HELP PLEASE -Simple but I have it WRONG

Thread Starter

usdiggs

Joined Dec 4, 2006
8
Hi,

I am trying to build a simple counter. I have had it all drawn on CAD software and tested and it worked fine but when I go to put it on the breadboard nothing happens.

When I test the voltage between the high and low rails I am only gettign 0.9V from the 9v battery.

At the moment nothing at all is happening, and I have tried resetting it etc.

Any help would be much appreciated.

Thanks
 

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hgmjr

Joined Jan 28, 2005
9,029
Problem number one is that you appear to be using TTL devices powered by 9 volts. That is a no-no. The maximum TTL power supply is 5.25V in most cases.

Second, I can't see clearly that the 7-segment driver has its power pin tied to the +power bus.

Before you proceed you need to find a +5 volt power source.

hgmjr
 

beenthere

Joined Apr 20, 2004
15,819
Hi,

Yep, it's less messy than when the production line put the 320 volt wiring into the 5 volt bus, but the chips are just as dead. One way out of this is to use a 7805 regulator to drop your battery voltage, or to substitute 4000 series CMOS chips so you can use the full nine volts.
 

Thread Starter

usdiggs

Joined Dec 4, 2006
8
I have added the regulator and replaced the chips, but am still getting no joy. THe common from the display is going to +ve.

I am very new to this so quite possible I have made a stupid mistake :)

Thanks for your help.
 

BobaMosfet

Joined Jul 1, 2009
1,075
Yeah, there are a lot of other things needed here. A voltage regulator, capacitors, a crystal... You also need to make sure you hooked the 7Seg Display up right and didn't burn it up.
 

SgtWookie

Joined Jul 17, 2007
22,210
When I test the voltage between the high and low rails I am only getting 0.9V from the 9v battery.
That 0.9v reading is a big clue as to what is wrong.

You very likely have an OUTPUT of one of the TTL ICs connected to the +V rail or ground.
Check to make sure that your pins 12 and 13 on the 74193 are disconnected.
Check to make sure that pin 4 on the 74247 is disconnected.
 

jj_alukkas

Joined Jan 8, 2009
753
How come your battery reads 0.9V?? Have you shorted something or is your battery dead? Track it first.

Posting a schematic would help a lot than a breadboard photo.
 

hgmjr

Joined Jan 28, 2005
9,029
Good comments, all.

This is an ancient thread from 2-years ago. I am afraid this member has moved on to other forums since he has not logged onto AAC since October 2007. I suspect we will never hear from him again.

hgmjr
 
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