Electronic Dice Timer Circuit

[KSpeel]

I am having trouble with a breadboard circuit that is supposed to work similar to a dice. I built it exactly to the circuit diagram, but it doesn't do anything. The pictures I put on might not be the greatest, but they should help. You can't see the battery in the pictures, but it is running about 5.5 Volts. Also, there is 4.2ish Volts going through the 7-segment display, so I also don't know why it isn't lighting up.
Any help would be appreciated. Thanks.

 

[AnalogKid]

7448 pins 3, 4, and 5 are not shown on the schematic. This is a serious error. Pin 4 can be ignored, but pins 3 and 5 must be connected correctly or the part will not drive the display. The datasheet has a table that shows the connections.

Also, this part will not drive the display directly to any real brightness. Don't expect the display to be as bright as the display on an alarm clock.

The circuit does not show any decoupling capacitors for the three chips. Ask your instructor about this.

ak

 

[KSpeel]

7448 pins 3, 4, and 5 are not shown on the schematic. This is a serious error. Pin 4 can be ignored, but pins 3 and 5 must be connected correctly or the part will not drive the display. The datasheet has a table that shows the connections.

Also, this part will not drive the display directly to any real brightness. Don't expect the display to be as bright as the display on an alarm clock.

The circuit does not show any decoupling capacitors for the three chips. Ask your instructor about this.

ak

I looked at the 7448 datasheet, but as I am fairly new to electronics, I can't decipher all of it and am still not sure what I should connect pins 3 and 5 to, if they must be connected to something.

I figured it wouldn't be that bright, but I know it isn't lighting up at all, despite it having voltage going through it.

Thanks for the help so far, but futher help is appreciated. Also, I can't ask my instructor for a lot of help, since it is not a specific electronics class, but rather a general physics class, and electronics is merely a small part of it.

 

[AnalogKid]

Are you sure you are using a common cathode display? Also, not all displays have identical pinouts. Can you post the datasheet for the one you are using?

ak

 

[kellys_eye]

I can't decipher all of it

What parts are you 'stuck' on? The general IC description is usually enough to glean what each pins purpose is and the logic states are verifiable from the tables they print.

If anything comes from your (current) exercise in electronics it should be an appreciation of data sheets and how to interpret them.

Download a copy and make specific requests for help in understanding the areas that aren't clear to you and we'll help you along. It really IS in your best interests.

 

[KSpeel]

Are you sure you are using a common cathode display? Also, not all displays have identical pinouts. Can you post the datasheet for the one you are using?

ak

I'm pretty sure it is a common cathode display. I've gotten the display to work in the past. I attached what I think is the datasheet for it as well.

What parts are you 'stuck' on? The general IC description is usually enough to glean what each pins purpose is and the logic states are verifiable from the tables they print.

If anything comes from your (current) exercise in electronics it should be an appreciation of data sheets and how to interpret them.

Download a copy and make specific requests for help in understanding the areas that aren't clear to you and we'll help you along. It really IS in your best interests.

I've never looked at a datasheet before. Like I said before, I'm not in an electronics class, but rather a different class and my project happens to be on electronics. I attached the datasheet for my 7448. I don't understand what LT, BI/RBO, and RBI mean. It was mentioned that pins 3 and 5 need to be connected, and 3 is the LT and 5 is the RBI, but I don't know what to connect them to because I don't know what they mean.

 

[kellys_eye]

That's not a 'data sheet' - that's just the pinout.

THIS is the datasheet:

http://pdf1.alldatasheet.com/datasheet-pdf/view/82377/ETC/7448.html

...and this snapshot of the page shows the 'mode of operation', explains the LT and other pin functions. There are other data sheets that have even more details if you care to search for them.

 

[AnalogKid]

For the display, yours has cathode connections on pins 4 and 12, while the schematic shows a single connection on pin 3. Obviously the schematic is based on a different part, so check all of the other pin assignments carefully.

Attached is an actual datasheet for the 7448. As noted on page 1, LT stands for Lamp Test and RBI stands for Ripple Blanking. The chart on page 3 shows the logic levels and how they interact.

Lamp Test is just that. Pull the pin low and all display segments come on no matter what character code is on the input pins.

Ripple Blanking is a way to suppress (not show) leading zeroes. For example, if the system is displaying a production line part count from 1 to 999,999 pieces, and the actual count is 4, it is easier to read "4" rather than "000004". The datasheet is a bit confusing, but Note 1 covers your application: 3, 4, and 5 all should be tied high.

ak