function simplification and implementation, MMExer3.24

Thread Starter

PG1995

Joined Apr 15, 2011
818
Hi

I thought I should share it with you. I have implemented the functions on a simulator, please have a look here.

Regards
PG
 

Thread Starter

PG1995

Joined Apr 15, 2011
818
I'm sorry if it sounds stupid.

GeoRacer said I can use three AA batteries to operate the ICs of 74xx family. I'm going to make this circuit which is going to use more than 10 ICs of 74xx family to implement AND, NOT and OR gates. Can I use one set of 3 AA batteries to operate all the ICs and 7-segment display? Please let me know. Thank you.

Regards
PG
 

Georacer

Joined Nov 25, 2009
5,182
Depending on which series of 74XX you will use, the power consumption will be different, but I think it's around 35mA at most. I 'm confident though that for 10 ICs 3AA batteries will be enough. You should include some decoupling capacitors in your design to prevent voltage drop in the rails.

What is the exact number of ICs you will use?
 

Thread Starter

PG1995

Joined Apr 15, 2011
818
Hi GeoRacer

These are the components I'm using.

1: 7432 IC (OR gate)
2: 7408 IC (AND gate)
3: 7404 IC (NOT gate)
4: 150 Ohm resistors to be put in series with connections to 7-Segment display
5: 7-Segment Display

Can I use 4 AA batteries? I'm asking this because I have 4 AA batteries holder.

Please let me know your opinion. Thank you.

Best regards
PG
 

Georacer

Joined Nov 25, 2009
5,182
No, 6V are too much. Check your ICs inscription. Which series are they? For example, is it an 74LS32 or an 74HC42? Check this out http://en.wikipedia.org/wiki/7400_series for details.

It makes a difference in tolerances and power consumption.

About the power supply, the manufacturers suggest 4.75 to 5.25V, but 4.5V often work in small projects. How many ICs do you have in total?
 

bertus

Joined Apr 5, 2008
20,659
Hello,

The 7400 series ia allowed to work on 4.75 - 5.25 Volts.
(The voltage of 3 AA batteries is to low and 4 AA batteries is to high).



As you can see there are some families in the TTL that allow a larger powersupply range.

More information on the logic circuits can be found on this page from TI:
http://www.ti.com/lsds/ti/logic/logic.page

Bertus
 

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Thread Starter

PG1995

Joined Apr 15, 2011
818
Thanks a lot, GeoRacer, Bertus.

No, 6V are too much. Check your ICs inscription. Which series are they? For example, is it an 74LS32 or an 74HC42? Check this out http://en.wikipedia.org/wiki/7400_series for details.

It makes a difference in tolerances and power consumption.

About the power supply, the manufacturers suggest 4.75 to 5.25V, but 4.5V often work in small projects. How many ICs do you have in total?
All the ICs are LS ones and there are ten ICs in total. Now please let me know. Thanks.

Regards
PG
 

Georacer

Joined Nov 25, 2009
5,182
Thanks for the link, bertus.

I can responsibly declare that I have driven a PCB with 6 74LS ICs, 6 LEDs and 1 7seg with a 3-pack of AA batteries, for short amounts of time.

It lies out of specifications, but I have seen it happening. I don't know what will happen once the batteries start dropping lower than, say, 1.4V.

I say, try with 3AA and if it doesn't work, use a 5V wall adapter.
 

bertus

Joined Apr 5, 2008
20,659
Hello,

Perhaps you can try to use 4 X NiCd or NiMH batteries.
Those have a lower voltage per battery.(about 1.2 - 1.4 Volts).

Bertus
 

Thread Starter

PG1995

Joined Apr 15, 2011
818
Do the output pins of the IC 74LS47N output LOW or HIGH signals? I believe the signals are LOW. I'm confused. I have checked the output of the IC on a logic trainer. Please let me know. Thanks.

Regards
PG
 

bertus

Joined Apr 5, 2008
20,659
Hello,

Look at the pages 258 and 259 of the provided PDF.
On those pages it says that the 74ls47 has open collector outputs.
It needs the leds with the corrosponding resistors to the powersupply from the outputs.

Bertus
 

Thread Starter

PG1995

Joined Apr 15, 2011
818
Hi

Please have a look on the attachment. I think the given solution is correct. I think two 8x1 and one 2x1 multiplexers can be used to implement Boolean function of five variables, i.e. its minterms. Please have a look here. Please help me with it. Thank you.

Regards
PG
 

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Georacer

Joined Nov 25, 2009
5,182
It is correct, as long as you have wired the input E correctly into the 8-to-1 MUXs. You haven't given a specific Boolean function, so I comment on the general case.
 
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