Controlling a seven segment display - Revision history

EricNickel: /* Circuit Wiring */

2008-03-19T17:46:50Z

Circuit Wiring

← Older revision		Revision as of 12:46, 19 March 2008
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	===Circuit Wiring===		===Circuit Wiring===

	[[image:CircuitDiag.jpg\|thumb\|300px\|[[Circuit diagram for the 7-segment display circuit]]\|right]]		[[image:CircuitDiag.jpg\|thumb\|300px\|[Circuit diagram for the 7-segment display circuit]\|right]]

	[[image:7SegmentCircuit4.jpg\|thumb\|300px\|[[Close-up picture of circuit wiring]]\|right]]		[[image:7SegmentCircuit4.jpg\|thumb\|300px\|[Close-up picture of circuit wiring]\|right]]

	For the simplest of cases (which is what this module will demonstrate), the decoder needs to receive the number to be displayed in 4-bit binary form. In addition, the 7-segment display will need the seven independent segment outputs from the decoder as well as one decimal point input and one digit select input for each digit being used (all others can be set to ground to ensure they are not active). In the simplest case (displaying one digit only) the PIC need not have an output to control which digit is active. For more complex displays which have multiple digits, up to three digits could reasonably be controlled by the PIC directly, or a decoder could be used for four or more digits so that the PIC need only output the binary number of the desired digit and the decoder would activate the appropriate digit on the display.		For the simplest of cases (which is what this module will demonstrate), the decoder needs to receive the number to be displayed in 4-bit binary form. In addition, the 7-segment display will need the seven independent segment outputs from the decoder as well as one decimal point input and one digit select input for each digit being used (all others can be set to ground to ensure they are not active). In the simplest case (displaying one digit only) the PIC need not have an output to control which digit is active. For more complex displays which have multiple digits, up to three digits could reasonably be controlled by the PIC directly, or a decoder could be used for four or more digits so that the PIC need only output the binary number of the desired digit and the decoder would activate the appropriate digit on the display.

EricNickel: /* 7-Segment Display */

2008-03-19T17:46:35Z

7-Segment Display

← Older revision		Revision as of 12:46, 19 March 2008
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	===7-Segment Display===		===7-Segment Display===

	[[image:LTD4708JS_Pic1.jpg\|thumb\|300px\|[[LTD 4708JS 7-Segment display]]\|right]]		[[image:LTD4708JS_Pic1.jpg\|thumb\|300px\|[LTD 4708JS 7-Segment display]\|right]]

	The [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS] 7-segment display has 10 pins. Seven pins correspond to the seven LED segments, one pin corresponds to the decimal point, and two pins select which digit is being activated. Both digits can be activated simultaneously, however they would not be able to display independent digits in such a manner. To achieve multi-digit display, the digits must alternate back and forth at a rate preferably greater than 45 Hz for a complete cycle of display (approximately the flicker fusion frequency for the human eye, allowing it to appear that all displayed digits are on continuously).		The [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS] 7-segment display has 10 pins. Seven pins correspond to the seven LED segments, one pin corresponds to the decimal point, and two pins select which digit is being activated. Both digits can be activated simultaneously, however they would not be able to display independent digits in such a manner. To achieve multi-digit display, the digits must alternate back and forth at a rate preferably greater than 45 Hz for a complete cycle of display (approximately the flicker fusion frequency for the human eye, allowing it to appear that all displayed digits are on continuously).

EricNickel: /* Circuit */

2008-03-19T17:46:22Z

Circuit

← Older revision		Revision as of 12:46, 19 March 2008
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	== Overview ==		== Overview ==

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	== Circuit ==		== Circuit ==
	[[image:7SegmentCircuit1.jpg\|thumb\|300px\|[[7-Segment display circuit with PIC]]\|right]]		[[image:7SegmentCircuit1.jpg\|thumb\|300px\|[7-Segment display circuit with PIC]\|right]]

	There are three primary elements required for a circuit involving a 7-segment display.		There are three primary elements required for a circuit involving a 7-segment display.

Lynch at 22:40, 2 March 2008

2008-03-02T22:40:02Z

← Older revision		Revision as of 17:40, 2 March 2008
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	== Original Assignment ==

	In this project you will use your PIC to display numbers on a seven-segment display.

	== Overview ==		== Overview ==

JamesYeung: /* Decoder */

2008-02-13T20:29:41Z

Decoder

← Older revision		Revision as of 15:29, 13 February 2008
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	===Decoder===		===Decoder===

	The decoder used in this demonstration was the [http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf HEF 4543B]. It receives a 4-bit binary input as an input and outputs seven logic pins which correspond to the respective segments of a 7-segment display unit. Some display units require that the inputs be logic low to set a segment active. To achieve this, the chip has a phase input pin which will invert the outputs when the pin is set high. There is also a Blanking pin which will inhibit outputs, ensuring a blank display when set high. For more information regarding this pin, click on the chip name to access the data sheet or [http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf ~~Click~~ ~~Here~~].		The decoder used in this demonstration was the [http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf HEF 4543B]. It receives a 4-bit binary input as an input and outputs seven logic pins which correspond to the respective segments of a 7-segment display unit. Some display units require that the inputs be logic low to set a segment active. To achieve this, the chip has a phase input pin which will invert the outputs when the pin is set high. There is also a Blanking pin which will inhibit outputs, ensuring a blank display when set high. For more information regarding this pin, click on the chip name to access the data sheet or [http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf click here].

	===Circuit Wiring===		===Circuit Wiring===

JamesYeung: /* 7-Segment Display */

2008-02-13T20:27:59Z

7-Segment Display

← Older revision		Revision as of 15:27, 13 February 2008
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	[[image:LTD4708JS_Pic1.jpg\|thumb\|300px\|[[LTD 4708JS 7-Segment display]]\|right]]		[[image:LTD4708JS_Pic1.jpg\|thumb\|300px\|[[LTD 4708JS 7-Segment display]]\|right]]

	The [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS] 7-segment display has 10 pins. Seven pins correspond to the seven LED segments, one pin corresponds to the decimal point, and two pins select which digit is being activated. Both digits can be activated simultaneously, however they would not be able to display ~~indepent~~ digits in such a manner. To achieve multi-digit display, the digits must alternate back and forth at a rate preferably greater than 45 Hz for a complete cycle of display (approximately the flicker fusion frequency for the human eye, allowing it to appear that all displayed digits are on continuously).		The [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS] 7-segment display has 10 pins. Seven pins correspond to the seven LED segments, one pin corresponds to the decimal point, and two pins select which digit is being activated. Both digits can be activated simultaneously, however they would not be able to display independent digits in such a manner. To achieve multi-digit display, the digits must alternate back and forth at a rate preferably greater than 45 Hz for a complete cycle of display (approximately the flicker fusion frequency for the human eye, allowing it to appear that all displayed digits are on continuously).

	The [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS] has 10 pins and they are designated as follows:		The [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS] has 10 pins and they are designated as follows:

JamesYeung: /* Overview */

2008-02-13T20:26:24Z

Overview

← Older revision		Revision as of 15:26, 13 February 2008
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	== Overview ==		== Overview ==

	In this example, we will be using PIC 18F4520 to control a double digit 7-segment display [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS]. A few notes about using this display is that it is only designed to display one ~~unit~~ at a time, so when trying to use both digits, you have to use a method to switch between the two digits fast enough to create the illusion that both are on simultaneously. We've made a simple loop that switches between the two digits every 5ms, but an ISR could also work.		In this example, we will be using PIC 18F4520 to control a double digit 7-segment display [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS]. A few notes about using this display is that it is only designed to display one digit at a time, so when trying to use both digits, you have to use a method to switch between the two digits fast enough to create the illusion that both are on simultaneously. We've made a simple loop that switches between the two digits every 5ms, but an ISR could also work.

	Now, since there are 7 segments, one would assume that you would need 7 outputs from the PIC to display 1 digit. But it is very wasteful to use outputs from the PIC for just displaying, so we will be using a chip ([http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf HEF 4543B]) that will take 4-bits and convert it to the 7-bit output for the 7-segment display.		Now, since there are 7 segments, one would assume that you would need 7 outputs from the PIC to display 1 digit. But it is very wasteful to use outputs from the PIC for just displaying, so we will be using a chip ([http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf HEF 4543B]) that will take 4-bits and convert it to the 7-bit output for the 7-segment display.

JamesYeung: /* Overview */

2008-02-13T20:24:09Z

Overview

← Older revision		Revision as of 15:24, 13 February 2008
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	=== Capabilities ===		=== Capabilities ===

	To display a 2-digit number where a decimal point is needed, you will need a total of 7 outputs from the PIC. 4 for the value, 1 for the decimal point, 2 for each of the digits. However, since you will only be displaying 1 of the 2 digits at any given moment, you can use a logic inverter gate (74LS05) to reduce 1 output needed for selecting which digit to display. A logic inverter gate is a chip that will take an input and return a high if the input is low or low if the input is high. Finally, you will need to make a loop with a delay of 5ms to switch between the digits, or use an ISR if you will be doing other computations with the PIC.		To display a 2-digit number where a decimal point is needed, you will need a total of 7 outputs from the PIC. 4 for the value, 1 for the decimal point, 2 for each of the digits. However, since you will only be displaying 1 of the 2 digits at any given moment, you can use a logic inverter gate ([http://www.ortodoxism.ro/datasheets/motorola/SN74LS05D.pdf 74LS05]) to reduce 1 output needed for selecting which digit to display. A logic inverter gate is a chip that will take an input and return a high if the input is low or low if the input is high. Finally, you will need to make a loop with a delay of 5ms to switch between the digits, or use an ISR if you will be doing other computations with the PIC.

	== Circuit ==		== Circuit ==

JamesYeung: /* Capabilities */

2008-02-13T20:23:51Z

Capabilities

← Older revision		Revision as of 15:23, 13 February 2008
Line 19:		Line 19:
	=== Capabilities ===		=== Capabilities ===

	To display a 2-digit number where a decimal point is needed, you will need a total of 7 outputs from the PIC. 4 for the value, 1 for the decimal point, 2 for each of the digits. However, since you will only be displaying 1 of the 2 digits at any given moment, you can use a logic inverter gate to reduce 1 output needed for selecting which digit to display. A logic inverter gate is a chip that will take an input and return a high if the input is low or low if the input is high. Finally, you will need to ~~use~~ an ~~ISR on the PIC~~ with an ~~interval~~ of 5ms to switch between the digits.		To display a 2-digit number where a decimal point is needed, you will need a total of 7 outputs from the PIC. 4 for the value, 1 for the decimal point, 2 for each of the digits. However, since you will only be displaying 1 of the 2 digits at any given moment, you can use a logic inverter gate (74LS05) to reduce 1 output needed for selecting which digit to display. A logic inverter gate is a chip that will take an input and return a high if the input is low or low if the input is high. Finally, you will need to make a loop with a delay of 5ms to switch between the digits, or use an ISR if you will be doing other computations with the PIC.

	== Circuit ==		== Circuit ==

JamesYeung: /* Overview */

2008-02-13T20:19:57Z

Overview

← Older revision		Revision as of 15:19, 13 February 2008
Line 5:		Line 5:
	== Overview ==		== Overview ==

	In this example, we will be using PIC 18F4520 to control a double digit 7-segment display [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS]. A few notes about using this display is that it is only designed to display one unit at a time, so when trying to use both digits, you have to use an ~~ISR~~ to switch between the two digits fast enough to create the illusion that both are on simultaneously.		In this example, we will be using PIC 18F4520 to control a double digit 7-segment display [http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTD-4708JS.pdf LTD-4708JS]. A few notes about using this display is that it is only designed to display one unit at a time, so when trying to use both digits, you have to use a method to switch between the two digits fast enough to create the illusion that both are on simultaneously. We've made a simple loop that switches between the two digits every 5ms, but an ISR could also work.

	Now, since there are 7 segments, one would assume that you would need 7 outputs from the PIC to display 1 digit. But it is very wasteful to use outputs from the PIC for just displaying, so we will be using a chip ([http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf HEF 4543B]) that will take 4-bits and convert it to the 7-bit output for the 7-segment display.		Now, since there are 7 segments, one would assume that you would need 7 outputs from the PIC to display 1 digit. But it is very wasteful to use outputs from the PIC for just displaying, so we will be using a chip ([http://www.standardics.nxp.com/products/hef/datasheet/hef4543b.pdf HEF 4543B]) that will take 4-bits and convert it to the 7-bit output for the 7-segment display.
Line 19:		Line 19:
	=== Capabilities ===		=== Capabilities ===

	To display a 2-digit number where a decimal point is needed, you will need a total of 7 outputs from the PIC. 4 for the value, 1 for the decimal point, 2 for each of the digits. However, since you will only be displaying 1 of the 2 digits at any given moment, you can use a logic inverter gate to reduce 1 output needed for selecting which digit to display. Finally, you will need to use an ISR on the PIC with an interval of 5ms to switch between the digits.		To display a 2-digit number where a decimal point is needed, you will need a total of 7 outputs from the PIC. 4 for the value, 1 for the decimal point, 2 for each of the digits. However, since you will only be displaying 1 of the 2 digits at any given moment, you can use a logic inverter gate to reduce 1 output needed for selecting which digit to display. A logic inverter gate is a chip that will take an input and return a high if the input is low or low if the input is high. Finally, you will need to use an ISR on the PIC with an interval of 5ms to switch between the digits.

	== Circuit ==		== Circuit ==