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Topic: Using a 74HC590 (Read 1 time) previous topic - next topic

mellink

Apr 07, 2011, 01:24 pm Last Edit: Apr 07, 2011, 01:28 pm by mellink Reason: 1
Hi all,
Im having a painful time trying to get a 74HC590 to simply count the number of pulses.

Outline :

My ideas was to use it to count the output from a sensor and then collect the data to the arduino (the arduino isnt fast enough because it running serveral scripts)

Problem :

The curcuit seems to count like crazy (but too quick to tell if its actually counting up in binary)

Why?!?!?

So i've rigged this up :

LEDs on output Q0 to Q4 (just for testing) (pins 15,1,2,3)
GND (pin 8 )
_RCO (not connected)
_MRC (pin 9) to GND
CPC (pin11) & CPR (pin 13) tied together to switch to +5v
_OE (not connected)
Vcc (+5V from arduino)

All power is supplied by the arduino

Questions :

Have a pinned it out right?
Do i need to use a PWM (pulse signal) on th eclocks? I have 555 chips so could set one up if needed.


I dont have a osciliscope and im finding it a pain to sort. Any help would be great.
Eventually i want to use the curcuit to count the pulses from a optointeruptor.

Thanks in advance
Rob

johnwasser

>  _MRC (pin 9) to GND

Uh, _MRC is an 'active low' signal so you are doing a Master Reset of the Counter all the time?  Try a pull-up on that pin.

>  _OE (not connected)

If you don't pull this low you won't see any outputs.  Try holding that one low.

You also don't mention _CE  (Counter Enable).  You should tie that low.

I don't know if it is true of 74HC chips (High-power CMOS?) but for most CMOS chips you have to provide inputs for every input pin.  If you let the input float it MAY cause an internal short and fry the chip.
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