Introduction: An LED Dice Using a PIC 16F84 (or 16F88)

Picture of An LED Dice Using a PIC 16F84 (or 16F88)

This is a re-print of a project that I made a number of years ago - I was trawling the web, and discovered that others had been making it, so I decided to put the detail here on - so that others can benefit.

Many Led Dice have been published in various forms over the years, using output methods including a 7 segment display to display the numbers 1 through 6, or having 6 individual LEDs or even having a Die shaped display.

All of these designs have been fairly complex in hardware, typically having at least 2 IC’s, 4 or so transistors, and many resistors and capacitors. Most have also been fairly current hungry, discharging a set of batteries in a short period if the device has been left on.

Using a single chip microprocessor allows us to implement 2 individual dice, using a single IC. In addition to this, we turn a hardware problem into a software problem. We can also add features that have previously not existed before, such as the ability to recall the last roll.

The Project

Before we start designing our Die, we need to decide exactly what it does, and how it does it. In doing this, we reduce the likelihood of ‘specification creep’ interfering with the completion of our project.

The specifications for our project are simple;

We will design an electronic simulation of 2 dice, implemented using LEDs. A single push button will control the rolling of the dice in the following manner;

    • When the button is pushed for a short period (say less that 0.5 sec), the dice turn on, and display the result of the last roll.
    • If the button is pushed for greater than about 0.5 Seconds, both dice are cleared then roll independently, eventually slowing, and stopping after the button is released.
    • In all cases, the result is displayed for 50 seconds, and then the dice turns itself off.

It would be desirable to have no power switch, so we have to minimise current consumption while the project is ‘off’.


Step 1: What Does a Die Pattern Look Like

Picture of What Does a Die Pattern Look Like

Lets look at a good old-fashioned dice. As we all know, it has 6 sides, and if we analyse the various dot patterns in Figure 1 below, we can see that the following rules apply;

  • Opposing Corner dots (1) and (3) appear simultaneously.
  • Opposing Corner dots (2) and (4) appear simultaneously.
  • Middle dots (5) and (6) appear simultaneously.
  • The Central dot (7) operates independently.
The neat thing that this means is that I can present a single die display using only 4 output pins on the micro.  To display 2 separate dies, I only need 8 pins.

Step 2: Driving LEDS Using a Microprocessor

Picture of Driving LEDS Using a Microprocessor
Driving LEDs with a PIC microcontroller is a simple exercise. Because the outputs can drive 50mA, we can drive the LED directly with a series current limiting resistor to protect the LED. The diagram below shows typical connection details.

The value of the current limiting resistor can be determined by using the equation;

                    Rser = (Vcc – VLed) / Iled

                   Rser Value of series resistor
                   Vcc Supply Voltage (5V)
                   VLed Forward voltage drop of the LED (typically 1.2V)
                   Iled Led Current (Typically 20mA)

So, for the single LED in the dice pattern, we need;

                    Rser = ( 5 - 1.2 ) / 20*10-3 = 220R.

And in the case of our dual LEDs, Rser becomes;
                    Rser = (5 - 2*1.2) / 20*10-3 = 100R.

Step 3: Input Circuit - a Button to Do Things!

Picture of Input Circuit - a Button to Do Things!

A single push button interface into a PIC can be implemented simply by connecting a push button between the supply voltage, (VCC) and an input that provides an interrupt capability (We’ll look at interrupts later). The figure below provides an example. Note that the input is held ‘low’ by a 4k7 resistor to ensure that random noise picked up on the input pin does not cause an input to be recorded.

The software can do many things with a single button.  In this case, the button will do the following;
  • Turn the project on - if it is currently off
  • Display the last thrown dice pattern - if pressed for less than 1 second
  • Roll the dice - If held down.
 But - thats a software problem - We will talk about that later. 

Step 4: Clock and Power Supply

Picture of Clock and Power Supply

Now that we have designed the inputs and the outputs, all that remains is to implement a power supply, and supply some sort of clock circuit to the microprocessor.

The most simple power supply we can have is to simply use 4 ‘AA’ batteries. This provides 6.0V. If a series reverse polarity protection diode is used, the available supply voltage drops to approx 5.4 Volts, which is within the PIC’s rated input voltage range of 4.0 – 6.0 volts. 

Traditionally, microprocessor systems have used some sort of 3 terminal voltage regulator to ensure that 5.0 volts is available to the CPU. We decided not to use a 78L05 or similar 3 terminal voltage regulator, as the 4mA stand by current drawn by the regulator would swamp the sleep current of the PIC (approx 7uA), and would cause poor battery life.

In our circuit, the microprocessor consumes approximately 7uA while it is in its standby ‘sleep’ mode. So in theory, a set of 4 ‘AA’ alkaline batteries with a capacity of approximately 800mA/H should be able to last about 114,000 hours (13 years… I suspect that the batteries will die of their own accord LONG before this time !!) while in sleep mode. Of course, current consumption will increase to about 120mA during operation.  As an aside - the project is STILL USING the same batteries I put in it in the year 2000 - And they haven't started leaking.

The PIC range of microprocessors can use a variety of clock circuits, ranging from crystal controlled oscillators, through to RC (resistor/capacitor) networks. If accurate timing is required, a crystal oscillator is recommended. In our application, we are not concerned about speed and clock accuracy, so we will use a RC oscillator for this design.

Our RC Oscillator is implemented by using a 10K resistor and a 1000pF Capacitor as shown in the following diagram;  (note the the cap in the diagram is wrong - it should read 1000pf)

Step 5: The Software Design

That’s it for the hardware design, now we need to design the software that will let our hardware become a dice.

One thing that you probably noticed was that the hardware implementation was done in a structured, building block manner. We need to approach our software design in the same way.

In designing our software, lets start by dividing the system into functional blocks. One easy division is to divide the problem into an input (The Button), some processing (actually rolling the dice), and an output (The LEDs).

Lets start by building the output part of our code first. It is the most visual component, and it lets us ‘put some runs on the board’ early. Before we start though, lets talk a little bit about the microprocessor instruction set, and the architecture.

The PIC range of microprocessors implement a Reduced Instruction Set Computer (RISC). Having a RISC core is one factor that makes these CPU’s so fast. A disadvantage of having a RISC core is that the PIC range of microprocessors only implement approximately 37 instructions, so it occasionally takes more instructions to do things, and often solutions don’t always appear to be as intuitive as they are on, for example, a Z80 or 6502.

In the PIC, the primary working register is the ‘W’ register. Most of our operations use the ‘W’ register in some way. Take, for example, a set of commands that will output a binary pattern ‘10101010’ to Port B.

MOVLW B’10101010’


First, the word that we want to write is loaded into the ‘W’ register, then the ‘W’ register is written to Port B.

We can use this sequence of operations to output the bit pattern to display a dice roll of 6. From the schematic diagram, we can see that the first die is attached to Port A, bits 0 – 3 in the following way;

Port A(0) - Centre LED

Port A(1) - Corner LEDs (1) and (3).

Port A(2) - Corner LEDs (2) and (4).

Port A(3) - Middle LEDs (5) and (6).

To display the pattern for a 6, all corner LEDs, and all middle LEDs are on, but the centre LED is off. This equates to bit pattern of b’00001110’. So, to display a 6, we simply execute the instructions;

MOVLW B’00001110’


Similarly, to display a 1 (the centre LED), we would use;

MOVLW B’00000001’


We have been referring to 6 as 00001110, and 1 as 00000001. It can be confusing to use numbers like this, especially when they are not really numbers, they are simply bit patterns. To ease the confusion, most assemblers allow the use of ‘Constants’ to provide a mapping between a text name, and a number. In the case of our dice display, we can use the word Die6 in place of 00001110, or Die1 in place of 00000001.

A list of constants that we would be able to use in our display would be;

Die1 B’00000001’

Die2 B’00000100’

Die3 B’00000101’

Die4 B’00000110’

Die5 B’00000111’

Die6 B’00001110’

DieOff B’00000000’

DieTest B’00001111’

The last 2 entries (DieOff and DieTest) are useful for turning off the display, or verifying that all LEDs are operational at start up by turning all LEDs on.

Now that we know how to display a number, we should produce the building block that allows us to supply a number, and the appropriate bit pattern is loaded into the display.

Before we discuss this display routine, it should be mentioned that software is best written in a modular fashion, one routine at a time. This allows functionality to be added component by component. We can then concentrate on writing each component individually, allowing complex software to be built layer by layer.

Back to our building block for displaying a dice roll. A routine to implement the display functionality could look like this;

; First, define the required constants….

Die1 EQU B’00000001’ ; some constants are defined

Die2 EQU B’00000100’ ; for the various LED DICE

Die3 EQU B’00000101’ ; bit patterns

Die4 EQU B’00000110’

Die5 EQU B’00000111’

Die6 EQU B’00001110’

DieOff EQU B’00000000’ ; ALL LEDs OFF

DieTest EQU B’00001111’ ; ALL LEDs ON

; Disp_Dice1 - Causes a particular number to be displayed on a dice face

; Input: Register W

; Output: A LED Pattern on the dice.

; Comments: For the values of register ‘W’ ; 0 = All LEDs off

; 1 – 6 = display the pattern for 1 – 6

; 7 = All LEDs ON (Test mode)





; This is a branching lookup table. Basically, whatever value is passed in via the W register is

; added to the program counter (PCL). This then results in the appropriate value for the

; lookup result being loaded into the W register, and control being returned to the calling

; sub routine.

; ie; if a 2 is passed in through the W register, the ADDWF PCL,f operation causes 2 to be

; added to the current program counter causing the RETLW Die2 instruction to be executed.

; This results in the constant Die2 (B’00000100’) to be loaded into the W register, and

; control being returned to the calling program.











Most of the above listing is comments ( lines preceded by the ‘;’ character), so it should be able to be followed.

The display routine can be used by executing the following code;



Step 6: Interrupts to Save Energy

As previously mentioned, the microprocessor will be spending most of it’s time in sleep mode. (Especially while it is sitting majestically on the mantelpiece!). In sleep mode, the internal oscillator is stopped, and the device basically consumes no current.

In order to wake up from sleep mode, we need to have an ‘interrupt’ occur. Interrupts can be caused from a variety of sources, but they always signal some external change.

The LED Dice project that we are building has the pushbutton connected to bit 1 of Port B (PB0). This pin is also functions as an ‘interrupt’ input. When the voltage level on this pin changes, an interrupt is generated, causing the PIC to stop whatever it was doing, and to do something else. It is this interrupt that causes the PIC to wake up from it’s sleep mode.

Interrupts in the PIC can be ‘global’ in nature (Global Interrupt Enable [GIE] bit set), or localised. In our example, we would like to continue executing instructions immediately following the ‘sleep’ command, so we need to ensure that the GIE bit is clear. Global interrupts cause program execution to branch to location 4, which is useful for a more traditional vectored interrupt approach which we will cover in later articles.

Code to implement the interrupt functionality would look like;



MOVFW PortB ; do a dummy read on port B

MOVLW B’0010000’ ; Leave the GIE bit off, and enable the

; PB0 Interrupt bit

MOVWF INTCON ; and load up the Interrupt control register

SLEEP ; wait quietly for an interrupt…..

MOVLW B’00000000’ ; disable interrupts.


; Continue code execution (where we wait for the button to be released…




; eventualy, we goto MAINLOOP, where we do it all again..


One thing to note is that once we have received an interrupt, we wake, and immediately disable any further interrupts. Just with us humans, there is nothing more irritating that being interrupted while you have been interrupted. Multiple levels of interrupts can cause unexpected program errors, so we stop any further interrupts from occurring.

Now that we have examined how to implement input, output, random number generation and interrupts, we can tie all of this together, and produce the code that will actually run the dice.

There is a small amount of ‘glue’ around these functions to produce actual running code. I recommend that you obtain the program listings, and study them for more information.

If you do study the listings, you may find that there are faster, more elegant ways to do what has been done. Remember that there are commercial realities as to the time spent on producing a particular solution, and that some times, doing something the ‘no brain’, long way is actually faster to develop. This is an embedded system, and in a simple system like this, the emphasis is on producing a result, not on producing the most elegant code available. (Have you actually looked at the code in your microwave oven controller…)

Step 7: Generating Random Numbers

Now that we can output data onto an individual LED Dice display, we need some way of generating a random number.

Mathematically, generating a truly random number is a very complex exercise. In our simple PIC circuit, we can generate a random number by a couple of means;

  • A seemingly random number can be obtained by timing how long the button is held down, using a timer that incremented VERY quickly. (It would be a very rare person who could hold the button down for exactly 2243 mS every time).
  • Alternately, we could implement a mathematical pseudo-random number generator. This requires the use of multiplication and division. A pseudo-random generator generates a very long sequence of numbers that eventually repeats, after many cycles.

In our project, the easiest method that we can use to generate a random number is to sample the internal timer (TMR0), which is constantly incrementing at ¼ of the clock speed (about 256KHz), and store it in a variable continuously, as long as the button is held down.

Our PIC 16F84 or 16F88 microprocessor has 68 memory locations that are able to be used as variables. To define a variable, we simply declare a constant that refers to a particular memory location, and store numbers in that memory location as required.

A short code routine to perform this function would be as follows;

; a memory location to store our random number

RandomA EQU 30 ; define memory address to

; store a random number


MOVFW TMR0 ; get the current timer value

MOVWF RandomA ; store it in RandomA

BTFSS PortB, 0 ; Is the button still down?

GOTO Roll_Down ; no, jump out and slow

; down the display

CALL Display_Result ; Yes,display the current roll

CALL Short_Delay ; wait a while

CLRF DieA ; clear both dice again


GOTO Button_Loop ; and loop again.

Roll_Down: ; the rest of the program goes here.

; RandomA contains a number that has been randomly selected

; dependant on how long the button has been held down.


Step 8: Programming the PIC

To make the LED Dice operate you need to program the LED Dice program into a PIC. You can either purchase a Pre-Programmed PIC or you can program one yourself. Programming one yourself allows you to enter the world of PIC software design.

In order to program the PIC, you need some basic tools;

Firstly, you need the Microchip assembler and simulator (MPLAB), available as a 9Mb download from the microchip web site ( This is a HUGE download, but you only need it once. (Remember to make a backup)

In addition to the assembler, you need a programmer.  I have made several programmers over the years from various designs on the web.

Initially, I had a significant amount of trouble getting the published programmer to operate, so I built the NOPPP-2 (Experimental) version that used a 74HC08 in place of the diode logic that was present in the initial version. It worked flawlessly.

Once you have the tools, you need to create a .hex file to feed to the programmer. Start by loading up the MPLAB software, and creating a project by selecting ‘Project’, ‘New Project’ from the menu and typing the name of the project (Led Dice) into the file name box, ensuring that the default directory is in a reasonable location for your system. You need to add a source (.asm) file by clicking on the ‘Add files’ button in the ‘Edit Project’ menu.

Now that the project has a source file associated with it, you can assemble it by pressing F10. The build process will start, and a .hex file will be produced in the default directory specified above.

Once the program has been assembled, exit the MPLAB environment, and start the programmer (noppp). Specify the type of PIC (16F84), and load the .hex file. Insert the PIC into the programmer, and select Program. The PIC will be programmed in about 6 seconds. Exit the programmer, and remove the PIC from the socket.

Step 9: Construction

Picture of Construction

The prototype was built using a strip of Veroboard®. This allowed a fast development time to be achieved on the hardware (about 1 hour). If you use Veroboard®, be very careful to support the board while cutting the hole for the pushbutton switch, otherwise, the board will snap in half.

The board is designed to mount on the top of a medium sized zippy box. This is to allow the simplicity of the circuit to be displayed to any curious office staff who have built a competing dice. If desired, the project can be mounted inside a slightly larger case, with the LEDs and push button mounted in the lid in a more conventional manner.

After the Veroboard is cut to size, ensure that it fits snugly in the lid of the zippy box. File the edges if the board is slightly too large. Now is also a good time to ensure that the push button fits snugly in the hole in the board. Use a small needle file to enlarge the hole if required.

Start assembly by installing the passive components first, such as the resistors and capacitors. You may find that it is beneficial to measure the values of the resistors with a multimeter to minimise errors. When bending component leads, remember that using a pair of needle nose pliers will minimise stress while performing the bend.

Continue assembly by soldering in the 18-pin IC socket, ensuring that the indentation on the socket is at the top of the PCB. Next, solder in the 14 LEDs. Be careful with their orientation, as they will not operate if they are installed backwards. The short leg is the cathode.

Mount the push button, and connect it to the PCB with 2 short (25mm) lengths of wire. Finally, connect the battery holder, ensuring that the batteries are not installed.

Examine the board for shorts caused during assembly, and install the batteries.

Verify that +6 volts is present on pin 14, and pin 4 (With respect to pin 5 [GND]).

Finally remove the batteries, install the pre-programmed PIC (16F84), and re-install the batteries. (Don’t insert the PIC with the power applied!!) You should be rewarded with a self test pattern.

Verify that the unit operates when the button is pressed as described earlier in this article. When you release the button, the display should ‘slow down’ and display the result for 50 seconds before turning off. Quickly touching the pushbutton should recall the last roll.

If the unit operates correctly, carefully mount the PCB in the top of the zippy box.

You may like to install a small piece of Perspex™ sheeting over the top of the project to protect it from small prying fingers. This can be mounted on 12mm brass standoffs on the top of the PCB, with a small hole placed over the pushbutton.

All that remains now is to instruct the kids on how to operate it, and to chain it to the table so that it doesn’t end up at the bottom of the toy box, which incidentally is where the 265 other dice went.

Have fun. And remember, unless you create some code to allow you to cheat, it is very hard to force the dice to roll a particular way. Remember also that the one disadvantage of this project over the real dice is that it isn’t built to survive 20G’s of deceleration, so throwing it would be bad.

Step 10: Troubleshooting

If for some reason the project fails to work, check all soldering carefully. Verify that all the LEDs have been installed correctly. You can check the hardware by removing the PIC, and placing a 10R resistor between pin 14 (VCC) and each of the LED drive lines (Pins 1,2,10,11,12,13,17, and 18) one at a time. The LEDs should light.

You can verify the push button operates by monitoring pin 6 with a logic probe, or multimeter while pushing the button. It should go to +6V when the button is down.

Finally, if you have a CRO, you can verify that the internal PIC oscillator is running by examining pin 15 (CLKOUT). You should see a 1MHz square wave for 3 seconds after the device is powered up, and for 3 seconds after the button is pressed.

If all of the hardware checks out, you should try re-programming the PIC. Perhaps it has the wrong code installed.

Good Luck. And remember that this is supposed to be fun!

Step 11: The Completed Circuit Diagram and Code for the Microcontroller

Picture of The Completed Circuit Diagram and Code for the Microcontroller

Here is the full circuit diagram, as well as the source and hex files for the micro.

Many thanks to "jman 31' who redrew the schematic to fix some irritating errors. :-)

Step 12: The Hardware - Other Ways of Making It

When I made the prototype, I used Veroboard as a lid of the case, and mounted parts on the lid to 'show off', as I was making a simpler project than a co-worker created.

I have seen others use point to point wiring as well.

Here are some links to some others who have built the project using an IC socket, and directly soldering components to the socket.  They have liberally used hot glue to make the project more robust.  I thought these were excellent solutions.  The important thing is to have an attitude of getting in there and just making it!

Have a go, and have fun!


aliogo (author)2014-07-16

using pic16f88

aliogo (author)2014-07-16

I love what you do. Please I wanna learn how to program is. For example, how to blink LED for say @ the rate of 2hz

marcelalfa (author)2013-05-12

does the same .asm code apply for the PIC16F88 ?

drj113 (author)marcelalfa2013-05-12

I am pretty sure that it does.

Give it a go and let me know if you have any problems.

superoldisgold (author)2013-03-02

I am confused at the led placement in a dice pattern according the schematic could you please give the diagram of how to place leds in a dice pattern with respect to the updated schematic including led no. that you have given in this instructable.

Lord_Vek (author)2010-11-22

samarahmikhail (author)Lord_Vek2011-02-05

very nice....where did you connect the slide switch?

drj113 (author)samarahmikhail2011-02-05

If the switch is connected between the cathodes of the LEDs on one Die, and ground, then when the switch is closed, the LEDs will be able to be used. When the switch is open, the LEDs will not be able to be illuminated.

That was a cool solution to a problem I would have solved in software!

samarahmikhail (author)drj1132011-02-05

will it affect the program if i add a slide switch between the two die so that i can be able switch the dice in a single mode?

drj113 (author)samarahmikhail2011-02-05

not at all - the program wont notice - it will still generate two numbers, and the hardware will simply only display one.

samarahmikhail (author)drj1132011-02-05

thank u so much sir..i will try making this one..^_^

mwils (author)2011-01-16

I made a few modifications to the original code. It no longer forces a 6 or a 4 when the random number generator comes up with a 7 or 0. I did this by having two additional variables that change while the button is held down. One variable gets substituted for the 0 and the other for the 7. I also extended the display time slightly and allow a new roll without having to wait for the display to time out. Use the link below to get the modified code. Cheers

mwils (author)2011-01-12

I have a few comments. The schematic calls for a .001 capacitor which would be 1000pf not 100pf, which is stated in the article. I made mine with 1000pf, and it looks like the speed is the same as the video. In addition, the statement about the display staying on for 50 seconds is also incorrect. It stay on for about 3 seconds.

drj113 (author)mwils2011-01-12

Thanks for the feedback - I will amend the article.

hum20005 (author)2010-12-18

hi i have been given a project to build a random number generator using pic 16F877 and display the result on lcd display. i have to use random number between 0 and 27.
can any1 help me in the software (assembly language). plz any help ?

i will really apperciate if someone can help me to write a complete program ?


drj113 (author)hum200052010-12-19

I am more than happy to give you some pointers - You can email me at

The easy way, is to take advantage of the fact that the micro can count very very fast, while an external event is occurring, set up a loop where you count between 1 and 27, while monitoring an input - when the input changes, bail out of the loop and use the last number counted to as the 'random' number.

You are very welcome to start on a skeleton program, and I can provide some guidance for you.


Lord_Vek (author)2010-11-22

I made it !!! Using a 16f84a and the PCB mentioned above, at

Admire it at :

I put it into an enclosure and gave it as a gift. Thanks for the instructable, my friend.

drj113 (author)Lord_Vek2010-11-22

Wow - Thats cool - I couldn't see the video though, it pointed me to my_videos. Is there is another link you can show me?

jman 31 (author)2009-11-01

I threw one of these together on my protoboard using a PIC16F628A . I only had seven led's laying around, so I only made one die. Seems to work great. Thanks for the ible.

The only thing is for beginners like myself, you might add pins 5 and 14 to the schematic and add their positive and ground connections just to clarify things.


jman 31 (author)jman 312009-11-01

I also hate to be negative, but there are a few small errors in you schematic. You have two R8's and two D7's. Second die should be D8 through D14?

I really appreciate you sharing this with us, so please don't take my comments as criticism, but more as a willingness to help this project.


drj113 (author)jman 312009-11-02

Thanks for your feedback - as I mentioned in the article, this was built a long time ago.

I will fix the schematic, incorporating your changes.  Thanks for highlighting them.


jman 31 (author)drj1132009-11-02

Cool man. I did a revised schematic in Eagle for myself so I could etch a PCB. If you want I can post it so you don't have to go through the trouble of redrawing it.


VIP168 (author)jman 312010-07-25

h , the cct you've posted is it the same as mention above? or its different.?thanks

p amit (author)2010-03-04

onizuka2 (author)2010-02-20

....mmmmhhhmmmmm...... o_O

patito (author)2010-02-05

Hi, drj113,

First of all, thank you for this project, it's really awesome!!
But I must say I've got a problem: I've checked everything and I can't find the mistake. Everything is OK, but the dice patterns are not good.
Would you please explain the position of each LED?


brooklynlord (author)patito2010-02-05

I believe there is something wrong with the code.....

0001 is top left and bottom right: that is good as 2
0010 is top right and bottom left: that is a mirror 2
0100 is top middle and botom middle, which doesn't exist. X
1000 is middle: 1.
0011 is the four corners, that is 4
0101 is top and bottom middle with top left and bottom right, doesn't exist. X
1001 is center, and top left and bottom right: thats a 3
0110 is top and bottom middle with top right and bottom left, doesn't exist. X
1010 is center, and top right and bottom left, thats a mirror 3
1100 is a line from top to bottom with center, doesn't exist. X
0111 is the four corners with the middle ones, thats a 6.
1110 is center, middles, and top right and bottom left, doesn't exist. X
1101 is center, middles, and top left and bottom right, doesn't exits. X
1011 is center with the two diagonals, which is a 5.
1111 is all on, which is a seven but that doesn't exist on a die. X

We have 7 "wrong" combinations with 8 "right" combinations.

Which means that about half of the rolls should be correctly displayed.

And is there a way to modify the "random" rolls? so that they only land on the certain binary numbers?

0001,0010,1000,0011,1001,1010,0111 and 1011 are the "correct" numbers. However, there are 2 twos and 2 threes....
A fair one:

No extra 2s and 3s.

In the picture below, the ones are being controlled by the last binary digit (- - - 1 for on, - - - 0 for off), the twos are being controlled by the second last binary digit (- - 1 - for on, - - 0 - for off), the threes are being controlled by the second binary digit (- 1 - - for on, - 0 - - for off), and the four is being controlled by the first binary digit (1 - - - for on, 0 - - - for off).

patito (author)brooklynlord2010-02-06

Thank you all!
Indeed, as I never can stay quiet, I begun to change the LEDs places, and I've found a good combination. If the dice picture (step 1) is 1-2-5-7-6-3-4 from top to bottom, left to right, I've found that if I change places to 1-6-4-7-2-5-3, the patterns are right.
I haven't touched the code, as I presume the random number generation is correct, isn't it?

Thank you again for the instructable, and for the answers!!

brooklynlord (author)patito2010-02-06

That is strange. I think theres a wrong connection in your circuit because if one and two are not the opposite corners, then you won't have a correct number 2.......

Unless number 1 is connected to number 3 in your circuit, it shouldn't display properly.

@ the author

What are the possible combinations in the code? i don't really want to wire things up wrong and have illeagal displays....

patito (author)brooklynlord2010-02-06

I noticed the explanation about dice numbers in step 1 is wrong (or I've misunderstood, sorry for my english), because opposing corners dots 1 and 3 do not appear simultaneously, nor 2 and 4. 5 and 6 yes, and 7 also.
The thing is, following the image of the dice, 1 and 4 will appear simultaneously, and 2 and 3. Perhaps this is the clue... Or perhaps, as I said, I misunderstood the directions.
Maybe something passed to me, but I've checked the connections about 10 times.

drj113 (author)brooklynlord2010-02-06


Your assessment is almost correct - the code never rolls numbers that end up on illegal combinations.


drj113 (author)patito2010-02-06


Broklynlord responded correctly beofre I could get to it.

I hope his response is helpful (The picture at the end of this comment thread)


Tarkov24 (author)2009-12-26
sir can you post the complete list of materials for this one?
brooklynlord (author)2009-11-19

I kinda have a problem....

The minimal voltage of 2 LEDs added together is more than the voltage that the PIC pin supports. What should i do?

drj113 (author)brooklynlord2009-11-20

Ahhh - Thats why I used Red ad Green LEDs.

there are 2 solutions:

1.  Use a driver transistor and a higher voltage supply - that may be overkill.
2.  Parallel the LED/resistor combinations off the one pin.  As long as you are not drawing greater than 50mA, everything will be ok.

brooklynlord (author)drj1132009-11-21

The LEDs im using are superbright ones. Is this the problem?

The red on draws 3.1-3.8 v 20-30 mA
The green on draws 2.8-3.2 v 20-30 mA

Also, can you draw a schematic in parraleling on 1 pin? it doesnt have to be fancy, i draw mine with MS paint.


jman 31 (author)2009-11-13

I've done an Eagle  PCB, Schematic and an etchable pdf for this project on my DIY website. You are more than welcome to check it out here. You will have to register to view the files.

brooklynlord (author)2009-11-06

uhh.... the schematic doesn't have a 5V -? please add that in?

jman 31 (author)brooklynlord2009-11-12

Take a look at the link I posted about 5 or 6 posts down. I uploaded a schematic with those connections on it.

brooklynlord (author)jman 312009-11-12


Oh i get it:

Ground is -5V correct?

I didnt really understand that at first.......

thanks anyways

Also, do the capacitors have to be polarized?

jman 31 (author)2009-11-12

Hi drj113,

I was wanting to make this where I could have either one die or two on at a time. My first thought was to add another momentary switch to the IC and adding some alternate code, but then I realized that you are using the only interrupt pin (as far as I could tell) for your switch.

My second option then was to use a simple on/off switch between leds 8-14 and ground. That would be simpler.

What do you recommend? I am very new to writing code for these chips, but I am willing to learn. Am I right about pin 6 being the only interrupt? Would cutting the ground on the leds cause any instability?


godofal (author)2009-10-30

is there a simple way to make the  code work for an attiny2313  or something other? i dont have a PIC programmer...
i dont have an attiny programmer for that matter, but i can program them with the my serial port :D

drj113 (author)godofal2009-10-30

Funny you should ask that.  I am working on an Arduino version at the moment.

Just have to help a friend move house today, and I should have something tomorrow ;-)

godofal (author)drj1132009-10-31


anyway, i dont know the first thing arduino does, but i believe it just programs  the chips u put in them right? so i could just program my chips the way i normally do and then use them?

thepelton (author)2009-10-30

Would it be possible to make it give you larger random numbers than 1 to 6?  I am thinking of how could it be adapted to role playing games that use 4, 8, 10, 12, and 20 sided dice as well as the standard six sided cube.  Otherwise, I like it!

About This Instructable




Bio: I have a background in digital electronics, and am very interested in computers. I love things that blink, and am in awe of the physics ... More »
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