BCD IC not working

[dave g]

hi

am using a MC14520B BCD IC, which according to its waveform diagram, counts up to 0-15 decimal.

I have built a test box, 555 timer generating 1hz clock , into BCD IC, then out to ADG406 multiplexer

test box is used to check 14 way multicore cable, each output from mux is connected to one end of cable, molex connector, then other end is connected to LED.

idea is , LEDS in box scroll on off individually, in squence, showing cable is connected correctly pin to pin.

what we observe at minute, is the MC14520B only seems to count to 8 ?

have i missed some connection out, does anyone have experience of using this IC ?

( i will try to upload photo of cad schematic. later )

 

[ericgibbs]

Hi,
The 4520 is a dual 4bit Binary counter, not BCD

If you post your circuit or a link to it, we can look it over.

 

[dave g]

attached pdf of schematic

 

[ericgibbs]

hi,
The first you should do is add these decoupling capacitors, it could be a noise problem.


EDIT:
Why are you powering the ADG from 24V and the 4520 from 12V.??

Have you checked the ADG switching threshold with these voltages.?

EDIT2:
Checking the ADG datasheet , states 44V max for dual supplies, it doesn't say its OK at 24V for a single supply, I would say +22V would be absolute max for a single supply

 

[dave g]

eric

thanks, running the mux from 24v , the LEDs are 24v type, panel mount,

I will try the extra caps.

Vo from the mux datasheet, the switching output, = v supply ( i think )