Need Help How to Make Schematic on a Basic Project - Electronic Scoreboard (bsktbll)

[barbaro]

Hi There,

I'm really new to Electronics and I'm very interested on how to build a small project - an electronic basketball scoreboard using series of LED's.

I have searched a couple of sites on what to use as IC's. So far I have some of the parts already.

- Decade counter 74HC192
- Display Decoder 74LS47
- 3mm LED's (to use 3 LEDs per segment)
- 150 ohms resistors
- 100 ohms resistors
- 0.1 uF capacitors
- 0.33 uF cap
- 47nF ca
- LM7805 Volt Reg
- 9V DC power supply
- 4 pins tact push switches

Could someone please make a Schematic Diagram for this?

Thanks so much.

Barbaro

 

[barbaro]

I really need HELP as Im newbie in elctronics. This will be my first simple project.

Please let me know how can I put this project together. Any new suggestion using other IC's is much appreciated.

thx...barbaro

 

[TBennettcc]

I suggest you choose a simpler project to start.

As a first step, I would recommend reading all of the material on this page:

http://www.opamp-electronics.com/tutorials/dc_theory.htm

Then grab your battery, a switch (single-pole, single-throw should work fine), a transistor, a resistor for the base of the transistor, an LED, a proper resistor for the LED (more on that here), and follow the second schematic here:

http://electtest-karim.blogspot.com/2010/10/blog-post_23.html

After that, try this simple 555 timer circuit, and make the LEDs alternate turning on and off... (It's the second circuit on the page, under the heading "Basic LED flasher circuit using NE555 timer IC"):

http://wild-bohemian.com/electronics/flasher.html

Then, you might want to grab the datasheet for each of the ICs you have (74HC192 and 74LS47), and try to design a schematic. Post the schematic, along with any questions you have. We'll be more than happy to help, but we need a better idea of where you are in your understanding of electronics and what you know. Those first two projects will give you an idea of how driving an LED works, and should give you some ideas on how you might want to construct your circuit. If you still plan on using the 74HC192, you'll have to use two pullup resistors (one each for UP and DOWN) to tie the UP and DOWN clocks high, and make them low when you want to trigger a number to change in either direction. Right now, I'm thinking a single-pole, double-throw momentary switch. Connect the NC (normally-closed) contacts between the pullup resistor and the input. Connect the NO (normally-open) contact to ground (0V). When you press the button, it will connect the input to ground, driving it low.

Get some more advice, because I'm sure someone will come up with something better and simpler than I, but that should get you started.

 

[barbaro]

Hi TBennettcc,

Thank so much for this very imformative sites you sent me.

I have a very basic knowledge in Electronics but I can understand some simple terms.

I have actually started my project already using a breadboard.

I had all teh information taken from the DATASHEET of both the IC's I used. the Up/Down Decade counter (74HC192) and the Display Decoder (74LS47). I understand these are both compatible IC's as I've seek advise from another friend. I used a 9V power supply for lighting my LED's but I realized that the IC's uses a 5V supply so, I used a Voltage Regulator LM7805. I connected the +9V to the INPUT first leg of the regulator and common on the second attaching a capacitor between the common (middle leg) and the ouput (leg no 3) towards all the +5V supply that runs the IC connections.
BTW, I constructed my 7 segement LED's using three LED's per segment as COMMON ANODE connections using 150 ohms resistors per segment. I have tested all the continuities and I was able to have all the segments lighted individually.
So, as I'm discussing this project with a friend he suggested to use three push button switches in which I picked a 4 pin tact switch. I called it B1 as my "to count -UP" and B2 as my Count-down and B3 is my RESET button with limiting resistor 100 ohms connected to my +5V and a 47nF capacitor between each "Button"connections.

I was really glad when I tested it and I was able to have it working. The only minor problem is, it doesn't count properly. When I press my B1, my 7 segment lights up giving me a number seven figure, press it one more time and the other segments blinks a bit and it gose to a number 8 fugure. Pressing the RESET button gives me a bright number 8 figure.

Could you please let me know how can I fix this. I will send you the URL of my connection image.

Thanks so much.

Barbaro

 

[barbaro]

Hi Mr. TBennettcc,

BTW, the values of my resistors are as follows;

- my 7 segments - 3 LED's per segment I used 150 ohms
- all other resistors are 100 ohms (this includes my pull-up resostors on my B1 and B2, B3 to Gnd.

Are the resistant tollerances OK to their specific functions?

Please advise.

Thanks,
Barbaro

 

[barbaro]

Here's antother image of the project.

 

[barbaro]

Please see attached another image of the project.

 

[(*steve*)]

We really need a schematic.

What was the circuit you were working from when you created this? From that we can probably use the photos of your breadboard to see if you've done it right.

Working just off your breadboard is not as easy

 

[TBennettcc]

If you're using 9 volts to drive your LEDs, and you are using 150-ohm resistors, following Ohm's Law: V=I*R. V/R = I. 9V / 150 ohms = 60 mA of current. Are your LEDs rated for 60mA? That seems like an awful lot of current, considering most LEDs are rated for 20mA.

A schematic would certainly help.

Any particular reason you chose common-anode versus common-cathode?

 

[barbaro]

Hi Timothy and *Steve*,

Here is an illustration of what I did based on a schematic I was given by someone I was talking to from other Forums.

So, what are your recommendations on what I will need to use for my LED as resistors instead of the 150 ohms?

I basically follow the schematic I was given with the Common Anode connections.

Please advise ASAP.

Thanks,
Barbaro

 

[(*steve*)]

There appears to be a lot of extraneous stuff covering the schematic, and it has been resized at some point so that many of the connections are no longer visible.

It is generally a bad thing to operate the displays like this from a higher voltage than the supply voltage of the IC as it can cause currents to flow in the protection network (designed to protect against damage due to static electricity) and then a nasty situation called "latch up".

As long as the voltage drop across the LEDs exceeds 4V you're fine -- and it almost certainly does in this case, however if your input voltage exceeds 9V (with a fresh battery for example) you may have problems. The problem actually occurs when the LEDs are OFF -- so without load to reduce the battery voltage.

The LEDs should have a current of around 20mA, so the series resistor should be about (for red LEDs) 200 ohms.

I note that you're mixing logic families with CMOS and LSTTL mixed. LSTTL is not afflicted with the same latchup problems as CMOS. But be careful because the two types of devices are not 100% compatible. The use of LSTTL also explains the common anode approach.

I do note that there are some capacitors shown in the "overlay" of the pdf that are not present on your board. If you're going to place the bypass capacitors on there (not a bad thing to do) then connect them directly to the row of connections fr the power supply pins (don't run wires to them). The same advice applies to the capacitors connected to the regulator.

Apart from that I see little wrong. But note that because of the poor quality of the schematic, I can't check you've actually got the pins wired up correctly, that the schematic is correct, or that some wiring is missing. -- I hope your copy was better.

 

[TBennettcc]

Steve,

Wouldn't V = I x R for 9V and 200 ohms give a current of 45mA?

By the way, I'll probably need your input soon on this thread. I'm trying to work out a solution, maybe using a 555 timer. We'll see how I do.

Barbaro,

Where did you get that schematic? Did you modify it yourself, adding all the 'pictures', or was it like that when you got it? Schematics are drawn without 'pictures' because it makes them easier to read. It looks like wires got disconnected or misplaced somehow in all of the manipulating that was done to that schematic. Have a clean copy somewhere? It looks like it was done in EAGLE CAD. Great program for drawing small schematics, but as the drawings get bigger, the amount of readable information you can fit on a page diminishes greatly.

Maybe you can split the circuit up, and put the digits on a separate page?

 

[(*steve*)]

Wouldn't V = I x R for 9V and 200 ohms give a current of 45mA?

It would if the LEDs were not dropping 5.1V (3 x 1.7) -- so you get 19.5mA which is probably close enough.

 

[barbaro]

HI Steve,

Here is a better image of the Illlustration / Schematic Layout that I used from a friend at other Forums..

Please give me your recommendation based on my original thread regarding the purpose of my project using what I already have as IC's adn other components otherwise suggest something else.

Thanks,
Barbaro

 

[(*steve*)]

At least that's readable.

firstly the resistors R1 to R14 need to be around 200 ohms (220 may be the nearest you can get). This assumes you have red LEDs with a typical forward voltage drop and nominally rated for 20mA.

Secondly, you are missing all the capacitors across the pins of the ICs that are shown on your "circuit diagram".

Thirdly, those capacitors don't seem to have any values marked. I'm assuming they're around 0.1uF.

Fourthly, you need to have a larger input and output capacitor on your voltage regulator. I suggest 10 to 100uF would be good. It ensures stability.

Once you've done those things, and checked the wiring one more time, report back on what it's doing.

 

[barbaro]

hi STEVE,

here is an image of what I've tested last week before started on this forum.

please take a look and let me know.

your suggestions;

- need to use 200-220hms (R1 - R14) - I used 150 ohms
- I used red LEDs with a typical forward voltage drop and nominally rated for 20mA
- I have connected a capacitor accross each of the IC's - 1 leg connected to the pin 16(Vcc) and the other is connected to pin 8 (GND). Values 0.1 uF
- I used around 0.33 uF on my Volt Regulator - I will change it to arount 10 - 100 uF

I'll check all other connections.

BUT, here is a result of what I tested current connections.

Thanks,
Barbaro

 

[TBennettcc]

Barbaro,

What numeral / logic value is that supposed to be displaying? Does the circuit step through any values? Does the circuit do anything else, other than displaying what you have pictured?

 

[barbaro]

Hi Timothy,

This supposed to be displaying numeric value - like counting from 1 to (two digit) from B1 (switch #1) and count up on B2, B3 is the reset button.

Please remember, my project is a digital scoreboard.

Any suggestions is much appreciated.

Thanks,
Barbaro

 

[TBennettcc]

Right. I understand what the circuit is supposed to do. The question is, what does it actually do?

Does it display any information correctly? When you press up, does the value actually increment? When you press down, does the value actually decrement? When you press reset, does the value actually reset?

When you step through all the values, do any of the digits display correctly? If some do, which digits mess up, and what do they look like when they mess up?

If nothing works right, does the pattern change at all? Or does it always stay in the configuration you have pictured?

 

[barbaro]

Hi Timothy,

Oh ok. No, it doesnt display the information directly, when I plug inthe power supply it defaulted to a figure seven "7" and if I press B1 to count up, it does increment to one which gives me figure "8" display but then when keep pressing any of the buttons B1 and B2 all the segments blinks and gives me back seven figure.
for some reason its really mess up, it doesn't display other figures other than 7 and 8. eight '8' being the default when you press the RESET B3.

The pattern seems stays in the same situation.

Please advice.

I really appreciate it.

Thanks,
Barbaro