I am trying to get a 7 segment display to work...

I have acess to some of the 7400 series integrated circuits
I also have a 4511 integrated circuit

I had for long time a 555 going out to two 7490 divide by 10's to create led's counting in binary.... unfortuently I could never get that to work into the 7 segment display... I am now redoing the circuit from the beginning.

Anyone who could generate a diagram on how to make a 7 segment display work with 7490's a 555 and a 4511 would be my hero

anyway thx
-Tom McCurdy

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Any diagram would be extemly useful... we are not exactly sure what to do... or maybe we just hooked something up wrong last time

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I dont think you need to redo your entire circuit, You should just be able to adapt the BCD counters to output to the BCD-7seg drivers.

You could use a multiplexer and another 555 to switch between the 2 7 seg displays.

How high are you looking to count up to?
Also, could you post a schematic of what you got?

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Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

www.quantumninja.com/hw/Circuit.pdf

this is a picture of what is currently hooked up... I redid it today. I am not sure what to do with the final 3 leads of the LN514rk seven segment display. Also I was told today that the display may be a common cathode, which I belive would require a change from the 7447 to the 7448 driver.

Any help would be great.

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First off, I dont think you need those current limiting resistors between the 7 seg and 7447, It has internal current limiting.

For the 3 remaining pins, I'm assuming that your 7 seg display has 10 leads total: 7 for the display (a,b,c,d,e,f,g) then you have 2 commons, (are they common annode?) and the final lead is for the decimal.
Usually the 2 commons are in the middle of the top and bottom.

It looks like the 7447 should be able to support common annodes. Just connect the 2 commons to your +5 volts.

looking at your drawing, You also need to connect pin 8 of the 7447 to ground.
Looking at the truth table for the 7447, you want pin 3 (Lamp test) high, if you bring this low, it should light every segment of your display, a good way to check it. You also want your blanking input (pin 4) high. and I think you will want pin 5 high as well.

Hope this isnt confusing, Feel free to send me an IM if you have any questions.

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Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

I am still a bit confused on what needs to be done...
www.alldatasheet.com if you look here you can find the specifics for the LN514rk 7 segment display I am using... I am not sure whether it is common anode or common cathode

also I was basing the reistors off a sheet I was scanned.
right here
http://www.quantumninja.com/hw/elec/7447.gif

hmm
why can't I ever get this thing working

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Looks like you have common cathode (the K in the 514RK) So you either need a common annode display or a 7448.
This is probably why your circuit isnt working. try connecting LED's to the 7447, connect all the annodes to +5 and each cathode to a,b,c,d,e,f,g. and see what happens.

How do you have pins 3,4,5 set on your 7447?

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Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

I haven't looked at your schematic carefully, but I think you should get rid of the LEDs on the 7490 outputs, or buffer them. 7490 can only source 0.4ma (worst case) and still maintain a valid logic "1".

 

Thanks a lot especially to you jrz126... I finally got my circuit working... I actually figured out to replace the 7448 before you told me to... but thanks anyway I didn't know that you could tell that the 7-segment display was a common cathode from the K that is very helpful now... anyway the thing is counting beautifully and tomorrow I am going to attempt to add a second 7490 and 7448 to have two 7-segment displays. :twisted: :twisted:

thx again for all the help... I actually added my projet into the projects section... you may want to take a look at the final diagram.

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