Bcd 7447, bi/rbo ,lt , bi - Electronic Circuits Projects Diagrams Free

D3422 · 19th October 2009, 06:12 PM

I'm trying to build the 7447 BCD from its
schematic, but I don't understand what to do with the BI/RBO, RBI, LT
inputs. I tried grounding them to no success. HELP!
When I plug a ground into those inputs the light blinks. I'm just starting to learn about datasheets so I haven't a clue on how to read the one from ti.

http://focus.ti.com/lit/ds/symlink/sn74ls47.pdf

technogeek · 19th October 2009, 06:18 PM

RBI is used if you don't want it to count from zero. Otherwise it must be +5V or open (no connection)

BI must always be +5V.

LT is lamp test and must also be +5v.

I got that info from the truth tables. +5V = high (H), Ground = low (L).

ericgibbs · 19th October 2009, 06:18 PM

Quote:

Originally Posted by D3422

I'm trying to build the 7447 BCD from its
schematic, but I don't understand what to do with the BI/RBO, RBI, LT
inputs. I tried grounding them to no success. HELP!
When I plug a ground into those inputs the light blinks. I'm just starting to learn about datasheets so I haven't a clue on how to read the one from ti.

http://focus.ti.com/lit/ds/symlink/sn74ls47.pdf

hi,
Look at this forum link, especially the picture posted.

Displaying Gibberish

D3422 · 20th October 2009, 10:18 PM

Thanks alot, It really helps. My number shows on the LED but it flickers to 8, says If I have a 2, f and c will flicker on and off, if I have 0, g will flicker. Its driving me mad, I checked my and triple checked my connections they're all fine.

wejos · 21st October 2009, 07:36 AM

if i may ask also the operating voltage of the IC that the OP posted earlier, or the 7448 kind and also the 74390 used in conjunction with it?

data sheet was not very helpful to me.. it just says VCC.

it could be 12 or 5 volts for all i know.

thanks alot guys and the OP.

ericgibbs · 21st October 2009, 07:43 AM

Quote:

Originally Posted by wejos

if i may ask also the operating voltage of the IC that the OP posted earlier, or the 7448 kind and also the 74390 used in conjunction with it?

data sheet was not very helpful to me.. it just says VCC.

it could be 12 or 5 volts for all i know.

thanks alot guys and the OP.

hi,
The early 74xxxx series is TTL +V is normally +5V.

wejos · 21st October 2009, 07:47 AM

okay eric thanks for your help.

ive been playing with them in a simulator it ran OK with 12v but i guess i'll have to take your word for it, you\re the expert here. i was scared to try it in-circuit before this lol.

ericgibbs · 21st October 2009, 07:53 AM

Quote:

Originally Posted by wejos

okay eric thanks for your help.

ive been playing with them in a simulator it ran OK with 12v but i guess i'll have to take your word for it, you\re the expert here. i was scared to try it in-circuit before this lol.

hi wejos,
This is one the 'pitfalls' with some sims, they are only a tool and the results should be verified with an actual circuit.

As they say, ' if all else fails, read the datasheet'...

MrDEB · 21st October 2009, 11:53 AM

from what little I know, pullup resistors are supposed to be used? or in this case pull down?
always thought HIGH was at or near Vcc.
look it up

D3422 · 22nd October 2009, 03:21 AM

Its working now. I had to change the current on the led.

D3422 · 22nd October 2009, 03:22 AM

Thanks everyone. I'm going to work on building a digital clock and post it on my wall.

wejos · 23rd October 2009, 05:55 AM

Quote:

Originally Posted by ericgibbs

hi wejos,
This is one the 'pitfalls' with some sims, they are only a tool and the results should be verified with an actual circuit.

As they say, ' if all else fails, read the datasheet'...

ill try bear that in mind eric, datasheets always come handy, glad people round here help decipher the voodoo content lol

very interesting stuff thuo, i mean electronics

thank you

thank you for this post OP also

tumbling down the rabbit hole again

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19th October 2009, 06:18 PM	#2
technogeek	RBI is used if you don't want it to count from zero. Otherwise it must be +5V or open (no connection) BI must always be +5V. LT is lamp test and must also be +5v. I got that info from the truth tables. +5V = high (H), Ground = low (L).

20th October 2009, 10:18 PM	#4
D3422	Thanks alot, It really helps. My number shows on the LED but it flickers to 8, says If I have a 2, f and c will flicker on and off, if I have 0, g will flicker. Its driving me mad, I checked my and triple checked my connections they're all fine.

21st October 2009, 07:36 AM	#5
wejos	if i may ask also the operating voltage of the IC that the OP posted earlier, or the 7448 kind and also the 74390 used in conjunction with it? data sheet was not very helpful to me.. it just says VCC. it could be 12 or 5 volts for all i know. thanks alot guys and the OP.

21st October 2009, 07:47 AM	#7
wejos	okay eric thanks for your help. ive been playing with them in a simulator it ran OK with 12v but i guess i'll have to take your word for it, you\re the expert here. i was scared to try it in-circuit before this lol.

21st October 2009, 11:53 AM	#9
MrDEB	Question what is X1, X2 and X5 from what little I know, pullup resistors are supposed to be used? or in this case pull down? always thought HIGH was at or near Vcc. look it up

22nd October 2009, 03:21 AM	#10
D3422	Its working now. I had to change the current on the led.

22nd October 2009, 03:22 AM	#11
D3422	Thanks everyone. I'm going to work on building a digital clock and post it on my wall.