:38:06Z

NickMarchuk at 16:39, 28 February 2012

2012-02-28T16:39:10Z

NickMarchuk at 16:22, 28 February 2012

2012-02-28T16:22:57Z

NickMarchuk at 16:16, 28 February 2012

2012-02-28T16:16:53Z

NickMarchuk at 16:16, 28 February 2012

2012-02-28T16:16:45Z

← Older revision		Revision as of 11:37, 16 January 2016
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			'''THIS PAGE REFERS TO A PRE-RELEASE VERSION OF THE NU32 PIC32 DEVELOPMENT BOARD. FOR INFORMATION, SAMPLE CODE, AND VIDEOS RELATED TO THE PRODUCTION VERSION (2016 AND LATER), AND TO THE CORRESPONDING BOOK "EMBEDDED COMPUTING AND MECHATRONICS WITH THE PIC32 MICROCONTROLLER," VISIT [[NU32\|THE NU32 PAGE]].'''


	Using the MAX9918 current sensor.		Using the MAX9918 current sensor.

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 == Wiring ==
-[[Image:MAX9918_wireup.png|thumb|600px|center]]
+[[Image:TB6612andMAX9918_wireup.png|thumb|600px|center]]
 == Calibration ==

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 == Wiring ==
-[[Image:MAX9918_wire.png|thumb|600px|center]]
+[[Image:MAX9918_wireup.png|thumb|600px|center]]
 == Calibration ==

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 To set the voltage gain the MAX9918 will apply to the voltage read across the current sense resistor, place a resistance R1 between REF and FB (pin 6) and R2 between FB and output. The voltage gain will be (1 + R2 / R1).
+The output voltage is then 1.65 [V] + (I [A] * 0.015 [Ohm] * gain).
 [[Image:MAX9918_sch.png|thumb|400px|center]]

@@ Line 24: / Line 24: @@
 To set the voltage gain the MAX9918 will apply to the voltage read across the current sense resistor, place a resistance R1 between REF and FB (pin 6) and R2 between FB and output. The voltage gain will be (1 + R2 / R1).
-[[Image:MAX9918_sch.png|thumb|600px|center]]
+[[Image:MAX9918_sch.png|thumb|400px|center]]
 == Wiring ==

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 == Overview ==
+[[Media:MAX9918.pdf|Datasheet]]
 The MAX9918 is a bi-directional current-sense amplifier.

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 To set the voltage gain the MAX9918 will apply to the voltage read across the current sense resistor, place a resistance R1 between REF and FB (pin 6) and R2 between FB and output. The voltage gain will be (1 + R2 / R1).
-== Library Functions ==
+== Calibration ==
+You should calibrate your MAX9918 circuit and note in your code what current the output voltage corresponds to.
-[[Media:NU32SerialExample.zip | This code]] How to get the count
+Note the output voltage when zero current passes through the current-sense resistor.
-The functions are:
-*void NU32_Initialize(void) - enables UART1 and UART4 at 115200 baud. UART4 starts with the interrupt at priority level 3, UART1 starts with no interrupt enabled
-*void NU32_EnableUART1Interrupt(void) - enables the UART1 interrupt
-*void NU32_WriteUART1(const char *) - call with the character array you wish to send, make the array with sprintf()
-*void NU32_ReadUART1(char *, int) - call with the array you want to read into, and the maximum size of the array. The code will wait at this function and buffer all characters received until you send a '\r' or '\n' (by pressing [enter] on your keyboard)
+Build a circuit that will pass positive current through the current-sense resistor (the RS+ voltage > the RS- voltage). Try to get 2 different values of current through, as large as you can, without burning the resistor you are using to create the current (remember the resistors in your kit are 0.25W). Note the output voltages of the MAX9918.
-NU32Example.c in the .zip file above demonstrates how to use the functions.
+Do the same for negative currents, and make a plot of the results. Note the slope and use it in your microcontroller code to convert the voltage it reads from the MAX9918 to the current through the load.
-== Sample Code ==
-To initialize the serial communication, call NU32_Initialize(), :
-<pre>
-  NU32_Initialize();
-</pre>
-To write a string to the computer, use NU32_WriteUART1(charArray). The special characters '\r' and '\n' are carriage return and newline. Using them together puts the cursor on the next line.
-<pre>
-  NU32_WriteUART1("\r\nHello World!\r\n");
-</pre>
-To write a string with the value of a variable in it, use sprintf(charArray,"%d") and NU32_WriteUART1(charArray).
 == More Information ==

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 Using the MAX9918 current sensor.
-[[Image:NU32_MAX9918.jpg|thumb|200px|The MAX9918 current sensor breakout board|left]]
+[[Image:NU32_MAX9918.jpg|thumb|200px|The MAX9918 current sensor breakout board|center]]
 == Overview ==

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 <BR>
-[[Image:MAX9918.png|thumb|600px|left]]
+[[Image:MAX9918.png|thumb|600px|center]]
 <BR>