Now, the long awaited OS 2.0, which will support those features, is expected to be released next week (February 21st as many speculate), so this is definitely good news! Also, the updated OS will allow the PlayBook to run Android apps. I’ve already installed the 2.0 beta version on mine, but haven’t really tested it fully. The beta had some of the features disabled, like the Video Chat, so I’m relieved that the 2.0 full version will be coming soon!

Please, RIM, don’t disappoint!

Also, I found out a couple days ago that there’s this really good resource website which actually provides free access to Cisco equipment for training purposes. The site is PacketLife.net. Lab equipment and other costs are provided or sponsored by the site’s owner, commercial sponsors, and voluntary contributions by the community members. I know of a few sites that allow you to use their equipment but for a fee, so hearing about this site was fantastic. Members can schedule to use 1 of 3 blocks of equipment that they have one session at a time.

I’ll be using that site as well from time to time when I need to work with more equipment than what I have.

INTRODUCTION

The seven-segment decoder is used in many applications. This can be used in displaying letters or numbers. It is most commonly used in digital clock displays, clock timers, and others. Using this has some advantages. For example, with a seven-segment decoder display, it is easier to read the time in a digital clock than with an analog one. It can be easily read because it easily catches the eye.

The group has chosen to create the digital project, Countdown Timer, in order to show one of the applications of the seven-segment decoder. This is only one of the many useful things that can be created with this component. Countdown timers can be started and then stopped at any time and then the display will be showing how much time had passed in between. This timer can be used in different activities. It can be used in sports, games, and in other areas.

We will be showing in the following pages the circuit schematic diagram, what components are to be used, and how the circuit operates.

SCHEMATIC DIAGRAM

Figure 1: Minute counter circuit, Figure 2: Second counter circuit, Figure 3: Count out detector, Figure 4: Start/Stop control circuit

Figure 5: Countdown Timer Circuit

Figure 6: Actual MultiSim 01 Simulated Circuit

LIST OF MULTISIM 01 MATERIALS USED

+12V Voltage Source
+5V Voltage Source
2 – BCD SW
4 – 7 SEG LED
2 – switch
Diode
Relay Switch
NAND and NOR IC’s

IC’s (Integrated Circuits):

74HC192
74LS247
NE555
74HC20
74HC00
74HC04
78L05

Capacitors:

2 – 0.01 μF
1 – 0.1 μF
2 – 10 μF
1 – 100 μF

Resistors:

14 – 3.3 KΩ
15 – 1.2 KΩ
8 – 10 KΩ
1 – 68 KΩ
1 – 1 KΩ
1 KΩ Potentiometer
2 – 5.6 KΩ

OPERATIONS

This countdown timer circuit can be subdivided into four sections; namely, the minute counter circuit, the second counter circuit, the count out detector, and the start/stop control circuit.

The timer is supplying +12 V and +5 V separately is the power supply. It uses the 3 terminal voltage regulator to work at only +12 V. When using the 3 terminal voltage regulator, don’t supply the +5 V power supply from outside. When supplying +5 V from outside, do not mount the 3 terminal voltage regulator.

In the configuration of the minute counter (Figure 1), the 74HC192 (Presettable Synchronous Up/Down BCD Counter) is used as the counter. There is 74HC190 in the counter which can be down in the count which is used as the clear terminal as the second counter. The pulse signal (being the once per minute) from the second counter is inputted to DW (Count Down). The counter is count-downed by the low to high transition of the signal. The output of the BR (Borrow) becomes the L (the low level: 0V) when the counter becomes 0. Next, it changes into H (the high level: +5V) when the counter becomes 9. The counter of the upper places is count-downed by the change of such BR.

When the LD (load) terminal is in the L condition, the original value of the counter can be set with BCD-SW. At the time of this condition, because the value which is the same as the set value of BCD-SW spreads through the display part, too, you can confirm the set value in the display part.

When the LD is not in the H condition, the counter does not work. The condition of the LD is controlled with the control circuit which is controlling the operation of the timer. The BCD (Binary Coded Decimal) counter is the counter which handles from 0 to 9.

Next is the second counter circuit section (Figure 2) where 74HC192 is being used. The point in the second counter circuit is to make the 59 seconds next of the 00 seconds. For this part, the output of the NAND gate becomes in the L level when the 10th of the second display becomes 9. It inputs this output to LD. The input of the presetting is set to the counter when the LD becomes the L level. The circuit this time set “5” as the presetting. The output of the counter becomes “5” when “5” is set to the counter. With it, the output of the NAND gate becomes the H level. Because “5” was already set to the counter, there has no (or very minimal) effect. After that, the countdown is done from 5. The output of the counter becomes “9” momentarily but it is immediately set to “5”. No change can be seen.

For the count out detector (Figure 3), the L level is output by the BR, terminal of the counter when the count value becomes 0. The BR signal of each counter is reversed by the inverter and is inputted to the NAND gate. Only when the BR terminal of all counters becomes the L level, the output of the NAND gate becomes the L level. In addition from the clock generator, the pulse in the 1 second is inputted to the count-down terminal (DW) of the counter and the count-down is done. When becoming at 0’0″, the count-down is made to stop. The stop of the count-down is done in making the input of N3 the L level. When making the counter stop, it makes the count-down terminal stop in the L level condition. When stopping in the H condition, the BR terminal of each counter runs out in the L condition. Therefore, the counter start can not be restrained in the setting in the 0 minutes.

Lastly, the start/stop control circuit (Figure 4) operation uses the SR-type flip-flop (FF) which uses the NAND gate as the circuit which controls the operation (start/stop) of the timer. N1 is for the stop and N2 is for the start.

At the start operation, when the set value of the minute counter is not 00, the time-out signal becomes H. When the start switch is pushed at this time, the output of I1 becomes H and the output of N3 becomes the L. The output of N2 becomes H when the output of N3 becomes the L. The power ON reset signal becomes the L immediately after the turning on but after that, it becomes H. Because the time-out signal is H too, all input of N1 becomes H and the output of N1 becomes the L. The output of N1 is connected with the clear terminal of the second counter. The cleared condition is canceled when the clear terminal becomes the L. The output of N3 becomes H when the start switch becomes OFF. However, because the output of N1 is connected with the input of N2, the output of N2 is as the H condition.

Consequently, when the setting of the minute counter is the 00 minutes, the time-out signal is the L. When the start switch becomes ON in this condition, the output of I1 becomes H but because the time-out signal is the L, the output of N3 is H. The condition of N1 and N2 does not change. The timer is as the stop condition.

LIMITATIONS

The countdown circuit cannot be stopped unless it is turned off at the power supply or main switch.

The circuit can only be preset by manipulating the 74HC192 pre-settable synchronous counter because the BCD coder is not available in the MultiSim 01.

Now, what is the TorIX exactly?

The TorIX is an entity designed to act as a junction between multiple points of Internet presence. Here, members are able to directly connect with one another in order to exchange local Internet traffic. [TorIX]

It was first started within the RACO facility about twelve years ago in 1999. After a few years, it was then within Switch and Data, and currently it is within Equinix. The TorIX, using a three-switch design, is located in three areas at 151 Front – two are in the Equinix colocation and one is in the Cologix colocation. The two (of the 7 or 8) Equinix areas being used are on the 7th floor, and Cologix is in the 6th floor where the core equipment and the main TorIX switch Cisco Nexus 7000 are located.

Some TorIX members have their own colocation facility within 151 Front, others colocate in the Equinix facility within 151 Front, and others are located outside of 151 Front. The bigger Equinix room on the 7th floor has about 8 to 9 peers there. In the smaller Equinix room, you will find the PRI switch there and some other peers. Teleglobe, who acts as a carrier for some peers like from Netherlands or Italy, and another carrier Level 3 (formerly Global Crossing) also colocates in that room. Some of those that colocate in the Equinix facility do not necessarily have their actual servers in the location; it is only their transport equipment and multiplexers there, like for example Google, as they have their own data centre somewhere else. CBC and Toronto Hydro are examples of some peers that are located outside 151 Front.

Peering at the TorIX would be cheaper than having to peer directly with each of the ISPs or hosting companies. The cost involved in peering at the TorIX only includes the cost incurred with a peering member’s telco provider, and the last mile connection between the member’s facility and the switch (install + yearly fee). This could be $1,200/year for some smaller company peers, or be something like $60,000/year for peers that want more bandwidth or faster speed. This would be tons cheaper as you would have the opportunity to get connected with many peers through this Internet Exchange.

TorIX members can choose whomever they want to peer with, and configure their own equipment to establish the peering sessions. On the other hand, there are also some others that just use the routeservers if they want to get all routes without individually setting up peering with the TorIX members. This wouldn’t really be all routes, but more like 80% of the routes.

For ten years, the TorIX has been using donated equipment, but now all the equipment are purchased with support contracts – just in case anything doesn’t work as it should, or needs replacement parts. Speaking of which, thanks go out to Jon for giving me a Cisco Catalyst 3524 switch from the spare stock pile, which led me to decide to get my own equipment for my home lab to practice with. I really need to get going in pursuing my Cisco certifications.

The TorIX currently has 7 Board of Directors and 3 Operations persons who all help run the ToriX in a volunteer capacity. Volunteering with TorIX would be great, in my opinion, so I would want to help out in some way, as it would be a good learning experience as well. They have monthly meetings, take part in conferences, have projects from time to time (like the current NTP server project with CIRA),  and others.

I don’t think I have mentioned it here yet before in this blog, though I know that some of my friends do know these two sides of me. Actually, there can be a lot of sides to me. I am unique. I am simple, but also complicated. I know that I’m not the only person who is like this though. Well, it’s different living in this side of the world, because not a lot of people are like me in the sense of interests – so some people can be surprised to hear what I do. FYI, dear people – this is not uncommon if you grew up in Asia.

These are just some thoughts that come to mind on this Wednesday night after a long day of some ‘performing arts’ stuff.

Back to regular programming soon on this blog.