LED Cube/Understanding The Electronics - Versionsgeschichte

Marvin am 28. April 2012 um 21:16 Uhr

2012-04-28T21:16:10Z

← Nächstältere Version		Version vom 28. April 2012, 21:16 Uhr
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	{{~~Template:~~LED Cube Series}}		{{LED Cube Series/en}}
	This page is meant to give you a understanding of the workings in your LED cube. We will try to avoid common electronics slang, thus this is especially suitable for you if you are not familiar with electronics. If you are, however, you are probably better off, simply having a look at the schematics and your cube itself - it is not complex in any aspect.		This page is meant to give you a understanding of the workings in your LED cube. We will try to avoid common electronics slang, thus this is especially suitable for you if you are not familiar with electronics. If you are, however, you are probably better off, simply having a look at the schematics and your cube itself - it is not complex in any aspect.

Marvin am 19. April 2012 um 21:34 Uhr

2012-04-19T21:34:42Z

← Nächstältere Version		Version vom 19. April 2012, 21:34 Uhr
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	{{Template:LED Cube Series}}		{{Template:LED Cube Series}}
	This page is meant to give you a understanding of the workings in your LED cube. We will try to avoid common electronics slang, thus this is especially suitable for you if you are not familiar with electronics. If you are, however, you are probably better of simply having a look at the schematics and your cube itself - it is not complex in any aspect.		This page is meant to give you a understanding of the workings in your LED cube. We will try to avoid common electronics slang, thus this is especially suitable for you if you are not familiar with electronics. If you are, however, you are probably better off, simply having a look at the schematics and your cube itself - it is not complex in any aspect.

	==The Cube Structure==		==The Cube Structure==

Marvin: /* USB */

2012-04-17T20:59:19Z

USB

← Nächstältere Version		Version vom 17. April 2012, 20:59 Uhr
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	The USB part is more interesting. We are using the [http://www.obdev.at/products/vusb/index.html V-USB Stack], a very nice, open source USB stack for hobby projects. However, the USB hardware implementation is not much more than a hack. With our LED cube we have quite a problem here: To use the internal switches of the microcontoller, we have to operate it at 5 V. However, the USB data lines do not tolerate much more than 3.3 V. This is the reason for the two diodes directly behind the USB connector: They limit the voltage we get from the microcontroller to acceptable levels.		The USB part is more interesting. We are using the [http://www.obdev.at/products/vusb/index.html V-USB Stack], a very nice, open source USB stack for hobby projects. However, the USB hardware implementation is not much more than a hack. With our LED cube we have quite a problem here: To use the internal switches of the microcontoller, we have to operate it at 5 V. However, the USB data lines do not tolerate much more than 3.3 V. This is the reason for the two diodes directly behind the USB connector: They limit the voltage we get from the microcontroller to acceptable levels.

	Then there are three resistors: Two times 68 Ohms are used for the voltage limiting and are "termination resistors". What this means is quite complex to explain, if you do not have some basic background in electronics. Maybe you remember an experiment about waves from your physics classes: If you lay a long rope on the ground and excite it, a wave will traverse this rope. When it reaches the end, it will come back to you! (see [http://www.youtube.com/watch?v=aVCqq5AkePI]) The same thing happens, if you tighten the end of the rope to a fixed object, but this time it is mirrored (see [http://www.youtube.com/watch?v=LTWHxZ6Jvjs]). If you could find something between a loose rope end and a fixed rope end, there will be no reflection. ~~This is what~~ the 68 Ohm resistors ~~are for~~.		Then there are three resistors: Two times 68 Ohms are used for the voltage limiting and are "termination resistors". What this means is quite complex to explain, if you do not have some basic background in electronics. Maybe you remember an experiment about waves from your physics classes: If you lay a long rope on the ground and excite it, a wave will traverse this rope. When it reaches the end, it will come back to you! (see [http://www.youtube.com/watch?v=aVCqq5AkePI]) The same thing happens, if you tighten the end of the rope to a fixed object, but this time it is mirrored (see [http://www.youtube.com/watch?v=LTWHxZ6Jvjs]). If you could find something between a loose rope end and a fixed rope end, there will be no reflection. Transmission lines experience a similar behaviour as the rope: The 68 Ohm resistors prevent reflections.

	At last there is one 1.5 kOhm resistor. Once a cube is connected to a USB port, one data line will automatically assume nearly the potential of the supply voltage. This is used to signal the USB host that there is a USB device connected on this port. Once the host and the device assume normal operation modes, this resistor has nearly no impact.		At last there is one 1.5 kOhm resistor. Once a cube is connected to a USB port, one data line will automatically assume nearly the potential of the supply voltage. This is used to signal the USB host that there is a USB device connected on this port. Once the host and the device assume normal operation modes, this resistor has nearly no impact.

Marvin am 17. April 2012 um 16:53 Uhr

2012-04-17T16:53:07Z

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	[[File:cube-structure-03.png]]		[[File:cube-structure-03.png]]

	This is quite a bit more complex. Please take some time ~~looking~~ at this diagram. You can clearly see that the "Switch-Resistor-LED" construct has simply been duplicated until we had nine of them. The battery is still only one - we can connect all of these constructs to the same battery. Notice especially that you can already recognize that this is one plane of your cube. The black wires are going downwards, the blue wire is used to connect the short pins of the LEDs together and is then going down separately, using only one wire. Using this pattern and our intelligent switches within our microcontroller we are already able to display two-dimensional patterns.		This is quite a bit more complex. Please take some time and look at this diagram. You can clearly see that the "Switch-Resistor-LED" construct has simply been duplicated until we had nine of them. The battery is still only one - we can connect all of these constructs to the same battery. Notice especially that you can already recognize that this is one plane of your cube. The black wires are going downwards, the blue wire is used to connect the short pins of the LEDs together and is then going down separately, using only one wire. Using this pattern and our intelligent switches within our microcontroller we are already able to display two-dimensional patterns.

	But, that's not enough! We need two additional planes. The first idea that comes to ones mind may be to again add two copies of that plane, leading to 27 LEDs, 27 Resistors and 27 Switches, and be done. However, this would be quite problematic: One would first of all require a device which has enough switches, is able to bear the current required by the LEDs to light up. Also, we would have a big mess of wires in our cube which will probably not be as nice at one would with their cube to be. So, we are now doing something which is called multiplexing. Don't be scared of this word, it is really easy and we will develop it step by step.		But, that's not enough! We need two additional planes. The first idea that comes to ones mind may be to again add two copies of that plane, leading to 27 LEDs, 27 Resistors and 27 Switches, and be done. However, this would be quite problematic: One would first of all require a device which has enough switches, is able to bear the current required by the LEDs to light up. Also, we would have a big mess of wires in our cube which will probably not be as nice at one would with their cube to be. So, we are now doing something which is called multiplexing. Don't be scared of this word, it is really easy and we will develop it step by step.

Marvin am 17. April 2012 um 13:33 Uhr

2012-04-17T13:33:33Z

← Nächstältere Version		Version vom 17. April 2012, 13:33 Uhr
Zeile 1:		Zeile 1:
			{{Template:LED Cube Series}}
	This page is meant to give you a understanding of the workings in your LED cube. We will try to avoid common electronics slang, thus this is especially suitable for you if you are not familiar with electronics. If you are, however, you are probably better of simply having a look at the schematics and your cube itself - it is not complex in any aspect.		This page is meant to give you a understanding of the workings in your LED cube. We will try to avoid common electronics slang, thus this is especially suitable for you if you are not familiar with electronics. If you are, however, you are probably better of simply having a look at the schematics and your cube itself - it is not complex in any aspect.

Marvin: /* The Microcontoller and Its Periphery */

2012-04-16T19:09:07Z

The Microcontoller and Its Periphery

← Nächstältere Version		Version vom 16. April 2012, 19:09 Uhr
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	The adjacent resistor is called "reset pullup". In normal operation of the microcontroller it will keep the reset pin at "logic high", which is the positive supply voltage. If the reset pin would actually go to "logic low", which is at a much lower voltage, the microcontroller would stop its operation until the pin assumes a "logic high" status.		The adjacent resistor is called "reset pullup". In normal operation of the microcontroller it will keep the reset pin at "logic high", which is the positive supply voltage. If the reset pin would actually go to "logic low", which is at a much lower voltage, the microcontroller would stop its operation until the pin assumes a "logic high" status.

	===~~Transistor Array~~===		===Bootloader Jumper===
	~~The aforementioned transistor array~~, which ~~contains~~ the ~~"blue" switches for~~ the ~~planes is connected~~ to ~~three microcontroller pins~~. ~~These three pins control which switch is currently closed~~.		One very important part is of course the bootloader jumper, which tells the microcontroller to accept an update or to run the old software. It works very much like the reset pin. If at the time of power-on the jumper connects the reset pin to the positive supply voltage, it runs the program. If it connects to the negative supply voltage, the bootloader starts.

	===Serial Connector===		===Serial Connector===
	Near the USB sockey, you will find four adjacent pins which don't hold components. These pins are going directly to the microcontroller and can be used for other stuff. Especially interesting should be that you can very easily use this connector to connect to your PC via a USB UART cable.		Near the USB sockey, you will find four adjacent pins which don't hold components. These pins are going directly to the microcontroller and can be used for other stuff. Especially interesting should be that you can very easily use this connector to connect to your PC via a USB UART cable.

			===Transistor Array===
			The aforementioned transistor array, which contains the "blue" switches for the planes is connected to three microcontroller pins. These three pins control which switch is currently closed.

	===USB===		===USB===

Marvin: /* The Microcontoller and Its Periphery */

2012-04-16T18:53:40Z

The Microcontoller and Its Periphery

← Nächstältere Version		Version vom 16. April 2012, 18:53 Uhr
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	===USB===		===USB===
			[[File:Ucper-02.png\|thumb\|300px]]
	The USB part is more interesting. We are using the [http://www.obdev.at/products/vusb/index.html V-USB Stack], a very nice, open source USB stack for hobby projects. However, the USB hardware implementation is not much more than a hack. With our LED cube we have quite a problem here: To use the internal switches of the microcontoller, we have to operate it at 5 V. However, the USB data lines do not tolerate much more than 3.3 V. This is the reason for the two diodes directly behind the USB connector: They limit the voltage we get from the microcontroller to acceptable levels.		The USB part is more interesting. We are using the [http://www.obdev.at/products/vusb/index.html V-USB Stack], a very nice, open source USB stack for hobby projects. However, the USB hardware implementation is not much more than a hack. With our LED cube we have quite a problem here: To use the internal switches of the microcontoller, we have to operate it at 5 V. However, the USB data lines do not tolerate much more than 3.3 V. This is the reason for the two diodes directly behind the USB connector: They limit the voltage we get from the microcontroller to acceptable levels.

Marvin: /* The Microcontoller and Its Periphery */

2012-04-16T18:53:00Z

The Microcontoller and Its Periphery

← Nächstältere Version		Version vom 16. April 2012, 18:53 Uhr
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	==The Microcontoller and Its Periphery==		==The Microcontoller and Its Periphery==
			[[File:Ucper-01.png\|thumb\|415px]]
	There is not as much to understand about the microcontroller than about the cube. However, there are some things we can show you:		There is not as much to understand about the microcontroller than about the cube. However, there are some things we can show you:
	===The Oscillator===		===The Oscillator===

Marvin: /* The Microcontoller and Its Periphery */

2012-04-16T17:02:26Z

The Microcontoller and Its Periphery

← Nächstältere Version		Version vom 16. April 2012, 17:02 Uhr
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	The clock for the microcontroller is provided by a crystal. To see how such a crystal works, have a look at [http://www.youtube.com/watch?v=1pM6uD8nePo]. The microcontroller basically excites a device like a tuning fork which then gives it a fairly accurate frequency. (There is much more behind that, but let's leave it at that.) It may be interesting to note that the fork is oscillating at 16 MHz, that are sixteen million oscillations per second.		The clock for the microcontroller is provided by a crystal. To see how such a crystal works, have a look at [http://www.youtube.com/watch?v=1pM6uD8nePo]. The microcontroller basically excites a device like a tuning fork which then gives it a fairly accurate frequency. (There is much more behind that, but let's leave it at that.) It may be interesting to note that the fork is oscillating at 16 MHz, that are sixteen million oscillations per second.

			===Decoupling Capacitors===
			On each side of the microcontroller, you find a 100 nF capacitor. The reason for these capacitors also has to do with the synchronousity of the microcontroller: As everything happens at the same time, the energy required at that time is really large compared to the average energy consumption of the microcontroller. Supplying this energy via the long USB cable would not work very good due to many reasons. (To name three: Resistance and Inductance of the USB line and the limited speed of light.) Thus these two capacitors are used to store some energy, which is available when required, directly at the microcontroller.

	===Programming Header and Reset Resistor===		===Programming Header and Reset Resistor===

Marvin am 16. April 2012 um 16:53 Uhr

2012-04-16T16:53:17Z

← Nächstältere Version		Version vom 16. April 2012, 16:53 Uhr
Zeile 53:		Zeile 53:
	There is not as much to understand about the microcontroller than about the cube. However, there are some things we can show you:		There is not as much to understand about the microcontroller than about the cube. However, there are some things we can show you:
	===The Oscillator===		===The Oscillator===
	The microcontroller is a ~~synchrnous~~ device - and as such it requires a clock. What synchronous means, is actually fairly irrelevant, but implied by the word: Everything happens synchronously. This is the ~~reasyon~~ this clock is required - as a signal when "things" should happen.		The microcontroller is a synchronous device - and as such it requires a clock. What synchronous means, is actually fairly irrelevant, but implied by the word: Everything happens synchronously - at the same time. This is the reason this clock is required - as a signal when "things" should happen.

	The clock for the microcontroller is provided by a crystal. To see how such a crystal works, have a look at [http://www.youtube.com/watch?v=1pM6uD8nePo]. The microcontroller basically excites a device like a tuning fork which then gives it a fairly accurate frequency. (There is much more behind that, but let's leave it at that.) It may be interesting to note that the fork is oscillating at 16 MHz, that are sixteen million oscillations per second.		The clock for the microcontroller is provided by a crystal. To see how such a crystal works, have a look at [http://www.youtube.com/watch?v=1pM6uD8nePo]. The microcontroller basically excites a device like a tuning fork which then gives it a fairly accurate frequency. (There is much more behind that, but let's leave it at that.) It may be interesting to note that the fork is oscillating at 16 MHz, that are sixteen million oscillations per second.