# Two seven segment displays

Discussion in 'Electronics Homework Help' started by Rudolph, Feb 13, 2017.

1. ### Rudolph

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Hello guys,

Could you please help me out on how to connect the following circuit on a breadboard, I'd really appreciate some video links which can help me understand how to interpret the questions and understand the logic behind connecting this circuits.

I'm new here so I'm not even sure if this types of questions are allowed....Anyways, Here's the experiment:

"
Demonstrate how to manually operate a serial display that uses two seven segment displays with decoders, latch and a shift register.

ASSESSMENT CRITERIA

The following is expected to be completed by the learner as preparation for the Practical Session:
 Build a circuit that shifts BCD data serially into a shift register (74164) and displays it, via a latch, on two seven segment displays with decoders.
 Place data at the input of the shift register using I/O circuits.
 Clock digital BCD data manually into a serial shift register using a mono-stable circuit"

Thanks!

Rudolph, Feb 13, 2017

2. ### Audioguru

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The assessment is looking for somebody who understands very old TTL logic ICs and can show a simple circuit assembled to do what is clearly asked for. It seems that you have no education or experience to do it.

If somebody here does it for you and you just copy it then you do not meet the expectation and learn nothing.

Audioguru, Feb 14, 2017
Harald Kapp likes this.

3. ### CDRIVEHauling 10' pipe on a Trek Shift3

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CDRIVE, Feb 14, 2017
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4. ### davennModerator

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moved

davenn, Feb 14, 2017
5. ### Harald KappModeratorModerator

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To get you started:

• The 74164 is an 8 bit shift register with serial input and parallel output.
• BCD data is a 4 bit format, te´herefore 2 BCD numbers can be stored by one 8 bit register.
You take the upper 4 bits of the 74164's output as one BCD number, th elower 4 bits as the second BCD number.
• Store the output of the 74164 into an 8 bit latch to avoid changing the display while the data is shifted into the 74164.
• You'll need a BCD to 7 segment decoder (in fact you'll need 2 of them, one for each BCD number) to decode the latch output into the control signals for a 7 segment display.
• Depending on whether teh outputs of your BCD to 7 segemnt decoer are active high or active low you need to select 7 segment displays with either common cathode or common anode. Or use inverters to match the logic levels of the decoder to those required by the display.
Assuming your 7 segment displays are LED based, you'll need also currentlimiting resistors.
Here is a list of 74xx circuits for you to choose from. And here is how to drive LEDs which you may need to correctly control the 7 segment displays.

For clocking you are advised to use a monostable circuit. Do you know what this is and why you have to use one (instead of a simple pushbutton)? What circuit are you going to use for this?

Show us your efforts and we will guide you. We will not 'solve' the task for you, as Chris has corrrectly remarked.

Harald Kapp, Feb 14, 2017